Earthquake three-dimensional fault fracture model construction method

Abstract

The invention discloses an earthquake three-dimensional fault fracture model construction method, and relates to the technical field of earthquake fault fracture model construction. The method comprises the following steps: collecting surface trace, tendency, dip angle and sliding angle parameters of active fracture; determining the geometric dimension of the fracture surface according to the relation between the moment magnitude of the set earthquake and the regional empirical relationship and in combination with the earth crust structure and the sedimentary layer thickness constraint; a crack-free and continuous underground three-dimensional fault curved surface is constructed through a deep mapping mechanism; and on the curved surface, determining the spatial position and range of the seismic fracture surface according to the depth of the initial fracture point and the proportion of the trend to the tendency. According to the method, the geometric simplification defect of a traditional rectangular fracture surface model is overcome, the physical authenticity of a seismic source model and the precision of high-frequency seismic oscillation simulation are remarkably improved, and the method is suitable for set seismic scene construction, historical seismic reconstruction and seismic risk assessment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of earthquake fault rupture model construction, and particularly relates to a method for constructing a three-dimensional earthquake fault rupture model. BACKGROUND

[0002] Reliable ground motion prediction is the cornerstone of mitigating earthquake disasters and conducting engineering seismic fortification. Currently, ground motion simulation generally uses a source model based on a point source or a simplified rectangular rupture surface. This type of model is widely used because of its simple mathematical processing and high computational efficiency, but the inherent geometric oversimplification problem is increasingly prominent.

[0003] Currently, ground motion simulation forcibly approximates a complex underground fault system as a single or multiple discontinuous rectangular planes, completely ignoring the real continuous curved surface characteristics of the fault in three-dimensional space, such as bending, turning and undulating. This distortion of geometric shape leads to significant deviations in the physical nature of the model from the real source, especially in the near-field region of a large earthquake, and cannot accurately depict the key control effect of fault geometry on the spatial distribution of ground motion.

[0004] The defects of existing earthquake rupture models are not only limited to the geometric level, but also directly lead to bottlenecks in engineering applications. Since the simplified model cannot truly reflect the coupling effect of rupture propagation and fault geometry, its accuracy is severely insufficient when simulating high-frequency ground motion. High-frequency ground motion is the main factor causing structural damage and destruction. The simplified model cannot reproduce the strong spatial variability of ground motion in the near-fault region, such as the hanging-wall and footwall effect and the rupture directionality effect, which directly affects the reliability and accuracy of major engineering projects (such as nuclear power plants, dams and long-life line projects) in seismic risk assessment and the construction of earthquake scenarios.

[0005] In summary, the technology for improving the physical reality and engineering applicability of ground motion simulation is an important bridge connecting seismogeology, geophysics and earthquake engineering, and can provide a more physically based and high-fidelity source input for scientific research and engineering applications. However, the development of this technology also faces great challenges:

[0006] First, how to integrate multi-disciplinary, multi-scale (from geological exploration to geophysical exploration) heterogeneous data to construct a three-dimensional fault geometry model that meets both geological facts and numerical simulation requirements; second, how to reasonably embed a rupture process that conforms to physical laws in the model, which involves a deep understanding and mathematical representation of the complex source physical mechanism.

[0007] Therefore, the present application provides a method for constructing a three-dimensional earthquake fault rupture model to solve the above technical problems. SUMMARY

[0008] The present application aims to provide a three-dimensional fault rupture model construction method, which comprehensively considers the three-dimensional fault rupture model construction method of regional active fault characteristics, crustal structure and source physical process, so as to improve the physical authenticity and engineering applicability of seismic motion simulation, and solve the problems of existing technology in geometric modeling simplification and insufficient physical fidelity.

[0009] To solve the above technical problems, the present application is realized by the following technical scheme:

[0010] The present application is a three-dimensional fault rupture model construction method, comprising the following steps:

[0011] S1: obtaining the surface trace coordinates, inclination and dip angle, and sliding angle information of the target active fault based on the database; wherein the database is the 1:400000 active fault database V2022 of China and adjacent areas, the active fault data of the earthquake active fault exploration data center, or the regional earthquake safety report, etc.;

[0012] S2: determining the length and width of the rupture surface according to the empirical relationship between the moment magnitude and the rupture area and the rupture length, the crustal structure constraint, and the average sliding amount; the empirical relationship is an empirical formula between the moment magnitude and the rupture area and the rupture length based on the source parameter statistical data of earthquakes;

[0013] S3: based on the surface trace, inclination and dip angle, sediment layer thickness, and brittle crust depth, the surface trace control points are projected and mapped underground through a deep mapping mechanism to construct a continuous underground three-dimensional fault surface without cracks;

[0014] S4: on the three-dimensional fault surface, the spatial position of the starting rupture point is determined according to the depth of the starting rupture point, the proportion along the strike and the inclination, and the spatial position and range of the earthquake rupture surface are determined according to the length and width of the rupture surface.

