deposit from a giant wave on the island of lanai hawaii limestone bearing gravel the newly named hulopoe gravel blankets the coastal slopes on lanai the deposit which reaches a maximum altitude of 326 meters formerly was believed to have been deposited along several different ancient marine strandlines but dated submerged coral reefs and tide gauge measurements indicate that the southeastern hawaiian islands sink so fast that former worldwide high stands of the sea now lie beneath local sea level evidence indicates that the hulopoe gravel and similar deposits on nearby islands were deposited during the pleistocene by a giant wave generated by a submarine landslide on a sea scarp south of lanai

calculated volumes of individual shield volcanoes at the young end of the hawaiian ridge abstract high resolution multibeam bathymetry and a digital elevation model of the hawaiian islands are used to calculate the volumes of individual shield volcanoes and island complexes niihau kauai oahu the maui nui complex and hawaii taking into account subsidence of the pacific plate under the load of the hawaiian ridge our calculated volume for the island of hawaii and its submarine extent 213 103 km3 is nearly twice the previous estimate 113 103 km3 due primarily to crustal subsidence that had not been accounted for in the earlier work the volcanoes that make up the island of hawaii mahukona kohala mauna kea hualalai mauna loa kilauea and loihi are generally considered to have been formed within the past million years and our revised volume for the island indicates that magma supply rates are greater than previously estimated 0 21 km3 yr as opposed to 0 1 km3 yr this result also shows that compared with rates calculated for the hawaiian islands 0 6 ma 0 095 km3 yr the hawaiian ridge 0 45 ma 0 017 km3 yr and the emperor seamounts 45 80 ma 0 010 km3 yr magma supply rates have increased dramatically to build the island of hawaii

soft sediment deformation in the shallow submarine slope off nice france as a result of a variably charged pliocene aquifer and mass wasting processes abstract along the ligurian slope near nice southeastern france a combination of natural and man made factors govern slope stability and contributed to a devastating tsunamigenic landslide near nice airport in 1979 based on a total of 72 gravity and kullenberg cores we characterise the architecture and facies of the subbottom sediment a total of six sedimentary facies types were observed three of which represent the pliocene holocene background sediment in the wider nice area while another three are associated with the 1979 landslide and tsunami the three primary facies types are soft silty clay clayey silt somewhat indurated silt sand interbeds and pliocene conglomerates underlying the former the three other facies are poorly sorted mass wasting deposits up to pebble size silt representing the finer fraction of the mobilised mass and a tsunami related bed into which plant debris and artefacts got amalgamated accompanying geotechnical results attest that significant strength variations exist when comparing measurements from the narrow shelf shelf break and shallow slope as well as the 1979 slide scar factors such as groundwater charging in the more permeable horizons further lower the effective stress and in places approach lithostatic above such permeable silt sand beds deformation of soft clay is observed suggesting that leaching of ions from the clay mineral surfaces and frayed edges also facilitates weakening and creep micro slumping and folding elevated water supply as well as hydraulic fracturing of the clayey sediment is further attested by pipes of cm diameter and several decimeters length which entrained very soupy mud in the shallowmost deposits in and landward of the slide scar we also observe remnants from the catastrophic deposition associated with the 2 3 m high tsunami wave triggered in 1979 as attested by amalgamated sea grass and artefacts based on our observations and measurements on core scale and earlier models based on in situ cptu we suggest that a significant part of the quaternary delta and slope apron deposits are prone to being mobilised without a large external trigger so that all in all a high risk for a landslide event of considerable size off nice international airport is identified

early pleistocene origin of reefs around lanai hawaii a sequence of submerged terraces l1 l12 offshore lanai was previously interpreted as reefal and correlated with a similar series of reef terraces offshore hawaii island whose ages are known to be 500 ka we present bathymetric observational lithologic and 51 87sr 86sr isotopic measurements for the submerged lanai terraces ranging from 300 to 1000 m l3 l12 that indicate that these terraces are drowned reef systems that grew in shallow coral reef to intermediate and deeper fore reef slope settings since the early pleistocene age estimates based on 87sr 86sr isotopic measurements on corals coralline algae echinoids and bulk sediments although lacking the precision not vert similar 0 23 ma to distinguish the age depth relationship and drowning times of individual reefs indicate that the l12 l3 reefs range in age from not vert similar 1 3 0 5 ma and are therefore about 0 5 0 8 ma older than the corresponding reefs around the flanks of hawaii these new age data despite their lack of precision and the influence of later stage submarine diagenesis on some analyzed corals clearly revise the previous correlations between the reefs off lanai and hawaii soon after the end of major shield building not vert similar 1 3 1 2 ma the lanai reefs initiated growth and went through a period of rapid subsidence and reef drowning associated with glacial interglacial cycles similar to that experienced by the hawaii reefs however their early pleistocene initiation means they experienced a longer more complex growth history than their hawaii counterparts

landslide tsunami vulnerability in the ligurian sea case study of the 1979 october 16 nice international airport submarine landslide and of identified geological mass failures summary the ligurian sea at the france italy boarder of the mediterranean sea has experienced in the past numerous submarine landslides within its very near continental slope the continental shelf being very narrow the most recent occurred on the 1979 october 16 near nice international airport and generated tsunami waves of order 3 m of amplitude in some specific locations more ancient landslides are also easily identified through bathymetric surveys of the seafloor for the 1979 event we propose two distinct tsunamigenic landslides based on identified scars observable on the seafloor the first one corresponds to the volume vol1 that slid at the airport in shallow water while the second one corresponds to the more substantial volume vol2 that has been localized at the slope former studies indicate that only the combination of the two slides may explain the event we complement these studies by asserting that when the two slides are taken separately they already explain a significant although not a total part of the event vol1 explains partly the tsunami observations in the vicinity of the airport while vol2 contributes to explain the ones away from the area in particular at antibes where the highest wave has been observed the modelling effort is then extended to evaluate the tsunamigenesis of selected but representative former landslides having a clear scar signature the vulnerability of the area to landslide triggered tsunami is then proposed to discussion along with possible mechanisms that can be responsible for local wave amplification

