Summary We review seismicity, surface faulting, and Coulomb stress changes associated with the 1994 Northridge, California, earthquake. All of the observed surface faulting is shallow, extending meters to tens of meters below the surface. Relocated aftershocks reveal no seismicity shallower than 2 km depth. Although many of the aftershocks lie along the thrust fault and its ... up-dip extension, there are also a significant number of aftershocks in the core of the gentle anticline above the thrust, and elsewhere on the up-thrown block. These aftershocks may be associated with secondary ramp thrusts or flexural slip faults at a depth of 2-4 km. The geological structures typically associated with a blind thrust fault, such as anticlinal uplift and an associated syncline, are obscured and complicated by surface thrust faults associated with the San Fernando fault that overly the Northridge structures. Thus the relationship of the geological structure and topography to the underlying thrust fault is much more complex for Northridge than it is for the 1983 Coalinga, California, earthquake. We show from a Coulomb stress analysis that secondary surface faulting, diffuse aftershocks, and triggered sequences of moderate-sized mainshocks, are expected features of moderate-sized blind thrust earthquakes.
Acticle consists of 17 pages, including 14 figures.
Name:
ROSS
STEIN Phone:
(650) 329-4840
Email:
rstein at usgs.gov
Contact Address:
345 Middlefield Rd MS 977 City:
Menlo Park
Province or State:
CA
Postal Code:
94025
Country:
USA
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Electronic Media: Online Internet (http)
Distribution Size:
7.7 MB
Distribution Format:
PDF Online
Fees:
Free
Personnel
ROSS
STEIN Role:
INVESTIGATOR
Role:
TECHNICAL CONTACT
Phone:
(650) 329-4840
Email:
rstein at usgs.gov
Contact Address:
345 Middlefield Rd MS 977 City:
Menlo Park
Province or State:
CA
Postal Code:
94025
Country:
USA
JIAN
LIN Role:
INVESTIGATOR
Phone:
508-289-2576
Fax:
508-457-2187
Email:
jlin at whoi.edu
Contact Address:
Department of Geology & Geophysics
Woods Hole Oceanographic Institution
Clark 242, MS#22 City:
Woods Hole
Province or State:
MA
Postal Code:
02543
Country:
USA
TYLER
B.
STEVENS Role:
DIF AUTHOR
Phone:
(301) 614-6898
Fax:
301-614-5268
Email:
Tyler.B.Stevens at nasa.gov
Contact Address:
NASA Goddard Space Flight Center
Global Change Master Directory City:
Greenbelt
Province or State:
MD
Postal Code:
20771
Country:
USA
Related URL
Link:
GET DATA
Description:
Access the USGS report.
Link:
VIEW RELATED INFORMATION
Description:
Lin, J., and Stein, R.S., 2006, Seismic constraints and Coulomb stress changes
of a blind thrust fault system, 1: Coalinga and Kettleman Hills, California:
U.S. Geological Survey Open-File Report 2006-1149 17 p.
Creation and Review Dates
DIF Creation Date:
2006-07-16
Last DIF Revision Date:
2008-05-27
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