Seismic oscillation simulation and landslide analysis method for DEM with different resolutions

Abstract

The invention relates to the technical field of seismic landslide prediction, and relates to a seismic oscillation simulation and landslide analysis method for DEMs with different resolutions, comprising the following steps: acquiring DEMs with different resolutions in a target area, establishing a site model of the target area, and acquiring topographic and geological parameters; acquiring earth crust wave velocity parameters and seismic source construction parameters of the target area, and constructing a kinematic seismic source model; carrying out seismic oscillation simulation under each resolution DEM based on a spectral element method, and obtaining a seismic oscillation record; and according to the obtained topographic and geological parameters, applying Newmark rigid body slide block analysis to obtain critical acceleration of the target area under the DEM of each resolution, and analyzing to obtain earthquake landslide risks of the target area under the DEM of different resolutions. The method can accurately reflect the influence of DEM with different resolutions on seismic oscillation simulation and seismic landslide evaluation, is high in calculation efficiency, is simple in modeling method, and can improve the rationality of seismic oscillation simulation and seismic landslide evaluation under the condition of lack of actually measured seismic oscillation information.

Description

Technical Field

[0001] The invention relates to the technical field of earthquake landslide prediction, and in particular to a method for earthquake motion simulation and landslide analysis oriented to DEMs with different resolutions. Background Art

[0002] Strong earthquakes in mountainous areas often induce a large number of secondary geological disasters, among which landslides can cause buildings to be buried or destroyed, and landslides can flow into and block the main river to form barrier lakes, which are important factors that aggravate earthquake disasters. Therefore, earthquake landslide disasters are an important geological risk that restricts regional development and stability. Scientific prediction of earthquake landslides is of great significance to regional infrastructure design, post-earthquake emergency rescue and restoration and reconstruction, especially in earthquake-prone areas.

[0003] The existing related technologies mainly include spectral element seismic motion simulation and Newmark rigid body slider analysis. Earthquake landslides often occur near rupture fault areas. In actual situations, due to the complexity of regional terrain, seismic motion response monitoring is difficult to carry out extensively, resulting in a lack of seismic motion record input required for landslide assessment. In this context, the spectral element method can effectively simulate seismic wave propagation while fully considering the complexity of local dynamic response, obtain the dynamic response of different sites in actual earthquakes, and thus provide effective input for earthquake landslide assessment. Therefore, it has become one of the effective methods to make up for this shortage; Newmark rigid body slider analysis can fully consider the occurrence mechanism of earthquake collapse landslides, and use the analysis results of slope instability mechanism and sliding process for quantitative classification of collapse landslide hazards. Its good timeliness and reliability make this method applicable to the assessment and prediction of earthquake landslides.

[0004] In the above methods, the use of DEM (Digital Elevation Model) data is crucial to the accuracy of calculations for earthquake simulation and landslide analysis, but there is still limited research on how DEM resolution affects calculation accuracy. Under current conditions, the accuracy of the final calculation results is far from ideal due to the difference in DEM resolution. Summary of the invention

[0005] The purpose of the present invention is to propose an earthquake landslide analysis method based on simulated ground motion, which can accurately reflect the influence of DEM resolution on ground motion simulation and earthquake landslide assessment, has high calculation efficiency and simple modeling method, can improve the validity of calculation results, and provides an important means for the prediction of earthquake landslides.

[0006] Based on the above purpose, the present invention proposes the following technical solutions:

[0007] A method for ground motion simulation and landslide analysis based on DEMs with different resolutions includes the following steps:

[0008] S1. Obtain DEMs of different resolutions in the target area, process the DEMs of different resolutions, establish a site model of the target area and obtain topographic and geological parameters;

[0009] S2, obtaining the crustal wave velocity parameters and source structure parameters of the target area, and constructing a kinematic source model;

[0010] S3, based on the spectral element method, carry out ground motion simulation under DEM of various resolutions to obtain ground motion records;

[0011] S4. Based on the acquired topographic and geological parameters, the Newmark rigid body slider analysis is used to obtain the critical acceleration under different resolution DEMs of the target area, that is, the critical threshold of landslide.

[0012] S5. According to the earthquake motion record obtained in step S3 and the landslide critical threshold obtained in step S4, the earthquake landslide risk of the target area under DEMs of different resolutions is analyzed and obtained.

[0013] Preferably, the topographic geological parameters in step S1 include slope distribution, aspect distribution, lithology data of the target area and its mechanical properties. The lithology data and its mechanical properties can be obtained from an existing lithology database, and the mechanical properties of the soil can be determined from a corresponding mechanical property relationship table.

