applications of geochemistry in tsunami research a review abstract much progress has been made since the first published studies of tsunami deposits nearly 30 years ago geochemistry is now a much more widely used proxy in tsunami research mainly due to its increasingly recognised value in the identification of historical and or prehistorical deposits at times even providing the conclusive proof when other proxies are missing or equivocal but also its significance in environmental impact assessments following recent tsunamis the rapid advance in analytical techniques has also made it a more approachable and popular method as it is now often faster and cheaper here we provide a review of the applications of geochemistry including the techniques used as well as a database of studies that used chemical proxies in their investigation of recent and old events including onshore and offshore tsunami deposits chemical signatures are often used as markers of marine inundation either as salinity indicators where they can also allow the identification of the limit of tsunami inundation or tracers of the incorporation of marine sourced carbonates their applications as indicators of source material are nevertheless expanding thereby potentially providing additional information on the hydrodynamic processes associated with tsunami inundation although they are largely site specific the effects of post depositional changes in different climatic regimes are examined with a particular emphasis on water leachable components and implications for post event recovery of coastal ecosystems we demonstrate the usefulness of chemical proxies in studies of the geological record of tsunamis extending back thousands of years suggest new approaches and discuss limitations and existing knowledge gaps

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

arc and intraplate volcanism in the spences bridge group implications for cretaceous tectonics in the canadian cordillera the spences bridge group a late albian 100 ma age volcanic succession built on the western margin of superterrane i comprises two stratigraphic units with contrasting geochemistry the lower unit the pimainus formation represents a set of stratovolcanoes with calcalkaline character lavas of the overlying spins formation deposited as a shield volcano are hybrids between pimainus arc magma and spins type melts of intraplate affinity integration of regional geology suggests that the pimainus formation was produced by short lived easterly dipping subduction beneath superterrane i that convergence closed a narrow oceanic basin now represented by the methow tyaughton trough bringing superterrane ii into collision with superterrane 1 accretion in the latest albian resulted in cessation of pimainus are volcanism the eruption of spins lavas and easterly directed deformation of methow tyaughton strata early to middle cretaceous are volcanism of the gambier group on superterrane ii was produced by a separate concurrently active subduction zone

error analysis for the determination of tectonic rotation from paleomagnetic data appendix b is available with entire article on microfiche order from american geophysical union 2000 florida avenue n w washington d c 20009 document b83 001 2 50 payment must accompany order recent determinations of tectonic rotation and flattening from paleomagnetic data have exaggerated the size of the confidence limits or error bars by about 25 this has been caused by the misuse of conventional error propagation formulas to derive one degree of freedom error bars from a two dimensional cone of confidence 95 an analytical calculation which is valid when error bars are small shows that the correct error bars are 75 to 80 of the values derived in previous studies i have used numerical integration to check on the applicability of the analytical solution and to calculate error bars when the analytical approximation cannot be used the analytical approximation may be used whenever 95 is less than 10 and the mean inclination is not too close to vertical confidence limits given for tectonic rotation and flattening in recent literature are too large and should be reduced by 20 25 narrowing the error bars in this way permits a more accurate interpretation of paleomagnetic data

reexamination of the a d 869 jogan earthquake size from tsunami deposit distribution simulated flow depth and velocity the rupture parameters and magnitude of the a d 869 jogan earthquake a predecessor of the 2011 tohoku earthquake were previously estimated by matching tsunami deposit distributions with simulated inundation areas the tsunami inundation associated with the 2011 tohoku earthquake however extended farther inland than the sandy tsunami deposits numerical simulation of the 2011 tsunami indicated that flow depths and velocities were approximately 1 m and 0 6 m s respectively at the most inland sand deposit sites on the ishinomaki and sendai plains while these values depend on the assumed bottom roughness we used these values to compare tsunami deposits and inundation simulation of the 869 jogan earthquake from both uniform slip and 2011 type variable slip fault models the results showed that the rupture length of the 869 jogan earthquake was at least 200 km and its minimum moment magnitude was 8 6

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

anomalous paleomagnetism of the crowsnest formation of the rocky mountains the volcanic crowsnest formation of albian age late early cretaceous from the rocky mountain fold and thrust belt of alberta has a stable remanent magnetization with a mean direction of 349 59 95 5 and paleopole at 78 n 108 e dm 7 dp 5 the inclination is lower than and the declination clockwise of the expected mid cretaceous paleogeomagnetic field for cratonic north america taken at face value the result indicates that the crowsnest formation and the thrust sheet in which it occurs have been transported from the south relative to cratonic north america by 17 6 about 1800 km and rotated 24 10 clockwise it is also possible that flattening of inclination is caused by magnetic anistropy but tests show this to be unlikely a third possibility is that the magnetization is secondary and of latest cretaceous age but there are good reasons for believing this is not so lastly it is possible that the unit could have been formed close to its present position relative to the craton

dynamics of vulcano island tyrrhenian sea italy investigated by long term 40 years geophysical data abstract vulcano island is a composite volcanic edifice located in the south central sector of the aeolian archipelago tyrrhenian sea italy historic activity has been characterized by frequent transitions from phreatomagmatic to minor magmatic activity the last eruption in 1888 90 saw powerful explosive pulses and this eruption defines what we call vulcanian also for other volcanoes since then volcanic activity has been in the form of fumarolic emanations of variable intensity and temperature mainly concentrated at la fossa crater we investigated vulcano dynamics through ca 40 years of ground deformation and seismicity data collected by the discrete and continuous ingv monitoring networks we considered levelling gps edm seismic and tilt data edm and levelling measurements began in the middle of the 1970s since the late 1990s the edm benchmarks have been measured using gps we performed a data inversion identifying for the 1999 2013 period the action of a deflating magmatic source located under vulcanello at 4 5 km a s l just at the top of a wide regional tectonic tabular source we analyzed data on different time space scales distinguishing the dynamics of different sectors of vulcano piano vulcanello la fossa cone and caldera and three periods 1974 1984 1984 1999 1999 2013 and the time evolution of the dynamics of the island we also show how the regional tectonic stress plays an important role in the transition of the volcanic system from a phase of stability to one of unrest inducing the heating and expansion of shallow hydrothermal fluids

