nonlinear soil response of a borehole station based on one dimensional inversion during the 2005 fukuoka prefecture western offshore earthquake the objective of this article is to present the nonlinear response of a soft sedimentary site based on a one dimensional inversion by a genetic algorithm of the shear wave velocity structure and damping factors of a borehole soil column during the 2005 fukuoka prefecture western offshore earthquake first we confirm that according to the source rupture mechanism the major and minor axes in the horizontal plane at the borehole station are the transverse and radial directions respectively then in order to corroborate in the linear domain the s wave transfer function of the borehole s logging we perform time dependent spectral ratios analyses on small aftershocks finally we show qualitative evidence of nonlinearity during the main shock associated with a significant shift toward low frequencies of several resonant modes and we evaluate the degree of nonlinearity by inverting the shear wave veloc ity structure and damping factors because of a directional effect present only in the major axis around 8 hz which prevents the use of the conventional objective function that minimizes the integrated residuals between observed and theoretical ratios we introduce a simple objective function that depends only on peaks frequency and amplitude the efficiency of the objective function and the robustness of the inversion are shown by performing eight independent inversions converging to very similar minima

transient sediment supply in a high altitude alpine environment evidenced through a 10be budget of the etages catchment french western alps although beryllium 10 10be concentrations in stream sediments provide useful synoptic views of catchment wide erosion rates little is known on the relative contributions of different sediment supply mechanisms to the acquisition of their initial signature in the headwaters here we address this issue by conducting a 10be budget of detrital materials that characterize the morphogenetic domains representative of high altitude environments of the european alps we focus on the etages catchment located in the ecrins pelvoux massif southeast france and illustrate how in situ 10be concentrations can be used for tracing the origin of the sand fraction from the bedload in the trunk stream the landscape of the etages catchment is characterized by a geomorphic transient state high topographic gradients and a large variety of modern geomorphic domains ranging from glacial environments to scarcely vegetated alluvial plains beryllium 10 concentrations measured in the etages catchment vary from similar to 1 x 104 to 4 5 x 105 atoms per gram quartz while displaying consistent 10be signatures within each representative morphogenetic unit we show that the basic requirements for inferring catchment wide denudation from 10be concentration measurements are not satisfied in this small dynamic catchment however the distinct 10be signature observed for the geomorphic domains can be used as a tracer we suggest that a terrestrial cosmogenic nuclide tcn budget approach provides a valuable tool for the tracing of material origin in basins where the let nature do the averaging principles may be violated

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

new 26al 10be and u th he constraints on the age of the upland complex central mississippi river valley abstract the upland complex is a widespread terrace of the ancestral mississippi river it has played a central role in studies of the pliocene mississippi river drainage as well as uplift and seismicity in the central mississippi river valley previous efforts to date the upland complex have yielded a range of age estimates spanning the miocene through pleistocene we dated gravels and fe oxide cements from quarries of the upland complex in arkansas kentucky mississippi and tennessee using 26al 10be burial dating and u th he geochronology our 26al 10be burial dates revealed possible pliocene to pleistocene depositional ages while u th he dating showed that the onset of weathering dates to at least the pliocene taken together the 26al 10be and u th he age constraints demonstrate that the upland complex is at least pliocene in age and likely formed during a prolonged period of base level stability that preceded pleistocene glaciations

active faulting and paleoseismology along the bree fault lower rhine graben belgium paleoseismic analysis of the 10 km long bree fault scarp in the lower rhine graben yields numerous lines of evidence of earthquake activity in the holocene and late pleistocene this active normal fault a part of the feldbiss fault system dips 70 ne and is expressed at the surface by a prominent nw se trending 7 to 20 m high scarp formed since the deposition of the maas river main terrace 700 kyr b p trenches and geophysical prospecting show that the fault which is known to have 100 m of vertical offset since the late pliocene breaks late pleistocene and holocene deposits ground penetrating radar seismic refraction and electric tomography suggest that at shallow depth the amount of displacement is larger than the youngest vertical offset visible in the trenches and corresponds to cumulative fault displacements the analysis of 36 leveling profiles across the scarp indicates that its height can be classified into three groups likely corresponding to different events a morphologic dating gives approximate ages of 2 1 5 kyr b p 14 5 kyr b p and 41 6 kyr b p for the past three surface faulting earthquakes analysis of faulted stratigraphy and earthquake induced deformation structures exposed in trenches suggests the occurrence of three large earthquakes during the past 45 l03 years and yields 0 07 mm yr of relative vertical deformation rate the most recent seismic event occurred between a d 610 and 890 the first identification of an active fault with surface ruptures in the lower rhine graben area emphasizes that large earthquake sources exist within intraplate europe and that at least some of these events are preserved in the geologic record

spatial prediction of permafrost occurrence in sikkim himalayas using logistic regression random forests support vector machines and neural networks abstract we have generated permafrost probability distribution maps 10 m resolution for the north eastern himalayan region in sikkim using remote sensing measurements and machine learning algorithms four machine learning algorithms logistic regression random forests support vector machines and neural networks and two different sets of input data set were used to generate a total of 8 machine learning models and hence 8 permafrost probability distribution maps the first set of input data set included surface reflectance from atmospherically corrected sentinel 2a spectral bands elevation and slope parameters while the second set of input data set included mean annul air temperature maat and potential incoming solar radiation pisr permafrost probability distribution maps obtained from the 8 models show reasonable agreement in the total spatial extent of permafrost occurrence but dissimilarities in the pattern of probability distribution accuracy assessment results are more optimistic towards models developed using spectral reflectance elevation and slope parameters as input data set nevertheless 5 out of 8 models agree that around 60 of total area under observation is highly likely to contain permafrost this congruence in outputs despite the use of different machine learning algorithms and separate sets of input data set establishes reliability in the application of machine learning models for the preliminary estimation of permafrost distribution for remote and data scarce himalayan region

continuous gps and broad scale deformation across the rhine graben and the alps in order to study the ongoing tectonic deformation in the rhine graben area we reconstruct the local crustal velocity and the strain rate field from gps array solutions following the aim of this work we compile the velocities of permanent gps stations belonging to various networks euref agnes regal and rgp in central western europe moreover the strain rate field is displayed in terms of principal axes and values while the normal and the shear components of the strain tensor are calculated perpendicular and parallel to the strike of major faults the results are compared with the fault plane solutions of earthquakes which have occurred in this area a broad scale kinematic deformation model across the rhine graben is provided on the basis of tectonics and velocity results of the gps permanent stations the area of study is divided into four rigid blocks between which there might be relative motions the velocity and the strain rate fields are reconstructed along their borders by estimating a uniform rotation for each block the tectonic behaviour is well represented by the four block model in the rhine graben area while a more detailed model will be needed for a better reconstruction of the strain field in the alpine region

frictionite as evidence for a large late quaternary rockslide near kanchenjunga sikkim himalayas india implications for extreme events in mountain relief destruction abstract we present sedimentologic and petrographic field evidence of an extremely large 2 5 109 m3 late quaternary rockslide around dzongri 24 km s of kanchenjunga 8585 m a s l widespread occurrence of shattered leucogranites and migmatites deposited discordantly on top of undisturbed augen gneisses and separated by micro brecciated sliding surfaces indicate rapid movement during a large rockslide event occurrence of frictionite hyalomylonite in mineral samples indicates short term temperatures of 600 c in the moving rockslide mass along a 12 sliding plane from a sw direction of movement we infer a source 8 km ne of the deposit 5 km s of pandim 6691 m a s l where today a thick leucogranite intrusion marks a zone of weakness and failure of a postulated former mountain crest the mechanism of movement the dip of the sliding surface and the deposit preservation along ridge tops require that the dzongri rockslide ran out over an ice filled prek chu valley hence we prefer earthquake shaking over undercutting and glacial debuttressing as a possible trigger mechanism a regional review of other similarly large and catastrophic himalayan rockslides indicates that leucogranite intrusions are highly conducive to large scale failure in the higher himalayan crystalline hhc importantly high erosion rates have rendered this large rockslide deposit undetectable by remote sensing or digital elevation data which are commonly used for identifying evidence of such extreme events quantifying the contribution of such giant landslides in destroying some of the highest relief on earth will thus need further research attention

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

a regional inventory of rock glaciers and protalus ramparts in the central italian alps abstract we present a regional inventory of rock glaciers n 1514 and protalus ramparts 228 for the lombardy region central italian alps to identify and classify the landforms we inspect three sequential air orthophoto mosaics and a 2 m dsm and conduct confirmatory field work the inventory forms an empirical basis to analyze i the relative contribution of hillslope i e talus slopes and glacial i e moraines sediment stores to rock glacier sediment supply ii linkages between the landforms inventoried and local topographic attributes iii the spatial variability of periglacial activity in relation to a parsimonious set of environmental variables i e elevation precipitation and lithology and iv the effects of the pleistocene holocene climatic transition on the distribution of intact and relict landforms this analysis reveals that the elevation of rock glacier termini can vary over 200 m as a function of slope aspect in turn the distribution of rock glaciers among aspect categories is controlled by the structure of the valley network that promotes nw and se exposures talus rock glaciers prevail numerically over the glacier related typology even though the latter population appears to have increased during the holocene relict and intact rock glaciers have distinct spatial patterns in that the former display on average a 400 m elevation drop and a less clustered distribution towards northern aspects suggesting that they have developed in more permafrost prone climatic conditions analyzing the study region through a 27 5 km grid has been instrumental for showing that the rock glacier specific area and terminus elevation are i positively correlated with terrain elevation and ii negatively correlated with mean annual precipitation as a consequence in relation to holocene generalized atmospheric temperature rise intact rock glaciers have progressively disappeared from the wetter and milder portions of the central italian alps analysis of rock glacier occurrence across litho tectonic sectors does not provide conclusive dependences and requires further analysis this inventory which represents a necessary preliminary step for modelling the spatial distribution of discontinuous permafrost at the regional scale fills a critical geographic gap in the context of ongoing permafrost research in the european alps e g permanet

