Earthquake Physics Revealed by Advanced Seismic Array Back-projections
活动时间：2024年11月21日11：00
活动地点：腾讯会议：243728085 密码：4629
主讲人：Lingsen Meng
Lingsen Meng，男，汉族，副教授，美国加利福尼亚大学洛杉矶分校。B.S., Geosciences, Nanjing University, China June 2007；M.S., Geophysics, California Institute of Technology May 2009； Ph.D., Geophysics, California Institute of Technology June 2013。
Recognitions：
• Hellman Fellowship Award, UCLA, 2015
• The Leon and Joann V.C. Knopoff Chair in physics and geophysics, UCLA, 2014
•Student Presentation Award, SSA (Seismological Society of America), 2012.
• Best Young Scientist Award, CTBT (Comprehensive Nuclear Test-Ban Treaty), 2011.
• Frontiers in Geochemistry Fellowship, Caltech, 2007-2008.
• Fundamental Geosciences Scholarship, Nanjing University, 2003-2006.
在Nature、Science、GRL、EPSL、JGR等顶刊上发表系列论文。
内容简介：
High-frequency seismic waveforms recorded by large regional arrays have enabled back-projections (BP), an emerging tool to probe kinematic rupture processes. In this talk, I present our effort of improving the resolution and reducing the uncertainty of BP imaging, which allows us to address the open questions of earthquake source dynamics. In the case study of the 2015 Mw 8.3 Chile earthquake, we observed the splitting of rupture fronts around the rim of a large barrier. This encircling pattern is analogous to the double-pincer movement in military tactics. Such a degree of complexity is previously only seen in simulations and it is observed for the first time in real earthquakes. The power of BP also allows us to investigate the frequency of supershear earthquakes, which occur when rupture speeds exceed the shear wave speed, causing intense ground shaking. These rare events provide insights into fault mechanics. Using slowness-enhanced back-projection and Rayleigh Mach wave identification, we systematically analyzed seismic data from large (Mw ≥ 6.7) shallow strike-slip earthquakes between 2000 and 2020. We identified four oceanic supershear events and found that 14.0% of large earthquakes during this period were supershear, with similar frequencies in oceanic and continental settings. Supershear events exhibited diverse rupture speeds, attributed to fault damage zones or slip obliqueness. Thicker seismogenic zones and material contrasts may promote supershear propagation in oceanic regions. In the last case study,
we investigated the 2024 Mw 7.5 Noto earthquake and its connection to preceding seismic swarms, we analyzed its rupture process using seismic and geodetic data. The rupture exhibited initial complexity, with a strong fault asperity resisting failure during swarms. The rupture slowed, then a second rupture initiated at the asperity’s opposite edge, leading to double-pincer fronts and asperity failure, driving the earthquake's large scale. This highlights the critical role of fault asperities in swarm migration and rupture propagation, emphasizing the importance of detailed studies for assessing seismic risk in swarm-prone regions.
