Methods and Systems for Seismic Hazard Assessment of Urban Direct-Strike Faults

Abstract

This invention discloses a method and system for assessing seismic hazard of urban direct-slip faults, belonging to the field of seismic hazard assessment technology. The method includes: collecting and preprocessing seismic data, wherein the seismic data includes seismic activity data, geological and geophysical data, topographic data, and engineering geological data; modeling a three-dimensional fault to determine seismic activity; simulating ground motion using SFFM (Scattered Finite Fault Method) based on localized parameters; performing seismic hazard analysis using PSHA (Probabilistic Seismic Hazard Analysis); and comparing the results of SFFM with the results of PSHA and verifying their consistency. This invention solves the technical problems of inaccurate hazard assessment results, poor interpretability, and unfavorable disaster scenario analysis in commonly used seismic hazard assessment methods in the prior art.

Description

Technical Field

[0001] This invention relates to the field of seismic hazard assessment technology, and in particular to a method and system for assessing seismic hazard along a direct-downward fault in an urban area. Background Technology

[0002] Existing technologies mainly employ the following two methods for seismic hazard assessment, and these two methods have the following main drawbacks:

[0003] (a) Empirical attenuation relationship method

[0004] This method is essentially a statistical regression model based on historical earthquake observation data. Its core lies in establishing the mathematical relationship between ground motion parameters and basic earthquake parameters and distance parameters. In practical applications, assessors substitute the potential earthquake magnitude of the target fault and the distance from the field point to the fault into these empirical equations to estimate the expected ground motion intensity. The main drawbacks are as follows:

[0005] Limitation 1: These empirical relationships are highly dependent on the datasets used to fit them. For regions like Yancheng, located on the eastern coast with thick overburden and lacking extensive strong earthquake records, the geological structure and site conditions differ significantly from the empirical relationships used to build the models. Directly applying models from other locations is likely to result in significant deviations due to incompatibility.

[0006] Second drawback: This method cannot accurately simulate complex near-field effects. Essentially, it simplifies the entire fault rupture process into a single point or line source, and its model framework lacks parameters describing the rupture process and fault geometry. Therefore, it cannot effectively simulate some of the real effects during an earthquake, such as the directional effects of rupture, hanging wall effects, and the complex influence of complex fault coupling relationships on seismic wave propagation.

[0007] Deficiency 3: The results are poorly interpretable. Because this method lacks a clear description of the fault rupture process, the prediction results are derived from data fitting rather than the objective rupture process, making it difficult for engineers and decision-makers to understand the specific causes of the risk and the sources of uncertainty.

[0008] (II) Traditional probabilistic seismic hazard analysis methods

[0009] This method is currently the most widely used probabilistic framework in seismic zoning and seismic design of engineering projects. By considering all potential seismic sources, all possible seismic events, and their probabilities of occurrence, it calculates the probability that ground motion parameters in a specified area will exceed a certain threshold within a given timeframe, ultimately generating a probabilistic ground motion parameter zoning map. Its advantages lie in its highly objective overall evaluation of a specific area and its ability to consider the coupling effects of multiple faults. However, it has the following main drawbacks:

[0010] Limitation 1: The ambiguity of this method for specific earthquake scenarios makes it unable to meet the needs of refined seismic fortification. The original design intent of probabilistic seismic hazard analysis was to provide statistical average risk under long-term, multi-source combined effects. Its calculation process "averages" all possibilities, and the output results are probabilities and expected values, which do not correspond to any specific, real earthquake event.

[0011] Second drawback: Although the probabilistic framework of probabilistic seismic hazard analysis is advanced, its core component, the General Ground Motion Prediction Equation (GMPE), is essentially still an empirical attenuation relationship. Therefore, all prediction biases of GMPE under near-field and complex geological conditions will be incorporated into the probabilistic calculations of probabilistic seismic hazard analysis and affect the final hazard assessment results.

[0012] Thirdly, the results lack intuitive visualization, which is not conducive to disaster scenario analysis and can only be used for pre-earthquake regional assessment. The output of probabilistic seismic hazard analysis (PSHA) is probability and expected value, rather than a simulation that considers the actual rupture process. It cannot provide a continuous spatial distribution map of the seismic field and it is difficult to intuitively show how seismic waves propagate from faults and how basin amplification effects occur. This makes it difficult to construct disaster scenarios and conduct emergency drills based on PSHA results.

