Powerline grid energy noise subtraction from microseismic resonance signal

Abstract

Methods of removing powerline grid energy noise from microseismic resonance signal can include establishing a fundamental power transmission frequency embedded in a microseismic resonance signal collected over a capture period, and processing the microseismic resonance signal to reduce the powerline grid energy noise. Processing can be carried out by dividing the microseismic resonance signal collected over the capture period into a plurality of time windows, determining an amplitude and phase shift for the fundamental power transmission frequency for each of the plurality of time windows, using the amplitude and phase shift to calculate one or more adjustment factors to facilitate adaption to changes in the fundamental power transmission frequency including shifts in the fundamental power transmission frequency that cause apparent phase shifting in the plurality of time windows, and applying the one or more adjustment factors to the plurality of time windows.

Description

[0001]Docket No.: 3295-010.PCT POWERLINE GRID ENERGY NOISE SUBTRACTION FROM MICROSEISMIC RESONANCE SIGNAL The present application claims priority to U.S. Patent Application 19 / 308,727, filed on August 25, 2025, which claims the benefit of U.S. Provisional Patent Application No.63 / 687,116, filed on August 26, 2024, each of which are incorporated herein by reference in their entirety. BACKGROUND Current techniques for detecting, tracking, or mapping subsurface regions of interest typically involve the use of any of a number of geophysical methods, such as various forms of galvanic resistivity, electromagnetic conductivity, nuclear magnetic resonance, drilling, etc. One particular technique utilizes various measurements of the magnetic field(s) created by electric currents flowing through underground water pathways, often referred to as the magnetometric approach. Others use various seismic techniques, such as one that detects microseismic resonance (MSR) signal. Sometimes, an MSR detector can be referred to a “geophone,” though there is other terminology used to describe the equipment used for obtaining these types of signals. MSR, for example, can involve collecting microseismic resonance signal from multiple surface locations over a subsurface region of interest using one or more resonance sensors that are sensitive enough to detect subsurface resonances, such as those related to subsurface vibrations of the earth crust, variations in subsurface earth material, movement of fluids, e.g., particularly ground water but also other fluids including oil, methane or other gases, etc. For example, in the case of detection of subsurface fluid(s), MSR detection can be used for fluid discovery, fluid mapping, fluid monitoring, and / or detection of conditions conducive to fluid flow, etc., and can be used to target subsurface reservoirs of fluid, flowing fluids, water springs under pressure, aquifers, moisture content contained with subsurface earth material, such as fields of rock, gravel, sand, Docket No.: 3295-010.PCT clay, etc., reservoirs of hydrocarbons, e.g., oil or gas, or any other subsurface dispersed or pooled collection of fluids that may be found beneath a surface of the earth or other large structure, e.g., industrial underground water channels, fluids coursing through a dam, etc. In collecting MSR signal for analysis, there is often powerline grid energy that returns into and through portions of the earth that can be picked up in the form of unwanted “noise” when operating MSR or geophone equipment. This type of noise, typically emanating from the fundamental power transmission frequency in the form of electromagnetic (EM) energy, influences seismicity based on the seismoelectric effect, where electrical and seismic energies are interrelated. In Europe, the fundamental power transmission frequency can be at or about 50 Hz and in North America, the fundamental power transmission frequency can be at or about 60 Hz. This noise can be problematic when interpreting MSR signal, as it can range from essentially non-existent to having an amplitude significant enough that the noise is overwhelming compared to the MSR signal being collected. Systems and methods of reliably removing this type of noise without substantially degrading the MSR signal would provide better data for interpretation by geophysicists. BRIEF DESCRIPTION OF THE DRAWINGS FIG.1 illustrates example circuitry options that can be used in microseismic resonance (MSR) detectors in accordance with the present disclosure; FIG. 2 illustrates an example MSR detector with a removable carrying stick in accordance with the present disclosure; FIG.3 illustrates an example plot comparing removal of powerline grid energy noise from MSR signal using notch filtering compared to harmonic noise subtraction, shown throughout the entire time of signal collection (4.5 seconds) as well as a zoomed in view of the signal collected (over the first one second), in accordance with the present disclosure; FIG.4A illustrates an example plot illustrating removal of powerline grid energy noise from MSR signal carrying a 50 Hz fundamental powerline harmonic signal via harmonic noise subtraction in accordance with the present disclosure; Docket No.: 3295-010.PCT FIG.4B illustrates a zoomed in view of the first one second of the MSR signal as shown in FIG.4A. FIG.5A illustrates an example plot illustrating removal of powerline grid energy noise from MSR signal carrying a 60 Hz fundamental powerline harmonic signal via harmonic noise subtraction in accordance with the present disclosure; and FIG.5B illustrates a zoomed in view of the first one second of the MSR signal as shown in FIG.5A. DETAILED DESCRIPTION In accordance with the present disclosure, methods and systems are provided that relate to the removal of powerline grid energy noise from microseismic resonance (MSR) signal. In some examples, a method of removing powerline grid energy noise from MSR signal can include establishing a fundamental power transmission frequency embedded in a microseismic resonance signal collected over a capture period, and also processing the microseismic resonance signal to reduce the powerline grid energy noise. Processing can be carried out by dividing the microseismic resonance signal collected over the capture period into a plurality of time windows, determining an amplitude and phase shift for the fundamental power transmission frequency for each of the plurality of time windows, using the amplitude and phase shift to calculate one or more adjustment factors to facilitate adaption to changes in the fundamental power transmission frequency including shifts in the fundamental power transmission frequency that cause apparent phase shifting in the plurality of time windows, and applying the one or more adjustment factors to the plurality of time windows to reduce the powerline grid energy noise of the microseismic resonance signal to generate a modified microseismic resonance signal. In another example, a system for removing powerline grid energy noise from microseismic resonance (MSR) signal can include a microseismic resonance detector including a resonance sensor configured to be in resonant contact with a resonant substrate, at least one processor, and at least one memory device including a data store. The microseismic resonance detector in this example can be configured to establish a fundamental power transmission frequency embedded in a microseismic resonance signal collected over a capture period, and process the microseismic resonance signal to reduce Docket No.: 3295-010.PCT the powerline grid energy noise. Processing the microseismic resonance signal can be carried out by dividing the microseismic resonance signal collected over the capture period into a plurality of time windows, determining an amplitude and phase shift for the fundamental power transmission frequency for each of the plurality of time windows, using the amplitude and phase shift to calculate one or more adjustment factors to facilitate adaption to changes in the fundamental power transmission frequency including shifts in the fundamental power transmission frequency that cause apparent phase shifting in the plurality of time windows, and applying the one or more adjustment factors to the plurality of time windows to reduce the powerline grid energy noise of the microseismic resonance signal to generate a modified microseismic resonance signal. In another example, a non-transitory machine-readable storage medium having instructions embodied thereon is disclosed. The instructions when executed by one or more processors can cause the one or more processors to remove powerline grid energy noise from microseismic resonance signal by establishing a fundamental power transmission frequency embedded in a microseismic resonance signal collected over a capture period, and processing the microseismic resonance signal to reduce the powerline grid energy noise. Processing the microseismic resonance signal can be carried out by dividing the microseismic resonance signal collected over the capture period into a plurality of time windows, determining an amplitude and phase shift for the fundamental power transmission frequency for each of the plurality of time windows, using the amplitude and phase shift to calculate one or more adjustment factors to facilitate adaption to changes in the fundamental power transmission frequency including shifts in the fundamental power transmission frequency that cause apparent phase shifting in the plurality of time windows, and applying the one or more adjustment factors to the plurality of time windows to reduce the powerline grid energy noise of the microseismic resonance signal to generate a modified microseismic resonance signal. In accordance with the methods, systems, and non-transitory machine-readable storage media described herein, additional details regarding the removal of powerline grid energy noise may include preliminarily detecting or manually entering a fundamental power transmission frequency. In this example, the power transmission frequency of each of the plurality of time windows may be determined to be within about + / -0.1% of a fundamental power transmission frequency (before accounting for amplitude and phase Docket No.: 3295-010.PCT shift). Thus, the “fundamental power transmission frequency” relates to the expected or ideal frequency for the region, which is usually a round number, 50 Hz in Europe, 60 Hz in North America, for example. Notably, this does not account for small frequency drift away from those values. For example, a portion of the electromagnetic powerline signal energy can be converted to seismic vibration in the earth, which can be picked up by the resonance sensor resulting in powerline grid energy noise comingled with the targeted microseismic resonance signal that is generated. Furthermore, the expected fundamental power transmission frequencies may undergo a phase shift, thus rendering the simple removal of the fundamental power transmission frequency as its “primary frequency” problematic. Furthermore, by starting with the incorrect value for this noise frequency, removal of harmonic frequencies, e.g., 2x harmonic, 3x harmonic, 4x harmonic, etc., frequencies targeted for subtraction become less and less accurate as the multiplier increases. In some examples, the fundamental power transmission frequency can be known and entered by a user (which includes the manufacturer), or it can be autodetected by the microseismic resonance detector, for example. With the fundamental power transmission frequency being known, individual time windows within the full capture period can be used to fine tune the fundamental power transmission frequency by determining the amplitude and phase shift for the fundamental power transmission frequency in order to account for such shifts in the fundamental power transmission frequency for a plurality of time windows, e.g., some or all of the time windows within the capture period. Determination of the amplitude and phase shift can provide a closer approximation of the amplitudes and frequencies within their respective time windows, or even across the entire capture period in some instances, for subtraction. Thus, the “fundamental power transmission frequency” is based on what is expected or idealized for the local power grid, and the amplitude and phase shifted power transmission frequency, or “shifted power transmission frequency” is based on actual values (or much closer values) within some or all of the time windows, which can be used to generate a more accurate subtraction of the powerline grid energy noise, including the primary frequency and a plurality of its harmonics. With the general examples set forth herein, it is noted in the present disclosure that when describing the methods, systems, and / or the machine readable storage media, individual or separate descriptions are considered applicable to one other, whether or not Docket No.: 3295-010.PCT explicitly discussed in the context of a particular example or embodiment. For example, in discussing a microseismic resonance in the context of the methods, such examples arealso related to any related systems and / or storage media, and vice versa. Furthermore,terms used herein will have their ordinary meaning in the relevant technical field unless specified otherwise. In some instances, there are terms defined more specifically throughout the specification, with a few more general terms included at the end of the specification. These more specifically defined terms have the meaning as described herein. Detection of Microseismic Resonance Microseismic resonances can be detected using a device analogous to a stethoscope, but instead of a human subject, the subject is a subsurface region beneath the surface of the earth where geological resonances (or microseismic resonances) are generated. These microseismic resonances can be generated by any of a number of subsurface discontinuities where there may be solid material boundaries, e.g., fractures, faults, joints, boulders, pebbles, rocks, etc., by natural phenomenon that may occur underground, e.g., natural expansion and contraction or earth tides causing the crust at fractures or other discontinuities to rub against one another. Moisture at these locations may contribute to the geological resonances that occur. For example, at areas where there are no fractures or discontinuities, and therefore very little or no passageways for fluids, there is little to no microseismic resonance signal that is detectable, which may be referred to as a dead zone. In addition to cracks beneath the surface in hard rock matrix, porous earth (gravel and sand) also generate geological resonances as the earth crust expands and contracts. Other sources of geological resonances also contribute to the microseismic resonance that can be detected using a microseismic resonance detector as described herein. In the resonance frequency spectrum, higher frequencies typically indicate microseismic resonances from sources nearer to the surface, whereas lower frequencies indicate microseismic resonances coming from deeper beneath the surface. Geological resonances, and thus microseismic resonance signals detected by an appropriate type of resonance sensor, e.g., piezoelectric sensor, MEMs sensor, mass-spring sensor, etc., Docket No.: 3295-010.PCT typically indicate a source location at a subsurface point below the resonance sensor, at a depth proportional to the inverse of frequency measured. As a general guide regarding sensing subsurface geological resonances, frequencies detected at various depths can range, as follows: from about 0.5 m to about 5 m, the frequency response may be from about 200 Hz to about 7,500 Hz; from about 5 m to about 20 m, the frequency response may be from about 50 Hz to about 1000 Hz; from about 20 m to about 100 m, the frequency response may be from about 10 Hz to about 250 Hz; from about 100 m to about 250 m, the frequency response may be from about 4 Hz to about 50 Hz; and from about 250 m and below, the frequency response may be from about 0.2 Hz to about 20 Hz. Note that these ranges overlap, as subsurface geological features and / or materials all have different seismic velocities, for example. Beneath the surface of a volume being measured for microseismic resonance signals, there may be solid materials that are hard and / or consolidated and solid materials that are soft and / or unconsolidated. The different types of materials resonate differently and can have a wide range of properties resulting in a wide range of seismic velocities. Microseismic emissions may occur from points of high stress where mechanical contact exists between solids. Furthermore, weak and / or broken rock may cause sharp reflections that more strongly reflect resonant microseismic waves. For example, open fracture systems are lacking the mechanical contact except at "hinge points" which are very high stress points. These various types of signals can be interpreted based on experience of the technician reading the collected data, for example. As there are typically subsurface regions or points of different types of material, weaker and / or stronger stresses involved with mechanical contact as reported by microseismic resonance signals amplitude at subsurface discontinuities, e.g., fractures, faults, boulders, pebbles, etc., and may provide additional information about the materials present and the likelihood of detecting subsurface conditions conducive to fluid transfer, which may lead to the discovery of water, oil, and / or gas, for example. In addition to the frequency detectable as microseismic resonance signals, the velocity of seismic waves to surface for detection as microseismic resonance signal(s) can also assist with understanding the depth of geological resonances. In some instances, signal stacking can be useful in detecting and recording locations of microseismic resonance signals because subsurface geological matrices or systems are complex and can Docket No.: 3295-010.PCT change fairly significantly over relatively short periods of time, e.g., a few seconds to a few hours. Microseismic Resonance (MSR) Detectors By way of example, detecting subsurface microseismic resonances can be carried out using a microseismic resonance (MSR) detector 100, such as that shown by way of example at FIG. 1 and in FIG. 2. FIG. 1 illustrates schematically some of the circuity and parts that may be assembled as part of an MSR detector, and FIG. 2 illustrates an example exterior view of one possible MSR detector that can be used. Other arrangements may be used, as this arrangement is exemplary only. Furthermore, in FIG.1, the boxes marked “digital” and “analog” do not infer that these components are on separate boards, nor does the presence of a component not shown as “digital” or “analog” infer it would or would not be present on a board. Furthermore, any of these components may be integrated as part of a single unit or device, or may be any of a number of multiple components connected together by cable, electrical traces, wireless communication, etc. Thus, the term “microseismic resonance detector” may be in the form of a single device or may be in the form of a system of interconnected components in communication with one another. In some examples, there may be instances where there is no analog amplifier used, as indicated by dashed lines in FIG.1 where the signal collected by a resonance sensor 10 is converted directly by digital signal by an analog / digital converter or ADC 40. As shown in the example microseismic resonance detector 100 of FIG. 1, a resonance sensor 10, which may be a piezoelectric sensor, a MEMs sensor, a mass-spring sensor, for example, is shown in contact with a resonant contact article 166, which in this example is a solid spike 166. In addition to the single location shown in this FIG., the spike can be placed at multiple surface locations within a region of interest to take MSR signal measurements. In this example, the solid spike is driven through the earth surface 190 through loose surface material 192, e.g., sand, gravel, etc., and into / onto a resonant substrate 194, e.g., rock, clay, compacted dirt, etc. The solid spike may be driven into the resonant substrate at a depth ranging from about one inch or more to an appropriate depth where microseismic resonance emissions may be more reliably measurable due to resonant contact with the resonance sensor. In other words, the microseismic resonance Docket No.: 3295-010.PCT signal can be collected via resonant contact of the solid spike with both the resonance sensor and the resonant substrate. The