three dimensional splay fault geometry and implications for tsunami generation megasplay faults very long thrust faults that rise from the subduction plate boundary megathrust and intersect the sea floor at the landward edge of the accretionary prism are thought to play a role in tsunami genesis we imaged a megasplay thrust system along the nankai trough in three dimensions which allowed us to map the splay fault geometry and its lateral continuity the megasplay is continuous from the main plate interface fault upwards to the sea floor where it cuts older thrust slices of the frontal accretionary prism the thrust geometry and evidence of large scale slumping of surficial sediments show that the fault is active and that the activity has evolved toward the landward direction with time contrary to the usual seaward progression of accretionary thrusts the megasplay fault has progressively steepened substantially increasing the potential for vertical uplift of the sea floor with slip we conclude that slip on the megasplay fault most likely contributed to generating devastating historic tsunamis such as the 1944 moment magnitude 8 1 tonankai event and it is this geometry that makes this margin and others like it particularly prone to tsunami genesis

holocene relative sea level change and rate of sea level rise from coastal deposits in the toyooka basin western japan this study presents relative sea level rsl change from 11 200 to 500 cal bp in the toyooka basin western japan diatom assemblage and sedimentary sulfur analyses were performed for 32 sediment

a new look at greenland flow distortion and its impact on barrier flow tip jets and coastal oceanography 1 a new diagnostic that partitions the occurrence of high speed surface wind events by wind direction is described that allows for a more complete view of the atmospheric flow distortion arising from greenland s high topography this flow distortion has previously been shown to result in the frequent occurrence of high speed surface wind events in the vicinity of cape farewell greenland s southernmost point as well along its southeast coast this new diagnostic is able to distinguish between easterly and westerly cape farewell tip jets in addition it clearly identifies the 2 locations along the southeast coast of greenland where barrier flow is enhanced and confirms previous work that indicated that these locations are collocated with regions of steep coastal topography it also results in the identification of new regions the northeast and southwest coasts of greenland as well as the southeast coast of iceland where tip jets and barrier flow also develop along the northeast coast these high speed wind events are proposed to be associated with the formation of the north east water polynya as well as contributing to the southward advection of sea ice along the southwest coast the high speed wind events which result in a reversal of the wind direction may contribute to the enhanced oceanic eddy activity observed to occur in this region

importance of latent heating in mesocyclones for the decay of cold air outbreaks a numerical process study from the pacific sector of the southern ocean abstractin this study the dynamical mechanisms shaping the evolution of a marine cold air outbreak cao that occurred over the ross amundsen and bellingshausen seas in june 2010 are investigated in an isentropic framework the drainage of cold air from west antarctica into the interior ross sea its subsequent export and the formation of a dome of cold air off the sea ice edge are shown to be intimately linked to a lower tropospheric cyclone as well as the cyclonic breaking of an upper level potential vorticity trough the dome formation is accompanied by an extreme deepening of the boundary layer whose top reaches to the height of the low lying tropopause within the trough potentially allowing for deep stratosphere troposphere exchange a crucial finding of this study is that the decay of the cao is essentially driven by the circulation associated with a train of mesocyclones and the release of latent heat in their warm sectors sensitivity experiments with switched off fluxes of sensible and late

reexamination of the near surface airflow over the antarctic continent and implications on atmospheric circulations at high southern latitudes abstract previous work has shown that winds in the lower atmosphere over the antarctic continent are among the most persistent on earth with directions coupled to the underlying ice topography in 1987 parish and bromwich used a diagnostic model to depict details of the antarctic near surface airflow a radially outward drainage pattern off the highest elevations of the ice sheets was displayed with wind speeds that generally increase from the high interior to the coast these winds are often referred to as katabatic with the implication that they are driven by radiational cooling of near surface air over the sloping ice terrain it has been shown that the antarctic orography constrains the low level wind regime through other forcing mechanisms as well dynamics of the lower atmosphere have been investigated increasingly by the use of numerical models since the observational network over the antarctic remains quite sparse real time numerical weather prediction for the u s antarctic program has been

late holocene tectonics and paleoseismicity southern cascadia subduction zone holocene deformation indicative of large subduction zone earthquakes has occurred on two large thrust fault systems in the humboldt bay region of northern california displaced stratigraphic markers record three offsets of 5 to 7 meters each on the little salmon fault during the past 1700 years smaller and less frequent holocene displacements have occurred in the mad river fault zone elsewhere as many as five episodes of sudden subsidence of marsh peats and fossil forests and uplift of marine terraces are recorded carbon 14 dates suggest that the faulting subsidence and uplift events were synchronous relations between magnitude and various fault offset parameters indicate that earthquakes accompanying displacements on the little salmon fault had magnitudes of at least 7 6 to 7 8 more likely this faulting accompanied rupture of the boundary between the gorda and north american plates and magnitudes were about 8 4 or greater

landslides caused by the m 7 6 tecoman mexico earthquake of january 21 2003 abstract the tecoman mexico earthquake also called the colima earthquake of january 21 2003 m 7 6 triggered several hundreds of landslides in the coastal cordilleras of colima state near the earthquake source and several thousands in the volcanic highlands north and northwest of colima city these landslides mostly shallow and disrupted failures caused minor damage to roads to a railroad and to irrigation systems in one area extensive post earthquake rock fall activity indicates a possible long term instability that could threaten dwellings and other infrastructure located nearby in the coastal cordilleras most of the landslides were generated by failures of artificially cut slopes especially along roads the rocks of the coastal cordilleras are generally well indurated and landslides occurred only where the rocks were made locally susceptible by weathering the presence of prominent discontinuities with unfavorable orientations or intense fracturing or shearing in contrast to the coastal cordilleras the volcanic rocks to the north were more susceptible to the occurrence of seismically triggered landslides the greatest number and concentrations of landslides occurred there and the landslides were larger than those in the coastal cordilleras even though this volcanic terrain was farther from the earthquake source here stretches of river bluffs several hundred meters long had been stripped of vegetation and surficial material by coalescing landslides and several days after the main shock thousands of small rock falls were still occurring each day indicating an ongoing hazard the high susceptibility of volcanic materials to earthquake generated landslides conforms to findings in other recent earthquakes

