National Geophysical Data Center
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, are now available for purchase from the National
Geophysical Data Center (NGDC).
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
Please contact NGDC for prices.