identification of tsunami deposits considering the tsunami waveform an example of subaqueous tsunami deposits in holocene shallow bay on southern boso peninsula central japan abstract this study proposes a tsunami depositional model based on observations of emerged holocene tsunami deposits in outcrops located in eastern japan the model is also applicable to the identification of other deposits such as those laid down by storms the tsunami deposits described were formed in a small bay of 10 20 m water depth and are mainly composed of sand and gravel they show various sedimentary structures including hummocky cross stratification hcs and inverse and normal grading although individually the sedimentary structures are similar to those commonly found in storm deposits the combination of vertical stacking in the tsunami deposits makes a unique pattern this vertical stacking of internal structures is due to the waveform of the source tsunamis reflecting 1 extremely long wavelengths and wave period and 2 temporal changes of wave sizes from the beginning to end of the tsunamis the tsunami deposits display many sub layers with scoured and graded structures each sub layer especially in sandy facies is characterized by hcs and inverse and normal grading that are the result of deposition from prolonged high energy sediment flows the vertical stack of sub layers shows incremental deposition from the repeated sediment flows mud drapes cover the sub layers and indicate the existence of flow velocity stagnant stages between each sediment flow current reversals within the sub layers indicate the repeated occurrence of the up and return flows the tsunami deposits are vertically divided into four depositional units tna to tnd in ascending order reflecting the temporal change of wave sizes in the tsunami wave trains unit tna is relatively fine grained and indicative of small tsunami waves during the early stage of the tsunami unit tnb is a protruding coarse grained and thickest stratified division and is the result of a relatively large wave group during the middle stage of the tsunami unit tnc is a fine alternation of thin sand sheets and mud drapes deposited from waning waves during the later stage of the tsunami unit tnd is deposited during the final stage of the tsunami and is composed mainly of suspension fallout cyclic build up of these sub layers and depositional units cannot be explained by storm waves with short wave periods of several to ten seconds common in small bays

landward fining from multiple sources in a sand sheet deposited by the 1929 grand banks tsunami newfoundland abstract a sandy deposit from the 1929 grand banks tsunami in newfoundland contains sediment from two distinct sources one from an inferred gravel shoreline close to the deposit and one from a sandy dune some 200 m seaward of the deposit the deposit ranges from 0 to 15 cm thick and is composed of a bimodal mix of fine and coarse sand we took approximately 100 core samples of this deposit in an attempt to characterize lateral grain size trends within the sand although the coarse fraction does fine with distance inland the fine fraction does not change size over the study area and the aggregate grain size changes in no systematic way we interpret this deposit to represent the mixture of material picked up at the bar with material picked up at the gravel shoreline the bar material does not fine in part because it is already fairly well sorted but also because it is far from its source the shoreline material on the other hand is poorly sorted so that the tsunami took only those grains it was capable of moving and deposited them near their source we estimated the size of the tsunami by determining the flow depth flow velocity combinations required to advect sand from the bar to the back of the deposit and by estimating the shear velocity required for motion of the largest grain we found during our survey this modeling indicates an average flow depth of about 2 5 2 8 m over the area at a flow velocity of 1 9 2 2 m s this estimate compares well with eyewitness accounts of a maximum flow depth of 7 m at the shoreline if our estimate represents an average over the whole study area

tsunami sediment characteristics at the thai andaman coast this paper describes and summarizes the 2004 indian ocean tsunami sediment characteristics at the thai andaman coast field investigations have been made approximately 3 years after the 2004 indian ocean tsunami event seven transects have been examined at five locations sediment samples have been collected for grain size analyses by wet sieve method tsunami sediments are compared to three deposits from coastal sub environments the mean grain size and standard deviation of deposits show that shoreface deposits are fine to very fine sand poorly to moderately well sorted swash zone deposits are coarse to fine sand poorly to well sorted berm dune deposits are medium to fine sand poorly to well sorted and tsunami deposits are coarse to very fine sand poorly to moderately well sorted a plot of deposit mean grain size versus sorting indicates that tsunami deposits are composed of shoreface deposits swash zone deposits and berm dune deposits as well the tsunami sediment is a gray sand layer deposited with an erosional base on a pre existing soil rooted soil the thickness of the tsunami sediment layer is variable the best location for observation of the recent tsunami sediment is at about 50 200 m inland from the coastline in most cases the sediment layer is normally graded in some cases the sediment contains rip up clasts of muddy soils and or organic matter the vertical variation of tsunami sediment texture shows that the mean grain size is fining upward and landward break points of slope in a plot of standard deviation versus depth mark a break in turbulence associated with a transition to a lower or higher reynolds number runup this can be used to evaluate tsunami sediment main layer and tsunami sediment sub layers the skewness of tsunami sediment indicates a grain size distribution with prominent finer grain or coarse grain particles the kurtosis of tsunami sediment indicates grain size distributions which are flat to peak distribution or multi modal to uni modal distribution upward generally the major origins of tsunami sediment are swash zone and berm dune zone sands where coarse to medium sands are the significant material at these locations the minor origin of tsunami sediment is the shoreface where the significant materials are fine to very fine sands however for a coastal area where the shoreface slope is mild the major origin of tsunami sediment is the shoreface the interpretation of runup number from tsunami sediment characteristics gets three runups for the 2004 indian ocean tsunami at the thai andaman coast it corresponds to field observations from local eyewitnesses the 1st runup transported and deposited more coarse particles than the following runups overall the pattern of onshore tsunami sediment transportation indicates erosion at swash zone and berm dune zone followed by dynamic equilibrium at an area behind the berm dune zone and after that deposition at inland zone until the limit of sediment inundation the total deposition is a major pattern in onshore tsunami sediment transportation at the deposition zone which the sediment must find in the direction of transport

marine incursions of the past 1500 years and evidence of tsunamis at suijin numa a coastal lake facing the japan trench sandy deposits of marine origin underlie the floor of suijin numa a coastal lake midway along the subduction zone marked by the japan trench the deposits form three units that are interbedded with lacustrine peat and mud above a foundation of marine probably littoral sand unlike the lacustrine deposits all three sandy units contain marine and brackish diatoms the middle unit b contains in addition graded beds sug gestive of multiple waves of long wavelength and period the uppermost unit c probably dates to a time in the area s written history when the lake was separated from the sea by a beach ridge plain at least 0 5 km wide and several metres high units a and b postdate ad 540 870 and unit c postdates ad 1030 1640 as judged from radiocarbon dating of leaves and seeds unit b pre dates ad 915 and unit c postdates that year as judged from a tephra within the peat that separates units b and c the age constraints permit correlation of unit b with a tsunami in ad 869 that reportedly devastated at least 100 km of coast approximately centred on sendai unit c may represent a later catastrophic tsunami in 1611 or perhaps a storm surge that inundated much of sendai the lake lacks obvious signs of tsunamis from the region s largest twentieth century earthquakes which were centred to the north in 1933 m 8 1 and directly offshore in 1936 m 7 5 and 1978 mw 7 6

wind profiler observations of a sting jet some of the most damaging surface winds experienced in midlatitude cyclonic storms have been attributed to a phenomenon known as a sting jet previous studies have deduced how sting jets develop from their midtropospheric origin but there have been no direct observations of these wind features in the midtroposphere during windstorm jeanette on 27 october 2002 the tip of the storm s cloud head passed over a vhf wind profiler at aberystwyth wales allowing the structure of a sting jet to be measured with high spatial and temporal resolution these observations showed a multiple slantwise structure to the sting jet region with two tails of increased winds that persisted after the passing of the cloud head aloft simulations by the met office unified model um showed that the slantwise structure followed w surfaces and that the sting jet descended along surfaces as it passed over the uk accelerating and drying during its descent the horizontal and vertical scales of the observed structures are compatible with slantwise convection releasing conditional symmetric instability within the cloud head further observations of the sting jet were obtained by a uhf wind profiler at cardington in eastern england where the sting jet had merged with the cold conveyor belt circulating around the storm an unstable temperature profile in the lowest kilometre over cardington enabled damaging gusts of strong winds to be brought to the surface in convective plumes however this strong vertical mixing was not represented correctly in the um copyright 2009 royal meteorological society

evidence of high energy events in shelly layers interbedded in coastal holocene sands in cadiz bay south west spain in some present day coastal areas recent inactive deposits now outside the reach of sea agents can be observed these deposits although formed under different climatic and sea level conditions often show similar facies to current littoral deposits they are frequently interpreted as old dunes and beach ridges or as abandoned spit bars representative of previous dynamic stages nevertheless in coastal areas which have been subjected to highly energetic events similar deposits can also be found when a dynamic event acts on several adjacent environments the transported and re deposited sediments can create homogeneous deposits with similar facies that are easily confused in this work shelly layers interbedded in relict littoral sands located in the la algaida pinewood on the edge of the rio san pedro tidal channel in cadiz bay south west spain have been studied the main constituents of the shelly beds are glycimeris valves organisms which are no longer found as live specimens in the present day sea bed of cadiz bay from their appearance the origin of these shelly beds could be related to sea washovers generated by tidal or storm action but their disposition and height over the present sea level implies that even higher energy agents were involved in their formation such as major storms or tsunami waves the most significant process was the mobilization of the sub tidal and littoral sediments and their dispersal and re sedimentation both lengthways and widthways of the coast giving way to homogeneous sandy deposits in all littoral environments some of which are now outside the reach of current sea agents the exception is the present day shore of the san pedro tidal channel where the sediments are being reworked by tidal and small wave action if the proximity of the study zone to the limit of the african and iberian plates is considered where several historical earthquakes and tsunamis have taken place it is possible to think that these deposits could be a consequence of sporadic and successive washovers generated by tsunamis occurring between ad 800 and ad 1200 sedimentological and historical data indicate an increase in seismic and tsunami activity during this period of time while the shelly layers would be the consequence of the most intense pulses occurring during these high energy events copyright 2009 john wiley sons ltd

intraseasonal variability in the upper layer currents observed in the eastern equatorial indian ocean 1 direct observations of the upper ocean velocity in the eastern equatorial indian ocean by an acoustic doppler current profiler from november 2000 to october 2001 on the equator at 90 e demonstrate that the dominant periods of variability in the upper layer zonal and meridional currents are in intraseasonal frequency bands with periods of 30 to 50 days and 10 to 20 days respectively the strong intraseasonal variability in the zonal current obscures the semiannual wyrtki jets which can be seen clearly in the monthly averaged field in addition a zone of strong vertical shear of the zonal current and a distinct equatorial undercurrent with semiannual period are observed the results provide us with a new perspective on importance of the energetic intraseasonal variability in the eastern equatorial indian ocean which indicates strong correlation with the wind variability near the mooring location

convective mixing in a tropopause fold we present a case study of the passage of a tropopause fold over the uk behind a cold front with emphasis on the mixing caused by convection extending into the fold the event took place on 15 16 january 1999 and was the subject of intensive observations using the met office c130 aircraft and the mesosphere stratosphere troposphere mst radar at aberystwyth here we concentrate on radar and satellite observations during the afternoon of 16 january when the surface cold front had passed over the uk a tongue of moist air moved north eastwards over wales at 700 hpa at this time which because of the very dry air in the fold above resulted in potential instability the resulting convection was clearly observed in noaa satellite images the mst radar depicted the passage of the cold front and tropopause fold as a layer of high echo power and vertical wind shear ascending with time spectral widths showed the fold to be free of turbulence until 1200 utc on 16 january when convection was observed reaching into the frontal zone and generating turbulence eddy dissipation and diffusivity rates of 8 6 mw kg 1 and 8 5 m2s 1 respectively were derived for this event to place these figures in context they are compared with corresponding rates derived for sixteen other passages of tropopause folds over the radar each resulting from shear rather than convective instability the convective event is found to be comparable to the strongest shear events and to correspond to moderate turbulence as experienced by an aircraft this process is of potential importance for atmospheric chemistry because it mixes boundary layer air directly with stratospheric air over a timescale of 1 2 hours copyright 2004 royal meteorological society