morphology and paleoclimatic significance of pleistocene lake bonneville spits abstract pleistocene lake bonneville of western utah contains a variety of spits associated with shorelines and other features that formed between 21 000 and 12 000 14 c yr bp field studies in the low lying mountain ranges of the central portion of lake bonneville identified 17 spits of various types the spits are connected to small mountain ranges and islands vary in size from 0 02 to 0 5 km 2 and are composed of coarse grained well rounded poorly sorted sedimentary material sixteen of the 17 spits have a northeasterly to southwesterly orientation implying that winds were from the northwest to northeast approximately 180 out of phase with modern winds in the eastern great basin lake bonneville spit orientation is best explained as the result of persistent northerly winds caused by the high atmospheric pressure cell of the continental ice sheet and passage of low pressure extratropical storms south of the lake similar strong persistent winds are a common feature of modern continental ice sheets and passing low pressure systems if so the north american jet stream tracked south of lake bonneville as recently as 12 000 14 c yr bp well past the height of the last glacial maximum

the forcing of antarctic katabatic winds abstract the temporal and spatial development of katabatic winds along an idealized slope representative of anmtarctic terrain is examined using a hydrostatic two dimensional primitive equation model with explicit longwave radiation parameterization a detailed diagnosis is made of a simulation in which katabatic flow develops from rest due to the strong radiational cooling of the underlying surface significant thermodynamic and dynamic differences are seen between the gravity driven flows over the gently sloping interior and over the steep ice slopes near the coast the strongest temperature inversions and largest static stabilities are found over the interior of the continent although the net cooling of the katabatic layer and magnitude of the downslope directed horizontal pressure gradient force are greatest at the coast the interior is characterized by low rossby number quasi geostrophic type flows while more intense near antitriptic winds occur at the coast model results are in reasonable agr

analysis of the ross ice shelf airstream forcing mechanisms using self organizing maps abstractthe ross ice shelf airstream ras a prominent transport mechanism of cold continental air to the north is the most common wind pattern over the ross ice shelf antarctica the forcing mechanisms of the ras include katabatic drainage mesoscale forcing and synoptic forcing this paper uses the 15 km output from the antarctic mesoscale prediction system amps and the method of self organizing maps som to analyze how the combination of these forcing mechanisms impacts the strength and position of the ras it is found that the strength and position of the ras is mainly driven by the thermal forcing in the region of the transantarctic mountains this forcing includes the pressure gradient associated with cold air pooling at the base of the transantarctic mountains as well as the pressure gradient associated with the temperature contrast between the cold air located over the east antarctic plateau and the warm ambient air over the ross ice shelf these forcing mechanisms are analyzed in a regi

a case study of a ross ice shelf airstream event a new perspective abstract a case study illustrating cloud processes and other features associated with the ross ice shelf airstream ras in antarctica is presented the ras is a semipermanent low level wind regime primarily over the western ross ice shelf linked to the midlatitude circulation and formed from terrain induced and large scale forcing effects an integrated approach utilizes moderate resolution imaging spectroradiometer modis satellite imagery automatic weather station aws data and antarctic mesoscale prediction system amps forecast output to study the synoptic scale and mesoscale phenomena involved in cloud formation over the ross ice shelf during a ras event a synoptic scale cyclone offshore of marie byrd land draws moisture across west antarctica to the southern base of the ross ice shelf vertical lifting associated with flow around the queen maud mountains leads to cloud formation that extends across the ross ice shelf to the north the low level cloud has a warm signature in thermal infrare

crustal block kinematics and seismic potential of the northernmost philippine sea plate and izu microplate central japan inferred from gps and leveling data 1 we clarify the contemporary deformation observed by gps and leveling for the greater tokyo kanto eastern tokai and the izu islands region where the izu ogasawara bonin arc is subducting and colliding with the central part of the japan arc from these data we develop a kinematic model of fault sources with variable components of seismic and aseismic slip under the assumption that the contemporary deformation during 1995 2000 is representative of the long term interseismic strain field the geodetic data are inverted to estimate the rotation poles of the crustal blocks the degree of elastic strain accumulation on faults and the volumetric inflation sources beneath volcanoes the present crustal movements are explained by four crustal blocks the izu microplate the central japan block the pacific plate and the philippine sea plate along the suruga and sagami margins of the philippine sea plate lie strongly coupled faults which include sites of the 1854 m 8 4 tokai 1923 m 7 9 kanto and 1703 m 8 2 genroku kanto earthquakes in contrast the philippine sea plate boundary immediately north of the izu peninsula site of m 7 5 collisional earthquakes is only weakly coupled the boundary between the izu microplate and the philippine sea plate experiences left lateral motion with the rate of 30 mm yr most of this boundary is locked and thus has a large potential of future earthquakes the izu microplate is found to rotate rapidly clockwise at 10 myr with a rotation pole relative to the central japan block located just north of its northern boundary the pole and angular velocity of the izu microplate depends however on the assumed location of the boundary with the exception of the site of the 1938 m 7 earthquake swarm which we infer has the current potential to produce a m 8 1 earthquake the pacific megathrust has a very low seismic potential although the geodetic data have little resolving power for much of the pacific plate interface east of tokyo

