knickzone propagation in the black hills and northern high plains a different perspective on the late cenozoic exhumation of the laramide rocky mountains geomorphic research in the black hills and northern high plains poses an intriguing hypothesis for the cenozoic evolution of this salient of the laramide rockies most recently geologists have appealed to late cenozoic epeirogenic uplift or climate change to explain the post laramide unroofing of the rockies on the basis of field mapping and the interpretation of long valley profiles we conclude that the propagation of knickzones is the primary mechanism for exhumation in the black hills long profiles of major drainages show discrete breaks in the slope of the channel gradient that are not coincident with changes in rock type we use the term knickzones to describe these features because their profiles are broadly convex over tens of kilometers at and below the knickzone the channel is incising into bedrock abandoning a flood plain and forming a terrace above the knickzone the channel is much less incised resulting in a broad valley bottom numerous examples of stream piracy are documented and in each case the capture is recorded in the same terrace level these observations are consistent with migrating knickzones that have swept through black hills streams rearranging drainages in their wake we demonstrate there are two knickzone fronts associated with mapped terraces preliminary field evidence of soil development shows that these terraces are time transgressive in nature our data strongly suggest that knickzone propagation must be considered a viable mechanism driving late cenozoic fluvial incision and exhumation of the northern high plains and adjacent northern rocky mountains

stream length gradient hotspot and cluster analysis sl hca to fine tune the detection and interpretation of knickzones on longitudinal profiles abstract this work presents a new approach for fine tuning the analysis of stream longitudinal profiles we show that applying hotspot and cluster analysis hca based on the getis ord gi statistic to the stream length gradient sl index improves the visualization of anomalous values assisting in the identification of tectonic structures and large landslides high positive gi values indicate the clustering of sl anomalies hotspots and mirror the occurrence of knickzones on the stream long profiles we applied this methodology to a mountainous sector of the eastern emilia romagna region in northern italy remote sensing and field surveys conducted on hotspot sites indicate that large landslides are the main process associated to over steepened long profile segments along streams connected to the valley slopes along stream changes in bedrock resistance accounts for the main anomalies within sectors where hillslopes and valley floors are disconnected we demonstrate that specific relationships between geometry and intensity of sl hotspots are indicative of the process responsible for the knickzone formation and in particular that tectonic structures generally provide the longest and highest anomalies the results of this work suggest that sl hca maps are more advantageous for detecting and interpreting knickzones compared with traditional sl maps since i they need less input data to be computed thus making them useful to investigate regions poorly covered by detailed geological data and or where field surveys are difficult to be carried out and ii the hotspot geometry can help discriminate the knickzones attributable to gravitational mass movements from litho structural ones

evaluation of mining induced energy and rockburst prediction at a diamond mine in canada using a full 3d elastoplastic finite element model abstract rockburst occurs when a volume of rock is strained beyond its elastic limit this type of failure is violent and instantaneous its occurrence is a major concern for the safety of underground personnel this paper reviews the current methods of rockburst prediction then a methodology is proposed to assess the extent and magnitude of the mining induced strain energy and its accumulation in a rock mass to predict the rockburst potentials in an underground mine both conventional and numerical methods have been combined to estimate the rockburst potentials in a real case study mine a case study of canadian diamond mine has been used to implement the proposed methodology site investigations have been conducted by traveling several times to the mine site and gathering essential data such as in situ stress states mining methods the geometry of underground openings mining and stoping sequences and rock mass classification kimberlite samples from both pipes have been collected for rock mechanics laboratory tests finally using the results of the numerical model two rockburst criteria ts and bpi have been used to assess the rockburst tendency in the understudy domain utilizing the proposed methodology potentially hazardous areas can be identified

evaluating knickpoint recession along an active fault for paleoseismological analysis the huoshan piedmont eastern china abstract ground rupturing earthquakes can generate tectonic knickpoints within upstream reaches of streams across active fault zones these knickpoints are characteristic of upstream propagation of time related process once generated by an earthquake so analysis of knickpoint series in streams which cross fault zones can be used to infer paleoearthquake events we studied the knickpoints along the huoshan piedmont fault hpf which is an active normal fault in the shanxi faulted basin zone china and demonstrate that analysis of knickpoints shows evidence for two paleoearthquakes in the hpf first we identified knickpoints in bedrock reaches upstream of the hpf using high resolution dems derived from irs p5 stereo images and the stream gradient method after excluding non faulting knickpoints 47 knickpoints were identified in 23 bedrock reaches upstream from the hpf analysis of the most recent knickpoints caused by the 1303 ce hongdong earthquake allowed for local calibration of the retreat rates applying these retreat rates across the study area allows for the estimation of the age of other knickpoints and constrains the age ranges of two knickpoint groups to be 2269 3336 a bp and 4504 5618 a bp these ages constrain the ages of two paleoearthquake events at 2710 102 and 4980 646 a bp the knickpoints along the hpf obey the parallel retreating model in which knickpoint morphology was roughly maintained during retreat so the heights of knickpoints represent the coseismic vertical displacements generated by the earthquakes along the hpf the vertical offsets for these three earthquake events are similar and are approximately 4 m which indicates that the ruptures on the hpf obey a characteristic slip model with a similar slip distribution for several successive earthquakes these results provide additional evidence of paleoearthquakes on the hpf and show that analysis of knickpoint recession along an active fault is a valuable tool for paleoseismology

tropical cyclone genesis factors in simulations of the last glacial maximum abstractlarge scale environmental factors that favor tropical cyclogenesis are calculated and examined in simulations of the last glacial maximum lgm from the paleoclimate modelling intercomparison project phase 2 pmip2 despite universally colder conditions at the lgm values of tropical cyclone potential intensity which both serves as an upper bound on thermodynamically achievable intensity and indicates regions supportive of the deep convection required are broadly similar in magnitude to those in preindustrial era control simulation some regions including large areas of the central and western north pacific feature higher potential intensities at the lgm than they do in the control runs while other regions including much of the atlantic and indian oceans are lower changes in potential intensity are strongly correlated with the degree of surface cooling during the lgm additionally two thermodynamic parameters one that measures midtropospheric entropy deficits relevant for tropical cyclogen

a statistical analysis of bottom hole temperature data in the hinton area of west central alberta abstract considerable differences in the spread of bottom hole temperature values from petroleum exploration well logs plotted as a function of depth are observed over a region of west central alberta the spatial variation of the spread is investigated and it is found to be greater toward the rocky mountain disturbed belt in the west the spatial variation there does not seem to correspond directly to local topography and may be partly due to faults or fractures and related water movement or other causes it also seems to coincide with the geothermal gradient anomaly reported by lam et al 1982 the variation of the spread is considered in terms of the extent to which subsurface isothermal surfaces follow variations in local topography

late quaternary large scale rotational slides induced by river incision the arroyo de gor area guadix basin se spain the arroyo de gor is a highly incised stream up to 200 m that has eroded into the pliocene pleistocene infill of the guadix basin in the betic cordillera se spain this paper concentrates on a particular reach of this stream namely the cenascuras gorafe reach where abundant inactive rotational slides can be recognized on both hillslopes of the canyon shaped valley the rotational slides have surface areas of 5 15 ha and volumes of mobilized material of 5 15 hm3 these rotational slides can be recognized by their main scarps which are still well featured at both margins of the valley as well as by the counter hillslope rotation of the strata in their bodies the surfaces of rupture are concave their width being greater than their length i e the landslides are elongated in a direction perpendicular to the landsliding displacement and parallel to the stream at depth the surfaces of rupture developed on fine grained sediments mostly clays underlying the conglomerates and sands affected by the rotational slides the clays at the surface of rupture are smectite rich and show several features produced by the landsliding such as striations and sigmoidal shaped structures the cenascuras gorafe canyon has been developed by a combination of entrenchment fracturing and landsliding initial deep entrenchment of the stream is attributed to a base level lowering related to the capture of the former endorheic basin by the gualdalquivir river in the late pleistocene this river incision created a canyon with subvertical unstable walls which due to gravitational instability would give way to vertical open tension cracks some distance from the canyon edge the tension cracks would end at depths equal to the base of the canyon which also coincides with the contact between the conglomerates and the underlying clays the rotational slides are thought to have occurred during heavy rains by a combination of piping which would have lengthened the tension cracks and infiltration which would reduce the shear strength along the gently dipping contact between conglomerates and the underlying clays thus the blocks bounded by the tension cracks and the subhorizontal lithological contact would slide under their own weight on the subhorizontal surfaces of reduced shear strength several age constraints lead us to tentatively assign the landslides to the isotope stage 5 around 32 ka an interglacial period agreed to be wetter and slightly warmer than the present day semi arid climate

geomorphic imprints of repeated tsunami waves in a coastal valley in northeastern japan abstract devastating tsunami waves induced by the 2011 off the pacific coast of tohoku earthquake severely inundated valleys along the ria type notched rocky coast in northeastern japan causing erosion of bedrock on valley side slopes using high resolution topographic data obtained by terrestrial and airborne laser scanning we investigated detailed morphology of the eroded valley in a typical site at aneyoshi we found several characteristic features likely affected by tsunami wave erosion 1 a series of small cliffs on the valley side slopes related to the tsunami flow depth 2 an inverse asymmetry of side slopes at ingrown meander bends 3 an exceptionally wide valley bottom near the coast and 4 a knickpoint located around the maximum tsunami run up point far back from the coast these topographic features are ascribable to repeated tsunami wave erosion since the mid holocene

