Method and device for detecting earthquakes

Abstract

A method for detecting an earthquake is described, comprising: receiving a signal representative of measurements of a three-dimensional acceleration of the device as a function of time; frequency filtering of the signal; determining, from the filtered signal, data representative of directions of acceleration as a function of time; an earthquake being detected if the magnitude of the acceleration is greater than a first threshold and the directions of acceleration are substantially collinear with each other during a first time interval; or the directions of acceleration are substantially collinear with each other during a second time interval and the directions of acceleration are substantially collinear with each other during a third time interval subsequent to the second time interval, and the directions of acceleration of the second interval and the third interval are substantially orthogonal. Figure for abstract: 6

Description

Title of the invention: Method and device for detecting earthquakes Technical field

[0001] A method and a device for detecting earthquakes are described. The method and the device can in particular be used to trigger alerts and security actions, for example to secure a resource distribution system. Technical background

[0002] Some earthquake detection systems implement vibration sensors or acoustic pressure sensors. Such systems can be expensive and difficult to install. Such systems can also implement trained predictive models (machine learning), but require computing resources that can be significant. Such resources are not available in certain usage contexts.

[0003] It is therefore desirable to have a method for detecting an earthquake that is economical in terms of computing resources. Abstract

[0004] One or more embodiments relate to a method for detecting an earthquake implemented by a device comprising at least one processor and a memory comprising software code, the at least one processor causing the device to implement the method when it executes the software code, the method comprising:

[0005] - receiving a signal representative of measurements of an acceleration in three di ground dimensions device as a function of time, the signal being received from an accelerometer sensor;

[0006] - frequency filtering of the signal, the filtering being configured with a frequency of low cutoff and a high cutoff frequency to exclude at least frequencies not corresponding to seismic wave frequencies;

[0007] - the determination, from the filtered signal, of data representative of directions of acceleration as a function of time;

[0008] - an earthquake being detected if

[0009] a) the magnitude of the acceleration is greater than a first threshold and the directions of the acceleration are substantially collinear with each other during a first time interval; or

[0010] b) the directions of acceleration are substantially collinear with each other during a second time interval and that the directions of acceleration are substantially collinear with each other during a third time interval subsequent to the second time interval, and that the directions of acceleration of the second interval and of the third interval are substantially orthogonal.

[0011] The method uses data from a three-dimensional accelerometer. Such a sensor may be simply integrated into or connected to a device with relatively modest computing resources to process the sensor data. Such a device may, for example, be a resource-counting device that may need to be secured.

[0012] The invention therefore makes it possible to propose a device for local earthquake detection at low cost. Local detection makes it possible to act accordingly to trigger security actions, even when the device is not connected to a communication network, or when this communication network is faulty.

[0013] According to one or more exemplary embodiments, the cut-off frequencies are adapted to exclude frequencies corresponding to noise coming from the environment of the device.

[0014] According to one or more exemplary embodiments, the determination of data representative of directions of acceleration as a function of time is only carried out if a magnitude of the acceleration exceeds a second threshold before filtering the signal and exceeds a third threshold after filtering the signal.

[0015] According to one or more exemplary embodiments, the second and third thresholds are adapted to be above acceleration magnitudes corresponding to noise coming from the environment of the device.

[0016] According to one or more exemplary embodiments, the method comprises adapting the cut-off frequencies, respectively of the second threshold and of the third threshold, as a function of historical labeled data of the acceleration in a location of operation of the device.

[0017] The method includes a calibration of certain thresholds to take into account ambient noise and thus avoid or at least limit untimely triggers, such as false positives or false negatives. Advantageously, this calibration is carried out using labeled historical data.

[0018] According to one or more exemplary embodiments, a determination of the collinearity of directions of acceleration is carried out, comprising:

[0019] - the determination of a hyperplane with respect to N consecutive measurement points from of the signal and the determination of a direction normal to this plane, with N>1;

[0020] - the iteration of the previous step on M sets of N points of an interval of time considered, with M>1;

[0021] - the conclusion that there is substantially collinearity over the time interval considered if the angles of the N normal directions taken two by two are in two ranges comprising respectively 0° and 180°.

