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Effect of source parameters on forward-directivity velocity pulse for vertical strike slip fault in half space

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Earthquake Engineering and Engineering Vibration 2006年第1期5卷 1-9页

作者：刘启方袁一凡金星 Institute of Engineering Mechanics China Earthquake Administration

It has been found that the large velocity pulse is one of the most important characteristics of near-fault strong ground motions. Some statistical relationships between pulse period and the moment magnitude for near-fault strong ground motions have been established by Somerville （1998）; Alavi and Krawinkler （2000）; and Mavroeidis and Papageorgiou （2003）, where no variety of rupture velocity, fault depth, and fault distance, etc. were considered. Since near-fault ground motions are significantly influenced by the rupture process and source parameters, the effects of some source parameters on the amplitude and the period ofa forward-directivity velocity pulse in a half space are analyzed by the finite difference method combined with the kinematic source model in this paper. The study shows that the rupture velocity, fault depth, position of the initial rupture point and distribution of asperities are the most important parameters to the velocity pulse. Generally, the pulse period decreases and the pulse amplitude increases as the rupture velocity increases for shallow crustal earthquakes. In a definite region besides the fault trace, the pulse period increases as the fault depth increases. For a uniform strike slip fault, rupture initiating from one end of a fault and propagating to the other always generates a higher pulse amplitude and longer pulse period than in other cases.

关键词： forward-directivity velocity pulse amplitude pulse period source parameters rupture velocity fault depth asperity

source　parameters　of　the　Gonghe,Qinghai　Province,China,earthquake　from　inversion　of　digital　broadband　waveform　data

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Acta Seismologica Sinica(English Edition) 1997年第2期10卷 2-18页

作者：许立生陈运泰

An earthquake of M S=6.9 occurred in Gonghe County, Qinghai Province, China on April 26, *** earthquake was followed by three larger aftershocks of M S=5.5 on May 7, 1990, M S=6.0 on Jan.3, 1994, and M S=5.7 on Feb.16, 1994, consecutively. The moment tensors of these earthquakes as function of time were obtained by the technique of moment tensor inversion in frequency domain . The results inverted indicate that these earthquakes had a very similar focal mechanism of predominantly reverse faulting on a plane striking NWW, dipping to *** scalar seismic moments of these earthquakes are M 0=9.4×10 18 Nm for the M S=6.9 event, 8.0×10 16 Nm for the M S=5.5 event, 4.9×10 17 Nm for the M S =6.0 event and 2.9×10 17 Nm for the M S=5.7 event, respectively. The results inverted also show that the source processes of these events were significantly different. The main shock had a very complex process, consisting of two distinct sub events with comparable sizes. The first sub event occurred in the first 12s, having a seismic moment of 4.7×10 18 Nm, and the second one continued from 31s to 41s, having a seismic moment of 2.5×10 18 Nm. In addition, a much smaller sub event, having a seismic moment of about 2.1×10 18 Nm, may exist in the interval of 12 s and 31 s, In contrast, the source processes of the three aftershocks are quite simple. The source time function of each of aftershocks is a single impulse, suggestting that each of aftershocks consists of a mainly uninterrupted rupture. The rise times and total rupture durations are 4 s and 11 s for the M S=5.5 event, 6 s and 16 s for the M S= 6.0 event and 6 s and 13 s for the M S=5.7 event, respectively.

关键词： Gonghe earthquake source parameters digital broadband waveform data

Changes in source parameters of foreshocks and aftershocks of the 2001 M_S=6.0 Yajiang, Sichuan, earthquake

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Acta Seismologica Sinica(English Edition) 2003年第4期16卷 371-381页

作者：程万正陈天长魏娅玲朱航 Seismological Bureau of Sichuan Province Chengdu 610041 China

In this paper changes in focal mechanisms, parameters of wave spectra, and stress drops for the MS=5.0 foreshock and MS=6.0 mainshock in February 2001 in Yajiang County, Sichuan, and seismicity in epicentral region are studied. Comparison of focal mechanisms for the Yajiang earthquakes with distribution patterns of aftershocks, the nodal plane I, striking in the direction of NEN, of the Yajiang M=5.0 event is chosen as the faulting plane; the nodal plane II, striking in the direction of WNW, of the M=6.0 event as the faulting plane. The strikes of the two faulting planes are nearly perpendicular to each other. The level of stress drops in the epicentral region before the occurrence of the M=6.0 earthquake increases, which is consistent with increase of seismicity in the epicentral region. The rate decay of the Yajiang earthquake sequence, changes in wave spectra for foreshocks and aftershocks, and focal mechanisms are complex.

