mid infrared lightcurve of vesta abstract we present a thermal mid infrared lightcurve of asteroid 4 vesta and use this to infer variations in thermophysical properties over the surface vesta was observed over three nights during the may 2007 opposition with the infrared telescope facility on mauna kea mid infrared observations are compared to a model based on the standard thermal model which is draped over a vesta shape model derived from hubble space telescope observations a visible lightcurve with similar aspect was used to estimate the albedo as vesta rotates shape and albedo can explain some of the features observed in the mid infrared lightcurve however variations in the thermophysical properties such as the beaming parameter over vesta s surface are required to completely explain the observations in order to match the mid infrared magnitudes observed of vesta a beaming parameter of 0 862 is required which is higher than other main belt asteroids such as ceres and pallas 0 756 indicating a smoother and or rockier surface on vesta variations in the beaming parameter with longitude are invoked to reproduce the observed thermal variations surface materials with relatively high beaming values indicating a smoother and or rockier surface in the eastern hemisphere of vesta coincide with locations where impact excavations may have produced surfaces that are younger and brighter relative to the western hemisphere

oil and gas developments in western canada in 1989 there were 5513 wells drilled in western canada during 1989 30 fewer than in 1988 total meterage drilled was 6 459 797 m for an average well depth of 1172 m exploratory drilling in 1989 dropped by 13 and development drilling by 40 from 1988 levels british columbia was the only area in western canada with increased activity the industry continued to acquire more acreage for less total bonus at provincial crown sales throughout western canada during 1989 3 564 827 ha were acquired for a total bonus of 484 872 000 footnote 5 although the total disposition of crown lands decreased only 4 the average bonus dropped to 136 ha down 26 from 1988 in alberta the most active exploration areas were the southern and eastern mesozoic gas play the western deep devonian gas play the oil plays on and adjacent to the peace river arch and the middle devonian carbonate oil plays in the northwest in british columbia the most active exploration areas were the mesozoic and paleozoic gas plays in the northeastern portion of the province for the first time in 5 years crown drilling rights were issued within the fraser valley in the southwest there was a focus on gas exploration in the province as pipeline reversal was implemented permitting access to canadian and california markets through the alberta transportation network in manitoba exploration and development activity continued to decline in northern canada exploratory drilling success offering of crown lands for exploration approval of gas exports and indications that many of the native lands claims may be approaching settlement all provided exploration encouragement for the next decade exploration activities occurred throughout the northwest territories from the offshore beaufort to the southern border in saskatchewan active exploration areas were shallow mesozoic gas plays in the western portions of the province and deep paleozoic oil plays in the south

geologic mapping of ejecta deposits in oppia quadrangle asteroid 4 vesta abstract oppia quadrangle av 10 288 360 e 22 is a junction of key geologic features that preserve a rough history of asteroid 4 vesta and serves as a case study of using geologic mapping to define a relative geologic timescale clear filter images stereo derived topography slope maps and multispectral color ratio images from the framing camera on nasa s dawn spacecraft served as basemaps to create a geologic map and investigate the spatial and temporal relationships of the local stratigraphy geologic mapping reveals the oldest map unit within av 10 is the cratered highlands terrain which possibly represents original crustal material on vesta that was then excavated by one or more impacts to form the basin feralia planitia saturnalia fossae and divalia fossae ridge and trough terrains intersect the wall of feralia planitia indicating that this impact basin is older than both the veneneia and rheasilvia impact structures representing pre veneneian crustal material two of the youngest geologic features in av 10 are lepida 45 km diameter and oppia 40 km diameter impact craters that formed on the northern and southern wall of feralia planitia and each cross cuts a trough terrain the ejecta blanket of oppia is mapped as dark mantle material because it appears dark orange in the framing camera clementine type color ratio image and has a diffuse gradational contact distributed to the south across the rim of rheasilvia mapping of surface material that appears light orange in color in the framing camera clementine type color ratio image as light mantle material supports previous interpretations of an impact ejecta origin some light mantle deposits are easily traced to nearby source craters but other deposits may represent distal ejecta deposits emplaced 5 crater radii away in a microgravity environment

origin of overpressure and pore pressure prediction in the baram province brunei accurate pore pressure prediction is critical in hydrocarbon exploration and is especially important in the rapidly deposited tertiary baram delta province where all economic fields exhibit overpressures commonly of high magnitude and with narrow transition zones a pore pressure database was compiled using wireline formation interval tests drillstem tests and mud weights from 157 wells in 61 fields throughout brunei overpressures are observed in 54 fields both in the inner shelf deltaic sequences and in the underlying prodelta shales porosity vs vertical effective stress plots from 31 fields reveal that overpressures are primarily generated by disequilibrium compaction in the prodelta shales but have been generated by fluid expansion in the inner shelf deltaic sequences however the geology of brunei precludes overpressures in the inner shelf deltaics being generated by any conventional fluid expansion mechanism e g kerogen to gas maturation and we propose that these overpressures have been vertically transferred into reservoir units via faults from the prodelta shales sediments overpressured by disequilibrium compaction exhibit different physical properties to those overpressured by vertical transfer and hence different pore pressure prediction strategies need to be applied in the prodelta shales and inner shelf deltaic sequences sonic and density log data detect overpressures generated by disequilibrium compaction and pore pressures are accurately predicted using an eaton exponent of 3 0 sonic log data detect vertically transferred overpressures even in the absence of a porosity anomaly and pore pressures are reasonably predicted using an eaton exponent of 6 5

spectral analysis of the quadrangles av 13 and av 14 on vesta abstract the av 13 tuccia and av 14 urbinia quadrangles are located in the south west region of vesta they are characterized by a large topographic variability from the highest vestalia terra highlands to the lowest rheasilvia basin many geological units in these quadrangles are not associated with mineralogical variability as shown by the color composite maps maps of mafic absorption band center position reveal that the principal lithology is eucrite rich howardite but diogenite rich howardite areas are also present corresponding to particular features such as antonia and justina craters which are characterized by strong mafic absorptions these quadrangles especially urbinia contain many bright ejecta such as those of tuccia crater which are the highest reflectance materials on vesta zambon et al 2014 dark areas are present and correspond to regions with deeper oh signature the two quadrangles contain many vertical ridge crests associated with the rheasilvia impact these ridges do not show mineralogical differences with respect to their surroundings but have a distinctive appearance in color ratio composite images

disequilibrium compaction overpressure in shales of the bavarian foreland molasse basin results and geographical distribution from velocity based analyses abstract shale velocity data from sonic logs and vertical seismic profiles drilling data and in situ pressure measurements from a total of 116 wells have been analyzed to gain an improved understanding of the lateral and vertical distribution and formation of overpressure in the bavarian foreland molasse basin pore pressure from sonic and vertical seismic profile velocities has been analyzed by establishing a normal compaction trend for cenozoic and mesozoic shales combined with a classical eaton approach the study demonstrates that a single shale normal compaction trend for the bavarian foreland molasse basin is sufficient to estimate pore pressure and thus overpressure from sonic and vertical seismic profile velocity maximum overpressure develops at depths between 1500 and 2500 m and increases with depth at a constant effective stress of 20 mpa the strong dependency of overpressure on burial depth constant effective stress and restriction to shale units that are overlain by sequences with very high sedimentation rates indicates that disequilibrium compaction is the main cause for overpressure also variable presence of cretaceous shales is a key control of overpressure occurrence in oligocene shales in the bavarian foreland molasse basin since cretaceous shales likely act as a pressure buffer to underpressured mesozoic carbonates successful detection and prediction of overpressure from vertical seismic profile data is encouraging for future pre drill prediction of overpressure from velocity data of seismic surveys in the bavarian foreland molasse basin resulting in improved well planning reliable calculation of project costs and improved safety during drilling activities in the bavarian foreland molasse basin the presented overpressure distributions will be a key input for future geomechanical basin and reservoir modelling studies in the bavarian foreland molasse basin

observed and numerically simulated structure of a mature supercell thunderstorm abstract through the interactive use of doppler radar analyses and a three dimensional numerical storm simulation the detailed structure of a supercell tornadic storm is analyzed this storm named the del city storm occurred in central oklahoma on 20 may 1977 the storm exhibits certain important features which are essential to maintaining its longevity and which promote the storm s transition to its tornadic phase these features are strongly influenced by the rotational character of the storm separates the precipitation from the updraft and which orients the resulting downdrafts to which reinforce low level convergence along the gust front and sustain the storm analyses of air parcel and rain trajectories within the storm provide a detailed visualization of this internal structure these trajectories reveal that air parcels rising through the cyclonically rotating updraft actually turn anticyclonically with height owing to the influence of the storm relative environmental wind field downdraft traj

variations in cloud to ground lightning characteristics among three adjacent tornadic supercell storms over the tennessee valley region the contrasting behavior of cloud to ground cg lightning associated with three adjacent supercell thunderstorms observed on 18 may 1995 is examined thunderstorm characteristics and anvil interactions are related to north south variations in cg lightning properties while tornadic activity was not consistently related to variations in cg properties radar reflectivity factor area greater than 65 db z was generally inversely related to cg frequency it is hypothesized that suppression of cg activity was produced by reduction of large number concentrations of precipitation sized particles i e presence of large hail in the particle interaction mixed phase region it is further hypothesized that seeding from upstream storm anvil ice was associated with nearly coincident enhancement of cg activity in downstream storms likewise it is hypothesized that the reduction in 65 dbz echo area inferred suppression of hail is related to this inferred anvil seeding process

neutron absorption constraints on the composition of 4 vesta global maps of the macroscopic thermal neutron absorption cross section of vesta s regolith by the gamma ray and neutron detector grand on board the nasa dawn spacecraft provide constraints on the abundance and distribution of fe ca al mg and other rock forming elements from a circular polar low altitude mapping orbit grand sampled the regolith to decimeter depths with a spatial resolution of about 300 km at this spatial scale the variation in neutron absorption is about seven times lower than that of the moon the observed variation is consistent with the range of absorption for howardite whole rock compositions which further supports the connection between vesta and the howardite eucrite and diogenite meteorites we find a strong correlation between neutron absorption and the percentage of eucritic materials in howardites and polymict breccias which enables petrologic mapping of vesta s surface the distribution of basaltic eucrite and diogenite determined from neutron absorption measurements is qualitatively similar to that indicated by visible and near infrared spectroscopy the rheasilvia basin and ejecta blanket has relatively low absorption consistent with mg rich orthopyroxene based on a combination of fe and neutron absorption measurements olivine rich lithologies are not detected on the spatial scales sampled by grand the sensitivity of grand to the presence of mantle material is described and implications for the absence of an olivine signature are discussed high absorption values found in vesta s dark hemisphere where exogenic hydrogen has accumulated indicate that this region is richer in basaltic eucrite representative of vesta s ancient upper crust

