报告地点：教学行政楼706 会议室
报告时间：2024-05-24 从15:00到17:00
报告人：Yunyue Elita Li（Purdue University）
报告人简介：
Dr. Yunyue Elita Li joined theDepartment of Earth, Atmospheric, and Planetary Science at Purdue University as a Mary J. Elmore New Frontiers Associate Professor in Data Science in August 2021. She was an assistant professor in the Department of Civil and Environmental Engineering at the National University of Singapore. Elita did her postdoctoral research at Massachusetts Institute of Technology after she received her Ph.D.degree in Geophysics from Stanford University.
She obtained her B.S. degree in Information and Computational Science from China University of Petroleum, Beijing. Elita received the2018 J.Clarence Karcher Award from the Society of Exploration Geophysicists, the 2022 SEG South & East Asia Honorary Lecturer Award, and the 2022 Young Innovator Award for Land Transport Excellence from the Land Transport Authority of Singapore.
报告题目：Stationary phase analysis: making sense of nonballistic arrivals in noise cross-correlation functions
报告内容简介：
The ambient seismic monitoring community has grown exponentially in the past few decades using the basic mathematical operation of cross-correlation. Triggered many empirical successes in monitoring weak changes (on the order of 0.1 %) in the earth with ambient noise correlations, skepticism and conviction of thecross-correlation coda method have become equally strong. In this talk, I will present analytical stationary phase solutions for ambient noise cross-correlations, with an explicit focus on non-ballistic arrivals. We establish the mathematical and corresponding physical conditions that drastically differentiate the non-ballistic arrivals in the stacked cross-correlation and the actual Green's functions. In ambient noise environments, the coda waves due to random medium scatterings of an impulsive source cannot be distinguished from the cross-talk artifacts due to overlapping random noise sources. Therefore, changes in the non-ballistic arrivals cannot be uniquely attributed to changes in the medium or changes in the noise source environment without additional constraints. The theoretical results demand that interpreting large-elapse-time arrivals in the stacked cross-correlation functions as coda waves for deterministic information about the propagation medium should be conducted only after the source influence is sufficiently ruled out. Once the source influence is eliminated, the stationary phase solutions for scattering waves provide solid basis for extracting reliable scattering information from the noise correlation functions for higher resolution imaging and monitoring.