[0015] Further, the crustal structure constraint is the constraint of the maximum rupture width, and the maximum rupture width W max is:

[0016] ;

[0017] wherein, ξ=5.9, 0.5, W max is the maximum rupture width, H c , H sed respectively represent the crustal thickness and the overburden thickness, and δ is the dip angle of the rupture surface.

[0018] Further, the deep mapping mechanism comprises:

[0019] For the section of the surface trace as the outward fan-shaped feature, each control point of the surface trace is mapped to two deep control points based on the first mapping function;

[0020] For the section of the surface trace as the inward fan-shaped feature, each control point of the surface trace is mapped to one deep control point based on the second mapping function;

[0021] Based on all the deep control points mapped, a three-dimensional fault surface is generated by surface interpolation.

[0022] Further, the determination method of the outward fan-shaped and inward fan-shaped features is as follows:

[0023] For the fault with the dip angle not being 90°, the fan-shaped type is determined according to the included angle of the continuous line segment of the surface trace along the strike in the direction of the dip;

[0024] When the included angle is greater than 180°, the outward fan-shaped feature is determined;

[0025] When the included angle is less than 180°, the inward fan-shaped feature is determined.

[0026] Further, the first mapping function and the second mapping function are respectively as follows:

[0027] The first mapping function is defined as calculating the coordinates after moving a specific distance along a specific azimuth angle with the control point of the surface trace as the center; and the second mapping function is defined as solving the end point coordinates of the intersection line of two spatial intersecting rectangular planes.

[0028] Further, the proportional value range of the initial rupture point along the direction of the dip is as follows:

[0029] Wherein, Y hyp is the proportion of the initial rupture point along the direction of the dip, H hyp is the depth of the initial rupture point, H sed is the thickness of the overburden, W is the width of the rupture surface, W max is the maximum rupture width, and δ is the dip angle of the rupture surface.

[0030] Further, the depth of the initial rupture point is determined based on the statistical characteristics of the focal depth of the historical earthquakes on the active fault or determined by using the regional analogy method.

[0031] Further, the method for obtaining the longitude and latitude coordinates of the initial rupture point is as follows:

[0032] Based on the epicenter position, the fault geometric parameters, the depth of the initial rupture point and the proportions along the strike and the direction of the dip, the longitude and latitude coordinates of the initial rupture point are located on the three-dimensional fault surface by back calculation.

[0033] Further, in S2, after determining the length and width of the rupture surface, fault grid division is further conducted, and the fault grid division method comprises the following steps:

[0034] The length dl and the width dw of the sub-fault grid are automatically selected according to the length L and the width W of the rupture surface;

[0035] L and W are adjusted to satisfy that the fault grid division number is an integer, and the average slip amount is adjusted on the basis of satisfying that the seismic moment is unchanged.

[0036] Further, the underground three-dimensional fault surface constructed is a smooth surface obtained through a spline surface interpolation method.

[0037] The present application has the following beneficial effects:

[0038] The present application collects the surface trace, tendency, dip angle and slip angle parameters of the active fault; determines the geometric size of the rupture surface according to the moment magnitude of the set earthquake and the regional experience relationship, and combines the crust structure and the sedimentary layer thickness constraint; constructs the underground three-dimensional fault surface without cracks and continuous through a deep mapping mechanism; and determines the spatial position and range of the earthquake rupture surface on the surface according to the depth of the starting rupture point, the proportion along the strike and the tendency. The present application overcomes the geometric simplification defects of the traditional rectangular rupture surface model, significantly improves the physical authenticity of the source model and the accuracy of the high-frequency ground motion simulation, and is suitable for setting earthquake scenario construction, historical earthquake reconstruction and earthquake risk assessment. The present application is suitable for the source model construction of the historical earthquake rupture process reconstruction or the set earthquake scenario.

[0039] Of course, implementing any product of the present application does not necessarily need to achieve all the advantages described above at the same time. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0041] Figure 1 The technical flow chart for determining the geometric size of the earthquake rupture surface of the present application;

[0042] Figure 2 The effect schematic diagram of the three-dimensional fault rupture surface of the present application The technical flow chart for determining the geometric size of the earthquake rupture surface of the present application;

[0043] Figure 3 The schematic diagram of the two types of fan surfaces of the present application;

[0044] Figure 4Figure 2 is a schematic diagram of surface trace latitude and longitude coordinates.

[0045] Figure 5 Figure 3 is a three-dimensional rupture model diagram of the 1679 Sanhe-Pingguo earthquake. DETAILED DESCRIPTION

[0046] In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular architectures, techniques, etc. in order to provide a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application can be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known methods, devices, circuits, and

[0047] It will be understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0048] It is also to be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items, and that the term "at least one of' denotes one, or a plurality of, or any combination of the listed items.

