joint inversion of gravity and geoelectrical data for groundwater and structural investigation application to the northwestern part of sinai egypt summary the simulated annealing method was applied to jointly invert gravity and resistivity data to obtain the geometry of the density resistivity interfaces and subsurface electrical resistivity distribution the results obtained from the inversions of synthetic data indicate that the joint inversion significantly improves the solution decreasing the ambiguity of the models the method was applied to gravity and resistivity data carried out in sinai northwestern egypt the results obtained revealed the geometry of the water bearing zone with thickness ranging from 80 to 180 m and of the limestone bedrock interface dipping northwards

passive micro seismic event detection by identifying embedded event anomalies within statistically describable background noise among engineers there is considerable interest in the real time identification of events within time series data with a low signal to noise ratio this is especially true for acoustic emission analysis which is utilized to assess the integrity and safety of many structures and is also applied in the field of passive seismic monitoring psm here an array of seismic receivers are used to acquire acoustic signals to monitor locations where seismic activity is expected underground excavations deep open pits and quarries reservoirs into which fluids are injected or from which fluids are produced permeable subsurface formations or sites of large underground explosions the most important element of psm is event detection the monitoring of seismic acoustic emissions is a continuous real time process which typically runs 24 h a day 7 days a week and therefore a psm system with poor event detection can easily acquire terabytes of useless data as it does not identify crucial acoustic events this paper outlines a new algorithm developed for this application the so called seed signal enhancement and event detection algorithm the seed algorithm uses real time bayesian recursive estimation digital filtering techniques for psm signal enhancement and event detection

integrated processing of muon radiography and gravity anomaly data toward the realization of high resolution 3 d density structural analysis of volcanoes case study of showa shinzan lava dome usu japan we have developed an integrated processing method for muon radiography and gravity anomaly data for determining the 3 d density structures of volcanoes with a higher spatial resolution than is possible by conventional gravity inversion in the present paper we demonstrate the performance of the proposed method by performing numerical tests using synthesized data and we present the results obtained by applying the proposed method to a volcano showa shinzan lava dome hokkaido japan we obtained the detailed shape of a vent beneath the dome and detected the presence of solidified dense lava near the top of the dome the results demonstrate the advantage of a hybrid measurement based on both gravity and muon radiography for imaging small structures with sizes of a few hundreds of meters near the surface of a volcano

inversion of controlled source audio frequency magnetotellurics data for a horizontally layered earth we present a technique for inverting controlled source audio frequency magnetotelluric csamt data to recover a 1 d conductivity structure the earth is modeled as a set of horizontal layers with constant conductivity and the data are apparent resistivities and phases computed from orthogonal electric and magnetic fields due to a finite dipole source the earth model has many layers compared to the number of data points and therefore the solution is nonunique among the possible solutions we seek a model with desired character by minimizing a particular model objective function traditionally csamt data are inverted either by using the far field data where magnetotelluric mt equations are valid or by correcting the near field data to an equivalent plane wave approximation here we invert both apparent resistivity and phase data from the near field transition zone and the far field regions in the full csamt inversion without any correction our inversion is compared with that obtained by inverting near field corrected data using an mt algorithm both synthetic and field data examples indicate that a full csamt inversion provides improved information about subsurface conductivity

three dimensional density structure of la soufriere de guadeloupe lava dome from simultaneous muon radiographies and gravity data muon imaging has recently emerged as a powerful method to complement standard geophysical tools in the understanding of the earth s subsurface muon measurements can yield a radiography of the average density along the muon path allowing to image large volumes of a geological body from a single observation point here we jointly invert muon data from three simultaneous telescope acquisitions together with gravity data to estimate the three dimensional density structure of the la soufriere de guadeloupe lava dome our unique datas et allows us to achieve an unprecedented spatial resolution with this novel technique the retrieved density model reveals an extensive low density anomaly where the most active part of the volcanic hydrothermal system is located supporting previous studies that indicate this region as the most likely to be involved in a partial edifice collapse

joint 3d inversion of multiple electromagnetic datasets electromagnetic methods are routinely applied to image the subsurface from shallow to regional structures individual electromagnetic methods differ in their sensitivities towards resistive and conductive structures and in their exploration depths if a good balance between different electromagnetic data can be be found joint 3d inversion of multiple electromagnetic datasets can result in significantly better resolution of subsurface structures than the individual inversions we present a weighting algorithm to combine magnetotelluric controlled source electromagnetic and geoelectric data magnetotelluric data are generally more sensitive to regional conductive structures whereas controlled source electromagnetic and geoelectric data are better suited to recover more shallow and resistive structures our new scheme is based on weighting individual components of the total data gradient after each model update norms of individual data residuals are used to assess how much of the total data gradient must be assigned to each method to achieve a balanced contribution of all datasets for the joint inverse model synthetic inversion tests demonstrate advantages of joint inversion in general and also the influence of the weighting in our tests the controlled source electromagnetic data gradients are larger than those of the magnetotelluric and geoelectric datasets consequently direct joint inversion of controlled source electromagnetic magnetotelluric and geoelectric data results in models that are mostly dominated by structures required by the controlled source electromagnetic data applying the new adaptive weighting scheme results in an inversion model that fits the data better and resembles more the original model we used the modular system electromagnetic as a framework to implement the new joint inversion and briefly describe the new modules for forward modelling and their interfaces to the modular system electromagnetic package

application of integrated methods in mapping waste disposal areas an integrated suite of environmental methods was used to characterize the hydrogeological geological and tectonic regime of the largest waste disposal landfill of crete island the fodele municipal solid waste site msw to determine the geometry of the landfill depth and spatial extent of electrically conductive anomalies to define the anisotropy caused by bedrock fabric fractures and to locate potential zones of electrically conductive contamination a combination of geophysical methods and chemical analysis was implemented for the characterization and management of the landfill five different types of geophysical surveys were performed 1 2d electrical resistance tomography ert 2 electromagnetic measurements using very low frequencies vlf 3 electromagnetic conductivity em31 4 seismic refraction measurements sr and 5 ambient noise measurements hvsr the above geophysical methods were used with the aim of studying the subsurface properties of the landfill and to define the exact geometrical characteristics of the site under investigation

hazard assessment during caldera unrest at the campi flegrei italy a contribution from gravity height gradients hazard assessment and risk mitigation at restless calderas is only possible with adequate geophysical monitoring we show here how detailed long term micro gravity and deformation surveys may contribute to hazard assessment at the campi flegrei caldera cfc in italy by evaluating gravity height change g h gradients obtained during ground inflation and deflation between 1981 and 2001 such gradients provide a framework from which to assess the likelihood and type of volcanic eruptions our new analysis of unrest at the cfc allows us to separate noise during the gravity survey from the signal of deep seated magmatic processes this facilitates identification of the dynamics within the magma reservoir beneath the cfc we found that magma replenishment during rapid uplift between 1982 and 1984 was insufficient probably by one to two orders of magnitude to trigger an eruption similar to the 1538 monte nuovo eruption the most recent volcanic eruption within the cfc furthermore our interpretation of g h gradients for the ongoing period of deflation since 1984 suggests that eruptive volcanic activity is not imminent short periods of minor inflation associated with large gravity changes since 1981 are interpreted to reflect noise which to some degree is probably due to sub surface mass density changes within shallow hydrothermal systems beneath the cfc indicating no risk of eruptive volcanic activity we propose that monitoring g h gradients at restless calderas is essential as a caldera develops from a state of unrest to a state where volcanic eruptions have to be anticipated adoption of this method for the several tens of restless calderas world wide will provide early warning of changes in or increase of activity at these supervolcanoes

simulation of electrical conduction in geomaterials by spice electrical responses of the subsurface can be used to identify geologic strata locate anomalies detect and delineate contamination among many other applications all these applications depend on the spatial variations of electrical properties in the subsurface and the resulting flow pattern of electric current due to the heterogeneity of the subsurface and complex boundary conditions three dimensional electric current flow problems are not easy to analyze in particular when the response is frequency and or time dependent in this paper a method of electric circuit analogy is proposed to simulate the electrical responses of geomaterials using the circuit simulator spice the technique will allow simulation of more complex electrical conduction behavior of geomaterials without much extra effort the excellent agreement between simulated results and analytical solutions developed for surface geophysical techniques establishes the viability of the method limitations of the approach and potential solutions to relax these limitations and other potential applications of the technique in geosciences are also discussed

significant resistivity changes in the fault zone associated with the 1999 chi chi earthquake west central taiwan abstract the purpose of this paper is to demonstrate the possible influence of an earthquake on the resistivity distribution in a fault zone we collected resistivity image profiles across a proposed fault trace prior to the 7 3 magnitude 1999 shallow earthquake in the chi chi area of taiwan significant positive resistivity anomalies were observed in the hanging wall after the earthquake however there were negligible resistivity changes in the footwall from an examination of geoelectric phenomena and surface rupture in the fault zone it is believed that geoelectric anomalies are associated with abrupt displacement along the active chelungpu fault this result indicates a potential for resistivity methods to provide a basis for the monitoring of an active fault

