on the resource evaluation of marine gas hydrate deposits using sea floor transient electric dipole dipole methods methane hydrates are solid nonstoichiometric mixtures of water and the gas methane they occur worldwide in sediment beneath the sea floor and estimates of the total mass available there exceed 1016kg since each volume of hydrate can yield up to 164 volumes of gas offshore methane hydrate is recognized as a very important natural energy resource the depth extent and stability of the hydrate zone is governed by the phase diagram for mixtures of methane and hydrate and determined by ambient pressures and temperatures in sea depths greater than about 300 m the pressure is high enough and the temperature low enough for hydrate to occur at the seafloor the fraction of hydrate in the sediment usually increases with increasing depth the base of the hydrate zone is a phase boundary between solid hydrate and free gas and water its depth is determined principally by the value of the geothermal gradient it stands out on seismic sections as a bright reflection the diffuse upper boundary is not as well mar

the geochemistry of mafic metavolcanics implications for the origin of the devonian massive sulfide deposits at zlate hory czechoslovakia mafic metavolcanic rocks in the area of the zlate hory massive sulfide deposits are interpreted as convergent plate margin basalts and basaltic andesites metamorphosed to the greenschist facies according to the major and trace element compositions the metabasites exhibit island arc tholeiitic to low k calc alkaline composition

a standoff focused beam land mine radar this paper describes a standoff focused beam ground penetrating radar gpr for detecting buried antipersonnel ap mines the radar features a 1 to 6 ghz pulsed stepped frequency microwave source with hardware range gate an ultrawide bandwidth feed antenna and an offset parabolic reflector a focused beam created by feeding the reflector from an offset position reduces the surface clutter and improves the detection of buried mines a processing technique based on spectral analysis prony method is developed in an attempt to reduce surface clutter tests conducted at the fort a p hill countermine test lanes showed excellent detection capability for both metallic and nonmetallic mines

glacial hydrologic conditions in the black sea reconstructed using geochemical pore water profiles abstract chloride and 18 o compositions of interstitial water extracted from a long sediment core retrieved from the nw coast of the black sea allowed us to constrain the main hydrologic changes of the back sea during the late pleistocene and holocene prior to its reconnection with the mediterranean sea through the marmara sea at approximately 9000 calendar yr before present 9 ka cal bp the black sea has evolved as a fresh to brackish water lake at the time of reconnection hydrologic changes were drastic bottom water salinities changed from a few psu practical salinity unit to 22 psu since solutes in the interstitial water column within sediments are advected and diffused the measured concentrations do not reflect those of past bottom waters in order to reconstruct these former concentrations we used an advection diffusion model different scenarios of bottom water chloride and 18 o variations were accounted for in this model in order to simulate present day vertical profiles for concentrations of interstitial water in order to compare them to measured ones the comparison suggests that the glacial black sea was a homogeneous freshwater lake with a 18 o of 10 and a salinity of 1 psu modern hydrologic conditions would only have been reached at 2 ka cal bp concomitant with the onset of coccolith rich thin layers that characterize modern basin sediments such delayed salinization over 7000 yr in the basin may have been due to higher precipitation during the early holocene we also simulated the impact of a catastrophic reconnection and a smoother reconnection both salinity scenarios lead to undistinguishable modelled present day profiles indicating that the precise impact of the last reconnection was lost due to the advection diffusion processes

geological and morphological setting of 2778 methane seeps in the dnepr paleo delta northwestern black sea abstract the dnepr paleo delta area in the nw black sea is characterized by an abundant presence of methane seeps during the expeditions of may june 2003 and 2004 within the eu funded crimea project detailed multibeam seismic and hydro acoustic water column investigations were carried out to study the relation between the spatial distribution of methane seeps sea floor morphology and sub surface structures 2778 new methane seeps were detected on echosounding records in an area of 1540 km 2 all seeps are located in the transition zone between the continental shelf and slope in water depths of 66 to 825 m the integration of the different geophysical datasets clearly indicates that methane seeps are not randomly distributed in this area but are concentrated in specific locations the depth limit for the majority of the detected seeps is 725 m water depth which corresponds more or less with the stability limit for pure methane hydrate at the ambient bottom temperature 8 9 c in this part of the black sea this suggests that where gas hydrates are stable they play the role of buffer for the upward migration of methane gas and thus prevent seepage of methane bubbles into the water column higher up on the margin gas seeps are widespread but accurate mapping illustrates that seeps occur preferentially in association with particular morphological and sub surface features on the shelf the highest concentration of seeps is found in elongated depressions pockmarks above the margins of filled channels on the continental slope where no pockmarks have been observed seepage occurs along crests of sedimentary ridges there seepage is focussed by a parallel stratified sediment cover that thins out towards the ridge crests on the slope seepage also appears in the vicinity of canyons bottom flanks and margins or near the scarps of submarine landslides where mass wasting breaches the fine grained sediment cover that acts as a stratigraphic seal the seismic data show the presence of a distinct gas front which has been used to map the depth of the free gas within the sea floor sediments the depth of this gas front is variable and locally domes up to the sea floor where the gas front approaches the seafloor gas bubbles were detected in the water column a regional map of the sub surface depth of the gas front emphasises this gas front versus seep relationship the integration of all data sets indicates that the spatial distribution of methane seeps in the dnepr paleo delta is mainly controlled by the gas hydrate stability zone as well as by stratigraphic and sedimentary factors

phase center of l band radar in polar snow and ice backscatter from an aggregate of inhomogeneities combine to form an apparent surface reflection particularly in relation to interferometric synthetic aperture radar the depth z of this reflection can reside well below the true surface when the transmissivity at the interface between air and the aggregate is high snow and ice provide good examples for which we calculate z with different accumulation history and physical properties using a 0 5 3 0 ghz ground penetrating radar we acquired our data along transects in antarctica and svalbard we find values of z 40 in low absorbing antarctic firn and 10 meters in glaciers and ice shelves where melt freeze cycles and lateral mass movement lead to an electrically more heterogeneous snow and ice column the heterogeneity reduces dielectric contrast more rapidly with depth thus z is found at shallower depth but still resides several meters beneath the snow surface

