CONTINUOUS SEISMIC PROFILING WITH MATCHED FILTER DETECTOR

Abstract

These experiments were made to study the application of pulse compression and continuous profiling techniques to deep‐sea geophysical research. Tests were made in several areas with low‐ and high‐frequency sources. Reflection profiles with a 125‐cps source were made in the Straits of Florida. The receiving hydrophone was towed behind the ship. The hydrophone consisted of a 75‐ft long array of 25 equally‐spaced acceleration‐balanced barium titanate elements inside an oil‐filled hose. The source transmitted either a ping or a chirp coded ping. The receiver included a shift‐register type of matched filter. Profiles were taken with both short pings and with chirp pings. The signal‐to‐noise gain of the chirping matched filter system was at least 12 db. Profiles were taken with a 400‐cps source and the low‐frequency source in Long Island Sound to compare operations with different source frequencies. The 400‐cps source did not penetrate beneath consolidated sediments whereas the low‐frequency source did. The 400‐cps source was used to study the reflections from the 15,500‐ft deep bottom in the basin near Eleuthera, B.W.I. Reflections at subbottom depths of about 75, 300, and 800 ft were observed. The shallow reflector was irregular in depth and appearance.