detection and monitoring of water filled voids using transient electromagnetic method a case study in shanxi china shanxi province is a major coal base for the rapid development in china but heavy production of coal resources has left abundant water filled voids creating significant geologic hazards around coal mines it is necessary to quickly investigate the position and distribution of voids with effective geophysical methods the feasibility of transient electromagnetic tem method in detecting and monitoring water filled voids is analyzed using 3d finite element numerical simulation results as well as a case study in this paper the case study was mainly to analyze and monitor the conditions around the site of a power transfer station under construction in the west of shanxi province where many water filled mined out voids existed central loop tem sounding was carried out three times from january 2010 to april 2011 around the building footprint the low resistivity abnormal area had been repeatedly located and the survey results showed that the area of voids increased with time which indicated that the ground at the site was in an unstable and dangerous state the surveys provided more detailed geological information to the government for further safety arrangement and building re design

karst collapse susceptibility assessment a case study on the amalfi coast southern italy abstract this paper presents a study to evaluate the collapse susceptibility of a karst cave located along a slope on the amalfi coast southern italy and the presumable geomorphological evolution of the whole slope as a result of cave roof collapse in the study area several natural karst caves with volumes varying between 1000 and 10 000 m 3 were inventoried and the most likely genetic processes were identified some of them proved to be remnants of already collapsed caves while others were in precarious stability conditions the caves are usually located upslope or very close to the main populated resorts a detailed geological geomorphological and geostructural study was performed on a very wide deep cave called the saraceno cave on which the resort town of conca de marini has been built the study was carried out through a multidisciplinary approach which included classical field geological observations sometimes requiring the support of rock climbing geologists experts in photogrammetric surveys and terrestrial laser scanning techniques tls tls surveys allowed the reconstruction of an accurate geometric and geostructural model of the cave and its relationship with the upslope conca de marini resort furthermore it allowed the thickness of the cave overburden to be determined in detail ground surfaces most susceptible to collapse were also identified in the event of possible widespread collapse several buildings and transportation infrastructures could be involved as the cave is located on a very steep slope a debris avalanche could be triggered in the event of a catastrophic failure and the landslide debris characterized by a presumably high magnitude and velocity could involve a wide slope area down to the coast the failure evolution could be very similar to that which took place in amalfi in the late 19th century

processing and inversion of commercial helicopter time domain electromagnetic data for environmental assessments and geologic and hydrologic mapping helicopter time domain electromagnetic htem surveying has historically been used for mineral exploration but over the past decade it has started to be used in environmental assessments and geologic and hydrologic mapping such surveying is a cost effective means of rapidly acquiring densely spaced data over large regions at the same time the quality of htem data can suffer from various inaccuracies we developed an effective strategy for processing and inverting a commercial htem data set affected by uncertainties and systematic errors the delivered data included early time gates contaminated by transmitter currents noise in late time gates and amplitude shifts between adjacent flights that appeared as artificial lineations in maps of the data and horizontal slices extracted from inversion models multiple processing steps were required to address these issues contaminated early time gates and noisy late time gates were semiautomatically identified and eliminated on a record by record basis timing errors between the transmitter and receiver electronics and inaccuracies in absolute amplitudes were corrected after calibrating selected htem data against data simulated from accurate ground based tem measurements after editing and calibration application of a quasi3d spatially constrained inversion scheme significantly reduced the artificial lineations residual lineations were effectively eliminated after incorporating the transmitter and receiver altitudes and line to line amplitude factors in the inversion process the final inverted model was very different from that generated from the original data provided by the contractor for example the average resistivity of the thick surface layer decreased from 1800 to 30 m the depths to the layer boundaries were reduced by 15 23 and the artificial lineations were practically eliminated our processing and inversion strategy is entirely general such that with minor system specific modifications it could be applied to any htem data set including those recorded many years ago

continental crust composition constrained by measurements of crustal poisson s ratio deciphering the geological evolution of the earth s continental crust requires knowledge of its bulk composition and global variability the main uncertainties are associated with the composition of the lower crust seismic measurements probe the elastic properties of the crust at depth from which composition can be inferred of particular note is poisson s ratio this elastic parameter can be determined uniquely from the ratio of p to s wave seismic velocity and provides a better diagnostic of crustal composition than either p or s wave velocity alone1 previous attempts to measure have been limited by difficulties in obtaining coincident p and s wave data sampling the entire crust2 here we report 76 new estimates of crustal spanning all of the continents except antarctica we find that on average increases with the age of the crust our results strongly support the presence of a mafic lower crust beneath cratons and suggest either a uniformitarian craton formation process involving delamination of the lower crust during continental collisions followed by magmatic underplating or a model in which crust formation processes have changed since the precambrian era

