estimating earthquake rupture rates on a fault or fault system previous approaches used to determine the rates of different earthquakes on a fault have made assumptions regarding segmentation have been difficult to document and reproduce and have lacked the ability to satisfy all available data constraints we present a relatively objective and reproducible inverse methodology for determining the rate of different ruptures on a fault or fault system the data used in the inversion include slip rate event rate and other constraints such as an optional a priori magnitude frequency distribution we demonstrate our methodology by solving for the long term rate of ruptures on the southern san andreas fault our results imply that a gutenberg richter distribution is consistent with the data available for this fault however more work is needed to test the robustness of this assertion more importantly the methodology is extensible to an entire fault system thereby including multifault ruptures and can be used to quantify the relative benefits of collecting additional paleoseismic data at different sites

palaeohydrology fires and vegetation succession in the southern baltic during the last 7500 years reconstructed from a raised bog based on multi proxy data we present the first 7500 yr long multi proxy record from a raised bog located at the southern baltic coast poland testate amoebae plant macrofossils pollen and microscopic charcoal were used to reconstruct environmental changes in pomerania northern poland kaszuby lakeland from a 7 m thick peat archive of st zki bog dated 5500 bc ad 1250 we obtained a record of proxies representing different spatial scales regional vegetation changed simultaneously with local vegetation and testate amoebae showed a pattern of change similar to that of pollen and plant macrofossils on the basis of the combined proxies we distinguished three hydroclimatic stages moist conditions 5500 3450 bc drier conditions with regionally increased fires up to 600 bc and again moist conditions from 600 bc onward during the drier interval a first climatic shift to wetter conditions at 1700 bc is indicated by regional pollen as the replacement of corylus by carpinus and locally by e g the increase of hyalosphenia elegans and mire plants such as sphagnum sec cuspidata furthermore we observed a correlation since 600 bc among the re expansion of carpinus after a sudden decline ca 950 bc increased peat accumulation increase of hyalosphenia species and fewer fires suggesting lower evapotranspiration and a stable high water table in the bog fagus started to expand after ad 810 gradually replacing carpinus which was possibly due to a gradually more oceanic climate though we cannot exclude human impact on the forests peat accumulation determined by radiocarbon dating varied with bog surface wetness the hydroclimatic phases found in st zki peatland are similar to moisture changes recorded in other sites from poland and europe this is the first detailed record of hydroclimatic change during the holocene in the southern baltic region so it forms a reference site for further studies on other southern baltic bogs that are in progress

probabilistic forecasting of earthquakes we present long term and short term forecasts for magnitude 5 8 and larger earthquakes we discuss a method for optimizing both procedures and testing their forecasting effectiveness using the likelihood function our forecasts are expressed as the rate density that is the probability per unit area and time anywhere on the earth our forecasts are for scientific testing only they are not to be construed as earthquake predictions or warnings and they carry no official endorsement for our long term forecast we assume that the rate density is proportional to a smoothed version of past seismicity using the harvard cmt catalogue this is in some ways antithetical to the seismic gap model which assumes that recent earthquakes deter future ones the estimated rate density depends linearly on the magnitude of past earthquakes and approximately on a negative power of the epicentral distance out to a few hundred kilometres we assume no explicit time dependence although the estimated rate density will vary slightly from day to day as earthquakes enter the catalogue the forecast applies to the ensemble of earthquakes during the test period it is not meant to predict any single earthquake and no single earthquake or lack of one is adequate to evaluate such a hypothesis we assume that 1 per cent of all earthquakes are surprises assumed uniformly likely to occur in those areas with no earthquakes since 1977 we have made specific forecasts for the calendar year 1999 for the northwest pacific and southwest pacific regions and we plan to expand the forecast to the whole earth we test the forecast against the earthquake catalogue using a likelihood test and present the results our short term forecast updated daily makes explicit use of statistical models describing earthquake clustering like the long term forecast the short term version is expressed as a rate density in location magnitude and time however the short term forecasts will change significantly from day to day in response to recent earthquakes the forecast applies to main shocks aftershocks aftershocks of aftershocks and main shocks preceded by foreshocks however there is no need to label each event and the method is completely automatic according to the model nearly 10 per cent of moderately sized earthquakes will be followed by larger ones within a few weeks

seismic moment distribution revisited i statistical results summary an accumulation of seismic moment data gathered over the previous decade justifies a new attempt at a comprehensive statistical analysis of these data herein more rigourous statistical techniques are introduced their properties investigated and these methods are employed for analysis of large modern data sets several theoretical distributions of earthquake size seismic moment frequency relations are described and compared we discuss the requirements for such distributions and introduce an upper bound or a corner moment for a distribution to have a finite energy or moment flux we derive expressions for probability density functions and statistical moments of the distributions we also describe parameter evaluation in particular how to estimate the seismic moment distribution for the largest earthquakes simulating earthquake size distributions allows for a more rigourous evaluation of distribution parameters and points to the limitations of the classical statistical analysis of earthquake data simulations suggest that several earthquakes approaching or exceeding the corner magnitude mc limit need to be registered to evaluate mc with reasonable accuracy using the harvard catalogue data we compare moment distribution parameters for various temporal spans of the catalogue for different tectonic provinces and depth ranges and for earthquakes with various focal mechanisms the statistical analysis suggests that the exponent b is universal b 0 60 0 65 for all moderate earthquakes the corner moment mc value determined by the maximum likelihood method both in subduction zones and globally is about 10 21 n m corresponding to the corner moment magnitude mc 8 0 for midoceanic earthquakes mc is apparently smaller for spreading ridges it is about 5 8 and for strike slip earthquakes on transform faults it decreases from 7 2 to 6 5 as the relative slip velocity of faults increases we investigate the seismic moment errors both random and systematic and their dependence on earthquake size the relative errors seem to decrease for larger events the influence of moment uncertainties on the parameter estimates is studied whereas the b values do not appear to be significantly influenced by the errors for the corner moment large errors can lead to substantially biased estimates we compare the harvard catalogue results with the earthquake data from instrumental catalogues in the first three quarters of the 20th century several very large earthquakes mi9 occurred around the middle of the century their magnitude values cannot be fitted by a modified gutenberg richter law with mc 8 0 8 5 among other factors this discrepancy can be explained by either substantially higher errors in the earlier magnitude values or by mc being higher for some subduction zones it is unlikely that data available presently or soon will be sufficient to determine the corner magnitude of 9 and above with reasonable precision using purely statistical methods

adaptive kernel estimation and continuous probability representation of historical earthquake catalogs to develop spatially continuous seismicity models earthquake probability distributions from a given earthquake catalog the method of kernel estimation has been suggested kernel estimations with a global spatially invariant bandwidth deal poorly with earthquake hypocenter distributions that have different spatially local features for example a typical earthquake catalog has several areas of high activity clusters and areas of low background seismicity an alternative approach is adaptive kernel estimation which uses a bandwidth parameter that is spatially variable its performance compared to kernel estimations with spatially invariant bandwidths suggests that discrete earthquake distributions require different degrees of local smoothing to provide useful spatial seismicity models using adaptive kernel estimation the local indices of temporal dispersion of any earthquake probability distribution can be estimated and used to model the spatial probability distribution of mainshocks the application of these methods to new zealand and australian earthquake catalogs shows that the spatial features earthquake clusters in which the mainshocks occurred have been reasonably stable throughout the observation period the observed regions of higher activity persisted throughout the observation period and none of these regions decreased to background activity during that time this suggests that these regions will continue to represent higher risk for the occurrence of moderate to large earthquakes within the next few years or decades furthermore it has been observed that shallow earthquakes are mostly part of temporal sequences e g aftershocks or swarms whereas the earthquakes within the subduction zones in new zealand showed only small temporal variation during the observation period

probabilistic seismic hazard assessment methodology for distributed seismicity this study deals with probabilistic seismic hazard analysis psha based on earthquakes that cannot be assigned to specific geologic structures distributed seismicity to calculate seismic hazard from distributed seismicity the psha methodology is extended in numerous ways a simple quantitative seismotectonic model enables statistical incorporation of certain seismotectonic knowledge and the application of attenuation relationships that are based on fault distance the influence of a large historic earthquake on seismic hazard is taken into account with an energy based seismic activity rate obtained by spatial distribution of the released seismic energy it will be shown that for at least a rough seismic hazard assessment the type of geometrical seismicity modeling is not a deciding factor to illustrate this the classical seismic source zone approach and the improved spatially smoothed seismicity approach are studied in detail to determine their common and distinctive components except the geometry of modeling the seismic activity there is no essential difference between the two approaches seismic activity in slovenia can be treated as distributed seismicity for this reason the presented methodology is applied to the calculation of seismic hazard maps of slovenia as a case study manuscript received 22 august 2002

holocene climate variability in sicily from a discontinuous stalagmite record and the mesolithic to neolithic transition abstract fabric and stable isotopic composition of a holocene stalagmite cr1 from a cave in northern sicily record changes in paleorainfall in the early holocene high 13c stable isotope values in the calcite deposited from ca 8500 to ca 7500 yr ago are interpreted as reflecting periods of high rainfall the wet phase was interrupted by two periods of multi century duration characterized by relatively cool and dry winters centered at ca 8200 and ca 7500 yr ago highlighted by low 13c and 18o values a high variability of 13c values is recorded from ca 7500 to ca 6500 yr ago and indicates that the transition from a pluvial early holocene to the present day climate conditions was punctuated by decadal scale periods of relatively dry winters in northern sicily the traditional elements of the neolithic appear at ca 7700 yr ago it is possible that changes in rainfall influenced the passage from hunter gathering to farming and sheep herding economies

a three thousand year record of north atlantic climate annual band counting on three radiometrically dated stalagmites from nw scotland provides a record of growth rate variations for the last 3000 years over the period of instrumental meteorological records we have a good historical calibration with local climate mean annual temperature mean annual precipitation regional climate north atlantic oscillation and sea surface temperature sst strongest at 65 70 n 15 20 w although the correlation with the latter breaks down prior to the instrumental record this suggests that the climatic factors that force nw scottish climate and therefore our stalagmite growth varied through time and include winter nao strength the strength of the thermohaline circulation and possibly solar output spectral analysis was performed on the stalagmite growth rate time series a spectral frequency of 50 70 years is predominant in two stalagmites that were deposited from 1000 to 3000 bp a slightly longer frequency of 72 94 years is dominant from 1000 bp to present these are the same as that observed in ocean gcm output for the north atlantic region ssts our stalagmites provide high resolution precisely dated evidence of a similar periodicity predominating over the last 3000 years in a climate proxy record known to be sensitive to changes in forcing functions relevant to the north atlantic sector

