large bedform generated by the 2011 tohoku oki tsunami at kesennuma bay japan abstract the 11 march 2011 m w 9 0 tohoku megathrust earthquake off the pacific coast of japan was a salient event in the history of japan the resultant huge tsunami the 2011 tohoku oki tsunami inundated a vast coastal area of northeastern japan causing widespread devastation twenty days after the tsunami we analyzed the impact of the tsunami on the sea bottom of the kesennuma inner bay using side scan sonar to explore the damage and bathymetric change in the harbor herein we present the first direct evidence that the sea bottom sediments of around 10 15 m were largely reworked by the tsunami to thickness of a few meters and that large dunes were formed by the tsunami considering that the sea wave influence is as weak as it is inside the inner bay the potential exists that even meter thick paleo tsunami deposits are preserved in shallow sea bottoms with large bedforms this finding will be a stepping stone to future geological studies of tsunami effects in shallow sea regions

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

quarrying transport and deposition of cliff top storm deposits during extreme events banneg island brittany abstract on 10 march 2008 a particularly high energy storm hit the french atlantic coast and the western part of the english channel this storm did not generate exceptionally high waves significant and maximum wave heights recorded in the iroise sea brittany reached 10 85 and 18 17 m respectively whereas during the 1989 90 winter storms they had reached 12 and 20 m respectively the exceptional character of the march 2008 storm event arises from the fact that it occurred during an exceptional spring tide from a morphogenetic point of view the effects of this storm in terms of block quarrying transport and deposition on banneg island brittany were significant this study shows that the weight of the blocks displaced during the event was between 0 07 and 42 64 t with a median value of 0 72 t more than 60 of the blocks were quarried from the wave scoured cliff top platform demonstrating that the favoured zone for supplying material was located inland of the cliff two dominant modes of transport were involved depending on the relationship between extreme water levels and cliff height at the centre of the island the height of the waves breaking over the top of the cliffs on the western coast resulted in a torrential surge that flowed out towards the eastern coast of the island over a landward sloping platform on the western coast of the island blocks weighing between 0 3 and 1 4 t were displaced between 50 and 90 m from the cliff edge by this flow at the flow outlet on the eastern coast 90 m from the western cliff edge a pit 1 6 m deep was excavated at porz ar bagou cove and some of the mobilised blocks were deposited in two parallel lobes about 40 m seaward of the eastern shoreline elsewhere on the island block transport occurred by airborne projection although wave heights were lower than the altitude of the cliffs the pressure exerted by breaking waves on the bedrock was sufficient to quarry and displace blocks a temporal comparison of the changes recorded in the double and triple boulder ridges showed that the most seaward ridges were practically untouched with the most important changes occurring in the second and third ridges these observations allow us to propose a spatio temporal model for the accretion of cliff top storm deposits ctsds with the various stages of ctsd formation being directly related to the morphological evolution of the cliff

nearshore tsunami inundation model validation toward sediment transport applications model predictions from a numerical model delft3d based on the nonlinear shallow water equations are compared with analytical results and laboratory observations from seven tsunami like benchmark experiments and with field observations from the 26 december 2004 indian ocean tsunami the model accurately predicts the magnitude and timing of the measured water levels and flow velocities as well as the magnitude of the maximum inundation distance and run up for both breaking and non breaking waves the shock capturing numerical scheme employed describes well the total decrease in wave height due to breaking but does not reproduce the observed shoaling near the break point the maximum water levels observed onshore near kuala meurisi sumatra following the 26 december 2004 tsunami are well predicted given the uncertainty in the model setup the good agreement between the model predictions and the analytical results and observations demonstrates that the numerical solution and wetting and drying methods employed are appropriate for modeling tsunami inundation for breaking and non breaking long waves extension of the model to include sediment transport may be appropriate for long non breaking tsunami waves using available sediment transport formulations the sediment deposit thickness at kuala meurisi is predicted generally within a factor of 2

bonaire s boulder fields revisited evidence for holocene tsunami impact on the leeward antilles abstract supralittoral boulders and blocks are prominent sedimentary features along rocky shorelines worldwide in most cases their deposition is attributed to high energy wave events tsunamis severe storms even though tsunami waves are expected to have higher transport capacities compared to storm waves megaclasts of up to 100 t were observed to have been moved laterally by the latter waveform the deduction of certain extreme wave events tsunamis severe storms from the boulder record thus remains a major challenge in palaeo event research the debate on their differentiation is ongoing at the eastern coast of bonaire leeward antilles in the southern caribbean numerous limestone blocks and boulders up to c 130 t are distributed on top of a 3 6 m a s l above mean sea level palaeo reef platform disagreement exists among a number of authors concerning the transport processes involved in the formation of the boulder fields in this paper state of the art modelling approaches of coastal boulder entrainment and transport were applied in order to provide new and more reliable data to support challenge the working hypothesis of tsunami deposition to improve the reliability of the boulder transport model more realistic input parameters were provided by new dgps measurements of the boulder dimensions and the calculation of bulk densities by taking into account the heterogeneity of the reef rock boulders existing hydrodynamic equations were modified to allow for the irregular shape and real dimensions of the boulders the results indicate that i boulder weight and dimension and thus ii calculated wave energy and wave heights were overestimated in most of the previous studies where calculations of boulder volume were based on multiplication of the main axes the results of this study and wave heights observed during recent severe tropical cyclones seem to rule out storm generated waves for the dislocation of the largest blocks however the majority of coarse clast deposits may have been generated by periodic hurricane swells the results underline the significance of more realistic field data in modelling boulder transports by waves

spatial thickness variability of the 2011 tohoku oki tsunami deposits along the coastline of sendai bay abstract soon after the 2011 tohoku oki event approximately 1300 tsunami deposit thickness data were collected spatially by the governors to cover the entire tsunami affected area sendai plain along the sendai bay coastline this dataset along with high resolution and high precision data of flow depth and pre tsunami and post tsunami elevation enables us first to conduct a direct comparison of the sedimentation and erosion volumes as well as the tsunami hydrodynamic features e g flow depth and sediment thickness the total balance of sedimentation and erosion volumes revealed that the volume of tsunami deposited sediments can be explained roughly using the erosion volumes at the beach and sand dunes for sandy deposits and at rice paddy fields for muddy deposits both the flow depth and sediment thickness showed positive correlations with the distance from the shoreline while sediment thickness is no correlation to the elevation except in the zone closest to the shoreline where erosion is present in addition a statistical relation was found between the flow depth and sediment thickness in fact the frequency distribution of sediment concentration defined here as the sediment thickness divided by the maximum flow depth at each survey site fits well with the logarithmic normal distribution with geometric average of about 2 this fit indicates that the tsunami deposits on the sendai plain can be explained generally if we simply assume that the saturated level of the sediment concentration in the flow is limited to about 2 on average irrespective of the grain size such a simple explanation might be applicable only for the tsunami deposits on the sendai plain because the topography is remarkably flat and low therefore the tsunami inundation process is relatively simple nevertheless a possible relation between tsunami flow depth and sediment thickness suggested here would be very useful to consider the ideal sedimentary process of the tsunami deposits and to improve forward and inverse modelings

