environmental impact assessment of the 2011 tohoku oki tsunami on the sendai plain abstract large areas of farmland in the sendai plain japan were inundated by the 11 march 2011 tohoku oki tsunami and covered by a discontinuous 30 0 2 cm thick sediment layer consisting of sand and or mud and generally thinning and fining inland two months after the tsunami numerous rice paddy fields and depressions remained ponded with brackish or saline water a series of field surveys in may august and october 2011 were carried out north of sendai airport in order to assess the environmental impact of the tsunami while evaporation had resulted in elevated conductivity in ponded water in may up to 68 2 ms cm 1 rainfall over the next five months led to dilution although brackish water was still recorded in depressions and on paddy fields tsunami sediments underlying soil and soil beyond the tsunami inundation limit were collected at 43 sites along and near a transect extending over 5 km inland and analysed for grain size organic content water leachable ions acid leachable metals and exchangeable metalloids water leachable anion and cation concentrations were elevated in sandy and muddy tsunami deposits and soils particularly in areas where seawater had stagnated for a longer period of time after the tsunami with up to 10 5 cl 6 6 na 2 8 so 4 440 mg kg 1 br measured in surface sediments the impact of saltwater inundation was documented in the chemistry of soils underlying tsunami sediments which were affected by salt contamination down to 15 cm depth and soils not covered by tsunami deposits the latter implies that the extent of tsunami inundation may successfully be determined using geochemical markers in absence of any sedimentological evidence water leachable ions mostly decreased over time however they remained high enough to impact on rice farming which was completely halted in 2011 although further work is required to assess the longer term impact of tsunami inundation flushing of salt with freshwater as well as the possible removal of sandy muddy sediments and underlying soil are recommended to allow crop production to resume

tsunami deposits in a lacustrine sequence of the sanriku coast northeast japan abstract lacustrine deposits of the pacific coast of northeast japan consisting mostly of black organic mud contain intercalated thin beds of well sorted medium sand examination of the deposits from a coastal site of sanriku has revealed that sand grains are of marine origin and are fractions of deposits in marshy ponds transported from the littoral environment by a great flooding of seawater the mode of sedimentation shown in the thin beds of sand implies that they were deposited by tsunamis each with a maximum rise of 1 m or more above sea level

assessing δ13c and c n ratios from organic material in archived cores as holocene sea level and palaeoenvironmental indicators in the humber estuary uk organic 13c and c n analyses of estuarine deposits provide proxies for changes in the source of organic matter which can be driven by fluctuations in relative sea level river discharge and catchment disturbance here we present the results of a comprehensive vegetation and sediment 13c and c n survey of welwich marsh outer humber estuary uk together with high resolution 13c and c n analyses of holocene cores collected nine years previously from the humber estuary and the lincolnshire marshes eastern england uk the contemporary intertidal 13c and c n dataset shows a gradual increase in surface sediment 13c with decreasing marsh height and suggests that 13c is controlled by the degree of tidal inundation and thus reflects organic matter source however sediment c n ratios are less sensitive to tidal changes and the recent introduction of c4 salt marsh species complicates the contemporary analogue the holocene 13c and c n records are in general agreement with existing microfossil data and provide additional palaeoenvironmental information this includes support for an estuary wide expansion of marine conditions from c 3 3 ka cal yr bp followed by a contraction of marine conditions after c 2 7 ka cal yr bp and evidence for an increase in delivery of terrigenous organic matter to the inner estuary in the late holocene bulk organic 13c and c n analysis is shown to be a reliable and independent indicator of coastal environmental change and is therefore a complementary technique to the more commonly used microfossil approach however this study also shows that in some circumstances the technique may be compromised when applied to sediments from cores that have been stored for a period of time

ecological effects of the paleozoic modern faunal transition comparing predation on paleozoic brachiopods and molluscs the shift from the paleozoic to the modern post paleozoic fauna involved a major influx of benthic molluscs gastropods and bivalves into offshore marine environments resulting in mixed brachiopod benthic mollusc paleocommunities as early as the late paleozoic era this change might be expected to have affected contemporaneous predators gastropods and productidine brachiopods from five upper pennsylvanian shales in texas united states show greater repair frequencies than do other taxa suggesting that crushing predators readily consumed gastropods early in the faunal transition but that some brachiopod taxa still composed an important component of predator diets in contrast drilling predators continued to prefer brachiopods almost exclusively over benthic molluscs paleozoic drillers may have been incapable of taking mobile prey contrary to previous hypotheses brachiopods were probably not mistaken prey at least during the paleozoic the addition of gastropods to the diet of crushing predators suggests a major change in ecological processes in response to the new fauna

tsunami history of an oregon coastal lake reveals a 4600 yr record of great earthquakes on the cascadia subduction zone bradley lake on the southern oregon coastal plain records local tsunamis and seismic shaking on the cascadia subduction zone over the last 7000 yr thirteen marine incursions delivered landward thinning sheets of sand to the lake from nearshore beach and dune environments to the west following each incursion a slug of marine water near the bottom of the freshwater lake instigated a few year to several decade period of a brackish 4 salinity lake four additional disturbances without marine incursions destabilized sideslopes and bottom sediment producing a suspension deposit that blanketed the lake bottom considering the magnitude and duration of the disturbances necessary to produce bradley lake s marine incursions a local tsunami generated by a great earthquake on the cascadia subduction zone is the only accountable mechanism extreme ocean levels must have been at least 5 8 m above sea level and the cumulative duration of each marine incursion must have been at least 10 min disturbances without marine incursions require seismic shaking as well over the 4600 yr period when bradley lake was an optimum tsunami recorder tsunamis from cascadia plate boundary earthquakes came in clusters between 4600 and 2800 cal yr b p tsunamis occurred at the average frequency of 3 4 every 1000 yr then starting 2800 cal yr b p there was a 930 1260 yr interval with no tsunamis that gap was followed by a 1000 yr period with 4 tsunamis in the last millennium a 670 750 yr gap preceded the a d 1700 earthquake and tsunami the a d 1700 earthquake may be the fi rst of a new cluster of plate boundary earthquakes and accompanying tsunamis local tsunamis entered bradley lake an average of every 390 yr whereas the portion of the cascadia plate boundary that underlies bradley lake ruptured in a great earthquake less frequently about once every 500 yr therefore the entire length of the subduction zone does not rupture in every earthquake and bradley lake has recorded earthquakes caused by rupture along the entire length of the cascadia plate boundary as well as earthquakes caused by rupture of shorter segments of the boundary the tsunami record from bradley lake indicates that at times most recently 1700 yr b p overlapping or adjoining segments of the cascadia plate boundary ruptured within decades of each other