[0022] According to one or more exemplary embodiments, a determination of the orthogonality of directions of acceleration is carried out, including:

[0023] - the determination of a hyperplane with respect to N consecutive measurement points from of the signal and the determination of a direction normal to this plane, with N>1;

[0024] - the iteration of the previous step on two sets of N points of an interval of time considered;

[0025] - the conclusion that there is substantially orthogonality if the angle between the directions normals of the two hyperplanes determined in the previous step are in two ranges comprising 90° and 270° respectively.

[0026] According to one or more exemplary embodiments, the method comprises, in response to the detection of an earthquake, the generation of a control signal for equipment for securing a resource counted by the device.

[0027] According to one or more exemplary embodiments, the method comprises, in response to the detection of an earthquake, the generation of an alert message to a server.

[0028] According to one or more exemplary embodiments, an earthquake is only detected in case b) if the magnitude of the acceleration exceeds a fourth threshold, lower than the first threshold.

[0029] One or more embodiments relate to an earthquake detection device comprising a memory comprising software code and the processor, the processor being adapted, when executing the code, to cause the device to implement one of the above methods.

[0030] According to one or more exemplary embodiments, the device comprises a three-dimensional accelerometer.

[0031] One or more embodiments relate to a computer program product comprising instructions which when executed by at least one processor cause the execution of one of the described methods by said at least one processor.

[0032] One or more embodiments relate to a non-transitory storage medium comprising instructions which when executed by at least one processor cause the at least one processor to execute one of the described methods. Brief description of the figures

[0033] Other characteristics and advantages will become apparent when reading the detailed description which follows, for the understanding of which reference will be made to the attached drawings among which:

[0034] [Fig-1] - [Fig.l] is a schematic diagram of a system comprising a device according to one or more embodiments;

[0035] [Fig.2] - [Fig.2] is a schematic diagram illustrating an XYZ reference frame of an acceleration sensor 200 and a QLT reference frame of the seismic waves;

[0036] [Fig.3] - [Fig.3] is a flowchart of a method according to one or more exemplary embodiments;

[0037] [Fig.4] - [Fig.4] is a graph illustrating an example of a bandpass filter according to an exemplary embodiment;

[0038] [Fig.5] - [Fig.5] is a flowchart of a calibration method according to an exemplary embodiment;

[0039] [Fig.6] - [Fig.6] is a flowchart of a method of analyzing 600 vector components according to a particular exemplary embodiment;

[0040] [Fig.7] - [Fig.7] is a non-limiting example of a method for determining collinearity and orthogonality;

[0041] [Fig.8] - [Fig.8] comprises two graphs (a) and (b) respectively representing the evolution of an angle used in the evaluation of the collinearity or orthogonality of displacements due to an earthquake as a function of time and illustrating the application of the method according to one or more examples of implementation and the magnitude of the acceleration. Detailed description

[0042] In the following description, identical, similar or analogous elements will be designated by the same reference numerals. The block diagrams, algorithms and message sequence diagrams in the figures illustrate the architecture, functionalities and operation of systems, devices, methods and computer program products according to one or more exemplary embodiments. Each block of a block diagram or each phase of an algorithm may represent a module or a portion of software code comprising instructions for implementing one or more functions. According to certain implementations, the order of the blocks or phases may be changed, or the corresponding functions may be implemented in parallel.The process blocks or phases may be implemented using circuitry, software, or a combination of circuitry and software, in a centralized manner or in a distributed manner for all or some of the blocks or phases. The systems, devices, processes, and methods described may be modified, added to, and / or deleted within the scope of this disclosure. For example, the components of a device or system may be integrated or separated. Also, the described functions may be implemented using more or fewer components or phases, or with other components or through other phases. Any suitable data processing system may be used for the implementation. A suitable data processing system or device, for example, includes a combination of software code and circuitry, such as a processor, controller, or other circuitry suitable for . execute the software code. When the software code is executed, the processor or controller causes the system or device to implement all or part of the functionalities of the blocks and / or phases of the processes or methods according to the exemplary embodiments. The software code may be stored in non-volatile memory or on a non-volatile storage medium (USB key, memory card or other medium) readable directly or through a suitable interface by the processor or controller.