cretaceous remagnetization in the sylvester allochthon limits to post 105 ma northward displacement of north central british columbia the sylvester allochthon of the slide mountain terrane in northern british columbia is a structurally interleaved assemblage of ocean floor lithologies ranging in age from late devonian to late triassic it is the most inboard of oceanic suspect terranes and rests as a vast klippe on miogeoclinal strata of the cassiar terrane the sylvester allochton and the cassiar terrane lie west of the northern rocky mountain trench fault both the sylvester allochthon and the cassiar terrane are intruded by mid cretaceous 105 ma granite of the cassiar batholith six oriented cores were collected at each of 12 sites in guadalupian parafusulina bearing limestone of the sylvester allochthon at a location 4 km from the batholith isothermal remanent magnetization irm acquisition and subsequent thermal demagnetization indicate that pyrrhotite is the dominant ferrimagnetic mineral least squares line fitting to four thermal demagnetization steps between 150 and 310 c was used to determine the characteristic natural re

tsuflind enkf inversion of tsunami flow depth and flow speed from deposits with quantified uncertainties abstract deciphering quantitative information from tsunami deposits is especially important for analyzing paleotsunami events in which deposits comprise one of the leftover physical evidences the physical meaning of the deciphered quantities depends on the physical assumptions that are applied the aim of our study is to estimate the characteristics of tsunamis and quantify the associated errors and uncertainties to achieve this goal we apply the tsuflind enkf inversion model to study the deposition of an idealized deposit created by a single tsunami wave and one real case from the 2004 indian ocean tsunami tsuflind enkf combines tsuflind for the deposition module with the ensemble kalman filtering enkf method in our modeling we assume that grain size distribution and thickness from the idealized deposits at different depths can be used as an observational variable our results indicate that sampling methods and sampling frequencies of tsunami deposits influence not only the magnitude of the inverted variables but also their errors and uncertainties an interesting result of our technique is that a larger number of samples from a given tsunami deposit does not automatically mean that the inversion results are more robust with smaller errors and decreased uncertainties tsuflind enkf presents the final inversion results as a probability density distribution function instead of only one value or range of values

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

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

experimental observations of tsunami induced scour at onshore structures tsunami inundation of the coastal environment can induce scour at structure foundations leading to failure a series of experiments are made using a unique pneumatic long wave generator to generate tsunami wave periods of 25 147 s equating to 3 17 3 min at 1 50 froude scale the waves propagate over a sloping bathymetry and impinge upon a square structure founded onshore in a flat sediment bed flow velocity height and scour depth are recorded as a function of time during tsunami inundation the rate of scour is observed to be time dependent equilibrium which is not attained is argued to be an inappropriate measure for time dependent transient flows such as tsunami in which the flow velocity depth and direction are variable the maximum scour depth is recorded and critically is observed not to be equal to the final depth due to significant sediment slumping when flow velocities reduce in the latter stages of inundation current and wave scour predictor equations over predict the scour while the asce 7 16 method under predicts comparisons with available data in the literature show longer inundation durations increase the amount of scour

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

geometric test for late cretaceous paleogene intracontinental transform faulting in the canadian cordillera the tintina trench northern rocky mountain trench tt nrmt fault zone and the fraser river straight creek fr sc fault zone are separate en echelon concentric small circle fault segments of a composite intracontinental transform fault zone more than 2500 km long that cuts diagonally across the canadian cordillera from the outboard part of a tectonic collage of accreted foreign terranes in the south into the north american preaccretionary continental margin in the north most of the 450 km of right hand slip on the tt nrmt fault zone was transformed southward during the late cretaceous and paleocene into oblique convergence in the southern canadian rockies the remainder probably comprising less than 100 km was transformed southwestward during early and middle eocene time via a zone of distributed shear and east west crustal stretching into right hand slip on the en echelon fr sc fault zone these interpretations based on regional systematic mapping of geologic structures are in conflict with interpretations of paleomagnetic measurements that call for more than 1000 km of post mid cretaceous right hand displacement along the general locus of the tt nrmt fault zone involving foreign terranes and the parts of north america to which they had been accreted this paradox must be resolved

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

historical tsunami deposits in peru sedimentology inverse modeling and optically stimulated luminescence dating the entire coast of peru was surveyed to document deposits of historical tsunami evidence of four tsunami was found at puerto casma in northern peru a graded heavy mineral rich layer with shell and rock fragments was detected osl dating revealed an age of 0 37 0 03 ka 1615e1667 ad inverse modelling of tsunami onshore flow parameters indicates a flow depth of w 6ma nd aflow speed of w8 m s at a distance of w60 m from the shoreline for the chimbote earthquake of 1619 ad a tsunami was not listed in the historical tsunami catalogues although it is seen as a predecessor of the 1996 chimbote earthquake and tsunami hence this study may provide the first evidence of a local tsunami triggered by this event a graded shell rich event layer that contains cobbles with attached marine organisms was found at vila vila in southern peru this layer was dated to 0 17 0 04 ka 1797e1871 ad and is most probably the result of the 1868 arica tsunami two additional event layers found in boca del rio southern peru were dated 2 26 0 37 ka 615 bce119 ad and 1 98 0 23 ka 207 bce255 ad thus the layers record for the first time tsunami much older than the events listed in tsunami catalogues these two events exhibit similar parameters with flow speeds of 7e8 m s and depths of 6 m in a distance of 460 m from the present shoreline the time that passed between the events is similar to the recurrence interval of the two arica tsunami of 1604 and 1868 ad hence giving evidence of another prehistoric earthquake and tsunami couplet

liquefaction as an important source of the a d 2011 tohoku oki tsunami deposits at sendai plain japan this paper describes the topographic change and the recovery process as well as the sediment sources for tsunami deposits based on field surveys and analysis of digital elevation model data before and after the a d 2011 tohoku oki tsunami at the sendai plain japan we found that the amount of sediment deposited on land was approximately four times greater than the eroded volume of sediment at the beach large amounts of the sediments deposited at the studied transect probably originated from liquefaction this result suggests that the vented sediments might have been an important source of the tsunami deposits if liquefaction is generated by the strong ground motion of a near field earthquake in contrast minor erosion was observed at the beach and the beach berm was rebuilt within three months after the tsunami moreover the erosional channel that had cut into the beach had been filled by sand within 13 days after the tsunami therefore it is not expected that a sedimentary record of the tsunami will be preserved in the nearshore zone along the sendai coast although remnants of small scours on land might remain long after the tsunami

