an integrated geophysical approach for water infiltration detection and characterization at monte cotugno rock fill dam southern italy abstract this study concerns with an integrated geophysical approach for the detection and spatial temporal characterization of the water infiltration into the monte cotugno dam embankment this strategic civil infrastructure is the largest rock fill dam in europe and represents the nodal point of the water system feeding the basilicata puglia and calabria regions southern italy here we propose an approach based on the combination of geophysical techniques as ground penetrating radar gpr and electrical resistivity tomography ert with thermal infrared mapping tir and geotechnical in situ measurements such an approach was applied for the diagnosis of the monte cotugno dam with the aim both to gain information about the geometry of visible micro fractures in the dam coverage and have a rapid mapping of the dam inner areas affected by water infiltration phenomena the sensing methods were deployed in a cascade modality where the thermal infrared tir method was used for surveying the dam along the overall length in order to achieve information about the dam coverage status in particular tir analysis allowed us to identify five areas affected by significant fractures and coating detachment afterwards gpr surveys were performed on the sloping side of the dam by investigating few areas among those identified by tir analysis in this way it was possible to get indications whether the water infiltration affected the deeper parts of the dam lastly electrical resistivity tomography ert method was applied in order to detect deeper inner areas affected by water leakages finally a joint interpretation of the three sensing methods was confirmed by shallow boreholes

ultrashallow depth imaging of a channel stratigraphy with first arrival traveltime inversion and prestack depth migration a case history from bull creek oklahoma depth imaging in ultrashallow 50 m environments presents twofold challenge 1 coda available for depth migration is very limited and 2 conventional time processing with limited coda generally fails to estimate reliable velocity models for depth migration we studied the combining of first arrival traveltime inversion and prestack depth migration psdm for depth imaging of ultrashallow paleochannel stratigraphy associated with the bull creek drainage system oklahoma restricted by a limited number of geophones 24 we acquired data for inversion and migration through two coincident profiles the first profile for inversion has a wider survey aperture 115 m maximum shot receiver spacing and consequently sparse cmp spacing 2 5 m whereas the second profile for psdm has denser cmp spacing 1 m and consequently a narrower survey aperture 46 m maximum shot receiver spacing we also found that the velocity model from traveltime inversion of the wider aperture data set is more preferable for dep

ultrashallow seismic experiment on a trenched section of the chelunpu fault zone taiwan ultrashallow p wave seismic reflection experiments were conducted at a model test site and in a trenched shallow fault zone along the chelunpu fault line the field layout was designed to have the shallowest undistorted reflection from about 1 m depth with 0 5 m vertical resolution the smallest group interval tested in this study was 0 05 m with a 0 25 ms sample interval which can avoid spatial aliasing of ground roll if the target is very shallow and the velocities are low data processing was designed to be simple but consistent as the ultrashallow reflections may be contaminated with high amplitude coherent noise in many aspects first break muting and surgical muting were performed on each file as detailed as possible and f k filtering was applied mainly for the purpose of attenuating the aliasing energy and back scattered noise data acquired in this study show that the low p wave velocities 200 m s and high dominant frequencies 120 200 hz of near surface layers may have a potential vertical resolution of 0 4 m or even better comparing the test profile with the ground penetrating radar gpr control profile of the same test site and correlating the results obtained from the study site with those of the geologic cross section of the trench this experiment demonstrates the possibility of using seismic methods in investigating shallow structures at depths of less than a few meters with vertical resolution comparable to the gpr technique

detection of water leakage from dams by self potential method abstract a self potential survey of streaming potentials along the eastern embankment of a dam was very successful in locating leakage areas and determining the relative intensity of discharge self potential measurements have shown negative anomalies of up to 100 mv in amplitude the width of the discharge areas ranged between about 40 m and 150 m repeated observations of sp data at two different reservoir levels showed no great change in the leakage flow behaviour detailed mapping of sp values in the area revealed the possible presence of two sinkholes the first with an estimated diameter of about 25 30 m and the second with a diameter of about 15 m based on a qualitative interpretation of the sp anomalies the location of these two sinkholes coincides well with the position of two subsurface normal faults in the area

crossline resistivity tomography for the delineation of anomalous seepage pathways in an embankment dam crossline resistivity tomography was developed to find out anomalous seepage pathways in an embankment dam by applying crossline tomography to the investigation of embankment dams leakage pathways can be effectively located because the crossline tomogram presents resistivity distribution in the horizontal plane of an embankment dam to test the effectiveness of crossline tomography we applied it to data from an experiment designed to delineate anomalous seepage pathways in the embankment dam the method yields relatively accurate geoelectric structure of the dam when applied to synthetic data in the crossline resistivity tomogram abrupt discontinuities of a low resistivity band corresponding to the core of the dam can be interpreted as leakage pathways application to real data obtained from an embankment dam in korea yields the result which accurately depicts two anomalous seepage pathways the identified pathways were consistent with low resistivity zones in the dipole dipole resistivity section obtained on the crest of the dam one pathway was confirmed by visual inspection of the dam and afterward by trenching

the influence of foliation on point load strength anisotropy of foliated rocks abstract the engineering behaviour of rocks depends upon whether the fabric is isotropic or anisotropic which is a reflection of its genetic environment even though anisotropy in fabric can occur in nearly all natural environments metamorphic terrains usually offer the main source of anisotropic fabric elements metamorphic anisotropic fabrics collectively known as foliation may be quantified by a foliation index determined from optical microscopic or x ray diffraction analysis depending upon the degree of coarseness or fineness of the rock on the basis of this index the role of foliation in conditioning anisotropy in point load strength has been quantified the practical significance of the resultant classification scheme lies in the fact that reliable predictions of point load strength anisotropy of foliated rocks can be made on the basis of a critical analysis of their primary anisotropic fabrics foliation

high frequency reflections in granite delineation of the weathering front in granodiorite at pinon flat california we analyze data from two orthogonal seismic lines 336 m in length collected at pinon flat california over weathered granodiorite bedrock each line was made up of 10 reversed segments 84 m in length we analyzed the first arrivals from these data and found dramatic variations in velocity along the profiles an upper layer approximately 2 m thick known from trenching to be composed of soil and sandy grus had measured velocities ranging from 400 to 700 m s velocities inferred from refraction analysis of first arrivals of the reversed lines revealed a heterogeneous lower layer below the soil with measured velocities of 1600 2700 m s by a depth of 15 m we interpret these data to be measuring velocities of a deeply weathered unit characterized by granodiorite corestones embedded in a matrix of saprolite the most remarkable feature of these data emerged from attempting to process the same data as reflection data simple bandpass filtering in the 250 400 hz band revealed a bright impulsive arrival with t

predicting the deformation moduli of rock masses abstract predictive empirical models for the mechanical properties of rock masses have been used in rock engineering because direct measurement of the properties is difficult due to the presence of discontinuities such empirical models are open to improvement because they are based on collected data the purposes of the present study are to assess the existing empirical equations and to develop a new empirical approach for this reason in the first stage of the study the prediction performance of the existing models proposed for predicting the deformation modulus of rock masses were evaluated statistically by using a database including 115 data values obtained from in situ plate loading and dilatometer tests a new empirical approach with higher prediction capacity than the existing empirical models was developed in the subsequent stage of the study the new empirical model considers the modulus ratio of intact rock e i ucs rock quality designation rqd and weathering degree wd although data obtained from very weak and weak rock masses were included in the development of the new empirical equation the type of rocks employed in the study were limited therefore a crosscheck between the new empirical equation and previous empirical approaches should be performed in the design stage

seismicity and seismic hazard in alexandria egypt and its surroundings alexandria city has suffered great damage due to earthquakes from near and distant sources both in historical and recent times sometimes the source of such damages is not well known seismogenic zones such as the red sea gulf of aqaba dead sea hellenic arc suez cairo alexandria eastern mediterranean cairo faiyoum and the egyptian costal area are located in the vicinity of this city the egyptian coastal zone has the lowest seismicity and therefore its tectonic setting is not well known

