surface track discontinuity of tropical cyclones crossing taiwan a statistical study surface tracks of some cross taiwan tropical cyclones were discontinuous as a result of the blockage of the north northeast south southwest oriented central mountain range cmr this paper tries to identify the variables that may be used to diagnose track continuity in advance the track records of 131 westbound crosstaiwan tropical cyclones between 1897 and 2009 are examined it is found that the track continuity of awestboundcross taiwantropicalcyclonedependsmostlyuponthelandfalllocation ylf theapproaching direction ang and the maximum wind vmx of the cyclone according to the empirical probability of track continuity estimated from the data the dependence on ylf which is nonlinear and remarkably asymmetric with respect to the midpoint of the east coast may be well approximated by a quadratic function of ylf the nonlinearity and asymmetry can be interpreted in terms of the length scale of the cmr and the north south antisymmetry of the cyclonic flow the estimated dependence of track continuity on cyclone intensity and size may be approximated by a linear function of vmx the estimated dependence of track continuity on ang may be approximated by a single term of the modified variable dir 5jang 2 110j where 110 is the direction in degrees perpendicular to the cmr s long axis usingthe64tracksbetween1944and1996asthetrainingsample alogisticregressionequationmodel built in terms of ylf ylf square dir and vmx gives an overall accuracy score of 89 as to the probability estimates of individual tracks 49 of the 64 tracks have estimated probabilities outside the 0 5 2 0 127 0 5 1 0 127 rms error range and are correctly classified a prediction test using another set of 67 tracks not included in the model training sample scores a success rate of 82 as to the probability predictions for individual tracks 49 of the 67 tracks have predicted probabilities outside the rms error range and are correctly predicted these results confirm the appropriateness of the model and moreover demonstrate that the three parameters ylf dir and vmx primarily control the surface track continuity of a westbound tropical cyclone crossing taiwan

the inland eyewall reintensification of typhoon fanapi 2010 documented from an observational perspective using multiple doppler radar and surface measurements abstractthis study documents observational changes in the eyewall of typhoon fanapi 2010 after landfall in taiwan the observations indicate that fanapi s eye and eyewall disappeared on the eastern side of taiwan s central mountain range cmr after landfall but reemerged on the western side of cmr the cyclonic circulation increasing wind speed a low level low pressure and high temperature zone the associated updrafts and downdrafts and surface pressure and rainfall measurements all support the existence of a reintensified eyewall the storm slowed down during the redeveloping stage thus prolonging the rainfall duration over taiwan on the western side of cmr a northwest southeast oriented rainband formed at an earlier stage possibly due to the large scale interaction between fanapi s remnant flow and the environment however the subsequent reintensification might be attributed to the interaction between the circulation and topography this is supported by the finding that adjacent to cmr stron

shatter cones and shocked rocks in southwestern montana the beaverhead impact structure shatter cones that point steeply upward are present in abundance over an area 100 km sup 2 in belt supergroup sandstone outcrops in beaverhead county southwestern montana crushed sandstone with fragments dispersed in a fluidal textured cryptocrystalline matrix of similar chemical composition has also been found absence of cones in adjacent units of mississippian and younger are suggests a late precambrian early paleozoic age for the formation of this newly discovered impact structure only a small part of which is preserved in the complexly faulted terrain

sensitivity of typhoon track to asymmetric latent heating rainfall induced by taiwan topography a numerical study of typhoon fanapi 2010 1 typhoon fanapi 2010 traveled westward across the central mountain range of taiwan on 19 september and its rainfall shifted from a symmetric to an asymmetric pattern with convection mostly to the south and southeast meanwhile the storm slowed down from 22 to 14 km h 1 for 12 h upon leaving taiwan and led to heavy rainfall 800 mm and serious flooding over the low lying southwestern plains through simulation and sensitivity tests using the cloud resolving storm simulator at 3 km grid size this study shows that the sudden and temporary speed reduction was caused by the asymmetric latent heating lh not the environmental flow specifically over a 9 h period the model storm moved westward at 16 km h 1 in the control run but increasingly faster and more toward the northwest when the moisture and thus the lh effect and its asymmetry is gradually reduced steering flow analysis and estimation using model results suggest an eastward motion vector of about 8 km h 1 consistent with the observation is produced by the asymmetric lh effect when the effects from the vertical wind shear and beta drift are both taken into account this result is further supported by the diagnosis on storm motion based on potential vorticity tendency although important such feedback to typhoon track from rainfall asymmetry that is induced by the blocking effect of topography have not been reported or studied

