formation and stability of transverse and longitudinal sand dunes the shape of dunes depends on the history of wind regimes and sand availability in deserts exposed to winds from two different directions but with comparable magnitude dunes are found to be linear ridges which are either perpendicular or parallel to the mean wind direction depending on the angle between the two wind directions these dunes respectively observed for small and large angles between winds are called transverse and longitudinal dunes in both cases their large width hundreds of meters and evolution time scale years strongly limit the investigation of their dynamics and thus our understanding of such structures here we show that under water similar structures can be obtained but at much smaller space and time scales performing controlled experiments together with numerical simulations we highlight the physical mechanisms at play in the formation and long term evolution of these structures we show in particular that while longitudinal dunes are stable and extend in time transverse dunes are unstable they evolve into wavy ridges and eventually break into barchans if the sand supply is too low this fundamental difference is understood through the study of single sand piles and bars exposed to two winds in the case of a large angle between winds a sand pile grows a finger pointing in the average wind direction and transforms into a longitudinal dune such an elongation does not occur for a small angle where a sand pile evolves into a barchan these results explain the morphological differences between straight and long longitudinal dunes and sinuous transverse dunes while giving keys to infer the wind history or pattern state of development from the observation of dune shapes in the field

mapping and characterization of small scale aeolian structures on mars an example from the msl landing site in gale crater abstract a new set of methodologies which allow a simple and fast mapping and characterization of small scale aeolian structures on mars is introduced in this work we follow an object based approach in which the bedform crestlines are automatically mapped and characterized from the methodology validation we conclude that the quality of the obtained results is comparable with human produced photointerpretations we show that the accuracy associated with the measurement of mean trends from the automatically mapped patterns is less than 10 through the analysis of two areas located near the msl landing site in gale crater we explore some of the possibilities that the automatic mapping technique enables namely for multitemporal surveys and ripple pattern analysis we demonstrate how the mapped ripple patterns can be used to assess local wind orientations and we analyze some examples that illustrate the diversity of wavelength spatial distributions that can be found on mars we try to relate these pattern wavelength variations with the possible local influence of granulometry and wind shear velocity

visible near infrared spectral diversity from in situ observations of the bagnold dune field sands in gale crater mars as part of the bagnold dune campaign conducted by mars science laboratory rover curiosity visible near infrared reflectance spectra of dune sands were acquired using mast camera mastcam multispectral imaging 445 1013 nm and chemistry and camera chemcam passive point spectroscopy 400 840 nm by comparing spectra from pristine and rover disturbed ripple crests and troughs within the dune field and through analysis of sieved grain size fractions constraints on mineral segregation from grain sorting could be determined in general the dune areas exhibited low relative reflectance a weak 530 nm absorption band an absorption band near 620 nm and a spectral downturn after 685 nm consistent with olivine bearing sands the finest grain size fractions occurred within ripple troughs and in the subsurface and typically exhibited the strongest 530 nm bands highest relative reflectances and weakest red near infrared ratios consistent with a combination of crystalline and amorphous ferric materials coarser grained samples were the darkest and bluest and exhibited weaker 530 nm bands lower relative reflectances and stronger downturns in the near infrared consistent with greater proportions of mafic minerals such as olivine and pyroxene these grains were typically segregated along ripple crests and among the upper surfaces of grain flows in disturbed sands sieved dune sands exhibited progressive decreases in reflectance with increasing grain size as observed in laboratory spectra of olivine size separates the continuum of spectral features observed between the coarse and fine grained dune sands suggests that mafic grains ferric materials and air fall dust mix in variable proportions depending on aeolian activity and grain sorting

large wind ripples on mars a record of atmospheric evolution wind blowing over sand on earth produces decimeter wavelength ripples and hundred meter to kilometer wavelength dunes bedforms of two distinct size modes observations from the mars science laboratory curiosity rover and the mars reconnaissance orbiter reveal that mars hosts a third stable wind driven bedform with meter scale wavelengths these bedforms are spatially uniform in size and typically have asymmetric profiles with angle of repose lee slopes and sinuous crest lines making them unlike terrestrial wind ripples rather these structures resemble fluid drag ripples which on earth include water worked current ripples but on mars instead form by wind because of the higher kinematic viscosity of the low density atmosphere a reevaluation of the wind deposited strata in the burns formation about 3 7 billion years old or younger identifies potential wind drag ripple stratification formed under a thin atmosphere

time frequency characteristics of tsunami magnetic signals from four pacific ocean events the recent deployment of highly sensitive seafloor magnetometers coinciding with the deep solar minimum has provided excellent opportunities for observing tsunami electromagnetic signals these fluctuating signals periods ranging from 10 20 min are generally found to be within pm sim 1 nt and coincide with the arrival of the tsunami waves previous studies focused on tsunami electromagnetic characteristics as well as modeling the signal for individual events this study instead aims to provide the time frequency characteristics for a range of tsunami signals and a method to separate the data s noise using additional data from a remote observatory we focus on four pacific ocean events of varying tsunami signal amplitude 1 the 2011 tohoku japan event m9 0 2 the 2010 chile event m8 8 3 the 2009 samoa event m8 0 and 4 the 2007 kuril islands event m8 1 we find possible tsunami signals in high pass filtered data and successfully isolate the signals from noise using a cross wavelet analysis the cross wavelet analysis reveals that the longer period signals precede the stronger shorter period signals our results are very encouraging for using tsunami magnetic signals in warning systems

chemistry mineralogy and grain properties at namib and high dunes bagnold dune field gale crater mars a synthesis of curiosity rover observations the mars science laboratory curiosity rover performed coordinated measurements to examine the textures and compositions of aeolian sands in the active bagnold dune field the bagnold sands are rounded to subrounded very fine to medium sized 45 500 m with 6 distinct grain colors in contrast to sands examined by curiosity in a dust covered inactive bedform called rocknest and soils at other landing sites bagnold sands are darker less red better sorted have fewer silt sized or smaller grains and show no evidence for cohesion nevertheless bagnold mineralogy and rocknest mineralogy are similar with plagioclase olivine and pyroxenes in similar proportions comprising 90 of crystalline phases along with a substantial amorphous component 35 15 yet bagnold and rocknest bulk chemistry differ bagnold sands are si enriched relative to other soils at gale crater and h 2o s and cl are lower relative to all previously measured martian soils and most gale crater rocks mg ni fe and mn are enriched in the coarse sieved fraction of bagnold sands corroborated by visible near infrared spectra that suggest enrichment of olivine collectively patterns in major element chemistry and volatile release data indicate two distinctive volatile reservoirs in martian soils 1 amorphous components in the sand sized fraction represented by bagnold that are si enriched hydroxylated alteration products and or h 2o or oh bearing impact or volcanic glasses and 2 amorphous components in the fine fraction 40 m represented by rocknest and other bright soils that are fe s and cl enriched with low si and adsorbed and structural h 2o

recent near surface wind directions inferred from mapping sand ripples on martian dunes abstract the high resolution imaging science experiment hirise provides the capability to obtain orbital images of mars that are of sufficient resolution to record wind ripple patterns on the surfaces of sand dunes ripple patterns provide valuable insights into aeolian erosion and deposition on earth and mars in this study we develop a systematic mapping procedure to examine sand ripple orientations and create surface process maps to evaluate the recent wind flow over the dunes as well as the interplay of wind and dune shape by carefully examining the morphology of the dunes and the location of grainflow and grainfall on dune slipfaces the recent near surface wind direction short term wind can be identified results from the analysis of three dune fields on the floors of craters west of hellas basin show regional n nw se and ese wind directions in the three adjacent dune fields surface process and flow maps suggest a complex wind pattern the comparison of short term wind with dune constructing wind long term wind shows ne and ese winds may be persistent at least for the past thousands of years the results also show that the orientation of inferred wind direction on linear dunes is correlated with the crestlines which suggest that form flow interaction may take place the results of local wind flow documentation should improve martian surface wind modeling and advance our understanding of sand transport as well as the rates of sand mobility on both mars and earth