doppler radar analysis of a low precipitation severe storm abstract this is a detailed study of the structure and evolution of a convective storm that formed along the dryline in oklahoma on 26 april 1984 and developed into a supercell dual doppler wind analyses analyses of surface mesonetwork and instrumented tower data storm intercept photographs analyses of raingage data from a dense network and storm reports are presented and discussed the storm exhibited the following low precipitation lp characteristics the absence of any strong evaporatively cooled storm scale downdraft near the surface a paucity of rain reaching the ground large hail long lived rotating updrafts and a strong relatively small in areal extent unicellular radar echo the storm split and its right moving member developed into an isolated high precipitation supercell it is suggested that the region under cloud base was associated with strong radar echo caused by widely spaced large water droplets and hailstones separate cyclonically and anticyclonically rotating updrafts

exogenic olivine on vesta from dawn framing camera color data abstract in this paper we present the results of a global survey of olivine rich lithologies on 4 vesta we investigated dawn framing camera fc high altitude mapping orbit hamo color cubes 60 m pixel resolution by using a method described in thangjam et al thangjam g nathues a mengel k hoffmann m schafer m reddy v cloutis e a christensen u sierks h le corre l vincent j b russell c t 2014b meteorit planet sci arxiv 1408 4687 astro ph ep in total we identified 15 impact craters exhibiting olivine rich 40 wt ol outcrops on their inner walls some showing olivine rich material also in their ejecta and floors olivine rich sites are concentrated in the bellicia arruntia and pomponia region on vesta s northern hemisphere from our multi color and stratigraphic analysis we conclude that most if not all of the olivine rich material identified is of exogenic origin i e remnants of a or and s type projectiles the olivine rich lithologies in the north are possibly ejecta of the 90 km diameter albana crater we cannot draw a final conclusion on their relative stratigraphic succession but it seems that the dark material nathues a hoffmann m cloutis e a schafer m reddy v christensen u sierks h thangjam g s le corre l mengel k vincent j b russell c t prettyman t schmedemann n kneissl t raymond c gutierrez marques p hall i buttner i 2014b icarus 239 222 237 and the olivine rich lithologies are of a similar age the origin of some potential olivine rich sites in the rheasilvia basin and at crater portia are ambiguous i e these are either of endogenic or exogenic origin however the small number and size of these sites led us to conclude that olivine rich mantle material containing more than 40 wt of olivine is basically absent on the present surface of vesta in combination with recent impact models of veneneia and rheasilvia clenet h jutzi m barrat j a gillet ph 2014 lunar planet sci 45 1349 jutzi m asphaug e gillet p barrat j a benz w 2013 nature 494 207 210 which predict an excavation depth of up to 80 km we are confident that the crust mantle depth is significantly deeper than predicted by most evolution models 30 km mittlefehldt d w 2014 asteroid 4 vesta a fully differentiated dwarf planet nasa technical reports server 20140004857 pdf or alternatively the olivine content of the upper mantle is lower than our detection limit which would lead to the conclusion that vesta s parent material was already depleted in olivine compared to ci meteorites

olivine rich exposures at bellicia and arruntia craters on 4 vesta from dawn fc we present an analysis of olivine rich exposures at bellicia and arruntia craters using dawn framing camera fc color data our results confirm the existence of olivine rich materials at these localities as described by ammannito et al 2013a using visual infrared spectrometer vir data analyzing laboratory spectra of various howardite eucrite diogenite meteorites high ca pyroxenes olivines and olivine orthopyroxene mixtures we derive three fc spectral band parameters that are indicators of olivine rich materials combining the three band parameters allows us for the first time to reliably identify sites showing modal olivine contents 40 the olivine rich exposures at bellicia and arruntia are mapped using higher spatial resolution fc data the exposures are located on the slopes of outer inner crater walls on the floor of arruntia in the ejecta as well as in nearby fresh small impact craters the spatial extent of the exposures ranges from a few hundred meters to few kilometers the olivine rich exposures are in accordance with both the magma ocean and the serial magmatism model e g righter and drake 1997 yamaguchi et al 1997 however it remains unsolved why the olivine rich materials are mainly concentrated in the northern hemisphere approximately 36 42 n 46 74 e and are almost absent in the rheasilvia basin

vesta s pinaria region original basaltic achondrite material derived from mixing upper and lower crust abstract analysis of data from the dawn mission shows that the pinaria region of vesta spanning a portion of the rim of the rheasilvia basin is bright and anhydrous reflectance spectra absorption band centers and their variations cover the range of pyroxenes from diogenite rich to howardite and eucrite compositions with no evidence of olivine in this region by examining band centers and depths of the floor walls and rims of six major craters in the region we find a lane of diogenite rich material next to howardite eucrite material that does not follow the local topography the source of this material is not clear and is probably ejecta from post rheasilvia impacts material of a howardite eucrite composition originating from beyond the rheasilvia basin is evident on the western edge of the region overall the pinaria region exposes the complete range of basaltic achondrite parent body material with little evidence of contamination of non basaltic achondrite material with both high reflectance and low abundance of hydrated material this region of vesta may be considered the pinaria desert

eucritic crust remnants and the effect of in falling hydrous carbonaceous chondrites characterizing the composition of vesta s marcia region abstract the equatorial marcia quadrangle region is characterized by the large relatively young impact craters marcia and calpurnia and their surrounding dark ejecta field a hill with a dark rayed crater named aricia tholus and an unusual diffuse material surrounding the impact crater octavia the spectral analysis indicates that while this region is relatively uniform in the pyroxene band centers it instead shows large differences in pyroxene band depths and reflectance a large variation of reflectance is seen in the quadrangle bright and dark materials are present as diffuse material and as concentrated spots and outcrops moreover oh signature is pervasive in the quadrangle with a few exceptions the region especially the marcia ejecta field is characterized by spectra showing the 2 m band shifted at long wavelengths this is commonly associated with eucritic material believed to have crystallized as lava on vesta s surface or within relatively shallow level dikes and plutons thus suggesting that this region is a remnant of the old vestan basaltic crust however other characteristics of the spectra do not fully fit the eucritic composition indicating an alternative explanation for the band center distribution including the presence of carbonaceous chondritic material mixed with the native vestan pyroxene the detailed mineralogical analysis of the marcia quadrangle indicates that this quadrangle is the result of the mixture of the vestan endogenic minerals with the exogenic carbonaceous chondrites the stratigraphic units around marcia clearly show the bright uncontaminated material interlaced and mixed with the dark material that contains a strong oh signature only few small areas can be considered as representative of the old vestan original material

three dimensional spectral analysis of compositional heterogeneity at arruntia crater on 4 vesta using dawn fc abstract we introduce an innovative three dimensional spectral approach three band parameter space with polyhedrons that can be used for both qualitative and quantitative analyzes improving the characterization of surface compositional heterogeneity of 4 vesta it is an advanced and more robust methodology compared to the standard two dimensional spectral approach two band parameter space the dawn framing camera fc color data obtained during high altitude mapping orbit resolution 60 m pixel is used the main focus is on the howardite eucrite diogenite hed lithologies containing carbonaceous chondritic material olivine and impact melt the archived spectra of heds and their mixtures from relab hoserlab and usgs databases as well as our laboratory measured spectra are used for this study three dimensional convex polyhedrons are defined using computed band parameter values of laboratory spectra polyhedrons based on the parameters of band tilt r0 92 m r0 96 m mid ratio r0 75 m r0 83 m r0 83 m r0 92 m and reflectance at 0 55 m r0 55 m are chosen for the present analysis an algorithm in idl programming language is employed to assign fc data points to the respective polyhedrons the arruntia region in the northern hemisphere of vesta is selected for a case study because of its geological and mineralogical importance we observe that this region is eucrite dominated howarditic in composition the extent of olivine rich exposures within an area of 2 5 crater radii is 12 larger than the previous finding thangjam g et al 2014 meteorit planet sci 49 1831 1850 lithologies of nearly pure cm2 chondrite olivine glass and diogenite are not found in this region although there are no unambiguous spectral features of impact melt the investigation of morphological features using fc clear filter data from low altitude mapping orbit resolution 18 m pixel suggests potential impact melt features inside and outside of the crater our spectral approach can be extended to the entire vestan surface to study the heterogeneous surface composition and its geology

surface lithologic heterogeneity of asteroid 4 vesta abstract high precision spectrophotometry of 4 vesta the third largest asteroid was used to establish the surface composition of this body and to investigate mineralogical variations across its surface the average surface of vesta is analogous to howardite and or polymict eucrite assemblages regolith derived members of the hed meteorite suite which consist of a eucrite matrix containing differing amounts of a diogenite component color and or spectral changes which exhibit a consistent relationship to rotational phasing are evident in 16 of 18 studies of vesta dating back to 1929 including the present work after elimination of possible sources of spurious spectral or color changes it is concluded that these variations arise from hemispheric variations in surface materials and hence provide a means of spatially resolving subhemispheric compositional units on the surface of vesta the background surface of vesta is a relatively dark howardite or polymict eucrite pyroxene plagioclase assemblage with several compositionally distinct bright regions clustered in one hemisphere viewed around the maximum in vesta s lightcurve these include what appears to be an olivine bearing unit suggested name leslie formation located near vesta s equator which probably represents an impact basin and or its associated ejecta that penetrated through the basaltic crust other high albedo compositional units including an apparently low calcium eucrite region and several diogenite pyroxenite regions at least one located near the southern pole may be smaller shallower impact basins by analogy to the eucrite meteorites which represent surface flows or shallow intrusions and which constitute the major component of the regolith derived howardites and polymict eucrites we conclude that the howardite polymict eucrite units represent a regolith gardened original surface of vesta it is probable that the low albedo of the background surface on vesta is due to an age related darkening effect similar to that inferred from the galileo images of gaspra and ida this mechanism is consistent with the correlation of absorption feature intensity with the lightcurve vesta appears to have an old eucritic surface darkened with age and represented among the meteorites by the regolith derived howardites and polymict eucrites on which several impacts on one hemisphere have exposed fresher brighter diogenite and olivine bearing material based on qualitative analysis of the mineralogical variations as a function of rotation a generalized lithologic map of vesta was produced there is reasonable control on the longitude of lithologic features but little control on their latitudes except where specifically noted in producing this map discrete circular features were used on the plausible assumption that impacts have been the most important geologic process on this surface for most of the age of the solar system the shape of the features has thus been assumed rather than derived and is subject to future revision as data improve

evidence for overpressure generation by kerogen to gas maturation in the northern malay basin gas generation is a commonly hypothesized mechanism for the development of high magnitude overpressure however overpressures developed by gas generation have been rarely measured in situ with the main evidence for such overpressures coming from source rock microfractures the physical necessity of overpressures for primary migration laboratory experiments and numerical modeling indeed previous in situ observations suggest that gas generation only creates highly localized overpressures within rich source rocks pore fluid pressure data and sonic velocity vertical effective stress plots from 30 wells reveal that overpressures in the northern malay basin are primarily generated by fluid expansion and are located basinwide within the miocene 2a 2b and 2c source rock formations the overpressures are predominantly associated with gas sampled in more than 83 of overpressure measurements and have a sonic density response consistent with gas generation the association of fluid expansion overpressures with gas combined with the sonic density response to overpressure and a regional geology that precludes other overpressuring mechanisms provides convincing in situ evidence for basinwide gas generation overpressuring overpressure magnitude analysis suggests that gas generation accounts for approximately one half to two thirds of the measured excess pore pressure in the region with the remainder being generated by coincident disequilibrium compaction thus the data herein suggest that gas generation if acting in isolation is producing a maximum pressure gradient of 15 3 mpa km 0 676 psi ft and not lithostatic magnitudes as commonly hypothesized the gas generation overpressures in this article are not associated with a significant porosity anomaly and represent a major drilling hazard with traditional pore pressure prediction techniques underestimating pressure gradients by 2 3 1 5 mpa km 0 1 0 07 psi ft

