a self regulating model of bedrock river channel geometry 1 the evolution of many mountain landscapes is controlled by the incision of bedrock river channels while the rate of incision is set by channel shape through its mediation of flow the channel shape is itself set by the history of bedrock erosion this feedback between channel geometry and incision determines the speed of landscape response to tectonic or climatic forcing here a model for the dynamics of bedrock channel shape is derived from geometric arguments a normal flow approximation for channel flow and a threshold bed shear stress assumption for bedrock abrasion the model dynamics describe the competing effects of channel widening tilting bending and variable flow depth transient solutions suggest that channels may take 1 10 ky to adapt to changes in discharge implying that channel disequilibrium is commonplace if so landscape evolution models will need to include bedrock channel dynamics if they are to probe the effects of climate change

observations on attenuation and shear wave velocity in fine grained marine sediments compressional p wave attenuation shear s wave attenuation and shear s wave velocity measurements compiled for fine grained unconsolidated sediments show trends that do not support empirical relationships hamilton j acoust soc am 68 1313 1340 1980 in acoustics and ocean bottom f a s e specialize conf madrid 1987 commonly used for geoacoustic modeling the exception is compressional wave attenuation data from 10 hz to 500 khz that essentially follow a frequency dependence of f1 2 standard deviations p wave attenuation with depth is difficult if not impossible to predict given the variability in the data examination of several attenuation depth profiles indicates that those of mitchell and focke j acoust soc am 67 1582 1589 1980 may be the best choice for predicting p wave attenuation with depth at the present time the assumption that s wave and p wave attenuations are proportional hamilton j acoust soc am 60 334 338 1976c in acoustics and ocean bottom

scale dependence of lithological control on topography bedrock channel geometry and catchment morphometry in western scotland abstract we propose that a scale dependent topographic signature of erodibility arises due to fluvial and glacial erosion acting on different parts of the landscape at different times for 14 catchments in western scotland we define three levels of substrate erodibility in order of decreasing resistance quartzite rocks nonquartzite rocks and zones of fault related fracture then using digital topographic and planimetric data coupled with field measurements we identify regression based scaling relationships between substrate erodibility and morphometric parameters at two spatial scales catchment scale morphometry shows a weak to variable relationship with substrate metrics overall erodibility can be inferred from catchment steepness indices i e channel steepness index and relief ratio but the existence of multiple exceptions could confound a more general application of this approach nonetheless major valley troughs trace fault zones and nonquartzite rocks leaving much of the higher and stee

dynamic equilibrium between an active uplift and the sevier river utah in a zone of active tectonic uplift one expects a river to change morphology simply because valley slope deforms but by cutting through a transverse uplift the sevier river in southern utah also adapts to the tectonics by eroding and depositing these localized changes of transport are caused by varying channel geometry pattern sedimentology and slope in the uplift the river is narrow efficiently shaped coarser grained and expends a greater proportion of energy on bed particles it deposits sediments downstream in exaggerated meandering reaches with wider less efficient channels localized erosion and deposition create a dynamic equilibrium with the structural growth but this equilibrium includes nonlinear responses like knickpoints and depositional lobes in response to the required erosion and deposition the river so dramatically alters channel grain size and channel geometry that the increase of sinuosity expected in the tectonically steepened valley does not occur

analysis of landslide dams induced by the 2008 wenchuan earthquake abstract landslide dams caused by earthquakes are extremely hazardous disruptions of the flow of water and sediment in mountain rivers capable of delivering large outburst floods that may devastate downstream areas we analyzed a unique inventory of 828 landslide dams triggered by the m w 7 9 2008 wenchuan tectonic earthquake china constituting 1 4 of the 60 000 coseismic slope failures mapped and attributed to this event while 501 landslides blocked the rivers completely the remainder caused only partial damming or channel diversion the spatial distribution of landslide dams follows the same trend of that of the total landslide distribution with landslide dams being most abundant in the steep watersheds of the hanging wall of the yingxiu beichuan thrust fault and in the northeastern part of the strike slip fault near qingchuan besides the co seismic landslide density the river width also played a key role in determining the landslide dam formation narrow rivers are more prone to be dammed than the wide rivers the correlation between river width and landslide dam volume follows a linear relation which can be used to roughly estimate the dam formation possibility however the applicability of this correlation needs to be validated in other regions the decay failure rate of dams defined here as the percentage of the number and area of landslide dams that have failed over time shows that 25 of dams accounting for 30 of total landslide dam area failed one week after the earthquake these percentages increased to 60 within 1 month and to 90 within 1 year the geomorphometric parameters were analyzed revealing power law relations between landslide area and dam width landslide source area and dam area as well as lake area and lake volume the inventory presented in this study will enrich the worldwide earthquake induced landslide dam database and will also contribute to a better understanding of the post earthquake dam decay