spectral signatures of characteristic spatial scales and nonfractal structure in landscapes 1 landscapes are sometimes argued to be scale invariant or random surfaces yet qualitative observations suggest that they contain characteristic spatial scales we quantitatively investigate the existence of characteristic landscape scales by analyzing two dimensional fourier power spectra derived from high resolution topographic maps of two landscapes in california in both cases we find that spectral power declines sharply above a frequency that corresponds roughly to hillslope length implying that the landscape is relatively smooth at finer scales the spectra also show that both landscapes contain quasiperiodic ridge and valley structures and we derive a robust measure of the ridge valley wavelength by comparing the spectra with the statistical properties of spectra derived from randomly generated topography we show that such uniform valley spacing is unlikely to occur in a random surface we describe several potential applications of spectral analysis in geomorphology beyond the identification of characteristic spatial scales including a filtering technique that can be used to measure topographic attributes such as local relief at specific scales or in specific orientations

review of the chronology of marine terraces in the hawaiian archipelago abstract this chronology of marine terraces in hawaii includes 236 published dates most samples are from the emerged reef terraces on oahu the holocene record of transgression is outlined by the available data but further detailed work is needed a mid holocene high stand has been documented for kauai and is currently being resolved for oahu a double marine transgression during the last interglacial is suggested by stratigraphy and electron spin resonance dates from a newly studies site on oahu precise radiometric dates are needed to confirm this interpretation attention is called to the emerged terraces above 10 m in the hawaiian islands which initial studies indicate are older than the last interglacial a reevaluation of oahu age data suggests that oahu has undergone uplift during the last 500 000 years and may not be a suitable stable platform for eustatic sea level comparisons a promising set of deeply submerged terraces representing eustatic low stands has been discovered off the island of hawaii these drowned reefs offer potential for paleoceanographic and paleoclimatic studies

long term base cation weathering rates in forested catchments of the canadian shield abstract a number of methods exist for estimating mineral weathering rates yet quantifying this crucial biogeochemical reaction in the field has always been a challenge because mineral weathering takes place in open systems whose initial state conditions are not well known and where material inputs and outputs vary in time and space here using the soil profile mass balance method we estimated long term weathering rates of base cations bcs for a set of 21 watersheds and we investigated the links between environmental variables and soil properties and the spatial variation in bc weathering rates in the study area the watersheds are located in southern quebec and vary with respect to hydro climatic conditions soil properties and forest cover average long term estimates of annual bc weathering rates for the study area were 0 16 0 10 0 09 and 0 06 kmolc ha 1 year 1 for ca mg na and k respectively overall redundancy analysis rda indicated that soil surface area percent deciduous canopy cover elevation as well as soil albite content were the most significant variables explaining together 56 of the total variation in bc weathering rates consistent with previous findings our results showed that beside soil properties climate related environmental variables played key roles in determining the variability of bc weathering rates in the study area in the context of global climate change more insights are needed for a better understanding of the effects of discrete climatic variables on bc weathering rates

uplift caused by lithospheric flexure in the hawaiian archipelago as revealed by elevated coral deposits the presence of definitive indicators of sea level such as corals found in growth position coralline beach deposits wave cut notches and wave eroded terraces all at elevations above known levels of eustatic sea level during the past 500 ka provides strong evidence that uplift has occurred in the central high hawaiian islands lithospheric flexure is proposed as the mechanism for uplift the modelled wavelength and amplitude of flexure roughly correspond to the distance and height of elevated coral rich deposits a trend of increasing age of coralline beach deposits with elevation on oahu and molokai adds support to the uplift hypothesis data and observations presented in this paper are inconsistent with a tsunami origin for most elevated deposits on lanai molokai and oahu a giant wave origin may only apply to scattered and localized deposits concentrated in low lying gulches 100 m such as those on lanai

vertical movements of ocean island volcanoes insights from a stationary plate environment abstract uplift reconstructions based on the cape verde s geological record provide a unique opportunity to study the long term isostatic movements associated with hotspot activity on a stationary plate environment the archipelago is considered stationary with respect to its melting source so the hotspot driven isostatic effects affecting the ocean islands are expected to be enhanced in this study ar ar and u th geochronology techniques were used to date a set of palaeo markers of sea level from santiago s and sao nicolau s edifices two of the main cape verde islands a comparison between relative sea level and eustatic sea level from a modern eustatic curve was established to extract the vertical displacement undergone by the markers and to reconstruct the uplift subsidence history of each island the resulting uplift reconstructions confirm that both santiago and sao nicolau experienced a general uplift trend over the last 6 ma seemingly synchronous with the vigorous volcanic activity that built their exposed edifices these islands however exhibit different uplift histories despite their common uplift trend several uplift mechanisms were tested and a local rather than regional mechanism is proposed as the main cause of uplift generally unrelated with far field effects of surface loading this mechanism is probably associated with magmatic additions at crustal level

seismicity and crustal structure beneath the western ligurian sea derived from local earthquake tomography abstract in this paper we present and comment on the results of a tomographic inversion of p arrival times of local earthquakes to better understand the structure and features of the ligurian sea an oceanic basin originated in the oligocene miocene this tomographic inversion is the last step in a long and careful revision of the data available for the ligurian sea an accurate catalogue derived from a controlled compilation of data from the numerous stations monitoring seismic activity in this young oceanic basin has been used for computation of a one dimensional 1d reference model a high quality subset of the new catalogue has been used for the non linear 3d tomographic inversion by iteratively solving the coupled hypocenter velocity problem in a least square sense careful analysis of the resolution capability of the used data set has revealed the better resolved features for interpretation the resulting 3d model shows a high velocity layer extending from the northeastern side of the model where it lays about 30 km deep to the southwestern part where it shallows to 15 km the shallow part of this high velocity body is located near the original area of the opening of the ligurian sea that took place between the oligocene and early miocene its velocity is comparable with that of an oceanic moho around 7 8 km s a lens shaped high velocity body about 25 km long located at a depth of 8 15 km is interpreted as a series of ophiolitic bodies intruded into the upper crust

