the great extinction that never happened the demise of the dinosaurs considered the concept of a sudden extinction of the dinosaurs consequent upon the impact of some extraterrestrial object is so dramatic that it has taken hold upon the imaginations of many scientists as w

source parameters and tectonic implications of aftershocks of the mw 7 6 bhuj earthquake of 26 january 2001 we present and discuss the spatial distribution of more than 1000 aftershocks of the largest continental intraplate earthquake to occur during the modern seismological period the data were recorded on a network of eight portable digital seismographs deployed for 3 weeks starting 17 days after the mainshock we have calculated high quality single event locations based on a 1d velocity model determined for the region for earthquakes with magnitudes between 2 and 5 aftershock locations reveal activity concentrated on a nearly east striking south dipping plane trapezoidal in outline the active zone tapers from about 45 km along strike at the shallow end which is about 5 km deep to no more than 25 km long at a depth of 35 km the total rupture area was about 1300 km 2 we estimate the static stress drop of the mainshock at 16 2 mpa aftershocks extend nearly through the entire crust with concentrations in the lower crust at about 26 km and in the upper crust at about 10 km the fault that ruptured was not mapped at the surface and not known to have been active prior to the 2001 earthquake the aftershock data are consistent with the bhuj earthquake resulting from reactivation in contraction of a fault formed under extension within a failed rift

iterative de convolution of the local waveforms characterization of the seismic sources in kachchh india abstract the deviatoric and double couple dc constrained moment tensor inversions of multiple point sources 10 20 s for regional or local earthquakes developed by zahradnik et al 2005 has been applied on the data of nine significant bhuj aftershocks of mw4 4 mw5 6 recorded at three component 5 15 accelerograph and 5 11 seismograph stations epicentral distances

constraints on the source parameters of the 26 january 2001 bhuj india earthquake from satellite images the bhuj earthquake of 26 january 2001 m w 7 6 was the largest in tracontinental earthquake of the modern era of seismology field investigations did not provide any evidence of coseismic surface rupture or ground deformation due to primary faulting we analyze pre and postearthquake satellite images of the epicen tral region to suggest that there was a significant change in the flooding pattern of the seasonal rann of kachchh lagoon after the 2001 and 2002 monsoons in the region of coseismic uplift the maximum uplift is located about 15 km north of the reported epicenter and acted as a barrier against the northward draining rainwater runoff furthermore the earthquake caused a northward shift in the southern limit of the rann of kachchh we use this information to place constraints on the location and geometry of the earthquake rupture and suggest that the depth of the updip edge of the rupture is about 10 km

radar interferometry and its application to changes in the earth s surface geophysical applications of radar interferometry to measure changes in the earth s surface have exploded in the early 1990s this new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times the resulting interferogram is a contour map of the change in distance between the ground and the radar instrument these maps provide an unsurpassed spatial sampling density 100 pixels km 2 a competitive precision 1 cm and a useful observation cadence 1 pass month 1 they record movements in the crust perturbations in the atmosphere dielectric modifications in the soil and relief in the topography they are also sensitive to technical effects such as relative variations in the radar s trajectory or variations in its frequency standard we describe how all these phenomena contribute to an interferogram then a practical summary explains the techniques for calculating and manipulating interferograms from various radar instruments including the four satellites currently in orbit ers 1 ers 2 jers 1 and radarsat the next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement respecting the limits of the technique assessing its uncertainty recognizing artifacts and discriminating different types of signal we then review the geophysical applications published to date most of which study deformation related to earthquakes volcanoes and glaciers using ers 1 data we also show examples of monitoring natural hazards and environmental alterations related to landslides subsidence and agriculture in addition we consider subtler geophysical signals such as postseismic relaxation tidal loading of coastal areas and interseismic strain accumulation we conclude with our perspectives on the future of radar interferometry the objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it