management of karst water resources in mining area dewatering in mines and demand for water supply in the dongshan mine of taiyuan shanxi province north china coalfields in north china contain six to seven coal seams in the permo carboniferous strata the coal seams are underlain by the ordovician limestone large scale dewatering or depressurizing of the karst aquifer was considered essential to avoid water inrushes and keep the mines safely operational this practice however has caused water supply shortage in the mining areas the most effective solution to this conflict is to use the uncontaminated karst water from the mines for water supply this paper explores a management model to maximize the utilization of the karst water while maintaining the safe operation of the mines the model can provide essential information on water resource distribution for decision makers the model was applied to the dongshan coal mine in taiyuan city china

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

controls on the channel width of rivers implications for modeling fluvial incision of bedrock on the basis of the manning equation and basic mass conser vation principles we derive an expression for scaling the steady state width w of river channels as a function of discharge q channel slope s roughness n and width to depth ratio a w 5 a a1 2 2 3 3 8 q 3 8 s 23 16 n 3 8 we propose that channel width to depth ratio in addition to roughness is a function of the material in which the channel is developed and that where a river is con fined to a given material width to depth ratio and roughness can be assumed constant given these simplifications the expression emulates traditional width discharge relationships for rivers incis ing bedrock with uniformly concave fluvial long profiles more sig nificantly this relationship describes river width trends in terrain with spatially nonuniform rock uplift rates where conventional discharge based width scaling laws are inadequate we suggest that much of observed channel width variability in river channels confined by bedrock is a simple consequence of the tendency for water to flow faster in steeper reaches and therefore occupy smaller channel cross sections we demonstrate that using conventional scaling relationships for channel width can result in underestima tion of stream power variability in channels incising bedrock and that our model improves estimates of spatial patterns of bedrock incision rates

bedrock channel adjustment to tectonic forcing implications for predicting river incision rates we present detailed data of channel morphology for a river undergoing a transient response to active normal faulting where excellent constraints exist on spatial and temporal variations in fault slip rates we show that traditional hydraulic scaling laws break down in this situation and that channel widths become decoupled from drainage area upstream of the fault unit stream powers are 4 times higher than those predicted by current scaling paradigms and imply that incision rates for rivers responding to active tectonics may be significantly higher than those heretofore modeled the loss of hydraulic scaling cannot be explained by increasing channel roughness and is an intrinsic response to tectonic forcing we show that channel aspect ratio is a strongly nonlinear function of local slope and demonstrate that fault induced adjustment of channel geometries has reset hillslope gradients the results give new insight into how rivers maintain their course in the face of tectonic uplift and illustrate the first order control the fluvial system exerts on the locus and magnitude of sediment supply to basins

temporal profiling of uplift rate along an active fault using river long profile in the kuchchh region western india abstract river long profiles are widely used as tectonic event markers incision uplift rate estimations based on the dating of river terrace or exposed scarp sediment give long term averaged uplift rate values with the limitation of not giving the intermediate phases of highs and lows on the other hand gps based estimates provide only decadal scale uplift rate estimates in our study we adopted the long profile inversion methodology to obtain a temporal profile of uplift rate history over the late pleistocene holocene time period along an active fault the kuchchh mainland fault in kuchchh region western india which has experienced several large magnitude earthquakes in recent past we also used long profiles analysis to quantify the transient response of kuchchh landscape to uplift activity along the kuchchh mainland fault steepness index and chi profiles were estimated to display the spatial variability in landscape disequilibrium integral method based chi profiles were used to obtain the optimum value of basin area exponent of the stream power incision model spim our estimates provide a mean uplift rate value of 1 1 1 4 mm yr along the kuchchh mainland fault during the late pleistocene holocene period which matches with the average uplift rate derived from other independent observations in this region further a chronology of major tectonic phases from the estimated uplift rate time series also corroborates with field based estimates of major incision events in kuchchh region we also tested the robustness and sensitivity of our uplift rate estimates to model parameters such data can be complementary to the existing sparsely both spatially and temporally distributed uplift rate database which is imperative to seismic hazard assessment

