joint inversion of 2d resistivity and seismic travel time data to image saltwater intrusion over karstic areas the simultaneous inversion of multiple geophysical data types has been proven to be a powerful tool to both improve subsurface imaging and help in the interpretation process the main goal of this paper was to develop joint inversion strategies to provide improved resistivity and seismic velocity images for delineating saline water zones in karstic geological formations the cross gradient constraint approach was adopted to jointly invert resistivity and seismic first arrival data the basic idea of this approach is to quantitatively estimate the structural similarity between resistivity and seismic velocity models using the cross product of their gradients and to achieve a unified geological model which satisfies both data sets initially synthetic data were employed to help develop a joint inversion strategy to be used over such complex geological structures the proposed strategy uses a weighting factor for the cross gradient constraints and separate damping factors for the resistivity and seismic data this strategy was applied successfully on field data from the karstic region of stilos crete greece

solutions of the inherent problem of the equivalence in direct current resistivity and electromagnetic methods through global optimization and joint inversion by successive refinement of model space the problem of equivalence in direct current dc resistivity and electromagnetic methods for a thin resistive and conducting layer is well known attempts have been made in the past to resolve this problem through joint inversion however equivalence still remains an unresolved problem in the present study an effort is made to reduce non uniqueness due to equivalence using global optimization and joint inversion by successive refinement of the model space a number of solutions derived for dc resistivity data using very fast simulated annealing global inversion that fits the observations equally well follow the equivalence principle and show a definite trend for a thin conductive layer the quotient between resistivity and thickness is constant while for a resistive one the product between these magnitudes is constant three approaches to obtain very fast simulated annealing solutions are tested in the first one layer resistivities and thicknesses are optimized in a linear domain in the second layer resistivities are optimized in the logarithmic domain and thicknesses in the linear domain lastly both layer resistivities and thicknesses are optimized in the logarithmic domain only model data from the mean models corresponding to very fast simulated annealing solutions obtained for approach three always fit the observations the mean model defined by multiple very fast simulated annealing solutions shows extremely large uncertainty almost 100 in the final solution after inversion of individual dc resistivity or electromagnetic em data sets uncertainty associated with the intermediate resistive and conducting layers after global optimization and joint inversion is still large in order to reduce the large uncertainty associated with the intermediate layer global optimization is performed over several iterations by reducing and redefining the search limits of model parameters according to the uncertainty in the solution the new minimum and maximum limits are obtained from the uncertainty in the previous iteration though the misfit error reduces in the solution after successive refinement of the model space in individual inversion it is observed that the mean model drifts away from the actual model however successive refinement of the model space using global optimization and joint inversion reduces uncertainty to a very low level in 4 5 iterations this approach works very well in resolving the problem of equivalence for resistive as well as for conducting layers the efficacy of the approach has been demonstrated using dc resistivity and em data however it can be applied to any geophysical data to solve the inherent ambiguities in the interpretations

the benguela current and associated upwelling on the southwest african margin a synthesis of the neogene quaternary sedimentary record at dsdp sites 362 and 532

the influence of an asymmetry in the sequence rock coal rock on the propagation of rayleigh seam waves small offsets in hard coal seams can be detected with the aid of seam channel waves transmission and reflection of seam waves depend among other parameters upon the symmetry properties of the sequence rock coal rock two typical unsymmetrical sequences are found in european coal deposits i coal seams with roof and floor of differing acoustic impedance and ii coal seams interlayered with rock and soil two dimensional analog models with appropriate impedance contrasts are used to study the effect of the unsymmetrical layers upon the propagation of rayleigh seam waves data analysis is based upon amplitude measurements both parallel and perpendicular to the layers and dispersion curves the effect of unsymmetrical roof rock 1 and floor rock 2 was studied with models containing homogeneous coal seams leaky mode wave groups with phase velocities cr in the range between the sv wave velocities r1 2 of the two rock materials i e r1 cr r2 form a characteristic part of the rayleigh seam wave signal using knott s energy coefficient calculations it is shown that in that range energy leakage into the surrounding rock by refracted sv waves is restricted to only one of the two interfaces namely coal rock 2 at the other interface coal rock 1 all waves are totally reflected thus the high amplitudes of these leaky mode wave groups are explained by quasi normal mode features the influence of a dirt bed on wave propagation was studied in models where the roof and the floor have the same elastic properties the maximum thickness of the dirt bed did not exceed 20 of the total seam thickness the effect of the bed s location within the seam was also investigated for all recorded normal mode wave groups either the total seam or the coal layers could be regarded as wave guides this was shown by the fact that the phases could be associated with the phase velocity dispersion curves calculated for the symmetrical sequence rock coal rock these curves are relevant under the condition that the thickness of the coal layer assumed under the calculation coincides with the thickness of the effective wave guide of the respective wave groups wave groups guided in the total seam are not influenced by either the thickness or the position of the dirt bed on the other hand for wave groups guided in the coal layers the quotient of signal amplitudes in the coal layers is influenced by the position of the dirt bed

