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We analyze the behavior of Total Electron Content (TEC) in the Ionosphere using the GPS data between 2009 and 2017 towards the western part of India. The GPS data used in the present study consists of 22 Continuously Operating Reference Sites (CORS), bounded between 200- 240 N Latitude and 680 - 740 E Longitude. All the GPS data used in the study are generated using the Leica 1200 receivers and AX1202GG antennas with a sampling interval of 0.03 Hz. The TEC value of this study is calculated using the L-band GPS frequencies L1 (1575.42 MHz) and L2 (1227.36 MHz). The results reveal maximum TEC values during the daytime (03.30–04.30 IST) for all the years and a maximum of 120 TECu (TEC unit) was observed during the year 2014. The reflection of seasonal variation was visible in the time-series of TEC in all the years, while E season (March, April, September and October) observed maximum TEC values in all the stations. The mean monthly TEC values of the present study illustrate the solar cycle-24 and the coefficient of correlation (r 2) of 0.74 indicates a close relationship between the sunspot number and TEC values. A fall of 35% TECu was observed on the annular solar eclipse day on 15 January 2010. [ABSTRACT FROM AUTHOR]

In this study, we present the first estimates of crustal deformation using the time series (2009–2015) from GPS Network of Gujarat (GNG), comprising 10 GPS continuous and 5 campaign mode stations in the seismically active Kachchh region. The GPS data were processed using GAMIT/GLOBK/GLORG software and results reveal very low amount of intra-plate deformation in this part of the Indian plate. International Terrestrial Reference Frame (ITRF) velocity of sites deduced in this study indicates 46–51 mm/yr of motion with one sigma uncertainty. A maximum of ≈3.0 ± 0.5 mm/yr of deformation has been estimated in the Kachchh region. However, estimated strain rate from the velocity field indicates a maximum strain of 5 nano-strain/yr. Our results indicate deformation of a weak zone, where earthquakes may trigger due to the combination of local as well as regional stress. The analysis of strain tensors near the major fault systems (KMF, KHF, SWF and GF) indicates strike normal compression in the area. The low rate of deformation, derived in the present study, is important to understand the seismic hazard level in this part of the Indian intra-Plate. [ABSTRACT FROM AUTHOR]

To understand the geodynamics in the vicinity of Dholavira, a Harappan Civilization Site (HCS), in Kachchh - western India, GPS data from 2009 to 2015 were processed and analyzed. Tectonically, this part of northern Kachchh is in the influence of Island Belt Fault (IBF) and Allah Bund Fault (ABF) and is seismically one of the most active intra-plate regions of India. The motion with respect to Indian plate is used for the estimation of deformation and strain rate while fault associated slip rate has been estimated by inverse modeling of observed site motions. The analysis reveals that the ABF deforms with an average rate of 1.8 mm/yr. However, the segmented IBF has a maximum deformation rate of 2.9 mm/yr towards the Pachham Island and minimum towards the Khadir Island. The computation discloses a maximum seismic moment (M 0) of 2.1 × 1024 dyne-cm in this part which corresponds to an earthquake of ≈Mw 6.0. The calculated maximum strain of 0.04 micro-strain/year is low but significant in the intra-plate region. The postseismic deformation, after the Mw 7.7, 2001 Bhuj earthquake is estimated to be low in this part. The reverse along with strike-slip motion of faults builds up stress in the area and accumulating more strain. [ABSTRACT FROM AUTHOR]

Paleoseismic and archaeological records of the Kachchh Rift Basin (KRB) of western India indicates that the region become tectonically active during the period of Middle to Late Holocene. To understand the relationship between strain accumulation, earthquake genesis, and landform development, we analyzed uplifted Late Quaternary terraces and archaeological evidence along the Kachchh Mainland Fault (KMF) zone. Dividing the elevation of the bedrock strath at each site by their ages, yields vertical uplift rates of 0.29–1.17 mm/y for the KMF zones. Archaeological data from the excavation of the Kotada Bhadli site suggest that the site was occupied during the Late mature Harappan (2300-2500 BCE) period and abandoned around 1900 BCE. The ruins of Harappan civilization at Kotada Bhadli location are resting over the Middle Holocene fluvial sediments. The oldest fluvial sediment is dated to 4 ka, whereas the youngest sediment yielded an age of 3 ka. The chronological constraints in geomorphic and archaeological records suggest that the area was hit by an earthquake around 2200 BC (∼3.5ka). The geomorphic and chronologically constrained uplift rates reveal that the KMF zone of the intraplate region of the Kachchh is geodynamically controlled by several fault segments, which are consistent with the ambient tectonic stress field owing to the northward movement of the Indian Plate concerning the Eurasian Plate. [ABSTRACT FROM AUTHOR]

An earthquake of 2006 Mw 5.7 occurred along east–west trending Gedi Fault (GF) to the north of the Kachchh rift basin in western India which had the epicenter in the Wagad upland, which is approximately 60 km northeast of the 2001 Mw 7.7 earthquake site (or epicenter). Development of an active fault scarp, shifting of a river channel, offsetting of streams and uplift of the ground indicate that the terrain is undergoing active deformation. Based on detailed field investigations, three major faults that control uplifts have been identified in the GF zone. These uplifts were developed in a step-over zone of the GF, and formed due to compressive force generated by left-lateral motion within the segmented blocks. In the present research, a terrace sequence along the north flowing Karaswali river in a tectonically active GF zone has been investigated. Reconstructions based on geomorphology and terrace stratigraphy supported by optical chronology suggest that the fluvial aggradation in the Wagad area was initiated during the strengthening (at ~ 8 ka) and declining (~ 4 ka) of the Indian Summer Monsoon (ISM). The presence of younger valley fill sediments which are dated ~ 1 ka is ascribed to a short lived phase of renewed strengthening of ISM before present day aridity. Based on terrace morphology two major phases of enhanced uplift have been estimated. The older uplift event dated to 8 ka is represented by the Tertiary bedrock surfaces which accommodated the onset of valley-fill aggradation. The younger event of enhanced uplift dated to 4 ka was responsible for the incision of the older valley fill sediments and the Tertiary bedrock. These ages suggest that the average rate of uplift ranges from 0.3 to 1.1 mm/yr during the last 9 ka implying active nature of the area. [ABSTRACT FROM AUTHOR]