challenges of anticipating the 2011 tohoku earthquake and tsunami using coastal geology 1 can the magnitude of a giant earthquake be estimated from paleoseismological data alone attempts to estimate the size of the jogan earthquake of ad 869 whose tsunami affected much of the same coast as the 2011 tohoku tsunami offers an excellent opportunity to address this question which is fundamental to assessing earthquake and tsunami hazards at subduction zones between 2004 and 2010 examining stratigraphy at 399 locations beneath paddy fields along 180 km of coast mainly south of sendai we learned that a tsunami deposit associated with the ad 869 jogan earthquake had run inland at least 1 5 km across multiple coastal lowlands and that one of the lowlands had subsided during the jogan earthquake and an earlier earthquake as well radiocarbon ages just below above sand deposits left by the pre jogan tsunamis suggested recurrence intervals in the range of 500 to 800 years modeling inundation and subsidence we estimated size of the jogan earthquake as moment magnitude 8 4 or larger and a fault rupture area 200 km long we did not consider a longer rupture like the one in 2011 because coastal landform and absence of a volcanic ash layer make any jogan layer difficult to identify along the sanriku coast still sendai tsunami geology might have reduced casualties by improving evacuation maps and informing public awareness campaigns

tertiary paleomagnetism of the north cascade range washington we have obtained paleomagnetic data for the southern tip of the middle tertiary chilliwack composite batholith located on the canada united states border about 125 km e of vancouver b c thirty four separately oriented samples were collected along a road traverse 1 5 km long located along state highway 22 about 20 km ne of marblemount washington the mean direction after magnetic cleaning is d 182 8 i 65 0 95 1 5 this corresponds to a paleomagnetic pole at 87 5 n 267 5 e close to other poles for tertiary plutons from the north cascades and only slightly displaced from tertiary reference poles from the craton we conclude that the north cascades block has not been rotated or suffered major internal disruption since perhaps late eocene time in marked contrast to all the terranes that surround it

ancient sedimentary dna reveals past tsunami deposits abstract palaeotsunami deposits are the primary sources of information on past large tsunami events and thereby are critical for earthquake and tsunami hazard assessments they usually form sandy layers preserved in coastal sediments and contain indicators of marine origins such as microfossils e g diatoms and foraminifera and geochemical signals of saltwater however these indicators are often modified or erased with time to address this issue we present the first application of a palaeogenetic approach to a series of up to approximately 2000 year old sandy palaeotsunami deposits from a coastal wetland on hokkaido island japan we found the dna of marine foraminiferal species preserved in palaeotsunami deposits in the absence of foraminifera tests the recovery and analysis of the ancient sedimentary dna of marine organisms preserved in coastal zone sediments for millennia represents a new and promising tool for the identification of past tsunamis

a model for tsunami flow inversion from deposits tsuflind abstract modern tsunami deposits are employed to estimate the overland flow characteristics of tsunamis with the help of the overland flow characteristics the characteristics of the causative tsunami wave can be estimated the understanding of tsunami deposits has tremendously improved over the last decades there are three prominent inversion models a moore s advection model moore et al 2007 b soulsby s model soulsby et al 2007 and c tsusedmod jaffe gelfenbuam 2007 tsuflind incorporates all three models and adds new modules to better simulate tsunami deposit formation and calculate flow condition tsuflind takes grain size distribution thickness water depth and topography information as inputs tsuflind computes sediment concentration grain size distribution of sediment source and initial flow condition to match the sediment thickness and grain size distribution from field observation furthermore tsuflind estimates the flow speed froude number and representative wave amplitude the model is tested by using field data collected at ranganathapuram india after the 2004 india ocean tsunami tsuflind reproduces the field measurement grain size distribution with less than 5 error tsunami speed in this test case is about 4 7 ms 1 at 150 m inland and decreases to 3 3 ms 1 350 m inland from the shoreline the estimated wave amplitude of the largest wave for this test case is about 5 to 7 m

paleomagnetism of the flores volcanics vancouver island in place by eocene time the eocene flores volcanics of the insular belt of southwestern vancouver island have u pb zircon ages of 51 50 ma and a mean direction of magnetization d i of 349 8 69 6 12 collecting sites

sediment transport modeling of multiple grain sizes for the 2011 tohoku tsunami on a steep coastal valley of numanohama northeast japan abstract the grain size distribution of a tsunami deposit may have a correlation with the tsunami inundation process and further with the tsunami source characteristics we test this hypothesis using thickness and grain size distribution data of the 2011 tohoku tsunami deposit in numanohama coast iwate prefecture japan here we build and validate a tsunami sediment transport model that can simulate deposit thickness and grain size distribution our numerical model has three layers parent bed deposit bed and suspended load layers the two bed layers contain information about the grain size distribution this numerical model can handle a wide range of grain sizes from 0 063 4 to 5 657 mm 2 5 the grain size distributions at 12 sample points along a 900 m transect from the beach through a marsh and up to the inundation limit are used to validate the tsunami sediment transport model we adopt a reference tsunami source model that can well reproduce the observed tsunami run up heights ranging from 16 to 35 m along the steep valley during the 2011 tsunami the simulated sand thickness distribution along the transect is consistent with the observed thickness ranging from 3 to 23 cm the computed net erosion and deposition suggest that most of the sand deposit was originated from the near shore the shapes of the simulated grain size distributions represented by their sorting skewness kurtosis and mean at most of the sample sites are similar to the observations the differences between the observed and simulated peak of grain size distributions are less than 1 to evaluate the sensitivity to the tsunami source model we test five tsunami scenarios which are modified from the reference source model while the tsunami scenario with 120 of the reference amplitude can also reproduce the thickness and grain size distribution the scenarios with amplitudes smaller than 80 of the reference or with wave periods shorter than 50 of the reference source model underestimate the thickness and cannot reproduce the grain size distributions our simulation results suggest that it is possible to estimate tsunami wave amplitude and wave period from sediment deposit thickness and grain size distribution data