[0014] Preferably, in step S2, the required crustal wave velocity parameters are obtained through seismic inversion calculation according to artificial seismic surveys and natural earthquake monitoring, including the shear wave propagation velocity and compression wave propagation velocity of each soil layer medium; on the basis of obtaining the source structural parameters, the final kinematic source model is calculated and output according to the strike, dip and sub-source standard seismic moment and slip angle of the seismic fault.

[0015] In the present invention, the basic idea of ​​conducting earthquake motion simulation is to divide the calculation area into finite units, use the pseudo-spectral method on each unit, and express the approximate solution of the unit as a truncated orthogonal polynomial expansion by configuring unevenly distributed nodes in each unit, and finally solve to obtain the global approximate solution, thereby completing the numerical simulation of the regional wave propagation process. In the construction of the kinematic source model, the sub-source slip velocity and rupture velocity are set, and the sub-source rise time is obtained according to the sub-source slip amount and slip velocity, and the rupture time of each sub-source is finally determined in combination with the relative position of the sub-source and the initial rupture point.

[0016] The specific process of constructing the kinematic source model is as follows:

[0017] The standard seismic moment of each sub-source is solved according to the empirical formula of source rise time and standard seismic moment. The specific formula is as follows:

[0018]

[0019] Where: T r is the rise time, and M0 is the standard seismic moment.

[0020] The moment tensor M of each sub-source is calculated according to the following formula:

[0021]

[0022] The values ​​in the sub-source moment tensor are calculated as follows:

[0023]

[0024] Where: M0 is the standard seismic moment; δ is the fault dip; λ is the sub-source slip angle; φ is the fault strike. When establishing the source model, the seismogenic fault is discretized into a certain number of sub-sources in consideration of the rupture of the seismogenic fault, so that the source is set as multiple dynamic sub-source seismic inversion superposition to construct a kinematic source model. Then, the seismic motion simulation work is carried out based on the site model to obtain the simulated seismic motion records under DEMs of various resolutions.

[0025] Preferably, in step S3, the seismic records include, but are not limited to: amplitude, frequency spectrum, duration characteristics of seismic motion, etc. The acquired seismic records are processed so as to provide seismic load input in subsequent landslide analysis.

[0026] In the present invention, the basic idea of ​​landslide assessment is to assume that a rigid block slides on an inclined base. When the acceleration exceeds a threshold value (yield value), the condition for the sliding block to slide is met and the block starts to slide. c The static safety factor can be indirectly solved by comparing the stress state of the slider under static and seismic dynamic conditions and using the infinite slope method to calculate the static safety factor. The formula is as follows:

[0027] a c =(F s -1)gsinα

[0028] In the above formula, the static safety factor F s The calculation of mainly depends on the inclination of the landslide surface and the physical parameters of the rock and soil:

[0029]

[0030] Where: a t is the acceleration value corresponding to time t, a c is the critical acceleration, F s is the static safety factor; g is the acceleration due to gravity; is the effective internal friction angle, c′ is the effective cohesion, α is the slope angle, γ is the unit weight of the material, and γ wis the unit weight of water; t is the thickness of the sliding body, and m is the ratio of the saturated plate thickness.

[0031] Based on the earthquake acceleration time history curve data, the critical acceleration a c Calculate the accumulated displacement of the slider. The acceleration value is less than or equal to a C The part of the slider does not produce displacement, but will be greater than the critical acceleration a c By integrating the acceleration time history with respect to t, the displacement time history curve of the slider corresponding to the time can be obtained. The formula is as follows:

[0032]

[0033] According to the acquired topographic and geological parameters, the Newmark rigid body slider analysis is used to obtain the critical threshold of landslide under DEM of different resolutions in the target area; the analysis is carried out in combination with the seismic motion records and landslide critical threshold obtained by simulation to obtain the earthquake landslide risk of the target area under DEM of different resolutions.

[0034] Preferably, in step S5, based on the earthquake record, the Newmark rigid body slider analysis method can be used to calculate the cumulative displacement D of the landslide at each point in the target area under each resolution DEM. n .

[0035] Preferably, in step S5, a landslide hazard classification standard and a slope instability probability function are used to carry out a landslide hazard assessment.

[0036] The landslide hazard classification standards are as follows:

[0037] Low risk: 0cm <D n <2cm

[0038] Medium risk: 2 cm <D n <5cm

[0039] High risk: 5cm <D n <10cm

[0040] Very high risk: D n >10cm.

