equilibrium disequilibrium and nonequilibrium landforms in the landscape abstract landscapes are composed of a diversity of landforms that may be characterized as equilibrium disequilibrium or nonequilibrium equilibrium is a constant relation between input and output or form toward which a landform tends or around which it fluctuates in time because of recent environmental changes and long relaxation times however many landforms are not adjusted to present inputs disequilibrium landforms are those that tend toward equilibrium but have not had sufficient time to reach such a condition some landforms called nonequilibrium do not tend toward equilibrium even with relatively long periods of environmental stability but rather undergo frequent and large change in form nonequilibrium may be caused by high magnitude thresholds that cause low frequency weather events to dominate form positive feedbacks and or nonlinearities that result in deterministic chaos landscapes contain mixtures of equilibrium disequilibrium and nonequilibrium landforms and these types of landforms interact in geomorphic systems such as sediment cascades the three types of behavior may coexist in the same landscape and the outputs of such mixed geomorphic systems reflect the combined effects of equilibrium disequilibrium and nonequilibrium subsystems this classification provides a framework for analysis and modeling of complex landscapes

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

a seismic refraction study of the crustal structure associated with the adamawa plateau and garoua rift cameroon west africa summary recordings of quarry blasts along a 300 km profile across the adamawa plateau at the eastern end of the cameroon volcanic line permitted the determination of the crustal structure of the region to the north of the plateau in the area of the garoua rift an eastern arm of benue trough the crust is about 23 km thick and is underlain by upper mantle with a p wave velocity of 7 8 kms 1 the southern part of the plateau by comparison is associated with a more normal crustal thickness of about 33 km and underlain by upper mantle with a velocity of 8 0 kms 1 between these two areas the seismological experiment was not able to delineate how the crust changes however if the topography and gravity field reflect crustal thickness then there is a rapid change in crustal thickness at the northern edge of the adamawa plateau the study thus provides the first seismic evidence for major crustal thinning beneath the garoua arm of the west african rift system as well as providing evidence for an alternative model for the formation of the cameroon volcanic line

effects of earthquake induced landslides on sediment budget and transport over a 50 yr period landsliding during a magnitude 7 7 earthquake in 1929 in northwestern south island new zealand delivered up to 400 000 m 3 km 2 of sediment to stream channels first to third order channels were buried to depths of as much as 10 m with sedimentary rock debris for distances ranging from 2 of the 92 km 2 study area because of the coarse grain size of the sedimentary rock debris and trapping of sediment in numerous landslide dammed lakes sand and pebble sized debris originating from landslides on a 6 6 km 2 area of granite has been transported downstream no more than 10 km at least 50 to 75 of this granitic debris is retained in the fourth order 92 km 2 catchment 50 yr after the earthquake the long retention times of sediment and the volume of debris supplied by landslides during a large earthquake suggest that earthquake induced landsliding is the principal sediment supply mechanism in the region

time reverse modelling of acoustic wave propagation in attenuating media summary time reverse modelling trm of acoustic wave propagation has been widely implemented in seismic migration and time reversal source imaging the basic assumption of this modelling is that the wave equation is time invariant in non attenuating media in the earth attenuation often invalidates this assumption of time invariance to overcome this problem i propose a trm approach that compensates for attenuation and dispersion effects during the wave propagation in attenuating media this approach is based on a viscoacoustic wave equation which explicitly separates attenuation and dispersion following a constant q model compensating for attenuation and dispersion during trm is achieved by reversing the sign of the attenuation operator coefficient while leaving the counterpart dispersion parameter unchanged in this viscoacoustic wave equation a low pass filter is included to avoid amplifying high frequency noise during trm i demonstrate the effects of the filter on the attenuation and the phase velocity by comparing with theoretical solutions in a 1 d pierre shale homogeneous medium three synthetic examples are used to demonstrate the feasibility of attenuation compensation during trm the first example uses a 1 d homogeneous model to demonstrate the accuracy of the numerical implementation of the methodology the second example shows the applicability of source location using a 2 d layering model the last example uses a 2 d cross well synthetic experiment to show that the methodology can also be implemented in conjunction with reverse time migration to image subsurface reflectors when attenuation compensation is included i find improved estimation of the source location the excitation timing of the point source the magnitude of the focused source wavelet and the reflectivity image of reflectors particularly for deep structures underneath strongly attenuating zones

microseismic rupture propagation imaging abstractwe have developed a method for tracing the rupture propagation of microseismic events we referred to it as microseismic rupture propagation imaging mrpi which is an adaptation of the back projection technique from global seismology hence we shifted back recorded waveforms to a grid of possible source locations and obtained a coherent phase stack that migrated according to the migration of the rupture front using synthetic ruptures and the corresponding waveforms obtained by finite difference modeling we tested the viability of the approach for a reservoir model with the properties and geometry of the monitoring system of the basel 1 geothermal reservoir first we found that an estimation of the rupture location orientation direction and length was feasible in this environment the method was then applied to the four largest events ml 3 1 3 4 recorded at the basel 1 reservoir we found that the obtained rupture lengths and orientations were reasonably consistent with independent estim

geomorphic imprint of landslides on alpine river systems southwest new zealand an inventory of 846 mass movements mainly landslides in two alpine regions of southwest new zealand was created to explore the geomorphic impacts of slope failure processes on river channels and valley floors in total 213 i e 27 per cent of the slope failures descended to valley floors affecting the geomorphology of trunk channels catchment area ac 10 km2 and valley floors in recurring patterns a nominal classification system is introduced for characterizing a the physical contact nature between landslides and river channels and b the resulting geomorphic consequences for drainage although landslide area a is useful for estimating the length of channel directly impacted by debris it does not necessarily predict the direction of fluvial response or type of impact dominant persistent geomorphic imprints of bedrock landslides include channel occlusions and landslide dams in south westland and fiordland respectively differences in size distribution and geomorphic effects on river systems between the two study regions are attributed to bedrock geology tectonics and sediment flux although south westland rivers are more frequently affected by landslides disrupting long term effects such as blockage are more persistent in fiordland copyright 2005 john wiley sons ltd

sediment generation and delivery from large historic landslides in the southern alps new zealand abstract there is much variability of sediment yield in mountain river systems because it is influenced by both periodic e g snowmelt monsoonal circulation and episodic high intensity rainstorms earthquakes controls in the southern alps of new zealand landslides are dominant mechanisms of conveying large amounts of debris to river channels this paper attempts to quantify catastrophic modes of sediment delivery by presenting three recent examples of large landslides on the western slopes of the southern alps a combination of ground surveys dem based volume calculations and air photo interpretation attributes immediate postfailure sediment yields in excess of 70 000 t km 2 a 1 in the short term such landslide derived sediment pulses pose significant hazards to downstream settlements and infrastructure on alluvial fans where they cause massive aggradation increased flooding frequency and large scale channel avulsion in addition to intramontane valley floor obliteration or channel metamorphosis these geomorphic impacts may thus occur far beyond the initial locations of slope failure these catastrophic off site effects involve apparent net sediment delivery rates in the order of 10 5 10 6 m 3 a 1 the accurate quantification of the relative contribution of debris from the disturbing landslide to overall sediment flux is extremely difficult nonetheless are quantitative estimates of landslide derived sediment production and delivery important data to develop a more comprehensive understanding of the variability in alpine sediment flux such data are essential not only for use in hydraulic engineering or catchment management but also in gauging potential future impacts from rainstorm and earthquake induced landsliding in the southern alps

