A method and system for earthquake hazard assessment in moderate-to-strong earthquake zones

Abstract

The present invention proposes a method and system for assessing seismic hazard in moderate-to-strong earthquake zones, belonging to the technical field of seismic hazard assessment. The method comprises: zoning the seismic zone to obtain multiple tectonic zones; fitting historical earthquake and modern small and medium earthquake data within each tectonic zone to obtain a magnitude-frequency relationship, and calculating the occurrence rate, probability, and recurrence interval of any magnitude earthquake within each tectonic zone; and using a spatial smoothing method to assign weights such as the occurrence rate, probability, and recurrence interval of each magnitude bin, and any magnitude earthquake within each tectonic zone, to each fault zone. The present invention uses the spatial smoothing method to establish a seismic activity model. After smoothing, the seismic hazard is generally improved, becoming closer to historical earthquake occurrence patterns. For areas with unclear seismogenic structures and relatively weak seismic activity, earthquakes with larger energy releases are given a more prominent position in the allocation, thereby more accurately reflecting the potential hazard of seismic activity.

Description

Technical Field

[0001] The present invention relates to the technical field of earthquake risk assessment, and in particular to a method and system for earthquake risk assessment in moderate to strong earthquake zones. Background Art

[0002] In areas of moderate to strong seismic activity, the maximum historical earthquake magnitude is less than 7. Modern seismic activity is rare and lacks clear zonation, so earthquakes do not closely match existing faults. Due to errors in the location of historical earthquakes, the matching between the locations of historical earthquakes and faults is generally poor, causing the spatial distribution of earthquakes to deviate from the actual situation. This leads to unclear seismogenic structures, inaccurate magnitude determinations, and, in turn, affects the calculation of earthquake energy. For fault zones, accumulated stress and released energy are important indicators for assessing hazard. If conventional statistical methods for seismic activity are used to assess fault hazard, the energy released by earthquakes near the fault will be underestimated due to location errors, leading to an erroneous assumption that the stress accumulation and release levels of the fault are low, thus reducing the assessment of its hazard. Summary of the Invention

[0003] To this end, one purpose of the present invention is to propose a method and system for earthquake hazard assessment in moderate to strong earthquake zones to solve the problems mentioned in the background art and overcome the deficiencies in the prior art.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] In a first aspect, the present invention provides a method for assessing seismic hazard in a moderate-to-strong earthquake zone, comprising:

[0006] The earthquake zone is divided into several structural zones;

[0007] The magnitude-frequency relationship was obtained by fitting the historical earthquake and modern small and medium earthquake data in each tectonic area, and the occurrence rate, probability and recurrence interval of any magnitude earthquake in each tectonic area were calculated.

[0008] For each tectonic zone, the spatial smoothing method is used to distribute the weights of each magnitude level, the occurrence rate of any magnitude earthquake in each tectonic zone, the probability of earthquake occurrence and the recurrence interval to each fault zone.

[0009] Preferably, the method of using a spatial smoothing method to distribute the weights of each magnitude level, the occurrence rate, probability of occurrence and recurrence interval of earthquakes of any magnitude in each tectonic zone to each fault zone includes:

[0010] The historical destructive earthquake catalog of the tectonic area and the regional network earthquake catalog are statistically analyzed to determine the magnitude bin that needs to be allocated to each tectonic area. According to the magnitude-frequency relationship, the annual occurrence rate of earthquakes at all levels in the tectonic area is calculated. The tectonic area is divided into uniform grids, and the seismicity of each grid is calculated as the weight. The moving average method is used to calculate the average value of the seismicity in similar grids to smooth the data. Then, based on the weights, the statistically obtained weights of each magnitude bin, the occurrence rate of earthquakes of any level in each tectonic area, the probability of earthquake occurrence and the recurrence interval are allocated to each fault zone without exceeding the maximum potential magnitude.

[0011] Preferably, dividing the structural area into uniform grids comprises dividing the structural area into grids of 0.1°×0.1° in the longitude and latitude directions.

[0012] Preferably, the magnitude-frequency relationship is as follows:

[0013]

[0014] in, for The annual occurrence rate of earthquakes For the magnitude, is the seismic activity constant, Relative scale factor.

[0015] Preferably, the seismic activity calculation formula is as follows:

[0016]

[0017] in, is seismic activity / seismic radiation energy, is the comprehensive magnitude of the tectonic zone.

[0018] Preferably, the method further comprises: determining the maximum potential magnitude of each tectonic zone based on the historical seismic activity, current seismic activity and the nature of the faults in the tectonic zone; including the maximum potential magnitude when the fault zone in the tectonic zone is active in the Early and Middle Pleistocene, the maximum potential magnitude when the fault zone in the tectonic zone is active in the Late Pleistocene, and the maximum potential magnitude when the fault zone in the tectonic zone is active before the Quaternary.

[0019] Preferably, the principle for determining the maximum potential magnitude of a fault zone in the tectonic area whose activity period is the Early-Middle Pleistocene is as follows:

[0020] If there is a fault intersection in the tectonic zone, the fault activity is strike-slip, the deep background of the fault is the edge of a depression and uplift, and the maximum magnitude of the historical earthquake is greater than or equal to 6, the maximum magnitude of the current small earthquake is greater than or equal to 4, and the length of the fault zone is greater than or equal to 30 kilometers, then the maximum potential magnitude of the fault zone in the tectonic zone is 6.5 if the fault zone activity is in the Early Pleistocene and 6.5 if the fault zone activity is in the Middle Pleistocene.

