October 1998 Press Releases

Press Release
Nevada Seismological Laboratory

October 30, 1998 4:30 AM, PST
A magnitude 4.9 earthquake occurred this morning about 4 miles north of Incline Village, Nevada. The details of the event location are as follows: 
Time:  1:53:30 AM PST
Latitude:  39.309 N
Longitude:  119.979 W
Depth:  11.5 km (7.2 miles)
Magnitude: 4.9
This location is just east of the California-Nevada border, and about 4.2 miles north of the junction the Mt. Rose Highway (SR 431) and Tahoe Blvd. (SR28) in Incline Village. It is apparently north of the Incline Village fault, which is the largest fault nearby. The mechanism is strike slip.

The Seismological Laboratory has received reports of items falling from shelves in Incline Village and southwest Reno. We have felt reports from as far as Fernley, Dayton, and locations in Calaveras and Tuolumne Counties, California.

This will probably be the largest earthquake in the sequence, but there is perhaps a 5% chance that a larger earthquake will follow in the next three days. Some aftershocks with magnitude over 3.0 should be expected. As of 4:00 AM, the two most significant aftershocks had M=2.8 at 2:06 AM and M=3.0 at 2:11 AM.

Previous significant earthquakes in this area include two events with magnitude of about 6.0 in the last 50 years. They are: 

 YEAR   MO DA ORIG TIME       LAT    LON      DEP  MAGNITUDE
 1948   Dec 29 12:53:28     39.55 -120.08          6.00
 1966   Sep 12 16:41:02     39.44 -120.16      10  6.00

The data reported here are preliminary. For more information, contact the Seismological Laboratory at (702) 784-4975, or at the WWW site http://www.seismo.unr.edu . People are encouraged to submit felt reports through our web pages. The free pamphlet Earthquakes in Nevada and How to Survive Them, is available on request.

Press Release
Nevada Seismological Laboratory

21 October 1998 1:00 PM PDT
The University of Nevada Seismological Laboratory has recorded a sequence of earthquakes near Portola, California, over the past 24 hours. The largest occurred this morning at 1:31 AM PDT (08:31 GMT). Our preliminary magnitude for this event is 4.0 and its location is 10 mi WSW of Portola. This location places the event near the Mohawk Valley fault zone. 
Preliminary Location: 
Latitude:   39 45.69'N 
Longitude: 120 40.26'W
Depth:     15 km.
The sequence apparently began with a foreshock yesterday at 11:39 AM (M 2.9). Subsequent to the main shock, we have recorded a moderate aftershock sequence with the largest events at 1:36 AM (M 2.4), 2:02 AM (M 1.9), 2:21 AM (M 1.9), 2:30 AM (M 3.2), and 9:16 AM (M 2.6).

Computer-estimated magnitudes of the foreshock and aftershocks are unchecked at this time and are subject to change. We will provide additional details as they become available.

The largest historical earthquake in this area occurred on April 29, 1888. The best estimate for the magnitude of that earthquake is 5.9, based on the extent of the region over which it was strongly felt.

The data reported here are preliminary. For more information, contact the Seismological Laboratory at (702) 784-4975, or at the WWW site http://www.seismo.unr.edu . The free pamphlet Earthquakes in Nevada and How to Survive Them, is available on request.