mapping the resistivity structure of walker ridge 313 in the gulf of mexico using the marine csem method abstract a marine controlled source electromagnetic csem campaign was carried out in the gulf of mexico to further develop marine electromagnetic techniques in order to aid the detection and mapping of gas hydrate deposits marine csem methods are used to obtain an electrical resistivity structure of the subsurface which can indicate the type of substance filling the pore space such as gas hydrates which are more resistive results from the walker ridge 313 study wr 313 are presented in this paper and compared with the gulf of mexico gas hydrate joint industry project ii jip2 logging while drilling lwd results and available seismic data the hydrate known to exist within sheeted sand deposits is mapped as a resistive region in the two dimensional 2d csem inversion models this is consistent with the jip2 lwd resistivity results csem inversions that use seismic horizons provide more realistic results compared to the unconstrained inversions by providing sharp boundaries and architectural control on the location of the resistive and conductive regions in the csem model the seismic horizons include 1 the base of the gas hydrate stability zone bghsz 2 the top of salt and 3 the top and bottom of a fine grained marine mud interval with near vertical hydrate filled fractures to constrain the csem inversion model the top of salt provides improved location for brines water saturated salt and resistive salt inversions of the csem data map the occurrence of a halo of conductive brines above salt the use of the bghsz as a constraint on the inversion helps distinguish between free gas and gas hydrate as well as gas hydrate and water saturated sediments

gas migration pathways and slope failures in the danube fan black sea abstract a large geophysical dataset including bathymetry and 2d and 3d p cable seismic data revealed evidence of numerous gas flares near the s2 canyon in the danube fan northwestern black sea this dataset allows us to investigate potential relationships between gas migration pathways gas vents observed at the seafloor and submarine slope failures vertical gas migration structures as revealed in the seismics appear to be concentrated near submarine slope failure structures where these seismically defined features extend upwards to the seafloor they correlate with the location of gas flares however not all these structures reach the seafloor in some cases because they are capped by overlying sediments a strong correlation is inferred between gas migration pathways heterogeneous mass transport deposits and contacts between adjacent units of contrasting lithology although missing age constrains prevent a final judgement we discuss the potential relationship between submarine slope failures and gas migration in order to determine if gas migration is a precursor to failure or if the presence of slope failures and associated mass transport deposits facilitates the migration of gas our observations indicate that lithological heterogeneity mass transport deposits and minor sediment deformation control gas migration pathways and the formation of gas chimney like features gas migration is focused and gradual resulting in gas flares where the chimney like features extend to the seafloor with no evidence of erosive features such as pockmarks

simulation of a surface penetrating radar for mars exploration 1 in the near future several exploratory missions to mars are planned which will include orbital radar sounders capable of characterizing the planet s subsurface structure to depths of up to a few kilometers due to the limited amount of resources concerning the properties of the martian soils in particular those governing electromagnetic propagation and scattering the ability of a radar system to detect and distinguish between subsurface interfaces is difficult to predict up to this time most radar sounding simulations have been based on simplified models and do not accurately account for many of the factors that influence the response to aid in the system evaluation and data interpretation for these missions we developed a radar simulator to accurately model the response for various geological conditions the simulator uses a frequency domain algorithm and is capable of modeling the effects of dielectric layering volume debris frequency dispersion ohmic losses and interface roughness in this paper a geophysical model appropriate to the radar simulator is described and the simulation algorithms are presented in detail factors influencing wave propagation and scattering are identified including those that directly impact radar performance specifically pertaining to expected penetration depths and unambiguous detection of water or ice finally using a set of standard crustal models of different geological regions simulation results are generated and presented

subsurface imaging in south central egypt using low frequency radar bir safsaf revisited we present the capabilities of low frequency radar systems to sound the subsurface for a site located in south central egypt the bir safsaf region this site was already intensively studied since the sir a and sir b orbital radars revealed buried paleodrainage channels our approach is based on the coupling between two complementary radar techniques the orbital synthetic aperture radar sar in c and l bands 5 3 and 1 25 ghz for imaging large scale subsurface structures and the ground penetrating radar gpr at 500 and 900 mhz for sounding the soil at a local scale we show that the total backscattered power computed from l band sar and 900 mhz gpr profiles can be correlated and we combined both data to derive the geological structure of the subsurface gpr data provide information on the geometry of the buried scatterers and layers while the analysis of polarimetric sar data provides information on the distribution of rocks in the sedimentary layers and at the interface between these layers the analysis of 500 mhz gpr data revealed some deeper structures that should be detected by lower frequency sars such as a p band system

ultrawideband gated step frequency ground penetrating radar we describe a prototype ultrawideband radar we show how the system was designed and how the hardware was developed for the radar prototype waveform generation radar parameters and signal processing for the stepped frequency waveform are discussed the radar operates from 500 mhz to 3 ghz with a nominal resolution of 6 cm in air the advantage of the stepped frequency approach over an impulse radar is better matching between the transmitted waveform and the receiver we use range gating to improve the system dynamic range the advantages are illustrated with laboratory measurements and field measurements from glacial ice and permafrost in svalbard showing penetration depths of 11 m antennas which do not require contact with the ground were developed and used in the experiments

joint interpretation of geophysical field experiments in the danube deep sea fan black sea abstract gas hydrates are naturally occurring solid compounds of gas and water within almost all sediment rich continental margins due to the large amounts of methane stored in submarine gas hydrates they might serve as future reservoirs for offshore marine gas production assessing the reservoir characteristics requires reliable estimates of both the gas and gas hydrate concentration which can be best addressed using geophysical and geological investigations here we demonstrate the power of joint interpretation of interdisciplinary geophysical techniques and geological laboratory experiments regional 2d multichannel seismic data provide the broad overview of a hydrate bearing area high resolution 2d and 3d seismic reflection data provide detailed images of two working areas the buried s1 channel levee system at 1500 m water depth well within the gas hydrate stability zone and a slope failure location located at 665 m water depth top limit of the hydrate formation next to the s2 channel detailed compressional and shear wave vs velocity depth models were derived from four component ocean bottom seismic data the latter from p to s conversion upon reflection due to their steep reflection angles shear wave events result in less resolved vs models nevertheless in case of a change in elasticity of the sediment matrix due to gas hydrate cementation shear wave events can be used as an indicator as such vs can give insight into the nature of hydrate formation throughout the ghsz we present new developments in the application of common reflection surface normal incidence point tomography and full waveform inversion techniques to enhance model resolution for the seismic data sets 2d and 3d controlled source electromagnetic measurements provide volume information of the resistivity depth distribution models electrical resistivity of the sediment formation depends on its porosity and the resistivity of the pore fluid gas hydrate and free gas generally have much higher electrical resistivities than saline pore fluid and can be assessed using empirical relationships if the porosity and pore fluid salinity are known calibration with logging data laboratory experiments on hydrate or ice bearing sediments and resulting velocity and resistivity values guide the joint interpretation into more accurate saturation estimations beyond that a joint inversion framework supporting forward calculation of specialized geophysical methods at distributed locations is under development in this paper we summarize these individual components of a multi parameter study and their joint application to investigate gas hydrate systems their equilibrium conditions and preservation of bottom simulating reflectors we analyze data from two working areas at different locations and depth levels along the slope of the danube fan which are both characterized by multiple bottom simulating reflectors indicating the presence of gas hydrate in the first working area we located two depth windows with indications for moderate 16 24 gas hydrate formation but no vertical gas migration in the second working area we observed fluid migration pathways and active gas seepage limiting gas hydrate formation to less than 10 at the bsr some discrepancies remain between seismic based and electromagnetic based models of gas and gas hydrate distribution and saturation estimates indicating that further in situ investigations are likely required to better understand the gas hydrate systems at our study areas and to calibrate the inversion processes which will be required for a joint inversion framework as well

