ground motion modeling of the 1906 san francisco earthquake part ii ground motion estimates for the 1906 earthquake and scenario events abstract we estimate the ground motions produced by the 1906 san francisco earthquake making use of the recently developed song et al 2008 source model that combines the available geodetic and seismic observations and recently constructed 3d geologic and seismic velocity models our estimates of the ground motions for the 1906 earthquake are consistent across five ground motion modeling groups employing different wave propagation codes and simulation domains the simulations successfully reproduce the main features of the boatwright and bundock 2005 shakemap but tend to over predict the intensity of shaking by 0 1 0 5 modified mercalli intensity mmi units velocity waveforms at sites throughout the san francisco bay area exhibit characteristics consistent with rupture directivity local geologic conditions e g sedimentary basins and the large size of the event e g durations of strong shaking lasting tens of seconds we also compute ground motions for seven hypothetical scenarios rupturing the same extent of the northern san andreas fault considering three additional hypocenters and an additional random distribution of slip rupture directivity exerts the strongest influence on the variations in shaking although sedimentary basins do consistently contribute to the response in some locations such as santa rosa livermore and san jose these scenarios suggest that future large earthquakes on the northern san andreas fault may subject the current san francisco bay urban area to stronger shaking than a repeat of the 1906 earthquake ruptures propagating southward towards san francisco appear to expose more of the urban area to a given intensity level than do ruptures propagating northward

litho1 0 an updated crust and lithospheric model of the earth we present the litho1 0 model which is a 1 tessellated model of the crust and uppermost mantle of the earth extending into the upper mantle to include the lithospheric lid and underlying asthenosphere the model is parameterized laterally by tessellated nodes and vertically as a series of geophysically identified layers such as water ice sediments crystalline crust lithospheric lid and asthenosphere litho1 0 is created by constructing an appropriate starting model and perturbing it to fit high resolution surface wave dispersion maps love and rayleigh group and phase over a wide frequency band 5 40 mhz we examine and discuss the model with respect to key lithospheric parameters such as average crustal velocity crustal thickness upper mantle velocity and lithospheric thickness we then compare the constructed model to those from a number of select studies at regional and global scales and find general consistency it appears that litho1 0 represents a reasonable starting model of the earth s shallow structure crust and uppermost mantle for the purposes in which these models are used such as traveltime tomography or in efforts to create a 3 d reference earth model the model matches surface wave dispersion over a frequency band wider than the band used in the inversion there are several avenues for improving the model in the future by including attenuation and anisotropy as well as making use of surface waves at higher frequency

developments in monitoring and modelling small scale river bed topography recent research in fluvial geomorphology has emphasized the spatially distributed feedbacks amongst river channel topography flow hydraulics and sediment transport although understanding of the behaviour of dynamic river channels has been increased markedly through detailed within channel process studies less attention has been given to the accurate monitoring and terrain modelling of river channel form using three dimensional measurements however such information is useful in two distinct senses firstly it is one of the necessary boundary conditions for a physically based deterministic modelling approach in which three dimensional topography and river discharge drive within channel flow hydraulics and ultimately spatial patterns of erosion and deposition and therefore channel change secondly research has shown that an alternative means of estimating the medium term bedload transport rate can be based upon monitoring spatial patterns of erosion and deposition within the river channel this paper presents a detailed assessment of the distributed monitoring and terrain modelling of river bed topography using a technique that combines rigorous analytical photogrammetry with rapid ground survey the availability of increasingly sophisticated terrain modelling packages developed for civil engineering application allows the representation of topographic information as a landform surface intercomparison of landform surfaces allows visualization and quantification of spatial patterns of erosion and deposition a detailed assessment is undertaken of the quality of the morphological information acquired this allow some general comments to be made concerning the use of more traditional methods to monitor and represent small scale river channel morphology

towards a protocol for laser scanning in fluvial geomorphology advances in spatial analytical software allow digital elevation models dems to be produced which accurately represent landform surface variability and offer an important opportunity to measure and monitor morphological change and sediment transfer across a variety of spatial scales many of the techniques presently employed aerial lidar edm theodolites gps photogrammetry suffer coverage or resolution limitations resulting in a trade off between spatial coverage and morphologic detail captured this issue is particularly important when rates of spatial and temporal change are considered for fluvial systems this paper describes the field and processing techniques required for oblique laser scanning to acquire 0 01 m resolution digital elevation data of an upland reach of the river wharfe in the uk the study site is variable with rapidly changing morphology diverse vegetation and the presence of water and these are evaluated with respect to laser data accuracy scan location frequency and distance are discussed with reference to survey accuracy and efficiency and a field protocol is proposed scan data cloud merging was achieved with a high degree of precision sub centimetre and positional data are shown to be very accurate for exposed surfaces vegetation and water decrease the accuracy as the laser pulse is often prevented from reaching the ground surface or is not returned copyright 2006 john wiley sons ltd

effect of transect location transect spacing and interpolation methods on river bathymetry accuracy digital elevation models dems of river channel bathymetries are developed by interpolating elevations between data collected at discrete points or along transects the accuracy of interpolated bathymetries depends on measurement error the density and distribution of point data and the interpolation method whereas point measurement errors can be minimized by selecting the most efficient equipment the effect of data density and interpolation method on river bathymetry is relatively unknown thus this study focuses on transect based collection methods and investigates the effects of transect location the spacing between transects and interpolation methods on the accuracy of interpolated bathymetry this is accomplished by comparing four control bathymetries generated from accurate and high resolution sub meter scale data to bathymetries interpolated from transect data extracted from the control bathymetries using two transect locating methods and four interpolation methods the transect locating methods are a morphologically spaced and an equally spaced model the four interpolation methods are ordinary kriging delaunay triangulation and simple linear which are applied in curvilinear coordinates delaunay triangulation is also applied in cartesian coordinates and natural neighbor only in cartesian coordinates the bathymetric data were obtained from morphologically simple and complex reaches of a large average bankfull width 90 m and a small average bankfull width 17 m river the accuracy of the developed dems is assessed using statistical analysis of the differences between the control and interpolated bathymetries and hydraulic parameters assessed from bankfull water surface elevations results indicate that dem accuracy is not influenced by the choice of transect location method with same averaged cross section spacing or a specific interpolation method but rather by the coordinate system for which the interpolation method is applied and the spacing between transects they also show negligible differences between the mean depths and surface areas calculated from bathymetries with dense or coarse spacing copyright 2016 john wiley sons ltd

regional seismic wave propagation lg and sn and pn attenuation in the arabian plate and surrounding regions an edited version of this paper was published by blackwell publishing copyright 2004 blackwell publishing see also http www blackwell synergy com doi abs 10 1111 j 1365 246x 2004 02246 x http atlas geo cornell edu middleeastnorthafrica publications al damegh2004 htm

hot spot activity and the break up of pangea abstract the mesozoic and cenozoic positions of the continents that formed pangea in the triassic jurassic were derived from paleomagnetic and intraplate volcanic data paleoclimatic observations such as reef and fossil flora distribution and geological observations major hot spots helped to determine the longitudinal position of pangea and to construct a model of plate motion during the pangean break up the position of the northern part of pangea was constrained using iceland and jan mayen hot spots the iceland hot spot was traced from its present day position to greenland in the paleocene to baffin bay in the late cretaceous to the alpha ridge in the early cretaceous to the chukchi borderland in the middle late jurassic to franz joseph land in the early jurassic the yenisei khatanga trough in the middle triassic and finally to west siberia in the late permian early triassic the hot spot activity is expressed by eastern and western greenland volcanics the siberian trap basalts and perhaps by alpha ridge and chukchi borderland volcanics the chukchi borderland volcanics are related to the early stage of the opening of the canadian basin the position of the southern part of pangea was constrained using the bouvet hot spot this hot spot was tracked from its present day position to western antarctica in the early cretaceous late jurassic and to south africa in the early jurassic late triassic this hot spot activity produced the ferrar and karoo volcanics the model of plate motion obtained agrees with other data on intraplate volcanics which are also related to hot spots at the time of the opening of the central atlantic the cape verde and canary island hot spots were located along the ocean s spreading axis the long lasting location of hot spot and associated mantle upwelling plumes could help to explain forces driving the tethys transit plates opening of the ligurian ocean and eastern mediterranean the european hot spots are related to the several mesozoic phases of rifting for example the rhine graben hot spot may have been located at the rifting axis in the north sea several authors have already discussed the contribution of hot spots to the opening of the south atlantic and indian oceans mantle plumes associated with hot spots play an active role in rifting and initial phases of spreading the lithospheric displacement caused by upwelling combined with sometimes remote collisional forces on the other side of continental plate may result in compression and basin inversion

mantle plumes and continental tectonics abstract it is now recognised that plumes originate from a thermal boundary layer deep in the mantle a new plume consists of a large head with a diameter of approximately 800 to 1200 km and it is followed by a smaller tail which has a diameter of 100 to 200 km at the top of its ascent the head flattens to form a disk 2000 to 2500 km in diameter that may melt to produce a continental flood basalt or oceanic plateau the tail melts to produce chains of volcanic activity such as the hawaiian emperor chain the ascent of a new plume leads to surface uplift of 500 to 1000 m over a length scale of 2000 km this places the lithosphere under tension but the horizontal forces produced do not result in runaway extension unless the continental lithosphere is already anomalously hot and therefore weak if the lithosphere is cold and strong slow extension leading to a new spreading ridge may postdate plume arrival by 10 to 40 m y the time difference being the time taken to conduct heat from the plume to the overlying lithosphere plume heads may control the timing and position of new ocean ridges but are not the fundamental force that drives plate tectonics the heat from plume tails may weaken the overlying plate and pin the position of spreading the ascent of a mantle plume can also have an important influence on subduction large oceanic plateaus such as the ontong java plateau are more buoyant than normal oceanic crust because they have a thicker basaltic layer and because they are underlain by a 200 km thick layer of hot material from a mantle plume head as a consequence oceanic plateaus are more difficult to subduct than normal oceanic crust this can lead to jamming of plates at subduction zones resulting in a flip in the sense of subduction as appears to have happened in the caribbean region or to obduction of the plateau finally when a plume head is emplaced beneath continental crust heat released from the plume may lead to melting of the overlying crust the granites associated with many greenstone belts and intercontinental magmatic provinces such as the paleozoic lachlan fold belt of eastern australia and the middle proterozoic anorogenic granites of the central and southwestern united states may have formed in this way

the development of an automated correction procedure for digital photogrammetry for the study of wide shallow gravel bed rivers this paper develops an automated correction procedure for dealing with point errors associated with through water photogrammetry for application in the study of clear water shallow gravel bed rivers the procedure involves combining digital photogrammetry and image analysis techniques to i correct for the effects of refraction at an air water interface and ii eliminate and reinterpolate points where the bed has not been seen the correction procedure was applied to raw digital elevation models dems generated using digital photogrammetry from 1 3000 scale aerial photography of a small reach of the north ashburton river new zealand the accuracy of corrected and uncorrected dems is evaluated using an independent data set a measure of geomorphological usefulness as well as dem external reliability is obtained from calculations of water depth distributions and mean bed level results show that digital photogrammetry used in conjunction with image analysis techniques can successfully be used for extracting high resolution dems of gravel river beds in exposed areas errors are small and random tending to cancel out over large numbers of points where water is shallow and following correction point elevation errors are statistically no different from those for exposed zones in deeper water despite an improvement following application of the correction procedure elevation errors scale with water depth the geomorphological potential of photogrammetric survey of large gravel river beds is demonstrated by the ease and accuracy of calculations of water depth distribution important for the assessment of a river s ecological and recreational characteristics and mean bed level important for the calculation of reach scale sediment volumes copyright 2000 john wiley sons ltd