[0021] If the fault zone in the tectonic area is a non-fault intersection, the active nature of the fault is a normal fault or a reverse fault, the deep background of the fault is the edge of a non-depression uplift, and the maximum magnitude of the historical earthquake is greater than or equal to 5, the maximum magnitude of the current small earthquake is greater than or equal to 3, and the length of the fault zone is less than 30 kilometers, then the maximum potential magnitude of the fault zone in the tectonic area is 6.0 when the activity era of the fault zone is the Early Pleistocene, and the maximum potential magnitude of the fault zone in the tectonic area is 6.0 when the activity era of the fault zone is the Middle Pleistocene.

[0022] Preferably, the principle for determining the maximum potential magnitude of an earthquake whose fault zone activity period is the Late Pleistocene in the tectonic area is as follows: the maximum potential magnitude of an earthquake whose fault zone activity period is the Late Pleistocene in the tectonic area is determined by calculating the regression relationship.

[0023] Preferably, the principle for determining the maximum potential magnitude of the fault zone in the tectonic area before the Quaternary period is as follows: it is determined according to the background magnitude of the seismic zone.

[0024] In a second aspect, the present invention provides a seismic hazard assessment system for moderate to strong earthquake zones, comprising:

[0025] Partition construction module: used to partition the earthquake zone to obtain multiple structural zones;

[0026] Fitting calculation module: used to fit the historical earthquake and modern small and medium earthquake data in each tectonic zone to obtain the magnitude-frequency relationship curve, and calculate the occurrence rate, probability of occurrence and recurrence interval of any magnitude earthquake in each tectonic zone;

[0027] Equal weight distribution module: For each tectonic zone, the spatial smoothing method is used to distribute the weights of each magnitude level, the occurrence rate of any magnitude earthquake in each tectonic zone, the probability of earthquake occurrence and the recurrence interval to each fault zone.

[0028] In a third aspect, the present invention provides a computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of the above-mentioned method for assessing earthquake hazards in moderate-to-strong earthquake zones are implemented.

[0029] In a fourth aspect, the present invention provides a readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-mentioned method for earthquake hazard assessment in moderate-to-strong earthquake zones.

[0030] Therefore, the present invention has the following beneficial effects:

[0031] The present invention provides a method and system for assessing earthquake hazard in moderate-to-strong earthquake zones. A spatial smoothing method is used to establish a seismic activity model. The seismic hazard in the structural zone is first statistically analyzed, and then smoothed according to the energy of the earthquake. The energy released by historical earthquakes on the fault zone is used as a weight to distribute the earthquake hazard data to each fault. After smoothing, the seismic hazard is generally improved and is closer to the historical earthquake occurrence. For areas with unclear seismogenic structures and relatively weak seismic activity, earthquakes with larger energy releases occupy a more important position in the distribution, which can more accurately reflect the potential hazard of seismic activity.

[0032] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0034] Figure 1 It is an overall flow chart of the method of the present invention;

[0035] Figure 2 This is a seismic tectonic zoning map according to an embodiment of the present invention;

[0036] Figure 3 This is a comprehensive assessment map of earthquake hazards of major faults in a certain province according to an embodiment of the present invention;

[0037] Figure 4 Schematic diagram of the system structure connection relationship of an embodiment of the present invention;

[0038] Figure 5 2 is a schematic diagram of the computer device structure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0040] Active Fault Detection (GB / T36072-2018) defines active fault seismic hazard assessment as the process of determining the segments (locations) along an active fault that are likely to experience moderate-to-strong or greater earthquakes within a certain period of time, the most likely earthquake, and the hazard level. While a relatively detailed assessment method is provided for active faults with surface outcrops, no practical evaluation method is provided for hidden faults. Instead, it states, "Based on the geometry of the active fault, the distribution of historical earthquake damage zones, the distribution of current earthquake epicenters, geophysical fields, and the relationship between deep and shallow structures, fault rupture segments with a risk of moderate or greater earthquakes are identified, and the magnitude of the most likely earthquake is comprehensively assessed." "The seismic hazard of each active fault segment should be assessed based on data such as the spatial and temporal migration of regional earthquakes, magnitude-time maps, and active and quiet phases."

[0041] In assessing the seismic hazard of active faults, how to account for the complexity of earthquake recurrence behavior, especially in the high-magnitude range, is a key issue. However, there is currently no consensus on the recurrence behavior of large earthquakes. Early characteristic earthquake models posited that small and medium earthquake activity on fault zones follows a relatively well-defined GR index model (Gutenberg and Richter, 1956). However, the frequency of large earthquakes deviated significantly from the magnitude-frequency relationship curve obtained by fitting small and medium earthquake data. This suggests that large earthquakes are characteristic, and that extrapolating the GR relationship derived from small and medium earthquakes will underestimate the frequency of large earthquakes.

[0042] For Late Pleistocene active faults and fault sections with historical strong earthquakes or frequent modern small and medium earthquakes, seismic hazard assessments based on geological data and statistical methods of seismic activity in seismic tectonic zones should be carried out as much as possible; and for the seismic hazard assessments of identified Middle Pleistocene active and pre-Quaternary active faults, the assessments should be mainly based on statistical methods of moderate and strong earthquake activity in seismic tectonic zones.

[0043] Due to the errors in the positioning of historical earthquakes, the location match between historical earthquakes and faults is generally poor. Directly using statistical methods based on seismic activity in seismic tectonic cells will greatly reduce the risk of faults.

[0044] like Figure 1 As shown, the present invention provides a method for assessing earthquake hazard in a moderate-to-strong earthquake zone, comprising:

[0045] The earthquake zone is divided into several structural zones;

[0046] The magnitude-frequency relationship was obtained by fitting the historical earthquake and modern small and medium earthquake data in each tectonic area, and the occurrence rate, probability and recurrence interval of any magnitude earthquake in each tectonic area were calculated.

