Stress rise precursor to earthquakes in the Tibetan Plateau

Zhenhan Wu,Patrick J Barosh,Daogong Hu,Hua Peng,Qunce Chen

doi:10.4236/ns.2013.58a1006

Abstract

Earthquake prediction thus far has proven to be a very difficult task, but changes in situ stress appear to offer a viable approach for forecasting large earthquakes in Tibet and perhaps other continental regions. High stress anomalies formed along active faults before large earthquakes and disappeared soon after the earthquakes occurred in the Tibetan Plateau. Principle stress increased up to ~2 - 5 times higher than background stress to form high stress anomalies along causative faults before the Ms 8.1 West Kunlun Pass earthquake in November 2001, Ms 8.0 Wenchuan earthquake in May 2008, Ms 6.6 Nimu earthquake in October 2009, Ms 7.1 Yushu earthquake in April 2010 and the Ms 7.0 Lushan earthquake in April 2013. Stress near the epicenters rapidly increased 0.10 - 0.12 MPa over 45 days, ~8 months before the Ms 6.6 Nimu earthquake occurred. The high principle stress anomalies decreased quickly to the normal stress state in ~8 - 12 months after the Ms 8.1 West Kunlun Pass and the Ms 8.0 Wenchuan earthquakes. These high stress anomalies and their demise appear directly related to the immediate stress rise along a fault prior to the earthquakes and the release during the event. Thus, the stress rise appears to be a viable precursor in prediction of large continental earthquakes as in the Tibetan Plateau.

Highlights

Large continental earthquakes are a major geologic hazard and commonly result in great disasters as recently occurred in China
The Ms 8.0 Wenchuan earthquake of May 12, 2008 formed a seismic rupture zone with a length of 240 - 270 km along the BeichuanYingxiu fault [18,19] and triggered thousands of largescale landslides, huge rock falls and debris flows in the Longmenshan Mountains [1], at the eastern margin of the Tibetan Plateau
The Ms 7.0 Lushan earthquake, which occurred on April 20, 2013, formed seismic hazards, landslides and rock falls without seismic rupture zone along the eastern marginal thrust in southwestern Longmenshan Mountains

Summary

INTRODUCTION

The Ms 8.0 Wenchuan earthquake of May 12, 2008 formed a seismic rupture zone with a length of 240 - 270 km along the BeichuanYingxiu fault [18,19] and triggered thousands of largescale landslides, huge rock falls and debris flows in the Longmenshan Mountains [1], at the eastern margin of the Tibetan Plateau. The Ms 7.0 Lushan earthquake, which occurred on April 20, 2013, formed seismic hazards, landslides and rock falls without seismic rupture zone along the eastern marginal thrust in southwestern Longmenshan Mountains These large earthquakes, together with the Ms 7.9 Mani earthquake that occurred on November 8, 1997, constitute the most recent activity on the faults bounding the Hohxil-Bayanhar-Garze structural block of the northern Tibetan Plateau (Figure 1). Occurred in the central Tibetan Plateau, such as the Ms 5.6 Dongco earthquake on March 7, 2004 and the Ms 6.6 Nimu earthquake on October 6, 2008, resulted from activity along the boundary normal faults of the YadongYangbajain-Gulu graben system

STRESS CHANGES BEFORE AND AFTER LARGE EARTHQUAKES

CONCLUSIONS AND DISCUSSION