USGS CMG C-1-94-WO Metadata

Feasibility study to determine if high resolution seismic reflection
data of reasonable quality could be collected in the Columbia River to help
assess earthquake hazards of the Portland, OR / Vancouver, WA metropolitan
area.

Seismic reflection profiles from Geopulse and trackline map.

Approximately 3 1/2 days of geopulse data were collected in six areas
of the Columbia River between Astoria, OR and Washougal, WA across the following
fault zones: Clatskanie, Columbia River, Chinook, Firn Hill, Portland Hills,and
Frontal fault zones, and unnamed faults near Portland International Airport, and
Trojan nuclear power plant. Navigation and seismic data were merged and recorded
on two optical disks. 14 rolls (representing different geographic locations) of
analog data were collected.

Navigation data are in USGS data base.  The rest of the data should be
input by 1/1/95, unless requested sooner.

(modified from 7/29/94 USGS Bulletin)

COLUMBIA RIVER CRUISE

Holly Ryan, Andy Stevenson, and Jim Vaughn are back from a successful but
HOT--+100d F!) 5-day reconnaissance cruise to the Columbia River collecting
high resolution geopulse data in search of recent upper crustal faulting, as
part of the Cascadia earthquake hazards project.

Al Niem from Oregon State University joined us for two days.

Data were collected aboard the Cathlamet Bay, a 26-foot Army Corps of
Engineering boat that allowed data acquisition in only a few meters of water.

The logistics of mounting all of the equipment on the boat was somewhat of a
headache, but the expertise of the boat driver, Terry Vance of the Corps, more
than made up for the lack of space, and contributed immensely to the success
of the cruise.

Although we were not able to image much more than about 10 to 20 m below the
river bottom, we did observe evidence suggestive of recent faulting at several
sites.

These included the northern and southern bounding faults of Portland Basin,
near Portland International Airport, near the now defunct Trojan nuclear power
plant, and along northwest trending faults in the lower Columbia River near
Astoria.

We hope to be able to go back at some time in the future using a larger source
to be able to confirm our results.

Ryan, H.F., and Stevenson, A.J., 1995, Cruise report for C1-94-OW:
Reconnaissance high resolution Geopulse data acquired for seismic
hazard studies along the Columbia River from July 18-22, 1994: U.S.
Geological Survey Open-File Report 95-668, 38 p.