[0047] For each tectonic zone, the spatial smoothing method is used to distribute the weights of each magnitude level, the occurrence rate of any magnitude earthquake in each tectonic zone, the probability of earthquake occurrence and the recurrence interval to each fault zone.

[0048] The present invention uses the magnitude-frequency relationship curve obtained by fitting historical earthquakes and modern small and medium-sized earthquakes in the tectonic zone. Taking into account the inaccuracy of historical earthquake positioning and the insufficient time scale of modern earthquakes, a smooth weighted method is used to distribute the average annual occurrence rate of seismic activity to each fault, and the average annual occurrence rate and average recurrence interval of each fault are obtained, as well as the probability of at least one earthquake occurring in the next 50, 100 and 200 years.

[0049] In order to better zoning the study area, the present invention first studies the basic characteristics of the Quaternary active faults in the region, analyzes the structural units to which they belong, the direction of the faults, and the main structural framework of the structural region.

[0050] Secondly, in order to identify the activity of the main faults in the study area, the research results of the faults in the study area, active fault mapping, urban active fault detection results, earthquake safety evaluation reports, and paper journal results were collected to determine the geometric structure and distribution of the faults, and preliminarily determine the activity of the faults and the latest active era.

[0051] Based on factors such as seismic activity, seismic tectonics, deep geophysics, and tectonic force fields, the basis and principles for delineating seismic tectonic zones are summarized: Tectonic zones should include earthquakes of magnitude 6 or greater to facilitate statistical analysis of the annual incidence of earthquakes of magnitude 6 or greater; the extension direction of seismic structures should be generally consistent; from a deep geophysical perspective, there should be no significant geomagnetic and gravity gradients within the tectonic zone; and there should be a relatively uniform tectonic stress field direction. Within different seismic tectonic zones, a complete analysis of seismic data from different time periods should also be conducted to determine the time period and magnitude range for earthquake statistics.

[0052] The present invention again identifies the seismogenic structure of the main faults in the region and determines the maximum potential earthquake.

[0053] Specifically, the maximum potential magnitude of each tectonic zone is determined based on the historical seismic activity, current seismic activity and the nature of the faults in the tectonic zone; this includes the maximum potential magnitude when the fault zone in the tectonic zone was active in the Early and Middle Pleistocene, the maximum potential magnitude when the fault zone in the tectonic zone was active in the Late Pleistocene, and the maximum potential magnitude when the fault zone in the tectonic zone was active before the Quaternary.

[0054] The principles for determining the maximum potential magnitude of fault zones in tectonic areas whose activity period is the Early to Middle Pleistocene are shown in Table 1.

[0055]

[0056] Specifically, if there is a fault intersection in the fault zone in the tectonic area, the active nature of the fault is a strike-slip fault, the deep background of the fault is the edge of a depression and uplift, and the maximum magnitude of the historical earthquake is greater than or equal to 6, the maximum magnitude of the current small earthquake is greater than or equal to 4, and the length of the fault zone is greater than or equal to 30 kilometers, then the maximum potential magnitude of the active era of the fault zone in the tectonic area is the Early Pleistocene, and the maximum potential magnitude of the active era of the fault zone in the tectonic area is 6.5; if the fault zone in the tectonic area is a non-fault intersection, the active nature of the fault is a normal fault or reverse fault, the deep background of the fault is the edge of a non-depression and uplift, and the maximum magnitude of the historical earthquake is greater than or equal to 5, the maximum magnitude of the current small earthquake is greater than or equal to 3, and the length of the fault zone is less than 30 kilometers, then the maximum potential magnitude of the active era of the fault zone in the tectonic area is the Early Pleistocene, and the maximum potential magnitude of the active era of the fault zone in the tectonic area is 6.0.

[0057] The principle for determining the maximum potential magnitude of an earthquake whose fault zone activity period is the Late Pleistocene in a tectonic area is as follows: The maximum potential magnitude of an earthquake whose fault zone activity period is the Late Pleistocene in a tectonic area is determined by calculating the regression relationship.

[0058] The empirical relationship for discriminating active tectonics since the Late Pleistocene is to comprehensively discriminate the maximum potential magnitude based on the empirical relationship between fault size and rupture length of magnitude, and the empirical relationship between magnitude, rupture length, and rupture area of ​​seismically active faults. The empirical relationship between fault size and rupture length of magnitude is as follows: Ms=3.821+1.860*log10(L), Mw=4.33+1.49lg(L), where L is the rupture length, Ms is the surface wave magnitude, and Mw is the moment magnitude.

[0059] The principle for determining the maximum potential magnitude of a fault zone in a tectonic area before the Quaternary period is as follows: it is determined according to the background magnitude of the seismic zone.

[0060] For faults before the Quaternary period, the maximum potential magnitude is no longer divided, and they are all considered according to the background magnitude of the earthquake zone (5.0-5.5).

[0061] The magnitude-frequency relationship was obtained by fitting the historical earthquake and modern small and medium earthquake data in each tectonic area, and the annual occurrence rate, probability of occurrence and recurrence interval of earthquakes of any magnitude in each tectonic area were calculated.

[0062] The earthquake probability and recurrence interval can be obtained by statistics and calculation of historical earthquakes and modern small and medium earthquake data in each tectonic area.

[0063] The magnitude-frequency relationship and Poisson model method are used to calculate the annual average earthquake occurrence rate at all levels in each seismic tectonic zone. The magnitude-frequency relationship is then used to estimate the reliability constants and the exponential function segment of the relationship (i.e., the G-R relationship): and : .