diatoms as an aid in identifying late holocene tsunami deposits diatoms bacillariophyta help identify the onshore deposits of tsunamis from earthquakes on the cascadia subduction zone along the pacific coast of oregon washington and british columbia and on faults high in the north american plate in the puget sound area of washington at the copalis river washington diatom analyses suggest that a tsunami deposit about 300 calendric years old 300 yr bp originated from sandy shoals of the lower estuary rather than nearby beaches or coastal dunes at cultus bay and west point washington well preserved benthic estuarine diatoms in sand sheets overlying tidal marsh peat indicate that the deposits came from intertidal or nearshore areas of puget sound on an abruptly uplifted mudflat at the landward end of hood canal at lynch cove washington tidal flat diatoms refute the possibility of a terrestrial source for the sand diatoms in 300 yr bp tsunami deposits on the niawiakum river washington confirm that the sand in these deposits had a marine source and help

eocene sedimentation and volcanism in the fig lake graben southwestern british columbia the fig lake graben is a narrow complex eocene basin that developed along part of the coldwater fault system in southwestern british columbia its origin as a pull apart basin is probably related to dextral wrench faulting along the fraser fault and low angle normal faulting of the okanagan shear zone within the graben are kamloops group volcanic and sedimentary rocks the thickness of which implies that one fault block has been downthrown at least 4 5 km geochemical interpretation of previously published analyses of kamloops group volcanic rocks indicates that magma production was genetically related to both extension and subduction

northward translation of baja british columbia along the late cretaceous to paleocene margin of western north america paleomagnetic data suggest that a large part of british columbia and southern alaska was at the latitude of baja california mexico in early late cretaceous time this allochthonous block baja bc includes the insular talkeetna in alaska and intermontane composite terranes the miniterranes between them and possibly part of the omineca metamorphic belt assuming that baja bc was adjacent to north america by middle cretaceous an analysis using plate kinematics of the pacific basin produces a model of northward movement of baja bc which is compatible with the known geology of the reconstructed margin of western north america baja bc moved north 2400 km as part of the kuia plate along a transform margin with north america from 85 to 66 ma this time interval is marked by the cessation of igneous activity in the sierra nevada development of wrench faults and basins along coastal california and initiation of laramide style tectonics to the east within baja bc diminished igneous activity to the west was coeval with possible wrench tectonic basins along its eastern margin by the end of the cretaceous baja bc was positioned from oregon to northern british columbia between 66 and 56 ma baja bc became attached to north america in a dextral transpressive stage during which the kula north america plate boundary expanded to encompass the whole block with a series of northwest trending strike slip faults a fold and thrust belt in the east and large scale uplifts and the formation of an incipient volcanic arc on the west southern alaska was the site of convergence during the whole of the period of northward translation of baja bc a late cretaceous subduction zone in alaska evolved into a major compressional belt as the basin and miniterranes on the northern margin of baja bc collided with interior alaska the collision culminated in the paleocene with formation of the mckinley granites and coeval dextral slip on the denali fault system

discordant paleomagnetic poles from the canadian coast plutonic complex regional tilt rather than large scale displacement stratigraphic petrologic and isotopic data indicate that parts of the coast plutonic complex and the north cascade range have been tilted northeast side up by angles of approximately 30 degree about north northwest trending axes these tilts can account for discordant paleomagnetic directions observed in mid cretaceous plutons from these regions without large scale displacement relative to north america

paleomagnetic results for eocene volcanic rocks from northeastern washington and the tertiary tectonics of the pacific northwest the direction of remanent magnetization for 102 sites in eocene volcanic and volcaniclastic rocks of the o brien creek formation sanpoil volcanics and klondike mountain formation suggests approximately 25 of clockwise rotation of a 100 by 200 km area in northeastern washington the volcanic rocks consist chiefly of rhyodacite and quartz latite flows with intercalated ash flow tuff and volcaniclastic layers these rocks have been sampled at 102 sites distributed among five volcanotectonic depressions the toroda creek republic keller and first thought grabens and the spokane enterprise lineament the volcanic rocks probably range in age from 55 m y to about 48 m y and the 50 to 48 m y old volcanic rocks within this suite appear to be rotated as much as the older rocks previous investigators have shown that 40 m y old and younger plutonic rocks of northwestern washington are not rotated hence we infer that the north central washington rocks were rotated to their present declination between 48 and 40 m y b p during the middle and or late eocene during early eocene time this region was extended in a westward direction through crustal necking gneiss doming diking and graben formation internal deformation of the region related to this crustal extension was extreme but most bedrock units that were formed concurrent with the crustal extension were probably in place prior to the rotation hence we infer that the rotation was chiefly accommodated by movement on faults peripheral to the sampled area faults active during paleogene time appear to define boundaries of a triangular crustal block the sanpoil block encompassing much of northeastern washington northern idaho northwestern montana and adjacent parts of british columbia the faults include the laramide thrusts of the rocky mountain thrust belt the strike slip faults of the lewis and clark line and strike slip faults of the straight creek fraser zone we suggest that during early eocene time the sanpoil block was extended westward through crustal necking and dilation and then during the middle eocene was rotated clockwise and thrust over the craton in a final stage of laramide thrusting the motor driving these deformations presumably was interaction of north america with oceanic lithosphere off its western margin such interaction probably involved right oblique underthrusting and dextral shear

vented sediments and tsunami deposits in the puget lowland washington differentiating sedimentary processes the sandy deposits produced by tsunamis and liquefaction share many sedimentary features and distinctions between the two are important in seismically active coastal zones both types of deposits are present in the wetlands bordering puget sound where one or more earthquakes about 1100 years ago caused both tsunami flooding and sediment venting this co occurrence allows an examination of the resulting deposits and a comparison with tsunami and liquefaction features of modern events vented sediments occur at four of five wetland field localities and tsunami deposits at two in comparison with tsunami deposits vented sediments in this study and from other studies tend to be thicker although they can be thin vented sediments also have more variable thickness at both outcrop and map scale are associated with injected dykes and contain clasts derived from underlying deposits further vented sediments tend to contain a greater variety of sedimentary structures and these structures vary laterally over metres tsunami deposits compared with vented sediments are commonly thinner fine and thin landward more consistently have more uniform thickness on outcrop and map scales and have the potential of containing coarser clasts up to boulders for both tsunami deposits and vented sediments the availability and grain size of source material condition the characteristics of the deposit in the cases presented in this paper both foraminifera and diatom assemblages within tsunami deposits and vented sediments consisted of brackish and marine species and no distinction between processes could be made based on microfossils in summary this study indicates a need for more careful analysis and mapping of coastal sediments associated with earthquakes to avoid misidentification of processes and misevaluation of hazards

