wind control of storm triggered shallow landslides 1 heavy rainstorms are a major control of shallow landsliding in mountainous areas the influence of three dimensional 3 d variability of precipitation is analyzed by coupling a fine resolution atmospheric model rams with a fine resolution topographic model dem to represent the 3 d precipitation flux generating the catastrophic flood that occurred in versilia central italy on 19 june 1996 matching of this flux with the observed scars and debris shows that 92 of the mass movements occurred where the normalized precipitation flux exceeds 0 80 and less then 2 where this is null these results give an insight of the detected role of exposure in explaining the spatial variability of observed landslides as emerging from multivariate statistical analysis the interaction of the wind driven precipitation field with topography is an important control of shallow landslides triggered by convective storms in upland catchments

volcaniclastic debris avalanche on motomachi area of izu oshima japan triggered by severe storm phenomenon and mechanisms abstract heavy rainfall and strong wind associated with typhoon wipha hit izu oshima island japan and triggered catastrophic landslides on the western slope of oshima volcano on 16 october 2013 these landslides were shallow but large in scale and the displaced landslide materials were characterized by rapid and long runout movement a massive landslide resulted in 36 people dead and 3 missing with 46 buildings being completely destroyed in the downstream area of motomachi district to understand the initiation and movement of these shallow landslides we surveyed the landslide area and found that in addition to heavy rainfall strong wind may also have played a key role in increasing the instability of the slopes we took samples from the source areas and examined their static and dynamic shear behaviors under naturally drained or undrained conditions test results showed that high pore water pressure can be built up and maintained within the displaced landslide material and increase landslide mobility even though the thickness of displaced landslide materials is 0 7 1 2 m this may then give a rational explanation on the fluidization process of the displaced landslide materials we also examined the windthrow features of trees subjected to different wind speed through monitoring the ground motion by seismometer and portable anemometer and then performed cyclic shear tests on the materials laying above the sliding surface the test results suggest that the windthrow may have promoted the buildup of excess pore water pressure within the saturated soil layer and thus favoured the occurrence of slope failure therefore it is suggested that in the prediction of shallow landslides on forested slopes subjected to heavy storm both the effects of rainfall and strong wind should be taken into account

the rift to break up evolution of the gulf of aden insights from 3d numerical lithospheric scale modelling abstract the gulf of aden provides an ideal setting to study oblique rifting since numerous structural data are available onshore and offshore recent surveys showed that the spatio temporal evolution of the gulf of aden rift system is dominated by three fault orientations displacement orthogonal wsw rift parallel wnw and an intermediate e w trend the oldest parts of the rift that are exposed onshore feature displacement orthogonal and intermediate directions whereas the subsequently active necking zone involves mainly rift parallel faults the final rift phase recorded at the distal margin is characterised by displacement orthogonal and intermediate fault orientations we investigate the evolution of the gulf of aden from rift initiation to break up by means of 3d numerical experiments on lithospheric scale we apply the finite element model slim3d which includes realistic elasto visco plastic rheology and a free surface despite recent advances 3d numerical experiments still require relatively coarse resolution so that individual faults are poorly resolved we address this issue by proposing a simple post processing method that uses the surface stress tensor to evaluate stress regime extensional strike slip compressional and preferred fault azimuth the described method is applicable to any geodynamic model and easy to introduce our model reproduces the observed fault pattern of the gulf of aden and illustrates how multiple fault directions arise from the interaction of local and far field tectonic stresses in an evolving rift system the numerical simulations robustly feature intermediate faults during the initial rift phase followed by rift parallel normal faulting at the rift flanks and strike slip faults in the central part of the rift system upon break up displacement orthogonal as well as intermediate faults occur this study corroborates and extends findings from previous analogue experiments of oblique rifting on lithospheric scale and allows new insights in the timing of fault successions of the gulf of aden and continental rifts in general

unsupervised seismic facies analysis via deep convolutional autoencoders abstractone of the most important goals of seismic stratigraphy studies is to interpret the elements of the seismic facies with respect to the geologic environment prestack seismic data carry rich information that can help us get higher resolution and more accurate facies maps therefore it is promising to use prestack seismic data for the seismic facies recognition task however because each identified object changes from the poststack trace vectors to a prestack trace matrix effective feature extraction becomes more challenging we have developed a novel data driven offset temporal feature extraction approach using the deep convolutional autoencoder dcae as an unsupervised deep learning method dcae learns nonlinear discriminant and invariant features from unlabeled data then seismic facies analysis can be accomplished through the use of conventional classification or clustering techniques e g k means or self organizing maps using a physical model and field prestack seismic surveys we c

