基于新疆区域数字地震台网记录,采用CAP（Cut and Paste）方法反演了2015年7月3日皮山6.5级主震和部分MS3.6以上余震的震源机制解和震源深度;采用HypoDD方法重新定位了序列中ML2.5以上地震序列的震源位置,并利用小震分布和区域应力场拟...基于新疆区域数字地震台网记录,采用CAP（Cut and Paste）方法反演了2015年7月3日皮山6.5级主震和部分MS3.6以上余震的震源机制解和震源深度;采用HypoDD方法重新定位了序列中ML2.5以上地震序列的震源位置,并利用小震分布和区域应力场拟合了可能存在的发震断层面参数.基于上述研究,综合分析了皮山6.5级地震序列的震源深度、震源机制和震源破裂面特征,探讨可能的发震构造.结果显示,利用CAP方法得到的最佳双力偶机制解节面I：走向280°/倾角60°/滑动角90°;节面II：走向100°/倾角30°/滑动角90°,矩心深度19km,表明该地震为一次逆冲型地震事件.大部分M_S3.6以上余震震源机制与主震具有一定的相似性.双差定位结果显示,M_L2.5以上的余震序列主要分布在主震的西南方向,深度主要分布在0~15km范围内,余震分布显示出与发震构造泽普隐伏断裂一致的倾向南西的特征.利用小震分布和区域应力场拟合得到发震断层参数为走向104°/倾角34°/滑动角94°,该结果与主震震源机制解中节面II的滑动角较为接近,绝大多数余震发生在断层面附近10km左右的区域.根据本研究得到的震源机制、精定位结果以及利用小震分布和区域应力场拟合得到的断层面的参数,结合震源区地质构造情况,初步给出了此次皮山6.5级地震的发震模式.展开更多
为了提高微震震源定位精度和算法鲁棒性,研究了基于到时的定位算法的目标函数构建和时空区域信息使用。仿真实验基于Numpy,采用理想到时+随机扰动来模拟生产情况。结果表明:到时定位算法中常用的L_(1)和L_(2)目标函数对实际震源存在偏...为了提高微震震源定位精度和算法鲁棒性,研究了基于到时的定位算法的目标函数构建和时空区域信息使用。仿真实验基于Numpy,采用理想到时+随机扰动来模拟生产情况。结果表明:到时定位算法中常用的L_(1)和L_(2)目标函数对实际震源存在偏离且偏离现象非常普遍。为了减轻伪震源问题,使用到时偏差的似然函数作为基础函数,聚合时空邻域的单点基础函数作为目标函数;新构建的4维区域分布算法(Distribution of 4-Dimention Area Algorithm,D4DA)在2次标定炮定位中将定位误差分别降低了14%和26%。展开更多
In this paper a method of relocating hypocenter in inhomogeneous medium is introduced.Based on the velocity from the latest results on the crust and mantle structure of the Bohai Sea and its adjacent areas,by using th...In this paper a method of relocating hypocenter in inhomogeneous medium is introduced.Based on the velocity from the latest results on the crust and mantle structure of the Bohai Sea and its adjacent areas,by using the data recorded in Shandong,Hebei,Beijing,and Liaoning networks around the Bohai Sea we apply the method to relocate hypocenter parameters of 598 events occurring in the Bohai Sea and its adjacent areas.The accuracy of hypocenter relocation is discussed.We present the results of events ML≥4.0 in the Bohai Sea in recent years and discussed the distribution of focal depths.展开更多
The concept of ＂numerical Green’s functions＂ （NGF or Green’s function database） is developed. The basic idea is： a large seismic fault is divided into subfaults of appropriate size, for which synthetic Green’s...The concept of ＂numerical Green’s functions＂ （NGF or Green’s function database） is developed. The basic idea is： a large seismic fault is divided into subfaults of appropriate size, for which synthetic Green’s functions at the surface （NGF） are calculated and stored. Consequently, ground motions from arbitrary kinematic sources can be simulated, rapidly, for the whole fault or parts of it by superposition. The target fault is a simplified, vertical model of the Newport-Inglewood fault in the Los Angeles basin. This approach and its functionality are illustrated by investigating the variations of ground motions （e.g. peak ground velocity and synthetic seismograms） due to the source complexity. The source complexities are considered with two respects： hypocenter location and slip history. The results show a complex behavior, with dependence of absolute peak ground velocity and their variation on source process directionality, hypocenter location, local structure, and static slip asperity location. We concluded that combining effect due to 3-D structure and finite-source is necessary to quan- tify ground motion characteristics and their variations. Our results will facilitate the earthquake hazard assessment projects.展开更多
