The Seismic Potential in the Seismic Gap Between the Wenchuan and Lushan Earthquakes Revealed by the Joint Inversion of Receiver Functions and Ambient Noise Data

Abstract

Based on a dense seismic array deployed to monitor the seismic gap between the Wenchuan and Lushan earthquakes, a joint inversion of dispersion curves and receiver functions yielded a fine velocity structure in this region with the highest resolution of approximately 20 km. The results show that the upper crust of the Songpan‐Ganzi terrane overthrusted onto the basement of the Sichuan Basin, indicating that the crustal shortening model may be the major mechanism that accounts for the growth of the Longmenshan. The results also show a low‐velocity zone (Vs < 3.5 km/s) and thickened crust (>67 km) beneath the seismic gap, which could be associated with partial melting. The heat transferred from the partial melting at the base of the seismic gap may increase the temperature of the faults to as high as 300–400 °C and cause the segment of the Longmenshan Fault in the seismic gap to become “aseismic.” In contrast, the Shuangshi‐Dachuan Fault, Dayi Fault, and other blind faults to the east‐southeast of the seismic gap are located above a high‐velocity body. The seismogenic environment of these faults is similar to the segments ruptured during the Wenchuan and Lushan earthquakes, both of which occurred above the westward extension of the strong Sichuan Basin. Higher seismic activity was also observed along these faults than that above the low‐velocity zone. Therefore, we deduce that a major earthquake on these faults is possible and that the magnitude could be larger than that of the Dayi earthquake (M 6.2).

Seismic Azimuthal Anisotropy for the Southeastern Tibetan Plateau Extracted by Wave Gradiometry Analysis

“…According to the sensitivity kernel curve shown in Figure S5, the results of T = 20, 40, and 60 s are mostly sensitive to the structures at depth ranges of approximately 25, 60, and 90 km, respectively. The isotropic velocity maps of the southeastern Tibetan Plateau are consistent with previous studies by either body wave tomography or surface wave tomography (Fan et al, 2015; He et al, 2017; Liu et al, 2018; Liu et al, 2014; Yao et al, 2010), and the other three WG's parameters are connected with velocity boundary and wave direction.…”

“…Journal of Geophysical Research: Solid Earth Liu et al, 2018;Liu et al, 2014;Yao et al, 2010), and the other three WG's parameters are connected with velocity boundary and wave direction.…”

“…Over the past 20 years, roughly 200 moderate and severe earthquakes (≥M5) occurred in this area (collecting from https://earthquake.usgs.gov), including the catastrophic Wenchuan, Lushan, and Jiuzhaigou earthquakes of the last 11 years. Current tectonic movement is still active (Cheng et al, 2012; Liang et al, 2018; Liu et al, 2018; Matsushita et al, 2019; Wang et al, 2018; Zhou, 2008), and future seismic risk is still very high. Therefore, understanding tectonic processes and deep geodynamics in the southeastern margins of the Tibetan Plateau is very important for scientific research, earthquake prevention, and hazard mitigation.…”

The Indo–Eurasia convergent margin and earthquakes in and around Tibetan Plateau

“…Based on Pg tomography and the theory of maximum effective moment, Pei et al (2014) argued that this region is weak and ductile in nature and cannot accumulate stress to generate large (M > 7) earthquakes. Liu et al (2018) observed a LVL and a thick crust in this region; they associated the LVL with partial melt to account for the aseismic feature. Based on paleoseismic activity, Shao et al (2019) also concluded that rocks in this gap are ductile with low strength, although they found four paleoseismic events.…”

Conjugate Fault Deformation Revealed by Aftershocks of the 2013 Mw6.6 Lushan Earthquake and Seismic Anisotropy Tomography

“…Both the Wenchuan and Lushan earthquakes led to rich aftershock sequences. It is worth noting that there is a gap in aftershocks in a ∼60 km segment between the Wenchuan earthquake and the Lushan earthquake on the LFS, the potential seismic hazard of which has been debated (Liu et al., 2018; Pei et al., 2014).…”