deposit from a giant wave on the island of lanai hawaii limestone bearing gravel the newly named hulopoe gravel blankets the coastal slopes on lanai the deposit which reaches a maximum altitude of 326 meters formerly was believed to have been deposited along several different ancient marine strandlines but dated submerged coral reefs and tide gauge measurements indicate that the southeastern hawaiian islands sink so fast that former worldwide high stands of the sea now lie beneath local sea level evidence indicates that the hulopoe gravel and similar deposits on nearby islands were deposited during the pleistocene by a giant wave generated by a submarine landslide on a sea scarp south of lanai

the largest local tsunami in 20th century hawaii abstract the 1975 kalapana tsunami had waves that ran up to 14 6 m high it deposited a discontinuous basalt boulder and carbonate sand veneer on the halape apua point coast of the island of hawaii these deposits fine up to 320 m inland and 10 4 masl the deposit is an unusual sedimentary association in which sand sized material is a minor component both boulders and sand fine inland over the same distance not in a continuum and they terminate at approximately the same point boulders were transported and deposited by only one wave the second whereas the sand deposit was in part reworked by subsequent smaller waves boulder transport by one wave in association with a relative paucity of finer sediment reduced internal clast interference and helped to impart a marked fining inland sequence this fining inland sequence is at odds with work that proposes a chaotic or random nature of boulder emplacement by tsunamis where there is abundant sediment clast interference during entrainment will impede the fining inland of larger material in cases where it is difficult to determine the nature of inundation or the number of tsunamis a chaotic pattern may simply reflect deposition by storm tsunami or a combination of the two

chaotic deposition by a giant wave molokai hawaii a coral basalt breccia conglomerate is exposed 60 m above present sea level and nearly 2 km inland from the present shoreline on the southwest side of east molokai volcano molokai the conglomerate is preserved mantling interfluves between gullies and forms a blanket like deposit 0 5 to 3 m thick no evidence of a wavecut terrace either within the blanket or at its upper or lower limits of exposure can be found no coral was found in growth position unsorted basalt clasts as large as boulder size are subrounded to angular randomly oriented and vary from 2 3 to 50 volume of the deposit the size of the largest basalt and coral fragments shows almost no systematic variation with elevation distance inland or lateral position parallel to the shore two indistinct rock units are present in a few places a lower carbonate rich unit that we interpret as an onwash facies and an upper basalt rich unit an offwash facies the carbonate rich onwash facies is dominated by biogenic debris especially fragments of coral and beach rock and gastropod and bivalve shells the offwash facies contains 40 to 90 basalt cobbles and boulders in a matrix of finely broken biogenic fragments where the distinct facies are lacking the proportion of basalt clasts increases crudely from the lower to the upper part of the conglomerate at a single place and from lower to higher elevation out crops where the deposit overlies a cinder cone several carbonate bearing elastic dikes extend from the conglomerate as much as 10 m down into the basalt cinders this deposit was apparently laid down by a giant wave that broke over an outer reef similar to the present fringing reef and advanced as a turbulent bore over the back reef flat picking up a slurry of carbonate rich debris and depositing it on the slopes inland as the wave advanced the offwash picked up loose basalt debris on its return flow u series dating of coral fragments indicates that the age of this deposit is 240 200 ka indicating the wave is distinct from that which produced a similar deposit on lanai about 100 ka this giant wave was most likely caused by one of the many large submarine landslides that have been identified on the lower slopes of the major hawaiian islands

sedimentary features of tsunami backwash deposits in a shallow marine miocene setting mejillones peninsula northern chile abstract miocene shoreface sandstones in the caleta herradura half graben northern chile contain an exceptionally coarse deposit that based on sedimentologic and stratigraphic features is regarded as having been laid down during a tsunami event by non cohesive and sediment laden subaqueous density flows interpretations of the principal sediment depositing mechanisms effective in the tsunami surges rely largely on field observations of deposit geometry and internal sedimentary characteristics this example comprises two erosively based sedimentation units that were probably deposited by successive waves in the tsunami wave train the lower unit consists of a clast supported polymodal boulder bearing breccia composed mostly of angular clasts and fewer well rounded clasts framework components are mostly chaotic but may also exhibit either inverse to normal grading or crude normal grading laterally changes in characters of depositional facies are common and abrupt the sand sized bioclastic rich matrix is poorly sorted and very similar to the underlying lower shoreface bioclastic sandstone implying that soft sediments eroded at the lower erosional surface contributed to the tsunami deposit the bulk of the upper unit is a poorly sorted breccia bearing sandstone pebbles and cobbles are scattered massive or normally graded sporadic outsized boulders emplaced as debris fall deposits may occur along the erosional base an array of signatures such as unusually coarse grain size in comparison to the surrounding deposits erosional bases the mixed sources of sediments multiple erosional and depositional events normal size grading or massive texture are all considered distinctive features of tsunamigenic deposits backwash deposition is indicated by the incorporation within the tsunami deposits of sediments derived from mixed sources such as angular clasts from nearby subaerial settings rounded clasts reworked from beach gravels and bioclastic sand eroded from older and unconsolidated shoreface deposits notwithstanding the absence of soft sediment deformation features the marked facies change from a lower shoreface into an upper shoreface environment through the tsunamiites provides directional information about the origin of the tsunami wave it was most likely produced by a sea floor fault displacement associated with an episode of sudden probably coseismic coastal uplift

