karst water control and management in the hanxing mining area of north china the hanxing mining area of north china includes three coalfields fengfeng handan and xingtai six or seven coal seams can be commercially mined in permo carboniferous strata among which the lower three accounting for 37 of the total reserves are threatened with karst water from the underlain ordovician limestone hundreds of water inrush accidents have occurred and over 30 mines have been flooded resulting in heavy economic losses and casualties in order to avoid water inrushes and keep the mines safely operational dewatering in the karst aquifer was considered an essential measure unfortunately this practice has caused serious environmental problems such as surface subsidence sinkhole dry spring and water supply shortage on the basis of a series of investigations and tests in the last 20 years an alternative method mining with water pressure has been proposed and is the main focus of this paper by using this method the karst water in the limestone can be preserved to some extent and the coals can be mined in a relatively safe way

the bright moho reflection in the 1986 nevada passcal seismic experiment abstract detailed study of the reflected phases from the moho identified in the seismic reflection recordings of the 1986 nevada passcal lithospheric seismic experiment place important constraints on the fine structure and geological nature of the mohorovicic discontinuity two different spectral ratio techniques are used to estimate the reflectivity of the moho we evaluate the ratio of the reflected pmp phase to the incident source amplitude we also calculated the spectral ratio of the pmp phase with a reference reflection reflectivity estimates calculated using both spectral ratio techniques are very consistent high reflectivity within the range 0 28 0 39 was obtained the analysis of the spectral characteristics suggests a layered structure for the moho with an average thickness between 85 and 250 m these results require a layered moho structure with high impedance contrasts amplitude modeling using a reflectivity algorithm demonstrates that constructive interference from a 1 0 1 5 km thick layered structure produces amplitudes and waveforms comparable to the data to achieve such high reflectivities 20 25 of the moho consists of layers with velocities below 6 5 km s the remaining layers have velocities between 7 7 and 8 1 km s geologically the low velocities are consistent with velocities characteristic of basaltic magmas partial melts the high velocities are characteristic of mantle material the partial melts may represent an expression of present day underplating

numerical simulation for groundwater distribution after mining in zhuanlongwan mining area based on visual modflow with large scale coal resources being discovered and mined in mid west china latent environment problems gradually come into view in arid and semi arid region environmental impact assessment of mining on groundwater distribution is a vital mission before mining works in zhuanlongwan mining area zma data of surface elevation were performed by remote sensing information and arcgis the study area was divided into clayey fine sand aeolian loose sand weathered fracture and low permeability zones according to hydrologic conductivities and borehole data by simplifying as a single layer system of phreatic groundwater and optimizing with geological parameters in each unit zone a reasonable model of the groundwater distribution in steady state was then found and calibrated combined with local climate variable groundwater behavior was discussed in relation to different precipitations which reduced the loss of the drain in degrees the study results may give benefit and safety to management in mining as well as being refined in the future

mars water isotope d h history in the strata of the north polar cap inferences about the water cycle abstract a time varying stable isotope model for the d h history of mars water cycle is developed with variable atmosphere space loss rate ground and ice cap flux rates it considers coupled ground reservoirs and traces d h in the air and reservoirs secularly and over obliquity cycles the various flux rates are prescribed time variables that simulate surface flux and solar driven space loss rates predicted bulk averages for the ice cap ground ice reservoirs and atmosphere span the observed ranges reported by mumma et al mumma m j novak r e disanti m a bonev b dello russo n magee sauer k 2003 the martian atmosphere conference reports of sixth international conference on mars atmosphere no 3186 when the dominant obliquity cycle variations are scaled so that the model delivers present seasonal variations the present long term bulk d h average for the ice cap is 2 7 equivalent to 1700 in d wrt smow the obliquity driven d h cycle in the ice cap s layers varies between 3 and 6 the smaller more accessible reservoirs have larger bulk averages with the smallest being able to reach d h values over 9 within 10 5 years small hypothetical solar activity driven variations in the escape rate to space and in the fractionation constant krasnopolsky v a feldman p d 2001 science 294 1914 1917 for the escape process can produce a solar wiggle whose d h amplitude can reach 0 1 d amplitude of 100 because of the temporal variability a single modern measured atmospheric d h ratio at a particular ls cannot tell very much about the total water inventory of mars a bulk average for the northern ice cap and better still a dated vertical profile of d h from the ice cap would however go a long way towards illuminating the modern water history of mars the age and stability of the northern ice cap and the d h history locked in the layering is discussed an ice cap that is very young and exchanges its mass through the atmosphere often will necessarily have a large d h

estimating the near surface amplification factor to minimize earthquake damage a case study at west wadi hagoul area egypt the damage caused by earthquake occurrences in different localities all over the world necessitates the evaluation of the underground and or sub soil structure for strategic projects the case study is the proposed area for a new factory construction that lies 3 km west of suez cement factory in the area between kottamiya and ain sokhna the shallow seismic refraction survey was carried out through 10 major lines grid lines comprising 30 seismic profiles the microtremor measurements were done at 25 locations at the grid intersection points the obtained compressional p and horizontal shear sh wave velocities with the horizontal to vertical h v spectral ratios are used to deduce the subsurface structures to evaluate the elastic and dynamic properties and the transfer function at both the surface and bedrock the results illustrate that there is a good correlation between the fundamental frequencies deduced through the theoretical transfer function and the h v spectral ratio the maximum value of ground motion amplification factor of the study area is 3 3 at a corresponding frequency of 7 8 hz

sublimation and transport of water from the north residual polar cap on mars several features of the viking mars atmospheric water detection observations have suggested that the residual north polar cap on mars is a major source of atmospheric water during northern summer and that the water it supplies to the atmosphere is transported equatorward to low northern latitudes by summer s end we have explored the role of the north residual cap in the current martian water cycle by constructing models to assess the ability of the cap to supply water to the atmosphere and the ability of the atmosphere to transport it out of the polar regions from our sublimation model we conclude that the residual cap can sublime the 7 1014 g of water that appears in the atmosphere after ls 80 provided surface winds are high 10 m s the cap emissivity is low 0 9 or the exposed soil in polar regions contains ice that is accessible to the atmosphere in our view these requirements seem unlikely and we are drawn to the conclusion that other sources of water exist this conclusion is further supported by the results of two dimensional transport simulations which show that most of the water sublimed from the cap remains at high latitudes the polar circulation simply lacks the intensity and scale to move water very far from the cap a weak circulation places additional constraints on cap sublimation rates since abundant clouds and significant ice deposits would form just equatorward of the cap edge according to the model if the cap is allowed to sublime 7 1014 g of water such predictions are inconsistent with available data we suggest that the nature of the additional source is water desorbing from the nonpolar regolith

