subrainband structure and dynamic characteristics in the principal rainband of typhoon hagupit 2008 abstractthe principal rainband in tropical cyclones is currently depicted as a solitary and continuous precipitation region however the airborne radar observations of the principal rainband in typhoon hagupit 2008 reveal multiple subrainband structures these subbands possess many characteristics of the squall lines with trailing stratiform in the midlatitudes and are different from those documented in previous principal rainband studies the updraft and reflectivity cores are upright and elevated the updraft is fed by a low level radial outflow from the inner side the tangential wind speed shows a clear midlevel jet on the inner side of the reflectivity core except for the structural similarities the dynamics of the subbands is also similar to the squall lines the local environment near the subbands shows little convective inhibition modest instability and vertical wind shear the temperature retrieval shows a cold pool structure in the stratiform precipitation region the estimated vertical w

spatial distribution of focal mechanisms for interplate and intraplate earthquakes associated with the subducting pacific plate beneath the northeastern japan arc a triple planed deep seismic zone the northeastern japan arc is located in one of the most seismically active subduction zones in the world in this study we relocated hypocenters and determined focal mechanisms of small earthquakes m 5 beneath the arc in order to investigate in detail the stress distribution in and around the descending oceanic plate in the hypocenter relocation we adopted a source region station correction method in which station corrections vary with hypocenter locations we have developed a new focal mechanism determination technique named master solution method which is analogous to the master event method in hypocenter determination we applied the method to p and sh wave amplitude data to obtain 1106 focal mechanism solutions from the new mechanism solutions and relocated hypocenters we found that there occur both low angle thrust fault lt type and downdip compression dc type earthquakes at depths from 40 to 70 km near the aseismic front the dc type events are underlying the lt type events almost all the earthquake clusters are composed of lt type events the western limit of the region where lt type events have occurred is subparallel to the trench axis although it undulates considerably it delineates the westernend of the active region of interplate seismicity furthermore we found that normal fault nf type events also occur at depths from 70 km in the upper plane of the double planed deep seismic zone which is characterized mainly by dc type event these nf type events are distributed only in a thin uppermost portion of the slab close to the plate boundary below these in the lower plane are downdip extension de type events this result indicates that the deep seismic zone in the northeastern japan arc is not double planed but triple planed even beneath the land area which cannot be explained by any simple models

accelerated pacific plate subduction following interplate thrust earthquakes at the japan trench interplate thrust earthquakes are usually followed by afterslips and they let the fore arc move slowly trenchward however we do not know if the subducting oceanic plate is accelerated landward after such earthquakes the westward velocity of global positioning system gps stations in ne japan show gradient decreasing from east to west reflecting the e w contractional strain built up by the inter plate coupling here we show that such coupling significantly enhanced 1 5 times after the 2003 tokachi oki earthquake mw 8 0 hokkaido in the segments adjacent to the ruptured fault the coupling seems to be further enhanced 3 times after the 2011 tohoku oki earthquake mw 9 0 it is unlikely that interplate friction suddenly increased over such a large region and relatively strong pre 2003 coupling there would not allow such enhancements even if full coupling is attained hence they are attributable to the temporary acceleration of the pacific plate subduction we propose a simple 2 dimensional model in which down dip acceleration of the slab let the force balance rapidly recover promoted by a thin low viscosity layer on the slab surface the accelerated subduction would account for temporary activations of regional interplate seismicity after megathrust earthquakes

geodetic imaging of plate motions slip rates and partitioning of deformation in japan 1 interseismic deformation in japan results from the combined effects of tectonic processes including rotation of crustal blocks and the earthquake cycle process of elastic strain accumulation about upper plate faults and subduction zone interfaces we use spherical linear block theory constrained by geodetic observations from densely spaced global positioning system gps stations to estimate plate motions fault slip rates and spatially variable interplate coupling on the japan kuril sagami and nankai subduction zones the reference model developed in this paper consists of 20 blocks produces a mean residual velocity magnitude of 1 84 mm yr at 950 stations and accounts for 96 of the observed interseismic deformation signal we estimate fault slip rates in excess of 15 mm yr along the niigata kobe tectonic zone and itoigawa shizuoka tectonic line through central japan confirming their hypothesized roles as major tectonic boundaries oblique convergence across the nankai trough is partitioned with 3 4 of the 30 mm yr of trench parallel motion accommodated by strike slip motion on the subduction interface and the remaining 1 4 accommodated by right lateral slip on the median tectonic line in contrast our models suggest negligible slip partitioning in eastern hokkaido where oblique slip on the japan kuril subduction interface accommodates all of the trench parallel component of relative plate motion inferred spatial variations in the rake and magnitude of slip deficit on subduction zone interfaces reflect the influences of megathrust geometry and earthquake cycle processes such as enhanced elastic strain accumulation about seismic asperities and coseismic sense fault motion indicative of silent slip events or afterslip following large earthquakes

high altitude aeolian research on the tibetan plateau aeolian processes and their role in desertification have been studied extensively at low elevations but have been rarely studied at high elevations in areas such as the tibetan plateau where aeolian processes were active in the geologic past and remain active today in this review we summarize research that improves our understanding of aeolian processes on the tibetan plateau including the distribution characteristics and provenance of aeolian sediments the history of aeolian activity aeolian geomorphology and wind driven land degradation contemporary aeolian processes primarily occur in dry basins in wide river valleys on lakeshores on mountain slopes and on gravel pavements sediment characteristics suggest a local origin and provide interesting contrasts with those of china s loess plateau the history of aeolian activity and its paleoclimatic implications reconstructed based on aeolian archives is short mostly since the late glacial and shows wide regional differences aeolian geomorphology is simple and suggests short formation time wind driven land degradation is less severe than previously thought driven by different factors in different areas and exhibited complex interactions with freeze thaw processes aeolian research has been conducted within the general framework of aeolian science but addresses issues specific to the tibetan plateau that arise due to the low air temperature low air density and the presence of a cryosphere we propose six priorities for future research aeolian physics the effect of freeze thaw cycles comparisons with other areas regional differences effects of wind driven land degradation and integrated observation and monitoring