comment on reconstructing tsunami run up from the characteristics of tsunami deposits on the thai andaman coast by srisutam and wagner 2010 abstract in this short comment we address several approximations and assumptions in a model of tsunami reconstruction from the characteristics of tsunami deposits presented by soulsby et al 2007 in a conference and adapted by srisutam and wagner 2010 to the 2004 tsunami deposits in thailand

gravity wave interactions around the jet stream 1 vhf radar measurements have been applied to study the interaction between a mountain wave and an inertia gravity wave above the jet stream in the tropopause region the mountain wave was observed to break and generate turbulence at a critical level that was induced by the inertia gravity wave this indicates that wave wave interactions can be an important source of turbulence and consequently mixing in the tropopause region

relationship between the maximum extent of tsunami sand and the inundation limit of the 2011 tohoku oki tsunami on the sendai plain japan abstract this paper focuses on the relationship between the maximum extent of sandy tsunami deposits and inundation distance of the 2011 tohoku oki tsunami inundation limits of the tohoku oki tsunami were assessed over seven shore normal transects along the sendai coastal plain inundation distances were found to range from 0 6 to 4 0 km at the maximum extent of the tsunami deposit the sand unit ranged in thicknesses from 0 1 to 4 0 cm the maximum limit of the 0 5 cm thick sand layer extended to over 90 of the inundation distance where the inundation distance was less than 2 5 km this observation is consistent with previous studies that examined characteristics of recent tsunami events that had inundation distances of at least 2 km the maximum limit of the 0 5 cm thick sand layer extended to 3 km 57 76 of the inundation distance where the inundation distance was more than 2 5 km our results are important for estimating paleo tsunami inundation distances based on the landward extent of sand deposits and valuable for the assessment of future tsunami risks in other coastal areas in the world which have been devastated by huge tsunamis in the past

reconstructing the pattern and depth of flow onshore in a palaeotsunami from associated deposits the widespread sheets of fine particulate sediment frequently deposited by tsunami constitute valuable evidence from which to reconstruct tsunami inundation this is illustrated with evidence from three sites near montrose in eastern scotland u k where a horizon of mainly sand laid down during the holocene storegga slide palaeotsunami of circa 8000 bp is examined the horizon is remarkably consistent in its distribution morphology stratigraphy and particle size characteristics these properties allow inferences to be made on the nature of tsunami flow onshore and run up it is suggested that estimates can be made of the possible depth of water involved from the characteristics of the sediment and thus of the extent of inundation involved in the tsunami at these sites

horizontal and vertical variation of 2004 indian tsunami deposits an example of two transects along the western coast of thailand abstract we investigated horizontal and vertical variations in modern tsunami deposits along two transects at nam khem and khao lak western coast of thailand deposited by the large tsunami associated with the earthquake magnitude 9 0 of 26 december 2004 off sumatra indonesia tsunami waves 6 10 m high struck the area approximately 2 h after the earthquake tsunami deposits cover the low lying coastal plains and extend more than 1 km inland from the shoreline no landward decrease in sediment thicknesses was found clearly at either transect terrace scarps and a steep slope behind the coastal plain probably stopped tsunami deposition further inland causing substantial sediments to be deposited in front of these features very clear vertical variations in grain size and multiple layers are found in the deposits to about 600 m inland at nam khem fine grained sediments overlie the coarse grained sediments of the basal layer of the tsunami deposits at some sites the fine grained sediments are overlain by another layer of coarse grained sediments suggesting deposits laid down in succession by multiple waves the basal coarse grained sediments at nam khem fine landward the up flow waned inland based on the assumption that the grain size of the basal deposits relates to the strength of the up flow these results are potentially useful in disaster prevention and coastal environmental change management as well as for interpreting paleotsunami deposits in geological records

comments to dawson a g and stewart i 2007 tsunami deposits in the geological record sedimentary geology 200 166 183

x ray tomography of tsunami deposits towards a new depositional model of tsunami deposits x ray computed microtomography is used to obtain high resolution imagery of a historical tsunami deposit in andalusia spain 1755 lisbon tsunami the technique allows characterization of grain size distribution structures component analysis and sedimentary fabric of fine grained unconsolidated tsunami deposits at resolutions down to particle scale the results are validated by comparing to data obtained using other techniques such as laser diffraction anisotropy of magnetic susceptibility and x ray microfluorescence on the same deposits specific technical details such as sampling scanning and image processing methods and further improvements are addressed the use of x ray computed microtomography provides new insights into the stratigraphy of the deposits and gives access to significantly more detailed view of key sedimentary features such as mudlines rip up clasts crude laminations convolutions floating outsized clasts and contacts between successive units this analysis of the 1755 tsunami deposits using x ray computed microtomography allows the proposal of new hypotheses for the sedimentary processes forming tsunami deposits deposition by settling is limited and the section analysed here is dominated by a high shear stress leading to the development of traction carpets with laminated mudlines corresponding to the basal frictional region of these carpets the onset of the tsunami backwash is marked by a micro vortex resembling kelvin helmoltz instabilities

numerical models of tsunami sediment transport current understanding and future directions abstract researchers who study tsunami deposits share common ultimate goals of their work which are to better assess the magnitude information of paleotsunamis and to contribute to the assessment of future tsunami risks numerical modeling of tsunami sediment transport is an important piece of interdisciplinary research that fills the gap between geological studies and practical utilization of tsunami deposits forward and inverse numerical models that address tsunami transport of sand and boulders have been developed over the last two decades forward models are capable of delineating the time evolution of tsunami hydrodynamics sediment transport and the resulting morphological changes associated with erosion and deposition inverse models estimate tsunami characteristics such as flow speed and depth from deposits numerical modeling can be used not only to quantify paleotsunamis but also to enhance our understanding of tsunami sedimentology and hydrodynamics to make progress towards the ultimate goal of improved tsunami risk assessment development of an in depth mutual understanding between modelers and geologists of the advantages limitations and uncertainties in both numerical modeling and geological records is an important challenge

break up of a stratospheric streamer observed by mst radar the break up of a stratospheric streamer over the british isles is described using satellite mesosphere stratosphere troposphere mst radar and in situ observations together with european centre for medium range weather forecasts analyses the streamer started as a thin ribbon of high potential vorticity to the west of the british isles as this was strained by the background flow it broke up into a series of mesoscale vortices mst radar and ozonesonde observations delineated a tropopause fold to the west of the initial streamer taking the form of a thin layer of stratospheric air embedded in a deep layer of descending upper tropospheric air the fold appears to have been mixed out by small scale turbulence as the streamer broke up this break up also generated strong inertia gravity waves which broke just above the tropopause introducing extensive mixing to the lowermost stratosphere one of the mesoscale vortices returned over the mst radar showing a very indistinct tropopause typical of a synoptic scale cut off low this vortex was also responsible for the development of a rain band on its eastern flank which brought significant rainfall to the british isles at a time when the synoptic flow pattern was strongly anticyclonic

climatology of tropopause folds at midlatitudes a statistical analysis of a 25 years time series of routine ozone soundings at uccle 51 48 n 4 21 e reveals that the frequency of tropopause folds is within the limits of uncertainty similar for all seasons on the average 4 8 of the ozone profiles show the presence of a fold whereas a shorter time series of soundings 1985 1993 obtained at the observatoire de haute provence 43 54 n 5 45 e yields only a 2 fraction of folds the difference between both stations is however riot entirely statistically significant the average wet and dry artificial radioactivity deposition in the sixties and early seventies was at a maximum at uccle around june in good agreement with global sr 90 wet deposition measurements volchok and kleinman 1971 suggesting that stratosphere troposphere exchange is more important during spring compared to the rest of the year this leads to the hypothesis that if tropopause folds are the major agent of stratosphere troposphere exchange ste they may be more efficient in spring than in autumn

airborne measurements of gravity wave breaking at the tropopause 1 a breaking atmospheric gravity wave was investigated with a combination of airborne in situ dynamical measurements and ground based vhf radar observations the wave was generated by flow over mountains and it was observed to break near the tropopause the measurements reveal that the wave was overturning at the tropopause and that the initial breakdown into turbulence involved the generation of smaller oscillations with a horizontal wavelength of around 500 m there was also evidence that the turbulence associated with the wave breaking can cause substantial mixing in the tropopause region

field signatures of the se asian mega tsunami along the west coast of thailand compared to holocene paleo tsunami from the atlantic region the andaman sumatra tsunami of dec 26 2004 was by far the largest tsunami catastrophe in human history an earthquake of 9 to 9 3 on the richter scale the extension of waves over more than 5000 km of ocean and run ups up to 35 m are its key features these characteristics suggest significant changes in coastal morphology and high sediment transport rates a field survey along the west coast of thailand phuket island khao lak region including some similan islands nang pha mangrove areas and phi phi don islands seven to nine weeks after the tsunami however discovered only small changes in coastal morphology and a limited amount of dislocated sediments restricted to the lower meters of the tsunami waves this is in striking contrast to many paleo tsunami s events of the atlantic region explanations for this discrepancy are sought in a mechanics of the earthquake a rather slow shock impulse on the water masses over the very long earthquake zone b shallow water in the earthquake zone and c bathymetry of the foreshore zone at the impacted sites shallow water west of thailand has diminished wave energy significantly the differences in geomorphological and sedimentological signatures of this tsunami compared with many paleo tsunami worldwide makes it unsuitable to be used as a model for old and future tsunami imprints by an event of this extreme energy and extension

tropopause folds in era interim global climatology and relation to extreme weather events tropopause folds are intimately linked to upper level frontogenesis and jet stream dynamics they play an important role for stratosphere troposphere exchange the dynamical coupling of upper and lower tropospheric levels and for generating severe weather events this study presents a global climatology of tropopause folds using era interim reanalysis data from 1979 to 2012 and a refined version of a previously developed 3 d labeling and fold identification algorithm this algorithm objectively separates stratospheric and tropospheric air in complex situations e g in regions with strong low level inversions and in extratropical cyclones where diabatically generated potential vorticity anomalies typically occur three classes of tropopause folds are defined shallow medium and deep and their geographical distribution vertical extent and seasonal cycle are investigated most shallow folds occur along the subtropical jet stream in agreement with previous studies hot spots of medium and deep tropopause folds are found west of australia and along the coast of antarctica in the southern hemisphere and around the east coast of north america in the northern hemisphere seasonal cycles show maxima in winter for all fold classes medium and deep folds are frequently associated with surface wind gust and precipitation extremes as quantified for folds over the southern indian ocean wind gust extremes occur mainly in an elongated band upstream and equatorward of folds whereas precipitation extremes occur mainly east and poleward of folds overall in the considered region about 20 of medium folds and 33 of deep folds are associated with surface wind or precipitation extremes in the vicinity of the fold

