Method for synthesizing destructive seismic acceleration waveform of fixed station

Abstract

The invention aims to provide a method for synthesizing a destructive seismic acceleration waveform of a fixed station, which depends on an empirical Green function method and comprises the following steps of: firstly, obtaining a relatively accurate seismic source model and seismic source parameters by synthesizing an acceleration time history of a strong-motion seismograph; and then using the obtained seismic source model and seismic source parameters in simulation of a large seismic acceleration waveform at a broadband seismograph, and synthesizing the large seismic acceleration waveform at the broadband seismograph by using a small seismic waveform recorded by the broadband seismograph as a Green function.

Description

Technical Field

[0001] The present application relates to a method for synthesizing a destructive earthquake acceleration waveform of a fixed station, which is applicable to the technical field of earthquake resistance services or post-earthquake emergency rescue. Background Art

[0002] In earthquake disasters, the destruction and collapse of engineering structures are mainly caused by strong earthquake motions, which are also external conditions for other disasters such as foundation failure and landslides. The empirical Green's function method is an existing achievement and theory that can be used as a numerical simulation tool. It refers to the use of small earthquake record data that can be obtained from public earthquake databases as Green's functions to synthesize large earthquake earthquake motions. The source of a large earthquake is regarded as composed of a series of sub-seismic sources. An aftershock or foreshock record of appropriate size is selected as the Green's function, and small earthquakes are equated with sub-seismic sources. According to a certain rupture mode, these empirical Green's functions are superimposed to obtain the large earthquake ground motion time history.

[0003] The ground motion input of destructive earthquakes is very important for the seismic design and earthquake damage response analysis of major projects. In sparsely populated areas, such as the western region, the earthquake monitoring capability is relatively weak. This is because seismic stations are mainly distributed in the relatively densely populated eastern region, and these areas are mainly equipped with fixed stations with broadband seismographs. This type of fixed station has high requirements for deployment and is a permanent station. Although the number of such stations in the western region is much smaller than that in the eastern region, they are the dominant number of seismic stations in the western region. Earthquake early warning networks are generally built in densely populated areas, and are still sparse in sparsely populated areas.

[0004] Broadband seismographs are instruments that continuously record waveforms, and they are still working even when no earthquake occurs. Broadband seismographs record signals such as background noise, and their characteristic is that the range of peak acceleration (PGA) is relatively narrow. Once a destructive earthquake or an earthquake with a large amplitude occurs, data outside the range often cannot be recorded.

[0005] A strong earthquake instrument is an automatically triggered seismograph that records near-ground motion of strong earthquakes. Generally, it will only start recording acceleration waveforms when encountering earthquakes of larger magnitudes. Moreover, the strong earthquake instrument has a wide range of peak acceleration, generally above ±2.0g, and can record acceleration waveforms of all destructive earthquakes.

[0006] In the prior art, earthquake monitoring is usually carried out mainly with broadband seismographs and supplemented by strong motion seismographs. For example, my country has two major seismic networks, namely the fixed network and the earthquake early warning network. Among them, all the fixed networks are broadband seismographs, and some stations in the earthquake early warning network are broadband seismographs. The number of these two networks in the western region is relatively small, and most of the stations are broadband seismographs. Once an earthquake occurs, only sporadic strong motion seismographs will record the complete acceleration waveform of the large earthquake. Therefore, in the western region of my country, there are a large number of broadband seismographs but they cannot record the waveform of a large earthquake; there are a small number of strong motion seismographs but they can fully record the waveform of a large earthquake. Summary of the invention

[0007] The purpose of the present invention is to provide a method for synthesizing the acceleration waveform of a destructive earthquake at a fixed station. The method relies on the empirical Green's function method, firstly obtains a relatively accurate source model and source parameters by synthesizing the acceleration time history of a strong earthquake instrument, and then uses the obtained source model and source parameters in the simulation of the large earthquake acceleration waveform at a wide-band seismograph, and uses the small earthquake waveform recorded by the wide-band seismograph as the Green's function to synthesize the large earthquake acceleration waveform at the wide-band seismograph.

