M. G. Thakkar

Paleoclimatology, Geology, Geomorphology

Ph. D. in Geology
20.48

Publications

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    ABSTRACT: The Kutch region of western India (Gujarat State) is today arid to semiarid and characterised by mostly ephemeral streams which carry water during the monsoon. The uneven distribution of rainfall and disturbed topography are the result of climate change during the Cenozoic period. Two fossil woods, namely Bauhinium palaeomalabaricum Prakash and Prasad (Fabaceae) and Ebenoxylon indicum Ghosh and Kazmi (Ebenaceae), are described from Kutch in order to provide insights into the palaeovegetation and palaeoclimate. Because the modern representatives of the present and previously described taxa from the same horizon are thermophilic in nature and grow in evergreen to deciduous forests, a warm and humid climate is interpreted. Furthermore, the finding of some mangrove taxa in the assemblage indicates the lagoonal to intertidal environment at the time of deposition.
    Historical Biology 12/2014; DOI:10.1080/08912963.2014.917088 · 0.99 Impact Factor
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    Shukla Zankhna, and, Thakkar M. G.
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    ABSTRACT: Paleochannels are remnants of stream channels cut in older sediments and filled by younger overlying sediments representing the distribution of valley systems as these existed at given geological time in the past. Reconstruction of paleodrainage network in Mainland Gujarat using remote sensing techniques has a societal relevance as the information is utilized as groundwater prospective zones and suitable sites for artificial recharge. Alluvial plain of Gujarat is a unique geomorphic province that constitutes hundreds of meters thick alluvial sediment making the region fertile and hospitable to many historic cultures of Gujarat. In the present study, we used IRS-LISS-III images for extracting information on geomorphology, vegetation cover and lineaments. The study carried out between Siddhpur in the East to the Little Rann of Kachchh (LRK) to the West forming West sloping narrow E–W stretching belt. Available groundwater, rainfall, irrigation practice, crop pattern, agriculture and soil data of last 15 years are superimposed with the Remote Sensing data gives a better understandings of potential Palaeochannels and aquifer zones. In spite of good rainfall in the area, the surface water tanks do not store adequate amount of water for irrigation purpose due to sandy and loamy soil type. It indicates good percolation power of the soil; where the rainwater when flows on very gentle ground with highly permeable soil cover, spars vegetation and scanty drainage systems, they constitute short-lived reservoirs and can readily recharge ground water. Hence, it is stated based of the palaeochannel study that in the alluvial terrain they could be a potential source of groundwater, irrigation and recharge structures and finally a good thrust area for economic growth. Key Words : Paleochannels, Saraswati River, IRS (Indian Remote Sensing), Groundwater recharge, Alluvial plain
    Journal of Environmental Research And Development 12/2014; 9(2):472. · 1.61 Impact Factor
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    Shukla Arjav, Thakkar M. G.
