vegetation and environmental changes in northern anatolia between 134 and 119 ka recorded in black sea sediments this multiproxy study on se black sea sediments provides the first detailed reconstruction of vegetation and environmental history of northern anatolia between 134 and 119 ka here the glacial interglacial transition is characterized by several short lived alternating cold and warm events preceding a meltwater pulse 130 4 131 7 ka the latter is reconstructed as a cold arid period correlated to heinrich event 11 the initial warming is evidenced at 130 4 ka by increased primary productivity in the black sea disappearance of ice rafted detritus and spreading of oaks in anatolia a younger dryas type event is not identifiable the eemian vegetation succession corresponds to the main climatic phases in europe i the quercus juniperus phase 128 7 126 4 ka indicates a dry continental climate ii the ostrya corylus quercus carpinus phase 126 4 122 9 ka suggests warm summers mild winters and high year round precipitation iii the fagus carpinus phase 122 9 119 5 ka indicates cooling and high precipitation and iv increasing pinus at 121 ka marks the onset of cooler drier conditions generally pollen reconstructions suggest altitudinal latitudinal migrations of vegetation belts in northern anatolia during the eemian caused by increased transport of moisture the evidence for the wide distribution of fagus around the black sea contrasts with the european records and is likely related to climatic and genetic factors

abrupt changes of temperature and water chemistry in the late pleistocene and early holocene black sea new mg ca sr ca and published stable oxygen isotope and 87sr 86sr data obtained on ostracods from gravity cores located on the northwestern black sea slope were used to infer changes in the black sea hydrology and water chemistry for the period between 30 to 8 ka b p calibrated radiocarbon years the period prior to 16 5 ka b p was characterized by stable conditions in all records until a distinct drop in 18o values combined with a sharp increase in 87sr 86sr occurred between 16 5 and 14 8 ka b p this event is attributed to an increased runoff from the northern drainage area of the black sea between heinrich event 1 and the onset of the bolling warm period while the mg ca and sr ca records remained rather unaffected by this inflow they show an abrupt rise with the onset of the bolling allerod warm period this rise was caused by calcite precipitation in the surface water which led to a sudden increase of the sr ca and mg ca ratios of the black sea water the stable oxygen isotopes also start to increase around 15 ka b p although in a more gradual manner due to isotopically enriched meteoric precipitation while sr ca remains constant during the following interval of the younger dryas cold period a decrease in the mg ca ratio implies that the intermediate water masses of the black sea temporarily cooled by 1 2 c during the younger dryas the 87sr 86sr values drop after the cessation of the water inflow at 15 ka b p to a lower level until the younger dryas where they reach values similar to those observed during the last glacial maximum this might point to a potential outflow to the mediterranean sea via the sea of marmara during this period the inflow of mediterranean water started around 9 3 ka b p which is clearly detectable in the abruptly increasing mg ca sr ca and 87sr 86sr values the accompanying increase in the 18o record is less pronounced and would fit to an inflow lasting 100 a

consistency of teleseismic reporting since 1963 abstract changes in the rate of occurrence of smaller events have been recognized in the rupture zones of upcoming large earthquakes in several postearthquake and one preearthquake study a data set in which a constant portion of the events in any magnitude band are consistently reported through time is crucial for the recognition of seismicity rate changes which are real related to some process change in the earth such a data set is termed a homogeneous data set the consistency of reporting of earthquakes in the noaa hypocenter data file hdf since 1963 is evaluated by examining the cumulative number of events reported as a function of time for the entire world in eight magnitude bands it is assumed that the rate of occurrence of events in the entire world is roughly constant on the time scale examined here because of the great size of the worldwide earthquake production system the rate of reporting of events with magnitudes above m b 4 5 has been constant or increasing since 1963 significant decreases in the number of events reported per month in the magnitude bands below m b 4 4 occurred during 1968 and 1976 these decreases are interpreted as indications of decreases in detection of events for two reasons first they occur at times of constant rates of occurrence and reporting of larger events second the decrease during the late 19609s has also been recognized in the teleseismic data reported by the international seismological centre isc this suggests that the decrease in the number of small events reported was related to facets of the earthquake reporting system which the isc and noaa share the most obvious candidate is the detection system during 1968 detection decreased in the united states central and south america and portions of the south pacific this decrease is probably due to the closure of the vela arrays bmo tfo cpo ubo and wmo during 1976 detection decreased in most of the seismically active regions of the western hemisphere as well as in the region between kamchatka and guam the cause of this detection decrease is unclear these detection decreases seriously affect the amount of homogeneous background period available for the study of teleseismic seismicity rate changes if events below the minimum magnitude of homogeneity are eliminated from the teleseismic data sets the resulting small numbers of events render many regions unsuitable for study many authors have reported seismicity rate decreases as possible precursors to great earthquakes few of these authors have considered detection decreases as possible explanations for their results this analysis indicates that such considerations cannot be avoided in studies of teleseismic data

