DOUBLE-DIFFERENCE EARTHQUAKE CATALOG FOR NORTHERN CALIFORNIA, 1984-2008 

NCAeqDD.v200812.1.1  --- Version: 200812.1.1  ---  July, 2010

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

Contact: felixw@ldeo.columbia.edu

This file includes high-precision hypocenter locations for 445,493
earthquakes that were recorded between January 1984 - December 2008 by 
stations of the Northern California Seismic Network (NCSN). Relative
locations were computed from a comprehensive double-difference 
inversion of NCSN phase pick data and cross-correlation differential 
times measured from correlated seismograms. Correlated earthquakes are
relocated to the precision of the cross-correlation data while those 
that don't correlate to the precision of the phase arrival time picks
(for details see Waldhauser and Schaff, JGR, 2008 and Schaff and 
Waldhauser, BSSA, 2005).

IMPORTANT: This catalog is NOT complete! It includes only 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 catlog.

This is Release 200812, Version 1.1 of the NCAeqDD catalog and should be 
referenced as Waldhauser and Schaff (2008) with version number (v200812.1.1) 
indicated. 

RELEASE/VERSION HISTORY:
This catalog is an update of the original DD catalog 
(1984-2003) described in detail in Waldhauser and Schaff (2008) and 
released as NCAeq_DD.1984-2003.v1.0 in January 2008. The same 
computational procedures and parameter settings were used to generate 
this update. This catalog replaces an earlier version (v200812.1.0) for 
the same time period, which included explosion and quary blasts by mistake.

NCAeq_DD.1984-2003.v1.0	 ---   Released January 2008
NCAeqDD.v200812.1.0	 ---   Released June 2010

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.
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.

DOWNLOADS:
www.ldeo.columbia.edu/~felixw/NCAeqDD/

DATA SOURCES:
U.S. Geological Survey, Menlo Park; University of California, Berkeley; 
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 
Northern California Earthquake Data Center (NCEDC) and the Northern 
California Seismic Network (NCSN).

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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