a thousand year speleothem proxy record of north atlantic climate from scotland luminescent organic matter in stalagmites may form annual bands allowing growth rate to be precisely determined stalagmite growth rate is controlled by precipitation so annual bands can be used to derive long precipitation records a continuously banded stalagmite from a cave in nw scotland was used to provide a 1100 year high resolution record of precipitation the location of the cave means that precipitation is closely linked to the north atlantic oscillation for which a record is also derived this suggests that changes in the north atlantic oscillation state was an important control on european climate over the past millennium

lateglacial calendar year chronology based on annually laminated sediments from lake meerfelder maar germany abstract annually laminated sediments from lake meerfelder maar mfm in the eifel germany provide an independent calendar year timescale for the last glacial interglacial transition changes in varve thickness and varve facies reflect significant environment variations during this period the general micro facies pattern confirms that diatomaceous organic varves are favoured during warm climatic phases while cold periods generate higher allochthonous sediment fluxes an exception is the significant increase in diatom blooms at the beginning of the younger dryas six lateglacial biozones have been defined by litt and stebich quaternary international 1999 the sediment record comprises two tephra layers as chronomarkers the laacher see tephra 12 880 varve years bp is a continent wide correlation horizon while the ulmener maar tephra provides regional chronological links the beginning of the lateglacial warming is dated at 14 450 varve years vyrs bp which is regarded as the minimum age three abrupt cold spells interrupted the lateglacial interstadial at 13 800 vyrs bp oldest dryas 13 540 vyrs bp older dryas and 12 680 vyrs bp younger dryas the oldest dryas 130 years and the older dryas 190 years were rather short while the younger dryas lasted much longer 1090 years the mfm chronology was compared with ice core timescales from gisp2 and grip there is a good agreement between these timescales with the grip model age ss09 providing the best match to the mfm chronology

static coulomb stress based southern california earthquake forecasts a pseudoprospective test many studies support the hypothesis that where earthquakes occur recent changes in resolved coulomb stress tend to be positive how about the converse hypothesis that where resolved coulomb stress recently increased earthquakes are more likely to occur successful earthquake forecasting by coulomb stress changes requires the converse to test this we calculated stress everywhere in our study area not just at earthquake locations we modeled stress accumulation in southern california since 1812 both from the elastic effect of slip below locked faults and from m 5 source earthquakes up to any given date to minimize the effect of secondary aftershocks not directly related to the source earthquakes we measured seismicity using a gridded binary map each 0 1 0 1 cell is activated if containing one or more test events receiver earthquakes of m 2 8 we then constructed an empirical relationship between resolved coulomb stress and activation rate within regions with similar stress values defining probabilities of activated cells during the test period within 11 years of the m7 1 hector mine earthquake we found that coulomb stress reliably indicates future earthquake locations at the 95 confidence interval however smoothed seismicity forecasts outperformed coulomb forecasts in some areas with large earthquakes due to aftershock clustering most earthquakes tend to nucleate in areas with coulomb stress changes greater than 0 5 mpa or less than 0 5 mpa within areas with increased coulomb stress from older earthquakes fewer earthquakes occurred than anticipated after reducing stress uncertainty impact coulomb rate and state forecasts may also improve upon statistical earthquake forecasts

a study on the background and clustering seismicity in the taiwan region by using point process models 1 this paper investigates the shallow seismicity occurring in the taiwan region during the 20th century using a stochastic declustering method that has been developed on the basis of the theory of the epidemic type aftershock sequence model it provides a probability based tool to objectively separate the space time occurrences of earthquakes into a background and a clustering component on the basis of the background and clustering seismicity rates we discuss the correlation between the distribution of the cluster ratio and the regional seismotectonic structures specifically we find that the areas of the highest clustering ratio correspond to the major strike slip fault traces in and around taiwan additionally in the taiwan inland region during the period 1960 1990 the outputs for the stochastically declustered catalogue show a clear quiescence in background seismicity preceding the recovery of activation and the occurrences of the 1999 chi chi earthquake of ml7 3 while the other active regions show stationary background activity this could be interpreted as an effect of the aseismic slip in the chi chi rupture fault whereby the inland region around the chi chi source becomes a stress shadow

disequilibrium carbon and oxygen isotope fractionation in recent cave calcite comparison of cave precipitates and model data abstract speleothem proxy data provide important information in continental palaeo climate research due to their precise chronology and wide geographic distribution despite a continuously growing number of field and numerical studies designed to study stable isotope fractionation effects many aspects remain a matter of debate here carbon and oxygen isotope ratios from cave drip water and calcite precipitates sampled on watch glasses in the bunker cave western germany are compared with the values expected for isotopic equilibrium furthermore the field data are compared with the results of a numerical model simulating stalagmite growth and stable isotope ratios two drip sites with different drip rates were investigated drip site ts 1 is characterised by a high drip rate and drip water of this site is characterised by a high saturation index with respect to calcite ts 1 shows no evidence of prior calcite precipitation conversely drip site ts 8 shows a low drip rate and drip water from this site is characterised by a low saturation index ts 8 shows evidence of prior calcite precipitation whereas the mean 13 c dic values of the drip water are significantly different between the two drip sites the mean 18 o drip water values are similar calcite precipitation rates are higher at watch glass site u i corresponding to drip site ts 1 this is probably due to the higher si calcite and drip rate the 18 o and 13 c values of the calcite precipitated on watch glasses u iv corresponding to drip site ts 8 are significantly higher than those of the calcite collected on watch glasses u i calcite precipitation occurs close to isotopic equilibrium at watch glass site u i whereas the calcite precipitated at watch glass site u iv shows clear evidence of isotopic disequilibrium the results suggest that cave calcites precipitated at lower drip rates have higher 13 c and 18 o values than predicted by equilibrium precipitation furthermore our data show that stalagmites from the same cave which are fed by drip water with similar 18 o values may have different 18 o calcite values the 13 c and 18 o values predicted by the numerical model are generally lower by 1 9 and 0 8 respectively than those of the natural cave calcite nevertheless the first order trends observed in the cave data are well reproduced by the model the offset between cave and model data is probably due to the fractionation factors used in the model

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

climatic change and contemporaneous land use phases north and south of the alps 2300 bc to 800 ad fluctuations in the 14c curve and subsequent gaps of archaeological findings at 800 650 and 400 100 bc in western and central europe may indicate major climate driven land abandonment phases to address this hypothesis radiocarbon dated sediments from four lakes in switzerland were studied palynologically pollen analysis indicates contemporaneous phases of forest clearances and of intensified land use at 1450 1250 bc 650 450 bc 50 bc 100 ad and around 700 ad these land use expansions coincided with periods of warm climate as recorded by the alpine dendroclimatic and greenland oxygen isotope records our results suggest that harvest yields would have increased synchronously over wide areas of central and southern europe during periods of warm and dry climate combined interpretation of palaeoecological and archaeological findings suggests that higher food production led to increased human populations positive long term trends in pollen values of cerealia and plantago lanceolata indicate that technical innovations during the bronze and iron age e g metal ploughs scythes hay production fertilising methods gradually increased agricultural productivity the successful adoption of yield increasing advances cannot be explained by climatic determinism alone combined with archaeological evidence our results suggest that despite considerable cycles of spatial and demographic reorganisation repeated land abandonments and expansions as well as large scale migrations and population decreases human societies were able to shift to lower subsistence levels without dramatic ruptures in material culture however our data imply that human societies were not able to compensate rapidly for harvest failures when climate deteriorated agriculture in marginal areas was abandoned and spontaneous reforestations took place on abandoned land south and north of the alps only when the climate changed again to drier and warmer conditions did a new wide spread phase of forest clearances and field extensions occur allowing the reoccupation of previously abandoned areas spatial distribution of cereal cultivation and growth requirements of cerealia species suggest that increases in precipitation were far more decisive in driving crop failures over central and southern europe than temperature decreases

replicated proxy climate signals over the last 2000 yr from two distant uk peat bogs new evidence for regional palaeoclimate teleconnections ombrotrophic peat is an established source of proxy climate data but previous records have been produced by different methods and have been difficult to compare high resolution plant macrofossil analysis has been applied to a lowland raised bog at fallahogy northern ireland and a montane blanket bog moine mhor in the cairngorms scotland although the bogs are 300 km apart and differ floristically the results demonstrate parallel responses to climatic forcing especially that of the little ice age this approach provides a powerful tool for reconstructing proxy climate records wherever suitable peat deposits exist in contrast to the ocean and ice core records these proxies are from a terrestrial source and related to climate changes on land over most of the holocene

seven tephra isochrones in scotland this paper reports the presence and geochemical characteristics of seven separate tephras in scotland that fell in ad 1510 and about 450 bp 2100 bp 3600 bp 3830 bp 5600 bp and around 6000 bp the results come from 14 peat bogs spread throughout the highlands and islands where 26 tephra deposits have been characterized using over 400 grain discrete electron probe micro analysis firstly tephras are identified and defined by major element characteristics at a reference site secondly tephras are linked between sites on the basis of geochemistry and dated informal names based on british sites are suggested for tephras not yet linked to precise sources in iceland despite some apparent variation in colour all analysed grains in these seven deposits are silicic or intermediate in composition sio2 57 this phenomenon does not appear to be an artifact of preservation for two reasons first small 40 m basic glass shards in peat bogs in northern iceland are found to have undergone minimal alte

new ice core evidence for a volcanic cause of the a d 536 dust veil in new zealand human cryptosporidiosis demonstrates spring and autumn peaks of incidence with the spring peak being three times greater in magnitude than the autumn peak the imbalance between the two peaks is notable and may be associated with the high livestock density in new zealand in the summer and autumn the cryptosporidiosis rate was positively associated with temperatures in the current and previous month highlighting the importance of outdoor recreation to transmission no associations between spring incidence and weather were found providing little support for the importance of drinking water pathways imported travel cases do not appear to be an important factor in the aetiology of cryptosporidiosis in new zealand