[0049] As used in the description of the application and the appended claims, the term "if' can be interpreted to mean "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrase "if it is determined" or "if [a described condition or event] is detected" can be interpreted to mean "upon determining" or "in response to determining" or "upon [the described condition or event] being detected" or "in response to [the described condition or event] being detected," depending on the context.

[0050] In addition, the terms "first," "second," "third," etc. are used herein only to describe different instances of elements, and are not intended to imply or create an ordinality between elements.

[0051] Reference within the specification of this application to "one embodiment" or "some embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in additional embodiments," and so on, in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily referring to one or more particular embodiments that differ from other embodiments. The terms "including," "comprising," "having," and variations thereof are meant to encompass the items listed thereafter, but do not exclude other items from also being present. Unless otherwise indicated, the terms "including," "comprising," "having," and variations thereof are meant to encompass the items listed thereafter, but do not exclude other items from also being present.

[0052] Embodiment One:

[0053] The application is a method for constructing a three-dimensional fault rupture model of an earthquake, comprising the following steps:

[0054] Step S1: Obtain the surface trace coordinates, tendency and dip angle, and slip angle information of the target active fault based on a database; wherein the database is the 1:400000 active fault database V2022 of China and adjacent regions, the active fault data of the Seismic Active Fault Exploration Data Center, or a regional seismic safety report, etc.

[0055] Step S2: Determine the length and width of the rupture surface according to the empirical relationship between the moment magnitude and the rupture area and the rupture length, and in combination with the average slip amount, and the crustal structure constraint;

[0056] Step S3: Based on the surface trace, the tendency and dip angle, the sedimentary layer thickness, and the brittle crust depth, the surface trace control points are projected and mapped underground through a deep mapping mechanism to construct a continuous three-dimensional fault surface without cracks;

[0057] Step S4: On the three-dimensional fault surface, determine the spatial position of the initial rupture point according to the depth of the initial rupture point, the proportion along the strike and the tendency, and according to the length and width of the rupture surface, determine the spatial position and range of the earthquake rupture surface.

[0058] It is suitable for engineering and scientific research applications such as seismic motion simulation, seismic hazard assessment, setting earthquake scenario construction, and seismic damage prediction.

[0059] Embodiment Two:

[0060] The application is a method for constructing a three-dimensional fault rupture model of an earthquake, based on Embodiment One, the active fault information collection and parameter determination of this embodiment comprises the following steps:

[0061] S11: Latitude and longitude coordinates of surface traces: According to the published active fault database, such as: China and adjacent areas 1:400000 active fault database V2022, active fault data of earthquake activity fault exploration data center or regional seismic safety report, etc., the latitude and longitude coordinates of the surface traces of the active fault of interest are collected, and for some historical earthquakes, the position of the seismogenic fault can also be determined by referring to the surface rupture field investigation data;

[0062] S12: Dip and inclination: For the dip and inclination of the fault, it is necessary to comprehensively determine on the basis of sufficient active fault exploration data, according to macroscopic seismic damage investigation, geological exploration profile, drilling data, deep exploration results, small earthquake precise positioning, focal mechanism solution, etc.

[0063] S13: Sliding angle: According to geological survey, historical earthquake focal mechanism solution, tectonic stress field, etc. Comprehensive determination of fault properties, clear fault movement mode and set fault average sliding angle λ, including pure left-lateral strike-slip λ~0°, left-lateral strike-slip dominated thrust fault λ~30°, left-lateral strike-slip dominated normal fault λ~-30°, thrust fault with left-lateral strike-slip λ~60°, normal fault with left-lateral strike-slip λ~-60°, pure normal fault λ~-90°, normal fault with right-lateral strike-slip λ~-120°, right-lateral strike-slip dominated normal fault λ~-150°, pure right-lateral strike-slip λ~180°; For historical large earthquakes, the average sliding angle can be calculated under the condition of field geological measurement of fault displacement.

[0064] Example three:

[0065] The application is a kind of three-dimensional fault rupture model construction method of earthquake, based on example one, the geometric size of the earthquake rupture surface of the embodiment includes the following steps:

[0066] For setting an earthquake, first, the rupture area is estimated according to the empirical relationship between the rupture area and the moment magnitude, and then the rupture length is estimated according to the empirical relationship between the rupture length and the moment magnitude. The rupture width is set as the smaller value of the ratio of the rupture area to the rupture length and the maximum rupture width, wherein the maximum rupture width is related to the regional crustal thickness, the sediment thickness and the rupture fault inclination. The maximum rupture width W max is expressed as:

[0067] ;

[0068] Wherein, ξ=5.9, W max is the maximum rupture width, H c , H sed respectively represent the crustal thickness and the overburden thickness, and δ is the inclination of the rupture surface.