bipolar modulation of millennial scale west african monsoon variability during the last glacial 75 000 25 000 years ago abstract time series of planktonic foraminiferal 18 o and ba ca based sea surface salinity sss estimates from the eastern gulf of guinea eastern equatorial atlantic indicate changes in runoff that reflect variability of spatially integrated precipitation over the equatorial west african monsoon area millennial scale and recurring runoff induced sss rises and declines in the range of 1 5 and 2 psu practical salinity unit reveal rapid oscillation between dry and wet phases the timing of decreased runoff coincides with oscillation of dansgaard oeschger stadials and heinrich events the most severe monsoon weakening correlating with the latter 18 o residual time series derived by removing temperature ice volume and salinity components from the foraminiferal 18 o record suggest that weak monsoon precipitation during stadials and heinrich events was accompanied by significant shifts in 18 o precipitation toward higher values furthermore 18 o analysis of individual tests of globigerinoides ruber pink 18 o indiv during dry episodes show a total range and variance of 2 3 and 0 25 n 121 indicating that seasonal contrast of sea surface freshening was significantly reduced during heinrich events relative to that of interstadials which show a total range and variance of 3 35 and 0 42 n 140 on the basis of the timing and magnitude of changes in the monsoon record it is evident that northern high latitude climate was the most dominant control on the west african monsoon variability however a southern high latitude imprint is also apparent during some episodes this centennially resolved climate record demonstrates that the equatorial west african monsoon experienced profound changes in the amount seasonal contrast and moisture source of summer monsoon precipitation during the last glacial the most plausible mechanism is a large scale southward displacement of the monsoon trough most likely initiated by large scale reorganization of atmospheric circulation in response to northern high cooling and southern high latitude warmth

lake agassiz outburst age and routing by labrador current and the 8 2 cal ka cold event abstract catastrophic drainage of glacial lake agassiz impounded by the laurentide ice sheet lis into hudson bay and strait is widely thought to have caused the 8 2 cal ka cold event though the path of its drainage in the north atlantic is poorly known analysis and compilation of 10 sediment cores from 8 sites distributed on the eastern canadian continental shelf and upper slope south of hudson strait revealed distinct beds with elevated detrital carbonate dc concentrations known by their distinct composition to originate from erosion of carbonate bedrock and carbonate rich glacial sediments in the hudson bay hudson strait region at all but one site radiocarbon ages bracketing and within the thickest and most widespread of these beds are coeval with the age constraints for the agassiz floods in hudson strait and southeastern hudson bay the dc distribution and concentration of this bed are consistent with southward transport in the labrador current transfer function analysis of dinoflagellate assemblage data from cores on the central labrador shelf in hudson bay and on the northeast newfoundland shelf reveal that early holocene seasonal ice cover was 5 6 months longer than at present requiring the application of a 200 year reduction to the radiocarbon age constraints on the lake agassiz outburst floods the age of the floods is reduced to about 8 33 cal ka 7 5 14 c ka from the previous determination of 8 47 cal ka 7 7 14 c ka with a similar reduction in their error ranges to 8 04 8 49 cal ka from 8 16 8 74 cal ka based on present current routing the agassiz floodwaters and icebergs are inferred to have travelled south in the labrador current and to have possibly become incorporated into the north atlantic current and transported to the nordic seas there the freshwater additions would have lessened deepwater production with a concomitant reduction in northward heat transport in the upper limb of the atlantic meridional overturning circulation thereby contributing to the 8 2 cal ka cold event variation in the calcite and dolomite content of the agassiz dc bed two salinity reductions during agassiz bed deposition and low level shorelines of lakes agassiz and ojibway suggest that more than one outburst was delivered during the final agassiz drainage the 8 2 cal ka cold event registered in greenland was coeval with a second or later flood which possibly accompanied the final collapse of the lis in hudson bay

monitoring of a quasi stationary eddy in the bay of biscay by means of satellite in situ and model results the presence of a quasi stationary anticyclonic eddy within the southeastern bay of biscay centred around 44 30 n 4 w has been reported on various occasions in the bibliography the analysis made in this study for the period 2003 2010 by using in situ and remote sensing measurements and model results shows that this mesoscale coherent structure is present almost every year from the end of winter beginning of spring to the beginning of fall during this period it remains in an area limited to the east by the landes plateau to the west by le danois bank and torrelavega canyon and to the northwest by the jovellanos seamount all the observations and analysis made in this contribution suggest that this structure is generated between capbreton and torrelavega canyons detailed monitoring from in situ and remote sensing data of an anticyclonic quasi stationary eddy in 2008 shows the origin of this structure from a warm water current located around 43 42 n 3 30 w in mid january this coherent structure is monitored until august around the same area where it has a marked influence on the sea level anomaly sea surface temperature and surface chlorophyll a concentration an eddy tracking method applied to the outputs of a numerical model shows that the model is able to reproduce this type of eddy with similar 2d characteristics and lifetimes to that suggested by the observations and previous works this is the case for instance of the simulated may04 eddy which was generated in may 2004 around torrelavega canyon and remained quasi stationary in the area for 4 months the diameter of this eddy ranged from 40 to 60 km its azimuthal velocity was less than 20 cm s 1 its vertical extension reached 3000 3500 m depth during april and may and it was observed to interact with other coherent structures

potential risks when using seismic attributes as predictors of reservoir properties the advance of our ability to generate seismic attributes and the growing emphasis on production geophysics has led to the widespread use of seismic attributes as predictors of reservoir properties in many cases we can show using seismic modeling or rock physics a physically justifiable relationship between a seismic attribute and the reservoir property of interest when this is true we are able to greatly reduce the uncertainty of interwell predictions of reservoir properties

