lisbon 1755 a case of triggered onshore rupture it has been widely recognized both in classical and in modern studies that the lisbon earthquake of 1755 was a multiple event composed of three shocks separated by a few minutes see e g reid 1914 attempts to constrain the location of the source have led to a diversity of proposals reflecting apparent contradictions in the data the tsunami and damage along the south and southwest iberian coast and in morocco favor an offshore source whereas the presence of an additional zone of strong shaking in the lower tagus valley ltv near lisbon favors a more northerly location by combining the contemporary accounts with intensity data from other earthquakes we favor a compound source with a large distance between the faults we propose that although the mainshock was offshore the resulting stress changes induced the rupture of the ltv fault at a distance on the order of 350 km but subject to large uncertainty in the offshore location a few minutes after the mainshock we favor this model rather than site effects causing high intensities in the lisbon area because the highest intensities show a negative correlation to soft soil several other phenomena described in the eyewitness accounts can also be explained by the local rupture now proposed such as a tsunamilike wave in the tagus river ground deformation affecting the course of the tagus river and the spatial pattern of damaging aftershocks recognition of this missing episode of rupture on the ltv fault significantly changes the hazard estimate for the lisbon area

reworked tsunami deposits by bottom currents circumstantial evidences from late pleistocene to early holocene in the gulf of cadiz abstract younger sand layers ysls have been identified in drill cores of a late glacial to early holocene muddy contourite succession from the gulf of cadiz in this study we evaluate the grain size characteristics of the ysl which display bi gradational grading with inverse grading from silt to fine or medium grained sand followed by normal grading from fine or medium grained sand to silt radiocarbon dating shows that the ysl formed at three distinct times 1 the bolling allerod sites u1387 and u1386 2 the younger dryas site u1390 and 3 the beginning of the boreal site u1389 ichnological analyses and radiocarbon dating of cores from drill site u1389c indicate that the ysls consist of reworked materials deposited at a high sedimentation rate the results of sedimentological analyses ichnological treatment spatial distributions and radiocarbon dating of the ysls suggest that the possibility of an origin of the ysls is tsunami related but later reworked by bottom current however the source areas of the sandy sediments remain unclear although our results show them to be variable and area dependent some sandy deposits are transported by the mediterranean outflow water mow from the proximal sector of the gulf of cadiz contourite depositional system cds which is close to the strait of gibraltar however in other cases it is more probable that local gravity flows which are the result of instability on adjacent margins provide the sandy material

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

holocene estuary development in the algarve region southern portugal a reconstruction of sedimentological and ecological evolution this paper presents a reconstruction of the former coastal estuaries of the quarteira and carcavai estuaries in southern portugal based on sedimentological geochemical and palynological analyses of holocene sediment cores the results show that each estuary developed differently depending on the morphology of the palaeovalley environmental conditions and especially the influence of the sea and the formation of barrier systems both estuaries were flooded between 7000 and 5500 cal bp by sea level rise and were almost completely filled by sediment by the beginning of the roman occupation 226 bc 2176 cal bp a clear change in sedimentological processes is evident in both estuaries between 5500 and 3000 cal bp and is interpreted as an erosion phase or evidence of high energy events such as storms or tsunamis

a coupled sheet conduit mechanism for jokulhlaup propagation 1 the largest glacier outburst flood jokulhlaup ever recorded in iceland occurred in 1996 and came from subglacial lake grimsvotn in vatnajokull ice cap among other noteworthy features this flood was characterized by an unprecedentedly high lake level prior to flood initiation extremely rapid linear rise in lake discharge delay between the onset of lake drainage and floodwater arrival at the glacier terminus formation of short lived supraglacial fountains and initially unchannelized outbursts of floodwater at the terminus observations suggest that the 1996 flood propagation mechanism was fundamentally different than that of previously observed floods from grimsvotn we advance a new model whereby floodwater initially propagates in a turbulent subglacial sheet which feeds a nascent system of conduits this model is able to explain key observations made of the 1996 jokulhlaup and may shed light on other outburst floods that do not conform to the standard model

the tagus river delta landslide off lisbon portugal implications for marine geo hazards abstract the stratigraphy of the tagus river ebb tidal delta off lisbon portugal is investigated using high resolution multichannel seismic reflection profiles with the purpose of searching for sedimentary or erosive features associated with landslides the tagus delta is sub divided in two prograding seismic units of 17 ky to 13 ky and 13 ky to present based on the calibration of seismic lines using gravity and box cores in the tagus pro delta we report the existence of a buried landslide with 11 km of length 3 5 km of width and a maximum thickness of 20 m that accounted for the collapse of half of the upper unit of the tagus river delta front in holocene times the non collapsed half of the delta front contains extensive shallow gas of still unknown origin and nature an estimated age of 8 ky bp for the tagus delta landslide is proposed based on stratigraphic correlation the trigger mechanisms of the newly identified tagus landslide are discussed as well as of the several landslides also found in the lower delta unit these findings present a first step towards a future assessment of the susceptibility of the nearby coastal areas and the off shore infrastructures to hazards related to such large collapses

a unique 4000 year long geological record of multiple tsunami inundations in the augusta bay eastern sicily italy abstract we present the geological evidence for a 4000 year long record of multiple tsunami inundations along the coast of the augusta bay eastern sicily and discuss its implications the research was carried out through a multi theme approach which benefited from an extraordinarily long historical record that we used to guide detailed geomorphologic and geologic surveys coring campaigns and laboratory analyses two sites named the augusta hospital and priolo reserve were selected and investigated in detail along the 25 km long coastline of augusta bay we found evidence for six possibly seven tsunami deposits three of them may be tentatively associated with the 1693 and 365 ad ionian sea historical tsunamis and the 3600 bp santorini event the other three possibly four deposits are evidence for unknown paleo inundations dated at about 650 770 ad 600 400 bc and 975 800 bc at augusta hospital site and 800 600 bc at priolo reserve site we use these ages to extend further back the historical record of tsunamis available for this coastal area the exceptional number of tsunami deposits found with this study allowed us to derive an average geologic tsunami recurrence interval in the augusta bay of about 600 years for the past 4 ka conversely the historical tsunami data for the past millennium suggest an average tsunami recurrence interval of about 250 years this difference in the average recurrence intervals suggests that only the strongest inundations may leave recognizable geological signatures at the investigated sites i e the evidence for the 1908 and 1169 tsunamis is missing but also that the geomorphological setting of the site and its erosional depositional history are critical aspects for the data recording thus an average recurrence interval derived from the geological record should be considered as a minimum figure the identification and age estimation of tsunami deposits represent a new and independent contribution to tsunami scenarios and modeling for coastal hazard assessment in civil protection applications furthermore our study cases provide new elements on tsunami deposit recognition related to exceptionally large events that occurred in the aegean sea

