Abstract
The seismically active Skagerrak region in the border area between Denmark and Norway has traditionally been associated with uncertain earthquake locations due to the limited station coverage in the region. A new seismic station in southern Norway and a recent update of the earthquake database of the Danish National Network have led to a much more complete and homogeneous data coverage of the Skagerrak area, giving the possibility of improved earthquake locations in the region. In this study, we relocate earthquakes in the Skagerrak area to obtain a more exact picture of the seismicity and investigate well-recorded events to determine the depth distribution. Hypocenter depths are found to be generally in the range 11–25 km. Furthermore, new composite focal mechanisms are determined for clusters of events with similar waveforms. Results indicate that the Skagerrak seismicity is associated with shallow, crustal faults oriented in the NS direction south of the Sorgenfrei–Tornquist Zone (STZ) as well as with the STZ itself. Mainly reverse faulting mechanisms along NE–SW oriented faults indicate maximum horizontal compression in the NW–SE direction. This is in agreement with World Stress Map generalizations, most likely associated with ridge push forces from the mid-Atlantic ridge, though modified probably by local crustal weaknesses.
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References
Berthelsen A (1998) The Tornquist zone Northwest of the Carpathians: an intraplate pseudostructure. Geol Fören Stockh Förh 120:223–230
Bungum H, Alsaker A, Kvamme LB, Hansen RA (1991) Seismicity and Seismotectonics of Norway and nearby continental shelf areas. J Geophys Res 96:2249–2265
Bungum H, Pettenati F, Schweitzer J, Sirovich L, Faleide JI (2009) The 23 October 1904 Ms5.4 Oslofjord Earthquake: reanalysis based on macroseismic and instrumental data. Bull Seismol Soc Am 99(5):2836–2854
Bungum H, Olesen O, Pascal P, Gibbons S, Londholm C, Vestøl O (2010) The what extent is the present day seismicity in Norway driven by post-glacial rebound? J Geol Soc (Lond) 167:373–384
Byrkjeland U, Bungum H, Eldholm O (2000) Seismotectonics of the Norwegian continental margin. J Geophys Res 105:6221–6236
Cassell BR, Mykkeltveit S, Kanestrøm R, Husebye ES (1983) A North Sea southern Norway seismic crustal profile. Geophys J R Astron Soc 72:733–753
Chapman CH, Orcutt JA (1985) The computation of body wave synthetic seismograms in laterally homogeneous media. Rev Geophys 23:105–163
Dehls JF, Olesen O, Bungum H, Hicks EC, Lindholm CD, Riis F (2000) Neotectonic map: Norway and adjacent areas. Geological Survey of Norway, Sluppen
Erlström M, Thomas SA, Deeks N, Sivhed U (1997) Structure and tectonic evolution of the Tornquist Zone and adjacent sedimentary basins in Scania and the southern Baltic Sea area. Tectonophysics 271:191–215
EUGENO-S Working Group (1988) Crustal structure and tectonic evolution of the transition between the Baltic Shield and theNorth German Caledonides (The EUGENO-S Project). Tectonophysics 150:253–348
Fejerskov M, Lindholm C, Myrvang A, Bungum H (2000) Crustal Stress in and around Norway: a compilation of in situ stress observations. In: Nøttvedt A et al (eds) Dynamics of the Norwegian Margin. Geological Society, London, Special Publications, vol 167, pp 327–378
Fjeldskaar W, Lindholm C, Dehls JF, Fjeldskaar I (2000) Postglacial uplift, neotectonics and seismicity in Fennoscandia. Quat Sci Rev 19:1413–1422
Grad M, Tiira T (2007) The Moho depth of the European plate. http://www.seismo.helsinki.fi/mohomap and http://www.igf.fuw.edu.pl/mohomap2007
Gregersen S (1979) Earthquakes in the Skagerrak recorded at small distances. Bull Geol Soc Den 28:5–9
Gregersen S (1992) Crustal stress regime in Fennoscandia from focal mechanisms. J Geophys Res 97:11821–11827
Gregersen S, Arvidsson R (1992) Atlas map 5, focal mechanisms. In: Blundell D, Freeman R, Mueller S (eds) A continent revealed: the european geotraverse. Cambridge University Press, Cambridge
Gregersen S, Voss P (2010) Irregularities in Scandinavian postglacial uplift/subsidence in time scales, tens, hundreds, thousands of years. J Geodyn 50:27–31
Gregersen S, Hjelme J, Hjortenberg E (1996a) Earthquakes in Denmark. Bull Geol Soc Denmark 44:115–127
Gregersen S, Leth J, Lind G, Lykke-Andersen H (1996b) Earthquake activity and its relationship with geologically recent motion in Denmark. Tectonophysics 257:265–273