resonance sensor 10, e.g., piezoelectric sensor, can detect microseismic resonance signals by placing the resonance sensor(s) directly on the multiple earth surface 190 locations where microseismic resonance emissions are measurable. Thus, the solid spike 166 can be used in instances where resonance can be detected better by driving into the resonant substrate 194 or it can be placed in direct contact with the resonant substrate with or without the use of the solid spike. As an example, the resonance sensor may be selected for use that has a sensitivity suitable for sensing all or a representative number of frequencies spanning the range of about 0.1 Hz to about 800 Hz, from about 1 Hz to about 800 Hz, or from about 4 Hz to about 800 Hz. In other examples, the resonance sensor can be selected that has an even wider window of frequency response, e.g., the ability to detect frequencies within the range of up to 7,500 Hz, e.g., from about 0.5 Hz to about 7,500 Hz. If a piezoelectric sensor is used as the resonance sensor 10, piezoelectric materials that can be selected for use include any material sensitive enough to detect subsurface geologic resonance within the frequency ranges of interest. Piezoelectric materials can be inorganic piezoelectric materials or organic piezoelectric materials. More specifically, the piezoelectric material may include a piezoelectric polycrystal or piezoelectric ceramics, with examples including barium titanate or lead zirconate titanate. In particular, piezoelectric polycrystals possess piezoelectric property with a high dielectric constant making them suitable for high power transducers. Having this property makes these materials effective for use in monitoring and / or detecting geologic resonance sufficient to collect microseismic resonance signals. Furthermore, by way of example, piezoelectric ceramics and / or PVDF piezoelectric films can likewise be used, among others. For example, the piezoelectric material can be any of a number of compounds, but zerconate titanate (PZT) works considerably well. Furthermore, even though PVDF piezoelectric films have been understood in the past to be less effective for detecting seismic waves than piezoelectric crystals and / or ceramics, it has been recognized that PVDF may provide good sensitivity in certain circumstances, and furthermore, are not as brittle as ceramics, and are not as prone to cracking. In further detail, piezoelectric sensors may include the piezoelectric material as described above by example, and may include any of Docket No.: 3295-010.PCT a number of vibration pick-up structures, such as cantilever beams, coil springs, elastic films, etc., which are configured for rapid deformation. As the resonance sensor 10 picks up microseismic resonance signals from subsurface geologic resonances, (through the solid spike 166 in this instance), the signal may be relayed to an amplifier 20, or multiple amplifiers. In this example, the amplifier could be a programmable instrumentation dual stage amplifier with two amplifiers connected in series, each capable of generating up to 8:1 gain. The amplifier in this example is an analog amplifier, as analog amplification can provide better resolution, particularly when amplifying at 16:1 gain, 32:1 gain, or 64:1 gain. To illustrate, if a single-stage amplifier can amplify microseismic resonance signals at 2:1 gain, 4:1 gain, or 8:1 gain, then a 2-stage amplifier could amplify the same signal at 16:1 gain, 32:1 gain, or 64:1 gain, for example. The analog amplified signal can then be filtered to remove unnecessary or unusable high frequencies, for example, using a low pass filter 30 or LPF. The low pass filter can be selected to remove frequencies above about 800 Hz, 2,000 Hz, 4,000 Hz, 6,000 Hz, or 7,500 Hz, or any other frequency that would provide a benefit for a specification application. Typically, filtering out frequencies above about 7,500 Hz is sufficient, but more filtration can be used if desired for excluding geologic resonances closer to the surface. In other words, the microseismic resonance signals can be filtered to remove signals outside of useful ranges for detecting subsurface conditions conducive to fluid transfer for the fluid depth being targeted. A lower threshold of high frequencies could be filtered out for use in discovery of very deep oil and / or gas, for example. Microseismic resonance signal filtration can be carried out using any of a number of filters, such as a maximally flat magnitude filter, e.g., a Butterworth filter, a Bessel filter, or a Chebyshev filter. The Butterworth filter, for example, may be a 5thOrder 7.5 kHz Butterworth Low Pass Filter, but any of a number of low pass filters can be used to filter out unneeded higher frequencies in many circumstances. In further detail, amplifying the microseismic resonance signals and / or filtering out the high frequencies, e.g., at least about 6,000 Hz, at least about 7,500 Hz, or at least about 9,000 Hz, can be carried out as analog signals to retain the low frequencies to be converted to a digital signal for digital processing. In some examples, at least some of the digital processing may occur onboard a microseismic resonance detector. In other examples, at least some of the digital processing can occur remotely after transfer to a computer or a network. In other Docket No.: 3295-010.PCT examples, the use of the analog amplifiers 20 and / or the low pass filter(s) 30 may be omitted from the process, converting vibrations from the MSR signal collected by the resonance sensor 10 directly to the analog / digital converter (ADC) 40 for subsequent digital processing. In some instance, oversampling and averaging with the ADC can improve noise reduction further. Thus, in either example (with or without analog processing), the microseismic resonance detector can be configured to convert the amplified and filtered microseismic resonance signal or the raw signal collected by the resonance sensor to digital signal processing by converting to a digital signal using the analog / digital converter 40. Either way, in some examples, the high frequencies above about 7,500 Hz may be filtered out, as mentioned above. An example analog digital converter that is suitable for use is a 16- bit 200 ksps analog / digital converter. The digital microseismic resonance signal may be combined in a single data file, for example, with data collected from a global navigation Satellite System (GNSS) receiver 80, such as a uBlox ZED-F9P multi-band GNSS receiver or other suitable GNSS receiver. Example GNSS receivers may include receivers suitable for receiving signals based on GPS, GLONASS, Galileo, BeiDou, and QZSS, etc., and / or cellular systems based on GSM-, UMTS-, 3G, LTE, 4G, 5G, etc. Others can likewise be used. In some examples, the onboard location data collected on the microseismic resonance detector may be collected using an onboard receiver adapted to receive RF signal from a terrestrial base station source and a second reference signal. For example, the microseismic resonance detector may include an on-board receiver adapted for real-time kinematic positioning. The use of more local RF signal from a terrestrial base can be used, for example, when much more highly accurate fluid detection would be useful, e.g., smaller areas with readings taken closer together. In further detail, the microseismic resonance signal can be obtained onboard a microseismic resonance detector which also collects onboard location data in some examples. This can be particularly useful when collecting subsurface data on large areas. The data file can be generated, and in some instances further processed, on a processor, such as a microcomputer unit 50 (MCU). The MCU may be enabled with WiFi and / or Bluetooth, for example. In some examples, the MCU may pass the digital signal to an embedded multimedia card 60, such as an eMMC Flash device for later upload to a Docket No.: 3295-010.PCT computer or computer network, for example. Alternatively, the device may likewise be enabled for transferring data by wireless communication to a computer or computer network on-site or over a cellular network, for example. A display 70 may be included, which may be a digital display such as a smartphone display, tablet display, computer display, an electronic paper display (e-ink or intelligent paper), etc. The display or other on-site readout device or system can be useful for providing the on-site operator with a second MSR signal, which is the MSR signal after undergoing harmonic noise subtraction. In this instance, the raw signal (including the powerline grid energy noise) can be retained and sent back to the lab for evaluation and / or carrying out the harmonic noise subtraction, perhaps in the same way as the operator or perhaps with different parameters, e.g., different time window durations or locations, etc. In some examples, when collecting microseismic resonance signal(s), individual locations can be established for collecting signal stacks to be processed for the generation of modified microseismic resonance signals that represent the multiple microseismic resonance signals collected at a single location. The signal stacks can be processed, for example, as mean microseismic resonance signals, arithmetic mean microseismic resonance signals, geometric mean microseismic resonance signals, median microseismic resonance signals, mid-point microseismic resonance signals, microseismic resonance signals with outlier signals filtered out, or a combination thereof. The signal stacks can be based on any of a number of multiple readings, but typically the signal stacks can be based on 2 to 10 sequentially obtained microseismic resonance signals. The spacing between signals can be negligible, e.g., from about 0 to about 1 second, or can be longer in time, multiple seconds to days or longer. The 2 to 10 individually obtained microseismic resonance signals can be obtained within about 15 minutes, within about 10 minutes, within about 5 minutes, within about 1 minute, etc., depending on how deep the signals are coming from beneath the surface. Deeper microseismic resonance signals may be particularly useful when exploring for oil and / or gas, e.g., methane, natural gas, etc. When discovering the location of subsurface water, shallower microseismic resonance signals may be more relevant and would thus typically