on the wave number spectrum of oceanic mesoscale variability observed by the seasat altimeter variations of sea surface height measured by the seasat altimeter in nearly repeat orbits during the last 24 days of the mission are used to compute the wave number spectrum of mesoscale variability in various parts of the oceans the instrument noise level 150 cm2 cycles km has limited the resulting oceanic spectrum to wavelengths longer than 100 km we found that the characteristics of the oceanic spectrum are dependent on the energy level of the mesoscale variability in the high energy areas close to major current systems most of the energy is contained at wavelengths longer than 250 km at wavelengths shorter than 250 km the spectrum basically follows a k 5 k is wave number dependence in the low energy areas remote from major current systems the spectrum follows a k 1 dependence at wave lengths from 100 to 1000 km based on the assumption of horizontal isotropy of mesoscale variability scalar wave number spectra of sea surface height and geostrophic kinetic energy are also presented dynamical implications of these spectra are discussed the effects of residual geoid and atmospheric water vapor on the computed oceanic spectra have been rigorously examined it was found that the general characteristics of the oceanic spectra were not significantly affected by them

slip distribution from the 1 april 2007 solomon islands earthquake a unique image of near trench rupture 1 we estimate the slip distribution from the mw 8 1 solomon islands earthquake in 2007 from two post seismic surveys measuring uplifted coral and submerged coastal features the occurrence of islands extremely proximal to the trench and nucleation of rupture allowed for the collection of unprecedented coseismic deformation dataset along a large megathrust earthquake using data from the two surveys along the southeastern half of the slip zone within five weeks of the event we model the elastic dislocation to identify the optimal 29 and alternate 20 dip and distribution of thrust along the southern rupture the vertical deformation which includes both coseismic and early postseismic deformation has highly variable and large slip within 25 km of the trench and straddling ranongga island the shallow focus of slip in the near trench area may explain the locally high tsunami run up on portions of simbo island however the aseismic contribution of afterslip remains unknown

late pleistocene holocene eolian deposits of the southern buenos aires province argentina a preliminary model abstract the aim is to reconstruct the sedimentological history of the late pleistocene holocene eolian deposits of southern buenos aires province hence a preliminary model is proposed in order to analyze the different stages of the sedimentological cycle the deposits include sandy loess fine sand sheets and dunefields the southern buenos aires province represents the depositional area whereas the source and transport environments are located in the northern patagonian andes and northern extra andean patagonia according to the mineralogical characteristics of the material explosive volcanism is considered the predominant process of particle formation particularly as generator of pyroclastic deposits which were reworked by different erosive processes glacial fluvial eolian during the late glacial maximum and the holocene alluvial deposits which were mainly generated by fluvial erosion of volcaniclastic sedimentary units were deposited along the floodplains of the colorado and negro rivers including those distal segments located in the emerged offshore platform the fluvial regime depended upon the regime of the glaciers hence it reflected the major glacial fluctuations which took place in the andes floodplains were deflated by southwest winds transporting the material towards the southern buenos aires province sandy loess and loessial sands and to la pampa province dunefields

inversion of complex body waves we have developed a method that inverts seismic body waves to determine the mechanism and rupture pattern of earthquakes the rupture pattern is represented as a sequence of subevents distributed on the fault plane this method is an extension of our earlier method in which the subevent mechanisms were fixed in the new method the subevent mechanisms are determined from the data and are allowed to vary during the sequence when subevent mechanisms are allowed to vary however the inversion often becomes unstable because of the complex trade offs between the mechanism the timing and the location of the subevents many different subevent sequences can explain the same data equally well and it is important to determine the range of allowable solutions some constraints must be imposed on the solution to stabilize the inversion we have developed a procedure to explore the range of allowable solutions and appropriate constraints in this procedure a network of grid points is constructed on the i plane where and i are respectively the onset time and the distance from the epicenter of a subevent the best fit subevent is determined at all grid points then the correlation is computed between the synthetic waveform for each subevent and the observed waveform the correlation as a function of and i and the best fit mechanisms computed at each i grid point depict the character of allowable solutions and facilitate a decision on the appropriate constraints to be imposed on the solution the method is illustrated using the data for the 1976 guatemala earthquake

origin and evolution of lunettes on the high plains of texas and new mexico lunettes isolated dunes on the lee side of playa basins are common landforms on the southern high plains of northwest texas and eastern new mexico the dunes contain calcareous 15 40 caco3 sandy loam or loamy sand with minor amounts of sepiolite deposited 25 000 800014c yr b p and derived by deflation of lacustrine carbonate in the basins the dunes also contain low carbonate 0 15 caco3 sand or loamy sand that was deposited 25 000 15 000 yr b p and 8000 5000 yr b p and was derived by deflation that created the basins or deflated from sand deposited in the basins buried soils are common in the lunettes a bk profiles characterize soils formed in the calcareous sandy loam the sandy low carbonate sediments contain a bt profiles in the oldest sand of some dunes and a bw a bt or a btk in the early and middle holocene sand the dune stratigraphy combined with carbon isotope data derived from dated a horizons in lunettes suggests the following scenario for the southern high plains the lunettes began forming as low carbonate sand dunes in the late pleistocene as playa basins were formed or deepened by wind erosion the erosion repeatedly alternated with stability the environment probably was cool and dry but one or more cool and wet intervals 25 000 15 000 yr b p resulted in a rise in the water table and deposition of lacustrine carbonate in the deepest basins there may have been short departures toward warmer and probably toward drier conditions throughout this time episodically dry conditions 15 000 8 000 yr b p resulted in deflation of the carbonate and further dune construction by repeated accretion of calcareous sandy loam or loamy sand the low carbonate sand was deposited during widespread drought and deflation 8000 5000 yr b p the dunes have been largely stable in the late holocene

playa lake basins on the southern high plains of texas and new mexico part i hydrologic geomorphic and geologic evidence for their development playa lake basins of the southern high plains texas and new mexico may originate wherever water periodically can collect in a surficial depression they expand however by hydrologic and geomorphic processes including 1 dissolution of lithologic carbonates by infiltrating water 2 transport downward of fine grained clastic and organic material by the infiltrating ground water leading to continuing processes of oxidation and carbonate dissolution in the subsurface and 3 eolian removal of clastic material from the floor of playa lakes which at some sites appears to have deepened playa depressions evidence for largely hydrologic processes of playa basin development on the southern high plains includes 1 a geographic occurrence restricted to relatively flat areas of the high plains surface that have poorly developed fluvial drainage and which are underlain by generally unsaturated clastic and calcrete beds 2 a tendency to occur where water collects and infiltrates as along ephemeral streams and lineations suggestive of fracture systems and 3 hydrologic geochemical petrographic and bore hole data which suggest that recharge to the high plains aquifer is principally from playa lakes that various geochemical changes including carbonate dissolution and enhancement of secondary porosity occur as water moves downward through the unsaturated zone beneath playa lakes and that calcrete beds often are missing or significantly dissolved beneath playa floors

