influence of man made cuts on the stability of pyroclastic covers campania southern italy a numerical modelling approach intense rainfall in may 1998 and december 1999 caused disastrous landslides in the sarno quindici and cervinara areas campania southern italy the landslides began with slips of the local pyroclastic covers mantling the carbonate relief and then evolved into debris flows avalanches the study discussed in this paper used a numerical modelling approach to assess the influence of man made cuts on the stability conditions of pyroclastic covers the model that was developed took into account initial failure conditions in order to better simulate the impact of man made cuts along the slopes with or without water seepage into the permeable pumiceous layers of the pyroclastic multilayer numerical analysis of stress strain field clearly showed that tracks or geomorphological discontinuities had a negative impact on the multilayer stability conditions consequently preservation of this vulnerable environment requires correct forest management practices

rupture area and displacement of past cascadia great earthquakes from coastal coseismic subsidence coastal marshes record a 6500 yr history of coseismic displacements in great earthquakes at the cascadia subduction zone we compiled estimates of coseismic displacement for past megathrust events based on correlations with megathrust triggered turbidites and estimated megathrust slip based on comparisons of marsh displacements with dislocation model predictions age correlated marsh data are compatible with event rupture extents defi ned by the published turbidite record and a 6500 yr mean recurrence interval that increases northward from 230 to 480 yr within the constraints of the marsh data the width of the coseismic rupture zone generally agrees with the downdip width of the interseismic locked zone inferred from geodetic and thermal data in southernmost cascadia where the model does not include the complex deformation near the mendocino triple junction the coastal data may be better fi t by a model with an 25 narrower rupture than that inferred from regional geophysical data at each coastal marsh site coseismic displacements are roughly similar from event to event independent of the time since the previous event slip in the a d 1700 earthquake was consistent with the preceding interval of strain accumulation 200 yr only at the northern and southern ends of the margin but it was apparently much higher in southern washington and northern oregon possibly indicating postseismic contamination and or catch up coseismic slip to make up for a defi cit in the preceding event overall agreement between the dislocation models and the marsh data for most of the margin implies that such models can be usefully applied to rupture and ground shaking predictions

age and significance of earthquake induced liquefaction near vancouver british columbia canada in late 1994 sand dykes large sand blows and deformed strata were exposed in the walls of an excavation at annacis island on the fraser river delta near vancouver british columbia the features record liquefaction during a large earthquake about 1700 years ago this was perhaps the largest earthquake to affect the vancouver area in the last 3500 years similar less well dated features have been reported from several other sites on the fraser delta and may be products of the same earthquake three radiocarbon ages that closely delimit the time of liquefaction on annacis island are similar to the most precise radiocarbon ages on coseismically subsided marsh soils at estuaries in southern washington and oregon both the liquefaction and the subsidence may have been produced by a single great plate boundary earthquake at the cascadia subduction zone alternatively liquefaction at annacis island may have been caused by a large crustal or subcrustal earthquake of about the same age as a plate boundary earthquake farther west the data from annacis island and other sites on the fraser delta suggest that earthquakes capable of producing extensive liquefaction in this area are rare events further liquefaction analysis using historical seismicity suggests that current assessment procedures may overestimate liquefaction risk

a high resolution record of the last deglaciation in the southern tyrrhenian sea environmental and climatic evolution a multidisciplinary study was carried out on core c106 collected in the salerno gulf southern tyrrhenian sea two tephra layers recovered in the core n 18 o record of globigerinoides ruber and globigerina bulloides and seven 14 c calibrated ages provided the stratigraphic framework the core sediments cover the last 28 kyr bp seismostratigraphic analysis of a high resolution acoustic profile integrated by the dated core samples allowed us to reconstruct the architecture and age of sedimentary bodies on the continental shelf an integrated study based on different taxonomic groups nannofossils pteropods foraminifera and palynomorphs provided palaeoclimatic trends in agreement with changes in the isotopic composition of oxygen the upper part of the last glacial period the deglaciation phase and the holocene were identified correlation between marine and continental records of palaeoenvironmental changes confirms a similar reconstruction of the last deglaciation as in the central and southern mediterranean sea the late pleistocene holocene boundary was recognised at about 11 7 kyr bp between about 9 5 and 6 kyr bpand at 3 3 kyr bpsome warmer episodes were recorded the measured lower isotopic values together with some features of the fossil assemblages recorded from 9 5 to 6 kyr bp may be related to the oceanographic setting that led to the deposition of sapropel s1 in the mediterranean basin 2002 elsevier science b v all rights reserved

characterisation and engineering properties of tectonically undisturbed but lithologically varied sedimentary rock masses tectonically undisturbed sedimentary rocks deposited in a quiescent shallow marine environment often include a sequence of strata that may present significant lithological variety at the scale of an engineering structure such rock masses exhibit engineering properties that are significantly different from tectonically disturbed rock masses of similar composition for example molasse consists of a series of tectonically undisturbed sediments of sandstones conglomerates siltstones and marls produced by the erosion of mountain ranges after the final phase of an orogeny they behave quite differently from flysch which has the same composition but which was tectonically disturbed during the orogeny the molasses behave as continuous rock masses when they are confined at depth and the bedding planes do not appear as clearly defined discontinuity surfaces close to the surface the layering of the formations is discernible and only then similarities may exist with the structure of some types of flysch therefore extreme care is necessary in the use of geotechnical classification systems for the selection of design parameters in order to avoid penalizing the rock mass unnecessarily a discussion on the use of the geological strength index gsi for the characterisation of such rock masses is presented two gsi charts are proposed for estimating the mechanical properties of these masses one mainly for tunnels and the second for surface excavations an example is given to illustrate the process of tunnel design in molassic rocks

landslide susceptibility hazard map in southwest sweden using artificial neural network landslides as major geo hazards in sweden adversely impact on nearby environments and socio economics in this paper a landslide susceptibility map using a proposed subdivision approach for a larg

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

plate boundary earthquakes and tsunamis of the past 5500 yr sixes river estuary southern oregon eleven plate boundary earthquakes over the past 5500 yr have left a stratigraphic signature in coastal wetland sediments at the lower sixes river valley in south coastal oregon within a 1 8 km2 abandoned meander valley 10 buried wetland soils record gradual and abrupt relative sea level changes back in time to 6000 yr ago an additional youngest buried soil at the mouth of the sixes river subsided during the a d 1700 cascadia earthquake multiple lines of evidence indicate that tectonic subsidence caused soil burial including permanent relative sea level rise following burial lateral continuity of buried soil horizons over hundreds of meters diatom assemblages showing that sea level rose abruptly at least 0 5 m and sand deposits on top of buried soils demonstrating coincidence of coseismic subsidence and tsunami inundation for at least two of the buried soils liquefaction of sediment accompanied subsidence the 11 soil burial events took place between 300 and 5400 yr ago yielding an average recurrence interval of plateboundary earthquakes of 510 yr comparing paleoseismic sites in southern washington and south coastal oregon with the sixes river site for the past 3500 yr indicates that the number and timing of recorded plate boundary earthquakes are not the same at all sites in particular a sixes earthquake at 2000 yr ago lacks a likely correlative in southern washington therefore unlike the a d 1700 cascadia earthquake some cascadia plate boundary earthquakes do not rupture the entire subduction zone from southern oregon to southern washington in the lower sixes river valley the upperplate cape blanco anticline deforms sediment of late pleistocene and holocene age directly above the subduction zone differential tectonic subsidence occurred during two of the plate boundary earthquakes when a blind upper plate reverse fault for which the cape blanco anticline is the surface fold slipped coseismically with rupture of the plate boundary during these two earthquakes sites 2 km from the anticline axis subsided 0 5 m more than sites 1 km from the axis

paleoseismicity of the southern end of the cascadia subduction zone northwestern california the southern end of the cascadia subduction zone csz in northwestern california poses a high seismic hazard this study uses the quaternary stratigraphy of the bays and estuaries to reconstruct coseismic subsidence caused by strong to great earthquakes we used lithology macrofossils and microfossils to estimate the amount of relative sea level change at contacts caused by coseismic subsidence our paleoseismic record contains evidence of four to six earthquakes over the past 2000 years using the pattern and magnitude of submergence and other paleoseismic information trenches and other sites we determine whether the earthquakes were local or regional we found that the record contained evidence for both smaller strong to major earthquakes on local structures m w 6 5 7 2 and larger regional subduction zone related great earthquakes m w 8 2 we compared our record to other records from oregon and washington and found three earthquakes likely caused by the rupture of the entire csz around approximately 230 270 the a d 1700 event 1150 1400 and 1750 1900 cal b p in addition two other local earthquakes likely occurred around 500 600 1000 1250 and possibly 1500 1650 cal b p online material table of radiocarbon ages obtained in the study

the late quaternary calcareous nannoplankton assemblages from three cores from the tasman sea abstract the composition of the late quaternary calcareous nannoplankton in three deep sea cores rc12 113 z 2108 and gc 3 located along a n s transect at three different latitudes 25 33 44 s in the tasman sea has been investigated the shift in floral dominance from small gephyrocapsa to small placoliths labelled here small placolith and then to emiliania huxleyi is recognized at stage 5 and stage 4 respectively in cores rc12 113 and z 2108 however the occurrence of small gephyrocapsa and small placolith displays a seesaw relationship in core gc 3 which is located today just north of the subtropical convergence east of tasmania gephyrocapsa muellerae and coccolithus pelagicus increase their abundance geographically southwards and stratigraphically during glacial periods whereas the percentage abundances of florisphaera profunda and umbilicosphaera sibogae demonstrate reverse patterns the relationships between the percentage abundance of each nannoplankton species and the 18 o record for three cores are discussed in detail a transfer function for estimating past sea surface temperatures tn is attempted here it is based on core top data from the tasman sea and provides a good relationship between some calcareous nannoplankton assemblages and modern mean summer sea surface temperatures the tn value shows a good correspondence with the 18 o record in all three cores core gc 3 is much affected by caco 3 dissolution in comparison with cores rc12 113 and z 2108 the calcareous nannoplankton dissolution patterns recognized in the three cores do not show a systematic correspondence with the 18 o record of interest however is the good preservation peaks that are recognized in all three cores at the transitions from glacial to interglacial events