[0043] The present description relates to an earthquake detection device. The context of the particular exemplary embodiments is a resource meter, as well as the implementation of security in the event of earthquake detection. This context is given for illustrative purposes and should not be interpreted to limit the invention to this context alone. The resources counted include, for example, fluids (gas, water, fuel, etc.) or electrical energy. Earthquake detection is more generally of interest for any meter whose resource may be lost or which may cause damage following an earthquake.

[0044] [Fig.l] is a schematic diagram of a system comprising a device 100 according to one or more embodiments. The device 100 is for example a counter of a resource. The device 100 receives data from a three-dimensional accelerometer 101. This sensor may also be an integral part of the device 100. The device 100 also comprises a processor and non-volatile memory comprising software code for implementing the earthquake detection method.

[0045] Optionally, the meter may also have a control interface configured to trigger a safety action, such as for example the closing of a valve 103.

[0046] Optionally, a communication interface 102 connected to the device 100 is configured to allow communication between the device 100 and a third party, for example the server 104. The communication interface 102 may be a wireless interface, for example cellular, or an interface to a wired network, for example a conventional telephone network. The device 100 is adapted to inform the server 104 of the detection of an earthquake. The server 104 can then trigger an action, for example information from a competent authority 106, and / or inform other devices 105, similar to the device 100 so that the latter can, if necessary, initiate security actions in turn.

[0047] Optionally, the device 100 is configured to transmit an earthquake alert directly to one or more other devices 105 so that the latter can, if necessary, initiate security actions in turn. According to an alternative embodiment, the transmission passes through the server 104, i.e. an alert is sent by the device 100 to the server 104, which transmits it to one or more devices 105, such as for example devices 105 close to device 100 and therefore also exposed to the risks of the earthquake.

[0048] The transmission of an alert by the device 100 to devices 105 and / or the triggering of an action by a device 105 may be subject to a criterion of geographical proximity between the device 100 and the device(s) 105.

[0049] Optionally, the server 104 is in communication with a plurality of devices 105 of the type of the device 100 and can receive earthquake alerts from several devices 100. This makes it possible to adapt the strategy for triggering an action - for example, it is possible to trigger an action only if several devices 100 have detected an earthquake.

[0050] In the context of a device 100 comprising a meter functionality, the device 100 may be required to communicate at regular intervals or on request consumption data for the resource that it is counting. This transmission is for example carried out with a periodicity of one day, and may be triggered by a request from the server. In the case of earthquake detection, the device 100 is, according to a particular embodiment, configured to force the transmission of a message, by overcoming the constraints linked to the transmission of the counting data.

[0051] Some physical principles related to an earthquake will now be described. During an earthquake, different types of seismic waves are present, defined by their propagation speed, their amplitude and their polarization. The main types of waves are as follows: - 'P' waves (for 'Primary') - these waves propagate quickly and are felt first; - 'S' waves (for 'Secondary') - these waves generally arrive after the P waves; - shear waves - these waves generally arrive after the two previous waves and are the most destructive.

[0052] Table 1 presents a summary of the main types of waves generated during an earthquake.

[0053] [Tableauxl] PS Love Rayleigh Waves Wave Type Compression Shear Shear Shear Velocity (km / s) ~5.6 ~3.2 ~3 ~3 Damage Low Medium High High Polarization Horizontal Vertical Horizontal Rotational

[0054] Table 1 shows that the later the waves, the more they are generally destructive. Securing actions and / or alerts must therefore be triggered as soon as possible. Early detection is therefore preferable.

[0055] [Fig.2] is a schematic diagram illustrating an XYZ reference frame of an acceleration sensor 200 and a QLT reference frame of the seismic waves. An orthogonal reference frame linked to the device has two axes X and Y in the plane of the surface 201 (assumed to be flat) and a Z axis vertical to this surface. The direction of propagation of the seismic waves from the source 202 to the sensor 200 is indicated by L and the direction orthogonal to the direction of propagation and in the plane comprising this direction L, the source 202 and the sensor 200 by Q. A T axis is perpendicular to the L and Q axes. In the example illustrated, the P waves generate accelerations along the X and Z axes, while the S waves generate accelerations along the X and Y axes.