numerical analysis of boulder transport by the 2004 indian ocean tsunami at pakarang cape thailand at pakarang cape thailand we conducted field observations and numerical modeling of the spatial and grain size distributions and sources of boulders deposited by the 2004 indian ocean tsunami the boulders are a very rare example of boulders for which a tsunami origin is well confirmed numerical modeling of the tsunami s boulder transport revealed that the grain size and spatial distributions of boulders are explainable by the initial distribution of boulders at the source and the tsunami s local behavior which is controlled strongly by the tsunami hydrodynamic features and local topography soon after the bore front reached at the beach the tsunami s hydraulic force on the tidal bench decreased suddenly below the critical force necessary to displace the boulder because of the seaward propagation of the reflected wave that had been generated at the beach slope consequently all boulders were deposited below the high tide line and subsequently concentrated at the western coast of the cape absence of boulders that had been originally deposited deeper than 10 m water depth is also explained by this reflected wave because the wave passed over boulders that had been originally deposited at 10 m water depth before the boulder crossed the reef edge our well tuned model elucidates how the tsunami was able to deposit large boulders on the tidal bench at the cape the results demonstrate that theoretically up to 250 tons of boulders might have been emplaced on the tidal bench by the 2004 indian ocean tsunami at the cape approximately 7 m wave height the calculated maximum weight is of comparable order to that of boulders around the world that are inferred to be of tsunami origin although we infer that the weight is determined based on the sensitive balance of the local topography hydrodynamic features of the tsunami and the initial distribution of boulders at the source

deposits flow characteristics and landscape change resulting from the september 2009 south pacific tsunami in the samoan islands the september 29th 2009 tsunami caused widespread coastal modification within the islands of samoa and northern tonga in the south pacific preliminary measurements indicate maximum runup values of around 17 m okal et al 2010 and shore normal inundation distances of up to 620 m jaffe et al 2010 geological field reconnaissance studies were conducted as part of an unesco ioc international tsunami survey team survey within three weeks of the event in order to document the erosion transport and deposition of sediment by the tsunami data collected included a general morphology and geological characteristics of the coast b evidence of tsunami flow inundation flow depth and direction wave height and runup c surficial and subsurface sediment samples including deposit thickness and extent d topographic mapping and e boulder size and location measurements four main types of sedimentary deposits were identified a gravel fields consisting mostly of isolated cobbles and boulders b sand sheets from a few to 25 cm thick c piles of organic mostly vegetation and man made material forming debris ramparts and d surface mud deposits that settled from suspension from standing water in the tsunami aftermath tsunami deposits within the reef system were not widespread however surficial changes to the reefs were observed

cliff top storm deposits on banneg island brittany france effects of giant waves in the eastern atlantic ocean this study is based on the morphosedimentary analysis of the cliff top storm deposits accumulated on the coast of banneg island located in the archipelago of molene brittany france these ctsds comprise large tabular clasts quarried from the upper part of the cliff and the backing scoured platform by giant oceanic storm waves impacting directly the western coast of the island an analysis of the distribution and the geomorphology of these accumulations were carried out using the dgps topographic surveys most of the clasts are organised into imbricate boulder clusters or ridges deposited between 7 5 and 14 5 masl 52 accumulations were inventoried from the north to the south of the island representing a global volume of 1000 m3 the median size of the clasts calculated is equivalent to 0 8 0 6 0 4 m and a weight of 0 6 t the largest one measuring 5 3 3 9 0 5 m 32 t is located in the centre of the island ridge 28 it has been deposited 14 m inland from the edge of the cliff at the elevation of 9 m sediment analysis shows that clast sizes become smaller with increasing distance from the shoreline but there is no relationship between the sorting and the distance inland a study of the hydrodynamic conditions inducing clast transport was undertaken by an analysis of the wave data from the 1989 to the 1990 winter storms models of wave runup indicate that their highest water levels may have reached up to 19 masl 5 to 10 m higher than the top of the cliff submersion by giant storm waves has been more important and frequent in the centre and the south of the island wave data over the 1979 to the 2007 period shows that no events as powerful as those of the 1989 to the 1990 winter were recorded during the last 30 years yet it appears that the 1979 1990 decade was characterized by important morphogeneous events while the following period 1990 2007 has experienced a sharp decrease in storm events these variations could be attributed to the inversion from a negative towards a positive phase in the north atlantic oscillation index

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

numerical assessment of bathymetric changes caused by the 2004 indian ocean tsunami at kirinda fishery harbor sri lanka abstract thus far various numerical models have been developed and improved to aid understanding of the sediment transport process due to tsunamis however the applicability of these models for the field scale bathymetric change remains a major issue due to the scarcity of measured bathymetric data immediately before and after tsunamis this study focuses on assessing the applicability of the sediment transport model by comparing the model results with measured bathymetry data obtained one month before and two months after the 2004 indian ocean tsunami at kirinda fishery harbor sri lanka obtained model results were compared with measured data along four different transects in particular similar to the measured data the model reproduced the bed level change at the harbor mouth well although it shows some discrepancy on bathymetric change along the shoreline which is directly affected by littoral drift therefore it is noted that the divergence of reproducing the local bathymetry change is due to the normal wind wave effect on measured data and the model limitations hence we included the wind wave effect in modeled data and the discrepancy between measured and modeled data was reduced furthermore the modeled bed level change indicates a dynamic behavior in terms of the net variation during the tsunami flow such that deposition dominates in the inflow and erosion dominates in the backflow both bed level variation and the suspended load concentration reveal that the large amount of eroded sediment attributable to tsunami waves was in suspended form and was deposited in the nearshore area after the water fluctuation had abated the model results further indicate that eroded sediment at the initial depth deeper than 11 m might be brought by the incoming tsunami waves and deposited in the nearshore area where the depth is shallower than 7 m

cliff top megaclast deposits of ireland a record of extreme waves in the north atlantic storms or tsunamis past occurrences of major tsunami in the global record have often been inferred from the presence of megaclast accumulations at significant heights above sea level which sometimes exhibit a pronounced seaward directed imbricate fabric the aran islands off the west coast of ireland exist in a marine environment which is totally unprotected from the most extreme sea states encountered in the north atlantic spectacular megaclast accumulations are found along the tops of vertical cliffs on these islands the elevation of these deposits varies from 0 m to 50 m above mean sea level and they include clasts weighing 250 tonnes at sea level over 117 tonnes at 12 m and 2 9 tonnes at 50 m above sea level imbrication measurements on these megaclasts indicate a well defined and consistent mean direction from the southwest for the emplacing waves one that is consistent with the prevalent storm wind direction for the area the megaclast accumulations are subject to episodic and on going erosion by cliff retreat but the existing accumulations are estimated to record events since at least 1839 recent emplacement and reworking is evidenced by trapped plastic detritus within the deposits and eyewitness accounts of large storms during which clasts have been emplaced similar deposits are found on the exposed coasts of the shetland and orkney islands off scotland there is at present no evidence of any tsunami in recorded history affecting the western irish and scottish coasts other than those generated by the lisbon earthquake of 1755 where the wave effects were slight thus the presence of megaclast accumulations at significant heights above sea level on exposed coasts and exhibiting imbrication should not be used as a definitive criterion for the past occurrence of tsunami these deposits attest to extreme wave conditions occasionally encountered in the north atlantic and act as a record of such events extending back at least 160 years such data on extreme wave conditions are essential for the prediction of the effects of deepwater waves on structures such as offshore drilling platforms