the geologic exploration of the bagnold dune field at gale crater by the curiosity rover the mars science laboratory rover curiosity engaged in a month long campaign investigating the bagnold dune field in gale crater what represents the first in situ investigation of a dune field on another planet has resulted in a number of discoveries collectively the curiosity rover team has compiled the most comprehensive survey of any extra terrestrial aeolian system visited to date with results that yield important insights into a number of processes including sediment transport bedform morphology and structure chemical and physical composition of aeolian sand and wind regime characteristics these findings and more are provided in detail by the jgr planets special issue curiosity s bagnold dunes campaign phase i

on the porphyroblastic eclogites of the śnieznik mountains in the polish sudetes abstract a rare textural variety of eclogite characterized by a two fold occurrence of omphacite as older microlites and as later porphyroblasts enclosing numerous microlites has been found at only two localities in the polish sudetes wojtowka and nowa wie the chemical compositions of 27 mineral grains in four samples of such eclogites have been determined by electron microprobe spot analysis all omphacite analyses of both porphyroblasts and microlites show almost identical compositions except for one microlite enclosed in an armoured relic of tremolite this microlite displays a lower na content and is considered to belong to an earlier stage of metamorphic evolution preceding the stage of eclogitization it is deduced that these porphyroblastic eclogites experienced three successive stages of metamorphic evolution 1 1 pre eclogite stage when the primary rocks developed the mineral composition of a low temperature metabasite greenschist facies 2 2 eclogite stage when the rock gained typical eclogite mineral compositions as a consequence of a strong increase in total pressure unaccompanied by an increase in ph2o eclogite facies 3 3 post eclogite stage when the garnet omphacite association ceased to be stable and was transformed into a hornblende plagioclase association as a result of the decrease of total pressure which became equal to ph2o amphibolite facies

bounded influence magnetotelluric response function estimation author posting blackwell 2004 this article is posted here by permission of blackwell for personal use not for redistribution the definitive version was published in geophysical journal international 157 2004 988 1006 doi 10 1111 j 1365 246x 2004 02203 x

aeolian processes and dune morphology in gale crater abstract datasets at resolutions many times greater than previously available were used to study aeolian features within gale crater high resolution thermal inertia data allowed for detailed particle size estimation with the data sufficient to resolve dunefields a wide range of grain sizes have now been identified in the gale crater dunefields ranging from medium to very coarse sand high resolution imaging science experiment hirise and themis vis data allowed for detailed analysis of the dune morphology and slip faces which shows that the dunes have responded to topographic influences on prevailing wind directions under a present day wind regime this result was corroborated by a regional mesoscale model for the crater under dust storm conditions the central mound and smaller scale crater floor topography has altered the prevailing wind regime and dune patterns aeolian activity has thus played and continues to play an important role in shaping many of the present surface features of gale crater the arrival of a future lander mission such as the mars science laboratory would be able to sample these surface features directly and add a wealth of data to the understanding of gale crater

mineralogy of an active eolian sediment from the namib dune gale crater mars the mars science laboratory rover curiosity is using a comprehensive scientific payload to explore rocks and soils in gale crater mars recent investigations of the bagnold dune field provided the first in situ assessment of an active dune on mars the chemistry and mineralogy chemin x ray diffraction instrument on curiosity performed quantitative mineralogical analyses of the 150 m size fraction of the namib dune at a location called gobabeb gobabeb is dominated by basaltic minerals plagioclase fo56 olivine and two ca mg fe pyroxenes account for the majority of crystalline phases along with minor magnetite quartz hematite and anhydrite in addition to the crystalline phases a minimum 42 wt of the gobabeb sample is x ray amorphous mineralogical analysis of the gobabeb data set provides insights into the origin s and geologic history of the dune material and offers an important opportunity for ground truth of orbital observations chemin s analysis of the mineralogy and phase chemistry of modern and ancient gale crater dune fields together with other measurements by curiosity s science payload provides new insights into present and past eolian processes on mars

numerical study of shear stress distribution over sand ripples under terrestrial and martian conditions author s siminovich a elperin t katra i kok jf sullivan r silvestro s yizhaq h

two dimensional simulations of the tsunami dynamo effect using the finite element method 1 conductive seawater moving in the geomagnetic main field generates electromotive force in the ocean this effect is well known as the oceanic dynamo effect recently it has been reported that tsunamis are also associated with the oceanic dynamo effect and tsunami induced electromagnetic field variations were actually observed on the seafloor for instance our research group succeeded in observing tsunami induced magnetic variations on the seafloor in the northwest pacific at the time of the 2011 tohoku earthquake in this study we developed a time domain tsunami dynamo simulation code using the finite element method to explain the tsunami induced electromagnetic variations observed on the seafloor our simulations successfully reproduced the observed seafloor magnetic variations as large as 3 nt it was also revealed that an initial rise in the horizontal magnetic component prior to the tsunami arrival as large as 1 nt was induced by the tsunami

evidence of glaucophane schist facies metamorphism in the east karkonosze complex west sudetes poland in the east karkonosze complex karkonosze riesengebirge which occurs at the northern margin of the bohemian massif rocks of the glaucophane schist facies and transitions between the glaucophane schist facies greenschist facies and epidote amphibolite facies are present they belong to the leszczyniec volcanic formation lvf of cambrian ordovician age and to the mainly metasedimentary czarnow schist formation csf of ordovician silurian age similar high pressure low temperature rocks occur in the southern karkonosze and in the kaczawa mountains within metavolcanic formations of approximately the same age petrographic and electron probe studies show complex relationships between minerals including chemical zoning in the east karkonosze three stages of metamorphism pre dating contact metamorphism by late variscan lowermost upper carboniferous granite intrusion were distinguished stage 1 ocean floor amphibolite facies observed only in part of the lvf stage 2 high pressure low temperature variably glaucophane schist facies high pressure greenschist facies and epidote amphibolite facies stage 3 medium pressure greenschist facies accompanied by strong deformations glaucophane schist facies rocks formed in stage 2 survived the later stages of metamorphism only in the southern part of east karkonosze i e in lasocki range and r chory using the maruyama et al 1986 geobarometer the glaucophane bearing rocks formed at 6 5 7 kb those with crossite at 5 6 kb and rocks with magnesioriebeckite riebeckite at 4 5 kb other estimates for glaucophane bearing rocks give somewhat higher values of pressure i e 7 12 kb at temperatures between 300 and 530 c the highest temperatures are recorded in the glaucophane and garnet bearing rocks stilpnomelane may occur in all of these rocks the subduction obduction episode responsible for this high pressure low temperature metamorphism is considered to have taken place in the early variscan although no geochronology is yet available to confirm this

tectonics and plate tectonics model for the variscan belt of europe abstract a plate tectonics model is presented to explain the tectonometamorphic characteristics of the european variscides after the closing of two oceanic domains by two sided subduction 500 420 ma and obduction 420 380 ma collision of the european and african continental plates occurred we propose that the subsequent complex intracontinental deformation 380 290 ma is the result of a double subduction of the continental lithosphere accompanied by crust mantle decollement this mechanism explains the progressive crustal thickening and migration of the deformation through time from the sutures toward the external parts of the variscan belt accounting for this model and for the relationships between the european variscides and the other paleozoic peri atlantic belts caledonides appalachian mauritanides and morocco we infer the relative positions of africa america and europe between the silurian and the permian