[0013] Therefore, there is an urgent need for a method and system for assessing the seismic hazard of urban direct-down faults, in order to solve the technical problems of inaccurate hazard assessment results, poor interpretability, and unfavorable disaster situation analysis in the existing commonly used seismic hazard assessment methods. Summary of the Invention

[0014] This invention provides a method and system for assessing the seismic hazard of urban direct-down faults, in order to solve the technical problems of inaccurate hazard assessment results, poor interpretability, and unfavorable conditions for subsequent disaster situation analysis in commonly used seismic hazard assessment methods in the prior art.

[0015] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0016] This invention provides a method for assessing the seismic hazard of urban areas along direct-strike faults, comprising:

[0017] S1: Collect earthquake data and perform preprocessing, wherein the earthquake data includes: earthquake activity data, geological and geophysical data, topographic data and engineering geological data;

[0018] S2: Model three-dimensional faults to determine seismic activity;

[0019] S3: Earthquake motion simulation is performed using SFFM based on localized parameters, wherein SFFM is the stochastic finite fault method;

[0020] S4: Seismic hazard analysis is performed using PSHA, where PSHA is the probabilistic seismic hazard analysis method;

[0021] S5: Compare the results of SFFM with the results of PSHA, and verify their consistency.

[0022] Furthermore, in S1, the preprocessing includes:

[0023] The seismic data is cleaned to remove outliers and duplicate data;

[0024] The earthquake data is standardized to make data from different sources and with different dimensions comparable and to ensure the control of variables.

[0025] The seismic data is interpolated by using spline interpolation to fill in missing data, making the data smooth and continuous.

[0026] The earthquake data is converted, a coordinate system is unified, and it is formatted as a raster.

[0027] Furthermore, S2 includes:

[0028] Based on shallow seismic exploration, drilling combined profiles, and high-precision topographic mapping, a parametric model of the target fault is constructed.

[0029] The maximum potential magnitude was determined by employing a triple constraint method of "empirical formula - paleoseismic evidence - tectonic analogy";

[0030] A time-dependent probabilistic recurrence model is introduced to calculate the average recurrence interval of characteristic earthquakes based on fault slip rate and coseismic displacement.

[0031] Furthermore, the method of using a triple constraint of "empirical formula - paleoseismic evidence - tectonic analogy" to determine the maximum potential magnitude includes:

[0032] The magnitude range can be estimated using the empirical relationship between fault length, rupture area, and coseismic displacement.

[0033] By combining the coseismic displacement and elapsed time obtained from paleoseismic trenches, the earthquake moment formula is used for verification; by analogy with known strong earthquakes with similar tectonic backgrounds in the region, a maximum potential earthquake magnitude is determined.

[0034] Furthermore, S3 includes:

[0035] Construct a parametric model;

[0036] Simulate multiple fracture scenarios;

[0037] For each scenario, the seismic motion contribution of all sub-faults to the regular grid points on the ground surface is calculated, and the seismic acceleration time history of each grid point is synthesized by considering the time history superposition of rupture propagation and wave propagation.

[0038] Output high-resolution spatial distribution maps of ground motion parameters under different rupture scenarios, intuitively demonstrating the strong spatial non-uniformity, directional effect, and attenuation effect of near-field ground motion.

[0039] Furthermore, S4 includes:

[0040] Divide seismic zones and determine seismic activity parameters;

[0041] Delineate potential seismic source zones and determine the upper limit of magnitude;

[0042] Determine the relationship between ground motion parameters and distance attenuation;

[0043] Seismic hazard calculation is performed using a dedicated seismic hazard analysis program.

[0044] Furthermore, S5 includes:

[0045] The spatial distribution of PGA under a specific rupture scenario simulated by the SFFM is spatially superimposed with the PGA distribution of the long regression period of the PSHA.

[0046] The system compares the attenuation curves of the ground motion parameters obtained by the SFFM and PSHA with fault distance.

[0047] Based on the consistency verification results, the spatial non-uniformity and directional effect mechanism of ground motion under specific rupture scenarios revealed by the SFFM are fused with the long-term exceedance probability provided by the PSHA.

[0048] This invention also provides a system for assessing the seismic hazard of urban direct-strike faults, comprising:

[0049] Collection module: used to collect earthquake data and perform preprocessing, wherein the earthquake data includes: seismic activity data, geological and geophysical data, topographic data and engineering geological data;

[0050] Modeling module: Used to model three-dimensional faults and determine seismic activity;

[0051] Simulation module: used for earthquake motion simulation using SFFM based on localized parameters, wherein SFFM is the stochastic finite fault method;

[0052] Analysis module: used for seismic hazard analysis using PSHA, where PSHA is the probabilistic seismic hazard analysis method;

[0053] Verification module: Used to compare the results of SFFM with the results of PSHA and verify their consistency.