Gregersen S, Voss P, Shomali ZH, Grad M, Roberts RG & TOR Working Group (2006) Physical differences in the deep lithosphere of Northern and Central Europe. Geol Soc, London, Memoirs 32:313–322. doi:10.1144/GSL.MEM.2006.032.01.18
Hardebeck JL, Shearer PM (2002) A new method for determining firstmotion focal mechanisms. Bull Seismol Soc Am 92:2264–2276
Hardebeck JL, Shearer PM (2003) Using S/P amplitude ratios to constrain the focal mechanisms of small earthquakes. Bull Seismol Soc Am 93:2434–2444
Havskov J, Bungum H (1987) Source parameters for earthquakes in the Northern North Sea. Nor Geol Tidsskr 67
Heidbach O, Reinecker J, Tingay M, Müller B, Sperner B, Fuchs K, Wenzel F (2007) Plate boundary forces are not enough: second- and third-order stress patterns highlighted in the World Stress Map database. Tectonics 26:TC6014. doi:10.1029/2007TC002133
Hicks EC (1996) Crustal stresses in Norway and surrounding areas as derived from earthquake focal mechanism solutions and in-situ stress measurements. Cand. Scient., University of Oslo
Hicks EC, Bungum H, Lindholm CD (2000) Stress inversion of earthquake focal mechanism solutions from onshore and offshore Norway. Nor Geol Tidsskr 80:235–250
Larsen TB, Gregersen S, Voss PH, Bidstrup T, Orozova-Bekkevold V (2008) The earthquake that shook central Sjælland, Denmark, November 6, 2001. Bull Geol Soc Denmark 56:1–11
Lehmann I (1956) Danish earthquakes. Medd Geol Soc Den 13:88–103 (in Danish)
Lie JE, Husebye ES (1993) Seismic imaging of upper crustal basement faults in the Skagerrak Sea. Tectonophysics 219:119–128
Lie JE, Husebye ES (1994) Simple-shear deformation of the Skagerrak lithosphere during the formation of the Oslo Rift. Tectonophysics 232:133–141
Lie JE, Andersson M (1998) The deep-seismic image of the crustal structure of the Tornquist Zone beneath the Skagerrak Sea, Northwestern Europe. Tectonophysics 287:139–155
Lindholm CD, Bungum H, Bratli RK, Aadnøy BS, Dahl N, Tørudbakken B, Atakan K (1995) Crustal Stress in the northern North Sea as inferred from borehole breakouts and earthquake focal mechanisms. Terra Nova 7:51–59
Lindholm C, Bungum H, Hicks E, Villagran M (2000) Crustal stress and tectonics in Norwegian regions determined from earthquake focal mechanisms. Geol Soc London, Special Publications 167:429–439
Longva O, Thorsnes T (1997) Skagerrak in the past and the present—and integrated study of geology, chemistry, hydrogeography and microfossil ecology. Nor Geol Unders 8:100
Medhus AB, Balling N, Jacobsen BH, Weidle C, Voss P, England RW, Kind R, Thybo H (2011) Upper mantle structure beneath the southern Scandes Mountains and the northern Tornquist Zone revealed by P-wave travel time tomography. Geophys J Int (in revision)
Pedersen T, Gregersen S, Tor Working Group (1999) Project Tor: deep lithospheric variation across the Sorgenfrei-Tornquist Zone, southern Scandinavia. Bull Geol Soc Den 46:13–24
Reinecker J, Heidbach O, Tinagy M, Sperner B, Müller B (2005) The release 2005 of the World Stress Map. Available online at www.world-stress-map.org
Scheck-Wenderoth M, Lamarche J (2005) Crustal memory and basin evolution in the Central European Basin System—new insights from a 3D structural model. Tectonophysics 297:143–165
Slunga R, Norrman P, Glans A-C (1984) The seismicity of southern Sweden. FOA Report C20545-T1, National Defense Research Institute
Tesauro M, Kaban MK, Cloetingh SAPL (2008) EuCRUST-07: a new reference model for the European crust. Geophys Res Lett 35:L05313. doi:10.1029/2007GL032244
Thybo H (1997) Geophysical characteristics of the Tornquist Fan area, northwest Trans-European Suture Zone: indication of late Carboneferous to early Permian dextral transtension. Geol Mag 134:597–606
Thybo H (2000) Crustal structure and tectonic evolution of the Tornquist fan region as revealed by geophysical methods. Bull Dan Geol Soc 46:145–160
Vejbæk OV, Britze P (1994) Geological map of Denmark 1: 750 000, top pre-Zechstein. Geological Survey of Denmark, Map series No. 45
Ziegler PA (1990) Geological atlas of Western and Central Europe. Elsevier, The Hague, Shell International Petrolium Maatschappij/Amsterdam
Zoback ML (1992) First- and second-order patterns of stress in the lithosphere: the world stress map project. J Geophys Res 97:11703–11728
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Sørensen, M.B., Voss, P.H., Havskov, J. et al. The seismotectonics of western Skagerrak. J Seismol 15, 599–611 (2011). https://doi.org/10.1007/s10950-011-9235-x
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DOI: https://doi.org/10.1007/s10950-011-9235-x