reflection seismology over azimuthally anisotropic media recent surveys have shown that azimuthal anisotropy due most plausibly to aligned fractures has an important effect on seismic shear waves previous work had discussed these effects on vsp data the same effects are seen in surface recording of reflections at small to moderate angles of incidence the anisotropic effects one different polarization components of vertically traveling shear waves permit the recognition and estimation of very small degrees of azimuthal anisotropy of order 2 1 percent as in an interferometer anisotropic effects on traveltime yield estimates of anisotropy which are averages over large depth intervals often raw field data must be corrected for these effects before the reflectors may be imaged two variations of a rotational algorithm to determine the principal time series are derived anisotropic effects on moveout lead to abnormal moveout unless the survey line is parallel to the fractures anisotropic effects on reflection amplitude permit the recognition and estimation of anisotropy hence fracture intensity differences at the reflecting horizon i e with high vertical resolution

fracture detection using p wave and s wave vertical seismic profiling at the geysers in a pilot vertical seismic profiling study p wave and cross polarized s wave vibrators were used to investigate the potential utility of shear wave anisotropy measurements in characterizing a fractured rock mass the caprock at the geysers geothermal field was found to exhibit about an 11 percent velocity variation between sh waves and sv waves generated by rotating the s wave vibrator orientation to two orthogonal polarizations for each survey level in the well the effect is generally consistent with the equivalent anisotropy expected from the known fracture geometry

stratigraphic relationships within martian polar cap deposits abstract deposits of layered ice and dust accumulate on the smooth and banded terrains of the north and south polar cap deposits while erosion of equator facing slopes of layered terrain expose these layers banded terrain occurs at exposures of irregular layers resulting from slight erosion of the feather edges of layers deposited on pole facing trough walls these deposits unconformably overlap onto adjacent layered terrain stripping of layers occurs in areas of strong multidirectional wind forming striped terrain local wind scour has also produced steep scarps with crescentic planform often associated with dune fields positioned immediately downwind unconformities are common within layered deposits in areas of complex topography at the north pole these indicate that episodes of deposition of 5 10 layers alternate with slight erosion of pole facing trough walls troughs that strike north south alternate between erosional widening and deepening and depositional infilling creating multiple unconformities troughs near the equatorward limit of polar deposits increase in relief by deposition on adjacent smooth terrain and locally by erosional deepening troughs may migrate poleward replacing the relief increase by depositional infilling when they near the poles

evaluation of anisotropy by shear wave splitting the polarizations of three component shear wavetrains carry unique information about the internal structure of the rock through which they pass specifically commonly observed shear wave splitting may contain information about the orientation of crack distributions this information cannot usually be recovered from shear waves recorded at the free surface because of interference with the interaction of the shear wave with the surface even for nearly vertical incidence however shear wave splitting in synthetic three component vertical seismic profiles in some cases may be interpreted directly in terms of the direction of strike of vertical cracks because the human eye is not skilled at identifying the phase relationships between three component seismograms played out conventionally as parallel time series the polarizations are displayed in orthogonal sections of the particle displacements to facilitate recognition and evaluation of the shear wave splitting estimating the orientations of cracks an

three component seismic land streamer study of an esker architecture through s and surface wave imaging we deployed a newly developed 3c microelectromechanical system based seismic land streamer over porous glacial sediments to delineate water table and bedrock in southwestern finland the seismic so

management of karst water resources in mining area dewatering in mines and demand for water supply in the dongshan mine of taiyuan shanxi province north china coalfields in north china contain six to seven coal seams in the permo carboniferous strata the coal seams are underlain by the ordovician limestone large scale dewatering or depressurizing of the karst aquifer was considered essential to avoid water inrushes and keep the mines safely operational this practice however has caused water supply shortage in the mining areas the most effective solution to this conflict is to use the uncontaminated karst water from the mines for water supply this paper explores a management model to maximize the utilization of the karst water while maintaining the safe operation of the mines the model can provide essential information on water resource distribution for decision makers the model was applied to the dongshan coal mine in taiyuan city china

internal layers in an accublation ice cap a test for flow abstract assuming the white areas of the north polar cap of mars accumulate water ice and the dark scarp trough spirals ablate and assuming there is ice motion from one type of zone to the other the question is asked what do the isochrone layers look like internally and on the surface a simple two dimensional time varying isothermal model is used to demonstrate that the layering internally and in the ablation zones is strongly determined by the migrating scarp system and that waviness and discontinuities are to be expected in the internal layering and in the surface expressions of the layers on the ablation scarps

observations of the north polar region of mars from the mars orbiter laser altimeter elevations from the mars orbiter laser altimeter mola have been used to construct a precise topographic map of the martian north polar region the northern ice cap has a maximum elevation of 3 kilometers above its surroundings but lies within a 5 kilometer deep hemispheric depression that is contiguous with the area into which most outflow channels emptied polar cap topography displays evidence of modification by ablation flow and wind and is consistent with a primarily h2o composition correlation of topography with images suggests that the cap was more spatially extensive in the past the cap volume of 1 2 3 10 6 to 1 7 3 10 6 cubic kilometers is about half that of the greenland ice cap clouds observed over the polar cap are likely composed of co 2 that condensed out of the atmosphere during northern hemisphere winter many clouds exhibit dynamical structure likely caused by the interaction of propagating wave fronts with surface topography

a geological assessment method of floor water inrush risk and its application abstract the risk assessment of floor water inrush is essential to assure the safe production in a coal pit floor aquifuge is the key factor controlling water inrush both the impermeability and the resistance to water pressure of an aquifuge vary with its lithology and structure features with the increase of mudstone content the permeability and resistance to water pressure of the floor drops the dense tectonic fissures in floor will transform intact blocky structure into very blocky or blocky disturbed structure lower the resistance to water pressure increase the permeability of floor aquifuge and thereby will raise the risk of water inrush considering the lithology and structure features and based on a conventional water inrush coefficient a coal floor water inrush risk assessment method is put forward with fangezhuang coal mine of china as a case study the implementation of this method is elaborated

