Anisotropic seismic structure of the lithosphere beneath the Adriatic coast of Italy constrained with mode‐converted body waves

PS converted waves observed near Ancona on the Adriatic coast of central Italy, as revealed by teleseismic receiver functions (RFs), vary with earthquake back‐azimuth and epicentral distance in a manner consistent with a 1‐D anisotropic seismic structure. Using reflectivity calculations, we develop a profile of anisotropic seismic velocity through the Adriatic lithosphere at this locality. We infer crustal thickness of ∼45 km. Anisotropy within the crust appears at ∼15‐km depth, suggesting a decollement between the subducting Adriatic lithosphere and the overriding crustal wedge. Lineation of inferred rock fabric is compatible with simple shear in ENE‐WSW direction. In the upper mantle, we infer an anisotropic layer at 80–90 km depth. If caused by olivine crystals alignment, the nearly north‐south lineation of the inferred rock fabric would be consistent with some nearby shear‐wave splitting observations. This anisotropic layer may be related to mantle deformation induced by the rollback of Adriatic lithosphere.

[1]  F. P. Lucente,et al.  SKS splitting measurements in the Apenninic‐Tyrrhenian domain (Italy) and their relation with lithospheric subduction and mantle convection , 2003 .

[2]  Jeffrey Park,et al.  Seismic Anisotropy: Tracing Plate Dynamics in the Mantle , 2002, Science.

[3]  W. Spakman,et al.  Subduction and slab detachment in the Mediterranean-Carpathian region. , 2000, Science.

[4]  Vadim Levin,et al.  Receiver Functions from Multiple-Taper Spectral Correlation Estimates , 2000 .

[5]  S. Pondrelli,et al.  Active stress map of Italy , 1999 .

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

[7]  M. Giudici,et al.  Application of revised ray tracing migration to imagine lateral variations of seismic fabric corresponding to different tectonic styles in the northern Apennines , 1998 .

[8]  A. Rovelli,et al.  Compressional velocity structure and anisotropy in the uppermost mantle beneath Italy and surrounding regions , 1998 .

[9]  Vadim Levin,et al.  P-SH conversions in a flat-layered medium with anisotropy of arbitrary orientation , 1997 .

[10]  M. Cocco,et al.  Seismic anisotropy beneath the Northern Apennines (Italy) and its tectonic implications , 1996 .

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

[12]  J. Cassidy,et al.  Numerical experiments in broadband receiver function analysis , 1992, Bulletin of the Seismological Society of America.

[13]  Walter H. F. Smith,et al.  Free software helps map and display data , 1991 .

[14]  M. Cara,et al.  Seismic Anisotropy in the Earth , 1991 .

[15]  F. Calamita,et al.  The arcuate shape of the Umbria-Marche-Sabina Apennines (central Italy) , 1988 .

[16]  Charles A. Langston,et al.  Corvallis, Oregon, crustal and upper mantle receiver structure from teleseismic P and S waves , 1977, Bulletin of the Seismological Society of America.

[17]  金子 徹一,et al.  地質調査と物理探査 Geology and geophysics , 1965 .

[18]  J. Dewey,et al.  Kinematics of the western Mediterranean , 1989, Geological Society, London, Special Publications.