AUTHOR=Wang Zibo , Liu Ruifeng , Liu Wei 

TITLE=Source characteristics of the aftershocks of the Wenchuan and Lushan earthquake sequences in the Longmen-Shan fault zone

JOURNAL=Frontiers in Earth Science

VOLUME=Volume 10 - 2022

YEAR=2023

URL=https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2022.1061754

DOI=10.3389/feart.2022.1061754

ISSN=2296-6463

ABSTRACT=We used high-quality seismic data from the Global Seismograph Network and National Earthquake Data Center of China to estimate the apparent stress and stress drop of 193 Mw 3.9-8.0 earthquakes from 2008 to 2022 in the Longmen-Shan Fault zone. The dataset included two sequences that occurred in the area, including the 2008 Wenchuan earthquake sequence and the 2013 Lushan earthquake sequence. First, our results suggested that the values of apparent stress varied from approximately 0.1 to 11 MPa (the median value was 0.89 MPa). The moderately high energy release from earthquakes may be associated with the high stress accumulation and the strong deformation characteristics in the intraplate environment of the Longmen-Shan Fault zone. For aftershocks, the values of the stress drop vary from approximately 0.24 to 39 MPa (the median value was 3.53 MPa) and radiation efficiency varied mostly between 0.1 and 0.3 (the median value was 0.23). The values of the stress drop appear to show a slightly increasing trend with the seismic moment. Second, we investigate the radiated energy enhancement factor (REEF) to quantify the source complexities. The REEF values of mainshocks were much higher than those of aftershocks, suggesting that large earthquakes have higher source complexity than small earthquakes. Most aftershocks have REEF values between 1.2 and 7.1, indicating that the REEF values of most aftershocks are consistent with expectations based on the Brune model, and there exist differences in the source complexity of earthquakes within the source area. Compared to radiation efficiency, the REEF would allow comparisons between different earthquakes and be not limited by earthquake size. The results of the study will help us understand the overall characteristics of the Longmen-Shan Fault zone and provide a reference for comparing the systematic differences among different source areas.