the role of sublimation for the formation of the northern ice cap results from the mars orbiter laser altimeter abstract the evolutionary history of the martian ice caps is practically unknown and the caps are key to understanding the climatic history of mars sublimation and ice flow are two hypotheses that have recently been suggested to explain the observed form of the northern ice cap here we present a sublimation model and compare the shape of the cap obtained from this model with mars orbiter laser altimeter mola observations of the north polar region this model can reproduce the shape of the cap and individual troughs sublimation is an important process as are flow and wind erosion we were able to constrain the time scales of sublimation only to about two orders of magnitude 1 100 million years this estimate depends on many unknown parameters such as friction velocity and wind speed over the ice caps these can be determined only by direct measurement over the surface

if martian ice caps flow ablation mechanisms and appearance abstract assuming that the northern ice cap of mars is thick enough to flow like terrestrial ice sheets a model is presented that explains i the origins movement and spiral nature of the scarp trough complexes ii the reentrant valleys like chasma boreale and iii the layered terrain accumulation and ablation are discussed in relation to the scarps and a model is developed relating them to ice flow and scarp velocities and to the particle paths within the ice cap a brief summary of terrestrial ice sheet flow and mass balance is given in order to illustrate and clarify the concepts used to model the martian ice caps

analysis of shear waves with respect to splitting near the san andreas fault summary shear wave recordings acquired by vertical seismic profiling in the cajon pass deep scientific drillhole california have been investigated with respect to shear wave splitting using various methods the methods used should enable detection of possible anisotropy induced ai shear wave splitting consistent with a system with hexagonal symmetry and a horizontally oriented axis of symmetry careful investigation of the direct shear waves leads to the conclusion that a1 shear wave splitting consistent with this simple model cannot be observed with the methods applied the lack of such a1 shear wave splitting is probably partly caused by the low difference between the maximum and minimum principal stress in the area which is probably too modest to vertically align cracks and microcracks to any significant degree the propagation and polarization of the shear waves in this area is thus probably more controlled by factors related to the complex geology rather than to the current stress field the lack of detected a1 shear wave splitting does not however imply that the medium is isotropic the polarization diagrams show clear evidence of shear wave splitting which most likely indicates the presence of an anisotropy of higher order

the use of seismic shear waves and compressional waves for lithological problems of shallow sediments from a great variety of in situ shear wave experiments i e reflection refraction and borehole surveys in the shallow sediments of the north german plains several specific properties have been derived shear waves s differ from compressional waves p in that correlations have been established between v s and the confining pressure and between reduced v s values and several lithological parameters like the grain size of sandy material more lithological and hydrological information is obtained by using s and p wave surveys along the same profile the best information on a sedimentological structure is obtained by the simultaneous observation of v s v p q s and q p

waxing and waning of the perennial north polar h2o ice cap of mars over obliquity cycles abstract the perennial north polar h2o ice cap of mars is investigated with the dynamic thermodynamic ice sheet model sicopolis computational results for flow velocities ice temperatures and surface accumulation ablation rates are presented for the steady state with present conditions as well as for transient scenarios over idealized obliquity cycles with periods of 1 3 myr and 125 kyr the transient simulations lead to a stop and go type dynamics with a cold and almost stagnant modern ice cap and a warmer flowing ice cap for past large obliquity periods the most likely scenario for the present ice cap comprises an ice volume of 1 2 million km3 a maximum thickness of 3 km the absence of pronounced local isostasy h2o ice accumulation rates of the order of tenth mm water equivalent w e per earth year yr flow velocities of the order of mm yr and an ice base far below pressure melting

seismological studies at parkfield ii search for temporal variations in wave propagation using vibroseis abstract for more than 3 years the propagation characteristics of shear waves have been monitored for paths near the 1966 hypocenter at parkfield the presumed nucleation site for the expected next m 6 earthquake there data have been collected repeatedly 33 sets as of april 1991 from eight s wave vibroseis source positions into the 10 borehole installed three component seismometers of the local high sensitivity digital network twenty second correlated records from a 6 to 24 hz sweep are acquired and the entire seismogram is viewed for analysis as the elastic response of the local crustal structure which includes the san andreas fault zone amplitudes travel times spectra and particle motions of the p and s waves are monitored for indications of any changes in these properties that may be attributed to processes associated with nucleation the horizontal vibrator at each source point is positioned at three surface orientations to study anisotropy unorthodox methods have been developed to display the waveform properties in time in order to visualize the resulting massive data sets the first order variations seen in some of the parameters are attributed to changes from dry to wet conditions in the shallow subsurface due to the seasonal rainfall which affects the source function of the vibrator corrections have been devised for these source specific variations secular variations not obviously coupled to seasonal near surface changes are also seen in some localized time intervals within the 20 sec records the most striking of such changes is a progressive travel time decrease at rates of 3 to 7 msec year seen for late arrivals 7 to 11 sec travel time on at least five paths into station vca which sample the region southeast of the anticipated epicenter at middle mountain this anomaly appears to be genuine and is now the subject of intensified study in the same general area along the fault in the southwestern block the direct s wave is clearly split with the faster of the split phases polarized parallel to the fault zone a result in agreement with that from the vsp survey in the varian well on the northeast side of the fault

groundwater dewatering optimization in the shengli no 1 open pit coalmine inner mongolia china impacted by groundwater faults lithology and other factors the slope of the shengli no 1 open pit coalmine has been in a state of instability among these factors groundwater in the quaternary aquifer is considered primary thus an optimum design for dewatering well pumping rates is presented in this paper a two dimensional groundwater simulation model is built to characterize the groundwater flow of the study area a steady state model was applied to the observed data head and discharge to verify and calibrate the groundwater model the pilot point method with a regularization option provided by parameter estimation was used to identify the hydraulic conductivity field afterward a groundwater optimization model is integrated with the calibrated simulation model to realize groundwater dewatering optimization in the studied open pit coalmine and an optimization method called modified pareto dominance based real coded genetic algorithm is adopted taking into account the safety of the mine slope and dewatering wells seepage discharge is added to objective function and the maximum aquifer saturated thickness is set as the constraint condition in the optimization model the results indicate that the dewatering optimization procedure developed in this paper can serve as a useful template and framework for solving mining related water problems

origin of reflections from the brevard fault zone the brevard fault zone is a belt of mylonitic metamorphic rocks that extends northeast over 700 km from alabama into virginia seismic reflection studies show that the fault zone produces excellent reflections which dip gently to the southeast and sole at depth the origin of these reflections has been investigated by measuring compressional wave velocities to 800 mpa confining pressure in 127 samples obtained from drill core which continuously sampled the fault zone to a depth of over 300 m densities are reported as well as chemical analyses at selected depths anisotropy at elevated pressures ranges within the fault zone from less than 5 to over 26 similarly the fault zone rocks show significant chemical variability with sio2 ranging from 58 0 to 70 4 by weight synthetic seismograms generated from the velocity and density measurements show that the reflections originate within the brevard fault zone from the complex interaction of compositional variations and seismic anisotropy resulting from ductile strain essential to this study has been the continuous coring of a major section of the brevard fault zone which has provided the necessary stratigraphic control as well as unweathered samples for laboratory studies

