elastic full waveform inversion of multi component obc seismic data elastic full waveform inversion of seismic reflection data represents a data driven form of analysis leading to quantification of sub surface parameters in depth in previous studies attention has been given to p wave data recorded in the marine environment using either acoustic or elastic inversion schemes in this paper we exploit both p waves and mode converted s waves in the marine environment in the inversion for both p and s wave velocities by using wide angle multi component ocean bottom cable seismic data an elastic waveform inversion scheme operating in the time domain was used allowing accurate modelling of the full wavefield including the elastic amplitude variation with offset response of reflected arrivals and mode converted events a series of one and two dimensional synthetic examples are presented demonstrating the ability to invert for and thereby to quantify both p and s wave velocities for different velocity models in particular for more realistic low velocity models including a typically soft seabed an effective strategy for inversion is proposed to exploit both p and mode converted ps waves whilst p wave events are exploited for inversion for p wave velocity examples show the contribution of both p and ps waves to the successful recovery of s wave velocity

landslides and climate change in the italian dolomites since the late glacial abstract the paper deals with the relationship between the temporal occurrence of landslides and climatic changes in the italian dolomites since the late glacial after an introduction on the state of the art with particular reference to the alpine region the results of recent investigations in the two study sites are illustrated at cortina d ampezzo several landslides were dated mainly by the radiocarbon method the most ancient landslide event there involved large rock slides which affected the dolomitic slopes following the withdrawal of glaciers after the last glacial maximum lgm and also slides and flows mainly occurring in pelitic materials of the valley floors from 13 000 to 10 000 cal bp a later series of flows occurred between 5500 and 2500 cal bp in the upper badia valley alta badia the most ancient events go back to 10 000 and 9000 cal bp and correspond with earth flows that followed vast rotational slides affecting the bedrock up to a depth of about 50 m more recent earth flows involving more modest amounts of material took place between 6500 and 2300 cal bp by analysing the dates from the two study areas it was possible to correlate the recorded increase of landslide activity with the climatic changes occurring at the boundary between the late glacial and the holocene and between the atlantic and the subboreal and to compare the results with those derived from other european regions the types and causes of landslides taking place in these two periods were substantially different reflecting the different morphoclimatic conditions that existed in the two areas when these mass movements were triggered finally notwithstanding the importance of non climatic causes such as geological structural factors and possible human influences it is concluded that many of the dated landslides can be considered as indicators of climatic change

monte carlo estimation and resolution analysis of seismic background velocities the complete solution to an inverse problem including information on accuracy and resolution is given by the a posteriori probability density in the model space by running a modified simulated annealing samples from the model space can be drawn in such a way that their frequencies of occurrence approximate their a posteriori likelihoods using this method maximum likelihood estimation and uncertainty analysis of seismic background velocity models are performed on multioffset seismic data the misfit between observed and synthetic waveforms within the time windows along computed multioffset travel times is used as an objective function for the simulated annealing approach the real medium is modeled as a series of layers separated by curved interfaces lateral velocity variations within the layers are determined by interpolation from specified values at a number of sampling points the input data consists of multioffset seismic data additionally zero offset times are used to migrate the reflectors in time to the depth domain the multioffset times are calculated by an efficient ray tracing algorithm which allows inversion of a large number of seismograms the a posteriori probability density for this problem is highly multidimensional and highly multimodal therefore the information contained in this distribution cannot be adequately represented by standard deviations and covariances however by sequentially displaying a large number of images computed from the a posteriori background velocity samples and the data it is possible to convey to the spectator a better understanding of what information we really have on the subsurface

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

pre stack full waveform inversion of ultra high frequency marine seismic reflection data the full waveform inversion fwi of seismic reflection data aims to reconstruct a detailed physical properties model of the subsurface fitting both the amplitude and the traveltime of the reflections generated at physical discontinuities in the propagation medium unlike reservoir scale seismic exploration where seismic inversion is a widely adopted remote characterization tool ultrahigh frequency uhf 0 2 4 0 khz multichannel marine reflection seismology is still most often limited to a qualitative interpretation of the reflections architecture here we propose an elastic fwi methodology custom tailored for pre stack uhf marine data in vertically heterogeneous media to obtain a decimetric scale distribution of p impedance density and poisson s ratio within the shallow subseabed sediments we address the deterministic multiparameter inversion in a sequential fashion the complex trace instantaneous phase is first inverted for the p wave velocity to make up for the lack of low frequency in the data and reduce the nonlinearity of the problem this is followed by a short offset p impedance optimization and a further step of full offset range poisson s ratio inversion provided that the seismogram contains wide reflection angles 40 we show that it is possible to invert for density and decompose a posteriori the relative contribution of p wave velocity and density to the p impedance a broad range of synthetic tests is used to prove the potential of the methodology and highlights sensitivity issues specific to uhf seismic an example application to real data is also presented in the real case trace normalization is applied to minimize the systematic error deriving from an inaccurate source wavelet estimation the inverted model for the top 15 m of the subseabed agrees with the local lithological information and core log data thus we can obtain a detailed remote characterization of the shallow sediments using a multichannel sub bottom profiler within a reasonable computing cost and with minimal pre processing this has the potential to reduce the need of extensive geotechnical coring campaigns

quantifying sediment supply at the end of the last glaciation dynamic reconstruction of an alpine debris flow fan in this paper we quantify the sediment dynamics in the formerly glaciated zielbach catchment in the italian alps from the end of the last glacial maximum lgm until today as a basis for our quantification we use the stratigraphic record offered by a 3 5 km2 large fan that we explore with a seismic survey stratigraphic analyses of drillhole material and 14c ages measured on organic matter encountered in these drillings in addition we calculate past denudation rate variability in the fan deposits using concentrations of cosmogenic 10be we merge this information into a scenario of how the sediment flux has changed through time and how this variability can be related to climatic variations framed within well known paraglacial models the results document a highly complex natural system from the lgm to the very early holocene ice melted discharge and climate variability promoted a high sediment flux sedimentation rate up to 40 mm yr this flux then dramatically decreased toward interglacial values 0 8 mm yr at 5 4 calibrated kyr b p however in contrast to the trend of classic paraglacial models the flux recorded at zielbach shows secondary peaks at 6 5 ka and 2 5 ka with values of 13 mm yr and 1 5 mm yr respectively paleo denudation rates also decrease from 33 mm yr at the beginning of the holocene to 0 42 mm yr at 5 ka with peaks of 6 mm yr and 1 1 mm yr at 6 5 ka and 2 5 ka high amplitude climate change is the most likely cause of the secondary peaks but anthropogenic activities may have contributed as well the good correlation between paleo sedimentation and paleo denudation rates suggests that the majority of the deglaciated material destocked from the zielbach catchment is stored in the alluvial fan

