Acceleration of Deep Slip Along the Longmenshan Fault Plane Before the 2008 M8.0 Wenchuan Earthquake

Abstract

The first step toward earthquake forecasting is the identification of variables whose spatio-temporal variation can be connected with pre-seismic crustal deformation. Four periods of campaign Global Positioning System (GPS) observations around the Longmenshan fault zone (LFZ) provide important insights in crustal deformation and deep fault slip before the 2008 M8.0 Wenchuan earthquake. By using TDEFNODE to invert the coupling fraction and dynamic slip deficit rate of the Longmenshan fault plane before the Wenchuan earthquake, we show that under a background of strong coupling, the compressive slip deficit rate perpendicular to fault increased slightly at first and then decreased; a value of ∼1.5–3.6 mm/a along the central–southern segment from 1999 to 2001 increased to ∼1.9–3.9 mm/a from 2001 to 2004, and then decreased to ∼1.1–2.6 mm/a from 2004 to 2007. The dextral slip deficit rate parallel to fault was ∼6 mm/a from 1999 to 2004, before increasing significantly to ∼9.5 mm/a from 2004 to 2007, when the compressive slip deficit rate decreased. At the same time, large-scale GPS velocity profiles show that compressive shortening deformation in the Eastern Tibet Block, perpendicular to fault, increased slightly from 2001 to 2004, and then decreased from 2004 to 2007. Meanwhile, the dextral shear deformation parallel to fault near the LFZ increased significantly from 2004 to 2007. These findings are in good agreement with those calculated using repeating earthquake sequences, indicating that the deep slip rate of the Longmenshan fault plane may have accelerated several years before the Wenchuan earthquake. Our results demonstrate that GPS data can record pre-seismic preparatory processes, and have the potential for use in medium-term large earthquake forecasting.

Reconciling High-resolution Strain Rate of Continental China from GNSS Data with the Spherical Spline Interpolation

“…On the eastern side of the Himalayan Main Thrust, the dilatation rate reaches about −80 × 10 −9 /𝑦𝑦𝑟𝑟, caused by the lateral extrusion of the Tibetan plateau being blocked by the SCB (Leigh H. Royden et al, 1997;Zhang et al, 2018;Zhang et al, 2004). The deformation of the Gan-Yushu Fault, XSHF, the Xiangjiang River Fault, and the Red River Fault region in the junction of the Tibetan Plateau and the SCB is to the vertical direction of the extrusion overflow and greater than the extrusion, so these areas generally exhibit a tensile nature Zhao et al, 2022). We believe that it is also due to the lateral extrusion of the Qinghai-Tibet Plateau caused by the South China plate blocking it from overflowing in the vertical direction.…”

Editorial: From preparation to faulting: multidisciplinary investigations on earthquake processes

“…to rapid rupture propagation (Yang et al, 2022), is significant to earthquake forecasting and demands a comprehension of the stress state and evolution during the time of geophysical observations around seismically active areas (Zhao et al, 2020;Zhao et al, 2022). The evidence from multiscale experiments (Ma and Guo, 2014;Huang et al, 2019;Huang et al, 2020;Martinelli et al, 2020), multidisciplinary monitoring system networks (Huang FQ.…”

“…A variety of geophysical and geochemical observations, ranging from ground-related deformation patterns (GPS, SAR, etc.) (Bürgmann et al, 2000;Zhao et al, 2020) to pre-earthquake changes (geochemical, electromagnetic, hydro-geological, geodetic, or thermodynamic) (Huang F. Q. et al, 2017;Zhou et al, 2020;Chen et al, 2021;Martinelli et al, 2021;Zhou et al, 2021), recorded by ground-based (Li et al, 2022) or satellite-based techniques (Li et al, 2020) may be related to stress variations in the lithosphere (Luo et al, 2023) prior to an eventual large earthquake (Zhao et al, 2022). Even though much effort has been invested, the earthquake "elephant in the room" is still in the process of being understood.…”