paleoecological evidence for coastal subsidence during five great earthquakes in the past 1500 years along the northern onshore continuation of the nankai subduction zone abstract during the last 1500 years a marsh on the north coast of suruga bay central japan has experienced as many as five rapid submergence events this conclusion is supported by analyses of depositional facies and pollen and diatom assemblages in sediment cores from the ukishimagahara lowland on the footwall side of the fujikawa kako fault zone fkz the northern extension of the nankai and suruga troughs light colored silt or clay beds 30 50 cm thick deposited as the result of submergence events that drowned the marshland cover terrestrial peat or humic soils produced by the marshland vegetation radiocarbon ages and dated tephras suggest that in this lowland submergence events have occurred at aperiodic intervals of 100 400 years atmospheric phenomena can cause increased precipitation and flooding by rivers and typhoons but they cannot explain the cyclic submergence events at centennial timescales during the late holocene sea levels have been declining relative to land around the japanese islands so high sea levels cannot explain the periodic submergence of the lowland the most likely cause of these events therefore is coseismic subsidence of the lowland related to great earthquakes m8 0 occurring in the fkz or the suruga trough coseismic coastal deformation around the study area during the 1854 ansei tokai earthquake supports this hypothesis

observations of near surface wind and temperature structures and their variations with topography and latitude in east antarctica received 10 december 2008 revised 30 march 2009 accepted 5 june 2009 published 15 september 2009 1 the first multiyear surface meteorological observations over dome a the highest ice feature in the entire antarctica continent are analyzed to understand the surface wind temperature and stability climatology over dome a and how it differs from the surface climatology at two lower latitude lower elevation sites along similar longitude in east antarctica the climatology is also compared with that over dome c in contrast to the surface winds at lower sites where moderate to strong northeasterly winds prevail with a distinct diurnal oscillation in wind speed in response to the diurnal change in katabatic forcing summertime surface winds over dome a are very weak are variable in direction and show little diurnal variation although both temperature and temperature gradient oscillate diurnally the gradient over dome a remained positive all day long indicating a persistent surface inversion while at the two lower sites as well as over dome c sufficient insolation leads to the breakup of inversion and the development of a convective boundary layer in the afternoon wavelet analysis of near surface stability revealed that besides the strong diurnal signal the near surface stability also exhibits annual semiannual and interseasonal period 50 days oscillations at all locations these oscillations in near surface stability are linked to the same peaks in the 500 hpa geopotential height spectra and therefore are believed to be caused by variations of synoptic conditions

seismically induced landslides by a low magnitude earthquake the mw 4 7 ossa de montiel event central spain this work has been funded by spanish ministry of economy and competitiveness research project cgl2011 30153 c02 02 and by the research groups rnm 374 junta de andalucia tectac ucm 910368 and vigrob 184 universidad de alicante mr loffredo acknowledges funding of the universita di roma la sapienza post graduate grant concorso a n 480 area cun 04

strong downslope wind events in ammassalik southeast greenland abstractammassalik in southeast greenland is known for strong wind events that can reach hurricane intensity and cause severe destruction in the local town yet these winds and their impact on the nearby fjord and shelf region have not been studied in detail here data from two meteorological stations and the european centre for medium range weather forecasts interim re analysis era interim are used to identify and characterize these strong downslope wind events which are especially pronounced at a major east greenland fjord sermilik fjord within ammassalik their local and regional characteristics their dynamics and their impacts on the regional sea ice cover and air sea fluxes are described based on a composite of the events it is concluded that wind events last for approximately a day and seven to eight events occur each winter downslope wind events are associated with a deep synoptic scale cyclone between iceland and greenland during the events cold dry air is advected down the ice sheet

dynamics of the foehn mechanism in the mcmurdo dry valleys of antarctica from polar wrf foehn events over the mcmurdo dry valleys mdvs the largest ice free region of antarctica promote glacial melt that supports biological activity in the lakes streams rocks and soils although mdvs foehn events are known to depend upon the synoptic scale circulation the physical processes responsible for foehn events are unknown a polar optimized version of the weather research and forecasting model polar wrf is used for a case study of a representative summer foehn event from 29 december 2006 to 1 january 2007 in order to identify and explain the mdvs foehn mechanism pressure differences across an elevated mountain gap upstream of the mdvs provide forcing for southerly flow into the western upvalley entrance of the mdvs complex terrain over the elevated gap and the mdvs leads to mountain wave effects such as leeside acceleration hydraulic jumps wave breaking and critical layers these mountain wave effects depend on the ambient geostrophic wind direction pressure driven channelling then brings the warm dry foehn air downvalley to eastern mdv sites brief easterly intrusions of maritime air into the eastern mdvs during foehn events previously have been attributed to either a sea breeze effect in summer or local cold pooling effects in winter in this particular case the easterly intrusions result from blocking effects of nearby ross island and the adjacent antarctic coast temperature variability during the summer foehn event which is important for meltwater production and biological activity when it exceeds 0 c primarily depends on the source airmass rather than differences in foehn dynamics

the role of wave dynamics and small scale topography for downslope wind events in southeast greenland abstractin ammassalik in southeast greenland downslope winds can reach hurricane intensity and represent a hazard for the local population and environment they advect cold air down the ice sheet and over the irminger sea where they drive large ocean atmosphere heat fluxes over an important ocean convection region earlier studies have found them to be associated with a strong katabatic acceleration over the steep coastal slopes flow convergence inside the valley of ammassalik and in one instance mountain wave breaking yet for the general occurrence of strong downslope wind events the importance of mesoscale processes is largely unknown here two wind events one weak and one strong are simulated with the atmospheric weather research and forecasting wrf model with different model and topography resolutions ranging from 1 67 to 60 km for both events but especially for the strong one it is found that lower resolutions underestimate the wind speed because they misrepresent the steepness of the

