Halldor Geirsson

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Halldor Geirsson

Halldor
Postdoctoral Scholar
Email: 
hgeirsson@psu.edu
Education: 

PhD, Penn State, 2014

Research Interests: 
  • Crustal deformation processes 
  • Magma plumbing systems
  • Crustal structure

Born in Iceland, my dedicated interest for volcanoes and earthquakes started relatively late, in my early twenties. After obtaining my B.Sc. degree in Geophysics from the University of Iceland in 1999 I worked for the Icelandic Meteorological Office (IMO) until 2010 where my primary responsibility was to run the Icelandic Continuous GPS network and integrate geodetic methods into natural hazard monitoring at IMO. During my early career at IMO I finished my M.Sc. degree from the University of Iceland. I left IMO at the end of 2009 to pursue my PhD degree with Dr. LaFemina at The Pennsylvania State University, partly working on data that I gathered during my years at IMO. For my thesis I studied crustal deformation at active plate boundaries in Iceland and Central America. This work included GPS studies of tectonics and volcano deformation in South Iceland; a multivariate study of explosive volcanism in Nicaragua; and a study of subduction zone processes and properties offshore El Salvador and Nicaragua. I completed my degree in August 2014 and currently hold a post-doctoral position at Penn State working for Dr. LaFemina or projects related to my Thesis.

Kobayashi, D., P. LaFemina, H. Geirsson, E. Chichaco, A. Abrego, H. Mora-Paez, E. Camacho, 2014 (in press). Kinematics of the Western Caribbean: Collision of the Cocos Ridge and Upper Plate Deformation. G-cubed, in press.

Hreinsdottir, S., F. Sigmundsson, M.J. Roberts, H. Bjornsson, R. Grapenthin, Th. Arason, Th. Arnadottir, J. Holmjarn, H. Geirsson, R.A. Bennett, M.T. Gudmundsson, B. Oddsson, B.G. Ofeigsson, T. Villemin, Th. Jonsson, E. Sturkell, A. Hoskuldsson, G. Larsen, Th. Thordarson, B.A. Oladottir, 2014. Volcanic plume height correlated with magma-pressure change at Grimsvotn Volcano, Iceland, Nature Geoscience, doi: 10.1038/ngeo2044M3.

Geirsson, H., M. Rodgers, P. LaFemina, M. Witter, D. Roman, A. Munoz, V. Tenorio, J. Alavarez, V. C. Jacobo, D. Nilsson, B. Galle, M. D. Feineman, T. Furman, A. Morales, 2014. Multidisciplinary observations of the 2011 explosive eruption of Telica volcano, Nicaragua: Implications for the dynamics of low-explosivity ash eruptions. J. Volc. Geotherm. Res., 271, 1, 55-69, doi: 10.1016/j.jvolgeores.2013.11.009.

Rodgers, M., D. C. Roman, H. Geirsson, P. LaFemina, A. Munoz, C. Guzman, V. Tenorio, 2013. Seismicity accompanying the 1999 eruptive episode at Telica Volcano, Nicaragua. J. Volc. Geotherm. Res., 265, 39-51, doi:10.1016/j.jvolgeores.2013.08.010.

Sturkell, E., K. Ágústsson, A. T. Linde, S.I. Sacks, P. Einarsson, F. Sigmundsson, H. Geirsson, R. Pedersen, P. C. LaFemina, H. Ólafsson, 2013. New insights into volcanic activity from strain and other deformation data for the Hekla 2000 eruption. J. Volc. Geotherm. Res., 256, 78-86, doi:10.1016/j.jvolgeores.2013.02.001.

Geirsson, H., P. LaFemina, T. Árnadóttir, E. Sturkell, F. Sigmundsson, M. Travis, P. Schmidt, B. Lund, S. Hreinsdóttir, and R. Bennett, 2012. Volcano deformation at active plate boundaries: Deep magma accumulation at Hekla volcano and plate boundary deformation in south Iceland. J. Geophys. Res., 117, B11409, doi:10.1029/2012JB009400.

Hooper, A., B. Ófeigsson, F. Sigmundsson, B. Lund, P. Einarsson, H. Geirsson, E. Sturkell, 2011. Increased capture of magma in the crust promoted by ice-cap retreat in Iceland. Nature Geoscience, 4, 783-786, doi:10.1038/NGEO1269.

