late quaternary climate and hydrology of tropical south america inferred from an isotopic and chemical model of lake titicaca bolivia and peru abstract a simple mass balance model provides insight into the hydrologic isotopic and chemical responses of lake titicaca to past climatic changes latest pleistocene climate of the altiplano is assumed to have been 20 wetter and 5 c colder than today based on previous modeling our simulation of lacustrine change since 15 000 cal yr b p is forced by these modeled climate changes the latest pleistocene lake titicaca was deep fresh and overflowing the latest pleistocene riverine discharge from the lake was about 8 times greater than the modern average sufficient to allow the expansion of the great paleolake tauca on the central altiplano the lake 18o value averaged about 13 smow the modern value is about 4 2 the early holocene decrease in precipitation caused lake titicaca to fall below its outlet and contributed to a rapid desiccation of paleolake tauca continued evaporation caused the 100 m drop in lake level but only a slight 1 2 increase relative to modern in 18o of early holocene lake waters this holocene lowstand level of nearly 100 m was most likely produced by a precipitation decrease relative to modern of about 40 the lake was saline as recently as 2000 cal yr b p the timing of these hydrologic changes is in general agreement with calculated changes of insolation forcing of the south american summer monsoon

impact of chi chi earthquake on the occurrence of landslides and debris flows example from the chenyulan river watershed nantou taiwan abstract the chenyulan river watershed in central taiwan was chosen for evaluating the impact of the chi chi earthquake on the occurrence of landslides and for exploring the initial conditions triggering debris flows interpretations of aerial photographs and spot images as well as field investigations were used to identify landslide and debris flow occurrences precipitation data were then utilized to investigate critical conditions leading to the debris flow comparison of five spot images taken between june 1996 before the july 1996 typhoon herb and september 1999 before the chi chi earthquake shows that the landslide area increased from 7 1 106 to 7 5 106 m2 during that time however by january 2000 after the chi chi earthquake the landslide area almost tripled to 20 8 106 m2 measurement of images taken in march and august 2001 reveals that the landslide area had further expanded to 24 2 106 and 27 5 106 m2 respectively significant differences before and after the earthquake are also noticed in 1 the intensity and amount of precipitation required for triggering debris flow 2 the size of contributing drainage basin in which debris flows occurred and 3 the frequency of debris flows after the chi chi earthquake maximum hourly rainfall intensity and critical accumulated precipitation necessary to initiate debris flow reduced to as low as 1 3 of the pre earthquake figures prior to the chi chi earthquake most debris flows occurred in gullies with slopes greater than 10 and in drainage basins larger than 0 1 km2 conversely after the earthquake debris flows were observed even in gullies with effective drainage area smaller than 0 03 km2 furthermore before the earthquake the debris flow recurrence time in the study area was greater than 5 years whereas six debris flow events have been observed in the 2 years since the earthquake

asymmetric vegetation responses to mid holocene aridity at the prairie forest ecotone in south central minnesota abstract the mid holocene ca 8000 4000 cal yr bp was a time of marked aridity throughout much of minnesota and the changes due to mid holocene aridity are seen as an analog for future responses to global warming in this study we compare the transition into ca 9000 7000 yr ago and out of ca 5000 2500 yr ago the mid holocene mh period at kimble pond and sharkey lake located along the prairie forest ecotone in south central minnesota using high resolution 5 36 yr sampling of pollen charcoal sediment magnetic and loss on ignition properties changes in vegetation were asymmetrical with increasing aridity being marked by a pronounced shift from woodland forest dominated landscape to a more open mix of grassland and woodland savanna in contrast at the end of the mh grassland remained an important component of the landscape despite increasing effective moisture and high charcoal influxes median 2 7 4 0 vs 0 6 1 7 mm 2 cm 2 yr 1 at start of mh suggest the role of fire in limiting woodland expansion asymmetric vegetation responses variation among and within proxies and the near absence of fire today suggest caution in using changes associated with mid holocene aridity at the prairie forest boundary as an analog for future responses to global warming

the variability of holocene climate change evidence from varved lake sediments varved sediments from a lake near the present forest prairie border in northwestern minnesota provide an annual record of climate change for the last 10 400 years climate sensitive mineral chemical and biological components show that the mid holocene dry interval between 8500 and 4000 years ago is asymmetrical and actually consists of two distinct drier pulses separated by a moister interval that lasted about 600 years cyclic fluctuations with periods of several hundred years were abrupt and persistent throughout the holocene and are most clearly recorded within the two drier pulses