the seasat altimeter data and its accuracy assessment the seasat satellite launched on june 27 1978 carried a radar altimeter designed to measure the altitude of the satellite above the ocean surface the surface wave height and the ocean surface backscatter coefficient from which wind speed can be inferred postlaunch engineering assessment indicated that the seasat altimeter met the performance specification for 10 cm precision noise in the altitude measurements however to determine the accuracy of this measurement as well as the accuracy of the wave height and wind speed measurements a significant calibration validation and model development effort was required this summary describes the instrument atmospheric and geophysical effects which influence the radar altimeter measurement accuracies and the attendant correction models adopted for the altimeter geophysical data record also summarized are the activities of the seasat altimeter precision orbit determination experiment team directed towards the validation and improvement of these models as well as the investigations required to assess the accuracy of the altimeter measurement and the computed satellite altitude ephemeris finally an accuracy assessment is made for the various altimeter measurement corrections which are included on the altimeter geophysical data record

tsunamis from the 29 march and 5 may 2015 papua new guinea earthquake doublet m w 7 5 and tsunamigenic potential of the new britain trench we characterized tsunamis from the 29 march and 5 may 2015 kokopo papua new guinea mw 7 5 earthquake doublet teleseismic body wave inversions using various rupture velocities vr showed similar source time functions and waveform agreements but the spatial distributions of the slips were different the rupture durations were 45 and 55 s for the march and may events with their peaks at 25 and at 17 s respectively tsunami simulations favored source models with vr 1 75 and 1 50 km s for the march and may earthquakes the largest slip on the fault was similar 2 1 and 1 7 m but the different depths and locations yielded maximum seafloor uplift of 0 4 and 0 2 m tsunami simulation from hypothetical great earthquakes m 8 4 and 8 5 on the new britain trench showed that tsunami amplitudes may reach up to 10 m in rabaul but most tsunami energy was confined within the solomon sea

ultralong period seismic study of the december 2004 indian ocean earthquake and implications for regional tectonics and the subduction process analysis of the earth s longest period normal modes shows that the december 2004 sumatra andaman earthquake was much larger mw 9 3 than ini tially inferred from surface wave data and involved slip on a much longer fault than initially inferred from body wave data the seismic moment and relative excitation of the normal modes indicate that the entire aftershock zone ruptured consistent with the large tsunami amplitudes in thailand sri lanka and india an apparent increase in seismic moment with period results from interference between parts of the fault the earthquake resulted from subduction of the indian plate beneath the burma microplate a sliver plate between the indian and sunda plates hence the rate and direction of convergence depends on the motion of the burma plate which is not well known convergence would be highly oblique if the rate of motion between burma and sunda is that inferred from spreading in the andaman sea and less if a slower rate is inferred from the sagaing fault the december earthquake was much larger than expected from a previously proposed relation based on the idea of seismic coupling in which such earthquakes occur only when young lithosphere subducts rapidly moreover a global reanalysis finds little support for this correlation hence we suspect that much of the apparent differences between subduction zones such as some trench segments but not others being prone to m w 8 5 events and hence oceanwide tsunamis may reflect the short earthquake history sampled this possi bility is supported by the variability in rupture mode at individual trench segments

rock block monitoring of rapid salt weathering in southern tunisia rectangular blocks of york stone and of concrete placed on a sodium chloride sabkha in southern tunisia for six years suffered very severe breakdown thereby indicating the power of salt weathering as a process in sabkha environments

fault slip distribution of the 2014 iquique chile earthquake estimated from ocean wide tsunami waveforms and gps data we applied a new method to compute tsunami green s functions for slip inversion of the 1 april 2014 iquique earthquake using both near field and far field tsunami waveforms inclusion of the effects of the elastic loading of seafloor compressibility of seawater and the geopotential variation in the computed green s functions reproduced the tsunami traveltime delay relative to long wave simulation and allowed us to use far field records in tsunami waveform inversion multiple time window inversion was applied to tsunami waveforms iteratively until the result resembles the stable moment rate function from teleseismic inversion we also used gps data for a joint inversion of tsunami waveforms and coseismic crustal deformation the major slip region with a size of 100 km 40 km is located downdip the epicenter at depth 28 km regardless of assumed rupture velocities the total seismic moment estimated from the slip distribution is 1 24 1021 n m mw 8 0

observing large scale temporal variability of ocean currents by satellite altimetry with application to the antarctic circumpolar current a new method is developed for studying large scale temporal variability of ocean currents from satellite altimetric sea level measurements at intersections crossovers of ascending and descending orbit ground tracks using this method sea level time series can be constructed from crossover sea level differences in small sample areas where altimetric crossovers are clustered the method is applied to seasat altimeter data to study the temporal evolution of the antarctic circumpolar current acc over the 3 month seasat mission july october 1978 the results reveal a generally eastward acceleration of the acc around the southern ocean with meridional disturbances which appear to be associated with bottom topographic features this is the first direct observational evidence for large scale coherence in the temporal variability of the acc it demonstrates the great potential of satellite altimetry for synoptic observation of temporal variability of the world ocean circulation

characterizing formation processes of rimrock lake a late pleistocene holocene playa harney basin south eastern oregon usa using an end member mixing analysis

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

landscape sensitivity and ecological change in western zambia the long term perspective from dambo cut and fill sediments a series of small shallow seasonally or interannually waterlogged depressions dambos in the upper zambezi valley in western zambia hold shallow peat deposits and are bounded on their western margin by sandy lunette dunes using luminescence dating of sands fossil pollen analyses and the macrocharcoal record from cored peat the long term stability of these landforms and the vegetation they now support is investigated at a site east of the upper zambezi although the upper lunette dune sediments accumulated between 14 2 and 6 1 ka the onset of peat accumulation and preservation within the dambo did not occur until 2800 cal a bp suggesting that only from this point onwards were conditions stable and wet enough year round to allow the formation and preservation of peat during this time results from this study indicate that the long term behaviour of the dambo conforms to a cut and fill dynamic where under more arid conditions the dambo becomes a dry pan providing a sediment source for the adjacent lunette dune in contrast during wetter times when the dambo holds surface water year round it becomes an organic rich sediment repository preserving a fossil pollen record of long term vegetation change

late quaternary evolution of lake urana new south wales australia lake urana is a well preserved relict lake in the semi arid riverine plain of southeastern australia a compound lunette at its eastern shoreline consists of a quartz sand dominated unit bimbadeen formation thermoluminescence tl dated at 30 ka to 12 ka and a clay and sand facies unit coonong formation dated at 55 ka to 35 ka the intervening period indicates a phase of periodically exposed lake floor and soil formation the older wet phase conforms well with similar environments recorded from the same period at lake mungo however the return to high water levels from 30 ka to 12 ka departs sharply from the generally accepted palaeoclimatic model from australia which demands severe glacial maximum desiccation and widespread construction of clay lunettes although hydrological budgets calculated for lake urana and nearby lake cullivel require high glacial maximum water levels they do not support higher precipitation

tsunamis from strike slip earthquakes in the wharton basin northeast indian ocean march 2016 mw7 8 event and its relationship with the april 2012 mw 8 6 event

mapping of the topography of continental ice by inversion of satellite altimeter data satellite altimeter data over ice sheets provide the best tool for mapping their topography and its possible climatic variations however these data are affected by measurement errors orbit errors and slope errors we develop here a three step inversion technique which accommodates the a priori information on the expected topography and correctly handles and propagates the data errors it estimates first a large scale reference surface then maps the residuals related to undulations and finally iteratively corrects the slope error the method is tested on overlapping small fragments of the antarctic ice sheet using a sub set of seasat data finally a topographic map of terre adelie is produced over areas of small slopes the a posteriori error should be of the order of 0 4 m using ers i data it is therefore expected that climatic variations in the ice sheet topography since the introduction of seasat will be observable