It is now common practice to perform simultaneous traveltime inversion for the velocity field and the reflector geometry in reflection/refraction tomography, or the velocity field and the hypocenter locations in regio...It is now common practice to perform simultaneous traveltime inversion for the velocity field and the reflector geometry in reflection/refraction tomography, or the velocity field and the hypocenter locations in regional earthquake tomography, but seldom are all three classes of model parameters updated simultaneously. This is mainly due to the trade-off between the different types of model parameters and the lack of different seismic phases to constrain the model parameters. Using a spherical-coordinate ray tracing algorithm for first and later（primary reflected） arrival tracing algorithm in combination with a popular linearized inversion solver, it is possible to simultaneously recover the three classes of model parameters in regional or global tomographic studies. In this paper we incorporate the multistage irregular shortest-path ray tracing algorithm（in a spherical coordinate system） with a subspace inversion solver to formulate a simultaneous inversion algorithm for triple model parameters updating using direct and later arrival time information.Comparison tests for two sets of data（noise free and added noise） indicate that the new triple-class parameter inversion algorithm is capable of obtaining nearly the same results as the double-class parameter inversion scheme. Furthermore,the proposed multi-parameter type inversion method is not sensitive to a modest level of picking error in the traveltime data, and also performs well with a relatively large uncertainty in earthquake hypocentral locations. This shows it to be a feasible and promising approach in regional or global tomographic applications.展开更多
Through the accurate determination of hypocenter location, the measurement of the main focal mechanism solutions and the analyses of time dependent processes for Sichuan Mianzhu earthquake sequence with M S=5 0 occurr...Through the accurate determination of hypocenter location, the measurement of the main focal mechanism solutions and the analyses of time dependent processes for Sichuan Mianzhu earthquake sequence with M S=5 0 occurred along the middle segment of Longmenshan fault zone on November 30, 1999, the distribution of focal depth section, the stress release and seismicity features are given to reveal the earthquake-generating structure of the earthquake sequence. The obtained results show the activity features for this sequence as follows: ① There is no obvious foreshock, the accumulated strain energy releases in nearly pulse way, fluctuation of the seismic activity level is not quite evident during the duration of the sequence, and the statistical relation between the large events and the small events is less compatible with the traditional G-R estimation; ② The epicenters of the earthquake sequence are not distributed on the main Longmenshan piedmont faults emerging out ground, but near the hidden Longmenshan piedmont faults. The direction of epicenter distribution is not very coincident with the fault strikes. The microscopic epicenters are relatively far from the macroscopic epicenters. The focal depths range from 5km to 16km; ③ The fractures of focal fault plane with the NE strike appear out the strike-slip displacement with a few overthrust components under the major principal compressive stress of NNE direction. From these, we consider it should be paid more attentions to the underground hidden faults near the ground fault zone on a large scale for their generating earthquake risk.展开更多
文摘基于新疆区域数字地震台网记录,采用CAP（Cut and Paste）方法反演了2015年7月3日皮山6.5级主震和部分MS3.6以上余震的震源机制解和震源深度;采用HypoDD方法重新定位了序列中ML2.5以上地震序列的震源位置,并利用小震分布和区域应力场拟合了可能存在的发震断层面参数.基于上述研究,综合分析了皮山6.5级地震序列的震源深度、震源机制和震源破裂面特征,探讨可能的发震构造.结果显示,利用CAP方法得到的最佳双力偶机制解节面I：走向280°/倾角60°/滑动角90°;节面II：走向100°/倾角30°/滑动角90°,矩心深度19km,表明该地震为一次逆冲型地震事件.大部分M_S3.6以上余震震源机制与主震具有一定的相似性.双差定位结果显示,M_L2.5以上的余震序列主要分布在主震的西南方向,深度主要分布在0~15km范围内,余震分布显示出与发震构造泽普隐伏断裂一致的倾向南西的特征.利用小震分布和区域应力场拟合得到发震断层参数为走向104°/倾角34°/滑动角94°,该结果与主震震源机制解中节面II的滑动角较为接近,绝大多数余震发生在断层面附近10km左右的区域.根据本研究得到的震源机制、精定位结果以及利用小震分布和区域应力场拟合得到的断层面的参数,结合震源区地质构造情况,初步给出了此次皮山6.5级地震的发震模式.