multiply polarized shear wave vsps from the cajon pass drillhole a 3 component vsp data set was acquired in the cajon pass drillhole with a multiply polarized shear wave source and a conventional p wave source producing a 9 component data set the vsp data show effects on the full wavefield from the sediment granite interface mode converted waves are identified with significant scattering of s wave energy from the leading p wavefront hodographs are used to display s wave particle motions in two dimensions shear wave splitting is observed in the hodographs the shear wave particle motion is used to infer anisotropy orientation with respect to the local strike of the san andreas fault stress induced fracturing is assumed to be a possible cause of the shear wave splitting a variation of particle motion orientation with depth is observed implying a variation in anisotropy orientation as a function of depth

a model for co isotopic signatures of evolving ground ice in the cold dry environments of earth and mars abstract the basics of the model rego are summarized including diffusive water vapor transport ice content adsorption and the isotopic ratios of the various water species inclusion of a temperature and stress strain solution is also described as are the effects of cracking when the tensile breaking strengths are exceeded cracking is viewed as a multi scale phenomena whereby the larger cracks are produced by chaining together smaller ones after some validation the model is applied to the upper university valley antarctic dry valleys data and to the phoenix landing site at lat 69n on mars for the university valley the model when forced by measured diurnal temperature cycles and known relative humidity reproduces some of the complex the ice content and isotope structure found in the upper university valley ground ice cores the model takes a few hundred years to fill the pores just under the ice table the excess ice observed in the university valley cores can be produced by thermal cracking combined with the diurnal temperature cycle time taken to achieve the observed excess ice content is of order 10 4 years there is limited subsurface data for the phoenix site but there are measured ice table depths surface thermal properties and met variables there is enough to do diurnal and seasonal runs of the rego model as with the university valley the upper few tens of centimeters icing are controlled by the diurnal temperatures largely in the warmer part of the year the observed ubiquitous pore full ice right at the ice table could be produced from a dry soil in about 10 3 a and the nearly pure ice patches could be produced by the cracking diffusion mechanism in about million years if shear stresses are included emplacement of ice down to 10 m is possible using the seasonal temperature cycle and cracking excess ice in the upper meter could produced by the model in about 6 10 6 a if the temperature at the phoenix site was 10 20 deg warmer

shear wave anisotropy and the stress field from borehole recordings at 2 5 km depth at cajon pass summary 53 local earthquakes recorded at 2 5 km depth in the cajon pass scientific borehole are analysed for shear wave splitting the time delays between the split shear waves can be positively identified for 32 of the events modelling these observations of polarizations and time delays using genetic algorithms suggests that the anisotropic structure near cajon pass has orthorhombic symmetry the polarization of the shear waves and the inferred strike of the stress aligned fluid filled intergranular microcracks and pores suggests that the maximum horizontal compressional stress direction is approximately n13 w this is consistent with previous results from earthquake source mechanisms and the right lateral strike slip motion on the nearby san andreas fault but not with stresses measured within the uppermost 3 km of the borehole this study suggests that the san andreas fault is driven by deeper tectonic stresses and the present understanding of a weak and frictionless san andreas fault may need to be modified the active secondary faulting and folding close to the fault are probably driven by the relatively shallow stress as measured in the 3 5 km deep borehole

on the orbital forcing of martian water and co2 cycles a general circulation model study with simplified volatile schemes 1 variations in the martian water and co2 cycles with changes in orbital and rotational parameters are examined using the geophysical fluid dynamics laboratory mars general circulation model the model allows for arbitrary specification of obliquity eccentricity and argument of perihelion as well as the position and thickness of surface ice exchange of co2 between the surface and atmosphere is modeled generating seasonal cycles of surface ice and surface pressure water is allowed to exchange between the surface and atmosphere cloud formation is treated and both cloud and vapor are transported by modeled winds and diffusion exchange of water and co2 with the subsurface is not allowed and radiative effects of water vapor and clouds are not treated the seasonal cycle of co2 is found to become more extreme at high obliquity as suggested by simple heat balance models maximum pressures remain largely the same but the minima decrease substantially as more co2 condenses in the more extensive polar night vapor and cloud abundances increase dramatically with obliquity the stable location for surface ice moves equatorward with increasing obliquity such that by 45 obliquity water ice is stable in the tropics only ice is not spatially uniform but rather found preferentially in regions of high thermal inertia or high topography eccentricity and argument of perihelion can provide a second order modification to the distribution of surface ice by altering the temporal distribution of insolation at the poles further model simulations reveal the robustness of these distributions for a variety of initial conditions our findings shed light on the nature of near surface ice rich deposits at midlatitudes and low latitudes on mars

the hydrostatic corer selcore a tool for sediment sampling and geophysical site characterization hydrostatic energy is used to power an active device for sediment sampling and geophysical site characterization in the selcore design a steel tank with built in drive unit constitutes the core head the difference between ambient water pressure and atmospheric pressure in the tank provides the energy the selcore prototype enters the seabed as a gravity corer and automatically shifts into pile driving mode with up to 52 duty cycles without the need for an external trigger mechanism the corer has operated in water depths from 300 to 3500 m operation at depths shallower than 300 m including on dry land can be facilitated using auxiliary water pressure penetration and recovery is generally more than two times the performance of a gravity corer of equivalent weight the added utilization of hydrostatic energy has particular advantage in cases of relatively high shear strength sediments as well as attempts to core shallow bedrock below a sediment cover selcore has potential as a seabed seismic hammer source and initial land tests show good signal repeatability estimates of sediment thickness and seismic velocity obtained from the inversion and interpretation of the dominant rayleigh surface waves corresponds closely to the shallow borehole stratigraphy at a land test site

influence of coal mining on regional karst groundwater system a case study in west mountain area of taiyuan city northern china karstic limestone formations in the west mountain area are important water resources for taiyuan city in shanxi province northern china which is also known for its large scale coal mining production in this study area groundwater is not only exploited for water supply purposes but also drained because of coal mining the process of coal mining changes both the quantity of the karst springs and the quality of karst groundwater system because of overexploitation and overdrainage in this paper the influence of coal mining on the groundwater is analyzed from a qualitative and quantitative perspective the hydrochemical analysis results reflect the relationship of the recharge runoff and drainage the features of the medium and water rock interactions based on a qualitative understanding of the geological deposition and characteristics of the groundwater flow system three dimensional groundwater flow models are established and applied to several scenarios to explore the quantitative influence and allow better protection of the groundwater environment and better utilization of water resources

