This research follows advances developed under a prior NSF grant where new techniques were formulated for the detection and characterization of earthquakes with anomalously long duration. A new 10-year catalog of normal-mode excitation events has been made that allows the systematic identification of slow earthquakes on a global scale. This has led to the discovery of a new type of earthquake which excites free oscillations but does not generate wave groups observable on long-period or short- period seismograms, called "quiet earthquakes." These unusually slow events may be precursory to fast ruptures, or normal earthquakes. This research will more precisely define the slow ruptures and investigate whether they are precursory to large damaging events and thus provide a means of short-term earthquake prediction. This research is a component of the National Earthquake Hazard Reduction Program.