stream analysis of small drainage basins in an ancient landform korean peninsula abstract much of the topography of korea is ancient but many quaternary fault outcrops and marine terraces have been observed in the southeastern part of the korean peninsula sufficient evidence of a quaternary fault is lacking in the geological features of the commercially developed jukbyun and uljin areas knickpoints that develop on streams can be formed by tectonic activity such as faulting and folding or can result simply from the differential erosion rates of bedrock in this study we investigated the relationship between stream steepness and faults in the jukbyun area stream profile analyses of the bugu and namdae basins were performed using a digital elevation model to estimate quaternary tectonic movements stream parameters obtained from analysis of the longitudinal stream profiles of the bugu and namdae drainage basins in the northeastern part of the korean peninsula indicated neotectonic movement thirty of the thirty nine knickpoints that developed in the downstream areas of the fluvial channels corresponded to fault zones it is thought that fault activity results in knickpoints in river systems the normalized relative slope k sn value 54 9 of the bs1 stream in the bugu drainage basin was higher than that 28 8 36 3 of the other streams in both basins despite a similar lithology to ns1 and ns2 therefore we concluded that stream steepness might be a result of tectonic forcing rather than a product of rock strength in the study area and that stream parameters could provide indirect evidence of quaternary tectonics in ancient landforms

fluvial geomorphology and paleohydrology in japan abstract an introduction to fluvial geomorphology and paleohydrology in japan is provided for researchers who are unfamiliar with these topics studies by japanese geomorphologists are reviewed including those published only in japanese language journals emphasis is placed upon the following aspects 1 abundant sediment yields from steep watersheds subjected to frequent heavy rains despite heavily vegetated conditions 2 extensive sedimentation in mountain piedmonts and coastal fluvial plains especially during the holocene 3 catastrophic hydro geomorphological events associated with earthquakes and volcanic eruptions and 4 the impacts of the increased heavy rainfall during the pleistocene holocene transition on the post glacial development of hillslopes and alluvial fans these geomorphological characteristics differ from those in continental regions such as europe and north america indicating that research on japanese fluvial systems can contribute a great deal to the understanding of the global variety of fluvial geomorphology recent work on paleohydrological reconstruction in japan is also reviewed

fluvial landscape response time how plausible is steady state denudation whether or not steady state topography and denudation are probable states depends on the timescale of system response to tectonic and climatic perturba tions relative to the frequency of those perturbations this paper presents analytical derivations of algebraic relations for the response time of detachment limited fluvial bedrock channel systems both to tectonic and climatic perturbations detachment limited fluvial erosion is described by the stream power incision model and the derivations are limited to the applicability of that model all factors likely to influence system response time that are not adequately captured by the stream power incision model will tend to increase the response time the calculations presented thus provide minimum estimates of landscape response time and therefore over predict the prob ability of attaining and sustaining steady state topography and denudation the central range of taiwan is used as a case study to estimate response times in a landscape often argued to be in steady state model parameters are fit to modern stream profiles by assuming that the topography represents a quasi steady state form estimated response times generally range from 0 25 to 2 5 ma depending on the non linearity of the incision rule and the magnitude and type of perturbation thus it may be reasonably argued that steady state topography and denudation are likely to prevail during periods of climatic stability response time is sufficiently short compared with plate tectonic timescales however rapid climatic fluctuation in the quaternary appears to preclude the attainment of steady state conditions in modern orogens motivation

gradient irregularity in the herbert gorge of northeastern australia the seventy kilometre long herbert gorge of northeastern australia preserves a record of past floods in slackwater deposits and palaeostage indicators step backwater modelling of water surface profiles indicates that discharges ranging from 11000 to 17000 m3s 1 have occurred six times in the gorge during the last 900 years these flood reconstructions provide insight into the role of extreme flows in shaping bedrock channel morphology in particular the hydraulics of extreme flows can be related to boulder transport and to the location of large boulder bars large boulder bars occur throughout the herbert gorge being best developed at loci of stream power minima along the inside of bends at tributary junctions and at obstructions in the channel caused by bedrock highs only the flows exceeding approximately 8000 m3 s 1 are competent to transport the boulders which constitute the bars in the straight channel reaches the boulder accumulations and bedrock highs have a fairly regular spacing which appears to be independent of lithologic or structural controls the bars provide an efficient means of energy dissipation and they are interpreted as a result of the inherent high turbulence of flow in a steep channel the regular spacing of the bars and their correspondence with the hydraulics of large flows suggest that the bars and associated bedrock highs may represent a self regulating mechanism akin to the pool riffle sequence of alluvial channels it may therefore be appropriate to view bedrock channels as deformable on the timescale of extreme discharges

heat flow of the eastern canadian rifted continental margin revisited continental shelves are regions where heat flow is not measured directly by conventional marine techniques but estimated from oil exploration data with possible bias in order to overcome this problem we recently proposed a method based on neural networks geophys j int 2006 166 115 that provides better constraints on thermal conductivity it allowed us to derive 161 heat flow estimates on the eastern margin of canada where previous studies had concluded to the existence of heat flow higher than that in the adjacent continent and ocean we conversely found rather homogeneous values 45 55 mw m 2 all along and across the margins from labrador to nova scotia the difference seems essentially related to the porosity of sediments that was not taken into account in previous studies our results support a high asymmetry for the conjugate iberian canadian margins and could indicate that mantle heat flow increases abruptly from the canadian shield to the margins

spatial analysis of stream length gradient sl index for detecting hillslope processes a case of the gallego river headwaters central pyrenees spain abstract a morphometric analysis of drainage networks and relief using geomorphic indices and geostatistical analyses of topographical data are useful tools for discussing the morphoevolution of a given area among the geomorphic indices the stream length gradient sl index represents a practical tool to highlight anomalous changes in river gradients perturbations of sl are usually indicative of 1 differences in the resistance of outcropping lithological units to erosion 2 sub surface processes such as active faulting and 3 slope failures that directly reach the stream channels particularly in small catchments in this work the sl index was calculated for the upstream sector of the gallego river basin in the central spanish pyrenees to test its accuracy and sensitivity for detecting the imprints of different surface processes a geostatistical procedure is proposed to obtain sl index maps through the interpolation and filtering of the values estimated along the drainage network this method allows computing of sl validation and assessing of its spatial distribution with robust statistical accuracy and objectively defining the anomalies in sl the anomalies in the sl map of the study area which coincide with knickpoints and knickzones were analyzed in detail the results indicate 1 perturbation in the drainage network caused by differences in the resistance to erosion of outcropping lithological units and 2 hillslopes affected by large landslides earth flows and rock falls directly reaching the stream bed this study indicates that the sl index has strong potential to solve geomorphological problems in different geological settings especially in detecting the role of active large scale features that influence landscape evolution

rock burst process of limestone and its acoustic emission characteristics under true triaxial unloading conditions abstract the rock failure process is associated with acoustic emission ae hence violent rock failure processes such as rock burst under different stress paths in laboratory can be studied using the ae monitoring technique in this paper single face dynamic unloading tests under true triaxial condition were carried out for paleozonic marine sedimentation limestone samples produced by blocks cored from 1140 m depth in jiahe coal mine of china frequency spectra analysis was conducted for the full wave ae data and figures showing the relationship of frequency amplitude of ae signals in rock burst stages were obtained the dynamical damage process and characteristics of limestone under the test condition are summarized it is found from the fast fourier transformation fft analysis of the ae signals that there exist two main frequency ranges i e lower 60 100 khz and higher 170 190 khz for the samples when the limestone samples are under relatively lower stress the ae signals are characterized by high frequency and low amplitude as the stress increases the ae signals tend to shift more towards a signature of high amplitude near the bursting failure of the rock samples it is observed that there are much higher amplitude and lower frequency events the ae accumulated energy release rapidly increases from the unloading state of the rock samples to its failure the dynamic unloading test facility provides a useful tool to gain an insight into the characteristics of rock bursts

calculation of electromagnetic radiation criterion for rockburst hazard forecast in coal mines intensive micro fracturing of rock close to mining operations accompanies an increase in the likelihood of rockbursting this fracturing causes an increase of the electromagnetic radiation emr level by up two orders of magnitude depending on the mining environment several examples of this enhanced emr are presented in this paper we first treat the emr theoretical criterion of rockburst hazard in coal mines and compare it with the empirical criterion of emr activity that was revealed on the basis of more than 400 different hazardous and non hazardous situations in underground coal mines only the following parameters are needed to estimate the emr criterion of rockburst hazard limiting value of gum volume mine working width coal seam thickness and coal elastic properties

timing duration and role of magmatism in wide rift systems insights from the jiaodong peninsula china east asia in east asia widespread extensional sedimentary basins together with the close association of metamorphic core complexes and magmatism are prominent features of the large scale wide rift system developed during late mesozoic times this region thus appears as a proper place to study continental extension as well as questions about the link between continental extension and magmatism this paper primarily provides pioneer exhumation time constraints on the linglong mcc jiaodong peninsula including cooling and deformation ages mcc cooling at mid crustal levels occurred at ca 143 ma besides last ductile deformation occurred at ca 134 ma while final exhumation stages under brittle 2 conditions occurred as late as ca 128 ma continuous crustal stretching were then recorded by the emplacement of a synkinematic pluton in the upper crust at ca 128 ma that cooled fast below an intracrustal shear zone crossing the ductile brittle transition at ca 123 ma the ca 120 118 ma age cluster is ascribed to the fast cooling of undeformed plutons marking the end of extension that lasted in the area over a minimum period of ca 30 my combining other mcc exhumation constraints and the onset of subsidence in the sedimentary basins total duration of late mesozoic extension in east asia could be estimated at ca 60 my related with a rather long process for extension from 160 to at least 100 ma east asian continental extension is heterogeneously distributed in space and time as revealed by fundamental differences between two end member classes of migmatite cored mcc already described in other wide rift systems extension seems to have first favoured partial melting which subsequently in turn maintained continental extension

