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The Accelerated Slip Deficit Rate of the Longmenshan Fault Plane Before the 2008 M8.0 Wenchuan Earthquake

Session: New Insights Into the Preparatory Phase of Earthquakes From Tectonic, Field and Lab Experiments III

Type: Oral

Date: 4/19/2021

Presentation Time: 05:00 PM Pacific

Description: 

Geodetic data can be used to invert the slip deficit rate at different depths of fault plane. In this study, GPS velocity field data of China from 1999-2001, 2001-2004 and 2004-2007 before the Wenchuan earthquake were used to construct the multi-fault system three-dimensional model of the Longmenshan structural belt, and the spatial-temporal evolution process of slip deficit rate at the Longmenshan fault plane before the 2008 M8.0 Wenchuan earthquake was obtained by the negative dislocation inversion. The results show that, under the background of strong coupling, the dextral slip deficit rate of the fault was about 6mm/a in 1999-2001 and 2001-2004, and the magnitude was stable, but it increased rapidly to about 9.5mm/a in 2004-2007. However, the compressive deficit rate of the fault plane changed little during the three time periods and basically remained at 3-4mm/a.

The dextral slip deficit rate of 6-9.5mm/a on the deep fault plane obtained in this study is much higher than the slip rate of 2-3mm/a on the surface, but it is close to the slip rate of about 3.5-9.6mm/a in the 4-18km range of the deep fault estimated by repeated earthquakes by Li et al. (2011), indicating that the slip rate on the deep fault plane of the Longmenshan fault is about 2-3 times that of the surface slip rate observed by GPS, geology and other superficial observations (Chen et al., 2018). At the same time, the dextral slip deficit rate increases rapidly to around 9.5 mm/a in 2004-2007, and this result is consistent with the short-term acceleration of slip around 2006 in Hongkou-Wenchuan and Beichuan obtained by Chen et al. (2018) using repeated seismic sequence, which indicates that the Longmenshan fault plane may have accelerated deep slip rate before the Wenchuan earthquake.

References

Chen Q F, Li L. Deep deformation of the Longmenshan fault zone related to the 2008 Wenchuan earthquake (in Chinese). Chin Sci Bull, 2018, 63: 1917–1933

Li L, Chen Q F, Niu F L, et al. Deep slip rates along the Longmen Shan fault zone estimated from repeating microearthquakes. J Geophys Res, 2011, 116: B09310

Presenting Author: Jing Zhao

Student Presenter: Yes

Authors