full scale cfd simulation of tsunamis part 2 boundary layers and bed shear stresses abstract this paper presents results from numerical simulations of the propagation and run up of full scale tsunamis using a reynolds averaged navier stokes model with emphasis on the resulting boundary layers and bed shear stresses spatial distributions of the shields and rouse parameters during run up and draw down show that for the tsunamis considered with a sediment grain size corresponding to medium sand considerable sediment transport shields parameter o 10 o 100 can be expected during run up and that the sediment transport can be expected to be dominated by suspended load the results likewise show that the expected sediment transport during draw down will similarly be considerable and dominated by suspension the tsunami induced boundary layers are monitored in time and the observed boundary layer thickness ranges from spanning only a small fraction of the water depth to spanning the entire depth the velocity profiles beneath the tsunamis are shown to have good correspondence with a logarithmic profile within the boundary layer similarly the bed shear stresses beneath the tsunamis are investigated and a new and simple engineering model is developed for predicting the temporal variation of the bed shear stress based only on a free stream velocity signal the new engineering model is shown give better predictions for the bed shear stress than a standard manning approach and is likewise shown in the appendix to produce reasonable predictions for shorter wind scale waves it is finally also shown how the temporal evolution of the boundary layer thickness can be predicted based on the free stream velocity signal alone the results presented here are part 2 of a larger study where part 1 presents the model validation and detailed descriptions of the run up process

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

inverse grading resulting from coarse sediment transport lag inverse grading in turbidites is conventionally ascribed to dispersive pressure caused by mutual collisions among grains within a traction carpet or grain flow the shearing traction carpet is supposed to become stratified with particle size increasing upward freezing of this traction carpet yields an inversely graded layer an alternative mechanism proposed here emerges from the fact that coarse sediment fractions are transported more slowly than fine fractions in a turbidity current a sufficiently heterogeneous mix of sediment sizes should undergo streamwise size segregation as the coarsest fractions lag behind if deposition begins before the coarsest fraction that will reach a particular station has arrived the lower part of the resulting deposit should be inversely graded a similar mechanism may produce inversely graded intervals in pyroclastic flow deposits because the head of a turbidity current typically travels only about 0 83 as fast as flow velocity in the body a short distance behind the head the coarsest grains able to keep up with the front of the flow are those having transport velocity v sed nearly equal 0 83 u body if coarser size fractions are available they will arrive later than the head permitting the development of inverse grading the proposed mechanism will not operate when the coarsest size fraction travels as fast as or faster than the head of the flow or when onset of deposition is delayed until after the coarsest size fraction has arrived assuming a logarithmic velocity profile below the maximum velocity streamline transport velocity can be calculated for particular sizes of suspended sediment and expressed as a fraction of flow velocity an upper limit for flow strength shear velocity can then be derived from the fall velocity of the coarsest grains at the base of an inversely graded interval u 4 w init where deposition of an inversely graded turbidite began immediately after passage of the head of the current u nearly equal 4 w init

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

inverse tsunami flow modeling including nonequilibrium sediment transport with application to deposits from the 2011 tohoku oki tsunami tsunami deposits provide important clues to understand ancient tsunami events several inverse models have been proposed to estimate the magnitude of paleotsunamis from their deposits however existing models consider neither non uniform transport of suspended sediment nor turbulent mixing which are essential factors governing sedimentation from suspension in tsunami flows here we propose a new inverse model of tsunami deposit emplacement considering both transport of non uniform suspended load and entrainment of basal sediments this inversion model requires the spatial distribution of deposit thickness and the pattern of grain size distributions of the tsunami deposit along a 1d shoreline normal transect as input data it produces as output run up flow velocity inundation depth and concentration of suspended sediment to solve for advection of non uniform suspended load a transformed coordinate system is adopted which increases computational efficiency tests of model inversions using artificial data successfully allow reconstruction of the original input values suggesting the effectiveness of our optimization method we apply our new inversion model to the 2011 tohoku oki tsunami deposit on sendai plain japan the thickness and grain size distribution of the tsunami deposit was measured along a 4 km long transect normal to the coastline the result of our inversion fits well with the observations from aerial videos and field surveys we conclude that this method is suitable for the analysis of ancient tsunami deposits and that it has the advantage of requiring relatively little information about the condition of the emplacing paleotsunami for reconstruction

on determining paleohorizontal and latitudinal shifts paleomagnetism of spences bridge group british columbia the spences bridge group of late albian age palynology and u pb zircon date of 104 5 ma is situated in the intermontane belt of the southern canadian cordillera zeolite grade andesite lavas and interbedded volcaniclastic rocks have been sampled through a thickness of about 2900 m sampling has been confined to localities whose bedding attitudes are well defined and to rocks that have not undergone internal deformation of the 27 sites studied 25 gave single component magnetizations with well grouped directions high coercivities and high unblocking temperatures applying corrections for geological tilt to all 25 sites yielded minimum dispersion after 65 untilting analysis indicates that this is a consequence of the interaction of two modes of behavior one exhibited by y magnetizations at 8 sites in which minimum dispersion occurs after 35 untilting and one x magnetizations at 17 sites in which minimum dispersion occurs after 100 correction actually the dispersion is essentially constant in the range 88 to 100 correction the y magnetizations are uninterpretable in terms of the paleofield because no estimate of paleohorizontal can be made because of their positive response to the tilt test the x magnetizations were acquired before tilting and it is argued that geologically determined bedding planes are good estimators of paleohorizontal at the time of remanence aquisition there may be errors because of paleoslope but arguments are presented for believing that these are small on this basis the best estimate of the mean direction of the paleofield in spences bridge time is estimated to be d i declination inclination 38 7 63 9 17 sites k 44 compared with k 11 in situ 95 5 4 with a paleopole at 64 4 n 321 0 e k 24 compared with k 5 in situ a95 7 5 when compared with the cratonic reference field for mid cretaceous time this pretilting magnetization indicates a clockwise rotation of the study area of 66 3 11 8 p 0 05 and an apparent displacement from the south of 15 5 7 1 1725 790 km when these and other data previously obtained from cretaceous rocks of the pacific northwest are compiled they show an increase in apparent displacement from east to west across the cordillera this result is discussed in terms of three hypotheses 1 no translation but systematic tilts of about 30 to the southwest 2 translation of a substantial part of the pacific northwest referred to as baja british columbia and is defined more exactly in the text by variable amounts up to more than 2000 km from the south together with clockwise rotations and 3 lesser translation of baja british columbia by about 1500 km combined with variable tilting predominantly to the south it is concluded that paleomagnetic data as they are presently known are consistent with hypotheses 2 and 3 but unless serious sources of error are present are not consistent with hypothesis 1 the most likely candidate for such errors is the uncertainty in estimating initial dip of beds paleoslope in volcanic rock units