take less time in obtaining microseismic resonance signals from each signal stack. As an example, a single measurement may be taken every few meters, e.g., 2 to 20 meters, along the surface in a straight line and the collected resonance signal can be mapped as shown at a subsurface Docket No.: 3295-010.PCT map. Alternatively, the same locations can be measured over the same region of interest, but at each location, multiple measurements can be taken e.g., from 2 to 10, and then data can be stacked or aggregated to generate statistically superior data and improved resolution of subsurface map. In further detail, there may be other onboard equipment associated with the microseismic resonance (MSR) detector 100 for collecting MSR signal onboard, such as an onboard receiver adapted for use with a global navigation satellite systems (GNNS) and / or RF signal from a terrestrial base station source and a second reference signal. Onboard equipment real-time kinematic positioning and / or orientation alignment can be included, e.g., x-, y-, and / or z- orientation accelerometers. Referring now to FIG.2, an exterior view of an example microseismic resonance (MSR) detector 100 is shown which includes an MSR sensor assembly 150 and a detachable carrying stick, which is shown attached to the MSR detector at 110A and detached at 110B. The MSR detector in this instance includes a housing 152 and a solid spike 166 that is coupled to a resonance sensor (not shown, but shown in FIG.1 at 10). This particular MSR sensor assembly includes a coupling ring 154 to provide a solid connection with a coupling notch 130 of a carrying stick when attached, though there are other coupling mechanisms that can be used. A GNNS antenna 170 (or some other positioning antenna) and associated receiver is shown above the housing which can position information regarding the location where the MSR data was collected. In addition to the solid spike and the GNNS antenna shown in FIG.2, other components that may be present include those components described in FIG. 1, for example. The carrying stick 110A,11B provides a convenient way for a user to drive the solid spike 166 of the MSR sensor assembly 150 through the surface of the earth and into a resonant substrate 194, sometimes through loose surface material 192 that may not be sufficiently resonant to gather MSR signal. The cone-shaped lower portion of the housing can provide a shape that can support the MSR sensor assembly upright, though this may not always be the case. In addition to providing a mechanism for contacting the solid spike with the resonant substrate and / or driving the solid spike into the resonant substrate, in this example, the carrying stick is removable, as shown at 110B. Once removed, the carrying stick can be used as an active energy-inducing rod for introducing active energy Docket No.: 3295-010.PCT into the resonant substrate near the MSR sensor assembly, which is described in greater detail hereinafter. To remove the carrying stick 110A, 110B from the MSR sensor assembly 150, a user may squeeze a lever arm 116 against a handle 112, causing an actuator 118 pivotably coupled to an extension shaft 114 to move upward in an essentially vertical direction for horizontal surface microseismic resonance measurements (or perpendicular to the resonant substrate being measured). Vertical movement of the actuator can cause a coupler 120 to disengage from the housing 152. The coupler can be, for example, a latch, a magnetic coupler, a spring-loaded coupler, etc. For example, if the coupler is a magnetic coupler and the housing is a ferromagnetic housing, the magnetism will not interfere with the MSR signal being collected, and the magnetic coupler can be engaged and disengaged from the ferromagnetic housing by exerting some force, or by a mechanical mechanism that facilitates disengagement of the magnetic coupler from the ferromagnetic housing, e.g., magnetic vice where magnetic attraction is broken by mechanically interrupting the magnetic attraction. The active energy can be introduced into the resonant substrate by impacting a top end of the carrying stick with a hammer 134 or other impacting tool. At the bottom of the extension shaft in this example is a ground impactor 132, which translates the impacting force through the extension shaft and into the resonant substrate 194. The impacting force tends to generate very shallow MSR vibrations that can be picked up by the resonance sensor of the MSR sensor assembly. In some examples, the active resonant energy of the microseismic resonant signal can dissipate within about 2 seconds. The capture period can thus be long enough to collect both the active resonant energy followed by passive resonant energy already inherently present within the resonate substrate to generate a passive resonance signal. The active energy signal can be consistent with active resonant energy introduced by a short directed force to a surface of the resonant substrate, such as by impacting the ground with the active energy rod, e.g., a short directed force may be generated by a impacting a rigid shaft on a first end that is in contact with a surface of the resonant substrate at a second end. The active resonant energy that is introduced into the resonant substrate can be used to initiate recording of the microseismic resonance signal by the microseismic resonance detector. In some examples, the microseismic resonance detector can operate with a time buffer such that when the microseismic resonance detector begins recording, a period of time up to about Docket No.: 3295-010.PCT 1 second prior to the active resonant energy being induced into the resonant substrate is also recorded. In some examples, determining the amplitude and phase shift for the fundamental power transmission frequency for each of the plurality of time windows can include processing at least one time window while the active resonant energy is generating the active resonance signal. Powerline Grid Energy Noise Processing and Subtraction In collecting MSR data using an MSR detector, subsurface resonant substrates can be susceptible to carrying powerline grid energy that returns into and through portions of the earth, which may be picked up by sensitive MSR devices or geophones, e.g., MSR detector as described herein, in the form of unwanted electric field and magnetic field “noise,” typically corresponding to the fundamental power transmission frequency and its multiple harmonic frequencies relative to the fundamental power transmission frequency. As mentioned, in Europe, the fundamental power transmission frequency can be at or about 50 Hz and in North America, the fundamental power transmission frequency can be at or about 60 Hz. This powerline grid energy noise can be problematic when interpreting MSR signal, as it can range from essentially non-existent to having an amplitude significant enough that the noise is overwhelming compared to the MSR signal being collected. Essentially, the noise occurs as electric and magnetic fields are at about the fundamental frequency of power transmission and its harmonics. For example, the noise can be particularly problematic during time-domain measurements of electric and magnetic fields and / or indirectly as introduced via MSR detector cables (if present) that may be present when acquiring seismic data, e.g., MSR signal. Harmonic noise subtraction can be carried out using harmonic solver software or firmware to process the raw MSR signal that is collected using an MSR detector, which can be at a single location or more typically collected from the various locations over an area of interest. The harmonic solver for subtracting harmonic noise from an MSR signal can include processing the microseismic resonance signal collected over a capture period by dividing the microseismic resonance signal over the capture period into a plurality of time windows. For example, the full capture period may be up to about 90 seconds or longer, e.g., from about 2 seconds to about 90 seconds, from about 2 seconds to about 30 seconds, from about 2 seconds to about 15 seconds, from about 2 seconds to about 10 Docket No.: 3295-010.PCT seconds, from about 2 seconds to about 5 seconds, from about 3 seconds to about 15 seconds, or from about 3 seconds to about 10 seconds. Within this full capture period, the harmonic solver can separate out time windows, ranging from about 1 / 60 second to about 10 seconds, from about 0.01667 (or 1 / 60) second to about 5 seconds, from about 0.1 second to about 10 seconds, from about 0.1 second to about 5 seconds, from about 0.1 second to about 3 seconds, from about 0.25 second to about 5 seconds, from about 0.25 second to about 3 seconds, from about 0.5 second to about 5 seconds, or from about 0.5 second to about 3 seconds. To provide some examples, the capture period can be up to about 90 seconds and the plurality of time windows can be from about 0.1 second to about 5 seconds in duration, or the capture period can be from about 2 seconds to about 30 seconds and the plurality of time windows can be from about 0.2 second to about 2 seconds in duration, or the capture period can be from about 4 seconds to about 15 seconds and the plurality of time windows can be from about 0.3 second to about 1.5 seconds in duration, to name a few. When selecting the time window increments, the full capture period can be long enough to encompass at least two time windows, at least three time windows, at least five time windows, or at least 10 time windows. For example, a four second capture period with 0.5 second time windows would be able to accommodate up to eight time windows, e.g., from two time windows (if not all of the signal is processed) to eight time windows. In some examples, the time windows can be equal in time length, but in other examples, the time windows can have different time lengths. For example, there may be utility to using a one second time window at or about where the active energy signal is recorded, and thereafter, and 0.5 second time windows may be selected throughout the balance of the capture period. Likewise, there may be some sub-periods of time during the full capture period that are not assigned time windows (or if assigned, they are not processed as described hereinafter). In other words, any combination of time windows (shorter than the capture period) can be assigned