when and where the aftershock activity was depressed contrasting decay patterns of the proximate large earthquakes in southern california 1 seismic quiescence has attracted attention as a possible precursor to a large earthquake however sensitive detection of quiescence requires accurate modeling of normal aftershock activity we apply the epidemic type aftershock sequence etas model that is a natural extension of the modified omori formula for aftershock decay allowing further clusters secondary aftershocks within an aftershock sequence the hector mine aftershock activity has been normal relative to the decay predicted by the etas model during the 14 months of available data in contrast although the aftershock sequence of the 1992 landers earthquake m 7 3 including the 1992 big bear earthquake m 6 4 and its aftershocks fits very well to the etas up until about 6 months after the main shock the activity showed clear lowering relative to the modeled rate relative quiescence and lasted nearly 7 years leading up to the hector mine earthquake m 7 1 in 1999 specifically the relative quiescence occurred only in the shallow aftershock activity down to depths of 5 6 km the sequence of deeper events showed clear normal aftershock activity well fitted to the etas throughout the whole period we argue several physical explanations for these results among them we strongly suspect aseismic slips within the hector mine rupture source that could inhibit the crustal relaxation process within shadow zones of the coulomb s failure stress change furthermore the aftershock activity of the 1992 joshua tree earthquake m 6 1 sharply lowered in the same day of the main shock which can be explained by a similar scenario

estimation of optimum average surficial density from gravity data an objective bayesian approach a new objective method is proposed for estimating an average surficial density bouguer density from gravity data which then may be correlated with the surface and or near surface geology in analyzed area the method assumes that a suitable bouguer density will lead to a smooth bouguer anomaly with this assumption the method fits a two dimensional curved function to the observed bouguer anomaly by finding a bouguer density that gives the optimum trade off between smoothness and goodness of fit to the bouguer anomalies this trade off is interpreted by an objective bayesian procedure and determined by minimization of akaike s bayesian information criterion abic further the distribution of bouguer density is assumed to be smooth enough to apply our method to any of the spatial windows with an area of 20 20 km2 in the district and therefore be obtainable by moving successively the windows the proposed method is tested against the gravitational data in kyushu district southwest japan the distribution of bouguer density which is obtained by this method agrees remarkably well with the geology of the relevant area

the effect of hydrothermal fluids on ordovician carbonate rocks southern ordos basin china abstract hydrothermal processes have an important influence on the spatial distribution and formation of carbonate reservoirs and play a critical role in certain deep reservoirs where hydrothermal fluid rock interaction may result in permeability creation due to carbonate dissolution or permeability destruction due to the deposition of cementing minerals this study analyzed certain hydrothermal indicator minerals quartz celestite multi stage calcareous fillings in carbonate rocks from the ordovician majiagou formation southern ordos basin china the petrological and geochemical characteristics of these indicator minerals imply that the majiagou formation was affected by two metasomatic events related to the hercynian indosinian and yanshanian orogenies and linked to magmatic hydrothermal fluids derived from basaltic melts most of the ce and eu values obtained from matrix dolomite samples were lower than one but u th and v c ratios showed positive anomalies the 13c and 18o values of the matrix dolomite were concentrated between 12 8 and 6 0 whereas 13c showed a bipolar distribution at the same depth elemental geochemistry results showed that the ordovician carbonate rocks were subjected to freshwater leaching followed by evaporation and widespread hydrothermal dissolution successively as a result of the multi episodic hydrothermal activity that affected the southern ordos basin and the path of migration channel a parental magmatic hydrothermal fluid fluid 1 that had been generated during the underplating of the southern north china craton by mesozoic alkaline basalt melts separated into two types of fluids with different chemical properties an acidic hydrocarbon bearing fluid fluid 2a mixed with cambrian oil and gas and a weakly to moderately alkaline brine fluid 2b not in contact with hydrocarbons both fluids 2a and 2b then interacted with the ordovician carbonate rocks with fluid 2a having undergone hydrothermal sulfate reduction with so42 in the layers in which gypsum was developed and convection of fluid 2a having resulted in brine formation the reaction products of h2s and co2 together with organic acid co dissolved carbonate minerals in the ordovician strata played a major role in the formation of a high porosity reservoir conversely owing to the progressive reduction of temperature and solubility during fluid ascent fluid 2b precipitated quartz calcite fillings in the residual pore spaces resulting in the localized destruction of the original reservoir permeability in summary this study analyzed the petrological and geochemical characteristics of 60 carbonate rock drill core samples established the likely formation mechanism of fluids 2a and 2b and determined the effects of these hydrothermal fluids on the ordovician majiagou formation carbonate reservoir