geological evidence and sediment transport modelling for the 1946 and 1960 tsunamis in shinmachi hilo hawaii abstract the japanese community of shinmachi established on low lying land between downtown hilo and waiakea hawaii was obliterated by the 1946 aleutian tsunami but was rebuilt only to be destroyed again by the 1960 chilean tsunami the aim of this study was to find out if any geological evidence of these well documented events had been preserved in the sedimentary record in wailoa river state park which replaced shinmachi after the 1960 tsunami this was achieved by collecting cores in the park and performing sedimentological chronological and geochemical analyses the latter also processed by principal component analysis sediment transport modelling was carried out for both tsunamis to infer the source of the sediment and areas of deposition on land the field survey revealed two distinct units within peat and soil a thin lower unit composed of weathered basalt fragments within mud unit 1 and an upper unit dominated by fine volcanic sand within fine silt exhibiting subtle upward fining and coarsening unit 2 consisting of unit 2a and unit 2b although these two anomalous units only occur on the western shore of waiakea mill pond analysis with an itrax core scanner shows that unit 1 is characterised by high mn fe rb la and ce counts combined with elevated magnetic susceptibility based on its chemical and sedimentological characteristics unit 1 is attributed to a flood event in wailoa river that occurred around 1520 1660 ce most probably as a result of a tropical storm the sharp lower contact of unit 2 coincides with the appearance of arsenic contemporaneous with an increase in ca sr si ti k zr mn fe la and ce in this study as is used as a chronological and source material marker as it is known to have been released into wailoa river estuary and waiakea mill pond by the canec factory between 1932 and 1963 thus not only the chemical and sedimentological evidence but also sediment transport modelling corroborating the historical record suggest that unit 2a was deposited by the 1946 tsunami and the sediment most likely originated from wailoa river estuary beach and nearshore seafloor the upper part of this unit unit 2b is believed to have been deposited by the 1960 tsunami as suggested by sediment transport modelling although limited accommodation space is likely to have resulted in the thin deposit 3 cm thickness present at that site limited accommodation space on the island of hawaii has led to only rare locations where tsunami deposits are preserved despite the repeated occurrence of tsunamis affecting the island

diagnostic study of a narrow cold frontal rainband and severe winds associated with a stratospheric intrusion a diagnostic study of a severe wind event associated with a cold front is presented based on output from an operational numerical weather prediction model together with radar and satellite imagery and detailed surface observations an intrusion of stratospheric air initially with a potential vorticity of 2 pv units is shown as part of a backward tilted filament to have plunged down to the lower troposphere where it was associated with a narrow cold frontal rainband at its leading edge and produced severe wind gusts up to 70 knots a close correspondence in time and space is revealed between these surface events and the appearance in the model of a pocket of diluted stratospheric air with pv 1 at the 2 km level the stratospheric intrusion produced two distinguishable wind surges one behind the narrow cold frontal rainband and another mainly dry about 200 km farther behind the strength of the winds was attributable to the downward transport of momentum as part of the large scale dynamics local moist processes played only a minor role at coarse resolution the radar echo from the narrow cold frontal rainband resembled line convection but it is shown that there were significant differences between this event and the archetypal form of line convection often seen in the british isles

episodic seafloor mud brecciation due to great subduction zone earthquakes the nankai trough off southwest japan has an 1300 yr historical record of great earthquakes including the most recent the a d 1944 tonankai m 8 2 earthquake evaluation of the activity of an individual submarine fault is difficult when only onland observations are available submarine core records can pinpoint individual fault activity here we present integrated ocean drilling program iodp nankai trough seismogenic zone experiment data from the shallow portion iodp expedition 316 drilled and cored several holes in the shallow portion of the offshore tonankai earthquake area including sites in the hanging wall of a margin dominating splay fault that has previously been interpreted to have ruptured coseismically during megathrust earthquakes x ray computed tomography scanning revealed that the uppermost core at one site contains repeated occurrences of mud breccia radioisotope dating of the uppermost mud breccia indicates a deposition time consistent with the 1944 tonankai earthquake suggesting that the mud breccia layers result from episodic brecciation caused by seismic shaking mud brecciation provides a potential new tool to reconstruct ancient earthquake history in subduction zones

fragmentation of stratospheric intrusions evidence is presented pointing to the existence of rich and coherent subsynoptic and mesoscale flow features at tropopause levels these features are related to and evolve from the classical v shaped intrusions of stratospheric air down to tropospheric elevations it is shown that intrusions can develop into elongated 2000 3000 km and slender 200 km streamers and that thereafter such a streamer can roll up to form a train of stalactite shaped vortex subentities with an accompanying substantial thinning of the intervening filament in addition there are indications that the vortices themselves can develop a spirallike interior structure of interleaved stratospheric and tropospheric air these inferences are based upon two independent but complementary sources analysis of the potential vorticity distribution on tropopause transcending isentropic surfaces derived from the analysis fields of the european centre for medium range weather forecasts either directly or indirectly using a contour advection technique and imagery from the water vapor channel of the european space agency meteosat 4 satellite streamers were observed to occur with a frequency of approximately one per week over central and southern europe during the winter of 1991 1992 the fragmentation is linked to the instability or self development of a filament of enhanced potential vorticity and it can modify or instigate surface weather systems moreover by inducing a substantial and rapid enlargement of the intrusion s surface area it greatly enhances the potential for local irreversible mixing of stratospheric and tropospheric air

a comparison of stratosphere troposphere transport in convection permitting and convection parameterizing simulations of three mesoscale convective systems 1 the transport of stratospheric air into the troposphere within deep convection was investigated using the met office unified model version 6 1 three cases were simulated in which convective systems formed over the uk in the summer of 2005 for each of these three cases simulations were performed on a grid having 4 km horizontal grid spacing in which the convection was parameterized and on a grid having 1 km horizontal grid spacing which permitted explicit representation of the largest energy containing scales of deep convection cross tropopause transport was diagnosed using passive tracers that were initialized above the dynamically defined tropopause 2 potential vorticity unit surface with a mixing ratio of 1 although the synoptic scale environment and triggering mechanisms varied between the cases the total simulated transport was similar in all three cases the total stratosphere to troposphere transport over the lifetime of the convective systems ranged from 25 to 100 kg m2 across the simulated convective systems and resolutions which corresponds to 5 20 of the total mass located within a stratospheric column extending 2 km above the tropopause in all simulations the transport into the lower troposphere defined as below 3 5 km elevation accounted for 1 of the total transport across the tropopause in the 4 km runs most of the transport was due to parameterized convection whereas in the 1 km runs the transport was due to explicitly resolved convection the largest difference between the simulations with different resolutions occurred in the one case of midlevel convection considered in which the total transport in the 1 km grid spacing simulation with explicit convection was 4 times that in the 4 km grid spacing simulation with parameterized convection although the total cross tropopause transport was similar stratospheric tracer was deposited more deeply to near surface elevations in the convection parameterizing simulations than in convection permitting simulations

large scale potential vorticity anomalies and deep convection the effect on deep convection of large scale potential vorticity pv anomalies and their associated tropospheric stable layers is complex and not well understood this article examines the meteorological events of 9 july 2007 iop7b of the convective and orographically induced precipitation study cops which was dominated by an upper level pv anomaly that stretched from the uk to southern france and as far northeast as denmark three precipitation regions were identified from the case lines of intense storms beneath the pv anomaly less intense more widespread convective precipitation to the east of the pv anomaly and in between a region of no precipitation the latter of these coincided with the high resolution measurements and model analyses from cops the extensive and varied data analyzed in this investigation show that convective available potential energy cape was present in this region the distribution of cape and convective inhibition cin is presented via an innovative pseudo 3d visualization that allows horizontal and vertical interactions to be considered however convection was capped by a complex arrangement of dry layers the base of the key layer was at 750 hpa these dry layers descended separately from the upper troposphere moving around the pv anomaly as it developed from a breaking rossby wave to the west during the seven days before the iop this case adds to other studies that show that descent of complex dry layers is an important mechanism for forming convection inhibiting atmospheric lids in western europe a simple conceptual model is developed that synthesizes the effect of large scale pv anomalies on deep convection from a series of consistent case studies this model has significant implications for storm forecasting and projections of storminess in future climates as it highlights the importance of thin structures that can advect hundreds of km before having an impact copyright 2012 royal meteorological society

inflow and outflow facies from the 1993 tsunami in southwest hokkaido abstract we describe in detail the sedimentary facies provenance and grain size distributions of the 1993 tsunami deposits in the lower reaches of usubetsu river only two lithofacies were recognized a gravel lobe facies glf and a sand sheet facies ssf the gravel lobe facies was deposited rapidly by a hydraulic jump in contrast the sand sheet facies which contains both current ripples and dunes was deposited by a traction current under subcritical flow conditions we identified four stratigraphic units unit 1 unit 2 unit 3 and unit 4 in ascending order we interpreted units 1 and 2 as having been deposited by the inflow and outflow events of the first run up and units 3 and 4 by the inflow and outflow events of the second run up respectively units 3 and 4 were more widely distributed and coarser grained than units 1 and 2 because the second run up was larger than the first run up furthermore unit 4 was more widely distributed than unit 3 because the outflow eroded the inflow deposits grain size distributions of the inflow and outflow deposits were clearly different unit 4 deposits had a peak at 2 5 phi p 1 population in contrast unit 3 deposits had a bimodal distribution with peaks at 0 5 1 5 phi p 2 population and at 2 5 phi p 1 population a comparison of the tsunami deposits with other sedimentary deposits near the study area showed that the tsunami deposits were mainly derived from the seabed at depths below 5 5 m in the offshore area where the marine sands are about 2 2 5 phi in size and thus are the source of the p 1 population the p 2 population is derived from coarse 0 5 2 phi fluvial materials eroded during the tsunami run up according to our calculations benthic foraminiferal tests were entrained from the comparatively deep seabed at depths up to 100 m during the tsunami run up and included in the tsunami deposits

expanding the proxy toolkit to help identify past events lessons from the 2004 indian ocean tsunami and the 2009 south pacific tsunami article i nfo some of the proxies used to identify palaeotsunamis are reviewed in light of new findings following the 2004 indian ocean tsunami and the 2009 south pacific tsunami and a revised toolkit provided the new application of anisotropy of magnetic susceptibility ams to the study of tsunami deposits and its usefulness to determine the hydrodynamic conditions during the emplacement of tsunami sequences together with data from grain size analysis are presented the value of chemical proxies as indicators of saltwater inundation associated marine shell and or coral high energy depositional environment and possible contamination is demonstrated and issues of preservation addressed we also provide new findings from detailed studies of heavy minerals new information gathered during the unesco international oceanographic commission ioc international tsunami survey of fine onshore sediments following the 2009 south pacific tsunami is presented and includes grain size chemical diatom and foraminifera data the tsunami deposit varied ranging from fining upward sand layers to thin sand layers overlain by a thick layer of organic debris and or a mud cap grain size characteristics chemical data and microfossil assemblages provide evidence for marine inundation from near shore and changes in flow dynamics during the tsunami

convective destabilization by a tropopause fold diagnosed using potential vorticity inversion there is observational evidence to suggest that at the time tropopause folds in extra tropical cyclones are descending into the mid troposphere there is frequently a destablization of the lower troposphere to moist convection here we consider the dynamical reasons for such a linkage using so called potential vorticity pv attribution concepts in particular pv inversion is used to find the wind shear attributable to the tropopause fold itself then this shear is used to quantify the tendency to generate regions of potential instability for an observed case of a modest tropopause fold it is found that the pv anomaly contained in the tropopause fold contributed substantially to the instantaneous convective destabilization in the sense of increasing the potential instability indeed at some locations it overcame a tendency to stabilize by the atmosphere without the fold on the other hand only a fraction of the region with increased potential instability experienced sufficient large scale ascent to lead to convection and it remains to be seen whether folds in general make a significant contribution to the generation of potential instability that can actually be realized the importance of tropopause folds or indeed of tropopause depressions in general in the context of convection is that their small horizontal scale has the potential to focus and amplify any convective destabilization locally this may account for the localization of outbreaks of severe convective weather which it is important to forecast accurately currently numerical weather prediction models often do not handle these small scales very accurately

