imaging alpine crust using ambient noise wave equation tomography we present an improved crustal vs model and moho depth map using ambient noise wave equation tomography the so called ambient noise wave equation tomography is a method to invert seismic ambient noise phase dispersion data based on elastic waveform simulation which accounts for 3 d and finite frequency effects we use cross correlations of up to four years of continuous vertical component ambient seismic noise recordings from 304 high quality broadband stations in the alpine region we use model lsp eucrust1 0 obtained from traditional ambient noise tomography as initial model and we iteratively improve the initial model by minimizing frequency dependent phase traveltime differences between the observed and synthetic waveforms of rayleigh waves in the period range 10 50 s we obtain the final model after 15 iterations with 65 total misfit reduction compared to the initial model at crustal depth the final model significantly enhances the amplitudes and adjusts the shapes of velocity anomalies at moho and upper mantle depth the final model corrects an obvious systematic velocity shift of the initial model the resulting iso velocity moho map confirms a moho step along the external side of the external crystalline massifs of the northwestern alps and reveals underplated gabbroic plutons in the lower most crust of the central and eastern alps ambient noise wave equation tomography turns out to be a useful tool to refine shear wave velocity models obtained by traditional ambient noise tomography based on ray theory

a gully erosion assessment model for the chinese loess plateau based on changes in gully length and area abstract gully erosion represents an important sediment source and gully volume changes can show the contribution of gully erosion to sediment yield on the chinese loess plateau where the gully erosion is a serious problem valley bank gullies are the main gully types in small catchments and the exploration of a valid method to assess the gully erosion at a large scale is needed the objective of this study was to develop a model to assess the gully volume using linear and areal parameters that can be determined from high resolution satellite images a 3 d scanner was used to measure the valley bank gully parameters and the two quickbird images taken over 6 or 9 year periods in two study areas in the central loess plateau were used to derive historical linear and areal gully parameters the results showed that the volume v m 3 of the 44 valley bank gullies calculated from a 0 15 0 15 m digital elevation model was closely related to gully length l m and gully area a g m 2 the power function relation between v and l was v 0 6529 l 2 1622 r 2 0 78 indicating the high erosional vulnerability of the area compared with the v l relation the relation between v and a g was more pronounced v 0 2762 a g 1 3971 r 2 0 91 the relative error and nash sutcliffe efficiency between the measured and predicted gully volumes suggested that the v a g relationship had a better predictive ability for gully volume another advantage of the v a g model is that the gully area can be easily measured from very high resolution satellite images thus the v a g relationship was suggested for modelling the gully volume on the loess plateau of china the gully erosion volume during the periods of 2007 to 2013 and 2004 to 2013 in the two study areas which was estimated based on the v a g relationship and parameters measured from quickbird imagery ranged from 0 41 to 36 76 m 3 year 1 and averaged 10 32 m 3 year 1 this study presented a feasible model for assessing gully volume and volume changes over a large scale with high resolution satellite images

the deep structure of the north anatolian fault zone abstract multi scale full waveform inversion of complete continental and regional scale seismograms reveals the crustal and upper mantle signature of the north anatolian fault zone which shapes the neotectonics of turkey and the eastern mediterranean within the crust the fault zone is mostly bounded by several high velocity blocks suggesting that it developed along the edges of continental fragments with high rigidity below the crust the surface expression of the eastern and central parts of the north anatolian fault zone correlate with a pronounced low velocity band that extends laterally over 600 km around 100 km depth the low velocity band merges into the shallow anatolian asthenosphere thereby providing a link to the kirka afyon isparta volcanic field and the central anatolian volcanics we interpret the low velocity band beneath the north anatolian fault zone as the upper mantle expression of the tethyan sutures that formed 60 15 ma ago as a result of africa eurasian convergence the structurally weak suture facilitated the formation of the younger less than 10 ma crustal fault zone in this sense the north anatolian fault zone is not only a crustal feature but a narrow zone of weakness that extends into the upper mantle

geomorphic threshold conditions for ephemeral gully incision abstract ephemeral gully erosion in cultivated land is an important source of sediment that is frequently being overlooked and not accounted for in soil erosion studies furthermore little is known about the factors controlling ephemeral gully erosion in this paper the available information on the initiation and location of ephemeral gullies is summarised focusing on the relationship between the upslope drainage area a and the critical slope gradient s cr for ephemeral gully initiation by plotting the non linear relationship between critical slope gradient measured immediately upstream of the incision head and drainage area at the incision head for gullied sites it was possible to draw a straight line on log log paper through the lower most points for each of the available datasets representing a critical slope area relationship for incision consequently below this line no incision occurs this line or critical relation can also be written as a power function between critical slope and area although many factors vary between the different datasets the exponent of the drainage area relationship 0 4 showed very little variation the observed critical slope area relationship can be related to a simple model of channel initiation by overland flow furthermore this relationship can be used to identify potentially unstable sites where control measures should be undertaken

characterizing the morphology of gully cross sections based on pca a case of yuanmou dry hot valley abstract a cross section of a gully gc is important not only for computing the volume and rate of erosion of the gully but also for understanding the relationship of the gullying process landforms land use and erosional features to effectively characterize the accurate morphology of gcs and to explain their statistical regularity this study proposes 26 morphological parameters for describing the cross sections of permanent gullies we surveyed 456 gcs with a laser distance meter located at the mouth middle and head of 152 gullies in the yuanmou dry hot valley of china mapped them with cass software and calculated the morphologic parameters based on principal component analysis pca the morphological characteristics can be notably expressed by four principal components and fewer parameters with heavier load information the first principal component pc reflected the dimensions of gcs with the key parameters of width depth and area of the cross section over 94 of the depth of the left side dl the top width wt and the area s were in the range of 0 12 m 3 27 m and 0 200 m2 respectively the second pc indicated the degree of the gully s asymmetry in terms of the parameter of asymmetry ratio of width there are 201 gcs of right deflection and 184 of left deflection the third pc expressed the degree of erosion in terms of erosiveness and shape there are 77 v shaped 25 u shaped and 354 intermediate shaped gullies the percentage of u shaped cross sections is noticeably higher at the gully head than at the gully mouth and middle the fourth pc reflects the erosional pattern difference the value of the width depth ratio was distributed and varied greatly within the range of 0 92 10 69 with an average value of 3 33 these key parameters differed at different locations and sites the shape of gcs differs at different stages of development weathering crusts soil properties and vegetation cover are important for controlling the morphology of gcs in the yuanmou dry hot valley this study will not only help to improve the content of gully morphology but will also contribute to understanding the controlling factors and evolution mechanism of gullies

separating intrinsic and apparent anisotropy abstract seismic anisotropy plays a key role in studies of the earth s rheology and deformation because of its relation to flow induced lattice preferred orientation lpo of intrinsically anisotropic minerals in addition to lpo small scale heterogeneity produces apparent anisotropy that need not be related to deformation in the same way as intrinsic anisotropy quantitative interpretations of observed anisotropy therefore require the separation of its intrinsic and apparent components we analyse the possibility to separate intrinsic and apparent anisotropy in media with hexagonal symmetry typically used in surface wave tomography and sks splitting studies our analysis is on the level of the wave equation which makes it general and independent of specific data types or tomographic techniques we find that observed anisotropy can be explained by isotropic heterogeneity when elastic parameters take specific combinations of values in practice the uncertainties of inferred anisotropy are large enough to ensure that such a combination is always within the error bars it follows that commonly observed anisotropy can always be explained completely by a purely isotropic laminated medium unless all anisotropic parameters are known with unrealistic accuracy most importantly minute changes in the poorly constrained p wave anisotropy and the parameter can switch between the possible or impossible existence of an isotropic equivalent important implications of our study include 1 intrinsic anisotropy over tomographically resolved length scales is never strictly required when reasonable error bars for anisotropic parameters are taken into account 2 currently available seismic observables provide weak constraints on the relative contributions of intrinsic and apparent anisotropy 3 therefore seismic observables alone are not sufficient to constrain the magnitude of mantle flow 4 quantitative interpretations of anisotropy in terms of mantle flow require combined seismic geodynamic inversions as well as the incorporation of additional data such as topography gravity and scattered waves

prediction of concentrated flow width in ephemeral gully channels empirical prediction equations of the form w d aq b have been reported for rills and rivers but not for ephemeral gullies in this study six experimental data sets are used to establish a relationship between channel width w m and flow discharge q m 3 s 1 for ephemeral gullies formed on cropland the resulting regression equation w d 2 51 q 0 412 r 2 d 0 72 n d 67 predicts observed channel width reasonably well owing to logistic limitations related to the respective experimental set ups only relatively small runoff discharges i e q 0 02 m 3 s 1 were covered using field data where measured ephemeral gully channel width was attributed to a calculated peak runoff discharge on sealed cropland the application field of the regression equation was extended towards larger discharges i e 5 10 4 m 3 s 1 q 0 1m 3 s 1 comparing w q relationships for concentrated flow channels revealed that the discharge exponent b varies from 0 3 for rills over 0 4 for gullies to 0 5 for rivers this shift in b may be the result of i differences in flow shear stress distribution over the wetted perimeter between rills gullies and rivers ii a decrease in probability of a channel formed in soil material with uniform erosion resistance from rills over gullies to rivers and iii a decrease in average surface slope from rills over gullies to rivers the proposed w q equation for ephemeral gullies is valid for sealed cropland with no significant change in erosion resistance with depth two examples illustrate limitations of the w q approach in a first example vertical erosion is hindered by a frozen subsoil the second example relates to a typical summer situation where the soil moisture profile of an agricultural field makes the top 0 02 m five times more erodible than the underlying soil material for both cases observed w values are larger than those predicted by the established channel width equation for concentrated flow on cropland for the frozen soils the equation w d 3 17 q 0 368 r 2 d 0 78 n d 617 was established but for the summer soils no equation could be established copyright 2002 john wiley sons ltd

quantifying temporal changes in gully erosion areas with object oriented analysis abstract mapping gully systems and quantifying their changes over time are essential for implementing soil conservation measures the aim of this study is to analyze the changes in the gully systems in the context of land management image analysis of remotely sensed data in combination with field verification has proven to be a good and practical approach for mapping gully features over large areas given the variability in gully size shape and occurrence recent work has shown object based image analysis also termed as object oriented analysis ooa to be superior to pixel based methods for the identification and characterization of gullies this study presents an improved procedure to map gully features one that has been extended to assess and quantify erosion area dynamics in addition to the convention of using suitable topographic and spectral thresholds in the method the use of contrast and edge filter information and process knowledge of erosion by overland flow was incorporated in the rule set to help recognize potential gullies in ikonos 2 and geoeye 1 data changes in the area enclosed by the gully system boundary estimated for three different sub watersheds sw1 sw2 and sw3 observed over a period of eight years ranged from moderate 11 in sw2 and 21 in sw1 to a very high increase 91 in sw3 however the changes seen in gully system density were much higher than the changes in the area enclosed by the gully system boundary 81 104 and 109 in the respective sws the complex gully systems were better identified semi automatically than was possible by manual digitization in particular the finer edges of the gully systems which in turn led to better quantification of changes in the gully systems the study also determined that the rule set developed for gully feature extraction is more sensitive to the spatial resolution of the imagery used than the quality or resolution of the digital terrain model and its derivatives determining suitable segmentation parameters selecting appropriate object features for the classification the thresholds used retain the trial error aspects in this analysis this limits its application to a regional scale the rule set developed is generic and transferable to other region imagery with adaptation the rule set will be made available on our website www itc nl ooa group