the erosion response to quaternary climate change quantified using uranium isotopes and in situ produced cosmogenic nuclides abstract studying how catchment erosion has responded to past climate change can help us better understand not only how landscape evolution operates but also predict the consequences of future climate change on soil resource availability recent years have seen the development of tools that allow a quantitative assessment of past changes in catchment erosion this work reviews the principles of the application of in situ produced cosmogenic nuclides and uranium isotopes to quantifying past erosion rates results highlight the role of periglacial processes and mass wasting in dictating how catchment erosion responds to climatic variability at the 10 kyr scale at the million year scale it is more difficult to untangle the role of climate and tectonics a strong coupling exists at the 10 kyr to 100 kyr scales between climatic cycles and the transfer time of regolith from source to sink this coupling reflects changes in sediment source that are either set by changes in vegetation cover at the catchment scale or by the storage of sediments on continental shelves at a larger scale although further analytical developments are required for these tools to reach their full potential existing works suggest that in the near future they will provide unprecedented quantitative insights on how soil and fluvial systems adapt to external perturbations climatic tectonic and or anthropic

time integrated 3d approach of late quaternary sediment depocenter migration in the tagus depositional system from river valley to abyssal plain quantification of sediment volumes in continental to deep ocean basins is key to understanding processes of sediment distribution in source to sink depositional systems using our own and published data we present the first quantification of sediment volume changes in basins along the course of a major southwest european river during the deglaciation the salient points of this quantitative record in the tagus and equivalent north atlantic basins show crucial roles for sea level climate and land use in the distribution of sediments the bypass of sediments starved the tagus basins and subsequently sedimentation mainly occurred on the tagus abyssal plain during the sea level lowstand of the last glacial maximum the main sediment depocenter rapidly shifted via the continental shelf to the lower tagus valley during sea level rise in the deglaciation period finally the main sediment depocenter shifted further landward into the lower tagus valley during sea level high stand in the holocene during the high stand phase last 7 ky sediment flux increased up to 2 5 times due to climate and land use changes the average catchment denudation rate during the last 12 ky 0 04 0 1 mm y is in agreement with those of other european catchments our study clearly demonstrates the added value of detailed knowledge of 3d depocenter distribution size and chronology this allowed us to identify an increased sediment flux during the last 7 ky which was not identified using local observations from boreholes alone the uniqueness of the tagus depositional system lies in the combination of a large accommodation space in the bedrock confined lower tagus valley the steep lowstand surface gradient and the narrow continental shelf with canyons indenting the shelf break

a stochastic method for investigating site effects by means of a borehole array sh and love waves abstract a stochastic method for investigating site effects by means of borehole array observation is proposed this method is based on a stochastic time series model that is derived from haskell9s matrix procedure for a layered medium and is applicable to transverse component recordings simultaneously obtained on the ground surface and at a depth the time series model not only accounts for the amplitude but also for the phase characteristics of the recordings by applying this method to actual downhole array recordings the following aspects of site effects can be investigated 1 an estimation of the wave transfer function for sh waves 2 the separation of upcoming and downgoing waves on a borehole seismogram at a depth that is an estimation of purely incident waves and 3 the enhancement of fundamental mode love waves on a surface seismogram are examined by applying this method to two borehole array recordings obtained at the fuchu observatory in japan a noteworthy point is that these aspects of site effects are examined using this method without any knowledge of the velocity structure beneath the site

higher erosion rates in the himalaya geochemical constraints on riverine fluxes the modern erosion rate of continental scale mountains is difficult to estimate and is usually based on measurement of the suspended load flux of rivers combined with assumptions about river bedload transport and sedimentation in flood plains these two parameters are very difficult to measure directly in continental scale basins in this paper we examine the chemical composition of the suspended load bedload and dissolved load of the ganga and brahmaputra rivers and compare them with the average composition of himalayan source rocks a mass balance equation of erosion fluxes shows that a si rich component is needed in addition to suspended and dissolved load fluxes to account for the composition of the source rock it corresponds to bedload sediment and flood plain deposits which are enriched in quartz by mineral sorting during transport the combined budget of si al and fe in the river system allows us to estimate this si rich flux by this method the total himalayan erosion is estimated to be twice the measured flux of suspended load the comparison between the brahmaputra and the ganga shows that the eastern himalaya has a higher erosion rate 2 9 mm yr than the western himalaya 2 1 mm yr this is likely the result of the higher runoff in the brahmaputra basin the intensity of the monsoon acts as a first order control of the erosion rate in the range

10be constrains the sediment sources and sediment yields to the great barrier reef from the tropical barron river catchment queensland australia abstract estimates of long term background sediment generation rates place current and future sediment fluxes to the great barrier reef in context without reliable estimates of sediment generation rates and without identification of the sources of sediment delivered to the reef prior to european settlement c 1850 determining the necessity and effectiveness of contemporary landscape management efforts is difficult here using the 2100 km 2 barron river catchment in queensland australia as a test case we use in situ produced 10 be to derive sediment generation rate estimates and use in situ and meteoric 10 be to identify the source of that sediment which enters the coral sea near cairns previous model based calculations suggested that background sediment yields were up to an order of magnitude lower than contemporary sediment yields in contrast in situ 10 be data indicate that background 43 t km 2 y 1 and contemporary sediment yields 45 t km 2 y 1 for the barron river are similar these data suggest that the reef became established in a sediment flux similar to what it receives today since western agricultural practices increased erosion rates large amounts of sediment mobilized from hillslopes during the last century are probably stored in queensland catchments and will eventually be transported to the coast most likely in flows triggered by rare but powerful tropical cyclones that were more common before european settlement and may increase in strength as climate change warms the south pacific ocean in situ and meteoric 10 be concentrations of coral sea beach sand near cairns are similar to those in rivers on the atherton tablelands suggesting that most sediment is derived from the extensive low gradient uplands rather than the steep more rapidly eroding but beach proximal escarpment

tilt motions recorded at two wise sites for the 2003 tokachi oki earthquake m 8 3 abstract broadband velocity seismographs installed at the ohtsu water level observatory and monsizu stations of the warning information system of earthquake wise network recorded long period pulses produced by tilt motions resulting from the 2003 tokachi oki earthquake m 8 3 of 25 september 2003 the long period pulse signal is represented using a low pass filtered expansion composed of intrinsic mode functions by eliminating the leading phases such as a direct p phase that appears before the onset of tilt motion from the expansion the transient signal produced by the tilt motion is approximately obtained a reverse filter which is defined by the inverse of the frequency characteristics of the broadband velocity seismometer for the acceleration input is applied to the transient signal to estimate the tilt motion the estimated permanent acceleration of tilt motion at the two sites ranges from 0 6 to 6 5 cm sec 2 the river embankment adjacent to the ohtsu water level observatory site collapsed due to liquefaction at the bottom of the embankment the monsizu site was constructed at a depth of 2 m in soft soil floodplain deposits these two broadband velocity seismograms involving the tilt motion reveal that the tilt motion is mainly generated under the influence of the collapsed soil structure or of the deformation of the soil deposits these observations indicate that the broadband velocity seismograph is more sensitive to tilt motion than acceleration type strong motion seismographs

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

estimates of the rate of regolith production using and from an alpine hillslope abstract the production of regolith is a fundamental geomorphic process because most surface processes transport only unconsolidated material we use concentrations of the cosmogenic radionuclides crns 10 be and 26 al in regolith and bedrock to deduce the rate of production of regolith on an alpine hillslope in the wind river range wy these calculations are based on a theoretical model which we develop here this model shows that it is important to consider dissolution of regolith in regolith production and in basin averaged erosion rate studies rates of production of regolith are uniform along the hillslope and the mean rates for the entire hillslope deduced from 10 be and 26 al are 14 3 4 0 and 13 0 4 0 m ma 1 respectively rates of production of regolith deduced from 10 be concentrations in regolith mantled bedrock support the rates deduced from regolith concentrations in the alpine environment examined here the rate of production of regolith beneath 90 cm of regolith is nearly twice as fast as the average rate of production of regolith on bare rock surfaces which small et al small e e anderson r s repka j l finkel r 1997 erosion rates of alpine bedrock summit surfaces deduced from in situ 10 be and 26 al earth and planetary science letters 150 413 425 previously documented rock mantled with regolith probably weathers more rapidly than bare rock because the water required for frost weathering is limited on bare rock surfaces because the hillslope examined here is convex with constant curvature and regolith production and thickness are uniform down the slope the regolith volume flux must be proportional to the local slope of the hillside therefore our results are consistent with gilbert s gilbert g k 1909 the convexity of hilltops journal of geology 17 344 350 steady state hillslope hypothesis if tor height and the difference between rates of weathering on bare and regolith mantled rock provide a fair estimate of the age of summit flats steady state hillslope conditions have been attained in less than several million years

role of in situ cosmogenic nuclides 10be and 26al in the study of diverse geomorphic processes the central premises of applications of the in situ cosmogenic dating method for studying specific problems in geomorphology are outlined for simple and complex exposure settings in the light of these general models we discuss the information that can be derived about geomorphic processes utilizing concentrations of in situ produced cosmogenic radionuclides 10be half life 1 5 ma and 26a1 half life 0 7 ma in a variety of geomorphic contexts glacial polish and tills meteorite impact craters alluvial fans paleo beach ridges marine terraces sand dunes and bedrock slopes we also compare 10be 26al data with results obtained by other dating methods we conclude that the technique of measuring in situ cosmic ray produced nuclides holds promise for quantitative studies of processes and time scales in a wide range of geomorphological problems