slope vulnerability to earthquakes at subregional scale using probabilistic techniques and geographic information systems abstract the susceptibility of slopes to failure during earthquakes is calculated in terms of critical horizontal acceleration on a subregional scale for the upper part of the serchio river basin tuscany italy according to the working scale 1 10 000 and to the availability and accuracy of the input data the infinite slope analysis was judged to be the most appropriate method but particular attention was devoted to the error evaluation due to spatial variability of the geotechnic geometric and hydrologic parameters a geologic geomorphologic and hydrologic survey of the area was therefore performed and the geotechnic parameters were collected at local administrations all the data were stored in a gis used as a tool to build the spatial and attribute data base and to prepare the input data layers for the stability analysis in order to assess the variability of geotechnic parameters a statistical analysis was performed to assign the best fitting probability distribution to cohesion angle of internal friction and unit weight of the soil as hydrogeologic data were not available for the area only surface hydrology information could be used a map of probability of spring occurrences was derived by a bayesian method the weight of evidence modelling and was used as groundwater indicator a monte carlo procedure and a first order second moment method were applied and compared as error estimators in assessing the slope susceptibility to failure the differences between the two methods are discussed and two maps showing respectively the critical horizontal acceleration and the probability of failure associated with each slope are presented together with the curve plotting the reliability index against the probability of failure

strength and consistency of artificial clay carbonate mixtures simulation of natural sediments abstract marl a common rock within carbonate sequences in israel occurs as an intimate mixture of varying proportions of clay and carbonate the diagenetic process involved in the formation of the rock is controlled by the physical and chemical properties of the material as it progresses from sedimentation through diagenesis to lithification to provide a better understanding of the formation of these rocks natural sediments were simulated in the laboratory this was done by mixing varying proportions of upper cretaceous smectites bentonite and montmorillonite clay and jurassic kaolinite from makhtesh ramon with eocene chalk from the northern negev the strength and consistency of these mixtures was then determined the relationship of plasticity index to liquid limit with a correlation coefficient of 0 945 0 982 shows that the bentonite mixtures are of medium to high compressibility in comparison to the kaolinite mixtures which have a low plasticity the montmorillonite mixtures have a medium plasticity free swell of the bentonite and montmorillonite mixtures is in general twice that of the kaolinite mixtures and decreases in all cases as the carbonate content increases the effective range in friction angle under drained conditions similar to those occurring in the natural environment and saturation of up to 80 is generally consistent with increasing carbonate being only slightly higher in the montmorillonite mixtures cohesion is higher in the bentonite mixtures marls containing bentonite or montmorillonite undergo relatively higher volume changes than kaolinite muds they also deform plastically being more sensitive to changes in natural water content generally kaolinite muds are more stable and less deformed during lithification

groundwater supported evapotranspiration within glaciated watersheds under conditions of climate change this paper analyzes the effects of geology and geomorphology on surface water groundwater interactions evapotranspiration and recharge under conditions of long term climatic change our analysis uses hydrologic data from the glaciated crow wing watershed in central minnesota usa combined with a hydrologic model of transient coupled unsaturated saturated flow hydrat2d analysis of historical water table 1970 1993 and lake level 1924 2002 records indicates that larger amplitude and longer period fluctuations occur within the upland portions of watersheds due to the response of the aquifer system to relatively short term climatic fluctuations under drought conditions lake and water table levels fell by as much as 2 4 m in the uplands but by 1 m in the lowlands the same pattern can be seen on millennial time scales analysis of holocene lake core records indicates that moody lake located near the outlet of the crow wing watershed fell by as much as 4 m between about 4400 and 7000 yr bp during the same time water levels in lake mina located near the upland watershed divide fell by about 15 m reconstructed holocene climate as represented by hydrat2d gives somewhat larger drops 6 and 24 m for moody lake and lake mina respectively the discrepancy is probably due to the effect of three dimensional flow a sensitivity analysis was also carried out to study how aquifer hydraulic conductivity and land surface topography can influence water table fluctuations wetlands formation and evapotranspiration the models were run by recycling a wet year 1985 87 cm annual precipitation over a 10 year period followed by 20 years of drier and warmer climate 1976 38 cm precipitation model results indicated that groundwater supported evapotranspiration accounted for as much as 12 10 cm of evapotranspiration the aquifers of highest hydraulic conductivity had the least amount of groundwater supported evapotranspiration owing to a deep water table recharge was even more sensitive to aquifer hydraulic conductivity especially in the lowland regions these findings have important implications for paleoclimatic studies because the hydrologic response of a surface water body will vary across the watershed to a given climate signal

