Jökull - 01.01.2015, Blaðsíða 58

J. Schuler et al.,
ÁGRIP
Jarðskjálftavirkni á Þeistareykjasvæðinu var könnuð
með neti færanlegra jarðskjálftamæla á árunum 2009–
2012. Skjálftavirknin var aðallega bundin við vest-
urhluta Bæjarfjalls, í þyrpingu með upptök á 2–5
km dýpi sunnan jarðhitasvæðisins. Dreif af mun
dýpri skjálftum mældust suðaustur af Þeistareykj-
um, á 8–20 km dýpi, í deiga hluta jarðskorpunnar.
Djúpu skjálftarnir liggja á milli sprungusveima Þeista-
reykja og Kröflu, nálægt upptökum Borgarhrauns og
gætu tengst kvikuhreyfingum innan gosbeltisins, en
einnig spennubreytingum innan Húsavíkur-Flateyjar-
brotabeltisins.
REFERENCES
Aki, K. 1965. Maximum likelihood estimate of b in the
formula logN = a – bM and its confidence limits. Bull.
Earthquake Res. Inst. 43, 237–239.
Ali, S. T., K. L. Feigl, B. B. Carr, T. Masterlark
and F. Sigmundsson 2014. Geodetic measurements
and numerical models of rifting in Northern Iceland
for 1993–2008. Geophys. J. Int. 196, 1267–1280,
doi:10.1093/gji/ggt462.
Ármannsson, H. 2014. The Þeistareykir geothermal sys-
tem, North East Iceland: case history. Short Course IX
on Exploration for Geothermal Resources, United Na-
tions University, Kenya, 11 pp.
Árnason, K., R. Karlsdóttir, H. Eysteinsson, Ó. G. Flóvenz
and S. T. Gudlaugsson 2008. The resistivity structure
of high-temperature geothermal systems in Iceland.
Short Course III on Exploration of Geothermal Re-
sources, United Nations University, Kenya, 11 pp.
Bender, B. 1983. Maximum likelihood estimation of b val-
ues for magnitude grouped data. Bull. Seism. Soc. Am.
73, 831–851.
Beyreuther, M., R. Barsch, L. Kirscher, T. Megies, Y. Behr
and J. Wassermann 2010. ObsPy: A Python Toolbox
for Seismology. Seism. Res. Lett. 81, 530–533.
Brandsdóttir, B., M. Parsons, R. S. White, Ó. Guðmunds-
son, J. Drew and B. S. Þorbjarnardóttir 2011. The
May 29th 2008 earthquake aftershock sequence within
the South Iceland Seismic Zone: Fault locations and
source parameters of aftershocks. Jökull 60, 23–46.
Drew, J., R. S. White, F. Tilmann and J. Tarasewicz 2013.
Coalsescence microseismic mapping. Geophys. J. Int.
195, 1773–1785.
Drouin, V., S. Hreinsdóttir, K. Spaans and F. Sigmundsson
2013. Crustal deformation in the Krafla, Gjástykki and
Þeistareykir areas inferred using GPS and InSAR tech-
niques, Status report for 2012. Landsvirkjun LV-2013-
038, and Nordic Volcanol. Center, Institute of Earth
Sciences report 1301, University of Iceland, 31 pp.
Einarsson, P. and K. Sæmundsson 1987. Earthquake epi-
centers 1982–1985 and volcanic systems in Iceland
(map). In: Sigfússon, Þ. I. (ed.) Í hlutarins eðli, Fest-
schrift for Þorbjörn Sigurgeirsson. Menningarsjóður,
Reykjavík.
Gíslason, G., G. V. Johnsen, H. Ármannsson, H. Torfa-
son and K. Árnason 1984. Þeistareykir: Surface explo-
ration of the high-temperature geothermal area (in Ice-
landic). Orkustofnun, report OS-84089/JHD-16, Ice-
land, 134 pp.
Greenfield, T. and R. S. White 2015. Building Icelandic
igneous crust by repeated melt injections. J. Geophys.
Res. 120, 7771–7788.
Hjaltadóttir, S. and K. S. Vogfjörð 2011. Sprungukort-
lagning við Þeistareyki og Bjarnarflag með háupp-
lausnarstaðsetningum smáskjálfta. (Subsurface faults
in Þeistareykir and Bjarnarflag delineated by relative
earthquake locations). Landsvirkjun report LV-2011-
116, 44 pp.
Hjartardóttir, A. R., P. Einarsson, S. Magnúsdóttir, Þ.
Björnsdóttir and B. Brandsdóttir 2015. Fracture sys-
tems of the Northern Volcanic Rift Zone, Iceland: an
onshore part of the Mid-Atlantic plate boundary. In:
Magmatic Rifting and Active Volcanism. Wright, T.
J., A. Ayele, D. J. Ferguson, T. Kidane and C. Vye-
Brown, (eds.). Geol. Soc. London Spec. Publ. 420,
doi:10.1144/SP420.1.
Karlsdóttir, R., A. M. Vilhjálmsson, K. Árnason and A. T.
Beyene 2012. Þeistareykir geothermal Area, Northern
Iceland: 3D inversion of MT and TEM data. ISOR-
2012/046 report, Iceland, 173 pp.
Kissling, E., W. L. Ellsworth, D. Eberhart-Philips and
U. Kradolfer 1994. Initial reference models in local
earthquake tomography. J. Geophys. Res. 99, 19635–
19646.
Lomax, A., A. Michelini and A. Curtis 2009. Earthquake
location, direct, global-search methods. Encyclope-
dia of Complexity and System Science. Meyers, R. A.
(ed.), 2449–2473, Springer, New York.
Maclennan, J., D. McKenzie, F. Hilton, K. Grönvold and
N. Shimizu 2003. Geochemical variability in a single
58 JÖKULL No. 65, 2015