cretaceous paleomagnetism of the methow pasayten belt washington detailed demagnetization experiments isolated a characteristic remanent magnetization in ten stable sites from the upper cretaceous winthrop and midnight peak formations in the methow pasayten belt of north central washington this remanence agrees best between opposite limbs of a fold the goat peak syncline when corrected for 46 of tilt this is consistent with magnetization acquired during deformation synfolding magnetization may have been facilitated by a thermo chemical event associated with synkinematic intrusions along the axis of folding the mean direction d 12 0 i 61 1 alpha 95 4 8 is highly discordant with respect to the expected direction for north central washington this discordance points to about 1 400 km of poleward transport and 48 of clockwise rotation between 93 and 45 48 ma

a geochemical approach for identifying marine incursions implications for tsunami geology on the pacific coast of northeast japan abstract potential tsunami inundation areas can be predicted by the distribution of paleo tsunami deposits on land which are mainly composed of marine derived sands and muds these exotic sandy and muddy layers have been identified by multiple approaches however there still remain uncertainties regarding the sources and weathering trends over the long term and other useful proxies need to be investigated to identify of tsunami deposits we examined the geochemical signatures of modern tsunami deposits from the pacific coast of northeast japan 2011 tohoku tsunami and those paleo tsunami deposits taken from the tohoku district jogan 1080 calibrated ages before present cal bp and yayoi ca 2000 cal bp a geochemical ternary diagram seawater rock as metals showed the weathering trends of tsunami deposits over approximately 2000 years in the sendai plain in the tohoku in the tsunami layers from the tohoku the na ti atomic ratios markedly increased to 23 4 with an average value of 19 3 3 0 jogan and yayoi tsunami deposits which was clearly higher than those of other layers soil deposits 10 3 3 5 on average these results show that na ti ratios and other geochemical proxies are useful indicators of marine incursions in our case and may contribute to the detection of muddy tsunami deposits close to the limit of inundation

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

paleomagnetism of the eocene kamloops group and the cratonization of terrane i of the canadian cordillera the lower middle eocene 49 4 2 4 ma kamloops group is exposed in the middle of the quesnellia subterrane of terrane i the group consists of the siliciclastic tranquille beds and the overlying dewdrop flats plateau basalts and andesites detailed alternating field af and thermal step demagnetization was carried out on 282 specimens from 26 flow sites and one conglomerate site and saturation isothermal remanent magnetization sirm tests were performed to examine the remanence carriers the petrology of the gently dipping flows the presence of antiparallel normal and reverse remanence the conglomerate test and the fold test all indicate that a primary remanence has been isolated it resides in both magnetite and hematite over a broad range of af coercivities blocking temperatures and domain sizes its mean direction of 355 0 73 4 95 6 9 gives a pole position of 138 4 w 81 4 n dp 11 0 dm 12 3 that is statistically indistinguishable from the 50 ma reference pole for the north a

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

the gang ranch big bar area south central british columbia stratigraphy geochronology and palynology of the tertiary beds and their relationship to the fraser fault tertiary rocks in the gang ranch big bar area south central british columbia consist of 1 early or middle eocene 50 ma lavas breccias and tuffs capped by a mappable unit of conglomerate a

flume experiments test grain size distribution of onshore tsunami deposits abstract we conducted flume experiments to examine the effects of grain size on the distribution of tsunami deposits using well sorted quartz sand with median diameters d50 of 0 064 0 134 0 215 and 0 250 mm in these experiments we investigated deposits transported onto a flat terrestrial area by a single tsunami like bore without a strong backwash flow the post tsunami distributions of the coarser d50 0 215 and 0 250 mm and finer d50 0 064 and 0 134 mm sands differed markedly the amount of the deposited coarser sand decreased landward across the entire terrestrial area whereas that of the deposited finer sand was either approximately uniform across the terrestrial area or increased gradually landward time series of flow depth and sediment transport observed via composited video frame images showed that suspension of the coarser sand did not reach the height of the maximum flow depth and decreased with distance from the sediment source and that the sediment settled gradually across the terrestrial surface with the amount deposited decreasing landward conversely the finer sand was densely suspended up to the maximum flow depth and was transported over longer distances across the terrestrial area with the amount deposited being relatively uniform or increasing slightly landward advection lengths that we calculated on the basis of our experimental parameters supported the dependence on grain size of the distribution patterns of onshore deposits shown by our flume experiments moreover advection lengths that we calculated for the 2011 tohoku oki tsunami from previously reported tsunami parameters were consistent with a deposit distribution similar to that observed in the field after the tsunami although we ignored some key factors e g geomorphology and sediment availability our flume experiments showed that the distribution patterns of identical tsunami flows differ for sediments of different grain size

assessing topographic controls on flow direction in washover deposits using measurements of magnetic fabric abstract a set of anomalous sand deposits enclosed between paleosol layers were identified in okains bay on eastern banks peninsula new zealand these were investigated to determine flow patterns during their deposition and the influence of topography on these patterns this was achieved using a combination of sedimentary analyses magnetic fabric mf and ground penetrating radar gpr two washover facies were identified based on stratigraphic context particle size analyses and flow direction during deposition from mf results these deposits which decrease in thickness with distance inland comprise two layers of fine medium sand and are situated 1 3 km from the coast on an estuary margin results show the sand sheets were deposited as overwash from the estuary with the extent and deposition patterns controlled by local topography and the presence of relict dune ridges mf is demonstrated as a versatile and important technique for determining flow patterns and depositional mechanisms flow patterns identified here from mf highlight the importance of river channels as conduits for short lived high energy marine inundation events additionally these results support the importance of topography in controlling deposition patterns which has important implications for the reconstruction of events where the paleotopography is unknown