assessment of gully erosion in eastern ethiopia using photogrammetric techniques abstract eastern ethiopia is severely affected by soil erosion as it is revealed by the commonly occurring deep and wide gullies these gullies are dynamically expanding into agricultural lands at an alarming rate they are also the chief sources of sediment causing siltation of lakes that are valuable sources of both drinking and irrigation water in the alemaya and harar areas a quantitative assessment of gully dynamics and the associated soil loss and a prognosis of areas susceptible to further gullying were deemed crucial aerial photographs from two different dates 1966 and 1996 with approximate scales of 1 45 000 were used to study the development and dynamics of gullies as indicated by volume changes between the two dates they were digitized at a pixel size of 20 m digital elevation models dem with grid widths of 20 and 2 m were derived from stereo image pairs separately gully breaklines and borderlines were measured for the identified gully systems gully profiles were positioned at regular intervals of 20 m along the gully length giving rise to gully sections that are portions of a gully between neighbouring profiles gully volume was computed for every gully section soil loss was estimated from the computed gully volumes using soil bulk density it showed that soil loss per unit of gully surface is very high 1 7 tons m 2 of gully surface over the 30 years time period indicating the severity of gully erosion in the subcatchment there was significant agreement between breakline measured and field measured gully depth and width for selected points this is an indication of the potential of the method for reliable gully volume estimation and hence quantification of soil loss due to gully erosion the possibility of predicting hill slope areas susceptible to further gullying based on the topographic attributes such as specific contributing area and local slope from an interpolated detailed dem with 2 m resolution was tested it was found that wetness index alone or a combination of the wetness index and the compound topographic index at the threshold values established in literature would give better results as viewed from better connectivity of flow lines and higher conformity of the predicted susceptible areas to natural gully headcut and expansion in a landscape reality

developing equations to explore relationships between aggregate stability and erodibility in ultisols of subtropical china abstract a soil aggregate represents a key soil structural unit that influences several physical soil properties such as water infiltration runoff and erosion the relationships between soil aggregate stability and interrill and rill erodibility are critical to process based erosion prediction models yet remain unclear likely due to the difficulty of distinguishing between interrill and rill eroded sediment during the erosion process this study was designed to partition interrill and rill erosion rates and relate them to the aggregate stability of ultisols in subtropical china six kinds of rare earth elements rees were applied as tracers mixed with two cultivated soils developed over quaternary red clay or shale at six slope positions soil aggregate stability was determined by the le bissonnais lb method simulated rainfall of three intensities 60 90 and 120 mm h 1 was applied to a soil plot 2 25 m long 0 5 m wide 0 2 m deep at three slope gradients 10 20 and 30 for a duration of 30 min after runoff initiation the results indicated that rill and interrill erosion rates in the soil developed over shale were considerably greater than those in the soil developed over quaternary red clay equations using an aggregate stability index a s to replace the erodibility factor of interrill and rill erosion in the water erosion prediction project wepp model were constructed after analysing the relationships between estimated and measured rill and interrill erosion data the results show that these equations based on a s have the potential to improve methods for assessing interrill and rill erosion erodibility synchronously for subtropical ultisols by using an ree tracing method

slope aspect affects geomorphic dynamics of coal mining spoil heaps in belgium abstract after the abandonment of coal mining in belgium in the 1960s 1980s many coal tips have been left to themselves increasingly these coal tips are regarded as socio cultural heritage and protected for their environmental value this research analyses the spatial distribution of the main geomorphic processes sheet and rill erosion landsliding rock fragment movement and root throw occurring on coal tips in belgium through mapping of the processes and their causal factors five spoil heaps spread over the major coal basins were studied in detail the spoil heaps were subdivided in homogeneous land units especially with regard to slope gradient vegetation cover and slope aspect qualitative and quantitative observations were done on processes and potential causal factors regressions showed that generally the expression of slope processes on the studied coal tips is 1 strongly dependent on westerly aspect of the slopes 2 independent of slope gradient which presents a narrow range 3 impeded by grass cover and 4 not fully predictable due to variability in type and age of dumped mine spoil

on the robustness of global radially anisotropic surface wave tomography a number of recent global tomographic studies have modeled three dimensional variations in the parameters of radial anisotropy as yet there is limited agreement among such studies suggesting significant uncertainties in the models which could lead to divergent geodynamical interpretations in this study we assess the robustness of lateral variations in radial anisotropy globally in the upper mantle and in the transition zone to determine the extent to which anisotropic parameters are constrained by a data set of over 10 000 000 fundamental and higher mode surface wave dispersion measurements we carry out inversions for isotropic and radially anisotropic shear wave velocity systematically changing regularization and using three different crustal models to remove the effects of the crust on the data using crustal corrections from different crustal models has an impact on the data fit comparable or larger than that obtained by including lateral variations of radial anisotropy in the modeling moreover the use of crustal corrections from different a priori crustal models may lead to different images of radial anisotropy suggesting divergent geodynamical interpretations this work suggests that the three dimensional determination of global radial anisotropy in the earth s mantle using surface wave dispersion data is still an ongoing experiment

joint inversion for three dimensional s velocity mantle structure along the tethyan margin abstract for purposes of studying the lateral heterogeneity as well as for ultimately predicting seismograms for this region we construct a new 3 d s velocity model by jointly inverting a variety of different seismic data we jointly invert regional waveforms surface wave group velocity measurements teleseismic s arrival times and crustal thickness estimates from receiver functions refraction lines and gravity surveys these data types have complementary resolving power for crust and mantle structures vertical and lateral variations shallow and deep mantle features local and global structure therefore a joint inversion of these data sets might help unravel the complexity of this tectonically diverse area these measurements are made from a combination of mantle investigation of the deep suture between europe and africa midsea program for array seismic studies of the continental lithosphere passcal geoscope geofon global seismographic network gsn international deployment of accelerometeres ida mednet national networks and local deployments throughout the study region which extends from the western mediterranean region to the hindu kush and encompasses northeastern africa the arabian peninsula the middle east and part of the atlantic ocean for reference we have fitted the waveforms of regional s and rayleigh waves from over 3800 seismograms using partitioned waveform inversion we include over 3000 crustal thickness estimates from receiver functions gravity measurements and refraction profiles we include rayleigh wave group velocities for hundred thousands of paths transecting the region we have over 3000 teleseismic s arrival times measured through cross correlation and over 170000 from picks originally reported to the international seismological centre isc

crust and upper mantle of the western mediterranean constraints from full waveform inversion abstract we present a full waveform tomographic model of the western mediterranean crust and mantle constructed from complete three component recordings from permanent and temporary networks the incorporation of body and multi mode surface waves in the period range from 12 150 s allows us to jointly resolve crustal and mantle structures including the guadalquivir tajo and ebro basins at shallow depth as well as the western mediterranean subduction system in the transition zone no mantle plumes can be detected beneath the european cenozoic rift system including the massif central in addition to the well studied alboran slab a strong e w trending high velocity anomaly is present around 200 300 km depth beneath the algerian coast this previously undetected african slab is detached from the surface and broken into two segments it may be interpreted as the slab that caused the opening of the liguro provencal basin through successive roll back between 35 15 ma

mantle dynamics in the mediterranean the mediterranean offers a unique opportunity to study the driving forces of tectonic deformation within a complex mobile belt lithospheric dynamics are affected by slab rollback and collision of two large slowly moving plates forcing fragments of continental and oceanic lithosphere to interact this paper reviews the rich and growing set of constraints from geological reconstructions geodetic data and crustal and upper mantle heterogeneity imaged by structural seismology we proceed to discuss a conceptual and quantitative framework for the causes of surface deformation exploring existing and newly developed tectonic and numerical geodynamic models we illustrate the role of mantle convection on surface geology a coherent picture emerges which can be outlined by two almost symmetric upper mantle convection cells the downwellings are found in the center of the mediterranean and are associated with the descent of the tyrrhenian and the hellenic slabs during plate convergence these slabs migrated backward with respect to the eurasian upper plate inducing a return flow of the asthenosphere from the backarc regions towards the subduction zones this flow can be found at large distance from the subduction zones and is at present expressed in two upwellings beneath anatolia and eastern iberia this convection system provides an explanation for the general pattern of seismic anisotropy in the mediterranean first order anatolia and adria microplate kinematics and may contribute to the high elevation of scarcely deformed areas such as anatolia and eastern iberia more generally the mediterranean is an illustration of how upper mantle small scale convection leads to intraplate deformation and complex plate boundary reconfiguration at the westernmost terminus of the tethyan collision

tethys atlantic interaction along the iberia africa plate boundary the betic rif orogenic system abstract initial se dipping slow subduction of the ligurian tethys lithosphere beneath africa from late cretaceous to middle oligocene twisting to a later faster e dipping subduction of the subcrustal lithosphere is proposed as an efficient geodynamic mechanism to structure the arcuate betic rif orogenic system this new subduction related geodynamic scenario is supported by a kinematic model constrained by well dated plate reconstructions tectonic sedimentary and metamorphic data sets the slow initial se dipping subduction of the ligurian tethys realm beneath the malaguide upper plate unit is sufficient to subduct alpujarride and nevado filabride rocks to few tens of kilometers of depth in middle eocene times the shift from se to e dipping subduction during latest oligocene early miocene was possibly caused by both the inherited geometry of the highly segmented ligurian tethys domain and by the fast roll back of the subducted lithospheric slab the early miocene rather synchronous multiple crustal and subcrustal processes comprising the collision along the betic front the exhumation of the hp lt metamorphic complexes the opening of the alboran basin its flooring by hp alpujarride rocks and subsequent ht imprint can be explained by the fast nw and w directed roll back of the ligurian tethys subcrustal lithospheric slab the w retreat of the ligurian tethys lithosphere in middle late miocene times could partly explain the initiation of its lateral tear and consequent subcrustal processes from latest miocene onward the betic rif system evolved under both the northerly push of africa resulting in tightening at crustal and subcrustal levels and by the distinct current dynamics of the steep lithospheric slab the sw directed scape of the rif fold belt is one of the most striking evidences linked to the recent evolution of the squeezed betic rif system between africa and iberia

measuring gullies by synergetic application of uav and close range photogrammetry a case study from andalusia spain abstract gullies naturally exhibit complex morphologies and hence are difficult to measure photogrammetric methods are promising tools to overcome such problems due to 3d reconstruction from overlapping images without disturbing the surface airborne e g unmanned aerial vehicles uav and terrestrial image acquisition platforms are possible data sources for comprehensive digital gully modelling in this study an approach for the synergetic utilisation of uav and terrestrial images for high resolution 3d model generation is introduced while proper uav mission planning is necessary terrestrial images can be acquired spontaneously and flexibly depending on the encountered terrain conditions to supplement uav data without confining accuracy demands terrestrial images are processed solely with additional information from already existent 3d models and orthophotos from uav image processing during this field campaign uavs are suitable for flexible and frequent gully monitoring however with the case specific flight configuration 3d modelling is restricted at steep gully walls above slope gradients of 50 60 as well as overhanging gully walls due to the limiting birds eye view additional terrestrial images are used to overcome these limitations and fill up data gaps in this study the final merged digital gully model reveals a resolution about 0 5 cm and an accuracy of 1 cm a gully headcut in andalusia spain is analysed to confirm the suitability of the synergetic data utilisation a study period of three months during winter season is investigated to measure multi temporal 3d volume changes the positive volume balance amounts to 5 m 3 for a gully area of 170 m 2 and is caused mainly by anthropogenic interactions concluding the combination of uav and terrestrial data allow for comprehensive gully models with high spatial resolution at frequent intervals