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

the geomorphic evolution and sediment balance of the lower rhone river southern france over the last 130 years hydropower dams versus other control factors article i nfo atthe end of thelittleice age lia agriculturalpractices and successive phasesof channel management involv ing embankments and dams however the respective roles of these various control factors in modifying sedi ment storage and channel stability are often difficult to identify the aim of this paper is to determine the main factors that have driven morphological changes over the past 130 years on the 120 km long downstream reach of the rhone river a gis based analysis of maps and aerial photographs available since 1860 coupled with chrono stratigraphic data on the river s alluvial deposits has enabled quantification of sediment storage and erosion in different morphological units changes measured include riverbed incision narrowing of the main channel in relation with accumulation of fine sediments along the channel margins and reduction of sed iment input at the mouth on the basis of local and reach scale sediment balances we show that these changes are synchronous with engineering works carried out at the end of the nineteenth century and beginning of the twentieth century a period that coincided with a decline in river sediment inputs largely generated by human activities the early stabilisation of mountain slopesresulting from a decline inrural agriculture rural exodus re forestation and engineered torrent control has had a much greater impact in geomorphically transforming the rhone than dams and gravel mining the major identified causes of river destabilisation in the world this calls for caution in the all too common and wholesale attribution of declining sediment budgets of european rivers

time reversal imaging of seismic sources and application to the great sumatra earthquake the increasing power of computers and numerical methods like spectral element methods allows continuously improving modelization of the propagation of seismic waves in heterogeneous media and the development of new applications in particular time reversal in the three dimensional earth the concept of time reversal hereafter referred to as tr was previously successfully applied for acoustic waves in many fields like medical imaging underwater acoustics and non destructive testing we present here the first application at the global scale of tr with associated reverse movies of seismic waves propagation by sending back long period time reversed seismograms we show that seismic wave energy is refocused at the right location and the right time of the earthquake when tr is applied to the sumatra andaman earthquake 26 dec 2004 the migration of the rupture from the south towards the north is retrieved therefore tr is potentially interesting for constraining the spatio temporal history of complex earthquakes

human influence and the changing geomorphology of mediterranean deltas and coasts over the last 6000 years from progradation to destruction phase the present geomorphology of the mediterranean s coasts is largely a product of an intricate long term relationship between nature and human societies a cradle of ancient civilisations the mediterranean has seen its shores occupied by humans since prehistory and is therefore a particularly pertinent unit of analysis the morphotectonic context and other forcing agents e g climate shaped out a highly diversified coastal morphology and generated a sediment supply regime potentially favourable to the formation of numerous open coast deltas and bay head deltas in infilled rias as sea level stabilised during the mid holocene this supply of riverine sediment has also been the key agent in mediating human occupation of the mediterranean s clastic coasts expressions of this relationship have been extensively archived in clastic coastal deposits including base level deltaic and estuarine sedimentary sinks which comprise records to explore the interactions between geosystems and the human environment the stratigraphic sequences in these coastal sedimentary archives comprise in many places a clearly identified anthropogenic signature notably in ancient harbours some of which underwent extremely rapid silting up due to massive sediment sourcing generated by new agricultural practices from the neolithic onwards increasing human influence especially over the last 3000 years has been in turn an important driver of changes in sediment supply strongly modulating deltaic development pulses of sediment supply from catchments rendered vulnerable by human perturbations during the roman period resulted in a new cycle of inception of many other deltas and in rapid delta growth e g the ebro the po the arno and the ombrone another progradation dynamic during the little ice age at a time of strong rural population growth river discharge increases technological developments and urbanisation further consolidated delta growth understanding the life cycle of these deltas since their initial formation is in turn key to unravelling the relative role of natural and anthropogenic forcing agents rapid climate changes are deemed to have contributed through both the stripping of landscapes rendered fragile by human activities and active fluvial sediment transport to the coast but disentangling climate change effects from human impacts in the mediterranean remains a challenge the patterns of subsequent deltaic growth and delta morphodynamics reflect adaptations to pulsed sediment supply river discharge variations the microtidal fetch limited context of the mediterranean and direct engineering interventions the progradation dynamic of the roman period and little ice age contrasts markedly with the situation of common coastal destabilisation over the last two centuries particularly well documented for the last 50 years this period has been characterised by reduced sediment flux to base level geosystems due to catchment reforestation retenion within reservoirs fluvial regulation and dredging resulting in the erosion of deltas and barrier lagoon and beach dune systems large stretches of shoreline and narrow coastal plains have been massively engineered for coastal defence and protection against erosion but also for the construction of marinas leisure harbours and artificial beaches resulting in the emergence of veritable artificial seafronts these interventions have collectively and progressively raised societies to a pervasive and overarching position in the geomorphic stability instability of the mediterranean s coasts a situation that will be exacerbated by pressures from sea level rise paving the way for rampant coastal erosion and delta destruction

variations of stress directions in the western alpine arc summary the western alpine arc originated during the cretaceous orogenesis as a consequence of the continental collision between the european and adriatic plates the distribution of forces acting in this sector of the alps is still somewhat uncertain in the past some evorts have been made to map the distribution of p and t axes but it is known that these can be substantially diverent from the principal stress directions in recent work we presented a first attempt to determine the directions of s 1 and s 3 which we could compute only for a local regime at the level of the magnitude of the larger events that occurred in the area to obtain the stress orientation we applied the technique developed by gephart and forsyth to invert fault plane solutions in this work we present the results of a detailed analysis performed on a larger area applying the same methodology a total of 86 earthquakes with magnitudes ranging from 2 5 to 5 3 has been used for inversion the results confirm the impossibility of defining within the available data a regional stress field in fact diverent local behaviours have been demonstrated in four subregions for the first subregion namely the northern part of the western alps the inversion of 28 earthquakes resulting in a misfit of 5 9 revealed a distensive regime orientated n s for the second subregion the outer part of the western alps the inversion of 16 earthquakes led to a misfit of 5 3 for a distensive e w orientated regime in the inner part of the chain an opposite result was obtained by the inversion of 14 earthquakes confirmed by a misfit of 4 7 finally the region of the ligurian sea revealed an almost horizontal nw se orientated s 1 whereas s 3 is ne sw orientated with a dip of around 30 40 the inversion for this subarea was carried out on a data set of 28 earthquakes and characterized by a misfit of 7 1 the uncertainty of the stress axis orientation 90 per cent confidence limits is on average for all inversions around 40

tchabal nganha volcano in adamawa cameroon petrology of a continental alkaline lava series abstract the mio pliocene tchabal nganha volcano in the adamawa plateau cameroon contains a broad range of rock types from ankaramites to phonolites and trachytes tchabal nganha is located on large n70 e strike slip faults that have been active since the cretaceous and delimit the adamawa plateau horst geological mapping revealed a succession of basaltic hawaiitic lava flow units mugearite benmoreite breccias phonolite and trachyte lava flows and plugs and finally tiny basaltic and intermediate outpourings olivine is fo 85 in basaltic lavas and has altered fayalitic compositions in trachytes clinopyroxene compositions range from ti rich salite in basaltic rocks to hedenbergite in phonolites and aegirine in trachytes kaersutite is present as megacrysts almost completely replaced by rhonite phlogopite salite olivine nepheline in ankaramites and as phenocrysts in phonolites the fe ti oxides indicate decreasing equilibration temperatures and oxygen fugacities from basalts to trachytes spinels occur as inclusions in ol and or cpx phenocrysts in ankaramitic basalts where al rich cr poor spinels are found exclusively in clinopyroxene phenocrysts feldspar occurs as phenocrysts of plagioclase in intermediate lavas and as sanidine and anorthoclase in phonolites and trachytes apatite is ubiquitous in intermediate and felsic lavas sphene is common in some phonolites and chevkinite in some trachytes differentiation indices vary from 17 to 93 with a gap in the range 60 75 ba may attain 4650 ppm in phonolites transition elements decrease strongly with differentiation in the basaltic lavas zr ta is constant along the series except in sphene bearing phonolites which are depleted in ta ree patterns are similar for basaltic and intermediate lavas some phonolites exhibit overall enriched ree patterns whereas peralkaline phonolites are strongly depleted in mree major and trace element variations confirm the dominance of crystal fractionation in the differentiation of the basaltic and phonolite series due to high ta contents along the series and to low sr isotope ratios

environmental signal propagation in sedimentary systems across timescales abstract earth surface processes operate across erosionally dominated landscapes and deliver sediment to depositional systems that can be preserved over a range of timescales the geomorphic and stratigraphic products of this source to sink sediment transfer record signals of external environmental forcings as well as internal or autogenic dynamics of the sedimentary system here we evaluate environmental signal propagation across sediment routing systems with emphasis on sediment supply qs as the carrier of up system forcings we review experimental numerical and natural examples of source to sink sediment routing and signal propagation during three timescales 1 historic which includes measurement and monitoring of events and processes of landscape change and deposition during decades to centuries 2 centuries to several millions of years referred to as intermediate timescale and 3 deep time we discuss issues related to autogenic dynamics of sediment transport transient storage and release that can introduce noise lags and or completely mask signals of external environmental forcings we provide a set of conceptual and practical tools for evaluating sediment supply within a source to sink context which can inform interpretations of signals from the sedimentary record these tools include stratigraphic and sediment routing system characterization sediment budgets geochronology detrital mineral analysis e g thermochronology comparative analog approaches and modeling techniques to measure calculate or estimate the magnitude and frequency of external forcings compared to the characteristic response time of the sediment routing systems

