three dimensional in situ stress evaluation using a new under coring technique the tseng wen reservoir transbasin water tunnel the tseng wen reservoir transbasin water tunnel has broken the historical record of the maximum overburden of a tunnel within taiwan the three dimensional in situ stresses at the tunnel were evaluated using acoustic emission ae and deformation rate analysis dra with an under coring technique this is the first time that the ae and dra have been used in evaluating an in situ stress in taiwan as cores drilled in different directions are required for the three dimensional stress evaluation but the in situ borehole drilling is usually limited to the vertical direction small samples 2 28 cm in diameter and 4 56 cm in length were under cored from the borehole cores in six directions to evaluate the in situ stresses cyclic uniaxial compressive loadings were artificially applied to the changchikeng sandstones under cored from the outcrops the experimental results validate the definitiveness of using under cored samples at different pre stresses with ae and dra then cores taken from the tseng wen reservoir transbasin water tunnel site at a great depth of 416 739 m underground were under cored the experimental results indicate that the major principle in situ stress is from 30 8 to 39 mpa and is in the directions of se nw and sw ne at different depths

stress evolution in southern california and triggering of moderate small and micro size earthquakes we calculate the evolution of stresses in southern california extending the study of deng and sykes 1997 by increasing from 6 to 36 the number of earthquakes for which coseismic changes in stress are computed and by expanding from m 6 to m 1 8 the range of magnitudes m of events whose focal mechanism solutions are examined in the context of the evolving stress field the cumulative stress on a given date is calculated with respect to an arbitrary zero baseline just before the 1812 wrightwood earthquake by taking into account the long term stress loading associated with 98 fault segments and coseismic stress changes for 36 significant earthquakes our calculations indicate that more than 85 of m 5 earthquakes from 1932 1995 occurred in regions of positive change in coulomb failure function cff most of the remaining about 15 earthquakes that occurred in areas of negative cff fall very close to boundaries between positive and negative cff some of which are sensitive to the less well controlled slip distributions of the earliest historic events calculations also show that from 1981 until just before the 1992 landers earthquake more than 85 of small m 3 and micro size m 1 8 shocks in the seeber and armbruster 1995 catalog with mechanisms involving either nw trending right lateral or ne trending left lateral strike slip faulting occurred in regions of positive cff the ratio of encouraged to all small and micro size events reaches a high value of about 88 if an apparent coefficient of friction between 0 0 and 0 6 is used the highest percentage of earthquakes occurred in areas where stress is about 1 mpa above the 1812 baseline most 66 events occurred in regions of cff between 0 0 and 2 0 mpa the upper limit indicates that the approximate range of stress variation in the earthquake cycle is of the order of 2 0 mpa the fact that the locations of most moderate small and micro size earthquakes are still related to stress changes remaining from large historical events might be used to constrain slip distribution of some of those earthquakes and to constrain the locations of future significant events

earthquake mechanisms of the adriatic sea and western greece implications for the oceanic subduction continental collision transition summary we present 21 focal solutions magnitude 5 5 reliably computed by body wave modelling for the western hellenic arc from yugoslavia to the southern peloponnese mechanisms located within the aegean show normal faulting the t axis trending n s in the centre and parallel to the active boundary in the external part mechanisms associated with the keffalinia fault are consistent with dextral strike slip motion reverse mechanisms located along the active boundary are remarkably consistent and do not depend on the nature of the active boundary continental collision or oceanic subduction the consistency in azimuth of the slip vectors and of the gps velocity relative to africa all along the active boundary suggests that the deformation is related to the same motion the discrepancy between seismic energy release and the amount of shortening confirms that the continental collision is achieved by seismic slip on faults but the oceanic subduction is partially aseismic the northward decrease in velocity between continental collision and oceanic subduction suggests the continental collision to be a recent evolution of the active subduction

back analysis of an excavated slope failure in highly fractured rock mass the case study of kargar slope failure iran this paper examines the failure of kargar cut slope located at the south part of esfahan subway using analytical and numerical back analysis methods the excavated trench has 27 m depth with near vertical walls due to the space limitation around it the geology of the area comprises weathered and heavily jointed shale and sandstone overlaid by alluvium deposits despite the slope being supported by shotcrete and fully grouted rock bolts a catastrophic failure occurred at the east wall due to the uncertainty about the causes of failure initiation back analyses have been performed via both the limit equilibrium and numerical method for considering various probable mechanisms in the back analysis with limit equilibrium method the rock mass is assumed as an equivalent continuum and hoek brown failure criterion and geological strength index gsi are applied to calculate the shear strength parameters the results show that gsi value was 33 in the failed mass in the numerical back analysis the distinct element method is applied to study the contribution of rock joints to the failure and progressive rock mass strength degradation until failure the results show that threshold values of joint cohesion and friction were 0 2 mpa and 30 respectively also the modeled slip surface being step shaped agrees with the observed one

kita uebaru natural rock slope failure and its back analysis a large landslide occurred in kita uebaru or asato area of nakagusuku village in okinawa island japan on 10 june 2006 after a rainy period of about 9 days the total rainfall was 126 mm from june 8 till the time of the landslide this period this landslide destroyed several buildings and roads and the total travel distance of the landslide was about 110 m in this article the authors were concerned with the initiation conditions of kita uebaru landslide and post failure motions of the landslide body the observations made in the landslide area structural geology analyses and outcomes of geotechnical investigations are described first then possible causes of the landslide are investigated through back analyses using as inputs the geological structure and the strength properties of planes of discontinuities involved in the sliding processes the final part of the article is concerned with the simulation of post failure motions of the landslide body the results of the investigations and back analyses indicate that the failure plane was bi planar and the heavy torrential rainy period for about 3 days was the main cause of initiation of the landslide the mechanical model presented in this article was capable of capturing the overall features of the landslide body following the initiation of the failure

evidence for transform faulting in the ionian sea the cephalonia island earthquake sequence of 1983 accurate locations of aftershocks of the january 17 1983 ms 7 0 main shock in the ionian islands have been determined as well as fault plane solutions for this main shock and its largest aftershock which are interpreted as a right lateral strike slip motion with a thrust component on a fault striking in about a ne sw direction

chlorofluorocarbon derived formation rates of the deep and bottom waters of the weddell sea the spreading and mixing of deep and bottom waters from the weddell sea originating with potential temperature 0 c are investigated through analysis of new and historical cfc measurements we investigate the component that enters the southern indian ocean with a simple one dimensional advection diffusion model of the deep boundary current this model does not require a condition of mixing solely with tracer free water to be imposed as boundary conditions we derive time histories for the cfc concentrations of newly formed weddell sea deep and bottom waters a range of best fit velocities is obtained by determining which model velocities produce model tracer concentrations closest to measured concentrations from this we derive a formation rate of 3 2 1 5 sv for the waters originating with temperatures lower than 0 c that subsequently enter the southern indian ocean this compares to an upper limit for these waters of 5 7 sv derived from the cfc 11 cfc 12 ratio whilst the former value is dependent on the highly idealized concepts of the model used the latter is a more robust upper limit using the cfc 11 cfc 12 ratio measured at vema channel during the world ocean circulation experiment cruise a23 an upper limit of 0 9 sv is derived for the formation rate of waters colder than 0 c that enter the south atlantic overall an upper limit of 6 6 sv is derived for the rate of formation of the deep and bottom waters of the weddell sea a better representation is obtained by combining the upper limit to the south atlantic component with the model derived southern indian ocean estimate we thus estimate the formation rate of the deep and bottom waters in the weddell sea to be 3 7 1 6 sv whilst the range obtained is large and the assumptions implicit in the calculations are potentially significant we believe this more realistically represents the true formation rate than estimates derived using an imposed condition of tracer free mixing the range can be narrowed in future as more data become available

formation of systematic joints in metamorphic rocks due to release of residual elastic strain energy otago schist new zealand abstract we present the first regional study of joints in the jurassic cretaceous otago schist new zealand the purpose of this study was to explore the origin and mechanism of joint formation in metamorphic rocks especially any possible association between brittle and previous ductile deformation the otago schist is cut by numerous systematic joints up to tens of metres long at any one exposure we measured the orientation of joints schist foliation planes and quartz rods mineral lineations at 46 sites across the otago schist and calculated the spherical angles between their means in relatively high metamorphic grade schists greenschist facies typically one systematic joint set has developed sub perpendicular to penetrative foliation and lineation irrespective of foliation and lineation orientations this relationship also holds in lower grade schists pumpellyite actinolite facies but more than one joint set is occasionally present the flanking unfoliated schist protoliths prehnite pumpellyite facies contain no systematic joint sets a late cretaceous age for schist joint formation is indicated on the basis of lack of joint continuation into late cretaceous conglomerates that unconformably overlie jointed schists cooling history consistent orthogonality of joints with foliation and lineation and lack of relationship of systematic joints to late cenozoic plate boundary features we propose a model for joint formation during late cretaceous exhumation of the schist and suggest that the systematic joints formed due to release of residual elastic strain energy preserved in the schists from early cretaceous ductile deformation

