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

Journal Article · · Tectonics
ORCiD logo [1];  [2];  [3];  [1];  [1]; ORCiD logo [4];  [1]; ORCiD logo [5]
  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)
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Following the mainshock of the 2008 M8 Wenchuan Earthquake, there were more than 300 ML ≥ 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 reorganization that activated numerous small faults in the system.

Research Organization:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Beijing Earthquake Agency (China); China Univ. of Petroleum, Beijing (China)
Sponsoring Organization:
USDOE; National Natural Science Foundation of China (NSFC); China Earthquake Administration (CEA); China Scholarship Council
Grant/Contract Number:
AC52-07NA27344
OSTI ID:
1513154
Report Number(s):
LLNL-JRNL--771048; 960868
Journal Information:
Tectonics, Journal Name: Tectonics Journal Issue: 3 Vol. 37; ISSN 0278-7407
Publisher:
Wiley/American Geophysical Union (AGU)Copyright Statement
Country of Publication:
United States
Language:
English

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Cited By (1)

A Gravity Study of the Longmenshan Fault Zone: New Insights Into the Nature and Evolution of the Fault Zone and Extrusion-Style Growth of the Tibetan Plateau Since 40 Ma journal January 2019

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58 GEOSCIENCES
Wenchuan earthquake
aftershock sequence
broadband waveforms
moment tensor solution