sulfur isotope variations from orebody to hand specimen scale at the mežica lead zinc deposit slovenia a predominantly biogenic pattern the mississippi valley type mvt pb zn ore district at me ica is hosted by middle to upper triassic platform carbonate rocks in the northern karavanke drau range geotectonic units of the eastern alps northeastern slovenia the mineralization at me ica covers an area of 64 km2 with more than 350 orebodies and numerous galena and sphalerite occurrences which formed epigenetically both conformable and discordant to bedding while knowledge on the style of mineralization has grown considerably the origin of discordant mineralization is still debated sulfur stable isotope analyses of 149 sulfide samples from the different types of orebodies provide new insights on the genesis of these mineralizations and their relationship over the whole mining district sphalerite and galena have 34s values in the range of 24 7 to 1 5 vcdt 13 5 5 0 and 24 7 to 1 4 10 7 5 9 respectively these values are in the range of the main mvt deposits of the drau range all sulfide 34s values are negative within a broad range with 34spyrite 34ssphalerite 34sgalena for both conformable and discordant orebodies indicating isotopically heterogeneous h2s in the ore forming fluids and precipitation of the sulfides at thermodynamic disequilibrium this clearly supports that the main sulfide sulfur originates from bacterially mediated reduction bsr of middle to upper triassic seawater sulfate or evaporite sulfate thermochemical sulfate reduction tsr by organic compounds contributed a minor amount of 34s enriched h2s to the ore fluid the variations of 34s values of galena and coarse grained sphalerite at orefield scale are generally larger than the differences observed in single hand specimens the progressively more negative 34s values with time along the different sphalerite generations are consistent with mixing of different h2s sources with a decreasing contribution of h2s from regional tsr and an increase from a local h2s reservoir produced by bsr i e sedimentary biogenic pyrite organo sulfur compounds galena in discordant ore 11 9 to 1 7 7 0 2 7 n 12 tends to be depleted in 34s compared with conformable ore 24 7 to 2 8 11 7 6 2 n 39 a similar trend is observed from fine crystalline sphalerite i to coarse open space filling sphalerite ii some variation of the sulfide 34s values is attributed to the inherent variability of bacterial sulfate reduction including metabolic recycling in a locally partially closed system and contribution of h2s from hydrolysis of biogenic pyrite and thermal cracking of organo sulfur compounds the results suggest that the conformable orebodies originated by mixing of hydrothermal saline metal rich fluid with h2s rich pore waters during late burial diagenesis while the discordant orebodies formed by mobilization of the earlier conformable mineralization

hydrothermal alteration of graywacke by brine and seawater roles of alteration and chloride complexing on metal solubilization at 200 degrees and 350 degrees c graywacke was reacted with seawater and with a saturated nacl brine containing ca mg and k using a solid liquid ratio of 1 10 the degree of reaction was minimal at 200 degrees c but significant at 350 degrees c in both fluids anorthite dolomite and some illite and quartz amounting to about 25 percent of the graywacke were converted to smectite chlorite and albite both fluids lost all their mg and gained k ca and co 2 only the brine gained and maintained significant concentrations of heavy metals indicating the importance of chloride complexing chloride concentration in seawater is apparently insufficient for extensive complexing under the experimental conditions chloride complexing however serves only to maintain metals in solution and prevents their reprecipitation as alteration products alteration involving production and consumption of hydrogen ions is required for the release of metals from the source matrix in the experiments mg metasomatism and dedolomitization provided the h super for the process metal solubilization by the brine followed the order of abundance in the graywacke zn ni cu pb sb cd suggesting a common matrix and no selective leaching effect in other words as a given increment of rock was altered all of its component metals were released metal concentration in solution therefore was not limited by sulfide solubility and represents minimum values changes in the bulk composition of the graywacke were minimal except for increases in mg content and the final rock would probably not be recognized as an altered source rock in the field the fluids generated during the experiments would likely subject wall rock at the site of ore deposition to hydrolytic alteration including potassium metasomatism

properties of aftershock sequences in southern california the temporal behavior of 39 aftershock sequences in southern california 1933 1988 was modeled by the modified omori relation minimum magnitudes for completeness of each sequence catalog were determined and the maximum likelihood estimates of the parameters k p and c with the standard errors on each were determined by the ogata algorithm the b value of each sequence was also calculated many of the active faults in the region both strike slip and thrust were sampled the p values were graded in terms of the size of the standard error relative to the p value itself most of the sequences were modeled well by the omori relation many of the sequences had p values close to the mean of the whole data set 1 11 0 25 but values significantly different from the mean as low as 0 7 and as high as 1 8 exist no correlation of p with either the b value of the sequence or the mainshock magnitude was found the results suggest a direct correlation of p values is with surface heat flow with high values in the salton trough high heat flow and one low value in the san bernardino mountains and on the edge of the ventura basin both low heat flow the large fraction of the sequences with p values near the mean are at locations where the heat flow is near the regional mean 74 mw m2 if the hypothesis that aftershock decay rate is controlled by temperature at depth is valid the effects of other factors such as heterogeneity of the fault zone properties are superimposed on the background rate determined by temperature surface heat flow is taken as an indicator of crustal temperature at hypocentral depths but the effects on heat flow of convective heat transport and variations in near surface thermal conductivity invalidate any simple association of local variations in heat flow with details of the subsurface temperature distribution the interpretation is that higher temperatures in the aftershock source volume caused shortened stress relaxation times in the fault zone materials leading to a faster decay rate higher p value in 1967 mogi proposed such a relation on the basis of japanese data seismic velocity distributions published for southern california generally support the hypothesis with low velocities higher temperatures corresponding to high p values and vice versa