microseimicity and strain pattern in northwestern greece during a 7 week microearthquake experiment conducted in epirus akarnania and the ionian islands of western greece we located approximately 600 earthquakes with magnitudes between 2 and 4 2 no event was deeper than 40 km the seismicity cannot be clearly associated with any single fault except the lixourion right lateral fault located west of the ionian islands focal mechanisms of about 100 earthquakes show for a narrow band of earthquakes located along the coast ene wsw shortening consistent with the surface tectonics farther east focal mechanisms show nnw sse extension beneath the foothills of the pindus mountains which is unrelated to surface faulting but is consistent with the presently subsiding basins this strain pattern is seen far north and south of the lixourion fault and is similar to the one observed in the peloponnese it suggests that a large scale mechanism is responsible for the recent geodynamics of both the northwestern and southwestern aegean

moment magnitude relations based on strong motion records in greece in this work the variation of the local magnitude mlsm derived from strong motion records at short distances is examined in terms of moment magnitude m w strong motion data from greek earthquakes are used to determine the strong motion local magnitude mlsm by performing an integration of the equation of mo tion of the wood anderson wa seismograph subjected to an input acceleration the most reliable strong motion data are utilized for earthquakes with seismic mo ments log m 0 22 0 dynecm and calculated local magnitudes mls m 3 7 the correlation between the seismic moments log m0 and the calculated local magni tudes mlsm using strong motion records is given by log m 0 1 5 mcsu 16 07 which is very similar to that proposed by hanks and kanamori 1979 moreover it is shown that mls m is equal to moment magnitude mw for a large mls m range 3 9 to 6 6 comparison of the strong motion local magnitude and the me magnitude estimated in greece ml n and surrounding area shows a systematic bias of 0 4 to 0 5 similar to the difference that has been found between m w and mlgr for the same area the contribution of the local site effects in the calculation of the local magni tude mlsm is also considered by taking into account two indices of soil classification namely rock and alluvium or the shear wave velocity vs30 of the first 30 m based on nehrp 1994 and ubc 1997 an increase of mls m by 0 16 is observed for alluvium sites alternative relations showing the mls m variation with v 3 are also presented finally examination of the wa amplitude attenuation log a0 with distance shows that the jennings and kanamori 1983 relation for a 100 km is appropriate for greece the same results confirm earlier suggestions that the 0 4 to 0 5 bias between mlgr and mw also mlsa4 should be attributed to a low static magnification 800 of the athens wa instrument on which all other m l relations in greece have been calibrated

mode of strong earthquake recurrence in the central ionian islands greece possible triggering due to coulomb stress changes generated by the occurrence of previous strong shocks the spatiotemporal distribution of shallow strong m 6 3 earthquakes occurring in the area of central ionian islands is analyzed these shocks are generated on two adjacent fault segments with different strike but both segments are associated with strike slip faulting constituting the boundary between continental collision to the north and oceanic subduction to the south seismic activity is concentrated in short time intervals alternating with much longer relatively quiescent periods each active period consists of a relatively large event or series two to four of events occurring closely both in space and time this alteration was observed to happen four times since 1867 the period when complete data exist for the study area since the phenomenon is not strictly periodic and during each active period multiple events occurred i attempted to interpret the seismic behavior on the basis of possible trig gering i then investigated how changes in coulomb failure function dcff asso ciated with one or more earthquakes may trigger subsequent events both the co seismic slip due to the generation of the strong earthquakes and stress buildup associated with the two major fault segments were taken into account for the dcff calculation earthquakes can be modeled as static dislocations in elastic half space and the stress pattern has been calculated according to the geometry and slip of each of the faults that ruptured in the chain of events these calculations show that 13 out of 14 earthquakes of m 6 3 were preceded by a static stress change that encouraged failure the magnitude of the stress increases transferred from one earthquake to another ranged from 0 01 mpa 0 1 bar to over 0 1 mpa 1 bar showing that stress transfer adequately explains the occurrence pattern of these events maps of current dcff provide additional information to long term earthquake prediction areas of positive dcff have been identified at two sites in kefalonia and lefkada faults respectively where the next strong events are expected to occur a fact that will substantiate the hypothesis elaborated in this article

bottom water circulation in the western equatorial pacific as inferred from carbon tetrachloride observations hydrographic and tracer data from the western equatorial pacific collected during cruise 113 of r v sonne in october november 1996 are discussed in the context of spreading of lower circumpolar deep water lcdw the horizontal distribution of ccl4 and other properties indicate a deep western boundary current north of the caroline seamounts elevated concentrations of ccl4 at the bottom show that a small fraction of lcdw in this region is younger than about 70 years this age is used to infer a minimum spreading rate of about 0 8 cm s for the young components of this water mass the current appears to bifurcate at about 143 e into topographically guided northward and westward currents

evolution of the stress field in the northern aegean sea greece summary the evolution of the stress field in the area of the northern aegean sea during the 20th century has been studied the area is dominated by dextral strike slip faulting and is characterized by frequent strong earthquakes coulomb stress changes dcff were calculated assuming that earthquakes can be modelled as static dislocations in an elastic half space and taking into account both the coseismic slip in large mi7 0 earthquakes and the slow tectonic stress build up along the major fault segments the stress change calculations were performed for strike slip faults of strike dip and rake appropriate to the large events we evaluate whether these stress changes brought a given large earthquake closer to or farther from failure it was found that each of the large events occurred in regions of increased calculated coulomb stress moreover the majority of smaller events for which reliable fault plane solutions are available were also located in areas of positive dcff by extending the calculations to 2020 and assuming that no additional large mi7 0 earthquake occurs between 1999 and 2020 possible sites of future large earthquakes are identified

investigation of key techniques on floor roadway support under the impacts of superimposed mining theoretical analysis and field study various sizes of coal pillars will be formed after the mining of close distance coal seams the concentrated stress formed on the coal pillars can cause serious deformation and failure to the roadway below floor roadway wantian coal mine in guizhou was taken as an example to study the stress propagation and distribution of roadway by kirsch equations based on the stope condition a numerical model was established to analyze the changes of stress displacement and plastic zones around roadways and the cause for roadway deformation during the mining of the upper coal seams the new support scheme was designed and applied at the study site the results show that the vertical stress the maximum shear stress and the plastic zones of the rock surrounding the roadway increase with the mining of the upper working faces roadway deformation and failure mainly occurs at floor sides and corners the key of roadway support was to control floor heave and then to recover the integrity and strength of the surrounding rock of two sides the developed omnidirectional rotatable drilling equipment can guarantee the success rate of floor drilling the broken surrounding rock of floor was enhanced through grouting the high prestress cable was used to support the roof and two sides and the birdcage cable was for the floor by the new support system the roadway deformation was controlled which could meet the support requirements

distribution of oxygen isotopes in the water masses of drake passage and the south atlantic measurements of the ratio of stable isotopes of oxygen 18o and 16o from samples collected on world ocean circulation experiment sections sr1b eastern drake passage and a11 punta arenas to cape town are used together with hydrographic data to deduce information about the formation and variability of south atlantic and southern ocean water masses the drake passage surface waters south of the polar front pf are isotopically light 18o around 0 4 owing to the influence of meteoric waters the salinity and 18o of the a11 surface waters yield an apparent freshwater end member which is much isotopically lighter than the local precipitation thus advection of these waters from farther south dominates over local effects in determining the surface water properties the drake passage section shows unusual proximity of the two main fronts of the antarctic circumpolar current the pf and subantarctic front saf and we observe cold fresh and isotopically light water derived from the temperature minimum winter water at the saf this water is of the correct density to freshen the intermediate water north of the saf and thus play a role in the formation of the comparatively fresh antarctic intermediate water aaiw of the south atlantic this confirms the role of antarctic water in forming the south atlantic variety of aaiw across the a11 section the oxygen isotope and salinity data at the aaiw core show very similar traces with waters in the malvinas current loop showing lowest values of both at the eastern boundary of the south atlantic the input of red sea water from east of south africa is observed via the presence of anomalously isotopically heavy aaiw we deduce potentially significant temporal variability in the isotopic composition of weddell sea deep water wsdw by comparing the drake passage data to earlier data covering the outflow of the weddell sea the a11 data show wsdw consistent with such variability indicating that its effects could persist in the waters as they flow north into the western south atlantic we speculate that such variability could be due to small changes in the amount of glacial ice melt in wsdw

application of 3d laser scanner optical transducers and digital image processing techniques in physical modelling of mining related strata movement a physical testing protocol for modelling mining related problems has been presented a new method for monitoring fracture propagation pattern has been introduced laser based and optical devices have been used for physical modelling of subsidence multiple seam subsidence has been measured by photogrammetry dic analysis optoncdt and 3d tls

