Earthquake Alert Bulletin No: 98-265

Preliminary data indicates a significant earthquake has occurred:

Regional Location:

Preliminary Magnitude:

Moment Magnitude:

Greenwich Mean Date:
Greenwich Mean Time:
Focal Depth (km):
Analysis Quality (A-D):


5.3 ML (NCSN), 4.9 ML (UNRSL)

4.8 Mw (UCBSL)

01:53:32 (1:53 a.m. PST)
14.2 km


An earthquake registering a preliminary magnitude of ML 5.3 (NCSN), ML 4.9 (UNRSL), Mw 4.8 (UCBSL) occurred at 09:53:32 UTC (1:53 a.m. PST), October 30, along the California/Nevada border region near the north shore of Lake Tahoe. The focal point was placed at a depth of 14.2 km for quick processing and the Moment magnitude is from the University of California, Berkeley, Geophysical Laboratory (UCBSL) Automatic Processor and has not been reviewed by humans as of yet. The preliminary UCBSL focal mechanism indicated strike-slip motion along a [likely] northwest trending fault plane. The University of Nevada, Reno, Seismology Laboratory (UNRSL) determined a slightly smaller local magnitude and confirmed the strike-slip fault motion. The quake was centered about 7 miles southeast of Truckee and 4 miles north-northwest of Incline, beneath the northern Carson Range, just inside the Nevada border at Mt. Baldy.

The epicenter is located slightly northwest of the main trace of the Incline fault, the largest nearby fault. The image iat the left s the actual seismogram trace of the North Tahoe M5.3 earthquake taken by the University of Nevada, Reno, Seismological Laboratory's "Seismo-Cam" moments after the quake. Previous significant events in this area include the Verdi M6.0 earthquake on December 29, 1948 and the Bocca Valley (Truckee) M6.0 earthquake on September 12, 1966. The most recent significant earthquake along the northern California/Nevada border was the Double Springs Flats M6.0 earthquake east of Markleeville and just inside the Nevada border on September 12, 1994.

Seismo-Watch received felt earthquake reports from several people in the Reno, Carson City, Lake Tahoe and Truckee region, and as far away as Loyalton, Silver City and Fallon. It was also felt at the office of Advanced Geologic Exploration where windows jiggled and walls shook for a few seconds. Many people felt a strong jolt (P-wave) followed by a short pause before moderate to strong shaking (S-wave). Some residents in the epicentral area reported a loud noise associated with the initial jolt. There are reports of light objects toppling from tables and shelves, pictures knocked from walls, and water sloshing from fish tanks, but there has been no reports of damage or injuries as of yet. One person in Kings Beach, just 4 miles from the epicenter reported their bed on wheels was tossed about the room. There were two aftershocks within the first 45 minutes, a M2.8 at 2:06 a.m. and and another registering M3.0 at 2:11 a.m. which was locally felt. Report your felt earthquake observations here. Be sure to leave your name and physical address if you would like to receive a FREE packet of information about earthquakes and earthquake preparedness.

The USGS has issued a Aftershock Forecast Warning for a 20% chance of strong or potentially damaging earthquake (M5 and larger) to occur within the next 7 days. They have also indicated a 5-10% chance for a shock to register larger than the main shock. These are statistical calculations and should be viewed with caution. Please consult the USGS in Menlo Park, California or at Seismo-Watch before using this information.

A similar copy of this earthquake report was faxed the Seismo-Watch Earthquake Alert Bulletins subscribers within hours of the event. Click HERE if you are interested in receiving these reports.

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Subtract 8 hours from Greenwich Mean Time to obtain PST or 5 hours for EDT
Location Quality: A (good), B (fair), C (poor), D (bad)
Magnitude: Ml (local or Richter magnitude), Lg (mblg), Md (duration), Mb (body wave), Ms (surface wave), Mw (moment)

Standard Sources Include:
U.S. Geological Survey, National Earthquake Information Center, Golden, CO (NEIC)
Harvard Geophysical Observatory, Harvard University, Cambridge, MA (HRV)
U.S. Geological Survey, Northern California Seismic Network (NCSN)
University of California, Berkeley, Seismological Laboratory (UCBSL)
California Institute of Technology, Pasadena, California (Caltech)
various wire reports and/or personal communications

All data are preliminary and subject to change.
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