flume experiments on the alignment of transverse oblique and longitudinal dunes in directionally varying flows for more than a century geologists have wondered why some bedforms are orientated roughly transverse to flow whereas others are parallel or oblique to flow this problem of bedform alignment was studied experimentally using subaqueous dunes on a 3 6 m diameter sand covered turntable on the floor of a 4 m wide flume in each experiment two flow directions relative to the bed were produced by alternating the turntable between two orientations the turntable was held in each orientation for a short time relative to the reconstitution time of the bedforms the resulting bedforms were in equilibrium with the time averaged conditions of the bimodal flows dune alignment was studied for five divergence angles the angle between the two flow directions 45 67 5 90 112 5 and 135 the flow depth during all experiments was approximately 30 cm mean velocity was approximately 50 cm s 1 and mean grain diameter was 0 6 mm each experiment continued for 30 75 min during which time the flume flow was steady and the turntable position changed every 2 min at the end of each experiment water was slowly drained from the flume and dune alignment was measured transverse dunes defined relative to the resultant transport direction were created when the divergence angle was 45 and 67 5 and longitudinal dunes were created when the divergence angle was 135 at intermediate divergence angles dunes with both orientations were produced but transverse dunes were dominant at 90 and longitudinal dunes were dominant at 112 5 one experiment was conducted with a divergence angle of 135 and with unequal amounts of transport in the two flow directions this was achieved by changing the orientation of the turntable at unequal time intervals thereby causing the amount of transport to be unequal in the two directions the dunes formed during this experiment were oblique to the resultant transport direction these experimental dunes follow the same rule of alignment as wind ripples studied in previous turntable experiments in both sets of experiments the bedforms developed with the orientation having the maximum gross bedform normal transport the orientation at which the sum of the bedform normal components of the two transport vectors reaches its maximum value in other words the bedforms develop with an orientation that is as transverse as possible to the two flows in those cases where the two flows diverge by more than 90 and transport equal amounts of sand bedforms that are as transverse as possible to the two separate flows will be parallel to the resultant of the two flow vectors although such bedforms have been defined by previous work as longitudinal bedforms they are intrinsically the same kind of bedform as transverse bedforms

tsunami source of the 2011 tohoku earthquake detected by an ocean bottom magnetometer abstract tsunami induced magnetic signals resulting from the 11 march 2011 tohoku earthquake m 9 0 were identified from an examination of the record of an ocean bottom electromagnetometer emplaced 50 km east of the japan trench the impulsive variation of the vertical magnetic field component directly indicates the tsunami wave height and arrival time at the station the impulsive variation of the horizontal magnetic components indicates east southeast as the tsunami propagation direction these data indicate that the tsunami source was located along the japan trench at approximately 39 0 n latitude which is about 100 km northeast from the main rupture area joint analysis of the observed magnetic variations and offshore sea level data supports this source location and indicates that the tsunami origin time was about 1 min after the earthquake origin time in addition the magnetic field variation and the sea level change indicate that the source area was elongated in the trench direction and had a narrow width

u pb ages from sw poland evidence for a caledonian suture zone between baltica and gondwana faunal and palaeomagnetic evidence suggests the existence of a c 3000 km wide tornquist sea between gondwana and baltica in early ordovician times which narrowed to 50 2 ma an unmetamorphosed ophiolite gives a 420 20 2 ma age whilst in two other terranes amphibolite facies island arc lavas have fossiliferous lower ludlow 424 415 ma sequences all are unconformably overlain by unmetamorphosed upper devonian conglomerates a sinistral transpressive regime is observed in regionally extensive mylonite zones titanite and zircon ages 338 2 3 and 339 4 ma record variscan magmatism the data suggest considerable narrowing of the tornquist sea during the ordovician continuing ocean floor and island arc activity in the silurian and final sinistral transpressive closure by the mid devonian

superposition of aeolian dust ripple patterns as a result of changing wind directions the effect of a change of wind direction on the orientation and some other morphometric characteristics of aeolian dust ripples is investigated ripple formation is simulated in a wind tunnel on surfaces that are already characterized by a previously established rippling the effect of a wind rotation of 45 degrees 90 degrees and 180 degrees is examined it is found that wind rotations of 45 and 180 degrees will lead towards a ripple alignment perpendicular to the last air flow a wind rotation of 90 degrees however leads towards a ripple alignment perpendicular to the resultant wind direction the faster the wind blows the more this effect is expressed no distinct relationship exists between the asymmetry of a dust ripple and a dust ripple field and the direction of the wind blowing as the ripples formed as the orientation and asymmetry of aeolian dust ripples do not necessarily reflect the air flow direction during which the ripples formed great care should be taken when reconstructing wind directions from such aeolian ripples

tsunami signals from the 2006 and 2007 kuril earthquakes detected at a seafloor geomagnetic observatory 1 a seafloor geomagnetic observatory in the northwest pacific detected clear electromagnetic em variations associated with tsunami passage from two earthquakes that occurred along the kuril trench previous seismological analyses indicated that the m8 3 earthquake on 15 november 2006 was an underthrust type on the landward slope of the trench while the m8 1 earthquake on 13 january 2007 was a normal fault type on the seaward side the em measurements enabled precise monitoring of the tsunami propagation direction as well as particle motion of the seawater the estimated horizontal water velocity differs significantly for the 2006 and 2007 tsunamis in terms of initial motion and dispersive characters being consistent with the hydrodynamic simulation results of the tsunamis namely the tsunami induced horizontal geomagnetic components showed opposite signs for the rise and retreat waves as expected from the electric current wall hypothesis the dispersion effect is more remarkable in the 2007 event with a smaller source region of its tsunamigenic earthquake the 2007 tsunamis therefore tend to violate the long wave approximation the boussinesq approximation was required to reproduce the dispersive character of the 2007 event in our numerical simulation in terms of tsunami forecast an important advantage of em sensors over conventional tsunami sensors such as seafloor pressure gauges is their capability of vector measurements in addition to their ability to monitor particle motions the first peak of the downward magnetic component always precedes the tsunami peak suggesting a significant improvement in global tsunami warning systems if vector em sensors are integrated into the existing systems

modelling of the total electronic content and magnetic field anomalies generated by the 2011 tohoku oki tsunami and associated acoustic gravity waves summary in this work numerical simulations of the atmospheric and ionospheric anomalies are performed for the tohoku oki tsunami 2011 march 11 the tsunami atmosphere ionosphere tai coupling mechanism via acoustic gravity waves agws is explored theoretically using the tai coupled model for the modelled tsunami wave as an input the coupled model simulates the wind density and temperature disturbances or anomalies in the atmosphere and electron density magnetic anomalies in the f region of the ionosphere also presented are the gps total electron content tec and ground based magnetometer measurements during the first hour of tsunami and good agreements are found between modelled and observed anomalies at first within 6 min from the tsunami origin the simulated wind anomaly at 250 km altitude and tec anomaly appear as the dipole shaped disturbances around the epicentre then as the concentric circular wave fronts radially moving away from the epicentre with the horizontal velocity 800 m s 1 after 12 min followed by the slow moving horizontal velocity 250 m s 1 wave disturbance after 30 min the detailed vertical horizontal propagation characteristics suggest that the anomalies appear before and after 30 min are associated with the acoustic and gravity waves respectively similar propagation characteristics are found from the gps tec and magnetic measurements presented here and also reported from recent studies the modelled magnetic anomaly in the f region ionosphere is found to have similar temporal variations with respect to the epicentre distance as that of the magnetic anomaly registered from the ground based magnetometers the high frequency component 10 min of the simulated wind tec and magnetic anomalies in the f region develops within 6 7 min after the initiation of the tsunami suggesting the importance of monitoring the high frequency atmospheric ionospheric anomalies for the early warning these anomalies are found to maximize across the epicentre in the direction opposite to the tsunami propagation suggesting that the large atmospheric ionospheric disturbances are excited in the region where tsunami does not travel