origin and consequences of cyclic ice rafting in the northeast atlantic ocean during the past 130 000 years deep sea sediment cores recovered from the northeast atlantic ocean were examined in order to elucidate the influence of the earth s orbital parameters on major ice rafting analyses of coarse grained ice rafted debris and planktonic foraminifers revealed a strong reaction to the precession signal since 130 000 yr b p dropstone layers have been deposited each half period of a precessional cycle 11 000 1000 yr ice rafting occurs during times of winter minimum summer maximum insolation and summer minimum winter maximum insolation in the first case high summer insolation forces meltwater discharge from the ice sheets into the polar seas which subsequently enhances formation of sea ice during the winter in the second case growth of continental ice enhances iceberg production which also leads to a salinity reduction of surface seawater both situations result in a southward penetration of polar water thus the marine record of dropstones documents ice rafting not only during weichselian stades but also during cold events within interstades the regularity of ice rafting yields a useful framework to calibrate and elucidate climatic changes not only in the region of the north atlantic ocean but also in remote areas such as the pacific ocean and the antarctic

rapid changes of glacial climate simulated in a coupled climate model abrupt changes in climate termed dansgaard oeschger and heinrich events have punctuated the last glacial period approximately 100 10 kyr ago but not the holocene the past 10 kyr here we use an intermediate complexity climate model to investigate the stability of glacial climate and we find that only one mode of atlantic ocean circulation is stable a cold mode with deep water formation in the atlantic ocean south of iceland however a warm circulation mode similar to the present day atlantic ocean is only marginally unstable and temporary transitions to this warm mode can easily be triggered this leads to abrupt warm events in the model which share many characteristics of the observed dansgaard oeschger events for a large freshwater input such as a large release of icebergs the model s deep water formation is temporarily switched off causing no strong cooling in greenland but warming in antarctica as is observed for heinrich events our stability analysis provides an explanation why glacial climate is much more variable than holocene climate

a method of studying variations in the clustering property of earthquakes application to the analysis of global seismicity we propose a formal algorithm for identification of aftershocks following a main event our approach is based on the analysis of the local statistics the number of events following the initial earthquake displayed as a function of distance and time by comparing this distribution with the random catalog we establish for several magnitude ranges spatiotemporal thresholds for detection of aftershocks high confidence thresholds correspond to the limit at which the number of events derived from the actual catalog corrected for the background seismicity exceeds by a factor of 10 the expected level of background seismicity marginal confidence thresholds correspond to the spatiotemporal boundary along which these two values are approximately equal after several iterations the final thresholds are derived the swarming parameter is defined as the number of aftershocks with a cut off lower magnitude range following an initial earthquake of certain magnitude if a correction for the recurrence law is applied we find that the swarming parameter is magnitude independent this allows us to apply this technique to the analysis of global seismicity using a catalog derived from the isc bulletin for the years from 1964 to 1975 we determine for shallow earthquakes the average values of the swarming parameter in 9 9 cells a global map produced in this manner shows a very wide range of variations in the swarming property undoubtedly reflecting variations in the local geological conditions triple junctions are among the areas with the highest swarming values at the present time there is an insufficient amount of data to study regional variations in the swarming property of deep earthquakes considering the clustering as a function of depth alone we find detectable swarming for two depth ranges from 100 to 250 km and from 450 to 650 km not a single aftershock has been detected among nearly 200 earthquakes withmb 5 in a depth range from 250 to 450 km the average swarming parameter for earthquakes deeper than 100 km is 10 times smaller than that for the shallow earthquakes

a reexamination of the bucaramanga colombia earthquake nest the bucaramanga earthquake nest is situated at a depth of about 160 km beneath colombia at 6 8 n 73 w and it produces about eight earthquakes of mb 4 7 or more each year from a source region having dimensions of about 10 km or less in this study we evaluate nest properties using reported locations focal mechanisms and moment tensors as well as relocations determined from teleseismic p pp and pkp arrivals we also introduce a novel method for determining the volume of a group of hypocenters and use this volume as a statistic for evaluating the accuracy of nest hypocenters we have relocated 26 nest earthquakes occurring between 1964 and 1986 using the jhd method and carefully reread teleseismic p pp and pkpdf arrivals the relocated earthquakes cluster within a region having a volume of 776 km3 and east west north south and vertical dimensions of 13 18 12 km a smaller region than any found previously from analysis of teleseismic data in practical terms this represents an approximate upper bound on the accuracy of relative earthquake locations possible using teleseismic data and standard relocation methods this compares with a volume of 11 km3 and dimensions of 5 1 3 4 3 8 km as determined by schneider et al 1987 from observations of microearthquakes collected over 16 days with a temporary local network these dimensions are comparable to those of the rupture dimensions of the largest observed nest earthquakes as determined from an analysis of their seismic moments 5 1024 dyne cm furthermore an evaluation of cumulative moment rate since 1964 indicates that strain rates within the nest volume must be between 10 13 sec and 10 11 sec the b values 2 0 and values 0 9 determined from available magnitudes and moments are remarkably high suggesting that earthquakes of all observed sizes 3 1020 to 5 1024 dyne cm contribute significantly to the moment release focal mechanisms determined from teleseismic observations exhibit a consistent pattern most having westward dipping p axes and eastward dipping t axes this differs from the more varied pattern reported by schneider et al 1987 for microseismic earthquakes

four climate cycles of recurring deep and surface water destabilizations on the iberian margin centennial climate variability over the last ice age exhibits clear bipolar behavior high resolution analyses of marine sediment cores from the iberian margin trace a number of associated changes simultaneously proxies of sea surface temperature and water mass distribution as well as relative biomarker content demonstrate that this typical north south coupling was pervasive for the cold phases of climate during the past 420 000 years cold episodes after relatively warm and largely ice free periods occurred when the predominance of deep water formation changed from northern to southern sources these results reinforce the connection between rapid climate changes at mediterranean latitudes and century to millennial variability in northern and southern polar regions

