Cammarano, Fabio

Guerri, Mattia

English

Copenhagen University Research Information System

u n i ve r s i t y  o f  co pe n h ag e n  Københavns UniversitetSeismic velocities - density relationship for the Earth’s crustGuerri, Mattia; Cammarano, FabioPublished in:Geophysical Research AbstractsPublication date:2014Document versionEarly version, also known as pre-printCitation for published version (APA):Guerri, M., & Cammarano, F. (2014). Seismic velocities - density relationship for the Earth’s crust: effects ofchemical compositions, amount of water, and implications on gravity and topography. Geophysical ResearchAbstracts, 16, [14440].Download date: 03. Feb. 2020Geophysical Research AbstractsVol. 16, EGU2014-14440-1, 2014EGU General Assembly 2014© Author(s) 2014. CC Attribution 3.0 License.Seismic velocities - density relationship for the Earth’s crust: effects ofchemical compositions, amount of water, and implications on gravity andtopographyMattia Guerri and Fabio CammaranoDepartment of Geosciences and Natural Resources Management, University of Copenhagen, Denmark(mattia.guerri@ign.ku.dk)Seismic velocities – density relationship for the Earth’s crust: effects of chemical compositions, amount of water,and implications on gravity and topographyMattia Guerri and Fabio CammaranoDepartment of Geosciences and Natural Resource Management, Section of Geology, University of Copenhagen,Denmark.A good knowledge of the Earth’s crust is not only important to understand its formation and dynamics, butalso essential to infer mantle seismic structure, dynamic topography and location of seismic events. Global andlocal crustal models available (Bassin et al., 2000; Nataf & Ricard, 1996; Molinari & Morelli, 2011) are basedon VP-density empirical relationships that do not fully exploit our knowledge on mineral phases forming crustalrocks and their compositions.We assess the effects of various average crustal chemical compositions on the conversion from seismic velocitiesto density, also testing the influence of water. We consider mineralogies at thermodynamic equilibrium andreference mineral assemblages at given P-T conditions to account for metastability. Stable mineral phases atequilibrium have been computed with the revised Holland and Powell (2002) EOS and thermodynamic databaseimplemented in Perple_X (Connolly 2005).We have computed models of physical properties for the crust following two approaches, i) calculation of seismicvelocities and density by assuming the same layers structure of the model CRUST 2.0 (Bassin et al., 2000) and a3-D thermal structure based on heat-flow measurements; ii) interpretation of the Vp model reported in CRUST 2.0to obtain density and shear wave velocity for the crustal layers, using the Vp-density relations obtained with thethermodynamic modeling.The obtained density models and CRUST 2.0 one have been used to calculate isostatic topography and gravityfield.Our main results consist in, i) phase transitions have a strong effect on the physical properties of crustal rocks,in particular on seismic velocities; ii) models based on different crustal chemical compositions show strongvariations on both seismic properties and density; iii) the amount of water is a main factor in determining thephysical properties of crustal rocks, drastically changing the phase stability in the mineralogical assemblages;iii) the differences between the various density models that we obtained, and the variations between them andCRUST2.0, translate into strong effects for the calculated isostatic topography and gravity field.Our approach, dealing directly with chemical compositions, is suitable to quantitatively investigate compositionalheterogeneity in the Earth’s crust.References− Bassin, C., Laske, G. & Masters, G., 2000. The current limits of resolution for surface wave tomography inNorth America, EOS, Trans. Am. Geophys. Un., 81, F897.− Nataf, H. & Ricard, Y., 1996. 3SMAC: an a priori tomographic model of the upper mantle based on geophysicalmodeling, Phys. Earth planet. Inter., 95(1-2), 101–122.− Molinari, I. & Morelli, A., 2011. Epcrust: a reference crustal model for the European Plate, Gepohys. J. Int.,185, 352-364.− Connolly JAD (2005) Computation of phase equilibria by linear programming: a tool for geodynamic modelingand its application to subduction zone decarbonation. Earth and Planetary Science Letters 236:524-541.

Seismic velocities - density relationship for the Earth’s crust:effects of chemical compositions, amount of water, and implications on gravity and topography

https://curis.ku.dk/portal/files/144211021/EGU2014_14440_1.pdf

Seismic velocities - density relationship for the Earth’s crust:effects of chemical compositions, amount of water, and implications on gravity and topography

Abstract

Similar works

Full text

Available Versions

Copenhagen University Research Information System