Late Quaternary faulting and historic seismicity in the western Lake Mead area, Nevada, Arizona and California
- Bureau of Reclamation, Denver, CO (United States)
As part of a regional seismic hazard study for Reclamation dams on the northern lower Colorado River, the age and distribution of known and suspected late Quaternary faults were investigated and historic seismicity was analyzed for the western Lake Mead area. Late Quaternary faults in the area consist of the Mead Slope, Black Hills, Frenchman Mountain, and California Wash faults. Geologic mapping and scarp profiles indicate that of these late Quaternary faults, the Black Hills fault displays evidence for the youngest (probably mid-Holocene) surface faulting. No information about the ages of older events was obtained for any of the faults; however, the ages of the most recent surface-rupturing events for individual faults suggest recurrence intervals of tens of thousands of years for specific faults and regional recurrence rates of several thousand years for M[sub 3] [>=] 6 1/2 events. Since 1936 when Hoover Dam was completed and the initial filling of Lake Mead began, the Boulder Basin area, the largest and deepest part of Lake Mead, has experienced abundant seismic activity that includes some of the largest historic earthquakes in southern Nevada (at least 21 M 4 events and one M 5). Based on earthquake locations from early networks (1937--1950) and those from temporary networks operating in 1975--1976 and 1988, earthquakes are clearly associated with the northeast-striking Mead Slope and Black Hills faults; one of the few associations of seismicity with late Quaternary faults in the Basin and Range. However, earthquakes also appear to be associated with the Fortification fault, a north-striking fault with no evidence of Quaternary surface faulting. Focal mechanisms for some of the 1975--1976 and 1988 events (all events M [<=] 3) suggest active strike-slip/oblique-slip motion on north-striking faults and normal/oblique-slip motion on northeast-striking structures.
- OSTI ID:
- 5449722
- Report Number(s):
- CONF-9305259--
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Journal Name: Geological Society of America, Abstracts with Programs; (United States) Vol. 25:5; ISSN GAAPBC; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
Similar Records
Tectonic stability and expected ground motion at Yucca Mountain. Final report. Revision 1. August 7-8, 1984-January 25-26, 1985
Holocene faulting on the Mission fault, northwest Montana
Related Subjects
130200* -- Hydro Energy-- Site Geology & Meteorology
58 GEOSCIENCES
580000 -- Geosciences
ARIZONA
CENOZOIC ERA
COLORADO RIVER
DAMS
DEVELOPED COUNTRIES
FUNCTIONS
GEOLOGIC AGES
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
HAZARDS
NEVADA
NORTH AMERICA
QUATERNARY PERIOD
RESPONSE FUNCTIONS
RISK ASSESSMENT
RIVERS
SEISMIC EFFECTS
SEISMIC EVENTS
SEISMICITY
SEISMOLOGY
SITE CHARACTERIZATION
STREAMS
SURFACE WATERS
USA