application of conditional geostatistical simulation to calculate the probability of occurrence of earthquakes belonging to a seismic series summary geostatistics overs various techniques of estimation and simulation that have been satisfactorily applied in solving geological problems in this sense conditional geostatistical simulation is applied to calculate the probability of occurrence of an earthquake with a lower than or equal magnitude to one determined during a seismic series it is possible to calculate the energy of the next most probable earthquake from a specific time given knowledge of the structure existing among earthquakes occurring prior to a specific moment

the mechanism of surtseyan volcanism during eruption the vent of a surtseyan volcano is occupied by a highly mobile slurry of tephra hyaloclastite and water as magma ascends rapidly through the slurry mixing occurs due to velocity shear acceleration of the fluid fluid contacts and mass incorporation consequent expansion of the admixed water causes the jetting and continuous up rush activity that characterizes surtseyan volcanism there is no evidence of the widely accepted fuel coolant interaction mechanism

diagnosis of time of increased probability of strong earthquakes in different regions of the world algorithm cn abstract an algorithm for intermediate term earthquake prediction is suggested which allows diagnosis of the times of increased probability of strong earthquakes tips tips are declared for the time period of one year and an area with linear dimensions of a few hundred kilometers and can be extended in time the algorithm is based on the following traits of an earthquake flow level of seismic activity its temporal variation clustering of earthquakes in space and time their concentration in space and their long range interaction the algorithm is normalized so that it can be applied in various regions without readaptation tips diagnosed by the algorithm precede 80 of strong earthquakes and take on average 24 of the total time

preliminary geology mineral chemistry and diamond results from the c29 30 candle lake volcanic complex saskatchewan canada abstract the c29 30 kimberlite is one of two diamondiferous kimberlites in the candle lake cluster located in east central saskatchewan canada approximately 70 km from the fort a la corne kimberlite field the kimberlites are hosted by a cretaceous sequence of marine mudstone and shale of the lower colorado group and underlying siltstone and sandstone of the mannville group this sequence overlies paleozoic carbonates that were deposited over the proterozoic crystalline basement based on the country rock stratigraphy and morphology of the body c29 30 is inferred to be cretaceous in age the elongated kimberlite body has a lateral extent of approximately 2 km with the long axis oriented in a south east to north west direction and an estimated surface expression of 75 3 ha the investigation of 47 drill cores suggests that this body is a single volcanic complex dominated by a single phase of volcaniclastic kimberlite that is characterised by absent to rare phlogopite within the groundmass of preserved juvenile clasts minor amounts of at least one other phase of kimberlite containing conspicuous groundmass phlogopite have also been documented the subsurface shape of c29 30 is complex and is interpreted to result from a combination of explosive volcanic activity that formed two craters from separate feeder vents the formation of the elongated trough is poorly understood it may have formed by a fissure style eruption or erosive processes related to the mass flow of material away from one of the craters or possible the collapse of an eruption column the c29 30 kimberlite is similar to bodies of the fort a la corne kimberlite field with respect to country rock setting pipe morphology and the dominant textural varieties present this contribution presents a preliminary geological model of c29 30 based on data obtained from the drilling programmes completed in 2006 2007 and 2008

formation of tuffisitic kimberlites by phreatomagmatic processes the rock type tuffisitic kimberlite tk occurs in the deeper diatremes of some southern african canadian and siberian kimberlite pipes and has been considered a unique rock type related to a particular emplacement process the key features of this rock type are its fragmental nature its massive well mixed appearance and a specific matrix mineralogy characterized by the presence of serpentine and microlitic clinopyroxene and the absence or scarcity of carbonate historically all these features were thought to be related to a highly specific intrusive extrusive magmatic emplacement process in this process the expansion of magmatic volatiles drives the fluidization of a pre existing shallow crustal vertical magma reservoir the embryonic pipe and its consequent evolution into the final diatreme after breakthrough to the surface the specific matrix mineralization is explained by the dissociation of carbonate into co2 and cao while the expanding co2 drives the fluidization process cao reacts with sio2 released from xenolith and olivine alteration to form microlitic clinopyroxene with the phreatomagmatic process chain we offer an alternative model that can readily explain this specific rock type ongoing explosions in a downward penetrating root zone excavate a pipe consisting of a rather regular cone shaped diatreme underlain by the irregular root zone at this stage the pipe in its majority is infilled by warm to hot pyroclastic tephra during thermohydraulic explosions in the root zone the expansion of water vapor homogenizes the overlying diatreme tephra and mixes it with the adjacent country rock lithologies this result in the massive well mixed volcaniclastic rock type typical for tkbs post emplacement hydrothermal alteration and mineralization under epi to mesothermal conditions are considered responsible for the observed specific matrix mineralogy carbonate is frequently present in coherent root zone rocks but is rare or absent due to its dissolution in hot hydrothermal fluids ascending from the lower diatreme which in turn precipitate their dissolved carbonate higher up in the cooler bedded upper diatreme region clinopyroxene also grows under epi to mesothermal conditions for the crystallization of serpentine a x h2o x co2 ratio of 20 1 is required which suggests both a high availability of groundwater and a low abundance of co2 after and likely during emplacement isotope studies h c o sr of matrix minerals suggest participation of groundwater in the formation of these minerals

seismic moment distribution summary we review possible errors in determining the size of earthquakes we propose that the size distribution can be effectively defined only for earthquake sequences not for individual earthquakes as a result of the error analysis we question the validity of many reported correlations between the 6 value and spatio temporal characteristics of tectonics and seismicity the study of the distribution of earthquake seismic moment largely avoids the influence of these errors and biases and is therefore superior to the standard analysis of the magnitude frequency law the gamma distribution is applied to describe the distribution of seismic moments of earthquake sequences this distribution which generalizes the well known gutenberg richter g r relation is characterized by two parameters we use the maximum likelihood method to determine the parameters of the gamma distribution for worldwide earthquakes in different depth ranges the empirical distribution is derived from the moment tensor catalogue compiled by the harvard group the p value for scalar seismic moment of earthquake sequences an analogue of the 6 value in the g r magnitude frequency law is close to 1 2 for all earthquakes the value predicted by a critical branching model of seismicity this result which will be improved as more seismic moment data become available provides input for modelling of seismicity based on percolation or on self organized criticality models if 3 equals 1 2 then using the critical branching model we find that most small earthquakes in available catalogues are dependent shocks i e aftershocks even among earthquakes of intermediate magnitudes the number of dependent events may exceed that of independent events

residual colluvio aeolian aprons in the negev highlands israel as palaeo climatic indicator abstract slope features treated previously mainly pedogenetically and described as alluvial terraces or as a catenary compound of stony loessial sierozem are shown to be remains of former colluvial loessial aprons the loess was deposited in the central negev during the uppermost pleistocene by dust laden rainstorms which triggered debris flows under conditions twice as humid as today during the holocene the aprons were selectively eroded by slope runoff resulting in a wide exposure of the basal slope truncation of the wadi fill and the final formation of the present day patchy slope morphology the dust laden rainy regime fits the last more humid period i e 70 000 10 000 yr b p