Metzger, S., S. Jónsson, and H. Geirsson, 2011. Locking depth and slip-rate of the Húsavík Flatey fault, North Iceland, derived from continuous GPS data 2006–2010. Geophys. J. Int., 187, 2, 564-576, doi: 10.1111/j.1365-246X.2011.05176.x.

Magnusson, E., H. Bjornsson, H. Rott, M.J. Roberts, F. Palsson, S. Gudmundsson, R.A. Bennett, H. Geirsson, E. Sturkell, 2011. Localized uplift of Vatnajökull, Iceland: subglacial water accumulation deduced from InSAR and GPS observations. Journal of Glaciology, 57, 203, 475-484.

Sigmundsson, F., S. Hreinsdóttir, A.Hooper, Th. Árnadóttir, R. Pedersen, M. Roberts, N. Óskarsson, A. Auriac, J. Decriem, P. Einarsson, H. Geirsson, M. Hensch, B. Ófeigsson, E. Sturkell, H. Sveinbjörnsson, K.L. Feigl, 2010. Intrusion triggering of the 2010 Eyjafjallajokull explosive eruption. Nature, 468, 426-430, doi:10.1038/nature09558.

Sigmundsson, F., V. Pinel, B. Lund, F. Albino, C. Pagli, H. Geirsson, E. Sturkell, 2010. Climate effects on volcanism: Influence on magmatic systems of loading and unloading from ice mass variations with examples from Iceland. Phil. Trans. Roy. Soc. A, Philosophical Transactions Royal Society A, 368, 1-16, doi:10.1098/rsta.2010.0042.

Decriem, J., Th. Árnadóttir, A. Hooper, H. Geirsson, M. Keiding, B.G. Ófeigsson, F. Sigmundsson, S. Hreinsdóttir, P. LaFemina and R. Bennett, 2010. The 29 May 2008 earthquake doublet in SW Iceland, Geophys. J. Int., 181(2), 1128-1146, doi: 10.1111/j.1365-246X.2010.04565.x.

Sturkell, E., P. Einarsson, F. Sigmundsson, A. Hooper, B.G. Ofeigsson, H. Geirsson and H. Olafsson, 2010. Katla and Eyjafjallajokull Volcanoes. In: Developments in Quaternary Science, eds. A. Schomacker, J. Kruger and K.H. Kjaer, Elsevier, Volume 13, The Myrdalsjokull Ice Cap, Iceland. Glacial processes, sediments and landforms on an active volcano, 5-21, doi:10.1016/S1571-0866(09)01302-5.

Geirsson, H., Th. Árnadóttir, S. Hreinsdóttir, J. Decriem, P.C. LaFemina, S. Jónsson, R. A. Bennett, S. Metzger, A. Holland, E. Sturkell, T. Villemin, C. Völksen, F. Sigmundsson, P. Einarsson, M. J. Roberts, H. Sveinbjörnsson, 2010. Overview of results from continuous GPS observations in Iceland from 1995 to 2010. Jökull, vol. 60, p. 3-22. 

Geirsson, H., Jakobsdóttir, S.S., Guðmundsson, G.B., Roberts, M.J., Decriem, J., 2009. A deep seated magmatic intrusion at Upptyppingar, Iceland, during 2007 and 2008 In: The VOLUME Project, VOLcanoes: Understaning subsurface mass moveMEnt, ed. C.J. Bean, A.K. Braiden, I. Lokmer, F. Martini, G.S. O'Brien. School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland.

Pinel, V., F. Albino, F. Sigmundsson, E. Sturkell, H. Geirsson, P. Einarsson & M. T. Gudmundsson, 2009. Consequences of local surface load variations for volcano monitoring: Application to Katla subglacial volcano, Iceland. In: The VOLUME Project, VOLcanoes: Understaning subsurface mass moveMEnt, ed. C.J. Bean, A.K. Braiden, I. Lokmer, F. Martini, G.S. O'Brien. School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland.

Árnadóttir, Th., B. Lund, W. Jiang, and H. Geirsson, H. Björnsson, P. Einarsson and T. Sigurdsson, 2009. Glacial rebound and plate spreading: Results from the first countrywide GPS observations in Iceland, Geophys. J. Int., 177(2), 691-716, doi: 10.1111/j.1365-246X.2008.04059.x. 

Hreinsdóttir, S., T. Árnadóttir, J. Decriem, H. Geirsson, A. Tryggvason, R. A. Bennett, and P. LaFemina, 2009. A complex earthquake sequence captured by the continuous GPS network in SW Iceland, Geophys. Res. Lett., 36, L12309, doi:10.1029/2009GL038391. 