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

mining induced strata stress changes fractures and gas flow dynamics in multi seam longwall mining abstract this paper presents key findings from a recent comprehensive study of longwall mining induced strata movement stress changes fractures and gas flow dynamics in a deep underground coal mine in anhui china the study includes field monitoring of overburden displacement stress and water pressure changes at the longwall panel 1115 1 of the guqiao mine in addition 3d modelling of strata behaviour at the longwall panel using a 3d finite element code and goaf gas flow simulations with a cfd code are carried out this research has resulted in many new insights into the complex dynamic interaction between mining induced strata stress changes fractures and gas flow patterns based on the findings from the field monitoring and numerical modelling a three dimensional annular shaped overlying zone along the perimeter of the longwall panel is identified for optimal methane drainage during mining a practical method that helps define the geometry and boundary of this zone is proposed this study provides a new methodology and a set of engineering principles for the design of optimal co extraction of coal and methane

repeated cfc sections at the greenwich meridian in the weddell sea 1 repeated observations of the tracer chlorofluorocarbon 11 cfc 11 for a section along the greenwich meridian from antarctica 70 s to about 50 s are presented for the period 1984 1998 the cfc sections display a highly persistent pattern a middepth cfc minimum in the central weddell sea is bounded laterally by elevated levels of dissolved cfcs at the southern margin of the weddell basin and by a column of elevated cfc concentrations around 55 s near to the northern margin part of the latter column covers waters of the antarctic circumpolar current which indicates that a moderate portion of these waters was ventilated in the weddell sea deep cfc maxima adjoining the southern and northern margins of the weddell basin indicate advective cores of recently ventilated waters the southern core supports previous notions of deep water import into the weddell sea from the east for all deep and bottom waters the portions ventilated on the cfc timescale 50 years are small effective initial cfc saturations for these portions are estimated to be between 60 and 70 using in part new data from off the filchner ronne ice shelf for various cfc features along the section mostly advective cores ventilated fractions and mean ages of these fractions were obtained with error limits the procedure was to fit an age distribution of a prescribed form to cfc 11 time series for these features constructed from the various realizations of the cfc section the ages are between 3 and 19 years and the ventilated fractions range between 6 and 23 indicating a rather limited ventilation of the interior weddell sea subsurface layer waters on the cfc timescale it is shown that the concurrent cfc 12 data provide little additional information the work demonstrates a high information content of repeated tracer observations and encourages similar approaches also in other ocean regions

on the sources of weddell gyre antarctic bottom water in march april 1995 as part of the world ocean circulation experiment section a23 we completed 49 hydrographic stations across the weddell gyre and southern antarctic circumpolar current from the antarctic continental shelf 72 5 s 16 5 w to south georgia 55 s 34 5 w chlorofluorocarbon cfc 11 cfc 12 and cfc 113 data collected at these stations reveal that distinct sources renew the antarctic bottom water defined as waters with potential temperatures less than 0 c of the weddell gyre weddell sea bottom water defined as waters with potential temperatures less than 0 7 c formed in the western weddell sea has cfc concentrations about 5 to 6 times higher in the eastward flowing northern weddell gyre than in the westward flowing southern limb our cfc measurements suggest that distinct sources of weddell sea bottom water exist in the western weddell sea in agreement with previous descriptions based on potential temperature and salinity signals in the northern weddell gyre high cfc concentrations in weddell sea deep water potential temperatures between 0 c and 0 7 c confirm the long recognized sources for this water mass in the western and southwestern weddell sea in the southern weddell gyre at about 20 w and along the antarctic continental slope weddell sea deep water with potential temperatures around 0 45 c shows a deep cfc maximum about 1000 m above the seafloor cfc concentrations in this deep southern core are about 80 of those of new weddell sea deep water in the northern weddell gyre near 30 w the a23 cfc and hydrographic data are not consistent with the hypothesis that weddell sea deep waters are derived from a single source in the western weddell sea instead these tracers suggest that an important portion of the weddell sea deep water in the southern weddell gyre originates outside the western weddell sea probably near the amery basin and environs around 75 e these features of the circulation and renewal of the deep weddell gyre should be carefully considered in simulations dealing with fluxes pathways and formation rates of antarctic bottom water

establishment of a continuous gps network across the kephalonia fault zone ionian islands greece abstract we report on the establishment of a continuous gps network across the kephalonia fault zone kfz central ionian islands greece the kfz is an important segment of the boundary zone between the rapidly moving aegean microplate and the apulian platform italy repeated gps measurements carried out between the northern ionian islands and the island of crete have shown rates of crustal motion of the aegean reaching 35 mm a oriented sw relative to southern italy the kfz coincides with a maximum shear strain rate 180 nano strain a and a very high level of seismicity in order to monitor the ongoing deformation across the kfz and correlate the strain accumulation with earthquakes a continuous gps network has been installed operating at a sampling rate of 5 s this paper describes the instrumental set up the data logging strategy and first preliminary results

an experimental and numerical investigation on the deformation of overlying coal seams above double seam extraction for controlling coal mine methane emissions abstract this study investigates the deformation and the resultant pressure relief of highly gassy coal seams where a double seam mining operation takes place at lower depths at the wulan coal mine china in order to predict the depressurization effect in the overlying coal seams we simulate the extraction process by constructing a scaled model in the laboratory using similar rock materials analyses of experimental results concluded that due to the mining induced stress redistribution the pressure within target coal seams which were 109 m above the mined seams could be fully relieved to attain the statutory approval for gas drainage in addition to scaled model studies computational modeling studies were conducted using udec universal distinct element code which showed that the features of deformation resulting from the double seam extraction were different from that of in the case of single seam extraction the results of the numerical studies revealed that in addition to the panel margin on the air return side areas near the intake entry could also be considered as borehole drilling positions besides it was found that the gob of the extracted seams below the gassy one provided a buffering effect for the would mined protective coal seam and that the depressurization effect was largely weakened the laboratorial findings are instructive to the field practice of methane drainage during the mining operation a displacement comparison method was adopted to measure the dilated amount of protected coal seams and as expected the maximum dilation percentage was much more than 0 2 the critical value upon which the target coal seam is appropriately depressurized to allow gas drainage to be safely and effectively implemented

the cephalonia transform fault and its extension to western lefkada island greece the central area of the ionian islands is dominated by the existence of a major tectonic structure called the cephalonia transform fault ctf its main part cephalonia segment has been identified by previous work based on the spatial distribution of earthquake foci fault plane solutions of strong earthquakes active tectonics structural studies and geodetic measurements this part cephalonia segment which exhibits strike slip motion with a thrust component strikes in a northeast direction dips to the southeast and has a length of 90 km in the present paper information concerning new fault plane solutions orientation of isoseismals sea bottom topography and recent gps results are used to further check the properties of this southern part of the ctf and to explore its northeastward prolongation to lefkada island it is shown that the ctf is extended to the western coast of lefkada this northern branch lefkada segment of the ctf which is also characterized by strike slip motion with a thrust component strikes in a north northeast direction dips to the east southeast and has a length of 40 km these two segments of the ctf form a major kinematic boundary where the slip rate is 2 3 cm yr

rupture zones in the aegean region rupture zones of strong shallow earthquakes can be investigated by field observations of surface fault traces sf accurate location of spatial clusters of aftershocks or other small earthquakes cl reliable fault plane solutions fp and information on the spatial distribution of sites with high i viii macroseismic intensities ma the validity of these four techniques was successfully tested by comparing the results of their application to several cases of strong shallow earthquakes these techniques were then applied to spatially define the rupture zones of 150 strong m 6 0 shallow earthquakes in the aegean and surrounding area the type of faulting was determined for all these zones by the use of reliable fault plane solutions which are available for this area the orientation of most of these rupture fault zones is in good agreement with the presently acting stress field with some exceptions which are attributed to the rupture of pre existing faults the tectonic implications of these zones are discussed 1999 elsevier science b v all rights reserved