关键词： Yajiang earthquake sequence characteristics source parameters

Analysis of the 1997 Zirkuh (Ghean-Birjand) aftershock sequence in east-central Iran

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Earthquake Science 2004年第1期17卷 38-46+124页

作者： Mohammad-Reza Gheitanchi,Mohammad Raeesi Institute of Geophysics Tehran University Institute of Geophysics Tehran University Tehran P.O.Box 13145-1137 Iran Tehran P.O.Box 13145-1137 Iran

In this study, the 1997 Zirkuh (Ghaen-Birjand) locally recorded aftershock sequence was analyzed. On the basis of the distribution of aftershocks, a NW-SE trend vertical faulting with an extension of at least 90 km could be esti-mated. The fault rupture causing the Zirkuh earthquake apparently initiated in the epicentral area and propagated unilaterally to southeast. The cross-section of aftershocks along the fault suggests that the aftershocks had a depth range of 20 km, indicating that the seismic activity was taking place within the upper crust and the seismogenic layer, in this region, had a thickness not greater than 20 km. The distribution of aftershocks suggested that the western block acted as hanging wall during the source process of the main shock. The time-space distribution of aftershocks showed two distinguished gaps coincided with the observed gaps on the surface faulting. It was con-cluded that the first gap acted as a barrier during the main shock and aftershocks, while the deeper part of second gap was ruptured either during the main shock or the aftershocks. The time-frequency pattern of aftershocks decay followed the Modified Omori relations for the first 10 days while the Omori model was best fitted for the later stage of the aftershock sequence.

关键词： Zirkuh earthquake seismicity of Khorasan Province source parameters focal mechanism seismotectonics active faults aftershock activity

A Reappraisal of the 2005 Kashmir Earthquake in the Northwestern Himalaya Syntaxis

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Acta Geologica Sinica(English Edition) 2021年第S1期95卷 22-24页

作者： BAI Ling SU Hui ZHOU Yuanze Institute of Tibetan Plateau Research Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 10086China

The collision of the Indian and Eurasian plates caused a massive surface uplift and formed the *** the 2500-km long Himalaya mountain range,significant earthquake hazards have occurred either on the interface between ... 详细信息

关键词： 2005 Mw7.5 Kashmir earthquake source parameters western Himalayan syntaxis

source Characteristics of the 2012 Ahar-Varzaghan Earthquake

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Open Journal of Geology 2016年第1期6卷 39-46页

作者： Maryam Aminipanah Manouchehr Ghorashi Mohsen Pourkermani Abdolmajid Asadi Katayoun Behzadafshar Department of Geology Fars Science and Research Branch Islamic Azad University Shiraz Iran

The August 11, 2012 Mw 6.4 earthquakes in northwestern Iran occurred as a result of oblique strike-slip faulting in the shallow crust of the Eurasia plate, approximately 300 kilometer east of the plate boundary between the Eurasia and Arabia plates. The seismotectonics of this region is controlled by the collision of the Arabia and Eurasia plates;at the latitude of the earthquakes, the Arabia plate moves almost due north with respect to the Eurasia plate at a rate of approximately 26 millimeter per year. Over the past forty years, seven earthquakes of Mw 6 or greater have occurred within 300 kilometer of today’s events. The nearest was a Mw 6.1 earthquake in February of 1997, approximately 100 kilometer to the east, which caused 1100 fatalities. The studied area encourage the authors to determine the focal mechanism, source time function and sub events’ features which can guide us to reliable judges.

关键词： Ahar-Varzaghan Earthquake source Time Function source Mechanism source parameters