an alternative strategy for non linear inversion of seismic waveforms1 a common example of a large scale non linear inverse problem is the inversion of seismic waveforms techniques used to solve this type of problem usually involve finding the minimum of some misfit function between observations and theoretical predictions as the size of the problem increases techniques requiring the inversion of large matrices become very cumbersome considerable storage and computational effort are required to perform the inversion and to avoid stability problems consequently methods which do not require any large scale matrix inversion have proved to be very popular currently descent type algorithms are in widespread use usually at each iteration a descent direction is derived from the gradient of the misfit function and an improvement is made to an existing model based on this and perhaps previous descent directions a common feature in nearly all geophysically relevant problems is the existence of separate parameter types in the inversion i e unknowns of different dimension and character however this fundamental difference in parameter types is not reflected in the inversion algorithms used usually gradient methods either mix parameter types together and take little notice of the individual character or assume some knowledge of their relative importance within the inversion process we propose a new strategy for the non linear inversion of multi offset reflection data the paper is entirely theoretical and its aim is to show how a technique which has been applied in reflection tomography and to the inversion of arrival times for 3d structure may be used in the waveform case specifically we show how to extend the algorithm presented by tarantola to incorporate the subspace scheme the proposed strategy involves no large scale matrix inversion but pays particular attention to different parameter types in the inversion we use the formulae of tarantola to state the problem as one of optimization and derive the same descent vectors the new technique splits the descent vector so that each part depends on a different parameter type and proceeds to minimize the misfit function within the sub space defined by these individual descent vectors in this way optimal use is made of the descent vector components i e one finds the combination which produces the greatest reduction in the misfit function based on a local linearization of the problem within the subspace this is not the case with other gradient methods by solving a linearized problem in the chosen subspace at each iteration one need only invert a small well conditioned matrix the projection of the full hessian on to the subspace the method is a hybrid between gradient and matrix inversion methods the proposed algorithm requires the same gradient vectors to be determined as in the algorithm of tarantola although its primary aim is to make better use of those calculations in minimizing the objective function

the schneeberg normal fault zone normal faulting associated with cretaceous se directed extrusion in the eastern alps italy austria abstract the cretaceous eo alpine collisional event in the european eastern alps is generally accepted to induce w nw directed thrusting both in basement and in sedimentary cover units this study presents the first evidence of eo alpine w nw directed normal kinematics along the schneeberg normal fault zone which separates eo alpine high pressure rocks in a footwall position from pre alpine basement rocks in a hanging wall position new garnet sm nd data indicate that exhumation of the high pressure rocks along the normal fault zone started around 95 ma ago and continued up to low greenschist brittle conditions at 76 ma as indicated by a rb sr age from a low temperature mylonite the occurrence of pre alpine basement rocks both in the hanging wall and the footwall of eo alpine high pressure rocks suggests exhumation by extrusion processes despite the displacement or removal of parts of the lower portion of the high pressure unit by tertiary strike slip faults eo alpine top to ese thrusting as expected for the structurally lower part of an extruding wedge was found at and below the base of the eo alpine high pressure rocks a rb sr age of 77 ma from a greenschist facies mylonite in this thrust shear zone shows the contemporaneity of deformation at the base and the top of the wedge the tectonic transport direction within the extruding wedge was e se opposite to the w nw direction so far reported for the eo alpine event in the eastern alps the contemporaneity of opposite tectonic transport directions during continental subduction may be explained by a double vergent wedge model with a narrow zone of ductile flow where the high pressure rocks were exhumed

large scale erosion rates from in situ produced cosmogenic nuclides in european river sediments abstract we have calculated long term erosion rates of 20 100 mm kyr from quartz contained 10be in the bedload of middle european rivers for catchments ranging from 102 to 105 km2 these rates average over 10 40 kyr and agree broadly with rock uplift incision and exhumation rates historic soil erosion rates and erosion rates calculated from the measured sediment loads of the same rivers moreover our new erosion rate estimates correlate well with lithology and relief however in the regen neckar loire and meuse catchments cosmogenic nuclide derived erosion rates are consistently 1 5 4 times greater than the equivalent rates derived from measured river loads this may be due to the systematic under representation of high magnitude low frequency transport events in the gauging records which cover less than a century alternatively the discrepancy may derive from spatially non uniform erosion and preferential tapping of deeper sections of the irradiation profile a third explanation relates the high cosmogenic nuclide derived erosion rates to inheritance of an elevated pleistocene erosion signal uncertainties associated with the cosmogenic nuclide derived erosion rate estimates are not greater than the potential errors in conventional estimates therefore the cosmogenic nuclide approach is an effective tool for rapid catchment wide assessment of time integrated rates of bedrock weathering and erosion and we anticipate its fruitful application to the quaternary sedimentary record

inversion migration tomography seismic inversion broadly enough defined is equivalent to doing migration and reflection tomography simultaneously diffraction tomography and inversion work best when sources and receivers surround the region of interest as in medical imaging applications theoretical studies have shown that high vertical wavenumber velocity perturbations are resolved by inverting surface seismic reflection data but the low vertical wavenumbers must be obtained using a separate step such as velocity analysis or reflection tomography i propose that a nonlinear iterative inversion that updates a varying background velocity obtains all wavenumbers that are resolvable separately by migration and tomography the background velocity must contain reflectors to provide data on both upward and downward transmission paths through the earth and hence the low wavenumbers by considering the downward transmission paths to be between surface sources and buried image geophones and the upward transmission paths to be between surfa

ultra rapid landscape response and sediment yield following glacier retreat icy bay southern alaska abstract glacial retreat and opening of taan fjord an arm of icy bay alaska in the last two decades drove a base level fall of 400 m at the outlets of four tributary valleys in the region of the current tyndall glacier terminus response in the tributary valleys to this base level fall includes evacuation of stored sediment incision of slot gorges into bedrock and landsliding on valley walls fluvial transfer of eroded bedrock glacial deposits and stored nonglacial fluvial deposits after 1983 resulted in progradation of fan deltas toward the fjord centerline at the outlet of each of the four catchments in the largest nonglacial tributary valley 0 08 km 3 8 of the 0 59 km 3 of 500 m thick stored fluvial and colluvial deposits has been transferred to the adjacent fjord a percentage of the fjord sedimentation in the last two decades thus includes material eroded from bedrock and stored in the landscape during the previous glacial expansions distal deltaic deposits extend across the fjord floor and likely interfinger with distal proglacial deltaic deposits sourced from the tyndall glacier a paraglacial landscape response such as the one exhibited in upper taan fjord where sediment delivery to fjords from tributary sources in synchrony with sediment produced by primary bedrock erosion by glaciers helps to explain the order of magnitude discrepancy between sediment yields from alaskan tidewater glaciers on 10 0 to 10 2 year timescales and sediment yields and exhumation rates on 10 4 to 10 6 year timescales

borehole guided avo analysis of p p and p s reflections quantifying uncertainty on density estimates seismic properties of isotropic elastic formations are characterized by the three parameters acoustic impedance poisson s ratio and density whilst the first two are usually well estimated by analysing the amplitude variation with angle ava of reflected p p waves density is known to be poorly resolved however density estimates would be useful in many situations encountered in oil and gas exploration in particular for minimizing risks in looking ahead while drilling we design a borehole seismic experiment to investigate the reliability of ava extracted density receivers are located downhole near the targeted reflectors and record reflected p p and converted p s waves a non linear wide angle based bayesian inversion is then used to access the a posteriori probability distributions associated with the estimation of the three isotropic elastic parameters the analysis of these distributions suggests that the angular variation of reflected p s amplitudes provides additional substantial information for estimating density thus reducing the estimate uncertainty variance by more than one order of magnitude compared to using only reflected p waves