quantifying submerged fluvial topography using hyperspatial resolution uas imagery and structure from motion photogrammetry quantifying the topography of rivers and their associated bedforms has been a fundamental concern of fluvial geomorphology for decades such data acquired at high temporal and spatial resolutions are increasingly in demand for process oriented investigations of flow hydraulics sediment dynamics and in stream habitat in these riverine environments the most challenging region for topographic measurement is the wetted submerged channel generally dry bed topography and submerged bathymetry are measured using different methods and technology this adds to the costs logistical challenges and data processing requirements of comprehensive river surveys however some technologies are capable of measuring the submerged topography through water photogrammetry and bathymetric lidar are capable of reasonably accurate measurements of channel beds in clear water whilst the cost of bathymetric lidar remains high and its resolution relatively coarse the recent developments in photogrammetry using structure from motion sfm algorithms promise a fundamental shift in the accessibility of topographic data for a wide range of settings here we present results demonstrating the potential of so called sfm photogrammetry for quantifying both exposed and submerged fluvial topography at the mesohabitat scale we show that imagery acquired from a rotary winged unmanned aerial system uas can be processed in order to produce digital elevation models dems with hyperspatial resolutions c 0 02 m for two different river systems over channel lengths of 50 100 m errors in submerged areas range from 0 016 m to 0 089 m which can be reduced to between 0 008 m and 0 053 m with the application of a simple refraction correction this work therefore demonstrates the potential of uas platforms and sfm photogrammetry as a single technique for surveying fluvial topography at the mesoscale defined as lengths of channel from c 10 m to a few hundred metres this article is protected by copyright all rights reserved

upper and middle crustal velocity structure of the colombian andes from ambient noise tomography investigating subduction related magmatism in the overriding plate e p acknowledges support from the coordenacao de aperfeicoamento de pessoal de nivel superior capes through a 4 year scholarship to complete his ph d j j thanks cnpq for his research fellowship cnpq grant 308171 2012 8 m s acknowledges support by brazilian science without border program grant 40 2174 2012 7

the march 11 2002 masafi united arab emirates earthquake insights into the seismotectonics of the northern oman mountains a moderate m approx 5 earthquake struck the northeastern united arab emirates uae and northern oman on march 11 2002 the event was felt over a wide area of the northern emirates and was accompanied by smaller felt events before and after the march 11 main shock the event was large enough to be detected and located by global networks at teleseismic distances we estimated focal mechanism and depth from broadband complete regional waveform modeling we report a normal mechanism with a slight right lateral strike slip component consistent with the large scale tectonics the normal component suggests relaxation of obducted crust of the semail ophilite specifically the khor fakkan block while the right lateral strike slip component of the mechanism is consistent with shear across the oman line felt earthquakes are rare in the region however no regional seismic network exists in the uae to determine local seismicity this event offers a unique opportunity to study the active tectonics of the region as well as inform future studies of seismic hazard in the uae and northern oman

finite difference simulations of seismic scattering implications for the propagation of short period seismic waves in the crust and models of crustal heterogeneity synthetic seismograms produced by the finite difference method are used to study the scattering of elastic and acoustic waves in two dimensional media with random spatial variations in seismic velocity the results of this study provide important insights about the propagation of short period 5 the self similar medium is characterized by a scattering q that is constant with frequency whereas theory predicts that the apparent q in an exponential medium is proportional to frequency these alternative models of crustal heterogeneity can thus be tested by improved measurements of the frequency dependence of crustal q at frequencies greater than about 1 hz assuming that scattering is responsible for most of the attenuation at these frequencies measurements of the time decay of the synthetic coda waves clearly show that the single scattering model of coda decay is not appropriate in the presence of moderate amounts of scattering attenuation scattering q 200 in these cases q values derived from the coda decay rate using the single scattering theory do not correspond to the transmission q of the medium the cross correlation of synthetic waveforms observed for an array of receivers along the free surface is observed to be dependent on the correlation distance of the medium the self similar random medium proposed here for the crust produces waveform variations at high frequencies 15 30 hz similar to those reported for actual small scale seismic arrays with apertures of hundreds of meters

steady state behaviour of the black ven mudslide the application of archival analytical photogrammetry to studies of landform change the concept of dynamic equilibrium has provided geomorphologists with a challenging paradigm for studying landform evolution but quantitative evidence for its existence has proved illusive particularly for complex geomorphological systems the authors believe that the principle has now been verified through the application of the archival photogrammetric technique to a sequence of historical photographs spanning 50 years of process at the black ven mudslide complex in dorset u k the principles and limitations of the archival photogrammetric technique are described the method is applied to oblique and vertical aerial photographs of black ven at five epochs commencing in 1946 continuing at approximately 10 year intervals until 1988 the technique is used to generate plans contours sections and a dense and accurate digital elevation model dem of the whole site at each epoch this is used to generate dems of difference and a distribution of slope angle which suggest that the mudslides are in equilibrium despite the removal of 200 000 m3 of sediment between 1958 and 1988 extrapolation of the slope distribution through time suggests that the frequency of an episodic landform change model at black ven may be approximately 60 years

changes in sediment connectivity following glacial debuttressing in an alpine valley system abstract increasing air temperature and declining winter snowfalls are resulting in rapid glacier recession and the expansion of proglacial margins in alpine regions such margins include substantial debris accumulations e g frontal lateral moraine ridges till covered and steep valley sidewalls which may be unstable due to glacial debuttressing rainfall snowmelt and ice melt out may then cause mass movements here we quantify the decadal scale erosion and deposition patterns and changes in connectivity for two valley sidewall geomorphological systems following retreat of the glacier d otemma switzerland we apply archival digital photogrammetric methods to the period 1964 to 2009 to determine high resolution digital elevation models these were differenced to calculate patterns of erosion and deposition and to quantify the evolution of sediment connectivity we found that gully headward erosion rates between ca 10 6 mm year and 1002 1 mm year was the main geomorphological process during glacier thinning but increasing depositional rates downslope of the gullies ca 21 3 to 298 5 mm year were recorded in the following years associated with significant alluvial fan growth at the slope base while gullying enhanced connectivity by removing glacially conditioned sediment transfer buffers so connecting side slopes to upstream sediment sinks the upslope contributing area between 1964 and 2009 increased by 73 8 and 195 1 in each subsystem alluvial fans reduced the rates of sediment transfer to the rapidly enlarging glacial forefields the detail of these responses is conditioned by three generic processes 1 the wider geomorphic setting here the presence of a moraine bastion as a primary part of the sediment cascade strongly influenced gully morphology evolution and the likely length of the paraglacial period length 2 the thickness of sediment left by the retreating glacier which controlled the influence of bedrock topographic buffers on connectivity and 3 the extent to which diffusive drainage systems develop in response to the deposition at the hillslope base which tend to disconnect sediment flux post glacially gully development has a self limiting effect on sediment connectivity in that while gullying increases sediment connectivity the eroded sediment leads to deposition on the alluvial plain that reduces sediment connectivity

significant decadal channel change 58 67 years post dam accounting for uncertainty in topographic change detection between contour maps and point cloud models abstract construction of digital elevation models dems and the subtraction of dems between different points in time as a method to determine temporal patterns of scour and fill is a highly valuable procedure emerging in geomorphology these dems of differences dods must be assessed for error in order to distinguish actual topographic change from uncertainty and surface error current methods include 1 uniformly excluding all values that fall below a minimum threshold 2 using a spatially variable approach such as the construction of minimum level of detection lod grids or 3 the creation of a fuzzy inference system although spatially variable methods for determining error have been more accurate in excluding noise without discarding large amounts of meaningful data a challenge remains in performing dods against preexisting contour based maps for which no original point data are available the goals of this study were to 1 develop a method that overcomes the unknown point density of contour and other historical data sets and allows for some assessment of dod uncertainty on the basis of information on topographic variability 2 perform comprehensive uncertainty analysis testing to understand the opportunities and constraints associated with this new method and 3 report and interpret the overall pattern and volume of decadal topographic change for a regulated river 67 years post dam in light of alternate conjectured mechanisms of post dam longitudinal profile adjustment the key feature of the new approach is the introduction of a high density artificial point grid that samples the topographic variability evident in the available historical data set the testbed used to develop and assess this new dod method was the 37 5 km lower yuba river california historical data consisted of 0 6 m contours from a 1999 survey while a more detailed point cloud was available for the most recent survey in 2006 2008 to evaluate uncertainty in the method this study applied seven different uncertainty metrics of varying strictness t 1 t 1 96 uniform 0 3 m exclusion t 1 plus uniform 0 3 m exclusion t 1 with lod minimum at 0 3 t 1 96 plus uniform 0 3 m exclusion and t 1 96 with lod minimum at 0 3 and two different dod adjustment methods exclusion and subtraction a stringent approach involving joint use of the contour half interval and the spatially distributed lod grid at a 95 confidence limit excluded 44 3 of the study area from spatial assessment of channel change and volumetric change computation this preferred approach yielded an estimated 2 518 million m 3 of total scour and 2 455 million m 3 of total fill in 7 9 years after considering different mapping epochs the net annual average export was 17 000 m 3 32 500 tons to the feather river and a river valley sediment yield of 2205 tons km 2 year this amount is 36 of the post dam annual yield of gravel and cobble to the upstream reservoir that blocks sediment conveyance into the study domain suggesting that the lowland system is still highly dynamic 67 years after the dam was built the scientific significance of this is that the response of rivers to dams can be far more long lasting and complex depending on the suite of cumulative societal impacts to rivers the ability to account for spatially explicit dod uncertainty i e data retention when uncertainty is low and data removal when uncertainty is high when comparing historic contour based and modern point cloud based dems will allow for more detailed and reliable dods and sediment budgets in these cases

