Ambient Noise Attenuation and Differential Adjoint Tomography Applied to the Hongkou Linear Array Across the Longmenshan Fault Behind the 2008 M 7.9 Sichuan Earthquake
Description:
The Longmenshan Fault is responsible for the 2008 M 7.9 Sichuan earthquake. In this study, we investigate the structure of the thrust fault zone using amplitude and phase information derived from ambient seismic noise. We analyze seismic noise data collected by a dense linear array of 51 3-C sensors across the Longmenshan Fault Zone at Hongkou Town, which is approximately 28 km northeast of the epicenter of 2008 Sichuan earthquake and within 100 km from the center of Chengdu, a metropolitan city with 16 million population. We extract amplitude decay information from the noise interferometry functions across the linear array by finding different combinations of station triplets (Liu et al. 2021), which cancel the effects of noise sources and unknown attenuation structure between the far-field noise sources and the linear array. In addition, we perform phase velocity tomography and convert the phase velocity map to S wave velocity in the top 5 km depth using Monte Carlo Markov Chain (MCMC). The results delineate the thrust-fold fault structure near Hongkou and suggest that the WFSD-1 drilling hole did not reach the main fault plane at Hongkou, which is situated further southeast and is associated with an asymmetric fault damage zone at ~1 km depth in the footwall of the Pengguan thrust fault. Our results agree with previous observations from seismic reflection profiles, InSAR data and WFSD drilling holes along the same line. Finally, we utilize ambient noise differential adjoint tomography (Liu et al. 2023) to improve velocity structure inversion, and the updated results will be presented at the meeting.
Session: 3D Wavefield Simulations: From Seismic Imaging to Ground Motion Modelling [Poster Session]
Type: Poster
Date: 5/2/2024
Presentation Time: 08:00 AM (local time)
Presenting Author: Xin
Student Presenter: No
Invited Presentation:
Authors
Xin Liu Presenting Author Corresponding Author liuxine@hku.hk University of Hong Kong |
Hongyi Li lih@cugb.edu.cn China University of Geosciences Beijing |
Gregory Beroza beroza@stanford.edu Stanford University |
Lei Yang yanglei2@mail.iggcas.ac.cn Chinese Academy of Sciences |
Guochun Zhao gzhao@hku.hk University of Hong Kong |
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Ambient Noise Attenuation and Differential Adjoint Tomography Applied to the Hongkou Linear Array Across the Longmenshan Fault Behind the 2008 M 7.9 Sichuan Earthquake
Session
3D Wavefield Simulations: From Seismic Imaging to Ground Motion Modelling