holocene climatic change in the northern midwest pollen derived estimates mapping of holocene pollen data in the midwestern united states has revealed several broadscale vegetational changes that can be interpreted in climatic terms these changes include 1 the early holocene northward movement of the spruce dominated forest and its later southward movement after 3000 yr b p and 2 the eastward movement of the prairie forest border into southwestern wisconsin by 8000 yr b p and its subsequent westward retreat after 6000 yr b p when certain basic assumptions are met multiple regression models can be derived from modern pollen and climate data and used to transform the pollen record of these vegetational changes into quantitative estimates of temperature or precipitation to maximize the reliability of the regression equations we followed a sequence of procedures that minimize violations of the assumptions that underlie regression analysis reconstructions of precipitation during the holocene indicated that from 9000 to 6000 yr b p precipitation decreased by 10 to 25 over much of the midwest while mean july temperature increased by 0 5 to 2 0 c at 6000 yr b p precipitation was less than 80 of its modern values over parts of wisconsin and minnesota after 6000 yr b p precipitation generally increased while mean july temperature decreased in the north and increased in the south the time of the maximum temperature varies within the midwest and is earlier in the north and later in the south

seismically induced landslide displacements a predictive model newmark s model for predicting earthquake induced landslide displacements provides a simple way to predict the coseismic displacements affecting a sliding mass subject to earthquake loading in this model seismic slope stability is measured in terms of critical acceleration which depends on the mechanical soil properties pore pressure distribution and slope geometry the triggering seismic forces are investigated in terms of energy radiation from the source propagation and site effects based on 190 accelerometric recordings from 17 italian earthquakes with magnitudes between 4 5 and 6 8 the method is based on the calibration of relations having the general form of an attenuation law that relates the energy of the seismic forces to the dynamic shear resistances of the sliding mass to propagate the expected landslide displacements as an inverse function of the distance from the fault rupture the amount of displacement computed through these relations provides a criterion to predict the occurrence of slope failures finally maps showing in a deterministic and a probabilistic way the potential of seismically induced landslide displacements are displayed as a tool to provide seismic landslide scenarios and earthquake induced landslide hazard maps respectively

the geotechnical effects of long human habitation 2000 years earthquake induced landslide hazard in the city of zefat northern israel abstract this work studies the effects of long human habitation on site geotechnical conditions it is focused on the city of zefat that is located on the borders of the dead sea transform in northern israel the city of zefat suffered severe damage and loss of life in historical earthquakes as a consequence of earthquake induced landslides eils in this work we evaluate the current eils hazard for the city of zefat using a gis based regional newmark analysis with calibration of the calculated newmark displacement representing eils hazard using maps of field evidence and historical documents testifying to slope instability that occurred in historical earthquakes we found that the core city of zefat is built on a layered anthropogenic material few meters deep which was deposited as a result of more than 2000 years of human habitation the anthropogenic material is mechanically weak susceptible to slope failure and to amplification of seismic shaking it is responsible for the city s devastation in historical earthquakes and it is the source for the current high seismic hazard as well our model shows that earthquakes of magnitudes mw 5 6 and 7 at distances of up to 10 km 50 km and more than 100 km respectively are likely to induce landslides in the core city of zefat the current engineering status of the city is poor and as a consequence severe damage and loss of life are expected in future earthquakes due to eils unless major engineering efforts are made cities in the eastern mediterranean with comparable long habitation histories e g jerusalem tiberias nablus amman are expected to have similar geotechnical problems in their old sections and are advised to take appropriate engineering steps to reduce damage and loss of life in future earthquakes evaluation of historical earthquake magnitudes based on reported local damage may however lead to overestimated magnitudes where the damaged sites are built on anthropogenic talus a common setting in the vicinity of the dead sea transform

evaluation of factors controlling earthquake induced landslides caused by chi chi earthquake and comparison with the northridge and loma prieta events over 10 000 landslides were triggered by the september 21 1999 chi chi earthquake a large number of these landslides have been mapped from spot images and a smaller number were described in a detailed field investigation geographic information systems gis was used to conduct a spatial characterization of the slope failures including distribution of type size slope angle bedrock geology ground motion and distance from earthquake source the most abundant landslides were shallow disaggregated rock and soil slides landslides occurred primarily in tertiary sedimentary rocks which are well known for their susceptibility to landsliding in many parts of the world landslide concentration values diminish beyond epicentral distances of 40 and 70 km from the epicenter and the surface projection of the fault plane respectively ground motion was found to be the most significant factor in triggering the shallow landslides in the chi chi earthquake overall 74 of all slope failures occurred in regions with vertical ground motions greater than 0 2g and 81 of all slope failures occurred in the region with mean horizontal peak ground accelerations pga greater than 0 15g these factors were used to compare landslides generated by the chi chi earthquake to the landslides triggered by the 1989 loma prieta earthquake and the 1994 northridge earthquake the major difference in distribution of landslides between the chi chi earthquake and the two california earthquakes was the distribution of slope angles in the chi chi earthquake 90 of the failures occurred on slopes steeper than 45 while more than 80 of failures occurred on slopes less than 50 in california apparently reflecting much steeper and tectonically more active geologic setting in taiwan

