mesozoic and cenozoic reconstructions of the south atlantic abstract the movement of antarctica with respect to south america has a number of implications for paleocirculation as well as for the reconstructions of gondwanaland recent papers on the southwest indian ridge have published new or revised poles of opening for africa and antarctica which can be combined with the poles of opening between south america and africa to give resultant motions between south america and antarctica the first indication of a complete closure between south america and the antarctic peninsula is at anomaly 28 time 64 ma as the two continents are now configured between anomaly 28 time 64 ma and anomaly m0 time 119 ma the amount of closure does not change greatly and the small computed overlap can be explained by minor uncertainties in the rotation poles used for the reconstructions or some slight extension between east and west antarctica by 135 ma some rotation or translation of the antarctic peninsula with respect to east antarctica must be postulated in addition to any presumed extension between east and west antarctica in order to avoid an overlap of south america with the antarctic peninsula having determined what we feel to be a viable reconstruction of western gondwanaland and holding south america fixed we rotated africa and antarctica with respect to south america for eight different times during the past africa moved away from south america in a more or less consistent manner throughout the time period closure to present while antarctica moved away from africa in a consistent manner only between 160 ma and 64 ma at 64 ma its motion changed abruptly it slowed its north south motion with respect to africa and began slow east west extension with respect to south america this change supports the hypothesis that a major reorganization of the triple junction between africa antarctica and south america occurred between 60 and 65 ma the triple junction changed from ridge ridge ridge to ridge fault fault at the time of the major westward jump of the mid atlantic ridge just south of the falkland agulhas fracture zone the mesozoic opening of the somali basin moved madagascar from its presumed original position with africa in gondwanaland the closure of sri lanka with india produces a unique fit for india and sri lanka with respect to africa madagascar and antarctica this fit juxtaposes geological localities in southeast india against similar localities in enderhy land east antarctica the late jurassic opening in the somali basin is tied to opening of the same age in the mozambique basin since this late jurassic movement represents the initial break up of gondwanaland it is assumed that similar movement must have occurred in what is now the western weddell sea and may also explain the opening evidenced by the rocas verdes region of southern south america

source characteristics of the nw himalaya and its adjoining region geodynamical implications abstract in this study we propose a novel interpretation of source parameters estimated using brune model for the nw himalaya and its adjoining region analysis of 157 events 2 2 mw 4 9 resulted in the scaling relationship between seismic moment m0 and corner frequency fc for the region as m0 8 1022 fc 2 89 which is in good unison to the garhwal and the kumaon himalaya with analogous seismogenic potential variability of kappa 0 01 s 0 08 s with varying number of events 2 5 m 5 0 at different depths is indicative of nature and extent of structural heterogeneity beneath the source zone which controls the propensity of background seismicity that provides enough testimony to complex geodynamical set up of the nw himalaya and its adjoining region source radii of source zone varying from 148 m to 975 m with static stress drops calculated for a given constant stress of 0 1 bar 1 bar 10 bar and 100 bar correspond to an average stress drop varied from 0 4 bar to 99 9 bar seismic moments of events vary from 2 64 1019 dyne cm to 2 32 1023 dyne cm with increase of the source radii we infer that variability in stress drop for seismic moment mo is attributed to different seismic sources of varying strengths associated with different structural heterogeneities stress drop of the events has good correspondence with source depth having the linear relationship of shear stress regime in the brittle crust with stress drop and source depth suggesting the presence of intricate subsurface seismogenic sources beneath the nw himalaya and its adjoining region

the dibdibba aquifer system at safwan zubair area southern iraq hydrogeology and environmental situation the objective of this research is to study the environment and hydrogeology of the dibdibba aquifer system in the safwan zubair area southern iraq in relation to the study area s geology and anthropogenic activities ten groundwater samples were collected from safwan zubair geochemical data aquachem and gis arcmap 10 1 were used as tools to identify natural and anthropogenic factors that affect geochemical data we analyzed water samples for major cations and anions polycyclic aromatic hydrocarbons pahs total uranium tu and heavy metals pb ni cr cd v zn as se cu fe mn as well as the metalloid b groundwater composition in the area of study is classified into six types ca mg cl ca mg na cl ca mg cl so4 ca mg na cl so4 ca na mg so4 cl and mg ca cl so4 the groundwater is influenced by natural factors particularly the concentrations of tu and major ions the concentrations of tu and major ions in some water samples exceed limits for drinking water however the average of all examined heavy metals except for fe and b was within the limits for drinking water as well as the concentrations of pahs the potential use of this groundwater for drinking and irrigation is discussed

geochemical and boron strontium and oxygen isotopic constraints on the origin of the salinity in groundwater from the mediterranean coast of israel in order to identify the origin of the salinity and formation of saline plumes in the central part of the mediterranean coastal aquifer of israel we determined the elemental and boron strontium and oxygen isotopic compositions of fresh and brackish groundwater cl up to 1500 mg l we distinguish between two key anthropogenic sources 1 sewage effluents used for irrigation with high na cl so4 cl and b c1 ratios and low br cl ratios relative to seawater ratios low 11b values 0 10 and high 18o values 4 and 2 imported water from the sea of galilee that is artificially recharged to the aquifer with high br cl 3 10 3 and 18o values 1 and a low 87sr 86sr ratio of 0 70753 the brackish groundwater from the saline plumes have relatively low na cl ratios 0 5 0 8 and high ca mg mg cl and ca so4 hco3 1 ratios relative to seawater ratios marine so4 cl and br cl ratios 11b values of 24 8 49 9 18o of 2 95 to 4 73 and 87sr 86sr ratios of 0 708275 0 708532 the composition of most of the investigated groundwater from the saline plumes differs from those of the anthropogenic sources imported water fresh uncontaminated groundwater 87sr 86sr of 0 70866 11b of 20 30 and saline water from the adjacent eocene aquitard only in areas of artificial recharge does local groundwater have high br cl and 18o values that are typical to the sea of galilee the linear relationships between chloride and most of the ions including b and sr the relatively high 11b 30 and low 18 o 4 values and the chemical signature of the saline plumes e g marine br cl and so4 cl ratios suggest that 1 mixing processes control the chemical composition of the brackish water within the aquifer and 2 the saline postulated end member has a chemical composition that resembles modified seawater with a marine and higher 11b values and a 87sr 86sr ratio of 0 7083 we propose that most of the salinization phenomena and the formation of saline plumes in the inner parts of the coastal aquifer are derived from upconing of underlying natural saline water bodies and enhanced by overexploitation and draw down of the overlying fresh groundwater