centennial climate variability in the british isles during the mid late holocene abstract multi millennial climate changes were relatively minor over the mid late holocene in the british isles because orbitally forced insolation changes were smaller than those at higher latitudes centennial climate variability is thus likely to have exerted a greater influence on the environment and human society of the region proxy climate records from the british isles covering the last 4500 years are assembled and re evaluated with the aim of identifying centennial climate variability reflected by multi proxy indicators the proxies include bog oak populations peatland surface wetness flooding episodes from fluvial deposits speleothem annual band width and oxygen isotopes chironomids from lake sediments and sand and dune deposition most proxies reflect water balance rather than temperature alone and records predominantly reflect warm season climate a series of 12 key periods of enhanced precipitation evaporation p e are identified by their presence in two or more proxy records variability in p e is much greater than that shown by temperature proxies and there is no necessary association between warm cool and dry wet periods although the data for temperature are less robust than those for p e a series of key temperature changes are proposed based on speleothem 18o and chironomid inferred july temperature records relatively cool before c 3100 years bp warmer 3100 2000 years bp cool 2000 1250 cal years bp warm 1250 650 cal years bp and cool 650 cal years bp onwards some key increases in p e 2750 1650 550 cal years bp show a strong correspondence with bond cycles in ocean proxy records for increased ice rafted debris decreased summer sea surface temperatures and sometimes decreased north atlantic deep water circulation other higher frequency changes in p e are also strongly related to sst variability whilst some of the main changes to cooler ssts and increased p e are approximately coincident with reduced solar output most are not and thus must be the result of the internal dynamics of the ocean and atmosphere future work should concentrate on firmly establishing the pattern of temperature change improving chronological accuracy and precision in existing records and improving process based understanding of proxies

a 5500 year proxy climate and vegetation record from blanket mire at talla moss borders scotland a monolith of peat taken from an upland blanket mire at talla moss southern scotland was sub jected to peat humification and pollen analyses to produce both a proxy climate record and a vegetational history covering the last 5500 years while the peat showed little visible stratigraphy with no intimation of major peat humification changes colorimetric data indicate a markedly oscillatory climate record which is apparently largely independent of or out of phase with major vegetational changes the raw data imply particular wet shifts in climate at c 3455 bp c 2600 bp c 1930 bp c 1095 bp with a markedly wet or cool and wet episode commencing at c 540 bp these are central age estimates and should not be regarded as precise dates for the inferred climate shifts other wet shifts apparently date from c 3070 bp c 2265 bp and c 1700 bp although the first of these corresponds with pollen evidence for significant prehistoric human activity in the locality spectral analysis of the peat h

environmental changes and the migration period in northern germany as reflected in the sediments of lake dudinghausen paleolimnological techniques were used to identify environmental changes in and around lake dudinghausen northern germany over the past 4800 yr diatom inferred total phosphorus di tp changes identify four phases of high nutrient levels 2600 2200 bc 1050 700 bc 500 bc ad 100 and ad 1850 1970 during these high di tp phases fossil pollen sediment geochemistry and archaeological records indicate human activities in the lake catchment although the same paleo indicators suggest increased human settlement and agriculture activity during the late slavonic age the medieval time and the modern time ad 1000 1850 di tp levels were low during this period in the sediments iron and total phosphorus were high from ad 100 to 1850 likely due to increased inflow of iron rich groundwater into the lake increased iron input would have lead to a simultaneous binding and precipitation of phosphate in the upper sediment and overlying water column as a result anthropogenic impact on lake dudinghausen was masked by these phosphorus controlling processes from ad 1000 to 1850 and was not evident by means of di tp in accordance with fossil pollen sediment geochemistry and limited archaeological records di tp levels were low from ad 100 1000 groundwater levels likely rose during this period as the climate gradually changed toward colder and or moister conditions such climate change likely led to reduced settlement activities and forest regeneration in the catchment area our results are concordant with similar studies from central europe which indicate rapid decreasing settlement activities from ad 100 to 1000

short and long term earthquake forecasts for california and nevada we present estimates of future earthquake rate density probability per unit area time and magnitude on a 0 1 degree grid for a region including california and nevada based only on data from past earthquakes our long term forecast is not explicitly time dependent but it can be updated at any time to incorporate information from recent earthquakes the present version founded on several decades worth of data is suitable for testing without updating over a five year period as part of the experiment conducted by the collaboratory for study of earthquake predictability csep the short term forecast is meant to be updated daily and tested against similar models by csep the short term forecast includes a fraction of our long term one plus time dependent contributions from all previous earthquakes those contributions decrease with time according to the omori law proportional to the reciprocal of the elapsed time both forecasts estimate rate density using a radially symmetric spatial smoothing kernel decreasing approximately as the reciprocal of the square of epicentral distance weighted according to the magnitude of each past earthquake we made two versions of both the long and short term forecasts based on the advanced national seismic system anss and preliminary determinations of epicenters pde catalogs respectively the two versions are quite consistent but for testing purposes we prefer those based on the anss catalog since it covers a longer time interval is complete to a lower magnitude threshold and has more precise locations both forecasts apply to shallow earthquakes only depth 25 km or less and assume a tapered gutenberg richter magnitude distribution extending to a lower threshold of 4 0

isotopic evidence of sea surface freshening enhanced productivity and improved organic matter preservation during sapropel deposition in the tyrrhenian sea multiple layers of sapropels occur widely in the sedimentary record of the mediterranean sea and record repetitions of paleoclimatic conditions that favored increased production and preservation of marine organic matter a combination of hydrogen and carbon isotope analyses of pleistocene sapropels from the tyrrhenian sea reveals new aspects of the factors leading to their deposition organic matter dd values that are significantly more negative in sapropels than in adjacent marls indicate a combination of dilution of surface waters by meteoric waters and increased burial of lipid rich organic matter during periods of sapropel deposition organic 13 c values in sapropels that are less negative than those in marls suggest periods of markedly elevated marine biological production the opposite but concordant excursions of these two isotopic parameters imply that the sapropel layers formed from increased export of marine organic matter from the photic zone to the sea floor during periods of greater fluvial delivery of continental nutrients to the mediterranean sea furthermore the isotopic evidence indicates that periods of wetter climate were widespread in southern europe at the same times as in northern africa

centennial scale climate change in ireland during the holocene we examine mid to late holocene centennial scale climate variability in ireland using proxy data from peatlands lakes and a speleothem a high degree of between record variability is apparent in the proxy data and significant chronological uncertainties are present however tephra layers provide a robust tool for correlation and improve the chronological precision of the records although we can find no statistically significant coherence in the dataset as a whole a selection of high quality peatland water table reconstructions co vary more than would be expected by chance alone a locally weighted regression model with bootstrapping can be used to construct a best estimate palaeoclimatic reconstruction from these datasets visual comparison and cross wavelet analysis of peatland water table compilations from ireland and northern britain show that there are some periods of coherence between these records some terrestrial palaeoclimatic changes in ireland appear to coincide with changes in the north atlantic thermohaline circulation and solar activity however these relationships are inconsistent and may be obscured by chronological uncertainties we conclude by suggesting an agenda for future holocene climate research in ireland

last millennium palaeoenvironmental changes from a baltic bog poland inferred from stable isotopes pollen plant macrofossils and testate amoebae the baltic coast of northern poland is a region of considerable potential interest for paleoclimatic studies because this region is under the influence of both oceanic and continental climates and that these two influences have likely changed through time also unlike many more intensively studied regions of europe human impact was more limited until the 19th century we present a multiproxy high resolution record from st zki mire an ombrotrophic mire located in northern poland 35 km from the baltic sea coast we combined four proxies from the peat testate amoebae stable isotopes 13c of sphagnum stems pollen and plant macrofossils supported by dendroecological data to assess the palaeoenvironmental changes that took place during the last millennium the general aim of this study was to test if a range of proxies testate amoebae pollen plant macrofossils and tree rings could allow inferring a climatic signal from a peat monolith despite the considerable anthropogenic impact on the pomerania landscape since the early medieval period combining internal e g macrofossils and testate amoebae and external pollen signals is key to distinguishing human from climatic signals in palaeoenvironmental studies of peatlands our more specific aims were to a reconstruct the last millennium palaeoenvironment in a baltic raised bog and its surroundings b identify the major wet dry shifts and correlate those events with climate change and human impact c assess the resilience of the baltic bog ecosystem following human impact we noted two disturbance periods in the history of the mire the two major disturbances in the history of the mire were dry periods i 1100 1500 ad and ii 1650 1900 2005 ad these are reflected in all indicators and can be interpreted as the mixture of climate impact and human activities however the pollen record shows little evidence of human indicators during the first dry shift the second disturbance can be related to local peat exploitation of the mire and then in the 20th century with limited artificial drainage from 1500 ad all proxies show that the water table abruptly rose in the mire the beginning of this shift occurred during the little ice age and therefore it is likely a climatic signal alternatively this wet shift could have been interpreted as a re wetting mire surface after peat burning but this interpretation is rejected because there is no evidence of major local fire in the macrofossil record the macrofossil data shows that sphagnum fuscum dominated the pristine mire vegetation but then declined and finally disappeared this pattern is comparable with the timing of extinction of sphagnum austinii in western europe this study illustrated the value of palynological analysis of peat archives especially for last millennium to assess the magnitude of anthropogenic land use changes for example the comparison of fagus beech and carpinus hornbeam history with the palaeohydrological record allowed us to exclude climate change as the most important factor for the decline and expansion of these tree species this study is the first direct comparison of testate amoeba and stable isotope data

a paleoclimate record of the last 17 600 years in stalagmites from the b7 cave sauerland germany abstract petrographical and geochemical parameters of stalagmites from the b7 cave in iserlohn letmathe northern rhenish massif nw germany record late and postglacial climate changes temperature and or precipitation fabrics and microfacies of the stalagmite profiles lead to a differentiation of four hierarchies of rhythms clastic layers in the stalagmites are caused by flooding events and are time markers twenty four tims th u age dates provide a time calibration of stalagmite growth phases one stalagmite reveals an early growth period between 17 6 and 16 7 ka bp between 9 6 and 5 5 ka bp atlantic episode of the holocene the growth rate of the stalagmites was higher than before and after this time with dominant light porous microfacial laminae and high 18 o and 13 c values representing partly kinetic fractionation effects this part of the holocene is interpreted as a mainly warm episode with frequent interruptions of dripping within the past 4 ka the profiles with predominant dark compact facies reveal low isotopic values which may be interpreted as a temperature proxy record the stalagmite records resemble records from an irish stalagmite correlation with the 14 c record from european tree rings suggests that colder periods in the north atlantic were accompanied by drier winters in central europe