[0069] As an embodiment provided by the present application, preferably, the crust thickness is referenced to a published underground structure velocity model or crust-mantle boundary model, such as CRUST1.0, Sichuan-Yunnan public velocity model 2.0 version SWChinaCVMv2.0, and 3D S-wave velocity model of the middle part of North China Craton. For a blind fault in a thick sedimentary layer area (North China Plain, etc.), the sedimentary layer thickness is set according to the basement structure depth of the research area given by the existing research or the related sedimentary layer thickness empirical model. The influence of the crust medium and site condition on the extension range of the fault three-dimensional model in the depth direction is fully reflected in the determination of the maximum rupture width. S30

[0070] As an embodiment provided by the present application, preferably, if the rupture width is the maximum rupture width, the rupture length needs to be recalculated according to the empirical result of the rupture area. After the rupture length and width are preliminarily determined, the relationship between the length of the seismogenic fault and the empirical rupture length still needs to be further judged. If the empirical rupture length obviously exceeds the length of the seismogenic fault, the rupture length needs to be forcibly set as the length of the seismogenic fault or slightly higher than the length of the seismogenic fault.

[0071] As an embodiment provided by the present application, preferably, for a historical earthquake, if there is no other rupture length related field investigation data, the determination method for setting the earthquake rupture length and width is consistent. If there is a clear earthquake rupture length, such as that given according to the surface rupture investigation data, the result given by the investigation data is adopted. The surface rupture zone data of domestic historical large earthquakes collected by the Seismic Fault Exploration Data Center can be referred to. The rupture width is the smaller value of the rupture width estimated by the maximum rupture width and the aspect ratio empirical relationship. The aspect ratio empirical relationship is:

[0072] Strike-slip earthquake:

[0073] W=2.8537L 0.4976 , L≤50km;

[0074] W=20.0km, L>50km;

[0075] Dip-slip earthquake:

[0076] W=2.172L 0.606 , L≤86km;

[0077] W=33.0km, L>86km;

[0078] After the rupture fault size is determined, the average slip amount is calculated according to the formula M0=μDLW of the seismic moment, wherein μ=ρβ 2 ​, and p, b are the density and velocity of the crustal medium, which can be determined by referring to the published underground structure velocity model, M0 is a physical quantity measuring the absolute size of the earthquake, the unit is Newton-meter, D represents the average slip amount, L and W are the length and width of the rupture surface.

[0079] As an embodiment provided by the present application, preferably, after the length and width of the rupture surface are determined, fault grid division is further performed, and the fault grid division method comprises the following steps:

[0080] The length dl and width dw of the sub-fault grid are automatically selected according to the length L and width W of the rupture surface;

[0081] L and W are adjusted to meet the integer number of fault grid division, and the average slip amount is adjusted on the basis of meeting the constant seismic moment;

[0082] wherein the grid size should be greater than 1.0 km, and dl and dw are automatically selected according to L, W and the set minimum size.

[0083] Embodiment four:

[0084] The present application is a method for constructing a three-dimensional fault rupture model of an earthquake, and based on embodiment one, the underground three-dimensional fault surface construction of the present embodiment comprises the following steps:

[0085] Based on the surface trace, the inclination and dip angle, the sedimentary layer thickness and the brittle crust depth, the surface trace control point is projected and mapped to the underground to construct a continuous underground three-dimensional fault surface without cracks;

[0086] The rupture surface of the earthquake source is set to be a three-dimensional continuous fault surface formed by the joint constraint of the fault surface trace, the fault inclination and dip angle δ, the thickness H sed of the surface covering soil layer and the thickness H bc of the brittle crust area, which meets the geometric shape of the rupture surface modeled by a fan-shaped surface, is continuous and has no physical discontinuity in the brittle crust range, and the intersection line of the extension direction of the surface and the surface is completely overlapped with the fault surface trace. Therefore, the core problem of determining the spatial position of the rupture surface is to give the relative position of the starting rupture point on the rupture fault surface on the basis of the known fault basic information and the reasonable setting of the starting rupture point, and further simulate the range of the rupture surface on the continuous three-dimensional fault surface underground.

[0087] As an embodiment provided by the present application, preferably, to avoid the disconnected (the included angle between the two continuous surface traces along the strike direction in the tendency direction is greater than 180 o ) or staggered overlap (the included angle between the two continuous surface traces along the strike direction in the tendency direction is less than 180 o ) of the extension rupture surface of the zigzag type surface trace underground when the dip angle is not 90 o , the following steps are further included in the method for constructing a three-dimensional fault rupture model of an earthquake.When the angle between any two segments of the surface trace along the strike in the tendency direction is greater than 180 o , the length of the bottom of the fan-shaped surface is greater than the length of the top, which is called an outward expanding fan-shaped surface, and vice versa, the length of the bottom of the fan-shaped surface is greater than the length of the top, which is called an inward contracting fan-shaped surface, which is different from the existing three-dimensional fault model. The existing model still uses discontinuous curved surfaces or overlapping continuous curved surfaces. Since the length of the curved surface varies with the depth, the present application assumes that the rupture length given based on the empirical relationship is the rupture length at the depth corresponding to the starting rupture point.