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

inner shelf to shoreface depositional sequence in the sendai coastal prism pacific coast of northeastern japan spatial and temporal growth patterns in relation to holocene relative sea level change abstract temporal and spatial growth patterns of the holocene wave dominated inner shelf to shoreface sequence in the sendai coastal plain pacific coast of northeastern japan are detailed in relation to high resolution ams 14c data the sequence deposited during about 10 000 years of rising to stable relative sea level is a 22 26 m thick tripartite inner shelf to shoreface unit that overlies a transgressive ravinement surface it is composed successively of laminated fine sand facies b alternating mud and laminated very fine sand facies c and burrowed laminated fine to coarse sand facies d facies b consists of transgressive ravinement deposits formed during transgression in a water depth of 12 18 m at the drill sites facies c is inner shelf storm deposits deposited during continued sea level rise to highstand facies d is regressive highstand shoreface deposits isochrons show highstand deposits were formed by seaward progradation of the inner shelf to shoreface system the stacking of deposits during rising sea level was mainly aggradational though there was probably accompanying progradation in the innermost shelf the significant shelfal aggradation was probably because of an abundant mud supply from coastal rivers during gradual rise of relative sea level

taphonomic signatures and patterns of test degradation on tropical intertidal benthic foraminifera the preservational condition of benthic foraminifera from tropical intertidal sediments in cleveland bay north queensland australia was examined in order to provide systematic descriptions of taphonomic signatures and semi quantitative estimates of test degradation the primary aim was to improve understanding of the processes of test degradation experienced by intertidal foraminifera during early burial eight common tropical intertidal foraminiferal species were examined arenoparrella mexicana miliammina fusca miliammina obliqua and trochammina inflata from two upper mangrove stations and ammonia aoteana elphidium excavatum clavatum pararotalia venusta and parrellina hispidula from two mudflat stations taphonomic alteration was broadly divided into surface textural features and larger scale structural losses to tests surface alteration of calcareous tests was dominated by the etching and roughening associated with dissolution processes with limited evidence for bioerosion and abrasion both surficial etching and larger scale structural damage were closely related to test architecture with degradation most intense on porous chamber walls as opposed to non porous areas interlocular walls and chamber tips furthermore all calcareous species exhibited consistent pathways of degradation whereby the most recently formed chambers were the most vulnerable to degradation the correspondence between larger scale test loss and these patterns of surface textural alteration suggests calcareous test degradation is primarily driven by dissolution degradation of agglutinated tests contrasts in a number of ways pristine tests of all four species examined exhibited a smooth outer organic coating which may be missing from other specimens the extent to which this initial loss effects further test breakdown is uncertain but appears to differ between species m obliqua and some specimens of a mexicana exhibited structural damage which corresponded to clear cement losses and agglutinant disaggregation more generally agglutinated species displayed fracturing and test breakages which bore no conspicuous relation to cement loss furthermore neither surface alteration nor structural loss affected any part of agglutinated tests preferentially and therefore pathways of degradation were inconsistent across specimens the fact that agglutinated tests degrade in a more arbitrary manner compared with calcareous tests is taken as evidence that their degradation is 1 not entirely controlled by test architecture and 2 at least partially driven by physical mechanical processes we suggest that if agglutinated tests are not already inherently weaker than their calcareous counterparts the loss of organic cements may sufficiently weaken agglutinated tests so as to increase susceptibility to physical damage tests were also graded according to the extent to which they were structurally degraded average taphonomic grades and taphonomic variability i e standard deviation for all species at cocoa creek were statistically invariant with depth contrary to expectations based on the concept of progressive burial through a taphonomically active zone this indicates that shallow sub surface sediments are significantly homogenised and that sediment mixing and infaunal test production imparts a considerable effect on the development of surface and sub surface dead assemblages at the study site

the storegga slide tsunami comparing field observations with numerical simulations abstract deposits from the storegga tsunami have been found in coastal areas around the norwegian sea and north sea from the northeast coast of england to beyond the arctic circle in northern norway the tsunami deposits reach onshore elevations of 10 12 m above sea level of their time in western norway 3 6 m in northeast scotland and above 20 m on the shetland islands these elevations are compared with surface wave elevations derived from a numerical simulation of the storegga slide a good agreement is obtained for a retrogressive slide that descends at 25 30 m s and that has short time lags of 15 20 s between each individual slide block

diatom evidence for earthquake induced subsidence and tsunami 300 yr ago in southern coastal washington fossil diatoms from four stratigraphic sections along the tidal niawiakum river southwestern washington provide an independent paleoecological test of a relative sea level rise that has been attributed to subsidence during an inferred earthquake in the cascadia subduction zone about 300 yr ago diatom assemblages in a buried soil and overlying mud indicate a sudden and lasting shift from marshes and forests near or above highest tides to mud flats and incipient tidal marshes with a progressive return to high level tidal marshes by sediment aggradation and perhaps gradual tectonic uplift the amount of coseismic submergence required to generate the paleoecological changes observed at these sites could have ranged from a minimum of 0 8 1 0 m to a maximum of 3 0 m fossil diatoms also provide an independent test of previous inferences that the subsidence was shortly followed by a tsunami the inferred tsunami deposit is a distinct sandy interval that widely overlies the buried marsh and forest soil diatoms from this interval consist of species observed on modern sand flats of the open bay identifying a bayward source for the sand occurrences of the same sand flat species above the buried soil in the farthest up valley outcrop where a sandy interval is not recognizable suggest that the tsunami extended farther landward than was previously inferred from the stratigraphy these data rule out proposed alternatives to the coseismic subsidence model that is climatically induced sea level rise temporary submergence caused by storms and support the hypothesis that a great earthquake struck southwestern washington 300 yr ago

δ13c and c n as potential coastal palaeoenvironmental indicators in the mersey estuary uk the reconstruction of former environments and ultimately relative sea level changes in coastal and estuarine environments normally utilises a range of microfossil proxies such as diatoms foraminifera and pollen as microfossils are sometimes poorly preserved sparse or absent from coastal sediments this study assesses the potential of using 13c and c n analysis of sedimentary organic matter as an alternative contemporary high inter tidal and sub tidal surface saltmarsh sediments of the mersey estuary uk reveal distinctly different 13c and c n values reflecting the contrasting sources of organic matter in relation to ground elevation within the tidal frame despite decomposition effects the relationship between ground elevation 13c and c n is preserved in the sediment record with a gradual increase in 13c and decrease in c n from supra tidal through to inter tidal and to sub tidal environments holocene variations in 13c and c n are compared with stratigraphical palaeoenvironmental changes inferred from diatom and pollen evidence and show a good correspondence although 13c and c n are not as accurate as microfossil analysis in terms of coastal palaeoenvironmental reconstruction they may be applied successfully in the field of relative sea level reconstruction by helping to verify sea level index points when microfossils are absent

revising estimates of spatially variable subsidence during the a d 1700 cascadia earthquake using a bayesian foraminiferal transfer function

assessing surficial foraminiferal distributions as an overwash indicator in sur lagoon sultanate of oman abstract the identification of tsunami and storm deposits in arid coastal environments can be problematic as overwash sediments may not show significant contrasting lithologic characters with lagoonal sediments in this study foraminifera were evaluated as an overwash indicator in a small 12 km2 intertidal lagoon located at sur in the sultanate of oman the lagoon is shallow