nature of environmental changes in south america at the last glacial maximum abstract a review is given of geomorphological evidence suggesting the nature of environmental changes in south america during the last glaciation maximum lgm the data are from glacial geocryogenic alluvial colluvial and aeolian systems and span 68 of latitude making the most complete land transect of major climatic systems in the southern hemisphere glaciers in the northern and central andes may have reached their maximal extent by 27 000 yr b p reduced precipitation at the lgm caused by lower temperatures and lower atmospheric humidity probably led to slight glacier recession in the tropical andes icefields in the southern andes were most expansive when global temperature and sea level were lowest because pacific westerlies supplied abundant moisture and western outlets advancing across the continental shelf were constrained by sea level low gradient river networks became incised by at least 100 m into narrow channels as global sea level fell by 120 m during the lgm draw down of water tables possibly impacted the forest cover enhancing the drying influence of reduced sea surface temperature and atmospheric humidity as forest and grass covers diminished in extent effecting greater atmospheric cooling because of reduced evapotranspiration and convective condensation colluvial and aeolian processes became more active and widespread almost 25 of the continent is covered with palaeo aeolian features presumed to have been active when airflow was stronger due to steeper atmospheric pressure and temperature gradients at the lgm substantial changes in precipitation totals and incidence and in ground water availability probably eliminated modern type tropical rainforest except in areas currently receiving ca 5000 mm of annual rainfall equivalent changes in vegetation cover spread across much of the guyana and brazilian highlands and throughout the southern temperate regions

application of avhrr to monitoring a climatically sensitive playa case study chott el djerid southern tunisia the importance of monitoring changes in the levels of lakes within endorheic basins using remotely sensed data as a means of assessing changes in regional aridity is noted large salt playas are highlighted as ephemeral lakes that can display extreme sensitivity to changes in regional rainfall patterns and which commonly do not have extensively managed catchments to explore the application of high temporal frequency monitoring of salt playas using remote sensing the chott el djerid a large salt playa situated in southern tunisia was targeted a short time series of 39 advanced very high resolution radiometer avhrr resolution 1 1km at nadir images of the chott el djerid spanning 36 months between 1987 and 1990 were compiled along with climate information from a weather station at tozeur using image histogram manipulation lake areas were extracted from the time series a good level of agreement was observed between recorded rainfall events and the presence of surface water on the playa and for a limited sample of large flood events it was found that there were significant relationships between rainfall evaporation and estimated lake areas r 2 98 5 p50 001 overall these data suggest that contemporary lake formation is largely controlled by temporal changes in effective precipitation within the basin in addition it was found that the coefficient of variation of the time series and a combination of temporal reflectance profiles extracted from it could be used to give a direct indication of which sedimentary surfaces on the playa are affected by large flood events and the extent to which these events may be preserved within the recent sedimentary record at these sites copyright 1999 john wiley sons ltd

ionospheric correction for seasat altimeter height measurement the ionosphere effect on signal speed and hence on the seasat radar altimeter measurement is directly proportional to the columnar electron content of the ionosphere this paper contains a description of the faraday rotation technique used by the seasat project to measure the ionosphere and of the mapping scheme used to map the measurements to the spacecraft location in addition it describes the evaluation procedure used for validation and accuracy assessment

a pleistocene sand sea on the alaskan arctic coastal plain a ridge and thermokarst basin landscape that is strikingly portrayed in landsat winter imagery consists of large pleistocene dunes that have been modified by younger eolian activity and thermokarst processes this is the most extensive area of large stabilized dunes yet reported in the north american arctic the landscape is of particular interest because it has been proposed as a first order analog for martian fretted terrain recognition of the large dunes permits a new interpretation for linear and curvilinear trends visible in landsat summer imagery

late quaternary lunette dune sedimentation in the southwestern kalahari desert south africa luminescence based chronologies of aeolian activity abstract through the application of luminescence dating techniques great advances have recently been made in the understanding of the late quaternary histories of many dryland regions including southern africa here this work has largely applied optical dating to sediments from the extensive linear dune systems which dominate the kalahari region of the central southern african interior relatively little attention has been given to localised aeolian accumulations such as lunette dunes despite their wide distribution over many parts of the region in particular the arid southwest kalahari to redress this we consider the palaeoenvironmental significance of pan margin lunettes and investigate the timing of lunette dune development in the southwest kalahari through the application of optical dating to sediments from lunette dunes associated with four closed basins pans ages show that localised aeolian activity occurred frequently throughout the past 18 ka indicating that the factors controlling lunette sedimentation are markedly different from those determining regional linear dune development it is proposed that the mechanisms controlling sediment supply to lunette dunes are controlled at both the regional and local pan specific scales by factors such as groundwater levels where pans support more than one discrete lunette the time since any individual lunette crest received significant accumulations of sediment increases with distance away from the pan margin outer and inner lunette sequences may be chronologically disparate features inner lunette formation may arise in response to modifications to the local atmospheric boundary conditions by the presence of large downwind outer lunette features or by shifts in sediment supply

glacial interglacial changes of southern hemisphere wind circulation from the geochemistry of south american dust abstract the latitudinal displacement of the southern westerlies and associated climate systems is a key parameter for understanding the variations of southern hemisphere atmospheric circulation during the late quaternary period to increase understanding of past atmospheric circulation and of the paleo environmental conditions associated with continental dust sources we dig deeper into dust provenance in paleo archives of the southern hemisphere we present here a sr nd isotopic and rare earth element study of surface sediments collected along a 4000 km latitudinal band from arid and semi arid terrains in southern south america findings from terrains that served as paleo dust suppliers are compared with modern dust collected from monitoring stations along the same latitudinal band which affords a test on how actual present day aeolian compositions compare to those of the past potential source areas moreover the comparison between past and present day datasets is useful for understanding present day atmospheric circulation armed with a new comprehensive dataset we revise previous interpretations of the provenance of dust trapped in the antarctic ice and sediments deposited in the south atlantic sector of the southern ocean these comparisons support multiple source regions in southern south america that changed with climates the findings reveal that although patagonia plays an important role in contributing dust to the higher latitudes central western argentina and to a lesser extent the southern puna region also emerge as potentially important dust sources during glacial times the southern altiplano appears to be a major contributor during interglacial periods as well we rely in part on an understanding of modern wind dust activities to conclude that the possible presence of southern south america source regions other than patagonia in east antarctic ice is consistent with an overall equatorward displacement during glacial times of both the mid latitude westerlies and the subtropical jet stream

terrestrial dunes man and the late quaternary environment in southern tasmania abstract three source bordering sand sheets that occur adjacent to the derwent estuary and were occupied by aboriginal groups have been examined two lunette sites in the tasmanian midlands one occupied by aboriginals the other not have also been examined geomorphologic stratigraphic pedologic and archaeologic evidence is used to decipher the broad sequence of late quaternary environmental changes and the effects of occupation a broadly parallel sequence of changes is suggested by the two areas the data suggest that relatively cold dry climatic conditions prevailed during the late last glacial stage 25 000 10 000 b p and that more humid conditions preceded and succeeded this period the aeolian landforms and events compare with similar forms and events recorded from se mainland australia