phase relations of epidote blueschists phase diagrams have been computed for minerals in the system ncmash using the optimised thermodynamic data base of berman 1988 augmented by data on glaucophane and pumpellyite to illustrate the relationships between rocks containing epidote and sodic amphibole and those containing assemblages characteristic of neighbouring metamorphic facies the stoichiometries of stable bounding equilibria yield a simple list of mineral parageneses that serves to define an epidote blueschist facies and surrounding metamorphic facies the calculations suggest that when iron free the pairs zoisite glaucophane and clinozoisite glaucophane do not possess a stability field the natural fe bearing paragenesis of epidote sodic amphibole occupies a closed field in the pt diagram whose size increases dramatically as the ratio fe3 al in the minerals is increased where garnet is involved in bounding reactions such as with respect to eclogite and garnet bearing albite epidote amphibolite the epidote blueschist field decreases in size as the ratio fe2 mg is increased the classic blueschist to greenschist transition reaction is best developed in rocks with large fe3 and fe2 contents and is possibly metastable in mgal rich rocks in the latter a wedge of albite epidote actinolite barroisite amphibolite separates the epidote blueschist from the greenschits paragenesis field a first occurrence of garnet divides the epidote blueschist field into a lower temperature garnet free zone and a higher temperature garnet bearing zone although the temperatures calculated for this garnet isograd seem high the locations of all the facies boundaries are influenced by h2o activity however even minor amounts of co2 in the fluid phase x co2 0 005 render the epidote sodic amphibole paragenesis metastable so that facies boundaries cannot be shifted by varying the co2 content of the fluid phase below 600 c no mutual boundaries exist between the amphibolite facies and the epidote blueschist and eclogite facies respectively the calculated low pressure limit for the eclogite paragenesis pyralspite omphacite jd 50 quartz typical metabasite compositions is 12 to 14 kbars with h2o activity 0 9 or 1 5 to 2 kbar lower for jd 30

compositional variations in sands of the bagnold dunes gale crater mars from visible shortwave infrared spectroscopy and comparison with ground truth from the curiosity rover during its ascent up mount sharp the mars science laboratory curiosity rover traversed the bagnold dune field we model sand modal mineralogy and grain size at four locations near the rover traverse using orbital shortwave infrared single scattering albedo spectra and a markov chain monte carlo implementation of hapke s radiative transfer theory to fully constrain uncertainties and permitted solutions these predictions evaluated against in situ measurements at one site from the curiosity rover show that x ray diffraction measured mineralogy of the basaltic sands is within the 95 confidence interval of model predictions however predictions are relatively insensitive to grain size and are nonunique especially when modeling the composition of minerals with solid solutions we find an overall basaltic mineralogy and show subtle spatial variations in composition in and around the bagnold dunes consistent with a mafic enrichment of sands with cumulative aeolian transport distance by sorting of olivine pyroxene and plagioclase grains furthermore the large variations in fe and mg abundances 20 wt at the bagnold dunes suggest that compositional variability may be enhanced by local mixing of well sorted sand with proximal sand sources our estimates demonstrate a method for orbital quantification of composition with rigorous uncertainty determination and provide key constraints for interpreting in situ measurements of compositional variability within martian aeolian sandstones

properties of electromagnetic fields generated by tsunami first arrivals classification based on the ocean depth tsunami flow coupled with the geomagnetic field generates electric currents and associated magnetic fields although electromagnetic em tsunami signals can be used for analysis and even forecasting tsunami propagation the dynamically self consistent effect of shoaling water depth on the fluid electrodynamics has not been adequately clarified in this study we classify tsunami em phenomena into three cases based on the ocean depth and find that the deeper ocean results in stronger self induction due to the increase in both tsunami phase velocity and ocean conductance in this deep ocean case the phase lead of the vertical magnetic variation relative to the sea surface elevation is smaller while an initial rise in the horizontal magnetic component becomes observable prior to tsunami arrival furthermore we confirm that the enhancement of tsunami height in shallower oceans shifts the ocean depth supplying maximum amplitudes of tsunami magnetic fields from approximately 2 0 km to 1 5 km

basaltic sand ripples at eagle crater as indirect evidence for the hysteresis effect in martian saltation abstract the rover opportunity documented small basaltic sand ripples at the bottom of eagle crater meridiani planum on mars these ripples are composed of fine basaltic sand 100 m diameter and their average wavelength and height are 10 cm and 1 cm respectively present theories on the transition between saltation and suspension predict that such light particles are suspended by turbulence at the fluid threshold which is the minimum wind speed required to initiate saltation consequently the existence of these 100 m ripples on mars indicates that either current suspension theories are incorrect or that saltation can take place at wind speeds substantially below the fluid threshold indeed recent studies point to the occurrence of hysteresis in martian saltation that is once initiated hysteresis can be maintained at much lower wind speeds than the fluid threshold we investigated the possible role of hysteresis in the formation of fine grained ripples on mars by coupling for the first time a detailed numerical saltation model comsalt with a dynamic model for sand ripple formation the results from the coupled model indicate that ripples with properties similar to those observed at eagle crater can be developed by the impact mechanism at shear velocities far below the fluid threshold these findings are consistent with the occurrence of hysteresis in martian saltation and support the hypothesis that hysteresis plays a role in the surprisingly large sand mobility observed at several locations on mars

why deposits of longitudinal dunes are rarely recognized in the geologic record dunes that are morphologically of linear type many of which are probably of longitudinal type in a morphodynamic sense are common in modern deserts but their deposits are rarely identified in aeolian sandstones one reason for non recognition of such dunes is that they can migrate laterally when they are not exactly parallel to the long term sand transport direction thereby depositing cross strata that have unimodal cross bed dip directions and consequently resemble deposits of transverse dunes dune parallel components of sand transport can be recognized in ancient aeolian sands by examining compound crossbedding formed by small dunes that migrated across the lee slopes of large dunes and documenting that the small dunes migrated with a component in a preferred along crest direction over the large dunes

traveling ionospheric disturbances propagating ahead of the tohoku oki tsunami a case study we document two kinds of traveling ionospheric disturbances namely ctids co tsunami traveling ionospheric disturbances and atids ahead of tsunami traveling ionospheric disturbances related to the tohoku oki tsunami of 2011 march 11 they are referred to the disturbances that remain behind and ahead of the principal tsunami wave front respectively we first note their presence in a numerical experiment performed using a simulation code coupling the tsunami atmosphere and ionosphere this code uses the tsunami wavefield as an input and simulates acoustic gravity waves agws in the atmosphere and tids in the form of total electron content tec disturbance in the ionosphere the simulated tec reveals the excitation of ctids at about 2 tecu and atids at about 1 tecu representing up to 5 per cent disturbance over the ambient electron density and they arise from the dissipation of agws in the thermosphere a novel outcome is that during the tsunami passage between 6 and 12 of epicentral distance strong atids arrive 20 60 min ahead of the tsunami wave front covering 3 10 of distance from the tsunami location simulation results are compared with the far field observations using gnss satellites and confirm that atids are the first detected tec maximum occurring 20 60 min ahead of the tsunami arrival our simulation also confirms the presence of largest tec maximum representing ctids 10 20 min after the first tsunami wave atids reported in this study have characteristics that can be potentially used for the early warning of the tsunami

hercynian blueschist metamorphism in north portugal tectonothermal implications aegirine jadeite clinopyroxene 60 mol jadeite locally occurs within blueschists of the lower allochthon exposed in the tras os montes region of northern portugal peak conditions attained during blueschist facies metamorphism are estimated to have been c 420 c and 11 kbar porphyroblastic white mica paragonite phengite within the blueschist assemblage records a 36ar 40ar versus 39ar 40ar isotope correlation age of 329 4 1 6 ma in view of the relatively low t nature of the metamorphism the c 330 ma age is interpreted to date closely the high p recrystallization this tectonothermal activity is interpreted to have resulted from structural emplacement of a previously assembled crystalline nappe complex upper allochthon ophiolite nappe onto iberian protoliths of the lower allochthon during terminal stages of the hercynian orogeny

