a strategy for coupled 3d imaging of large scale seismic and electromagnetic data sets application to subsalt imaging abstractoffshore seismic and electromagnetic em imaging for hydrocarbons can require up to tens of millions of parameters to describe the 3d distribution of complex seabed geology and relevant geophysical attributes the imaging and data volumes for such problems are enormous descent based methods are the only viable imaging approach where it is often challenging to manage the convergence of stand alone seismic and em inversion experiments when a joint seismic em inversion is implemented convergence problems with descent based methods are further aggravated moreover resolution mismatches between seismic and em pose another challenge for joint inversion to overcome these problems we evaluated a coupled seismic em inversion workflow and applied it to a set of full wave seismic magnetotelluric mt and controlled source electromagnetic csem data for subsalt imaging in our workflow we address disparate resolution properties between seismic and em data by implementing the seismic inversion in th

joint two dimensional dc resistivity and seismic travel time inversion with cross gradients constraints it is now common practice to perform collocated dc resistivity and seismic refraction surveys that complement each other in the search for more accurate characterization of the subsurface although conventional separate dc resistivity and seismic models can be diagnostic we posit that better results can be derived from jointly estimated models we make the assumption that both methods must be sensing the same underlying geology and have developed an innovative resistivity velocity cross gradients relationship to evaluate the structural features common to both methods the cross gradients function is incorporated as a constraint in a nonlinear least squares problem formulation which is solved using the lagrange multiplier method the resultant iterative two dimensional 2 d joint inversion scheme is successfully applied to synthetic data serving as validation tests here and to field data from collocated dc resistivity and seismic refraction profiling experiments and also compared to conventional separate inversion results the joint inversion results are shown to be superior to those from separate 2 d inversions of the respective data sets since our algorithm leads to resistivity and velocity models with remarkable structural agreement

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

joint two dimensional cross gradient imaging of magnetotelluric and seismic traveltime data for structural and lithological classification summary collocated magnetotelluric mt and seismic profiling is emerging as a necessary combined approach for deep and near surface imaging but the resulting experimental data are typically interpreted separately since no production programs exist for multidimensional joint inversion of mt and seismic data we present a joint 2 d inversion approach for imaging collocated mt and seismic refraction data with cross gradient structural constraints we describe the main features of the algorithm and first apply it to synthetic data generated for a hypothetical complex geological model for the synthetic data we find that the scheme leads to models with remarkable structural resemblance and improved estimates of electrical resistivity and seismic velocity we apply the scheme to near surface field data to test the consistency of a previously suggested resistivity velocity interrelationship and its potential use for subsurface lithofacies discrimination or structural classification the mt seismic relationship is found to be in excellent accord with that derived previously for dc resistivity and seismic data set at the test site our results suggest that joint mt seismic cross gradient imaging leads to improved characterization of heterogeneous geological targets at near surface to mantle depths

finite difference calculation of traveltimes in three dimensions the traveltimes of first arriving seismic rays through most velocity structures can be computed rapidly on a three dimensional numerical grid by finite difference extrapolation head waves are properly treated and shadow zones are filled by the appropriate diffractions differences of less than 0 11 percent are found between the results of this technique and ray tracing for a complex but smooth model this scheme has proven useful for earthquake location and shows promise as an inexpensive well behaved substitute for ray tracing in forward modeling and kirchhoff inversion applications

influence of temperature on seismic velocities and complex conductivity of heavy oil bearing sands abstractthe joint inversion of seismic and electromagnetic data can be of great use to monitor the steam assisted production of heavy oils in field conditions seismic velocity and complex conductivity laboratory measurements were performed on three heavy oil bearing sands at confining and pore pressures similar to field conditions one of the samples 8h was initially oil wet and the two other samples 5p 3a and p 1a were initially water wet low frequency stress strain measurements and complex conductivity measurements were performed during two heating cycles at constant temperature 10 c steps in the range 20 c 70 c the temperature was first increased from 20 c 70 c simulating initial stage in a thermal recovery process during this temperature increase sample 8h changed to water wet with a clear irreversible signature on the seismic and electrical data then the temperature was decreased and cycled a second time in the temperature range 20 c 70 c the seismic and complex conductivity responses w