[0056] Table 2 shows an earthquake intensity scale, and for each level of the scale: acceleration, speed, felt shaking, potential damage and effect on certain resources. The table shows (a) that an earthquake can be felt from an acceleration amplitude of about 3 mg (2.97 mg in the table) and (b) that damage appears from an acceleration amplitude of about 27 mg.

[0057] [Tables2] Measured intensity Acceleration (g) Speed ​​(cm / s) Tremor felt Potential damage Resources I <0.000464 <0.0215 Not felt None II-III 0.000464 - 0.00297 0.135- 1.41 Low None IV 0.00297 - 0.00276 1.41-4.65 Light None V 0.0276 - 0.115 4.65 - 9.64 Moderate Very light Automatic domestic gas valves triggered. Some water pipes interrupted. Power cuts. VI 0.115- 0.215 9.64 - 20 High Light Water and gas pipes damaged. Gas and water supply interrupted in some areas. VII 0.215- 0.401 20-41.4 Very severe Moderate As in the previous row. VIII 0.401 - 0.747 41.4-85.8 Severe Moderate to severe Damaged water and gas pipes. Interruption of gas, water and electricity supply. IX 0.747 - 1.39 85.8-178 Severe Severe X >1.39 >178 Extreme Very severe important

[0058] According to one or more embodiments, an earthquake is sought to be detected: i. at a time between the arrival of P waves and before the arrival of surface waves (Love and Rayleigh waves), and / or ii. the transition from P waves to S waves.

[0059] It is proposed to implement a three-dimensional accelerometer to capture the waves due to the earthquake. The signals from the accelerometer are then used for earthquake detection.

[0060] Regarding the first point, i, above, a check on the magnitude of the acceleration is carried out. If the magnitude exceeds a threshold, then an earthquake is detected.

[0061] Regarding the second point, ii, above, since P waves and S waves are orthogonal, the transition from P waves to S waves can be detected by performing a directional analysis and testing the orthogonality of the acceleration axes over time.

[0062] It should be noted that the displacements generated by the P waves are collinear with each other, and that the displacements generated by the S waves are collinear with each other.

[0063] It should be noted that an earthquake can be detected according to the second case without it necessarily being detected first according to the first case. This can happen, for example, when the detected P waves do not meet the detection criteria of the first case.

[0064] Furthermore, seismic waves generally have a frequency between 0 and 50 Hz. The propagation speed generally increases with frequency. According to certain embodiments, a low-pass frequency filter is applied to limit the bandwidth to the frequency components corresponding to seismic waves.

[0065] According to certain embodiments, a bandpass frequency filter is applied to limit the bandwidth to the useful components. The low and / or high cutoff frequencies of this filter are adjusted during a calibration phase described later to reduce the impact of ambient noise on earthquake detection.

[0066] According to the embodiments, the low-pass and band-pass filters are combined into a single filter, namely that the high frequency of this combined filter substantially filters frequencies above 50 Hz, but can be adjusted for a high cutoff frequency lower than 50 Hz.

[0067] According to one or more exemplary embodiments, a calibration is carried out at the installation site, with the aim of distinguishing ambient noise from signals due to an earthquake. Ambient noise includes, for example, noise generated by an elevator, by traffic (road, rail, air), by various devices and machines, etc. The calibration is, for example, carried out on the basis of a week of measurements in order to adjust the parameters implemented in the method, and in particular one or more thresholds. Ambient noise will thus be filtered to limit both false positives and false negatives. According to certain embodiments, the adjustable parameters comprise at least one of: the low cutoff frequency of the bandpass filter, the high cutoff frequency of the bandpass filter, a threshold SA of magnitude of the acceleration for initial triggering of the earthquake detection based on the accelerometer signal, and a threshold SB of magnitude of the acceleration applied after filtering the accelerometer signal.

