RESEARCH ON GENESIS OF M4.2 AND M4.5 EARTHQUAKE SEQUENCES IN MARCH 2014 IN ZIGUI COUNTY,HUBEI PROVINCE |
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| Authors: | WANG Qiu-liang ZHANG Li-fen LIAO Wu-lin LI Jing-gang |
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| Institution: | 1. Key Laboratory of Earthquake Geodesy, Institute of Seismology, China Earthquake Administration, Wuhan 430071, China;
2. Key Seismic Monitoring Station of the Ecological and Environmental Monitoring System of Three Gorges Project, Wuhan 430071, China;
3. Institute of Geophysics, China Earthquake Administration, Beijing 100081, China |
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| Abstract: | On 27th and 30th March 2014, an M4.2 and M4.5 earthquake sequence occurred in Zigui County, Hubei Province, and the earthquake sequence type is double seismic type. The two earthquake sequences occurred at the water unloading stage of the 175m trial impounding, and G-R relations showed the similar characteristics with that of the tectonic earthquakes. In order to verify the influences of dam reservoir on earthquake triggering, ETAS model was introduced, the results showed that the slow water level changes had little impact on the occurrence of earthquake. Double difference precision relocation results indicated that the two earthquake sequences occurred at the intersection part of a NE-striking fault and the NNW-striking Xiannvshan Fault, and the preferred direction of aftershock distribution was separately NE and NNW. Moment tensor inversion method and P wave initial motion method were used to determine the focal mechanisms of the two earthquakes, and the results indicated that the two earthquakes were controlled by the regional tectonic stress field and were of reverse-slip type. Comprehensive analysis showed that the M4.2 earthquake was caused by a small-scale fault striking NE with a big dip angle. From the hypocenter profile, it can be seen that the M4.2 earthquake sequence was restrained by an east-dip fault, and the M4.5 earthquake sequence was the product under the conjugate action of the NE-striking fault and the NNW-striking Xiannvshan fault. |
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| Keywords: | earthquake sequence focal depth profile focal mechanism ETAS model |
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