shallow water eruption fed mafic pyroclastic deposits along a paleoproterozoic coastline kangerluluk volcano sedimentary sequence southeast greenland abstract the 200 300 m thick volcano sedimentary sequence at kangerluluk is part of the psammite zone one of four major zones which constitute the 1 8 ga ketilidian orogen in south greenland three lithofacies are emphasized in the study 1 the conglomerate sandstone 2 the volcanic and 3 the pyroclastic lithofacies the 2 40 m thick conglomerate sandstone lithofacies represents a subaerial to subaqueous fan delta deposit matrix and clast supported conglomerates are interpreted as debris flow and longitudinal gravel bar deposits erosive based conglomerate channel fills attest to stream incision trough crossbedded sandstone interpreted as lunate megaripples planar bedded sandstone indicative of upper flow regime bar top sands and small scale trough crossbeds reflecting ripples follow up section form collectively with the conglomerate 0 40 2 50 m thick fining upward sequences the sandstone dominated unit up section from the conglomerates and composed of planar and low angle crossbeds minor ripples and graded beds as well as mudstone is indicative of a lower shoreface deposit below normal wave base the clastic sedimentary rocks are suggestive of a fan delta setting the 100 200 m thick volcanic lithofacies composed of pillowed and pillow brecciated lava flows is consistent with shallow water deposition interstratification of lava flows with both conglomerate sandstone and pyroclastic lithofacies intrusion of dykes into volcaniclastic rocks and peperite formation accentuate contemporaneity between volcanism and sedimentation and is a common feature of island arcs the 1 50 m thick pyroclastic lithofacies with sharp depositional contacts to the overlying volcanic and underlying conglomerate sandstone lithofacies was emplaced in a subaqueous setting the lithofacies is divided into a planar to crossbedded tuff lapilli tuff and a bedded lapilli tuff breccia whereby both deposits are inferred to result from shallow water surtseyan type eruptions the 5 15 m thick bedded lapilli tuff breccia with abundant bomb sag structures and graded beds is considered a result of subaqueous eruptions strong enough to form an insulating steam cupola characterized by ballistically emplaced bombs that rapidly collapsed allowing for transport via mass flow processes the deposits are considered proximal to the vent the 2 50 cm thick planar to crossbedded tuff lapilli tuff featuring abundant euhedral and broken crystals of feldspar 2cm and minor pyroxene 1 cm are massive graded crossbedded and stratified the planar but laterally discontinuous beds characterized by abundant low angle scours are interpreted as low to high concentration sediment gravity flows produced directly from subaqueous tephra jets that collapsed due to massive water ingestion local breccia size pyroclasts disrupting beds are interpreted as bomb sags the mafic eruption fed surtseyan type deposits postulated to be a subaqueous counterpart of cold subaerial base surges originate from subaqueous tuff cones formed along a rugged volcanic dominated shoreline featuring high energy fan deltas

stochastic synthesis of earthquake catalogs a model of earthquake occurrence is proposed that is based on results of statistical studies of earthquake catalogs we assume that each earthquake generates additional a probability that depends on time as t 1 this assumption together with one regarding the independence of branching events on adjacent branches of the event tree is sufficient to permit the generation of complete catalogs of earthquakes that have the same time magnitude statistical properties as real earthquake catalogs if is about 0 5 the process generates sequences that have statistical properties similar to those for shallow earthquakes many well known relations are reproduced including the magnitude frequency law omori s law of the rate of aftershock and foreshock occurrence the duration of a recorded seismic event versus its magnitude the self similarity or lack of scale of rate of earthquake occurrence in different magnitude ranges etc a value of closer to 0 8 or 0 9 seems to simulate the statistical properties of intermediate and deep shocks a formula for seismic risk prediction is proposed and the implications of the model for risk evaluation are outlined the possibilities of the determination of long term risk from real or synthetic catalogs that have the property of self similarity are dim

factors controlling the internal facies architecture of maar diatreme volcanoes most if not all kimberlite pipes show a multitude of facies types which imply that the pipes were emplaced under an episodic re occurrence of eruptive phases often with inter mittent phases of volcanic quiescence the majority of these facies can be related to either the fragmentation behaviour of the magma during emplacement or changing conditions dur ing sedimentation of volcaniclastic deposits as well as their alteration and compaction after deposition an additional factor controlling pipe facies architecture is the degree of mobility of the loci of explosions in the explosion chambers of the root zone or root zones at the base of the maar diatreme volcano in a growing pipe the root zone moves downward and with that movement the overlying diatreme enlarges both in size and diameter however during the life span of the volcano the explosion chamber can also move upward backintothelower diatreme where renewedexplosionsresult inthedestructionofolderdepositsandtheirstructures nextto vertical shifts of explosion chambers the loci of explosions can also move laterally along the feeder dyke or dyke swarm this mobility of explosion chambers results in a highly com plex facies architecture in which a pipe can be composed of several separate root zones that are overlain by an amalgam ated crosscutting diatreme and maar crater with several lobes pipe complexity is amplified by periodic changes of the fragmentation behaviour and explosivity of kimberlite mag ma recent mapping and logging results of canadian and african kimberlite pipes suggest that kimberlite magma frag mentation ranges from highly explosive with abundant entrained country rock fragments to weakly explosive spatter like production with scarce xenoliths on occasions spatter may even reconstitute and form a texturally coherent deposit on the crater floor in addition ascending kimberlite magma can pass the loci of earlier fragmentation events in the root zone and intrudes as coherent hypabyssal kimberlite dykes in high pipe levels or forms extrusive lava lakes or flows on the crater floor or the syneruptive land surface respectively this highly variable emplacement behaviour is typical for basaltic maar diatreme volcanoes and since similar deposits can also be found in kimberlites it can be concluded thatalsothevolcanologicalprocessesleadingtothesedeposits are similar to the ones observed in basaltic pipes

quaternary subsurface paleosols in haifa bay israel a new perspective on stratigraphic correlations in coastal settings abstract this study presents the first in depth analysis of properties micromorphology clay mineralogy magnetic susceptibility and general properties of quaternary paleosols from two boreholes in haifa bay subsurface whose chronostratigraphic position was determined previously the current analytical results allowed us to identify the type hydrologic regime polygenesis mode of pedosedimentary evolution and some subsequent alterations of paleosols the analogs of polygenic haplo and rhodo xeralf soils brown mollic and ortho hamra are associated with marine isotope stages mis 3 1 5 4 6 and 8 0 or 7 4 and likely developed in response to a changing climate paleosols prior to mis 12 yet difficult to attribute to specific mis are distinct from hamra soils by striking mottling poor preservation of argillic horizons abundant deformations in microfabric and overprinting processes of gley and calcium carbonate accumulation it is assumed that calcification may have affected the earlier formed clay illuviation and amorphous features and was related with marine coastal groundwater interface the older calcic gleyed paleosols of earlier middle pleistocene likely indicate that coastal paleogeography was characterized by both high discharge of the ancient qishon river and a high water table the thin section micromorphology is particularly valuable for refined paleopedological taxonomy identified pleistocene paleosols including their type hydrology and mode of evolution are proposed to serve additional stratigraphic markers in coastal settings

pyroclastic kimberlite deposits from the victor northwest pipe ontario canada the transition from phreatomagmatic to magmatic explosivity magmas of all compositions including kimberlites may undergo both magmatic and phreatomagmatic fragmentation during emplacement in this contribution we assess the extent of phreatomagmatism at different stages of the pipe formation for the victor northwest kimberlite northern ontario canada detailed drill core and petrographic observations of all volcanic facies within the pipe suggest emplacement in two volcanic cycles each consisting of three repeated eruptive phases pyroclastic kimberlite formed at the start of both cycles is characterized by the presence of fine grained poorly sorted deposits containing broken olivine crystals angular country rock fragments accretionary lapilli and variably vesicular irregular shaped juvenile pyroclasts all observations indicate these deposits formed by phreatomagmatism subsequent clastogenic coherent kimberlite deposits were formed as a result of hawaiian fire fountaining during the second phase of both cycles these phases were followed by mass wastin

spatial and temporal analysis of a seismic series using a new version of the three point method application to the 1989 antequera spain earthquakes abstract the three point method tpm has been successfully applied to several seismic series and has provided information about the spatial characteristics azimuth and dip of the fault planes activated in the rupture process a new development of the tpm to determine temporal characteristics is presented to obtain the evolution of the fracturing process of an active fault system for the analysis of the 158 microearthquakes and earthquakes that took place in the seismic series of antequera in june 1989 the choice of a threshold magnitude m u 2 5 has permitted the events related to the most relevant fractures to be distinguished secondly only the events between two concentric spheres here named spatial crown with respect to a given earthquake have been used in order to avoid taking into account earthquakes that are too close to each other together with the very distant events that have little relation to the event analysed the spatial crown has permitted some clear results in the antequera series where we have found that the fracturing process began fundamentally with n 80 e planes and evolved to n 65 w planes finally an error analysis enables an estimation of the uncertainty in the results to be obtained from the errors in the data