[0088] As an embodiment provided by the present application, preferably, according to the set of longitude and latitude coordinates of the surface trace control points, the fault tendency and the dip angle, the surface trace coordinates are projected along the tendency direction according to the dip angle to obtain a series of depth mapping coordinates of the surface trace at the starting rupture depth and at a series of equidistant depths in the depth range of the sedimentary layer burial depth-fragile crust region along the tendency.

[0089] As an embodiment provided by the present application, preferably, the determination method of the outward expanding fan-shaped surface and the inward contracting fan-shaped surface is as follows:

[0090] For the fault with a dip angle not equal to 90°, the type of the fan-shaped surface is determined according to the angle between the continuous line segments of the surface trace along the strike in the tendency direction;

[0091] When the angle is greater than 180°, the outward expanding fan-shaped surface is determined;

[0092] When the angle is less than 180°, the inward contracting fan-shaped surface is determined.

[0093] As an embodiment provided by the present application, preferably, the deep mapping mechanism comprises:

[0094] For the section of the surface trace with the outward expanding fan-shaped feature, each control point of the surface trace is mapped into two deep control points based on a first mapping function;

[0095] For the section of the surface trace with the inward contracting fan-shaped feature, each control point of the surface trace is mapped into one deep control point based on a second mapping function;

[0096] Based on all the deep control points mapped, a three-dimensional fault curved surface is generated through curved surface interpolation.

[0097] As an embodiment provided by the present application, preferably,

[0098] When the dip angle is not equal to 90 o , each control point i of the surface trace with the outward expanding fan-shaped feature (the angle >180 o ) has two depth mapping control points, namely

[0099]

[0100] where x, y represent longitude and latitude respectively; subscript i represents the i-th surface trace control point, arranged in the strike direction; j1 and j2 represent the mapping control points corresponding to the depth H k of the i-th surface trace control point, arranged in the strike direction; δ i represents the dip angle of the fault surface trace segment defined by the i-th and i+1-th surface trace control points, and the mapping relationship f1 is defined as a relationship formula for calculating the longitude and latitude coordinates at the center of the surface trace control point (coordinates x i , y i ), the azimuth angle θ i -90 o (θ i is the strike angle of the fault surface trace segment defined by the i-th and i+1-th surface trace control points) and the distance H k / tan(δ i ).

[0101] As an embodiment provided by the present application, preferably, when the dip angle is not 90 o , for each control point i in the surface trace that embodies the inward fan-shaped feature (included angle <180 o ), there is a depth mapping control point, that is:

[0102]

[0103] where x, y represent longitude and latitude respectively; subscript i represents the i-th surface trace control point, arranged in the strike direction; j represents a mapping control point corresponding to the depth H k of the i-th surface trace control point; δ i represents the dip angle of the fault surface trace segment defined by the i-th and i+1-th surface trace control points, and the mapping relationship f2 is defined as solving the intersection line coordinates of two spatial intersecting surfaces, and the specific steps are determining the equations of the planes where the two rectangles are located, then calculating the intersection line of the two planes (an infinitely long straight line), and finally determining the end point coordinates of the intersection line segment by solving the intersection points of the intersection line and the boundaries of the two rectangles.

[0104] Through the two mapping point mechanisms, the geometric conflict problem caused by the dip angle of the non-vertical fault is solved while the continuity of the surface is maintained, and the construction of the continuous three-dimensional spatial surface without cracks and overlap is realized. Further, according to the deep mapping coordinates, a non-smooth underground three-dimensional fracture surface is constructed, and an underground three-dimensional smooth surface can also be obtained through the spline surface interpolation method.

[0105] Example Five:

[0106] The application is a method for constructing a three-dimensional fault rupture model of an earthquake. Based on embodiment one, the method for constructing a three-dimensional rupture surface of an earthquake comprises the following steps:

[0107] Step S401: setting the depth H of the starting rupture point hyp Setting

[0108] Data-driven method: according to the statistical characteristics of the focal depth of historical earthquakes on the active fault, the statistical mean is used as the depth H of the starting rupture point of the earthquake hyp ;

[0109] Regional analogy method: if there is no sufficient historical earthquake information available for the active fault, the statistical results of the historical earthquake depth in the region are used to set H hyp .