when the sky fell on our heads identification and interpretation of impact products in the sedimentary record research on impact products mechanisms and consequences has benefited greatly in the last ten years from the highly publicized cretaceous tertiary kt boundary debate this debate has led to an increasing awareness among earth scientists of the importance and potential effects of impact events in earth history with more and more researchers realizing the role played by impacts and becoming familiar with the characteristics of impact materials it is likely that in the coming years an increasing number of impact events will be identified in agreement with the earth cratering rate estimations grieve 1984 shoemaker et al 1990 the increasing recognition of impact event is demonstrated by the discovery or identification in recent years of several impact craters some of large diameter chicxulub 180 km in yucatan mjolnir 40 km in the barents sea ames 16 km in oklahoma avak 12 km in alaska pretoria saltpan 1 1 km and kalkkop 640 m both in south africa sediments record impact events in the form of impact glass shocked minerals ir anomalies and perhaps also polymic chaotic breccias and or tsunami deposits identification of impact products particularly in ancient rocks is hampered by poor preservation diagenetic alteration metamorphism misinterpretation or even lack of interest or awareness of their significance impact products represent very short term events most likely geographically localized and stratigraphically concentrated over a thin interval of sediments and often diluted by normal background deposition finding these impact signatures requires very detailed petrographic and geochemical investigations with closely spaced sampling a few cm such detail is not commonly used when studying ancient mesozoic and paleozoic sediments

the geochronology of large igneous provinces terrestrial impact craters and their relationship to mass extinctions on earth the relationship between sudden catastrophic events and sudden mass extinctions on earth has attracted a great deal of research effort including measurements of the absolute and relative ages of these events the result has been a rapid improvement in the precision and accuracy of radiometric dates for large igneous provinces lips for which there is now a consensus on the peak eruption times over the last 250 ma in parallel there has been a more gradual improvement in the radiometric dates for craters formed by hypervelocity impacts hvis of asteroids and comets with earth the absolute ages of the largest craters are known to within a few million years but the ages of many smaller craters are poorly constrained in addition whereas relatively few lips have formed in the last 250 ma at least one hvi crater larger than 20 km diameter has formed on earth every million years only 25 such craters have been discovered so coincidence between the ages of hvi crater formation and ages of mass extinctions is related as much to crater preservation as to coincidence of the events the difference in quality of geochronology between hvis and lips is the result of differing availability of samples lips cover large areas and present an array of basalt samples suitable for dating whereas hvi craters are often poorly preserved and present few datable samples the radiometric data for preserved hvis and lips are now sufficiently precise and accurate for us to be confident that there is no one to one correlation between either lips or hvis and global mass extinctions of life on earth however there is a close association between a significant number of lips and sudden environmental change and a very close association between at least one massive hvi crater formation and a mass extinction further there is no apparent correlation between hvis and lips and thus no reason to suggest a causative relationship finally the radiometric dating of hvi craters indicates several clusters in the geological record but the correlation with sudden environmental change is no better than for large craters

luminescence chronometry and geomorphic evidence of active fold growth along the kachchh mainland fault kmf kachchh india seismotectonic implications abstract the kachchh region of western india is a pericratonic basin experiencing periodic high magnitude earthquakes events in 2001 a catastrophic seismic event occurred at bhuj measuring mw 7 7 the epicenters of both the 1956 and 2001 earthquakes were along the kachchh mainland fault kmf proximal to the eastern end of the northern hill range nhr the latter is a topographic expression of an active fault related fold on the hanging wall and is controlled by a south dipping blind thrust the present study deals with the eastern sector of nhr and uses optical dating to reconstruct the chronology of tectonically caused incisions along the backlimb of the nhr incision ages on channel fills and valley fill terraces progressively decrease from 12 ka to 4 3 ka this age progression along with geomorphic evidences decrease in topographic relief drainage capture and drainage migration across the fold nose suggests an active vertical and lateral fold growth along the kmf optical ages suggest that during the late holocene the average uplift rate along the eastern nhr was 10 1 mm a recent gps based estimates on crustal shortening are 12 mm a the kmf and the south wagad fault swf represent the bounding faults of a transtensional basin that formed during the initial rifting this basin is termed as the samakhiali basin the compressive stresses on account of structural inversion from normal to reverse phase resulted in lobate shaped anticlines along kmf and swf zone these anticlines subsequently coalesced and formed linked and overlap segments the present study suggests that eastward lateral deformation across the eastern portion of kmf has continued and has now resulted in its interaction with a left step over transfer fault called the south wagad master fault swmf this implies an increasing transpersional deformation of the samakhiali basin we therefore suggest that the eastward nhr ridge propagation along kmf resulted in the thrust faulting on the south dipping swmf resulting in the bhuj 2001 event the increasing strain on this basin may cause enhanced seismicity in the future along the eastern kmf and wagad region