2d joint inversion of rmt and ert data versus individual 3d inversion of full tensor rmt data an example from trecate site in italy tensor radiomagnetotelluric rmt and electrical resistivity tomography ert data were acquired along 10 parallel lines to image electrical resistivity of the vadose and the saturated zone in an a

absolute gravity change associated with magma mass movement in the conduit of asama volcano central japan revealed by physical modeling of hydrological gravity disturbances the gravity signal originating from magma mass movement in a volcanic conduit is retrieved from the hydrologically disturbed absolute gravity data obtained at asama volcano central japan in 2004 using a three dimensional hydrological model we improve the hydrological model of the previous study using realistic soil parameters and boundary conditions to better estimate the spatiotemporal land water distributions and the consequent hydrological gravity disturbances the newly estimated gravity disturbances agree with the absolute gravity values observed by fg5 gravimeters in 2004 2009 within about 2 6 gal by additionally accounting for the excess discharge of groundwater mass associated with a sloping impermeable surface below the discharge area after the gravity disturbance of 20 gal amplitude is subtracted from the absolute gravity data observed during the 2004 eruptive event the gravity residual of 5 gal amplitude shows a significant decrease in synchronization with eruptions because the ascending magma mass in the conduit affects the upward attraction force to the gravimeters installed on the flank of asama volcano the magma head altitude to which the residual gravity is converted assuming a homogeneous linear density in the conduit shows a comprehensive agreement of the time variation in the magma head with those in other volcanic observations such as gas emission rate and earthquake frequency by correcting the hydrological gravity disturbances using this hydrological model and simultaneously obtained meteorological data in real time spatiotemporal variations in the magma mass can be instantaneously monitored at asama volcano even before eruptions during future volcanic events

delineation of groundwater aquifer and subsurface structures on north cairo egypt using integrated interpretation of magnetic gravity geoelectrical and geochemical data

high resolution seismic and resistivity profiling of a buried quaternary subglacial valley northern alberta canada high resolution seismic and resistivity profiles were acquired to assist in the delineation of a buried quaternary subglacial valley the existence of which was first discovered by drilling one aspect of this valley is the glacial sediments that host substantial methane at shallow depths 50 m or less geophysical well logs indicate that the glacial sediments in this area generally have lower compressional wave speeds v p 10 m than adjacent undisturbed cretaceous age rocks which have v p 2200 m s and r 300 m valley the reflection profile reveals a complex series of events consistent with heterogeneous deposition one major reflection dips eastward across the valley the reflection character changes abruptly on either side of this event with dipping clinoform reflections beneath and nearly horizontal reflections above these may be related to changes in deposition processes beneath a retreating ice sheet as has been suggested by earlier workers the buried valley s basal reflections are complex and possibly reflect glaciotectonic deformation or block plucking the near surface methane gas is within but at the edge of the valley the methane gas saturated zone displays anomalously high resistivities both in the well logs and in resistivity tomography

time lapse monitoring of fluid induced geophysical property variations within an unstable earthwork using p wave refraction abstracta significant portion of the uk s transportation system relies on a network of geotechnical earthworks cuttings and embankments that were constructed more than 100 years ago whose stability is affected by the change in precipitation patterns experienced over the past few decades the vulnerability of these structures requires a reliable cost and time effective monitoring of their geomechanical condition we have assessed the potential application of p wave refraction for tracking the seasonal variations of seismic properties within an aged clay filled railway embankment located in southwest england seismic data were acquired repeatedly along the crest of the earthwork at regular time intervals for a total period of 16 months p wave first break times were picked from all available recorded traces to obtain a set of hodocrones referenced to the same spatial locations for various dates along the surveyed period of time traveltimes extracted from each acquisition were then compared to trac

the latest explosive eruptions of ciomadul csomad volcano east carpathians a tephrostratigraphic approach for the 51 29 ka bp time interval abstract the most recent mainly explosive eruptions of ciomadul the youngest volcano in the carpatho pannonian region have been constrained by detailed field volcanological studies major element pumice glass geochemistry luminescence and radiocarbon dating and a critical evaluation of available geochronological data these investigations were complemented by the first tephrostratigraphic studies of the lacustrine infill of ciomadul s twin craters st ana and mohos that received tephra deposition during the last eruptions of the volcano our analysis shows that significant explosive activity collectively called eppa early phreatomagmatic and plinian activity started at ciomadul in or around the present day mohos the older crater at 51 ka bp these eruptions resulted in a thick succession of pyroclastic fall deposits found in both proximal and medial distal localities around the volcano characterized by highly silicic rhyolitic glass chemical compositions ca 75 2 79 8 wt sio 2 the eppa stage was terminated by a subplinian plinian eruption at 43 ka bp producing pumiceous pyroclastic fall and flow deposits of similar glass composition probably from a proto st ana vent located at or around the younger crater hosting the present day lake st ana after a quiescent period with a proposed lava dome growth in the st ana crater a new explosive stage began defined as mpa middle plinian activity in particular a significant two phase eruption occurred at 31 5 ka bp producing pyroclastic flows from vulcanian explosions disrupting the preexisting lava dome of sf ana and followed by pumiceous fallout from a plinian eruption column related pyroclastic deposits show a characteristic less evolved rhyolitic glass composition ca 70 2 74 5 wt sio 2 and occur both in proximal and medial distal localities up to 21 km from source the mpa eruptions that may have pre shaped a crater similar to but possibly smaller than the present day st ana crater was followed by a so far unknown but likewise violent last eruptive stage from the same vent creating the final morphology of the crater this stage referred to as lspa latest st ana phreatomagmatic activity produced pyroclastic fall deposits of more evolved rhyolitic glass composition ca 72 8 78 8 wt sio 2 compared to that of the previous mpa stage according to radiocarbon age constraints on bulk sediment charcoal and organic matter from lacustrine sediments recovered from both craters the last of these phreatomagmatic eruptions that draped the landscape toward the east and southeast of the volcano occurred at 29 6 ka bp some 2000 years later than the previously suggested last eruption of ciomadul

drain back process of basaltic magma in the summit conduit detected by microgravity observation at izu oshima volcano japan basalt magma sometimes moves through volcanic conduits causing only minor deformation in that case we may detect magma movements directly by microgravity observations after the 1986 eruption of izu oshima volcano we observed anomalous gravity variations localized at the summit based on a vertical cylindrical conduit model we estimate the time variations of the head of magma in the summit conduit and clarify the magma drain back process after the 1986 eruption

2 5d resistivity modeling of embankment dams to assess influence from geometry and material properties repeated resistivity measurement is a potentially powerful method for monitoring development of internal erosion and anomalous seepage in earth embankment dams this study is part of a project to improve current longterm monitoring routines and data interpretation and increasing the understanding when interpreting existing data this is accomplished by modeling various occurrences typical of embankment structures using properties from two rockfill embankment dams with central till cores in the north of sweden the study evaluates the influence from 3d effects created by specific dam geometry and effects of water level fluctuations in the reservoir moreover a comparison between different layout locations is carried out and detectability of internal erosion scenarios is estimated through modeling of simulated damage situations software was especially developed to model apparent resistivity for geometries and material distributions for embankment dams the model shows that the 3d effect from the embankment geometry is clearly significant when measuring along dam crests for dams constructed with a conductive core of fine grained soil and high resistive rockfill the effect becomes greatly enhanced also water level fluctuations have a clear effect on apparent resistivities only small differences were found between the investigated arrays a layout along the top of the crest is optimal for monitoring on existing dams where intrusive investigations are normally avoided because it is important to pass the current through the conductive core which is often the main target of investigation the investigation technique has proven beneficial for improving monitoring routines and increasing the understanding of results from the ongoing monitoring programs although the technique and software are developed for dam modeling it could be used for estimation of 3d influence on any elongated structure with a 2d cross section

transdimensional change point modeling as a tool to investigate uncertainty in applied geophysical inference an example using borehole geophysical logs recently developed methods for inferring abrupt changes in data series enable such change points in time or space to be identified and also allow us to estimate noise levels of the observed data the inferred probability distributions of these parameters provide insights into the capacity of the observed data to constrain the geophysical analysis and hence the magnitudes and likely sources of uncertainty we carry out a change point analysis of sections of four borehole geophysical logs density neutron absorption sonic interval time and electrical resistivity using transdimensional bayesian markov chain monte carlo to sample a model parameter space the output is an ensemble of values which approximate the posterior distribution of model parameters we compare the modeled change points borehole log parameters and the variance of the noise distribution of each log with the observed lithology classes down the borehole to make an appraisal of the uncertainty characteristics inherent in the data our two examples one with well defined lithology changes and one with more subtle contrasts show quantitatively the nature of the lithology contrasts for which the geophysical borehole log data will produce a detectable response in terms of inferred change points we highlight the different components of variation in the observed data due to the geologic process dominant lithology changes that we hope to be able to infer geologic noise due to variability within each lithology and analytical noise due to the measurement process this inference process will be a practical addition to the analytical tool box for borehole and other geophysical data series it reveals the level of uncertainties in the relationships between the data and the observed lithologies and would be of great use in planning and interpreting the results of subsequent routine processing

comparative study of geophysical and soil gas investigations at the hartousov czech republic natural co2 degassing site our study at this natural analog site contributes to the evaluation of methods within a hierarchical monitoring concept suited for the control of co2 degassing it supports the development of an effective monitoring concept for geological co2 storage sites carbon capture and storage as one of the pillars of the european climate change efforts this study presents results of comprehensive investigations along a 500 m long profile within the hartousov czech republic natural co2 degassing site and gives structural information about the subsurface and interaction processes in relation to parameters measured measurements of co2 concentrations and investigation of the subsurface using electrical resistivity tomography and self potential methods provide information about subsurface properties for their successful application it is necessary to take seasonal variations e g soil moisture temperature meteorological conditions into consideration due to their influence on these parameters locations of high co2 concentration in shallow depths are related to positive self potential anomalies low soil moistures and high resistivity distributions as well as high 13c values and increased radon concentrations co2 ascends from deep geological sources via preferential pathways and accumulates in coarser sediments repetition of measurements which includes the effects of seasonal variations revealed similar trends and allows us to identify a clear prominent zone of anomalous values coarser unconsolidated sedimentary layers are beneficial for the accumulation of co2 gas the distribution of such shallow geological structures needs to be considered as a significant environmental risk potential whenever sudden degassing of large gas volumes occurs