time scales of tectonic landscapes and their sediment routing systems abstract in regions undergoing active tectonics the coupling between the tectonic displacement field the overlying landscape and the redistribution of mass at the earth9s surface in the form of sediment routing systems is particularly marked and variable coupling between deformation and surface processes takes place at a range of scales from the whole orogen to individual extensional fault blocks or contractional anticlines at the large scale the attainment of a steady state between the overlying topography and the prevailing tectonic conditions in active contractional orogens requires an efficient erosional system with a time scale dependent on the vigour of the erosional system generally in the range 10 6 10 7 years the catchment fan systems associated with extensional fault blocks and basins of the western usa are valuable natural examples to study the coupling between tectonic deformation landscape and sediment routing systems even relatively simple coupled systems such as an extensional fault block and its associated basin margin fans have a range of time scales in response to a tectonic perturbation these response times originate from the development of uniform steady state relief during the accumulation of displacement on a normal fault c 10 6 years the upstream propagation of a bedrock knickpoint in transverse catchments following a change in tectonic uplift rate c 10 6 years or the relaxation times of the integrated catchment fan system in response to changes in climatic and tectonic boundary conditions 10 5 10 6 years the presence of extensive bedrock or alluvial piedmonts increases response times significantly the sediment efflux of a mountain catchment is a boundary condition for far field fluvial transport but the fluvial system is much more than a simple transmitter of the sediment supply signal to a neighbouring depocentre fluvial systems appear to act as buffers to incoming sediment supply signals with a diffusive time scale c 10 5 10 6 years dependent on the length of the system and the extent of its floodplains stream channels and proximal gravel fans the vocabulary for explaining landscapes would benefit from a greater recognition of the importance of the repeat time and magnitude of perturbations in relation to the response and relaxation times of the landscape and its sediment routing systems landscapes are best differentiated as buffered or reactive depending on the ratio of the response time to the repeat time of the perturbation furthermore landscapes may be regarded as steady or transient depending on the ratio of the response time to the time elapsed since the most recent change in boundary conditions the response of tectonically and climatically perturbed landscapes has profound implications for the interpretation of stratigraphic architecture

10be and 26al production rates deduced from an instantaneous event within the dendro calibration curve the landslide of kofels otz valley austria surface exposure dating requires the knowledge of cosmogenic nuclide production rates when determining time integrated production rates the exposure ages of the calibration samples need to be accurately known the landslide of kofels austria is very well suited for this purpose it is the largest landslide in the crystalline alps of austria dating back to 7800 100 years bc ams 14c dating of buried wood which is well within the 14c dendro calibration curve exposed quartz veins were sampled from the tops of large boulders from the toe of the landslide for analysis of 10be and 26al to calculate sea level high geomagnetic latitude 60 open sky radionuclide production rates corrections were applied for altitude and latitude for shielding by surrounding mountains for sample geometry vegetation and snow cover and for sample thickness the production rates for an exposure age of 10 000 years are 5 75 0 24 10be atoms yr g sio2 and 37 4 1 9 26al atoms yr g sio2 a 26al 10be ratio of 6 52 0 43 can be calculated the influence of the geomagnetic field on these production rates has been estimated using two different geomagnetic field records our production rates should be a good approximation for the use of surface exposure dating between about 5000 and 13 000 years bp

contemporary versus long term denudation along a passive plate margin the role of extreme events short term contemporary and long term denudation rates were determined for the blue mountains plateau in the western sydney basin australia to explore the role of extreme events wildfires and catastrophic floods in landscape denudation along a passive plate margin contemporary denudation rates were reconstructed using 40 years of river sediment load data from the nattai catchment in the south west of the basin combined with an analysis of hillslope erosion following recent wildfires long term denudation rates 10 kyr 10 myr were determined from terrestrial cosmogenic nuclides apatite fission track thermochronology and post basalt flow valley incision contemporary denudation rates average several times lower than the long term average 5 5 4 mm kyr 1 versus 21 5 7 mm kyr 1 erosion of sediment following wildfires accounts for only a small proportion 5 of the contemporary rate most post fire sediment is stored on the lower slopes and valley floor with the amount transported to the river network dependent on rainfall run off conditions within the first few years following the fire historical catastrophic floods account for a much larger proportion 35 of the contemporary erosion rate and highlight the importance of these events in reworking stored material evidence for palaeofloods much larger than those experienced over the past 200 years suggests even greater sediment export potential mass movement on hillslopes along valleys incised into softer lithology appears to be a dominant erosion process that supplies substantial volumes of material to the valley floor it is possible that a combination of infrequent mass movement events and high fluvial discharge could account for a significant proportion of the discrepancy between the contemporary and long term denudation rates copyright 2006 john wiley sons ltd

continental erosion and large scale relief a worldwide investigation of continental erosion is carried out by the study of large drainage basins on the basis of hydrological data environmental factors and basin relief distribution inside each basin mean geochemical and mechanical denudation rates are defined a multicorrelation analysis shows that the mechanical denudation rates ds are uncorrelated with environmental factors and correlated with mean basin elevation h while chemical denudation rates dd are insensitive to relief but correlated with mean annual precipitation furthermore two linear relationships between h and ds are detected 1 ds m 10 yr 419 10 6 h m 0 245 with v explained variance 95 1 this law concerns basins related to orogenies younger than 250 ma the negative intercept is interpreted as a continental sedimentation rate of 245 m m y an alternative model in which one invokes a critical elevation separating erosion from sedimentation is equally successful and leads to lower sedimentation rates 60 110 m m y for both models one derives from the slope of the adjustments erosion time constants on the order of 2 5 m y 2 ds m 10 yr 61 10 6 h m with v 86 5 this law concerns basins related to older orogenies the null intercept suggests the lack of continental storage because of the more important dispersion of the data the erosion time constant is calculated separately for each basin it ranges from 15 to 360 m y the tectonic implications of these results are discussed in particular the short time constant 2 5 m y agrees with orogenic uplift rates on the order of 1 mm yr observed in active mountain chains

complex exposure histories of chert clasts in the late pleistocene shorelines of lake lisan southern israel activities of 26 al and 10 be in five chert clasts sampled from two beach ridges of late pleistocene lake lisan precursor of the dead sea in southern israel indicate low rates of chert bedrock erosion and complex exposure burial and by inference transport histories the chert clasts were derived from the senonian mishash formation a chert bearing chalk which is widely exposed in the nahal zin drainage basin the drainage system that supplied most of the material to the beach ridges simple exposure ages assuming only exposure at the beach ridge sampling sites range from 35 to 354 ky using the ratio 26 al 10 be total clast histories range from 0 46 to 4 3 my unrelated to the clasts current position and exposure period on the late pleistocene beach ridges 160 177 m below sea level optically stimulated luminescence dating of fine sediments from the same and nearby beach ridges yielded ages of 20 0 s 1 4 ka and 36 1 s 3 3 ka these ages are supported by the degree of soil development on the beach ridges and correspond well with previously determined ages of lake lisan which suggest that the lake reached its highest stand around 27 000 cal years bp if the clasts were exposed only once and than buried beyond the range of significant cosmogenic nuclide production then the minimum initial exposure and the total burial times before delivery to the beach ridge are in the ranges 50 1300 ky and 390 3130 ky respectively alternatively the initial cosmogenic dosing could have occurred during steady erosion of the source bedrock back calculating such rates of rock erosion suggests values between 0 4 and 12 m my 1 t he relatively long burial periods indicate extended sediment storage as colluvium on slopes and or as alluvial deposits in river terraces some clasts may have been stored for long periods in abandoned pliocene and early pleistocene routes of nahal zin to the mediterranean before being transported again back into the nahal zin drainage system and washed on to the shores of lake lisan during the late pleistocene copyright 2003 john wiley sons ltd

long term evolution of denudational escarpments in southeastern brazil article i nfo topographic relief in southeastern brazil consists of a sequence of stepped surfaces that formed after the frag mentation of gondwana during the cretaceous tertiary and quaternary tectonic pulses this region is drained by four major rivers within four major river basins with interfluves that contain denudational escarpments fault escarpments and mountain ranges this study presents an analysis of the long term evolution of two denudational escarpments the cristiano otoni and the sao geraldo steps which divide the river basins of the sao francisco doce and paraiba do sul rivers in southeastern brazil denudation rates were obtained through the measurement of mean concentrations of in situ produced cosmogenic 10

the probable importance of snow and sediment shielding on cosmogenic ages of north central colorado pinedale and pre pinedale moraines abstract eight uncorrected 36 cl ages for pinedale boulders in north central colorado fall in the range 16 5 to 20 9 kyr 10 be age determinations on four of five boulders are in close agreement 6 difference with 36 cl determinations hypothetical corrections for snow shielding increased the 36 cl ages of pinedale boulder surfaces by an average of 12 most ages for pre pinedale bull lake boulders fall within marine isotope stage mis 5 a time when continental and sierran ice accumulations were small or nonexistent under the assumption that these boulders were deposited on moraines that formed before the end of mis 6 140 kyr bp calculations indicated that rock surface erosion rates would have had to range from 5 9 to 10 7 mm kyr 1 to produce the observed 36 cl values when compared to rates that have been documented for the past 20 kyr these erosion rates are extremely high snow shielding accounts for 0 48 of the additional years needed to shift pre pinedale dates to mis 6 this suggests that some combination of snow shielding sediment shielding or 36 cl leakage has greatly decreased the apparent ages of most pre pinedale boulders inability to account for the effects of these processes seriously hinders the use of cosmogenic ages of pre pinedale boulders as estimators of the timing of alpine glaciation