positive cloud to ground lightning flashes in severe storms the occurrence of cloud to ground flashes that effectively lower positive charge to earth cg flash over flat terrain has been documented in the mature stage of severe thunderstorms of the 31 documented cg flashes most had only one return stroke zero to peak rise times for the strokes averaged 7 s the cg flashes averaged 520 ms in duration with 25 percent lasting more than 800 ms many of these had field changes suggestive of continuing current positive flashes have been observed to emanate from several regions of severe storms high on the back of the main storm tower through the wall cloud and from the downshear anvil visually most of these positive flashes have emanated from high in the storm and acoustic mapping of two shows thunder sources to a height of about 15 km

study of a prehistoric landslide using seismic reflection methods integrated with geological data in the wasatch mountains utah usa an integration of geological and geophysical techniques characterizes the internal and basal structure of a landslide along the western margin of the wasatch mountains in northern utah usa the study area is within a region of planned and continuing residential development the little valley landslide is a prehistoric landslide as old as 13 ka b p drilling and trenching at the site indicate that the landslide consists of chaotic and disturbed weathered volcanic material derived from tertiary age volcanic rocks that comprise a great portion of the wasatch range five short high resolution common mid point seismic reflection profiles over selected portions of the site examine the feasibility of using seismic reflection to study prehistoric landslides in the wasatch mountain region due to the expected complexity of the near surface geology we have pursued an experimental approach in the data processing examining the effects of muting first arrivals frequency filtering model based static corrections and seismic migration the results provide a framework for understanding the overall configuration of the landslide its basal failure surface and the structure immediately underlying this surface a glide surface or decollement is interpreted to underlie the landslide suggesting a large mass movement the interpretation of a glide surface is based on the onset of coherent reflectivity calibrated by information from a borehole located along one of the seismic profiles the glide surface is deepest in the center portion of the landslide and shallows up slope suggesting a trough like feature this study shows that seismic reflection techniques can be successfully used in complex alpine landslide regions to 1 provide a framework in which to link geological data and 2 reduce the need for an extensive trenching and drilling program

a modified seismic reflection approach for engineering geology investigation in fractured rock zones abstract delineating soil rock interface is critical for geotechnical and tunnel site investigations in engineering geology in singapore we also need to draw attention to local faults and fractured rock zones because the regional geology of peninsular malaysia and singapore contains some minor steep and brittle faults propagating at some areas in the island city in addition to drilling boreholes seismic reflection survey is a viable option to mitigate the uncertainties in areas without boreholes however the current practice of seismic reflection still follows the methods used in the petroleum exploration community this investigation reviews and modifies the seismic reflection approach specifically customized for geotechnical and tunnel site investigation which is partly different from petroleum exploration we demonstrate the modified approach through a field testing in singapore the resultant image from the field test fairly captures the soil rock interface and it is validated based on the vertically drilled boreholes a local fault or a fracture rock zone is also identified in the migrated image the extent and location match with the record of horizontal directional coring hdc this addresses the concern of fracture rock zone raised from the regional and local geology and provides useful information for geotechnical and tunnel engineers in addition we further discuss the general challenges of using the modified seismic reflection approach this work aims to help the geotechnical and tunnel community better understand the non invasive seismic reflection survey

mapping the geometry of an aquifer system with a high resolution reflection seismic profile a high resolution p wave seismic reflection survey was conducted in the area of lambro park within the city of milan northern italy several high permeability channel sequences were identified and the stratigraphy of the infill was accurately mapped the seismic signature imaged a previously undefined unit and also established the lateral correlation of some depositional units within the three major aquifer groups along the survey line the complexity of the acoustic framework and the reduced depth of the source location limited effective elastic wave generation the geological setting also caused propagation of strong coherent noise patterns further interference observed in the recorded data was due to the traffic noise from the nearby highway the attenuation of the undesired events required the design of specific filters and their multistep implementation the results of forward modelling based on borehole information and of noise tests were crucial factors in the design of the processing parameters and in the stratigraphic interpretation of the final stacked section

three dimensional seismic reflection imaging of a shallow buried paleochannel a suite of reflection seismology investigations of the shallow subsurface was conducted at hill air force base ogden utah at a groundwater contamination site with very large subsurface mechanical heterogeneity the investigations were designed to expand and improve understanding of the subsurface environment developed from well data and previous seismic investigations the goal of the investigations was to image the sides and bottom of a paleochannel eroded in a clay layer 10 15 m below the surface the paleochannel is filled with a mix of sands clays and gravels of different compaction and water saturation the paleochannel acts as a contaminant trap for dense nonaqueous phase liquids dnapls therefore a detailed map of its geometry lateral boundaries and depth is crucial to remediation efforts the results of processing a 3d reflection data set over the channel showed that it is possible to image and delineate the geometry and depth of a very shallow structure seismic results agreed well with

research on the fracture structure and activity of the qinling mountains thrust nappe system in western hubei the western hubei section of the liangyun fault is an important structural belt of the southern qinling mountains thrust nappe system as the significant activity of the liangyun fault since the qu

geophysical geological and hydrogeological characterization of a tributary buried bedrock valley in southern ontario buried bedrock valleys infilled with quaternary aged sediment have the potential to become productive aquifers owing to prevalent sand and gravel deposits often associated with these topographic lo

strontium and carbon isotope tracers and the origins of soil carbonate in south australia and victoria abstract calcium carbonate occurs in soils in association with a variety of rock types in coastal and inland south australia and victoria the 87 sr 86 sr ratios of the coastal soil carbonates fall between 0 7094 and 0 7098 showing that the ocean is the principal source of calcium to nearly all soils near the coast and that contributions from bedrock are generally small an exception is the soil formed on the young volcano at mt gambier in which the average ratio for carbonate is about 0 7070 compared to 0 7041 for the volcanic ash the basaltic ash of the volcano is readily weathered and rich in calcium roughly 40 of strontium and 10 to 20 of the calcium in the soil carbonate derives from the ash and the balance from marine sources the 87 sr 86 sr ratios from soil carbonate gradually increase inland reaching values of 0 7152 these higher ratios reflect at least in part the increasing 87 sr 86 sr ratio of inland dust in contrast the ocean does not contribute significantly to the carbon pool of the soils we studied the 13 c pdb values of soil carbonates on kangaroo island and the higher rainfall areas of eastern victoria fall between 11 0 and 8 7 indicating that the carbonate formed in equilibrium with the c3 dominated vegetation typical of the region in the warmer inland areas to the north such as the eyre peninsula the 13 c value of soil carbonate averages 5 3 reflecting the higher proportion of c4 plants in the local biomass mixing with marine sources of carbonate cannot account for the observed carbon isotopic patterns the flux of carbon into soils from the ocean therefore must be small compared to that derived from plant respiration and decay

geophone ground coupling for frequencies much lower than the coupling resonant frequency the geophone accurately follows the ground motion but for higher frequencies the coupling can alter both the amplitude and phase of the seismic signal the normal planting of vertical geophones in the field results in coupling adequate for conventional recording that uses frequencies less than 100 hz however for very loose soils or for high frequency seismic recording i recommend that the geophones be buried to place the geophones in firmer soil the coupling resonant frequency for vertical geophones is determined by the firmness of the soil and i have measured resonant frequency ranging from 100 to 500 hz at different locations because the firmness of the soil increases with depth the coupling resonant frequency can be increased by burial of the geophones or by the use of longer spikes the rocking of horizontal geophones causes a low frequency coupling resonance it is crucial that horizontal geophones be planted with their bases firmly contacting the soil geophones so planted have a resonance around 130 hz whereas those 1 cm off the ground can have a resonance of 30 hz or lower soil conditions have little effect on the resonant frequency horizontal geophones with 1 inch spikes are as well coupled as those with longer spikes but the best coupling is achieved by burial of the geophones modified journal abstract