uplift of oahu hawaii during the past 500 k y as recorded by elevated reef deposits studies of paleo sea level and past climate have focused upon proxy methods in ice and deep sea cores and more direct information provided by past shorelines in some cases preserved as raised or submerged reef deposits in tropical areas paleo shorelines need to be constrained by accurate tectonic history because these environments and their marine deposits can be confused with past tsunami deposits and vice versa a maximum 21 m high extensive emerged reef on oahu hawaii u series dated to 334 17 ka together with a mean u series age of 335 22 ka n 5 for slightly higher energetic shoreline deposits nearby suggest a marine isotope stage 9 mis 9 highstand and extend the earlier work indicating a linear uplift for oahu of 0 060 0 001 mm yr over the past 500 k y five of the past six major emerged interglacial highstand reefs on oahu have been identified and these data provide little evidence for past maximum sea levels significantly greater than 2 m above the sea level datum at that time there is currently no evidence for a mis 11 highstand on oahu

a reexamination of the flexural deformation beneath the hawaiian islands seismically derived depth estimates to the top of the oceanic crust beneath the hawaiian islands indicate that the curvature of the deflected lithosphere is much larger than commonly believed the conservative and model independent curvature estimates exceed 10 7 m 1 and are comparable in magnitude to curvatures at trenches and outer rise systems the depth estimates are used to constrain both two dimensional 2 d and three dimensional 3 d flexural models the curvature constraints require a 2 d variable elastic thickness that decreases from 35 km in areas away from the volcanic load to 25 km directly beneath the load in an attempt to understand the nature of the yielding beneath the hawaiian islands we introduce two new 3 d models the first model combines a realistic yield strength based rheology with a new technique for 3 d flexure calculations in which the elastic plate thickness is curvature dependent the new variable rigidity model predicts an undeformed mechanical plate thickness of 44 km decreasing to 33 km beneath the big island of hawaii the best fitting mechanical thickness corresponds approximately to the depth to the 600 c isotherm in 90 m y old lithosphere the second model uses a broken plate but here the crack is oriented along the weak molokai fracture zone rather than along the island chain trend this unconventional flexure model can explain the observed asymmetry in the depth data across the fracture zone without requiring the excessively large elastic thickness of more conventional broken plate models both the proposed models imply that modeling with constant thickness plates may underestimate the true mechanical plate thickness by being unduly influenced by the weak zone beneath the seamounts

3 d slope stability analysis a probability approach applied to the nice slope se france recent geophysical and geotechnical data acquired on the nice shelf to the east of the 1979 landslide source area suggest slow deformations processes which could lead to future catastrophic slope failure according to these preliminary interpretations it is of major interest to perform a slope stability evaluation to define the hazard and quantify the danger related to a probable instability on this slope a probabilistic approach is proposed here using a modified version of the samu 3d model a 3 d slope stability software recently developed by sultan and others to account for complex geometry the 3 d analysis is based on the upper bound theorem of plasticity developed by chen and others one of the main features of the original model is to allow complex critical failure surfaces suitable for complex bathymetry i e canyons a probabilistic approach was added to the former deterministic model to consider the effect of sediment parameter variability and uncertainty undrained shear strength and unit weight on the likelihood of failure such an approach allows an estimation of the reliability of the results monte carlo simulation was used to represent the variability of the factor of safety given a specific number of trials identification of the critical failure surface previously based on a deterministic analysis is thus performed in terms of probability of failure or probability of a factor of safety lower than a reference value according to the undrained shear strength distribution profiles with depth obtained using different models down to 30 and 60 m depth at several sites and to the parameter uncertainty high probability of failure around 50 is found for the nice slope indicating that the sediment in this area is highly metastable

seismic stratigraphy of the flexural moat flanking the hawaiian islands the elastic thickness of oceanic lithosphere based on flexure studies in the region of surface loads is two to three times smaller than its seismic thickness1 thus as a load ages the thickness of the mechanically supportive part of the lithosphere must decrease from its short term seismic thickness to its long term mechanical thickness extrapolation of data from experimental rock mechanics suggests that thinning occurs by brittle failure in the uppermost part of the lithosphere and thermally activated creep in its lower part2 modelling shows that for load ages less than about 1 myr flexural moats change shape and the peripheral bulges migrate in towards the load3 these transient changes in flexure are best manifest we believe in the stratigraphical sequences that infill flexural moats the largest thicknesses of sediments occur in moats flanking orogenic belts4 5 however the stratigraphical record in these basins is complicated by the effects of compaction sub aerial erosion and sea level changes and by the fact that the loading history extends over very long periods of time here we describe a multichannel seismic reflection profile across a flexural moat flanking the volcanic load of oahu in the hawaiian islands the advantages of oahu are that it is located in the interior of a plate the load is 2 7 myr old and formed within 1 myr6 and the flexural moat was not significantly affected by sea level changes and erosion we show that the observed stratigraphical patterns cannot be explained by changes in material influx load distribution and rapid relaxation of the lithosphere to its long term mechanical thickness rather the observed patterns suggest a prolonged relaxation 1 myr due to either local or regional re heating of the lithosphere this re heating has important implications for the relationship between elastic thickness and age of the lithosphere at the time of loadings

holocene environmental change and river mouth sedimentation in the baie des anges french riviera abstract river mouths on the steep high relief coast of the french riviera exhibit thick sequences of holocene marine estuarine deltaic and river channel floodplain sediments that overlie basal fluvial pleistocene gravel gravel is uncommon in most of the early to middle holocene aggradational progradational marine estuarine deltaic sediments despite an ample supply from rock units in the steep adjoining uplands river mouth gravel is common only in late holocene river channels and in barrier beaches perched on finer grained nearshore sediments neither downslope grain size fining on alluvial fans nor sediment stacking patterns during sea level base level rise readily account for the lack of early to middle holocene gravel in the river mouth sediment wedges holocene sea level rise led to the storage of fine grained sediments in shallow marine estuarine and deltaic environments in the present coastal zone we infer that humid temperate conditions a dense forest cover landscape stabilization and a regular quiescent river flow regime associated with the atlantic climatic optimum limited gravel supply in the adjoining catchments and gravel entrainment downstream during the early holocene sea level stabilization in the middle and late holocene coincided with a marked change in bioclimatic conditions toward the present mediterranean type regime which is characterized by a less dense forest cover soil erosion and episodic catastrophic floods the late holocene was thus a time of downstream bedload channel aggradation fine grained floodplain and paludal sedimentation and seaward flushing of clasts leading to the formation and consolidation of the gravel barrier beaches that bound the rivermouths and embayments