stochastic model of earthquake fault geometry summary an earthquake fault pattern is assumed to consist of a system of infinitesimal elementary dislocation loops after an initial dislocation subsequent ruptures occur according to a critical branching process the position of each secondary dislocation loop is randomly shifted along the initial fault plane from the location of the main shock in addition the orientations of the fault plane and slip vector of the secondary dislocations are rotated according to a three dimensional cauchy distribution which has one intrinsic scaling parameter in their turn the secondary dislocations produce new dependent shocks according to the same law the process cascades indefinitely we simulate an earthquake fault system by the monte carlo method this fault pattern is both visually and statistically similar to real earthquake faults the model yields statistical spatial distributions that correspond to those of the analysis of the catalogue data of real earthquakes we incorporate in our scheme the time magnitude model of earthquake occurrence developed earlier by the monte carlo method we then simulate synthetic sequences that reproduce all known magnitude space time statistical properties of real earthquake catalogues the results of these simulations make us question the suitability of some terms that are commonly used in the theory of an earthquake source for example as a consequence of the validity of the stochastic model the concepts like an individual earthquake fault plane or fault surface crack tip or fault tip and friction do not have an unambiguous definition

intermediate term prediction of occurrence times of strong earthquakes pattern recognition procedures for infrequent events are adapted to the problem of identifying patterns of clustering of small and intermediate scale seismicity before large earthquakes identification procedures derived from analysis of large california and nevada earthquakes yield a high success rate when applied to other parts of the world

micromorphological indications on the nature of the late quaternary paleosols in the southern coastal plain of israel abstract the nature of alternating layers of clayey soil material and calcareous soil material in the desert fringe area is discussed in earlier work by other researchers these soil materials were considered as representing different climatic environments the clayey layers a wet period and the calcareous layers a dry period based on a pedogenic approach supported by micromorphological indications however it is concluded that the clayey layers together with the calcareous layers form a single pedogenic unit developed in the same climatic environment the calcareous layers are in fact calcic horizons accumulated from the overlying leached clayey material and their appearance is similar to the modern brown grumusolic soils that occur in the semiarid area of the coastal plain a sequence of four superimposed brown grumusolic paleosols developed during the last glacial period was recognized in the western part of the coastal plain quartzic brown soils and husmas soils which developed on sand dunes occur the former has an argilic horizon with a calcic horizon below microcalcites of eolian dust origin are homogeneously distributed in the plasma the soil representing a monogenetic soil type developed during a semiarid climate the latter is a reddish brown mediterranean polygenetic soil with leached soil material in which the calcic horizon accumulated from a loessial soil cover that settled during a drier climate both soils also developed during the last glacial period in the eastern coastal plain older paleosols which developed on sand dunes occur below the brown grumusolic soils one type is a polygenetic leached quartzic gray brown paleosol not recognized in previous studies which overlies a red hamra soil sandy red mediterranean soil

on the geometry of an earthquake fault system abstract invariants of a two point correlation function of the seismic moment tensor were used to investigate an earthquake fault system the geometry of the fault system is significantly different from the standard model of an earthquake fault i e coherent rupture on a planar surface contrary to the flat fault model we see clear evidence for non planarity of the fault system geometry and observe that the focal mechanisms of neighboring events may have very different orientation i e they undergo large three dimensional rotations therefore earthquake deformation models need to be fully three dimensional and should include large rotations the spatial behavior of the invariants is approximately the same for earthquakes in different depth intervals shallow intermediate and deep the temporal behavior of the invariants differs only in that shallow earthquakes are clustered in time whereas for deeper events the clustering is much less pronounced as soon as we decluster shallow seismicity the invariants temporal properties become similar for earthquakes of all depths this demonstrates that the basic geometrical properties of earthquake rupture do not depend on depth and therefore they are generally independent of rheological properties of rocks lithostatic pressure or the presence of a free boundary for strong shallow earthquakes

neural dynamic modelling on earthquake magnitude series summary earthquake magnitude prediction is of vital importance for human safety the earthquake is a very complicated and non linear dynamic process it cannot be described adequately by any deterministic models in this paper a neural dynamic modelling for earthquake magnitude prediction is reported historical records of earthquake magnitude series are used to construct the optimal non linear dynamic model and the consequent outcome of the earthquake behaviour is then predicted by this model in turn the latest recorded data set can be fed back to improve the accuracy of the neural dynamic model the modelling of experiments of three earthquake magnitude series in china and japan and their extrapolated predictions are included in this paper the values predicted by extrapolation are in good agreement with the historical data

contrasting eruption styles of the 147 kimberlite fort a la corne saskatchewan canada abstract the cretaceous fort a la corne falc kimberlite field was active over a time span of 20 ma with contemporaneous terrestrial mannville group to marine lower colorado group background sedimentation steep sided pipes craters and positive landform volcanoes such as scoria or tuff cones are thought to have formed during that period the 147 kimberlite is located in the se section of the field s main cluster and is part of the large 377 5 ha orion north volcanic complex based on logging of 25 drill cores the morphology of the country rock kimberlite interface suggests excavation of a complex crater field down to the upper portion of the mannville group sedimentary deposits at least two types of volcaniclastic deposits are identified a main kimberlite unit that is typically characterized by crustal xenolith poor 1 2 normal graded beds possibly deposited as turbidites in a subaqueous environment originating from the nearby 148 tephra cone and infilling the adjacent 147 crater and a second unit located on the ne margin of the 147 kimberlite that represents a thick 60 m sequence of large up to 22 m sedimentary country rock blocks located at least 60 m above their original stratigraphic position we suggest the following time sequence of events crater excavation as a consequence of a shallow magma fragmentation level within the uppermost country rock sequences together with several closely spaced eruptive centres initially formed the complex intercalated crater field subsequently ongoing eruptions with a fragmentation level above the country rock produced the lithic fragment poor main infill of the 148 kimberlite resedimentation from the outer flanks of the 148 tephra cone resulted in the deposition of turbidites in the 147 area a consolidation phase solidified the lowermost portion of the main infill in 147 a subsequent explosion s occurred within the mannville group in the 147 area ejecting large blocks of sedimentary country rocks and fracturing the overlying volcaniclastic main infill finally blocks of the main infill tilted and possibly slumped into the subsidence structure developed above the emptied explosion chamber of 147 the different volcanic deposits reflect a change in eruption style and fragmentation level from highly explosive to spatter activity with little fragmentation potential cap rocks to build up the volatile overpressure necessary to blast the craters were not present at the time of emplacement no diatremes were observed in the study area assuming that the magma properties remained constant over time the change in eruption style has to be attributed to external factors such as water access to the rising magma the volcanic behaviour of the kimberlite magma appears to be comparable to that of other magmatic systems both in eruptive style and production rate no evidence was found for a high possibly plinian production rate or dispersion

canadian kimberlites geological characteristics relevant to emplacement in canada more than 770 kimberlites have erupted in diverse tectonic settings over a period of 1000 ma and over an area at least 5000 km across the kimberlites represent at least 30 comagmatic fields one pipe type dominates each of the different kimberlite fields even with the discovery of a significant number of new kimberlite fields this review of recent data substantiates the previous proposal that there are at least three distinct classes of kimberlite pipes which show a correlation with the nature of the country rocks into which they were emplaced new data show that a variation on the prairies pipe type occurs when kimberlites were emplaced into competent paleozoic sediments resulting in steeper sided pipes infilled with similar pyroclastic kimberlite new data for each pipe type are summarised and the contrasting characteristics of the three pipe types are considered to reflect fundamentally different styles of eruption and deposition apparently uniform near surface olivine and volatile rich kimberlite magmas were modified differently during the contrasting emplacement processes resulting in distinct textural rock types pyroclastic kimberlite pk tuffisitic kimberlite tk and associated hypabyssal kimberlite hk or resedimented kimberlite rvk dominating each type of pipe the substantiated correlation of pipe type with country rock geology could indicate variable constraints on volatile exsolution which affected the nature of the magmatic eruptions in different settings

