Northern California Seismic Network (NCSN) data: Northern California Earthquake Data Center (NCEDC)

Since 1967 the U.S. Geological Survey has operated the Northern California
Seismic Network (NCSN) to provide earthquake data for a wide range of research
topics and hazard-reduction activities. The NCSN is designed to detect all
local earthquakes having signal strength above the background level of
microseisms. The network configuration was motivated by the need to monitor
active faults and volcanoes with a station density sufficient to determine the
focal depth of shallow (0-15 km) crustal earthquakes. Depending on the
concentration of stations in a region, the magnitude (M) level at which
earthquake detection is complete varies from approximately 1.4 in parts of the
central Coast Ranges to 2.6 in the Klamath Mountain range. However, earthquakes
with M<1.0 are routinely detected throughout the network.

The NCSN operates 412 stations in northern and central California and records
an additional 100 stations maintained by 4 other institutions. It records a
total of 924 channels of data using a mix of digital and analog systems. Nearly
one fourth of the stations in the network are now digital, and 11 of the
digital stations have broadband sensors, 92 have strong-motion sensors, and 11
are borehole installations. The remainder of the stations are mostly comprised
of short-period vertical-component sensors. The NCSN telemetry system utlizes
local collection nodes which are linked to Menlo Park via analog microwave,
digital satellite telemetry, and leased digital circuits. The network also
utilizes direct radio telemetry to Menlo Park and operates an extensive LAN
that links urban stations located in the San Francisco Bay region.

NCSN network geometry is illustrated in a map of northern and central
California located at the following URL:
"http://quake.geo.berkeley.edu/ncsn/map.html".

Data Access:
An earthquake catalog is produced from analysis of the NCSN data. Locations,
magnitude, phases, coda durations, and first-motion mechanisms are available
using the earthquake catalog search,
"http://quake.geo.berkeley.edu/ncedc/catalog-search.html".

At this point in time, NCSN waveform data are not available in SEED format.
However, effort is underway to provide this capability. For the present, NCSN
waveform data are available through the EVT_FAST waveform request form,
"http://quake.geo.berkeley.edu/ncedc/evt_fast_form.html", or through research
accounts.