Non-double-couple earthquakes at the Hengill-Grensdalur volcanic omplex, Iceland: Are they artifacts of crustal heterogeneity
Earthquakes with anomalous non-double-couple (non-DC) mechanisms have been observed at many geothermal and volcanic areas, and possible physical explanations have been offered for them that involve tensile fracture caused by high fluid pressure or thermal contraction due to cooling. Nevertheless, th...
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ftciteseerx:oai:CiteSeerX.psu:10.1.1.575.7255 2023-05-15T16:47:57+02:00 Non-double-couple earthquakes at the Hengill-Grensdalur volcanic omplex, Iceland: Are they artifacts of crustal heterogeneity R. Foulger Bruce R. Julian The Pennsylvania State University CiteSeerX Archives 1993 application/pdf http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.575.7255 http://community.dur.ac.uk/g.r.foulger/Offprints/BSSA.pdf en eng http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.575.7255 http://community.dur.ac.uk/g.r.foulger/Offprints/BSSA.pdf Metadata may be used without restrictions as long as the oai identifier remains attached to it. http://community.dur.ac.uk/g.r.foulger/Offprints/BSSA.pdf text 1993 ftciteseerx 2016-01-08T12:44:45Z Earthquakes with anomalous non-double-couple (non-DC) mechanisms have been observed at many geothermal and volcanic areas, and possible physical explanations have been offered for them that involve tensile fracture caused by high fluid pressure or thermal contraction due to cooling. Nevertheless, the possible biasing effects of wave propagation in structurally complicated vol-canic regions has made the identification of non-DC mechanisms as true source phenomena uncertain. Non-DC earthquakes are common at the HengilI-Grensdalur volcanic com-plex in southwestern Iceland. Of 178 microearthquakes recorded by a 23-station network in the summer of 1981, 84, or 47%, have non-DC mechanisms, based on conventional interpretation of P-wave first motions using a one-dimensional crustal model. In this paper, we re-analyze the best constrained of these events by numerically tracing rays in a three-dimensional tomographi-cally derived model of the crust. Computed positions of rays on the focal spheres change by as much as 35 °, with the largest changes being caused by revision of focal depths. The number of earthquakes with clearly non-DC mechanisms remains large, however (56 out of 131 or 43%); the anomalous mechanisms are not artifacts of the mis-mapping of rays onto the focal sphere. Text Iceland Unknown Hengill ENVELOPE(-21.306,-21.306,64.078,64.078) Grensdalur ENVELOPE(-21.962,-21.962,65.170,65.170) |
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English |
description |
Earthquakes with anomalous non-double-couple (non-DC) mechanisms have been observed at many geothermal and volcanic areas, and possible physical explanations have been offered for them that involve tensile fracture caused by high fluid pressure or thermal contraction due to cooling. Nevertheless, the possible biasing effects of wave propagation in structurally complicated vol-canic regions has made the identification of non-DC mechanisms as true source phenomena uncertain. Non-DC earthquakes are common at the HengilI-Grensdalur volcanic com-plex in southwestern Iceland. Of 178 microearthquakes recorded by a 23-station network in the summer of 1981, 84, or 47%, have non-DC mechanisms, based on conventional interpretation of P-wave first motions using a one-dimensional crustal model. In this paper, we re-analyze the best constrained of these events by numerically tracing rays in a three-dimensional tomographi-cally derived model of the crust. Computed positions of rays on the focal spheres change by as much as 35 °, with the largest changes being caused by revision of focal depths. The number of earthquakes with clearly non-DC mechanisms remains large, however (56 out of 131 or 43%); the anomalous mechanisms are not artifacts of the mis-mapping of rays onto the focal sphere. |
author2 |
The Pennsylvania State University CiteSeerX Archives |
format |
Text |
author |
R. Foulger Bruce R. Julian |
spellingShingle |
R. Foulger Bruce R. Julian Non-double-couple earthquakes at the Hengill-Grensdalur volcanic omplex, Iceland: Are they artifacts of crustal heterogeneity |
author_facet |
R. Foulger Bruce R. Julian |
author_sort |
R. Foulger |
title |
Non-double-couple earthquakes at the Hengill-Grensdalur volcanic omplex, Iceland: Are they artifacts of crustal heterogeneity |
title_short |
Non-double-couple earthquakes at the Hengill-Grensdalur volcanic omplex, Iceland: Are they artifacts of crustal heterogeneity |
title_full |
Non-double-couple earthquakes at the Hengill-Grensdalur volcanic omplex, Iceland: Are they artifacts of crustal heterogeneity |
title_fullStr |
Non-double-couple earthquakes at the Hengill-Grensdalur volcanic omplex, Iceland: Are they artifacts of crustal heterogeneity |
title_full_unstemmed |
Non-double-couple earthquakes at the Hengill-Grensdalur volcanic omplex, Iceland: Are they artifacts of crustal heterogeneity |
title_sort |
non-double-couple earthquakes at the hengill-grensdalur volcanic omplex, iceland: are they artifacts of crustal heterogeneity |
publishDate |
1993 |
url |
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.575.7255 http://community.dur.ac.uk/g.r.foulger/Offprints/BSSA.pdf |
long_lat |
ENVELOPE(-21.306,-21.306,64.078,64.078) ENVELOPE(-21.962,-21.962,65.170,65.170) |
geographic |
Hengill Grensdalur |
geographic_facet |
Hengill Grensdalur |
genre |
Iceland |
genre_facet |
Iceland |
op_source |
http://community.dur.ac.uk/g.r.foulger/Offprints/BSSA.pdf |
op_relation |
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.575.7255 http://community.dur.ac.uk/g.r.foulger/Offprints/BSSA.pdf |
op_rights |
Metadata may be used without restrictions as long as the oai identifier remains attached to it. |
_version_ |
1766038050323824640 |