Final Report: Offshore Alaska Seismic Movements Program




Frohlich, Cliff
Nakamura, Yosio

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Institute for Geophysics


This report summarizes the results of 18 deployments of the Texas strong motion ocean bottom seismograph (SM-OBS) which took place between July 1980 and July 1982 offshore of Alaska. From these deployments, 12 instruments were recovered, and 10 recorded data. Some of the instruments were successfully recovered after more than 240 days, longer than any previous OBS deployment that we know of. Two of the instruments apparently recorded data from four different earthquakes. The recorded ground accelerations for these events were in the 10cm/sec2 to 20 cm/sec2 range. Unfortunately, only one earthquake of magnitude larger than 6.0 occurred near the SM-OBS instruments in the July 1980 - July 1982 period, and this was not recorded by the instruments. The main effort of the program was on the development of this new technology. Countless difficult problems encountered during the program were solved, but a few problems remained resulting in some instrumental malfunctions which affected all of the OBS deployments and prevented us from obtaining more data or data of uniformly high quality during this period. This report also evaluates some of these problems and suggests ways to avoid these problems in future SM-OBS programs. Considering the high potential for serious earthquake damage in the offshore Alaska region, it is imperative that the effort to obtain SM-OBS data continues.


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Frohlich, Cliff and Nakamura, Yosio. "Final Report: Offshore Alaska Seismic Movements Program." University of Texas Institute for Geophysics Technical Report No. 35 (1982), 128p.