new uranium series ages of the waimanalo limestone oahu hawaii implications for sea level during the last interglacial period abstract the waimanalo formation limestone of oahu has been correlated with the last interglacial period based on u series dating of corals by t l ku and colleagues the limestone consists of growth position corals and overlying coral conglomerate an apparent bimodal distribution of ages for the growth position corals mean age 133 ka and the overlying coral conglomerate mean age 119 ka has been interpreted to represent two distinct high stands of sea that occurred within the last interglacial period both growth position corals and overlying conglomerate coral occur in an outcrop east of kaena point and consist mainly of pocillopora and porites u series ages of growth position corals that show closed system conditions are 120 3 ka and 127 4 ka overlying conglomerate corals have u series ages that range from 120 3 ka to 138 4 ka at kahe point conglomerate corals have ages of 120 3 ka and 134 4 ka these data show that the growth position corals are not systematically older than the conglomerate corals thus there is no evidence for two distinct high stands of sea waimanalo deposits at kahe point and mokapu point new u series ages of 134 4 ka and 127 3 ka have beach deposits as high as 12 5 m and at mokapu point growth position corals as high as 8 5 m a last interglacial sea level stand of 8 5 to 12 5 m conflicts with estimates of 6 m from a number of tectonically stable coastlines and islands in the western atlantic ocean we infer therefore that oahu may be undergoing uplift at a low rate this uplift may be due to compensatory lithospheric flexure because the island of hawaii has been subsiding throughout much of the quaternary from volcanic loading because of this possible uplift oahu and islands like it elsewhere in the pacific cannot be used as reference points for sea level during the last interglacial period

crustal structure flexure and subsidence history of the hawaiian islands seismic reflection profile data have been used to estimate the long term 106 years mechanical properties of the oceanic lithosphere underlying the hawaiian islands the data show prominent reflectors associated with the top of the oceanic crust reflector 2 the m discontinuity and the base of the crust reflector 3 the two way travel time to the reflectors has been depth converted using velocity depth functions derived from seismic refraction expanding spread profile data and compared to calculated depths based on simple three dimensional elastic plate models a good fit to the reflector depths was obtained for a model with an effective elastic thickness of the lithosphere te of 40 km the main discrepancies with the refraction data occur beneath oahu and molokai where the predicted depth of the base of the flexed crust is too shallow and beneath the southeast flank of hawaii where it is too deep we attribute the thickened crust beneath oahu to ponding of magma at the base of the crust following the last phases of tholeiitic shield building and the thinned crust beneath the flanks of hawaii to crustal melting beneath the youngest part of the chain the effective te of 40 km is higher than expected for 80 m y oceanic lithosphere possibly due to the effects of subsurface loads that act at or near the base of the flexed crust according to free air gravity anomaly and bathymetry data te does not change significantly along the island chain retaining a similar value for hawaii as it does for oahu we have used this result to estimate the pattern of subsidence and uplift that would be expected along the hawaiian islands because of flexural loading of hawaii the observed depth of the haleakala wave cut terrace northeast of maui can be generally explained by the flexure model the main discrepancies between observed and the predicted depths occur northwest of hawaii where they suggest a somewhat higher value of te possibly due to incomplete adjustment of the lithosphere we suggest that the addition of loads to the end of a volcanic chain generated as a plate moves over a mantle hotspot is accommodated by progressive flexing downstream causing subsidence of preexisting volcanos that lie in the flexural moat and uplift of islands on the flanking bulge the progressive flexure model predicts a characteristic pattern of offlap and onlap in the regions flanking the hawaiian islands that is generally similar to stratigraphic relationships observed along previously published seismic profiles of the moat a progressive flexure model may also apply to the case of a continental plate moving over a mantle hotspot and could explain the observations of 1 a clinoform pattern of stratigraphy in some flood basalt provinces and 2 a seaward dipping reflector sequence at some passive continental margins

temporal variations of flexural deformation in hawaii we present a simple time progressive model for the hawaiian island chain bathymetry and the associated flexural response of the elastic oceanic lithosphere the model is used to study the vertical tectonic history of cross seamount a cretaceous guyot brought close to the hawaiian hot spot by plate motion geological evidence indicates that cross was truncated at sea level but its flat top is presently 400 m below sea level our reconstruction suggests the seamount was elevated on the hawaiian swell and truncated about 3 2 m y ago the post truncation subsidence is attributed to the flexural moat that developed around the growing hawaiian islands flexural isostatic adjustment explains the current depth of cross seamount provided the elastic plate thickness is in the 30 35 km range

investigation of a possible submarine landslide at the var delta front nice continental slope southeast france the var prodelta progrades across a straight narrow shelf less than 2 km wide with a very steep continental slope reaching locally more than 30 historically the var delta front is sadly famou

a 20th century acceleration in global sea level rise 1 multi century sea level records and climate models indicate an acceleration of sea level rise but no 20th century acceleration has previously been detected a reconstruction of global sea level using tide gauge data from 1950 to 2000 indicates a larger rate of rise after 1993 and other periods of rapid sea level rise but no significant acceleration over this period here we extend the reconstruction of global mean sea level back to 1870 and find a sea level rise from january 1870 to december 2004 of 195 mm a 20th century rate of sea level rise of 1 7 0 3 mm yr 1 and a significant acceleration of sea level rise of 0 013 0 006 mm yr 2 this acceleration is an important confirmation of climate change simulations which show an acceleration not previously observed if this acceleration remained constant then the 1990 to 2100 rise would range from 280 to 340 mm consistent with projections in the ipcc tar

