Category: "Magnitude"

Double Difference Locations Now Available

June 2nd, 2014
June 2nd, 2014 The NCEDC is pleased to announce the availability of double difference (DD) hypocenter solutions from 1984 to the present for earthquakes recorded by the Northern California Seismic System (NCSS). The NCSS catalog can be searched via… more »

NCSS event review threshold change

May 27th, 2013
The Northern California Seismic System (NCSS), operated by the US Geological Survey in Menlo Park and UC Berkeley Seismological Laboratory, locates ~20,000 earthquakes per year in the Geysers geothermal region (Figure 1). Since 2007/07/23, when data… more »

Discrepancy in magnitude from database search

June 14th, 2004
We have discovered an inconsistency between the magnitudes reported in the new database search of the UC Berkeley earthquake catalogs ( http://www.ncedc.org/db/Search/PI/dbselect.html) and the older, flat file search (… more »

Calpine/LBL Geysers data added to the NCEDC

April 3rd, 2004
The NCEDC is pleased to announce the availability of seismic phase and waveform data from the Calpine/Lawrence Berkeley Labs seismic network that monitors seismicity in the vicinity of the Geysers geothermal field. The phase data begins 2003/04/04.… more »

Earthquake Catalog Search and Map

January 8th, 2003
January 8, 2003 In response to requests from many teachers, the NCEDC has created an experimental earthquake catalog search which provides seismicity maps as well as lists of earthquakes. The simplified search allows a user to select a catalog and one… more »

Changes to Northern California earthquake catalog search

November 21st, 2002
November 21, 2002 Today the NCEDC implemented modifications to eqselect and catlist, programs which search and reformat earthquake catalogs. These programs are used by the Web catalog search as well as by users with research accounts. The changes will… more »

Revision of NCSN Catalog

April 20th, 1997
April 29, 1997 On April 29, 1997, the USGS Northern California Seismic Network (NCSN) revised the format and relocated the entire earthquake catalog at the Northern California Earthquake Data Center. We undertook the catalog revision for the following… more »

Magnitude change in UC Berkeley Earthquake Catalog

January 23rd, 1996
The UC Berkeley Seismological Laboratory recently recomputed the station adjustments used to calculate local magnitude. Using a data set of over 1000 events, Dr. Robert Uhrhammer has estimated new station adjustments for the stations of the Berkeley… more »

Change in NCSN Earthquake Catalog

August 1st, 1995
The USGS Northern California Seismic Network (NCSN) has implemented a new policy regarding the archival of automatically timed (RTP) earthquake data in their catalog at the NCEDC. The RTP is an automated system that automatically picks seismic phases,… more »

Magnitude change in UC Berkeley Earthquake Catalog

February 8th, 1995
February 8, 1995 The UC Berkeley Seismological Laboratory recently discovered a bug in the program used to compute earthquake magnitudes in the UCB catalog. Under certain conditions some station corrections were not always applied to the magnitude… more »

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