tsunami source of the 2004 sumatra andaman earthquake inferred from tide gauge and satellite data tsunami source of the 2004 sumatra andaman earthquake was esti mated from a joint inversion of tsunami waveforms recorded on tide gauges and sea surface heights captured by satellite altimetry measurements the earthquake the largest in the past 40 years caused devastating tsunami damage to countries around the indian ocean but the tsunami source in particular its northern end was not well resolved although aftershocks and crustal deformation extended from off north western sumatra island through the nicobar islands to the andaman islands some seismic wave analyses indicated a shorter source length several hundred kilometers we used tsunami waveforms recorded at 12 tide gauge stations around the source and the sea surface heights measured by three satellites jason1 topex poseidon and envisat we numerically computed tsunami propagation using realistic bathym etry more than 66 000 depth points were digitized from nautical charts and combined with the etopo2 data inversion of satellite data indicates that the tsunami source extended to the andaman islands with a total length of 1 400 km but such a model produces much larger tsunami waveforms than observed at indian tide gauge stations inversion of tide gauge records and the joint inversion indicate that the tsunami source was about 900 km long the largest slip about 13 to 25 m was located off sumatra island and the second largest slip up to 7 m near the nicobar islands the slip distribution is similar for different rupture velocities and rise times with a slow velocity of 1 km sec and a rise time of 3 min yielding the largest variance reduction

active aeolian processes on mars a regional study in arabia and meridiani terrae 1 we present evidence of widespread aeolian activity in the arabia terra meridiani region mars where different kinds of aeolian modifications have been detected and classified passing from the regional to the local scale we describe one particular dune field in meridiani planum where two ripple populations are distinguished by means of different migration rates moreover a consistent change in the ripple pattern is accompanied by significant dune advancement between 0 4 1 meter in one martian year that is locally triggered by large avalanche features this suggests that dune advancement may be common throughout the martian tropics

the meteorology of gale crater as determined from rover environmental monitoring station observations and numerical modeling part ii interpretation abstract numerical modeling results from the mars regional atmospheric modeling system are used to interpret the landed meteorological data from the rover environmental monitoring station onboard the mars science laboratory rover curiosity in order to characterize seasonal changes throughout the martian year simulations are conducted at ls 0 90 180 and 270 two additional simulations at ls 225 and 315 are explored to better understand the unique meteorological setting centered on ls 270 the synergistic combination of model and observations reveals a complex meteorological environment within the crater seasonal planetary circulations the thermal tide slope flows along the topographic dichotomy mesoscale waves slope flows along the crater slopes and mt sharp and turbulent motions all interact in nonlinear ways to produce the observed weather ls 270 is shown to be an anomalous season when air within and outside the crater is well mixed by strong flushing northerly flow and large amplitude breaking mountain waves at other seasons the air in the crater is more isolated from the surrounding environment the potential impact of the partially isolated crater air mass on the dust water noncondensable and methane cycles is also considered in contrast to previous studies the large amplitude diurnal pressure signal is attributed primarily to necessary hydrostatic adjustments associated with topography of different elevations with contributions of less than 25 to the diurnal amplitude from the crater circulation itself the crater circulation is shown to induce a suppressed boundary layer

aeolian saltation on mars at low wind speeds laboratory experiments indicate that the fluid threshold friction speed u tf required to initiate fully developed aeolian saltation is much higher on mars than on earth a discrepancy exists between mars climate models that do not predict winds this strong and observations that sand sized particles are indeed moving this paper describes how wind friction speeds well below u tf but above the impact threshold u ti required to sustain saltation can initiate sustained saltation on mars but at relatively low flux numerical experiments indicate that a sand grain on mars mobilized sporadically between u ti and u tf will develop over fetch lengths longer than generally available within low pressure wind tunnels trajectories capable of splashing grains that propagate saltation and collectively form a cluster of saltating grains that migrate downwind together the passage of a saltation cluster should leave behind a narrow zone of affected surface grains the cumulative effect of many clusters represents a low flux phenomenon that should produce slow changes to aeolian bedforms over periods in which winds remain close to u ti and never or rarely reach u tf field evidence from small impact ripples along rover traverses is consistent with effects of saltation at these low friction speeds without obvious evidence for events u tf the potential utility of this grain mobility process is that it can operate entirely at more common winds well below u tf and so help explain widespread sand movements observed on mars wherever evidence might be mostly absent for u tf being exceeded

a unified model of ripples and dunes in water and planetary environments subaqueous and aeolian bedforms are ubiquitous on earth and other planetary environments however it is still unclear which hydrodynamic mechanisms lead to the observed variety of morphologies of self organized natural patterns such as ripples dunes or compound bedforms here we present simulations with a coupled hydrodynamic and sediment transport model that resolve the initial and mature stages of subaqueous and aeolian bedform evolution in the limit of large flow thickness we identify two types of bedforms consistent with subaqueous ripples and dunes and separated by a gap in wavelength this gap is explained in terms of an anomalous hydrodynamic response in the structure of the inner boundary layer that leads to a shift of the position of the maximum shear stress from upstream to downstream of the crest this anomaly gradually disappears when the bed becomes hydrodynamically rough by also considering the effect of the spatial relaxation of sediment transport we provide a new unifying framework to compare ripples and dunes in planetary environments to their terrestrial counterparts terrestrial and planetary subaqueous and aeolian ripples and dunes can be compared in a unified framework according to simulations with a hydrodynamic and sediment transport model

megaripple migration on mars aeolian megaripples with 5 to 50 m spacing are abundant on the surface of mars these features were repeatedly targeted by high resolution orbital images but they have never been observed to move thus aeolian megaripples especially the bright toned ones often referred as transverse aeolian ridges tars have been interpreted as relict features of a past climate in this report we show evidence for the migration of bright toned megaripples spaced 1 to 35 m 5 m on average in two equatorial areas on mars indicating that megaripples and small tars can be active today the moving megaripples display sand fluxes that are 2 orders of magnitudes lower than the surrounding dunes on average and unlike similar bedforms on earth can migrate obliquely and longitudinally in addition the active megaripples in the two study areas of syrtis major and mawrth vallis show very similar flux distributions echoing the similarities between dune crest fluxes in the two study areas and suggesting the existence of a relationship between dune and megaripple fluxes that can be explored elsewhere active megaripples together with high sand flux dunes represent a key indicator of strong winds at the surface of mars a past climate with a denser atmosphere is not necessary to explain their accumulation and migration

a simple formula for estimating the magnetic fields generated by tsunami flow 1 ocean flow is known to generate magnetic fields which reach land and satellite observatories with detectable amplitudes but because the expected signal to noise ratio is poor one must typically know in advance of the data analyses much about the expected behavior in order to identify these small oceanic contributions we show that in the case of ocean flow associated with tsunamis a very simple formula relating both amplitudes and phase allows the expected magnetic fields to be directly related to the sea surface displacement using sea surface data from jason 1 the formula gives maximum magnetic amplitudes of about 2 nt for the recent dec 26 2004 tsunami which occurred near the magnetic equator but near the magnetic poles the maximum amplitudes reach about 20 nt per meter sea surface displacement determining the feasibility for extraction of tsunami generated magnetic signals is of interest in designing early warning systems and for remotely tracking tsunami development

object based dune analysis automated dune mapping and pattern characterization for ganges chasma and gale crater mars abstract a method that enables the automated mapping and characterization of dune fields on mars is described using ctx image mosaics the introduced object based dune analysis obda technique produces an objective and reproducible mapping of dune morphologies over extensive areas the data set thus obtained integrates a large variety of data allowing a simple cross analysis of dune patterns spectral and morphometric information and mesoscale wind models two dune fields located in gale crater and ganges chasma were used to test and validate the methodology the segmentation of dune related morphologies is highly efficient reaching overall accuracies of 95 in addition we show that the automated segmentation of slipface traces is also possible with expected accuracies of 85 90 a qualitative and quantitative comparison of the final outputs with photointerpretations is performed and the precision of the directional characterization of the dune patterns is evaluated we demonstrate a good agreement between the obda outputs and the photointerpreted dune morphologies with local trend deviations below 45 for 80 95 of the mapped areas because the developed algorithm is tuned for the recognition of linear features from the imagery the slipfaces of small barchans can be preferentially overlooked owing to their small extent at the spatial resolution of the ctx mosaics dune types composed of longer linear morphologies are much better represented including correct mapping of secondary structures having proved the effectiveness and accuracy of the mapping procedure we discuss its future applications for the improvement of dune catalogs on mars