a stochastic forecast of california earthquakes based on fault slip and smoothed seismicity we present a testable stochastic earthquake source model for intermedi ate to long term forecasts the model is based on fundamental observations the frequency magnitude distribution slip rates on major faults long term strain rates and source parameter values of instrumentally recorded and historic earthquakes the basic building blocks of the model are two pairs of probability density maps the first pair consists of smoothed seismicity and weighted focal mechanisms based on observed earthquakes the second pair corresponds to mapped faults and their slip rates and consists of smoothed moment rate and weighted focal mechanisms based on fault geometry we construct from the model a stochastic event set that is to say a large set of simulated earthquakes that are relevant for seismic hazard calculations and earthquake forecast development their complete descriptions are determined in the following order magnitude epicenter moment tensor length displacement and down dip width our approach assures by construction that the simulated magnitudes are consistent with the observed frequency magnitude distribution we employ a magnitude dependent weighting procedure that tends to place the largest simulated earthquakes near major faults with consistent focal mechanisms nevertheless our stochastic model allows for surprises such as large off fault earthquakes events that comply with the observation that several recent destructive earthquakes occurred on previously unknown fault structures we apply our model to california to illustrate its features

uniform california earthquake rupture forecast version 2 ucerf 2 the 2007 working group on california earthquake probabilities wgcep 2007 presents the uniform california earthquake rupture forecast version 2 ucerf 2 this model comprises a time independent poisson process earthquake rate model developed jointly with the national seismic hazard mapping program and a time dependent earthquake probability model based on recent earthquake rates and stress renewal statistics conditioned on the date of last event the models were developed from updated statewide earthquake catalogs and fault deformation databases using a uniform methodology across all regions and implemented in the modular extensible open seismic hazard analysis framework the rate model satisfies integrating measures of deformation across the plate boundary zone and is consistent with historical seismicity data an overprediction of earthquake rates found at intermediate magnitudes 6 5 m 7 0 in previous models has been reduced to within the 95 confidence bounds of the historical earthquake catalog a logic tree with 480 branches represents the epistemic uncertainties of the full time dependent model the mean ucerf 2 time dependent probability of one or more m 6 7 earthquakes in the california region during the next 30 yr is 99 7 this probability decreases to 46 for m 7 5 and to 4 5 for m 8 0 these probabilities do not include the cascadia subduction zone largely north of california for which the estimated 30 yr m 8 0 time dependent probability is 10 the m 6 7 probabilities on major strike slip faults are consistent with the wgcep 2003 study in the san francisco bay area and the wgcep 1995 study in southern california except for significantly lower estimates along the san jacinto and elsinore faults owing to provisions for larger multisegment ruptures important model limitations are discussed

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

fennoscandian summers from ad 500 temperature changes on short and long timescales quantitative estimates of 1480 years of summer temperatures in northern fennoscandia have previously been derived from continuous treering records from northern sweden here we show the results of spectral analyses of these data only a few peaks in the spectra are consistently significant when the data are analyzed over a number of sub periods relatively timestable peaks are apparent at periods of 2 1 2 5 3 1 3 6 4 8 32 33 and for a range between 55 100 years these results offer no strong evidence for solar related forcing of summer temperatures in these regions our previously published reconstruction was limited in its ability to represent long timescale temperature change because of the method used to standardize the original tree ring data here we employ an alternative standardization technique which enables us to capture temperature change on longer timescales considerable variance is now reconstructed on timescales of several centuries in comparison with modern normals 1951 70 generally extended periods when cool conditions prevailed prior to the start of the instrumental record include 500 700 790 870 1110 1150 1190 1360 1570 1750 a d with the most significant cold troughs centred on about 660 800 1140 1580 1620 and 1640 predominantly warm conditions occurred in 720 790 870 1110 and 1360 1570 with peaks of warmth around 750 930 990 1060 1090 1160 1410 1430 1760 and 1820

black sea impact on the formation of eastern mediterranean sapropel s1 evidence from the marmara sea abstract water exchange between the black sea and the mediterranean sea has been a major focus of the paleohydrography of the eastern mediterranean glacial melt water released from the black sea is a potential factor in the formation of sapropel s1 an organic rich sediment layer that accumulated during the early holocene a high resolution study done on sediments from the marmara sea the gateway between the mediterranean and the black sea sheds light on the holocene exchange processes past sea surface temperature and sea surface salinity sss were derived from stable oxygen isotope ratios 18o of foraminiferal calcite and alkenone unsaturation ratios uk 37 heavy 18o values and high sss in the marmara sea suggest absence of low salinity water from the black sea during s1 the comparison with data from the levantine basin and southern aegean sea outlines gradients of freshening in the eastern mediterranean sea whereby the major sources of freshwater were closer to the levantine basin it is thus concluded that the black sea was not a major freshwater source contributing to formation of s1 given the absence of a low salinity layer the deposition of organic rich sediments corresponding to s1 in the marmara sea is likely the result of the global transgression and the concomitant re organization of biogeochemical cycles leading to enhanced productivity as shown by globigerina bulloides

holocene evolution of a lowland scottish landscape kirkpatrick fleming part i peat and pollen stratigraphic evidence for raised moss development and climatic change this series of papers addresses the principal natural and anthropogenic environmental changes that have transformed a typical lowland scottish landscape during the holocene sediment and pollen stratigraphic techniques together with radiocarbon dating are applied in this paper to the stratigraphy of a raised bog at burnfoothill moss eastern dumfriesshire to deduce changes in groundwater levels within the bog and by inference changes in effective precipitation the basin initially a shallow pond was rapidly colonized by fen peat at 9600 bp possibly during a phase of drier climate which ended at c 8700 bp short lived fluctuations in bog surface wetness are identified before a major change to a wetter bog surface at around 7700 cal bp representing the transformation from fen peat to raised moss anthropogenic interference with surrounding woodland is believed to have destabilized the water balance within the peat drier bog surface conditions occur at c 6700 cal bp and a shift to a wetter

near prospective test of coulomb stress triggering numerous studies retrospectively observed a strong association between earthquake location and increased static coulomb stress in addition to confirming these results for southern california seismicity we observed prospective forecasting potential in static stress evolution with 141 seismic and 98 aseismic stress sources we considered alternate choices of stress components and receiver fault orientations examined the effect of coulomb triggering on earthquake magnitude calculated stress histories for receiver quakes to see if some occurred after their stress had peaked examined whether stress changes from the hector mine earthquake alone changed the earthquake rate as expected and estimated the conditional distribution of earthquake occurrence given resolved coulomb stress change we found that with 95 confidence m 2 8 receiver earthquakes nucleate in areas of shear or coulomb stress change increase on average 59 of earthquakes occurred within stress enhanced zones regardless of the choice of rupture plane or type of stress change the 1999 hector mine california earthquake increased the seismicity in regions of positive and negative stress change but more so in the positive regions earthquakes frequently occur after their calculated peak stress has occurred indicating that elastic calculations do not tell the whole story we found no significant evidence that stress change affects the magnitude of receiver quakes thus instantaneous coulomb and shear stress change apparently influence the locations but not the magnitudes of future earthquakes

gear1 a global earthquake activity rate model constructed from geodetic strain rates and smoothed seismicity global earthquake activity rate model 1 gear1 estimates the rate of shallow earthquakes with magnitudes 6 9 everywhere on earth it was designed to be reproducible and testable our preferred hybrid forecast is a log linear blend of two parent forecasts based on the global centroid moment tensor cmt catalog smoothing 4602 m 5 767 shallow earthquakes 1977 2004 and the global strain rate map version 2 1 smoothing 22 415 global positioning system velocities optimized to best forecast the 2005 2012 global cmt catalog strain rate is a proxy for fault stress accumulation and earthquakes indicate stress release so a multiplicative blend is desirable capturing the strengths of both approaches this preferred hybrid forecast outperforms its seismicity and strain rate parents the chance that this improvement stems from random seismicity fluctuations is less than 1 the preferred hybrid is also tested against the independent parts of the international seismological centre global earthquake model catalog m 6 8 during 1918 1976 with similar success gear1 is an update of this preferred hybrid comparing gear1 to the uniform california earthquake rupture forecast version 3 ucerf3 net earthquake rates agree within 4 at m 5 8 and at m 7 0 the spatial distribution of ucerf3 epicentroids most resembles gear1 after ucerf3 is smoothed with a 30 km kernel because ucerf3 has been constructed to derive useful information from fault geometry slip rates paleoseismic data and enhanced seismic catalogs not used in our model this is encouraging to build parametric catastrophe bonds from gear1 one could calculate the magnitude for which there is a 1 or any annual probability of occurrence in local regions online material discussion of forecast scoring metrics tables of scoring results and source code and data files needed to reproduce forecast

multiplicative earthquake likelihood models based on fault and earthquake data abstract potential earthquake sources are revealed by the locations of earthquakes in historical and instrumental catalogs and of geologically mapped faults including plate boundaries we derive a set of multiplicative hybrid earthquake likelihood models that combine earthquake and fault data for the new zealand region in these models the cell rates in a spatially uniform baseline model are scaled using selected subsets of five covariates derived from the magnitudes and locations of past earthquakes the location of the boundary between the australian and pacific plates and the location and slip rate of mapped faults the hybrid model parameters are optimized for earthquakes of m 5 and greater over the period 1987 2006 and tested on earthquakes from the period 2007 2014 no updating of models is undertaken during the fitting or testing period but we consider two cases of the earthquake based covariates in the tests 1 all data prior to 1987 and 2 all data prior to 2007 respectively hybrids containing the earthquake based covariates perform better in the latter case the most informative hybrid models in the fitting and testing period are composed of three and four covariates respectively including both earthquake and fault based variables proximity to mapped faults is overall the most informative individual covariate these results can be used to inform better modeling of long term earthquake occurrence rates for probabilistic seismic hazard analysis

seismic hazard estimate from background seismicity in southern california abstract we analyzed the historical seismicity in southern california to develop a rational approach for calculating the seismic hazard from background seismicity of magnitude 6 5 or smaller the basic assumption for the approach is that future earthquakes will be clustered spatially near locations of historical mainshocks of magnitudes equal to or greater than 4 we analyzed the declustered california seismicity catalog to compute the rate of earthquakes on a grid and then smoothed these rates to account for the spatial distribution of future earthquakes to find a suitable spatial smoothing function we studied the distance r correlation for southern california earthquakes and found that they follow a 1 r power law relation where increases with magnitude this result suggests that larger events are more clustered in space than smaller earthquakes assuming the seismicity follows the gutenberg richter distribution we calculated peak ground accelerations pga for 10 probability of exceedance in 50 yr pga estimates range between 0 25 and 0 35 g across much of southern california these ground motion levels are generally less than half the levels of hazard that are obtained using the entire seismic source model that also includes geologic and geodetic data we also calculated the overall uncertainty for the hazard map using a monte carlo method and found that the coefficient of variation is about 0 24 0 01 for much of the region

