T44A-07
High Resolution Topography and Multiple Seismic Uplift on the Main Frontal Thrust near the Ratu River, Eastern Nepal
Thursday, 17 December 2015: 17:30
302 (Moscone South)
Cagil Karakas1, Paul Tapponnier2, Soma Nath Sapkota3, Aurelie Coudurier Curveur1, Sorvigenaleon Ildefonso1, Mingxing Gao2, Laurent Bollinger4, Yann Klinger5 and Dilli Ram Tiwari3, (1)Earth Observatory of Singapore, Singapore, Singapore, (2)Nanyang Technological University, Singapore, Singapore, (3)National Seismological Centre, Department of Mines and Geology, Kathmandu, Nepal, (4)CEA, Bruyeres Le Chatel, France, (5)Institut de Physique du Globe de Paris, Paris, France
Abstract:
New data at several more sites along the Main Frontal Thrust between 85°49’ to 86°27’ E corroborates the surface emergence of the great M ≈ 8.4, 1934 Bihar-Nepal and 1255 AD earthquakes. Here we show unambiguous evidences of surface rupture and co-seismic uplift in the Ratu river area based on high-resolution geomorphic surveys. We present a refined map of uplifted terrace surfaces and abandoned paleo-channels truncated by the MFT, obtained by newly acquired high resolution Digital Elevation Models from Total station, Terrestrial Lidar Scanner (TLS), Unmanned Aerial Vehicle (UAV) and kinematic GPS surveys. In the Ratu valley, using these new high resolution topographic datasets, we identify five and possibly seven distinct terrace levels uplifted parallel to the riverbed, that cap the folded Siwaliks. Such measurements may be taken to imply broadly characteristic increments of throw during sequences of at least five to seven events of riverbed abandonment related to co-seismic uplifts. Newly collected detrital charcoals from several pits and from a rejuvenated paleoseismological wall will help assess more precisely uplift and shortening rates over the length of segments of the MFT east and west of Bardibas. A regional comparison of comparable long term paleoseismological data at other sites along the 1934 rupture length is in progress.