or not assigned throughout the full capture period. After the time windows are established within the full capture period, some or all of the time windows can be used to determine a shifted power transmission frequency (with amplitude and phase) within each of the plurality of time windows. The “shifted” fundamental power transmission frequency within each window may independently be the same, slightly different, or substantially different than the fundamental power Docket No.: 3295-010.PCT transmission frequency of the region, e.g., typically a round number such as about 50 Hz or 60 Hz. When perpetuating within the resonant substrate, and as sensed by the MSR detector, the measured amplitude and frequency may deviate from the fundamental power transmission frequency that would be expected to be present. Typically, that deviation in frequency within the plurality of time windows that are processed are often within about + / -0.1%, + / -0.08%, + / -0.06%, + / -0.05%, or + / -0.03% of the fundamental power transmission frequency that would otherwise be expected. This shift in frequency can be referred to as a slight “phase shift” relative to the fundamental power transmission frequency. Thus, for a power grid that emits 60 Hz, a 0.5% deviation from that expected frequency when determined within one or more of the time windows can range from about 59.7 Hz to about 60.3 Hz on average (per each time window). Amplitudes can also be measured within each of the time windows to be processed to determine how much of the shifted power transmission amplitude and phase is to be subtracted. Once the time windows are established and the shifted power transmission amplitude and phase for at least a plurality of the time windows is measured and calculated, the shifted power transmission amplitude and phase can be subtracted out based on the measured amplitude within each time window at the shifted frequency. In further detail, it is noted that the shifted power transmission amplitude and phase often perpetuates harmonic signal, or “harmonics,” that may also present as noise within the MSR signal being collected, and various numbers of harmonics can also be subtracted from the MSR signal to improve signal clarity. In one example, the harmonic solver can be used to identify 1 to 30 powerline grid energy noise frequencies, including the shifted power transmission amplitude and phase and some (or all) of its harmonics, e.g., 2x, 3x, 4x, 5x, etc., of the shifted power transmission amplitude and phase. Notably, the various frequencies can be characterized with both their individual frequencies and their amplitudes for subtraction. Thus, within one time window of 0.3 seconds, if the shifted power transmission amplitude and phase is averaged to be 60.1 Hz (which is the first harmonic), then subsequent harmonics would be 120.2 Hz, 180.3 Hz, 240.4 Hz, 300.5 Hz, 360.6 Hz, 420.7 Hz, 480.8 Hz, 540.9 Hz, 601 Hz, ... 1803 Hz (which is the 30thharmonic). In addition to subtracting the amplitude of the shifted phase, any number of additional harmonics can be subtracted at their measured amplitudes. This more precise way of locating the average frequency within each time window and subtracting Docket No.: 3295-010.PCT the noise out in a more precise, time-sensitive manner provides a resultant MSR signal that is cleaner and devoid of noise that could impact interpretation of the MSR signal that is collected for subsurface geological mapping, etc. In some examples, in addition to subtracting at least the primary shifted power transmission amplitude and phase, at least one harmonic (or integer multiple of the shifted power transmission amplitude and phase) can be subtracted from the MSR signal, such as at least the 2x harmonic, multiple consecutive harmonics, at least the 2x-5x harmonics, multiple non-consecutive harmonics, at least the 2x-10x harmonics, at least the 2x-16x harmonics, at least the 2x- 30x harmonics, or any of about 8 to about 20 or even about 8 to about 30 different integer harmonics of the measured power transmission amplitude and phase (or primary frequency), etc. In further detail, the harmonic solver can be used to generate the one or more adjustment factors based on the plurality of time windows. Adjustment factors can be applied by generating a match signal to each of the time windows allowing for removal of the powerline grid energy noise to be removed from each of the plurality of time windows. The term “match signal” refers to the shifted power transmission amplitude and phase that can be used that closely aligns with the signal that is to be removed. Once matched (more closely than that of the fundamental power transmission frequency), that signal can then be subtracted out. Applying the one or more adjustment factors to the plurality of time windows can be carried out individually for each of the plurality of time windows, or can be applied uniformly with a single adjustment across all of the plurality of time windows, e.g., up to across the entire capture period. As amplitude and phase shift of each of the plurality of time windows result in a shifted fundamental power transmission frequency, this can be corrected by applying the one or more adjustment factors by subtracting at least one harmonic integer multiple of the shifted fundamental power transmission frequency. In some examples, at least two harmonic integer multiples of the shifted power transmission amplitude and phase can be subtracted. In other examples, at least a 2-times multiple, a 3-times multiple, a 4-times multiple, and a 5-times multiple of the shifted power transmission amplitude and phase can be subtracted. In other examples, applying the one or more adjustment factors can include subtracting non- consecutive integer multiples of the shifter power transmission amplitude and phase. In still other examples, applying the one or more adjustment factors includes subtracting Docket No.: 3295-010.PCT from about 8 to 20 different integer multiples of the shifted power transmission amplitude and phase. In some examples, generating a match for the entire capture period can be carried out using the shifted power transmission amplitude and phase. In further detail, fine-tuning each of the plurality of time windows can be carried out by allowing adaptation related to transient change in the fundamental power transmission frequency. In other examples, applying the one or more adjustment factors includes subtracting a single adjustment factor based on a matched signal of the amplitude and phase shift for the fundamental power transmission frequency from the plurality of time windows. Thus, the harmonic solver that may be onboard the MSR sensor assembly in the form of firmware or software, or located remotely at a server or other device for wireless or wired communication with the MSR sensor assembly, can process the microseismic resonance signal collected by dividing the microseismic resonance signal over the capture period into a plurality of time windows, and individually determining a shifted power transmission amplitude and phase and amplitude for a plurality of time windows based on shifted frequencies and amplitudes of the fundamental power transmission frequency within each of the plurality of time windows. The harmonic solver can also subtract from about 1 to 30 powerline grid energy noise frequencies individually from the plurality of time windows (including at least the shifted power transmission amplitude and phase of the primary frequency) and any of a number of the harmonics as may be useable in subtracting powerline grid energy noise originating from the power grid as powerline grid energy. In some examples, the harmonic solver can be programmed for additional tasks, such as determining and selecting the fundamental power transmission frequency of a power signal (e.g., 50 Hz or 60 Hz) as a starting place for measuring individual time window amplitudes and frequencies. This can be autodetected by the MSR sensor assembly or it can be manually set based on geography or the expected power grid frequency. Furthermore, the MSR signal collected can include the use of an MSR sensor assembly with a resonance sensor, as shown in FIGS.1 and 2, and in some examples, the resonance sensor can be in resonant contact with a solid spike or some other structure that provides a good resonant connection between the resonant substrate and the resonance sensor. In some examples, when collecting MSR signal, active energy can be introduced Docket No.: 3295-010.PCT in the resonant substrate, such as by impaction by a hammer, stick, stake, or other structure suitable for generating near-surface resonant frequencies. The introduction of this active energy can be used in some examples to initiate recording of the MSR signal. In some examples, the MSR detector (or MSR sensor assembly portion) operates with a time buffer such that when the microseismic resonance detector begins recording due to sensing the active resonant energy from the impactor, a period of time up to about 1 second prior to the active resonant energy being induced into the resonant substrate is also recorded. Thus, in some examples, recording a resonance signal over a capture period can be sufficiently long in duration that the resonance signal recorded includes at least the active resonance generated by an impactor or other source at the resonant substrate, which dissipation of this energy at or near the resonant substrate may be followed by a passive resonance that is inherently present within the resonant substrate that can be recorded as MSR signal. Referring now to FIG.3, two examples are shown where simple notch filtering was used to remove 60 Hz powerline grid energy noise from MSR signal collected, and that are compared to removal of the 60 Hz power grid energy noise using the harmonic noise subtraction technology of the present disclosure. In these plots 200, the full capture period 240 of 4.5 seconds is shown for both notch filtering and harmonic noise subtraction, followed by a zoomed in view of the same signal shown over the first 1 second for both the notch filtering and harmonic noise subtraction. The thinner line represents the original signal 220 captured and the thicker line represents the signal after either undergoing notch filtering or harmonic noise subtraction 230. Notably, shown at about 0.13 second in all of the plots is