a reappraisal of earthquake focal mechanisms and active shortening in the zagros mountains of iran summary the zagros mountains of sw iran are one of the most seismically active intra continental fold and thrust belts on earth and an important element in the active tectonics of the middle east surface faulting associated with earthquakes is extremely rare and so most information about the active faulting comes from earthquakes we use long period teleseismic p and sh body waves to determine the orientation and depth of faulting in 16 new earthquakes and then evaluate and synthesize all the available teleseismic data on earthquake source parameters in the zagros we use this information to investigate the style and distribution of active faulting in the zagros and how it contributes to the n s shortening of the arabia eurasia collision when the data are ranked in quality and carefully evaluated simple patterns are seen that are not apparent when routine catalogue data are taken at face value an important change in the fault configuration occurs along strike of the belt in the nw overall convergence is oblique to the trend of the belt and the surface anticlines and is achieved by a spatial separation partitioning of the orthogonal strike slip and shortening components on separate parallel fault systems by contrast in the se overall convergence is orthogonal to the regional strike and achieved purely by thrusting in the central zagros between these two structural regimes deformation involves parallel strike slip faults that rotate about vertical axes allowing extension along the strike of the belt the overall configuration is similar to that seen in other curved shortening belts such as the himalaya and the java sumatra trench all the zagros earthquakes we have been able to check have centroids shallower than 20 km and are confined to the upper crust many of the larger earthquakes are likely to occur in the basement beneath the sedimentary cover which is active even beneath areas of known shallow structural decollement such as the dezful embayment the dominant style of shortening is high angle reverse faulting with dips 30 though some lower angle thrusting occurs in places active thrust and reverse faulting is relatively confined to the lower topography on the sw edge of the belt today and only strike slip faulting affects the higher topography profound vertical changes in structural and stratigraphic level indicate that a similar style of deformation was once active across the width of the simple folded belt but has progressively migrated sw over the last 5 ma there is no evidence for a seismically active structural decollement such as a low angle thrust beneath the zagros nor is there any seismic evidence for active subduction either beneath the zagros or beneath central iran instead the arabian margin seems to have shortened by distributed thickening of the basement only in the syntaxis of the oman line at the se end of the zagros is there any evidence for a low angle thrust of regional extent here earthquakes continue 50 km north of the zagros thrust line the geological suture between the arabian margin and central iran reaching depths of 30 km and may represent thrusting of arabian basement beneath central iran to this extent

hyperscale terrain modelling of braided rivers fusing mobile terrestrial laser scanning and optical bathymetric mapping quantifying the morphology of braided rivers is a key task for understanding braided river behaviour in the last decade developments in geomatics technologies and associated data processing methods have transformed the production of precise reach scale topographic datasets nevertheless generating accurate digital elevation models dems remains a demanding task particularly in fluvial systems this paper identifies a threefold set of challenges associated with surveying these dynamic landforms complex relief inundated shallow channels and high rates of sediment transport and terms these challenges the morphological wetted channel and mobility problems respectively in an attempt to confront these issues directly this paper presents a novel survey methodology that combines mobile terrestrial laser scanning and non metric aerial photography with data reduction and surface modelling techniques to render dems from the resulting very high resolution datasets the approach is used to generate and model a precise dense topographic dataset for a 2 5 km reach of the braided rees river new zealand data were acquired rapidly between high flow events and incorporate over 5 x 109 raw survey observations with point densities of 1600 pts m 2 on exposed bar and channel surfaces a detailed error analysis of the resulting sub metre resolution is described to quantify dem quality across the entire surface model this reveals unparalleled low vertical errors for such a large and complex surface model between 0 03 and 0 12 m in exposed and inundated areas of the model respectively copyright 2013 john wiley sons ltd

surveyed and modelled one year morphodynamics in the braided lower tana river field measurements and morphodynamic simulations were carried out along a 5 km reach of the sandy braided lower tana river in order to detect temporal and spatial variations in river bed modifications and to determine the relative importance of different magnitude discharges on river bed and braid channel evolution during a time span of one year i e 2008 2009 fulfilling these aims required testing the morphodynamic model s capability to simulate changes in the braided reach we performed the simulations using a 2 d morphodynamic model and different transport equations the survey showed that more deposition than erosion occurred during 2008 2009 continuous bed load transport and bed elevation changes of 1 m and a 70 188 m downstream migration of the thalweg occurred simulation results indicated that during low water periods modifications occurred in both the main channel and in other braid channels thus unlike some gravel bed rivers the sandy lower tana river does not behave like a single thread channel at low discharge however at higher discharge i e exceeding 497 m3 s the river channel resembled a single thread channel when channel banks confined the flow although the spring discharge peaks caused more rapid modifications than slower flows the cumulative volumetric changes of the low water period were greater the importance of low water period flows for channel modifications is emphasized although the 2 d model requires further improvements the results were nevertheless promising for the future use of this approach in braided rivers

ground motion modeling in the eastern caucasus in this study we analyzed the performance of a preliminary three dimensional 3d velocity model of the eastern caucasus covering most of the azerbaijan the model was developed in support to long period ground motion simulations and seismic hazard assessment from regional earthquakes in azerbaijan the model s performance was investigated by simulating ground motion from the damaging mw 5 9 2012 zaqatala earthquake which was well recorded throughout the region by broadband seismic instruments in our simulations we use a parallelized finite difference method of fourth order accuracy the comparison between the simulated and recorded ground motion velocity in the modeled period range of 3 20 s shows that in general the 3d velocity model performs well areas in which the model needs improvements are located mainly in the central part of the kura basin and in the caspian sea coastal areas comparisons of simulated ground motion using our 3d velocity model and corresponding 1d regional velocity model were used to locate areas with strong 3d wave propagation effects in areas with complex underground structure the 1d model fails to produce the observed ground motion amplitude and duration and spatial extend of ground motion amplification caused by wave propagation effects

petrochemistry and tectonic significance of cretaceous island arc rocks cordillera oriental dominican republic abstract cretaceous island arc rocks of the caribbean island arc system have been exposed by cenozoic faulting in the cordillera oriental in eastern hispaniola high k 2 o intermediate to felsic volcanic rocks loma la vega volcanics are interbedded with marine epiclastic sedimentary rocks and tuffs las guajabas tuffs and unconformably overlie pre aptian sedimentary rocks low k 2 o volcanic rocks guamira volcanics and a granodioritic to tonalitic intrusion el valle pluton the petrology and geochemistry of these units in conjunction with regional stratigraphic data are used to speculate on the tectonics of the newly developing caribbean island arc system during early and late cretaceous time the loma la vega volcanics are characterized by the presence of large phenocrysts of sanidine and minor amounts of clinopyroxene opaque oxides and rare leucite in a devitrified matrix of chlorite and clay although the volcanic rocks have undergone some low temperature alteration metamorphism which redistributed some major elements and large ion litho phile trace elements the high field strength elements rare earth elements and radiogenic isotopes appear to have been minimally affected based on abundances of the relatively immobile elements trace element enrichment patterns and isotopic compositions the loma la vega volcanics are considered part of the high k calc alkaline ca or shoshonitic island arc volcanic series in contrast pre aptian early cretaceous volcanic and plutonic rocks of the underlying los ranchos formation have chemical characteristics similar to rocks in the island arc tholeiitic or primitive island arc pia series that form coeval and along strike sections of the early cretaceous caribbean island arc in other parts of present day hispaniola cuba puerto rico and the virgin islands an abrupt and regional change in composition from island arc tholeiites to high k calc alkaline rocks is coincident with a hypothesized reversal in subduction polarity in pre aptian time as inferred from previously published tectonic models polarity reversal may have been triggered by attempted subduction of the caribbean oceanic plateau beneath this segment of the caribbean island arc the observed magmatic and tectonic effects of the proposed cretaceous caribbean arc reversal are similar to the better documented neogene subduction reversal event in the solomon islands arc in the southwest pacific

propagation characteristics of short period sn and lg in the middle east abstract we present propagation characteristics of the short period regional seismic phases sn and lg for the middle east digital waveform data from the iranian long period array ilpa and the global seismic network gsn stations abkt alibek turkmenistan anto ankara turkey keg kottamya egypt and kiv kislovodsk georgia were used in this study three component rotated seismograms were bandpass filtered 0 5 to 5 0 hz and examined for the presence and strength amplitude of sn and lg relative to the pn and pg phases the short period sn and lg waveforms show great variability sn propagates efficiently for paths crossing the mediterranean black and caspian seas as well as for paths passing north of the greater caucasus alborz and kopet dag mountains generally sn is not observed or propagates inefficiently for paths with segments beneath the turkish plateau and northern iranian plateau consistent with a previous study by kadinsky cade et al 1981 this study finds that the zone of inefficient sn propagation coincides with a zone of low pn velocities pn tomography lg is consistently not observed for paths crossing the mediterranean black and caspian seas lg propagates efficiently for paths crossing the northern arabian shield generally lg propagates efficiently for paths contained within the turkish iranian plateau paths in the middle east greater than about 2000 km consistently show no or little lg energy the correspondence of zones of inefficient sn propagation and low pn velocities suggests that high temperatures and partial melt lie at shallow depths in the upper mantle beneath the turkish plateau and northern iranian plateau the presence of water presumably due to subduction of hydrated oceanic crust lowers the solidus temperature and enhances partial melt lg is blocked by oceanic crustal structures as well as by structural and topographic variations associated with tectonic boundaries

gravel transport in the braided waimakariri river mechanisms measurements and predictions abstract yields of grabel bed load in the braided lower waimakariri river in new zealand are investigated by several methods and for different timescales short term several months medium term several years and long term 1967 1983 short term estimates of gravel yield were made for five such periods in 1986 1987 by a morphological method bed morphology in a selected reach was mapped before and after flood events the gross volume of scour in that time period measured and a mean transport rate through the reach computed on the basis of the step distance of gravel movement from scour zones to areas of accretion the findings indicate that a considerable fraction of the annual gravel load is derived from scour of braid banks with the gravel being shunted downstream from one zone of temporary storage to another computation of bed load yields during the same period by the meyer peter and muller mpm equation revealed excellent agreement with the morphological estimate comparison of the mpm prediction based on flow duration data for 1967 1983 also showed excellent agreement with the long term rate assessed by stadia survey of cross sections in the reach of accumulation downstream of the study reach predictions using the mpm formula for the medium term however while acceptable showed greater differences from the surveyed rates evidence indicates that this is related to highly dynamic bed conditions in which the availability of more mobile finer grained gravel in the reach changes from year to year as slugs of such sediment move intermittently downstream thus while prediction of a short term yield based on bed conditions at the time of study and a long term yield based on temporal mean conditions as inferred from bed conditions averaged along the river are realistic goals the accurate prediction of successive short term or medium term yields seems to be impossible unless detailed analysis of bed conditions especially grain size is undertaken in each time period a major task

cdw photogrammetry of low relief fluvial features accuracy and implications for reach scale sediment budgeting terrestrial photogrammetry enables rapid survey to be undertaken in the fluvial environment a crucial factor when assessing highly dynamic features in addition it permits the generation of terrain surfaces at a level of detail which given equal time constraints in the field far exceeds the detail permitted by conventional tacheometric survey this study details the levels of accuracy that can be achieved using the rolleimetric close range digital workstation cdw photogrammetric survey technique on a variety of low relief fluvial geomorphic features lateral point and mid channel bars ranging from 10 m 2 to 100 m 2 the cdw software processes image data from an array of photographs and establishes a set of three dimensional co ordinates for the photographed object the accuracies achieved across all bar surfaces were well within the resolution defined by the maximum size of the gravel on the bar surface mean errors were between 0 026 and 0 057 m the use of cdw photogrammetry does not require experienced personnel however care must be taken during the survey to minimize edge effects and to ensure that target density is sufficient to produce a terrain model that is accurate to within the limits of the surface sediment size guidance on target density as a function of terrain roughness is given to aid the user a methodology is suggested that will allow cdw to be incorporated into sediment budgeting techniques improving the level of achievable accuracy 1998 john wiley sons ltd

