an insight into crack density saturation rate and porosity model of the 2001 bhuj earthquake in the stable continental region of western india abstract the 2001 bhuj earthquake mw 7 6 source zone is examined in the light of crack density e saturation rate and porosity parameter using new data set derived from a large aftershock sequence recorded by the gujarat seismic network gsnet during november 2006 december 2009 processes of rupture initiations of the mainshock and its aftershock sequence are better understood by synthesizing the dynamic snapshots of the source zone using the new dataset pattern of crustal heterogeneities associated with high e high and high anomalies at depths varying from 20 km to 25 km is similar to those of earlier study by mishra and zhao 2003 the anomalous zone is found extended distinctly by 50 60 km in the lateral direction indicating the reinforcement of cracks and fractured volume of rock matrix due to long aftershock sequence since 2001 bhuj earthquake in the source area it is inferred that the presence of a fluid filled fractured rock matrix with super saturation may have affected the structural and seismogenic strengths of the source zone and is still contributing significantly to the geneses of earthquakes in and around the source zone anomalous pattern of high e with wider distribution of high indicates the existence of micro cracks in the lower crust while high suggests the cementation of cracks through permeation of residual magma metamorphic fluids into the hypocenter zone the results suggest that the existence of residual fluids in the fractured rock matrix in the mid to lower crust might have played a key role in triggering the 2001 mainshock and is still responsible for its continued long aftershock sequences

subsurface profiling along banni plains and bounding faults kachchh western india using microtremors method the present article is a maiden attempt to map shallow subsurface rheological interfaces laterally across the banni plains and to decode geometry of the antecedent faults associated with the kachchh mainland fault using the microtremor method we conducted microtremor data acquisition for thirty one sites along n s transect from loriya in mainland kachchh to bhirandiara towards patcham island results from h v spectral ratio technique show presence of two distinct rheological interfaces characterised by the resonant frequency f r ranges 0 23 0 27 hz and 0 8252 1 5931 hz respectively the above frequency ranges are correlated with the depths of the mesozoic basement m b interface and the quaternary tertiary q t interface using either the velocity vs of seismic waves at the m b and q t interfaces calculated as 1830 m s and 411 m s respectively or the standard non linear regression relationship derived for the banni plains h 110 18f r 1 97 we estimate the depth range for m b interface to be 1442 1965 m and for q t interface to be 44 160 in the subsurface profile across the banni plains educe cluster of four faults that develop an array of imbricate faults at the forefront of the kachchh mainland fault within the banni footwall syncline the geometry of the faults suggests a positive flower structure indicating step overs and strain restraining bends displaying push ups resulting from localized shortening between converging bends of kachchh mainland fault and the south wagad fault the banni footwall syncline preserves evidence of two episodes of deformations the initial deformation event led to subsidence within the kachchh mainland fault zone bringing mesozoic sequence juxtaposed to the basement rocks whereas the later event is dominated by an uplift developing a positive flower structure in the kachchh mainland fault zone finally the present study provides a mechanism to investigate faults and fault geometries correlating surface structural grains with subsurface structures

ichnological evidence for quadrupedal locomotion in pterodactyloid pterosaurs trackways from the late jurassic of crayssac southwestern france abstract more than 30 well preserved pterosaurian trackways have been excavated from the site of crayssac lower tithonian southwestern france along with hundreds of isolated imprints the general pattern of pterosaurian trackways is described and corresponds to the morphology of the ichnogenus pteraichnus stokes 1957 a crocodilian origin for pteraichnus is rejected the morphology of the pes and manus prints is described and discussed and exhibits a great dynamic variability the three manus digit prints are confirmed as the marks of digits i iii but the high angle of divarication may reflect strong digit abduction as well as a backward folding of the digit iii the manus gait width is as much as 3 the pes gait width the narrowest manus trackways corresponds to low velocity walking in a semi erect stance whereas the widest manus trackways corresponds to higher velocity walking perhaps even running with a subhorizontal body