scaling craters in carbonates electron paramagnetic resonance analysis of shock damage carbonate samples from the 8 9 mt nuclear near surface explosion crater oak and a terrestrial impact crater meteor crater were analyzed for shock damage using electron paramagnetic resonance epr samples from below the oak apparent crater floor were obtained from six boreholes as well as ejecta recovered from the crater floor the degree of shock damage in the carbonate material was assessed by comparing the sample spectra to spectra of solenhofen and kaibab limestone which had been shocked to known pressures analysis of the oak crater borehole samples has identified a thin zone of allocthonous highly shocked 10 13 gpa carbonate material underneath the apparent crater floor this 5 to 15 m thick zone occurs at a maximum depth of 125 m below current seafloor at the borehole sited at the initial position of the oak explosive and decreases in depth towards the apparent crater edge because this zone of allocthonous shocked rock delineates deformed rock below and a breccia of mobilized sand and collapse debris above it appears to outline the transient crater the transient crater volume inferred in this way is found to be 3 2 0 2 10 6 m 3 which is in good agreement with a volume of 5 3 10 6 m 3 inferred from gravity scaling of laboratory experiments schmidt et al 1986 a layer of highly shocked material is also found near the surface outside the crater the latter material could represent a fallout ejecta layer the ejecta boulders recovered from the present crater floor experienced a range of shock pressures from 0 to 15 gpa with the more heavily shocked samples all occurring between radii of 360 and 600 m moreover the fossil content lithology and sr isotopic composition all demonstrate that the initial position of the bulk of the heavily shocked rock ejecta sampled was originally near surface rock at initial depths in the 32 to 45 m depth below sea level range the epr technique is also sensitive to prehistoric shock damage this is demonstrated by our study of shocked kaibab limestone from the 49 000 year old meteor barringer crater arizona we found shock damage present in the member of the kaibab formation exposed in the crater walls corresponding to peak shock stress in the 0 3 to 0 6 gpa range carbonate ejecta recovered from within the crater experienced shock pressures of up to 0 6 gpa assuming shock damage levels of 0 3 to 0 6 gpa for the lightly shocked carbonate on the walls of the meteor crater combined with the shock pressure versus distance model of moss 1988 and lamb et al 1991 meteor crater impact energies of 2 4 to 8 9 mt are obtained this approximately agrees with energies of 3 3 to 7 1 mt calculated from the crater scaling of schmidt and housen 1987

petrographic x ray diffraction and electron spin resonance analysis of deformed calcite meteor crater arizona calcite crystals within the kaibab limestone in meteor crater arizona are examined to understand how calcite is deformed during a meteorite impact the kaibab limestone is a silty finegrained and fossiliferous dolomudstone and the calcite crystals occur as replaced evaporite nodules with impact induced twinning twinning in the calcite is variable with deformational regimes based on abundances of crystals with twins and twin densities within crystals the twins are similar to those that are seen in low tectonically deformed regimes low levels of shock are inferred from minor peak broadening of the x ray diffraction patterns xrd of the calcite crystals in addition electron spin resonance esr spectroscopy data also indicates low shock levels 3 0 gpa quantitative shock pressures and correlation between the xrd and esr results are poor due to the inferred low shock levels in conjunction with the analytical error associated in calculation of the shock pressures

a numerical study of the track deflection of supertyphoon haitang 2005 prior to its landfall in taiwan abstract a series of numerical simulations are conducted using the advanced research version of the weather research and forecasting model with a 4 km fine mesh to examine the physical processes responsible for the significant track deflection and looping motion before the landfall of supertyphoon haitang 2005 in taiwan which poses a unique scientific and forecasting issue in the control experiment a low level northerly jet induced by the channeling effect forms in the western quadrant of the approaching storm where the inner core circulation is constrained by the presence of taiwan s terrain because of the channeling effect the strongest winds of the storm are shifted to the western portion of the eyewall the northerly advection flow averaged asymmetric winds within 100 km radius results in a sharp southward turn of the westward moving storm the time series of the advection flow shows that the advection wind vectors rotate cyclonically in time and well match the motion of the simulated vortex

geological and geochemical record of 3400 million year old terrestrial meteorite impacts beds of sand sized spherules in the 3400 million year old fig tree group barberton greenstone belt south africa formed by the fall of quenched liquid silicate droplets into a range of shallow to deep water depositional environments the regional extent of the layers their compositional complexity and lack of included volcanic debris suggest that they are not products of volcanic activity the layers are greatly enriched in iridium and other platinum group elements in roughly chondritic proportions geochemical modeling based on immobile element abundances suggests that the original average spherule composition can be approximated by a mixture of fractionated tholeiitic basalt komatiite and ci carbonaceous chondrite the spherules are thought to be the products of large meteorite impacts on the archean earth