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    ABSTRACT: advantageous and predictive application to study the behavior and estimation of local sites. The fundamentals of site response studies are to estimate the response of a particular site to seismicity in the earthquake prone regions. In recent years, a sum up of specified relative techniques and operations for microzonation in reference of site response has been established. The relative techniques for microzonation studies in civil engineering practice are Ambient Noise measurements, Multichannel Analysis of Surface Waves (MASW), Borehole Logging (PS Logging) etc. have been established to validate the response of a particular site to seismicity. Ambient Noise measurement practice is relatively an inexpensive technique for microtremor recording in site response study, apart from other relevant microzonation practices. The seismic vibrations and emplacements of ambient noise oscillations due all three horizontal to vertical (H/V ratio) components are characterized by dominant soil properties of the particular site. Since the region of Kachchh is considered as intra-plate seismic zone, site response studies are required to be undertaken. The Kachchh basin has short recurrence for large to strong earthquake, hence the vulnerability study in urban, semi-urban and coastal industrial regions are needed to mitigate seismic hazard. In the present study a geophysical instrument, City Shark-ІІ is used to carry out the ambient noise measurement survey. The site response data collected from varied rock units of Kachchh including sandstones, limestones and shales of Mesozoic to Cenozoic time. Further, the data also collected from soft sediments of the plain of Banni and the Great Rann of Kachchh to understand frequency amplitude variation in varied deposits. It is found that soft sediments show more amplitude variation compared to the hard rocks, irrespective of the hard rock lithologies and gain of the microtremor recorder. Hence, the sites, which are places on Quaternary sediments with > 3m thickness and hard rock basements, are vulnerable for seismic hazards in active intra-plate basin like Kachchh. Key Words : Ambient noise, H/V Ratio, Microzonation, Kachchh Seismic Zone, City Shark-II, Seismic hazard
    Journal of Environmental Research And Development 12/2014; 9(2):446. · 1.61 Impact Factor
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    M. G. Thakkar, Kajal Chhaya
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    ABSTRACT: Existence of all living beings on our planet has reasons to be or not to be. Beyond it also has a reason for non-living elements on our planet or cosmic elements in this universe, which we know or all unknown to our mind even though it is fact that every creation is living element. The harmony is governed by some media, though it is amongst the human beings, within animal or plant kingdoms or within various spheres exists on earth. We may assign it as a way of communication or interaction or integration but that medium is the force of transformation and modification of forms in the cosmos. Music as a complex and varied form of sounds has a mystic and eternal effect on human cyclic psyche and same as for all creations, but we may not percept. They too play with this form of energy, so as all kingdoms. The conception of the world to universe cannot be as exception that the sound dominate or influence on their subsistence. The essence of this piece of study lies in the strong influence of a harmonized and complex forms of sound as Ragas known in Indian music that effectively stimulate physical, physico-chemical and bio-chemical reactions through the medium of abstract form of human psyche and surrounding context. The Ragas as a perfect form of harmonized and rythmized group of naad, strongly related to perceptions of our minds. As speech and words are coded sounds that make suggestions and that controls all human beings and other living kingdoms too. Ragas could be eternal suggestions with no specific codes as universal harmony may not be codified but to percept. The total cosmos as a larger unit, believed to be formed with a big sound that enforce the elements to unite, disperse to transform or to make the complex elemental world that of ours. Each form of sound, element and compound has a special sound attached with, so as each human beings. Hence, a way of performing a harmonized complex group of sounds influence on abstract sphere of the human beings to the physical forms of energy exists in the entire universe. With years of experiments on various ragas and their strong influence on humans’ psyche, the authors have construed that the sounds/ the ragas govern the human relations, controls over all the living, physical to abstract reactions and that of entire cosmos. Key Words : Ragas, Human psyche, Cosmic reactions, Plant kingdom, Mystic
    Environmental Research Letters 07/2014; 9(1):260-270. · 4.09 Impact Factor
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    ABSTRACT: The tectonically active Kachchh peninsula in western India lies in the southwest monsoon trajectory and hence provides a rare opportunity to decipher the temporal changes in climate–tectonics interaction in the evolution of the fluvial landforms. Reconstructions based on geomorphology, sedimentology, and geochemistry supported by optical chronology suggest that the fluvial aggradation in the region was initiated during the onset of the Indian Summer Monsoon (ISM) after the Last Glacial Maximum (LGM). The sedimentary characteristics and major elemental concentrations suggest that the sediments are dominated by fluvially reworked miliolites with subordinate contribution from the Mesozoic sandstones and shales and were deposited with the initiation of the ISM after the LGM. Temporal changes in facies architecture and major element concentrations suggest a progressive strengthening of the monsoon between 17 and 12 ka. This was succeeded by an overall strengthened ISM phase with fluctuations after 12 ka and <8 ka. Following this, a gradual decline in the ISM is inferred until around 3 ka. However, presence of the younger valley-fill sediments which are dated to ∼1 ka are ascribed to a short-lived phase of renewed strengthened ISM in the region before the onset of present day aridity. Based on the morphology of the fluvial landforms, two major events of enhanced uplift can be suggested. The geomorphic expression of the older uplift event dated to >17 ka is represented by the beveled Mesozoic bedrock surfaces which accommodated the post LGM valley-fill aggradation. The younger event of enhanced uplift which is assigned to <3 ka was responsible for the incision of the fill sediments and the Mesozoic bedrock, and the evolution of the present day fluvial landforms. The time averaged incision/uplift rate indicates that the Katrol Hill Range is uplifting at the rate of ∼4 mm per year, implying seismically active terrain.