linear and nonlinear computations of the 1992 nicaragua earthquake tsunami numerical computations of tsunamis are made for the 1992 nicaragua earthquake using different governing equations bottom frictional values and bathymetry data the results are compared with each other as well as with the observations both tide gauge records and runup heights comparison of the observed and computed tsunami waveforms indicates that the use of detailed bathymetry data with a small grid size is more effective than to include nonlinear terms in tsunami computation linear computation overestimates the amplitude for the later phase than the first arrival particularly when the amplitude becomes large the computed amplitudes along the coast from nonlinear computation are much smaller than the observed tsunami runup heights the average ratio or the amplification factor is estimated to be 3 in the present case when the grid size of 1 minute is used the factor however may depend on the grid size for the computation

qualitative and quantitative evaluation of the influence of anthropic pressure on subsidence in a sedimentary basin near rome this paper presents the results of analyses measuring variations in anthropic pressure and the influence of anthropic pressure on the variations in subsidence rates from 1954 to 2005 in the tivoli guidonia area located to the east of rome italy in the last 60 years this area underwent exceptional demographic growth as well as an increase in the quarrying and hydrothermal industries the calculation of the increase in anthropic pressure was based on two factors the expansion of built up areas and the increase in quarrying photogrammetric techniques permitted a multi temporal analysis of aerial photos taken in 1954 1985 1993 1998 and 2005 the aim of this analysis was to estimate the increase in both urban surface area and travertine quarrying non conventional techniques such as the reconstruction of photograms using photo retouching software allowed for the use of aerial photos from 1954 these photos were fundamental for establishing a medium term evaluation of anthropic activity in the area the results of the photogrammetric analysis were compared to the phases of acceleration and stabilization in subsidence phenomena deduced from a radar interferometry study published by the italian ministry of the environment this comparison showed a close relationship between the rise and temporary halt of anthropic development and the rise and fall of subsidence rates furthermore data on the distribution of private wells in the study area variations in the groundwater table level and the precipitation regime were analyzed but although helpful in defining the geological context and considerable transformations of the territory they were considered as qualitative data due to the lack of systematic measures or an unclear relationship to the variations in subsidence rate despite the difficulties involved in evaluating both the amount of anthropic pressure and the role of different human activities on environmental change it was possible to estimate the variations in anthropic pressure and their influence on potentially dangerous geological processes

ionospheric anomalies immediately before mw7 0 8 0 earthquakes recent observations suggested that ionospheric anomalies appear immediately before large earthquakes with moment magnitudes mw of 8 2 or more do similar phenomena precede smaller earthquakes here we answer this question by analyzing vertical total electron contents vtec observed near the epicenters before and after 32 earthquakes with mw7 0 8 0 using data from nearby global navigation satellite systems stations to detect anomalies we defined the reference curves to fit the observed vtec and considered the departure from the curves as anomalies in estimating the reference curves we excluded time windows prescribed for individual earthquakes considering mw possibly affected by earthquakes we validated the method using synthetic vtec data assuming both preseismic coseismic and postseismic anomalies out of the 32 mw7 0 8 0 earthquakes eight earthquakes showed possible preseismic anomalies starting 10 20 min before earthquakes for earthquakes of this mw range we can observe preseismic ionospheric changes probably when the background vtec is large say 50 tecu total electron content unit 1 tecu 1016 el m 2 or more

quaternary lakes of argentina abstract the quaternary lakes of argentina are grouped into eight main environments swamps and playas of the hernandaries formation middle quaternary of northeastern argentina pampean swamps chaco swamps swamps and shallow lakes of the parana system salt lakes of the puna northwestern salt lakes and playas glacial lakes of the southern cordillera and patagonian closed depressions

dissolution on titan and on earth toward the age of titan s karstic landscapes titan s polar surface is dotted with hundreds of lacustrine depressions based on the hypothesis that they are karstic in origin we aim at determining the efficiency of surface dissolution as a landshaping process on titan in a comparative planetology perspective with the earth as reference our approach is based on the calculation of solutional denudation rates and allow inference of formation timescales for topographic depressions developed by chemical erosion on both planetary bodies the model depends on the solubility of solids in liquids the density of solids and liquids and the average annual net rainfall rates we compute and compare the denudation rates of pure solid organics in liquid hydrocarbons and of minerals in liquid water over titan and earth timescales we then investigate the denudation rates of a superficial organic layer in liquid methane over one titan year at this timescale such a layer on titan would behave like salts or carbonates on earth depending on its composition which means that dissolution processes would likely occur but would be 30 times slower on titan compared to the earth due to the seasonality of precipitation assuming an average depth of 100 m for titan s lacustrine depressions these could have developed in a few tens of millions of years at polar latitudes higher than 70 n and s and a few hundreds of million years at lower polar latitudes the ages determined are consistent with the youth of the surface 1 gyr and the repartition of dissolution related landforms on titan

a change detection application on the evolution of kahak playa south khorasan province iran kahak salt playa in south khorasan province of iran have special geomorphological characteristics by the presence of ephemeral saline lakes wetlands salt crusts surface accumulations of salt and zones of patterned ground salt crusts in the soil surface are unique in the region and have laminated horizons in the playa soil soil surface salt accumulations are dominated by nacl and gypsum it has been found that distribution of chemical soluble is not uniform across the playa landscape and this result influences on the variety form of patterned ground in this study the percent changes in some of the chemical elements such as nacl gypsum and also brine extent have been calculated in the playa indicating changes in kahak salt playa is the main aim of this study by using remote sensing and gis techniques in this paper techniques such as spectral un mixing maximum likelihood classification band rationing fuzzy classification and correlation relationships are discussed this contribution presents modeling of temporal and spatial changes of salinity and playa developing using combined approaches that incorporate different data fusion and data integration techniques for two periods of date furthermore percent changes in the surface patterned ground of the playa have been calculated using texture and pattern analysis of the pca1 results have revealed that in the playa developing chemical materials such as sodium nacl gypsum and also brine extent are positively correlated with each other and the most increased changes are related to gypsum and the most decreased changes are related to the nacl also changes in the amount of agricultural area in the playa lakes margin show low effects in the desertification process

tropical and mid latitude north pacific sea surface temperature variabililty from the seasat smmr sea surface temperature sst data from the scanning multichannel microwave radiometer smmr for the entire seasat mission july 6 to october 10 1978 was obtained from the seasat project office and has been analyzed for the mid latitude north pacific 20 n 50 n 145 e 130 w and the eastern tropical pacific 10 s 20 n 95 w 145 w systematic cross scan sst biases were observed in the smmr data strongly dependent upon latitude solar elevation time of day and month the cross scan biases are ascribed to incomplete accounting for faraday rotation of polarized microwave energy propagating upward through the ionosphere a second systematic sst bias occurred between data of ascending and descending passes nearly 12 hours apart the bias increased steadily through the mission as the seasat orbit moved from 6 a m p m to 12 a m p m local sun time coverage the ascending descending bias is ascribed to measurements being made at different times in the diurnal cycle of sst corrections for the two systematic effects were derived and applied to the smmr data to produce maps of sst in mid latitude 10 and 30 day maps of smmr sst were compared with similar maps produced from routine shipboard sst observations mostly engine injection temperatures the monthly smmr and shipbased maps agreed at the 0 5 0 7 c rms level in july and september but exhibited a 0 5 c rms scatter about a significant 1 0 c bias in august the august bias may be a reflection of true midsummer vertical differences in temperature between the 1 cm depth of smmr observations and the typically 5 m depth of ship observations monthly sst anomalies deviation from climatology for smmr and ship exhibited similar patterns but the smmr maps appear superior because of their better spatial data coverage in the eastern tropical pacific a sequence of 15 8 day interval maps were constructed the maps reproduce known climatological features in particular the cold tongue of water along the equator week to week variations occur in the intensity of the cold tongue in addition wave like patterns occur along the meridional gradient just north of the equator having 1000 km wavelength and propagating west at about 42 km day