modelling sea level data from china and malay thailand to estimate holocene ice volume equivalent sea level change abstract this study presents a new model of holocene ice volume equivalent sea level esl extending a previously published global ice sheet model bassett et al 2005 which was unconstrained from 10 kyr bp to present this new model was developed by comparing relative sea level rsl predictions from a glacial isostatic adjustment gia model to a suite of holocene sea level index points from china and malay thailand three consistent data model misfits were found using the bassett et al 2005 model an over prediction in the height of maximum sea level the timing of this maximum and the temporal variation of sea level from the time of the highstand to present the data model misfits were examined for a large suite of esl scenarios and a range of earth model parameters to determine an optimum model of holocene esl this model is characterised by a slowdown in melting at 7 kyr bp associated with the final deglaciation of the laurentide ice sheet followed by a continued rise in esl until 1 kyr bp of 5 8 m associated with melting from the antarctic ice sheet it was not possible to identify an earth viscosity model that provided good fits for both regions with the china data preferring viscosity values in the upper mantle of less than 1 5 10 20 pa s and the malay thailand data preferring greater values we suggest that this inference of a very weak upper mantle for the china data originates from the nearby subduction zone and hainan plume the low viscosity values may also account for the lack of a well defined highstand at the china sites

unsupervised seismic facies analysis using wavelet transform and self organizing maps unsupervised seismic facies analysis provides an effective way to estimate reservoir properties by combining different seismic attributes through pattern recognition algorithms however without consistent geological information parameters such as the number of facies and even the input seismic attributes are usually chosen in an empirical way in this context we propose two new semiautomatic alternative methods in the first one we use the clustering of the kohonen self organizing maps soms as a new way to build seismic facies maps and to estimate the number of seismic facies in the second method we use wavelet transforms to identify seismic trace singularities in each geologically oriented segment and then we build the seismic facies map using the clustering of the som we tested both methods using synthetic and real seismic data from the namorado deepwater giant oilfield in campos basin offshore brazil the results confirm that we can estimate the appropriate number of seismic facies through the clustering of the som we also showed that we can improve the seismic facies analysis by using trace singularities detected by the wavelet transform technique this workflow presents the advantage of being less sensitive to horizon interpretation errors thus resulting in an improved seismic facies analysis

impact airblast triggers dust avalanches on mars visible images from the mars reconnaissance orbiter have revealed more than 200 new impact sites on mars almost all in dust mantled regions containing 1 50 m diameter craters often in clusters we count approximately 65 000 small scale slope streaks within 2 to 3 km of one such cluster and categorize them into four morphologically distinct types here we show that these slope streaks interpreted as dust avalanches are triggered by the impact event but surprisingly are not due to seismic shaking instead the dust avalanches are due to airblasts created by the supersonic meteor s before impact sixteen of the new impact sites are associated with high areal densities of dust avalanches the observed dust avalanche frequency suggests that impact generated airblasts constitute a locally important and previously unrecognized process for inducing slope degradation on mars

a drifting gps buoy for retrieving effective riverbed bathymetry summary spatially distributed riverbed bathymetry information are rarely available but mandatory for accurate hydrodynamic modeling this study aims at evaluating the potential of the global navigation satellite system gnss like for instance global positioning system gps for retrieving such data drifting buoys equipped with navigation systems such as gps enable the quasi continuous measurement of water surface elevation from virtually any point in the world the present study investigates the potential of assimilating gnss derived water surface elevation measurements into hydraulic models in order to retrieve effective riverbed bathymetry first tests with a gps dual frequency receiver show that the root mean squared error rmse on the elevation measurement equals 30 cm provided that a differential post processing is performed next synthetic observations of a drifting buoy were generated assuming a 30 cm average error of water surface elevation wse measurements by assimilating the synthetic observation into a 1d hydrodynamic model we show that the riverbed bathymetry can be retrieved with an accuracy of 36 cm moreover the wses simulated by the hydrodynamic model using the retrieved bathymetry are in good agreement with the synthetic truth exhibiting an rmse of 27 cm

ecohydrological evolution of lake naivasha central rift valley kenya during the past 1650 years as recorded by ostracod assemblages and stable isotope geochemistry abstract lake naivasha central rift valley kenya is regionally unique in having accumulated a continuous sediment record of climate driven palaeohydrological change over the past 1650 years attesting to dramatic shifts between freshwater high stands and either fresh or saline low stands this study employs fossil ostracod assemblages and stable isotope 18o and 13c signatures to disclose the lake s ecohydrological history and explain the evolving non linearity between lake level and salinity the original age model and lithology based lake level reconstruction are revised and the diatom inferred salinity reconstruction is expanded to the lower pre 770 ce part of the record the stable isotope time series showed limited coherence with the other proxies probably due to complexities related to hydrological connections between different surface and groundwater components shifting through time ostracod palaeoecological data indicate that between ca 350 and 1200 ce the system often veered towards hydrological closure with frequent and high amplitude shifts in lake level and salinity preventing long term establishment of wetland vegetation low lake level and saline conditions dominated between ca 900 and 1200 ce after that time and particularly since the onset of more permanent malewa river inflow ca 1430 ce hydrologically open conditions prevailed salinity shifts exhibited lower amplitude and frequency promoting the expansion of wetland vegetation and associated biota including benthivorous fish with lake water balance strongly influenced by variation in river inflow high amplitude lake level fluctuations continued throughout the freshwater phase of the past 600 years notably creating a pronounced high stand dated to ca 1600 1780 ce and the well documented extreme low stand of the early 1800s

