Seismic structure of the Icelandic crust above layer three and the relation between body wave velocity and the alteration of the basaltic crust

Main Article Content

O.G. Flovenz


Seismic refraction profiles from Iceland are studied with the aid of synthetic seismograms. The classical layered model of the Icelandic crust is shown to be an unacceptable interpretation of the available data. This is because the layered model does not satisfy the observed amplitude variation. On the other hand, a model which assumes continuously increasing velocity with depth does not contradict the observations and is therefore acceptable although it is not the only possible interpretation. The model represented here shows that the surface value of the P-velocity is variable from 2.0 km/s to 5.0 km/s, depending primarily on the degree of metamorphism. The P-velocity increases rapidly with depth in the velocity interval 2.0-3.5 km/s followed by an approximately constant gradient of about 0.57 s-1. This constant gradient continues down to the 6.5 km/s isovelocity surface below which the P-velocity becomes nearly constant. In view of this, it is more reasonable to divide the Icelandic crust into two parts: the upper crust with velocity continuously increasing with depth (corresponding to layers 0, 1, 2 in the layered model) and the lower crust with almost constant velocity (corresponding to layer 3 in the layered model). The depth to the lower crust is variable and depends on how deep the crust is eroded. A typical depth to the lower crust is 5-6 km for an uneroded basalt pile but can be considerable less where the basalt pile is deeply eroded, especially below extinct central volcanoes.

Google Scholar         ARK:



Article Details

How to Cite
Flovenz, O.G. 1980. “Seismic Structure of the Icelandic Crust above Layer Three and the Relation Between Body Wave Velocity and the Alteration of the Basaltic Crust”. Journal of Geophysics 47 (1), 211-20.
Bookmark and Share


Bath, M. (1960) Crustal structure of Iceland. J. Geophys. Res. 65:1793-1807

Berge, A.M. (1976) Program for beregning av hastighets-dybde fordelingen ut fra gangtidskurva, nar hastigheten oker kontinuerkig med dypet. Seismological Observatory Internal report, University of Bergen

Flovenz, O.G. (1979) Analyse av refraksjonsseismiske og teleseismiske data fra Island. Cand real thesis, Seismological Observatory, University of Bergen

Fuchs, K., Muller, G. (1971) Computation of synthetic seismograms with the reflectivity method and comparison with observations. Geophys. J. R. Astron. Soc. 23:417-433

Hughes, D.S., Maurette, C. (1957) Variation of elastic wave velocities in basic igneous rocks with pressure and temperature. Geophysics 21:23-31

Kennett, B.L.N., Orcutt, J.A. (1976) A comparison of travel time inversions for marine refraction profiles. J. Geophys. Res. 81:4061-4070

Lewis, B.T.R. (1978) Evolution of ocean crust velocities. Annu. Rev. Earth Planet. Sci. 6:377-404

McDougall, I., Saemundsson, K., Johannesson, H., Watkins, N.D., Kristjansson, L. (1977) Extension of the geomagnetic polarity time scale to 6.5 m.y. K-Ar dating, geological and paleomagnetic study of a 3500-m lava succession in western Iceland. Bull. Geol. Soc. Am. 88:1-15

Mykkeltveit, S. (1978) Computation of synthetic body wave seismograms, theory, program description and application. Internal report, Seismological Observatory, University of Bergen

Palmason, G. (1963) Seismic refraction investigation of the basalt lavas in northern and eastern Iceland. JOkull 13:39-60

Palmason, G. (1971) Crustal structure of Iceland from explosion seismology. Soc. Sci. Isl. XL

Palmason, G. (1973) Kinematics and heat flow in a volcanic rift zone with application to Iceland. Geophys. J. R. Astron. Soc. 33:451-481

Palmason, G., Arnorsson, S., Fridleifsson, LB., Kristmannsdottir, H., Saemundsson, K., Stefansson, V., Steingrimsson, B., Tomasson, J. (1978) The Icelandic crust. Evidence from drillhole data on structure and process. Second Maurice Ewing Symp., Am. Geophys. Union. In press

Palmason, G., Saemundsson, K. (1974) Iceland in relation to the Mid-Atlantic Ridge. Annu. Rev. Earth Planet. Sci. 2:25-50

Tryggvason, E., Bath, M. (1961) Upper crustal structure of Iceland. J. Geophys. Res. 66:1913-1925

Walker, G.P.L. (1974) The structure of eastern Iceland. In: Kristjansson, L. (ed.) Geodynamics of Iceland and the North Atlantic Area, pp 177-188, Reidel, Dordrecht