sediments deposited by the 2004 indian ocean tsunami along the malaysia thailand peninsula stratigraphy grain size distribution and foraminiferal assemblages of pre tsunami and tsunami sediment from the indian ocean tsunami at five sites along the malaysia thailand peninsula were analyzed to gain information on tsunami sediment source and deposition style between three and five stratigraphic units were identified at each site and contained between one and three fining upward sequences reflecting waning flow or pre backwash deposition coarser sand layers reflecting uprush high energy flow separated the fining upward sequences with the exception of one site sungai burong which contained a coarsening upward sequence all contacts between the pre tsunami and tsunami sediment were sharp or erosional medium and coarse sand dominated all of the tsunami sediment deposits and often contained shell fragments foraminiferal assemblages were able to differentiate pre tsunami sediment from tsunami sediment where no lithological or grain size distribution change was evident between two and four foraminiferal zones were identified at each of the five sites and provided estimates of sediment source and wave characteristics

tsunami waves generated by the santorini eruption reached eastern mediterranean shores a sedimentary deposit on the continental shelf off caesarea maritima israel is identified dated and attributed to tsunami waves produced during the late bronze age ca 1630 1550 b c e eruption of santorini greece the sheet like deposit was found as a layer as much as 40 cm thick in four cores collected from 10 to 20 m water depths particle size distribution planar bedding shell taphoecoensis dating radiocarbon optically stimulated luminescence and pottery and comparison of the horizon to more recent tsunamigenic layers distinguish it from normal storm and typical marine conditions across a wide 1 km 2 lateral area the presence of this deposit is evidence that tsunami waves from the santorini eruption radiated throughout the eastern mediterranean sea affecting the coastal people living there dates for the tsunami deposit bracket both the so called high and low chronology for the santorini eruption in addition to resolving the question of the extent of tsunami impact from the santorini eruption the research presented also provides a new means of discovering identifying and studying continuous records of paleotsunami deposits in the upper shelf coastal environment the latter is key to understanding past events better interpreting sedimentological records and creating stronger models for understanding tsunami propagation coastal management and hazard preparation worldwide

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

accommodation space relative sea level and the archiving of paleo earthquakes along subduction zones the spatial variability of holocene relative sea level rsl change influences the capacities of coastal environments to accommodate a sedimentary record of paleoenvironmental change in this study we couch a specific investigation in more general terms in order to demonstrate the applicability of the relative sea level history approach to paleoseismic investigations using subsidence stratigraphy we trace the different modes of coastal sedimentation over the course of time in the eastern indian ocean where rsl change evolved from rapidly rising to static from 8000 yr ago to present initially the coastal sites from the aceh sumatra coastal plain which are subject to repeated great earthquakes and tsunamis built up a sedimentary sequence in response to a rsl rise of 1 4 mm yr the sequence found at 2 sites 8 km apart contained 3 soils of a mangrove origin rhizophora bruguiera ceriops avicennia pollen and or intertidal foraminifera buried by sudden submergence related to coseismic subsidence and 6 tsunami sands that contain pristine subtidal and planktic foraminifera after 3800 cal yr b p years before a d 1950 sea level stabilized and remained such to the present the stable relative sea level reduced accommodation space in the late holocene suggesting that the continued aggradation of the coastal plain was a consequence of periodic coastal inundation by tsunamis

the tohoku tsunami of 11 march 2011 the key event to understanding tsunami sedimentation on the coasts of closed bays of the lesser kuril islands the tohoku tsunami of 11 march 2011 manifested in the region of the south kuril islands although as a rule the run up heights in this region did not exceed 3 m in closed bays that were covered with ice before the tsunami the eroding capacity of tsunami waves was aggravated by the ice fragments they carried here mud sheets formed reaching up to 106 m inland the 2012 studies have shown well preserved tsunami deposits evident 1 5 years after the event a comparative analysis of tsunami deposits from the periphery and from the near field area close to the tsunami source was performed this was important for understanding the deposition mechanism during the event as it had different strengths on different shores the difference in run up heights determined the considerable differences in erosion sedimentation distribution of tsunami deposits the formation of sedimentary structures grain size composition and diatom and foraminifera assemblages the sources of the material also varied significantly from each other the material came from offshore in closed bays located in the tsunami source periphery while in the near field region close to the epicenter the most active erosion occurred in the inundation area in the latter area the main sources of sand were beaches and dunes while soil erosion was the source of mud studies of the tohoku tsunami on the coasts of the lesser kuril islands demonstrated that mud layers in the sections of coastal lowlands in closed bays could contain preserved detailed geological records of paleotsunamis even those with a small height run up in the sections of coastal peatlands of closed bays on shikotan island up to 7 9 layers of mud and silty sands were found these can easily be traced for more than 500 m inland the grain size composition of the mud is similar to the deposits of the 2011 tohoku tsunami the marine origin of these deposits is confirmed by the diatom analysis data

sedimentary and foraminiferal evidence of the 2011 tōhoku oki tsunami on the sendai coastal plain japan abstract the 2011 t hoku oki megathrust earthquake mw 9 0 generated a tsunami that reached the sendai coastal plain with flow heights of 2 to 11 m above tp tokyo peil we examined the tsunami deposit exposed in 14 shallow trenches along a 4 5 km transect perpendicular to the coast we primarily document the stratigraphical sedimentological foraminiferal and geochemical characteristics of the t hoku oki tsunami deposit and perform a preliminary comparison with sediments deposited by the j gan tsunami of a d 869 in the coastal forest and rice fields inundated by the t hoku oki tsunami a poorly sorted dark brown soil is buried by a poorly sorted brown medium grained sand deposit in some trenches located more than 1 2 km inland the sand is capped by a thin muddy sand layer the tsunami deposit although highly variable in thickness is generally thickest 25 cm near the coastal dune and thins to less than 5 mm at 4 5 km inland the tsunami deposit was discriminated from the underlying soil by the appearance of recent and fossil foraminifera and a pronounced increase in grain size that fined upward and landward the recent foraminifera preserved in the sandy facies of the deposit are rare and showed evidence of prolonged subaerial exposure e g pitting corrosion fragmentation recent foraminifera likely originated from coastal dune and beach sediments that were breached by the tsunami calcified and sediment in filled fossil foraminifera are abundant and were eroded from sedimentary units and transported by fluvial or wave activity to sendai bay trends associated with test size e g decreasing concentration of large test sizes with distance inland are in agreement with grain size data at two locations a decrease in total organic carbon and an increase in 13c were found in the tsunami sand compared with the underlying soil supporting a beach to intertidal origin for the upper unit

the 2011 tohoku oki earthquake tsunami similarities and differences to the 869 jogan tsunami on the sendai plain a post tsunami field survey following the 2011 tohoku oki earthquake tsunami was carried out to asses inundated area in sendai plain northeast japan the type of inundation was classified into two categories major and minor according to the amount of accumulated debris garbage and sediment major and minor inundations were identified up to 4 and 5 km from the coastline respectively many artificial geomorphological features such as roadway embankments and canals were believed to have affected the run up process of the tsunami the inundation area of the 2011 tsunami on the sendai plain is compared with that of the 869 jogan tsunami which was reconstructed using numerical modeling based on available historical and geological records the inundation area of the 2011 tohoku oki tsunami is comparable to that of the 869 jogan tsunami although a direct comparison is difficult due to differences in geomorphological contexts between the paleo period and the present