aftershock zone scaling we investigate the distribution of aftershock zones for large earthquakes scalar seismic moment m 10 19 5 n m moment magnitude m 7 mainshocks are selected from the harvard centroid moment tensor catalog and aftershocks are selected from the preliminary determination of epicenters neic catalog the aftershock epicenter maps are approximated by a two dimensional gaussian distribution the major ellipse axis is taken as a quantitative measure of the mainshock focal zone size the dependence of zone length l on earthquake size is studied for three representative focal mechanisms thrust normal and strike slip although the numbers of mainshocks available for analysis are limited maximum a few tens of events in each case all earthquakes show the same scaling m l 3 no observable scaling break or saturation occurs for the largest earthquakes m 10 21 n m m 8 therefore it seems that earthquake geometrical focal zone parameters are self similar

a 2800 year palaeoclimatic record from tore hill moss strathspey scotland the need for a multi proxy approach to peat based climate reconstructions analyses of plant macrofossils testate amoebae and humification have been carried out on a 2800 year core from tore hill moss a raised bog in the strathspey region of scotland all three analyses were carried out at the same 4 cm intervals allowing exact correlation and the core was dated by nine accelerator mass spectrometry radiocarbon dates and the glen garry tephra layer the results have been combined and compared to present a bog surface wetness bsw record within which the limitations of each proxy method can be assessed and this has highlighted the advantages of a combined rather than a single proxy approach significant wet shifts are recorded at ca cal 560 bc 60 bc ad 430 ad 570 ad 700 ad 1090 and ad 1640 significant shifts to drier periods are also suggested ca cal ad 220 ad 500 and ad 820 some of the recorded shifts and phases are related to phases of wetter and drier climate such as the sub boreal sub atlantic transition the dark age deterioration and the romano british warm period the dark ages are notable as a period of rapid peat accumulation and frequent water table fluctuations time series analysis revealed a significant wet shift cycle of 560 years from the testate amoebae data

kernel estimation methods for seismic hazard area source modeling in probabilistic seismic hazard analysis the representation of seismic sources by area zones is a standard means of data reduction however where the association between seismicity and geology is complex as it is in many tectonic regimes the construction of zone geometry may become contentiously subjective and ambiguities may end up being resolved through appeal to the nonscientific rule of conservatism or pragmatism although consideration of alternative zonations within a logic tree framework provides a channel for some of the uncertainty it does not address the fundamental validity of the zonation procedure itself in particular neither the minimal assumption of uniform seismicity within a zone nor the euclidean geometry of a zone accord with the fractal spatial distribution of seismicity and the magnitude insensitivity of zonation ignores the spatial extent and correlations of different sized earthquakes an alternative procedure for area source modeling avoids euclidean zones and is based statistically on kernel estimation of the activity rate density inferred from the regional earthquake catalog the form of kernel is governed by the concepts of fractal geometry and self organized criticality with the bandwidth scaling according to magnitude in contrast with zonal models for intraplate regions the kernel estimation methodology makes provision for moderate earthquakes to cluster spatially while larger events may migrate over sizeable distances

monitoring bunker cave nw germany a prerequisite to interpret geochemical proxy data of speleothems from this site summary monitoring cave environments is important to understand processes in karst systems if stalagmites from a specific cave are used as archives of past climate variability a quantitative understanding of the soil karst speleothem system is crucial the monitoring program performed in bunker cave nw germany which includes monthly collection of climatological data as well as air and water samples from the cave and the overlying soil since 2006 is a prerequisite for the interpretation of speleothem data from the cave in terms of climate variability the results show that bunker cave is a homogeneously ventilated cave with rather low pco2 values of 580 1200 ppmv which lacks strong seasonal variations the 18o value of cave drip water reflects the mean annual composition of the rain water and the seasonal variability is strongly attenuated indicating a well mixed karst aquifer hence stalagmites from bunker cave should be well suited to record interannual decadal climate trends seven drip sites in two cave chambers show three different types of discharge behaviour including slow seasonal drip fast seasonal drip and seepage flow the drip rate patterns of most drip sites are consistent with the main infiltration events taking into account a delay of several months an instantaneous response to precipitation i e piston flow is not observed for any drip site indicating a specific water capacity threshold in the soil karst aquifer prior calcite precipitation pcp was also identified especially during times of low discharge though pcp is not as pronounced at bunker cave as in other caves it probably has an influence on the mg ca ratios of the stalagmites

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

structure and origin of holocene cold events abstract the present interglacial the holocene spans the period of the last 11 700 years it has sustained the growth and development of modern society the millennial scale decreasing solar insolation in the northern hemisphere summer lead to northern hemisphere cooling a southern shift of the intertropical convergence zone itcz and a weakening of the northern hemisphere summer monsoon systems on the multidecadal to multicentury scale periods of more stable and warmer climate were interrupted by several cold relapses at least in the northern hemisphere extra tropical area based on carefully selected 10 000 year long time series of temperature and humidity precipitation as well as reconstructions of glacier advances the spatiotemporal pattern of six cold relapses during the last 10 000 years was analysed and presented in form of a holocene climate atlas hoclat see http www oeschger unibe ch research projects holocene atlas a clear cyclicity was not found and the spatiotemporal variability of temperature and humidity precipitation during the six specific cold events 8200 6300 4700 2700 1550 and 550 years bp was very high different dynamical processes such as meltwater flux into the north atlantic low solar activity explosive volcanic eruptions and fluctuations of the thermohaline circulation likely played a major role in addition internal dynamics in the north atlantic and pacific area including their complex interaction were likely involved

a new gis approach for reconstructing and mapping dynamic late holocene coastal plain palaeogeography the geomorphological development of holocene coastal plains around the world has been studied since the beginning of the twentieth century from various disciplines resulting in large amounts of data however the overwhelming quantities and heterogeneous nature of this data have caused the divided knowledge to remain inconsistent and fragmented to keep improving the understanding of coastal plain geomorphology and geology cataloguing of data and integration of knowledge are essential in this paper we present a gis that incorporates the accumulated data of the netherlands coastal plain and functions as a storage and integration tool for coastal plain mapped data the gis stores redigitised architectural elements beach barriers tidal channels intertidal flats supratidal flats and coastal fresh water peat from earlier mappings in separate map layers a coupled catalogue style database stores the dating information of these elements besides references to source studies and annotations regarding changed insights using scripts the system automatically establishes palaeogeographical maps for any chosen moment combining the above mapping and dating information in our approach we strip the information to architectural element level and we separate mapping from dating information serving the automatic generation of time slice maps it enables a workflow in which the maker can iteratively regenerate maps which speeds up fine tuning and thus the quality of palaeogeographical reconstruction the gis currently covers the late holocene coastal plain development of the netherlands this period witnessed widespread renewed flooding along the southern north sea coast coinciding with large scale reclamation and human occupation our gis method is generic and can be expanded and adapted to allow faster integrated processing of growing amounts of data for many coastal areas and other large urbanising lowlands around the world it allows maintaining actual data overview and facilitates new ways of analysis at national regional and local scales 2016 elsevier b v

last millennium northern hemisphere summer temperatures from tree rings part i the long term context abstract large scale millennial length northern hemisphere nh temperature reconstructions have been progressively improved over the last 20 years as new datasets have been developed this paper and its companion part ii anchukaitis et al in prep details the latest tree ring tr based nh land air temperature reconstruction from a temporal and spatial perspective this work is the first product of a consortium called n trend n orthern hemisphere tre e ring n etwork d evelopment which brings together dendroclimatologists to identify a collective strategy for improving large scale summer temperature reconstructions the new reconstruction n trend2015 utilises 54 records a significant expansion compared with previous tr studies and yields an improved reconstruction with stronger statistical calibration metrics n trend2015 is relatively insensitive to the compositing method and spatial weighting used and validation metrics indicate that the new record portrays reasonable coherence with large scale summer temperatures and is robust at all time scales from 918 to 2004 where at least 3 tr records exist from each major continental mass n trend2015 indicates a longer and warmer medieval period 900 1170 than portrayed by previous tr nh reconstructions and by the cmip5 model ensemble but with better overall agreement between records for the last 600 years future dendroclimatic projects should focus on developing new long records from data sparse regions such as north america and eastern eurasia as well as ensuring the measurement of parameters related to latewood density to complement ring width records which can improve local based calibration substantially

reconstructing palaeoprecipitation from an active cave flowstone several drill cores were obtained from a laminated actively forming flowstone from a shallow cave in austria highly resolved petrographic and geochemical analyses combined with multi annual cave monitoring reveal a distinct sensitivity of flowstone growth and composition to late holocene meteoric precipitation the regular sub millimetre scale lamination consists of thicker translucent laminae and thinner organic inclusion rich laminae there is also a macroscopic millimetre scale banding of darker and lighter bands comprising several laminae stable isotope analyses of drill cores and modern calcite precipitates show a pronounced positive covariation of 13c and 18o values indicative of kinetic isotope effects comparing the isotope values with petrography shows gradual changes across several of the annual laminae i e changes of several per mille on a multi annual to decadal timescale the stable isotope and trace element composition as well as the flowstone petrography are mainly controlled by the variable drip water discharge controlling the water film thickness and water residence time on the flowstone surface and consequently the intensity of co2 degassing kinetic isotope enrichment and concomitant calcite precipitation drill core pfu6 provides an isotope record of the last ca 3000 years at near annual resolution a distinct phase of low c and o isotope values interpreted as increased discharge and hence higher meteoric precipitation occurred from ca 300 to 140 a b2k second half of the little ice age and another wet interval occurred around 700 a corresponding to reported medieval glacier advances the roman warm period was also dominated by relatively wet conditions although significant decadal variability prevailed increased precipitation further characterized the intervals from ca 2480 to 2430 and 2950 to 2770 a dry conditions persisted during the medieval climate anomaly although this trend towards reduced precipitation started earlier the highest c isotope values of the last 2 ka are recorded around 750 a and another dry phase is centred at 1480 a this new record shows that inter annual to decadal oscillations are a dominant mode of variation during the last 3 ka in the alps copyright 2011 john wiley sons ltd