slope stabilization and landslide size on mt 99 peaks after chichi earthquake in taiwan the study focuses on the landslide characteristics of mt 99 peaks in nantou county the most serious landslide prone area caused by chichi earthquake in taiwan several investigations and field surveys were made on mt 99 peaks for 5 years to research the landslide area and depth rainfall trend and slope stabilization the total landslide volume caused by the earthquake on mt 99 peaks was about 1 47 106 m3 and the mean landslide thickness was about 0 22 m gravel layers with a volume of more than 80 of total soil profile dominated mt 99 peaks the landslide on mt 99 peaks was induced by heavy rainfall from july to september because the rainfall on mt 99 peaks had a nonuniform distribution in time although the vegetation recovery on mt 99 peaks was in progress the soil slope had remained unstable as a result typhoon mindulle occurred in july 2004 collapsed the hillslope again after 5 years of chichi earthquake this study suggests that vegetation recovery on mt 99 peaks for 5 years was insufficient to stabilize the landslide affected area

the 1759 earthquake in the bekaa valley implications for earthquake hazard assessment in the eastern mediterranean region analysis of macroseismic data based on primary sources for large though infrequent historical earthquakes ms 6 5 that occurred along an approximately 350 km long segment of the northern part of the dead sea fault system primarily in lebanon and syria for the period 1100 1988 reveals the following 1 ten events occurred in three relatively short periods tens of years with repeat times of 200 350 years 2 the events most probably broke this north segment of the dead sea fault system possibly including the westernmost segment of the east anatolian fault system near the border between syria and turkey 3 the lack of such large events during the past 100 years should not be interpreted to minimize potential earthquake hazard in this region and 4 the ms 7 plus earthquake on november 25 1759 almost certainly produced surface faulting probably along the yammouneh fault in the bekaa valley and caused heavy destruction with great loss of life in numerous villages and towns including safad damascus beirut and baalbek this main event was preceded by a ms 6 plus foreshock on october 30 1759 in the southern part of the epicentral area of the main shock near the towns of safad and qunaitra which were almost totally destroyed with considerable loss of life

post deformational annealing of calcite rocks abstract the evolution of microstructure and crystallographic preferred orientation cpo during post deformational annealing was studied on three calcite rock types differing in purity and grain size carrara marble 98 calcite mean grain size of 115 m solnhofen limestone 96 5 m and synthetic calcite aggregates 99 7 m samples were first deformed in torsion at 727 c at a shear strain rate of 3 10 4 s 1 to a shear strain of 5 and subsequently heat treated at 727 c for various durations between 0 and 24 h microstructures and cpos were analysed by optical microscopy image analysis and electron backscatter diffraction ebsd all rock types deformed in the dislocation creep field at the same applied conditions but their microstructures and cpos after deformation and after annealing differed depending on starting grain size and material composition in carrara marble and in the synthetic calcite aggregate a strong cpo developed during deformation accompanied by dynamic recrystallisation with significant changes in grain size during annealing widespread grain growth and subtle changes of cpo occurred and equilibrated foam microstructures were approached after long annealing times the cpo is the only feature in annealed samples indicating an earlier deformation phase although it is not always identical to the cpo formed during deformation in the more impure solnhofen limestone secondary phases on grain boundaries suppressed grain boundary mobility and prevented both the formation of a recrystallisation cpo during deformation and grain size modification during deformation and annealing

holocene climatic change and the development of the lake effect snowbelt in michigan usa lake effect snow is an important constraint on ecological and socio economic systems near the north american great lakes little is known about the holocene history of lake effect snowbelts and it is difficult to decipher how lake effect snowfall abundance affected ecosystem development we conducted oxygen isotope analysis of calcite in lake sediment cores from northern lower michigan to infer holocene climatic variation and assess snowbelt development the two lakes experience the same synoptic scale climatic systems but only one of them huffman lake receives a significant amount of lake effect snow a 177 cm difference in annual snowfall causes groundwater inflow at huffman lake to be 18o depleted by 2 3 relative to o brien lake to assess when the lake effect snowbelt became established we compared calcite 18o profiles of the last 11 500 years from these two sites the chronologies are based on accelerator mass spectrometry 14c ages of 11 and 17 terrestrial plant samples from huffman and o brien lakes respectively the values of 18o are low at both sites from 11 500 to 9500 cal yr bp when the laurentide ice sheet lis exerted a dominant control over the regional climate and provided periodic pulses of meltwater to the great lakes basin carbonate 18o increases by 2 6 at o brien lake and by 1 4 at huffman lake between 9500 and 7000 cal yr bp suggesting a regional decline in the proportion of runoff derived from winter precipitation the great lakes snowbelt probably developed between 9500 and 5500 cal yr bp as inferred from the progressive 18o depletion at huffman lake relative to o brien lake with the largest increase of lake effect snow around 7000 cal yr bp lake effect snow became possible at this time because of increasing contact between the great lakes and frigid arctic air these changes resulted from enhanced westerly flow over the great lakes as the lis collapsed and from rapidly rising great lakes levels during the nipissing transgression the 18o difference between huffman and o brien lakes declines after 5500 cal yr bp probably because of a northward shift of the polar vortex that brought increasing winter precipitation to the entire region however 18o remains depleted at huffman lake relative to o brien lake because of the continued production of lake effect snow

