U.S. Department of the Interior
                              
     U.S. Geological Survey Digital Data Series DDS-16
                              
                              
           Deep Seismic Reflection Studies in the
              Pacific Northwest United States
                              
                              
                          OVERVIEW
                              
                              
     From its inception in May of 1982, the U.S. Department
of Energy Deep Source Gas project has investigated the
possibility that significant quantities of hydrocarbons,
natural gas in particular, may be generated during and
following convergent plate tectonic sediment subduction.
Sediment subduction is believed to have been an important
process during the past 180 million years along the western
margin of North America.  Several years of regional
geological, and limited geochemical investigations led to
the theory that some portion of these subducted sedimentary
units may have been left in place in the upper crust of the
continental plate margin of this region.  The potential for
these, in part, deeply buried rocks to generate petroleum,
and to contain important quantities of natural gas at
drillable depths, was at the heart of this effort.  Along
with Gas Hydrates, the Deep Source Gas program of the
Morgantown Energy Technology Center was structured under the
heading of Speculative Gas Resources being investigated in
frontier areas of the U.S.

     Following an initial reconnaissance geophysical effort
in the Pacific Northwest and Alaska, which included the use
of magnetotellurics (MT), gravity, and magnetics
information, an important high conductivity MT anomaly was
identified in southwest Washington.  This feature later
identified as the Southern Washington Cascades Conductor, or
SWCC, was of sufficient areal extent to warrant further
study for its potential as a deeply buried subduction system
with significant sedimentary section.  Approximately 238
kilometers of 1024 channel deep seismic reflection data were
collected in 1988, 1989 and 1990 across the SWCC anomaly in
six seismic lines.  At this time approximately half of the
data has been analyzed and released in the following
publications:  U.S. Geological Survey, Open File Report 91-
119 entitled "Are Hydrocarbon Source Rocks Hidden Beneath
the Volcanic Flows in the Southern Washington Cascades?" by
W. D. Stanley, W. J. Gwilliam, G. V. Latham, and J. K.
Westhusing, 41 p., 12 figs.;  American Association of
Petroleum Geologists 1990 Annual Convention, San Francisco,
abstract entitled "Deep Seismic Surveys of a Dormant
Subduction Zone in the Pacific Northwest United States", by
W. J. Gwilliam, W. D. Stanley, G. V. Latham and J. K.
Westhusing;  U.S. Department of Energy, Morgantown Energy
Technology Center Proceedings of the 1990 Natural Gas
Research and Development Contractors Review Meeting,
entitled "Exploration For Deep Source Hydrocarbons in
Subduction Terrain of the Pacific Northwest" by Keith
Westhusing and Steve Krehbiel, 22 p. 18 figs., available
through the National Technical Information Service (NTIS)
Publication No.DE9100203035;  U.S. Department of Energy
Morgantown Energy Technology Center Proceedings of the 1992
Natural Gas Research and Development Contractors Review
Meeting, abstract, entitled "Deep Source Gas Seismic Survey
- Washington State" by Steven C. Krehbiel, Mary Rafalowski-
Guide and Mark H. Thomas, available through NTIS Publication
No. DE92001278;  American Association of Petroleum
Geologists Bulletin vol. 76, no. 10, October 1992 paper
entitled "The Southern Washington Cascades Conductor-A
Previously Unrecognized Thick Sedimentary Sequence?" by W.
D. Stanley, W. J. Gwilliam, Gary Latham, and Keith
Westhusing, 16 p., 11 figs.

   (The OVERVIEW given above was previously published on
the U.S. Geological Survey OFR 92-714 CD-ROM containing the
SEG-Y format seismic data.)