Himalayan Geology, Vol. 42 (2), 2021, pp. 290-298, Printed in India

Microseismicity study in the Siang Valley of Arunachal Himalaya: Tectonic Implications of the 2019 Mw 5.9 Mechuka earthquake

DILIP KUMAR YADAV*, DEVAJIT HAZARIKA, NARESH KUMAR, A. KRISHNAKANTA SINGH

Wadia Institute of Himalayan Geology, Dehradun 248001, India

*Email (Corresponding Author): yadavdk@wihg.res.in

Abstract: Recent seismicity and its tectonic linkage are investigated in the Siang valley, Arunachal Himalaya and the adjacent regions of northeast India. The study is based on local earthquakes recorded during six months, December 2018 - May 2019, by a recently established network of eight Broadband stations. A severely felt earthquake Mw 5.9 that occurred on April 23, 2019, near Mechuka, Arunachal Himalaya was well recorded by the network. The focal mechanism solution (FMS) of this earthquake based on waveform modelling infers a low angle thrust faulting that matches with the Main Central Thrust located at the western limb of the Siang Window. This is the strongest event during the last 15 years in the Siang Valley that holds a good control on major tectonics and geodynamics of the Eastern Himalayan Syntaxis zone. It is observed that the Siang valley is seismically active; the western part of the valley is more active compared to the eastern part.  Further, the earthquakes are deeper down to 40 km. The FMS of the Mechuka earthquake and available 11 Global Centroid Moment Tensor solutions in the region suggest a regional NE-SW compressive stress.

Keywords: Siang Window, Mechuka Earthquake, Seismicity, Northeast Himalaya