hydrologic response of the crow wing watershed minnesota to mid holocene climate change in this study we have integrated a suite of holocene paleoclimatic proxies with mathematical modeling in an attempt to obtain a comprehensive picture of how watersheds respond to past climate change a three dimensional surface water groundwater model was developed to assess the effects of mid holocene climate change on water resources within the crow wing watershed upper mississippi basin in north central minnesota the model was first calibrated to a 50 yr historical record of average annual surface water discharge monthly ground water levels and lake level fluctuations the model was able to reproduce reasonably well long term historical records 1949 1999 of water table and lake level fluctuations across the watershed as well as stream discharge near the watershed outlet the calibrated model was then used to reproduce paleo groundwater and lake levels using climate reconstructions based on pollen transfer functions from williams lake just outside the watershed computed declines in mid holocene lake levels for two lakes at opposite ends of the watershed were between 6 and 18 m simulated streamflow near the outlet of the watershed decreased to 70 of modern average annual discharge after 200 yr the area covered by wetlands for the entire watershed was reduced by 16 the mid holocene hydrologic changes indicated by these model results and corroborated by several lake core records across the crow wing watershed may serve as a useful proxy of the hydrologic response to future warm dry climatic forecasts ca 2050 made by some atmospheric general circulation models for the glaciated midwestern united states

mid holocene hydrologic model of the shingobee watershed minnesota abstract a hydrologic model of the shingobee watershed in north central minnesota was developed to reconstruct mid holocene paleo lake levels for williams lake a surface water body located in the southern portion of the watershed hydrologic parameters for the model were first estimated in a calibration exercise using a 9 yr historical record 1990 1998 of climatic and hydrologic stresses the model reproduced observed temporal and spatial trends in surface groundwater levels across the watershed mid holocene aquifer and lake levels were then reconstructed using two paleoclimatic data sets ccm1 atmospheric general circulation model output and pollen transfer functions using sediment core data from williams lake calculated paleo lake levels based on pollen derived paleoclimatic reconstructions indicated a 3 5 m drop in simulated lake levels and were in good agreement with the position of mid holocene beach sands observed in a williams lake sediment core transect however calculated paleolake levels based on ccm1 climate forcing produced only a 0 05 m drop in lake levels we found that decreases in winter precipitation rather than temperature increases had the largest effect on simulated mid holocene lake levels the study illustrates how watershed models can be used to critically evaluate paleoclimatic reconstructions by integrating geologic climatic limnologic and hydrogeologic data sets

regression models for estimating coseismic landslide displacement newmark s sliding block model is widely used to estimate coseismic slope performance early efforts to develop simple regression models to estimate newmark displacement were based on analysis of the small number of strong motion records then available the current availability of a much larger set of strong motion records dictates that these regression equations be updated regression equations were generated using data derived from a collection of 2270 strong motion records from 30 worldwide earthquakes the regression equations predict newmark displacement in terms of 1 critical acceleration ratio 2 critical acceleration ratio and earthquake magnitude 3 arias intensity and critical acceleration and 4 arias intensity and critical acceleration ratio these equations are well constrained and fit the data well 71 br 2 b88 but they have standard deviations of about 0 5 log units such that the range defined by the mean one standard deviation spans about an order of magnitude these regression models therefore are not recommended for use in site specific design but rather for regional scale seismic landslide hazard mapping or for rapid preliminary screening of sites 2007 elsevier b v all rights reserved

source parameters and scaling relationships of earthquakes in israel abstract determination of earthquake dynamic source parameters such as the seismic moment stress drop and rupture area are often based purely on theoretical considerations in reality however some of the corrected coefficients utilized in the computations should preferably be defined empirically in the present study 39 earthquakes of ml between 3 0 and 6 7 are used to define the correction coefficients associated with distance geometric and unelastic attenuation and ratios between zero frequency spectral amplitides of s waves recorded by vertical and horizontal seismographs these are used in turn to determine the seismic moment m0 and the empirical correlation between log m0 and ml magnitudes for that region the validity of using constant stress drop assumption and correlation between moment and corner frequency is also discussed

crusader castle torn apart by earthquake at dawn 20 may 1202 the crusader castle of vadum jacob an outpost overlooking the jordan river was deformed during a destructive earthquake triggered by motion along the dead sea transform the m 7 earthquake occurred at dawn 20 may 1202 and offset the castle walls by 1 6 m this exceptional precision in dating and estimating displacement was achieved by combining accounts from primary historical sources by excavating the dead sea transform where it bisects the castle and by dating faulted archaeological strata the earthquakes of october 1759 and or january 1837 may account for the remaining 0 5 m out of a total 2 1 m of offset our study exploits the potential embodied in interdisciplinary historical archaeological geological research and illustrates how detailed histories of seismogenic faults can be reconstructed

