tectonic analysis of mine tremor mechanisms from the upper silesian coal basin fault network of the upper silesian coal basin uscb is built of sets of strike slip oblique slip and dip slip faults it is a typical product of force couple which acts evenly with the parallel of latitude causing horizontal and anti clockwise smovement of rock mass earlier research of focal mechanisms of mine tremors using a standard fault plane solution has shown that some events are related to tectonic directions in main structural units of the uscb an attempt was undertaken to analyze the records of mine tremors from the period 1992 1994 in the selected coal fields the digital records of about 200 mine tremors with energy larger than 1 x 104 j m l 1 23 were analyzed with smt software for seismic moment tensor inversion the decomposition of seismic moment tensor of mine tremors was segmented into isotropic i part compensated linear vector dipole clvd part and double couple dc part the dc part is prevalent up to 70 in the majority of quakes from the central region of the uscb a group of mine tremors with large i element up to 50 can also be observed the spatial orientation of the fault and auxiliary planes were obtained from the computations for the seismic moment dc part study of the dc part of the seismic moment tensor made it possible for us to separate the group of events which might be acknowledged to have their origin in unstable energy release on surfaces of faults forming a regional structural pattern the possible influence of the cainozoic tectonic history of the uscb on the recent shape of stress field is discussed

ion probe determinations of the rare earth concentrations of individual meteoritic phosphate grains abstract a new ion probe method for quantitative measurements of the concentrations of all the ree down to the ppm level in 5 20 m spots is presented the first application of the method is the determination of ree abundances in meteoritic phosphates results are shown to be in good agreement with previous inaa and ion probe determinations the merrillites in the st severin amphoterite are richer in ree than the apatites the enrichment factors for various ree range from 2 3 to 14 2 in contradiction with the results of ebihara and honda 1 provided good standards for other mineral phases are found or implanted marker ion techniques are used the method should find a wide range of applications for the study of both terrestrial and extraterrestrial crystals at the microscopic level

rare earth abundances in chondritic phosphates and their implications for early stage chronologies abstract the abundances of nine rare earth elements ree in phosphate separates from three ordinary chondrites saint severin ll6 bruderheim l6 and richardton h5 were measured by instrumental neutron activation analysis all ree except europium are enriched in the phosphate minerals merrillite and chlorapatite by factor of 200 300 relative to the chondritic average whereas eu is enriched by a factor of 40 50 electron microprobe analysis showed no significant differences in phosphate mineral composition among the three chondrites studied though the relative proportions of two minerals varied according to our data ree are enriched by almost the same factor in merrillite and chlorapatite in the bruderheim and with less certainty in the other two chondrites this behavior of ree contrast with that of the actinoid elements th u and pu which are also enriched in phosphate but are fractionated between merrillite and chlorapatite since pu and ree show different fractionation behavior in chondritic phosphates it may be difficult to use ree as stand ins for pu in 244 pu chronology

comparison of body wave displacement with damage observations of a rockburst coeur d alene mining district idaho fault plane solutions for seismic events in the deep underground mines of the coeur d alene mining district in northern idaho have been difficult to reconcile with actual observations of mine damage examination of rockburst damage in stopes as well as measurements of slip movements on bedding planes suggests that rockbursts in the lucky friday mine are closely associated with gradual bedding plane slip this progressive slip reduces the physical dimensions of stopes and increases compressive stress resulting in sudden implosive failure of the stope margins thus much of the difficulty in evaluating seismological data arises from the implosional nature of these rockbursts making the first motion of the events difficult to interpret in the summer of 1998 we acquired several months of high quality seismic data from five stations in the vicinity of the lucky friday mine this is the first time that a network of high dynamic range three component instruments has been deployed in this mining district on 29 august 1988 at 6 09 utc a m l 2 9 event occurred at the lucky friday mine this event resulted from bedding plane slip and caused extensive damage in the mine that was carefully documented using a least squares procedure we were able to find a well constrained moment tensor solution that matches the p and s displacement amplitudes measured at the five temporary stations we derived a model of the mechanism to compare with the underground observations of bedding plane slip and damage we conclude that high quality seismological instrumentation is required if meaningful results are to be obtained for understanding the source mechanisms of shear implosional rockbursts manuscript received 1 february 2001

in situ trace element microanalysis we define in situ trace element microanalysis as the measurement of concentrations of trace elements 1000 ppm in individual mineral phases in polished sections analogous to electron microprobe analysis for major elements it is our opinion that such measurements are important and can provide a new dimension to petrology and geochemistry this article is both a review of work already done and a summary of potential advances in the future the advantages of in situ analyses as opposed to methods involving physical and or chemical mineral separations are that the trace element data can be interpreted in a petrographic context and that ambiguities associated with the purity of the mineral separates can be avoided with data on individual grains comparisons of intergrain and intragrain zoning variations between major and trace elements can be made and the importance of inclusions can be assessed within the spatial resolution of the microanalysis technique

some comparisons between mining induced and laboratory earthquakes although laboratory stick slip friction experiments have long been regarded as analogs to natural crustal earthquakes the potential use of laboratory results for understanding the earthquake source mechanism has not been fully exploited because of essential difficulties in relating seismographic data to measurements made in the controlled laboratory environment mining induced earthquakes however provide a means of calibrating the seismic data in terms of laboratory results because in contrast to natural earthquakes the causative forces as well as the hypocentral conditions are known a comparison of stick slip friction events in a large granite sample with mining induced earthquakes in south africa and canada indicates both similarities and differences between the two phenomena the physics of unstable fault slip appears to be largely the same for both types of events for example both laboratory and mining induced earthquakes have very low seismic efficiencies eta tau a bar tau where a is the apparent stress and bar tau is the average stress acting on the fault plane to cause slip nearly all of the energy released by faulting is consumed in overcoming friction in more detail the mining induced earthquakes differ from the laboratory events in the behavior of as a function of seismic momentm0 whereas for the laboratory events 0 06 independent ofm0 depends quite strongly onm0 for each set of induced earthquakes with 0 06 serving apparently as an upper bound it seems most likely that this observed scaling difference is due to variations in slip distribution over the fault plane in the laboratory a stick slip event entails homogeneous slip over a fault of fixed area for each set of induced earthquakes the fault area appears to be approximately fixed but the slip is inhomogeneous due presumably to barriers zones of no slip distributed over the fault plane at constant bar tau larger events correspond to larger a as a consequence of fewer barriers to slip if the inequality a bar tau 0 06 has general validity then measurements of a ea m0 where is the modulus of rigidity andea is the seismically radiated energy can be used to infer the absolute level of deviatoric stress at the hypocenter

source parameters of injection induced microseismicity we analyze source parameters of microseismic events m 1 associated with high flow rate water injections in a shale formation at a depth of 220 m two types of events were observed several hundred impulsive events with clear p and s wave arrivals and continuous emissions with peaked spectra detected well into the experiment for a representative collection of impulsive events an 2 model provided satisfactory fits to displacement spectra corrected for attenuation and average quality factors of 34 and 15 were obtained for p and s waves p wave first motion analysis and e s e p ratios indicated the existence of a non double couple component in some events particularly early in the experiment a clear difference was observed for estimates of stress release parameters as non doublecouple events had smaller stress drops and apparent stresses the seismic efficiency of double couple and non double couple events was limited to 0 9 and 0 05 respectively with average values being 0 25 and 0 02 a comparison of our results with those reported for a similar magnitude range in a hard rock formation indicates considerably smaller estimates of stress drop and apparent stress in our case while seismic efficiencies are comparable

hypocenter determination in strongly heterogeneous earth models using the shortest path method the shortest path method moser 1991 for the calculation of seismic ray paths and travel times along them can be applied directly in the hypocenter location method proposed by tarantola and valette 1982 it uses the analogy between seismic rays in the earth and shortest paths in networks to construct first arrival times from one point to all other points of a three dimensional grid simultaneously in a fast robust way in earth models of arbitrary complexity doing this for all stations of a seismic array one can find the hypocenter location by minimizing the difference between the observed and the calculated travel times at the stations over the three dimensional grid the concept of probability density functions allows then for a fully nonlinear examination of the uncertainties in the hypocenter location due to uncertainties in the travel time data numerical errors in the calculated travel times and to a limited extent incomplete knowledge about the earth model the result is a three dimensional contour map of regions of equal confidence for the earthquake location the method becomes especially attractive when more than one event recorded by the same array is studied because the calculation of the travel times which is relatively the most time consuming operation has to be done only once the method is applied on the location of an event that occurred on january 18 1989 in israel

