The Ar-Hötöl surface rupture along the Khovd fault (Mongolian Altay)

The Ar-Hötöl surface rupture along the Khovd fault (Mongolian Altay)

 

Battogtokh Davaasambuu^1,2, Matthieu Ferry^1,*, Jean-Francois Ritz¹ and Ulziibat Munkhuu²

• Géosciences Montpellier, University of Montpellier, CNRS, France
• Institute of Astronomy and Geophysics, Mongolian Academy of Sciences, Mongolia

 

Abstract

The Khovd fault is one of the major active faults of the Altay but has been little studied. Detailed mapping based on satellite imagery shows that the Khovd structure exceeds 550 km in length and displays different types of complex rupture segmentation, fresh and mature surface ruptures and a number of co-seismic and cumulative offsets along its entire length.

We present a 1:200,000 scale map of the Ar-Hötöl surface rupture along the Khovd Fault in the Mongolian Altay, presumed to be the surface expression of a Mw ~ 7.8 earthquake that was felt regionally in 1761 CE. The detailed mapping is based on a multi-scale approach combining a range of airborne and terrestrial imaging and topographic techniques: Sentinel-2, Pleiades, TanDEM-X, UAV, and terrestrial laser scanning. This effort led to the detailed quantification of right-lateral and vertical offsets ranging from ~ 1 m to ~ 4 km over a continuous rupture length of 238 km. The distribution of the smaller offset class documents the surface deformation associated with the last surface-rupturing earthquake. Its analysis yields a robust segmentation model comprising 6 segments 18 to 55 km in length, a maximum co-seismic slip value of 4.5 m ± 0.5 m located near the center of the rupture. Our detailed remote sensing and field observations precise the varying kinematics along strike, bring new evidence of repeated faulting and confirm a moment magnitude of 7.8 ± 0.3.

The aim of the present research work is to reveal the main sources of potential destructive earthquakes by identifying the location of past large earthquakes along the fault and estimate their magnitude and recurrence period. Our results would contribute to improve seismic hazard estimation for population of the Altay Mountains.

 

Keywords: active fault, surface rupture, Altay Range