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Analytical study on the topographic effect of Feitsui canyon
Gao Yufeng, Dai Denghui, Zhang Ning
, Available online  , doi: 10.11939/jass.20210099
The local amplification or attenuation of ground motion is often caused by the surface topography, which is due to the scattering phenomenon when the seismic wave propagates to the local topography. Although the topographic effect was first discovered in the anomalous seismic records, the ground motion data recorded by the topographic influence array are very few. There are five earthquakes recorded by six strong-motion accelerometers deployed along the Feitsui canyon recorded from the Hualien earthquake in 1992. Using our analytical theory of seismic wave propagation around a non-symmetrical V-shaped canyon, the strong motion accelerations of the site were simulated. The influences of topographic effect on the ground motion of the Feitsui canyon are revealed. The comparison between the simulated results and those ground motion accelerations recorded indicates that the proposed analytical theory of seismic wave propagation around V-shaped canyon is suitable for simulating the topographic effects on ground motions.
Research on bandwidth of ground motion simulated using FK approach
Cao Zelin, Tao Xiaxin, Tao Zhengru, Wang Keyi
, Available online  , doi: 10.11939/jass.20210093
The application prospect of ground motion simulation approach is closely related to the effective bandwidth of synthetics. Hence we studied the simulation approach based on the frequency-wavenumber Green’s function (called FK approach), and analyzed the key factors affecting the bandwidth and the treatment measures. On the basis of the calculation principle introduction, we summarized the main factors influencing the ground motion simulated using FK approach, and analyzed the influences of the crustal velocity model on sub-source seismic moment, rupture time and propagation time. Then, we analyzed the ability of the Green’s function to propagate broadband seismic waves, and put forward the recommended values of parameters affecting bandwidth in the calculation of Green’s function. The source time function and the rise time controlling the sub-source slip process are investigated to analyze the ability of source model in FK approach to radiate broadband seismic waves. Results show that the FK approach has the ability to simulate broadband ground motion, provided the parameters and models are reasonable.
Relocation and focal mechanism solutions of the MS6.9 Menyuan earthquake sequence on January 8,2022 in Qinghai Province
Xu Yingcai, Guo Xiangyun, Feng Lili
, Available online  , doi: 10.11939/jass.20220008
On January 8, 2022, an MS6.9 earthquake occurred in Menyuan County, Haibei Prefecture of Qinghai Province. The earthquake ruptured a nearly 22 km long zone and strong tremors were felt through the regions of Qinghai, Gansu and Ningxia Province. In this paper, the early events of the Menyuan MS 6.9 earthquake sequence from January 8 to 12, 2022 were relocated by multi-step locating method. Meanwhile, the focal mechanism and focal depth of mainshock and MS≥3.4 after shocks were inverted by gCAP method. Based on focal mechanism result of the mainshock, the relative shear stress and normal stress on the two nodal planes of the focal mechanism solutions were also calculated under the existing stress field system. The result indicates that the initial rupture depth of Menyuan MS6.9 earthquake was 7.8 km, and the focal moment center depth was 4 km. The dominant initial rupture depths of early earthquake sequence were mainly between 7 and 8 km, while the focal moment center depth of MS≥3.4 after shocks varied between 3 km and 7 km. The focal depth profile shows that the sequence length within 24 hours after the mainshock was about 25 km, which was roughly consistent with the length of the surface rupture zone, and the overall sequence length was about 30 km. The early earthquake sequence, includes the MS6.9 mainshock and MS5.1 aftershock on January 8, located in the western part of the aftershock region, also includes the MS5.2 earthquake on January 12 located in the eastern part of the aftershock region. The focal mechanism solution of the MS6.9 main shock was strike 290°, dip 81°, rake 16° for the nodal plane I, and strike 197°, dip 74°, rake 171° for the nodal plane II. Based on the spatial distribution of aftershocks, it is estimated that the strike of the fault plane is 290 º, indicating that the earthquake is a left-lateral strike slip event on a nearly vertical fault plane. The results of focal mechanism solution of MS≥3.4 aftershocks show that these earthquakes were mainly strike-slip earthquakes, and the principal compressive stress axis varied from NE to EW from the west to the east of the aftershock region.Under the current stress field system, the relative shear stress generated on the nodal plane I of the Menyuan MS6.9 earthquake is 0.638, while on the focal mechanism solution nodal plane II is 0.522. The two focal mechanism nodal planes are not the maximum released nodal plane of the tectonic stress field, which is obviously different from the thrust focal mechanism of the Menyuan MS 6.4 earthquake in 2016, which is the optimal released nodal plane of tectonic stress field. Combined with the geological structure, focal mechanisms and aftershock distribution, the seismogenic structure of Menyuan MS6.9 earthquake on January 8, 2022 may be the western segment of Lenglongling fault, and its seismic dislocation mode is left-lateral strike-slip. According to the results of relocation, the magnitude-rupture relationship and the shear stress, it is concluded that there is a certain stress accumulation and stress has not been fully released in Menyuan area, and the risk of strong earthquakes still exists in this area.