amount and controls of the quaternary denudation in the ardennes massif western europe it is still debated whether the primary control on the middle pleistocene denudation of the uplifted ardennes massif western europe is tectonic or climatic here based on geomorphological observations we calculate the amount of river incision and interfluve denudation in the meuse basin upstream of maastricht since 0 7 ma and we show that the main response to tectonic forcing was incision this allows us to provide first order estimates of the tectonic and climatic contributions to the denudation of the ardennes from a dataset of 71 remnants of a terrace level dated 0 7 ma we first derive a basin scale functional relationship linking incision with distances to the regional base level lc and to the source ls in the ourthe basin pertaining to the ardennian part of the meuse basin expressed as i i0 1 a lcb lsc i0 being the incision measured at the basin outlet this relationship calculates that river incision has removed 84 km3 of rock in the meuse basin upstream of maastricht since 0 7 ma in the same time 292 km3 were eroded from the interfluves a comparison of these volumes shows that the tectonically forced river incision accounts for 22 of the total post 0 7 ma denudation furthermore the mean denudation rate corresponding to our geomorphological estimate of the overall denudation in the meuse basin since 0 7 ma amounts to 27 mm ky a figure significantly lower than the 40 mm ky mean rate derived from 10be studies of terrace deposits of the meuse schaller et al 2004 this suggests that taken as a basin average the 10be derived rate is overestimated probably due to an overrepresentation of the erosion products of the rapidly incising valleys in the alluvial deposits copyright 2009 john wiley sons ltd

holocene floodplain sediment storage and hillslope erosion within the rhine catchment the response of fluvial systems to land use and climate change varies depending on catchment size while forcing response mechanisms of small catchments are reasonably well understood the response of larger drainage basins is less clear in particular the impact of land use and climate change on the rhine system is poorly understood because of the catchment size 185 000 km 2 and the long history of human cultivation which started approximately 7500 years ago a sediment budget is calculated to specify the amount of alluvial sediment that was deposited during the holocene and to estimate long term soil erosion rates the results suggest that 599 14 10 9 t of holocene alluvial sediment is stored in the non alpine part of the rhine catchment south and central germany eastern france the netherlands about 50 of holocene alluvial sediment is deposited along the trunk valley and the delta upper rhine lower rhine coastal plain while the rest is stored along the tributary valleys the floodplain sediment storage corresponds to a mean erosion rate of 0 559 0 16 t ha per yr 38 59 10 7 mm kyr across the rhine catchment outside the alps this holocene averaged estimate amounts for sediments that were delivered to the channel network and is at the lower limit of erosion rates from other studies of different methodology

an active rock glacier wavbal pass jammu and kashmir himalaya india a currently active rock glacier with a snout elevation of 4055 m was observed in the j ammu and kashmir himalaya its formation is ascribed to stagnation of the terminal area of a true glacier resume un glacier rocheux actif wavbal pass jammu et kashmir himalaya inde on a observe dans le jammu et kashmir himalaya un glacier rocheux en activite avec une altitude de la langue de 4055 m sa formation est attribuee a la stagnation de la zone terminale d un vrai glacier zusammenfassung ein aktiver blockgletscher am wavbal pass jammuund kashmir himalaya i ndien ein derzeit aktiver blockgletscher dessen zunge auf 4055 m meeresh6he liegt wurde im jammuund kashmir himalaya beobachtet seine entstehung wird der stagnation des zungengebietes eines echten gletschers zugeschrieben d uring our recent glaciologicaljglacial geologic studies national science foundation grant atm792 i 1288 in the j am mu and kashmir himalaya we noted what might be the lowest level active rock glacier fig i in this part of the himalaya the rock glacier is located at lat 34 07 30 n long 75 30 00 e and is a long one of the first major slope rises on the south western edge of the greater himalaya it faces north east has a snout elevation of approximately 4390 m and is approximately i km long evidence of its currently active state is indicated by its surface micro relief a terminus th at fig 1 wavbal pass rock glacier jammu and kashmir himalaya view looking south west

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

recent height changes in the central segment of the rhinegraben and its adjacent shoulders abstract zippelt k and malzer h 1981 recent height changes in the central segment of the rhinegraben and its adjacent shoulders in j h illies editor mechanism of graben formation tectonophysics 73 119 123 the height changes in the central segment of the rhinegraben its shoulders included are computed from first order levelling data the network for investigation with regard to recent vertical crustal movements extends the graben segment between karlsruhe and worms and overlaps the shoulders of the pfalzer wald in the west and the kraichgau in the east the investigated area is characterized by negative height changes subsidence in its eastern shoulder and by positive values uplift in its western one in the graben positive height changes were found in its western part but in the eastern part negative values dominate over thick unconsolidated pleistocene sediments tectonically controlled ground motions cannot be separated from atectonic processes like subsidence as caused by changing groundwater levels

rockglacier activity studies on a regional scale comparison of geomorphological mapping and photogrammetric monitoring in their spatial distribution as well as in their different states of activity rockglaciers imply important information on former and recent permafrost conditions two different methods were applied in one study area turtmann valley swiss alps in order to compare their suitability in assessing rockglacier activity the comparison of geomorphological mapping and photogrammetric monitoring demonstrated a good accordance especially on a regional scale on a local scale some differences in delimitation of the landforms as well as in the degree of activity were found one reason for the observed differences is the qualitative character of geomorphological mapping resulting from the variable suitability of single parameters and combinations thereof in the determination of rockglacier activity based on these results geomorphological mapping of rockglaciers can be improved by data from photogrammetric monitoring therefore at best the two methods are combined when analysing former and present permafrost distribution copyright 2007 john wiley sons ltd

mountain permafrost development and challenges of a young research field an overview is given of the relatively short history important issues and primary challenges of research on permafrost in cold mountain regions the systematic application of diverse approaches and technologies contributes to a rapidly growing knowledge base about the existence characteristics and evolution in time of perennially frozen ground at high altitudes and on steep slopes these approaches and technologies include 1 drilling borehole measurement geophysical sounding photogrammetry laser altimetry gps sar surveying and miniature temperature data logging in remote areas that are often difficult to access 2 laboratory investigations e g rheology and stability of ice rock mixtures 3 analyses of digital terrain information 4 numerical simulations e g subsurface thermal conditions under complex topography and 5 spatial models e g distribution of permafrost where surface and microclimatic conditions are highly variable spatially a sound knowledge base and improved understanding of governing processes are urgently needed to deal effectively with the consequences of climate change on the evolution of mountain landscapes and especially of steep mountain slope hazards as the stabilizing permafrost warms and degrades interactions between glaciers and permafrost in cold mountain regions have so far received comparatively little attention and need more systematic investigation

hysteretic and dilatant behavior of cohesionless soils and their effects on nonlinear site response field data observations and modeling in this study we present evidence that nonlinearity can be directly observed in acceleration time histories such as those recorded at the wildlife refuge and kushiro port downhole arrays from the 1987 superstition hills california and the 1993 kushiro oki japan earthquakes respectively these accelerograms and others compiled in this study present a characteristic waveform composed of intermittent high frequency peaks riding on a low frequency carrier in addition soil amplification of the surface records is strongly observed compared to their downhole counterpart this is contrary to the expected amplification reduction produced by the nonlinear soil behavior laboratory studies show that the physical mechanism that produces such phenomena is the dilatant nature of cohesionless soils which introduces the partial recovery of the shear strength under cyclic loads this recovery translates into the ability to produce large deformations followed by large and spiky shear stresses the spikes observed in the acceleration records are directly related to these periods of dilatancy and generation of pore pressure these results are significant in strong motion seismology because these spikes produce large if not the largest acceleration they are site related not source related using the in situ observations from the kushiro port downhole array we have modeled the 1993 kushiro oki earthquake the synthetic accelerograms show the development of intermittent behavior high frequency peaks as observed in the recorded acceleration time histories shear modulus degradation due to pore pressure produces large strains in the soil with large amplification in the low frequency band of the ground motion we also modeled data from the 1987 superstition hills earthquake recorded at the wildlife refuge station the results show the importance of better soil characterization when pore pressure may develop and the effects of dilatancy in the understanding of nonlinear site response

trampoline effect in extreme ground motion in earthquake hazard assessment studies the focus is usually on horizontal ground motion however records from the 14 june 2008 iwate miyagi earthquake in japan a crustal event with a moment magnitude of 6 9 revealed an unprecedented vertical surface acceleration of nearly four times gravity more than twice its horizontal counterpart the vertical acceleration was distinctly asymmetric the waveform envelope was about 1 6 times as large in the upward direction as in the downward direction which is not explained by existing models of the soil response we present a simple model of a mass bouncing on a trampoline to account for this asymmetry and the large vertical amplitude the finding of a hitherto unknown mode of strong ground motion may prompt major progress in near source shaking assessments

erosional equilibrium and disequilibrium in the sierra nevada inferred from cosmogenic 26al and 10be in alluvial sediment we used cosmogenic 26 al and 10 be in stream sediment to measure landscape scale erosion rates for topographically diverse catchments at seven sierra nevada sites at three sites erosion rates and hillslope gradients are strongly correlated increasing with proximity to fault scarps and river canyons which appear to have accelerated local base level lowering rates and thus increased catchment erosion rates by up to 15 fold at four other sites far from fault scarps and river canyons erosion rates are much more uniform and less sensitive to average hillslope gradient our measurements show that contrasts in landscape erosion rates cannot be inferred from hillslope gradients alone because landscapes can evolve toward a state of erosional equilibrium in which steep and gentle slopes erode at similar rates