flow speed estimated by inverse modeling of sandy sediment deposited by the 29 september 2009 tsunami near satitoa east upolu samoa abstract sandy deposits from the 29 september 2009 tsunami on the east coast of upolu samoa were investigated to document their characteristics and used to apply an inverse sediment transport model to estimate tsunami flow speed sandy deposits 6 to 15 cm thick formed from 25 to 250 m inland sedimentary layers in the deposits that are defined by vertical grain size variation and contacts are interpreted to have formed during onshore runup of two waves deposits at 3 locations 100 170 and 240 m inland contained two layers that are predominately normally graded 80 but contained massive sections 15 and inversely graded sections 5 at their bases about 75 of the total thickness of normally graded intervals exhibits a signature of sediment falling out of suspension at their top this type of grading termed suspension grading here was first recognized in turbidity current deposits and is characterized by the entire distribution shifting finer upwards in a layer as high settling velocity coarser material deposits first and low settling velocity finer material deposits last the jaffe and gelfenbaum 2007 inverse sediment transport model was applied to intervals within layers that exhibited suspension grading to estimate tsunami flow speed and was able to reproduce the general trends of the observed suspension grading a key unknown input in the modeling is the bottom roughness for a bottom roughness parameterization using a manning s n of 0 03 equivalent to a z0 0 006 m for the observed flow depths of 2 3 m flow speeds calculated for the 2 layers at the 3 locations were 3 8 3 6 and 3 7 m s bottom layer earlier wave and 4 4 4 4 and 4 1 m s top layer later wave at 100 170 and 240 m inland respectively these estimates are consistent with the 3 8 m s tsunami flow speed from boulder transport calculations and result in froude numbers of 0 7 1 0 when maximum measured flow depths are used because the inverse model assumes the deposit was formed by sediment falling out of suspension care must be taken to model only intervals of the deposit exhibiting suspension grading including intervals deposited by either bedload or suspended load transport convergences result in higher and sometimes unrealistic tsunami flow speed estimates

large scale washover sedimentation in a freshwater lagoon from the southeast australian coast sea level change tsunami or exceptionally large storm a distinct lens of marine sand up to 90 cm thick confined vertically by peat is found in the upper fill of a closed freshwater back barrier lagoon on the southeast australian coast coring of the deposit suggests it extends continuously up to 600 m inland and tapers landward rising to 1 6 m above principle datum in places the sand is overlain by accumulations of organic rich silt that contain charophytes indicating re estab lishment of lagoon conditions hypotheses considered for the deposition of the sandsheet are higher holocene sea level storms and tsunami ground penetrating radar transects of the seaward dune system suggest a penecontemporaneous erosional contact between a series of truncated pre event dunes and several small over lying post event dunes dating the sandsheet was problematic but it is confined to the last 800 years the young age combined with a lack of associated beach deposits and evidence of wave scouring suggest that a higher sea level hypothesis is unlikely this sand lens is attributed to a large scale washover event from the southeast based on comparisons with modern storm deposits from the same coast and sedimentological diagnostic crite ria derived from studies of modern storm and tsunami deposited sandsheets it is concluded that this sand deposit is the product of a short lived large scale overwash event attributed to a late holocene tsunami

analysis of environmental controls on tsunami deposit texture abstract tsunamis transport large amounts of sediment and can leave recognisable signatures in the landscape the form and composition of onshore tsunami deposits are a function of wave dynamics sediment availability and characteristics of the local environment the latter of which also partially controls preservation of the deposit this research reviews these relationships in a global context and assesses the connection between tsunami deposit particle size and four controlling parameters climate temperature and rainfall density of tsunami sediments degree of coastal protection and distance between tsunami source and sediment deposition an international dataset of tsunami deposit locations and texture was compiled from published literature and existing databases values for environmental variables were calculated for each location from global datasets of temperature rainfall coastline shape and tsunami source locations spearman s rank order correlation principal component analysis pca and hierarchical cluster analysis ca were used to analyse relationships between these variables pca results show an inverse relationship between particle size and sediment density climate variables and distance from source ca results support this suggesting a cluster structure controlled primarily by particle size and secondly by climate and sediment density these relationships can be explained by the influence of the environment on antecedent morphology and the composition of sediments available for tsunami transport

geoarchaeological investigations of a prominent quay wall in ancient corcyra implications for harbour development palaeoenvironmental changes and tectonic geomorphology of corfu island ionian islands greece abstract in antiquity the harbour city of corcyra modern corfu was a prevailing naval power in the mediterranean and had several harbours to host a considerable fleet today these harbours are totally or partly silted and concealed under modern urban infrastructure comprehensive geoarchaeological studies were conducted on the northeastern fringe of the analipsis peninsula where excavations have revealed the archaeological remains of a massive quay wall pierri and arion sites these remains are located east of known ancient harbour structures that belong to the alkinoos harbour our study aimed to reconstruct the palaeoenvironmental setting of the harbour facilities at the pierri site including the analysis of the local sedimentary record in order to detect and differentiate natural and man made triggers that caused environmental shifts at the pierri site we found geoarchaeological evidence for an ancient harbour basin related to the prominent quay wall associated harbour sediments indicate a protected harbour which was developed from an open shallow marine environment most probably by the construction of breakwaters harbour deposits were dated using radiocarbon analyses and diagnostic ceramic fragments to the 4 th to 3 rd cent bc this is in good agreement with the age of the harbour installations as such archaeologically assigned to the classical and hellenistic period the pierri site was possibly in function as a harbour facility even before the 4th cent bc in any case it was strongly hit by an earthquake and associated tsunami event during classical to hellenistic times by this event the harbour was uplifted and covered by event deposits so that it was not usable any more it was subsequently buried by anthropogenic and colluvial sediments overall the pierri coastal archive allowed to identify three distinct tsunami landfall events namely before 2483 2400 cal bc event i after 2483 2400 cal bc and before 370 214 cal bc event ii and during classical to hellenistic times most probably between the 4 th and 3 rd cent bc event iii another tsunami event event iv potentially hit the site when it was dry land ages of tsunami events i ii and candidate tsunami iv are consistent with tsunamis known from the coasts of western greece and southern italy and where thus classified as supra regional tele events event iii was identified as associated to a local earthquake and tsunami by which corfu island was uplifted and at the same time tilted with a vertical offset of 1 74 m from w to e

measurements of dissipation rate in frontal zones summary this paper demonstrates that it is possible to use measurements of the doppler spectrum width from a highresolution radar to obtain quantitative estimates of dissipation rate during the passage of precipitating frontal zones using the high resolution chilbolton radar this method has been applied for the first time to infer the rate at which kinetic energy is dissipated by turbulence within mid and lower tropospheric frontal zones analysis of detailed measurements for one cold frontal region showed multiple shallow sheets of high dissipation rate with spatially averaged values around i x m2s 3 comparable values were also observed in a warm frontal zone the magnitude of the observed dissipation rate supports the hypothesis that mixing played a major role in determining the mean properties of the fronts in that the turbulence acted to destroy the frontal shear layer on a tirne scale of several hours these issues have particular relevance to the representation of fronts within future very high resolution numerical weather prediction models

a five year radar based climatology of tropopause folds and deep convection over wales united kingdom abstracta five year 2006 10 radar based climatology of tropopause folds and convective storms was constructed for wales united kingdom to determine how deep moist convection is modulated by tropopause folds based on the continuous high resolution data from a very high frequency vhf wind profiling radar located at capel dewi wales 183 tropopause folds were identified tropopause folds were most frequent in january with a secondary maximum in july based on data from the u k weather radar network a climatology of 685 convective storms was developed the occurrence of convective storms was relatively high year round except for an abrupt minimum in february april multicellular lines 43 5 were the most common morphology with a maximum in october followed by isolated cells 33 1 with a maximum in may september and nonlinear clusters 23 4 with a maximum in november january convective storms were associated with 104 56 8 of the tropopause folds identified in this study with the associ

convective injection into stratospheric intrusions 1 stratospheric intrusions tropopause folds are known to be major contributors to stratosphere troposphere exchange the specific mixing processes that lead to irreversible exchange between stratospheric intrusions and the surrounding troposphere however are not entirely understood this study presents direct observations of moist convection penetrating into stratospheric intrusions the characteristics of convective injection are shown by using in situ aircraft measurements radar reflectivities and model analyses convective injection is observed at altitudes up to 5 km above the bottom of a stratospheric intrusion aircraft measurements from the stratosphere troposphere analyses of regional transport 2008 start08 experiment show that convective injection in stratospheric intrusions can be uniquely identified by coincident observations of water vapor greater than about 100 ppmv and ozone greater than about 125 ppbv trajectory analyses show that convective injection can impact transport in both directions from troposphere to stratosphere and from stratosphere to troposphere we present a conceptual model of the synoptic meteorological conditions conducive to convective injection in stratospheric intrusions in particular convective injection is found to be associated with a split front where the upper level frontal boundary outruns the surface cold front

distinguishing tsunami and storm deposits an example from martinhal sw portugal abstract geological identification of past tsunamis is important for risk assessment studies especially in areas where the historical record is limited or absent the main problem when using the geological evidence is to distinguish between tsunami and storm deposits both are high energy events that may leave marine traces in coastal stratigraphic sequences at martinhal sw portugal both storm surge and tsunami deposits are present at the same site within a single stratigraphic sequence which makes it suitable to study the differences between them excluding variations caused by local factors the tsunami associated with the lisbon earthquake of november 1st 1755 ad had a major impact on the geomorphology and sedimentology of martinhal it breached the barrier and laid down an extensive sheet of sand as described in eyewitness reports besides the tsunami deposit the stratigraphy of martinhal also displays evidence for storm surges that have breached and overtopped the barrier flooding the lowland and leaving sand layers both marine derived flood deposits show similar grain size characteristics and distinctive marine foraminifera the most important differences are the rip up clasts and boulders exclusively found in the tsunami deposit and the landward extent of the tsunami deposit that everywhere exceeds that of the storm deposits identification of both depositional units was only possible using a collection of different data and extensive stratigraphical information from cores as well as trenches

the holocene storegga slide tsunami in the united kingdom all currently known sites in the united kingdom with evidence for the holocene storegga slide tsunami are described information on the altitude distribution stratigraphical context age particle size profile and microfossil characteristics of the deposits is presented the tsunami involved a greater area than previously described reaching a coastline over 600 km long the ubiquitous sand layer which forms the main deposit associated with the event is shown to exhibit a consistent morphology and a particle size profile marked by fining upwards sequences an analysis of new and previously published radiocarbon dates indicates that from evidence in the united kingdom the event took place sometime around 7100 radiocarbon years bp 7900 calibrated years bp a new isobase model for mainland scotland and adjacent areas providing a preliminary estimate of land uplift since the tsunami is presented the model estimates contemporary sea surface level offshore at 14 m below the present day mean high water spring tides tsunami sediment run up is greatest in inlets where it reaches at least 25 m on shetland and at least 5 m along the mainland coastline to the south and run up of the tsunami would have exceeded these values the tsunami sediments identified here are considered particularly valuable as a synchronous marker horizon