antarctic local wind dynamics and polynya effects on the adelie land coast mesoscale winds on the sloping coast of adelie land in east antarctica were studied via idealized clear sky integrations with a two dimensional model the calm case vg 0 wintertime surface winds were steady katabatic southeasterlies they were enhanced to a strong downslope low level jet llj during a southerly geostrophic flow but damped during a moderate westerly counter katabatic flow a strong westerly flow could overwhelm the katabatic component while a northerly vg induced strong coastal easterlies with an easterly llj on slope flow without the katabatic forcing generated a barrier effect an ice free wintertime zone a coastal polynya increased the coastal 2 m winds by about 50 and drag on the ice floes by 125 through the induced extra land breeze circulation and unstable stratification the midsummer morning coastal winds were also katabatic in the morning as the slopes cooled rapidly after midnight in a prevailing flow these behaved much as in wintertime but were strong only at 0400 0700 hours local time by 0800 0900 hours local time the snowy slopes were melting in sunshine with vg 0 this induced weak anabatic winds up the slope at the coast a midday sea breeze like circulation was present insensitive however to the sea state frozen vs open or the coast state snowy vs black rock of the model these anabatic winds were quite weak and hence easily overwhelmed by any larger scale flow surviving only during a weak westerly flow the typically easterly vg along the east antarctica coast induced katabatic like surface winds throughout the day as is commonly observed despite the midday solar heating copyright 2011 royal meteorological society

a reexamination of the mechanism of the semiannual oscillation in the southern hemisphere the local pressure changes associated with the twice annual contraction intensification and expansion weakening of the circumpolar trough of low pressure around antarctica termed the semiannual oscillation sao was the dominant signal in the annual cycle at mid and high southern latitudes before 1979 the mechanism as shown by van loon 1967 arises from diverent response to the surface heat budget over the polar continent and the midlatitude ocean it has subsequently been shown that in most years since 1979 the sao has weakened considerably evidence is presented here from surface temperature data 500 mb temperatures from a station pair and zonal mean 500 mb temperatures from the ncar ncep reanalyses to show that a warming trend since 1979 has not been evenly distributed through the year at each latitude thus an anomalous change in the temperature gradient between 50 s and 65 s with peaks in roughly may and november has modulated the mechanism that produces the sao with its peaks in march and september consequently the magnitude of the sao has decreased in the more recent period

an analysis of strong wind events simulated in a gcm near casey in the antarctic abstract strong wind events occurring near casey antarctica in a long july gcm simulation have been studied to determine the relative roles played by the synoptic situation and the katabatic flow in producing these episodes it has been found that the events are associated with strong katabatic and strong gradient flow operating together both components are found to increase threefold on average for these strong winds and although the geostrophic flow is the stronger it rarely produces strong winds without katabatic flow becoming stronger than it is in the mean the two wind components do not flow in the same direction indeed there is some cancellation between them since katabatic flow acts in a predominant downslope direction while the geostrophic wind acts across slope the stronger geostrophic flow is associated with higher than average pressures over the continent and the approach of a strong cyclonic system toward the mast and a blocking system downstream the anomalous synoptic patterns lea

strong wind speed events over antarctica and its surrounding oceans abstractstrong wind events swes over antarctica and its surrounding oceans are investigated using gridded surface wind data from the era interim for the 1979 2017 period throughout the year swe

coseismic and pre seismic subsidence associated with great earthquakes in alaska abstract alternating beds of peat and mud in sediment sequences on the south central alaskan coast record coseismic and inter seismic relative land and sea level movements caused by repeated great earthquakes on the alaska aleutian subduction zone during the ad 1964 mw 9 2 earthquake tidal marshes and wetlands around upper cook inlet experienced up to 2 m of subsidence burying peat forming communities with intertidal mud here we use quantitative analyses of fossil diatoms within peat mud couplets to reconstruct land sea level changes for the 1964 and five earlier great earthquakes during the past 3300 years in contrast to geodetic observations that are limited to the present post seismic phase we quantify varying spatial patterns of uplift and subsidence through complete earthquake cycles relative land uplift characterises most of the inter seismic phase of each cycle at our sites whereas each great earthquake was preceded by a short period of pre seismic relative land subsidence

an analysis of the nonhydrostatic dynamics in numerically simulated antarctic katabatic flows abstract a series of two dimensional numerical experiments was conducted in order to describe the role of nonhydrostatic dynamics in simple antarctic katabatic flows the results presented include a comparison of the thermodynamic and dynamic fields produced by hydrostatic and nonhydrostatic numerical simulations the source of the differences in the simulations was diagnosed based on an analysis of the model equation tendencies as well as calculated components of the pressure gradient force over most of the terrain slope the nonhydrostatic effects were found to be insensitive to the model horizontal resolution for a grid spacing ranging from 5 to 100 km

transport of late pleistocene loess particles by katabatic winds during the lowstands of the english channel studies of the submerged pleistocene conglomerate cored and dredged in the english channel show that it resulted from the cementation of stony beaches under a loess blanket although the loess cover was later washed out by younger transgressions the northern limit of the conglomerate corresponds to the original offshore extension of the loess deposits compilation of offshore and onshore altitudes of the limits of these deposits shows that loess was deposited by low level wind fields never thicker than 200 m mapping surveys show that the present limits of loess are probably close to their original boundaries the past proximity of the british ice sheet the accumulation of dusty sediments coating north facing cliffs of brittany originating in the outwash of the british irish ice sheet and in the palaeo rivers of the english channel as well as the southeastward orientation of the palaeo winds deduced from particle size analysis and heavy minerals distribution suggest that large volumes of loess were transported by strong katabatic winds blowing from the northern ice covered regions towards brittany and normandy the existence of katabatic winds is also consistent with the drift of ice rafts that transported icelandic basalts now grounded in brittany and possibly with the orientation of homo neandertalensis shelters

influence of earthquakes on the stability of slopes earthquakes are a major trigger for instability of natural and man made slopes often the instability of slopes due to an earthquake causes more destruction and kills more people than the actual earthquake itself a comparison is made between different methodologies to analyze the potential stability of slopes during earthquakes theoretically it seems simple to calculate the stability of a slope during an earthquake in reality however the stability is influenced by so many parameters that are either not known or which influence is so poorly known that a decent estimation of stability cannot be made offshore the situation is worse because proper data required for stability calculations are even less available than onshore on and offshore erosion and weathering create continuously slopes that may become unstable during a future earthquake offshore also sedimentation creates continuously new slopes another fundamental problem in stability analysis is the complicated and largely unknown behavior of seismic waves in three dimensions in natural materials the lack of accurate data and the unknown behavior of seismic waves in three dimensions make estimations of slope stability during an earthquake unreliable

