Study to Determine the Merit of Ocean Borehole Systems for Acoustic Detection

摘要

Data obtained by an ocean borehole experiment at 44 deg N, 160 deg E was analyzed in order to evaluate the detection capability of a borehole seismic system as compared to an ocean bottom system. Absolute noise levels for the complete duration of the 64-day experiment were also determined, indicating the borehole site to be one of the quietest sites in the world. This report presents results of analysis of active and passive seismic signals and background noise recorded on an ocean subbottom (OSS-IV) and ocean bottom seismometers (OBS), for the purpose of determining their relative merits for acoustic detection. Results from OSS-IV noise and signal propagation studies document the increase in signal fidelity and signal-to-noise ratio obtained at this site. Attenuation analysis of short line data indicates that loss at OSS-IV is more than expected from spherical spreading, but the low noise level of the instrument makes it sensitive to sources in the ocean for long ranges.