Seismotectonic analysis of the Tjörnes Fracture Zone, an active transform fault in north Iceland

RöGnvaldsson, Sigurã°Ur T.; Guðmundsson, Ágúst; Slunga, Ragnar

doi:10.1029/98jb02789

Cited by 135 publications

(141 citation statements)

References 30 publications

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“…However, bathymetric data from the Axarfjördur region does not reveal any geomorphic features typical of prolonged right‐lateral strike‐slip activity. Major NNW‐SSE trending scarps are clearly visible in the bathymetry, typical of normal faults, suggesting that the Krafla rift zone continues northward beyond the location of the 1976 earthquake epicenter Rögnvaldsson et al [1998]…”

Section: Discussionmentioning

confidence: 99%

Deformation during the 1975–1984 Krafla rifting crisis, NE Iceland, measured from historical optical imagery

Hollingsworth¹,

Leprince²,

Ayoub³

et al. 2012

J. Geophys. Res.

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[1] We measure the displacement field resulting from the 1975-1984 Krafla rifting crisis, NE Iceland, using optical image correlation. Images are processed using the COSI-Corr software package. Surface extension is accommodated on normal faults and fissures which bound the rift zone, in response to dike injection at depth. Correlation of declassified KH-9 spy and SPOT5 satellite images reveals extension between 1977-2002 (2.5 m average opening over 80 km), while correlation of aerial photos between 1957-1990 provide measurements of the total extension (average 4.3 m opening over 80 km). Our results show $8 m of opening immediately north of Krafla caldera, decreasing to 3-4 m at the northern end of the rift. Correlation of aerial photos from 1957-1976 reveal a bi-modal pattern of opening along the rift during the early crisis, which may indicate either two different magma sources located at either end of the rift zone (a similar pattern of opening was observed in the 2005 Afar rift crisis in East Africa), or variations in rock strength along the rift. Our results provide new information on how past dike injection events accommodate long-term plate spreading, as well as providing more details on the Krafla rift crisis. This study also highlights the potential of optical image correlation using inexpensive declassified spy satellite and aerial photos to measure deformation of the Earth's surface going back many decades, thus providing a new tool for measuring Earth surface dynamics, e.g. glaciers, landsliding, coastal erosion, volcano monitoring and earthquake studies, when InSAR and GPS data are not available.

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Section: Discussionmentioning

confidence: 99%

Deformation during the 1975–1984 Krafla rifting crisis, NE Iceland, measured from historical optical imagery

Hollingsworth¹,

Leprince²,

Ayoub³

et al. 2012

J. Geophys. Res.

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“…For example, a fault zone may contain numerous faults at different scales that interact in various ways and often give rise to complex local stress fields (e.g., ZOBACK et al, 1987;ANGELIER et al, 1996;HOMBERG et al, 1997;BERGERAT et al, 1998;RÖ GNVALDSSON et al, 1998). This stress-field complexity makes general earthquake prediction, where the aim is accurate forecast of the time, place and size of the predicted earthquake, theoretically very difficult.…”

Section: Introductionmentioning

confidence: 99%

Evolution of Stress Fields and Faulting in Seismic Zones

Guðmundsson¹,

Homberg²

1999

Pure and Applied Geophysics

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Measurements indicate that stress magnitudes in the crust are normally limited by the frictional equilibrium on pre-existing, optimally oriented faults. Fault zones where these limitations are frequently reached are referred to as seismic zones. Fault zones in the crust concentrate stresses because their material properties are different from those of the host rock. Most fault zones are spatially relatively stable structures, however the associated seismicity in these zones is quite variable in space and time. Here we propose that this variability is attributable to stress-concentration zones that migrate and expand through the fault zone. We suggest that following a large earthquake and the associated stress relaxation, shear stresses of a magnitude sufficient to produce earthquakes occur only in those small parts of the seismic zone that, because of material properties and boundary conditions, encourage concentration of shear stress. During the earthquake cycle, the conditions for seismogenic fault slip migrate from these stress-concentration regions throughout the entire seismic zone. Thus, while the stress-concentration regions continue to produce small slips and small earthquakes throughout the seismic cycle, the conditions for slip and earthquakes are gradually reached in larger parts of, and eventually the whole, seismogenic layer of the seismic zone. Prior to the propagation of an earthquake fracture that gives rise to a large earthquake, the stress conditions in the zone along the whole potential rupture plane must be essentially similar. This follows because if they were not, then, on entering crustal parts where the state of stress was unfavourable to this type of faulting, the fault propagation would be arrested. The proposed necessary homogenisation of the stress field in a seismic zone as a precursor to large earthquakes implies that by monitoring the state of stress in a seismic zone, its large earthquakes may possibly be forecasted. We test the model on data from Iceland and demonstrate that it broadly explains the historical, as well as the current, patterns of seismogenic faulting in the South Iceland Seismic Zone.

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“…The larger earthquakes of the Grímsey Zone seem to be associated with leftlateral strike-slip faulting on NNE-striking faults (Rögnvaldsson et al 1998). The zone has the characteristics of an oblique rift.…”

Section: Tjörnes Fracture Zonementioning

confidence: 98%

Mechanisms of Earthquakes in Iceland

Einarsson

2014

Encyclopedia of Earthquake Engineering

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Seismotectonic analysis of the Tjörnes Fracture Zone, an active transform fault in north Iceland

Cited by 135 publications

References 30 publications

Deformation during the 1975–1984 Krafla rifting crisis, NE Iceland, measured from historical optical imagery

Deformation during the 1975–1984 Krafla rifting crisis, NE Iceland, measured from historical optical imagery

Evolution of Stress Fields and Faulting in Seismic Zones

Mechanisms of Earthquakes in Iceland

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