salton trough regional deformation estimated from combined trilateration and survey mode gps data the salton trough in southeastern california united states has one of the highest seismicity and deformation rates in southern california including 20 earthquakes m 6 or larger since 1892 from 1972 through 1987 the u s geological survey usgs measured a 41 station trilateration network in this region we re measured 37 of the usgs baselines using survey mode global positioning system methods from 1995 through 1999 we estimate the salton trough deformation field over a nearly 30 year period through combined analysis of baseline length time series from these two datasets our primary result is that strain accumulation has been steady over our observation span at a resolution of about 0 05 strain yr at 95 confidence with no evidence for significant long term strain transients despite the occurrence of seven large regional earthquakes during our observation period similar to earlier studies we find that the regional strain field is consistent with 0 5 0 03 strain yr total engineering shear strain along an axis oriented 311 6 23 east of north approximately parallel to the strike of the major regional faults the san andreas and san jacinto all uncertainties in the text and tables are standard deviations unless otherwise noted we also find that 1 the shear strain rate near the san jacinto fault is at least as high as it is near the san andreas fault 2 the areal dilatation near the southeastern salton sea is significant and 3 one station near the southeastern salton sea moved anomalously during the period 1987 95 1995 11 online material tables of stations used in this study and of estimated strain fields manuscript received 8 january 2003

the roles of asymmetric inflow forcing induced by outer rainbands in tropical cyclone secondary eyewall formation abstractthis study analyzes the secondary eyewall formation sef process in an idealized cloud resolving simulation of a tropical cyclone in particular the unbalanced boundary layer response to asymmetric inflow forcing induced by outer rainbands orbs is examined in order to understand the mechanisms driving the sustained convection outside the primary eyewall during the early phase of sef the enhancement of convection in the sef region follows the formation and inward contraction of an orb the azimuthal distribution of the enhanced convection is highly asymmetric but regular generally along a half circle starting from the downwind portion of the orb it turns out that the descending radial inflow in the middle and downwind portions of the orb initiates maintains a strong inflow in the boundary layer the latter is able to penetrate into the inner core region sharpens the gradient of radial velocity and reinforces convergence consequently warm and moist air is continuously lifted up at the lead

dynamics of the stratiform sector of a tropical cyclone rainband abstractairborne doppler radar documented the stratiform sector of a rainband within the stationary rainband complex of hurricane rita the stratiform rainband sector is a mesoscale feature consisting of nearly uniform precipitation and weak vertical velocities from collapsing convective cells upward transport and associated latent heating occur within the stratiform cloud layer in the form of rising radial outflow beneath downward transport is organized into descending radial inflow in response to two regions of latent cooling in the outer upper regions of the rainband sublimational cooling introduces horizontal buoyancy gradients which produce horizontal vorticity and descending inflow similar to that of the trailing stratiform region of a mesoscale convective system within the zone of heavier stratiform precipitation melting cooling along the outer rainband edge creates a midlevel horizontal buoyancy gradient across the rainband that drives air farther inward beneath the brightband the organi

are the frictional properties of creeping faults persistent evidence from rapid afterslip following the 2011 tohoku oki earthquake 1 geophysical observations and numerical studies have shown that creeping portions of faults have persistent rate strengthening frictional properties and can act as barriers to earthquake rupture propagation on the basis of gps data following the 2011 mw 9 0 tohoku oki earthquake in japan we find that the evolution of afterslip and postseismic shear stress on the plate interface is inconsistent with persistent rate strengthening frictional properties but is consistent with slip rate dependent frictional properties that exhibit less rate strengthening with increasing slip rate such slip rate dependent frictional properties tend to prevent creeping regions from acting as barriers to rupture propagation and therefore could be an important factor in determining the spatial extent of individual earthquakes

a decadal scale deformation transient prior to the 2011 mw 9 0 tohoku oki earthquake gps time series in northeast japan exhibit nonlinear trends from 1996 to 2011 before the mw 9 0 2011 tohoku oki earthquake after removing reference frame noise we model time series as linear trends plus constant acceleration correcting for coseismic and postseismic effects from the numerous mw 6 5 earthquakes during this period we find spatially coherent and statistically significant accelerations throughout northern honshu large areas of japan outside the tohoku region show insignificant accelerations demonstrating that the observation is not due to network wide artifacts while the accelerations in northern tohoku sanriku area can be explained by decaying postseismic deformation from pre 1996 earthquakes the accelerations in south central tohoku appear unrelated to postseismic effects the latter accelerations are associated with a decrease in average trench normal strain rate and can be explained by increasing slip rate on the japan trench plate interface and or updip migration of deep aseismic slip in the decades before the 2011 tohoku oki earthquake

how does the boundary layer contribute to eyewall replacement cycles in axisymmetric tropical cyclones abstractthree diagnostic models of the axisymmetric tropical cyclone boundary layer with different levels of approximation are applied to the problem of tropical cyclones with concentric eyewalls the outer eyewall is shown to have an inherently stronger frictional updraft than the inner because it is in an environment of lower vorticity similarly a relatively weak local enhancement of the radial vorticity gradient outside the primary radius of maximum winds can produce a significant frictional updraft even if there is no outer wind maximum based on these results it is proposed that the boundary layer contributes to the formation of outer eyewalls through a positive feedback among the local enhancement of the radial vorticity gradient the frictional updraft and convection the friction induced secondary circulation associated with the inner eyewall is shown to weaken as the outer wind maximum strengthens and or contracts so boundary layer processes will contribute along with the heating induced

optical dating of tibetan human hand and footprints an implication for the palaeoenvironment of the last glaciation of the tibetan plateau 1 the tibetan plateau is a cold and arid environment with poor archaeological finds it is generally assumed to have been covered by ice sheet during the last ice age nineteen handprints and footprints of homo sapiens on hot spring travertine and the remnant of a fireplace have been found at an elevation of 4200 m on the tibetan plateau based on the optically stimulated luminescence of quartz extracted from samples of the baked and unheated travertine the age of the prints and the fireplace are around 20 000 these finds suggest that there were humans living in this area around the time of the last glacial maximum lgm and that the ice sheet did not cover the entire tibetan plateau at this time