a spike in resonant signal, which corresponds with active energy 210 being introduced to the resonant substrate by striking the carrying stick (after removal from the MSR sensor assembly) with an impactor (shown at 134 in FIG. 2), namely a hammer, at a distance of about six (6) inches from the location where the ground spike is embedded in the resonant substrate. In this example, the active energy may be introduced at the resonant substrate to start recording of the MSR signal. However, in this example, the MSR detector or detection system can be configured with a recording buffer so that the capture period begins recording a short period of time prior to the introduction of the active energy. In this instance, the recording buffer period is set at about 0.1 second, but could be shorter, longer, or non-existent in some examples. Docket No.: 3295-010.PCT Recording buffer time periods may be, for example, from about 0.01 second to about 1 second, from about 0.05 second to about 0.5 second, or from about 0.02 second to about 0.2 second, though these ranges are not intended to be limiting. In further detail, two time windows t1 and t2 are shown at 0.5 second each, though those time windows could be shorter or longer than that shown by way of example. Some notable differences between notch filtering compared to harmonic noise subtraction are particularly evident when looking at the zoomed in views of each, where the filtered signal before introduction of the active energy is significantly removed via harmonic noise subtraction, which is not the case with simple notch filtering. For example, unlike notch filters, harmonic noise subtraction provides a way of suppressing or ameliorating many frequencies without distorting or attenuating the MSR signal significantly, e.g., reductions of up to about 45 dB in the ambient noise level can be obtained, with subtraction of up to 25-30 harmonics at 60 Hz and up to 30-36 harmonics at 50 Hz. As an example, when using a single notch filter at 60 Hz, inadequate filtering occurs because of the many harmonics that are also perpetuated, and furthermore, because some of the desired signal that is being collected may overlap or fall in the range to which the 50 Hz or 60 Hz notch filter is applied, which can render that section of MSR signal inaccurate. On the other hand, the use of harmonic noise subtraction of the present disclosure involves the subtracting sinusoids of the appropriate frequency, amplitude, and phase, which in the present disclosure, includes subtracting the shifted frequencies (and its harmonics) rather than the fundamental power transmission frequency. An iterative algorithm can be used to measure these values in each of the plurality of time windows to which the processing is applied and simply subtract those values. Subtraction of the powerline grid energy noise can be carried out in accordance with the following equation,where r(t) representing the MSR signal over time equals the sum of a signal s(t), theprimary frequency noise e(t), and harmonic noise p(t) based on the shifted powertransmission amplitude and phase (f0), which is measured for each relevant time window. Equation 1 illustrates one example of such a calculation. r(t) = s(t) + e(t) + p(t), where Docket No.: 3295-010.PCT p(t) = ck cos (2 kf0t + k) In this example, though the amplitude, phase, and frequency of the powerline harmonics may be assumed to remain constant over the entire length of the capture period based on the fundamental power transmission frequency of 60 Hz, 50 Hz etc., in accordance with the present disclosure, the subtraction becomes more accurate by utilizing a plurality of shorter time windows and solving for some or all of the time windows based on measured values. Even if the phase shift of the frequency typically only varies up to about 0.05 Hz or about 0.03 Hz on either side of the fundamental power transmission frequency that is expected, that small amount, perpetuated over a few to up to 30 harmonics, can be problematic, particularly for harmonics occurring further away from the primary frequency that is measured. With harmonic noise subtraction using a sinusoid subtraction methodology, the amplitude and phase of the harmonics can be estimated for each harmonic contributing to p(t) based on the average power transmission frequency for each time window, and can be subtracted from the MSR signal that is collected. Computing Systems and / or Devices The methods, systems, and / or non-transitory machine-readable storage media described herein can utilize any of a number of computing devices and / or systems. Any of the computing devices or systems shown or described herein can include a single computing device, multiple computing devices, a cluster of computing devices, or the like. A computing device can include one or more physical processors communicatively coupled to memory devices, input / output devices, or the like. As used herein, a central processing unit (CPU), a microcomputer unit (MCU), or the like may be used interchangeably and may be referred to here as a “processor.” Additionally, as used herein, a processor can include one or more devices capable of executing instructions encoding arithmetic, logical, and / or I / O operations. In one illustrative example, a processor may implement a Von Neumann architectural model and Docket No.: 3295-010.PCT may include an arithmetic logic unit (ALU), a control unit, and / or a plurality of registers. In some aspects, a processor may be a single core processor that is typically capable of executing one instruction at a time (or process a single pipeline of instructions) and / or a multi-core processor that may simultaneously execute multiple instructions. In some examples, a processor may be implemented as a single integrated circuit, two or more integrated circuits, and / or may be a component of a multi-chip module in which individual microprocessor dies are included in a single integrated circuit package and hence share a single socket. As described herein, a memory refers to a volatile or non- volatile memory device, such as RAM, ROM, EEPROM, or any other device capable of storing data. Input / output devices can include a network device (e.g., a network adapter or any other component that connects a computer to a computer network), a peripheral component interconnect (PCI) device, storage devices, disk drives, sound or video adaptors, photo / video cameras, printer devices, keyboards, displays, etc. In some aspects, a computing device provides an interface, such as an API or web service, which provides some or all of the data to other computing devices for further processing. Access to the interface can be open and / or secured using any of a variety of techniques, such as by using client authorization keys, as appropriate to the requirements of specific applications of the disclosure. When a network is used, the network can include a LAN (local area network), a WAN (wide area network), telephone network (e.g., Public Switched Telephone Network (PSTN)), Session Initiation Protocol (SIP) network, wireless network, point-to-point network, star network, token ring network, hub network, wireless networks (including protocols such as EDGE, 3G, 4G LTE, Wi-Fi, 5G, WiMAX, and the like), the Internet, or the like. A variety of authorization and authentication techniques, such as username / password, Open Authorization (OAuth), Kerberos, SecureID, digital certificates, and more, may be used to secure the communications. EXAMPLES The following examples illustrate embodiments of the present disclosure. However, it is to be understood that these examples are merely illustrative of the application of the principles of the present disclosure. Numerous modifications and Docket No.: 3295-010.PCT alternative compositions, methods, and systems may be devised without departing from the scope of the present disclosure.Example 1 - Powerline Grid Energy Noise Subtraction from MSR Signal Carrying 50Hz Fundamental Powerline Harmonic Signal Multiple experiments were carried out in areas of interest where there was a fundamental power transmission frequency of about 50 Hz. One of the data sets is shown by way of several plots for reference. More specifically, as shown in FIG. 4A, an example plot illustrating the recording of 4.6 seconds of an MSR signal is shown, along with the corrected signal having the shifted powerline grid energy noise signal removed based on subtraction of the shifted power transmission amplitude and phase (the primary frequency) and about 15 harmonics. In this example, the time windows for these corrections were each about 0.2 seconds in duration with a total of 23 time windows of equal time duration, thus having multiple time windows for independent correction across the entire capture period. FIG.4 B shows the first one (1) second of the same data as a zoomed in view to assist in illustrating the MSR signal correction with more resolution.Example 2 - Powerline Grid Energy Noise Subtraction from MSR Signal CarryingUnwanted 60 Hz Fundamental Powerline Harmonic Signal Multiple experiments were carried out in areas of interest where there was a fundamental power transmission frequency of about 60 Hz. One of the data sets is shown by way of several plots for reference. More specifically, as shown in FIG. 5A, an example plot illustrating the recording of 4.5 seconds of an MSR signal is shown, along with the corrected signal having the shifted powerline grid energy signal removed based on subtraction of the shifted power transmission amplitude and phase (including at least the primary frequency) and about 15 harmonics. In this example, the time windows for these corrections were each about 0.2 seconds in duration with a total of 23 time windows of equal time duration, thus having multiple time windows for independent correction across the entire capture period. FIG.5B shows the first one (1) second of the same data as a zoomed in view to assist in illustrating the MSR signal correction with more resolution. Docket No.: 3295-010.PCT While the present technology has been described with reference to certain examples, it will be appreciated that various modifications, changes, omissions, and substitutions can be made without departing from the spirit of the disclosure. It is intended, therefore, that the disclosure be limited only by the scope of the following claims.