differences in coastal subsidence in southern oregon usa during at least six prehistoric megathrust earthquakes abstract stratigraphic sedimentologic including ct 3d x ray tomography scans foraminiferal and radiocarbon analyses show that at least six of seven abrupt peat to mud contacts in cores from a tidal marsh at talbot creek south slough coos bay record sudden subsidence relative sea level rise during great megathrust earthquakes at the cascadia subduction zone data for one contact are insufficient to infer whether or not it records a great earthquake it may also have formed through local non seismic hydrographic processes to estimate the amount of subsidence marked by each contact we expanded a previous regional modern foraminiferal dataset to 174 samples from six oregon estuaries using a transfer function derived from the new dataset estimates of coseismic subsidence across the six earthquake contacts vary from 0 31 m to 0 75 m comparison of subsidence estimates for three contacts in adjacent cores shows within site differences of 0 10 m about half the 0 22 m error although some estimates may be minimums due to uncertain ecological preferences for balticammina pseudomacrescens in brackish environments and almost monospecific assemblages of miliammina fusca on tidal flats we also account for the influence of taphonomic processes such as infiltration of mud with mixed foraminiferal assemblages into peat on subsidence estimates comparisons of our subsidence estimates with values for correlative contacts at other oregon sites suggest that some of our estimates are minimums and that cascadia s megathrust earthquake ruptures have been heterogeneous over the past 3500 years

an integrated micropalaeontological approach applied to late pleistocene holocene palaeoclimatic and palaeoenvironmental changes gaeta bay tyrrhenian sea

were they all giants perspectives on late holocene plate boundary earthquakes at the northern end of the cascadia subduction zone abstract the relative magnitude of plate boundary earthquakes at the northern end of the cascadia subduction zone was assessed from the temporal concordance between the ages of coseismically buried late holocene soils in southwest washington their counterparts in central and southern cascadia offshore turbidites and paleoseismic deposits on the west coast of vancouver island only three of the seven buried soils in southwest washington that can be reliably traced as buried soils or paleotsunami deposits in the coastal lowlands of south central and southern cascadia have well dated counterparts in northern cascadia the three wide ranging events date from cascadia earthquakes y 250 cal bp u 1260 cal bp and n 2520 cal bp all three likely ruptured the entire plate margin and therefore potentially qualify as giants m w 9 deposits that may derive from tsunamis generated by earthquakes s 1570 cal bp l 2870 cal bp and j 3360 cal bp can also be found in northern cascadia but the ages of these deposits are not yet well enough constrained to determine whether they are coeval with their southern counterparts earthquake w 850 cal bp appears to be present in the northern cascadia paleoseismic record but yields considerably older ages than in central cascadia and may be missing from southernmost cascadia the onshore record of an offshore turbidite t2 displays a similar spatio temporal pattern to that of earthquake w

late glacial holocene paleoclimatic and paleoceanographic evolution of the aegean sea micropaleontological and stable isotopic evidence abstract late glacial to holocene paleoclimatic and paleoceanographic changes are examined using records of calcareous and organic walled marine microfossils pollen and terrestrial spores and oxygen isotope data in cores from the aegean sea basins planktic foraminiferal coccolith and dinoflagellate data show that the late glacial holocene transition in the region was associated with a large warming of surface water mediterranean based paleotransfer functions for planktic foraminifera show a 5 10 c increase in surface water temperature from 14 000 to 9600 yr b p estimates of surface water oxygen isotopic composition 18 o w derived from planktic foraminiferal oxygen isotopic and transfer function data indicate that this warming was associated with a 2 0 to 2 5 reduction in 18 o w transfer function results indicate corresponding 1 0 to 1 5 salinity reductions for this tim ca 6400 9600 yr b p throughout the aegean sea pollen dinoflagellate and isotopic data show that the early holocene excess fresh water originated from rapid melting of the northern european and siberian ice sheets supplied primarily from the black sea by the opening of bosphorus and dardanelles channels during the post glacial sea level rise and supplemented by major rivers entering the aegean sea continuous outflow of fresh water into the aegean sea provided a low salinity surface lid preventing the ventilation of the deep water benthic foraminifera shows a major turn over that indicates low dissolved oxygen however bottom waters were not anoxic sapropel level s1 resulted from a combination of stagnant deep water in isolated depressions increased terrigenous organic matter and periods of high primary productivity as indicated by pollen and dinocysts respectively the surface water temperature and salinity reached present day values at 6400 yr b p with little subsequent change despite the major deforestation onshore

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

coseismic subsidence in the 1700 great cascadia earthquake coastal estimates versus elastic dislocation models seismic hazard assessments for a cascadia subduction zone earthquake are largely based on the rupture area predictions of dislocation models constrained by geodetic and geothermal data this paper tests the consistency of the models for the 1700 great cascadia earthquake with compiled coastal coseismic subsidence as estimated from paleoelevation studies coastal estimates have large uncertainties but show a consistent pattern greatest coseismic subsidence 1 2 m occurred in northern oregon southern washington subsidence elsewhere was 0 1 m elastic dislocation models constrained by interseismic geodetic and thermal data are used to predict the coseismic subsidence for two likely strain accumulation periods of i 800 and ii 550 yr of plate convergence and for uniform megathrust slip of 10 20 30 and 50 m the former two models provide a better and equally good fit predicted subsidence is in broad agreement with marsh estimates discrepancies exist however at the ends of the subduction zone in the south misfit may be due to breakup of the gorda plate the discrepancy in the north may be explained if the 1700 event released only part of the accumulated strain there consistent with long term net uplift in excess of eustatic sea level rise the coseismic slip magnitude estimated by comparing uniform slip model predictions with marsh coseismic subsidence estimates is consistent with the m 9 earthquake indicated by japanese tsunami records the coseismic slip was greatest in northern oregon southern washington declining to the north and south

great cascadia earthquakes and tsunamis of the past 6700 years coquille river estuary southern coastal oregon cascadia subduction zone earthquakes dropped tidal marshes and low lying forests to tidal flat elevations 12 times in the last 6700 cal yr b p at the coquille river estuary in southwestern oregon the youngest buried soil preserved in tidal marsh deposits near the estuary mouth records the a d 1700 earthquake that ruptured the entire cascadia margin eleven other buried marsh and upland soils found in tributary valleys of the estuary provide repeated evidence for rapid lasting relative sea level rise interpreted as coseismic subsidence additional stratigraphic criteria supporting a coseismic origin for soil burial include lateral soil correlation over hundreds of meters fossil diatom assemblages that indicate a maximum of 1 2 3 0 m of submergence and sand deposits overlying buried soils consistent with earthquakeinduced tsunamis that traveled 10 km up the estuary twelve earthquakes occurred in the last 6500 6720 cal yr b p recurring on average every 570 590 yr intervals between earthquakes varied from a few hundred years to over 1000 comparisons of the coquille record to earthquake histories from adjacent sites in oregon southwestern washington and northwestern california suggest that at least two earthquakes in the last 4000 yr did not rupture the entire length of the subduction zone an earthquake 760 1140 cal yr b p in southwestern washington may have ruptured as far south as coos bay but probably stopped before it reached the coquille estuary because no buried soil records the event and tidal marsh conditions were set to record an earthquake an earthquake limited to a southern segment of the cascadia margin 1940 2130 cal yr b p probably did not rupture north of the coquille estuary an analysis of relative sea level histories from either side of the coquille fault failed to find conclusive evidence for late holocene vertical deformation however we cannot preclude recent upper plate faulting if the fault is active as geomorphic features suggest then constraints on the highest possible elevation of mean tide level allow a maximum vertical slip rate of 0 2 0 4 mm yr in the past 6200 6310 cal yr b p

distribution of recent nannofossils beneath the benguela system southwest african continental margin abstract one hundred and forty eight surface samples recovered from the southwest african continental margin 35 17 s have been examined for their nannofossil content coccolith abundance is high in sediments from the deep water areas but declines toward the coast under the main areas of upwelling five distinct bathymetric oceanographic assemblages can be characterized by their nannofossil content coastal upwelling orange bank intermediate southern deep water and northern deep water angola current these distinctions are based on the distribution of eight ecologically significant taxa in order of decreasing abundance they are gephyrocapsa oceanica helicopontosphaera kamptneri cyclococcolithina leptopora coccolithus pelagicus syracosphaera div sp thoracosphaera div sp rhabdosphaera div sp and umbilicosphaera sibogae sea surface temperature and salinity variations which correlate with the extent and intensity of the main upwelling cells are thought to be the most important controls on coccolith distribution although nutrient availability and reduction of surface water transparency may be of local importance the exclusion of three stratigraphical index species for the quaternary emiliania huxleyi gephyrocapsa caribbeanica and g ericsonii from the quantitative analysis will permit the future application of these results to paleoceanographic reconstructions of the benguela system in pleistocene core sections