sources and transportation modes of the 2011 tohoku oki tsunami deposits on the central east japan coast abstract we evaluated sediment sources of the 2011 tohoku oki tsunami deposits along a 4500 m inland transect from the central east japan coast using grain size mineralogy and foraminifera analyses the tsunami run up height in our study area was 13 to 20 m near the coastline 1 4 to 2 8 m in the middle of the valley and 1 3 m around the inundation limit the inundation distance was around 4800 m the deposits are composed of sand and mud and show a fining and thinning trend mineral composition of the tsunami deposits was similar to that of coastal dune and beach deposits indicating that most of the tsunami sediment originated from there a minor foraminifera population in the deposit 15 specimens per 5 g of sample compared with 100 specimens per 1 g for typical marine sediment indicates that marine sediment source was not dominant topography played an important role in sediment transport process and deposit distribution the run up wave accelerated faster in concave topography became more erosive and resulted in a thin deposit in topographic lows we infer that the deposits up to 2300 m from the coastline were deposited by bedload and suspension whereas suspension was responsible for deposits farther inland

sedimentology of rocky shorelines 1 a review of the problem with analytical methods and insights gained from the hulopoe gravel and the modern rocky shoreline of lanai hawaii abstract hypotheses advanced concerning the origin of the pleistocene hulopoe gravel on lanai include mega tsunami abandoned beach multiple event rocky shoreline and for parts of the deposit native hawaiian constructions and degraded lava flow fronts uplift of lanai shorelines has been suggested for deposits occurring up to at least 190 m these conflicting hypotheses highlight problems with the interpretation of coarse gravel deposits containing marine biotic remains the geological records of the processes implied by these hypotheses should look very different discrimination among these or any other hypotheses for the origins of the hulopoe gravel will require careful study of vertical and lateral variations in litho and biofacies facies architecture contact relationships and stratal geometries of this deposit observations of modern rocky shorelines particularly on lanai adjacent to hulopoe gravel outcrops have shown that distinctive coarse gravel facies are present several of which occur in specific geomorphic settings tectonic isostatic and eustatic changes which cause rapid shoreline translations on steep slopes favour preservation of former rocky shorelines and associated sedimentary deposits both above and below sea level the sedimentary record of those shorelines is likely to be complex the modern rocky shoreline sedimentary environment is a hostile one largely neglected by sedimentologists a range of high energy processes characterize these shorelines long period swell tsunami and storm waves can erode hard bedrock and generate coarse gravel they also erode older deposits depositing fresh ones containing mixtures of materials of different ages additional gravelly material may be contributed by rivers draining steep hinterlands to fully evaluate rocky shoreline deposition in the broadest sense for both the hulopoe gravel and other deposits sedimentary facies models are needed for rocky shorelines occurring in a range of settings recognition and description of rocky shoreline deposits are crucial for correctly interpreting the geological history of oceanic and volcanic arc islands for distinguishing between ancient tsunami and storm deposits and for interpreting coarse grained deposits preserved on high energy coasts of continents problems include not only the absence of appropriate sedimentary facies models linking rocky shoreline deposits and environments but also until recently lack of a systematic descriptive scheme applicable to coarse gravel deposits generally two complementary methods serve to integrate the wide range of bed and clast attributes and parameters which characterize complex coarse gravel deposits the composition and fabric caf method has a materials focus providing detailed description of attributes of the constituent clasts petrology the proportions of gravel sand and mud and the ways in which these materials are organized the sedimentary facies model building fmb method emphasizes the organization of a deposit on a bed by bed basis to identify facies and infer depositional processes the systematic use of a comprehensive gravel fabric and petrography log gfpl in conjunction with detailed vertical profiles provides visual representations of a range of deposit characteristics criteria useful for distinguishing sedimentary facies in the hulopoe gravel are grain size modes amount of matrix bed geometry sedimentary structures bed fabric and clast roundness

aircraft measurements of potential vorticity and richardson number in baroclinic zones this paper describes a novel technique for deriving potential vorticity and richardson number from aircraft cross sections of baroclinic zones it exploits the fact that gravity waves distort isentropic surfaces so that an aircraft flying horizontally can measure a vertical profile of temperature and wind under favourable conditions the technique is applied to two flights of the uk meteorological research flight s c 130 hercules aircraft in april 1983 and june 1991 it is found to work reasonably well only when large amplitude gravity waves are present values of potential vorticity so derived agree with those calculated in the conventional manner from cross sections and are found to correlate well with ozone mixing ratio

a synthesis and review of the geological evidence for palaeotsunamis along the coast of southeast australia the evidence issues and potential ways forward abstract in recent years the role of extreme events such as tsunamis and storms in shaping coastal evolution and change has been increasingly appreciated around the world tsunami geologists are increasingly recognising the signatures of palaeotsunamis almost everywhere they look and in many cases base their interpretations on similar evidence for quaternary tsunamis first identified in australia geological research suggests that the coast of south east australia and others worldwide may have been impacted by palaeotsunamis many times larger than the catastrophic 2004 indian ocean and 2011 t hoku events in australia the debate centres on the hypothesis that the coast of south east australia preserves evidence for repeated large magnitude quaternary tsunamis if independently validated this hypothesis has profound implications for risk despite the potential importance of this hypothesis no synthesis or comprehensive review of the proposed geological evidence and chronology exists as a result it is difficult to assess the evidence and to draw conclusions about the nature of the hazard and risk along the coast this synthesis details the spatial distribution of reported palaeotsunami deposits along the coast of new south wales south east australia and summarises the distribution of different types of sedimentary and erosional evidence the age range of reported palaeotsunami deposits is identified and mapped before discussing same age chronologically correlated deposits these data are then used to draw broad conclusions about the evidence and identify future research questions to aid in the testing of the hypothesis for repeated tsunami inundation we show that 60 sites are purported to contain evidence of tsunami inundation over 650 km of the south east australian coast with a spatial concentration south of sydney geomorphic evidence distinctly different to that used elsewhere in global palaeotsunami studies is reported at 54 sites with erosional features described as the most frequent indication of inundation proposed tsunami deposits are evident at 44 sites with the dominant deposit type being imbricated boulder stacks radiocarbon dating at 39 of the sites led to a proposition of nine events during the quaternary eight of which occurred during the holocene interestingly 18 sites have no chronological data associated with them alternative interpretations are offered at six type field sites purported to contain palaeotsunami evidence attention is drawn to the disjunct between historical and geological scales of tsunami inundation in the region in addition to the contrast between the scale of reported palaeotsunamis and the robust evidence of smaller events a synthesis of research into the nature of the evidence is offered including critiques of evidence type and mechanisms a critical review of the chronological data is also presented in addition to the recalibration and analysis of published radiocarbon data the paper concludes with an outline of research questions for further work on proposed palaeotsunami sites in australia as well as a statement about likely risk in south east australia it also advocates the need for caution when interpreting evidence for palaeotsunamis elsewhere around the world when those interpretations are based on signatures originally reported in south east australia

coastal sedimentation associated with the december 26 2004 tsunami in lhok nga west banda aceh sumatra indonesia abstract with wave heights of 30 m and runups reaching 50 m a s l and 6 km inland the december 26 2004 tsunami in sumatra was one of the largest tsunamis in recorded human history in this paper we present a description of the event in the lhok nga bay west coast of banda aceh and an interpretation of the tsunami sand deposits mostly based upon grain size analysis the 3 5 km long transect of lampuuk displays two landward fining thinning and sorting sequences the thickest cross sections of the first sequence of deposits 0 1 5 km inland suggest a deposition by three consecutive runups inflows and a final backwash return flow or outflow from 1 5 to 3 5 km inland the record is dominated by the second and highest wave 15 30 m normally graded couplets or triplets of layers were used to identify the runup of each wave the topmost layers interpreted as the backwash deposition describe a seaward sequence of increasing mean grain size and decreasing degree of sorting the local effects of the topography could be identified thickest deposits in the topographic lows 50 80 cm great spatial variations in thickness and upper laminated texture when the sedimentation was limited by steep slopes landward coarsening and very poor sorting at the wave breaking point bimodal grain size distributions reflecting different sources of sediments finally by coupling the longitudinal and vertical trends of the 26 cross sections we propose a model of sediment transport and deposition in a large tsunami wave

impact induced sediment deposition on an offshore mud substrate continental shelf cretaceous paleogene boundary brazos river texas u s a abstract data from twenty brazos river stratigraphic sections of the k pg event deposit are compiled to provide a record of changing depositional processes on the texas continental shelf that left a record of disturbance triggered by the chicxulub impact foraminiferal paleobathymetric depth control of enclosing sediments indicates paleo water depths of 75 125 m with gradual deepening above the k pg boundary outcrop scale observations indicate that the most complete deposits have a basal unit of mudstone clast bearing mass flows indicative of movement by noncohesive laminar flow these mudflows were mobilized by impact generated seismic shaking of seafloor sediment the material of the mass flows consists of reworked shell rich mud matrix containing outsize clasts of consolidated mudstone and cemented concretions the upper parts of the k pg event deposit consist of units of high energy upward fining sandstones each with a basal lag layer of spherule rich coarse sandstone lag overlain by poorly or moderately sorted hummocky cross bedded sandstone the last deposited sandstone is capped with a silt mud suspension settling layer that as much as 10 cm thick where cemented with calcite but is much thinner elsewhere the provenance of these k pg brazos river event deposit sediments is offshore marine muds lower units and shallow water sands higher units with admixed impact spherules and no identifiable land derived component deposition was the result of secondary processes activated by energy from seismic disturbance or by atmospheric disturbance with no deposits directly attributable to tsunami wave control

coastal sedimentation associated with the december 12th 1992 tsunami in flores indonesia this paper presents the result of a detailed granulometric investigation of sediments deposited by a modern tsunami the 1992 tsunami in flores indonesia eyewitness accounts indicate that sediments were deposited upon coastal lowlands over wide areas as a result of the tsunami inundation distinctive vertical and lateral variations in particle size composition are characteristic features of the tsunami deposits and these are intimately related to sedimentary processes associated with flood inundation the geomorphological and sedimentary evidence is used here to establish a preliminary model of tsunami sedimentation this information is believed to be of great value in understanding sedimentary processes associated with tsunami flooding and in the interpretation of palaeo tsunami deposits

the sedimentary record of the 1960 tsunami in two coastal lakes on isla de chiloe south central chile abstract this study describes sediments deposited by the tsunami following the 1960 great chilean earthquake mw 9 5 in two coastal lakes lakes cucao and huelde on the west coast of isla de chiloe south central chile 42 6 s sub bottom profiles and side scan sonar mosaics illustrate the sedimentary context of transects of gravity cores the stratigraphy of both lakes features gyttja sedimentation interrupted by the abrupt emplacement of a sandy layer with mud rip up clasts and a mud cap this sandy layer reflects a sudden change in sedimentary environment most probably caused by a high energy inundation radionuclide analyses 137cs and 210pb date the inundation deposit to shortly before the mid 1960s the only known event that matches the sedimentological and chronological criteria is the ad 1960 tsunami using grain size analysis and comparisons with samples from modern environments we demonstrate that the proximal seaward part of the deposit consists of a mixture of sand derived from subaerial sources and reworked gyttja lake sediment in the distal landward part of lake cucao the sand component is lost and the deposit consists entirely of remobilised lake sediments the repetition of tsunami deposit sequences in lake huelde suggests a minimum of three inundating waves sub bottom profiles and side scan sonar mosaics reveal tsunami inundation over the barrier and more prominently through the outlet river channel the dominant role of the river channel as a pathway for sediment transport is also described in core samples by tsunami deposits that fine away from the channel mouth the identification and description of the deposit left by a known tsunami provide important insights into tsunami sedimentation in coastal lakes and have the potential to help in the search for paleotsunami evidence