Sturkell, E., P. Einarsson, H. Geirsson, E. Tryggvason, J.G. Moore, and R. Ólafsdóttir, 2009. Precision levelling and geodetic GPS observations performed on Surtsey between 1967 and 2002, Surtsey Research, 12, 39-47.

Volksen, C., Th. Arnadottir, H. Geirsson, G. Valsson, 2009. Present day geodynamics in Iceland monitored by a permanent network of continuous GPS stations, Journal of Geodynamics, 48, 279-283, doi: 10.1016/j.jog.2009.09.033.

Sturkell, E., F. Sigmundsson, H. Geirsson, H., Ólafsson, Th. Theodórsson, 2008. Multiple volcano deformation sources in a post-rifting period: 1989–2005 behaviour of Krafla, Iceland constrained by levelling, tilt and GPS observations. J. Volc. Geotherm. Res., 177, 405–417, doi:10.1016/j.jvolgeores.2008.06.013.

Sturkell, E., Einarsson, P., Roberts, M.J., Geirsson, H., Gudmundsson, M.T., Sigmundsson, F., Pinel, V., Guðmundsson, G.B., Ólafsson, H., & Stefánsson, R., 2008. Seismic and geodetic insights into magma accumulation at Katla subglacial volcano, Iceland: 1999 to 2005. Journal of Geophysical Research, 113, B03212, doi:10.1029/2006JB004851

Keiding, M., Árnadóttir, Th., Sturkell, E., & Geirsson, H., 2008. Contemporary strain accumulation along the Reykjanes Peninsula, South Iceland. Geophysical Journal International, 172, 861–872 doi: 10.1111/j.1365-246X.2007.03655.x

Jakobsdottir, S.S., M.J. Roberts, G.B. Gudmundsson, H. Geirsson, R. Slunga, 2008. Earthquake swarms at Upptyppingar, North-East Iceland: A sign of magma intrusion? Stud. Geophys. Geod., 52, 513-528, doi: 10.1007/s11200-008-0035-x.

Árnadóttir, Th. H. Geirsson, W. Jiang, 2008. Crustal deformation in Iceland: Plate spreading and earthquake deformation. Jökull, 58, 59-74.

Pagli, C., F. Sigmundsson, B. Lund, E. Sturkell, H. Geirsson, P. Einarsson, Th. Árnadóttir, 2007. Glacio-isostatic deformation around the Vatnajökull ice cap, Iceland, induced by recent climate warming: GPS observations and Finite Element Modeling. J. Geophys. Res., 112, B8, B08405, doi: 10.1029/2006JB004421.

Pinel, V., Sigmundsson, F., Sturkell, E., Geirsson, H., Einarsson, P., Gudmundsson, M.T. & Högnadóttir, T., 2007. Green's function estimates of Earth response to variable surface loads: Application to deformation of the subglacial Katla volcano, Iceland. Geophysical Journal International, 169, 325–338, doi: 10.1111/j.1365-246X.2006.03267.x

Geirsson, H., Th. Árnadóttir, C. Völksen, W. Jiang, E. Sturkell, T. Villemin, P. Einarsson, F. Sigmundsson, R. Stefánsson, 2006. Current plate movements across the Mid-Atlantic Ridge determined from 5 years of continuous GPS measurements in Iceland, J. Geophys. Res., 111, B9, B09407, doi: 10.1029/2005JB004092.

Sturkell, E., P. Einarsson, F. Sigmundsson, H. Geirsson, H. Olafsson, R. Pedersen, E. de Zeeuw-van Dalfsen, A. L. Linde, I. S. Sacks, and R. Stefansson, 2006. Volcano geodesy and magma dynamics in Iceland, J. Volc. Geotherm. Res., 150, 14-34.

Arnadóttir, Th., Jiang, W., Feigl, K.L., Geirsson, H. & Sturkell, E., 2006. Kinematic models of plate boundary deformation in southwest Iceland derived from GPS observations. Journal of Geophysical Research, 111, B07402, doi:10.1029/2005JB003907.

Grapenthin, R., F. Sigmundsson, H. Geirsson, Þ. Árnadóttir, V. Pinel, 2006. Icelandic rhythmics: Annual modulation of land elevation and plate spreading by snow load. Geophysical Research Letters, 33(24), L24305, doi: 10.1029/2006GL028081.

