• NARESH RANA

Articles written in Journal of Earth System Science

• Interpreting the geomorphometric indices for neotectonic implications: An example of Alaknanda valley, Garhwal Himalaya, India

Tectonic process can influence the erosion and exert the first order impression on hydrographic networkof an area. Geomorphometry, a mathematical analysis of the configuration of the landforms, allows quantifyingthe degree of landform evolution and is widely used as a measure of tectonic deformation/uplift.Alaknanda valley lies in the tectonically active Garhwal Himalaya which has experienced two disastrouslarge earthquakes in the last two decades. Morphometric analyses of the valley were carried out in a fluvialerosion dominated regime and the morphometric indices were derived from the ASTER (30 m × 30 mpixel) Digital Elevation Model (DEM) using Arc GIS. The results of the analyses reveal two zones ofhigh deformation/uplift in the valley, viz., the zone of high deformation proximal to the Main CentralThrust (MCT) in the Inner Lesser Himalaya (ILH) and the second zone of moderate deformation/upliftin the Outer Lesser Himalaya (OLH), south of the Tons Thrust (TT). The high deformation in the ILHis ascribed to the focussed convergence and high precipitation; however, the causes for the moderatedeformation in the OLH are yet to be established.

• A preliminary assessment of the 7th February 2021 flashflood in lower Dhauli Ganga valley, Central Himalaya, India

A short-lived flashflood in Rishi and Dhauli Ganga rivers on 7th February 2021, Uttarakhand Himalaya, killed 65 people with 141 reported missing (official estimate) and devastated two hydropower projects. Geomorphological observations supported by meteorological data suggest that the flood was triggered by a combination of avalanche and debris flow. The Dhauli Ganga valley has preserved ponded sedimentary sequences (laminated sand and silty-clay), suggesting that the valley is prone to episodic mega foods in the recent geological past. Considering that the receding glaciers in the higher Himalaya have left behind enormous sediment, unusual weather events are likely to generate such disasters more frequently as the climate becomes warmer. Thus, the study calls for not only incorporating the disaster risk assessment in the developmental planning of the Himalayan region but also recommends routine monitoring of the potential areas of structural failures in the glaciated valleys along with supra-glacial lakes.

• Monsoonal rainfall induced shallow earthquake Swarm in the Amravati district of the central India

Sadrabadi and Zilphi villages of Dharni Taluka in Amravati district, Maharashtra, experienced small magnitude earthquakes between September 1, 2018 and December 9, 2018. We deployed a four station temporary network of three component broadband seismographs to understand and characterize the earthquake sequence. We find that the short lived (${\sim}$2 months) micro-earthquake (M $\leq$2.4) swarm, accompanying rumbling sound, was highly clustered (3$\times$3 km$^{2}$) and occurred at extremely shallow depth (<0.4 km). Analysis of the data reveal that the earthquake swarm might have been induced by the percolation of monsoonal rainwaters (reaching (${\sim}$100 mm/day) through the cracked volume of soil/rock, associated with the fault system of the Narmada Son failed rift region. Besides revealing the science of earthquake swarm and characterizing it, the monitoring of earthquake swarm and its analysis contributed significantly in reducing the public panic.

$\bf{Highlights}$

$\bullet$ We report a case of monsoonal rainfall induced earthquakes from the Narmada Son failed rift region in Amravati district.

$\bullet$ The earthquake sequence is referred here as an earthquake swarm.

$\bullet$ The near surface shallow focused micro earthquakes (M$\leq$2.4) occurred in a small region (3$\times$3 km$^{2}$) immediately after the monsoon of 2018.

$\bullet$ Monitoring of such sequence is important to declare whether the sequence is a swarm activity that may not lead to the occurrence of a strong earthquake in the region.

• # Journal of Earth System Science

Volume 131, 2022
All articles
Continuous Article Publishing mode

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019