an algorithm to extract more accurate stream longitudinal profiles from unfilled dems abstract morphometric features observed from a stream longitudinal profile slp reflect channel responses to lithological variation and changes in uplift or climate therefore they constitute essential indicators in the studies for the dynamics between tectonics climate and surface processes the widespread availability of digital elevation models dems and their processing enable semi automatic extraction of slps as well as additional stream profile parameters thus reducing the time spent for extracting them and simultaneously allowing regional scale studies of slps however careful consideration is required to extract slps directly from a dem because the dem must be altered by depression filling process to ensure the continuity of flows across it such alteration inevitably introduces distortions to the slp such as stair steps bias of elevation values and inaccurate stream paths this paper proposes a new algorithm called maximum depth tracing algorithm mdta to extract more accurate slps using depression unfilled dems the mdta supposes that depressions in dems are not necessarily artifacts to be removed and that elevation values within them are useful to represent more accurately the real landscape to ensure the continuity of flows even across the unfilled dem the mdta first determines the outlet of each depression and then reverses flow directions of the cells on the line of maximum depth within each depression beginning from the outlet and toward the sink it also calculates flow accumulation without disruption across the unfilled dem comparative analysis with the profiles extracted by the hydrologic functions implemented in the arcgis was performed to illustrate the benefits from the mdta it shows that the mdta provides more accurate stream paths on depression areas and consequently reduces distortions of the slps derived from the paths such as exaggerated elevation values and negatively biased slopes that are commonly observed in the slps built using the arcgis the algorithm proposed here therefore could aid all the studies requiring more reliable stream paths and slps from dems

gis analysis of fluvial knickzone distribution in japanese mountain watersheds although a knickzone a location at which stream gradient is locally large and intense erosion occurs has been regarded as an important geomorphic feature in bedrock river morphology the distribution of knickzones has not been well investigated especially for broad area this study examines the distribution of fluvial knickzones along mountain rivers for the entire japanese archipelago whereas conventional manual methods of identifying knickzones based on map readings or field observations tend to be subjective and are impractical for a broad scale analysis this study employs a semi automated method of knickzone extraction using dems and gis in a recent study by the authors this method has been shown to enable efficient examination of knickzone distribution over a broad area investigations on major mountain rivers revealed that knickzones are generally abundant in upstream steep river reaches suggesting hydraulic origins for the knickzones the broad presence of such knickzones in the steep japanese mountain rivers indicates that rivers subjected to active erosion show complex morphology induced by natural irregularities of water flow hydraulics as well as various environmental perturbations such as climatic changes there also seems to be a characteristic frequency of knickzone distribution common to moderately steep to very steep bedrock reaches in japan although volcanic products such as lavas and welded pyroclastic flow deposits in valleys can cause distinct knickzones substrate geology plays only a limited role in determining the distribution and form of knickzones

the climatic signature of incised river meanders climate controls landscape evolution but quantitative signatures of climatic drivers have yet to be found in topography on a broad scale here we describe how a topographic signature of typhoon rainfall is recorded in the meandering of incising mountain rivers in the western north pacific spatially averaged river sinuosity generated from digital elevation data peaks in the typhoon dominated subtropics where extreme rainfall and flood events are common and decreases toward the equatorial tropics and mid latitudes where such extremes are rare once climatic trends are removed the primary control on sinuosity is rock weakness our results indicate that the weakness of bedrock channel walls and their weakening by heavy rainfall together modulate rates of meander propagation and sinuosity development in incising rivers

bedrock channel incision along piccaninny creek australia piccaninny creek in northwestern australia drains approximately 60 km 2 of high relief sandstone and conglomerate terrain the drainage basin lies within the seasonal tropics and is characterized by ephemeral high magnitude flows flood flows of 50 to 100 m 3 s 1 are probably primarily responsible for the spectacular erosional features along the bedrock channel segments of the creek these erosional features occur in two basic forms as parallel longitudinal grooves and as a downstream sequence that begins with shallow linear depressions parallel to flow and ends in a deep narrow inner channel the longitudinal grooves are assumed to result from longitudinal vortices while the erosional sequences which closely resemble von karman vortex streets are interpreted to result from turbulent vortices shed off irregularities of the channel bed the longitudinal grooves and the inner channel sequence alternate with each other and with gravel floored depositional reaches downstream along the channe

the thermal regime in the jeanne d arc basin offshore eastern canada heat flow density values within the jeanne d arc basin from a previous study are compared with calculated heat flow densities based on a two dimensional conductive numerical model three profiles across the basin are considered and it is found that although water motion may affect the temperature distribution at shallow depths it is unlikely that the thermal field is perturbed by water motion at great depths it is found that the temperature at 20 km depth lies between 420 and 440 c and that the heat flow density from the upper crust beneath the basin is about 45 mw m2

evidence from high resolution topography for multiple earthquakes on high slip to length fault scarps the bilila mtakataka fault malawi geomorphological features such as fault scarps and stream knickpoints are indicators of recent fault activity determining whether these features formed during a single earthquake or over multiple earthquakes cycles has important implications for the interpretation of the size and frequency of past events here we focus on the bilila mtakataka fault malawi where the 20 m high fault scarps exceed the height expected from a single earthquake rupture we use a high resolution digital elevation model 1 m to identify complexity in the fault scarp and knickpoints in river profiles of 39 selected scarp profiles 20 showed evidence of either multi scarps or composite scarps and of the seven selected river and stream profiles five showed evidence for multiple knickpoints a near uniform distribution of vertical offsets on the sub scarps suggests they were formed by separate earthquakes these independent methods agree that at least two earthquakes have occurred with an average vertical offset per event of 10 and 12 m this contrasts earlier studies which proposed that this scarp formed during a single event and demonstrates the importance of high resolution topographic data for understanding tectonic geomorphology we use a one dimensional diffusion model of scarp degradation to demonstrate how fault splays form multi scarps and estimate the diffusion age t of the bilila mtakataka fault scarp to be 48 m25 m2 corresponding to 6400 4000 years since formation we calculate that a continuous rupture would equate to a mw 7 8 0 3 earthquake greater than the largest seismic event previously recorded in east africa

substrate influences on incised channel morphology abstract surveys of channel geometry and substrate resistance along an incised ephemeral channel in southern india were used to examine the influence of substrate on channel geometry the surveys indicate that as substrate resistance increases the channel grows narrower and deeper with undulating wall and bed topography more localized erosion in the form of potholes and longitudinal grooves and a steeper and more variable bed gradient

active forearc shortening in tohoku japan constraints on fault geometry from erosion rates and fluvial longitudinal profiles abstract convexities in the longitudinal profiles of actively incising rivers are typically considered to represent the morphologic signal of a transient response to external perturbations in tectonic or climatic forcing distinguishing such knickzones from those that may be anchored to the channel network by spatial variations in rock uplift however can be challenging here we combine stream profile analysis 10be watershed averaged erosion rates and numerical modeling of stream profile evolution to evaluate whether knickzones in the abukuma massif of northeast japan represent a temporal or spatial change in rock uplift rate in relation to forearc shortening knickzones in channels that drain the eastern flank of the abukuma massif are characterized by breaks in slope area scaling and separate low gradient alluvial upper channel segments from high gradient deeply incised lower channel segments average erosion rates inferred from 10be concentrations in modern sediment below knickzones exceed erosion rates above knickzones by 20 50 although profile convexities could be interpreted as a transient response to an increase in rock uplift rate associated with slip on the range bounding fault geologic constraints on the initiation of fault slip and the magnitude of displacement cannot be reconciled with a recent spatially uniform increase in slip rate rather we find that knickzone position stream profile gradients and basin averaged erosion rates are best explained by a relatively abrupt spatial increase in uplift rate localized above a flat ramp transition in the fault system these analyses highlight the importance of considering spatially non uniform uplift in the interpretation of stream profile evolution and demonstrate that the adjustment of river profiles to fault displacement can provide constraints on fault geometry in actively eroding landscapes

terrestrial heat flow density estimates for the jeanne d arc basin offshore eastern canada corrected bottom hole temperatures from 35 wells together with measured and assumed rock thermal conductivities are used to estimate linear geothermal gradients and effective thermal conductivities in the jeanne d arc basin in offshore eastern canada heat flow density values calculated for each well location indicate that heat flow density is slightly higher in the deeper northern part of the basin than in the southern part it appears that the heat flow density distribution is affected by fluid motion within the sediments and not by heat generation or basement topography dehydration is suggested as the mechanism that produces the fluid flow pattern that influences the heat flow density distribution in the basin and a simple fluid flow model of the jeanne d arc basin is presented