spatial scales of mesoscale variability in the north atlantic as deduced from geosat data two years of geosat data were used to systematically investigate the mesoscale variability and spatial scales of the north atlantic we first calculated sea surface height variability and eddy kinetic energy these compare well with the eddy kinetic energy obtained with surface drifters then the spatial scales of mesoscale variability were characterized in 10 latitude 10 longitude areas by their wave number spectra and autocorrelation functions comparison with existing in situ data shows good agreement and it is believed that the total error budget is globally below that of the oceanic signal the wave number spectra show significant differences as a function of latitude and longitude and these can be related to different types of forcing instability of a mean current or fluctuating wind scales typically decrease from west to east and south to north simple proportionality with respect to the first internal rossby radii does not apply everywhere

comparative study of two tsunamigenic earthquakes in the solomon islands 2015 mw 7 0 normal fault and 2013 santa cruz mw 8 0 megathrust earthquakes the july 2015 mw 7 0 solomon islands tsunamigenic earthquake occurred 40 km north of the february 2013 mw 8 0 santa cruz earthquake the proximity of the two epicenters provided unique opportunities for a comparative study of their source mechanisms and tsunami generation the 2013 earthquake was an interplate event having a thrust focal mechanism at a depth of 30 km while the 2015 event was a normal fault earthquake occurring at a shallow depth of 10 km in the overriding pacific plate a combined use of tsunami and teleseismic data from the 2015 event revealed the north dipping fault plane and a rupture velocity of 3 6 km s stress transfer analysis revealed that the 2015 earthquake occurred in a region with increased coulomb stress following the 2013 earthquake spectral deconvolution assuming the 2015 tsunami as empirical green s function indicated the source periods of the 2013 santa cruz tsunami as 10 and 22 min

spatial variability and hydrologic evolution of australian lake basins analogue for pleistocene hydrologic change and evaporite formation abstract processes evident in basins across hydrologic gradients from humid to arid regions today provide analogues for systems that may have operated in some individual basins during periods of past hydrologic change thus lakes in humid regions today with low salinity sedimentary facies and with morphology controlled largely by wave action may closely resemble past lacustral pluvial phases experienced in zones which today are relatively arid and saline conversely playas controlled today by groundwater and in some cases subject to defletion may resemble those arid and dune building stages experienced by basins in sub humid regions today as they underwent glacial age desiccation in any such sequence of spatial or temporal gradients from humid to more arid conditions the frequency of basin filling and drying modulates the rate of evaporitive loss of interstitial waters from the exposed basin surface this in turn controls the salinity evolution of the interstitial and local groundwaters the notion of closed systems for terminal lakes while satisfactory for analysis of surface water budgets is quite inapplicable to the evolution of brines where surfacewater groundwater exchange during the high salinity drying stages becomes a controlling factor affecting all salt budgets in these systems evaporites may only be preserved when the sub surface waters have evolved to salinites near saturation for the salts concerned if sub surface waters are frequently diluted by surfacewater groundwater exchange evaporites will not be preserved in the record even though the surface system appears hydrologically closed the process of interstitial water evolution which controls efflorescence deflation and salt weathering exerts a dominating influence on basin geomorphic expression as well as on hydrochemical fractionation

fault size and depth extent of the ecuador earthquake m w 7 8 of 16 april 2016 from teleseismic and tsunami data the april 2016 ecuador mw 7 8 earthquake was the first megathrust tsunamigenic earthquake along the ecuador colombia subduction zone since 1979 mw 8 2 with 200 deaths from tsunami while there was no tsunami damage from the 2016 earthquake small tsunamis were recorded at deep ocean assessment and reporting of tsunami and tide gauges here we designed various fault models with and without shallow slip area and compared the computed teleseismic and tsunami waveforms with the observations while teleseismic inversions were indifferent about inclusion or exclusion of the shallow slip tsunami waveforms strongly favored the slip model without shallow slip our final slip model has a depth range of 15 44 km and its western shallowest limit is located at the distance of 60 km from the trench maximum and average slips were 2 5 and 0 7 m respectively the large slip area was 80 km along strike 60 km along dip in the depth range of 15 35 km

description and numerical model of pleistocene iceberg scours and ice keel turbated facies at toronto canada near toronto in southern ontario canada glaciolacustrine muds and shoreface sands of late pleistocene age early wisconsin glaciation 45 ka were deformed by icebergs ploughing the floor of an ancestral ice dammed lake ontario outcrop mapping and a ground penetrating radar survey identify ice scour structures up to 4 m deep up to 10 m wide and at least several hundred metres long with high standing lateral margins berms ploughing of lake floor sediment is also recorded by ice keel turbated facies in which storm deposited shoreface sands have been mechanically mixed with underlying muds palaeoenvironmental information for one prominent scour such as water depths estimates of the mass and draft of the ice mass and scouring forces can be determined using a simple finite element numerical model a mass of 0 04 million tonnes a keel draft of between 10 and 30 m and a scouring force of 5 103 kn is consistent with scouring by a small iceberg bergy bit or pressure ridged lake ice the former is preferred because of the considerable depth of the scour and the overall glacial depositional setting estimates of ice mass dimensions agree with independent reconstructions of palaeobathymetry no greater than 20 m derived from storm deposited hummocky and swaley cross stratified facies that fill the scour data presented here aid the identification of ice scour structures and turbated sediment in the ancient record despite being a common process on modern high latitude shelves descriptions of ancient structures and facies are few

surface sediment dynamics in a dust source from spaceborne multispectral thermal infrared data abstract this study utilized spaceborne multispectral thermal infrared tir data to document spatial relationships of surface sediments over time in a modern depositional environment associated with dust emissions soda lake playa mojave desert united states the approach employed here involved time series tir data acquired from advanced spaceborne thermal emission and reflection radiometer aster and a linear spectral mixture analysis an automated algorithm was applied to derive emissivity image endmembers evaluation of the chosen endmembers revealed that they can be categorized into five major spectra classes based on diagnostic absorption features each spectrum has been identified in relation to mineral abundance and soil arrangement that are common in playa settings a clayey silt rich crust b intermediate salt crust c quartz rich deposit d salt rich rough crust e sulfate rich crust spectral classes a b c d yielded the lowest rms errors 0 0 025 over time in the iterative deconvolution algorithm between the measured and modeled spectra the produced fractional abundance images show high areal concentrations for clayey silt rich crust salt rich rough crust and quartz rich deposit as the first surficial mapping of soda lake significant changes in the spatial relationships of the major surface sediments in soda lake were observed after a flooding event 2005 and a relatively dry period 2006 the approach utilized in this study can be advantageous for continuous monitoring of environments characterized by a small area and a complex surface which may enable a better understanding of their responses to climate changes and potential for dust emissions