[0064] For each tectonic zone, the spatial smoothing method is used to distribute the weights of each magnitude level, the occurrence rate of any magnitude earthquake in each tectonic zone, the probability of earthquake occurrence and the recurrence interval to each fault zone.

[0065] According to the empirical relationship between earthquake radiation energy / seismic capacity and magnitude:

[0066]

[0067] To calculate the seismic capacity of the district where each fault is located, both historical and current earthquakes are uniformly weighted to 500 years. Taking into account the uncertainty of earthquake location, a smooth weighted method is used to calculate the weighted value for each district, and then the occurrence rate of each fault is assigned based on the upper limit of the magnitude of each fault.

[0068] Specifically, the historical destructive earthquake catalog of the tectonic area and the regional network earthquake catalog are statistically analyzed to determine the magnitude range that needs to be allocated to each tectonic area. According to the magnitude-frequency relationship, the annual occurrence rate of earthquakes at all levels in the tectonic area is calculated. The tectonic area is divided into uniform grids, and the seismic activity of each grid is calculated as a weight. The moving average method is used to calculate the average value of the seismic activity in similar grids to smooth the data. Then, based on the weights, the statistically obtained weights of each magnitude range, the occurrence rate of earthquakes of any level in each tectonic area, the probability of earthquake occurrence and the recurrence interval are allocated to each fault zone without exceeding the maximum potential magnitude.

[0069] It should be noted that the spatial smoothing method of the present invention is a post-spatial smoothing method.

[0070] Existing technologies have proposed a method for building a seismicity model using spatial smoothing. This involves constructing seismicity models using modern small and medium-sized earthquakes, destructive historical earthquakes, and uniform background earthquakes, and then weighting these models to determine seismicity parameters. The key advantage of this method is that it does not rely on seismotectonic seismicity models to delineate potential focal areas. Instead, earthquake hazard can be calculated directly using earthquake catalogs, making it simple and easy to implement.

[0071] Based on the basic assumption of the spatially smoothed model that future earthquakes are highly concentrated in areas where past earthquakes occurred, the smoothed seismicity rate is concentrated in areas where earthquakes have occurred in the past, essentially reflecting the pattern of future moderate-to-strong earthquake activity. Research on the in-situ recurrence rate of moderate-to-strong earthquakes in South China shows that, when the distance of in-situ recurrence is 50 km, the recurrence rate for earthquakes of magnitude 5 or above in the region is as high as 61%, higher than the national in-situ recurrence rate of strong earthquakes of 53.3%, indicating that South China has a high in-situ recurrence rate for moderate-to-strong earthquakes. These results also validate the rationale for using spatially smoothed methods to estimate the average annual earthquake occurrence rate in this study area.

[0072] The study area was divided into 0.1°×0.1° grids, and the earthquake frequency in each grid was counted. , and then smooth the earthquakes in the grid to other spatial grid points through the smoothing function, so as to obtain the earthquake occurrence rate in each grid after smoothing:

[0073] In the formula As a smooth function, the Gaussian smooth function reflects the spatial heterogeneity of earthquakes and is more consistent with the randomness of earthquake occurrence. is the earthquake frequency of each grid, Refers to The earthquake frequency after smoothing the grid, Refers to the current grids, Refers to A grid.

[0074] The above method can be used to calculate the annual occurrence rate of earthquakes with M ≥ 4.7 and M ≥ 2.0 in the study area. Furthermore, the magnitude-frequency relationship can be used to derive the annual occurrence rate of earthquakes in different magnitude bins. The magnitude bins obtained from the statistical analysis of the study area are assigned equal weights to each fault.

[0075] The aforementioned pre-spatial smoothing method applies spatial smoothing techniques before performing other data analysis or processing. Therefore, it relies heavily on the original data, and its effectiveness depends largely on its quality and distribution. However, modern earthquake activity is rare and lacks clear zonation, so earthquakes and existing faults are not well matched. Due to historical earthquake location errors, the location match between historical earthquakes and faults is generally poor, causing the spatial distribution of earthquakes to deviate from the actual situation. This leads to unclear seismogenic structures, inaccurate magnitude estimations, and, in turn, affects earthquake energy calculations. Pre-spatial smoothing cannot correct these problems and may even introduce new biases, reducing the assessment of earthquake hazard.

[0076] The post-spatial smoothing method of the present invention is different from the above method in that it first counts the historical destructive earthquake catalog (M≥4.7) and the regional network earthquake catalog (M≥2.0) in the study area (tectonic area), and then jointly counts the magnitude-frequency relationship: Calculate the annual occurrence rate of earthquakes at all levels in the study area , and then calculate the seismic activity of each grid as the weight. The formula for seismic activity (earthquake energy) is: The moving average method is used to smooth the data by calculating the average value within similar grids. Then, based on the weights, the weights of the magnitude bins obtained from the statistical analysis of the study area are assigned to each fault. The large earthquake recurrence period and probability of occurrence for each fault are obtained.

[0077] Among them, the seismic activity of each grid is calculated as the weight. Assuming that the energy of each earthquake is E, the frequency of earthquakes of different magnitudes can be weighted according to the energy size. For example, for a grid area, the weighted earthquake frequency is calculated as , we can first calculate the earthquake energy Calculating weights (in is the sum of all earthquake energies in the region), and then the frequency of earthquakes of different magnitudes is calculated. Perform weighted summation This can make earthquakes with larger energy release occupy a more important position in frequency statistics and more accurately reflect the potential danger of earthquake activities.