boulders transport by catastrophic waves along the ionian coast of apulia southern italy abstract several tracts of the ionian coast of apulia southern italy are characterized by large boulders up to 80 t in weight scattered some meters above present sea level the largest boulder is about 80 t in weight and slid for about 40 m from the mean sea level up to about 1 8 m of altitude elongated boulders show a remarkably narrow range of orientation of the long axis as well as of the imbrication axis suggesting that they had been transported by a single catastrophic event most likely a tsunami connected to a wave train approaching the coast from the south stratigraphic morphological and historical data suggest that this event occurred during the late holocene conventional radiocarbon age determination performed on lithophag shells collected from a large boulder yielded a calibrated age between 1421 and 1568 a d then the catastrophic wave train probably a tsunami could be a local effect of the strong earthquake which hit southern italy on december 5th 1456

tsunami imprints on the leeward netherlands antilles aruba curacao bonaire and their relation to other coastal problems abstract tsunami are one of the major natural hazards in the caribbean the historical record lists 88 tsunami from local events to teletsunami in the time period from 1489 to 1998 this study focuses on the spatial distribution and geomorphologic evidence related to coarse littoral sediment and boulder deposition by tsunami events of holocene age in the southern caribbean at a worldwide scale these debris deposits represent the most extensive and impressive records of holocene paleo tsunami so far studied hitherto the leeward lesser antilles consisting of the islands of aruba curacao and bonaire were not known to have had tsunami affecting their coastlines the possible contribution of tsunami to configuring coastlines e g the questions of embayment development the coastal environment changes and the absence of holocene fringing reefs along the windward coasts is discussed

boulder deposits from large waves during the last interglaciation on north eleuthera island bahamas abstract seven boulders measuring 100 to 1000 m 3 are scattered along the coastal ridge of north eleuthera some are situated on ridge crests up to 20 m above present sea level the boulders were probably deposited during oxygen isotope substage 5e or 5d as shown by their stratigraphic setting and by amino acid racemization ratios d alloisoleucine l isoleucine ratios were determined for land snails and oolite of both marine and eolian origin was associated with the boulders like the boulders the probable source rocks exposed in the adjacent cliffs are composed of marine and eolian limestone of oolitic and peloidal composition the source beds are correlated with stage 9 or 11 the largest boulder is about 10 times the size of the largest holocene ones moved by waves in the area tsunamis are a reasonable possibility as a transporting mechanism of the pleistocene boulders however if deposited instead by storms during the last interglaciation the storms were of much greater intensity than those occurring in the region during the late holocene

chevron ridges and runup deposits in the bahamas from storms late in oxygen isotope substage 5e abstract landward pointing v shaped sand ridges several kilometers long are common along the windward margin of the bahama islands their axes share a northeast southwest trend internally the ridges contain low angle oolitic beds with few erosional truncations commonly interbedded are tabular fenestrae rich beds such as those formed by the sheet flow of water over dry sand defined here as chevron ridges these landforms appear to have originated in the rapid remobilization of bank margin ooid bodies by the action of long period waves from a northeasterly source deposits along adjacent coastlines also preserve evidence of the impact of large waves reworked eolian sand bodies preserve beach fenestrae and hydraulic scour traces up to 40 m on older ridges on cliffed coasts 1000 ton boulders have been thrown well inland recording the impact of large waves amino acid ratios confirm a correlation of the ridges across the archipelago while stratigraphy spacing and cross cutting relationships indicate emplacement as sea level fell rapidly from the substage 5e maximum at or above 6 m

unusual sedimentary deposits on the se side of stromboli volcano italy products of a tsunami caused by the ca 5000 years bp sciara del fuoco collapse abstract the role of sector collapse in the generation of catastrophic volcanigenic tsunami has become well understood only recently in part because of the problems in the preservation and recognition of tsunami deposits tinti et al tinti s bortolucci e romagnoli c 2000 computer simulations of tsunamis due to sector collapse at stromboli italy j volcanol geotherm res 96 103 128 modeled a tsunami produced by the c 5 000 years bp collapse of the sciara del fuoco on the island volcano stromboli although deposits associated with this event are generally lacking on the island volcaniclastic breccias on the se side of the island extending to an elevation above 120 m a s l may have been generated by this tsunami deposits above 100 m are dominated by coarse breccias comprising disorganized poorly sorted nonbedded angular to subangular lava blocks in a matrix of finer pyroclastic debris these breccias are interpreted as a water induced mass flow possibly a noncohesive debris flow generated as colluvial material on steep slopes was remobilized by the return flow of the tsunami wave the run up of which reached an elevation exceeding 120 m a s l finer breccias of subrounded to rounded lava blocks cropping out at 15 m a s l are similar to modern high energy beach deposits and are interpreted as beach material redeposited by the advancing tsunami wave the location of these deposits matches the predicted location of the maximum tsunami wave amplitude as calculated by modeling studies of tinti et al tinti s bortolucci e romagnoli c 2000 computer simulations of tsunamis due to sector collapse at stromboli italy j volcanol geotherm res 96 103 128 whereas the identification and modeling of paleo tsunami events is typically based on the observation of the sedimentary deposits of the tsunami run up return flow may be equally or more important in controlling patterns of sedimentation

