Data from the CASN(Capital Area Seismograph Network),NSNC(National Seismograph Network of China),and IRIS(Incorporated Research Institutions for Seismology) are compared with data from a temporary North China Seismic ...Data from the CASN(Capital Area Seismograph Network),NSNC(National Seismograph Network of China),and IRIS(Incorporated Research Institutions for Seismology) are compared with data from a temporary North China Seismic Array to obtain the background orientation of the horizontal crustal principal compressive stress at NE 95.1°±15.4° in North China.Data are corrected for disturbances of faults and irregular tectonics,and are used to constrain the fast SKS polarization at NE 110.2°±15.8° in North China.Individual station analyses suggests that there is consistently more than 10° difference between the polarizations of fast shear-wave in the crust and those of fast SKS phases.Azimuthally anisotropic phase velocities of Rayleigh waves at different periods also indicate an orientation change for fast velocity with depth.It suggests the crust-mantle coupling in North China follows neither the simple decoupling model nor the strong coupling model.Instead,it is possibly some inhomogeneous combination of two models or some gradual-change model of physical characteristics.This study shows that anisotropy in the crust and mantle could be multiply characterized more correctly and crust-mantle coupling could be analyzed further,if increasing near-field shear-wave splitting data that indicate crustal anisotropy,combined with the azimuthal anisotropy of Rayleigh waves,besides the result of SKS splitting travelling through lithosphere and surface GPS measurements.展开更多
The 1861 M6. 0 earthquake occurring in the east of Pulandian is another strong earthquake with M ≥ 6. 0 besides the 1975 Haicheng MT. 3 earthquake in the Liaodong peninsula. Through repeated investigations, the epice...The 1861 M6. 0 earthquake occurring in the east of Pulandian is another strong earthquake with M ≥ 6. 0 besides the 1975 Haicheng MT. 3 earthquake in the Liaodong peninsula. Through repeated investigations, the epicenter of the 1861 earthquake was located at Gupao, a village east of Pulandian. Based on the analyses of damage survey and precise location of modern instrumental earthquake data, the activity and seismic risk of the Jinzhou fault, Pulandian bay fault and the NW-trending Pulandian fault were analyzed. And by comparing the deep seismogenic environment between Pulandian and Haicheng, it is found that, as a neogenic active fault, the NW-trending fault, conjugated with the Jinzhou fault, has a higher seismic risk. The NW-trending fault is the seismogenic structure of the 1861 M6. 0 earthquake. And the Jinzhou fault, as a major fault in the Liaodong Peninsula, has controlled the seismicity of the region. The Pulandian bay fault is relatively inactive, with weak seismicity, and unrelated to the earthquake.展开更多
The coseismic surface rupture zone of the seismogenic fault of the Ms7.1 Yushu earthquake includes three left-stepping main ruptures, striking 300°- 320°, in general. An approximately 2km-long en echelon ten...The coseismic surface rupture zone of the seismogenic fault of the Ms7.1 Yushu earthquake includes three left-stepping main ruptures, striking 300°- 320°, in general. An approximately 2km-long en echelon tension fissure zone was found at Longbao town. The main rupture in the northern part is about 16km long, about 9kin long in the middle part, and about 7km long in the southern part, with a total length of 34km. Each of the main ruptures consists of a series of en echelon sub-ruptures represented by a series of compression bulges alternating with tension fissures or by en echelon fissures. The rupture at Changusi, the southernmost of the ruptures, is characterized by vertical displacement, with a value of 50cm. The rupture zone shows left-lateral strike-slip characteristics. The maximal horizontal slip is on the northern main rupture, with a value of 1.8m.展开更多
Earthquake events from the Indonesian subduction zone recorded in northern Australia show a long and high-frequency coda associated with both P and S waves. Regional events recorded by Warramunga array in northern Aus...Earthquake events from the Indonesian subduction zone recorded in northern Australia show a long and high-frequency coda associated with both P and S waves. Regional events recorded by Warramunga array in northern Australia can separate out wave propagation through the mantle by focusing on the coherent signal across the medium-aperture array. Most of the incoherent wave components result from structures in the vicinity of the array with small-scale lengths of 1-2 km or smaller. The coherent phases with relatively rapid changes in waveforms are associated with the scattering of seismic waves by crustal and mantle heterogeneity, but in some case can be related to structural effects near the source. As the depth of the source increases, the coherent portion of the seismic wavefield tends to become much simpler, which suggests that the heterogeneity tends to weaken at depth with larger-scale length. We compare the coherent signal features of earthquakes from the Indonesian subduction zone that have occurred in recent years with those in the early 1980s, first studied by Kennett （Phys Earth Planet Inter 47： 319-332, 1987）. The general characteristics of the coherent signal variation with depth in recent years are the same as those observed in 1980s, but the variations are larger. This change suggests a stringer var- iation in heterogeneity with depth than before, which may bear important information about the dynamic processes and evolution of the crust and upper mantle.展开更多