pattern of shallow ground water flow at mount princeton hot springs colorado using geoelectrical methods abstract in geothermal fields open faults and fractures often act as high permeability pathways bringing hydrothermal fluids to the surface from deep reservoirs the mount princeton area in south central colorado is an area that has an active geothermal system related to faulting and is therefore a suitable natural laboratory to test geophysical methods the sawatch range front normal fault bordering the half graben of the upper arkansas valley is characterized by a right lateral offset at mount princeton hot springs this offset is associated with the chalk cliffs of hydrothermally altered quartz monzonite because fault identification in this area is complicated by quaternary deposits including glacial and fluvial deposits we use dc electrical resistivity tomography and self potential mapping to identify preferential fluid flow pathways the geophysical data over 5600 resistivity and 2700 self potential measurements provide evidence of the existence of a dextral strike slip fault zone fault b responsible for the offset of the sawatch fault a segment of this dextral strike slip fault termed u1 is acting as the dominant vertical flow path bringing thermal waters to a shallow unconfined aquifer upwelling of the thermal waters is also observed at two zones u2 and u3 of an open fracture called fault a this fault is located at the tip of the sawatch fault and is likely associated with an extensional strain regime in this area self potential measurements are used to estimate the flux of upwelling thermal water the upflow estimate 4 1 10 3 m 3 day for the open segment of the fault b and 2 1 10 3 m 3 day for fault a from the geophysical data is remarkably consistent with the downstream mt princeton hot water production 4 3 4 9 10 3 m 3 day at approximately 60 86 c a temperature map indicates that a third upwelling zone termed u4 may exist at the southern tip of the sawatch fault

computations of secondary potential for 3d dc resistivity modelling using an incomplete choleski conjugate gradient method an accurate and efficient 3d finite difference fd forward algorithm for dc resistivity modelling is developed in general the most time consuming part of fd calculation is to solve large sets of linear equations where a is a large sparse band symmetric matrix the direct method using complete choleski decomposition is quite slow and requires much more computer storage we have introduced a row indexed sparse storage mode to store the coefficient matrix a and an incomplete choleski conjugate gradient iccg method to solve the large linear systems by taking advantage of the matrix symmetry and sparsity the iccg method converges much more quickly and requires much less computer storage it takes approximately 15 s on a 533 mhz pentium computer for a grid with 46 020 nodes which is approximately 700 times faster than the direct method and 2 5 times faster than the symmetric successive over relaxation ssor conjugate gradient method compared with 3d finite element resistivity modelling with the improved iccg solver our algorithm is more efficient in terms of number of iterations and computer time in addition we solve for the secondary potential in 3d dc resistivity modelling by a simple manipulation of the fd equations two numerical examples of a two layered model and a vertical contact show that the method can achieve much higher accuracy than solving for the total potential directly with the same grid nodes in addition a 3d cubic body is simulated for which the dipole dipole apparent resistivities agree well with the results obtained with the finite element and integral equation methods in conclusion the combination of several techniques provides a rapid and accurate 3d fd forward modelling method which is fundamental to 3d resistivity inversion

an algorithm for fast 3d inversion of surface electrical resistivity tomography data application on imaging buried antiquities in this work a new algorithm for the fast and efficient 3d inversion of conventional 2d surface electrical resistivity tomography lines is presented the proposed approach lies on the assumption that for every surface measurement there is a large number of 3d parameters with very small absolute jacobian matrix values which can be excluded in advance from the jacobian matrix calculation as they do not contribute significant information in the inversion procedure a sensitivity analysis for both homogeneous and inhomogeneous earth models showed that each measurement has a specific region of influence which can be limited to parameters in a critical rectangular prism volume application of the proposed algorithm accelerated almost three times the jacobian sensitivity matrix calculation for the data sets tested in this work moreover application of the least squares regression iterative inversion technique resulted in a new 3d resistivity inversion algorithm more than 2 7 times faster and with computer memory requirements less than half compared to the original algorithm the efficiency and accuracy of the algorithm was verified using synthetic models representing typical archaeological structures as well as field data collected from two archaeological sites in greece employing different electrode configurations the applicability of the presented approach is demonstrated for archaeological investigations and the basic idea of the proposed algorithm can be easily extended for the inversion of other geophysical data

determination of mechanisms and hydrogeological environments of gangxianlane landslides using geoelectrical and geological data in central taiwan electrical resistivity tomography ert single point resistance logging with time lapse and geological and groundwater level data are utilized to determine the mechanism of and a hydrogeological model of the gangxianlane landslide in the west central part of taiwan the rock surface and geometry of the colluviums were found by integrating ert and borehole data the iso resistivity line in the bedrock broadly followed the bedding plane indicating that the contribution of lithology to resistivity exceeds that of groundwater the results of single point resistance logging with time lapse and borehole data reveal that the bedrock has low permeability which is associated with poorly developed joints and fractures the fine grain content part including the clayey layer almost parallel to the bedding plane of the bedrock and between the colluvium and the bedrock in the upper part of the landslide served as the slip surface and is believed to have been recently produced it can block and retain water in the colluviums accordingly this slip surface has the potential to re slip in the future another slope failure involved rock collapse by a well developed open release joint close to the huoshaoping terrace it is also related to groundwater flow over a large gradient from the huoshaoping terrace it is a key to determining whether this landslide will expand in the future

application of 3d electrical resistivity imaging for mapping frozen ground conditions exemplified by three case studies abstract periglacial landscapes comprise landforms that are inherently 3d structures often exhibiting small scale spatial heterogeneity of surface and subsurface conditions the objectives of the present paper are to illustrate the potential of the novel application of 3d electrical resistivity imaging for mapping frozen ground conditions exemplified by three case studies with different geomorphological problems to be addressed and to consider the efficacy of the 3d approach to geomorphological investigations in mid latitude high alpine and high latitude lowland permafrost environments the approach described in the three case studies includes reconnaissance surveys using two dimensional electrical resistivity tomography 2d ert followed by a detailed mapping using three dimensional electrical resistivity imaging 3d eri the latter approach enables a spatial imaging of the subsurface resistivity distribution and clearly improves the delineation and characterization of subsurface structures compared to state of the art 2d ert that is limited to findings gained along single profiles or extrapolation between several profiles although it can be challenging and time consuming to apply this technique in periglacial environments the promising results demonstrate its value for the 3d delineation of frozen ground conditions in the case of the described case study sites characterizing the subsurface heterogeneity is close to impossible using drilling or 2d geophysical surveying alone because of the complex 3d nature of the frozen ground characteristics comprising permafrost and permafrost free areas alpine permafrost test site as well as permafrost with variable characteristics subarctic lowland permafrost test site at close distance even in environments that seem homogeneous at first sight this method allows us to detect substantial subsurface property variations that can be attributed to different frozen ground conditions furthermore 3d eri allows the linking of different data sources e g site specific geomorphology and hydrology to enhance the spatial understanding of surface and subsurface characteristics and dynamics in permafrost environments the improved knowledge of the geophysical anatomy and subsurface architecture of the permafrost occurrences revealed by this study suggests a more widespread use for glacial and periglacial landform studies in the future

the jettencave southern harz mountains germany geophysical observations and a structural model of a shallow cave in gypsum anhydrite bearing rocks abstract gypsum and anhydrite are soluble rocks where fissures and bedding partings can be enlarged with time by the dissolution of the mineral species through water the selective enlargement results in sub surface voids acting as preferential flow path for the drainage of the rock with time larger cavities develop and a network of cave passages can evolve if the enlarged cave voids are not too deep under the surface geophysical measurements can be used to detect identify and trace these structures we have used gravity measurements grav electrical resistivity imaging eri self potential measurements sp electrical conductivity measurements ec and ground penetrating radar gpr above the cave jettenhohle a cave located in the southern harz mountains in germany the jettencave is developed in the hauptanhydrit formation of the permian zechstein sequence characterised by large breakdown rooms and an exposed water table the overburden of the cave is only around 10 15 m and dolomitic rocks are located in close vicinity we present results from our geophysical surveys in vicinity of the cave we are able to identify the cave geometry from grav eri and gpr measurements which distinguish the local lithology of the permian zechstein rocks in the area from the eri and ec measurements we derive information on the void volume in the soluble rocks we finally present a three dimensional structural model of the jettencave and its surroundings based on our geophysical results and the hydrological interpretation

3d density modeling with gravity and muon radiographic observations in showa shinzan lava dome usu japan we performed three dimensional density modeling of showa shinzan lava dome usu japan by joint inversion of the gravity anomaly and recently obtained muon radiography data our multilayer emulsion muon detector significantly reduces the background noise in our measurements of the muon flux through the dome the high quality muon data enables us to more accurately reconstruct the density structure of the lava dome compared with our own previous work we find that the lava dome consists of a cylindrical column of massive lava with a diameter of 300 m and that there is no evidence of magma intrusion in the shallow part of the plateau located east of the dome

a review of least squares inversion and its application to geophysical problems geophysical inversion involves the estimation of the parameters of a postulated earth model from a set of observations since the associated model responses can be nonlinear functions of the model parameters nonlinear least squares techniques prove to be useful for performing the inversion a common type of inversion applies iterative damped linear least squares through use of the marquardt levenberg method traditionally this method has been implemented by solving the associated normal equations in conventional ways however singular value decomposition svd produces significant improvements in computational precision when applied to the same system of normal equations iterative least squares modeling finds application in a wide variety of geophysical problems two examples illustrate the approach 1 seismic wavelet deconvolution and 2 the location of a buried wedge from surface gravity data more generally nonlinear least squares inversion can be used to estimate earth models for any set of geophysical observations for which an appropriate mathematical description is available

two and three dimensional heterogeneity in carbonate sediments using resistivity imaging abstract volume heterogeneity was investigated in carbonate sediments using fine scale electrical resistivity data which are sensitive to porosity and to sediment macrostructure and microstructure variability in sediment density and porosity was assessed by x radiographic and two dimensional 2d electrical resistivity measurements in 3 cm thick slabs collected from the dry tortugas in the lower florida keys a comparison of the 2d correlation lengths calculated from each assessment indicates that using methods that differ in resolution these two methods measure quite different horizontal and vertical fluctuations in sediment density and porosity other electrical resistivity experiments were conducted using a 2d network of resistivity electrodes on the surface of freshly collected box cores the resulting three dimensional 3d resistivity data provide a unique insight into the spatial variability of sediment porosity and structure at the cm scale complementary x radiograph cores provide 2d datasets of resistivity and porosity at higher resolution these data are used to establish the porosity resistivity microstructure relationships for these carbonate sediments with microstructure being described in terms of tortuosity these relationships are used to extend our interpretation in terms of porosity and tortuosity to the corresponding 3d box core resistivity datasets sediment tortuosity is investigated by numerically modeling the flow of electrical currents through a range of pore morphologies in three dimensions the results show particular sensitivity to the intra particle porosity particle shape and the relative sizes of pores and throats the 3d methodology shows promise as a non invasive measurement of buried inhomogeneities that could lead to improving models for predicting acoustic backscattering from the sediment volume