geological effects and implications of the 2010 tsunami along the central coast of chile abstract geological effects of the 2010 chilean tsunami were quantified at five near field sites along a 200 km segment of coast located between the two zones of predominant fault slip field measurements including topography flow depths flow directions scour depths and deposit thicknesses provide insights into the processes and morphological changes associated with tsunami inundation and return flow the superposition of downed trees recorded multiple strong onshore and alongshore flows that arrived at different times and from different directions the most likely explanation for the diverse directions and timing of coastal inundation combines 1 variable fault rupture and asymmetrical slip displacement of the seafloor away from the epicenter with 2 resonant amplification of coastal edge waves other possible contributing factors include local interaction of incoming flow and return flow and delayed wave reflection by the southern coast of peru coastal embayments amplified the maximum inundation distances at two sites 2 4 and 2 6 km respectively tsunami vertical erosion included scour and planation of the land surface inundation scour around the bases of trees and channel incision from return flow sheets and wedges of sand and gravel were deposited at all of the sites locally derived boulders up to 1 m in diameter were transported as much as 400 m inland and deposited as fields of dispersed clasts the presence of lobate bedforms at one site indicates that at least some of the late stage sediment transport was as bed load and not as suspended load most of the tsunami deposits were less than 25 cm thick exceptions were thick deposits near open ocean river mouths where sediment supply was abundant human alterations of the land surface at most of the sites provided opportunities to examine some tsunami effects that otherwise would not have been possible including flow histories boulder dispersion and vegetation controls on deposit thickness

tsunami deposits from the 1993 southwest hokkaido earthquake and the 1640 hokkaido komagatake eruption northern japan the southwest hokkaido tsunami of july 12th 1993 left continuous onshore sand deposits along the west coast of oshima peninsuka hokkaido northern japan we investigated spatial distribution and lithofacies of the new tsunami deposits for its identification of ancient tsunami deposits an eyewitness acount and bent plants helped our interpretation of the onshore tsunami behavior we regard the following properties as typical of the coastal tsunami sand deposits 1 the deposits cover the surface almost continuously on gentle topography 2 deposit thicknesses and mean grain sizes descrease with distance from the sea 3 deposit thicknesses and lithofacies vary greatly across local surface undulation 4 graded bedding reflecting tsunami runup and backwash is present in thick deposits 5 the deposits are widely distributed along the coast and extend inland several tens of meters to 100 m we examined a candidate for the paleo tsunami deposits associated with the 1640 komagatake eruption and confirmed that the similar patterns are typical of ancient tsunami deposits

tsunami sedimentation associated with the lisbon earthquake of 1 november ad 1755 boca do rio algarve portugal a description is given of a distinctive marine deposit at boca do rio on the algarve coast of portugal it is proposed here that the sediment accumulation was deposited by the tsunami generated by the lisbon earthquake of 1 november ad 1755 the deposit exhibits sedimentary characteristics quite unlike other coastal sediment accumulations that are deposited by more moderate wave regimes these include laterally continuous sand layers chaotic pebble horizons large amounts of gravel sized shell debris and distinctive assemblages of marine microfossils a preliminary attempt is made here to use the empirical field and laboratory data to define more clearly the processes of coastal sedimentation that characterize tsunami runup the use of tsunami sediments as time synchronous marker horizons is also discussed

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

tsunami induced conglomerates in miocene upper bathyal deposits chita peninsula central japan abstract the tsubutegaura conglomeratic tsunamiites occur in the middle section of the miocene storm related sand silt alternation system in the chita peninsula central japan deposition of the system in the upper bathyal environment in a bay and synsedimentary seismic activity has been elucidated by palaeontological palaeogeographical and sedimentological studies two coupled units each built up by a conglomerate layer with an overlying sandstone layer and the alignment of lenticular sedimentary bodies are exceptional in this sequence some typical lenticular bodies confined within sedimentary troughs consist of a boulder bearing conglomerate layer and calcareous sandstone layer of the lower couple and another conglomerate layer of the upper couple the tuffaceous sandstone layer of the upper couple is distributed more widely than the other lithologies the framework gravels in the coupled conglomerates form a clast supported fabric and are quite notably monomictic the clasts are angular and imbricated partly forming peculiar gravel clusters due to traction current transportation conspicuous laminations develop in the coupled sandstone layers antidunes with chute and pool structure in the upper couple sandstone layer indicate deposition from an upper flow regime current on the other hand the calcareous composition of the lower couple sandstone layer reveals shallow water provenance thixotropic deformations and diastasis cracks in the siltstone bed immediately beneath the layers of the couples show that a severe earthquake tremor and a rapid change of water pressure occurred just before the deposition of the tsunamiites submarine debris flows due to collapse of a fault scarp in a shallow bank and the ensuing wash by two pulses of the tsunami induced ebb current comprise the scenario for the formation of the tsubutegaura conglomeratic tsunamiites