fault slip and seismic moment of the 1700 cascadia earthquake inferred from japanese tsunami descriptions 1 the 1700 cascadia earthquake attained moment magnitude 9 according to new estimates based on effects of its tsunami in japan computed coseismic seafloor deformation for hypothetical ruptures in cascadia and tsunami modeling in the pacific ocean reports of damage and flooding show that the 1700 cascadia tsunami reached 1 5 m heights at seven shoreline sites in japan three sets of estimated heights express uncertainty about location and depth of reported flooding landward decline in tsunami heights from shorelines and post 1700 land level changes we compare each set with tsunami heights computed from six cascadia sources each source is vertical seafloor displacement calculated with a three dimensional elastic dislocation model for three sources the rupture extends the 1100 km length of the subduction zone and differs in width and shallow dip for the other sources ruptures of ordinary width extend 360 670 km to compute tsunami waveforms we use a linear long wave approximation with a finite difference method and we employ modern bathymetry with nearshore grid spacing as small as 0 4 km the various combinations of japanese tsunami heights and cascadia sources give seismic moment of 1 9 1022 n m equivalent to moment magnitude 8 7 9 2 this range excludes several unquantified uncertainties the most likely earthquake of moment magnitude 9 0 has 19 m of coseismic slip on an offshore full slip zone 1100 km long with linearly decreasing slip on a downdip partial slip zone the shorter rupture models require up to 40 m offshore slip and predict land level changes inconsistent with coastal paleoseismological evidence

extremely high energy wave deposits inside the great barrier reef australia determining the cause tsunami or tropical cyclone abstract a hydrodynamic approach is used to determine whether tsunami or cyclone generated waves were responsible for the deposition of fields of well imbricated rock boulders up to 290 tonnes along the coast of cairns inside the great barrier reef australia calculations of the overturning moments show that only tsunami are capable of moving such large boulders in this environment it is hypothesised that large tsunami 11 m have been able to penetrate the great barrier reef through wide 5 10 km 50 70 m deep passages between individual reefs three such passages each approximately 35 km apart and oriented in the same direction exist in the cairns region it is possible that these passages have funnelled and amplified palaeotsunamis the preferential location of eroded coral boulders up to 3 m in length on reef flats alongside these passages and their absence on other reefs throughout the region provide further evidence that extremely high energy waves have been able to penetrate the great barrier reef into the inner channel adjacent to the mainland carbon 14 ages of the coral boulders on these reef flats matches closely the ages of coral fragments pinned below the very large rock boulders along the coast these ages suggest that the cairns region has experienced large tsunami twice over the last millennium

large boulders along the south eastern ionian coast of sicily storm or tsunami deposits abstract this study investigates the size shape position pre transport setting and long axis orientation of 175 boulders found along the south eastern ionian coast of sicily these megaclasts were deposited by the sea or moved from the same rocky coast to the shore platform and distributed within 60 m of the shoreline most boulders are rectangular to ellipsoidal with sharp broken edges they are calcarenite fragments up to 27 t in mass some of the boulders up to 32 m from shore were observed to have moved after strong winter storms occurring during december 2008 january 2009 whereas the positions of many boulders were unchanged we use wave transport equations jointly with statistical analysis of boulders in order to determine the extreme events geological or meteorological responsible for these singular accumulations using the significant wave height and period of maximum observed storms and historical tsunamis 1693 and 1908 events along the ionian coast of sicily we have estimated the approximate transport distance of boulders by these waves at the coast results show that the largest storm waves were probably responsible for the current distribution of most boulders however since the size and horizontal displacement distance of some boulders scattered randomly along the shoreline at distance 40 m cannot be explained by storm wave action we suggest that they are likely deposited by tsunamis radiocarbon dating performed on three of these anomalous boulders at a distance 40 m from the shoreline gave an age suggesting that two of them were likely deposited by the 1693 or 1908 tsunamis whereas the third was emplaced by a tsunami that occurred after 650 930 a d we show that both wave processes storm and tsunami can deposit boulders we find that the significant difference between storm and tsunami waves is not the breaking wave height but the wave period that influences attenuation and then the flooding distance hence if the boulder transport limit of the largest storm waves in the past at the study area is estimated then it is possible to recognize that the boulders deposited far beyond this limit because of their size and shape were not transported by storm waves but could have been emplaced by waves with longer period such as the tsunamis

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

the role of porosity in discriminating between tsunami and hurricane emplacement of boulders a case study from the lesser antilles southern caribbean coastal boulder deposits are a consequence of high energy wave impacts such as storms hurricanes or tsunami parameters useful for distinguishing between hurricane and tsunami origins include distance of a deposit from the coast boulder weight and inferred wave height in order to investigate the role of porosity on boulder transport and elucidate the distinction between tsunami and hurricane impacts we performed archimedean and optical 3d profilometry measurements for the determination of accurate physical parameters for porous reef and coral limestone boulders from the islands of aruba bonaire and curacao abc islands netherlands antilles leeward islands subsets of different coral species and lithotypes constituting the boulders were sampled the physical parameters of boulders were analyzed and each boulder component was attributed to a certain range of porosity and density lowest porosities were observed in calcarenite 5 8 whereas highest porosities were measured for serpulid reef rock 47 68 porous serpulid reef rock 0 8 1 2 g cm 3 and the coral diploria sp 0 6 1 0 g cm 3 possess the lowest bulk densities while less porous calcarenite 2 0 2 7 g cm 3 and the coral montastrea cavernosa yield the highest bulk density values 1 6 2 7 g cm 3 the obtained physical parameters were used to calculate boulder weights and both hurricane and tsunami wave heights necessary to initiate transport of these boulders boulders are up to 5 6 times lighter than given in previously published data and hence required minimum hurricane or tsunami waves are lower than hitherto assumed the calculated wave heights the high frequency of tropical storms and hurricanes in the southern caribbean and the occurrence of boulders exclusively on the windward sides of the islands implicate that for boulders on the abc islands a hurricane origin is more likely than a tsunami origin 2008 elsevier b v all rights reserved

testing the hypothesis for tsunami boulder deposition from suspension tsunamis are known to deposit boulders but it is not clear if they are transported solely as bed load or whether suspended load can be involved it has been reported that numerous individual boulders and imbricated boulder stacks at elevations above normal storm tide levels along the new south wales nsw coast of se australia have been deposited out of suspension by tsunamis the nsw coast therefore provides an important natural laboratory to test the hypothesis that tsunamis can deposit large boulders from suspension using standard hydrodynamic equations to formulate the relationship between boulder transport and flow depth we provide a test of the suspension hypothesis we show that the tsunami flow depths required for deposition from suspension are most probably physically unrealistic the nsw boulders are therefore not indicative of deposition from suspension and an alternative explanation must be sought for their mechanism of emplacement this analysis has important implications for the emerging sub branch of tsunami boulder geology