subduction induced strain in the upper mantle east of the mendocino triple junction california we observe splitting of teleseismic shear waves at five stations of the berkeley digital seismic network located east of the mendocino triple junction in northeastern california that is dependent on the arrival direction of the seismic phases the observed variations with back azimuth cannot be explained with laterally varying anisotropy with a horizontal symmetry axis and are attributed to the presence of fabric with an inclined symmetry axis we assume that the anisotropy is caused by the preferred alignment of olivine crystals a grid search over possible orientations of the olivine a axes reveals that south of the mendocino triple junction they dip to the east whereas north of the triple junction they dip to the northeast on the basis of a comparison of the ray paths of our data to the spatial distribution of fast and slow p wave velocity anomalies in the upper mantle we conclude that the anisotropy is located within seismically slow regions and that the directions are controlled by the geometry of a steeply dipping fast p wave velocity anomaly assuming that the fast p velocity anomaly represents subducted slab material we conclude that the fabric beneath the stations north of the triple junction is most likely caused by the differential motion between this rigid strong down going plate and the surrounding mantle south of the triple junction the fabric may have developed while subduction of the farallon plate was still ongoing in this region prior to 6 ma however we prefer to attribute the observations to more recent asthenospheric flow associated with the opening of a slabless window beneath the north american lithosphere the flow is modulated by the presence of rigid lithosphere to the north and east

complicated seismic anisotropy beneath south central mongolia and its geodynamic implications abstract two years of high quality broadband seismic data from 69 temporary stations deployed in south central mongolia provide an opportunity to study the anisotropy forming mechanisms in this area the majority of shear wave splitting observations determined from the analysis of teleseismic sks phase are characterized by nw se trending fast directions with large splitting delay times greater than 2 0 s at six stations which is inferred to be generated by active asthenospheric flow the variation of the fast direction may be associated with deflection of asthenosphere around the deep siberian cratonic keel at the base of the lithosphere several of the ne sw trending fast directions with relatively small delay times observed in the gobi desert are parallel to the strike of the main faults and sutures which may represent lithospheric deformation in addition it is inferred that small scale hot mantle upwelling is responsible for generating a cluster of null measurements observed on the south of the hentiy mountain

anomalously thin transition zone and apparently isotropic upper mantle beneath bermuda evidence for upwelling 1 the origin of the bermuda swell and volcanism remains enigmatic the lack of an associated time progressive hotspot track and absence of present day volcanic activity make it difficult to reconcile with a deep mantle plume model we analyze shear wave splitting measurements to estimate mantle flow direction and receiver function stacks to place constraints on the mantle transition zone thermal structure ks phases exhibit well resolved null arrivals no splitting beneath the swell over a range of back azimuths we find that the 410 and 660 km discontinuities are 49 5 km and 19 5 km deeper than the global average respectively leading to a transition zone thickness that is 27 4 km thinner than the average together an apparently isotropic upper mantle and a thinned mantle transition zone suggest that mantle flow is primarily vertical beneath the swell consistent with the presence of hot buoyant mantle at depth

mechanism and mechanical model of karst collapse in an over pumping area through geological investigation of karst collapses at zaozhuang city china it was found that the mechanism of karst collapse in areas of excess water extraction is characterized by a seepage effect and that the seepage pressure effect is the initial factor that induces karst collapse the causation mechanisms for karst collapse can be divided into two phases the inter collapse phase and the surface collapse phase therefore based on the limit equilibrium theory this paper has established mechanical models for the surface collapse phase and determined values for the stability of the arch formed by the soil hole in an inter collapse phase in addition an evaluation of a karst collapses at zaozhuang city china was completed using mechanical models the results show that the mechanical models agree with the theory of karst collapse at zaozhuang city thus it is proved that the karst collapse models can be used for the evaluation of karst collapse in areas that are over pumped

detecting shallow caverns in china using tem to detect shallow anomalies under certain conditions electromagnetic methods can be more effective in reconnaissance surveying than high resolution surface seismic this case study describes the results of the transient electromagnetic method tem in an environment where initial field trials showed that surface seismic was difficult to employ effectively and expensive to implement