structural and geomorphological constraints on active normal faulting and landscape evolution in calabria italy calabria is one of the fastest uplifting and most seismically active regions in the mediterranean yet the time averaged c 10 6 years rates of normal faulting remain poorly constrained here we use digital elevation model analysis geological cross sections and a compilation of published data to quantify systematically along strike the fault throws and time averaged throw rates of the serre cittanova armo east crati and west crati faults we show that regional uplift has uplifted both their hanging wall and footwall blocks by c 200 400 m and the aspromonte massif by up to c 1150 1300 m we find that these faults have throws between c 640 and 1430 m and throw rates between c 0 6 and 1 4 mm a 1 their footwall ranges have variable proportions of inherited relief up to c 300 800 m the channels draining these ranges reflect the active normal faulting and relief in their steepness indices becoming c 5 8 m 0 9 steeper for each 0 1 mm a 1 throw rate increment and each 100 m relief increase finally the presence of knickpoints suggests that these channels are transiently responding to changes in relative base level which could be due to fault linkage or regional strain rate increases for the southern calabrian faults and to regional uplift acceleration in the case of the crati faults supplementary material topographic profiles of the marine terraces and long profiles of rivers are available at https doi org 10 6084 m9 figshare c 3689464

holocene record of slip predictable earthquakes on the kenchreai fault gulf of corinth greece abstract we present the quaternary slip history of the kenchreai fault gulf of corinth based on geomorphological palaeoseismological geo archaeological data and literally determined events we also applied a series of geomorphic indices such as the hypsometric curve asymmetry factor the stream length gradient index sl the valley floor width to valley height ratio vf the drainage basin shape bs and the mountain front sinuosity smf in drainage basins flowing perpendicular to the fault these indices are representative for longer time period and are analyzed as follows values of sl are relatively high close to the fault trace smf values range from 1 01 to 1 85 vf mean values range between 0 29 and 1 07 bs values range from 1 16 to 4 78 lateral fault growth was likely achieved by propagation primarily towards east while its western end appears to act as persistent barrier the holocene palaeoseismic history of the fault investigated by a palaeoseismological trench and 14 c dating of ten samples suggest four linear morphogenic earthquakes in the last 10 ka the kenchreai fault displays a holocene slip rate in the order of 0 15 mm a 1 and a recurrence interval ranging between 1300 and 4700 years thus the fault is classified as a fault of moderate activity with moderate to well developed geomorphic evidence of activity and an overall slip predictable earthquake model

fluvial archives a valuable record of vertical crustal deformation abstract the study of drainage network response to uplift is important not only for understanding river system dynamics and associated channel properties and fluvial landforms but also for identifying the nature of crustal deformation and its history in recent decades geomorphic analysis of rivers has proved powerful in elucidating the tectonic evolution of actively uplifting and eroding orogens here we review the main recent developments that have improved and expanded qualitative and quantitative information about vertical tectonic motions the effects of horizontal deformation are not addressed channel long profiles have received considerable attention in the literature and we briefly introduce basic aspects of the behaviour of bedrock rivers from field and numerical modelling perspectives before describing the various metrics that have been proposed to identify the information on crustal deformation contained within their steady state characteristics then we review the literature dealing with the transient response of rivers to tectonic perturbation through the production of knickpoints propagating through the drainage network inverse modelling of river profiles for uplift in time and space is also shown to be very effective in reconstructing regional tectonic histories finally we present a synthetic morphometric approach for deducing the tectonic record of fluvial landscapes as well as the erosional imprint of tectonic forcing sedimentary deposits such as fluvial terrace staircases are also considered as a classical component of tectonic geomorphology we show that these studies have recently benefited from rapid advances in dating techniques allowing more reliable reconstruction of incision histories and estimation of incision rates the combination of progress in the understanding of transient river profiles and larger more rigorous data sets of terrace ages has led to improved understanding of river erosion and the implications for terrace profile correlation i e extrapolation of local data to entire profiles finally planform changes in fluvial systems are considered at the channel scale in alluvial rivers and regional level in terms of drainage reorganisation examples are given of how numerical modelling can efficiently combine with topographic data to shed new light on the dis equilibrium state of drainage systems across regional drainage divides

