National Geophysical Data Center

MULTICHANNEL SEISMIC-REFLECTION PROFILES
Washington-Oregon Coast
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 magnetic tape.

* "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 ordering).

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.