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| 1 | Source mechanism of strong aftershocks (M_s≥5.6) of the 2008/05/12 Wenchuan earthquake and the implication for seismotectonics显示文摘Dozens of >M5, hundreds of >M4, and much more >M3 aftershocks occurred after the 2008/05/12 Wenchuan earthquake, which were well recorded by permanent and portable seismic stations. After relocated with P arrival, the >M3 aftershocks show two trends of distribution, with most of the aftershocks located along the north-east strike consistent with Longmenshan fault system, yet there is a north-west trend around the epicenter. It seems that substantially more aftershocks occur in regions with crystalline bedrocks. Then we collected waveform data from National Digital Seismograph Network and regional seismograph network of China, and employed 'Cut and Paste' method to obtain focal mechanisms and depths of the big aftershocks (M≥5.6). While most of those aftershocks show thrust mechanism, there are some strike slip earthquakes in the northern-most end of the rupture. Focal mechanisms show that the events located on the southern part of central Beichuan-Yingxiu Fault (BY) are mainly thrust earthquakes, which is consistent with initial mechanism of the main shock rupture. In the north part the aftershocks along the BY are also dominated by thrust slip, which is quite different from the right slip rupture of the main shock. Around Qingchuan-Pingwu Fault, the focal mechanisms are dominated by right-slip rupture with large depths (~18 km). So we suspected that in the north part the main shock might rupture on two faults: Beichuan Fault and Qingchuan-Pingwu Fault. The complex pattern of aftershock mechanisms argues for presence of a complicated fault system in the Longmenshan area. | ZHENG Yong1,2,MA HongSheng3,Lü Jian4,NI SiDao5,LI YingChun6 & WEI ShengJi2 1 Institute of Geodesy and Geophysics,Chinese Academy of Sciences,Wuhan 430077,China 2 Institute of Geophysics,Chinese Earthquake Administration,Beijing 100086,China 3 Institute of Earthquake Science,Chinese Earthquake Administration,Beijing 100086,China 4 Earthquake Administration of Jiangxi Province,Nanchang 330039,China 5 School of Earth and Space Science,University of Science and Technology of China,Hefei 230026,China 6 Earthquake Administration of Jiangsu Province,Nanjing 210014,China | 2009 | Science China Earth Sciences2009，52，6： | 100 |
| 2 | Spatial distribution and focal mechanism solutions of the Wenchuan earthquake series:Results and implications显示文摘We relocate the spatial distribution of the devastating 12 May 2008 Wenchuan earthquake and its aftershocks.The relocation database is obtained from 89 stations deployed by the China Earthquake Administration,including 54 525 seismograms from 1 376 local earthquakes over MS3.5 between 12 May 2008 and 3 August 2008.The cross-correlation technique used in this paper has greatly improved the relocation precision by giving much more accurate P-wave differential travel-time measurements than those obtained from routinely picked phase onsets.At the same time,we pick P-wave polarity observations of the Wenchuan earthquake series (hereafter referred to as WES) from 1 023 stations in China and 59 IRIS (Incorporated Research Institutions of Seismology) stations.Then,employing a newly developed program CHNYTX,we obtain 83 well-determined focal mechanism solutions (hereafter referred to as FMSs).Based on spatial distribution and FMSs of the WES,we draw following conclusions:(1) The region near the main shock exhibits a buried low-angle northwest-dipping seismic zone with the main shock at its upper end and two conjugated seismic zones dipping southeast with roughly equal dip-angle;(2) The compressional directions of all kinds of FMSs of the WES are subhorizontal,which reflects the dominant stress in this area is compressional;(3) The principal compressional direction of the regional stress around Wenchuan is roughly perpendicular to the strike of Beichuan-Yingxiu fault,while around Qingchuan it is roughly parallel to the strike of Qingchuan fault.In intermediate part of the Longmenshan area,the principal compressional direction of the stress should be in-between;(4) The possibly existed molten materials in the lower crust of Songpan-Garze terrain have small contribution to the local stress state in Longmenshan area.The listric geometries of the Longmenshan faults most probably resulted from subhorizontal compression along NW-SE direction in history. | Chen Cai Chunquan Yu Kai Tao Xingping Hu Yuan Tian Hao Zhang Xiaofeng Cui Jieyuan Ning | 2011 | Earthquake Science2011，24，1： | 13 |