source mechanism of mining induced seismic events resolution of double couple and non double couple models abstract traditional assumption about a seismic source as a double couple dc can represent a serious limitation for describing mechanisms of mining induced seismic events in mining conditions more general process than a shear slip can occur due to stress concentration on mined out areas we assume both non dc components within the dipole description of the source the moment tensor and a single force we processed five seismic events recorded at driefontein gold mine in south africa to demonstrate that waveform modeling is not successful enough due to poor information about the medium inversion of amplitudes of direct p and s waves is more prospective due to their smaller sensitivity to detail of the medium and possibility to correct them for ray bending and shear wave splitting prior to the inversion moreover we are able to estimate the error of the resulting mechanism due to neglect of ray bending all five events processed display non dc mechanisms which are significant at 95 considering the mismodelling of the rock mass by a homogeneous isotropic medium the source mechanisms are in agreement with the underground mining and geological structures one event has a sub vertical pressure single dipole complemented by an implosion which is the body force equivalent of a collapsing horizontal crack or a burst of a pillar supporting the hangingwall of a mined out area two events have mechanisms close to a pressure single couple all three events are located on pillars two out of these three events can be assigned with a downward single force as an alternative mechanism which matches the amplitude data successfully it is the force equivalent of a mined out area collapse when a rock mass falls from the hangingwall to the footwall the events are however rather strong which would require too large rock mass fallen one of the remaining events is a nearly horizontal tensile single couple corresponding to a vertical tensional fault it could be originated by a break of the hangingwall of a mined out area however the hypocenter of this event is deep into the footwall were there is no mining taking place the last event is mostly dc accompanied by a compensated compressive dipole which may be associated to nearly vertical dip slip along a fault in the hangingwall this event is located on the margin of a wide pillar which supports the interpretation

monitoring velocity variations in the crust using earthquake doublets an application to the calaveras fault california we present a technique that greatly improves the precision in measuring temporal variations of crustal velocities using an earthquake doublet or pair of microearthquakes that have nearly identical waveforms and the same hypocenter and magnitude but occur on different dates we compute differences in arrival times between seismograms recorded at the same station in the freqency domain by cross correlation of short windows of signal a moving window analysis of the entire seismograms including the coda gives t the difference in arrival times versus running time along the seismogram the time resolution of the method is an order of magnitude better than the digitization interval the t technique is illustrated with a pair of microearthquakes m 1 7 and 2 0 that occurred before and after the coyote lake california earthquake m 5 9 of august 6 1979 and on the same segment of the calaveras fault that ruptured during the earthquake the coda wave arrivals for some stations are progressively delayed for the second earthquake in the doublet so that its seismogram appears as a stretched version of the earlier event we interpret this systematic variation in t along the coda as a change in the average s velocity in the upper crust in the time interval between the two doublets s wave velocities appear to have decreased by 0 2 in an oblong region 5 10 km in radius at the south end of the aftershock zone

deep fault plane geometry inferred from multiplet relative relocation beneath the south flank of kilauea dense microearthquake swarms occur in the upper south flank of kilauea providing multiplets composed of hundreds of events the similarity of their waveforms and the quality of the data have been sufficient to provide accurate relative relocations of their hypocenters a simple and efficient method has been developed which allowed the relative relocation of more than 250 events with an average precision of about 50 m horizontally and 75 m vertically relocation of these events greatly improves the definition of the seismic image of the fault that generates them indeed relative relocations define a plane dipping about 6 northward although corresponding absolute locations are widely dispersed in the swarm a composite focal mechanism built from events providing a correct spatial sampling of the multiplet also gives a well constrained northward dip of about 5 to the near horizontal plane this technique thus collapses the clouds of hypocenters of single event locations to a plane coinciding with the slip plane revealed by previous focal mechanism studies we cannot conclude that all south flank earthquakes collapse to a single plane there may locally be several planes perhaps with different dips and depths throughout the south flank volume the 6 northward dipping plane we found is too steep to represent the overall flexure of the oceanic crust under the load of the island of hawaii this plane is probably an important feature that characterizes the basal slip layer below the upper south flank of kilauea volcano differences in seismicity rate and surface deformations between the upper and lower south flank could be related to the geometry of this deep fault plane the present work illustrates how high precision relative relocations of similar events in dense swarms combined with the analysis of geodetic measurements can help to describe deep fault plane geometry systematic selection and extensive relative relocation of similar earthquakes could be attempted in other well instrumented highly seismic areas to provide reliable basic information especially useful for understanding of earthquake generation processes

a tensile model for the interpretation of microseismic events near underground openings for small scale microseismic events the source sizes provided by shear models are unrealistically large when compared to visual observations of rock fractures near underground openings a detailed analysis of the energy components in data from a mine by experiment and from some mines showed that there is a depletion of s wave energy for events close to the excavations indicating that tensile cracking is the dominant mechanism in these microseismic events

the effect of post pangea subduction on global mantle tomography and convection there is an excellent correlation between tomographic patterns and global tectonics in the upper 200 km of the mantle below this depth there is little relationship with present tectonic provinces most of the power in the tomography is in the longest wavelengths l 1 3 with l 2 generally dominant this is quite different from expectations based on mantle convection models the question then arises what causes the long wavelength variations mapped by seismic techniques we investigate the hypotheses that past locations of supercontinents and subduction may control temperature variations in the mantle we look for correlations between pangea and post pangeatic subduction and seismic velocity variations at various depths the best correlations with time integrated slab locations occur near the base of the uppermantle suggesting that slabs bottom out in the mesosphere the pangea hemisphere has a colder than average uppermantle probably due to circum and intra pangea subduction hotspots and ridges avoid regions cooled by subduction over the past 180 ma the presence of large continents at the surface and large areas of cold slab at depth explain the dominance of long wavelengths in the mantle s thermal structure despite the high rayleigh number

on the influence of stratification and continental shelf and slope topography on the dispersion of subinertial coastally trapped waves abstract the behavior of subinertial coastally trapped free waves in a continuously stratified ocean is examined using a two slope topography in which the continental shelf and slope are each represented by a single uniform slope surface intensified stratification is assumed in which the squared buoyancy frequency profile is of the form n2e z where n is the buoyancy frequency at the surface z 0 and the vertical decay scale normalized by the deep sea depth the continental slope is typically assumed to be steeper than the shelf two qualitatively different types of dispersive behavior are distinguished when n f a2 e h 2 where f is the coriolis parameter a2 the bottom slope of the continental slope and h the shelf break depth normalized by the deep sea depth then free waves may occur at any subinertial frequency and each dispersion curve rises to f at some finite alongshore wavenumber as in the case of baroclinic kelvin waves if n f a2 e h 2 then all of the free wave dispersion curves a

seismic events with non shear component ii rock bursts with implosive source component the rock burst mechanism of an implosive character is introduced and discussed it is based on the idea that the compressional component of the stress field around the loaded stress concentrator can participate in the rock burst event for easier classification of the rock burst from this viewpoint a set of p wave radiation patterns of the rock burst with a varying portion of the implosive component and varying propagation velocity of the displacements is presented and discussed to support the credibility of the rock burst mechanism of an implosive character the seismic signals of the rock bursts from the mid bohemian coal district with negative signs of the p wave first onsets are presented

coastally trapped waves in the presence of a shelf edge density front a numerical model is developed to analyze the stability and propagation characteristics of coastally trapped waves on a shelf with a shelf edge density front the model is applied to the saglek bank on the labrador shelf in an attempt to explain the ice edge undulations observed in noaa 5 satellite images it was found that the instability is suppressed by the bottom slope if the entire shelf slope is below the front however if the front intersects the bottom at about 1000 m depth with an associated current speed of 50 cm s 1 an upper limit for the labrador current the front could be unstable with a wavelength of 70 90 km and phase speed of 30 45 cm s 1 in approximate agreement with the estimates from satellite images furthermore the neutral propagating modes will be modified by the front some modes will be transformed from barotropic shelf waves to bottom trapped frontal waves the presence of a density front on a continental shelf also results in either restricting or eliminating the backward propagation of energy on the shelf and hence has a significant effect on the energy propagation along the shelf

low frequency current variability on the labrador shelf current meter measurements from two locations on the northern part of the labrador shelf have been analyzed using empirical orthogonal function eof analysis in the three frequency bands 0 09 0 18 cpd 0 18 0 36 cpd and 0 36 0 54 cpd to describe the measurements in each frequency band a numerical circulation model was developed for the shelf driven by alongshore and onshore wind stresses and by flow through hudson strait the latter flow is taken to arise from the atmospheric pressure variations over hudson bay and from the along static wind stress over hudson strait the model appears to be quite successful in describing the circulation in the center frequency band this suggests that the forcing within this band is primarily due to the alongshore wind stress over the shelf and to the flow through hudson strait the model indicates that in the region of study the mode 1 shelf wave dominates the velocity field over the upper part of the shelf whereas mode 2 dominates the flow near the shelf break in the first and third frequency bands the model is less successful in describing the measured currents it is likely that this failure is at least in part due to the neglect of other forcing mechanisms such as shelf waves propagating southward out of baffin bay

