a 3000 years old sequence of extreme events revealed by marine and shore deposits east of taiwan we have discovered in a marine core located 20 km east of the coastal range of taiwan at the top of a 1200 m deep submarine high sheltered from rivers discharges and gravitational flows a 23 cm thick anomalous sequence topped with broken bivalves and wood fragments based on radiocarbon dating we distinguish five sub events within 100 yrs about 3000 years ago the oldest four sub events are interpreted as the record of local submarine landslides likely triggered by clustered earthquakes that are common in this tectonically active area the last event including shells and wood has a different origin despite the high level of climatic and tectonic recent activity no comparable event has been observed at the same site since that time making it unique during the last 3 75 ka hydrodynamical modeling stimulated with a set of submarine landslide triggered tsunami sources and combined with the regional oceanic circulation dominated by the kuroshio current allow us to better constrain the transport paths of the suspended material the expected run up at the coast and ultimately the trigger and source that best fit our observations the kuroshio current appears as a strong constraint that generally prevents cross shore transport of suspended material even during a major tsunami since the largest aerial debris flow observed along the east coast of taiwan during the last 4 ka was synchronous with the marine deposit our preferred scenario starts with the occurrence of four distinct large earthquakes within less than a century triggering both submarine and aerial landslides in the study area then a giant typhoon reworked the nearshore material as well as the slided material stored upstream resulting in a debris flow it deeply modified the surface current allowing the wood debris and shells to fastly reach the core site

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

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

tsunami recurrence revealed by porites coral boulders in the southern ryukyu islands japan information about past tsunami hazards such as their recurrence interval and magnitude is needed for future disaster prediction and mitigation we examined radiocarbon ages of the surfaces of massive coral boulders cast ashore by past tsunamis in the southern ryukyu islands japan where few historical and geological records of past tsunamis are available we selected only non eroded porites coral boulders along the shoreline because their characteristics make it possible to determine the probable timing of their deposition by tsunamis and we applied a dating method that uses the cumulative probability distributions of large numbers of radiocarbon measurements of those boulders to determine the timing of past tsunamis the results demonstrate that the southern ryukyu islands have repeatedly experienced tsunami events since at least 2400 yr ago with a recurrence interval of 150 400 yr the largest porites tsunami boulder that we studied long axis 9 m which is probably the largest single colony tsunami boulder in the world was displaced by the a d 1771 meiwa tsunami although the 1771 meiwa tsunami was likely the largest event in at least the past 700 yr calculations of current velocity show that all identified tsunamis occurring before 1771 were probably large enough to cause considerable damage to human built structures and loss of life this study demonstrates that by reliably dating large numbers of selected coastal boulders it is possible to ascertain the timing recurrence interval and magnitude of past tsunamis in a location where few adequate survey sites of sandy tsunami deposits exist

identification of extreme event deposits on the coastal ilan plain northeastern taiwan abstract sedimentary deposits of past extreme events such as tsunamis typhoons or floods on coastal plains are important records for understanding such events and for hazard preparation of future similar events on the coastal ilan plain in northeastern taiwan there has been no report for any of these types of event deposits toward this end this study aims to identify event deposits on the ilan plain with geomorphic and sedimentological analyses north of the lanyang river we identified one event layer that was likely produced by a flood river channel avulsion event south of the river we also found an event that was probably a flood that covered the area without significant erosion consistent with the well preserved beach ridges and inter ridge lowlands of the area our experiences in the ilan plain area suggest that it is important to search for sites with high potentials of event layer deposition and preservation as well as with multiple ways to distinguish the sources of the deposits in future similar studies