use of c band ground penetrating radar to determine backscatter sources within glaciers the question of penetration of synthetic aperture radar sar signals at c band frequency into polar glaciers is addressed by comparing ground penetrating radar gpr and sar backscatter signatures profiles of the kongsvegen glacier svalbard were obtained with a c band gpr the received signal is converted to the equivalent radar cross section using the standard radar equation thus mapping the effective scattering sources within the glacier at this frequency the depth of the observed scattering sources is greatest in the superimposed ice where layers are clearly seen to a depth of approximately 14 m the very high scattering properties of the upper firn layers preclude layers deeper than approximately 6 m from being imaged integrating the radar cross sections over the depth gives a single backscatter value that we compare with the backscatter coefficient scattering cross section per unit area of the processed sar data for the same profile the comparison indicates that for coincidentally acquired gpr and sar data the radar cross section measured by the gpr does represent the features that contribute to the sar signal

physical properties and core log seismic integration from drilling at the danube deep sea fan black sea abstract drilling coring and geophysical logging were performed with the marum mebo200 seafloor drilling rig to investigate gas hydrate occurrences of the danube deep sea fan off romania black sea three sites within a channel levee complex were investigated geophysical log data of p wave velocity electrical resistivity and spectral gamma ray are combined with core derived physical properties of porosity magnetic susceptibility and bulk density core and log physical property data are used to define a time depth conversion by synthetic seismogram modeling which is then used to interpret the seismic data individual polarity reversed reflectors within the stratigraphic column drilled are linked to reduction in p wave velocity and bulk density those reflectors and associated reflection packages are accompanied by distinct and systematic changes in sediment porosity magnetic susceptibility and electrical resistivity overall the sediments at drill site geob22605 mebo 17 represent the younger upper levee sequence of the channel that has been eroded at drill site geob22603 mebo 16 splicing seismic data across the channel from the east mebo 16 to the west mebo 17 demonstrates the continuation of reflectors underneath the channel the upper 50 m below seafloor mbsf at site mebo 16 do not stratigraphically belong to the same sequence of the deeper levee deposits above the marked erosional unconformity sediments at site mebo 16 are likely derived by a mixture of repeated slump events identified as seismically transparent units interbedded with hemi pelagic sedimentation similarly sediments within the upper 20 mbsf at site mebo 17 are not stratigraphically the same levee deposits but are derived by a mixture of slump events also seen in the marked seafloor amphitheatre architecture of a large failure complex extending further upslope and hemi pelagic sedimentation all observations combined show that the seismically observed stratigraphic pattern represents a reflectivity sequence mostly driven by variations in density porosity and correspondingly by changes in p wave velocity and electrical resistivity observations from the geophysical log and core as well as geochemical data show no evidence for the presence of any significant gas hydrates within the drilled cored sequences

1300 m high rising bubbles from mud volcanoes at 2080m in the black sea hydroacoustic characteristics and temporal variability a mud volcano area in the deep waters 2000 m of the black sea was studied by hydroacoustic measurements during several cruises between january 2002 and june 2004 gas bubbles in the water column give strong backscatter signals and thus can be detected even in great water depths by echosounders as the 38 khz ek500 scientific split beam system that was used during the surveys because of their shape in echograms and to differentiate against geochemical plumes and real upwelling bubble water plumes we call these hydroacoustic manifestations of bubbles in the water column flares digital recording and processing of the data allows a 3d visualization and data comparison over the entire observation period without artefacts caused by changing system settings during our surveys we discovered bubble release from three separate mud volcanoes dvurechenskiy dmv vodianitskiy vmv and the nameless seep site nss in about 2080 m water depth simultaneously bubble release was observed between 9 june 2003 and 5 june 2004 the most frequently surveyed dmv was found to be inactive during very intensive studies in january 2002 the first activity was observed on 27 june 2002 which finally ceased between 5 and 15 june 2004 after a period of continuously decreasing activity this observed 2 yr bubble release period at a mud volcano may give an indication for the duration of active periods the absence of short term variations within days or hours may indicate that the bubble release from the observed mud volcanoes does not undergo rapid changes the recorded echograms show that bubbles rise about 1300 m high through the water column to a final water depth of about 770 m which is 75 m below the phase boundary of pure methane hydrate in the black sea with a release depth from 2068 m and a detected rise height of 1300 m the flare at vmv is among the deepest and highest reported so far and gives evidence of highly extended bubble life times up to 108 min in deep marine environments to better understand how a methane bubble gas analyses of the pore water and gas hydrate gave 99 4 methane can rise so high without dissolving we applied a recently developed bubble dissolution model that takes into account a decreased mass transfer due to an immediately formed gas hydrate rim using the hydroacoustically determined bubble rising speeds 19 22 cm s at the bottom 12 14 cm s at the flare top and the relation between the rising speed of dirty gas hydrate rimmed bubbles and the bubble size we could validate that a gas hydrate rimmed bubble with a diameter of 9 mm could survive the 1300 m rise through the water column before it is finally dissolved a diameter of about 9 mm is reasonable for bubbles released at seep sites and the coincidence between the observed bubble rising speed and the model approach of a 9 mm bubble supports the assumption of gas hydrate rimmed bubbles