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

sedimentological record of tsunamis on shallow shelf areas the case of the 1969 ad and 1755 ad tsunamis on the portuguese shelf off lisbon one of the aims of the sedport project esf euromargins eurocores program was to investigate the depositional features on the shelf and upper slope of the portuguese margin tagus system during the holocene to fulfill the objectives two shallow box cores and two sedimentary sequences were studied po287 26b and the spliced sequence of sites d13902 po287 26g recovered on the portuguese continental shelf ssw off the tagus river mouth and the box po287 28b and gravity core geob8903 collected towards the w of the river mouth magnetic susceptibility grain size and xrf fe data as well as 210 pb and ams 14 c dating of these sedimentary sequences have allowed the identification of an instantaneous deposit at about 20 cm in the box cores downcore we could establish a hiatus corresponding to 355 yr of sedimentation at both sites a 39 cm instantaneous deposit of coarse material including carbonate broken shells on the ssw site and a 1 5 m instantaneous deposit of fine material on the w site both hiatus and instantaneous deposits are considered to be of tsunamigenic origin the box cores deposit has an estimated age of 1969 ad and it is attributed to the 1969 earthquake caused tsunami the hiatus and deposits found downcore are due to the age limits encountered believed to represent the tsunami related to the 1755 lisbon major earthquake these data further indicate a sediment deposit similar in type and thickness on both ssw and w sites in 1969 while the 1755 ad record indicates a higher energy backwash along the ssw and a preferential deposition of fine suspended matter towards the w c 2007 elsevier b v all rights reserved

a new chalcolithic era tsunami event identified in the offshore sedimentary record of jisr al zarka israel abstract tsunami field evidence is a critical resource for determining coastal risk however in many cases there is low potential for long term preservation of such deposits on land a growing body of evidence suggests that tsunami deposits can be present in the shallow offshore realm and may present a largely untapped but important worldwide sedimentological reference set for investigating past tsunami events here different proxies for tsunami sediment identification and differentiation granulometry xrd xrf ft ir were used to determine the presence or absence of such deposits in a core collected offshore at jisr al zarka midway between tel aviv and haifa the study aimed to recognize anomalous deposits and test different analytical methods to define their origins five anomalous sedimentological horizons were identified four of which were interpreted as tsunamigenic by comparison to previously identified poorly sorted shell rich tsunamites found nearby in caesarea and contrast to the fine sand nile derived background sediments the remaining anomaly was distinctive but not determined to be tsunamigenic due to a lack of coarse shell in the matrix the oldest tsunamigenic layer coinciding with the chalcholithic cultural period 5 7 ka is the oldest such deposit identified offshore israel to date and the non tsunamigenic anomalous horizon may correspond with a transitional climatic phase 5 5 ka this research reinforces the importance of offshore investigations as a means of improving tsunami catalogues and identifying environment altering events

influence of deposition in dam reservoir on the deep marine hemipelagic environment off niigata central japan it has been well known that dam construction on rivers can cause a decrease in sediment supply and serious coastal erosion while influence of dams on the sedimentary environment beyond the coastal area has not been well known the mass accumulation rate mar in the hemipelagic environment 500 700 m water depth off niigata central japan since the early half of the twentieth century was obtained from core samples based on excess 210pb activity decreases in mar during the mid twentieth century were recognized in several core samples located northern off the agano and shinano river mouths using the cic model combining correction for the influence of surface bioturbation based on the ratio of mars decreases in mar were estimated as occurring during 1959 1964 and 1949 1955 these dates correspond with construction of the okutadami dam 1956 1961 possessing the largest capacity and reservoir sediment volume of 3 9 107 m3 in the agano and shinano river systems the other core located nw off the agano river mouth showed constant mar through the mid twentieth century a synchronicity of huge dam construction and decrease in mar in deep marine environment the similarity between silt clay sized grain size of dam reservoir sediment and that seen in the hemipelagic environment and horizontal distribution of decreasing mar in cores according to north northeastward sediment transport on shelf makes it reasonable to interpret that the decrease in mar in hemipelagic environment was caused by entrapment of silt clay grains in the huge dam reservoir

water pressure and basal sliding on storglaciaren northern sweden the subglacial hydrology of the ablation area of storglaciaren a small valley glacier in northern sweden is dramatically affected by a subglacial ridge or riegel water pressures above this riegel are relatively constant while down glacier from it they vary significantly the lower part of the glacier accelerates in response to peaks in basal water pressure the upper part may be weakly coupled to the lower part during these peaks a power law fit of observed basal water pressures and measured surface velocities yields where u s is the surface velocity and p e is the effective water pressure ice overburden pressure minus subglacial water pressure data from findelengletscher reported by iken and bindschadler 1986 yield an identical exponent and a coefficient one order of magnitude larger the similar exponent implies that the process producing the velocity variations on both glaciers is similar the variations in velocity are inferred to be due to hydraulic jacking on both glaciers

high frequency surface water changes in the tagus prodelta off lisbon eastern north atlantic during the last two millennia abstract a high resolution sedimentary sequence recovered from the tagus prodelta has been studied with the objective to reconstruct multi decadal to centennial scale climate variability on the western iberian margin and to discuss the observations in a wider oceanographic and climatic context between ca 100 bc and ad 400 the foraminiferal fauna and high abundance of globorotalia inflata indicate advection of subtropical waters via the azores current and the winter time warm portugal coastal current between ca ad 400 and 1350 encompassing the medieval climate anomaly mca enhanced upwelling is indicated by the planktonic foraminiferal fauna in particular by the high abundance of upwelling indicator species globigerina bulloides relatively light 18o values and high sea surface temperature sst reconstructed from foraminiferal assemblages point to upwelling of subtropical eastern north atlantic central water between ca ad 1350 and 1750 i e most of the little ice age relatively heavy 18o values and low reconstructed sst as well as high abundances of neogloboquadrina incompta indicate the advection of cold subpolar waters to the area and a southward deflection of the subpolar front in the north atlantic as well as changes in the mode of the north atlantic oscillation in addition the assemblage composition together with the other proxy data reveals less upwelling and stronger river input than during the mca stronger azores current influence on the iberian margin and strong anthropogenic effect on the climate after ad 1750 is indicated by the foraminiferal fauna the foraminiferal assemblage shows a significant change in surface water conditions at ca ad 1900 including enhanced river runoff a rapid increase in temperature and increased influence of the azores current the tagus record displays a high degree of similarity to other north atlantic records indicating that the site is influenced by atmospheric oceanic processes operating throughout the north atlantic as well as by local changes