[0054] Compared with the prior art, the technical solution disclosed in this invention has the following beneficial effects:

[0055] This invention determines seismic activity by modeling three-dimensional faults; it uses SFFM to simulate ground motion based on localized parameters and PSHA to perform seismic hazard analysis, comparing the results of SFFM and PSHA and verifying their consistency. Compared with existing technologies, this invention breaks through the simplification assumptions of traditional models, significantly improving the near-field assessment effect; it achieves a dual revelation of earthquake rupture mechanisms and probabilistic risks, resulting in a more comprehensive evaluation conclusion; it provides targeted outputs corresponding to scenarios and probabilities, offering strong engineering guidance; and it establishes a standardized analysis process, promoting the advancement of industry methods and the refinement of standards. This invention solves the technical problems of inaccurate hazard assessment results, poor interpretability, and unfavorable conditions for subsequent disaster scenario analysis in commonly used seismic hazard assessment methods in existing technologies. Attached Figure Description

[0056] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0057] Figure 1 This is a schematic diagram of the process for assessing the seismic hazard of urban direct-strike faults provided in an embodiment of the present invention;

[0058] Figure 2 A schematic diagram illustrating the principle of the urban direct-down fault seismic hazard assessment method provided in this embodiment of the invention:

[0059] Figure 3 This is a schematic diagram of potential source partitioning provided in an embodiment of the present invention;

[0060] Figure 4 a is a result diagram of SFFM at a focal depth of 10km provided in an embodiment of the present invention;

[0061] Figure 4 b is a diagram showing the SFFM results at a focal depth of 15 km provided in an embodiment of the present invention;

[0062] Figure 4 c is a graph showing the PSHA results at a focal depth of 10 km provided in an embodiment of the present invention.

[0063] Figure 4d is a result diagram of PSHA at a focal depth of 15km provided in an embodiment of the present invention;

[0064] Figure 5 a is a schematic diagram of quantized near-field vibration attenuation provided in an embodiment of the present invention;

[0065] Figure 5 b is a schematic diagram of quantized near-field vibration attenuation provided in an embodiment of the present invention;

[0066] Figure 5 c is a schematic diagram of quantized near-field vibration attenuation provided in an embodiment of the present invention;

[0067] Figure 5 d is a schematic diagram of quantized near-field vibration attenuation provided in an embodiment of the present invention;

[0068] Figure 6 A schematic diagram of the seismic hazard curve provided for an embodiment of the present invention. Detailed Implementation

[0069] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0070] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0071] This invention provides a method for assessing the seismic hazard of urban areas directly under faults, which can solve the technical problems of inaccurate hazard assessment results, poor interpretability, and unfavorable conditions for subsequent disaster situation analysis in commonly used seismic hazard assessment methods in the prior art.

[0072] like Figures 1-6 As shown, Embodiment 1 of the present invention provides a method for assessing the seismic hazard of a city's direct-down fault, such as... Figures 1-2 As shown, it includes:

[0073] S1: Collect earthquake data and perform preprocessing, wherein the earthquake data includes: earthquake activity data, geological and geophysical data, topographic data and engineering geological data.

[0074] In this embodiment, the seismic data includes seismic activity data (such as historical earthquake catalogs, earthquake sequence data, and precise location results of minor earthquakes), geological and geophysical data (such as geometric parameters of active faults, slip rates, and paleoseismic event records), topographic data (such as topographic elevations), and engineering geological data (such as site shear wave velocities, site classifications, and site magnification factors). These data are acquired through various means, including geological surveys, earthquake monitoring, topographic mapping, and remote sensing imagery, to ensure the comprehensiveness and accuracy of the data.

[0075] Preprocessing includes: cleaning the seismic data to remove outliers and duplicate data; and standardizing the seismic data to make data from different sources and units comparable and to ensure the control of variables.

[0076] The seismic data is interpolated using spline interpolation to fill in missing data, making the data smooth and continuous. The seismic data is then transformed to a unified coordinate system and formatted as a raster. These preprocessing steps ensure data quality and consistency, providing reliable data support for subsequent model construction and analysis.