[0110] Step S402: setting the proportion Y of the starting rupture point along the dip direction hyp Constraint

[0111] To ensure that the earthquake rupture surface does not penetrate the ground surface or the brittle crust bottom boundary, according to the maximum rupture width W max , the overburden thickness H sed , and the fault dip angle δ, the value range of the proportion Y of the starting rupture point along the rupture width at the given starting rupture point depth is determined, that is,

[0112] where Y hyp is the proportion of the starting rupture point along the dip direction, H hyp is the depth of the starting rupture point, H sed is the thickness of the overburden, W is the width of the rupture surface, W max is the maximum rupture width, and δ is the dip angle of the rupture surface.

[0113] The maximum value range of Y hyp may be 0-1, where 0 indicates that the starting rupture point is at the top of the rupture surface, and 1 indicates that it is at the bottom of the rupture surface. According to the empirical relationship between the position Y of the starting rupture point along the dip direction and the width W of the rupture surface, Y hyp is determined, and the empirical proportion Y hyp is determined. If Y hyp does not satisfy the value range, Y hyp with the closest value to the empirical proportion in the value range is selected.

[0114] Step S403: determining the position of the starting rupture point

[0115] The latitude and longitude position of the starting rupture point (epicenter position) is not given in advance, and only the starting rupture point is assumed to be located on a certain section of the seismogenic activity fault, which can be a random position (random along the strike direction of the fault trace). The approximate position can be given according to the proportion X of the starting rupture point along the strike direction hyp , the length of the fault surface trace, and the length of the fault. According to the empirical relationship between the position (X) of the starting rupture point along the strike direction and the length L of the rupture surface, X is given hyp , or according to the specific engineering requirements, the rupture directionality of the earthquake is considered to be set.

[0116] The earthquake rupture surface is a three-dimensional continuous surface in the underground constrained by the surface trace, the fault tendency and inclination, the thickness of the surface cover layer, and the range of the brittle crust in the depth direction. The intersection between the three-dimensional continuous surface and the ground surface is the surface trace. For known H hyp , W, Y hyp , δ, H sed , the extension of the simulated rupture surface in the direction of the ground surface should satisfy complete coincidence with the fault surface trace, so as to completely constrain the epicenter position, that is, the starting rupture point set must be on the three-dimensional continuous fault surface in the underground.

[0117] Step S404: earthquake rupture surface determination

[0118] According to the depth and latitude and longitude coordinates of the starting rupture point, the rupture length L, the proportion X of the starting rupture point along the strike direction hyp , and the starting rupture point position, the range of the rupture along the strike in the deep fault mapping is determined, and the two end point coordinates are given. According to the sub-fault width dw, the inclination δ, the fault width W, the depth H hyp of the starting rupture point, and the proportion X of the starting rupture point along the strike direction hyp , the two end point coordinates are mapped to obtain a series of end point mapping coordinates of the sub-fault along the tendency direction on the rupture surface. On the curved surface connecting any end point mapping coordinates of the sub-fault along the tendency, a series of center point coordinates of the sub-fault grid are obtained according to the sub-fault length dl. At the same time, the coordinates of the edge of the rupture fault surface can also be given.

[0119] Embodiment six:

[0120] A three-dimensional rupture model of the Sanhe-Pinggu earthquake in 1679 is constructed, as shown in Figures 1-5 , the present application is a method for constructing a three-dimensional fault rupture model of an earthquake, based on embodiments one to five, the present application comprises the following steps:

[0121] Step S1: active fault information collection and parameter determination, in order to determine the basic geometric and kinematic parameters of the seismogenic fault-Xiamadi fault;

[0122] Fault identification and surface trace extraction:

[0123] According to the authoritative data provided by the 1:400000 active fault database of China and adjacent areas V2022 and the seismic active fault exploration data center, combined with historical earthquake surface rupture survey data, the latitude and longitude coordinate sequence of the surface trace of Xiadui fault is determined, and it is confirmed that the total length of the fault trace is about 49 km, and the overall strike is 40°-45°;

[0124] Fault geometric parameter setting:

[0125] Dip and dip angle: according to the east liu hutundongbeidakeng profile of Xiadui fault, the dip of Xiadui fault is set to SE (southeast), and the dip angle is 71°;

[0126] Slip angle: according to the historical surface displacement data, Xiadui fault is a right-lateral strike-slip fault with normal fault component. According to the strike-slip and dip-slip displacement data, the average slip angle of this earthquake is calculated and set to-141° (normal fault with right-lateral strike-slip characteristics);

[0127] Regional crustal structure parameter determination:

[0128] Sedimentary layer thickness: using the research results of existing technology, the thickness of the upper overburden soil layer H sed is set to 2.0 km.

[0129] Brittle crustal depth H bc : according to the same study, the upper crustal depth in the region is about 21-23 km, and considering the distribution of low-velocity anomaly body, the brittle crustal depth used for model construction is finally determined to be 19.5 km.

