Abstract:
Estimates of interseismic deformation in northeastern India based on GPS measurements at eight permanent stations (2003–2006)
and six campaign sites (1997–2006) are presented here. The Euler pole of rotation of Indian tectonic plate in ITRF2000 determined from
the present data set is located at 51.7±0.5 °N, −15.1±1.5 °E with angular velocity of 0.469±0.01Myr−1. The results show that there is a
statistically insignificant present-day active deformation within the Shillong Plateau and in the foreland spur north of the plateau in the
Brahmaputra valley. Convergence rate of the northeastern GPS sites with respect to the IGS station Lhasa along baselines that are normal
to the Himalayan arc in this region is 16±0.5 mm/yr. This represents the arc-normal Indo-Eurasian convergence rate across the
northeastern boundary, similar to arc-normal convergence rates determined in central Nepal along the Himalayan arc. However, unlike
central Nepal, in the Arunachal Himalaya the 16 mm/yr shortening is distributed between the Lesser as well as Higher and Tethyan
Himalayas. Baselines between sites on the Indo-Burmese Fold and Thrust Belt (IBFTB) and Shillong Plateau indicate variations in the
shortening rate from 1.5 mm/yr on the Tripura–Mizoram salient (TRS) south of the plateau, to 6 mm/yr in the Imphal Recess (IR) to the
east and 8 mm/yr in Naga salient (NS) to the northeast. This suggests that the deformation in the IBFTB is segmented into N–S blocks
along E–Wtransverse zones exhibiting dextral slip between NS–IR and sinistral slip between IRandTRS. Baselines between the IBFTB
sites also show 10±0.6 mm/yr convergence pointing to the existence of an active transverse zone between Aizawl and Imphal.