[0077] S2: Modeling three-dimensional faults to determine seismic activity. S2 includes:

[0078] Based on shallow seismic exploration, drilling combined profiles, and high-precision topographic mapping, a parametric model of the target fault is constructed. The key innovation is to clearly identify and digitize the geometric segmentation characteristics of the fault (such as the strike reversal of the eastern and western segments of the Yancheng-Nanyang'an fault and the dip change of the Nankou-Sunhe fault), and to independently set parameters such as strike, dip angle, and dip angle for each segment, abandoning the traditional assumption of a single linear fault.

[0079] A triple-constraint method of "empirical formula - paleoseismic evidence - tectonic analogy" was adopted to determine the maximum potential magnitude. Specifically, this includes: first, estimating the magnitude range using various empirical relationships such as fault length, rupture area, and coseismic displacement; second, verifying the magnitude using the seismic moment formula by combining the coseismic displacement and elapsed time obtained from paleoseismic trenches; and finally, comparing the magnitude with known strong earthquakes with similar tectonic backgrounds in the region to comprehensively determine a maximum potential earthquake magnitude that is both empirically reasonable and engineering conservative.

[0080] A time-dependent probabilistic recurrence model is introduced to calculate the average recurrence interval of characteristic earthquakes based on fault slip rate and coseismic displacement. The core improvement lies in the introduction of a time-dependent probabilistic model that considers the elapsed time since the last event and calculates the conditional probability of the characteristic earthquake occurring within different future time periods (e.g., 50 years, 100 years, 200 years). This provides differentiated risk indicators for projects with different service lives. The introduction of this model also facilitates the comparison of SFFM and PSHA results over the same period.

[0081] S3: Seismic motion simulation using SFFM based on localized parameters, wherein SFFM is the stochastic finite fault method; including:

[0082] The parametric model is constructed through the following steps: First, the entire fault plane is discretized into a dense sub-fault grid along its strike and dip. Second, using microseismic monitoring data and active fault detection results within the target area, stress drop, Kappa value, and quality factor are regionally calibrated to ensure that the high-frequency characteristics conform to local realities, thus helping to achieve targeted simulation of near-field ground motion effects in the specified area. Third, considering complex structures, asperities are introduced into the model, typically placed at locations where the fault strike or dip changes significantly, to simulate the non-uniformity of slip distribution on the fault plane. For areas with sedimentary basins (such as eastern Yancheng), the site magnification factor is increased by 0.1 to 0.3 times to match the basin waveguide effect.

[0083] Simulating multi-fracture scenarios involves setting multiple rupture initiation points during the simulation. These are typically located at the midpoint of each fault segment or at points of unevenness or depression to ensure the comprehensiveness of the simulated seismic effects. Furthermore, both unidirectional and bidirectional rupture propagation modes are set to facilitate comprehensive analysis and conclusions. (Note: Multiple rupture initiation points do not necessarily mean multiple rupture initiation points simultaneously; generally, there is only one rupture initiation point.)

[0084] For each scenario, the seismic motion contribution of all sub-faults to the regular grid points on the ground surface is calculated, and the seismic acceleration time history of each grid point is synthesized by considering the time history superposition of rupture propagation and wave propagation.

[0085] Output high-resolution spatial distribution maps of ground motion parameters under different rupture scenarios, intuitively demonstrating the strong spatial non-uniformity, directional effect, and attenuation effect of near-field ground motion.

[0086] S4: Seismic hazard analysis using PSHA, where PSHA is a probabilistic seismic hazard analysis method. S4 includes:

[0087] Seismic zones are delineated and seismic activity parameters are determined. Specifically, the target area is delineated to its corresponding seismic zone, the b-value obtained from regional seismic statistics is used, and the annual average occurrence rate v4 of the potential seismic source area is calculated based on the length or area proportion of the potential seismic source area in the regional seismic statistics.

[0088] Potential seismic source zones are delineated, and upper magnitude limits are determined. Specifically, based on fault geometry, potential seismic source zones are generally defined as the area between the minimum fault distance of 5 km and the maximum fault distance of 10 km. The maximum potential earthquake magnitude of the fault, as assessed in the examples provided in this specification, is then used as the upper magnitude limit.

[0089] Determine the relationship between ground motion parameters and distance attenuation. Specifically, select a ground motion prediction equation (GMPE) that is applicable to the tectonic environment and site type of the target area. For example, give priority to the attenuation relationship that has been locally verified in the "China Ground Motion Parameter Zoning Map" (GB18306-2015) to ensure the regional applicability of the attenuation relationship.