interpretation of sks waves using samples from the subcontinental lithosphere abstract the seismic properties of five south african kimberlite nodules have been calculated from petrofabric measurements these garnet lherzolite and harzburgite composition nodules 56 80 olivine are known from previous studies to have originated at depths of 120 170 km in the subcontinental lithosphere their in situ seismic properties have been calculated by extrapolating the elastic constants to the appropriate temperature 900 1050 c and pressure 3 0 3 5 gpa conditions the average of the five samples has a maximum s wave anisotropy v s of 3 7 which is sufficiently high to explain previously reported teleseismic sks delay times t in continental shield areas of up to 1 7 s the biggest delay time is observed when the foliation is vertical the lineation horizontal and the fastest s wave polarized parallel to the lineation i e an orientation for transcurrent motion delay times of over 1 s can only be generated by this orientation a strong mantle crust mechanical coupling is suggested for such situations the potential use of seismic anisotropy as an indicator of strain in the lithosphere has been investigated using experimental and simulated fabric data for olivine the most abundant phase 70 in the upper mantle the v p and v s seismic anisotropy increases with fabric strength and finite strain recrystallization tends to reduce fabric strength and seismic anisotropy resulting in saturation values for experimental and simulated fabrics which correspond to approximately 50 60 strain or 8 9 v s for pure olivine aggregates a survey of 25 naturally deformed peridotites of oceanic origin suggests an average maximum s wave anisotropy for the olivine component of 9 or about 8 for a lherzolite or harzburgite rock composition when the orthopyroxene component is taken into account the ophiolite samples are twice as anisotropic as the kimberlite nodules if an average anisotropy value is representative of the lithosphere then the sks delay times represent variations in anisotropic layer thickness for delay times over 1 s as the orientation is constrained to be foliation vertical and lineation horizontal the magnitude of s wave anisotropy is less sensitive than v p to variations in olivine volume fraction in range 50 100 and to deformation or fabric intensity further suggesting that s wave anisotropy is particularly apt for the determination of the anisotropic lithosphere thickness for smaller delay times there is some trade off between structural orientation and thickness

seismic reflection investigations of sinkholes beneath interstate highway 70 in kansas seismic reflection studies were performed across actively developing sinkholes located astride interstate highway 70 in russell county kansas results indicate that high resolution seismic reflection surveys are useful in the subsurface investigation of some sinkholes in particular we were able to delineate the subsurface vertical and horizontal extent of the sinkholes because of the excellent acoustical marker bed characteristics of the stone corral anhydrite the seismic reflection evidence presented here combined with borehole information from 1967 suggest that the stone corral anhydrite has been down dropped within one of the sinkholes as much as 30 m in 13 years the seismic reflection method is potentially useful in engineering studies of other sinkholes and karst features the seismic data presented here were obtained in the presence of relatively heavy highway traffic i e up to a few dozen vehicles per minute using the minisosie recording technique

the baikal rift zone the effect of mantle plumes on older structure abstract the main chain of sw ne striking cenozoic half grabens of the baikal rift zone brz follows the frontal parts of early paleozoic thrusts which have northwestern and northern vergency most of the large rift half grabens are bounded by normal faults at the northwestern and northern sides we suggest that the rift basins were formed as a result of transformation of ancient thrusts into normal listric faults during cenozoic extension seismic velocities in the uppermost mantle beneath the whole rift zone are less than those in the mantle beneath the platform this suggests thinning of the lithosphere under the rift zone by asthenosphere upwarp the geometry of this upwarp and the southeastward spread of its material control the crustal extension in the rift zone this nw se extension cannot be blocked by sw ne compression generated by pressure from the indian lithospheric block against central asia the geochemical and isotopic data from late cenozoic volcanics suggest that the hot material in the asthenospheric upwarp is probably provided by mantle plumes to distinguish and locate these plumes we use regional isostatic gravity anomalies calculated under the assumption that topography is only partially compensated by moho depth variations variations of the lithosphere asthenosphere discontinuity depth play a significant role in isostatic compensation we construct three dimensional gravity models of the plume tails the results of this analysis of the gravity field are in agreement with the seismic data the group velocities of long period rayleigh waves are reduced in the areas where most of the recognized plumes are located and azimuthal seismic anisotropy shows that these plumes influence the flow directions in the mantle above their tails the baikal rift formation like the kenya rio grande and rhine continental rifts achauer u granet m 1997 complexity of continental rifts as revealed by seismic tomography and gravity modeling in jacob a w b delvaux d khan m a eds lithosphere structure evolution and sedimentation in continental rifts proceedings of the igcp 400 meeting dublin march 20 22 1997 institute of advanced studies dublin pp 161 171 is controlled by the three following factors i mantle plumes ii older prerift linear lithosphere structures favorably positioned relative to the plumes and iii favorable orientation of the far field forces