uniformitarianism as a guide to rocky shore ecosystems in the geological record literature on pleistocene and neogene rocky shores is reviewed from a uniformitarian perspective to assess the fidelity of physical and biological information entrained in the geological record through present day processes coverage by latitude spans tropical to subarctic shores variations in paleotopography are illustrated by unconformities between sedimentary accumulations and rocks of igneous or non igneous origin former rocky shores occur across a range of geographic scales that include i spot localities ii embayments with continuous transition from exposed outer to protected inner shores and iii entire islands with windward and leeward shores differences in rate and mag nitude of sea level change affect rocky shore physiography terrace deposits characterize the pleistocene but ramp de posits typify older neogene shores on average species with hard parts account for about 50 of the modern rocky intertidal fauna on a regional basis regardless of latitude biodiversity is highest in mid latitudes fixed organisms with encrusting wedging or boring habits corals barnacles oysters other bivalves and vermetid gastropods show high potential for fossilization in growth position mobile organisms that cling to rocks gastropods crabs and echinoids suffer post mortem transport but may be immured within neptunian dikes or interstices among cobbles and boulders at best localized fossil deposits from the pleistocene reflect 30 of the biodiversity of skeletonized organisms tabulated from modern rocky shores on a regional basis uniformitarianism provides little insight into the diversity of soft bodied organisms excluding stromatolites that joined the ecosystem in precambrian times and the extent to which soft bodied organisms dominated shore life through later times

emplacement of cretaceous tertiary boundary shocked quartz from chicxulub crater observations on shocked quartz in cretaceous tertiary k t boundary sediments compellingly tied to chicxulub crater raise three problems first in north america shocked quartz occurs above the main k t ejecta layer second shocked quartz is more abundant west than east of chicxulub third shocked quartz reached distances requiring initial velocities up to 8 kilometers per second corresponding to shock pressures that would produce melt not the moderate pressure shock lamellae observed shock devolatilization and the expansion of carbon dioxide and water from impacted wet carbonate producing a warm accelerating fireball after the initial hot fireball of silicate vapor may explain all three problems

assessing the previous activity at the source zone of the 2001 bhuj earthquake based on the near source and distant paleoseismological indicators 1 the m w 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

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

damage due to the mw 7 7 kutch india earthquake of 2001 abstract this paper presents a study of the damage due to the m w 7 6 7 7 intraplate kutch earthquake of 26 january 2001 it was a powerful earthquake with a high stress drop of about 20 mpa aftershocks up to m 4 have continued for 2 5 years the distribution of early aftershocks indicates a rupture plane of 20 25 km radius at depths of 10 45 km along an e w trending and south dipping hidden fault situated approximately 25 km north of the kutch mainland fault the moment tensor solution determined from regional broadband data indicates reverse motion along a south dipping by 47 fault the earthquake is the largest event in india in the last 50 years and the most destructive in the recorded history in terms of socioeconomic losses with 13 819 deaths including 14 in pakistan collapse severe damage of over a million houses and us 10 billion economic loss surface faulting was not observed however intense land deformations have been observed in a 40 20 km meizoseismal area these include lateral spreading ground uplifts about a meter ground slumping and deep cracks liquefaction with ejection of sand and copious water was widespread in the banni grassland rann areas salt plains along rivers and also in the coastal areas up to 200 km distance from the epicenter in areas of intensity vii to x stray incidences of liquefaction have occurred up to distances of at least 300 km for the first time in india multistory buildings have been destroyed damaged by an earthquake the maximum acceleration is inferred to be 700 cm s 2 and intensities are 1 3 units higher in soil covered areas than expected from the decay rate of acceleration for hard rock