motion tracking of discontinuous sea ice the purpose of this paper is twofold 1 to develop a high resolution sea ice motion tracking system at the geospatial mesoscale 1 100 km2 and 2 to propose an algorithm that measures motion at close proximity to discontinuous regions here we present a motion tracking system that computes differential motion at 400 m resolution and validate the accuracy precision of this system via four studies the first study measures the accuracy against displacements measured from in situ global positioning system gps buoys deployed at the sea ice experiment dynamic nature of the arctic sedna and the surface heat budget of the arctic ocean sheba experiments the estimates are found to be statistically comparable with gps with an average error of 361 9 and 600 6 m for the experiments respectively the second study compares the estimated displacements to those measured by the radarsat geophysical processing system a precision error of 75 7 m is found between the two motion tracking systems the third study uses intensity warping of randomly sampled measurements to evaluate discontinuous motion tracking a one tailed wilcoxon signed rank test is used to validate these measurements at 0 01 results from this paper prove that anisotropic smoothing produces significantly smaller errors at discontinuous locations w 4240 and p 0 001 over conventional isotropic smoothing the fourth study compares displacements measured by anisotropic smoothing against manual measurements this paper demonstrates an average reduction of the estimation error by 50 m with the use of anisotropic smoothing over the conventional isotropic smoothing

palaeoichnology of an mis 3 cave bear settlement ursilor cave western carpathians romania abstract the palaeoichnology of the cave bear ursus spelaeus was studied at ursilor cave apuseni mountains romania to acquire new data about the ethology and the metrics of this extinct species eight stations containing footprints scratch marks and nests were surveyed using laser scanning to build tridimensional models for several cave bear nests wall scratch marks and footprints morphological observations were made using the models and precise measurements of the breadth or depth of the scratch marks were performed in addition 100 cave bear nests and 10 footprints were measured and analyzed the palaeoichnogical data were corroborated with previously obtained information on the taphonomy geomorphology sedimentology and geochronology from this site several bioglyphs e g scratch marks footprints were indirectly dated to marine isotope stage mis 3 by identifying and assigning them to co occurring cave bear skeletons as a consequence we stress the need for a multidisciplinary approach in order to assess the palaeoichnology of cave bear sites findings fill a gap in our knowledge because cave bear bioglyphs are one of the less studied branches of cave bear research due to the scarcity and fragility of ichnological features

variations of seismic velocities in the kachchh rift zone gujarat india during 2001 2013 abstract we herein study variations of seismic velocities in the main rupture zone mrz of the mw 7 7 2001 bhuj earthquake for the time periods 2001 05 2006 08 2009 10 and 2011 13 by constructing dvp dvs and d vp vs tomograms using high quality arrival times of 28 902 p and 28 696 s waves from 4644 precise jhd joint hypocentral determination relocations of local events differential tomograms for 2001 05 reveal a marked decrease in seismic velocities low dvp low dvs and high d vp vs in the mrz at 5 35 km depths during 2001 10 which is attributed to an increase in crack fracture density higher pore fluid pressure resulted from the intense fracturing that occurred during the mainshock and post seismic periods while we observe a slight recovery or increase in seismic velocities 2011 13 this could be related to the healing process lower pore fluid pressure due to sealing of cracks of the causative fault zone of the 2001 bhuj mainshock the temporal reduction in seismic velocities is observed to be higher at deeper levels more fluid enrichment under near lithostatic pressure than that at shallower levels fluid source for low velocity zone lvz at 0 10 km depths with high d vp vs could be attributed to the presence of meteoric water or soft alluvium sediments with higher water content while fluid source for lvz at 10 35 km depths could be due to the presence of brine fluids released from the metamorphic dewatering and volatile co2 emanating from the crystallization of carbonatite melts in the asthenosphere in fractures and pores we also imaged two prominent lvzs associated with the katrol hill fault zone and island belt fault zone extending from shallow upper crust to sub crustal depth which might be facilitating the deeper circulation of metamorphic fluids volatile co2 thereby the generation of lower crustal earthquakes occurring in the kachchh rift zone

true tracks undertracks and eroded tracks experimental work with tetrapod tracks in laboratory and field abstract to be able to distinguish between true tracks undertracks and tracks altered by erosion is of great importance in tetrapod track ichnotaxonomy this paper reports three experimental approaches to the study of undertracks using the footprints of an emu dromaius novaehollandiae experiment 1 describes successive horizontal sections down through a plaster cast of an emu footprint emplaced in soft mud revealing a steady downward decrease in the area of the track particularly the length this is the result of the movements of the trackmaking limb during impact forward swing of the body and final kick off experiments 2 and 3 describe vertical sections cut through footprints emplaced in packages of layered coloured cement admixed with water to produce different consistencies firm and semi fluid after hardening the cement block was serial sectioned vertically and removal of a lightly cemented layer gave access to two undertrack bedding plane views successive undertracks downward show an increase in horizontal dimensions and decrease in vertical topography of the structure representing gradual degradation of the track anatomy with depth in experiment 3 the true track at the tracking surface was deformed by collapse and flow of the substrate after withdrawal of the foot in this case the undertracks that were formed in layers subjacent to the foot reproduced the morphology of the foot more faithfully than did the true track

