5:00 PM PDT
1 August 1999
The University of Nevada Seismological Laboratory is recording an on-going sequence of earthquakes today, 7 miles (11 km) north of Scottys Junction, Nevada. The main shock was a magnitude 5.7 earthquake at 9:06 AM (PDT) this morning. It was located at latitude 37.385 degrees north, longitude 117.085 degrees west. The depth was computed to be approximately 7 miles (12 km), but depth is not well determined due the large distance to the nearest recording stations.
The sequence began at 9:17 PM (PDT) last night, with an earthquake between magnitude 3 and 4. At least 12 additional foreshocks above magnitude 2 were recorded before the main shock.
The earthquake is being followed by a vigorous aftershock sequence. As of 5:00 PM (PDT) today, the Seismological Laboratory was locating earthquakes at a rate of more than twenty per hour, including more than a dozen aftershocks above magnitude 3.0. The latest large aftershock occurred at 4:39 PM (PDT), with a preliminary magnitude of 3.7 from the Nevada Broadcast of Earthquakes.
The main shock was felt extensively in southern Nevada. We have received numerous reports from Las Vegas, as well as from Amargosa Valley, Tonopah, Goldfield, and Round Mountain. Rattling dishes and some fallen objects were reported from Tonopah, but we have not received any reports of more significant damage.
The earthquake sequence is occurring in a region with a southwest-northeast pattern of historical earthquakes. The Nevada Seismological Laboratory's catalog includes at least five historical earthquakes above magnitude 5 since 1910. Considering this history, today's earthquake is not surprising. The area of Scottys Junction includes several mapped faults. The preliminary mechanism is consistent with today's earthquake having occurred on a northeastward extension of one of three mapped faults: the Slate Ridge, Gold Mountain, or Bonnie Claire faults. All of these faults show possible evidence for prehistoric earthquake activity. Future studies are expected to provide more details.
The data reported here are preliminary. For more information, contact the Seismological Laboratory, (775) 784-4975 or on the Internet at http://www.seismo.unr.edu. The free pamphlet "Earthquakes in Nevada and How to Survive Them, is available on request.