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

runout evaluation of the oso landslide with the material point method long runout landslides can cause significant damage and represent one of the most important problems in geotechnical engineering understanding the mechanics of the landslide runout process is impo

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

historic 1771 meiwa tsunami confirmed by high resolution u th dating of massive porites coral boulders at ishigaki island in the ryukyus japan 1 the chronicles of the ryukyu kingdom describe at least four coastal inundation events at ishigaki island during the seventeenth through nineteenth centuries the 1771 meiwa earthquake tsunami which killed 12 000 people another earthquake tsunami 1687 and two events with unrecorded causes 1625 and 1714 we used a high resolution u th method to date well preserved surface parts of massive porites spp coral head boulders that had been cast ashore and found that the ages of two boulders correspond to the 1771 event one large porites boulder diameter 4 m was dated to 1625 suggesting that that event was also a large inundation event calibrated 14c ages based on a newly estimated local value for the radiocarbon marine reservoir effect clustered around 1625 and 1771 suggesting that these events were larger than the others our study demonstrated that porites boulders have enormous potential value for studies of paleoinundation events such as tsunamis and extreme storms

2004 indian ocean tsunami inflow and outflow at phuket thailand at bangtao beach phuket the 2004 indian ocean tsunami produced a repeated sequence in which rapid inflow of turbulent water was followed by ponding and then by gradual outflow photographs and eyewitness accounts show an initial withdrawal followed by series of inflows the tsunami left behind a sand sheet as much as 25 cm thick that contains parallel inclined landward and seaward lamina in addition to the normal grading commonly reported from tsunami deposits the sheet contains evidence for two times of vigorous inflow each of these is marked by mud rip ups medium to coarse sand that grades upward to fine landward inclined laminae and a sharp basal contact the top of the sand sheet when observed in the first days after the tsunami abounded in current dune and ripple bedforms of mostly landward orientation the tsunami s first positive wave left noonshore sedimentary record in this pitting area the second wave deposited sand that is much less extensive and slightly finer than that of the third wave the deposit of both these waves contains multiple fining upward sequences possibly due to multiple surges in one wave train the depth averaged flow velocity estimated from thickness and grain size are in the range 7 21 m s whereas a near bottom threshold velocity calculated from bedforms reveals the order of magnitude difference from 1 74 to 1 03 m s 2007 elsevier b v all rights reserved

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

competing mechanisms for boulder deposition on the southeast australian coast this study investigates the role of late holocene sea level change large storms and possible pre historic tsunami in the deposition of boulder features on an exposed headland and sheltered rock ramp large accumulations of boulders are found on coastal rock platforms cliff tops and ramps in the jervis bay region of southeastern australia these deposits are elevated above sea level and in places exhibit obvious signs of imbrication as a response to flow in a landward direction the event history of these features is controversial and holocene sea level change storms and tsunami can be considered as possible non mutually exclusive mechanisms of deposition it is apparent that even if the detachment site transport distance elevation and final orientation of a boulder can be identified deciphering the event history remains a difficult task

discrimination of boulders deposited by tsunamis and storm waves at ishigaki island japan abstract the ryukyu islands japan where numerous boulders are deposited on the reef and on land might be ideal research fields of boulders deposited by tsunami and storm waves because many typhoons and several tsunamis attacked the same area during its history this study investigates the size position and the long axis orientation of 626 boulders at ibaruma and shiraho reefs at ishigaki island japan to elucidate the sedimentary differences of boulders deposited by tsunamis and storm waves in one area two distinct groups of boulders were found at these reefs boulders on the reef crest group 1 and along the shoreline group 2 boulders in group 1 porites sp of moat origin the group 2 boulders were remarkably heavier 14 c age based on results of this study we infer that tsunami boulders in these islands so called tsunami ishi can be discriminated from boulders of storm wave origin based on their sedimentary differences this sedimentological approach is expected to be applicable to other boulder fields throughout the world our results further suggest that the spatial and grain size distribution of tsunami boulders are very useful to elucidate local flow characteristics of the tsunami for example the group 2 tsunami boulders were deposited below the high tide line irrespective of size some were split into several pieces they were probably deposited below the high tide line by the remarkable reduction of the current velocity of the tsunami because of the local topography the reduction of the current velocity must have been drastic to have made the boulders hit the ground with sufficient force to split them

wave emplaced coarse debris and megaclasts in ireland and scotland boulder transport in a high energy littoral environment a discussion scheffers et al 2009 describe a reconnaissance survey of boulder accumulations along parts of the atlantic coasts of the british isles a substantial part of their report concerns the characteristics of wave transported boulder deposits found high above sea level on cliffs these boulder deposits reach perhaps their ultimate development along the coasts of the aran islands galway bay western ireland and eshaness shetland northern scotland where evidence of wave action reaches elevations of 50 m above sea level a s l we have previously investigated in detail these and numerous other similar localities and concluded that the boulder deposits are cliff top storm deposits ctsds part of an assemblage of features found on certain cliffs on these very high energy coasts that relate to the impacts of extreme waves during major storms williams and hall 2004 hall et al 2006 2008 hansom et al 2008 hansom and hall 2009 however scheffers et al 2009 p 571 claim that at these and other sites no evidence exists for storm wave dislocation of boulders found at altitudes of 120 m a s l indeed no calculations of possible storm wave heights storm wave physics or ages of the deposits and no descriptions of extraordinary storms are sufficient to explain these displacements p 568 and alternative explanations such as tsunamis should be considered p 571 here we rebut these claims by briefly restat

distribution and sedimentary characteristics of tsunami deposits along the cascadia margin of western north america abstract tsunami deposits have been found at more than 60 sites along the cascadia margin of western north america and here we review and synthesize their distribution and sedimentary characteristics based on the published record cascadia tsunami deposits are best preserved and most easily identified in low energy coastal environments such as tidal marshes back barrier marshes and coastal lakes where they occur as anomalous layers of sand within peat and mud they extend up to a kilometer inland in open coastal settings and several kilometers up river valleys they are distinguished from other sediments by a combination of sedimentary character and stratigraphic context recurrence intervals range from 300 1000 years with an average of 500 600 years the tsunami deposits have been used to help evaluate and mitigate tsunami hazards in cascadia they show that the cascadia subduction zone is prone to great earthquakes that generate large tsunamis the inclusion of tsunami deposits on inundation maps used in conjunction with results from inundation models allows a more accurate assessment of areas subject to tsunami inundation the application of sediment transport models can help estimate tsunami flow velocity and wave height parameters which are necessary to help establish evacuation routes and plan development in tsunami prone areas