measuring rill erosion at plot scale by a drone based technology the traditional direct method i e metric ruler and rillmeter of monitoring rill erosion at plot scale is time consuming and invasive because it modifies the surface of the rilled area measuring rill features using a drone based technology is considered a non invasive method allowing a fast field relief in the experimental sparacia area a survey by a quadricopter microdrones md4 200 was carried out and this relief allowed the generation of a digital elevation model dem with a mesh size of 1 cm and a resolution elevation equal to 2 mm for three plots l g and c affected by rill erosion at first for the experimental l plot which is 44 m long the rill features were surveyed by a manual method which was carried out by drawing on the pc screen the rill paths obtained by a visual orthophoto interpretation this manual method was not applicable for the plots in which rills of limited depth occurred and were not detectable then for both l plot and the other experimental plots having a length ranging from 22 to 44 m an automatic extraction method of rills from dem was applied using an appropriate calculation routine a vector coverage of transects orthogonal to the main flow direction i e the maximum slope steepness path was generated the intersection of each plot dem with the transect coverage allowed to obtain both the cross sections and the main rill morphological features for the l plot the comparison between the rill morphological features obtained by the two different methods manual automatic was carried out finally the length volume relationship and a dimensionless relationship proposed in literature were tested for all studied experimental plots copyright 2015 john wiley sons ltd

deformation and failure of the tymfristos tunnel greece the tymfristos tunnel a 1 365m long road tunnel with an 11m section diameter was excavated through the highly tectonized low strength flysch formation of central greece about 1 year after the completion of the excavation in 1995 convergence of up to 20 followed by failure of the support system was recorded a 501m long segment in which the failure occurred was reexcavated based on a more detailed study of the ground conditions however this second phase was also followed by an up to 6 convergence the detailed geodetic study of the three dimensional kinematics of the support shell in relation time ring closure delays and support measures reveals an unusual time history of convergence occasionally continuing even after the ring closure and a nonuniform distortion of the lining furthermore uncontrolled deformation of certain weak sections propagated bidirectionally to adjacent previously stabilized sections producing a chain effect responsible for destabilization and resumed convergence

finite frequency rayleigh wave tomography of the western mediterranean mapping its lithospheric structure 1 we present a 3 d shear wave velocity model for the crust and upper mantle of the western mediterranean from rayleigh wave tomography we analyzed the fundamental mode in the 20 167 s period band 6 0 50 0 mhz from earthquakes recorded by a number of temporary and permanent seismograph arrays using the two plane wave method we obtained phase velocity dispersion curves that were inverted for an isotropic vs model that extends from the southern iberian massif across the gibraltar arc and the atlas mountains to the saharan craton the area of the western mediterranean that we have studied has been the site of complex subduction slab rollback and simultaneous compression and extension during african european convergence since the oligocene the shear velocity model shows high velocities beneath the rif from 65 km depth and beneath the granada basin from 70 km depth that extend beneath the alboran domain to more than 250 km depth which we interpret as a near vertical slab dangling from beneath the western alboran sea the slab appears to be attached to the crust beneath the rif and possibly beneath the granada basin and sierra nevada where low shear velocities 3 8 km s are mapped to 55 km depth the attached slab is pulling down the gibraltar arc crust thickening it and removing the continental margin lithospheric mantle beneath both iberia and morocco as it descends into the deeper mantle thin lithosphere is indicated by very low upper mantle velocities beneath the alboran sea above and east of the dangling slab and beneath the cenozoic volcanics

deep structure of the continental margin and basin off greater kabylia algeria new insights from wide angle seismic data modeling and multichannel seismic interpretation abstract during the algerian french spiral survey aimed at investigating the deep structure of the algerian margin and basin two coincident wide angle and reflection seismic profiles were acquired in central algeria offshore greater kabylia together with gravimetric bathymetric and magnetic data this 260 km long offshore onshore profile spans the balearic basin the central algerian margin and the greater kabylia block up to the southward limit of the internal zones onshore results are obtained from modeling and interpretation of the combined data sets the algerian basin offshore greater kabylia is floored by a thin oceanic crust 4 km with p wave velocities ranging between 5 2 and 6 8 km s in the northern hannibal high region the atypical 3 layer crustal structure is interpreted as volcanic products stacked over a thin crust similar to that bordering the margin and related to miocene post accretion volcanism these results support a two step back arc opening of the west algerian basin comprising oceanic crust accretion during the first southward stage and a magmatic and probably tectonic reworking of this young oceanic basement during the second westward opening phase the structure of the central algerian margin is that of a narrow 70 km magma poor rifted margin with a wider zone of distal thinned continental crust than on the other margin segments there is no evidence for mantle exhumation in the sharp ocean continent transition but transcurrent movements during the second opening phase may have changed its initial geometry the plio quaternary inversion of the margin related to ongoing convergence between africa and eurasia is expressed by a blind thrust system under the margin rising toward the surface at the slope toe and by an isostatic disequilibrium resulting from opposite flexures of two plates decoupled at the continental slope this disequilibrium is likely responsible for the peculiar asymmetrical shape of the crustal neck that may thus be a characteristic feature of inverted rifted margins

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

factors controlling the morphology and volume v length l relations of permanent gullies in the northern ethiopian highlands small scale aerial photographs and high resolution satellite images available for ethiopia since the second half of the twentieth century as for most countries allow only the length of gullies to be determined understanding the development of gully volumes therefore requires that empirical relations between gully volume v and length l are established in the field so far such v l relations have been proposed for a limited number of gullies environments and were especially developed for ephemeral gullies in this study v l relations were established for permanent gullies in northern ethiopia having a total length of 152 km in order to take the regional variability in environmental characteristics into account factors that control gully cross sectional morphology were studied from 811 cross sections this indicated that the lithology and the presence of check dams or low active channels were the most important controls of gully cross sectional shape and size cross sectional size could be fairly well predicted by their drainage area the v l relation for the complete dataset was v 0 562 l 1 381 n 33 r2 0 94 with 34 9 of the network having check dams and or being low active producing such relations for the different lithologies and percentages of the gully network having check dams and or being low active allows historical gully development from historical remote sensing data to be assessed in addition gully volume was also related to its catchments area a and catchment slope gradient sc this study demonstrates that v l and v a sc relations can be very suitable for planners to assess gully volume but that the establishment of such relations is necessarily region specific copyright 2013 john wiley sons ltd

evidence for slab rollback in westernmost mediterranean from improved upper mantle imaging this work is funded by the picasso project nsf grant ear 0808939 the deployment and data processing for spanish stations was funded by consolider ingenio 2010 project topo iberia csd2006 00041 as well as alert es cgl2010 19803 c03 02

subduction and the depth of convection in the mediterranean mantle 1 we tie together geological data paleotectonic reconstruction plate motion and tomographic analysis to unravel the history of subduction and back arc extension of the eastern and central mediterranean in these two regions extensional processes started contemporaneously around 30 myr ago but with marked differences in the eastern region the aegean basin opened slowly 1 cm yr behind a shallow dipping slab 40 45 the corresponding high velocity anomaly extends inside the upper mantle and can be also followed in the midmantle down to a depth of at least 1500 km its descent into the midmantle initiated most probably during the late cretaceous and the trench moved northeastward following the path of the eurasian plate and under the persistent push of the african plate conversely in the central mediterranean region subduction initiated later and the motion of the subducting slab is confined to the upper mantle causing punctuated and rapid episodes of back arc extension provencal and tyrrhenian basins behind a slab that dips steeply 75 we explore the causes that control how the slab subducted and interacted with the lower more viscous part of the mantle

dating of small gully formation and establishing erosion rates in old gullies under forest by means of anatomical changes in exposed tree roots southern poland abstract small gullies occur in forested gully systems on the undulating loess plateau in southern poland the old gully hillslopes are mainly covered with 200 year old beech trees in contrast with the surface of the summit plateau which is cultivated agricultural land beech roots are exposed in the gullies through erosion wood vessels in the root tree rings divide into early wood and late wood and after the roots are exposed start to make fewer vessels these anatomical changes in root tree rings allow us to date erosion episodes small gullies form in a different manner on the valley floor and on hillslopes in valley bottoms erosion features are often formed at some distance from one another and in time small gullies combine to form a single longer one depending on local conditions such as the hillslope profile hillslopes may exhibit headward erosion or may be eroded downwards hilllope gullies may be transformed into side valleys as a result of gradual widening and deepening dating the exposure of roots indicates that small gullies had already formed in the valley system by 1949 intensive gully erosion was recorded between 1984 and 2002 during intense precipitation in 1984 and of particular note during the extraordinary flood of 1997 which affected all of central europe the mean rate of small gully erosion in the old gully system studied is 0 63 m year on hillslopes the mean gully erosion rate is 0 21 0 52 m year and on the valley bottoms 0 18 1 98 m year high bottom erosion rates resulted from the emergence of long gullies during the erosion episodes in 1984 and 1997 sheet flow in valley floors intensifies at times of heavy rainfall which causes long gullies to form taking into account the fact that conditions favoured erosion the rate at which the old gullies under forest were transformed should be considered slow new side gullies form slowly within the valley and it appears that if erosion progressed at the rate observed new side valleys would take a few hundred years to form

characteristics and controlling factors of old gullies under forest in a temperate humid climate a case study from the meerdaal forest central belgium abstract in many forests of northwestern europe old gullies can be found but few studies have reported their genesis and characteristics this study investigates these old gullies under forest in the large case study area of meerdaal forest in the central belgian loess belt the objectives are 1 to determine the spatial distribution of these gullies 2 to measure their morphological and topographical characteristics and 3 to reconstruct the factors that led to their development in the 1329 ha study area 252 channel like incisions were mapped different types of incisions could be distinguished besides small and large gullies many incisions were sunken lanes or road gullies these road gullies are aligned along north south oriented lines whereas the concentration of old gullies is strongly related to the distribution of archaeological sites out of the 252 mapped incisions 43 large gullies and 21 representative road gullies were selected for detailed morphological and topographical measurements the characteristics of these two types of incisions were compared with ephemeral gullies formed under nearby cropland significant differences in morphology between the three types could be demonstrated ephemeral gullies under cropland and large gullies under forest differ significantly in all measured parameters except bottom width both the old gullies and road gullies under forest have a significantly larger cross section and total eroded volume compared with the ephemeral gullies observed under cropland this indicates that once formed the old gullies were not ploughed in nor were they filled by sediment originating in their drainage areas because of limited sediment production comparing topographical characteristics i e slope at the gully head and runoff contributing area of forest gullies and ephemeral gullies that formed under cropland yields important indications about their formation the larger sedimentation slope of forest gullies compared with ephemeral gullies and road gullies suggests that the forest gullies incised on vegetated slopes as a consequence of runoff from the adjacent plateau where the forest cover was disturbed for the old gullies under forest no relation between slope at the gully head and runoff contributing area is observed probably because most gullies occur on very steep slopes when simulating arable land use in the study area zones where ephemeral gullies are expected to develop can be predicted using published topographical threshold relationships comparing the zones where ephemeral gullies are predicted with the position of old gullies under forest leads to the conclusion that gully incision was most probably not triggered by extreme rainfall events and that they are not of periglacial origin the observed gully pattern can best be explained by local anthropogenically determined land use changes