puxe dating of eucrites abstract we report the results of xe analyses of the eucrites bereba cachari caldera camel donga chervony kut ibitira jonzac juvinas milbillillie moore county padvarninkai pasamonte pomozdino sioux county and vetluga and the howardite petersburg the obtained data together with data from the literature were utilized for the calculation of pu xe ages using a modified method where the concentration of the reference element nd that is used in the traditional pu xe dating is replaced by that of spallation 126 xe originating from rare earth elements the fraction of spallation 126 xe from ree in total spallation 126 xe is calculated via the ba ree ratios that are very similar in different samples of a given meteorite in comparison with the traditional pu xe dating the present method avoids problems of sampling heterogeneity and uncertainties in absolute instrument sensitivity and can be used when the concentration of nd in a sample is not known the pu xe ages for different samples of individual meteorites show good reproducibility ages of the eucrites bouvante chervony kut ibitira juvinas moore county pasamonte pca82502 pomozdino of the howardite petersburg and of the angrite lew86010 are old and most likely date the time of crystallization at 4 56 ga almost complete retention of fission xe in these meteorites is in a stark contrast with the apparent 1 retention of radiogenic 129 xe the eucrites bereba cachari caldera camel donga jonzac millbillillie neuvo laredo padvarninkai sioux county stannern and vetluga are distinctly younger this can be interpreted in different ways the ages may represent crystallization and or metamorphic ages or may simply reflect the different extent of diffusive fission xe losses during later events comparison of the pu xe ages with those from the sm nd and pb pb isotope chronometers yields in most cases a reasonable agreement in some meteorites however the pb pb chronometer appears to have been reset during secondary events while the pu xe isotope system is seen to be more resistant to such events

experimental geochemistry of pu and sm and the thermodynamics of trace element partitioning the partitioning of pu and sm between diopside liquid and whitlockite liquid has been investigated experimentally to evaluate the geochemical coherence of pu and the light rees pu d sm d is 2 for both diopsidic pyroxene and whitlockite this small amount of fractionation would be decreased further if pu were compared to ce or nd our experimental results thus validate the suggestion that pu behaves as a lree during igneous processes in reducing environments our data and the data of ray et al 1983 indicate that temperature rather than melt composition is the most important control on elemental partitioning this is true even though we demonstrate that additions of only 1 2 wt of p2 o 5 to the diopside anorthite albite system change pu d cpx by a factor of two our data suggest that p 2o 5 in aluminosilicate melts serves as a complexing agent for the actinides and lanthanides

evidence for remotely triggered microearthquakes during salt cavern collapse summary microseismicity is a good indicator of spatio temporal evolution of physical properties of rocks prior to catastrophic events like volcanic eruptions or landslides and may be triggered by a number of causes including dynamic characteristics of processes in play or and external forces we show evidence of triggered microseismicity observed in the vicinity of an underground salt cavern prone to collapse by a remote m 7 2 earthquake which occurred 12 000 km away high dynamic range broad band records reveal the strong time correlation between a dramatic change in the rate of local high frequency microseismicity and the passage of low frequency seismic waves including body love and rayleigh surface waves pressure was lowered in the cavern by pumping operations of brine out of the cavern we demonstrate the near critical state of the cavern before the collapse by means of 2 d axisymmetric elastic finite element simulations on this basis we show that the increment of stress necessary for the failure of the dolomite layer which ensures the stability of the whole system is of the same order of magnitude as the maximum dynamic stress magnitude observed during the passage of the earthquakes waves this suggests that the stress oscillations due to the seismic waves correlated with the recorded microearthquakes induced damage of the overburden which eventually led to the collapse of the salt cavern we show that the contribution of rayleigh waves is the most efficient to trigger microseismicity at periods close to the natural fundamental frequency of the cavern system found at about 10 20 s by investigating the impulse response of the cavern overburden brine system

automated full moment tensor inversion of coal mining induced seismicity seismicity induced by coal mining in the ruhr region germany has been monitored continuously over the last 25 yr in 2006 a dense temporary network hamnet was deployed to locally monitor seismicity induced by longwall mining close to the town of hamm between 2006 july and 2007 july more than 7000 events with magnitudes m l from 1 7 to 2 0 were detected the spatiotemporal distribution of seismicity shows high correlation with the mining activity in order to monitor rupture processes we set up an automated source inversion routine and successfully perform double couple and full moment tensor mt inversions for more than 1000 events with magnitudes above m l 0 5 the source inversion is based on a full waveform approach both in the frequency and in the time domain providing information about the centroid location focal mechanism scalar moment and full mt inversion results indicate a strong dominance of normal faulting focal mechanisms with a steeper plane and a subhorizontal one fault planes are oriented parallel to the mining stopes we classify the focal mechanisms based on their orientation and observe different frequency magnitude distributions for families of events with different focal mechanisms the overall frequency magnitude distribution is not fitting the gutenberg richter relation full mts indicate that non negligible opening tensile components accompanied normal faulting source mechanisms finally extended source models are investigated for largest events results suggest that the rupture processes mostly occurred along the subvertical planes

moment tensors of ten witwatersrand mine tremors ground motions recorded both underground and on the surface in two of the south african gold mining districts were inverted to determine complete moment tensors for 10 mining induced tremors in the magnitude range 1 9 to 3 3 the resulting moment tensors fall into two separate categories seven of the events involve substantial coseismic volumetric reduction v together with normal faulting entailing shear deformation ad where the summation is over fault planes of areaa and average slipd for these events the ratio v ad ranges from 0 58 to 0 92 with an average value of 0 71 for the remaining three events v is not significantly different from zero these events are largely double couple sources involving normal faulting surprisingly the two types of source mechanism appear to be very distinct in that there is not a continuous distribution of the source mix from v 0 to v ad presumably the coseismic closure indicates substantial interaction between a mine stope and adjacent shear failure in the surrounding rock under the influence of an ambient stress for which the maximum principal stress is oriented vertically

pre collapse identification of sinkholes in unconsolidated media at dead sea area by nanoseismic monitoring graphical jackknife location of weak sources by few low snr records summary the sudden failure of near surface cavities and the resulting sinkholes have constituted a recent hazard affecting the populations lifelines and the economy of the dead sea region this paper describes how seismic monitoring techniques could detect the extremely low energy signals produced by cavitation in unconsolidated layered media dozens of such events were recorded within a radius of 200 m during several night time experiments carried out along the western dead sea shores the absence of prior knowledge about cavitation induced events in unconsolidated media required an initial signal characterization for which a series of source processes were simulated in the field under controlled conditions the waveform analysis by sonograms recognizes two main groups of seismic events impacts on dry material and impacts in liquid our analysis demonstrates that the discrimination between both types of source functions is robust despite the extreme nature of the scatter media in addition to their association with specific source processes these events can be precisely located by a graphical error resistant jackknifing approach using an extended m l scale their source energy can be quantified and related to standard seismic activity in summary it is now possible to monitor subsurface material failures before sinkhole collapse since the discrimination of impact signals on the basis of their frequency content is indicative of the maturity of the cavitation process

coastally trapped waves in the presence of a barotropic shelf edge jet the structures and propagation characteristics of coastally trapped waves on a continental shelf with a barotropic coastal current are analyzed when the current located on the shelf edge has a velocity in the direction of the phase propagation of the topographic shelf waves and when the topography stabilizes the shear instability the linearized perturbations on the mean flow consist of propagating shelf and shear wave modes and the evanescent shelf shelf and shelf shear coalescence modes at complex wave numbers at low rossby numbers the shear waves and backward propagating shelf waves coalesce at low frequencies as the rossby number is increased the coalescence occurs at higher and higher frequencies and lower wave numbers for sufficiently high rossby numbers the coalescence may occur directly between the forward propagating shelf wave and the shear wave the backward propagating shelf wave being eliminated entirely hence the manner in which energy is transported along a continental shelf can be fundamentally altered by the presence of a mean current

analysis of microtremors within the provadia region near a salt leaching mine by analysis of microtremors recorded with digital seismological monitoring equipment near the provadia sait diapir bulgaria two groups of events showing different characteristics have been detected in the vicinity of the salt production area the first group of events has low magnitudes and is located at a distance of about 1 km from the top of the salt diapir these events show low stress drops the second group of tremors is located outside the salt diapir the corresponding magnitudes and stress drops are larger the first class of events seems to be related to processes at the contour of the salt leaching caverns whereas the origin of the second group seems to be connected with stress redistribution processes around the salt body based on this analysis the tectonic model of the provadia salt diapir has been modified