the tsunami hypothesis comparisons of the field evidence against the effects on the western australian coast of some of the most powerful storms on earth the tsunami hypothesis proposes that prehistoric tsunamis may have been larger than historic ones along coasts normally historically not associated with major tsunamis the evidence for the hypothesis rests with the types of unusual sedimentary deposits and erosional forms along coasts where the largest historic and prehistoric storm waves do not appear capable of forming the features this is especially the case at locations where boundary conditions i e offshore water depth coastal geomorphology and meteorological limitations are not conducive to the propagation of sufficiently large storm waves at the shore the tsunami hypothesis has been barely debated in the literature this is despite the view of some who suggest that storms have been overlooked or underestimated as a cause few comparisons have been made of the supposed tsunami generated features and the impacts on coasts of extreme intensity storms four of the most powerful tropical cyclones anywhere in the world in recent times struck the western australian coast between 1999 and 2002 the results of post event surveys of these storms showed that none of them produced the enigmatic forms attributed elsewhere to tsunamis

waves coastal boulder deposits and the importance of the pre transport setting the pre transport environment of a coastal boulder along with its shape size and density determines the height of wave required for it to be transported different forces act on sub aerial boulders as opposed to submerged boulders when struck by a wave boulders derived from joint bounded blocks on shore platforms predominantly experience lift force and require a wave of greater height to be transported than boulders in other environments no one equation is applicable to determine the height of palaeo waves responsible for depositing a field or ridge of imbricated coastal boulders a range of equations and their derivation is presented here which can be applied to the respective pre transport environment of a boulder such an approach is necessary when attempting to reconstruct the frequency and magnitude of past coastal wave hazards and for differentiating between tsunami and storm wave deposited boulder fields

evaluation of tsunami flooding using geomorphologic evidence abstract whatever the generating mechanism of a tsunami may be this event can discharge destructive energy along coastal areas and produce widespread inundation the presence of large boulders along rocky coasts could be a useful indicator to understand the extent of the impact of past tsunami floods a detailed study of the deposited boulder features size shape and rock density and their initial position prior to the transport is extremely important when reconstructing the possible morphodynamic scenario s applying the appropriate equations is important when aiming to assess the maximum extent of flooding the integration of morphological and hydrodynamic data allows for an estimation of the water level during the tsunami event responsible for boulder transport moreover it is possible to calculate how far the impacting wave flooded inland this is a function of the wave parameters and of the degree of roughness of the flooded terrain that is expressed by the manning number to evaluate its probable average value experimental data computer simulations and post tsunami surveys have been performed in two sectors of the southern apulia coastline characterised by the presence of tsunami boulder fields and or ridges the surveys in each site have allowed for the calculation of the boulder sizes the estimation of their pre transport location and the extent of inland flooding data have been processed using a geographic information system gis as a result a flooding map useful in planning future possible actions for coastal area use has been produced

sedimentology of rocky shorelines 2 shoreline megaclasts on the north shore of oahu hawaii origins and history abstract limestone megaclasts up to 96 t in weight rest on a coastal rock platform near sunset beach on the north shore of oahu hawaii they occur in seaward dipping imbricate clusters and as solitary clasts the rock platform is subject to large swell waves and very large waves associated with winter storms and tsunami a series of photographs covering the period from ca 1905 to 1996 show episodic rearrangement of megaclasts on the platform and the appearance of new megaclasts near the platform edge the largest solitary megaclast ca 96 t was emplaced on the platform between 1940 and 1950 possibly by the 1946 aleutian tsunami and has moved twice since then in ca 30 m jumps along two different trajectories larger clasts have been broken from the platform edge and emplaced on the platform only by very large wave events whereas formation and movement of smaller tabular clasts ca 30 40 t appear to be a continuously ongoing process on the surface of the rock platform partial detachment of clasts by marine erosion processes along joints and cracks in the limestone bedrock facilitates their complete detachment from both the platform edge and platform surface the larger numbers of megaclasts emplaced on the north and northwest sectors of the platform relative to other sectors are attributed to exertion of maximum wave power on these sectors due to a combination of steep slope and ramp like submarine topography

real time experimental forecast of the peruvian tsunami of august 2007 for u s coastlines 1 at 23 41 utc on 15 august 2007 an offshore earthquake of magnitude 8 0 severely damaged central peru and generated a tsunami severe shaking by the earthquake collapsed buildings throughout the region and caused 514 fatalities the tsunami resulted in three casualties and a representative maximum runup height of 7 m in the near field the first real time tsunami data available came from a deep ocean tsunami detection buoy within 1 hour of tsunami generation these tsunami data were used to produce initial experimental forecasts within 2 hours of tsunami generation the far field forecasts indicated that the tsunami would not flood any of the 14 u s communities comparison with real time tide gage data showed very accurate forecasts

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

emplacement and movement of boulders by known storm waves field evidence from the okinawa islands japan abstract field observations from previous studies of boulder movements were compiled to augment our own work on boulders that have been displaced by storm waves during recent typhoon events in the okinawa islands japan to elucidate the ability of storm waves to move boulders our observations reveal that recent storm waves displaced by sliding and overturning 100 ton boulders emplacing them on the reef or high cliff tops and that storm waves might also be capable of displacing 200 ton boulders on the reef the weights of storm wave boulders at the okinawa islands are of comparable order to those boulders displaced by historical tsunami origins consequently boulder weight alone is an inappropriate parameter to discriminate between tsunami or storm wave processes however these heavy storm wave boulders are close to the reef and cliff edges while tsunami boulders can be deposited much further inland hence horizontal displacement distance of boulders could be a useful parameter to discriminate boulders deposited by the tsunami and storm waves on the wide fringing reef the storm wave boulders were characteristically concentrated on the southeastern pacific ocean sides of each island but large boulders are rarely found on the northwestern east china sea side this is probably because the storm wave intensities are generally stronger at the southeastern side than at the northwestern side although differences of reef strength and initial condition of boulders should also be taken into account consideration of the high frequency of typhoons at the area suggests that effects of the storm waves and the consequent displacement of boulders on the reef might have contributed to the formation of the reef moat framework that typifies the okinawa islands especially if the moat is located within the transport limit of the storm wave boulders approximately 300 m from the reef edge at the islands

catastrophic wave erosion on the southeastern coast of australia impact of the lanai tsunamis ca 105 ka sand barriers along the coast of southern new south wales dating from the last interglacial have been almost completely destroyed most probably by a catastrophic tsunami evidence for catastrophic wave erosion can also be traced to heights of at least 15 m above present sea level on coastal abrasion ramps these erosional features lie above the range of effective erosion by contemporary storm waves and cannot be attributed to either eustatic fluctuations or local uplift chronological evidence for the timing of the destruction of the last interglacial barriers suggests that tsunamis generated by the submarine slide off lanai in the hawaiian islands 105 ka traveled across the pacific and eroded this coast