deposition of channel deposits near the cretaceous tertiary boundary in northeastern mexico catastrophic or normal sedimentary deposits comments and replies and is there evidence for cretaceous tertiary boundary age deep water deposits in the caribbean and gulf of mexico comment and reply

multiple factors in the origin of the cretaceous tertiary boundary the role of environmental stress and deccan trap volcanism a review of the scenarios for the cretaceous tertiary k t boundary event is presented and a coherent hypothesis for the origin of the event is formulated many scientists now accept that the event was caused by a meteorite impact at chicxulub in the yucatan peninsula mexico our investigations show that the oceans were already stressed by the end of the late cretaceous as a result of the long term drop in atmospheric co2 the long term drop in sea level and the frequent development of oceanic anoxia extinction of some marine species was already occurring several million years prior to the k t boundary the biota were therefore susceptible to change the eruption of the deccan traps which began at 66 2 ma coincides with the k t boundary events it erupted huge quantities of h2so4 hcl co2 dust and soot into the atmosphere and led to a significant drop in sea level and marked changes in ocean temperature the result was a major reduction in oceanic productivity and the creation of an almost dead ocean the volcanism lasted almost 0 7 m y extinction of biological species was graded and appeared to correlate with the main eruptive events elements such as ir were incorporated into the volcanic ash possibly on soot particles this horizon accumulated under anoxic conditions in local depressions and became the marker horizon for the k t boundary an oxidation front penetrated this horizon leading to the redistribution of elements the eruption of the deccan traps is the largest volcanic event since the permian triassic event at 245 ma it followed a period of 36 m y in which the earth s magnetic field failed to reverse instabilities in the mantle are thought to be responsible for this eruption and therefore for the k t event we therefore believe that the k t event can be explained in terms of the effects of the deccan volcanism on an already stressed biosphere the meteorite impact at chicxulub took place after the onset of deccan volcanism it probably played a regional rather than a global role in the k t extinctions

sedimentology and paleoecology of pliocene shallow marine conglomerates salton trough region california abstract the basal portion of the pliocene imperial formation salton trough region california includes conglomerates which were deposited in a rift related setting at the head of the gulf of california conglomerates and associated pebbly sandstones contain a fully marine fauna and form a transgressive sequence which unconformably overlies a basement of miocene volcanics sequences deposited adjacent to rock cliffs include stratified conglomerate of beach origin and clast supported boulder conglomerate which formed as talus these types of sediment were also transported downslope as sediment gravity flows and accumulated in topographically irregular nearshore areas as a variety of boulder to pebble conglomerates the conglomerates contain two types of displaced faunal assemblages which reflect different types of rocky shore to shallow subtidal communities an assemblage dominated by small oysters and barnacles represents a low diversity community which lived on and among volcanic clasts in muddy protected coves another assemblage represents a diverse community of corals bryozoans gastropods bivalves annelids barnacles decapods and echinoids which lived on and among boulders along coastlines both assemblages have analogues in the modern gulf of california local depletion of volcanic clasts resulted in deposition of nearshore sandstone which prograded over conglomerate deposits this sandstone is composed of volcanic rock fragments and abundant skeletal fragments which represent taxa from several coastal communities

active segmentation assessment of the tectonically active south wagad fault in kachchh western peninsular india abstract in present study the results of integrated studies of landform development and geomorphic indices of drainage networks across the south wagad fault swf zone have been presented the swf is a structure that is morphogenic in nature creating a 40 m high e w trending escarpment that extends 80 km at the southern end of the wagad uplift the swf got reactivated during the bhuj earthquake of 2001 continued aftershock activity of m 4 levels were recorded in the epicentral zone north of the kachchh mainland fault and west of the swf strath terraces along the river valleys and the truncation of alluvial fans along the mountain front incision and offset of rivers suggests an active nature of the swf to assess the relative tectonic activity morphometric indices such as stream gradient sl index hypsometric integral hi basin asymmetry af mountain front sinuosity smf index sinuosity index si and basin shape bs have been analyzed the landform development along the river valley in the swf zone suggests reactivation of the swf between 12 and 3 ka the southern front of wagad is found to be uplifting at the rate of 2 8 mm y during the last 12 ka as estimated through osl dates the relative index of active tectonics riat by the study of different geomorphic parameters and field checks indicates that most of the wagad highland is active the compressional strain of 0 05 strain y inferred from the gps study in the swf area attests to the activeness

