seminar: Seismic focal spot imaging applied on USArray records

Author: Christina Tsarsitalidou
Time: 11H00
Language: French/English
Place: Conference Room at LabTAU

Abstract: Seismic imaging constitutes a fundamental building block of Earth Science research as the obtained
images or snapshots of our planet’s interior challenge our understanding of plate tectonics, yield
information on fault zone environments and inform many near-surface engineering applications. In
this work, we explore the imaging potential of refocusing surface waves reconstructed from noise
correlation functions so as to estimate the seismic velocity. At zero lag-time, converging surface
wave fields create a large amplitude feature at the origin referred to as focal spot. Its properties are
governed by local medium properties and have long been used in medical imaging approaches such
as passive elastography. We treat dense seismic arrays equivalent to medical ultrasound transducers
that allow the reconstruction of focal spots at near-field distances. We focus on demonstrating the
general applicability of the method using the USArray dataset, but we also investigate the biasing
effects of ambient wave field properties on our estimates, like impinging body wave energy and
non-isotropic energy flux.