dawn completes its mission at 4 vesta the dawn mission was designed to test our hypothesis about the origin and evolution of the early solar system by visiting the largest differentiated basaltic asteroid 4 vesta believed to be a survivor from the earliest times of rocky body formation observations from orbit show that vesta is the parent body of the howardite eucrite diogenite meteorites vesta has an iron core and a eucritic diogenitic crust its surface is characterized by abundant impact craters but with no evident volcanic features it has two ancient impact basins in the southern hemisphere that are associated with circum planetary troughs the northern hemisphere is the more heavily cratered and contains the oldest terrains the surface of vesta is diverse with north south and east west dichotomies in the eucrite to diogenite ratio its surface contains both very bright and very dark material and its color varies strongly from region to region both the mineralogical and the elemental compositions agree with that expected for the hed parent body significant oh or h may be present in the upper crust and the presence of pits in fresh craters is consistent with the devolatilization of the surface after a collision either brought to or tapped a source of water on vesta the presence of dark material on the surface of vesta suggests efficient transport pathways for organic material and the mixing of the dark material with the more pristine pyroxene explains the varying albedo across the surface vesta has proven to be a reliable witness to the formation of the solar system

mineralogic mapping of the av 9 numisia quadrangle of vesta abstract in this manuscript we present the mineralogic mapping of the av 9 numisia quadrangle of vesta using the most up to date data from the nasa dawn mission this quadrangle is located in vesta s equatorial zone 22 south to 22 north 218 to 288 east in claudia coordinate system and takes its name from the impact crater numisia the main feature which dominates the quadrangle is the vestalia terra plateau a topographic high about 10 km above the surrounding areas to the south this region fades into the rheasilvia basin while to the north it is bounded by the steep scarp of postumia basin the visible and infrared mapping spectrometer vir onboard nasa dawn provided the main data source for this work at an unprecedented level of spatial and spectral resolution in particular we are using spectral parameters to synthesize characteristics of the whole spectra into a single value pyroxene related spectral parameters allow for the detection of lower crust or mantle material diogenites and upper crust material eucrites in the study area the combined analysis of albedo from the framing camera the geologic map and the spectroscopic data offer an interesting opportunity to understand better the surface features of this region of vesta and their evolution numisia cornelia fabia teia and drusilla are the main craters in the study area rich in bright and dark material outcrops pitted terrains and oh rich materials using the spectral parameters we demonstrate that the internal composition of vestalia terra is mainly diogenite rich howardite as shown by materials excavated by cornelia and fabia and the composition of the slope north of vestalia terra this agrees with the strong positive bouguer anomaly observed in the area indicating a higher density of these features in relation to the surrounding areas besides the recently published works based on gravimetric modeling and geologic interpretation the mineralogic mapping presented herein gives an additional contribution in order to depict a more complete geologic history of the numisia quadrangle of vesta

elevated fluid pressure and extreme mechanical weakness of a plate boundary thrust nankai trough subduction zone pore fluid pressure is a key parameter governing both the shear strength of faults and the conditions for seismic and tsunamigenic slip on subduction zone megathrusts however quantitative constraints on this parameter based on in situ data in these or any faults have proven elusive using seismic interval velocities derived from a three dimensional seismic reflection survey we compute porosity fluid pressure and effective stress at the plate interface in the nankai trough subduction zone offshore southwestern japan to 20 km down the fault dip using well constrained locally calibrated empirical relationships between velocity porosity and effective stress we show that the fault and immediately subjacent footwall are nearly undrained implying that the subduction megathrust slips under a shear stress of

a study of the tornadic region within a supercell thunderstorm abstract the transition of a supercell thunderstorm into its tornadic phase is investigated through high resolution numerical cloud model simulations initiated within the interior portion of a previously simulated mature supercell storm with the enhanced grid resolution the low level cyclonic vorticity increases dramatically and the gust front rapidly occludes as small scale downdrafts develop in the vicinity of the low level center of circulation as the occlusion progresses a ring of high vorticity air surrounds the circulation center and could be conducive to multiple vortex tornado formation numerous features of the simulated transition bear resemblance to those observed in tornadic storms in the model simulation the large low level vorticity is generated through the tilting and intense stretching of air from the inflow side of the storm this vertical vorticity is derived from the horizontal vorticity of the environmental shear and also from horizontal vorticity generated solenoidally as low l

airborne doppler radar analysis of supercells during cops 91 abstract on 26 may 1991 noaa p 3 airborne doppler radar data were collected near two tornadic supercells in the southern plains during the cooperative oklahoma profiler studies cops 91 field program the 3 cm radar mounted in the tail of the aircraft was operated using the fore aft scanning technique fast both storms were sampled just minutes after each had produced a tornado the cops 91 storms are the first tornadic supercells to be sampled extensively by airborne doppler radar using the fast methodology pseudo dual doppler analyses of a dissipating storm in southwest kansas show no remaining low level circulation even though the storm had just produced a tornado the analyses of a storm in northwest oklahoma reveal better defined features in the wind field near the surface in contrast to what has been previously observed in post tornadic supercells the cyclonic vorticity in both storms was greater aloft than at low levels the 26 may 1991 storms provide further evidence that supercells often

evolution of cloud to ground lightning characteristics and storm structure in the spearman texas tornadic supercells of 31 may 1990 abstract on 31 may 1990 four tornadic supercell storms formed sequentially near the intersection of a dryline and an outflow boundary in the northern texas panhandle staccato lightning flashes which have been hypothesized to be positive ground flashes were observed beneath the anvil of one storm during the most violent tornado that the storm produced evidence was found from a lightning mapping system that at least some of the staccato flashes were negative ground flashes although the four supercell storms on this day formed in approximately the same area traveled over roughly the same region and produced tornadoes and large hail the relationship between the genesis and evolution of tornadoes and the polarity and flash rates of ground flashes varied widely as in previous studies the second of the supercell storms had low precipitation supercell characteristics the third and fourth did not in previously studied storms ground flash activity in low precipitation supercell storms has always bee

impact excavation on asteroid 4 vesta hubble space telescope results hubble space telescope images of asteroid 4 vesta obtained during the favorable 1996 apparition show an impact crater 460 kilometers in diameter near the south pole color measurements within the 13 kilometer deep crater are consistent with excavation deep into a high calcium pyroxene rich crust or olivine upper mantle about 1 percent of vesta was excavated by the crater formation event a volume sufficient to account for the family of small vesta like asteroids that extends to dynamical source regions for meteorites this crater may be the site of origin for the howardite eucrite and diogenite classes of basaltic achondrite meteorites

origin of abnormal pressure in the upper paleozoic shale of the ordos basin china abstract overpressure in the upper paleozoic shale of the ordos basin upsob in china occurred mainly in the early cretaceous and is modeled using the petromod simulation method in this paper the origin of paleo overpressure was analyzed based on the multiple logging combination method bowers method and the velocity density cross plot method using logging data and shale porosity the causes of the underpressure and normal pressure and the history of their evolution were investigated based on a large amount of drilling and pressure data for the basin the results indicate that paleo overpressure in the upsob produced in the early cretaceous was not the cause of disequilibrium compaction but this occurred owing to increased hydrocarbon generation since the late cretaceous during the overall uplift of the ordos basin the decrease in temperature has led to a reduction in pore pressure of 23 93 34 35 mpa accounting for 56 69 69 47 of total pressure loss a combination of the expansion and diffusion of natural gas has led to a decrease in pore pressure of 9 52 22 60 mpa accounting for 27 63 41 83 of total pressure loss the effects of pore rebound on pressure loss were weak therefore temperature decrease alone could not have led to the current underpressure and normal pressure and the expulsion of gas owing to tectonic uplifting might have been the most important factor the upsob likely had a relatively high gas expulsion efficiency especially during late stage tectonic uplifting which may be a major risk for shale gas exploration

near at eros imaging and spectral results eros is a very elongated 34 kilometers by 11 kilometers by 11 kilometers asteroid most of the surface of which is saturated with craters smaller than 1 kilometer in diameter the largest crater is 5 5 kilometers across but there is a 10 kilometer saddle like depression with attributes of a large degraded crater surface lineations both grooves and ridges are prominent on eros some probably exploit planes of weakness produced by collisions on eros and or its parent body ejecta blocks 30 to 100 meters across are abundant but not uniformly distributed over the surface albedo variations are restricted to the inner walls of certain craters and may be related to downslope movement of regolith on scales of 200 meters to 1 kilometer eros is more bland in terms of color variations than gaspra or ida spectra 800 to 2500 nanometers are consistent with an ordinary chondrite composition for which the measured mean density of 2 67 0 1 grams per cubic centimeter implies internal porosities ranging from about 10 to 30 percent

spectral analysis of the bright materials on the asteroid vesta vesta spectra have prominent near infrared absorption bands characteristic of pyroxenes indicating a direct link to the howardite eucrite and diogenite meteorites many localized dark and bright materials are present on vesta s surface here we focus on the bright material bm units to determine their spectral properties their origin the presence of mineralogical phases different from pyroxenes and whether different bright units share a common lithology vir the visible and infrared spectrometer onboard dawn allows us to first do a detailed analysis of the spectral properties of a large number of bright material units on vesta including examples of the different morphological classes the spectral parameters used are band centers band depths and band area ratio bar for the pyroxene bands at 0 9 and 1 9 m the mineralogies of most bright regions are consistent with those of the howardite eucrite and diogenite meteorites typical of vesta s surface we find that bright material units exhibit the full range of hed pyroxene composition from eucrites to diogenites large part of the bright materials are eucrite rich according with the vesta s mineralogy in most cases the bright materials have the same mineralogy of the surrounding terrain but have larger band depth values the band depths can be related to the abundance of the absorbing minerals the abundance of fe2 grain size and or to the abundance of opaque materials we found a positive correlation between albedo and band depth which suggests that the grain size is not the main factor responsible for the higher albedo the analysis of the band parameters indicates that most of the bright materials excluding the few olivine rich units represent fresh uncontaminated vestan pyroxenes from a variety of lithologies exposed from beneath the surface by impacts

spectroscopic characterization of mineralogy and its diversity across vesta the mineralogy of vesta based on data obtained by the dawn spacecraft s visible and infrared spectrometer is consistent with howardite eucrite diogenite meteorites there are considerable regional and local variations across the asteroid spectrally distinct regions include the south polar rheasilvia basin which displays a higher diogenitic component and equatorial regions which show a higher eucritic component the lithologic distribution indicates a deeper diogenitic crust exposed after excavation by the impact that formed rheasilvia and an upper eucritic crust evidence for mineralogical stratigraphic layering is observed on crater walls and in ejecta this is broadly consistent with magma ocean models but spectral variability highlights local variations which suggests that the crust can be a complex assemblage of eucritic basalts and pyroxene cumulates overall vesta mineralogy indicates a complex magmatic evolution that led to a differentiated crust and mantle