thermoluminescence measurements on shock metamorphosed sandstone and dolomite from meteor crater arizona 2 thermoluminescence age of meteor crater thermoluminescence tl dating measurements were performed on shock metamorphosed rocks from meteor crater arizona il ages were obtained for eight specimens four coconino sandstone and four kaibab dolomite which experienced sufficient shock heating during the impact to reset their preimpact tl postimpact radiation doses were determined for each shocked fragment from thermoluminescence measurements on quartz mineral separates effective radiation dose rates were calculated from concentrations of uranium thorium potassium and rubidium in the rocks and their burial environment and the distributions of these elements as determined by fission track and microprobe analyses cosmic radiation dose rates were estimated by altitude scaling of sea level data and were corroborated by tl dosimeter measurements at the crater the mean tl ages for the two rock types were reasonably concordant 50 400 2900 and 46 000 3100 years for sandstones and dolomites respectively the overall mean age 49 000 3000 years is significantly older than the 25 000 year age estimate based on the inferred correlation of the oldest pluvial episode at the crater with radiometrically dated 18o maxima

rietveld analysis of x ray powder diffraction patterns as a potential tool for the identification of impact deformed carbonate rocks previous x ray powder diffraction xrd studies revealed that shock deformed carbonates and quartz have broader xrd patterns than those of unshocked samples entire xrd patterns single peak profiles and rietveld refined parameters of carbonate samples from the sierra madera impact crater west texas unshocked equivalent samples from 95 miles north of the crater and the mission canyon formation of southwest montana and western wyoming were used to evaluate the use of x ray powder diffraction as a potential tool for distinguishing impact deformed rocks from unshocked and tectonically deformed rocks at sierra madera dolostone and limestone samples were collected from the crater rim lower shock intensity and the central uplift higher shock intensity unshocked equivalent dolostone samples were collected from well cores drilled outside of the impact crater carbonate rocks of the mission canyon formation were sampled along a transect across the tectonic front of the sevier and laramide orogenic belts whereas calcite subjected to significant shock intensities at the sierra madera impact crater can be differentiated from tectonically deformed calcite from the mission canyon formation using rietveld refined peak profiles weakly shocked calcite from the crater rim appears to be indistinguishable from the tectonically deformed calcite in contrast rietveld analysis readily distinguishes shocked sierra madera dolomite from unshocked equivalent dolostone samples from outside the crater and tectonically deformed mission canyon formation dolomite

ca carbonate in the orgueil ci carbonaceous chondrite mineralogy microstructure and implications for parent body history the orgueil ci carbonaceous chondrite is a breccia and some of its constituent clasts contain ca carbonate grains whose mineralogy is undetermined but may yield new information on the history of its asteroidal or cometary parent body characterisation of one such clast shows that in addition to ca carbonate it contains magnetite olivine and orthopyroxene grains that are supported within a finely crystalline saponite serpentine ferrihydrite groundmass the ca carbonate grains are typically rounded less than 10 m in diameter and backscatter kikuchi patterns identify all those analysed as calcite electron backscatter diffraction orientation contrast maps show that most calcites have sub m sized e twins some of which are cut by corroded grain margins these microstructures demonstrate that the clast experienced very mild shock during aqueous alteration and probably accompanying impact gardening of the parent body regolith the sample studied hosts several other millimeter sized clasts and a fine grained clastic matrix that are free of ca carbonate olivine and orthopyroxene although can contain apatite dolomite and pyrrhotite within one of these clasts is a network of phyllosilicate magnetite veins that are inferred to have acted as fluid flow conduits during parent body aqueous alteration sulphur rich reaction rims within the same clast are likely to have formed during post fall remobilization and crystallization of pre terrestrial sulphates this study provides good evidence for alteration of the ci carbonaceous chondrites in a dynamic parent body regolith

