uranium series ages of travertines and timing of the last glaciation in the northern yellowstone area wyoming montana uranium series age determinations by mass spectrometric methods were done for travertines and associated carbonate veins related to clastic deposits of the last glaciation pinedale in the northern yellowstone area dramatic variations in the hydrologic head are inferred from variations in the elevation of travertine deposition with time and are consistent with the expected hydrologic effects of glaciation we determine the following chronology of the pinedale glaciation with the key assumption that travertine deposits and associated carbonate veins perched high above present thermal springs were deposited when glaciers filled the valley below these perched deposits 1 the early pinedale outlet glacier advanced well downvalley between 47 000 and 34 000 yr b p 2 the outlet glacier receded to an interstadial position between 34 000 and 30 000 yr b p 3 an extensive pinedale ice advance occurred between 30 000 and 22 500 yr b p 4 a major recession occurred between 22 500 and 19 500 yr b p 5 a minor readvance deckard flats culminated after 19 500 yr b p and 6 recession from the deckard flats position was completed before 15 500 yr b p this chronology is consistent with the general trend of climatic changes in the northern hemisphere as revealed by recent high resolution ice core records from the greenland ice sheet

age limits on the late quaternary evolution of the upper loire river abstract the loire river is one of the largest rivers in europe draining a basin area of southern france which exceeds 100 000 km 2 despite its significance the loire remains poorly studied and has a very limited amount of chronological control on the deposited sedimentary record of fluvial activity these factors coupled with the availability of a set of 10 radiocarbon dates on younger c

electric and magnetic field changes observed during a seismic swarm in pollino area southern italy abstract over the last few years seismic activity in the pollino area a sector of the calabro lucanian apennines in southern italy known as a seismic gap has been very weak however in 2011 the seismicity gradually intensified culminating in an earthquake of m w 5 0 occurred on 25 october 2012 the depth of the 2011 2012 earthquake hypocenters ranges between 2 and 10 km the seismicity results in two separate clusters and traces a north northwest south southeast fracture more evident in the western sector in this area an mt station was installed on 26 september 2012 by the institute of methodologies for environmental analysis national research council of italy imaa cnr italy at about 50 km from another mt station operating since 2003 in the agri valley tramutola southern italy such a seismic swarm occurred in the pollino area more than 3600 events in last two years with local magnitude m l 0 1 it has provided a rare opportunity to study the earthquake related temporal patterns of electromagnetic em signals and is potentially informative about ongoing seismogenic processes in this study we present several cases of em field variations associated with the passage of seismic waves the maximum amplitude of the electrical signals registered at the two mt sites and the earthquake magnitude are related by an attenuation factor that depends on the distance between the hypocenter and the mt station furthermore at the two mt sites the maximum electrical anomalies seem to be more appreciable predominantly in different directions indicating a certain directivity in the propagation of the electric field a deep analysis of em time series recorded during the mainshock m w 5 0 was performed in particular by applying time frequency misfit criteria based on the continuous wavelet transform we compared the electric field with seismic recordings and we found a good waveform similarity between signals moreover we also found an em signal that significantly anticipates the theoretical first p wave arrival at the tramutola mt station

seismoelectromagnetic effect associated with the izmit earthquake and its aftershocks in order to investigate the resistivity structure beneath the northern and the southern branches of the western part of the north anatolian fault zone nafz which has been known as a seismic gap area we started wideband magnetotelluric mt measurements on 27 july 1999 along a north south profile crossing the northern branch near izmit and the southern branch near iznik when the izmit kocaeli earthquake m w 7 4 occurred on 17 august 1999 mt fields were being measured at five sites four of which happened to be located near the surface rupture zone associated with the mainshock and large variations in the mt fields were observed in association with seismic waves we propose motional electromagnetic induction in the electrically conducting crust which vibrates under the earth s magnetic field as one of the possible generation mechanisms for such mt field variations for more detailed studies of such a mechanism we installed a wideband mt instrument and a three component seismometer at two of the four sites on 16 september 1999 and made simultaneous measurements during several aftershocks the estimate of the order of the magnitude of motional electromagnetic response derived from the mt fields and ground motion observed during a large aftershock m 4 5 supports our claim that the seismo dynamo effect is a plausible mechanism for variations in the mt fields associated with the seismic waves manuscript received 31 july 2000

interpreting climate modulated processes of terrace development along the colorado front range using a landscape evolution model flights of terraces that flank range fronts throughout the rocky mountains record episodic stream incision over the past 1 5 ma studies dating terraces in the denver basin along the colorado front range suggest that these high surfaces were formed during glacial intervals and were rapidly incised and abandoned during interglacials modulation of sediment supply or transport capacity associated with climate change related to glacial interglacial cycles have been suggested as possible drivers for the repeated aggradation and abandonment of these high surfaces potential mechanisms for increasing sediment supply and transport in rivers include variations over time in sediment flux from intermittently glaciated major valleys the efficiency of hillslope sediment transport and the magnitude and timing of rainfall intensity and stream flow in this study we use a landscape evolution model to determine whether any of these processes in isolation or in combination is sufficient to explain the observed rates and patterns of terrace formation and abandonment along the colorado piedmont cycles of channel aggradation and incision are apparent in the models when either mean rainfall intensity is varied or a glacial source of sediment is added the models suggest that in the absence of a large addition of sediment to the streams changes in stream power are necessary to allow channel aggradation and the planation of bedrock surfaces and increased sediment flux from hillslopes is necessary to match observations of increased denudation rates that coincide with the deposition of terrace capping gravels