a review of geological records of large tsunamis at vancouver island british columbia and implications for hazard abstract large tsunamis strike the british columbia coast an average of once every several hundred years some of the tsunamis including one from alaska in 1964 are the result of distant great earthquakes most however are triggered by earthquakes at the cascadia subduction zone which extends along the pacific coast from vancouver island to northern california evidence of these tsunamis has been found in tidal marshes and low elevation coastal lakes on western vancouver island the tsunamis deposited sheets of sand and gravel now preserved in sequences of peat and mud these sheets commonly contain marine fossils and they thin and fine landward consistent with deposition by landward surges of water they occur in low energy settings where other possible depositional processes such as stream flooding and storm surges can be ruled out the most recent large tsunami generated by an earthquake at the cascadia subduction zone has been dated in washington and japan to ad 1700 the spatial distribution of the deposits of the 1700 tsunami together with theoretical numerical modelling indicate wave run ups of up to 5 m asl along the outer coast of vancouver island and up to 15 20 m asl at the heads of some inlets the waves attenuated as they moved eastward along juan de fuca strait and into puget sound and the strait of georgia no deposits of the 1700 event or for that matter any other tsunami have yet been found in the strait of georgia suggesting that waves were probably no more than 1 m high in this area if a tsunami like the 1700 event were to occur today communities along the outer pacific coast from southern british columbia to northern california would be severely damaged there would be little time to evacuate these communities because the tsunami would strike the outer coast within minutes of the first ground shaking fortunately such tsunamis are infrequent perhaps as few as seven have occurred in the last 3500 yr other tsunamis that are much smaller and more localized although probably more frequent are caused by local crustal earthquakes and landslides along the british columbia coast two such tsunamis have occurred in british columbia in recent years one in 1946 in the strait of georgia and another in 1975 at the head of a fiord on the northern mainland coast

localized tsunamigenic earthquakes inferred from preferential distribution of coastal boulders on the ryukyu islands japan the occurrence of large earthquakes and tsunamis along the ryukyu trench is a subject of continuing interest the key to which is the long term geological record here we describe the clast size and spatial distributions of 2900 boulders on the reefs of the ryukyu islands japan as markers of paleotsunamis and causative tsunamigenic earthquakes boulders of tsunami origin were observed only at a specific island group at the southern end suggesting the local occurrence of tsunamigenic earthquakes there in contrast in the central to northern ryukyu islands no evidence exists of tsunamis larger than those at the southern end of the ryukyu islands during the past 2000 3000 yr these islands have numerous boulders deposited by storm waves during the past 2300 yr or earlier their spatial distribution has not been disturbed by large tsunamis this suggests that large tsunamis did not strike this area during that period nevertheless these regions are seismically active our study shows that coastal boulder deposits present great potential to not only ascertain the histories and effects of paleotsunamis but also to constrain fault models of the causative earthquakes

high precision and high resolution carbonate 230th dating by mc icp ms with sem protocols abstract to facilitate the measurement of u th isotopic compositions suitable for high precision and high resolution 230th dating of coral and speleothem carbonates secondary electron multiplier sem protocol techniques for multicollector inductively coupled plasma mass spectrometry mc icp ms have been developed the instrumental sensitivities are 1 2 with a precision of 1 2 2 for abundance determination of 50 200 fg 234u 1 4 ng 238u or 230th this method features chemistry refinements improvements to procedural and instrumental blanks spectral inference reductions and careful consideration of non linear sem behavior measurement consistency of this mc icp ms combined with previous mass spectrometric results on u th standards and a variety of carbonates demonstrates the validity of the sem protocol method for fossil corals a routine u th isotopic determination at permil level precision requires only 10 50 mg of carbonate as little as 200 mg of young coral with an age of less than 20 yr can be dated with a precision of 0 3 0 8 yr about 20 200 mg speleothem samples with sub ppm to ppm u are required to earn a 5 precision on ages from 5 to 100 kyr requirement of small sample size 10 100s mg carbonate can permit high temporal resolution to date speleothems with slow growth rates i e 1 10 mm kyr this high precision 230th chronology is critical to accurately establish age models date events and splice geochemical proxy time series records from multiple samples in the fields of paleoclimatology and paleoceanography the u th isotopic determination techniques described here can also be applied to different environmental samples such as waters rocks and sediments