a review of mining induced seismicity in china active seismicity and rockbursting have been an emerging problem in chinese mines the distribution and characteristics of mining induced seismicity in china and its monitoring mitigation and research are reviewed in this paper mining at depth and the activity of current tectonic stress field are the two major factors leading to rockburst hazards three critical depths i e critical initiation depth roof upper bound depth and floor lower bound depth have been identified based on hypocenter data of seismic events in coalmines a strong correlation between rockbursts and gas outbursts in coalmines has also been established and it is recommended to use this correlation for rockburst and gas outburst hazard assessment and warning interchangeably we find that the key problems of rockburst hazard mitigation in china are the lack of mine seismicity monitoring networks in most mines and the need for improvement of the accuracy of the monitoring systems for mines that have been equipped with such systems because the demand for minerals resources is extremely high and the mining activities are progressing deeper and deeper an increasing trend of mining induced seismicity hazards in china may be anticipated for the near future mining induced seismicities are hazards but at the same time they have been found useful for studying geophysical problems in deep ground particularly in the field of earthquake prediction with the enforcement of relevant laws for the mining industry and the continuous effort to study rockburst problems using rock mechanics and geophysics principles and methods it is believed that new approaches for rockburst hazard control and mitigation can be developed

knickpoint initiation and distribution within fluvial networks 236 waterfalls in the waipaoa river north island new zealand if knickpoints transmit signals of base level fall in river networks then improvements in our understanding of their retreat rate and basin wide distribution helps constrain the transient response following perturbation many studies of knickpoint retreat focus on the response of trunk streams to base level fall here we examine the response of an entire fluvial network as recorded by 236 active knickpoints distributed within the waipaoa river on the north island of new zealand base level fall within the waipaoa catchment initiated 18 000 years ago in response to a climatically triggered and tectonically exacerbated pulse of incision using observations from field work aerial photo analysis and a digital elevation model dem we study the knickpoint positions within the network we find that 70 of the knickpoints are located at drainage areas between 1 10 5 m 2 and 1 10 6 m 2 and more than half are b1 km upstream of a large change in drainage area for the knickpoints b1 km upstream of large tributary junctions we find that the retreat distances were well correlated with the tributaries drainage areas in order to determine how a pulse of incision distributes itself throughout a fluvial network we develop two simple end member models and compare their behavior to the observed knickpoint distribution in the waipaoa in the first model we propose that a knickpoint initiated at the basin outlet retreats upstream and distributes the signal throughout the network at a rate that is a power law function of drainage area in the second model we propose that knickpoints form near a threshold drainage area below which channels cannot incise with the same efficiency as possible in downstream reaches though neither model addresses the along stream variability in substrate or knickpoint form the misfit between the modeled and the observed knickpoints along stream positions are surprisingly low b1 km 1 25 of the total stream length for knickpoints with drainage areas b1 10 6 m 2 large misfits up to 3 5 km are observed for knickpoints with present day drainage areas greater than 1 10 6 m 2 the large single step in channel elevation that characterizes knickpoints presently observed in tributaries of the waipaoa river may not characterize the base level fall signal that propagated through the trunk streams evidence for progressive rather than instantaneous incision in the trunk streams the knickpoints vicinities to tributary junctions and the equivalent success of the two end member models lead us to conclude that the present positions of the 236 observed knickpoints are largely a consequence of thresholds in channel incision at low drainage areas

the influence of bedrock geology on knickpoint development and channel bed degradation along downcutting streams in south central indiana geologic controls on knickpoint development and the mechanics of channel bed degradation were eluci dated by comparison of downcutting streams in south central indiana developed in lithologically homoge neous carbonate units and layered siliciclastic strata knickpoints formed in a single lithologic unit are stepped each step consists of a knickpoint face and tread the height of each step is equal to and controlled by bed thickness spatially knickpoints in homogeneous terrain are limited to jointed strata that dip 1 upstream or 2 downstream at angles less than the channel gradient knickpoints observed in lithologically layered strata are characterized by a single step in which resistant jointed rocks overlie and protect weaker units total knickpoint relief is influenced by thickness of the weaker strata knickpoints in layered siliciclastic strata are spatially limited to bedrock reaches produced by differential rates of channel incision knickpoint distribution is also influenced by joint

transient basin as indicator of tectonic expressions in bedrock landscape approach based on matlab geomorphic tool transient profiler abstract the tectonic and erosional processes sculpture the earth s surface producing a landscape that preserves the evolutionary history of rock uplift and incision the bedrock channels act as an efficient gradation agent where the river profile adjusts to changing tectonic climatic or topological e g river capture boundary conditions and develops a transient basin a suite of slope break knickpoints at comparable elevations in the channel profiles of the transient basin act as important markers we developed a set of comprehensive and interactive matlab tools called a transient profiler to extract the geomorphic indices from the digital elevation model for a basin characterization and landscape evolution period the paleo channel reconstruction from the relict reach in the three studied transient drainage basins palar umiam and dibang suggest a varying surface uplift from 514 1246 and 1981 m with a respective relief gain of 158 230 and 95 respectively we found that the horizontal knickpoint retreat rate is faster in the himalayan thrust system as compared to the shillong pop up system whereas the vertical knickpoint retreat rate is faster in the latter

underground measurements of electromagnetic radiation related to stress induced fractures in the odenwald mountains germany the regional stress field at wald michelbach odenwald mountains germany induces a secondary stress field around the space of the local railway tunnel resulting maximum shear stresses produce microfractures which emit electromagnetic radiation emr from emr measured along the cross section and the long axis of the tunnel the regional stress field is determined by a correlation of detected impulses per time with stresses calculated from the orientation of the tunnel its diameter and topographic load the major horizontal principal stress has an azimuth of 103 at times strongly alternating emr values are observed which indicate electromagnetic disturbances of unknown origin such disturbances are identified by repeated measurements and are not evaluated the repeated measurements which are not disturbed differ with median 112 impulses per 100 ms this difference corresponds to 0 037 mpa and indicates a good reproducibility of the results regional stress magnitudes and the wnw ese orientation of the major horizontal principal stress indicate a minor n s directed tensional force at the western shoulder of the upper rhine graben

landscape response to tectonic forcing digital elevation model analysis of stream profiles in the mendocino triple junction region northern california the topographic evolution of orogens is fundamentally dictated by rates and patterns of bedrock channel incision quantitative field assessments of process based laws are needed to accurately describe landscape uplift and denudation in response to tectonics and climate we evaluate and calibrate the shear stress or similar unit stream power bedrock incision model by studying stream profiles in a tectonically active mountain range previous work on emergent marine terraces in the mendocino triple junction region of northern california provides spatial and temporal control on rock uplift rates digital elevation models and field data are used to quantify differences in landscape morphology associated with along strike northwest to southeast changes in tectonic and climatic conditions analysis of longitudinal profiles supports the hypothesis that the study area channels are in equilibrium with current uplift and climatic conditions consistent with theoretical calculations of system response time based on the shear stress model within uncertainty the profile concavity of the trunk streams is constant throughout the study area 0 43 as predicted by the model channel steepness correlates with uplift rate these data help constrain the two key unknown model parameters the coefficient of erosion k and the exponent associated with channel gradient n this analysis shows that k cannot be treated as a constant throughout the study area despite generally homogeneous substrate properties for a reasonable range of slope exponent values n best fit values of k are positively correlated with uplift rate this correlation has important implications for landscape evolution models and likely reflects dynamic adjustment of k to tectonic changes due to variations in orographic precipitation and perhaps channel width sediment load and frequency of debris flows the apparent variation in k makes a unique value of n impossible to constrain with present data

dem analysis on longitudinal and transverse profiles of steep mountainous watersheds longitudinal and transverse characteristics of watersheds are fundamental to describe watershed topography only a limited number of studies however have analyzed the characteristics of transverse profiles in watersheds and almost no studies have examined longitudinal and transverse profiles at the same time how transverse profiles change within a watershed and how longitudinal and transverse characteristics of watersheds are related remain to be examined to address these issues this study employs dems gis and computer programming techniques to acquire a series of longitudinal and transverse profiles of watersheds basic morphometric parameters representing the shape of these profiles were analyzed methods to classify the profiles and to identify points where the morphometric characteristics change abruptly were also developed these methods were then applied to severely dissected steep watersheds in the japanese alps the results show that spatial change in transverse characteristics reflects two factors general topography of the watersheds and local differences in channel development the form of the transverse profiles is also affected by erosion processes that create mature v shaped valleys with a characteristic slope angle the longitudinal and transverse profiles play different roles in determining watershed topography and the overall longitudinal slope exerts a major influence on the mean watershed slope the discontinuity of the longitudinal and transverse profiles however tends to occur at the same location which may reflect the occurrence of knickzones and their influences on the development of valley side slopes

controls on bedrock channel incision along nahal paran israel nahal paran drains 3600 km2 of egypt s sinai peninsula and israel s negev desert much of the channel is alluvial but a canyon 10 5 km long has been incised into late cretaceous chert and dolomite in the lower portion of the basin slackwater deposits and paleostage indicators preserved within the canyon record approximately 10 floods of 200 to 2500 m3 s 1 over a period of at least 350 years step backwater simulations of flood flow hydraulics indicate extreme variations in stream power per unit area along the length of the canyon and associated variability in energy expenditure and sediment transport these variations reflect channel cross sectional morphology the greatest values of stream power occur along the lower half of the study reach in association with three pronounced knickpoints and an inner channel the locations of these features reflect the exposure of thick resistant chert layers along the channel the presence of several similar but buried and inactive knickpoints along the upper study reach indicates that the locus of most active channel incision has shifted with time probably in response to baselevel changes associated with tectonic activity along the dead sea rift thus the rate and manner of channel incision along the canyon of nahal paran are controlled by lithologic variability and tectonic uplift as they influence channel morphology and gradient which in turn influence hydraulics and sediment transport