limits of downstream hydraulic geometry adjustments to flow width depth and velocity in response to changes in discharge are commonly characterized by using downstream hydraulic geometry relationships the spatial limits of these relationships within a drainage basin have not been systematically quantified where the erosional resistance of the channel substrate is sufficiently large hydraulic driving forces presumably will be unable to adjust channel form data sets from 10 mountain rivers in the united states panama nepal and new zealand are used in this study to explore the limits of downstream hydraulic geometry relationships where the ratio of stream power to sediment size d 84 exceeds 10 000 kg s3 downstream hydraulic geometry is well developed where the ratio falls below 10 000 kg s3 downstream hydraulic geometry relationships are poorly developed these limitations on downstream hydraulic geometry have important implications for channel engineering and simulations of landscape change

measurement of acoustic properties of near surface soils using an ultrasonic waveguide a technique is presented that uses a circular ultrasonic waveguide to measure the bulk shear s wave and longitudinal p wave velocities of unconsolidated media with particular application to near surface soils the technique requires measuring the attenuation characteristics of the fundamental longitudinal mode that propagates along an embedded bar from which the acoustic properties of the surrounding medium are inferred the principles behind the technique are discussed and the results of an experimental laboratory validation are presented followed by details of in situ soil property measurements obtained at various sites in urban areas of the united kingdom

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

implications of sediment flux dependent river incision models for landscape evolution 1 developing a quantitative understanding of the factors that control the rate of river incision into bedrock is critical to studies of landscape evolution and the linkages between climate erosion and tectonics current models of long term river network incision differ significantly in their treatment of the role of sediment flux we analyze the implications of various sediment flux dependent incision models for large scale topography in an attempt 1 to identify quantifiable and diagnostic differences between models that could be detected from topographic data or from the transient responses of perturbed systems and 2 to explain the apparent ubiquity of mixed bedrock alluvial channels in active orogens although certain forms of the various models can be discarded as inconsistent with morphological data we find that the relative intrinsic concavity indices of detachment and transport limited systems defined herein largely dictate whether the various models can be tied to distinctive steady state morphologies preliminary data suggest that no such diagnostic differences may exist and other methods must be developed to test models accordingly we develop and explore differences in the scaling behavior of topographic relief and the extent of detachment versus transport limited channels as a function of rock uplift rate that may allow discrimination among various models further we explore potentially diagnostic differences in the rates and patterns of transient channel response to changes in rock uplift rate in addition to general differences between detachment and transport limited systems our analysis identifies an interesting hysteresis in landscape evolution hybrid channels at the threshold between detachment and transport limited conditions are expected to act as detachment limited systems in response to an increase in rock uplift rate or base level fall and as transport limited systems in response to a decrease in rock uplift rate especially during postorogenic topographic decline the analyses presented set the stage for field studies designed to test quantitatively the various river incision models that have been proposed

normal fault growth and linkage in the gediz alasehir graben western turkey revealed by transient river long profiles and slope break knickpoints the gediz alasehir graben is located in the highly tectonically active and seismogenic region of western turkey the rivers upstream of the normal fault bounded graben each contain a non lithologic knickpoint including those that drain through inferred fault segment boundaries knickpoint heights measured vertically from the fault scale with footwall relief and documented fault throw vertical displacement consequently we deduce these knickpoints were initiated by an increase in slip rate on the basin bounding fault driven by linkage of the three main fault segments of the high angle graben bounding fault array fault interaction theory and ratios of channel steepness suggest that the slip rate enhancement factor on linkage was a factor of 3 we combine this information with geomorphic and structural constraints to estimate that linkage took place between 0 6 ma and 1 ma calculated pre and post linkage throw rates are 0 6 and 2 mm yr respectively maximum knickpoint retreat rates upstream of the faults range from 4 5 to 28 mm yr faster than for similar catchments upstream of normal faults in the central apennines and the hatay graben of turkey and implying a fluvial landscape response time of 1 6 to 2 7 myr we explore the relative controls of drainage area and precipitation on these retreat rates and conclude that while climate variation and fault throw rate partially explain the variations seen lithology remains a potentially important but poorly characterised variable this article is protected by copyright all rights reserved