tsunami deposits and recurrence on a typhoon prone coast of northern taiwan from the last millennium abstract widely known for its hazardous history taiwan holds valuable records of nw pacific tsunamis and typhoons despite the similarity between tsunami and typhoon deposits historical accounts enabled the identification of the 1867 tsunami deposit on the northern coast through matching with the record setting inundation however the identification of prehistoric tsunami deposits has been hindered by severe sediment reworking and post depositional changes produced by the typhoon prone tropical and humid climate in this study we investigated the upper holocene facies and their sediment sources and radiocarbon ages on distal floodplains and rocky backshores of the northern coast where sediment reworking is less intense four decimetre thick gravelly layers were identified intercalated with fluvial mud and colluvium the gravelly layers are composed of beach derived quartz rich sand and rounded gravels of the sedimentary basement rocks longshore drift andesite and stranded pumice the remarkable layer thickness gravel size and quartz richness were determined to have endured post depositional changes the event layers are sharp based matrix supported and poorly sorted and have recorded scouring sediment entrainment and rapid fallout of suspension rich turbulent flows that probably originated with tsunamis the event layers occur 0 5 0 8 km inland and 3 11 5 m above sea level matching the 1867 tsunami inundation and wave height respectively radiocarbon dating tied the event layers to the 1867 tsunami and three prehistoric events that occurred in the periods 1545 to 1810 1293 to 1414 and 1090 to 1235 representing a recurrence interval of 83 436 years over the last millennium

storm cycles in the last millennium recorded in yongshu reef southern south china sea large storm relocated porites coral blocks are widespread on the reef flats of nansha area southern south china sea detailed investigations of coral reef ecology geomorphology and sedimentation on yongshu reef indicate that such storm relocated blocks originated from large porites lutea corals growing on the spurs within the reef front living coral zone because the coral reef has experienced sustained subsidence and reef development during the holocene dead corals were continuously covered by newly growing coral colonies for this reason the coral blocks must have been relocated by storms from the living sites and therefore the ages of these storm relocated corals should approximate the times when the storms occurred rapid emplacement of these blocks is also evidenced by the lack of coral overgrowth encrustation or subtidal alteration u series dating of the storm relocated blocks as well as of in situ reef flat corals suggests that during the last 1000 years at least six strong storms occurred in 1064 30 1210 5 1201 4 1336 9 1443 9 1685 8 1680 6 1872 15 ad respectively with an average 160 year cycle 110 240 years the last storm which occurred in 1872 15 ad also led to mortality of the reef flat corals dated at similar to 130 years ago thus the storm had significant impacts on coral reef ecology and morphology c 2004 elsevier b v all rights reserved

a wide rainband in a developing tropical cyclone abstract on 18 january 1987 the three aircraft from the equatorial mesoscale experiment emex completed a mission designed to identify the mesoscale reflectivity kinematic and thermodynamic structure of a convectively active rainband on the leading edge of developing tropical cyclone irma the reflectivity structure determined from land based and aircraft radars reveals that the band consisted of an unusually wide 80 km region of convective clouds that did not maintain a linear organization high e air entered from both sides in the subcloud and lower cloud layer thermodynamically the rainband was benign in the sense that it did not produce cold downdrafts or large regions of low e air that would limit the energy of the low level inflow to the developing eyewall region kinematically the band was a preferred location for the enhancement of the wind component parallel to the band the low level flow was along rather than across the major axis of the band above 4 5 km flow was from the inner to

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

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

the neoproterozoic pan african basement from the alpine lower danubian nappe system south carpathians romania abstract the south carpathians which were thrust to the moesian platform in the alpine orogeny late cretaceous to tertiary include the danubian nappe system the danubian pre alpine basement comprises two variscan nappes each one made up of partially retrogressed amphibolite facies rocks intruded by granitoids and capped by an ordovician devonian volcano sedimentary cover no lithological correlation can be established between the pre ordovician basements of these two units the metamorphic basement from the first variscan nappe the dr gsan group is composed of banded amphibolites with some augen and aluminous gneisses intruded by granodioritic to tonalitic plutons the banded structure of the amphibolites together with their geochemistry suggests a volcano sedimentary sequence zircon u pb data on an intercalated augen gneiss have given an age of 777 3 ma for the emplacement of the protolith of this gneiss nd model ages t dm for the amphibolites range from 717 ma to 817 ma at 777 ma nd values cluster is at 8 3 to 9 8 and sr initial ratios range between 0 7007 and 0 7023 indicating an oceanic origin without continental crust contamination major and trace elements from the dr gsan amphibolites consistently display an island arc signature with three differentiation trends evolving from an early tholeiitic trend to a more differentiated low k calc alkaline one the dr gsan terrane is similar to the early pan african juvenile terranes of the sahara the basement of the second variscan nappe the lainici p ius group is made up of metasedimentary rocks mainly quartzites marbles and graphitic mica gneisses cut by early leucogranitic dykes medium k calc alkaline and alkali calcic mainly granitic plutons and late medium k porphyry diorite dykes this magmatism can be bracketed between 588 ma and 567 ma u pb zircon ages the best preserved pluton tismana 567 ma old displays a composite alkali calcic very high k calc alkaline magmatic sequence ranging from gabbro diorite to monzogranite including an ultramafic pod ages and geochemical signatures resemble the saharan late pan african granitoids the existence of late precambrian partly juvenile terrains is thus confirmed within the basement of south carpathians which renders then a segment of the european alpine belt that can be successfully compared to the pan african trans saharan belt