source parameters of the bhuj earthquake india of january 26 2001 from height and gravity changes 1 height and gravity measurements observed along a profile across the epicentral area before and after the january 26 2001 mw 7 6 bhuj earthquake show a maximum uplift of 1 57 0 5 m and a corresponding gravity change of 393 18 gal a best fit single dislocation model inverted from the height changes using non linear optimization methods indicates that the high slip rupture was well contained in the aftershock zone and likely did not break to depths shallower than 10 km source parameters arrived in the present study agree well with those provided by seismic inversions and the distribution of aftershocks gravity data over the epicentral area are well modeled by the preferred model however a strong influence of shallow hydrological processes is inferred for three sites two located on the banni plains whose mean gravity change 280 gal suggests a total mass redistribution of as much as 2 9 mt

characterization of the causative fault system for the 2001 bhuj earthquake of mw 7 7 abstract precise hypocenters erh m w 2 0 5 3 delineate a east west trending blind thrust dipping 45 towards south named as north wagad fault nwf about 25 km north of kachchh main land fault kmf as the causative fault for the 2001 bhuj earthquake of m w 7 7 the aftershock zone involves a crustal volume of 60 40 35 km 3 lying between kmf and nwf the waveform inversion of 45 aftershocks of m 3 0 5 3 suggest that the e w trending south dipping reverse faulting mainly characterizes the aftershock zone however some reverse faulting along nw se as well as ne sw planes and some strike slip faulting along nw se trending vertical plane are also noticed the estimated p axes point on an average towards n s while t axes orient in e w agreeing well with the prevailing regional plate tectonic stress directions the estimated velocity model from one dimensional inversion of 8000 p and 5000 s travel times from 600 aftershocks deciphers a detailed crustal structure of the region upper 0 6 km on an average suggests a low velocity zone characterizing the jurassic and younger sediments the depth range 6 42 km is characterized on an average by larger values of v p 6 31 to 6 98 km s with an average of 6 71 km s v s 3 64 to 4 05 km s with an average of 3 85 km s and v p v s 1 69 to 1 81 with an average of 1 75 the high crustal velocities can be attributed to the existence of a high velocity mafic intrusive rift pillow structure beneath the region probably emplaced during the rifting time this brittle competent high velocity zone beneath the epicentral area in response to the compression due to the northward movement of the indian plate could induce sufficient local stress perturbation for generating large intraplate earthquakes of m w 7 5 in the lower crust further within the overall higher velocity depth range a layer characterized by large values of v p 6 98 km s v s 3 854 km s and v p v s 1 81 is found in the depth range of 20 5 30 km which is inferred to be fractured and saturated high crack density and probably fluid filled presence of numerous fractures in this layer is confirmed by a high b value 0 75 1 1 in this layer this layer might have facilitated the nucleation process of the 2001 bhuj earthquake the major rupture and 47 of the aftershocks have occurred within this layer

mid tertiary transgressive rocky coast sedimentation central western cascade range oregon abstract sediments of the scotts mills formation exposed on the flanks of oregon s central western cascade range accumulated along a storm dominated rocky coastline during the oligocene miocene transition during this time the development of depositional facies was controlled by the physiography of the underlying erosional surface lithofacies include a cross stratified barnacle limestone headland facies a fossiliferous graded conglomerate wave cut platform sea stack facies a burrowed claystone tidal flat facies an amalgamated sandstone coastal sand tongue facies and a graded mudstone proximal tempestite facies the transgressive sedimentary deposits described here are characterized by 1 oligomictic intrabasinal detritus 2 epilithic invertebrate faunas 3 mass transport dep sits and 4 abrupt basinward gradation of conglomeratic nearshore sediments to offshore muds the development of these depositional environments and their relationship to the physiography of the underlying unconformity has been translated here into a rocky coast facies model