[0078] The post-spatial smoothing method of the present invention can address specific spatial issues arising from the previous analysis process in a targeted manner. Because post-spatial smoothing is performed after other processing steps, the previous processing steps have already extracted or retained important data information. This method can improve the spatial characteristics of the data while minimizing the impact on this critical information. Specifically, the present invention first calculates the seismic hazard of a tectonic zone, then smoothes the data based on the energy of the earthquake. Using the energy released by historical earthquakes on the fault zone as a weight, the seismic hazard data is assigned to each fault. After smoothing, the seismic hazard is generally improved, becoming closer to historical earthquake occurrences. For areas with unclear seismogenic structures and relatively weak seismic activity, earthquakes with larger energy releases are given a more prominent position in the allocation, more accurately reflecting the potential hazard of seismic activity.

[0079] The following describes the method for assessing seismic risk in moderate-to-strong earthquake zones of the present invention by taking a seismic tectonic exploration project in a certain province as an example.

[0080] The example region belongs to a zone of moderate to strong seismic activity. Therefore, fault seismic hazard assessment requires the use of multiple, appropriate methods for comparison. For example, using fault size or scale to estimate an upper magnitude limit may not be applicable to all faults, requiring classification of fault activity (age of activity) before conducting this assessment. Furthermore, the weighting of assessment methods should differ between areas with sparse minor earthquake activity and those with relatively high seismic activity.

[0081] Most importantly, the maximum potential seismic capacity of a fault is determined comprehensively based on the segmented characteristics and evidence of fault activity (including at depth), combined with the precise location of small earthquakes, the rupture area and magnitude, and structural analogies. Extrapolating the maximum magnitude using the GR relationship is supplemented, while determining the maximum magnitude for a specific structure or tectonic zone primarily involves structural analogies or empirical statistical relationships.

[0082] The province is divided into six tectonic zones, including one with a maximum potential magnitude of 7.5, two with a magnitude of 7.0, one in northwestern Henan and Sanmenxia, ​​and three with a magnitude of 6.5, one in central Henan, one in eastern Henan, and one in Qinling-Dabie. See Table 2 and Table 3 for the zones below. Figure 2 .

[0083]

[0084] The magnitude bin interval is 0.3. The destructive earthquake catalog begins in 1484 and ends in December 2022. The current small and medium earthquake catalog is primarily based on the China Earthquake Networks Center's observation catalog, which begins in 1970 and ends in December 2022.

[0085] Based on the fitted magnitude-frequency relationship, the relevant parameters of each structural partition are summarized. The relationship , see Table 3.

[0086]

[0087] According to the empirical relationship between earthquake radiation energy and magnitude: The earthquake capacity of each fault area is calculated. Historical earthquakes and current earthquakes are uniformly weighted to 500 years. Taking into account the uncertainty of earthquake location, the weight is calculated for each tectonic area using the average smooth equal addition method. Then, the occurrence rate of each fault is allocated according to the magnitude upper limit of each fault. The results are as follows: Figure 3 shown.

[0088] The beneficial effects of the present invention are also reflected in the following aspects:

[0089] The physical meaning is clear: Earthquake energy is usually calculated by magnitude. For every increase in magnitude, the energy increases approximately 32 times. For example, a magnitude 5 earthquake has 32 times the energy of a magnitude 4 earthquake. It is more reasonable to use earthquake energy as a smooth statistical parameter, rather than the traditional method of using the number of earthquakes as a statistical parameter.

[0090] Follow the principle of historical earthquake recurrence: use the size of historical earthquakes on the fault zone as a weight to predict the size of future earthquakes intuitively, that is, earthquakes of the same magnitude will occur in the place where historical earthquakes occurred in the past.

[0091] Quantitative calculation is simplified: In the past, the smoothed value of the number of earthquakes in each grid and each magnitude level was calculated first, and then the hazard of the fault was counted, which required a lot of calculation. Now, the earthquake hazard of the tectonic zone is counted first, and then smoothed according to the energy of the earthquake. The smoothed result is used as the weight to distribute the earthquake hazard to each fault, which greatly reduces the amount of calculation.

[0092] Improved calculation accuracy: The seismic hazard level of each fault obtained by previous calculation methods is generally low. After the smoothing process of the present invention, the seismic hazard level is generally improved, which is closer to people's subjective understanding and historical earthquake occurrence.

[0093] Existing research methods for earthquake recurrence intervals include the fault slip method and the earthquake moment rate method.

[0094] For the fault slip method, given the long-term average slip rate of the Holocene fault segment and the average coseismic displacement of the most recent event, the formula can usually be used to estimate the recurrence interval of large earthquakes: , where u is the average coseismic displacement, which is calculated from the statistical relationship between coseismic displacement and fault rupture scale; v is the average slip rate of the fault zone, , is the average slip rate of the fault over a long period of time obtained by geological methods. is the average rate of long-term, earthquake-free creep on the fault.

[0095] For the earthquake moment rate method, the earthquake recurrence interval is calculated using the earthquake moment rate. The calculation formula is: , where is the characteristic seismic moment, which can be obtained from the quantitative research results of active faults; is the seismic moment rate, which can be obtained from Brune's formula: , where is the shear modulus of the crustal elastic layer, is the fault area, is the fault slip rate.

[0096] The fault slip method and the earthquake moment rate method are applied to active faults since the late Pleistocene. Both methods require the average slip rate of the fault zone. .

[0097] For the probability model of a major earthquake, since earthquakes can be viewed as the result of strain energy accumulating over time at a certain rate, the probability of earthquake recurrence in the case of in-situ recurrence is related to the time elapsed since the last earthquake, i.e., the elapsed time. If an earthquake has not occurred within a certain time period, then, based on this condition, the probability of earthquake recurrence within the period up to +Δt is expressed as:

[0098]

[0099] Where, is the recurrence interval probability density function, is the cumulative probability distribution function, is the recurrence interval, For the passing time, Forecast period.

