The Hector Mine Earthquake
The Hector Mine earthquake was a magnitude 7.1 event, upgraded from 7.0 on October 18, 1999 based on in-depth analysis of "teleseismic" data recorded worldwide. The epicenter was located in a remote, sparsely-populated part of the Mojave desert, approximately 47 miles east-southeast of Barstow and 32 miles north of Joshua Tree. The earthquake occurred on the Lavic Lake fault, one of a series of north-northwest trending faults through the eastern Mojave shear zone. This fault runs parallel to the San Andreas fault, and its movement is a result of tectonic forces along the North American and Pacific plate boundary.
Earth's crust, the thin skin of solid rock that forms the outer layer of our planet, is divided up into plates. These plates spread apart, slide against each other, or collide. Earthquakes are a sign of this movement. California, which sits on the boundary of two major plates, is earthquake territory. Earthquakes have been a part of our regionís history for millions of years.
This is a seismogram or signature of the Hector Mine earthquake and its aftershocks. The vertical movement of the rock beneath the Museum is recorded on the seismograph's spinning drum. The first arrow indicates the arrival of the shock waves from the earthquake (#1). Arrows #2 and #3 are aftershocks.
Online Earthquake Resources
Southern California Earthquake Hazards Program
The Earthquake Preparedness Handbook