coastal evidence for holocene subduction zone earthquakes and tsunamis in central chile abstract the 500 year historical record of seismicity along the central chile coast 30 34 s is characterized by a series of m 8 0 8 5 earthquakes followed by low tsunamis 10 m but the frequency of such large events is unknown we extend the seismic history of central chile through a study of a lowland stratigraphic sequence along the metropolitan coast north of valparaiso 33 s at this site higher relative sea level during the mid holocene created a tidal marsh and the accommodation space necessary for sediment that preserves earthquake and tsunami evidence within this 2600 yr long sequence we traced six laterally continuous sand beds probably deposited by high tsunamis plant remains that underlie the sand beds were radiocarbon dated to 6200 5600 5000 4400 3800 and 3700 cal yr bp sediment properties and diatom assemblages of the sand beds for example anomalous marine planktonic diatoms and upward fining of silt sized diatom valves point to a marine sediment source and high energy deposition grain size analysis shows a strong similarity between inferred tsunami deposits and modern coastal sediment upward fining sequences characteristic of suspension deposition are present in five of the six sand beds despite the lack of significant lithologic changes between the sedimentary units under and overlying tsunami deposits we infer that the increase in freshwater siliceous microfossils in overlying units records coseismic uplift concurrent with the deposition of five of the sand beds during our mid holocene window of evidence preservation the mean recurrence interval of earthquakes and tsunamis is 500 years our findings imply that the frequency of historical earthquakes in central chile is not representative of the greatest earthquakes and tsunamis that the central chilean subduction zone has produced

the application of intertidal foraminifera to reconstruct coastal subsidence during the giant cascadia earthquake of ad 1700 in oregon usa abstract changes in species assemblages of intertidal foraminifera can be used to estimate the amount of earthquake related subsidence during plate boundary earthquakes at the cascadia subduction zone the accuracy and precision of foraminiferal methods in paleoenvironmental reconstruction is underpinned by the relations between contemporary taxa and their environment which are used to calibrate fossil foraminiferal assemblages in sediment sequences a contemporary training set of surface sediment samples from five intertidal marshes along the oregon coast was used to determine foraminiferal distributions and prevailing environmental control s along elevational transects dominant taxa include balticammina pseudomacrescens trochamminita irregularis haplophragmoides wilberti trochammina inflata jadammina macrescens and miliammina fusca unconstrained cluster analysis and detrended correspondence analysis was used to identify two elevation dependent faunal zones faunal zone i upland high marsh middle marsh dominated by balticammina pseudomacrescens haplophragmoides wilberti and trochammina inflata and faunal zone ii low marsh and tidal flat dominated by miliammina fusca site specific differences in assemblages at three marshes enabled further subdivision of faunal zone i zone ia is based on one or more of balticammina pseudomacrescens trochammina inflata trochamminita irregularis and haplophragmoides sp and zone ib on jadammina macrescens haplophragmoides sp trochammina inflata and miliammina fusca canonical correspondence analysis cca and partial cca of the training set from the nehalem river marsh transect was used to infer that the zonation of foraminifera is elevation dependent 39 of explained variance a transfer function was developed to reconstruct sudden changes in relative sea level during plate boundary earthquakes in oregon the results indicate a robust performance of the transfer function r jack 2 0 82 with the error estimate rmsep jack 0 20 m comparable to local and regional transfer functions from other temperate marshes to illustrate the potential of the technique the transfer function was applied to reconstruct subsidence during the ad 1700 earthquake using at alsea bay oregon the reconstruction 0 18 0 20 m is less than half the subsidence estimate of nelson et al 2008 great earthquake palogeoesy and tsunamis of the past 2000 years at alsea bay central oregon coast usa quaternary science reviews 27 747 768 using their foraminiferal transfer function perhaps because of differences in taxonomy and the species relationship to elevation

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

ground water behaviour in karst example of the ombla spring croatia abstract the hydro electric power plant hepp which will exclusively use water from a karst underground storage basin will be built in the vicinity of the abundant karst spring ombla in croatia this paper presents the results obtained by hydrogeologic hydrologic and hydraulic investigations related to the principles of ground water circulation in the karst the analyses included the determination of the effective porosity ne of the karst aquifer and the definition of the volume of large conduits and small fractures in the karst which form the aquifer volume the position and dimensions of large karst conduits have also been defined it was established that in three small springs zaton zavrelje and slavljan water overflows from the ombla spring in periods of high ground water levels it was also discovered that at certain periods the dupuit expression for steady state flow in an unconfined aquifer can be used in accordance with this it was possible to determine the values of hydraulic conductivity k in m s 1 for the ombla aquifer they range from 2 10 3 to 5 10 3 m s 1 and are inversely proportional to the ombla spring discharge continuous measurements of the ground water level by several piezometers located in the karst hinterland of the ombla spring and simultaneous measurement of the discharge made it possible to define discharge curves of the ombla spring dependent upon the ground water levels at various locations characteristic features of the discharge curves made the identification of the position and dimensions of the main karst conduits possible

slope instability mechanisms in dipping interbedded conglomerates and weathered marls the 1999 rufi landslide switzerland in may of 1999 melting snow cover combined with heavy rainfalls in the northeastern part of switzerland resulted in the occurrence of numerous shallow landslides many of these slides were located in the subalpine molasse a series of interbedded marls conglomerates and sandstones the subalpine molasse is highly prone to such sliding activity given the dip of bedding the surface topography and the weak nature of the marls that rapidly degrade when exposed to weathering historically the subalpine molasse has been the source of numerous slides of varying orders of magnitude and the surficial morphology is primarily dictated by previous rockslides which periodically reactivate as secondary soil slips given the conditions contributing to the slope failure and the history of previous sliding similar slides within the region are highly probable this paper presents the findings from a detailed investigation of one such slide the 1999 rufi slide results from a detailed engineering geological investigation show that the initial rockslide failure plane predominantly developed and passed through the marl beds as dictated by the penetration of the weathering front into the marls and not along reactivated shears or the bedding plane contact between the marls and overlying conglomerates numerical modelling results based on a coupled hydromechanical distinct element analysis were able to reproduce this mechanism by incorporating a progressive strength degradation procedure correlated to mapped weathering grades

tidal wetland record of holocene sea level movements and climate history abstract paleontological geochemical and lithological indicators of former marine and nonmarine influence are correlated between 13 cores from a tidal wetland wolfe glade on the southeast coast of delaware bay twenty new radiocarbon dates are used to establish the chronostratigraphy of marsh facies sediment iron content weight loss on ignition and remains of plants diatoms and foraminifera known to tolerate specific tidal inundation cycles are used to describe cored facies originating from supratidal intertidal and subtidal salt marsh subenvironments pollen assemblages are used to infer local holocene climate fluctuations and to reconstruct paleoenvironments during marsh evolution the record of paleoclimatology suggests the atlantic chron was warm with variable humidity in the region whereas the subboreal was dominated by cool and humid conditions the subatlantic was warmer and initially dryer with a cool humid phase prior to about 1 ka returning to warmer humid conditions in the last several centuries local relative sea level movements are characterized by five rapid short term episodes when the rate of sea level rise accelerated relative to the rate of marsh aggradation these episodes are recorded by transgressive facies contacts at 5 3 0 2 ka 4 4 0 2 ka 3 25 0 2 ka and 1 8 0 2 ka sidereal years an earlier transgressive facies contact dated 6 9 0 2 ka is probably not the product of a true sea level movement sea level movements are recorded throughout the marsh as palustrine or high marsh peats or peaty overlain by lower intertidal or subtidal marine deposits several features suggest that these episodes are local relative transgressions produced by short term accelerations in the rate of sea level rise relative to marsh aggradation the contemporaneity and apparent suddenness of marine inundations the sequence of facies indicating marine drowning the presence of similar events in marshes elsewhere in delaware bay and the marsh wide extent of indicative facies transitions we propose that the rapid and frequent sea level movements observed in wolfe glade are the result of surges and relaxations in the gulf stream and associated spin up and partial collapse of the north atlantic gyre in response to winds generated by changes in the north atlantic atmospheric thermal gradient associated with holocene climate fluctuations

coseismic slip on the southern cascadia megathrust implied by tsunami deposits in an oregon lake and earthquake triggered marine turbidites 1 we test hypothetical tsunami scenarios against a 4 600 year record of sandy deposits in a southern oregon coastal lake that offer minimum inundation limits for prehistoric cascadia tsunamis tsunami simulations constrain coseismic slip estimates for the southern cascadia megathrust and contrast with slip deficits implied by earthquake recurrence intervals from turbidite paleoseismology we model the tsunamigenic seafloor deformation using a three dimensional elastic dislocation model and test three cascadia earthquake rupture scenarios slip partitioned to a splay fault slip distributed symmetrically on the megathrust and slip skewed seaward numerical tsunami simulations use the hydrodynamic finite element model selfe that solves nonlinear shallow water wave equations on unstructured grids our simulations of the 1700 cascadia tsunami require 12 13 m of peak slip on the southern cascadia megathrust offshore southern oregon the simulations account for tidal and shoreline variability and must crest the 6 m high lake outlet to satisfy geological evidence of inundation accumulating this slip deficit requires 360 400 years at the plate convergence rate exceeding the 330 year span of two earthquake cycles preceding 1700 predecessors of the 1700 earthquake likely involved 8 9 m of coseismic slip accrued over 260 years simple slip budgets constrained by tsunami simulations allow an average of 5 2 m of slip per event for 11 additional earthquakes inferred from the southern cascadia turbidite record by comparison slip deficits inferred from time intervals separating earthquake triggered turbidites are poor predictors of coseismic slip because they meet geological constraints for only 4 out of 12 33 cascadia tsunamis