palaeoseismic investigations along the kachchh mainland fault a comprehensive review and new insights of the past earthquakes in the kachchh basin western india abstract the intraplate kachchh rift basin has been hit by several devastating earthquakes in the historic past including the 1819 allah bund earthquake and the 2001 bhuj earthquake the source region of these earthquakes within the basin have been studied by several workers in the last two decades to understand their potential for earthquake recurrence however very little information is available on the palaeoseismic and geomorphic characterization of kachchh mainland fault kmf therefore in the present study six trenches were excavated across the kmf between lakhpat and nirona to understand ground deformation pattern and timing of the historic earthquakes based on geomorphic and palaeoseismic investigations five palaeoearthquakes of early to late holocene have been identified between 10 000 890 yrs apart from the holocene an earthquake of late quaternary period was also identified which possibly occurred around 19 800 yrs bp fault related parameters were analyzed to understand the geometry of the active fault scarp along kmf the results of the analyzed fault geometric parameters show that the vertical displacement along the kmf is higher than the horizontal displacement the slip rate of the kmf from the western portion to the middle portion decreases from 0 08 to 0 04 mm yr and increases towards east from 0 22 mm yr to 0 36 mm yr as the kachchh district of the gujarat state is rapidly developing in terms of infrastructural development the outcome of this research might provide significant inputs for micro zonation studies and also in the evaluation of the seismic hazard in the kachchh region

a review and new data on neotectonic evolution of active faults in the kachchh basin western india legacy of post deccan trap tectonic inversion

transient electromagnetic investigations in a tectonic domain of the kachchh intraplate region western india a morphotectonic study of the kachchh mainland fault

crustal heterogeneities beneath the 2011 talala saurashtra earthquake gujarat india source zone seismological evidence for neo tectonics abstract during the 1st decade of the 21st century the study area of talala saurashtra of western india witnessed three damaging earthquakes of moderate magnitude year 2007 mw 5 0 mw 4 8 and in the year 2011 mw 5 1 that generated public panic in the region the last damaging moderate earthquake of the 20th october 2011 in talala region 21 09 n 70 45 e located at about 200 km south to the devastating 2001 bhuj 23 412 n 70 232 e mainshock mw 7 6 jolted the entire saurashtra region of gujarat a long series of aftershocks followed hereafter recorded at nine seismograph accelerograph stations hypocenters of aftershocks were relocated accurately using absolute and relative travel time double difference method in this study we for the first time determined 3 d tomographic images of the upper crust beneath the 2011 talala earthquake source zone by inverting about 1135 p and 1125 s wave arrival time data estimates of seismic velocities v p v s and poisson s ratio structures offer a reliable interpretation of crustal heterogeneities and their bearing on geneses of moderate earthquakes and their aftershock sequences beneath the source zone it is found that the 2011 talala mainshock hypocenter depth 6 km is located near the boundary of the low and high velocity v p v s and the source zone is associated with low anomalies guarded by the prominent high anomalies along the active fault zone having strike slip motion beneath the earthquake source zone the pattern of distribution of v p v s and its association with occurrences of aftershocks provide seismological evidence for the neo tectonics in the region having left lateral strike slip motion of the fault