[0041] Preferably, the slope instability probability function is:

[0042]

[0043] In the above formula, P(f) represents the cumulative displacement of the slope under earthquake action, which is D n The probability of landslide occurrence. It can be seen from this formula that as the landslide cumulative displacement D n As the value increases, the possibility of slope instability increases, and the maximum value is 0.335.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention can accurately reflect the impact of different resolution DEMs on ground motion simulation and earthquake landslide assessment, has high computational efficiency and simple modeling method, can fully consider the input ground motion characteristics, and can improve the rationality of ground motion simulation and earthquake landslide assessment under the condition of lack of measured ground motion information. It provides an important means for the prediction of earthquake landslides and provides a more reliable scientific basis for the disaster prevention and mitigation design of regional infrastructure. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A schematic flow chart of a method for simulating ground motion and analyzing landslides based on DEMs with different resolutions provided in an embodiment of the present invention;

[0047] Figure 2 It is a definition diagram of Newmark rigid body slider analysis in an embodiment of the present invention;

[0048] Figure 3 A slope distribution calculation difference map of the target area under the DEMs of different resolutions provided in the embodiment of the present invention;

[0049] Figure 4 In the figure: (a) is a velocity wave field cloud diagram of the x-direction simulation of the spectral element seismic motion in the study area provided in an embodiment of the present invention; (b) is a velocity wave field cloud diagram of the y-direction simulation of the spectral element seismic motion in the study area provided in an embodiment of the present invention; (c) is a velocity wave field cloud diagram of the z-direction simulation of the spectral element seismic motion in the study area provided in an embodiment of the present invention;

[0050] Figure 5 A comparison diagram of acceleration time history calculation results of spectral element ground motion simulation in the study area provided in an embodiment of the present invention;

[0051] Figure 6 A comparison diagram of peak acceleration calculation results of spectral element ground motion simulation in the study area provided in an embodiment of the present invention;

[0052] Figure 7 A comparison diagram of the cumulative displacement distribution results of the Newmark slider in the study area provided in the embodiment of the present invention;

[0053] Figure 8 A comparison chart of landslide hazard area ratio results of the study area provided in the embodiment of the present invention;

[0054] Fig. 9 A comparison diagram of slope instability probability calculation results of a study area provided in an embodiment of the present invention;

[0055] Fig.10This is a comparison and verification diagram of the landslide assessment and the measured results in the embodiment of the present invention. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiment of the present invention. Obviously, the described embodiment is intended to explain the present invention and cannot be understood as limiting the present invention.

[0057] Example

[0058] The embodiment of the present invention provides a method for simulating earthquake motion and analyzing landslides based on DEMs with different resolutions, such as Figure 1 The method specifically comprises the following steps:

[0059] In step (1), DEMs of different spatial resolutions of the target area are obtained, and the DEMs of various resolutions are processed to establish a site model of the target area and obtain topographic and geological parameters; wherein the topographic parameters include the slope distribution and aspect distribution of the target area, and the geological parameters mainly include the lithological data and mechanical properties of the target area.

[0060] For example, after obtaining corresponding data for the study area, the embodiment of the present invention can construct a site model of the study area taking into account the actual terrain under the DEM of each resolution through modeling software such as Rhino and Civil3D, for subsequent earthquake simulation calculations. At the same time, terrain parameter calculations are performed on the ArcGIS platform to obtain and compare the slope distribution under the DEM of each resolution of the target area, such as Figure 3 The lithology data and its mechanical properties can be obtained based on the existing lithology database, and the mechanical properties of the soil can be determined based on the corresponding mechanical property relationship table.

[0061] In step (2), the crustal wave velocity parameters and source structure parameters of the target area are obtained to construct a kinematic source model.

[0062] It can be understood that the crustal wave velocity parameters required by the embodiment of the present invention can be obtained through seismic inversion calculation in combination with artificial seismic survey and natural earthquake monitoring, including the shear wave propagation velocity and compression wave propagation velocity of each soil layer medium; on the basis of obtaining the source structural parameters, the embodiment of the present invention can calculate and output the final kinematic source model according to the strike, dip and sub-source standard seismic moment and slip angle of the seismic fault. Considering the rupture phenomenon of the seismic fault, the embodiment of the present invention sets the source model as a plurality of dynamic sub-source seismic inversion superpositions, and the moment tensor M of each sub-source can be obtained by equations (1) and (2), wherein the standard seismic moment M0 in equation (2) can be calculated by equation (3):

[0063]

[0064] Where: M0 is the standard seismic moment; δ is the fault dip; λ is the sub-source slip angle; φ is the fault strike; T r is the rise time, and M0 is the standard seismic moment.

