Title: Spatial and Temporal Variations in the Moment Tensor Solutions of the 2008 Wenchuan Earthquake Aftershocks and Their Tectonic Implications

Abstract

Following the mainshock of the 2008 M8 Wenchuan Earthquake, there were more than 300 M_L ≥ 4.0 aftershocks that occurred between 12 May 2008 and 8 September 2010. We analyzed here the broadband waveforms for these events and found 160 events with sufficient signal-to-noise levels to invert for seismic moment tensors. Considering the length of the activated fault and the distances to the recording stations, four velocity models were employed to account for variability in crustal structure. The moment tensor solutions show considerable variations with a mixture of mainly reverse and strike-slip mechanisms and a small number of normal events and ambiguous events. We analyzed the spatial and temporal distribution of the aftershocks and their mechanism types to characterize the structure and the deformation occurring in the Longmen Shan fold and thrust belt. Our results suggest that the stress is very complex at the Longmen Shan fault zone. The moment tensors have both a spatial segmentation with two major categories of the moment tensor of thrust and strike slip; and a temporal pattern that the majority of the aftershocks gradually migrated to thrust-type events. The variability of aftershock mechanisms is a strong indication of significant tectonic release and stress reorganizationmore » that activated numerous small faults in the system.« less

Authors:

Lin, X.  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-3247-242X"

Dreger, D. ^[2]; Ge, H. ^[3]; Xu, P. ^[1]; Wu, M. ^[1]; Chiang, A.  ^[4];

• Search DOE PAGES for author "Chiang, A."
• Search DOE PAGES for ORCID "0000-0001-8513-4363"

Zhao, G. ^[1]; Yuan, H.  ^[5]

• Search DOE PAGES for author "Yuan, H."
• Search DOE PAGES for ORCID "0000-0003-3512-7856"

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+ Show Author Affiliations

1. Beijing Earthquake Agency (China)
2. Univ. of California, Berkeley, CA (United States). Berkeley Seismological Lab.
3. China Univ. of Petroleum, Beijing (China). Unconventional Natural Gas Inst.
4. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
5. Macquarie Univ., North Ryde, NSW (Australia). ARC Centre of Excellence from Core to Crust Fluid Systems; Univ. of Western Australia, Perth, WA (Australia). Centre for Exploration Targeting; Geological Survey of Western Australia, East Perth, WA (Australia)

Publication Date:

Sat Mar 10 00:00:00 EST 2018

Research Org.:

Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Beijing Earthquake Agency (China); China Univ. of Petroleum, Beijing (China)

Sponsoring Org.:

USDOE; National Natural Science Foundation of China (NSFC); China Earthquake Administration (CEA); China Scholarship Council

OSTI Identifier:

1513154

Report Number(s):

LLNL-JRNL-771048
Journal ID: ISSN 0278-7407; 960868

Grant/Contract Number:  

AC52-07NA27344; 41604045; 41474087; XH16004Y

Resource Type:

Accepted Manuscript

Journal Name:

Tectonics

Additional Journal Information:

Journal Volume: 37; Journal Issue: 3; Journal ID: ISSN 0278-7407

Publisher:

Wiley/American Geophysical Union (AGU)

Country of Publication:

United States

Language:

English

Subject:

58 GEOSCIENCES; aftershock sequence; moment tensor solution; broadband waveforms; Wenchuan earthquake