environmental humidity changes inferred from multi indicators in the jianghan plain central china during the last 12 700 years abstract time sequence of the jz 2010 profile derived from ams 14 c dating and the content of the sediment elements ti rb and sr the rb sr values as well as the granularity and the magnetic susceptibility are utilized to reconstruct the environmental humidity changes in the jianghan plain since 12 700 cal bp the comprehensive analyses of multiple alternative indicators indicate that the regional moisture turned from relatively dry to wet after the late glacial period and reached its optimum until the mid holocene however the trend was punctuated by several decreased humidity phases beginning with the severe dry event approximately 4400 4100 cal bp the environment was dry as a whole with modest humidity from approximately 3900 cal bp humidity changes in the study area are dominated by the east asian monsoon system which is under the influence of the gradual southward migration of the itcz driven by the summer solar insolation changes in the northern hemisphere due to orbital forcing as the first attempt to apply rb sr value and ti concentration in tracing moisture evolution in a region with typical subtropical humid climate this study highlights the different effects and consequences of the proxies throughout the palaeoenvironmental change process and the impacts of regional topography that sustained tectonic subsidence since the cretaceous as well as the southeast tilt that opened the plain to the summer monsoon moreover the fluctuation of magnetic susceptibility is associated with the granularity feature the reduction oxidation conditions and the impact of human factors on the natural sedimentary environments during the historic period in the jianghan plain

the relationship between storm motion vertical wind shear and convective asymmetries in tropical cyclones abstract the influence of the direction of storm motion on the azimuthal distribution of electrified convection in 35 atlantic basin tropical cyclones from 1985 to 1999 was examined using data from the national lightning detection network in the inner 100 km flashes most often occurred in the front half of storms with a preference for the right front quadrant in the outer rainbands r 100 300 km flashes occurred predominantly to the right of motion although the maximum remained in the right front quadrant the results are shown to be consistent with previous studies of asymmetries in rainfall radar reflectivity and vertical motion with respect to tropical cyclone motion the motion effect has been attributed to the influence of asymmetric friction in the tropical cyclone boundary layer the authors previously found a strong signature in the azimuthal distribution of lightning with respect to vertical wind shear because both effects show clearly vertical wind shear and storm motion must themse

the boundary layer dynamics of tropical cyclone rainbands abstractspiral bands are ubiquitous features in tropical cyclones and significantly affect boundary layer thermodynamics yet knowledge of their boundary layer dynamics is lacking prompted by rece

postseismic relaxation driven by brittle creep a possible mechanism to reconcile geodetic measurements and the decay rate of aftershocks application to the chi chi earthquake taiwan we evaluate the effect of coseismic stress changes on the fault slip at midcrustal depth assuming a velocity strengthening brittle creep rheology we show that this model can help reconcile the time evolution of afterslip as measured from geodesy with aftershocks decay we propose an analytical expression for slip of the brittle creeping fault zone bcfz that applies to any dynamic or static stress perturbation including shear stress and normal stress changes the model predicts an initial logarithmic increase of slip with time postseismic slip rate decays over a characteristic time t r a that does not depend on the amplitude of the stress perturbation and it asymptotically joins the long term creep imposed by interseismic stress buildup given that the seismicity rate might be considered proportional to the sliding velocity of the bcfz the model predicts a decay rate of aftershocks that follows omori s law with a mathematical formalism identical to that of dieterich 1994 although based on a different mechanical rationale our model also differs from dieterich s model in that it requires that aftershock sequences and deep afterslip as constrained from geodetic measurements should follow the same temporal evolution we test this for the 1999 chi chi earthquake m w 7 6 and find that both sets of data are consistent with a model of afterslip due to the response of the bcfz the inferred relaxation time t r 8 5 years requires a value for a log v being the coefficient of friction in the range between 1 3 10 3 and 10 2

postseismic crustal deformation following the 1993 hokkaido nansei oki earthquake northern japan evidence for a low viscosity zone in the uppermost mantle 1 postseismic crustal deformation following the 1993 hokkaido nansei oki earthquake m 7 8 northern japan was observed by gps tide gauge and leveling measurements in southwestern hokkaido as a result of comprehensively analyzing these three kinds of geodetic data we found the chief cause of the postseismic deformation to be viscoelastic relaxation of the coseismic stress change in the uppermost mantle afterslip on the main shock fault and its extension by contrast cannot explain the deformation without unrealistic assumptions the viscoelastic structure which we estimated from the postseismic deformation consists of three layers an elastic first layer with thickness of 40 km a viscoelastic second layer with thickness of 50 km and viscosity of 4 1018 pa s and an elastic half space this model suggests the presence of an anomalously low viscosity zone in the uppermost mantle the depth of the viscoelastic layer roughly agrees with that of the high temperature portion and the low vp zones of the mantle wedge beneath the coast of the japan sea in northern honshu these correlations suggest that the low viscosity primarily results from high temperature of the mantle material combined with partial melt and the presence of h2o these correlations also suggest that the low viscosity zone in the uppermost mantle is widely distributed in the back arc side of the volcanic front and that postseismic deformation induced by viscoelastic relaxation may be frequently observed after large earthquakes in this area

boundary layer structure and dynamics in outer hurricane rainbands part i mesoscale rainfall and kinematic structure abstract results of hurricane boundary layer experiments conducted in outer rainbands of hurricanes josephine 1984 and earl 1986 are presented comparisons of precipitation and kinematic structures in these storms and in hurricane floyd 1981 indicate that principal rainbands have common characteristic mesoscale and convective scale features in the boundary layer the two dimensional mesoscale structure suggests that these rainbands are made up of a linear aggregate of cellular reflectivity elements on the inner upshear side of the band and stratiform rain on the outer downshear side the bands are oriented perpendicular to the shear above the boundary layer and cells move downband at about 85 of the density weighted mean wind speed of the 0 2 6 km layer the boundary layer wind field is strongly influenced by the rainband with alongband and crossband wind maxima located on the outer side of the band axis and minima 4 8 km to the inner side maximum crossband convergence and cyclonic shear vor