the loess of north central china geotechnical properties and their relation to slope stability abstract loess is an aeolian deposit consisting of predominantly silt sized quartz particles and containing variable amounts of clay sized minerals loess is generally classified as a water softening material because upon wetting the loess fabric rapidly weakens or collapses the strain hardening of malan loess and the brittle failure of lishi and wucheng loess are in strong contrast to the failure behaviour of these loess deposits in a remoulded state from tests carried out on samples with varying moisture contents using a modified bromhead ring shear apparatus it was found that the effective apparent cohesion gradually increases and the effective internal friction angle decreases with an increase in moisture content when the moisture content reaches a material specific threshold the effective cohesion decreases rapidly and the effective internal friction angle stabilises at a residual value the frequent failure of loess slopes in the western part of the chinese loess plateau is closely related to progressive weathering along zones in these slopes which causes a dramatic decrease in strength from the peak strength condition progressive weathering is common in the loess slopes in the western part of the chinese loess plateau during the process shear strength reduction along potential slip surfaces may be achieved by leaching of readily soluble salts destruction of cementation bonds and redistribution of particles localized collapse of the loess fabric causes internal deformation and consequently peak strength conditions are concentrated on a progressively smaller area of the failure plane therefore the mode of failure of loess slopes is generally determined by brittle failure of the undisturbed and unweathered central parts of the slopes it is important that both the weathered and unweathered strength of the loessmaterials in this area be established in order to analyze the stability of existing loessslopes many of which are steepand lie directly above domestic and industrial urban areas

cooperative inversion of geophysical data geophysical inversion by iterative modeling involves fitting observations by adjusting model parameters both seismic and potential field model responses can be influenced by the adjustment of the parameters of the rock properties the objective of this cooperative in version is to obtain a model which is consistent with all available surface and borehole geophysical data al though inversion of geophysical data is generally non unique and ambiguous we can lessen the ambiguities by inverting all available surface and borehole data this paper illustrates this concept with a case history in which surface seismic data sonic logs surface gravity data and borehole gravity meter bhgm data are ad equately modeled by using least squares inversion and a series offorward modeling steps the traditional analysis of various geophysical data sets has been termed integrated interpretation such analysis has traditionally involved much processing modeling and subjec tive interpretation in order to develop a geologic model which is consistent with various surface and borehole geophysical data a method which automates some of the above pro cedures is least squares inversion this procedure perturbs an initial set of model parameters in order to fit the observed data least squares inversion is described in many papers in cluding those of jackson 1972 wiggins 1972 jupp and vozoff 1975 and lines and treitel 1984 this inversion technique could also be termed automated iterative mod eling in terms of modeling different geophysical data sets there are many possible approaches which allow inversion of a given data set and it is doubtful whether one single recipe will prove suitable for all problems nevertheless by jointly invert ing various types of geophysical observations we may lessen the extent of some of the ambiguities inherent in individual data sets lafehr 1984 gives a germane discussion of several reasons for this type of coordinated geophysical effort in the present study we define cooperative inversion as the esti mation of a subsurface model which is consistent with various independent geophysical data sets in the case discussed in this paper these data sets include surface and borehole observa tions of the seismic and gravity responses in our definition cooperative inversion may include either joint inversion or sequential inversion

an efficient sequential strategy for realizing cross gradient joint inversion method and its application to 2 d cross borehole seismic traveltime and dc resistivity tomography

hydroconsolidation and subsidence of loess studies from china russia north america and europe abstract various approaches to the widespread problem of the hydroconsolidation and subsidence of loess have been suggested these include considerations of rheology thermodynamics phase movements particle packing interparticle bonding pore structure and distribution catastrophe theory topology and simple structural frameworks chinese north american and most european investigators tend to concentrate on mechanisms of loess collapse the russian literature however retains an extra dimension two approaches the syngenetic and the epigenetic approach to the formation of subsiding loess have been defined in the literature most investigators follow a syngenetic approach which appears to be a consequence of the aeolian idea of loess deposition some russian writers in contrast promote an epigenetic approach in which collapsibility can develop in an originally noncollapsible material which can then suffer from hydroconsolidation and subsidence the basis of the phenomenon is a change in the packing structure of the major loess particles and this can be modelled using simple monte carlo methods to develop appropriate structures this paper aims to review the work done on this important subject serious investigation of hydroconsolidation and subsidence of loess began in the early nineteen forties fifty years ago and this has been reported in a piecemeal manner a detailed critical review of this diverse work is now overdue and this is presented herein in the light of recent work in the united kingdom an attempt is made to describe the process in a phenomenological and a structural sense inherent in this the role of n ya denisov as subsidence pioneer is considered