detection of overpressure zones and a statistical model for pore pressure estimation from well logs in the krishna godavari basin india abnormally high pressures measured by repeat formation tester rft and detected by well log data from 10 wells in the krishna godavari k g basin occur in the vadaparru shale of miocene and raghavapuram shale of early cretaceous age overpressures generated by disequilibrium compaction and pore pressures have been estimated using the conventional eaton sonic equation with an exponent of 3 0 the observed abnormal pore pressure gradient ranges from 11 85 to 13 10 mpa km whereas fracture pressure gradient varies from 17 40 to 19 78 mpa km the magnitude of vertical stress sv has a gradient from 21 00 to 23 10 mpa km the minimum horizontal principal stress sh magnitude is found to vary from 64 to 77 of the sv in normally pressured to overpressured sediments a multiple linear regression model with a squared multiple correlation coefficient r2 of 0 94 is proposed for pore pressure prediction from gamma ray density and sonic logs to focus on efficient drilling operations and to prevent borehole instability the statistical model has been calibrated with the rft data from five wells covering about 3400 sq km area of the onshore k g basin the model predicted pore pressure values are in close agreement with the actual rft data for another four wells including a well in the offshore k g basin hence the proposed regression model may be useful for predicting pore pressure from other well logs in the k g basin

olivine in an unexpected location on vesta s surface although olivine was expected to occur within the deep south pole basins of asteroid vesta which are thought to be excavated mantle rocks spectral data from nasa s dawn spacecraft show that it instead occurs as near surface materials in vesta s northern hemisphere between july 2011 and september 2012 nasa s dawn spacecraft was in orbit around the asteroid vesta in this paper dawn s visible and infrared mapping spectrometer vir team presents a surprising finding the signature of olivine on the asteroid s surface olivine is a major component of the mantle of differentiated bodies including earth vesta is a large asteroid large enough to have differentiated into an earth like layered structure and the expectation was that olivine would be found within vesta s deep south pole basins thought to be excavated mantle rocks yet the spectroscopic data reveal olivine rich material close to the surface in the northern hemisphere an understanding of the differentiation processes that have occurred on vesta will be invaluable as a window on the primordial solar system but these latest findings show that vesta s evolutionary history is more complicated than was thought olivine is a major component of the mantle of differentiated bodies including earth howardite eucrite and diogenite hed meteorites represent regolith basaltic crust lower crust and possibly ultramafic mantle samples of asteroid vesta which is the lone surviving large differentiated basaltic rocky protoplanet in the solar system1 only a few of these meteorites the orthopyroxene rich diogenites contain olivine typically with a concentration of less than 25 per cent by volume2 olivine was tentatively identified on vesta3 4 on the basis of spectral and colour data but other observations did not confirm its presence5 here we report that olivine is indeed present locally on vesta s surface but that unexpectedly it has not been found within the deep south pole basins which are thought to be excavated mantle rocks6 7 8 instead it occurs as near surface materials in the northern hemisphere unlike the meteorites the olivine rich more than 50 per cent by volume material is not associated with diogenite but seems to be mixed with howardite the most common7 9 surface material olivine is exposed in crater walls and in ejecta scattered diffusely over a broad area the size of the olivine exposures and the absence of associated diogenite favour a mantle source but the exposures are located far from the deep impact basins the amount and distribution of observed olivine rich material suggest a complex evolutionary history for vesta

olivine or impact melt nature of the orange material on vesta from dawn abstract nasa s dawn mission observed a great variety of colored terrains on asteroid 4 vesta during its survey with the framing camera fc here we present a detailed study of the orange material on vesta which was first observed in color ratio images obtained by the fc and presents a red spectral slope the orange material deposits can be classified into three types a diffuse ejecta deposited by recent medium size impact craters such as oppia b lobate patches with well defined edges nicknamed pumpkin patches and c ejecta rays from fresh looking impact craters the location of the orange diffuse ejecta from oppia corresponds to the olivine spot nicknamed leslie feature first identified by gaffey gaffey m j 1997 icarus 127 130 157 from ground based spectral observations the distribution of the orange material in the fc mosaic is concentrated on the equatorial region and almost exclusively outside the rheasilvia basin our in depth analysis of the composition of this material uses complementary observations from fc the visible and infrared spectrometer vir and the gamma ray and neutron detector grand several possible options for the composition of the orange material are investigated including cumulate eucrite layer exposed during impact metal delivered by impactor olivine orthopyroxene mixture and impact melt based on our analysis the orange material on vesta is unlikely to be metal or olivine originally proposed by gaffey gaffey m j 1997 icarus 127 130 157 analysis of the elemental composition of oppia ejecta blanket with grand suggests that its orange material has 25 cumulate eucrite component in a howarditic mixture whereas two other craters with orange material in their ejecta octavia and arruntia show no sign of cumulate eucrites morphology and topography of the orange material in oppia and octavia ejecta and orange patches suggests an impact melt origin a majority of the orange patches appear to be related to the formation of the rheasilvia basin combining the interpretations from the topography geomorphology color and spectral parameters and elemental abundances the most probable analog for the orange material on vesta is impact melt

elemental mapping by dawn reveals exogenic h in vesta s regolith using dawn s gamma ray and neutron detector we tested models of vesta s evolution based on studies of howardite eucrite and diogenite hed meteorites global fe o and fe si ratios are consistent with hed compositions neutron measurements confirm that a thick diogenitic lower crust is exposed in the rheasilvia basin which is consistent with global magmatic differentiation vesta s regolith contains substantial amounts of hydrogen the highest hydrogen concentrations coincide with older low albedo regions near the equator where water ice is unstable the young rheasilvia basin contains the lowest concentrations these observations are consistent with gradual accumulation of hydrogen by infall of carbonaceous chondrites observed as clasts in some howardites and subsequent removal or burial of this material by large impacts

a global database and statistical analyses of 4 vesta craters abstract in this paper we present a global database of craters larger than 0 7 km in diameter on the surface of 4 vesta which we created based on a global mosaic of the dawn spacecraft s high altitude mapping orbit hamo images at a resolution of 60 m pixel and cross checked using the images from the low altitude mapping orbit lamo mission phase the method to produce the crater database consists of visual crater identification and mathematical shape determination to give precise measurements topographic corrections have also been considered by combining the digital elevation model dem data in this global survey we calculated the morphometric parameters of the craters which consist of diameter depth depth to diameter ratio ellipticity and azimuth of the major axis our results show that the craters on 4 vesta are very shallow with a mean depth to diameter ratio of 0 065 which is similar to that of the craters on 1 ceres and 25143 itokawa but lower than for craters on other solid bodies the results also show that the fractions of craters with an ellipticity greater than 1 1 or 1 2 are smaller than those of craters on the martian surface which is probably because few secondaries exist on the surface of 4 vesta in addition the azimuths of the major axis are almost uniformly distributed in different directions our globally consistent crater database has many potential applications for future studies such as geologic mapping and surface age dating

detecting high overpressure normal pressure is pore fluid pressure that equals the hydrostatic pressure of a column of formation water extending to the surface overpressure is pore fluid pressure greater than normal pressure however no standard definition exists for what constitutes high overpressure what can be said is that high overpressure often means trouble for an explorationist it could mean blown reservoir seals for a driller it could mean excessive time spent fighting formation fluid influxes and or drilling fluid losses

photometric mapping of asteroid 4 vesta s southern hemisphere with hubble space telescope abstract we present the surface mapping of the southern hemisphere of asteroid 4 vesta obtained from hubble space telescope hst from 105 images of vesta through four filters in the wavelengths best to characterize the 1 m pyroxene band we constructed albedo and color ratio maps of vesta these new maps cover latitudes 50 to 20 the southern hemisphere of vesta displays more diverse albedo and color features than the northern hemisphere with about 15 new albedo and color features identified the overall longitudinal albedo and color variations in the southern hemisphere are comparable with that of the northern hemisphere with a range of about 20 and 10 respectively the eastern hemisphere is brighter and displays more diogenitic minerals than the western hemisphere correlations between 1 m band depth and band width as well as between 1 m band depth and albedo are present on a global scale attributed to pyroxene composition variations the lack of correlations between albedo and the spectral slope indicates the absence of globalized space weathering the lack of a global correlation between 1 m band depth and topography suggests that the surface composition of vesta is not completely controlled by a single impact the distribution of compositional variation on vesta suggests a possible large impact basin evidence of space weathering is found in regions including the bright rim of the south pole crater where the steepest gravitational slope on vesta is and a dark area near a gravitationally flat area we propose to divide the surface of vesta into six geological units different from the background according to their 1 m absorption features and spectral slopes including two eucrite rich units a low ca eucrite unit a diogenite rich unit a space weathered unit and a freshly exposed unit no evidence of olivine rich area is present in these data

39ar 40ar ages of eucrites and thermal history of asteroid 4 vesta eucrite meteorites are igneous rocks that derived from a large asteroid probably 4 vesta past studies have shown that after most eucrites formed they underwent metamorphism in temperatures up to 800 c much later many were brecciated and heated by large impacts into the parent body surface the less common basaltic unbrecciated eucrites also formed near the surface but presumably escaped later brecciation while the cumulate eucrites formed at depths where metamorphism may havepersisted for a considerable period to further understand the complex hed parent body thermal history we determined new 39ar 40ar ages for 9 eucrites classified as basaltic but unbrecciated 6 eucrites classified as cumulate and several basaltic brecciated eucrites precise ar ar ages of 2 cumulate eucrites moama and eet 87520 and 4 unbrecciated eucrites give a tight cluster at 4 48 0 02 gyr not including any uncertainties in the flux monitor age ar ar ages of 6 additional unbrecciated eucrites are consistent with this age within theirrelatively larger age uncertainties by contrast available literature data on pb pb isochron ages of 4 cumulate eucrites and 1 unbrecciated eucrite vary over 4 4 4 515 gyr and 147sm 143nd isochron ages of 4 cumulate and 3 unbrecciated eucrites vary over 4 41 4 55 gyr similar ar ar ages for cumulate and unbrecciated eucrites imply that cumulate eucrites do not have a younger formation age than basaltic eucrites as was previously proposed we suggest that these cumulate and unbrecciated eucrites resided at a depth where parent body temperatures were sufficiently high to cause the k ar and some other chronometers to remain as open diffusion systems from the strong clustering of ar ar ages at 4 48 gyr we propose that these meteorites were excavated from depth in a single large impact event 4 48 gyr ago which quickly cooled the samples and started the k ar chronometer a large 460 km crater postulated to exist on vesta may be the source of these eucrites and of many smaller asteroids thought to be spectrally or physically associated with vesta some pb pb and sm nd ages of cumulate and unbrecciated eucrites are consistent with the ar ar age of 4 48 gyr and the few older pb pb and sm nd ages may reflect an isotopic closure before the large cratering event one cumulate eucrite gives an ar ar age of 4 25 gyr 3 additional cumulate eucrites give ar ar ages of 3 4 3 7 gyr and 2 unbrecciated eucrites give ar ar ages of 3 55 gyr we attribute these younger ages to a later impact heating furthermore the ar ar impact reset ages of several brecciated eucrites and eucritic clasts in howardites fall within the range of 3 5 4 1 gyr among these piplia kalan the first eucrite to show evidence for extinct 26al was strongly impact heated 3 5 gyr ago when these data are combined with eucrite ar ar ages in the literature they confirm that several large impact heating events occurred on vesta between 4 1 3 4 gyr ago the onset of major impact heating may have occurred at similar times for both vesta and the moon but impact heating appears to have persisted for a somewhat later time on vesta