[0008] The present application relates to a method for synthesizing a destructive earthquake acceleration waveform of a fixed station, comprising the following steps:

[0009] (1) After an earthquake occurs, determine the location of the broadband fixed station to be calculated based on actual needs; select the location of the strong earthquake station that is closest to the epicenter and has complete data;

[0010] (2) Collect and summarize the required earthquake source parameters based on the locations of the selected broadband fixed stations and strong earthquake stations;

[0011] (3) performing different permutations and combinations of the earthquake source parameters to obtain a permutation and combination scheme of the earthquake source parameters;

[0012] (4) Determine the small earthquakes that can be used as Green's functions at the strong earthquake stations, determine the permutation and combination scheme of the small earthquakes according to the number and position of the asperities, and then further permutate and combine the small earthquakes and the source parameters with the permutation and combination scheme of the obtained source parameters;

[0013] (5) Using the empirical Green's function method, the acceleration waveform of the strong earthquake station is calculated for each permutation and combination obtained in the above steps in turn, and the acceleration calculation results of all permutations and combinations are obtained;

[0014] (6) Based on the characteristics of the acceleration waveforms of the three components of this earthquake recorded by the strong earthquake station, the calculation results obtained in step (5) are screened;

[0015] (7) According to the calculation results after screening in step (6), all the results are counted, the frequency of occurrence of each source parameter is reversed, and the source parameter with the highest frequency of occurrence is selected as the reliable parameter;

[0016] (8) Selecting small earthquakes of broadband fixed stations as Green's functions, determining the permutation and combination of small earthquakes of broadband fixed stations to be used according to the number and position of asperities, applying the reliable parameters obtained in step (7) to the calculation of the acceleration waveform of broadband fixed stations by using the empirical Green's function method, and obtaining all possible acceleration results of broadband fixed stations;

[0017] (9) The results of step (8) are screened according to the seismic motion characteristics of the three components of the strong earthquake station and the attenuation relationship of the local area to obtain the final reliable acceleration waveform of the broadband fixed station.

[0018] Among them, the waveform segment intercepted by the small earthquake is the waveform data 40s after the initial motion of the P wave as the available waveform segment; the selected small earthquake has the following characteristics at the same time: the distance between the epicenter of the small earthquake and the epicenter of the main shock does not exceed 500m; when each asperity is selected for a small earthquake, the condition to be met is that the distance between the epicenter of the small earthquake and the initial rupture position of each asperity does not exceed 500m; the error between the focal depth of the small earthquake selected for each asperity and the initial rupture position of each asperity does not exceed 500m.

[0019] Wherein, in step (6), the screening criteria are: select three strong earthquake stations closest to the epicenter, and the epicenter distance of the strong earthquake stations should be within 200 km; obtain the average value of the PGA of the three-component acceleration waveforms of the three strong earthquake stations, and calculate the ratio of the EW / NS component, the ratio of the NS / EW component, the ratio of the EW / UD component, the ratio of the UD / EW component, the ratio of the NS / UD component, and the ratio of the UD / NS component of each strong earthquake station;

[0020] Take the average value of the six ratios of the three strong earthquake stations, and then you will get the value ranges of EW / NS and NS / EW, the value ranges of EW / UD and UD / EW, and the value ranges of NS / UD and UD / NS; the PGA of the three components of all simulation values ​​should be within the above three ranges respectively, and the waveform that conforms to the three value ranges is taken as the final simulation result of the large earthquake acceleration waveform of the wide-band fixed station.

[0021] Preferably, the range of the envelope of all response spectra that meet the requirements is used as the value range of the response spectrum of the MAD station; the maximum and minimum values ​​of the PGA of each component of all results are used as the value range of the PGA of each component of the MAD station; and finally, the acceleration waveform that meets the requirements, the range of the acceleration response spectrum and the value range of the PGA of the MAD station are obtained.

[0022] This application uses an indirect method to synthesize the acceleration waveform of a broadband seismograph, which can provide good data support for post-earthquake emergency rescue, local engineering seismic design, ground motion input, and local earthquake disaster prevention and mitigation planning. This application can provide relatively accurate acceleration waveforms of large earthquakes in areas lacking strong earthquake stations, which helps to obtain more accurate earthquake damage response analysis results, and thus serve seismic design and earthquake damage prevention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a comparison chart of the observed value and simulated value of the acceleration waveform of a certain station.

