Sigurður Th. Rögnvaldsson
Sigurður Thorlacius Rögnvaldsson was born in Reykjavík in January 1964. He was married to Nanna Lind Svavarsdóttir and they have two children, Svanhvít Sif, born in 1988, and Ari Thorlacius, born in 1995. Sadly Sigurður died in a car accident in October 1999.
Sigurður graduated from the Menntaskólinn við Hamrahlíð junior college in 1982 and received his BS degree in geophysics from the University of Iceland in 1987. During his undergraduate years, Sigurður worked summers at the Icelandic Energy Authority, carrying out electromagnetic resistivity survey and other field work for geothermal prospecting.
Sigurður continued his geophysics studies in Sweden at the University of Uppsala. He finished a Fil. lic. degree in 1992 and a Ph.D. degree in 1994. His supervisors were Ragnar Slunga and Reynir Böðvarsson. His thesis research focused on developing and testing geophysical algorithms implemented as part of the SIL (South Iceland Lowland) digital seismic network for analysis of earthquake data. In collaboration with Ragnar Slunga, his most important contributions were in automatic estimation of fault-plane solutions for microearthquakes by inverting observed polarities and spectral amplitudes of P- and S-waves, and in relative locations of microearthquakes. Sigurður’s research thus demonstrated that microearthquakes contain information about large-scale tectonic processes.
During his student years in Uppsala, Sigurður traveled to Mozambique where he organized and supervised resistivity measurements for mapping groundwater levels. Sigurður also participated in refraction measurement campaigns in Poland and Sweden.
Upon graduation Sigurður first held a postdoctoral position at the Nordic Volcanological Center in Reykjavík, and then moved to the Geophysical Department of the Icelandic Meteorological Office (IMO) in the fall of 1995. At IMO, Sigurður participated in the deployment and day-to-day maintenance of the SIL system as well as its development. The map on the IMO web site showing daily seismic activity was implemented by Sigurður during a seismic crisis in Hengill in 1998, and it is an example of his creativity and efforts to rapidly display SIL earthquake data.
Sigurður participated in a number of different Icelandic and international research projects after his return to Iceland but the focal point of his research continued to be analyzing microseismicity in Iceland, building on his doctoral work in Uppsala. These studies included mapping of faults in the Tjörnes fracture zone, the South Iceland seismic zone and the Hengill regions, using relative relocations and earthquake focal mechanisms. Mapping of seismically active faults at depth using relative relocations of microearthquakes provide important information on the seismotectonics of a region, and the method is now also used in geothermal exploration.
Sigurður’s contributions to the field of seismology during his short career demonstrate the enthusiasm that he held for the subject. He was a great colleague and a true friend - always ready to help, whether the problem involved deciphering convoluted computer codes, delving into the mysteries of the SIL system, making presentable documents using LaTeX, or discussing life, the universe and everything.
Publications
Sigurður Th. Rögnvaldsson
Sigurður Th. Rögnvaldsson, Gylfi P. Hersir og Knútur Árnason 1987. Viðnámsmælingar, fræðileg úttekt, mæling og túlkun á línu VIII á Nesjavöllum. Skýrsla Orkustofnunar OS-87024/JHD-15 B. Orkustofnun, Reykjavík.
Sigurður Th. Rögnvaldsson 1992. Fault plane solutions by combined use of polarities and body wave amplitudes. Fil. lic. ritgerð við Uppsala Háskóla, ISSN 1170 7320.
Sigurður Th. Rögnvaldsson 1994. Microearthquakes in South Iceland: Fault plane solutions and relative locations. Doktorsritgerð við Uppsala Háskóla.
Sigurður Th. Rögnvaldsson 1996. Athugun á horntíðni í fasatilkynningum SIL stöðva. Greinargerð Veðurstofu Íslands VÍ-G96030-JA02.
Sigurður Th. Rögnvaldsson 1999. Frammistaða SIL kerfisins frá ágúst 1998 til mars 1999. Greinargerð Veðurstofu Íslands VÍ-G99004-JA01.
Sigurður Th. Rögnvaldsson 1999. LATEX stýriskrár fyrir rit, greinargerðir og smárit Veðurstofu Íslands. Greinargerð Veðurstofu Íslands VÍ-G99007-JA02.
Sigurður Th. Rögnvaldsson 1999. Kort yfir sjálfvirkt ákvarðaðar staðsetningar jarðskjálfta á Íslandi. URL: http://hraun.vedur.is/ja/englishweb/index.html, 21.06.1999.
Sigurður Th. Rögnvaldsson og R. Slunga 1993. Routine fault plane solutions for local networks: A test with synthetic data. Bull. Seism. Soc. Am. 83, pp. 1232 1247.
Sigurður Th. Rögnvaldsson og R. Slunga 1994. Single and joint fault plane solutions for microearthquakes in South Iceland. Tectonophysics 237, 73 86.
Sigurður Th. Rögnvaldsson og Grímur Björnsson 1995. Upptakagreining smáskjálfta á Nesjavöllum í ársbyrjun 1995. Skýrsla Orkustofnunar OS-95034/JHD-05.
Sigurður Th. Rögnvaldsson og R. Slunga 1999. Kortlagning virkra misgengis ata. URL: http://hraun.vedur.is/ja/sprungur.html, 21.06.1999.
Sigurður Th. Rögnvaldsson, Reynir Böðvarsson, R. Slunga og Steinunn S. Jakobsdóttir 1997. The transfer function of the SIL seismic data acquisition system. Rit Veðurstofu Íslands VÍ-R97001-JA01.