the behavior of actinides phosphorus and rare earth elements during chondrite metamorphism new data on the u pu and p distributions in less metamorphosed h chondrites type 3 5 coupled with literature results permit a provisional picture to be assembled of the chemistry of these elements and for the rare earth elements in ordinary chondrites and the changes brought about by chondritic metamorphism preferential associations of phosphates with metals and or sulndes in all chondrites strongly indicate an initially siderophile or conceivably chalcophile character for p in ordinary chondrite precursor materials with phosphate subsequently formed by oxidation this oxidation occurred prior to or during chondritic metal silicate fractionation uranium is initially concentrated in chondrule glass at 100 ppb levels with phosphates primarily merrillite in h 3 chondrites being essentially u free 20 ppb as chondrule glass devitrified during metamorphism u migrated into phosphates reaching 50 ppb in nadiabondi h 5 merrillite and 200 300 ppb in merrillite from equilibrated chondrites but froze out before total concentration in phosphates occurred relative 244 pu fission track densities in the outer 5 m of olivine and pyroxene grains in contact with merrillite and with chondrule mesostasis in bremervorde h 3 give pu mesostasis pu merrillite 0 01 implying total concentration of pu in phosphates similarly no detectable pu 0 1 ppb was found in chondrule mesostasis in tieschitz and sharps whereas direct measurements of tracks in phosphates in h 3 chondrites are consistent with high 10 ppb pu concentrations thus a strong pu p correlation is indicated for ordinary chondrites there is variable pu u fractionation in all chondritic phosphates reaching an extreme degree in the unequilibrated chondrites therefore the pu u ratio in phosphates appears relatively useless for relative meteorite chronology literature data indicate that the ree are located in chondrules in unequilibrated chondrites most likely in glass thus there may also be strong pu nd fractionation within these meteorites like u the ree migrate into phosphates during metamorphism but unlike u appear to be quantitatively concentrated in phosphates in equilibrated chondrites thus relative ages based on pu nd may be possible for equilibrated chondrites but the same chronological conclusions are probably obtainable from pu concentrations in phosphates i e on the pu p ratio however pu p chronology is possible only for ordinary chondrites so there appears to be no universal reference element to cancel the effects of pu chemical fractionation in all meteorites available data are consistent with but certainly do not prove that variations in pu p represent age differences but if these age differences do not exist then it is conceivable that the solar system 244 pu 238 u ratio important for cosmochronology is still lower than the presently accepted value of 0 007

observations of mine seismicity in the eastern wasatch plateau utah u s a a possible case of implosional failure in the summer of 1984 a three dimensional high resolution microearthquake network was operated in the vicinity of two coal mines beneath gentry mountain in the eastern wasatch plateau utah during a six week period approximately 3 000 seismic events were observed of which the majority were impulsive higher frequency 10 hz short duration 2 3 sec events probably associated with the caving of the roof from a longwall operation in contrast 234 of the largest located events appeared to occur predominantly beneath the mines to a depth of 2 to 3 km consistent with previous studies the magnitudes of these events ranged from less than m c 0 to 1 6 in addition to the unusual depths of these latter events an anomalous aspect displayed by the events was an apparent dilatational focal mechanism suggesting a non double couple possibly implosional source implosional events have been observed in other studies of mine seismicity however the generally inadequate instrumental coverage of the focal sphere has cast some doubt on the validity of such mechanisms previously suggested source mechanisms for such implosional events have included tensional failure through strata collapse and a shear implosional displacement mechanism shear failure must be involved in the failure process of the gentry mountain implosional events as evidenced by well defined shear waves in the observed seismograms simultaneous monitoring in the east mountain coal mining area to the south by the university of utah revealed typical shear failure events mixed with implosional events the observed double couple reverse focal mechanisms at east mountain were similar to mechanisms determined in previous studies and a composite focal mechanism determined in this study for a sequence outside the mining areas this suggested that the shear events within the mining areas are being influenced by the regional tectonic stress field thus in addition to the seismic events associated with caving of the roof from the longwall operation there appear to be at least two other types of mining induced seismic events occurring in the eastern wasatch plateau both submine in origin 1 events characterized by apparent non double couple possibly implosional focal mechanisms and well defined shear waves and 2 shear events which are indistinguishable from tectonic earthquakes and may be considered mining triggered earthquakes the small mining induced stress changes that occur beyond a few hundred meters from the mine workings suggest both types of seismic events are occurring on critically stressed pre existing zones of weakness topography overburden method of mining and mine configuration also appear to be significant factors influencing the occurrence of the implosional submine events

an implosive component in the seismic moment tensor of a mining induced tremor in early 1988 a special study in one of the major south african gold fields yielded seismograms that indicate seismic moment tensors having substantial implosive components the moment tensor resulting from the inversion of the ground motion data from the best recorded event was decomposed into isotropic and deviatoric components from which both the coseismic volumetric closure v and the total shear deformation ad where a is fault area and d is average slip could be estimated the finding here that v ad is consistent with earlier analyses of how the tabular mine stopes interact with the surrounding rock mass to produce seismic deformation

aftershocks of an explosively induced mine collapse at white pine michigan abstract we recorded an explosively induced 320 m deep mine collapse and subsequent aftershocks at white pine michigan using an array of 12 seismic stations sited within 1 km of surface ground zero the collapse which followed the rubblizing of a 2 10 4 m 2 panel of a room and pillar copper mine was induced to facilitate leaching operations the explosions produced little seismic energy however fracturing and collapse stages produced large signals that were observed at distances up to 900 km yielding a magnitude m blg of 2 8 previous work showed the initial collapse to be an expanding seismic source interpreted as an opening tensile crack opposite to the implosional character most often observed for natural mine collapses yang et al 1998 we counted over 4000 aftershocks their occurrence rate followed the modified omori law rate 560 time 0 01 1 3 with time in hours based on p wave polarities we identified events of shear slip implosional and tensile character in the aftershock sequence for shear slip events we found stress drops of 1 bar or less seismic moments of 10 15 10 17 dyne cm m w 0 8 0 5 and source radii of 10 50 m corner frequencies for implosional events were relatively low an indication that the collapsed cavity played a role in the source process this caused implosional events to separate from other events in source parameter plots providing a technique for classifying events of unknown type we obtained locations of 135 aftershocks using p and s wave data the aftershock zone was less than 100 m thick situated just above and along the western mined edge of the collapsed mine panel implosional events occurred at the bottom of the active volume while shear slip events were distributed throughout shear slip focal mechanisms indicated thrusting along north striking planes consistent with the high eastwest regional compressive stress coupled with a local decrease in vertical stress the inferred deficit of vertical stress above the western panel edge following collapse indicated that overburden load shifted preferentially to the surrounding unmined areas consistent with lower than predicted stresses measured in the first row of intact pillars

the mechanism of small mining tremors from amplitude inversion a method of inverting seismic wave amplitudes from mining tremors is proposed to reveal their mechanism a simple shear implosive model of a mechanism is proposed the shapes of theoretical and observed radiation patterns are compared in the least squares norm and the parameters describing the shear slip together with the ratio of implosive and shear dislocations are optimized the efficiency of the method even in the case of a small number of stations is demonstrated by applying it to weak mining tremors from two mine regions in czechoslovakia

seismic tomography in the ostrava karvina mining region the effective algorithm of seismic tomography was applied to the simultaneous determination of the velocity field in the medium and the location of hypocentres of events in the area of the underground seismological network in the ostrava karvina mining region okr although the configuration of the network is unsuitable and the used data are relatively unreliable after classifying the data it is possible to obtain representative information that demonstrates the existence of significant inhomogeneities of the medium in the area under study in addition it is possible to obtain more precise hypocentre parameters of local seismic events

microseismic investigation of an unstable mountain slope in the swiss alps 1 risks associated with unstable rocky slopes are growing as a result of climate change and rapid expansions of human habitats and critical infrastructure in mountainous regions to improve our understanding of mountain slope instability we developed a microseismic monitoring system that operates autonomously in remote areas afflicted by harsh weather our microseismic system comprising 12 three component geophones was deployed across 60 000 m 2 of rugged crystalline terrain above a huge 30 million m 3 recent rockfall in the swiss alps during its 31 month lifetime signals from 223 microearthquakes with approximate moment magnitudes ranging from 2 to 0 were recorded determining the hypocenters was challenging for several reasons 1 p wave velocities were highly heterogeneous varying abruptly from 3 8 km s 2 first break picks were either inaccurate or lacking for some microearthquakes 3 there were no reliable s wave picks 4 numerous microearthquakes occurred just outside the network boundaries these issues were addressed by using a three dimensional 3 d p wave velocity model of the mountain slope determined from refraction tomography in a nonlinear inversion for hypocenter parameters and their probability density functions recordings from geophones at different altitudes and in boreholes constrained microearthquake depth estimates most microearthquakes were concentrated within 50 100 m of the surface in two zones one that followed the recent rockslide scarp and one that spanned the volume of highest fracture zone fault density these two active zones delineated a mass of rock that according to geodetic measurements has moved toward the scarp at 1 2 cm yr

mining induced microseismic event location errors accuracy and precision of two location systems the accuracy and precision of microseismic event locations were measured analyzed and compared for two types of location systems anolog and digital in the first system relative times of first arrival were estimated from analog signals using automated hardware circuitry station positions were estimated from mine map coordinates and event locations were determined using the bld blake leighton and duvall direct solution method in the second system arrival times were manually measured during interactive displays of digital waveforms station coordinates were surveyed and the sw gbm salamon and wiebols godson bridges and mckavanagh direct basis function was used to solve for locations both systems assume constant isotropic seismic velocity of slightly different signals data sets calibration blast signals with known source site and origin time and microseismic event signals were recorded by each location system employing the same array of high frequency 5 khz accelerometers with 150 m maximum dimension the calibration blast tests indicated a location precision of 2 m and accuracy of 10 m for the analog system location precision and accuracy for the digital system measured 1 m and 8 m respectively numerical experiments were used to assess the contributions of errors in velocity arrival times and station positions on the location accuracy and precision for each system measured and estimated errors appropriate to each system for microseismic events were simulated in computing source locations for comparison with exact synthetic event locations discrepancy vectors between exact locations and locations calculated with known data errors averaged 7 7 and 1 4 m for the analog and digital systems respectively these averages are probably more representative of the location precision of microseismic events since the calibration blast tests produce impulsive seismic arrivals resulting in smaller arrival time pick errors in the analog system for both systems location accuracy is limited by inadequate modeling of the velocity structure consequently when isotropic velocity models are used in the travel time inversions the increased effort expended with the digital location system does not for the particular systems studied result in increased accuracy

