Establishing primary surface rupture evidence and magnitude of the 1697 CE Sadiya earthquake at the Eastern Himalayan Frontal thrust, India

Arjun Pandey,Hari B Srivastava,Rao Singh Priyanka,R Jayangondaperumal,Pradeep Srivastava,Ishwar Singh,György Hetényi

doi:10.1038/s41598-020-79571-w

Abstract

Historical archives refer to often recurring earthquakes along the Eastern Himalaya for which geological evidence is lacking, raising the question of whether these events ruptured the surface or remained blind, and how do they contribute to the seismic budget of the region, which is home to millions of inhabitants. We report a first mega trench excavation at Himebasti village, Arunachal Pradesh, India, and analyze it with modern geological techniques. The study includes twenty-one radiocarbon dates to limit the timing of displacement after 1445 CE, suggesting that the area was devastated in the 1697 CE event, known as Sadiya Earthquake, with a dip-slip displacement of 15.3 ± 4.6 m. Intensity prediction equations and scaling laws for earthquake rupture size allow us to constraints a magnitude of Mw 7.7–8.1 and a minimum rupture length of ~ 100 km for the 1697 CE earthquake.

Highlights

Historical archives refer to often recurring earthquakes along the Eastern Himalaya for which geological evidence is lacking, raising the question of whether these events ruptured the surface or remained blind, and how do they contribute to the seismic budget of the region, which is home to millions of inhabitants
Despite an increasing number of paleoseismological studies in the central Himalaya during the last d ecade[5,6,7,8,9,10,11,12], only a few investigations have been conducted along the eastern Himalayan front, and the studied trench sites are rather sparsely spaced at ~ 50 to ~ 200 km apart[13,14,15,16,17]
To better understand the seismogenic potential of the east Himalayan front, we conducted a palaeoseismological investigation between the Subansiri and Siang river valleys at Himebasti village in Arunachal Pradesh, India

Summary

Introduction

Historical archives refer to often recurring earthquakes along the Eastern Himalaya for which geological evidence is lacking, raising the question of whether these events ruptured the surface or remained blind, and how do they contribute to the seismic budget of the region, which is home to millions of inhabitants. Historical archives document massive destruction in the eastern Himalaya during closely time-spaced earthquakes in Late-Medieval t imes[1,2] These earthquakes sometimes ruptured the Himalayan Frontal Thrust (HFT) at the surface, or remained blind, like the 2015 Gorkha e arthquake[3]. The T3 terrace is preserved on either bank of Geuka Nala and the eastern bank of the Dulang Nala, and it sits at the height of ~ 27 m from the current Subansiri River grade (Fig. 2). The T2 terrace is affected by a fault scarp and sits at the height of ~ 20 m from the current grade of a small local stream, Hime Nala (Fig. 2). We observed many dried and beheaded channels near the trench site

Methods

Findings

Discussion

Conclusion