seismic imaging of the shallow subsurface shear wave case histories obtaining high resolution images of the geology and hydrogeology of the subsurface in the depth range from ground level to 50 m is one of the major challenges of modern geophysics the methods which are commonly used such as compressional wave surveys and ground penetrating radar often suffer from adverse effects caused by the near surface conditions changes in water saturation and various sources of noise this paper demonstrates some of the advantages offered by the use of shear wave seismology and by the combination of shear and compressional wave seismic methods in shallow subsurface investigations multicomponent shallow seismic tests were carried out at four different sites to examine the effectiveness of different acquisition geometries under a variety of near surface geological conditions near surface conditions encountered at the sites included thick clays clay sand sequences overlying chalk mudstone overlying granodiorite bedrock and landfill material under all conditions shear wave data acquisition was found to have advantages over compressional wave acquisition for the investigation of the shallow subsurface shear head waves being unaffected by water saturation achieved penetration to greater depths at a site in crewkerne dorset where compressional head wave penetration was limited to the near surface layers better vertical resolution was achieved at shallow depths using shear wave reflection energy at a landfill site shear wave reflections from shallow interfaces were in some cases less affected by noise compared with the equivalent compressional wave reflections combinations of shear and compressional wave data recording allowed the measurement of a poisson s ratio log and gave indications of seismic anisotropy at two sites where dipping clay layers were present

radiation and receiver pattern of shear and compressional waves as a function of poisson s ratio shear s wave studies in addition to compressional p wave surveys have revealed that s wave velocities are much more variable than p wave velocities this strongly affects poisson s ratio especially in young sediments it is shown that has a great influence on the directivity pattern i e on the radiation and receiving characteristic of horizontal sources and receivers for their calculation well known surface boundary conditions and white s statement of the reciprocity relation white 1965 are used they also form the basis for the combination of source and receiver patterns essential for practical field work the various combinations of horizontally and vertically arranged sources and receivers are investigated with regard to their directivity pattern their amplitude ratio and in general to their usefulness in seismic prospecting

shear wave vibrator signals in transversely isotropic shale the experiments of robertson and corrigan 1983 on shale are among the first three component field observations of shear waves in transversely isotropic media to be published their data are reprocessed to highlight the effects of the shale s anisotropy on shear waves two results emerge first shear wave splitting in a transversely isotropic substrate is most easily observed when the vibrator baseplate is oriented so that both sh and sv waves reach the geophone second the sv wave polarization deviates significantly from perpendicular to the raypath both results may significantly affect the interpretation both are found to agree with theoretical results and are modeled successfully by synthetic seismograms

shear wave anisotropy in the parkfield varian well vsp abstract a vertical seismic profile vsp survey was run to 1334 m depth in the instrumented varian well 1 4 km from the san andreas fault trace at parkfield california to test the sensor string shortly after its permanent installation the cable subsequently failed near the 1000 m level so the test survey represents the deepest data acquired in the study a shear wave vibrator source was used at three ofsets and two orthogonal orientations and the data have been processed for p and s wave velocities and for s wave velocity anisotropy velocities are well determined 3 3 and 1 9 km sec respectively at the deeper levels and the s waves are seen clearly to be split by anisotropy below about 400 m some 8 per cent velocity difference is apparent between polarizations parallel to and perpendicular to the san andreas fault faster and slower respectively and the difference seems to decrease with distance from the fault suggesting that the cause may be the fabric of the fault zone repeated surveys at the 1000 m depth are being conducted as part of the parkfield monitoring program

migration of noisy crustal seismic data a slowness weighted diffraction stack algorithm is used to migrate crustal seismic reflection data slowness information is extracted from the data using a slant stack beam forming process the main purpose of beam forming is to improve the signal to noise ratio over a given range of slowness values localized slant stacks are used to design a coherency weighted slowness filter in the time distance domain through migration the subsurface structure and the observed seismic data are tied via slownessselective diffraction curves a combination of nonlinear slowness filtering with migration gives excellent noise rejection and leads to an improved image in the depth domain the method which is particularly effective for migrating moderate to steep dipping events with low signal to noise ratio is applied to various poststack and prestack synthetic data examples and to a deep crustal data set collected on vancouver island as part of the canadian lithoprobe project

introduction to the 4th mars polar science and exploration conference special issue five top questions in mars polar science abstract as an introduction to this icarus special issue for the 4th mars polar science and exploration conference we discuss five key questions in mars polar science gleaned from plenary discussions and presentations held at the conference these questions highlight major unknowns in the field 1 what are the physical characteristics of the polar layered deposits pld and how are the different geologic units within beneath and surrounding the pld related 2 how old are the pld and what are their glacial fluvial depositional and erosional histories 3 what are the mass and energy budgets of the pld and what processes control these budgets on seasonal and longer timescales 4 what chronology compositional variability and record of climatic change is expressed in the stratigraphy of the pld 5 how have volatiles and dust been exchanged between polar and non polar reservoirs and how has this exchange affected the past and present distribution of surface and subsurface ice

meteoritic evidence for a previously unrecognized hydrogen reservoir on mars abstract fluvial landforms on mars suggest that it was once warm enough to maintain persistent liquid water on its surface the transition to the present cold and dry mars is closely linked to the history of surface water yet the evolution of surficial water is poorly constrained based on in situ hydrogen isotope d h analyses of quenched and impact glasses in martian meteorites we provide evidence for the existence of a distinct but ubiquitous water ice reservoir d h 2 3 times earth s ocean water that lasted from at least the time when the meteorites crystallized 173 472 million years ago to the time they were ejected by impacts 0 7 3 3 million years ago but possibly much longer the origin of this reservoir appears to predate the current martian atmospheric water d h 5 6 times earth s ocean water and is unlikely to be a simple mixture of atmospheric and primordial water retained in the martian mantle d h earth s ocean water this reservoir could represent hydrated crust and or ground ice interbedded within sediments our results corroborate the hypothesis that a buried cryosphere accounts for a large part of the initial water budget of mars