results from local earthquake velocity tomography implications toward the source process involved in generating the 2001 bhuj earthquake in the lower crust beneath kachchh india to comprehend the source processes of the 26 january 2001 bhuj earthquake sequence of m w 7 7 and its influence on the seismic hazard of the kachchh we estimate various seismological parameters using reliable and accurate aftershock data the estimated parameters led to several important findings including the delineation of an east west trending south dipping 45 fault north wagad fault nwf which touches the surface about 25 km north of kachchh mainland fault kmf the aftershock zone is confined to a 60 km long and 40 km wide region lying between the kmf to the south and nwf to the north extending from 10 to 45 km depth focal mechanism solutions of the mainshock and 25 significant aftershocks of m w 3 0 obtained from waveform inversion of broadband data and local earthquake moment tensor inversion suggest that the region between the kmf and nwf is mainly characterized by reverse faults with east west trend and southerly dip matching with the geological faults in the region the tomographic inversion technique is used to invert 5516 p wave travel times and 4061 s p travel time differences from 600 aftershocks recorded at 8 18 stations tomographic results suggest a regional high velocity body characterized by high v p 7 0 8 5 km sec high v s 4 0 4 8 km sec and low 0 24 0 26 with a head extending 60 km in north south and 40 km in east west at 10 40 km depths this high velocity anomaly is inferred to be a mafic pluton rift pillow which might have intruded during the rifting time 135 ma this crustal mafic pluton must be contributing significantly in accumulating large crustal stresses resulting in the generation of large earthquakes in this intraplate area another important result of our study is the detection of a low velocity zone low v p 6 5 7 0 km sec low v s 3 6 4 0 km sec large 0 26 0 265 within the mafic body at the hypocentral depth of the mainshock 18 25 km which is inferred to be a fluid filled trapped aqueous fluid resulting from metamorphism fractured rock mass the analysis of depth distribution of b values suggests a high b value zone between 15 and 25 km depths which further supports this contention hence the presence of fluids at the hypocenter might have facilitated the occurrence of the 2001 bhuj earthquake within the inferred mafic body in the lower crust

magnetotellurics study to identify subsurface resistivity structure in the eastern part of kachchh little rann area of gujarat india a magnetotelluric mt survey has been conducted in the eastern part of the kachchh region of gujarat state crossing little rann starting from adesar village in the north to enjar village in the south where limited geophysical data is available the profile has been acquired in the n s direction having a total length of 52 km with the interstation spacing of 3 4 km from two dimensional 2d inversion of the mt data four conductive zones are identified the analysis reveals that the depth of the basement varies from 1 2 km in the south to 1 8 km in the north the first conductive zone is found at a distance of 3 km in the south of adesar and is identified at the location of the kanmer fault kf the eastern extension of south wagad fault swf and might be the kf the second conductive zone is found at a distance of 42 km in the south of adesar and 13 km north of enjar village and is located at the contact zone of kachchh and saurashtra peninsula at the location of the north kathiawar fault nkf it is inferred as the nkf the third conductive zone at a distance of 27 km in the south of adesar is found between the first and second conductor this is interpreted as a step fault formed during the rifting process of kachchh the lower crust below 20 km is found conductive 120 m and might indicate the presence of fluid filled mafic ultramafic rocks in the lower crust

three dimensional gravity modelling of kutch region india abstract understanding the crustal architecture of kutch rift region india is important due to the presence of thick mesozoic sediments and also due to occurrence of earthquakes we present here three dimensional gravity models the major features of our shallow crustal model are 1 thickness of deccan traps is almost negligible towards northern side of vigodi fault and katrol hill fault 2 mesozoic sediment thickness is about 3 km on the southern side and 3 several undulations in the basement on the wagad uplift the model is consistent with the geological observation that the basin slopes towards southwest the observed bouguer gravity anomalies are explained by 10 km thick granitic upper crust of 2 7 g cm 3 10 km thick intermediate mid crust of 2 82 g cm 3 15 km thick mafic lower crust of 2 91 g cm 3 density crustal thickness is about 40 45 km on wagad uplift and near katrol hill fault the modelled gravity data do not require presence of anomalous amount of fluids melts and or magma chambers in the deep crust of kutch region

reconstructing the evolution of cave systems as a key to understanding the taphonomy of fossil accumulations the case of ursilor cave western carpathians romania abstract the ursilor cave nw romania is a famous cave bear paleontological site hosting an important late pleistocene faunal assemblage and subject to systematic excavation works to better understand the origin of fossil assemblages the sedimentary history of the cave must be reconstructed we conducted a series of investigations on various cave deposits which included sedimentology and grain size analyses u series dating of speleothems osl dating of sediments and ams radiocarbon dating of fossil remains the results allowed for the identification of several major chronological controls for the evolution of the cave during the last 300 000 years five evolutionary stages or key moments were dated and a tentative speleogenetic scenario is presented the combined numerical dates and sedimentological study show that the evolution of the cave was more complex than previously thought in particular the fossil accumulation was related to a succession of rapid flooding events at 47 40 ka alternating depositional and erosional phases have occurred since at least 210 ka complicating the sediment structures the results suggest that the upper and lower levels of the cave may have been functioned occasionally as hydrologically separated karst systems and that the animal populations from what is now a single cave system may not necessarily be synchronous this case study shows that reconstructing sedimentary history of a given cave is crucial for the correct understanding of its thanatocenosis