source parameters for aftershocks of the oroville california earthquake abstract a suite of 111 strong motion accelerograms for 14 aftershocks of the oroville california earthquake m l 5 7 1 august 1975 that range in local magnitude m l from 2 8 to 5 2 has been analyzed to obtain estimates of seismic moment m o source radius r o and stress drop in addition to the focal parameters of location depth and fault plane solution this data set which is unusually complete for near source 20 km on scale readings allows for greater precision in the calculation of various measures of stress difference as represented by the brune stress drop the apparent stress the a rms stress drop and the dynamic stress drop in addition the seismicity following each aftershock and state of stress seem to correlate with particular estimates of stress drop seismic moments were calculated from the asymptotic long period spectral levels which were corrected for the radiation pattern of a double couple point source they range from 1 4 10 21 dyne cm for a m l 2 8 shock to 3 3 10 23 dyne cm for a m l 5 1 event a least squares fit between m l and the logarithm m o yields log m 0 1 36 0 22 m l 16 8 1 1 for m l 4 3 and log m 0 1 1 0 14 m l 18 0 51 for m l 4 1 these relationships are qualitatively in agreement with the response of the wood anderson instrument to a brune pulse stress drops from the brune formulation range about 14 to 170 bars stress drop is correlated with depth in that the deepest events have the largest stress drops and no large stress drops occur at the shallow depths apparent stresses are smaller than the brune stress drops and show a weaker depth dependence over the depth interval for which they are available the stress drop calculated from the rms of acceleration a rms was approximately constant at about 90 bars for 5 of the 7 larger events analyzed the two high values of 160 and 190 bars were obtained only for the two events which had marked aftershock sequences of their own these results may be interpreted in terms of the state of stress simple fracture criteria and mechanisms for the generation of aftershocks the increase with depth of the envelope of the brune stress drops may be caused by an increase in shear stress from overburden pressure smaller stress drop events can occur at any depth interval the causal mechanism of aftershocks is not known but probably includes a change in the frictional properties of the fault suggesting that the a rms stress drop is a measure of the frictional or dynamic stress release

geochemical characterization of groundwater from an arid region in india a study on the geochemical processes in arid region of western india kachchh district was carried out using major minor trace metal data and isotopic composition 2h 18o of groundwaters results indicate that the distribution of chemical species in groundwater of this district is controlled by leaching of marine sediments dissolution of salts in root zone and incongruent dissolution of carbonate minerals common inorganic contaminants such as fluoride nitrate and phosphate are within drinking water permissible limits however most of the samples analyzed contain total dissolved salts more than desirable limits and fall in doubtful to unsuitable category with regard to irrigational purpose trace metal data indicates no contamination from toxic elements such as arsenic and lead an increased salt content is observed in groundwater at shallower depths indicating mixing with surface water sources the chemical characteristics of the groundwater have found to be strongly dependent on the local lithological composition environmental isotopic data indicates that the groundwater is of meteoric origin and has undergone limited modification before its recharge the processes responsible for observed brackishness are identified using chemical and isotope indicators which are in agreement with subsurface lithology and hydrochemistry these data though represent hydrochemical scenario of 2001 can still be used for understanding the long term fluctuations in water chemistry and would be quite useful for the planners in validating groundwater quality models

revisiting the 1956 anjar earthquake in western india empirical green s function approach we estimated ground motions at 12 selected sites in the kachchh rift basin of gujarat in the western peninsular shield area of india where the damaging 1956 anjar earthquake m w 6 0 was experienced the ground motions are estimated by applying the empirical green s function approach using an earthquake of m w 4 5 which occurred on the inferred rupture plane of the anjar earthquake with a nearly similar fault mechanism the estimated peak ground acceleration pga varies between 114 and 22 cm s2 at these sites located at distances of 21 127 km from the epicenter respectively the maximum accelerations are correlated with the modified mercalli intensity reported for the anjar earthquake using the empirical relationship between the pga and intensity at most of the sites the level of acceleration could explain the reported damage at a few sites the instrumental intensity estimated using the acceleration values obtained from the synthesis is larger than the felt intensity the ground motion prediction equation gmpe developed for the region estimates the maximum pga near the epicenter area in the 250 300 cm s2 range and the acceleration obtained by our analysis is found to be closer to the predicted acceleration obtained by gmpe our analysis assesses the level of ground motion that was experienced during the 1956 anjar earthquake fairly well and corroborates that reasonable prediction of the ground motion of a historical earthquake is achievable if strong motion recordings are available from the rupture plane of the historical earthquake