the source scanning algorithm mapping the distribution of seismic sources in time and space summary we introduce a new method which we call the source scanning algorithm ssa for imaging the distribution of seismic sources in both time and space using trial locations and origin times the method calculates the brightness function by summing the absolute amplitudes observed at all stations at their respective predicted arrival times the spatial and temporal distribution of sources is then identified by a systematic search throughout the model space and time for the maximum brightness the greatest advantages of this method are that 1 it exploits waveform information both arrival times and relative amplitudes without the need to calculate highfrequency synthetic seismograms and 2 it requires neither pre assembled phase picking data nor any a priori assumptions about the source geometry a series of tests using synthetic data have shown that this method is robust and can faithfully recover the input source configuration to within 1 grid interval finally we demonstrate the value of the algorithm by locating a typical tremor event with emergent waveforms that occurred during the recent episodic tremor and slip ets sequence in the northern cascadia subduction zone

applying fluvial geomorphology to river channel management background for progress towards a palaeohydrology protocol significant developments have been achieved in applicable and applied fluvial geomorphology as shown in publications of the last three decades analyzed as the basis for using results of studies of environmental change as a basis for management the range of types of publications and of activities are more pertinent to river channel management as a result of concern with sustainability global climate change environmental ethics ecosystem health concepts and public participation possible applications with particular reference to river channel changes include those concerned with form and process assessment of channel change urbanization channelization extractive industries impact of engineering works historical changes in land use and restoration with specific examples illustrated in table 1 in order to achieve general significance for fluvial geomorphology more theory and extension by modelling methods is needed and examples related to morphology and process characteristics integrated approaches and changes of the fluvial system are collected in table 2 the ways in which potential applications are communicated to decision makers range from applicable outputs including publications ranging from review papers book chapters and books to applied outputs which include interdisciplinary problem solving educational outreach and direct involvement with examples summarized in table 3 on the basis of results gained from investigations covering periods longer than continuous records a protocol embracing palaeohydrological inputs for application to river channel management is illustrated and developed as a synopsis version table 4 demonstrating how conclusions from geomorphological research can be expressed in a format which can be considered by managers

reverse modelling for seismic event characterization summary the localization of seismic events is of utmost importance in seismology and exploration current techniques rely on the fact that the recorded event is detectable at most of the stations of a seismic network weak events not visible in the individual seismogram of the network are missed out we present an approach where no picking of events in the seismograms of the recording network is required the observed wavefield of the network is reversed in time and then considered as the boundary value for the reverse modelling assuming the correct velocity model the reversely modelled wavefield focuses on the hypocentre of the seismic event the origin time of the event is given by the time where maximum focussing is observed the spatial extent of the focus resembles the resolution power of the recorded wavefield and the acquisition this automatically provides the uncertainty in the localization with respect to the bandwidth of the recorded data the method is particularly useful for the upcoming large passive networks since no picking is required it has great potential for localizing very weak events not detectable in the individual seismogram since the reverse modelling sums the energy of all recorded traces and therefore enhances the signal to noise ratio similar to stacking in seismic exploration the method is demonstrated by 2 d and 3 d numerical case studies which show the potential of the technique events with a s n ratio smaller than 1 where the events cannot be identified in the individual seismogram of the network are localized very well by the method

improved seismic velocity reference model from local earthquake data in northwestern italy resolution and reliability estimates of results obtained by seismic tomography strongly depend on the reference model inadequate initial reference models may severely distort tomographic images or introduce artefacts that lead to misinterpretations of the results reference models are usually obtained by means of a priori near surface geological information or by geophysical information derived by controlled source seismology starting from the idea that a reference model must approximate the weighted average of data selected for the three dimensional 3d inversion one dimensional 1d model for northwestern italy is derived that is able to minimize mean of rms of a set of well locatable earthquakes by computing a solution of the coupled hypocentre 1d velocity problem such a model termed the minimum 1d model can be used both as an initial reference model for 3d inversion and as a reference velocity model for high quality routine earthquake location

types of crust beneath the ligurian sea the structural setting beneath the ligurian sea resujts from several tectonic events reflected in the nature of the crust the central western sector called the ligurian basin is part of the northwestern mediterranean it is a marginal basin that was generated in oligocene miocene time by subduction of the adriatic plate beneath the european plate and by the eastward drift of the corsica sardinia block the eastern sector belongs to the tyrrhenian basin system and is characterized by extensional activity which since tortonian time superimposed an earlier compressional regime our effort has been addressed in particular towards simplifying the complex nature of the crust of the ligurian basin by modelling its genesis using uniform extension and sea floor depth variation with age in the rift stage of the basin s evolution the initial subsidence reaches the isostatic equilibrium level of the asthenosphere by a thinning factor of 3 15 the additional passive process corresponding to the cooling of the lithosphere since 21 ma leads to a total tectonic subsidence of 3 4 km representing the boundary of the extended continental crust for values up to 4 1 km a transitional type crust is expected whereas for higher tectonic subsidence values a typical oceanic crust should exist after setting these constraints the boundaries of the different crust types have been drawn based on total tectonic subsidence observations deduced from bathymetry and post rift sediment thickness although there is a general agreement with the previous reconstructions deduced from other experimental data the oceanic realm has wider extent and more complex shape the northernmost part of this realm shows crust of sub oceanic type altemating basement highs with lower subsidence values the observed surface heat flux is consistent with the predicted geothermal held in the alpine provencal continental margin and in the oceanic domain however a characteristic thermal asymmetry is clearly visible astride the basin due to the enhanced heat flux of the corsica margin even if the uniform extension model accounts well at a regional level for the present basement depth a remarkable tectonic subsidence excess has been found in the alpine provencal continental margin this evidence agrees with the reprise in compression of the margin the direction of the greatest principal stress is n120 e on average

morphology and structure of the 1999 lava flows at mount cameroon volcano west africa and their bearing on the emplacement dynamics of volume limited flows the morphology and structure of the 1999 lava flows at mount cameroon volcano are documented and discussed in relation to local and source dynamics structures are analysed qualitatively and more detailed arguments are developed on the processes of levee formation and systematic links between flow dynamics and levee channel interface geometry the flows have clear channels bordered by four main types of levees initial accretionary rubble and overflow levees thermally immature pahoehoe lava units with overflow drapes define the proximal zone whereas rubble and accretionary levees are common in the distal region bordering thermally mature aa clinker or blocky aa flow channels pressure ridges squeeze ups and pahoehoe ropes are the prevalent compressive structures standlines displayed on clinkery breccias are interpreted to represent levee channel interactions in response to changing flow levels these data complement previous knowledge on lava flow morphology thus far dominated by etnean and hawaiian examples

aspects of landslide activity in the mercantour massif and the french riviera southeastern france abstract landslides pose serious hazards in the mercantour massif and the french riviera in southeastern france the context for landslide development is a particularly favourable one both in terms of the geomorphic and structural setting of this alpine region and of the climatic hydrologic and seismic factors that trigger such failures high mountain relief and steep slopes constitute a very favourable setting for failures affecting massive basement rocks and a very heterogeneous sedimentary cover whose resistance has been weakened by weathering tectonic stresses and cambering due to gravity among trigger factors the important appears to be the precipitation regime rainfalls are commonly concentrated into short high intensity downpours or into bursts of sustained falls over periods of several days leading to soil saturation and lubrication of potential failure planes snowmelt also contributes to these lubrication processes earthquakes affecting this region are also a potentially important landslide trigger however while a lot of work has been done on the relationship between extreme climatic events and landslide activity much less is known of the trigger effects of earthquakes both the background factors that promote landslide development and the factors that trigger such failures are discussed within a time frame of landslide development progressive changes in soil strength due to weathering rock cambering and shattering processes lead to long term reduction in resistance superimposed on these progressive changes are episodic triggerings related to rainfall and snowmelt episodes or earthquakes landslides may occur as shallow low volume one time events or may be part of a progressive long term failure the former generally affect unconsolidated or clay rich sedimentary rocks especially on the coastal hillslopes of the french riviera a notable exception of a major voluminous one time event was the submarine landslide of the var delta in 1979 this landslide like numerous other smaller subaerial landslides onland was largely a result of human activities this landslide occurred following extensive modification of the var delta and notably reclamation of the steep fine grained delta front deforestation quarrying urbanisation and road network developments are various ways in which human activity has destabilized the coastal hillslopes favouring the development of numerous shallow landslides following each episode of heavy rainfall progressive landslides on the upper hillslopes of the mercantour massif have developed over long time spans order of 101 to 105 yrs and have involved more complex interactions between lithological controls slope characteristics and trigger factors the collelongue and bois de malbosc landslides have evolved into now stable failures buttressed by resistant migmatitic diorites or amphibolites the more voluminous and well monitored clapiere landslide is a relatively simple rotational landslide of the toe failure type this active landslide poses a serious to inhabitants and infrastructure in the tinee valley the importance of continued field monitoring modelling and mapping of landslides and their hazards is emphasised

compositional variation of naturally occurring rhoenite new electron microprobe analyses of rhoenite from an exceptionally oxidized alkali gabbro from kauai hawaii are presented which greatly expand the range in composition known for this mineral the kauai rhoenites contain more abundant mg ivfe3 vife3 and na and less abundant fe2 viiica and ti than any previously reported terrestrial example the abundances of si and ival are among the lowest and highest respectively yet reported these analyses are compared to all other available rhoenite analyses and a representative set of aenigmatite analyses the twelve dimensional rhoenite composition space is defined with aenigmatite as an additive component and a set of eight linearly independent simple and coupled ionic exchange components

