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The present study is an attempt to understand the antiquity of the preserved fluvial landforms and its response to the climate–tectonics nexus through geomorphological investigations along the Jadukata, Umpung, Umngot and Umtongoi rivers in the southern front of the Shillong plateau (SP), NE India. Sedimentological characteristics, chronological analyses and morphotectonic parameters were used to describe the spatial and temporal variability in the patterns of aggradation, landform evolution and neotectonic influences in the study. Our results indicate that valley aggradation processes occurred around the transitional zone in the southern front of the SP during the mid–late Holocene era along with a hiatus in sediment deposition after 4.3 ka. Sediment generation and aggradation is modulated by precipitation anomalies associated with the Indian Summer Monsoon (ISM) variability whereas morphometric analysis suggests that activity along the Dauki–Dapsi fault has been contributing to the uplift-related deformation. Sedimentological observation supported by optically stimulated luminescence chronology obtained on palaeoflood deposits, valley-fill fluvial terraces and alluvial fans indicate their deposition during three pluvial phases: (i) 5.3–4.3 ka, (ii) 2.4–1.0 ka and (ii) 0.7–0.3 ka. Our data indicate that valley aggradation and geomorphic processes in the southern part of SP responded to short-term changes in the ISM variability with contributions from the morphotectonic activities associated with the Dauki–Dapsi fault during the late Holocene period.

Although the M=w8.7, 1950 Assam earthquake endures as the largest continental earthquake ever recorded, its exact source and mechanism remain contentious. In this paper, we jointly analyze the spatial distributions of reappraised aftershocks and landslides, and provide new field evidence for its hitherto unknown surface rupture extent along the Mishmi and Abor Hills. Within both mountain fronts, relocated aftershocks and fresh landslide scars spread over an area of ≈330 km by 100 km. The former are more abundant in the Abor Hills while the later mostly affect the front of the Mishmi Hills. We found steep seismic scarps cutting across fluvial deposits and bounding recently uplifted terraces, some of which less than two thousand years or even a couple centuries old, at several sites along both mountain fronts. They likely attest to a minimum 200 km-long 1950 surface rupture on both the Mishmi and Main Himalayan Frontal Thrusts (MT and MFT, respectively), crossing the East Himalayan Syntaxis. At two key sites (Wakro and Pasighat), co-seismic surface throw appears to have been over twice as large on the MT as on the MFT (7.6 ± 0.2 m vs. >2.6 ± 0.1 m), in keeping with the relative, average mountain heights (3200 m vs. 1400 m), mapped landslide scar numbers (182 vs. 96), and average thrust dips (25–28° vs. 13–15°) consistent with relocated aftershocks depths. Corresponding average slip amounts at depth would have been ≈17 and ≈11 m on the MT and MFT, respectively, while surface slip at Wakro might have reached ≈34 m. Note that this amount of superficial slip would be out of reach using classic paleo-seismological trenching to reconstruct paleo-earthquake history. Most of the 1950 first arrivals fit with a composite focal mechanism co-involving the two shallow-dipping thrust planes. Their intersection lies roughly beneath the Dibang Valley, implying forced slip parallel to GPS vectors across the East Himalayan Syntaxis. Successive, near-identical, terrace uplifts at Wakro suggest near-characteristic slip during the last two surface rupturing earthquakes, while terrace boulder ages may be taken to imply bi-millennial return time for 1950-size events. As in Nepal, East-Himalayan mega-quakes are not blind and release most of the elastic, interseismic shortening that accumulates across the range. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Published version

The present study is undertaken in the Kulsi River valley, a tributary of the Brahmaputra River that drains through the tectonically active Shillong Plateau in northeast India. Based on the fluvial geomorphic parameters and Landsat satellite images, it has been observed that the Kulsi River migrated 0.7–2 km westward in its middle course in the past 30 years. Geomorphic parameters such as longitudinal profile analysis, stream length gradient index (SL), ratio of valley floor width to valley height (Vf), steepness index ( $$k_{s})$$ indicate that the upstream segment of the Kulsi River is tectonically more active than the downstream segment which is ascribed to the tectonic activities along the Guwahati Fault. $$^{14}\hbox {C}$$ ages obtained from the submerged tree trunks of the Chandubi Lake, which is located in the central part of the Kulsi River catchment suggests inundation (high lake levels) during 160 ± 50 AD, 970 ± 50 AD, 1190 ± 80 AD and 1520 ± 30 AD, respectively. These periods broadly coincide with the late Holocene strengthened Indian Summer Monsoon (ISM), Medieval Warm Period (MWP) and the early part of the Little Ice Age (LIA). The debris which clogged the course of the river in the vicinity of the Chandubi Lake is attributed to tectonically induced increase in sediment supply during high magnitude flooding events.