quantification of thermal conductivity uncertainty for basin modeling thermal conductivity is a major influencing factor on subsurface conductive heat transport and resulting temperature distribution which in turn is a key parameter in basin modeling basin modeling studies commonly use representative literature values of thermal conductivity despite their impact on modeling results we introduce a workflow for quantifying the effect of uncertain thermal conductivity on subsurface temperature distribution and thus on basin modeling results and test this workflow on a two dimensional generic model from the nordkapp basin a prior ensemble of possible models is conditioned according to bayes theorem to incorporate prior knowledge of temperature data this conditional probability yields a posterior ensemble of temperature fields with a significantly reduced standard deviation to verify our approach we use five characteristic scenarios from the posterior ensemble for transient petroleum systems modeling how considering uncertain thermal conductivity affects variance in hydrocarbon generation is assessed by modeling corresponding vitrinite reflectances ro temperature uncertainty increases with depth it also increases with increasing offset from the salt diapirs which can be associated with a large lateral heat flow component in the complex tectonic environment of the nordkapp basin the introduced workflow can reduce temperature uncertainty significantly especially in regions with high prior uncertainty the ro is very sensitive to changes in thermal conductivity because the onset depth of the gas window in the nordkapp basin may vary by up to 800 m 2600 ft within the 95 confidence interval this demonstrates the importance of quantification of the uncertainty in thermal conductivity on thermal basin modeling

drainage network morphometry and evolution in the eastern lesotho highlands southern africa abstract present day drainage patterns in mountain regions are strongly affected by antecedent tectonic and geologic factors in the mountains of eastern lesotho southern africa bedrock comprises flat lying jurassic basalts which have given rise to a relatively uniform initial land surface here we present key morphometric measurements of river drainage patterns from this region from six 4th order river basins including principal river sinuosity river long profiles and valley cross profiles in order to evaluate geological controls on drainage evolution and the potential ages of river elements results show that there are highly variable spatial patterns of river morphometric properties even between adjacent basins despite identical geologies and altitudes across the region however northerly catchments show knickpoints variable long profiles and have steep sided and v shaped valley cross profiles southerly catchments have much smoother long profiles no knickpoints and concavo convex valley cross profiles there are also differences in river sinuosity values both for the catchments as a whole and for reaches of different lengths within the catchments these spatially varying river morphometric and drainage properties most likely are the long preserved outcomes of epeirogenic forcing on the land surface including tectonic uplift mantle relaxation and rebound during the cenozoic and subtle long term variations in climate from north to south across the region including in precipitation and weathering

canyons with undulating walls channels incised into cohesive substrates commonly develop undulating walls characterized by regular repetitive variations in channel width canyons with undulating walls are found in a variety of lithologic climatic and tectonic regimes and are most commonly present downstream from a knick zone of active incision flume experiments and natural channel morphologic patterns lead us to infer that wall undulations are the remnants of breached offset potholes or of sinuous longitudinal grooves formed during incision of the knick zone substrate characteristics seem to have little influence on these undulations using measurements from eight channels incised into the navajo sandstone of southern utah we found that intact rock strength rock mass strength joint orientation and spacing bedding and porosity did not differ significantly between channel reaches with straight walls undulating walls and meanders the wavelength and amplitude of wall undulations also did not correlate with any substrate characteristic these results lead us to conclude that the primary control on formation of undulating walls is hydraulic processes along the study channels deep narrow reaches with undulating walls alternate with wider straight or meandering reaches using flume simulations and one and two dimensional hydraulic modeling we found that the wall undulations act to reduce interreach spatial variability in energy expenditure and to minimize energy expenditure within a reach we propose that the wall undulations and flow hydraulics create a feedback whereby the wall undulations are preserved following knickpoint incision the wall undulations then act to regulate downstream energy expenditure in a manner analogous to bedforms this implies that generalized principles of uniform energy expenditure developed for alluvial channels may also apply at the reach scale to bedrock channels with relatively homogeneous substrates

high bedrock incision rates in the atenguillo river valley jalisco western mexico lava flows from three basaltic shield volcanoes preserve pliocene pleistocene river levels in the atenguillo river basin western mexico k ar dates of these basalt flows together with present and palaeoriver levels allow calculation of bedrock incision rates at three points along the length of the atenguillo river at volcan la laja dated at 0 65 ma incision rates are 25 cm ka 1 at volcan la cienega 2 2 ma incision rates are 23 cm ka 1 and at volcan el vigia 2 7 ma incision rates are 23 cm ka 1 these high incision rates as well as two distinct knickpoints along the profile of the atenguillo river are related to a base level c hange at the northern end of the basin the dynamics of this river basin are controlled by the ongoing process of continental fragmentation associated with the opening of the gulf of california 1997 by john wiley sons ltd

geomorphic limits to climate induced increases in topographic relief recognition of the potential for strong dynamic coupling between atmospheric and tectonic processes has sparked intense cross disciplinary investigation and debate on the question of whether tectonics have driven long term climate change or vice versa it has been proposed that climate change might have driven the uplift of mountain summits through an isostatic response to valley incision because isostasy acts to compensate mean elevations the debate hinges on the question of whether climate change can significantly increase topographic relief or more precisely increase the volume of missing mass between summits and ridges here we show that in tectonically active mountain ranges geomorphic constraints allow only a relatively small increase in topographic relief in response to climate change thus although climate change may cause significant increases in denudation rates potentially establishing an important feedback between surficial and crustal processes neither fluvial nor glacial erosion is likely to induce significant isostatic peak uplift

experimental study on the prediction of rockburst hazards induced by dynamic structural plane shearing in deeply buried hard rock tunnels abstract to investigate methods for predicting bursts induced by the shear failure of structural planes in the deeply buried hard rock tunnels shear tests were performed under various normal stresses on completely occlusive granite joints that were created via tension splitting in these experiments stress drops resulting from shear off of asperities on the surface of granite rigid structural plane which can trigger a fault slip rockburst were reproduced and the acoustic emissions aes were monitored during shearing the ae characteristics were analysed and a method based on the ae b value was developed to predict stress drops and the fault slip rockbursts induced by the stress drops the b value continuously decreased before the stress drop and dropped to approximately 0 8 or less at the point of the violent post peak shear stress drop moreover the b value tended to decrease to a relative minimum during the stick slip period when the energy increased sharply if the energy rate was greater than 104 and a lower b value was associated with a higher rockburst probability and intensity the b value generally decreased as the normal stress increased which increased the risk of rockburst induced by the dynamic shear failure of granite joints moreover the static and dynamic shear failure of the joints was easily distinguished when the b value was used as a predictor

knickpoint recession rate and catchment area the case of uplifted rivers in eastern scotland knickpoint behaviour is a key to understanding both the landscape responses to a base level fall and the corresponding sediment fluxes from rejuvenated catchments and must be accommodated in numerical models of large scale landscape evolution knickpoint recession in streams draining to glacio isostatically uplifted shorelines in eastern scotland is used to assess whether knickpoint recession is a function of discharge here represented by its surrogate catchment area knickpoints are identified using ds plots log slope versus log downstream distance a statistically significant power relationship is found between distance of headward recession and catchment area such knickpoint recession data may be used to determine the values of m and n in the stream power law e kamsn the data have too many uncertainties however to judge definitively whether they are consistent with m n 1 bedrock erosion is proportional to stream power and kps should be maintained and propagate headwards or m 0 3 n 0 7 bedrock incision is proportional to shear stress and kps do not propagate but degrade in place by rotation or replacement nonetheless the e scotland m and n values point to the dominance of catchment area discharge in determining knickpoint retreat rates and are therefore more consistent with the stream power law formulation in which bedrock erosion is proportional to stream power copyright 2005 john wiley sons ltd

new insights into the effect of the quaternary fault activity on river knickpoints in the central alborz iran abstract this study examines the knickpoints in a region to provide new insights for assessing the tectonically formed knickpoints tfks in this paper we have used a quantitative method to recognize tfks using two different river steepness methods the stream gradient gd and the normalized steepness index ksn analysis of the extracted tfks with the longitudinal profile logarithm slope area plots and natural logarithm gradient distance plots suggests that these knickpoints correlate with the active segments of faults in addition evaluation of the tfks indicates that the different length and height of the tfks can be related to the different features of each fault the investigation of tfks was implemented in the central alborz located at the southern margin of the caspian basin in northern iran which is a part of an active deformation region of the arabian and eurasian plate collision zone the investigation of tfks suggests that the quaternary faults activities are related to the recent tectonic activity in the northern flank of the central alborz as well as the central part of the central alborz which is consistent with global positioning system gps studies and increased uplift rate the results are in agreement with field observations in terms of geomorphic features and geology