on the origin of multiple bsrs in the danube deep sea fan black sea highlights a stack of four bsrs were identified in levee deposits of the danube deep sea fan the multiple bsrs are not caused by overpressure compartments the multiple bsrs reflect stages of stable sealevel lowstands during glacial times gas underneath the previous ghsz does not start to migrate for thousands of years abstract high resolution 2d seismic data reveal the character and distribution of up to four stacked bottom simulating reflectors bsr within the channel levee systems of the danube deep sea fan the theoretical base of the gas hydrate stability zone ghsz calculated from regional geothermal gradients and salinity data is in agreement with the shallowest bsr for the deeper bsrs bsr formation due to overpressure compartments can be excluded because the necessary gas column would exceed the vertical distance between two overlying bsrs we show instead that the deeper bsrs are likely paleo bsrs caused by a change in pressure and temperature conditions during different limnic phases of the black sea this is supported by the observation that the bsrs correspond to paleo seafloor horizons located in a layer between a buried channel levee system and the levee deposits of the danube channel the good match of the observed bsrs and the bsrs predicted from deposition of these sediment layers indicates that the multiple bsrs reflect stages of stable sealevel lowstands possibly during glacial times the observation of sharp bsrs several 10 000 of years but possibly up to 300 000 yr after they have left the ghsz demonstrates that either hydrate dissociation does not take place within this time frame or that only small amounts of gas are released that can be transported by diffusion the gas underneath the previous ghsz does not start to migrate for several thousands of years

electromagnetic propagation of gpr signals in martian subsurface scenarios including material losses and scattering a study on the electromagnetic propagation in various models of the martian subsurface is performed with a relevance to ground penetrating radar gpr operating onboard rover missions measurements of the electromagnetic properties of mars soil simulants are obtained on this basis the attenuation features of the gpr signals are estimated including both electric and magnetic losses the effect on propagation of inhomogeneities inside the soil is also taken into account by means of a specific model with randomly distributed scatterers the gpr performance in terms of resolution and maximum penetration depth is evaluated in the considered scenarios for different operating frequencies thus providing a basic information for the design of systems for future subsurface sounding investigations on mars

high intensity gas seepage causes rafting of shallow gas hydrates in the southeastern black sea abstract submarine gas hydrates are a major global reservoir of the potent greenhouse gas methane since current assessments of worldwide hydrate bound carbon vary by one order of magnitude new technical efforts are required for improved and accurate hydrate quantifications here we present hydrate abundances determined for surface sediments at the high flux batumi seep area in the southeastern black sea at 840 m water depth using state of the art autoclave technology pressure sediment cores of up to 2 65 m in length were recovered with an autoclave piston corer backed by conventional gravity cores quantitative core degassing yielded volumetric gas bulk sediment ratios of up to 20 3 proving hydrate presence the cores represented late glacial to holocene hemipelagic sediments with the shallowest hydrates found at 90 cmbsf calculated methane concentrations in the different cores surpassed methane equilibrium concentrations in the two lowermost lithological black sea units sampled the results indicated hydrate fractions of 5 2 of pore volume in the sapropelic unit 2 and mean values of 21 pore volume in the lacustrine unit 3 we calculate that the studied area of 0 5 km2 currently contains about 11 3 kt of methane bound in shallow hydrates episodic detachment and rafting of such hydrates is suggested by a rugged seafloor topography along with variable thicknesses in lithologies we propose that sealing by hydrate precipitation in coarse grained deposits and gas accumulation beneath induces detachment of hydrate sediment chunks floating hydrates will rapidly transport methane into shallower waters and potentially to the sea atmosphere boundary in contrast persistent in situ dissociation of shallow hydrates appears unlikely in the near future as deep water warming by about 1 6 c and or decrease in hydrostatic pressure corresponding to a sea level drop of about 130 m would be required because hydrate detachment should be primarily controlled by internal factors in this area and in similar hydrated settings it serves as source of methane in shallow waters and the atmosphere which is mainly decoupled from external forcing

combined interpretation of marine controlled source electromagnetic and reflection seismic data in the german north sea a case study this paper focuses on the combined analysis and interpretation of controlled source electromagnetic csem and multichannel reflection seismic mcs data along one profile in the german north sea with the goal to reduce ambiguities in interpretation the shallow water environment of the north sea is characterized by a complex geological development which includes rifting several ice age cycles a propagating shelf margin mass transport deposits and salt dome formation seismic and electromagnetic methods are sensitive to different physical properties of the seabed and therefore complement each other we analyse the mcs data with a migration velocity tomography and an amplitude variation with offset analysis and discuss seismic velocities and densities for true amplitude recovery the amplitude distortions are calibrated with in situ logging data the csem data are analysed in 2 d for which for the first time data were included that were acquired while the instrument was towed on the seafloor in addition to the stationary sites the csem inversions are constrained by seismic horizons the joint interpretation focuses on two seismic reflectors one can be interpreted as an unconformity marking a lithological change from fresh water bearing glacial deposits to compacted sediments below and the other one as a layer of fine grained deposits potentially capping patchy shallow gas occurrences this exemplary case study shows how the combination of both methods can benefit by interpreting complex geology and eliminating ambiguous explanations

hydrate occurrence in europe a review of available evidence abstract large national programs in the united states and several asian countries have defined and characterised their marine methane hydrate occurrences in some detail but european hydrate occurrence has received less attention the european union funded project marine gas hydrate an indigenous resource of natural gas for europe migrate aimed to determine the european potential inventory of exploitable gas hydrate to assess current technologies for their production and to evaluate the associated risks we present a synthesis of results from a migrate working group that focused on the definition and assessment of hydrate in europe our review includes the western and eastern margins of greenland the barents sea and onshore and offshore svalbard the atlantic margin of europe extending south to the northwestern margin of morocco the mediterranean sea the sea of marmara and the western and southern margins of the black sea we have not attempted to cover the high arctic the russian ukrainian and georgian sectors of the black sea or overseas territories of european nations following a formalised process we defined a range of indicators of hydrate presence based on geophysical geochemical and geological data our study was framed by the constraint of the hydrate stability field in european seas direct hydrate indicators included sampling of hydrate the presence of bottom simulating reflectors in seismic reflection profiles gas seepage into the ocean and chlorinity anomalies in sediment cores indirect indicators included geophysical survey evidence for seismic velocity and or resistivity anomalies seismic reflectivity anomalies or subsurface gas escape structures various seabed features associated with gas escape and the presence of an underlying conventional petroleum system we used these indicators to develop a database of hydrate occurrence across europe we identified a series of regions where there is substantial evidence for hydrate occurrence some areas offshore greenland offshore west svalbard the barents sea the mid norwegian margin the gulf of cadiz parts of the eastern mediterranean the sea of marmara and the black sea and regions where the evidence is more tenuous other areas offshore greenland and of the eastern mediterranean onshore svalbard offshore ireland and offshore northwest iberia we provide an overview of the evidence for hydrate occurrence in each of these regions we conclude that around europe areas with strong evidence for the presence of hydrate commonly coincide with conventional thermogenic hydrocarbon provinces

