The stress shadow induced by the 1975-1984 Krafla rifting episode

Handle URI:
http://hdl.handle.net/10754/552163
Title:
The stress shadow induced by the 1975-1984 Krafla rifting episode
Authors:
Maccaferri, F.; Rivalta, E.; Passarelli, L.; Jonsson, Sigurjon ( 0000-0001-5378-7079 )
Abstract:
It has been posited that the 1975–1984 Krafla rifting episode in northern Iceland was responsible for a significant drop in the rate of earthquakes along the Húsavík-Flatey Fault (HFF), a transform fault that had previously been the source of several magnitude 6–7 earthquakes. This compelling case of the existence of a stress shadow has never been studied in detail, and the implications of such a stress shadow remain an open question. According to rate-state models, intense stress shadows cause tens of years of low seismicity rate followed by a faster recovery phase of rate increase. Here, we compare the long-term predictions from a Coulomb stress model of the rifting episode with seismological observations from the SIL catalog (1995–2011) in northern Iceland. In the analyzed time frame, we find that the rift-induced stress shadow coincides with the eastern half of the fault where the observed seismicity rates are found to be significantly lower than expected, given the historical earthquake activity there. We also find that the seismicity rates on the central part of the HFF increased significantly in the last 17 years, with the seismicity progressively recovering from west to east. Our observations confirm that rate-state theory successfully describes the long-term seismic rate variation during the reloading phase of a fault invested by a negative Coulomb stress. Coincident with this recovery, we find that the b-value of the frequency-magnitude distribution changed significantly over time. We conclude that the rift-induced stress shadow not only decreased the seismic rate on the eastern part of the HFF but also temporarily modified how the system releases seismic energy, with more large magnitude events in proportion to small ones. This behavior is currently being overturned, as rift-induced locking is now being compensated by tectonic forcing.
KAUST Department:
Physical Sciences and Engineering (PSE) Division
Citation:
The stress shadow induced by the 1975-1984 Krafla rifting episode 2013, 118 (3):1109 Journal of Geophysical Research: Solid Earth
Journal:
Journal of Geophysical Research: Solid Earth
Issue Date:
Mar-2013
DOI:
10.1002/jgrb.50134
Type:
Article
ISSN:
21699313
Additional Links:
http://doi.wiley.com/10.1002/jgrb.50134
Appears in Collections:
Articles; Physical Sciences and Engineering (PSE) Division

Full metadata record

DC FieldValue Language
dc.contributor.authorMaccaferri, F.en
dc.contributor.authorRivalta, E.en
dc.contributor.authorPassarelli, L.en
dc.contributor.authorJonsson, Sigurjonen
dc.date.accessioned2015-05-04T16:25:38Zen
dc.date.available2015-05-04T16:25:38Zen
dc.date.issued2013-03en
dc.identifier.citationThe stress shadow induced by the 1975-1984 Krafla rifting episode 2013, 118 (3):1109 Journal of Geophysical Research: Solid Earthen
dc.identifier.issn21699313en
dc.identifier.doi10.1002/jgrb.50134en
dc.identifier.urihttp://hdl.handle.net/10754/552163en
dc.description.abstractIt has been posited that the 1975–1984 Krafla rifting episode in northern Iceland was responsible for a significant drop in the rate of earthquakes along the Húsavík-Flatey Fault (HFF), a transform fault that had previously been the source of several magnitude 6–7 earthquakes. This compelling case of the existence of a stress shadow has never been studied in detail, and the implications of such a stress shadow remain an open question. According to rate-state models, intense stress shadows cause tens of years of low seismicity rate followed by a faster recovery phase of rate increase. Here, we compare the long-term predictions from a Coulomb stress model of the rifting episode with seismological observations from the SIL catalog (1995–2011) in northern Iceland. In the analyzed time frame, we find that the rift-induced stress shadow coincides with the eastern half of the fault where the observed seismicity rates are found to be significantly lower than expected, given the historical earthquake activity there. We also find that the seismicity rates on the central part of the HFF increased significantly in the last 17 years, with the seismicity progressively recovering from west to east. Our observations confirm that rate-state theory successfully describes the long-term seismic rate variation during the reloading phase of a fault invested by a negative Coulomb stress. Coincident with this recovery, we find that the b-value of the frequency-magnitude distribution changed significantly over time. We conclude that the rift-induced stress shadow not only decreased the seismic rate on the eastern part of the HFF but also temporarily modified how the system releases seismic energy, with more large magnitude events in proportion to small ones. This behavior is currently being overturned, as rift-induced locking is now being compensated by tectonic forcing.en
dc.relation.urlhttp://doi.wiley.com/10.1002/jgrb.50134en
dc.rightsArchived with thanks to Journal of Geophysical Research: Solid Earthen
dc.titleThe stress shadow induced by the 1975-1984 Krafla rifting episodeen
dc.typeArticleen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.identifier.journalJournal of Geophysical Research: Solid Earthen
dc.eprint.versionPublisher's Version/PDFen
dc.contributor.institutionGeoForschungsZentrum Potsdam, Potsdam, Germanyen
dc.contributor.institutionInstitute of Geophysics, University of Hamburg, Hamburg, Germanyen
kaust.authorJonsson, Sigurjonen
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