LAUSR

Abstract The April 2015 Mw 7.8 Gorkha (Nepal) earthquake caused moderate liquefaction in the Kathmandu Valley. Shallow pits within these sites exposed previous earthquake induced liquefactions. The multiple exposures allow us to constrain the sand blows/sills at the mid-level of two shallow sections that point to a suite of medieval earthquakes (around 14th century CE). The timing of this liquefaction event overlaps with age constraints for the late medieval fault offsets excavated previously in the western part of central Himalaya; variously attributed to the ancient earthquakes of 1255 and 1344 CE. The earthquakes of 1833 and 1934 had impacted the Kathmandu Valley and the sedimentary exposures revealing liquefaction features also provide constraints on these earthquakes. The 1934 earthquake (Mw 8.2) had maximally liquefied the distant Bihar Plains, while the 1833 earthquake (Mw ~7.7) had a minimal impact, a characteristic that is comparable to the 2015 Gorkha earthquake. Thus, combining with the historical reports from Kathmandu, our findings imply that the 1833 earthquake may have been analogous to the 2015 earthquake whose rupture arrested midway on the Himalayan decollement in contrast to the 1934 earthquake that propagated further southward to the frontal thrust, generating massive liquefaction field in the northern Bihar Plains. The age constraints obtained on the liquefaction features from the Kathmandu Valley along with the data already available from the Bihar Plains imply a long-elapsed time between the medieval (11th to 14th centuries) pulse of earthquakes and the 17th and 20th century events.