splitting rivers at their seams bifurcations and avulsion river bifurcations are critical but poorly understood elements of many geomorphological systems they are integralelements of alluvial fans braided rivers fluvial lowland plains and deltas and control the partitioning of water and sediment throughthese systems bifurcations are commonly unstable but their lifespan varies greatly in braided rivers bars and channels migrate splitand merge at annual or shorter timescales thereby creating and abandoning bifurcations this behaviour has been studied mainly bygeomorphologists and fluid dynamicists bifurcations also exist during avulsion the process of a river changing course on afloodplain or in a delta which may take 102 103years and has been studied mainly by sedimentologists this review synthesizesour current understanding of bifurcations and brings together insights from different research communities and different environmen tal settings we consider the causes and initiation of bifurcations and avulsion the physical mechanisms controlling bifurcation andavulsion evolution mathematical and numerical modelling of these processes and the possibility of stable bifurcations we end thereview with some open questions copyright 2012 john wiley sons ltd

discharge and sediment supply controls on erosion and deposition in a dynamic alluvial channel research on dynamic alluvial channels has recognised the influence on river channel change of both discharge and sediment supply although it has proved difficult to measure the latter this paper presents the first accurate data from a dynamic alluvial channel that describe the interrelated effect on channel morphological change of both discharge and sediment supply variations over different timescales reliable information on the spatial patterns of erosion and deposition were obtained using combined photogrammetry and tacheometric survey of the meltwater stream of a glacierised catchment over a 5 week period over the full time period the morphological evidence suggested the passage of a wave of sediment counter intuitively the period of aggradation was associated with increasing diurnal peak and base flow discharge magnitude while degradation occurred during a period of steady peak diurnal discharge this suggests that the channel change was controlled by variation in upstream sediment supply over a shorter timescale information on diurnal changes in morphology reveals that although discharge was responsible for some aspects of channel change this was modified by the effects of upstream sediment supply consideration of the spatial patterns of erosion and deposition at the within reach scale reinforces this point with spatial aspects of morphological change being driven by discharge and sediment supply fluctuations but modified by spatial feedbacks associated with internal channel morphology the implications of these findings for fluvial geomorphology in general are considered

earthquake ground motion prediction equations for eastern north america new earthquake ground motion relations for hard rock and soil sites in eastern north america ena including estimates of their aleatory uncertainty vari ability have been developed based on a stochastic finite fault model the model incorporates new information obtained from ena seismographic data gathered over the past 10 years including three component broadband data that provide new in formation on ena source and path effects our new prediction equations are similar to the previous ground motion prediction equations of atkinson and boore 1995 which were based on a stochastic point source model the main difference is that high frequency amplitudes f 5 hz are less than previously predicted by about a factor of 1 6 within 100 km because of a slightly lower average stress parameter 140 bars versus 180 bars and a steeper near source attenuation at frequencies less than 5 hz the predicted ground motions from the new equations are generally within 25 of those predicted by atkinson and boore 1995 the prediction equations agree well with available ena ground motion data as evidenced by near zero average residuals within a factor of 1 2 for all frequencies and the lack of any significant residual trends with distance however there is a tendency to positive residuals for moderate events at high frequencies in the distance range from 30 to 100 km by as much as a factor of 2 this indicates epistemic uncertainty in the prediction model the positive residuals for moderate events at 100 km could be eliminated by an increased stress parameter at the cost of producing negative residuals in other magnitude distance ranges adjustment factors to the equations are provided that may be used to model this effect

observations of dune interactions from dems using through water structure from motion abstract the role of three dimensionality 3d in modulating both flow and sediment transport remains poorly understood 3d bed elevation measurements are difficult to obtain due to irregular dune shapes and submergence using photogrammetric tools for topographic reconstruction has become popular in surface studies yet water refraction makes through water image capturing of submerged dunes still challenging we show that through water images and structure from motion sfm tools can produce accurate digital elevation models dems of a measured dune field with a high level of detail it is a low cost and non intrusive alternative for submerged bed elevation measurements we provide a detailed sfm workflow introduce and discuss the use of camera coordinates and underwater ground control points and processing steps needed to obtain high accuracy dems our method results in dems with mm resolution in controlled laboratory conditions new data for 23 dune field dems from 6 experiments were obtained and are presented the dune field dem time series provide insights on dune interaction processes in our experiments merging and defect creation were most common merging decreases the number of bedforms and defect creation is responsible for more bedforms dunes continue to interact and jostle after achieving equilibrium simple crests are much more frequently observed than irregular sinuous or double crests two dimensional 2d crest shapes were observed although crest shapes were generally of 3d nature observed dune migration rates are not steady and vary in time and space bedform splitting speeds up dune migration whilst neighbouring dunes tend to accelerate or decelerate we identify a cascade of processes and show that 3d dems at high frequency are required to resolve observed rapid deformations and interaction of dunes the identified dune interaction processes are inherent to sediment flux variability whereas the temporal component of the underlying sediment transport processes is still not well understood in relation to average transport

responses of the braided channel to reduced discharge and lateral inputs of aeolian sand in the ulan buh desert reach of the upper yellow river the ulanbuh desert reach belongs to the upper reaches of the yellow river located in inner mongolia autonomous region china which has developed a sandy bed this reach that flows across aeolian dunes field of the ulanbuh desert has caused large lateral infusion of aeolian sands into riverbed an abrupt addition of the bedload and a sharp channel widening forming a typical braided channel in addition to traditional driving factors such as discharge suspended sediments and slope here we also focus on the lateral infusion of aeolian sands into the yellow river which may have a significant impact on channel form to further recognize the desert braided channel change here based on a long time series of field dataset from 1966 to 2013 results show that lateral infusion of aeolian sand is the same as discharge as a significant factor to channel form which is mainly controlled by aeolian activity and discharge conditions before the early 1990s higher discharge and greater intensity of aeolian activity caused a frequent lateral movement and large lateral inputs of aeolian sands into river this reach showed an unsteady and wider braided channel with a higher braiding intensity from the early 1990s to 2013 a reduced discharge that caused a decreasing lateral movement coupled with the decreasing aeolian activity have resulted in the main flow of the yellow river far away from sand dunes which led to a reduction in lateral inputs of aeolian sands thus the braided channel of the ulanbuh desert reach presented a shrinkage state gradually changing from a wider and unsteady braided channel to a narrower and relative steady channel form

the crustal and upper mantle structure of the interior arabian platform summary the crustal and upper mantle velocity structure of the interior arabian platform is derived using the spectral analysis of long period p wave amplitude ratios the ratio of the vertical to the horizontal component is utilized to obtain crustal transfer functions using the thomson haskell matrix formulation for horizontally layered crustal models 20 earthquakes recorded at the long period station ryd between azimuths n20 w and n150 e were selected for the analysis based on the following criteria focal depths in the range 5 to 215 km body wave magnitudes greater than 5 0 and epicentral distances in the range 7 to 97 a careful quality check of the data left us with six events out of 29 that had short epicentral distances 20 to be analysed the selection criterion for the final model in the forward modelling process was based on the correlation coeycient between observed and theoretical transfer function the model suggested that the crust consists of five distinct layers the upper crustal layer has a p wave velocity of about 5 6 km s 1 and is about 3 km thick the second layer has a velocity of about 6 3 km s 1 and is 10 km thick the third layer has a velocity of 6 6 km s 1 and is 8 km thick the fourth layer has a velocity of 6 9 km s 1 and is 15 km thick the lower layer has a velocity of about 7 6 km s 1 and is 10 km thick for the mohorovicic discontinuity a velocity of 8 3 km s 1 for the upper mantle and 46 km depth are indicated

quantification of braided river channel change using archival digital image analysis historical archives of grey scale river channel imagery are extensive here we present and test a methodology to extract detailed quantitative topographic date from such imagery of sand bed rivers extracting elevation information from rivers is difficult as they are characterized by a low relative relief less than 4 m the area of interest may be spatially extensive e g active channel widths 500 m in large braided rivers the rate of change of surface elevation is generally low except in the vicinity of individual channel banks where the rate of change is very high there is the complication that comes from innundation and there may be an added complication caused by blockage of the field of view by vegetation here we couple archival photogrammetric techniques with image processing methods and test these for quantification of sand bed braided river dynamics illustrated for a 500 m wide 3 km long reach of the spouth sasketchewan river canada digitial photogrammetry was used to quantify dry areas and water edge elevations a methodology was then used to calibrate the special signature of inundated areas by combining established two media digital photogrammetric methods and image matching this allowed determination of detailed depth maps for inundated area and when combined with dry area data creation of depths detectable from sequential digital elevation models the result was a series of elevation models that demonstrate the potential for acquiring detailed and precise elevation data from any historical aerial imagery of rivers without needing associated calibration data provided that imagery is of the necessary scale to capture the features of interest we use these data to highlight several aspects of channel change on the south saskatchewan river including bar movement bank erosion and channel infilling

remote sensing of stream depths with hydraulically assisted bathymetry hab models this article introduces a technique for using a combination of remote sensing imagery and open channel flow principles to estimate depths for each pixel in an imaged river this technique which we term hydraulically assisted bathymetry hab uses a combination of local stream gage information on discharge image brightness data and manning based estimates of stream resistance to calculate water depth the hab technique does not require ground truth depth information at the time of flight hab can be accomplished with multispectral or hyperspectral data and therefore can be applied over entire watersheds using standard high spatial resolution satellite or aerial images hab also has the potential to be applied retroactively to historic imagery allowing researchers to map temporal changes in depth we present two versions of the technique hab 1 and hab 2 hab 1 is based primarily on the geometry discharge and velocity relationships of river channels manning s equation assuming average depth approximates the hydraulic radius the discharge equation and the assumption that the frequency distribution of depths within a cross section approximates that of a triangle are combined with discharge data from a local station width measurements from imagery and slope measurements from maps to estimate minimum average and maximum depths at a multiple cross sections these depths are assigned to pixels of maximum average and minimum brightness within the cross sections to develop a brightness depth relation to estimate depths throughout the remainder of the river hab 2 is similar to hab 1 in operation but the assumption that the distribution of depths approximates that of a triangle is replaced by an optical beer lambert law of light absorbance in this case the flow equations and the optical equations are used to iteratively scale the river pixel values until their depths produce a discharge that matches that of a nearby gage r 2 values for measured depths versus depths estimated by hab 1 and hab 2 are 0 51 and 0 77 respectively in the relatively simple brazos river texas r 2 values for hab 1 and hab 2 are 0 46 and 0 26 respectively in the lamar river a complex mountain river system in yellowstone national park although the r 2 values are moderate depth maps and crosssections derived from the hab techniques are consistent with typical stream geomorphology patterns and provide far greater