an ams radiocarbon method to determine the emplacement time of recent deep sea turbidites abstract this paper reports the evaluation of a novel method based on accelerator mass spectrometer ams radiocarbon dating of planktonic foraminifera to evaluate the times of emplacement of recent deep sea turbidites it assumes that the standing stock of relatively large 150 m planktonic foraminifera in the bioturbated surface mixed layer of box cores represents an integration of the flux from the water column since the turbidite was emplaced and exploits the potential of the ams method to analyse the resultant small samples which can be readily separated the method is evaluated by application to three atlantic turbidites which form the present day sediment surfaces on the horseshoe madeira and tagus abyssal plains the time of emplacement of madeira abyssal plain turbidite is estimated at 1120 730 and 870 years before present each 120 140 years in three different cores the resultant weighted mean emplacement time 930 76 years before present is somewhat older than previous estimates by geochemical methods the times of emplacement for the horseshoe 240 and 140 years before present each 120 years and tagus 300 120 years before present abyssal plains are both consistent with initiation by the lisbon earthquake of 1755

the ad 1755 tsunami deposits onshore and offshore of algarve south portugal sediment transport interpretations based on the study of foraminifera assemblages abstract tsunamis are amongst the most catastrophic natural hazards affecting worldwide coastal areas their impacts are recorded in the geological archives and its study provides crucial insights into the dynamics and intensity of these events the accurate establishment of return periods can also be derived using sedimentological data onshore tsunami deposits have been extensively described over recent years through the application of a wide range of sedimentological proxies including micropalaeontological analysis in this work the identification of palaeotsunami evidence in both the onshore and offshore sedimentary record of south portugal was performed relying mostly on the study of foraminifera assemblages three onshore trenches and one offshore core were analyzed and imprints of the ad 1755 tsunami were observed based in the identification of allochthonous foraminiferal species increase in the number of broken abraded tests and its correlation with coarser mean grain size this was possible after micropalaeontological environmental characterization of both low energy onshore and offshore present day sedimentation regimes in the onshore record three distinct sediment transport phases were differentiated within the tsunamigenic unit the basal phase portraying the initial inundation represented by the dominance of marine foraminifera species in a highly diverse assemblage the higher energetic character of this phase was also reflected in the identification of the highest number of broken abraded tests the intermediate phase reflects an unspecified number of inundation and backwash pulses that were recognized based in the well balanced presence of estuarine brackish and marine species the sharp decrease in the diversity index and in the number of broken abraded tests the final phase recorded in the tsunamigenic unit registers the imprint of the last relevant backwash which was identified based on the dominance of estuarine brackish fauna the overlying unit is dominated by tidal marsh species demonstrating the start of the coastal system recovery phase in the offshore record it was possible to identify 2 distinct historical tsunami events ad 1755 and ad 1969 this was achieved through the identification of significant increases in coastal foraminifera species coupled with the presence of coarser layers this interpretation was sustained by indirect age estimation methods radiocarbon and 210 pb that ascribed compatible ages to the historical tsunami events the results obtained in this study stress the relevance and innovative character of this onshore and offshore multiproxy approach in the recognition and understanding of tsunami events

shallow marine sediment cores record climate variability and earthquake activity off lisbon portugal for the last 2000 years abstract sea surface temperature sst river discharge and biological productivity have been reconstructed from a multi proxy study of a high temporal resolution sedimentary sequence recovered from the tagus deposition center off lisbon portugal for the last 2000 years sst shows 2 c variability on a century scale that allows the identification of the medieval warm period mwp and the little ice age lia high iron fe and fine sediment deposition accompanied by high n alkane concentrations and presence of freshwater diatoms during the lia 1300 1900 ad science 292 2001 662 suggest augmented river discharge whereas higher total alkenone concentrations point to increased river induced productivity during the mwp 550 1300 ad science 292 2001 662 larger mean grain size and low values of magnetic susceptibility and concentrations of fe n alkanes and n alcohols are interpreted to reflect decreased runoff at the same time increased benthic and planktonic foraminifera abundances and presence of upwelling related diatoms point to increased oceanic productivity on the basis of the excellent match found between the negative phases of the north atlantic oscillation nao index and the intensified tagus river discharge observed for the last century it is hypothesized that the increased influx of terrigenous material during the lia reflects a negative nao like state or the occurrence of frequent extreme nao minima during the milder few centuries of the mwp stronger coastal upwelling conditions are attributed to a persistent positive nao like state or the frequent occurrence of extreme nao maxima the peak in magnetic susceptibility centered at 90 cm composite core depth ccd is interpreted as the result of the well known 1755 ad lisbon earthquake the lisbon earthquake and accompanying tsunami are estimated to have caused the loss of 39 cm of sediment 355 years of record most of the lia and the instantaneous deposition of a 19 cm sediment bed

large submarine landslides offshore mt etna 1 high resolution seismic data we collected in the ionian sea reveal large submarine landslide deposits offshore from mt etna italy spatially consistent with the eastern flank collapse of this volcano a large debris avalanche deposit we relate to the valle del bove scar displays long offshore run outs till 20 km and a volume of a few tens of cubic kilometres 16 21 km 3 other landslide deposits are also imaged in particular a striking unique record of the relative timing of multiple submarine large slump events

tsunamigenic seismogenic structures neotectonics sedimentary processes and slope instability on the southwest portuguese margin tectonically active structures prone to cause devastating earthquakes and tsunamis e g the lisbon 1755 earthquake were investigated during the unesco ioc training through research 10 ttr 10 cruise on the southwest portuguese continental margin using single channel seismic profiles a 3 5 khz hull mounted sea bottom profiler 10 khz okean long range side scan sonar 30 khz oretech deep towed side scan sonar and a high resolution deep towed sea bottom profiler these data allowed the definition of new active faults and the establishment of morphological criteria for the classification of active faults in the study area landslides associated with the activity of a major tectonic structure the marques de pombal fault and other areas with clear signs of mass wasting phenomena were mapped a slope to basin sedimentary system comprising 21 sedimentary ridges up to 20 km long was mapped and described it was found that the sediments are mainly transported into the deep basins by mass transport processes across the steepest fault scarps forming a channel levee system while gravitational slides slumps dominate the shallower slopes the sedimentary ridges with an elevation of 40 50 m 50 60 ms twt above the seafloor are imaged on the high resolution seismic profiles as an alternation of high and low amplitude reflectors it is shown that the pereira de sousa fault its plateau and the principes de avis plateau are experiencing uplift according to sedimentary and morphological criteria