chemical signatures of palaeotsunamis a forgotten proxy article i nfo article history a range of diagnostic criteria are required to help identify palaeotsunami deposits although chemical signatures have long been used as indicators of palaeosalinity in sedimentary sequences their use in the studies of palaeotsunami deposits is rarely applied and is yet to be widely recognised the chemical composition of interstitial water in coastal ponds and sedimentary sequences in coastal marshes and lagoons has been used successfullyasanindicatoroftsunamiinundation chemicalsignaturescanalsoprovidecluesaboutthelandward limit of runup of a tsunami beyond the area of sediment deposition like most palaeotsunami proxies however the preservation of chemical signatures varies with environmental conditions

micropaleontology of the 2013 typhoon haiyan overwash sediments from the leyte gulf philippines abstract coastal geologic records allow for the assessment of long term patterns of tropical cyclone variability however the accuracy of geologic reconstructions of tropical cyclones is limited by the lack of modern analogues we describe the microfossil foraminifera and testate amoebae assemblages contained within overwash sediments deposited by typhoon haiyan when it made landfall on the islands of leyte and samar in the philippines on 7 november 2013 as a category 5 super typhoon the overwash sediments were transported up to 1 7 km inland at four study sites the sediments consisted of light brown medium sand in a layer

heavy minerals in the 2011 tohoku oki tsunami deposits insights into sediment sources and hydrodynamics abstract the 2011 tohoku oki tsunami left sand and mud deposits more than 4 km inland on the coastal plain of sendai japan the tsunami deposits pre tsunami soils and beach sediments were analysed for grain size and heavy mineral content and assemblages to test the applicability of heavy mineral analyses in the identification of tsunami deposits and interpretation of associated sedimentation processes heavy minerals comprised on average 35 of the tsunami deposit in the 0 125 0 25 mm grain size fraction the most common were orthopyroxenes clinopyroxenes amphiboles limonites and opaque minerals heavy mineral concentrations and assemblages were similar in the tsunami deposits beach and pre tsunami soils and sediments and thus tsunami deposits could not simply be identified based on their heavy minerals sediment provenance analysis revealed that tsunami deposits left within 1 5 km of the shoreline were mostly eroded from the beach dune and local soils while deposits farther inland 1 5 km were mostly derived from local soil erosion no evidence was found for a significant contribution of offshore sediments detailed analyses revealed that the lowermost portion of tsunami deposits was mostly of local origin while the sediment source of the upper portion was variable a comparison with a previous study of heavy minerals in 2004 iot deposits confirms that heavy minerals in tsunami deposits are mostly source dependent and may represent a useful supplementary tool in studies of tsunami deposits however the interpretation must always be placed in the local geological context and corroborated with other tsunami proxies

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

a millennial scale record of holocene tsunamis on the kronotskiy bay coast kamchatka russia abstract deposits from as many as 50 large tsunamis during the last 7000 years are preserved on the pacific coast of the kamchatka peninsula near the mouth of the zhupanova river southern kronotskiy bay these deposits are dated and correlated using holocene marker tephra layers the combined preserved record of tsunami deposits and of numerous marker tephras on kamchatka offers an unprecedented opportunity to study tsunami frequency for example from the stratigraphy along southern kronotskiy bay we estimate frequency of large tsunamis 5 m runup in the last 3000 years the minimum frequency is about one large tsunami per 100 years and the maximum about one large tsunami per 30 years the latter frequency occurred from about 0 to 1000 a d this time interval corresponds to a period of increased seismicity and volcanic activity that appears to be recorded in many places on the kamchatka peninsula

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

historical nankai suruga megathrust earthquakes recorded by tsunami and terrestrial mass movement deposits on the shirasuka coastal lowlands shizuoka prefecture japan geological investigations of coastal sediment sequences play a key role in verifying earthquake and tsunami characteristics inferred from historical records in this paper we present a multi proxy investigation of a coastal lowland site facing the nankai suruga megathrust and appraise evidence for tsunamis and earthquake triggered terrestrial mass movements occurring over the last 800 years combining a high resolution chronology with x ray computed tomography and analyses of particle size diatoms pollen non pollen palynomorphs and aerial photographs we present the most compelling geological evidence of the 1361 ce koan also known as shohei tsunami reported to date from any site along the megathrust this finding is consistent with either of two recent hypotheses a single larger rupture of both the nankai and tnankai regions or two smaller ruptures separated by a few days enhancing the site chronology using bayesian age modelling we verify evidence for inundation during the 1498 ce mei tsunami while previous investigations identified evidence for historically recorded tsunamis in 1605 1707 and 1854 ce and a storm surge in 1680 or 1699 ce we encountered a thick sand layer rather than discrete extreme wave deposits in this interval the overprinting of evidence highlights the potential for geological records to underestimate the frequency of these events a terrestrial mass movement also deposited a sand layer at the site radionuclide dating and aerial photographs provide independent confirmation that this may have been triggered by intense shaking in 1944 ce during the most recent great nankai suruga megathrust earthquake

erosion deposition and landscape change on the sendai coastal plain japan resulting from the march 11 2011 tohoku oki tsunami case studies of recent tsunami impacts have proven to be extremely useful in understanding the geologic processes involved during inundation and return flow and refining the criteria used to identify paleotsunami deposits in the geologic record here we report on erosion deposition and associated landscape change resulting from the march 11 2011 tohoku oki tsunami along a nearly 4 5 km shore normal transect on the coastal plain near sendai japan the study area on the broad low relief prograding coastal sendai plain comprised a sand beach backed by 3 m high sand dunes and a forest a wetland the teizan canal agricultural rice fields buildings and roads field observations focused on measurements of tsunami flow characteristics height and direction mapping of erosion features and assessing sediment deposition based on shallow trenches at 50 100 m spacing recorded tsunami inundation heights reached up to about 11 m above mean sea level within the first 500 m from the shoreline and then ranged between 3 and 5 m for the next 2 km gradually decreasing to about 3 m close to the inundation limit the tsunami deposit generally thinned landward from an average maximum 30 cm thick sand deposit in the coastal forest to a thin mud drape several mm thick near the inundation limit a discontinuous sand dominated sheet was prevalent to about 2800 m from the shoreline where mud content then gradually increased further landward eventually resulting in a mud dominated deposit ranging from 3 5 cm to a few mm thickness the overall thinning and fining of the deposit was often interrupted by localized features that led to complex sedimentological relationships over short distances satellite imagery taken on 14 march 2011 3 days after the tohoku oki tsunami shows prominent foreshore incisions with 100 s meters spacing alongshore a foredune ridge that underwent severe erosion and development of a prominent shore parallel elongated scour depression our field survey in early may 2011 revealed that the foreshore recovered quickly with rapid post tsunami sediment deposition from incident waves whereas the dune ridge complex had undergone only minor re working from eolian processes