two dimensional joint inversions of cross hole resistivity data and resolution analysis of combined arrays in this study a new two dimensional inversion algorithm was developed for the inversion of cross hole direct current resistivity measurements in the last decades various array optimisation methods were suggested for resistivity tomography however researchers have still collected data by using classical electrode arrays in most cross hole applications therefore we investigated the accuracy of both the individual and the joint inversion of the classical cross hole arrays by using both synthetic and field data with the developed algorithm we showed that the joint inversion of bipole bipole pole bipole bipole pole and pole tripole electrode arrays gives inverse solutions that are closer to the real model than the individual inversions of the electrode array datasets for the synthetic data inversion the model resolution matrix of the suggested arrays was used to analyse the inversion results this model resolution analysis also showed the advantage of the joint inversion of bipole bipole pole bipole bipole pole and pole tripole arrays we also used sensitivity sections from each of the arrays and their superpositions to explain why joint inversion gives better resolution than the any individual inversion result

methodology for processing seismograms containing total internal reflections a very common problem encountered in downhole seismic testing dst and crosshole seismic testing cst is the processing of seismograms that contain total internal reflections tirs tirs arise when the incident angle exceeds the critical angle and they are associated with reflected source wave distortions due to the fact that the reflection coefficients become complex tirs are typical in cst investigations since horizontally traveling source waves have high angles of incidence on bounding stratigraphic layers whereas in dst investigations tirs are encountered whenever there are significant man made structures piles stone columns and deep underground structures such as deep basements parking garages and dam structures to process seismograms containing tirs time variant blind seismic deconvolution bsdtv techniques are required and this paper outlines a new formulation of a previously published concept in blind seismic deconvolution referred to as principle phase decomposition ppd this new ppd filter formulation allows for bsdtv where the direct source wave is isolated from the reflected source waves the bsdtv ppd filter formulation is referred to as bsdsolver tv

a survey of current trends in near surface electrical and electromagnetic methods electricalandelectromagnetice emmethodsfornearsurface investigations have undergone rapid improvements over the past few decades besides the traditional applications in groundwater investigations natural resource exploration and geological mapping a number of new applications have appeared these include hazardous waste characterizationstudies precision agricultureapplications archeological surveys and geotechnical investigations the inclusion of microprocessors in survey instruments development ofnewinterpretationalgorithms andeasyaccesstopowerful computers have supported innovation throughout the geophysical community and the e em community is no exception most notable are development of continuous measurement systems that generate large dense data sets efficiently these have contributed significantly to the usefulness of e em methods by allowing measurements over wide areas without sacrificing lateral resolution the availability of theseluxuriantdatasetsinturnspurreddevelopmentofinterpretation algorithms including laterally constrained 1d inversionaswellasinnovative2d and3d inversionmethods taken together these developments can be expected to improve the resolution and usefulness of e em methods and permit them to be applied economically the trend is clearly towarddensesurveyingoverlargerareas followedbyhighly automated post acquisition processing and interpretation to provide improved resolution of the shallow subsurface in a cost effectivemanner

vertical electrical sounding ves and multi electrode resistivity in environmental impact assessment studies over some selected lakes a case study a combined geophysical investigation consisting of vertical electrical sounding ves and multielectrode system was carried out to map the subsurface resistivity in all major lakes which are highly polluted by the discharge of sewage and other chemical effluents in greater hyderabad india the structural features identified in the study area play a major role in groundwater flow and storage the interpretation of geophysical data and lithologs indicates that a silt clay zone predominantly silt has a thickness of 5 10 m all along the drainage from patelcheruvu to the musi river the silt clay zone inferred close to the lakes is a mixture of clay silt and sand with more silt content as indicated from the lithologs during drilling the low resistivity values obtained can be attributed to the pollutant accumulated in the silt which can reduce the resistivity values further the tds of the water samples in these wells are more than 1 000 mg l which further confirms the above scenario the pollution spread is less in the upstream areas whereas it is more in the downstream which can be attributed to the shallow water table conditions and also due to the interaction of surface water and groundwater

characterization of active and closed landfill sites using 2d resistivity ip imaging case studies in penang malaysia an interpretation approach for analysis of electrical resistivity and chargeability inverse models generated at two upgraded semi aerobic landfill sites was developed the inverse models produced from a 2d inversion program res2dinv were used to set up a grid of electrical resistivity and chargeability imaging at the landfill sites the investigations confirmed a high chargeability unit 70 ms depicting waste deposits and a saturated clayey layer while the leachate plume showed low resistivity 10 m and weak chargeability zone 20 ms moreover the ip responses of a diffused leachate plume downstream of a separate semi aerobic landfill site in a similar geological setting were evaluated obtaining an analogous result the ion dominated plume that exhibited a weak chargeability promoted membrane polarization rather than electrode polarization in its ip responses however the high concentration of ions in the diffused leachate restrained the ionic polarization diminishing the ip effects in host sediments the interpretation of the resistivity and chargeability profiles at the characterization sites allowed delineating the different zones of the subsurface strata in particular comparison of the leachate zones at the two locations revealed that the active landfill with a lesser proportion of waste deposits contained a greater accumulation of leachate than the closed site the results in this study support the effectiveness of contaminant plume monitoring through the joint application of resistivity and ip methods these non invasive rapid and cost effective geophysical techniques could lead to a promising reconnaissance tool for remediation or reclamation of solid waste disposal sites

rapid least squares inversion of apparent resistivity pseudosections by a quasi newton method1 a fast inversion technique for the interpretation of data from resistivity tomography surveys has been developed for operation on a microcomputer this technique is based on the smoothness constrained least squares method and it produces a two dimensional subsurface model from the apparent resistivity pseudosection in the first iteration a homogeneous earth model is used as the starting model for which the apparent resistivity partial derivative values can be calculated analytically for subsequent iterations a quasi newton method is used to estimate the partial derivatives which reduces the computer time and memory space required by about eight and twelve times respectively compared to the conventional least squares method tests with a variety of computer models and data from field surveys show that this technique is insensitive to random noise and converges rapidly this technique takes about one minute to invert a single data set on an 80486dx microcomputer

electrical resistivity tomography to investigate geological structures of the earth s upper crust it is important to have detailed knowledge of the electrical properties of the earth s crust in order to recognize geological structures and to understand tectonic processes in the area surrounding the german continental deep drilling project ktb we have used dc dipole dipole soundings to investigate the electrical conductivity distribution down to a depth of several kilometres we have adapted the electrical resistivity tomography ert technique a well established near surface method to large scale experiments independent transmitting and receiving units were used to realize the concept of simultaneous multichannel registration of the scalar electrical potential at 44 dipoles the measured data yielded apparent resistivities which were inverted to a 2d resistivity model ranging from the surface down to a depth of 4 km two highly conductive structures with steep inclination were detected they are expected to be major fault zones embedded in a metamorphic body the rather low resistivity 10 m can be explained by the existence of graphitic minerals and or electrolytic fluids

magnetic imaging and electrical resistivity tomography studies in a roman military installation found in satala archaeological site northeastern anatolia turkey abstract satala is one of the last great military centers in the roman east available for archaeological and historical investigations this archaeological site is situated on the crossing of two singularly important routes in north east asia minor only little archaeological fieldwork in and around satala has so far been carried out thus delimiting our knowledge of the site and its role within the roman military structure of the east in order to provide further data on the site we carried out geophysical surveys including the application of magnetic and electrical resistivity techniques in an area north of the sadak village the geophysical surveys within this area supposedly part of the roman military camp proceeded in two stages the first stage saw magnetic gradiometer imaging studies being carried out on 2 1 ha measured by a geoscan fm 36 fluxgate gradiometer by using 0 5 1 m grid intervals for the second stage a different geophysical technique was used resistivity tomography resistivity data were collected using a number of combined 2d resistivity pseudosections in the eastern part of the area which contained very regular magnetic anomalies the 3d data were obtained by the combination of all survey lines collected from 2d data sets and thereafter the arranged data were processed by using the 3d robust inversion modified from the smoothness constrained algorithm electrical resistivity tomography investigations revealed that the buried archaeological structures might be located near the surface except for some structures found in the middle of the studied area the archaeological structures were furthermore determined by realistic model sections and volumetric representations magnetic imaging and electrical resistivity tomography surveys show that the combined usage of these techniques advances the understanding of archaeological structures beneath the surface

bedrock detection beneath river terrace deposits using three dimensional electrical resistivity tomography abstract we describe the use of a fully volumetric geophysical imaging approach three dimensional electrical resistivity 3d ert for bedrock detection below mixed sand and gravel deposits typical of fluvial valley fill terraces we illustrate the method through an analysis of terrace deposits of the great ouse river uk where up to 4 m of sand and gravel have filled the valley bottom during the latest pleistocene we use an edge detector to identify the steepest gradient in first derivative resistivity profiles which yields an estimate of bedrock depth verified by drilling to a precision better than 0 2 m average and 0 4 m standard deviation comparison of a range of drilling techniques at the site has revealed that borehole derived interface depths suffered from levels of uncertainty similar to those associated with the 3d ert indicating that the reliability of bedrock interface depths determined using these two approaches is comparable in this case the 3d ert method provides a high spatial resolution that enabled a previously unknown erosional bedrock structure associated with the change from deeper first terrace to second terrace deposits to be identified in the great ouse valley the method provides a relatively quick method to quantify terrace fill volume over large sites to a greater degree of precision than currently available