martian aeolian activity at the bagnold dunes gale crater the view from the surface and orbit the first in situ investigation of an active dune field on another planetary surface occurred in 2015 2016 when the msl curiosity rover investigated the bagnold dunes on mars hirise images show clear seasonal variations that are in good agreement with atmospheric model predictions of intra annual sand flux and migration directions that together indicate that the campaign occurred during a period of low wind activity curiosity surface images show that limited changes nevertheless occurred with movement of large grains particularly on freshly exposed surfaces two occurrences of secondary grain flow on the slip face of namib dune and a slump on a freshly exposed surface of a large ripple these changes are seen at sol to sol time scales grains on a rippled sand deposit and unconsolidated dump piles show limited movement of large grains over a few hours during which mean friction speeds are estimated at 0 3 0 4 m s 1 overall the correlation between changes and peak rems winds is moderate with high wind events associated with changes in some cases but not in others suggesting that other factors are also at work the distribution of rems 1 hz wind speeds show a tail up to the 20 m s 1 showing that even higher speed winds occur non aeolian triggering mechanisms are also possible the low activity period at the dunes documented by curiosity provides clues to processes that dominated in the martian past under conditions of lower obliquity

bedform spacing from defect dynamics spacing is a time varying characteristic of bedform fields deriving from the behavior of defects ends of crest lines in the bedform pattern in a model based on this hypothesis crest line length is lost and spacing increases because bedform defects which are smaller in height and faster migrating than surrounding bedform crest lines merge with larger bedforms as defects migrate through bedform fields spacing in large bedform fields asymptotically increases with the logarithm of time as pairs of oppositely facing defects meet and annihilate spacing in small bedform fields such as flumes exponentially approaches a fixed value as defects are eliminated at the boundaries of the field model predictions are compatible with observed spacing of transverse bedforms ripples formed under waves and linear dunes calling into question the widespread assumption that bedform spacing approaches a steady state value characteristic of fluid flow and sediment transport over two dimensional bedforms

bedform alignment in directionally varying flows many kinds of sediment bedforms are presumed to trend either normal or parallel to the direction of sediment transport for this reason the trend of bedforms observed by remote sensing or by field observations is commonly used as an indicator of the direction of sediment transport such presumptions regarding bedform trend were tested experimentally in bidirectional flows by rotating a sand covered board in steady winds transverse oblique and longitudinal bedforms were created by changing only two parameters the angle between the two winds and the proportions of sand transported in the two directions regardless of whether the experimental bedforms were transverse oblique or longitudinal as defined by the bedform trend relative to the resultant transport direction they all had trends that yielded the maximum gross transport across the bedforms the fact that many of the experimental bedforms were neither transverse nor parallel to the resultant transport direction suggests that transport directions cannot be accurately determined by presuming such alignment

sedimentary processes of the bagnold dunes implications for the eolian rock record of mars the mars science laboratory rover curiosity visited two active wind blown sand dunes within gale crater mars which provided the first ground based opportunity to compare martian and terrestrial eolian dune sedimentary processes and study a modern analog for the martian eolian rock record orbital and rover images of these dunes reveal terrestrial like and uniquely martian processes the presence of grainfall grainflow and impact ripples resembled terrestrial dunes impact ripples were present on all dune slopes and had a size and shape similar to their terrestrial counterpart grainfall and grainflow occurred on dune and large ripple lee slopes lee slopes were 29 where grainflows were present and 33 where grainfall was present these slopes are interpreted as the dynamic and static angles of repose respectively grain size measured on an undisturbed impact ripple ranges between 50 m and 350 m with an intermediate axis mean size of 113 m median 103 m dissimilar to dune eolian processes on earth large meter scale ripples were present on all dune slopes large ripples had nearly symmetric to strongly asymmetric topographic profiles and heights ranging between 12 cm and 28 cm the composite observations of the modern sedimentary processes highlight that the martian eolian rock record is likely different from its terrestrial counterpart because of the large ripples which are expected to engender a unique scale of cross stratification more broadly however in the bagnold dune field as on earth dune field pattern dynamics and basin scale boundary conditions will dictate the style and distribution of sedimentary processes

morphologic diversity of martian ripples implications for large ripple formation large ripples with meter scale wavelengths are ubiquitous across mars curiosity s traverse of the bagnold dune field revealed a morphologic diversity of large martian ripples that helps constrain their formative mechanism large ripples develop in isolated fields and on dunes they form transversely and obliquely to longitudinally to the net sand flux direction in unimodally and bimodally distributed very fine to very coarse sand they have either straight or sinuous crestlines inactive ripples are covered with dust whereas migrating ripples are dust free here we present a unifying view of ripples that form in near bed sediment transport conditions encompassing fluid drag and coarse grained ripples to explain the range of large martian ripple morphologies and expand the use of bedforms as environmental indicators

water abundance of dunes in gale crater mars from active neutron experiments and implications for amorphous phases we report the water abundance of bagnold dune sand in gale crater mars by analyzing active neutron experiments using the dynamic albedo of neutrons instrument we report a bulk water equivalent hydrogen abundance of 0 68 0 15 wt which is similar to measurements several kilometers away and from those taken of the dune surface thus the dune is likely dehydrated throughout furthermore we use geochemical constraints including bulk water content to develop compositional models of the amorphous fraction for which little information is known we find the amorphous fraction contains 26 to 64 wt basaltic glass and up to 24 wt rhyolitic glass suggesting at least one volcanic source for the dune material we also find a range of hydrated phases may be present in appreciable abundances either from the incorporation of eroded aqueously altered sediments or the direct alteration of the dune sand

advantage of wavelet technique to highlight the observed geomagnetic perturbations linked to the chilean tsunami 2010 the vertical component z of the geomagnetic field observed by ground based observatories of the international real time magnetic observatory network has been used to analyze the induced magnetic fields produced by the movement of a tsunami electrically conducting sea water through the geomagnetic field we focus on the survey of minutely sampled geomagnetic variations induced by the tsunami of 27 february 2010 at easter island ipm and papeete ppt observatories in order to detect the tsunami disturbances in the geomagnetic data we used wavelet techniques we have observed an 85 correlation between the z component variation and the tide gauge measurements in period range of 10 to 30 min which may be due to two physical mechanisms gravity waves and the electric currents in the sea as an auxiliary tool to verify the disturbed magnetic fields we used the maximum variance analysis mva at ppt the analyses show local magnetic variations associated with the tsunami arriving in advance of sea surface fluctuations by about 2 h the first interpretation of the results suggests that wavelet techniques and mva can be effectively used to characterize the tsunami contributions to the geomagnetic field and further used to calibrate tsunami models and implemented to real time analysis for forecast tsunami scenarios