    Quaternary International 05/2014; 333. DOI:10.1016/j.quaint.2014.03.002 · 2.13 Impact Factor
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    ABSTRACT: A channel fill sequence in the upper catchment of the Khari river in the south of the Katrol Hill Fault (KHF) has been investigated to understand the role of climate and tectonics in the evolution of fluvial land-forms. Detailed sedimentology and limited optical chronology suggest that the channel incision occurred during weak summer monsoon (prior to 19.9 ka) and is attributed to the activity along the KHF and its subsidiary faults. The post-glacial to early Holocene was a phase of landscape stability (subdued tectonics) which persisted until around 7.1 ka. Particularly, between 9.4 ka and 7.1 ka, an enhanced monsoon activity is inferred. A renewed phase of uplift is suggested after 7.1 ka that probably continues till present.
    Journal of Asian Earth Sciences 09/2013; 73:114-120. DOI:10.1016/j.jseaes.2013.04.030 · 2.83 Impact Factor
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    ABSTRACT: Verma P, Mandal N, Rao MR, Thakkar MG & Bajpai Sunil 2013. Palynological record from Chhasra Formation (Early Miocene), Eastern Kutch, Gujarat. The Palaeobotanist 62(2): 149-155. A moderately diverse palynoflora consisting of angiospermous pollen and pteridophytic spores has been recorded from poorly known Chhasra Formation (Early Miocene) exposed in a section near Palasawa in eastern Kutch, Gujarat, western India. Dinoflagellate cysts are absent in the section, whereas the fresh water Centropyxis, a testate amoeba, is recorded. Among the important genera recovered are: Ericipites. Preliminary qualitative and quantitative assessment reveals the dominance of angiospermous pollen grains over pteridophytic spores, and an overall warm and humid coastal climate with tropical rain forest in a lowland coastal setting. Ongoing work in this newly identified section may reveal greater insights into diversity and significance of the Chhasra palynoflora.
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    ABSTRACT: We report here the development of a drainage network following the 1819 Allah Bund earthquake in the western Great Rann of Kachchh. The juvenile nature of the drainage network, particularly along the scarp, indicates that earth surface processes have not yet attained equilibrium with the base level even after 200 years. Hence it serves as an ideal model of resurrection of topography dominantly controlled by the tecto-nics. Another important observation has been the identification of a submerged/subsided tax collection port around 60 km southwest of Sindri. Optical dating of pottery indicates that the subsidence is coeval with that of the Sindri fort. This would imply that during 1819 there were two subsiding areas separated by a marginally high land mass (Sunda high). In the absence of detailed structural data, a preliminary inference has been drawn based on field and satellite data. It suggests flexure folding of the footwall during the 1819 earthquake. THE Kachchh rift basin is passing through the rift reversal phase in response to the compressive stresses active on Indian plate 1. The salt-encrusted terrain known as Ranns of Kachchh are recent depositional basins within the structural depressions resembling half graben formed during the later phase of uplift 2,3. The Ranns existed as a shallow embayment and inlets of the sea from the Terti-ary until Recent 4–6. Nevertheless, in the last 2 ka, silting of the area, probably accompanied by elevation of the land has converted the marine embayment into dry salt-covered mud flats slightly above the tidal range of the Arabian Sea 7. The present observations pertain to the geomorphological changes that have occurred after the 1819 earthquake in the western Great Rann (Figure 1). We have attempted to find a mechanism that could be responsible for regional topographic changes in a single earthquake of large magnitude in intra-plate settings and the response of erosion over the rejuvenated landscape. There are historical evidences to suggest that the Great Rann witnessed moderate to strong earthquakes. For example , earthquakes of AD 893 and AD 1668 were reported to be severe, which occurred to the north and northwest of the Great Rann in Sind area, Pakistan 8,9. Their impact on the terrain morphology is still uncertain. Compared to this, the 