The Tehri Dam is located in a seismotectonically active region in the Indian Himalayan belt. This 260.5 m high dam has a live water storage of 2615 × 106 m3 and is capable of generating crustal deformation corresponding to water fluctuation. Filling of the reservoir started in October 2005. Seismic data around the dam between 2000 and 2010 shows that seismicity is corresponding to drawdown levels of the reservoir rather than to higher water levels. GPS data at twelve local benchmarks were collected from 2006 to 2008 during filling and drawdown reservoir levels. The velocity vectors show ground motion to be between ∼0.69–1.50 mm in the different filling-drawdown cycles with reference to the permanent station at Ghuttu. The motion appears to be inwards into the reservoir when the reservoir is filled and outwards when the reservoir is drained. This ground motion corresponds to elastic deformation and rebound due to effect of the oscillating water levels.

Stress accumulated in rocks in tectonically active areas may manifest itself as electromagnetic radiation emission and temperature variation through a process of energy transformation. Land surface temperature (LST) changes before an impending earthquake can be detected with thermal infrared (TIR) sensors such as NOAA-AVHRR, Terra/Aqua-MODIS, etc. TIR anomalies produced by 10 recent earthquakes in Iran during the period of Jun 2002–Jun 2006 in the tectonically active belt have been studied using pre- and post-earthquake NOAA-AVHRR datasets. Data analysis revealed a transient TIR rise in LST ranging 2–13°C in and around epicentral areas. The thermal anomalies started developing about 1–10 days prior to the main event depending upon the magnitude and focal depth, and disappeared after the main shock. In the case of moderate earthquakes (

During the morning (03:50:40 UTC) of 8 October 2005 a major (M w 7.6) shallow focus (26 km) earthquake struck Kashmir (Himalayan region). Its epicentre was located 10 km NNE of Muzaffarabad (USGS 2005, Magnitude 7.6-Pakistan, available online at http://earthquake.usgs.gov/eqcenter/eqinthenews/2005/usdyae/). The present manuscript is an attempt to study the development of thermal anomaly in land surface temperature (LST) preceding this earthquake. Using data from Moderate Resolution Imaging Spectroradiometer (MODIS) onboard National Aeronautics and Space Administration (NASA) Terra satellite, the daily daytime LST images have been analysed for the correlation between LST variations and Kashmir earthquakes. An evident correlation of thermal anomaly in LST that is apparently related to pre-seismic activity has been identified. An attempt has also been made to quantify the change in LST (in °C) with reference to previous day temperature values and background data (MODIS LST data from 2000-2004). A 4-8°C rise in LST to the south of the earthquake epicentre has been observed seven days before the major event. Air temperature data from two meteorological stations (Islamabad and Srinagar) also supports the observations made through MODIS LST data. The role of terrain parameters like rock types, vegetation and topography upon the spatial and temporal variations of anomalous temperature area have been studied.

In India, the Indo-Gangetic plain (part of Northern India) is invariably affected by dense fog in the winter months every year due to typical meteorological, environmental and prevailing terrain conditions. Pollution also plays an important role in the formation of fog (smoke+fog = smog) in India. Using National Oceanic and Space Administration-advanced very high resolution radiometer data the fog-affected regions in Northern India were delineated and the spatial extent of fog for the winter months of the years 2002-03, 2003-04 and 2004-05 (December-February) were studied and mapped. Forecast for future fog based on the analysis of satellite and meteorological (air temperature, relative humidity and wind speed) data was also done. The fog-affected areas were classified into maximum-fog-affected area, moderately fog-affected area and least fog-affected area. It has been found that in the winter months of the years 2002-03, 2003-04 and 2004-05, the fog-affected area in Northern India was about 867 000 km2, 625 000 km2 and 706 800 km2 respectively. The maximum fog-affected area was found to be 606 400 km2, the moderately fog-affected area was found to be 230 400 km2 and the least fog-affected area was found to be 404 500 km2. Further, based on meteorological parameters, such as temperature, humidity and wind speed along with elevation data was used to derive an approach for future fog prediction in this region.