sedimentation stratigraphy and petroleum potential of krishna godavari basin east coast of india the krishna godavari basin is located in the central part of the eastern passive continental margin of india the structural grain of the basin is northeast southwest exposures of upper cretaceous sedimentary rocks demarcate the basin margin toward the north west where the northwest southeast trending pranahita godavari graben abuts the basin the basin contains thick sequences of sediments with several cycles of deposition ranging in age from late carboniferous to holocene a major delta with a thick argillaceous facies that has prograded seaward since the late cretaceous is a hydrocarbon exploration target magnetic and gravity data predicted the basin architecture which was subsequently confirmed by a multichannel seismic sur vey the basin is divided into subbasins by fault controlled ridges sediments accumulated in subbasins more than 5 km thick above the basement ridges thin sediments are found until the jurassic period sediments were deposited in the rift valley and in topo graphic lows this sequence is completely overlain by a lower cretaceous transgressive sedimentary wedge later continued delta progradation characterized basin sedimentation with an areal extent of approximately 45 000 km2 this proven petroliferous basin has potential reservoirs ranging in age from the permian to the pliocene exploratory drilling of more than 350 wells in more than 160 structures has resulted in the discovery of 42 oil and gas bearing structures good source rocks are known from sequences ranging in age from permian carboniferous to early miocene because the reservoir sand bodies have limited lateral variation understanding the stratigraphy and depositional sub environments in different sequences is essential to decipher the favorable locales for reservoir sands tilted fault blocks growth faults and related rollover anticlines provide the structural traps begin page 1624

mineralogical analysis of the oppia quadrangle of asteroid 4 vesta evidence for occurrence of moderate reflectance hydrated minerals abstract quadrangle av 10 oppia is one of five quadrangles that cover the equatorial region of asteroid 4 vesta this quadrangle is notable for the broad spectrally distinct ejecta that extend south of the oppia crater these ejecta exhibit the steepest reddest visible spectral slope observed across the asteroid and have distinct color properties as seen in multispectral composite images compared to previous works that focused on the composition and nature of unusual orange ejecta found on vesta here we take into account a broader area that includes several features of interest with an emphasis on mineralogy as inferred from data obtained by dawn s visible infrared mapping spectrometer vir our analysis shows that the older northern and northeastern part of av 10 is dominated by howardite like material while the younger southwestern part including oppia and its ejecta blanket has a markedly eucritic mineralogy the association of the mineralogical information with the geologic and topographic contexts allows for the establishment of relationships between the age of the main formations observed in this quadrangle and their composition a major point of interest in the oppia quadrangle is the spectral signature of hydrous material seen at the local scale this material can be mapped by using high resolution vir data combined with multispectral image products from the dawn framing camera fc so as to enable a clear correlation with specific geologic features hydrated mineral phases studied previously on vesta generally correlate with low albedo material delivered by carbonaceous asteroids however our analysis shows that the strongest oh signature in av 10 is found in a unit west of oppia previously mapped as light mantle material and showing moderate reflectance and a red visible slope with the available data we cannot yet assess the presence of water in this material however we offer a possible explanation for its origin

a synoptic and photographic climatology of low precipitation severe thunderstorms in the southern plains abstract the occurrence of an unusual type of severe thunderstorm difficult to identify by radar has been documented in the southern plains all of the three storms previously studied occurred near the dryline although tornadoes and large hail were produced little rain was observed at the ground and there was no evidence of a strong surface downdraft two were described as bell shaped ten more cases of this rare type of storm have been recently documented visually and on radar a photographic and synoptic climatology of this class of storm the low precipitation severe storm is suggested on the basis of an analysis of the comparison among 11 of these cases it is found that these storms form in a supercell like environment which is drier in the moist layer and more weakly sheared than that of well documented supercells in oklahoma implications of our findings and additional storm characteristics are discussed in light of the larger sample size

the heating history of vesta and the onset of differentiation in this work we study the link between the evolution of the internal structure of vesta and thermal heating due to 26 al and 60 fe and long lived radionuclides taking into account the chemical differentiation of the body and the affinity of 26 al with silicates we explored several thermal and structural scenarios differing in the available strength of energy due to the radiogenic heating and in the postsintering macroporosity by comparing them with the data supplied by the heds and the dawn nasa mission we use our results to constrain the accretion and differentiation time as well as the physical properties of the core differentiation takes place in all scenarios in which vesta completes its accretion in 1 4 ma after the injection of 26 al into the solar nebula in all those scenarios where vesta completes its formation in 1 ma from the injection of 26 al the degree of silicate melting reaches 100 vol throughout the whole asteroid if vesta completed its formation between 1 and 1 4 ma after 26 al injection the degree of silicate melting exceeds 50 vol over the whole asteroid but reaches 100 vol only in the hottest outermost part of the mantle in all scenarios where the porosity is lower than 5 vol if the formation of vesta occurred later than 1 5 ma after the injection of 26 al the degree of silicate melting is always lower than 50 vol and is limited only to a small region of the asteroid the radiation at the surface dominates the evolution of the crust which ranges in thickness from 8 to about 30 km after 5 ma a layer about 3 20 km thick is composed of primitive unmelted chondritic material while a layer of about 5 10 km is eucritic

global photometric properties of asteroid 4 vesta observed with dawn framing camera abstract dawn spacecraft orbited vesta for more than one year and collected a huge volume of multispectral high resolution data in the visible wavelengths with the framing camera we present a detailed disk integrated and disk resolved photometric analysis using the framing camera images with the minnaert model and the hapke model and report our results about the global photometric properties of vesta the photometric properties of vesta show weak or no dependence on wavelengths except for the albedo at 554 nm the global average geometric albedo of vesta is 0 38 0 04 and the bond albedo range is 0 20 0 02 the bolometric bond albedo is 0 18 0 01 the phase function of vesta is similar to those of s type asteroids vesta s surface shows a single peaked albedo distribution with a full width half max 17 relative to the global average this width is much smaller than the full range of albedos from 0 55 to 2 global average in localized bright and dark areas of a few tens of km in sizes and is probably a consequence of significant regolith mixing on the global scale rheasilvia basin is 10 brighter than the global average the phase reddening of vesta measured from dawn framing camera images is comparable or slightly stronger than that of eros as measured by the near earth asteroid rendezvous mission but weaker than previous measurements based on ground based observations of vesta and laboratory measurements of hed meteorites the photometric behaviors of vesta are best described by the hapke model and the akimov disk function when compared with the minnaert model lommel seeliger model and lommel seeliger lambertian model the traditional approach for photometric correction is validated for vesta for 99 of its surface where reflectance is within 30 of global average

basin architecture and petroleum system of krishna godavari basin east coast of india krishna godavari basin is a peri cratonic passive margin basin on the east coast of india figure 1 the onland part consists of 28 000 km2 and is mostly alluvium covered krishna and godavari are the two major river systems which drain the area and discharge in the bay of bengal the offshore basinal area covers 24 000 km2 to the isobath of 200 m however the basin extends into deeper water and covers a much larger area the basin s characteristic feature is its en echelon horst and graben system which is filled with a thick pile of sediments of permian to recent age and emerging as one of india s most promising petroliferous areas commercial accumulation of hydrocarbons occurs in sediments from the permian to as young as the pliocene

vestan lithologies mapped by the visual and infrared spectrometer on dawn we present global lithological maps of the vestan surface based on dawn mission s visible infrared vir spectrometer acquisitions with a spatial sampling of 200 m the maps confirm the results obtained with the data set acquired by vir with a spatial sampling of 700 m that the reflectance spectra of vesta s surface are dominated by pyroxene absorptions that can be interpreted within the context of the distribution of howardites eucrites and diogenites heds the maps also partially agree with the ground and hubble space telescope observations they confirm the background surface being an assemblage of howardite or polymict eucrite as well as the location of a diogenitic rich spot however there is no evidence of extended olivine rich regions in the equatorial latitudes diogenite is revealed on the rheasilvia basin floor indicating that material of the lower crust mantle was exposed vir also detected diogenites along the scarp of matronalia rupes and the rims of severina and a nearby unnamed crater and as ejecta of antonia crater the diogenite distribution is fully consistent with petrological constraints although the mapped distribution does not provide unambiguous constraints it favors the hypothesis of a magma ocean

the role of midtropospheric winds in the evolution and maintenance of low level mesocyclones abstract using a three dimensional numerical model supercell simulations initialized in environments characterized by hodographs with large curvature in the lowest 3 km and a range of linear midlevel shears are investigated for low values of the midlevel shear 0 005 s 1 the storm develops a mesocyclone at the lowest model level within the first hour of the simulation the gust front starts to move ahead of the main updraft and cuts off the inflow to the storm by approximately 2 h resulting in decay of the initial storm and growth of a new rotating storm on the outflow as the midlevel shear increases to approximately 0 010 s 1 the initial development of the low level mesocyclone is delayed but the mesocyclone that develops is more persistent lasting for over 2 h further increases of the shear to 0 015 s 1 result in the suppression of any low level mesocyclone despite the presence of intense rotation at midlevels of the storm we hypothesize that differences in the distribution of precipitation

magnitude mechanisms and prediction of abnormal pore pressure using well data in the krishna godavari basin east coast of india abnormal pressures are encountered during exploration drilling in different parts of krishna godavari basin on the east coast of india the nature and stratigraphic occurrences of the overpressure zones vary across the basin three different clusters of wells covering a large part of the basin encompassing both onshore and offshore drilled wells are analyzed to capture this variation a wide range of pore pressure gradients from normal to as high as 18 mpa km was observed in the present data set the tops of overpressure zones demonstrate a large range from 2200 to 3000 m 6562 to 9842 ft these depths generally correspond to either a miocene deltaic sequence or cretaceous synrift and postrift sequences available well data reveal two main reasons for the development of overpressure considerably high pore pressure regimes in the cretaceous sequence in the eastern corner of the basin are found to be mainly caused by gas generation whereas disequilibrium compaction is proposed as the main cause for overpressure in the other parts of the basin the outcome of this analysis provides a fair idea of the nature magnitude and distribution of the overpressure and this will also help to strategize further exploration activities in the basin