estimation of elastic contrasts in a layered model from seismic ps to pp amplitude ratios summary we present a method to estimate seismic velocity and density contrasts at a given interface in a 1 d layered model using ps to pp reflection amplitude ratios the velocity structure above the reflector is constrained by traveltime modelling and the amplitude ratios are determined using the same source receiver pair for the measured pp and ps amplitudes commonoffset geometry thereby source and receiver site effects are cancelled and the remaining propagation effects are included in the ray theoretical forward modelling of theoretical ps topp ratios a minimization of the least squares misfit between observed and modelled ratios provides the remaining elastic parameters below the reflector of interest p velocity p to s velocity ratio density 1 d examples and a 2 d synthetic case study with a dipping reflector and a laterally varying overburden demonstrate the possibilities and limitations of the method an application of the method to a 0 6 km deep reflector below the campi flegrei caldera italy reveals a strong contrast with a p velocity increase from less than 2 to 3 5 km s 1 and a decrease of the p to s velocity ratio from 3 6 to 1 75 the proposed ps to pp amplitude ratio analysis is applicable for wide angle seismic reflection data especially when strong elastic parameter contrasts are expected and when source amplitudes or site effects are poorly known

dynamic and isotopic evolution of ice reservoirs on mars abstract the layered polar caps of mars have long been thought to be related to variations in orbit and axial tilt we dynamically link mars s past climate variations with the stratigraphy and isotopic composition of its ice by modeling the exchange of h2o and hdo among three reservoirs the model shows that the interplay among equatorial mid latitude and north polar layered deposits npld induces significant isotopic changes in the cap the diffusive properties of the sublimation lags and dust content in our model result in a cap size consistent with current mars the layer thicknesses are mostly controlled by obliquity variations but the precession period of 50 kyr dominates the variations in the isotopic composition during epochs of relatively low and nearly constant obliquity such as at present isotopic sampling of the top 100 m may reveal climate oscillations unseen in the layer thicknesses and would thus probe recent precession driven climate cycles

p and sv velocity structure of the south portuguese zone fold and thrust belt sw iberia from traveltime tomography imaging the architecture of the shallow crust of the south portuguese zone fold and thrust belt is essential to extend surface mapped geological information to depth and to help in developing model

correlation of paleotectonic fracture and microfracture orientations in cores with seismic anisotropy at cajon pass drill hole southern california fractures and microfractures in oriented cores from the cajon pass drill hole southern california have strong preferred orientations there are two major sets of extensional fractures and microfractures that have northwest and northeast strikes and vertical dips relative and absolute densities of both sets vary greatly within a single core the regional tectonic history implies that these fractures and microfractures probably formed before late miocene pliocene vertical seismic profiling experiments in the drill hole show shear wave splitting with polarization directions parallel to the fracture and microfracture orientations the measured seismic anisotropy is due to these inherited deformation fabrics and does not appear to be caused by the current local stress field

fracture related reflectors in basement rock from vertical seismic profiling at cajon pass multi azimuth vsp data acquired between 500 and 2000 meters deep in crystalline rock penetrated by the cajon pass deep scientific borehole show several reflectors intersecting the hole the reflectors correlate with vsp amplitude data drilling and cutting logs and various geophysical logs most appear to be related to fracture zones or lithologic transitions accompaanied by fracturing mineral alteration and fluid circulation amplitude systematics from two azimuthally different offsets are consistent with the presence of a high angle fault in the neighborhood of the well

microearthquake s wave observations from 0 to 1 km in the varian well at parkfield california abstract high gain three component seismometers from 0 to 1 km deep along the varian a 1 well at parkfield california were used to record the waveforms of nearby microearthquakes despite being in the thick tertiary sediments of the parkfield syncline the s wave amplification at this site is only about a factor of 3 the spectral content and spectral ratios of s waves along the well show that the average qs in the top 1 km at this site is 37 with the qs in different subintervals varying between 8 and 65 based on initial s wave polarizations a complex s wave velocity structure must exist at and below the varian site this structure appears to include position dependent anisotropy as well as steep lateral velocity gradients at a depth of 1 km s wave splitting parallel and normal to the san andreas fault zone is consistently observed this splitting scales at roughly 0 01 sec km subsequent to the split s waves the particle motion seems to be controlled by event focal mechanism above 1 km the upgoing s waves attenuate and change directions of polarization with a new splitting rate of 0 1 sec km uniquely for some events on the san andreas fault immediately below the varian site large post s wave signals with normal dispersion are present we propose that these phases are fault zone guided waves channeled from the san andreas fault to the varian site along the gold hill fault

shear source multiazimuth near and far offset vertical seismic profiles asal rift republic of djibouti a three component borehole seismic data set obtained in the asal rift zone shows that azimuthal anisotropy may be present with the fast propagation direction aligned with the present day rift axis this is seen on the near and far offset vertical seismic profile vsp data from the two source points lying parallel to the rift axis the third orthogonal source point gives propagation times characteristic of near horizontal paths along the detected slow direction the reflected vsp wave field contains both p and s energy the main p and s reflections correlate well and correspond to thin clay and siltstone layers interspersed within the lava flow series some evidence exists for a change with depth of the amount or direction of the anisotropy found in the uppermost 400 m

hydrogeological analysis and salvage of a deep coalmine after a groundwater inrush this paper presents a case history of the permanent salvage of the sanhejian coalmine in china after a sudden groundwater inrush which includes emergency responses hydrogeological analyses and design and performance of bulkheads the inrush accident occurred in october 2002 in the mined out area with a high water pressure of 7 6 mpa and a high water temperature of 51 c the emergency response quickly followed up to provide the time required to perform a detailed hydrogeological analysis to identify the source and pathway of groundwater the sanhejian coalmine is geologically located in the tengxian anticline hydrogeological setting the sunshidian fault the northern boundary of the mine was assumed impermeable in the original hydrogeological report after the accident and hydrogeological analysis this assessment was revised and the fault was considered to be permeable the sunshidian fault connects the strata in the mine and the excellent water productive middle ordovician majiagou formation in the core of the tengxian anticline it was concluded that the water inrush was from the underlying ordovician karst aquifer and the pathway was a hidden tectonic structure in the strata overlying the aquifer this assessment served as the guideline for salvaging the mine in this project after a detailed technical and economic analysis a concrete bulkhead design was selected from several alternatives including dewatering and surface grouting the performance of the bulkheads has been sufficient for the last 6 years since their construction this case history shows that the hydrogeological analysis plays an essential role in successfully salvaging the coalmine from the water inrush by identifying the source and pathway of groundwater