chronology of holocene glaciation central brooks range alaska the central brooks range was glacierized in the highest north facing cirques during late middle to late holocene neoglacial time this neoglaciation involved at least 5 major cirque glacier expansions of similar magnitude as based on lichenometric mapping of more than 50 glaciers and radiocarbon dates directly associated with 5 moraines initial stabilization of debris covered glaciers took place by early holocene time but evidently no moraines formed during this interval few morainal ridges are preserved that date from the older expansions but they have been lichenometrically dated 20 age reliability to 3 separate intervals 4400 3500 and 2900 yr b p twelve morainal complexes have ridges indicative of glacial advance that lichenometrically date at 1800 500 yr b p relict lichens that are now emerging undisturbed from beneath a receding glacier toe imply that this time was one of prolonged recession in at least some parts of the brooks range however radiocarbon analysis of dead moss at this same site dates a subsequent neoglacial advance across the cirque floor at 1120 180 yr b p our data suggest that for the past 1 100 yr cirque glaciers have been continuously in more extended positions than they are today during this glaciologically favorable interval the last two major advances occurred at 800 150 and 390 90 yr b p a d 1410 1600 glaciers across the central brooks range stayed close to their maxima until a d 1640 1750 historical photographs and lichenometry show that retreat was most rapid after a d 1870 and decelerated after the mid 1900s recession from this most recent neoglacial maximum has amounted to 150 700 m and continues at present the cirque glacier advances were accompanied by equilibrium line altitude ela depressions of 100 to 200 m below levels maintained in the late 1970s environmental lapse rate estimates and 1977 1981 glaciologic meteorologic measurements suggest that summer air temperatures accompanying neoglacial maxima were respectively 1 c or 3 to 4 c cooler than those of the late 1970s across the central brooks range the neoglacial maxima elas rise northeastward and northward from 2 to 5 m km 1

seismic attribute technology for reservoir forecasting and monitoring during the 1970s and 1980s the seismic attributes most used in petroleum exploration were amplitude based instantaneous attributes however in the 1990s seismic attribute technology has dramatically advanced in several directions techniques now range from single trace instantaneous event attribute computations to more complex multitrace windowed seismic event attribute extractions to the generation of seismic attribute volumes applications run from simple amplitude anomaly detection to monitoring fluid front movement over time

vertical and temporal variability in concentration and distribution of thaumarchaeotal tetraether lipids in lake superior and the implications for the application of the tex86 temperature proxy abstract this study investigated the vertical and temporal distribution of thaumarchaeota derived core isoprenoid glycerol dialkyl glycerol tetraether gdgt lipids through sampling and analysis of both suspended particulate matter from the water column at different times in the annual cycle and a 3 year long record of settling particles in two sediment traps at different depths at an open lake location in lake superior results from these analyses suggest that thaumarchaeota were present throughout the water column during times of overturning but mainly resided below the depth of the thermocline 20 40 m during the period of thermal stratification fluxes of thaumarchaeotal produced gdgts were highly periodic and mainly occurred during two periods of the annual cycle winter and late spring early summer a covariance of both branched and isoprenoid gdgt fluxes with the mass accumulation flux combined with the observation that those periods of maximum fluxes were associated with increased bit index values however suggest that these two periods of elevated fluxes may be related to an influx of resuspended particles transported from shallower near shore regions of lake superior during all sampling periods tex 86 inferred temperatures from spm were in good agreement with in situ water temperatures of the depths at which the spm was sampled the observed range of tex 86 inferred temperatures in 3 years of settling particles is relatively small and does not show significantly higher inferred temperatures during the thermally stratified period indicating that the sedimentary tex 86 signal during the summer thermally stratified period mainly originated from depths below the relatively shallow thermocline additionally tex 86 values during the winter period of increased fluxes did not capture the decrease in water temperatures observed throughout the water column during this period and thus may be a further indication that the thaumarchaeotal lipid flux was the result of sediment focusing flux weighted tex 86 inferred temperatures from both sediment traps were in good agreement with tex 86 temperatures from surface sediments from the same location in lake superior both flux weighted tex 86 temperatures from the sediment traps and average tex 86 temperatures from surface sediments were similar to averaged measured water temperatures at below 40 m depth within the error of the lacustrine tex 86 calibration based on the observed depths of thaumarchaeota in the water column tex 86 values in sediments of lake superior likely reflect a combination of mixed season and sub thermocline temperatures this is effectively the same as the annual averaged water temperature observed at depths below 40 m in lake superior thus trends in tex 86 inferred temperatures in sediment records of lake superior and similar lakes are likely to reflect subsurface temperature variability rather than that of surface temperatures