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

petrology of the plio quaternary volcanism of the south central and meridional andes plio quaternary volcanoes lay upon a continental crust which is thick and of precambrian paleozoic age in the south central andes sca 18 28 s whereas it is relatively thin and of mesozoic cenozoic age in the meridional andes ma 32 42 s eleven calc alkaline volcanic massifs or groups of small volcanoes and two shoshonitic volcanoes have been studied in the sca eleven calc alkaline volcanic massifs have been studied in the ma one alkaline volcano has been approached in argentinian patagonia calc alkaline lavas are mostly andesites and dacites in the sca and high al basalts and basic andesites in the ma shoshonitic lavas are absarokites shoshonites and banakites no cognate xenoliths were found in the lavas the texture of the lavas is microlitic with abundant calc alkaline lavas or rare shoshonitic lavas phenocrysts distribution of phenocrysts opposes calc alkaline lavas of the sca with hornblende and biotite to those of the ma with olivine in calc alkaline lavas plagioclase is the most abundant mineral phase from high al basalts an90 to rhyolites an20 olivine is fo78 65 phenocrysts in basic lavas clinopyroxene ca mg rich augite and orthopyroxene bronzite show little compositional variation with lava differentiation amphibole is pargasitic or edenetic hornblende crystal clots which result from resorption of hornblende are found biotite is ti rich phenocrysts of quartz are found in rhyolites and rimmed by pyroxenes in basic lavas of the sca microlites of magnetite are ubiquitous and phenocrysts occur only in the sca in the sca geothermometers and geobarometers give the following results equilibration temperatures which decrease from 1000 c in andesites to 900 c in dacites h2o pressures vary between 1 and 4 kbar and oxygen fugacities are higher than the ni nio buffer basic lavas may have equilibrated at 50 km depth in shoshonitic lavas plagioclase and k feldspar are present olivine is fo85 phenocrysts and fo65 microlites clinopyroxene is cr rich orthopyroxene is bronzite in shoshonites microlites and banakites microlites and phenocrysts hornblende is pargasitic biotite is t rich in banakites conditions of differentiation of the lavas are high temperatures 850 1050 c water pressures inferior to 2 kbar oxygen fugacities above the ni nio buffer and total pressures which correspond to depths of 80 120 km major and trace element distributions emphasize differences between calc alkaline associations of the sca and ma and between calc alkaline and shoshonitic associations in shoshonitic lavas decreases in mgo and ni cao and cr al2o3 and sr correspond to respective olivine clinopyroxene and plagioclase fractionations incompatible elements circum pacific characteristics high al2o3 constant na2o3 increasing k2o with differentiation andean characteristics low cao and peculiar characteristics ma lavas have lower mgo olivine fractionation in the sca lavas have lower tio2 and feo fractionations of magnetite pyroxenes and hornblende the origin of the andean magmatism is not consistent with single stage models anatexis of continental crust crystal fractionation of basaltic magma under amphibolite or eclogite facies partial melting of peridotitic upper mantle material a three stage model is proposed the first stage consists of partial melting of upper mantle material loss in fluids of the subducted oceanic crust induces the melting bubbles of primary magma are generated the second stage consists of selective crustal contamination during the stay of the magma at the base of the continental crust the third stage consists of low pressure crystal fractionation which governs the differentiation of the lava series the present model considers transversal and longitudinal zonation of the andes high degrees of melting low rate of contamination and reduced crystal fractionation characterize the ma whereas low degrees of melting high rate of contamination and considerable crystal fractionation characterize the sca garnet is involved in the genesis of shoshonitic lavas

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

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

earthquake relocation in the ligurian sea western mediterranean geological interpretation abstract relocated epicenters are computed with a model based on complex local structure i e oceanic floor in the central ligurian basin and thinned continental margins by superposing these relocated earthquakes on a basement bathymetric map the structural relations are clearly demonstrated compressive stress towards the west northwest is confirmed in the northern ligurian basin by focal mechanism study according to our results most of the earthquakes appear to be shallow and linked to rejuvenation of older distensive and strike slip structures on margins as in the basin by a compressional motion

petrology of the bimodal cenozoic volcanism of the kapsiki plateau northernmost cameroon central africa the kapsiki plateau is the northernmost volcanic zone of the cameroon line the volcanism 27 35 ma is of alkaline type and has a typical bimodal lava series diversity with basalts and hawaiite as mafic lavas and phonolites trachytes and rhyolites as felsic lavas mg rich olivine phenocrysts occur only in basalts the hawaiite contains andesine olivine and ca rich pyroxene phenocrysts and sanidine and quartz xenocrysts the phonolites contain alkali feldspar and na rich clinopyroxene phenocrysts two types of trachytes occur peralkaline trachytes with ti na and f rich aegirine augite richterite arfvedsonite phenocrysts and non peralkaline trachytes with an aenigmatite type undetermined mineral ti rich biotite and zircon phenocrysts similarly two types of rhyolites occur peralkaline with quartz and arfvedsonite phenocrysts and non peralkaline with quartz and biotite phenocrysts differentiation indices thornton and tuttle 1960 of the lavas range from 22 to 97 with a large gap in the range 34 82 some basalts are primitive 530 ppm ni 1100 ppm cr in basaltic lavas phonolites and non peralkaline trachytes and rhyolites zr and nb covary with approximately constant ratios o3 1 zr nb 5 3u however peralkaline trachytes and rhyolites have high concentrations in zr up to 2180 ppm and nb up to 780 ppm with correlative higher zr nb ratios 6 3 8 3 some rhyolites have abnormal ree patterns with kinks depleted in light ree probably resulting from stability of na ree f complexes under hydrothermal conditions despite a large gap between basaltic and felsic lavas major and trace element distributions indicate co magmatism for both the basaltic and felsic lavas the differentiation of the lava series is dominated by crystal fractionation the role of fluids in rhyolite genesis being of minor effect as evidenced by constant values of y ho and zr hf throughout the series the kapsiki plateau basalts are similar in their chemical and isotopic data character to other basalts from both the continental and oceanic sectors of the cameroon line the continental crust appears to have no significant role in their genesis the hawaiite mineralogical and geochemical characteristics are consistent with an origin by mixing of basaltic and felsic phonolitic magmas the kapsiki plateau basaltic magmas may have originated from an infra asthenospheric reservoir similarly to other basaltic magmas generated throughout the cameroon line the sr isotope variations observed in trachytes and rhyolites point to some contamination of the magmas by crustal materials while the nd isotopic composition is only slightly affected q 2000 elsevier science b v all rights reserved

time reverse modeling of low frequency microtremors application to hydrocarbon reservoir localization 1 time reverse modeling is applied to synthetic and real low frequency microtremors measured at the earth surface with synchronized seismometers in contrast to previous time reverse applications no single event or first arrival time identification is applied for microtremor localization synthetic low frequency microtremors are numerically generated within a small underground area and modeled with a finite difference algorithm simulating two dimensional elastic wave propagation time reverse modeling using synthetic microtremors shows that small underground source areas can be accurately located different source characteristics which emit mainly p waves or s waves vertically influence the localization accuracy time reverse modeling is applied to two real microtremor data sets acquired 16 months apart above known oil reservoirs nearby voitsdorf austria to investigate whether spectral anomalies observed above the reservoirs originate from the reservoirs time reverse modeling indicates that low frequency microtremor signals originate from the reservoir locations and provides a possible method for reservoir localization

geochemistry of pyroxene inclusions from the warrumbungle volcano new south wales australia pyroxenes provide an elegant key to understanding the tangled petrogenesis of the diverse midalkaline rocks of the warrumbungle volcano these rocks evolved from two primary magmas and the pyroxenes record the various stages in their origin and evolution trace element abundance patterns for chromian diopside crystals from a spinel lherzolite xenolith provide evidence of an early mantle depletion event depleted spinel lherzolite is an appropriate mantle source for the itep incompatible trace element poor series of rocks subcalcic augite megacrysts are common in the basic rocks of this series they crystallized in a high pressure intratelluric environment where they controlled the initial magmatic differentiation of the itep series aluminian augite occurs as megacrysts and also in gabbronorite xenoliths found in one of the more differentiated rocks of the itep series this pyroxene crystallized in a lower crustal magma chamber where its host magma was peraluminous and intermediate in composition a few clinopyroxene cpx megacrysts are fe rich and exceptionally enriched in rare earth elements ree they crystallized from a moderately differentiated magma locally contaminated by crustal material or were later subjected to a metasomatic event one of the nepheline normative basic rocks of the iter incompatible trace element rich series contains small inclusions of k rich omphacite this phase contains one of the highest k contents 0 6 2 3 wt ever reported in a cpx and crystallized from a k rich liquid at a greater depth than any of the other pyroxenes probably deep within the upper mantle orthopyroxene opx megacrysts are rare and belong to at least three geochemically distinct types in association with chromian diopside with subcalcic augite and with aluminian augite megacrysts each type of opx crystallized in a separate chemical and physical environment