lithospheric structure of the arabian shield and platform from complete regional waveform modelling and surface wave group velocities summary regional seismic waveforms reveal significant differences in the structure of the arabian shield and the arabian platform we estimate lithospheric velocity structure by modelling regional waveforms recorded by the 1995 1997 saudi arabian temporary broadband deployment using a grid search scheme we employ a new method whereby we narrow the waveform modelling grid search by first fitting the fundamental mode love and rayleigh wave group velocities the group velocities constrain the average crustal thickness and velocities as well as the crustal velocity gradients because the group velocity fitting is computationally much faster than the synthetic seismogram calculation this method allows us to determine good average starting models quickly waveform fits of the jon and sn body wave arrivals constrain the mantle velocities the resulting lithospheric structures indicate that the arabian platform has an average crustal thickness of 40 km with relatively low crustal velocities average crustal p and s wave velocities of 6 07 and 3 50 km s 1 respectively without a strong velocity gradient the moho is shallower 36 km and crustal velocities are 6 per cent higher with a velocity increase with depth for the arabian shield fast crustal velocities of the arabian shield result from a predominantly mafic composition in the lower crust lower velocities in the arabian platform crust indicate a bulk felsic composition consistent with orogenesis of this former active margin p and s wave velocities immediately below the moho are slower in the arabian shield than in the arabian platform 7 9 and 4 30 km s 1 and 8 10 and 4 55 km s respectively this indicates that the poisson s ratios for the uppermost mantle of the arabian shield and platform are 0 29 and 0 27 respectively the lower mantle velocities and higher poisson s ratio beneath the arabian shield probably arise from a partially molten mantle associated with red sea spreading and continental volcanism although we cannot constrain the lateral extent of a zone of partially molten mantle

ground motion in kuwait from regional and local earthquakes potential effects on tall buildings in recent years the construction of tall buildings has been increasing in many countries including kuwait and other gulf states these tall buildings are especially sensitive to ground shaking due to long period seismic surface waves although kuwait is relatively aseismic it has been affected by large mw 6 regional earthquakes in the zagros fold thrust belt zftb accurate ground motion prediction for large earthquakes is important to assess the seismic hazard to tall buildings in this study we first analyze the observed ground motions due to two earthquakes widely felt in kuwait the 08 18 2014 mw 6 2 earthquake 360 km nne of kuwait city and the 11 12 2017 mw 7 3 earthquake 642 km nne of kuwait city the peak spectral displacement periods of the ground motion from the 08 18 2014 mw 6 2 earthquake matched well with the ambient vibration spectra of the tallest building the al hamra tower we calculate the ground motions from potential regional and local earthquakes we use a velocity model obtained by matching the observed seismograms of the 2014 and 2017 earthquakes we calculate ground motions in kuwait due to a regional mw 7 5 earthquake and a local mw 5 0 earthquakes our study shows that a significant source of seismic hazard to tall buildings in kuwait comes from the regional tectonic earthquakes however local earthquakes have the potential to generate high peak ground accelerations 98 cm s2 close to their epicenters

making riverscapes real abstract the structure and function of rivers have long been characterized either by 1 qualitative models such as the river continuum concept or serial discontinuity concept which paint broad descriptive portraits of how river habitats and communities vary or 2 quantitative models such as downstream hydraulic geometry which rely on a limited number of measurements spread widely throughout a river basin in contrast authors such as fausch et al 2002 and wiens 2002 proposed applying existing quantitative spatially comprehensive ecology and landscape ecology methods to rivers this new framework for river sciences which preserves variability and spatial relationships is called a riverine landscape or a riverscape application of this riverscape concept requires information on the spatial distribution of organism scale habitats throughout entire river systems this article examines the ways in which recent technical and methodological developments can allow us to quantitatively implement and realize the riverscape concept using 3 cm true color aerial photos and 5 m resolution elevation data from the river tromie scotland we apply the newly developed fluvial information system which integrates a suite of cutting edge high resolution remote sensing methods in a spatially explicit framework this new integrated approach allows for the extraction of primary fluvial variables such as width depth particle size and elevation from these first order variables we derive second order geomorphic and hydraulic variables including velocity stream power froude number and shear stress channel slope can be approximated from available topographic data based on these first and second order variables we produce riverscape metrics that begin to explore how geomorphic structures may influence river habitats including connectivity patchiness of habitat and habitat distributions the results show a complex interplay of geomorphic variable and habitat patchiness that is not predicted by existing fluvial theory riverscapes thus challenge the existing understanding of how rivers structure themselves and will force development of new paradigms

regional transect across the western caribbean sea based on integration of geologic seismic reflection gravity and magnetic data we analyze western caribbean structural styles and depositional controls associated with late cretaceous cenozoic deformational events using a 1600 km 994 mi long regional northwest southeast transect extending from the cayman trough in honduras to northern colombia different structural provinces defined along the transect include 1 the cayman trough and adjacent honduran borderlands marking the north american caribbean transtensional plate boundary characterized by late eocene holocene fault controlled depocenters 2 the nicaraguan rise that includes continental paleocene eocene rocks deposited in sag basins which are overlain by relatively undeformed miocene holocene carbonate and clastic shelf deposits of the northern nicaraguan rise following a late cretaceous convergent phase 3 the colombian basin that includes thick miocene clastic depocenters and the localized presence of upper cretaceous rocks overlying the basement and where much of the subsidence is likely isostatic and flexurally driven given its proximity to the subduction zone of northern colombia 4 the south caribbean deformed belt an active accretionary prism produced by the subduction of the caribbean large igneous province beneath the south american plate which has deformed the cenozoic prism and fore arc section and produced thrust fault controlled accommodation space for upper miocene holocene piggyback deposits and 5 the onshore cesar rancheria basin in northern colombia which has recorded the uplift of its bounding mountain ranges the sierra de santa marta massif to the west and perija range to the east plate reconstructions place the various crustal provinces along the transect into the context of the late cretaceous cenozoic deformation events that can be partitioned into strike slip convergent and extensional components

long period ground motion in the arabian gulf from earthquakes in the zagros mountains thrust belt the arabian gulf is adjacent to the zagros mountains one of the most seismically active regions in the world we observe that broadband seismic records of zagros earthquakes recorded on the arabian side of the gulf display long duration surface waves while shorter periods 10 km of the gulf basin the long period energy is enhanced and transmitted efficiently consequently large earthquakes in the zagros could result in amplified ground motions at long periods 2 10 s relative to average behavior such ground motions are of concern for large engineered structures such as tall buildings and long bridges with resonant periods in the same period range here we present results of investigations of the characteristics of ground motions recorded on the western shore of the gulf from selected earthquakes in the zagros mountains region exceptionally long duration seismic waves as compared with standard models are shown to occur with periods of 2 10 s this may be due to waveguide effects in the deep sedimentary basin structure of the arabian platform in addition to analyzing recorded ground motion we performed 3d wave propagation simulations using a finite difference method and experimental velocity models of the gulf with different shallow sedimentary layers structures the simulation results confirm our hypothesis that long period waves with extremely long duration and relatively large amplitudes are caused by the geometry of the basin sedimentary layers and to some extent by shallow earthquake depths combined effects of basin edge geometry with sharp velocity contrasts and shallow sources 10 km on the eastern side of the arabian gulf can cause large long period ground motion on the western side of the gulf in contrast the short period content of ground motion 2 s at long distances is relatively weak this is mainly due to wave propagation scattering and attenuation in the shallow sedimentary layers of the gulf basin

expanding the active layer discussion of church and haschenburger 2017 what is the active layer water resources research 53 5 10 doi 10 1002 2016wr019675 church and haschenburger 2017 https doi org 10 1002 2016wr019675 make helpful distinctions around the issue of defining the active layer with which we agree we propose expanding discussion and definition of the active layer in fluvial bedload transport to include the concept of the morphological active layer this is particularly applicable to laterally unstable rivers such as braided rivers in which progressive morphological change over short time periods is the process by which much of the bedload transport occurs the morphological active layer is also distinguished by variable lateral and longitudinal extent continuity over a range of flows and transport intensity we suggest that the issue of forms of active layer raised by church and haschenburger opens up an important discussion on the nature of bedload transport in relation to river morpho dynamics over the range of river types

sediment export transient landscape response and catchment scale connectivity following rapid climate warming and alpine glacier recession abstract in the face of rapid climate warming rapid glacier recession should lead to a marked increase in the spatial extent of the paraglacial zone in glaciated drainage basins the extent of the paraglacial zone has been well established to be transient but there are very few studies of this transient response and what it means for sediment export there is good reason to expect that glacier recession could increase basin scale sediment connectivity as sediment becomes less dependent on glacier surface transport proglacial streams are more able to migrate laterally than subglacial streams and so access sediment for transport and glacier debuttressing may aid the development of gullies that can dissect moraines and so aid hillslope to proglacial zone connectivity by using records of the flushing of hydroelectric power installations we were able to develop a record of coarse sediment sand and gravel export from a basin with a rapidly retreating valley glacier the haut glacier d arolla from 1977 to 2014 modelling suggested that these data could only be partially controlled by transport capacity implying an important role for sediment supply and potentially for the influence of changing sediment connectivity indeed there was evidence of the effects of glacial debuttressing upon gullying processes and hence a possible increase in the ease of connection of upstream basins to the proglacial area more recently we were able to show possible temperature control on sediment export which may only have become apparent because of the progressive development of better sediment connectivity however whilst rapid glacier recession should result in theory in a progressive increase in connectivity of sediment sources to the basin outlet the supply to capacity ratio does not increase continually with glacier recession until maximum capacity is reached we identified two possible examples of why first gullying was also accompanied by the sediment accumulation at the base of moraines that was too coarse to be transported by the proglacial stream maintaining disconnection of the upper basins second the sediment capacity ratio appeared to be elevated during periods of more rapid retreat and we attribute this to the importance of a continued supply of unworked glacial till before fluvial reworking and sorting of freshly exposed sediment increased the resistance of sediment to entrainment and hence export rates thus the transient geomorphic response of glaciated basins to glacier recession may involve negative feedbacks that can reduce the extent to which increases in connectivity elsewhere in the basin lead to increased sediment export

crustal structure of iraq from receiver functions and surface wave dispersion implications for understanding the deformation history of the arabian eurasian collision summary we report the crustal structure for two locations in iraq estimated by joint inversion of p wave receiver functions rfs and surface rayleigh wave group velocity dispersion rfs were computed from teleseismic recordings at two temporary broad band seismic stations located in mosul msl in the zagros fold belt and baghdad bhd in the mesopotamian foredeep group velocity dispersion curves at the sites were derived from continental scale tomography the inversion results show that the crustal thicknesses are 39 km at msl and 43 km at bhd we observe a strong psmoho at bhd consistent with a sharp moho discontinuity however at msl we observe a weak psmoho suggesting a transitional moho where crustal thickening is likely to be occurring in the deep crust both sites reveal low velocity surface layers consistent with sedimentary thickness of about 3 km at station msl and 7 km at bhd and agreeing well with the previous reports ignoring the sediments the crystalline crustal velocities and thicknesses are remarkably similar at both stations the similarity of crustal structure suggests that the crust of the northeastern proto arabian platform was uniform before subsidence and deposition of the sediments in the cenozoic if crystalline crustal structure is uniform across the northern arabian platform then crustal thickness variations in the zagros fold belt and thrust zone should reveal the history of deformation and crustal shortening in the arabian eurasian collision zone and not reflect pre existing crustal thickness variations in the arabian plate

