Seismological Investigations of Earthquakes and Deep Earth Structure

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The increasing availability of large numbers of high-quality digital records from the global seismic networks has made possible a variety of new ways to study earthquakes and deep Earth structure. By analyzing hundreds or thousands of seismograms, it is often possible to resolve new features in the data, or to perform more comprehensive analyses of problems that were previously addressed on smaller scales. This project will continue analyses of global seismic data at U.C. San Diego to examine a variety of geophysical issues. These include: (1) Examining the lithosphere-asthenosphere boundary using receiver functions and SS precursors, (2) Imaging earthquake rupture using back-projection methods, (3) Observation and modeling of scattered energy between major body-wave seismic phases to constrain the statistical properties of mantle heterogeneity at scale lengths shorter than can be resolved using seismic tomography, (4) Systematic searches for (and tests of prior claims of) the inner-core shear phase PKJKP. This project supports the educational program at U.C. San Diego by providing funds for graduate and postdoctoral students. This research is likely to lead to improved models of Earth structure and earthquake rupture processes, which will be of interest to the tectonics, geodynamics and mineral physics communities. Results will be widely disseminated through publications, conference presentations, and material provided to SIO?s education and outreach programs. Networks of global seismic stations now record vast amounts of data, which have a wealth of information about both earthquakes and deep Earth structure. However, analysis of these data has lagged because traditional methods are time-intensive and do not fully exploit the capabilities of modern computers. By applying automated methods to hundreds or thousands of seismograms, it is often possible to resolve new features in the data, or to perform more comprehensive analyses of problems that were previously addressed on smaller scales. This U.C. San Diego project develops and applies these new methods to examine a variety of topics. These include: (1) Probing the boundary between Earth's relatively rigid upper layer and the more plastic layer below, (2) Examining earthquake rupture using high-frequency seismic waves, (3) Studying scattered seismic waves to understand the frequency and strength of small-scale structures in the deep Earth, and (4) Testing the solidity of Earth's inner core through study of a hard-to-observe seismic wave arrival called PKJKP. This research is likely to lead to improved models of Earth structure and earthquake rupture processes.