modeling of the influence of gas hydrate content on the electrical properties of porous sediments the geophysical investigation of gas hydrate accumulations within marine sediments and the sediments of permafrost regions suffer from a lack of information on the influence of the hydrate content on the physical sediment properties the estimation of the hydrate content using downhole electrical measurements based on archie s law requires the knowledge of the saturation exponent the saturation exponent is an empirical parameter that includes influences from the internal rock structure such as pore shape connectivity and constrictivity of the pore network and the distribution of the conducting phase based on different models that account for the different morphological forms of gas hydrates found during gas hydrate sampling in various research wells the influence of gas hydrate content on the electrical properties of the hydrate bearing sediment was investigated for all studied forms of hydrate occurrence disseminated in the pore space nodular and layered the saturation exponent depends on the sediment properties and on saturation itself the growth of gas hydrate nodules lenses and layers is a process that is assumed to result in the displacement and compaction of the surrounding sediment because of this change of sediment properties during hydrate generation the saturation exponent for these forms of hydrate occurrence depends strongly on the relationship between porosity and formation resistivity factor expressed in the form of archie s cementation exponent for the case that hydrate occurs disseminated in the pore space and the assumption that capillary effects are important for hydrate generation the saturation exponent depends on grain size and grain size sorting for the parameters chosen for these model calculations the saturation exponent varies between 0 5 and 4 the use of a constant mean value for the saturation exponent of approximately 2 can result in both underestimation and overestimation of the hydrate content

amplitude versus offset modeling of the bottom simulating reflection associated with submarine gas hydrates abstract a bottom simulating seismic reflection bsr that parallels the sea floor occurs worldwide on seismic profiles from outer continental margins the bsr coincides with the base of the gas hydrate stability field and is commonly used as indicator of natural submarine gas hydrates despite the widespread assumption that the bsr marks the base of gas hydrate bearing sediments the occurrence and importance of low velocity free gas in the sediments beneath the bsr has long been a subject of debate this paper investigates the relative abundance of hydrate and free gas associated with the bsr by modeling the reflection coefficient or amplitude variation with offset avo of the bsr at two separate sites offshore oregon and the beaufort sea the models are based on multichannel seismic profiles seismic velocity data from both sites and downhole log data from oregon odp site 892 avo studies of the bsr can determine whether free gas exists beneath the bsr if the saturation of gas hydrate above the bsr is less than approximately 30 of the pore volume gas hydrate saturation above the bsr can be roughly estimated from avo studies but the saturation of free gas beneath the bsr cannot be constrained from the seismic data alone the avo analyses at the two study locations indicate that the high amplitude bsr results primarily from free gas beneath the bsr hydrate concentrations above the bsr are calculated to be less than 10 of the pore volume for both locations studied

development test and evaluation of exploitation technologies for the application of gas production from natural gas hydrate reservoirs and their potential application in the danube delta black sea abstract one important scientific objective of the national research project sugar submarine gas hydrate reservoirs was the development improvement and test of innovative concepts for the production of methane from natural gas hydrate reservoirs therefore different production methods such as the thermal stimulation using in situ combustion the chemical stimulation via injection of co2 as a gaseous liquid or supercritical phase and depressurization were tested alone or in combination at different scales in the laboratory experiments these ranged from pore and hydrate grain scale to 425 l reactor volume whereas numerical models were applied to describe the related processes from molecular to reservoir scale in addition the numerical simulations also evaluated the feasibility and efficiency of the application of these methods in selected areas such as the danube paleodelta in the black sea addressing the two dominant methane hydrate reservoir settings buried channel levee and turbidite systems it turned out that the injection of co2 or a co2 n2 gas mixture is not applicable for the danube paleodelta in the black sea because the local pressure and temperature conditions are too close to the equilibrium conditions of both the co2 hydrate and a co2 n2 mixed hydrate stability fields experiments using thermal stimulation and depressurization showed promising results but also some issues such as sufficient heat transfer in summary it can be said that the applicability and efficiency of each method has to be proven for each specific hydrate reservoir conditions based on the results obtained by numerical simulations the most promising and safe method for the production of ch4 from hydrate bearing sediments in the danube paleodelta would be the depressurization technique this study summarizes the main experimental and modeling results

low melt rates with seasonal variability at the base of fimbul ice shelf east antarctica revealed by in situ interferometric radar measurements basal melt is a major cause of ice shelf thinning affecting the stability of the ice shelf and reducing its buttressing effect on the inland ice the fimbul ice shelf fis in dronning maud land dml east antarctica is fed by the fast flowing jutulstraumen glacier responsible for 10 of ice discharge from the dml sector of the ice sheet current estimates of the basal melt rates of the fis come from regional ocean models autosub measurements and satellite observations which vary considerably this discrepancy hampers evaluation of the stability of the jutulstraumen catchment here we present estimates of basal melt rates of the fis using ground based interferometric radar we find a low average basal melt rate on the order of 1 m yr with the highest rates located at the ice shelf front which extends beyond the continental shelf break furthermore our results provide evidence for a significant seasonal variability

upper paleozoic oceanic crust in the polish sudetes ndsr isotope and trace element evidence the two main mafic ultramafic complexes outcropping in the polish sudetes around the sowie gory high grade massif mt sleza and nowa ruda have been studied for trace elements and nd sr isotopes upper paleozoic sm nd whole rock isochron ages are obtained for both massifs 353 21 ma 2 with i 8 8 0 1 mt sleza and 351 16 ma with i 8 5 0 1 nowa ruda the high initial nd point to a source characterized by a strong time integrated lree depletion and along with incompatible trace element patterns they substantiate the oceanic derivation of these massifs although a subduction related marginal basin setting cannot be totally precluded trace element and isotopic data rather suggest a normal mid ocean ridge origin for the sudetic ophiolites while these results are in marked contrast with previously inferred precambrian or early paleozoic ages remnants of oceanic crust as young as the early carboniferous are consistent with the local sedimentary record of pelagic facies from the frasnian to the tournaisian and they may provide a suitable explanation for the contrasted evolution displayed by different domains of the sudetes the sudetic ophiolites might tentatively be correlated with the upper paleozoic prasinites of the saxon lineament if a late hercynian ca 150 km dextral offset is assumed along the elbe fracture in that case they might represent the latest stage remnants of an oceanic suture zone between the saxo thuringian and moldanubian zones together with several other examples throughout europe these ophiolites provide compelling evidence for the involvement of oceanic crust and plate tectonic processes in the variscan belt