tsunami deposits related to flank collapse in oceanic volcanoes the agaete valley evidence gran canaria canary islands abstract enigmatic marine conglomerates are attached at 41 188 m asl to the walls of the valley of agaete on the northwest coast of gran canaria canary islands they are formed by heterogeneous angular to rounded heterometric volcanic clasts roundness and maximal size decreasing with altitude and fossils rhodolites and marine shells never found in growth position and often broken the deposits are internally stratified into several layers most of them showing very poor sorting matrix supported and reverse grading they present lenticular morphologies with poor lateral continuity in transversal and longitudinal sections slopes show values and orientations similar to those of the relief of the substratum to which they seem to adapt although they show clear evidence of erosive contact with the substratum rip up clasts they do not tend to form horizontal terraces soft materials soils and colluviums are preserved in the contact with the substratum in outcrops with deposit slopes of up to 15 the age of the deposits is constrained between 1 75 ma and 32 ka their altitude and slope distributions are not related to pleistocene interglacial sea level changes storm deposits or isostatic movements all the above suggests that the agaete marine deposits were generated by tsunami waves the most probable source being a flank failure at least nine major such events having occurred in the canary islands during the pleistocene the guimar sector collapse east coast of tenerife 30 km 3 is the closest possible source for the tsunami and the sole flank failure that is directed towards another island in the canaries

tidal marsh stratigraphy sea level change and large earthquakes i a 5000 year record in washington u s a abstract many of the estuaries of the pacific northwest of the u s a and canada contain stratigraphic sequences typified by alternating peat mud couplets recent studies in this region interpret such couplets as the product of repeated large magnitude s or 9 earthquakes on the cascadia subduction zone the resultant pattern of land level movements is described by a model the earthquake deformation cycle of coseismic land subsidence followed by land uplift during interseismic strain accumulation however peat mud couplets similar to those recorded in the pacific northwest are found on other less tectonically active temperate latitude coasts such as northwest europe and the atlantic coast of the u s a where they have been interpreted as the product of non seismic coastal processes in this paper we apply the methods and scientific framework common to sea level investigations in northwest europe to a sequence of peat mud couplets recorded in the lower johns river an estuary in southern washington to provide a test of the earthquake deformation cycle stratigraphic investigations of the intertidal sediments along the lower johns river using lithological pollen diatom and foraminiferal data show evidence for eight coastal submergence events during the last 5000 years to evaluate the earthquake deformation cycle we assess the lateral extent of peat mud couplets the synchroneity of submergence the presence of tsunami deposits accompanying submergence and the suddenness and amount of submergence each submergence is shown to be accompanied by changes in coastal sedimentation broadly commensurate with those predicted by the earthquake deformation cycle demonstrating the continued intermittent seismic activity of the cascadia subduction zone throughout the mid and late holocene quantitative analyses of contemporary and fossil biostratigraphic data using twinspan and detrended correspondence analysis enable us to estimate the magnitude of submergence accompanying each peat mud couplet one event was accompanied by submergence of about 1 5 m or more four events by intermediate submergence of about 1 0 5 m and a further three events by submergence of

tsunami sedimentary facies deposited by the storegga tsunami in shallow marine basins and coastal lakes western norway sedimentary successions in small coastal lakes situated from 0 to 11 m above the 7000 year bp shoreline along the western coast of norway contain a distinctive deposit very different from the sediments above and below the deposit is interpreted to be the result of a tsunami inundating the coastal lakes an erosional unconformity underlies the tsunami facies and is traced throughout the basins with most erosion found at the seaward portion of the lakes the lowermost tsunami facies is a graded or massive sand that locally contains marine fossils the sand thins and decreases in grain size in a landward direction above follows coarse organic detritus with rip up clasts here termed organic conglomerate and finer organic detritus the tsunami unit generally fines and thins upwards the higher basins 6 11 m above the 7000 year shoreline show one sand bed whereas basins closer to the sea level 7000 years ago may show several sand beds separated by organic detritus these alternations in the lower basins may reflect repeated waves of sea water entering the lakes in basins that were some few metres below sea level at 7000 years bp the tsunami deposit is more minerogenic and commonly present as graded sand beds but also in some of these shallow marine basins organic rich facies occur between the sand beds the total thickness of the tsunami deposit is 20 100 cm in most studied sites an erosional and depositional model of the tsunami facies is developed

evidence for three north sea tsunamis at the shetland islands between 8000 and 1500 years ago abstract coastal fen and lake deposits enclose sand layers that record at least three holocene tsunamis at the shetland islands the oldest is the well known storegga tsunami ca 8100 cal yr bp which at the shetlands invaded coastal lakes and ran up peaty hillsides where it deposited sand layers up to 9 2 m above present high tide level because sea level at ca 8100 cal yr bp was at least 10 15 m below present day sea level the runup exceeded 20 m in two lakes we also found deposits from a younger tsunami dated to ca 5500 cal yr bp the sediment facies are similar to those of the storegga tsunami rip up clasts sand layers re deposited material and marine diatoms runup was probably more than 10 m yet another sand layer in peat outcrops dates to ca 1500 cal yr bp this sand layer thins and fines inland and was found at two sites 40 km apart and traced to ca 5 6 m above present high tide the oldest tsunami was generated by the storegga slide on the norwegian continental slope we do not know what triggered the two younger events