cave detection using multiple geophysical methods unicorn cave harz mountains germany unicorn cave in the southern harz mountains of germany is a show cave in dolomitic rocks of the zechstein formation the cave s trunk passage is interrupted by larger rooms the overburden is only around 15 m the passages are filled with sediments that can be up to 50 m thick we used gravimetry and electrical resistivity imaging over the cave area to identify the subsurface voids and the extent of the sediment infill of the cave passages our choice of methods was based on several conditions unique to the cave 1 well surveyed 2 shallow overburden 3 large air filled passages and 4 thick sediment cover concealing true passage size using the cave survey as an initial model for the subsurface structure we successfully identified the air filled cave with both methods we then inferred the thickness of the sediment infill by forward modeling and identified a possible southward continuation beyond the currently explored passages

combined electrical resistivity imaging and ground penetrating radar study for detection of buried utilities in federal university of agriculture abeokuta nigeria the knowledge of the exact location and depth of buried utility such as pipes assists greatly for prevention of accidents and wastage of resources this study addresses the application of integrated geophysical methods for detections of buried utility in student s residential hostels federal university of agriculture abeokuta southwestern nigeria the goals of the surveys are to determine the effectiveness of the applied methods in detection of buried utilities locations and their depths as well as verification of obtained depths to the top of target by excavation method 2d electrical resistivity imaging eri using wenner array with electrode separation ranging from 0 25 to 1 25 m and ground penetrating radar gpr survey using a common offset profiling and center frequency of 400 mhz were carried out along ten traverses in the study area the field data were processed using res2dinv and radan 7 softwares for resistivity and gpr data respectively inverted resistivity sections and radar images generated information up to a depth of 0 80 m and 3 00 m respectively the position size and depth of buried pipes cannot be determined precisely by ert compared to gpr survey the depths to the top of buried pipes by ert ranges from 0 20 to 0 46 m while the gpr measured depths ranged from 0 16 to 0 55 m from the surface integrated interpretation showed that gpr can effectively provide information about locations and depths to the top of buried pipes with a higher precision than ert method comparisons of measured gpr depths with in situ verification using excavation method correlate fairly well

electrical resistivity tomography ert applied to karst carbonate aquifers case study from amdoun northwestern tunisia the amdoun region is characterized by a high degree of karstification due to the climate impact 1500 mm year 1 and the development of fracture network survey using electrical resistivity tomography ert is deployed to provide a cost effective characterization of the subsurface karst environments a total of seven ert profiles with lengths of 315 m were evaluated at the beja governorate nw tunisia the area represents a small syncline of boudabbous limestone rocks lower eocene which is covered by a thin layer of clay in this study an ert survey was conducted to examine the spatial distribution and shape of underground cavities in the karst area in jebel sabah anticline and ain sallem zahret medien syncline in this study geological hydro geological and electrical resistivity tomography ert methods were applied to determine the geometry of the perched aquifer in the amdoun region nw tunisia the area is characterized by fractured and karstic limestone aquifer of late cretaceous abiod fm and lower eocene boudabbous fm the aquifers have a karstic functioning and drain aquifers of economical interest despite some wells exploiting them seven resistivity profiles were conducted along the survey area at three sites the orientation extension and the degree of inclination of those profiles are shown in the location map the correct resistivity data were interpreted using earth imager 2d software the results of the interpreted geo electrical sections showed that the resistivity of the carbonate aquifer varied between 2 5 to over 5794 m the thickness of the perched aquifer ranged from 15 to 50 m while its depth from the surface lies between 10 and 60 m the ert not only provided precise near surface information but was also very useful for establishing the 3d geometry and the position of several potential cavities and karts the results show the presence of small to large isolated cavities at various depths the low resistivity of cavities in the boudabbous formation has been explained by the groundwater saturation the ert technique could be effectively used for 3d detection of underground limestone cavities

high resolution imaging in the inhomogeneous crust with cosmic ray muon radiography the density structure below the volcanic crater floor of mt asama japan we have developed a novel radiographic imaging method to survey the inhomogeneous structure of the crust as an example we performed measurements at mt asama volcano and studied the feasibility of using an azimuthally isotropic flux of cosmicray muons in the energy range up to a few tev the principle of the technique is that by measuring muon absorption along different nearly horizontal paths through a solid body one can deduce the density distribution in the interior of the object a muon detector with an area of 4000 cm 2 was installed in a 1 m deep instrument vault located about 1 km from the summit crater of mt asama muon tracks within emulsion layers in the detector were analyzed by 3d image processing to determine the level of energy absorption along different ray paths through the summit crater region a typical angular resolution of the muon detector of 10 milliradians mrad corresponds to a spatial resolution of 10 m at a distance of 1 km the measurements would be ideal for studying the shallow structure of the crust at sites which cannot be well resolved because of their strong structural heterogeneity and potential difficulty to be accessed and which therefore cannot have their structure determined by conventional electromagnetic or seismic techniques the present method can also provide three dimensional images of the subsurface by making measurements from two or more different points in this work we have radiographically imaged a few hundred meters below the crater floor of mt asama japan and have detected a dense region which corresponds to the position and shape of a lava mound created during the last eruption urabe b watanabe n murakami m topographic change of the summit crater of asama volcano during the 2004 eruption derived from airborne synthetic aperture radar sar measurements bulletin of geographical survey institute 53 1 6 2006 right below the lava mound we found a low density region that suggests a drain back induced porous conduit urabe b watanabe n murakami m topographic change of the summit crater of asama volcano during the 2004 eruption derived from airborne synthetic aperture radar sar measurements bulletin of geographical survey institute 53 1 6 2006 the density contrast was resolved with a precision of 1 3 this method

two and three dimensional electrical resistivity imaging at a heterogeneous remediation site geometrically complex heterogeneities at a decommissioned sour gas plant could not be adequately characterized with drilling and 2d electrical resistivity surveys alone in addition 2d electrical resistivity imaging profiles produced misleading images as a result of out of plane resistivity anomalies and violation of the 2d assumption accurate amplitude and positioning of electrical conductivity anomalies associated with the subsurface geochemical distribution were required to effectively analyze remediation alternatives forward and inverse modeling and field examples demonstrated that 3d resistivity images were needed to properly reconstruct the amplitude and geometry of the complex resistivity anomalies problematic 3d artifacts in 2d images led to poor inversion fits and spurious conductivity values in the images at depths close to the horizontal offset of the off line anomaly three dimensional surveys were conducted with orthogonal sets of wenner and dipole dipole 2d resistivity survey lines the

utilizing 2d electrical resistivity tomography and very low frequency electromagnetics to investigate the hydrogeology of natural cold springs near virginia city southwest montana virginia city montana is located in the northern rocky mountains of the united states two natural springs supply the city s water however the source of that water is poorly understood the springs are located on the east side of the city on the edge of an area affected by landslides 2d electric resistivity tomography ert and very low frequency electromagnetics vlf em were used to explore the springs and landslides two intersecting 2d resistivity profiles were measured at each spring and two vlf profiles were measured in a landslide zone the inverted 2d resistivity profiles at the springs reveal high resistivity basalt flows juxtaposed with low resistivity volcanic ash the vlf profiles within the landslide show a series of fracture zones in the basalt which are interpreted to be a series of landslide scarps results show a strong correlation between the inferred scarps and local topography this study provides valuable geological information to help understand the source of water to the springs the contact between the fractured basalt and the ash provides a sharp contrast in permeability which causes water to flow along the contact and discharge at outcrop the fracture zones along the scarps in the landslide deposits provide conduits of high secondary permeability to transmit water to the springs the fracture zones near the scarps may also provide targets for municipal supply wells

practical techniques for 3d resistivity surveys and data inversion1 techniques to reduce the time needed to carry out 3d resistivity surveys with a moderate number 25 to 100 of electrodes and the computing time required to interpret the data have been developed the electrodes in a 3d survey are normally arranged in a square grid and the pole pole array is used to make the potential measurements the number of measurements required can be reduced to about one third of the maximum possible number without seriously degrading the resolution of the resulting inversion model by making measurements along the horizontal vertical and 45 diagonal rows of electrodes passing through the current electrode the smoothness constrained least squares inversion method is used for the data interpretation the computing time required by this technique can be greatly reduced by using a homogeneous half space as the starting model so that the jacobian matrix of partial derivatives can be calculated analytically a quasi newton updating method is then used to estimate the partial derivatives for subsequent iterations this inversion technique has been tested on synthetic and field data where a satisfactory model is obtained using a modest amount of computer time on an 80486dx2 66 microcomputer it takes about 20 minutes to invert the data from a 7 by 7 electrode survey grid using the techniques described below 3d resistivity surveys and data inversion can be carried out using commercially available field equipment and an inexpensive microcomputer

numerical simulation of seismic cone signals numerical analysis can provide insight into the effect of ground conditions on seismic signals recorded in downhole seismic testing as part of a study of the interpretation of seismic cone data in

resistivity imaging technique to delineate shallow subsurface cavities associated with old coal working a numerical study subsidence is an environmental hazard due to subsurface cavities associated with abandoned coal workings in the eastern indian coalfields these cavities pose danger to coal mining of deeper coal seams most of these subsurface cavities are unapproachable as no mine plans are available here an attempt has been made to detect and possible delineation of air and as well as water filled cavities applying electrical resistivity imaging eri technique using dipole dipole pole dipole and wenner schlumberger arrays models are simulated with a reasonable resistivity value of formations considering board and pillar mining environment in multilayer earth the inverted resistivity section corresponding to water filled cavities without a barrier could be able to detect three cavities for dipole dipole and wenner schlumberger arrays whereas pole dipole array could detect all four cavities later on with inclusion of 1 m coal as a barrier in the model the dipole dipole array could be able to bring the signature of cavities whereas pole dipole and wenner schlumberger configuration is unable to provide any signature similar resistivity responses are noticed for air filled cavities with and without barrier conditions when all three arrays data are jointly inverted there is a significant improvement in resistivity response which enables the detection of water filled as well as air filled cavities with and without a barrier