All Sun-synchronous remote sensing satellites, during day passes always acquire images when the illumination source (i.e. Sun position) is from the SE direction. The typical solar-illumination-source-observer position creates a false topographic perception phenomenon (FTPP) in the images of any rugged terrain (e.g. Himalayas, Alps etc.). Due to the presence of FTPP, valleys appear as ridges and vice versa, especially in rugged terrain. The correction of FTPP is necessary because it creates confusion in the minds of interpreters due to inherent inverse topographic perception. This paper explains the development of a new approach to remove FTPP. It has been successfully demonstrated using an IRS-1D-LISS-III image of part of the Himalayas, which represents highly rugged terrain. In this newly developed image-processing technique; a red-green-blue (RGB) image is first transformed into intensity-hue-saturation (IHS) channels, then the original intensity channel is inverted and later retransformed back from an IHS to a RGB image. After this retransformation, the RGB image is then colour balanced with original false colour composite. The final image product is free from FTPP and also contains almost the same image information. This method is an easy and quicker method to remove FTPP in comparison to the already available methods (e.g. image rotation by 180°; creating an image negative; using an opposite illuminated shaded relief model as an intensity image during IHS to RGB retransformation) for FTPP correction. Further, this paper discusses the relative advantages of this new method in comparison to previous methods in light of image classification and lineament interpretation carried out using images with and without FTPP.

Stresses acting before an earthquake in tectonically active regions can augment the near ground temperature of the region. Such changes detected through thermal remote sensing can provide important clues about future earthquakes. A post‐earthquake analysis through NOAA‐AVHRR data showed pre‐earthquake thermal anomalies prior to the Bam earthquake on 26 December 2003 and the Dahoeieh‐Zarand earthquake on 21 February 2005 in Iran. It was observed in these earthquakes that there was short‐term temporal increase in land surface temperature (LST) of the regions around the epicenters. The rise in temperature was about 5–10°C. Further, temperature variation curves prepared from air temperature data collected from several meteorological stations around epicentres confirmed the appearance of thermal anomalies prior to several earthquakes between February and March 2005 in Iran. The thermal anomalies went away along with the earthquake events. Release of greenhouse gases from rocks due to the induced pressure befor...

On 21 May 2003, Algeria was hit by a powerful shallow focus earthquake of magnitude Mw = 6.8 (http://neic.usgs.gov/neis/bulletin/03_EVENTS/eq_030521/) at 18:44 (UTC) which led to the death of 2276 ...

Generally, almost all Sun‐synchronous satellites' orbits are designed in such a way that their equatorial crossing timings are during morning hours (normally between 09:30 to 10:30 hours). Remote s...

Digital elevation model (DEM) is a storehouse of a variety of hydrological information along with terrain characteristics. In recent years, automatic extraction of drainage network from DEM with the help of Geographical Information System (GIS) has become possible and is now being practised the world over for hydrological studies. In the present study, a comparative analysis of the drainage network derived from DEM and drainage extracted from surveyed topographical maps has been carried out. A comparative analysis based on nearest neighbour analysis on an intersection theme of two drainage networks showed that there is clustering (randomness

Study of quantitative morphometric parameters was taken up in four major river valleys in the southern part of Shillong Plateau using SRTM DEM in GIS. The study indicates that the region is undergoing differential uplift. This is evidenced by preferential tilting towards east, while the central part of the plateau exhibits higher rate of uplift than the eastern and western segments. We ascribed the higher rate of uplift in the central segment of Shillong Plateau to the activity along the Dapsi Thrust and Dauki Fault.

‘Himalaya’ means ‘abode of snow’—a term coined by the ancient pilgrims of India who travelled in these mountains. The Himalayas, home to the top 10 highest peaks in the world including the Mount Ev...