detection and monitoring of ongoing aseismic slip in the tokai region central japan analysis of global positioning system data shows that the rate of crustal deformations in the tokai region of japan a seismic gap area changed over the past 18 months kalman filtering analysis shows aseismic slip on the plate boundary in the western tokai region centered on lake hamana adjacent to the anticipated tokai earthquake source area the cumulative moment magnitude reaches 6 7 in june 2002 with a relative slip increase northeast of lake haman from january 2002 an existence of aseismic slip in the western tokai supports the hypothesis of a silent event as the cause of uplifting several days before the 1944 tonankai earthquake

statistical features of foreshocks in comparison with other earthquake clusters summary when earthquakes occur in a cluster the probability that they will be foreshocks of a forthcoming significantly larger earthquake appears dependent on the magnitude differences origin time spans and distances between several of the earliest events in a cluster the earthquake catalogue of the japan meteorological agency jma 1926 91 mj 2 4 is decomposed into numbers of clusters in time and space to compare statistical features of foreshocks with those of swarms and main shockaftershock sequences since the number of foreshocks in individual earthquake clusters is usually small two types of data stacking are considered first we consider the spatial and temporal distribution of events relative to the location and time of the coming main shock for the foreshocks a relative doughnut shaped pattern which converges in time to the main shock s epicentre is seen while this pattern is weak for swarms next we consider the temporal spatial and magnitude distributions of events relative to the time location and magnitude of earlier events in every sequence then a statistical discrimination of foreshocks from earthquakes of other types of clusters is explored the search for significant trends of relative frequency of foreshocks in comparison with other cluster types revealed the following features of foreshocks 1 their relative frequency is high when the inter event time span is less than several days but the maximum is attained at about several hours span 2 their relative frequency is high at short distances between epicentres especially within 10 km and then decreases as the distance gets larger and 3 their relative frequency increases as the magnitude increases among the earliest shocks in a cluster the stability of the results is confirmed by finding similar trends using different cluster identification methods and different threshold magnitudes further microearthquakes in the japan university network data file 1983 87 m 2 2 and moderate to large earthquakes in the international seismological centre world catalogue isc 1979 90 mh 2 5 are examined to see some effects of the magnitude thresholds of these catalogues similar features to those obtained in the jma catalogue are also found for these catalogues

sulphur isotope distribution in the pb zn deposit bleiberg carinthia austria the sulphur isotope composition of 233 sulphides and 40 sulphates has been investigated and evaluated in combination with 29 earlier published data the total variation of 34s values for the sulphides and the sulphates ranges from 40 up to 1 and from 7 up to 20 respectively for the mineral species the variations are with number of samples in brackets galena 96 32 up to 2 sphalerite 141 30 up to 4 marcasite 16 27 up to 1 pyrite 10 26 up to 13 molybedenite 3 40 up to 29 anhydrite and gypsum 8 15 up to 20 coelestine 1 19 and barite 33 7 up to 18 the frequency distribution of the 34s values corresponds with the complexity of the ore forming processes which resulted in six strata bound ore mineralizations the sulphate values clearly show that the sulphate sulphur originates from sea water sulphate the sulphides are formed by bacteriogeneric processes from seawater sulphate and their sulphur isotope composition depends on the lithofacies of the sediments as well as on the following diagenetic processes

quaternary glacial interglacial climate cycles in hawaii abstract the upper kilometer of the hawaiian scientific drilling program core consists of lavas that were emplaced subaerially burying paleosols these paleosols were preserved with minimal alteration and are used to construct a 330 kyr quaternary climate record within the temporal resolution of this record there appears to be a 100 kyr climate oscillation between cool dry and warm wet conditions indicating that tropical regions such as hawaii have responded to the same global climate forcings as have higher latitude areas during at least the past three glacial interglacial cycles it is also suggested that hawaiian climate may have become progressively warmer and wetter over the same period