changes in chemical and 87sr 86sr signature distribution patterns of suspended matter and bed sediments in the upper loire river basin france abstract the mineralogy of the suspended particulate matter spm transported by the upper loire river consists mainly of quartz and k feldspar during periods of high river flow with an increase in calcite concentration during periods of low flow concurrently large fluctuations are observed in the levels of cao and fe2o3 the main oxides present in the spm along with sio2 the analysed trace elements also fluctuate significantly the bed sediments bs have a similar oxide content to the spm but lower zn and pb levels and higher zr levels fluctuations in the chemical element concentrations with river discharge are related to fluctuation in the mineral assemblages present in the spm thus k ti and rb levels increase with increasing in k feldspar abundance during high flow and ca and sr levels decrease with increasing discharge due to a decrease in calcite abundance these mineralogical and chemical variations relate to different sources of sediments under different flow conditions sources that can be distinguished by sr isotopic study the sr isotopic composition fluctuates according to the rate of river discharge i e the 87 sr 86 sr ratio increases with increasing discharge and reaches a maximum with peak flow and vice versa the 87 sr 86 sr ratio also increases with the combined increase in k feldspar abundance and decrease in calcite abundance these similarities suggest the existence of at least two particulate matter reservoirs one with detrital silicates and the other with carbonates finally the relationship between the 87 sr 86 sr ratios in the suspended and dissolved loads suggests the coexistence of authigenic calcite in the carbonate reservoir the spm flow is related to a specific mechanical erosion rate over the whole loire watershed ranging from 9 to 23 t km 2 yr 1 during the survey at orleans the spm flow of the loire river was 37 104 t yr 1 providing an estimate of the specific erosion rate of around 9 8 t km 2 yr 1 from the shift in the spm flux between the sampling point and the mouth of the loire river and the divergence in the mean annual discharge a calculation was made of the input of solid matter by the tributaries and by supplementary erosion processes along the river

the geomorphic significance of rock glaciers estimates of rock glacier debris volumes and headwall recession rates in west greenland to obtain knowledge on rockwall retreat rates at sites with rock glaciers an inventory of about 400 individual rock glacier sites in west greenland was carried out by means of field studies and using aerial photographs and topographic maps a number of sites with ice cored moraines beyond normal glaciers were included in the analysis for comparative purposes the estimated debris volume was compared with the size of the source headwall the result of the inventory suggests that the presence of rock glaciers indicates extraordinary high retreat rates for rock free faces above especially headwalls above glacier derived rock glaciers are exposed to high weathering rates and thereby presumably delimit critical ranges regarding altitude for headwall retreat rates the relation of such a critical altitudinal range to other regional concepts such as glaciation level gl and glacier equilibrium line is discussed from this comments are also made on the relation between various permafrost zones and the typical regional climate within the maximum headwall weathering altitude at sites with active rock glaciers finally the potential importance of this range of maximum weathering for understanding the long term evolution of high relief cold climate landscapes is emphasised

squeezing river catchments through tectonics shortening and erosion across the indus valley nw himalaya tectonic displacement of drainage divides and the consequent deformation of river networks during crustal shortening have been proposed for a number of mountain ranges but never tested in order to preserve crustal strain in surface topography surface displacements across thrust faults must be retained without being recovered by consequent erosion quantification of these competing processes and the implications for catchment topography have not previously been demonstrated here we use structural mapping combined with dating of terrace sediments to measure quaternary shortening across the indus river valley in ladakh nw himalaya we demonstrate 0 21 m k y 1 of horizontal displacement since ca 45 ka on the stok thrust in ladakh which defines the southwestern margin of the indus valley catchment and is the major back thrust to the tethyan himalaya in this region we use normalized river channel gradients of the tributaries that drain into the indus river to show that the lateral continuation of the stok thrust was active for at least 70 km along strike shortening rates combined with fault geometries yield vertical displacement rates that are compared to time equivalent erosion rates in the hanging wall derived from published detrital 10be analyses the results demonstrate that vertical displacement rates across the stok thrust were approximately twice that of the time equivalent erosion rates implying a net horizontal displacement of the surface topography and hence narrowing of the indus valley at 0 1 m k y 1 a fill terrace records debris flow emplacement linked to thrust activity resulting in damming of the valley and extensive lake development conglomerates beneath some of the modern alluvial fans indicate a northeastward shift of the indus river channel since ca 45 ka to its present course against the opposite side of the valley from the stok thrust the integration of structural topographic erosional and sedimentological data provides the first demonstration of the tectonic convergence of drainage divides in a mountain range and yields a model of the surface processes involved

active transverse features in the central portion of the himalaya abstract many transverse lineaments or faults across the himalaya are already known interpretation of satellite images of the central portion of the himalaya given here adds to that number and suggests their continuity from the himalaya to its foredeep several such faults appear to be seismically active their shear motion recognized from geologic data and focal mechanism solutions compares well with a classical stress model when applied to northward progress of india under the himalayan collision front

fluvial geochemistry of the eastern slope of the northeastern andes and its foredeep in the drainage of the orinoco in colombia and venezuela abstract the fluvial geochemistry of the tributaries of the orinoco draining the eastern branch of the northern andes in colombia and venezuela is determined by lithology and ranges from rivers dominated by aluminosilicate weathering mainly of shales and mafic rocks to those bearing the signatures of dissolution of marine limestones and evaporites and of continental playa deposits these left bank tributaries of the orinoco provide the overwhelming proportion of the suspended and dissolved loads transported by the main stem although feeding only half the discharge however due to the extreme severity of weathering on the guayana shield the right bank tributaries supply about half the silica and 40 of the k carried by the orinoco there is a similar partitioning between the andes and the lowlands in the amazon drainage in contrast the mackenzie which drains the northern extremity of the continental arc of the western americas is completely dominated by the weathering of limestones and evaporites and transports very little silica this again appears to be a reflection of lithology since the yukon in similar latitudes and terrain has silica concentrations comparable to the tropical systems in addition a conservative deconvolution of the data gives estimates of the net consumption of atmospheric co 2 by aluminosilicate weathering that follows the same pattern thus the available evidence from the western americas indicates that exposure and lithology rather than the climatic variables temperature and runoff dominate the weathering yields in active orogenic belts these observations contradict the conventional view of weathering processes and their controls and are at complete variance with the assumptions parameterised in most models of the geochemical cycle

strong rocks sustain ancient postorogenic topography in southern africa the cape mountains of southern africa exhibit an alpine like topography in conjunction with some of the lowest denudation rates in the world this presents an exception to the often cited coupling of topography and denudation rates and suggests that steep slopes alone are not sufficient to incite the high denudation rates with which they are commonly associated within the cape mountains slope angles are often in excess of 30 degrees and relief frequently exceeds 1 km yet be 10 based catchment averaged denudation rates vary between 2 32 0 29 m m y and 7 95 0 90 m m y we attribute the maintenance of rugged topography and suppression of denudation rates primarily to the presence of physically robust and chemically inert quartzites that constitute the backbone of the mountains be 10 based bedrock denudation rates on the interfluves of the mountains vary between 1 98 0 23 m m y and 4 61 0 53 m m y the close agreement between the rates of catchment averaged and interfluve denudation indicates topography in steady state these low denudation rates in conjunction with the suggestion of geomorphic stability are in agreement with the low denudation rates 20 m m y estimated for southern africa during the late cenozoic by means of cosmogenic nuclide thermochronology and offshore sedimentation analyses accumulatively these data suggest that the coastal hinterland of the subcontinent may have experienced relative tectonic stability throughout the cenozoic

increasing risks related to landslides from degrading permafrost into new lakes in de glaciating mountain ranges abstract while glacier volumes in most cold mountain ranges rapidly decrease due to continued global warming degradation of permafrost at altitudes above and below glaciers is much slower as a consequence many still existing glacier and permafrost landscapes probably transform within decades into new landscapes of bare bedrock loose debris sparse vegetation numerous new lakes and steep slopes with slowly degrading permafrost these new landscapes are likely to persist for centuries if not millennia to come during variable but mostly extended future time periods such new landscapes will be characterized by pronounced disequilibria within their geo and ecosystems this especially involves long term stability reduction of steep icy mountain slopes as a slow and delayed reaction to stress redistribution following de buttressing by vanishing glaciers and to changes in mechanical strength and hydraulic permeability caused by permafrost degradation thereby the probability of far reaching flood waves from large mass movements into lakes systematically increases with the formation of many new lakes and systems of lakes in close neighborhood to or even directly at the foot of so affected slopes results of recent studies in the swiss alps are reviewed and complemented with examples from the cordillera blanca in peru and the mount everest region in nepal hot spots of future hazards from potential flood waves caused by large rock falls into new lakes can already now be recognized to this end integrated spatial information on glacier permafrost evolution and lake formation can be used together with scenario based models for rapid mass movements impact waves and flood propagation the resulting information must then be combined with exposure and vulnerability considerations related to settlements and infrastructure this enables timely planning of risk reduction options such risk reduction options consist of two components mitigation of hazards which in the present context are due to effects from climate change and reduction in consequences which result from societal conditions and changes hazard mitigation may include artificial lake drainage or lake level lowering and flood retention optimally in connection with multipurpose structures for hydropower production and or irrigation reduction in damage potential exposure vulnerability can be accomplished by installing early warning systems adapting spatial planning and or by improving preparedness of local people and institutions

study of permafrost distribution in sikkim himalayas using sentinel 2 satellite images and logistic regression modelling abstract in this study sentinel 2a s 2a multi spectral instrument msi level 1c l1c products are used for identification and mapping of rock glaciers within a transect under observation in sikkim himalayas the mapped rock glaciers were classified on the basis of their activity intact or relict and their origin glacier derived or talus derived logistic regression models were applied to calculate the probability of permafrost distribution within transect under observation we observed that freely available high resolution s 2a msi l1c products are a valuable addition to the already existing freely available high resolution satellite images that can be exploited to study rock glaciers in himalayan region the distribution of rock glaciers in sikkim himalayas is found to be strongly controlled by elevation and aspect topoclimatic conditions above 5000 m a s l are favourable for the presence of permafrost in sikkim himalayas more glacier derived rock glaciers than talus derived rock glaciers were observed within transect under observation outputs from logistic regression models were capable to reasonably estimate the spatially distributed probability of permafrost occurrence in the region however outputs from these models depended upon the selection of the initiation line location points of rock glaciers and topoclimatic and topographic variables used as predictors for model computation based on probability distribution maps more than 60 800 km2 area of transect under observation could contain permafrost this high areal abundance of permafrost in sikkim himalayas suggests increased risks of thawing permafrost under the influence of climate warming in future