tsunami deposits in a super large wave flume abstract understanding the process of sediment transport under tsunami inundation is essential to providing credible information about potential tsunamis from tsunami deposits in this study a super large wave flume 205 m long and 3 4 m wide was used to investigate the hydraulic process of tsunami inundation and sedimentary features of the resulting tsunami deposit a uniformly sloping topography 1 50 with a sand dune 0 2 m high was built in the flume and the topography change induced by a solitary wave was measured the maximum wave height at the shoreline was 0 6 m and the horizontal velocity reached up to 3 5 m s resulting in a sediment concentration of up to 5 by volume the inundation and return flow completely eroded the dune and caused deposition which showed landward and seaward thinning and fining the vertical distribution of grain size and density in the inundation flow indicated upward fining and an upward decrease in density and the deposits showed inverse grading at the base in addition to normal grading therefore the inverse grading was attributed to the depositional process instead of the vertical distribution of grain size in the flow such as via a traction carpet the inundation flow was classified into two phases the first phase flow which appeared at the front of the inundation flow was governed by the wave speed at the shoreline the second phase flow which occurred near the dune was controlled by the difference in wave levels in front of and behind the dune the deposits caused by the first phase flow near the inundation limit were constant regardless of the presence of the dune indicating that the effect of the dune on the deposits was limited in the nearshore region the deposits near the inundation limit showing rapid fining and different chemical compositions were carried by muddy foam floating on the water surface the sediment supply from offshore to onshore over the dune was small and the erosion of the sand dune accounted for 36 of the onshore deposits the offshore deposits were mainly caused by wave motion and the contribution of the onshore sediment brought by the return flow was small 24 however the return flow had a large effect on the sedimentary structure of the offshore deposits such as seaward fining our results will help to examine the physical processes resulting in the empirically established common sedimentary characteristics of tsunami deposits and will provide a detailed data set to validate sediment transport models used in numerical simulations

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

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

age of magnetization of the axelgold gabbro north central british columbia k ar and rb sr dates ranging from 101 2 to 158 6 ma are reviewed to arrive at an absolute minimum age of 115 119 ma and probable age of 125 5 ma for the axelgold gabbro consistent with geologic evidence the magnetization with blocking temperature of 500 600 c was almost certainly acquired between these limits the result provides an important constraint on the determination of the paleolatitudinal displacement of the axelgold gabbro with respect to the craton and supports the earlier contention of monger and irving that post mid cretaceous displacement from the south was in excess of 1000 km

paleomagnetism of the late cretaceous early tertiary north central montana alkalic province paleomagnetic results have been obtained from the late cretaceous early tertiary igneous complexes of the north central montana alkalic province data from 94 sites in eocene volcanic and intrusive rocks give a paleomagnetic pole located at 82 0 n 170 2 e a95 3 5 k 18 6 while 36 sites in paleocene intrusions yield a paleomagnetic pole at 81 8 n 181 4 e a95 5 4 k 20 2 these poles differ by only 1 6 and are not significantly different statistically the 130 site virtual geomagnetic poles show no significant elongation and suggest no significant apparent polar wander apw during the period of magnetization of the igneous centers postmagnetization structural complications in these rocks are minimal the presence of a single predominant polarity in these intrusive complexes reinforces the radiometric age data that suggest that igneous activity within individual centers was of short duration the northcentral montana data together with other early tertiary cretaceous and mid tertiary paleomagnetic results require modification of our earlier apw chronology diehl et al 1980 it now appears that apw relative to north america since the early cretaceous consists of a polar still stand during much of the cretaceous 120 75 m y b p a period of rapid movement in latest cretaceous time 75 65 m y b p and a period of slow polar movement thereafter the onset of this period of rapid apw correlates well with a major change in plate motions at 80 m y and the beginning of the laramide orogeny

estimation of tsunami characteristics from deposits inverse modeling using a deep learning neural network tsunami deposits provide information for estimating the magnitude and flow conditions of paleotsunamis and inverse models have potential for reconstructing hydraulic conditions of tsunamis from th

experimental tsunami deposits linking hydrodynamics to sediment entrainment advection lengths and downstream fining abstract a goal of paleotsunami research is to quantitatively reconstruct wave hydraulics from sediment deposits in order to better understand coastal hazards simple models have been proposed to predict wave heights and velocities based largely on deposit grain size distributions gsds although seemingly consistent with some recent tsunamis little independent data exist to test these equations we conducted laboratory experiments to evaluate inversion assumptions and uncertainties a computer controlled lift gate instantaneously released 6 5 m 3 of water into a 32 m flume with shallow ponded water creating a hydraulic bore that transported sand from an upstream source dune differences in initial gsds and ponded water depths influenced entrainment transport and deposition while the source dune sand was fully suspendable based on size alone experimental tsunamis produced deposits dominated by bed load sand transport in the upstream 1 3 of the flume and suspension dominated transport downstream the suspension deposits exhibited downstream fining and thinning at 95 confidence a published advection settling model predicts time averaged flow depths to approximately a factor of two and time averaged downstream flow velocities to within a factor of 1 5 finally reasonable scaling is found between flume and field cases by comparing flow depths inundation distances froude numbers rouse numbers and grain size trends in suspension dominated tsunami deposits justifying laboratory study of sediment transport and deposition by tsunamis