geometry kinematics and deformation rates along the active normal fault system in the southern apennines implications for fault growth throw rates throws and kinematic data have been collected from a localised system of active normal faults in the southern apennines italy to assess how its growth history differs from that for a distributed fault system in the central apennines both show evidence for fault interaction in that 1 faults located centrally along strike have higher throws and throw rates than distal faults and 2 cumulative throw and throw rate profiles summed across strike show central maxima with values decreasing to zero at fault system tips however although throw rates increased through time in the central apennines we are unable to resolve such changes if they exist for the southern apennines specifically throw rates derived from offsets of 18 ka geomorphic surfaces are consistent with total throws in the southern apennines when extrapolated back through time but overestimate total throws in the central apennines by a factor of 2 4 suggesting an increase in throw rate through time for the latter we discuss why some fault systems appear to have throw rates that are constant through time whilst others accelerate during growth interaction

temporal variation of seismic velocity and anisotropy before the 2009 mw 6 3 l aquila earthquake italy we describe a set of seismological observations of the foreshock sequence preceding the 6 april 2009 m w 6 3 l9aquila earthquake the dense configuration of the seismic network in the epicenter area and the occurrence of a long foreshock sequence provide the opportunity for a detailed reconstruction of the preparatory phase of the main shock approaching the earthquake we observed clear variations in the seismic wave propagation properties the elastic properties of rocks in the fault region underwent a sharp change about a week before the earthquake from our observations we infer that a complex sequence of dilatancy diffusion processes takes place and that fluids play a key role in the fault failure process

late quaternary floodplain development along the stung sen river in the lower mekong basin cambodia abstract the stung sen river the biggest tributary to lake tonle sap in the lower mekong basin in cambodia is characterized by large seasonal changes of water discharge under the asian monsoon climate and seasonal changes in water level that reach at least 7 m and are controlled by the water level of the lake the stung sen river floodplain consists of two geomorphic units meander belt along the river channel and backmarsh coupled observations of outcrops along the river channel and arrays of sediment cores across the floodplain north of kampong chheuteal village and kampong thom city c 150 km and c 70 km respectively reveal that floodplain environmental changes at c 11 ka were possibly associated with the holocene onset of the southeast asian monsoon and probably with the emergence of lake tonle sap these observations also show that the present backmarsh meander belt system was established about 5 5 ka along with the unique mekong tonle sap connection characterized by a reversal in flow direction during the monsoon season the meander belt materials are replaced as the river channel shifts on a decadal to centennial timescale backmarsh sediments at sites kampong chheuteal and kampong thom had a constant accumulation rate of about 0 5 mm y during the holocene contrasting with rates of 0 1 mm y during the late pleistocene at around 11 ka a sand layer was deposited over all of the valley around kampong chheuteal while wetlands enlarged around kampong thom probably because of increased rainfall triggered by an enhancement of the asian summer monsoon this 11 ka horizon has since been covered by clayey sediments keeping pace with the accumulation of lacustrine sediments in lake tonle sap

paleohydrological implications of late quaternary fluvial deposits in and around archaeological sites in syria abstract the importance of fluvial processes to the development of late quaternary landforms in arid regions is well established particularly for the american southwest in contrast much less information exists about past fluvial processes for other arid regions such as arabic countries in the middle east this paper reviews the characteristics of late quaternary fluvial deposits and landforms in syria an arid country with little previous quaternary geomorphic research relatively detailed information has been obtained from areas adjacent to archaeological sites because of collaborative activities with geomorphologists and other geoscientists such activities have resulted in intensive field surveys and associated results of complementary archaeological studies of lithic artifacts are useful for establishing the chronology of fluvial deposits although the number of existing studies is limited the available information points to marked changes in the mode of fluvial processes in response to late quaternary climatic change fluvial sedimentation was enhanced during the wet periods of mis 3 4 the pleistocene holocene transition and the mid holocene in contrast the lgm was characterized by limited fluvial sedimentation under a drier climate as well as enhanced carbonate precipitation near the land surface to form calcrete and oncoids

resolving time space histories of late cenozoic bedrock incision along the upper colorado river usa abstract the upper colorado river basin drains the western slope of the rocky mountains province of north america and hosts a rich record of fluvial terraces and volcanic deposits that provide an archive of bedrock river incision since the late miocene here we present new geochronology from fluvial deposits and associated volcanic units using multiple methods luminescence cosmogenic burial 40ar 39ar basalt and detrital sanidine and u pb detrital zircon to reconstruct a detailed record of bedrock incision in the upper colorado river over timescales ranging from miocene to late pleistocene late miocene ca 11 8 ma basalt flows perched 800 1700 m above the colorado river and the oldest known ancestral colorado river deposits preserved beneath basalt flows on grand mesa provide the basis for average long term 107 yr incision rates rates range from 110 160 m ma between grand junction downstream and glenwood canyon upstream with rates decreasing upvalley intermediate scale 105 106 yr incision rates are 200 320 m m y over the past 1 3 ma and these rates are faster than the average over the past 8 11 ma short term

mechanisms of shallow landslides on soil mantled hillslopes with permeable and impermeable bedrocks in the boso peninsula japan abstract rainfall induced shallow landslides play a vital role in hillslope denudation processes in humid temperate regions this study demonstrates the contrasting mechanisms of landslides in adjoining hills with permeable sandstone and impermeable mudstone bedrock in the boso peninsula japan the characteristics of slope hydrology were inferred from pressure head monitoring and rainfall runoff observations an analysis of slope stability provided critical conditions for several previously occurring landslides the results are as follows 1 in slopes with the permeable sandstone infiltrated rainwater percolates through the bedrock as an unsaturated gravitational flow the wetting front migration results in a decrease of soil cohesion and causes landsliding at the steep lower part of the hillslopes 2 in contrast the impermeable mudstone beneath a thin soil layer causes a transient positive pressure head that generates a saturated subsurface storm flow the reduction in effective normal stress triggers shallow soil slipping at the uppermost part of a hollow