aftershock sequences of intermediate depth earthquakes in the pamir hindu kush seismic zone we examine the space time seismicity patterns associated with the 40 largest m 5 6 intermediate depth earthquakes that occurred in the pamir hindu kush zone between 1962 and 1984 to determine if any of these events were followed by aftershock sequences to address this issue we examined data from the soviet central asia regional earthquake catalog with two complementary techniques 1 a subjective technique based on inspection of epicentral maps and 2 a quantitative method which assumed that the background seismicity was a poisson process and which detected aftershocks as significant departures as quantified by the poisson model from background rates of the 40 events we examined only three were identified by both methods as having clearly defined aftershock sequences these three events are also remarkably similar in several other ways 1 they occurred at almost the same point in space 2 they have indistinguishable focal mechanisms 3 they have similar magnitudes and 4 they define two nearly equal time intervals 9 37 and 9 41 years no other events in the pamir hindu kush zone exhibit comparable aftershock behavior six other events show rate anomalies but the subjective method rated them negative or at least ambiguous four of these six we argue are caused by coincidental or man made rate increases at the time of the mainshock the remaining two are noteworthy because they are the two largest events to have occurred beneath the central pamir each of these events shows a small short burst of seismicity around the time period of the largest event in the sequence we suggest two alternative hypotheses to explain our observations 1 more events may have aftershock sequences but the aftershocks are too small to be detected or 2 the three events that had clear aftershocks are unique and trigger a burst of aftershocks only because they have a special relationship to the the most active nest of activity in the hindu kush zone

aftershocks and temporal clustering of deep earthquakes this paper evaluates how the focal depth the geographic location and magnitude affect the incidence of aftershocks and the occurrence of temporal clustering of nearby events for selected deep earthquakes h 70 km in the catalog of the international seismological centre for comparison we also evaluate shallow h 70 km and deep earthquakes for which locations and moment tensors are reported by the harvard group the primary conclusions are as follows 1 the incidence of aftershocks depends strongly on focal depth with aftershocks being less common for events between 100 and 450 km depth than for shallower or deeper events events with focal depth shallower than 40 km have a higher incidence of aftershocks and more pronounced temporal clustering than do deeper events 2 for the data available at present the incidence of aftershocks and amount of temporal clustering for deep events are independent of geographic region except for dependence caused by regional differences in the focal depths of events 3 deep earthquakes with large magnitudes are more likely to have aftershocks than are smaller magnitude events in accordance with models where the number of aftershocks is a poisson random variable that is a function of magnitude however several large events are anomalous in that they have many more aftershocks or many fewer aftershocks in the catalog than predicted by the model

multicentennial scale hydrological changes in the black sea and northern red sea during the holocene and the arctic north atlantic oscillation 1 paleoenvironmental proxy data for ocean properties eolian sediment input and continental rainfall based on high resolution analyses of sediment cores from the southwestern black sea and the northernmost gulf of aqaba were used to infer hydroclimatic changes in northern anatolia and the northern red sea region during the last 7500 years pronounced and coherent multicentennial variations in these records reveal patterns that strongly resemble modern temperature and rainfall anomalies related to the arctic oscillation north atlantic oscillation ao nao these patterns suggest a prominent role of ao nao like atmospheric variability during the holocene beyond interannual to interdecadal timescales most likely originating from solar output changes

correlations between mining and seismicity for re entry protocol development abstract re entry protocols are a strategic approach for controlling risk after large magnitude events or blasts in seismically active mines by monitoring the return of seismicity to background levels restricting access to areas of a mine affected by seismicity for sufficient time to allow this decay to occur is the main approach in most re entry protocols in the present study mining and seismicity are correlated for re entry protocol development by using a uniform statistical technique for the identification of background levels the relations are established relying on a theoretical framework that links the productivity of seismicity with the decay time of seismic sequences three case histories are presented and analyzed selected to illustrate the possible effects of factors such as volume of mined rock depth and magnitude of large events on the decay time of mining induced seismic sequences positive significant correlations between the decay time and the mining factors studied here are found

seismic parameters of mining induced aftershock sequences for re entry protocol development a common characteristic of deep mines in hard rock is induced seismicity this results from stress changes and rock failure around mining excavations following large seismic events there is an increase in the levels of seismicity which gradually decay with time restricting access to areas of a mine for enough time to allow this decay of seismic events is the main approach in re entry strategies the statistical properties of aftershock sequences can be studied with three scaling relations 1 gutenberg richter frequency magnitude 2 the modified omori s law mol for the temporal decay and 3 bath s law for the magnitude of the largest aftershock in this paper these three scaling relations in addition to the stochastic reasenberg jones model are applied to study the characteristic parameters of 11 large magnitude mining induced aftershock sequences in four mines in ontario canada to provide guidelines for re entry protocol development the dependence of the scaling relation parameters on the magnitude of the main event are studied some relations between the parameters and the magnitude of the main event are found using these relationships and the scaling relations a space time magnitude re entry protocol is developed these findings provide a first approximation to concise and well justified guidelines for re entry protocol development applicable to the range of mining conditions found in ontario canada