interaction of typhoons with the taiwan orography part ii continuous and discontinuous tracks across the island abstract numerical model simulations of west moving tropical cyclones approaching and crossing the taiwan orography are shown to contain many of the observed surface features vortices tend to track continuously around the northern end of the island due to the deflection of the deep layer mean flow and the vortex circulation is modified less because the higher winds to the right of the center do not have a strong interaction with the barrier discontinuous tracks predominate for vortices approaching the central southern portions of the taiwan orography severe distortions of the inner core circulation occur and the surface pressure and surface wind centers become decoupled and may be dissipated at different rates numerical sensitivity studies demonstrate that more intense and rapidly moving vortices are more like to cross directly over the barrier and thus maintain a continuous track in one special case of a weak but fast moving vortex approaching the southern end the model simulates the existence of

microscopic planar deformation features in quartz of the vredefort structure anomalous but still suggestive of an impact origin abstract the orientation and distribution of diagnostic shock produced planar features in quartz has been examined in over 80 samples from both the core and collar rocks of the vredefort structure in south africa these features are widespread occurring in all but four samples the majority of the planar features have a basal 0001 orientation with a few higher pressure so called features and three features occurring near the center of the structure their relative distribution and preservation are however anomalous compared to those at other large terrestrial impact structures and recorded shock pressures calculated on the basis of planar feature orientation do not show a regular decrease radially outward as observed at other known impact structures the apparently anomalous development of planar features is interpreted as a result of post shock recrystallization if the effect of recrystallization of quartz which generally increases inward toward the core of the structure is considered and only the highest pressure type planar feature present in any one sample is taken as a measure of shock pressure then higher pressures are recorded in the core compared to the collar rocks no evidence of a previously reported additional post recrystallization shock event is found in this study although previous researchers report that pseudotachylite which may or may not be associated with the shock event cuts recrystallized quartzites in is concluded that although anomalous the evidence from planar features in quartz is still consistent with the vredefort structure being an erosional remnant of a large complex impact structure

terminal cretaceous environmental events the geologic record of terminal cretaceous environmental events indicates that iridium and other associated elements were not deposited instantaneously but during a time interval spanning some 10 000 to 100 000 years the available geologic evidence favors a mantle rather than meteoritic origin for these elements these results are in accord with the scenario of a series of intense eruptive volcanic events occurring during a relatively short geologic time interval and not with the scenario of a single large asteroid impact event

marble mylonites in the bancroft shear zone ontario canada microstructures and deformation mechanisms abstract mylonitization of medium grade marbles in the bancroft shear zone ontario canada is characterized by decreasing grain size of both calcite and graphite and a variety of textures calcite grain sizes vary from several millimeters in the protolith to 50 200 m in mylonite to m in ultramylonite corresponding calcite grain shapes are equant in the protolith elongate in protomylonite first developed dimensional preferred orientation equant in coarse mylonite elongate in fine mylonite second developed dimensional preferred orientation and generally equant in ultramylonite which suggests that external energy applied stress that tends to elongate grains competed with internal energy sources e g distortional strain that favor equant shapes graphite grain size changes from several millimeters to centimeters in the protolith to submicroscopic in ultramylonite in the mylonitic stages graphite is present as dark bands while in the ultramylonitic stage it is preserved as a fine coating on calcite grains based on textural evidence twinning exponential creep regime i dynamic recrystallization power law creep regime ii and possibly grain boundary sliding superplasticity regime iii are considered the dominant deformation mechanisms with increasing intensity of mylonitization their activity is largely controlled by calcite grain size calcite grain size reduction occurred predominantly by the process of rotation recrystallization during the early stages of mylonitization as indicated by the occurrence of core and mantle or mortar structures and by the grain size of subgrains and recrystallized grains grain elongation in s c structures indicates the activity of migration recrystallization these structures are not the result of flattening of originally equant grains differential stress estimates in coarse mylonites and ultramylonites based on recrystallized grain size are 2 5 and 14 38 mpa respectively initial grain size reduction of graphite occurred by progressive separation along basal planes analogous to mica fish formation in quartzo feldspathic mylonites calcite graphite thermometry on mylonitic and ultramylonitic samples shows that the metamorphic conditions during mylonitization were 475 50 c which combined with a differential stress value of 26 mpa gives a strain rate of 1 2 x 10 10 s 1 based on constitutive equations corresponding displacement rates are mm yr 1

