An excavation across the Himalayan Frontal Thrust near Damak in eastern Nepal shows displacement on a fault plane dipping ~22° has produced vertical separation across a scarp equal to 5.5 m. Stratigraphic, structural, geometrical, and radiocarbon observations are interpreted to indicate that the displacement is the result of a single earthquake of 11.3 ± 3.5 m of dip‐slip displacement that occurred 1146–1256 A.D. Empirical scaling laws indicate that thrust earthquakes characterized by average displacements of this size may produce rupture lengths of 450 to >800 km and moment magnitudesM_wof 8.6 to >9. Sufficient strain has accumulated along this portion of the Himalayan arc during the roughly 800 years since the 1146–1256 A.D. earthquake to produce another earthquake displacement of similar size.

Reinvestigation reveals observations that do not support prior claims that the great Mw 8.4 Bihar‐Nepal earthquake produced surface rupture along the Himalayan Frontal Thrust of Nepal. While it may be viewed as reasonable to suggest that the Main Himalayan Frontal Thrust was the source of the 1934 Bihar‐Nepal earthquake on geophysical grounds, decisive and substantiating geological evidence that it produced surface rupture along the trace of the Himalayan Frontal Thrust remains lacking.

Shallow bedrock strength controls both landslide hazard and the rate and form of erosion, yet regional patterns in near‐surface mechanical properties are rarely known quantitatively due to the challenge in collecting in situ measurements. Here we present seismic and geomechanical characterizations of the shallow subsurface across the central Himalayan Range in Nepal. By pairing widely distributed 1D shear wave velocity surveys and engineering outcrop descriptions per the Geological Strength Index classification system, we evaluate landscape‐scale patterns in near‐surface mechanical characteristics and their relation to environmental factors known to affect rock strength. We find that shallow bedrock strength is more dependent on the degree of chemical and physical weathering, rather than the mineral and textural differences between the metamorphic lithologies found in the central Himalaya. Furthermore, weathering varies systematically with topography. Bedrock ridge top sites are highly weathered and have S‐wave seismic velocities and shear strength characteristics that are more typical of soils, whereas sites near valley bottoms tend to be less weathered and characterized by high S‐wave velocities and shear strength estimates typical of rock. Weathering on hillslopes is significantly more variable, resulting in S‐wave velocities that range between the ridge and channel endmembers. We speculate that variability in the hillslope environment may be partly explained by the episodic nature of mass wasting, which clears away weathered material where landslide scars are recent. These results underscore the mechanical heterogeneity in the shallow subsurface and highlight the need to account for variable bedrock weathering when estimating strength parameters for regional landslide hazard analysis.