National Centers for Environmental Information (NCEI)
MULTICHANNEL SEISMIC-REFLECTION PROFILES
USGS Open File Report 87-607*
Data Announcement 89-MGG-03
Approximately 1004 km of 24-channel seismic-reflection data,
collected by the U.S. Geological Survey (USGS) in June of 1976 in
the northeastern Pacific Ocean off of the Washington-Oregon
Coast, for purchase from the National Geophysical Data Center (NGDC) (now the National Centers for Environmental Information (NCEI)).
The data were collected on the USGS Research Vessel S.P. LEE
(cruise identifier L3-76-WO) using a sound source of five airguns
totaling 1326 cubic inches of air compressed to approximately
1900 psi. The recording system consisted of a 24-group streamer,
2400 meters long, and a GUS (Global Universal Science) model 4200
digital recording instrument. Shots were fired every 50 meters,
and records were sampled in the field at a 2-millisecond rate,
but resampled to a 4-millisecond rate prior to processing.
Record lengths vary from 6 to 13 seconds, depending on water
depth, in order to obtain 6 to 7 seconds of data below the
seafloor. Navigational control for the survey was by a Marconi
integrated satellite-doppler sonar navigation system.
Processing was done in the following sequence: editing-
demultiplexing, automatic gain control, deconvolution-filtering,
velocity analysis and normal-moveout correction, trace-balancing,
bandpass-filtering, muting, normalized stacking, and finally
plotting on an electrostatic plotter. In areas of shallow
seafloor, early arrivals on far-offset traces were muted to
remove refracted energy and the direct-arrival of the outgoing
pulse. In deeper water, the near-offset traces were muted at and
below approximately twice the water-bottom time to suppress the
water-bottom multiples on the stacked traces. The seismic lines
are available on plastic, paper sepia, paper blackline and
* "Multichannel Seismic-Reflection Profiles Collected in 1976 off
of the Washington-Oregon Coast" By P.H. McClellan and P.D.
Snavely, Jr., U.S.G.S. Open File Report 87-607, U.S. Geological
Survey, Menlo Park, California.
DATA AVAILABLE (please refer to 9-digit product numbers when
1 multichannel seismic-reflection profile (23 lines)
(plastic sepia) Product #976F20172
(paper sepia) Product #976F19172
(blackline) Product #976F18172
1 trackline chart (scale: 1:736560). Product #976A18172.
1 magnetic tape containing shotpoint navigation and magnetics
data. Product #976H07172.
23 digital stack tapes. Product #976L07172.
23 digital demultiplexed tapes (edited for missed shots and
muting times). Product #976L07173. This is also available on CD-
ROM, Product #129F27001