mesoscale climatology and variation of surface winds over the chukchi beaufort coastal areas abstractthe detailed mesoscale climatology of surface winds in the chukchi beaufort seas and adjacent arctic slope region is analyzed using the recently developed chukchi beaufort high resolution atmospheric reanalysis cbhar within the study area surface winds are mainly driven by the prevailing synoptic weather patterns of the beaufort high and aleutian low and are further modulated by local geographic features through thermodynamic and dynamic processes sea breezes up or downslope winds and the mountain barrier jets are all clearly captured by cbhar sea breezes emerge in june september and last most of the day with a maximum spatial extent 100 km inland and 50 km offshore and maximum speed around 1 3 m s 1 in the late afternoon 1500 alaska standard time akst thermodynamic impacts of mountains on the surface winds vary from time to time drainage flows begin to build at the mountaintop in september and reach the strongest during november february occupying the entire slope upslope winds

regression models for estimating coseismic landslide displacement newmark s sliding block model is widely used to estimate coseismic slope performance early efforts to develop simple regression models to estimate newmark displacement were based on analysis of the small number of strong motion records then available the current availability of a much larger set of strong motion records dictates that these regression equations be updated regression equations were generated using data derived from a collection of 2270 strong motion records from 30 worldwide earthquakes the regression equations predict newmark displacement in terms of 1 critical acceleration ratio 2 critical acceleration ratio and earthquake magnitude 3 arias intensity and critical acceleration and 4 arias intensity and critical acceleration ratio these equations are well constrained and fit the data well 71 br 2 b88 but they have standard deviations of about 0 5 log units such that the range defined by the mean one standard deviation spans about an order of magnitude these regression models therefore are not recommended for use in site specific design but rather for regional scale seismic landslide hazard mapping or for rapid preliminary screening of sites 2007 elsevier b v all rights reserved

a description of the ross ice shelf air stream ras through the use of self organizing maps soms 1 the low level wind field across the ross ice shelf region antarctica is studied through the method of self organizing maps soms emphasis is placed on identifying and characterizing the ross ice shelf air stream ras the ras is a dominant northward stream of air resulting in significant transport of atmospheric mass from the interior of antarctica two soms are created for the lowest model level 13 m and the 5th lowest model level 150 m from archived real time numerical weather prediction output of the antarctic mesoscale prediction system amps a verification of the som for the lowest model level is completed by comparing select nodes to automatic weather station wind rose plots the winds depicted in the lowest model level som are dominated by the position of the cyclone in the ross sea and the changes in wind speeds on the antarctic plateau the 5th lowest model level provides a better depiction of the ras the ras is found to be present primarily when associated with a cyclone in the ross sea there is a strong seasonality to the ras with the ras occurring frequently during the winter months and rarely during the summer months the structure and position of the ras is strongly dependent on the position of the ross sea cyclone

fragmentary evidence of great earthquake subsidence during holocene emergence valdivia estuary south central chile a reconnaissance of holocene stratigraphy beneath fringing marshes of the valdivia estuary where an m 9 5 earthquake caused 1 2 m of regional coseismic subsidence in 1960 shows only fragmentary evidence of prehistoric coseismic sub sidence in most of the 150 hand driven cores that were examined a distinct uncon formity separates 0 5 1 5 m of late holocene tidal and floodplain mud peat and sand from underlying middle holocene subtidal mud and sand at the las coloradas site where stratigraphy is best preserved two a horizons of marsh and meadow soils abruptly overlain by sand and mud probably record coseismic subsidence shortly fol lowed by tsunamis the amount of subsidence during the earthquakes proved difficult to reconstruct with a diatom transfer function because of differences between modern and fossil diatom assemblages maximum 14 c ages on macrofossils from the two a horizons at the las coloradas site of 1 7 1 3 ka and 2 7 1 7 ka allow correlation of the younger horizon with either of two of six 14 c dated a horizons buried by tsunami sand or post tsunami tidal sand 200 km to the south at maullin and with a lake wide mass wasting event in lago puyehue 100 km to the southeast tidal records of prehistoric coseismic subsidence at valdivia are scarce because of a sea level fall of 3 8 m over the past 6000 years erosion of marsh and meadow soils during subsidence induced flooding of the estuary and largely complete land level recovery during cycles of coseismic subsidence and postseismic uplift online material diatom species data from the las coloradas site valdivia estuary

episodic emergence in the past 3000 years at the akkeshi estuary hokkaido northern japan at the akkeshi estuary rapid emergence interrupted holocene submergence at least four times in the past 3000 years each emergence event produced an upward change from estuarine mud to freshwater peat while the estuarine mud abounds in brackish and marine diatoms freshwater taxa dominate the peat emergence events occurred from 1700 to 2300 1000 to 1300 and 500 to 700 cal yr b p an additional emergence event predated by several decades a volcanic ash that erupted in a d 1694 at least three of the events produced contacts abrupt enough to represent uplift during earthquakes such uplift may reconcile seemingly conflicting records of vertical crustal movement in eastern hokkaido this tectonically active area which is being subducted by the pacific plate at 8 cm yr contains marine terraces that imply 0 1 0 5 mm yr of net uplift in the late quaternary however these terraces adjoin tide gages that recorded 8 9 mm yr of steady submergence in the 20th century the terrace uplift need not conflict with the gaged submergence if the region is subject to occasional coseismic uplift as during the emergence events implied by holocene geology near akkeshi