computation of optimized arrays for 3 d electrical imaging surveys 3 d electrical resistivity surveys and inversion models are required to accurately resolve structures in areas with very complex geology where 2 d models might suffer from artefacts many 3 d surveys use a grid where the number of electrodes along one direction x is much greater than in the perpendicular direction y frequently due to limitations in the number of independent electrodes in the multi electrode system the surveys use a roll along system with a small number of parallel survey lines aligned along the x direction the compare r array optimization method previously used for 2 d surveys is adapted for such 3 d surveys offset versions of the inline arrays used in 2 d surveys are included in the number of possible arrays the comprehensive data set to improve the sensitivity to structures in between the lines the array geometric factor and its relative error are used to filter out potentially unstable arrays in the construction of the comprehensive data set comparisons of the conventional consisting of dipole dipole and wenner schlumberger arrays and optimized arrays are made using a synthetic model and experimental measurements in a tank the tests show that structures located between the lines are better resolved with the optimized arrays the optimized arrays also have significantly better depth resolution compared to the conventional arrays

using dc resistivity tomography to detect and characterize mountain permafrost direct current dc resistivity tomography has been applied to different mountain permafrost regions despite problems with the very high resistivities of the frozen material plausible results were obtained inversions with synthetic data revealed that an appropriate choice of regularization constraints was important and that a joint analysis of several tomograms computed with different constraints was required to judge the reliability of individual features the theoretical results were verified with three field experiments conducted in the swiss and the italian alps at the first site near zermatt switzerland the location and the approximate lateral and vertical extent of an ice core within a moraine could be delineated on the murtel rock glacier eastern swiss alps a steeply dipping boundary at its frontal part was observed and extremely high resistivities of several m indicated a high ice content the base of the rock glacier remained unresolved by the dc resistivity measurements but it could be constrained with transient em soundings on another rock glacier near the stelvio pass eastern italian alps dc resistivity tomography allowed delineation of the rock glacier base and the only moderately high resistivities within the rock glacier body indicated that the ice content must be lower compared with the murtel rock glacier

cosmic ray muon imaging of magma in a conduit degassing process of satsuma iwojima volcano japan 1 muon radiography can provide essentially a cross section through the object parallel to the plane of the detector on which the average density along all the muon paths is projected somewhat like x ray radiography very recently the use of emulsion films has given us a clue for visualization of the interior of volcanoes to image a larger volcano in shorter time we need a larger detector to collect more muon events however the time required for imaging will be proportional to the detection area in order to overcome this problem we developed a portable assembly type cosmic ray muon telescope module to image the density distribution of magma in the conduit of mt iwodake volcano japan a muon detector with an area of 1 m2 was set up at the foot of the volcano we mapped differentially absorbed cosmic ray muons which depend on the varying thickness and density beneath the crater floor we successfully imaged density distribution in the conduit as well as the conduit shape assuming the density anomaly is localized in the vent area the observed location of the magma head is consistent with the degassing model of rhyolitic systems proposed by k kazahaya et al in 2002

electrical resistivity tomography determines the spatial distribution of clay layer thickness and aquifer vulnerability kandal province cambodia despite being rich in water resources many areas of south east asia face difficulties in securing clean water supply this is particularly problematic in regions with a rapidly growing population in this study the spatial variability of the thickness of a clay layer controlling surface groundwater interactions that affect aquifer vulnerability was investigated using electrical resistivity tomography ert data were acquired along two transects showing significant differences in the imaged resistivities borehole samples were analyzed regarding particle density and composition and linked to their resistivity the obtained relationships were used to translate the field electrical resistivities into lithologies those revealed considerable variations in the thickness of the clay layer ranging from 0 m up to 25 m geochemical data highlighting zones of increased ingress of surface water into the groundwater confirmed areas of discontinuities in the clay layer which act as preferential flow paths the results may guide urban planning of the phnom penh city expansion in order to supply the growing population with safe water the presented approach of using geophysics to estimate groundwater availability accessibility and vulnerability is not only applicable to kandal province cambodia but also to many other areas of fast urbanization in south east asia and beyond

out of plane effects in 2d borehole to surface resistivity tomography and applications in mineral exploration in this paper we discuss the effects of anomalous out of plane bodies in two dimensional 2d borehole to surface electrical resistivity tomography with numerical resistivity modelling and synthetic inversion tests the results of the two groups of synthetic resistivity model tests illustrate that anomalous bodies out of the plane of interest have an effect on two dimensional inversion and that the degree of influence of out of plane body on inverted images varies the different influences are derived from two cases one case is different resistivity models with the same electrode array and the other case is the same resistivity model with different electrode arrays qualitative interpretation based on the inversion tests shows that we cannot find a reasonable electrode array to determine the best inverse solution and reveal the subsurface resistivity distribution for all types of geoelectrical models because of the three dimensional effect arising from neighbouring anomalous bodies the qualitative interpretation of inverted images from the two dimensional inversion of electrical resistivity tomography data without prior information can be misleading two dimensional inversion with drilling data can decrease the three dimensional effect we employed two and three dimensional borehole to surface electrical resistivity tomography methods with a pole pole array and a bipole bipole array for mineral exploration at abag banner and hexigten banner in inner mongolia china different inverse schemes were carried out for different cases the subsurface resistivity distribution obtained from the two dimensional inversion of the field electrical resistivity tomography data with sufficient prior information such as drilling data and other non electrical data can better describe the actual geological situation when there is not enough prior information to carry out constrained two dimensional inversion the three dimensional electrical resistivity tomography survey is the better choice

imaging the conduit size of the dome with cosmic ray muons the structure beneath showa shinzan lava dome japan 1 we developed a radiographic technique to image a subsurface conduit shape using cosmic ray muons the test measurement was performed in showa shinzan lava dome located in hokkaido japan as an example a muon detector with an area of 6000 cm2 was set up at the foot of the lava dome muon tracks recorded in nuclear emulsion films in the detector were analyzed to determine the level of energy absorption along different ray paths through subsurface beneath the lava dome a typical angular resolution of the muon detector of 10 mrad corresponds to a spatial resolution of 10 m at a distance of 1 km which is difficult to be addressed with seismological technique we mapped differentially absorbed cosmic ray muons which depend upon the varying thickness and density beneath the dome we successfully imaged the conduit shape and determined a conduit diameter of 102 15 m assuming the observed high absorption region beneath the dome is localized in the vent area

salinization processes in the unconfined aquifer of bou areg ne morocco a geostatistical geochemical and tomographic study hydrogeological and geochemical data in conjunction with the results of an electrical imaging tomographic survey were examined to determine the main factors and mechanisms controlling the groundwater chemistry and salinity of the unconfined aquifer of bou areg on the mediterranean coast of ne morocco in addition statistical and geochemical interpretation methods were used to identify the distribution of the salinity multivariate statistical analysis cluster and principal component factors revealed the main sources of contamination groups a b and c in the cluster analysis and factors 1 3 factor 1 ce cl k so42 and mg2 factor 2 ca2 hco3 and ph factor 3 no3 represent the signature of seawater intrusion in the coastal zone the influence of marly gypsum outcrops in the upstream zone and anthropogenic sources respectively the ionic delta the ionic ratio the saturation index and stuyfzand s method were applied to evaluate geochemical processes the results obtained indicate on the one hand the phenomenon of salinization in both the coastal and the upstream zones and on the other the dilution of groundwater by recharge cation exchange is shown to modify the concentration of ions in groundwater locally with respect to salinization processes in the coastal zone the results of electrical imaging tomography show that salinity increases both with depth and laterally inland from the coastline due to seawater intrusion

investigation of the inner structure of la crosa de sant dalmai maar catalan volcanic zone spain abstract la crosa de sant dalmai volcano is the largest volcanic edifice of the catalan volcanic zone ne spain it is a very well preserved maar type structure 1 5 km in diameter excavated at the contact between a hard substrate and a soft substrate formed by palaeozoic granites and pliocene and quaternary gravels respectively in order to infer the uppermost inner structure of la crosa de sant dalmai maar and to characterise its main geological and tectonic constraints we have performed a multiparametric geophysical study including gravimetry magnetometry self potential and electrical resistivity tomography the results obtained together with a field geology revision and additional geological data from two drill cores provide a detailed picture of the post eruptive maar infill sequence as well as of the uppermost part of the maar diatreme structure this information helps in understanding the origin and subsequent evolution of the volcano which included an alternation of phreatomagmatic and strombolian phases geophysical data show that the last strombolian phase which culminated with the formation of a scoria cone inside the maar was associated with a nw se trending regional fault the little erosion and degradation of the original tephra ring suggest a much younger age of la crosa de sant dalmai maar than was previously stated

geoelectrical mapping of contamination in the cemeteries the case study in piracicaba sao paulo brazil this paper presents the results of electrical resistivity methods in the area delineation that was potentially contaminated by liquefaction products which are also called putrefactive liquids in vila rezende municipal cemetery piracicaba sao paulo brazil the results indicate a depth of water table between 3 1 and 5 1 m with two groundwater direction flows one to the sw and another to the se due to the contamination plumes which have the same groundwater direction flow as well the conductive anomalies observed in the geoelectric sections the contamination suspicions in the area were confirmed the probable plume to the se extends beyond the limits of the cemetery the location of the conductive anomalies and the probable contamination plumes showed that the contamination is linked with the depth of the water table and the burial time mapping using the geostatistical method of ordinary kriging applied to the work drew structural characteristics of the regional phenomenon and spatial behavior of the electrical resistivity data resulting in continued surfaces thus this method has proved to be an important tool for mapping contamination plumes in cemeteries

integration of controlled source and radio magnetotellurics electric resistivity tomography and reflection seismics to delineate 3d structures of a quick clay landslide site in southwest of sweden abstractquick clay which is the main cause of landslides that occur in the northern countries liquefies easily and its presence implies an increased risk of landslide geophysical methods have been increasingly used in landslide investigations three dimensional electric resistivity tomography radio magnetotelluric rmt controlled source rmt csrmt and high resolution reflection seismic data were acquired at a quick clay landslide site in the southwest of sweden the main objectives were to evaluate the capability of each method in delineating different subsurface geologic structures that controlled a peculiar and hazardous retrogressive type landslide in the study area a 3d resistivity model from the inversion of csrmt data showed the best correlation with the reflection seismic data and borehole information thanks to the broad frequency range of the data set it better imaged the resistive crystalline bedrock underlying the marine conductive clays and showed considerable correlations with the