calculated volume and pressure changes during the thermal cracking of oil to gas in reservoirs 1 the rising temperature that accompanies increasing burial depth converts oil in a reservoir into thermal gas a consideration of hydrogen balance during this cracking shows that approximately 3000 cubic ft 85 cubic meters of gas at standard temperature and pressure is generated from each barrel of oil in addition a graphitic residue is precipitated if the volume relationships among oil thermal gas and the graphitic residue are combined with data for gas solubility in pore water and gas nonideality z factor then pressure can be calculated for any degree of thermal cracking these calculations show that in an effectively isolated system pressures would become very high and could considerably exceed the rock load so that fracturing must occur causing pressure b eed off and loss of gas the lithostatic gradient 1 0 psi ft or 22 6 kpa m is reached after only about 1 0 of the oil is cracked if the reservoir system remains open i e at hydrostatic pressure and is initially filled with oil that is subsequently cracked to gas then roughly 75 of the gas will be lost or the reservoir volume must effectively increase in size for example by moving the gas water contact downward

composition and mineralogy of dark material units on vesta vesta is the asteroid with the largest albedo variation among the known rocky solar system objects and shows a widespread occurrence of dark material dm and bright material bm units in the first observation phases by the dawn spacecraft two main extensions of low albedo areas were identified on vesta and found to be closely correlated with carbonaceous oh rich material in this work we use the hyperspectral data provided by the vir dawn imaging spectrometer onboard dawn to detect and analyze individual well defined dark material units we define dm units assuming a relative criterion i e reflectance lower than the surroundings by coupling visible and infrared images of the same area we are able to select real dark material units discarding false detections created by shadowing effects a detailed final catalogue of 123 dark units is presented containing the geographical parameters and the main spectral characteristics for each unit independently of the geological context of the dark units all dms show similar spectral properties dominated by the pyroxene absorption features as is the average spectrum of vesta this finding suggests a similar composition with the presence of darkening agents that also weaken pyroxene band depths the majority 90 of the dm units shows a positive correlation between low albedo and an oh band centered at 2 8 lm confirming the hypothesis that the darkening agents are carbonaceous chondrites probably delivered by low velocity impacts of primitive asteroids a comparison with laboratory spectra allows us to better constrain the size and the composition of the darkening agents these dm areas seem to be made of eucritic material the regolith grain size seems to be nearly constant around an average value of 25 lm and is quite homogenous at least in the first hundreds of meters beneath the vesta surface suggesting similar processing mechanisms for both dm and bm

overpressuring mechanisms in the yinggehai basin south china sea yinggehai basin is an elongate cenozoic rift basin on the northwestern margin of the south china sea continental shelf its thick 17 km basin fill is characterized by high geothermal gradient and high overpressure overpressure associated with nonequilibrium compaction mainly occurs at depths more than 2800 m at the basin center and more than 4000 m at the basin margin because the shallow buried neogene and quaternary strata lack effective seals this regional overpressure distribution however is disrupted at basin center where high overpressure occurs in permeable formations at a depth as shallow as 1400 m on top of a series of deep seated faults and fractures we studied the processes and mechanisms of overpressuring via numerical modeling that couples basin filling sediment compaction and thermal and pressure fields to approach the origin of the shallow high overpressure model results indicated that an increase of fluid volume due to natural gas generation by organic cracking is not large enough to generate the overpressure because of the limited amount of organic matter the shallow overpressure has probably been generated allogenically deep open faults have served as vertical hydraulic conduits and channeled the deep high pressure into shallow permeable formations

geomorphology and structural geology of saturnalia fossae and adjacent structures in the northern hemisphere of vesta vesta is a unique intermediate class of rocky body in the solar system between terrestrial planets and small asteroids because of its size average radius of 263 km and differentiation with a crust mantle and core vesta s low surface gravity 0 25 m s2 has led to the continual absence of a protective atmosphere and consequently impact cratering and impact related processes are prevalent previous work has shown that the formation of the rheasilvia impact basin induced the equatorial divalia fossae whereas the formation of the veneneia impact basin induced the northern saturnalia fossae expanding upon this earlier work we conducted photogeologic mapping of the saturnalia fossae adjacent structures and geomorphic units in two of vesta s northern quadrangles caparronia and domitia our work indicates that impact processes created and or modified all mapped structures and geomorphic units the mapped units ordered from oldest to youngest age based mainly on cross cutting relationships are 1 vestalia terra unit 2 cratered highlands unit 3 saturnalia fossae trough unit 4 saturnalia fossae cratered unit 5 undifferentiated ejecta unit 6 dark lobate unit 7 dark crater ray unit and 8 lobate crater unit the saturnalia fossae consist of five separate structures saturnalia fossa a is the largest maximum width of 43 km and is interpreted as a graben whereas saturnalia fossa b e are smaller maximum width of 15 km and are interpreted as half grabens formed by synthetic faults smaller second order structures maximum width of 1 km are distinguished from the saturnalia fossae a first order structure by the use of the general descriptive term adjacent structures which encompasses minor ridges grooves and crater chains for classification purposes the general descriptive term minor ridges characterizes ridges that are not part of the saturnalia fossae and are an order of magnitude smaller maximum width of 1 km vs maximum width of 43 km shear deformation resulting from the large scale diameter of 100 km rheasilvia impact is proposed to form minor ridges 2 km to 25 km in length which are interpreted as the surface expression of thrust faults as well as grooves 3 km to 25 km in length and pit crater chains 1 km to 25 km in length which are interpreted as the surface expression of extension fractures and or dilational normal faults secondary crater material ejected from small scale and medium scale impacts diameters of 100 km are interpreted to form ejecta ray systems of grooves and crater chains by bouncing and scouring across the surface furthermore seismic shaking also resulting from small scale and medium scale impacts is interpreted to form minor ridges because seismic shaking induces flow of regolith which subsequently accumulates as minor ridges that are roughly parallel to the regional slope in this work we expand upon the link between impact processes and structural features on vesta by presenting findings of a photogeologic structural mapping study which highlights how impact cratering and impact related processes are expressed on this unique intermediate solar system body

radar observations and shape model of asteroid 16 psyche abstract using the s band radar at arecibo observatory we observed 16 psyche the largest m class asteroid in the main belt we obtained 18 radar imaging and 6 continuous wave runs in november and december 2015 and combined these with 16 continuous wave runs from 2005 and 6 recent adaptive optics ao images drummond et al 2016 to generate a three dimensional shape model of psyche our model is consistent with a previously published ao image hanus et al 2013 and three multi chord occultations our shape model has dimensions 279 232 189 km 10 deff 226 23 km and is 6 larger than but within the uncertainties of the most recently published size and shape model generated from the inversion of lightcurves hanus et al 2013 psyche is roughly ellipsoidal but displays a mass deficit over a region spanning 90 of longitude there is also evidence for two 50 70 km wide depressions near its south pole our size and published masses lead to an overall bulk density estimate of 4500 1400 kgm 3 psyche s mean radar albedo of 0 37 0 09 is consistent with a near surface regolith composed largely of iron nickel and 40 porosity its radar reflectivity varies by a factor of 1 6 as the asteroid rotates suggesting global variations in metal abundance or bulk density in the near surface the variations in radar albedo appear to correlate with large and small scale shape features our size and psyche s published absolute magnitude lead to an optical albedo of pv 0 15 0 03 and there is evidence for albedo variegations that correlate with shape features

assessment of β the compression coefficient of mudstones and its relationship with detailed lithology abstract the mechanical compaction of soils and fine grained sediments is commonly described in soil mechanics by a relationship between void ratio and effective stress the relationship is defined by two parameters derived from the slope of the line relating void ratio and log effective stress and e the void ratio at a chosen effective stress e g 100 kpa and e are strongly correlated and are related to the atterburg liquid limit which is itself related in a general way to the grain size and mineralogy of the sediment in general finer grained sediments have higher initial void ratios and compact faster than coarser sediments porosity depth trends for mudstones in sedimentary basins are therefore strongly influenced by lithology steps or changes in the slope of porosity depth trends can be caused by lithological change rather than changes in the pressure regime a method is presented to evaluate for mechanically compacted mudstones using porosities determined from the density log fdc and based on the relationship between effective stress and void ratio developed in soil mechanics the method allows one to obtain rapidly approximate values for materials for which it is essentially impossible to obtain compaction parameters experimentally calculated values for mudstones in wells 8 3 2 and 30 2 1 on the norwegian margin vary between 0 2 and 0 65 the values correlate positively with the clay particle content of the mudstones which we have determined for 50 mudstone samples from the same wells the strong link between mudstone lithology and suggests that a downhole log may be a useful way to visualize downhole variations in mudstone lithology the log also shows how lithology affects the rate of porosity loss with depth or effective stress for example porosity in mudstones within both wells 8 3 2 and 30 2 1 is essentially constant over 700 m sections of normally pressured mudstones the log and grain size data indicate that this reflects changes in the lithological character and of the muds and not as commonly inferred a change in the pressure regime

influence of overpressure on formation velocity evaluation of neogene strata from the eastern bengal basin bangladesh abstract interpretation of sonic log data of anticlinal structures from eastern bangladesh reveals significant variations of acoustic velocity of subsurface strata the amount of variation in velocity is 32 from miocene to pliocene stratigraphic units in titas and bakhrabad structure whereas 21 in rashidpur structure velocity fluctuations are influenced by the presence of gas bearing horizons with velocities of gas producing strata 3 7 lower than laterally equivalent strata at similar depth average velocities of miocene boka bil and bhuban formations are respectively 2630 and 3480 m s at titas structure 2820 and 3750 m s at bakhrabad and 3430 and 3843 m s at the rashidpur structure from the overall velocity depth distribution for a common depth range of 915 3000 m the titas bakhrabad and rashidpur structures show a gradual increase in velocity with depth in contrast the sitakund anticline in se bangladesh reveals a decrease in velocity with depth from 3000 to 4000 m probably due to the presence of overpressured mudrocks of the bhuban formation tectonic compression associated with the indo burmese plate convergence likely contributed the most toward formation of subsurface overpressure in the sitakund structure situated in the chittagong tripura fold belt of the eastern bengal basin bangladesh

vesta vestoids and the hed meteorites interconnections and differences based on dawn framing camera observations 1 the framing camera fc on the dawn spacecraft provided the first view of 4 vesta at sufficiently high spatial resolution to enable a detailed correlation of the asteroid s spectral properties with geologic features and with the vestoid v type asteroids and the howardite eucrite diogenite hed class of meteorites both of which are believed to originate on vesta we combine a spectral analysis of the basin with visible and near ir spectroscopy of vestoids and with archived data over the same spectral range for hed meteorites the vestoids are only slightly more akin to the rheasilvia basin than to vesta as a whole suggesting that the crustal material ejected is a well mixed collection of eucritic and diogenitic materials the basin itself is more diogenitic implying vesta is differentiated and the impact that created rheasilvia uncovered a mineralogically distinct layer the rheasilvia basin exhibits a larger range in pyroxene band strengths than vesta as a whole further implying that the basin offers a view into a complex differentiated protoplanet the discrepancy between the spectral properties of the hed meteorites and vesta in particular the meteorites deeper pyroxene absorption band and the redder color of the vestoids can be explained by the abundance of smaller particles on vesta and by the addition of low albedo exogenous particles to its surface which in turn are due to its larger gravity and longer exposure time to impact processing solar phase effects are slight and do not explain the spectral discrepancies between the heds vesta and the vestoids

