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Fault-scarp features and cascading-rupture model for the M (sub w) 7.9 Wenchuan earthquake, eastern Tibetan Plateau, China

G. Yu, Xu Xiwei, Yann Klinger, G. Diao, G. Chen, X. Feng, C. Li, A. Zhu, R. Yuan, T. Guo, X. Sun, X. Tan and Y. An
Fault-scarp features and cascading-rupture model for the M (sub w) 7.9 Wenchuan earthquake, eastern Tibetan Plateau, China (in The 2008 Wenchuan, China earthquake, Anonymous)
Bulletin of the Seismological Society of America (November 2010) 100 (5B): 2590-2614

Abstract

On 12 May 2008, the M (sub w) 7.9 Wenchuan earthquake ruptured two northeast-striking imbricated reverse faults and one northwest-striking reverse fault along the middle Longmen Shan thrust belt, at the eastern margin of the Tibetan plateau. The morphology of the coseismic scarp varies drastically along strike. We distinguish eight different categories: (1) simple thrust scarp, (2) hanging-wall collapse scarp, (3) simple pressure ridge, (4) dextral pressure ridge, (5) fault-related fold scarp, (6) backthrust pressure ridge, (7) local normal fault scarp, and (8) pavement suprathrust scarp. The coseismic surface ruptures confirm that the Wenchuan earthquake is dominated by reverse faulting with some right-lateral component that varies from site to site. The surface rupture can be divided into two parts, the Yingxiu segment and the Beichuan segment. When the earthquake is split into two subevents accordingly, they correspond to an M (sub w) 7.8 event and an M (sub w) 7.6 event, respectively. These two segments can in turn be divided into four second-order subsegments, which are equivalent to four subevents of M (sub w) 7.5, M (sub w) 7.7, M (sub w) 7.0, and M (sub w) 7.5, respectively. The segmentation of the rupture is consistent with a cascading-rupture pattern, responsible for the total 110 s of the earthquake rupture. In addition to surface ruptures, the focal mechanisms determined for the aftershocks recorded by the local seismic network are used to constrain the fault geometry of the subsegments. They show that the dip of the fault responsible for the earthquake varies along strike, and the fault tends to flatten at depth. In addition, the fault plane gets steeper northward, enabling the fault to accommodate a larger strike-slip component along a lateral ramp. This major earthquake confirms that crustal shortening could be the main driving force for the growth of high topography along the eastern margin of the Tibetan Plateau and that lower crustal flow is not required.


ISSN: 0037-1106
EISSN: 1943-3573
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 100
Serial Issue: 5B
Title: Fault-scarp features and cascading-rupture model for the M (sub w) 7.9 Wenchuan earthquake, eastern Tibetan Plateau, China
Title: The 2008 Wenchuan, China earthquake
Affiliation: China Earthquake Administration, Institute of Geology, Beijing, China
Pages: 2590-2614
Published: 201011
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 80
Accession Number: 2010-100825
Categories: SeismologyStructural geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables, geol. sketch maps
N31°00'00" - N33°00'00", E103°00'00" - E106°00'00"
Secondary Affiliation: Institut de Physique du Globe de Paris, CNRS-INSU, FRA, FranceEarthquake Administration of Hebei Province, CHN, ChinaEarthquake Administration of Shanghai Province, CHN, China
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201052
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