variations of sulfur isotopes trace element compositions and cathodoluminescence of mississippi valley type pb zn ores from the drau range eastern alps slovenia austria implications for ore deposition on a regional versus microscale the sulfur isotope composition of sulfide ore minerals of the drau range varies considerably down to centimeter scale variations both on a regional and a local scale broadly scattering 34s values ranging between 2 and 25 per mil with a mean around 17 per mil are probably related to both local bacteriogenic and thermal reduction of late triassic marine sulfate the 34s is typically more depleted in ore deposited in subtidal carbonate rocks than in the economic zn and pb ore preferably deposited within intratidal carbonate host rock the 34s 32s ratio increases on the order of fes2 pbs zns which reflects disequilibrium and low temperature formation the strong depletion of 34s in botryoidal sphalerite ranging between 24 and 32 per mil appears to be correlated with the crystal mode wurtzite sphalerite fibers and the enrichment of the trace elements fe as tl and ge sphalerite generations of specific cathodoluminescense color and closely related trace element composition are correlated district wide a decrease of the trace elements fe as tl and ge in the sphalerite generations is coeval with a minor depletion of 34s in the range of 3 and 12 per mil for 34s values in several hand specimens variations in 34s values and trace element zonation on a regional to local scale indicates mixing of local sulfur sources with a regional metal rich brine however distinct peaks in some ore deposits and more positive 34s values of between 5 and 10 per mil are also compatible with derivation of the sulfur from basement rocks the enrichment of the trace element cu in orange luminescing sphalerite negatively correlated with fe as tl and ge and therefore strongly suggests leaching of copper from late permian to early triassic continental red beds frequent evaporites in this stratigraphic section might have supplied sulfur of relatively heavy isotopic composition to the brine hence some sulfur may also have been transported with a metal rich brine

the use of earthquake rate changes as a stress meter at kilauea volcano stress changes in the earth s crust are generally estimated from model calculations that use near surface deformation as an observational constraint but the widespread correlation of changes of earthquake activity with stress has led to suggestions that stress changes might be calculated from earthquake occurrence rates obtained from seismicity catalogues although this possibility has considerable appeal because seismicity data are routinely collected and have good spatial and temporal resolution the method has not yet proven successful owing to the non linearity of earthquake rate changes with respect to both stress and time here however we present two methods for inverting earthquake rate data to infer stress changes using a formulation for the stress and time dependence of earthquake rates application of these methods at kilauea volcano in hawaii yields good agreement with independent estimates indicating that earthquake rates can provide a practical remote sensing stress meter

increased probability of large earthquakes near aftershock regions with relative quiescence it is shown that after a large earthquake of m6 class or over has taken place another event of similar size or larger is relatively more likely in the sense of rate per unit area to occur in the near field than in the far field in particular we show that the aftershock activity of the first event provides useful information for assessing the probability of a following large event in the neighborhood within a distance of a few degrees namely if the aftershock activity from the first event becomes relatively quiet compared to the normal decay the occurrence rate of larger events in the neighborhood is several times higher during the first decade after the main shock than would be the case for normal aftershock activity for measuring such phenomena precisely we need to model the normal aftershock activity in fact many aftershock sequences are more complex than the simple inverse power decay represented by the modified omori formula the epidemic type aftershock sequences etas model is a generalized version of the modified omori formula which fits well with various aftershock sequences including nonvolcanic type swarms using this model aftershock sequences are investigated for the 76 main shocks that occurred in and around japan during the last three quarters of a century the focus is placed on objective examination of whether or not in an aftershock sequence there exists a significant change point followed by relative quiescence that is a significant lowering of the seismicity from that predicted by the etas model relative quiescence can take place regardless of the seismicity level the extent of such quiescence if it exists is seen from the diagrams of cumulative numbers versus the transformed occurrence times based on the predicted occurrence rate by the estimated etas model it is thus demonstrated that relative quiescence can be a helpful factor in detecting anomalous aftershock activity this can then be used to forecast whether or not a large event is more likely to follow shortly within 6 years in the neighborhood within a distance of 3 of the initial event

the unusual cyclicity of the triassic carnian bleiberg facies of the wetterstein formation drau range austria the carbonate platform of the upper wetterstein formation cordevol of the drau range austria shows a distinct facies differentiation which depends on the palaeotopography although most areas of the platform were permanently flooded a periodically emergent palaeotopographic high bleiberg facies occurred near to the centre of the platform the resulting cyclic sequences are composed of subtidal and intertidal to supratidal carbonates and emersion horizons typical shallowing upward cycles occur as well as deepening upward symmetrical and incomplete cycles these types of cycles with long term emersion phases can be explained by eustatic sea level oscillations it can be shown due to an excellent lithostratigraphy based on distinct emersion horizons that the cycle type varies along a marker bed while the vertical distance between the emersion horizons is retained therefore the cycles cannot be explained by eustatic sea level oscillations alone local events which produce a local relief are necessary