evidence for right lateral strike slip environment in the kutch basin of northwestern india from moment tensor inversion studies abstract the kutch region located in northwestern part of india is an ancient rift basin that was active until cretaceous period the region falls close to the india arabia and the india eurasia plate boundaries and has experienced devastating earthquakes in the past namely the 1819 allah bund earthquake the 1956 anjar earthquake and the 2001 bhuj earthquake to understand the tectonics of this region with respect to the adjacent plate boundaries we invert seismic waveform data of 11 earthquakes in this region recorded by a network of the institute of seismological research isr during 2007 2009 the study yields focal mechanism solutions of reverse fault and strike slip type mechanism the inferred fault planes correlate well with the local trends of the known tectonic faults while the principal stress directions derived from stress inversion based on a linearized least squares approach trend agreeably with the ambient stress field directions a consistently right lateral sense of shear is found on all the local faults as derived from each of the matching planes of the focal mechanism solutions computed in the present study it is inferred that in the kutch region a right lateral strike slip environment prevails along predominantly ew to nw se oriented deep seated pre existing faults in an otherwise compressive stress regime this in conjunction with the left lateral movements along the girnar mountain in southern saurashtra inferred from previous studies indicates a westward escape of the kutch saurashtra block as a consequence of the northward collision of the indian plate with respect to the eurasian landmass

estimation of active surface deformation in the eastern kachchh region western india application of multi sensor dinsar technique abstract the focus of the present study is to estimate the active surface deformation displacement affecting the landscape of the eastern kachchh basin with a particular emphasis on the wagad khadir island bela island chorar island and adjoining regions by implementing differential interferometry synthetic aperture radar dinsar technique using envisat and sentinel 1a radar imagery to evaluate the deformation pattern using dinsar we used envisat asar 2003 to 2005 and 2006 to 2009 data products and sentinel 1a data set of 2018 2020 the cumulative displacement of 0 2 0 3 cm for the period of 2003 2005 and 0 19 0 22 cm for the period of 2006 2009 has been observed for the south wagad fault region similarly the results acquired from sentinel 1a data set revealed a cumulative displacement of 0 16 0 18 cm for the period of 2018 2020 the island belt fault zone shows 0 27 cm displacement while it is 0 10 0 17 cm for the gedi fault zone the rate of deformation estimated from the present study is well corroborated with the existing results of gps driven uplift rates the combined results of dinsar and gps indicate that the northern part of the wagad region is deforming much faster than the south wagad region the displacement detected to the east of the epicentral zone of the 2001 bhuj earthquake indicates the presence of a zone of weaker structures which may trigger a large magnitude earthquake in the future our estimated results of the short term ground displacement are well corroborated with the existing geological information this ground displacement is attributed to the tectonic subsidence towards the eastern part of the south wagad fault region and within the wide zone of the island belt fault and gedi fault zones the areas with a high amount of displacement have experienced continuous seismicity during the last two decades in the eastern kachchh region and might encounter moderate to high seismicity in the near future the results also provide a better understanding of the active surface deformation pattern taking place in the seismically sensitive eastern kachchh region