linking long term gully and river channel dynamics to environmental change using repeat photography northern ethiopia abstract in the highlands of northern ethiopia gully occurrence is linked to poverty driven unsustainable use of the land in a vulnerable semi arid and mountainous environment where intensive rainfall challenges the physical integrity of the landscape trends in gully and river channel erosion and their relation to triggering environmental changes can proffer valuable insights into sustainable development in northern ethiopia in order to assess the region wide change in gully and river channel morphology over 140 years a set of 57 historical photographs taken in tigray and clearly displaying gully cross sections were precisely repeated from 2006 till 2009 ninety two percent of the gully and river sections n 38 increased in cross sectional area during the studied period especially after 1975 two repeatedly photographed catchments of lake ashenge and atsela allowed a detailed study of gully development from 1936 until 2009 a conceptual hydrogeomorphic model was devised for these catchments and validated for the northern ethiopian highlands three major phases can be distinguished in the hydrological regime of the catchments in the first phase between 1868 or earlier and ca 1965 the relatively stable channels showed an oversized morphology inherited from a previous period when external forcing in environmental conditions had caused the channels to shape in the second phase ca 1965 ca 2000 increased aridity and continued vegetation clearance accelerated the channel dynamics of the gully and river system the third phase ca 2000 present started after the large scale implementation of soil and water conservation measures in 2009 23 of the gully and river sections were stabilizing this paper validates previous research indicating severe land degradation in the second half of the 20th century additionally it demonstrates that the recent erosive cycle started around 1965 and that at the present time improved land management stabilizes headwater streams

in situ monitoring of tunnel deformation evolutions from auxiliary tunnel in deep mine abstract deformation caused by excavation is of great effects on tunnel stability and tunnel support design monitoring using instruments that are installed in place within the examined tunnel cannot record a large amount of surrounding rock deformation that usually takes place ahead and close to the tunnel face for this important reason the overall deformation process was observed using instruments installed prior to excavation from auxiliary tunnel in a 900 m deep coal mine tunnel two monitoring methods i e multipoint extensometers and wave velocity tomography were used at two monitoring sections with different rock lithology the results showed that a large amount of deformation at both monitoring sections had already been occurred when the excavation face passed the monitoring sections at a very small distance the size of the plastic zone at monitoring section 1 is identified as 1 8 m 0 36 d d denotes the diameter of the examined tunnel and the velocities within this zone decreased from 4 5 km s to 2 km s the primary deformation was generated in a distance from 0 8 d ahead the excavation face to 2 3 d behind the excavation face the induced deformation was also observed after the primary deformation period and some additional deformation was still occurred in the plastic zone although the size of plastic zone remains constant the displacements and p wave velocities at the two monitoring sections showed little differences

p wave tomography of the mantle under the alpine mediterranean area 1 we study the upper mantle p wave velocity structure below the euro mediterranean area down to 1000 km depth by seismic travel time tomography we invert summary residuals constructed with both regional and teleseismic first arrival data reported by the international seismological centre isc 1964 1995 introducing some alternative strategies in the travel time tomographic approach and a new scheme to correct teleseismic data for global mantle structure our high resolution model pm0 5 is parameterized with three dimensional 3 d linear splines on a grid of nodes with 0 5 spacing in both horizontal directions and 50 km vertical spacing we obtain about 26 root mean square rms reduction of residuals by inversion in addition to roughly 31 reduction after summary rays formation and selection sensitivity analyses are performed through several test inversions to explore the resolution characteristics of the model at different spatial scales the distribution of large scale fast anomalies suggests that two different stages of a convection process presently coexist in very close regions the mantle dynamics of western central europe is dominated by blockage of subducted slabs at the 660 km discontinuity and ponding of seismically fast material in the transition zone contrarily in the eastern mediterranean fast velocity material sinks into the lower mantle suggesting that the flow of the cold downwelling here is not blocked by the 660 km discontinuity on a smaller scale the existence of tears in the subducted slab lithospheric detachment all along both margins of the adriatic plate as proposed by some authors is not supported by our tomographic images

gully erosion in the siwalik hills nepal estimation of sediment production from active ephemeral gullies a simple field based monitoring programme was established in a small catchment area 4 6 km2 to find the rates of gully erosion in the siwalik hills nepal the rates are used to estimate the amount of sediment produced by gully erosion in the catchment three large and active gullies were selected with areas ranging from 0 44 to 0 78 ha aerial photographs taken in 1964 1978 and 1992 were ortho rectified and used to study the dynamics of gully heads the same gullies were also monitored manually using an orthogonal reference system fixed by erosion pins around the gully heads results from the aerial photos indicated that the gullies expanded remarkably over the period from 1964 to 1992 by 34 to 58 per cent head retreat rates during that period were 0 48 0 55 and 0 73 m a 1 and average annual sediment evacuation was estimated as 2534 171 959 60 and 2783 118 m3 a 1 for the three gullies respectively from the field measurement estimated volumes were found to vary from 731 57 to 2793 201 m3 a 1 over the monitoring period of two years it was also found that the gullies produce sediment which accounts for up to 59 per cent of the sediment produced from surface erosion in the headwater catchment the findings are useful for planning and executing appropriate control measures and constructing a sediment hazard map at the catchment scale copyright 2006 john wiley sons ltd

assessment of soil losses by ephemeral gully erosion using high altitude stereo aerial photographs the objective of this study is to explore in a critical way the potential of high altitude stereo aerial photographs for the assessment of ephemeral gully erosion rates on 28 may 1995 an intensive rainfall event 30 mm h 1 during 30 min return period 3 years occurred in central belgium ephemeral gullies formed within an area of 218 ha study area 1 were mapped and measured both in the field and by high altitude aerial photos taken at the same time comparison of these two methods shows that if only one of the two surveying techniques had been used only 75 per cent of the total ephemeral gully length would have been detected so that the combination of aerial and field data leads in fact to the best possible determination of total gully length within the selected area a correction factor c is proposed so that the results of an ephemeral gully erosion survey based on high altitude stereo aerial photos can be adjusted for the undetected gullies next a sequential series of high altitude stereo aerial photographs taken in six different years was analysed in order to determine ephemeral gully erosion rates in three selected study areas study areas 2 3 and 4 selection criteria were chosen so that these three areas were similar to study area 1 and representative for the cultivated areas in central belgium where intense soil erosion regularly occurs ephemeral gullies were mapped and their total length was measured from the aerial photos using a mean gully cross section of 0 2635 m2 determined in study area 1 the average eroded volume is 1 89 m3 ha 1 in six months for study area 1 0 86 m3 ha 1 in six months for area 2 1 44 m3 ha 1 in six months for area 3 and 2 37 m3 ha 1 in six months for area 4 according to the correction factor c these mean ephemeral gully erosion volumes have to be increased by 44 per cent the ephemeral gully erosion rates based on high altitude stereo aerial photos correspond well with the results of other surveys carried out in the belgian loess belt copyright 1999 john wiley sons ltd

the value of a physically based model versus an empirical approach in the prediction of ephemeral gully erosion for loess derived soils abstract a data set on soil losses and controlling factors for 58 ephemeral gullies has been collected in the belgian loess belt from march 1997 to march 1999 of the observed ephemeral gullies 32 developed at the end of winter or in early spring winter gullies and 26 ephemeral gullies developed during summer summer gullies the assessed data have been used to test the physically based ephemeral gully erosion model egem and to compare its performance with the value of simple topographical and morphological indices in the prediction of ephemeral gully erosion analysis shows that egem is not capable of predicting ephemeral gully cross sections well although conditions for input parameter assessment were ideal some parameters such as channel erodibility critical flow shear stress and local rainfall depth showed great uncertainty rather than revealing egem s inability of predicting ephemeral gully erosion this analysis stresses the problematic nature of physically based models since they often require input parameters that are not available or can hardly be obtained with respect to the value of simple topographical and morphological indices in predicting ephemeral gully erosion this study shows that for winter gullies and summer gullies respectively over 80 and about 75 of the variation in ephemeral gully volume can be explained when ephemeral gully length is known moreover when previously collected data for ephemeral gullies in two mediterranean study areas and the data for summer gullies formed in the belgian loess belt are pooled it appears that one single length l volume v relation exists v 0 048 l 1 29 r 2 0 91 these findings imply that predicting ephemeral gully length is a valuable alternative for the prediction of ephemeral gully volume a simple procedure to predict ephemeral gully length based on topographical thresholds is presented here secondly the empirical length volume relation can also be used to convert ephemeral gully length data extracted from aerial photos into ephemeral gully volumes

what is the contribution of time dependent deformation in tunnel convergence tunnel excavation produces stress changes to the ground and strain to the support lining leading to the closure convergence or instability of the excavated area convergence recorded after section excavation is assigned to i strain resulting from the progressive tunnel front advance face advance effect and ii the time dependent properties of the soil material ground creep effect in the present study based on the geodetic monitoring records of two recent road tunnels in greece a simple methodology to estimate the contribution of each of the two effects is presented our analysis reveals that at least half of the total deformation of the examined tunnel sections is due to ground creep indicating that the major portion of tunnel deformation is due to the time dependent properties of the ground a result supported by previous studies from other tunnels as well

coulomb stress changes from earthquakes to underground excavation failures abstract evidence from shallow tunnels and mines indicates that in certain cases deformation and failure are not confined to the vicinity of the excavation front as is widely believed this situation has recently been described as lateral strain propagation from a source to remote parts of the excavation through low strength rocks a similar situation is observed in deep excavations mainly expressed by rock bursts and micro earthquakes we suggest that slow propagation or seismic radiation of deformation away from the excavation front can be explained on the basis of the theory of coulomb failure stress changes in analogy to faulting in large earthquakes local increase of stresses due to the excavation or failure in a certain point leads to a slight increase of stresses around this point if adjacent points are already at a critical level for failure this slight increase triggers a laterally domino style propagating new failure yet in contrast to earthquakes triggered deformation in mining can in principle be predicted and counteracted

relative changes in sediment supply and sediment transport capacity in a bedrock controlled river rivers can be affected by multiple natural and human induced changes to sediment supply and to sediment transport capacity assessment of the relative importance of these changes enables appropriate river management here assessments are made of the relative changes in sediment supply and sediment transport capacity of an 83 km section of the bedrock controlled coxs river new south wales australia these relative changes are estimated in turn for land degradation historical climate variations and dam closure measurements of gully erosion extent from aerial photographs indicate that since european settlement the average annual sediment supply to the river has increased by a factor of 20 rainfall records and flow gauging records show a climate shift in the mid 1940s on the basis of hydrologic modeling the increased streamflow in the period since the mid 1940s is estimated to have increased sediment transport capacity by a factor of almost 3 closure of lyell dam in 1982 stopped sediment supply from the upper catchment on the basis of hydrologic modeling the flow regulation and abstraction at the dam is estimated to have reduced the long term average sediment transport capacity downstream by 15 the current sediment transport capacity after the climate shift and dam closure is 2 6 times higher that in the first half of this century in spite of this net increase in sediment transport capacity the huge volume of sediment delivered to the channel from gully erosion has led to widespread sand deposition along much of the river much of the river bed that was previously dominated by bedrock is now alluvial in character only the steepest reaches remain bedrock dominated

