Seismic constraints on the thermal structure of the Italian crust

Author(s)

C. Gao, G. Diaferia, F. Cammarano, N. Piana Agostinetti, V. Lekic, I. Molinari

Abstract

Temperature distribution at depth is of key importance to characterize

the crust, defining its role and behavior in relation to neighboring

plates and the mantle underneath. Temperature can be retrieved by heat

flow measurements in boreholes, but data are sparse and shallow and do

not provide the necessary coverage and reliability, especially in active

and geologically recent areas. Laboratory data and thermodynamic

modeling demonstrate that temperature exerts a strong control on the

seismic properties of rocks, supporting the hypothesis that seismic data

can be used to unravel the thermal structure of the crust. We use

Rayleigh wave dispersion curves (SWD) and receiver functions (RFs),

jointly inverted with a trans-dimensional Monte Carlo Markov Chain

algorithm, to retrieve the VS and VP/VS

at crustal depth for the Italian peninsula. Except for the areas where

the geological complexities have hampered the retrieval of a

satisfactory model, the obtained subsurface models are exploited for the

crustal characterization. The high values (>1.9) of

VP/VS suggest a relevant role of filled-fluid

cracks in the middle and lower crust. Intra-crustal discontinuities

associated with large values of VP/VS are

interpreted as the α-β quartz transition and used for the

estimation of geothermal gradients. The use of thermodynamics to

translate shear-wave velocities into temperature leads to similar

estimates, in agreement with the known tectonic and geodynamic setting

of the Italian Peninsula. Seismological data are therefore a viable

alternative to heat flow measurements for the thermal characterization

of the crust.

Organisation(s)

Department of Geology

External organisation(s)

University of Maryland, College Park, Università Degli Studi Roma Tre, University of Copenhagen, Dublin Institute for Advanced Studies, Istituto Nazionale di Fisica Nucleare (INFN), Roma

Publication date

12-2018

Peer reviewed

Yes

Austrian Fields of Science 2012

105102 General geophysics

Keywords

Portal url

https://ucrisportal.univie.ac.at/en/publications/1c6fb070-cdb9-409f-9f24-6059df0f61bb