[0090] Seismic hazard calculations were performed using a dedicated seismic hazard analysis program. Specifically, the refined input parameters were integrated, and calculations were performed within a consistent high-precision grid (0.01° × 0.01°). The calculation results included peak ground acceleration (PGA) corresponding to return periods of 475 years (basic ground motion) and 2475 years (rare ground motion), as well as PGA corresponding to the maximum potential recurrence interval of the fault. These results served as a benchmark for consistency comparison with the results of the stochastic finite fault method (SFFM) simulation, together forming a comprehensive assessment conclusion combining probabilistic and deterministic approaches.

[0091] S5: Compare the results of SFFM with the results of PSHA, and verify their consistency.

[0092] S5 includes: performing spatial overlay analysis on the PGA spatial distribution under a specific rupture scenario simulated by SFFM and the PGA distribution with a long regression period of PSHA; specifically, performing spatial overlay analysis on the PGA spatial distribution under a specific rupture scenario simulated by SFFM and the PGA distribution with a long regression period of PSHA (e.g., 2600 years). The focus is on examining whether the high-value areas, morphological characteristics, and strike extensions of the two distributions in the near-field region of the fault match. A highly consistent spatial distribution pattern can prove the rationality of the SFFM model parameter settings and provide dual evidence for defining key seismic defense zones for engineering projects.

[0093] The system compares the attenuation curves of seismic motion parameters obtained from SFFM and PSHA with fault distance; specifically, it analyzes the similarities and differences in the trends of the two in the near-field rapid attenuation segment and the far-field slow attenuation segment, and explores their intrinsic relationship with fault rupture mechanism and site amplification effect. This joint analysis can reveal the true propagation law of seismic waves and provide differentiated guidance for seismic fortification strategies in areas with different distances.

[0094] Based on the consistency verification results, the spatial non-uniformity and directional effect mechanism of ground motion under specific rupture scenarios revealed by the SFFM are fused with the long-term exceedance probability provided by the PSHA to form a comprehensive seismic hazard zoning result that includes both the ground motion effect image of the "worst credible scenario" and the quantification of the "long-term risk level", providing a unified and complete scientific basis for different decision-making needs.

[0095] Compared with existing technologies, the seismic hazard assessment process provided in the above embodiments has the following advantages:

[0096] (i) Breaking through the simplification assumptions of traditional models, significantly improving the near-field evaluation effect.

[0097] For urban direct-strike faults, the accuracy of near-field (within approximately 10 kilometers) ground motion assessment is crucial, but it is also a weakness of traditional methods. This specification's embodiments achieve a breakthrough in accuracy through three refined modeling techniques: (1) Geometric refinement: abandoning the assumption of a single linear fault, independently modeling faults with turning points or segments (such as the eastern and western segments of the Yancheng fault); (2) Parameter localization: calibrating key source parameters (such as stress drop Δσ) using regional microseismic data to ensure the model conforms to local site characteristics; (3) Consideration of site effects: explicitly considering the waveguide amplification effect of sedimentary basins (such as the soft soil layer in eastern Yancheng) in the model. These measures significantly improve the simulation capability for complex phenomena such as the spatial distribution of near-fault peak ground acceleration (PGA) and abrupt attenuation zones, resulting in a higher degree of agreement between the predicted results and actual earthquake rupture.

[0098] (ii) It achieves a dual revelation of earthquake rupture mechanism and probabilistic risk, resulting in a more comprehensive evaluation conclusion.

[0099] Traditional methods often force users to choose between "deterministic physical scenarios" and "statistical probabilistic risks," leading to biased decision-making information. This specification overcomes this limitation by coupling the Stochastic Finite Fault Method (SFFM) with a probabilistic seismic hazard analysis (PSHA) method. SFFM considers the actual ground motion process, including how faults rupture and seismic waves propagate, accurately characterizing the spatial non-uniformity, directional effects, and depth effects of near-fault ground motions; while PSHA provides long-term probabilistic risk spectra beyond ground motions of varying intensities. These two methods mutually validate and complement each other, making the final assessment more reliable and providing crucial information support for parameters and standards for seismic design in urban planning and major engineering projects.

[0100] (iii) It provides targeted outputs corresponding to scenarios and probabilities, which have strong engineering guidance significance.