sediment flux from a mountain belt derived by landslide mapping in humid uplands landsliding is the dominant mass wasting process in the western southern alps of new zealand landslides are scale invariant and have a power law magnitude frequency distribution independent studies from other regions suggest that this is a general property of landsliding this observation is of critical importance to the evaluation of the impact of events of different length scales over different time intervals on landscape evolution it is particularly useful when estimating regional geomorphic rates because it constrains the frequency and overall significance of extreme events which cannot otherwise be evaluated by integrating the complete response of the system we estimate the regional denudation rate due to landsliding to be 9 4 mm yr 1 sediment discharge from the western southern alps is dominated by landslide derived material

patterns of hydroclimatic change in the rocky mountains and surrounding regions since the last glacial maximum abstract the paleohydrologic record of western north america since the last glacial maximum reveals a wide range of hydroclimatic variability in time and space to improve the understanding of abrupt hydroclimatic shifts and millennial scale hydrologic changes in the central rocky mountains we reconstruct the lake level histories of two small lakes in the beartooth and bighorn mountains in northern wyoming over the past 17 ka to do so we use ground penetrating radar gpr and sediment cores to track the elevations of shoreline sediments within the lakes through time we compare the stratigraphies with those from four other lakes in wyoming and colorado and find widespread evidence for a terminal pleistocene drought from 15 to 11 ka an early holocene humid period from 11 to 8 ka and mid holocene aridity from 8 to 5 5 ka the northern wyoming lakes also provide evidence of high levels in the pleistocene possibly before ca 15 ka and rapid hydroclimatic changes that may have correlated with heinrich event 1 ca 16 8 ka we place the changes in a broad context by summarizing and mapping water level changes from 107 additional previously studied lakes important patterns include 1 extensive drying across the western u s after 15 ka 2 sub regional differences during the pleistocene holocene transition 3 a north south contrast from 9 to 6 ka consistent with a northward shift in storm tracks as the influence of the laurentide ice sheet diminished and 4 rapid increases in effective moisture across much of western north america from 6 to 4 ka

hydrologic variation in the northern great plains during the last two millennia abstract reconstructions of lake water salinity at decadal resolution for the last 2000 yr are compared among three lakes in north dakota to infer regional patterns of drought the intersite comparisons are used to distinguish local variation in climate or hydrology from regional patterns of change at one lake diatom inferred salinity and lake water mg ca inferred from ostracode shell chemistry are coherent both in terms of direction and magnitude of change indicating that each is a robust technique for reconstructing lake water chemistry the data show that the last 2000 yr have been characterized by frequent shifts between high and low salinity suggesting shifts between dry and moist periods long intervals of high salinity suggest periods of multiple decades when droughts were intense and frequent thus indicating times when drought was more persistent than in the 20th century both the medieval period and little ice age were hydrologically complex and there is no clear evidence to suggest that either interval was coherent or unusual in effective moisture relative to long term patterns differences among the three sites may be attributed to variation in local hydrology and these differences emphasize the need for multiple sites in deriving regional climate interpretations from paleoecological data

computerized seismic intensities of recently felt earthquakes in israel the traditional process of evaluating seismic intensities from questionnaires is laborious and very subjective an attempt here is made to introduce computerized processing of questionnaires this is made possible by modifying the questionnaire forms and developing a computer program that performs the evaluation in a rather objective manner the prime assumption behind this procedure is that observed intensities in a certain location are normally distributed this new approach has been tested successfully with recently obtained data on earthquakes in israel yielding evaluated intensities and isoseismal maps for earthquakes in the jordan valley january 13 1982 lebanon june 3 1983 the gulf of suez june 12 1983 the jezreel valley august 24 1984 and near jericho january 25 1985

statistical analysis of an earthquake induced landslide distribution the 1989 loma prieta california event the 1989 loma prieta california earthquake moment magnitude m 6 9 generated landslides throughout an area of about 15 000 km2 in central california most of these landslides occurred in an area of about 2000 km2 in the mountainous terrain around the epicenter where they were mapped during field investigations immediately following the earthquake the distribution of these landslides is investigated statistically using regression and one way analysis of variance anova techniques to determine how the occurrence of landslides correlates with distance from the earthquake source slope steepness and rock type the landslide concentration defined as the number of landslide sources per unit area has a strong inverse correlation with distance from the earthquake source and a strong positive correlation with slope steepness the landslide concentration differs substantially among the various geologic units in the area the differences correlate to some degree with differences in lithology and degree of induration but this correlation is less clear suggesting a more complex relationship between landslide occurrence and rock properties