identification of gypsum karstification using an electrical resistivity tomography technique the case study of the sivas gypsum karst area turkey abstract the sivas district is the most important gypsum karstified area in turkey the oldest evaporites in the region were formed during the sedimentation process of the oligocene period generally these units extend along the southern part of the sivas basin after the early miocene sea drained from this region extensive evaporite deposition developed an electrical resistivity tomography ert study was carried out between the hafik and imranli districts of the sivas gypsum karstified area in this research the prior aim was to determine the general characterization geometry sedimentary cover and resistivity properties of gypsums in addition the study includes the synthetic modelling of different gypsum karstification types the evaluation and interpretation were based on ert data that was collected from the hafik imranli region first the different karstifications were identified together with the characteristic features of gypsum in the area the ert studies showed that there are large and old karst structures between the hafik and zara district however the karst structures that are located between the zara and imranli regions were interpreted as smaller and younger the characteristics of both of the regions are different in terms of the morphometric properties it is certain that the kizilirmak river has an important impact on the formation of these structures ert studies have shown that the cover and bedrock type collapse sinkholes are very spread out across the area and their geometries are different throughout time the suffosion type of cavities formed inside the cover type sinkholes as a consequence of geological and geomorphological events the ert sections showed that certain parts of these structures collapsed and then alluvial materials filled in the shallow groundwater level in the drilling results and the conductive zone in the ert results are compatible with each other ert studies clearly determined the various karstification typologies of gypsums in the region which also contributed to the creation of a detailed conceptual geological model

high resolution integrated geophysical investigation at the lancaster gold mine krugersdorp south africa an integrated geophysical approach using seismics and geoelectrical techniques was employed to investigate the architecture of historic narrow reef workings and a proposed open pit mine at lancaster gold mine near krugersdorp south africa the mining activities in the area were mainly carried out within the kimberley reef package in the upper central rand group of the witwatersrand supergroup which hosts several gold bearing conglomerates locally known as reefs the reefs are generally thin 2 m thick and dip between 28 and 32 south the low velocity weathered layer introduces significant static shifts in the reflection seismic data moreover environmental noise from drilling and trucking and the prominent bedrock overburden contact that produces various wave conversions p s conversion caused undesirable noise that contaminates the shot gathers as high amplitude source generated and monochromatic noise the noise was removed from the shot gathers using frequency and velocity filtering techniques the final depth migrated sections are characterised by high resolution images of the subsurface from 10 to 150 m depth which are constrained by the borehole information the reflection seismic data delineate the interfaces between different rock layers and the stopes the refraction and resistivity tomograms on the other hand provide more detailed images of the top 20 50 m of the subsurface and depict the approximate shallow geometry of fluid migration paths mined out areas and bedrock overburden boundaries the integrated results indicate that the study area is characterised by a weathered surface layer with variable low p wave velocity 400 1200 m s and resistivity 150 800 m the deeper layer reveals an increase in resistivity and velocity and it s characterized by discontinuities weak zones cavities or water bearing zones due to the mining activities the combined borehole and geophysical data provide valuable information regarding the physical characteristics of the subsurface and can be helpful for future risk management decisions environmental and engineering studies in the area

spatiotemporal gravity changes at miyakejima volcano japan caldera collapse explosive eruptions and magma movement 1 calderas are ubiquitous topographic features of volcanos yet caldera formation itself has not been recorded intensively by modern measurement techniques here we report the spatiotemporal gravity changes before and after caldera collapse at the miyakejima volcano japan in 2000 a gravity decrease of as much as 145 gal 1 gal 10 8 m s2 at the summit area since june 1998 was detected 2 days prior to the collapse interpreted as reflecting the formation of a large void beneath the volcano gravity changes detected after the initiation of collapse can mostly be corrected by the effect of collapsed topography from which a rapid rate of collapse of more than 1 6 107 m3 d can be inferred correcting for the effect of topography change we identified a temporal decrease in gravity from the middle of july to late august despite ground subsidence the gravity decrease is interpreted as a reduction of the density in a cylindrical conduit attributed to water inflow from an ambient aquifer that also promoted intensive magma water interaction and subsequent explosive eruptions from september to at least november 2000 gravity values at all sites increased significantly by a degree that cannot be explained by ground displacement alone we interpret this temporal evolution as primarily due to magma ascent and refilling of the conduit

detection and 2d modelling of cavities using pole dipole array the resistivity method is often used in cave prospecting in this paper the pole dipole array ability to detect cavities at different depths and with different water contents is investigated the research was performed using analogical and numerical modelling according to the results empty caves at a depth less than four times its diameter can be easily detected the ability of the pole dipole array to detect water filled caves reaches a minimum at filling percentages of 30 50 overburden effects research shows that low resistivity overburden reduces the resolution capability of the array this study shows that equivalent results can be obtained by modelling the empty caves as infinite resistivity bodies or alternatively as very high resistivity ones the analysis of field data acquired in the macico calcario estremenho portugal shows the practical importance of the pole dipole array in cavities prospecting

current transition from glacial to periglacial processes in the dolomites south eastern alps abstract a close relationship between glacial and periglacial landforms is frequently observed in alpine environments where a transition from glacial to periglacial processes often took place after the end of the little ice age lia understanding the origin of these landforms is challenging and assessing the current spatial domain of glacial and periglacial processes may be a difficult task in high relief areas where thick and widespread debris cover often characterize rapidly decaying glaciers here we present a comprehensive study of a composite landform located in the dolomites south eastern alps combining geomorphological geophysical and topographic surveys with ground surface temperature measurements results indicate that a debris covered glacier persists in the upper part rather large compared to the lia extent but currently inactive and rapidly losing mass an active rock glacier exists in the lower part surrounded by discontinuous permafrost a frozen body about 10 m thick was detected in the rock glacier and geomorphological evidence suggests that this ice mass is completely detached from the debris covered glacier our findings suggest that the lower part of the composite landform is probably a remnant of the ancient glacier tongue and is currently evolving under periglacial conditions periglacial processes are therefore replacing glacial processes which dominated in this site during the lia

electric and magnetic tomographic approach for the geophysical investigation of an unexplored area in the archaeological site of pompeii southern italy the joint application of electric and magnetic techniques for near surface exploration represents a very useful tool for archaeological investigation and can provide a quantitative contribution to describe the spatial distribution of buried objects in this work we show a new advanced tomographic approach based on the parallel inversion of magnetic and electric observed data aimed at the reconstruction of the subsoil of a still unexplored area of the archaeological site of pompeii southern italy the survey was performed in collaboration with pompeii s archaeological commission the comparison between the results obtained from the tomographic inversions of both electrical and magnetic data was carried out in terms of the data inversions which allowed us to obtain information about the location of the buried geophysical sources in the investigated subsoil the results obtained seem to be in a good agreement both for the position of the geophysical sources and for their dimensions

resistivity imaging survey to delineate subsurface seepage of hydrocarbon contaminated water at karbala governorate iraq this research is an attempt to accomplish a 3 d resistivity imaging survey which was carried out near a water well contaminated with hydrocarbon materials in karbala governorate two dimensional resistivity imaging measurements were collected along four parallel profiles using a wenner array with electrode spacing of 1 m the res3dinv program was used to invert the apparent resistivity data the results displayed a resistivity distribution of the subsurface in a three dimensional volume thus both the horizontal and vertical extents of the contaminated zone were displayed this technique revealed a low resistivity zone at depth ranges from 3 to 6 m in the investigation area but the seepage starts at depth ranges between 2 and 3 m and continues down depth may be to the groundwater level this low resistivity zone is the most likely location for a subsurface seepage of contaminated water it is clear that the sufficient measurement points along 2 d lines in a small area can increase the 3 d imaging resolution and nearly real 3 d imaging can be achieved when the size of subsurface anomaly compared with the electrode spacing a of the wenner array is taken into consideration

evaluation of landfill disposal boundary by means of electrical resistivity imaging this paper deals with an employment of electrical resistivity imaging eri for survey of leachate content on the waste disposal site in northern israel the research consisted of conducting ten eri lines and drilling investigation wells data simulation used a 2d earthimager inversion program analysis of 2d eri interpretation results shows that determination of the boundary between the landfill body bottom intensively saturated with leachates and underlying layers of highly water saturated fat nonconsolidated clays presents a challenge however statistical analysis of eri data indicates that standard deviation and confidence interval of a set of resistivity data measured in the landfill body are significantly larger than those in underlying clays moreover maximum changes of these parameters are found on the boundary between landfill body and underlying soil thus reflecting natural differences in scattering of resistivity data measured in these two objects

an electric and electromagnetic geophysical approach for subsurface investigation of anthropogenic mounds in an urban environment abstract scientific interest in mounds as geomorphological features that currently represent topographic anomalies in flat urban landscapes mainly lies on the understanding of their origin either purely natural or anthropogenic in this second circumstance another question is whether traces of lost buildings are preserved within the mound subsurface and can be mapped as remnants testifying past settlement when these landforms have been modified in centuries for civilian use structural stability is a further element of concern to address these issues we applied a geophysical approach based on a very low frequency electromagnetic vlf em technique and two dimensional electrical resistivity tomography 2d ert and integrated it with well established surface survey methods within a diagnostic workflow of structural assessment we demonstrate the practical benefits of this method in the english cemetery of florence italy whose mixed nature and history of morphological changes are suggested by archival records the combination of the two selected geophysical techniques allowed us to overcome the physical obstacles caused by tomb density and to prevent interference from the urban vehicular traffic on the geophysical signals eighty two vlf em profiles and five 2d erts were collected to maximise the spatial coverage of the subsurface prospection while surface indicators of instability e g tomb tilt location and direction of ground fractures and wall cracks were mapped by standard metric survey high resistive anomalies 300 and 400 m observed in vlf em tomographies are attributed to remnants of the ancient perimeter wall that are still buried along the southern side of the mound while no apparent correlation is found between the causes of tomb and ground movements the crack pattern map supplements the overall structural assessment the main outcome is that the northern portion of the retaining wall is classed with the highest hazard rate the impact of this cost effective approach is to inform the design of maintenance and restoration measures based on improved geognostic knowledge the geophysical and surface evidence informs decisions on where interventions are to be prioritised and whether costly invasive investigations are needed

