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|Authors: ||Eva, Claudio*|
|Title: ||Can local tomography settle the matter about subduction in the central and northern Apennines?|
|Issue Date: ||2010|
|Abstract: ||The many studies conducted on the Italian area led to several models to explain the present-day
structural setting. Some of the most debated questions are the presence or not of continuous subduction
and the presence or not of a slab detachment in the northern or in the central part of the Apenninic
The absence of a continuous, high velocity body beneath the Apennines has been interpreted by some
researchers as an evidence of the detachment of the Apenninic slab. According to this view the Apenninic
slab is expected to be inactive whether the Ionian lithosphere subducting underneath Calabria is
considered to be on the verge of detaching or just detached. Other researchers however, suggest that a
fairly continuous and fast slab exists beneath the Apennines and the Calabrian arc. Different geodynamical
models have also been proposed for the Tyrrhenian area considering it as an active or as a passive margin.
Our working group has conducted several seismic tomographies in the search of the geometry, size and
extension with depth of the subduction under the Italian peninsula.
While the images resulting from teleseismic data were clearly showing a subducting slab under the
Calabrian arc, they were not conclusive for the rest of the Apennines since they were showing, only in the
Northern sector, a likely subduction in the shallower part apparently detached from other high velocities
body in the deeper zone. At that stage it was not possible to distinguish between thrust and subduction
due to the poor horizontal resolution of the applied methodology.
In order to analyze in more details this apparent discrepancy, a new seismic local tomography has been
conducted with a very dense grid, the selection of a smaller area to be investigated (limited to the
Apennines only) and the addition of new data: all these features contributed to partly improve the
results, which cannot anyway extend beyond the maximum depth of seismic events. The main limitation in
this kind of experiment is the lack of seismic events deeper than 60-70 km under the northern and central
Apennines although, as many authors assume, is not itself an evidence against subduction.
Analyzing different cross sections of the enhanced resolution tomography results, we do not see any slab
in the northern-central Apennines in the first 80-100 km depth. The downgoing material (Adriatic plate)
of this area has a rather low dip angle, as also partly shown by the distribution of the (few) deep seismic
events. Along the central and also the northern part of the Apennines there are more overlapping than
|Appears in Collections:||04.06.07. Tomography and anisotropy|
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