the mystery of boulders moved by tsunamis and storms abstract boulders are moved differently in storm and tsunami and produce different characteristics of the boulder deposits this contribution is motivated by two observations one by bourgeois and macinnes 2010 which described that boulders were moved selectively due to different bed roughness during 15 november 2006 tsunami on the island of matua the second topic is motivated by the boulder lines on ishigaki island by goto et al 2010 both topics are approached with linear wave theory and stability analysis from both the safety factor is derived for a spherical boulder with bed roughness and exposure as moment arms with which we are able to quantify the influence of bed roughness on the incipient motion of boulders for constant forces a bed roughness of about 30 of the boulder radius will prevent boulder transport furthermore the comparison between storm and tsunami waves in terms of the amplitude necessary to move boulders revealed that amplitude of storm waves is smaller than tsunami which we ascribe to the contribution of both velocity components to lift forces the comparison of total energy and number of waves revealed that storms have a larger total energy and a much larger number of waves which lead us to the conclusion that tsunamis produce unorganized boulder deposits whereas storms are capable of organizing boulders along lines and in clusters

numerical modeling of the 2011 tohoku oki tsunami in the offshore and onshore of sendai plain japan abstract this paper examines the results of a numerical modeling of the 2011 tohoku oki earthquake tsunami to investigate its offshore propagation and inundation along a shore normal transect located in the center of the sendai plain the inundation distance flow depth and flow speed were compared with the available data measured during a post tsunami field survey and estimated from the video records the calculated inundation distance reached 4 5 5 5 km from the coastline which is comparable to the actual inundation distance the variation of tsunami heights from 2 4 6 m and flow speeds from 3 4 6 2 m s along the transect is generally consistent with the measured heights and estimated speeds the waveform on the beach showed that the wave train was composed of a high 10 11 m first wave followed by low 4 m waves considering the waveform and the topographic change the erosion of the beach and the sedimentation inland are explained mainly by the first wave in addition the calculated flow speed and friction velocities in the offshore may account for the formation of the possible tsunami deposits which were reported recently by a sea bottom survey the modeling results are generally consistent with the available data and are considered to be useful for understanding the inundation pattern and sedimentation process of the tohoku oki tsunami on the sendai plain

2004 indian ocean tsunami flow velocity measurements from survivor videos 1 the tsunami of 26th december 2004 severely affected banda aceh along the north tip of sumatra indonesia at a distance of 250 km from the epicenter of the magnitude 9 0 earthquake this tsunami flow velocity analysis focused on two survivor videos recorded within banda aceh more than 3 km from the open ocean the exact locations of the tsunami eyewitness video recordings were revisited by the survey team between february 22 and 25 2005 to record camera calibration ground control points the motion of the camera during the recordings was determined the individual video images were rectified with a direct linear transformation dlt assuming a planar water surface at the level finally a cross correlation based particle image velocimetry piv analysis was applied to the rectified video images to determine instantaneous tsunami flow velocity fields the measured tsunami flow velocities were within the range of 2 to 5 m s

sedimentology of rocky shorelines 3 hydrodynamics of megaclast emplacement and transport on a shore platform oahu hawaii abstract megaclasts of well cemented coralgal limestone have been emplaced onto a shore platform by large waves on the north shore of oahu hi emplacement and movements of the largest ca 96 ton megaclast have been dated using aerial photographs hydrodynamic forces at the low submerged shoreline cliff are computed using design wave characteristics based on linear wave theory and experimental results considering the local wave climate and near shore bottom topography force exerted by a tsunami has been estimated based on the 1946 aleutian tsunami the computed forces are evaluated in terms of the initial fracturing along a given failure plane that is required in order for the detachment to occur the analysis shows that tsunami as well as large swell waves are capable of quarrying the megaclast provided that sufficient initial fracturing is present dislodgement and emplacement most likely occurred in a sequence during impact of a single wave on the shoreline cliff swell waves however are seldom capable of emplacing large blocks onto the platform due to their rapid disintegration after breaking so that most blocks quarried from the cliff edge fall back onto the submarine terrace emplacement of large boulders seems to require extreme sea waves with periods longer than storms or north pacific swells usually produce transport mechanisms on the shore platform vary depending on megaclast shape sliding is a common mechanism of transport for larger and irregular megaclasts whereas somewhat smaller and platy megaclasts are occasionally found in overturned positions

basalts water or shear zones in the lower continental crust abstract bright sub horizontal laterally extensive multi cyclic layered reflections have now been recorded in the lower continental crust from many areas in contrast this reflection signature is rare in the continental upper crystalline crust and upper mantle and in the oceanic lithosphere with the present state of knowledge it is sensible to seek a single quantitative explanation for all such layering qualitative explanations for lower crustal layering abound and include igneous metamorphic structural and fluid related models measurements of reflection coefficients from the lower crust place strong quantitative constraints on possible models structurally induced anisotropy metamorphic layering or free fluids cannot realistically produce sufficiently bright reflections igneous layering or the juxtaposition of pre existing heterogeneities by shear zones can produce strong reflections results from crustal xenoliths helium isotope ratios palaeo geothermal gradients and chemistry of flood basalts together with numerical modelling of lithospheric extension and asthenospheric melting suggest that underplating and intrusion of the lower crust with mantle derived mafic igneous rocks is common the apparent spatial relationship between lower crustal layering and continental extension and the strength and continuity of the reflections suggest that underplating related to extension and or elevated mantle temperatures is a good explanation for lower crustal layering

the use of boulders for characterising past tsunamis lessons from the 2004 indian ocean and 2009 south pacific tsunamis tsunamis are high energy events capable of transporting extremely heavy loads including boulders we compare boulder deposits created by two modern tsunami events the 2004 indian ocean and the 2009 south pacific tsunamis where the boulder sources were in similar topographic settings and for which we have accurate data on the wave characteristics boulder distribution preferential orientation and numerical simulation of boulder transport are discussed a comparison between the impacts of the south pacific and indian ocean tsunamis shows similar characteristics such as limited landward extent and the absence of landward fining differences between the results from modelling and field data are most probably caused by variables such as coastal plain roughness buildings trees microtopography particle shape and boulder collision during transport that are summarised as coefficients in the mathematical models characterising modern events through coarse sediment deposits provides valuable information to help identify and interpret palaeo tsunami imprints on coastal landscapes

process based modeling of tsunami inundation and sediment transport 1 the infrequent and unpredictable nature of tsunamis precludes the use of field experiments to measure the hydrodynamic and sediment transport processes that occur instead these processes are often approximated from laboratory numerical and theoretical studies or inferred from observations of the resultant sediment deposits here delft3d a three dimensional numerical model is used to simulate the inundation and sediment transport of a tsunami similar in magnitude to the 26 december 2004 indian ocean tsunami over one measured and three idealized morphologies the model is first shown to match well the observations taken at kuala meurisi sumatra and then used to examine in detail the processes that occur during the tsunami the model predicts that at a given cross shore location the onshore flow accelerates rapidly to a maximum as the wavefront passes and then gradually decelerates before reversing direction and flowing offshore the onshore flow does not tend to zero everywhere at maximum inundation but instead flow reversal occurs near the shoreline even as the wavefront continues to inundate landward while some sediment is eroded by the passing wavefront the suspension of sandy sediment is dominated by the long duration high velocity backwash that occurs along the beach face and offshore of the shoreline some of the sediment suspended during backwash is advected shoreward by the subsequent wave creating large spatial gradients in the suspended sediment concentrations which may not be in equilibrium with the local hydrodynamics the inundation and transport of sediment during a tsunami can be affected by complexities in the morphological profile and interactions between multiple waves and many of the hydrodynamic and sediment transport processes predicted here are similar to analogous processes previously observed in the swash zone