alteration styles in the orion central volcanic complex fort a la corne kimberlite field saskatchewan and their effects on primary volcaniclastic textures implications for facies mapping and diamond exploration diamond grade distributions within individual kimberlite bodies are controlled by physical emplacement processes which are generally determined from volcaniclastic facies characteristics however the effects and distribution of secondary alteration styles which usually mask primary kimberlite facies have been given little attention at the fort a la corne kimberlite field saskatchewan complex overprinting alteration textures and mineral phases are recognized this study documents the characteristics overprinting relationships and spatial distribution of alteration styles within a crater filling volcaniclastic deposit body 219 of the orion central volcanic complex data were acquired from macroscopic drill core observations microscopic petrography sem imaging eds element mapping and xrd analyses olivine crystals display a mesh fracture pattern and have been replaced by multiple generations of serpentine and magnetite late stage serpentine has migrated into the interstitial medium bulk rock alteration textures include 1 fine grained crystal rich domains which are alteration pseudoclasts and or relict juvenile pyroclasts 2 a heterogeneous interstitial medium varying from early stage disseminated calcite rich serpentine to amorphous serpentine and crystalline calcite and 3 overprinting serpentine carbonate and magnetite veins and serpentine nodules alteration styles defined by unique alteration characteristics are spatially zoned through the body 219 volcaniclastic deposit and this is a result of multiple reaction fronts associated with the influx of fluids of varying composition over time and permeating different parts of the deposit recognition of alteration processes their paragenesis and spatial controls can assist in defining and constraining the distribution of primary kimberlite facies and by consequence the distribution of diamond grades

prediction probabilities from foreshocks when any earthquake occurs the possibility that it might be a foreshock increases the probability that a larger earthquake will occur nearby within the next few days clearly the probability of a very large earthquake ought to be higher if the candidate foreshock were on or near a fault capable of producing that very large mainshock especially if the fault is towards the end of its seismic cycle we derive an expression for the probability of a major earthquake characteristic to a particular fault segment given the occurrence of a potential foreshock near the fault to evaluate this expression we need 1 the rate of background seismic activity in the area 2 the long term probability of a large earthquake on the fault and 3 the rate at which foreshocks precede large earthquakes as a function of time magnitude and spatial location for this last function we assume the average properties of foreshocks to moderate earthquakes in california 1 the rate of mainshock occurrence after foreshocks decays roughly as t 1 so that most foreshocks are within three days of their mainshock 2 foreshocks and mainshocks occur within 10 km of each other and 3 the fraction of mainshocks with foreshocks increases linearly as the magnitude threshold for foreshocks decreases with 50 of the mainshocks having foreshocks with magnitudes within three units of the mainshock magnitude within three days we apply our results to the san andreas hayward san jacinto and imperial faults using the probabilities of large earthquakes from the report of the working group on california earthquake probabilities 1988 the magnitude of candidate event required to produce a 1 probability of a large earthquake on the san andreas fault within three days ranges from a high of 5 3 for the segment in san gorgonio pass to a low of 3 6 for the carrizo plain

spatial temporal analysis of a seismic series using the principal components method the antequera series spain 1989 a method for the characterization of a seismically active zone from a distribution of hypocenters is presented this method is based on principal components analysis a powerful multivariant statistical technique that is used to find the rupture local ellipsoid rle the ellipsoid is a planar structure with which two variations of the method are developed the spatial principal components analysis and the spatial temporal principal components analysis using these methods it is possible to find the dominating tendencies in the fracturing of the seismically active volume as well as the temporal evolution of the process the methodology developed has been applied to a series of earthquakes that occurred near antequera spain with the result that the main fracture series trends n70 80 e moreover the temporal evolution of the system from the most relevant rle has been characterized

geoarchaeological context of the later phases of mousterian occupation 80 115 ka at nesher ramla israel soil erosion deposition and pedogenic processes a new open air mousterian site was found in karst depression on hilly limestone terrain of central israel at nesher ramla the paper highlights the complex history of depositional post depositional and pedogenic processes that took place at the later phases of mousterian site formation during the osl age interval between 80 and 115 ka the upper sequence is divided into unit i and unit ii both comprising rather uniform calcareous gravel rich silty clay deposits gravel largely consists of calcrete nari and possibly some chalky limestone unit i is darker partially decarbonated magnetically enhanced and shows microscopic features of shrink swell process analogous to vertisols mousterian artifacts chunks of ochre and animal bones are scarce in this unit unit ii has increased gravel magnetic susceptibility values drop and humus and carbonate content both increase mousterian artifact density significantly increases in the middle part of unit ii lithologic characteristics thin sections and sem eds all indicate that the upper sequence originated from periodic erosion of loess derived soils developed upon chalky hillslopes intermittent with more stable periods when hominins occupied the site the proposed model relates the upper sequence to heterogeneous anthropogenic pedosediments with high proportions of eroded soil materials and signs of in situ pedogenesis apart from singular mm sized pyrogenic features remnants of bedded combustion features in the upper sequence are lacking probably because of pedogenic and diagenetic alterations on the site

evidence of bias in estimations of earthquake size magnitudes of earthquakes determined using traditional methods show systematic deviations dependent on tectonic setting from accurate estimates of earthquake size magnitudes are overestimated for most of the continental earthquakes underestimated for mid oceanic ridges and differences of varying sign are obtained for subduction zones this is important in evaluating the seismic risk or consideration of effects such as the seismic versus aseismic strain release as seismic moments determined from magnitudes can be wrong by as much as a factor of four

sedimentologic and stratigraphic constraints on emplacement of the star kimberlite east central saskatchewan abstract diamond bearing kimberlites in the fort a la corne region east central saskatchewan consist primarily of extra crater pyroclastic deposits which are interstratified with lower cretaceous albian and cenomanian marine marginal marine and continental sediments approximately 70 individual kimberlite occurrences have been documented the star kimberlite occurring at the southeastern end of the main fort a la corne trend has been identified as being of economic interest and is characterized by an excellent drill core database integration of multi disciplinary data sets has helped to refine and resolve models for emplacement of the star kimberlite detailed core logging has provided the foundation for sedimentological and volcanological studies and for construction of a regionally consistent stratigraphic and architectural framework for the kimberlite complex micropaleontologic and biostratigraphic analysis of selected sedimentary rocks and u pb perovskite geochronology on kimberlite samples have been integrated to define periods of kimberlite emplacement radiometric age determination and micropaleontologic evidence support the hypothesis that multiple kimberlite eruptive phases occurred at star the oldest kimberlite in the star body erupted during deposition of the predominantly continental strata of the lower mannville group cantuar formation kimberlites within the cantuar formation include terrestrial airfall deposits as well as fluvially transported kimberlitic sandstone and conglomerate successive eruptive events occurred contemporaneous with deposition of the marginal marine upper mannville group pense formation kimberlites within the pense formation consist primarily of terrestrial airfall deposits fine to medium grained cross stratified kimberlitic olivine dominated sandstone in this interval reflects reworking of airfall deposits during a regional marine transgression the location of the source feeder vents of the cantuar and pense kimberlite deposits has not been identified the youngest and volumetrically most significant eruptive events associated with the star kimberlite occur within the predominantly marine lower colorado group joli fou and viking formations kimberlite beds which occur at several horizons within these units consist of subaerial and marine fall deposits the latter commonly exhibiting evidence of wave reworking black shale encased resedimented kimberlite beds likely deposited as subaqueous debris flows and turbidites are particularly common in the lower colorado group during its multi eruptive history the star kimberlite body is interpreted to have evolved from a feeder vent and overlying positive relief tephra ring into a tephra cone initial early joli fou volcanism resulted in formation of a feeder vent 200 m diameter and tephra ring subsequent eruptions dominated by subaerial deposits partly infilled the crater and constructed a tephra cone a late joli fou eruption formed a small 70 m diameter feeder pipe slightly offset to the nw of the early joli fou feeder vent deposits from this event further infilled the crater and were deposited on top of early joli fou kimberlite proximal to the vent and sediments of the joli fou formation distal to the vent the shape of the tephra cone was modified during multiple marine transgression and regression cycles coeval with deposition of the lower colorado group resulting in wave reworked kimberlite sand along the fringes of the cone and kimberlitic event deposits tempestites turbidites debris flows in more distal settings