[0130] Step S2: determination of the geometric size of the earthquake rupture surface, based on the magnitude and geological constraints, the length and width of the rupture surface are determined.

[0131] Moment magnitude determination:

[0132] The historical surface wave magnitude M S is estimated to be 8.0, and the M S -M W conversion relationship of existing technology is considered, and the seismic moment calculated by the average slip amount 1.28 m through various empirical relationships is comprehensively considered, and finally the moment magnitude of this earthquake is set to 7.13.

[0133] Determination of rupture length L and width W:

[0134] If only according to the empirical relationship, the rupture length corresponding to the moment magnitude 7.13 can reach 244 km, which is far beyond the actual length of Xiadui fault, and does not conform to the geological facts. Therefore, the geological constraints are given priority to, and the rupture length L = 50 km is set, that is, it is considered that the earthquake completely ruptured the Xiadui fault.

[0135] Maximum rupture width calculation: According to the maximum value of rupture width W ma Equation, substituting H bc = 19.5 km, H sed = 2.0 km, δ = 71°, W max = 18.5 km. Finally, the rupture width W = 18.5 km is determined.

[0136] Average slip amount D avg is determined:

[0137] According to the historical surface displacement data (maximum vertical displacement 1.75 m, maximum dextral strike-slip displacement 2.16 m), the maximum combined displacement near Pangzhuang is estimated to be about 2.78 m. According to the statistical relationship between the maximum slip amount and the average slip amount, the average slip amount D avg = 1.28 m of this earthquake is inferred and set. Using the seismic moment formula M0 = μD avg LW, the result is consistent with the set 7.13, ensuring self-consistent parameters.

[0138] Step S3: Construction of underground three-dimensional fracture surface, constructing the continuous three-dimensional geometric shape of Xiadai fault underground.

[0139] Surface type determination:

[0140] According to the surface trace coordinates of Xiadai fault and the SE tendency and 71° inclination, it is determined that the deep mapping conforms to the characteristics of outward expanding fan, and the corresponding mapping function f1 is used for construction.

[0141] Deep mapping point calculation:

[0142] Taking the surface trace control point coordinates as the starting point, according to the tendency and inclination, a series of mapping point coordinates at equal interval depths (from H sed = 2.0 km to H bc = 19.5 km) are calculated underground.

[0143] The mapping function f1 is defined as follows: taking the surface control point as the center, moving a distance of H i / tan(δ i ) along the azimuth θ k - 90° (θ i is the local strike angle), the longitude and latitude coordinates at the depth H k are obtained.

[0144] Three-dimensional surface generation:

[0145] The mapping points at all depths are taken as control points, and a smooth, continuous, and non-cracked or overlapped summer mat fracture three-dimensional surface is generated by using spline surface interpolation algorithm, and the intersection line of the surface and the ground surface is strictly coincident with the known ground trace.

[0146] Step S4: Seismic three-dimensional fracture surface construction, the specific fracture range of this earthquake is determined on the three-dimensional fracture surface.

[0147] Starting fracture point depth H hyp Setting:

[0148] According to the prior art, the focal depth of the region is concentrated at about 10 km. Combined with the statistical distribution of the starting rupture point along the inclination ratio Y hyp (Laplace distribution, peak value is 0.5), the final H hyp = 12 km is set.

[0149] Starting rupture point along the inclination ratio Y hyp Determination and verification:

[0150] When H hyp = 12 km, the corresponding Y hyp = (12-2.0) / 18.5≈0.575.

[0151] Verify that it satisfies the constraint condition, that is: 2.0 / 18.5≈0.11≤0.575≤(19.5-2.0) / 18.5≈0.95, the result is valid.

[0152] Starting rupture point along the strike ratio X hyp and epicenter setting:

[0153] According to the historical research indication of "asymmetric bilateral rupture, the north segment is larger than the south segment", the starting rupture point along the strike ratio X hyp = 0.4, that is, the fracture surface extends about 30 km to the north and about 20 km to the south.

[0154] Combined with the macro-epicenter (Panguangzhuang, 40.0°N, 117.0°E), fault inclination / angle, H hyp and X hyp , the longitude and latitude coordinates of the starting rupture point (epicenter) are accurately calculated on the three-dimensional fault surface as 116.95°E, 39.94°N.

[0155] Fracture surface range determination:

[0156] With the determined starting rupture point as the center, L = 50 km and W = 18.5 km as the size, according to X hyp= 0.4 and Y hyp = 0.575 Determine the extension along strike and dip, and accurately delineate the three-dimensional rupture surface of the earthquake on the constructed three-dimensional fault surface.

[0157] The three-dimensional fault rupture model construction method of the earthquake overcomes the geometric simplification defects of the traditional rectangular rupture surface model, significantly improves the physical authenticity of the source model and the accuracy of high-frequency ground motion simulation, and is suitable for setting earthquake scenarios, reconstructing historical earthquakes, and evaluating seismic risk.