[0024] Figure 2 It is a comparison chart of the simulated average value and the observed value of the response spectrum of the acceleration waveform of a certain station. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present application more clear, the embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other arbitrarily without conflict.

[0026] The present application relates to a method for synthesizing a destructive earthquake acceleration waveform of a fixed station, comprising the following steps:

[0027] (1) After an earthquake occurs, determine the location of the broadband fixed station to be calculated based on actual needs; select the location of the strong earthquake station that is closest to the epicenter and has complete data;

[0028] (2) Collect and summarize the required earthquake source parameters based on the locations of the selected broadband fixed stations and strong earthquake stations;

[0029] (3) performing different permutations and combinations of the earthquake source parameters to obtain a permutation and combination scheme of the earthquake source parameters;

[0030] (4) Determine the small earthquakes that can be used as Green's functions at the strong earthquake stations, determine the permutation and combination scheme of the small earthquakes according to the number and position of the asperities, and then further permutate and combine the small earthquakes and the source parameters with the permutation and combination scheme of the obtained source parameters;

[0031] (5) Using the empirical Green's function method, the acceleration waveform of the strong earthquake station is calculated for each permutation and combination obtained in the above steps in turn, and the acceleration calculation results of all permutations and combinations are obtained;

[0032] (6) Based on the characteristics of the acceleration waveforms of the three components of this earthquake recorded by the strong earthquake station, the calculation results obtained in step (5) are screened to eliminate the results that do not meet the requirements;

[0033] (7) According to the calculation results after screening in step (6), all the results are counted, the frequency of occurrence of each source parameter is reversed, and the source parameter with the highest frequency of occurrence is selected as the reliable parameter;

[0034] (8) Selecting small earthquakes of broadband fixed stations as Green's functions, determining the permutation and combination of small earthquakes of broadband fixed stations to be used according to the number and position of asperities, applying the reliable parameters obtained in step (7) to the calculation of the acceleration waveform of broadband fixed stations by using the empirical Green's function method, and obtaining all possible acceleration results of broadband fixed stations;

[0035] (9) The results of step (8) are screened according to the seismic characteristics of the three components of the strong earthquake station and the attenuation relationship of the local area to obtain the final reliable acceleration waveform of the broadband fixed station. This result can be represented by several acceleration waveforms and the value range of PGA of these waveforms.

[0036] The method for synthesizing the acceleration waveform of a destructive earthquake at a fixed station involved in this application is actually based on the actual small earthquake waveform as the Green's function to synthesize the ground motion to obtain a more accurate acceleration waveform. The more detailed specific steps are as follows:

[0037] (1) After a destructive earthquake occurs, the magnitude and epicenter of the earthquake are obtained based on the measurement results of the seismic network. According to the epicenter, the waveform information of several strong earthquake stations with strong earthquake instruments installed closest to the epicenter is obtained, and the strong earthquake station with complete waveform is selected as the reference station. The epicenter distance of the strong earthquake station should not exceed 200km. This step is mainly for the next step to select appropriate strong earthquake stations. From the beginning of the earthquake to the end of the earthquake, if the waveform does not show head clipping, it can be regarded as meeting the waveform completeness requirement.

[0038] (2) Determine the source parameters

[0039] The source parameters that need to be determined include the focal mechanism of the main shock, the focal depth, the focal rise time of the main shock, the number of sub-faults on the main shock fault plane, the shear wave velocity and rupture velocity, the initial rupture position of the earthquake, the azimuth and epicentral distance of the station, the number and position of asperities, the ratio of stress drops of large and small earthquakes, etc. These parameters can be obtained from public channels. Among them, the number of sub-faults on the main shock fault plane, the number and position of asperities are determined by the dislocation distribution model on the main shock fault rupture surface. The asperities refer to the definition of Somerville et al. (1999), that is, the area with relatively large sliding dislocation on the fault rupture surface. The simplified asperity model is estimated based on the inversion results of different scholars. Generally, squares of different numbers and positions are used to characterize the spatial position characteristics of the asperities. However, different simplified models will have differences in size, position and number, as long as they are within an acceptable range.