the scattering of sh channel waves by a fault in a coal seam the imaging of faults in coal seams by the in seam seismic method has now become standard practice in the uk over 300 surveys have been undertaken and the technique is now part of the exploration arsenal of colliery planners from these users comes the pressure for two major improvements namely an increase in range and target identification this paper is directed towards the latter problem it has long been recognized that the reflected channel waves must contain information on the fault structure that caused the reflection and model experiments have been undertaken to investigate the reflection process only recently however have attempts been made to quantify the reflection process calculations using both the finite difference and finite element techniques have been carried out and estimates of the reflection coefficient as a function of frequency have been obtained the object of this paper is to extend these considerations by calculating analytically the scattering matrix of an sh channel wave after interaction at a fault plane the scattering matrix is calculated as a function of frequency hade angle and fault throw the method employed is based on the decomposition of the incident sh channel wave into fourier components the calculation of plane wave reflection and transmission coefficients within the constraints of geometrical acoustics and finally the synthesis of the scattering matrix by application of the helmholtz kirchhoff integral the calculation throughout is restricted to normal modes

joint inversion of 1 d magnetotelluric and surface wave dispersion data with an improved multi objective genetic algorithm and application to the data of the longmenshan fault zone magnetotellurics and seismic surface waves are two prominent geophysical methods for deep underground exploration joint inversion of these two datasets can help enhance the accuracy of inversion in this paper we describe a method for developing an improved multi objective genetic algorithm nsga sbx and applying it to two numerical tests to verify the advantages of the algorithm our findings show that joint inversion with the nsga sbx method can improve the inversion results by strengthening structural coupling when the discontinuities of the electrical and velocity models are consistent and in case of inconsistent discontinuities between these models joint inversion can retain the advantages of individual inversions by applying the algorithm to four detection points along the longmenshan fault zone we observe several features the sichuan basin demonstrates low s wave velocity and high conductivity in the shallow crust probably due to thick sedimentary layers the eastern margin of the tibetan plateau shows high velocity and high resistivity in the shallow crust while two low velocity layers and a high conductivity layer are observed in the middle lower crust probably indicating the mid crustal channel flow along the longmenshan fault zone a high conductivity layer from 8 to 20 km is observed beneath the northern segment and decreases with depth beneath the middle segment which might be caused by the elevated fluid content of the fault zone

love type seam waves in washout models of coal seams the propagation of love seam waves across washouts of coal seams was studied by calculating synthetic seismograms with a finite difference method seam interruption seam end and seam thinning models ere investigated the horizontal offset the dip of the discontinuities and the degree of erosion served as variable parameters maximum displacement amplitudes relative spectral amplitudes and phase and group slowness curves were extracted from the synthetic seismograms both seam interruption and seam thinning reduce the maximum displacement amplitudes of the transmitted love seam waves the degree of amplitude reduction depends on the horizontal offset and the degree of erosion it is four times greater for a total seam interruption than for an equivalent seam thinning with a horizontal offset of four times the seam thickness in a seam cut vertically the impedance contrast between the coal and the washout filling determines the maximum displacement amplitudes of the reflected love seam waves they diminish by a maximum factor of four in oblique interruption zone discontinuities with a dip of maximum 27 sup 0 and by a maximum factor of ten in a seam thinning with a degree of erosion of at least 22

parameter estimation and fault detection by three component seismic and geoelectrical surveys in a coal mine three component seismic and geoelectrical in mine surveys were carried out in lyukobanya colliery near miskolc hungary to determine the in situ petrophysical parameter distributions and to detect inhomogeneities in the coal seam the seismic measurements comprise an underground vertical seismic profile using body waves and an in seam seismic amplitude depth distribution and transmission survey using channel waves the geoelectrical measurements are based on the drift and seam sounding method interval traveltime amplitude multiple filter and polarization analysis methods are applied to the seismic data they lead to a five layer model for the strata including the coal seam the coal seam and two underlying beds act as a seismic waveguide the layer sequence supports the propagation of both normal and leaky mode channel waves of the love and rayleigh type a calculation of the total reflected energy for each interface using knott s energy coefficients shows that the velocity ranges of high reflection energy and of normal and leaky mode wavegroups coincide the excitation of wavegroups strongly depends on the seismic source a simultaneous inversion of a geoelectrical drift and seam sounding survey prevents misinterpretations of the seismic data by clearly identifying the low velocity coal seam as a high resistivity bed calculations of dispersion and sounding curves improve the resolution of the slowness and resistivity in each layer both diminished amplitudes and distortions in the polarization of transmission seismo grams and decreasing resistivities in a geoelectrical pseudosection of the coal seam are related to an inhomogeneity a calculation of synthetic seismograms for love and rayleigh channel waves with the finite difference and the alekseev mikhailenko method agrees well with the field data for the main features i e particular arrivals in the wave train wavegroups velocities and symmetries or asymmetries this in mine experiment demonstrates that the simultaneous acquisition processing and interpretation of seismic and geoelectrical data improve the lithological interpretation of petrophysical parameter distributions coal seam inhomogeneities can also be detected more reliably by the two independent surveys than by one alone