impact origin of the vesta family the compelling petrographic link consolmagno and drake 1977 gaffey 1983 between basaltic achondrite meteorites and the 530 km diameter asteroid 4 vesta has been tempered by a perceived difficulty in launching rocks from this asteroid s surface at speeds sufficient to bring them to earth wasson and wetherill 1979 without obliterating vesta s signature crust i address this impasse in response to recent imaging zellner et al 1996 dumas and hainaut 1996 of a 450 km impact basin across vesta s southern hemisphere thomas et al 1997 and model the basin forming collision using a detailed two dimensional hydrocode with brittle fracture including self gravitational compression cf asphaug and melosh 1993 a 42 km diameter asteroid striking vesta s basaltic crust atop a denser mantle and iron core at 5 4 km s launches multikilometer fragments up to 600 m s without inverting distal stratigraphy according to the code this modeling together with collisional dynamical rheological and exposure age timescales marzari et al 1996 welten et al 1996 and observations of v type asteroids binzel and xu 1993 suggests a recent 1 ga impact origin for the vesta family and a possible vesta origin for earth approaching v type asteroids cruik shank et al 1991

the influence of the shear induced pressure gradient on thunderstorm motion abstract in the present investigation we propose a simple theory to explain how a veering environmental wind shear vector can cause an initially symmetric updraft to grow preferentially to the right of the shear vector and acquire cyclonic rotation the explanation offered is based on linear theory which predicts that interaction of the mean shear with the updraft produces favorable vertical pressure gradients along its right flank to asses the validity of linear theory for large amplitude updrafts the three dimensional shallow anelastic equations are numerically integrated using a simple parameterization for latent heating within a cloud and the linear and nonlinear forcing terms are separately analyzed these results suggest that although the nonlinear effects strongly promote splitting of the updraft the linear forcing remains the dominant factor in preferentially enhancing updraft growth on the right flank we believe this differential forcing is a major contributor to the observed predominance o

an observational study of the dryline abstract this study presents analyses of data collected in the vicinity of a cloud free dryline that occurred in western oklahoma on 24 may 1989 observations reveal sharp contrasts across the quasi stationary north south dryline during midafternoon of greatest significance is a pronounced gradient of virtual potential temperature although horizontal convergence and vorticity also maximize at the dryline the environment of the 24 may dryline is dominated by vertical mixing that maintains a convective boundary layer cbl on both sides of the dryline the dryline resembles a mixing zone containing varying proportions of hot dry air to the west side and warm moist air from the lowest 200 m within 10 km to the east of the dryline the mixing zone slopes eastward from the surface dryline location then becomes a quasi horizontal elevated moist layer above the cbl east of the dryline saturation point analysis indicates that the mixing zone is characterized by a single mixing line structure defined by

vesta s mineralogical composition as revealed by the visible and infrared spectrometer on dawn the dawn spacecraft mission has provided extensive new and detailed data on vesta that confirm and strengthen the vesta howardite eucrite diogenite hed meteorite link and the concept that vesta is differentiated as derived from earlier telescopic observations here we present results derived by newly calibrated spectra of vesta the comparison between data from the dawn imaging spectrometer vir and the different class of hed meteorites shows that average spectrum of vesta resembles howardite spectra nevertheless the vesta spectra at high spatial resolution reveal variations in the distribution of hed like mineralogies on the asteroid the data have been used to derive hed distribution on vesta reported in ammannito et al 2013 and to compute the average vestan spectra of the different hed lithologies reported here the spectra indicate that not only are all the different hed lithologies present on vesta but also carbonaceous chondritic material which constitutes the most abundant inclusion type found in howardites is widespread however the hydration feature used to identify carbonaceous chondrite material varies significantly on vesta revealing different band shapes the characteristic of these hydration features cannot be explained solely by infalling of carbonaceous chondrite meteorites and other possible origins must be considered the relative proportion of heds on vesta s surface is computed and results show that most of the vestan surface is compatible with eucrite rich howardites and or cumulate or polymict eucrites a very small percentage of surface is covered by diogenite and basaltic eucrite terrains are relatively few compared with the abundance of basaltic eucrites in the hed suite the largest abundance of diogenitic material is found in the rheasilvia region a deep basin where it clearly occurs below a basaltic upper crust however diogenite is also found elsewhere although the depth to diogenite is consistent with one magma ocean model its lateral extent is not well constrained

in flight calibration of the dawn framing camera ii flat fields and stray light correction abstract the nasa dawn spacecraft acquired thousands of images of asteroid vesta during its year long orbital tour and is now on its way to asteroid ceres a method for calibrating images acquired by the onboard framing camera was described by schroder et al schroder et al 2013 icarus 226 1304 however their method is only valid for point sources in this paper we extend the calibration to images of extended sources like vesta for this we devise a first order correction for in field stray light which is known to plague images taken through the narrow band filters and revise the flat fields that were acquired in an integrating sphere before launch we used calibrated images of the vesta surface to construct simple photometric models for all filters that allow us to study how the spectrum changes with increasing phase angle phase reddening in combination with these models our calibration method can be used to create near seamless mosaics that are radiometrically accurate to a few percent such mosaics are provided in jvesta the vesta version of the jmars geographic information system

geologic mapping of vesta from 1994 hubble space telescope images we utilize the 56 images of asteroid 4 vesta obtained through four mineralogically diagnostic filters by the hubble space telescope zellneret al 1997 icarus to construct a geologic map vesta s surface is found to be geologically diverse and to be dichotomous at a hemispheric scale the eastern hemisphere longitude definition from thomaset al 1997 icarus is dominated by units interpreted to be impact excavated plutonic material composed of magnesium rich and calcium poor pyroxene the mineralogy of this region is most analogous to diogenite meteorites several eastern hemisphere units which have the deepest and broadest 1 m absorption bands may contain a substantial olivine component the locations of these units are consistent with a previous map based on rotationally resolved groundbased spectroscopy gaffey 1997 icarus the western hemisphere is dominated by units interpreted to consist of a single component of iron rich and relatively calcium rich pyroxene analogous to surface basalts such as eucrite meteorites we investigate the spectral properties of 20 representative surface regions and find a correlation between the 1 m absorption band depth and albedo the units with lower albedos have shallower band depths such a relation could arise from differences in lithologies differences in surface particle sizes or from a weathering effect which decreases albedo and band depth over time because of vesta s geologic diversity and hemispheric dichotomy it is apparent that any major impact events such as those possibly related to the formation of the vesta family binzel and xu 1993 science260 186 191 did not globally resurface the planet the spectral evidence for remnants of a basaltic crust implies that the oldest units on the surface date back to the time of their emplacement most likely 4 5 byr ago if a weathering process exists which alters the albedo then the lowest albedo units such as the feature with the proposed name olbers most likely represent remnants of vesta s ancient basaltic crust

relative chronology of crust formation on asteroid vesta insights from the geochemistry of diogenites abstract the eucrites and diogenites are meteorites that probably originate from asteroid 4 vesta the upper part of the crust of this body is certainly composed of eucrites which are basaltic or gabbroic rocks diogenites are ultramafic cumulates whose relationships with eucritic lithologies are unknown here we show that the orthopyroxenes of some diogenites display very deep negative eu anomalies eu eu close to 0 1 or lower the contamination of the parental magmas of diogenites by melts derived by partial melting of the eucritic crust can satisfactorily explain the range of the eu anomalies displayed by diogenites thus these anomalies are the first firm indication that parental melts of diogenites have intruded the eucritic crust and consequently are younger than eucrites

space weathering on eros constraints from albedo and spectral measurements of psyche crater we present combined multi spectral imager msi 0 95 m and near infrared spectrometer nis 0 8 2 4 m observations of psyche crater on s type asteroid 433 eros obtained by the near earth asteroid rendezvous near shoemaker spacecraft at 5 3 km in diameter psyche is one of the largest craters on eros which exhibit distinctive brightness patterns consistent with downslope motion of dark regolith material overlying a substrate of brighter material at spatial scales of 620 m spectrum psyche crater wall materials exhibit albedo contrasts of 32 40 at 0 946 m associated spectral variations occur at a much lower level of 4 8 2 4 we report results of scattering model and lunar analogy investigations into several possible causes for these albedo and spectral trends grain size differences olivine pyroxene and troilite variations and optical surface maturation we find that the albedo contrasts in psyche crater are not consistent with a cause due solely to variations in grain size olivine pyroxene or lunar like optical maturation a grain size change sufficient to explain the observed albedo contrasts would result in strong color variations that are not observed olivine and pyroxene variations would produce strong band correlated variations that are not observed a simple lunar like optical maturation effect would produce strong reddening that is not observed the contrasts and associated spectral variation trends are most consistent with a combination of enhanced troilite a dark spectrally neutral component simulating optical effects of shock and lunar like optical maturation these results suggest that space weathering processes may affect the spectral properties of eros materials causing surface exposures to differ optically from subsurface bedrock however there are significant spectral differences between eros proposed analog meteorites ordinary chondrites and or primitive achondrites and eros freshest exposures of subsurface bright materials after accounting for all differences in the measurement units of our reflectance comparisons we have found that the bright materials on eros have reflectance values at 0 946 m consistent with meteorites but spectral continua that are much redder than meteorites from 1 5 to 2 4 m most importantly we calculate that average eros surface materials are 30 40 darker than meteorites

precipitation growth trajectories in a ccope storm abstract the growth trajectories of precipitation particles that attain diameters from 0 5 to 2 0 cm are modeled within the wind field of a small relatively steady state southeastern montana thunderstorm the trajectories are calculated backwards from systematic arrays of particles of specified sizes at a level near cloud base using a simple set of criteria for rejecting the obviously impossible trajectories the patterns of accepted trajectory end points are compared with the radar echo patterns good agreement lends credence to the qualitative aspects of the trajectories for a given size of precipitation particle the method helps one to assign different trajectory types to specific regions within the horizontal plant on which the calculations were started the relative importance of the different types of trajectories can thus be estimated particle origin mechanisms are discussed in terms of the regions in which the trajectories are found to start the variety of successful trajectories leading t

compositional variations in the vestan rheasilvia basin abstract we present and describe the maps of spectral parameters such as pyroxene band centers and depths reflectance at 1 4 m and 2 8 m band depth in the rheasilvia quadrangle we found a broad anti correlation between pyroxene band centers and depths while the reflectance is not correlated with the pyroxene spectral parameters in addition we found that the rheasilvia quadrangle is free of oh absorption signatures we also derived lithological maps with improvements in the spatial resolution with respect to previous lithological maps of the same region we confirm that the central mound is dominated by eucritic howarditic pyroxene while diogenitic lithology has been found mainly in a region delineated by tarpeia severina and mariamne craters we found small scale variations in the composition of pyroxene these variations identify lithological units that extend for tens of km although small units of less than 1 km have also been found we consider this fact as an indication of a high level of compositional heterogeneity within the vestan crust

