Wide and Asymmetric Low-Velocity Zone Surrounding the Immature Jiangcuo Fault that Ruptured During the 2021 Mw 7.4 Maduo Earthquake, China

Abstract Fault damage zones critically influence seismic wave propagation, rupture dynamics, and seismic hazard assessment, yet the relationship between damage zone width and cumulative fault displacement remains uncertain. In this study, we investigate the internal structures of the Jiangcuo fault that ruptured in the 2021 Mw 7.4 Maduo earthquake in the northern Tibetan plateau, Western China. A 60-station dense linear seismic array was deployed across the Jiangcuo fault, 30 km east of the epicenter. Utilizing teleseismic P-wave delays recorded by the array, we identify a low-velocity zone (LVZ) approximately 2.5–3.3 km wide situated asymmetrically south of the 2021 earthquake surface rupture. This wide damage zone is inconsistent with the expectations of the immature Jiangcuo fault but is best explained by the asymmetrically growing Jiangcuo fault zone, where abandoned fault strands preserve damage accumulated from past ruptures. We suggest that comparisons of LVZ widths are only meaningful when the same method and similar array geometry are employed. Our findings highlight the importance of incorporating structural complexities and geological history when evaluating rupture dynamics and fault zone properties in strike-slip tectonic environments.