QLg wave tomography beneath Norway
Tóm tắt
The propagation of seismic waves is influenced by changes in crustal structure as for example the transition from continental to oceanic crust along the Norwegian margin. We analyzed Lg wave propagation to map lateral crustal changes in Norway and adjacent areas. We used 1369 observations from 279 earthquakes recorded mostly by the Norwegian National Seismic Network between 1990 and 2017. First, we classified Lg wave propagation in terms of efficiency through Lg/Pn ratios and found significant changes between ray paths crossing offshore and onshore areas. Then we derived an average QLg(f) = 529 f0.42 model for Norway, which is in the expected range for a stable tectonic environment. This was used as starting model for a tomographic inversion. We present tomographic models of Lg wave attenuation at frequencies 2 Hz, 4 Hz, and 6 Hz, respectively. We observed the most significant variation between offshore and onshore regions. This can be explained by changes in crustal structure and the occurrence of unconsolidated sediments in the offshore areas.
Tài liệu tham khảo
Aki K (1980) Scattering and attenuation of shear waves in the lithosphere. J Geophys Res 85 (B11):6496–6504
Alsaker A, Kvamme LB, Hansen RA, Dahle A, Bungum H (1991) The ML scale in Norway. Bull Seismol Soc Am 81(2):379–398
Barmin MP, Ritzwoller MH, Levshin AL (2001) A fast and reliable method for surface wave tomography. Pure Appl Geophys 158:1351–1375
Benz HM, Frankel A, Boore DM (1997) Regional Lg attenuation for the continental United States. Bull Seismol Soc Am 87(3):606–619
Bouchon M (1982) The complete synthesis of seismic crustal phases at regional distances. J Geophys Res 87(B3):1735–1741
Campillo M, Plantet JL (1991) Frequency dependence and spatial distribution of seismic attenuation in France: experimental results and possible interpretation. Phys Earth Planet In 67:48–64
Eldholm O, Tsikalas F, Faleide JI (2002) Continental margin off Norway 62∘-75∘N: Palaeogene tectono-magmatic segmentation and sedimentation. The North Atlantic Igneous Province: stratigraphy, tectonics, volcanic and magmatic processes: geological society, vol 197, London, pp 39–68
Erickson D, McNamara DE, Benz HM (2004) Frequency-dependent Lg Q within the continental United States. Bull Seismol Soc Am 94(5):1630–1643
Faleide JI, Tsikalas F, Breivik AJ, Mjelde R, Ritzmann O, Engen Ø, Wilson J, Eldholm O (2008) Structure and evolution of the continental margin off Norway and the Barents Sea. Episodes 3:82–91
Fan G, Lay T (2002) Characteristics of Lg attenuation in the Tibetan Plateau. J Geophys Res 107(B10):2256. https://doi.org/10.1029/2001JB000804 https://doi.org/10.1029/2001JB000804
Ford SR, Dreger DS, Mayeda K, Walter WR, Malagnini L, Phillips WS (2008) Regional attenuation in northern California: a comparison of five 1D Q methods. Bull Seismol Soc Am 98 (4):2033–2046. https://doi.org/10.1785/0120070218 https://doi.org/10.1785/0120070218
Gaal G, Gorbatschev R (1987) An outline of the precambrian evolution of the baltic shield. Precambrian Res 35:15–52
Grad M, Tiira T, Group EW (2009) The Moho depth map of the European Plate. Geophys J Int 176:279–292. https://doi.org/10.1111/j.1365-246X.2008.03919.x https://doi.org/10.1111/j.1365-246X.2008.03919.x
Gregersen S (1984) Crustal structure anomalies detected with Lg waves in grabens near continental margins in Greenland and the North Sea. Mar Geophys Res 6:409–413
Herrmann RB, Kijko A (1983) Modeling some empirical vertical component Lg relations. Bull Seismol Soc Am 73(1): 157–171
Hjelstuen BO, Eldholm O, Skogseid J (1999) Cenozoic evolution of the northern Vøring margin. GSA Bull 111(12): 1792–1807
Hong TK (2010) Lg attenuation in a region with both continental and oceanic enviroments. Bull Seismol Soc Am 100(2):851–858. https://doi.org/10.1785/0120090057
Kennett B, Mykkeltveit S (1984) Guided wave propagation in laterally varying media - II. Lg-waves in north-western Europe. Geophys J R Astron Soc 79:257–267
Kinck JJ, Husebye ES, Larsson FR (1993) The Moho depth distribution in Fennoscandia and the regional tectonic evolution from Archean to Permian times. Precambrian Res 64: 23–51
Kvamme LB, Hansen RA, Bungum H (1995) Seismic-source and wave-propagation effect of Lg waves in Scandinavia. Geophys J Int 120:525–536
Maupin V, Agostini A, Artemieva I, Balling N, Beekman F, Ebbing J, England RW, Frassetto A, Gradmann S, Jacobsen BH, Köhler A, Kvarven T, Medhus AB, Mjelde R, Ritter J, Sokoutis D, Stratford W, Thybo H, Wawerzinek B, Weidle C (2013) The deep structure of the Scandes and its relation to tectonic history and present-day topography. Tectonophysics 602:15–37. https://doi.org/10.1016/j.tecto.2013.03.010
