Deep‐sea measurements without wires or cables

Abstract

In the deep‐sea seismic measurements which were commenced last summer on the Atlantis, the principal problems for which no good solution is in sight are connected with the cable. It seems likely that the best solution is to dispense with the cable altogether. Figure 1 shows the apparatus as used last year. It consists of a series of bombs, a series of seismographs, and an oscillograph‐chamber. The cable leading from the ship to the oscillograph is a wire rope which serves only to lower and hoist the apparatus. It is necessary to place the 600‐pound oscillograph‐chamber on the bottom of the ocean in such a way that the 4200‐foot string of seismographs and bombs shall lead away from it in a line which is very nearly straight. The actual distances from each bomb to each seismograph are determined from the travel‐time of the water‐wave. Only three tests have been made to date, but it is revealed by the water‐waves that the line of instruments did not extend to nearly its full length in any test. In one test the 20‐pound bomb was actually less than 600 feet from the oscillograph. Perhaps further practice in the maneuver of laying out the apparatus would overcome this difficulty to some extent, but it will always be difficult to stretch this line out straight without parting it. This is the first problem to be solved.

Relationship between pressure variations at the ocean bottom and the acceleration of its motion during a submarine earthquake

“…Till the second half of the Twentieth century, earthquakes and tsunamis were only registered by land-based seismic stations and coastal mareographs. The development of ocean bottom seismology-not to consider individual early experiments, e.g., (Ewing and Vine 1938)-originated in the 1960s (Bradner 1964). The "hydrophysical" method of tsunami forecasting, based on pressure gauges installed at the ocean bottom detecting waves at long distances from the coast (Soloviev 1968;Jaque and Soloviev 1971), was proposed at about the same time.…”

The future of passive seismic acquisition

“…While a submarine global seismic network has not yet materialized, great strides have been made in deploying seismometers in the oceans. As early as 1937, seismometers were deployed on the ocean floor (Ewing & Vine 1938), but technological problems linked to the high-pressure environment, power and communication presented significant challenges. Seismologists rose to these challenges by developing self-contained systems that can sit on the sea floor before floating back to the surface on receiving a signal from a ship above (see Suetsugu & Shiobara 2014 for a review).…”

Ocean bottom seismometer technology

“…Seismometers have been placed on the ocean bottom for about 45 years, beginning with the work of Ewing and Vine [1938], and their current use to measure signals from earthquakes and explosions constitutes an im portant research method for seismological studies. Approximately 20 research groups are active in the United Kingdom, France, West Germany, Japan, Canada, and the Unit ed States.…”