a detailed study of the active crustal deformation in the aegean and surrounding area abstract a detailed study of the active crustal deformation in the aegean sea and surrounding area is presented the estimation of the deformation velocities is not performed in broad seismic zones but in seismogenic sources of limited spatial extent where the seismic energy is practically released in order to describe the spatial variations of the components of the strain rate tensor the deformation analysis is based on previous work where the seismicity and the available focal mechanisms are used separately for estimating the rate and shape of the deformation respectively the calculations were performed for 63 seismogenic sources identified in the aegean sea and surrounding area which belong to eight belts with an almost uniform orientation of the stress field along the coasts of albania and northwestern greece up to leukada island the collision of the adria plate with eurasia results in a compressional velocity of about 4 mm yr in a direction n49 e almost normal to the coast line the dextral movement with almost 3 cm yr along the cephalonia transform fault with strike n45 e is expressed as an almost equal extension and compression in n s and e w direction respectively along the convex outer part of the hellenic arc a crustal shortening of 1 3 cm yr is observed in a mean direction n34 e the direction of this shortening is almost constant from the southern ionian islands zakynthos up to rodos while the shortening rate does not significantly change from the outer sources to the inner ones the aegean sea and surrounding area is characterised by an extensional deformation the direction of the maximum extension in the northern part of this area shows an anticlockwise rotation from east to west thus this extension has a nne direction in northwestern turkey n11 e a nnw direction in central and northern greece as well as along the southern aegean volcanic arc and its extension to southwestern turkey n12 w and a wnw direction in the westernmost part of this extensional area n72 w the mean value of the extensional velocities in this area is 5 mm yr the northern part of asia minor and of the aegean sea is characterised by the dextral strike slip movement of about 2 cm yr of the north anatolian fault and its continuation in the northern aegean where this movement gradually decreases to about 6 mm yr the vertical crustal upper 10 km of the crust thickening is about 2 mm yr along the convex side of the hellenic arc and the vertical crustal thinning is about 1 mm yr in the aegean sea these values were obtained from the component u 33 of the velocity tensor

earthquake source scaling relationships from 1 to 5 ml using seismograms recorded at 2 5 km depth the scaling relationships of earthquake sources less than about magnitude 3 have been the subject of considerable controversy over the last two decades studies of such events have shown a tendency for the constant stress drop self similarity of larger earthquakes to breakdown at small magnitudes and an apparent minimum source dimension of about 100 m has been observed other studies showed that this apparent breakdown in scaling could be an artifact of severe near surface attenuation limiting the spatial resolution of surface data in this study source parameters are determined for over 100 nearby tectonic earthquakes from recordings at a depth of 2 5 km in granite in the cajon pass scientific drill hole southern california comparison of the seismograms recorded at this depth with those at the wellhead clearly demonstrates the effect of the severe attenuation in the upper kilometers of the earth s crust source parameters are calculated by spectral modeling of three component p and s waves assuming four source models based on the brune 2 n 2 model in model l n 2 is fixed and q of p and s waves is determined to be 912 581 1433 and 1078 879 1323 respectively the numbers in parentheses are 1 standard deviation in model 2 qp qs 1000 is assumed and n is allowed to vary the 2 model is a good average for the data set but there is some real scatter supported by the data in model 3 qp qs 1000 is also assumed and 2 is constrained and in model 4 attenuation is ignored and n is allowed to vary source dimensions of less than 10m are observed for all four models 10 times smaller than the proposed minimum no breakdown in constant stress drop scaling is seen in the downhole data approximately ml 1 to 5 5 m0 109 1016 nm the ratio between radiated seismic energy estimated by integrating the velocity squared spectra with adequate signal bandwidth and seismic moment appears to decrease gradually with decreasing moment in the magnitude range 1 to 7 this is not incompatible with a constant stress drop but could result from errors in calculating energy the ratio of the s wave energy to that radiated by the p waves is about 14 after correction for attenuation this low value is consistent with the corner frequency shift of about 1 3 this corner frequency shift is observed for all four source models and therefore is interpreted as being source controlled

on the use of carbon tetrachloride as a transient tracer of weddell sea deep and bottom waters antarctic bottom waters have long been known to be a mixture of circumpolar deep water and shelf water recent observations show that in the antarctic bottom waters of the scotia sea and northern weddell sea the ratios of carbon tetrachloride ccl4 to chlorofluorocarbons cfc 11 12 are inconsistent with the ratios observed in the surface layer of the weddell sea this is the result of a deficit of ccl4 in the bottom waters and renders the compound unsuitable for use as a transient tracer from which apparent ages can be derived directly the summer near surface temperature minimum of antarctic surface water exhibits a similar inconsistency demonstrating that ccl4 can be removed from cold waters with high oxygen levels probably through a biological process it is inferred that shelf water features a similar ccl4 deficit which is transferred to the new antarctic bottom waters upon formation accounting for the observed deep ccl4 deficit

a first study of sf6 as a transient tracer in the southern ocean abstract halogenated transient tracers such as the chlorofluorocarbons cfc 11 cfc 12 and cfc 113 are commonly used in oceanographic studies these compounds enter the ocean via the atmosphere and their transient atmospheric concentrations make them valuable as oceanic tracers the trends of rapidly rising atmospheric concentrations of these tracers are however broken and the oceanic signal becomes increasingly more difficult to decipher there is a need for a new transient tracer to complement the existing suit of tracers especially for recently ventilated water masses one compound that looks promising in this respect is sulphur hexafluoride sf 6 an inert gas whose atmospheric concentration is rising rapidly in this paper the use of sf 6 as a transient tracer in recently ventilated waters is discussed and the method for determination of sf 6 in seawater is described tracer data from a section in the atlantic sector of the southern ocean along 6 e from 60 s to 40 s occupied during january 1998 are presented the antarctic polar front found close to 50 s was studied with a densely sampled section down to 400 m depth and sf 6 cfc 12 ratios are used to deduce ventilation ages and dilution factors a comparison of apparent ages derived from a variety of tracers is presented together with the uncertainties in these estimates this work demonstrates that sf 6 is a useful and valuable transient tracer for waters ventilated during the last 20 years

geotechnical assessments of the stability of slopes at the cakmakkaya and damar open pit mines turkey a case study the on site observations monitoring data and results of back analyses of failures showed that large scale failures occurred along both the interconnected sliding surfaces consisting of a discontinuities in the dacites and the contact zone and b the circular surfaces through the weathered soil like dacites at the cakmakkaya and damar open pit mines surface water infiltration through the weathered soil like material after a short duration of rainfall contributed to the circular shaped failures after a heavy rainy period an increase in the groundwater table above the contact zone played a major role in the initiation of bi planar wedge failures in addition the stability of the slopes is likely to have been controlled by the orientation of this zone the results of back analyses indicated that the shear strengths of the soil like materials in the weathered dacites and the contact zone had reduced to their residual values at the time of initial sliding the flattening of the slope angles with an effective surface drainage and long term monitoring of the groundwater level is proposed as the most suitable remedial measure

small earthquakes tectonic forces earthquake scaling and frequency of occurrence relations require that small earthquakes be just as important as larger ones in redistributing the forces that drive relative displacements across active faults of any dimension including plate boundaries

physical modelling of subsidence from sequential extraction of partially overlapping longwall panels and study of substrata movement characteristics field examples of subsidence from sequential extraction of overlapping coal longwall panels have shown that complex and unexpected subsidence effects can occur physical models comprising sand and plaster obeying relevant similarity rules were used to investigate the subsidence mechanisms displacements within the models were measured using a combination of optical transducers photogrammetry and laser scanning the observed results were compared with finite element models the models demonstrate that the incremental subsidence and substrata movement profiles after lower seam extraction can be separated into three different zones these zones undergo different horizontal and vertical movement characteristics the zone of overlap of the two longwall panels undergoes greater total subsidence compared to a single seam of equivalent thickness the limit angle of the subsidence also differs at the two ends of the lower extraction as a result of the effects of the previously mined out area above

field measurement and failure forecast during the remediation of a failed cut slope a large number of deep cuts are formed during the construction of expressways in mountainous areas inadequate interpretation of ground conditions is a major contributing factor to the failure of cut slopes this study focuses on the hongyan landslide along the s26 expressway due to lack of an adequate pre construction investigation a landslide was triggered by small scale excavation at the toe part of the slope the potential slip surface was incorrectly located consequently two rows of stabilizing piles were not long enough to reach stable rocks to overcome the mistake two additional rows of piles were installed during construction both slope deformation and the stress of reinforced bars in piles were monitored for safety considerations a verhulst model based failure forecast was also utilized to insure the stability of the slope during remedial works reviewing this landslide reveals a number of lessons first sufficient geological investigation and careful interpretation of ground conditions are mandatory prior to the design of a cut slope second systematic field monitoring is strongly recommended especially when the geology of the slope is complex and it is difficult to determine failure patterns third the failure forecast can serve as a supplementary measure to insure the safety of workers and slopes last it always takes some time for stabilizing piles to mobilize