文摘为了提高微震震源定位精度和算法鲁棒性,研究了基于到时的定位算法的目标函数构建和时空区域信息使用。仿真实验基于Numpy,采用理想到时+随机扰动来模拟生产情况。结果表明:到时定位算法中常用的L_(1)和L_(2)目标函数对实际震源存在偏离且偏离现象非常普遍。为了减轻伪震源问题,使用到时偏差的似然函数作为基础函数,聚合时空邻域的单点基础函数作为目标函数;新构建的4维区域分布算法(Distribution of 4-Dimention Area Algorithm,D4DA)在2次标定炮定位中将定位误差分别降低了14%和26%。
基金This project was sponsored by the Earthquake Science Foundation, China
文摘In this paper a method of relocating hypocenter in inhomogeneous medium is introduced.Based on the velocity from the latest results on the crust and mantle structure of the Bohai Sea and its adjacent areas,by using the data recorded in Shandong,Hebei,Beijing,and Liaoning networks around the Bohai Sea we apply the method to relocate hypocenter parameters of 598 events occurring in the Bohai Sea and its adjacent areas.The accuracy of hypocenter relocation is discussed.We present the results of events ML≥4.0 in the Bohai Sea in recent years and discussed the distribution of focal depths.
基金funding from the International Quality Network:Georisk (Ger-man Academic Exchange Service),and the Elite Gradu-ate College THESIS (Bavarian Government)support from the European Hu-man Resources Mobility Program (Research Training Network SPICE)
文摘The concept of ＂numerical Green’s functions＂ （NGF or Green’s function database） is developed. The basic idea is： a large seismic fault is divided into subfaults of appropriate size, for which synthetic Green’s functions at the surface （NGF） are calculated and stored. Consequently, ground motions from arbitrary kinematic sources can be simulated, rapidly, for the whole fault or parts of it by superposition. The target fault is a simplified, vertical model of the Newport-Inglewood fault in the Los Angeles basin. This approach and its functionality are illustrated by investigating the variations of ground motions （e.g. peak ground velocity and synthetic seismograms） due to the source complexity. The source complexities are considered with two respects： hypocenter location and slip history. The results show a complex behavior, with dependence of absolute peak ground velocity and their variation on source process directionality, hypocenter location, local structure, and static slip asperity location. We concluded that combining effect due to 3-D structure and finite-source is necessary to quan- tify ground motion characteristics and their variations. Our results will facilitate the earthquake hazard assessment projects.
基金partially supported by the Doctoral Programming Research Fund of Higher Education, Chinese Ministry of Education (No. 20110205110010)
文摘It is now common practice to perform simultaneous traveltime inversion for the velocity field and the reflector geometry in reflection/refraction tomography, or the velocity field and the hypocenter locations in regional earthquake tomography, but seldom are all three classes of model parameters updated simultaneously. This is mainly due to the trade-off between the different types of model parameters and the lack of different seismic phases to constrain the model parameters. Using a spherical-coordinate ray tracing algorithm for first and later（primary reflected） arrival tracing algorithm in combination with a popular linearized inversion solver, it is possible to simultaneously recover the three classes of model parameters in regional or global tomographic studies. In this paper we incorporate the multistage irregular shortest-path ray tracing algorithm（in a spherical coordinate system） with a subspace inversion solver to formulate a simultaneous inversion algorithm for triple model parameters updating using direct and later arrival time information.Comparison tests for two sets of data（noise free and added noise） indicate that the new triple-class parameter inversion algorithm is capable of obtaining nearly the same results as the double-class parameter inversion scheme. Furthermore,the proposed multi-parameter type inversion method is not sensitive to a modest level of picking error in the traveltime data, and also performs well with a relatively large uncertainty in earthquake hypocentral locations. This shows it to be a feasible and promising approach in regional or global tomographic applications.
文摘Through the accurate determination of hypocenter location, the measurement of the main focal mechanism solutions and the analyses of time dependent processes for Sichuan Mianzhu earthquake sequence with M S=5 0 occurred along the middle segment of Longmenshan fault zone on November 30, 1999, the distribution of focal depth section, the stress release and seismicity features are given to reveal the earthquake-generating structure of the earthquake sequence. The obtained results show the activity features for this sequence as follows: ① There is no obvious foreshock, the accumulated strain energy releases in nearly pulse way, fluctuation of the seismic activity level is not quite evident during the duration of the sequence, and the statistical relation between the large events and the small events is less compatible with the traditional G-R estimation; ② The epicenters of the earthquake sequence are not distributed on the main Longmenshan piedmont faults emerging out ground, but near the hidden Longmenshan piedmont faults. The direction of epicenter distribution is not very coincident with the fault strikes. The microscopic epicenters are relatively far from the macroscopic epicenters. The focal depths range from 5km to 16km; ③ The fractures of focal fault plane with the NE strike appear out the strike-slip displacement with a few overthrust components under the major principal compressive stress of NNE direction. From these, we consider it should be paid more attentions to the underground hidden faults near the ground fault zone on a large scale for their generating earthquake risk.