coral boulders along the coast of the lanyu island offshore southeastern taiwan as potential paleotsunami records abstract in the last decade several disastrous tsunamis hit a large area of coastal east asia and produced numerous casualties and economic losses as a country that is also prone to tsunami hazards taiwan is in urgent need for more knowledge of past tsunami records and potential tsunamigenic sources on the basis of detailed geomorphic mapping and field investigations we identified six sites in the northern part of the lanyu island offshore southeastern taiwan with large coral boulders resting on holocene uplifted coral reef terraces boulders of these six sites are all likely moved by extremely strong waves and four sites have better constraints to suggest that the boulders may indeed be transported during a paleotsunami event the ages of the boulders suggest that the extremely strong wave events occurred at least several times since the mid holocene high stand of sea level the youngest event may correlate with the 1771 meiwa tsunami of the southern ryukyu islands but it is more likely to be produced by some undocumented event along the eastern coast of taiwan the locations of the coral boulder sites along the northern coast of the lanyu island suggest that the sources of the events are located to the north of the island we believe that our results would provide further information for future tsunami hazard assessments along the eastern coastal area of taiwan as well as surrounding areas

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

resolution of the age structure of the detrital zircon populations of two lower cretaceous sandstones from the weald of england by fission track dating modes in the frequency of distribution of fission track ages obtained from detrital zircon grains may prove characteristic of individual sandstone bodies supporting the identification of the sources from which a particular flow of sedimentary detritus was derived and thus allowing new inferences to be made concerning palaeogeography a computer program has been written and used to identify modes in the zircon fission track age distribution within two lower cretaceous sandstone samples from the weald of southern england pronounced modes appear in one rock around 119 ma 160 ma 243 ma and 309 ma and in the other around 141 ma 175 ma 257 to 277 ma and 394 to 453 ma the geological implications of these quite dissimilar zircon age spectra are discussed it is concluded that they support the palaeogeographical models of allen 1981 and indicate that the provenance of the first sample from the top ashdown sandstone member at dallington in east sussex was almost entirely southerly while that of the second from the netherside sand member at northchapel in west sussex was more varied but predominantly westerly and northerly

high precision u series ages of transported coral blocks on heron reef southern great barrier reef and storm activity during the past century transported coral blocks scattered on reef flats have previously been identified as useful proxies for past storm occurrences high precision tims u series dating and detailed field observations of 110 coral samples collected from 102 individual transported coral colonies coral blocks and 4 transported sections of reef matrix reef blocks from the northern side of heron reef southern great barrier reef indicate that 1 the youngest age of corals attached to reef blocks may represent the age of possible past storm occurrence providing a proxy for historical storm reconstruction 2 most ages of dated storm transported coral and reef blocks match well relatively with known cyclone and storm events further supporting that they are good indicators of past storm events and 3 age distribution and relative probability frequency analysis of the dated coral and reef blocks suggest that there have been eight broad periods of storm occurrence since 1900 ad 1904 1909 1914 1916 1935 1941 1945 1960 1965 1967 1976 1977 1983 1988 and 2001 2007 roughly showing decadal variations the coral based storm reconstruction therefore extended the database of past storm occurrences around heron reef area these findings suggest that coral reefs in the southern great barrier reef are frequently influenced by periods of high storm activity and show strong resilience to natural disturbances over the past century additionally our results show for the first time that the blue skeletal coral heliopora coerulea order helioporacae has u concentrations of only 0 12 to 0 30 ppm similar to 5 10 that of common reef building corals with white skeletons order scleractinia which may be a unique chemical signature of the only living species of the helioporidae family c 2012 elsevier b v all rights reserved