new constraints on the rapid crustal motion of the aegean region recent results inferred from gps measurements 1993 1998 across the west hellenic arc greece abstract in this paper we present the most recent observations of crustal motion across the entire west hellenic arc wha these are based on repeated gps measurements carried out in the period from 1993 to 1998 the results are presented in terms of trajectories and rates relative to eurasia within these five years southwestern greece has moved to the southwest by an average rate of 30 mm a increasing from 10 mm a at the island of lefkada in the center of the ionian islands to nearly 40 mm a along the southwest part of the peloponnesus and to 35 mm a on the islands of crete and gavdhos the data provide strong evidence that distributed shear strain starts at the kephalonia fault zone kfz were an anomalously high earthquake activity is also observed a striking interruption of the motion is seen at the island of strofades at the southwest leading edge of the wha where a south oriented displacement of 12 cm was detected coincident with the m 6 4 strofades earthquake of nov 18 1997

mechanism of strata deformation under protective seam and its application for relieved methane control abstract in this paper an equation correlated with normal stress and permeability was developed and flac3d software was used to investigate the rock mass stress evolution and distribution to understand the methane flow characteristics research results show that the rock mass under the protective coal seam can be divided into three belts zones in the vertical direction including total de stressed belt vertical de stressed belt and original stress belt methane in the total de stressed belt can flow into the working face of protective coal seam by its own pressure gradient methane in the vertical de stressed belt can only be extracted by boreholes in the horizontal direction the rock mass was also divided into five zones including original zone compression zone expansion zone recovering zone and re compacted zone which have been proved correct by the field experiments the rock mass permeability in the de stressed belts doesn t increase until stepping into the expansion zone and from then on higher concentration of methane can be extracted the methane in original regions is difficult to extract because rock stresses stay the same the division of three belts and five zones reveals the rock mass stress and permeability distribution and evolution and supplies theoretical guidance for relieved methane control

winter mixed layer entrainment of weddell deep water observations from the somov during the us ussr weddell polynya expedition show that the mixed layer below the sea ice just prior to the austral spring retreat in the 60 s greenwich meridian region has an oxygen content of 7 4 ml 1 this is 86 of full oxygen saturation representing an oxygen deficit relative to full saturation of 1 1 ml 1 the source of this deficit is believed to be a consequence of oxygen poor 4 5 ml 1 weddell deep water wdw entrainment by the winter mixed layer assuming effective cutoff of ocean atmosphere oxygen exchange by the nearly complete snow and sea ice cover with no net impact of oxygen content as a result of biological factors a mixing ratio of 1 3 for wdw to beginning of winter surface water is required to explain the end of winter mixed layer oxygen content accompanying the wdw transfer into the mixed layer is heat transfer of approximately 7 103 cal cm2 2 9 108 j m2 during the five winter months of sea ice coverage as well as salt transfer which requires 34 cm of fresh water to produce typical mixed layer salinity during the seven ice free months when entrainment is expected to be minor diffusive heat and salt flux continues a mean annual heat flux of 12 w m2 is suggested with an annual demand for freshwater of 46 cm yr consideration of the winter period salinity budget indicates net sea ice melting of 20 cm which can be attributed to regional convergence of sea ice the remaining freshwater is derived from excess precipitation and possibly iceberg melt oxygen undersaturation of the winter surface water suggests slightly less potential for abyssal water ventilation than might be expected from a fully saturated condition

seismic gap hypothesis ten years after the seismic gap hypothesis states that earthquake hazard increases with time since the last large earthquake on certain faults or plate boundaries one of the earliest and clearest applications of the seismic gap theory to earthquake forecasting was by mccann et al 1979 who postulated zones of high medium and low seismic potential around the pacific rim in the 10 years since there have been over 40 large m 7 0 earthquakes enough to test statistically the earlier forecast we also analyze another forecast of long term earthquake risk that by kelleher et al 1973 the hypothesis of increased earthquake potential after a long quiet period can be rejected with a large confidence the data suggest that contrary to these forecasts places of recent earthquake activity have larger than usual seismic hazard whereas the segments of the circum pacific belt with no large earthquakes in recent decades have remained relatively quiet the clustering of earthquake times does not contradict the plate tectonic model which constrains only the long term average slip rate not the regularity of earthquakes

a new transient tracer measured vertical distribution of ccl2fcclf2 f 113 in the north pacific subarctic gyre the first quantitative marine measurements of trichlorotrifluoroethane f 113 were made in the north pacific subarctic gyre in july of 1986 using a modification of the analytical procedure developed for the transient tracers f 11 and f 12 gammon et al 1982 wisegarver and cline 1985 the measured mixed layer concentration was 0 29 0 02 pm l the corresponding atmospheric mixing ratio was 35 1 pptv rasmussen scale below a subsurface maximum both f 11 and f 113 were found to fall off exponentially with increasing depth f 113 reaching effective blank levels first the significance of adding f 113 to the existing suite of measurable oceanic transient tracers rests in the possibility of age dating water masses by their f 113 f 11 ratio with near annual resolution for the period since 1977

the kephalonia transform fault and the rotation of the apulian platform evidence from satellite geodesy this paper describes a collaborative gps project to determine recent crustal movements and deformations across the ne ionian sea this region is characterized by rifting in the african foreland pelagian sea subduction along the calabrian and west hellenic arcs rotation of the italian peninsula and distributed normal faulting in central greece from gps campaigns on the ionian islands and in nw greece performed in 1989 and 1991 a kinematic field is deduced which is controlled by the deep trough following the nw coast of kephalonia island it is concluded that this prominent bathymetric feature resembles an active fault system kephalonia fault which has the signature of a right lateral transform fault

in the shadow of 1857 the effect of the great ft tejon earthquake on subsequent earthquakes in southern california the great 1857 fort tejon earthquake is the largest earthquake to have hit southern california during the historic period we investigated if seismicity patterns following 1857 could be due to static stress changes generated by the 1857 earthquake when post 1857 earthquakes with unknown focal mechanisms were assigned strike slip mechanisms with strike and rake determined by the nearest active fault 13 of the 13 southern california m 5 5 earthquakes between 1857 and 1907 were encouraged by the 1857 rupture when post 1857 earthquakes in the transverse ranges with unknown focal mechanisms were assigned reverse mechanisms and all other events were assumed strike slip 11 of the 13 earthquakes were encouraged by the 1857 earthquake these results show significant correlations between static stress changes and seismicity patterns the correlation disappears around 1907 suggesting that tectonic loading began to overwhelm the effect of the 1857 earthquake early in the 20th century

aspects of sand behaviour by modified constant shear drained tests constant shear drained tests csd are probably the most suitable to simulate the strength and deformation behaviour of soils in slopes under water infiltration conditions or lateral stress relief this is significant because soil behaviour following a csd stress path could differ from that of traditional compression triaxial tests in this paper csd tests on sand following an alternative procedure are presented and discussed the modified csd tests were conducted by increasing the pore water pressure at a constant rate from one end of the specimen with water free to drain from the opposite end among the results from specimens consolidated at variable initial void ratios and principal stress ratios it was revealed that specimens showed a tendency to dilate even for loose sands failure was reached at low axial strains and a pre failure type of instability could be identified the modified procedure has the potential to provide new insights into the failure mechanisms of slopes under a water infiltration condition

irregular recurrence of large earthquakes an analysis of historic and paleoseismic catalogs assessment of a region s seismic hazard requires knowledge of the repeat times and the regularity of earthquake recurrence for most areas the earthquake catalog is too short to determine recurrence parameters reliably using a large set of events for many regions however it should be possible to constrain the average characteristics of earthquake recurrence behavior this study compiles a set of the most complete historic and paleoseismic series of m 7 earthquakes from the middle american trench alaska chile japan and the san andreas fault the 52 recurrence series show a large average aperiodicity that is variations in recurrence time are larger than 40 of the average recurrence interval aperiodicity may decrease with increasing magnitude neither the use of different magnitude thresholds the exclusion of foreshocks and aftershocks the type of statistics normal or lognormal used nor the choice of segmentation results in a significantly smaller aperiodicity the irregular recurrence behavior exhibited by the data implies that earthquakes are more unpredictable than often assumed in hazard analyses