combined use of relative and absolute dating techniques for detecting signals of alpine landscape evolution during the late pleistocene and early holocene article i nfo a combination of three relative and two absolute numerical dating techniques applied on nine soil profiles in an alpine environment located in val di rabbi trentino northern italy was used to improve the investigation methodology of alpine sites in response to climate change and to reconstruct the chronology of late pleistocene and early holocene landscape evolution the degree of podzolisation clay mineral evolution and the element mass balances of each site were investigated furthermore the stable fraction of the soil organic matter som was extracted with 10 h2o2 and 14 c dated the age of the organic residues was compared with the age of charcoal fragments found in one of the studied soils and with the age of rock boulders obtained by surface exposure dating sed with cosmogenic 10 be numerical dating and weathering characteristics of the soils showed a fairly good agreement and enabled a relative and absolute differentiation of landscape elements the combination of 14 c dating of som and sed indicated that deglaciation processes in val di rabbi were already far advanced by around 14000 cal bp and that glacier oscillations affected the highest part of the region until about 9000 cal bp the development of clay minerals is time dependent and reflects weathering intensity we found a close link between secondary clay minerals like smectite or vermiculite and soil age as obtained by the dating of the organic residues after the h2o2 treatment calculated element mass balances strongly correlated with the ages derived from 14 c measurements old soils have lost a major part of base cations up to 75 compared to the parent material fe and al which indicates a continuous high weathering intensity results of the chemical and mineralogical analyses were in good agreement with numerical dating techniques showing the dynamics of an alpine landscape within a relatively small area the combination of relative and absolute dating techniques is a promising tool for the reconstruction of landscape history in high elevation alpine areas on siliceous substrates

erosion driven uplift of the modern central alps abstract we present a compilation of data of modern tectono geomorphic processes in the central european alps which suggest that observed rock uplift is a response to climate driven denudation this interpretation is predominantly based on the recent quantification of basin averaged late holocene denudation rates that are so similar to the pattern and rates of rock uplift rates as determined by geodetic leveling furthermore a gps data based synthesis of adriatic microplate kinematics suggests that the central alps are currently not in a state of active convergence finally we illustrate that the central alps have acted as a closed system for holocene redistribution of sediment in which the peri alpine lakes have operated as a sink for the erosional products of the inner central alps while various hypotheses have been put forward to explain central alpine rock uplift e g lithospheric forcing by convergence mantle processes or ice melting we show with an elastic model of lithospheric deformation that the correlation between erosion and rock uplift rates reflects a positive feedback between denudation and the associated isostatic response to unloading thus erosion does not passively respond to advection of crustal material as might be the case in actively converging orogens rather we suggest that the geomorphic response of the alpine topography to glacial and fluvial erosion and the resulting disequilibrium for modern channelized and associated hillslope processes explains much of the pattern of modern denudation and hence rock uplift therefore in a non convergent orogen such as the central european alps the observed vertical rock uplift is primarily a consequence of passive unloading due to erosion

seismic tomography of the southern california crust based on spectral element and adjoint methods we iteratively improve a 3 d tomographic model of the southern california crust using numerical simulations of seismic wave propagation based on a spectral element method sem in combination with an adjoint method the initial 3 d model is provided by the southern california earthquake center the data set comprises three component seismic waveforms i e both body and surface waves filtered over the period range 2 30 s from 143 local earthquakes recorded by a network of 203 stations time windows for measurements are automatically selected by the flexwin algorithm the misfit function in the tomographic inversion is based on frequency dependent multitaper traveltime differences the gradient of the misfit function and related finite frequency sensitivity kernels for each earthquake are computed using an adjoint technique the kernels are combined using a source subspace projection method to compute a model update at each iteration of a gradient based minimization algorithm the inversion involved 16 iterations which required 6800 wavefield simulations the new crustal model m 16 is described in terms of independent shear v s and bulk sound v b wave speed variations it exhibits strong heterogeneity including local changes of 30 per cent with respect to the initial 3 d model the model reveals several features that relate to geological observations such as sedimentary basins exhumed batholiths and contrasting lithologies across faults the quality of the new model is validated by quantifying waveform misfits of full length seismograms from 91 earthquakes that were not used in the tomographic inversion the new model provides more accurate synthetic seismograms that will benefit seismic hazard assessment

seismic identification of a karstified reservoir in the adriatic sea in this study an elastic prestack migration inversion m i scheme was applied to a 2 d seismic line collected in the adriatic sea the objective was to use m i images to describe a hydrocarbon reservoir consisting of karstified brine saturated limestones the m i technique offers the benefit of extracting maximum information from seismic reflection data to describe and in some cases characterize the reservoir target m i images are calibrated with well data and represent approximate changes in p and s wave impedances across the reservoir combining these two images yields a poisson s ratio image

coherence of mach fronts during heterogeneous supershear earthquake rupture propagation simulations and comparison with observations 1 we study how heterogeneous rupture propagation affects the coherence of shear and rayleigh mach wavefronts radiated by supershear earthquakes we address this question using numerical simulations of ruptures on a planar vertical strike slip fault embedded in a three dimensional homogeneous linear elastic half space ruptures propagate spontaneously in accordance with a linear slip weakening friction law through both homogeneous and heterogeneous initial shear stress fields in the 3 d homogeneous case rupture fronts are curved owing to interactions with the free surface and the finite fault width however this curvature does not greatly diminish the coherence of mach fronts relative to cases in which the rupture front is constrained to be straight as studied by dunham and bhat 2008a introducing heterogeneity in the initial shear stress distribution causes ruptures to propagate at speeds that locally fluctuate above and below the shear wave speed calculations of the fourier amplitude spectra fas of ground velocity time histories corroborate the kinematic results of bizzarri and spudich 2008a 1 the ground motion of a supershear rupture is richer in high frequency with respect to a subshear one 2 when a mach pulse is present its high frequency content overwhelms that arising from stress heterogeneity present numerical experiments indicate that a mach pulse causes approximately an 1 7 high frequency falloff in the fas of ground displacement moreover within the context of the employed representation of heterogeneities and over the range of parameter space that is accessible with current computational resources our simulations suggest that while heterogeneities reduce peak ground velocity and diminish the coherence of the mach fronts ground motion at stations experiencing mach pulses should be richer in high frequencies compared to stations without mach pulses in contrast to the foregoing theoretical results we find no average elevation of 5 damped absolute response spectral accelerations sa in the period band 0 05 0 4 s observed at stations that presumably experienced mach pulses during the 1979 imperial valley 1999 kocaeli and 2002 denali fault earthquakes compared to sa observed at non mach pulse stations in the same earthquakes a 20 amplification of short period sa is seen only at a few of the imperial valley stations closest to the fault this lack of elevated sa suggests that either mach pulses in real earthquakes are even more incoherent that in our simulations or that mach pulses are vulnerable to attenuation through nonlinear soil response in any case this result might imply that current engineering models of high frequency earthquake ground motions do not need to be modified by more than 20 close to the fault to account for mach pulses provided that the existing data are adequately representative of ground motions from supershear earthquakes