the state of stress in subducting slabs as revealed by earthquakes analysed by moment tensor inversion abstract we have used a data set of earthquakes whose mechanisms have been studied here or elsewhere by moment tensor inversion to confirm some earlier ideas concerning the state of stress in subducting slabs the moment tensor method offers the advantages of speed and objectivity over earlier methods usually based exclusively on first motion data deep earthquakes below 300 400 km tend to have compression axes aligned with the dip of the subducting slab the behavior of intermediate earthquakes from 70 to 300 km is less clear there is some evidence for down dip tension but the alignment is not as obvious as it is in the case of the compression axes of deep events tonga shows a tendency toward down dip compression at intermediate depths but other deep extending slabs as well as shallow extending slabs slabs with maximum depths shallower than 300 km seem to be closer to down dip tension

identification of aftershocks of deep earthquakes by a new ratios method we describe a new statistical method for identifying pairs or groups of related events in sequences which resemble but are not identical to a poisson process for a particular earthquake we form the ratio r nb na of the relative origin times of the na th subsequent event and the nb th previous event we then find the probability that such a ratio could occur if the sequence were a poisson process presumably sequences where the ratio is too small to be probable contain related events and the subsequent events are aftershocks since the method requires knowledge of the origin times of only a few preceding and subsequent events it is more powerful than methods which require knowledge of the mean activity rate of the poisson process using this ratios method we searched the isc catalog for aftershocks of earthquakes with focal depths exceeding 70 km from the world as a whole events with at least one aftershock can be found in all depth ranges including 250 km to 450 km however the incidence of aftershocks is significantly lower for events between 100 and 450 km than for shallower or deeper events

northern hemisphere climate control on the environmental dynamics in the glacial black sea lake abstract the marine isotope stage mis 3 stands out due to its abrupt changes from cold and dry stadials to warm and humid interstadials the so called dansgaard oeschger cycles that also affected temperature and rainfall in the black sea region this study is based on a gravity core from the southeastern se black sea that covers the last glacial lake stage from 64 to 20 ka bp by using the composition of major and trace elements in the sediments terrestrial plant derived n alkane flux and sr ca from benthic ostracods we reconstruct the variability of riverine and aeolian input salinity and productivity in the se black sea region in response to the northern hemisphere climate oscillations during colder and drier stadials the aeolian input increased relative to the riverine discharge potentially due to southward shifted and or stronger westerly winds and due to changes in the vegetation cover an evaporation exceeding freshwater supply by rainfall and rivers possibly caused higher salinity and a lower lake level the environmental status during mis 4 and 2 is very much comparable with the stadial conditions during mis 3 during warmer and more humid interstadials lower salinity and presumably positive lake level changes most likely resulted from increased precipitation and river discharge this likely increased primary productivity through an augmented nutrient supply lowest average salinities are suggested for the middle part of mis 3 in response to enhanced meltwater from the disintegrating fennoscandian ice sheet and or by generally more humid conditions

ecological thresholds and patterns of millennial scale climate variability the response of vegetation in greece during the last glacial period the regional expression of millennial scale climate variability during the last glacial is examined with particular reference to the vegetation response in greece inspection of three pollen records from contrasting bioclimatic areas suggests that differences in the magnitude of cold events as recognized in the north atlantic and western mediterranean are expressed in terms of tree population changes only in areas with a range of favorable habitats by contrast records from sites where populations approach their tolerance threshold do not appear to resolve differences in the amplitude of the climate oscillations understanding the importance of local factors in modulating the biological response to climate change is critical when attempting to establish the spatial pattern of millennial variability

variability in ostracod partition coefficients d sr and d mg implications for lacustrine palaeoenvironmental reconstructions living and sub recent ostracods were collected from four lakes and foul springs located in belgium france and spain characterized by low water mg ca ratios from 0 08 to 0 65 valves of ostracods belonging to cyprideis torosa candona neglecta c marchica and c candida have been extensively analysed for their magnesium and strontium contents with respect to calcium comparisons of these results are made using the same elements from the waters in which the ostracod valves calcified our results offer new and somewhat different interpretations with respect to the uptake of mg and sr in the calcitic ostracod valves these findings include the following 1 the partition coefficient l sr for ostracods belonging to the same genus candona is not a constant the observed variability in d sr values could be due to the rare of biological calcification although more investigations are necessary to assess the influence of this factor it is possible that some taxa grouped under the genus candona belong to a different genus 2 even at the species level cyprideis torosa the ostracod d sr cannot be considered to be constant at low water mg ca ratio 0 65 our d sr value for c torosa is higher than those determined by others for c torosa calcified in evolved marine water 3 the mg ca ratio of the water appears as a major factor influencing d mg for ostracods for low water mg ca values similar to 2 d mg drastically increases this phenomenon is also effective for inorganic calcite implying a non biologic effect that could be linked to mg2 adsorption consequently large variations in me content of fossil ostracod valves from selected lacustrine sequences with expected low water mg ca similar to 2 can be due to small variations in water mg ca c 1998 elsevier science b v all rights reserved

