Evidence for anthropogenic surface loading as trigger mechanism of the 2008 Wenchuan earthquake
- 321 Downloads
Two and a half years prior to China’s M7.9 Wenchuan earthquake of May 2008, at least 300 million metric tons of water accumulated with additional seasonal water level changes in the Minjiang River Valley at the eastern margin of the Longmen Shan. This article shows that static surface loading in the Zipingpu water reservoir induced Coulomb failure stresses on the nearby Beichuan thrust fault system at <17 km depth. Triggering stresses exceeded levels of daily lunar and solar tides and perturbed a fault area measuring 416 ± 96 km2. These stress perturbations, in turn, likely advanced the clock of the mainshock and directed the initial rupture propagation upward towards the reservoir on the "Coulomb-like" Beichuan fault with rate- and state-dependent frictional behavior. Static triggering perturbations produced up to 60 years (0.6%) of equivalent tectonic loading, and show strong correlations to the coseismic slip. Moreover, correlations between clock advancement and coseismic slip, observed during the mainshock beneath the reservoir, are strongest for a longer seismic cycle (10kyr) of M > 7 earthquakes. Finally, the daily event rate of the micro-seismicity (M ≥ 0.5) correlates well with the static stress perturbations, indicating destabilization.
KeywordsEarthquake Geomechanics Geoengineering Triggered Earthquakes Water Reservoir Tides Sun Moon Gravitation Seismology
The author is grateful to Think Geohazards for its generous financial support. He also thanks the five anonymous reviewers for their constructive critiques and C.H. Scholz and L. Seeber from Lamont-Doherty Earth Observatory for their suggestions and comments to improve this manuscript.
- Bartels J (1985) Tidal Forces. In: Harrison JC (eds) Earth tides. Van Nostrand Reinhold Company, New YorkGoogle Scholar
- Boussinesq J (1885) Application des Potentials a I ’Etude de l ’Equilibre et du Mouvement des Solides Elastiques. Gauthier Villars, ParisGoogle Scholar
- Hu X-M (2007) Natural earthquake activities before the Zipingpu dam began to store water. Earthq Res China 2:16–21Google Scholar
- Klose CD (2008) The 2008 M7.9 Wenchuan earthquake—result of Local and Abnormal Mass Imbalances? EOS Trans AGU 89(53), Fall Meet Suppl, Abstract U21C-08. http://adsabs.harvard.edu/abs/2008AGUFM.U21C..08K
- Klose CD (2009) On to what extent stresses resulting from the earth’s surface trigger earthquakes, AGU Fall Meet. S54A-08S54A-08. http://adsabs.harvard.edu/abs/2009AGUFM.S54A.08K
- Klose CD, Seeber L (2007) Shallow seismicity in stable continental regions. SRL 78:554Google Scholar
- Lei X-L, Ma S-L, Wen X-Z, Su JR, Du F (2008) Integrated analysis of stress and regional seismicity by surface loading—a case study of Zipingpu reservoir. Seismol Geol 30(4):1046Google Scholar
- Lockner DA, Beeler NM (2003) Stress-induced anisotropic poroelasticity response in sandstone. In: 16th ASCE Engineering Mechanics Conference, University of Washington, SeattleGoogle Scholar
- Love AEH (1944) A treatise on the mathematical theory of elasticity, 4th edn. Cambridge University Press, Cambridge 655 ppGoogle Scholar
- Terzaghi K (1938) Einfluß des Porenwasserdrucks auf den Scherwiderstand der Tone. vol 33. BerlinGoogle Scholar
- Wang W-M, Zhao L-F, Li J, Yao Z-X (2008) Rupture process of the Ms8.0 Wenchuan eartquake of Sichuan, China. Chin J Geophys 51(5):1403Google Scholar