osl over dispersion a pilot study for the characterisation of extreme events in the shallow marine realm abstract identification of extreme events in the sedimentary record relies on the correct characterisation of the deposit by means of multiple parameters and different diagnostic criteria multiple proxies based on well tested geological biological and chemical analyses have been used to distinguish tsunami layers from other marine extreme events however few proxies distinguish or compare the degree of sedimentary chaos of an event relative to background sediments and between other extreme events in this pilot study the potential of optically stimulated luminescence osl normally used as a dating method is demonstrated and a new potential sedimentological proxy is proposed when analysing in depth the osl signal from single grain measurements to distinguish between underwater deposits derived from marine extreme events embedded in the texturally and compositionally homogeneous shallow shelf archive of the eastern mediterranean newly and previously collected sediment samples from underwater excavations and a sediment core offshore caesarea maritima israel were used in this experiment each sample was associated with either tsunami storm or fair weather normal marine conditions based on multiple proxies in this study single grain over dispersion sg od values and ranges are used as a potentially novel way to quantify the degree of sedimentary chaos thus the degree of scatter of the dose distribution as a function of the efficiency of exposure to sunlight zeroing of the quartz grains entrained during transport and deposition given that turbidity of a fluid should be associated with lower light penetration and higher energy flow with greater sediment density as can occur in tsunamis relative to storms these conditions should be reflected in variations in single grain over dispersion values hence identifying luminescence distribution patterns related to known depositional conditions this quantification is coupled with detailed statistical analysis of the resulting single grain equivalent dose distributions minimally used in osl dating three types of underwater deposits were categorised based on three distribution typologies to which preliminary conservative single grain over dispersion ranges were assigned 60 for tsunami related deposits showing asymmetric distributions with strong positive skewness this new tool provides a means to study offshore extreme marine events without potential dismissal of other identification criteria and proxies based on these results single grain over dispersion osl could be considered as a potential new sedimentological proxy for identification comparison and characterisation of marine derived extreme events in the shallow shelf such as tsunami deposits as it is intrinsic to the sediment grain and the degree of sedimentary chaos of the event itself

identifying instrumental and historical earthquake records in the sw iberian margin using 210pb turbidite chronology 1 textural mineralogical and geochemical analyses of near surface sediments from six different stations offshore sw iberian peninsula revealed the presence of thin detrital intervals corresponding to very fine grained turbidites precise dating of the two most recent sedimentary layers based on 210pb and 137cs geochronology provides ages of 1971 3 ad and 1908 8 ad these ages correspond to high magnitude historical and instrumental earthquakes that occurred in the region the 1969 horseshoe earthquake mw 8 0 and the 1909 benavente earthquake mw 6 0 such a good correlation between turbidites and high magnitude mw 6 historical and instrumental seismic events suggests that the record of mass transport deposits can also be used as a paleoseismic indicator in low convergence margins

possible tsunami signatures from an integrated study in the augusta bay offshore eastern sicily italy abstract twelve anomalous layers marked by a high concentration of displaced epiphytic foraminifera species growing in vegetated substrates like the posidonia oceanica and subtle grain size changes were found in a 6 7 m long fine sediment core ms 06 sampled 2 km off the shore of the augusta harbor eastern sicily at a depth of 72 m recording the past 4500 yrs of deposition because concentrations of epiphytic foraminifera are quite common in infralittoral zones but not expected at 72 m we believe that these anomalous layers might be related to the occurrence of tsunamis causing substantial uprooting and seaward displacement of p oceanica blades with their benthic biota our approach involved the study of geophysical data morphobathymetry seismic reflection and seafloor reflectivity and sediment samples including x ray imaging physical properties isotopic dating tephrochronology grain size and micropaleontology correlations between anomalous layers and tsunami events have been supported by a multivariate analysis on benthic foraminifera assemblage and dates of historical tsunami records we found that four out of the eleven layers were embedded in age intervals encompassing the dates of major tsunamis that hit eastern sicily 1908 1693 and 1169 and the broader eastern mediterranean santorini at about bp 3600 one more layer even if less distinct than the others was also defined and may be the evidence for the ad 365 crete tsunami

hydraulics of subglacial cavities modele theorique du comportement a l etat stationnaire des cavites remplies d eau et interconnectees sur le lit du glacier

deep sea tsunami deposits in the eastern mediterranean new evidence and depositional models the tsunami wave induced by the collapse of the santorini caldera after the bronze age minoan eruption 3500 bp produced turbidites and large volume mega turbidites in the abyssal plains of the ionian sea as well as on the floor of small basins of the mediterranean and calabrian ridges characterized by the so called cobblestone topography since the first discovery in 1978 a holocene mud layer which has been termed homogenite and which typically shows a graded interval at its base has been identified and correlated in over 50 deep sea cores recovered in the eastern mediterranean four types of homogenite can be distinguished each related to a particular depositional setting 1 a closed cobblestone these are from a few decimetres to several metres thick pelagic turbidites of local provenance exclusively found at the bottom of small sized ponded basins of the mediterranean and calabrian ridges a debris flow may be present at the base of the turbidite where the vertical relief of the basins is over 200 m 2 b abyssal plain a 10 to 20 m thick megaturbidite recorded in the ionian and sirte abyssal plains the source area is the african continental margin possibly the continental shelf it can be easily identified as a transparent acoustic layer that shows recent deformation across the deformation front of the mediterranean ridge accretionary prism the volume of the minoan homogenite in the ionian abyssal plain has been calculated at a minimum of 11 km3 3 c open cobblestone this type is exclusively found on the outer slope of the mediterranean ridge near the deformation front unlike types a and b the base of the turbidite here is erosional instead of depositional this homogenite has been deposited in small basins and occasionally on topographic highs of the mediterranean ridge by the up slope flow of turbidity currents of african provenance that formed the abyssal plain deposit type b 4 d a fourth depositional model has been identified homogenites present in deep anoxic basins of the mediterranean ridge this setting is substantially similar to type a but the vertical relief of the basin is much higher up to 800 m and the deposition occurs in high density anoxic brines which modify the settling rate and hence the resulting sedimentological characters

a tsunami record in the sedimentary archive of the central algarve coast portugal characterizing sediment reconstructing sources and inundation paths this study describes sedimentation associated with the tsunami generated by the lisbon earthquake of ad 1755 it is argued here that the tsunami deposited a sand sheet across the lagoa dos salgados