the search for active marsquakes using subpixel coregistration and correlation best practice and first results the state of seismic activity on mars is currently unknown on earth coseismic displacement has been observed using visible wavelength images and subpixel coregistration and correlation techniques we apply this method to mars with the cosi corr co registration of optically sensed images and correlation software package using high resolution imaging science experiment hirise images focusing on part of the cerberus fossae fault system we derive best practices for applying this method to the study of coseismic displacements on mars using a time series of eight overlapping hirise images we achieve pixel coregistration with a mean accuracy of about 1 50 of a pixel we see no clear evidence for coseismic displacement in this region during a time period of over 8 years one possible displacement signal 1 2 m of west east displacement over a length scale of about 50 m that has similarities to terrestrial coseismic deformation was dismissed as the result of incomplete correction of steep topography during the coregistration stage ancillary observations of recurring slope lineae rsl activity in the surrounding fault system offer no supporting evidence for the occurrence of coseismic displacement but do seem to suggest rsl activity that does not fit into previous seasonal timescales although it is unlikely that we have observed coseismic displacement in our study area during this time period the best practice method and the accuracy of our results offer encouragement for future studies hirise context camera and color and stereo surface imaging system images can be used to complement and independently verify in situ seismic observations by the insight interior exploration using seismic investigations geodesy and heat transport lander or source location changes from the exomars trace gas orbiter spacecraft

two modes for dune orientation earth s sand seas dune fields experience winds that blow with different strengths and from different directions in line with the seasons in response dune fields show a rich variety of shapes from crescentic barchans to star and linear dunes these dunes commonly exhibit complex and compound patterns with a range of length scales and various orientations which up to now have remained difficult to relate to wind cycles here we develop a model for dune orientation that explains the coexistence of bedforms with different alignments in multidirectional wind regimes this model derives from subaqueous experiments which show that a single bidirectional flow regime can lead to two different dune orientations depending on sediment availability i e the erodibility of the bed sediment availability selects the overriding mechanism for the formation of dunes increasing in height from the destabilization of a sand bed with no restriction in sediment availability or elongating in a finger on a non erodible surface from a localized sand source these mechanisms drive the dune orientation therefore dune alignment maximizes dune orthogonality to sand fluxes in the bed instability mode while dunes are aligned with the mean sand transport direction in the fingering mode applied to earth s deserts the model quantitatively predicts the orientation of rectilinear dunes and their superimposed patterns this field study suggests that many linear dunes on earth elongate from sources and are simply aligned with the mean sand transport direction

synchronous diversification of laurentian and baltic rhynchonelliform brachiopods implications for regional versus global triggers of the great ordovician biodiversification event the profound global impact of marine radiations during the great ordovician biodiversification event gobe is widely appreciated however diversification varied among paleocontinents and these individual trajectories are less understood here we present a new species level diversity curve for rhynchonelliform brachiopods from midcontinental laurentia based on bed by bed analysis of the simpson group of oklahoma usa diversity and abundance data span the dapingian through sandbian stages which encompass the interval of maximum global diversification a rapid statistically significant increase in brachiopod diversity was observed in the early darriwilian histiodella holodentata biozone we interpret this as a biological signal because the increase cannot be explained by sampling intensity facies types or position along depositional gradient diversifications on laurentia and baltica were temporally synchronous at the biozone level and cumulative diversity curves for the regions show similar patterns suggesting a global driver for the radiations the taxonomic composition of the brachiopod faunas however differs substantially highlighting the importance of regional controls on diversification thus both global and local factors controlled diversity increase during the gobe

the martian dust storm of sol 1742 after nearly five earth years on mars the mutch memorial station viking lander 1 finally witnessed a local dust storm that eroded trenches conical piles and other disturbed surfaces in the sample field and near the lander the event called the dust storm of sol 1742 occurred late in the third winter of lander observations between sols 1728 and 1757 analyses of tiny new wind tails and movement of materials indicate that the eroding winds were variable but more northeasterly than those that had previously shaped the surface pebbly residues and movement of 4 5 mm clods suggest drag velocities or friction speeds of the winds were about 2 2 4 0 m s wind speeds at the height of the meteorology boom 1 6 m were probably about 40 50 m s much of the observed erosion could have occurred in a few to several tens of seconds but somewhat longer times are suggested by analogy with the erosion of terrestrial soils most of the erosion occurred where preexisting equilibrium conditions of surface configurations and surface material properties had been altered by the lander during landing and during surface sampler activities but thin layers of bright fine grained dust were also removed and redistributed surfaces where preexisting equilibrium conditions were unaltered appeared to be uneroded

time and space distribution of coseismic slip of the 2011 tohoku earthquake as inferred from tsunami waveform data a multiple time window inversion of 53 high sampling tsunami waveforms on ocean bottom pressure global positioning system coastal wave and tide gauges shows a temporal and spatial slip distribution during the 2011 tohoku earthquake the fault rupture started near the hypocenter and propagated into both deep and shallow parts of the plate interface a very large slip approximately 25 m in the deep part off miyagi at a location similar to the previous 869 jogan earthquake model was responsible for the initial rise of tsunami waveforms and the recorded tsunami inundation in the sendai and ishinomaki plains a huge slip up to 69 m occurred in the shallow part near the trench axis 3 min after the rupture initiation this delayed shallow rupture extended for 400 km with more than a 10 m slip at a location similar to the 1896 sanriku tsunami earthquake and was responsible for the peak amplitudes of the tsunami waveforms and the maximum tsunami heights measured on the northern sanriku coast 100 km north of the largest slip the average slip on the entire fault was 9 5 m and the total seismic moment was 4 2 1022 n m m w 9 0 the large horizontal displacement of seafloor slope was responsible for 20 40 of tsunami amplitudes the 2011 deep slip alone could reproduce the distribution of the 869 tsunami deposits indicating that the 869 jogan earthquake source could be similar to the 2011 earthquake at least in the deep plate interface the large tsunami at the fukushima nuclear power station is due to either the combination of a deep and shallow slip or a triggering of a shallow slip by a deep slip which was not accounted for in the previous tsunami hazard assessments online material table of estimated slip for all subfaults at 0 5 min invervals

glaucophane bearing assemblage overprinted by greenschist facies metamorphism in the variscan kaczawa complex sudetes poland an early palaeozoic ordovician metamudstone sequence near wojcieszow kaczawa mts western sudetes poland contains numerous metabasite sills up to 50 m thick these subvolcanic rocks are of within plate alkali basalt type primary igneous phases in the metabasites clinopyroxene salite and kaersutite are veined and partly replaced by complex metamorphic mineral assemblages particularly the kaersutite is corroded and rimmed by zoned sodic sodic calcic and calcic amphiboles the matrix is composed of actinolite pycnochlorite albite an 0 5 epidote ps 27 33 titanite calcite opaques and occasionally biotite phengite and stilpnomelane the sodic amphiboles are glaucophane to crossite in composition with nab from 1 9 to 1 6 they are rimmed successively by sodic calcic and calcic amphiboles with compositions ranging from magnesioferri winchite to actinolite no compositions between nab 0 92 and nab 1 56 have been ascertained the textures may be interpreted as representing a greenschist facies overprint on an earlier blueschist or blueschist greenschist transitional assemblage the presence of glaucophane and no traces of a jadeitic pyroxene quartz association indicate pressures between 6 and 12 kbar during the high pressure episode temperature is difficult to assess in this metamorphic event the replacement of glaucophane by actinolite chlorite albite with associated epidote allows restriction of the upper pressure limit of the greenschist recrystallization to 8 kbar between 350 and 450 c the mineral assemblage representing the greenschist episode suggests the p t conditions of the high pressure part of the chlorite or lower biotite zone the latest metamorphic recrystallization under the greenschist facies may have taken place in the visean

patterns in mobility and modification of middle and high latitude southern hemisphere dunes on mars nasa mars data analysis program mdap nnx14ao96g mdap grant nnx12aj38g nnx16aj43g 123117