on the fidelity of shell derived δ18oseawater estimates article i nfo 18 oseawater a robustproxyforsurfacesalinity we assessthe fidelity of shell derived 18 oseawater estimates for the surface dwelling foraminifer globigerinoides ruber white using an atlantic meridional coretop transect spanning basin scale temperature and salinity gradients shell derived and observed 18 oseawater values are well correlated r 2 0 77 but a large systematic bias is observed shell mg ca ratios are significantly elevated above values expected from observed and isotopic calcification temperatures in the saline subtropical gyres of both hemispheres this temperature independent shell mg ca ratio variability termed excess mg ca i s highly correlated with surface salinity r 2 0 77 and the observed salinity dependence 27 4 is much higher than indicated by culture studies 6 2 our coretop data are used to develop new atlantic basin temperature and salinity calibration equations that are accurate 1 1 c and 0 20 respectively precise r 2 0 82 and 0 81 respectively and verifiable using previously published data these results are valid for the relatively high salinities of the subtropical atlantic 35 5 37 3 we discover that inclusion of other published data from lower salinity regions b35 indicates little or no excess mg ca taken together these results point to a strongly non linear positive salinity effect on shell mg ca ratios that significantly affects the accuracy of sst and 18

the influence of the geological and geomorphological settings on shallow landslides an example in a temperate climate environment the june 19 1996 event in northwestern tuscany italy on june 19 1996 an extremely heavy rainstorm hit a restricted area in the apuan alps northwestern tuscany italy its max intensity concentrated over an area of about 150 km2 astride the apuan chain where 474 mm was recorded in about 12 h 21 of the mean annual precipitation with an intensity up to 158 mm h the storm caused floods and hundreds of landslides and debris flows which produced huge damage hundreds of millions of euros partially destroyed villages and killed 14 people this paper reports the results obtained from a detailed field survey and aerial view interpretation in the most severely involved area 647 main landslides were investigated mapped and related to the geologic geomorphic and vegetational factors of the source areas this was in order to define the influence of these factors and contribute to an evaluation of the landslide hazard in the study area an assessment was also made of the total area and volume of material mobilised by landsliding the study area about 46 km2 wide includes three typically mountainous basins characterised by narrow deep cut valleys and steep slopes where many rock types outcrop most of the landslides were shallow and linear referable to complex earth and debris translational slide which quickly developed into flow soil slip debris flow usually they involved colluvium and started in hollows underlain by metamorphic rock metasandstone and phyllite often dipping downslope therefore bedrock lithology and impermeability appeared to be important factors in the localisation of the landslide phenomena the investigation of the geomorphic and land use features in the source areas also frequently highlighted a rectilinear profile of the slope a high slope gradient 31 45 and dense chestnut wood cover in the area about 985 000 m2 2 1 of 46 km2 was affected by landsliding and about 700 000 m2 of this area was covered by chestnut forest the landslides removed about 7000 trees the volume of mobilised material was about 1 360 000 m3 about 220 000 m3 remained on the slopes while the rest poured into the streams in addition about 945 000 m3 was mobilised by the torrential erosion in the riverbeds

seismic facies classification and identification by competitive neural networks we present an approach based on competitive neural networks for the classification and identification of reservoir facies from seismic data this approach can be adapted to perform either classification of the seismic facies based entirely on the characteristics of the seismic response without requiring the use of any well information or automatic identification and labeling of the facies where well information is available the former is of prime use for oil prospecting in new regions where few or no wells have been drilled whereas the latter is most useful in development fields where the information gained at the wells can be conveniently extended to the interwell regions cross validation tests on synthetic and real seismic data demonstrated that the method can be an effective means of mapping the reservoir heterogeneity for synthetic data the output of the method showed considerable agreement with the actual geologic model used to generate the seismic data for the real data application the predicted facies accurately matched those observed at the wells moreover the resulting map corroborates our existing understanding of the reservoir and shows substantial similarity to the low frequency geologic model constructed by interpolating the well information while adding significant detail and enhanced resolution to that model

on the accuracy of lichenometric dates an assessment based on the little ice age moraine sequence of nigardsbreen southern norway families of lichenometric dating curves are constructed using four historically dated moraine ridges on the glacier foreland of nigardsbreen jostedalsbreen ice cap southern norway a further 20 little ice age moraine ridges are dated in terms of median predicted dates derived from the families of curves four approaches are used to assess the accuracy of the median predicted dates 1 the extent to which the dates form a temporal sequence 2 the extent to which they agree with local independent evidence of glacier variations 3 the extent to which dates agree when the moraine sequences on the two sides of the glacier foreland are dated separately and 4 the extent to which they agree when section rhizocarpon is differentiated from lichens of the rhizocarpon subgenus as a whole it is concluded that under conditions favourable for lichenometric dating median predicted dates have attained an accuracy of 10 on the little ice age timescale realistic error limits are considered to be of the o