tunnelling through the young himalayas a case history of the maneri uttarkashi power tunnel abstract a 8 56 km long circular tunnel with a finished diameter of 4 75 m has been constructed for the maneri hydel hydro electric project on the river bhagirthi the tunnel passes through quartzitic and metabasic rock formations of the young himalayas the tunnel excavation was accomplished from four headings one from the upstream end at maneri two from an intermediate adit at heena and one from the downstream end near uttarkashi where an 80 mw power house is located problems of tunnel face collapse with or without heavy ingress of water cavity formation and large tunnel closures leading to buckling of steel ribs on account of squeezing ground conditions were encountered methods to combat these problems are described the absence of advance knowledge of the frequently chanigng rock mass and ground water conditions and therefore the inability of the tunnelling engineers to modify the construction method and the support system was responsible for these problems predic values of support pressure obtained from the empirical methods of terzaghi barton et al and the one proposed by singh et al have been compared with the observed values of checking the reliability of various methods particularly for poor rock masses

monitoring the earthquake source process in north america with the implementation of the usgs national earthquake information center prompt assessment of global earthquakes for response system pager rapid determination of earthquake moment magnitude is essential especially for earthquakes that are felt within the contiguous united states we report an implementation of moment tensor processing for application to broad seismically active areas of north america this effort focuses on the selection of regional crustal velocity models codification of data quality tests and the development of procedures for rapid computation of the seismic moment tensor we systematically apply these techniques to earthquakes with reported magnitude greater than 3 5 in continental north america that are not associated with a tectonic plate boundary using the 0 02 0 10 hz passband we can usually determine with few exceptions moment tensor solutions for earthquakes with m w as small as 3 7 the threshold is significantly influenced by the density of stations the location of the earthquake relative to the seismic stations and of course the signal to noise ratio with the existing permanent broadband stations in north america operated for rapid earthquake response the seismic moment tensor of most earthquakes that are m w 4 or larger can be routinely computed as expected the nonuniform spatial pattern of these solutions reflects the seismicity pattern however the orientation of the direction of maximum compressive stress and the predominant style of faulting is spatially coherent across large regions of the continent

oxygen isotopes reveal crustal contamination and a large still partially molten magma chamber in chaine des puys french massif central the two main magmatic properties associated with explosive eruptions are high viscosity of silica rich magmas and or high volatile contents magmatic processes responsible for the genesis of such magmas are differentiation through crystallization and crustal contamination or assimilation as this process has the potential to enhance crystallization and add volatiles to the initial budget in the chaine des puy series french massif central silica and h2o rich magmas were only emitted during the most recent eruptions ca 6 15 ka here we use in situ measurements of oxygen isotopes in zircons from two of the main trachytic eruptions from the chaine des puys to track the crustal contamination component in a sequence that was previously presented as an archetypal fractional crystallization series zircons from sarcoui volcano and puy de dome display homogeneous oxygen isotope compositions with 18o 5 6 0 25 and 5 6 0 3 respectively and have therefore crystallized from homogeneous melts with 18omelt 7 1 0 3 compared to mantle derived melts resulting from pure fractional crystallization 18odif mant 6 4 0 4 those 18omelt values are enriched in 18o and support a significant role of crustal contamination in the genesis of silica rich melts in the chaine des puys assimilation fractional crystallization models highlight that the degree of contamination was probably restricted to 5 5 9 5 with rcrystallization rassimilation varying between 8 and 14 the very strong intra site homogeneity of the isotopic data highlights that magmas were well homogenized before eruption and consequently that crustal contamination was not the trigger of silica rich eruptions in the chaine des puys the exceptionally strong inter site homogeneity of the isotopic data brings to light that sarcoui volcano and puy de dome were fed by a single large magma chamber our results together with recent thermo kinetic models and an experimental simulation martel et al 2013 support the existence of a large 6 15 km3 still partially molten mid crustal reservoir 10 12 km deep that is filled with silica rich magma

engineering geological and geotechnical investigations along the head race tunnel in teesta stage iii hydroelectric project india abstract an investigation of the engineering geological properties and geotechnical parameters of rock masses along a horseshoe shaped head race tunnel hrt in the teesta stage iii hydroelectric project sikkim india was carried out to analyze the rock mass properties for optimum support system the empirical methods field tests and numerical modeling were employed to determine rock mass properties several empirical equations and statistical analysis were performed to obtain the rational and reasonable results the tunnel passes through different geological formations and critical zones the field investigations indicate the presence of five joint sets which contribute towards the development of unforeseen wedges along the tunnel alignment the attitudes of joints were measured by brunton compass and analyzed with dips v 5 1 software the potential wedge block analysis and factor of safety fs were determined using unwedge v 3 0 software the rock mass classification assessment of tunnel stability and necessary support types were carried out with q rmr and rmi systems as empirical tunnel support design methods the numerical method phase2 v 6 0 was used to quantify plastic zone and squeezing potential of the tunnel the installed support systems as per empirical methods were cross checked by means of numerical modeling field observations and engineering judgments according to the results from different methods 3 0 4 4 m rock bolts shotcrete 0 1 0 15 m wire mesh and final concrete lining were proposed it was observed that the plastic and deformed zones surrounding the excavation area got appreciably reduced after the recommended support installation

the potential of 3d gully monitoring with gis using high resolution aerial photography and a digital photogrammetry system although gully erosion is generally considered a major process of land degradation its contribution to total soil loss by erosion has recently been a subject of much discussion the lack of adequate methods for the documentation and monitoring of gullies resulted in the shortage of quantitative data therefore a high resolution remote sensing system for aerial surveys by blimp or kite has been developed which meets spatial and temporal image resolutions required for short term gully monitoring the objective of this paper is to examine the potential of a method using non metric digital photogrammetry and gis for gully surface modelling and monitoring two bank gullies representing different morphological types of gullies v shaped and u shaped were chosen from a dataset of gully systems in semi arid spain the considerable relief energy and complex topography of the gullies in a natural vegetated landscape were found to be a challenge to digital photogrammetric techniques introducing errors which inhibit fully automated dem generation using a hybrid method combining stereomatching for mass point extraction with manual 3d editing and digitizing high resolution dems 5 and 7 5 cm pixel size were created for the study sites gis analysis of the dems for different monitoring periods 2 to 4 years allowed the computation of gully area and volume as well as their changes with an accuracy and detail sufficient to represent the geomorphological forms and processes involved furthermore the spatially continuous survey of the entire form offered the possibility of distinguishing different zones of activity both at the gully rim and within the gully interior identifying patterns of erosion and deposition which indicate the limited use of headcut retreat rates for the assessment of sediment production on a short term basis

evaluation of a gully headcut retreat model using multitemporal aerial photographs and digital elevation models 1 a large fraction of soil erosion in temperate climate systems proceeds from gully headcut growth processes nevertheless headcut retreat is not well understood few erosion models include gully headcut growth processes and none of the existing headcut retreat models have been tested against long term retreat rate estimates in this work the headcut retreat resulting from plunge pool erosion in the channel hillslope integrated landscape development child model is calibrated and compared to long term evolution measurements of six gullies at the bardenas reales northeast spain the headcut retreat module of child was calibrated by adjusting the shape factor parameter to fit the observed retreat and volumetric soil loss of one gully during a 36 year period using reported and collected field data to parameterize the rest of the model to test the calibrated model estimates by child were compared to observations of headcut retreat from five other neighboring gullies the differences in volumetric soil loss rates between the simulations and observations were less than 0 05 m3 yr 1 on average with standard deviations smaller than 0 35 m3 yr 1 these results are the first evaluation of the headcut retreat module implemented in child with a field data set these results also show the usefulness of the model as a tool for simulating long term volumetric gully evolution due to plunge pool erosion

the success of recent land management efforts to reduce soil erosion in northern france abstract soil erosion is an important problem in open field agricultural landscapes with almost no permanent vegetation in small headwater catchments and with few physical obstacles to reduce runoff velocities runoff concentration along linear landscape elements plot boundaries or thalwegs frequently causes ephemeral gullies to form the latter reflecting the poor hydrogeomorphic condition of the land and soilscape to address this problem and to remediate negative on and off site effects land management efforts have multiplied over the past decades in many regions this includes amongst other measures the implementation of vegetation barriers called fascines in the loess dominated aa river basin of northern france where cropland accounts for 67 of the cover we investigated the effect of fascines on ephemeral gully erosion dynamics together with rainfall characteristics and cropland management this was accomplished through a spatially explicit study of 269 sites prone to ephemeral gullying using a diachronic analysis of historical aerial photographs between 1947 and 2012 ephemeral gully densities at the scale of the aa river basin 643 km2 varied between 0 39 and 1 31 m ha 1 long term average of 0 68 m ha 1 with local maxima up to 9 35 m ha 1 densities are however much higher when only considering the most erosion vulnerable municipalities long term average of 2 23 4 30 m ha 1 those values should be used when comparing results from this study to other reports of ephemeral gully erosion fascines were introduced in 2001 and were present in 30 of the gully erosion sites by 2012 although the presence of fascines has an effect on gully length reduction spatial and temporal variations in gully length were mainly driven by cumulative precipitation measurement of sediment deposition at 29 fascines in 2016 showed that only 47 of the fascines functioned as sediment sinks they stored on average 1 7 mg of sediment per winter half year corresponding to 0 009 mg ha 1 the results suggest that fascines positively impact the landscape s resilience and reduce ephemeral gully erosion rates the use of vegetation barriers such as fascines are increasingly implemented for erosion control in western europe but pose problems for the management of open field landscapes

slab break offs in the alpine subduction zone after the onset of plate collision in the alps at 32 34 ma the deep structure of the orogen is inferred to have changed dramatically european plate break offs in various places of the alpine arc as well as a possible reversal of subduction polarity in the eastern alps have been proposed we review different high resolution tomographic studies of the upper mantle and combine shear and body wave models to assess the most reliable geometries of the slabs several hypotheses for the tectonic evolution are presented and tested against the tomographic model interpretations and constraints from geologic and geodetic observations we favor the interpretation of a recent european slab break off under the western alps in the eastern alps we review three published scenarios for the subduction structure and propose a fourth one to reconcile the results from tomography and geology we suggest that the fast slab anomalies are mainly due to european subduction adriatic subduction plays no or only a minor role along the tauern window sections possibly increasing towards the dinarides the apparent northward dip of the slab under the eastern alps may be caused by imaging a combination of adriatic slab from the dinaric subduction system and a deeper lying european one as well as by an overturned retreating european slab