spatial patterns of aftershocks of deep focus earthquakes this paper presents precise relative relocations for aftershocks of 59 intermediate and deep earthquakes using p pp and pkp arrival times read by us or reported in the literature these aftershocks included 36 rupture subevents occurring within 1 min of the initial event and 71 true aftershocks occurring later and identified statistically as being related to the initial event we compare the relative locations with the orientations of the wadati benioff zones and with the available focal mechanisms using statistical methods not previously applied to earthquake data surprisingly neither true aftershocks nor rupture subevents cluster along the nodal planes of intermediate or deep earthquake focal mechanisms aftershocks more than 20 km from the initial events occur preferentially in the plane of the wadati benioff zone while those lying closer have isotropically distributed directions rupture subevents occur after the travel time of the s wave from the initial event larger magnitude earthquakes generally possess rupture subevents lying farther from the initial event whereas true aftershocks can occur 50 km or more from initial events having magnitudes as small as 5 3 except following a few unusually large earthquakes with focal depths of about 100 km we find no rupture subevents or true aftershocks more than about 80 km from the initial hypocenter the existence of many aftershocks far from nodal planes does not favor models in which deep earthquake failure is simply slip along a planar fault rather the aftershocks may occur in response to a general redistribution of stress caused either by the occurrence of the initial event or possibly by nearby continuing phase transitions alternatively the failure zones of deep earthquakes may be surfaces which are frequently curved by 40 or more from the orientation of the initial nodal plane perhaps due to inhomogeneous stress distributions

pleistocene environmental dynamics recorded in the loess of the middle and lower danube basin abstract the substantial loess deposits of the middle and lower danube basin in southeastern europe represent one of the thickest and most comprehensive terrestrial palaeoenvironmental records on the continent yet are also the least well understood environmental conditions over the last million years have resulted in relatively continuous deposits uninterrupted by glaciation and tundra conditions which nevertheless reflect oscillations between relatively warm humid interglacial and cold dry glacial intervals this relative environmental stability may have proven important for hominins migrating into and through the region the loess stratigraphy comprises distinct loess paleosol sequences reflecting glacial interglacial phases which can be quantified for intensity using environmental magnetism and geochemistry these phases are emphasised by variations in vegetation and malacofauna which respond to climatic change the loess deposits demonstrate broadly similar sedimentological characteristics across the basin danubian loess deposits initiated in response to the tectonic formation of the pannonian basin retreat of the large palaeolakes and increased sediment supply from the danube the period from 1 ma 500 ka mis 27 13 was characterised by alternating loess deposition and pedogenesis during glacial and interglacial periods respectively in response to relatively humid forested conditions this period represents the opening of the danube corridor and provides the backdrop for initial hominin arrival into europe after 500 ka and particularly after mis 9 loess accumulation rates increased in response to relatively more steppic arid environments mis 9 and 13 15 were the most humid phases of the last 600 ky the mis 5 interglacial period was the warmest and relatively most humid period preceding the holocene and was followed by substantially increased loess accumulation during mis 4 which may be linked to north atlantic circulation the complexity of the mis 3 interstadial paleosol suggests that conditions were not uniformly warm and wet during this time mis 3 corresponds with the first arrival of anatomically modern humans to europe the last glacial maximum and younger dryas of mis 2 were characterised by substantially increased loess accumulation indicating cold steppe environments most likely influenced by the north atlantic although conditions were sufficiently mild that the region acted as a refugium for thermophilic biota as may also have been the case for most of the pleistocene glacial cycles the holocene soil represents relatively wamer and more humid conditions corresponding to the current interglacial

space clustering properties of the betic alboran earthquakes in the period 1962 1989 abstract in order to obtain a way to quantify the spatial dependence between earthquakes in the betic alboran south spain region the single link clustering slc method has been applied to a catalogue of earthquakes with magnitude greater or equal to 4 0 that occurred in this region from 1962 to 1989 the significant distances of links obtained which show alignments whose direction is similar to the direction of some surface faults are 15 30 and 40 km and the limit of inconsistency appears at distances greater than or equal to 70 km most of the historical destructive earthquakes have taken place within the clusters obtained and the majority within the dc 30 km cluster this implies that the most relevant seismic activity occurs in some source areas where there is a strong nesting of activity

geochemical characterization and origin of southeastern and eastern european loesses serbia romania ukraine abstract the loess paleosol sections of batajnica stari slankamen serbia mircea voda romania and stary kaydaky ukraine were geochemically characterized based on discriminant analysis of major and trace elements the ratios of al ti fe ti and al fe the a cn k ternary plot and element enrichment depletion relative to the average composition of the upper continental crust the origin of the loess material in the southern pannonian basin vojvodina the lower danube basin dobrudja and the dnieper area was evaluated by comparison with the representative element composition of possible source areas and by considering the geomorphodynamic setting also the background values of the initial magnetic susceptibility of the loesses were taken into account for the lower danube basin dobrudja and the ukraine paleowind direction was reconstructed based on the geographic distribution of sandy soil texture and dunes related to river systems finally loesses were evaluated as possible samples of the average upper continental crust our results show that danube and dnieper loess areas can be clearly distinguished the former reveal higher al and fe contents the latter higher si zr hf content and indications of effective mineral and grain size sorting we can confirm that vojvodina loess originated from danube alluvial material and loess of the dnieper area from glaciofluvial sediments of the fennoscandinavian ice sheet the dobrudja loess derived also predominantly from danube alluvium but shows significant contribution of a second loess source probably the glaciofluvial sediments of the ukraine this was forced by northerly katabatic winds from the fennoscandinavian ice sheet whereas wnw winds prevailed in the western walachian plain the studied loesses reflect the average composition of the upper continental crust yet biases exist due to selective mineral element enrichment and depletion in the course of previous sedimentary recycling phases respectively material of all studied loess deposits seems to derive originally from sedimentary rocks