induced seismicity monitoring of an underground salt cavern prone to collapse within the framework of a large research project launched to assess the feasibility of microseismic monitoring of growing underground caverns this specific work focuses on the analysis of the induced seismicity recorded in a salt mine environment a local seismic network has been installed over an underground salt cavern located in the lorraine basin northeast of france the microseismic network includes four 3 components and three single component geophones deployed at depths between 30 and 125 m in cemented boreholes drilled in the vicinity of the study area the underground cavern under monitoring is located within a salt layer at 180 m depth and it presents a rather irregular shape that can be approximated by a cylindrical volume of 50 m height and 180 m diameter presently the cavern is full of saturated brine inducing a significant pressure on its walls 2 0 mpa to keep the overburden mechanically stable nevertheless some small microseismic events were recorded by the network and analyzed approximately 2 000 events in 2 years of recording in october 2005 and april 2007 two controlled pressure transient experiments were carried out in the cavern in order to analyze the mechanical response of the overburden by tracking the induced microseismicity the recorded events were mainly grouped in clusters of 3 30 s of signal duration with emergent first arrivals and rather low frequency content between 20 and 120 hz some of these events have been spatially located by travel time picking close to the actual cavern and its immediate roof preliminary spectral analysis of isolated microearthquakes suggests sources with non negligible tensile components possibly related to fluid filled cracks rock debris falling into the cavern from delamination of clay marls in the immediate roof is probably another source of seismic excitation this was later confirmed when the most important seismic swarms occurred at the site during may 2007 accompanied by the detachment of more than 8 104 m3 of marly material on top of the cavern roof in any case no clear evidence of classical brittle ruptures in the most competent layers of the overburden has been observed during the analyzed period current work is focused on the discrimination of all these possible mechanisms to better understand the damage processes in the cavern overburden and to assess its final collapse hazard

probabilistic earthquake location in complex three dimensional velocity models application to switzerland 1 we present a new approach to determine precise and reliable hypocenter locations in the tectonically complex region of switzerland a three dimensional 3 d p wave velocity model to be used for earthquake relocation is obtained by simultaneously inverting arrival times of local earthquakes for hypocenter locations and 3 d p wave velocity structure a 3 d p wave velocity model derived from controlled source seismology css is used as an initial reference model the final 3 d model thus combines all available information from both css and local earthquake data the probabilistic nonlinear formulation of the earthquake location problem includes a complete description of location uncertainties and can be used with any kind of velocity model in particular the combination of nonlinear global search algorithms such as the oct tree importance sampling with probabilistic earthquake location provides a fast and reliable tool for earthquake location the comparison of hypocenter locations obtained routinely by the swiss seismological service sed to those relocated in the new 3 d velocity model using a probabilistic approach reveals no systematic shifts but does exhibit large individual shifts in some epicenter locations and focal depths we can attribute these large shifts in part to large uncertainties in the hypocenter location events with a low number of observations 8 and no observation within the critical focal depth distance typically show large location uncertainties improved hypocentral locations particularly for mine blasts and earthquakes whose routine hypocenter locations had been questionable confirm that improved velocity model and probabilistic earthquake location yield more precise and reliable hypocenter locations and associated location uncertainties for switzerland

evidence for extensile crack initiation in point source time dependent moment tensor solutions abstract a time dependent moment tensor inversion technique is applied to 20 seismic events recorded ahead of an advancing tunnel excavation at the underground research laboratory url in canada the data are recorded on a 16 sensor triaxial accelerometer array and the events are chosen from a section of the tunnel such that the event sensor paths are unaffected by the presence of the tunnel factorization of the moment tensor rate functions for each event and subsequent decomposition of the subevents into isotropic and deviatoric components indicate that the events are of three types the first group shows implosional shear failure source mechanisms these are associated with the observed collapse of excavation holes drilled at the side of the tunnel and provide confidence that the method is producing realistic results the second group of events occurs in the region ahead of the face and show tensile shear failure mechanisms these are interpreted in terms of crack initiation ahead of the face and may explain why the tunnel undergoes notching and failure in the floor and roof when the modeled stresses are below the measured rock strength the third group of events shows predominant shear failure throughout their rupture history these are interpreted in terms of failure on pre existing crack surfaces this study highlights the value of using source mechanism studies of associated seismicity to understand the processes that may be taking place in environments where the stress field is complex both spatially and temporally

energy budgets of mining induced earthquakes and their interactions with nearby stopes abstract in the early 1960 s n g w cook using an underground network of geophones demonstrated that most witwatersrand tremors are closely associated with deep level gold mining operations he also showed that the energy released by the closure of the tabular stopes at depths of the order of 2 km was more than sufficient to account for the mining induced earthquakes i report here updated versions of these two results based on more modern underground data acquired in the witwatersrand gold fields firstly an extensive suite of in situ stress data indicate that the ambient state of crustal stress here is close to the failure state in the absence of mining even though the tectonic setting is thoroughly stable mining initially stabilizes the rock mass by reducing the pore fluid pressure from its initial hydrostatic state to nearly zero the extensive mine excavations as cook showed concentrate the deviatoric stresses in localized regions of the abutments back into a failure state resulting in seismicity secondly there appears to be two distinct types of mining induced earthquakes the first is strongly coupled to the mining and involves shear failure plus a coseismic volume reduction the second type is not evidently coupled to any particular mine face shows purely deviatoric failure and is presumably caused by more regional changes in the state of stress due to mining thirdly energy budgets for mining induced earthquakes of both types indicate that of the available released energy only a few per cent is radiated by the seismic waves with the majority being consumed in overcoming fault friction

moment tensor inversion of induced microseisnmic events evidence of non shear failures in the 4 m 2 moment magnitude range to assess objectively the source mechanism of mining induced seismic events we developed an algorithm to invert for the moment tensor components from this inversion the ratio of isotropic deviatoric component in the source is obtained we are applying this method to microseismic events 4 m 2 recorded at the underground research laboratory url in pinawa manitoba where a tunnel is being excavated at 420 m depth to monitor the seismic activity induced by this opening an array of 16 triaxial accelerometers was installed around the planned tunnel results from the moment tensor inversion on a fist data set provide evidence of non shear failure mechanisms furthermore the location of events displaying a tensile component corresponds to a breakout observed underground in the roof of the tunnel

seismic events with implosional focal mechanisms in the coeur d alene mining district northern idaho rockbursts are a major hazard in the coeur d alene mining district of northern idaho to study the source mechanisms of mining related seismicity we operated 15 portable seismographs in the coeur d alene mining district for one week in september 1990 we found the velocity model of the district to consist of a halfspace with a p wave velocity of 5 74 km s and an s wave velocity of 3 47 km s in mine seismic monitoring systems provided excellent control on the velocity model and most hypocenter locations twenty one events with sufficient focal sphere coverage for fault plane solutions were recorded eleven of the events produced all dilatational first motions for all events 90 of first motions observed were dilatational ten events produced unsolvable first motion data in terms of the usual double couple mechanism but seven of these unsolvable events were found consistent with an implosional source and two others were consistent with a shear implosional source our results provide firm observational evidence that dilatational first motions are predominant in this deep metal mining district probably the result of implosional and shear implosional source mechanisms

frictional continental shelf waves and the circulation response of a continental shelf to wind forcing abstract this paper is an examination of the wind forced circulation on continental shelves with bottom friction since the response is integrally dependent on the cross shelf structures and dispersion characteristics of continental shelf waves modified by bottom friction these are examined first theoretical shelf wave forms are obtained for the north west shelf of australia a wide shelf for which bottom friction is expected to be of major dynamic importance the presence of strong bottom friction r 0 1 cm s 1 introduces substantial modifications to the shelf wave structures on the inner part of the shelf and also causes decay of the wave forms in the direction of energy propagation as for the frictionless case the wind driven circulation with bottom friction can be expanded in terms of the appropriate set of continental shelf waves even with strong bottom friction the circulation close to the coast is still mostly due to low mode shelf waves generated along an extended section of shelf however