anisotropic elastic full waveform inversion of walkaway vertical seismic profiling data from the arabian gulf abstract borehole seismic addresses the need for high resolution images and elastic parameters of the subsurface full waveform inversion of vertical seismic profile data is a promising technology with the potential to recover quantitative information about elastic properties of the medium full waveform inversion has the capability to process the entire wavefield and to address the wave propagation effects contained in the borehole data multi component measurements anisotropic effects compressional and shear waves and transmitted converted and reflected waves and multiples full waveform inversion therefore has the potential to provide a more accurate result compared with conventional processing methods we present a feasibility study with results of the application of high frequency up to 60 hz anisotropic elastic full waveform inversion to a walkaway vertical seismic profile data from the arabian gulf full waveform inversion has reproduced the majority of the wave events and recovered a geologically plausible layered model with physically meaningful values of the medium

elastic full waveform inversion of multicomponent ocean bottom cable seismic data application to alba field u k north sea elastic full waveform inversion of multichannel seismic data represents a data driven form of analysis leading to direct quantification of the subsurface elastic parameters in the depth domain previous studies have focused on marine streamer data using acoustic or elastic inversion schemes for the inversion of p wave data in this paper p and s wave velocities are inverted for using wide angle multicomponent ocean bottom cable obc seismic data inversion is undertaken using a two dimensional elastic algorithm operating in the time domain which allows accurate modeling and inversion of the full elastic wavefield including p and mode converted ps waves and their respective amplitude variation with offset avo responses results are presented from the application of this technique to an obc seismic data set from the alba field north sea after building an initial velocity model and extracting a seismic wavelet the data are inverted instages in the first stage the intermediate wavelength p wave v

changes in erosion patterns during the holocene in a currently treeless subalpine catchment inferred from lake sediment geochemistry lake anterne 2063 m a s l nw french alps the role of climate and human activities a high resolution sedimentological and geochemical study was performed on a 20 m long core from the alpine lake anterne 2063 m a s l nw french alps spanning the last 10 ka sedimentation is mainly of minerogenic origin the organic matter quantity toc as well as its quality hydrogen hi and oxygen oi indices both indicate the progressive onset and subsequent stabilization of vegetation cover in the catchment from 9950 to 5550 cal bp during this phase the pedogenic process of carbonate dissolution is marked by a decrease in the calcium content in the sediment record between 7850 and 5550 cal bp very low manganese concentrations suggest anoxic conditions in the bottom water of lake anterne these are caused by a relatively high organic matter terrestrial and lacustrine content a low flood frequency and longer summer stratification triggered by warmer conditions from 5550 cal bp a decrease in toc stabilization of hi and higher sedimentation rates together reflect increased erosion rates of leptosols and developed soils probably due to a colder and wetter climate then three periods of important soil destabilization are marked by an increased frequency and thickness of flood deposits during the bronze age and by increases in topsoil erosion relative to leptosols hi increases during the late iron age roman period and the medieval periods these periods are also characterized by higher sedimentation rates according to palynological data human impact deforestation and or pasturing activity probably triggered these periods of increased soil erosion

effective attenuation lengths of cosmic rays producing 10be and 26al in quartz implications for exposure age dating we have measured cosmic ray produced 10be t 1 5 my and 26al t 0 72 my as functions of depth in a core of quartz sandstone bedrock collected in south victoria land antarctica these data were used to place limits on the exposure age and erosion rate of the exposed surface and to calculate the effective attenuation lengths of cosmic rays producing these nuclides these latter results indicate that the production attenuation length for 26al is comparable to that for 10be this suggests that the production ratio 26al 10be does not vary substantially with depth in a rock and that its value at the surface of exposed rock is not strongly affected by erosional losses allowing wider use of the ratio in determining exposure ages

multiparameter full waveform inversion of multicomponent ocean bottom cable data from the valhall field part 2 imaging compressive wave and shear wave velocities

information on elastic parameters obtained from the amplitudes of reflected waves seismic amplitude variation with offset data contain information on the elastic parameters of geological layers as the general solution of the inverse problem consists of a probability over the space of all possible earth models we look at the probabilities obtained using amplitude variation with offset avo data for different choices of elastic parameters a proper analysis of the information in the data requires a nontrivial definition of the probability defining the state of total ignorance on different elastic parameters seismic velocities lame s parameters etc we conclude that mass density seismic impedance and poisson s ratio constitute the best resolved parameter set when inverting seismic amplitude variation with offset data

a review of least squares inversion and its application to geophysical problems geophysical inversion involves the estimation of the parameters of a postulated earth model from a set of observations since the associated model responses can be nonlinear functions of the model parameters nonlinear least squares techniques prove to be useful for performing the inversion a common type of inversion applies iterative damped linear least squares through use of the marquardt levenberg method traditionally this method has been implemented by solving the associated normal equations in conventional ways however singular value decomposition svd produces significant improvements in computational precision when applied to the same system of normal equations iterative least squares modeling finds application in a wide variety of geophysical problems two examples illustrate the approach 1 seismic wavelet deconvolution and 2 the location of a buried wedge from surface gravity data more generally nonlinear least squares inversion can be used to estimate earth models for any set of geophysical observations for which an appropriate mathematical description is available

chronology of the last glacial cycle in the european alps chronological data for glacier advances in the european alps between the last interglacial eemian and the holocene are summarised 115 to 11 ka during this time glaciers were most extensive extending tens of kilometres out onto the forelands between 30 and 18 ka that is synchronous with the global ice volume maximum of marine isotope stage mis 2 evidence for ice expanding to just past the mountain front for an earlier major glacier advance comes from swiss sites where advances have been luminescence dated to mis 5d 100 ka and mis 4 70 ka up to now no such evidence has been found in the eastern alps by 18 ka more than 80 of the late wurmian ice volume had gone subsequently glaciers readvanced reaching into the upper reaches of the main valleys during the lateglacial gschnitz stadial which likely occurred around 17 ka with final moraine stabilisation no later than 15 4 ka the link of the egesen stadial with the younger dryas climate deterioration is supported by exposure ages from four sites as well as minimum limiting radiocarbon dates from bogs within former glacier tongue areas key questions on the spatial and temporal variability of ice extents throughout the last glacial cycle have yet to be answered copyright 2008 john wiley sons ltd

multiparameter l 1 norm waveform fitting interpretation of gulf of mexico reflection seismograms estimation of the elastic properties of the crust from surface seismic recordings is of great importance for the understanding of lithology and for the detection of mineral resources although in marine reflection experiments only p waves are recorded information on shear properties of the medium is contained in multioffset reflection seismograms being able to retrieve both dilatational and shear properties gives stronger constraints on the lithology it is therefore desirable to recover isotropic elastic parameters from multioffset seismograms unfortunately most classical waveform fitting methods used for extracting shear properties of the subsurface are based on a 1 d earth model assumption and on linear approximations of the wave equations in this paper a 2 5 d elastic waveform inversion method is used to extract the variations of acoustic impedance and poisson s ratio from marine multioffset reflection seismograms collected in the gulf of mexico area a complete seismic profile is interpreted i