failure mechanisms in loess and the effects of moisture content changes on remoulded strength abstract investigations into the failure mechanisms of loess slopes in the loess region of north central china have shown that a majority of mass movements are associated with shallow slab slides predominantly moving under tension the effects of soil moisture content are of paramount importance when dry vertical slopes in loess may exceed 15 m in height but under conditions close to saturation the structural strength of loess rapidly decreases causing failure of the slopes mass failure of loess occurs as collapse due to hydroconsolidation and disintegration of the loess fabric as a result of liquefaction or fluidization and can be associated with progressive failure processes local destruction of the openwork fabric of the loess can lead to small plastic movements within the loess deposits this is as close as loess can come to creep

joint electromagnetic and seismic inversion using structural constraints we have developed a frequency domain joint electromagnetic em and seismic inversion algorithm for reservoir evaluation and exploration applications em and seismic data are jointly inverted using a cross gradient constraint that enforces structural similarity between the conductivity image and the compressional wave p wave velocity image the inversion algorithm is based on a gauss newton optimization approach because of the ill posed nature of the inverse problem regularization is used to constrain the solution the multiplicative regularization technique selects the regularization parameters automatically improving the robustness of the algorithm a multifrequency data weighting scheme prevents the high frequency data from dominating the inversion process when the joint inversion algorithm is applied in integrating marine controlled source electromagnetic data with surface seismic data for subsea reservoir exploration applications and in integrating crosswell em and sonic data for reservoir monitoring and evaluation applications results improve significantly over those obtained from separate em or seismic inversions

3d joint inversion of geophysical data with gramian constraints a case study from the carrapateena iocg deposit south australia explorers are moving to increase the discovery space by exploring under cover and to greater depths e g subsalt and sub basalt exploration for oil and gas and beneath transported cover for minerals with this shift there becomes an increased reliance on geophysical methods to delineate resources with no recognized geological or geochemical expressions different geophysical fields provide information about different physical properties of the earth multiple geophysical surveys spanning gravity magnetic electromagnetic and seismic methods are often interpreted to infer geology from models of different physical properties in many cases the various geophysical data are complementary making it natural to consider a formal mathematical framework for their joint inversion to a shared earth model there are different approaches to joint inversion the simplest case of joint inversion is where the physical properties are identical between different geophysical methods e g jupp and vozoff 1975 in other cases joint inversion may infer theoretical empirical or statistical correlations between different physical properties e g hoversten et al 2003 2006 in cases where the physical properties are not correlated but nevertheless can be assumed to share a similar structure joint inversions have been formulated as a minimization of the cross gradients between different physical properties e g haber and oldenburg 1997 gallardo and meju 2003 2004 the latter has now been widely adopted by joint inversion practitioners as the de facto standard e g colombo and de stefano 2007 hu et al 2009 jegen et al 2009 de stefano et al 2011

joint inversion of lake floor electrical resistivity tomography and boat towed radio magnetotelluric data illustrated on synthetic data and an application from the aspo hard rock laboratory site sweden joint inversion of lake floor electrical resistivity tomography and boat towed radio magnetotelluric data illustrated on synthetic data and an application from the aspo hard rock laboratory site sweden

cooperative constrained inversion of multiple electromagnetic data sets abstractwe evaluated a method for cooperatively inverting multiple electromagnetic em data sets with bound constraints to produce a consistent 3d resistivity model with improved resolution field data from the antonio gold deposit in peru and synthetic data were used to demonstrate this technique we first separately inverted field airborne time domain em aem controlled source audio frequency magnetotellurics csamt and direct current resistivity measurements each individual inversion recovered a resistor related to gold hosted silica alteration within a relatively conductive background the outline of the resistor in each inversion was in reasonable agreement with the mapped extent of known near surface silica alteration variations between resistor recoveries in each 3d inversion model motivated a subsequent cooperative method in which aem data were inverted sequentially with a combined csamt and dc data set this cooperative approach was first applied to a synthetic inversion over an antonio l