electrical conductance map for the kachchh rift basin constraint on tectonic evolution and seismotectonic implications geomagnetic field variations recorded by an array of magnetometers spread across the kachchh rift basin are reduced to a set of induction arrows as a diagnostic of lateral electrical conductivity variations a non uniform thin sheet electrical conductance model is developed to account for the salient induction patterns it indicates that the imaged conductivity anomalies can be related to the sediment filled structural lows in between the fault bounded uplifts it is suggested that sagging structural lows preserved the marine sediments deposited during the mesozoic sea transgression and later developed into first order embayment basins for the deposition of sediments in association with late eocene transgression depth integrated electrical conductance helped in mapping two depo centres along the ene wsw trending banni half graben bounded by the kachchh main fault on the south and second along the vinjan depression formed in response to the subsidence between the vigodi fault and westward extension of the katrol hill fault together with the westward bending of the median high presence of metamorphosed graphite schist clasts in shale dominated mesozoic sequence and or thin films of carbon resulting from the thermal influence of deccan activity on carbonate rich formations can account for the high electrical conductivity anomalies seen in the depo centres of thick mesozoic and tertiary sediments additionally two high conductivity zones are imaged encompassing a block defined by the 2001 bhuj earthquake and its aftershocks in agreement with gravity magnetic and seismic velocity signatures aqueous fluids released by recrystallizing magmatic bodies intruded in association with deccan trap activity account for mapped high conductivity zones high fluid pressure in such a fractured domain surrounding the intruded magmatic plugs perturb the regional stress concentrations to produce frequent and low magnitude aftershocks in the shallow section of the epicentral track of the 2001 bhuj earthquake

subsurface profiling of granite pluton using microtremor method southern aravalli gujarat india we report using the microtremor method a subsurface granitic pluton underneath the narukot dome and in its western extension along a wnw profile in proximity of eastern fringe of cambay rift india the dome and its extension is a part of the champaner group of rocks belonging to the mesoproterozoic aravalli supergroup the present finding elucidates development of an asymmetric double plunge along narukot dome microtremor measurements at 32 sites were carried out along the axial trace n95 of the dome fourier amplitude spectral studies were applied to obtain the ratio between the horizontal and vertical components of persisting rayleigh waves as local ambient noise fundamental resonant frequencies with amplitude 1 sigma for each site are considered to distinguish rheological boundary two distinct rheological boundaries are identified based on frequency ranges determined in the terrain 1 0 2219 10 364 hz recorded at 31 stations identified as the champaner metasediment and granite boundary and 2 10 902 27 1119 hz recorded at 22 stations identified as the phyllite and quartzite boundary the proposed equation describing frequency depth relationship between granite and overlaying regolith matches with those already published in the literature the morphology of granite pluton highlights the rootless character of champaner group showing sharp discordance with granitic pluton the findings of manifestation of pluton at a shallower depth imply a steep easterly plunge within the champaner metasediments whereas signature of pluton at a deeper level implies a gentle westerly plunge the present method enables to assess how granite emplacement influences the surface structure

electrical imaging of deep crustal features of kutch india summary a regional magnetotelluric mt study was carried out with 55 mt soundings distributed along five traverses across the kutch mainland unit kmu on the west coast of india a region characterized by a series of successive uplifts and intervening depressions in the form of half graben bounded by master faults we obtain the deeper electrical structure of the crust beneath kutch from 2 d modelling of mt data along the 5 traverses in order to evaluate the geo electrical signatures if any of the known primary tectonic structures in this region the results show that the deeper electrical structure in the kutch region presents a mosaic of high resistive crustal blocks separated by deep rooted conductive features two such crustal conductive features spatially correlate with the known tectonic features viz the kutch mainland fault kmf and the katrol hill fault khf an impressive feature of the geo electrical sections is an additional well defined conductive feature running between jakhau and mundra located at the southern end of each of the five mt traverses and interpreted to be the electrical signature of yet another hidden fault at the southern margin of the kmu this new feature is named as jakhau mundra fault jmf it is inferred that the presence of jmf together with the kathiawar fault nkf further south located at the northern boundary of the saurashtra horst would enhance the possibility of occurrence of a thick sedimentary column in the gulf of kutch the region between the newly delineated fault jmf and the kathiawar fault nkf could thus be significant for hydrocarbon exploration

