Quaternary Deformation and Active Normal Faulting at Kala Amb, Northwestern Himalaya, India

Kala Amb is a tectonically active region in the Northwestern Himalaya, India. We report a newly discovered normal fault namely Moginand Fault (MF) exposed in an excavated section at Moginand (Kala Amb), India. The MF is formed on Himalayan Frontal Thrust (HFT) sheet, bounded in the north by MBT and towards the south by HFT which is structurally displaced by the Kala Amb Tear Fault. Data collected during the field work indicates presence of an anticline in the hanging wall of the HFT; previous studies suggest a blind thrust for fault-propagation fold. The trench is located in front of the anticlinal structure and above the inferred blind thrust. The strike of MF is N 1350 E and dips 600 SW. The MF has displaced and dragged the black mudstone bed of the Tatrot Formation of Upper Siwalik by ~ 9 meters along the fault plane and overlying Quaternary deposits, therefore indicating Holocene activity. The beds in the hanging wall form rollover anticline due to the displacement along the fault. The evidence of two large surface rupture earthquakes during the past 650 years was reported along Kala Amb Tear Fault with minimum displacements of 4.6 meters and 2.4 to 4.0 meters, respectively. Previous studies have established that crustal extension in the interior of the Himalayan orogen is active and dominantly occurs both in ~E-W and ~N-S directions. The MF at Kala Amb has strike N 1350 E which is oblique to the previously reported normal faults in the Himalayan orogen. The work presented here shows that MF is tectonically induced active normal fault in the Sub-Himalaya. This study will help to understand the tectonic evolution of the preexisting structures with respect to MF and its long-term dynamics.