analysis of marine controlled source electromagnetic data for the assessment of gas hydrates in the danube deep sea fan black sea abstract marine controlled source electromagnetic csem data have been analyzed as part of a larger interdisciplinary field study to reveal the distribution and concentration of gas hydrates and free gas in two working areas was in the offshore danube fan in the western black sea the areas are located in the bulgarian sector in about 1500 m water depth wa1 and in the romanian sector in about 650 m water depth wa2 both areas are characterized by channel levee systems and wide spread occurrences of multiple bottom simulating reflections bsrs suggesting the presence of gas hydrates electrical resistivity models have been derived from two dimensional 2d inversions of inline csem data using a seafloor towed electric dipole dipole system comparing the resistivity models with coincident reflection seismic profiles reveals insight in the sediment stratigraphy of the gas hydrate stability zone ghsz gas hydrate and free gas saturation estimates have been derived with a stochastic approach of archie s relationship considering uncertainties in the input parameters available from drilling with the mebo 200 seafloor rig in wa2 the resistivity models generally reflect the transition of marine to lacustrine conditions expressed by a sharp decay of pore water salinities in the top 30 40 m below seafloor caused by freshwater phases of the black sea due to sea level low stands in the past in wa1 we derived saturation estimates of 10 20 within a 100 m thick layer at around 50 m depth below the channel which compares well with estimates from seismic p wave velocities the layer extends below the western levee with even higher saturations of 20 30 but high gas hydrate saturations are unlikely within the fine grained clayey sediment section and the high resistivities may reflect different lithologies of lower permeability and porosity the resistive layer terminates below the eastern levee where increasing resistivities at depth towards a stack of multiple bsrs indicate gas hydrate and free gas concentrations in the order of 10 to locally 30 wa2 is characterized by a major slope failure at the landward edge of the gas hydrate stability field next to the channel gas hydrate saturation estimates within the slump area are close to zero within the ghsz which is in agreement with coring results of the nearby mebo drill sites elevated resistivities below the steeply upward bending bsr lead to saturation estimates less than 10 of free gas that may have accumulated

sensitivity studies applied to a two dimensional resistivity model from the central andes summary long period magnetotelluric mt data have been collected along an e w profile across the central andes in northern chile and southern bolivia a 2 d resistivity model explaining these data was found by inverse modelling the model includes a prominent conductivity anomaly in the backarc of the south american subduction zone below the bolivian altiplano another comparatively localized anomaly occurs beneath the precordillera in the forearc the enhanced conductivity in the backarc correlates with reflective zones low seismic velocities and high seismic attenuation in contrast no correlation can be found in the forearc a strong seismic reflector in context with the down going slab and another reflector in the middle crust below the pre and western cordillera do not coincide with anomalous conductivity other 2 d models may also be consistent with the data we applied different techniques to find the range of relevant models one simple but useful approach is the direct use of the sensitivity matrix containing the partial derivatives of the data with respect to the model parameters the sensitivity of the model parameters to the data or data subsets can be visualized by calculating columnwise sums from the sensitivity matrix these sensitivities may be used to indicate model parameters that are less resolved by the data and thus should not form part of an interpretation another approach is to perform systematic studies to establish the validity of geologically important features of the model these studies comprise forward modelling and the use of a priori information combining all approaches generates a more complete assessment of the principal model features we conclude that a minimum depth extent of the altiplano conductor can be specified as approximately 50 km low sensitivity in the forearc beneath the longitudinal valley indicates a limited structure resolution and therefore may explain the absence of a conductive slab in the model the existence of the localized conductor below the precordillera can be established by high sensitivity finally we included the two seismic reflectors in the forearc as a priori information in the inversion process as a result the absence of a conductive slab in the model is probably a result of low sensitivity but cannot be totally excluded a conductive zone coinciding with the strong reflector below the pre and western cordillera is not manifested by the mt data

a numerical comparison of time and frequency domain marine electromagnetic methods for hydrocarbon exploration in shallow water in shallow water the frequency domain controlled source electromagnetic method is subject to airwave saturation that strongly limits the sensitivity to resistive hydrocarbon targets at depth it has been suggested that time domain csem may offer an improved sensitivity and resolution of these deep targets in the presence of the airwave in order to examine and test these claims this work presents a side by side investigation of both methods with a main focus on practical considerations and how these effect the resolution of a hydrocarbon reservoir synthetic noisy data for both time domain and frequency domain methods are simulated using a realistic frequency dependent noise model and frequency dependent scaling for representative source waveforms the synthetic data studied here include the frequency domain response from a compact broadband waveform the time domain step response from a low frequency square wave and the time domain impulse response obtained from pseudo random binary sequences these data are used in a systematic resolution study of each method as a function of water depth relative noise and stacking length the results indicate that the broadband frequency domain data have the best resolution for a given stacking time whereas the time domain data require prohibitively longer stacking times to achieve similar resolution

basin wide estimates of the input of methane from seeps and clathrates to the black sea numerous methane emitting bottom features such as seeps methane clathrate hydrates clathrates and mud volcanoes have been identified recently in the black sea the fluxes of methane from these sources averaged over large spatial scales are unknown here we take advantage of the fact that the black sea is a semi enclosed basin with restricted deep water circulation to establish first order estimates of basin wide fluxes of methane from these sources to the water column and atmosphere first we measured the natural radiocarbon content of methane 14c ch4 dissolved in the water column and emitted from seeps the 14c ch4 results showed that the dominant source of methane to the water column is emitted from seeps and a smaller source is diagenetically produced in relatively modern sediments the 14c ch4 results were then used to partition a basin wide total methane budget this analysis estimated the basin wide flux of methane from seeps and clathrates to the water column to be 3 60 to 4 28 tg yr 1 second a geochemical box model was used to calculate possible distributions of methane inputs from seeps and clathrates as well as provide additional estimates of the basin wide flux of methane from seeps and clathrates to the water column 4 95 to 5 65 tg yr 1 2006 elsevier b v all rights reserved