spatial variability of seismicity parameters in aftershock zones the spatial variability of the b value of the frequency magnitude relationship and the decay rate of aftershocks as described by the p value of the modified omori law is investigated by using dense spatial grids we map out the distribution of b and p values within the landers northridge morgan hill and kobe aftershock sequences considerable spatial variability is found with b values of independent subvolumes ranging from 0 6 to 1 4 and p values ranging from 0 6 to 1 8 these systematic and statistically highly significant differences argue that it is an oversimplification to assign one single p and b value to an aftershock sequence that extends up to 100 km the spatial distribution of these two parameters is compared with the slip distribution during the mainshock suggesting that the areas of largest slip release correlate with high b value regions we hypothesize that the frictional heat created during the event may influence the p value distribution within an aftershock zone while applied shear stress crack density and pore pressure govern the frequency magnitude distribution by investigating the frequency magnitude distribution separately for preseismic and postseismic periods for the morgan hill mainshock we find that only the volume in the vicinity of the highest slip release shows a significant increase in the b value which decays to premainshock values within a year surrounding areas of the aftershock zone show an approximately constant b value with time because the aftershock hazard after a mainshock depends strongly on both the b and p value we propose that aftershock hazard assessment can be improved by taking into account the spatial distribution of the parameters

earthquake hazard after a mainshock in california after a strong earthquake the possibility of the occurrence of either significant aftershocks or an even stronger mainshock is a continuing hazard that threatens the resumption of critical services and reoccupation of essential but partially damaged structures a stochastic parametric model allows determination of probabilities for aftershocks and larger mainshocks during intervals following the mainshock the probabilities depend strongly on the model parameters which are estimated with bayesian statistics from both the ongoing aftershock sequence and from a suite of historic california aftershock sequences probabilities for damaging aftershocks and greater mainshocks are typically well constrained after the first day of the sequence with accuracy increasing with time

space time model for regional seismicity and detection of crustal stress changes 1 the regional occurrence rate of earthquakes is modeled as a function of previous activity the specific form of which is based on empirical laws in time and space such as the modified omori formula and the utsu seki scaling law of aftershock area against magnitude respectively its parameters including the p value of the aftershock decay rate vary from place to place in such a way that for example the regional p value at the locations around the main shock is similar to the one estimated from the corresponding individual aftershock sequence the estimated space time model is used to visualize features of the regional seismic activity the utility is demonstrated by applying the model to the events of m 5 in and around japan for the period 1926 1995 among the parameters of the model this paper is particularly concerned with the normalized k value of the modified omori function indicating the aftershock productivity this takes high values around the boundaries of asperities that are estimated in the wide area off the east coast of tohoku district japan by the inversion of historical strong motion seismograms furthermore this space time model enables us to identify the anomalous period and regions where the actual occurrence rates deviate systematically from the modeled one such an anomaly activation and quiescence relative to the model could sensitively reveal the change of stresses in the regions we attempt to relate this relative activation and lowering of the seismicity to the pattern of coulomb stress changes due to a rupture or silent slip elsewhere for example such anomalies seen in the seismic activity in the central japan m 2 5 during 1995 1999 and during 2001 are respectively likely the consequence of the coulomb stress changes due to the 1995 kobe rupture and the interplate aseismic slip during 2001 beneath the western tokai region

possible mechanism of precursory seismic quiescence regional stress relaxation due to preseismic sliding we propose a new model to physically explain the seismic quiescence precursory to a large interplate earthquake a numerical simulation is performed to quantitatively examine possible stress changes prior to a great interplate earthquake in a subduction zone in the present study the frictional force following a laboratory derived friction law in which the friction coefficient is dependent on slip rate and slip history is assumed to act on a dip slip fault plane of infinite width in a uniform elastic half space the values of friction parameters are determined so that the result of numerical simulation may explain some properties of great interplate earthquakes in subduction zones such as the recurrence interval and the seismic coupling coefficient the result of simulation reveals that significant quasi stable sliding occurs prior to a great earthquake and accordingly stresses are changed on and around the plate boundary in a relatively wide area of the overriding continental plate the compres sional horizontal stress perpendicular to the trench axis is decreased for a few years before the occurrence of a great earthquake this decrease in regional compressional stress may account for the appearance of seismic quiescence prior to a great interplate earthquake