experimental generation of volcanic pseudotachylytes constraining rheology volcanic systems are highly dynamic environments that comprise rocks and magmas which in the process of strain localisation e g in catastrophic flank collapse or dome building events are candidate materials for the occurrence of frictional melting and the formation of pseudotachylytes we evaluate the frictional behaviour of a plagioclase two pyroxene and glass bearing andesite and introduce an approach to constrain the rheology of frictional melts frictional slip at a rate of 1 3 m s under an axial stress of 1 5 mpa induces heating at a rate approximating 130 c per meter of slip and frictional melting of the andesite occurs at 1000 c which corresponds to a peak in shear stress with continuing displacement the shear stress decreases by 25 from the peak strength and stabilises while the temperature equilibrates to 1230 1290 c the shear stress for the system is congruent with a non arrhenian temperature dependent frictional melt rheology exhibiting a non newtonian viscosity evolving from approximately 104 2 to 103 4 pa s post experiment analysis show a gradation from 1 the host rock to 2 an extraordinary zone of unmelted yet viscously deformed material to 3 a thin outer region of chemically heterogeneous protomelts and to 4 an inner region of chemically homogeneous frictionally generated modified melt in the core of the slip zone we discuss the role and identification of frictional melting in volcanic systems and the implication of viscous remobilisation of magmatic plugs during frictional slip of glass bearing volcanic materials

seismic attributes a historical perspective a seismic attribute is a quantitative measure of a seismic characteristic of interest analysis of attributes has been integral to reflection seismic interpretation since the 1930s when geophysicists started to pick traveltimes to coherent reflections on seismic field records there are now more than 50 distinct seismic attributes calculated from seismic data and applied to the interpretation of geologic structure stratigraphy and rock pore fluid properties the evolution of seismic attributes is closely linked to advances in computer technology as examples the advent of digital recording in the 1960s produced improved measurements of seismic amplitude and pointed out the correlation between hydrocarbon pore fluids and strong amplitudes bright spots the introduction of color printers in the early 1970s allowed color displays of reflection strength frequency phase and interval velocity to be overlain routinely on black and white seismic records interpretation workstations in the 1980s provided

seismic facies analysis based on speech recognition feature parameters abstractseismic facies analysis plays an important role in seismic stratigraphy seismic attributes have been widely applied to seismic facies analysis one of the most important steps is to optimize the most sensitive attributes with regard to reservoir characteristics using different attribute combinations in multidimensional analyses will yield different solutions acoustic waves and seismic waves propagating in an elastic medium follow the same law of physics the generation process of a speech signal based on the acoustic model is similar to the seismic data of the convolution model we have developed the mel frequency cepstrum coefficients mfccs which have been successfully applied in speech recognition as feature parameters for seismic facies analysis information about the wavelet and reflection coefficients is well separated in these cepstrum domain parameters specifically information about the wavelet mainly appears in the low domain part and information about the reflection coefficients

speleothem records decadal to multidecadal hydroclimate variations in southwestern morocco during the last millennium abstract this study presents the first well dated high resolution stable isotope 18 o and 13 c and trace element mg and sr speleothem records from southwestern morocco covering the last 1000 yrs our records reveal substantial decadal to multidecadal swings between dry and humid periods consistent with regional paleorecords with prevailing dry conditions during the medieval climate anomaly mca wetter conditions during the second part of the little ice age lia and a trend towards dry conditions during the current warm period these coherent regional climate signals suggest common climate controls statistical analyses indicate that the climate of southwestern morocco remained under the combined influence of both the north atlantic oscillation nao and the atlantic multidecadal oscillation amo over the last millennium interestingly the generally warmer mca and colder lia at longer multidecadal timescales probably influenced the regional climate in north africa through the influence on sahara low which weakened and strengthened the mean moisture inflow from the atlantic ocean during the mca and lia respectively

impact of wind on the spatial distribution of rain over micro scale topography numerical modelling and experimental verification the wind driven rain effect refers to the redistribution of rainfall over micro scale topography due to the existence of local perturbed wind flow patterns rainfall measurements reported in the literature point to the fact that the wind driven rain distribution can show large variations over micro scale topography these variations should be taken into account in hillslope hydrology in runoff and erosion studies and in the design of rainfall monitoring networks in practice measurements are often not suitable for determining the wind driven rain distribution therefore a few researchers have employed numerical modelling in order to provide confidence in using numerical models experimental verification for a range of different topographic features is imperative the objective of this study is to investigate the adequacy of a two dimensional computational fluid dynamics cfd model to predict the wind driven rain distribution over small scale topography the numerical model is applied to a number of topographic features including a succession of cliffs a small isolated hill a small valley and a field with ridges and furrows the numerical results are compared with the corresponding measurement results reported in the literature it is shown that two dimensional numerical modelling can provide a good indication of the wind driven rain distribution over each type of micro scale topography that is considered in this study it is concluded that more detailed verification procedures are currently inhibited due to the lack of available and detailed spatial and temporal rainfall data from field measurements copyright 2005 john wiley sons ltd

