Stratigraphic Evidence for Late Quaternary Temporal Clustering of Large Earthquakes on the Puente Hills Segment of the Elysian Park Thrust, Eastern Los Angeles.....

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9416321 Wells The Puente Hills, in the eastern Los Angeles Basin, are the surface expression of the Santa Monica Mountains - Elysian Park anticlinorium which is forming the response to movement on blind thrust ramps. This study will address the likelihood of the entire fault rupturing simultaneously, in one very large earthquake event, or in several smaller events of Northridge- type, or in numerous small events of Whittier-Narrows-type. By analysis of Quaternary sediments in three meandering rivers that cross the structure and that contain alternating coarse sand and organic-rich beds, it will be possible to determine and compare the timing of past deformation events on the Puente Hills thrust ramp. The research will involve analyses at two distinct scales using oil and water well logs and fluvial and marine terrace deposits, and high- precision radiocarbon dating and logging of boreholes excavated specifically for this project. The results will provide constraints on the timing and magnitude of past earthquakes connected with the Santa Monica Mountains - Elysian Park anticlinorium.