order and diversity in the modes of circum pacific earthquake recurrence recurrence characteristics of great circum pacific earthquakes and determinations of spatial distribution of seismic moment release are surveyed in order to delineate their general features and relate earthquake slip distribution to models of recurrent rupture as noted by others the pattern of moment release is typically very irregular with strong concentrations in a few isolated regions of a much larger aftershock zone despite this complexity rupture nucleation is notably systematic with mainshock epicenter showing a strong tendency to locate in or immediately adjacent to identified regions of high moment release this generalization suggests that earthquake recurrence is more likely to be controlled by maximum rather than average fault slip well documented case histories from twelve plate boundary regions demonstrate that seismic strain release tends to be temporally well ordered while source dimensions slip and cumulative moment release vary considerably from cycle to cycle on none of the segments studied do earthquakes consistently recur in nearly identical events instead individual great earthquakes differ significantly from cycle to cycle or rerupture takes place in a sequence of two or more smaller events despite these differences the duration of the seismic cycle is approximately uniform furthermore when strain release occurs in a sequence of large earthquakes these events take place towards the end of the cycle and occur with increasing rupture length and magnitude these ordered and irregular features of earthquake recurrence argue for the existence of corresponding elements on plate boundary faults the ordered characteristics are identified with zones of concentrated moment release that slip comparable amounts in each cycle and have high shear strength the irregular features are associated with intervening weaker regions that move in response to the stress concentration of dynamic rupture and slip by differing amounts in each event although these mechanistic associations are indirect and tentative the features of recurrent behavior documented here have implications for long term earthquake hazard assessment that are not dependent on the models proposed to explain them chief among these are the cycle to cycle differences among gap filling events and the absence of shocks that fill major slip deficient regions early in the seismic cycle

stress coupling between earthquakes in northwest turkey and the north aegean sea we have investigated the coulomb stress interactions of 29 earthquakes m s greater than or equal to 6 0 that have occurred in the region of northwest turkey and north aegean sea since 1912 of these events 23 may be related to earlier events and 16 are clearly related to earlier events all events after 1967 are related to previous events events in the early part of our time interval that show no correlation could be related to historical events as yet unidentified in some cases faults that have received a stress reduction from earlier events are prepared for an event by an earthquake occurring a few years before that creates a local coulomb stress rise thus regions of coulomb stress shadow can become regions where a damaging earthquake may occur the relation between smaller events and the coulomb stress distribution is less clear but may be related to poor data quality and practical limitations of our modeling technique nonetheless there are 4 times as many events per unit area in regions of enhanced stress than where stress is reduced we discuss the contemporary distribution of coulomb stress and argue that it is possible to identify the likely locations of future damaging earthquakes including identifying the most likely candidate faults

stress damage flow coupling model and its application to pressure relief coal bed methane in deep coal seam abstract long distance pressure relief gas drainage technology has recently been applied in mining areas with multiple coal seams of low permeability in china this study briefly described a coupled stress damage flow model which combined the evolution of stress damage and gas permeability with the deformation of coal and rock the coupled model was then used to investigate the deformation and fracture characteristics of overburden strata the evolution of gas permeability and gas flow in target coal seams the effectiveness of long distance pressure relief gas drainage was evaluated on the basis of the calculated results from a dynamic modelling of extraction of protective coal seam at great depths the numerical results revealed that the stress was remarkably relieved in the target coal seam above 67 m away from the coal seam being mined moreover the range of stress relief extended above 70 m and the gas permeability increased by more than 2000 times the modelled results reasonably well agreed with the field results observed in the panyi coal mine it was concluded that the long distance pressure relief gas drainage technology could effectively improve the safety and productivity in underground coal mines especially in mining areas with multiple coal seams of low permeability

the strain field in northwestern greece and the ionian islands results inferred from gps measurements abstract recent crustal movements detected by the analysis of repeated satellite geodetic measurements reflect the ongoing geodynamic processes in the alpine mediterranean area superimposed on the large scale counterclockwise rotation of the african plate complex dynamic processes are affecting the lithospheric fragments between the african and eurasian plates key features to better understand the driving forces and associated seismic activity in the africa eurasia collision zone are the calabrian and hellenic arcs in this paper geodynamic investigations along the west hellenic arc are discussed they are based on two epochs 1989 and 1993 of satellite geodetic measurements carried out using the us global positioning system gps the results are presented in terms of relative displacements and strain rates within the time span of 4 years southwestern greece has moved to the southwest relative to southeastern italy by an average of 120 mm increasing from 80 mm at lefkada in the center of the ionian islands to 160 mm at the peloponnesus the maximum strain rate is 0 18 strain a located in the vicinity of lefkada where anomalously high earthquake activity is observed the data provide strong evidence for dextral strike slip motion on the order of 25 mm a along the kephalonia fault zone kfz the deformation field of the kfz is interpreted as a transition zone between the kinematics of the apulian platform and the west hellenic fold and thrust belts

application of the geomechanical facies approach and comparison of exploration and evaluation methods used at soultz sous forets france and spa urach germany geothermal sites earth reservoirs are increasingly exploited today with the extraction of resources such as heat and hydrocarbons and the large scale emplacement of waste such as co2 sequestration the characterization site investigation predictive modeling and long term monitoring are dependent on the processes being investigated and modeled in most cases complex coupled processes have to be addressed in a geologically complex rock mass system in this paper we present a conceptual holistic framework known as geomechanical facies linking all the scales of investigation characterization and reservoir development methods we demonstrate this concept on the work undertaken during the design and development of the enhanced geothermal systems egs systems at the forefront of european hot dry rock hdr technology soultz sous forets france and spa urach germany soultz sous forets is situated within granitic rocks and an active tectonic graben system in the central part of the rhine graben it presents conditions of lithology temperature stress hydraulics and geochemistry that are very different from those at spa urach located in a very dense gneiss formation in the south german crystalline complex spa urach exhibits more elastic behavior and is set tectonically within an almost inactive strike slip stress field described in more detail in sects drill core analysis and hydraulic stimulation at spa urach this paper compares the exploration and field development methods used at these two sites against the back drop of the geomechanical facies concept issues addressed include the key parameters for flow and heat transport properties coupled hydro mechanical process identification the success of the hdr reservoir as a heat exchanger and exploration techniques applicable to the different facies identification of the key geomechanical facies gives an indication as to which technologies will prove more efficient in the application of hdr technology the results of this study will hopefully help in developing heat recovery schemes for the long term economical operation of future hdr plants and egs as well as assist in the understanding of engineered geosystems

long term earthquake clustering summary we analyse statistically the long term properties of several instrumental earthquake catalogues complete catalogues exhibit both short and long term clustering for earthquakes of all depth ranges after accounting for the effect of short term clustering we find that in residual declustered catalogues long term clustering not periodicity characterizes the occurrence of all earthquakes shallow intermediate and deep the degree of clustering in residual catalogues is the same for earthquakes in different depth ranges circumstantial evidence indicates that the long term v ariation of seismicity is governed by a power law temporal distribution as in short term clustering it is scale invariant the fractal dimension of an earthquake set on the time axis is of the order of 0 8 0 9 therefore mainshock occurrence is closer to a stationary poisson process than standard aftershock sequences of shallow earthquakes

changes in state of stress on the southern san andreas fault resulting from the california earthquake sequence of april to june 1992 the april to june 1992 landers earthquake sequence in southern california modified the state of stress along nearby segments of the san andreas fault causing a 50 kilometer segment of the fault to move significantly closer to failure where it passes through a compressional bend near san gorgonio pass the decrease in compressive normal stress may also have reduced fluid pressures along that fault segment as pressures are reequilibrated by diffusion that fault segment should move closer to failure with time that fault segment and another to the southeast probably have not ruptured in a great earthquake in about 300 years

chlorofluoromethanes in the northeast pacific ocean measured vertical distributions and application as transient tracers of upper ocean mixing the vertical distributions of the man made chlorofluoromethanes ccl3f f 11 and ccl2f2 f 12 have been measured at two locations in the eastern north pacific ocean to depths greater than 500 m at both sites 46 n 125 w off the washington oregon coast and 50 n 140 w in the gulf of alaska the halomethane concentrations were found to fall off exponentially with increasing depth below the mixed layer for f 11 at 50 n the surface concentration 3 2 10 12 mol l was found to be in saturation equilibrium with the measured atmospheric concentration 190 pptv the measured chlorofluoromethane profiles have been interpreted in terms of a one dimensional model for the vertical diffusion advection of an exponentially driven conservative tracer into a bottomless ocean in the appropriate limit of transient steady state the projected profiles are simple exponentials described by an advective diffusive scale depth h which is a function of the vertical eddy diffusivity kz the upwelling velocity w and the characteristic time for the exponential growth of the tracer concentration at the boundary at the two ocean locations studied the freon thermocline depth scales were in the range h 120 140 m with f 12 generally 10 20 deeper than f 11 at 50 n the f 11 and f 12 vertical profiles gave consistent values of vertical diffusivity kz 1 2 1 3 cm2 s 1 and upwelling velocity w 12 14 m yr 1 the model also allows a simple scaling from one exponentially driven transient tracer freon to another fossil fuel co2 leading to a predicted mean depth of penetration of fossil fuel co2 of approximately 300 m in the eastern north pacific

