1887

Abstract

A sea-bottom seismic source, patterned after the so-called “Buffalo Gun” land source, has been<br>developed and tested for shallow water (river, lake, sea) applications. The sea-bottom source is<br>designed to be lowered on a tether, and to penetrate into soft bottom sediments to a selectable depth<br>(O-O.5 m). The device uses various strengths of water-proofed 8-gauge blank loads, and is fired<br>remotely from the surface. Zero time is measured by a transducer electrically connected to the<br>surface vessel. The source is relatively lightweight (14.4 kg) and can be operated from a small boat<br>or through ice. It uses environmentally friendly blank loads detonated within the bottom sediments<br>(i.e. not in direct hydraulic contact with fish). The loads are a fraction of the cost of seismocaps and<br>do not have the same handling/shipping restrictions.<br>Tests have been conducted in both fresh and salt water to water depths of 30 m. Comparative tests<br>with a seismocap in contact with the water bottom, fired beneath a 10 kg steel plate, showed that the<br>sea-bottom source produces significantly more energy, particularly in the low frequency range (30-<br>150 Hz). Based on these results, this device has potential applications in a variety of problems in<br>exploration, engineering, and environmental seismology in shallow water areas, such as:<br>i) seismic refraction surveys beneath lakes and rivers using water-bottom or surface hydrophone<br>arrays (mapping bedrock surface, velocity variations);<br>ii) seismic reflection surveys using water-bottom geophones (or hydrophones) to map gelogical<br>structure of surficial sediments/bedrock for through-ice applications;<br>iii) water-bottom Spectral Analysis of Surface Waves (SASW), utilizing the Scholte wave, whereby<br>the sub-bottom, shear-wave, velocity-depth profile (hence dynamic shear moduli) can be determined.

Loading

Article metrics loading...

/content/papers/10.3997/2214-4609-pdb.202.1999_017
1999-03-14
2024-03-29
Loading full text...

Full text loading...

http://instance.metastore.ingenta.com/content/papers/10.3997/2214-4609-pdb.202.1999_017
Loading
This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error