evaluation of trenching ground penetrating radar gpr and electrical resistivity tomography ert for sinkhole characterization this paper explores the suitability and advantages of combining the trenching technique with geophysical surveys ground penetrating radar gpr and electrical resistivity tomography ert for sinkhole characterization in a mantled karst area the approach is applied to two active sinkholes concealed by anthropogenic deposits and formed by contrasting subsidence mechanisms collapse and sagging the ert section acquired across the collapse sinkhole images the clayey fill of the depression as an obvious low resistivity area showing the approximate location of the sinkhole edges spatially dense gpr surveys provide information on the position of the boundaries of the concealed subsidence structures and their three dimensional 3d internal geometry revealing the dominant subsidence mechanism we illustrate the impact of several factors on the quality of the gpr data such as sinkhole size nominal frequency of the antennas antenna shielding and the presence of backfilled excavations and above surface objects trenches provided detailed information on the subsurface structure of the sinkhole subsidence magnitude partitioning of the strain and the position of the sinkhole edges especially when they are deep enough and excavated across the central sector and perpendicular to the boundaries the stratigraphic and structural relationships observed in the trench were then used to infer the spatial evolution of the sinkholes e g enlargement their kinematic behavior episodic versus progressive and to differentiate discrete subsidence events and their associated magnitude numerical dates were used to estimate average subsidence rates and the recurrence of subsidence events such integrated data sets may be used as an objective basis to forecast the future behavior of potentially damaging sinkholes and to assess the associated hazard and risk copyright 2013 john wiley sons ltd

upper mantle flow beneath and around the hangay dome central mongolia mongolia represents the northernmost area affected by the india asia collision and it is actively deformed along transpressive belts closely associated with large scale strike slip faults the active and past mantle flow beneath this region is however poorly known in order to investigate deep mantle deformation beneath central mongolia and its relation with the surrounding major structures such as the siberian craton the gobi altay belt and the baikal rift a ns trending profile of broadband seismic stations has been deployed in the summer 2003 from the southern siberian craton to the gobi altay range crossing the entire hangay dome mantle flow is deduced from the splitting of teleseismic shear waves such as sks phases in eastern mongolia the permanent station uln in ulaanbaatar reveals the presence of two anisotropic layers the upper one being oriented ne sw close to the trend of lithospheric structures and the lower one nw se close to the trend of eurasia absolute plate motion along the ns profile in central mongolia seismic anisotropy deduced from sks splitting reveals a homogeneous nw se trending structure fully consistent with the observations made in the altay sayan in western mongolia the observed delay times of 1 5 to more than 2 0 s favor consistent mantle flow over large mantle thicknesses since the lithosphere is less than 100 km thick beneath central mongolia and since the observed fast directions are parallel to the trend of the lithospheric structures but also close to the trend of the absolute plate motion we propose that both the lithosphere and the asthenosphere may join their anisotropic effects beneath central mongolia to explain the large delay times although gps vectors represent the instantaneous displacement of the earth s surface and sks splitting the time and vertical integration of finite strain at depth we use the opportunity of the dense geodetic measurements available in this region to discuss the anisotropy pattern in term of present day deformation in the eurasia fixed reference frame gps and sks both depict a similar trend beneath central mongolia suggesting a lithospheric block escaping toward the east that could orient olivine a axes in the upper mantle within a transpressive tectonic regime a different behaviour is observed in western mongolia the gps vectors trend ns close to the regional compression direction whereas the fast sks directions trend ew suggesting a tectonic regime close to a mode of axial shortening generating the development of an ew trending foliation at depth we therefore propose that mongolia is a place where active and frozen lithospheric deformation may add their effects together with the sublithospheric flow in the three sources of anisotropy inferred a fundamental role is played by the siberian craton that acted as an undeformable core of the continent through time the frozen paleozoic and mesozoic structures wrap around the craton building up the fast anisotropic direction pattern the present day sublithospheric flow induced by the plate motion is likely deflecting around its deep roots finally the present day tectonic regime appears to be controlled by the presence of the craton to the north