100 kyr fluvial cut and fill terrace cycles since the middle pleistocene in the southern central andes nw argentina abstract fluvial fill terraces in intermontane basins are valuable geomorphic archives that can record tectonically and or climatically driven changes of the earth surface process system however often the preservation of fill terrace sequences is incomplete and or they may form far away from their source areas complicating the identification of causal links between forcing mechanisms and landscape response especially over multi millennial timescales the intermontane toro basin in the southern central andes exhibits at least five generations of fluvial terraces that have been sculpted into several hundred meter thick quaternary valley fill conglomerates new surface exposure dating using nine cosmogenic 10be depth profiles reveals the successive abandonment of these terraces with a 100 kyr cyclicity between 75 7 and 487 34 ka depositional ages of the conglomerates determined by four 26al 10be burial samples and u pb zircon ages of three intercalated volcanic ash beds range from 18 141 to 936 170 ka indicating that there were multiple cut and fill episodes although the initial onset of aggradation at 1 ma and the overall net incision since ca 500 ka can be linked to tectonic processes at the narrow basin outlet the superimposed 100 kyr cycles of aggradation and incision are best explained by eccentricity driven climate change within these cycles the onset of river incision can be correlated with global cold periods and enhanced humid phases recorded in paleoclimate archives on the adjacent bolivian altiplano whereas deposition occurred mainly during more arid phases on the altiplano and global interglacial periods we suggest that enhanced runoff during global cold phases due to increased regional precipitation rates reduced evapotranspiration or both resulted in an increased sediment transport capacity in the toro basin which outweighed any possible increases in upstream sediment supply and thus triggered incision compared with two nearby basins that record precessional 21 kyr and long eccentricity 400 kyr forcing within sedimentary and geomorphic archives the recorded cyclicity scales with the square of the drainage basin length

shear wave velocity imaging of the avignonet landslide france using ambient noise cross correlation 1 the avignonet landslide affects a 2 by 2 km area covered by clayey deposits this paper presents the use of the seismic ambient noise cross correlation technique to retrieve a 3 d model of the shear wave velocity of the area seismic ambient noise was recorded during 15 days at 13 stations located on the landslide cross correlations computed between the vertical components of all station pairs allow the retrieval of the rayleigh wave green s functions and the estimation of their group velocity dispersion curves in the 1 7 5 hz frequency range at frequencies lower than 1 5 hz the anisotropy of the wavefield strongly influences the apparent rayleigh wave velocities moreover the analysis of the convergence of the cross correlations shows that at frequencies higher than 5 hz the recording time length was not sufficient for the cross correlation to be stable these 1 7 5 hz passive group dispersion curves are complementary to the ones computed from shot signals in the 3 7 hz frequency range a tomographic inversion of the resulting 1 7 7 hz rayleigh wave group dispersion curves provides local group dispersion curves at each cell of the tomographic grid these are inverted with a neighborhood algorithm to retrieve the 3 d model of the landslide despite the complex wave propagation in the eastern part of the landslide and the sparse ray coverage estimated velocities and first order features are in good agreement with previous investigations

waveform joint inversion of seismograms and electrograms for moment tensor characterization of fracking events electromagnetic signals have been observed in association with fracking experiments in the laboratory and in the field we have developed a seismoelectric forward modeling approach to produce synthetic seismograms and electrograms generated by fracking events using the finite element method with perfect matched layer boundary conditions the poroelastodynamic equations are solved in the frequency domain using a formulation based on the solid phase displacement and the pore pressure these results are used to compute the electrical field disturbances of electrokinetic nature three types of electrical signals are generated type i disturbance is associated with the seismic source itself type ii disturbance corresponds to seismoelectric conversions and type iii corresponds to coseismic signals this model is applied to simulate the seismic and electrical signals corresponding to the occurrence of a fracking event in a two layers system we perform a stochastic joint inversion of the seismograms and electrograms using the adaptive metropolis algorithm ama to obtain the posterior probability density functions of the parameters characterizing the seismic source assuming that the velocity model is perfectly known the joint waveform inversion is performed on synthetic noise free data and the ama algorithm is successful in retrieving the true values of the unknown parameters the proposed approach is then tested on the same synthetic data after being contaminated with 15 random noise with respect to the maximum amplitude of the signals the model parameters are better determined for the joint inversion of seismic and electrical data by comparison with the inversion of the seismic time series alone we also propose a deterministic tomographic algorithm that is successful in locating the in situ source current density distribution for types i and ii anomalies from the electrical data alone

the distribution of apparent dose as determined by optically stimulated luminescence in small aliquots of fluvial quartz implications for dating young sediments abstract we noted recently murray et al 1995 that quartz samples taken from in channel fluvial deposits have apparent doses ranging over several orders of magnitude we suggested that these dose distributions are best explained by a mixture of a small number of poorly bleached grains and a larger number of well bleached grains in this paper we examine the distribution of apparent dose in small aliquots each composed of 2000 grains of different particle size fractions 63 90 m 90 125 m 125 180 m 180 212 m 212 250 m diameter from two samples collected from the murrumbidgee river new south wales australia the samples are of known burial age the first being 70 years old and the second being its modern equivalent 0 2 gy the difference in the lowest apparent dose in the two samples is considered to be the result of their different burial times we suggest a method for dating recently deposited