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

further testing of the bedding plane slip model for hydraulic fracture opening using moment tensor inversions abstractmoment tensors are calculated by using the p wave first motion peak amplitudes of 59 microseismic events with high signal to noise ratio these events are from a surface microseismic data set gathered during hydraulic fracture stimulation of the marcellus gas shale in washington county pennsylvania usa the majority of these 59 events have a horizontal nodal plane a few degrees characteristic of a dip slip horizontal slip moment tensor if the horizontal nodal plane is an auxiliary the vertical nodal plane has a pure dip slip motion which is inconsistent with the opening motion for vertical hydraulic fractures that enables proppant loading this points to slip on horizontal nodal planes with the auxiliary vertical nodal planes aligned with the local maximum horizontal stress orientation as indicated by drilling induced fractures in nearby vertical wells these 59 microseismic events are caused by slip on horizontal mechanical discontinuities such as bedding planes during the opening of ver

a closing ligurian sea two earthquakes occurred in the ligurian sea in december 1989 and april 1990 both were widely felt along the french and italian rivieras thus reminding us of the seismic risk in this region the significant increase in the number of seismic stations in the area facilitated the study of these two shocks and their related aftershocks using different techniques absolute and relative hypocentral locations doublet analysis and waveform modeling we computed accurate hypocentral locations and estimated the location error range for earthquakes in this area we also computed the focal mechanisms for both mainshocks and we present here a synthesis that integrates previous data the reactivation in compression of the ligurian sea sphenochasm is confirmed which would eventually result in the closing of an aborted oceanic domain as the seismic activity is clearly restricted to the northern margin we suggest it locally results from the lateral expulsion of the south western alps along the apulian indenter

focusing of elastic waves for microseismic imaging microseismic events generate compressive waves and shear waves which can be recorded at receivers we present a theory that shows how elastic p and s waves separately backpropagate to the original source location these refocused p and s wavefields are free of singularities we also demonstrate a technique that enhances the ability to image the spatial focus for each wave type using elastic waves the improved spatial focus obtained is achieved in a velocity model for which the interface boundaries are approximate but where the mean slowness is correct deconvolution designs a signal to be rebroadcasted from the receivers using only the waves recorded at each receiver such that the wavefield has an optimal temporal focus at the source location we demonstrate theoretically and numerically that improved temporal focusing of elastic waves leads to improved spatial focusing for each wave type this proposed technique only involves a simple preprocessing step to the recorded data and its cost is hence negligible compared to the total cost of microseismic imaging

high frequency monitoring of debris flow propagation along the real torrent southern french prealps abstract the real torrent 2 3 km2 drainage area is a very active debris flow torrent in the french prealps it was equipped with three high frequency monitoring stations in late 2010 to investigate the triggering conditions and propagation of debris flows along the 2 km long torrent channel the monitoring system combines different techniques including rain gauges and measurements of ground vibrations and flow elevations in spring and summer of 2011 five rainfall triggered debris flow events occurred along the torrent most debris fronts deposited in the upstream part of the channel but one large front 1 9 2 0 m high propagated to the catchment outlet with a mean velocity of about 3 m s 1 the volume of this main debris surge was 3900 m3 near the hillslope sources and increased downstream 5500 m3 in the middle part and 8600 m3 near the catchment outlet the debris flow developed a more mature flow pattern as it progressed downstream multiple debris and hyperconcentrated surges were observed upstream while a single debris surge occurred near the catchment outlet the front height remained relatively constant during its propagation whereas its viscosity and velocity tended to decrease downstream as the channel slope decreases the growth of this main debris surge could be explained by the entrainment of in channel sediments and the coalescence of the multiple preliminary surges for the 2011 events rainfall burst duration and intensity were the main factors controlling the occurrence volume and runout distance of debris flows antecedent channel conditions sediment recharge bed wetness and antecedent rainfall are also important factors but further investigations are necessary to better understand the role of these factors regarding the triggering and propagation of debris flows in the real torrent

locating microseismic sources using migration based deconvolution abstractwe have developed a method for finding microseismic hypocenters from data recorded by arrays of triaxial motion sensors the method reconstructs the elastic time series signatures for possible microseismic sources at any point in 3d space using full waveform migration of the recorded vector wavefield the imaging condition for the migration is based on a semblance weighted deconvolution between two or more reconstructed source signatures requiring similarity and simultaneity of the reconstructed signatures this imaging condition eliminates the need for an absolute timing of the data gives optimum resolution for the location of the microseismic sources better than correlation based approaches and ensures numerical stability by adapting to the signal and noise conditions of the data because the method eliminates time consuming phase picking and traditional event association it should be well suited for fully or semiautomated data processing the method was tested by an application to field dat

the suture between the alps and apennines in the ligurian sector based on geological and geomagnetic data abstract a ground magnetic survey was carried out over a wide area of northwestern italy including western and central liguria the southeastern piedmont and a part of the ligurian sea several cross sections cutting the main structural elements the ligurian sea the ligurian alps the monferrato hills have been performed and magnetic models have been developed the interpretation of the most characteristic cross section a1 nnw is presented in this paper a model involving the presence of a major suture between the ligurian alps and the monferrato hills fits the positive magnetic anomaly running from the surroundings of turin towards asti this model implies that slabs of upper mantle or lower continental crust were trapped in the suture as in the internal zone of the western alps where the ivrea body comes in contact at depth with the pennidic nappes to the south this suture line does not appear throughout the ligurian sea probably owing to the recent crustal thinning which is revealed by both the magnetic and the gravimetric features

on the use of global potential field models for regional interpretation of the west and central african rift system abstract the use in regional interpretations of the earth gravity model egm08 and earth magnetic model emag2 is evaluated by comparison to ground gravity and aeromagnetic data in the central sector of the west and central african rift system wcars the comparison includes upward continuation spectral analysis and pseudogravity calculation and statistical evaluation a correlation between emag2 which contains roughly 25 km resolution aeromagnetic data in the region and near surface aeromagnetic data over wcars is only true for the very low wavelength part but a strong similarity between egm08 and ground gravity data can be confirmed interpretation of the egm08 data allows identifying and confirming the position of major structural trends and provides new information on the crustal architecture the lineaments limiting different grabens forming the logone birni basin and in the southern chad basin are identified the results presented here show the use of egm08 data for regional interpretations over cameroon and adjacent countries which can overcome the absence and sparseness of data in developing countries and remote areas

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

reservoir characterization using surface microseismic monitoring microseismic monitoring of reservoir processes can be performed using surface or near surface arrays we review the published technical basis for the use of the arrays and the historical development of the method beginning with locating earthquakes through geothermal exploration to the growing field of hydraulic fracture monitoring practical considerations for the array deployment and data processing are presented the road ahead for the technology includes a move toward life of field buried arrays as well as opportunities for extended interpretation of the data particularly inversion for source mechanism estimation and measurement of anisotropy in the monitored subsurface

