DOUBLE-DIFFERENCE EARTHQUAKE CATALOG FOR NORTHERN CALIFORNIA, 1984-2011
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NCAeqDD.v201112.1 --- Version: 201112.1 --- June, 2013

Felix Waldhauser and David Schaff
Lamont-Doherty Earth Observatory
Columbia University

CONTACT: felixw@ldeo.columbia.edu

DOWNLOAD: http://www.ldeo.columbia.edu/~felixw/NCAeqDD/

OVERVIEW:
This file includes high-precision hypocenter locations for 513,474
earthquakes recorded between January 1984 - December 2011 by stations of 
the Northern California Seismic System (NCSS). Relative locations were 
computed from a comprehensive double-difference inversion of a combination 
of NCSS phase pick data and cross-correlation differential times measured 
from correlated seismograms. This catalog is an update of the original DD 
catalog (1984-2003) described in detail in Waldhauser and Schaff (2008) and 
released as NCAeqDD.1984-2003.v1.0 in January 2008. The same computational 
procedures and parameter settings were used to generate this update.

Important: This catalog includes events that were recorded by 7 or more 
stations. Ongoing efforts are aimed at lowering the number of required 
recording stations in order to improve the completeness of the catalog. 
However, the primary goal of this project is to produce earthquake catalogs 
of highest possible resolution.

CITATION:
This is version v201112.1 of the NCAeqDD catalog series and should be 
referenced as Waldhauser and Schaff (2008) with version number 
indicated.

VERSION HISTORY:
NCAeq_DD.1984-2003.v1.0	 ---   Released January 2008
NCAeqDD.v200812.1.0	 ---   Released June 2010
NCAeqDD.v200812.1.1    	 ---   Released July, 2010
NCAeqDD.v200912.1    	 ---   Released June, 2011 
NCAeqDD.v201112.1    	 ---   Released June, 2013  (this file)

REFERENCES:
Waldhauser, F. and D.P. Schaff (2008), Large-scale relocation of two 
   decades of Northern California seismicity using cross-correlation 
   and double-difference methods, J. Geophys. Res., 113, B08311, 
   doi:10.1029/2007JB005479.

See also:
Schaff, D.P. and F. Waldhauser (2005), Waveform Cross-Correlation-Based 
   Differential Travel-Time Measurements at the Northern California 
   Seismic Network, Bull.  Seism. Soc. Am., 95, 2446-2461. 
Waldhauser F. and W.L. Ellsworth (2000), A double-difference earthquake 
   location algorithm: Method and application to the northern Hayward 
   fault, Bull. Seism. Soc. Am., 90, 1353-1368. 

DATA SOURCES:
U.S. Geological Survey, Menlo Park; University of California, Berkeley; 
Northern California Earthquake Data Center (NCEDC) and the Northern 
California Seismic Network (NCSN); California Institute of Technology; 
University of Nevada, Reno; California Division of Water Resources; 
University of Utah; University of Southern California. 
Seismic archives were obtained from the NCEDC.

FORMAT DESCRIPTION:
DATE......... Year, Month, Day
TIME......... Hour, Minute, Second
LAT/LON...... Location
DEP.......... Depth [km]
EH1/EH2/AZ... Horizontal major/minor axis [km] and azimuth of the 95% 
              relative location error ellipses. (-1 if not available).
EV........... Vertical relative location error [km] at the 95%
              confidence level. (-1 if not available).
MAG.......... Magnitude, ML, as listed in the NCSN catalog. 
ID........... CUSP event ID.


   DATE        TIME         LAT          LON         DEP     EH1     EH2   AZ    EZ    MAG       ID
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