Unraveling the Seismic History of the Himalayas: Paleoseismological Insights from a Surface Rupture in Eastern Bhutan
Date
2024-04-11
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Abstract
The Himalayas are known for large, destructive earthquakes. The study of paleoseismology in this area encounters challenges due to the sparse historical records of earthquakes and the inadequacy of paleoseismic data. Thus, investigating newly identified surface ruptures becomes essential for enhancing the earthquake catalog of this region.
The seismic history was elucidated by investigating a surface rupture recently identified along the Main Frontal Thrust (MFT) in eastern Bhutan. At least three large paleo-earthquakes occurred along this fault over the past 10,000 years. The initial two events (E2‒E3) are dated back to pre-medieval times. Paleoseismological evidence recorded near our study area, one or two significant medieval earthquakes (the ~1100 or 1255 event) likely have occurred in Bhutan. The most recent event (E1) is identified as the 1714 earthquake, characterized by a surface rupture of 175 to ~290 km, a maximum coseismic slip of ~10.5 m, and estimated magnitudes 7.7–8.5.
Description
The study of surface-rupturing paleoseismic events in eastern Bhutan reveals the timing of major earthquakes and their return time in this region. It also infers the possibility of southward propagation of the Main Himalayan Thrust (MHT) as a blind basal décollement with the Coulomb stress changes calculations. This study contributes to the Himalayan research regarding paleoseismology, i.e., one putative seismic gap in eastern Bhutan has been removed from the Himalayan paleo-earthquake map.
Keywords
Surface Rupture, Paleo-earthquake, Retro-deformation, Coseismic Slip, OxCal Chronostratigraphic Model, Most Likely Magnitude, Earthquake Recurrence Interval, CST Calculations, Himalayas