random stress and earthquake statistics spatial dependence summary we calculate the 3 d stochastic rotations of focal mechanisms disorientations caused by stresses arising from the presence of many small random point defects that may surround the tip of an earthquake fault these random stresses can be shown to be distributed according to a cauchy distribution as a consequence the next episode of fracture of a fault cannot be planar the disorientation of focal mechanisms of these new rupture episodes is closely approximated by a rotational cauchy distribution as observed previously the geometry of fault systems for natural earthquakes is consistent with these observations since it too can be modelled by the cauchy distribution these observations indicate how the 3 d rupture process in rocks and other materials can be modelled we also calculate distributions of disorientations caused by a uniformly random 3 d rotation of sources these distributions are governed by symmetry properties of earthquake focal mechanisms to take into account the source symmetry we compare the cauchy distribution which is due to influence of random stresses to the distributions caused by random rotations

simulating a seismic series using geostatistical and stochastic methods application to the seismic series in the alboran sea 1997 june 24 summary seismic series can be taken as examples of correlated unstationary sets of timestochastic sequences we investigate the possibility of estimating what is most probable to occur subsequently if we know the events that have occurred up to a given moment the stochastic methods can be used with data of the seismic series irrespective of their genesis and origin using three stochastic methods namely 1 simulating the likelihood of occurrence by conditional geostatistical simulation 2 developing a stochastic analysis of the energy release by means of energy packages and 3 calculating the occurrence time of the most probable next earthquake we were able to simulate

ideal probabilistic earthquake prediction abstract the state of the art in earthquake prediction can be displayed graphically and compared with the ideal in terms of the estimated probability of earthquake occurrence in the next unit of time as a function of time before the earthquake

special climatological conditions in the deserts of sinai and the negev during the latest pleistocene abstract results of hydrological and geological investigations carried out during the last ten years in the deserts of the sinai and the negev indicate that unique climatological and hydrological conditions prevailed between ca 100 000 and ca 10 000 yr b p the uniqueness was expressed by the following characteristics 1 1 higher precipitation and recharge rates caused the nubian sandstone aquifers to be filled up through the outcrops in central sinai and to overflow through big springs emerging along the faults of the syrian african rift system this water is of special isotopic composition namely depleted in 18o and deuterium and with a lower excess of the latter 2 2 dust laden rainstorms prevailed probably mainly during the autumn season causing the deposition of thick layers of loess the quantity of rain during the humid periods was double that of the present 3 3 the drainage system of many western and northern wadis of sinai as well as the negev could not drain out all the silt loaded water during the rainy season and shallow lakes and marshes extended in many wadis during this season 4 4 the floods and the springs flowing into the dead sea rift valley contributed to the lisan lake which was 200 m above the level of the contemporary dead sea

elephants at the middle pleistocene acheulian open air site of revadim quarry israel abstract lower paleolithic faunal and lithic assemblages serve as a major source of information on the behavior and capabilities of early and middle pleistocene hominins the multi layered late acheulian site of revadim quarry provides a rare opportunity to study hominin elephant interactions during the late lower paleolithic period in the levant a large proportion of this open air site was excavated ca 250 m 2 and yielded a wealth of lithic and faunal remains in this paper the proboscideans from revadim are presented for the first time within the broader geomorphological stratigraphic and archaeological context in order to allow a better understanding of elephants within the acheulian in the southern levant the unprecedented quantity of elephant remains at the site is accompanied by large and rich lithic assemblages of special interest are several elephant bones with cut marks and the earliest appearance in the southern levant of bones that seem to have been shaped to resemble tools the site bears testimony to complex exploitation of proboscideans

the submarine eruption and erosion of surtla surtsey iceland abstract surtla is the site of a short lived submarine vent which built basaltic elastic deposits almost to sea level in 1963 early in the eruption of surtsey since then wave and current activity have eroded the volcanic pile such that in july 1981 its top was a fairly level plateau 45 m below sea level and its surface comprised a lag deposit of sparse blocks of lava in a bed mainly of glass granules this winnowed layer was underlain by a nonreworked poorly sorted and finer deposit of glassy clasts formed by a combination of disruption by magmatic volatiles steam explosions and quench brecciation during the eruption the explosion violence and associated comminution increased as the pile built up to shallower water depths it is argued that at times of continuous effusion a cupola of steam was situated over the vent as indicated by scoriaceous spatter which shows agglutination and bread crust features that can only have developed in conditions more akin to subaerial than hitherto envisaged in a subaqueous eruption

climate of the last 53 000 years in the eastern mediterranean based on soil sequence stratigraphy in the coastal plain of israel abstract in this paper we present a detailed record of proxy climatic events in the coastal belt of the eastern mediterranean during the past 53 000 years a sequence of alternating palaeosols aeolianites and dune sands which have been dated by luminescence and by 14c was studied by the magnetic susceptibility particle size distribution clay mineralogy and soil micromorphology thirteen proxy climatic events demonstrating fluctuations of relatively dry and wet episodes were recognized the soil parent materials as well as the different soil types were rated in a semi quantitative dry to wet scale the palaeosol sequence is compared to a proxy climatic record of oxygen and carbon isotopes in speleothems from a karstic cave in central israel and to a record of lake levels of lake lisan and its successor which is known as the dead sea a genuine red mediterranean soil rhodoxeralfs localy designated as hamra soil developed during the last glacial stage from 40 to 12 5 thousand calendar years bp climatic fluctuations that were recorded in speleothems and in changing lake levels were not preserved in this soil during the cold and dry younger dryas ca 12 5 to 11 5 calendar ka bp a thick bed of loess material deriving from atmospheric dust of the sahara and arabian deserts covered the entire coastal belt during this phase lake lisan was desiccated and turned into the modern smaller dead sea during the early holocene some 10 7 5 calendar ka bp a second red hamra soil developed in warm and wet environments associated with a relatively high stand of the dead sea level a depletion of 18o and a significant enrichment of 13c in the speleothems were recorded during this episode this event was in phase with the widespread distribution of freshwater lakes in the sahara desert and the accumulation of the s1 sapropel in the eastern mediterranean several small scale dry and somewhat wet fluctuations of the late holocene from 7 5 calendar ka bp to the present were recorded in the coastal belt changes in human history as reflected in archaeological records are associated with proxy climatic fluctuations periods of desertification and deterioration are coupled with dry episodes periods of relative human prosperity are coupled with wetter episodes

micromorphological fabrics and developmental stages of carbonate nodular forms related to soil characteristics abstract carbonate nodules often constitute the first stage of calcrete formation micromorphological analysis of carbonate nodules and nodular fabrics in different soil materials shows that their development is a function of several factors nature of the host matrix texture porosity carbonate and non carbonate clay distribution bulk density and the interactions among them different micromorphological stages therefore exist in different soil materials in calcareous medium textured soil materials the stages of nodule formation are related to the increase of the density of the nodule caused by the accumulation of microcalcites in such a soil material the following stages occur 1 microcalcites within the low to moderate density matrix 2 microcalcites of moderate to high density and moderately dense diffuse nodules parallel calcans may occur 3 microcalcites of high density with dense microcalcitic nodules during these stages the amount of non carbonate clay decreases but is homogeneously dispersed and disseminated with the microcalcites in general the size of microcalcites 1 8 m is inversely related to the clay content in non calcareous medium to fine textured soil materials secondary carbonate precipitates in intrapedal and or interpedal voids as large sparry crystals due to pedoturbation processes the nodules thus formed are subjected to recrystallization resulting in a microsparry pattern the development stages are 1 few calcans and crystal chambers 2 crystic nodules mainly of sparry crystals and an increase of calcans and crystic chambers 3 recrystallized nodules composed mainly of microspars in coarse grained materials secondary carbonates precipitate directly in voids as sparry crystals and the resulting nodules are of the crystic type the large crystals are often subjected to recrystallization in partly calcareous coarse grained materials with additions of calcareous dust particular micromorphological carbonate forms occur in the c horizon cutanic calciasepic fabric forms besides zones of crystic fabric which gradually become calciasepic in the b horizon and include the typical nodular forms of the calcareous medium textured soil material together with appreciable amounts of glaebular halos the processes leading to the formation of these stages occur essentially without a significant biogenic influence where carbonate segregation occurs as rhizomorphs surrounding active roots the fabric is always micritic even in coarse textural soil material