[0040] After an earthquake occurs, many scientific research units, business departments, and scientific researchers will give the calculation results of the above-mentioned source parameters. Considering various uncertainties, each source parameter should select at least 3 reliable source parameters from these calculation results, and then arrange and combine all the parameters. In the end, N all The corresponding input into the program will obtain N earthquake source model parameters. all The results of the earthquake simulation.

[0041] (3) Permutations and combinations of solutions

[0042] Among them, small earthquake data can be applied from the National Strong Motion Network Center or from the China Earthquake Network Center. The epicenter of the small earthquake should be selected from the longitude and latitude after re-precision positioning. The magnitude range of the selected small earthquake can be 3-5. This method selects the acceleration waveform of the small earthquake as the Green function to synthesize the large earthquake. Therefore, the waveform segment intercepted by the small earthquake can generally be the waveform data 40s after the initial motion of the P wave as the available waveform segment.

[0043] If the main shock has multiple asperities, according to the earthquake rupture process, when the earthquake rupture starts from the initial rupture point and propagates to each asperity, there will be the initial rupture position on each asperity. It is necessary to find small earthquakes within 500m of the initial rupture point of each asperity in each asperity as the Green's function, that is, each asperity will select different small earthquakes as the Green's function. There may be more than one small earthquake that meets the conditions in each asperity, and all small earthquakes that meet the conditions should be used as the Green's function of each asperity. The selected small earthquakes should also have the following characteristics: the distance between the epicenter position of the small earthquake after precise positioning and the epicenter position of the main shock should not exceed 500m. At the same time, when selecting small earthquakes for each asperity, the condition to be met is that the epicenter position of the small earthquake should be close to the initial rupture position of each asperity, and should not exceed 500m. The focal depth of the small earthquake selected for each asperity should be close to the initial rupture position of each asperity, with an error of no more than 500m. After obtaining the appropriate small earthquake on each asperity, all the source parameters in the above steps are fully arranged and combined to obtain all possible arrangements and combinations.

[0044] The input part of the calculation process consists of two parts. One part is the parameter part. As mentioned above, there will be N all The second part is the selection of small earthquakes, that is, the number of small earthquakes that meet the requirements for each concave-convex body. The combination content of this link is mainly the number of concave-convex bodies and the number of small earthquakes for each concave-convex body. Assume that there are i (i≤3) concave-convex bodies, and the number of small earthquakes for each concave-convex body is M i (i=1, 2, 3), there are M combinations of small earthquakes. When i=1, there are M=M1 combinations of small earthquakes; when i=2, there are M=M1*M2 combinations of small earthquakes; when i=3, there are M=M1*M2*M3 combinations of small earthquakes. The total number of parameters and combinations of small earthquakes is N. all *M. N all *M combinations are sequentially input into the empirical Green's function method as Green's functions, and finally N all *M results.

[0045] (4) The screening process of simulation results.

[0046] The acceleration waveform of a strong earthquake at a strong earthquake station is certain. all *The results of M acceleration waveforms must be compared and analyzed with the observed value waveforms, and the results with large differences must be eliminated. The criteria for elimination can be as follows:

[0047] Three-point PGA should be in PGA obs 0.8-1.2 times, PGA obs Indicates the PGA value of the observed value. The three components are EW component, NS component, and UD component.

[0048] The waveform of the simulated value should be similar to that of the observed value. This step can be screened by referring to the 90% energy duration parameters of the simulated value and the observed value. The 90% energy duration of the simulated value should also be within the range of 0.8-1.2 times of the 90% energy duration of the observed value. Figure 1 As shown, a comparison chart of the observed and simulated values ​​of the acceleration waveform of a certain station is shown, with the observed values ​​on the top and the simulated values ​​on the bottom.

