High-Resolution Studies of Complex Faulting: Chi-Chi, Taiwan Earthquake

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Abstract for proposal EAR0106701 (PH #18x)Title: High-Resolution Studies of Complex Faulting: Chi-Chi, Taiwan Earthquake PI's: Donald V. Helmberger, CalTechIn recent years, geologists and geophysicists have witnessed a revolution in the development and implementation of an array of new tools for measuring motions of the earth's crust, including global positioning satellites, interferometric synthetic aperture radar, and broadband digital seismic systems, allowing tremendous advances in motion detection accuracy. Japan and Taiwan took the lead in the installation of these instruments, and the recent Chi-Chi, Taiwan earthquake (1999) sequence has produced a remarkable set of data. Over 300 strong-motion acceleration records at distances less than 50 km are now available for the main event, Mw = 7.7. Eleven aftershocks with local magnitudes greater than 6 occurred in the first week, several as large as Northridge. About 10,000 digital 3-component waveforms can now be studied to answer questions about variation in rupture velocity, rise-time, nonlinear behavior, basin amplification, etc. We plan to apply an assortment of newly developed analytical tools involving wavelet transforms, modified annealing, and Pseudo-Green's Functions to explore these new data. In particular, we plan to fix the slip-histories or various sub faults using the static data and using calibrated seismic paths to constrain the rise-time and rupture velocity