community fault model cfm for southern california we present a new three dimensional model of the major fault systems in southern california the model describes the san andreas fault and associated strike slip fault systems in the eastern california shear zone and peninsular ranges as well as active blind thrust and reverse faults in the los angeles basin and transverse ranges the model consists of triangulated surface representations t surfs of more than 140 active faults that are defined based on surfaces traces seismicity seismic reflection profiles wells and geologic cross sections and models the majority of earthquakes and more than 95 of the regional seismic moment release occur along faults represented in the model this suggests that the model describes a comprehen sive set of major earthquake sources in the region the model serves the southern california earthquake center scec as a unified resource for physics based fault systems modeling strong ground motion prediction and probabilistic seismic hazards assessment

reconstruction of temperature in the central alps during the past 2000 yr from a δ18o stalagmite record the precisely dated isotopic composition of a stalagmite from spannagel cave in the central alps is translated into a highly resolved record of temperature at high elevation during the past 2000 yr temperature maxima during the medieval warm period between 800 and 1300 ad are in average about 1 7 8c higher than the minima in the little ice age and similar to present day values the high correlation of this record to d 14 c suggests that solar variability was a major driver of climate in central europe during the past 2 millennia d 2005 elsevier b v all rights reserved

paleoclimatic and paleoceanographic conditions leading to development of sapropel layer s1 in the aegean sea abstract sapropel s1 occurs as 25 35 cm thick black weakly laminated muds in aegean sea cores s1 was deposited between 9600 and 6400 yr b p during a period of isotopically depleted and relatively cool surface waters micro faunal and floral data indicate a major reduction in surface waters salinity during the deposition of s1 and oxygen isotopic data show a northerly fresh water source relatively light 13 c org and high pollen spore concentrations in s1 suggest increased influx of terrestrial organic carbon probably supplied by major rivers draining into the northern aegean sea benthic foraminifera indicate high nutrient low oxygen bottom waters for s1 and together with silt sized hematite and manganese coatings suggest that during the deposition of s1 surface sediments were oxic visual and xrd evidence of pyrite in s1 together with enrichments in s cu zn as ni cr and fe suggest that subsurface conditions were sufficiently reducing for so 4 2 reduction to occur probably by diffusion from surface oxic into subsurface anoxic sediments palynomorphs in s1 show large increases in terrestrial pollen and spores with the floral assemblage indicating significant influx from northern european rivers and minor african components associated with increased summer monsoonal rain abundance of dinoflagellates and amorphogen suggests some increase in primary productivity in response to increased influx of humic compounds however there is no evidence of upwelling the clay fraction in s1 shows notable decreases in smectite and kaolinite and reciprocal increases in illite and chlorite the combined data suggested that the evolution of s1 in the aegean sea largely resulted from stagnation of the surface waters during the final disintegration of the continental ice sheets rather than an increase in primary productivity and higher preservation of organic carbon on the sea floor

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

an earthquake likelihood model based on proximity to mapped faults and cataloged earthquakes abstract known earthquake sources include mapped active faults and locations where historical earthquakes have occurred we propose a long term earthquake likelihood model that makes use of both types of sources but does not invoke the concepts of fault segmentation or characteristic earthquakes the model has two components one based on proximity to the locations of past earthquakes taking into account their magnitudes and another based on proximity to mapped faults taking into account their slip rates the gutenberg richter law is invoked for earthquake magnitudes and an inverse power law for the diminution of earthquake rate density with distance from past earthquakes and mapped faults the model is applied to the new zealand region using the national seismic hazard model fault source model and the earthquake catalog since 1951 the parameters of each component are optimized for the period 1987 1996 and the rate density of the combined model is estimated as an optimal linear combination of the two components in a test on the independent period from 1997 2006 the combined model has an information gain log likelihood increase per earthquake of about 0 1 over each of the component models the model is also optimized over the longer period 1987 2006 for comparison with other long term models in the new zealand earthquake forecast testing centre

temperature and salinity records of the tyrrhenian sea during the last 18 000 years abstract we have used the modern analogue technique to derive sea surface temperature sst records of the last 18 000 years from two well dated deep sea cores recovered in the tyrrhenian sea results show two major cooling events synchronous with the european and north atlantic oldest and younger dryas events a later cooling of lower amplitude is observed between about 8000 and 4500 yr bp tyrrhenian ssts were similar to those of the upper holocene only during the bolling allerod event and at the beginning of the holocene we compared the sst and the planktonic foraminiferal oxygen isotope records to estimate the surface salinity variations our reconstruction shows that salinity decreased in the tyrrhenian sea during the three cold events whereas high ssts correlate with high salinities during most of the last 18 000 years tyrrhenian sea salinity variations were similar to those of the north atlantic ocean near the entrance of the mediterranean sea the salinity gradient between the two basins was thus constant indicating that the western mediterranean circulation pattern and the freshwater budget were not significantly different from the modern one the case was however different during the middle holocene when the strong salinity decrease associated with the sapropel deposit in the eastern mediterranean basin had no equivalent in the north atlantic ocean this peculiar event can only be explained by a local climatic change and an increase of precipitation

tohoku earthquake a surprise abstract we consider three questions related to the 2011 tohoku mega earthquake 1 why was the event size so grossly underestimated by japan s national hazard map 2 how should we evaluate the chances of giant earthquakes in subduction zones 3 what is the repeat time for magnitude 9 earthquakes off the tohoku coast the maximum earthquake size is often guessed from the available history of earthquakes a method known for its significant downward bias we show that historical magnitudes systematically underestimate this maximum size of future events but the discrepancy shrinks with time there are two quantitative methods for estimating the corner magnitude in any region a statistical analysis of the available earthquake record and the moment conservation principle however for individual zones the statistical method is usually ineffective in estimating the maximum magnitude only the lower limit can be evaluated the moment conservation technique which we prefer matches the tectonic deformation rate to that predicted by earthquakes with a truncated or tapered magnitude frequency distribution for subduction zones the seismic or historical record is insufficient to constrain either the maximum or corner magnitude however the moment conservation principle yields consistent estimates for all the subduction zones the corner magnitude is of the order 9 0 9 7 moreover moment conservation indicates that variations in estimated corner magnitude among subduction zones are not statistically significant another moment conservation method applied at a point on a major fault or plate boundary also suggests that magnitude 9 events are required to explain observed displacement rates at least for the tohoku area the global rate of magnitude 9 earthquakes in subduction zones predicted from statistical analysis of seismicity as well as from moment conservation is about five per century five actually happened

a review of climate reconstructions from terrestrial climate archives covering the first millennium ad in northwestern europe large changes in landscape vegetation and culture in northwestern nw europe during the first millennium ad seem concurrent with climatic shifts understanding of this relation requires high resolution palaeoclimate reconstructions therefore we compiled available climate reconstructions from sites across nw europe extent research area 10 w 20 e 45 60 n through review of literature and the underlying data to identify supraregional climatic changes in this region all reconstructions cover the period from ad 1 to 1000 and have a temporal resolution of 50 yr this resulted in 22 climate reconstructions proxy records based on different palaeoclimate archives chironomids 1 pollen 6 sphagnum mosses 1 stalagmites 8 testate amoebae 4 and tree rings 2 comparing all temperature reconstructions we conclude that summer temperatures between ad 1 and 250 were relatively high and the period between ad 250 and 700 was characterised by colder summer conditions the period from ad 700 to 1000 was again characterised by warmer summers these temperature shifts occurred in the whole of nw europe in contrast the compilation of precipitation reconstructions does not show a common pattern across nw europe either as a result of a heterogeneous precipitation pattern or the lack of suitable and consistent precipitation proxies

a new seismic hazard model for new zealand we present a new probabilistic seismic hazard analysis psha for new zealand an important feature of the analysis is the application of a new method for the treatment of historical distributed seismicity data in psha the psha uses the seismicity recorded across and beneath the country to define a three dimensional grid of a values i e parameter a of a gutenberg richter distribution log n yr a bm in which n yr is the number of earthquakes per year recorded inside each grid cell equal to or greater than magnitude m parameter b and the limiting maximum cutoff magnitude of the gutenberg richter distribution are defined from the surrounding region 14 crustal and 23 subcrustal seismotectonic zones are defined for the country and then smoothed across the boundaries of the zones the methodology therefore combines the modern method of defining continuous distributions of seismicity parameters frankel 1995 frankel et al 1996 with the traditional method of defining large area sources and the associated seismicity parameters e g algermissen et al 1990 the methodology provides a means of including deep subduction zone seismicity in a psha preserves the finer scale spatial variations of seismicity rates across a region avoids the undesirable edge effects produced in the traditional method when adjacent area sources enclose areas of significantly different seismicity rates and also enables parameters most reliably defined at a regional scale parameter b and maximum cutoff magnitude of a gutenberg richter distribution and slip type to be incorporated into the psha the psha combines the modeled seismicity data with geological data describing the location and earthquake recurrence behavior of 305 active faults and new attenuation relationships for peak ground acceleration and spectral acceleration developed specifically for new zealand different attenuation expressions are used for crustal and subduction zone earthquakes the resulting psh maps for a 150 year return period show the highest hazard to occur in the center and southwest of the country in the areas of highest historical crustal and deep subduction zone seismicity in contrast the longer return period maps 475 and 1000 year return period show the highest hazard to occur from the southwest to northeast ends of the country along the faults that accommodate the majority of the motion between the pacific and australian plates the maps are currently being used to revise new zealand s building code which has previously been based on pshas that did not explicitly include individual faults as earthquake sources manuscript received 10 april 2001

a smoothed stochastic earthquake rate model considering seismicity and fault moment release for europe ec research fp7 projects share under grant agreement no 226967 and nera under grant agreement no 262330