the 40ar 39ar dating of core recovered by the hawaii scientific drilling project phase 2 hilo hawaii 1 the hawaii scientific drilling project phase 2 hsdp 2 recovered core from a 3 1 km thick section through the eastern flanks of mauna loa and mauna kea volcanoes we report results of 40ar 39ar incremental heating by broad beam infrared laser of 16 basaltic groundmass samples and 1 plagioclase separate mostly from k poor tholeiites the tholeiites generally have mean radiogenic 40ar enrichments of 1 3 and some contain excess 40ar however isochron ages of glass poor samples preserve stratigraphic order in all cases a 246 m thick sequence of mauna loa tholeiitic lavas yields an isochron age of 122 86 kyr all errors 2 at its base beneath the mauna loa overlap sequence lie mauna kea s postshield and shield sequences a postshield alkalic lava yields an age of 236 16 kyr in agreement with an age of 240 14 kyr for a geochemically correlative flow in the nearby hsdp 1 core hole where more complete dating of the postshield sequence shows it to have accumulated at 0 9 0 4 m kyr from about 330 to 200 ka mauna kea s shield consists of subaerial tholeiitic flows to a depth of 1079 m below sea level then shallow submarine flows hyaloclastites pillow lavas and minor intrusions to core bottom at 3098 m most subaerial tholeiitic flows fail to form isochrons however a sample at 984 m yields an age of 370 180 kyr consistent with ages from similar levels in hsdp 1 submarine tholeiites including shallow marine vitrophyres clasts from hyaloclastites and pillow lavas were analyzed however only pillow lava cores from 2243 2614 and 2789 m yield reliable ages of 482 67 560 150 and 683 82 kyr respectively a linear fit to ages for shield samples defines a mean accumulation rate of 8 6 3 1 m kyr and extrapolates to 635 kyr at core bottom alternatively a model relating mauna kea s growth to transport across the hawaiian hot spot that predicts downward accelerating accumulation rates that reach 20 m kyr at core bottom depaolo and stolper 1996 is also consistent with all reliable ages except the deepest

dominant influence of volcanic loading on vertical motions of the hawaiian islands abstract rates of island vertical motion above intra plate hotspots record the processes that arise from interactions between lithospheric plates and mantle plumes to assess the contribution of mantle and lithospheric processes to surface motion above the hawaiian hotspot we compare simple models of lithospheric deformation to vertical motion rates measured from dated paleoshorelines and tide gauge records in the hawaiian islands our analysis shows that observed uplift and subsidence rates mainly record the flexural response of the lithosphere to volcanic loads the effective elastic plate thickness that best fits the spatial distribution of subsidence and uplift rates is 40 km consistent with previous estimates based on total vertical deflection because volcanic loading dominates the vertical motion signal hawaiian islands appear to follow a predictable trajectory of vertical motion when they reside within one flexural half wavelength of the active volcanic center islands initially subside at rapid and decreasing rates in the first 1 myr following their construction uplift relatively slowly 1 2 5 myr following their construction and eventually subside again but at slow rates within 5 myr of their construction this observed pattern of uplift and subsidence is consistent with the pattern of vertical motion predicted to result from volcanic loading at the hawaiian hotspot lithospheric migration over the long wavelength topographic swell associated with the hawaiian hotspot has a comparatively minor influence on island uplift and subsidence its contribution to island vertical motion is not readily observed in our data with the possible exception of some uplift observed in the past 500 kyr on o ahu that might correspond to non steady state behavior of the hawaiian plume

a signature of transience in bedrock river incision rates over timescales of 10 4 10 7 years measured rates of river incision into bedrock are commonly interpreted as proxies for rates of rock uplift see refs 1 and 2 for example and indices of the strength of climatic forcing of erosion over time see refs 3 and 4 for example this approach implicitly assumes that river incision rates are in equilibrium with external forcings over a wide range of timescales here we directly test this assumption by examining the temporal scaling of bedrock river incision from 155 independent measurements of river incision compiled from 14 sites of these sites 11 exhibit a negative power law dependence of bedrock river incision rate on measurement interval a relationship that is apparent over timescales of 10 4 10 7 years and is independent of tectonic and geomorphic setting thus like rates of sediment accumulation rates of river incision into bedrock exhibit non steady state behaviour even over very long measurement intervals non steady state behaviour can be explained by episodic hiatuses in river incision triggered by alluvial deposition if such hiatuses have a heavy tailed length distribution regardless of its cause the dependence of incision rate on measurement interval complicates efforts to infer tectonic or climatic forcing from changes in rates of river incision over time or from comparison of rates computed over different timescales

ice volume and sea level during the last interglacial during the last interglacial period 125 000 years ago sea level was at least several meters higher than at present with substantial variability observed for peak sea level at geographically diverse sites speculation that the west antarctic ice sheet collapsed during the last interglacial period has drawn particular interest to understanding climate and ice sheet dynamics during this time interval we provide an internally consistent database of coral u th ages to assess last interglacial sea level observations in the context of isostatic modeling and stratigraphic evidence these data indicate that global eustatic sea level peaked 5 5 to 9 meters above present sea level requiring smaller ice sheets in both greenland and antarctica relative to today and indicating strong sea level sensitivity to small changes in radiative forcing

observational constraints on models of the hawaiian hot spot swell a detailed analysis of the topography and geoid associated with the hawaii emperor seamount chain reveals that while geoid topography ratios are high over the southeastern part of the chain they fall off with distance away from the current hot spot location the topographic expression of the swell has two maxima near the intersections between the seamount chain and the murray and molokai fracture zones respectively both geoid and topography rapidly decrease westward of the intersection with the murray fracture zone it appears that the region of the pacific plate between the two fracture zones has been more susceptible to reheating and hot spot penetration than elsewhere along the chain alternatively the observed pattern may be indicative of time variation in the strength of the hawaiian hot spot