groundwater responses to the recent canterbury earthquakes a comparison summary the recent canterbury christchurch earthquakes and aftershocks generated groundwater level responses throughout new zealand however the greater part of damage has been sustained by the city of christchurch which is built on a layered sequence of artesian aquifers in this paper we focus on responses in these coastal aquifers we quantify groundwater responses with a simple model which differentiates between immediate earthquake induced response spike and post seismic change offset the most significant feature of our analysis is the consistent pattern of groundwater response to the earthquakes deeper wells correlate with negative offset and shallower wells correlate with positive offset this is consistent with the upwards vertical movement of water we consider the hydrological and engineering consequences

profiles of katabatic flow in summer and winter over coats land antarctica observations from a novel autonomous doppler sodar wind profiling system are described and analysed these include the first continuous wintertime soundings of katabatic winds over antarctica a continent with which they are synonymous during 2002 and 2003 over 2600 wind profiles were taken during case studies of high resolution sounding lasting hours to days these case studies have been subjectively classified as synoptically driven katabatically influenced 28 days primarily katabatically driven flows a subset of 16 days or other flow types the doppler sodar observations were augmented by automatic weather station observations at the field site and further up the slope as well as synoptic and upper air observations at halley research station some 50 km distant on the brunt ice shelf in primarily katabatic flows there is a systematic change in the shape and depth of the low level katabatic jet with wind speed relatively strong katabatic flows maximum winds of typically 8 10 m s 1 have a jet maximum between 20 and 60 m above the surface and are relatively deep up to 200 m while moderate katabatic flows 4 8 m s 1 typically have a jet maximum between 3 and 30 m and are shallower 100 m although they can also be more diffuse in structure with a wind speed maximum at higher altitude in all katabatic flows there is backing of wind direction with height consistent with decreasing friction away from the surface during summertime katabatic flows there is a clear diurnal signature at all heights although this is less pronounced in the surface layer where there seems to be a persistent 2 4 m s 1 katabatic flow during all case studies where the diurnal forcing results in an abrupt katabatic flow deceleration i e what may be a katabatic jump there is a concurrent vertical acceleration wind profiles from a recent numerical weather prediction study of idealized katabatic flows at this site compare favourably with selected mean profiles the only significant difference is that the model s wind speed is too low over the lowest 10 m copyright 2006 royal meteorological society

aperiodic recurrence of geologically recorded tsunamis during the past 5500 years in eastern hokkaido japan 1 along hokkaido s pacific coast near the town of kiritappu sandy deposits in a muddy lagoon and on a nearby beach ridge plain provide evidence for 15 tsunamis between 200 and 6000 years ago additional sand beds at the lagoon probably represent the historical tsunamis of a d 1843 and 1894 we observed the sequences of sandy deposits in continuous slices 2 to 4 m deep some of the deposits consist of just a single sand bed whereas others contain multiple units of sand muddy sand or sandy mud and mud caps including plant detritus we also found at the lagoon a 17th century tsunami deposit that thickens and thins regardless of elevation or distance inland we bracketed the ages of most of the inferred tsunamis by radiocarbon dating of detritus mainly seeds and leaves at the lagoon and charcoal at the beach ridge plain from pretsunami and posttsunami beds tsunami dates computed from the bracketing ages commonly have uncertainties spanning 2 to 4 centuries within these uncertainties the inferred sequence of 15 prehistoric tsunamis at the lagoon beginning almost 6000 years ago can be matched tsunami by tsunami with the inferred history at the beach ridge plain 15 km away the sand sheet extents suggest that most of these tsunamis were larger than any generated at hokkaido in the last 200 years the intervals between these inferred outsized tsunamis average nearly 400 years but range widely from about 100 to about 800 years

effect of shaking strength on the seismic response of liquefiable level ground abstract shaking strength is one of the most important parameters that characterize earthquake events in the past it was common to apply shaking of different strengths consecutively on a soil model to investigate the effect of shaking level on seismic ground response without considering the effect of loading history in this study a series of dynamic centrifuge tests under different shaking levels was performed on fresh saturated sand models with the same initial conditions to investigate the effect of shaking strength on the seismic response of liquefiable level ground the experimental observations indicate the following effects 1 shaking strength has pronounced effect on the excess pore pressure buildup in the saturated sand deposit the maximum excess pore pressure at the deep part of the deposit increased by 184 and 109 as the peak input acceleration along the x direction increased from approximately 0 064 g to 0 098 g and from 0 098 g to 0 189 g respectively 2 shaking strength has significant effect on the development of shear strain in soil however the permanent settlement is sensitive to the shaking strength at low shaking level but the increment rate tends to slow down as the shaking strength becomes stronger 3 the peak acceleration along the x direction at the ground surface was 0 126 0 079 and 0 087 g at peak input accelerations of 0 064 0 098 and 0 189 g respectively the peak acceleration at the ground surface under slight shaking was greater than that under strong shaking 4 the amplification pattern of acceleration varied continuously during shaking the amplification factor decreased quickly as the excess pore pressure accumulated under strong shaking but continued to increase at an early stage under low strength earthquake the natural frequency of the soil column also evolved with the development of the shaking induced excess pore pressure which had adversely affected the wave propagation and ground response the data presented in this paper enrich the ground response database and can be used to validate the current site response analysis methods

splay fault branching along the nankai subduction zone seismic reflection profiles reveal steeply landward dipping splay faults in the rupture area of the magnitude m 8 1 tonankai earthquake in the nankai subduction zone these splay faults branch upward from the plate boundary interface that is the subduction zone at a depth of approximately 10 kilometers approximately 50 to 55 kilometers landward of the trough axis breaking through the upper crustal plate slip on the active splay fault may be an important mechanism that accommodates the elastic strain caused by relative plate motion