applications of twin analysis to studying meteorite impact structures abstract this paper describes a technique twin analysis of dolomite and calcite which was used to estimate the level of erosion of an impact crater if the age of impact is known the level of erosion gives the amount of sediments present at that time the estimate of the level of erosion and the presence or absence of tectonic strains in calcite constrains the age of impact this technique might also be useful in identifying deeply eroded impact structures twin analysis gives the greatest shortening direction e 1 tilt corrected e 1 directions converge at or above the present day surface if a shallow gas explosion or meteorite impact explains the structure rather than a deep gas or cryptovolcanic explosion the energy density recorded by twinning distinguishes an impact from a shallow gas explosion for structures 100 m diameter at serpent mound a well established impact structure e 1 directions converge at 1400 390 m 95 confidence interval of the mean above the present day structure and the sample closest to the center of the structure records an energy density of 1 7 10 7 j m 3 these results are consistent with previous studies showing that serpent mound is an impact e g r w carlton c koeberl m t baranoski g a schumacker discovery of microscopic evidence for shock metamorphism at the serpent mound structure south central ohio confirmation of an origin by impact earth and planet sci lett 162 1998 177 185 the level of erosion and other data suggests that serpent mound formed between 290 and 256 ma and was originally 8 5 to 11 km in diameter dolomite twinning is not observed at serpent mound suggesting that this technique may only be useful for studying larger more deeply eroded structures

interaction of typhoons with the taiwan orography part i upstream track deflections abstract a combined observational and numerical modeling approach is used to study the upstream track deflections of westward moving tropical cyclones approaching the mountainous terrain of taiwan although the standard deviations are large the mean track deflections are larger and have a different orientation for storms approaching the southern end of the island from those approaching the northern end the deflections tend to be larger for weaker and slower moving storms two distinct regions of upstream track deflections that are detected in the observations are explored in a sensitivity study with a 45 km horizontal resolution and 16 layer numerical model as the outer circulation of the tropical cyclone begins to interact with the mountain barrier the zonal decelerations and southward track deflections are explained by an enhanced blocking and deflection of the environmental flow advecting the cyclone the larger effect for southern approaching storms compared to northern storms is because the stron

impact metamorphism of caco3 bearing sandstones at the haughton structure canada impact metamorphosed caco3 bearing sandstones at the haughton structure have been divided into 6 classes based to a large extent on a previous classification developed for sandstones at meteor crater class 1a sandstones 10 30 gpa consist almost entirely of lechatelierite a new class of shocked sandstones class 6 consists of sio2 rich melt that recrystallized to microcrystalline quartz calcite within class 4 to 6 sandstones also underwent melting and is preserved as globules and euhedral crystals within sio2 phases demonstrating the importance of impact melting and not decomposition in these caco3 bearing sandstones

new early jurassic tetrapod assemblages constrain triassic jurassic tetrapod extinction event the discovery of the first definitively correlated earliest jurassic 200 million years before present tetrapod assemblage fundy basin newark supergroup nova scotia allows reevaluation of the duration of the triassic jurassic tetrapod extinction event present are tritheledont and mammal like reptiles prosauropod theropod and ornithischian dinosaurs protosuchian and sphenosuchian crocodylomorphs sphenodontids and hybodont semionotid and palaeonisciform fishes all of the families are known from late triassic and jurassic strata from elsewhere however pollen and spore radiometric and geochemical correlation indicate an early hettangian age for these assemblages because all typical triassic forms are absent from these assemblages most triassic jurassic tetrapod extinctions occurred before this time and without the introduction of new families as was previously suggested by studies of marine invertebrates this pattern is consistent with a global extinction event at the triassic jurassic boundary the manicouagan impact structure of quebec provides dates broadly compatible with the triassic jurassic boundary and following the impact theory of mass extinctions may be implicated in the cause

texture development in experimentally deformed two phase aggregates of calcite and anhydrite abstract fully quantitative textures have been measured from experimentally deformed two phase aggregates of calcite and anhydrite two sets of deformation experiments were performed firstly to investigate the development of microstructure and texture with composition samples with varying volume proportions of calcite and anhydrite were deformed to 20 strain at identical conditions secondly to study the texture development of the two materials with strain and explore the possible use of texture index as a strain gauge in polyphase materials pure calcite and pure anhydrite were deformed at the same conditions as the two phase rocks to strains of 6 12 and 20 the textures in both calcite and anhydrite were found to be similar but not identical to those reported in previous studies for pure samples our experimental investigations and measured textures show that the textures both of the pure materials and of the two phase rocks depend not only on strain but also on stress and grain size through their influence on the deformation mechanisms the dependence of texture index with change in deformation mechanism is particularly pronounced in the anhydrite component where the texture index decreases with grain size which decreases with anhydrite content the texture in the pure calcite and in the calcite component of the two phase rocks was influenced by a preexisting fabric the intensity of the texture in the deformed samples seems to correlate with the stress in the calcite rather than with strain