finite element analysis of an embankment on a soft estuarine deposit using an elastic viscoplastic soil model a new elastic viscoplastic evp soil model has been used to simulate the measured deformation response of a soft estuarine soil loaded by a stage constructed embankment the simulation incorporate

seismic imaging of the 2001 bhuj mw7 7 earthquake source zone b value fractal dimension and seismic velocity tomography studies abstract we use precisely located aftershocks of the 2001 mw7 7 bhuj earthquake 2001 2009 to explore the structure of the kachchh seismic zone by mapping the 3 d distributions of b value fractal dimension d and seismic velocities from frequency magnitude analysis we find that the catalog is complete above mw 3 0 thus we analyze 2159 aftershocks with mw 3 0 to estimate the 3 d distribution of b value and fractal dimensions using maximum likelihood and spatial correlation dimension approaches respectively our results show an area of high b d and vp vs ratio values at 15 35 km depth in the main rupture zone mrz while relatively low b and d values characterize the surrounding rigid regions and gedi fault gf zone we propose that higher material heterogeneities in the vicinity of the mrz and or circulation of deep aqueous fluid volatile co2 is the main cause of the increased b d and vp vs ratio values at 15 35 km depth seismic velocity images also show some low velocity zones continuing in to the deep lower crust supporting the existence of circulation of deep aqueous fluid volatile co2 in the region probably released from the eclogitasation of olivine rich lower crustal rocks the presence of number of high and low velocity patches further reveals the heterogeneous and fractured nature of the mrz interestingly we observe that aki 1981 s relation d 2b is not valid for the spatial b d correlation of the events in the gf d2 1 2b zone however the events in the mrz d2 1 7b show a fair agreement with the d 2b relationship while the earthquakes associated with the remaining parts of the aftershock zone d2 1 95b show a strong correlation with the aki 1981 s relationship thus we infer that the remaining parts of the aftershock zone are probably behaving like locked un ruptured zones where larger stresses accumulate we also propose that deep fluid involvement may play a key role in generating seismic activity in the mrz therefore a similar episode of deep fluid inflow could play a crucial role in causing the next strong earthquakes in the surrounding blocks of nwf

crustal structure along mehmadabad billimora profile in the cambay basin india from deep seismic soundings abstract deep seismic sounding dss investigations were carried out along a 220 km long n s profile from mehmadabad 22 50 n 72 46 e to billimora 20 46 n 72 58 e in the cambay basin india for studying the detailed crustal structure in the region seismic refraction as well as narrow and wide angle reflection travel time data were obtained for various crustal boundaries starting from the sedimentary section down to the moho by continuous profiling analysis of reversed reflection and refraction travel time data has yielded crustal velocity depth functions for the mehmadabad broach and broach navsari sections along the profile which are significantly different from each other the average velocities at depths in the magmadabad broach section have been found to be considerably lower than those in the broach navsari section by about 25 at 5 km 17 at 10 km 7 at 20 km and 2 at the moho depth and even deeper down in the upper mantle the presence of a relatively thicker sedimentary section especially in the jambusar broach area as revealed by the reversed refraction data analysis is responsible for this gross difference in the average velocity functions for the two parts of the profile and the same have therefore been used for obtaining the detailed crustal depth along the profile the cambay basin which is well known to be bounded by step faults on the eastern and western margins is also dissected into seven major crustal blocks in the n s direction from mehmadabad to billimora the various crustal blocks identified are from the north 1 i mehmadabad block 2 ii tarapur block 3 iii petlad katana block 4 iv jambusar broach block 5 v kosamba block 6 vi surat block and 7 vii navsari billimora block these blocks are displaced up or down relative to the adjacent blocks due to movements along the faults bounding them most of the faults have been found to extend quite deep and to affect the moho boundary considerably as is quite evident from the relief of the moho found along the profile further the seismic activity observed in the region during historical as well as modern times suggests that these deep faults may even be currently active the jambusar broach block which is well known as a broad regional syncline with the maximum thickness of cenozoic sediments has been found to be a major graben revealing a maximum crustal thickness of 38 40 km the granitic basement in this graben is also the deepest at 6 0 6 5 km depth towards the north and south of this major graben the moho as well as the granitic basement are found to be at relatively shallower depths in various crustal blocks the boundary velocity at the moho has been found to be 8 1 8 2 km sec whereas at the granitic basement level there seems to be a lateral velocity variation from 5 7 to 6 3 km sec the crustal depth section obtained in the present study reveals a close relationship between the deep and shallow structural features in this region the deccan traps which form the basement of the overlying tertiary sediments over most part of the profile vary in thickness from 1 0 to 1 8 km however the trap surface rises to very shallow depths on the southern part of the profile the boundary velocity in the deccan traps has been found to vary between 4 8 and 5 2 km sec in the anklesvar kosamba area there is also evidence for the presence of a 1 2 km thick layer of mesozoic sediments with a velocity of about 4 0 km sec underlying the 1 1 km thick deccan traps layer