relationship between earthquake induced excess pore water pressure and strong ground motion observed in a monitored fill slope abstract the generation of excess pore water pressures during ground shaking can be an important earthquake induced landslide trigger we measured pore water pressures and seismic ground motion in filled slopes and examined their relationships obtained from 29 observed earthquakes we characterized pore water pressure and seismic waveforms by calculating several parameters that described their magnitudes and durations we demonstrate that whilst the instantaneous magnitude of strong ground motion is responsible for the generation of excess pore water pressure the magnitude of excess pore water pressure generated is related to the peak ground acceleration pga and arias intensity ai in the observed pga range of 0 12 1 9 m s2 the magnitude of peak ground velocity pgv also produced a strong correlation although a few exceptional events where long period component 1 s of seismic waves is dominant were observed lastly the time span over which excess pore water pressure continues to rise is affected by the duration of seismic ground motion our study shows how excess pore water pressures can be generated in fill slopes during seismic events this new knowledge could be used to improve future earthquake induced landslide hazard assessment

topographic effects on the mean tropospheric flow patterns around antarctica abstract topographically induced flows around antarctica in a rotating tank experiment with both homogeneous and stratified fluid are analyzed and compared with the mean tropospheric circulation a circular tank of fluid was brought to a state of near rigid clockwise rotation and a topographic model of the antarctic continent was then rotated counterclockwise to simulate a mean westerly zonal wind stratification was chosen to give the same ratios of topographic and dynamical length scales as in the atmosphere as was the rossby number based on the ratio of rotation rates after the onset of the relative rotation of the antarctic model cyclonic eddies evolved in the coastal areas with in the homogeneous case anticyclonic eddies over the antarctic dome after about ten tank rotation periods a dominant wavenumber 3 structure with cyclonic eddies in the ross and weddell seas and prydz bay is observed as an approximately steady state flow over the topography is relatively stagnant with weak anticycloni

the role of katabatic winds on the antarctic surface wind regime abstract antarctica is known for its strong and persistent surface winds that are directed along topographic pathways surface winds are especially strong during the winter period the high directional constancy of the wind and the close relationship of the wind direction to the underlying terrain can be interpreted as evidence of katabatic wind activity observations show that the directional constancy of the antarctic surface wind displays little seasonal variation summertime winds cannot be expected to contain a significant katabatic component owing to enhanced solar heating of the ice slopes observations also show that the coastal environs are subjected to wide variation in atmospheric pressure associated with frequent cyclone activity the robust unidirectional nature of the antarctic surface wind throughout the year implies that significant topographic influences other than those from katabatic forcing must be acting idealized numerical simulations have been performed to illustrate the potential

characteristics of the ross ice shelf air stream as depicted in antarctic mesoscale prediction system simulations 1 streamlines of the mean annual near surface winds over the antarctic continent suggest a confluent channeling of the drainage flows off the ice sheets and onto the ross ice shelf a persistent cyclonic circulation to the north of the ice shelf supports a large scale pressure field that reinforces the continental drainage flows owing to these two processes an enhanced low level airflow is present along the southern and western sections of the ross ice shelf the resulting air stream known as the ross ice shelf air stream ras is one of the persistent and prominent low level wind features seen in the antarctic real time mesoscale simulations of the antarctic atmosphere and high southern latitudes using a modified version of the pennsylvania state university national center for atmospheric research mesoscale modeling system have been ongoing since the 1999 2000 austral field season model results from the 1 year period november 2001 to october 2002 have been analyzed to investigate the mean structure and modulation of the ross ice shelf air stream analyses of model results show the low level air stream over the western ross ice shelf has a wind speed maxima that is linked to the steep topography to the west individual cases of strong wind events appear to contain a significant barrier wind component that arises from cold air damming against the transantarctic mountains cyclones that frequently form in the ross sea are shown to establish conditions that promote barrier wind dynamics and thus significantly modulate the intensity of the ras

diagnosis of the katabatic wind influence on the wintertime antarctic surface wind field from numerical simulations abstract katabatic winds have long been recognized as one of the key climatic variables of the low level antarctic environment antarctic surface winds display a high degree of persistence with mean directions related to the local topographic configuration of the ice sheet consistent with katabatic forcing continental orography also constrains the atmospheric boundary layer motions through blocking and cold air damming finally the coastal rim about the antarctic continent is among the most active baroclinic zones on earth the establishment of the low level wind field over antarctica is thus potentially the result of a number of interacting processes to quantify the forcing of the wintertime surface wind field over the antarctic continent two numerical strategies are presented first idealized numerical simulations are conducted to illustrate the strong orographic control of the low level wind field second a series of daily numerical simulations using the fifth generation pennsylvania state unive

surface airflow over east antarctica abstract surface winds over the antarctic interior occur mainly due to the strong radiational cooling of the ice slopes as a consequence such winds exhibit a high degree of persistence with a predominant direction closely related to the terrain orientation using detailed contour maps of the interior ice topography and representative values of the mean wintertime strength of the temperature inversion it is possible to infer the terrain induced accelerations a simple diagnostic equation system is formulated from which a time averaged surface airflow pattern of east antarctica is generated the results appear consistent with observations the occurrence of localized anomalously strong katabatic winds is explained as a result of typographically forced patterns of cold air convergence depicted in the airflow analysis

met office unified model high resolution simulations of a strong wind event in antarctica during winter much of the antarctic coast is susceptible to severe and hazardous strong wind events swes associated with the enhancement of katabatic winds by synoptic weather systems in this study a swe that occurred at mawson east antarctica involving a hurricane force wind speed of 39 m s 1 is simulated by the met office unified model at high horizontal resolutions with grid lengths between 12 and 1 5 km it is shown that all the simulations capture the qualitative evolution of the swe but underestimate its peak wind speed the extent of the underestimate is dependent on horizontal resolution with the 4 and 1 5 km 12 km models underforecasting the peak wind speed by around 15 36 in addition to a strengthening of the katabatic flow the simulated low level cyclonic winds associated with the depression responsible for the swe caused the formation of a barrier type jet parallel to the coast resulting in strong wind convergence interaction at the coastline and suggesting a strong topographic influence on the dynamics responsible for swe formation moreover it suggests that mawson is influenced by small scale gravity waves that formed in response to the stronger winds and that representation of this was particularly sensitive to horizontal resolution additional experiments suggest that the met office unified model simulation of the swe is most sensitive to the representation of turbulent mixing under stable conditions this study is important to identify shortcomings in the performance of the met office unified model near antarctica s coastal regions as well as to improve understanding of the processes responsible for swes