1819 Allah Bund earthquake estimated to be of M w 7.9 that occurred within the western Great Rann, uplifted the 80 km long and 16 km wide region of the Rann 8,10–12. It has uplifted the Rann sediment to variable heights (3–6 m) and obstructed the Nara River till 1826 (refs 9 and 11). Besides causing large-scale devastation in the Kachchh region, a coseismic Sindri depression was created against the uplifted land mass which led to the submergence of the Sindri fort 9 (Figure 1). During monsoon , the depression is inundated by sea water pushed inland by the storm-induced tides of the Arabian Sea from the west and southwest. Frequent inundation and evaporation led to the formation of vast salt-encrusted land masses 10,13. The only detailed description on the post-1819 earthquake-induced landform changes was attempted by Rajendran and Rajendran 9 with emphasis on the scarp morphology and seismically induced deformations. In this communication, we have studied the evolution and modification of the drainage network in the vicinity of Allah Bund scarp and ascertained the regional impact of the 1819 earthquake, particularly on the less studied southwestern part, viz. the Kori Creek area (Figures 1 and 2). Carless 14 surveyed the area between Koteshwar and Lakhpat and concluded that compared to the mainland Kachchh, the Kori Creek (deltaic area) was depressed after the 1819 Allah Bund earthquake. He also mentioned two ruined forts; one proximal to Lakhpat was attributed to the 1819 earthquake, whereas the other lying at the western bank of Kori Creek called the Basta Bunder was destroyed prior to the 1819 earthquake. A systematic study is warranted in the Kori Creek that lies ~60 km southwest of the Sindri depression to understand the style of deformation and extent of the 1819 earthquake-induced landform changes (Figure 1). The south-facing Allah Bund scarp owes its genesis to the north-dipping thrust that was activated during the 1819 earthquake 9,15,16. The northern hanging wall is dominated by young gullies and ravines, whereas the southern footwall is frequently occupied by marine ingression during monsoon (Figure 2). Some of the streams follow the regional tilt (towards north), but majority of them tend to incise the uplifted scarp in order to meet the Nara River bed. The Nara River has attained the local base level of the Sindri depression over the last 200 years. Compared to this, the juvenile streams are still in the process of attaining the equilibrium profile of the 1819 uplifted terrain. Further, based on the headward extent of incision, we could demarcate the northern limit of coseismic uplift, which seems to vary between 3 and
    Current science 06/2012; 103(2):208-212. · 0.83 Impact Factor
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    ABSTRACT: This study is an attempt to reconstruct the history of sedimentation and landform evolution in the western Great Rann of Kachchh. Field stratigraphy, sedimentology, geochemistry, optical and radiocarbon dating suggest dominance of tidal flat sedimentation with subordinate contribution coming from the southern-draining streams during 5.5 to 2 ka. Variability in the geochemical proxies are interpreted as a surrogate for tidal energy (viz. Zr and Cr) which, along with the major elemental ratios (TiO2/Al2O3 and K2O/ Al2O3), indicate enhanced tidal energy condition during 5.5 to 5 ka and around 3 ka. A close correspondence of the major and trace elements with those of the Indus River sediment and the dominance of illite suggest the Indus River was a major contributor for western Rann sedimentation during the mid-Holocene. These sediments were routed through the Kori Creek during marginally high sea level until around 2.2 ka and the present landscape was largely sculptured after the 1819 Allah Bund earthquake.
    Geomorphology 05/2012; DOI:10.1016/j.geomorph.2012.01.018 · 2.79 Impact Factor
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    ABSTRACT: The liquefaction attributes and crater geometry related to 2001 Bhuj earthquake has been reconstructed by trenching along large known craters formed near Umedpar in Kachchh. The study characterises the liquefied sediments in a large reactivated crater and distinguishes it from a non-reactivated crater located nearby. These characteristics can help in the interpretation of large paleocraters formed as a result of earthquake induced liquefaction.