global review of human induced earthquakes the human induced earthquake database hiquake is a comprehensive record of earthquake sequences postulated to be induced by anthropogenic activity it contains over 700 cases spanning the period 1868 2016 activities that have been proposed to induce earthquakes include the impoundment of water reservoirs erecting tall buildings coastal engineering quarrying extraction of groundwater coal minerals gas oil and geothermal fluids excavation of tunnels and adding material to the subsurface by allowing abandoned mines to flood and injecting fluid for waste disposal enhanced oil recovery hydrofracturing gas storage and carbon sequestration nuclear explosions induce earthquakes but evidence for chemical explosions doing so is weak because it is currently impossible to determine with 100 certainty which earthquakes are induced and which not hiquake includes all earthquake sequences proposed on scientific grounds to have been human induced regardless of credibility challenges to constructing hiquake include under reporting which is 30 of m 4 events 60 of m 3 events and 90 of m 2 events the amount of stress released in an induced earthquake is not necessarily the same as the anthropogenic stress added because pre existing tectonic stress may also be released thus earthquakes disproportionately large compared with the associated industrial activity may be induced knowledge of the magnitude of the largest earthquake that might be induced by a project mmax is important for hazard reduction observed mmax correlates positively with the scale of associated industrial projects fluid injection pressure and rate and the yield of nuclear devices it correlates negatively with calculated inducing stress change likely because the latter correlates inversely with project scale the largest earthquake reported to date to be induced by fluid injection is the 2016 m 5 8 pawnee oklahoma earthquake by water reservoir impoundment the 2008 m 8 wenchuan people s republic of china earthquake and by mass removal the 1976 m 7 3 gazli uzbekistan earthquake the minimum amount of anthropogenic stress needed to induce an earthquake is an unsound concept since earthquakes occur in the absence of industrial activity the minimum amount of stress observed to modulate earthquake activity is a few hundredths of a megapascal and possibly as little as a few thousandths equivalent to a few tens of centimeters of water table depth faults near to failure are pervasive in the continental crust and induced earthquakes may thus occur essentially anywhere in intraplate regions neither infrastructure nor populations may be prepared for earthquakes human induced earthquakes that cause nuisance are rare but in some cases may be a significant problem e g in the hydrocarbon producing areas of oklahoma usa as the size of projects and density of populations increase the potential nuisance of induced earthquakes is also increasing and effective management strategies are needed

space time variations in source parameters of mining induced seismic events with m 0 space time variations in source parameters and fault plane solutions are related to structural mapping data and local regional stress field measurements in an attempt to characterize the behavior of a rock mass in the vicinity of an excavation in a mine source parameters i e total seismic energy p and s wave energy seismic moment static stress drop and apparent stress were analyzed for 85 events with moment magnitudes between 2 2 m 0 3 within a 90 m microseismic envelope ahead of an excavation these data allowed three types of failure mechanisms to be postulated a zone of flat lying extensional failures next to the excavation a zone of subvertical shear failures at the microseismic envelope boundary and a transition zone between these two where both shear and shear extensional failures occur two spatially distinct event clusters occurred at distance from the excavation for early and late stages of the excavation and next to the excavation during intermediate stages worth noting was an apparent change in p axis orientation with excavation where the average p axes before and following ore extraction were compatible with the local maximum principal stress and the p axes during intermediate excavation stages were compatible with the regional maximum principal stress or local intermediate principal stress distinct from these trends was the general increase in the values of each of the above source parameters over the duration of the excavation suggesting that stress levels were increasing as a result of the excavation geometry and procedure this was considered to be significant as rockbursts mn 1 8 to 2 7 occurred above the study area 6 months following the completion of the excavation

ground vibrations produced by rock motions and debris flows 1 in this study we compare ground vibrations generated by various rocks and debris flows at the same channel to explore the origin of ground vibrations caused by debris flows in field experiments we identified the ground vibrations caused by motions of individual rocks ground vibrations were detected by geophones and analyzed in the time frequency domains we found that ground vibrations caused by individual rocks were 10 150 hz and that larger stones generate ground vibrations with lower peak frequencies a sphere packing model of granular rocks was used to estimate the propagation speed of ground vibrations this was found to be underestimated when compared with our experimental data the signal decay rate was obtained under the assumption that ground vibrations propagate as exponentially attenuating cylindrical waves ground vibrations produced by a debris flow at ai yu zi creek nan tou taiwan on 2 july 2004 revealed that the debris flow forefront produced vibrations lower than 50 hz and ranged between 50 and 100 hz after the front had passed when the main front was closest to the sensor the frequency spectrum covered a wide range from 10 to 250 hz the mean velocity of the debris flow front was 13 3 m s frequencies of ground vibrations caused by individual rocks are within the frequency range of ground vibrations captured during the debris flow confirming that one of the main sources of ground vibration caused by debris flows is the interaction of rocks or boulders with the channel bed

crystal chemical effects on the partitioning of trace elements between mineral and melt an experimental study of melilite with applications to refractory inclusions from carbonaceous chondrites the partitioning behavior of the trace elements be sc ba la ce and tm between melilite and liquid has been determined using stepwise integration of a rayleigh fractionation equation for ion microprobe analyses of synthetic zoned melilite crystals distribution coefficients between melilite and liquid d mel l i were determined over the entire range of melilite spinel crystallization for one bulk composition corresponding to that of an average type b inclusion from the allende c3v carbonaceous chondrite beryllium is incompatible in gehlenitic meliliters e g d mel l b e 0 5 for x ak 0 3 but compatible in akermanitic melilites e g d mel l b e 1 9 for x ak 0 75 barium d mel l b a 0 04 0 05 sc d mel l s c 0 01 0 02 la d mel l l 0 07 0 29 ce d mel l c e 0 05 0 21 and tm d mel l t m 0 03 0 14 are all incompatible in melilites in the range ak25 ak75 variations in d mel l i as a function of x ak are explicable in terms of a simple thermodynamic treatment of trace element partitioning based on crystal chemical considerations characteristic trace element zoning patterns are predicted for early crystallizing melilite from meliliterich type b inclusions for example concentrations of the rees in melilite should continually decrease with increasing degrees of crystallization opposite the behavior normally expected of an incompatible element concentrations of be should rise with increasing degrees of crystallization even when the element is compatible again opposite the behavior normally expected of compatible elements in general zoning patterns of trace elements in melilite from type b inclusions are consistent with those predicted for fractional crystallization from a melt in a closed system trace element zoning patterns in meteoritic melilite crystals constrain the origin and thermal histories of ca al rich inclusions from carbonaceous chondrites

analysis of exceptionally large tremors in two gold mining districts of south africa an investigation of ground motion recorded using broad band wide dynamic range digital seismographs of large mine tremors from two south african mining districts with different geologic settings reveals some essential differences in both seismic source and ground motion parameters in the klerksdorp district where the strata are offset by major throughgoing normal faults the largest tremors with magnitudes ranging as high as 5 2 tend to be associated with slip on these pre existing faults moreover the seismic source and ground motion parameters are quite similar to those of natural crustal earthquakes in the carletonville district by contrast where substantial faults do not exist the large magnitude tremors appear to result from the failure of relatively intact rock and cause seismic stress drops and ground motion parameters higher than normally observed for natural shocks additionally there appears to be an upper magnitude limit of about 4 in the carletonville district detailed analyses of an exceptionally large event recorded locally from each of these districts serve to highlight these contrasts

the use of waveform similarity to define planes of mining induced seismic events abstract mining induced seismicity results from a complex interaction of ambient and mining induced stresses acting on a rock mass that has been intersected by a variety of geological weaknesses and discontinuities a major challenge is to improve mine design methodology by identifying the geological features that are seismically active and then changing the direction of mining to reduce the potential for shear slip on these features in this paper we classify seismic events with similar waveforms doublets into multiplets relocate them simultaneously using arrival time differences based on cross correlations between all event pairs and then identify the orientation of the most likely plane on which the events are located identification of multiplets has been automated even including events that have not previously been located in contrast to the conventional master event method no single master event is used each event is a master event for each other event the absolute location of each multiplet is stabilised by using all manually selected arrival times vectors are drawn between all pairs of events and principal component analysis applied to obtain the orientation of the most likely plane of the events in each multiplet we tested this method on seismic data recorded underground at a site in blyvooruitzicht gold mine south africa in which a strike stabilising pillar has been mined from one end with the aid of precondition blasting we found that 39 of events that were previously located in a diffuse cloud within a mine pillar were formed into three distinct multiplets two multiplets were oriented parallel to directions of dominant mining induced stresses i e along the long axis of the pillar and parallel to the active mining face and the third along a pervasive joint set

source parameters of mining induced seismic events an evaluation of homogeneous and inhomogeneous faulting models for assessing damage potential source parameter estimates based on the homogeneous and inhomogeneous source models have been examined for an anomalous sequence of seven mine induced events located between 640 and 825 m depth at strathcona mine ontario and having magnitudes ranging betweenmn 0 8 and 2 7 the derived brune static stress drops were found to be similar to those observed for natural earthquakes 30 bars whereas dynamic stress drops were found to range up to 250 300 bars source radii derived from madariaga s model better fit documented evidence of underground damage these values of source radii were similar to those observed for the inhomogeneous model the displacement at the source based on the observed attenuation relationship was about 60 mm for three magnitude 2 7 events this is in agreement with slip values calculated using peak velocities and assuming the asperity as a brune source within itself 72 mm by using madariaga s model for the asperity the slip was over 3 times larger than observed peak velocity and acceleration scaling relations with magnitude were investigated by incorporating available south african data appropriately reduced to canadian geophysical conditions the dynamic stress drop scaled as the square root of the seismic moment similar to reported results in the literature for crustal earthquakes this behavior suggests that the size of the asperities responsible for the peak ground motion with respect to the overall source size follow distributions that may be similar over a wide range of magnitudes measurements of source rupture complexity ranging from 2 to 4 were found to agree with estimates of overall source to asperity radii suggesting together with the observed low rupture velocities 0 3 to 0 6 that the sources were somewhat complex validation of source model appropriateness was achieved by direct comparison of the predicted ground motion level to observed underground damage in creighton mine located within the same regional stress and geological regime as strathcona mine close to the source 100 m corresponding to relatively higher damage levels a good agreement was found between the predicted peak particle velocities for the inhomogeneous model and velocities derived based on established geomechanical relationships the similarity between asperity radii and the regions of the highest observed damage provided additional support for the use of the inhomogeneous source model in the assessment of damage potential

