Introduction:
The Himalayan Frontal Thrust (HFT), also known as the Main Frontal Thrust (MFT), is a geological fault situated in the Himalayas, marking the boundary between the Himalayan foothills and the Indo-Gangetic Plain.
It represents the youngest and southernmost thrust structure in the deformation front of the Himalayas.
Seismic gaps refer to segments of active faults that are prone to significant earthquakes but have not experienced significant movement for an unusually extended period compared to other fault segments.
Body:
Geomorphic Significance of Himalayan Frontal Thrust (HFT):
Demarcation: The series of reverse faults constituting the Himalayan frontal faults delineate the transition between the Shivalik hills and the expansive Indo- Gangetic plains.
It defines the active tectonic displacement area, with a convergence rate of 10–15 mm/yr, between the stable Indian plate and the Himalayas.
Active deformation between the Sub-Himalaya and the Indian plain is marked by the HFT.
Southward Migration: The primary thrusts – Main Central Thrust (MCT), Main Boundary Thrust (MBT), and HFT – display younger ages and shallower depths, suggesting a southward migration of the primary deformation zone.
Insight into Seismic Structure and Evolution: The HFT remains the only active fault in the Himalayas, accommodating overall deformation while other thrusts are locked.
Study of Orogenic Belts: Faults serve as indicators of the obliteration of oceanic lithosphere during subduction, aiding in comprehending the continental welding process in orogenic belts.
The study of HFT aids in understanding the final outcomes of plate tectonics across time and space.
Geomorphic Significance of Seismic Gaps:
Seismicity Indicator: Seismic gaps denote regions susceptible to earthquakes due to the accumulation of strain beneath the surface.
Statistically, a major earthquake becomes more likely when the time since the last significant earthquake exceeds the average time gap between two such events as per historical records.
E.g., the Kumaon-Garhwal strong earthquakes in 1505 CE and 1803 CE were attributed to the fractures along the HFT.
Planning Basis: Identifying seismic gaps aids in strategic planning and development considerations.
In regions with multiple seismic gaps, caution should be exercised in planning significant projects such as irrigation, housing, and roads.
For instance, the presence of numerous seismic gaps in the Himalayan region implies the need to avoid extensive irrigation or large-scale infrastructure projects.
Conclusion:
India’s susceptibility to earthquakes, owing to the presence of active young fold mountains like the Himalayas, necessitates continued research into tectonic movements, utilizing advanced techniques and a broader geological database.
The escalating frequency of earthquakes in the Delhi-NCR region and incidents like the Dhauli Ganga Uttarakhand avalanche emphasize the urgency for such studies. With heightened awareness and informed planning, the nation can mitigate the risks posed by these seismic phenomena and enhance its overall disaster preparedness.