the terrestrial impact cratering record approximately 130 terrestrial hypervelocity impact craters are currently known due to variations in preservation and in geologic knowledge this sample is biased towards young x 20 km craters on the cratons of australia europe including the former u s s r and north america the rate of discovery of new craters is 3 5 craters per year although modified by erosion terrestrial impact craters exhibit the range of morphologies observed for craters on other terrestrial planetary bodies such as the moon terrestrial craters provide essential ground truth data on the geologic effects of impact and the subsurface structure of impact craters which can be used to constrain interpretations of lunar samples and models of crater formation due to erosion and its effects on form terrestrial craters are recognized primarily by the occurrence of shock metamorphic effects these include shatter cones microscopic planar deformation features solid state and fusion glasses high pressure polymorphs and whole rock melting and vaporization shock recovery experiments indicate that these features occur over shock pressures of 5 gpa to x 100 gpa terrestrial craters have a set of geophysical characteristics which are largely the result of the passage of a shock wave and impact induced fracturing they include gravity and magnetic lows and reductions in seismic velocity the gravity anomalies are seldom greater than 30 mgal due to the limiting effects of lithostatic pressure on fracturing at large complex craters the gravity signature may include a central relative gravity high due to uplift and short wavelength central magnetic anomalies due to a variety of processes much current work is focused on the effects of impact on earth evolution previous work on shock metamorphism and the contamination of impact melt rocks by meteoritic siderophile elements provides a basis for the interpretation of the physical and chemical evidence from cretaceous tertiary boundary sites as resulting from a major impact suggestions that other biological boundaries in the stratigraphie record are due to periodic impacts are not supported by time series analysis of the terrestrial cratering record by analogy with the lunar record and modelling of the effects of very large impacts it has been proposed that biological and atmospheric evolution of the earth could not stabilize before the end of the late heavy bombardment 3 8 ga ago the present terrestrial cratering rate is 5 4 2 7 10 15 km 2a 1 for a diameter 20 km this represents a local threat on historic time scales on a global scale a major impact sufficient to cripple human civilization severely will occur on time scales of 106 a

deformational features and impact generated breccia from the sierra madera impact structure west texas deformational features from the sierra madera impact structure west texas were studied to estimate shock temperature and shock pressure values involved during its formation sandstone limestone and polymict impact generated breccia samples occur within the central uplift the sandstones host several shock related deformational features including toasted quartz grains and planar microstructures planar fractures and planar deformation features in quartz zircon mineral grains separated from the sandstone samples provide evidence of shock deformation in the form of planar fractures and granular surface textures both sandstone and carbonate within the central uplift contain shatter cones whereas polymict impact generated breccia samples contain shatter cone fragments and clasts of mixed lithology most high temperature features e g high temperature mineral phases and a melt sheet typically associated with less eroded structures of similar size are lacking however some small millimeter size possible devitrified glass clasts within polymict breccias occur at several locations deformational features within zircon mineral grains shatter cones and quartz grains with multiple planar microstructures record pressure and temperature conditions during the impact of 3 20 gpa and postshock temperatures between 350 and 1000 c deformational conditions during the impact event were almost certainly higher given that erosion has presumably removed most of the more severely shocked rocks

origin of the sudbury complex by meteoritic impact neodymium isotopic evidence samarium neodymium isotopic data on whole rocks and minerals of the sudbury complex in canada gave an igneous crystallization age of 1840 21 x 10 6 years the initial epsilon neodymium values for 15 whole rocks are similar to those for average upper continental crust falling on the crustal trend of neodymium isotopic evolution as defined by shales the rare earth element concentration patterns of sudbury rocks are also similar to upper crustal averages these data suggest that the sudbury complex formed from melts generated in the upper crust and are consistent with a meteoritic impact

scale effects on tension capacity for rough piles buried in dense sand this paper examines the effect of pile diameter on the unit shaft friction that can develop on a pile in sand the study is based on a series of tension tests conducted on centrifuge model piles with a range of pile diameters and average initial stress levels the inferred significant increases in lateral effective stresses on the shafts of these piles at peak capacity are shown to be consistent with the normal displacement dilation stiffness relationship measured in appropriate constant normal stiffness cns interface tests the determination of the lateral stress increases and hence shaft capacity also requires measurement or prediction of the non linear cavity expansion stiffness of the sand surrounding the pile shaft predictions obtained for this stiffness using a numerical technique indicate that the operational stiffness surrounding a model pile is well below that assuming the very small strain elastic stiffness and that the degree of normal displacement and hence the lateral stress increa

