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| Titel |
The Stress Pattern of Iceland |
| VerfasserIn |
Moritz Ziegler, Mojtaba Rajabi, Oliver Heidbach, Gylfi Páll Hersir, Kristjan Ágústsson, Sigurveig Árnadóttir, Arno Zang |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250124405
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| Publikation (Nr.) |
 EGU/EGU2016-3834.pdf |
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| Zusammenfassung |
| Iceland is one of the few places on earth where an active spreading can be observed onshore,
yet the contemporary crustal stress state has not been investigated intesively. We
compiled the first comprehensive stress map of Iceland from different stress indicators
and analysed data from 57 Icelandic geothermal boreholes. In total we interpreted
appox. 37 km of acoustic image logs for stress indicators, i.e. borehole breakouts and
drilling induced tensile fractures. Furthermore we revised the 38 data records for
Iceland from the World Stress Map 2008 and conducted an extensive literature
research to compile all available focal mechanism solutions and geological stress
indicators.
The new stress compilation consists of 495 data records for the orientation of the
maximum horizontal stress (SHmax) in and around Iceland with 318 data records of A-D
qualities according to the World Stress Map ranking scheme. Most of the data records are
derived from focal mechanism solutions (35%) and geological fault inversions (26%).
Borehole related indicators (breakouts, drilling induced fractures, hydro-fractures) have a
share of 20%. Minor contributions to the dataset are provided by the alignment of volcanic
vents and fissures and overcoring measurements.
The mean orientation of SHmax is 17˚ ± 39˚ for all A-D quality data. A closer look at
subregions reveals four different provinces with fairly consistent SHmax orientation. They are
in the Capital area and Southern Lowlands (mean SHmax = 38˚ ± 29˚ ), the eastern
Highlands and Eastfjords (mean SHmax = 8˚ ± 25˚ ), the Tjörnes Fracture Zone and
Akureyri (mean SHmax = 151˚ ± 21˚ ), and the Westfjords (mean SHmax = 137˚ ± 17˚
).
This distribution of SHmax orientations is in agreement with the prevailing tectonic
structure. At the spreading ridges Reykjanes and Kolbeinsey in the South and North
respectively an orientation of SHmax parallel to the plate boundary is observed. The same is
observed in the Northern and Eastern Volcanic Zones and it is also indicated by
the few indicators associated with the Western Volcanic Zone. In the transform
South Iceland Seismic Zone and Tjörnes Fracture Zone which produce Icelands
largest earthquakes, SHmax is at an angle of approximately 20˚ to 60˚ to the
transform faults which define the plate boundary. A rotation from ridge parallel
to the general intraplate ridge normal SHmax is expected at some distance from
the plate boundary. Such a rotation is observed in the Westfjords, NW-Iceland. |
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