low coda qc in the epicentral region of the 2001 bhuj earthquake of mw 7 7 on 26 january 2001 03 46 55 ut a devastating intraplate earthquake of m w 7 7 occurred in a region about 5 km nw of bhachau gujarat 23 42 n 70 23 e the epicentral distribution of aftershocks defines a marked concentration along an e w trending and southerly dipping 45 zone covering an area of 60 40 km2 the presence of high seismicity including two earthquakes of magnitudes exceeding 7 7 in the 200 years is presumed to have caused a higher level of shallow crustal heterogeneity in the kutch area a site lying in the seismic zone v zone of the highest seismicity for potentially m8 earthquakes on the seismic zoning map of india attenuation property of the medium around the epicentral area of the bhuj earthquake covering a circular area of 61 500 km2 with a radius of 140 km is studied by estimating the coda q c from 200 local earthquakes of magnitudes varying from 3 0 4 6 the estimated q 0 values at locations in the aftershock zone high seismicity are found to be low in comparison to areas at a distance from it this can be attributed to the fact that seismic waves are highly scattered for paths through the seismically active and fractured zone but they are well behaved outside the aftershock zone distribution of q 0 values suggests that the local variation in q 0 values is probably controlled by local geology the estimated q 0 values at different stations suggest a low value of q 102 0 80 f 0 98 0 02 indicating an attenuative crust beneath the entire region the frequency dependent relation indicates a relatively low q c at lower frequencies 1 3 hz that can be attributed to the loss of energy due to scattering attenuation associated with heterogeneities and or intrinsic attenuation due to fluid movement in the fault zone and fluid filled cracks the large q c at higher frequencies may be related to the propagation of backscattered body waves through deeper parts of the lithosphere where less heterogeneity is expected based on the attenuation curve estimated for q 0 102 the ground acceleration at 240 km distance is 13 of 1 g i e 0 13 g agreeing well with the ground acceleration recorded by an accelerograph at ahmedabad 0 11 g hence it is inferred that the q 0 value obtained from this study seems to be apt for prediction of ground motion for the region

the motion and active deformation of india measurements of surface displacements using gps constrain the motion and deformation of india and india eurasia plate boundary deformation along the himalaya the gps velocities of plate interior sites constrain the pole of the angular velocity vector of india with respect to eurasia to lie at 25 6 1 0 n 11 1 9 0 e approximately 6 west of the nuvel 1a pole of 3 ma plate motion the angular rotation rate of 0 44 0 03 myr 1 is 14 slower than the long term rate of 0 51 myr 1 insignificant velocities between plate interior sites indicate that the exposed indian plate is stable to within 7 10 9 yr 1 the observed contraction vector across the himalaya 20 mm yr veers from n20 e in the northwest himalaya to n25 w in east nepal consistent with east west extension of southern tibet

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

numerical modelling of a centrifuged embankment on soft clay biot coupled consolidation numerical analyses have been applied to a stage constructed embankment on soft clay in the centrifuge in the test the sand embankment was constructed on a clay foundation consisting of an overconsolidated crust overlying a normally consolidated layer measurements were taken of pore pressures dissipation rates and displacements in the foundation clay predictions of these were made using a simple cam clay model for the clay and the cambridge crisp computer program a linear elastic idealization was used for the embankment with some exceptions pore pressures and dissipation rates were very well predicted as were maximum values of both horizontal and vertical displacements however displacement profiles with depth were not so well predicted particular attention is given in the paper to the determination of relevant values of shear modulus g and the difference in behaviour resulting from using constant permeability and permeability varying with void ratio

settlement patterns of soft soil foundations under embankments the settlement pattern of an embankment may not always be the typical one in which the maximum settlement occurs at the center other patterns may develop with changes of embankment width or surcha

using hydrochemical and isotopic data to determine sources of recharge and groundwater evolution in an arid region a case study in the upper middle reaches of the shule river basin northwestern china understanding sources of recharge and mechanisms for hydrogeochemical evolution of groundwater in the shule river basin an arid inland river basin in northwestern china is essential for successful water resource management sources of water and associated groundwater recharge processes were investigated using hydrogeological hydrogeochemical and isotopic methods the study area was divided into three parts changma the shule valley and the beishan area the hydrogeochemical and isotopic analysis results show that groundwater in changma mainly originated from precipitation in the qilian mountains lateral flow from changma is the primary recharge mechanism while direct recharge by infiltration of precipitation can be neglected in the shule valley minerals within the aquifer material e g halite calcite dolomite and gypsum dissolve into water that recharges the groundwater system therefore strong linear relationships were found between na and cl and between ca2 mg2 and so42 hco3 with stoichiometry ratios of approximately 1 1 in both cases groundwater quality in the region is generally good with low salinity and hardness local precipitation is the only source of recharge for groundwater in the beishan area low groundwater velocity and dry climatic conditions suggest that dissolution of minerals from the aquifer material controls hydrogeochemical evolution water rarely travels from the beishan area to the shule valley therefore almost all the groundwater in the shule valley originates from changma global climate change and loss of glaciers in the qilian mountains may lead to a reduction of recharge therefore the groundwater resources of the shule valley must be managed to sustain water supply

crustal structure of the indian shield new constraints from teleseismic receiver functions teleseismic earthquake waveform data from 10 broadband stations spread over the indian shield and in operation since 1997 were analyzed to infer the crustal structure using the receiver function technique the south indian shield is characterized by a 33 39 km thick and remarkably simple crust with an average poisson s ratio close to 0 25 the archaean crust is devoid of any prominent intra crustal discontinuities the velocity contrast at the well developed moho is large resulting in very clear p to s conversions as well as first order multiples in contrast the predominantly proterozoic crust in the northern part of the shield exhibits a complex character due to the presence of additional seismic discontinuities moho conversions which are considerably weaker compared to the archaean terrains indicate crustal thicknesses of more than 40 km