contamination of tsunami sediments in a coastal zone inundated by the 26 december 2004 tsunami in thailand tsunami sediments deposited in a coastal zone of thailand by the 26 december 2004 tsunami wave were sampled within 50 days after the event all surface and ground waters in tsunami inundated zone revealed significant salinity at that time the tsunami sediments composed mainly of fine to medium sand contain significantly elevated contents of salts na k ca 2 mg 2 cl and so4 2 in water soluble fraction and of cd cu zn pb in the bioavailable fraction and as in the exchangeable fraction in relation to the reference sample the origin of contaminants is marine as well as litho and anthropogenic the salts and pb zn and cu reveal high correlation to each other and to the mean grain size pore size and porosity serious environmental hazard exists in that region because due to gentle morphology there is a risk of migration of the contaminants into ground waters and food chain

instantaneous movement of krill swarms in the antarctic circumpolar current antarctic krill are known to have strong swimming capabilities but direct observations of the speed and direction of krill swarm movement within their natural environment are rare we identified and examined 4060 swarms within the main flow of the antarctic circumpolar current scotia sea using a combination of an ek60 echosounder a 153 6 khz acoustic doppler current profiler and ground truthing nets net displacement magnitude m and net angle of deviation d were determined by vector subtraction from the background flow immediately below them values were compared against control data sets in which swarms were absent with greater background flow m became increasingly lower than predicted which suggests that drag influences swarm movement the characteristics of the flow regime influenced swarm behavior given that both m and d varied according to the direction of background flow furthermore multiple regression analysis indicated that swarm area the vicinity of the sea ice edge and salinity had a significant influence on m with levels of displacement being greatest in larger swarms and in low salinity regions close to the ice edge the ice edge is a key environment for antarctic krill and swarm behavior may assist in retaining this location only fluorescence was found to have a significant influence on d with deviations being greatest in regions of highest fluorescence this agrees with laboratory observations of krill turning more frequently within food patches we demonstrate that it is possible to measure instantaneous movement patterns in antarctic krill swarms and at large scales these movements are consistent with current understanding of responses of krill to local stimuli such as sea ice and patches of food swarms of antarctic krill form some of the highest concentrations of animal biomass found in any of the world s ocean reaching densities of up to 2 million tons over an area of 100 km2 nowacek et al 2011 krill swarm

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

traces of tsunami preserved in inter tidal lacustrine and marsh deposits some examples from northeast japan the japan sea earthquake of may 26 1983 triggered a large scale tsunami that surged over the coast of ne japan and caused considerable damage the tsunami resulted in peculiar sedimentary processes on the coast depending on the hydraulic scale of the tsunami three kinds of sedimentary processes were recognized each of which left unique deposits such deposits are expected to remain in sedimentary sequences preserving remarkable sedimentary facies borehole samples drilled at different localities in coastal regions have been examined to detect traces of ancient tsunamis sedimentological and geochemical studies of the samples reveal that layered deposits similar to those developed by the tsunami of the japan sea earthquake are common in the drilled cores estimated ages of these deposits are exactly equivalent to the dates of ancient tsunamis documented in historical records these results show that the invasion of tsunamis is recorded in coastal depositional sequences from analyses of long borehol

coastal sedimentation associated with the june 2nd and 3rd 1994 tsunami in rajegwesi java abstract this paper presents the second detailed study of sediments deposited by modern tusnamis the first being that of the flores indonesia tsunami of december 1992 shi et al 1995 sediment cores were collected from areas in which eyewitnesses reported sediment deposition grain size analysis shows pronounced vertical variations in grain size as well as changes in standard deviation skewness and kurtosis that appear to be indicative of complex tsunami flooding vertical variations in grain size in individual cores are greater than spatial variations between cores taken along a transect completed perpendicular to the coastline the java tsunami deposited sediments do not show unequivocal evidence of local erosion but instead evidence for sediment transport and deposition is clear and is characterised by dominantly unimodal sediments with fine tailed distributions

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

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

the sedimentology of middle holocene tsunami facies in northern sutherland scotland uk abstract lagoonal sediments attributed to the main holocene marine transgression in strath halladale northern sutherland contain a complex coarser layer believed to have been deposited during the tsunami associated with the second storegga slide off south west norway the coarser sequence is dated at between 7590 50 and 7290 50 radiocarbon years bp 6507 6260 cal bc and 6228 6029 cal bc detailed stratigraphical analysis has determined a distinctive suite of sedimentary sub units within the coarser layer in marked contrast to the sediments which occur above and below a pronounced erosional unconformity with the underlying sediments is recorded with the base of the tsunami layer characterised by eroded material from the underlying peat the presence of a mixed diatom assemblage although fragmentary indicates a chaotic accumulation of the deposit with all habitats represented variations in particle size within the sequence disclose striking similarities with those from contemporary tsunami deposits the run up of the tsunami sediments is calculated at a minimum of 4 6 m this is the first occasion on which a deposit of the second storegga slide tsunami has been found outside the north sea basin and indicates that the area affected by the tsunami may have been larger than has been previously described