seismic reflection analysis of the manson impact structure iowa our combined interpretation of new high resolution seismic reflection data and reprocessed but previously published industrial vibroseis data indicates that the manson impact structure iowa has an apparent crater diameter of 35 kin an annular trough diameter of around 21 km a shallow floor 0 6 0 7 kin and a central uplift that has a minimum diameter of 7 5 kin the two reflection lines are coincidentally located along an east west radial transect and are consmined by shallow drill information results from the two data sets are correlative both data sets were instnunental to the final interpretation due to the trade offbetween resolution and depth of energy penetration based on the combined interpretation structural uplift of the central peak is estimated to be around 2 8 kin onlapping seismic sequences are present at the eastern edge of the central uplift these seismic packages observed only in the high resolution line are interpreted to represent impact breccia or debris material that was shed from the central peak or dynamically transported from outside of the crater

high resolution shallow seismic experiments in sand part ii velocities in shallow unconsolidated sand we conducted a shallow high resolution seismic reflection and refraction experiment on a sandy beach the depth of investigation was about 2 m we interpret the data using the hertz mindlin contact theory combined with gassmann s equation these were used to obtain the vertical velocity profile then the profile was computed from seismic data using the turning rays approximation the normal moveout nmo velocity at the depth of 2 m matches the velocity profile as a result we developed a method to invert measured velocity from first arrivals i e velocity versus distance into velocity versus depth using only one adjustable parameter this parameter contains all the information about the internal structure and elasticity of the sand the lowest velocity observed was about 40 m s it is noteworthy that the theoretical lower bound for velocity in dry sand with air is as low as 13 m s we find that modeling sand as a quartz sphere pack does not quantitatively agree with the measured data however the the

depth characterization of shallow aquifers with seismic reflection part ii prestack depth migration and field examples it is common in shallow seismic studies for the compressional wave velocity in unconsolidated sediments to increase by a factor of four or more at the transition from dry or partial water saturation to full saturation under these conditions conventional nmo velocity analysis fails and leads to large depth and layer thickness estimates if the dix equation is assumed valid prestack depth migration psdm is a means of improving image accuracy a comparison of psdm with conventional nmo processing for three field examples from differing hydrogeologic environments illustrates that psdm can significantly improve image quality and accuracy

seismic ray tracing using linear traveltime interpolation a new ray tracing method called linear traveltime interpolation lti is proposed this method computes traveltimes and raypaths in a 2d velocity structure more rapidly and accurately than other conventional methods the lti method is formulated for a 2d cell model and calculations of traveltimes and raypaths are carried out only on cell boundaries therefore a raypath is considered to be always straight in a cell with uniform velocity this approach is suitable to tomography analysis the algorithm of lti consists of two separate steps step 1 calculates traveltimes on all cell boundaries step 2 traces raypaths for all pairs of receivers and the shot a traveltime at an arbitrary point on a cell boundary is assumed to be linearly interpolated between traveltimes at the adjacent discrete points at which we calculate traveltimes fermat s principle is used as the criterion for choosing the correct traveltimes and raypaths from several candidates routinely the lti method has been compared numerically with the shooting method and the finite difference method fdm of the eikonal equation the results show that the lti method has great advantages of high speed and high accuracy in the calculation of both traveltimes and raypaths the lti method can be regarded as an advanced version of the conventional fdm of the eikonal equation because the formulae of fdm are independently derived from lti in the process of derivation it is shown theoretically that lti is more accurate than fdm moreover in the lti method we can avoid the numerical instability that occurs in vidale s method where the velocity changes abruptly

shallow seismic reflection mapping of the overburden bedrock interface with the engineering seismograph some simple techniques where unconsolidated overburden exceeds 20 m in thickness the reflection method may be efficiently used with a 12 channel engineering seismograph to map topography on the overburden bedrock interface as well as possible structure within the overburden the two techniques we suggest are the simplest forms of reflection profiling which can be applied with a minimum amount of equipment which we suggest is a 12 channel enhancement seismograph a 12 geophone array and a hammer source these techniques require good transmission characteristics of the overburden as well as a sharp velocity discontinuity at the overburden bedrock interface for data processing and display a microcomputer is essential

reevaluation of carbonate concentration and oxygen isotope records from lake qinghai the northeastern tibetan plateau abstract lake qinghai is the largest lake on the tibetan plateau and it is also one of the important sites for studying global environmental changes over the past 30 years many studies have used oxygen isotope of authigenic carbonates from the lake as the proxy to infer past environmental and climate changes on the plateau however debate on interpretations of isotopic data and their environmental implications still exist largely due to the complex arid environment settings and multiple sources species for carbonate minerals within the lake in this study we systematically analyze 18 o values in different type carbonates collected i e bulk carbonates ostracode shells chara encrustations and fine grain 18 o values of bulk fine grain carbonates since the last glacial maximum together with previously published 18 o records from ostracode shells we try to re evaluate the controlling factors of variations in lacustrine carbonate 18 o data and to infer environmental changes on the northeastern tibetan plateau since the last glacial maximum our results show that the lake depth or the size of the water body is an important factor to influence the lake water and carbonate 18 o values a shallow and small lake would be more easily influenced by precipitation 18 o which is characterized by negative values at lake qinghai region while a deep and large lake would be better to reflect environmental changes such as the precipitation evaporation balance the lake volume effect might be an explanation for the negative carbonate 18 o values during the early holocene which was likely caused by an increased influence of negative 18 o values in precipitation and glacial melt water under a small and shallow water body the 18 o values of ostracode shells and bulk carbonates show similar variations since both of them are dominated by lake water oxygen isotopic composition but they still have distinct geochemical information the isotopic differences between ostracode and bulk carbonates probably reflect the temperature differences between the surface and the bottom of lake water in addition the 18 o values of evaporative induced carbonates may correlate with carbonate contents while those of chara encrustations do not show any correlation with carbonate contents our results suggest that special caution would be necessary when using lacustrine 18 o values of authigenic carbonates to infer past hydrological and climate changes in an arid environment

detailed images of the shallow alpine fault zone new zealand determined from narrow azimuth 3d seismic reflection data previous high resolution seismic reflection investigations of active faults have been based on 2d profiles unfortunately 2d data may be contaminated by out of the plane reflections and diffractions that may be difficult to identify and eliminate although full 3d seismic reflection methods allow out of the plane events to be recognized and provide superior resolution to 2d methods they are only rarely applied in environmental and engineering studies because of high costs a narrow azimuth 3d acquisition and processing strategy is introduced to produce a high resolution seismic reflection volume centered on the alpine fault zone new zealand the shallow 3d images reveal late quaternary deformation structures associated with this major transpressional plate boundary fault the relatively inexpensive narrow azimuth 3d acquisition pattern consisting of inline source and receiver lines was easily implemented in the field to provide 2 by 4 m cmp coverage over an approximately 500 by 200 m area the narrow

cloud to ground lightning observations from toga coare selected results and lightning location algorithms abstract recently observations of electrified oceanic convection and associated cloud to ground cg lightning were obtained over the tropical western pacific ocean during toga coare tropical ocean global atmosphere coupled ocean atmosphere response experiment during coare observations of convection were made using a variety of instrument platforms including ship and airborne doppler radars an advanced lightning direction finder aldf network and a shipborne inverted electric field mill this study focuses on data collected by the coare aldf network fusion of those data with observations and the methods used to calculate accurate cg return stroke locations analysis of cg lightning data and doppler radar data indicates that lightning producing oceanic convection is characterized by deep vertically developed convective cells with radar reflectivities exceeding 30 dbz above the height of the 10 c level in several cases a peak in cg frequency occurred coincident with the descent of precipitation