[0065] In step (3), the ground motion simulation is carried out under the DEM of each resolution based on the spectral element method to obtain the ground motion record;

[0066] In one embodiment of the present invention, the acquired simulated earthquake records include, but are not limited to: earthquake amplitude, spectrum, duration characteristics, etc. The acquired earthquake records are processed to provide earthquake load input in subsequent landslide analysis.

[0067] In step (4), the Newmark rigid body slider analysis is used to obtain the critical landslide thresholds under DEMs of various resolutions in the target area based on the acquired topographic and geological parameters.

[0068] Specifically, the landslide analysis is carried out using the Newmark rigid body slider analysis, which is widely used in earthquake landslide analysis and risk prediction, such as Figure 2 As shown in . It is assumed that the landslide body is a rigid body and the deformation inside the landslide body is not considered. When the ground vibration acceleration exceeds the critical acceleration of the landslide, that is, the critical threshold of the landslide, the landslide body will produce permanent displacement, as shown in formula (4). The critical threshold of the landslide can be obtained by formula (5) and (6):

[0069]

[0070] a c =(F s -1)gsinα (5)

[0071]

[0072] Where: a t is the acceleration value corresponding to time t, a c is the critical acceleration, F s is the static safety factor; g is the acceleration due to gravity; is the effective internal friction angle, c′ is the effective cohesion, α is the slope angle, γ is the unit weight of the material, and γ w is the unit weight of water; t is the thickness of the sliding body, and m is the ratio of the saturated plate thickness, which can generally be taken as m=0. c′ and γ can be calculated based on the corresponding lithology data.

[0073] In step (5), calculations are performed based on the simulated seismic records and landslide critical thresholds to obtain the earthquake landslide risk of the target area under DEMs of different resolutions.

[0074] Specifically, the simulated seismic records are processed and input into the above corresponding formulas, and the permanent displacement of each point in the target area under each resolution DEM can be calculated using the Newmark rigid body slider analysis method. The calculation is based on the hazard standard defined by existing results, such as the literature (Rodríguez-Peces, MJ, García-Mayordomo, J., JM, & Jabaloy, A. GIS application for regional assessment of seismically induced slope failures in the Sierra Nevada Range, South Spain, along the Padul Fault. Environmental Earth Sciences). According to the accumulated displacement of the landslide, the hazard level is divided as shown in Table 1. The embodiment of the present invention carries out landslide hazard assessment according to the classification standard.

[0075] Table 1 Landslide hazard classification standards

[0076] Hazard level Grading Standards Low risk <![CDATA[0cm<D n <2cm]]> Medium risk <![CDATA[2cm<D n <5cm]]> High risk <![CDATA[5cm<D n <10cm]]> Very high risk <![CDATA[D n >10cm]]>

[0077] Furthermore, considering that the critical displacements of different types of slope instability are quite different, the cumulative displacement D of the landslide obtained based on the simulation calculation is n The hazard standards defined by existing results can be used for calculation, such as the instability probability function proposed in the literature (Jibson, RW, Harp, EL, & Michael, JAA method for producing digital probabilistic seismiclandslide hazard maps. Engineering Geology) to calculate the slope instability probability of the entire area.

[0078] The embodiment of the present invention calculates the probability of slope instability based on this, and the formula is as follows:

[0079]

[0080] Where: P(f) represents the cumulative displacement of the slope under earthquake action, which is D n The probability of landslide occurrence. It can be seen from this formula that as the landslide cumulative displacement D n As the value increases, the possibility of slope instability increases, and the maximum value is 0.335.

[0081] Taking the 2013 Sichuan-Lushan earthquake as an example, the embodiment of the present invention carries out ground motion simulation of DEMs with different resolutions based on the spectral element method. The ground motion velocity wave field propagation is as follows: Figure 4 As shown. It should be noted that the velocity wave field trends under different resolution DEMs are relatively close. This is because the impact of each resolution DEM on the simulation of seismic motion is mainly reflected in the local area, and has little impact on the overall seismic motion propagation. Therefore, only the calculation results under one resolution DEM are shown. Set the simulated seismic records of the target station and the peak acceleration distribution obtained by calculation as shown in Figure 5 , Figure 6 As shown in the figure, the difference is compared to analyze the impact of different resolution DEM on seismic motion simulation. The terrain parameters such as slope distribution of the target area are obtained, and the critical acceleration of the study area, that is, the critical threshold of landslide, is calculated according to the mechanical properties of the rock and soil in the target area. Combined with the input simulated seismic records and the landslide hazard classification standards and slope instability probability functions used, the landslide hazard assessment is carried out based on the Newmark rigid slider analysis method, as shown in the figure. Figure 7 , Figure 8 and Fig. 9 As shown, the differences are compared to analyze the impact of DEMs with different resolutions on landslide assessment.