moroccan speleothem and tree ring records suggest a variable positive state of the north atlantic oscillation during the medieval warm period we present a magnesium mg and strontium sr record from an aragonitic speleothem grotte de piste morocco 34 n 04 w providing a reconstruction of effective rainfall from 619 to 1962 ad the corresponding drip site was monitored over 2 yr for drip water mg ca and sr ca ratios results show evidence for prior aragonite precipitation which can explain negative correlations between speleothem mg and sr concentrations the data shown here have important climate implications concerning the evolution of the north atlantic oscillation nao a comparison of the stalagmite data from grotte de piste with an updated tree ring based drought reconstruction from morocco and other nao related proxy records confirms that the medieval warm period mwp was dominated by nao conditions the stalagmite record and multiple proxy records from the iberian peninsula however suggest that considerable rainfall variability occurred during the mwp this implies that the nao has been more variable during the mwp than formerly suggested

rayleigh wave tomography of the british isles from ambient seismic noise we present the first rayleigh wave group speed maps of the british isles constructed from ambient seismic noise the maps also constitute the first surface wave tomography study of the crust under the british isles at a relatively high resolution we computed interferometric interstation rayleigh waves from vertical component records of ambient seismic noise recorded on 63 broad band and short period stations across the uk and ireland group velocity measurements were made from the resulting surface wave dispersion curves between 5 and 25 s using a multiple phase matched filter method uncertainties in the group velocities were computed by calculating the standard deviation of four dispersion curves constructed by stacking a random selection of daily cross correlations where an uncertainty could not be obtained for a ray path using this method we estimated it as a function of the interreceiver distance group velocity maps were computed for 5 25 s period using the fast marching forward solution of the eikonal equation and iterative linearized inversion at short and intermediate periods the maps show remarkable agreement with the major geological features of the british isles including terrane boundaries in scotland regions of late palaeozoic basement uplift areas of exposed late proterozoic early palaeozoic rocks in southwest scotland northern england and northwest wales and sedimentary basins formed during the mesozoic such as the irish sea basin the chester basin the worcester graben and the wessex basin the maps also show a consistent low velocity anomaly in the region of the midlands platform a proterozoic crustal block in the english midlands at longer periods which are sensitive velocities in the lower crustal upper mantle the maps suggest that the depth of moho beneath the british isles decreases towards the north and west areas of fast velocity in the lower crust also coincide with areas thought to be associated with underplating of the lower crust such as northern ireland the eastern irish sea and northwest wales

holocene glaciation of alaska and adjoining yukon territory canada abstract holocene glacial fluctuations between arctic central interior and southern maritime alaska are broadly synchronous this synchrony is evident from a review of work in 11 study areas with varying numbers of glaciers 3 100 glacier types subpolar cirque temperate valley tidewater surging and dating methodologies the pattern is temporally and spatially consistent with vegetation data and generally with climatic deteriorations culminating in the little ice age early holocene glacial advances are confirmed for 7 6 5 8 lichen ka bp at 4 of 97 glaciers in the brooks range advances also occurred by 5 85 and 5 7 ka bp at separate glacier tongues in the northern alaska range at least by 6 5 ka bp in lituya bay and possibly also in the malaspina and aleutian islands areas a sharp increase in glacier activity began by 4 4 ka bp in the arctic and glacier bay areas and by about 3 ka bp major glacier advances probably were initiated or well underway throughout alaska during holocene glacial maxima ice filled glacier and lituya bays as well as fjords of prince william sound and massive moraines buried forests in the northeastern st elias mountains area minor recession is recorded directly or implied in most of alaska about 2 ka bp or locally through the following millennium subsequently distinct but locally weak advances occurred by about 1 2 ka bp in most areas again followed by intervals of glacier recession most pervasive and ubiquitous were the little ice age advances initiated about 700 bp these generally culminated in two major advances between about 400 and 50 bp in the arctic those of a d 1600 dominated those of the late 1800s in the gulf of alaska those of the middle 1700s or late 1800s dominated large scale asynchronous advances and retreats of calving tidewater glaciers have been recorded during the twentieth century but most such movements are only indirectly related to climate

late holocene glaciation and twentieth century retreat northeastern brooks range alaska lichenometric dating of moraines deposited by eight glaciers in the northeastern brooks range suggests major glacial advances or stillstands at about 2600 1000 450 and 60 lichenometric l years bp the latter two advances of the early middle and latest part of the little ice age respectively formed promi nent moraines at all glaciers studied in response to overall twentieth century warming these glaciers have retreated at average rates of 2 to 19 m yr 1 from the distinct ridges formed in ad 1890 glacier thinning at rates of 0 7 to 0 9 m yr 1 accounts for over 90 of the ice loss

multivariate statistical analyses applied to seismic facies recognition one of the most important goals of seismic stratigraphy is to recognize and analyze seismic facies with regard to the geologic environment the first problem is to determine which seismic parameters are discriminant for characterizing the facies then to take into account all those parameters simultaneously the second problem is to be sure that there is a link between the seismic parameters and the geologic facies we are investigating this paper presents a methodology for automatic facies recognition based upon two steps the first or learning step begins with the definition of learning seismic traces for each facies we wish to recognize the choice of learning traces is based upon either well data or a seismic stratigraphic interpretation a large number of seismic parameters are then computed from the learning traces multidimensional analyses are carried out in order to validate the choice of learning traces and to select among all the available parameters those that discriminate best at this st