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

teleseismic p wave imaging of the 26 december 2004 sumatra andaman and 28 march 2005 sumatra earthquake ruptures using the hi net array 1 seismograms from a dense high quality seismic network in japan are used to investigate the characteristics of the 26 december 2004 sumatra andaman and the 28 march 2005 sumatran earthquakes the onset of the p waveforms are aligned through cross correlation and a simple concept of back projecting seismic energy to a grid of potential source locations is applied the waveform alignment removes the effects due to lateral variations in wave speed between the hypocenter and each station to better approximate the effects of three dimensional heterogeneity for paths originating from grid points away from the hypocenter cross correlation results of the p waveforms from aftershocks are introduced this additional information leads to improved resolution of smaller scale features near many of the aftershocks by reducing wavefront distortion the back projection analysis provides a quick assessment of the spatiotemporal extent and variability of relative high frequency energy release which can be translated into an estimate of the moment magnitude as well as an unparalleled view of high frequency rupture propagation the results are in general consistent with those obtained from more involved source inversion methods the 2004 sumatra andaman earthquake released most energy in a region northwest of the sumatra island and the rupture extended to the northern andaman islands about 1300 km from the epicenter this northern portion of the rupture radiated a considerable amount of energy but there is little evidence of slow slip the 2005 event is imaged to have bilateral rupture with northwestern slip occurring for about 50 s before it moved to the southeast of the epicenter

three dimensional velocity structure in northern california coast ranges from inversion of local earthquake arrival times abstract the three dimensional p wave velocity structure in the upper crust in the northern california coast ranges from santa rosa to ukiah is obtained by simultaneous inversion of local earthquake and refraction travel time data for velocity and hypocentral parameters in this region where there are lateral heterogeneities the three dimensional inversion provides important results not found in two dimensional refraction studies the medium is parameterized with velocities at the intersections gridpoints of a nonuniform three dimensional grid travel times are calculated with approximate ray tracing along arcuate paths which are reasonable for lateral distances less than 45 km inversions with 5 to 10 and 2 to 3 km gridspacing achieved 80 per cent decreases in data variance the inversion with 2 to 3 km gridspacing reduced the rms residual level to approximately the level of timing error anomalously low velocities to at least 6 km depth are found along the maacama and healdsburg rodgers creek hrc fault zones the low velocity region is widest at the en echelon junction of the maacama and hrc fault zones low velocities are associated with the clear lake basin where there is a thick sequence of volcanics interbedded with sedimentary deposits there is a high velocity body located southeast of the geysers between the maacama and collayomi fault zones which may be associated with igneous intrusives or high grade metamorphism related to an underlying inferred partial melt body modeled in previous teleseismic travel time studies there is some indication in the vapor dominated geothermal reservoir of lower velocities relative to surrounding water saturated rock as has been shown in some laboratory experiments hypocenter locations obtained in the inversion show little variation from hypocenters obtained through inversion for one dimensional velocity model and station corrections for the inversion with 2 to 3 km gridspacing however some groups of events become more tightly clustered

several location methods for underwater shots in the gulf of genoa western mediterranean structural implications abstract during the egt survey 50 underwater shots were detonated on a n s section through the gulf of genoa running from the northern margin 44 12 n towards corsica 42 90 n along the 9 e meridian the aim of this work is in a first stage to establish the propagation model of regional phases in this region and consequently to improve the location of epicentres and afterwards to refine our structural knowledge of this complex crustal area the relocation of these shots was carried out with arrival times of seismic signals recorded at land stations we have used different location methods all of which led to similar crustal models they reveal a low p n velocity area in the northern ligurian sea and in the gulf of genoa with a 20 km thick crust in the southern part approximately south of latitude 43 7n a 4 km thick oceanic crust covered by 8 km of sediments is clearly confirmed using these models a significant improvement of epicentre locations was obtained these improvements to propagation models lead to the two main structural conclusions 1 1 in the southern part of the investigated area the spread of an oceanic type domain as far as the foot of the continental margin 2 2 a sharp transition between the two domains of different stretching rate the northern one with a moho depth of about 20 km and the southern one with an average moho depth of about 14 km these observations substantiate the presence of a transform margin between the rifted gulf of genoa and the oceanic type ligurian basin

cone penetration testing to assess slope stability in the 1979 nice landslide area ligurian margin se france abstract in the landslide prone area near the nice international airport southeastern france an interdisciplinary approach is applied to develop realistic lithological geometrical profiles and geotechnical strength sub seafloor models such models are indispensable for slope stability assessments using limit equilibrium or finite element methods regression analyses based on the undrained shear strength s u of intact gassy sediments are used to generate a sub seafloor strength model based on 37 short dynamic and eight long static piezocone penetration tests and laboratory experiments on one calypso piston and 10 gravity cores significant strength variations were detected when comparing measurements from the shelf and the shelf break with a significant drop in s u to 5 5 kpa being interpreted as a weak zone at a depth between 6 5 and 8 5 m below seafloor mbsf here a 10 reduction of the in situ total unit weight compared to the surrounding sediments is found to coincide with coarse grained layers that turn into a weak zone and detachment plane for former and present day gravitational retrogressive slide events as seen in 2d chirp profiles the combination of high resolution chirp profiles and comprehensive geotechnical information allows us to compute enhanced 2d finite element slope stability analysis with undrained sediment response compared to previous 2d numerical and 3d limit equilibrium assessments those models suggest that significant portions detachment planes at 20 m or even 55 mbsf of the quaternary delta and slope apron deposits may be mobilized given that factors of safety are equal or less than 1 when further considering the effect of free gas a high risk for a landslide event of considerable size off nice international airport is identified

geochemistry of highly undersaturated ocean island basalt suites from the south atlantic ocean fernando de noronha and trindade islands the volcanic rocks of the south atlantic ocean islands of fernando de noronha and trindade comprise a diverse magmatic series ranging from nephelinites and basanites to phonolites and on fernando de noronha trachytes all rock types are highly silica undersaturated with the exception of fernando de noronha trachytes and have high abundances of incompatible trace elements and strongly lree light rare earth element enriched ree patterns crystal fractionation of parental basanitic magmas produced evolved phonolites and trachytes which display severe trace element fractionation even among trace elements nb ta zr hf which normally behave highly incompatibly during crystallisation of alkaline magmas moderately to highly evolved compositions develop strongly mree middle ree depleted ree patterns and become increasingly depleted in elements such as nb and in particular ta ratios of nb ta and zr hf are highly fractionated in phonolites 60 65 64 77 respectively in fernando de noronha phonolites compared to ratios in basanites 14 45 respectively the compatibility of nb ta and the ree and the strong fractionation of nb ta and zr hf ratios and the mree during crystallisation from basanite to phonolite are attributable to the crystallisation of small amounts 5 of sphene trace element behaviour is relatively insensitive to the major phenocryst phases and is controlled by minor phases in highly undersaturated alkaline suites incompatible trace element ratios e g la nb th ta in nephelinites and basanites from fernando de noronha and trindade are generally comparable with those in basaltic and hawaiitic oib ocean island basalt lavas from other south atlantic islands but are distinct from those of gough and tristan da cunha oib the mantle source for the highly undersaturated volcanism on fernando de noronha and trindade is similar in trace element characteristics to the typical oib source which produces alkaline lavas with significant relative enrichment in nb and ta compared to other trace elements as expressed by low la nb ba nb and th ta ratios the highly undersaturated nature of the magmas and the slight fractionation of some incompatible element ratios elevated ba nb ba rb ba th etc is consistent with a smaller degree of melting of a typical oib source but with residual phlogopite in the source to account for significant k depletion and lil element fractionation

earthquake relocation using a 3d a priori geological velocity model from the western alps to corsica implication for seismic hazard the region between the inner zones of the alps and corsica juxtaposes an overthickened crust to an oceanic domain which makes difficult to ascertain the focal depth of seismic events using routine location codes and average 1d velocity models the aim of this article is to show that even with a rather lose monitoring network accurate routine locations can be achieved by using realistic 3d modelling and advanced location techniques previous earthquake tomography studies cover the whole region with spatial resolutions of several tens of kilometres on land but they fail to resolve the marine domain due to the absence of station coverage and sparse seismicity to overcome these limitations we first construct a 3d a priori p and s velocity model integrating known geophysical and geological information significant progress has been achieved in the 3d numerical modelling of complex geological structures by the development of dedicated softwares e g 3d geomodeller capable at once of elaborating a 3d structural model from geological and geophysical constraints and possibly of refining it by inversion processes calcagno et al 2008 then we build an arrival time catalogue of 1500 events recorded from 2000 to 2011 hypocentres are then located in this model using a numerical code based on the maximum intersection method font et al 2004 updated by theunissen et al 2012 as well as another 3d location technique the nonlinloc software lomax and curtis 2001 the reduction of arrival time residuals and uncertainties dh dz with respect to classical 1d locations demonstrates the improved accuracy allowed by our approach and confirms the coherence of the 3d geological model built and used in this study our results are also compared with previous works that benefitted from the installation of dense temporary networks surrounding the studied epicentre area the resulting 3d location catalogue allows us to improve the regional seismic hazard assessment more particularly in the south of the argentera massif and in the ligurian basin