major and trace elements of stream sediments from the lowermost amazon river geochemical results from river bottom sediments taken from the lowermost amazon river are presented bedload sediments were analyzed for 10 major and 38 minor elements mud bulk sediments exhibit a tendency to a slight enrichment in cr mn rb sr zr cs ba and hf pointing to the importance of these elements in the silt fraction generally cu zn rb cs ba and sn are clearly associated with clay minerals while y zr hf th and u are associated with heavy minerals the location of this area in an intensive chemical weathering environment results in the strong modification of sediment composition chemical weathering processes strongly modify original sediment composition and can be recognized apart from provenance processes on the basis of their geochemical signature discriminant analysis makes the detection of less marked differences in sediment characteristics possible thus improving the accuracy of distinctions between groups the amazon mouth and xingu mouth xm are discriminated principally by the textural maturity of their sediments the jari mouth jm shows highest co and fe2o3 contents despite similarities between the amazon north branch anb and amazon south branch asb the anb can be differentiated on the basis of its higher sr p2o5 and na2o contents the asb on the basis of its higher zn mno and cao contents and the estreitos de breves est based on its higher abundance of ni and cu higher contents in p2o5 fe and mn are related to laterite covers

effects of low level flow orientation and vertical shear on the structure and intensity of tropical cyclones abstractthis article explores the simultaneous effect of vertical wind shear vws and low level mean flow lmf on tropical cyclone tc structure evolution the structural evolution of 180 wester

concentric eyewall formation in typhoon sinlaku 2008 part ii axisymmetric dynamical processes abstractin part i of this study the association between the secondary eyewall formation sef and the broadening of the outer swirling wind in typhoon sinlaku 2008 was documented the findings from part i help lay the groundwork for the application of a newly proposed intensification paradigm to sef part ii presents a new model for sef that utilizes this new paradigm and its axisymmetric view of the dynamics the findings point to a sequence of structure changes that occur in the vortex s outer core region culminating in sef the sequence begins with a broadening of the tangential winds followed by an increase of the corresponding boundary layer bl inflow and an enhancement of convergence in the bl where the secondary eyewall forms the narrow region of strong bl convergence is associated with the generation of supergradient winds in and just above the bl that acts to rapidly decelerate inflow there the progressive strengthening of bl inflow and the generation of an effective adverse radial force

convectively generated potential vorticity in rainbands and formation of the secondary eyewall in hurricane rita of 2005 abstracteyewall replacements in mature tropical cyclones usually cause intensity fluctuations one reason for eyewall replacements remaining a forecasting challenge is the lack of understanding of how secondary eyewalls form this study uses high resolution full physics model forecast fields of hurricanes katrina and rita 2005 to better understand potential vorticity pv generation in the rainbands and the role that convectively generated pv played in the formation of a secondary eyewall in hurricane rita previous studies have focused on dynamic processes in the inner core and or the effects of certain specified pv distributions however the initial development of a concentric pv ring in the rainband region has not been fully addressed katrina and rita were extensively observed by three research aircraft during the hurricane rainband and intensity change experiment rainex which was designed to study the interaction of the rainbands and the inner core rita developed a secondary eyewall and went

mesoscale and convective structure of a hurricane rainband abstract the mesoscale thermodynamic kinematic and radar structure of a hurricane floyd rainband observed on 7 september 1981 is presented data are from 26 aircraft passes through the rainband from 150 to 6400 m a composite technique which presents rainband structure as a function of distance from the storm circulation center reveals inflow from the outer edge of the band and a partial barrier to this flow below 3 km in the direction parallel to rainband orientation radar reveals cellular reflectivity structure on the upwind and central portions of the rainband the frequency of cellular precipitation decreases in favor of stratiform precipitation further downwind as the band spirals gradually towards the eyewall in the radial direction a decrease of 12 k in e is observed across the rainband in the subcloud layer convective scale up and downdrafts that are associated with cellular reflectivity structure are hypothesized to be responsible for the thermodynamic modification of the cloud and subc

spatial correlation of interseismic coupling and coseismic rupture extent of the 2011 mw 9 0 tohoku oki earthquake 1 imaging the extent to which the rupture areas of great earthquakes coincide with regions of pre seismic interplate coupling is central to understanding patterns of strain accumulation and release through the earthquake cycle both geodetic and seismic estimates of the coseismic rupture extent for the march 11 2011 mw 8 9 9 0 earthquake tohoku oki earthquake may be spatially correlated 0 26 0 05 to 0 82 0 05 with a region estimated to be partially to fully coupled in the interseismic period preceding the earthquake though there is substantial variation in the estimated distribution and magnitude of coseismic slip the 400 km long region estimated to have slipped 4 m corresponds to an area of the subduction zone interface that was coupled at 30 of long term plate convergence rate with peak slip near a region coupled 80 the northern termination of rupture is collocated with a region of relatively low 20 interseismic coupling near the epicenter of the 1994 mw 7 6 sanriku oki earthquake and near a region of potential long term low coupling or ongoing slow slip slip on the subduction interface beneath the coastline 40 50 km depth is best constrained by the land based gps data and least constrained on the shallowest portion of the plate interface due to the 230 km distance between geodetic observations and the japan trench