stress drop variations and source scaling relations of moderate earthquakes of the indian tectonic plate we investigate the source characteristics of 53 earthquakes in and around the indian subcontinent through a grid search technique applied to the p and s wave displacement spectra of regional waveforms registered at 42 broadband seismic stations in addition we estimate the p and s wave attenuation factors representative of the various tectonic regions that constitute the indian shield we discuss the sensitivity of the displacement spectrum to various parameters and demonstrate that for a brune type source model the seismic moment is the best estimated parameter compared to others such as the corner frequency our estimates of moment magnitudes are within the range of 1014 1020 n m with the crack radii being less than 12 km the nonuniform distribution of the static stress drop along the himalaya burmese arc and the western indian regions indicates that the central himalayas are prone to frequent failures owing to the lesser stress drop in contrast with the northwestern himalaya and burmese arc regions our results suggest that median stress drops are independent of the earthquake mechanism online material list of events and associated estimated parameters

groundwater δ18o and δd from central indian peninsula influence of the arabian sea and the bay of bengal branches of the summer monsoon abstract results of oxygen and hydrogen isotopic investigations of shallow groundwater and river water samples from the central indian peninsula are reported the study was undertaken to isotopically characterise the near surface water sources and identify the influence of the two branches of the indian summer monsoon june september in this region the western part of the study area receives vapour flux largely from the arabian sea branch whereas the eastern part receives significant vapour flux from the bay of bengal branch no significant rainfall occurs in the study area during northeast winter monsoon period of october december or the remaining part of the year therefore the isotopic character of shallow groundwater from this region could be used to study the relative influence of the vapour sources from the arabian sea and the bay of bengal the study shows that i the northeast part receiving significant rainfall from the bay of bengal branch has a distinctly depleted isotopic composition 18 o 5 2 compared to areas receiving dominant rain from the arabian sea branch 18 o 1 1 ii in the west coastal belt the average 18 o in groundwater is close to the average 18 o of precipitation at bombay 1 4 1 1 but groundwater samples in the entire deccan plateau region show signatures of evaporative enrichment in the form of a low slope 6 5 of 18 o d regression line b low d excess 0 5 and c slightly enriched 18 o values 1 1 compared to those expected from the limited precipitation data from stations in maner basin approximately in the middle of the study area iii depleted ground waters along the central indian east coast could arise due to continental rainout of the arabian sea vapour source as the moisture laden monsoon winds crossover to the bay of bengal alternatively it is necessary to postulate that the surface waters of the bay of bengal contributing to inland vapour flux are significantly more depleted during the monsoon period than the known depletion of 1 it is also possible that both factors are operative

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

estimation of earthquake source parameters in the kachchh seismic zone gujarat india from strong motion network data using a generalized inversion technique the generalized inversion of s wave spectral amplitude data from 18 strong motion sites in the kachchh seismic zone gujarat india has been carried out to estimate source parameters of 38 aftershocks m w 2 93 5 32 from the 2001 bhuj earthquake m w 7 7 the result shows that the seismic moment m and source radius r of aftershocks are between 3 1 1013 and graphic 1 and 226 889 m respectively while stress drops vary from 0 11 to 7 44 mpa the regression analysis between m and r shows a break in linear scaling at graphic 2 the estimated stress drop values scatter significantly with m graphic 3 for larger aftershocks graphic 4 but vary in proportion with m graphic 5 in case of smaller magnitude events this can be due to the complex rupture process associated with relatively larger aftershocks in comparison to circular rupture for smaller events the high stress drop values are observed for events located on the north wagad fault at 15 30 km depths and gedi fault at 0 5 km depths this could be attributed to the large stress develop at the hypocentral depth as a result of high pore fluid pressure beneath these two fault zones the regression between m and corner frequency f c shows m is proportional to graphic 6 which is consistent for earthquakes with short rupture lengths and high stress drop values high stress drop values commonly associated with the events from kachchh and adjacent narmada son lineament rift zones indicate strong potential for generating high peak ground accelerations and hence high seismic hazard 1 embed inline graphic 1 gif 2 embed inline graphic 2 gif 3 embed inline graphic 3 gif 4 embed inline graphic 4 gif 5 embed inline graphic 5 gif 6 embed inline graphic 6 gif

source parameters of the 1980 mammoth lakes california earthquake sequence from the more than 1500 mammoth lakes earthquakes recorded on three component digital seismographs spudich et al 1981 150 were used in an analysis of the locations mechanism and source parameters a composite fault plane solution of nine earthquakes 3 9 m 5 1 defines a right lateral strike slip mechanism on a steeply dipping nearly east west plane striking s75 e or left lateral strike slip on a nearly north south plane striking n10 e vertical cross sections of well located aftershocks indicate possibly three east west planes that coincide with the locations of the four largest earthquakes with ml 6 0 using the spectral analysis of s waves brune 1970 source parameters for 67 earthquakes were determined forty eight had magnitudes greater than or equal to 3 0 seismic moments ranged from 9 20 1018 dyn cm to 2 33 1024 dyn cm earthquakes with seismic moment greater than about 1 0 1021 dyn cm had nearly constant stress drops 50 bars earthquakes with seismic moment less than about 1 0 1021 dyn cm had stress drops that apparently decrease as seismic moment decreases

estimation of source parameters for the aftershocks of the 2001 mw 7 7 bhuj earthquake india the source parameters for 213 bhuj aftershocks of moment magnitude varying from 2 16 to 5 74 have been estimated using the spectral analysis of the sh waveform on the transverse component of the three componnet digital seismograms as well as accelerograms the estimated stress drop values for bhuj aftershocks show more scatter mo0 5 to 1 toward the larger seismic moment values log mo 1014 5 n m larger aftershocks whereas they show a more systematic nature mo3 for smaller seismic moment log mo 15 mpa lying in 22 26km depth range beneath the region we suggest that the concentration of large stress drop values at 10 36km depth may be related to the large stress strain associvated with a brittle competent intrusive body of mafic nature