[0049] The waveform of the simulated value should also be similar to the acceleration response spectrum of the observed value. Figure 2 As shown in the figure, the average value of the response spectrum of all simulated acceleration waveforms should be very close to the acceleration response spectrum of the observed value. If the average value is far away from the acceleration response spectrum of the observed value, it is necessary to continuously delete the simulation values ​​to make the average value of the simulated acceleration response spectrum closer to the observed value response spectrum. The standard for closeness can be that the observed value acceleration response spectrum and the average value response spectrum of the simulated value have at least 3 intersections from left to right, such as Figure 2 The final acceleration simulation value that meets the above three screening conditions is the final acceleration simulation value that meets the requirements.

[0050] (5) After a certain number of acceleration results are obtained in step (4), the statistical results of the source parameters of all simulated acceleration waveforms are counted. That is, the parameter corresponding to each simulated acceleration waveform is selected, and the value with the highest occurrence frequency of each parameter is selected as the parameter with higher accuracy. The value with the highest total occurrence frequency of all parameters will be used in the subsequent calculation of the simulated broadband fixed station acceleration waveform.

[0051] (6) After obtaining relatively accurate source parameters of the large earthquake, we start calculating the acceleration waveform of the large earthquake at the broadband fixed station. The acceleration waveforms of all small earthquakes at the broadband fixed station can be obtained from the network database. The waveform segment intercepted by the small earthquake is generally the waveform data of 40 seconds after the initial motion of the P wave as the available waveform segment.

[0052] First, the basic information of the magnitude 3-5 aftershocks of the earthquake is obtained from the network database. The epicenter of the aftershock is selected from the new longitude and latitude of the aftershock precise positioning. The distance between the new epicenter of the small earthquake and the epicenter of the main shock is no more than 500m. The steps and standards for selecting small earthquakes for each asperity are consistent with the standards and steps for selecting small earthquakes by the strong earthquake station in step (3).

[0053] (7) The M combinations of small earthquakes obtained in step (6) and the source parameters obtained in steps (4) and (5) are sequentially input into the empirical Green's function method, and finally the simulation results of the acceleration waveforms of M three-component broadband fixed stations are obtained. The results of the M simulated broadband seismograph acceleration waveforms are further screened.

[0054] The screening criteria are as follows: Select the three strong earthquake stations closest to the epicenter, and the epicenter distance of the strong earthquake stations should be within 200km. Obtain the average value of the PGA of the three-component acceleration waveforms of the three strong earthquake stations, such as the three closest strong earthquake stations within 200km. Calculate the ratio of the EW / NS component, the ratio of the NS / EW component, the ratio of the EW / UD component, the ratio of the UD / EW component, the ratio of the NS / UD component, and the ratio of the UD / NS component for each strong earthquake station. Take the average value of the six ratios of the three strong earthquake stations, and then you will get three value ranges, such as the value range of EW / NS and NS / EW, the value range of EW / UD and UD / EW, and the value range of NS / UD and UD / NS. The PGA of the M types of wide-band seismographs obtained in this step should conform to the above three value ranges, that is, the PGA of the three components of all simulation values ​​should be within the above three ranges respectively. Only waveforms that meet the three value ranges at the same time can be used as the final simulation results of the large earthquake acceleration waveform of the broadband fixed station (MAD) station.

[0055] The envelope range of all response spectra that meet the requirements is used as the response spectrum range of the MAD station. The maximum and minimum values ​​of the PGA of each component of all results are used as the PGA range of each component of the MAD station. Finally, the acceleration waveform, acceleration response spectrum range, and PGA range of the MAD station that meet the requirements are obtained. The above three angles can comprehensively characterize the comprehensive seismic characteristics of this large earthquake at the wide-band fixed station. The acceleration waveform of the large earthquake obtained through this step is considered to be close to the actual acceleration waveform of the large earthquake at the station, and can be used for earthquake prevention and disaster reduction applications such as seismic input for local building seismic design.

[0056] Although the implementation methods disclosed in this application are as above, the contents described are only implementation methods adopted for facilitating the understanding of this application, and are not intended to limit this application. Any technician in the technical field to which this application belongs can make any modifications and changes in the form and details of implementation without departing from the spirit and scope disclosed in this application, but the scope of patent protection of this application shall still be based on the scope defined in the attached claims.