Claims

Docket No.: 3295-010.PCT CLAIMS What Is Claimed Is:

1. A method of removing powerline grid energy noise from microseismic resonance signal, comprising: establishing a fundamental power transmission frequency embedded in a microseismic resonance signal collected over a capture period; and processing the microseismic resonance signal to reduce the powerline grid energy noise by: dividing the microseismic resonance signal collected over the capture period into a plurality of time windows, determining an amplitude and phase shift for the fundamental power transmission frequency for each of the plurality of time windows, using the amplitude and phase shift to calculate one or more adjustment factors to facilitate adaption to changes in the fundamental power transmission frequency including shifts in the fundamental power transmission frequency that cause apparent phase shifting in the plurality of time windows, and applying the one or more adjustment factors to the plurality of time windows to reduce the powerline grid energy noise of the microseismic resonance signal to generate a modified microseismic resonance signal.

2. The method of claim 1, wherein establishing the fundamental power transmission frequency further includes preliminarily detecting or manually entering a fundamental power transmission frequency selected from 50 Hz or 60 Hz.Docket No.: 3295-010.PCT 3. The method of claim 1, wherein the amplitude and phase shift of each of the plurality of time windows result in detection of subtle differences in the fundamental power transmission frequency in the order of + / -0.1% resulting in a shifted fundamental power transmission amplitude and phase.

4. The method of claim 1, wherein establishing the fundamental power transmission frequency is carried out by autodetecting the fundamental power transmission frequency.

5. The method of claim 1, wherein the microseismic resonance detector includes a resonance sensor in contact with a resonance contact article, and wherein the microseismic resonance signal is collected via resonant contact of the resonance contact article with both the resonance sensor and the resonant substrate.

6. The method of claim 5, wherein the resonance contact article is a solid spike to contact or be driven through a surface of the resonant and into the subsurface region of interest at a depth ranging from at least one inch to a depth where microseismic resonance emissions are reliably measurable.

7. The method of claim 1, wherein the microseismic resonance signal is collected using a resonance sensor selected from a piezoelectric sensor, a MEMS sensor, a mass- spring sensor, or a combination thereof.

8. The method of claim 7, wherein the resonance sensor is a piezoelectric sensor having a sensitivity suitable for sensing frequencies within the range of about 0.1 Hz to about 800 Hz.

9. The method of claim 1, wherein multiple microseismic resonance signals are collected from a resonance sensor in resonant contact over time at multiple resonant substrate locations where microseismic resonance emissions are measurable.Docket No.: 3295-010.PCT 10. The method of claim 1, wherein a portion of the microseismic resonance signal collected within a capture period also includes an active resonance signal generated by an active energy source that generates active resonant energy into the resonant substrate, wherein the active resonant energy is of a sufficient magnitude and close proximity to the microseismic resonance detector that the microseismic resonant detector records the active resonant energy as active resonance signal.

11. The method of claim 10, wherein the active resonant energy of the microseismic resonant signal dissipates within about 2 seconds, and wherein the capture period is long enough to collect both the active resonant energy followed by passive resonant energy already inherently present within the resonate substrate to generate a passive resonance signal.

12. The method of claim 10, wherein the active energy signal is consistent with active resonant energy introduced by a short directed force to a surface of the resonant substrate.

13. The method of claim 12, wherein the short directed force is generated by a impacting a rigid shaft on a first end that is in contact with a surface of the resonant substrate at a second end.

14. The method of claim 10, wherein the active resonant energy that is introduced into the resonant substrate initiates recording of the microseismic resonance signal by the microseismic resonance detector.

15. The method of claim 14, wherein the microseismic resonance detector operates with a time buffer such that when the microseismic resonance detector begins recording, a period of time up to about 1 second prior to the active resonant energy being induced into the resonant substrate is also recorded.

16. The method of claim 10, wherein determining the amplitude and phase shift for the fundamental power transmission frequency for each of the plurality of timeDocket No.: 3295-010.PCT windows includes processing at least one time window while the active resonant energy is generating the active resonance signal.

17. The method of claim 1, wherein the capture period is up to about 90 seconds, and the plurality of time windows are from about 0.1 second to about 5 seconds in duration.

18. The method of claim 1, wherein the capture period is from about 2 seconds to about 30 seconds, and the plurality of time windows are from about 0.15 second to about 2 seconds in duration.

19. The method of claim 1, wherein the capture period is from about 4 seconds to about 15 seconds, and the plurality of time windows are from about 0.2 second to about 1.5 seconds in duration.

20. The method of claim 1, wherein the one or more adjustment factors based on the plurality of time windows are applied by generating a match signal to each of the time windows allowing for removal of the powerline grid energy noise to be removed from each of the plurality of time windows.

21. The method of claim 1, wherein applying the one or more adjustment factors to the plurality of time windows is carried out individually for each of the plurality of time windows.

22. The method of claim 1, wherein the one or more adjustment factors based on the plurality of time windows are applied uniformly with a single adjustment across all of the plurality of time windows.

23. The method of claim 1, wherein the amplitude and phase shift of each of the plurality of time windows result in a shifted fundamental power transmission frequency, and wherein applying the one or more adjustment factors includes subtracting at least one harmonic integer multiple of the shifted fundamental power transmission frequency.Docket No.: 3295-010.PCT 24. The method of claim 23, wherein applying the one or more adjustment factors includes subtracting at least two harmonic integer multiples of the shifted power transmission amplitude and phase.

25. The method of claim 23, wherein applying the one or more adjustment factors includes subtracting at least a 2-times multiple, a 3-times multiple, a 4-times multiple, and a 5-times multiple of the shifted power transmission amplitude and phase.

26. The method of claim 23, wherein applying the one or more adjustment factors includes subtracting non-consecutive integer multiples of the shifter power transmission amplitude and phase.

27. The method of claim 23, wherein applying the one or more adjustment factors includes subtracting from about 8 to 20 different integer multiples of the shifted power transmission amplitude and phase.