the origin of the transverse instability of aeolian megaripples abstract flat sand beds subjected to wind stress are unstable and the wind action results in two types of aeolian sand ripples normal ripples and megaripples the distinction between the two types is based on two characteristics i the normal ripple pattern usually has a wavelength of up to 30 cm while the megaripple wavelength is on the order of meters and ii unimodal distributions of sand grain size lead to normal ripples while bimodal distributions result in megaripples on mars the distinction between the two types is more difficult to ascertain because the length scales of normal ripples and megaripples can overlap and often there is no detailed information regarding their grain size distribution unlike normal ripples megaripples show transverse instability whose mechanism remains elusive resulting in a much larger sinuosity of the crestline than normal ripples in this study we investigate the megaripples transverse instability by using field measurements wind tunnel experiments and numerical simulations of a three dimensional ripple model we show that a coarse grains accumulate at megaripple crests with a corresponding reduction of the lateral sand transport along the crest and b the transverse instability of megaripples is generated by a positive feedback between the height of the crest and the accumulation of coarse grains with more grains accumulating on the higher portions of the crest the outcomes of this positive feedback are that the thickness of the coarse grain armoring layer along the crest is not uniform and that it correlates with the crest height in turn these height differences drive the transverse instability such that higher portions of the ripple migrate more slowly than the lower sections creating a wavy crestline an analysis of martian ripple images shows variations in the sinuosity index suggesting that this characteristic can be useful in distinguishing between normal ripples and megaripples on mars

multiple origins of linear dunes on earth and titan the formation of dunes is controlled by the direction of the prevailing winds and the characteristics of the sediments linear dunes in the qaidam basin china are shown to form from cohesive sediments a model that could be applicable to dunes on titan

tectonometamorphic evolution of the bohemian massif evidence from high pressure metamorphic rocks the variscan orogenic belt of which the bohemian massif is a part is typically recognized for its characteristic low pressure high temperature metamorphism and a large volume of granites however there are also bodies of high pressure rocks eclogites garnet peridotites and high pressure granulites which are small in size but widely distributed throughtout the massif initially the high pressure rocks were considered to be relicts of a much older orogenic event but the increasing data derived from isotopic and geochronological investigations show that many of these rocks have palaeozoic protoliths metamorphic ages from the high pressure rocks define no single event instead a number of discrete clusters of ages are found between about 430 ma and the time of the dominant low pressure event at around 320 330 ma

three dimensional simulation of the electromagnetic fields induced by the 2011 tohoku tsunami the motion of seawater induces electromotive force of significant intensity due to faraday s law and the resulting electromagnetic em field can be recorded by instruments installed on land or on the ocean bottom however few studies have successfully made a quantitative interpretation to obtain geophysical information from observations of tsunami induced em signals by an exact and accurate application of maxwell equations we built a scheme for three dimensional numerical simulation to calculate em fields due to ocean tidal flow and tested the system s accuracy by using the source currents in the ocean as expected from a tohoku tsunami simulation here we show examples of a comparison of data from one land observatory in the tohoku district one island observatory in the izu bonin arc and one seafloor station in the northwest pacific ocean the water motion that generates source current in the sea consists of both the primary poloidal and toroidal magnetic modes our numerical simulation shows that the field of the primary toroidal magnetic mode can be effective for seafloor observations but only when the seafloor is highly conductive we examined how the conductivity of the shallower part of the seabed composed of sediments can be constrained by the tsunami induced em field observations which is difficult in case of using ordinary seafloor magnetotelluric signals we also defined the motional impedance just as the case of ordinary magnetotellurics and showed that both modeled and observed impedances approximately indicate the phase velocity of the long wave as predicted by a simple theory

a unifying model for planform straightness of ripples and dunes in air and water abstract geologists physicists and mathematicians have studied ripples and dunes for more than a century but despite considerable effort no general model has been proposed to explain perhaps the most fundamental property of their morphology why are some bedforms straight continuous parallel and uniform in planform geometry i e two dimensional whereas others are irregular three dimensional here we argue that physical coupling along the crest of a bedform is required to produce straight crests and that along crest flow and sand transport provide effective physical mechanisms for that coupling ripples and dunes with the straightest and most continuous crests include longitudinal and oblique dunes in unidirectional flows wave ripples dunes in reversing flows wind ripples and ripples migrating along a slope at first glance these bedforms appear quite different ripples and dunes air and water transverse oblique and longitudinal orientations relative to the net sand transport direction but they all have one property in common a process that increases the amount of along crest sand transport that lengthens and straightens their crests relative to the across crest transport that makes them migrate and take the more typical and more three dimensional planform geometry in unidirectional flows that produce straight bedforms along crest transport of sand is caused by along crest flow non transverse bedform orientation gravitational transport along an inclined crest or ballistic splash in air bedforms in reversing flows tend to be straighter than their unidirectional counterparts because reverse transport across the bedform crest reduces the net across crest transport that causes the more typical irregular geometry relative to the along crest transport that smoothes and straightens planform geometry

geomagnetic field changes in response to the 2011 off the pacific coast of tohoku earthquake and tsunami abstract does the geomagnetic field change in association with earthquakes this question was first raised more than 100 years ago and since that time theoretical and observational researches have been conducted in order to obtain an answer to this question large earthquakes provide an opportunity to examine this problem because large signals are generally expected in association with large earthquakes we herein present a brief report on simultaneous measurements of the geomagnetic field in association with the 2011 tohoku earthquake m9 0 and tsunami by magnetometers at 14 stations operating in japan since the earthquake occurred during a geomagnetic storm we used time series after correcting the effect of external disturbances and induced fields a coseismic change of the geomagnetic field was observed at several stations located relatively close to the epicenter the magnitude of this coseismic change was only about 0 8 nt at one station and much smaller at other stations which prevented us from quantitatively comparing these observations with predictions based on piezomagnetic theory more distinct and rapid changes were observed during the hours following the main shock these changes are supposed to be caused either by motional induction of the tsunami or by ionospheric disturbance contrary to the significant observations of these coseismic and postseismic geomagnetic changes in response to the tohoku earthquake and tsunami we did not observe any clear precursors

pervasive aeolian activity along rover curiosity s traverse in gale crater mars the nasa mars science laboratory msl rover curiosity has safely landed near a 35 km long dark dune field in gale crater on mars this dune field crosses the landing site from the northeast to the southwest and lies along curiosity s traverse to aeolis mons here we present the first evidence of recent aeolian activity in the form of ripple and dune migration and further estimate wind directions within the dune field through analysis of ripple and dune morphologies and the mars regional atmospheric modeling system mrams we measured a minimum ripple migration rate of 0 66 m per earth year and dune migration rate of 0 4 m per earth year in the southwest portion of the field a strongly bidirectional ripple crestline orientation nearly orthogonal dune slipfaces and linear seif or oblique dunes indicate a bidirectional wind regime with winds mainly coming from the ene and from the northwest however mrams results indicate primary winds from the ene our constraints on the wind regime provide the unique opportunity to use ground measurements from msl to test the accuracy of winds predicted from orbital data

magnetic signals at easter island during the 2010 and 2015 chilean tsunamis compared with numerical models tsunami flow across the geomagnetic field induces electric currents in both the ocean and the ionosphere these currents generate secondary magnetic fields observable at the seafloor and on land magnetic field disturbances during two chilean tsunamis 2010 and 2015 were recorded at easter island observatory these tsunamis were produced after the earthquakes in chile on february 27 2010 at 06 34 utc and september 16 2015 at 22 55 utc respectively differences between existing studies regarding the origin of the tsunamigenic disturbances and the lack of studies using a numerical model for both the water velocity and the induced magnetic field motivated us to compare magnetic records with computed magnetic fields for the two events modeled disturbances were calculated by applying the biot savart law to tsunami simulations our model can calculate tsunami induced perturbations in the vertical component of the geomagnetic field obtaining a good agreement with the observations we hypothesize that the magnetic measurements may be produced by a combination of oceanic and ionospheric electric currents our analysis further reveals that even a relatively small tsunami such as the one produced by the 2015 m text w 8 2 earthquake induces an observable magnetic perturbation due to the water movement future improvements to our model may allow us to identify situations in which magnetic variations precede the tsunami arrival thereby allowing early tsunami detection