probabilistic location of seismic sequences in heterogeneous media we have developed a method for the bayesian location of seismic sequences in 3d heterogeneous velocity models the method is based on a bayesian algorithm for single earthquake location joint location of seismic sequences is performed by summing the probability density functions for individual earthquake locations one of the main features of the method is the ability to accumulate travel times in the heterogeneous model as a function of both the seismic stations and the grid points simulating the seismogenic volume the ability to compute travel times just once separately from the location process allows for fast 3d locations this is a very attractive feature for real time monitoring probabilistic location of seismic sequences visualized in terms of contours of earthquake density moment and energy release etc can be obtained to give a much more seismotectonic insight than classical location algorithms the continuous character of the output quantities is particularly indicated for seismic network testing purposes it is in fact possible to compute the response of the location procedure given the seismic network geometry to various input earthquake distributions some applications of the method are also shown in this work both to the location of synthetic earthquakes and of real sequences seismic sequences at vesuvius and campi flegrei volcanic areas southern italy have been located by the probability algorithm allowing a better picture of the primary seismogenic structures we also apply the method to assess the resolution of the operating monitoring networks at the two areas

earthquake rupture at focal depth part ii mechanics of the 2004 m2 2 earthquake along the pretorius fault tautona mine south africa we analyze here the rupture mechanics of the 2004 m2 2 earthquake based on our observations and measurements at focal depth part i this event ruptured the archean pretorius fault that has been inactive for at least 2 ga and was reactivated due to mining operations down to a depth of 3 6 km depth thus it was expected that the pretorius fault zone will fail similarly to an intact rock body independently of its ancient healed structure our analysis reveals a few puzzling features of the m2 2 rupture zone 1 the earthquake ruptured four non parallel cataclasite bearing segments of the ancient pretorius fault zone 2 slip occurred almost exclusively along the cataclasite host rock contacts of the slipping segments 3 the local in situ stress field is not favorable to slip along any of these four segments and 4 the archean cataclasite is pervasively sintered and cemented to become brittle and strong to resolve these observations we conducted rock mechanics experiments on the fault rocks and host rocks and found a strong mechanical contrast between the quartzitic cataclasite zones with elastic brittle rheology and the host quartzites with damage elastic plastic rheology the finite element modeling of a heterogeneous fault zone with the measured mechanical contrast indicates that the slip is likely to reactivate the ancient cataclasite bearing segments as observed due to the strong mechanical contrast between the cataclasite and the host quartzitic rock

experimental studies of trace element partitioning in ca al rich compositions anorthite and perovskite using electron probe and ion probe techniques experimental crystal liquid partition coefficients d have been measured in meteoritic ca al rich inclusion cai compositions for mg zr y and rees in anorthite and perovskite partitioning data for ti in anorthite and al in perovskite are also reported where cross comparisons are possible between electron and ion probe data agreement is good concentration variations in anorthite for many elements are beyond what can be explained by fractional crystallization but show well defined interelement correlations which could reflect the temperature dependence of the d values or could result from liquid boundary layers for anorthite our d values for rees are lower and they decrease more rapidly with decreasing ionic radius than most in the literature most of the older ree d patterns for plagioclase in the literature are too flat because of insufficient purity of mineral separates or because of analytical problems new ion probe data for minor and trace elements in anorthite from type b cais permit detailed comparisons with fractional crystallization models based on the measured d values for most comparisons models and observations do not agree for amounts of crystallization less than 90 it is possible that anorthite does not appear until after 95 crystallization compared to about 40 which would be expected from isothermal equilibrium crystallization experiments the lrees are highly compatible elements in perovskite but d values drop sharply for the hrees y and zr d values for rees increase strongly from air to highly reducing conditions as coupled ree ti 3 substitutions become possible model calculations show that ree patterns in igneous perovskites from cais will reflect the d pattern and the models can explain some ree patterns from compact type a cais however there are other sets of trace element data for perovskite in cais that cannot easily be explained by igneous processes

a simple theory for the fate of buoyant coastal discharges abstract a simple theory that predicts the vertical structure and offshore spreading of a localized buoyant inflow onto a continental shelf is formulated the theory is based on two competing mechanisms that move the buoyant fluid offshore 1 the radial spread of the lighter water over the ambient water being deflected by the coriolis force and producing an anticyclonic cyclostrophic plume and 2 offshore transport of buoyant water in the frictional bottom boundary layer that moves the entire plume offshore while maintaining contact with the bottom the surface expression of the cyclostrophic plume moves offshore a distance ys 2 3g h0 2i 2g h0 2i 1 2f where g is reduced gravity based on the inflow density anomaly h0 is the inflow depth i is the inflow velocity and f is the coriolis parameter the plume remains attached to the bottom to a depth given by hb 2l ih0f g 1 2 where l is the inflow width both scales are based solely on parameters of the buoyant inflow at its source there

injection induced microseismicity in colorado shales imperial oil resources limited uses cyclic steam stimulation to recover oil from their cold lake oil field in alberta this operation in particular situations can be associated with the failure of well casings in the colorado shales above the oil bearing formation a number of fluid injection operations was undertaken at this site and the associated microseismicity was detected using two three component geophones and fifteen hydrophones the purpose of this experiment was to simulate the occurrence of a casing failure determine the feasibility of monitoring in a shallow environment and characterize the microseismic activity a calibration survey provided values of 1786 108 m s for p wave velocity 643 56 mks for s wave velocity and 0 428 0 017 for poisson s ratio in the shale formation estimates of the quality factor q p were 15 for the horizontal direction and 38 for the vertical direction corroborating the evidence of velocity anisotropy calibration shots were located to within 10 m of the actual shot points using triangulation and polarization techniques several hundred microseismic events were recorded and 135 events were located the results showed that microseismic activity was confined to depths within 10 meters of the injection depth the experiment clearly established the feasibility of detecting microseismicity induced by fluid injection rates typical of casing failures in shales at distances over 100 m

the geochemical coherence of pu and nd and the pu 244 u 238 ratio of the early solar system abstract two very different sets of 244 pu 238 u ratios have been reported for early solar system materials one group of samples yields high 0 015 0 016 ratios podosek 1970a 1972 drozd et al 1977 and calculations based on another group of analyses yield low ratios 0 004 marti et al 1977 recently measured partition coefficients for pu and sm are used to evaluate the data of marti et al and sol 244 pu 238 u ratios from other sources are also considered a low sol 244 pu 238 u ratio 0 005 is favored and some implications of this low ratio to galactic nucleosynthesis and meteorite age dating are briefly discussed

interactions between western boundary currents and shelf waters a mechanism for coastal upwelling a geostrophic adjustment model has been developed to describe interactions between shelf waters and an offshore current such as a western boundary current a simple analysis demonstrates the response of coastal waters to the gradual encroachment of a western boundary current and reveals how this can lead to strong upwelling when bottom friction is taken into account conditions favorable to upwelling actually occur well before the western boundary current comes into direct contact with the bottom some aspects of the theory have been compared with laboratory experiments on interacting currents over sloping topography the comparisons are quite favorable for relatively stable flows however under other conditions baroclinic instabilities grow into large eddies which dramatically enhance exchange between the two currents results from the study are used to interpret documented observations of coastal encroachment by the east australian current and associated phytoplankton blooms

plutonium uranium and rare earths in the phosphates of ordinary chondrites the quest for a chronometer abstract the distributions of pu u and the ree in particular nd in single crystals of the calcium phosphates merrillite and apatite of ordinary chondrites were studied to establish whether 244 pu can be used to determine time differences in meteorite formation uranium was measured by an induced fission track technique and the ree by secondary ion mass spectrometry limits on pu concentrations at the time of track retention were inferred from fossil track measurements it is argued here that most previous estimates of pu concentrations obtained from fossil tracks in phosphates failed to correct adequately for spallation induced tracks and were probably not correct plutonium is preferentially enriched in merrillite relative to apatite in contrast u concentrations are on the average 15 times higher in apatite than in merrillite there are grain to grain variations in the same phosphate phase from a given meteorite for both elements on the other hand in the merrillite of a given meteorite the ree concentrations are remarkably constant typical grain to grain variations for type 5 and 6 chondrites are in most cases less than 10 average nd concentrations in the merrillite of 15 different chondrites range from 96 to 164 ppm ree abundances in apatite show more variations average nd concentrations in the apatite of 13 chondrites range from 8 to 54 ppm and the ratios of nd concentrations in merrillite relative to apatite range from 2 7 to 11 despite the higher affinity of both pu and the ree for merrillite than for apatite there is no quantitative correlation between the abundances of these elements in merrillite grains from a given ordinary chondrite because of this lack of geochemical coherence between pu and any of the ree it is concluded that 244 pu cannot be used to determine the relative formation times of chondrites bulk measurements that avoid the problems associated with fossil track measurements are discussed however they have so far proven to be of little utility