trans dimensional bayesian inversion of controlled source electromagnetic data in the german north sea this paper presents the first controlled source electromagnetic survey carried out in the german north sea with a recently developed seafloor towed electrical dipole dipole system i e hydra ii controlled source electromagnetic data are measured processed and inverted in the time domain to estimate an electrical resistivity model of the sub seafloor the controlled source electromagnetic survey targeted a shallow phase reversed seismic reflector which potentially indicates free gas to compare the resistivity model to reflection seismic data and draw a combined interpretation we apply a trans dimensional bayesian inversion that estimates model parameters and uncertainties and samples probabilistically over the number of layers of the resistivity model the controlled source electromagnetic data errors show time varying correlations and we therefore apply a non toeplitz data covariance matrix in the inversion that is estimated from residual analysis the geological interpretation drawn from controlled source electromagnetic inversion results and borehole and reflection seismic data yield resistivities of 1 m at the seafloor which are typical for fine grained marine deposits whereas resistivities below 20 mbsf increase to 2 4 m and can be related to a transition from fine grained holocene age to unsorted coarse grained and compacted glacial sediments pleistocene age interface depths from controlled source electromagnetic inversion generally match the seismic reflector related to the contrast between the different depositional environments resistivities decrease again at greater depths to 1 m with a minimum resistivity at 300 mbsf where a seismic reflector that marks a major flooding surface of late miocene age correlates with an increased gamma ray count indicating an increased amount of fine grained sediments we suggest that the grain size may have a major impact on the electrical resistivity of the sediment with lower resistivities for fine grained sediments concerning the phase reversed seismic reflector that was targeted by the survey controlled source electromagnetic inversion results yield no indication for free gas below it as resistivities are generally elevated above the reflector we suggest that the elevated resistivities are caused by an overall decrease in porosity in the glacial sediments and that the seismic reflector could be caused by an impedance contrast at a thin low velocity layer controlled source electromagnetic interface depths near the reflector are quite uncertain and variable we conclude that the seismic interface cannot be resolved with the controlled source electromagnetic data but the thickness of the corresponding resistive layer follows the trend of the reflector that is inclined towards the west

supergene processes on ore deposits a source of heavy metals the study of supergene processes i e secondary processes running in ore deposits and driven by thermodynamic nonequilibrium between ore and rock forming minerals and natural waters gasses etc is important in order to understand the migration of heavy metals from ore into their adjacent surroundings the contamination of the local environment can be characterized by the composition of pore waters the pb zn cu ore deposits of zlate hory czech republic have been chosen for a detailed study of pore solutions a simple model has been created to describe the evolution of supergene processes in the ore deposits this model is based on the determination of chemical composition of pore solutions the dilution of pore solutions of such mineral deposits results in acid mine drainage pore solutions can have during specific stages of their evolution relatively high concentrations of cu 0 09 mol kg zn 0 1 mol kg so4 0 8 mol kg and an extremely low ph 1 38 the supergene alteration of pyrite is the most important process determining the character of pore water this reaction causes significant acidification and is a leading source of acid mine drainage the leached zone originates from the interaction of pyrite and limonite increased concentrations of heavy metals and sulfates occur in pore waters the dynamic composition of pore waters within ore deposits undergoing the supergene process can be used to distinguish 1 three main zoneslimonite transition and primary zone and 2 two areas an area with the highest intensity of weathering processes and an area of weathering initiation in these areas the rate of sulfide oxidation is higher as a result of low ph from the study of these zones and areas we can further our knowledge of ore body pore solution acid mine drainage and contamination of the local environment

a seismic study of methane hydrate marine bottom simulating reflectors multichannel seismic reflection data have been analyzed from an area of clear bottom simulating reflectors bsrs on the northern cascadia subduction zone margin off vancouver island the reflector at a depth of about 300 m subbottom is interpreted to represent the base of a layer of methane hydrate or clathrate the shallow water depth of 1300 m and the 3600 m long hydrophone array have allowed bsr amplitude versus offset and high resolution velocity analysis as well as modelling of vertical incidence data the results of all three types of analysis can be best explained by a 10 to 30 m thick high velocity layer located immediately above the bsr about 300 m below the seafloor having a sharp base and transitional top in the layer about one third of the sediment pore spaces must be filled with hydrate ice there is no seismically detectable free gas beneath the bsrs these results put important constraints on models for the distribution and formation of bsr hydrate

marine controlled source electromagnetic study of methane seeps and gas hydrates at opouawe bank hikurangi margin new zealand marine controlled source electromagnetic csem data have been collected to investigate methane seep sites and associated gas hydrate deposits at opouawe bank on the southern tip of the hikurangi margin new zealand the bank is located in about 1000 m water depth within the gas hydrate stability field the seep sites are characterized by active venting and typical methane seep fauna accompanied with patchy carbonate outcrops at the seafloor below the seeps gas migration pathways reach from below the bottom simulating reflector at around 380 m sediment depth toward the seafloor indicating free gas transport into the shallow hydrate stability field the csem data have been acquired with a seafloor towed electric multi dipole system measuring the inline component of the electric field csem data from three profiles have been analyzed by using 1 d and 2 d inversion techniques high resolution 2 d and 3 d multichannel seismic data have been collected in the same area the electrical resistivity models show several zones of highly anomalous resistivities 50 m which correlate with high amplitude reflections located on top of narrow vertical gas conduits indicating the coexistence of free gas and gas hydrates within the hydrate stability zone away from the seeps the csem models show normal background resistivities between 1 and 2 m archie s law has been applied to estimate gas gas hydrate saturations below the seeps at intermediate depths between 50 and 200 m below seafloor saturations are between 40 and 80 and gas hydrate may be the dominating pore filling constituent at shallow depths from 10 m to the seafloor free gas dominates as seismic data and gas plumes suggest