abrupt temperature changes in the western mediterranean over the past 250 000 years a continuous high resolution western mediterranean sea surface temperature sst alkenone record spanning the past 250 000 years shows that abrupt changes were more common at warming than at cooling during marine isotope stage mis 6 sst oscillated following a stadial interstadial pattern but at lower intensities and rates of change than in the dansgaard oeschger events of mis 3 some of the most prominent events occurred over miss 5 and 7 after prolonged warm periods of high stability climate during the whole period was predominantly maintained in interglacial interstadial conditions whereas the duration of stadials was much shorter

omori s law applied to mining induced seismicity and re entry protocol development this paper describes a detailed study of the modified omori s law n t k c t p applied to 163 mining induced aftershock sequences from four different mine environments in ontario canada we demonstrate using a rigorous statistical analysis that this equation can be adequately used to describe the decay rate of mining induced aftershock sequences the parameters k p and c are estimated using a uniform method that employs the maximum likelihood procedure and the anderson darling statistic to estimate consistent decay parameters the method considers only the time interval that satisfies power law behavior the p value differs from sequence to sequence with most 98 ranging from 0 4 to 1 6 the parameter k can be satisfactorily expressed by k n1 where is an activity ratio and n1 is the measured number of events occurring during the first hour after the principal event the average values are in a well defined range theoretically 0 8 and empirically 0 3 0 5 these two findings enable us to develop a real time event rate re entry protocol 1 h after the principal event despite the fact that the omori formula is temporally self similar we found a characteristic time tmc at the maximum curvature point which is a function of omori s law parameters for a time sequence obeying an omori process tmc marks the transition from highest to lowest event rate change using solely the aftershock decay rate therefore we recommend tmc as a preliminary estimate of the time at which it may be considered appropriate to re enter an area affected by a blast or large event we found that tmc can be estimated without specifying a p value by the expression tmc an1b where a and b are two parameters dependent on local conditions both parameters presented well constrained empirical ranges for the sites analyzed a 0 3 0 5 and b 0 5 0 7 these findings provide concise and well justified guidelines for event rate re entry protocol development

evolution of the danube deep sea fan since the last glacial maximum new insights into black sea water level fluctuations abstract the danube deep sea fan nw black sea is one of the most developed deep sea sediment depositional systems in europe although the morphology and the architecture have been widely described in the past years little is known about the stratigraphy of this depositional system for the late quaternary this results from the lack of significant stratigraphic markers the scarcity of radiocarbon ages and the difficulty in constraining reservoir ages recent robust quantification of reservoir ages has allowed the construction of a new stratigraphic framework for the black sea from the end of the last glacial period to the holocene thus giving the opportunity to correlate sedimentological and geochemical features previously described on the nw black sea margin with climatic events identified in the northern hemisphere based on this approach we propose an improved chrono lithostratigraphic framework for the danube deep sea fan channel levees since the last glacial maximum we show that the danube deep sea fan was active during the last glacial maximum until the younger dryas early holocene transition ca 11 700 cal a bp when the turbidite activity abruptly terminated in the whole system throughout this period the danube river was the main source of the deep depositional system except between ca 17 200 cal a bp and 15 700 300 cal a bp at that time the deposition of red turbidites in the deep basin concomitant with the deposition of the so called red layers onto the continental shelf and the upper slope emphasises the direct impact of the increased meltwater runoff of the dnieper river as far as the danube deep sea fan some significant changes in the location of the depocentre of the danube deep sea fan occurred through time the main change in depocentre location occurred at ca 28 000 cal a bp with the northward avulsion leading to the formation of the middle channel although the middle and northern channel became the preferential turbidite depocentres after this event the deposition of turbidites has persisted in the southern channel levee until 14 700 cal a bp indicating that the southern channel was definitely not abandoned after the upstream northward avulsion unsurprisingly water level fluctuations and river sediment flux acted as the main forcings on the evolution of the danube deep sea fan based on these results and on the morphology of the danube canyon we propose that i lowstand conditions 110 m prevailed during the last glacial maximum and possibly between 15 700 300 cal a bp and 14 700 cal a bp ii water level ranged from 110 and 70 m between 14 700 and 11 700 cal a bp and iii water level ranged from 70 and 30 m from 11 700 cal a bp and until the reconnection of the black sea lake with the global ocean at ca 9000 cal a bp

distribution of glacial geomorphic features on the antarctic continental shelf and correlation with substrate implications for ice behavior surveys were conducted seaward of all the major drainage outlets of the antarctic ice sheet from the pennell coast north victoria land to marguerite bay antarctic peninsula the results show that the ice sheet extended onto the outer shelf glacial troughs occur offshore of all major glacial outlets where the substrate is crystalline bedrock ice flow tended to follow the structural grain of the bedrock deposited little sediment and eroded the underlying bedrock where ice flowed over relatively soft more easily eroded sedimentary strata the direction of ice flow was more directly offshore and depositional features characterize the sea floor in these areas the signature of the grounded ice consists of till deposits and large scale geomorphic features drumlins occur within the region of contact between crystalline and sedimentary substrates the different geological substrates are interpreted to have exerted a fundamental control on the behavior of past ice sheets the troughs in the areas of bedrock composed of sedimentary substrate are interpreted to have been occupied by relatively fast flowing ice ice streams and the troughs in the areas of crystalline substrate are interpreted to have been occupied by slower moving ice the area between these two zones was characterized by ice acceleration and is marked by drumlins

