Crustal shear-wave splitting from local earthquakes in the Hengill triple junction, southwest Iceland
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Abstract
The Hengill region in SW Iceland is an unstable ridge-ridge-transform triple junction between an active and a waning segment of the mid-Atlantic spreading center and a transform that is transgressing southward. The triple junction contains active and extinct spreading segments and a widespread geothermal area. We evaluated shear-wave birefringence for locally recorded upper-crustal earthquakes using an array of 30 three-component digital seismographs. Fast-polarization directions, ϕ, are mostly NE to NNE, subparallel to the spreading axis and probably caused by fissures and microcracks related to spreading. However, there is significant variability in ϕ throughout the array. The lag from fast to slow S is not proportional to earthquake depth (ray length), being scattered at all depths. The average wave-speed difference between qS1 and qS2 in the upper 2–5 km of the crust is 2–5%. Our results suggest considerable heterogeneity or strong S scattering.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Crustal shear-wave splitting from local earthquakes in the Hengill triple junction, southwest Iceland |
| Series title | Geophysical Research Letters |
| DOI | 10.1029/96GL00261 |
| Volume | 23 |
| Issue | 5 |
| Year Published | 1996 |
| Language | English |
| Publisher | American Geophysical Union |
| Description | 4 p. |
| First page | 455 |
| Last page | 458 |
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