laboratory study of the underground sound generated by debris flows 1 this experimental study investigates the underground sound generated by different kinds of rock motions that occur in debris flows the experiments were divided into two parts the first part consisted of measuring the main characteristics of the underground sound caused by friction of a rock rubbed against a bed of gravel and of that caused by a free falling rock hitting a similar bed of gravel in the second part a hydrophone was installed at the bottom of a laboratory channel to measure the underground sound of debris flows in that channel the sound signals were analyzed using both the fast fourier transform and the gabor transform to represent the signals in both the frequency and time frequency domains the measurement results reveal that the frequency of the sound generated by the rock gravel bed friction is relatively low being mostly between 20 and 80 hz in contrast the frequency range of the collision sound is relatively higher between 10 and 500 hz finally the frequency of the underground sound caused by the debris flows in the flume is in the range of 20 300 hz

a typical evolution of seismicity patterns resulting from the coupled natural human induced and coseismic stresses in a longwall coal mining environment abstract a very unusual time space distribution of seismicity accompanying coal exploitation has been observed in a polish mine the earthquakes did not follow the depth of mining but exhibited changing depths from far below to close to the mined seam one of the deep events which occurred at close epicentral distance to the active mining front was m l 3 7 event this paper presents the study of possible coupling of natural human induced and coseismic stresses in a longwall coal mining environment the full moment tensor solution showed that the strong earthquake occurred on an almost vertical plane consistent with approximate strike of local tectonic structure the signal correlation analysis revealed some highly correlated pairs within both deep and shallow event groups to evaluate inducing factor of ongoing and past exploitation geomechanical modelling of its influence on strain and stress at the target depth has been performed the results exhibited a changing vertical stress regime which might have promoted failure on preexisting almost vertical planes of weakness the earthquakes rate variation in time showed no increase in activity right after the occurrence of m l 3 7 event the p s wave spectra corner frequency ratio had an average of 1 0 suggesting slow rupture however the coulomb stress change analysis showed that the magnitude of stress changes due to coseismic slip of m l 3 7 event at the hypocentral depth is of the same order as the stress changes caused by mining thus the distribution of seismicity at this level could have been driven by both exploitation and coseismic stresses moreover the seismicity which occurred within first few weeks after m l 3 7 event followed positive stress changes all the obtained results let us prove that the m l 3 7 event was a tectonic earthquake triggered by ongoing exploitation and that the distribution of following seismicity was affected by coupled natural exploitation induced and coseismic stresses

precise hypocentre relocation of microearthquakes in a high temperature geothermal field the torfajokull central volcano iceland the torfaj okull volcanic system is one of approximately 30 active volcanoes comprising the neovolcanic zones of iceland the central volcano of the system is the largest silicic centre in iceland with a caldera of approximately 12 km diameter its high temperature geothermal system is one of the most powerful in iceland torfaj okull is a source of persistent seismicity where both high and low frequency earthquakes occur to study this microseismicity in detail a temporary array of 20 broad band seismic stations was deployed between 2002 june and november these temporary stations were embedded in the permanent south iceland lowland sil network and data from nine adjacent sil stationswere included in this study aminimum one dimensional 1 d velocity model with station corrections was computed for earthquake relocation by inverting manually picked p and s wave arrival times from events occurring in the torfaj okull volcanic centre and its surroundings high frequency earthquakes from the torfaj okull volcanic centre were then relocated calculating a non linear probabilistic solution to the earthquake location problem subsequently we correlated the waveforms of these 121 events 2000 observations to define linked events calculated the relative traveltime difference between event pairs and solved for the hypocentral separation between these events the resulting high resolution pattern shows a tighter clustering in epicentre and focal depth when compared with original locations earthquakes are mainly located beneath the caldera with hypocentres between 1 and 6 km depth and lie almost exclusively within the geothermal system a sharp cut off in seismicity at 3 km suggests either that there is a marked temperature increase or that this is a structural boundary no seismic activity was observed in the fissure swarms to the northeast ne and southwest sw of the volcanic centre

composition and isotopic constraints on the petrogenesis of alkaline arc lavas lihir island papua new guinea the sio2 undersaturated lavas from lihir island papua new guinea like most arc lavas are highly enriched in sr ba k rb and cs and depleted in hf ta nb and ti relative to ocean floor basalts and oceanic island basalts these alkali rich lavas have arc trace element signatures and nd sr and pb isotopic systematics however they are not a product of present day subduction as this volcanism has tapped mantle which was enriched by prior subduction episodes the narrow range of pb 206pb 204pb 18 74 18 76 and nd 143nd 144nd 0 51297 0 51304 isotopic compositions suggest a cogenetic origin for these lavas during the fractionation of the primitive lihir lavas elements normally considered incompatible i e the light rare earth elements lree rb th and p have high bulk solid melt partition coefficients 0 15 1 5 relatively higher partition coefficients during forma tion of the evolved lavas produced crossing rare earth element ree patterns and primitive lavas have higher incompatible elements abundances than evolved lavas this results from 1 changes in the amount of apatite in the fractionating assemblage and 2 the abnormal partitioning of trace elements into apatite microphenocrysts which nucleate at the crystal liquid interface of rapidly growing clinopyroxene phenocrysts the lihir lavas have lower alkali sr ba k rb cs and lree abundances than other tabar feni lavas they are derived from a less enriched mantle source rather than by a higher degree of melting of a source similar to that of the other islands the similarity of sm nd ratios of these undersaturated arc lavas to those of tholeiitic and calc alkaline arc lavas and the moderate chondrite normalized la yb la ybcn 3 7 indicates that there has been limited enrichment of the lree relative to the heavy ree during generation of the arc modified source mantle the alkaline nature of these lavas reflects their generation in a tensional tectonic environment from a fossil arc mantle region that has undergone extreme arc enrichment of alkali and alkaline earth elements during two earlier subduction episodes

source mechanisms of mine related seismicity savuka mine south africa we report full moment tensor solutions for 76 mine tremors with moment magnitudes mw between 0 5 and 2 6 recorded by a network of 20 high frequency geophones in a deep gold mine in south africa source mechanisms convey important information on how in mine stresses are relaxed and understanding the nature of such mechanisms is essential for improving our assessment of rock mass response to mining our approach has consisted of minimizing the l2 norm of the difference between observed and predicted p sv and sh spectral amplitudes with visually assigned polarities to constrain all six independent components of the seismic moment tensor our results reveal the largest principal stresses in the mine are com pressive oriented near vertically and relaxed through a mix of volumetric closure and normal faulting consistent with a gravity driven closure of the mined out areas pre vious moment tensor studies in deep mines had suggested that the distribution of seis mic sources in terms of the volumetric shear mix was bimodal a bimodal distribution is compatible with our moment tensor solutions only for moment magnitudes above 2 2 events in the 0 5 mw 2 2 moment magnitude range display a continuous distribution of their volumetric shear mix online material focal parameters for mine tremors at savuka

location of microseismic swarms induced by salt solution mining ground failures caving processes and collapses of large natural or man made underground cavities can produce significant socio economic damages and represent a serious risk envisaged by the mine managements and municipalities in order to improve our understanding of the mechanisms governing such a geohazard and to test the potential of geophysical methods to prevent them the development and collapse of a salt solution mining cavity was monitored in the lorraine basin in northeastern france during the experiment a huge microseismic data set similar to 50 000 event files was recorded by a local microseismic network 80 per cent of the data comprised unusual swarming sequences with complex clusters of superimposed microseismic events which could not be processed through standard automatic detection and location routines here we present two probabilistic methods which provide a powerful tool to assess the spatio temporal characteristics of these swarming sequences in an automatic manner both methods take advantage of strong attenuation effects and significantly polarized p wave energies at higher frequencies 100 hz the first location approach uses simple signal amplitude estimates for different frequency bands and an attenuation model to constrain the hypocentre locations the second approach was designed to identify significantly polarized p wave energies and the associated polarization angles which provide very valuable information on the hypocentre location both methods are applied to a microseismic data set recorded during an important step of the development of the cavity that is before its collapse from our results systematic spatio temporal epicentre migration trends are observed in the order of seconds to minutes and several tens of meters which are partially associated with cyclic behaviours in addition from spatio temporal distribution of epicentre clusters we observed similar epicentre migration in the order of hours and days all together we suggest that the recorded microseismicity mainly represents detachment and block breakage processes acting at the cavity s roof indicating a zone of critical state of stress and where partial fractures cause chain reaction failures as a result of stress redistribution processes