Hjaltadottir, S., H. Geirsson, Th. Skaftadottir, 2005. Seismic activity in Iceland during 2004. Jökull, 55, 107-119.

Vogfjörð, K. S., S. S. Jakobsdóttir, G. B. Guðmundsson, M. J. Roberts, K. Ágústsson, Þ. Arason, H. Geirsson, S. Karlsdóttir, S. Hjaltadóttir, U. Ólafsdóttir, B. S. Þorbjarnardóttir, Þ. Skaftadóttir, E. Sturkell, E. B. Jónasdóttir, G. Hafsteinsson, H. Sveinbjörnsson, R. Stefánsson, Þ. V. Jónsson, 2005. Forecasting and monitoring a subglacial eruption in Iceland. EOS transactions, 86(26), 245, 248.

Arnadottir, Th., H. Geirsson, P. Einarsson, 2004. Coseismic stress changes and crustal deformation on the Reykjanes Peninsula due to triggered earthquakes on 17 June 2000. J. Geophys. Res., 109, B09307, doi: 10.1029/2004JB003130. 

Sturkell, E., P. Einarsson, F. Sigmundsson, S. Hreinsdóttir, H. Geirsson, 2003. Deformation of Grímsvötn volcano, Iceland: 1998 eruption and subsequent inflation. Geophysical Research Letters, 30,4, 1182, doi:10.1029/2002GL016460.

Selected Conference Proceedings:

Geirsson, H., P. C. LaFemina, C. DeMets, D. A. Hernandez, G. S. Mattioli, R. Rogers, M. Rodriguez, 2013. Geodetically resolved slip distribution of the 27 August 2012 Mw=7.3 El Salvador Earthquake. AGU Fall Meeting, abstract G23B-0793, 9-13 Dec., 2013, San Francisco, CA.

LaFemina, P. C., H. Geirsson, Th. Arnadottir, B. Lund, E. C. Sturkell, F. Sigmundsson, S. Jonsson, 2013. Uplift in Iceland observed with 20 years of GPS data: Impact on models of plate motion and volcanic unrest. AGU Fall Meeting, abstract G41C-07, 9-13 Dec., 2013, San Francisco, CA.

Rodgers, M., D. Roman, H. Geirsson, P. C. LaFemina, A. Munoz, V. Tenorio, 2013. Short-term seismic quiescence immediately preceding explosions during the 2011 eruption of Telica Volcano, Nicaragua. AGU Fall Meeting, abstract V51E-2720, 9-13 Dec., 2013, San Francisco, CA.

Sigmundsson, F., B. Ofeigsson, S. Hreinsdottir, M. Hensch, G. Gudmundsson, K. S. Vogfjord, M. J. Roberts, H. Geirsson, P. LaFemina, A. J. Hooper, E. C. Sturkell, P. Einarsson, M. T. Gudmundsson, B. Brandsdottir, S. C. Loughlin, 2013. Magma movements and Iceland’s next eruptions. AGU Fall Meeting, abstract V34B-03, 9-13 Dec., 2013, San Francisco, CA.

Sturkell, E., T. M. Islam, F. Sigmundsson, H. Geirsson, P. C. LaFemina, 2013. Continuous subsidence in the Thingvellir rift graben, Iceland: Geodetic observations since 1966 compared to rheological models of plate spreading. AGU Fall Meeting, abstract G41A-0921, 9-13 Dec., 2013, San Francisco, CA.

Witter, M., T. Furman, P. LaFemina, H. Geirsson, 2013. Understanding magmatic processes at Telica volcano, Nicaragua: crystal size distribution and textural analysis. GSA Annual Meeting, Abstract 154-10, Denver, CO, US, 27-30 October, 2013.

Sturkell, E., P. Einarsson, H. Geirsson, J. Moore, S. P. Jakobsson, F. Sigmundsson, 2013. Continuing subsidence and deformation of the Surtsey volcano since 1991. Surtsey 50th Anniversary Conference, Reykjavik, Iceland, August 12-15, 2013.

Geirsson, H., P. LaFemina, C. DeMets, G. S. Mattioli, D. A. Hernandez, 2013. Co-seismic deformation of the August 27, 2012 Mw 7.3 El Salvador and September 5, 2012 Mw 7.6 Costa Rica Earthquakes. AGU Meeting of the Americas, abstract T51A-03, Cancun, Mexico, 14-17 May, 2013.