a combined hillslope hydrology stability model for low gradient clay slopes in the italian dolomites abstract the temporal trend of displacement of a landslide on a low gradient clay slope in the italian dolomites as a function of precipitation was simulated with a combined hydrological slope stability model based on groundwater and surficial displacement observations piezometric records and lithological profiles from boreholes suggest the occurrence of preferential groundwater flow through a very permeable top layer of about 1 m thickness which overlies a less permeable compact clay layer penetrated by dead end cracks to simulate groundwater levels in this system a linear reservoir model with two outlets was applied where the upper outlet drains the permeable top layer and the lower outlet drains the dead end cracks in the clay layer the reservoir was assigned a bottom boundary level varying in time this was done to represent an inferred yearly fluctuation of a matric groundwater level due to regional flow which controls the thickness of the unsaturated part of the clay layer absorbing water from the cracks groundwater output from the model was used in a visco plastic stability model to simulate the velocity of landslide movement taking into account a phenomenon of strength regain that occurs in the clays along the slip surfaces calibration and validation on 3 years of groundwater and displacement data showed that both models yield good results thus good estimates of cumulative landslide displacement were obtained as a function of precipitation the general concepts underlying the models offer possibilities for regionalization because from a geological point of view this landslide is typical of many others in the dolomites

fluvial terrace formation along wyoming s laramie range as a response to increased late pleistocene flood magnitudes abstract this study evaluates the potential climatic mechanisms involved in fluvial terrace genesis along wyoming s laramie range we used optical dating methods to determine depositional ages for fluvial fills and to calculate incision rates for terrace suites along two of the region s larger rivers optical ages were determined for the five lowest terrace levels t5 t1 which were deposited at 59 6 39 2 26 3 22 7 and 18 5 ka and incision rates calculated for the two rivers were 0 29 0 34 m kyr over the last 60 kyr the formation of fluvial terraces in the central rocky mountains is commonly attributed to climatically induced changes in sediment input according to most studies relatively low incision rates existed during the colder periods of the pleistocene due to high stream sediment loads but terraces were formed during warmer interglacial periods when reduced sediment availability facilitated higher incision rates however this conceptual model cannot explain the incision records presented here which show that the streams incised 9 10 m in two to three events during oxygen isotope stage 2 but only 1 2 m during the warmer climates of the last 18 5 ka the stream power model we adapted to this setting suggests that late quaternary streams operated under two basic states during the colder conditions of the pleistocene higher flood magnitudes resulted in higher lateral erosion and incision rates however the lower stream discharge common to the warmer interglacial periods resulted in relatively inactive streams when both lateral erosion and incision rates were lowered this model can explain the high incision rates during the cold conditions of oxygen isotope stage 2 the occurrence of terrace fill ages near cold to warm transitions and the apparent acceleration in incision rates toward the end of the last glacial cycle finally this study suggests that terrace fill ages and incision rates are similar for the distally glaciated laramie river nonglaciated sybille creek and the proximally glaciated streams that drain the wind river range this implies that rivers responded synchronously to late quaternary climate changes regardless of their influence by alpine glaciation

triggering mechanism and reactivation probability of loess mudstone landslides induced by rainfall infiltration a case study in qinghai province northwestern china rainfall especially rainstorm is a major factor in inducing loess mudstone landslides and plays an essential role in landslide reactivation the aim of the paper is to study the triggering mechanism and reactivation probability of a loess mudstone landslide induced by rainfall infiltration in qinghai province northwestern china according to the numerical model of elastic plastic mechanics the triggering mechanism of loess mudstone landslides was revealed then the reactivation probability of the potential landslide was evaluated by the combination of the limit equilibrium and monte carlo methods for one thing the relationship between water content and shear strength of media was analyzed based on the mechanical test of materials for another the effects of rainfall conditions were analyzed on the distribution of water content in the aerated zone with the two dimensional coupling model of unsaturated saturated seepage the results show that the shear strength of media is very sensitive to water content because of water rock interaction including hydration and dissolution besides the water content significantly increases at the interface between the loess and mudstone after the rainstorm occurring owing to the permeability heterogeneous of media and topographic feature which leads to the strength deterioration although the whole landslide is stable in the rainstorm conditions its middle part can be reactivated along the original sliding zone with high probability by a geomechanical model of sliding tension therefore the landslide reactivation is controlled by the water sensitivity of media the permeability heterogeneous of media the topographic feature and the original sliding zone especially the original sliding zone this research provides a valuable reference for the occurrence and reactivation of similar landslides

measurement of equivalent doses in quartz from contemporary water lain sediments using optically stimulated luminescence the single aliquot technique and its derivatives are very attractive for the measurement of the very small doses found in young materials because they inherently avoid concerns about low dose non linearity and can offer high precisions a modification is outlined to the single aliquot regeneration and added dose sara protocol mejdahl and botter jensen 1994 quaternary geochronology quaternary science reviews 13 551 5541 to permit its application to sedimentary quartz using the optically stimulated luminescence signal this revised protocol is then used to determine the doses found in several contemporary fluvial sediments and one coastal beach sand thought to be deposi ted by recent wave action two over bank river deposits were both homogeneously well bleached with doses of 0 4 gy although most of the grains in three channel deposits from a range of catchment sizes were also well bleached contamination by a small proportion of very poorly bleached quartz grains prevented the measurement of the dose in the majority the beach deposit was homogeneously bleached and contained a dose of about 0 02 gy it is concluded that over bank sites may provide accurate dates for samples older than a few hundred years but that the heterogeneity of the channel sites limits the accuracy of dates less than a few thousand years