observations on rock glaciers in the himalayas and karakoram mountains of northern pakistan and india abstract rock glaciers are abundant in the lahul and garhwal himalayas of northern india and the karakoram mountains of northern pakistan they exhibit morainic and protalus forms and are restricted altitudinally and climatically to sites above approximately 4000 m asl and regions where annual precipitation is less than 1000 mm in these areas morainic rock glaciers are large usually 1 km long 100 m wide and 15 m thick they are advancing over recent fluvial terraces and modern floodplains the morainic rock glaciers record the advance of ice cored moraines following retreat of glaciers likely since the little ice age these rock glaciers form a major component of the landscape and are important conveyors of debris down valley under the influence of gravity

using in situ produced cosmogenic isotopes to estimate rates of landscape evolution a review from the geomorphic perspective the application of in situ produced cosmogenic isotopes to problems in geomorphology has increased rapidly over the past decade at least 57 papers and numerous abstracts have been published since the mid 1980s when the first mass spectrometric measurements of terrestrially produced cosmogenic isotopes were made taken at face value these studies provide quantitative information about rates of landscape evolution and landform age however the significance of calculated erosion rates and exposure ages depends strongly on the models used to interpret isotopic data the validity of assumptions inherent to these models and the geologic surroundings in which the samples were collected this paper attempts to place cosmogenic isotope studies in a geomorphic context by reviewing fundamentals of the method and evaluating the validity of assumptions under which these data have been interpreted at present the establishment of high precision cosmogenically based glacial and alluvial chronologies is stymied by the evolution of geomorphic surfaces the erosion of rock from sampled boulders the potential for isotope inheritance from previous exposure and the uncertainty of isotopic measurements uncertainties in isotope production rates and the observed variability of exposure ages on individual geomorphic surfaces limit the confidence with which cosmogenic ages can be correlated reliably with those obtained by other techniques estimation of erosion rates at single points on the landscape gives useful small scale information extrapolation of these rates over longer time and larger spatial scales is less sure and most likely biased toward lower erosion rates by die inadvertent selection of resistant sample sites however because erosion rates are so poorly constrained at present even estimates to within a factor of 2 may be of significant value to geomorphologists and tectonicists

landslide hazards and mitigation measures at gangtok sikkim himalaya landslides and other mass movements are serious geo environmental hazards in the himalayas massive landslides killing tens of thousands of people with catastrophic damages have occurred in the eastern himalayan state of sikkim which shares common borders with tibet nepal and bhutan this paper describes the investigations carried out on recent landslides in gangtok sikkim india with emphasis on the triggering mechanisms that have contributed to the release and creep of natural slopes in the region it is believed that the intense rainfall in the region not only contributes to rapid erosion and weathering of the rock mass but also increases the groundwater level that leads to reduction in the stability of natural slopes a landslide instrumentation programme that includes placement of settlement pillars and piezometers is underway to predict the behaviour of landslides in the area

correction of in situ cosmogenic nuclide production rates for geomagnetic field intensity variations during the past 800 000 years we present integrated relative production rates for cosmogenic nuclides in rock surfaces which take into account reported variations of the geomagnetic field intensity during the past 800 000 yr the calculations are based on the model simulating cosmic ray particle interactions with the earth s atmosphere given by masarik and beer simulation of particle fluxes and cosmogenic nuclide production in the earth s atmosphere j geophys res 104 d10 12099 12111 1999 corrections are nearly independent on altitude between sea level and at least 5000 m the correction factors are essentially identical for all stable and radioactive cosmogenic nuclides with half lives longer than a few hundred thousand years at the equator integrated production rates for exposure ages between 40 000 to 800 000 yr are 10 to 12 higher than the present day values whereas at latitudes 40 geomagnetic field intensity variations have hardly influenced in situ cosmogenic nuclide production correction factors for in situ 14c production rates differ from those of longer lived nuclides they are always smaller than 2 because the magnetic field intensity remained rather constant during the past 10 kyr when the major fraction of the 14c extant today was produced

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

geology geography and humans battle for dominance over the delivery of fluvial sediment to the coastal ocean abstract sediment flux to the coastal zone is conditioned by geomorphic and tectonic influences basin area and relief geography temperature runoff geology lithology ice cover and human activities reservoir trapping soil erosion a new model termed bqart in recognition of those factors accounts for these varied influences when applied to a database of 488 rivers the bqart model showed no ensemble over or underprediction had a bias of just 3 across six orders of magnitude in observational values and accounted for 96 of the between river variation in the long term 30 years sediment load or yield of these rivers the geographical range of the 488 rivers covers 63 of the global land surface and is highly representative of global geology climate and socioeconomic conditions based strictly on geological parameters basin area relief lithology ice erosion 65 of the between river sediment load is explained climatic factors precipitation and temperature account for an additi

denudation rates determined from the accumulation of in situ produced 10be in the luquillo experimental forest puerto rico we present a simple method for estimation of long term mean denudation rates using in situ produced cosmogenic 10be in fluvial sediments procedures are discussed to account for the effects of soil bioturbation mass wasting and attenuation of cosmic rays by biomass and by local topography our analyses of 10be in quartz from bedrock outcrops soils mass wasting sites and riverine sediment from the icacos river basin in the luquillo experimental forest puerto rico are used to characterize denudation for major landform elements in that basin the 10be concentration of a discharge weighted average of size classes of river sediment corresponds to a long term average denudation of 43 m ma 1 consistent with mass balance results

active tectonics of the southeastern upper rhine graben freiburg area germany the upper rhine graben has two plio quaternary depocentres usually interpreted as resulting from tectonic reactivation the southern basin near freiburg im breisgau germany contains up to 250 m of sediments beneath the younger alluvial deposits related to the current drainage system a former river network deeply entrenched in the substratum reveals a very low regional base level of early pleistocene age the offset of channels at faults allows us to infer a pleistocene reactivation of the syn rift fault pattern and the estimation of slip rates maximum vertical movements along the faults have not exceeded 0 1 mm yr since the middle pleistocene current activity is concentrated along the westernmost faults morphologic markers indicate late pleistocene reactivation of the rhine river fault and geophysical prospecting suggests a near surface offset of young sedimentary deposits the size of the fault segments potentially reactivated suggests that earthquakes with magnitude larger than mw 6 3mw 6 3 could be expected in the area with a return interval of about 8000 years extrapolated to the duration of the plio pleistocene the strain rate estimates reveal that the tectonic forcing may account for only one third to one half of the whole thickness of the plio pleistocene sediments of the basin fill thus other processes must be invoked to understand the growth of the plio pleistocene basin especially the piracy of the rhine river to the north during the early pleistocene could explain these effects

evidence of episodically accelerated denudation on the tibetan namche barwa massif by megafloods abstract megafloods cause widespread mobilization of sediments that have strong potential to control the geodynamic evolution of the namche barwa nb massif by changing the landscape morphology within a short time however the impact of catastrophic events on the denudation of the massif over the longer time scale has not been explored in detail this contribution assesses the impact of catastrophic floods on the denudation style of the namche barwa nb massif over millennial time scales towards this 21 optical ages and 1700 detrital thermochronometric ages of zircon and apatite minerals extracted from paleoflood sediments downstream of the massif were integrated with decadal sediment load and aggradation data to estimate the minimum denudation rate during paleoflood events the results indicate that the 7 ka flood eroded 71 m of material from the nb massif this denudation is equivalent to the material that would be produced over 8000 years of erosion at a rate of 9 mm a the 3 5 ka flood eroded 24 m of material equaling 2500 years worth of erosion at a rate of 9 mm a such relatively instantaneous denudations are three orders of magnitude higher than averaged denudation rates over million year time scale this study therefore provides the first evidence of the strong interplay of catastrophic flood events and tectonics for the rapid exhumation of the namche barwa massif megafloods from the failure of dammed lakes provide valuable information to understand the flood surge risk for human settlements in the siang and the assam valleys

spatially averaged long term erosion rates measured from in situ produced cosmogenic nuclides in alluvial sediment spatially averaged erosion rates of small catchments can be accurately inferred from the concentrations of cosmogenic nuclides in stream sediment here we test this technique at two catchments by comparing erosion rates inferred from cosmogenic nuclides with rates of alluvial fan deposition over the past 16 000 years these two independent estimates agree within one standard error demonstrating that cosmogenic nuclide signatures of stream sediment can be used to measure spatially averaged long term erosion rates using this technique we show that long term erosion rates are an exponential function of average hillslope gradient at these sites

impediments to predicting site response seismic property estimation and modeling simplifications abstract we compare estimates of the empirical transfer function etf to the plane sh wave theoretical transfer function ttf within a laterally constant medium for invasive and noninvasive estimates of the seismic shear wave slownesses at 13 kiban kyoshin network stations throughout japan the difference between the etf and either of the ttfs is substantially larger than the difference between the two ttfs computed from different estimates of the seismic properties we show that the plane sh wave ttf through a laterally homogeneous medium at vertical incidence inadequately models observed amplifications at most sites for both slowness estimates obtained via downhole measurements and the spectral analysis of surface waves strategies to improve the predictions can be separated into two broad categories improving the measurement of soil properties and improving the theory that maps the 1d soil profile onto spectral amplification using an example site where the 1d plane sh wave formulation poorly predicts the etf we find a more satisfactory fit to the etf by modeling the full wavefield and incorporating spatially correlated variability of the seismic properties we conclude that our ability to model the observed site response transfer function is limited largely by the assumptions of the theoretical formulation rather than the uncertainty of the soil property estimates

