Evidence of 5 to 6m repetitive uplift of MFT hangingwall and channel abandonment in Suklaha Khola valley, Eastern Nepal
Abstract
The Main Frontal Thrust (MFT), the youngest and most active thrust in the Himalayas, has generated multiple magnitude 8+ earthquakes in the past. However, their source, extent and recurrence times are yet to be better constrained. Recent work on the 1934 Bihar-Nepal earthquake, that has ruptured at least a 150 km-long segment of the MFT, has addressed these questions using a multi-methodological approach (field observations, quantitative geomorphology, cosmogenic and radiocarbon dating). Two main areas - Bardibas (North-West) and Lahan regions (South-East) displayed evident multiple seismic uplift recorded by surficial deposits along riverbeds of rivers cutting across the thrust. Here, we focus on the Suklaha Khola (86°13'E), a key location SE of the Kamala river to correlate the western and eastern areas. We use high-resolution topographic data (4 data points /m2) extracted from airborne and terrestrial Lidar Surveys (1) to map the surface rupture of the 1934 event and (2) to map and quantify geomorphic markers of relative co-seismic uplift (such as terraces levels, abandoned paleochannels, active river beds and alluvial cones). We identify 3 uplifted terrace levels of about 5 to 6 m each corresponding to 3 seismic events, and a striking example of channel abandonment likely caused by the most recent event (1934 earthquake). These results corroborate with previous studies performed in the region suggesting a characteristic uplift behaviour along this segment of the MFT.
- Publication:
-
EGU General Assembly Conference Abstracts
- Pub Date:
- April 2018
- Bibcode:
- 2018EGUGA..2017577B