exhumation and relief history of the southern carpathians romania as evaluated from apatite fission track chronology in crystalline basement and intramontane sedimentary rocks the combination of apatite fission track ft thermochronology from basement units and the ft age distributions of apatites in the miocene intramontane sedimentary rocks allows describing the exhumation history of the central segment of the southern carpathians romania exhumation and cooling from the total track annealing temperature 120 c of the cozia and cibin massifs occurred in the palaeocene early eocene between the eocene and middle miocene there was a stagnation period concerning vertical displacement the presently exposed part of the basement was buried in shallow depth the present crests of the cozia and cibin mountains were at temperatures around 80 c and 50 c respectively the second exhumation period occurred in middle miocene times the magnitude of the miocene vertical displacement is on the order of the present day relief the vertical apatite ft age distribution in the basement and the age clusters in the sedimentary rocks prove that the levels of the crests were already close to the surface in palaeogene times therefore the post palaeocene erosional removal from the crest zones is very limited

huge erratic boulders in tonga deposited by a prehistoric tsunami along some coastlines there are erratic boulders apparently emplaced by tsunamis or cyclonic storms evaluating their origin and time of emplacement places constraints on the frequency severity and location of coastal hazards seven such large coral limestone boulders are present near fahefa village on tongatapu island southwest pacific apparently emplaced by a prehistoric tsunami these boulders are 10 20 m above sea level and above any possible source and all are 100 400 m from the present shoreline coral 230th ages indicate that the limestone formed during the last interglacial sea level highstand ca 120 130 ka the largest boulder is 20 times more massive than any reported boulders emplaced by historically documented storms and may be the largest known tsunami or storm erratic worldwide situated above its source we performed computer simulations to assess whether tsunamis produced by earthquakes undersea landslides or volcanoes could emplace the boulders the simulations indicate that either volcanic flank collapse along the tofua arc 30 40 km to the southwest or undersea landslides on the submarine slopes of tongatapu could be responsible either could explain why these boulders are not widespread on tongatapu and instead occur in a localized group along the western coast this study demonstrates that small 1 km3 submarine slope failures sometimes generate locally large tsunamis the fahefa boulders are in a well studied and well populated area yet were unknown to the scientific community until recently this suggests that systematic searches elsewhere for erratic boulders and other tsunami deposits might provide new information for assessing the size and extent of prehistoric tsunamis

variation of initial 230th 232th and limits of high precision u th dating of shallow water corals one hundred eighty u th data including 23 isochrons on 24 pristine modern and holocene corals and 33 seawater samples were analyzed using sector field mass spectrometry to understand the variability of initial 230th 232th 230th 232th0 this dataset allows us to further assess the accuracy and precision of coral 230th dating method by applying quality control including careful sampling and subsampling protocols and the use of contamination free storage and workbench spaces the resulting low procedural blanks give an equivalent uncertainty in age of only 0 2 0 3 yr for 1 2 g of coral sample using site specific 230th 232th0 values or isochron techniques our study demonstrates that corals with an age less than 100 yrs can be 230th dated with precisions of 1 yr six living subtidal coral samples were collected from two continental shelf sites nanwan off southern taiwan in the western pacific and son tra off central vietnam in the south china sea one coral core was drilled from an open ocean site santo island vanuatu in the western tropical pacific and modern and fossil intertidal coral slabs 17 in total were cut from six sites around the islands of simeulue lago north pagai and south pagai of sumatra in the eastern indian ocean the results indicate that the main source of thorium is the dissolved phase of seawater with variation of 230th 232th0 depending on local hydrology with intense input of terrestrial material low 230th 232th0 atomic ratios of 4 9 10 6 and 3 2 10 6 with a 10 variation are observed in nanwan and son tra respectively at the santo site we find a value of 5 6 10 6 at 4 horizons and one high value of 24 10 6 in a sample from ad 1974 6 0 5 likely due to the upwelling of cold water during a la nina event between ad 1973 and 1976 the natural dynamics of 230th 232th0 recorded in the intertidal corals at sites in the sumatran islands are complicated so that this value varies significantly from 3 0 to 9 4 10 6 three of the 141 modern coral 230th ages differ from their true ages by 23 to 4 indicating the presence of detrital material with anomalous 230th 232th values duplicate measurement of coeval subsamples is therefore recommended to verify the age accuracy this improved high precision coral 230th dating method raises the prospects of refining the age models for band counted and tracer tuned chronologies and of advancing coral paleoclimate research