kinematic structure of convective scale elements in the rainbands of hurricanes katrina and rita 2005 1 airborne doppler radar data collected during the hurricane rainband and intensity change experiment rainex show the convective scale air motions embedded in the principal rainbands of hurricanes katrina and rita these embedded convective cells have overturning updrafts and low level downdrafts originating at 2 4 km that enter the rainband on its radially outward side and cross over each other within the rainband as well as a strong downdraft emanating from upper levels 6 km on the radially inward side these vertical motion structures repeat from one convective cell to another along each rainband the resulting net vertical mass transport is upward in the upwind portion of the band and greatest in the middle sector of the principal rainband where the updraft motions contribute generally to an increase of potential vorticity below the 3 4 km level because the convective cells in the middle sector are systematically located radially just inside the secondary horizontal wind maximum shwm the local increase in vorticity implied by the convective mass transport is manifest locally as an increase in the strength of the shwm at midlevels 4 km the overturning updrafts of the convective cells tilt stretch and vertically transport vorticity such that the convergence of the vertical flux of vorticity strengthens the vorticity anomaly associated with the shwm this process could strengthen the shwm by several meters per second per hour and may explain how high wave number convective scale features can influence a low wave number feature such as the principal rainband and subsequently influence the primary vortex

intensity and structure changes during hurricane eyewall replacement cycles abstracta flight level aircraft dataset consisting of 79 atlantic basin hurricanes from 1977 to 2007 was used to develop an unprecedented climatology of inner core intensity and structure changes associated with eyewall replacement cycles ercs during an erc the inner core structure was found to undergo dramatic changes that result in an intensity oscillation and rapid broadening of the wind field concentrated temporal sampling by reconnaissance aircraft in 14 of the 79 hurricanes captured virtually the entire evolution of 24 erc events the analysis of this large dataset extends the phenomenological paradigm of ercs described in previous observational case studies by identifying and exploring three distinct phases of ercs intensification weakening and reintensification in general hurricanes intensify sometimes rapidly when outer wind maxima are first encountered by aircraft the mean locations of the inner and outer wind maximum at the start of an erc are 35 and 106 km from storm center respe

luminescence dated aeolian deposits of late quaternary age in the southern tibetan plateau and their implications for landscape history abstract aeolian deposits are widely distributed in the interior of the tibetan plateau and their chronology is poorly known it is not yet clear whether they accumulated only after the last deglaciation or over a longer time we applied quartz osl dating to aeolian samples from the lhasa area with osl ages ranging from 2 9 0 2 to at least 118 11 ka the probability density frequency pdf distribution of 24 ages reveals age clusters at about 3 8 16 21 33 and 79 83 ka indicating enhanced sediment accumulation then the results show that aeolian deposition occurred throughout most of the last 100 ka this implies that 1 an ice sheet covering the whole tibetan plateau during the last glacial maximum lgm could not have existed and 2 erosion during the last deglaciation was not as strong as previously proposed such that not all pre holocene loess was removed the age distribution shown in the pdf indicates that aeolian accumulation is episodic sand formation events revealed by age clusters at 3 8 and 16 21 ka imply roughly synchronous environmental responses to corresponding global scale arid events

a squall line like principal rainband in typhoon hagupit 2008 observed by airborne doppler radar this study examines the structure and dynamics of typhoon hagupit s 2008 principal rainband using airborne radar and dropsonde observations the convection in hagupit s principal rainband was organized into a well defined line with trailing stratiform precipitation on the inner side individual convective cells had intense updrafts and downdrafts and were aligned in a wavelike pattern along the line the line averaged vertical cross section possessed a slightly inward tilting convective core and two branches of low level inflow feeding the convection the result of a thermodynamic retrieval showed a pronounced cold pool behind the convective line the horizontal and vertical structures of this principal rainband show characteristics that are different than the existing conceptual model and are more similar to squall lines and outer rainbands the unique convective structure of hagupit s principal rainband was associated with veering low level vertical wind shear and large convective instability in the environment a quantitative assessment of the cold pool strength showed that it was quasi balanced with that of the low level vertical wind shear the balanced state and the structural characteristics of convection in hagupit s principal rainband were dynamically consistentwith the theory ofcold pooldynamicswidely appliedtostrong andlong livedsquall lines theanalyses suggest that cold pool dynamics played a role in determining the principal rainband structure in addition to storm scale vortex dynamics

dynamics of the transition from spiral rainbands to a secondary eyewall in hurricane earl 2010 abstractairborne doppler radar captured the inner core of hurricane earl during the early stages of secondary eyewall formation sef providing needed insight into the sef dynamics an organized r

reflectivity ice scattering and lightning characteristics of hurricane eyewalls and rainbands part ii intercomparison of observations abstract part i of this two part paper treats tropical rainfall measuring mission trmm radar passive microwave and lightning observations in hurricanes individually this paper part ii examines relationships between these parameters and implications of the relationships quantitative relationships between lightning occurrence and 85 ghz brightness temperature 37 ghz brightness temperature and radar reflectivity in the mixed phase region are established separately for hurricane eyewall regions inner rainband regions and outer rainband regions other tropical oceanic regions and tropical continental regions when any of the brightness temperature or radar parameters are held constant as controls lightning is more frequent in hurricane outer rainbands than elsewhere over tropical oceans and more frequent over continents than even in the outer rainbands reflectivity profiles associated with specific brightness temperatures are presented demonstrating a link between high altitude ice phase pre

importance of horizontal seafloor motion on tsunami height for the 2011 mw 9 0 tohoku oki earthquake abstract it is now clear that the 2011 tohoku oki earthquake ruptured the subduction interface all the way to the japan trench however there is significant disagreement about just how much slip occurred at the trench with most geodetic studies locating only a small fraction of the maximum slip there whereas broadband seismic studies put the majority of the slip near the trench measurements of seafloor displacement near the trench also imply more slip there than is estimated by the geodetic studies here by means of a joint inversion of displacement measurements and seafloor pressure data we show that it is possible to reconcile geodetic and seismic studies and that a considerable amount of slip indeed occurred at the trench with slip magnitudes reaching 57 74 of the maximum slip the seafloor displacement predicted by our model agrees very well with independent measurements made close to the trench we also find good agreement between our tsunami model and independent measurements of tsunami height in the ocean and on land re running of the inversion without the near field pressure gauge data however leads to underprediction of the flooding on land even when the seafloor geodetic data are still included thus even if the seafloor geodetic measurements had been available in real time they would still not have allowed reliable prediction of near field tsunami inundation close to the trench the dip of the plate interface is shallow which serves to decrease the vertical motion of the sea floor for any given slip however the horizontal motion is conversely larger because the ocean floor slopes steeply near the trench it acted like a giant wedge converting the horizontal motion of the ground into an uplift of the water column and causing the peak initial tsunami wave height to be twice as high as it would have been from vertical displacement alone