flotation and free surface flow in a model for subglacial drainage part 1 distributed drainage we present a continuum model for melt water drainage through a spatially distributed system of connected subglacial cavities and consider in this context the complications introduced when effective pressure or water pressure drops to zero instead of unphysically allowing water pressure to become negative we model the formation of a partially vapour or air filled space between ice and bed likewise instead of allowing sustained negative effective pressures we allow ice to separate from the bed at zero effective pressure the resulting model is a free boundary problem in which an elliptic obstacle problem determines hydraulic potential and therefore also determines regions of zero effective pressure and zero water pressure this is coupled with a transport problem for stored water and the coupled system bears some similarities with hele shaw and squeeze film models we present a numerical method for computing time dependent solutions and find close agreement with semi analytical travelling wave and steady state solutions as may be expected we find that ice bed separation is favoured by high fluxes and low ice surface slopes and low bed slopes while partially filled cavities are favoured by low fluxes and high slopes at the boundaries of regions with zero water or effective pressure discontinuities in water level are frequently present either in the form of propagating shocks or as stationary hydraulic jumps accompanied by discontinuities in potential gradient

palaeotsunami in the east china sea for the past two millennia a perspective from the sedimentary characteristics of mud deposit on the continental shelf palaeotsunami studies have revealed that a great tsunami occurred in the south china sea scs and hit xisha archipelago a thousand years ago suggesting the risk of tsunami hazard in this region however knowledge about palaeotsunamis in the east china sea ecs is still limited in this study the grain size sequence of a marine sediment core was analyzed and the history of tsunamis in the east china sea for the past two millennia is presented we first conducted a numerical simulation of the scs tsunami to see its impact on the ecs the results suggest that the impact of an mw 8 0 earthquake induced tsunami is small for the sediment core according to its mean grain size distribution the sediments were formed by two components the 57 8 m fraction consisting about 90 and 10 of the core the most significant change in the grain size sequence of the 57 8 m fraction is consistent with the scs tsunami temporally and this might be the result of the westward transportation of coarse grains by the tsunami for other abrupt changes in the grain size sequence they have not exhibited greater amplitudes than the tsunami affected layer indicating that the impact of the scs tsunami was the most significant during this period thus the east china sea has not been struck by great tsunamis in the past two millennia for palaeotsunamis occurring before the late holocene more studies based on various proxies are required to reveal their history

erratum to identification of tsunami induced deposits using numerical modeling and rock magnetism techniques a study case of the 1755 lisbon tsunami in algarve portugal physics of the earth and planetary interiors volume 182 issues 3 4 pages 187 198 october 2010 abstract storm and tsunami deposits are generated by similar depositional mechanisms making their discrimination hard to establish using classic sedimentologic methods here we propose an original approach to identify tsunami induced deposits by combining numerical simulation and rock magnetism to test our method we investigate the tsunami deposit of the boca do rio estuary generated by the 1755 earthquake in lisbon which is well described in the literature we first test the 1755 tsunami scenario using a numerical inundation model to provide physical parameters for the tsunami wave then we use concentration ms sirm and grain size arm arm b1 2 arm sirm sensitive magnetic proxies coupled with sem microscopy to unravel the magnetic mineralogy of the tsunami induced deposit and its associated depositional mechanisms in order to study the connection between the tsunami deposit and the different sedimentologic units present in the estuary magnetic data were processed by multivariate statistical analyses our numerical simulation show a large inundation of the estuary with flow depths varying from 0 5 to 6 m and run up of 7 m magnetic data show a dominance of paramagnetic minerals quartz mixed with lesser amount of ferromagnetic minerals namely titanomagnetite and titanohematite both of a detrital origin and reworked from the underlying units multivariate statistical analyses indicate a better connection between the tsunami induced deposit and a mixture of units c and d all these results point to a scenario where the energy released by the tsunami wave was strong enough to overtop and erode important amount of sand from the littoral dune and mixed it with reworked materials from underlying layers at least 1 m in depth the method tested here represents an original and promising tool to identify tsunami induced deposits in similar embayed beach environments

variations in benthic foraminiferal assemblages in the tagus mud belt during the last 5700 years implications for tagus river discharge the netherlands organization for scientific research nwo hamoc anr project national research foundation of korea nrf

twentieth century warming and hydrographical changes in the tagus prodelta eastern north atlantic pluri annualproxyrecordsofmarinesedimentcoresfromthetagusprodeltaofflisbon portugal havebeengeneratedtogaininsightintotheclimaticandhydrographicchangesintheareaduringthetwentieth century thestudyincludesbenthicandplanktonicforaminiferalfaunasandthestableisotopiccompositionof one benthic uvigerina celtica and two planktonic globigerina bulloides and globorotalia inflata foraminiferal species sea bottom and surface water temperatures were estimated based on the 18 o values of

basal hydraulic system of a west antarctic ice stream constraints from borehole observations pressure and tracer measurements in boreholes drilled to the bottom of ice stream b west antarctica are used to obtain information about the basal water conduit system in which high water pressures are developed these high pressures presumably make possible the rapid movement of the ice stream pressure in the system is indicated by the borehole water level once connection to the conduit system is made on initial connection here also called breakthrough to the basal water system the water level drops in a few minutes to an initial depth in the range 96 117 m below the surface these water levels are near but mostly somewhat deeper than the flotation level of about 100m depth water level at which basal water pressure and ice overburden pressure are equal which is calculated from depth density profiles and is measured in one borehole the conduit system can be modelled as a continuous or somewhat discontinuous gap between ice and bed the thickness of the gap has to be about 2 mm to account for the water level drop on breakthrough and about 4 mm to fit the results of a salt tracer experiment indicating downstream transport at a speed of 7 5 mm s 1 the above gap conduit model is however ruled out by the way a pressure pulse injected into the basal water system at breakthrough propagates outward from the injection hole and also by the large hole to hole variation in measured basal pressure which if present in a gap conduit system with 2 or 4 mm would result in unacceptably large local water fluxes an alternative model that avoids the e objections called the gap opening model involves opening a gap as injection proceeds starting with a thin film the injection of water under pressure lifts the ice mass a round the borehole creating a gap 3 or 4 mm wide at the ice bed interface evaluated quantitatively the gap opening model accounts for the volume of water that the basal watery system accepts on breakthrough which obviates the gap conduit model in order to transport basal meltwater from upstream it is then necessary for the complete hydraulic model to contain also a network of relatively large conduits of which the most promising type is the canal conduit proposed theoretically by walder and fowler 1994 flat low conduits incised into the till 0 1 m deep and perhaps 1 m wide with a flat ice roof the basal water pressure data suggest that the canals are spaced 50 300 m apart much closer than r tunnel would be the deepest observed water level 117 m i the most likely to reflect the actual water pressure in the canals corresponding to a basal effective pressure of 1 6 bar in this interpretation the shallower water levels are affected by loss of hydraulic head in the narrow passageway s that connect along the bed from borehole to canal s once a borehole has frozen up and any passageways connecting with canals have become closed a pressure sensor in contact with the unfrozen till that underlies the ice will measure the pore pressure in the till given enough time for pressure equilibration this pressure varies considerably with time over the equivalent water level range from 100 to 113 m basal pressure sensors 500 m apart report uncorrelated variations whereas sensors in boreholes 25 m apart report mostly but not entirely well correlated variations of unknown origin in part of the record remarkable anticorrelated variations are interspersed with positively correlated one and there are rare abrupt excursions to extreme water levels as deep as 125m and as shallow as 74 m a diurnal pressure fluctuation intermittently observed may possibly be caused by the ocean tide in the ross sea the lack of any observed variation in ice stream motion when large percentagewise variations in basal effective pressure were occurring according to our data suggests that the observed pressure variations are sufficiently local and so randomly variable from place to place that they are averaged out in the process by which the basal motion of the ice stream is determined by an integration over a large area of the bed