structure and variability of the abyssal water masses in the ionian sea in the period 2003 2010 1 this study presents aspects of the spatial and temporal variability of abyssal water masses in the ionian sea as derived from recent temperature salinity dissolved oxygen and velocity observations and from comparisons between these and former observations previous studies showed how in the southern adriatic sea the adriatic deep water addw became fresher s 0 08 and colder t 0 1 c after experiencing warming and salinification between 2003 and 2007 our data collected from october 2009 to july 2010 from two bottom moorings one within the strait of otranto and the other in the northern ionian confirm this tendency a bottom vein of southward flowing addw whose temperature and salinity continuously decreased during the observation time was detected there typically the vein travel time between the two stations ranged between 45 and 50 days this gave us a temporal estimate for addw anomaly propagation towards the ionian abyss from their adriatic generation region the density excess of the observed vein was always enough to enable its existence as a bottom arrested current this evidence confirms that at that time 2009 and 2010 the adriatic sea was greatly contributing to the formation of eastern mediterranean deep water emdw the bottom water of the eastern mediterranean hence based on these results and on the evidence that from 2003 to 2009 abyssal ionian waters became saltier and warmer under the time lagged influence of addw possible future changes in the emdw characteristics as a response to adriatic variability are discussed

a three dimensional eddy census of a high resolution global ocean simulation 1 a three dimensional eddy census data set was obtained from a global ocean simulation with one tenth degree resolution and a duration of 7 years the census includes 6 7 million eddies in daily data which comprise 152 000 eddies tracked over their lifetimes using a minimum lifetime cutoff of 28 days variables of interest include eddy diameter thickness vertical extent minimum and maximum depth location rotational direction lifetime and translational speed distributions of these traits show a predominance of small thin short lived and slow eddies still a significant number of eddies possess traits at the opposite extreme thousands of eddies larger than 200 km in diameter appeared in daily data each year a tracking algorithm found hundreds of eddies with lifetimes longer than 200 days a third of the eddies are at least 1000 m tall and many penetrate the full depth of the water column the antarctic circumpolar current contains the thickest and highest density of eddies thick eddies are also common in the gulf stream kuroshio current and agulhas ring pathway the great majority of eddies extend all the way to the surface confirming that eddy censuses from surface observations are a good proxy for the full depth ocean correlations between variables show that larger diameter eddies tend to be thicker and longer lived than small eddies

arctic sea ice cover from the early holocene the role of atmospheric circulation patterns abstract proxy evidence suggests that a mean atmospheric state reminiscent of the positive phase of the north atlantic arctic oscillation nao persisted throughout the early holocene and resulted in a dipole pattern in sea ice concentration between the north eastern and north western north atlantic a dynamic thermodynamic coupled sea ice ocean model is used to simulate the sea ice concentration and thickness in the arctic during the early holocene it is forced with winds ocean currents and surface air temperatures sat from recent years with a positive phase of the nao in conjunction with altered long and shortwave radiation and surface air ocean temperatures the simulation reproduces an east west dipole in sea ice cover of the arctic and is compatible with reconstructed sea ice conditions in the chukchi sea inferred from dinoflagellate cyst analysis of ocean sediment cores sensitivity studies were performed to investigate the individual effects of radiation ocean forcing sat and winds on sea ice cover results show that in the east siberian sea sat is the dominant forcing for changes in sea ice thickness whereas winds and sat are the dominant factors in sea ice concentration anomalies in the barents sea sea ice anomalies are influenced by air and sea surface temperatures and ocean currents

amazon flood wave hydraulics summary a bathymetric survey of 575 km of the central amazon river and one of its tributaries the purus are combined with gauged data to characterise the amazon flood wave and for hydraulic modelling of the main channel for the period june 1995 march 1997 with the lisflood fp and hec ras hydraulic models our investigations show that the amazon flood wave is subcritical and diffusive in character and due to shallow bed slopes backwater conditions control significant reach lengths and are present for low and high water states comparison of the different models shows that it is necessary to include at least the diffusion term in any model and the rmse error in predicted water elevation at all cross sections introduced by ignoring the acceleration and advection terms is of the order of 0 02 0 03 m the use of a wide rectangular channel approximation introduces an error of 0 10 0 15 m on the predicted water levels reducing the bathymetry to a simple bed slope and with mean cross section only introduces an error in the order of 0 5 m these results show that when compared to the mean annual amplitude of the amazon flood wave of 11 12 m water levels are relatively insensitive to the bathymetry of the channel model the implication for remote sensing studies of the central amazon channel such as those proposed with the surface water and ocean topography mission swot is that even relatively crude assumptions regarding the channel bathymetry will be valid in order to derive discharge from water surface slope of the main channel as long as the mean channel area is approximately correct