| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Article |
U.S. Geological Survey
345 Middlefield Road, MS 977
Menlo
Park, California
94025
mrymer{at}usgs.gov
(J.D.H.,
M.J.R)
Lawrence Livermore National Laboratory
7000 East Avenue,
L-397
Livermore, California 94551
(G.G.S.)
William Lettis & Associates, Inc.
28470 Avenue Stanford,
Suite 120
Valencia, California 91355
(K.D.W.)
San Diego State University
Department of Geological
Sciences
5500 Campanile Drive
San Diego, California 92182
(G.F.,
A.O.)
URS Corporation
2020 East First Street
Santa Ana,
California 92705
(C.G.)
Paleoseismic investigations of the Lavic Lake fault at Lavic Lake playa place constraints on the timing of a possible earlier earthquake along the 1999 Hector Mine rupture trace and reveal evidence of the timing of the penultimate earthquake on a strand of the Lavic Lake fault that did not rupture in 1999. Three of our four trenches, trenches A, B, and C, were excavated across the 1999 Hector Mine rupture; a fourth trench, D, was excavated across a vegetation lineament that had only minor slip at its southern end in 1999. Trenches A–C exposed strata that are broken only by the 1999 rupture; trench D exposed horizontal bedding that is locally warped and offset by faults. Stratigraphic evidence for the timing of an earlier earthquake along the 1999 rupture across Lavic Lake playa was not exposed. Thus, an earlier event, if there was one along that rupture trace, predates the lowest stratigraphic level exposed in our trenches. Radiocarbon dating of strata near the bottom of trenches constrains a possible earlier event to some time earlier than about 4950 B.C.
Buried faults revealed in trench D are below a vegetation lineament at the ground surface. A depositional contact about 80 cm below the ground surface acts as the upward termination of fault breaks in trench D. Thus, this contact may be the event horizon for a surface-rupturing earthquake prior to 1999—the penultimate earthquake on the Lavic Lake fault. Radiocarbon ages of detrital charcoal samples from immediately below the event horizon indicate that the earthquake associated with the faulting occurred later than A.D. 260. An approximately 1300-year age difference between two samples at about the same stratigraphic level below the event horizon suggests the potential for a long residence time of detrital charcoal in the area. Coupled with a lack of bioturbation that could introduce young organic material into the stratigraphic section, the charcoal ages provide only a maximum bounding age; thus, the recognized event may be younger.
There is abundant, subtle evidence for pre-1999 activity of the Lavic Lake fault in the playa area, even though the fault was not mapped near the playa prior to the Hector Mine earthquake. The most notable indicators for long-term presence of the fault are pronounced, persistent vegetation lineaments and uplifted basalt exposures. Primary and secondary slip occurred in 1999 on two southern vegetation lineaments, and minor slip locally formed on a northern lineament; trench exposures across the northern vegetation lineament revealed the post-A.D. 260 earthquake, and a geomorphic trough extends northward into alluvial fan deposits in line with this lineament. The presence of two basalt exposures in Lavic Lake playa indicates the presence of persistent compressional steps and uplift along the fault. Fault-line scarps are additional geomorphic markers of repeated slip events in basalt exposures.
This article has been cited by other articles:
|
|
 |
|
  M. Oskin, L. Perg, E. Shelef, M. Strane, E. Gurney, B. Singer, and X. Zhang Elevated shear zone loading rate during an earthquake cluster in eastern California Geology, June 1, 2008; 36(6): 507 - 510. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. F. Dolan, D. D. Bowman, and C. G. Sammis Long-range and long-term fault interactions in Southern California Geology, September 1, 2007; 35(9): 855 - 858. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. L. Madden, C. M. Rubin, and A. Streig Holocene and Latest Pleistocene Activity on the Mesquite Lake Fault near Twentynine Palms, Eastern California Shear Zone: Implications for Fault Interaction Bulletin of the Seismological Society of America, August 1, 2006; 96(4A): 1305 - 1320. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Anooshehpoor, J. N. Brune, and Y. Zeng Methodology for Obtaining Constraints on Ground Motion from Precariously Balanced Rocks Bulletin of the Seismological Society of America, February 1, 2004; 94(1): 285 - 303. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. D. Catchings, M. J. Rymer, and M. R. Goldman Reply to "Comment on 'Faulting Apparently Related to the 1994 Northridge, California, Earthquake and Possible Co-Seismic Origin of Surface Cracks in Potrero Canyon, Los Angeles County, California,' by R. D. Catchings, M. R. Goldman, W.H.K. Lee, M. J. Rymer, and D. J. Ponti," by Brian J. Swanson, Allan E. Seward, Perry L. Ehlig, and James E. Slosson Bulletin of the Seismological Society of America, August 1, 2002; 92(6): 2539 - 2550. [Full Text] [PDF]
|
|
|
|
|
|
Early Postseismic Deformation from the 16 October 1999 Mw 7.1 Hector Mine, California, Earthquake as Measured by Survey-Mode GPS Bulletin of the Seismological Society of America, May 1, 2002; 92(4): 1423 - 1432.
|
|
|
|
|
|
High-Resolution Topography along Surface Rupture of the 16 October 1999 Hector Mine, California, Earthquake (Mw 7.1) from Airborne Laser Swath Mapping Bulletin of the Seismological Society of America, May 1, 2002; 92(4): 1570 - 1576.
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