silicic magmas from the continental cameroon volcanic line oku bambouto and ngaoundere 40 ar 39 ar dates petrology sr nd o isotopes and their petrogenetic significance the intraplate cameroon volcanic line cvl straddles the african south atlantic continent ocean boundary and is composed mainly of alkaline basic volcanic rocks voluminous silicic volcanics characterize the continental sector of the cvl we present here new geochemical isotopic sr nd o and 40ar 39ar geochronological data on the main silicic volcanic centres of the western mt oku sabga and mt bambouto and eastern ngaoundere plateau cameroon highlands the silicic volcanism of mt oku sabga and mt bambouto occurred between 25 and 15 ma and is represented by voluminous quartz normative trachytes and minor rhyolitic ignimbrites at mt bambouto central volcano about 700 m of silicic volcanics erupted in less than 2 7 million years these silicic volcanics are associated with slightly to moderately alkaline basalts and minor basanites in general onset of the silicic volcanism migrated from ne oku 25 ma to sw sabga 23 ma bambouto 18 ma and mt manengouba 12 ma the silicic volcanism of the ngaoundere plateau eastern branch of the cvl is instead dominated by nepheline normative trachytes which are associated with strongly alkaline basalts and basanitic rocks these ne trachytes are younger 11 9 ma than the q trachytes of the western highlands the least differentiated silicic volcanics are isotopically similar 87sr 86sr 0 51278 to the associated alkaline basalts suggesting differentiation processes without appreciable interaction with crustal materials such interactions may however have played some role in the genesis of the most evolved silicic volcanics which have 87sr 86sr as high as 0 705 0 714 fractional crystallization is the preferred mechanism for genesis of the silicic melts of both western and eastern highlands as shown by modeling major and trace element variations the genesis of the least evolved q trachytes from the western highlands starting from slightly to moderately alkaline basalts is compatible with fractionation of dominantly plagioclase clinopyroxene and magnetite crystal fractionation may have occurred at low pressure and at qfm buffer f o2conditions parental magmas of the ngaoundere ne trachytes are likely instead to have been strongly alkaline basalts which evolved through crystal fractionation at higher p 6 2 kbar and f o2 qfm 2 the migration 25 to 12 ma of the silicic volcanism from ne to sw in the continental sector of the cvl is reminiscent of that 31 5 ma of the onset of the basic volcanism in the oceanic sector principe to pagalu islands of the cvl these ages and that 11 9 ma of the silicic volcanism of the ngaoundere plateau indicate that the cameroon volcanic line as a whole may not be easily interpreted as the surface expression of hot spot magmatism

rheology and seismotectonic regime in the northern central mediterranean abstract the connection between thermal field and mechanical properties is analysed in the northern central mediterranean region extending from the ligurian provencal basin to the adriatic foredeep as the thermal regime is still far from equilibrium in most of the tectonic units transient thermal models are used the temperature depth distribution is estimated in four areas affected by the volcanic activity which from the neogene to the present shifted from corsica to the apenninic arc in the adriatic foredeep the thermal effects of the recent thrust faulting phase in the buried sectors of the northern apennines are taken into account the general context consists of convergence involving westward subduction of the adriatic plate this process caused anti clockwise rotation of corsica and sardinia which led to formation of the ligurian marginal basin and also resulted in crustal doubling and overthrusting in the northern apennines and rifting in the northern tyrrhenian seismic activity is focused in the internal and external zones of the apenninic arc where low surface heat flux is observed and in the western margin of the ligurian provencal basin this is a consequence not only of lateral variations in the thermal field but also of the different tectonic settings regional extensional patterns in the shallow crust with minimum principal stress axes trending n60 e and e w are observed in the northern and in the southern sectors of the apenninic arc respectively a compressional regime at depths greater than 30 km is observed below the northern sector of the arc while to the south a change in the structure of the lithosphere is marked by a decrease in deeper seismic activity thrust faults and strike slip faults with a thrust component support a compressional regime along the western margin of the ligurian basin with maximum principal stress axis oriented n120 e two lithospheric cross sections across the study region are constructed based on structural thermal gravity rheological and seismic data there is clear evidence of the presence of the subducting slab of the adriatic plate corresponding to a thickening of the uppermost brittle layer the crustal seismicity cut off corresponds to temperatures of 320 390 c a brittle layer of considerable thickness is present in the uppermost mantle beneath variscan corsica and the adriatic foredeep with estimated seismic cut off temperature of about 550 50 c

crustal structure from the ligurian sea to the northern apennines a wide angle seismic transect abstract a new wide angle seismic reflection profile 250 km long was shot along a line extending from parma in the apennines to the deepest part of the ligurian sea thirty seismic land stations lobs and 25 ocean bottom seismographs obs recorded 54 shots fired at sea the resulting 55 record sections allowed the definition of the transition from continental to oceanic crust in a geologically complex and hitherto poorly understood region the subducted continental crust beneath the northern apennines has a thickness of 40 km consisting of 30 km of igneous crust overlain by 10 km of sediments two sedimentary layers are identified with vp velocities in the range from 2 8 to 5 5 km s the igneous portion of continental crust thins gradually to approx 11 km across a 120 km wide zone extending from the southwestern part of the apennines some 20 km inland into the ligurian sea an easterly thinning low velocity body 7 2 7 5 km s immediately beneath the base of the crust is interpreted as an underplated unit emplaced prior to the onset of seafloor spreading this may have been initiated by magmatic activity along the incipient continental oceanic boundary a basement high coincides with the northeastern edge of the ligurian sea and is interpreted as part of the alpine ophiolite belt indicating strike slip motion the two sedimentary layers above the transition zone are typically 5 km thick and have slightly lower velocities than those further to the northeast a sharp continent ocean break is recognised in the ligurian sea oceanic crust is 6 7 km thick and is overlain by a two layered sedimentary succession approx 5 km thick mantle velocities in the region range from 7 9 km s beneath the thinned crust to 8 1 km s beneath the thick crust the ratio c o of continental to oceanic crustal thickness at the continent ocean transition is approx 1 5 and the overall crust stretching factor at that boundary is approx 3 5 these values are similar to other continent ocean boundaries and indicate that the oceanic crust in the ligurian sea formed largely by stretching with a small pull apart component

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

european geotraverse a seismic refraction profile across the ligurian sea abstract a seismic refraction profile was shot in the ligurian sea between italy and corsica in september 1983 the profile which is part of the southern portion of the european geotraverse was shot using small dynamite charges and the seismograms were recorded by ocean bottom seismometers and land stations resulting in a number of partially overlapping reversed profiles the refraction data were interpreted by means of the velocity intercept and ray tracing methods using seismic reflection derived velocity depth information for the sedimentary section refraction velocities of 4 8 6 0 and 6 6 km s 1 were calculated for the base of the sedimentary section crystalline basement and lower crust respectively an upper mantle velocity of 7 4 km s 1 was inferred using the refraction profiles recorded on corsica the interpretation of the data indicates a prominent high in the crystalline basement in the northern part of the profile while the sedimentary section increases in thickness from about 1 5 km over the basement high to over 6 km between the basement high and corsica and includes a considerable thickness of pre miocene sediments the crust mantle boundary shows shoaling towards the centre of the profile where a minimum crustal thickness of 16 km is reached the model therefore is that of a stretched and thinned continental crust which was rifted in oligo miocene times the presence of a low velocity upper mantle may be indicative of the present renewal of subcrustal activity under the ligurian sea

high frequency of sediment gravity flow events in the var submarine canyon mediterranean sea this study aimed to analyze the role river floods play in triggering gravity flows and to investigate the role of submarine canyon systems as a conduit for terrigenous material to the deep sea two years of measurements in the var canyon at depths ranging from 1200 m to 2350 m indicate that six floods of the var river triggered hyperpycnal flows an important mechanism for transporting particulate matter to the deep sea floor these sediment gravity flows were characterized by a sudden increase of current velocity that lasted 8 to 22 h and by downward particle fluxes that reached up to 600 g m 2 d 1