coastal changes in the sendai area from the impact of the 2011 tōhoku oki tsunami interpretations of time series satellite images helicopter borne video footage and field observations a combination of time series satellite imagery helicopter borne video footage and field observation is used to identify the impact of a major tsunami on a low lying coastal zone located in eastern japan a comparison is made between the coast protected by armoured engineered sea walls and the coast without changes are mapped from before and after imagery and sedimentary processes identified from the video footage the results are validated by field observations the impact along a natural coast with minimal defences is erosion focussed on the back beach along coasts with hard engineered protection constructed to defend against erosion the presence of three to six metre high concrete faced embankments results in severe erosion on their landward faces the erosion is due to the tsunami wave accelerating through a hydraulic jump as it passes over the embankment resulting in the formation of a ditch into which the foundations collapse engineered coastal defences are thus found to be small defence against highly energetic tsunami waves that overtop them there is little erosion or sedimentation of the whole beach and where active it mainly forms v shaped channels these channels are probably initiated during tsunami inflow and then further developed during tsunami backflow tsunami backflow on such a low lying area takes place energetically as sheet flow immediately after tsunami flooding has ceased subsequently when the water level landward of the coastal dune ridges falls below their elevation flow becomes confined to rivers and breaches in the coast formed during tsunami inflow enigmatic short lived strand lines are attributed to the slow fall of sea level after such a major tsunami immediately after the tsunami coastal reconstruction begins sourced from the sediment recently flushed into the sea by tsunami backflow

combining constraints from tsunami modeling and sedimentology to untangle the 1969 ozernoi and 1971 kamchatskii tsunamis 1 large tsunamigenic earthquakes occurred in 1969 mw 7 7 and 1971 mw 7 8 along the bering sea and northernmost pacific coast of kamchatka both resultant tsunamis were recorded on tide gauges but only the 1969 tsunami has cataloged observations of runup and these observations are limited and questionable we used a combination of field mapping of tsunami deposits and tsunami modeling to augment this historical record we mapped tsunami deposits above a d 1956 and 1964 volcanic ash layers along more than 200 km of shoreline however the 1969 and 1971 tsunami deposits are not distinguishable in the field the distribution of tsunami deposit elevation has two latitudinal peaks from 58 to 57 sediment runup typically ranges from 2 to 4 m decreasing to the south from 57 to 56 sediment runup typically ranges from 3 to 6 m maximum more than 10 m increasing to the south models of local runup for the 1969 and 1971 tsunamis explain most of the sediment distribution differentiate the two tsunamis in some localities and elucidate the earthquakes focal mechanisms and rupture areas

sediment transport part i bed load transport a method is presented which enables the computation of the bed load transport as the product of the saltation height the particle velocity and the bed load concentration the equations of motions for a solitary particle are solved numerically to determine the saltation height and particle velocity experiments with gravel particles transported as bed load are selected to calibrate the mathematical model using the lift coefficient as a free parameter the model is used to compute the saltation heights and lengths for a range of flow conditions the computational results are used to determine simple relationships for the saltation characteristics measured transport rates of the bed load are used to compute the sediment concentration in the bed load layer a simple expression specifying the bed load concentration as a function of the flow and sediment conditions is proposed a verification analysis using about 600 alternative data shows that about 77 of the predicted bed load transport rates are within 0 5 and 2 times the observed values

a numerical model for the transport of a boulder by tsunami 1 we have conducted hydraulic experiments in an open channel with cubic and rectangular shaped solid blocks on the slope for investigating the boulder transport process by tsunami in our experiments the block was mainly seen to be transported by a bore due to rolling or saltation rather than by sliding previous models for the boulder transport by tsunamis assumed sliding as a mode of transport for the boulder therefore these models underestimated the distance of the boulder moved by the tsunami when it was transported due to rolling or saltation in this study we have developed a practical model for the transport of a boulder by tsunami which takes into account the various transport modes we introduce an empirical variable coefficient of friction by assuming that the coefficient decreases with decrease in ground contact time when the block was transported by rolling or saltation with the aid of this parameter the model can explain various modes of transport i e sliding rolling and saltation and reproduces the experimental results well we further applied this improved model to a tsunami boulder at inoda area in ishigaki island japan which was transported by the 1771 meiwa tsunami the calculated distance of transport of the boulder was approximately 650 m which is consistent with the description in the historical document based on our calculations we estimated hydraulic values of the tsunamis estimation of such hydraulic values is important for understanding the behavior and power of the historical tsunamis besides aiding future disaster mitigation efforts

reassessment of hydrodynamic equations minimum flow velocity to initiate boulder transport by high energy events storms tsunamis abstract coastal boulders are good evidence of high energy events but the distinction between storm and tsunami boulders remains difficult to identify and mathematical models are still in their preliminary stages in a pioneering contribution nott 1997 2003 developed hydrodynamic equations to assess the minimum wave height required to initiate transport of a coastal boulder by tsunamis or storm surges these equations are widely cited and used but they can be improved in this study nott s equations have been revised 1 the equation for the submerged boulder scenario has been revised by rearranging the lift area of the lift force 2 the subaerial boulder scenario has been reconsidered by rearranging lift area and omitting inappropriate use of inertia force and 3 the joint bounded scenario was revised by balancing force components in the lifting direction and the effect of slope at the pre transport location is tested calculations are performed for four case studies boulders in western and eastern australia data after nott 1997 2003 boulders in southeastern italy data after scicchitano et al 2007 storm boulders in iceland data after etienne and paris 2010 and 2004 tsunami boulders in sumatra data after paris et al 2009 the minimum flow velocity required to initiate the transport of submerged boulders in the revised equation is less than that in nott s equation e g reductions up to 56 for submerged boulders and 65 for joint bounded blocks the minimum flow velocity required to initiate the transport of subaerial boulders from the revised equation also differed in comparison with nott s equation e g 4 22 for boulders detached from a seawall by the 2004 tsunami in sumatra while nott s equation was not applicable to some boulders e g beach rock boulders transported from the nearshore by the 2004 tsunami if we consider a joint bounded scenario for storm boulders in iceland the minimum flow velocity differs 43 to 41 from the results from nott s equation a boulder transport histogram is then introduced to represent the range of flow velocity that satisfies the requirements for initial transport of a boulder in different modes sliding rolling and saltation the boulder transport histogram can be used to predict the possible initial transport mode of a boulder from the flow velocity these theoretical results are compared to field data thus suggesting the initial transport mode of boulders and their pre transport locations the boulder transport histogram would be a valuable tool to reconstruct the magnitude of prehistoric high energy events such as tsunamis or storm surges in terms of flow velocity

reconstruction of tsunami inland propagation on december 26 2004 in banda aceh indonesia through field investigations this paper presents the results from an extensive field data collection effort following the december 26 2004 earthquake and tsunami in banda aceh sumatra the data were collected under the auspices of tsunarisque a joint french indonesian program dedicated to tsunami research and hazard mitigation which has been active since before the 2004 event in total data from three months of field investigations are presented which detail important aspects of the tsunami inundation dynamics in banda aceh these include measurements of runup tsunami wave heights flow depths flow directions event chronology and building damage patterns the result is a series of detailed inundation maps of the northern and western coasts of sumatra including banda aceh and lhok nga