[0100] Currently, the main probability models that can be used for earthquake hazard analysis are: Poisson distribution, lognormal distribution, and BPT model (Brownian PassageTime model).

[0101] The Poisson model is based on the following assumptions: earthquakes occur randomly in time and space on a fault zone, and the number of earthquakes and their magnitudes conform to the Gutenberg-Richter relationship, which is an exponential relationship. Its main feature is that it assumes that the probability of future earthquakes is independent of the time elapsed from the last earthquake. This model is more suitable when little is known about the laws and causes of earthquake development and occurrence, and because it requires fewer constraint parameters, even now, in areas where geological and seismic data are relatively scarce, the Poisson model still plays an important role. The probability density function and conditional probability of the Poisson model are:

[0102]

[0103] in, is the average annual occurrence rate of earthquakes on the fault segment, .

[0104] The probability density function of the lognormal model is:

[0105]

[0106] Where, is the earthquake recurrence interval, For the passing time; is the average earthquake recurrence interval; is the mean, is the standard deviation (uncertainty), which includes parametric uncertainty (aleatory uncertainty) and intrinsic uncertainty (epistemic uncertainty).

[0107] The BPT model is a strong earthquake recurrence update model with an inherent physical basis, proposed on the basis of elastic rebound theory. According to the elastic rebound theory, a strong earthquake will only occur when the stress accumulation of the active fault reaches a fixed upper limit, and then the stress of the fault will drop to a fixed extremely low level, and the next cycle will begin. With the deepening of research and observation of actual earthquake cases, it is found that the upper and lower limits of stress are not fixed values, but fluctuate (this fluctuation can be expressed by the coefficient of variation), that is, the structural loading process will be disturbed by some random events, which manifests as a random loading process of stable loading plus Brownian perturbation. The recurrence interval between earthquake events follows the Brownian process time distribution. Its probability density function is as follows:

[0108]

[0109] Where, is the probability density function of the BPT model; is the average earthquake recurrence interval; is the coefficient of variation, also known as the non-periodic factor, which is equal to the ratio of the standard deviation to the average recurrence interval of earthquakes.

[0110] The Poisson model assumes that the probability of an earthquake remains constant. The two results of the BPT model and the Lognormal model imply two different explanations for the intrinsic tectonic movement: the Lognormal model believes that the fault has become an inactive fault; while the BPT model believes that the fault itself is still accumulating or receiving strain energy transmitted by adjacent faults, but its own stress state remains stable, and the strain energy it accumulates or receives is released through other means (such as creep or small earthquakes).

[0111] In another embodiment, Figure 4 As shown, the present invention provides a seismic risk assessment system for moderate to strong earthquake areas, comprising:

[0112] Partition construction module: used to partition the earthquake zone to obtain multiple structural zones;

[0113] Fitting calculation module: used to fit the historical earthquake and modern small and medium earthquake data in each tectonic zone to obtain the magnitude-frequency relationship curve, and calculate the occurrence rate, probability of occurrence and recurrence interval of any magnitude earthquake in each tectonic zone;

[0114] Equal weight distribution module: For each tectonic zone, the spatial smoothing method is used to distribute the weights of each magnitude level, the occurrence rate of any magnitude earthquake in each tectonic zone, the probability of earthquake occurrence and the recurrence interval to each fault zone.

[0115] Furthermore, the spatial smoothing method is used to distribute the weights of each magnitude level, the occurrence rate, probability and recurrence interval of any magnitude earthquake in each tectonic zone to each fault zone, including:

[0116] The historical destructive earthquake catalog of the tectonic area and the regional network earthquake catalog are statistically analyzed to determine the magnitude bin that needs to be allocated to each tectonic area. According to the magnitude-frequency relationship, the annual occurrence rate of earthquakes at all levels in the tectonic area is calculated. The tectonic area is divided into uniform grids, and the seismicity of each grid is calculated as the weight. The moving average method is used to calculate the average value of the seismicity in similar grids to smooth the data. Then, based on the weights, the statistically obtained weights of each magnitude bin, the occurrence rate of earthquakes of any level in each tectonic area, the probability of earthquake occurrence and the recurrence interval are allocated to each fault zone without exceeding the maximum potential magnitude.

[0117] Furthermore, dividing the structural area into uniform grids includes dividing the structural area into grids of 0.1°×0.1° in the latitude and longitude directions.

[0118] Furthermore, the magnitude-frequency relationship is as follows:

[0119]

[0120] in, for The annual occurrence rate of earthquakes For the magnitude, is the seismic activity constant, Relative scale factor.

[0121] Furthermore, the formula for calculating seismic activity is as follows:

[0122]

[0123] in, is seismic activity / seismic radiation energy, is the comprehensive magnitude of the tectonic zone.

[0124] Furthermore, the method also includes: determining the maximum potential magnitude of each tectonic zone based on the historical seismic activity, current seismic activity and nature of the fault in the tectonic zone; including the maximum potential magnitude when the fault zone in the tectonic zone is active in the Early and Middle Pleistocene, the maximum potential magnitude when the fault zone in the tectonic zone is active in the Late Pleistocene, and the maximum potential magnitude when the fault zone in the tectonic zone is active before the Quaternary.

[0125] Furthermore, the principles for determining the maximum potential magnitude of fault zones in tectonic areas that are active in the Early to Middle Pleistocene are as follows:

[0126] If there is a fault intersection in the tectonic zone, the fault activity is strike-slip, the deep background of the fault is the edge of a depression and uplift, and the maximum magnitude of the historical earthquake is greater than or equal to 6, the maximum magnitude of the current small earthquake is greater than or equal to 4, and the length of the fault zone is greater than or equal to 30 kilometers, then the maximum potential magnitude of the fault zone in the tectonic zone is 6.5 if the fault zone activity is in the Early Pleistocene and 6.5 if the fault zone activity is in the Middle Pleistocene.

