SCEC Award Number 07155 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Defining the geometry, segmentation, and slip rate of the Compton blind-thrust fault, Los Angeles basin, California
Investigator(s)
Name Organization
James Dolan University of Southern California John H. Shaw Harvard University
Other Participants Andreas Plesch
Charles Brankman
Lorraine Leon
SCEC Priorities A3, A4, A7 SCEC Groups Geology, USR
Report Due Date N/A Date Report Submitted N/A
Project Abstract
 We propose to constrain the late Pleistocene to Holocene slip rate, ages and displacements in paleo-earthquakes, and subsurface geometry of the Compton thrust through a multidisciplinary study of folding above this active blind-thrust system. The Compton fault, which was originally identified by Shaw and Suppe (1996) using industry seismic reflection profiles and well data, consists of two geometric segments that extend nearly 40 km beneath the Los Angeles Basin. Uncertainties about the late Pleistocene to Holocene activity of the fault, however, led the CGS to delete the Compton thrust from their active fault database. Last year, we used SCEC support to excavate a series of boreholes across the growth fold that overlies the northern segment of this blind-thrust system. These data establish the presence of a buried, 8-m-high fold scarp at the Holocene – Pleistocene boundary, as well as stratigraphically discrete folding events in Holocene sediments (Fig. 1), demonstrating that the underlying fault system is indeed active. Although we
await the results of 14C dating, the geometries constrained by the borehole transect imply a Holocene slip rate on the underlying blind thrust of 1-2 mm/yr, and that the fault has ruptured in a series of large (Mw > 7.0) Holocene earthquakes.