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

reconstruction of storm tsunami records over the last 4000 years using transported coral blocks and lagoon sediments in the southern south china sea large transported coral blocks on reef flats and elevated sedimentation rates in atoll lagoons were demonstrated to be excellent proxies for past strong storms tsunamis in the southern south china sea here we introduce another important proxy coarse fraction contents of lagoon sediments this proxy is based on the principle that coarse fractions of enclosed lagoon sediments are usually controlled by strong sedimentary dynamics on the surrounding reef flat and thus increases in the weight percentages of coarse grained fractions of the lagoon sediments should also reflect strong storm tsunami events or increases in storminess with the size of the content peak as the proxy for the degree of storminess bearing this in mind we measured the contents of the 1 mm grain size fractions referred to as coarse fraction content in an undisturbed lagoon core precisely dated to cover the last 4000 years the decadal resolution data show a systematic variation with some peaks strongly correlated with in timing with strong storm tsunami events dated at ad 1872 15 1685 8 similar to 1680 6 1443 9 1336 9 1210 5 similar to 1201 4 and 1064 30 using wave transported coral blocks using the mean coarsefraction content 9 2 for the entire core as a reference line a total of 77 peaks were identified for the past 4000 years twenty of these peaks are higher than 23 the mean value for peaks that are correlated in age with the six strong storm events identified using independently dated coral blocks among these 23 peaks 13 occurred within the last 1000 years the concentration of contentpeaks in the last millennium could be partially due to higher deposition rates and sampling resolution over the last similar to 4000 years there appears to be a weakly increasing trend in coarse fraction contents towards present time but this trend is not obvious within the last millennium this long term variation may be related to changes in both storminess and reef lagoon morphology however the data do suggest three extremely stormy periods centring around ad similar to 1200 similar to 400 bc and similar to 1200 bc respectively overall this study demonstrates that combined use of transported coral blocks and coarse fraction contents of lagoon sediments provides an excellent means for comprehensive reconstruction of past storm tsunami activity c 2008 elsevier ltd and inqua all rights reserved

neotectonic architecture of taiwan and its implications for future large earthquakes the disastrous effects of the 1999 chi chi earthquake in taiwan demonstrated an urgent need for better knowledge of the island s potential earthquake sources toward this end we have prepared a neotectonic map of taiwan the map and related cross sections are based upon structural and geomorphic expression of active faults and folds both in the field and on shaded relief maps prepared from a 40 m resolution digital elevation model augmented by geodetic and seismologic data the active tandem suturing and tandem disengagement of a volcanic arc and a continental sliver to and from the eurasian continental margin have created two neotectonic belts in taiwan in the southern part of the orogen both belts are in the final stage of consuming oceanic crust collision and suturing occur in the middle part of both belts and postcollisional collapse and extension dominate the island s northern and northeastern flanks both belts consist of several distinct neotectonic domains seven domains kaoping chiayi taichung miaoli hsinchu ilan and taipei constitute the western belt and four domains lutao lanyu taitung hualien and ryukyu make up the eastern belt each domain is defined by a distinct suite of active structures for example the chelungpu fault source of the 1999 earthquake and its western neighbor the changhua fault are the principal components of the taichung domain whereas both its neighboring domains the chiayi and miaoli domains are dominated by major blind faults in most of the domains the size of the principal active fault is large enough to produce future earthquakes with magnitudes in the mid 7 values