2 d and 3 d resistivity image reconstruction using crosshole data theoretical changes in the distribution of electrical potential near subsurface resistivity anomalies have been studied using two resistivity models the results suggest that the greatest response from such anomalies can be observed with buried electrodes and that the resistivity model of a volume between boreholes can be accurately reconstructed by using crosshole data the distributive properties of crosshole electrical potential data obtained by the pole pole array method have also been examined using the calculated partial derivative of the observed apparent resistivity with respect to a small cell within a given volume the results show that for optimum two dimensional 2 d and three dimensional 3 d target imaging in line data and crossline data should be combined and an area outside the zone of exploration should be included in the analysis in this paper the 2 d and 3 d resistivity images presented are reconstructed from crosshole data by the combination of two inversion algorithms the first algorithm uses the alpha center method for forward modeling and reconstructs a resistivity model by a nonlinear least squares inversion alpha centers ex press a continuously varying resistivity model and the distribution of the electrical potential from the model can be calculated quickly an initial general model is determined by the resistivity backprojection technique rbpt prior to the first inversion step the second process uses finite elements and a linear inversion algorithm to improve the resolution of the resistivity model created by the first step simple 2 d and 3 d numerical models are discussed to illustrate the inversion method used in processing data from several field studies are also presented to demonstrate the capabilities of using crosshole resistivity exploration techniques the numerical experiments show that by using the combined reconstruction algorithm thin conductive layers can be imaged with good resolution for 2 d and 3 d cases the integration of finite element computations is shown to improve the image obtained by the alpha center inversion process for 3 d applications the first field test uses horizontal galleries to evaluate complex 2 d features of a zinc mine the second field test illustrates the use of three boreholes at a dam site to investigate base rock features and define the distribution of an altered zone in three dimensions

comparison between four electrode arrays in delineating sedimentary layers of alluvial fan deposits in eastern iraq using a 2d imaging technique a resistivity survey is performed in the northern badra area eastern iraq using a two dimensional 2d imaging technique the mean goal is to compare four electrode arrays dipole dipole wenner schlumberger schlumberger reciprocal and wenner to examine their resolution and ability in delineating the layers in complex sedimentary deposits six 2d imaging stations applied in the study area the first two stations 2ds1 and 2ds2 are selected to make the comparison the comparison results showed that wenner schlumberger s inverse models provide optimal results corresponding to the deep subsurface layers and they show the best resolution with depth compared to the other arrays therefore it is useful in determining the layers especially in areas with high inhomogeneity and also with the long survey line the wenner array presents a high sensitivity to high background noise and or a long survey line its inverse model is incapable of recognizing the layers in 2ds1 but it gives good images when the noise level becomes small and or a shorter long survey line is used however its resolution is still less than that of the wenner schlumberger array the schlumberger reciprocal array successfully delineates the layers but its inverse models do not show optimal matching with the lithology sections of the boreholes bh1 and bh2 the dipole dipole array is incapable of determining the underlying layers due to the decrease in its vertical resolution when there is an increase in depth and or noise contamination however it is suitable to use in very shallow investigations no more 30 40 m depth and needs high quality data measurements

a 3 d resistivity investigation of a contaminated site at lernacken sweden a contaminated site at lernacken in southern sweden formerly used for sludge disposal was investigated using a 3 d resistivity imaging technique the data acquisition was carried out using a roll along technique for 3 d data acquisition that allows using standard multielectrode equipment designed for engineering and environmental applications the technique allows for the measurement of large true 3 d resistivity data sets and data were measured using two perpendicular electrode orientation directions with only one layout of the cables the data were plotted as two sets of pseudo depth slices using the two electrode orientation directions which resulted in markedly different plots the complete data set was inverted to form a resistivity depth model of the ground using a 3 d least squares smoothness constrained inversion technique the results obtained were compared to other geophysical and background data and a good agreement was found the results show that the 3 d roll along technique in combination with 3 d inversion can be highly useful for engineering and environmental applications however multichannel measurement equipment is necessary to speed up the data acquisition process for routine application

integrated application of geophysical methods for investigation of the al berktain archaeological site in the city of jerash jordan the application of electrical resistivity tomography ert techniques involving the wenner and schlumberger electrode configurations was conducted at the ancient site of al berktain of jerash n jordan during june 2011 it may be considered as the first archaeogeophysical survey at this site the city lived by succession of ancient cultures and still has archaeological remains e g water pools which gave it historical value and boosted the archaeological interest to make this study the objective of the work was to determine the layout dimension and the depth of expected buried structures i e water channels related to the pool structure within the site and to provide recommendations for future excavation projects the results showed high resistivity anomalies red color located within the site these anomalies were interpreted as a part of a general infrastructure of ancient man made buried channels or supporting basins draining out or feeding water to the two the water pools especially at the western and eastern sides inside the pool the main structure in the site results of the survey showed anomalous thin shallow zone interpreted as a layer limestone pavement of a thickness of 1 m the ert successfully determined the dimensions of the buried features and proved that this site was water reservoirs to serve the ancient city of jerash or irrigations purposes beside its use for leisure i e presence of the theatre roman path and the pools

intelligent estimation of spatially distributed soil physical properties abstract spatial analysis of soil samples is often times not possible when measurements are limited in number or clustered to obviate potential problems we propose a new approach based on the self organizing map som technique this approach exploits underlying nonlinear relation of the steady state geomorphic concave convex nature of hillslopes from hilltop to bottom of the valley to spatially limited soil textural data the topographic features are extracted from shuttle radar topographic mission elevation data whereas soil textural clay silt and sand and hydraulic data were collected in 29 spatially random locations 50 to 75 cm depth in contrast to traditional principal component analysis the som identifies relations among relief features such as slope horizontal curvature and vertical curvature stochastic cross validation indicates that the som is unbiased and provides a way to measure the magnitude of prediction uncertainty for all variables the som cross component plots of the soil texture reveals higher clay proportions at concave areas with convergent hydrological flux and lower proportions for convex areas with divergent flux the sand ratio has an opposite pattern with higher values near the ridge and lower values near the valley silt has a trend similar to sand although less pronounced the relation between soil texture and concave convex hillslope features reveals that subsurface weathering and transport is an important process that changed from loss to gain at the rectilinear hillslope point these results illustrate that the som can be used to capture and predict nonlinear hillslope relations among relief soil texture and hydraulic conductivity data

inversion of induced polarization data we present an algorithm for inverting induced polarization ip data acquired in a 3 d environment the algorithm is based upon the linearized equation for the ip response and the inverse problem is solved by minimizing an objective function of the chargeability model subject to data and bound constraints the minimization is carried out using an interior point method in which the bounds are incorporated by using a logarithmic barrier and the solution of the linear equations is accelerated using wavelet transforms inversion of ip data requires knowledge of the background conductivity we study the effect of different approximations to the background conductivity by comparing ip inversions performed using different conductivity models including a uniform half space and conductivities recovered from one pass 3 d inversions composite 2 d inversions limited aim updates and full 3 d nonlinear inversions of the dc resistivity data we demonstrate that when the background conductivity is simple reasonable ip results are obtainable without using the best conductivity estimate derived from full 3 d inversion of the dc resistivity data as a final area of investigation we study the joint use of surface and borehole data to improve the resolution of the recovered chargeability models we demonstrate that the joint inversion of surface and crosshole data produces chargeability models superior to those obtained from inversions of individual data sets

application of 2d and 3d geoelectrical resistivity imaging for engineering site investigation in a crystalline basement terrain southwestern nigeria orthogonal set of 2d geoelectrical resistivity field data consisting of six parallel and five perpendicular profiles were collected in an investigation site using the conventional wenner array seven schlumberger soundings were also conducted on the site to provide id layering information and supplement the orthogonal 2d profiles the observed 2d apparent resistivity data were first processed individually and then collated into 3d data set which was processed using a 3d inversion code the 3d model resistivity images obtained from the inversion are presented as horizontal depth slices some distortions observed in the 2d images from the inversion of the 2d profiles are not observed in the 2d images extracted from the 3d inversion the survey was conducted with the aim of investigating the degree of weathering and fracturing in the weathered profile and thereby ascertaining the suitability of the site for engineering constructions as well as determining its groundwater potential

three dimensional geophysical anatomy of an active landslide in lias group mudrocks cleveland basin uk a geoelectrical investigation of a slow moving earth slide earth flow in lower jurassic lias group rocks of the cleveland basin uk is described these mudrock slopes are particularly prone to failure and are a major source of lowland landslides in the uk but few attempts have been made to spatially or volumetrically characterise the subsurface form of these slides the primary aim of this study was to consider the efficacy of fully three dimensional geoelectrical imaging for landslide investigation with reference to a geological setting typical of lias group escarpments the approach described here included a reconnaissance survey phase using two dimensional electrical resistivity tomography ert resistivity mapping self potential sp profiling and mapping followed by a detailed investigation of an area of the landslide using three dimensional 3d ert and self potential tomography spt interpretation of the geophysical data sets was supported by surface observations aerial lidar and differential gps geomorphological surveys and intrusive investigations boreholes and auger holes the initial phase of the study revealed the existence of a strong sp signature at the site consistent with a streaming potential source and established the relationships between the main geological units the geomorphologic expression of the landslide and the resistivity of the materials in and around the study area the 3d spt model generated during the second phase of the study indicated drainage patterns across the landslide and preferential flow from the low permeability mud rocks into the underlying more permeable sandstone formation because of favourable resistivity contrasts between the clay rich whitby mudstone formation landslide material and the underlying staithes sandstone formation the volumetric 3d ert image allowed a number of surface and subsurface landslide features to be identified and spatially located these included the lateral extent of slipped material and zones of depletion and accumulation the surface of separation and the thickness of individual earth flow lobes and the dipping in situ geological boundary between the whitby mudstone and staithes sandstone bedrock formations