calcareous nannofossils planktonic foraminifera and oxygen isotopes in the late quaternary sapropels of the ionian sea core m 25 4 12 a long piston core 12 20 m recovered in the ionian sea during cruise m25 4 of the r v meteor summer 1993 at a water depth of 2467 m shows an almost complete sequence of sapropels s 1 s 3 to s 10 over the last 330 ka this paper presents the results of an integrated study based on quantitative biostratigraphic analyses performed on both calcareous nannofossils and planktonic foraminifera coupled with the 18o record a decrease in syracosphaera sp 1 and an increase in the abundance of the genus rhabdosphaera and of helicosphaera carteri florisphaera profunda and of the reworked specimens has been found in the calcareous nannofossil assemblage within the sapropels the planktonic foraminiferal assemblage of the sapropels is characterized by a peak in the frequency of globigerinoides ruber var alba and rosea and neogloboquadrina dutertrei the 18o record of globigerinoides ruber and globigerina bulloides allows recognition of isotope stages 1 to 9 and shows a negative fluctuation that corresponds to the sapropel layers these features support the idea of increased productivity coupled to the presence of reduced salinity surface waters that caused the deposition of the sapropels however the need for a good understanding of the ecological requirements of modern assemblages is stressed this is necessary to correctly interpret fossil assemblages this in turn will allow a better understanding of the palaeoceanographic conditions leading to sapropel deposition

the slope movements within the mondores graben drome france the interaction between geology hydrology and typology the mondores graben in the south eastern french alps is an uncommon structural feature which originates in a complex polyphasic tectonic evolution in contrast with its immediate surroundings with hardly any huge landslides the mondores graben is characterised by various types of landslides a huge sagging caused part of the limestone cliff to subside some 50 m within 50 years two recent mud flows that occurred were considered a potential threat to some inhabited places downstream the hydrologic aspects of the boulc mondores landslide resemble the geology infiltration and karst input in the rock sliding zone and exfiltration in the marls resulting in slumps and mud flows the mass movement interactions could be explained by a structural geology analysis with geodetic monitoring using different techniques it is also shown that hydrochemistry as well as geophysical surveys are of importance in unravelling the hydrologic systems and the geological subsurface structures the present paper aims at explaining the geological control of the different slides in view of estimating their potential danger understanding the geological structure and its evolution therefore is a necessary prerequisite

3d characteristic analysis based targeting of concealed kiruna type fe oxide apatite mineralization within the yangzhuang deposit of the zhonggu orefield southern ningwu volcanic basin middle lower yangtze river metallogenic belt china abstract the computer based modeling of geological and geophysical data allows the construction of 3d geological models that can predict the location of differing lithologies intrusive units and orebodies this 3d modeling allows the identification and quantification of the 3d controls on the location and grade and tonnage of mineralization in a given mineral deposit these controls include factors such as the spatial relationship between mineralization and distinct geological units or features and the record of tectonic movements in an area such as the uplifting or subsidence of individual rock masses during faulting or intrusion these controls on mineralization can then be combined with the location of areas of known mineralization in an approach termed characteristic analysis which allows the identification of areas that are prospective for previously unknown mineralization as well as the 3d targeting of areas for future mineral exploration here we present a case study that focuses on the yangzhuang deposit within the zhonggu orefield of the southern ningwu volcanic basin an important mineral deposit within the middle lower yangtze river metallogenic belt china this case study uses the 3d metallogenic prospectivity modeling approach outlined above our research indicates that areas of known mineralization i e already identified orebodies can be used to train 3d datasets to identify areas that are highly prospective for future exploration in this case a highly prospective region to the north northeast of the known mineralization in this area this region is coincident with a distinct magnetic anomaly suggesting that this area is likely to host significant mineralization a hypothesis that will be tested during future exploration this study outlines an approach to 3d prospectivity modeling that can be used in both greenfield and brownfield exploration and provides a new method for the exploration targeting of concealed or deep mineralization representing a significant advance over the more widely used 2d prospectivity modeling techniques

radiocarbon evidence for extensive plate boundary rupture about 300 years ago at the cascadia subduction zone the cascadia subduction zone a region of converging tectonic plates along the pacific coast of north america has a geological history of very large plate boundary earthquakes1 2 but no such earthquakes have struck this region since euro american settlement about 150 years ago geophysical estimates of the moment magnitudes mw of the largest such earthquakes range from 8 ref 3 to 9 1 2 ref 4 radiocarbon dating of earthquake killed vegetation can set upper bounds on earthquake size by constraining the length of plate boundary that ruptured in individual earth quakes such dating has shown that the most recent rupture or series of ruptures extended at least 55 km along the washington coast within a period of a few decades about 300 years ago5 here we report 85 new 14c ages which suggest that this most recent rupture or series extended at least 900 km between southern british columbia and northern california by comparing the 14c ages with written records of the past 150 years we conclude that a single magnitude 9 earthquake or a series of lesser earthquakes ruptured most of the length of the cascadia subduction zone between the late 1600s and early 1800s and probably in the early 1700s

the last 100 000 years in the western mediterranean sea surface water and frontal dynamics as revealed by coccolithophores a quantitative analysis was carried out on coccolith assemblages from two pleistocene cores k1 and k10 from the western mediterranean the distribution of selected coccolithophore species provides new paleoclimatic and paleoceano graphic data a continuous sequence from the top of isotope stage 5 to the holocene was recorded the reversal in dominance between gephyrocapsa muellerae and emiliania huxleyi was dated in both cores at ca 73 ka at about 47 ka e huxleyi shows a regular increase whereas g muellerae progressively decreases in abundance during interglacial periods high concentrations of coccoliths are observed whereas in glacial times coccoliths are more diluted and the percentage of reworked forms increases as a consequence of the higher terrigenous input after taking careful account of the dilution factor we conclude that the production of coccolithophores was higher during warm periods maxima in coccolith concentrations coincide with highstand episodes probably as a result of the intensification of the atlantic flux into the mediterranean across the gibraltar strait this intensification could have produced an increase in nutrient content in the surface mediterranean waters during cold periods the western mediterranean front underwent a reduction in activity probably due to an increase in the saline and or thermal gradients between the superficial waters and intermediate waters in the liguro provencal basin

poisson s ratio values for rocks abstract compared to other basic mechanical properties of rocks poisson s ratio is an elastic constant of which the significance is generally underrated yet in rock mechanics there is a considerable number of diverse areas which require a prior knowledge or estimation of the value of poisson s ratio this paper examines the values and applications of poisson s ratio in rock mechanics following an historical account of the initial controversy whether it was a material constant or not the effects of poisson s ratio in the elastic deformation of materials intact rocks and rock masses are briefly reviewed also the reported values of poisson s ratio for some elements materials and minerals are compiled while typical ranges of values are presented for some rocks and granular soils finally poisson s ratio classifications are recommended for isotropic intact rocks

a tsunami about 1000 years ago in puget sound washington water surged from puget sound sometime between 1000 and 1100 years ago overrunning tidal marshes and mantling them with centimeters of sand one overrun site is 10 kilometers northwest of downtown seattle another is on whidbey island some 30 kilometers farther north neither site has been widely mantled with sand at any other time in the past 2000 years deposition of the sand coincided to the year or less with abrupt probably tectonic subsidence at the seattle site and with landsliding into nearby lake washington these findings show that a tsunami was generated in puget sound and they tend to confirm that a large shallow earthquake occurred in the seattle area about 1000 years ago

analysis of environmental controls on tsunami deposit texture abstract tsunamis transport large amounts of sediment and can leave recognisable signatures in the landscape the form and composition of onshore tsunami deposits are a function of wave dynamics sediment availability and characteristics of the local environment the latter of which also partially controls preservation of the deposit this research reviews these relationships in a global context and assesses the connection between tsunami deposit particle size and four controlling parameters climate temperature and rainfall density of tsunami sediments degree of coastal protection and distance between tsunami source and sediment deposition an international dataset of tsunami deposit locations and texture was compiled from published literature and existing databases values for environmental variables were calculated for each location from global datasets of temperature rainfall coastline shape and tsunami source locations spearman s rank order correlation principal component analysis pca and hierarchical cluster analysis ca were used to analyse relationships between these variables pca results show an inverse relationship between particle size and sediment density climate variables and distance from source ca results support this suggesting a cluster structure controlled primarily by particle size and secondly by climate and sediment density these relationships can be explained by the influence of the environment on antecedent morphology and the composition of sediments available for tsunami transport

crustal earthquake triggering by pre historic great earthquakes on subduction zone thrusts triggering of earthquakes on upper plate faults during and shortly after recent great m 8 0 subduction thrust earthquakes raises concerns about earthquake triggering following cascadia subduction zone earthquakes of particular regard to cascadia was the previously noted but only qualitatively identified clustering of m 6 5 crustal earthquakes in the puget sound region between about 1200 900 cal years b p and the possibility that this was triggered by a great cascadia thrust subduction thrust earthquake and therefore portends future such clusters we confirm quantitatively the extraordinary nature of the puget sound region crustal earthquake clustering between 1200 900 cal years b p at least over the last 16 000 we conclude that this cluster was not triggered by the penultimate and possibly full margin great cascadia subduction thrust earthquake however we also show that the paleoseismic record for cascadia is consistent with conclusions of our companion study of the global modern record outside cascadia that m 8 6 subduction thrust events have a high probability of triggering at least one or more m 6 5 crustal earthquakes