composition of the rheasilvia basin a window into vesta s interior 1 the estimated excavation depth of the huge rheasilvia impact basin is nearly twice the likely thickness of the vestan basaltic crust so the mantle should be exposed spectral mapping by the dawn spacecraft reveals orthopyroxene rich materials similar to diogenite meteorites in the deepest parts of the basin and within its walls significant amounts of olivine are predicted for the mantles of bulk chondritic bodies like vesta and its occurrence is demonstrated by some diogenites that are harzburgite and dunite however olivine has so far escaped detection by dawn s instruments spectral detection of olivine in the presence of orthopyroxene is difficult in samples with 25 olivine and olivine in rheasilvia might have been diluted during impact mixing or covered by the collapse of basin walls the distribution of diogenite inferred from its exposures in and around rheasilvia provides a geologic context for the formation of these meteorites but does not clearly distinguish between a magmatic cumulate versus partial melting restite origin for diogenites the former is favored by geochemical arguments and crystallization in either a magma ocean or multiple plutons emplaced near the crust mantle boundary is permitted by dawn observations

modeling the occurrence of overpressures on the scotian shelf offshore eastern canada many wells on the scotian shelf offshore from nova scotia have drilled into overpressured zones in particular the wells comprising the venture gas field have all encountered overpressures at depths below 4 5 km the characteristics of the overpressure zones in the venture field vary in some important details from overpressured zones on the u s gulf coast in the venture field the shales in the overpressured zones are observed to be normally compacted and interbedded with layers of overpressured sandstones this is in contrast to the gulf coast where the shales in the overpressure zone are undercompacted resistivity logs sonic logs and bulk density logs all provide some indications of overpressures in the venture field but are not as unequivocal indicators of overpressure as they are on the gulf coast theoretical investigations of the causes of overpressures in an environment such as the venture field show that overpressures are unlikely to be caused by loading of sediments the most probable cause of overpressures is recent and continuing fluid generation which is related to the transformation of kerogen to hydrocarbons limits are placed on the average permeabilities and fluid generation rates which are required if overpressures are to be produced by fluid generation

color and albedo heterogeneity of vesta from dawn multispectral images 0 44 to 0 98 m of asteroid 4 vesta obtained by the dawn framing cameras reveal global color variations that uncover and help understand the north south hemispherical dichotomy the signature of deep lithologies excavated during the formation of the rheasilvia basin on the south pole has been preserved on the surface color variations band depth spectral slope and eucrite diogenite abundance clearly correlate with distinct compositional units vesta displays the greatest variation of geometric albedo 0 10 to 0 67 of any asteroid yet observed four distinct color units are recognized that chronicle processes including impact excavation mass wasting and space weathering that shaped the asteroid s surface vesta s color and photometric diversity are indicative of its status as a preserved differentiated protoplanet

on the reliability of hook echoes as tornado indicators abstract a study of radar echoes associated with the tornadoes of the 3 april 1974 outbreak was performed to evaluate the usefulness of echo shape as an indicator of tornadic thunderstorms the hook shape was usually successful in characterizing an echo as tornadic with a false alarm rate of 169 because hook echoes were relatively rare however a less restrictive shape called distinctive was more successful at detecting tornadic thunderstorms identifying 65 of the tornadic echoes an echo had a distinctive shape if it possessed a marked appendage on its right rear flank or was in the shape of a spiral comma or line echo wave pattern lewp characteristics of the distinctive echo are given

variations in supercell morphology part i observations of the role of upper level storm relative flow abstract it is hypothesized that the precipitation intensity beneath a supercell updraft is strongly influenced by the amount of hydrometeors that are reingested into the updraft after being transported away in the divergent upper level flow of the anvil this paper presents the results of a climatological analysis of soundings associated with three types of isolated supercells having distinctive precipitation distributions the so called classic low precipitation lp and high precipitation hp storms it is shown that storm relative flow at 9 10 km above the ground is strongest in the environments of lp storms and relatively weak in the environments of hp storms with classic storms occurring in environments with intermediate magnitudes of upper storm relative flow it is plausible that comparatively strong flow in the anvil bearing levels of lp storms transports hydrometeors far enough from the updraft that they are relatively unlikely to be reingested into the updraft leading to greatly diminishe

fugitives from the vesta family abstract spectroscopic observations of asteroid 4 vesta and numerous members of the vesta family located in the inner asteroid belt have determined that these objects have reflectance properties of basaltic material a plausible hypothesis is that the surface of vesta was punctured by large impacts in the past which dispersed fragments of its basaltic crust into space and produced one of the most prominent asteroid families ever created in the belt until recently vesta was the only known object in the asteroid belt which underwent differentiation and survived to the present epoch since 2000 many new small basaltic asteroids have been discovered in the inner and outer parts of the asteroid belt possibly representing fragments from distinct differentiated bodies these discoveries may help us to better understand the number and nature of objects in the inner solar system that underwent geological differentiation to investigate these issues we performed extensive numerical simulations whose aim was to reproduce as precisely as possible the dynamical evolution of vesta s ejected fragments over timescales comparable to the family s age specifically we numerically integrated the orbital evolution of 6600 test bodies with orbits that started within the vesta family and dynamically evolved over 2 gy our model included gravitational perturbation of all planets except mercury and the yarkovsky effect the results show that a relatively large fraction of the original vesta family members may have evolved out of the family borders defined by clustering algorithms and are now dispersed over the inner asteroid belt we compared the orbital distribution of our model fragments with the orbital locations of known basaltic asteroids in various parts of the inner main belt to find that i most basaltic asteroids with semimajor axis a 2 3 au located outside the vesta family s borders in the inner main belt including 809 lundia and 956 elisa are most likely fugitives from the vesta family that have evolved to their current orbits via various identified dynamical pathways our results also suggest that the vesta family is at least 1 gy old ii interestingly orbits of many basaltic asteroids with 2 3 a 2 5 au like those of 4796 lewis and 5379 abehiroshi are displaced from the vesta family to low inclinations and are not obtained in our simulations with sufficient efficiency we propose that i these small basaltic asteroids may be fragments of differentiated bodies other than 4 vesta or ii they were liberated from the vesta s surface before or during the late heavy bombardment epoch 3 8 gy ago and their orbital inclinations separated from that of vesta when secular resonances swept through the region

first disk resolved spectroscopy of 4 vesta abstract vesta the second largest main belt asteroid will be the first to be explored in 2011 by nasa s dawn mission it is a dry likely differentiated body with spectrum suggesting that is has been resurfaced by basaltic lava flows not too different from the lunar maria here we present the first disk resolved spectroscopic observations of an asteroid from the ground we observed 4 vesta with the eso vlt adaptive optics equipped integral field near infrared spectrograph sinfoni as part of its science verification campaign the highest spatial resolution of 90 km on vesta s surface was obtained during excellent seeing conditions 0 5 in october 2004 we observe spectral variations across vesta surface that can be interpreted as variations of either the pyroxene composition or the effect of surface aging we compare vesta s 2 m absorption band to that of howardite eucrite diogenite hed meteorites that are thought to originate from vesta and establish particular links between specific regions and hed subclasses the overall composition is found to be mostly compatible with howardite meteorites although a small area around 180 e longitude could be attributed to a diogenite rich spot we finally focus our spectral analysis on the characteristics of vesta s bright and dark regions as seen from hubble space telescope s visible and keck ii s near infrared images

geomechanical modeling using finite element method for prediction of in situ stress in krishna godavari basin india abstract this study provides quantitative rock mechanical properties and analyses of in situ stress and pore pressure in several oil gas fields of east and west godavari sub basins high pore pressure gradients varying from 11 85 to 12 80 mpa km exist within these oil gas fields vertical stress sv gradients in the range 21 00 to 22 85 mpa km are seen to exist minimum horizontal principal stress sh magnitude is found to vary from 64 to 76 of sv while maximum horizontal principal stress sh magnitude is observed to vary from 90 to 92 of sv within normally pressured to over pressured sediments the breakout derived sh orientation from two well varies from n14 e to n22 5 e in the krishna godavari basin rock mechanical properties such as young s modulus poisson s ratio and unconfined compressive strength have been estimated from logs of compressional and shear wave travel time two dimensional 2d stress modeling using finite element analysis has been carried out for some important oil gas fields situated within east and west godavari sub basins as a part of the current study regional sh orientation has been used for application of stress at the model boundary discontinuities in the stress pattern which can be associated with interfaces between weak and competent layers have been commonly observed and especially where silici clastic and volcanic inter bedded sequences are encountered the model predicted stress orientations are verified with the formation micro imager fmi log data of wells at the above mentioned sub basins

geophysical log responses and their correlation with bed to bed stress contrasts in paleozoic rocks appalachian plateau new york a 1 km profile of in situ stress and geophysical log data was acquired in the wilkins well to study the relationship between rock properties and in situ stress contrasts the wilkins well penetrates devonian clastic rocks on the appalachian plateau near the town of south canisteo new york open hole hydraulic fracture stress measurements were made in stratigraphic sequences where geophysical logs indicated significant bed to bed variations in elastic and lithologic properties analysis of stress magnitudes and interval averaged geophysical data shows that principal horizontal stress magnitudes correlate directly with elastic stiffness and inversely with clay content a similar relation is found for older paleozoic strata penetrated by a well at auburn new york correlations between stress magnitude and geophysical properties observed in the wilkins and auburn wells provide strong evidence that bed to bed stress variations arise from a uniform ene wsw directed strain acting on beds of different young s modulus rather than from variations in rock shear strength because of their high young s modulus sandstones siltstones and limestones in the northern appalachian basin are likely to be stronger barriers to hydraulic fracture propagation than shales porosity logs in the wilkins well show that the large decrease in horizontal stress found at the base of the rhine street formation occurs where shales are less compacted the correlation with undercompaction is consistent with a paleo overpressure drainage mechanism as the cause for the stress decrease

vertically transferred overpressures in brunei evidence for a new mechanism for the formation of high magnitude overpressure overpressures in sedimentary basins are commonly assumed to be the result of two distinct and separate mechanisms disequilibrium compaction and fluid expansion however the potential for overpressures to be redistributed or transferred to other pressure compartments over time has been seldom considered and rarely demonstrated pore pressure data and velocity effective stress plots from 61 fields across the baram delta province of brunei northwest borneo reveal that two different types of overpressure occur in stratigraphically defined sections the basal pro delta shales contain overpressures generated by disequilibrium compaction whereas the overlying sand shale deltaic sequence contains overpressures that appear to be generated by fluid expansion however the geology of the deltaic sequences and high magnitude of the pore pressures precludes the overpressures in the deltaic sequences being generated by any conventional fluid expansion mechanism such as kerogen to gas maturation or clay diagenesis the fluid expansion overpressures are located in fields that were inverted during the pliocene an event that resulted in large scale fluid migration from the pro delta shales into the deltaic sequences including charging of the numerous oil fields in the inner shelf hence we propose that the overpressures in brunei provide the first evidence for a new overpressuring mechanism whereby overpressured fluids have been vertically transferred from the pro delta shales into the deltaic sequences during basin inversion furthermore vertical transfer may be a mechanism for explaining overpressures observed in basins that have been recently uplifted or inverted