failure of a breakwater founded on a thick normally consolidated clay layer two breakwaters 890 m and 670 m long were constructed on 55 m and 35 m thick normally consolidated clay layers in busan korea the design incorporated 12 m and 17 m deep trenches excavated in the clay and backfilled with sand the two were similar in type and size and their construction started simultaneously at adjacent sites the east breakwater was successfully completed but the west breakwater failed during the final stage of its construction vertical and horizontal displacements and pore pressure had been measured at a section for each breakwater throughout the construction process using the results obtained from the instrumentation the behaviours of the two breakwaters are compared the original breakwater design is re evaluated with design parameters obtained from an additional investigation prior to the construction it is revealed that the safety factor for arc sliding did not provide enough safety even when the drainage effect due to consolidation was taken into account possible methods

geochemistry s vital contribution to solving water resource problems abstract as part of the events celebrating 40 a of iagc it is fitting to trace the modern evolution and development of hydrogeochemistry however fascination with water quality can be traced back more than 2 ka in the post war years hydrogeochemistry was influenced heavily by the advances in other disciplines including physical chemistry metallurgy and oceanography hydrological applications of isotope science also developed rapidly at this time and important advances in analytical chemistry allowed multi element and trace element applications to be made experimental studies on equilibrium processes and reaction kinetics allowed bench scale insight into water rock interaction consolidation of knowledge on processes in groundwaters and the current awareness of hydrogeochemistry by water professionals owe much to the work of robert garrels john hem and co workers in the early 1960s studies of down gradient evolution enabled a field scale understanding of groundwater quality and geochemical processes as a function of residence time dissolution and precipitation processes in carbonate and non carbonate aquifers redox processes cation exchange and salinity origins emerging water resource and water quality issues in the 1960s and 70s permitted the application of hydrogeochemistry to contaminant and related problems and this trend continues the impacts of diffuse pollution from intensive agriculture waste disposal and point source pollution from urban and industrial sources relied on geochemistry to solve questions of origin and attenuation in semi arid regions facing water scarcity geochemical approaches have been vital in the assessment of renewability and characterising palaeowaters the protection and new incoming regulation of water resources will rely increasingly on a sound geochemical basis for management

isotopic characteristics of indian precipitation 1 hydrogen 2h 1h and oxygen 18o 16o isotopic ratios were measured in precipitation 900 samples collected from several locations in india during the period 2003 2006 12 locations in 2003 and 18 locations in 2004 2006 the amount of rainfall along with air temperature and humidity were also measured the meteoric water line developed for india using isotopic data of precipitation samples namely 2h 7 93 0 06 18o 9 94 0 51 n 272 r2 0 98 differs slightly from the global meteoric water line regional meteoric water lines were developed for several indian regions i e northern and southern regions of india western himalayas and found to be different from each other southern indian meteoric water line slope is 7 82 intercept or d excess is 10 23 northern indian meteoric water line slope is 8 15 intercept is 9 55 which is attributed to differences in their geographic and meteorological conditions and their associated atmospheric processes i e ambient temperature humidity organ and source of vapor masses the local meteoric water lines developed for a number of locations show wide variations in the slope and intercept these variations are due to different vapor sources such as the northeast ne monsoon that originates in the bay of bengal the southwest monsoon sw that originates in the arabian sea a mixture of ne and sw monsoons retreat of ne and sw monsoons and western disturbances that originate in the mediterranean sea the altitude effect in the isotopic composition of precipitation estimated for western himalayan region also varies from month to month

modelling seasonal ratcheting and progressive failure in clay slopes a validation seasonal wetting and drying stress cycles can lead to long term deterioration of high plasticity clay slopes through the accumulation of outward and downward deformations leading to plastic strain

drinking quality assessment of some groundwater sources along the stretch of jhelum river in kashmir himalaya the physicochemical properties and major ion chemistry of the groundwater sources from alluvial aquifers along the stretch 60 km of jhelum river in kashmir himalaya were determined in order to identify hydro geochemical processes and their suitability for drinking purposes the data depicted that calcium and bicarbonates were dominating among the cations and anions the results indicate the trend of cation dominance as ca2 na mg2 k whereas anion dominance was in the order of hco3 cl so4 2 ratio of calcium to magnesium indicated the dissolution of ca2 from caco3 which results in an increased levels of ca2 in the groundwater interpretation of piper trilinear plot understands the various geochemical processes affecting the groundwater quality and shows groundwater was dominated by ca hco3 type the ph was recorded in the slightly alkalinity range 7 2 7 8 and was showing positive correlation with hco3 the chloro alkaline indices revealed 86 of the sources exchange by a type of base exchange reactions rest by cation anion exchange gibbs diagram revealed groundwater sources fall in the category of rock dominance the concentration of the nitrogen compounds was in the progression of no3 n nh4 n no2 n and the po4 fluctuated from 0 12 to 0 22 mg l moreover corrosivity ratio indicated that water from the majority of sources 71 is safe to supply using pipes without any corrosive effects while 29 of sources are corrosive in nature and need non corrosive pipes for transporting and lifting of groundwater the results revealed groundwater samples were within permissible limits as prescribed by international and national standards for drinking purposes the state government and ngo s can show their interest in utilizing such water resources to overcome the shortage of drinking water in a sustainable way for the daily consumption of the people living in the vicinity of jhelum river