seismic reflectivity of the whipple mountain shear zone in southern california the whipple mountains shear zone of southeastern california comprises part of the whipple mountains metamorphic core complex of the north american cordillera the 3 9 km thick shear zone displays excellent exposures of ductilely deformed mid tertiary mylonitic gneisses as well as kinematically related but younger cataclasites which underlie a major low angle normal fault the whipple detachment fault prominent crustal reflections beginning at 3 4 s were recorded on calcrust seismic profiles southwest of the whipple mountains in order to interpret these seismic reflections and to understand why detachment faults are imaged on some profiles but not on others we collected oriented rock specimens from all major structural units in the whipple mountains and determined p wave velocities for these samples parallel to three principal fabric directions under laboratory induced confining pressures up to 500 mpa using a geologic section through the mylonitic gneisses from a previous investigation we then constructed a detailed acoustic impedance section for the whipple mountain shear zone based upon laboratory results this section was in turn used to compose two dimensional synthetic reflection seismograms for comparison with the calcrust records significant impedance contrasts are enhanced by the opposing fabric orientations between the interlayered but structurally isolated relict domains of nonmylonitized rocks and the surrounding mylonitic gneisses the finite thickness and lateral extent of these rock units cause constructive interference in seismic modeling to create the seismic fabric of strong laterally discontinuous but subparallel reflections as seen in the calcrust profiles southwest of the whipple mountains chloritic breccias beneath the whipple detachment fault wdf have much lower seismic impedance than that of rocks occurring both structurally above and below however the significant thinning of the chloritic breccia zone to the southwest of the whipple mountains may have caused the poor image of the wdf on the calcrust profiles the absence of a detachment reflection is thus not necessarily indicative of the absence of a subsurface fault zone

receiver function studies in the trans hudson orogen saskatchewan teleseismic events were recorded on an array of three component broadband and short period seismographs in the trans hudson orogen over a period of almost 3 years receiver functions calculated from these data were used in a forward modelling study to derive the local shear wave velocity structure beneath 20 stations station ffc flin flon located within the flin flon belt was one of two stations situated on bedrock and produced the highest quality receiver functions the ffc velocity model correlates well with an interpretation of nearby reflection data and features a distinct lower crust interpreted as archean basement which cores the entire reindeer zone both radial and tangential receiver functions at ffc show strong evidence for a northeasterly dipping shallow boundary within rocks of the flin flon belt with a dip angle of 20 total crustal thickness is 37 km eighteen stations are situated on phanerozoic sedimentary cover ranging in thickness from 0 4 km to greater than 2 km receiver function

subsonic near surface p velocity and low s velocity observations using propagator inversion detailed knowledge of near surface p and s wave velocities is important for processing and interpreting multicomponent land seismic data because 1 the entire wavefield passes through and is influenced by the near surface soil conditions 2 both source repeatability and receiver coupling also depend on these conditions and 3 nearsurface p and s wave velocities are required for wavefield decomposition and demultiple methods however it is often difficult to measure these velocities with conventional techniques because sensitivity to shallow wave velocities is low and because of the presence of sharp velocity contrasts or gradients close to the earth s free surface we demonstrate that these near surface p and s wave velocities can be obtained using a propagator inversion this approach requires data recorded by at least one multicomponent geophone at the surface and an additional multicomponent geophone at depth the propagator between them then contains all information on the medium parameters governing wave propagation between the geophones at the surface and at depth hence inverting the propagator gives local estimates for these parameters this technique has been applied to data acquired in zeist the netherlands the near surface sediments at this site are unconsolidated sands with a thin vegetation soil on top and the sediments considered are located above the groundwater table a buried geophone was positioned 1 05 m beneath receivers on the surface propagator inversion yielded low near surface velocities namely 270 15 m s for the compressional wave velocity which is well below the sound velocity in air and 150 9 m s for the shear velocity existing methods designed for imaging deeper structures cannot resolve these shallow material properties furthermore velocities usually increase rapidly with depth close to the earth s surface because of increasing confining pressure we suspect that for this reason subsonic near surface p wave velocities are not commonly observed

simulation of groundwater flow within observation boreholes for confined aquifers summary observation wells around a pumping well are the primary means of monitoring the change of hydraulic head in an aquifer pipe flow in open observation boreholes will affect the measurement of hydraulic head in the observation wells and alter the flow patterns around the wells but the influences of non darcian pipe flow in observation wells on the accuracy of hydraulic head measurements are not fully recognized this paper presents a coupled seepage pipe flow theory which integrates the aquifer and well as a continuous medium for assessing the influences the objective of this study is to examine the pipe flow effects in observation wells of varied diameters under several pumping scenarios including different penetration lengths of the pumping well a numerical model based on the galerkin finite element method and the finite difference method was developed for the study numerical simulations were conducted for a homogeneous and isotropic confined aquifer in which a pumping well penetrated a different thickness of the aquifer and a number of full penetrating observation wells were placed to obtain drawdowns the simulation results indicated that vertical pipe flow within the observation wells was significant and the flow was non linear the pipe flow resulted in a conduit effect that disturbed the distribution of the hydraulic head within the observation wells after comparing with the results of the hantush 1961 integral by using the case study which neglected the wellbore effect on the groundwater flow system the authors found that the hantush integral may be only conditionally applicable for estimating the drawdown within the observation wells when well diameter is greater than 0 20 m and radial distance is greater than the thickness of the aquifer our study suggests that use of hydraulic heads from observation wells for the evaluation of groundwater flow systems must be cautious before the pipe flow effect can be assumed to be negligible

coupled simulation optimization model for draining confined aquifer via underground boreholes to prevent water inrush of coal mines in north china groundwater drainage is commonly applied by coal mines to prevent water inrush from confined aquifers underlying coal seams which can also cause environmental problems the previous research has proposed dual factor and triple factor models to manage water resources in coal mines however three features of draining confined water via underground boreholes have not been sufficiently considered the geological heterogeneity workface relocation and draining principle of underground boreholes this paper aims to incorporate the three features into an optimization model for underground borehole draining a novel mathematical model was proposed that included the three features a workflow framework was proposed to conduct the optimization based on gis and a coupled simulation optimization approach an algorithm was designed and a c program was developed to couple feflow with a modified genetic algorithm to search for the optimal solution the application to the liangbei coal mine indicates that the aquifer has been over drained about 69 and 36 of the water could be saved in the first two stages the total draining rate significantly changes with the workface relocation the boreholes located at the headwaters and closer to the workface that are mined now or in the next stage usually have higher rates than other boreholes the distribution of the draining rates is also related to the workface geometry and the aquifer anisotropy the optimization should be repeated as new monitoring data are acquired