coastal subsidence in oregon usa during the giant cascadia earthquake of ad 1700 quantitative estimates of land level change during the giant ad 1700 cascadia earthquake along the oregon coast are inferred from relative sea level changes reconstructed from fossil foraminiferal assemblages preserved within the stratigraphic record a transfer function based upon a regional training set of modern sediment samples from oregon estuaries is calibrated to fossil assemblages in sequences of samples across buried peat mud and peat sand contacts marking the ad 1700 earthquake reconstructions of sample elevations with sample specific errors estimate the amount of coastal subsidence during the earthquake at six sites along 400 km of coast the elevation estimates are supported by lithological carbon isotope and faunal tidal zonation data coseismic subsidence at nehalem river nestucca river salmon river alsea bay siuslaw river and south slough varies between 0 18 m and 0 85 m with errors between 0 18 m and 0 32 m these subsidence estimates are more precise consistent and generally lower than previous semi quantitative estimates following earlier comparisons of semi quantitative subsidence estimates with elastic dislocation models of megathrust rupture during great earthquakes our lower estimates for central and northern oregon are consistent with modeled rates of strain accumulation and amounts of slip on the subduction megathrust and thus with a magnitude of 9 for the ad 1700 earthquake

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

scenario of the 1996 volcanic tsunamis in karymskoye lake kamchatka inferred from x ray tomography of heavy minerals in tsunami deposits abstract the concentration and distribution of heavy minerals in tsunami deposits is not random and mostly source dependent heavy minerals may thus be good indicators of sediment provenance and tsunami flow dynamics the tsunamis generated by the 1996 phreato magmatic eruption in karymskoye lake represent a relevant case study because the provenance of the abundant heavy minerals found in the tsunami deposits is well constrained the on going basaltic eruption itself x ray computed tomography x ct of cores of tsunami sediments is used to identify heavy minerals and characterise their source and spatial distribution in the tsunami deposit and to propose a scenario of the coupled eruption and tsunamis an original combination of methods including x ct sem and xrf core scanner allows distinguishing subunits corresponding to pulses of sediments deposition and associated inputs of heavy minerals together with erosive contacts laminations and rip up clasts of the substratum the structure of the tsunami deposits suggests that a major tsunami consisting of two main waves inundated the coastal terrace up to 100 m inland on the eastern shore of the lake a scenario that is consistent with waves generated by experimental explosions this largest tsunami might have occurred when underwater explosions were at a critical water depth of 40 m corresponding to a two third submerged explosion in the 60 m deep lake however more investigations are needed to better understand the critical conditions leading to a tsunami during underwater eruptions

evidence for 17th century tsunamis generated on the kuril kamchatka subduction zone lake tokotan hokkaido japan abstract in the seventeenth century two tsunamis that were generated by earthquakes on the kuril kamchatka subduction zone inundated the eastern coast of hokkaido northern japan stratigraphic evidence for these two tsunamis and related land level change in coastal hokkaido consists of two landward thinning sand layers in the sediments of lake tokotan a coastal lagoon on the hokkaido coast the marine origin of these sand layers is indicated by the presence of brackish marine diatoms the rarity and high degree of fragmentation of diatom valves suggests that the sands were transported in a short time over a considerable distance tsunamis at this site were probably generated by great earthquakes along the kuril kamchatka trench volcanic ash deposits lying just above the sands suggest that tsunamis occurred in the late 17th century tsunamis during the historic period are not recorded in lake tokotan which suggests that the sand layers were deposited by tsunamis substantially larger than historic tsunamis

geochemical signatures up to the maximum inundation of the 2011 tohoku oki tsunami implications for the 869 ad jogan and other palaeotsunamis abstract the geochemical signature of the tohoku oki tsunami deposit and underlying soil was assessed two months five months and seven months after the 11 march 2011 tsunami inundated the sendai plain the extent of the recognisable sand deposit was traced up to 2 9 km inland while a mud deposit was found up to 4 65 km inland representing 60 and nearly 95 of the maximum tsunami inundation respectively the limit of tsunami inundation was identified 4 85 km from the shore using geochemical marine markers s and cl two months after the tsunami in the absence of any sedimentological evidence concentrations of other geochemical markers k ca sr indicative of the marine incursion and associated minerals were found to decrease landward 13 c and 15 n and c n ratios suggested a mixture of terrestrial and marine organic sources in the sediment while 34 s of sulphate reflected the marine source of water soluble salts the chemical composition of the 869 ad jogan tsunami sand deposit was characterised by high sr and rb concentrations and was comparable to that of the tohoku oki tsunami deposit suggesting that the sources of sediment may be similar marked decreases in s and cl with time indicated that rainfall resulted in the leaching of salts from the sandy sediments however both s and cl markers as well as sr were still well preserved in the muddy sediments and underlying soil beyond the limit of the recognisable sand deposit seven months after the tsunami this suggests that geochemical indicators may well be useful in identifying the extent of historical and palaeotsunamis by determining the marine origin of fine grained sediments beyond the limit of recognisable sand deposition in particular when marine microfossils are sparse or lacking as is the case on the sendai plain this would allow researchers to redraw palaeotsunami inundation maps and re assess the magnitude of events such as the jogan tsunami and other palaeotsunamis not only on the sendai plain but also elsewhere around the world this has important implications for tsunami risk assessment hazard mitigation and preparedness

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

sediment sources and sedimentation processes of 2011 tohoku oki tsunami deposits on the sendai plain japan insights from diatoms nannoliths and grain size distribution abstract the 11th march 2011 tohoku oki tsunami inundated the low lying sendai plain japan more than 5 km inland leaving sand and mud deposits over most of the area in order to establish the sources of the tsunami deposits and interpret processes of their sedimentation samples were collected from the deposits underlying soils and the beach along a shore perpendicular transect and analysed for grain size diatom assemblages and nannoliths the fining inland tsunami deposits consisted of poorly to moderately sorted medium to coarse sand within 2 km of the coastline and very poorly to poorly sorted mud farther inland more specifically there was a slight fining of the coarse to medium sand mode within the sandy deposits and an increased contribution of the coarse and very coarse silt fraction in the mud deposits the tsunami deposits also exhibited vertical changes including fining upward and coupled coarsening fining upward trends few diatoms were present in beach sediments soils and tsunami deposits within 1 km of the coastline while diatoms were more abundant farther inland diatom assemblages in the soil and tsunami deposits were similar and dominated by species typical of freshwater brackish habitats while no typically marine species were encountered nannoliths were generally absent in the studied sediments except for few specimens our data indicate that there was probably no or only a very minor component of marine sediments transported onland by the tsunami the sandy tsunami deposits within 1 km of the coastline were mostly derived from beach and dune erosion from 1 to 2 km landward the contribution of these sources decreased while sources comprising local soil erosion and the entrainment of sediments from the teizan bori canal increased farther inland local soil erosion was the major sediment source for the mud deposits the tsunami deposits were most likely deposited during at least two inundations mostly out from suspension resulting in an upward grain size fining trend however bed load deposition was also important in the sandy deposits as suggested by a common grain size upward coarsening position on c m diagrams and frequent horizontal lamination the present study reveals that even very large tsunamis may not transport marine sediments onland and thus many commonly applied indicators of tsunami deposits based on the assumption of their offshore origin marine diatoms foraminifera nannoliths marine sediments may be of limited use

