Active fault growth with geologic inheritance –through the lens of earthquake rupture

Fault maturity has been proposed to exert a first-order control on earthquake rupture, yet direct observations linking individual rupture to long-term fault growth are rare. The 2021 Mw 7.4 Maduo earthquake ruptured the east-growing end of the slow-moving (~1 mm/yr) Jiangcuo fault in north Tibet, providing an opportunity to examine the relation between rupture characteristics and fault structure. Here, we combine field and multiple remote sensing techniques to map the surface rupture at cm-resolution and document comprehensively on-fault offsets and off-fault deformation. The 158 km-long surface rupture consists of misoriented structurally inherited N110°-striking segments and younger optimally oriented N093°-striking segments, relative to the regional stress field. Despite being comparatively newly formed, the ~N093°-striking fault segments accommodate more localized strain, with up to 3 m on-fault left-lateral slip and 25-50% off-fault deformation, and possibly faster rupture speed. These results are in contrast with previous findings showing more localized strain and faster rupture speed on more mature fault segments; instead, our observations suggest that fault orientation with respect to the regional stress can exert a more important control than fault maturity on coseismic rupture behaviors when both factors are at play.