Arnadottir, Th., S. Hreinsdottir, K. Michalczewska, H. Geirsson, B. Ofeigsson, 2013. Transient deformation indicating rheological variation in the South Iceland Seismic Zone. EGU General Assembly, Abstract EGU2013-11612, Vienna, Austria, 7-12 April, 2013.

Ofeigsson, B. G., S. Hreinsdóttir, F. Sigmundsson, Th. Arnadottir, K. Vogfjord, H. Geirsson, P. Einarsson, S. Jonsson, T. Villemin, S. F. Sigurdsson, M. Roberts, E. Sturkell, P. C. Lafemina, R. Bennett, C. Voelksen, G. Valsson, and Th. Sigurdsson, 2013. Geodetic observations in Iceland: divergent plate boundary influenced by a hotspot, EGU General Assembly, Abstract EGU2013-12560, Vienna, Austria, 7-12 April, 2013.

Geirsson, H., M. Witter, P. LaFemina, M. Rodgers, D. Roman, A. Munos, V. Tenorio, D. Chavarria, A. Morales, V. Conde, D. Nilsson, B. Galle, M. Feineman, T. Furman, 2012. Multidisciplinary observations of the 2011 explosive eruption of Telica volcano, Nicaragua. Cities on Volcanoes 7, 19-23 November 2012, Colima, Mexico.

Rodgers, M., H. Geirsson, M. R. Witter, D. C. Roman, P. C. La Femina, A. Muñoz, V. Tenorio, 2012. Decreases in LP seismicity before the May 2011 eruption of the persistently restless Telica Volcano, Nicaragua, AGU fall meeting, V53B-2822, 3-7 December, San Francisco, CA.

Kobayashi, D., P. C. La Femina, H. Geirsson, E. Chichaco, A. A. Abrego M, D. M. Fisher, E. I. Camacho, 2011. Effects of Cocos Ridge Collision on the Western Caribbean: Is there a Panama Block?. Abs. G11A-0861, 2011 AGU Fall Meeting, San Francisco, CA., 5-9 Dec.

Michalczewska, K., S, Hreinsdóttir, Þ. Árnadóttir, A. Auriac, Th. Agustsdottir, H. Geirsson, A. Hooper, G. Gudmundsson, P. Einarsson, F. Sigmundsson, K. Feigl, R. Bennett, 2012. The inflation and deflation episodes in the Krísuvík geothermal area. 30th Nordic Geological Winter Meeting, abstract GD-07, Reykjavik, Iceland, January 9-12, 2012.

Malservisi, R., M. Hackl, P.C. LaFemina, J.S. Oldow, and H. Geirsson, 2011. Diffuse plate boundary and microplate motion: kinematic effects of partial coupling between blocks in Western North America. EGU general assembly, Abs. EGU2011-11734, Vienna, 3.-8. April.

Villemin, T., H. Geirsson, E. Sturkell, and F. Jouanne, 2009. Active deformation at Grímsvötn subglacial volcano: a composite evolution to be deciphered. EGU General Assembly 2009, Vienna, EGU2009-11177.

Geirsson, H., F. Sigmundsson, B. G. Ófeigsson, E. Sturkell, Th. Árnadóttir, A. Hooper, P. Einarsson, G.B. Guðmundsson, M. Jackson, F. Blume, 2008. Crustal deformation associated with the deep-seated seismic swarm at Upptyppingar, north of Vatnajökull, Iceland. IAVCEI General Assembly, 18.-22. August, Reykjavík, Iceland.

Geirsson, H., Th. Árnadóttir, R. Bennett, S. Hreinsdóttir, S. Jónsson, P. LaFemina, E. Sturkell, T. Villemin, and S. Miyazaki, 2006. Establishment of a high-rate continuous GPS network in Iceland. Eos Trans. AGU, 87(52), Fall Meet. Suppl., Abstract G43B-1003.

Geirsson, H., Th. Árnadóttir, and B. H. Bergsson, 2000. ISGPS - The Icelandic permanent GPS network. IGS Network Workshop 2000, Oslo, Norway, 12-14 July.

The focus of my research is to understand processes that generate crustal deformation. In my research I seek to use the multiple deformation signals recorded in continuous or episodic GPS networks to the fullest, to study the causes of ongoing deformation at volcanoes, geothermal areas, plate boundaries, and near glaciers. My main research tool is the Global Positioning System (GPS). However, I also work with other deformation data (InSAR, tilt, leveling), seismic data, petrology, gas measurements, and whatever can help me understand the specific process in question. It always gives research a deeper meaning to incorporate multidisciplinary methods.