seismotectonic zoning in east central italy deduced from an analysis of the neogene to present deformations and related stress fields this paper concerns the space time evolution of the late miocene to present contractional and extensional deformations within east central italy with an analysis of the pattern and orientation of the related stress field an insight into the cover basement relations and a discussion of the seismotectonic implications the pattern and orientation of the deformation and stress fields have remained unchanged since late miocene time and have been always characterized by the coexistence and parallelism in contiguous areas in a given time of shortening to the east and elongation to the west with time during a multistage deformation history both the contraction and the extension fields have moved eastward basement involved tectonics with a west dipping multiple detachment system would have allowed the progressive eastward shift of crustal slices corresponding at the surface to well defined tectonic domains with consequent crustal thinning in the tuscan zone and crustal thickening beneath the apennine mountain chain by comparing macroseismic epicenters hypocenters and focal mechanisms with crustal structure and independently known active faults it appears evident that the pattern frequency and distribution of the crustal seismicity are tectonically controlled and that a contraction extension pair is active also at the present time in fact along the adriatic coastline contractional deformation prevails with involvement of pleistocene layers whereas beneath the apennine range extensional deformation prevails both t axes in the inner domain and p axes in the outer domain are oriented southwest northeast or west south west east northeast and this coaxiality reflects the situation depicted by the geologic stress field on this basis we have produced a seismotectonic zoning of east central italy with three distinct domains intramountain seismic zone isz foothills seismic zone fsz and coastal seismic zone csz a plausible explanation for the genesis of the active seismic deformations of east central italy is that the locally intense extensional upper crustal seismicity of the intramountain seismic zone is confined to the hanging wall of a major west dipping active extensional discontinuity whereas the less frequent contractional seismic activity of the coastal seismic zone is within the hanging wall of an outer major active west dipping contractional discontinuity an area of overlap between these two zones is represented by the foothills seismic zone where superposed epicentral patterns from different surfaces of weakness at different depths are the predictable result of the asymmetry of the deformation

fluvial incision and tectonic uplift across the himalayas of central nepal the pattern of fluvial incision across the himalayas of central nepal is estimated from the distribution of holocene and pleistocene terraces and from the geometry of modern channels along major rivers draining across the range the terraces provide good constraints on incision rates across the himalayan frontal folds sub himalaya or siwaliks hills where rivers are forced to cut down into rising anticlines and have abandoned numerous strath terraces farther north and upstream in the lesser himalaya prominent fill terraces were deposited probably during the late pleistocene and were subsequently incised the amount of bedrock incision beneath the fill deposits is generally small suggesting a slow rate of fluvial incision in the lesser himalaya the terrace record is lost in the high range where the rivers are cutting steep gorges to complement the terrace study fluvial incision was also estimated from the modern channel geometries using an estimate of the shear stress exerted by the flowing water at the bottom of the channel as a proxy for river incision rate this approach allows quantification of the effect of variations in channel slope width and discharge on the incision rate of a river the determination of incision rates requires an additional lithological calibration the two approaches are shown to yield consistent results when applied to the same reach or if incision profiles along nearby parallel reaches are compared in the sub himalaya river incision is rapid with values up to 10 15 mm yr it does not exceed a few millimeters per year in the lesser himalaya and rises abruptly at the front of the high range to reach values of 4 8 mm yr within a 50 km wide zone that coincides with the position of the highest himalayan peaks sediment yield derived from the measurement of suspended load in himalayan rivers suggests that fluvial incision drives hillslope denudation of the landscape at the scale of the whole range the observed pattern of erosion is found to closely mimic uplift as predicted by a mechanical model taking into account erosion and slip along the flat ramp flat geometry of the main himalayan thrust fault the morphology of the range reflects a dynamic equilibrium between present day tectonics and surface processes the sharp relief together with the high uplift rates in the higher himalaya reflects thrusting over the midcrustal ramp rather than the isostatic response to reincision of the tibetan plateau driven by late cenozoic climate change or late miocene reactivation of the main central thrust

in situ high frequency p wave velocity measurements within 1 m of the earth s surface seismic p wave velocities in near surface materials can be much slower than the speed of sound waves in air normally 335 m s or 1100 ft s difficulties often arise when measuring these low velocity p waves because of interference by the air wave and the air coupled waves near the seismic source at least when gathering data with the more commonly used shallow p wave sources additional problems in separating the direct and refracted arrivals within 2 m of the source arise from source generated nonlinear displacement even when small energy sources such as sledgehammers small caliber rifles and seismic blasting caps are used using an automotive spark plug as an energy source allowed us to measure seismic p wave velocities accurately in situ from a few decimeters to a few meters from the shotpoint we were able to observe three distinct p wave velocities at our test site 130m s 180m s and 300m s even the third layer which would normally constitute the first detected layer in a shallow seismic

