Broadband Seismological Investigations of Earth Structure and Earthquake Sources

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In this four-year renewal proposal the PI consolidates his research efforts using broadband digital seismic data to address fundamental questions about earthquake rupture processes and deep earth structure. The primary focus is on quantitative analysis of seismic wave recordings to determine how large earthquakes rupture, how ground shaking from the ruptures is affected by the faulting process, how tsunami are generated by submarine faulting, and how stress changes from one earthquake affect other earthquakes. This effort is directly relevant to the global mitigation of earthquake and tsunami damage and development of resilience to natural earthquake and tsunami events. Broader impacts of this project include training of graduate students, public outreach and contributing to seismic hazard assessment along subduction zones around the world.The proposed research will build upon the significant progress made under the expiring four-year grant in the following areas: (1) joint modeling and inversion of broadband seismic body and surface waves, tsunami observations, and high-rate geodetic data that exploits their complementary sensitivity to source processes will be sustained, with application to recent great earthquakes in Mexico and the Komandorsky Islands; (2) development of new seismological procedures for evaluating the up-dip extent of rupture in subduction zone plate boundary earthquakes will be undertaken, with 3D numerical modeling of water multiple excitation to constrain near-trench-rupture; (3) synthesis of large earthquake seismological parameters for different categories of faulting will be extended from completed work on megathrust events, including further exploration of the Radiated Energy Enhancement Factor (REEF), which is a new measure of relative seismic energy release for large earthquakes that characterizes differences in rupture complexity; and (4) stacking and modeling of multi-scale arrays of seismograms from deep earthquakes will be performed to enhance images of P and S velocity structure in end-member regions of the lowermost mantle applying constraints from phase equilibria for lower mantle phases, with procedures for separating source, receiver and deep contributions to the waveforms. This overall research effort will involve the PI and two graduate students who will engage in both earthquake source and structure research problems, along with continuing collaborations with colleagues at other institutions. We anticipate sustaining progress in characterizing important dynamical processes associated with earthquake processes and the Earth's internal dynamical structures as the primary intellectual merit of the project. The broader impacts will be on graduate student training, contribution to seismic/tsunami hazard assessment in developing nations, enhancing public awareness of earthquake processes and earth dynamics, graduate student interaction with STEM-oriented undergraduate freshmen, and contribution to multidisciplinary research on geophysical grand challenge problems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.