Studies of Global and Regional Seismicity

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This project involves studies of global and regional seismicity.Central to the project is a continuation of the HarvardCentroid-Moment-Tensor (CMT) Project, which now represents a22-year-long effort to analyze global earthquake activity and tomaintain a comprehensive and authoritative catalog of earthquakefocal mechanisms, the CMT Catalog. In addition to the systematicanalysis and of earthquakes and dissemination of earthquake information,the research also includes the development of a dynamic earthquakemoment-tensor database. The new catalog will be searchable on theweb, and will include auxiliary data, such as information about theseismograms and Earth model used in the analysis, the quality ofthe solution, and any history of updates to the results.A second component of the project is an examination of previouslyundetected earthquakes. More than 1,800 events with magnitudes greaterthan 4.7 have recently been found using a new detection algorithm, anda substantial subset of these are clearly not common earthquakes.The effort will involve a first-order, systematic analysisof the new events to determine why they eluded earlierdetection (e.g., whether all of the events lack high-frequencyradiation and are thus slow earthquakes) and the specific tectonic(or non-tectonic) explanations for several specific groups ofdetections, including (1) events associated with volcanic eruptionsor collapses; (2) events associated with glaciers in Alaska, Antarctica,and Greenland; and (3) events off the coast of North Carolina,possibly associated with submarine slumping.