a more precise chronology of earthquakes produced by the san andreas fault in southern california improved methods of radiocarbon analysis have enabled us to date more precisely the earthquake ruptures of the san andreas fault that are recorded in the sediments at pallett creek previous dates of these events had 95 confidence errors of 50 100 calendar years new error limits are less than 23 calendar years for all but two of the dated events this greater precision is due to larger sample size longer counting time lower background noise levels more precise conversion of radiocarbon ages to calendric dates and better stratigraphic constraints and statistical techniques the new date ranges with one exception fall within the broader ranges estimated previously but our estimate of the average interval between the latest 10 episodes of faulting is now about 132 years variability about the mean interval is much greater than was suspected previously five of the nine intervals are shorter than a century three of the remaining four intervals are about two to three centuries long despite the wide range of these intervals a pattern in the occurrence of large earthquakes at pallett creek is apparent in the new data the past 10 earthquakes occur in four clusters each of which consists of two or three events earthquakes within the clusters are separated by periods of several decades but the clusters are separated by dormant periods of two to three centuries this pattern may reflect important mechanical aspects of the fault s behavior if this pattern continues into the future the current period of dormancy will probably be greater than two centuries this would mean that the section of the fault represented by the pallett creek site is currently in the middle of one of its longer periods of repose between clusters and sections of the fault farther to the southeast are much more likely to produce the next great earthquake in california the greater precision of dates now available for large earthquakes recorded at the pallett creek site enables speculative correlation of events between paleoseismic sites along the southern half of the san andreas fault a history of great earthquakes with overlapping rupture zones along the mojave section of the fault remains one of the more attractive possibilities

influence of continuous rainfall on surrounding rock initial support system of shallow decomposed rock tunnel a case study is presented to identify the influence of continuous rainfall on surrounding rock initial support system of shallow decomposed rock tunnel from march 21 to april 29 2006 rainfall with intensities ranging from 25 mm day fell several hours every day resulting in the collapse of the tunnel crown after the initial support of the surrounding rock in a part of shallow tunneling bench sections of xiang an subsea tunnel located in xiamen fujian china the applied calculation method of 3d elastic plastic numerical back analysis based upon flac3d is presented through site investigation test and in situ monitoring the surrounding rock physical mechanics parameters and support parameters were obtained by the calculation of elastic plastic back analysis method presented here furthermore the influence of continuous rainfall on the stability of shallow decomposed rock tunnel was investigated using the proposed method the results show that 1 rainwater infiltration makes the surrounding rock of the shallow decomposed rock tunnel continuously softened due to the continuous rain resulting in decreasing surrounding rock stiffness and coefficient of confinement pressure 2 the negative influence of groundwater must be considered on the initial setting and initial strength of shotcreting of shallow decomposed rock tunnel under the action of continuous rainfall to ensure the stabilization of surrounding rock initial support system and 3 tunnel stability analysis by the back analysis method proposed in this study is reasonable and reliable which could be used as a reference for the estimation of stability of the same type of tunnels and their design

deep and bottom water of the weddell sea s western rim oceanographic observations from the ice station weddell 1 show that the western rim of the weddell gyre contributes to weddell sea bottom water a thin 300 meters highly oxygenated benthic layer is composed of a low salinity type of bottom water overlying a high salinity component this complex layering disappears near 66 s because of vertical mixing and further inflow from the continental margin the bottom water flowing out of the western rim is a blend of the two types additionally the data show that a narrow band of warmer weddell deep water hugged the continental margin as it flowed into the western rim providing the continental margin with the salt required for bottom water production

fault behavior and characteristic earthquakes examples from the wasatch and san andreas fault zones paleoseismological data for the wasatch and san andreas fault zones have led to the formulation of the characteristic earthquake model which postulates that individual faults and fault segments tend to generate essentially same size or characteristic earthquakes having a relatively narrow range of magnitudes near the maximum analysis of scarp derived colluvium in trench exposures across the wasatch fault provides estimates of the timing and displacement associated with individual surface faulting earthquakes at all of the sites studied the displacement per event has been consistently large measured values range from 1 6 to 2 6 m and the average is about 2 m on the basis of variability in the timing of individual events as well as changes in scarp morphology and fault geometry six major segments are recognized along the wasatch fault on the basis of the most likely number of surface faulting events 18 that have occurred on segments of the wasatch fault zone during the past 8000 years an average recurrence interval of 400 666 years with a preferred average of 444 years is calculated for the entire zone geologic data on the distribution of slip associated with prehistoric earthquakes and slip rates along the south central segment of the san andreas fault suggest that the m 8 1857 earthquake is a characteristic earthquake for this segment comparisons of earthquake recurrence relationships on both the wasatch and san andreas faults based on historical seismicity data and geologic data show that a linear constant b value extrapolation of the cumulative recurrence curve from the smaller magnitudes leads to gross underestimates of the frequency of occurrence of the large or characteristic earthquakes only by assuming a low b value in the moderate magnitude range can the seismicity data on small earthquakes be reconciled with geologic data on large earthquakes the characteristic earthquake appears to be a fundamental aspect of the behavior of the wasatch and san andreas faults and may apply to many other faults as well

evolution of the stress field in southern california and triggering of moderate size earthquakes a 200 year perspective changes in stress in southern california are modeled from 1812 to 2025 using as input 1 stress drops associated with six large 7 0 7 5 earthquakes through 1995 and 2 stress buildup associated with major faults with slip rates 3 mm yr as constrained by geodetic paleoseismic and seismic measurements evolution of stress and the triggering of moderate to large earthquakes are treated in a tensoffal rather than a scalar manner we present snapshots of the cumulative coulomb failure function acff as a function of time for faults of various strike dip and rake throughout southern california we take acff to be zero everywhere just prior to the great shock of 1812 we find that about 95 of those well located m 6 earthquakes whose mechanisms involve either strike slip or reverse faulting are consistent with the coulomb stress evolutionary model that is they occurred in areas of positive acff the interaction between slow moving faults and stresses generated by faster moving faults significantly advanced the occurrence of the 1933 long beach and 1992 landers events in their earthquake cycles coulomb stresses near major thrust faults of the western and central transverse ranges have been accumulating for a long time future great earthquakes along the san andreas fault especially if the san bernardino and coachella valley segments rupture together can trigger moderate to large earthquakes in the transverse ranges as appears to have happened in the santa barbara earthquake that occurred 13 days after the great san andreas shock of 1812 maps of current acff provide additional guides to long term earthquake prediction

global positioning system constraints on plate kinematics and dynamics in the eastern mediterranean and caucasus we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1997 at 189 sites extending east west from the caucasus mountains to the adriatic sea and north south from the southern edge of the eurasian plate to the northern edge of the african plate sites on the northern arabian platform move 18 2 mm yr at n25 5 w relative to eurasia less than the nuvel 1a circuit closure rate 25 1 mm yr at n21 7 w preliminary motion estimates 1994 1997 for stations located in egypt on the northeastern part of africa show northward motion at 5 6 2 mm yr also slower than nuvel ia estimates 10 1 mm yr at n2 4 e eastern turkey is characterized by distributed deformation while central turkey is characterized by coherent plate motion internal deformation of 2 mm yr involving westward displacement and counterclockwise rotation of the anatolian plate the anatolian plate is de coupled from eurasia along the right lateral strike slip north anatolian fault naf we derive a best fitting euler vector for anatolia eurasia motion of 30 7 0 8 n 32 6 0 4 e 1 2 0 1 myr the euler vector gives an upper bound for naf slip rate of 24 1 mm yr we determine a preliminary gps arabia anatolia euler vector of 32 9 1 2 n 40 3 1 1 e 0 8 0 2 myr and an upper bound on left lateral slip on the east anatolian fault eaf of 9 1 mm yr the central and southern aegean is characterized by coherent motion internal deformation of 2 mm yr toward the sw at 30 1 mm yr relative to eurasia stations in the se aegean deviate significantly from the overall motion of the southern aegean showing increasing velocities toward the trench and reaching 10 1 mm yr relative to the southern aegean as a whole