combining borehole log stratigraphies and ambient vibration data to build a 3d model of the lower var valley nice france abstract in seismic hazard studies site effects assessment is based on an accurate knowledge of mechanical properties and geometry of superficial geological formations the lower var valley nice southeastern france is a 2 km wide fluvial sedimentary basin where site effects have been observed on earthquake recordings in addition this area is a significant economically developing zone including the second largest airport of france therefore it is highly important to define a 3d sub surface model of the basin to understand the ground motion amplifications based on the compilation of several years of geotechnical and geophysical studies the quaternary alluvial deposits of the lower var valley were investigated using 331 borehole log stratigraphies and 439 ambient vibration measurements these data were combined in a commercial software that models and allows to visualize geoscientific data and geological models in 3d the borehole log stratigraphies helped to define a representative lithostratigraphic soil profile and the geometry of the different sedimentary layers only few boreholes are reaching the engineering bedrock pliocene conglomerates characterized by a s wave velocity larger than 800 m s 1 from the ambient vibration data the fundamental resonance frequency identified from h v curves indicates the bedrock depth using the well known f0 vs 4h relationship these h v curves were interpreted using geological knowledge of the studied zone our results show that the bedrock depth varies in the center of the valley between 50 m in the northern part of the studied zone and more than 100 m on the river estuary first the average s wave velocity in the alluvial deposits is estimated according to combined analysis of the borehole log stratigraphies and h v calculations on ambient vibration measurements the spatial variability of this velocity has been translated into a velocity zonation of the valley second this zonation allows us to extrapolate the quaternary pliocene limit in the whole valley the 3d model of the lower var valley will be useful in future numerical simulations of seismic ground motions in order to evaluate and mitigate seismic risk in the area

reappraisal of the 1887 ligurian earthquake western mediterranean from macroseismicity active tectonics and tsunami modelling summary early in the morning of 1887 february 23 a damaging earthquake hit the towns along the italian and french riviera the earthquake was followed by a tsunami with a maximum run up of 2 m near imperia italy at least 600 people died mainly due to collapsing buildings this ligurian earthquake occurred at the junction between the southern french italian alps and the ligurian basin for such a historical event the epicentre and the equivalent magnitude are difficult to characterize with any degree of precision and the tectonic fault responsible for the earthquake is still under debate today the recent malisar marine geophysical survey allowed the identification of a large system of active faults we propose that the rupture of some of the segments belonging to this 80 km long northern ligurian faults system connected to a shallow dipping major thrust plane at depth was the source of the 1887 ligurian earthquake we investigated the macroseismic data from the sisfrance 08 and dbmi 04 historical databases using several models of intensity attenuation with distance and focal depth the modelling results are consistent with the off shore location with an epicentre around 43 70 43 78 n and 7 81 8 07 e and with a magnitude mw in the range of 6 3 7 5 numerous earthquake source scenarios have been tested on the tide gauge record at genoa harbour as a result we present seven characteristic source earthquake scenarios for a shallow strong earthquake occurring below the northern ligurian margin the modelled tide gauge records were analysed with the help of basic statistical tools and a simple harmonic analysis to extract the wave spectrum characteristics this analysis indicates that scenarios of a magnitude mw of 6 8 6 9 along a reverse n55 e striking fault are the best candidates to explain the known characteristics of the tsunami that followed the best fitting scenarios comprise a 70 dipping southward fault plane with mw 6 8 and a 16 dipping northward fault plane with mw 6 9 both with reverse kinematics taking into account the geometry of the active faults the location of the macroseismic epicentre and the morphotectonic evolution of the continental slope we propose that the 1887 ligurian earthquake corresponded to the reverse faulting of a n55 e striking fault plane dipping to the north with a coseismic slip of 1 5 m

source to sink sediment transfers environmental engineering and hazard mitigation in the steep var river catchment french riviera southeastern france steep coastal margins are potentially subject to mass wasting processes involving notable landslide activity and sediment evacuation downstream by steep gradient streams sediment transfer from short source to sink segments coupled with mountain hydrological regimes regulate patterns of river channel aggradation and coastal sediment supply in such geomorphic settings on the steep french riviera margin sediment transfers from existing landslides or from various minor mass wasting processes to stream channels may result following bursts of heavy concentrated rainfall high magnitude flooding and massive sediment transport downstream are generally related to unpredictable extreme rainfalls both mass movements and channel sediment storage pose serious hazards to downvalley settlements and infrastructure a consideration of channel sediment storage patterns in the var river catchment the most important catchment in this area highlights two important shortcomings relative to environmental engineering and hazard mitigation practices in the first place the appreciation of geomorphic processes is rather poor this is illustrated by the undersized nature of engineering works constructed to mitigate hazards in the upstream bedload dominated channels and by the unforeseen effects that ten rock dams constructed in the early 1970s have had on downstream and coastal sediment storage and on sediment dispersal patterns and consequently valley flooding secondly planners and environmental engineers have lacked foresight in valley and coastal management issues on this steep setting notably as regards the reclaimed areas of the lower var channel and delta liable to flooding urbanization and transport and environmental engineering works have progressively affected patterns of storage and transport of fine grained sediments in the lower var channel and delta meanwhile the problems raised by these changes have not been adequately addressed in terms of scientific research a necessary future step in bettering the engineering solutions implemented to contain natural hazards or to harness water and sediment resources is that of fine scale analysis of source to sink sediment transfer processes of sediment budgets of time scales of storage in stream channels and finally of high magnitude hydrometeorological forcing events in this area the way all these aspects have been modulated by engineering practices and socioeconomic development should also be an important part of such an analysis