in situ stress measurements and regional stress field assessment of the beishan area china abstract knowledge of the in situ stress field in the rock mass at depth is important to provide stress boundary conditions for underground excavation design stability evaluation and the optimization of ground support systems in the present study in situ stress measurement using hydraulic fracturing method is conducted in the beishan area in gansu province china a preferred candidate site for china s high level radioactive waste repository information on the stress magnitudes and orientations in three sub areas is obtained from 136 measurement points in nine sub vertical boreholes at depths ranging from 30 to 700 m and the distribution characteristics of the in situ stress field is analyzed the pressure time records obtained from the test intervals with pre existing fractures are discussed according to the acoustic borehole televiewer bhtv images the measurement results indicate that the regional stress field is dominated by horizontal stress within most of the measurement depth ranges a piecewise distribution of the principal stresses reveals approximately three stress domains with increasing depth at shallow and medium depths the stress fields are characterized by h h v and h v h respectively where h h and v are maximum horizontal minimum horizontal and vertical stresses respectively with further increase of depth the maximum principal stress changes from horizontal to vertical i e v h h fracture impression results reveal that the maximum horizontal stress is dominantly oriented in the nne nee direction which is in agreement with the orientation of regional tectonic stress field generated from movement of the earth s tectonic plates in addition it is found that the orientations of h are affected by the geological structures significantly

hillslope and channel evolution in a marine terraced landscape santa cruz california a flight of marine terraces along the central california coastline provides a unique setting for the study of topographic evolution wavecut platforms mantled by 2 6 m of marine terrace cover deposits are separated by 10 50 m tall decaying sea cliffs paleocliff edges become more rounded with age yet the details of the profiles and frequent bedrock exposure on the upper slopes imply weathering limited transport five bedrock stream channels etched through the marine terrace sequence display one to three distinct convexities in their longitudinal profiles detailed hand level surveys of the hillslopes and of the stream channel longitudinal profiles constrain hillslope evolution and channel incision components of a numerical model of landscape evolution we account for regolith production as a function of regolith depth in accord with the field observation that hillslope processes are presently dominated by the activities of burrowing rodents the transport process is taken to be diffusive stream incision is assumed to be controlled by stream power for which we use the surrogate of local drainage area slope product best fits of the numerical model to field data imply hillslope diffusivity is 10 m2 kyr 1 regolith production rate on bare bedrock is 0 3 m kyr 1 and falls off rapidly with regolith cover and the constant controlling the efficiency of stream incision is 5 to 7 10 7m 1 kyr1

an automated method for producing synoptic regional maps of river gradient variation procedure accuracy tests and comparison with other knickpoint mapping methods abstract the study of abrupt changes in longitudinal river profiles or knickpoints is currently approached through an empirical power law the slope area relationship results based on digital elevation model dem analyses and stream extractions are generally intended to determine crustal uplift rates and identify transient landscape conditions in this article we present an alternative geomorphometric method for locating knickpoints and knickzones based on local slope gradient and curvature attributes intended as a rapid regional scale automated knickpoint detection technique the accuracy of this slope curvature method is tested on two digital elevation grids nasa s srtm ground resolution of 90 m resampled here to 75 m and the aster dem 15 m in the sierra nacimiento new mexico usa a basement cored mountain range recently exhumed by waves of headward drainage integration in response to remote tectonic deformation in the adjacent rio grande rift out of every 10 gradient anomalies detected by the srtm derived numeric routine up to 8 are certifiable knickpoints recognized among a population of georeferenced occurrences surveyed in the field an independent comparison with the slope area method provided a further accuracy test which was particularly useful at sites that could not be validated in the field for practical reasons given the low tectonic activity of the study area the majority of knickpoints was also found to coincide with lithologic boundaries making it difficult without further geomorphological data to single out dynamic knickpoints directly caused by the upstream propagation of channel instabilities relating to base level change

dem and gis analysis of the stream gradient index to evaluate effects of tectonics the normandy intraplate area nw france computer based geomorphometry using a dem digital elevation model allows the analysis of the three dimensional properties of landscape this methodology is particularly useful in an intraplate region like western europe where the simple visual inspection of the topography cannot resolve the evolutionary trends of landforms in these domains the morphologies of the topographic surface may be controlled mainly by climate under a low rate of tectonic deformation among the geomorphometric parameters the stream length index sl has been used to characterize fluvial systems in relation to tectonics movements this work develops an algorithm to derive and map the sl index using a dem and gis to investigate its spatial variations in a broad area the algorithm is applied to a zone of weak intraplate deformation the coastal lowlands of normandy france the obtained spatial distributions of sl point to anomalous zones with high sl values these zones are adjacent to mapped fault scarps and characterized by changes in flow direction a kruskal wallis test shows that the bedrock lithology has no impact on the sl value therefore the sl variations can be related mainly to a differential uplift due to quaternary tectonic forcing quaternary sea level fluctuations may also be responsible for high sl values in a part of the coastal lowland

late quaternary erosion in southeastern australia a field example using cosmogenic nuclides late quaternary rates of apparent soil production bedrock incision and average erosion are determined for the southeastern highlands of australia using in situ produced cosmogenic nuclide concentrations of 10 be and 26 al apparent soil production rates define a steep inverse exponential function of soil depth with a maximum of 143 m ma 1 under zero soil depth there were no observed soil depths between about 25 cm and zero however such that the maximum observed rate is about 50 m ma 1 the bredbo river catchment average erosion rate is 157 1mm a 1 and is similar to the average hillslope erosion rate of 167 1mm a 1 bedrock incision rates average 9 mma 1 and suggest that the higher rates of hillslope erosion may be in response to a pulse of incision perhaps generated by knickpoint propagation bedrock erosion rates inferred froma tor profile average 3 8 mma 1 with higher rates on other more weathered tor tops an aboveground tor profile of nuclide concentrations is consistent with a simple model of rapid stripping of the surrounding saprolite supporting the view that at least one episodic period of increased denudation has affected the landscape evolution of the highlands we test this hypothesis by using a simple landscape evolution model to reasonably predict the spatial variation of soil depth as well as the emergence of tors r 2001 elsevier science ltd and inqua all rights reserved

tectono geomorphic indices of the erin basin ne kashmir valley india abstract the present study aims to assess the tectonic activity in the erin basin ne kashmir on the basis of several relevant geomorphic indices and field observations we use digital elevation model srtm and survey of india soi topographic maps in gis environment to compute the geomorphic indices the indices i e convex hypsometric curve high hypsometric integral value h i 0 5 low basin elongation ratio eb 0 17 low mountain front sinuosity values s mf 1 08 average low valley floor width ratios vf 4 suggest that the area is tectonically active moreover prominent irregularities knickpoints knickzones along longitudinal profile of the erin river even in homogenous resistant lithology panjal trap and anomalous stream gradient index sl values reflect that the erin basin is dissected by two faults ef 1 and ef 2 with nnw sse and ssw nne trends respectively the results of this preliminary study further substantiate the recent gps studies which argue that the maximum strain is accumulating in the ne part of the kashmir himalaya

quantification of principal horizontal stresses inside a tunnel an application of fracture induced electromagnetic radiation femr technique in the darjeeling sikkim himalayas abstract characterization of recent stresses delineation of the locations of active faults landslide prone slip planes and forecasting earthquakes are some of the emerging applications of the fracture induced electromagnetic radiation femr technique it is believed that such radiation is polarized along the direction of maximum compression and proportional to the maximum applied shear stress in this paper we have demonstrated the use of the femr technique to calculate the magnitude and directions of principal horizontal stresses inside a tunnel of 240 m length over a hilly road between jorethang and mayong near the village of miyong in sikkim india by taking 11 cross sectional measurements using a portable femr recording device called angel m although a reverse stress regime is obvious and established over the himalayas the results show a normal stress regime prevailing over this shallow near surface region of the tunnel and the direction of maximum shear stress changes along the tunnel length the results were explained with the aid of a simple clay analogue model where normal reactivation of a thrust plane with changing dips was simulated with this communication we hope to encourage scientists and engineers to deploy the femr technique which is lesser known but quicker non destructive cheaper and more accessible than conventional methods in evaluating tunnel safety by calculating shallow stresses locally modified inside a tunnel

correlations of fluvial knickzones with landslide dams lithologic contacts and faults in the southwestern annapurna range central nepalese himalaya 1 we investigate the role of landslide dams spatial changes in lithology and rock uplift on faults in the formation of knickzones on bedrock rivers we focus our analysis in the southwestern annapurna range of the central nepalese himalaya where detailed geologic maps topographic data field observations and aerial photographs are available we identified knickzones in our study area from normalized river steepness indices ksn values extracted from river longitudinal profiles derived from a 25 m digital elevation model we interpolated from digitized topographic map contours we compared the location of these knickzones with 1 lithologic contacts and faults from a detailed geologic map of the modi khola valley and 2 inferred ancient landslide dam features mapped from field observations and aerial photographs the steepest location on the modi khola occurs near the same latitude as the steepest reach on the mardi khola located directly to the east potentially highlighting a major topographic transition across the annapurna however we find that landslide dams once blocked the flow of the modi khola and damming followed by incision after landslide breaching can explain the location of these knickzones without the need for active faulting near the main central thrust we also conclude that 1 knickzones do not correlate with any spatial changes in lithology and 2 knickzones generated by rock uplift on unmapped faults cannot be ruled out we emphasize that disentangling the processes responsible for knickzone formation remains challenging even when high resolution geologic and topographic data are available