styles of early diagenesis and the preservation potential of onshore tsunami deposits a re survey of isla mocha central chile 2 years after the february 27 2010 maule tsunami abstract the style of early diagenesis and preservation of onshore tsunami deposits are poorly constrained only tsunami surveys and subsequent re surveys can fill this information gap here we present the results of a first re survey in 2012 on isla mocha following the original survey in 2010 in the wake of the february 27 2010 maule earthquake and tsunami in central chile as a result of this tsunami a large number of boulders consisting of clay rich fine sandstones representing the miocene age bedrock of the island had been transferred from the tidal to shallow subtidal zone onto the coastal plain coarse clastic sediment mixtures of pebbles granules and sand entrained at coastal plain terraces and transported up to the maximum runup position c 600 m from the coast by the inflow had been left behind as extensive backflow blankets on the lower coastal plain in 2012 vegetation had covered the 2010 tsunami deposits sediment beyond 200 m from the coast had been removed by a combination of surface processes and grazing cattle grain size distributions of the preserved sediment show an increase of the sand fraction at the expense of the coarser grain sizes boulders show patterns resembling mud cracks on the surface and evidence of disintegration into smaller fragments and sand veneers of dried algae documenting the derivation of the boulders from the tidal zones had flaked off partly or completely from most rock surfaces at the northern wind facing coast of the island a c 130 m long and 1 2 m high beach ridge had accumulated most likely from reworked tsunami sediment boulders deposited by tsunamis are commonly assigned a high preservation potential we demonstrate for the first time that such boulders may in fact disintegrate rapidly and disappear from the record over short geological time scales given a lithology susceptible to weathering the degree of modification to the lsla mocha tsunami boulders and deposits strongly questions the applicability of inverse models using paleotsunami deposit thickness and grain size distributions to infer parameters and magnitudes of the causative tsunamis inverse models would consequently underestimate tsunami flow parameters and may result in the inference of erroneous transport modes and event magnitudes our study gives strong evidence in support of re survey studies following the deposition of tsunami sediments by tracing and quantifying the changes affecting them

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

geomorphological effects of tsunami run up and backwash abstract geomorphological processes associated with tsunami run up and backwash are highly complex to date most studies have considered the sedimentology of palaeo tsunamis while almost no detailed studies have been undertaken in areas known to have been affected by tsunamis in recent times research on contemporary tsunamis show that coastal landscapes may be greatly altered not only by direct tsunami run up orthogonal to the shoreline but also by episodes of vigorous backwash and by water flow sub parallel to the coastline the combined effect of these processes produces hitherto unrecognised coastal landforms that are dominated by the effects of high magnitude erosion and deposition deposition of large boulders is also associated with severe tsunamis while in adjacent areas run up processes often result in the deposition of continuous and discontinuous sediment sheets in many instances the upper limit of sediment deposition lies well below the upper limit of wave run up which is frequently marked by a well defined zone of stripped vegetation and soil the processes described have considerable implications for models of coastal evolution it may even be the case that the evolution of particular stretches of coastline are dominated by such high magnitude low frequency events

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

onshore tsunami deposits caused by the 1993 southwest hokkaido and 1983 japan sea earthquakes onshore tsunami deposits resulting from the 1993 southwest hokkaido and 1983 japan sea earthquakes were described to evaluate the feasibility of tsunami deposits for inferring paleoseismic events along submarine faults tsunami deposits were divided into three types based on their composition and aerial distribution a deposits consisting only of floating materials b locally distributed siliclastic deposits and c widespread siliclastic deposits the most widely distributed tsunami deposits consist of the first two types type c deposits are mostly limited to areas where the higher tsunami runup was observed the scale of tsunami represented by vertical tsunami runup is an important factor controlling the volume of tsunami deposits the thickest deposits about 10 cm occur behind coastal dunes to produce thick siliclastic tsunami deposits a suitable source area such as sand bar or dune must be available in addition to sufficient vertical tsunami runup estimation of the amounts of erosion and deposition indicates that tsunami deposits were derived from both onshore and shoreface regions the composition and grain size of the tsunami deposits strongly reflect the nature of the sedimentary materials of their source area sedimentary structures of the tsunami deposits suggest both low and high flow regimes consequently it seems very difficult to identify tsunami deposits based only on grain size distribution or sedimentary structure of a single site in ancient successions

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

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

sedimentation et fracturation de haute energie en milieu recifal tsunamis ouragans et cyclones et leurs effets sur la sedimentologie et la geomorphologie d un atoll motu et hoa a rangiroa tuamotu pacifique se abstract a longitudinal festoon fracture of the reef flat widened by slow biological and mechanical erosion transverse along the grooves divides the nw coral rim of rangiroa tuamotu se pacific into colossal blocks 15 10 5 m 1500 t the elaboration of these blocks can be attributed to the dislocation of the top of the reef flat by catastrophic events tsunamis or hurricanes typhoons in the sw and s pacific the shifting of these blocks mega boulders would necessitate a considerable amount of energy and at present we cannot decide which one of these phenomena was responsible various examples observed in the pacific are cited to illustrate abrupt changes in the sea level these could be attributed either to meteorological events hurricanes cyclones or typhoons or to seismic events of very high energy ground sea or tsunamis the reader is reminded of the different characteristics that these phenomena produce this study is mainly concerned with tsunamis especially the frequency of their occurrence energy and effects on the coasts of small oceanic islands hurricanes cyclones and typhoons roughly originate from the n ne and e whereas tsunamis originate from all directions except from se s and sw angle these very high energy events hurricanes and tsunamis seem then to be responsible for 1 the decreasing grain size of the coral rim sediments from the ocean to the lagoon through the range of colossal blocks smaller boulders scree gravels coarse and fine sands 2 the sedimentary accretion of the motu itself at each very high energy so called catastrophic event they are also responsible for the preservation of the two characteristic geomorphic forms of an atoll motu and hoa 3 finally the alternation motu hoa motu etc on the coral rim this alternation seems to result from the interaction between oceanic disturbances hurricanes or tsunamis and the water volume which must flow over the coral rim the transported material the reef flat and the angle of incidence between the swell and the coast during these catastrophic events