Mendi CD, Ruud BO, Husebye ES (1997) The North Sea Lg-blockage puzzle. Geophys J Int 130:669–680
Mjelde R, Raum T, Digranes P, Shimamura H, Shiobara H, Kodair S (2003) Vp/Vs ratio along the Vøring Margin, NE Atlantic, derived from OBS data: implications on lithology and stress field. Tectonophysics 369:175–197. https://doi.org/10.1016/S0040-1951(03)00198-7
Mjelde R, Raum T, Myhren B, Shimamura H, Murai Y, Takanami T, Karpuz R, Næss U (2005) Continent-ocean transition on the Vøring Plareau, NE Atlantic, derived from densely sampled ocean bottom seismometer data. J Geophys Res 110:B05,101. https://doi.org/10.1029/2004JB003026
Mosar J (2003) Scandinavia’s North Atlantic passive margin. J Geophys Res 108(B8):2360. https://doi.org/10.1029/2002JB002134
Mousavi SM, Cramer CH, Langston CA (2014) Average Q Lg, Q Sn and observation of Lg blockage in the Continental Margin of Nova Scotia. J Geophys Res Solid Earth 119: 7722–7744. https://doi.org/10.1002/2014JB011237
Nielsen SB, Gallagher K, Leighton C, Balling N, Svenningsen L, Jacobsen BH, Thomsen E, Nielsen OB, Heilmann-Clausen C, Egholm DL, Summerfield MA, Clausen OR, Piotrowski JA, Thorsen MR, Huuse M, Abrahamsen N, King C, Lykke-Andersen H (2009) The evolution of western Scandinavian topography: a review of Neogene uplift versus the ICE (isostasy-climate-erosion) hypothesis. J Geodyn 47:72–95
Noriega R, Ugalde A, Villaseñor A, Harnafi M (2015) Frequency-dependent Lg-wave attenuation in northern Morocco. Tectonophysics 663:250–260
Olesen O, Lundin E, Nordgulen Ø, Osmundsen PT, Skilbrei JR, Smethurst MA, Solli A, Bugge T, Fichler C (2002) Bridging the gap between the onshore and offshore geology in Nordland, Northern Norway. Nor J Geol 82:243–262
Olesen O, Brönner M, Ebbing J, Gellein J, Gernigon L, Koziel J, Lauritsen T, Myklebust R, Pascal C, Sand M, Solheim D, Usov S (2010) New aeromagnetic and gravity compilations from Norway and adjacent areas: method and applications. Petroleum Geol Conf Series 7:559–586. https://doi.org/10.1144/0070559
Ottemöller L (2002) Lg wave Q tomography in Central America. Geophys J Int 150:295–302
Ottemöller L, Midizi V (2003) The crustal structure of Norway from inversion of teleseismic receiver functions. J Seismol 7:35–48
Ottemöller L, Shapiro M, Singh SK, Pacheco JF (2002) Lateral variation of Lg wave propagation in southern Mexico. J Geophys Res 107(B1):ESE 3–1– ESE 3–13. https://doi.org/10.1029/2001JB000206
Sargeant S, Ottemöller L (2009) Lg wave attenuation in Britain. Geophys J Int 179:1593–1606. https://doi.org/10.1111/j.1365-246X.2009.04325.x
Sclater JG, Christie PAF (1980) Continental stretching: an explanation of the Post-Mid-Cretaceous subsidence of the central North Sea basin. J Geophys Res 85(B7):3711–3739. https://doi.org/10.1029/JB085iB07p03711
Sereno TJ, Bratt SR, Bache TC (1988) Simultaneous inversion of regional wave spectra for attenuation and seismic moment in Scandinavia. J Geophys Res 93(B3):2019– 2035
Shapiro N, Béthoux N, Campillo M, Paul A (1996) Regional seismic phases across the Ligurian Sea: Lg blockage and oceanic propagation. Physics of the Earth and Planetary Interiors
Singh S, Herrmann RB (1983) Regionalization of crustal coda Q in the continental United States. J Geophys Res 88(B1):527–538. https://doi.org/10.1016/j.gloplacha.2006.12.005
Skilbrei JR, Olesen O, Osmundsen PT, Kihle O, Aaro S, Fjellanger E (2002) A study of basement structures and onshore-offshore correlations in Central Norway. Nor J Geol 82:263–279
Stratford W, Thybo H, Faleide JI, Olesen O, Tryggvason A (2009) New Moho Map onshore southern Norway. Geophys J Int 178:1755–1765. https://doi.org/10.1111/j.1365-246X.2009.04240.x
Talwani M, Eldholm O (1977) Evolution of the Norwegian-Greenland Sea. Geol Soc Am Bull 88 (70708):969–999
Tsikalas F, Eldholm O, Faleide JI (2005a) Crustal structure of the Lofoten-Vesterȧlen continental margin, off Norway. Tectonophysics 404:151–174. https://doi.org/10.1016/j.tecto.2005.04.002
Tsikalas F, Faleide JI, Eldholdm O, Wilson J (2005b) Late Mesozoic-Cenozoic structural and stratigraphic correlations between the conjugate mid-Norway and NE Greenland contiental margins. Geol Soc London Petroleum Geol Con Series 6:785–801. https://doi.org/10.1144/0060785
Zhang TR, Lay T (1995) Why Lg phase does not traverse oceanic crust. Bull Seismol Soc Am 85:1665–1678
Zhao LF, Xie XB, Wang WM, Zhang JH, Yao ZX (2010) Seismic Lg-wave Q tomography in and around Northeast China. J Geophys Res 115:B08,307. https://doi.org/10.1029/2009JB007157