cosmogenic cl 36 dating of postglacial landsliding at the storr isle of skye scotland major postglacial rock slope failures are a common feature of the scottish highlands and other mountainous areas that were deglaciated at the end of the pleistocene but evaluation of the causes and triggers of failure has been hindered by a lack of reliable dating evidence we report the result of a pilot study designed to establish the absolute age of a large postglacial rotational rockslide at the storr on the isle of skye scotland using 36cl surface exposure dating exposure ages of 6 3 0 7 cal ka bp and 6 6 0 8 cal ka bp were obtained for rock samples from two separate landslide blocks giving an overall age estimate of 6 5 0 5 cal ka bp for rock slope failure at this site this date is consistent with ams radiocarbon dating of windblown sand derived from the failure scarp and with previous inferences based on relative dating evidence concerning an early holocene age for most rock slope failures in the scottish highlands the long time lag 7 ka between deglaciation and failure sugge

structure and origin of holocene cold events abstract the present interglacial the holocene spans the period of the last 11 700 years it has sustained the growth and development of modern society the millennial scale decreasing solar insolation in the northern hemisphere summer lead to northern hemisphere cooling a southern shift of the intertropical convergence zone itcz and a weakening of the northern hemisphere summer monsoon systems on the multidecadal to multicentury scale periods of more stable and warmer climate were interrupted by several cold relapses at least in the northern hemisphere extra tropical area based on carefully selected 10 000 year long time series of temperature and humidity precipitation as well as reconstructions of glacier advances the spatiotemporal pattern of six cold relapses during the last 10 000 years was analysed and presented in form of a holocene climate atlas hoclat see http www oeschger unibe ch research projects holocene atlas a clear cyclicity was not found and the spatiotemporal variability of temperature and humidity precipitation during the six specific cold events 8200 6300 4700 2700 1550 and 550 years bp was very high different dynamical processes such as meltwater flux into the north atlantic low solar activity explosive volcanic eruptions and fluctuations of the thermohaline circulation likely played a major role in addition internal dynamics in the north atlantic and pacific area including their complex interaction were likely involved

high resolution greenland ice core data show abrupt climate change happens in few years the last two abrupt warmings at the onset of our present warm interglacial period interrupted by the younger dryas cooling event were investigated at high temporal resolution from the north greenland ice core project ice core the deuterium excess a proxy of greenland precipitation moisture source switched mode within 1 to 3 years over these transitions and initiated a more gradual change over 50 years of the greenland air temperature as recorded by stable water isotopes the onsets of both abrupt greenland warmings were slightly preceded by decreasing greenland dust deposition reflecting the wetting of asian deserts a northern shift of the intertropical convergence zone could be the trigger of these abrupt shifts of northern hemisphere atmospheric circulation resulting in changes of 2 to 4 kelvin in greenland moisture source temperature from one year to the next

relation between rock uplift and denudation from cosmogenic nuclides in river sediment in the central alps of switzerland 1 a north south traverse through the swiss central alps reveals that denudation rates correlate with recent rock uplift rates in both magnitude and spatial distribution this result emerges from a study of in situ produced cosmogenic 10be in riverborne quartz in central alpine catchments as a prerequisite we took care to investigate the potential influence of shielding from cosmic rays due to snow glaciers and topographic obstructions to calculate a possible memory from last glacial maximum lgm glaciation and to identify a watershed size that is appropriate for systematic sampling mean denudation rates are 0 27 0 14 mm a for the alpine foreland and 0 9 0 3 mm a for the crystalline central alps the measured cosmogenic nuclide derived denudation rates are in good agreement with post lgm lake infill rates and are about twice as high as denudation rates from apatite fission track ages that record denudation from 9 to 5 ma in general denudation rates are high in areas of high topography and high crustal thickness the similarity in the spatial distribution and magnitude of denudation rates and those of rock uplift rates can be interpreted in several ways 1 postglacial rebound or climate change has introduced a transient change in which both uplift and denudation follow each other with a short lag time 2 the amplitude of glacial to interglacial changes in both is small and is contained in the scatter of the data 3 both are driven by ongoing convergence where their similarity might hint at some form of long term quasi steady state or 4 enhanced continuous quaternary erosion and isostatic compensation of the mass removed accounts for the distribution of present day rock uplift

quaternary erosion induced isostatic rebound in the western alps the high elevation and deep incision of the alps have traditionally been used as an argument for recent tectonic activity that has elevated the belt and increased erosion rates normal faulting and horizontal extension however dominate current tectonic activity and isostatic compensation of thinning crust should lead not to increased but to decreased mean elevations here we test the idea that enhanced quaternary erosion of the alps and isostatic compensation of the mass removed can account for the distribution of present day geodetically measured rates of vertical movement in the western alps using geophysical relief and kuhlemann s estimated average erosion rate for the alps we quantify the spatial distribution of erosion and the volume of eroded rock respectively from these we obtain a map of rock eroded within a given time span the calculated isostatic response of the alpine lithosphere to erosional unloading for a variety of values of the flexural rigidity of the alpine lithosphere reaches a maximum of 500 m since 1 ma in the inner swiss alps and vertical movement extends across the entire belt including peri alpine basins assuming a steady erosion rate since 1 ma this rebound accounts for half of the measured vertical motion of 1 1 mm yr in the southern valais thus a significant fraction 50 of the present day vertical movement results from the isostatic response to enhanced erosion during plio quaternary time

waveform inversion of marine reflection seismograms for p impedance and poisson s ratio summary the estimation of the elastic properties o the crust from surface seismic recordings is of great importance for an understanding of the lithology and the detection of mineral resources although in marine reflection experiments only p waves are recorded information on shear properties o the medium si contained in the reflection amplitudes recorded at different distances from the source being able to estimate both dialatational and shear properties gives stronger constraints on the lithology it is therefore desirable to recover both types of elastic parameters from multi offset seismograms in the real data example presented here the amplitude of the reflections cannot be explained by one parameter related to the dilatational properties p impedance only when trying to minimize the least squares fit between synthetic and real multi offset seismograms when adding an additional parameter related to the shear properties poisson s ratio the fit between synthetic and real seismograms improves synthetic wavefrom fitting experiments underline the possibility of recovering poisson s ration when the p impedance model is well known from fitting waeveforms recorded at small offsetts in the real data example the resulting models for p impedance and poisson s ratio are anticorrelated in most depth regions but are correlated in particular depth region indicating a sudden change in lithology