seismic fracture anisotropy in the earth s crust an overview fluid filled fractures and microcracks are the most stress sensitive component of crustal rock and often determine the pathways and volume of crustal fluid movement if we are to comprehend the role of fractures and fluids in tectonic processes to formulate an accurate hypothesis for phenomena precursory to catastrophic seismic failure or to monitor hydrocarbon and geothermal reservoirs for the presence or absence of major fluid pathways we must understand how seismic waves interact with the fracture crack and microcrack structures within the rock mass a salient feature of fracture related rock structure is the effective seismic anisotropy of aligned fractures and microcracks with the advent of large volume digital seismic data sets it is feasible to use polarized shear waves to explore the anisotropic fracture properties of the crust crustal fracture structures which may be monitored by polarized shear waves range in dimensions from the 10 100 km scale of crustal stress orientation and preseismic stress buildup through the 100 1000 m scale of fluid reservoir structure and characterization and the 1 10 scale of mining and geoengineering rock strain monitoring to millimeter and micrometer or possibly smaller fluid filled inclusions determining the elastic response of the intact rock mass to focus developments in seismic anisotropic studies of crustal fracture phenomena the american geophysical union and the society of exploration geophysicists sponsored a chapman conference on seismic anisotropy in the earth s crust held may 31 to june 4 1988 at the lawrence berkeley laboratory of the university of california this was the third international workshop on seismic anisotropy 3iwsa nineteen conference papers are presented in this special section of the journal of geophysical research

deuteronomy a puzzle of deuterium and oxygen on mars mars is covered by channels that were likely formed by liquid water sometime in its past among the very few available clues to a wetter and warmer ancient climate on mars are the isotopic signatures left by processes that have modified its atmosphere over time in their research commentary yung and kass discuss two sets of results in the same issue krasnopolsky et al have used the hubble space telescope to detect the presence of deuterium in the upper atmosphere of mars and farquhar et al report measurements of the martian meteorite alh84001 showing that the oxygen isotopes in the carbonate are fractionated with respect to silicate minerals the findings suggest the presence of chemical processes operating in mars atmosphere that have yet to be fully understood

influence of ice rheology and dust content on the dynamics of the north polar cap of mars abstract the evolution and dynamics of the north polar cap residual ice cap layered deposits complex of mars is simulated with a thermomechanical ice sheet model we consider a scenario with ice free initial conditions at 5 ma before present due to the large obliquities which prevailed prior to this time the north polar cap is then built up to its present shape driven by a parameterized climate forcing surface temperature surface mass balance based on the obliquity and eccentricity history the effects of different ice rheologies and different dust contents are investigated it is found that the build up scenarios require an accumulation rate of approximately 0 15 0 2 mm a 1 at present the topography evolution is essentially independent of the ice dynamics due to the slow ice flow owing to the uncertainties associated with the ice rheology and the dust content flow velocities can only be predicted within a range of two orders of magnitude likely present values are of the order of 0 1 1 mm a 1 and a strong variation over the climatic cycles is found for all cases computed basal temperatures are far below pressure melting

separation of p and s waves in combined p and sv observations with vertical and in line horizontal geophones recognition and separation of the individual p and s arrivals may form a considerable problem due to the geophone receiving characteristics p and s waves are observed on both horizontal and vertical geophones a new method of separating p and s waves is presented that inverts the geophone records for the receiving characteristics thereby separating the two wavetypes the filter coefficients are determined from the near surface p and s wave velocity and from the geometry of the geophone groups the p s separation filter was tested on synthetic data with good results even ps and sp converted reflections which are completely coinciding for horizontal reflectors could be well separated the filter appears to be stable and to have low sensitivity to noise in the data or to errors in the near surface p and s wave velocity the filter is superior to other separation methods which were applied to the same dataset for comparison this method can also be applied to vsp data

analysis of p and s wave vertical seismic profile data from the salton sea scientific drilling project as part of the salton sea scientific drilling project at california state well 2 14 vertical seismic profile vsp data were collected from p and s wave sources at two distances from the well use of a three component geophone along with rotation of the recorded data traces into a wave front based coordinate system allows analysis of many aspects of seismic wave propagation properties around the well standard vsp analysis techniques were used to measure interval p and s wave velocities and to identify reflecting horizons both within and below the survey interval from 455 to 1735 m a reflection from below the survey interval seen with both p and s sources seems to be associated with a fractured reservoir near 2100 m indications of fracturing were observed including vertical scattering of p waves from a zone near 915 m orthogonally polarized shear waves were generated at each offset to study anisotropy by travel time measurement and particle motion analysis of the shear wave arrivals three component particle motion analysis of shear wave arrivals was found to be effective for characterizing the subtleties in the s wave splitting throughout the various zones in the well the sht source horizontal and transverse to the well produced complicated elliptical particle motion while the sv source in line with the well produced linear particle motion the difference in linearity of particle motion from orthogonally polarized shear wave sources was unexpected and may be related to regional tectonics anomalous zones may be related to transition depths in the salton sea geothermal field travel time difference between sv and sh waves while clearly observable indicates only about 1 average anisotropy

full wavefield inversion to estimate impact source orientation from multicomponent land seismic data orientation of an impact source is estimated from multicomponent land data the seismic wavefield produced by an arbitrarily oriented impact source is represented by the linear combination of the nine independent wavefield components green s functions for a full vector source coefficients of this linear combination are expressed in terms of the parameters that define source orientation the parameters are an azimuthal angle a vertical angle and source strength which are the unknowns of the inverse problem once the green s functions are computed source parameters are estimated by full wavefield inversion using a grid search over the source parameters this inverse procedure also provides information about the uniqueness and resolution of the solution information on the source orientation is dominated by the relative amplitudes between components so the inversion can be performed even when the source time wavelet is not well known the approach is tested using a synthetic common source gather res

the variation of delays in stress induced anisotropic polarization anomalies summary polarization anomalies in seismic shear wavetrains diagnostic of propagation through anisotropic media have now been observed in dilatancy zones in seismic regions stress induced dilatancy will open cracks with preferred orientations which will be effectively anisotropic to short period seismic waves the polarization anomalies are due to the shear waves splitting in propagation through anisotropic media into components with different polarizations and different velocities this writes characteristic signatures into the shear wavetrains the paper examines ways in which the differential shear wave anisotropy the delay between the split shear waves varies with direction by plotting stereograms of the relative delays and their polarizations for possible dilatancy symmetry systems it seems likely that if sufficient observations of these anomalies can be obtained at each stage of the dilatancy episode it will be possible to estimate the symmetry directions of the dilatancy and the geometry of the stress induced crack system as well as monitoring the progress of the dilatancy episode