Observation and inversion of seismo-acoustic waves in a complex Artic ice environment
Submitted in partial fulfillment of the requirements for the degree of Ocean Engineer at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 1990 The propagation of low frequency seismo-acoustic waves in the Arctic Ocean ice canopy is examined through the...
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Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
1990
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ftwhoas:oai:darchive.mblwhoilibrary.org:1912/5416 2023-05-15T15:03:46+02:00 Observation and inversion of seismo-acoustic waves in a complex Artic ice environment Miller, Bruce E. Arctic Ocean 1990-09 application/pdf https://hdl.handle.net/1912/5416 en_US eng Massachusetts Institute of Technology and Woods Hole Oceanographic Institution WHOI Theses https://hdl.handle.net/1912/5416 doi:10.1575/1912/5416 doi:10.1575/1912/5416 Underwater acoustics Elastic waves Thesis 1990 ftwhoas https://doi.org/10.1575/1912/5416 2022-05-28T22:58:40Z Submitted in partial fulfillment of the requirements for the degree of Ocean Engineer at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 1990 The propagation of low frequency seismo-acoustic waves in the Arctic Ocean ice canopy is examined through the analysis of hydrophone and geophone data sets collected in 1987 at an ice camp designated PRUDEX in the Beaufort Sea. Study of the geophone time series generated by under-ice explosive detonations reveals not only the expected longitudinal and flexural waves in the ice plate, but also an unexpected horizontally-polarized transverse (SH) wave arriving at a higher amplitude than the other wave types. The travel paths of all three observed wave types are found to be refracted in the horizontal plane along a line coincident with a known ridge separating the ice canopy locally into two distinct half-plates, the first of thin first year ice and the second of thicker multi-year ice. The origin of the SH wave appears to be near the detonation and not associated with the interaction of longitudinal, flexural or waterborne waves with the ridge line. The need to determine the exact location of each detonation from the received time series highlights the dramatic superiority of geophones over hydrophones in this application, as does the ability to detect the anomalous SH waves and the refracted ray paths, neither of which are visible in the hydrophone data. Inversion of the geophone data sets for the low frequency elastic parameters of the ice is conducted initially by treating the ice as a single homogeneous isotropic plate to demonstrate the power of SAFARI numerical modeling in this application. A modified stationary phase approach is then used to extend SAFARI modeling to invert the data sets for the elastic parameters of the two ice half-plates simultaneously. The compressional/shear bulk wave speeds estimated in the half-plates, 3500/1750 m/s in the multi-year ice and 3000/1590 m/ s in the new ice, are comparable to ... Thesis Arctic Arctic Ocean Beaufort Sea Woods Hole Scientific Community: WHOAS (Woods Hole Open Access Server) Arctic Arctic Ocean Woods Hole, MA |
institution |
Open Polar |
collection |
Woods Hole Scientific Community: WHOAS (Woods Hole Open Access Server) |
op_collection_id |
ftwhoas |
language |
English |
topic |
Underwater acoustics Elastic waves |
spellingShingle |
Underwater acoustics Elastic waves Miller, Bruce E. Observation and inversion of seismo-acoustic waves in a complex Artic ice environment |
topic_facet |
Underwater acoustics Elastic waves |
description |
Submitted in partial fulfillment of the requirements for the degree of Ocean Engineer at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 1990 The propagation of low frequency seismo-acoustic waves in the Arctic Ocean ice canopy is examined through the analysis of hydrophone and geophone data sets collected in 1987 at an ice camp designated PRUDEX in the Beaufort Sea. Study of the geophone time series generated by under-ice explosive detonations reveals not only the expected longitudinal and flexural waves in the ice plate, but also an unexpected horizontally-polarized transverse (SH) wave arriving at a higher amplitude than the other wave types. The travel paths of all three observed wave types are found to be refracted in the horizontal plane along a line coincident with a known ridge separating the ice canopy locally into two distinct half-plates, the first of thin first year ice and the second of thicker multi-year ice. The origin of the SH wave appears to be near the detonation and not associated with the interaction of longitudinal, flexural or waterborne waves with the ridge line. The need to determine the exact location of each detonation from the received time series highlights the dramatic superiority of geophones over hydrophones in this application, as does the ability to detect the anomalous SH waves and the refracted ray paths, neither of which are visible in the hydrophone data. Inversion of the geophone data sets for the low frequency elastic parameters of the ice is conducted initially by treating the ice as a single homogeneous isotropic plate to demonstrate the power of SAFARI numerical modeling in this application. A modified stationary phase approach is then used to extend SAFARI modeling to invert the data sets for the elastic parameters of the two ice half-plates simultaneously. The compressional/shear bulk wave speeds estimated in the half-plates, 3500/1750 m/s in the multi-year ice and 3000/1590 m/ s in the new ice, are comparable to ... |
format |
Thesis |
author |
Miller, Bruce E. |
author_facet |
Miller, Bruce E. |
author_sort |
Miller, Bruce E. |
title |
Observation and inversion of seismo-acoustic waves in a complex Artic ice environment |
title_short |
Observation and inversion of seismo-acoustic waves in a complex Artic ice environment |
title_full |
Observation and inversion of seismo-acoustic waves in a complex Artic ice environment |
title_fullStr |
Observation and inversion of seismo-acoustic waves in a complex Artic ice environment |
title_full_unstemmed |
Observation and inversion of seismo-acoustic waves in a complex Artic ice environment |
title_sort |
observation and inversion of seismo-acoustic waves in a complex artic ice environment |
publisher |
Massachusetts Institute of Technology and Woods Hole Oceanographic Institution |
publishDate |
1990 |
url |
https://hdl.handle.net/1912/5416 |
op_coverage |
Arctic Ocean |
geographic |
Arctic Arctic Ocean |
geographic_facet |
Arctic Arctic Ocean |
genre |
Arctic Arctic Ocean Beaufort Sea |
genre_facet |
Arctic Arctic Ocean Beaufort Sea |
op_source |
doi:10.1575/1912/5416 |
op_relation |
WHOI Theses https://hdl.handle.net/1912/5416 doi:10.1575/1912/5416 |
op_doi |
https://doi.org/10.1575/1912/5416 |
op_publisher_place |
Woods Hole, MA |
_version_ |
1766335609382633472 |