Geomagnetic depth sounding in the Northern Apennines (Italy)

A Geomagnetic Depth Sounding (GDS) survey covering the Northern Apennines of Italy has been carried out in the period 1992–94. Induction arrows maps and hypothetical event Fourier maps were constructed to obtain an electromagnetic imaging of this area. Since the two dimensional (2-D) character comes out from those maps for periods greater than 32 minutes, a 2-D inverse modeling was carried out. The model responses show that a deep conductive layer (>5000 S) underlies the Apennine chain at about 20 km depth. The transition between the Adriatic and the Tyrrhenian domains is marked by a rather sharp vertical offset in this conducting layer. In the northwest sector of the studied area an anomalous high conductivity behavior is superimposed on the regional trend, which corresponds to the geothermal field of Larderello-Travale.

[1]  Gerald W. Hohmann,et al.  Magnetotelluric responses of three-dimensional bodies in layered earths , 1984 .

[2]  G. Lavecchia.  The tyrrhenian-apennines system: structural setting and seismotectogenesis , 1988 .

[3]  S. Hjelt,et al.  Lithospheric and upper-mantle structures, results of electromagnetic soundings in Europe , 1993 .

[4]  W. D. Parkinson.  The analysis of single site induction data , 1989 .

[5]  B. Arora,et al.  Magnetometer Array Study in North-Northeast Brazil: Conductivity Image Building and Functional Induction Modes , 1998 .

[6]  V. Pasquale,et al.  Dependence of the seismotectonic regime on the thermal state in the northern italian apennines , 1993 .

[7]  Gerald W. Hohmann,et al.  Magnetotelluric responses of three-dimensional bodies in layered earths , 1982 .

[8]  J. Pek,et al.  Numerical solution of the two-dimensional inverse geomagnetic induction problem , 1981 .

[9]  G. B. Cimini,et al.  Tomographic constraints on the geodynamic evolution of the Italian region , 1999 .

[10]  R. Hyndman,et al.  Geomagnetic variations and electrical conductivity structure in south-western Australia , 1967 .

[11]  S. Constable,et al.  Occam's inversion to generate smooth, two-dimensional models from magnetotelluric data , 1990 .

[12]  Consiglio Nazionale delle Ricerche . Progetto Finalizzato Geodinamica.  Structural model of Italy and gravity map , 1990 .

[13]  R. Hyndman,et al.  The origin of electrically conductive lower continental crust: saline water or graphite? , 1993 .

[14]  D. Beamish,et al.  Local and regional induction in the British Isles , 1984 .

[15]  D. Gough.  Magnetometer array studies, Earth structure, and tectonic processes , 1989 .

[16]  Robert D. van der Hilst,et al.  Travel-time tomography of the European-Mediterranean mantle down to 1400 km , 1993 .

[17]  U. Harms,et al.  KTB and the electrical conductivity of the crust ELEKTB Group , 1997 .

[18]  F. Innocenti,et al.  Geochemical and petrological evidence of the subduction of delaminated Adriatic continental lithosphere in the genesis of the Neogene-Quaternary magmatism of central Italy , 1993 .

[19]  F. Mongelli,et al.  Interpretation of heat flow density of the Apennine chain, Italy , 1989 .

[20]  G. Egbert,et al.  Robust estimation of geomagnetic transfer functions , 1986 .

[21]  R. N. Edwards,et al.  Electrical Conductivity Studies over a Tectonically Active Area in Eastern Canada , 1974 .

[22]  R. N. Edwards,et al.  Conductivity anomalies: lower crust or asthenosphere? , 1981 .

[23]  Gary D. Egbert,et al.  An efficient data-subspace inversion method for 2-D magnetotelluric data , 2000 .

[24]  F. W. Jones,et al.  The geomagnetic coast effect , 1979 .

[25]  Numerical inversion of 2D MT data by models with variable geometry , 1987 .

[26]  N. D’Agostino,et al.  Midcrustal shear zones in postorogenic extension: Example from the northern Tyrrhenian Sea , 1998 .

[27]  J. Channell,et al.  Delamination and asymmetric lithospheric thickening in the development of the Tyrrhenian Rift , 1989, Geological Society, London, Special Publications.

[28]  G. W. Hohmann,et al.  Integral equation modeling of three-dimensional magnetotelluric response , 1981 .

[29]  R. Cataldi,et al.  Geothermal ranking of Italian territory , 1995 .

[30]  V. Pasquale,et al.  Rheology and seismotectonic regime in the northern central Mediterranean , 1997 .

[31]  Roel Snieder,et al.  Large-scale waveform inversions of surface waves for lateral heterogeneity , 1988 .

[32]  G. Selvaggi,et al.  Subcrustal earthquakes in the northern Apennines (Italy): Evidence for a still active subduction? , 1992 .

[33]  R. Hyndman,et al.  Geophysical support for aqueous fluids in the deep crust: seismic and electrical relationships , 1992 .

[34]  Frederick Edward Mulhearin Lilley,et al.  The Sign Convention for Quadrature Parkinson Arrows in Geomagnetic Induction Studies (Paper 2R0609) , 1982 .

[35]  Alan G. Jones,et al.  Electrical conductivity of the continental lower crust , 1992 .

[36]  A. Rovelli,et al.  Shear wave attenuation in the lithosphere beneath Italy and surrounding regions: Tectonic implications , 1997 .

[37]  D. Gough.  Electromagnetic exploration for fluids in the Earth's crust , 1992 .

[38]  G. Egbert,et al.  Multivariate analysis of geomagnetic array data. 1 The response space , 1989 .