microbial sphalerite formation in carbonate hosted zn pb ores bleiberg austria micro to nanotextural and sulfur isotope evidence microglobular sphalerite 90 180 m is a major form of sphalerite in the abandoned triassic carbonate hosted zn pb deposit at bleiberg austria it is common in ores from the crest horizon and the first cardita horizon which contain about 0 5 to 3 mm thick and up to 5 cm long wavy discontinuous sphalerite rich bands composed of agglomerations of microglobular sphalerite based on comparisons with modern environments these textures are interpreted as peloids and probably represent fossil microbial mats these are inter layered with carbonate and marcasite rich as well as finely banded sphalerite layers fibrous galena and relics of oxysulfides resulting in the characteristic rhythmically banded macrotexture of these zn dominated ores microbial nanotextures made visible by field emission scanning electron microscopy fesem after etching include sphalerite nanospheres 10 90 nm and bacterial filaments the sphalerite nanospheres are identical to those previously reported for mixed calcite sphalerite peloids from bleiberg and are very similar to nanotextures observed in recent bacterial biofilms made by desulfobacteriaceae the observed sphalerite nanospheres are interpreted as in situ metabolic products of sulfate reducing bacteria micro and nanotextures suggest that the larger m sized sphalerite globules formed by agglomeration of sphalerite nanospheres as well as by replacement of peloids representing former bacterial colonies the latter are now composed of zn calcite cores surounded by serrated sphalerite rims most samples studied evidence recrystallization of sphalerite that is broadly coeval with formation of fluorite involvement of sulfate reducing bacteria in the formation of this early sphalerite mineralization is supported by sulfur isotope data sphalerite is generally characterized by isotopic light sulfur with 34 s per mil values ranging from 30 5 to 20 3 per mil the most negative sulfur isotope values are recorded from sphalerite 30 5 30 2 and galena with unusual fibrous to dendritic morphology 31 9 31 8 both are associated with oxysulfides microglobular sphalerite with well preserved sphalerite globules has a 34 s value of 28 8 to 28 2 per mil colloform sphalerite schalenblende ranges from 29 0 to 25 0 per mil microglobular sphalerite associated with fine grained fluorite and euhedral sphalerite formed through recrystallization processes show a trend to less negative values i e 26 3 to 22 2 per mil and 22 9 to 20 3 per mil respectively we suggest that the combined biogenic nano to macrotextures and sulfur isotope data are evidence that microbes played a key role in formation of alpine carbonate hosted zn pb deposits results of this study contradict the mvt model suggested for alpine pb zn deposits which calls for formation of pb zn mineralization during late diagenetic burial in the late triassic early jurassic

3 d spatial variation of b values of magnitude frequency distribution beneath the kanto district japan summary a method is developed for estimation and interpolation of 6 values in space a 3 d spline function is considered for the logarithm of the 6 value at each location in the space since many parameters for the spline coefficients are required to obtain a sensible estimate of the spatial variation of 6 values we consider the penalized log likelihood with the standard roughness penalties for the spline function further the error bands of the b value estimation at each location can be calculated using the current method the spatial distribution of 6 values beneath the kanto district down to the depth of 100km is determined based on hypocentral data of microearthquakes from the kanto tokai observational network of the national research center for disaster prevention the stability of the estimated pattern is checked by comparing with the results using alternative cut off magnitudes this is further ensured by comparison with the result obtained by an alternative model using equally divided blocks on the whole the vertical change in 6 value is greater than the horizontal one it is high in the crust of the eurasian plate especially above the upper boundary of the subducting pacific plate and in the northwest part or the volcanic area in the kanto district a steep decrease of the 6 values is seen to take place in perpendicular direction to the subducting pacific plate boundary also a similar change is seen in the boundary between the eurasian and phillippine sea plates especially beneath the southern part of the kanto plain the 6 value is low in the upper boundary of the subducting plates but high in the lower plane of the double seismic zone in the pacific plate it appears that even within a narrow area of aftershocks the 6 value can change significantly it is also found that the variation of the 6 value estimate is in good agreement with the structure of seismic wave fractional velocity perturbations the regions of high and low 6 values correspond respectively to the lower and higher parts of the p wave velocity the similar relationship is seen with the spatial structure of the seismic wave attenuation

behavior of critical metals in metamorphosed pb zn ore deposits example from the pyrenean axial zone rare metals ge ga in cd are key resources for the development of green technologies and are commonly found as trace elements in base metal mineral deposits many of these deposits are in orogenic belts and the impact of recrystallization on rare metal content and distribution in sphalerite needs to be evaluated based on laser ablation inductively coupled plasma mass spectrometry la icp ms analyses and micro imaging techniques such as laser induced breakdown spectroscopy libs and electron backscattered diffraction ebsd we investigate the minor and trace element composition related to sphalerite texture for three types of mineralization from the pyrenean axial zone paz vein mineralization type 2b appears significantly enriched in ge and ga compared to disseminated and stratabound mineralizations type 1 and type 2a respectively in vein mineralization the partial recrystallization induced by deformation led to the remobilization of ge ga and cu from the sphalerite crystal lattice into accessory minerals we propose that the association of intragranular diffusion and fluid rock reaction were likely responsible for the formation of patchy oscillatory zoning in sphalerite and the crystallization of ge rich accessory minerals chemical and textural heterogeneity is common in sphalerite from various world class deposits and a full understanding of these heterogeneities is now crucial to assess the rare metal potential and associated extraction processes of deformed base metal ores