sedimentological and geoarchaeological evidence of multiple tsunamigenic imprint on the bay of palairos pogonia akarnania nw greece abstract this paper presents evidence of multiple tsunami impact on the bay of palairos pogonia nw greece during the holocene based on detailed geo scientific studies altogether 41 vibracores were drilled to detect high energy influence in the stratigraphical record layers of coarse grained allochthonous marine deposits were found intersecting autochthonous fine grained back beach sediments in the palairos coastal plain on top of beach or marly bedrock units at pogonia beach and along the pogonia cliff section high energy deposits are associated with specific sedimentary structures such as fining upward sequences rip up clasts basal erosional contact bi to multimodal grain size distribution lamination and co existence of both well rounded and angular sharply edged components all of them typical of tsunami impact macro and microfaunal analyses revealed tsunami related input of numerous ex situ marine species and mostly angular shell debris into quiescent fresh to brackish water environments by high energy and long distance transport geophysical methods helped to find subsurface structures and to seize the lateral extent of tsunami layers ca fe ratios derived from xrf measurements were used to trace tsunami influence inland most important is the widespread spatial distribution of the tsunamites with a lateral extent between 70 m at the pogonia cliff section 200 m at pogonia beach and 1 km in the central palairos plain and overall tendencies of fining and thinning towards inland highest elevations of tsunamites were found around pogonia village at ca 7 5 m a s l vibracore data give evidence that the overall coastal evolution has been strongly affected locally even controlled by multiple high energy impact a conspicuous geoarchaeological tsunamite up to 1 5 m thick was found at pogonia cliff consisting of mixed marine sand pebbles bio erosively altered stones shell debris foraminifers and terrigenous material abundant ceramic fragments bones building material it is directly associated with the submerged remains of an ancient mole which was destroyed and its building material partly dislocated by the same event dating of tsunamites was accomplished by archaeological age determination of diagnostic sherds and by radiocarbon and luminescence dating techniques strong tsunami events were dated to the beginning of the 6th the mid 5th the 4th 3rd and the late 2nd millennia bc as well as to the 4th 3rd century bc on a regional scale the recurrence interval for large events is ca 500 1000 years at least twice during the late holocene the palairos coastal plain was flooded quasi contemporaneously from both the northern and southern side

invigoration and capping of a convective rainband ahead of a potential vorticity anomaly abstractdeep convection frequently occurs on the eastern side of upper level troughs or potential vorticity pv anomalies this is consistent with uplift ahead of a cyclonic pv anomaly and consequent reduction in static stability and increase of convective available potential energy cape nevertheless the causal link between upper level pv and deep convection has not been proven and given that lift moisture and instability must all be present for deep convection to occur it is not clear that upper level forcing is sufficient in this paper a convective rainband that intensified ahead of a cyclonic pv anomaly in an environment with little cape 10 j kg 1 is examined to determine the factors responsible for its intensification the key feature was a low level convergence line arising from the remnants of an occluded front embedded in the low level cyclonic flow the rainband s intensity and morphology was influenced by the remnants of a tropopause fold that capped convection at midlevels in the

determining flow patterns and emplacement dynamics from tsunami deposits with no visible sedimentary structure in the absence of eyewitness reports or clear sedimentary structures it can be difficult to interpret tsunami deposits or reconstruct tsunami inundation patterns the emplacement dynamics of two historical tsunami deposits were investigated at seven transects in okains bay new zealand using a combined geospatial geomagnetic and sedimentological approach the tsunami deposits are present as layers of sand and silt intercalated between soils and become finer and thinner with distance inland the deposits are attributed to the 1960 and possibly the 1868 tsunamis based on radiometric dating and correlation with historical records measurements of magnetic fabric mf anisotropy of magnetic susceptibility and particle size were used to reconstruct the evolution of flow dynamics laterally and vertically a combination of statistical methods including spatial autocorrelation testing spearman s rank order correlation principal component analysis pca and k means cluster analysis was applied to examine relationships between mf parameters and sediment texture and infer depositional hydrodynamics flow patterns deduced from mf show the estuary channel acted as a conduit for inundation with flow commonly aligned sub perpendicular to the estuary bed mf and sediment data suggest deposition occurred from settling during laminar flow evidence of both uprush and backwash deposition as well as wave reflection from infrastructure was found statistical analysis of data showed significant relationships between grain size parameters and mf parameters associated with flow speed and magnetic fabric type pca and cluster analysis differentiated samples into two primary hydrodynamic groups 1 samples deposited from laminar flow and 2 samples deposited close to the limit of inundation which includes samples deposited further inland those affected by flow convergence and those in the upper part of tsunami deposits this approach has potential as a tool for reconstructing hydrodynamic conditions for palaeotsunamis and by combining spatial and statistical analyses large scale investigations can be more easily performed this article is protected by copyright all rights reserved

geological and historical records of tsunami in australia abstract the indian ocean tsunami iot of 2004 has resulted in significant interest within australia about the record of tsunami for the continent because an understanding of tsunami hazard begins with a catalogue of past events here a preliminary catalogue of tsunami affecting australia is presented the catalogue contains entries for 57 tsunami events the oldest event is dated at 3 47 ga the most recent is the july 17th 2006 forty four tsunami were recorded on the new south wales coast although the nw coast of western australia records a significant number of events forty seven events have affected australia since ad1858 maximum run up for an historic event is 6 m asl whilst the maximum run up for a palaeotsunami event is reported at an elevation of at least 100 m asl twenty three percent of historic australian tsunami were generated by unknown causes and papua new guinea the solomon islands and indonesia collectively represent the most important source area of historic tsunami for australia geological records for palaeo and historic tsunami are identified and summarised the geological record of tsunami represents a potentially important source of information for australian tsunami however at the present time the geological record is both limited and controversial and future research should seek to re examine proposed geological evidence of tsunami from an analysis of this preliminary catalogue of australian tsunami a series of key research priorities have been identified to guide future research in the region

a systematic review of geological evidence for holocene earthquakes and tsunamis along the nankai suruga trough japan the nankai suruga trough the subduction zone that lies immediately south of japan s densely populated southern coastline generates devastating great earthquakes magnitude 8 characterised by intense shaking crustal deformation and tsunami generation forecasting the hazards associated with future earthquakes along this 700 km long fault requires a comprehensive understanding of past fault behaviour while the region benefits from a long and detailed historical record palaeoseismology has the potential to provide a longer term perspective and additional crucial insights in this paper we summarise the current state of knowledge regarding geological evidence for past earthquakes and tsunamis along the nankai suruga trough incorporating literature originally published in both japanese and english and enhancing available results with new age modelling approaches we summarise and critically evaluate evidence from a wide variety of sources palaeoseismic evidence includes uplifted marine terraces and biota marine and lacustrine turbidites liquefaction features subsided marshes and tsunami deposits in coastal lakes and lowlands while 75 publications describe proposed evidence from 70 sites only a limited number provide compelling well dated evidence the best available records enable us to map the most likely rupture zones of twelve earthquakes that occurred during the historical period this spatiotemporal compilation suggests that the 1707 ce earthquake ruptured almost the full length of the subduction zone and that earthquakes in 1361 ce and 684 ce may have been predecessors of similar magnitude intervening earthquakes were of lesser magnitude highlighting the variability in rupture mode that characterises the nankai suruga trough intervals between ruptures of the same seismic segment range from 450 years during the historical period over longer timescales palaeoseismic evidence suggests intervals between earthquakes ranging from 100 to 700 years however these figures reflect a range of thresholds controlling the creation and preservation of evidence at any given site as well as the genuine intervals between earthquakes at present there is no geological data that suggest the occurrence of a larger magnitude earthquake than that experienced in 1707 ce however few studies have sought to establish the relative magnitudes of different earthquake and tsunami events along the nankai suruga trough alongside the lack of research designed to quantify the maximum magnitude of past earthquakes we emphasise issues over alternative hypotheses for proposed palaeoseismic evidence the paucity of robust chronological frameworks and insufficient appreciation of changing thresholds of evidence creation and preservation over time as key issues that must be addressed by future research

sedimentology of the december 26 2004 sumatra tsunami deposits in eastern india tamil nadu and kenya the december 26 2004 sumatra tsunami caused severe damage at the coasts of the indian ocean we report results of a sedimentological study of tsunami run up parameters and the sediments laid down by the tsunami at the coast of tamil nadu india and between malindi and lamu kenya in india evidence of three tsunami waves is preserved on the beaches in the form of characteristic debris accumulations we measured the maximum run up distance at 580 m and the maximum run up height at 4 85 m flow depth over land was at least 3 5 m the tsunami deposited an up to 30 cm thick blanket of moderately well to well sorted coarse and medium sand that overlies older beach deposits or soil with an erosional unconformity the sand sheet thins inland without a decrease of grain size the deposits consist frequently of three layers the lower one may be cross bedded with foresets dipping landward and indicating deposition during run up the overlying two sand layers are graded or parallel laminated without indicators of current directions thus it remains undecided whether they formed during run up or return flow thin dark laminae rich in heavy minerals frequently mark the contacts between successive layers benthic foraminifera indicate an entrainment of sediment by the tsunami from water depths less than ca 30 m water depth on the indian shelf these depths are present at distances of up to 5 km from the coast in kenya only one wave is recorded which attained a run up height of 3 m at a run up distance of ca 35 m from the tidal water line at the time of the tsunami impact only one layer of fine sand was deposited by the tsunami it consists predominantly of heavy minerals supplied to the sea by a nearby river the sand layer thins landward with a minor decrease in grain size benthic foraminifera indicate an entrainment of sediment by the tsunami from water depths less than ca 30 m water depth reaching down potentially to ca 80 m the presence of only one tsunami related sediment layer in kenya but three in india reflects the impact of only one wave at the coast of kenya as opposed to several in india grain size distributions in the indian and kenyan deposits are mostly normal to slightly positively skewed and indicate that the detritus was entrained by the tsunami from well sorted pre tsunami deposits in nearshore swash zone and beach environments

evaluation of trace metal enrichments from the 26 december 2004 tsunami sediments along the southeast coast of india the tsunami sediments deposited after the december 2004 tsunami were sampled immediately in the coastal environment of tamil nadu state on the southeast coast of india fifty four sediment samples were collected and 14 representative samples were selected to identify the level of metal contamination in tsunami sediments the results indicate that the sediments are mainly of fine to medium grained sand and contain significantly high contents of dissolved salts in sediments na k ca 2 mg 2 cl in water soluble fraction due to seawater deposition and evaporation correlation of acid leachable trace metals cr cu ni co pb zn indicate that fe mn oxyhydroxides might play an important role in controlling their association between them enrichment of trace metals is observed in all the locations with reference to the background samples high values of trace metals in the southern part of the study area are due to the large scale industries along the coast and they are probably anthropogenic in nature and of marine origin which could cause serious environmental problems

