Improved Data Access From the Northern California Earthquake Data Center

Authors:
	Douglas Neuhauser
	David Oppenheimer
	Stephane Zuzlewski
	Fred Klein
	Gray Jensen
	Lind Gee
	Mark Murray
	Barbara Romanowicz

The NCEDC is a joint project of the UC Berkeley
Seismological Laboratory and the USGS Menlo Park to provide
a long-term archive and distribution center for geophysical
data for northern California.  Most data are available via
the Web at http://ncedc.org and research
accounts are available for access to specialized datasets.
Current efforts continue to expand the available datasets,
enhance distribution methods, and to provide rapid access to
all datasets.
 
The NCEDC archives continuous and event-based seismic and
geophysical time-series data from the BDSN, the USGS NCSN,
the UNR Seismic Network, the Parkfield HRSN, and the
Calpine/Unocal Geysers network.  In collaboration with the
USGS, the NCEDC has archived a total of 887 channels from
139 sites of the "USGS low-frequency" geophysical network
(UL), including data from strainmeters, creep meters,
magnetometers, water well levels, and tiltmeters.  There are
336 active continuous data channels that are updated at the
NCEDC on a daily basis.

Geodetic data from the BARD network of over 40 continuously
recording GPS sites are archived at the NCEDC in both raw
and RINEX format. The NCEDC is the primary archive for
survey-mode GPS and other geodetic data collected in
northern California by the USGS, universities, and other
agencies.  All of the BARD data and GPS data archived from
USGS Menlo Park surveys are now available through the GPS
Seamless Archive Centers (GSAC), and by FTP directly from
the NCEDC.

Virtually all time-series data at the NCEDC are now
available in SEED with complete instrument responses.
Assembling, verifying, and maintaining the response
information for these networks is a huge task, and is
accomplished through the collaborative efforts of the NCEDC
and the contributing agencies.

Until recently, the NCSN waveform data were available only
through research accounts and special request methods due to
incomplete instrument responses.  In the last year, the USGS
compiled the necessary descriptions for for both historic
and current NCSN instrumentation.  The NCEDC and USGS
jointly developed a procedure to create and maintain the
hardware attributes and instrument responses at the NCEDC
for the 3500 NCSN channels.  As a result, the NCSN waveform 
data can now be distributed in SEED format.

The NCEDC provides access to waveform data through Web
forms, email requests, and programming interfaces.  The
SeismiQuery Web interface provides information about data
holdings.  NetDC allows users to retrieve inventory
information, instrument responses, and waveforms in SEED
format.  STP provides both a Web and programming interface
to retrieve data in SEED or other user-friendly formats.
Through the newly formed California Integrated Seismic
Network, we are working with the SCEDC to provide unified
access to California earthquake data.