preceding coseismic and postseismic slips of the 2011 tohoku earthquake japan 1 we estimated the spatial and temporal evolution of the preceding aseismic slip from january 2003 to january 2011 the coseismic slip of the tohoku earthquake and the postseismic slip after the earthquake based on global positioning system gps data time dependent analysis indicates aseismic slip offshore of miyagi and fukushima prefectures from 2004 associated with a series of subduction earthquakes that overlap the aseismic slip area these preceding aseismic and coseismic slip areas are centered between the centers of the coseismic and afterslip areas of the tohoku earthquake offshore of miyagi prefecture while they overlap the coseismic and afterslip areas of the tohoku earthquake off fukushima prefecture the timing of moment magnitude nine mw9 class earthquakes appears to be controlled by multiple preceding slip events smaller earthquakes and their afterslip the preceding aseismic and coseismic slip decreased the coupling rate off the tohoku coast suggesting the possibility that the preceding slip represented a precursive stage of the tohoku earthquake the afterslip of the tohoku earthquake occurred in an area where the coseismic slip was not large complementing the large coseismic slip zone the afterslip along iwate miyagi extends up to 80 km in depth and is currently the sole mechanism of strain release in this depth range the source region of the anticipated miyagi oki earthquake shows small postseismic slip after the tohoku earthquake reflecting the energy release at the time of the earthquake aftershock activity is roughly governed by an afterslip process

nonlinear strain buildup and the earthquake cycle on the san andreas fault two contrasting models of the earthquake deformation cycle on strike slip faults predict significant temporal declines in shear strain rate near the fault accompanied by a progressive broadening of the zone of deformation adjacent to it in the thin lithosphere model transient deformation results from flow in the asthenosphere due to stress relaxation following faulting through most or all of the lithosphere for an earth model with a thick elastic lithosphere plate thickness depth of seismic slip transient motions are due to postearthquake aseisrnic slip below the coseismic fault plane data from the san andreas fault indicate a long term temporal decrease in strain rate that persists for at least 30 years and may extend through the entire earthquake cycle observations support a cycle long rate decrease and a temporal spreading of the deformation profile only if movement cycles on the northern and southern locked sections of the fault are basically similar if so the usually lower strain rates and broader deformation zone currently observed on the southern san andreas represent a later evolutionary stage of the northern locked section where a great earthquake is a more recent occurrence although the data allow some extreme models to be discarded no sufficiently strong constraints exist to decide between the thin and thick lithosphere models regardless of the appropriate model the geodetic observations themselves indicate that strain buildup is sufficiently nonlinear to cause significant departures from recurrence estimates based on linear strain accumulation and the time predictable model

concentric eye walls secondary wind maxima and the evolution of the hurricane vortex abstract research aircraft observations in recent hurricanes support the model of shapiro and willoughby 1982 for the tropical cyclone s response to circularly symmetric convective heat sources convective rings in both nature and the numerical model the tangential wind commonly increases rapidly just inside the radius of maximum wind and decreases inside the eye near the central axis of the vortex thus both secondary outer wind maxima and eyewall wind maxima often contract as they intensify this response is independent of the horizontal spatial scale of the maximum an outer maximum is frequently observed to constrict about a pre existing eye and replace it this chain of events often coincides with a weakening or at least a pause in intensification of the vortex as a whole the concentric eye phenomenon is a common but by no means universal feature of tropical cyclones it is most frequently observed in intense highly symmetric systems

aseismic slip and fault normal strain along the central creeping section of the san andreas fault 1 we use gps data to measure the aseismic slip along the central san andreas fault csaf and the deformation across adjacent faults comparison of edm and gps data sets implies that except for small scale transients the fault motion has been steady over the last 40 years we add 42 new gps velocities along the csaf to constrain the regional strain distribution shear strain rates are less than 0 083 0 010 strain yr adjacent to the creeping saf with 1 4 5 mm yr of contraction across the coast ranges dislocation modeling of the data gives a deep long term slip rate of 31 35 mm yr and a shallow 0 12 km creep rate of 28 mm yr along the central portion of the csaf consistent with surface creep measurements the lower shallow slip rate may be due to the effect of partial locking along the csaf or reflect reduced creep rates late in the earthquake cycle of the adjoining saf rupture zones

interplate seismogenic zones along the kuril japan trench inferred from gps data inversion stress accumulation between earthquakes results from slip that is insufficient to fully accommodate plate movement an inverse analysis of gps data from the kuril japan trench reveals a trench parallel belt of stress accumulation with six peaks in the depth range of 10 40 km suggesting potential source regions for future earthquakes in the subduction zones around japan where four plates interact with one another large earthquakes have occurred repeatedly1 these interplate earthquakes are part of the process of tectonic stress accumulation and release that is driven by relative plate motion2 3 4 stress accumulation between earthquakes results from slip deficit slip that is insufficient to fully accommodate plate movement for the prediction of large earthquakes it is therefore important to monitor the distribution of slip deficit on plate interfaces here we apply an inversion method based on bayesian modelling using direct and indirect prior information on the magnitude and distribution of fault slip5 to horizontal and vertical velocities from global positioning system data for the seismically calm period between 1996 and 2000 we obtain a precise distribution of slip deficit rates on the interface between the north american and pacific plates around japan which reveals a trench parallel belt of slip deficit with six peaks in the depth range of 10 40 km these peaks agree with the source regions of past large interplate earthquakes along the kuril japan trench we conclude that the slip deficit zones identified with our method are potential source regions of large earthquakes