a perspective on the evidence for periodic cometary impacts on earth abstract recent suggestions of periodic cometary showers coincident with mass extinctions have prompted a review of the terrestrial cratering record from the point of view of completeness of search and crater retention the record used to argue for statistical periodicities is incomplete and may not be representative estimates of crater ages are of variable accuracy and precision and in some cases different dating methods yield discordant results it is possible to define through time series analysis a number of periodicities of different magnitude 29 m y 21 m y 18 5 m y 13 5 m y and phase depending on which craters are considered the most representative sample of the record arguing against periodic cometary showers is the observation that estimates of the average cratering rate in recent time and observations on apollo bodies are equivalent in addition siderophile element data from impact melt rocks suggest a variely of projectile types were responsible for relatively large terrestrial craters given these observations it is concluded that statements regarding periodic cometary showers are not categorical and require evidence beyond arguments based on time series analyses of an incomplete cratering record

an investigation on how inner core structures obtained through radar data assimilation affect track forecasting of typhoon jangmi 2008 near taiwan island the impacts of radar data assimilation da on the westward track deflection of typhoon jangmi 2008 near taiwan island and the deflection mechanism are investigated initial conditions from two data assimilation experiments with significant track forecast differences are analyzed and compared the environmental axisymmetric wavenumber 1 to 3 asymmetric fields of the typhoon are decomposed using vortex separation and fourier decomposition methods the components are selectively recomposed into new initial conditions that include different vortex scale components to examine the impact of individual components on the track prediction the wavenumber 1 asymmetric structure is found to play a dominant role in the westward deflection of typhoon jangmi and the accurate analysis of this component with radar da helps to improve the track forecast the wavenumber 1 asymmetric circulation is manifested as a pair of cyclonic and anticyclonic gyres with well defined ventilation flows through the inner core region which provides additional steering of the typhoon vortex the layer mean environmental steering flow and ventilation flow associated with the wavenumber 1 gyres are further calculated to quantitatively evaluate the impact of ventilation flow the ventilation flow is shown to be responsible for most of the westward motion component suggesting again its role in causing the westward track deflection of typhoon jangmi the results also suggest the importance of analyzing vortex scale asymmetric structures for accurate tropical cyclone track forecasting especially when there is a significant track deflection

effects of terrain on the surface structure of typhoons over taiwan abstract the island of taiwan is situated in the main path of western north pacific typhoons its dominant central mountain range cmr with a hoizontal scale comparable to the radius of a typhoon often produces significant distortions in the typhoon circulation a 20 year dataset from 22 surface stations is used to describe the effects of the taiwan terrain on the surface structure of typhoons empirical orthogonal function analysis on the pressure field is used to identify the primary structure modes the first mode is a uniform sign anomaly pattern portraying the decrease in pressure as a typhoon is approaching the second mode represents the strong terrain induced west east pressure gradient that is normal to the main axis of the cmr the third mode results mainly from the west cast pressure gradient arising from the relative location of the typhoon center to the east or west of taiwan but it also contains a weak south north pressure gradient that can he attributed to the terrain a regression tech

control parameters for the influence of a mesoscale mountain range on cyclone track continuity and deflection abstract in this study prospective control parameters are identified for diagnosing the continuity and deflection of cyclone tracks across a mesoscale mountain range based on idealized simulations of a westward moving cyclone it was found that the cyclone track becomes a discontinuous continuous track and the cyclone experiences more less deflection with a combination of small large values of vmax nh u nh r ly u flx and vmax fr and large small value of h lx the symbols are defined as follows vmax the maximum tangential wind n the brunt vaisala frequency h the mountain height u the basic wind speed r the radius of vmax f the coriolis parameter and lx and ly the horizontal scales of the mountain in x and y directions respectively a conceptual model is proposed to explain track deflection and continuity for a westward moving cyclone encountering idealized topography representative of the central mountain range of taiwan with weak orographic blocking a cyclone crosses over the mount

liquefaction resistance of clean and nonplastic silty sands based on cone penetration resistance liquefaction of granular soil deposits is one of the major causes of loss resulting from earthquakes the accuracy in the assessment of the likelihood of liquefaction at a site affects the safety and economy of the design in this paper curves of cyclic resistance ratio crr versus cone penetration test cpt stress normalized cone resistance qc1 are developed from a combination of analysis and laboratory testing the approach consists of two steps 1 determination of the crr as a function of relative density from cyclic triaxial tests performed on samples isotropically consolidated to 100 kpa and 2 estimation of the stress normalized cone resistance qc1 for the relative densities at which the soil liquefaction tests were performed a well tested penetration resistance analysis based on cavity expansion analysis was used to calculate qc1 for the various soil densities a set of 64 cyclic triaxial tests were performed on specimens of ottawa sand with nonplastic silt content in the range of 0 15 by