intrusive dike complexes cumulate cores and the extrusive growth of hawaiian volcanoes 1 the hawaiian islands are the most geologically studied hot spot islands in the world yet surprisingly the only large scale compilation of marine and land gravity data is more than 45 years old early surveys served as reconnaissance studies only and detailed analyses of the crustal density structure have been limited here we present a new chain wide gravity compilation that incorporates historical island surveys recently published work on the islands of hawai i kaua i and ni ihau and 122 000 km of newly compiled marine gravity data positive residual gravity anomalies reflect dense intrusive bodies allowing us to locate current and former volcanic centers major rift zones and a previously suggested volcano on ka ena ridge by inverting the residual gravity data we generate a 3 d view of the dense intrusive complexes and olivine rich cumulate cores within individual volcanoes and rift zones we find that the h na and ka ena ridges are underlain by particularly high density intrusive material 2 85 g cm3 not observed beneath other hawaiian rift zones contrary to previous estimates volcanoes along the chain are shown to be composed of a small proportion of intrusive material 30 by volume implying that the islands are predominately built extrusively

origin of intraplate volcanoes from guyot heights and oceanic paleodepth the height of a guyot as measured from the surrounding regional sea floor to the vol cano s slope break records the water depth at the time the guyot submerged thus guyot heights may be used as indicators of the paleodepth of the surrounding ocean floor we compile data on the heights of 68 intraplate guyots and atolls in the pacific ocean as well as 46 volcanic islands in the pacific atlantic and indian oceans we find that guyot heights generally increase with the age of the lithosphere upon which they werc cmplaced although therc is a large amount of scattcr in nearly all cases seamount height and thus seafloor paleodepth is less than expzcted of normal seafloor these results suggest that most of the volcanoes in this study formed on anomalously shallow seafloor consistent with formation at hotspots to characterize thermal anomalies associ ated with these hotspot swells we model guyot heights by calculating the isostatic uplift predicted for normal lithosphere that has been partly reheated and is underlain by anomalously hot mantle this model is able to explain the anomalous water depth at most of the seamounts with hotspot thermal anomalies of 100 30o0c the heights of a few volcanic chains however are not anomalously low suggesting that these volcanoes are not associated with hotspots in addition the observed trend of hawaiian emperor guyot heights as well as the subdued morphology and gravity signature of the oldest emperor seamounts supports our hypothesis that cretaceous age meiji seamount may have formed on or near a spreading center

sea level higher than present 3500 years ago on the northern main hawaiian islands new data from an emerged coastal bench and associated fossil beach on kapapa island oahu hawaii preserve a detailed history of middle to late holocene sea level these include 29 new calibrated radiocarbon ages and elevations indicating mean sea level reached a maximum position of 2 00 0 35 m ca 3500 yr b p these results correlate with additional evidence from hawaii and other pacific islands and provide constraints on oahu s long term uplift rate 0 03 0 07 mm yr previously based solely on pleistocene age shorelines our sea level reconstruction is consistent with geophysical model predictions of earth s geoid response to the last deglaciation and with observations of increased antarctic ice volume during the late holocene

unraveling the tilting history of the submerged reefs surrounding oahu and the maui nui complex hawaii there is considerable uncertainty concerning the history of lithospheric flexure of oahu and the maui nui complex associated with the hawaiian hot spot previous reconstructions based on models and sparse observational data place the zone of maximum uplift forebulge either under oahu or between oahu and molokai to address this issue we have compiled and analyzed all existing and new high resolution multibeam bathymetry dive observations and chronologic data from submerged terraces in the region we have identified 89 separate submarine terraces and mapped their distribution across the volcanic flanks of oahu and the maui nui complex these data are used to systematically measure the direction and amplitude of terrace tilting within the maui nui complex and to provide new constraints on lithospheric flexure associated with volcanic loading at the hot spot the terraces are divided into six separate geographic regions oahu molokai penguin bank lanai maui and east maui defined by significant discontinuities in either terrace morphology or depth following the sequential development of new substrate as the new volcanoes formed throughout the development of the mnc 18 new and 51 published 87sr 86sr isotopic ages show that the terraces in these regions were also initiated at different times and the tilting data show that they also responded to lithospheric flexure independently the general pattern of terrace tilting records the plate s response to lithospheric flexure with each region continually tilting toward the zone of maximum subsidence since their formation our individual tilt calculations are based on the most complete and highest resolution bathymetric data available and they show that plate response to volcanic loading is a gradual process finally we demonstrate that the shallowest terraces we identified in the oahu and molokai regions tilt toward the north away from the current zone of maximum subsidence indicating that these regions have recently passed the zone of maximum uplift we compare our results with two separate published numerical models and differentiate between these resolving a long standing uncertainty in the position of the forebulge

subsidence and volcanism of the haleakala ridge hawaii abstract side looking sonar gloria mapping has revealed a series of four arcuate bands of high sonic backscatter on the crest of the haleakala ridge a major rift zone ridge extending 135 km east of the island of maui dredge recovery indicates that the shallowest of these bands is a drowned coral reef and the deeper bands are also inferred to be coral reefs the reefs occur above a prominent submarine bench 1500 2500 m deep on the ridge h terrace that marks the shoreline at the end of vigorous shield building of haleakala volcano when lava flows ceased crossing and reworking the shoreline since their growth these reefs have subsided as much as 2200 m and have tilted systematically about 20 m km southward as a result of post reef volcanic loading on the island of hawaii whose center of mass is about directly south of the haleakala ridge the 234u 238u age of the dredged coral is 750 13 ka in reasonable agreement with an age of 850 ka for the underlying h terrace previously estimated from its relationship to other dated reefs to the southwest basalt glass fragments dredged from the haleakala ridge below the h terrace are tholeiitic and contain high sulfur indicative of eruption in water deeper than 200 m basalt glass fragments associated with the reefs above the h terrace are dominantly tholeiitic and contain intermediate sulfur contents indicative of subaqueous eruption in shallow near shore conditions one alkalic glass fragment was recovered above the h terrace these relations indicate that the morphologic end of shield building as recorded by construction of the h terrace was not accompanyed by a change from tholeiitic to alkalic basalt instead tholeiite eruptions continued for some time before the erupted lava became alkalic