modelling of rayleigh type seam waves in disturbed coal seams and around a coal mine roadway summary wave propagation in coal seams is numerically modelled in order to identify approaches towards the reconnaissance beyond the heading face of an advancing coal mine roadway complete synthetic wavefields including p sv body waves and rayleigh type seam waves are calculated using a green s function approach for simple laterally homogeneous models and a parallel elastic 2 d 3 d finite difference modelling code for more realistic geometries for a simple three layer model the wavefield within the seam is dominated by a fundamental rayleigh seam mode symmetrical with respect to the centre of the seam on the vertical component and antisymmetrical on the horizontal component if the seam contains an interleaved dirt band with higher velocities and density higher modes dominate the wave propagation depending on the thickness of the dirt band wave propagation in laterally inhomogeneous coal seam models with disturbances like seam ends faults thinning washouts and seam splitting is strongly influenced by the type of disturbance amplitudes of seam waves reflected from these disturbances strongly depend on the fault throw and the degree of thinning or washout in some cases conversion to higher modes can occur in all investigated models those rayleigh seam wave phases are preferably reflected which have frequencies above the fundamental mode airy phase lower frequency phases are preferably transmitted however seam waves are not reflected from a seam splitting disturbance thus a detection of seam splitting with reflected seam waves appears to be impossible fd computations for 3 d models containing an ending tunnel parallel to the seam and a source beyond the heading face of the tunnel show that seam waves are converted into rayleigh waves at the tunnel face they propagate along the surface of the tunnel and interfere with the seam waves propagating beside the tunnel this effect has to be taken into account for subsequent treatment of experimental data where the locations of sources and receivers are restricted to a small seismic layout in the vicinity of the tunnel as tunnel surface waves have slightly lower frequencies than seam waves it may be feasible to separate tunnel waves from the seam wave reflections particularly because higher frequency phases of the seam wave are preferably reflected at seam disturbances polarization analysis showed that the elliptically polarized rayleigh type seam waves in the vertical radial plane can be distinguished from rayleigh tunnel waves propagating on the sidewall of the tunnel adjoining the coal layer with elliptical polarization in the radial transversal plane

sedimentation rates off sw africa since the late miocene deciphered from spectral analyses of borehole and gra bulk density profiles odp sites 1081 1084 abstract sedimentation rates srs off sw africa were calculated by performing spectral analyses in the depth domain on borehole and gamma ray attenuation gra bulk density data from odp sites 1081 1084 inversion and integration of srs versus depth from spectral analysis yielded detailed sr profiles in the time domain our technique allowed the detection of excursions in calculated srs that not only often differed from those established through coarse scaled biostratigraphic data but also revealed a greater regional variability in the sediment accumulation over time high resolution bulk density data exhibited distinct periodicity in the waveband of milankovitch cycles precession at 19 23 kyr obliquity at 41 kyr eccentricity at 100 kyr the pronounced milankovitch cyclicity suggests that climate variability and trends in srs along the benguela current system bcs were responding to insolation patterns during the past 6 myr we find relatively low srs when evolutive amplitude spectra are dominated by obliquity and eccentricity periods in contrast significant sr peaks at all sites often occur when strong precessional amplitudes coexist with obliquity and eccentricity cycles episodes of high srs often coincide with peaks in organic carbon mass accumulation rates mar c org and reduced sea surface temperature sst in the southern walvis basin which have been associated with increased regional upwelling this suggests that the high srs reflect high productivity high mar c org attributed to strong wind and upwelling intensity during cool climate periods low ssts in accordance with orbital forcing patterns observed in our spectra

theoretical and practical aspects of absorption in the application of in seam seismic coal exploration during the last two decades the detection of coal seam discontinuities by seismic waves guided by the seam has become a special branch of exploration seismics in europe waves consisting purely of sh motion so called waves of love type are of special interest and the rather high frequencies of the airy phase in thin seams are most important because they present very high reflectivity at seam interruptions absorption increases with frequency in most layers and therefore attenuates the high airy phase frequencies more severely than the earlier low frequency part of the guided waves another fact additionally impairs the airy phase signal the quality factor q is much lower in coal than in the schists and sandstones of the carboniferous country rock unfortunately most of the energy of the airy phase is transferred by the coal whereas the lower frequencies have their main energy conveyed by the country rock above and below the seam in order to allow a better understanding of the influence of absor