on the growth of colloform textures a case study of sphalerite from the galmoy ore body ireland abstract colloform textures have been described from many of the world9s sulphide ore deposits and involve formation of distinct microcrystalline layers these textures provide information related to sequential stages of ore formation yet their mechanism of growth is poorly understood this study has analysed a series of colloform samples from the galmoy zn pb mine ireland results indicate that the growth sequence is not always intuitive and layers that appear stratigraphic upon cursory observation may not be the crystal preferred orientation cpo of discrete colloform layers abruptly switches between different orientation axes examination of the same layers using in situ laser sulphur isotope analysis reveals equally striking changes in 34 s signature between end member bacteriogenic 25 and hydrothermal 10 sources although these results combined with petrographic observation allow the determination of a probable growth history there is no correlation between shifting cpo and 34 s signature trace element analysis reveals changes in trace element sequestration between colloform layers cadmium and chlorine rich layers correspond to a hydrothermal sulphur source whereas iron rich layers correspond to a bacteriogenic sulphur source in the absence of alternative mechanisms we suggest that the most likely factors influencing cpo changes are temperature and degree of supersaturation during two fluid mixing

from alpine type sulfides to nonsulfides in the gorno zn project bergamo italy recent exploration of the gorno zn pb ag deposit in northern italy identified 3 3 mt of sulfides at 4 9 zn 1 3 pb and 27 2 g t ag indicated inferred resources and a further mineralized nucleus of mixed sulfides nonsulfides in the val vedra area currently under evaluation the ores are hosted in triassic limestone and shale sulfides sphalerite ag bearing galena minor pyrite and chalcopyrite paragenetically follow mn fe bearing saddle dolomite and sparry calcite the mineral association and the carbon and oxygen isotope ratios of the sparry calcite avg 13c 1 0 0 6 v pdb avg 18o 19 63 1 25 v smow are in agreement with precipitation from hydrothermal fluids in a deep burial setting sulfide emplacement occurred before the alpine orogeny likely during the early middle jurassic in analogy to other alpine type deposits the nonsulfide ore formed at the expense of sulfides and mainly consists of smithsonite hydrozincite hemimorphite and cerussite the c o isotope values of the early generations of zn carbonates are characterized by 18o between 24 1 and 26 8 v smow and 13c ratios between 3 1 and 1 7 v pdb the later generations have lower 18o 21 9 to 23 9 and lower 13c 6 2 to 3 9 these compositions as those measured on cerussite 13c 6 3 and 7 7 18o 14 0 and 15 3 agree with the formation of the nonsulfides in a supergene environment under climatic conditions warmer than today the 18o decrease from early to late generations suggests progressive involvement of meteoric water sourced from higher altitudes these characteristics indicate that the nonsulfides formed during the exhumation of the gorno area from miocene to pliocene

bacteria were responsible for the magnitude of the world class hydrothermal base metal sulfide orebody at navan ireland we report sulfur and lead isotope analyses of mine concentrates from navan the largest zinc deposit in ireland these samples each representing up to a million tonnes of ore show very limited isotopic variation with mean 34 s 13 6 2 per mil n 20 and galena concentrate mean 206 pb 204 pb 18 19 0 03 n 7 calculations suggest 90 percent of the navan sulfides were derived through bacteriogenic reduction of mississippian seawater sulfate whereas metals were acquired from a local orogenic crustal source beneath the orebody enhanced bacterial activity was fundamental to ore deposition at navan no bacteria no giant ore deposit

statistical model for standard seismicity and detection of anomalies by residual analysis abstract a statistical point process model is derived to describe the standard activity of earthquake occurrences by assuming that general seismicity is given by the superposition of aftershock sequences the parameters are estimated ty the maximum likelihood method using the estimated model the residual point process of the data is defined and used to find the anomalies which are included in the data set but not captured in the considered model for the standard seismicity for instance seismic quiescences can be measured quantitatively by using the residual process some examples are provided to illustrate such analyses furthermore a time series of the magnitudes on the residual point process is considered to investigate its dependence either on the time or on the history of the seismicity by assuming the exponential distribution at each time and modelling of the b value we can examine such dependences and estimate them two practical examples are shown

trace and minor element variations and sulfur isotopes in crystalline and colloform zns incorporation mechanisms and implications for their genesis abstract various models have been proposed to explain the formation mechanism of colloform sphalerite but the origin is still under debate in order to decipher influences on trace element incorporation and sulfur isotope composition crystalline and colloform sphalerite from the carbonate hosted mississippi valley type mvt deposit near wiesloch sw germany were investigated and compared to sphalerite samples from 52 hydrothermal vein type deposits in the schwarzwald ore district sw germany to study the influence of different host rocks formation mechanisms and fluid origin on trace element incorporation trace and minor element incorporation in sphalerite shows some correlation to their host rock and or origin of fluid gangue paragenetic minerals and precipitation mechanisms e g diagenetic processes fluid cooling or fluid mixing furthermore crystalline sphalerite is generally enriched in elements like cd cu sb and ag compared to colloform sphalerite that mainly incorporates elements like as pb and tl in addition sulfur isotopes are characterized by positive values for crystalline and strongly negative values for colloform sphalerite the combination of trace element contents typical minerals associated with colloform sphalerite from wiesloch sulfur isotopes and thermodynamic considerations helped to evaluate the involvement of sulfate reducing bacteria in water filled karst cavities sulfate reducing bacteria cause a sulfide rich environment that leads in case of a metal rich fluid supply to a sudden oversaturation of the fluid with respect to galena sphalerite and pyrite this however exactly coincides with the observed crystallization sequence of samples involving colloform sphalerite from the wiesloch mvt deposit