observation guided constitutive modelling for creeping landslides creeping landslides are common in mountainous areas causing significant damage to buildings and infrastructure the major difficulty in modelling of these landslides is the inability of laboratory tests to reproduce adequately the macro behaviour in the creeping soil masses the proposed approach of observation guided constitutive modelling addresses this issue by considering a creeping landslide as a series of macro elements where monitoring of displacements and pore water pressures allows the derivation of suitable constitutive models and their parameters the paper proposes three generalised models describing the behaviour of pore water pressures sliding layer and slip surface which can be adapted to fit the observational data the three models are integrated into the boundary value problem the solution of which helps to explain the evolution of the landslide and to predict its future behaviour using probabilistic approaches when applied to the st moritz brattas landslide in switzerland the calibrated landslide models proved to be successful in describing the complex behaviour of all three distinctive regions of the landslide the paper also explores possible ways for predicting the landslide reaction to extreme rains and forecasting the long term displacement evolution in the vicinity of the leaning tower of st moritz which will be critical for planning its future stabilisation

alluvial sequence in the north piedmont of the chinese tian shan over the past 550 kyr and its relationship to climate change abstract a new division of middle and late pleistocene alluvial sequence in the north piedmont of the chinese tian shan based on geomorphologic stratigraphic and chronologic criteria provides a framework for examining their relationship to climate change during glacial interglacial transitions over the past 550 kyr at least four major alluviation episodes occurred within the piedmont along the major river valleys in this region each episode of alluvial fan deposition morphologically correlates with a major river terrace these correlations create a regionally applicable framework for subdivision of the quaternary alluvial sequence in the study area where seven stepped river terraces are defined our new chronology of this fluvial sequence suggests that following intervals of aggradation three highest river terraces and equivalent alluvial fans were abandoned at 530 ka 300 ka and 10 ka respectively paleosols at the base of the loess sequences that directly overlie the older terraces and fans suggest that episodes of aggradation occurred late in the glacial cycles the subsequent incision that caused abandonment stabilization of these terraces and fans occurred near to glacial interglacial transitions a relatively high degree of synchrony in major river incision events across the piedmont despite disruption by several discrete structure zones with asychronous tectonic activities supports the dominant control exerted by climatic conditions on alluvial deposition and terrace creation during the quaternary across the north piedmont of the chinese tian shan

cosmogenic dating of fluvial terraces fremont river utah absolute dating of river terraces can yield long term incision rates clarify the role of climate in setting times of aggradation and incision and establish the rates of pedogenic processes while surface exposure dating using cosmogenic 10be and 26al would seem to be an ideal dating method the surfaces are composed of individual clasts each with its own complex history of exposure and burial the stochastic nature of burial depth and hence in nuclide production in these clasts during exhumation and fluvial transport and during post depositional stirring results in great variability in clast nuclide concentrations we present a method for dealing with the problem of pre depositional inheritance of cosmogenic nuclides we generate samples by amalgamating many individual clasts in order to average over their widely different exposure histories depth profiles of such amalgamated samples allow us to constrain the mean inheritance to test for the possible importance of stirring and to estimate the age of the surface working with samples from terraces of the fremont river we demonstrate that samples amalgamated from 30 clasts represent well the mean concentration depth profiles show the expected shifted exponential concentration profile that we attribute to the sum of uniform mean inheritance and depth dependent post depositional nuclide production that the depth dependent parts of the profiles are exponential argues against significant post depositional displacement of clasts within the deposit our technique yields 10be age estimates of 60 9 102 16 and 151 24 ka for the three highest terraces corresponding to isotope stages 4 5d and 6 respectively the mean inheritance is similar from terrace to terrace and would correspond to an error of 30 40 ka if not taken into account the inheritance likely reflects primarily the mean exhumation rates in the headwaters of order 30 m ma

geophysical investigation of a large landslide in glaciolacustrine clays in the trieves area french alps abstract slope movements in clay deposits are spread all over the world and result from complex deformation processes including internal strains in the landslide body and slipping along rupture surfaces such mass movements are likely to generate changes in the geophysical parameters characterizing the ground which can be used to map the landslide body in the last decade geophysical techniques have been increasingly used for landslide investigation purposes however the success of any geophysical technique is overall controlled by the existence of a geophysical contrast differentiating the body to be mapped for landslides affecting thick clay materials from soft clay to shale or marl electrical and seismic techniques have been mainly applied in the past in this study we attempt to physically characterize the deformation within a large slide avignonet affecting laminated clays which were deposited in a glacially dammed lake during the wurm period clay deposits which cover an area of 300 km2 south of grenoble french alps and have a maximum thickness of 200 m overlay compact alluvial layers and marly limestone of mesozoic age piezometric data at avignonet show that the water table is very shallow implying that the slide developed in saturated clay several seismic and electrical profiles were performed in order to tentatively correlate the variations of p wave vp velocity s wave velocity vs and electrical resistivity with geotechnical data and morphological observations in such saturated and fine material it turned out that only the s wave velocity exhibits significant variations with the displacement rates and the morphological features vs values at shallow depth were found to be inversely correlated with displacement rates measured by gps with a division by at least a factor of 2 between the zones unaffected and strongly deformed by the landslide these results suggest that vs mapping could provide valuable information on the deformation state of the clay material and that the evolution of vs with time could be used as an indicator for characterizing the landslide activity in the subsurface including the evolution into a flow

