A Prototype Ocean Seismic Network (OSN) Deep-Sea Borehole Seismograph

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The research objective is modification and testing of an existing broadband seismometer for eventual installation in ocean borehole OSN-1, drilled by the ODP in March of 1991 (Leg 136). Augmentation of world-wide seismograph coverage through the addition of ocean floor seismic observatories will improve earthquake location, and allow the more accurate determination of deep Earth velocity structure. %%% Understanding why and where earthquakes occur is essential to mitigating these natural hazards. The earth motions induced by earthquakes also provide detailed information on deep earth structure. Such information is crucial to understanding such phenomena as the Earth's magnetic field, and the distribution of mineral resources on the Earth's surface. Our ability to measure earthquakes, however, is severely limited by geographic constraints on the placement of seismometers. Heretofore, the two-thirds of the Earth's surface that is water-covered has been inaccessible to seismometer coverage. Emplacement of borehole seismometers in ocean-sub-seafloor observatories is one solution proposed. This research is the first step in the creation of a network of ocean observatories: the modification and land-testing of a bore-hole seismometer capable of recording earth motions over a wide band of frequencies.