Joint approach combining damage and paleoseismology observations constrains the 1714AD Bhutan earthquake at magnitude 8 +/- 0.5

Gyorgy Hetenyi (1) , Romain Le Roux-Mallouf (2) , Theo Berthet (3) , Rodolphe Cattin (2) , Carlo Cauzzi (4) , Karma Phuntsho (5) , Remo Grolimund (4)

1 UNIL - Université de Lausanne = University of Lausanne
2 Géosciences Montpellier
3 Uppsala University
4 SED - Swiss Seismological Service [ETH Zurich]
5 Shejun Agency for Bhutan's Cultural Documentation and Research, Thimphu

The region of Bhutan is thought to be the only segment of the Himalayas not having experienced a major earthquake over the past half millennium. A proposed explanation for this apparent seismic gap is partial accommodation of the India-Asia convergence further south across the Shillong Plateau, yet the seismic behavior of the Himalayan megathrust in Bhutan is unknown. Here we present historical documents from the region reporting on an earthquake in 1714 A.D. and geological evidence of surface rupture to constrain the latest large event in this area. We compute various earthquake scenarios using empirical scaling relationships relating magnitude with intensity, source location and rupture geometry. Our results constrain the 1714 A.D. earthquake to have ruptured the megathrust in Bhutan, most likely during a M7.5–8.5 event. This finding reclassifies the apparent seismic gap to a former information gap and implies that the entire Himalayan arc has a high level of earthquake potential.

Mots clés: Bhutan

Domaines: Tectonique

Gyorgy Hetenyi, Romain Le Roux-Mallouf, Theo Berthet, Rodolphe Cattin, Carlo Cauzzi, et al.. Joint approach combining damage and paleoseismology observations constrains the 1714AD Bhutan earthquake at magnitude 8 +/- 0.5. Geophysical Research Letters, 2016, 43 (20), pp.10695-10702. ⟨10.1002/2016GL071033⟩. ⟨hal-01467822⟩