kinematics of the secondary eyewall observed in hurricane rita 2005 abstractairborne doppler radar data collected from the concentric eyewalls of hurricane rita 2005 provide detailed three dimensional kinematic observations of the secondary eyewall feature the secondary eyewall radar echo shows a ring of heavy precipitation containing embedded convective cells which have no consistent orientation or radial location the axisymmetric mean structure has a tangential wind maximum within the reflectivity maximum at 2 km altitude and an elevated distribution of its strongest winds on the radially outer edge the corresponding vertical vorticity field contains a low level maximum on the inside edge which is part of a tube of increased vorticity that rises through the center of the reflectivity tower and into the midlevels the secondary circulation consists of boundary layer inflow that radially overshoots the secondary eyewall a portion of this inflowing air experiences convergence and supergradient forces that cause the air to rise and flow radially outward back into th

western north pacific typhoons with concentric eyewalls abstract this study examines the intensity change and moat dynamics of typhoons with concentric eyewalls using passive microwave data and best track data in the western north pacific between 1997 and 2006 of the 225 typhoons examined 55 typhoons and 62 cases with concentric eyewalls have been identified the data indicate that approximately 57 of category 4 and 72 of category 5 typhoons possessed concentric eyewalls at some point during their lifetime while major typhoons are most likely to form concentric eyewalls the formation of the concentric structure may not be necessarily at the lifetime maximum intensity approximately one third of concentric eyewall cases are formed at the time of maximum intensity the moat is known to be heavily influenced by the subsidence forced by the two eyewalls rozoff et al proposed that the rapid filamentation dynamics may also contribute to the organization of the moat this paper examines the possibility of rapid filamentation dynamics by devising a filamentati

how do ghost transients from past earthquakes affect gps slip rate estimates on southern california faults 1 in this study we investigate the extent to which viscoelastic velocity perturbations or ghost transients from individual fault segments can affect elastic block model based inferences of fault slip rates from gps velocity fields we focus on the southern california gps velocity field exploring the effects of known large earthquakes for two end member rheological structures our approach is to compute at each gps site the velocity perturbation relative to a cycle average for earthquake cycles on particular fault segments we then correct the scec cmm4 0 velocity field for this perturbation and invert the corrected field for fault slip rates we find that if asthenosphere viscosities are low 3 1018 pa s the current gps velocity field is significantly perturbed by viscoelastic earthquake cycle effects associated with the san andreas fault segment that last ruptured in 1857 mw 7 9 correcting the gps velocity field for this perturbation or ghost transient adds about 5 mm a to the saf slip rate along the mojave and san bernardino segments the gps velocity perturbations due to large earthquakes on the garlock fault most recently events in the early 1600s and the white wolf fault most recently the mw 7 3 1952 kern county earthquake are smaller and do not influence block model inverted fault slip rates this suggests that either the large discrepancy between geodetic and geologic slip rates for the garlock fault is not due to a ghost transient or that un modeled transients from recent mojave earthquakes may influence the gps velocity field

hurricane intensity and eyewall replacement observations made during the historic 2005 hurricane season document a case of eyewall replacement clouds outside the hurricane eyewall coalesce to form a new eyewall at a greater radius from the storm center and the old eyewall dies the winds in the new eyewall are initially weaker than those in the original eyewall but as the new eyewall contracts the storm reintensifies understanding this replacement mechanism is vital to forecasting variations in hurricane intensity processes in the moat region between the new and old eyewall have been particularly unclear aircraft data now show that the moat becomes dynamically similar to the eye and thus is converted into a region inimical to survival of the inner eyewall we suggest that targeting aircraft to key parts of the storm to gain crucial input to high resolution numerical models can lead to improvements in forecasting hurricane intensity

holocene glacier fluctuations and migration of neolithic yak pastoralists into the high valleys of northwest bhutan abstract here we present geomorphologic palaeoenvironmental and archaeo botanical data which elucidate the late pleistocene and holocene glacial history of the high mountain locked himalayan valleys in northwest bhutan and provide one of the earliest proofs of human activity yet known for the high himalaya range in this area difficult to access close linkage between climatic change glacier fluctuations and human migration patterns has been discovered glacier systems in the studied area are characterized by avalanching and debris mantled glacier snouts with the significant local influence of the indian summer monsoon causing decoupling of glacier responses from temperature changes but supporting the idea of monsoonal forcing geomorphologic mapping together with optically stimulated luminescence osl and radiocarbon dating of ice proximal sediments has been used to construct a local glacial chronology local ice stream networks developed during the early holocene ca 10 000 9000 a ago and during the early part of the mid holocene 6710 90 4680 155 cal a bp at which times there were ice advances of about 5 km from the modern glacier termini at such times the intensity of pro and periglacial processes would have intensified and ice dammed lakes were probably common as well rendering human colonization of the high valleys in northwest bhutan impossible an abrupt shift to dry climatic conditions on the tibetan plateau between 5000 and 4500 a bp coincided with glacial decay and the onset of morphodynamically stable conditions on the broad valley floors of the high valleys in this part of the himalaya palynological data suggest that the sudden disappearance of juniper and rhododendron pollen the immediate onset of pollen input from cereals confirmed by detailed sem analysis and a clear pattern of over grazing trampling and peat deterioration can be linked to human arrival in the valleys at ca 4280 130 cal a bp extensive charcoal horizons dating to 4745 250 and 4680 155 cal a bp are interpreted as evidence for human use of fire and forest clearances and agree spatially and temporally with the pollen based picture charcoal occurrences as old as 6710 90 cal a bp might be linked to yet earlier exploration of these himalayan valleys during phases of low glacial activity we provide an account of the colonization of these high valleys in response to glacial and monsoonal change and argue that the most likely founder societies come from the tibetan plateau where yak and barley based pastoralism and neolithic settlements are known to have existed since the mid holocene