a constitutive law for rate of earthquake production and its application to earthquake clustering seismicity is modeled as a sequence of earthquake nucleation events in which the distribution of initial conditions over the population of nucleation sources and stress ing history control the timing of earthquakes the model is implemented using solutions for nucleation of unstable fault slip on faults with experimentally derived rate and state dependent fault properties this yields a general state variable constitutive formulation for rate of earthquake production resulting from an applied stressing history to illustrate and test the model some characteristics of seismicity following a stress step have been explored it is proposed that various features of earthquake clustering arise from sensi tivity of nucleation times to the stress changes induced by prior earthquakes the model gives the characteristic omori aftershock decay law and interprets aftershock parameters in terms of stress change and stressing rate earthquake data appear to support a model prediction that aftershock duration defined as the time for rates to return to the back ground seismicity rate is proportional to mainshock recurrence time observed spatial and temporal clustering of earthquake pairs arises as a consequence of the spatial depen dence of stress changes of the first event of the pair and stress sensitive time dependent nucleation applications of the constitutive formulation are not restricted to the simple stress step models investigated here it may be applied to stressing histories of arbitrary complexity the apparent success at modeling clustering phenomena suggests the possibil ity of using the formulation to estimate short to intermediate term earthquake probabil ities following occurrence of other earthquakes and for inversion of temporal variations of earthquake rates for changes in driving stress

evolution and effect of the stress concentration and rock failure in the deep multi seam coal mining supports crushing accident occasionally occurs in the protected seam exploitation of deep multi seam coal mining structure and results in adverse effect to the production to prevent its recurrence in a newly developed working field a 3d numerical extraction model was built based on the geologic and mining conditions of jining coal mine to evolve the changes state and characteristics of the reconstructed vertical and lateral stress in rock interlayer after protective seam exploitation stress release and increase zones of this mining structure were separated mining induced localized stress concentration and the interlayer rock failure behavior were explored the action of concentrated stress on the hydraulic supports in protected seam was discussed upon the major stress redistribution using the infinitesimal strain method a mechanical model was created to further explore from the vertical and lateral directions the cause and mechanism of localized stress concentration and rock failure behavior in rock interlayer the field investigation was finally performed to verify the numerical and mechanical results and the essential control measures were proposed to prevent this accident key findings of this study bring some new insights into the deep multi seam coal extraction and help to promote a more reliable underground mining

kuril islands arc two seismic cycles of great earthquakes during which the complete history of seismicity ms 6 is observed two adjacent segments of pacific eurasia plate boundary along the kuril islands arc were broken during two great shallow thrust earthquakes that occurred in 1963 moment magnitude m w 8 5 and 1969 m w 8 2 respectively in 1994 a great shock m w 8 3 rebroke the 200 km long plate boundary segment previously broken by the 1969 event and a series of shocks in 1991 m w 7 6 1995 m w 7 9 and 1996 m w 7 2 rebroke major portions of the 300 km long segment previously ruptured by the 1963 event due to the heterogeneities and incompleteness of the instrumental seismicity catalog for shallow focal depth h m s 6 particularly for the first half of the century this is one of the first times that a complete history of instrumental seismicity at an energy level as low as m s 6 occurring in a focal region of great earthquakes during a full seismic cycle has been observed my findings indicate that significant activity at the m s 6 and m s 7 levels took place both within and as well as along the downdip edges of the forthcoming 19909s ruptures during most of the seismic cycle whereas the adjacent regions of the plate boundary were relatively less active the average displacements and repeat times 28 5 yr 3 5 observed for these great earthquakes along this section of the plate boundary as a whole are consistent with the strain energy accumulated during that time by subduction of the pacific plate under the eurasian plate at a rate of 10 cm yr

stress transferred by the 1995 mw 6 9 kobe japan shock effect on aftershocks and future earthquake probabilities the kobe earthquake struck at the edge of the densely populated osaka kyoto corridor in southwest japan we investigate how the earthquake transferred stress to nearby faults altering their proximity to failure and thus changing earthquake probabilities we find that relative to the pre kobe seismicity kobe aftershocks were concentrated in regions of calculated coulomb stress increase and less common in regions of stress decrease we quantify this relationship by forming the spatial correlation between the seismicity rate change and the coulomb stress change the correlation is significant for stress changes greater than 0 2 1 0 bars 0 02 0 1 mpa and the nonlinear dependence of seismicity rate change on stress change is compatible with a state and rate dependent formulation for earthquake occurrence we extend this analysis to future mainshocks by resolving the stress changes on major faults within 100 km of kobe and calculating the change in probability caused by these stress changes transient effects of the stress changes are incorporated by the state dependent constitutive relation which amplifies the permanent stress changes during the aftershock period earthquake probability framed in this manner is highly time dependent much more so than is assumed in current practice because the probabilities depend on several poorly known parameters of the major faults we estimate uncertainties of the probabilities by monte carlo simulation this enables us to include uncertainties on the elapsed time since the last earthquake the repeat time and its variability and the period of aftershock decay we estimate that a calculated 3 bar 0 3 mpa stress increase on the eastern section of the arima takatsuki tectonic line attl near kyoto causes fivefold increase in the 30 year probability of a subsequent large earthquake near kyoto a 2 bar 0 2 mpa stress decrease on the western section of the attl results in a reduction in probability by a factor of 140 to 2000 the probability of a mw 6 9 earthquake within 50 km of osaka during 1997 2007 is estimated to have risen from 5 6 before the kobe earthquake to 7 11 afterward during 1997 2027 it is estimated to have risen from 14 16 before kobe to 16 22

moment tensor inversion of the 1983 january 17 kefallinia event of ionian islands greece summary the source parameters of the recent 1983 january 17 ionian island event are obtained by the inversion of body waves an optimum source depth of 8 km is determined and the source parameters of the major double couple are strike 60 dip 47 rake 174 and seismic moment m0 7 3 1025 dyne cm this mechanism implies a strike slip dextral fault with a small thrust component this solution ascertains the existence of a transform fault connecting the northwestern edge of the hellenic are with the compressional zone which is produced by the collision of the apulian plate with the eurasian plate along the adriatic north ionian coast this right lateral strike slip fault probably terminates the hellenic subduction zone

long term seismic behavior of the focal and adjacent regions of great earthquakes during the time between two successive shocks we analyze the spatial temporal energy distribution of shallow depth h 70 km seismicity surface wave magnitude ms 7 occurring in the focal and adjacent regions of very great shallow earthquakes rupture lengths of the order of hundreds of kilometers in the circum pacific seismic belt for as many decades as possible before and after the occurrence of the main shock for this purpose we have revised the catalog of data for the world instrumental seismicity 1900 1995 by removing a series of heterogeneities in the earthquake reporting and magnitude determination this revised catalog is fairly complete for earthquakes with m 7 since early in the century our findings indicate that once a main shock aftershock sequence occurs the focal region enters a period of relative quiescence for large ms 7 earthquakes significant seismic activity ms 7 occurs during many decades prior to the next main shock this activity is fairly continuous or random in time and lasts until the onset of the main event but clusters in space around the ends of the forthcoming rupture and or in the vicinity of the principal epicenter except in the case of rare bilateral breaks the main epicenter is located at one of these ends thus major portions of the rupture zone experience no events with ms 7 during the seismic cycle larger aftershocks also cluster near the edges of the rupture and near the principal epicenter preshock activity minutes to weeks before the main shock if any occurs in general near the main epicenter we also find that the nucleation and ends of the rupture often coincide in space with recognizable geometrical and or geological inhomogeneities barriers existing in the lithosphere it appears that while strain energy accumulates high stress concentrations often occur at the ends of the future rupture zone which results in the long term foreshock activity and in the subsequent initiation of the main rupture from within those regions we suggest a simple mechanical model that explains the observed pattern of earthquake occurrence for both unilateral and bilateral ruptures in all cases of great earthquakes that have occurred this century for which a long and complete to a level of 2 to 3 orders of magnitude smaller than the moment of the main shock catalog of prior seismicity exists we can not recognize any statistically significant quiescent or doughnut patterns in the preceding seismicity at the ms 7 level

geodetic determination of the kinematics of central greece with respect to europe implications for eastern mediterranean tectonics we use a new satellite laser ranging global positioning system slr gps solution at seven sites in anatolia and aegea to obtain a better definition of the extrusion motion of the anatolian aegean block with respect to europe we show that this motion can be described in a first approximation by a counterclockwise rotation which transfers most of the motion of arabia to anatolia we combine 78 displacement vectors obtained at common points of two triangulation nets measured in central greece in 1895 and 1975 with the slr gps measurements to compute the velocity field over greece with respect to europe these measurements indicate that central greece is a zone of extension between the anatolian aegean counterclockwise rotation to the south and the northern greece clockwise rotation to the north this extension is principally localized within the gulf of corinth to the east but is distributed to the west we then extrapolate this velocity field to the whole aegea and western anatolia using recently published gps results as well as the slr results the narrow dextral north anatolian fault which limits the velocity field to the north progressively gives way to a much wider boundary zone where extension becomes dominant we show that the collision between the mediterranean ridge and africa began 3 6 ma and we describe the modifications that this collision has produced on the kinematic pattern both in aegea and on the mediterranean ridge