pliocene variations in the position of the antarctic convergence in the southwest atlantic middle to late pliocene 4 1 1 9 ma variations in the positions of surface water masses and migrations of the polar front in the southwest atlantic are inferred from a factor analysis of radiolarian assemblages from dsdp site 514 faunal results suggest that surface water masses underwent progressive cooling as the polar front zone pfz advanced northward during the latest gilbert to late gauss chron the late gilbert chron 4 12 3 86 ma was the waning phase of a mid gilbert warm interval northern subantarctic surface water prevailed between 4 12 and 3 97 ma indicative of surface water temperatures warmer than those during the succeeding pliocene a long term sea surface cooling trend began between 3 97 and 3 86 ma which moved the pfz northward and closer to site 514 bringing cooler southern subantarctic surface waters to the site this movement northward of cooler surface waters is inferred to be related to the initial growth of sea ice and ice shelves throughout regions of west antarctica which were deglaciated or unglaciated during the prior warming interval of the gilbert chron a major late gilbert early gauss chron increase in the production of antarctic bottom water aabw resulted in an erosional or nondepositional hiatus at site 514 spanning 3 86 to 3 18 ma increased aabw activity at this time is linked to continued growth of expansive ice shelves and sea ice in the west antarctic region in the east antarctic margin and possibly in the marine embayments of east antarctica decreased aabw production led to a 3 2 ma resumption of sedimentation at site 514 and elsewhere in the southern ocean antarctic surface water assemblages above the hiatus 3 18 3 16 ma suggest that the pfz first passed over site 514 during the 3 86 3 18 ma interval of the hiatus following this initial invasion of antarctic surface waters between 3 16 and 2 94 ma the pfz retreated to a position near or south of the site this slight retreat of the pfz with a corresponding decrease in aabw activity is possibly related to a significant reduction in the area of shelf and sea ice as grounded ice expanded in the west antarctic region we interpret the widespread global enrichment of 18o at approximately 3 2 ma to be partially related to a cooling of surface waters the production of cooler bottom waters and an expansion of west antarctic ice volume associated with its grounding phase between 3 5 and 2 7 ma based on surface water mass migrations at site 514 the west antarctic ice volume increased significantly slightly prior to or at approximately 3 2 ma decreased between 3 14 and 2 7 ma and then increased by 2 67 ma to a more stable configuration with a volume at least as great as that at 3 2 ma during the late gauss 2 94 2 47 ma four northward advances of the pfz led to the migration of antarctic surface waters over the site by 2 67 ma and continued dominance of antarctic surface water through the remainder of the pliocene we suggest that this permanent change from subantarctic to antarctic surface water mass dominance was linked indirectly to the initial growth of northern hemisphere ice and a reduction of sea level we propose a model of simultaneous northern and southern hemisphere ice volume growth induced by interhemisphere positive feedback which is responsible for the major late gauss advance of antarctic surface waters and the global enrichment of 18o at 2 5 ma

quasi 2d hybrid joint inversion of seismic and geoelectric data many joint inversion schemes use 1d forward modelling in the integrated interpretation of various geophysical data in extending the joint inversion approach to the investigation of 2d structures the discretization of the model parameters and the appropriate choice of the forward modelling procedure play a very important role in this paper a hybrid seismic geoelectric joint inversion method is proposed for the investigation of 2d near surface geological structures the electric and seismic models are coupled together through the use of common boundaries between the adjacent layers assuming a 2d model composed of homogeneous layers with curved boundaries a fast ray tracing algorithm is used for the calculation of refraction seismic traveltime data in the geoelectric forward modelling a locally 1d approximation is used the boundary surfaces are written in the form of series expansion the inversion algorithms are formulated for the expansion coefficients and the petrophysical parameters as unknowns two versions of the inversion method are proposed in versions a and b interval wise constant functions and chebyshev polynomials are respectively used as basis functions of the series expansion the versions are tested by means of synthetic and in situ measured data the tests show that both methods are stable and accurate

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

measurements and interpretations of tilt strain gauges in seismically active areas abstract an overview of different aspects of deformation measurements is given an introduction to the general theory of point crustal deformations with an application to the stress strain relations at the earth surface is made the instrumentation used in crustal deformation measurements is briefly explained emphasizing different constructions of tilt and strainmeters the problems connected with the housing of the instruments i e the cavity and topography effects and with the ambient noise factors as the hydrological and pressure effects are discussed the last part of the paper is concerned with the relation between deformation measurements and seismic events both from a theoretical and observational standpoint a number of examples are shown that report on pre co and post seismic and the secular term deformation in different areas of the world

joint inversion of geophysical data summary by jointly inverting several different kinds of geophysical measurements at a site we avoid some of the ambiguity inherent in the individual methods we show how this can be done for the combination of dc resistivity and magnetotelluric measurements on a layered medium by considering a simple 3 layer model the combination resolves the resistivity of the thin resistive second layer even though neither of the two methods can do so alone the method is then applied to field data from a shallow sedimentary basin a blind zone occurs beneath a thick near surface conductive shale by a study of the eigenvalue structure of the model it can be seen that resolution in this zone would be slightly enhanced by higher frequency magnetotelluric data but additional dc data at larger spacing would yield no improvement