stable carbon isotopes as potential sea level indicators in salt marshes north carolina usa we compared the use of 13c values and c n ratios from salt marsh sediments to reconstruct relative sea level rsl with an established approach using foraminifera analysis of bulk organic sediment and plant samples collected along transects at two sites in north carolina usa demonstrates that sediment 13c values can be used to distinguish between spartina alterniflora dominated low marsh c photosynthetic pathway 13c values from 17 6 to 16 1 and juncus roemerianus dominated high marsh c 3 photosynthetic pathway 13c values from 28 2 to 21 8 environments juncus roemerianus plants undergo little decompositional change in 13c average 0 8 although there is a clear difference between spartina alterniflora tissue and bulk organic sediments approximately 4 c n ratios on bulk organic sediment from freshwater upland and salt marsh environments converge during early diagenesis rendering them of little use in reconstructing rsl the utility of 13c values as a sea level indicator is limited by the elevational range of c4 plants making it difficult to recognize salt marsh subenvironments and improve the precision of rsl reconstructions furthermore juncus roemerianus dominated high marsh and freshwater upland sediments cannot be adequately distinguished with 13c values

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

anthropogenic pollutants and biomarkers for the identification of 2011 tohoku oki tsunami deposits japan abstract organic geochemistry is commonly used in environmental studies in tsunami research however its applications are in their infancy and it is still rarely used we present results for two types of organic geochemical markers biomarkers and anthropogenic markers present in deposits left by 2011 tohoku oki tsunami on the sendai plain japan as the tsunami inundated the coastal lowland up to 4 85 km inland sediments from various sources were eroded transported and deposited this led to the distribution of biomarkers from different sources across the sendai plain creating a unique geochemical signature in the tsunami deposits the tsunami also caused destruction along the sendai coastline leading to the release of large quantities of environmental pollutants e g fossil fuels tarmac pesticides plastics etc that were distributed across the inundated area these anthropogenic markers represented by three main compound groups polycyclic aromatic hydrocarbons pesticides and halogenated compounds were preserved in tsunami deposits at least until 2013 prior to land clearing their concentrations differed significantly from the pre and post tsunami background contamination levels organic proxy concentrations can differ for sand and mud deposits due to various factors e g preservation dilution microbial alteration however it can be concluded that anthropogenic markers and biomarkers have the potential to be a valuable proxy for future studies of recent tsunami deposits because of their high source specificity and relatively good preservation potential providing information about sediment sources and transport pathways e g marine source evidence of backwash

storm erosion during the past 2000 years along the north shore of delaware bay usa abstract the recent impacts of tropical cyclones and severe storms on the u s atlantic coast brought into focus the need for extended records of storm activity from different geomorphologic settings such reconstructions are typically developed from sites that experienced repeated overwash of sand into low energy depositional environments however salt marsh sediment may also preserve a record of repeated erosion from tropical cyclones and storms we describe late holocene sediments beneath the sea breeze salt marsh delaware bay new jersey from more than 200 gouge cores positioned along seven transects the stratigraphic record documents at least seven depositional sequences consisting of salt marsh peat and mud couplets that represent dramatic changes in sedimentation regime there are a number of processes that could produce these stratigraphic sequences against a background of rising relative sea level including lateral migration of tidal creeks tidal channel network and or drainage ditch expansion changes in sediment delivery rates rapid relative sea level change tsunami and formation of salt pans the abrupt contacts between the salt marsh peat and overlying intertidal mud suggest that erosion of the peat was followed by rapid infilling of accommodation space correlation of erosional surfaces across 2 5 km suggests a common mechanism and we propose that the erosion was caused by tropical cyclones and or storms we developed a chronology of repeated salt marsh erosion and recovery using 137cs metal pollution pb concentration and stable isotopes and radiocarbon data two recent episodes of salt marsh erosion may correlate with historic tropical cyclones in ad 1903 and ad 1821 1788 that impacted the atlantic coast of new jersey but the erosive nature of the sea breeze site hinders definitive correlation prehistoric erosional sequences correlate with overwash fans preserved in the regional sedimentary record we estimated that it takes from several decades to almost 200 years for salt marshes to recover from storm erosion

bed thickness characteristics of inner shelf storm deposits associated with a transgressive to regressive holocene wave dominated shelf sendai coastal plain japan holocene inner shelf storm deposits preserved beneath the sendai coastal plain facing the pacific coast of north eastern japan were formed during a transgressive regressive cycle the evolution of the holocene wave dominated depositional system along the sendai coast is reconstructed using 76 ams accelerator mass spectrometers 14c ages and the origin of bed thickness variations in the inner shelf storm deposits is explored the holocene succession is 30 m thick and overlies latest pleistocene to early holocene non marine deposits above a transgressive ravinement surface it comprises transgressive ravinement and inner shelf deposits and regressive inner shelf shoreface and coastal plain deposits the inner shelf deposits comprise alternating sand and mud layers interpreted as stacked storm beds the average preservation interval of a single storm bed is shortest during the transgression 5 7 20 6 years and then increases to a maximum during the early regression 83 3 250 0 years decreasing to 7 7 31 3 years with shoreline progradation average accumulation rates decreased during the transgression and then increased during the regression but the sand mud ratio varies little reflecting inefficient sediment segregation downdip on the inner shelf the vertical pattern of sand layer thicknesses also shows no relationship to position within the cycle although small scale intervals of upward thickening and thinning probably relate to lateral switching of river mouths and or random storm processes the average thickness of storm beds is the highest in the interval deposited during the period from maximum flooding to early regression this is probably because of the low preservation potential of thin beds associated with frequent low magnitude storms during this period of low accumulation rates and extensive reworking this preservation bias and the nature of the sendai inner shelf resulted in an absence of characteristic bed thickness trends in the preserved storm deposits

frontal wedge deformation near the source region of the 2011 tohoku oki earthquake 1 we report an uplift of 5 m with a horizontal displacement of more than 60 m due to the 2011 tohoku oki earthquake the uplift was measured by an ocean bottom pressure gauge installed before the earthquake on a frontal wedge which formed an uplift system near the japan trench horizontal displacements of the frontal wedge were measured using local benchmark displacements obtained by acoustic ranging before and after the earthquake the average displacements at the frontal wedge were 58 m east and 74 m east southeast these results strongly suggest a huge coseismic slip beneath the frontal wedge on the plate boundary the estimated magnitude of the slip along the main fault was 80 m near the trench our results suggest that the horizontal and vertical deformations of the frontal wedge due to the slip generated the tremendous tsunami that struck the coastal area of northeastern japan

survey of 2011 tohoku earthquake tsunami inundation and run up 1 at 14 46 local time on march 11 2011 a magnitude 9 0 earthquake occurred off the coast of northeast japan this earthquake generated a tsunami that struck japan as well as various locations around the pacific ocean with the participation of researchers from throughout japan joint research groups conducted a tsunami survey along a 2000 km stretch of the japanese coast more than 5300 locations have been surveyed to date generating the largest tsunami survey dataset in the world on the sendai plain the maximum inundation height was 19 5 m and the tsunami bore propagated more than 5 km inland along the ria coast from about 50 to 200 km north of sendai the narrow bays focused the tsunami waves generating the largest inundation heights and run ups the survey data clearly show a regional dependence of tsunami characteristics