long term probabilistic forecasting of earthquakes we estimate long term worldwide earthquake probabilities by extrapolating catalogs of seismic moment solutions we base the forecast on correlations of seismic moment tensor solutions the forecast is expressed as a map showing predicted rate densities for earthquake occurrence and for focal mechanism orientation focal mechanisms are used first to smooth seismicity maps to obtain expected hazard maps and then to forecast mechanisms for future earthquakes several types of smoothing kernels are used in space domain we use the 1 distance kernel for the distribution of seismicity around any epicenter the kernel is parameterized using two adjustable parameters maximum distance and directivity distribution of seismicity around an epicenter with regard to the focal mechanism of an earthquake for temporal prediction we use the poisson hypothesis of earthquake temporal behavior we test these forecasts we use the first half of a catalog to smooth seismicity level and the second half of the catalog is used to validate and optimize the prediction to illustrate the technique we use available data in the harvard catalog of seismic moment solutions to evaluate seismicity maps for several seismic regions the method can be used with similar catalogs the technique is completely formal and does not require human operator intervention hence the prediction results can be objectively tested moreover the maps can be used as the poisson null hypothesis for testing by the likelihood method against any other prediction model which shares the same sample space the same zones time window and acceptance criteria

geology and evaluation strategy of the star and orion south kimberlites fort a la corne canada abstract diamond bearing kimberlites in the fort a la corne field east central saskatchewan consist primarily of volcaniclastic deposits which are interstratified with lower cretaceous continental marginal marine and marine sediments seventy kimberlite occurrences have been drill confirmed with the majority of those occurring in the fort a la corne main trend the star 352 ha and orion south 358 ha kimberlite complexes are located at the south eastern extremity of the main trend and contain some of the world s best examples of preserved primary volcaniclastic kimberlite deposits the advanced exploration programs on both the star and orion south complexes offer a rare opportunity to examine a wide variety of in situ volcaniclastic kimberlite deposits both kimberlite complexes are composed of multiple eruptive units that were deposited episodically over 4 to 6 million years separated by periods of volcanic quiescence marked by reworking of kimberlite and siliciclastic sedimentation detailed logging of core from 100 m spacing grid drilling has revealed well defined tuff ring tuff cone crater and extra crater deposits evaluation of these large tonnage lower grade coarse diamond size frequency kimberlite complexes requires a methodical and multi branched exploration strategy utilizing 1 grid pattern core drilling to gain an understanding of the three dimensional architecture of the kimberlite complexes 2 underground bulk sampling to provide appreciable carats for accurate estimates of diamond grade and price and 3 grid pattern mini bulk sampling via large diameter drilling to obtain an understanding of the diamond grade across the breadth of each kimberlite

the miocene costa giardini diatreme iblean mountains southern italy model for maar diatreme formation on a submerged carbonate platform in this paper we present a model for the growth of a maar diatreme complex in a shallow marine environment the miocene age costa giardini diatreme near sortino in the region of the iblei mountains of southern sicily has an outer tuff ring formed by the accumulation of debris flows and surge deposits during hydromagmatic eruptions vesicular lava clasts accretionary lapilli and bombs in the older ejecta indicate that initial eruptions were of gas rich magma abundant xenoliths in the upper late deposited beds of the ring suggest rapid magma ascent and deepening of the eruptive vent is shown by the change in slope of the country rock the interior of the diatreme contains nonbedded breccia composed of both volcanic and country rock clasts of variable size and amount the occurrence of bedded hyaloclastite breccia in an isolated outcrop in the middle lower part of the diatreme suggests subaqueous effusion at a low rate following the end of explosive activity intrusions of nonvesicular magma forming plugs and dikes occur on the western side of the diatreme and at the margins close to the contact between breccia deposits and country rock they indicate involvement of volatile poor magma possibly during late stages of activity we propose that initial hydromagmatic explosive activity occurred in a shallow marine environment and the ejecta created a rampart that isolated for a short time the inner crater from the surrounding marine environment this allowed explosive activity to draw down the water table in the vicinity of the vent and caused deepening of the explosive center a subsequent decrease in the effusion rate and cessation of explosive eruptions allowed the crater to refill with water at which time the hyaloclastite was deposited emplacement of dikes and plugs occurred nonexplosively while the breccia sediment was mostly still soft and unconsolidated locally forming peperites the sheltered low energy lagoon filled with marine limestones mixed with volcaniclastic material eroded from the surrounding ramparts ultimately lagoonal sediments accumulated in the crater until subsidence or erosion of the tuff ring caused a return to normal shallow marine conditions

root zone processes in the phreatomagmatic pipe emplacement model and consequences for the evolution of maar diatreme volcanoes abstract the understanding of processes within the root zone of maar diatreme volcanoes is important for the interpretation of the geology volcanology and even hazard assessment of these volcanoes in the phreatomagmatic model of pipe formation the irregularly shaped root zone is the site of the phreatomagmatic explosions and thus functions as the engine for pipe formation in this model the root zone grows over a period of time in a series of many single thermohydraulic i e phreatomagmatic explosions the explosions initially occur close to the surface and with ongoing explosive activity penetrate towards deeper levels the ejection of country rock clasts from the root zone results in a mass deficiency in the root zone that causes the overlying tephra and the adjacent country rocks to subside passively in a sinkhole like fashion into the root zone many phreatomagmatic eruptions consequently result in the formation of a cone shaped diatreme thus with ongoing eruptions the cone shaped diatreme has to grow systematically both in depth and diameter during its growth processes in the lower diatreme levels successively destroy the upper levels of the evolving root zone at the surface the maar crater in turn reacts to the underlying subsidence processes and also grows both in depth and diameter thermohydraulic explosions which fragment both magma and the surrounding country rocks mostly occur within the bottom part of the root zone violent explosions in small pipes may clear the overlying diatreme for a short period of time before tephra fall and collapse of the walls of the new crater refill the small initial diatreme in larger pipes via expansion of the mixture of highly pressurized water vapor juvenile gas phases and explosively produced tephra the confined and expanding eruption cloud has to pierce through the diatreme fill in a feeder conduit in order to erupt diatreme clearing events in large pipes are difficult or impossible to maintain since the explosive force in the root zone is only in exceptional instances strong enough to lift or entrain the entire diatreme tephra knowledge of the genetic relationships between root zones and diatremes is critical to understand pipe growth processes the combination of such processes can lead to substantial variation in volcanic behavior and thus produce fundamentally different volcano and rock types it is the purpose of this paper to outline important features of root zones and suggest their significance for the genesis and evolution of maar diatreme and related volcanoes

chronostratigraphy of aeolianites from the sharon coastal plain of israel abstract the sharon coastal plain in israel is composed mainly of sand dune fields and aeolianite ridges three major sand accumulation periods are documented in the terrestrial record along the cliffs of the sharon coastal plain between 65 to 50 ka from 7 to 5 ka and from 5 to 0 2 ka these seem to correlate with the periods of sapropel formation in the mediterranean sea and so with periods of strongly increased african monsoon activity the accumulation of the stratigraphically oldest aeolianite kurkar unit 5 appears to correlate with sapropel s2 formed about 55 ka bp the uppermost aeolianite calcareous sandstone unit 2 seems to correlate with sapropel s1 formed at about 7 8 4 0 ka bp major soil formations occurred between 35 and 25 ka resulting in a rhodoxeralf soil grumusolic dark brown soil and between 15 and 12 ka resulting in a rhodoxeralf hamra soil at least seven weak weathering horizons regosol type soils are intercalated in the aeolianite of unit v and two regosols are present in the holocene aeolian sand of unit i