bathymetric prediction from seasat altimeter data the linear response function technique is used to analyze two 1300 km tracks of seasat altimeter data and corresponding bathymetry in the musician seamounts region north of hawaii bathymetry and geoid height are highly correlated in the 50 to 300 km wavelength range a predictive filter is developed which can operate on seasat altimetry in poorly surveyed oceanic regions to indicate the presence of major bathymetrie anomalies modeling of the bathymetry geoid correlation in the musician region is attempted using the elastic plate model the flexural rigidity d of the plate is not well constrained by our data but appears to lie in the range 5 1021 n m 5 1022 n m at the time of loading since the musician seamounts and the crust on which they lie are both late cretaceous in age this value represents the effective flexural rigidity of very young lithosphere that was frozen in at the time of voicanism the modeling indicates that the general form of a predictive filter will strongly depend on various geologic parameters especially the effective flexural rigidity hence some a priori geologic constraints are necessary to estimate successfully the bathymetry from the altimeter data alternately if high quality bathymetry is available a crude estimate of the age of loading i e voicanism can be made from the altimeter data

subduction of the woodlark basin at new britain trench solomon islands region abstract the woodlark basin located south of the solomon islands arc region is a young 5 ma oceanic basin that subducts beneath the new britain trench this region is one of only a few subduction zones in the world where it is possible to study a young plate subduction of several ma to obtain the image of the subducting slab at the western side of the woodlark basin a 40 day ocean bottom seismometer obs survey was conducted in 1998 to detect the micro seismic activity it was the first time such a survey had been performed in this location and over 600 hypocenters were located the seismic activity is concentrated at the 10 60 km depth range along the plate boundary the upper limit just about coincides with the leading edge of the accretionary wedge the upper limit boundary was identified as the up dip limit of the seismogenic zone whereas the down dip limit of the seismogenic zone was difficult to define the dip angle of the plate at the high seismicity zone was found to average about 30 using the cascadia subduction zone for comparison which is a typical example of a young plate subduction suggests that the subduction of the woodlark basin was differentiated by a high dip angle and rather landward location of the seismic front from the trench axis 30 km landward from the trench axis furthermore as pointed out by previous researchers the convergent margin of the solomon islands region is imposed with a high stress state probably due to the collision of the ontong java plateau and a rather rapid convergence rate 10 cm year the results of the high angle plate subduction and inner crust earthquakes beneath the shortland basin strongly support the high stress state the collision of the ontong java plateau the relatively rapid convergence rate and moderately cold slab as evidenced by low heat flow rather than the plate age may be dominantly responsible for the geometry of the seismogenic zone in the western part of the woodlark basin subduction zone

origin of the qattara depression egypt as a working hypothesis we propose that the qattara depression originated as a stream valley that was subsequently dismembered by karstic processes during the late miocene epoch and afterward was deepened by deflation and otherwise modified by mass wasting and fluviatile processes the depression is excavated in sedimentary rocks of tertiary age that have a regional dip of a few degrees toward the mediterranean sea the precipitous northern wall is the scarp slope of a cuesta capped by carbonate rocks of middle miocene age its cliffy slopes descend to pediments graded southward to an axial valley that valley now extensively covered by saline crusts sabakha deposits and salt marshes slopes westward into the deeper quadrangular part of the basin where elevations as much as 134 m below sea level have been measured nearby sinkholes and cavernous subsurficial limestone attest to past karstic activity presumably karstification reached a peak during the recession of the mediterranean sea late in the miocene epoch when the north dipping aquifers discharged into the then almost empty basin as the mediterranean sea receded what is now the western desert of egypt and its off shore continuations were subjected to extensive erosion by streams a major stream issuing from the gilf kebir highlands flowed northward to near the present site of siwa oasis its alluvium now mostly covered by aeolian deposits of the great sand sea if it reached the mediterranean basin then it may have done so through the sahabi channel system of libya or by a much shorter route through the qattara area to an exit near the head of the ras alam er rum submarine canyon offshore near alexandria in either case the stream responsible for the qattara cuesta whether a tributary of the gilf river or a part of that river9s descending course into the mediterranean basin apparently became inactive after its waters were diverted into underground courses through sinks and caverns with the refilling of the mediterranean and the accompanying diminution of subsurface aqueous activities and with the advent of more and climatic regimes surface processes associated with deserts have completed the shaping of the depression to give it its present configuration and character

scaling relations of seismic moment rupture area average slip and asperity size for m 9 subduction zone earthquakes 1 scaling relations for seismic moment m0 rupture area s average slip d and asperity size sa were obtained for large great and giant mw 6 7 9 2 subduction zone earthquakes we compiled the source parameters for seven giant mw 9 earthquakes globally for which the heterogeneous slip distributions were estimated from tsunami and geodetic data we defined sa for subfaults exhibiting slip greater than 1 5 times d adding 25 slip models of 10 great earthquakes around japan we recalculated regression relations for 32 slip models s 1 34 10 10 m02 3 d 1 66 10 7 m01 3 sa 2 81 10 11 m02 3 and sa s 0 2 where s and sa are in square kilometers m0 is in newton meters and d is in meters these scaling relations are very similar to those obtained by murotani et al 2008 for large and great earthquakes thus both scaling relations can be used for future tsunami hazard assessment associated with a giant earthquake

ancestral heritage saves tribes during 1 april 2007 solomon islands tsunami 1 the 1 april 2007 magnitude ms 8 1 earthquake off the new georgia group in the solomon islands generated a tsunami that killed 52 with locally focused run up heights of 12 m local flow depths of 5 m as well as tectonic uplift up to 3 6 m and subsidence down to 1 5 m a reconnaissance team deployed within one week investigated 65 coastal settlements on 13 remote islands the ancestral heritage run to high ground after an earthquake passed on to younger generations by survivors of smaller historic tsunamis triggered an immediate spontaneous self evacuation containing the death toll

subsidence beneath a playa basin on the southern high plains u s a evidence from shallow seismic data shallow seismic data from sevenmile basin a large ephemeral lake playa basin in the texas panhandle reveal that subsidence has been an important agent in basin formation several hypotheses exist for the origin of thousands of playa basins on the southern high plains of texas and new mexico including eolian deflation evaporite or carbonate dissolution and subsidence piping and animal activity sevenmile basin is 5 5 x 3 6 km across and 14 m deep and contains 20 m of lacustrine and eolian sediments that interfinger with the quaternary blackwater draw formation below these sediments is the upper tertiary ogallala formation which overlies permian or triassic bedrock seismic reflection and refraction data were collected from the unlithified and variably saturated clastic sequence beneath sevenmile basin to investigate the geological history and hydrogeological framework of playa basins which recharge the regionally important ogallala aquifer three layer velocity models provide good solutions for reversed refraction data near surface p wave velocities layer 1 range from 349 to 505 m s layer 2 velocities range from 806 to 851 m s and layer 3 velocities range from 2 037 to 2 161 m s shallow test holes and drillers logs suggest that layer 1 is composed of playa and upper blackwater draw formation deposits layer 2 consists of lower blackwater draw formation and upper ogallala formation deposits and layer 3 represents a competent and partly saturated zone near the top of the ogallala aquifer reflection sections show a middle ogallala reflector a reflector at the top of permian or triassic bedrock and internal bedrock reflectors that indicate a structural low beneath sevenmile basin increasing relief with age from 14 m at the surface to 70 m on the middle ogallala reflector to 110 m at the base of the ogallala is interpreted as evidence of subsidence of underlying permian evaporite bearing strata before or during ogallala deposition ogallala and blackwater draw formation thicknesses greater than bedrock ogallala deposition and may continue to the present virtually all playa basins on the southern high plains are underlain by permian evaporite bearing strata some basins have been affected by dissolution induced subsidence shallow seismic methods are an ideal approach to determine the relative importance of subsidence in basin formation