the effect of topography on earthquake ground motion a review and new results a brief review of experimental and theoretical results about the effect of topography on seismic motion shows that they are consistent only on a qualitative basis amplification at mountain tops for wavelengths comparable with mountain widths is predicted and observed but the numerical simulations often underestimate the actual observed effects we propose that this disagreement is because current models are not complex enough we therefore computed the response to incident sh waves of a set of different complex configurations that include two dimensional surface topography with or without periodic ridges and subsurface layering the results show that 1 the topographic effect in itself is difficult to isolate from other effects like surface layering and therefore the amplification on top of geomorphologically complex sites cannot be predicted by a priori estimations based solely on topography and 2 the high crest base amplification ratio observed in the field cannot usually be matched even with complex two dimensional structures with incident plane sh waves which suggests that more complex models are needed to incorporate more complex wave fields e g sv surface and three dimensional geologic configurations

submarine groundwater discharge within a landslide scar at the french mediterranean coast abstract submarine groundwater discharge sgd the flow of fresh and saline groundwater from the seabed into the coastal ocean has been intensively investigated in the recent years this research has usually been restricted to shallow water and intertidal areas whereas knowledge about groundwater seepage in deeper water is mainly limited to point sources from karstic aquifers in this study we observed submarine groundwater seepage and a subterranean estuary in sediments at water depths of 20 44 m located within the ligurian margin western mediterranean sea here a catastrophic submarine landslide occurred near the nice airport french ligurian coast in the fall of 1979 after a period of heavy rainfall during two research cruises gravity cores were recovered in and around the area of the landslide scar pore water samples collected from sediment cores indicated sediments containing freshwater within the landslide scar pore water profiles of selected ions such as chloride ammonium manganese sulfate and barium were used to assess transport and reaction processes within the sediment a 1 dimensional transport model indicates in most cores upward pore water velocities of 2 3 8 8 cm yr 1 this study shows that submarine groundwater seepage along the french mediterranean coastline can occur at water depths reaching 44 m

frequency and triggering of small scale submarine landslides on decadal timescales analysis of 4d bathymetric data from the continental slope offshore nice france time series bathymetric data acquired from 1967 to 2011 are used to evaluate the morphological evolution of the continental shelf and upper continental slope off the city of nice se france ligurian sea mapping in water depths of 0 300 m was undertaken to identify the changing morphology of landslide scars and their erosive chutes quantitative digital terrain model dtm comparisons reveal areas of erosion and deposition over intervals of 5 8 years sediment remobilization events on the upper slope above depths of 200 m are frequent and significant landslide scars with volumes 25 000 m3 can occur with frequencies of 200 m periods of quiescence 1980 1990 and 2006 2011 are seen to alternate with periods when rapid retrogressive failure increase sediment volumes eroded from the upper slope shelf transition by an order of magnitude 1999 2006 temporal variations in landslide activity were correlated to several potential triggering factors that individually would not induce failures including earthquake activity rapid deposition of fine grained sediments on a steep slope and rainfall leading to fresh groundwater circulation below the shelf this 4d bathymetric study suggests that over the last 50 years the most important factor triggering landslides offshore nice is overpressure due to freshwater outflows

plio pleistocene evolution of the var deep sea fan off the french riviera abstract the var deep sea fan was deposited during the pliocene and quaternary seaward progradation of the var delta within a steep sided flat floored basin formed during the messinian salinity crisis the prominent palaeo var canyon was cut on the slope at the same time following the early pliocene transgression var sediments were initially trapped in the coastal ria formed by sea level incursion of the head of the messinian valley by middle pliocene time gilbert type deltas had prograded to the break of slope modern coastline allowing coarse sediment to reach the basin quaternary coastal uplift and sediment supply from the glaciated alps resulted in a supply of coarse sediment to the fan by the braided var river throughout the quaternary even during sea level highstands such as the present in the earliest pliocene hemipelagic clays accumulated while coarse sediment was trapped in the var ria through the rest of the pliocene a leveed fan valley extended southward from the var canyon which periodically switched locations through avulsion to the east at about the beginning of the quaternary this eastward spillover channel became the main distributary and re occupation of the older south trending channels was blocked by rapid levee progradation and aggradation of mud waves by overbanking of turbidity flows on the var sedimentary ridge during the quaternary channel shifting to the north occurred the quaternary var fan has an unusually steep concave longitudinal profile compared with most passive margin fans the laurentian fan has a similar profile to the var both have a high levee and a gravel and pebble floored fan valley that is essentially a bypass zone compared with the aggradational channel levee systems with lower levees in most passive margin fans this is a consequence of the constant supply of coarse sand gravel and pebbles to the fan even during highstands of sea level the erosive capability of this coarse sediment in ignitive turbidity currents resulted in flushing out of the upper and middle fan valley system thick muddy turbidity currents probably resulting from slumping caused by canyon incision produced the prominent mud waves on the levee the concave longitudinal profile led to rapid sediment deposition at critical points in the valley system as a result of turbidity flow expansion this in turn promoted the development of a left hook in the valley system

the selborne cutting stability experiment the paper describes a field experiment in which a 9 m deep cut slope in gault clay was brought to failure by pore pressure recharge the geology of the site is described and the procedures used to

hydrogeology and its effect on slope stability along the coastal aquifer of nice france abstract along the ligurian continental margin off nice western mediterranean a considerable portion of the sediments is affected by pore pressure transients resulting from groundwater charging by the nearby river var and also from leaching clay mineral bearing deposits which results in sensitive weak clays in 1979 the area suffered a tsunamigenic landslide that generated several casualties and material damage to the coastal zone the seafloor presently shows evidence for soft sediment deformation and pore water freshening in this paper we present the first comprehensive in situ pore pressure data set collected over space and time between 2006 and 2009 in a landslide prone area using piezometers ifremer brest france and dynamic cone penetrometers ff cptu marum bremen germany as well as a simple modelling approach we illuminate what governing factors control strength and pore pressure in marine slope sediments affected by the var aquifer our results attest i a strong link between pore pressure transients and local precipitation over a period of 11 months ii overpressure at levels where groundwater flow occurs coarse intervals containing sand and gravel and iii fluidised fractures and channels that indicate high pore pressures at least temporarily in essence seepage and repeated pore pressure fluctuations weaken the sediment effectively so that it cannot be ruled out that the currently stable portion adjacent to nice airport may fail in the near future