Layered Crustal Anisotropy in Eastern Iran

عنوان دوره: نوزدهمین کنفرانس ژئوفیزیک ایران
کد مقاله : 1553-NIGS
نویسندگان
1پژوهشگاه زلزله شناسی و مهندسی زلزله
2پژوهشگاه بین المللی زلزله شناسی و مهندسی زلزله
3موسسه ژئوفیزیک، دانشگاه تهران
چکیده
The continental collision between the Afghan and Lut blocks has led to vast deformations with a northwest trend in eastern Iran. The radial receiver functions obtained at 11 stations in this region exhibit strong P to S conversions. We analyze crustal seismic anisotropy with the use of arrival time variations (cosine moveout) of converted shear phases as a function of back-azimuth. We fit harmonic functions to the arrival time variations of Ps phases to obtain dipping interfaces and plunging anisotropy beneath a station. Simple crustal models with one or two anisotropic layers can justify the cosine moveout variations of the converted phases. This method gives us the apparent splitting parameters for a stack of anisotropic layers above a converting interface. Using a layer-stripping approach, the effect of seismic anisotropy in the shallower layers could be corrected on deeper discontinuities. The average fast axis, which is parallel to the Sistan suture zone, might be related to the direction of faults and the presence of highly deformed flysch as a response to continental collision.
کلیدواژه ها
 
Title
Layered Crustal Anisotropy in Eastern Iran
Authors
Meysam Mahmoodabadi, Farzam Yaminifard, Mohammad Tatar, Ali Moradi
Abstract
The continental collision between the Afghan and Lut blocks has led to vast deformations with a northwest trend in eastern Iran. The radial receiver functions obtained at 11 stations in this region exhibit strong P to S conversions. We analyze crustal seismic anisotropy with the use of arrival time variations (cosine moveout) of converted shear phases as a function of back-azimuth. We fit harmonic functions to the arrival time variations of Ps phases to obtain dipping interfaces and plunging anisotropy beneath a station. Simple crustal models with one or two anisotropic layers can justify the cosine moveout variations of the converted phases. This method gives us the apparent splitting parameters for a stack of anisotropic layers above a converting interface. Using a layer-stripping approach, the effect of seismic anisotropy in the shallower layers could be corrected on deeper discontinuities. The average fast axis, which is parallel to the Sistan suture zone, might be related to the direction of faults and the presence of highly deformed flysch as a response to continental collision.
Keywords
seismic anisotropy, Crust, Receiver Functions, Continental collision