tsunami and palaeotsunami depositional signatures and their potential value in understanding the late holocene tsunami record in recent years much research on modern and palaeotsunami deposits has been published from these studies a range of signature types has been identified identifying and dating such deposits is an important element in understanding late holocene tsunami hazard and risk however important questions such as do modern and palaeotsunami leave similar or dissimilar traces do tsunami leave the same signatures all around the world or are there significant variations and what is the actual record of tsunami in different parts of the world still remain answering these questions is not an easy task but examining megatsunami flood deposits should shed some light on these questions because such high magnitude events should leave very clear and detailed traces within the coastal landscape the coast of se australia is reported to have been affected by numerous palaeomegatsunami in the late holocene as such the coast of new south wales offers an important natural laboratory to examine in detail deposits associated with such events here we summarize the published characteristics of modern and palaeotsunami deposits globally and within australia we briefly outline the tsunami risk to australia before examining a site called minnamurra point on the coastline of se australia south of sydney that has previously been described as containing evidence for a palaeomegatsunami of an unknown age we describe the results of a detailed coastal survey field stratigraphic investigation and various standard laboratory analyses surprisingly we are unable to replicate the previously reported findings of tsunami deposits whilst we prefer the interpretation that the sequence is an in situ soil the sediment sequence examined contains none of the usually reported lines of evidence to demonstrate tsunami provenance we recognize and discuss the significance and difficulty of identifying tsunami deposits in the field and consider the implications of our findings to the wider debate about the preservation of tsunami deposited sediments

subduction zone paleoseismology along the pacific coast of northeast japan progress and remaining problems abstract this paper reviews recent progress in tsunami geology and the history of coastal uplift subsidence along the pacific coasts of hokkaido and tohoku facing the kuril and japan trenches respectively in the last 20 years research by tsunami geologists in northeast japan has focused on extending the record of tsunamis beyond the range of historical documents in the region which span too little time to reveal much of the earthquake history over the last millennia along the coast of hokkaido recurrent sandy deposits are evidence of historical and prehistoric large tsunamis at kiritappu marsh for example at least 15 identified tsunami deposits occurred between 200 and 6 000 years ago the spatial distribution of the most recent prehistoric tsunami deposit that of the so called 17th century earthquake and tsunami exceeds historical and recent tsunami inundations in eastern hokkaido numerical simulations of this event require a multi segment fault model with variable slip mw 8 8 encompassing both the tokachi oki and nemuro oki regions to reproduce the observed deposit distribution in eastern hokkaido the recurrence interval of such multi segment earthquakes along the southern kuril trench is estimated to be 100 800 years based on tephrochronological and radiocarbon evidence tsunami deposits are also associated with historical earthquakes in 1843 and 1894 in eastern hokkaido and with the 1640 komagatake eruption in western hokkaido the 17th century earthquake probably triggered postseismic coastal deformation diatom based transfer functions suggest rapid subsidence before the event and gradual uplift afterward and historical volcanic ash layers indicate that gradual postseismic uplift occurred over decades a simple dislocation model can explain such gradual uplift as an aseismic fault extension after the 17th century event in the tohoku region a tsunami deposit associated with the 869 jogan earthquake has been identified and the inundation area of this event has been constrained based on the lateral extent of the tsunami deposit and its stratigraphic position beneath the historical to a tephra 915 ce land level changes at odaka fukushima prefecture associated with the jogan event have been estimated based on changes of fossil diatom assemblages below and above the tsunami deposit numerical simulations based on geological evidence and observations of the 2011 tohoku tsunami deposit suggest that the jogan event was a plate boundary rupture at least 200 km long along the japan trench mw 8 3 8 6 the 1454 kyotoku tsunami is also considered to have been generated by a rupture area including the miyagi oki region part of the jogan rupture it remains unclear whether the 869 1454 and 2011 tsunamis were similar in size and source if they were the recurrence intervals of such events near sendai are less than 600 years and more regular than those for multi segment earthquakes along the kuril trench

a simple model for calculating tsunami flow speed from tsunami deposits abstract this paper presents a simple model for tsunami sedimentation that can be applied to calculate tsunami flow speed from the thickness and grain size of a tsunami deposit the inverse problem for sandy tsunami deposits where grain size and thickness vary gradually in the direction of transport tsunami sediment transport is modeled as a steady spatially uniform process the amount of sediment in suspension is assumed to be in equilibrium with the steady portion of the long period slowing varying uprush portion of the tsunami spatial flow deceleration is assumed to be small and not to contribute significantly to the tsunami deposit tsunami deposits are formed from sediment settling from the water column when flow speeds on land go to zero everywhere at the time of maximum tsunami inundation there is little erosion of the deposit by return flow because it is a slow flow and is concentrated in topographic lows variations in grain size of the deposit are found to have more effect on calculated tsunami flow speed than deposit thickness the model is tested using field data collected at arop papua new guinea soon after the 1998 tsunami speed estimates of 14 m s at 200 m inland from the shoreline compare favorably with those from a 1 d inundation model and from application of bernoulli s principle to water levels on buildings left standing after the tsunami as evidence that the model is applicable to some sandy tsunami deposits the model reproduces the observed normal grading and vertical variation in sorting and skewness of a deposit formed by the 1998 tsunami

recent marine lithofacies in cadiz bay sw spain sequences processes and control factors abstract the analysis of the lithofacies preserved in recent marine sediments in cadiz bay shows major fluctuations in the depositional regime which are characterized by significant energy variations drilling and geophysical data indicate the presence of coarse materials such as gravel imbricated shells and plant remains and frequent flow structures which have been interpreted as a result of the action of high energy events while the finest sediments present in the cores are interpreted as a consequence of the ordinary depositional regime fundamentally controlled by normal storm surge and tidal currents three types of sequence are differentiated very high energy vhe sequences high energy he sequences and low energy le sequences the vhe and he sequences were caused by highly energetic oceanic agents such as great waves generated by major storms or tsunamis there is no historical evidence of the action of sufficiently energetic storms while the geological setting of cadiz bay is located near the azores gibraltar fault the limit between the african and european plates points to tsunami action as being the most plausible option to explain the origin of these deposits the radiocarbon age indicates that these high energy events happened between 898 120 bc and 849 121 ad some of which coincide with several historically documented tsunamis affecting the cadiz coast this data indicates that the period from 849 ad to 1200 ad was a time of intense seismic and tsunamigenic activity

sedimentologic and geomorphologic tsunami imprints worldwide a review abstract tsunami events with extreme effects on sedimentary transport or considerable alterations of the coastal configuration are rather rare regarding human history but considering geological timescales they occur frequently at least 100 megatsunami in different parts of the world have been recorded in the past 2000 years but presumably far more have failed to be noticed during historical times and are not mentioned either in written or oral ancient records therefore the topic of paleotsunami requires inevitable sedimentological and geomorphological research however field research concerning paleotsunami is astonishingly rare within the scientific approach and only 5 of the existing tsunami literature is related to this subject future efforts in paleotsunami research should focus on the geological evidence of these mega events to clarify their contribution to coastal forming processes this paper reviews the state of the art knowledge of sedimentologic and geomorphic imprints of tsunami along the world s coastlines in order to highlight the need for more detailed studies of paleotsunami depositional and geomorphological traces

sedimentary features of tsunami deposits in carbonate dominated beach environments a case study from the 25 october 2010 mentawai tsunami this study provides a case history of tsunami deposition in a carbonate dominated environmental setting we present the results of a sedimentological investigation conducted on deposits formed by the 25 october 2010 mentawai island tsunami and report on deposits analyzed at three sites on north pagai island sabeu gunggung macaroni resort and tumalei the deposits are mainly composed of medium to coarse sand sized fragments of corals shells and foraminifera with thickness ranging from 3 to 26 cm the deposits consist of two to five layers with fining upward trends dominating local topography noticeably affects the thickness number of layers and distribution of tsunami deposits the foraminiferal assemblage and diversity vary at each sample point along transect and between different transects based on the foraminiferal content most of the deposit material likely came from shallower depths in addition density distribution of the tsunami deposit material exhibits some degree of variability in terms of the range of densities in each sample and the trend of the overall density along each transect in contrast to heavy mineral dominated deposits the density of carbonate grains as a function of size may be an important consideration when carbonate dominated deposits are used to interpret hydraulic conditions that created a particular tsunami deposit since there are relatively few studies of tsunami deposits in carbonate dominated environmental settings such as the mentawai islands our study provides a useful case history of tsunami deposition in such an environmental setting

stratosphere troposphere transport in a numerical simulation of midlatitude convection 1 the transport of stratospheric air deep into the troposphere via convection is investigated numerically using the uk met office unified model a convective system that formed on 27 june 2004 near southeast england in the vicinity an upper level potential vorticity anomaly and a lowered tropopause provides the basis for analysis transport is diagnosed using a stratospheric tracer that can either be passed through or withheld from the model s convective parameterization scheme three simulations are performed at increasingly finer resolutions with horizontal grid lengths of 12 4 and 1 km in the 12 and 4 km simulations tracer is transported deeply into the troposphere by the parameterized convection in the 1 km simulation for which the convective parameterization is disengaged deep transport is still accomplished but with a much smaller magnitude however the 1 km simulation resolves stirring along the tropopause that does not exist in the coarser simulations in all three simulations the concentration of the deeply transported tracer is small three orders of magnitude less than that of the shallow transport near the tropopause most likely because of the efficient dilution of parcels in the lower troposphere

flow speed estimated by inverse modeling of sandy tsunami deposits results from the 11 march 2011 tsunami on the coastal plain near the sendai airport honshu japan abstract tsunami deposits contain information about the flow that created them which can be interpreted to estimate tsunami magnitude sandy deposits near sendai airport are modeled using an inverse sediment transport model to explore the spatial and temporal variation of tsunami flow speed in the 11 march 2011 tohoku oki tsunami the 2011 deposits contain grain size signatures of both sediment transport convergences and sediment settling out of suspension sediment transport convergences form massive or inversely graded intervals sediment falling out of suspension forms a specific type of normal grading termed suspension grading the jaffe and gelfenbaum 2007 inverse sediment transport model which relates the thickness and bulk grain size of suspension graded intervals to tsunami flow speed was applied to 24 suspension graded intervals ranging in thickness from 2 to 4 cm at 7 trenches located from about 250 to 1350 m inland from the shoreline modeled tsunami flow speeds range from 2 2 to 9 0 m s and were strongly dependent on the choice of manning s n roughness parameterization flow speeds were highest from about 75 300 m landward of the forested sand dunes where the tsunami encountered lower roughness in a low lying area as it traveled downslope and decreased by 16 as the tsunami moved inland over the subsequent 596 m as many as 5 suspension graded intervals interpreted as forming during the onshore flow of up to 5 waves were identified at each location with a tendency for an inland decrease in the number of suspension graded intervals suggesting fewer waves inland tsunami flows tended to be fastest in the lower two intervals earlier waves and slowest in the uppermost interval last wave of the deposits modeled reconstructions of the suspension graded intervals at a vertical resolution of 1 cm reproduced observed upward fining of the distributions reasonably well supporting the use of the inverse model estimates of the time required to form 99 of the thickness of the suspension graded intervals ranged 2 to 5 min allowing that sediment falling from suspension could have formed these portions of the deposits in the time between waves application of the inverse model to determine paleotsunami flow speeds from deposits although now possible is complicated by uncertainty in roughness as inverse approaches to estimating roughness and tsunami flow speed improve the magnitude of paleotsunamis will be better understood and the ability to assess tsunami hazard from paleotsunami deposits will improve

