The global pattern of crustal seismic anisotropy inferred from teleseismic converted phases

• Applicant: Privatdozent Dr. Ayoub Kaviani
• Subject Area: Geophysics
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 314979650

The enormous amount of seismological data, which has now become available from long-running (permanent) globally-distributed stations, opens up unique opportunities for applying new methods to test current hypotheses about the relative significance of seismic anisotropy in the crust and mantle beneath the continents. This unique temporal and spatial data coverage enables us to study crustal seismic anisotropy at unprecedented resolution and to correlate the observations with surface geological features and/or previously derived patterns of mantle anisotropy.This study is motivated by a number of unanswered questions, including:1) How significant is the relative amount of crustal anisotropy for seismological observations on a global scale?2) Is the crustal anisotropy continuous across the geological/tectonic boundaries or is it distinct and correlated with such provinces?3) What is the relationship between the deformation in the crust and mantle portions of lithosphere in various tectonic environments? (Is the previously proposed Vertical Coherent Deformation of the lithosphere really valid?)4) How much are shear wave (SKS) splitting measurements affected by crustal seismic anisotropy?5) How does the corrected mantle anisotropy vary across diverse tectonic environments?The data required for the proposed investigation will be assembled from global 3-component broad-band permanent stations through the international data repositories such as the IRIS DMC, GEOSCOPE, GEOFON and ORFEUS. The dataset will be supplemented by additional data from local and regional seismic networks from Europe and the Middle-East.New methods to exploit P-to-S waves converted (Ps) phases from the crust-mantle boundary (Moho discontinuity) have recently become available and will be used to infer the strength and direction of crustal anisotropy as well as the crustal thickness and average Vp/Vs ratios on a global scale. The parameters of crustal anisotropy will be subsequently used to correct the mantle splitting parameters available through the present SKS data bases.An automatic procedure will be developed to make the analysis of such a great amount of data feasible. The study will also include the development and setup of an internet-based reference database for crustal and (corrected) mantle anisotropy.

• DFG Programme: Research Grants