    Journal of the Geological Society of India 04/2012; 79(4). DOI:10.1007/s12594-012-0057-4 · 0.51 Impact Factor
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    Current science 01/2012; · 0.83 Impact Factor
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    Himansu Kumar Kundu, M. G. Thakkar
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    ABSTRACT: Elemental concentrations of U, Th and K were determined using alpha counter and gamma-ray spectrometer to study the natural environmental radiation over a wide tectonically active region of Khari river basin in Kachchh, western India. Activity concentrations of 238U, 232Th and 40K estimated in different types of sediments deposited/relocated in the Khari river cliff due to neotectonic activity near Bharasar (23°11′36.5″N, 69°35′22.6″E) and Kodki transverse fault (23°14′37.37″N, 69°34′59.99″E) near Bhuj in the Khari River basin. Distribution of these radioactive elements on the earth’s surface is controlled by geological features like faults, shear zones, metamorphism etc. Mainland Kachchh has two E–W trending major faults viz. Kachchh Mainland Fault and Katrol Hill Fault, which exhibits evidences of active tectonics during Quaternary. Kodki transverse fault is one of several NNE-SSW and NNW-SSE trending transverse faults affecting the Katrol Hill Range. The River Khari flows from the Katrol Ridge and traverses through Cretaceous sediments of Bhuj Formation (fluvio-deltaic, comprised dominantly of sandstones) in its course. All the three tectonically relocated sediments in the Khari river cliff have similar 238U and much lower 232Th activity concentration values corresponding to the worldwide median values of 35 and 30 Bqkg−1, respectively, while 40K activity concentrations were quite lower for two sediments and almost similar for the scarp-derived colluvium compared to the worldwide median value of 400 Bqkg−1. Kodki transverse fault, however, has higher 238U and 232Th and almost half of 40K activity concentration values relative to the worldwide median value.
    Journal of Radioanalytical and Nuclear Chemistry 10/2011; 290(1). DOI:10.1007/s10967-011-1200-1 · 1.42 Impact Factor
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    ABSTRACT: In the central region of Mainland Kachchh, Western India, the Katrol Hill Fault (KHF) is one of the major E-W trending faults. An understanding of the episodes of reactivation during the past has a bearing on the future seismicity in the region. These reactivations are manifested by offset of elevation of fluvial sediments and scarp-derived colluvium in the Khari River basin, SE of Bharasar (23º11'36.5"N, 69º35'22.6"E). Stratigraphic offsets of the sediments at this site suggest three episodes of reactivation of the KHF during the late Quaternary. Optical dating of samples from sediment strata and top layer of scarp-derived colluvium using Natural Sensitivity Corrected – Single Aliquot Regenerative (NCF-SAR) protocol suggested that these events occurred during the past ~30 ka, with the most recent historic episode around 3.0 ka. Given that a part of the slip recorded in the form of sediments offset, was lost due to erosion after faulting, a lower bound to the time averaged slip rate of the segment of KHF, is inferred to be > 0.23 mm/a during the past 30 ka.