基金supported by the National Natural Science Foundation of China (40674021)partly by IES project of Institute of Earthquake Science,China Earthquake Administration (2007-13)
文摘Data from the CASN(Capital Area Seismograph Network),NSNC(National Seismograph Network of China),and IRIS(Incorporated Research Institutions for Seismology) are compared with data from a temporary North China Seismic Array to obtain the background orientation of the horizontal crustal principal compressive stress at NE 95.1°±15.4° in North China.Data are corrected for disturbances of faults and irregular tectonics,and are used to constrain the fast SKS polarization at NE 110.2°±15.8° in North China.Individual station analyses suggests that there is consistently more than 10° difference between the polarizations of fast shear-wave in the crust and those of fast SKS phases.Azimuthally anisotropic phase velocities of Rayleigh waves at different periods also indicate an orientation change for fast velocity with depth.It suggests the crust-mantle coupling in North China follows neither the simple decoupling model nor the strong coupling model.Instead,it is possibly some inhomogeneous combination of two models or some gradual-change model of physical characteristics.This study shows that anisotropy in the crust and mantle could be multiply characterized more correctly and crust-mantle coupling could be analyzed further,if increasing near-field shear-wave splitting data that indicate crustal anisotropy,combined with the azimuthal anisotropy of Rayleigh waves,besides the result of SKS splitting travelling through lithosphere and surface GPS measurements.
基金funded by the project of"Studyon Key Technology of Strong Earthquake Risk Zoning(2006BAC13B01)"under the National Key Technology R&D Program of Ministry of Science and Technology of China
文摘The 1861 M6. 0 earthquake occurring in the east of Pulandian is another strong earthquake with M ≥ 6. 0 besides the 1975 Haicheng MT. 3 earthquake in the Liaodong peninsula. Through repeated investigations, the epicenter of the 1861 earthquake was located at Gupao, a village east of Pulandian. Based on the analyses of damage survey and precise location of modern instrumental earthquake data, the activity and seismic risk of the Jinzhou fault, Pulandian bay fault and the NW-trending Pulandian fault were analyzed. And by comparing the deep seismogenic environment between Pulandian and Haicheng, it is found that, as a neogenic active fault, the NW-trending fault, conjugated with the Jinzhou fault, has a higher seismic risk. The NW-trending fault is the seismogenic structure of the 1861 M6. 0 earthquake. And the Jinzhou fault, as a major fault in the Liaodong Peninsula, has controlled the seismicity of the region. The Pulandian bay fault is relatively inactive, with weak seismicity, and unrelated to the earthquake.
基金supported by special R&D project in earthquake science,Seismic risk assessment of active faults in the national key earthquake monitoring and prevention regions(20070851)
文摘The coseismic surface rupture zone of the seismogenic fault of the Ms7.1 Yushu earthquake includes three left-stepping main ruptures, striking 300°- 320°, in general. An approximately 2km-long en echelon tension fissure zone was found at Longbao town. The main rupture in the northern part is about 16km long, about 9kin long in the middle part, and about 7km long in the southern part, with a total length of 34km. Each of the main ruptures consists of a series of en echelon sub-ruptures represented by a series of compression bulges alternating with tension fissures or by en echelon fissures. The rupture at Changusi, the southernmost of the ruptures, is characterized by vertical displacement, with a value of 50cm. The rupture zone shows left-lateral strike-slip characteristics. The maximal horizontal slip is on the northern main rupture, with a value of 1.8m.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40925013, 41104079 and 41130418)
文摘Earthquake events from the Indonesian subduction zone recorded in northern Australia show a long and high-frequency coda associated with both P and S waves. Regional events recorded by Warramunga array in northern Australia can separate out wave propagation through the mantle by focusing on the coherent signal across the medium-aperture array. Most of the incoherent wave components result from structures in the vicinity of the array with small-scale lengths of 1-2 km or smaller. The coherent phases with relatively rapid changes in waveforms are associated with the scattering of seismic waves by crustal and mantle heterogeneity, but in some case can be related to structural effects near the source. As the depth of the source increases, the coherent portion of the seismic wavefield tends to become much simpler, which suggests that the heterogeneity tends to weaken at depth with larger-scale length. We compare the coherent signal features of earthquakes from the Indonesian subduction zone that have occurred in recent years with those in the early 1980s, first studied by Kennett （Phys Earth Planet Inter 47： 319-332, 1987）. The general characteristics of the coherent signal variation with depth in recent years are the same as those observed in 1980s, but the variations are larger. This change suggests a stringer var- iation in heterogeneity with depth than before, which may bear important information about the dynamic processes and evolution of the crust and upper mantle.