a dynamical explanation of the topographically bound easterly low level jet surrounding antarctica this study investigates the topographically bound easterly low level jet surrounding antarctica this jet is modeled as a balanced flow that satisfies the potential vorticity invertibility principle based on local linear balance in spherical coordinates and expressed in isentropic coordinates in this way this easterly low level jet is shown to be the balanced flow associated with the topography of the antarctic plateau moderated by a shallow potential vorticity anomaly atop the plateau produced by radiative cooling the dynamical connection of the jet with katabatic winds can be understood through the meridional circulation equation model results based on the simple theoretical arguments developed here are found to be consistent with high resolution reanalysis data from the european centre for medium range weather forecasts ecmwf for the 2008 2010 period

influence of west antarctic ice sheet collapse on antarctic surface climate climate model simulations are used to examine the impact of a collapse of the west antarctic ice sheet wais on the surface climate of antarctica the lowered topography following wais collapse produces anomalous cyclonic circulation with increased flow of warm maritime air toward the south pole and cold air advection from the east antarctic plateau toward the ross sea and marie byrd land west antarctica relative to the background climate areas in east antarctica that are adjacent to the wais warm while substantial cooling several c occurs over parts of west antarctica anomalously low isotope paleotemperature values at mount moulton west antarctica compared with ice core records in east antarctica are consistent with collapse of the wais during the last interglacial period marine isotope stage 5e more definitive evidence might be recoverable from an ice core record at hercules dome east antarctica which would experience significant warming and positive oxygen isotope anomalies if the wais collapsed

the surface windfield over the antarctic ice sheets the intense radiative cooling of air over the ice slopes of antarctica generates a surface wind regime that is strongly controlled by topography and plays a key role in determining the behaviour of the atmosphere and ocean in high southern latitudes1 7 resultant surface winds are intimately linked to the orientation of the ice terrain fig 1 and display the highest degree of persistence found on earth the close coupling between wind and topography allows estimation of the former if the latter is known with some precision here we report on time averaged near surface airflow over the antarctic continent during winter diagnosed from a recent accurate synthesis of terrain slopes and from estimates of the lower atmospheric temperature structure the simulated drainage pat tern exhibits strong spatial variability with the airflow concentrated into several zones near the coastal margin these confluence regions are responsible for strong persistent katabatic winds over downstream coastal stretches and are indicative of zones of greatest katabatic potential

local and synoptic mechanisms causing southern california s santa ana winds the atmospheric conditions that lead to strong offshore surface winds in southern california commonly referred to as santa ana winds are investigated using the north american regional reanalysis and a 12 year 6 km resolution regional climate simulation of southern california we first construct an index to characterize santa ana events based on offshore wind strength this index is then used to identify the average synoptic conditions associated with santa ana events a high pressure anomaly over the great basin this pressure anomaly causes offshore geostrophic winds roughly perpendicular to the region s mountain ranges which in turn cause surface flow as the offshore momentum is transferred to the surface we find however that there are large variations in the synoptic conditions during santa ana conditions and that there are many days with strong offshore flow and weak synoptic forcing this is due to local thermodynamic forcing that also causes strong offshore surface flow a large temperature gradient between the cold desert surface and the warm ocean air at the same altitude creates an offshore pressure gradient at that altitude in turn causing katabatic like offshore flow in a thin layer near the surface we quantify the contribution of synoptic and local thermodynamic mechanisms using a bivariate linear regression model and find that unless synoptic conditions force strongly onshore winds the local thermodynamic forcing is the primary control on santa ana variability

late holocene great earthquakes in the eastern part of the aleutian megathrust abstract the great earthquake mw 9 2 of ad 1964 may not be typical of other megathrust earthquakes in the region during the last 4000 years we present new field data from three sites copper river delta the lower katalla river valley and puffy slough to enhance the temporal and spatial resolutions of the paleoseismic records of multiple great earthquakes differences in the spatial patterns of coseismic uplift and subsidence suggest different rupture combinations of the kodiak prince william sound and western yakutat segments of the plate boundary the longest and most comprehensive records all come from the prince william sound segment most sites here reveal net subsidence over multiple earthquake cycles except where probable upper plate faulting contributes locally to net uplift with measurable differences between sites only a few kilometres apart we identify the katalla area as a source of local seismic hazard similar to other locations in the western part of the yakutat microplate including the two mw8 ruptures in ad 1899 we use a bayesian radiocarbon modelling approach to estimate the age and recurrence intervals of multiple great earthquakes for the prince william sound segment of the megathrust the long interval 883 34 2 years between the penultimate earthquake and ad 1964 contrasts with the older earthquakes that have intervals ranging from 420 to 610 years with a mean of 535 years

pore pressure generation and fluidization in a loess landslide triggered by the 1920 haiyuan earthquake china a case study abstract during the 1920 haiyuan earthquake numerous catastrophic landslides were triggered in the loess area in northwest china we investigated in detail a large example of these landslides referred to as dangjiacha landslide in this paper this landslide originated from a slope of about 20 and the displaced soil mass traveled about 3200 m damming a valley we performed a field survey and found that standing water existed in the landslide area and the loess had high porosity we infer that it was the liquefaction of the water saturated loess layer rather than the suspension of silt in the pore air in the loess that caused the great mobility of this landslide to test this inference we performed undrained triaxial compression and ring shear tests on loess samples to examine the shear behavior of loess saturated by either air or water the test results showed that the water saturated loess soil was highly susceptible to flow liquefaction failure fast shear tests on naturally air dried loess samples revealed that the generated pore air pressure was small under the undrained condition and no significant reduction in the shear resistance was observed implying that air entrapped in the loess was unlikely to be the main contributor to the high mobility of this large scale landslide