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

quantification of non ideal effects on diagenetic processes along extreme salinity gradients at the mercator mud volcano in the gulf of cadiz abstract we present a transport reaction model traction specifically designed to account for non ideal transport effects in the presence of thermodynamic e g salinity or temperature gradients the model relies on the most fundamental concept of solute diffusion which states that the chemical potential gradient maxwell s model rather than the concentration gradient fick s law is the driving force for diffusion in turn this requires accounting for species interactions by applying pitzer s method to derive species chemical potentials and onsager coefficients instead of using the classical diffusion coefficients electrical imbalances arising from varying diffusive fluxes in multicomponent systems like seawater are avoided by applying an electrostatic gradient as an additional transport contribution we apply the model to pore water data derived from the seawater mixing zone at the submarine mercator mud volcano mmv in the gulf of cadiz two features are particularly striking at this site i ascending halite saturated fluids create strong salinity nacl gradients in the seawater mixing zone that result in marked chemical activity and thus chemical potential gradients the model predicts strong transport driven deviations from the mixing profile derived from the commonly used fick s diffusion model and is capable of matching well with the profile shapes observed in the pore water concentration data even better agreement to the observed data is achieved when ion pairs are transported separately ii the formation of authigenic gypsum several wt occurs in the surface sediments which is typically restricted to evaporitic surface processes very little is known about the gypsum paragenesis in the subseafloor and we first present possible controls on gypsum solubility such as pressure temperature and salinity pts as well as the common ion and ion pairing effects due to leaching of deep diapiric salt rising fluids of the mmv are saturated with respect to gypsum as well as celestite and barite several processes that could drive these fluids towards gypsum supersaturation and hence precipitation were postulated and numerically quantified in line with the varied morphology of the observed gypsum crystals gypsum paragenesis at the mmv is likely a combination of two temperature related processes gypsum solubility increases with increasing temperature especially in strong electrolyte solutions and the first mechanism involves the cooling of saturated fluids along the geothermal gradient during their ascent secondly local temperature changes i e cooling during the transition from mmv activity towards dormancy results in the cyclic build up of gypsum the model showed that the interpretation of field data can be majorly misguided when ignoring non ideal effects in extreme diagenetic settings while at first glance the pore water profiles at the mercator mud volcano would indicate strong reactive influences in the seawater mixing zone our model shows that the observed species distributions are in fact primarily transport controlled the model results for so4 are particularly intriguing as so4 is shown to diffuse into the sediment along its increasing concentration gradient also a pronounced gypsum saturation peak can be observed in the seawater mixing zone this peak is not related to the dissolution of gypsum but is simply a result of the non ideal transport forces acting on the activity profile of so4 and ca profiles

pseudo seismic wavelet transformation of transient electromagnetic response in engineering geology exploration 1 this paper presents some new theoretical analysis and numerical simulations of that transient electromagnetic diffusion field response is transformed into a pseudo seismic wavelet in engineering geology exploration it can clearly reveal the electric interface under ground to simplify the integral equation used in the transformation the integral range is separated into seven windows and each window is compiled into a group of integral coefficients then the accuracy of the coefficients is tested and the calculated coefficients are used to derive the pseudo seismic wavelet by optimization method finally several geo electric models are designed so that model responses are transformed into the pseudo seismic wavelet the transformed imaginary wave shows that some reflection and refraction phenomena appear when the wave meets the electric interface this result supports the introduction of the seismic interpretation in data processing of transient electromagnetic method

geodynamics of the western part of the mongolia okhotsk collisional belt trans baikal region russia and mongolia abstract after the western edge of the mongolian microcontinent joined the siberian continent in the region of central mongolia in the earliest permian these two continental blocks remained turned at an angle of about 120 with respect to each other and separated on greater extent of their present day boundary by an enormous gulf of the paleopacific called the mongolia okhotsk ocean closure of this ocean at the early middle jurassic boundary led to the complete collision of siberia and mongolia which by then had already become part of the mongolia north china continent this main collisional episode which lasted through the middle and late jurassic involved thrusting folding and magmatism and produced the mongolia okhotsk belt the onon island arc which was located in the mongolia okhotsk ocean was squeezed between the two major continents inasmuch as the third element the island arc was involved in the collision it is reasonable to distinguish two branches of the mongolia okhotsk suture these branches control the spatial distribution of gold mineralization in the trans baikal region on the southeastern periphery of siberia the crust thickened considerably after the collision and a plateau like uplift formed in the early cretaceous when compression ceased the collisional uplift collapsed and the thrusts were transformed into low angle normal faults the motions on which were responsible for the formation of rift basins and exhumation of metamorphic core complexes