depositional facies and sedimentary successions of earthquake induced tsunami deposits in upper pleistocene incised valley fills central japan abstract two anomalous deposits with well preserved sedimentary structures were discovered in a drowned valley and in relict barrier sand body deposits in the furuya mud and kyomatsubara sand of the upper pleistocene incised valley fills the sedimentary features of both deposits are interpreted as earthquake induced tsunami deposits which were deposited in incised valley fills the tsunami deposit in the drowned valley furuya mud is 150 cm thick and shows a contorted structured bed in the lower part and cross laminated sand in the upper part the tsunami deposit in barrier sand body kyomatsubara sand is 270 cm thick and shows structureless sand with mud clasts in the lower part cross laminated sand with mud drapes in the middle part and mud with small wave ripples in the upper part taken together these sedimentary features suggest a model for the composite succession which is comprised of three units a lower earthquake shock influenced anomalous convoluted part a middle part dominated by tsunami generated tractional currents and an upper suspended sediment part the lower part is interpreted as earthquake event deposits seismites and the middle and upper parts as tsunami current deposits tsunamiites

evaluating the impacts of huge waves on rocky shorelines an essay review of the book tsunami the underrated hazard abstract tsunami the underrated hazard draws together and summarizes a wealth of information about the nature impacts and causes of tsunamis written from a natural hazards perspective the book stresses that large tsunamis can affect even protected coasts that have not experienced large tsunamis historically many deposits and erosional features described and discussed as tsunami signatures have yet to be linked specifically with tsunamis cited references in the book do not necessarily support a tsunami origin for these features because accepted scientific citation practices have not been followed although rocky shorelines in southeastern australia the hawaiian islands and elsewhere generate and preserve a variety of boulder and block deposits and erosional features their sediment dynamics and geomorphology are poorly studied and unequivocal criteria for distinguishing between deposits of storms and tsunamis have yet to be developed despite its shortcomings this book should be on the library shelves of all marine geoscientists who study modern and ancient shorelines however it should be used with great circumspection because the process product relationships it assumes are equivocal

discovery of minoan tsunami deposits the hellenic arc is a terrane of extensive quaternary volcanism one of the main centers of explosive eruptions is located on thera santorini and the eruption of the thera volcano in late minoan time 1600 1300 b c is considered to have been the most significant aegean explosive volcanism during the late holocene the last eruptive phase of thera resulted in an enormous submarine caldera which is believed to have produced tsunamis on a large scale evidence suggesting seawater inundation was found previously at some archaeological sites on the coast of crete however the cause of the tsunami and its effects on the area have not been well understood on the aegean sea coast of western turkey didim and fethye and crete gouves we have found traces of tsunami deposits related to the thera eruption the sedimentological consequences and the hydraulics of a thera caused tsunami indicate that the eruption of thera volcano was earlier than the previous estimates and the tsunami did not have disruptive influence on minoan civilization

multiple sources for late holocene tsunamis at discovery bay washington state usa nine muddy sand beds interrupt a 2500 yr old sequence of peat deposits beneath a tidal marsh at the head of discovery bay on the south shore of the strait of juan de fuca washington an inferred tsunami origin for the sand beds is assessed by means of six criteria although all the sand beds contain marine diatoms and almost all the beds display internal stratification the areal extent of the oldest beds is too limited to confirm their origin as tsunami deposits the ages of four beds overlap with known late holocene tsunamis generated by plate boundary earthquakes at the cascadia subduction zone diatom assemblages in peat deposits bracketing these four beds do not indicate concurrent change in elevation at discovery bay diatoms in the peat bracketing a tsunami bed deposited about 1000 cal yr bp indicate a few decimeters of submergence suggesting deformation on a nearby upper plate fault other beds may mark tsunamis caused by more distant upper plate earthquakes or local submarine landslides trigg

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

record of enhanced late pliocene tectono volcanic activity in the lesser antilles forearc basin insights into the long term behaviour of the lesser antilles subduction zone in this study we investigate the lesser antilles forearc basin focusing on the late pliocene to pleistocene sedimentary archives in order to track the occurrence of extreme events triggered by enhanced subduction related tectono volcanic activity we identify late piacenzian deposits covering a major regional erosional surface displaying sedimentary dykes and large marine boulders embedded in a mixed continental marine matrix characteristic of tsunamites we interpret this episode of platform emersion and the successive cataclysmic deposits as resulting from enhanced tectonic activity at the interface of the subduction zone synchronous with the initiation of the lesser antilles volcanic arc we then discuss the implications in terms of the mechanical behaviour of the lesser antilles subduction zone this article is protected by copyright all rights reserved

