SHIPS - Bellingham

Bellingham SHIPS - May 10-May 20th 2002

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The U.S. Geological Survey has conducted an earthquake hazards investigation in the greater Bellingham area between May 11th and May 19th, 2002. During this time the U.S. Geological Survey installed a number of earthquake recorders in the Bellingham area, Orcas Island, and Lummi Island (see photo above, figure below). The seismic equipment recorded tiny seismic waves generated by a small airgun source towed around Lummi Island and other parts of the southern Strait of Georgia.

Although the plan for the Tully was to acquire multichannel seismic reflection data, the streamer was not working, so most of the data in US waters was single channel seismic reflection data.

The multichannel seismic streamer was repaired on Friday, May 17th, and the goals of the planned work in Canada are expected to be met.

graphic shows location of marine recording line and stations on land near Bellingham. The marine line crosses the Outer Islands fault in many places.

Map showing Tully tracklines in dash-dot lines from the start of the cruise Wednesday morning, May 15th, through Friday evening (May 17th). These tracklines complete what we call "Bellingham SHIPS". Triangles show locations of 18 RefTeks installed by the USGS to record the airgun signals. These sites were removed on Sunday, May 19th, and appear to have recorded data properly. Filled circles show the locations of 30 RefTeks installed by the University of Victoria in Canada. The RefTeks installed in Canada will be recording data until May 27th, when the Tully cruise will end. Dashed lines show squares where the Tully will acquire 3-D multichannel seismic reflection data.

The work will help the U.S. Geological Survey to better characterize earthquake hazards in the greater Bellingham area by determining the subsurface location of the Lummi Island fault and the subsurface geometry of the Bellingham (Georgia) basin. In all, nearly 50 seismic recorders were installed in Washington and British Columbia for this international study of earthquake hazard. The work was a follow-up to an earlier Seismic Hazards Investigation in Puget Sound (SHIPS) project conducted in May 1998.

Each of the seismic recorders consisted of a small motion sensor (geophone), a data recorder (computer hard drive), a small GPS antenna (wallet sized), and a 12-V car battery. The soda-can-sized geophone was buried in a small hole about one foot deep and had a volume of a cubic foot: no other disturbance of the recorder site was made. The rest of the recorder system was placed into a large “picnic cooler” and left on the ground. The recorder posed no risks to animals or humans.

Nothing was left behind at the sites: at the end of our work we refilled the hand-dug hole for the geophone and restored the site to its original configuration. No samples were collected. The environmental impact of these recording sites was minimal.

The instruments were installed after May 11th and were removed on by May 20th. Property owners were not liable for any potential loss of or damage to any seismic equipment installed on their property.

For further information on Bellingham SHIPS or previous SHIPS studies please contact us or visit our web site: http://earthquake.usgs.gov/regional/pacnw/ships/.

Scientist-in-Charge:
Tom Brocher, Chief Scientist, Bellingham SHIPS Project
USGS, 345 Middlefield Road, Menlo Park, CA 94025
(650) 329-4737, brocher@usgs.gov

Local Contact:
Karen Meagher, SHIPS Coordinator
USGS at UW, Dept. of Earth and Space Sciences
Box 35160, University of Washington, Seattle, WA 98195
(206) 685-3812, ships@ess.washington.edu