ground motion modelling in the gujarat region of western india using empirical green s function approach abstract in this study ground motions are estimated for scenario earthquakes of mw 6 0 6 5 and 7 0 at 17 sites in gujarat region using empirical green s function technique the dholavira earthquake of june 19 2012 mw 5 1 which occurred in the kachchh region of gujarat is considered as an element earthquake we estimated the focal mechanism and source parameters of the element earthquake using standard methodologies the moment tensor inversion technique is used to determine the fault plane solution strike 8 dip 51 and rake 7 the seismic moment and the stress drop are 5 6 10 16 nm and 120 bars respectively the validity of the approach was tested for a smaller earthquake a few possible directivity scenarios were also tested to find out the effect of directivity on the level of ground motions our study reveals that source complexities and site effects play a very important role in deciding the level of ground motions at a site which are difficult to model by gmpes our results shed new light on the expected accelerations in the region and suggest that the kachchh region can expect maximum acceleration of around 500 cm s 2 at few sites near source and around 200 cm s 2 at most of the sites located within 50 km from the epicentre for a mw 7 0 earthquake the estimated ground accelerations can be used by the administrators and planners for providing a guiding framework to undertake mitigation investments and activities in the region

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

stability analysis of two dimensional excavated slopes considering strength anisotropy using the finite element method a cohesive horizontal ground is sequentially excavated until the stress state along a potential slip surface of the excavated slope reaches the critical state mobilized friction angle and stress ratio contours in the slope generated by the finite element solution are examined to quantify the part of the slip surface that undergoes extension resulting in anisotropic conditions the effects of factors such as excavation depths drainage boundary conditions slope angles and initial stress conditions on slope stability are investigated it is shown that excavated slopes display anisotropic behavior and that the consideration of strength anisotropy in slope stability analysis is essential for the example considered it was found that the extent of the extension zone of the slip surface increases as the slope angle decreases and that this relationship is linear key words slope stability strength anisotropy finite element method limiting equilibrium

fluvial geomorphology and neotectonic activity based on field and gpr data katrol hill range kachchh western india 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

scaling differences between large interplate and intraplate earthquakes a study of large intraplate earthquakes with well determined source parameters shows that these earthquakes obey a scaling law similar to large interplate earthquakes in which m 0 l 2 or u l where l is rupture length and u is slip in contrast to interplate earthquakes for which 1 10 5 for for the intraplate events 6 10 5 which implies that these earthquakes have stress drops about 6 times higher than interplate events this result is independent of focal mechanism type this implies that intraplate faults have a higher frictional strength than do plate boundaries and hence that faults are velocity or slip weakening in their behavior this factor may be important in producing the concentrated deformation that creates and maintains plate boundaries

isotopic fingerprints of paleoclimates during the last 30 000 years in deep confined groundwaters of southern india isotopic and geochemical evidence of paleoclimates especially for the last glaciation has been obtained from deep confined groundwaters of southern india the 13c 18o chloride and deuterium analyses of groundwaters show distinct excursions inferred to be related to climatic variations the arid climatic episode associated with the last glaciation 18 000 2000 yr b p is conspicuously identified by signatures of relatively enriched 13c 10 to 12 pdb and 18o 5 3 to 4 8 smow values and high chloride concentration 80 to 160 mg l the transition from an arid to humid period ca 12 000 8000 yr b p is shown by a decreasing trend in the 13c 9 5 to 17 and 18o 4 5 to 6 3 contents of groundwaters the late holocene since 4000 yr b p marked by a more humid but unstable climate is identified by further depletion of 13c 13 to 20 and 18o 5 2 to 6 3 similar variation between 18o and chloride values in confined groundwaters further demonstrates two distinct climatic excursions arid and humid governed by the amount effect this is the first time that isotopic and geochemical signatures related to changing paleoclimates have been identified in the confined groundwaters of the southern indian landmass

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

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

moment energy stress drop and source spectra of western united states earthquakes from regional coda envelopes we present a new method to estimate stable seismic source parameters such as energy moment and orowan stress drop using regional coda envelopes from as few as one broadband station we use the method to compute path and site corrected seismic moment rate spectra for 117 recent western united states earthquakes empirical green s function corrections were applied to our surface and body wave coda envelope measurements to generate s wave source spectra these source spectra provide stable single station estimates of radiated seismic energy es and seismic moment mo that for common events are in excellent agreement with network averaged estimates obtained using local and regional data teleseismic moment estimates are compatible with our regional results but teleseismic energy estimates appear to be nearly an order of magnitude low we estimated the seismic moment of events ranging between mw 2 2 and 7 3 and energy estimates for which we had measured at least 70 of the total energy generally events above mw 3 3 we use these estimates to examine the behavior of derived parameters such as the orowan stress drop 2 es mo while the earthquakes we studied have a small range in orowan stress drop generally between 0 1 and 20 mpa they show a strong tendency for orowan stress drop to increase with moment approximately as mo0 25 we believe this is a source effect and is not due to inadequate bandwidth or attenuation correction and note that this trend appears to continue for microearthquakes as described in a recent deep borehole study in southern california many of the large high stress drop earthquakes show complexity in their moment rate spectra near the corner frequency and cannot be fit by a simple square model instead above the first corner frequency the spectral decay ranges between f 1 0 and f 1 5 this leads to larger estimates of radiated energy than predicted with a simple square model and has implications for seismic hazard estimation coda envelopes have three main advantages over direct arrivals for estimating seismic moment and energy 1 coda amplitudes vary little with geology and source radiation anisotropy and allow accurate single station applications 2 path corrected coda amplitude measurements can be applied to very large regions allowing a comparison of source parameters throughout the western united states using a common methodology and stations 3 because long period coda can last for hours for large local and regional events it allows the analysis of seismograms with clipped early arrivals