micro scale sulfur isotope and chemical variations in sphalerite from the bleiberg pb zn deposit eastern alps austria abstract the bleiberg pb zn deposit in the drau range is the type locality of alpine type carbonate hosted pb zn deposits its origin has been the subject of on going controversy with two contrasting genetic models proposed 1 the sedex model with ore forming contemporaneously with sedimentation of the triassic host rocks at about 220 ma vs 2 the epigenetic mvt model with ores forming after host rock sedimentation at about 200 ma or later both models assume that on a deposit or even district scale a fixed paragenetic sequence of ore minerals can be established the results of our detailed petrographic chemical and sulfur isotope study of two key ore samples from two major ore horizons in the wetterstein formation at bleiberg ehk02 erzkalk horizon and blb17 maxer banke horizon demonstrate that there is no fixed paragenetic sequence of ore minerals small scale non systematic variations are recorded in textures sphalerite chemistry and 34 s in each sample texturally different sphalerite types colloform schalenblende fine and coarse grained crystalline sphalerite co occur on a millimeter to centimeter scale these sphalerites represent multiple mineralization stages pulses since they differ in their trace element inventory and in their 34 s nonetheless there is some correspondence of sphalerite micro textures sulfur isotope and chemical composition between the two samples with microcrystalline colloform schalenblende being fe rich having high fe cd 15 and 9 respectively and a light sulfur isotope composition 34 s 26 0 to 16 2 cadmium rich and fe poor sphalerite in both samples has relatively heavier sulfur isotope composition in sample ehk02 this sphalerite has fe cd of 0 5 and 34 s from 6 6 to 4 6 in sample blb17 fe cd is 0 1 and 34 s ranges from 15 0 to 1 5 barite which is restricted to sample ehk02 has 34 s 17 the large variations in 34 s recorded on the mm to cm scale is consistent with variable contributions of reduced sulfur from two different sulfur reservoirs the dominant reservoir with 34 s values 34 s about 5 suggests a hydrothermal source likely linked with thermochemical sulfate reduction tsr based on this small to micro scale study no simple deposit wide paragenetic and sulfur isotope evolution with time can be established in the erzkalk ore sample ehk02 an earlier pb zn ba stage characterized by heavy sulfur isotope values is succeeded by a light 34 s dominated zn pb f stage in contrast the several mineralization pulses identified in the stratiform zn pb f maxer banke ore sample blb17 define a broad trend to heavier sulfur isotope values with time the interaction documented in these samples between two sulfur reservoirs is considered a key mechanism of ore formation

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

triggering of the 1999 mw 7 1 hector mine earthquake by aftershocks of the 1992 mw 7 3 landers earthquake 1 there is strong observational evidence that the 1999 mw 7 1 hector mine earthquake in the mojave desert california was triggered by the nearby 1992 mw 7 3 landers earthquake many authors have proposed that the landers earthquake directly stressed the hector mine fault our model of the landers aftershock sequence however suggests there is an 85 chance that the hector mine hypocenter was actually triggered by a chain of smaller earthquakes that was initiated by the landers main shock we perform our model simulations using the monte carlo method based on the gutenberg richter relationship omori s law bath s law and assumptions that all earthquakes including aftershocks are capable of producing aftershocks and that aftershocks produce their own aftershocks at the same rate that other earthquakes do in general our simulations show that if it has been more than several days since an m 7 main shock most new aftershocks will be the result of secondary triggering these secondary aftershocks are not physically constrained to occur where the original main shock increased stress this may explain the significant fraction of aftershocks that have been found to occur in main shock stress shadows in static coulomb stress triggering studies

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

likelihood analysis of earthquake catalogues summary we apply several classes of stochastic multidimensional models to statistical analysis of earthquake catalogues using likelihood methods we investigate the importance of including different earthquake parameters in the model epicentral coordinates hypocentral depth time limits for interearthquake interaction and especially spatial distribution of earthquakes as well as spatial aftershock patterns results of this study combined with other investigations suggest that most distributions controlling earthquake interaction have a fractal or scale invariant form developed models are used for statistical analysis of several earthquake catalogues to evaluate parameters of earthquake occurrence these parameters are shown to be similar for shallow earthquakes of different magnitude ranges and seismogenic regions confirming self similarity of the earthquake process whereas intermediate earthquakes seem to emulate the pattern of shallow earthquake occurrence albeit at a much smaller aftershock rate deep earthquakes differ significantly in their properties predictability of standard shallow earthquake catalogues has been analysed we present evidence that for the best availabfe catalogues the predictability is close to 10 bits per earthquake several synthetic earthquake catalogues have been created and processed through the likelihood inversion scheme the results from likelihood analysis of these catalogues confirm our approach