subtropical western boundary currents over slopes detaching from coasts with inshore pool regions an indication to the kuroshio nearshore path abstractthe dynamics of subtropical western boundary currents over slopes detaching from coasts with inshore pool regions where the water of the subtropical gyre does not enter and the velocity is small are investigated this study is intended to understand the dynamics of the nearshore path of the kuroshio which has a distinct boundary between the boundary current and the coastal water numerical experiments under idealized conditions are made the results show flow patterns with pool regions similar to the kuroshio under simple conditions a deep countercurrent is present on the lower bottom slope which represents observed deep currents this is part of a deep cyclonic recirculation north of the jet which extends to the lower bottom slope despite steep topography this extension can be explained by the geostrophic contours in this region the upper boundary current feels the bottom slope and the westward intensification is blocked in the other region where the bottom layer velocity is very small

a comparative study of the 2013 typhoon haiyan overwash sediments from a coastal cave and beach system at salcedo eastern samar central philippines abstract typhoon haiyan crossed the central philippines on 8 november 2013 and generated storm surge up to 7 m with runup reaching 12 m which deposited overwash sediments inland in many different locations and environments collectively these overwash sediments serve as key modern analogs to compare with geological records of storm events in the region to date comparatively few studies have been conducted on sandy storm deposits in carbonate coasts with none to date on storm sediments in coastal caves here we report the grain size and microfossil assemblages of the typhoon haiyan overwash sediments from a coastal cave and carbonate beach system in eastern samar central philippines and infer the source of the haiyan overwash sediments we show that overwash sediments inside and immediately outside the cave beach system are similar but they can be discriminated from the underlying pre haiyan soil through field evidence grain size organic matter and microfossil content to investigate the source of both the cave and non cave overwash sediments and in the absence of pre storm beach sediment samples we collected post haiyan beach sediments in february 2018 when the beach has indicated recovery to its pre storm condition we assume that these post haiyan beach sediments are representative of pre storm sediments the underlying pre haiyan soil comprises poorly sorted coarse to very coarse sands with higher organic matter content and a lower microfossil concentration also the pre haiyan soil contains foraminifera species similar to those identified in the haiyan overwash sediments but rarely containing subtidal foraminifera species in comparison the haiyan overwash sediments share similar attributes with the post haiyan coastal sediments consisting of moderately sorted gravelly sands predominantly carbonate grains with low organic matter content the typhoon haiyan overwash sediments contain foraminifera species dominated by amphistegina radiata baculogypsina sphaerulata calcarina gaudichaudii calcarina splengeri suggesting an intertidal environment although lower abundances of benthic species peneroplis planatus and quinqueloculina parkeri imply contributions from the subtidal environment notably the haiyan overwash sediments dominantly contain intertidal foraminifera species with abraded tests similar to foraminifera found in the post haiyan beach sediments the similarity of foraminiferal assemblage and taphonomic condition strongly indicates that the overwash sediments found on the coastal cave were most likely sourced from the beach and reef flat our results show overwash sediments in coastal caves are indistinct from those in the nearby beach system indicating the potential of coastal caves to harbor well preserved archives of paleo storm deposits

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

new insights of tsunami hazard from the 2011 tohoku oki event we report initial results from our recent field survey documenting the inundation and resultant deposits of the 2011 tohoku oki tsunami from sendai plain japan the tsunami inundated up to 4 5 km inland but the 0 5 cm thick sand deposit extended only 2 8 km 62 of the inundation distance the deposit however continued as a mud layer to the inundation limit the mud deposit contained high concentrations of water leachable chloride and we conclude that geochemical markers and microfossil data may prove to be useful in identifying the maximum inundation limit of paleotsunamis that could extend well beyond any preserved sand layer our newly acquired data on the 2011 event suggest that previous estimates of paleotsunamis e g 869 ad j gan earthquake and tsunami in this area have probably been underestimated if the 2011 and 869 ad events are indeed comparable the risk from these natural hazards in japan is much greater than previously recognized

geochemical and micropaleontological impacts caused by the 2011 tohoku oki tsunami in matsushima bay northeastern japan abstract we present stratigraphic geochemical cns elemental analysis and micropaleontological ostracode assemblages evidence for the 2011 tohoku oki tsunami impact in matsushima bay northeastern japan and examine the recovery process after the impact to the bay environment using short sediment cores from two different topographic settings at a water depth of approximately 4 m at both sites tsunami deposits are composed of two sedimentary layers that recorded the first tsunami run up and backwash at the western site near the channel that connects the bay with the pacific ocean the first tsunami wave eroded the bay floor sediments and left the tsunami deposits composed of medium sand rich in shell fragments but with sparse numbers of meiobenthic ostracodes by contrast at the eastern site which is surrounded by many small islands the first wave eroded very little of the bay floor sediments and left tsunami deposits consisting of sandy mud rich in exotic ostracodes such as phytal species shallow marine sand dwelling species and brackish water species overlying post tsunami deposits are composed mainly of organic rich mud in which organic matter was derived primarily from marine plankton ostracode assemblages in the tsunami deposits lack the offshore species that live in water depths 50 m and are dominated by the species from matsushima bay and its adjacent nearshore upper sublittoral areas and brackish water environments the distance from deep water offshore areas to the core sites is too far to transport ostracode valves by tsunami waves

displacement above the hypocenter of the 2011 tohoku oki earthquake the moment magnitude m w 9 0 2011 tohoku oki mega thrust earthquake occurred off the coast of northeastern japan combining global positioning system gps and acoustic data we detected very large sea floor movements associated with this event directly above the focal region an area with more than 20 meters of horizontal displacement that is four times larger than those detected on land stretches several tens of kilometers long along the trench the largest amount reaches about 24 meters toward east southeast just above the hypocenter furthermore nearly 3 meters of vertical uplift occurred contrary to observed terrestrial subsidence

microfossils from coastal environments as indicators of paleo earthquakes tsunamis and storms abstract coastal risk assessment and hazard mitigation require datasets on centennial and millennial temporal scales to capture natural variability and multiple occurrences of the largest but least frequent events coastal sediments from low energy depositional environments archive geologic evidence of paleo earthquakes tsunamis and storms many of the best reconstructions of these events are derived from changes in microfossil diatoms foraminifera and pollen assemblages in this review we explain how microfossils are used to reconstruct records of paleoearthquakes by quantifying the amount of coseismic and interseismic vertical land movements along tectonically active coastlines examples from the united states alaska and the pacific northwest japan and chile show that microfossil based transfer functions may provide continuous records of vertical land movement during earthquake deformation cycles we discuss how microfossil habitat preferences and taphonomic character are used to constrain sediment provenance e g beach nearshore or offshore sources and identify overwash deposits and how this information can be used to reconstruct the recurrence of tsunamis and storms analysis of overwash deposits from thailand and malaysia indicates the ability of microfossils to resolve individual waves within tsunami sediments and an example from the sendai coastal plain in japan uses foraminifera to ascribe a beach to nearshore provenance for the 2011 tohoku tsunami deposit finally we present recent examples from the gulf of mexico on the use of foraminifera to estimate the volume and distance of transport of storm overwash from hurricanes