an earthquake history derived from stratigraphic and microfossil evidence of relative sea level change at coos bay southern coastal oregon much of the uncertainty in determining the number and magnitude of past great earthquakes in the cascadia subduction zone of western north america stems from difficulties in using estuarine stratigraphy to infer the size and rate of late holocene relative sea level changes a sequence of interbedded peaty and muddy intertidal sediment beneath a small protected tidal marsh in a narrow inlet of coos bay oregon records ten rapid to instantaneous rises in relative sea level each rise is marked by a contact that records an upward transition from peaty to muddy sediment but only two contacts dating from about 1700 and 2300 yr ago show the site wide extent and abrupt changes in lithology and foraminiferal and diatom assemblages that can be used to infer at least half a meter of sudden coseismic subsidence although the characteristics of a third gradual contact do not differ from those of some contacts produced by nonseismic processes regional correlation with other similar sequences and high precision 14 c dating suggest that the third contact records a great plate boundary earthquake about 300 yr ago a fourth contact formed too slowly to have been caused by coseismic subsidence because lithologic and microfossil data are not sufficient to distinguish a coseismic from a nonseismic origin for the other six peat mud contacts we cannot determine earthquake recurrence intervals at this site similar uncertainties in great earthquake recurrence and magnitude prevail at similar sites elsewhere in the cascadia subduction zone except those with sequences showing changes in fossils indicative of 1 m of sudden subsidence sand sheets deposited by tsunamis or liquefaction features

coccolithus pelagicus a productivity proxy related to moderate fronts off western iberia abstract the traditional interpretation of coccolithus pelagicus as a cold water proxy is examined based on its distribution patterns in the water column off the portuguese coast using data from eleven cruises and in holocene surface sediment samples and quaternary cores from the same region coccolithus pelagicus is common in the portuguese upwelling system an area where surface waters are predominantly of subtropical origin although revealing an affinity for low temperature upwelled waters the species was found in waters up to 18 c associated with riverine plume and shelf break fronts c pelagicus seemed to consistently occupy a particular ecological niche between other phytoplankton groups related to moderate turbulence conditions combined with nutrient availability from this behaviour it is proposed that c pelagicus can be used as a tracer of the periphery of areas of enhanced productivity coccolithus pelagicus preferences for fronts of moderate temperature and salinity gradients are tentatively used to explain particular features of its sedimentary record the repeated increase of c pelagicus in thanatocoenoses surface sediment assemblages close to three river mouths on the portuguese shelf are interpreted as a positive response to the development of riverine plumes on the other hand inconsistencies in the correlation between sea surface cooler glacial and warmer interglacial isotope stages and the relative abundance pattern of c pelagicus during the late quaternary as registered in two galicia bank piston cores 42 n are tentatively explained in terms of shifts in the extent of the outer limit of the local palaeoproductivity belt off the iberian peninsula

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

landslides in iliolitic and marly formations examples from north westem greece abstract landslides in iliolitic and marly formations are investigated at two representative sites in northern greece the first case concerns an iliolitic tectonic formation between pindos and ionian flysch while the second concerns the marls of the molasses of the mesohellenic basin both areas present a high relief with steep slopes and significant rainfall the above formations were studied using both in situ and laboratory techniques according to our study these formations present more or less similar mechanical properties but different behaviour in relation to landslide occurrence they are very hard in dry conditions but lose their resistance rapidly under wet conditions in the first case the rainwater penetrates the iliolite causing landslides of soil type in the second the rainwater does not penetrate the marl creating a surface saturated zone the material drys rapidly creating cracks and flakes which accumulate at the toe of the slope this weathering causes caving at the base of the overlying sandstone which presents toppling and sliding phenomena

great earthquakes and tsunamis of the past 2000 years at the salmon river estuary central oregon coast usa four buried tidal marsh soils at a protected inlet near the mouth of the salmon river yield definitive to equivocal evidence for coseismic subsidence and burial by tsunami deposited sand during great earthquakes at the cascadia subduction zone an extensive landward tapering sheet of sand overlies a peaty tidal marsh soil over much of the lower estuary limited pollen and macrofossil data suggest that the soil suddenly subsided 0 3 1 0 m shortly before burial regional correlation of similar soils at tens of estuaries to the north and south and precise 14c ages from one salmon river site imply that the youngest soil subsided during the great earthquake of 26 january a d 1700 evidence for sudden subsidence of three older soils during great earthquakes is more equivocal because older soil stratigraphy can be explained by local hydrographic changes in the estuary regional 14c correlation of two of the three older soils with soils at sites that better meet criteria for a great earthquake origin is consistent with the older soils recording subsidence and tsunamis during at least two great earthquakes pollen evidence of sudden coseismic subsidence from the older soils is inconclusive probably because the amount of subsidence was small 0 5 m the shallow depths of the older soils yield rates of relative sea level rise substantially less than rates previously calculated for oregon estuaries manuscript received 10 october 2003

great earthquake paleogeodesy and tsunamis of the past 2000 years at alsea bay central oregon coast usa the width of plate boundary fault rupture at the cascadia subduction zone a dimension related to earthquake magnitude remains uncertain because of the lack of quantitative information about land level movements during past great earthquake deformation cycles beneath a marsh at alsea bay on the central oregon coast four sheets of tsunami deposited sand blanket contacts between tidal mud and peat radiocarbon ages for the sheets match ages for similar evidence of regional coseismic subsidence and tsunamis during four of cascadia s great earthquakes barring rapid unrecorded postseismic uplift reconstruction of changes in land level from core samples using diatom and foraminiferal transfer functions includes modest coseismic subsidence 0 470 2 m during the four earthquakes interpretation is complicated however by the 30 38 of potentially unreliable transfer function values from samples with poor analogs in modern diatom and foraminiferal assemblages reconstructions of coseismic subsidence using good analog samples range from 0 4670 12 to 0 0970 20 m showing greater variability than implied by sample specific errors from apparent high rates of land uplift following subsidence and tsunamis we infer that postseismic rebound caused by slip on deep parts of the plate boundary and or viscoelastic stress relaxation in the upper plate may be almost as large as coseismic subsidence modest coseismic subsidence 100 km landward of the deformation front implies that plate boundary ruptures in central oregon were largely offshore ruptures may have been long and narrow during earthquakes near magnitude 9 as suggested for the ad 1700 earthquake or of smaller and more variable dimensions and magnitudes r 2008 elsevier ltd all rights reserved

calcareous nannofossil paleoecology in the sapropel s1 of the eastern ionian sea paleoceanographic implications a high resolution study performed by means of calcareous nannofossils on two box cores located in the south eastern ionian basin allowed recognition of fluctuations in the assemblage which can be related to the climatic and paleoceanographic changes that occurred during the deposition of the holocene sapropel s1 this study reports a decrease of the coccolith abundance and of the genus reticulofenestra in the s1 sapropel interval considered as whole with its mn and fe oxidized intervals florisphaera profunda shows an increase at the base of the dark corg rich interval while helicosphaera carteri and rhabdosphaera claviger show an increase in abundance within the fe enriched interval of the oxidized sapropel braarudosphaera bigelowii is very rare in the interval studied as a whole however it shows a small but significant increase in abundance in the mn enriched interval of the oxidized sapropel sapropel deposition is probably related to important climatic changes that influenced the abundance of the various nannofossil species as a function of their paleoecological preferences our results indicate that three different paleoceanographic phases exist in s1 suggesting eutrophication at the beginning of s1 deposition followed by an intermediate stage characterized by nutrient depletion and finally by stagnation

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

discordant 14c ages from buried tidal marsh soils in the cascadia subduction zone southern oregon coast peaty tidal marsh soils interbedded with estuarine mud in late holocene stratigraphic sequences near coos bay oregon may have been submerged and buried during great m 8 subduction earthquakes smaller localized earthquakes or by nontectonic processes radiocarbon dating might help distinguish among these alternatives by showing that soils at different sites were submerged at different times along this part of the cascadia subduction zone but comparison of conventional 14c ages for different materials from the same buried soils shows that they contain materials that differ in age by many hundreds of years errors in calibrated soil ages represent about the same length of time as recurrence times for submergence events 150 500 yr this similarity precludes using conventional 14c ages to distinguish buried soils along the southern oregon coast accelerator mass spectrometer 14c ages of carefully selected macrofossils from the tops of peaty soils should provide more precise estimates of the times of submergence events

detection of large holocene earthquakes using diatom analysis of coastal sedimentary sequences wellington new zealand abstract paleoenvironmental reconstructions of three coastal waterbodies in wellington new zealand reveal that sites were isolated from the sea within the last 7500 years through coseismic uplift and barrier growth evidence for coseismic uplift consists of distinct transitions in diatom assemblages representing large changes in relative sea level or water table level commonly in association with sedimentological evidence for catchment disturbance or marine influx transitions are abrupt laterally extensive and synchronous within each waterbody amount of change across transition horizons is assessed using quantitative estimates of paleosalinity and waterbody type as proxies for relative sea level change seven transitions involve large paleoenvironmental changes and provide evidence for earthquakes occurring at approximately 5100 3200 recorded at two sites 2300 recorded at two sites 1000 cal years bp and 1855 ad five other transitions involve smaller paleoenvironmental changes and are considered to be consistent with effects of earthquakes but do not provide independent evidence for earthquake occurrence these smaller transitions occur at approximately 6800 3600 2200 1000 coincident with a large transition and 500 cal years bp the data refine ages and provide information about the extent and effects of past large earthquakes in the region these are the first paleoecologically derived earthquake signatures for wellington and they contribute to the sparse collection worldwide of off fault sedimentary earthquake records for predominantly strike slip faults

detection of large prehistoric earthquakes in the pacific northwest by microfossil analysis geologic and palynological evidence for rapid sea level change 3400 and 2000 carbon 14 years ago 3600 and 1900 calendar years ago has been found at sites up to 110 kilometers apart in southwestern british columbia submergence on southern vancouver island and slight emergence on the mainland during the older event are consistent with a great magnitude m 8 earthquake on the cascadia subduction zone the younger event is characterized by submergence throughout the region and may also record a plate boundary earthquake or a very large crustal or intraplate earthquake microfossil analysis can detect small amounts of coseismic uplift and subsidence that leave little or no lithostratigraphic signature