surface precipitation electric current produced by convective rains during the mesoscale alpine program 1 this paper presents data from measurements of electric field precipitation current density and rainfall parameters performed during the mesoscale alpine program experiment in northern italy during autumn 1999 several days of the period provided substantially charged rainfall of both polarities the average proportions of each polarity are close but the negative one is slightly larger 54 three doppler radars provided a description of the cells development and dynamics a case of a deeply convective cell occurred on 17 september 1999 in this case the precipitation current density is first positive reaches more than 100 na m 2 and changes its polarity when the rainfall is maximum with a value close to 200 mm h 1 we also consider several shallow convective cells passing over the experimental site on 3 october two cells among a set of eight did not produce electrical parameter variations although they displayed development and radar reflectivity structure similar to that of the others the dynamical study shows that the vertical velocity averaged over 1 km 1 km mesh was weaker within these two cells with a value of only 0 5 m s 1 while it reached 1 5 m s 1 within the other cells both charge polarities were observed on the rain produced by electrified cells first the negative one and then the positive one a very tight correlation between surface electric field and precipitation current is observed out at the surface displaying the mirror image effect the ground electric field is due to the cloud charge in contrast with that carried down to the ground by the rainfall in order to reproduce the field evolution created by the cell passage we test different models of charge distribution a model including a horizontal distribution is found to provide a field evolution in best agreement with the observations according to this model the net charge of the cloud above the site is chronologically positive and negative which can be the result of the evacuation of an opposite charge by the rain

detecting young slow slipping active faults by geologic and multidisciplinary high resolution geophysical investigations a case study from the apennine seismic belt italy 1 the southern apennines range of italy presents significant challenges for active fault detection due to the complex structural setting inherited from previous contractional tectonics coupled to very recent middle pleistocene onset and slow slip rates of active normal faults as shown by the irpinia fault source of a m6 9 earthquake in 1980 major faults might have small cumulative deformation and subtle geomorphic expression a multidisciplinary study including morphological tectonic paleoseismological and geophysical investigations has been carried out across the extensional monte aquila fault a poorly known structure that similarly to the irpinia fault runs across a ridge and is weakly expressed at the surface by small scarps warps the joint application of shallow reflection profiling seismic and electrical resistivity tomography and physical logging of cored sediments has proved crucial for proper fault detection because performance of each technique was markedly different and very dependent on local geologic conditions geophysical data clearly 1 image a fault zone beneath suspected warps 2 constrain the cumulative vertical slip to only 25 30 m 3 delineate colluvial packages suggesting coseismic surface faulting episodes paleoseismological investigations document at least three deformation events during the very late pleistocene 20 ka and holocene the clue to surface rupturing episodes together with the fault dimension inferred by geological mapping and microseismicity distribution suggest a seismogenic potential of m6 3 our study provides the second documentation of a major active fault in southern italy that as the irpinia fault does not bound a large intermontane basin but it is nested within the mountain range weakly modifying the landscape this demonstrates that standard geomorphological approaches are insufficient to define a proper framework of active faults in this region more in general our applications have wide methodological implications for shallow imaging in complex terrains because they clearly illustrate the benefits of combining electrical resistivity and seismic techniques the proposed multidisciplinary methodology can be effective in regions characterized by young and or slow slipping active faults

on the detection of objects buried at a shallow depth using seismic wave reflections this paper concerns the detection of shallow of the order 1 m buried objects using seismic excitation time extended signals are used to generate a compressional wave using a shaker attached to the ground the wave propagates through the ground reflects off a buried object and is captured by an array of geophones on the surface the envelopes of the cross correlation functions between the measured ground velocities and the excitation signal are calculated and summed to generate a cross sectional image of the ground the wide cross correlation peaks caused by high ground attenuation are partially compensated for by using the generalized cross correlation function called the phase transform simple simulations are conducted to demonstrate the method and some field experiments have been carried out aimed at the detection of a buried concrete pipe in the experiments the pipe could be detected using the method proposed with experimental and simulated data producing good agreement

field comparison of shallow seismic sources near chino california data from a shallow seismic source comparison test conducted in an area with a water table depth in excess of 30 m and near surface velocities less than 330 m s were acquired from 13 different sources at a single site near chino california the sources included sledgehammer explosives weight drop projectile impacts and various buffalo guns a possible reflecting event can be interpreted at about 70 ms at this particular test site the lowly sledgehammer is among the best sources to provide data to see the possible reflection our previous work and that of our colleagues suggests that any source could dominate the comparison categories addressed here given the appropriate set of site characteristics

response of alluvial fan systems to the late pleistocene to holocene climatic transition contrasts between the margins of pluvial lakes lahontan and mojave nevada and california usa abstract dated shorelines of late pleistocene pluvial lakes lahontan great basin desert northwest nevada and mojave mojave desert eastern california provide timelines for the assessment of alluvial fan sedimentation at the lake margins during the late pleistocene to early holocene two sets of alluvial fan systems have been mapped the stillwater fans feeding lake lahontan and the zzyzx fans feeding lake mojave their contrasting morphologies suggest different responses of the two fan systems to late pleistocene to early holocene climatic change at the time the stillwater fan systems underwent minimal sedimentation with the catchment hillslopes apparently stable the zzyzx fans experienced major changes in water and sediment supply from the catchment hillslopes there was a major phase of hillslope debris flow activity followed by fanhead trenching and distal fan progradation both areas were wetter and colder in the late pleistocene than they are today but during the transition to the holocene the zzyzx area was more likely to experience intense rains associated with the monsoonal penetration of warm moist tropical air into the southwest vegetation reconstructions for the late pleistocene to the early holocene suggest that catchment hillslopes in the mojave supported a desert shrub vegetation but those in the stillwaters supported juniper woodland and grasses at low elevations and pine at higher elevations contrasts in hillslope vegetation cover together with storm activity may account for the different responses of the alluvial fans to climatic change during the pleistocene to holocene climatic transition after the falls in lake levels of lakes lahontan and mojave in the early holocene both areas underwent aridification resulting in reductions in hillslope vegetation cover increased storm runoff led to fanhead trenching and distal progradation of the alluvial fans variations in fan style at that time may relate primarily to base level conditions resulting from different gradients on the exposed lake shores

poisson s ratio values for rocks abstract compared to other basic mechanical properties of rocks poisson s ratio is an elastic constant of which the significance is generally underrated yet in rock mechanics there is a considerable number of diverse areas which require a prior knowledge or estimation of the value of poisson s ratio this paper examines the values and applications of poisson s ratio in rock mechanics following an historical account of the initial controversy whether it was a material constant or not the effects of poisson s ratio in the elastic deformation of materials intact rocks and rock masses are briefly reviewed also the reported values of poisson s ratio for some elements materials and minerals are compiled while typical ranges of values are presented for some rocks and granular soils finally poisson s ratio classifications are recommended for isotropic intact rocks

middle holocene dry climate caused by change in atmospheric circulation patterns evidence from lake levels and stable isotopes sediment hiatuses detritus layers and inwashed terrestrial moss layers in five cores at crawford lake ontario canada show that the lake level was low between ca 4 8 and 2 ka 1 ka 1000 14 c yr b p this low level is attributed to a dry and warm climate which has also been documented at other sites in southern ontario southern michigan and southern wisconsin oxygen isotope 18 o values from authigenic marl show a negative shift of 2 4 from 9 to 11 4 vienna peedee belemnite between ca 5 and 2 ka enhanced evaporation under dry and likely closed basin conditions would lead to more enrichment in 18 o so we suggest that the trend to depleted 18 o indicates a significant change in the 18 o value of the source meteoric water the major moisture source for the great lakes region is the gulf of mexico from which the amount and seasonality of precipitation are affected by the interplay of air masses from the gulf of mexico and north pacific probably controlled by jet stream positions and storm tracks in the late middle holocene the isotopically heavy moisture from the gulf might have contributed less precipitation and or a higher proportion in winter months probably caused by more frequent eastward extension of dry pacific air depleted in 18 o this hypothesis implies that the 18 o values of paleoprecipitation in the middle holocene reflected moisture source history more strongly than paleotemperature