    Geochronometria 01/2010; 37:21-28. DOI:10.2478/v10003-010-0018-0 · 1.24 Impact Factor
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    ABSTRACT: The present study attempts to describe the geomorphic peculiarities of the Little Rann sedimentary basin. The Little Rann is a unique terrain located in the southeastern part of the seismically active Kachchh palaeorift graben and represents the uplifted floor of a former gulf that existed upto ∼2 ka B.P. In general, the surface of the Little Rann is a flat, almost gradientless expanse that is dotted by several islands. Two linear E-W trending belts of islands, with faults at their southern margin and exposing rocks of late Cretaceous age, are the most significant features of the Little Rann. Based on this, the Little Rann basin is divided into three tectonogeomorphic zones. One is the Outer subbasin that opens to the Gulf of Kachchh in the SW while the Central subbasin and the Inner subbasin are located successively to the north. The outer line of bets particularly the Keshmari bet and the Bhangarwa bet are characterized by well developed wave cut cliffs at their southern margins. The formation of the wave cut cliffs on the southern margins of the islands of the outer belt is conformity with the present day Gulf of Kachchh to the SW of the Little Rann basin. It is envisaged that the Outer subbasin was occupied by a shallow sea that had considerable erosive energy. However, the erosive energy of the waves did not extend further north as the outer belt of islands provided an effective barrier to the waves coming from the open sea towards the SW. We also believe that the Outer subbasin was possibly the deepest part of the basin and therefore may have preserved the maximum thickness of Holocene shallow marine sediments. The Central subbasin may have been shallower while the Inner subbasin formed the shallowest part of the basin as evidenced by the presence of large number of randomly arranged islands. Geomorphic evidence from the Little Rann, including the islands, point to strong control of subsurface structural elements, which influenced the Holocene palaeooceanographic conditions and the marine sedimentation as well. The strong control of structural set up of the South Wagad Fault System (SWFS) on the tectonogeomorphic setting of the Little Rann reveals its potential for neotectonic and seismotectonic studies for unraveling the seismic history of the Kachchh palaeorift.
    Zeitschrift für Geomorphologie 02/2009; 53(1):69-80. DOI:10.1127/0372-8854/2009/0053-0069 · 0.66 Impact Factor
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    Journal of Coastal Research 05/2008; 24(3):746-758. DOI:10.2112/05-0500.1 · 0.76 Impact Factor
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    ABSTRACT: The Mw 7.7 2001 Bhuj (Kachchh) earthquake was not associated with any primary surface rupture, but it produced secondary faulting, folding and liquefaction. This study highlights the potential of a secondary rupture and proxies like lateral spreads and sandblows in unraveling the past activity related to the 2001 source. Chronological constraints of an older lateral spread and far-field paleoliquefaction features, combined with archeological data, provide evidence for occurrences of two previous earthquakes at the 2001 source zone about 4000 and 9000 years, ago. Distinct stratigraphic evidence for at least one previous offset dated at 4424 ± 656 years could be detected at a stepover zone associated with a dextral secondary fault, reactivated during the 2001 earthquake. The studies imply longer interseismic intervals for the 2001 source zone, in comparison with the source zone of the 1819 earthquake located toward the northwestern part of the Rann of Kachchh. The spatial and temporal correlation of previous events derived on the basis of the available paleoseismic data from the region suggest not only repeated activity at the 2001 source, but possibility for additional potential sources in parts of Kachchh and Cambay basins. Although we infer a longer recurrence interval for the 2001 Bhuj earthquake source, our study points to the fact that these additional sources may have the potential to rupture in the future, considering the long elapsed time.
    Journal of Geophysical Research Atmospheres 01/2008; 113(B5). DOI:10.1029/2006JB004845 · 3.44 Impact Factor
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    ABSTRACT: The largely rocky and rugged landscape of the Katrol hill range, composed of Mesozoic rocks and structurally controlled occurrences of Quaternary sediments, is delimited to the north by north-facing range front scarps of the seismically active E–W trending Katrol Hill Fault (KHF). The landscape and drainage characteristics of the Katrol hill range are documented together with ground penetrating radar (GPR) investigations along the KHF to delineate its nature for understanding neotectonic activity in the contemporary tectonic setting. The overall geomorphology is controlled by the south oriented tilt block structure of the range, indicated by its pronounced influence on the morphology and drainage network. The drainage comprises north-flowing and south-flowing rivers with the drainage divide located close to the northern edge of the range, which also marks the highest topographic elevations. The narrow zone between the crest line and the drainage divide has been identified as the zone of gorges, where gorges and deeply incised fluvial valleys have been formed within Quaternary sediments by the various north-flowing streams. The Quaternary sediments consist of bouldery colluvial deposits in front of the range front scarps, valley fill miliolites and alluvial deposits of late Pleistocene age within the back valleys and scarp-derived colluvium forming the youngest deposit.Based on the geomorphic and stratigraphic evidence, three major phases of Quaternary tectonic uplift in the Katrol hill range are inferred. The oldest pre-miliolite phase (middle Pleistocene) was followed by a prominent phase of fluvial incision with formation of gorges during early Holocene, and then by the last one during late Holocene, continuing at present. Uplift of the range occurred in well-marked phases during the Quaternary in response to differential uplift along the KHF under an overall compressive stress regime. GPR investigations at selected sites show that the KHF is a steep south-dipping reverse fault near the surface, which becomes vertical at depth. This suggests neotectonic reactivation of the KHF under a compressive stress regime, responsible for active southward tilting of the Katrol hill range.
