Publication Date:
2022-05-25
Description:
This report describes a preliminary analysis of borehole seismic data to
determine VLF/Sub-bottom Seismic Noise in the Atlantic and the preliminary
results of finite difference modelling for a Cape Fear environment.
Noise levels were not a simple function of depth and there are indications
that noise levels may depend on local geology about a given receiver position
and/or on clamping. Coherency of the noise was generally poor (〈0.8) and
was independent of depth. There is no evidence for distinct polarizations or
directionality of the noise. The lowest determined value for ambient noise
power on the vertical component was 10-4 nm2/Hz in the frequency range
from 5-50 Hz. The better clamped horizontal component had comparable power
values. In conclusion, although the drill ship was on the site and drill pipe
was in the hole, analysis of the data for a large number of windows can
provide meaningful upper bounds on the ambient noise levels in the upper crust.
Description:
Prepared for the Naval Ocean Research and Development Activity as the
final report for Contract Purchase Order No. N62306-86-l4-7589
Keywords:
Ambient sounds
;
Seismology
Repository Name:
Woods Hole Open Access Server
Type:
Working Paper
Format:
application/pdf
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