Spectral element method simulation of near-fault ground motions in complex sites based on CPU-GPU heterogeneous parallelism
Ba Zhenning, Zhao Jingxuan, Wu Mengtao, Liang Jianwen
, Available online  , doi: 10.11939/jass.20210076
Base on CUDA programming platform, the workstation-level CPU-GPU heterogeneous parallel method was implemented, and the spectral element method is used to simulate ground motion near-fault in real site. In this paper, the computational accuracy and efficiency of the proposed workstation-level CPU-GPU heterogeneous parallel method are tested by simulating the spontaneous rupture model TPV15 provided by SECE/USGS. Furthermore, the proposed method is applied to the simulation of M8.0 strong ground motion in 1679 Sanhe-Pinggu, and the applicability of the proposed method to the simulation of real ground motion is verified. The simulation results show that CPU-GPU heterogeneous parallel computing time is significantly reducedhan CPU parallel computing time, and the highest acceleration ratio is 3.04 and 2.16 times of CPU (36 core) and (72 core) respectively. The simulation results of M8.0 in Sanhe-Pinggu in 1679 clearly show the characteristics of near-fault ground motion, such as near-fault ground motion concentration, fault rupture directivity effect, velocity pulse and permanent displacement, and the influence of real terrain on near-fault ground motion. The results show that the CPU-GPU heterogeneous parallel method can effectively improve the computational efficiency of spectral element method simulation, and it has a good prospect to be applied to seismic wave field simulation of large-scale complex sites.
Application of an optimized transmitting boundary with multiple artificial wave velocities in spectral-element simulation of seismic wave propagation
Xing Haojie, Liu Aiwen, Li Xiaojun, Chen Su, Fu Lei
, Available online  , doi: 10.11939/jass.20210090
This paper applied an optimized transmitting boundary with multiple artificial velocities (denoted as caj-MTF) that is recently proposed by the authors to the high-accuracy spectral-element simulation of seismic wave propagation, and made a comparison study with several other classical artificial (or absorbing) boundary conditions, which include Liao’s multi-transmitting formula (MTF) boundary, Perfectly Matched Layer (PML) boundary, viscous-spring boundary and first-order Clayton-Engquist paraxial-approximation boundary. The results obtained from theoretical analysis and numerical tests are as follows: ① The formulation of caj-MTF is very similar to that of MTF, so it has most of the advantages of the latter, i.e., very simple expressions, easy to be implemented, adjustable accuracy, minimal computation cost, and general applicability. ② Unlike the traditional MTF boundary that has only a single artificial wave velocity (i.e., computational wave velocity), caj-MTF has a set of artificial wave velocities corresponding to the boundary order. In the simulation of elastic waves, the computational wave velocity parameters of caj-MTF can be set to be P- and S-wave velocities, respectively. The consistency between computational and physical wave velocities makes a significant improvement in the boundary accuracy. ③ caj-MTF boundary has an slightly lower accuracy than that of PML boundary, whereas it is significantly superior to MTF, viscous-spring boundary and the first-order paraxial-approximation boundary. ④ caj-MTF is superior to PML as it has much simpler formulations and better versatility. This work provides a convenient and high-efficient artificial boundary (or absorbing boundary) for spectral-element simulation of seismic wave propagation.