intercomparison of simulated global vegetation distributions in response to 6 kyr bp orbital forcing abstract the response of ten atmospheric general circulation models to orbital forcing at 6 kyr bp has been investigated using the biome model which predicts equilibrium vegetation distribution as a diagnostic several common features emerge a reduced tropical rain forest as a consequence of increased aridity in the equatorial zone b expansion of moisture demanding vegetation in the old world subtropics as a consequence of the expansion of the afro asian monsoon c an increase in warm grass shrub in the northern hemisphere continental interiors in response to warming and enhanced aridity and d a northward shift in the tundra forest boundary in response to a warmer growing season at high northern latitudes these broadscale features are consistent from model to model but there are differences in their expression at a regional scale vegetation changes associated with monsoon enhancement and high latitude summer warming are consistent with palaeoenvironmental observations but the simulated sh

dynamic stability analysis of jointed rock slopes using the dda method king herod s palace masada israel abstract a dynamic two dimensional stability analysis of a highly discontinuous rock slope is demonstrated in this paper the studied rock slope is the upper terrace of king herod s palace in masada situated on the western margins of the seismically active dead sea rift the slope consists of sub horizontally bedded and sub vertically jointed stiff dolomite blocks the dynamic deformation of the slope is calculated using a fully dynamic version of dda in which time dependent acceleration is used as input the analytically determined failure modes of critical keyblocks in the jointed rock slope are clearly predicted by dda at the end of the dynamic calculation it is found however that for realistic displacement estimates some amount of energy dissipation must be introduced into the otherwise fully elastic un damped dda formulation comparison of predicted damage with actual slope performance over a historic time span of 2000 years allows us to conclude that introduction of 2 kinetic damping should suffice for realistic damage predictions this conclusion is in agreement with recent results of tsesarsky et al in y h hatzor ed stability of rock structures proceedings of the fifth international conference of analysis of discontinuous deformation balkema publishers lisse 2002 pp 195 203 who compared displacements of a single block on an inclined plane subjected to dynamic loading obtained by dda and by shaking table experiments using dynamic dda it is shown that introduction of a simple rock bolting pattern completely stabilizes the slope

interactions of climate and fire at two sites in the northern great plains usa abstract the relationship of fire and climate in explaining the origin and maintenance of the grasslands of the northern great plains has long been of interest i examined the hypothesis that burning was more frequent during wet years using charcoal to reconstruct fire histories near coldwater lake in southcentral nd and rice lake in northcentral nd and published records of ostracod mg ca ratios as a proxy for climate at these same two sites over the past 10 000 years charcoal influx rates for coldwater 0 04 5 68 mm 2 cm 2 year 1 greatly exceeded influx rates for rice 2 cm 2 year 1 both sites showed strong significant periodicities of 1500 1800 800 900 and 130 140 years but charcoal maxima and minima were only similar at 4200 cal years bp charcoal influx during the past 2000 years also revealed strong periodicities of between 310 400 and 140 years at both sites comparison of smoothed charcoal influxes and ostracod mg ca ratios suggests that both proxies are responding to changes in climate when smoothed with a 320 400 year window increases in charcoal influx typically preceded rises in ostracod mg ca ratio by 50 100 years and further smoothing 140 year window of the residuals suggested a variable relationship between mg ca ratios and charcoal influx these results do not clearly support or reject the fuel limitation hypothesis and this lack of clear support may result from a climate driven shifts in the mix of c 3 and c 4 grasses resulting in maximum productivity at intermediate moisture levels b possibly different responses of charcoal and mg ca ratios to summer vs winter precipitation or c ground water driven lags in the response of mg ca ratios to shifts in climate comparison of the results from this study with other studies suggests that links between fire and fuels at finer time scales 0 100 years may be broadly constrained by longer term 500 2000 years patterns of climate in the northern great plains

seismic activity along fault branches of the dead sea jordan transform system the carmel tirtza fault system abstract about 550 earthquakes 1 0 m l 5 3 along the carmel tirtza fault a branching fault of the jordandashdead sea transform system recorded by the israel seismograph network isn between 1984 and 1994 were analyzed the seismicity pattern reveals significant activity often confined to known surface traces of active faults or within local grabens earthquake clusters are also observed the seismicity pattern within the mediterranean seems more diffuse possibly due to observational inaccuracies and insufficient knowledge of how the carmel tirtza fault system extends towards the northwest the seismicity along the carmel tirtza fault system since the beginning of this century is characterized by a b value of about 0 9 for 15 events with 3 1 m l 5 3 we found seismic moment estimates m 0 of 0 7 10 14 m 0 10 17 nm and brune stress drop estimates between 0 9 and 16 4 mpa these characteristics are comparable to those for events occurring on the main dead sea jordan transform fault ten individual earthquake focal mechanisms and three joint focal mechanisms for earthquake clusters have been obtained towards the northeastern part of the carmel tirtza fault system a left lateral motion seems to dominate while the seismicity pattern and the focal mechanism solutions near the branching of the carmel tirtza fault and the dead sea jordan rift suggest the present day existence of a complicated tectonic regime stress inversion assuming one stress tensor for the whole region indicates nne ssw extension and wnw ese compression