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

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

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

chronic offshore loss of nourishment on nice beach french riviera a case of over nourishment of a steep beach abstract the 4 5 km long gravel beach fronting the exclusive resort of the city of nice on the french riviera in southeastern france was artificially nourished from 1976 to 2005 to the tune of 558 000 m3 making this long term operation one of the most significant for gravel beaches in the world nourishment has ranged from nil in certain years 1979 1980 1983 85 and 2001 2002 to a peak of over 97 000 m3 in 2000 analyses of 50 transects covering the beach highlight no significant change in net beach width over this 30 year period of massive gravel nourishment a principal components analysis and a cluster analysis used to detect patterns in the 87 beach width measurement dataset show no clear spatial trends in transect groups that can be interpreted in terms of the morphology of the beach and the steep inner shoreface significant wave height off nice shows no change over the period 1979 2005 since there is no possibility for alongshore gravel leakage on the strongly embayed nice beach the relative stability in beach width clearly implies loss of recharged gravel offshore gravel loss following nourishment is favoured by 1 the steep inner shoreface inherited from the geological context of nice beach at the flanks of the southern alps and 2 the practise of artificial beach widening through flattening in summer of a narrow 5 15 m wide mobile zone of the profile in order to enhance the carrying capacity of this highly touristic beach beach widening and flattening following nourishment bring close to the very steep inner shoreface zone several cubic metres of gravel for each metre of beach that may be permanently lost downslope during autumn and winter storms recharged gravel is redistributed alongshore and offshore leakage is probably enhanced where small narrow submarine canyon heads impinge on the beach resulting in a very narrow shoreface mean beach width shows an oscillating alongshore pattern that may be due to the influence of these canyons as pathways of gravel loss offshore however there is no correlation between mean beach width and distance to the 10 m isobath used as a surrogate for inner shoreface width storms are associated with plunging waves that are particularly effective and concentrated on this almost tideless shore over the narrow mobile zone of the beach profile where a series of steep reflective berms are built during storms the high dynamic pressures associated with this narrow zone of concentrated wave breaking and energy reflection from the steepened profile are deemed to contribute to the permanent downslope loss of gravel this situation of long term gravel loss is probably accepted by the beach management authority because of the low cost of obtaining nourishment material and the advantages derived from a temporarily wider beach in terms of recreational space

3d crustal structure from local earthquake tomography around the gulf of arta ionian region nw greece during summer of 1995 local seismicity was recorded in the area around the gulf of arta in northwestern greece by a dense temporary seismic network of the 441 local events observed at 37 stations 232 well locatable events with a total of 2776 p phase readings were selected applying the criteria of a minimum of 6 p observations and an azimuthal gap less than 180 this data set is used to compute a minimum 1d velocity model for the region several tests are conducted to estimate model stability and hypocenter uncertainties leading to the conclusion that relative hypocenter location accuracy is about 500 m in latitude and longitude and 1 km in depth the minimum 1d velocity model serves as initial model in the non linear inversion for three dimensional p velocity crustal structure by iteratively solving the coupled hypocenter velocity problem in a least squares sense careful analysis of the resolution capability of our data set outlines the well resolved features for interpretation the resulting 3d velocity model shows generally higher average crustal velocities in the east and the well resolved area of the eastern gulf of arta exhibits a homogeneous velocity around 6 km s for the whole upper crust a pronounced north south trending zone of low velocities in the upper 5 10 km is observed in the area of the katouna fault zone kfz at greater depths below 10 km the kfz is underlain by high velocity material e w profiles suggest a horst graben structure associated with the kfz

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

earthquake locations and three dimensional crustal structure in the coyote lake area central california previous work on the simultaneous inversion method has been improved and extended to incorporate iterative solution for earthquake locations and laterally heterogeneous structure approximate ray tracing and parameter separation are important elements of the improved method application of the method to p wave arrival time data recorded by stations of the u s geological survey central california network yields a three dimensional model for the velocity structure of the upper crust in an area encompassing the rupture zone of the coyote lake earthquake of august 1979 very strong correlations between the velocity model and the geology and gravity and magnetic anomalies are observed improved estimates of the locations of earthquakes in the study area are also determined the relocation of explosions indicates epicentral accuracies of the order of a kilometer or better based on the revised hypocentral locations it is concluded that the san andreas fault is vertical in this area with no actual offset between the epicenters and the fault trace in contrast the calaveras has two or more active fault surfaces one nearly vertical and another dipping 75 to the northeast

the influence of debris flows on channels and valley floors in the oregon coast range u s a debris flows are one of the most important processes which influence the morphology of channels and valley floors in the oregon coast range debris flows that initiate in bedrock hollows at heads of first order basins erode the long accumulated sediment and organic debris from the floors of headwater first and second order channels this material is deposited on valley floors in the form of fans levees and terraces in channels deposits of debris flows control the distribution of boulders the stochastic nature of sediment supply to alluvial channels by debris flows promotes cycling between channel aggradation which results in a gravel bed morphology and channel degradation which results in a mixed bedrock and boulder bed morphology temporal and spatial variability of channel bed morphology is expected in other landscapes where debris flows are an important process

landslide induced river channel avulsions in mountain catchments of southwest new zealand pulsed or chronic supply of landslide debris to valley floors has historically caused substantial aggradation and channel instability in several alpine catchments of sw new zealand in this regional investigation of landslide impacts on river morphology three types of landslide induced channel avulsion are discerned i upstream backwater avulsions ii contact avulsions and iii downstream loading avulsions the basis for this qualitative geomorphic process response framework is the principal direction of fluvial response with respect to its position relative to the causative landslide emplacement site downstream avulsions have the highest damage potential to land use and infrastructure on unconfined mountain fringe alluvial fans in the wake of such events catastrophic aggradation may obliterate up to several km2 of mature floodplain forests by burial under several metres within a few decades estimates of mean aggradation rates are high 220 mm year 1 and exceed long term 103 year trends of fluvial degradation by an order of magnitude future potential avulsion routeways may be detected by geomorphic mapping of abandoned channels which are preferentially reactivated in the wake of landslide induced sediment waves

a new tectonic model for the cameroon line central africa abstract the cameroon line a major geological feature in central africa has been considered successively as a series of horsts and grabens a continental rift and a mega shear zone it is marked out by about 60 anorogenic complexes and a dozen volcanic centres all of which have alkaline affinity remote sensing allows us recognition of the main lineament trends n70 n s n135 and e w while autocorrelation analysis reveals a major fault zone striking n30 in western cameroon and n15 in the northern region a mega left lateral shear zone is the model that best accounts for the fracture pattern and associated features such as linear and circular structures alignment of subvolcanic complexes syntectonic leucogranites marking out older shear zones and vein dykes the n70 adamawa fault zone a pan african fracture reworked during albian aptian times is the only shear zone of continental scale that could have initiated en echelon mega tension gashes within the cameroon line during a cainozoic left lateral transcurrent movement

evaluating weathering of palaeosols in cameroon central africa as a tool for paleoenvironmental reconstruction abstract palaeosols formed from different igneous rocks have been identified and characterized in the humid savannas 1400 mm mean annual rainfall 22 c mean annual temperature of the adamaoua region in north central cameroon by means of macro and micromorphology geochemical analyses and bulk mineralogy the studied sequence at mangoli is about 11 m deep and is divided into three sections in terms of weathering products 1 precambrian granite located in the base 2 vesicular porphyritic basalt in the middle section 3 aphanitic basalt in the uppermost layer the products of weathering from the precambrian granite consist of the following horizons from bottom to top a saprolite with granite structure a yellowish to whitish fine saprolite and btg and bt horizons the saprolite horizon is dominated by quartz feldspars plagioclases and microcline and muscovite primary minerals except quartz show weathering while clay fills the pores and fractures and kaolinite dominates the clay mineralogy the granite weathering products are slightly acidic ph ranging from 5 9 to 6 3 and display low values of fe extracted with dithionite soluble fe fed and high chemical index of alteration cia and mineral index of alteration mia values the middle section of the sequence consists of different areas of the basalt s spheroidal weathering zone from the more advanced to the less weathered phase the clay mineralogy is dominated by kaolinite the zones with the most alteration are the fractures where thick reddish clay coatings are observable in these areas the minerals are well crystallized the kaolinite crystals share areas with fe oxides the upper section of the sequence constitutes the modern soil from the aphanitic basalt and consists of a spheroidal weathering zone divided into three horizons the lowest is a c horizon overlaid by bt horizons the c horizon shows a high degree of weathering in some areas but it is still possible to identify the primary minerals their products of weathering are slightly acidic ph 6 and have high fed cia and mia values which are indicative of intense weathering the results suggest warm and humid climates during the formation of all of the palaeosols similar to modern environmental conditions we conclude that palaeosol 1 formed from the granite represents a soil formed during the mid miocene climatic optimum when the temperatures are assumed to have been 3 6 c warmer than today features discovered during field investigations reveal that the former valley at the surface of the landscape has been filled by lava flows and today occupies the top of the plateau meanwhile the former top of the plateau is located on the slopes and lower altitudes the burial of soils by volcanic materials at mangoli increased the altitudes of the former plateau and resulted in landscape inversion slopes these palaeosols and their top layers that induced the slope inversion have not yet been described and appear as a unique example worldwide