alteration characteristics of granite contact zone and treatment measures for inrush hazards during tunnel construction a case study abstract several large scale mud and water inrush events occurred during excavation of the denghuazhai tunnel at a depth of 175 m in the contact zone between geodic granite and tuff by analyzing the inrush process the characteristics of the inrush hazards such as high pressure abundant water high mud and sand content and strong destructive power were revealed in addition the inrush hazards were intermittent uncertain and sudden an intrusive contact zone between geodic granite and tuff was revealed by regional geological investigation large scale alteration occurred both in geodic granite and tuff near the contact zone petrographic analyses indicated that alteration to albite sericite and kaolinite occurred in geodic granite and alteration to quartz and montmorillonite took place in tuff gradually toward the contact zone furthermore the changes were gradational within and between various alteration grades the closer to the contact zone the higher degree of alteration the less the primary minerals including quartz k feldspar and plagioclase the more the secondary minerals such as sericite and clay minerals tests on porosity saturated water content and uniaxial compressive strength indicated that alteration led to significant deterioration of physical and mechanical properties of rocks except for silicified tuff especially for the zonal clay in the central area of contact zone the physical and mechanical properties were poor and obvious swelling disintegration and argillation were observed tunnel excavation triggered swelling disintegration and argillation of clay leading to several large scale inrush events in terms of treatment of inrush hazards first of all a comprehensive exploration method based on petrographic analyses geophysical detection and borehole drilling was established according to the alteration characteristics so as to identify the scale and composition of the altered zone the principle of consolidation before removal was adopted to deal with the inrush deposits for breach sealing and reinforcement energy release and stress reduction during tunnel construction and regular drainage during operation were achieved by dewatering measures namely drainage supplemented by sealing water drainage and solids remaining reinforcement measures including full face curtain grouting and double layer pipe sheds were adopted to reinforce and seal the highly disturbed rock and soil in advance finally technical measures including bench excavation enhancement of support stiffness and timely installation of secondary support were employed to effectively prevent large deformation in disturbed rock masses with the above measures the left and right tunnels of the denghuozhai tunnel have passed through the altered zone successfully

full 3d tomography for the crustal structure of the los angeles region we apply full 3d tomography f3dt to a regional dataset in the los angeles area in f3dt the starting model as well as the model perturbation is three dimensional and the sensitivity frechet kernels are computed using numerical schemes that account for the full physics of 3d wave propagation f3dt can account for the nonlinearity of structural inverse problem through iteration thus providing the most efficient means for assimilating seismic observations into dynamic ground motion models we have successfully applied a scattering integral si formulation of f3dt to improve a 3d elastic structure model the southern california earthquake center scec community velocity model version 3 0 cvm3 0 with lowest shear velocity clamped at 1 km sec in the los angeles region our data are time and frequency localized measurements of phase delay anomalies relative to synthetics computed from the 3d elastic starting model the frechet kernels for our measurements were computed by convolving the earthquake wave fields generated by point earthquake sources with the receiver green tensors rgts which are the spatial temporal fields produced by three orthogonal unit impulsive point forces acting at the receiver locations we inverted 7364 phase delay measurements of p and s body waves by using the lsqr method the revised 3d model laf3d provides substantially better fit to the observed waveform data than the 3d starting model to our knowledge this study is the first successful application of f3dt using real data in structural seismology

medium term gully headcut retreat rates in southeast spain determined from aerial photographs and ground measurements this paper deals with gully retreat rates at different time scales whereby the short term time scale may span a time interval of 1 5 years the medium term time scale a time interval of 5 50 years and the long term time scale a time interval of more than 50 years an analysis of high altitude aerial photographs in combination with ground measurements allowed us to quantify volumetric gully head retreat rates for 12 permanent gullies in southeast spain guadalentin and guadix study areas over a 40 43 year time interval medium term time scale this resulted in an average retreat rate ve of 17 4 m3 year 1 a power relationship between drainage basin area a and medium term volumetric gully head retreat rate ve 0 069a0 380 r2 0 51 n 21 was found by combining the gully head retreat rates obtained in this study with those obtained by a dendrochronological method the exponent b and the coefficient of determination r2 of the power relationships ve aab increases from the short term to the long term time scale expressing the increasing importance of drainage basin area in gully development with time considerable differences between gully head retreat rates measured at the short and medium term time scales at individual gullies showed the importance of land use changes and unsuccessful management practices on gully head retreat and the episodic nature of gully head retreat when piping and tension cracking are involved higher gully head retreat rates are obtained at the medium term time scale compared to the short term time scale but the differences are not significantly different at 10 the medium term methods tend to measure proportionally more high gully retreat rates but less extreme values compared to the short term method this is explained by a more equal distribution of extreme rainfall events both in space and time at a longer term time scale and hence a higher probability of measuring the average effect of both small and extreme rainfall events at each gully

accuracy of high resolution photogrammetric measurements of gullies with contrasting morphology field techniques allow accurate direct measurements on gully geometry even in three dimensional 3d coordinates accuracy and detail reproduction is limited mainly by experimental setup and density of measurements and less so by the precision of the measuring equipment in contrast remote sensing techniques permit the coverage of large study areas with a minimum of time and effort however the indirect measurements from imagery are known to depend on factors like image resolution quality of ground control vegetation cover and image evaluation technique which strongly influence the measurement accuracy the objective of the present study was to investigate to what extent the accuracy of 3d gully measurement using photogrammetric techniques depends on gully morphology at a study site in the bardenas reales navarre spain field measurements of cross sections were taken for five gullies with contrasting morphology and dimensions and used as reference data for analysing the errors associated with a corresponding dataset obtained using small format aerial photogrammetry whose pixel size on the ground is 16 mm results show that volumetric gully measurements by means of photogrammetric techniques are strongly affected by the gully morphology in particular by its width depth w d ratio because of the increasing sun shadowing and sight shadowing effects associated with narrower gullies only wide shallow gullies are little affected by this problem for gullies of an intermediate typology w d between 0 5 and 2 5 the accuracy of photogrammetric measurements will much depend on the time of day and the period of the year when the photographs are taken and narrow deep gullies w d 0 5 will be likely to be highly inaccurate at any time although this study was conducted with a large measurement scale for small mostly ephemeral gullies the w d ratios judged challenging for photogrammetric analysis in this study are also common for larger sized gullies of the permanent bank gully type

the impact of snowmelt and heavy rainfall runoff on erosion rates in a gully system lublin upland poland the study examines water runoff and geomorphic processes within a permanent gully located in an agricultural catchment of the lublin upland southeast poland the studies were conducted in the period 2003 to 2006 during which time the volume and intensity of precipitation were recorded and water runoff and sediment concentration at the outlet of the main gully were measured after large surface runoff events that resulted in geomorphic effects erosion and accumulation forms were examined the role of snowmelt and heavy rains in the runoff of water and suspended solids from the catchment as well as their effect on the dynamics of certain processes such as rill erosion piping and accumulation within the gully all were evaluated it was observed that the gully developed spatially through piping and headcut processes during snowmelt while the main gully form became shallower as a result of accumulation processes headcut erosion at the gully bottom and transport of the material out of the catchment predominantly during pluvial runoff events were much less intensive it was estimated that the intensity of snowmelt runoff in the years 2003 to 2006 was similar to the multi annual average while the intensity of pluvial runoff was significantly lower an attempt was made to describe the dynamics of gully erosion and the direction of gully system evolution on a medium term time scale 50 to 100 years it was found that the roles of snowmelt and heavy rains in such catchments are in opposition snowmelt runoff events lead to the spatial development of the gullies and make them shallower while pluvial runoff events add to the deepening of the gully and result in transporting the material outward these two processes keep the gully system in relative balance copyright 2009 john wiley sons ltd

a spatial information technology approach for the mapping and quantification of gully erosion abstract in contrast to the effort during the last decades to investigate sheet interrill and rill soil erosion processes relatively few studies have been focused on quantifying and or predicting gully erosion the extension of the use of modern spatial information technologies such as geographical information systems gis digital elevation modelling dem and remote sensing have created new possibilities for research in this field a key issue to be addressed as the basis for predicting the effects of global changes such as land use and climate changes is the mapping and quantification of gully erosion rates including rate of retreat of gully walls and rate of sediment production this research work presents a method to compute the rate of retreat of gully walls and the associated rate of sediment production caused by gully erosion the proposed method uses multitemporal aerial photographs and multitemporal digital elevation models both of which have been processed using gis techniques the research was applied to a sample catchment of 25 km2 located in catalonia spain aerial photographs at scale of 1 30 000 from 1957 and orthophotos from 1993 were used to map gully erosion and determine erosion rates between 1957 and 1993 the rates of channel incision and sediment production were computed from the subtraction of multitemporal digital elevation models the rate of gully walls retreat was 0 2 m year 1 representing a rate of 0 9 m2 year 1 the maximum rate of channel incision 0 7 0 8 m year 1 occurred at the head of the gully and at meandering zones the rate of sediment production caused by gully erosion was 1322 142 ton ha 1 year 1 in comparison with other methods to compute sediment production caused by gully erosion processes the proposed method integrates the losses due to overland flow mass movements and gully deepening and supposes an improvement to locate the areas within the gullies with higher erosional activity

ephemeral gully erosion in northwestern spain this study aimed to describe types of ephemeral gullies and to determine their origin evolution and importance as sediment sources in a coruna province northwest spain ephemeral gullies and or rills have been measured in a representative sample of medium textured soils most prone to crusting developed over basic schist this sample consisted of 11 small sites ranging from 0 63 to 7 34 ha a case study of concentrated rill gully erosion in a 0 47 ha catchment with coarse textured soils developed over granite was also reported the mean slope of the sites studied ranged from 6 1 to 16 8 main periods when soil surface was poorly covered were late spring maize seedbeds and late autumn early winter grassland and winter cereal seedbeds case studies where fields were left bare in winter were also investigated soil incision and channel formation were observed even with relatively low rainfall intensities when the soil surface was sealed but also after a single short intense rainfall event on recently tilled surfaces concentrated erosion took place mainly on seedbeds and newly tilled soils in late spring and by autumn or early winter but gullies also appeared in other seasons when the soil surface was left bare in most of the cases studied ephemeral gully erosion caused significant soil losses ranging between 2 and 5 m3 ha for a single season to locally over 25 m3 ha gully development was significantly affected by agricultural operations such as lineal elements often acting as initial axes of concentrated erosion main gullies tended to reappear at the same position

testing the use of an image based technique to measure gully erosion at sparacia experimental area the first part of this investigation was aimed at testing the use of a three dimensional 3d digital terrain model dtm and a quasi tridimensional 2 5d digital elevation model dem obtained by a large series of oblique images of eroded channels taken from consumer un calibrated and non metric cameras for two closed earth channels having a different sinuosity the ground measurement of some cross sections by a profilometer p was carried out the real volume of each channel was also measured by waterproofing it by a plastic film and filling it with a known volume of water the comparison among the three methods 3d 2 5d and p pointed out that a limited underestimation of the total volume always occurs and that the 3d method is characterized by the minimum difference between measured and real volume this preliminary analysis allowed to conclude that 3d model can be used as benchmark and the 2 5d model is accurate enough to describe the investigated earth channels in the subsequent part of the investigation the three ground measurement methods were applied for surveying of an ephemeral gully eg channel at the sparacia area using the 3d model as benchmark the morphological and hydraulic variable values of the 24 surveyed cross sections determined by both 2 5d model and profilometer were compared this comparison showed that the estimate error is generally less than 10 the eg measurements carried out by the three methods agreed with the available literature measurements and supported the applicability both of the empirical relationship between eg length and its eroded volume and the theoretical dimensionless relationship among the morphological variables describing the channelized erosion process finally it was demonstrated that the effect of the distance interval on the eg volume measurement by 3d and 2 5d models is negligible for the investigated eg

outstanding issues in excavation of deep and long rock tunnels a case study excavation of deep and long tunnels faces several distinctive challenges such as unknown geological structures high groundwater pressure and high in situ stress as compared with conventional tunnels the deep and long taining tunnel in fujian province south china was excavated in complex geological settings this tunnel had to pass through various squeezing fault zones and intensely jointed zones large deformations and high pressure groundwater were frequently encountered during excavation to predict the potential adverse geological structures a comprehensive method which included tunnel seismic prediction and ground penetration radar detection as well as horizontal drilling was developed energy release and pressure reduction as well as timely sealing pre excavation curtain grouting and radial grouting were adopted to control the high pressure groundwater countermeasures including improvement of support stiffness double layered primary support and pre support increase of preset deformati

