Real-Time Seismic Data from the Coastal Ocean

A moored-buoy system for collecting real-time seismic data from the coastal ocean has been developed and will be deployed for its initial field trial in the fall of 2003. The key component in this moored system is an ultra-stretchy mooring hose that provides compliance for waves and currents and protects the electrical conductors connecting an Ocean Bottom Seismometer (OBS) to a surface buoy from the effects of bending and stretching. This hose is able to stretch to more than twice its unstretched length of 30 m without putting excessive strain on the electrical conductors embedded in its wall. In the initial trials of this system, the OBS will be deployed on the bottom in 40 m of water and connected to the mooring hose through a cable on the seafloor. It will transmit continuous data at a rate of about 5,000 bps to a radio link in the surface buoy. A repeater modem located at the Gay Head lighthouse on Martha’s Vineyard about 18 km from the mooring site will receive the transmissions and forward the data to our laboratory at WHOI, about 46 km distant. A GPS receiver on the surface buoy will be configured to send accurate and synchronized time to the OBS on the seafloor, which will make it possible to include data from these undersea systems in the existing seismic data network without the need for any preprocessing. Power to operate the RF link and the OBS will be supplied by solar panels and rechargeable batteries on the surface buoy.