high spatial resolution hyperspectral mapping of in stream habitats depths and woody debris in mountain streams this article evaluates the potential of 1 m resolution 128 band hyperspectral imagery for mapping in stream habitats depths and woody debris in third to fifth order streams in the northern yellowstone region maximum likelihood supervised classification using principal component images provided overall classification accuracies for in stream habitats glides riffles pools and eddy drop zones ranging from 69 for third order streams to 86 for fifth order streams this scale dependency of classification accuracy was probably driven by the greater proportion of transitional boundary areas in the smaller streams multiple regressions of measured depths y versus principal component scores x1 x2 xn generated r 2 values ranging from 67 for high gradient riffles to 99 for glides in a fifth order reach r 2 values were lower in third order reaches ranging from 28 for runs and glides to 94 for pools the less accurate depth estimates obtained for smaller streams probably resulted from the relative increase in the number of mixed pixels where a wide range of depths and surface turbulence occurred within a single pixel matched filter mf mapping of woody debris generated overall accuracies of 83 in the fifth order lamar river accuracy figures for the in stream habitat and wood mapping may have been misleadingly low because the fine resolution imagery captured fine scale variations not mapped by field teams which in turn generated false misclassifications when the image and field maps were compared the use of high spatial resolution hyperspectral hsrh imagery for stream mapping is limited by the need for clear water to measure depth by any tree cover obscuring the stream and by the limited availability of airborne hyperspectral sensors nonetheless the high accuracies achieved in northern yellowstone streams indicate that hsrh imagery can be a powerful tool for watershed wide mapping monitoring and modeling of streams d 2003 elsevier science b v all rights reserved

can we distinguish flood frequency and magnitude in the sedimentological record of rivers consideration of the origin of alluvial deposits and their paleoenvironmental interpretation has traditionally involved two schools of thought that they are either the result of processes that on average have acted uniformly through time or that they are related to exceptional events that occur infrequently despite the long running debate of gradualism versus catastrophism within the earth sciences there are surprisingly few quantitative data to assess the magnitude of events that produce alluvial sedimentary successions this paper reports on a unique natural experiment where surface digital elevation model dem and subsurface ground penetrating radar gpr data were taken immediately prior to and after a large 1 in 40 yr flood event on the sandy braided south saskatchewan river canada results show that although this high magnitude flood reworked the entire braidplain the scale of scour and style of deposition was similar to that associated with lower magnitude annual floods the absence of a distinct imprint of this large flood within the deposits is related to the fact that as river discharge rises and begins to flow overbank channel width increases at a much faster rate than flow depth and thus the rate of increase in channel bed shear stress declines hence rather than being a product of either frequent or rare events alluvial deposits will likely be created by a range of different magnitude floods but discriminating between these different scale events in the rock record may be extremely difficult

quantification of bedform dynamics and bedload sediment flux in sandy braided rivers from airborne and satellite imagery images from specially commissioned aeroplane sorties manned aerial vehicle mav repeat unmanned aerial vehicle uav surveys and planet cubesat satellites are used to quantify dune and bar dynamics in the sandy braided south saskatchewan river canada structure from motion sfm techniques and application of a depth brightness model are used to produce a series of digital surface models dsms at low and near bankfull flows a number of technical and image processing challenges are described that arise from the application of sfm in dry and submerged environments a model for best practice is presented and analysis suggests a depth brightness model approach can represent the different scales of bedforms present in sandy braided rivers with low turbidity and shallow 2 m deep water the aerial imagery is used to quantify the spatial distribution of unit bar and dune migration rate in an 18 km reach and three 1 km long reaches respectively dune and unit bar migration rates are highly variable in response to local variations in planform morphology sediment transport rates for dunes and unit bars obtained by integrating migration rates from uav with the volume of sediment moved from dsms using mav imagery show near equivalence in sediment flux hence reach based sediment transport rate estimates can be derived from unit bar data alone moreover it is shown that reasonable estimates of sediment transport rate can be made using just unit bar migration rates as measured from 2d imagery including from satellite images so long as informed assumptions are made regarding average bar shape and height with recent availability of frequent repeat satellite imagery and the ease of undertaking repeat mav and uav surveys for the first time it may be possible to provide global estimates of bedload sediment flux for large or inaccessible low turbidity rivers that currently have sparse information on bedload sediment transport rates

dryland anabranching river morphodynamics rio capilla salar de uyuni bolivia the dryland anabranching river rio capilla is characterized by nonvegetated and vegetated reaches with prominent channel morphology to identify the morphodynamics of such dryland anabranching systems and their controls we investigated the rio capilla of the southern altiplano plateau using high resolution satellite imagery and field measurements comparison of high resolution satellite data reveals that erosion exceeds deposition for the main channel accompanied by changes in channel planform such as meander and channel morphology on site surveys combined with high precision gps and high resolution satellite imagery show that channels are characterized by shallowness and poor development of levees the study area of the rio capilla is divided into two zones of different slopes zone 1 with a high slope and zone 2 with a low slope zone 1 has a relatively straight main channel with few anabranches and grass covered banks that are stable despite the high gradient whereas zone 2 is typified by more anabranches with nonvegetated banks and the main channel experiences prominent bank accretion and erosion excavations show that point bar deposits are fine sand dominated in two reaches and that river banks primarily consist of silt and clay the limited vegetation cover and abundance of desiccation cracks and macropores make the river bank more erodible leading to pronounced lateral migration in this low gradient dryland river system shallow channels and poor development of levees in combination with in channel accretionary benches result in frequent overbank flooding which results in a high density of crevasse splays over unconsolidated river banks and accretionary benches connection of headcuts and crevasse channels together with lateral migration and chute channels and reactivation of partially abandoned meanders produces an anabranching pattern in such dryland river systems

multiple optimal depth predictors analysis modpa for river bathymetry findings from spectroradiometry simulations and satellite imagery abstract remote mapping of bathymetry can play a key role in gaining spatial and temporal insight into fluvial processes ranging from hydraulics and morphodynamics to habitat conditions this research introduces multiple optimal depth predictors analysis modpa which combines previously developed depth predictors along with additional predictors derived from the intensity component of the hsi color space transformation modpa empirically selects a set of optimal predictors among all candidates utilizing partial least squares pls stepwise or principal component pc regression models the primary focus of this study was on shallow

the topographic signature of vegetation development along a braided river results of a combined analysis of airborne lidar color air photographs and ground measurements 1 this paper combines archived remotely sensed data airborne lidar and digital color air photographs with nonsynchronous ground observations including observations of topographic form and vegetation cover and growth to test the hypothesis that colonization of exposed river sediments by riparian trees has an impact on channel form and to quantify any impact that is identified this is achieved along a 21 km reach of the braided gravel bed tagliamento river in northeast italy where the width of the braided corridor typically exceeds 800 m lidar data are analyzed to extract a 2 m resolution digital evolution model dem and determine riparian vegetation extent height and structure within the active corridor aerial photographs are used to map the topography of the submerged parts of the corridor these data are divided into 1 km length subreaches which possess strong contrasts in vegetation height and extent joint analysis of vegetation and morphological properties of these subreaches reveals significant associations between vegetation properties and reach morphology residuals from a gamma function fitted to the topographic data for each subreach show a good fit with poorly vegetated reaches but a weakening fit with increasing vegetation cover largely as a result of the appearance of secondary peaks in the elevation frequency distribution associated with the heavily vegetated areas furthermore the overall skewness and kurtosis of the elevation frequency distribution within each of the subreaches are both significantly correlated with vegetation extent height median elevation and growth rate indicating a clear topographic signature of vegetation development along this braided river that reflects sediment accumulation within and around the vegetated patches

upper crustal structure of the western colombian basin caribbean sea multichannel seismic reflection profiles show that most of the western colombian basin is underlain by a large oceanic plateau the crust of this plateau has a smooth upper surface an oceanic velocity structure and a thickness at least twice that of typical oceanic crust locally well defined reflections within the plateau crust are related to layered basalt flows and interbedded sediments a mounded reflection pattern within acoustic basement at the crest of the plateau mono rise may represent volcanic knolls smooth surfaced basement of the western colombian basin is probably equivalent to the upper cretaceous basement complex below seismic reflection horizon b in the central venezuelan basin and resembles the basements of some cretaceous oceanic plateaus and aseismic rises in the western pacific an area of apparently typical oceanic crust lies adjacent to the colombian basin plateau and may represent relatively unmodified oceanic crust upon which the plateau was constructed reflections within the flank of the colombian basin plateau appear to overlap this crust indicating that the plateau is younger than the oceanic crust oceanic plateau crust extends to panama and costa rica without apparent structural break and may be continuous with the basement complex of southern central america

monitoring river channel and flume surfaces with digital photogrammetry this paper describes and illustrates a technique for high resolution monitoring of the surface morphology of water worked sediments the monitoring uses close range digital photogrammetry while photogrammetry is a long established technique more recent developments in digital photogrammetry allow application in fluvial research to be highly cost effective in both flume and natural river channel studies results are presented that involve two scales of laboratory flume a smaller scale application associated with sediment sorting processes in a straight channel and a larger scale application involving sediment transport and bed material feedbacks in a meandering channel subject to overbank flows a preliminary assessment of data quality is undertaken with encouraging results the precision of elevation estimates corresponds to the scale of the imagery acquired and hence may be controlled by design of the image acquisition process

bathymetric structure from motion extracting shallow stream bathymetry from multi view stereo photogrammetry stream bathymetry is a critical variable in a number of river science applications in larger rivers bathymetry can be measured with instruments such as sonar single or multi beam bathymetric airborne lidar light detection and ranging or acoustic doppler current profilers however in smaller streams with depths less than 2 m bathymetry is one of the more difficult variables to map at high resolution optical remote sensing techniques offer several potential solutions for collecting high resolution bathymetry in this research i focus on direct photogrammetric measurements of bathymetry using multi view stereo photogrammetry specifically structure from motion sfm the main barrier to accurate bathymetric mapping with any photogrammetric technique is correcting for the refraction of light as it passes between the two different media air and water which causes water depths to appear shallower than they are i propose and test an iterative approach that calculates a series of refraction correction equations for every point camera combination in a sfm point cloud this new method is meant to address shortcomings of other correction techniques and works within the current preferred method for sfm data collection oblique and highly convergent photographs the multi camera refraction correction presented here produces bathymetric datasets with accuracies of 0 02 of the flying height and precisions of 0 1 of the flying height this methodology like many fluvial remote sensing methods will only work under ideal conditions e g clear water but it provides an additional tool for collecting high resolution bathymetric datasets for a variety of river coastal and estuary systems copyright 2016 john wiley sons ltd