cosmogenic 36cl and 10be ages of quaternary glacial and fluvial deposits of the wind river range wyoming we measured cosmogenic 36 cl in 56 samples from boulders on moraines and fluvial terraces in the vicinity of the wind river range wyoming we also measured 10 be in 10 of the same samples most of the 10 be ages were in good agreement with the 36 cl ages indicating that rock surface erosion rates were very low the oldest moraine investigated the type sacagewea ridge site yielded only a limiting minimum age of 232 ka the oldest moraines in the type bull lake complex also could be constrained only to 130 ka the main sequence of type bull lake moraines yielded age distributions indicating deposition within the intervals 130 to 100 ka and 120 to 100 ka the best estimates are closer to the upper limits of these ranges and associated uncertainties are in the range of 10 to 15 these uncertainties could permit deposition in either marine isotope stage 6 or stage 5d we found no evidence of glacial deposits dating to marine isotope stage 4 both bull lake age moraines from fremont lake on the opposite side of the wind river range and boulders on a fluvial terrace above the wind river gave age distributions very similar to that of the second oldest bull lake advance ca 130 to 100 ka the distribution of boulder ages for pinedale moraines at bull lake indicated deposition between 23 and 16 ka nearly identical to the distribution of 10 be ages previously reported for the type pinedale moraines at fremont lake

the evolution of a terrace sequence along the yellow river huanghe in hequ shanxi china as inferred from optical dating abstract investigations of river terraces are often seriously hindered by difficulties in dating the formation of terraces using conventional and well established methods such as 14c dating in this paper recently developed optical dating techniques were applied to a yellow river terrace sequence in the hequ area shanxi province china based on field investigations four terraces were identified systematic sampling for optical dating was carried out on these terrace deposits the single aliquot regenerative dose method was used to determine equivalent dose by analyzing the degree of bleaching of fluvial samples maximum and minimum optical ages were obtained for these samples the minimum optical dates obtained are geomorphologically and stratigraphically consistent with each other suggesting that the dates are reliable the formation ages of the four terraces are 3 4 10 20 25 30 and 90 ka respectively on the basis of these optical dates the geomorphological evolution of the terrace sequence was established and the factors affecting the terrace development discussed

a view on some hydrological triggering systems in landslides abstract in this paper different types of hydrological triggering systems for debris flows shallow and deeper landslides are described the generation of surface run off and high peak discharges in first order alpine catchments is an important triggering mechanism for debris flows failure conditions in shallow landslides can occur when at a critical depth which is determined by the cohesion of the soil and the slope angle the moisture content in the soil becomes close to saturation resulting in a considerable reduction of soil strength deeper landslides 5 20 m depth are in most cases triggered by positive pore pressures on the slip plane induced by a rising ground water level the assessment of meteorological threshold conditions for shallow landslides 1 2 m needs more detailed meteorological information than for deeper landslides in the analyses of the hydrological triggering systems of deeper landslides the presence of a permeable top layer and fissures has to be taken into consideration

hydrological triggering conditions of landslides in varved clays in the french alps abstract in this paper the meteorological and hydrological conditions are analyzed which trigger shallow and deeper landslides in glacio lacustrine deposits varved or laminated clays in the french alps the hydrological system of these landslides consists of a colluvial cover which supplies water into the fissures of the underlying varved clays from these fissures water can infiltrate more or less horizontally into the silt layers of the varved clays a combined reservoirs model was used to simulate the water fluctuations in the colluvial cover and the fissures both the water level in the fissures and the residence time of water in the fissures are mainly controlled by the amount of water storage in the colluvial cover simulations over the last 25 years show that almost each year the fissures are completely filled with water for several months a year infiltration experiments in the field show that infiltration into the varved clays occurs mainly by horizontal infiltration into the silt laminae calculated infiltration rates from these fissures into the silt layers show that the mean yearly residence time of water in the fissures is not sufficient to fully saturate the clay mass each year it is therefore concluded that the triggering of the landslide movements is mainly controlled by the development of positive pore water pressures in the fissure system and that the rise of pore water pressures induced by the matrix system of the varved clays only plays a minor role the calculations also show that drainage of the colluvial cover is a very efficient measure to stabilize the deeper landslides

on the reactivation of a large landslide induced by rainfall in highly fissured clays abstract the paper discusses the field investigations geotechnical characterization and time evolution of horizontal displacements in a wide landslide the latter triggered by an earthquake occurring in september 2002 is located in sicily and involves a thick body of stiff and highly fissured clays belonging to a varicoloured clay formation in order to characterise the reactivation of landslide mechanisms induced by rainfall a three year monitoring programme 2008 2011 was implemented to measure rain pore water pressures and deep and superficial displacements the monitoring data made it possible to recognize three distinct landslides which evolve at variable rates in different directions within the overall landslide area the landslides were reactivated by the increase in pore water pressures in the period autumn 2009 spring 2010 the data clearly show the mechanical role of pore water pressures in the stability of the slope and point out the dependence of the time evolution of the horizontal displacement on the pore water pressure variation induced by rainfall back analysis carried out on the single landslides confirmed that they are reactivated ones since the residual shear strength is mobilised on the pre existing sliding surfaces the pore water pressure variation and the landslide body displacement rates can be effectively related to 5 month cumulative rainfall by simple models characterised by three parameters these models calibrated on the period october 2009 september 2010 made it possible to predict the horizontal displacement rates in the ensuing time period the displacements forecasted by the model in the period september 2010 may 2011 agree very well with the measured ones