temporal change in site response caused by earthquake strong motion as revealed from coda spectral ratio measurement 1 the spectral ratios of coda waves of local earthquakes have been often used as measures of relative amplification factors of different sites applying this method to coda waves registered by seismometers installed on the surface and at the bottom of a borehole we succeeded in stably measuring the temporal change in site response associated with the occurrence of a large earthquake strong motion a remarkable drop of coda spectral ratio and a shift of the peak frequency were observed during strong shake at two sites by the 2000 western tottori earthquake and at a site by the 2003 tokachi oki earthquake in japan the reduction of the peak frequency reached 30 70 at all the sites after that the peak frequency logarithmically recovered to the value before the strong motions for a few years at two sites whereas the other one quickly recovered in a few tens of minutes

natural controls of fluvial denudation rates in major world drainage basins we present a new compilation of estimates of modern rates of mechanical and chemical denudation for externally drained basins exceeding 5 105 km2 in area these estimates are based on sediment and solute load data selected in order to represent natural rates as far as possible chemical denudation rates have been calculated by deducting the nondenudational component of solute load mechanical denudation rates range from 1 mm kyr 1 for the st lawrence and dnepr basins to 670 mm kyr 1 for the brahmaputra basin chemical denudation rates vary from 1 mm kyr 1 kolyma niger nile and rio grande basins to 27 mm kyr 1 chiang jiang basin the kolyma basin has the lowest 4 mm kyr 1 and the brahmaputra basin the highest overall rate of denudation 688 mm kyr 1 relationships between denudation rates and a range of morphometric hydrologic and climatic variables are investigated through correlation and regression analysis morphometric variables such as mean local relief are accurately calculated for large basins for the first time by using the national geophysical data center 10 minute topographic database variables expressing basin relief characteristics and runoff are found to be most strongly associated with both mechanical and chemical denudation rates with more than 60 of the variance in total denudation being accounted for by basin relief ratio and runoff basin area runoff variability and mean temperature however are only weakly associated with rates of denudation although direct comparisons cannot be made it appears that rates of basin denudation derived from present day mass flux estimates are not overall significantly different from estimates of long term rates based on sediment volume and thermochronologic data it therefore appears that the key factors identified as controlling denudation rates here are also applicable to the geological time spans relevant to the interaction between tectonic and denudational processes

estimating rates of denudation using cosmogenic isotope abundances in sediment we propose as a testable hypothesis a basin scale approach for interpreting the abundance of in situ produced cosmogenic isotopes an approach which considers explicitly both the isotope and sediment flux through a drainage basin unlike most existing models which are appropriate for evaluating in situ produced cosmogenic isotope abundance at discrete points on earth s surface our model is designed for interpreting isotope abundance in sediment because sediment is a mixture of materials in favourable cases derived from throughout a drainage basin we suggest that measured isotope abundances may reflect spatially averaged rates of erosion we investigate the assumptions and behaviour of our model and conclude that it could provide geomorphologists with a relatively simple means by which to constrain the rate of landscape evolution if a basin is in isotopic steady state and if sampled sediments are well mixed

dissolved load of the loire river chemical and isotopic characterization the loire river with one of the largest watersheds in france has been monitored just outside the city of orleans since 1994 physico chemical parameters and major and trace elements were measured between 2 day and 1 week intervals according to the river flow the sampling site represents 34 of the total loire watershed with 76 silicate rocks and 24 carbonate rocks elements are transported mainly in the dissolved phase with the ratio of total dissolved salts tds to suspended matter sm ranging between 1 6 and 17 4 chemical weathering of rocks and soils are thus the dominant mechanisms in the loire waters composition the highest tds sm ratios are due to dissolved anthropogenic inputs the database shows no link between no3 content and river flow the na k mg2 so42 and cl concentrations are seen to decrease with increasing discharge in agreement with a mixing process involving at least two components the first component during low flow is concentrated and may be related with input from the groundwater and sewage station water the second component during high flow is more dilute and is in agreement with bedrock weathering and rainwater inputs a geochemical behaviour pattern is also observed for hco3 and ca2 species their concentrations increase with increasing discharge up to 300 m3 s after which they decrease with increasing discharge the sr isotopic composition of the dissolved load is controlled by at least five components a series of natural components represented by a waters draining the silicate and carbonate bedrock b groundwater and c rainwaters and two kinds of anthropogenic components the aim of this study is to describe the mixing model in order to estimate the contribution of each component finally specific export rates in the upper loire watershed were evaluated close to 12 t year 1 km 2 for the silicate rate and 47 t year 1 km 2 for the carbonate rate

rates of surface processes on slopes slope retreat and denudation results taken from 270 publications on rates are summarized and collated with those from 149 publications reviewed previously young 1969 1974 the data are classified by major climatic zone normal or steep relief and consolidated or unconsolidated rocks representative rates and their ranges are given for soil creep solifluction surface wash solution chemical denudation rock weathering slope retreat cliff free face retreat marine cliff retreat and denudation the last being compared with representative rates of uplift solifluction is of the order of 10 times faster than soil creep but both cause only very slow ground loss solution is an important cause of ground loss for siliceous rocks on which it may be half as rapid as on limestones total denudation brought about mainly by surface wash reaches a maximum in the semi arid and probably also the tropical savanna zones acceleration of natural erosion rates by human activities ranges from 2 3 times with moderately intense land use to about 10 times with intensive land use and considerably higher still where there is recognized accelerated soil erosion where there is active uplift typical rates are of the order of 10 times faster than denudation although in some high steep mountain ranges these may approach equality

cosmic ray production rates of 10be and 26al in quartz from glacially polished rocks we have studied the concentrations of 10be and 26al in quartz crystals extracted from glacially polished granitic surfaces from the sierra nevada range these surfaces were identified with the glacial advance during the tioga period 11 000 years ago our measurements yield the most accurate estimates to date for the absolute production rates of these nuclides in sio2 due to cosmic ray nucleons and muons for geomagnetic latitudes 43 8 44 6 n and altitudes 2 1 3 6 km the estimates are relatively free from uncertainties in snow cover since we studied a suite of rock surfaces inclined 0 75 with respect to the horizontal the principal uncertainty arises due to the lack of a precise date for the glacial retreat event about 10 the 26al 10be ratio at production 6 0 is determined more accurately since the exposure age of the samples is 2 orders of magnitude smaller than the mean lives of the two nuclides production rates of 10be and 26al in quartz at other latitudes and altitudes in the troposphere can be determined from the present measurements by scaling using the known altitude and latitude dependence of cosmic ray fluxes of nucleons and negative muons knowledge of the production rates of these nuclides is a prerequisite for their application in erosion and geomorphological studies

a stochastic approach for evaluating the nonlinear dynamics of vertical motion recorded at the iwth25 site for the 2008 mw 6 9 iwate miyagi inland earthquake the vertical accelerogram recorded at the iwth25 site located just above the earthquake fault of the 2008 m w 6 9 iwate miyagi inland earthquake showed nonlinear dynamics because of intrawave frequency modulation with a maximum amplitude close to 4 g due to the nonlinear response of the near surface layer at the site in the present paper a stochastic second order model is proposed to explain these observations the dynamics of the model are determined by the configuration of three pairs of complex conjugated poles in the z transform domain and the dynamics of these poles are interpreted in terms of the instantaneous frequency of the recorded acceleration signal the results of simulations using the proposed model show overall agreement with the recorded accelerogram including its maximum amplitude and its time of appearance the physical mechanism producing the displacement waveform is found to be analogous to a ball bouncing on a vibrating surface from the simulated and recorded seismograms it was apparent that at least two consecutive high bounces are required to produce extremely high accelerations of close to 4 g

sediment yield during late glacial and holocene periods in the lac chambon watershed massif central france a sediment budget for the late glacial and holocene periods was calculated for the lac chambon watershed which is located in a formerly glaciated temperate crystalline mountain area it appears that over 15 500 years 1 69 per cent of eroded particles have been displaced by gravity processes and then stored within the watershed compared to 31 per cent that have been displaced by running water and evacuated outward 2 the mean mechanical erosion due to gravity processes on the slopes amounted to 16 1 6 m and only developed on a quarter of the watershed surface whereas the mean mechanical erosion due to running water amounted 1 24 0 37 m and involved the whole watershed surface the mean sediment yields due to gravity processes on slopes were 2300 1360 1770 960 and 380 100 m 3 km 3 a 1 respectively for basalts and basic and acidic trachyandesites values of sediment yield due to running water were 49 15 120 36 and 79 24 m 3 km 2 a 1 respectively during the bolling allerod the younger dryas and the pre boreal boreal periods they were 56 17 and 166 50 m 3 km 2 a 1 during the sub atlantic period before and after 1360 a bp respectively these values reflect variations in the natural environment and the impact of human induced deforestation 1997 by john wiley sons ltd

scaling factors for production rates of in situ produced cosmogenic nuclides a critical reevaluation abstract new scaling factors are presented describing the altitude and latitudinal dependence of production rates for in situ produced cosmogenic nuclides the new factors incorporate the influence of the non dipole contributions to the geomagnetic field on the cosmic ray flux the currently used scaling factors of lal earth planet sci lett 104 1991 424 439 are based on the assumption of a dipole field the overall strategy used in deriving the new scaling factors is however very similar to that of lal and relies on the same and or similar nuclear data in this reevaluation data are only used if the effective geomagnetic parameters inclination horizontal field strength can be reconstructed for the time of measurement the absorption free pathlengths for cosmic rays selected for this study are based on observational data at altitudes relevant for exposure age dating sea level to 7000 m at sea level and latitudes between 20 and 40 the new factors are up to 18 lower and at high altitudes more than 30 higher than those of lal in addition to accounting for the influence of the effective geomagnetic field and providing more applicable estimates of the new factors also allow for correction for the significant deviations from the standard pressure altitude relationship that exist in the atmosphere 10

