Today's earthquake ranks among the highest and potentially deadliest due to its magnitude and location near populated areas. Right now the USGS communications team is in emergency mode and may be hard to contact.
Below is data selected from our archives on past major earthquakes so that you can anticipate the potential damage of today's earthquake. Using that data, you can see how abnormal and potentially catastrophic a M8.0 earthquake is.
Of particular note is the aftershocks that occur after each major earthquake. After Loma Prieta, there were more than 80 M3.0 aftershocks 3 weeks later (which were relatively harmless).
It is too soon to tell how the quantity or size of aftershocks for today'd earthquake.
Customize your own earthquake search: https://earthquake.usgs.gov/earthquakes/search/
Executive summaries on past big earthquakes, including shake maps and narrative information:
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South Napa, M6.0, 2014-08-24: http://earthquake.usgs.gov/earthquakes/eventpage/nc72282711#executive
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Loma Prieta, Mw7.2, 1989-10-17: http://earthquake.usgs.gov/earthquakes/eventpage/usp00040t8#executive
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San Fernando, M6.6, 1971-02-09: http://earthquake.usgs.gov/earthquakes/eventpage/ci3347678#executive
Today at 1:38 p.m. local time, the northern San Francisco Bay Area was struck by the largest earthquake to impact the Bay Area since the 1989 M6.9 Loma Prieta earthquake. Today’s earthquake appears to have ruptured on or just northwest of San Andreas Fault. USGS has named the earthquake the “Palo Alto earthquake.” Today’s M8.0 earthquake caused significant damage in San Mateo and Santa Clara Counties. It occurred in the broad zone of deformation that accommodates the relative motion of the North American and Pacific Plates.
“USGS scientists are working to understand the earthquake and relay information to emergency managers and the public,” stated Dan Nguyen, Director of the USGS’s Earthquake Science Center Palo Alto office.
Damage is localized primarily in the region surrounding Palo Alto due to the rupture directivity to the northwest. Stanford University campus and downtown Palo Alto are particularly affected. The surface ruptures show a northward shift west of the San Andreas fault of about two inches. GPS receivers operated by the USGS and others also measured a shift of the earth of a few inches caused by the earthquake. USGS geophysicists have made additional measurements of the earth’s movement that will refine models for the earthquake movement. At this time the probability of a strong and possibly damaging aftershock in the next seven days is approximately 1 in 4. Today, USGS technicians will be retrieving additional seismic data from several seismic stations that either do not automatically communicate their data to us or failed to do so. They will also be deploying additional recorders in Palo Alto. These data should help refine the ShakeMap showing the intensity of shaking throughout the Bay Area and better understand the strong shaking experienced in Palo Alto. The Earthquake Early Warning test system functioned as designed in the earthquake. Within five seconds of the earthquake it produced a warning (estimated at magnitude 7.8 within three seconds of its occurrence), sufficient to provide warning to nearby areas.