| 3 | A new stacking technique in ambient noise tomography显示文摘We have developed a new stacking technique in ambient noise tomography to obtain high-quality dispersion curves of Rayleigh waves.This technique is used to stack the vertical components of the Estimated Green Functions(EGFs) obtained respectively from cross correlation of the ambient noise data recorded by a remote seismic station and one of the short distance seismic stations of a seismic array.It is based on a phase-matched filter and is implemented by a four-step iterative process:signal compression,stacking,signal extraction and signal decompression.The iterative process ends and gives the dispersion curve of Rayleigh wave when the predicted one and the processing result converge.We have tested the method using the vertical components of synthetic Rayleigh wave records.Results show that this new stacking method is stable and it can improve the quality of dispersion curves.In addition,we have applied this method to real data.We see that the results given by our new technique are obviously better than the ones employing the traditional method which is a three-step process:signal compression,signal extraction and signal decompression.In conclusion,the new method proposed in this paper can improve the signal to noise ratio of EGFs,and can therefore potentially improve the resolution of ambient noise tomography. | Yongshun John Chen | 2010 | Earthquake Science2010，23，6： | 1 |
| 4 | Eastern Kunlun Active Fault Zone and Its Seismic Activity显示文摘In addition to a brief description of the tectonic background and evolutionary history of the Eastern Kunlun active fault zone,this paper emphatically describes the spatial distribution,geometry,Quaternary movement,and strong earthquake activities of this fault zone.The fault zone is characterized by a long evolutionary history,deep seated tectonic background,and intense Quaternary,even Holocene,activities.It played an important role in the tectonic evolution of China,especially in the uplifting and formation of the Qinghai-Xizang Plateau.It is also a major pleistoseismic belt in western China.Based on modern strong earthquake records as well as the newly discovered evidence of multiple Holocene paleoearthquakes and their surface rupture zones along the entire fault zone,the spatial and temporal distribution pattern of strong earthquakes along the fauit zone is analyzed.Finally,the macroscopic epicenter location of the 1937 Huashixia earthquake with M=7.5 and the distribution and scope of its surface | Liu GuangxunInstitute of Crustal Dynamics,SSB,Beijing,100085,China | 1996 | Earthquake Research in China1996，10，4： | 1 |
| 5 | Upper crustal Poisson's ratio and coda-wave attenuation beneath Eastern Anatolia显示文摘The attenuation of seismic waves reflects the elastic nature of the media within which the waves propagate.In this study,we calculate the Coda-Q(Qc),frequency dependence(η),Vp/Vs and Poisson's(υ)ratios by using 2621 vertical component seismograms generated by 987 earthquakes recorded by 13 seismic stations in Eastern Anatolia,and creat a 2-D seismic tomographic Qc model for the region.The obtained model provides significant information for exploring the boundaries of adjacent tectonic units within the upper crust and interpreting their dynamic characteristics.The 2-D Qc model and the other parameters are consistent with the seismotectonic features of Eastern Anatolia.Highly heterogeneous Qc values are observed in the study area dividing it into north-south directed bands of low and high attenuation.The highestηvalues were obtained beneath the northwestern and eastern parts of the study region.Clear,high and lowυvalues are obtained in the western and eastern parts of the study area,respectively.The spatial variations in the measured parameters are consistent with many geophysical observations including low Pn velocities,efficient Sn blockage,high heat flow,and widespread volcanism.Different upper crustal thicknesses and inhomogeneous stress distribution along the East and North Anatolian Fault Zones may also contribute to the observed heterogeneities. | Ufuk Aydin Sakir Sahin Mohamed K.Salah | 2020 | Earthquake Engineering and Engineering Vibration2020，19，2： | 0 |
| 6 | Interplate coupling and seismotectonics under the fore-arc regions of Japan显示文摘Three-dimensional P-and S-wave velocities(vP,vS),Poisson's ratio(σ),crack-density(ε) and bulk-sound velocity(vφ) structures along the slab upper boundary beneath the fore-arc regions were determined using a large number of high-quality P-wave and S-wave arrival times from both onshore and offshore earthquakes in Japan.The velocity and Poisson's ratio images provide a compelling evidence for a highly hydrated and serpentinized fore-arc mantle and fluid-bearing anomalous low velocity and high Poisson's ratio associated with slab dehydration under the fore-arc areas.Most great thrust earthquakes(M>7.5) occurred at or close to the high-velocity areas along the slab interface under the fore-arc areas,suggesting