investigating decadal scale geomorphic dynamics in an alpine mountain setting we know little about the effect of recent climate variability upon landscapes at the timescale of decades because of 1 the complex nonlinear and path dependent nature of the response of a landscape to climate forcing and 2 the difficulty of quantifying spatially distributed impacts at the timescale of decades to centuries despite this being the timescale over which significant hypotheses have been raised over human impacts upon climate change and hence geomorphic systems a unique resource to investigate the linkages between climatic variability and geomorphic response is provided by the extensive coverage of aerial imagery commonly available since the 1950s here we use archival digital photogrammetry to produce high precision digital elevation models over large spatial scales and so to reconstruct the quantitative history of surface downwasting and sediment flux in a high mountain alpine system over the timescales of decades propagation of error methods is used to identify locations of significant landscape response and to compute volumes of significant surface change orthorectified aerial images are used in an image correlation framework to detect horizontal and vertical displacements of components of the landscape results are coupled to extant climate data and modeled snow cover to show how the landscape responds to climate forcing and to geomorphological maps to understand how this response varies between landscape elements the results show distinct landscape response to both warming and cooling periods and a tendency for the acceleration of surface displacement under warming conditions precipitation and snow cover are critical in controlling glacier dynamics and rock glacier displacement velocities however while some landforms might lead to locally high sediment flux landscape heritage can disconnect zones of high change rates from the valley bottom hence the landscape response to climate forcing is not necessarily reflected in valley system processes or sediment deposits

evaluation of an experimental lidar for surveying a shallow braided sand bedded river reaches of a shallow 1 0 m braided sand bedded river were surveyed in 2002 and 2005 with the national aeronautics and space administration s experimental advanced airborne research lidar eaarl and concurrently with conventional survey grade real time kinematic global positioning system technology the laser pulses transmitted by the eaarl instrument and the return backscatter waveforms from exposed sand and submerged sand targets in the river were completely digitized and stored for postflight processing the vertical mapping accuracy of the eaarl was evaluated by comparing the ellipsoidal heights computed from ranging measurements made using an eaarl terrestrial algorithm to nearby 0 5 m apart ground truth ellipsoidal heights after correcting for apparent systematic bias in the surveys the root mean square error of these heights with the terrestrial algorithm in the 2002 survey was 0 11 m for the 26 measurements taken on exposed sand and 0 18 m for the 59 measurements taken on submerged sand in the 2005 survey the root mean square error was 0 18 m for 92 measurements taken on exposed sand and 0 24 m for 434 measurements on submerged sand in submerged areas the waveforms were complicated by reflections from the surface water column entrained turbidity and potentially the riverbed when applied to these waveforms especially in depths greater than 0 4 m the terrestrial algorithm calculated the range above the riverbed a bathymetric algorithm has been developed to approximate the position of the riverbed in these convolved waveforms and preliminary results are encouraging

regional waveform propagation in the arabian peninsula regional waveform propagation is characterized in the arabian peninsula using data from a temporary network of broadband seismometers between november 1995 and march 1997 332 regional delta 15 events were recorded from nine stations deployed across the arabian shield regional phase propagation was analyzed in two ways by individual inspection of the waveforms and by stacking of waveforms inspection of the waveforms revealed consistent variations in individual seismograms according to the region of origin waveforms from events in the gulf of aqaba northwest of the network possess weak pn pg and sn but show a prominent lg phase in contrast clear pn sn and lg are observed for events located in the zagros a region northeast of the network events near the straits of hormuz also display pn and sn but lack a strong high frequency lg southern red sea and african earthquakes have moderate amplitude body phases with some lg for the stacks the data were high pass filtered at 1 hz rectified binned and then stacked by time distance or by time slowness the time distance stacks show clear differences between regions that correspond to the variations observed in individual seismograms the time slowness stacks allow comparison of relative phase velocities and amplitudes pn velocity under the network was estimated to be 8 0 0 2 km s consistent with data from prior refraction profiles the area of inefficient pn and sn propagation coincides with an area of holocene volcanism and suggests that anomalous upper mantle underlies much of the arabian shield

short term geomorphic analysis in a disturbed fluvial environment by fusion of lidar colour bathymetry and dgps surveys abstract objective estimating river s underwater bed elevations is a necessary but challenging task the objective of this study is to develop a revised approach to generate accurate and detailed digital terrain models dtms of a river reach by merging lidar data for the dry area with water depth indirectly derived from aerial imagery for wet areas methods this approach was applied along three sub reaches of the brenta river italy before and after two major flood events a regression model relating water depth and intensity of the three colour bands derived from aerial photos was implemented more than 2400 in channel depth calibration points were taken using a differential global positioning system dgps along a wide range of underwater bed forms results the resulting dtms closely matched the field surveyed bed surface and allowed to assess that a 10 year recurrence interval flood generated a predominance of erosion processes erosion dominated in the upper part of the study segment 104 082 m3 whereas a near equilibrium is featured on the lower reach 45 232 m3 the dtms allowed the detection of processes such as riffle pool downstream migration and the progressive scour of a pool located near a rip rap conclusion the presented approach provides an adequate topographical description of the river bed to explore channel adjustments due to flood events practice combining colour bathymetry and dgps surveys proved to represent a useful tool for many fluvial engineering ecology and management purposes implications the proposed approach represents a valuable tool for river topography description river management ecology and restoration purposes when bathymetric data are not available

effects of channel morphology and sensor spatial resolution on image derived depth estimates the utility of remote sensing in the study of fluvial systems depends upon the extent to which image data can be used to derive quantitative information of sufficient accuracy and precision for specific applications in this study we evaluate the effects of channel morphology on depth retrieval by coupling a radiative transfer model to various morphologic scenarios upwelling radiance l u spectra generated for a range of depths 2 150 cm and benthic cover types limestone periphyton and gravel were linearly mixed to simulate subpixel bed topography and substrate heterogeneity for sloping bottoms solar streambed geometry modified l u relative to a level bottom especially for beds sloping steeply away from the sun aggregate pixel scale l u spectra were compared to a database of simulated spectra to determine the radiance equivalent depth of a uniform bottom redub redub spectra for hypothetical stepped streambeds indicated underestimation of the actual area weighted mean depth but the ln l u l 560 l u l 690 redub ratio consistently reproduced the pixel scale mean for beta distributions of depths similarly when both dark periphyton and bright limestone substrates occurred within a pixel redub spectra produced large errors while the ratio proved robust along channel banks pixels will inevitably be mixed and our simulations indicated that although bank fractions estimated by spectral mixture analysis were highly accurate for vegetated cutbanks gravel bars were sensitive to the selection of both aquatic and terrestrial end members and subject to relatively large fraction errors these theoretical results were tested using a ratio based relative depth map and two end member mixture models derived from a hyperspectral image of the lamar river in yellowstone national park which also served to illustrate the importance and applicability of our simulations the primary conclusions of this study are that 1 the ratio based algorithm is well suited to complex river channels 2 channel morphology and sensor spatial resolution must be considered jointly during data collection and analysis and 3 the accuracy and precision of depth estimates are influenced by channel morphology and thus vary spatially

deposits of the sandy braided south saskatchewan river implications for the use of modern analogs in reconstructing channel dimensions in reservoir characterization estimation of the dimensions of fluvial geobodies from core data is a notoriously difficult problem in reservoir modeling to try and improve such estimates and hence reduce uncertainty in geomodels data on dunes unit bars cross bar channels and compound bars and their associated deposits are presented herein from the sand bed braided south saskatchewan river canada these data are used to test models that relate the scale of the formative bed forms to the dimensions of the preserved deposits and therefore provide an insight as to how such deposits may be preserved over geologic time the preservation of bed form geometry is quantified by comparing the alluvial architecture above and below the maximum erosion depth of the modern channel deposits this comparison shows that there is no significant difference in the mean set thickness of dune cross strata above and below the basal erosion surface of the contemporary channel thus suggesting that dimensional relationships between dune deposits and the formative bed form dimensions are likely to be valid from both recent and older deposits the data show that estimates of mean bankfull flow depth derived from dune unit bar and cross bar channel deposits are all very similar thus the use of all these metrics together can provide a useful check that all components and scales of the alluvial architecture have been identified correctly when building reservoir models the data also highlight several practical issues with identifying and applying data relating to cross strata for example the deposits of unit bars were found to be severely truncated in length and width with only approximately 10 of the mean bar form length remaining and thus making identification in section difficult for similar reasons the deposits of compound bars were found to be especially difficult to recognize and hence estimates of channel depth based on this method may be problematic where only core data are available i e no outcrop data exist formative flow depths are suggested to be best reconstructed using cross strata formed by dunes however theoretical relationships between the distribution of set thicknesses and formative dune height are found to result in slight overestimates of the latter and hence mean bankfull flow depths derived from these measurements this article illustrates that the preservation of fluvial cross strata and thus the paleohydraulic inferences that can be drawn from them are a function of the ratio of the size and migration rate of bed forms and the time scale of aggradation and channel migration these factors must thus be considered when deciding on appropriate length thickness ratios for the purposes of object based modeling in reservoir characterization

seismic tomography with local earthquakes in costa rica abstract the costarican isthmus is located at the western limit of the caribbean oceanic plateau where the cocos plate subducts along the middle american trench this plate shows strong lateral variations in its morphology and structure the main objective of this study is to investigate the effects of subduction related magmatism as a function of morphology and structure of the subducting plate by performing a simultaneous inversion of the 3 d crustal velocity field and hypocenter locations from local earthquakes for that we used the traveltimes of p waves first arrivals from more than 5000 events recorded at the costarican seismic networks between 1991 and 1998 in order to prevent data and modeling inaccuracies we followed an inversion scheme consisting of four steps 1 selection of an adequate data subset for tomographic inversion 2 estimation of the best reference 1 d model 3 determination of the finest parameterization and 4 evaluation of resolution the results show that the uppermost levels of the crust 0 6 km are consistent with geology since the velocity anomalies reflect the most meaningful geological features observed in the surface below these levels 6 20 km deep we found two different zones separated by a sw ne seismic alignment the northern part is characterized by a highly heterogeneous velocity field and is seismically active while the southern part is much more homogeneous and practically inactive moreover the northern part shows a certain accumulation of low velocity material within the upper mantle we suggest and illustrate that the structural differences between the northern and southern zones can be a consequence of the differences on the geometry and structure of the subducting slab

late cretaceous miocene diachronous onset of back thrusting along the south caribbean deformed belt and its importance for understanding processes of arc collision and crustal growth 1 the venezuelan basin is obliquely subducted to the east southeast beneath the continental south american plate at the east west trending south caribbean deformed belt scdb a 50 100 km wide wedge of accreted sedimentary rocks derived both from offscraping of the 0 5 to 1 km thick sedimentary cover of the subducting venezuelan basin and from incorporation of clastic sediments derived from the continental margin of south america in this paper we describe the structure and sequence stratigraphy of five late cretaceous to recent sedimentary sequences overlying a 230 000 km2 area of the southern venezuelan basin and beata ridge the data set includes 5900 km of 2d seismic reflection data that are tied to lithologic and age data taken from dsdp sites 146 149 and 150 in the central part of the venezuelan basin we use observed patterns of wedging in mapped and dated sedimentary sequences adjacent to the scdb to determine the age of the diachronous west to east initiation of thrusting and subduction at the scdb the onset of subduction in the scdb corresponds with the cessation of thrusting from west to east along the zone of collision between the intraoceanic caribbean arc and the south american continent this correlation in the age of deformation indicates that collision between the caribbean arc and the south american continent led to subduction polarity reversal a process that is commonly observed at various stages of tectonic evolution in other areas of active arc continent collision including japan and sunda

