Slow tilt reversal of the lesser himalaya between 1862 and 1992 at 78°E, and bounds to the southeast rupture of the 1905 kangra earthquake

Abstract

Measurements between 1862 and 1992 of a 77-km-long spirit levelling line that crosses the main frontal thrust of the Himalaya near Dehra Dun (78°E) reveal a slow reversal of tilt in the early part of the last century, unperturbed by the destructive 1905 April 4 Kangra earthquake, 200 km to the northwest. The Lesser Himalaya are inferred to be tilting currently to the northeast at 0.08 μrad yr-1, with similar rate but opposite sign to their tilt in 1862. The absence of co-seismic deformation near Dehra Dun in 1905 indicates that the Kangra rupture terminated short of Dehra Dun, consistent with a revised Ms = 7.8 estimate for the size of the Kangra earthquake, but inconsistent with previous analyses of the levelling data that interpret a large slope-dependent systematic error as co-seismic slip. The reversal in tilt corresponds to a linear northeast-down tilt acceleration of 0.0015 ± 0.0004 μrad yr-2.