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Mantle Deformation in a Young Mountain Belt: Insights From Shear Wave Splitting in the Greater Caucasus

Description: 

The convergence of the Arabian and Eurasian plates during the Cenozoic led to the formation of the Greater and Lesser Caucasus, whose tectonic history is not yet well understood. The purpose of this research is to better understand mantle deformational fabrics by analyzing local direct-S derived azimuthal seismic anisotropy using only mantle earthquakes. We have used eigenvalue minimization to determine the shear wave splitting parameters for local seismic S-waves. The data used in this study was collected from permanent and temporary broadband seismic stations deployed across southern Russia and Azerbaijan. We have found that within the mountain range, the uppermost mantle fast polarization direction is parallel to the orogen, but as you move from the mountain belt to the Scythian platform (northward) and Kura basin (southward), the fast polarization direction shifts to orogen perpendicular. We have found north-south fast polarization directions in the Apsheron Peninsula which may be due to the slab rollback in the Caspian subduction zone. The splitting time delays primarily falls between 0.2 to 1.0 seconds. Splitting time delays shorter than 0.4 seconds are likely to be the result of crustal anisotropy and larger lag times likely have significant component in the uppermost mantle. We have also found that fast polarization directions tend to be homogeneous for larger splitting delays, but inconsistent for smaller delays. We have also conducted a preliminary study of deeper source anisotropy using receiver-side corrected teleseismic S-waves. The variations of these measurements combined with our local measurements should give us an idea of how mantle anisotropy varies with depth in the Caucasus region. Future research work plans to include more data from significant earthquake events to gain a more comprehensive understanding of how seismic anisotropy changes with depth across the Greater Caucasus.

Session: Subduction Zone Structure From Trench to Arc [Poster]

Type: Poster

Date: 4/19/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Astha Singh

Student Presenter: Yes

Invited Presentation: 

Authors