Writers : shokraei, S. F.; Hoseini, S. K.; Kaviani, A.; Rahimi, B.
Refference : 27th Symposium on Geosciences and the 13th Symposium on Geological Society of Iran
Publishing Year : 1388

Abstract :

We investigate shear wave splitting measurements in the phases SKS and SKKS beneath NE of Iran performed on 43 distant earthquakes between 90 to 145 Azimuth degrees, recorded at seven broadband stations of Earthquake Research Center (EQRC) - Ferdowsi University of Mashhad. The polarization of the fast component of a shear wave and the time delay between the fast and slow components may lead us to characterize the seismic anisotropy of the upper most mantle. Delay times changes from 0.5 s to 1.5 s with average of 1 s. The largest delay time is found in the Quchan area by 1.5 s. The splitting observations may be related to the strain-induced lattice preferred orientation of olivine in upper mantle. Our study shows that we may divide the East and North east of Iran into three regions due to the parameter differences of its seismic anisotropy. In the studied region, the azimuth direction of obtained fast axes of shear wave, have a good coincidence with closing direction of paleo tethys ocean in about 300 Ma, considering 135 counter clockwise rotation of Iranian central East plate.
So, we can introduce the direction of seismic anisotropy of This region as a remanent one (fossil anisotropy) in the basis of lithosphere.

Subject List : Teleseismic waves