[0068] [Fig. 3] is a flowchart of an earthquake detection method according to one or more non-limiting exemplary embodiments. The signal from the accelerometer is received as input. It is checked at 301 whether the magnitude of the acceleration exceeds the initial trigger threshold SA. This trigger threshold is chosen to avoid unnecessary calculations and / or limit false positives. If the trigger threshold SA is not exceeded, then no further signal processing is undertaken - which saves signal processing resources - and no earthquake is detected (302). If the initial trigger threshold SA is exceeded, then the signal from the accelerometer is subjected to low-pass frequency filtering 303 limiting the bandwidth to that of waves generated during an earthquake. The implementation of the threshold SA is however optional and it is entirely possible to go directly to signal filtering.In 304, an additional filtering is applied to the signal, in order to eliminate or at least limit the influence of ambient noise. In 305, the magnitude of the acceleration is compared after filtering to a threshold SB. If the threshold SB is not exceeded, then no earthquake is detected (302). If the threshold SB is exceeded, then an analysis of the directional components of the acceleration is carried out in 306. According to the results of this analysis verified in 307, either no earthquake is detected (302), or an earthquake is detected (308).

[0069] According to certain embodiments, in the event of earthquake detection, safety actions triggered by the detection may in particular include the actuation of a cut-off element of the resource associated with the meter (valve, disconnector, etc.).

[0070] According to certain embodiments, in the event of detection of an earthquake, an alert is transmitted to a distributor or supplier of the resource and / or to a competent authority.

[0071] [Fig.4] is a graph illustrating an example of a band-pass filter resulting from the combination of a low-pass filter and a high-pass filter and performing the filtering at 303 and 304. The high-pass and low-pass filters can be realized numerically on the respective basis of equations 1 and 2:

[0072] [Math.l] -3— l-(e 4

[0073] [Math.2] 1

[0074] fO is the cutoff frequency of the high-pass filter, fl is the cutoff frequency of the low-pass filter and f is the frequency.

[0075] Table 3 gives examples of values ​​of the different parameters:

[0076] [Tables3] f

[0077] A calibration of one or more parameters is carried out in order to limit the impact of ambient noise on the detection of an earthquake. The ambient noise may for example include environmental noise and / or noise generated where appropriate by the resource itself (noise generated by a liquid for example).

[0078] [Fig.5] is a flowchart of a calibration method according to an exemplary embodiment. This flowchart adjusts several parameters. It should be noted that it is entirely possible, depending on the implementation, to adjust only part of these parameters.

[0079] The calibration method 500 illustrated by [Fig.5] receives as input a duration 501 of the calibration data interval. This duration can be fixed or adjustable. It is for example one week, to cover a variety of events during working days and at the end of the week. The method also receives as input initial values ​​502 of the thresholds SA and SB and the cut-off frequencies f0 (low-pass) and fl (high-pass).

[0080] Measurements 503 are then obtained over the specified duration and an earthquake detection is then carried out in 504 on the basis of these measurements. The false positives 505 and false negatives 506 are then manually labeled. An adjustment of the parameters is carried out on this basis in 507. If for example parasitic noises fall within the frequency band of the filter, then the cut-off frequencies can be adjusted to exclude the frequencies of these noises. If the parasitic noises have a magnitude that is too high, in relation to the thresholds, these are raised.

[0081] The analysis of the vector components of the acceleration aims to characterize the presence of P waves or the transition from P waves to S waves. This analysis is based on the fact that the displacements generated by a type of wave are collinear with each other and that the displacements between the P and S waves are orthogonal. The presence of seismic waves can therefore be determined by estimating the collinearity of the movements represented by successive measurement points where a point is a measurement of the acceleration in the three dimensions. If the collinearity is proven over a certain duration, then this can mean the presence of a wave. In addition, the orthogonality of the movements between two series of collinear points can indicate the transition from P waves to S waves.

[0082] [Fig.6] is a flowchart of a method for analyzing 600 vector components according to a particular embodiment. The method of [Fig.6] receives as input (at 601) an N cloud of measurement points, with N>1. According to one embodiment, N is configurable according to the desired sensitivity, the computing capabilities and the performance of the accelerometer. A cloud comprises a plurality of measurement points, the number of which can be variable according to the sampling frequency. For example, a sampling frequency of around 100Hz, between 3 and 100 points per cloud, and up to 50 clouds can be considered. These values ​​are given for illustrative purposes and other values ​​can of course be envisaged.