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

relative influences of the metocean forcings on the drifting ice pack and estimation of internal ice stress gradients in the labrador sea understanding the relative influences of the metocean forcings on the drift of sea ice floes is a crucial component to the overall characterization of an ice environment and to developing an understanding of the factors controlling the ice dynamics in addition estimating the magnitude of the internal stress gradients on drifting sea ice floes generated by surrounding ice cover is important for modeling operations informing the design of offshore structures and vessels in ice environments and for the proper calibration of discrete element models dem of fields of drifting ice floes in the spring of 2015 and 2016 four sea ice floes offshore makkovik labrador were tagged with satellite linked ice tracking buoys along with one satellite linked weather station on each floe to transmit wind speed and direction twenty satellite linked lagrangian surface ocean current tracking buoys were also deployed in the open water adjacent to the targeted ice floes in this paper the dynamics of the four ice floes are explored in terms of the relative proportions which were forced by the wind current sea surface topography coriolis and internal stress gradients the internal ice stress gradients are calculated as residuals between the observed accelerations of the floes as measured by the tracking buoys and the sums of the other metocean forcings results show that internal ice stress gradients accounted for up to 50 of the observed forcing on the floes and may have reached up to around 0 19kpa

the 17 july 1998 tsunami papua new guinea evidence and initial interpretation abstract a m w 7 1 earthquake that occurred at 08 49 hours 17 july 1998 utc 6 49 pm local time off the north coast of papua new guinea generated a locally destructive tsunami more than 2189 people died and virtually no structures were left standing along 19 km of coast a fast moving wall of sand laden water left fishing nets and other detritus in trees up to 17 5 m above sea level concrete was stripped to the reinforcing metal and some trees were ripped out and carried more than a kilometre back into sissano lagoon the site is in an active sedimentary basin the aitape trough with 4500 m thickness of neogene sediments between the bewani fault zone and the wewak trench there is some debate about the form of tsunami propagation for this event however we present evidence for subsidence of 30 40 cm on the landward side of the spit fronting sissano lagoon furthermore the area may have subsided up to three times this century in situ stumps of drowned trees in the lagoon record at least one earlier event the low angle harvard university cmt solution m w 7 1 depth 6 0 km 10 landward dip on fault with northward displacement is consistent with the tectonic setting and pattern of aftershocks elastic modelling of the energy release suggests 2 m horizontal displacement over 600 km 2 40 cm subsidence landward and 60 cm uplift seaward convergent flow of the displaced water into the area of subsidence focused wave energy on the coast and generated the locally high wave the record of tsunami at sissano lagoon indicates that the spit fronting the lagoon is unsafe for habitation there is potential for similar coseismic coastal subsidence to focus tsunami in other areas with similar tectonic settings

tsunami deposits in holocene bay mud in southern kanto region pacific coast of central japan abstract tsunami have probably deposited sand sheets that are intercalated in holocene bay floor mud exposed on the boso and miura peninsulas facing the convergent boundary of the pacific philippine sea and eurasian plates we have identified seven sand sheets at four drowned valleys and correlated these by 137 radiocarbon dates of shells and wood the sheets consist of poorly sorted muddy sand and well sorted sand layers in fining upward sequences containing abundant transported shells rip up clasts and wood fragments the sheets erosionally overlie bioturbated bay floor mud that contains molluscan shells in life position most of the sheets are less than 20 cm thick and rarely more than 50 cm thick some molluscan shells are older in these layers than in underlying mud both landward and seaward paleocurrents are shown in a few cases by imbrication of shells and by low angle wedge shaped lamination at least five of the sand sheets contain molluscan fossils derived from rocky coasts or shore platforms although they intercalated in mud deposited within bays at depths of 10 15 m two other sand sheets are dominated by open seashore ostracode assemblages although they were deposited in the brackish inner bay and muddy central bay five of the layers may correlate with emergences recorded by nearby holocene marine terraces these correlations suggest that great earthquakes triggered the inferred tsunami the tsunami occurred at intervals of 300 2000 years beginning about 10 000 years ago

field survey of the 2018 sulawesi tsunami deposits on 28 september 2018 a mw 7 5 earthquake struck sulawesi island soon followed by a destructive tsunami this study provides a case history of tsunami deposition where submarine landslides or coastal collapses have contributed to and intensified tsunami generation the sedimentary features resulting from this complex tsunami mechanism are not yet well understood we surveyed tsunami deposits at six locations along the coastline of palu bay in addition to measuring tsunami flow depth run up height and inundation distance at each site in general the tsunami height was less than 8 m with a maximum inundation distance of 310 m the tsunami deposits are thin with simple sedimentary structures such as fining upward sequences these sedimentary characteristics are typical of tsunami deposits elsewhere around the world this work is a preliminary study in that numerical modeling including sediment transport has not been performed further work is needed to distinguish tsunamis with different source mechanisms

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

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

palaeotsunami deposits a new zealand perspective abstract over the past few years geological investigations of coastal sediments in new zealand have provided evidence of past tsunami the identification of palaeotsunami deposits is helping to increase our knowledge about the sources magnitude and frequency of these events this paper briefly outlines both the key diagnostic characteristics used in new zealand to identify palaeotsunami deposits and the emerging findings related to recent research