challenging the rate state asperity model afterslip following the 2011 m9 tohoku oki japan earthquake 1 prior to the 2011 m9 tohoku oki earthquake subduction at the japan trench was characterized by m7 8 earthquakes sometimes rupturing the same source regions seismic asperities followed by extensive afterslip detected by gps measurements a physically based model consisting of velocity weakening asperities surrounded by aseismic creep on velocity strengthening regions the rate state asperity model became the prevailing conceptual model for earthquakes in this region theory and numerical simulation indicates that velocity weakening areas do not exhibit sustained afterslip while velocity strengthening regions do not accumulate stress interseismically here we demonstrate that the rate state asperity model is contradicted by models of postseismic deformation following the tohoku oki earthquake afterslip in the first eight months either occurred on historical seismic asperities or stress accumulated in regions surrounding the asperities unsmoothed inversions of cumulative 8 month postseismic gps displacements that restrict afterslip to areas outside of historical ruptures cannot fit the data without afterslip exceeding the slip that fully relaxes the coseismic stress change in contrast similarly constrained inversions allowing slip within historical ruptures can satisfactorily fit the postseismic displacements these results require a modification of the rate state asperity model and raise new questions about physical processes and properties of the subduction interface

osl chronology of the liena archeological site in the yarlung tsangpo valley throws new light on human occupation of the tibetan plateau recent environmental archeological evidence has started to throw light on both the timing and processes of human colonization of the tibetan plateau tp yarlung tsangpo yt valley a very import

an axisymmetric view of concentric eyewall evolution in hurricane rita 2005 abstractmultiplatform observations of hurricane rita 2005 were collected as part of the hurricane rainband and intensity change experiment rainex field campaign during a concentric eyewall stage of the storm s life cycle that occurred during 21 22 september satellite aircraft dropwindsonde and doppler radar data are used here to examine the symmetric evolution of the hurricane as it underwent eyewall replacement during the approximately 1 day observation period developing convection associated with the secondary eyewall became more symmetric and contracted inward latent heating in the emergent secondary eyewall led to the development of a distinct toroidal overturning circulation with inertially constrained radial inflow above the boundary layer and compensating subsidence in the moat region properties that are consistent broadly with the balanced vortex response to an imposed ring of diabatic heating outside the primary eyewall the primary eyewall s convection became more asymmetric during

a window into the complexity of the dynamic rupture of the 2011 mw 9 tohoku oki earthquake the 2011 mw 9 tohoku oki earthquake recorded by over 1000 near field stations and multiple large aperture arrays is by far the best recorded earthquake in the history of seismology and provides unique opportunities to address fundamental issues in earthquake source dynamics here we conduct a high resolution array analysis based on recordings from the usarray and the european network the mutually consistent results from both arrays reveal rupture complexity with unprecedented resolution involving phases of diverse rupture speed and intermittent high frequency bursts within slow speed phases which suggests spatially heterogeneous material properties the earthquake initially propagates down dip with a slow initiation phase followed by sustained propagation at speeds of 3 km s the rupture then slows down to 1 5 km s for 60 seconds a rich sequence of bursts is generated along the down dip rim of this slow and roughly circular rupture front before the end of the slow phase an extremely fast rupture front detaches at about 5 km s towards the north finally a rupture front propagates towards the south running at about 2 5 km s for over 100 km key features of the rupture process are confirmed by the strong motion data recorded by k net and kik net the energetic high frequency radiation episodes within a slow rupture phase suggests a patchy image of the brittle ductile transition zone composed of discrete brittle asperities within a ductile matrix the high frequency is generated mainly at the down dip edge of the principal slip regions constrained by geodesy suggesting a variation along dip of the mechanical properties of the mega thrust fault or their spatial heterogeneity that affects rise time

reflectivity ice scattering and lightning characteristics of hurricane eyewalls and rainbands part i quantitative description abstract covering december 1997 through december 1998 261 overpasses of 45 hurricanes by the tropical rainfall measuring mission trmm satellite are used to document the observed radar reflectivity values passive microwave ice scattering magnitudes and total lightning cloud to ground plus in cloud these parameters are interpreted as describing convective vigor or intensity with greater reflectivities particularly aloft greater ice scattering lower 85 and 37 ghz brightness temperatures and increased lightning frequency indicating more intense convection for each parameter the full distribution of values observed during the trmm satellite s first year is presented for specific regions properties of three regions of the hurricane eyewall inner rainband and outer rainband are treated separately and compared to other tropical oceanic and tropical continental precipitation systems reflectivity profiles and ice scattering signatures are found to be fairly similar for both hurricane and non

temporal change of interplate coupling in northeastern japan during 1995 2002 estimated from continuous gps observations summary temporal change of deformation in northeastern japan is clarified by continuous global positioning system gps observations from 1995 april to 2002 march the observed gps velocity is approximately parallel to the direction of plate convergence on east and west plate boundaries of northeastern japan and shows post seismic transient deformation around source regions of the mw 7 8 1993 hokkaido nansei oki and the mw 7 7 1994 sanriku haruka oki earthquakes we interpret the source of the observed deformation as contemporary interplate coupling on the east subducting boundary to the pacific plate and the west collision boundary to the amurian plate using elastic dislocation theory we inverted horizontal and vertical velocities of 212 gps stations to estimate interplate coupling on both boundaries the estimated coupling during 1995 2002 is spatially heterogeneous however it is temporally almost constant except for the region around the 1993 and 1994 earthquakes after slip of the 1994 earthquake occurred over the coseismic rupture area and its downdip extension on the plate boundary for 0 3 1 3 yr after the earthquake after slip continued only in the downdip extension for later periods and decayed with time weak coupling was recovered in the eastern part of the coseismic rupture area 3 3 yr after the earthquake interplate coupling on the pacific plate was strong in two regions miyagi oki and tokachi oki the west plate boundary is tightly coupled except for the source areas of three large earthquakes that occurred in 1964 1983 and 1993 the apparent decoupling of the source areas of these earthquakes implies long term post seismic deformation as a result of viscoelastic relaxation in the subseismogenic lithosphere

chronology of a late neolithic age site near the southern coastal region of fujian china an archaeological site at anshan in the coastal area of fujian province southern china was excavated in 2007 2009 and 2015 abundant artefacts including adzes cores bronze fishhook pottery an

an integrated perspective of the continuum between earthquakes and slow slip phenomena slow slip a mechanism by which faults can relieve stress was thought to be distinct from earthquakes however a global review of slow slip phenomena suggests that instead there is a continuum between the two types of event