heat flow structure and evolution of the lithosphere of mongolia abstract the geothermal characteristics of mongolia are presented based on heat flow measurements taken in boreholes and at the bottom of lake khubsugul and on heat flow values inferred from 3he 4he isotope ratios in spontaneous spring gases three types of regional heat flow distribution are recognized a narrow linear anomaly in the khubsugul segment of the baikal rift zone an area of regularly varying heat flow controlled by the age of the last tectonomagmatic activity in central mongolia and a zone of anomalously low heat flow in the south mongolian hercynian belt the radiogenic contribution to the terrestrial heat flow is determined a contribution which proved to be different in the southern and northern megablocks of mongolia variations in the thermal regime of the northern central and southern megablocks of mongolia are accounted for by their tectonic evolution

application of electrical resistivity tomography ert technique to detect underground cavities in a karst area of south korea recently the electrical resistivity tomography ert technique has been increasingly applied to underground cavity detection filled with groundwater and or clay in this study an ert survey was conducted to examine the spatial distribution and shape of underground cavities in a karst area in korea numerical ert modeling and inversion were carried out to select appropriate field survey parameters two geological structures similar to those that exist in the field survey area were modeled a sinkhole model and a vein type structure electrode configurations using pole pole pole dipole dipole pole and dipole dipole arrays were tested with the two geologic models and compared the numerical modeling showed that the resistivity distribution of the ert tomogram using the pole dipole array produced the best representation of the two models the pole dipole and pole pole array configurations were applied in an ert field survey using six boreholes the field ert results show that cavity areas filled with clay or groundwater appeared as low resistivity anomalies in the limestone formation this was particularly evident in the inclined vein type structures attributed to fracture zones where the field data were similar to the modeling results therefore the ert technique could be effectively used for detecting underground limestone cavities under similar geological conditions as those at our study area

faulting associated with large earthquakes and the average rate of deformation in central and eastern asia we determine approximate average rates of deformation in portions of eastern and central asia for the last 80 years these rates are based on estimates of source dimensions average displacements seismic moments and orientations of faults of all large earthquakes m 7 5 and as many other major earthquakes m 7 0 as possible in asia since 1900 a major part of this study is the compilation of these data for separate parts of asia we combine seismic moment tensors to estimate the average rotational strain or deformation tensors for these regions for the last 80 years we estimate that shortening across the tien shan has occurred at 11 mm yr between 5 and 19 mm yr left lateral shear on easterly trending planes in mongolia in northwestern tibet gansu and ningxia and on the xianshuihe fault in western sichuan has been very rapid more than 10 mm yr in each region and apparently as rapid as 40 mm yr in northwestern tibet gansu and ningxia slower rates of a few to 10 mm yr appear to characterize east west extension and conjugate north south shortening of tibet the earthquake history of the himalaya is consistent with rates of underthrusting of more than 10 mm yr but is probably less than the convergence rate of india with eurasia of about 50 mm yr the overall strain field is consistent with a large part of india s penetration into eurasia being absorbed by the extrusion of material out of india s way as a result southeast china moved at about 21 mm yr east southeast with respect to eurasia in the last 80 years with an uncertainty of about a factor of 2 in this estimated rate

application of the pole dipole resistivity technique to the detection of solution cavities beneath highways using a multiconductor electrode cable and a 30 post switching system pole dipole electrical resistivity measurements with a linear electrode array demonstrated a strong correlation between resistivity anomalies and subsurface voids at four sites in florida solution cavities below the water table are filled with a groundwater solute mixture which is characterized by a lower electrical resistivity than the enclosing country rock eocene and younger limestone air filled cavities above the water table exhibit markedly high resistivity anomalies confirmation drilling of postulated cavities and other anomalies suggests the method can be used with confidence for identification and location of highway threatening solution cavities with diameters as small as 3 to 5 m to a depth of 25 to 30 m

near surface site investigation and imaging of karst cave using comprehensive geophysical and laser scanning a case study in shandong china the karst development of jiao dong peninsula in shandong province has formed a unique karst landform and has become one of the typical karst areas in the north of china karst collapse occurred during the construction of high speed railways and caused many environmental problems to reveal the development situation of karst area in shandong the conventional surface geophysical techniques were used for karst exploration and location of key area and the results of drilling verification were in good agreement with the results of geophysical exploration at the same time the new technology in the field of surveying and mapping 3d laser scanning technology is cited in the engineering geophysical exploration and the key issue is the shape and size of the karst it makes up for the shortcomings of traditional geophysical exploration technology that can only be qualitative and cannot be quantitatively analyzed it realizes the transformation of karst exploration from regional detection to single cave exploration and better implements the concept of information construction it has contributed to the smooth progress of the project and environmental protection