    Quaternary International 01/2007; 159(1):74-92. DOI:10.1016/j.quaint.2006.08.013 · 2.13 Impact Factor
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    ABSTRACT: The 2001 Bhuj earthquake (Mw 7.7) formed several medium to large sand blow craters due to extensive liquefaction of the sediments comprising the Banni plain and Great Rann of Kachchh. We investigated two large closely spaced sand blow craters of different morphologies using Ground Penetrating Radar (GPR) with a view to understand the subsurface deformation, identify the vents and source of the vented sediments. The study comprises velocity surveys, GPR surveys using 200 MHz antennae along three selected transects that is supplemented by data from two trenches excavated. The GPR was able to provide good data on stratigraphy and deformation up to a depth of 6.5 m with good resolution. The GPR successfully imaged the subsurface characteristics of the craters based on the contrasting lithologies of the host sediments and the sediments emplaced in the craters. The GPR also detected three vertical vents of ∼ 1 m width continuing throughout the profile which are reflected as high amplitude vertical events. We conclude that the large sand blows during the 2001 Bhuj earthquake were produced due to liquefaction of sediments in the subsurface at > 6.5 m depth and that the clay-rich sediments of the Banni plain have behaved as the fine grained cap over it. The present study provides a modern analogue for comparing the liquefaction features of past great earthquakes (for example, the 1819 earthquake) that have occurred in the Kachchh region to understand the phenomena of liquefaction.
    Journal of Applied Geophysics 10/2006; DOI:10.1016/j.jappgeo.2006.02.001 · 1.30 Impact Factor
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    ABSTRACT: The 2001 Bhuj earthquake (Mw 7.7) formed several medium to large sand blow craters due to extensive liq-uefaction of the sediments in the clay sediments of the Banni plain and Great Rann of Kachchh. We investigated three large sand blow craters using Ground Penetrating Radar (GPR) with a view to understand the subsurface deformation , identify the vents and source of the vented sediments. The GPR was able to provide good resolution on stratigraphy and deformation upto a depth of 6.5 m. The GPR successfully imaged the subsurface characteristics of the craters based on the contrasting lithologies of the host sediments and the sediments emplaced in the craters. The GPR also detected vents continuing throughout the profile which are reflected as high amplitude vertical events. We conclude that the large sand blows during the 2001 Bhuj earthquake were produced due to liquefaction of sediments in the subsurface at >6.5 m depth. The study provides a modern analogue for comparing the liquefaction features of past great earthquakes. Keywords – Ground Penetrating Radar (GPR), liquefaction, sand blow crater, 2001 Bhuj earthquake, Kachchh, western India. I. INTRODUCTION The present study intends to demonstrate the applicability of the GPR in investigating large liquefaction features and provide modern analogues for comparing similar liquefac-tion features produced by past earthquakes. Liquefaction of subsurface sediments induced by high magnitude earthquakes produce large sand blows, however, their manifestations depend on local geologic and geographic setting (Sims and Garvin, 1995). GPR based studies on such features are important from the point of view of understanding the intricacies of internal and external geometry of the liquefaction features, which can be used for precise identification and characterization of the similar features produced by ancient earthquakes and locating the source of the sediments vented on the surface. Here, we present the
    11th International Conference on Ground Penetrating Radar, Columbus Ohio, USA; 06/2006

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