inversions for earthquake focal mechanisms and regional stress in the kachchh rift basin western india tectonic implications abstract more than a decade after the 2001 m w 7 7 bhuj earthquake in western india aftershocks up to m w 5 0 are still continuing around the rupture zone in the kachchh rift basin over the years some surrounding faults in the region have been activated and a transverse fault generated an m w 5 1 earthquake in 2012 most of the earthquakes occur in the lower crust at depths between 15 and 35 km we have determined focal mechanism solutions of 47 earthquakes m w 3 2 5 1 that were recorded by a 60 station broadband network during 2007 2014 within an area of 50 km radius of the 2001 main shock south dipping nodal planes in most of the solutions correlate well with the active faults the earthquakes near the epicenter of the 2001 main shock primarily show reverse faulting mechanisms the surrounding earthquakes in the area however show predominantly strike slip mechanisms the p axes of the earthquakes mostly oriented in north south and the t axes in east west however the orientations of the p and t axes exhibit more complexity near the source area of the main shock stress field inversion of the solutions yields a dominant north south compression which is consistent with the ambient tectonic stress field owing to the northward movement of the indian plate with respect to the eurasian plate the geodetic measurements are in reasonable agreement with our results

3d crustal resistivity structure beneath the wagad aftershock zone of the 2001 bhuj earthquake kutch india heterogeneous resistivity structure controlled by widespread fluid infiltration and clues to aftershocks pattern abstract the epicentral region of the 26 january 2001 bhuj earthquake 7 7 m w in the kutch region of india has been experiencing a vigorous and unique intraplate aftershock activity which shows a v shaped pattern and n ne migration along the western margin of the wagad uplift located to the northeast of the mainshock this study presents 3d resistivity structure of the wagad aftershock zone imaged using magnetotelluric mt data to understand the crustal geoelectric structure and subsurface geometry of faults lineaments which could provide critical inputs to evaluate and strengthen the earthquake generation mechanism and aftershocks pattern the obtained 3d conductivity structure showed a thick 3 km and homogeneous conductive 1 30 m layer of tertiary mesozoic sedimentary cover in the area a highly heterogeneous upper and middle crust characterized by a mix of conductive 300 m structures is imaged below the sedimentary cover enhanced conductivity zones showed spatial correlation with the surface trace of various faults lineaments and are interpreted as fluid enriched zones in the crust which play a critical role in earthquake triggering significantly higher fluid enrichment noticed in the crust below two minor faults khadir transverse fault ktf and manfara fault mf which are hitherto considered to have an insignificant role in the seismogenesis of the area the aftershock events seem to occur mostly on the resistive parts of the crust and its pattern shows good alignment with the anomalous conductive zones associated to the above two faults the results provide a strong clue to infer that the ktf and mf have a vital role in the observed aftershock activity and control the v shaped aftershocks pattern

regional tectonic framework structure and evolution of the western marginal basins of india abstract the kutch saurashtra cambay and narmada basins are pericontinental rift basins in the western margin of the indian craton these basins were formed by rifting along precambrian tectonic trends interplay of three major precambrian tectonic trends of western india dharwar nnw sse aravalli delhi ne sw and satpura ene wsw controlled the tectonic style of the basins the geological history of the basins indicates that these basins were formed by sequential reactivation of primordial faults the kutch basin opened up first in the early jurassic rifting was initiated in late triassic along the delhi trend followed by the cambay basin in the early cretaceous along the dharwar trend and the narmada basin in late cretaceous time along the satpura trend the evolution of the basins took place in four stages these stages are synchronous with the important events in the evolution of the indian sub continent its breakup from gondwanaland in the late triassic early jurassic its northward drifting during the jurassic cretaceous and collision with the asian continent in the early tertiary the most important tectonic events occurred in late cretaceous time the present style of the continental margins of india evolved during early tertiary time the saurashtra arch the extension of the aravalli range across the western continental shelf subsided along the eastern margin fault of the cambay basin during the early cretaceous it formed an extensive depositional platform continuous with the kutch shelf for the accumulation of thick deltaic sediments a part of the saurashtra arch was uplifted as a horst during the main tectonic phase in the late cretaceous the present high thermal regime of the cambay bombay high region is suggestive of a renewed rifting phase