paleomagnetic results from the upper cretaceous maudlow and livingston formations southwest montana a paleomagnetic investigation of welded tuff units from the late cretaceous livingston and maudlow formations was undertaken to refine the late cretaceous to paleocene apwp for cratonic north america after progressive af and thermal demagnetization the maudlow formation 46 1 n 248 9 e yields a paleomagnetic pole at 70 n 208 e 11 sites a95 9 k 22 tectonic correction improves the directional grouping and the change is statistically significant two normal polarity intervals bounding a single reversed polarity interval are present we interpret the reversed interval to be chron 33r on the basis of 1 stratigraphic correlation of the maudlow formation with the campanian sedan formation located 40 km to the east and 2 k ar dates of 83 2 ma at the middle of the sampled section and 74 9 1 ma near the top of the sampled section the livingston formation 45 5 n 250 1 e yields a high hc magnetization with a negative fold test suggesting a post folding secondary magnetization the livingston mean direction yields a paleomagnetic pole at 72 n 218 e 10 sites a95 4 k 107 and is clearly distinguishable from a co existing lower hc component reflecting a recent viscous overprint we interpret the high hc magnetization as late cretaceous to paleocene in age neither the maudlow formation pole nor the pole derived from the high hc overprint in the livingston formation agree with previously published poles for either the late cretaceous or tertiary but they do lie on a simple continuation of the apwp between late cretaceous and paleocene mean poles secondary magnetizations found in the franciscan complex of california also yield poles which lie on a proposed extension of the apwp if the franciscan secondary poles represent an overprint event associated with early tertiary accretion and if the livingston secondary pole represents a deformational event related to laramide uplift of the nearby beartooth range then together these three poles suggest that the north american apwp may continue farther to the east and south to define a cretaceous tertiary cusp

tsunami inundation and sediment transport in a sediment limited embayment on american samoa abstract field observations and numerical simulations are used to explore tsunami inundation and sediment transport in an embayment fagafue bay on the north side of tutuila american samoa during the 29 september 2009 south pacific tsunami field observations of the nearshore bathymetry and topography tsunami flow depth and sediment deposition and extent of movable sandy sediment remaining on the beach were collected during two field surveys approximately two and five weeks after the tsunami onshore measurements of flow depth at forty eight locations indicate the wave inundated almost 250 m onshore with a depth exceeding 7 m locally the tsunami deposited patchy areas of sediment up to 0 2 m thick interspersed with a thin dusting

modelling the sedimentary signature of long waves on coasts implications for tsunami reconstruction abstract we describe a process based mathematical model of suspended and bedload sediment transport under long non breaking waves on a plane beach and we use this model to investigate the relationship between the hydrodynamics of run up and run down and the resulting erosive and depositional signature which the wave leaves in particular we compare the results of our forward model with several recently proposed methods for reconstructing tsunami hydrodynamics from their deposits we find that sediment transport both as bedload and in suspension is strongly controlled by asymmetries in the direction of maximum velocity in the latter case it is also affected by settling lag especially around the point of maximum run up the combination of these effects appears to preclude simple methods of reconstructing tsunami hydrodynamics from the large scale features of their signatures however our results suggest some promising avenues for further investigation

cretaceous sedimentation and tectonics tyaughton methow basin southwestern british columbia the mesozoic tyaughton methow basin straddles the fraser yalakom pasayten straight creek fypsc strike slip fault zone between six tectono stratigraphic terranes in southwestern british columbia data from hauterivian cenomanian basin fill provide constraints for reconstruction of fault displacement and paleogeography the early cretaceous eastern margin of the basin was a region of uplifted jurassic plutons and active intermediate volcanism detritus shed southwestward from that margin was deposited as the marine jackass mountain group albian inner to mid fan facies of the jackass mountain group can be correlated across the yalakom fault suggesting 150 25 km of post albian dextral offset deposits of the jackass mountain group overlap the major strike slip zone fypsc if that zone represents the eastern boundary of the tectono stratigraphic terrane wrangellia then accretion of wrangellia to terranes to the east occurred before late early cretaceous time the western margin of the basin first b

effects of tsunami magnitude and terrestrial topography on sedimentary processes and distribution of tsunami deposits in flume experiments abstract to identify and interpret tsunami deposits correctly a better understanding of the effects of both tsunami magnitude and topographic setting are required in the present study laboratory experiments were performed to model these effects on sedimentary processes and the distribution of tsunami deposits on coastal lowlands the experiments directed tsunamis of eight different magnitudes on to three different models of terrestrial topography one with flat topography one with a shallow water filled pool and one with a deep water filled pool the results suggested a relationship between the distribution of tsunami deposits and the hydraulic condition of the tsunami flow onto the terrestrial topography in particular the tsunami deposits in the pools were spatially more variable than those on land because of the variation in flow intensity associated with transformation of the flow from supercritical to subcritical with a hydraulic jump we observed a gap between the landward extent of deposits and the tsunami inundation distance particularly in the experiments with a pool the total amount of sediment in tsunami deposits on the terrestrial area was found to depend on the magnitude of the tsunami but the thickness of the deposits at any one given spot did not always depend on the tsunami magnitude even in the same topographic these results show that terrestrial topography has significant effects on the spatial distribution of tsunami deposits that must be taken into consideration when interpreting the history and magnitude of paleotsunami events from tsunami deposits

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

on the mechanism of tectonic transport in zones of oblique subduction abstract many cases of oblique subduction are known throughout the world today and many more must have existed in the past in at least one modern case sumatra the over riding plate has responded to oblique subduction by forming a strike slip fault that traverses the magmatic arc and displaces its leading edge in the direction of the transverse component of oblique convergence conditions favoring this sort of tectonic response are shown to be 1 1 a high angle of oblique convergence 2 2 a low angle of subduction and 3 3 relative thermal softening of the magmatic arc this mechanism may have been responsible in part for northward transport of western cordilleran magmatic arc and subduction zone rocks in the late cretaceous and earliest tertiary it also may help to explain evidence of southward transport and left lateral shear in northern mexico and the caribbean region in pre jurassic time

paleomagnetism and tectonics of the cretaceous mt stuart batholith of washington translation or tilt abstract the mt stuart batholith is a composite pluton of late cretaceous age that intrudes the crystalline north cascades terrane of northwestern washington its paleomagnetic direction d 10 0 i 45 5 95 4 9 is markedly different from the direction expected for cretaceous rocks from northwestern washington d 330 5 i 73 0 which means that the mt stuart batholith either has moved relative to the north american interior or has been tilted through a substantial angle or both since it acquired its magnetism either tilt or translation are possible geometrically but translation is more likely because 1 local geology apparently does not support tilt in the required direction 2 it probably is not possible for a panel of rock the size of the mt stuart batholith to tilt through the necessary angle ca 35 after its deeper parts have cooled sufficiently to retain remanent magnetization 3 the sense of paleomagnetic discordance found in the mt stuart batholith clockwise rotation of declination flattened inclination is identical to that found in nearly every other allochthonous terrane in the western north american cordillera including every other cretaceous batholith studied except the sierra nevada