late quaternary tectonic deformation in the cape arago bandon region of coastal oregon as deduced from wave cut platforms the cape arago region of south central oregon sits on the upper plate of the cascadia subduction zone about 80 km east of the base of the continental slope the style of late pleistocene deformation along the cascadia forearc near cape arago is well expressed by the altitudinal variation of a set of five uplifted wave cut platforms these platforms record open folding with a half wavelength of about 6 7 km as well as late quaternary offset on flexural slip reverse faults that parallel bedding in the underlying bedrock the folds have produced both landward and seaward tilts to the uplifted wave cut platforms because the folds cut obliquely across the coastline the magnitude of coastal uplift is variable in the case of the lowest 80 ka wave cut platform this variable uplift has resulted in coastal deformation ranging from subsidence to a maximum uplift of 0 8 m kyr quantitative analysis of the mechanism of flexural slip folding for the south slough syncline near cape arago indicates that the late quaternary strain rate has decreased in the last 200 kyr evidence of past great subduction style earthquakes such as regional uplift and regional landward tilting of wave cut platforms or regional submergence of coastlands is lacking inmore the cape arago region instead the deformational style is controlled by folding though localized folding is dominant the occurrence of great subduction style earthquakes is not precluded because localized folding could occur concurrently with regional coseismic deformation less

identifying coseismic subsidence in tidal wetland stratigraphic sequences at the cascadia subduction zone of western north america tidal wetland stratigraphy reveals that great plate boundary earthquakes have caused hundreds of kilometers of coast to subside at the cascadia subduction zone however determining earthquake recurrence intervals and mapping the coastal extent of past great earthquake ruptures in this region are complicated by the effects of many sedimentologic hydrographic and oceanographic processes that occur on the coasts of tectonically passive as well as active continental margins tidal wetland stratigraphy at many cascadia estuaries differs little from that at similar sites on passive margin coasts where stratigraphic sequences form through nonseismic processes unrelated to coseismic land level changes methods developed through study of similar stratigraphic sequences in europe provide a framework for investigating the cascadia estuarine record five kinds of criteria must be evaluated when inferring regional coastal subsidence due to great plate boundary earthquakes the suddenness and amount of submergence the lateral extent of submerged tidal wetland soils the coincidence of submergence with tsunami deposits and the degree of synchroneity of submergence events at widely spaced sites evaluation of such criteria at the cascadia subduction zone indicates regional coastal subsidence during at least two great earthquakes evidence for a coseismic origin remains equivocal however for the many peat mud contacts in cascadia stratigraphic sequences that lack 1 contrasts in lithology or fossils indicative of more than half a meter of submergence 2 well studied tsunami deposits or 3 precise ages needed for regional correlation paleoecologic studies of fossil assemblages are particularly important in estimating the size of sudden sea level changes recorded by abrupt peat mud contacts and in helping to distinguish erosional and gradually formed contacts from coseismic contacts reconstruction of a history of great earthquakes for the cascadia subduction zone will require rigorous application of the above criteria and many detailed investigations

renewal of tidal forests in washington state after a subduction earthquake in a d 1700 abstract with few exceptions today s tidal trees near washington s pacific coast postdate an earthquake that lowered the region by 1 m or more the earthquake which occurred in a d 1700 is the most recent to have ruptured much of the plate boundary at this central part of the cascadia subduction zone because of the coseismic subsidence lowland forests became tidal flats where thousands of trees died most of the trees killed were sitka spruce picea sitchensis in the centuries since the earthquake tidal deposits have built new land that has been colonized by new sitka spruce all but several tens of the region s tidal spruce consequently postdate 1700 as shown by counts of annual rings in 121 of the largest spruce in tidal forests at copalis river grays harbor and willapa bay forests began to return to each of these estuaries in the early 1700s and spread seaward in the late 1700s and 1800s annual rings in the oldest of the trees thus record a large fraction of the earthquake recurrence interval that began with the 1700 earthquake

abrupt uplift within the past 1700 years at southern puget sound washington shorelines rose as much as 7 meters along southern puget sound and hood canal between 500 and 1700 years ago evidence for this uplift consists of elevated wave cut shore platforms near seattle and emerged peat covered tidal flats as much as 60 kilometers to the southwest the uplift was too rapid for waves to leave intermediate shorelines on even the best preserved platform the tidal flats also emerged abruptly they changed into freshwater swamps and meadows without first becoming tidal marshes where uplift was greatest it adjoined an inferred fault that crosses puget sound at seattle and it probably accompanied reverse slip on that fault 1000 to 1100 years ago the uplift and probable fault slip show that the crust of the north america plate contains potential sources of damaging earthquakes in the puget sound region

biotic signals from nannoflora across the iridium anomaly in the upper eocene of the massignano section evidence from statistical analysis abstract strong evidence for a major late eocene impact including an iridium rich layer and shocked quartz has been found in the massignano section central italy stratotype of the eocene oligocene boundary quantitative calcareous nannofossils analyses have been performed and classical and multivariate statistical techniques have been applied to assess the paleonvironmental effect of this impact on the nannoflora abundance patterns indicate 1 a warming episode just above the iridium layer 2 a subsequent slight cooling trend probably related to the global cooling during late eocene to early oligocene 3 marked fluctuations in the trophic resources and an increase in near shore taxa in the upper part of the interval 4 increase in low nutrient taxa in biotite rich layers just above the iridium level possibly related to lowered productivity linked to volcanic activity all these signals appear most likely to be the result of long term climatic changes rather than to short term effects of extraterrestrial impact in addition cluster analysis was performed on the assemblage data this delineated similarities among different taxa and grouped samples with similar assemblages several groups related to temperature trophic and unknown preference conditions have been distinguished a consistent difference in the abundances of the taxa and in their correlation has been detected between samples above and below the iridium level this change appears to be related to two important sedimentary features which are found in the interval above the iridium occurrence 1 the presence of biotite rich layers linked to increasing volcanism and 2 a conspicuous color transition from reddish to greenish related to changes in sedimentary environments e g variations in trace element abundance these environmental changes rather than the impact may have affected the nannoflora assemblages

great earthquakes of variable magnitude at the cascadia subduction zone comparison of histories of great earthquakes and accompanying tsunamis at eight coastal sites suggests plate boundary ruptures of varying length implying great earthquakes of variable magnitude at the cascadia subduction zone inference of rupture length relies on degree of overlap on radiocarbon age ranges for earthquakes and tsunamis and relative amounts of coseismic subsidence and heights of tsunamis written records of a tsunami in japan provide the most conclusive evidence for rupture of much of the plate boundary during the earthquake of 26 january 1700 cascadia stratigraphic evidence dating from about 1600 cal yr b p similar to that for the 1700 earthquake implies a similarly long rupture with substantial subsidence and a high tsunami correlations are consistent with other long ruptures about 1350 cal yr b p 2500 cal yr b p 3400 cal yr b p 3800 cal yr b p 4400 cal yr b p and 4900 cal yr b p a rupture about 700 1100 cal yr b p was limited to the northern and central parts of the subduction zone and a northern rupture about 2900 cal yr b p may have been similarly limited times of probable short ruptures in southern cascadia include about 1100 cal yr b p 1700 cal yr b p 3200 cal yr b p 4200 cal yr b p 4600 cal yr b p and 4700 cal yr b p rupture patterns suggest that the plate boundary in northern cascadia usually breaks in long ruptures during the greatest earthquakes ruptures in southernmost cascadia vary in length and recurrence intervals more than ruptures in northern cascadia

slope instability mechanisms in dipping conglomerates over weathered marls bol landslide croatia in february 2005 a landslide of significant dimensions occurred at bol on the island of brac in croatia the location of the landslide was in a geological structure of weakly bounded conglomerates lying above a flysch in an area where numerous slides have been previously reported in the paper the results of a geological engineering investigation of the bol landslide are presented the investigation results show that the landslide was triggered by a combination of improperly started earthworks an increase in air temperature in days preceding landslide that caused snow melt and abundant rainfall but the primary cause of the landslide was weathering of the flysch in other words despite the fact that contact between the flysch and the conglomerates slopes is in approximate correspondence with the slope of the hillside the landslide surface was not in contact between the conglomerates and marl but deeper in the flysch provoked by the penetration of the weathering front into the flysch numerical modelling results were able to reproduce this mechanism by incorporating strength degradation into the weathered zone determined by field investigation the results of the research can be used to predict potential slides not only in the area under study

insights into late quaternary calcareous nannoplankton assemblages under the theory of statistical analysis for compositional data abstract the investigation of changes in abundance of calcareous nannofossil associations is fundamental for palaeoclimatic and palaeoceanographic reconstructions in general since the number of recognised species is high the numerical and graphical treatments of the data play an important role to validate hypotheses about the influence of physico chemical factors on the quality of past environments as reflected by changes in abundance moreover the application of multivariate procedures may be useful for improving interpretation of the overall data structure calcareous nannofossil associations analysed in this work are related to core gns84 c106 collected in the gulf of salerno campania southern italy under a national interdisciplinary research programme aimed at recognising the impact of natural events on biological communities during the last 20 kyr biplot analysis of compositional data was applied to indicate the presence of subcompositions or in other words to identify strong relationships among a limited number of species that can be interpreted from a palaeoenvironmental point of view this investigation was followed by the application of simplicial principal component analysis with the aim of determining from a numerical point of view the laws for describing and modelling the behaviour of the species involved in these subcompositions in this work all statistical methods were applied by taking rigorously into account the sample space of compositional data i e data matrices whose rows sum to 100 from a general point of view the results obtained related to the detection of new parameters to be used for monitoring the quality of the past environment have encouraged us to promote the application of statistical methodologies that take into account the correct sample space for compositional data in this context inferential applications and modelling can be developed under a correct theoretical framework