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

post seismic crustal deformation and strain rate in bhuj region western india after the 2001 january 26 earthquake summary the mw 7 6 bhuj earthquake in gujarat western india which occurred on 2001 january 26 was a major intraplate event in the indian subcontinent to study the characteristics of transient post seismic deformation at the earth s surface to elucidate the distribution of strain accumulation rate and so understand the earthquake recurrence process five gps campaigns were conducted at 14 sites in bhuj region during 2001 2002 the daily variations in the site position coordinates and the baselines during the early after shock period i e for 21 d starting from 2001 february 10 march 2 showed no short term post seismic crustal deformation neither logarithmic nor exponential function could be well fitted to any of the components of the time series of the position co coordinates indicating no discernable contribution from viscoelastic relaxation poroelastic rebound or afterslip mechanisms the estimated velocity field in itrf2000 spanning five epochs during 2001 2002 has an average of 50 mm yr 1 in north northeast direction to obtain a better perspective of post seismic deformation in the epicentral track the residual velocity field has been expressed in an india fixed reference frame the residual velocity of 11 62 mm yr 1 in a north northwest direction and 5 24 mm yr 1 towards the south seen at sites south and north of the epicentre respectively indicates localized ongoing convergence in the epicentral region at sites away from the epicentre no significant deformation took place the estimated principal strain from the velocity field gives average compression and extension rates of 0 07 and 0 04 micro strain yr 1 respectively a zone of maximum compressive strain rate of 0 30 micro strain yr 1 with azimuth of 11 delineated north of the epicentral region shows good agreement with seismic deformation along the blind fault derived from earthquake focal mechanisms these results suggest ongoing transpressional deformation across the area with a blocked structure embedded between the north wagad fault and south wagad fault this deformation may be related to the present neo tectonic compressive stress regime of the indian plate due to its nne movement against the collision front in the north and its proximity to the triple junction in the western continental margin of the study area

dinsar measurements of ground deformation by sinkholes mining subsidence and landslides ebro river spain differential interferometric synthetic aperture radar dinsar has been applied to detect and measure ground deformation in a stretch of the ebro river valley spain excavated in salt bearing evaporites the capability of the small baseline subset sbas dinsar technique to detect ground displacement is analyzed comparing the dinsar results with the available geomorphological information the deformation map derived from 27 european remote sensing ers satellite images covering more than five years provides sub centimeter displacement measurements in zones coinciding with known active sinkholes and landslides moreover the map provides the first account of mining subsidence in the area the measured deformation rates reach 1 68 cm y for the sinkholes 0 80 cm y for the landslides and 1 45 cm y for the area affected by mining subsidence the sbas dinsar technique provided deformation measurements in a small proportion 5 10 of the known active sinkholes and landslides this limitation is mainly due to the lack of coherence in agricultural areas the spatial resolution of the deformation map pixel size of 90 m and the parallelism between the ers satellite line of sight and the linear escarpment on which most of the landslides occur despite this the interferometric technique provides valuable data that complement traditional geomorphological studies including the quantification of the deformation phenomena the identification of mining subsidence otherwise only recognizable by geodetic methods and the detection of creep deformation which might correspond to premonitory indicators of catastrophic sinkholes and landslides capable of causing the loss of lives detailed dinsar studies combined with field data would be required to improve the analysis of each deformation area copyright 2009 john wiley sons ltd

radar interferogram filtering for geophysical applications the use of sar interferometry is often impeded by decorrelation from thermal noise temporal change and baseline geometry power spectra of interferograms are typically the sum of a narrow band component combined with broad band noise we describe a new adaptive filtering algorithm that dramatically lowers phase noise improving both measurement accuracy and phase unwrapping while demonstrating graceful degradation in regions of pure noise the performance of the filter is demonstrated with sar data from the ers satellites over the jakobshavns glacier of greenland

rupture process of the 26 january 2001 mw 7 6 bhuj india earthquake from teleseismic broadband data we investigate the rupture process of the 26 january 2001 bhuj india m w 7 6 earthquake through inversion of teleseismic broadband body waves this earthquake ranks as one of the most important recent events due to its occurrence within a stable continental interior where such events are rare the bhuj earthquake occurred on a moderately dipping blind thrust fault within an ancient failed rift about 70 of the seismic moment released in the earthquake was confined to a very small area 375 km2 surrounding the hypocenter and at depths below 12 km the static stress drop of the bhuj earthquake is anomalously high 20 mpa the source time history of the event indicates very rapid onset to the moment release and most likely high slip velocities within the deep asperity this suggests that some of the damage near the epicenter may have been caused by anomalously high frequency ground motions the teleseismic data also indicate the presence of a second area of large slip in the shallow part of the bhuj fault although the depth extent of this shallow large slip area is not resolved comparisons of the predicted ground motions with observed intensities suggest that substantial slip occurred in the upper 10 km of the fault in order to explain the distribution of high intensities to the west and northwest of the fault the upper surface layers near the bhuj fault consist of unconsolidated low rigidity sediments and alluvium the upper 10 km of the bhuj fault may therefore be in a conditionally stable region that normally deforms through aseismic creep and can sustain seismic rupture only when dynamically stressed by rupture of the high strength deep asperity we suggest that this deep asperity may be related to a lithologic anomaly of ultramafic composition

