| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Article |
Department of Earth Sciences
University of Southern California
Los Angeles, CA 90089-0740
(J. D.)
The Raymond fault extends for 20 km in a broad convex-to-the-south arc
across the densely populated San Gabriel Valley northeast of Los Angeles.
Although south-facing scarps characterize much of the fault, geomorphic and
seismological evidence indicate a predominance of left-lateral motion. An
apparent 3.4-km left-lateral offset of a crystalline basement ridge at the
east end of the fault may approximate total slip on the fault. Data from one
of our paleoseismologic trenches, in combination with published data, indicate
that the most recent Raymond fault surface rupture occurred 
1–2 ka.
Estimates of fault-plane area suggest that rupture of the entire Raymond fault
could generate an earthquake of Mw 6.7. The similar
kinematics of the Raymond fault and the Hollywood fault, along strike to the
west, together with a pronounced fault-parallel gravity lineament and sparse
geomorphic evidence, suggests that there may be a through-going mechanical
connection between the two faults, and that they could conceivably rupture
together in large earthquakes. Published data, however, indicate that the
Hollywood fault ruptured to the surface most recently 6–9 ka,
indicating that the most recent Raymond fault surface rupture apparently did
not extend westward onto the Hollywood fault. Data from another of our
paleoseismologic trenches yielded evidence for at least five latest
Pleistocene earthquakes, including at least four surface ruptures that
occurred during a brief, 
10,000-year-long period between 31.5 and
41.5 ka. The 3300 year-long, average recurrence interval for these events
is much shorter than the interval suggested for the past 40,000 years by
the frequency of paleoearthquakes recognized in previous trenches. Thus,
either the 31.5 ka to 41.5 ka events represent a temporal cluster, and the
recurrence interval for the fault is highly irregular, or at least half of all
Raymond fault earthquakes that have occurred since 31.5 ka have not yet
been recognized.
This article has been cited by other articles:
|
|
 |
|
  A. J. Meigs, M. L. Cooke, and S. T. Marshall Using Vertical Rock Uplift Patterns to Constrain the Three-Dimensional Fault Configuration in the Los Angeles Basin Bulletin of the Seismological Society of America, February 1, 2008; 98(1): 106 - 123. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W.-S. Chen, C.-C. Yang, I-C. Yen, L.-S. Lee, K.-J. Lee, H.-C. Yang, H.-C. Chang, Y. Ota, C.-W. Lin, W.-H. Lin, et al. Late Holocene Paleoseismicity of the Southern Part of the Chelungpu Fault in Central Taiwan: Evidence from the Chushan Excavation Site Bulletin of the Seismological Society of America, February 1, 2007; 97(1B): 1 - 13. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. S. Yeats Tectonics of the San Gabriel Basin and surroundings, southern California GSA Bulletin, September 1, 2004; 116(9-10): 1158 - 1182. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Geology of the Continental Margin beneath Santa Monica Bay, Southern California, from Seismic-Reflection Data Bulletin of the Seismological Society of America, October 1, 2003; 93(5): 1955 - 1983.
|
|
|
|
|
|
Paleoseismologic Evidence for a >8 Ka Age of the Most Recent Surface Rupture on the Eastern Sierra Madre Fault, Northern Los Angeles Metropolitan Region, California Bulletin of the Seismological Society of America, April 1, 2001; 91(2): 232 - 249.
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