[0101] Seismic hazard assessment results can simultaneously meet the seismic fortification standards required for engineering seismic design. On the one hand, ground motion parameters with different regression periods calculated by PSHA and aligned with codes (such as 475-year and 2475-year periods) can be directly used as probabilistic benchmarks for regional seismic fortification. On the other hand, the results of various rupture scenarios simulated by SFFM provide input ground motions with clear seismic occurrence patterns and significant spatial differences for dynamic time-history analysis of major projects or lifeline projects. This dual-method output mechanism enables seismic design to meet both universal code requirements and to conduct refined verification and protection for specific high-risk scenarios.

[0102] (iv) Establish standardized analysis processes to promote the advancement of industry methods and refinement of standards.

[0103] This specification outlines the seemingly complex multi-method, multi-angle coupling process into a standardized and reproducible technical workflow, encompassing data acquisition, parameter determination, ground motion simulation, probabilistic analysis, and consistency verification. This workflow not only enhances the scientific rigor and reliability of individual project assessments but also has significant industry-wide application value. Its results can be directly used for: (1) optimizing seismic codes: providing solid case studies and theoretical support for determining design ground motions in near-fault areas and refining near-field effect coefficients; (2) guiding risk assessment practices: providing a complete technical paradigm for other cities to conduct similar direct-down fault hazard assessments, helping to promote the transformation of the entire industry from experience-based judgment to model- and data-driven refined assessments.

[0104] The key technical points of the embodiments in this specification are as follows:

[0105] 1. Multi-scale coupled modeling technology for complex faults: In view of the complex geometry and large variation of overlying soil in urban direct-subsurface faults, key technologies such as refined fault geometry modeling, local calibration of regional source parameters, and direct characterization of basin site effects are systematically coupled to construct an integrated parameter model of "source-path-site" that can simultaneously reflect source complexity, path specificity, and site amplification effect. This is the foundation for achieving high-precision simulation.

[0106] 2. Two-way verification and fusion technology for seismic motion simulation and probabilistic seismic hazard analysis: The core lies in the design of a comparative verification mechanism using multiple seismic recurrence cycles as time nodes. The maximum credible ground motion results from SFFM simulation are compared with the long-recurrence period ground motion distribution calculated in PSHA based on the same magnitude and recurrence interval, performing multi-faceted consistency analysis on spatial morphology, magnitude, and attenuation characteristics. This technology ensures that the two methods mutually verify each other in terms of spatial variation mechanisms and statistical significance, forming a reliable assessment closed loop.

[0107] 3. Integrated Seismic Hazard Zoning and Representation Technology Based on Consistent Results: Building upon the validation of consistency, this technology innovatively integrates high-resolution ground motion field details from SFFM simulations with probabilistic risk levels from PSHA outputs to generate a novel integrated seismic hazard zoning map. This map not only displays ground motion intensity zones under different exceedance probabilities but also overlays potential ground motion characteristics (such as strong ground motion directions) under specific rupture scenarios in key areas, achieving a unification of risk quantification and physical characterization.

[0108] Compared with the prior art, the embodiments in this specification have the following outstanding technical features:

[0109] 1. Evaluation framework of integration and cross-verification: The protection systematically integrates the ground motion simulation of the stochastic finite fault method with the probabilistic assessment of probabilistic seismic hazard analysis, and for the first time conducts multi-dimensional consistency cross-verification of the results of the two (especially the results of long regression periods) in terms of space, magnitude and attenuation characteristics, and finally forms a unified risk assessment conclusion.

[0110] 2. Refined segmentation modeling technology for complex faults: When modeling, the core step is to segment the fault based on the actual geometric turning point (such as change of strike) or activity difference of the urban direct-down fault (e.g., the east-west segment of the Yancheng fault, the north-central-south segment of the Nankou-Sunhe fault), and set parameters independently for each segment to simulate the ground motion field, so as to accurately characterize the control of non-uniform faults on the ground motion field.

[0111] 3. Localized calibration technology for source parameters: This is a core aspect of protecting the practice of using data such as microseismic monitoring specific to the target area to perform regionally specific calibration of key source parameters (especially stress drop Δσ and kappa value κ) in stochastic finite fault simulation, replacing the direct use of global or regional average parameters, thereby significantly improving the realism of near-field simulation.

[0112] 4. Long regression period probabilistic analysis for the maximum potential earthquake: In probabilistic seismic hazard analysis, the distribution of ground motions in long regression periods (such as 2600 years or 3500 years) that strictly correspond to the recurrence interval of the maximum potential earthquake of the target fault is specifically calculated, and this result is used as a "baseline scenario" for direct comparison with the results of deterministic physical simulation.