the nature distribution and formation of pans in arid zones abstract pans closed depressions are a widespread feature of many of the world s drylands by using literature survey air photographs topographic maps orbital photographs and imagery combined with field work it is possible to describe the major areas where these features occur their distribution is controlled to a great extent by the availability of susceptible surfaces they also develop in certain particular environmental settings palaeolacustrine basins palaeodrainages interdunes and on coastal plains many of the pans have a distinctive morphology while on their lee sides they may have lunette dunes many processes combine to create and maintain pans and these can be considered in a general model which has certain key elements the first of these is that the area should not be one where fluvial processes are fully integrated it should also not be one where aeolian accumulation is such as to infill any irregularities in the land s surface if these two predisposing conditions are fulfilled then under dryland conditions if susceptible surfaces are present there are various circumstances that may lead to hollow development and enlargement although in some cases such processes as solution suffosion and animal activities may play a role we believe that the predominant reason why pans have the characteristics that they do including their shapes lunettes alignments etc is that they result from the operation of the twin processes of salt weathering and aeolian deflation

a seismological study of the eastern new guinea and the western solomon sea regions and its tectonic implications summary we use new and pre existing seismological data to study the neotectonics and the state of stress in the seismic zones of eastern papua new guinea and the western solomon sea regions earthquake hypocentres for the period 1964 90 were relocated using the joint hypocentre determination jhd technique we show that the t axes of earthquakes in the 100 250km depth range beneath eastern papua new guinea are aligned parallel to the seismic zone with no seismicity below 250 km this intermediate depth seismic zone forms an inverted u shaped zone with limbs dipping to the north and south and is interpreted to be seismicity along the subducted solomon sea plate the northern and southern limbs of the seismic zone are connected by a flattened zone of seismicity which is marked by predominantly strike slip and a few normal fault mechanisms we suggest that the solomon sea plate at depth beneath the finisterre mountains is no longer influenced by the tectonic forces acting at the surface but breaking up and sinking under its own gravitational forces a significant north dipping seismic zone is imaged above the deeper seismic zone this feature characterized by thrust mechanisms extrapolates to the surface along the ramu markham valley and is attributed to the ramu markham fault rmf the rmf has an average dip of about 40 to the north east but its detailed geometry would appear to be complex the rmf is interpreted to ramp steeply in the uppermost 10 20 km flattening out sharply to a dip of 15 at a depth of about 20km the rmf marks the suture between the finisterre terrane and the australia new guinea plate and may extend to a depth of 90km beneath the western limit of the finisterre mountains there is a clear gap in seismicity between the rmf and the deeper solomon sea plate seismic zone beneath the finisterre mountains which together with the alignment of the t axes of earthquakes along the seismic zone at depths 100km indicates that these are indeed two distinct features the seismicity in the depth range 50 80 km along the new britain arc follows the trend of the 2000m bathymetric contour of the new britain trench and the finsch deep far more closely than it does the trend of the surface plate boundary indicating that the increase in the distance between the solomon sea south bismarck plate boundary and the active volcanos along the new britain arc west of 6 83 150 o e is only a shallow phenomenon and does not reflect the geometry of the solomon sea plate at depths greater than 50 km

edge detection applied to cassini images reveals no measurable displacement of ontario lacus margin between 2005 and 2010 1 ontario lacus is thus far the largest flat floored topographic depression of titan s southern hemisphere interpreted as a permanent or ephemeral lake from 2005 to 2010 it was imaged several times and at various wavelengths by iss vims and radar instruments onboard cassini s spacecraft we analyze the position and uncertainty of ontario lacus margin in all these images using an edge detection method based on image derivation we find that given the range of uncertainties in contour locations derived from images no measurable displacement of ontario lacus margin can be detected between 2005 and 2010 at the actual image spatial resolutions the discrepancy between this result and previous ones is attributable to differences in 1 the basics behind the methods used 2 the actual spatial resolutions and contrasts of the available images due to differential atmospheric scattering effects at different wavelengths and 3 the geomorphological interpretation of contours derived from images acquired at different wavelengths this lack of measurable displacement in the images suggests that the imaged contour corresponds either 1 to the border of a surface liquid body provided that potential changes in its extent over five terrestrial years were not sufficiently large to be measured or 2 to the stationary topographic border between ontario lacus depression and the surrounding alluvial plain potential displacements of ontario lacus margin between 2005 and 2010 are thus below the actual resolution of currently available images or have to be sought for within the extent of the topographic depression rather than along its borders

distribution patterns of gypsum and kalistrontite in a dry lake basin of the southwestern kalahari omongwa pan namibia the deposits of the omongwa pan southwestern kalahari namibia are partly gypsiferous and locally contain small amounts of kalistrontite the distribution patterns of gypsum caso4 2h2o and kalistrontite k2sr so4 2 are mainly determined by groundwater depth and by the lithological composition of the deposits the latter determines the hydraulic conductivity for saturated and unsaturated flow and therefore controls the depth of the interval within the deposits where evaporation and mineral precipitation can take place other factors that affect the distribution of the evaporite minerals are the patterns of groundwater flow within the basin and the occurrence of a redistribution of salts during short flooding stages gypsum occurs as crystals of four distinct morphological types which each developed in different conditions prismatic crystals formed both as subaqueous precipitates and as crystals that developed within the sediment matrix of a brine saturated surface layer sub euhedral tabular crystals formed within brine filled macropores hemi bipyramidal crystals formed in a nearly permanently brine saturated part of a subsurface horizon phreatic zone as the product of recrystallization of an older gypsum occurrence and lenticular crystals formed by intrasediment growth in the vadose zone the development of these morphological types of gypsum crystals is marked by differences in the differential inhibition of growth of the various crystal forms the further growth of lenticular crystals which are most strongly affected by differential growth inhibition is still characterized by a difference in degree of inhibition between the 111 and 103 forms expressed as a change in orientation of the plane of flattening copyright 1999 john wiley sons ltd

insights into the kinematic rupture of the 2015 m w 8 3 illapel chile earthquake from joint analysis of geodetic seismological tsunami and superconductive gravimeter observations