stable carbon and oxygen isotopes in sub fossil sphagnum assessment of their applicability for palaeoclimatology abstract to investigate the potential of stable isotopes of sphagnum peat deposits for palaeoclimate research and to inform sampling strategies we present results from a study of selected sphagnum plant constituents we report a combined stable carbon and oxygen isotope record of cellulose separately extracted from sphagnum branches and stem sections manually sampled from a 4000 year old peat deposited in a small dry maar crater located in the westeifel volcanic field germany we have determined the species composition of each individual sample of sphagnum branches to address the sensitivity of the stable isotope records to potential changes in sphagnum assemblages the youngest approximately 3000 years old peat section consists of scarcely decomposed sphagnum plant material from the bog s surface to a depth of 60 cm the predominant species is sphagnum magellanicum between 60 and 550 cm the peat predominantly consists of sphagnum capillifolium var rubellum at greater depths the decomposition status increases species identification is however solely achievable if the record under examination consists of moderately decomposed peat the stable carbon and oxygen isotope values of cellulose from sphagnum stem sections are significantly lighter than those of the branches both isotopic offsets between the different plant compounds exhibit a strong degree of correlation are statistically highly significant and observable down core the stable carbon isotope offset averages to 1 5 however presumably decreases with increasing age of the plant material in contrast the averaged oxygen isotope offset of 0 9 is consistent in time our results imply that if no differentiation into sphagnum branches and stem sections prior to stable isotope analyses is possible erroneous interpretations of the isotope records are likely since down core changes in the ratio of branches to stem sections in the peat profile are most likely this also implies that the removal of all non sphagnum plants or plant fragments is insufficient to retrieve stable isotope signals from peat deposits exclusively reflecting palaeo environmental conditions even isotopic records from bulk sphagnum cellulose comprise of two different signals firstly an environmental signal based on the plant response to external controls this signal is however masked by a second plant physiological signal originating from the isotopic offset between branches and stem sections

a precisely dated climate record for the last 9 kyr from three high alpine stalagmites spannagel cave austria 1 here we use the 18o time series of three stalagmites from the high alpine spannagel cave austria which grew in small distance from each other to construct a precisely dated continuous 18o curve for the last 9 kyr comnispa this speleothem record is not influenced by effects of kinetic isotope fractionation due to the low temperatures in the cave thus the variations in 18o can be interpreted in terms of past climate change comnispa exhibits several oscillations within the holocene and their timing and duration is in agreement with that documented by other alpine archives

a mutually consistent seismic hazard source model for southern california abstract a previous attempt to integrate geological geodetic and observed seismicity data into a probabilistic hazard source model predicted a rate of magnitude 6 to 7 earthquakes significantly greater than that observed historically one explanation was that the discrepancy or apparent earthquake deficit is an artifact of the upper magnitude limit built into the model this was controversial however because removing the discrepancy required earthquakes larger than are seen in the geological record and larger than implied from empirical relationships between fault dimension and magnitude although several articles have addressed this issue an alternative integrated source model without an apparent deficit has not yet appeared we present a simple geologically based approach for constructing such a model that agrees well with the historical record and does not invoke any unsubstantiated phenomena the following factors are found to be influential the b value and minimum magnitude applied to gutenberg richter seismicity the percentage of moment released in characteristic earthquakes a round off error in the moment magnitude definition bias due to historical catalog incompleteness careful adherence to the conservation of seismic moment rate uncertainty in magnitude estimates obtained from empirical regressions allowing multi segment ruptures cascades and the time dependence of recurrence rates the previous apparent deficit is shown to have resulted from a combination of these factors none alone caused the problem nor solves it the model presented here is relatively robust with respect to these factors

speleothem based paleoclimate record from northern oman u th age dating and stable isotope measurements of speleothems from hoti cave in northern oman yield paleoclimate information from the region extending to 125 ka the results 1 provide further confirmation of an early holocene wet period in southern arabia extending from some time prior to 9 7 ka and ending at 6 2 ka 2 demonstrate a second period of wetness closely coinciding with the last interglacial period marine isotope stage mis 5e 3 indicate that during mis 5e southern arabia was considerably wetter than during the early holocene and 4 demonstrate that periods of increased monsoon wind strength based on data from marine sediments do not always coincide with evidence of greatly increased precipitation even from nearby continental areas

plate tectonic analysis of shallow seismicity apparent boundary width beta corner magnitude coupled lithosphere thickness and coupling in seven tectonic settings a new plate model is used to analyze the mean seismicities of seven types of plate boundary crb continental rift boundary ctf continental transform fault ccb continental convergent boundary osr oceanic spreading ridge otf oceanic transform fault ocb oceanic convergent boundary sub subduction zone we compare the platelike nonorogen regions of model pb2002 bird 2003 with the centroid moment tensor cmt catalog to select apparent boundary half widths and then assign 95 of shallow earthquakes to one of these settings a tapered gutenberg richter model of the frequency moment relation is fit to the subcatalog for each setting by maximum likelihood best fitting values range from 0 53 to 0 92 but all 95 confidence ranges are consistent with a common value of 0 61 0 66 to better determine some corner magnitudes we expand the subcatalogs by 1 inclusion of orogens and 2 inclusion of years 1900 1975 from the catalog of pacheco and sykes 1992 combining both earthquake statistics and the plate tectonic constraint on moment rate corner magnitudes include the following crb graphic 1 ctf graphic 2 ccb graphic 3 ocb graphic 4 and sub graphic 5 coupled lithosphere thicknesses are found to be the following crb graphic 6 ctf graphic 7 ccb graphic 8 osr graphic 9 for normal faulting and graphic 10 for strike slip otf graphic 11 and graphic 12 at low medium and high velocities ocb graphic 13 and sub graphic 14 in general high coupling of subduction and continental plate boundaries suggests that here all seismic gaps are dangerous unless proven to be creeping in general low coupling within oceanic lithosphere suggests a different model of isolated seismic fault patches surrounded by large seismic gaps that may be permanent online material global seismic subcatalogs of shallow earthquakes 1 embed inline graphic 1 gif 2 embed inline graphic 2 gif 3 embed inline graphic 3 gif 4 embed inline graphic 4 gif 5 embed inline graphic 5 gif 6 embed inline graphic 6 gif 7 embed inline graphic 7 gif 8 embed inline graphic 8 gif 9 embed inline graphic 9 gif 10 embed inline graphic 10 gif 11 embed inline graphic 11 gif 12 embed inline graphic 12 gif 13 embed inline graphic 13 gif 14 embed inline graphic 14 gif

a synchronized dating of three greenland ice cores throughout the holocene as part of the effort to create the new greenland ice core chronology 2005 gicc05 a synchronized stratigraphical timescale for the holocene parts of the dye 3 grip and ngrip ice cores is made by using volcanic reference horizons in electri cal conductivity measurements to match the cores the main annual layer counting is carried out on the most suited records only exploit ing that the three ice cores have been drilled at locations with different climatic con ditions and differences in ice flow however supplemental counting on data from all cores has been performed between each set of reference horizons in order to verify the valid ity of the match after the verification the main dating is transferred to all records us ing the volcanic reference horizons as tie points an assessment of the mean annual layer thickness in each core section confirms that the new synchronized dating is consistent for all three cores the data used for the main annual layer counting of the past 7900 years are the dye 3 grip and ngrip stable isotope records as the high accumulation rate at the dye 3 drill site makes the seasonal cycle in the dye 3 stable isotopes very resistant to firn diffusion an effort has been made to extend the dye 3 holocene record the new syn chronized dating relies heavily on this record of 75 000 stable isotope samples the dat ing of the early holocene consists of an already established part of gicc05 for grip and ngrip which has now been transferred to the dye 3 core gicc05 dates the younger dryas termination as defined from deuterium excess to 11 703 b2k 130 years earlier than the previous grip dating

centennial scale holocene climate variability revealed by a high resolution speleothem δ18o record from sw ireland evaluating the significance of holocene submillennial 18 o variability in the greenland ice cores is crucial for understanding how natural climate oscillations may modulate future anthropogenic warming a high resolution oxygen isotope record from a speleothem in southwestern ireland provides evidence for centennial scale 18 o variations that correlate with subtle 18 o changes in the greenland ice cores indicating regionally coherent variability in the early holocene evidence for previously undetected early holocene cooling events is presented but mid to late holocene ice rafting in the north atlantic appears to have had little impact on 18 o at this ocean margin site

mid to late holocene climate change an overview the last 6000 years are of particular interest to the understanding of the earth system because the boundary conditions of the climate system did not change dramatically in comparison to larger glacial interglacial changes and because abundant detailed regional palaeoclimatic proxy records cover this period we use selected proxy based reconstructions of different climate variables together with state of the art time series of natural forcings orbital variations solar activity variations large tropical volcanic eruptions land cover and greenhouse gases underpinned by results from general circulation models gcms and earth system models of intermediate complexity emics to establish a comprehensive explanatory framework for climate changes from the mid holocene mh to pre industrial time the redistribution of solar energy due to orbital forcing on a millennial timescale was the cause of a progressive southward shift of the northern hemisphere nh summer position of the intertropical convergence zone itcz this was accompanied by a pronounced weakening of the monsoon systems in africa and asia and increasing dryness and desertification on both continents the associated summertime cooling of the nh combined with changing temperature gradients in the world oceans likely led to an increasing amplitude of the el nin o southern oscillation enso and possibly increasingly negative north atlantic oscillation nao indices up to the beginning of the last millennium on decadal to multi century timescales a worldwide coincidence between solar irradiance minima tropical volcanic eruptions and decadal to multi century scale cooling events was not found however reconstructions show that widespread decadal to multi century scale cooling events accompanied by advances of mountain glaciers occurred in the nh e g in scandinavia and the european alps this occurred namely during the little ice age lia between ad w1350 and 1850 when the lower summer insolation in the nh due to orbital forcing coincided with solar activity minima and several strong tropical volcanic eruptions the role of orbital forcing in the nh cooling the southward itcz shift and the desertifi cation of the sahara are supported by numerous model simulations other simulations have suggested that the fingerprint of solar activity variations should be strongest in the tropics but there is also evidence that changes in the ocean heat transport took place during the lia at high northern latitudes with possible additional implications for climates of the southern hemisphere sh

a multi proxy study of lake development in response to catchment changes during the holocene at lochnagar north east scotland abstract this paper describes a multi core lake sediment study using pollen diatoms and chironomids together with magnetics and sediment biogeochemistry as biotic and abiotic proxies to infer lake development in response to environmental change during the holocene at lochnagar in the eastern highlands of scotland diatoms are used to infer ph chironomids to infer temperature with pollen and plant megafossils acting as an independent proxy to validate these records and to provide insights into changes in catchment vegetation and soils lipid biomarkers are explored for their potential to provide additional information on lake productivity the results indicate highly distinctive fluctuations in the loss on ignition loi record which are in phase with changes in some biotic chironomid head capsule concentration and abiotic coarse silt particle size fraction and lipid and chlorine fractions variables catchment driven changes due to the development and degredation of soils and the natural succession and human intervention on terrestrial catchment vegetation have the strongest influence on the diatom and chironomid assemblages these catchment processes resulted in the natural acidification of the lake water post industrial acidification of the lake was also influential on the lake biota climate driven temperature change appears to have had only a weak influence on the biota with declines in cold stenothermic chironomid taxa in response to early holocene warming and declines in thermophilic chironomids in response to cooling at about 2600 cal yr bp