single link cluster analysis of earthquake aftershocks decay laws and regional variations using single link cluster analysis the authors investigate how various properties of aftershock sequences depend on their tectonic regime and focal depth for international seismological centre earthquakes of m sub b ge 4 8 they find that earthquakes deeper than 70 km have the fewest and smallest aftershock sequences even after accounting for differences in detectability and maximum magnitude they find that ridge transform earthquakes have smaller aftershock sequences that shallow subduction zone earthquakes among different subduction zones they find that zones with high moment release rates possess larger aftershock sequences comparing ridge transform zones they find those with slower spreading rates possess larger aftershock sequences by transposing origin times of several different aftershock sequences as if all had main shocks occurring at time zero they are able to study the properties of aftershock sequences which individually have too few aftershocks to study by other means secondary events determined by single link cluster analysis follow a modified omori s power law decay for time separations of 0 1 day to 20 days from the parent event with p values ranging from 0 539 plus minus 0 022 intermediate and deep focus earthquakes to 0 928 plus minus 0 024 ridge transform earthquakes they find that earthquake foreshocks and multiplets also follow a modified omori s law atmore greater times from the main shock the decay is steeper than a power law decay more like an exponential decay aftershocks in the adak catalog m sub b ge 2 0 show a marked decrease in activity between 40 and 50 km depth they speculate that the observed differences in number of aftershocks and p values may be caused by variations in fault heterogeneity or in fluid pressures less

a comparison of characteristic parameters of mining related and tectonic seismic aftershock sequences abstract the temporal decay pattern of seismicity following rock bursts and large magnitude events is studied for aftershock sequences in several mines in ontario canada the decay phenomenon is described by the so called modified omori s law the dependency of the parameters k c and p with the magnitude of large mine seismic events is analyzed a total of eleven mining related seismic sequences with mainshock magnitudes ranging from 0 5 to 4 0 mn nuttli magnitude scale and from four different mine environments are examined results including the calculation of the gutenberg richter s and reasenberg jones parameters b and a are compared with previous research in tectonic seismicity using available data from new zealand italy and u s a further parameters were derived and applied in a correlation study of mining related and tectonic events the study revealed a good correlation between the productivity parameter a and b values particularly the b values show significant different number ranges for mining related and tectonic data which was applied to derive a direct numerical relationship between mining related and tectonic parameters and the aftershock number estimation finally numerical values for the b values in mining related seismic activity were obtained

second order moment of central california seismicity 1969 1982 the second order moment cross correlation function of earthquakes in the u s geological survey central california catalog between 1969 and 1982 was calculated with respect to a magnitude threshold m 4 0 over interevent distances up to 80 km and interevent times up to 320 days the statistical procedure results in a representation of the spatial temporal structure of the catalog associated with m 4 0 earthquakes and is capable of revealing patterns too weak to be detected in the space time distribution of seismicity for individual earthquake sequences a method is introduced for identifying aftershocks based on a physical two parameter model of the earthquake interaction process the results show that the aftershock process dominates the second order moment and may even obscure the statistical expression of a precursory process a concentration of foreshocks within 15 km and 3 days of m 4 0 main shocks exhibits an apparent migration toward the main shock loci with velocity 2 6 5 3 km d this concentration may be related to an observed tendency for m 4 0 events to cluster auto correlate over this interevent range with the identified aftershocks removed the residual catalog is poissonion in space and time when two m 4 0 earthquakes occur within 80 km and 40 days of each other aftershock productivity appears to be relatively enhanced in the earlier sequence this suggests that aftershock populations are not solely dependent on their main shocks and that unusually productive aftershock sequences may be predictors of future moderate earthquakes

holocene and late glacial palaeoceanography and palaeolimnology of the black sea changing sediment provenance and basin hydrography over the past 20 000 years abstract the elemental geochemistry of late pleistocene and holocene sediments of the black sea recovered in box cores from the basin margins and a 5 m gravity core from the central abyssal region of the basin identifies two terrigenous sediment sources over the last 20 kyrs one source region includes anatolia and the southern caucasus the second region is the area drained by rivers entering the black sea from eastern europe alkali metal al and heavy light rare earth element ratios reveal that the relative contribution of the two sources shifted abruptly every few thousand years during the late glacial and early holocene lacustrine phase of the basin the shifts in source were coeval with changes in the lake level as determined from the distribution of quartz and the heavy mineral hosted trace elements ti and zr the geochemistry of the abyssal sediments further recorded a sequence of changes to the geochemistry of the water column following the lacustrine phase when high salinity mediterranean water entered the basin beginning 9 3 kyrs bp bottom water that had been oxic throughout the lake phase became anoxic at approximately 8 4 kyrs bp as recorded by the accumulation from the water column of several redox sensitive trace metals mo re u the accumulation of organic carbon and several trace nutrients cd cu ni zn increased sharply ca 0 4 kyrs later at 8 0 kyrs bp reflecting an increase of primary productivity its increase was coeval with a shift in the dinoflagellate ecology from stenohaline to euryhaline assemblages during this profound environmental change from the lacustrine to the marine phase the accumulation rate of the lithogenous sediment fraction decreased as much as 10 fold in response to the rise of the water level in the basin from a low stand ca 9 3 ka to its current level

