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See also T-1-98-PS (Thompson) & T-2-98-PS (Tully)
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From February 27, 1998 Coastal and Marine Geology Bulletin
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SHIPS IS ON ITS WAY!
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Late this past week 5 48-foot trucks and some smaller cargo carriers left Marfac
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loaded with compressors, generators, airguns, and myriad
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other gear, all of which is destined for the SHIPS program in Seattle. Another
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truck left Texas with the 50-ton multichannel streamer. If all
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goes well, nearly 100 tons of mechanical and electrical equipment will be
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installed on the University of Washington's 275-foot research
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vessel, Thomas G. Thompson. This ship will be joined by the 240-foot Canadian
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research ship, John P. Tully, and the two ships will conduct
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intricate seismic experiments in the Puget Sound region. While airguns are
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discharged behind the Thompson, the resulting seismic waves
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will be recorded by the Tully as well as by 250 temporary seismometers that will
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be scattered around the region. About 50 fixed earthquake
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seismometers will also record these data. This survey is the most complex ever
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mounted by the USGS to investigate earthquake hazards in an
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urban setting. Cooperating institutions include the U.S. and Canadian Geological
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Surveys and six universities. The US Navy lent us critical
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infra-red gear, which was almost diverted to the Iraq conflict, and MMS
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contributed funds toward studying marine mammals. Funding comes
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almost entirely from within the USGS; the external NEHRP, Urban Hazards, and the
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Coastal and Marine Programs all contributed. Coastal and
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Marine has the honor of having chipped in the greatest share. Permission to use
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airguns in Puget Sound and the Straits of Juan de Fuca and
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Georgia, which are home to many marine mammals, took almost a year to obtain.
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Part of the stipulations in the permit are that when the
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airguns are operating, marine mammal biologists must remain vigilant aboard both
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survey ships and aboard an aircraft. Eleven biologists will
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work closely with geologists to obtain seismic data while minimizing harm to
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marine life. These biologists have responsibility for shutting
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off the array whenever a marine mammal enters a specific zone around the airguns
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where it might suffer hearing damage. The size of the
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protective zone varies with mammal species, hence the need for expert
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assistance. With close cooperation, we will obtain three-dimensional
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seismic data and information on the behavior of marine mammals in response to
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airgun signals. The data about mammals will help us and
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other groups plan the next airgun surveys; the seismic data will help city
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planners allocate scarce funds for seismic strengthening of
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important infrastructure. Crew from Marfac CMG and EQ leave early next week.
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Mike Fisher
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