[0158] In the description of the present specification, the description referring to the terms "one embodiment", "an example", "a specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0159] The preferred embodiments of the application disclosed above are only used to help explain the application. The preferred embodiments do not describe all the details and limit the application to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of the present specification. The present specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the application, so that those skilled in the art can well understand and utilize the application. The application is limited only by the claims and their full scope and equivalents.

Claims

1. A method for constructing a three-dimensional fault rupture model for earthquakes, characterized in that, Includes the following steps: S1: Obtain the surface trace coordinates, dip and dip angle, and slip angle information of the target active fault based on the database; S2: Determine the length and width of the rupture surface based on the empirical relationship between moment magnitude and rupture area and rupture length, as well as crustal structural constraints and the average slip. S3: Based on surface traces, dip and dip angle, sedimentary layer thickness, and brittle crust depth, the surface trace control points are projected and mapped to the subsurface through a deep mapping mechanism to construct a crack-free and continuous three-dimensional subsurface fault surface. S4: On the three-dimensional fault surface, the spatial location of the initial rupture point is determined based on the depth of the initial rupture point, the proportion along the strike and the dip, and the spatial location and extent of the earthquake rupture surface are delineated based on the length and width of the rupture surface.

2. The method for constructing a three-dimensional earthquake fault rupture model according to claim 1, characterized in that, The crustal structure constraint is the constraint of the maximum fracture width, where the maximum fracture width W is... max for: ； Where ξ=5.9, The value is 0.5, W max For the maximum fracture width, H c H sed These represent the thickness of the crust and the thickness of the overlying soil layer, respectively, with δ being the dip angle of the rupture surface.

3. The method for constructing a three-dimensional earthquake fault rupture model according to claim 1, characterized in that, The deep mapping mechanism includes: For sections of the surface trace that have an outward fan-shaped feature, each control point of the surface trace is mapped to two deep control points based on the first mapping function; For sections of the surface trace that have an inwardly converging fan-shaped feature, each control point of the surface trace is mapped to a deep control point based on the second mapping function; Based on all the deep control points mapped, a three-dimensional fault surface is generated by surface interpolation.

4. The method for constructing a three-dimensional earthquake fault rupture model according to claim 3, characterized in that, The method for determining the expanding and contracting fan shapes is as follows: For faults with a dip angle not equal to 90°, the fan-shaped type can be determined based on the angle between the continuous line segments of the surface trace along the strike and the dip direction. When the included angle is greater than 180°, it is determined to be an outward-expanding sector; When the included angle is less than 180°, it is determined to be an inward-facing sector.

5. The method for constructing a three-dimensional earthquake fault rupture model according to claim 3, characterized in that, The first mapping function and the second mapping function are respectively: The first mapping function is defined as calculating the coordinates after moving a specific distance along a specific azimuth angle with the control point of the ground trace as the center; the second mapping function is defined as solving for the coordinates of the endpoints of the intersection line of two intersecting rectangular planes.

6. The method for constructing a three-dimensional earthquake fault rupture model according to claim 1, characterized in that, The range of values ​​for the proportion of the initiation fracture point along the dip direction is: Among them, Y hyp H represents the proportion of the initiation point along the dip direction. hyp H represents the depth of the initial fracture point. sed The thickness of the overburden layer, W, is the width of the fracture surface. max δ represents the maximum fracture width, and δ represents the fracture surface dip angle.

7. The method for constructing a three-dimensional earthquake fault rupture model according to claim 1, characterized in that, The depth of the initiation rupture point is determined based on the statistical characteristics of the focal depth of historical earthquakes on the active fault or by using a regional analogy method.

8. The method for constructing a three-dimensional earthquake fault rupture model according to claim 1, characterized in that, The method for obtaining the latitude and longitude coordinates of the initial rupture point is as follows: Based on the epicenter location, fault geometry parameters, the depth of the initial rupture point, and its proportions along the strike and dip, inverse calculations are performed on the constructed three-dimensional fault surface to ensure that the latitude and longitude coordinates of the initial rupture point are located on the three-dimensional fault surface.

9. The method for constructing a three-dimensional earthquake fault rupture model according to claim 1, characterized in that, In S2, after determining the length and width of the rupture surface, fault mesh generation is performed. Fault mesh generation methods include: The length dl and width dw of the sub-fault grid are automatically selected based on the length L and width W of the rupture surface. Adjust L and W to ensure that the number of fault grid divisions is an integer, and adjust the average slip while keeping the seismic moment constant.

10. The method for constructing a three-dimensional earthquake fault rupture model according to claim 1, characterized in that, The constructed underground three-dimensional fault surface is a smooth surface obtained by spline surface interpolation.

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