sedimentary processes associated with sand and boulder deposits formed by the 2011 tohoku oki tsunami at sabusawa island japan abstract this paper reports on the sedimentary processes of sand and boulder deposition at sabusawa island japan as a result of the 2011 tohoku oki tsunami boulders were composed of tuffaceous rocks and sourced from an earthquake triggered slope failure as well as concrete fragments of seawall they were scattered over the ground surface and did not form boulder ridges although there was some local imbrication the boulders were deposited on top of a sand layer indicating that the latter possibly deposited from bed load covered the ground surface first this sand layer probably reduced friction allowing boulders to be transported more easily than might be expected across a hard ground with a high bottom friction sand deposits showed landward thinning and fining features while the boulders showed a landward coarsening tuffaceous boulders or a landward fining concrete boulders indicating that large clasts were not necessarily scattered randomly but rather might have a clast size gradient with distance inland these features are explained by the local topographic setting that constrained the directions of incoming and returning tsunami flows some clasts at the inland extent of the boulder field were covered by an upward fining sand layer this feature suggests that the boulders were deposited prior to the suspended sands with the latter subsequently laid down before the water level dropped below the top of the boulders such modern investigations of the sedimentary features of various sizes of grains and clasts immediately after a tsunami provide invaluable data for the reconstruction of inundation processes

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

sedimentary deposits from the 17 july 2006 western java tsunami indonesia use of grain size analyses to assess tsunami flow depth speed and traction carpet characteristics the 2006 western java tsunami deposited a discontinuous sheet of sand up to 20 cm thick flooded coastal southern java to a depth of at least 8 m and inundated up to 1 km inland in most places the primarily heavy mineral sand sheet is normally graded and in some it contains complex internal stratigraphy structures within the sand sheet probably record the passage of up to two individual waves a point noted in eyewitness accounts we studied the 2006 tsunami deposits in detail along a flow parallel transect about 750 m long 15 km east of cilacap the tsunami deposit first becomes discernable from the underlying sediment 70 m from the shoreline from 75 to 300 m inland the deposit has been laid down in rice paddies and maintains a thickness of 10 20 cm landward of 300 m the deposit thins dramatically reaching 1 mm by 450 m inland from 450 m to the edge of deposition around 700 m inland the deposit remains 1 mm thick deposition generally attended inundation along the transect the tsunami deposited sand to within about 40 m of the inundation limit the thicker part of the deposit contains primarily sand indistinguishable from that found on the beach 3 weeks after the event but after about 450 m and roughly coinciding with the decrease in thickness the tsunami sediment shifts to become more like the underlying paddy soil than the beach sand grain sizes within the deposit tend to fine upward and landward although overall upward fining takes place in two discrete pulses with an initial section of inverse grading followed by a section of normal grading the two inversely graded sections are also density graded with denser grains at the base and less dense grains at the top the two normally graded sections show no trends in density the inversely graded sections show high density sediment to the base and become less dense upward and represents traction carpet flows at the base of the tsunami these are suggestive of high shear rates in the flow because of the grain sorting in the traction carpet the landward fining trends usually seen in tsunami deposits are masked although lateral changes of mean sediment grain size along the transect do show overall landward fining with more variation as the deposit tapers off the deposit is also thicker in the more seaward portions than would be produced by tsunamis lacking traction carpets

sequence of sedimentation processes caused by the 1992 flores tsunami evidence from babi island sedimentation processes caused by a modern tsunami have been discussed from the point of view of geologic and numerical investigations of the 1992 flores tsunami in indonesia geologic evidence on babi island shows an invasion of two waves of different direction and magnitude which resulted in widespread deposition of marine sand on the north and south southwest shores on the latter coarse and well sorted carbonate sand containing molluscan shells suggests that much more destructive waves swept across the southern coast as compared with the northern coast where the deposit included medium carbonate sand with a silty component a physical explanation for such destructive waves on the southern coast of babi is provided by a numerical simulation of the tsunami generation and propagation the geologic and numerical results indicate that an isolated island surrounded by a circular shoreline or reef edge will be subject to the most destructive waves on the coast on the back side of the island relative to the tsunami source

recent storm and tsunami coarse clast deposit characteristics southeast hawaiʻi abstract deposits formed by extreme waves can be useful in elucidating the type and characteristics of the depositional event the study area on the southeast coast of the island of hawai i is characterized by the presence of geologically young basalts of known age that are mantled by recent wave derived sedimentary deposits the area has been impacted by large swells storms and tsunamis over the last century and in combination with known substrate ages makes this an ideal location to study recent deposits produced by such events three distinct coarse clast deposit assemblages can be recognized based on clast size composition angularity orientation packing elevation and inland distance of the deposit these deposits are characterized as one of three types 1 gravel fields of isolated clasts primarily boulder size material and scattered pockets of concentrated sand and gravel in topographic lows 2 shore parallel and cuspate ridges composed mostly of rounded basalt gravel and sand with small amounts of carbonate detritus the ridges range in height from about 1 to 3 m and are 10s of m wide 3 cliff top deposits of scattered angular and sub angular clasts along sea cliffs that are generally greater than 5 m elevation the gravel fields are primarily of tsunami origin from either the 1975 kalapana event or a combination of the 1975 tsunami and 1868 tsunami or earlier events the ridge deposits are presently active and sediment continues to be added during high wave events the cliff top deposits contain evidence of deposition by both tsunami and storm processes and require further investigation

large boulder accumulations by extreme waves along the adriatic coast of southern apulia italy abstract the adriatic coast of southern apulia italy is marked by the presence of large boulder accumulations boulders are up to 8 t in weight and arranged either in small groups or rows composed of a few imbricated elements the lower surface of some of the boulders is covered by biogenic encrustation which suggests that they were possibly carved from the mid or sublittoral zone and that they capsized during their transport other boulders detached from the supratidal zone have their surface affected by tilted rock pools new horizontal solution pans are continually forming a detailed survey of a large boulder accumulation was carried out at torre santa sabina direct observations were also made concerning the carving out and transportation of one single boulder during the severe storms in that area on january 4th 2002 and on january 12th 2003 collated data from both the survey and the direct observations including some radiocarbon age determinations and hydrodynamic calculations suggest that the studied accumulation was due to the superimposed effects of one or two tsunami as well as of storm waves tsunami would be responsible for the detachment and transportation of the largest boulders while storm waves may have been responsible for the carving out and transportation of the newer smaller blocks and for moving once again the largest boulders it was in this way that a typical boulder accumulation was produced the collated data suggest that two tsunami may have recently struck the adriatic coast of southern apulia the first possibly took place on the dalmatian coast as a result of the earthquake on april 6 1667 which destroyed ragusa modern day dubrovnik the second tsunami would have accompanied the strong earthquake which took place in southern apulia on february 20 1743