denudation rates of the southern espinhaco range minas gerais brazil determined by in situ produced cosmogenic beryllium 10 article to investigate denudation rates in the southern part of the espinhaco range central eastern brazil and to understand how this important resistant and residual relief has evolved in the past 1 38 my cosmogenic 10 be concentrations produced in situ were measured in alluvial sediments from the three main regional ba sins whose substratum is composed primarily of quartzites the long term denudation rates up to 1 38 my estimated from these measurements were compared with those that affect the western sao francisco river and eastern doce and jequitinhonha rivers basins which face the west san francisco craton and the atlantic respectively denudation rates were measured in 27 samples collected in catchments of different sizes 6 970 km 2 and were compared with geomorphic parameters the mean denudation rates determined in the northern part are low and similar to those determined in the southern part despite slightly different geomorphic parameter values catchment relief and mean slope for the southern catchments the values are 4 91 1 01 mmy 1 and 3 65 1 26 mmy 1 for the doce and sao francisco river basins respectively for the northern catchments they are 4 40 1 06 mmy 1 and 3 96 0 91 mmy 1 for the jequitinhonha and sao francisco river basins respectively these low values of denudation rates suggest no direct correlation if plotted against geomorphic parameters such as the catchment area maximum elevation catchment relief average relief and mean slope gradients these values show that the regional landscape evolves slowly and is strongly controlled by resistant lithology with similar erosional rates in the three studied basins

geomorphology of anomalously high glaciated mountains at the northwestern end of tibet muztag ata and kongur shan article i nfo muztag ata and kongur shan massifs represent a significant area of anomalously high topography at the northwestern end of the tibetan plateau rising to n7500 m above sea level asl from the plateau that has an average elevation of 3500 m asl these massifs provide an excellent opportunity to test geomorphic concepts such as the glacial buzz saw model using remote sensing digital elevation modeling field mapping and terrestrial cosmogenic nuclide tcn methods the massifs were examined to determine the relative importance of tectonics and geomorphic processes in shaping the regional landscape and to provide a framework for testing geomorphic models the gneiss domes that underlie the peaks are the result of exhumation along the kongur detachment fault that has unroofed the massifs at a rate of between 4 6 km ma over the last few million years this has resulted in rapid uplift and active seismicity which is exemplified by the numerous fresh fault scarps throughout the region and large historic earthquakes the geomorphic system is dominated by glaciation and the region contains extensive successions of moraines and paraglacial landforms including fans terraces and landslides glaciers have oscillated considerably throughout the latter part of the quaternary and three major glacier stages are recognized karasu oldest olimde and subaxh youngest glacial stage that include at least 10 smaller glacial advance the style of glaciation has changed over time from expanded ice caps to piedmont glaciers to valley and cirque glaciers this possibly reflects a change in climate and or topographic constraints as the massifs grew and became incised the topography and glaciers in the region vary across the massifs divided by a broadly n s trending high ridge and watershed the western portion situated upwind the stoss slopes of the mid latitude westerlies that bring moisture to the region has gentle high topography and small valley glaciers in contrast on the eastern leeward slopes gradients are higher and long debris covered valley glaciers are present the hypsometry of the region indicate two peaks in the distribution frequency of elevation 3600 4100 m and 4400 4800 m asl these two elevation zones are consistent in space with the former equilibrium line altitudes during the olimde and subaxh glacial stages and suggest that glacial erosion most effective at the ela has helped control topography this observation supports the glacial buzz saw hypothesis which argues that glaciers determine hypsometry by means of rapid surface erosion based on tcn methods basin wide rates of erosion range from 0 1 to 1 4 km ma and are five to ten times lower than the unroofing rate of both massifs the discrepancy over different time scales suggests that initial unroofing was produced by abrupt tectonic uplift and that the unroofing of the massifs has continued at a slower pace during the late quaternary

numerical analysis of near field asymmetric vertical motion abstract during the 2008 iwate miyagi nairiku japan earthquake m w 6 9 an unprecedented vertical surface acceleration of nearly four times gravity was measured at the kik net iwth25 station located 3 km southwest of the epicenter the station is equipped with three component accelerometers installed at both the free surface and the bottom of a 260 m borehole the waveform of the vertical acceleration shows a clearly asymmetric form with large amplitude in the upward direction aoi et al 2008 reported and qualitatively explained the mechanism of this phenomenon by the analogy of bouncing a piece of matter on a trampoline thus they called it the trampoline effect to study this recently discovered nonlinear behavior of the surface ground motion numerical analysis with a two dimensional finite element method has been conducted with parameters derived from the borehole data at the station the analysis successfully simulates the asymmetric vertical motion results indicate that the asymmetric motion may be characterized by the existence of a lower bound of negative acceleration which in most cases corresponds to the acceleration of gravity and high positive pulses caused by the compression stress of the disturbed surface ground material

geological and geophysical evidence for large palaeo earthquakes with surface faulting in the roer graben northwest europe from the analysis of geological geodetic and geophysical data we provide clear evidence of seismogenic faults capable of producing large earthquakes in intraplate europe previous studies paulissen vandenberghe gullentops 1985 van den berg et al 1994 geluk et al 1994 have yielded some constraints on the rate of crustal deformation along the roer valley a graben structure crossing the netherlands belgium and germany and have allowed us to address the fundamental questions can intraplate earthquakes rupture the surface in this part of stable continental europe and if so what is their return period detailed palaeoseismic investigations have been carried out in belgium along a 10 km long fault scarp which is the morphological expression of the feldbiss fault the southwestern border fault of the roer graben camelbeeck meghraoui 1996 the scarp is multiple and the frontal fault scarp offsets young deposits and alluvial terraces field investigations using geological and geomorphological methodologies combined with geophysical prospecting provide evidence of holocene seismic surface faulting from 14c dating it is suggested that the last earthquake along the fault scarp occurred between 610 ad and 890 ad levelling profiles across the scarp suggest that it produced a vertical coseismic displacement of 0 5 1 m along the scarp if we suppose that the last surface faulting earthquake ruptured the whole seismogenic layer 17 km thickness over a minimum length 10 km corresponding to the length of the bree scarp with an average slip of 0 6 m its seismic moment was at least 3 1 1018 n m mw 6 3 for an average rigidity 3 1010 pa by estimating the offset of the main terrace of the maas river by slippage along the feldbiss fault we calculate the average late pleistocene vertical deformation rate as 0 08 0 04 mm yr 1 palaeoseismic information combining the trench and geomorphic observations suggests the occurrence of two surface faulting earthquakes during the last 20 kyr a third dates before 28 35 kyr bp then if the time distribution of earthquakes is uniform a return period of 12 5 ka and a vertical deformation rate of 0 06 0 04 mm yr 1 are inferred

relict landscape resistance to dissection by upstream migrating knickpoints expanses of subdued topographies are common at high elevation in mountain ranges they are often interpreted as relict landscapes and are expected to be replaced by steeper topography as erosion proceeds preservation of such relict fragments can merely reflect the fact that it takes time to remove any preexisting topography however relict fragments could also possess intrinsic characteristics that make them resilient to dissection we document here the propagation of a wave of dissection across an uplifted relict landscape in puerto rico using 10be 26al burial dating on cave sediments we show that uplift started 4 ma and that river knickpoints have since migrated very slowly across the landscape modern detrital 10be erosion rates are consistent with these long term rates of knickpoint retreat analysis of knickpoint distribution combined with visual observations along the streambeds indicates that incision by abrasion and plucking is so slow that bedrock weathering becomes a competing process of knickpoint retreat the studied rivers flow over a massive stock of quartz diorite surrounded by an aureole of metavolcanic rocks earlier studies have shown that vegetation over the relict topography efficiently limits erosion allowing for the formation of a thick saprolite underneath such slow erosion reduces streambed load fluxes delivered to the knickpoints as well as bed load grain size both processes limit abrasion compounding the effect of slow abrasion wide joint spacing in the bedrock makes plucking infrequent thus the characteristics of the relict upstream landscape have a direct effect on stream incision farther downstream reducing the celerity at which the relict subdued landscape is dissected we conclude that similar top down controls on river incision rate may help many relict landscapes to persist amidst highly dissected topographies

landscape development in an hyperarid sandstone environment along the margins of the dead sea fault implications from dated rock falls in this study we explored the spatial and temporal relations between boulders and their original in situ locations on sandstone bedrock cliffs thiswas accomplished bycombining field observations withdating methods using cosmogenicisotopes 10 be and 14 c and optically stimulated luminescence osl our conclusions bear both on the landscape evolution and cliff retreat process in the hyperarid region of timna and on the methodology of estimating exposure ages using cosmogenic isotopes we recognize three discrete rock fall events at 31 ka 15 ka and 4 ka in this hyperarid region the most plausible triggering mechanism for rock fall events is strong ground acceleration caused by earthquakes generated by the nearby dead sea fault dsf our record however under represents the regional earthquake record implying that ongoing development of detachment cracks prior to the triggering event might be slower than the earthquake cycle cliff retreat rates calculated using the timing of rock fall events and estimated thickness of rock removed in each event range between 0 14 m ky 1 and 2 m ky 1 when only full cycles are considered we derive a more realistic range of 0 4 m ky 1 to 0 7 mk y 1 these rates are an order of magnitude faster than the calculated rate of surface lowering in the area we conclude that sandstone cliffs at timna retreat through episodic rock fall events that preserve the sharp imposing landscape characteristic to this region and that ongoing weathering of the cliff faces is minor a 10 20 difference in the 10 be concentrations in samples from matching boulder and cliff faces that have identical exposure histories and are located only a few meters apart indicates that cosmogenic nuclide production rates are sensitive to