[0127] If the fault zone in the tectonic area is a non-fault intersection, the active nature of the fault is a normal fault or a reverse fault, the deep background of the fault is the edge of a non-depression uplift, and the maximum magnitude of the historical earthquake is greater than or equal to 5, the maximum magnitude of the current small earthquake is greater than or equal to 3, and the length of the fault zone is less than 30 kilometers, then the maximum potential magnitude of the fault zone in the tectonic area is 6.0 when the activity era of the fault zone is the Early Pleistocene, and the maximum potential magnitude of the fault zone in the tectonic area is 6.0 when the activity era of the fault zone is the Middle Pleistocene.

[0128] Furthermore, the principle for determining the maximum potential magnitude of an earthquake when the fault zone in the tectonic area is active in the late Pleistocene is as follows: the maximum potential magnitude of an earthquake when the fault zone in the tectonic area is active in the late Pleistocene is determined by calculating the regression relationship.

[0129] Furthermore, the principle for determining the maximum potential magnitude of a fault zone in a tectonic area whose activity period is before the Quaternary period is as follows: it is determined according to the background magnitude of the seismic zone.

[0130] Furthermore, it should be understood that since the configuration of each module is merely to illustrate the functional units of the system disclosed herein, the physical devices corresponding to these modules may be the processor itself, or a portion of the software in the processor, a portion of the hardware, or a combination of software and hardware. Therefore, the number of modules in the figure is merely illustrative.

[0131] Various embodiments of the systems and techniques described herein can be implemented in digital electronic circuit systems, integrated circuit systems, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on chips (SOCs), programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various embodiments can include being implemented in one or more computer programs that are executable and / or interpreted on a programmable system comprising at least one programmable processor, which can be a special purpose or general purpose programmable processor that can receive data and instructions from a storage system, at least one input device, and at least one output device, and transmit data and instructions to the storage system, the at least one input device, and the at least one output device.

[0132] In order to solve the above technical problems, an embodiment of the present invention also provides a computer device / electronic device, including a memory, a processor and a computer program stored in the memory and runnable on the processor. When the processor executes the program, the steps of the above-mentioned method for earthquake hazard assessment in moderate-to-strong earthquake zones are implemented.

[0133] like Figure 5 As shown, the computer / electronic device includes a memory, a processor, and a network interface that are interconnected and communicated through a system bus. It should be noted that the figure only shows a computer device with component memory, a processor, a network interface, and an operating system, but it should be understood that it is not required to implement all the components shown, and more or fewer components can be implemented instead. Among them, those skilled in the art can understand that the computer / electronic device here is a device that can automatically perform numerical calculations and / or information processing according to pre-set or stored instructions, and its hardware includes but is not limited to a microprocessor, an application specific integrated circuit (ASIC), a programmable gate array (FPGA), a digital signal processor (DSP), an embedded device, etc.

[0134] Computers / electronic devices can be desktop computers, laptops, PDAs, cloud servers, and other computing devices. Computers / electronic devices can interact with users through keyboards, mice, remote controls, touchpads, or voice-activated devices.

[0135] The memory may be one or more than one, and may include at least one type of readable storage medium, including flash memory, a hard disk, a multimedia card, card-type memory (e.g., SD or DX memory), random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), programmable read-only memory (PROM), magnetic storage, magnetic disks, optical disks, and the like. In some embodiments, the memory may be an internal storage unit of a computer device, such as the computer device's hard disk or internal memory. In other embodiments, the memory may also be an external storage device of the computer device, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) card, a flash memory card, and the like. Of course, the memory may also include both the internal storage unit and external storage devices of the computer device. In this embodiment, the memory is typically used to store the operating system and various application software installed on the computer device, such as the program code for a method for assessing seismic hazard in moderate-to-strong earthquake zones. Furthermore, the memory may also be used to temporarily store various types of data that have been output or are about to be output.

[0136] In some embodiments, the processor can be a central processing unit (CPU), a controller, a microcontroller, a microprocessor, or other data processing chip. Such a processor is typically used to control the overall operation of a computer device. In this embodiment, the processor is used to execute program code stored in a memory or process data, such as executing program code for a method for assessing seismic hazard in moderate-to-strong earthquake zones.

[0137] The network interface may include a wireless network interface and / or a wired network interface, which is generally used to establish a communication connection between a computer device and other electronic devices.

[0138] The present invention also provides another embodiment, namely, providing a readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-mentioned method for assessing earthquake hazard in moderate-to-strong earthquake zones.

[0139] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0140] Those skilled in the art will readily understand that the present invention encompasses any combination of the components described in the Summary and Detailed Description of the Invention and the accompanying drawings. Due to space limitations and for the sake of clarity, not all of the various solutions resulting from these combinations are described. Any modifications, equivalent substitutions, and improvements within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