flood alluviation and entrenchment holocene valley floor development and transformation in the british uplands the morphology sedimentary properties and sequence of recent coarse grained flood deposits and earlier holocene alluvial fills were investigated in thinhope burn a small 12 km2 catchment in the northern pennine uplands northern england twenty one large flood events are recorded by distinctive cobble boulder bars sheets and splays and boulder berms and lobes lichenometric analysis showed that all but one of these floods dated from the mid eighteenth century the timing of large floods between 1766 and 1960 corresponds with major hydroclimatic trends evident in northern britain and northwest europe over this period discharge estimates suggest that flood magnitudes have decreased since the mid eighteenth century channel and flood plain metamorphosis in late roman times and in the eighteenth century following major valley floor entrenchment locally as much as 8 m would appear to have been caused by increased runoff and flood magnitude this was linked to a shift to a wetter climate with flow augmented by iron age and roman woodland clearance and drainage of the catchment in more recent times results from this study suggest that current models of longer term holocene and pleistocene valley floor development in the british uplands may need to be re evaluated

space time clustering of seismicity in california and the distance dependence of earthquake triggering 1 using two recent high resolution earthquake catalogs i examine clustering in california seismicity by plotting the average rate of earthquakes as a function of both space and time from target events of m 2 to 5 comparisons between pre and post target event activity can be used to resolve earthquake to earthquake triggering associated with target events of different magnitudes the results are more complicated than predicted by computer simulations of earthquake triggering that begin with background events occurring at random times in particular at least some of the temporal clustering of seismicity at short scales 0 1 to 5 km does not appear to be caused by local earthquake triggering but instead reflects an underlying physical process that temporarily increases the seismicity rate such as is often hypothesized to drive earthquake swarms earthquake triggering for m 4 5 earthquakes is only resolvable in average seismicity rates at times less than about one day and to distances of less than about 10 km and its linear density decreases as r 1 5 to r 2 5 significantly steeper than some previous studies have found

space time landslide predictive modelling abstract landslides are nearly ubiquitous phenomena and pose severe threats to people properties and the environment in many areas investigators have for long attempted to estimate landslide hazard in an effort to determine where when or how frequently and how large or how destructive landslides are expected to be in an area this information may prove useful to design landslide mitigation strategies and to reduce landslide risk and societal and economic losses in the geomorphology literature most of the attempts at predicting the occurrence of populations of landslides by adopting statistical approaches are based on the empirical observation that landslides occur as a result of multiple interacting conditioning and triggering factors based on this observation and under the assumption that at the spatial and temporal scales of our investigation individual landslides are discrete point events in the landscape we propose a bayesian modelling framework for the prediction of the spatio temporal occurrence of landslides of the slide type caused by weather triggers we build our modelling effort on a log gaussian cox process lgcp by assuming that individual landslides in an area are the result of a point process described by an unknown intensity function the modelling framework has two stochastic components i a poisson component which models the observed random landslide count in each terrain subdivision for a given landslide intensity i e the expected number of landslides per terrain subdivision which may be transformed into a corresponding landslide susceptibility and ii a gaussian component used to account for the spatial distribution of the local environmental conditions that influence landslide occurrence and for the spatio temporal distribution of unobserved latent environmental controls on landslide occurrence we tested our prediction framework in the collazzone area umbria central italy for which a detailed multi temporal landslide inventory covering the period from before 1941 to 2014 is available together with lithological and bedding data we subdivided the 79 km2 area into 889 slope units sus in each su we computed the mean and standard deviation of 16 morphometric covariates derived from a 10 m 10 m digital elevation model for 13 lithological and bedding attitude covariates obtained from a 1 10 000 scale geological map we computed the proportion of each thematic class intersecting the given su we further counted how many of the 3 379 landslides in the multi temporal inventory affect each su and grouped them into six periods we used this complex space time information to prepare five models of increasing complexity our baseline model mod1 carries the spatial information only through the covariates mentioned above it does not include any additional information about the spatial and temporal structure of the data and it is therefore equivalent to the predominantly used landslide susceptibility model in the literature the second model mod2 is analogous but it allows for time interval specific regression constants our next two models are more complex in particular our third model mod3 also accounts for latent spatial dependencies among neighboring sus these are inferred for each of the six time intervals to explain variations in the landslide intensity and susceptibility not explained by the thematic covariates by contrast our fourth model mod4 accounts for the latent temporal dependence separately for each su disregarding neighboring influences ultimately our most complex model mod5 contextually features all these relations it contains the information carried by morphometric and thematic covariates six time interval specific regression constants and it also accounts for the latent temporal effects between consecutive slope instabilities at specific sus as well as the latent spatial effects between adjacent sus we also show that the intensity is strongly related to the aggregated landslide area per su because of this our most complex model largely fulfills the definition of landslide hazard commonly accepted in the literature at least for this study area we quantified the spatial predictive performance of each of the five models using a 10 fold cross validation procedure and the temporal predictive performance using a leave one out cross validation procedure we found that mod5 performed better than the others we then used it to test a novel strategy to classify the model results in terms of both landslide intensity and susceptibility which provides more information than traditional susceptibility zonations for land planning and management hereafter we use the term traditional simply to refer to the majority of modelling procedures in the literature we discuss the advantages and limitations of the new modelling framework and its potential application in other areas making specific and general hazard and geomorphological considerations we also give a perspective on possible developments in landslide prediction modelling and zoning we expect our novel approach to the spatio temporal prediction of landslides to enhance the currently limited ability to evaluate landslide hazard and its temporal and spatial variations we further expect it to lead to better projections of future landslides and to improve our collective understanding of the evolution of complex landscapes dominated by mass wasting processes under multiple geophysical and weather triggers