simultaneous core sample measurements of elastic properties and resistivity at reservoir conditions employing a modified triaxial cell a feasibility study adaptations of existing triaxial cells for ultrasonic p and s wave measurements are well documented this paper proposes further modification of such a cell so that also resistivity measurements can be carried out simultaneously at reservoir conditions by employing the top cap and the pedestal of the cell as electrodes axial resistivity measurements are now feasible in order to minimize the polarization effect of this two electrode arrangement careful analyses have been carried out to optimize the choice of electrode coating and measurement frequency band radial resistivity measurements are also included in the system by introducing a strap electrode system in a reservoir under production changes in both saturations temperature if steam injection and stresses can take place therefore the modified triaxial system should be able to measure the integrated effects on the acoustic parameters and electric responses caused by variations in each of these parameters the feasibility of the system to obtain such reliable information is demonstrated employing a small selection of core samples in the future such combined measurements on reservoir core samples can be used to link both seismic and electromagnetic observations to the actual earth model and constrain both modelling and inversion

engineering geological problems of loess in poland abstract grabowska olszewska b 1988 engineering geological problems of loess in poland eng geol 25 177 199 in poland loess covers are limited to a latitudinal belt in the southern part of the country the covers vary from 2 to 30 m in thickness and the loesses are developed in three major facies eolian deluvial and alluvial stratigraphically they represent four major horizons correlated with the vistulian wurm glaciation and some older ones the paper presents characteristics of granulometric mineral and chemical compositions with reference to origin facies and stratigraphic position of these soils as well as their lithofacies classification the classification gives the basis for analysis of local and regional variability in engineering geological properties of the loess

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

three dimensional seismic refraction tomography a comparison of two methods applied to data from the faeroe basin this paper presents a comparison of two tomographic methods for determining three dimensional 3 d velocity structure from first arrival travel time data the first method is backprojection in which travel time residuals are distributed along their ray paths independently of all other rays the second method is regularized inversion in which a combination of data misfit and model roughness is minimized to provide the smoothest model appropriate for the data errors both methods are nonlinear in that a starting model is required and new ray paths are calculated at each iteration travel times are calculated using an efficient implementation of an existing method for solving the eikonal equation by finite differencing both inverse methods are applied to 3 d ocean bottom seismometer obs data collected in 1993 over the faeroe basin consisting of 53 479 travel times recorded at 29 obss this is one of the most densely spaced large scale 3 d seismic refraction experiments to date different starting models and values for the free parameters of each tomographic method are tested a new form of backprojection that converges more rapidly than similar methods compares favorably with regularized inversion but the latter method provides a simpler model for little additional computational expense when applied to the faeroe basin data bounds on two model features are assessed using regularized inversion with combined smoothness and flatness constraints an inversion of synthetic data corresponding to 100 data recovery from the real experiment shows a marked improvement in lateral resolution at deeper depths and demonstrates the potential of currently feasible 3 d refraction experiments to provide well resolved long wavelength velocity models the similarity of the final models derived from the two tomographic methods suggests that the results from the new form of backprojection can be relied on when limited computational resources rule out regularized inversion

structure coupled 3 d imaging of magnetotelluric and wide angle seismic reflection refraction data with interfaces magnetotelluric mt and wide angle seismic reflection refraction surveys play a fundamental role in understanding the crustal rheology and lithospheric structure of the earth in recent years the

using gpr data as constraints in rmt data inversion for water content estimation a case study in heby sweden this study uses ground penetrating radar gpr data as constraints in the inversion of radio magnetotelluric rmt data to provide an improved model at shallow depth we show that modification of the model regularization matrix using all gpr common offset co reflections can mislead the constrained inversion of rmt data to avoid such problems common mid point cmp gpr data are translated to a resistivity model by introducing a new petrophysical relationship based on a combination of topp s and archie s equations this model is updated through a semi iterative method and is employed as an initial and prior model in the subsequent inversion of rmt data finally a water content model that fits the gpr cmp and rmt data is derived from the resistivity model computed by the constrained inversion of rmt data to assess the proposed scheme it is applied to a synthetic data set then real rmt data collected along an 870 m long profile across a known aquifer situated in the north of heby central sweden are inverted by removing the smoothness constraints across gpr co interfaces or using cmp based inversion thick 10 m vadose and saturated zones are resolved and shown to correlate with logs from nearby boreholes nevertheless the application of our cmp based inversion was the only efficient scheme to retrieve thin 3 m saturated zones and the water table at a depth of 7 15 m in the rmt models the estimated models of water content are in good agreement with the available hydrogeological information in the study area