high resolution analysis of a tsunami deposit case study from the 1755 lisbon tsunami in southwestern spain abstract a multi proxy approach using trench sediment analysis on the southwestern coast of spain los lances bay andalusia provides a high resolution record of the 1755 lisbon tsunami and offers new means to interpret tsunami deposits a combination of sedimentological grain size sorting ams micromorphological x ray tomography and radiography thin sections and geochemical analyses x ray microfluorescence icp aes combines to provide a comprehensive reconstruction of the different phases of tsunami deposition and flow dynamics vertical variations in sediment texture fabric and composition of the 1755 tsunami deposits in los lances are then discussed with reference to existing literature on diagnostic criteria commonly used for identifying and interpreting tsunami deposits finally possible leads for future investigation are proposed

tsunami sediments and their foraminiferal assemblages abstract tsunami hazard assessment begins with a compilation of past events that have affected a specific location given the inherent limitations of historical archives the geological record has the potential to provide an independent dataset useful for establishing a richer chronologically deeper time series of past events recent geological studies of tsunami are helping to improve our understanding of the nature and character of tsunami sediments wherever possible geologists should be working to improve the research tool kit available to identify past tsunami events marine foraminifera single celled heterotrophic protists have often been reported as present within tsunami deposited sediments but in reality little information about environmental conditions and by analogy the tsunami that deposited them has been reported even though foraminifera have an enormous capacity to provide meaningful palaeo environmental data here we review what foraminifera are describe their basic form and significance summarise where they have been reported in tsunami sediments and identify what can be learnt from them we review the gaps in our understanding and make recommendations to assist researchers who examine foraminiferal assemblages in order to enhance their use within tsunami geology

reconstructing tsunami run up from the characteristics of tsunami deposits on the thai andaman coast abstract tsunamis can leave deposits on the land surface they inundate the characteristics of tsunami deposits can be used to calculate tsunami run up height and velocity this paper presents a reconstruction of tsunami run up from tsunami deposit characteristics in a simple mathematical model the model is modified and applied to reconstruct tsunami run ups at ao kheuy beach and khuk khak beach phangnga province thailand the input parameters are grain size and maximum run up distance of the sediment the reconstructed run up heights are 4 16 4 91 m at ao kheuy beach and 5 43 9 46 m at khuk khak beach the estimated run up velocities maximum velocity at the still water level are 12 78 19 21 m s in the area located 70 140 m inland to the end of run up inundation estimated mean run up velocities decrease from approximately 1 93 m s to 0 m s reasonably good agreements are found between reconstructed and observed run up heights the tsunami run up height and velocity can be used for risk assessment and coastal development programs in the tsunami affected area the results show that the area from 0 to 140 m inland was flooded by high velocity run ups and those run up energies were dissipated mainly in this area the area should be designated as either an area where settlement is not permitted or an area where effective protection is provided for example with flood barriers or forest

use of anisotropy of magnetic susceptibility ams in the study of tsunami deposits application to the 2004 deposits on the eastern coast of banda aceh north sumatra indonesia abstract we studied emplacement dynamics of the december 26 2004 tsunami deposits in artificial shallow ponds and in shallow lagoons along the northern coast of sumatra in banda aceh area successive tsunami waves inundated topographic lows which acted as sediment traps and favored preservation of deposits individual waves led to the deposition of fining upwards sedimentary sequences this multiple normal grading deposit with a thickness ranging from 2 to 80 cm constitutes a site of major interest for the study of the deposits emplaced by a tsunami wave train the main interest lies in the characteristics of the deposits that can be correlated to the behavior of the waves attested by numerous testimonies in this setting we aimed at testing the applicability of the ams anisotropy of magnetic susceptibility technique as a proxy of unconsolidated sediment fabric the combination of this proxy and traditional sedimentary analysis helped reconstructing the hydrodynamic conditions particularly the flow direction prevailing during sedimentation we applied the ams technique on eight sections stretching inland from 1 5 km to 2 2 km from the pre tsunami coastline grain size and ams data from these deposits provide similar and partially complementary information traction dominates in the basal parts of the deposits and occurs mainly for the basal layers of the sequences whereas settling dominates for the upper layers of these sequences the vertical evolution of the ams parameters within the deposits is related to the arrival of the successive waves with variations in the traction and decantation processes during deposition variations of current strength during sedimentation are related to the wave s momentum and to the progressive infill of topographic depressions the vertical change of the fifth coarsest percentile vs the median grain sizes of the deposits suggests strong variations of the energy of the currents and confirms the evolution of the ams parameters in the present study the fabric of the deposits which developed exclusively during the uprush phase of the cycle also allows the reconstruction of flood directions that are both normal and parallel to the shoreline with variations related to flow dynamics mean grain size and local topographic control due to the absence of backwash in between the waves and low velocity of the final backwash information about the sedimentation conditions of the tsunami deposits appears to be better preserved in topographic depressions in areas located remote from the seashore the ams proxy appears to be a promising tool for further studies of recent and paleo tsunami deposits

maximum sand sedimentation distance after backwash current of tsunami simple inverse model and laboratory experiments abstract estimating the magnitude of a past tsunami is important in tsunami hazard assessment and protection in particular sand deposition data provide important information in such processes the effects of the backwash current of a tsunami on the sand distribution should be considered in estimating the historical tsunami magnitude by field survey data a simple inverse model was developed to estimate the maximum distance of a sand deposit from a tsunami considering not only sedimentation but also re erosion by the backwash current laboratory experiments were conducted to understand the characteristics of the effects of backwash current and estimate the parameters needed for the model development the proposed simple model consists of several macroscopic characteristics of both non tsunami terms such as land slope and sand characteristics and comprehensive tsunami properties such as the energy gradient of the backwash current and tsunami height it was assumed that the velocity and water depth of the backwash current are linearly approximated by the law of tsunami current conservation on a land slope to estimate the decrease in sand layer depth due to re erosion by the backwash current the tractive force of the current and the drag force of the sand removed were related with one empirical parameter e laboratory flume experiments were conducted to calibrate the parameter sensitivity analysis confirmed the effect on the changes in the value of e on the sand deposition distance to be smaller than that of other parameters in spite of many simple assumptions the estimate agreed well with the sand deposit distance of the 2011 great east japan earthquake tsunami finally the limitations and effectiveness of the model are discussed this study developed a useful method for measuring backwash in a relatively extensive land slope where the effect of the backwash current is large and regional topography and land use effects are small

linking tsunami deposits submarine slides and offshore earthquakes abstract the recognition that many tsunamis are associated with coastal sedimentation has been of great value in the study of tsunamis prehistorically geological investigation of such sediments has resulted in the identification of a series of palaeotsunamis that appear to have taken place in different areas of the world in most cases however it has proved difficult to link former tsunamis to specific source mechanisms studies of modern tsunamis have also faced difficulties in the recognition of the specific source mechanisms for example offshore earthquakes may trigger submarine slides that combine to produce complex patterns of tsunami flooding at the coast

boulder accumulations related to storms on the south coast of the reykjanes peninsula iceland coastal boulder accumulations are often mentioned in the literature even though their interpretation remains difficult especially along rock coasts affected both by storms and tsunamis studies on the geomorphic impact of such high energy events are actually of great interest since their intensity and frequency are key issues for the future evolution of coasts in the framework of the global change the southwest coast of iceland faces the powerful storms of the north atlantic ocean with wave heights of more than 15 m the probability for past and present tsunamis to hit this coast is very low in this paper we describe boulder accumulations along the volcanic rock coast of reykjanes southwest iceland they consist of cliff top boulders clusters and ridges beaches and boulder fields large boulders up to 70 t in weight have been transported and deposited up to 65 m inland 6 masl the maximum limit of boulder deposition and driftwood was found respectively 210 m and 550 m inland storms appear to be a predominant factor in the geomorphic evolution of reykjanes coasts our observations also give new insight for the interpretation of coastal boulder accumulations processes of erosion and deposition by tsunamis are a rising topic in the literature and the effects of recurrent and powerful storms are neglected

tsunami inundation sediment transport and deposition process of tsunami deposits on coastal lowland inferred from the tsunami sand transport laboratory experiment tstle abstract the processes of tsunami inundation sediment transport and deposition on coastal lowlands are investigated experimentally we conducted large scale experiments with land slopes of 0 00 and 0 01 and compared them with experiments conducted previously with a slope of 0 02 the ratio of marine originated sediment in the inland deposits decreased as the land slope decreased reflecting the strong inundation flow and weak return flow the sediment concentration near the bed increased remarkably and supplied a greater quantity of coarse sand inland when the land slope decreased indicating the strong influence of land slope on bed load the extent of sandy deposits and the inundation limit nearly corresponded with the sloping topographies however the inundation flow reached much farther inland than the sandy deposits on the flat i e level topography this was because the extent of sandy deposits was determined by the flow speed which depended in turn on the wave speed whereas the inundation limit was determined by the inland water mass which depended in turn on the waveform the floating load reached the inundation limit and formed very thin and sparse muddy deposits considering the uncertainty of the waveform and the difficulty of detecting muddy deposits it is more feasible to estimate the wave speed from the extent of sandy deposits the spatial distributions of sandy deposits for various waves land slopes and topographies were characterized by the nondimensional area density and inundation distance this result suggested the possibility of quantitative comparison among field investigations of tsunami deposits under various conditions the formation of an inverse grading layer experimentally observed in a wide range of inland deposits was attributed to kinetic sieving the bed load under slow deposition was speculated to thicken the inverse grading layer by reworking the coarse sand additionally the sediment behind dunes became liquefied and showed shear deformation during the erosion the shear deformation of liquefied sediment below the erosional surface might leave sedimentary characteristics specific to earthquake tsunamis

tsunamis as geomorphic crises lessons from the december 26 2004 tsunami in lhok nga west banda aceh sumatra indonesia abstract large tsunamis are major geomorphic crises since they imply extensive erosion sediment transport and deposition in a few minutes and over hundreds of kilometres of coast nevertheless little is known about their geomorphologic imprints the december 26 2004 tsunami in sumatra indonesia was one of the largest and deadliest tsunamis in recorded human history we present a description of the coastal erosion and boulder deposition induced by the 2004 tsunami in the lhok nga bay located to the west of banda aceh northwest sumatra the geomorphological impact of the tsunami is evidenced by beach erosion some beaches have almost disappeared destruction of sand barriers protecting the lagoons or at river mouths numerous erosion escarpments typically in the order of 0 5 1 5 m when capped by soil and more than 2 m in dunes bank erosion in the river beds the retreat along the main river is in the order of 5 15 m with local retreats exceeding 30 m large scars typically 20 50 cm deep on slopes dislodgement of blocks along fractures and structural ramps on cliffs the upper limit of erosion appears as a continuous trimline at 20 30 m a s l locally reaching 50 m the erosional imprints of the tsunami extend to 500 m from the shoreline and exceed 2 km along riverbeds the overall coastal retreat from lampuuk to leupung was 60 m 550 000 m 2 and locally exceeded 150 m over 276 000 m 3 of coastal sediments were eroded by the tsunami along the 9 2 km of sandy coast the mean erosion rate of the beaches was 30 m 3 m of coast and locally exceeded 80 m 3 m the most eroded coasts were tangent to the tsunami wave train which was coming from the southwest the fringing reefs were not efficient in reducing the erosional impact of the tsunami the 220 boulders measured range from 0 3 to 7 2 m large typically 0 7 1 5 m with weights from over 50 kg up to 85 t we found one boulder less than 1 m large at 1 km from the coastline but all the others were transported less than 450 m 30 m and the moderate tsunamis height