Map
of California & Nevada earthquakes
Behind the Weekly Maps
The map of global seismicity is based on earthquakes contributed to the ANSS/CNSS Global earthquake catalog. Most of these events have been reported by the National Earthquake Information Center (NEIC) in Golden, Colorado. Earthquakes with magnitude 5.5 and larger are plotted in a Mercator projection. The color and symbol type indicate the depth range (red - less than 70 km; green - 71-300 km; yellow - 301 km and deeper), while the size indicates the magnitude. The "beach ball" figures are seismic moment tensors computed by seismologists at Harvard University. The solid grey lines indicate major plate boundaries and are taken from the NUVEL1 model of DeMets et al. (1990). Often, more details about a particular earthquake may be found in the QED (Quick Epicenter Determination) list.
The map of northern California seismicity is based on earthquakes reported by the Berkeley Seismological Laboratory and the USGS Menlo Park in the Northern California earthquake catalog. Earthquakes with magnitude 3.0 and larger are plotted with red circles in a Mercator projection. The "beach ball" figures are regional seismic moment tensors computed by scientists at the Berkeley Seismological Laboratory. Grey lines indicate major faults. In California, these faults are from the map of Jennings (1972), published by the California Division of Mines & Geology.
The detail maps of northern California are also based on the earthquake catalogs of the Berkeley Seismological Laboratory and the USGS Menlo Park. Earthquakes with magnitude 2.0 and larger are plotted with red circles. Major faults are indicated in blue (active in historical times), light blue (active in the Holocene), and black (active in the Quaternary) and are solid where known and dashed where inferred. These faults are from the map of Jennings (1994), published by the California Geological Survey.
The earthquake lists contain information on the origin time, location, depth, and magnitude of these events. In addition, a number of parameters are provided which measure how well the earthquake is located. For an explanation of the output format, please read the manual page. Please note: The earthquake origin time is reported in UTC - not in local time.
The maps are updated every Friday. All maps are generated using the GMT software.
If you want to know about an earthquake that just occurred, please visit the Global Near Real Time earthquake list for world-wide earthquakes and the recent earthquakes Web page for events in California and Nevada.
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Berkeley Seismological Lab
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Copyright 1995-2005, The Regents of the University of California.
Last modified: Wed Aug 27 12:03:22 PDT 2008