[0082] At the same time, the calculation results of the 30m resolution DEM were compared with the landslide distribution of the field survey, such as Fig.10 Shown (by Figure 7 and Fig. 9 It can be seen that the calculation results of other resolution DEM near the epicenter are similar, so they are not compared one by one). From the comparison results, it can be seen that the prediction results of this method are consistent with the actual distribution of earthquake landslides. While deeply analyzing the impact of the data source used in landslide assessment, it also illustrates the rationality of this method for earthquake landslide assessment, which can provide an important reference for post-earthquake emergency rescue.

[0083] Therefore, through the above cases, it can be concluded that the seismic motion simulation and landslide analysis method for DEMs with different resolutions proposed in the embodiment of the present invention can simultaneously calculate and compare the impact of the resolution of different DEM data sources on the seismic motion simulation and landslide assessment results, and can improve the rationality of seismic motion simulation and earthquake landslide assessment under the condition of lack of measured seismic motion information. In addition, the embodiment of the present invention adopts Newmark rigid slider analysis, which can fully consider the input seismic motion characteristics and effectively support the final decision by providing different data calculation results.

[0084] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0085] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present invention belong.

[0086] The above-described embodiments merely express the implementation methods of the present invention, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for ground motion simulation and landslide analysis based on DEMs with different resolutions, characterized in that: The steps include: S1. Obtain DEMs of different resolutions in the target area, process the DEMs of different resolutions, establish a site model of the target area and obtain topographic and geological parameters; S2, obtaining the crustal wave velocity parameters and source structure parameters of the target area, and constructing a kinematic source model; S3, based on the spectral element method, carry out ground motion simulation under DEM of various resolutions to obtain ground motion records; S4. Based on the acquired topographic and geological parameters, the Newmark rigid body slider analysis is used to obtain the critical acceleration under different resolution DEMs of the target area, i.e. the critical threshold of landslide; S5. According to the earthquake motion record obtained in step S3 and the landslide critical threshold obtained in step S4, the earthquake landslide risk of the target area under DEMs of different resolutions is analyzed and obtained.

2. The method for earthquake motion simulation and landslide analysis based on DEMs with different resolutions according to claim 1, characterized in that: The topographic geological parameters in step S1 include slope distribution, aspect distribution, lithology data of the target area and its mechanical properties.

3. The method for earthquake motion simulation and landslide analysis based on DEMs with different resolutions according to claim 1 is characterized in that: In step S2, the required crustal wave velocity parameters are obtained through seismic inversion calculation based on artificial seismic surveys and natural earthquake monitoring, including the shear wave propagation velocity and compression wave propagation velocity of each soil layer medium; on the basis of obtaining the source structural parameters, the final kinematic source model is calculated and output according to the strike, dip and sub-source standard seismic moment and slip angle of the seismic fault.

4. The method for earthquake motion simulation and landslide analysis based on DEMs with different resolutions according to claim 1, characterized in that: In step S3, the earthquake record includes the amplitude, frequency spectrum and duration of the earthquake.

5. The method for earthquake motion simulation and landslide analysis based on DEMs with different resolutions according to claim 1, characterized in that: In step S5, based on the seismic records, the Newmark rigid body slider analysis method can be used to calculate the cumulative displacement D of the landslide at each point in the target area under each resolution DEM. n .

6. The method for earthquake motion simulation and landslide analysis based on DEMs with different resolutions according to claim 5, characterized in that: In step S5, landslide hazard assessment is carried out using the landslide hazard classification standard and the slope instability probability function.

7. The method for earthquake motion simulation and landslide analysis based on DEMs with different resolutions according to claim 6, characterized in that: The landslide hazard classification standards are as follows: Low risk: 0cm <D n <2cm Medium risk: 2 cm <D n <5cm High risk: 5cm <D n <10cm Very high risk: D n >10cm.

8. The method for earthquake motion simulation and landslide analysis based on DEMs with different resolutions according to claim 6, characterized in that: The slope instability probability function is: In the above formula, P(f) represents the cumulative displacement of the slope under earthquake action, which is D n The probability of landslide occurring.

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