NOW i REMEMBER
The October 16, 1999 M7.1 Hector Mine Earthquake
Date/Time: October 16, 1999 02:46:44.1am PDT
Magnitude Mw 7.1
Location/Depth: 34.59N 116.27W depth=5±3 km
Descriptive location: 47 miles ESE of Barstow
Faulting type: right-lateral strike-slip
Faults involved: Lavic Lake fault & central section of Bullion fault
Length of surface rupture: 41 km
Maximum surface offset 5.2 meters
Above is a diagrammatic representation of surface faulting produced by the M7.1 Hector Mine earthquake of October, 16, 1999. This figure was derived
from mapping by more than 40 geologists from the U.S. Geological Survey, Southern California Earthquake Center, and the California Division of Mines
and Geology. The principal rupture is shown in yellow. It extends for more than 41 km, although the portion of the rupture with observed displacement
of >1 cm (shown here) is barely more than 35 km long.
The rupture involves portions of two previously mapped fault zones - the Bullion fault, and an unnamed, more northerly trending fault that is now
informally referred to as the Lavic Lake fault. This pattern of rupture along more than one named fault was also observed from the 1992 Landers
earthquake. The closely spaced nature of the surface faults in this area (other major mapped faults in the region are shown with dashed green lines)
suggests that they are interrelated and connected to a fewer number of "master" faults at depth.
Much of the fault zone that produced the Hector Mine earthquake had been buried by relatively young stream deposits and the fault scarps in bedrock
have a subdued morphology. Thus it appears that these faults have not experienced significant offset for perhaps 10,000 years or more. Planned future
investigations will refine the age of the last event on these faults. The portion of the Lavic Lake fault that ruptured between the northern end of
the Bullion Mountains and Lavic Lake had not previously been mapped. However, our current field investigations have identified ancient, subdued fault
scarps along the 1999 rupture zone in this area. Thus, it appears that the entire Lavic Lake fault that was involved in the 1999 event had ruptured
The greatest fault displacement, about 5.2 m of right-lateral strike slip (largest value measured as of 10/23/1999), occurs on the Lavic Lake fault,
near the epicenter in the Bullion Mountains (see Preliminary Fault-Slip Distribution from Geologic Investigations). For the whole fault zone, average
surface displacement may approach 3 m. In the Bullion Mountains the surface faulting is relatively simple, with most displacement occurring on a
single trace, or closely spaced parallel traces. However, to the north and south of the Bullion Mountains faulting patterns become quite complex and
slip is distributed across broad zones of faults with various orientations.
On October 24, helicopter and ground reconnaissance teams found additional rupture within a zone that occurs southwest, and parallel to, the Bullion
fault (shown in pink on the figure). The continuity and amount of right-lateral slip associated with this zone is presently unknown. In addition,
small cracks, with no consistent lateral displacement have been observed near Lavic Road NE of Lavic Lake, and near Hector Mine (~ 8 km NW of Lavic
WHY THIS AREA NEEDS WATCHING!!!!!!!!!!!!!!!!!!
SO HOW ABOUT EVERYONE CUT THE CRAP.
edit on 27-7-2011 by BobAthome because: (no reason given)