oceanographic processes and morphosedimentary products along the iberian margins a new multidisciplinary approach abstract our understanding of bottom currents and associated oceanographic processes e g overflows barotropic tidal currents including intermittent processes e g vertical eddies deep sea storms horizontal vortices internal waves and tsunamis is rapidly evolving many deep water processes remain poorly understood due to limited direct observations but can generate significant depositional and erosional features on both short and long term time scales this paper represents a review work which describes for the first time these oceanographic processes and examines their potential role in the sedimentary features along the iberian continental margins this review explores the implications of the studied processes given their secondary role relative to other factors such as mass transport and turbiditic processes and highlights three major results a contourite depositional and erosional features are ubiquitous along the margins indicating that bottom currents and associated oceanographic processes control the physiography and sedimentation b the position of interfaces between major water masses and their vertical and spatial variation in time specifically appears to exert primary control in determining major morphologic changes along the slope gradient including the contourite terraces development and c contourites deposits exhibit greater variation than the established facies model suggests therefore a consistent facies model however faces substantial challenges in terms of the wide range of oceanographic processes that can influence in their development an integrated interpretation of these oceanographic processes requires an understanding of contourites seafloor features their spatial and temporal evolution and the near bottom flows that form them this approach will synthesize oceanographic data seafloor morphology sediments and seismic images to improve our knowledge of permanent and intermittent processes around iberia and evaluate their conceptual and regional role in the margin s sedimentary evolution given their complexes three dimensional and temporally variable nature integration of these processes into sedimentary oceanographic and climatological frameworks will require a multidisciplinary approach that includes geology physical oceanography paleoceanography and benthic biology

preservation potential of tsunami deposits on arid siliciclastic coasts abstract numerous post tsunami surveys have been conducted in the last two decades especially since the 2004 indian ocean tsunami these studies have documented a variety of characteristic sedimentary and erosional features that can be ascribed to known events nevertheless the question arises whether these structures are just ephemeral or have a potential to be preserved in the geological record this review describes the changes that have affected muddy to sandy siliciclastic tsunami deposits in peru each of these was surveyed in the first months after the tsunami chimbote 1996 camana 2001 and pisco paracas 2007 here we describe the changes we observed during re surveys in 2007 and 2008 it has long been recognized that onshore tsunami deposits may suffer from surficial processes tectonic movements and anthropogenic alteration earthquake induced uplift or subsidence may subject a tsunami deposit to erosion or burial respectively quick burial in rapidly subsiding coastal areas may enhance preservation deposits of the last or most landward reaching wave may be preferentially preserved if they escape erosion by subsequent tsunami waves however inland areas are also vulnerable to subaerial reworking including by wind and by humans the peruvian examples reviewed here show that the preservation of arid coast tsunami deposits depends on interactions that are more complex that hitherto perceived these involve sediment type grain size depositional setting co seismic movement bioturbation winds and anthropogenic modification in one example all traces of the tsunami have been removed or reworked by flash floods and ocean waves in another example clasts on a coastal plain from tsunami backwash began to be rounded and abraded by eolian sands immediately after the event eolian processes also smoothed and filled tsunami scours by contrast muddy tsunami deposits in certain areas escaped erosion by wind probably because of their greater cohesion in still another example 0 5 m of co seismic uplift was not enough to prevent ocean waves from removing a tsunami sand sheet that had mantled a coastal marsh the buried record of tsunami deposits on modern coasts may therefore not fully represent the vulnerability of these regions to tsunamigenic hazards

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

boulder deposition during major tsunami events a remarkable accumulation of marine boulders located above the present spring tide level has occurred in two coastal lowlands of the algarve portugal the size interval of the particles studied here is seldom reported in the literature in association with extreme events of coastal inundation thus making this study of relevance to many other coasts worldwide the spreads of boulders extend several hundred meters inland and well beyond the present landward limit of storm activity the marine origin of the boulders is demonstrated by well developed macro bioerosion sculpturing and in situ skeletal remains of endolithic shallow marine bivalves the good state preservation of the fossils within the boulders indicates that abrasion during transport and redeposition was not significant we envisage boulder deposition as having taken place during the lisbon tsunami of ad 1755 through the simultaneous landward entrainment of coarse particles from nearshore followed by rapid shoreward suspended dominated transport and non graded redeposition that excluded significant sorting by weight or boulder dimensions we use numerical hydrodynamic modeling of tsunami and storm waves to test the observational data on boulder dimensions density size distribution on the most likely processes of sediment deposition this work demonstrates the effectiveness of the study of boulder deposits in tsunami reconstruction copyright 2011 john wiley sons ltd

