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Tectonic Stress State Changes Before and After the Wenchuan M s 8.0 Earthquake in the Eastern Margin of the Tibetan Plateau
Author(s) -
Wen MENG,
Qunce CHEN,
Manlu WU,
Chengjun FENG,
Xianghui QIN
Publication year - 2015
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/1755-6724.12396
Subject(s) - geology , seismology , stress field , fault (geology) , stress (linguistics) , plateau (mathematics) , tectonics , shear stress , active fault , shear (geology) , earthquake rupture , petrology , finite element method , mechanics , mathematical analysis , linguistics , philosophy , physics , mathematics , thermodynamics
Crustal tectonic activities are essentially the consequences of the accumulation and release of in situ stress. Therefore, studying the stress state near active faults is important for understanding crustal dynamics and earthquake occurrences. In this paper, using in situ stress measurement results obtained by hydraulic fracturing in the vicinity of the Longmenshan fault zone before and after the Wenchuan M s 8.0 earthquake and finite element modeling, the variation of stress state before and after the Wenchuan M s 8.0 earthquake is investigated. The results show that the shear stress, which is proportional to the difference between principal stresses, increases with depth and distance from the active fault in the calm period or after the earthquakes, and tends to approach to the regional stress level outside the zone influenced by the fault. This distribution appears to gradually reverse with time and the change of fault properties such as frictional strength. With an increase in friction coefficient, low stress areas are reduced and areas with increased stress accumulation are more obvious near the fault. In sections of the fault with high frictional strengths, in situ stress clearly increases in the fault. Stress accumulates more rapidly in the fault zone relative to the surrounding areas, eventually leading to a stress field that peaks at the fault zone. Such a reversal in the stress field between the fault zone and surrounding areas in the magnitude of the stress field is a potential indicator for the occurrence of strong earthquakes.