seismic velocities and poisson s ratio of shallow unconsolidated sands we determined p and s wave velocity depth profiles in shallow unconsolidated beach sand by analyzing three component surface seismic data p and s wave velocity profiles were calculated from traveltime measurements of vertical and tangential component seismograms respectively the results reveal two discrepancies between theory and data whereas both velocities were found to be proportional to the pressure raised to the power of 1 6 as predicted by the hertz mindlin contact theory the actual values of the velocities are less than half of those calculated from this theory we attribute this discrepancy to the angularity of the sand grains assuming that the average radii of curvature at the grain contacts are smaller than the average radii of the grains we modify the hertz mindlin theory accordingly we found that the ratio of the contact radius to the grain radius is about 0 086 the second disparity is between the observed poisson s ratio of 0 15 and the theoretical value 0 008 for random pack of quartz spheres this discrepancy can be reconciled by assuming slip at the grain contacts because slip decreases the shearing between grains poisson s ratio increases

consistency of scaling relations among bedrock and alluvial channels 1 this paper presents field data on channel geometry and potential control variables from 47 field settings representing a diverse range of environments these data are used to evaluate existing scaling relationships used in models of the evolution of bedrock channel geometry and to test the hypothesis that channel width w increases more slowly and depth d more rapidly in relation to discharge q or drainage area a as substrate resistance increases for this data set w a0 3 w q0 5 d a0 2 and d q0 3 the w a and w q relations are close to those found by previous investigators the d a and d q relations have not previously been reported for bedrock channels examination of trends within the data does not support the hypothesis and instead suggests that the erosional resistance of channel boundaries is not the primary control on scaling relations for channel geometry

response of a landscape to tectonics using channel steepness indices ksn and osl a case of study from the jalisco block western mexico abstract rapid tectonic uplift is known to increase river incision rates and to trigger the propagation of knickpoints along a river profile augmenting local relief thus the topography of mountainous landscapes records long term interactions between tectonics and climate we evaluate the geomorphic response to differential rock uplift with topographic analysis of 16 river basins including the normalized channel steepness index k sn our study focuses on rivers incising the northern and western sectors of the jalisco block western mexico a crustal unit bounded by plio quaternary extensional faulting we use osl signals from 17 riverbed samples to assess erosion rates the results indicate that basins in the northern sector have higher rates of rock uplift and erosion mean k sn 111 18 m 0 9 than those in the southwest mean k sn 77 23 m 0 9 in spite of the plio quaternary lavas that cap large areas of the northern sector the development of plio quaternary grabens and half grabens along the northern boundary of the jalisco block has increased the erosion rates augmenting the local relief by contrast the topography of the basins in the southwestern sector has resulted from a long erosional history controlled by the migration of old tectonic signals farther upstream in this region the landscape seems to have reached the steady state and is currently experiencing the propagation of knickpoints due to the increase in the rate of rock uplift in the coast of jalisco during the holocene

downstream variations in the width of bedrock channels field surveys of channel width w and drainage area a in bedrock channel reaches reveal relationships where w 5 ca b similar to the classic hydraulic geometry of alluvial channels data from five mountain channel networks support the assumption used in many landscape evolution models that an alluvial hydraulic geometry relationship where b 5 0 3 0 5 holds for bedrock channel systems although there is substantial local variability in channel width in bedrock channel systems there is no systematic difference in width versus drainage area relations for the surveyed bedrock and alluvial reaches in sedimentary lithologies in coastal oregon and washington in contrast bedrock channels were narrower and therefore had deeper flow than alluvial channels with equal drainage areas in the granite and limestone terrain of the yuba river california in addition data from the mokelumne river show that bedrock channel width decreases substantially downstream at the contact between relatively weak limestone and more erosion resistant granite but that channel slope does not change appreciably across contacts between these two lithologies data from coastal oregon drainage basins further show systematic channel widening after flood flows and debris flow impacts we conclude that downstream variations in the width of bedrock channels generally follow traditional hydraulic geometry relations but also reflect the local influence of longitudinal patterns of bedrock erosivity and disturbance history