character of vegetational and environmental changes in southern europe during the last glacial period evidence from lesvos island greece this paper presents high resolution results of palynological and sedimentological analyses undertaken on two sediment cores from the megali limni ml basin an area characterised by serpentine soils in the southeastern part of lesvos island greece six tephra horizons and multiple radiocarbon dates provide independent controls towards the development of a chronological framework the composite pollen record spans the period from 22 to 62 thousand years ago ka bp and shows a number of oscillations between steppe forest steppe and forest in concert with north atlantic millennial scale variability vegetation during the late marine isotope stage mis 4 was grassland steppe indicating cold and arid conditions while sediment composition suggests increased erosion rates arboreal populations dominated by pinus and to a lesser extent deciduous quercus expanded during mis 3 interstadials suggesting increases in precipitation and temperature within the course of the longer interstadials changes in vegetation composition point to a trend towards increased aridity and sometimes decreasing winter temperatures during intervening stadials vegetation was composed mainly of artemisia chenopodiaceae and gramineae indicating reversals to arid and cold conditions with most extreme conditions recorded during stadials corresponding to heinrich events during the course of mis 3 the basin was progressively infilled with sediments only a small portion of mis 2 is represented in the sequence showing a short lived expansion of arboreal populations comparisons with other pollen sequences from southern europe underscore the important role of pinus throughout the last glacial period a reflection of the serpentine soils of the megali limni area where pinus brutia dominates today

single link cluster analysis as a method to evaluate spatial and temporal properties of earthquake catalogues summary single link cluster analysis is a straightforward method to quantitatively measure the degree of clustering or isolation of groups of elements in a set such as a catalogue of earthquakes to apply single link cluster analysis to a set of n earthquakes individual earthquakes are first linked to their nearest neighbours to form event sub groups the process is then repeated and each sub group linked to its nearest neighbour recursively until n 1 links are found to join all the earthquakes this paper shows how knowledge of these links can be used to divide a group of earthquakes into any number of spatial clusters with various modifications this analysis can identify earthquake nests isolated events aftershock sequences and zones of seismic quiescence to illustrate this method we apply it to i a global data set of 2178 earthquakes having mb of 5 8 or greater reported by the international seismological centre isc between 1964 and february 1986 and ii sets of earthquakes having mb of 4 9 and greater as reported by the isc occurring in central america and in the aleutians to facilitate comparison with real data this study also investigates the distribution of link lengths for synthetic events placed randomly on 1 d circular line 2 d circular area and 3 d spherical volume geometries if we remove links between nuclear explosions from the isc data the resulting link distribution is quite similar to that for synthetic events placed along a 1 d fault for the shortest links the similarity improves markedly if the synthetic fault has a finite width or if relative location errors cause events to be located away from the fault trace with a standard deviation of about 15 km

hydrological impact of heinrich events in the subtropical northeast atlantic reconstructing the impact of heinrich events outside the main belt of ice rafting is crucial to understanding the underlying causes of these abrupt climatic events a high resolution study of a marine sediment core from the iberian margin demonstrates that this midlatitude area was strongly affected both by cooling and advection of low salinity arctic water masses during the last three heinrich events these paleoclimatic time series reveal the internal complexity of each of the last three heinrich events and illustrate the value of parallel studies of the organic and inorganic fractions of the sediments

north atlantic control on precipitation pattern in the eastern mediterranean black sea region during the last glacial based on proxy records from western black sea cores we provide a comprehensive study of climate change during the last glacial maximum and late glacial period in the black sea region for the first time we present a record of relative changes in precipitation for nw anatolia based on variations in the terrigenous supply expressed as detrital carbonate concentration the good correspondence between reconstructed rainfall intensity in nw anatolia and past western mediterranean sea surface temperatures ssts implies that during the glacial period the precipitation variability was controlled like today by mediterranean cyclonic disturbances periods of reduced precipitation correlate well with low ssts in the mediterranean related to heinrich events h1 and h2 stable oxygen isotopes and lithological and mineralogical data point to a significant modification in the dominant freshwater sediment source concomitant to the meltwater inflow after 16 4 cal ka bp this change implies intensification of the northern sediment source and with other records from the mediterranean region consistently suggests a reorganization of the atmospheric circulation pattern affecting the hydrology of the european continent the early deglacial northward retreat of both atmospheric and oceanic polar fronts was responsible for the warming in the mediterranean region leading simultaneously to more humid conditions in central and northern europe

the detailed tephrostratigraphy of a core from the south east black sea spanning the last 60 ka one visible volcanic ash layer and 21 non visible cryptotephra horizons have been identified in the m72 5 25 gc1 core from the south east black sea that spans the last 60 ka glass chemistry suggests that the tephras derive from italian hellenic and turkish sources the visible tephra layer is trachytic in composition and has been correlated to the 39 ka campanian ignimbrite super eruption from campi flegrei caldera italy two cryptotephra layers are associated with eruptions from acigol volcano turkey around the last glacial maximum another is linked to activity at erciyes dagi in the early holocene perikartini or karagullu and a cryptotephra layer near the top of the core correlates to the 3 6k cal a bp minoan marine z2 tephra from santorini thera greece this extends the known dispersal area for all these volcanic ash units many other calc alkaline rhyolite layers preserved in the core are likely to be from central anatolian sources but the lack of detailed proximal data for many of the volcanoes in the region prohibits further correlations the tephrostratigraphy and glass compositional data presented here allow the tephra layers to be used to correlate sedimentary archives across the region and help to extend the mediterranean tephrochronology framework towards the east