a new insight into crustal heterogeneity beneath the 2001 bhuj earthquake region of northwest india and its implications for rupture initiations the seismic characteristics of the 2001 bhuj earthquake mw 7 6 has been examined from the proxy indicators relative size distribution 3d b value mapping and seismic tomography using a new data set to understand the role of crustal heterogeneities in rupture initiations of the 2001 bhuj earthquake of the gujarat india one of the disastrous indian earthquakes of the new millennium the aftershocks sequence recorded by 22 seismograph stations of gujarat seismic network gsnet during the period from 2006 to 2009 encompassing approximately 80 km 70 km rupture area had revealed clustering of aftershocks at depth of 5 35 km which is seismogenic layer responsible for the occurrence of continued aftershocks activity in the study region the 3d b value mapping estimated from a total of 3850 precisely located aftershocks with magnitude of completeness mc 2 7 shows that a high b value region is sandwiched within the main shock hypocenter at the depth of 20 25 km and low b value region above and below of the 2001 bhuj main shock hypocenter estimates of 3 d seismic velocity vp vs and poisson s ratio structure beneath the region demonstrated a very close correspondence with the b value mapping that supports the similar physicochemical processes of retaining fluids within the fractured rock matrix beneath the 2001 bhuj mainshock hypocenter the overall b value is estimated close to 1 0 which reveals that seismogenesis is related to crustal heterogeneity which in turn also supported by low vs and high structures the high b value and high anomaly at the depth of 20 25 km indicate the presence of highly fractured heterogeneous rock matrix with fluid intrusions into it at deeper depth beneath the main shock hypocenter region low b value and high vp in the region is observed towards the north east and north west of the main shock that might be an indication of the existence of relatively competent rock masses with negligible volume of cracks that may have contained over pressurized fluids without molten rocks

partial melting below the magmatic arc in the central andes deduced from geoelectromagnetic field experiments and laboratory data abstract magnetotelluric and geomagnetic deep soudings in northern chile revealed a pronounced high conductivity zone hcz below the western cordillera which constitutes the present magmatic arc with active volcanism of the south american continental margin conductivities in the range of 1 s m are observed the anomalously high conductivities in a broad depth range from approximately 20 km to at least 60 km are interpreted in terms of partial melting other geophysical observations such as a zone of low seismic velocities lvz at similar depths high heat flow values 100 mw m2 and a pronounced negative anomaly in the residual gravity field are also considered impedance spectroscopic laboratory experiments up to and in the temperature range of partial melting were performed under controlled oxygen fugacities at sub solidus temperatures electrical behavior is described by defect electrons with an activation energy of 1 34 ev and a conductivity of 2 5 ms m at 900 c model calculations using a modified brick layer model mbl were compared with experimental observations a good agreement between calculations and experiments is achieved with an electrical resistivity of the melt phase of 7 s m at 1250 c assuming an activation energy of 1 ev the same mbl model is used to calculate melt proportions beneath the western cordillera between 14 and 27 vol of interconnected melt are necessary to explain the observed hcz the stability of the melt rich crust is explained by a dynamic melting crystallisation behavior during crustal anatexis and by magma filled dikes

