What are the sources of future earthquakes in southern California? Research tasks include estimating the location and focal mechanisms of earthquakes, estimating the geometry and slip rates of active faults, determining the size and extent of past ruptures on these faults, geophysical measurements of fault properties, and measuring the strain-rate field.

What are the probabilities, as a function of magnitude, location, and time, of earthquakes in southern California. Research tasks include formulating and testing stationary or time-dependent seismicity models, formulating and testing hypotheses of fault segmentation, modeling stress interactions among faults and earthquakes, and simulation of long-term earthquake recurrence. Proposals that infer characteristic earthquake magnitudes from fault geometry using existing models address Question 1, while projects to test these models or to develop new ones respond to Question 2.

What are the characteristics of earthquake rupture? Research tasks include geological and geodetic investigations of the detailed slip distributions of recent earthquakes; inversion of seismic waveform data to determine rupture progression in recorded earthquakes; examining seismic waveform data for effects of segmentation; postseismic investigations to detect seismic velocity, stress, or heat flow variations caused by recent earthquakes, and theoretical rupture calculations.

How do source, path and site effects influence seismic ground motion? Research tasks include construction of velocity models for use in waveform modeling; collection of shear-wave velocity, surface geology, and other data relevant to site effects; statistical studies of the effectiveness of techniques for modeling linear and nonlinear site effects; numerical modeling of waveforms; investigations of the non-uniqueness in interpreting observed waveforms; testing of complete seismogram calculations using available full-waveform data; and calculation of theoretical seismograms for scenario earthquakes.

1997 Progress Reports