state dependant dilatancy in critical state constitutive modelling of sand a bounding surface hypoplasticity model is modified to incorporate the basic premises of critical state soil mechanics and cover both dense and loose sand behavior the modification consists of ren

calcite twins their geometry appearance and significance as stress strain markers and indicators of tectonic regime a review twin lamellae are a widespread feature in calcites of any type and origin twinning in calcite is an important intracrystalline deformation mechanism with low critical resolved shear stress and virtually no temperature dependence in contrast to most slip systems in rock forming minerals twinning therefore permits intracrystalline deformation at very low temperature and very little confining pressure twinning alone however cannot lead to large strains because only one independent slip system is effectively available twins lead to discontinuous shearing on the grain scale which gives rise to considerable strain incompatibilities at grain boundaries twinning consequently leads to strain hardening detailed observations of the geometry of twin lamellae show that incompatibilities at grain boundaries are eliminated by pressure solution on the grain scale at low temperature and dynamic recovery processes at higher temperatures twins are found in various tectonic environments and record very small strains in rocks deformed under very little cover different twinning strain and twinning stress methods and palaeopiezometers are critically reviewed all methods are limited to strains of less than 15 shortening or extension by twinning twinning nevertheless is an important although not directly measurable contribution to the total strain in highly strained calcite rocks at least up to middle greenschist facies under which conditions it is the most effective contributor to the formation of strong lattice preferred orientations in calcite tectonites the appearance of calcite twin lamellae changes systematically as a function of deformation temperature micro twins and straight narrow 1 5 m but fewer twins are developed above approximately 200 c curved twins twinned twins and completely twinned grains indicate the progressive importance of other slip systems and larger intracrystalline strains are possible at ca 250 c and above ancient straight twin lamellae are modified into irregular geometries by recrystallization and grain boundary migration the appearance of calcite twins is proposed as an approximate but rapid and easy to use geothermometer in low temperature environments

the coefficient of earth pressure at rest laboratory experiments on undisturbed specimens of a large number of soft clay deposits as well as previous measurements on clays and granular soils were used to examine and explain the magnitude and behavior of the coefficient of earth pressure at rest k0 i after sedimentation primary consolidation ii during secondary compression aging iii after active or passive preshearing away from the laterally constrained condition iv during a decrease in effective vertical stress and v during an increase in effective vertical stress in the recompression or compression range in terms of the slope of the effective horizontal versus effective vertical stress path the behavior of k0 is explained using the concept of mobilized angle of friction in laterally constrained deformation condition the jaky equation provides in terms of the angle of internal friction a good estimate of k0 of sedimented normally consolidated young clays and granular soils as well as of of presheared clays and sands

dynamics of track deflection associated with the passage of tropical cyclones over a mesoscale mountain abstract in this study the fifth generation pennsylvania state university national center for atmospheric research psu ncar mesoscale model mm5 was used to simulate supertyphoon bilis in 2000 and typhoon toraji in 2001 in order to investigate the dynamics of track deflection caused by the central mountain range cmr of taiwan the mm5 predicted the track of each storm reasonably well bilis was stronger and had a relatively faster forward motion which helped make the track continuous as it crossed the cmr the use of a bogus vortex in the initialization process helped produce a storm closer to the observed strength bilis is a classic example of a typhoon crossing taiwan with a continuous track for comparison typhoon toraji a typical typhoon having a discontinuous track was also studied toraji was weaker and had a relatively slower forward speed which prevented the original low center from crossing over the cmr and forced more air parcels to go around the northern tip of the cmr as a r

reflection seismic investigations of the siljan impact structure sweden reflection seismic measurements were carried out during 1985 in the area of the siljan impact structure of sweden a total profile length of 80 km was shot to get a clearer picture of the subsurface geometry of impact structures and the processes that formed them than could be obtained from surface observations or theoretical modeling studies standard stacked sections have been interpreted in terms of current impact models the transient crater diameter is found to be approximately 22 km considerably smaller than current estimates based on interpretation of surface geology the structural uplift is estimated to be 3 km at the 5 to 8 km level and the material flow necessary to support the uplift is mainly horizontal rather than vertical