long term perspectives on giant earthquakes and tsunamis at subduction histories of earthquakes and tsunamis inferred from geological evidence aid in anticipating future catastrophes this natural warning system now influences building codes and tsunami planning in the united states canada and japan particularly where geology demonstrates the past occurrence of earthquakes and tsunamis larger than those known from written and instrumental records under favorable circumstances paleoseismology can thus provide long term advisories of unusually large tsunamis the extraordinary indian ocean tsunami of 2004 resulted from a fault rupture more than 1000 km in length that included and dwarfed fault patches that had broken historically during lesser shocks such variation in rupture mode known from written history at a few subduction zones is also characteristic of earthquake histories inferred from geology on the pacific rim

climatic variations in the argentine plains during the last 18 000 years the last deglacial hemicycle was characterized by a general increase in temperature and precipitation in the region with a few significant departures from this general trend the present ne sw climatic gradient was maintained throughout the entire period except in the upper holocene the following sequence of events is apparent if the present climate is taken as a reference base 1 a 18 000 8500 yr b p arid and cool with aeolian sand ad loess deposition patagonian fauna climatic isolines temperature precipitation etc were located some 750 km northeast of their present positions 2 b 8500 3500 yr b p humid subtropical with brazilian fauna pedogenesis and fluvial dynamics climatic limits migrated about 800 900 km southwest of their former positions 3 c 3500 1000 yr b p dry subtropical aeolian dynamics the normal latitudinal climatic gradient was interrupted by the occurrence of an anticyclonic centre which stabilized the climate over an area of some 1 600 000 km2 4 d 1000 yr b p little ice age climate was similar to the present one over much of the plains but the northeastern extremity was warmer 5 e little ice age climatic deterioration in the southern belt was characterized by generalized aeolian activity and migration of isolines more than 150 km to the northeast in that area 6 f present climate 19th and 20th centuries subtropical humid in the east and dry in the west

present day lunette sediment cycling at witpan in the arid southwestern kalahari desert abstract witpan is a pan depression in the southwestern kalahari desert the pan fringing lunette dune has a number of notable characteristics a highly active crest the lower lunette pediment is cemented and the lower lunette supports a highly developed and active gully system geomorphological and sedimentological considerations are used to evaluate the interaction of wind and water in shaping contemporary lunette processes it is considered that like other pans in the area groundwater activity influences pan floor sediment availability and transport that the present highly sea sonal climatic regime permits the interaction of aeolian transport of sediment to the dune and its return to the pan floor by water during storm events creating a cycling process favoured by sedimentary properties that promote surface runoff

source model of the 16 september 2015 illapel chile m w 8 4 earthquake based on teleseismic and tsunami data teleseismic data were provided by the incorporated research institutions for seismology http www iris edu wilber3 find event tide gauge data can be found at the intergovernmental oceanographic commission website http www ioc sealevelmonitoring org dart records were provided by noaa http nctr pmel noaa gov dart earthquake catalogs by the usgs national earthquake information center http earthquake usgs gov earthquakes search and global instrumental earthquake catalogue 1900 2009 of international seismological centre global earthquake model http www globalquakemodel org what seismic hazard instrumental catalogue were used in this study we used the gmt software for drawing the figures wessel and smith 1998 this article benefited from constructive review comments by costas e synolakis university of southern california usa and yuichiro tanioka hokkaido university japan for which we are grateful we acknowledge financial supports from the japan society for the promotion of science

origin of rectangular and aligned lakes in the beni basin of bolivia abstract the origin of aligned rectangular shaped lakes in the beni basin of bolivia has been investigated utilizing landsat imagery shuttle imaging radar and the available scientific literature the lakes tend to line up in two preferred orientations northwest and northeast they occur in cenozoic sediments of the beni basin situated between the brazilian shield and the andean foredeep available evidence suggests that the shapes and orientations of the lakes are primarily controlled by a nearly orthogonal fracture pattern propagated upward from the underlying granitic brazilian shield basement these orientations and shapes may reflect a reactivated ancient global fracture pattern or may be the result of an e w greatest principal compressive stress 1 and subsequent downwarping and uplifting of the beni basin during the cenozoic andean orogeny the lakes themselves may occupy down dropped basement blocks induced in the gently upwarped basement while unusual these lakes are not unique this suggests that transmission of basement structure through overlying sediments may occur in other regions but that special conditions such as little or no lateral compression of the sediments the absence of high trees and vegetation stability of surface material from drifting and a high water table are necessary to preserve and enhance such surface features

ground satellite observations and atmospheric modeling of dust storms originating in the high puna altiplano deserts south america implications for the interpretation of paleo climatic archives 1 this study provides a detailed description of the sources transport dispersion and deposition of two major dust events originating from the high altitude subtropical puna altiplano plateau 15 26 s 65 69 w in south america a long and severe drought provided the right conditions for the onset of both events in july 2009 and 2010 dust was transported se and deposited over the pampas region and was observed to continue to the atlantic ocean dust monitoring stations located downwind recorded both events and samples were characterized through chemical and textural analysis through a combination of meteorological data and satellite observations calipso and modis detectors we estimate the emission flux for the 2010 event this estimate was used to constrain the hybrid single particle lagrangian integrated trajectory hysplit transport model and simulate the dust event both satellite imagery and model results agree in the location and extension of the dust cloud calipso detected dust between 6000 and 8500 m a s l which remained at this height during most of its trajectory the dust cloud mixed with a strong convective system in the region and the associated precipitation brought down significant amounts of dust to the ground dust particle size analysis for both events indicates that near the sources dust samples show median modes of 12 4 14 1 m similar to modes observed 1300 km away chemical composition of sediments from potential dust sources shows distinct signatures within the puna altiplano plateau the puna sector being clearly different from the altiplano area in addition both sources are markedly different from the patagonian chemical fingerprint these results have important implications to improve the interpretation of paleo environmental archives preserved on the argentine loess antarctic ice cores and southern ocean marine sediments

origin and morphology of barchan and linear clay dunes in the shuhongtu basin alashan plateau china abstract clay dunes are characterized by a relatively high content of silt and clay and are typically developed on the lee side margin of closed basins in arid and semi arid areas although they are widely distributed aeolian landforms on earth little is known about their development and distribution in asia our field investigations have identified for the first time the occurrence of clay dunes in the alashan plateau north china the clay dunes occur in three isolated lowland areas of the suhongtu sht basin and their morphologies barchans hooked barchans asymmetrical barchans and linear or seif dunes differ substantially from those of the well studied clay dunes in australia africa and north america these differences could be mainly attributed to the asymmetrical bimodal wind regime prolonged drought and sediment physical properties which indicate that dunes of any type can be formed in sand silt or clay based on the known evolution of the sht paleo lake basin and regional climate change we infer that the landscape of modern clay dunes in the desert of the alashan plateau does not predate mis 5 and probably formed during the late holocene analyses of grain size distributions and the contents of trace and rare earth elements combined with geomorphological characteristics indicate that the source sediments of the clay dunes are mainly local cretaceous tertiary and quaternary red fluvial lacustrine mudstone and sediments while the ultimate source is the weathered and denuded products of granitoids of the east altay mountains comparison of the morphology and alignment of the clay dunes with the prevailing wind pattern tends to support tsoar s 1984 model of the transition in dune shape from barchans to seif or linear dunes during 2003 2013 the seif or linear dunes of the sht basin migrated laterally and elongated northeastward at rates of about 2 4 m yr and 16 20 m yr respectively