the importance of the transport system in shaping the growth and form of kimberlite volcanoes transport of kimberlite magma from the mantle to the surface is a complex process that involves many often sudden and dramatic changes in transport style the pace and magnitude of changes in the transport system acclerate as the magma nears the surface culminating in eruptions during which multiple transport events take place simultaneously as well as single transport events that change significantly from their point of origin to final deposition understanding the range of transport styles recorded by kimberlite deposits is key to describing the type and style of eruptions the growth of cones and craters and the distribution geometry and structure of the deposits that make up kimberlite volcanoes in an economic context building a clear picture of the processes that shape deposits is essential for selecting exploration targets and evaluating the grade and value of diamond bearing kimberlites variations in diamond grade reflect differences in the diamond content of different magma parcels erupted during the lifetime of the kimberlite volcano sorting during transport of eruption products or re working of diamonds during crater growth cone collapse and erosion deep transport systems control delivery of magma and diamonds to eruption sites the initial stages of kimberlite transport involve rise of magma in narrow interconnected networks of fluidfilled fractures there is compelling evidence that kimberlite magmas are extracted from their source region and erupted without significant residence times in the crust many single kimberlite volcanoes have significant variations in diamond grade between different kimberlite phases suggesting eruption of distinct perhaps unrelated magma parcels at the same site

statistical discrimination of foreshocks from other earthquake clusters summary when earthquake activity begins it may be a foreshock sequence to a larger earthquake a swarm or a simple main shock aftershock sequence this paper is concerned with the conditional probability that it will be foreshock activity of a later larger earthquake depending on the occurrence pattern of some early events in the sequence the earthquake catalogue of the japan meteorological agency 1926 1993 m 24 is decomposed into a large number of clusters in time and space in order to compare statistical features of foreshocks with those of swarms and aftershocks using such a data set ogata utsu katsura 1995 revealed some discriminating features of foreshocks relative to the other types of clusters for example the events closer proximity in time and space and a tendency towards chronologically increasing magnitudes which encouraged us to construct models which forecast the probability of the earthquakes being foreshocks specifically the probability is a function of the history of magnitude differences spans between origin times and distances between epicentres within a cluster for purposes of illustration the models were fitted to the early part of the data 1926 1975 and the validity of the forecasting procedure was checked on data from the later period 1976 1993 two procedures for evaluating the performance of the probability forecast are suggested furthermore for the case where only a single event is available i e either it is the first event in a cluster or an isolated event we also forecast the probability of the event being a foreshock as a function of its geographic location then the validity of the forecast is demonstrated in a similar manner finally making use of the multi element prediction formula we show that the forecasting performance is enhanced by the joint use of the information in the location of the first event and that in the subsequent interevent history in the cluster

maar diatreme volcanoes a review maar diatreme volcanoes are produced by explosive eruptions that cut deeply into the country rock a maar is the crater cut into the ground and surrounded by an ejecta ring while the diatreme structure continues downward and encloses diatreme and root zone deposits here we attempt an evenhanded review of maar diatreme volcanology that extends from mafic to kimberlitic varieties and from historical maar eruptions to deeply eroded or mined diatreme structures we conclude that maar diatreme eruptions are episodic ejecta rings provide invaluable insight into eruption processes and sequence but are incomplete records of diatreme formation deposits within the diatreme structure include in varying proportions lower unbedded deposits sometimes typified by subvertical contacts among domains of debris emplaced sequentially and upper bedded deposits formed by sedimentation on surfaces open to the atmosphere a basal root zone comprises the transition from coherent magmatic feeder dike to clastic deposits formed by fragmentation of magma and enclosing country rock root zones are irregular in form and the clastic deposits are typically intruded by contorted dikes irregular root zone like chaotic breccias cut by contorted dikes are also present within diatreme deposits where they represent intra diatreme fragmentation zones and record changes in the location of the explosion locus during eruption

foreshocks aftershocks and earthquake probabilities accounting for the landers earthquake the equation to determine the probability that an earthquake occurring near a major fault will be a foreshock to a mainshock on that fault is modified to include the case of aftershocks to a previous earthquake occurring near the fault the addition of aftershocks to the background seismicity makes its less probable that an earthquake will be a foreshock because nonforeshocks have become more common as the aftershocks decay with time the probability that an earthquake will be a foreshock increases however fault interactions between the first mainshock and the major fault can increase the long term probability of a characteristic earthquake on that fault which will in turn increase the probability that an event is a foreshock compensating for the decrease caused by the aftershocks

self organized criticality and earthquake predictability abstract we analyse a seismic catalogue of south california to investigate the possibility of earthquake prediction using the hypothesis that the seismic events are self organized critical phenomena the relation found previously is valid only in a mean field approximation but cannot be used for earthquake prediction because the time clustering of seismic events makes the definition of a standard deviation of waiting times of earthquakes impossible

statistics of characteristic earthquakes statistical methods are used to test the characteristic earthquake hypothesis several distributions of earthquake size seismic moment frequency relations are described based on the results of other researchers as well as my own tests evidence of the characteristic earthquake hypothesis can be explained either by statistical bias or statistical artifact since other distributions of earthquake size provide a simpler explanation for available information the hypothesis cannot be regarded as proven

aeolian beach ridges and their significance for climate and sea level concept and insight from the levant coast east mediterranean abstract relict beach ridges of aeolian origin and associated soils are often used for inferring relative sea level and climate with contrasting results most studies link the aeolian coastal deposits to regressive phases some to high sea level stands and a few to intermediate relative sea level positions we interpret the apparent contradictions as indicating the lack of an over arching concept and the inconsistent usage of sea level related terms in this paper we present an integrated morpho sedimentological concept for a microtidal mid latitudinal coast and review existing data from the levant east mediterranean coast to evaluate the concept and to eliminate nomenclatural confusion a coastal depositional environment in a semi arid environment consists of shallow marine aeolian and alluvial facies which together form an aeolian beach ridge complex as a package of strata which respond simultaneously to sea level change a transgressive complex forms through reworking or overstepping of the coastal foredune and a regressive complex forms by downstepping under transgression the aeolian beach ridge represents the highstand deposit and its adjacent shallow marine sediment is the transgressive deposit under regression the complex represents the falling stage and the associated downdip surface marks the lowstand on the levant coast we find chronologically well constrained offlapping aeolian beach ridges as parts of six downstepping beach ridge complexes formed between 200 ka and 10 ka the complexes represent the falling stage systems tract fsst of a short lived 5th order depositional sequence when the shoreline shifted from a position close to the modern coastline to the shelf or below the shelf edge three of these fssts and their up dip and down dip super bounding surface together form the 4th order 100 ka sequence of the last interglacial glacial cycle the absence of transgressive highstand and lowstand systems tract is explained by the poor preservation potential due to the small sediment budget of the complex the falling stage complex has a high preservation potential because sediment source area increases while the sand drift potential remains above the local threshold on the levant coast sand delivery to the backshore continued during relative sea level falls for distances of up to 10 km between dune and coastline which is unprecedented in most modern analogues the significance of the dune soil succession for climate is limited because the dunes are governed by relative sea level change the vegetation response to changes in precipitation is non linear and the dune dynamics are characterised by low resilience and hysteresis

geology and diamond distribution of the 140 141 kimberlite fort a la corne central saskatchewan canada abstract the cretaceous age fort a la corne falc kimberlite province comprises at least 70 bodies which were emplaced near the edge of the western canadian interior seaway during cycles of marine transgression and regression many of the bodies were formed during a marine regression by a two stage process firstly the excavation of shallow but wide craters and then subsequent infilling by xenolith poor crater facies subaerial primary pyroclastic kimberlite the bodies range in size up to 2000 m in diameter but are mainly less than 200 m thick and thus comprise relatively thin but high volume pyroclastic kimberlite deposits each body is composed of contrasting types of kimberlite reflecting different volcanic histories and therefore are considered separately the 140 141 kimberlite is the largest delineated body in the province estimated to have an areal extent below glacial quaternary sediments in excess of 200 ha the infilling of the 140 141 crater is complex resulting from multiple phases of kimberlite the central part of the infill is dominated by several contrasting phases of kimberlite one of these phases is a primary pyroclastic airfall mega graded bed up to 130 m in thickness the constituents grade in size from very fine to coarse macrocrystic kimberlite through to a basal breccia the mega graded bed is a widespread feature within parts of the body examined to date and at this current stage of evaluation appears to explain a variable diamond distribution within a tested portion of the pipe a second different phase of kimberlite is interpreted as representing a younger nested crater within the mega graded bed centrally located thicker intersections 450 m of this younger kimberlite may indicate a vent for the kimberlite crater the thickness of the mega graded bed increases with proximity to the younger kimberlite in the study area macrodiamond minibulk sample grades from the mega graded bed have been obtained from nine large diameter drill holes located within the northwest part of the body from an area of 20 ha which represents approximately 10 of the currently modeled kimberlite outline diamond grade increases with depth within the mega graded bed and also increases within the same unit towards the centrally positioned younger kimberlite macrodiamond sample grades vary from low at the top of the mega graded bed to considerably higher grades near the base total sample grade per drill hole varies from moderate near the vent feature to lower grades 200 300 m from the vent feature macrodiamond stone frequency measured in stones per tonne shows a pronounced relationship with depth and proximity to the vent feature within the mega graded bed there is a strong correlation between depth and increased stones per tonne and a similar correlation between stones per tonne and proximity to the vent feature the data supports the emplacement model of the mega graded bed and in turn this information is useful in understanding the macrodiamond distribution within this bed