[0113] 5. Construction technology of seismic motion simulation set with multiple rupture scenarios: In seismic motion simulation, a "maximum credible seismic motion scenario set" covering the main uncertainties can be constructed by setting different rupture initiation points and rupture propagation directions (such as unidirectional and bidirectional) in the system. This provides a specific method for major projects to input seismic motions with diversified and clearly defined physical meanings.

[0114] 6. Verification criteria for consistency comparison between the two methods: The high-resolution spatial distribution map of ground motion (physical field) obtained by the random finite fault method is systematically superimposed and compared with the corresponding long regression period ground motion distribution map (probability field) obtained by probability analysis. The specific technical link is to take the consistency of the high value area morphology, range and attenuation trend as the core verification criteria for the rationality of the model and the reliability of the results.

[0115] Based on the same approach, Embodiment 2 of this specification also provides a system for assessing the seismic hazard of urban direct-strike faults, comprising:

[0116] Collection module: used to collect earthquake data and perform preprocessing, wherein the earthquake data includes: seismic activity data, geological and geophysical data, topographic data and engineering geological data;

[0117] Modeling module: Used to model three-dimensional faults and determine seismic activity;

[0118] Simulation module: used for earthquake motion simulation using SFFM based on localized parameters, wherein SFFM is the stochastic finite fault method;

[0119] Analysis module: used for seismic hazard analysis using PSHA, where PSHA is the probabilistic seismic hazard analysis method;

[0120] Verification module: Used to compare the results of SFFM with the results of PSHA and verify their consistency.

[0121] In Embodiment 3 of the invention, taking the Nankou-Sunhe Fault as an example, the seismic hazard assessment process is as follows:

[0122] (I) Potential source delineation: Generally, the scope of potential source delineation in seismic hazard analysis is defined as having a minimum fault distance greater than 5 km and a maximum fault distance not exceeding 10 km. Figure 3 As shown.

[0123] (II) Spatial Distribution Consistency Analysis and Depth Effect Consistency Analysis: Taking the Nankou-Sunhe Fault as an example, under a 3500-year return period, the spatial overlap between the high PGA value area calculated by PSHA and the simulation results of SFFM is relatively high. In the middle section of the Shahe-Sunhe area, due to the stable control of the central section's concave-convex body, the phenomenon of concentrated high PGA values ​​in the middle section of the fault is completely consistent with both methods. At a depth of 10km, the PGA values ​​obtained by both methods are stable at 520-530gal, forming a continuous high-value zone along the fault strike. In the northern section, the Changping Baishan area is affected by stress concentration caused by the superposition of flower-shaped structural branch faults, and the local PGA peak values ​​are highly consistent (SFFM 530gal, PSHA 520gal). In the southern section, the western Tongzhou area has a slightly reduced overlap due to the uncertainty of the distribution of concealed structures and the amplification effect of the 200m thick Quaternary sedimentary layer, but the core high-value range is still consistent, which can define the high-risk area with engineering significance and meet the requirements of engineering risk assessment. Figure 4 As shown in a, 4b, 4c, and 4d.

[0124] (III) Quantification of Near-Field Seismic Attenuation: Taking the Nankou-Sunhe Fault as an example, the attenuation of its near-field seismic effects is quantified. In a 10km depth scenario, the PGA attenuation rate within 5km of the fault reaches 29 gal / km, rapidly decreasing from 525 gal at the fault to 380 gal; within a horizontal distance of 5-10km from the fault, with increasing seismic wave propagation distance and energy diffusion, the attenuation rate slows to 16 gal / km, and the PGA decreases from 390 gal to 310 gal. For example... Figure 5 As shown in a, 5b, 5c, and 5d.

[0125] (iv) Seismic hazard curve, such as Figure 6 As shown, the Yancheng-Nanyang fjord is used as an example. The simulation results of the PSHA method with a recurrence period of 475 years, a recurrence period of 2600 years, and SFFM are marked in the figure. The SFFM simulation results are in high agreement with the PSHA results with a recurrence period of 2600 years, which verifies the accuracy of SFFM simulation in capturing the core features of ground motion response.

[0126] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0127] The block diagrams of devices, apparatuses, devices, and systems involved in this invention are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0128] It should also be noted that in the apparatus, device, and method of the present invention, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered as equivalent solutions of the present invention.

[0129] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of the invention. Therefore, the invention is not intended to be limited to the aspects shown herein, but rather to be carried out within the widest scope consistent with the principles and novel features disclosed herein.

