报告地点：腾讯会议ID：987 727 704
报告时间：2022-05-13 从 10:30 到 12:00
裘鸿瑞，2013年于中国科学技术大学获得本科学士学位，郭沫若奖学金获得者，2019年博士毕业于美国南加州大学，后分别于美国莱斯大学和麻省理工学院任博士后职位。主要研究方向包括基于背景噪声的面波成像和监测、基于密集台阵技术对断裂带进行多尺度成像和监测、以及机器学习在速度模型反演和评估中的应用。近五年，在PNAS, GRL, JGR, GJI等杂志发表论文共17篇，其中一作/通讯作者论文8篇，并荣获2021年AGU优秀审稿人奖。
报告题目：Imaging and Monitoring Internal Structures of San Jacinto Fault Zones in Southern California
The San Jacinto Fault Zone (SJFZ) is a component of the San Andreas transform system, the most seismically active fault zone in southern California, and accommodates a large portion of the plate motion in the region. Paleoseismic and historic records indicate that the SJFZ is capable of producing Mw > 7 earthquakes and poses a significant seismic hazard to large urban areas nearby.
Fault zone structures contain important information on various aspects of earthquake and fault mechanics ranging from long-term evolutionary processes to brittle rock rheology and dynamic stress fields operating during the occurrence of earthquakes. Thus, in the first part of this talk, we image the internal structure of the SJFZ using seismograms recorded by dense linear arrays (with station spacing < 100 m) crossing the surface trace of the fault. Analyses of fault zone head waves, delay times of P wave, and fault zone trapped waves illuminate the fault zone internal structure as a combination of an impedance contrast and low-velocity zones. The resulting high-resolution fault zone image (e.g., cross-fault velocity contrast, fault zone geometry, and attenuation), in complement to regional tomographic models with a nominal resolution of 1-2 km, can have profound implications for seismic hazard assessment associated with the SJFZ.
Measuring velocity changes within seismically active fault zones, particularly at depth, has been a long-sought goal of seismology. In the second part of this talk, we study temporal changes in seismic velocities associated with a moderate (Mw 5.2) earthquake that occurred in the SJFZ. Coda waves in daily cross-correlations of ambient noise recorded by two dense linear arrays close to the epicenter are used to estimate the co- and post-seismic structural perturbations in the fault zone. The high-resolution 4-D imaging of the internal structure of the SJFZ provides extra constraints for better simulations of dynamic rupture and ground motion for future earthquakes on the SJFZ.
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