a joint inversion algorithm to process geoelectric and surface wave seismic data part ii applications for the exploration of near surface structures seismic and geoelectric methods are often applied usually these two types of method give independently of each other a sufficiently exact model of the geological structure however sometimes the inversion of the seismic or geoelectric data fails these failures can be avoided by combining various methods in one joint inversion which feads to much better parameter estimations of the model than the independent inversions a suitable seismic method for exploring near surface structures is the use of dispersive surface waves the dispersive characteristics of rayleigh and love surface waves depend strongly on the structural and petrophysical seismic velocities features of the near surface underground geoelectric exploration of the structure underground may be carried out with the well known methods of dc resistivity sounding such as the schlumberger the radial dipole and the two electrode arrays the joint inversion algorithm is tested by means of synthetic data it is demonstrated that the geoelectric joint inversion of schlumberger radial dipole and two electrode sounding data yields more reliable results than the single inversion of a single set of these data the same holds for the seismic joint inversion of love and rayleigh group slowness data the best inversion result is achieved by performing a joint inversion of both geoelectric and surface wave data the effect of noise on the accuracy of the solution for both gaussian and non gaussian sparsely distributed large errors is analysed after a comparison between least square lsq and least absolute deviation lad inversion results the lad joint inversion is found to be an accurate and robust method

deciphering late cenozoic development of the western svalbard margin from odp site 986 results abstract the present work is based on sedimentological data from odp site 986 drilled off western svalbard the data include grain size distribution bulk mineralogy clay mineralogy total carbon total organic carbon and carbonate determinations from over 500 samples the results show interesting trends across the seismic sequence boundaries defined earlier and can be related to changes in climate and depositional styles the interpretation of these results together with the seismic observations and interpretations made earlier have shed new light on the timing of the onset of major glaciations and sedimentary processes on the svalbard margin during plio pleistocene the estimate for the timing of the first major glacial advance is revised to 1 6 ma from the earlier estimate of 2 3 ma barents sea was the likely source for the sediments in the 2 3 1 6 ma interval followed by svalbard as the main sediment source in the post 1 6 ma interval it is also suggested that in view of their morphology and proposed sedimentary processes the sedimentary wedges off svalbard barents sea margin are better described as slope aprons than in terms of glacial fans or trough mouth fans used earlier in the literature

laser holographic measurements of tidal deformation of a tunnel summary a new technique based on holographic interferometry has been developed for measuring crustal deformations the holographic recording system consisting of an he ne gas laser and associated optical elements was first installed in a tunnel at the amagase crustal movement observatory in 1984 tunnel deformations caused by tidal and tectonic forces have been precisely determined using the real time technique of holographic interferometry in this procedure a hologram of the tunnel wall within a section 1 2 m in diameter is directly recorded on a photographic plate and then the plate is carefully reset in the position at which the hologram was taken when the reconstructed image of the hologram is superimposed on the current image of the tunnel wall many interference fringes can be seen through the hologram the fringe displacement formed by the deformation of the tunnel is continuously recorded on a video cassette tape using a video camera and a time lapse video recorder the change in the fringe patterns is analysed using the image processing system tidal deformations obtained from the holographic method are consistent with the strain changes observed with laser extensometers in the same tunnel these observational results substantiate the tunnel deformation estimated by finite element calculations

african monsoons an immediate climate response to orbital insolation the croll milankovitch astronomical theory of climate1 3 has received strong support from the evidence of a linear climatic forcing by obliquity and precession although nonlinearity had to be assumed for eccentricity4 5 moreover interglacials have appeared to be controlled by the orbital insolation6 although a phase shift of 6 000 5 000 yr is seen between an astronomical climate index and terrestrial climate indicators dominated by the northern ice sheet dynamics climate proxy data of low latitudes are less directly dependent on the ice sheets here it is shown that during the past 464 000 yr african monsoons signalled by the east mediterranean sapropels were heaviest always and only when a northern summer monsoon index computed from the orbital variation of insolation reached maximum values this occurred during all the interglacials but also twice during glacial periods thus tropical aridity is not the single climatic pattern of glacial periods an immediate terrestrial climate response to orbital variations of insolation is established

joint inversion of seismic and geoelectric data recorded in an underground coal mine1 until the present time the rock coal rock layer sequence and offsets in coal seams in underground coal mines have been detected with the aid of seismic waves and geoelectric measurements in order to determine the geometrical and petrophysical parameters of the coal seam situation the data recorded using seismic and geoelectric methods have been inverted independently in consequence the inversion of partially inaccurate data resulted in a certain degree of ambiguity this paper presents the first results of a joint inversion scheme to process underground vertical seismic profiling data geolectric resistivity and resistance data the joint inversion algorithm makes use of the damped least squares method and its weighted version to solve the linearized set of equations for the seismic and geolectric unknowns in order to estimate the accuracy and reliability of the derived geometrical and petrophysical layer parameters both a model covariance matrix and a correlation matrix are calculated the weighted least squares algorithm is based on the method of most frequent values mfv the weight factors depend on the difference between measured data and those calculated by an iteration process the joint inversion algorithm is tested by means of synthetic data compared to the damped least squares algorithm the mfv inversion leads to smaller estimation errors as well as lower sensitivities due to the choice of the initial model it is shown that compared to an independent inversion the correlation between the model parameters is definitely reduced while the accuracy of the parameter estimation is appreciably increased by the joint inversion process thus the ambiguity is significantly reduced finally the joint inversion algorithm the mfv method is applied to underground field data the model parameters can be derived with a sufficient degree of accuracy even in the case of noisy data