Numerical simulation of coupling failure between subway station and cross bridge
Dong Rui, Jing Liping, Shan Zhendong, Li Yadong
, Available online  , doi: 10.11939/jass.20210078
In this paper, a typical two-story and three-span subway station is taken as the research object. The nonlinear dynamic time-history analysis method is adopted to conduct numerical simulation analysis on the model of the subway station and the upper bridge in soft site. A potential coupling failure mode of subway station and bridge is presented. The seismic interaction between the subway station and the upper bridge is studied. Numerical simulation results show that: 1) the bridge has little effect on the seismic response of the station, and the damage of the station mainly depends on the earthquake action and structure strength. 2) The destruction of the subway station will cause a large horizontal and vertical deformation of the soil in adjacent area, and make the bridge beam fall; 3) After the destruction of the station, the bridge foundation makes the soil move towards the station, which aggravates the earthquake damage of subway station.
Variation law of optimal seismic peak intensity measures for underground structures with burial depth
Zhao Mi, Guo Mengyuan, Zhong Zilan, Du Xiuli
, Available online  , doi: 10.11939/jass.20210094
Determination of a reasonable seismic intensity measure is very important for structural seismic performance evaluation. The seismic response of the underground structure is closely related to the deformation of the engineering site under earthquake excitation due to the constraint of the surrounding rock and soil. Besides, the burial depth of the underground structure also has critical effects on its seismic response. Therefore it is of great significance to investigate the variation of the optimal seismic intensity measure with burial depths of underground structures in engineering sites. In this paper, one-dimensional equivalent-linear earthquake site response analyses was performed by using 50 actual seismic records as the input motions to estimate the seismic response of homogeneous half-space sites and layered half-space sites. For the convenience of comparison among different numerical results, the engineering bedrock is assumed to be a linear elastic medium herein and the earthquake ground motions are input in the engineering bedrock at a same burial depth of 200 m from the ground surface. Based on the proficiency of the results, the optimal peak seismic intensity measure (peak ground acceleration PGA, peak ground velocity PGV, peak ground displacement PGD) varying with the burial depth of the site were investigated herein. The numerical results show that for the selected two types of sites, the optimal peak seismic intensity measure changes with the burial depth of the site. When the burial depth is small, the proficiency of PGA is the best. With the increase of the burial depth, the optimal proficiency changes from PGA to PGV. Moreover, although the critical burial depth corresponding to the transition from PGA to PGV are different for different sites, it exhibits linear correlation with shear wave velocity of the engineering sites.
Afterslip distribution of 2017 Iran MW7.3 earthquake and its triggering effects on the 2018 MW6.0 earthquake
Jiang Ziqin, Yang Yinhui, Chen Qiang, Xu Qian, Xu Lang, Huang Xiaomei
, Available online  , doi: 10.11939/jass.20200140
In this study, a set of radar images acquired by the Sentinel-1 satellite that covers the interested seismically-effected area was collected. The time series surface deformation of the 283-day time span after the 2017 Sarpol Zahab, Iran, MW7.3 earthquake was extracted by using small baseline subset technique, then the two-step procedure inversion is carried out to obtain the afterslip model. In order to analyze the triggering effects of the 2017 strong earthquake and its post-seismic faulting on the 2018 Javanrud MW6.0 earthquake, the coseismic deformation field covering the whole MW6.0 earthquake region was obtained by using differential interferometry technique, and the inversion results of seismogenic fault parameters were used as receiving fault parameters for stress calculation. The results show that the post-seismic deformation of the Sarpol Zahab earthquake is mainly dominated by the afterslip effect. 283 days after the earthquake, the maximum accumulative slip of the after-slip model reaches up to 0.7 m. The co-seismic source model of the Javanrud MW6.0 earthquake indicates that the fault strike is 355.6°, the dip angle is 89.4°, and the movement is characterized by the right-lateral strike-slip together with some normal dip-slip component. Moreover, the calculated Coulomb stress modulation suggests that the MW7.3 earthquake and its afterslip have positive effect on triggering the subsequent Javanrud MW6.0 earthquake, and the occurrence of Javanrud earthquake could also be contributed by the regional plate activity.