two dimensional full wavefield inversion of wide aperture marine seismic streamer data summary a 2 d full wavefield inversion method is presented for the processing of wide aperture data the diversity of information contained within such datasets may be handled in a complete manner by first matching the traveltimes of the main events and then progressing to waveform fitting of the data through explicit full wavefield modelling our wavefield inversion scheme is based upon a finite difference solution of the 2 d elastic wave equation in the time distance domain the strength of adopting such an approach is the ability to generate all possible wave types within a given 2 d model multiples converted waves etc and thus to simulate and accurately model complex seismic wavefields the aim of the inversion is to find the 2 d p wave velocity model that minimizes the least squared difference between the observed and synthetic data across the full range of offsets following extensive testing on synthetic data the wavefield inversion scheme has been applied to wide aperture real marine seismic streamer datasets we present results from the synthetic testing and the wavefield inversion of wide aperture real data out to 12 km offset that was recorded on a single streamer even though current computational restrictions allow only a small subsection of the data to be analysed these examples demonstrate the potential value of wide aperture 2 d full wavefield inversion

amplitude versus offset variations in gas sands seismic reflections from gas sands exhibit a wide range of amplitude versus offset avo characteristics the two factors that most strongly determine the avo behavior of a gas sand reflection are the normal incidence reflection coefficient r0 and the contrast in poisson s ratio at the reflector of these two factors r0 is the least constrained based on their avo characteristics gas sand reflectors can be grouped into three classes defined in terms of r0 at the top of the gas sand class 1 gas sands have higher impedance than the encasing shale with relatively large positive values for r0 class 2 gas sands have nearly the same impedance as the encasing shale and are characterized by values of r0 near zero class 3 sands have lower impedance than the encasing shale with negative large magnitude values for r0 each of these sand classes has a distinct avo characteristic an example of a gas sand from each of the three classes is presented in the paper the class 1 example involves a hartshorn channel s

quasi cylindrical 2 5d wave modeling for large scale seismic surveys 1 the most common form of seismic exploration remains a nearly linear survey with data acquisition lines including the source and receivers the interpretation of amplitude and waveform information for such linear acquisition requires consideration of 3d seismic wavefields in many scenarios the structure is approximately 2d but still modeling is needed for point sources in recent years 2 5d modeling methods have been developed for the simulation of 3d seismic wavefields in media varying in two dimensions although the computer memory requirements are only slightly larger than those for 2d computations the computation times are too long for ready application to actual surveys to overcome this problem we propose a new approach for modeling 2 5d seismic wavefields using a quasi cylindrical representation we show an implementation of this approach using the finite difference method and demonstrate the validity and efficiency of the technique with numerical examples including a profile across a realistic model of subduction zone structure

cosmogenic 10be derived denudation rates of the eastern and southern european alps denudation rates from cosmogenic 10be measured in quartz from recent river sediment have previously been used in the central alps to argue that rock uplift occurs through isostatic response to erosion in the absence of ongoing convergence we present new basin averaged denudation rates from large rivers in the eastern and southern european alps together with a detailed topographic analysis in order to infer the forces driving erosion denudation rates in the eastern and southern alps of 170 1 400 mm ky 1 are within a similar range to those in the central alps for similar lithologies however these denudation rates vary considerably with lithology and their variability generally increases with steeper landscapes where correlations with topographic metrics also become poorer tertiary igneous rocks are associated with steep hillslopes and channels and low denudation rates whereas pre alpine gneisses usually exhibit steep hillslopes and higher denudation rates molasse flysch and schists display lower mean basin slopes and channel gradients and despite their high erodibility low erosion rates exceptionally low denudation rates are also measured in permian rhyolite which has high mean basin slopes we invoke geomorphic inheritance as a major factor controlling erosion such that large erosive glaciers in the late quaternary cold periods were more effective in priming landscapes in the central alps for erosion than in the interior eastern alps however the difference in tectonic evolution of the eastern and central alps potentially adds to differences in their geomorphic response their deep structures differ significantly and unlike the central alps the eastern alps are affected by ongoing tectonic influx due to the slow motion and rotation of adria the result is a complex pattern of high mountain erosion in the eastern alps which has evolved from one confined to the narrow belt of the tauern window in late tertiary time to one affecting the entire underthrust basement orogenic lid and parts of the southern alps today

holocene glacier culminations in the western alps and their hemispheric relevance the natural variability of holocene climate defi nes the baseline to assess ongoing climate change greenland ice core records indicate warming superimposed by abrupt climate oscillations in the early holocene followed by a general cooling trend throughout the middle and late holocene that culminated during the little ice age lia tropical precipitation changes correlate with these patterns throughout the holocene here we use mountain glaciers in the european alps to reconstruct the regional holocene climate evolution and to test for a link between mid latitude north atlantic and tropical climate our precise 10 be chronology from tsidjiore nouve glacier western swiss alps indicates a glacier culmination during the earliest holocene 11 4 k y ago likely related to the preboreal oscillation based on our data no holocene glacier advance of similar amplitude occurred until 3 8 k y ago when the glacier reached lia limits the 10 be ages between 500 and 170 yr correspond to the lia while the youngest 10 be ages overlap with the historically recorded post lia glacier positions integrating our data with existing records we propose a hemispheric climate link between the alps north atlantic temperature and tropical precipitation patterns for the holocene supporting the concept of a pervasive climate driver these fi ndings from northern mid latitudes are consistent with the hypothesis formulated for the tropics that the earth s thermal equator responding to north atlantic temperature changes might have migrated southward throughout the holocene reaching the southern turning point toward the end of the lia

glacial conditioning as an erosional driving force in the central alps unparalleled data availability in the european alps has led to an ongoing debate about the driving mechanism behind the concurrent patterns of surface denudation and modern rock uplift analysis of stream channels reveals that oversteepened stream segments are primarily located in landscapes with strong glacial inheritance this leads to a transient signal in the landscape with the result that erosion is spatially focused by a combination of glacial conditioning and lithologic controls we postulate that the effect of glacial forcing is a positive feedback cycle between erosion and rock uplift driving rapid rates of both in the alpine landscape this mechanism may explain the observed increases in sediment flux since the late pliocene

cosmogenic nuclide based investigation of spatial erosion and hillslope channel coupling in the transient foreland of the swiss alps abstract transient landscape disequilibrium is a common response to climatic fluctuations between glacial and interglacial conditions such landscapes are best suited to the investigation of catchment wide response to changes in incision the geomorphology of the trub and grosse fontanne adjacent stream systems in the napf region of the swiss molasse was analyzed using a 2 m lidar dem the two catchments were impacted by the last glacial maximum lgm even though the glaciers never overrode this region they did however cause base levels to drop by as much as 80 m despite their similar tectonic lithologic and climatic settings these two basins show very different responses to the changing boundary conditions stream profiles in the trub tend to be smooth while in the fontanne numerous knickzones are visible similarly cut and fill terraces are abundant in the trub watershed but absent in the fontanne where deep valleys have been incised the trub appears to be a coupled hillslope channel system because the morphometrics throughout the basin are uniform the morphology of hillslopes upstream of the knickzones in the fontanne is identical to that of the trub basin but different downstream of the knickzones suggesting that the lower reaches of the fontanne have been decoupled from the hillslopes however the rapid incision of the fontanne is having little effect on the adjacent upper hillslopes we tested this interpretation using cosmogenic 10 be derived basin averaged denudation rates and terrace dating the coupled nature of the trub basin is supported by the similarity of denudation rates 350 50 mm ky 1 at a variety of spatial scales upstream of the knickzones rates in the fontanne 380 50 mm ky 1 match those of the trub downstream of the knickzones denudation rates increase to 540 100 mm ky 1 the elevated rates in the downstream areas of the fontanne are due to rapid incision causing a decoupling of the hillslope from the channel basin response time and the magnitude of base level drop exert the principal control over the difference in geomorphic response between the two basins the timing of the filling of the trub valley 17 2 ka and the initial incision of the fontanne 16 3 ka were calculated verifying that these are responses to late glacial perturbations unique lithologic controls allow for one of the fastest regolith production rates yet to be reported 380 mm ky 1