earthquake induced landslides in central america central america is a region of high seismic activity and the impact of destructive earthquakes is often aggravated by the triggering of landslides data are presented for earthquake triggered landslides in the region and their characteristics are compared with global relationships between the area of landsliding and earthquake magnitude we find that the areas affected by landslides are similar to other parts of the world but in certain parts of central america the numbers of slides are disproportionate for the size of the earthquakes we also find that there are important differences between the characteristics of landslides in different parts of the central american isthmus soil falls and slides in steep slopes in volcanic soils predominate in guatemala and el salvador whereas extensive translational slides in lateritic soils on large slopes are the principal hazard in costa rica and panama methods for assessing landslide hazards considering both rainfall and earthquakes as triggering mechanisms developed in costa rica appear not to be suitable for direct application in the northern countries of the isthmus for which modified approaches are required

holocene precipitation seasonality captured by a dual hydrogen and oxygen isotope approach at steel lake minnesota abstract middle holocene 8 to 4 ka bp warmth and aridity are well recorded in sediment archives from midcontinental north america however neither the climatic driver nor the seasonal character of precipitation during this period is well understood because of the limitations of available proxy indicators for example an important challenge is to distinguish among the interacting effects of evaporation temperature or precipitation seasonality in existing 18 o records from the region here we combine hydrogen isotopes of palmitic acid and oxygen isotopes of carbonate to derive lake water isotopic values during the holocene at steel lake in north central minnesota in combination these data enable us to separate variations in evaporation from variations in the isotopic composition of input waters to lake variations in evaporation are used as a proxy for aridity and lake water input isotopic values are used as a proxy for the isotopic values of meteoric precipitation our results suggest that lake water input isotopic values were more negative during the middle holocene than at present to test whether these more negative values are related to temperature or precipitation seasonality we compare pollen inferred temperatures and the expected isotopic value of precipitation resulting from these temperatures to the reconstructed precipitation isotopic values results suggest that middle holocene warmth and aridity were associated with increased evaporation rates and decreased summer precipitation these inferences are consistent with climate simulations that highlight the role of seasonal insolation and sea surface temperatures in driving variations in precipitation seasonality during the holocene results also suggest that changes in holocene precipitation seasonality may have influenced the expansion of the prairie forest border in minnesota as well as regional variations in grassland community composition this study demonstrates the efficacy of the dual hydrogen and oxygen isotope approach for distinguishing changes in evaporation and precipitation seasonality in the paleolimnological record

sources of the large a d 1202 and 1759 near east earthquakes the sources of the may 1202 and november 1759 m 7 5 near east earthquakes remain controversial because their macroseismal areas coincide straddling subparallel active faults in the lebanese restraining bend paleoseismic trenching in the yammouneh basin yields unambiguous evidence both for slip on the yammou neh fault in the twelfth thirteenth centuries and for the lack of a posterior event this conclusion is supported by comparing the freshest visible fault scarps which imply more recent slip on the r chaiya serghaya system than on the yammouneh fault our results suggest that the recurrence of an a d 1202 type earthquake might be due this century as part of a sequence similar to that of a d 1033 1202 possibly heralded by the occurrence of the 1995 mw 7 3 aqaba earthquake the seismic behavior of the levant fault might thus be characterized by millennial periods of quiescence separated by clusters of large earthquakes

the influence of seasonal precipitation and temperature regimes on lake levels in the northeastern united states during the holocene abstract ams dated sediment cores combined with ground penetrating radar profiles from two lakes in southeastern massachusetts demonstrate that regional water levels rose and fell multiple times during the holocene when the known climatic controls i e ice extent and insolation underwent unidirectional changes the lakes were lowest between 10 000 and 9000 and between 5500 and 3000 cal yr b p using a heuristic moisture budget model we explore the hypothesis that changes in seasonal precipitation regimes driven by monotonic trends in ice extent and insolation plausibly explain the multiple lake level changes simulated lake levels resulting from low summer precipitation rates match observed low lake levels of 10 000 9000 cal yr b p whereas a model experiment that simply shifts the seasonality of the modern massachusetts precipitation regime i e moving the peak monthly precipitation from winter to summer produces levels that are 2 m lower than today as observed for 5500 3000 cal yr b p the influence of the laurentide ice sheet could explain dry summers before ca 8000 cal yr b p a later shift from a summer wet to a winter wet moisture balance regime could have resulted from insolation driven changes in the influence of the bermuda subtropical high temperature changes probably further modified lake levels by affecting snowmelt and transpiration