Journal Article

Ivrea seismic array: a study of continental crust and upper mantle

R. de Franco, G. Biella, G. Boniolo, A. Corsi, M. Demartin, M. Maistrello and A. Morrone

in Geophysical Journal International

Volume 128, issue 3, pages 723-736
Published in print March 1997 | ISSN: 0956-540X
Published online March 1997 | e-ISSN: 1365-246X | DOI: http://dx.doi.org/10.1111/j.1365-246X.1997.tb05332.x
Ivrea seismic array: a study of continental crust and upper mantle

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Summary

A seismic-array study of the continental crust and upper mantle in the Ivrea-Yerbano and Strona-Ceneri zones (northwestern Italy) is presented. A short-period network is used to define crustal P- and S-wave velocity models from earthquakes. The analysis of the seismic-refraction profile LOND of the CROP-ECORS project provided independent information and control on the array-data interpretation.

Apparent-velocity measurements from both local and regional earthquakes, and time-term analysis are used to estimate the velocity in the lower crust and in the upper mantle. The geometry of the upper-lower crust and Moho boundaries is determined from the station delay times.

We have obtained a three-layer crustal seismic model. The P-wave velocity in the upper crust, lower crust and upper mantle is 6.1±0.2 km s−1, 6.5±0.3 km s−1 and 7.8±0.3 km s−1 respectively. Pronounced low-velocity zones in the upper and lower crust are not observed. A clear change in the velocity structure between the upper and lower crust is documented, constraining the petrological interpretation of the Ivrea-type reflective lower continental crust derived from small-scale petrophysical data. Moreover, we found a VP/VS ratio of 1.69±0.04 for the upper crust and 1.82±0.08 for the lower crust and upper mantle. This is consistent with the structural and petrophysical differences between a compositionally uniform and seismically transparent upper crust and a layered and reflective lower crust. The thickness of the lower crust ranges from about 8 km in front of the Ivrea body (ARVO, Arvonio station) in the northern part of the array to a maximum of about 15 km in the southern part of the array. The lower crust reaches a minimum depth of 5 km below the PROV (Provola) station.

Keywords: Ivrea body; lower crust; mantle; seismic array

Journal Article.  0 words. 

Subjects: Geophysics

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