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

the influence of the south west indian monsoon on continental deposition over the past 130 kyr gujarat western india ocean and ice core records of the intensity of the south west indian monsoon swim show rapid shifts in most proxy indicators of climate over the past 125 kyr on decadal to millenial scales however the responses of continental environments to such perturbations remain unknown due to the absence of a suitable long term continental record the stratigraphic record from gujarat western india an area where all sedimentological processes are governed by the vagaries of the swim reveals three aggradation phases that represent deposits of seasonal rivers ap1 ephemeral rivers ap2 and dust storms ap3 based on a review of available dates and new esr dates on the oldest exposed calcretes from palaeovertisols these phases are assigned the time brackets 135 100 kyr bp ap1 100 20 kyr bp ap2 and 20 6 kyr bp ap3 these results suggest that continental depositional environments respond in a subdued manner and are separated by thresholds for climate shifts to effect durable changes in the continental depositional environment a period between 5 kyr and 16 kyr is the minimum time required to permanently change the landscape of an area alternatively catastrophic changes in terrestrial depositional environments may also be effected by abrupt climatic shifts that are beyond the tolerance limits of the depositional systems

the oroville earthquakes a study of source characteristics and site effects half space modeling in the time domain of broadband seismic records from the oroville aftershock sequence demonstrates that these events have simple sources systematic scaling between the far field source duration and seismic moment for the aftershocks studied here and other california earthquakes confirms brune s 1970 source model and shows that the stress drops for california earthquakes range between 10 and 100 bars these events also show no trend in stress drop as a function of size for 3 0 or m sub l or 6 4 analysis of the static deformation associated with the main shock shows that the slip occurred on a fault 81 km sup 2 in area corresponding to the zone defined by the first 3 days of aftershocks teleseismic studies indicate that the seismic source area was 50 km sup 2 corresponding to a zone completely free of aftershocks in the middle of the aftershock zone both results imply a stress drop of 29 39 bars and seismic moment between 5 7 and 8 7 x 10 sup 24 dyn cm the evidence suggests that faulting occurred seismically on the central portion of the fault and propagated out slowly enlarging the fault plane complicated waveforms recorded for the same events at nearby sites on alluvium indicatemore the critical role that propagation through complex structure plays in determining the character of the observed seismic signal at close in stations modeling of these records show that dipping structure may account for the observed waveform complexities less

estimation of source parameters and scaling relations for moderate size earthquakes in north west himalaya abstract the scaling relation and self similarity of earthquake process have been investigated by estimating the source parameters of 34 moderate size earthquakes m b 3 4 5 8 occurred in the nw himalaya the spectral analysis of body waves of 217 accelerograms recorded at 48 sites have been carried out using in the present analysis the brune s 2 model has been adopted for this purpose the average ratio of the p wave corner frequency fc p to the s wave corner frequency fc s has been found to be 1 39 with fc p fc s for 90 of the events analyzed here this implies the shift in the corner frequency in agreement with many other similar studies done for different regions the static stress drop values for all the events analyzed here lie in the range 10 100 bars average stress drop value of the order of 43 19 bars for the region this suggests the likely estimate of the dynamic stress drop which is 2 3 times the static stress drop is in the range of about 80 120 bars this suggests the relatively high seismic hazard in the nw himalaya as high frequency strong ground motions are governed by the stress drop the estimated values of stress drop do not show significant variation with seismic moment for the range 5 10 14 2 10 17 n m this observation along with the cube root scaling of corner frequencies suggests the self similarity of the moderate size earthquakes in the region the scaling relation between seismic moment and corner frequency m o f c 3 3 47 10 16 n m s 3 estimated in the present study can be utilized to estimate the source dimension given the seismic moment of the earthquake for the hazard assessment the present study puts the constrains on the important parameters stress drop and source dimension required for the synthesis of strong ground motion from the future expected earthquakes in the region therefore the present study is useful for the seismic hazard and risk related studies for nw himalaya

baseline geochemical conditions in the chalk aquifer berkshire u k a basis for groundwater quality management the chalk aquifer is the most important british aquifer and is also important over much of northern europe aquifer protection requires a sound knowledge of the baseline conditions and how these might vary or have varied with time this detailed geochemical study of a representative area of chalk in berkshire u k includes a consideration of several components 1 the inputs from the atmosphere 2 the interstitial water of the soil and the unsaturated zone 3 the interstitial water in the confined and unconfined sections of the aquifer and 4 the saturated mainly fissure flow along the hydraulic gradient which forms an important water supply of the thames valley region atmospheric inputs form an important source of some elements but the dominant chemical characteristics of the chalk groundwater are acquired during percolation through the soil and the upper unsaturated zone during saturated flow downgradient the chemistry is modified mainly by incongruent reactions of the carbonate matrix and by redox reactions and only to a minor extent by exchange reactions and mixing with residual saline connate water the incongruent reaction of carbonate results in a marked increase in the mg ca ratio and the sr and 13c contents of the groundwater with increased residence time oxygen concentrations are reduced mainly by oxidation of fe2 and the onset of reducing conditions allows dissolved fe2 to increase and rapid denitrification to occur the salinity profile through the confined chalk confirms that residual connate water up to one fifth sea water concentration still remains at depth and this accounts for some salinity increase in the confined groundwater resulting from fissure water pore water diffusional exchange timescales for groundwater movement have been established using tritium radiocarbon and indirectly using inert gas ratios and stable isotope ratios on balance it is concluded that all abstracted water is of holocene age although inert gas temperatures indicate cooler climatic conditions for recharge for some of the confined groundwater the implications for development and aquifer protection are discussed especially the prospect of natural in situ denitrification problems of fe solubility and the recognition of groundwater of different maturities