trees and herbs killed by an earthquake 300 yr ago at humboldt bay california evidence of rapid seismic induced subsidence at humboldt bay california is produced by analyses of annual growth rings of relict sitka spruce picea sitchensis bong carr roots and entombed herbaceous plants these results add to previously reported evidence that an earthquake caused subsidence 300 yr ago at mad river slough california both types of remains are rooted in buried soils that stood at or above the high tide level until the area subsided at least 0 5 m into the intertidal zone burial by intertidal muds took place quickly enough to preserve the herbs in the growth position analysis of the annual growth rings of the tree roots shows that all died within four growing seasons but the time of root death varies even among roots of the same tree with no central nervous system tree cells do not die simultaneously throughout the organism the 0 5 to 1 5 m of subsidence as evidenced by stratigraphy and sedimentology was not enough to kill all the trees even in one season although such gradual death could be due to rapid aseismic subsidence the tree deaths and preserved herbs are much better explained by sudden coseismic subsidence

stratigraphic and microfossil evidence for a 4500 year history of cascadia subduction zone earthquakes and tsunamis at yaquina river estuary oregon usa we infer that each buried soil represents a cascadia subduction zone earthquake because the soils are laterally extensive and abruptly overlain by sandy deposits and mud preservation of coseismically buried soils occurred from 4500 yr ago until 500 600 yr ago after which preservation was compromised by cessation of gradual relative sea level rise which in turn precluded drowning of marsh soils during instances of coseismic subsidence based on grain size and microfossil data sandy deposits overlying buried soils accumulated immediately after a subduction zone earthquake during tsunami incursion into sallys bend the possibility that the sandy deposits were sourced directly from landslides triggered upstream in the yaquina river basin by seismic shaking was discounted based on sedimentologic microfossil and depositional site characteristics of the sandy deposits which were inconsistent with a fluvial origin biostratigraphic analyses of sediment above two buried soils in the case of two earthquakes one occurring shortly before 1541 1708 cal yr b p and the other occurring shortly before 3227 3444 cal yr b p provide estimates that coseismic subsidence was a minimum of 0 4 m the average recurrence interval of subduction zone earthquakes is 420 580 yr based on an 3750 4050 yr long record and seven to nine interearthquake intervals

engineering geological assessments of the repeated plane shear slope instability threatening babadag turkey and its environmental impacts babadag in the denizli province of turkey is one of the oldest textile industry settlements the town has suffered from a very slow slope movement for about 60 years one third of the population lives in the unstable area the slope movement resulted in significant ground deformations and damage to buildings roads and buried utilities and negatively affects socioeconomic life in the town this paper contributes to the understanding of the long term plane shear slope movement at the town analyzes the main causes of the movement and describes the slope instability and its effects movement occurs at an annual rate of between 3 8 cm and 15 cm along weak bedding planes in the alternating marl and sandstone beds forming the slope engineering geological assessments based on movement groundwater and rainfall monitoring data laboratory testing and stability analyses indicate the following main factors contributing to the movement a the unfavorable orientations and low shear strength of the bedding planes b variations in the groundwater table related to precipitation and waste water seeping from the damaged sewage system and c undercutting at the toe of the slope by a creek particularly due to fluctuations in the groundwater table or variations in pore pressures the slope movement exhibits increasing and decreasing rates of movement without catastrophic failure

tectonostratigraphy of the chazyan late middle early late ordovician mixed siliciclastic carbonate platform quebec embayment abstract the middle to lower upper ordovician chazyan platform succession of eastern north america extends landward of the ancient quebec embayment along the laurentian margin part of a foreland basin peripheral to an arc collisional plate boundary the platform grades from seaward reefal carbonate chazy group champlain valley into platform and foreland interior tide and wave dominated siliciclastics rockcliffe formation and restricted peritidal muddy carbonate hog s back formation the latter two formations occur in the sedimentary ottawa embayment which overlies the trace of a neoproterozoic rift prominent tectonostratigraphic surfaces bound and subdivide the chazyan platform interior succession and are characterized by abrupt marine transgressions local synsedimentary faults and seismogenic beds the depositional history includes 1 accumulation of shallow marine siliciclastics rockcliffe fm across a differentially faulted paleoplatform 2 abrupt regional retrogradation 100 km of this siliciclastic system replaced by an intraplatform shale basin lower hog s back formation 3 basin fill and development of a low energy muddy carbonate platform interior upper hog s back formation coincident with regional fall in sea level and change in subsidence along the laurentian margin and 4 abrupt high frequency base level changes preceding regional onlap of mohawkian turinian shale contemporary with local synsedimentary deformation and rapid subsidence along the distal arc collisional plate boundary structurally controlled sedimentation patterns in the platform and foreland interior document episodic tectonism coincident with relatively sustained deposition along the outer platform the chazy group this difference is interpreted to be a response to foreland interior flexuring modified by local reactivation of the precambrian rift that was coincident with preferential subsidence at seaward sites more proximal to structural loading along the arc collision plate boundary

coupled atmospheric and marine palaeoclimatic reconstruction for the last 35 ka in the sele plain gulf of salerno area southern italy abstract planktonic foraminifera and pollen data from core gns84 c106 gulf of salerno tyrrhenian sea were analysed through the modern analogue technique constrained cluster analysis and relative variation biplots a long period of mild climate centred around 25 ka bp is evident in both marine and continental reconstructions the cooling phase from 17 to 14 7 ka bp correlated to the h1 heinrich event is indicated by a sea surface temperature sst decrease which roughly coincides with the cold arid phase identified by annual and january temperatures a rapid increase in atmospheric temperatures and precipitation culminating at 13 8 ka bp marks the ba cronozone the corresponding increase in summer and winter ssts of 11 and 6 5 c respectively occurred over 600 years the beginning of the yd centred around 12 5 ka bp is marked by a decrease in summer and winter ssts of respectively 4 5 and 3 5 c in one century the atmospheric evidence of the yd is primarily reflected in low january temperatures reaching 6 c the lowest values ever experienced in the analysed time interval the late glacial holocene transition is clearly recorded in both the continental and marine realms from 11 5 to 9 ka bp atmospheric temperatures record a period of substantial stability followed by a drop at 8 9 ka bp which chronologically fall within the first rcc event 9 8 ka bp of mayewski et al 2004 holocene climate variability quaternary research 62 243 255 in correspondence with a phase of relatively high seasonality indicated by foraminifera

amount of subsidence during a late holocene earthquake evidence from fossil tidal marsh foraminifera at vancouver island west coast of canada abstract fossil foraminifera in intertidal deposits beneath a marsh near tofino on west central vancouver island british columbia provide a basis for estimating the amount of subsidence during a large earthquake less than 400 years ago we compared the fossil foraminiferal assemblages with present day assemblages along a surveyed transect across the marsh and we estimated paleo elevation by means of both subjective and quantitative methods the comparisons suggest that the site subsided at least 0 2 m and perhaps more than 1 m during the earthquake most of the subsidence was tectonic for the deposits rest on a pleistocene substrate unlikely to have compacted much when shaken soon after the earthquake the land began to rebound tectonically most of the 0 2 1 m of recorded subsidence was recovered during deposition of the first 6 cm of sediment above the buried marsh surface probably within a few decades after the earthquake because of the speed at which the land rebounded some recovery may have occurred before the first post earthquake sediments were deposited if so the actual amount of subsidence is larger than the foraminiferal data indicate

episodic tectonic subsidence of late holocene salt marshes northern oregon central cascadia margin salt marsh subsurface deposits 0 4 m depth in netarts bay a small coastal lagoon of northern oregon record six events of marsh burial in the last several thousand years five of the buried marsh surfaces show sharp nonerosional upper contacts with either anomalous sand layers tsunami deposits or tidal flat mud deposits these sequences indicate episodic abrupt subsidence of the marsh surfaces to low intertidal levels in contrast lower marsh contacts with underlying intertidal muds are gradational indicating gradual uplift and development of the marsh three independent measures of deposit elevation relative to mean tidal level percent organics diatom assemblages and percent eolian sand have been used to estimate vertical displacements of marsh surfaces abrupt subsidence displacements of 1 1 5 m alternate with gradual uplift displacements of the order of 0 5 1 0 m the vertical tectonic movements are interpreted to reflect coseismic strain release abrupt subsidence following interseismic strain accumulation gradual uplift associated with interplate coupling between the juan de fuca plate and the north american plate in the cascadia subduction zone recurrence intervals between subsidence events range from possibly less than 300 years to at least 1000 years with the last dated event likely occurring 300 400 radiocarbon years before present rcybp significant 14c age overlaps of at least four subsidence events recorded at netarts and reported for southern washington and other northern oregon bays at 300 500 1000 1300 1400 1800 and 3000 3300 rcybp suggest the potential for event synchroneity over at least 200 km of the central part of the cascadia subduction zone additional work is needed to test the synchroneity of these episodic events of coseismic subsidence

history of the last deglaciation in the alboran sea western mediterranean and adjacent north atlantic as revealed by coccolith floras abstract a series of cores recovered from the alboran sea western mediterranean and the adjacent part of the north atlantic has revealed very high rates of accumulation which have enabled us to identify the stages of the last deglaciation in great detail isotopic analyses of the cores show the two steps of the deglaciation terminations 1a and 1b separated by the bolling allerod warm phase 14 c dating of the cores has allowed the dating og the climatic succession we have identified each event of the deglaciation on the basis of changes in the coccolith flora especially in species of the genus gephyrocapsa such changes reflect surface water changes since coccolith live only in the photic zone the abundance of g muellerae in the cold intervals prior to each termination is greater than that in the bolling allerod and holocene warm intervals which follow the terminations coversely g oceanica is virtually absent during cold intervals but becoms more common during the warmer periods during the first deglacial warming there is a large influx of fine grained detrital material presumably derived from increased run off from the nearby mountains of southern spain and north west africa in the alboran sea cores with the most expanded sections there is a marked increase in the percentage of syracosphaera histrica at the beginning of this increase of detritus no increase was found in the atlantic core at this time