holocene and latest pleistocene climate and glacier fluctuations in iceland abstract multiproxy climate records from iceland document complex changes in terrestrial climate and glacier fluctuations through the holocene revealing some coherent patterns of change as well as significant spatial variability most studies on the last glacial maximum and subsequent deglaciation reveal a dynamic iceland ice sheet iis that responded abruptly to changes in ocean currents and sea level the iis broke up catastrophically around 15 ka as the polar front migrated northward and sea level rose indications of regional advance or halt of the glaciers are seen in late allerod early younger dryas time and again in preboreal time due to the apparent rise of relative sea level in iceland during this time most sites contain evidence for fluctuating tidewater glacier termini occupying paleo fjords and bays the time between the end of the younger dryas and the preboreal was characterized by repeated jokulhlaups that eroded glacial deposits by 10 3 ka the main ice sheet was in rapid retreat across the highlands of iceland the holocene thermal maximum htm was reached after 8 ka with land temperatures estimated to be 3 c higher than the 1961 1990 reference and net precipitation similar to modern such temperatures imply largely ice free conditions across iceland in the early to mid holocene several marine and lacustrine sediment climate proxies record substantial summer temperature depression between 8 5 and 8 ka but no moraines have been detected from that time termination of the htm and onset of neoglacial cooling took place sometime after 6 ka with increased glacier activity between 4 5 and 4 0 ka intensifying between 3 0 and 2 5 ka although a distinct warming during the medieval warm period is not dramatically apparent in icelandic records the interval from ca ad 0 to 1200 is commonly characterized by relative stability with slow rates of change the literature most commonly describes little ice age moraines ca ad 1250 1900 as representing the most extensive ice margins since early holocene deglaciation with temperature depressions of 1 2 c compared to the ad 1961 1990 average steep north south and west east temperature gradients are reconstructed in the holocene records of iceland suggesting a strong maritime influence on the terrestrial climate of iceland

uranium series chronology and environmental applications of speleothems an increasing number of scientists recognize the value of speleothems1 as often extremely well preserved archives of information about past climate vegetation hydrology sea level nuclide migration water rock interaction landscape evolution tectonics and human action well constrained data are required to document past changes reconstruct past patterns and predict future responses of the earth system at a wide range of spatial and temporal scales speleothems are particularly useful in this regard because they can be found in many locations of the globe sampled at high resolution and reliably dated using high precision uranium series techniques speleothems are bodies of mineral material formed in caves as the result of chemical precipitation from groundwater flowing or dripping in a cave most speleothems are composed of calcite formed by slow degassing of co2 from supersaturated groundwater but aragonite and gypsum forms are also common particularly near cave entrances where evaporative effects are important a host of different speleothem types decorate the walls ceilings and floors of caves and their mineralogy and morphology is a function of fluid flow and chemistry of waters feeding a particular location as well as the ambient conditions temperature chemistry light in the air or water filled void subaerial forms include the familiar stalagmites stalactites draperies flowstones subaqueous forms include rimstone pools rafts mammillary calcite wall coatings and dog tooth spar for an extensive review of the types of speleothem that have been observed see hill and forti 1997 speleothems are used in a multitude of ways to explore past environmental conditions perhaps the most fundamental of which is their very presence or absence deposition of speleothems relies on sufficient water supply and soil co2 to enable dissolution and transport of reactants in the vadose zone to underlying caves in arid or glacial times conditions may not have been favorable for speleothem formation

paleosalinity and δ18o a critical assessment in paleoceanography a traditional application of oxygen isotope ratios in fossil carbonate from deep sea cores concerns the reconstruction of paleotemperatures recently isotopic data have been increasingly employed in the reconstruction of paleosalinities as well this application involves a number of basic assumptions a critical review of which is presented here as the calculation of paleosalinity from 18o residuals assumes constant and linear surface water salinity s 18o relationships we investigate this basic assumption for areas with important and variable freshwater budget and or sea ice influences we show that it is particularly unwarranted to assume such temporally invariant linearity in temperate and subpolar seas because of the effects of freezing and melting more critically we argue that the determinant of many regions s 18o is advection not the local water balance so that the basic 18o of seawater in many regions of the world ocean would likely have changed in a manner somewhat different from that expected from the ice volume record although the differences may not be significant for the gross reconstruction of such features as past sea level we believe they do potentially bias paleosalinity reconstructions mostly toward high salinities to fully exploit the potential of oxygen isotope records as quantitative paleosalinity indicators both the spatial and temporal variabilities need to be constrained hence we recommend that 1 for any time slice of specific interest to paleoceanographic and paleoclimatological studies a coupled ocean atmosphere isotope model or at least an ocean isotope model driven by a paleoclimate isotope model should be used to define the distribution of the base mixing end member 18o of sea water 2 much further regional scale research is needed on flux rates and isotopic compositions of the various terms in the freshwater budget as well as on the variability in the various advective terms the latter variability may be assessed from reconstructions of past seaice distributions and of volume fluxes isotopic compositions of outflow from marginal seas and through sea straits passages

a 1052 year tree ring proxy for alpine summer temperatures a june august alpine temperature proxy series is developed back to ad 951 using 1 527 ring width measurements from living trees and relict wood the reconstruction is composed of larch data from four alpine valleys in switzerland and pine data from the western austrian alps these regions are situated in high elevation alpine environments where a spatially homogenous summer temperature signal exists in an attempt to capture the full frequency range of summer temperatures over the past millennium from inter annual to multi centennial scales the regional curve standardization technique is applied to the ring width measurements correlations of 0 65 and 0 86 after decadal smoothing with high elevation meteorological stations since 1864 indicate an optimal response of the rcs chronology to june august mean temperatures the proxy record reveals warm conditions from before ad 1000 into the thirteenth century followed by a prolonged cool period reaching minimum values in the 1820s and a warming trend into the twentieth century this latter trend and the higher frequency variations compare well with the actual high elevation temperature record the new central alpine proxy suggests that summer temperatures during the last decade are unprecedented over the past millennium it also reveals significant similarities at inter decadal to multi centennial frequencies with large scale temperature reconstructions however deviating during certain periods from h h lamb s european north atlantic temperature history

late holocene ecological shifts and chironomid inferred summer temperature changes reconstructed from lake uddelermeer the netherlands abstract this paper presents a late holocene chironomid inferred record of july air temperature from a core obtained from lake uddelermeer in the netherlands the core interval which dates from 2500 to 400 cal yr bp was analysed at multi decadal resolution for organic content pollen spores and npps non pollen palynomorphs and chironomid head capsules these proxies indicate that from 2500 to 1140 cal yr bp the lake was mesotrophic and sustained a littorellion community while the chironomid assemblage was dominated by littoral species associated with macrophytes at 1140 cal yr bp a shift in the lake ecology occurred from low nutrient to high nutrient conditions dominated by algae this shift might be linked to a concurrent increase in human impact and is reflected in the chironomid assemblage by increases in eurytopic taxa which are resistant to disturbances shifts in the chironomid record between 2500 and 1140 cal yr bp do not coincide with changes in lake ecology and are presumably driven by climate change using a norwegian swiss calibration dataset as a modern analogue we produced a chironomid inferred temperature c it reconstruction this reconstruction compares well to other regional temperature reconstructions in timing and duration showing a roman warm period between 2240 and 1760 cal yr bp a dark age cold period starting at 1760 cal yr bp and the medieval climate anomaly beginning at 1280 cal yr bp the c it record indicates a temperature drop of 1 5 c from the roman warm period to the dark age cold period findings improve knowledge of the first millennium ad in nw europe which was characterised by changes in landscape vegetation society and climate

annually dated late weichselian continental paleoclimate record from the eifel germany a record extending back to 23 220 calendar yr b p was obtained from varved sediments from lake holzmaar germany by applying multiple dating methods and interlake comparison with meerfelder maar variations in the weichselian inorganic carbon content resulting from intensified eolian activities coincide with proxy parameters of dust accumulation in greenland the timing for the end of the last glacial maximum at holzmaar agrees with the greenland ice sheet project gisp2 data but suggests dating discrepancies with the greenland ice core project data grip assuming that periods of maximum dust deposition in the eifel and greenland coincide with ice advances in northeastern germany the holzmaar record provides a means of dating three late weichselian terminal moraines

the magnitude distribution of earthquakes near southern california faults we investigate seismicity near faults in the southern california earthquake center community fault model we search for anomalously large events that might be signs of a characteristic earthquake distribution we find that seismicity near major fault zones in southern california is well modeled by a gutenberg richter distribution with no evidence of characteristic earthquakes within the resolution limits of the modern instrumental catalog however the b value of the locally observed magnitude distribution is found to depend on distance to the nearest mapped fault segment which suggests that earthquakes nucleating near major faults are likely to have larger magnitudes relative to earthquakes nucleating far from major faults

a 7500 year peat based palaeoclimatic reconstruction and evidence for an 1100 year cyclicity in bog surface wetness from temple hill moss pentland hills southeast scotland analyses of plant macrofossils peat humification and testate amoebae were used to reconstruct a proxy climate record spanning the last 7500 years from an ombrotrophic bog temple hill moss in southeast scotland the plant macrofossil data were subjected to detrended correspondence analysis dca which modelled effectively the significant wet shifts within the record a mean water table depth transfer function was applied to the testate amoebae data to provide quantifiable changes the three proxy records show coherent phase changes which are interpreted as variability in past effective precipitation two tephra horizons glen garry and lairg a were used in conjunction with radiocarbon dates to construct an age depth model producing a robust geochronology from which a time series was calculated the palaeoclimatic reconstruction identified major wet shifts throughout the holocene with specific events occurring around cal 6650 5850 5300 4500 3850 3400 2800 2450 1450 1350 and 250 150 bp spectral analysis of the plant macrofossil dca and colorimetric humification data produced a millennial scale periodicity of 1100 years the same periodicity has also been found in a palaeoclimatic reconstruction from a site in cumbria walton moss and may be linked with millennial scale periodicities found in oceanic palaeoclimatic records