source parameters of the anjar earthquake of july 21 1956 india and its seismotectonic implications for the kutch rift basin abstract the kutch rift basin is a major seismic region in india characterized by a low earthquake occurrence rate but a very high maximum intensity the largest event in the region is the great kutch earthquake of 1819 estimated m w 7 8 however lacking instrumental data its exact source parameters are not well known the anjar or rann of kutch earthquake of july 21 1956 m w 6 0 took place very close to the 1819 kutch event and caused considerable damage and casualties our modeled waveforms of teleseismic p and sh waves and p wave first motions determine a reverse faulting mechanism strike 235 dip 46 5 and rake 85 as well as source parameters for the anjar earthquake a previous strike slip mechanism for this event has been eliminated on the basis of waveform constraints the two nodal planes of our solution both strike northeast sub parallel to the trend of the kutch rift very close to the trend of the isoseismals the seismic moment is 1 19 10 25 dyne cm the focal depth and the stress drop are 15 km and 162 bar respectively the anjar reverse fault may represent a reactivated normal fault undergoing tectonic inversion in the kutch rift zone under present day compressional stress two larger earthquakes adjacent to anjar but outside of the kutch rift are also found to be mainly reverse faulting with a minor strike slip component judging from available information the great kutch event of 1819 is most likely a reverse faulting event

high resolution planktonic foraminiferal analysis from the cretaceous tertiary boundary at ain settara tunisia evidence of an extended mass extinction the ain settara section located in the kalaat senan area of north central tunisia spans the cretaceous tertiary k t boundary which is characterized by a red layer and a thin non bioturbated boundary clay sediment accumulation across the k t boundary at ain settara was probably interrupted by three short hiatuses and or condensed sedimentation the first hiatus occurs at the top of the cf1 zone the second hiatus condensation occurred just below the boundary clay and the third hiatus at the p0 p1a boundary in the earliest danian these hiatuses are marked by weak unconformities bioturbation and sudden disappearances appearances of species which are known to disappear evolve sequentially in continuous sections quantitative high resolution planktonic foraminiferal analysis across zones cf1 upper p0 and p1a 1 reveals an extended and selective mass extinction all 41 of the species which disappeared at or below the k t boundary are rare to very rare and primarily ecologically specialized keeled deeper dwelling tropical subtropical forms globotruncana globotruncanita gublerina planoglobulina rosita contusotruncana racemiguembelina their combined relative abundance varies between 10 and 15 of the total population at the end of the maastrichtian the k t crisis thus appears more catastrophic when viewed in tropical subtropical assemblages and based on analysis of larger species 200 m which preferentially includes the more specialized forms though in fact the k t mass extinction actually involved a relatively small part of the foraminiferal population in terms of relative abundance the pattern of extinction and changes in dominant population at ain settara appear to be very similar to the planktonic foraminiferal turnover of the other north central tunisian sections el kef elles the selective mass extinction pattern suggests that the catastrophic effects of the bolide impact superimposed those related to long term environmental changes such as variations in temperature sea level and associated water mass changes

size and orientation of the fault plane for the 2001 gujarat india earthquake mw7 7 from aftershock observations a high stress drop event 1 we used a small array of portable seismographs to determine aftershock locations of the 2001 gujarat earthquake our aftershock locations show a trend that dips toward the south at about 50 which is interpreted as the fault plane of the mainshock the depth range of the aftershocks is from 10 to 35 km which is somewhat deeper than other crustal earthquakes and indicates that the faulting did not reach the surface the area of the fault is about 40 40 km2 which is small for a mw7 7 earthquake and results in a high static stress drop of 13 to 25 mpa there are no mapped faults or obvious topographic features along the surface projection of this fault these findings show that very large damaging earthquakes can occur without producing surface faulting which is an important issue for earthquake hazard assessments in continental regions