neotectonics and slope stabilization at the alhambra granada spain abstract over 600 years the alhambra palace of granada spain a world heritage site has been damaged by earthquakes and slope instability the western part of san pedro cliff on the northern slope of the palace is a compound fault scarp fault line scarp modified by river erosion and latterly by successive slab falls the plane of the fault with the largest throw c 7 m outcrops in the innermost part of the escarpment and is a normal fault with a nw se strike and steep se dip it is part of a set outcropping along the alhambra hill fault activity may be very recent perhaps related to historical earthquakes seismic risk at the alhambra is considered to be moderate there is earthquake damage of the arab walls and barrier the most significant historical damage occurred in 1431 and partially collapsed the arab barrier extension associated with the faults loosens the ground and contributes to slab falls the faults are also preferential water paths both the many cracks of the walls and collapses of the alhambra barrier appear concentrated and aligned with the fault set stability analyses suggest that the factor of safety of the san pedro slope under 1000 yr return period earthquake loading may drop below 1 0 and the critical slip surface could penetrate the alhambra walls to raise the safety factor above 1 0 and to counteract extensional stress in the cliff an apparently environmentally acceptable solution with minimal visual impact is proposed it consists of high yield stress wire mesh post tensioned by anchors and coloured to blend with the cliff

an example of seismic occurrence modelling by a several state random process summary a statistical model of the microearthquake occurrence in the messina area assuming periodic transitions among several generalized poisson states is proposed four states are defined of different duration cluster mean rate and earthquake interdependence level their sequence is cyclically repeated with annual period the findings of this work can be seen as a generalization of the approach of bender 1984 who considered transition phenomena of the seismic temporal pattern among distinct states of the simple poisson type further the investigation aims at identifying possible factors leading to the observed periodic changes in the earthquake statistical parameters and to the main deviations of experimental data from the model the rainfall and regional tectonic stress patterns appear to be reasonable candidates for explaining the microearthquake periodicity and the most relevant anomaly of the observed seismic temporal pattern with respect to the model respectively

the cyclic and fractal seismic series preceding an mb 4 8 earthquake on 1980 february 14 near the virgin islands summary seismic activity in the 10 months preceding the 1980 february 14 mb 4 8 earthquake in the virgin islands reported on by frankel in 1982 consisted of four principal cycles each cycle began with a relatively large event or series of closely spaced events and the duration of the cycles progressively shortened by a factor of about 3 4 had this regular shortening of the cycles been recognized prior to the earthquake the time of the next episode of seismicity the main shock might have been closely estimated 41 days in advance that this event could be much larger than the previous events is indicated from time to failure analysis of the accelerating rise in released seismic energy using a non linear time and slip predictable foreshock model examination of the timing of all events in the sequence shows an even higher degree of order rates of seismicity measured by consecutive interevent times when plotted on an iteration diagram of a rate versus the succeeding rate form a triangular circulating trajectory the trajectory becomes an ascending helix if extended in a third dimension time this construction reveals additional and precise relations among the time intervals between times of relatively high or relatively low rates of seismic activity including period halving and doubling the set of 666 time intervals between all possible pairs of the 37 recorded events appears to be a fractal the set of time points that define the intervals has a finite non integer correlation dimension of 0 70 in contrast the average correlation dimension of 50 random sequences of 37 events is significantly higher close to 1 0 in a similar analysis the set of distances between pairs of epicentres has a fractal correlation dimension of 1 52 well defined cycles numerous precise ratios among time intervals and a non random temporal fractal dimension suggest that the seismic series is not a random process but rather the product of a deterministic dynamic system

physical characteristics of kimberlite and basaltic intraplate volcanism and implications of a biased kimberlite record we assess bias in the record of kimberlite volcanism by using newly acquired size data on more than 900 kimberlite bodies from 12 kimberlite fields eroded to depths of between 0 m and 1200 m and by a comparison with intraplate monogenetic basaltic volcanic fields eroded kimberlite fields are composed of pipes or diatremes and dikes and within any one kimberlite field regardless of erosion level kimberlite bodies vary in area at earth s surface over 2 3 orders of magnitude typically 60 70 of the bodies are

eruption of kimberlite magmas physical volcanology geomorphology and age of the youngest kimberlitic volcanoes known on earth the upper pleistocene holocene igwisi hills volcanoes tanzania the igwisi hills volcanoes ihv tanzania are unique and important in preserving extra crater lavas and pyroclastic edifices they provide critical insights into the eruptive behaviour of kimberlite magmas that are not available at other known kimberlite volcanoes cosmogenic 3he dating of olivine crystals from ihv lavas and palaeomagnetic analyses indicates that they are upper pleistocene to holocene in age this makes them the youngest known kimberlite bodies on earth by 30 ma and may indicate a new phase of kimberlite volcanism on the tanzania craton geological mapping global positioning system surveying and field investigations reveal that each volcano comprises partially eroded pyroclastic edifices craters and lavas the volcanoes stand 102 to 106 pa s for kimberlite attributed to degassing and in vent cooling each volcano is inferred to be the result of a small volume short lived days to weeks monogenetic eruption the eruptive processes of each igwisi volcano were broadly similar and developed through three phases 1 fallout of lithic bearing pyroclastic rocks during explosive excavation of craters and conduits 2 fallout of juvenile lapilli from unsteady eruption columns and the construction of pyroclastic edifices around the vent and 3 effusion of degassed viscous magma as lava flows these processes are similar to those observed for other small volume monogenetic eruptions e g of basaltic magma

nonstationary poisson model for earthquake occurrences abstract a nonstationary poisson model describing the occurrences of clustering earthquakes is developed this model characterized by a u shape mean occurrence rate function simulates the decreasing nearly constant and increasing variations of the mean occurrence rates at the instants soon after the last event in the current cluster in the waiting period between the current and the next clusters and just before the next cluster respectively the parameters of such a u shape function are determined empirically from the earthquake catalog a simple example is presented to show the difference in the estimated mean occurrence rate and in the induced seismic risk between different poisson occurrence models

structure and eruptive mechanisms at surtsey volcano iceland glassy basalt tuff was the primary material cored in 1979 from a 181 m deep drill hole on the east tuff ring of surtsey volcano despite the fact that the hole extends 122 m below sea level all the core is similar to the exposed tephra composing the two tuff rings of the island the tuff includes abundant accretionary lapilli and tuff vesicles indicating that it was all deposited subaerially during the growth of the tuff rings repeated hydromagmatic explosion cycles began with a series of intermittent tephra finger explosions leading up to continuous uprush explosions which lasted for several minutes to several hours this nozzle like continuous activity produced eruption columns 100 250 m in diameter and 500 2000 m in height which probably quarried several hundred metres below the ground surface the continuous uprush explosion type provides a reasonable mechanism to excavate a diatreme from the top down during construction of the tuff rings concentric faults repeatedly downdropped a funnel like structure 400 800 m in diameter several hundred metres thus accounting for the presence of subaerially deposited tephra in the drill core far beneath sea level ring dykes later intruded upward along these faults and fed small lava flows heat in the surface tephra probably originated primarily from these shallow intrusions