[0083] Firstly, at 602, a magnitude of the acceleration determined for a cloud is compared to a first threshold SL. This magnitude corresponds - for example - to the median of the points of the cloud, but other ways of calculating this magnitude can be envisaged. The threshold SI is - for example - located between 10mg and 100mg. If the threshold SI is reached or exceeded, then an estimation of the collinearity of the movements corresponding to two successive clouds is carried out on M clouds, at 603. M is taken to be greater than or equal to 2. If the movements are collinear on the M clouds, then an earthquake is detected (604). This corresponds to case 'i' mentioned above - P-type waves, with a relatively high magnitude of the acceleration exceeding a threshold SL. However, it may be that the detected magnitude of the P waves is below the threshold SL. In this case, the P-type waves go unnoticed.However, we then test in 605 whether the magnitude is greater than a threshold S2, with S2. <s1. si c’est le cas, alors on teste en 606 pour une colinéarité, la présence d’une orthogonalité 607, suivi colinéarité 608. chacun de ces trois tests peut être effectué sur m nuages successifs, mais nombre différent chacun des tests.

[0084] For purely illustrative purposes, SI and S2 have, for example, the respective values ​​of 20 mg and 10 mg.

[0085] According to one embodiment, successive point clouds are considered over time. A hyperplane is associated with each point cloud. Each plane is associated with a direction of movement. A collinearity and / or orthogonality criterion is evaluated for the directions of successive hyperplanes.

[0086] [Fig.7] is a non-limiting example of a method 700 for determining collinearity and orthogonality.

[0087] The method receives as input at 701 the three-dimensional measurement points of one of the clouds. A filtering of the aberrant points can then be carried out according to a method known as such to limit noisy measurements, at 702. Filtered measurement points are thus obtained at 703. The points are then normalized at 704. On the basis of these normalized points (705), a collinearity score is established at 706. This score can for example be based on a covariance calculation. If this score is below a collinearity threshold, then it is judged that the points of the cloud are not collinear and we move on to another point cloud. This test is performed in 707. If the collinearity score is greater than or equal to the threshold, then the hyperplane relative to the points of the cloud is determined in 708, for example on the basis of a polynomial function by which a plane is determined minimizing the distance between the points of the cloud and this plane.The obtained hyperplane (709) is used to determine in 710 a vector normal to this hyperplane.

[0088] A normal vector is determined per cloud. For example, for two consecutive clouds n-1 and n (referenced 712 and 713 in [Fig.7]), two normal vectors A and B (references 714 and 715) are obtained. An angle 0 between the two normal vectors is determined (716). Depending on the value of 0, the collinearity of the two vectors or their orthogonality is determined. The two vectors can also be neither collinear nor orthogonal. According to the present exemplary embodiment, the two vectors are considered as collinear if 0 is between -10° and +10° or between 170° and 190°, and as orthogonal if 0 is between -80° and -100° or between +80° and +100°.

[0089] These thresholds can optionally be adjustable, for example to take into account the dispersion of the accelerometer.

[0090] [Fig.8] shows two examples of graphs illustrating the application of the method according to one or more exemplary embodiments. The upper graph (a) of [Fig.8] represents the angle 0 between successive point clouds in degrees as a function of time, while the lower graph (b) represents the magnitude of the accelerations in g represented on a logarithmic scale as a function of time. The unit of time is 1 / 10th of a second. Graph (a) highlights a first part 801 of the curve, representing an angle value of less than 10 degrees over a relatively long time interval. This part corresponds to a collinearity zone. A second part 802 of the curve, following the first part, shows a strong peak of the angle, cor corresponding to an orthogonality, followed by a third part 803, where the angle returns to a value around 10° for a certain time interval, corresponding to a second collinearity zone. It should be noted that the graph in [Fig.8] is smoothed and therefore the threshold value of 80° previously indicated does not seem to be reached in this graph. The first collinearity zone corresponds to P-type waves, while the second collinearity zone corresponds to S-type waves, because it is preceded by a zone indicating orthogonality between the movements between the first and second collinearity zones respectively. Graph (b) includes a horizontal line 804 corresponding to an acceleration magnitude of 20mg. We see that the first collinearity zone, corresponding to P-type waves, coincides with a significant increase in the magnitude of the acceleration.