seismic assessment of the weihe graben central china insights from geomorphological analyses and 10be derived catchment denudation rates abstract the tectonic activity and potential for linkage of adjacent active faults are crucial for seismic assessment as the two largest faults that bound the weihe graben central china the qinling northern piedmont fault qnf 200 km and the huashan piedmont fault hpf 150 km are mainly responsible for seismic risk in this densely populated area where the 1556 m 8 5 huaxian earthquake occurred with 830 000 fatalities however their tectonic activity and the degree of interaction remain poorly constrained hampering an adequate seismic risk assessment of the weihe graben here we integrate 23 new 10be derived catchment averaged denudation rates of 0 06 0 32 mm yr with topographic metrics to evaluate the seismic risk the results demonstrate that the landscape of the qinling and huashan mountains is in transient state in response to the tectonic perturbations of the qnf and the hpf with tectonic knickpoints formed along main streams and tributaries and widespread unstable drainage divides these two faults have comparable tectonic activity and are potentially capable of generating earthquakes with the maximum magnitude of mw 7 7 7 9 moreover they have likely started linking posing a greater seismic risk than previously estimated

decoding temporal and spatial patterns of fault uplift using transient river long profiles we present detailed observations of rivers crossing active normal faults in the central apennines italy where excellent constraints exist on the temporal and spatial history of fault movement we demonstrate that rivers with drainage areas 10 km2 and crossing faults that have undergone an increase in throw rate within the last 1 my have significant long profile convexities in contrast channels that cross faults that have had a constant slip rate for 3 my have concave up profiles and have similar concavities and steepness indices to rivers that do not cross any active fault structures this trend is consistent across the central apennines and cannot be explained by appeal to lithology or regional base level change the data challenge the belief that active faulting must always be reflected in river profiles instead the long profile convexities are best explained as a transient response of the river system to a change in tectonic uplift rate moreover for these rivers we demonstrate that the height of the profile convexity as measured from the fault scales with the magnitude of the uplift rate increase on the fault and we establish that this relationship holds for throw rate variation along strike for the same fault segment as well as between faults these findings are shown to be consistent with predictions of channel response to changing uplift rate rates using a detachment limited fluvial erosion model and they illustrate that analysis of the magnitude of profile convexities has considerable predictive potential for extracting tectonic information we also demonstrate that the migration rate of the profile convexities varies from 1 5 10 mm y and is a function of the slip rate increase as well as the drainage area this is consistent with n 1 for the slope exponent in a classical detachment limited stream power erosion law but could potentially be explained by incorporating an erosion threshold or an explicit role for sediment in enhancing erosion rates finally we show that for rivers in extensional settings where the response times to tectonic perturbation are long in this case 1 my attempts to extract tectonic uplift rates from normalised steepness indices are likely to be flawed because topographic steady state has not yet been achieved

distribution of active rock uplift along the eastern margin of the tibetan plateau inferences from bedrock channel longitudinal profiles 1 current models of long term river incision into bedrock suggest that the local rate of differential rock uplift should exert a primary control on the gradient of channel longitudinal profiles however discrimination of this effect from the influence of variations in substrate erodibility sediment flux precipitation and transient changes in profile shape has proved difficult in practice here we investigate the controls on the spatial distribution of bedrock channel gradients adjacent to the sichuan basin in an effort to assess the degree and nature of active deformation along this margin of the tibetan plateau analysis of river longitudinal profiles utilizing a channel steepness index a measure of profile gradient normalized for drainage area reveals a zone of anomalously steep channels adjacent to the topographic front of the plateau margin channel profiles are systematically less steep in their headwater reaches on the plateau and in their lower reaches east of the plateau margin comparison of steepness indices to mapped lithologic variations reveals that lithology has only a limited influence on channel gradient in this field area we observe no systematic relationship between steepness indices and upstream drainage area channels of all size are steeper near the plateau margin we argue that these systematic changes are not readily explained as a consequence of increased sediment flux or of orographic precipitation we are led to conclude that steep channel profiles along the topographic front of the plateau reflect active differential rock uplift between this region and the foreland

