THE 1989 GRAND CANYON EARTHQUAKE LIGHTS

On March 5, 1989 two magnitude 4.0 earthquakes occurred about three hours apart near the south rim of the Grand Canyon.The earthquakes were accompanied by reports of earthquake lights. These two earthquakes are the smallest to be associated with earthquake lights. The lights occurred at night and observor reports allow an estimation of the source of the lights to be 8-10 kilometers northwest of the epicenters.Preliminary examination of the literature indicates that there is a rough distance relationship between epicenter and source that is proportional to the magnitude of the earthquake. Lights have been seen at the time of large earthquakes (M~7-8) as far away from the epicenter as 300-400 kilometers. Although the mechanism of the production of the lights is unknown, there may also be a relationship between stress concentration and slip direction of the earthquake source.