magnetotelluric study to characterize kachchh mainland fault kmf and katrol hill fault khf in the western part of kachchh region of gujarat india abstract the kachchh mainland fault kmf is a major e w trending fault in the kachchh region of gujarat extending 150 km from lakhpat village in the west to the bhachau town in the east the katrol hill fault khf is an e w trending intrabasinal fault located in the central region of kachchh basin and the south of kmf the western parts of both of the faults are characterized and the sediment thickness has been estimated in the region using a magnetotelluric mt survey at 17 sites along a 55 km long north south profile with a site spacing of 2 3 km the analysis reveals that the maximum sediment thickness is 2 3 km quaternary tertiary and mesozoic in the region out of which the mesozoic sediments feature a maximum thickness of 2 km the estimated sediment thickness is found consistent with the thickness suggested by a deep borehole depth approx 2 5 km drilled by oil and natural gas corporation ongc at nirona northern part of the study area from 2 d inversion of the mt data three conductive zones are identified from north to south the first conductive zone is dipping nearly vertical down to 7 8 km depth it becomes north dipping below 8 km depth and is inferred as kmf the second conductive zone is found steeply dipping into the southern limbs near manjal village 28 km south of nirona which is inferred as the khf a vertical dipping down to 20 km depth conductive zone has also been observed near ulat village located 16 km north of manjal village and 12 km south of nirona village this conductive zone becomes listric north dipping beyond 20 km depth it is reported first time by a geophysical survey in the region

a new hypothesis for the deep subsurface structures near the bhuj 2001 earthquake mw 7 6 hypocentre zone and its tectonic implications summary we provide a new hypothesis for the deep subsurface structures near the bhuj 2001 earthquake region based on magnetotelluric mt investigations carried out close to the epicentre zone 2 d inversion of broad band mt data of two profiles of lengths 32 km aa and 52 km bb revealed a thick 3 km highly conductive 1 4 m surface layer of fluvio marine mesozoic cenozoic sediments the models delineate the hypocentre zone located at 20 25 km depth that manifests the high resistivity conductivity transition zone the accumulation of compressive stresses post rifting along this weak zone has resulted in the reverse slip of bhuj 2001 earthquake the reverse fault f1 associated with the earthquake is believed to be an ancient normal fault formed during the rifting phase contrary to earlier suggested theories we suggest that f1 got initiated along the high resistivity conductivity transition zone causing the bhuj 2001 event the geoelectric models revealed a laterally extending partially resistive zone at 20 30 km depth range showing a tendency to extend further deep model calculations using synthetic data also support this observation therefore we hypothesize the presence of a basal detachment marking the transition zone between the continental crust and the lithospheric upper mantle at 40 km depth intersected by the f1 the geoelectric models suggest that the crustal thinning caused the asthenospheric upwelling and or serpentinization leading to the ascent of volatiles and melts the subsurface geometry in kachchh basin suggests the thick skinned deformation

three dimensional preservation of foot movements in triassic theropod dinosaurs dinosaur footprints have been used extensively as biostratigraphic markers environmental indicators measures of faunal diversity and evidence of group behaviour1 2 3 4 trackways have also been used to estimate locomotor posture gait and speed6 7 8 9 10 11 but most prints being shallow impressions of a foot s plantar surface provide little evidence of the details of limb excursion here we describe late triassic trackways from east greenland made by theropods walking on substrates of different consistency and sinking to variable depths that preserve three dimensional records of foot movement triassic theropod prints share many features with those of ground dwelling birds but also demonstrate significant functional differences in position of the hallux digit i foot posture and hindlimb excursion

tracks and trackways of myotragus balearicus bate artiodactyla caprinae in pleistocene aeolianites from mallorca balearic islands western mediterranean tracks and trackways of the ruminant goat myotragus balearicus bate 1909 are abundant in the late pleistocene aeolianites of the south coast of mallorca spain the carbonate aeolianites form impressive dunes and related sand ramps that were initiated as echo dunes in front of a 20 40 m high paleocliff of miocene reefal limestone where the dunes built up to the cliff top they covered it as an aeolian ramp the dunes and sand ramps were active during the dry summer months but were passive during the wet winter period the small goat like animals were abundant on the island and for unknown reasons crossed the aeolian accumulations in large numbers this study deals with the tracks formed in the dune deposits all preserved trackways indicate impression into moist sand special features of the tracks include the structure produced by the withdrawal of the foot here called the axis and a disturbance zone of plastic deformation around this on dune crests the disturbance zone surrounds the axis more or less symmetrically however in addition a pressure pad of dislocated slightly rotated sediment bound by curved microfaults is commonly produced posterior to the axis by propulsive pressure of the foot on steep stoss and lee slopes the pressure pad becomes oriented in a down slope position as a result of gravitational slip of the walking animal combination of disturbance of the sediment in this way by manus followed by overprinting of similar disturbance by pes produces highly complicated track structure this structure may be characteristic of artiodactylous mammals in soft sand particularly aeolian deposits the structure is designated as bifidipes aeolis isp nov