Claims

Claims

1. A method for detecting an earthquake implemented by a device (100) comprising at least one processor and a memory comprising software code, the at least one processor causing the device to implement the method when it executes the software code, the method comprising: - receiving a signal representative of measurements of a three-dimensional acceleration of the device as a function of time, the signal being received from an accelerometer sensor; - frequency filtering of the signal (303, 304), the filtering being configured with a low cut-off frequency (fl) and a high cut-off frequency (fO) to exclude at least frequencies not corresponding to seismic wave frequencies; - determining (306, 600), from the filtered signal, data representative of directions of the acceleration as a function of time; - an earthquake being detected (604) if a.the magnitude of the acceleration is greater (603) than a first threshold (SI) and the directions of the acceleration are substantially collinear with each other during a first time interval; or b. the directions of the acceleration are substantially collinear with each other during a second time interval (606) and the directions of the acceleration are substantially collinear with each other during a third time interval (608) subsequent to the second time interval, and the directions of the acceleration of the second interval and the third interval are substantially orthogonal (607).

2. A method according to claim 1, wherein the cutoff frequencies are adapted (507) to exclude frequencies corresponding to noise from the environment of the device.

3. A method according to claim 1, wherein determining data representative of directions of acceleration as a function of the time is only performed if a magnitude of the acceleration exceeds a second threshold (SA) before signal filtering (301) and exceeds a third threshold (SB) after signal filtering (305).

4. A method according to claim 3, wherein the second and third thresholds are adapted (507) to be above acceleration magnitudes corresponding to noise from the environment of the device.

5. Method according to claim 3, respectively claim 5, comprising adapting the cut-off frequencies, respectively of the second threshold and of the third threshold, as a function of historical labeled data of the acceleration in a place of operation of the device.

6. Method according to one of claims 1 to 5, in which a determination of the collinearity of directions of acceleration is carried out, comprising: - the determination of a hyperplane (709) with respect to N consecutive measurement points from the signal and the determination of a direction normal to this plane, with N>1; - the iteration of the previous step on M sets of N points of a time interval considered, with M>1; - the conclusion (717) that there is substantially collinearity over the time interval considered if the angles of the N normal directions taken two by two are in two ranges comprising respectively 0° and 180°.

7. Method according to one of claims 1 to 6, in which a determination of the orthogonality of directions of acceleration is carried out, comprising: - the determination of a hyperplane (709) with respect to N consecutive measurement points from the signal and the determination of a direction normal to this plane, with N>1; - the iteration of the previous step on two sets of N points of a time interval considered; - the conclusion (717) that there is substantially orthogonality if the angle between the normal directions of the two hyperplanes determined in the previous step are in two ranges comprising respectively 90° and 270°.

8. Method according to one of claims 1 to 7, comprising, in response to the detection of an earthquake, the generation of a control signal of equipment for securing a resource counted by the device.

9. Method according to one of claims 1 to 8, comprising, in response to the detection of an earthquake, the generation of an alert message to a server.

10. Method according to one of claims 1 to 9, in which an earthquake is detected in case b) only if the magnitude of the acceleration exceeds a fourth threshold (S2), lower than the first threshold.

11. An earthquake detection device (100) comprising a memory comprising software code and the processor, the processor being adapted, when it executes the code, to cause the device to implement the method according to one of claims 1 to 9.

12. A device according to claim 11, comprising the three-dimensional accelerometer (101).

13. Computer program product comprising instructions which when executed by at least one processor cause the execution of the method according to one of claims 1 to 10 by said at least one processor.

14. A non-transitory storage medium comprising instructions which when executed by at least one processor cause the method according to one of claims 1 to 10 to be executed by said at least one processor.

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