significance of shallow seismic reflection ssr and ground penetrating radar gpr profiling on the modern coast line history of the bedre area egirdir lake isparta turkey abstract lake level changes and settlement places constitute the main problems in controlling the coastal environment along the egirdir lake sw turkey the quaternary geology in the bedre coast was studied based on shallow seismic reflection ssr survey ground penetrating radar gpr profiles and the data derived from boreholes and investigations in the field thus six seismic and five radar facies were determined respectively the geological units from the basement rock to the holocene deposits were imaged by the ssr technique gpr technique is used for the shallower part ranging from the ancient to the modern lacustrin sediments the quaternary lake level changes borehole seismic and radar data indicate that a pond with a connected to the lake around the bedre area existed in the last century sand barriers climate topographical elevation and erosions of the basement rocks control the sedimentation of the back barrier of the coastal line marsh muddies and ancient beach sands are the main sediments of the pond area from the profiles ancient buried sand barriers were also seen in the lake side in our view as the previous lake level dropped from the highstand the ancient sand barrier was formed which divided the lake and the pond and isolated a small inland lake which lies 4 m below the level of the coastal barrier for agricultural purposes artificial man made constructions were done on the barrier and channels thus dry agricultural land appeared in the last 50 years on the pond side

failure analysis of the granite for a dam foundation this paper presents the numerical and experimental investigation of a dam foundation the site consists of granite and especially weathered granite numerical and analytical analyses have been conducted to evaluate suitability of the granite for a dam foundation mohr coulomb failure criterion has been used to calculate the compressive strength of the rock mass finite element implementation of mohr coulomb criterion has been used for deformation and settlement analysis packer testing and in situ estimation of rock mass deformability using the goodman jack have been performed the results of the evaluations show that very small normal and differential settlements can be expected in structural regions due to dam construction and the compacted concrete dam can safely be constructed on either the competent granite or the weathered granite however the dam foundation on the weathered granite has high conductivity potential problems for the reservoir

surface and borehole geophysics for the rehabilitation of a concrete dam penne central italy abstract in this paper surface and borehole geophysical surveys are employed to improve the effectiveness of a rehabilitation intervention cut off wall to be executed on the right abutment of a leaking concrete dam penne central italy in a first step surface geophysical measurements electrical resistivity and p wave velocity data were collected to provide a geophysical model to be compared to the preliminary geological model available before the geophysical survey because significant differences emerged between the geophysical and the preliminary geological models a second phase of borehole investigations was planned to validate the geophysical reconstruction obtained from surface data the final geological model resulting from the geophysical results differs significantly from the preliminary model available at the time of the geophysical survey therefore the planned cut off wall needs to be extended both laterally and in depth beyond the position estimated before the geophysical campaign so that the low permeability bedrock is intercepted at a depth equal or lower than the critical one at the end the low cost geophysical campaign 1 5 of the entire costs of the intervention was highly beneficial to this project minimizing subsurface geological uncertainty to design an effective anti seepage intervention and stressing the importance of a representative geological model for engineering design

pitfalls in three dimensional seismic interpretation footprints of an irregular source receiver layout abstract this paper shows how nonuniform source receiver spacing in a three dimensional 3 d land acquisition creates footprints that could easily be mistaken for geology in a 3 d time migrated seismic volume from the midcontinent united states amplitude extraction along the top of the mississippian limestone formation shows a sinkhole like feature which is justified from a depositional perspective however an inspection of the acquisition layout shows that the sinkhole is a replica of the fold distribution in land surveys where source and receivers seldom have a regular distribution and for unconventional plays that are not developed through patterned drilling a thorough review of processing and acquisition parameters is necessary before interpreting amplitude maps

an application of csamt for detecting weak geological structures near the deeply buried long tunnel of the shijiazhuang taiyuan passenger railway line in the taihang mountains abstract the shijiazhuang taiyuan shitai high speed railway line is designed to cross the taihang mountains the line will include the construction of a 27 85 km long tunnel with a maximum depth of 450 m the taihang mountain tunnel is the key to the successful construction of the railway the geological structure of the tunnel is highly complex and the lithology changes dramatically throughout fault zones karst and groundwater ingress are the main geological engineering problems for the tunnel construction however conventional geophysical methods are not effective for detecting these geological structures in a region with such a complex terrain therefore the controlled source audio frequency magnetotellurics csamt method was used to effectively characterize the resistivity distribution of the underground rock this technique is highly sensitive to low resistivity geological structures such as fault zones and it is effective for studying the geological engineering conditions of the tunnel various corrections designed denoising and inversion methods are used in csamt data processing to obtain the resistivity profile of the entire tunnel based on the resistivity results and existing core information the underground lithological distribution is inferred the location of the fault zone is determined and the distribution of dangerous geological bodies is delineated the interpretation of the csamt results is verified by boreholes and related geological information these results are important for understanding the subsurface geological engineering conditions and have provided stability safety and cost evaluation support for the construction of a long deeply buried tunnel in taihang mountains

electrical and multiparameter radar observations of a severe hailstorm using data from the 11 cm csu chill multiparameter radar the simultaneous evolution of the radar inferred precipitation structure and electrical characteristics of a severe hailstorm is investigated we compare the substorm point discharge current intracloud ic lightning flash rate cloud to ground cg lightning flash rate ground strike location and flash polarity to the progression of precipitation types and amounts this study is unique in that it presents multiparameter radar observations of a thunderstorm complex which exhibited an extremely high ic to cg ratio ic cg 20 70 and predominantly positive cg lightning over 74 after it became severe producing large hail and weak tornadoes in particular we investigate the reported relationship between large hail and positive cg lightning although a direct correlation is found between a rapid increase in ic cg the first positive cg lightning flashes and the initial production of hail aloft the temporal and spatial behavior of large hail and positive cg lightning appear to be anticorrelated as broad peaks in the positive cg flash rate lag relative maxima in the fallout of large hail by up to 30 min the majority of positive ground strikes were adjacent to the main precipitation core in a region of light rain and little or no hail at the surface aloft radar data indicated that ice crystals were aligned vertically in a strong electric field corona point observations at the surface indicate that these regions adjacent to the convective core were characterized by net positive charge aloft possible mechanisms to explain these observations are discussed

serapeum temple and the ancient annex daughter library in alexandria egypt geotechnical geophysical investigations and stability analysis under static and seismic conditions abstract the serapeum temple and the ancient annex library in alexandria egypt from the greek roman era represent cultural heritage of outstanding universal values they suffer weathering aging as well as multiple geotechnical and earthquake hazards a pilot study has been carried out in order a to define the pathology and the causes of deterioration and degradation b to study the seismic performance of this kind of monuments c to assess the global risk due to combined hazards and d to define the appropriate retrofitting techniques in the paper a general outline of the various tests surveys and analyses is presented highlighting the most important issues related to the static and seismic stability of the above monuments a particular feature of serapeum is the column of diocletian founded just above it the paper presents the comprehensive field and laboratory surveys and tests undertaken in the site and the numerical analysis of the monument under static conditions and seismic conditions the field testing program comprises various geotechnical and geophysical field and laboratory tests aiming to define the physical mechanical and dynamic properties of the soils and soft rock materials of the site where the monuments is founded then an extensive parametric 2d and 3d numerical analyses were performed for the pillar and the serapeum subjected to seismic motions having different values of peak ground acceleration pga and frequency content advanced soil and rock elasto plastic modeling has been used throughout the different phases of the numerical analysis the seismic analysis combined with the static one allowed us to define the pathology of the monuments and to estimate the ultimate load that they can survive under their present conditions