Claims

1. A method for synthesizing a destructive earthquake acceleration waveform at a fixed station, characterized in that: The following steps are involved: (1) After an earthquake occurs, determine the location of the broadband fixed station to be calculated based on actual needs; select the location of the strong earthquake station that is closest to the epicenter and has complete data; (2) Collect and summarize the required earthquake source parameters based on the locations of the selected broadband fixed stations and strong earthquake stations; (3) performing different permutations and combinations of the earthquake source parameters to obtain a permutation and combination scheme of the earthquake source parameters; (4) Determine the small earthquakes that can be used as Green's functions at the strong earthquake stations, determine the permutation and combination scheme of the small earthquakes according to the number and position of the asperities, and then further permutate and combine the small earthquakes and the source parameters with the permutation and combination scheme of the obtained source parameters; (5) Using the empirical Green's function method, the acceleration waveform of the strong earthquake station is calculated for each permutation and combination obtained in the above steps in turn, and the acceleration calculation results of all permutations and combinations are obtained; (6) Based on the characteristics of the acceleration waveforms of the three components of this earthquake recorded by the strong earthquake station, the calculation results obtained in step (5) are screened; (7) According to the calculation results after screening in step (6), all the results are counted, the frequency of occurrence of each source parameter is reversed, and the source parameter with the highest frequency of occurrence is selected as the reliable parameter; (8) Selecting small earthquakes of broadband fixed stations as Green's functions, determining the permutation and combination of small earthquakes of broadband fixed stations to be used according to the number and position of asperities, applying the reliable parameters obtained in step (7) to the calculation of the acceleration waveform of broadband fixed stations by using the empirical Green's function method, and obtaining all possible acceleration results of broadband fixed stations; (9) The results of step (8) are screened according to the seismic motion characteristics of the three components of the strong earthquake station and the attenuation relationship of the local area to obtain the final reliable acceleration waveform of the broadband fixed station.

2. The method for synthesizing a destructive earthquake acceleration waveform of a fixed station according to claim 1, characterized in that: The waveform segment intercepted by the small earthquake is the waveform data of 40 seconds after the initial movement of the P wave as the available waveform segment.

3. The method for synthesizing the destructive earthquake acceleration waveform of a fixed station according to claim 1, characterized in that: The selected small earthquakes have the following characteristics: the distance between the epicenter of the small earthquake and the epicenter of the main earthquake does not exceed 500m; when selecting small earthquakes for each asperity, the condition to be met is that the distance between the epicenter of the small earthquake and the initial rupture position of each asperity does not exceed 500m; the error between the focal depth of the small earthquake selected for each asperity and the initial rupture position of each asperity does not exceed 500m.

4. The method for synthesizing the destructive earthquake acceleration waveform of a fixed station according to any one of claims 1 to 3, characterized in that: In step (6), the screening criteria are: select three strong earthquake stations closest to the epicenter, and the epicenter distance of the strong earthquake stations should be within 200 km; obtain the average value of the PGA of the three-component acceleration waveforms of the three strong earthquake stations, and calculate the ratio of the EW / NS component, the ratio of the NS / EW component, the ratio of the EW / UD component, the ratio of the UD / EW component, the ratio of the NS / UD component, and the ratio of the UD / NS component of each strong earthquake station; Take the average value of the six ratios of the three strong earthquake stations, and then you will get the value ranges of EW / NS and NS / EW, the value ranges of EW / UD and UD / EW, and the value ranges of NS / UD and UD / NS; the PGA of the three components of all simulation values ​​should be within the above three ranges respectively, and the waveform that conforms to the three value ranges is taken as the final simulation result of the large earthquake acceleration waveform of the wide-band fixed station.

5. The method for synthesizing the destructive earthquake acceleration waveform of a fixed station according to claim 4, characterized in that: The envelope range of all response spectra that meet the requirements is used as the value range of the response spectrum of the MAD station; the maximum and minimum values ​​of the PGA of each component of all results are used as the value range of the PGA of each component of the MAD station; finally, the acceleration waveform that meets the requirements, the range of the acceleration response spectrum and the value range of the PGA of the MAD station are obtained.

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