strong interplate coupling(asperities) with slab subduction.On the other hand,prominent low-velocity anomalies were revealed along the slab upper boundary,which may reflect weak coupled or decoupled patches(aseismicity) of the plates due to serpentinization of the fore-arc mantle wedge.The crack-density and bulk-sound velocity images,calculated from the corresponding velocity models,indicate that the interplate coupling in northeastern Japan is different from that under central and southwestern Japan owing to differences between the tectonic backgrounds of the subduction system,such as the geological age,thermal regime and dipping angle of the oceanic plates.A comparison between fluid-related anomalies of Japan,Cascadia,Chile,and Costa Rica subduction zones suggests that seismic mantle may be common in fore-arc settings and these reflect similar 3-D seismic structures relatively to fluid liberating processes.We consider that the fluid-bearing anomalies along the interface of the subducting slab,attributing to processes such as slab dehydration and serpentinization of the fore-arc mantle,are mainly contributed to the interplate coupling and the repeated generation of the great thrust earthquakes under the fore-arc regions in Japan. | Zhi Wang | 2010 | Earthquake Science2010，23，6： | 0 |
| 7 | Investigation of Seismotectonics and Seismicity in South of Caspian Sea显示文摘In this study region,those fault-lines with northwestern -southeastern trend are the oldest structures of the region,whose formation is believed to date back to orogeny phase of Katanga.Besides the mentioned trend the northwestern southwestern trends also had outcrop in the studied region and recent seismic data indicate that in the studied region the active presence of North Firouzabad transpressional fault-line causes formation of fault scarps and very deep valleys | Z.S.Riazi-Rad | 2009 | 地学前缘2009，16，S1： | 0 |
| 8 | Seismotectonic Environment for Zhangbei-Shangyi Earthquake and Characteristics of Macroscopic Damage显示文摘The regional seismotectonic environment for the Zhangbei- Shangyi earthquake is described, and in combination with the distribution of macroscopic seismic intensity, source mechanism solution, and interpretation of lineaments on satellite images, the seismogenic structure for the earthquake and possible seismogenic fault are discussed in this paper. It is suggested that the Zhangbei-Shangyi earthquake is a result of the latest movement along the northwestern termination of the Zhangjiakou-Penglai fault zone and we should pay serious attention to the future trend of seismic activity along this fault zone. | Xu Xiwei, Rang Yongkang, Zhou Bengang, Yin Gongming, Li Jianhua, and Liu WuzhouInstitute of Geology, CSB, Beijing 100029, China | 1999 | Earthquake Research in China1999，13，3： | 0 |
| 9 | Seismotectonics and consequences of the 1930s large earthquakes in eastern Mazandaran,north of Iran显示文摘Early in the 1930 s,two relatively large earthquakes(Kosout,magnitude 6.8,and Talarrud,magnitude 5.8)shook the eastern Mazandaran,northern Iran.Despite the historical and instrumental seismic activity of the eastern region of Mazandaran,little is known about the status of seismotectonics and consequences of these earthquakes.This paper presents a compilation of available data from early reports of these earthquakes with new structural,geomorphic and local data on the effects of this earthquake,especially co-seismic landslides and liquefaction,to assess the seismotectonics and probable causative faults of the earthquakes.It is proposed that the close times of occurrence of two earthquakes might be due to local loading or triggering effect of the first earthquake on the second one.Like many other instrumental earthquakes in the Central Alborz,it is difficult to find the exact causative faults of important earthquakes,however the Qadikola,Chachkam or North Alborz Fault have the potential of producing Kosout earthquake and the Lalehband fault is more promising for Talarrud earthquake.Additionally,the structural complexity of the area is also discussed in the form of a hybrid tectonic model.In this model,the boundary zone of thick-skinned and active thin-skinned domains has more structural complexity than outer portions.Konim-Badeleh Shahvar pop-up structure is bounded by major faults with thick-skinned deformation style.The role of older inherited fault structures and their interaction with low-slope Neogene thrusts driven from north to south by crustal tectonics and deformation is discussed.Co-seismic landslides and rock falls have great potential to be investigated in the Alborz Range for identification of prehistoric earthquakes. | Mohsen EHTESHAMI-MOINABADI Ehsan ABBASI Ali SAKET | 2022 | Journal of Mountain Science2022，19，2： | 0 |
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