Primary surface rupture of the 1950 Tibet-Assam great earthquake along the eastern Himalayan front, India

Abstract

The pattern of strain accumulation and its release during earthquakes along the eastern Himalayan syntaxis is unclear due to its structural complexity and lack of primary surface signatures associated with large-to-great earthquakes. This led to a consensus that these earthquakes occurred on blind faults. Toward understanding this issue, palaeoseismic trenching was conducted across a ~3.1 m high fault scarp preserved along the mountain front at Pasighat (95.33°E, 28.07°N). Multi-proxy radiometric dating employed to the stratigraphic units and detrital charcoals obtained from the trench exposures provide chronological constraint on the discovered palaeoearthquake surface rupture clearly suggesting that the 15th August, 1950 Tibet-Assam earthquake (Mw ~ 8.6) did break the eastern Himalayan front producing a co-seismic slip of 5.5 ± 0.7 meters. This study corroborates the first instance in using post-bomb radiogenic isotopes to help identify an earthquake rupture.

Himalayan earthquakes: a review of historical seismicity and early 21st century slip potential

“…Until quite recently, there was no evidence that the earthquake had ruptured the surface. Recent investigations describe features that may represent a 200 km-long surface scarp associated with the earthquake, but details at the time of writing are unavailable (Burgess et al 2012;Coudurier-Curveur et al 2016Priyanka et al 2017).…”

Active tectonics of Himalaya, rift basins in Central India and those related to crustal deformation at different time scales

“…To understand the occurrence of large magnitude earthquakes in the Himalayan region, investigations of the active tectonic character of the Himalayan Frontal Thrust (HFT) and its palaeoseismology along the entire length of the Himalaya have been carried out at several localities (Fig. 1;Jayangondaperumal et al, 2017a;Malik et al, 2016Rajendran et al, 2017Rajendran et al, , 2018Mishra et al, 2016;Priyanka et al, 2017;Priyanka, 2018). Although there are limitations on the constraints of timing of large events and extent of surface rupture, these studies have provided insight into the pattern of strain accommodation and release by paleoearthquakes along the Himalayan front.…”

“…The work of attracted acute criticism by Naresh Rana and Shubhra Sharma (2017) which was published as a commentary article. In the commentary article, Rana and Sharma (2017) argued that the paper by was based on mere inferences drawn by authors from adequate and vague field observations supported by misquoted references.…”

“…The work of attracted acute criticism by Naresh Rana and Shubhra Sharma (2017) which was published as a commentary article. In the commentary article, Rana and Sharma (2017) argued that the paper by was based on mere inferences drawn by authors from adequate and vague field observations supported by misquoted references. They argued that the claim of landform evolution in the area due to the tectonic activity of the North Almora Thrust along with other subsidiary faults, as suggested by is wrong and biased towards tectonics only, without considering the aspect of the climatic role in the landform development and ignoring the possibility of climate-tectonic interaction.…”

“…This continued convergence has resulted in the occurrence of large to great earthquakes of magnitudes >7 in the past 100 years. Historical accounts suggest many destructing earthquakes like the A.D. 1255 Kathmandu, 1505Kashmir, 1713Bhutan-Arunachal, 1803Garhwal, 1897 Shillong Plateau, in addition to instrumentally documented earthquakes of 1905 Kangra, 1934Bihar-Nepal, 1950 Tibet-Assam (Priyanka et al, 2017). Officially, the Indian Meteorological Department (IMD) monitors seismicity of the country.…”