geoelectric determination of quality changes and tectonic disturbances in coal deposits a new underground geoelectric method is presented for the determination of small tectonic disturbances and barrenings in coal seams the distribution of the apparent resistivity can be mapped from the measured apparent resistance data by using a recently developed geoelectric imaging method the applicability of the methods are proved by in situ measurements and by a model experiment

most frequent value based factor analysis of direct push logging data an improved iteratively re weighted factor analysis procedure is presented to interpret engineering geophysical sounding logs in shallow unsaturated sediments we simultaneously process cone resistance electric resistivity and nuclear data acquired by direct push tools to give robust estimates of factor variables and water content in unconsolidated heterogeneous formations the statistical procedure is based on the iterative re weighting of the deviations between the measured and calculated data using the most frequent value method famous for its robustness and high statistical efficiency the iterative approach improves the result of factor analysis for not normally distributed data and extremely noisy measurements by detecting a strong regression relation between one of the extracted factors and the fractional volume of water we establish an independent method for water content estimation along the penetration hole we verify the estimated values of water volume by using a highly overdetermined quality checked interval inversion procedure the multidimensional extension of the statistical method allows the estimation of water content distribution along both the vertical and horizontal coordinates numerical tests using engineering geophysical sounding data measured in a hungarian loessy sandy formation demonstrate the feasibility of the most frequent value based factor analysis which can be efficiently used for a more reliable hydrogeophysical characterization of the unsaturated zone this article is protected by copyright all rights reserved

study of failure mechanisms of rock under compressive shear loading using real time laser holography abstract failure of rock is quite commonly induced by compressive and shear coupling loading the knowledge of the mechanism and process of deformation and failure of rock under compressive shear loading condition is an important basis for the study of stability of rock engineering based on the principles of laser holographic interferometry an experimental system with high precision has been established through the experiment the real time laser holographic interferential fringes under compressive shear loading are simultaneously observed and recorded the active fringes can visually display the distribution mode moving path and dynamic evolution of deformation and cracking in rock on the basis of interpretation and quantitative analysis of the active fringes the whole process of deformation and failure of rock including time spatial evolution law of initiating propagating growing and closing of cracks in rock is quantitatively described from the experimental results some conclusions on the mechanism and characters of deformation and failure of rock under compressive shear loading condition are drawn out

modern and palaeo oceanographic environments under benguela upwelling cells off southern namibia averaged benthic physical and chemical and key microfaunal ostracoda parameters of the bottom waters and substrate allow a ranking of the intensity of upwelling in the modern cells off southwestern africa b1 b6 b1 namib cell temperature salinity dissolved oxygen total organic matter 10 3 c 34 94 1 2 ml l 6 2 palmoconcha walvisbaiensis cytherella namibensis garciaella knysnaensis robusta and neocaudites lordi b2 walvis cell 11 0 c 35 00 1 0 ml l 9 2 palmoconcha walvisbaiensis cytherella namibensis garciaella knysnaensis robusta buntonia rogersi neocaudites lordi and ruggieria cytheropteroides leeward side only b3 luderitz cell 9 1 c 34 77 1 8 ml l 6 3 palmoconcha walvisbaiensis cytherella namibensis incongruellina venusta kuiperiana angulata and ruggieria cytheropteroides leeward side only b4 namaqua cell 10 0 c 34 82 2 4 ml l 3 1 pseudokeijella lepralioides and ruggieria cytheropteroides b5 columbine cell 8 3 c 34 70 3 1 ml l 3 9 ruggieria cytheropteroides pseudokeijella lepralioides poseidonamicus panopsus and ambostracon a flabellicostata b6 peninsula cell 8 9 c 34 63 3 6 ml l 1 9 pseudokeijella lepralioides ambostracon a keeleri cytherella dromedaria neocytherideis boomeri xestoleberis africana neocaudites osseus coquimba birchi and urocythereis arcana pleistocene palaeo upwelling characteristics of the shelf north west of luderitz are investigated by analysing the ostracod faunas sediment textures and mineralogy of three large volume gravity cores q mode factor analyses using previously published transfer functions allow predictions for benthic environmental parameters during the late pleistocene the area experienced less intense upwelling and lower primary productivity than at present in an environment equated with a modified peninsula cell b6 b7 cell 9 6 c 34 73 3 2 ml l 3 9 neocaudites lordi ambostracon a keeleri bairdoppilata simplex paracypris lacrimata parakrithella simpsoni xestoleberis hartmanni ruggieria cytheropteroides and pseudokeijella lepralioides in middle and early pleistocene late pliocene times the core sites lay closer inshore adjacent to evaporite halite and authigenic phosphorite rich lagoons with a high intensity upwelling walvis like cell b1 to the north west and a low intensity upwelling cell b7 to the south