[0130] It should be understood that the qualifying terms "first", "second", "third", "fourth", "fifth" and "sixth" used in the description of the embodiments of the present invention are only used to more clearly illustrate the technical solutions and are not intended to limit the scope of protection of the present invention.

[0131] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of the invention to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations therein.

Claims

1. A method for assessing the seismic hazard of a city's direct-down fault, characterized in that, include: S1: Collect earthquake data and perform preprocessing, wherein the earthquake data includes: earthquake activity data, geological and geophysical data, topographic data and engineering geological data; S2: Model three-dimensional faults to determine seismic activity; S3: Earthquake motion simulation is performed using SFFM based on localized parameters, wherein SFFM is the stochastic finite fault method; S4: Seismic hazard analysis is performed using PSHA, where PSHA is the probabilistic seismic hazard analysis method; S5: Compare the results of SFFM with the results of PSHA, and verify their consistency.

2. The method for assessing seismic hazard of urban direct-down faults according to claim 1, characterized in that, In step S1, the preprocessing includes: The seismic data is cleaned to remove outliers and duplicate data; The earthquake data is standardized to make data from different sources and with different dimensions comparable and to ensure the control of variables. The seismic data is interpolated by using spline interpolation to fill in missing data, making the data smooth and continuous. The earthquake data is converted, a coordinate system is unified, and it is formatted as a raster.

3. The method for assessing seismic hazard of urban direct-down faults according to claim 1, characterized in that, S2 includes: Based on shallow seismic exploration, drilling combined profiles, and high-precision topographic mapping, a parametric model of the target fault is constructed. The maximum potential magnitude was determined by a triple constraint method of "empirical formula - paleoseismic evidence - tectonic analogy"; A time-dependent probabilistic recurrence model is introduced to calculate the average recurrence interval of characteristic earthquakes based on fault slip rate and coseismic displacement.

4. The method for assessing seismic hazard of urban direct-down faults according to claim 1, characterized in that, The method employing a triple constraint approach—empirical formula, paleoseismic evidence, and tectonic analogy—to determine the maximum potential magnitude includes: The magnitude range can be estimated using the empirical relationship between fault length, rupture area, and coseismic displacement. By combining the coseismic displacement and elapsed time obtained from paleoseismic trenches, the earthquake moment formula is used for verification; by analogy with known strong earthquakes with similar tectonic backgrounds in the region, a maximum potential earthquake magnitude is determined.

5. The method for assessing seismic hazard of urban direct-down faults according to claim 1, characterized in that, S3 includes: Construct a parametric model; Simulate multiple fracture scenarios; For each scenario, the seismic motion contribution of all sub-faults to the regular grid points on the ground surface is calculated, and the seismic acceleration time history of each grid point is synthesized by considering the time history superposition of rupture propagation and wave propagation. Output high-resolution spatial distribution maps of ground motion parameters under different rupture scenarios, intuitively demonstrating the strong spatial non-uniformity, directional effect, and attenuation effect of near-field ground motion.

6. The method for assessing seismic hazard of urban direct-down faults according to claim 1, characterized in that, S4 includes: Divide seismic zones and determine seismic activity parameters; Delineate potential seismic source zones and determine the upper limit of magnitude; Determine the relationship between ground motion parameters and distance attenuation; Seismic hazard calculation is performed using a dedicated seismic hazard analysis program.

7. The method for assessing seismic hazard of urban direct-down faults according to claim 1, characterized in that, S5 includes: The spatial distribution of PGA under a specific rupture scenario simulated by the SFFM is spatially superimposed with the PGA distribution of the long regression period of the PSHA. The system compares the attenuation curves of the ground motion parameters obtained by the SFFM and PSHA with fault distance. Based on the consistency verification results, the spatial non-uniformity and directional effect mechanism of ground motion under specific rupture scenarios revealed by the SFFM are fused with the long-term exceedance probability provided by the PSHA.

8. The urban direct-down fault seismic hazard assessment system according to claim 1, characterized in that, include: Collection module: used to collect earthquake data and perform preprocessing, wherein the earthquake data includes: seismic activity data, geological and geophysical data, topographic data and engineering geological data; Modeling module: Used to model three-dimensional faults and determine seismic activity; Simulation module: used for earthquake motion simulation using SFFM based on localized parameters, wherein SFFM is the stochastic finite fault method; Analysis module: used for seismic hazard analysis using PSHA, where PSHA is the probabilistic seismic hazard analysis method; Verification module: Used to compare the results of SFFM with the results of PSHA and verify their consistency.

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