Collaborative Research: Patterns of Serial Fault Rupture in Taiwan

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Kerry SiehEAR-0208505This project undertakes studies of two active fault systems in Taiwan, the Chelungpu and Longitudinal Valley faults, which ruptured during large earthquakes in 1999 and 1951, in order to address recurrence fault behavior and the temporal variability of rupture modes. Acquisition of rupture time series on the Chelungpu and Longitudinal Valley faults provide constraints on physical models of serial fault rupture and fault interactions. These results bear on seismic hazard analysis, by considering the physical processes that lead to an earthquake, including the interaction of adjacent fault ruptures, the effect of prior ruptures on a fault, the influence of geologic structure and fault geometry on rupture termination and aseismic versus seismic behavior.Paleoseismic studies along the Chelungpu fault are characterizing its earthquake recurrence and displacement history. For example, if the recurrence of 1999-like earthquakes is far less frequent, then other structures at the same latitude would have to play an important role in strain relief. Results from these investigations have implications for understanding the physical processes of strain relief on individual faults and of mountain building. End-member hypotheses, ranging from unpatterned or random recurrence to highly clustered behavior, are being tested using earthquake time histories obtained along the Chelungpu and adjacent reverse faults.The project also characterizes the active faults of the Longitudinal Valley faults. Determining the elevations of shoreline angles for a select handful of coastal marine terraces is constraining the millennial rates along the Longitudinal Valley. Geologic mapping and dating of the fluvial terraces along Shiouguluan River are providing the time-averaged uplift rates between the Longitudinal Valley and the eastern coastal region.