factors influencing the recession rate of niagara falls since the 19th century abstract the rate of recession of niagara falls horseshoe and american falls in northeastern north america has been documented since the 19th century it shows a decreasing trend from ca 1 m y 1 a century ago to ca 0 1 m y 1 at present reduction of the flow volume in the niagara river due to diversion into bypassing hydroelectric schemes has often been taken to be the factor responsible but other factors such as changes in the waterfall shape could play a role and call for a quantitative study here we examine the effect of physical factors on the historically varying recession rates of niagara falls using an empirical equation which has previously been proposed based on a non dimensional multiparametric model which incorporates flow volume waterfall shape and bedrock strength the changes in recession rates of niagara falls in the last century are successfully modeled by this empirical equation these changes are caused by variations in flow volume and lip length this result supports the validity of the empirical equation for waterfalls in rivers carrying little transported sediment our analysis also suggests that the decrease in the recession rate of horseshoe falls is related to both artificial reduction in river discharge and natural increase in waterfall lip length whereas that of american falls is solely due to the reduction in flow volume

longitudinal profile development into bedrock an analysis of hawaiian channels analysis of topographic maps of rivers incised into dated hawaiian lava flows shows that the long term average bedrock erosion rate along certain reaches is linearly related to stream power field observations suggest that two processes may control hawaiian channel downcutting 1 stream power dependent erosion including abrasion of the channel bed by transported particles and 2 step wise lowering caused by knickpoint propagation modeling results indicate that a simple stream power dependent erosion law predicts the straight to weakly convex longitudinal profiles characteristic of kauai channels but is insufficient to predict two other characteristic features the upslope propagation of knickpoints and the straight 5 8 channel slopes below the knickpoints thus more than this single transport law is apparently required to model bedrock channel incision field surveys also indicate that significant portions of the channel lengths below the knickpoints are mantled with large boulders we propose that

gis and sda applications in geomorphology abstract this special issue of geomorphology consists mainly of selected papers from the s15 session gis and sda applications in geomorphology at the 6th international conference on geomorphology held in zaragoza spain in september 2005 for this session 53 abstracts from europe asia the americas africa and oceania were submitted and 18 oral communications and 35 posters were presented the session provided an opportunity to overview discuss and evaluate new advances of gis geographical information systems and sda spatial data analysis applications in the field of geomorphology eight of the manuscripts submitted for the publication call for this special issue survived the review process and two other invited contributions together form this special issue with 10 papers

recession rates of waterfalls in boso peninsula japan and a predictive equation rates of waterfall recession and major factors that influence the rate were studied using waterfalls in boso peninsula japan the mean rate of waterfall recession was estimated by determining the age and original location the principal factor in determining the rate of waterfall recession is the ratio of the erosive force of stream to the bedrock resistance this is expressed in terms of measurable variables which include the discharge drainage area and precipitation the width and height of the waterfall and the unconfined compressive strength of the bedrock an empirical equation connecting the force resistance ratios and the rates of waterfall recession is derived copyright 2003 john wiley sons ltd

rockburst prediction and stability analysis of the access tunnel in the main powerhouse of a hydropower station based on microseismic monitoring abstract the access tunnel in the main powerhouse of the shuangjiangkou hydropower station in china has complex geological conditions and is subject to high in situ stress in deep buried sections microseismic activity in the surrounding rock mass of the tunnel was monitored by a microseismic monitoring system and rockburst was effectively predicted based on abundant data obtained from the microseismic monitoring statistical parameters which include cumulative apparent volume the energy index cumulative released energy and the es ep value were used to analyze the microseismic activity before and after rockburst to determine a more accurate early warning period and construction safety period a sharp decrease in the energy index and a rapid increase in the cumulative apparent volume indicated a deterioration of the surrounding rock mass stability the change characteristics of es ep values revealed that the rockburst process underwent a transformation of compression shear damage tension shear mixed damage and tension damage finally based on the number of daily events n and the b value of the microseismic events lgn b was first established to evaluate the rockburst risk of tunnels when the value of lgn b was greater than 1 rockburst was more likely to occur the larger the lgn b value the more severe the rockburst was the research results provide an important reference value for the prediction of rockbursts in deep tunnels and the regulation of site construction progress

multi channel patterns of bedrock rivers an example from the central narmada basin india abstract an anomalous multiple channel pattern in bedrock is observed on a predominantly downcutting reach of the narmada river the multi channel reach 800 2750 m in width and 8500 m in length is bounded by major faults and is underlain by granite and gneiss bedrock geomorphological investigations reveal differences among the upstream middle and downstream sub reaches of the multi channel study area whereas the upstream sub reach is dominated by deep flows and fine sediments the lower sub reach is characterized by a steep gradient and rapids the middle sub reach is the widest and is marked by thickly forested islands and boulder berms the characteristics of the three different sub reaches suggest control by the interactions of lithology flood processes and tectonics estimations of hack s 1973 stream gradient index values indicate considerable variations for the sl values along the length of narmada river the highest value of gradient index sl 797 is associated with the multi channel reach implying lithologic or tectonic control given the dimensions of the reach and its channels it appears that the present hydrological regime is inadequate to produce the feature we hypothesize that the multi channel pattern development in bedrock was initiated by block or domal uplift enhanced gradients and extreme floods permitted the system to exploit linear weaknesses in the bedrock leading to the development of anabranches and establishment of multiple channels in bedrock abrupt changes in the channel planform and morphology at the study site indicate that the river is adjusting its channel geometry width depth gradient and plan configuration to a new equilibrium channel morphology through the action of the extreme floods characteristic of this fluvial environment

channel response to tectonic forcing field analysis of stream morphology and hydrology in the mendocino triple junction region northern california abstract an empirical calibration of the shear stress model for bedrock incision is presented using field and hydrologic data from a series of small coastal drainage basins near the mendocino triple junction in northern california previous work comparing basins from the high uplift zone huz uplift rates around 4 mm year to ones in the low uplift zone luz 0 5 mm year indicates that the huz channels are about twice as steep for a given drainage area this observation suggests that incision processes are more effective in the huz it motivates a detailed field study of channel morphology in the differing tectonic settings to test whether various factors that are hypothesized to influence incision rates discharge channel width lithology sediment load change in response to uplift or otherwise differ between the huz and luz analysis of regional stream gaging data for mean annual discharge and individual floods yields a linear relationship between discharge and drainage area increased orographic precipitation in the huz accounts for about a twofold increase in discharge in this area corresponding to an assumed increase in the erosional efficiency of the streams field measurements of channel width indicate a power law relationship between width and drainage area with an exponent of 0 4 and no significant change in width between the uplift rate zones although interpretation is hampered by a difference in land use between the zones the huz channel width dataset reveals a scaling break interpreted to be the transition between colluvial and fluvial dominated incision processes assessments of lithologic resistance using a schmidt hammer and joint surveys show that the rocks of the study area should be fairly similar in their susceptibility to erosion the huz channels generally have more exposed bedrock than those in the luz which is consistent with protection by sediment cover inhibiting incision in the luz however this difference is likely the result of a recent pulse of sediment due to land use in the luz therefore the role of sediment flux in setting incision rates cannot be constrained with any certainty to summarize of the four response mechanisms analyzed the only factor that demonstrably varies between uplift rate zones is discharge although this change is likely insufficient to explain the relationship between channel slope and uplift rate the calibrated model allows us to make a prediction of channel concavity that is consistent with a previous estimate from slope drainage area data we show that the inclusion of nonzero values of critical shear stress in the model has important implications for the theoretical relationship between steady state slope and uplift rate and might provide an explanation for the observations this analysis underscores the importance of further work to constrain quantitatively threshold shear stress for bedrock incision

fluvial responses to volcanism resedimentation of the 1800a taupo ignimbrite eruption in the rangitaiki river catchment north island new zealand abstract the potential for the generation of dangerous and damaging lahars and floods in response to the eruption of voluminous pyroclastic debris has become increasingly appreciated in recent years the style and tempo of this response varies both between eruptions and between individual catchments impacted by a single eruption so that an understanding of the factors controlling this variation is necessary for precise hazard assessment the 1800a taupo eruption from the taupo volcanic centre in the central north island of new zealand devastated an area of 20 000 km 2 during eruption of a climactic ignimbrite impacting the headwaters of all major rivers draining radially from this region the rangitaiki river the subject of this paper differs from other catchments in that the taupo ignimbrite buried an essentially flat land surface inherited from a suite of welded ignimbrite sheets erupted between 320 340 and 230 ka the middle reaches of the catchment are characterised by narrow steep gorges alternating with low gradient basins developed in tectonic half grabens initially remobilisation of pyroclastic material in the headwaters was dominated by hyperconcentrated sheet flows resulting in shallow reworking in higher gradient areas reintegration of drainage networks was achieved by incision of deep channels and gullies assisted by breakouts from ephemeral lakelets developed in ignimbrite dammed depressions braided and later meandering streams superseded this pattern as rill and gully systems stabilised and sediment yields fell leading to a decline in drainage density gorge reaches acted as efficient conduits for remobilised material while the basins acted as local depocentres for the temporary storage of volcaniclastic sediments mediating the transfer of pyroclastic debris to the bay of plenty coast 100 km to the north reworking and resedimentation of pyroclastic debris began immediately after the eruption peaking early and then rapidly declining so that most geomorphic adjustments occurred within one or two decades of the initial disturbance