modeling the influence of rainfall gradients on discharge bedrock erodibility and river profile evolution with application to the big island hawai i motivated by convex concave bedrock river profiles developed across a climate gradient on the wetside of the kohala peninsula of the big island of hawai i we numerically model how rainfall gradients may influence longitudinal fluvial incision patterns first we model transient profile adjustment with two tectonic boundary conditions subsidence and uplift in this generalized analysis we assume that rainfall gradients only influence incision by modifying the relation between upstream drainage area and local discharge using a detachment limited model downstream increases in rainfall lead to profile convexities during transient adjustment in both tectonic settings and this is the opposite of the predicted increase in profile concavity that would develop in a steady state uplifting profile a transport limited erosion model develops only concave channel profiles without clear signatures of the rainfall pattern second we model the development of convex concave transient profiles and incision patterns on kohala using a detachment limited model if rainfall gradients only influence incision through the local discharge reasonable rainfall gradients can only develop channel convexities that are much smaller than those observed instead we hypothesize that local bedrock erodibility increases with the degree of rainfall dependent chemical weathering when local erodibility is assumed to scale with local rainfall rate the model can produce convex concave profiles similar to those observed in kohala our results suggest that changes in local bedrock erodibility due to local climate dependent weathering may be an important mechanism by which climate influences landscape form and rates of evolution this hypothesis requires further testing in this study area and beyond

spatial and temporal variations in growth rates along active normal fault systems an example from the lazio abruzzo apennines central italy abstract the geometry kinematics and rates of active extension in lazio abruzzo italian apennines have been measured in order to gain a better understanding of the spatial and temporal variations in fault growth rates and seismic hazards associated with active normal fault systems we present fault map traces throws throw rates and slip directions for 17 parallel en echelon or end on active normal faults whose 20 40 km lengths combine to form a soft linked fault array ca 155 km in length and ca 55 km across strike throw rates derived from observations of faulted late glacial features and holocene soils show that both maximum throw rates and throw rate gradients are greater on centrally located faults along the strike of the array total throws and throw gradients show similar spatial variations but with weaker relationships with distance along strike when summed across strike throw rates are increasingly high towards the centre of the array relative to summed throws we interpret the above to suggest that throw rates have changed in the recent past ca 0 7 ma from spatially random fault growth rates initiating at 2 5 3 3 ma to growth rates that are greater on centrally located faults we interpret this as evidence for fault interaction producing throw rate variations that drive throw profile readjustment on these crustal scale soft linked faults the results are used to discuss seismic hazards in the region which are quantified in a second paper in this issue

downhole seismic logging for high resolution reflection surveying in unconsolidated overburden downhole seismic velocity logging techniques have been developed and applied in support of high resolution reflection seismic surveys for shallow high resolution reflection surveying within unconsolidated overburden velocity depth control can sometimes be difficult to achieve as well unambiguous correlation of reflections with overburden stratigraphy is often problematic data obtained from downhole seismic logging can provide accurate velocity depth functions and directly correlate seismic reflections to depth the methodologies described in this paper are designed for slimhole applications in plastic cased boreholes minimum id of 50 mm and with source and detector arrays that yield similar frequency ranges and vertical depth resolutions as the surface reflection surveys compressional p wave logging uses a multichannel hydrophone array with 0 5 m detector spacings in a fluid filled borehole and a high frequency in hole shotgun source at the surface overlapping array positions downhole result

using hilltop curvature to derive the spatial distribution of erosion rates 1 erosion rates dictate the morphology of landscapes and therefore quantifying them is a critical part of many geomorphic studies methods to directly measure erosion rates are expensive and time consuming whereas topographic analysis facilitates prediction of erosion rates rapidly and over large spatial extents if hillslope sediment flux is nonlinearly dependent on slope then the curvature of hilltops will be linearly proportional to erosion rates in this contribution we develop new techniques to extract hilltop networks and sample their adjacent hillslopes in order to test the utility of hilltop curvature for estimating erosion rates using high resolution 1 m digital elevation data published and new cosmogenic radionuclide analyses in the feather river basin california suggest that erosion rates vary by over an order of magnitude 10 to 250 mm kyr 1 hilltop curvature increases with erosion rates allowing calibration of the hillslope sediment transport coefficient which controls the relationship between gradient and sediment flux having constraints on sediment transport efficiency allows estimation of erosion rates throughout the landscape by mapping the spatial distribution of hilltop curvature additionally we show that hilltop curvature continues to increase with rising erosion rates after gradient limited hillslopes have emerged hence hilltop curvature can potentially reflect higher erosion rates than can be predicted by hillslope gradient providing soil production on hilltops can keep pace with erosion finally hilltop curvature can be used to estimate erosion rates in landscapes undergoing a transient adjustment to changing boundary conditions if the response timescale of hillslopes is short relative to channels