vsp interval velocities from traveltime inversion a principal use of the vertical seismic profile vsp is to determine the variation of seismic velocity with depth presented here is a discussion of the errors involved with the time picks of a vsp survey and several methods currently used to calculate a velocity section from these time picks another technique is proposed based on the least squares inversion of the traveltimes to arrive at a better estimate and statistical description of the velocity section this technique uses the levenberg marquardt damped least squares formulation and ray tracing through a horizontally layered medium to iteratively refine the velocity section the accuracy and robustness of the procedure are investigated by inverting noisy traveltime curves and comparing these results to the original model velocity section agreement is found to be good one interesting feature of the inverse procedure is that for certain geometries it can resolve a few velocity layers even though there are no measurements made inside those layers three actual vsp surveys are analyzed and compared to their corresponding sonic logs in two of the surveys it appears that there is some velocity dispersion velocity changes associated with gas saturation are evident on one of the surveys

the history of coastal upwelling off peru 11 s odp leg 112 site 680b over the past 650 000 years the coarse sediment fraction 63 m and benthic foraminiferal composition of quaternary sediment cores from odp leg 112 hole 680b 252 5 m water depth were sampled from the upwelling area off peru high resolution oxygen isotope stratigraphy based on analyses of the benthic foraminifera bolivina seminuda allows a detailed reconstruction of the upwelling history since oxygen isotope stage 16 variations in the relative abundances of the benthic foraminiferal species nonionella auris bolivina costata and bolivina seminuda document changes in fertility which were found to be enhanced during interglacial stages 1 3 5 7 9 and 11 generally bioturbated sediments are dominated by the genera cassidulina epistominella gyroidina trifarina and valvulineria these benthic foraminifera are members of the undercurrent fauna which is commonly associated with sediments that have a high terrigenous detrital component and a low organic carbon content 6 ml l o2 the entire core interval investigated in hole 680b appears to have been affected by the peruvian undercurrent generally undercurrent dominated sections were found to correspond with glacial oxygen isotope stages

in seam seismic love wave scattering modeled by the finite element method the dynamic finite element method allows frequency dependent reflection and transmission coefficients to be computed for love waves scattered by two dimensional inhomogeneities in coal seams clean faults of zero hade angle show a throw dependent cross over frequency in reflection spectra and throw dependent conversion from fundamental to first higher mode energy in transmission spectra oblique faults show mode conversion in reflection spectra which is relatable to the fault hade angle by simple huygens theory models thin fracture zones or dykes normal to the seam show a reflection maximum when thickness of the zone is of order one quarter of the seam wave wavelength published field data from two known faults and a dyke are compared with the modeling results and support the belief that broad band seam wave data are capable of characterizing a seam discontinuity throw hade angle dyke thickness as well as locating it development of such procedures will require extensions to existing field practice and processing 19 references

upwelling intensification as part of the pliocene pleistocene climate transition a deep sea sediment core underlying the benguela upwelling system off southwest africa provides a continuous time series of sea surface temperature sst for the past 4 5 million years our results indicate that temperatures in the region have declined by about 10 c since 3 2 million years ago records of paleoproductivity suggest that this cooling was associated with an increase in wind driven upwelling tied to a shift from relatively stable global warmth during the mid pliocene to the high amplitude glacial interglacial cycles of the late quaternary these observations imply that atlantic ocean surface water circulation was radically different during the mid pliocene

on reducing ambiguity in the interpretation of transient electromagnetic sounding data1 an attempt to resolve non uniqueness in the interpretation of transient electromagnetic tem sounding data using measured data alone is made it is shown in the various examples studied that sufficiently early time measurements can be the determining factor in reducing the ambiguity caused by model equivalence the early delay times thus play a dual role in transient soundings they are responsible for resolving shallow structures and they may eliminate the ambiguity in the interpretation of geoelectric parameters of deeper targets this is illustrated by the results of a follow up tem survey at the dead sea coast of israel where the use of supplementary early time measurements allowed non uniqueness in the determination of the depth to fresh saline groundwater interface to be resolved

p sv wave scattering by coal seam inhomogeneities the dynamic finite element method is used to calculate the normal incidence p sv guided wave scattering spectra of 124 models of coal seam obstructions commonly encountered in in seam seismology the models are faults of varying throw and dip thick faults with an associated region of fracturing dikes of varying width hardness and dip sills of varying hardness stone rolls of varying height and seam washouts reflection and transmission spectra including mode conversion are studied for incident fundamental symmetric p sv seam modes the dynamic finite element method is adapted to the calculation of scattering parameters through the consistent boundary condition of lysmer and waas the results complement an earlier study of sh seam wave scattering they show that faults reflect a much higher percentage of sh wave energy than p sv but that p sv waves undergo substantially greater mode conversion on scattering from faults dikes exhibit thin film interferometric effects for both sh and p sv waves sil

