Broadband Seismological Investigations of Earth Structure and Earthquake Sources

University Of California-Santa Cruz, Santa Cruz CA

Investigators

Abstract

The UCSC seismological research program supervised by Professor Thorne Lay uses global broadband digital seismic data (as well as high-rate GPS data and tsunami recordings) to address fundamental questions about earth structure and earthquake rupture processes. Quantitative analysis of recorded wave-fields generated by earthquakes will be used to address the following fundamental questions: (1) joint inversions of high-rate GPS data, broadband seismic body waves and surface waves, and tsunami observations will be undertaken for recent huge earthquakes in Chile, Mentawai, and off-Sumatra, for the purpose of understanding how the ruptures grew and how the faults slipped in each case; (2) spectral analysis of earthquakes on and near plate boundary megathrust faults will be conducted using strong-motion and teleseismic recordings of seismic wave vibrations to further develop and test a recently introduced model of depth-dependent variations in seismic radiation from megathrust faults; (3) stacking and migration of seismograms from deep focus earthquakes will be performed to develop images of upper mantle reflectivity and heterogeneity spectrum in the vicinity of subduction zones; and (4) new stacking and migration approaches will be applied to imaging of deep mantle scattering from structures near the core-mantle boundary and near mantle down-wellings and up-wellings to better characterize the thermal and dynamical nature of these planetary features. This overall research effort will engage the PI and two graduate students in both earthquake source and earth structure research problems using quantitative analysis of various wave types generated by earthquake sources. We hope to fully characterize the depth-dependence of seismic radiation from earthquakes, and to evaluate the implications for earthquake shaking hazard. We anticipate sustaining progress in characterizing important dynamical processes associated with the Earth's major boundary layers near the surface and near the core-mantle boundary, drawing upon this information to understand the heat flow in the Earth and the dynamical processes that drive earthquakes and volcanoes at the surface.