the effects of buoyant crust on the gravitational instability of thickened mantle lithosphere at zones of intracontinental convergence summary using both numerical experiments and approximate linear theory we examine the stability of a 2 d three layered viscous system that represents crust over mantle lithosphere overlying asthenosphere if horizontal shortening of lithosphere occurs as in mountain building the development of gravitational instability may follow one of two distinct paths localized downwelling occurs beneath the region of horizontal shortening and crustal thickening if the layer representing crust has a large viscosity coefficient is relatively dense or is thin relative to the underlying layer that represents mantle lithosphere conversely for a low viscosity ratio or buoyant crust downwelling flow develops on the flanks of the zone of convergence and the mantle lithosphere layer thins beneath the central region thinning in such a setting would facilitate volcanism and high temperature metamorphism during the development of a mountain belt a series of numerical experiments with different density and viscosity structures including runs with non newtonian viscosity show that this general description is insensitive to minor differences in the depth distributions of density and viscosity the tendency of structures with relatively thick crustal layers or relatively thin lithospheric mantle to favour paired marginal downwellings may account for sustained volcanism during intracontinental deformation where lithosphere initially is warm thin and weak the western part of the tien shan in asia and the region including and surrounding the alboran sea illustrate some of the features associated with paired marginal downwellings the western transverse ranges of california and the southern alps of new zealand share features associated with single downwelling flow beneath the axes of the belts

engineering geological studies of the diversion tunnel focusing on stabilization analysis and support design iran abstract in this paper a detailed engineering geological assessment of rock masses and support design studies at garmi chay dam site has been carried out this project is located in the northwest of iran and will be used for flow control and water storage the diversion tunnel of the dam has a diameter of 5 5 m and a length of 420 m and will be driven in slightly to highly weathered micaschist and trachy andesite rock units the geological studies include field and laboratory investigations that based on the results for more exact investigation tunnel alignment was divided into three geotechnical zones these zones consist mainly of highly weathered gray micaschists dark red trachy andesites and slightly weathered gray micaschists respectively then for every zone support capacity of rock masses was evaluated by means of empirical and numerical methods the rock mass classification systems rmr q gsi rsr src and rmi the convergence confinement method and a 2d finite element computer software phase2 were used for empirical and numerical method respectively according to the results acquired from these methods some stability problems were expected in the tunnel especially in highly weathered micaschist zone so that in practice two big collapses occurred because of high weathering low constants of rock masses and their soil like behavior the stability analysis by analytical method does not give illogical results in lightly weathered micaschist zone the support system suggested by empirical method was applied and its performance was evaluated by means of numerical modeling after installation the support suggested by phase2 program the thickness of plastic zone and deformations around the tunnel decreased significantly consequently the agreement of these methods with each other was resulted and using combination of them was recommended for more reliable support design

medium term evolution of a gully developed in a loess derived soil field surveys in the belgian loess belt revealed the presence in many forested areas of large permanent gully systems most of which are currently inactive in cultivated areas such gullies can only be observed in cross sectional soil profiles through hollows as virtually all such large gullies are currently infilled with colluvium little is known about the spatial distribution initiation and temporal evolution of these large permanent gully systems on loess derived soils therefore the medium term evolution of a gully initiated in a cultivated area on loess derived soils southwest of leuven belgium in may june 1986 was studied over 13 years two intense rainfall events created this ephemeral gully which was not erased by subsequent tillage between june 1986 and the december 1999 eight field surveys were conducted to measure gully dimensions during two surveys topographic indices e g slope and drainage area were also measured daily rainfall for the measuring period were obtained from a rainfall station located some 10 km southwest of the gully analysis of rainfall data showed that no extreme rainfall event was required to initiate such large permanent gullies as observed in forested areas and through cross sectional profiles in cultivated fields in the belgian loess belt return periods of the event that caused the gully varied between 1 year and 25 years depending on the assumptions used for defining event rain intensity once established length surface area and volume of the studied gully evolved with time cumulative rainfall or cumulative runoff following a negative exponential relation this accords with observations reported for gullies in australia and the usa this study shows that a degressive increase of gully extension can be largely explained by the evolution of a slope drainage area factor s a which is proportional to stream power with time while gully length and gully surface area asymptotically evolve towards a final value gully volume decreased at a given point in time from this it is inferred that sediment deposition will potentially infill the gully to such an extent that the farmer can drive across it from this moment on the combined effect of water and tillage erosion in the gully drainage area will lead towards rapid infilling this expected evolution of a gully in cultivated fields accords with observations of large infilled gully systems in cultivated areas in eastern belgium the permanent gullies observed under forest are attributed to the fact that after severe gully erosion this area was reforested or abandoned therefore the sediment source was cut off and the gully was not filled in by sediment deposition

imaging a mantle plume beneath the french massif central abstract teleseismic tomography is now widely recognised as a very powerful tool for studying the velocity structure of the lithosphere asthenosphere system on both local and regional scales a prime objective is to identify velocity perturbations and to constrain their location and intensity here we use the arrival times of p waves from teleseismic events recorded by a dense network of mobile and permanent stations within the french massif central to derive a 3d p velocity model for an area of 425 km 300 km combined with knowledge of the basement geology of the area and the timing and geochemical characteristics of tertiary quaternary volcanic activity we consider that the velocity model provides unequivocal evidence for the ascent of a thermally and chemically anomalous mantle plume beneath the massif central during tertiary times our model is consistent with regional bouger gravity anomalies documented patterns of neogene recent uplift and deformation fabrics within lithosphere derived mantle xenoliths exhumed by the volcanics

assessment of sidewall erosion in large gullies using multi temporal dems and logistic regression analysis although in the last decades gully erosion has been a thriving research field few studies have specifically addressed the contribution and location of sidewall erosion processes in gullies in this paper sidewall erosion in some large gullies in a mediterranean area anoia penedes ne spain is mapped and assessed for two time intervals 1975 1995 and 1995 2002 using detailed digital elevation models derived from aerial photographs at a scale of 1 5000 to 1 7000 logistic regression analysis is applied to compute the probability of occurrence of gully sidewall erosion from terrain variables the results confirm the complex nature of sidewall processes whose intensity is most probably related to rainfall characteristics prolonged wet soil conditions in the period 1995 2002 together with the large and high intensity rainfall of an extreme event occurred on 10th june 2000 help to explain the different sediment production rates 16 0 4 mg ha 1 year 1 in 1975 1995 and 83 6 3 mg ha 1 year 1 in 1995 2002 the logistic regression analysis revealed that gully wall slope angle was the main factor controlling gully sidewall failure in gully walls with high slope angles tension crack development is the main process promoting wall collapse the application of the logistic regression model showed a high overall accuracy 87 but over 50 of commission and omission errors for the class of interest sidewall erosion in agreement with the variance explained by the model

the effect of some watershed soil characteristics and morphometric factors on the relationship between the gully volume and length in fars province iran abstract a survey consisting of 146 first order gullies selected from five sites with different land use soil and watershed properties was carried out to estimate the parameters of the empirical power function in order to describe the relationship between the gully volume and length in fars province iran subsequently the gullies were clustered into seven groups a to g based on nine morphometric factors the linearized functions were fitted to the natural logarithms of the volume and length in each group and the parameters a and b were determined the obtained a and b parameters are in the ranges of 1 0 10 8 and 0 8 1 4 respectively comparison of a and b parameters in each group with the mean of nine factors and the mean soil watershed and land use characteristics in each group showed that the gully volume and average cross section are correlated with the gully depths in different sections and the gully head slopes also it was shown that the parameters of fitted functions to the plots of gully volumes versus gully lengths are proportional to width at the gully heads the gully widths at the top and bottom of the five meter sections are correlated with the average upstream watershed area of the gullies

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

shear wave velocities in the upper mantle of the western alps new constraints using array analysis of seismic surface waves it remains challenging to obtain absolute shear wave velocities of heterogeneities of small lateral extension in the uppermost mantle this study presents a cross section of vs across the strongly heterogeneous 3 d structure of the western european alps based on array analysis of data from 92 broad band seismic stations from the cifalps experiment and from permanent networks in france and italy half of the stations were located along a dense sublinear array using a combination of these stations and off profile stations fundamental mode rayleigh wave dispersion curves were calculated using a combined frequency time beamforming approach we calculated dispersion curves for seven arrays of approximately 100 km aperture and 14 arrays of approximately 50 km aperture the latter with the aim of obtaining a 2 d vertical cross section of vs beneath the western alps the dispersion curves were inverted for vs z with crustal interfaces imposed from a previous receiver function study the array approach proved feasible as vs z from independent arrays vary smoothly across the profile length results from the seven large arrays show that the shear velocity of the upper mantle beneath the european plate is overall low compared to ak135 with the lowest velocities in the internal part of the western alps and higher velocities east of the alps beneath the po plain the 2 d vs model is coherent with i a 100 km thick eastward dipping european lithosphere west of the alps ii very high velocities beneath the po plain coherent with the presence of the alpine european slab and iii a narrow low velocity anomaly beneath the core of the western alps from the brianconnais to the dora maira massif and approximately colocated with a similar anomaly observed in a recent teleseismic p wave tomography this intriguing anomaly is also supported by traveltime variations of subvertically propagating body waves from two teleseismic events that are approximately located on the profile great circle

the jurassic evolution of the africa iberia conjugate margin and its implications on the evolution of the atlantic tethys triple junction abstract the central atlantic north atlantic and maghrebian tethys formed a triple junction during the mesozoic break up of pangea plate reconstructions of this triple junction have concentrated on the atlantic branches for which there are abundant geophysical data over their conjugate margins and associated oceanic domains this is not the case for the maghrebian tethys where both the mesozoic iberian and african margins and the intervening ocean are mostly overthrust by the betic rif tell orogenic systems the resulting lack of constraints on the evolution of the africa iberia system has led most authors to treat the evolution of this system as a secondary problem in the more global atlantic and tethys systems in this paper the evolution of the basins of iberia and northwest africa is discussed and geological constraints are used to propose a new late triassic fit of iberia with north america and africa this late triassic fit and its implications for jurassic evolution are compared with the evolution of the sedimentary basins of the atlantic tethys triple junction and in particular those of the africa iberia margins the geological evidence and the resulting plate reconstructions are consistent with a jurassic evolution of the africa iberia system that is dominated by three major events 1 the early to middle jurassic transition in which oblique rifting gives way to transtensional rifting 2 the middle to late jurassic transition marking the termination of most rifting in the system and interpreted to coincide with exhumation of sub continental mantle and formation of oceanic crust in a setting dominated by transcurrence between africa and iberia and 3 the late jurassic to early cretaceous transition in which the rate of relative motion between and iberia and africa decreased significantly as rifting in the north atlantic gained momentum