Sigurður Th. Rögnvaldsson, Ágúst Guðmundsson og R. Slunga 1998. Seismotectonic analysis of the Tjörnes Fracture Zone, an active transform fault in north Iceland. J. Geophys. Res. 103, 30117 30129.
Sigurður Th. Rögnvaldsson, Kristján Ágústsson, Bergur H. Bergsson og Grímur Björnsson 1998. Jarðskjálftamælanet í nágrenni Reykjavíkur - lýsing á mælaneti og fyrstu niðurstöður. Rit Veðurstofu Íslands VÍ-R98001-JA01.
Sigurður Th. Rögnvaldsson, Gunnar B. Guðmundsson, Kristján Ágústsson, Steinunn S. Jakobsdóttir, R. Slunga og Ragnar Stefánsson 1998. Overview of the 1993 1996 seismicity near Hengill. Rit Veðurstofu Íslands VÍ-R98006-JA05.
Sigurður Th. Rögnvaldsson, Þóra Árnadóttir, Kristján Ágústsson, Þórunn Skaftadóttir, Gunnar B. Guðmundsson, Grímur Björnsson, Kristín S. Vogfjörð, Ragnar Stefánsson, Reynir Böðvarsson, R. Slunga, Steinunn S. Jakobsdóttir, Einar Kjartansson, Bergþóra Þorbjarnardóttir, Pálmi Erlendsson, Bergur H. Bergsson, Sturla Ragnarsson, Páll Halldórsson, Barði Þorkelsson og Margrét Ásgeirsdóttir 1998. Skjálftahrina í Ölfusi í nóvember 1998. Greinargerð Veðurstofu Íslands VÍ-G98046-JA09. Veðurstofa Íslands, Reykjavík.
Sigurður Th. Rögnvaldsson, Kristín S. Vogfjörð og R. Slunga 1999. Kortlagning brotflata á Hengilssvæði með smáskjálftum. Rit Veðurstofu Íslands VÍ-R99002-JA01.
Angelier, J., Sigurður Th. Rögnvaldsson, F. Bergerat, Ágúst Guðmundsson, Steinunn S. Jakobsdóttir og Ragnar Stefánsson 1996. Earthquake focal mechanisms and recent faulting: A seismotectonic analysis of the Vörðufell area, South Iceland seismic zone. Í Seismology in Europe, Barði Þorkelsson, ritstjóri. Veðurstofa Íslands, Reykjavík.
Ari Tryggvason, Sigurður Th. Rögnvaldsson og Ólafur G. Flóvenz 2002. Three-dimensional imaging of the P- and S-wave velocity structure and earthquake locations beneath Southwest Iceland. Geophys. J. Int. 151, 848 866.
Bergerat, F., Ágúst Guðmundsson, J. Angelier og Sigurður Th. Rögnvaldsson 1998. Seismotectonics of the central part of the South Iceland Seismic Zone. Tectonophysics 298, 319 335.
Freysteinn Sigmundsson, Páll Einarsson, Sigurður Th. Rögnvaldsson, G.R. Foulger, K.M. Hodgkinson og Gunnar Þorbergsson 1997. The 1994-1995 seismicity and deformation at the Hengill triple junction, Iceland: Triggering of earthquakes by minor magma injection in a zone of horizontal shear stress. J. Geophys. Res. 102, 15151 15161.
Grímur Björnsson og Sigurður Th. Rögnvaldsson 1995. Upptök jarðskjálfta á Hengilssvæði árin 1992 1994. Greinargerð Orkustofnunar GrB/SThR-95/01.
Hu, G., W. Menke og Sigurður Th. Rögnvaldsson 1993. A demonstration of the joint use of P wave polarization and travel-time data in tomographic inversion: Crustal velocity structure near the South Iceland Lowland network. Geophys. Res. Lett. 20, 1407-1410.
Kristín S. Vogfjörð og Sigurður Th. Rögnvaldsson 1999. Identification and modeling of secondary phases in short-period seismograms from local earthquakes in the South Iceland seismic zone. Óbirt grein.
Kristján Ágústsson, Sigurður Th. Rögnvaldsson, Bergur H. Bergsson og Ragnar Stefánsson 1998. Jarðskjálftamælanet Veðurstofu Íslands og Hitaveitu Suðurnesja - lýsing á mælaneti og fyrstu niðurstöður. Rit Veðurstofu Íslands VÍ-R98002-JA02.
Reynir Böðvarsson og Sigurður Th. Rögnvaldsson 1992. The SIL acquisition system, a new tool for earthquake prediction research. Í Proceedings of the International Conference on Preparedness and Mitigation for Natural Disasters '92, 28 29 Maí, Reykjavík.
Reynir Böðvarsson, Sigurður Th. Rögnvaldsson, Steinunn S. Jakobsdóttir, R. Slunga og Ragnar Stefánsson 1996. The SIL data acquisition and monitoring system. Seism. Res. Lett. 67, 35 46.
Reynir Böðvarsson, Sigurður Th. Rögnvaldsson, R. Slunga og Einar Kjartansson 1999. The SIL data acquisition system - at present and beyond year 2000. Phys. Earth Planet. Inter. 113, 89 101.
Roberts, R. G., A. Lindfors, A. Christoffersson, Reynir Böðvarsson og Sigurður Th. Rögnvaldsson 1993. Three-component data as an aid to seismic event detection and asociation: A case study using data from the SIL (Iceland) network. Computers and Geosciences 19, pp. 123 134.
Slunga, R., Sigurður Th. Rögnvaldsson og Reynir Böðvarsson 1995. Absolute and relative locations of similar events with application to microearthquakes in southern Iceland. Geophys. J. Int. 123, 409 -419.