28. The method of claim 23, further comprising generating a match for the entire capture period using the shifted power transmission amplitude and phase, and fine-tuning each of the plurality of time windows by allowing adaptation related to transient change in the fundamental power transmission frequency.

29. The method of claim 23, wherein applying the one or more adjustment factors includes subtracting a single adjustment factor based on a matched signal of the amplitude and phase shift for the fundamental power transmission frequency from the plurality of time windows.

30. The method of claim 1, further comprising displaying the modified microseismic resonance signal to an operator of the microseismic resonance detector on- site where the microseismic resonance signal was collected.Docket No.: 3295-010.PCT 31. The method of claim 30, further comprising retaining the microseismic resonance signal in raw form without subtraction of the powerline grid energy noise.

32. The method of claim 1, wherein the microseismic resonance detector is controlled by software or firmware programmed with a harmonic solver that determines and applies the one or more adjustment factors resulting in a shifted power transmission amplitude and phase, and also calculates the from about 1 to 30 harmonics of the shifted power transmission amplitude and phase to subtract out the powerline grid energy noise from the microseismic resonance signal.

33. The method of claim 32, wherein the harmonic solver establishes lengths of the time windows.

34. The method of claim 32, wherein a user sets the lengths of the time windows.

35. The method of claim 1, wherein individual microseismic resonance signals are obtained onboard the microseismic resonance detector which also collects onboard location data.

36. The method of claim 35, wherein the onboard location data collected on the microseismic resonance detector is from an onboard receiver adapted for: use with a global navigation satellite system, use with RF signal from a terrestrial base station source and a second reference signal, or a combination thereof.

37. The method of claim 35, wherein the onboard location data collected on the microseismic resonance detector is from an onboard receiver adapted for real-time kinematic positioning.

38. The method of claim 1, further comprising amplifying the microseismic resonance signals and filtering out the high frequencies.Docket No.: 3295-010.PCT 39. The method of claim 38, wherein amplifying the microseismic resonance signals is carried out by analog amplification followed by conversion to a digital signal.

40. The method of claim 1, further comprising filtering out the high frequencies at least above about 7,500 Hz and retaining low frequencies below the high frequencies that have been filtered out.

41. A system for removing powerline grid energy noise from microseismic resonance signal, comprising a microseismic resonance detector including a resonance sensor configured to be in resonant contact with a resonant substrate, at least one processor, and at least one memory device including a data store, wherein the microseismic resonance detector is configured to: establish a fundamental power transmission frequency embedded in a microseismic resonance signal collected over a capture period; and process the microseismic resonance signal to reduce the powerline grid energy noise by: dividing the microseismic resonance signal collected over the capture period into a plurality of time windows, determining an amplitude and phase shift for the fundamental power transmission frequency for each of the plurality of time windows, using the amplitude and phase shift to calculate one or more adjustment factors to facilitate adaption to changes in the fundamental power transmission frequency including shifts in the fundamental power transmission frequency that cause apparent phase shifting in the plurality of time windows, and applying the one or more adjustment factors to the plurality of time windows to reduce the powerline grid energy noise of the microseismic resonance signal to generate a modified microseismic resonance signal.Docket No.: 3295-010.PCT 42. The method of claim 41, wherein the system establishes the fundamental power transmission frequency further by preliminarily detecting or manually entering a fundamental power transmission frequency selected from 50 Hz or 60 Hz.

43. The method of claim 41, wherein the amplitude and phase shift of each of the plurality of time windows result in detection of subtle differences in the fundamental power transmission frequency in the order of + / -0.1% resulting in a shifted fundamental power transmission amplitude and phase.

44. The method of claim 41, wherein the microseismic resonance detector includes a resonance contact article, and wherein the microseismic resonance signal is collected via resonant contact of the resonance contact article with both the resonance sensor and the resonant substrate.

45. The method of claim 41, wherein the resonance sensor includes a piezoelectric sensor, a MEMS sensor, a mass-spring sensor, or a combination thereof.

46. The method of claim 41, wherein the microseismic resonance detector operates with a time buffer such that when the microseismic resonance detector begins recording, a period of time up to about 1 second prior to the active resonant energy being induced into the resonant substrate is also recorded.

47. The method of claim 41, wherein the capture period is up to about 90 seconds, and the plurality of time windows are from about 0.1 second to about 5 seconds in duration.

48. The method of claim 41, wherein the microseismic resonance detector is controlled by software or firmware programmed with a harmonic solver that determines and applies the one or more adjustment factors resulting in a shifted power transmission amplitude and phase, and also calculates the from about 1 to 30 harmonics of the shifted power transmission amplitude and phase to subtract out the powerline grid energy noise from the microseismic resonance signal.Docket No.: 3295-010.PCT 49. The method of claim 41, further comprising an onboard receiver adapted for: use with a global navigation satellite system, use with RF signal from a terrestrial base station source and a second reference signal, real-time kinematic positioning, or a combination thereof.

50. The method of claim 41, further comprising: an amplifier to amplify the microseismic resonance signal, a low pass filter to filter out high frequencies at least above about 7,500 Hz, or both.

51. A non-transitory machine-readable storage medium having instructions embodied thereon, the instructions when executed by one or more processors, cause the one or more processors to remove powerline grid energy noise from microseismic resonance signal by: establishing a fundamental power transmission frequency embedded in a microseismic resonance signal collected over a capture period; and processing the microseismic resonance signal to reduce the powerline grid energy noise by: dividing the microseismic resonance signal collected over the capture period into a plurality of time windows, determining an amplitude and phase shift for the fundamental power transmission frequency for each of the plurality of time windows, using the amplitude and phase shift to calculate one or more adjustment factors to facilitate adaption to changes in the fundamental power transmission frequency including shifts in the fundamental power transmission frequency that cause apparent phase shifting in the plurality of time windows, and applying the one or more adjustment factors to the plurality of time windows to reduce the powerline grid energy noise of theDocket No.: 3295-010.PCT microseismic resonance signal to generate a modified microseismic resonance signal.

52. The method of claim 51, wherein establishing the fundamental power transmission frequency further includes preliminarily detecting or manually entering a fundamental power transmission frequency selected from 50 Hz or 60 Hz.

53. The method of claim 51, wherein the amplitude and phase shift of each of the plurality of time windows result in detection of subtle differences in the fundamental power transmission frequency in the order of + / -0.1% resulting in a shifted fundamental power transmission amplitude and phase.

54. The method of claim 51, wherein the capture period is up to about 90 seconds, and the plurality of time windows are from about 0.1 second to about 5 seconds in duration.

55. The method of claim 51, wherein applying the one or more adjustment factors to the plurality of time windows is carried out individually for each of the plurality of time windows.

56. The method of claim 51, wherein the one or more adjustment factors based on the plurality of time windows are applied by generating a match signal to each of the time windows allowing for removal of the powerline grid energy noise to be removed from each of the plurality of time windows.

57. The method of claim 51, wherein the one or more adjustment factors based on the plurality of time windows are applied uniformly with a single adjustment across all of the plurality of time windows.

58. The method of claim 51, wherein the amplitude and phase shift of each of the plurality of time windows result in a shifted fundamental power transmission frequency,Docket No.: 3295-010.PCT and wherein applying the one or more adjustment factors includes subtracting at least one harmonic integer multiple of the shifted fundamental power transmission frequency.

59. The method of claim 51, wherein the instructions when executed by one or more processors cause the one or more processors to also retain the microseismic resonance signal in raw form without subtraction of the powerline grid energy noise.

60. The method of claim 1, wherein the microseismic resonance detector is controlled by software or firmware programmed with a harmonic solver that determines and applies the one or more adjustment factors resulting in a shifted power transmission amplitude and phase, and also calculates the from about 1 to 30 harmonics of the shifted power transmission amplitude and phase to subtract out the powerline grid energy noise from the microseismic resonance signal.

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