quantitative determination of stress by inversion of speckle interferometer fringe patterns experimental laboratory tests summary quantitative determination of crustal stress states remains problematic here we provide a synopsis of work that is leading towards the development of an optical interferometric method that may be applied in boreholes the major obstacle to the continued development of this technique has been the problem of determining the state of stress within a stressed continuum we demonstrate the solution of both the technical and analytical issues in this contribution specifically dual beam digital electronic speckle interferometry is used to record the stressrelief displacements induced by the drilling of blind holes into blocks subject to uniaxial compressive stresses speckle interferograms are produced at rates near 4 hz using a local pearson s correlation method and are stored for analysis this time lapse capability is useful when transient effects such as thermal expansion displacements produced by the heat of drilling or ongoing time dependent deformation are active four acrylic blocks subject to uniaxial compressions from 3 8 to 5 5 mpa with the compressions oriented at different angles with respect to the axes of the interferometry system were studied relative fringe phase information was extracted from appropriate interferograms and inverted to provide a quantitative measure of the 2 d stress field within the block in general the largest value of the stress obtained in the inversion agreed with the known stress to better than 70 per cent these measurements suggest the levels of uncertainty that might be expected by use of such optical interferometric techniques this technique may show promise for quantitative stress determination in the earth to complement existing techniques as well while the interferometric principles are not exactly the same as for the popular satellite based insar techniques the optical method here has the potential to be useful in analogue physical model laboratory studies of deformation in complex structures

effect of the formation of the isthmus of panama on atlantic ocean thermohaline circulation the late cenozoic closure of the seaway between the north andsouth american continents is thought to have caused extensive changes in ocean circulation and northern hemisphere climate1 2 but the timing and consequences of the emergence of the isthmus of panama which closed the seaway remain controversial1 2 3 4 5 here we present stable isotope and carbonate sand fraction records from caribbean sediments which when compared to atlantic and pacific palaeoceanographic records indicate that the closure caused a marked reorganization of ocean circulation starting 4 6 million years ago shallowing of the seaway intensified the gulf stream and introduced warm and saline water masses to high northern latitudes these changes strengthened deep water formation in the labrador sea over the next million years as indicated by an increased deep water ventilation and carbonate preservation in the caribbean sea and favoured early pliocene warming of the northern hemisphere the evaporative cooling of surface waters during north atlantic deep water formation would have introduced moisture to the northern hemisphere although the pronounced intensification of northern hemisphere glaciation between 3 1 and 2 5 million years ago substantially lagged the full development of north atlantic deep water formation we propose that the increased atmospheric moisture content was a necessary precondition for ice sheet growth which was then triggered by the incremental changes in the earth s orbital obliquity

calculation of dispersion curves and amplitude depth distributions of love channel waves in horizontally layered media we present dispersion curves and amplitude depth distributions of the fundamental and first higher mode of love seam waves for two characteristic seam models the first model consists of four layers representing a coal seam underlain by a root clay of variable thickness the second model consists of five layers representing coal seams containing a dirt band with variable position and thickness the simple three layer model is used for reference it is shown that at higher frequencies depending on the thickness of the root clay and the dirt band the coal layers alone act as a wave guide whereas at low frequencies all layers act together as a channel depending on the thickness and position of the dirt band and the root clay in the dispersion curves of the group velocity secondary minima grow in addition to the absolute minima furthermore the dispersion curves of the group velocity of the two modes can overlap in all these cases wave groups in addition to the airy phase of the fundamental mode propagating with minimum group velocity occur on the seismograms recorded in in seam seismic surveys thus impeding their interpretation hence we suggest the estimation of the dispersion characteristics of love seam waves in coal seams under investigation preceding actual field surveys all numerical calculations were performed using a fast and stable phase recursion algorithm

fault location by channel wave seismology in united kingdom coal seams about 80 percent of british deep mined coal is obtained from advance longwall faces this mining method is highly capital intensive therefore it is important to know the geologic structure prior to mining small faults can have a large effect on production rates channel wave seismology offers a possible method for locating these faults a coal seam resembles a dispersive acoustic duct and energy from a seismic source within the seam can be coupled into channel wave modes scattered waves from defects within the seam can be recorded and the data analyzed to produce a map of the seam it has been shown that dispersion does not present a fundamental limitation to the resolution that can be obtained in addition broadband numerical holographic mapping procedures in the form of lag sums can be implemented these techniques have been described previously by mason et al 1980a this paper is divided into two main parts first we show how the basic lag sum techniques have been extended to produce an adapt

application of laser holographic techniques to investigate crustal deformations laser holographic techniques can be used to detect small deformations of three dimensional objects of the order of the wavelength of the laser light we report the use of laser holography to measure the crustal deformation in a deep tunnel at amagase kyoto japan a recording system consisting of a helium neon gas laser and associated optical elements was installed in the observation tunnel in 1984 using this sytem holograms of a section of the tunnel wall 2m in diameter are directly recorded on photographic plates when the reconstructed image of a hologram is superposed on the current real time image of the tunnel wall many interference fringes can be seen through the developed photographic plate the fringe displacement formed by the deformation of the tunnel is continuously monitored with a video camera and a video cassette recorder the measured fringe displacement in the interference pattern is consistent with strain changes obtained from extensometers which have been installed in the same tunnel