stratigraphy and structure of the indus suture in the lower swat pakistan nw himalaya abstract we present a geological map detailed structural description and new subdivisions of the indus suture zone lithologies in northeast pakistan lower swat region the indus suture zone is a dominantly fore arc related assemblage obducted onto the indian plate initial southward thrusting was followed by the reactivation of the indus suture as a ductile brittle normal fault significant strike slip faulting may have taken place at this stage later brittle reverse faults demonstrate that shortening outlasted normal faulting the comparison of the structural evolution of the indus suture zone and the indian plate shows that both terrains were sharing the deformational history possibly since the earliest stage of collision the lower swat area records a full orogenic cycle from early rifting through continent arc collision to orogenic collapse we present a geodynamic model that integrates all these elements

local earthquake le tomography with joint inversion for p and s wave velocities using structural constraints local earthquake le tomography with joint inversion for p and s wave velocities using structural constraints

characterization of heterogeneous near surface materials by joint 2d inversion of dc resistivity and seismic data 1 we have developed a robust 2d joint inversion scheme incorporating the new concept of cross gradients of electrical resistivity and seismic velocity as constraints so as to investigate more precisely the resistivity velocity relationships in complex near surface environments the results of joint inversion of dc resistivity and seismic traveltime data from collocated experiments suggest that one can distinguish between different types or facies of unconsolidated and consolidated materials refining a previously proposed resistivity velocity interrelationship derived from separate inversions of the respective data sets a consistent interpretive structural model can be obtained from the joint inversion models

two dimensional data space joint inversion of magnetotelluric gravity magnetic and seismic data with cross gradient constraints in recent years joint inversion has been widely used for integrated geological interpretation we extended a data space joint inversion algorithm of magnetotelluric gravity and magnetic data to include first arrival seismic travel time and normalized cross gradient constraints we describe the main features of the algorithm and apply it to synthetic data generated for hypothetical models for the synthetic data we find that the joint inversion with multiple parameters is superior to the joint inversion with two or even three parameters which can reduce the multisolution of inversion results more effectively furthermore data space joint inversion involves fewer memory requirements and better calculation speeds than traditional model space joint inversion the normalized cross gradient constraints can better couple model parameters of different magnitudes compared with traditional unnormalized cross gradient constraints resulting in higher levels of structural similarity among resistivity density magnetic susceptibility and velocity models

two dimensional joint inversion of magnetotelluric and local earthquake data discussion on the contribution to the solution of deep subsurface structures abstract joint inversion of data sets collected by using several geophysical exploration methods has gained importance and associated algorithms have been developed to explore the deep subsurface structures magnetotelluric and local earthquake tomography algorithms are generally used individually due to the usage of natural resources in both methods it is not possible to increase data quality and resolution of model parameters for this reason the solution of the deep structures with the individual usage of the methods cannot be fully attained in this paper we firstly focused on the effects of both magnetotelluric and local earthquake data sets on the solution of deep structures and discussed the results on the basis of the resolving power of the methods the presence of deep focus seismic sources increase the resolution of deep structures moreover conductivity distribution of relatively shallow structures can be solved with high resolution by using mt algorithm therefore we developed a new joint inversion algorithm based on the cross gradient function in order to jointly invert magnetotelluric and local earthquake data sets in the study we added a new regularization parameter into the second term of the parameter correction vector of gallardo and meju 2003 the new regularization parameter is enhancing the stability of the algorithm and controls the contribution of the cross gradient term in the solution the results show that even in cases where resistivity and velocity boundaries are different both methods influence each other positively in addition the region of common structural boundaries of the models are clearly mapped compared with original models furthermore deep structures are identified satisfactorily even with using the minimum number of seismic sources in this paper in order to understand the future studies we discussed joint inversion of magnetotelluric and local earthquake data sets only in two dimensional space in the light of these results and by means of the acceleration on the three dimensional modelling and inversion algorithms it is thought that it may be easier to identify underground structures with high resolution