Seismic anisotropy beneath the Kumaun–Garhwal Himalaya using core-refracted shear wave phases

Abstract

Summary We investigate the nature of seismic anisotropy in the Kumaun—Garhwal Himalaya by analyzing the core refracted shear wave splitting phases (SK(K)S, PKS) recorded at 42 broadband seismic stations. The mean fast anisotropy directions are mostly in ∼E-W and a few in the ∼NE-SW directions. The mean delay time decreases progressively from ∼1.0s beneath the Sub Himalaya to ∼0.5s at the Higher Himalaya. The observed seismic anisotropy suggests that the ongoing deformation beneath the Kumaun—Garhwal Himalaya has a large contribution by the relative rotation of the asthenospheric flow by the compression along the Indian Plate motion direction in this collision zone. Also, the southward transportation of the mid-crustal flow is probably responsible for the reduction in the delay times in the MCT zone and further north than in the Sub-to-Lower Himalaya. The splitting parameters indicate a complex pattern of deformation beneath the Kumaun—Garhwal Himalaya with contribution from crust, lithospheric mantle and asthenospheric mantle.

INSA National Report on Seismological Research in India: 2019 – 2022

“…The FPAs are mainly oriented along the ENE-WSW and ∼ E-W directions, respectively, and a few in the NE direction (see Fig. 4 of Kumar, V.P., et al, 2022). Also, very few observations in the Kumaun-Garhwal Himalaya are oriented along the ∼ SE-NW direction.…”

“…Of these 62 stations, around 18 stations are located along a linear profile in the Kumaun-Garhwal Himalaya traversing the Himalaya from south to north. The study region mostly comprises of Himachal (Biswal et al, 2020) and Kumaun-Garhwal (Kumar V.P., et al, 2022) Himalaya. The FPAs are mainly oriented along the ENE-WSW and ∼ E-W directions, respectively, and a few in the NE direction (see Fig.…”

INSA National Report on Seismological Research in India: 2019 – 2022

“…Upper mantle anisotropy beneath the western Himalaya is investigated using data from 62 broadband seismic stations (Biswal et al, 2020;Kumar V.P., et al, 2022). Of these 62 stations, around 18 stations are located along a linear profile in the Kumaun-Garhwal Himalaya traversing the Himalaya from south to north.…”

“…Of these 62 stations, around 18 stations are located along a linear profile in the Kumaun-Garhwal Himalaya traversing the Himalaya from south to north. The study region mostly comprises of Himachal (Biswal et al, 2020) and Kumaun-Garhwal (Kumar V.P., et al, 2022) Himalaya. The FPAs are mainly oriented along the ENE-WSW and ∼ E-W directions, respectively, and a few in the NE direction (Fig.…”