on the importance of measuring thermal conductivities for heat flow density estimates an example from the jeanne d arc basin offshore eastern canada abstract temperature data from petroleum exploration wells can be used to study the thermal regimes of sedimentary basins in this it is common to consider many wells and to multiply the average geothermal gradient measured in each well by the effective thermal conductivity of the rocks across the interval over which the gradient is determined to obtain a heat flow density estimate for the location of each well it is often not possible to measure the thermal conductivities of the rocks present in the basin and the usual approach is to assign thermal conductivity values based on published values to those rocks it is shown that at least in jeanne d arc basin to use assumed thermal conductivity values to calculate heat flow densities at the locations of the 35 wells considered is misleading and results in heat flow density estimates that can be one half those found using thermal conductivities based on values obtained from measurements on rocks from some of the wells in the basin these differences in heat flow densities can lead to differences in the extrapolated temperatures using the two sets of thermal conductivities as high as 264 c at 20 km depth higher temperatures are obtained when the measured thermal conductivity data set is used

analysis of temperatures in sedimentary basins the michigan basin we develop an analytical and numerical methodology for the analysis of large bottom hole temperature bht data sets from sedimentary basins and test the methodology using temperature stratigraphic and lithologic data from 411 boreholes in the michigan basin least squares estimates of temperature gradients in the formations and lithologies present are calculated as solutions to a large system of linear equations at each borehole the temperature difference between the bottom and top of the hole is represented as a sum of temperature increments through the various formations or lithologies penetrated by the borehole quadratic programming techniques enable bounds to be placed on the gradient solutions in order to suppress or exclude improbable gradient estimates numerical experiments with synthetic data reveal that the estimates of temperature gradients for a given formation or lithology are sensitive to the degree of representation of that unit well represented units have more stable gradient estima

electromagnetic radiation induced by mining rock failure abstract anticipating roof fall in mine workings has been a problem for centuries the focus in the search for early warning indicators has been on observing seismic acoustic events prior to the fall these precursors have been studied in great detail at many places but none has been fully successful so far no valid effective early warning system based on low frequency seismic precursors has been established in this paper we investigated a promising new technique which is not yet completely understood or been widely tested in mines the new method is the sensing of the embryonic stages of roof fall by detection of high frequency electromagnetic radiation emr emitted from rock microcracks two examples of combined observations of emr and low frequency acoustic emission prior to roof fall at moonee colliery are presented anomalously high emr was detected more than 1 h before roof fall giving a significant time advantage over the first indicators of low frequency acoustic emission analysis of benioff strain release diagrams of emr emanating from developing medium scale failure in the mine enabled us to fill the gap between previously known microscale rock fracture in lab and macroscale earthquake emr observations and to conclude that indeed a common fundamental relationship must lie behind this multi scale phenomenon

regional stress field as determined from electromagnetic radiation in a tunnel abstract the paper presents the results of electromagnetic radiation emr measurements in the feuerberg tunnel in southwest germany emr is associated with small scale fracturing processes the measured numbers of emr impulses are shown to be proportional to shear stresses from the correlation of emr and shear stresses along the long axis of the tunnel orientations and magnitudes of the horizontal principal stresses are determined the major horizontal principal stress is 3 6 0 3 mpa and has an azimuth of 143 6 the minor principal horizontal stress is 2 1 0 3 mpa zones in the tunnel are located where low shear stresses occur because vertical overburden and horizontal stresses are equal in these zones also minimum radiation was detected a possible stress accumulation close to a fault is suggested by higher emr values in a part of the tunnel orientations and magnitudes of the horizontal principal stresses which are derived from the measurements of emr correlate well with conventional stress measurements it is suggested that the cross section measuring method described in the study is used to determine regional stress fields as well as to investigate endangered zones with high stresses in underground facilities which may be critical with regard to stability

spatial organization of process domains in headwater drainage basins of a glaciated foothills region with complex longitudinal profiles 1 lithologic transitions and glaciations create complex longitudinal profiles that control contemporary erosion and deposition processes in areas with these characteristics traditional morphometric approaches for predicting process domains such as area slope plots can be augmented by considering other predictors measured from high resolution lidar derived digital elevation models dems ordinal logistic regression was used to model the distribution of hillslope swale colluvial channel and fluvial channel domains as identified during field surveys the study area was a glaciated region of the rocky mountain foothills with a complex lithostructural setting relationships between domains and a suite of geographic information system derived descriptors were explored predictors included profile anomalies measured at the reach and basin scale using a normalized stream length gradient sl k index drainage area was the dominant factor controlling domains a model with area as the only predictor was 82 accurate reach slope relations were not consistent a model that also included lithology and basin scale sl k index variation was 87 accurate domain transitions had larger area thresholds in basins with resistant conglomerate versus sandstone or shale formations and where sl k index was more variable along a profile in a restricted model of hillslope swale and colluvial channel domains profile curvature measured over 100 m was also related to domain occurrence a model for regional scale mapping applications with six additional predictors was 95 accurate the results showed that ordinal logistic regression can be used to predict and map process domains in regions with complex physiography using descriptors measured from high resolution dems

geohazards of tunnel excavation in interbedded layers under high in situ stress abstract in situ stress is one of the most important parameters that affect rock mass stability during tunnel excavation high in situ stress may induce a series of geohazards such as rockburst in strong rock and squeezing in weak rock this paper presents a case study of a tunnel excavated using a tunnel boring machine across interbedded strong and weak rock layers under high in situ stress in pakistan to estimate the induced geohazards during tunnel excavation in situ stress was measured and the stability of the tunnel was analyzed using the finite element method in situ stress measured in the strong rock layers shows that the maximum compressive stress is very high and its direction is almost perpendicular to the tunnel axis using a simple analytical method stress distribution in weak layers was determined and the results show that the magnitude of the maximum compressive stress in the weak layers is much less than that in strong layers and the direction is almost parallel with the tunnel axis the fem simulation reveals that the redistributed stress due to the tunnel excavation is more concentrated in strong layers and less concentrated in weak layers both the initial in situ stress distribution and the stress redistribution after tunnel excavation predict geohazard in strong layers rather than in weak layers this point is consistent with the field records which indicated that rockbursts were frequent in the strong rock layers and no squeezing occurred in the weak rock layers

hillslope response to knickpoint migration in the southern appalachians implications for the evolution of post orogenic landscapes the southern appalachians represent a landscape characterized by locally high topographic relief steep slopes and frequent mass movement in the absence of significant tectonic forcing for at least the last 200 ma the fundamental processes responsible for landscape evolution in a post orogenic landscape remain enigmatic the non glaciated cullasaja river basin of south western north carolina with uniform lithology frequent debris flows and the availability of high resolution airborne lidar dems is an ideal natural setting to study landscape evolution in a post orogenic landscape through the lens of hillslope channel coupling this investigation is limited to channels with upslope contributing areas 2 7 km2 a conservative estimate of the transition from fluvial to debris flow dominated channel processes values of normalized hypsometry hypsometric integral and mean slope vs elevation are used for 14 tributary basins and the cullasaja basin as a whole to characterize landscape evolution following upstream knickpoint migration results highlight the existence of a transient spatial relationship between knickpoints present along the fluvial network of the cullasaja basin and adjacent hillslopes metrics of topography relief slope gradient and hillslope activity landslide frequency exhibit significant downstream increases below the current position of major knickpoints the transient effect of knickpoint driven channel incision on basin hillslopes is captured by measuring the relief mean slope steepness and mass movement frequency of tributary basins and comparing these results with the distance from major knickpoints along the cullasaja river a conceptual model of area elevation and slope distributions is presented that may be representative of post orogenic landscape evolution in analogous geologic settings importantly the model explains how knickpoint migration and channel hillslope coupling is an important factor in tectonically inactive i e post orogenic orogens for the maintenance of significant relief steep slopes and weathering limited hillslopes copyright 2011 john wiley sons ltd

dem based identification of fluvial knickzones and its application to japanese mountain rivers stream gradients of mountain bedrock rivers in central japan were examined using gis and 50 m digital elevation models to discuss the distribution of knickzones the gradients are classified into local and trend types based on the measurement lengths the transition rate from the local to trend gradients i e the decreasing rate of gradient with increasing measurement length is then obtained as the indicator of relative steepness of a river segment which permits the objective identification of fluvial knickzones the identified knickzones occur widely in the study area and indicate that the knickzone is one of the common landforms in japanese mountain rivers the knickzones are more abundant in steep upstream reaches of the rivers subjected to active erosion and rapid rock uplift this suggests a hydraulic origin of the knickzones which is similar to step pool morphology but on a much larger scale some knickzones in piedmont areas can be on the other hand consistent with tectonic faulting at the mountain foot although some influences of volcanic activities on the formation of knickzones are observed regional lithology seems to exert a relatively weak influence on the abundance of knickzones knickzones are more consistent with other local mechanisms of fluvial erosion including reach scale processes

disequilibrium profile of the potomac river near washington d c a result of lowered base level or quaternary tectonics along the fall line longitudinal profiles of major rivers in maryland and virginia are generally closely adjusted to the resistance of the rocks over which they flow but they all show major discontinuities at or just above the fall line the amount of discrepancy at the fall line between the actual profiles and the projection of the profiles of the upstream reaches increases from about 27 m at the james river to about 50 m at the susquehanna river at the potomac river it is about 45 m detailed study of the terraces along the potomac in the piedmont above washington d c suggests that the discontinuity in longitudinal profile is the result of quaternary downcutting in response to a lowered base level changes in base level during sea level fluctuations in the pleistocene must have been an important factor but strong circumstantial evidence suggests that the discontinuities in river profiles may in part be due to differential uplift of the piedmont with respect to the coastal plain along a zone of flexure or distributed faulting near the fall line