theoretical background for continental and global scale full waveform inversion in the time frequency domain summary we propose a new approach to full seismic waveform inversion on continental and global scales this is based on the time frequency transform of both data and synthetic seismograms with the use of time and frequency dependent phase and envelope misfits these misfits allow us to provide a complete quantification of the differences between data and synthetics while separating phase and amplitude information the result is an efficient exploitation of waveform information that is robust and quasi linearly related to earth s structure thus the phase and envelope misfits are usable for continental and global scale tomography that is in a scenario where the seismic wavefield is spatially undersampled and where a 3 d reference model is usually unavailable body waves surface waves and interfering phases are naturally included in the analysis we discuss and illustrate technical details of phase measurements such as the treatment of phase jumps and instability in the case of small amplitudes the frechet kernels for phase and envelope misfits can be expressed in terms of their corresponding adjoint wavefields and the forward wavefield the adjoint wavefields are uniquely determined by their respective adjoint source time functions we derive the adjoint source time functions for phase and envelope misfits the adjoint sources can be expressed as inverse time frequency transforms of a weighted phase difference or a weighted envelope difference in a comparative study we establish connections between the phase and envelope misfits and the following widely used measures of seismic waveform differences 1 cross correlation time shifts 2 relative rms amplitude differences 3 generalized seismological data functionals and 4 the l2 distance between data and synthetics used in time domain full waveform inversion we illustrate the computation of frechet kernels for phase and envelope misfits with data from an event in the west irian region of indonesia recorded on the australian continent the synthetic seismograms are computed for a heterogeneous 3 d velocity model of the australian upper mantle with a spectral element method the examples include p body waves rayleigh waves and s waves interfering with higher mode surface waves all the kernels differ from the more familar kernels for cross correlation time shifts or relative rms amplitude differences the differences arise from interference effects 3 d earth s structure and waveform dissimilarities that are due to waveform dispersion in the heterogeneous earth

decimetric resolution stochastic inversion of shallow marine seismic reflection data dedicated strategy and application to a geohazard case study characterisation of the top 10 50 m of the subseabed is key for landslide hazard assessment offshore structure engineering design and underground gas storage monitoring in this paper we present a methodology for the stochastic inversion of ultra high frequency uhf 0 2 4 0 khz pre stack seismic reflection waveforms designed to obtain a decimetric resolution re mote elastic characterisation of the shallow sediments with minimal pre processing and lit tle a priori information we use a genetic algorithm in which the space of possible solutions is sampled by explicitly decoupling the short and long wavelengths of the p wave velocity model this approach combined with an objective function robust to cycle skipping outperforms a conventional model parametrisation when the ground truth is offset from the centre of the search domain the robust p wave velocity model is used to precondition the width of the search range of the multi parameter elastic inversion thereby improving the efficiency in high dimensional parametrizations multiple independent runs provide a set of independent results from which the reproducibility of the solution can be estimated in a real dataset acquired in finneidfjord norway we also demonstrate the sensitivity of uhf seismic inversion to shallow subseabed anomalies that play a role in submarine slope stability thus the methodology has the potential to become an important practical tool for marine ground model building in spatially heterogeneous areas reducing the reliance on expensive and time consuming coring campaigns for geohazard mitigation in marine areas

climatic control of denudation in the deglaciated landscape of the washington cascades erosion in the washington cascades mountains was dominated by glacier activity until the end of the last glacial maximum when fluvial incision and mass wasting became the dominant drivers an analysis of millennial scale rates of denudation in the range suggest erosion is sensitive both to spatial variations in precipitation and inherited topography

the temperature of europe during the holocene reconstructed from pollen data we present the first area average time series reconstructions of warmest month coldest month and mean annual surface air temperatures across europe during the last 12 000 years these series are based on quantitative pollen climate reconstructions from over 500 pollen sites assimilated using an innovative four dimensional gridding procedure this approach combines three dimensional spatial gridding with a fourth dimension represented by time allowing data from irregular time series to be focussed onto a regular time step we provide six regional reconstructed temperature time series as well as summary time series for the whole of europe the results suggest major spatial and seasonal differences in holocene temperature trends within a remarkably balanced regional and annual energy budget the traditional mid holocene thermal maximum is observed only over northern europe and principally during the summer this warming was balanced by a mid holocene cooling over southern europe whilst central europe occupied an intermediary position changes in annual mean temperatures for europe as a whole suggest an almost linear increase in thermal budget up to 7800 bp followed by stable conditions for the remainder of the holocene this early holocene warming and later equilibrium has been mainly modulated by increasing winter temperatures in the west which have continued to rise at a progressively decreasing rate up to the present day

dating sediment burial with in situ produced cosmogenic nuclides theory techniques and limitations abstract dating sediment burial over million year time scales is crucial in many areas of the earth sciences and archeology but is often difficult using traditional techniques sediment burial can be dated by the radioactive decay of cosmogenic nuclides provided that the sediment was exposed to cosmic rays prior to burial dating calculations are straightforward if sediment is buried deeply and rapidly enough to prevent cosmogenic nuclide production after burial however the analysis can be complicated by postburial production if sediment is insufficiently shielded from secondary cosmic ray nucleons and muons this paper discusses how buried sediments can be dated over timescales up to 5 myr using 26 al and 10 be in quartz

wave propagation effects on amplitude variation with offset measurements a modeling study wave propagation effects can significantly affect amplitude variation with offset avo measurements these effects include spreading losses transmission losses interbed multiples surface multiple reflections p sv mode converted waves and inelastic attenuation examination of prestack elastic synthetic seismograms suggests that spreading losses and the transmission losses plus compressional interbed multiples are manifest mainly as a time and offset effect on the primary reflections the surface related multiples and the p sv mode converted waves interfere with prestack amplitudes inducing distortions in the avo pattern such distortions cause large variances in avo model fitting prestack viscoelastic synthetic seismograms also suggest that inelastic attenuation further complicates the avo response because of the offset and time variant amplitude decay effects and the phase change due to dispersion together all these effects severely alter avo behavior and result in serious errors in avo parameter

dating bedrock gorge incision in the french western alps ecrins pelvoux massif using cosmogenic 10be terra nova 22 18 25 2010 abstract we report in situ produced 10be data from the gorge du diable french western alps to date and quantify bedrock gorge incision into a glacial hanging valley we sampled gorge sidewalls and the active channel bed to derive both long term and present day incision rates 10be ages of sidewall profiles reveal rapid incision through the late holocene ca 5 ka at rates ranging from 6 5 to 13 mm yr 1 present day incision rates are significantly lower and vary from 0 5 to 3 mm yr 1 within the gorge our data imply either delayed initiation of gorge incision after final ice retreat from internal alpine valleys at ca 12 ka or post glacial surface reburial of the gorge our results suggest that fluvial incision rates 1 cm yr 1 into crystalline bedrock may be encountered in transient landscape features induced by glacial interglacial transitions