geophysical and geochemical signatures associated with gas hydrate related venting in the northern cascadia margin this paper presents a comprehensive multidisciplinary study of cold vents associated with near seafloor gas hydrate several cold vents characterized by seismic blank zones have been identified on the northern cascadia margin near ocean drilling program odp site 889 890 the most prominent vent site bullseye vent has been the subject of intense geophysical and geochemical studies including two and three dimensional 2d 3d seismic imaging heat flow measurements piston coring with measurements of sediment physical properties and pore fluid geochemistry seafloor video observation and sampling with the unmanned submersible ropos the main seismically derived constraining observations are 1 blanking increases with seismic frequency 2 at low frequencies layers can be traced through the zones 3 blank zones widen with depth 4 blank zones are underlain by a bottom simulating reflector bsr and 5 no velocity anomalies were detected across the vents constraints from piston core and thermal probe analyses are 1 massive hydrate was recovered just below the seafloor at bullseye vent and 2 chemical alteration of sediments was observed by reduced magnetic susceptibility increased thermal conductivity and an elevated sulfate methane interface additional constraints are 1 no thermal anomaly was observed 2 widespread carbonates and active chemosynthetic communities were found and 3 elevated levels of methane were detected in the water column above bullseye vent we present a model for the seismic blanking at bullseye vent that honors the constraints from all observations the cold vents represent channels or networks of filamentous fractures containing hydrate and or free gas free gas can be present within the hydrate stability field only in fractures which may be coated with hydrate that prevents the inflow of water the overall concentration of hydrate or gas within the vent must be small because there was no observable velocity anomaly

multiple bottom simulating reflections in the black sea potential proxies of past climate conditions abstract a previously unknown pattern of multiple bottom simulating reflections bsrs occurs on high resolution reflection seismic data in the danube deep sea fan associated with acoustic features indicating free gas our study provides evidence that this pattern is developed in relation with the architecture of distinct channel levee systems of the danube fan channel levee systems hosting multiple bsrs act as relatively sealed gas bearing systems whose top is situated above the base of the gas hydrate stability zone bghsz inside these systems free gas accumulates below the bghsz under a combined lithological structural and stratigraphical control the uppermost bsr marks the current equilibrium bghsz for a gas composition of more than 99 methane model derived depths of the bghsz for different gas compositions and pressure temperature conditions show that multiple bsrs would correspond to the bghsz either for 1 layers of gas hydrates with high contents of heavy hydrocarbons or hydrogen sulphide or 2 stable climatic episodes with temperatures between glacial values and the present day conditions as the gas hydrate compositions required by hypothesis 1 are in sharp contradiction with the general background of the gas composition in the study area we suggest that multiple bsrs are most probably relics of former positions of the bghsz corresponding to successive steps of climate warming in this case they can provide sea bottom paleotemperature values for these episodes and hence they are potential new proxies for deciphering past climate conditions

complex network of channels beneath an antarctic ice shelf ice shelves play an important role in stabilizing the interior grounded ice of the large ice sheets the thinning of major ice shelves observed in recent years possibly in connection to warmer ocean waters coming into contact with the ice shelf base has focused attention on the ice ocean interface here we reveal a complex network of sub ice shelf channels under the fimbul ice shelf antarctica mapped using ground penetrating radar over a 100 km2 grid the channels are 300 500 m wide and 50 m high among the narrowest of any reported observing narrow channels beneath an ice shelf that is mainly surrounded by cold ocean waters with temperatures close to the surface freezing point shows that channelized basal melting is not restricted to rapidly melting ice shelves indicating that spatial melt patterns around antarctica are likely to vary on scales that are not yet incorporated in ice ocean models

the comparison of strata bound massive sulfide deposits using the fuzzy linguistic diagnosis of the zlate hory deposits czechoslovakia as an example the zlate hory ore deposits as an example of volcanogenic strata bound massive base metal sulfides occurring in the devonian formations of the jeseniky mts are compared with distinctive phanerozoic types representing this type of ore deposit i e with kuroko type rosebery type besshi type and cyprus type deposits the results of comparison performed with fuzzy linguistic diagnosis indicate close resemblance of the zlate hory deposits to rosebery type massive sulfides with regard to primary features however individual features point to certain original similarity with kuroko type deposits too the metamorphic history of the ore deposits studied was similar to that of the rosebery and besshi types

acoustic investigation of cold seeps offshore georgia eastern black sea several gas seeps and near surface gas hydrate deposits have been identified in 850 900 m water depth on the continental slope offshore batumi georgia eastern black sea using deep towed high resolution sidescan sonar data the seeps are located on a ridge named kobuleti ridge separating two canyons the supsa canyon north of the ridge and the deeply incised central canyon south of it the southern wall of this canyon shows signs for additional gas seeps gas seeps are shown by acoustic anomalies in the water column on raw sonar records and as high backscatter intensity areas on processed data the seeps on kobuleti ridge are characterised by carbonate deposits at the centre and a much wider area where finely disseminated gas hydrates are present fractures of a nw se direction are present at the seep sites and are probably related to the formation and decomposition of gas individual sites of gas emission apparently exert their influence for a circular area of up to 40 m in diameter gas geochemistry from gravity cores shows high gas content and a mixture of biogenic and thermogenic gases together with the presence of gas hydrates the seeps offshore georgia are different from other known cold seeps in the black sea such as shallow water seeps of biogenic gas and deep water mud volcanoes they are located in deep water within the zone of gas hydrate stability lack significant relief and are characterised by active gas emission and the absence of mud volcanism

the connection between natural gas hydrate and bottom simulating reflectors bottom simulating reflectors bsrs on marine seismic data are commonly used to identify the presence of natural gas hydrate in marine sediments although the exact relationship between gas hydrate and bsrs is undefined to clarify this relationship we compile a data set of probable gas hydrate occurrence as appraised from well logs of 788 industry wells in the northern gulf of mexico we combine the well log data set with a data set of bsr distribution in the same area identified from 3 d seismic data we find that a bsr increases the chances of finding gas hydrate by 2 6 times as opposed to drilling outside a bsr and that the wells within a bsr also contain thicker and higher resistivity hydrate accumulations even so over half of the wells drilled through bsrs have no detectable gas hydrate accumulations and gas hydrate occurrences and bsrs do not coincide in most cases

ground penetrating radar as a tool for probing the shallow subsurface of mars 1 design and testing of an impulse ground penetrating radar gpr for possible rover deployment on mars in 2009 is well underway the gpr has mass power volume and data rate targets of 0 5 kg 3 w peak 3400 cm3 and 0 3 mb d and will possess easily modified bistatic high frequency e g 500 600 mhz and monostatic rat tail e g 100 mhz antennas the gpr should be capable of measuring in situ radar properties on mars to depths of up to 10 20 m thereby helping to constrain near surface geology and structure initial gpr tests at the site of the 2001 fido rover field trials near cronese lake california confirm the value of the instrument in defining local geologic setting and in providing context for data collected using other rover science payload elements a rover deployed gpr may enable three dimensional mapping of local stratigraphy which in turn can assist in evaluating the history of aqueous activity and the accessibility of near surface water