a geo engineering classification for rocks and rock masses abstract in this article an attempt is made to assess the reliability of predicting the uniaxial compressive strength and the corresponding modulus of a rock mass by current approaches these two basic engineering properties when estimated from rock mass rating rmr q and geological strength index gsi indicate hardly any change in the modulus ratio with the change in the quality of the rock mass from very good to very poor however the modulus ratio obtained from the relations involving the joint factor j f indicate a definite decrease in the modulus ratio with a decrease in the quality of the rock mass the strength and modulus in the unconfined and confined states the modulus ratio and failure strain in the unconfined case were linked to j f in earlier publications based on a large experimental database some of these relations were adopted to verify the response of jointed test specimens the response of the rock mass during excavations for mining and civil underground chambers in establishing ground reaction curves including the extent of the broken zone and the bearing capacity of shallow foundations the joint factor is now linked to rmr q and gsi the prediction of compressive strength and modulus of the rock mass appears to be more suitable for classifying the rock based on these properties the deere and miller engineering classification applicable to intact rocks has been suitably modified and adopted the results of different modes of failure of jointed specimens establish definite trends of changes in the modulus ratio originating from the intact rock value on the modified deere and miller plot a geo engineering classification is evolved by considering strength modulus quantifiable weathering index and lithological aspects of the rock

the last pluvial climatic episodes in the deserts of southwestern north america long term variations in the effective moisture of deserts are linked both to glacial interglacial climatic cycles and through the milankovitch theory to orbitally induced changes in solar radiation intensity1 4 for southwestern north america comparison of palaeobotanical data with model predictions of palaeoclimate reveals two distinct pluvial regimes during the late wisconsin and early holocene 23 8 kyr bp southward displacement of the aleutian low pressure centre and strengthened westerlies from 40 to 30 n were important features of the full glacial 18 kyr bp pluvial maximum increased cyclonic storms and weakened monsoons led to a winter precipitation regime a feature seen both in the fossil record5 6 and climate models7 8 dominantly zonal flow during this period contrasts with the latest wisconsin and early holocene 12 8 kyr bp when meridional circulation transported maritime tropical air into the desert interior we now show that plant macrofossil assemblages from packrat neotoma spp middens9 in the mojave desert provide evidence for increased temperatures and summer rainfall during this period10 12 the anomalously late persistence to 8 kyr bp of woodland in low latitude low elevation deserts of the south west13 is attributed to enhanced monsoonal circulation3

underground cavity investigation within the city of rome italy a multi disciplinary approach combining geological and geophysical data abstract large areas of rome italy are prone to sudden ground collapse because of the degradation of a cavity network related to the long lasting underground quarrying activity of volcanic pleistocene deposits in recent years the municipality authorities have promoted scientific research in the field of engineering geology to locate these underground voids and to establish a standard methodology to assess the associated risk affecting the overlying structures in this paper a multidisciplinary geophysical and geological method oriented to cavity location is described tested and validated within this investigation electrical resistivity tomography ert is selected as the primary geophysical survey method the potential for underground cavity mapping is assessed using synthetic simulations and observations at a test site where the position of underground voids is known consequently the ert diagnostic capability is quantitatively evaluated in the geological scenario of interest and possible interpretation pitfalls when interpreting resistivity anomalies in a geological sense are pointed out on this basis an integrated investigation program encompassing ert measurements and borehole drilling is carried out at a site where the cavity network is unknown the physical reconstruction offered by ert when supported by a detailed geological model was found very useful in defining the geometry of the subsoil and consequently increasing the percentage of success in cavity location when compared to the one obtained by drilling alone two test sites are described one is characterized by a well known cavity network and the other has an unknown tunnel arrangement the corresponding geological models resulting from in situ investigation are discussed when assisted by a detailed conceptual geological model ert is proven to be a very useful tool to detect unknown galleries and consequently to optimize the drilling investigation program in addition to that the extensive in situ testing of the near surface volcanic deposits of the rome urban area permitted to characterize extensively both the electrical resistivity and the seismic p and s waves velocities of these formations whose in situ properties have never been studied to this extent in previous literature

combined geophysical surveys for the characterization of a reconstructed river embankment abstract the managing and monitoring of natural and artificial river levees are crucial in order to reduce the hydrological risk as these hydraulic structures are very extensive the typically applied techniques e g geotechnical soundings and visual inspections provide only punctual information that are generally focused on areas already recognized as troublesome to overcome these well known issues non invasive and cost effective geophysical measurements have been proposed and used to supply spatially extensive data that should be integrated with direct investigations therefore in this paper we present the joint use of multichannel analysis of surface waves masw electrical resistivity tomography ert and ground penetrating radar gpr to characterize a reconstructed river embankment made of concrete and tout venant prone to serious leakages we compare common lengthwise ert profiles performed from the levee crest with cross embankment and cross river profiles showing how relying only on the first type of surveys may lead to misinterpretations furthermore we take advantage of a land streamer for the masw surveys and of a trans illumination approach to improve the gpr application the comparison between geophysical and geotechnical data helps identify the spatial extent of the volume actually invaded by grouting injections which appears as a highly electrically conductive mean the lack of homogeneity within this domain highlighted by the cross embankment ert profiles can be related to the seepage phenomena affecting this artificial levee therefore this case study demonstrates the effectiveness of combining direct and non invasive investigations for the characterization of river embankments

internal structural architecture of a soft linkage transfer zone using outcrop and dc resistivity data implications for preliminary engineering assessment abstract the current study presents a new integrative approach for detailed structural mapping of a soft linkage transfer zone using outcrop boreholes and dcr data in the form of soundings and 2d electrical resistivity tomography 2d ert as a case study the present approach is implied for studying the geo engineering conditions of a highly deformed desert land entry to reclaim at cairo suez district egypt the approach has led to the spatial understanding of the subsurface heterogeneity and complex structures at a level of accuracy unattainable with traditional surface structural mapping alone for preliminary geotechnical assessment some physical and geotechnical properties are characterized by field and laboratory measurements for collected soil samples moreover the inverted dcr data are used to predict the rqd values using a polynomial relationship between rqd and the intrinsic resistivity notably the calculated and actual values of rqd are in general in the same order considering the error factor value and hence the derived equation for rqd prediction is satisfactory therefore the proposed approach reduces the uncertainty of the constructed structural model for engineering design in addition merging outcrop with dcr data allows us with a limited frame of time to partially mitigate disasters to civilization by better i potential location understanding and ii remediation plans tuning for a complex structured site

fossil fruit identification by sem investigations a tool for palaeoenvironmental reconstruction of dmanisi site georgia abstract archaeological excavations and multidisciplinary studies at the site of dmanisi lesser caucasus georgia have provided an assemblage of lithic artefacts and numerous palaeontological and human remains in a volcano sedimentary context dating to the early lower pleistocene the sieving of archaeological sediments from dmanisi also yielded mineralised botanical macro remains that were analysed according to a particular protocol the use of scanning electron microscopy sem allowed the comparison between fossil fruit remains and modern specimens leading to a precise identification of the earlier seed remains recognised by this method belonging to several taxa from the boraginaceae family as well as to the genus celtis l of the ulmaceae family the ecological requirements of these taxa suggest the presence of xeric conditions a result that is in accordance with data obtained by faunal and stratigraphic studies

avoiding pitfalls in shallow seismic reflection surveys acquiring shallow reflection data requires the use of high frequencies preferably accompanied by broad bandwidths problems that sometimes arise with this type of seismic information include spatial aliasing of ground roll erroneous interpretation of processed airwaves and air coupled waves as reflected seismic waves misinterpretation of refractions as reflections on stacked common midpoint cmp sections and emergence of processing artifacts processing and interpreting near surface reflection data correctly often requires more than a simple scaling down of the methods used in oil and gas exploration or crustal studies for example even under favorable conditions separating shallow reflections from shallow refractions during processing may prove difficult if not impossible artifacts emanating from inadequate velocity analysis and inaccurate static corrections during processing are at least as troublesome when they emerge on shallow reflection sections as they are on sections typical of petroleum

portable dense geophone array for shallow and very shallow 3d seismic reflection surveying part 1 data acquisition quality control and processing a strategy is presented for 3d seismic reflection imaging of shallow and very shallow targets utilizing a portable dense geophone array a dense 2d geophone array identifies faint shallow reflections and suppresses coherent noise fixing the receiver locations enables the design of quality control qc procedures that improve event identification the number of shots shot locations and their effect on target illumination can be evaluated with various qc tools during acquisition to improve overall data quality at the same time the portability of the array increases the cost effectiveness radially projected supergathers enable the choice of efficient processing parameters with sufficiently high fold and 3d frequency wavenumber filtering the dense geophone array is shown to image reflectors from 8 to 50 ms along with a dominant 20 ms water table reflection