three dimensional simulation of the near fault ground motion for the 1995 hyogo ken nanbu kobe japan earthquake abstract the 17 january 1995 hyogo ken nanbu earthquake is a typical example showing that the ground motions along basin edge faults can be very destructive in this study we simulate the near fault ground motion from this earthquake based on a kinematic fault model and a simplified 3d velocity structure of the kobe area the kinematic earthquake rupture and the wave propagation are modeled using a 3d finite difference method fdm our simulation identifies the basin edge effect as an important factor that influenced the ground motion amplification pattern in the kobe area we found that the coupling of the source directivity and basin edge effects causes impulsive ground motions with extremely high amplitude at periods greater than 1 sec and in a narrow zone offset less than 1 km from the basin edge the combination of these effects acted to create a fairly continuous band of amplification that extends about 30 km in an elongated zone parallel to the basin edge boundary in some areas localized site effects might have been as important as the abovementioned effects but they cannot explain the continuity of the extended east west zone of damage

extraction of multithread channel networks with a reduced complexity flow model quantitative measures of channel network geometry inform diverse applications in hydrology sediment transport ecology hazard assessment and stratigraphic prediction these uses require a clear objectively defined channel network automated techniques for extracting channels from topography are well developed for convergent channel networks and identify flow paths based on land surface gradients these techniques even when they allow multiple flow paths do not consistently capture channel networks with frequent bifurcations e g in rivers deltas and alluvial fans this paper uses multithread rivers as a template to develop a new approach for channel extraction suitable for channel networks with divergences multithread channels are commonly mapped using observed inundation extent and i generalize this approach using a depth resolving reduced complexity flow model to map inundation patterns for fixed topography across an arbitrary range of discharge a case study for the platte river nebraska reveals that 1 the number of bars exposed above the water surface bar area and the number of wetted channel threads i e braiding index peak at intermediate discharge 2 the anisotropic scaling of bar dimensions occurs for a range of discharge 3 the maximum braiding index occurs at a corresponding reference discharge that provides an objective basis for comparing the planform geometry of multithread rivers mapping by flow depth overestimates braiding index by a factor of two the new approach extends channel network extraction from topography to the full spectrum of channel patterns with the potential for comparing diverse channel patterns at scales from laboratory experiments to natural landscapes

the crustal structure of the western arabian platform from the spectral analysis of long period p wave amplitude ratios abstract the crustal structure of the western arabian platform is derived using the spectral analysis of long period p wave amplitude ratios the ratio of the vertical to the horizontal component is used to obtain the crustal transfer function based on thickness variations crustal velocities densities and the angle of emergence at the lower crust and upper mantle interface eleven well defined earthquakes recorded at the long period ryd station during the period from 1985 to 1994 were selected for analysis based on the following criteria focal depths with a range between 7 and 89 km body wave magnitudes greater than 4 7 epicentral distances with a range from 8 8 to 26 5 and back azimuthal coverage from 196 to 340 spectral analysis calculations were based on the comparison of the observed spectral ratios with those computed from theoretical p wave motion obtained using the thomson haskell matrix formulation for horizontally layered crustal models the selection of the most suitable model was based on the identification of the theoretical model which exhibits the highest cross correlation coefficient with the observed transfer function ratio by comparing the spectral peak positions of the observed and theoretical values the thickness and velocity can be resolved within 3 km and 1 km s respectively of the observed values the spectral analysis of long period p waves can detect a thin layer near the surface of about 1 6 km thick and a velocity contrast of about 10 with that of the underlying layer a strong velocity gradient of about 0 05 km s per km was found in the upper crust and 0 02 km s per km in the lower crust the derived crustal model is not unique due to the theoretical assumptions horizontal layering constant densities and velocities in each layer quality of the data and complexities of the crustal structure the crustal model suggests that the crust consists of five distinct layers the upper crustal layer has a p wave velocity of about 5 6 km s and is about 1 6 km thick the second layer has a velocity of about 6 2 km s and is 10 2 km thick the third layer shows a velocity of 6 6 km s and is 6 8 km thick the fourth layer has a velocity of about 6 8 km s and is 12 3 km thick the lower crustal layer has a velocity of about 7 5 km s and is 9 3 km thick the mohorovicic discontinuity beneath the western arabian platform indicates a velocity of 8 2 km s of the upper mantle and 42 km depth

reconstructing the development of sampled sites on fluvial island surfaces of the tagliamento river italy from historical sources in parallel with research on surface sediment characteristics of evolving island features patches along an island braided reach of the tagliamento river italy the present research reconstructed the development of the sampled sites using historical information coupled with field measurements since any field sediment sampling programme inevitably focuses on small areas of the order of a few metres the historical sources were assessed bearing in mind their spatial resolution and geographical accuracy in relation to the size of the sampled sites and the information they could provide regarding the historical evolution of those sites the analysis combined four sources of information i river stage records revealed flood events that had the potential to reset bar surfaces and float in wood and seeds to initiate vegetation colonization ii oblique ground photographs identified areas of the river s active corridor where riparian vegetation colonization appeared to have been initiated by specific flood events iii dendrochronology was used to estimate the age of sampled sites iv field measured geographical locations of the sampled sites were combined with historical vertical areal imagery to further establish sampling site age and changes in vegetation cover from 1944 to 2012 a chronosequence of sampled sites 0 2 8 12 40 years was established vegetation colonization and island development showed a statistically significant development trajectory among sites of each age across the 40 year period following formative floods in 1965 1966 2000 2004 and a flow pulse in 2010 the trajectory progressed through pioneer and building island stages until vegetated areas became part of established islands evidence from the younger sites indicates that the pioneer island phase lasts up to eight years evidence from the oldest site indicates a building island phase lasting a maximum of 30 years but probably a lot less copyright 2014 john wiley sons ltd

seismic stratigraphy and structure of the caribbean igneous province multichannel seismic reflection profiles reveal the tectonic and stratigraphic complexity of the caribbean province a smooth reflector b forms the top of widespread cretaceous volcanic flows drilled during dsdp leg 15 and odp leg 165 in addition we also show other seismic evidence of volcanism sills and dipping horizons the southern parts of the venezuela and colombia basins are underlain by rough basement that shows many characteristics of oceanic crust several thick volcanic plateaus separated by deep basins with thin crust comprise the caribbean volcanic province in the venezuela basin only normal oceanic crust is present but in other basins this crust is underlain by underplated volcanic material the crust of the venezuela basin is less than 5 km thick and was probably formed in the pacific during the jurassic refraction data indicate that a thin layer 2v is formed by original oceanic crust overlain by a thin volcanic layer an intra basement reflection sub b marks the top of original oceanic crust that is sandwiched between an upper volcanic layer and lower underplated material this underplated layer forms a very thick layer 3v beneath the beata and nicaragua volcanic plateaus the upper part of layer 3v is gabbroic and outcrops on the beata ridge the thickening occurs mainly in the high velocity lower part of layer 3v and is attributed to the presence of magnesian rocks picrites or ultramafic cumulates a highly reflective horizon r is located at the top of this layer we present a model where the galapagos plume is 2500 km wide but has narrow heads that formed the caribbean volcanic plateaus separated by deep basins the caribbean igneous province is compared to similar volcanic features in the indian ocean kerguelen plateau and in the western pacific ocean ontong java plateau nauru and pigafetta basins the thick plateaus of the caribbean province resemble the kerguelen and ontong java plateaus whereas the deep basins present some similarities with the nauru and pigafetta basins the caribbean igneous province is younger 90 75 ma than the indian and pacific plateaus 110 130 ma however several geological evidences from land and geophysical offshore observations indicate that the onset of volcanic activity in the caribbean province could be as old as 115 ma

a multistep approach for joint modeling of surface wave dispersion and teleseismic receiver functions implications for lithospheric structure of the arabian peninsula 1 we present a multiple step procedure for joint modeling of surface wave group velocity dispersion curves and teleseismic receiver functions for lithospheric velocity structure the method relies on an initial grid search for a simple crustal structure followed by a formal iterative inversion an additional grid search for shear wave velocity in the mantle and finally forward modeling of transverse isotropy to resolve love rayleigh surface wave dispersion discrepancy it considers longer period surface wave group velocity swgv dispersion allowing for the resolution of deeper structure compared to previous joint inversions the grid search for simple crustal structure is facilitated using a library of precomputed receiver functions and swgv dispersion curves the iterative inversion improves fit to the data by increasing the number of layers in the crust when necessary in order to fit the swgv for periods greater than about 50 s we perform a grid search over mantle velocities including the mantle lid and low velocity zone keeping the crustal structure fixed to the values from the previous step in some cases a clear love rayleigh discrepancy prevents a simultaneous fit of the group velocities with an isotropic model the love rayleigh discrepancy can be resolved by allowing shear wave transverse isotropy with a vertical symmetry axis vsh vsv differences in the uppermost mantle the method is applied to 10 stations in the arabian peninsula sampling various tectonic environments including active continental rifting and stable regions the resulting shear velocity models confirm rapid crustal thinning of the arabian shield toward the red sea however we do not find strong evidence for crustal thickening toward the arabian platform our results suggest that the mantle lithosphere thickness varies regionally but that the mantle shear velocities beneath the arabian shield and red sea coast are generally anomalously low furthermore our results indicate the presence of strong polarization anisotropy up to about 10 in the lithospheric upper mantle in the vicinity of as well as farther away from the red sea our modeling yields vsv vsh in the southwestern part of the arabian peninsula consistent with vertical flow and vsh vsv in the northwestern part of the arabian peninsula and the continental interior consistent with horizontal flow indicating that the mantle flow pattern is not uniform along the axis of the red sea

geomorphic classification of rivers a new methodology applied in an atlantic region galicia nw iberian peninsula the classification of rivers based on geomorphological criteria played in the past a secondary role for management decision making although in the last years they have experienced a shift from the scientific field to that of the technical currently managers require the most simplified form of classifications in order to use them in plans and planning projects management and restoration on the one hand this means that classifications should be directed toward simplifying the diversity of fluvial environments in a number of manageable types and on the other hand to apply to each geomorphic type a management model in this study we have developed a method of geomorphic classification of rivers according to specific stream power variables and median grain size the new method is dynamic ability to readjust and gain robustness with the incorporation of new data and predictive we obtained six types directly from the method although we added a seventh type bedrock rivers for its special singularity each geomorphic type presents concrete values of specific stream power and median grain size which additionally involves a hydraulic geometry adjusted to terms of balance the change from a geomorphic type to another would reflect a geomorphologic imbalance in the form of greater power and sediment size our results have been compared with six commonly used classifications e g rosgen classification system or river styles framework geomorphic classification of rivers stands as a flexible tool that allows the development of a personalized geomorphic classification for rivers of the same geomorphological province through the temporary revision of various sites that act as control points we can learn should the case arise the intensity and geomorphic change of the site geomorphic classification of rivers acts as an alert system for any geomorphologic disturbance its simple application and interpretation facilitate the implementation in the administrative environment or its attachment to other commonly used classifications