tsunami deposits beneath tidal marshes on vancouver island british columbia thin sheets of sand occur within holocene mud and peat deposits beneath tidal marshes at tofino ucluelet and port alberni on vancouver island british columbia the sand sheets are extensive and have sharp upper and lower contacts in most cases they consist of moderately sorted massive sand and silty sand with abundant wood and other plant detritus at port alberni the thickest sheet has gravel and is graded the upper two sand sheets in the tofino ucluelet area and possibly the third are also present at port alberni eyewitness accounts and 137 cs analysis suggest that the uppermost thinnest sand was deposited by the tsunami triggered by the great alaska earthquake in 1964 the next oldest sand sheet has been radiocarbon dated at our data suggest that large tsunamis have struck the southern british columbia coast several times during the late holocene and that some were much larger than the 1964 tsunami which caused about 10 million damage 1964 canadian dollars to communities on vancouver island because such tsunamis can be expected in the future they pose a hazard to people and property in some coastal areas

seismic or hydrodynamic control of rapid late holocene sea level rises in southern coastal oregon usa intertidal stratigraphy has been instrumental in demonstrating the hazard posed by great earthquakes at the cascadia subduction zone but inferring an earthquake history from interbedded sequences of peat and mud is complicated by many factors that influence sedimentation and relative sea level change on both tectonic and nontectonic coasts rapid to sudden rises in relative sea level marked by sharp contacts between intertidal peat and overlying mud or sand may reflect coseismic coastal subsidence and tsunami deposition or alterna tively nonseismic hydrodynamic changes in estuaries reconnaissance coring at 16 sites in the marshes fringing a narrow protected tidal inlet of coos bay supplemented by diatom and 14c analyses at four sites reveals a stratigraphic record too fragmentary and ambiguous to distinguish seismic from hydrodynamic causes for more than three of the 10 rises in relative sea level identified only three sharp contacts have the wide extent and evidence of substantial 0 5 m submergence that distinguish them from similar contacts produced by nonseis mic processes correlation with stratigraphic sequences at other estuaries shows that the fringing marshes suddenly subsided and were partially buried by tsunami sand during a great plate boundary earthquake about 300 years ago similar contacts were produced by earthquakes about 1500 1800 years ago and perhaps about 2400 2700 years ago other earthquakes with substantially less subsidence may also have occurred but evi dence is too ambiguous to reconstruct a more complete history

statistical empirical index of chemical weathering in igneous rocks a new tool for evaluating the degree of weathering abstract chemical weathering indices are useful tools in characterizing weathering profiles and determining the extent of weathering however the predictive performance of the conventional indices is critically dependent on the composition of the unweathered parent rock to overcome this limitation the present paper introduces an alternative statistical empirical index of chemical weathering that is extracted by the principal component analysis pca of a large dataset derived from unweathered igneous rocks and their weathering profiles the pca analysis yields two principal components pc1 and pc2 which capture 39 23 and 35 17 of total variability respectively the extent of weathering is reflected by variation along pc1 primarily due to the loss of na 2 o and cao during weathering in contrast pc2 is the direction along which the projections of unweathered felsic intermediate and mafic igneous rocks appear to be best discriminated therefore pc1 and pc2 represent independent latent variables that correspond to the extent of weathering and the chemistry of the unweathered parent rock subsequently pc1 and pc2 were then mapped onto a ternary diagram mfw diagram the m and f vertices characterize mafic and felsic rock source respectively while the w vertex identifies the degree of weathering of these sources independent of the chemistry of the unweathered parent rock the w index has a number of significant properties that are not found in conventional weathering indices first the w index is sensitive to chemical changes that occur during weathering because it is based on eight major oxides whereas most conventional indices are defined by between two and four oxides second the w index provides robust results even for highly weathered sesquioxide rich samples third the w index is applicable to a wide range of felsic intermediate and mafic igneous rock types finally the mfw diagram is expected to facilitate provenance analysis of sedimentary rocks by identifying their weathering trends and thereby enabling a backward estimate of the composition of the unweathered source rock

microfossil evidence for land movements associated with the ad 1964 alaska earthquake microfossil diatom and pollen data from a number of cores at coastal marshes at girdwood flats and kenai flats in cook inlet alaska suggest that there was a phase of gradual land subsidence prior to the main shock of the ad 1964 earthquake this phase followed a long period of gradual land uplift since the last large earthquake which occurred about 730 900 years ago caesium 137cs records indicate that subsidence started approximately 15 years before the 1964 earthquake this pre seismic subsidence is evident in the coastal marsh sediment sequences in changes in diatom and pollen assemblages that indicate changes in tidal marsh environments or a change from raised bog to marsh conditions the microfossil evidence indicates 0 15 m pre seismic land subsidence at both girdwood flats and kenai flats and co seismic subsidence of 1 8 m and 0 2 m respectively

time and size of a giant earthquake in cascadia inferred from japanese tsunami records of january 1700 geological evidence shows that great earthquakes have occurred in the recent prehistoric past in the cascadia subduction zone off the pacific coast of north america the most recent event or series of events is dated at about 300 years ago1 4 but the precise date and magnitude have not been determined geological investigations have not been able to distinguish a single giant earthquake from a series of great earthquakes occurring over a timespan of a decade or two4 although this information is important for the assessment of future hazard5 we have found several tsunami records in japan from ad 1700 with no indication of a local cause historical earthquake records and palaeoseismic evidence indicate the absence of a large earthquake in 1700 in south america alaska or kamchatka leaving cascadia as the most likely source of this tsunami the estimated time of the earthquake is the evening about 21 00 local time of 26 january 1700 the magnitude is estimated as 9 from the tsunami heights in which case the earthquake ruptured the entire length of the cascadia subduction zone2 these estimates are consistent with native american legends that an earthquake occurred on a winter night6

coastal storm deposition salt marsh response to a severe extratropical storm march 1993 west central florida on march 12 13 1993 the passage of a severe extratropical storm popularly referred to as the storm of the century resulted in the deposition of storm suspended sediments along florida west central coastline in waccasassa bay surge waters near 3 m in height inundated the coast and transported resuspended nearshore sediments onto the open marine marshes rimming the embayment the thickness of the resulting storm deposit reached 12 cm on the levees and up to 2 cm on the marsh surface and visible sedimentation occurred several hundred metres from the creek banks into the marsh interior the tan to gray storm layer was composed of mixed clays silt to very fine sand sized quartz and marine biogenic sediments all similar to those of the underlying marsh sediments despite the evidence for severe storm conditions this event was characterized further by the absence of shoreline erosion along the marsh coast this condition contrasts with sandy coasts where strong storms often result in shoreline erosion as compared to sandy shorelines the stability of this marsh fronted coast is enhanced by the cohesive nature of the fine grained marsh muds baffling by the marsh grass canopy and sediment binding by plant root matrices locally the waccasassa bay coastal system has developed under sediment poor sand starved and low energy conditions and large scale storm events may be an important component in sediment transport processes and marsh surface accumulation the response of the waccasassa bay system to this event offers a different view of storm related shoreline effects and in particular the role that storms may play in long term shoreline stability

instability conditions of marly hillslopes towards landsliding or gullying the case of the barcelonnette basin south east france abstract black marl hillslopes in the french alps are strongly affected either by mass movements or by gully erosion due to their susceptibility to weathering processes this paper presents experimental data geomorphological geotechnical geomechanical and hydrological on the parameters of the material of three well known earthflows and of the two stratigraphic parts of the callovo oxfordian black marl the main objectives are to define the geomechanical behaviour of the various formations using different characterisations grain size distribution mineralogy retention capacity consolidation test direct shear test and triaxial test and to demonstrate how such soils can affect the stability of natural slopes particular care must be taken when interpreting the geomechanical tests on this evolving and very heterogeneous clay rich material there are strong relationships between the parent rock and the landslide materials this paper presents a conceptual model of the development of strength over a period of time and investigates the parameters of the material for use in slope stability analysis and risk assessment

analysis of a retrogressive landslide with double sliding surfaces a case study in 2014 a cutting slope was excavated in guizhou province in china during the construction of the yande highway when a previously unknown ancient landslide was encountered it has subsequently been named the longjiayan ancient landslide large surface cracks and severe building damage occurred as well as apparent ground subsidence this work reports the results of a comprehensive investigation performed to identify the mechanism and process of reactivation of the ancient landside in situ surveys and mapping activities were first carried out to obtain a preliminary delineation of the landslide surface and 19 boreholes were set up in the reactivation area to determine the landslide structure as well as create a picture of the sliding surfaces involved then 41 surface cracks and deep displacements in eleven boreholes were monitored for over 40 days a numerical 2d analysis was also undertaken to back analyze the landside a conceptual model is proposed for interpreting the mechanisms responsible for reactivation of ancient landslides based on the longjiayan landslide thereafter based on the formation mechanism of the landslide detailed reinforcement measures were proposed to control it the results reveal that the landslide was a retrogressive soil mass slide involving two sliding surfaces these surfaces have different depths one is shallow and located in a silty clay layer the other is deep and lies in a completely weathered shale layer the soil mass primarily slid towards the free surface along the deep sliding surface up to three failure stages have been identified in the landslide which was triggered by excavation in the toe region rainfall and adverse dip direction of weak intercalations further promoted the development of the landslide during this process the shallow landslide played a key role in the formation of the deep landslide appropriate use of anti slide piles and water interception drainage is an effective approach to controlling such landslides

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr