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Seismic imaging of the shallow crust beneath the Krafla central volcano, NE Iceland

Schuler, Juerg and Greenfield, Tim and White, Robert S. and Roecker, Steven W. and Brandsdóttir, Bryndís and Stock, Joann M. and Tarasewicz, Jon and Martens, Hilary R. and Pugh, David (2015) Seismic imaging of the shallow crust beneath the Krafla central volcano, NE Iceland. Journal of Geophysical Research. Solid Earth, 120 (10). pp. 7156-7173. ISSN 2169-9313. doi:10.1002/2015JB012350.

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We studied the seismic velocity structure beneath the Krafla central volcano, NE Iceland, by performing 3-D tomographic inversions of 1453 earthquakes recorded by a temporary local seismic network between 2009 and 2012. The seismicity is concentrated primarily around the Leirhnjúkur geothermal field near the center of the Krafla caldera. To obtain robust velocity models, we incorporated active seismic data from previous surveys. The Krafla central volcano has a relatively complex velocity structure with higher P wave velocities (V_p) underneath regions of higher topographic relief and two distinct low-V_p anomalies beneath the Leirhnjúkur geothermal field. The latter match well with two attenuating bodies inferred from S wave shadows during the Krafla rifting episode of 1974–1985. Within the Leirhnjúkur geothermalreservoir, we resolved a shallow (−0.5 to 0.5 km below sea level; bsl) region with low-V_p/V_s values and a deeper (0.5–1.5 km bsl) high-V_p/V_s zone. We interpret the difference in the velocity ratios of the two zones to be caused by higher rock porosities and crack densities in the shallow region and lower porosities and crack densities in the deeper region. A strong low-V_p/V_s anomaly underlies these zones, where a superheated steam zone within felsic rock overlies rhyolitic melt.

Item Type:Article
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URLURL TypeDescription
Stock, Joann M.0000-0003-4816-7865
Martens, Hilary R.0000-0003-2860-9013
Additional Information:© 2015 American Geophysical Union. Received 11 JUL 2015; Accepted 1 OCT 2015; Accepted article online 10 OCT 2015; Published online 30 OCT 2015. We thank Julian Drew for use of his CMM location algorithm. Seismometers were provided by SEIS-UK under loan 891, with additional data from local SIL network stations kindly provided by the Icelandic Meteorological Office. The data will be stored at IRIS ( and accessible from there. Funding was provided to R.S.W. by a grant from the Natural Environment Research Council and to T.G. from a Shell UK studentship. Landsvirkjun allowed us to use well information and assisted with logistics during our field campaigns. We are grateful to Sveinbjörn Steinþórsson, Heidi Soosalu, Janet Tibbitts, and the students who helped in the field. The figures were generated using the Generic Mapping Tools. We are grateful to S. Arnott for discussing his data set as well as R. Zierenberg and B. Kennedy for discussing their results on the quenched glasses from Krafla. We thank Páll Einarsson, Knútur Árnason, and the JGR Associate Editor for constructive comments. J.S. gratefully acknowledges support from the Swiss National Science Foundation, Department of Earth Sciences, Cambridge contribution number ESC.3491.
Group:Seismological Laboratory
Funding AgencyGrant Number
Natural Environment Research Council (NERC)UNSPECIFIED
Shell UK studentshipUNSPECIFIED
Swiss National Science Foundation (SNSF)UNSPECIFIED
Issue or Number:10
Record Number:CaltechAUTHORS:20160119-093854474
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Official Citation:Schuler, J., T. Greenfield, R. S. White, S. W. Roecker, B. Brandsdóttir, J. M. Stock, J. Tarasewicz, H. Martens, and D. Pugh (2015), Seismic imaging of the shallow crust beneath the Krafla central volcano, NE Iceland, J. Geophys. Res. Solid Earth, 120, 7156–7173, doi:10.1002/2015JB012350
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:63757
Deposited By: Tony Diaz
Deposited On:19 Jan 2016 23:22
Last Modified:10 Nov 2021 23:21

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