engineering geological study of the second part of water supply karaj to tehran tunnel with emphasis on squeezing problems abstract this research is concerned with the assessment of squeezing potential along the second part of water supply karaj to tehran tunnel one of the new components of water conveyance system in the north of iran is the karaj to tehran water conveyance tunnel that has been excavated by a double shield tbm this research has been performed on the second part of the tunnel with 14 km long passes mainly through the pyroclastic and igneous rocks of eocene age the geological studies include field and laboratory investigations based on the results and for more exact investigation tunnel alignment has been divided into 20 geological engineering units rock mass classifications have been performed for all units then rock mass properties were calculated using empirical equations because of high overburden up to 800 m and the presence of faults and crushed zones it was necessary to evaluate squeezing potential along the critical section of the tunnel therefore empirical and semi empirical approaches and a new method as critical strain have been used for evaluation of squeezing potential some experimental equations were used for estimation of critical strain and also phase 2 program has been used to calculate tunnel convergence consequently squeezing index was estimated this index is used for determination of squeezing degree as a result fair squeezing potential was found in crushed zones along the tunnel route

induced deformation during tunnel excavation evidence from geodetic monitoring abstract during tunnel excavation convergence i e a tendency for reduction of the section area of the void formed is observed due to the stress redistribution around the excavation free surface this deformation accumulates with a gradually decreasing rate until an equilibrium level is obtained its amplitude depends on the rock mass conditions the support system and the excavation procedure as well as on the state of stress and is usually recognized as a two dimensional effect i e a deformation confined to a plane normal to the tunnel axis not affecting neighboring sections in the last years electronic theodolites a new generation of geodetic instruments which can describe in detail the 3 d changes in the shape of tunnels during their excavation stage relative to fixed reference frames became available making possible the understanding of the detailed pattern of such changes especially the effect of rejuvenation of deformation in previously stabilized sections while tunnel excavation is progressing analysis of geodetic monitoring records of certain recently constructed tunnels indicates that occasionally large deformation from specific source sections is transferred along the tunnel axis to host neighboring sections causing additional time delayed deformation of previously stabilized sections and necking of the tunnel this induced deformation is not due to effects such as nearby excavations changes in the hydrological conditions etc and to tertiary creep its distribution along the tunnel axis seems to depend on the potential of host sections to accommodate additional stresses from neighboring deformation source sections and it may lead to a progressive domino type failure the overall process is reminiscent of the triggering of new earthquakes by coulomb static stress changes caused by a certain earthquake on the condition that the stress level in the epicentral areas of the new events was close to the rupture limit

paleogeographic evolution of a segmented oblique passive margin the case of the sw iberian margin the sw iberian margin is an oblique passive margin developed during the mesozoic as part of the opening of the westernmost ligurian tethys the algarve basin developed on the sw iberian margin and its sedimentary record was strongly controlled by tectonics the algarve basin was dominated during the mesozoic by wsw ene trending extensional faults and their associated depocenters segmented by oblique nw se transfer zones two major nw se trending transfer zones connected the algarve basin to the gorringe bank in the west and to the betic basin in the east the sw iberian margin was later inverted during late cretaceous to cenozoic times due to convergence between africa and iberia inversion of the algarve basin and the sw iberian margin was controlled by both the wsw ene and nw se trending structures formed during the passive margin phase the evolution of the algarve basin during the mesozoic and up to the paleogene is documented in this paper through paleogeographic reconstructions based on field geology and reinterpretation of offshore seismic and well data

measurements of rill and gully erosion in sicily this article reports the results of a field investigation aimed to characterize the morphology of both rills monitored at sparacia experimental area and two ephemeral gullies egs located in the tremamargi basin sicily italy at first the available literature data together with the measurements carried out in this investigation were used to show that the eg length is a key parameter for the estimation of the eroded volume then the comparison among the pairs length and volume corresponding to measured rills egs and gullies showed that the exponent of the power relationship is independent of the channelized erosion type rill eg and gully while a different scale factor has to be used for each erosion process finally a single relationship applicable to all channelized erosion processes was deduced applying the dimensional analysis and the self similarity theory copyright 2011 john wiley sons ltd

a grassed waterway and earthen dams to control muddy floods from a cultivated catchment of the belgian loess belt muddy floods i e runoff from cultivated areas carrying large quantities of soil are frequent and widespread in the european loess belt they are mainly generated in dry zero order valleys and are nowadays considered as the most likely process transferring material eroded from cultivated hillslopes during the holocene to the flood plain the huge costs of muddy flood damages justify the urgent installation of control measures in the framework of the soil erosion decree of the belgian flemish region a 12 ha grassed waterway and three earthen dams have been installed between 2002 2004 in the thalweg of a 300 ha cultivated dry valley in the belgian loess belt the measures served their purpose by preventing any muddy flood in the downstream village despite the occurrence of several extreme rainfall events with a maximum return period of 150 years the catchment has been intensively monitored from 2005 2007 and 39 runoff events were recorded in that period peak discharge per ha was reduced by 69 between the upstream and the downstream extremities of the grassed waterway gww furthermore runoff was buffered for 5 12 h behind the dams and the lag time at the outlet of the catchment was thereby increased by 75 reinfiltration was also observed within the waterway runoff coefficients decreasing by a mean of 50 between both extremities of the gww sediment discharge was also reduced by 93 between the gww s inflow and the outlet before the installation of the control measures specific sediment yield ssy of the catchment reached 3 5 t ha 1 yr 1 and an ephemeral gully was observed nearly each year in the catchment since the control measures have been installed no ephemeral gully has developed and the ssy of the catchment dropped to a mean of 0 5 t ha 1 yr 1 hence sediment transfer from the cultivated dry valley to the alluvial plain should dramatically decrease total cost of the control measures that are built fora 20 year period is very low 126 sic ha 1 compared to the mean damage cost associated with muddy floods in the study area 54 sic ha 1 yr 1 similar measures should therefore be installed to protect other flooded villages of the belgian loess belt and comparable environments c 2008 elsevier b v all rights reserved

a method for dendrochronological assessment of medium term gully erosion rates abstract a method based on dendrochronology to estimate gully erosion rates was developed as an alternative of traditional methods for assessing medium term gully retreat rates such as field monitoring of headcuts or aerial photo interpretation of gully retreat the method makes use of trees or parts of a tree affected by gully erosion revealing information on the history of the erosion process by datable deviations of their normal growth pattern hence defined as datable objects these include roots exposed by erosion browsing scars made by ungulates on exposed roots or on above ground parts of fallen trees exposed and dead root ends root suckers stems branches and leading shoots of fallen trees and a sequence of trees within a gully the method is based on the differentiation between three main conditions depending on the relation between the dynamics of the datable object part of the tree and the development of the gully the first condition implies that the datable object was created before erosion of the gully volume to be dated e g exposed tree roots according to the second condition the datable object developed as an immediate consequence of the erosion event e g growth reactions of a fallen tree the third condition implies that the datable object was created some time after the erosion event took place e g trees colonising the gully bed each principle has consequences for the accuracy and the correct interpretation of the estimated erosion rate i e whether the true erosion rate is underestimated exact or overestimated in spite of methodological limitations and dendrochronological dating problems the method was successfully applied in southeast spain conservative estimations of gully head retreat rate resulted in an average medium term 3 46 years value of 6 m3 year 1 n 9 for gully sidewall processes the average minimum erosion rate per unit sidewall length amounted 0 1 m3 year 1 m 1 n 9 a strong correlation was found between the headcut retreat rate vm ortho m3 year 1 and the drainage basin area a m2 of the gullies expressed by vm ortho 0 02a0 57 r2 0 93 n 9 comparing the findings from this study with those obtained by short term headcut retreat monitoring suggests a high reliability of the estimated retreat rates supporting the applicability of the developed dendrochronological method

travel time tomography of the european mediterranean mantle down to 1400 km abstract the 3 d p wave velocity structure of the mantle below europe the mediterranean region and a part of asia minor is investigated this study is a considerable extension of an earlier tomographic experiment that was limited to imaging upper mantle structure only here the earth s volume under study encompasses the mantle to a depth of 1400 km and we increase the number of international seismological centre isc data for inversion by a factor of four by taking more years of observation and by including data from teleseismic events the most important departure from the earlier study is that we do not use the jeffreys bullen model as a reference model but an improved radially symmetric velocity model the pm2 model which is appropriate for the european mediterranean mantle our inversion procedure consists of two steps first the radial model pm2 is determined from the isc delay times by a nonlinear trial and error inversion of the data as opposed to the jeffreys bullen model the new reference model has a high velocity lithosphere a low velocity zone and seismic discontinuities at depths of 400 and 670 km next the isc data are corrected for effects related to the change in reference model and inverted for 3 d heterogeneity relative to the pm2 model we follow this two step approach to attain a better linearizable tomographic problem in which ray paths computed in the pm2 model provide a better approximation of the actual ray paths than those computed from the jeffreys bullen model hence the two step scheme leads to a more credible application of fermat s principle in linearizing the tomographic equations inversion results for the 3 d heterogeneity are computed for both the uncorrected isc data and for the pm2 data the data fit obtained in the two step approach is slightly better than in the inversion of isc data using the jeffreys bullen reference model a comparison of the tomographic results demonstrates that the pm2 data inversion is to be preferred to assess the spatial resolution an analysis is given of hit count patterns sampling of the mantle by ray paths and results of sensitivity tests with 3 d synthetic velocity models the spatial resolution obtained varies with position in the mantle and is studied both in map view and in cross section in the well sampled regions of the mantle the spatial resolution for larger scale structure can qualitatively be denoted as reasonable to good and at least sufficient to allow interpretation of larger scale anomalies a comparison is made of the results of this study with independent models of s velocity heterogeneity obtained in a number of investigations and with a prediction of the seismic velocity structure of the mantle computed from tectonic reconstructions of the mediterranean region in the context of this comparison interpretations of large scale positive anomalies found in the mediterranean upper mantle in terms of subducted lithosphere are given specifically addressed are subduction below southern spain below the western mediterranean and italy and below the aegean in the last region a slab anomaly is mapped down to depths of 800 km

p and s velocity anomalies in the upper mantle beneath europe from tomographic inversion of isc data we present a new tomographic model for p and s velocity anomalies beneath europe 30 n 55 n 5 w 40 e extending in depth up to 700 km and constrained by inversion of data from the international seismological center isc catalogue the algorithm uses the traveltimes from events located in the study area recorded by all available worldwide stations as well as times from teleseismic events recorded by european stations the events from the isc catalogue have been relocated and combined into composite events all the traveltimes were corrected for crustal structure using the reference model eucrust 07 the resulting velocity anomalies show similar large scale patterns as observed in previous studies but have a higher resolution which allows detection of some features in more detail for example it is now possible to assess the depth extension of the small slow velocity body beneath the eifel region and eger graben the p and the s model show a good consistency in the uppermost 200 km below most of the european area and in some parts even in the deeper layers e g beneath the apennines and the hellenic arc the new model provides clear images of some principal features which were previously detected in a limited number of studies while the comparison between p and s velocity anomalies provides novel constraints to address on their nature e g the gap in the adriatic plate subducted below the central southern apennines in this paper we pay special attention to testing the reliability of the results the random noise effect is evaluated using a test with independent inversion of two data subsets with odd even events the spatial resolution is estimated using different checkerboard tests furthermore we present a synthetic model with realistic patterns which reproduces after performing forward and inverse modelling the same shape and amplitudes of the anomalies as in the case of the real data inversion in this case the parameters of the model can be used to assess the amplitudes of p and s anomalies that is critical for evaluation of other petrophysical parameters temperature density composition etc in the upper mantle 2009 the authors journal compilation 2009 ras