地球与行星物理学术报告通知（202613期）- 韦生吉

报告人简介：

1982年出生，博士生导师，国家高层次人才，现任中国科学院地质与地球物理研究所研究员，深层油气理论与智能勘探开发重点实验室主任。长期致力于地震震源物理、多圈层地球速度结构等地震学及测地学研究，研究内容包括大地震破裂过程、地壳-上地幔结构反演、火山地震学、环境地球物理等，这些前沿的科学探索为理解地震震源物理、板块构造及其地球动力学过程等核心科学问题提供原创性见解。以第一/通讯作者在Science（3篇）、NG、NC、CEE、EPSL、GRL等期刊发表论文40余篇。现任BSSA，Geoscience Letters期刊副主编和Tectonophysics期刊编委。

报告内容摘要：

Global observations reveal faults respond to earthquake ruptures through localized on-fault slip and distributed off-fault deformation (OFD). Deformation becomes increasingly delocalized along faults that are immature or geometrically complex, rupture slowly, or propagate through sediment-rich regions. However, the physical processes by which sediments control this delocalization remain largely unresolved. Here we utilize high-resolution optical imagery to characterize surface rupture and OFD of the 2025 Mw 7.8 Myanmar earthquake, a supershear rupture event on a mature fault topping with thick sediments including the Quaternary alluvium and Irrawaddy Formation. Our results show averaging 32% OFD, far exceeding 13-19% expectation from global observations of such mature faults with simple geometry and supershear rupture speeds. Sediment-rich terrains along this rupture significantly amplify OFD to ~31-42%, nearly double the 19% observed in bedrock, and generate two highly diffused deformation sections lacking clear surface rupture. Dynamic rupture simulations incorporating variations in shear-wave velocity and frictional properties reproduce the observed OFD spectrum (from localized to fully delocalized deformation, revealing that plastic yielding of sediments dramatically delocalizes fault strain in the uppermost few hundreds of meters. We suggest such process should be integrated into models of shallow faulting and seismic hazard assessment in sediment-rich regions worldwide.