nepartak typhoon influenced bottom sediments from the yangtze river estuary and adjacent east china sea foraminiferal evidence foraminiferal taphocoenose characteristics notably allochthonous tests in surface sediment samples from the yangtze river estuary and adjacent areas in the east china sea were examined during july 2016 and after typhoon nepartak february 2017 crossed this region a comparison of transport indices from five sample stations reveals that this typhoon significantly strengthened sediment transport although the transport in predominate direction twcnorth branch occurs all year moreover findings from a comprehensive impact of currents topography test size and shape as well as other abiotic factors show that transport occurs in the order from stronger to weaker south north path southeast northwest path nearshore northeast path along the south north path the twcnorth branch transports larger tests of taxa ammonia compressiuscula and cavarotalia annectens as bed load along the gentle seabed in a rolling or saltating process results from the southeast northwest path show smaller and bulging tests of the dominant species epistominella naraensis and bolivina robusta may be transported as suspension load along the steep submarine valley by the twcnorthwest branch on the nearshore northeast path only part of allochthonous tests ammonia beccarii vars was transported probably due to distance travelled and weakening of the typhoon furthermore we also infer the northeastern area as a sink zone that accumulates grains of allochthonous tests predominantly from the southern source zone and a selection of tests from littoral species originating from the nearshore source zone it is important to identify and independently count allochthonous test samples if a large number of these tests are recorded findings from this study provide a reference to identify and investigate typhoon modern effects in areas with complex currents and frequent strong physical dynamic events as well as their geological records

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

testing foraminiferal taphonomy as a tsunami indicator in a shallow arid system lagoon sur sultanate of oman abstract the tsunami produced by the 1945 makran trench earthquake is considered to be the second deadliest in the indian ocean after the 26 december 2004 indonesian event the tsunami struck iran pakistan india and oman however historical records outside of india and pakistan are sparse due to limited populations in those regions and little communication with larger cities sur lagoon oman a small microtidal lagoon contains stratigraphic evidence of the 1945 tsunami the goal of this study is to test the utility of foraminiferal provenance and taphonomy as an indicator of the 1945 event and examine its potential in detecting older events in the geologic record foraminiferal taxa and taphonomy and high resolution particle size analysis show that high abundances of predominantly marine taxa amphistegina spp ammonia inflata and planktics associated with the tsunami bed indicate an outside marine origin for the sediment influxes of large test sizes and fossil specimens support a shallow marine provenance findings indicate that foraminiferal analysis when combined with other proxies e g mollusc taphonomy particle size distribution can be used to delineate tsunami units from normal background sedimentation in intertidal systems this technique holds potential for detecting older events in sur lagoon which are documented in historical texts but as of yet have not been ground truthed

a tsunami ca 6300 years bp and other holocene environmental changes northern hawke s bay new zealand abstract sediment cores collected in a coastal lagoon a few kilometres east of wairoa northern hawke s bay new zealand were examined using sedimentological geochemical palynological and micropaleontological analyses a distinct short lived catastrophic saltwater inundation csi about 6300 years bp and possibly other minor marine incursions are preserved in the coastal estuarine to lagoonal freshwater sedimentary sequences which have been deposited in the last 6500 years the csi is characterised by a gravel unit that thins landward and decreases in particle size to sand within a sequence consisting mainly of brackish estuarine muds diatom assemblages indicate a marked change from the shallow brackish estuarine muds to marine gravels and sands to brackish estuarine muds the marine influence in the gravel and sand is also shown by the presence of marine dinoflagellates and a peak in na rb sedimentological chemical and paleontological in particular diatoms evidence indicates it is a csi we conclude that this was a tsunami and propose the most likely propagating mechanisms marine influence decreases upcore and totally freshwater conditions are evident in the upper section of the cores the geochemistry of the sediments mainly reflects the change in stratigraphy with distinct signatures for tephra na fe cr organic rich and peat units as br and the coarse gravel sand csi unit na rb cr fe but it is also indicative of changes in depositional environment the change in chemistry na rb in the csi event is indicative of a saltwater influence whereas a marked change in s content suggests a sudden change from brackish to freshwater conditions shortly after 4800 years bp another peak in s and br content about 3200 years bp may indicate another temporary change to brackish conditions

a late holocene record of environmental changes from coastal wetlands abel tasman national park new zealand abstract article size organic content loss on ignition loi geochemistry radiocarbon and 137cs analyses were carried out on paired cores taken from wainui totaranui and awaroa inlets abel tasman national park a 1700 year record of long and short term environmental changes was produced representing a sedimentary and geochemical sequence from tidal flat to mature salt marsh the sequence is punctuated by a series of short term environmental changes namely tsunami establishment of salt marsh and european settlement long term environmental changes include fluctuating accretion rates and relative sea level rise tsunami signatures include i a peak in fines ii contemporaneous or delayed peak in organic content and or loi iii contemporaneous peaks in fe and or s iv dilution of anthropogenic contaminants and v visible change in the sediments ruptures of the wellington and west wairarapa faults are considered to be the tsunamigenic sources pre european sediment accretion rates in abel tasman national park range from 0 5 to 1 7 mm a with post european settlement rates increasing to 1 6 2 7 mm a in the past 30 years rates have increased to 2 3 3 3 mm a the component of relative sea level rise is estimated to be about 1 3 2 2 mm a which compares favourably with the nearest tidal records from wellington

the future of tsunami research following the 2011 tohoku oki event abstract in this paper we summarize the regional setting our previous understanding of historical and pre historical tsunamis on the pacific coast of tohoku japan prior to the 2011 tohoku oki tsunami and our current understanding of the sedimentological geochemical and paleontological features of the onshore and offshore deposits of the event post tsunami surveys revealed many new insights such as 1 the maximum extent of the sand deposit is sometimes only 60 of the inundation distance 2 the inundation limit can be estimated by geochemical analysis even a few months after the event 3 a minor amount of marine sediment was transported inland by the tsunami on the sendai and adjacent plains with the major sediment sources being from beach and dune erosion or vented sediments from liquefaction although nearshore and offshore surveys revealed that there was a significant amount of sediment transport on the seafloor 4 coarse gravel deposits 1 m in thickness were usually thicker than the sand ones 30 cm in thickness and 5 beach erosion was minimal in some places while severe in others another important aspect of this event is that it was a large infrequent tsunami that took place where possible predecessors e g ad869 j gan were already known to have occurred based on historical and geological evidence the ad869 j gan tsunami deposits are noticeably similar to the 2011 tohoku oki sands therefore suggesting that the j gan and its source mechanism may have been larger than previously thought while we have learned many lessons from the 2011 tohoku oki event more research is needed to provide reliable tsunami risk assessments around the world

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