proxy calibration to instrumental data set implications for paleoceanographic reconstructions 1 high resolution proxy data analyzed on two high sedimentation shallow water sedimentary sequences po287 26b and po287 28b recovered off lisbon portugal provide the means for comparison to long term instrumental time series of marine and atmospheric parameters sea surface temperature sst precipitation total river flow and upwelling intensity computed from sea level pressure and the possibility to do the necessary calibration for the quantification of past climate conditions xrf fe is used as proxy for river flow and the upwelling related diatom genus chaetoceros is our upwelling proxy sst is estimated from the coccolithophore synthesized alkenones and u37k index comparison of the fe record to the instrumental data reveals its similarity to a mean average run of the instrumentally measured winter jfma river flow on both sites the upwelling diatom record concurs with the upwelling indices at both sites however high opal dissolution below 20 25 cm prevents its use for quantitative reconstructions alkenone derived sst at site 28b does not show interannual variation it has a mean value around 16 c and compares quite well with the instrumental winter spring temperature at site 26b the mean sst is the same but a high degree of interannual variability up to 4 c appears to be determined by summer upwelling conditions stepwise regression analyses of the instrumental and proxy data sets provided regressions that explain from 65 to 94 of the variability contained in the original data and reflect spring and summer river flow as well as summer and winter upwelling indices substantiating the relevance of seasons to the interpretation of the different proxy signals the lack of analogs and the small data set available do not allow quantitative reconstructions at this time but this might be a powerful tool for reconstructing past north atlantic oscillation conditions should we be able to find continuous high resolution records and overcome the analog problem

the role of pore water circulation during the deformation of foreland fold and thrust belts volume loss strain accompanying pressure solution of calcite occurred within both the umbria marches apennines of italy and the appalachian mountains of western new york data from strain markers show that volume loss strain was greater within the shallow portions of the apennines than within the appalachians within the deeper portions of both fold and thrust belts strain was nearly volume constant calcite solubility data suggest that downward circulation of meteoric water is necessary for the 35 volume loss strain of the limestones within the apennines strain at a depth of about 1 km was volume constant and is interpretated as indicative of restricted pore fluid circulation in the appalachians calcite comprises less than 1 of the clastic rocks and a 10 volume loss of this calcite may occur during circulation of connate or dehydration water derived from dewatering of the shales but in an environment that restricts the circulation of meteoric water here the volume of calcite removed 0 1 of the total rock is so small that circulation of meteoric water is not necessary for strain by pressure solution

depositional age and triggering event of turbidites in the western kumano trough central japan during the last ca 100 years abstract for correlating a turbidite record with a detailed land record of natural disasters during the last ca 100 years the depositional age of the surface hemipelagic sediments of the kumano trough located in central japan were estimated we attempted to extract mass accumulation rate of hemipelagic fallout from hemipelagic intervals on the basis of 137 cs geochronology x radiograph dry bulk density and grain size distribution based on assumptions of the biogenic mixing effect on the 137 cs appearance horizon and hemipelagite erosion by turbidity current the reconstructed turbidite record from hemipelagic fallout mass accumulation rate is well correlated with the record of major natural disasters in the kumano area based on the correlation most of turbidite layers are flood storm origin except for a well sorted seismo turbidite induced by the tonankai earthquake that occurred the mid 20th century although the wide distribution of a flood induced turbidite layer due to the 19th century tostukawa flood which was a huge disaster in the area caused by heavy rain and dams breaching it does not show a hyperpycnite succession the flood by dams breaching may cause surge like flow angular to subangular sand sized lithic fragments in the turbidite show that sand grains were transported from the kumano river directly plant debris and microfossils are common in both seismo turbidite and flood storm induced turbidites

reconstruction of holocene coastal progradation on the east coast of korea based on osl dating and gpr surveys of beach foredune ridges coastal dunefields along the east coast of korea have long been thought to have originated from beach ridges that prograded during the holocene but there has been little chronological evidence based on absolute dating in this paper we use optically stimulated luminescence osl dating and ground penetrating radar gpr surveys to reconstruct the coastal progradation of anin dunefield in the gangneung area on the east coast of korea gpr profiles and sedimentological analyses of four beach foredune ridges reveal that the ridges are composed mainly of beach deposits showing seaward dipping and horizontal laminae capped by eolian sands with landward dipping laminae the beach deposits are in places underlain by fluvial sands with gravels coupled with data from osl dating we interpret these results to mean that the fluvial sands and rounded cobbles were deposited in the study area during the last glacial period between the mid holocene 6 5 kyr and c 3 5 3 0 kyr the transgression rate of the sea

new coring study in augusta bay expands understanding of offshore tsunami deposits eastern sicily italy this is the peer reviewed version of the following article smedile a molisso f chague c iorio m de martini p m pinzi s collins p e f sagnotti l pantosti d 2019 new coring study in augusta bay expands understanding of offshore tsunami deposits eastern sicily italy sedimentology which has been published in final form at doi 10 1111 sed 12581 this article may be used for non commercial purposes in accordance with wiley terms and conditions for use of self archived versions 2019 the authors sedimentology 2019 international association of sedimentologists

cortex a shipboard xrf scanner for element analyses in split sediment cores abstract the cortex corescanner texel is a non destructive xrf system for the logging of split sediment cores it is a seaworthy instrument that remains active during heavy weather conditions the scanner produces reliable counts for k to sr highly correlated with concentrations measured with atomic absorption spectrometry aas the option to scan al si and elements heavier than sr is in preparation a core section of 1 m can be scanned at 2 cm intervals within an hour a maximum resolution of 1 mm can be achieved at present each region and sedimentary environment requires separate calibration in the nearby future the generator settings will be standardized which may result in the development of a standard calibration procedure because of the high resolution of its semi quantitative records the cortex is a useful tool for detailed time series analysis inter core correlation and shipboard analysis

identification of tsunami induced deposits using numerical modeling and rock magnetism techniques a study case of the 1755 lisbon tsunami in algarve portugal abstract storm and tsunami deposits are generated by similar depositional mechanisms making their discrimination hard to establish using classic sedimentologic methods here we propose an original approach to identify tsunami induced deposits by combining numerical simulation and rock magnetism to test our method we investigate the tsunami deposit of the boca do rio estuary generated by the 1755 earthquake in lisbon which is well described in the literature we first test the 1755 tsunami scenario using a numerical inundation model to provide physical parameters for the tsunami wave then we use concentration ms sirm and grain size arm arm b1 2 arm sirm sensitive magnetic proxies coupled with sem microscopy to unravel the magnetic mineralogy of the tsunami induced deposit and its associated depositional mechanisms in order to study the connection between the tsunami deposit and the different sedimentologic units present in the estuary magnetic data were processed by multivariate statistical analyses our numerical simulation show a large inundation of the estuary with flow depths varying from 0 5 to 6 m and run up of 7 m magnetic data show a dominance of paramagnetic minerals quartz mixed with lesser amount of ferromagnetic minerals namely titanomagnetite and titanohematite both of a detrital origin and reworked from the underlying units multivariate statistical analyses indicate a better connection between the tsunami induced deposit and a mixture of units c and d all these results point to a scenario where the energy released by the tsunami wave was strong enough to overtop and erode important amount of sand from the littoral dune and mixed it with reworked materials from underlying layers at least 1 m in depth the method tested here represents an original and promising tool to identify tsunami induced deposits in similar embayed beach environments