automated large scale full seismic waveform inversion for north america and the north atlantic we present a new anisotropic seismic tomography model based on a multiscale full seismic waveform inversion for crustal and upper mantle structure from the western edge of north america across the north atlantic and into europe the gradient based inversion strategy utilizes the adjoint state method coupled with an l bfgs quasi newton optimization scheme to improve the handling of large data quantities in the context of full seismic waveform inversions we developed a workflow framework automating the procedure across all stages enabling us to confidently invert for waveforms from 72 events recorded at 7 737 unique stations resulting in a total of 144 693 raypaths most of them with three component recordings the final model after 20 iterations is able to explain complete waveforms including body as well as surface waves of earthquakes that were not used in the inversion down to periods of around 30s the model is complemented by a detailed resolution analysis in the form of 3 d distributions of direction dependent resolution lengths

combined traveltime and frequency domain seismic waveform inversion a case study on multi offset ultrasonic data we present the acquisition and processing of a multi offset ultrasonic tomography experiment in which we aim to precisely reconstruct the image and kinematic properties of two scatterers that contrast strongly with the water background the resultant non linearity causes the failure of a frequency domain waveform fitting strategy for retrieving the whole range of experimentally covered wavenumbers a mixed tomographic approach is instead adopted in which traveltime and waveform inversion are combined iteratively this strategy helps in overcoming the waveform inverse problem non linearity and the data computed in our final tomographic model match most of the observed features in the experimental seismograms this model is in good agreement with what is known concerning the properties of the scatterers and it is characterized by both the high focusing of waveform tomography and the accurate kinematics of traveltime tomography these achievements are reached in spite of a limited but nevertheless uniform geometric coverage our strategy of using two different tomographic tools sequentially therefore appears to be a possible solution to addressing the issue of highly non linear seismic inverse problems

lateglacial and holocene climate oscillations in the south western alps an attempt at quantitative reconstruction abstract the high topographic complexity of the alpine region is the origin of important climate differences that characterise the different areas of the alps these differences might have had a strong influence on vegetation and on migrations of human populations in the past based on an improved database containing about 3000 modern pollen samples the standard modern analogue technique has been applied to five pollen sequences from the subalpine belt of the south western italian alps laghi dell orgials 2240 m lago delle fate 2130 m torbiera del biecai 1920 m rifugio mondovi 1760 m pian marchisio 1624 m to provide quantitative climate estimates for the lateglacial and holocene periods consistent climate trends are reconstructed for the different sequences sites recorded in detail the climate variations when they were located at the limit of two ecotones sites above the tree line recorded lower temperature values and less important variations climate was cold and dry during the oldest and younger dryas and close to present day values during the bolling allerod interstadial at the beginning of the holocene climate changed to warmer and moister conditions a high number of climate fluctuations are recorded at several sites a climate optimum is recorded in the atlantic period which caused a development of fir above its present day altitudinal distribution climatic differences recorded at the various sites are discussed taking into account the limits of the method

tectonic vs gravitational morphostructures in the central eastern alps italy constraints on the recent evolution of the mountain range abstract deep seated gravitational slope deformations dsgsds influence landscape development in tectonically active mountain ranges nevertheless the relationships among tectonics dsgsds and topography are poorly known in this paper the distribution of dsgsds and their relationships with tectonic structures and active processes surface processes and topography were investigated at different scales over 100 dsgsds were mapped in a 5000 km2 sector of the central eastern alps between the valtellina engadine and venosta valleys detailed lineament mapping was carried out by photo interpretation in a smaller area about 750 km2 including the upper valtellina and val venosta fault populations were also analysed in the field and their mechanisms unravelled allowing to identify different structural stages the youngest being consistent with the regional pattern of the ongoing crustal deformation finally four dsgsd examples have been investigated in detail by geological and 2d geomechanical modelling dsgsds affect more than 10 of the study area and mainly cluster in areas where anisotropic fractured rock mass and high local relief occur their onset and development is subjected to a strong passive control by mesoscopic and major tectonic features including regional nappe boundaries as well as nw se n s and ne sw trending recent brittle structures the kinematic consistency between these structures and the pattern of seismicity suggests that active tectonics may force dsgsds although field evidence and numerical models indicate slope debuttressing related to deglaciation as a primary triggering mechanism

some effects of velocity variation on avo and its interpretation in recent years interest has increased in the interpretation of the amplitude variation of reflected signals as a function of offset avo a more meaningful relationship for interpreting reflection coefficients at the target horizon is amplitude variation with incident angle ava the challenge is to convert from avo to ava the effects of velocity variation in the overburden on amplitude variation with offset avo and on the final inversion of avo data into velocity density and poisson s ratio can be significant examples are given here for subsurface medium with a vertical velocity gradient range of 0 2s 1 to 0 8s 1 when the medium is treated as homogeneous in the conversion from avo to ava this velocity variation causes significant errors about 10 percent in both the gradient of ava and in the normal incident reflection coefficient such errors produce errors of similar magnitude in the inversion of ava data into the elastic parameters of velocity poisson s ratio and density the errors dep

paraglacial slope adjustment since the end of the last glacial maximum and its long lasting effects on secondary mass wasting processes hauser kaibling austria abstract this study indicates the possible long lasting impacts of deep seated gravitational slope deformation dgsd on erosional and mass movement processes dgsd features are common large scale landforms in the crystalline basement rocks of the central alps of austria inactive forms are related to paraglacial nonglacial processes directly conditioned by former glaciation and deglaciation rock slope adjustment processes acting after glacier retreat towards the end of the late glacial period the near surface metamorphic bedrock of dgsd features is generally disintegrated such rock type favours erosion and the formation of small landslides field data laboratory analyses aerial photographs and gis based terrain analyses are used to describe the different geomorphic effects of an extremely disintegrated rock slope the studied dgsd hauser kaibling 13 6 km2 is located in central austria during the last glacial maximum the adjacent valley glacier reached an altitude of approximately 1900 m a s l glacier retreat in combination with the unfavourable tectono metamorphic setting caused gravity induced stresses to act subsequent sediment build up in the main valley restabilised the slope linear erosion cut a number of gullies into the lower part of the dgsd calculated mean erosional denudation rates at incised valley sections range from 0 5 to 2 6 mm a 1 since deglaciation smaller active landslides on the sides of the steep gullies draining the dgsd contribute to high denudation rates active landsliding is favoured by i fragmented rock ii steep slopes iii supply of surface and subsurface water by rain and snowmelt and iv human impact debris flows and debris charged flood events occurred frequently in the past during such events material was transported from the unstable slopes to the populated alluvial fans thus knowledge about the spatial distribution and the stage of development of dgsds active and currently inactive provides an important basis for risk management measures