stress dependent mechanical properties and bounds of poisson s ratio for fractured rock masses investigated by a dfn dem technique stress dependent mechanical properties and bounds of poisson s ratio for fractured rock masses investigated by a dfn dem technique

paleoclimatic reconstruction using the correlation in δ18o of hackberry carbonate and environmental water north america abstract celtis sp commonly known as hackberry fruits were collected from 101 north american sites located in 13 states and one canadian province between the years of 1979 1994 the biomineralized carbonate endocarp of the hackberry which is a common botanical fossil found throughout the quaternary sediments of the great plains was analyzed for its 18o value and plotted against the 18o value of site environmental water to demonstrate the potential of the hackberry as a paleoclimate indicator this correlation was reinforced by intensive studies on extracted tissue water 18o value and hackberry endocarp carbonate 18o value from three trees in sterling colorado the observed correlation in the large data set between hackberry endocarp carbonate 18o value and environmental water is endocarp 18o 38 56 0 69 environmental water 18o r 0 88 r2 0 78 p value

electrical structure and updraft speeds in thunderstorms over the southern great plains we have acquired 11 balloon soundings of the electric field and thermodynamics in large and sometimes severe and tornadic thunderstorms over the southern great plains the ascent rates of the balloons were used to divide the soundings into weak and strong updrafts all 11 soundings had magnitudes of charge densities and thicknesses of charge regions similar to those reported previously in small thunderstorms the five weak updraft soundings had complex charge structures of 7 9 charge regions below 10 km altitude the magnitude of the maximum measured electric field in these soundings was 100 150 k v m 1 the four soundings in strong updrafts had balloon ascent rates of at least 15 m s 1 for at least 1 km these soundings had simpler electrical structures of 3 5 charge regions below 10 km altitude their maximum measured electric fields ranged from 85 to 130 kv m 1 the data may support an earlier hypothesis that charge is elevated in strong updrafts in addition the data may suggest that simpler charge structures are associated with proximity to strong updrafts rather than with different storm types

climatic correlations in the stable isotope records of silver fir abies pindrow trees from kashmir india a high degree of coherence in the annual stable isotopic records along different radial directions of a silver fir tree and between two members of this species from the kashmir valley has recently been reported by us since such a common pattern of isotopic variability is most likely due to the climatic fluctuations in the site we have compared the mean d 13c and 18o records of these trees with instrumentally measured climatic parameters recorded in a nearby weather station to identify the climatic parameters predominantly influencing the isotopic record a multiple regression analysis of the two records for the period 1903 1932 yields the following 1 d is most sensitive to the amount of growing season precipitation followed by mean maximum temperature tree cellulose shows an amount effect analogous to precipitation samples the temperature coefficient for d is in good agreement with earlier estimates based on spatial correlations 2 13c is significantly related to humidity and cloud amount the signs of the regression coefficients are consistent with the recent model of francey and farquhar for13c 12c fractionation in c3 plants 3 18o of cellulose appears to be controlled significantly by relative humidity 18o shows less overall correlation with climatic parameters than d and 13c 4 d of carbon bound hydrogen and 18o of tree cellulose are linearly related with a slope of7 9 0 3 suggesting evaporative enrichment in leaf water

ray tracing in elliptical anisotropic media using the linear traveltime interpolation lti method applied to traveltime seismic tomography the linear traveltime interpolation lti method is a suitable ray tracing technique for modelling first arrival times in isotropic media lti is extended to elliptical anisotropic media and applied to a tomographic inversion procedure a theoretical formulation is first derived and then lti implementation is discussed in terms of source receiver arrays and cell size the method is then combined with the tomographic inversion procedure adopted the matching of the ray tracing with inversion in elliptical anisotropic media posed a double non linear problem thus two assumptions were made the velocity in each cell is uniform and the main directions of anisotropy are known to take into account the geometrical characteristics of the area under investigation depth and velocity of the weathering and thickness of the inner media cells of varying size were considered no hypothesis was made on anisotropy weakness the algorithm was first tested on synthetic models and then applied to a field survey on comparing the results of the synthetic models and the field survey with those obtained with a linear raypath approximation it was found that there were fewer data misfits

crustal scattering and some artifacts in receiver function images the existing 2d and 3d depth imaging approaches using multichannel teleseismic receiver functions rfs can result in significant artifacts caused by misinterpretation of signal generated noise resulting from broadside scattering within the crust a synthetic example using acquisition geometry of the 1993 cascadia experiment shows that scattering of the primary p wave arrivals from a sedimentary accretionary wedge could produce rf events close to those observed in real data quasi linear crustal structures with significant velocity contrasts near moho depths such as subduction zones should create particularly strong and coherent noise arrivals conventional interpretations of these arrivals based on assumptions of their origin in mode conversions could lead to images of spurious dipping structures of landward dips steeper than 10 that may be very difficult to distinguish from the true structures detailed analysis of prestack premigration rf data is required for correct identification of the signal generated noise and validation of the resulting depth images identification of scattered events in rf records could also help constrain major crustal structures such as crustal sutures and subduction fault zones and particularly those with strong moho expressions manuscript received 10 june 2003

potential for14c dating of biogenic carbonate in hackberry celtis endocarps abstract hackberry endocarp celtissp contains significant amounts up to 70 wt of biogenic carbonate that is nearly pure aragonite caco3 because of their high mineral content hackberry endocarps are found abundantly in tertiary and quaternary sediments and are very common in many north american archaeological sites we analyzed the14c content of different components of modern hackberries including the biogenic carbonate in hackberry endocarps collected at known times over the past century the14c content of the endocarp carbonate accurately records the14c content of the atmosphere 14c dates of fossil endocarp carbonates compared favorably with dates obtained by other means at archaeological and geological sites ranging in age from the late pleistocene through the early holocene we therefore suggest that hackberry endocarp is a suitable substrate for14c dating provided that its morphological and mineralogical integrity is preserved

the correlation between 18o 16o ratios of meteoric water and surface temperature its use in investigating terrestrial climate change over geologic time abstract correlations between mean annual temperature mat and the weighted average oxygen isotope composition of yearly precipitation 18opt are well known but the utility of modern relations to make reliable estimates of temperature change over geological time is uncertain this question has been addressed by using seasonal subsets of the global data base of temperature and isotopic measurements to represent two different climate modes a comparison of middle to high latitude 18opt temperature relations for each climate mode reveals 1 a significant offset between them and 2 a difference in the strength of their correlations the offset in relations is due to differences in temperature and water vapor budget in the tropics and can lead to serious underestimates of temperature change differences in the strength of correlations arise from the influence of climate mode specific non temperature factors on 18opt the overall result is that no single relation can be used in all cases to make unambiguous temperature estimates using a temporal record of 18opt values one way to overcome these problems is to reconstruct 18opt temperature relations for the time periods being investigated if an appropriate proxy for 18opt is available it may also be possible to estimate temperature without relying on 18opt temperature relations a promising alternative to these options is to use records of 18opt to test predictions of global climate models an approach that may allow a reliable and more complete reconstruction to be made of climate change over geologic time

field comparison of shallow seismic sources choosing a seismic source for a shallow reflection survey can be the most pivotal decision for the engineering geophysicist the intent of this paper is to present data that will assist in selection of a shallow seismic source best meeting the goals within the constraints of specific projects particularly in areas where the water table is near the surface the data were collected and displayed as seismograms and amplitude spectra for 15 different shallow seismic sources in october 1985 at a single site in new jersey they show the different characteristics of each source considering the almost three orders of magnitude difference in total source energy between the largest and smallest source we chose a display format that presented the data as objectively as possible while still allowing direct source to source comparisons two strong reflections at about 100 and 130 ms probably mark the top and bottom of a clay unit 80 m below the surface at this site our previous work and that of our colleagues