sedimentologic and geomorphologic tsunami imprints worldwide a review abstract tsunami events with extreme effects on sedimentary transport or considerable alterations of the coastal configuration are rather rare regarding human history but considering geological timescales they occur frequently at least 100 megatsunami in different parts of the world have been recorded in the past 2000 years but presumably far more have failed to be noticed during historical times and are not mentioned either in written or oral ancient records therefore the topic of paleotsunami requires inevitable sedimentological and geomorphological research however field research concerning paleotsunami is astonishingly rare within the scientific approach and only 5 of the existing tsunami literature is related to this subject future efforts in paleotsunami research should focus on the geological evidence of these mega events to clarify their contribution to coastal forming processes this paper reviews the state of the art knowledge of sedimentologic and geomorphic imprints of tsunami along the world s coastlines in order to highlight the need for more detailed studies of paleotsunami depositional and geomorphological traces

shallow marine tsunami deposits in teluk banten nw java indonesia generated by the 1883 krakatau eruption teluk banten tb is a tropical shallow marine embayment with coral reef islands close to the krakatau volcanic complex the 1883 krakatau eruption generated a tsunami which had a devastating effect on the neighboring coastal areas the effects of the 1883 krakatau eruption and the associated tsunami on the bottom sediments in tb are assessed using textural compositional and 210 pb geochronological data an important diagnostic criterion consists of the occurrence of tephra conform descriptions of the 1883 eruption tephra the tsunamite consists of a sandy layer with abundant reworked shell and other carbonate fragments coarse components in the tsunamite consist of locally derived material eroded from the seabed land derived components are incorporated in the tsunamite only in close proximity to the coast the tsunamite is thickest in localized areas of the central part of the bay along the northern open sea facing slope of tb the tsunamite is relatively thin 6 7 cm thick but well preserved as little postdepositional modifications have occurred in the eastern bay area recent erosion since the redirection of the ciujung river in the 1920s has removed the krakatau tsunamite along the west coast of tb the only signature of the 1883 krakatau eruption consists of tephra and evidence for a high energy event is lacking presumably the western area was sheltered from the tsunami wave coming from the northwest at the shallower stations with low accumulation rates the tephra has been thoroughly mixed by bioturbation 2003 elsevier science b v all rights reserved

high resolution analysis of a tsunami deposit case study from the 1755 lisbon tsunami in southwestern spain abstract a multi proxy approach using trench sediment analysis on the southwestern coast of spain los lances bay andalusia provides a high resolution record of the 1755 lisbon tsunami and offers new means to interpret tsunami deposits a combination of sedimentological grain size sorting ams micromorphological x ray tomography and radiography thin sections and geochemical analyses x ray microfluorescence icp aes combines to provide a comprehensive reconstruction of the different phases of tsunami deposition and flow dynamics vertical variations in sediment texture fabric and composition of the 1755 tsunami deposits in los lances are then discussed with reference to existing literature on diagnostic criteria commonly used for identifying and interpreting tsunami deposits finally possible leads for future investigation are proposed

seismic triggering of landslides and turbidity currents offshore portugal 1 sediments in deep water basins often include turbidites that record sediment input from adjacent continental margins in seismically active areas where turbidity currents are triggered by earthquakes the basinal turbidite sequence may thus contain a record of palaeoseismicity which can be used to infer the frequency of earthquakes affecting the margins of the basin this is particularly useful where large earthquakes have a recurrence interval than is greater than the historical record however turbidity currents can be triggered by several processes and it is often difficult to trace individual turbidites to their precise source areas and to assign a definite trigger to a particular turbidite here we demonstrate that turbidites emplaced at 6600 and 8300 cal yr bp in the tagus abyssal plain off portugal correlate with erosional hiatuses in two submarine canyons on the continental margin the turbidites are sourced from simultaneous landsliding in both canyons requiring regional triggers interpreted as earthquakes an earthquake recurrence interval for the continental margin of 4000 years is estimated by extrapolation to deeper turbidites in the basin sequence however the example of the 1755 earthquake which caused widespread devastation in southwest iberia shows that palaeoseismic interpretations must be made with caution the 1755 earthquake had a magnitude 8 5 and yet the associated turbidite in the abyssal plain is typically 5 cm thick while older turbidites can be 1 m thick given the large 1755 earthquake magnitude the difference in turbidite thickness is unlikely to be related to the relative size of triggering earthquakes instead we suggest that the offshore location of the 1755 earthquake coupled with low sedimentation rates during the holocene may have limited the size of the associated turbidite

the sediment fill of pago pago bay tutuila island american samoa new insights on the sediment record of past tsunamis extensive bathymetric and two dimensional seismic surveys have been carried out and cores collected in pago pago bay tutuila american samoa in order to describe and gain a better understanding of the sediment fill of the bay which was affected by the 2009 south pacific tsunami eight sedimentary units were identified over the volcanic bedrock the basal transgressive unit displays retrograding onlaps towards the shore whereas the overlying seven aggradational layers alternate between four draping units and three pinching out seaward units core to seismic correlation reveals that draping units are composed of homogeneous silts while pinching out units are dominated by very coarse coral fragments showing fresh cuts mixed with halimeda plates the basal unit is attributed to transgressive sedimentation in response to flooding of the bay after the last glacial maximum followed by the upper aggrada tional units corresponding to highstand sedimentation the changeovers in these upper units indicate an alternation between low energy silt units and high energy coral debris units interpreted as tsunami induced deposits the 14 c dating reveals that high energy sedimentation units can last up to approximately 2000 years while low energy sedimentation units can last up to approximately 1000 years this alternation deposited during the last high stand may be explained by cycles of tectonic activity and quiescence of the tonga trench subduction which is the main source of tsunamigenic earthquakes impacting the samoan archipelago in the uppermost silt unit only the geochemical signature of the terrestrial input of the 2009 spt backwash deposits was detected between 7 cm and 9 cm depth hence pago pago bay offers a unique sediment record of holocene bay fill under the impact of past tsunamis intermittently during the last 7000 years

combined measurements of subglacial water pressure and surface velocity of findelengletscher switzerland conclusions about drainage system and sliding mechanism interpretation des mesures de pression dans les forages et des vitesses superficielles la comparaison avec les modeles suggere que l on a neglige le frottement du aux debris dans les modeles et qu il n existe jamais de chenaux cylindriques rectilignes