[0141] Although the embodiments of the present invention have been shown and described above, it should be understood that the above embodiments are illustrative and are not to be construed as limiting the present invention. Those skilled in the art may make changes, modifications, substitutions, and variations to the above embodiments without departing from the principles and intent of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for assessing earthquake hazard in moderate-to-strong earthquake zones, characterized in that: include: The earthquake zone is divided into several structural zones; The magnitude-frequency relationship was obtained by fitting the historical earthquake and modern small and medium earthquake data in each tectonic area, and the annual occurrence rate, probability of occurrence and recurrence interval of earthquakes of any magnitude in each tectonic area were calculated. For each tectonic zone, a spatial smoothing method is used to distribute weights such as the annual occurrence rate, earthquake probability, and recurrence interval of each magnitude level, each tectonic zone, to each fault zone, wherein the spatial smoothing method is a post-spatial smoothing method, including: The historical destructive earthquake catalog of the tectonic area and the regional network earthquake catalog are compiled to determine the magnitude bins that need to be assigned to each tectonic area. Based on the magnitude-frequency relationship, the annual occurrence rate of earthquakes at all levels in the tectonic area is calculated. The tectonic area is divided into uniform grids, and the seismicity of each grid is calculated as a weight. The moving average method is used to calculate the average value of seismicity within similar grids to smooth the data. Based on the weights, the statistically obtained annual occurrence rate of earthquakes of any magnitude in each tectonic area, the probability of earthquake occurrence, and the recurrence interval are then assigned to each fault zone without exceeding the maximum potential magnitude. The calculation formula of seismic activity is as follows: ； in, is the seismic activity, For the magnitude.

2. A method for earthquake risk assessment in a moderate to strong earthquake zone according to claim 1, characterized in that: The dividing the structural area into uniform grids includes dividing the structural area into grids of 0.1°×0.1° in the latitude and longitude directions.

3. A method for assessing earthquake risk in a moderate-to-strong earthquake zone according to claim 1, characterized in that: The magnitude-frequency relationship is as follows: ； in, for The annual occurrence rate of earthquakes For the magnitude, is the seismic activity constant, is the relative proportional coefficient.

4. A method for earthquake risk assessment in a moderate to strong earthquake zone according to claim 1, characterized in that: Also includes: The maximum potential magnitude of each tectonic zone is determined based on the historical seismic activity, current seismic activity and the nature of the faults in the tectonic zone; this includes the maximum potential magnitude when the fault zone in the tectonic zone was active in the Early and Middle Pleistocene, the maximum potential magnitude when the fault zone in the tectonic zone was active in the Late Pleistocene, and the maximum potential magnitude when the fault zone in the tectonic zone was active before the Quaternary.

5. The method for earthquake risk assessment in a moderate-to-strong earthquake zone according to claim 1, characterized in that: The principles for determining the maximum potential magnitude of a fault zone in the tectonic area that is active in the Early to Middle Pleistocene are as follows: If there is a fault intersection in the tectonic zone, the fault activity is strike-slip, the deep background of the fault is the edge of a depression and uplift, and the maximum magnitude of the historical earthquake is greater than or equal to 6, the maximum magnitude of the current small earthquake is greater than or equal to 4, and the length of the fault zone is greater than or equal to 30 kilometers, then the maximum potential magnitude of the fault zone in the tectonic zone is 6.5 if the fault zone activity is in the Early Pleistocene and 6.5 if the fault zone activity is in the Middle Pleistocene. If the fault zone in the tectonic area is a non-fault intersection, the active nature of the fault is a normal fault or a reverse fault, the deep background of the fault is the edge of a non-depression uplift, and the maximum magnitude of the historical earthquake is greater than or equal to 5, the maximum magnitude of the current small earthquake is greater than or equal to 3, and the length of the fault zone is less than 30 kilometers, then the maximum potential magnitude of the fault zone in the tectonic area is 6.0 when the activity era of the fault zone is the Early Pleistocene, and the maximum potential magnitude of the fault zone in the tectonic area is 6.0 when the activity era of the fault zone is the Middle Pleistocene.

6. A method for assessing earthquake risk in a moderate-to-strong earthquake zone according to claim 1, characterized in that: The principle for determining the maximum potential magnitude of an earthquake whose fault zone activity period is the Late Pleistocene in the tectonic area is as follows: the maximum potential magnitude of an earthquake whose fault zone activity period is the Late Pleistocene in the tectonic area is determined by calculating the regression relationship.

7. A method for assessing earthquake risk in a moderate-to-strong earthquake zone according to claim 1, characterized in that: The principle for determining the maximum potential magnitude of a fault zone in the tectonic area whose activity period is before the Quaternary period is as follows: it is determined according to the background magnitude of the seismic zone.

8. A seismic risk assessment system for moderate to strong earthquake zones, characterized by: include: Partition construction module: used to partition the earthquake zone to obtain multiple structural zones; Fitting calculation module: used to fit the historical earthquake and modern small and medium earthquake data in each tectonic zone to obtain the magnitude-frequency relationship curve, and calculate the occurrence rate, probability of occurrence and recurrence interval of any magnitude earthquake in each tectonic zone; Equal weight distribution module: For each tectonic zone, the weights of each magnitude level, the occurrence rate of any magnitude earthquake in each tectonic zone, the probability of earthquake occurrence, and the recurrence interval are distributed to each fault zone using the spatial smoothing method. The spatial smoothing method is a post-spatial smoothing method, which includes: The historical destructive earthquake catalog of the tectonic area and the regional network earthquake catalog are compiled to determine the magnitude bins that need to be assigned to each tectonic area. Based on the magnitude-frequency relationship, the annual occurrence rate of earthquakes at all levels in the tectonic area is calculated. The tectonic area is divided into uniform grids, and the seismicity of each grid is calculated as a weight. The moving average method is used to calculate the average value of seismicity within similar grids to smooth the data. Based on the weights, the statistically obtained annual occurrence rate of earthquakes of any magnitude in each tectonic area, the probability of earthquake occurrence, and the recurrence interval are then assigned to each fault zone without exceeding the maximum potential magnitude. The calculation formula of seismic activity is as follows: ； in, is the seismic activity, For the magnitude.

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