isotopic evidence for shifts in atmospheric circulation patterns during the late quaternary in mid north america wyoming is now at the eastern margin of westerlies originating in the pacific but in the pleistocene appears to have received moisture from elsewhere possibly the gulf of mexico oxygen isotope ratios of pedogenic carbonate in postglacial terraces correspond to ratios in equilibrium with present meteoric waters which show a strong relation to precipitation seasonality and storm sources in contrast the oxygen isotope ratios of all pre holocene soils are significantly more positive even though the carbon isotope composition of coexisting organic matter suggests that the carbonate formed in temperatures cooler than today the oxygen isotope ratios of paleowaters in mid north america appear to be more useful for identifying past storm sources than for estimating paleotemperatures

detection of seepage paths in earth dams using self potential and electrical resistivity methods abstract earth and rockfill dams are designed to operate under steady state seepage anomalous seepage may be a threat to the integrity of the structure in spite of advances made in the fields of geotechnical engineering it is not possible to have 100 leak proof structure any excessive and unplanned seepage may lead to the failure of the dam especially in unconsolidated or fractured terrains geophysical methods play an important role in mapping seepage paths and monitoring the changes of the seepage with time enabling to plan technically and economically worthwhile remedial measures in the present paper utilisation of electrical methods for delineation of seepage zones at two of the four saddle dams of the som kamla amba project rajasthan state india which is founded on heterogeneous rock mass is discussed electrical resistivity method was used to delineate zones favourable for seepage whereas self potential sp method was used to delineate the seepage paths sp measurements have shown negative anomaly of the order of 10 20 mv in amplitude indicating low seepage coinciding with the seepage measurements made by the project authorities

the lower cretaceous king lear formation northwest nevada implications for mesozoic orogenesis in the western u s cordillera cretaceous paleogeography of the u s cordillera west of the sevier fold and thrust belt is poorly known due to the scarcity of cretaceous supracrustal rocks in the arc and backarc regions the lower cretaceous king lear formation exposed in the jackson mountains and the krum hills of northwest nevada provides a rare and important record of early cretaceous tectonism and paleogeography our work shows that the king lear formation everywhere overlies deformed and metamorphosed triassic jurassic rocks across a major unconformity the king lear formation is dominated by conglomerates and sandstones deposited in subaerial alluvial fan and gravelly braided river systems and it can be divided into three new members based on differences in clast provenance a lower member derived from local arc and backarc rocks a middle member dominated by externally derived quartzite and chert clasts and an upper member derived largely from an intrabasinal volcanic complex sedimentary features and provenance analysis indicate that clasts in the middle member were derived from nearby exposures of paleozoic rocks such as the roberts mountains and golconda allochthons which must have formed a topographically elevated area in central nevada during the early cretaceous the stratigraphic record provides evidence of deposition in a tectonically active basin in contrast with some prior studies inferring that deposition was synchronous with contractional deformation our new field observations structural data and a shallow seismic reflection profile confirm that the king lear formation was deposited in an active half graben in the jackson mountains these results provide new upper age constraints on the timing of shortening deformation in the arc and backarc regions shortening must have been complete not only before deposition of the king lear formation in the middle early cretaceous but also prior to several kilometers of exhumation of its depositional basement possible driving forces for extension leading to development of the king lear basin include relaxation of thick crust in the hinterland of thrust belts to the east stresses associated with regional tilting and development of dynamic topography and stresses related to dextral strike slip deformation to the west

seismic model studies of the overburden bedrock reflection one aspect of the modification of seismic waves on passage through the earth is the partitioning of energy at subsurface interfaces as described by the zoeppritz equations these equations have been applied to simple two and three layer models to determine the variations in the amplitude and phase of a reflection signal at nonnormal angles of incidence synthetic seismograms have been produced to illustrate the effect of these variations on a seismic wavelet it is found that the phase variations can lead to substantial changes in the character of the reflected wavelet as the source geophone distance increases these changes are dependent on the angle of incidence and on the elastic properties of the subsurface layers in particular for models approximating an overburden over bedrock situation the reflected pulse is predicted to change phase when the velocity contrast between the two layers is relatively small this effect has been observed on field records geophysicists should be aware of this phen

sediment borne seeds from sand creek northwestern kansas taphonomic significance and paleoecological and paleoenvironmental implications abstract a study of seeds fruits and reproductive bracts collectively seeds collected during 1986 1988 from recent sediments along a small perennial stream in northwestern kansas was conducted to determine the taphonomic significance of sediment borne seeds and the implications for studies of similar accumulations of fossil plants the samples were collected from sediments in but at the margin of a flowing stream the abundant and diverse assemblage of aquatic and marginal aquatic plants recovered in the sediments shows that the sediment borne seeds accurately reflect the marginal aquatic habitat next to the channel and temperate climate of the region the sediments also contained a wide assortment of other taxa that represented native riparian floodplain and upland habitats as well as cultivated croplands overall these taxa are indicative of temperate grasslands disturbance of the study site by trampling by livestock and perphaps by lowered stream flow during the last year reduced the variety of taxa and numbers of specimens in samples but these influences did not change the marginal aquatic habitat suggested by sediment borne seeds comparison of a late miocene 7 8 m y b p assemblage of seeds from the minium quarry in northwestern kansas with the sand creek results suggests that the habitat nearest the deposition site of the fossils was a marginal aquatic setting similar to that sand creek the comparison alos suggests that the miocene landscape beyond the depositional site was dominated by warm temperate to subtropical grasslands an interpretation supported by faunal evidence

black mats spring fed streams and late glacial age recharge in the southern great basin black mats are prominent features of the late pleistocene and holocene stratigraphic record in the southern great basin faunal geochemical and sedimentological evidence shows that the black mats formed in several microenvironments related to spring discharge ranging from wet meadows to shallow ponds small land snails such asgastrocopta tappanianaandvertigo berryiare the most common mollusk taxa present semiaquatic and aquatic taxa are less abundant and include catinellids fossaria parva gyraulus parvus and others living today in and around perennial seeps and ponds the ostracodescypridopsis okeechobiandscottia tumida typical of seeps and low discharge springs today as well as other taxa typical of springs and wetlands are common in the black mats several new species that lived in the saturated subsurface also are present but lacustrine ostracodes are absent the 13c values of organic matter in the black mats range from 12 to 26 reflecting contributions of tissue from both c3 sedges most shrubs and trees and c4 saltbush saltgrass plants carbon 14 dates on the humate fraction of 55 black mats fall between 11 800 to 6300 and 230014c yr b p to modern the total absence of mats in our sample between 6300 and 230014c yr b p likely reflects increased aridity associated with the mid holocene altithermal the oldest black mats date to 11 800 11 60014c yr b p and the peak in the14c black mat distribution falls at 10 00014c yr b p as the formation of black mats is spring related their abundance reflects refilling of valley aquifers starting no later than 11 800 and peaking after 11 00014c yr b p reactivation of spring fed channels shortly before 11 20014c yr b p is also apparent in the stratigraphic records from the las vegas and pahrump valleys this age distribution suggests that black mats and related spring fed channels in part may have formed in response to younger dryas yd age recharge in the region however the inception of black mat formation precedes that of the yd by at least 40014c yr and hydrological change is gradual not rapid

empirical estimation of rock mass modulus the deformation modulus of a rock mass is an important input parameter in any analysis of rock mass behaviour that includes deformations field tests to determine this parameter directly are time consuming expensive and the reliability of the results of these tests is sometimes questionable consequently several authors have proposed empirical relationships for estimating the value of rock mass deformation modulus on the basis of classification schemes these relationships are reviewed and their limitations are discussed based on data from a large number of in situ measurements from china and taiwan a new relationship based upon a sigmoid function is proposed the properties of the intact rock as well as the effects of disturbance due to blast damage and or stress relaxation are also included in this new relationship