initiation and evolution of gullies along the shoreline of lake huron over one hundred gullies are deeply incised into algonquin bluff along the eastern shoreline of lake huron aerial photographs between 1930 and 1992 were used to measure temporal changes in area and length of a sample of forty four gullies regression analysis shows that gully area and length have increased in a linear fashion and that gully initiation occurred in the nineteenth century gully initiation coincides with deforestation and settlement of the area surface drainage was redirected into drainage ditches concentrating the flow and enhancing gully erosion natural processes associated with climatic fluctuations are probably insufficient to cause gully initiation but may contribute to ongoing gully expansion

numerical modeling of fluvial strath terrace formation in response to oscillating climate many river systems in western north america retain a fluvial strath terrace rec ord of discontinuous downcutting into bedrock through the quaternary their importance lies in their use to interpret climatic events in the headwaters and to determine long term incision rates terrace formation has been ascribed to changes in sediment supply and or water discharge produced by late quaternary climatic fluctuations we use a one dimensional channel evolution model to explore whether temporal variations in sediment and water discharge can generate terrace sequences the model includes sediment transport vertical bedrock erosion limited by alluvial cover and lateral valley wall erosion we set limits on our modeling by using data collected from the terraced wind river basin two types of experiments were performed constant period sinusoidal input histories and variable period inputs scaled by the marine 18 o rec ord our simulations indicate that strath terrace formation requires input variability that produces a changing ratio of vertical to lateral erosion rates straths are cut when the channel floor is protected from erosion by sediment and are abandoned and terraces formed when incision can resume following sediment cover thinning high sediment supply promotes wide valley floors that are abandoned as sediment supply decreases in contrast wide valleys are promoted by low effective water discharge and are abandoned as discharge increases widening of the valley floors that become terraces occurs over many thousands of years the transition from valley widening to downcutting and terrace creation occurs in response to subtle input changes affecting local divergence of sediment transport capacity formation of terraces lags by several thousand years the input changes that cause their formation our results suggest that use of terrace ages to set limits on the timing of a specific event must be done with the knowledge that the system can take thousands of years to respond to a perturbation the incision rate calculated in the field from the lowest terrace in these systems will likely be higher than the rate calculated by using older terraces because the most recent fluvial response in the field is commonly downcutting associated with declining sediment input since the last glacial maximum this apparent increase in incision rates is observed in many river systems and should not necessarily be interpreted as a response to an increase in rock uplift rate

late quaternary stream piracy and strath terrace formation along the belle fourche and lower cheyenne rivers south dakota and wyoming abstract stream piracy substantially affected the geomorphic evolution of the missouri river watershed and drainages within including the little missouri cheyenne belle fourche bad and white rivers the ancestral cheyenne river eroded headward in an annular pattern around the eastern and southern black hills and pirated the headwaters of the ancestral bad and white rivers after 660 ka the headwaters of the ancestral little missouri river were pirated by the ancestral belle fourche river a tributary to the cheyenne river that currently drains much of the northern black hills optically stimulated luminescence osl dating techniques were used to estimate the timing of this piracy event at 22 21 ka the geomorphic evolution of the cheyenne and belle fourche rivers is also expressed by regionally recognized strath terraces that include from oldest to youngest the sturgis bear butte and farmingdale terraces radiocarbon and osl dates from fluvial deposits on these terraces indicate incision to the level of the bear butte terrace by 63 ka incision to the level of the farmingdale terrace at 40 ka and incision to the level of the modern channel after 12 9 ka similar dates of terrace incision have been reported for the laramie and wind river ranges hypothesized causes of incision are the onset of colder climate during the middle wisconsinan and the transition to the full glacial climate of the late wisconsinan pinedale glaciation incision during the holocene of the lower cheyenne river is as much as 80 m and is 3 to 4 times the magnitude of incision at 63 ka and 40 ka the magnitude of incision during the holocene might be due to a combined effect of three geomorphic processes acting in concert glacial isostatic rebound in lower reaches 40 m a change from glacial to interglacial climate and adjustments to increased watershed area resulting from piracy of the ancestral headwaters of the little missouri river

mechanism and failure process of qianjiangping landslide in the three gorges reservoir china the qianjiangping landslide is a large planar rock slide which occurred in july 14 2003 shortly after the water level reached 135 m in the three gorges reservoir china the landslide destroyed 4 factories and 129 houses took 24 lives and made 1 200 people homeless field investigation shows that the contributing factors for the landslide are the geological structure of the slope the previous surface of rupture the water level rise and continuous rainfall in order to reveal the mechanism and failure process of the landslide numerical simulation was conducted on qianjiangping slope before sliding based on the characteristics and the engineering conditions of the landslide the topography and the geological profiles of qianjiangping slope before sliding is reconstructed the seepage field of qianjiangping slope before sliding was simulated with the geostudio software the results show that ground water table rises and bends to the slope during the rise of water level and the slope surface becomes partially saturated within the period of continuous rainfall using the ground water table obtained above the failure process of qianjiangping slope is simulated with the flac3d software the results demonstrate that the shear strain increment displacement and shear failure area of the slope increased greatly after the water level rose and continuous rained and the landslide was triggered by the combined effect both of water level rise and continuous rainfall the development of shear strain increment displacement and shear failure area of the slope shows that the landslide was retrogressive in the lower part of the slope and progressive in the upper part of the slope

environmental history and tephrostratigraphy at carp lake southwestern columbia basin washington usa sediment cores from carp lake provide a pollen record of the last ca 125 000 years that helps disclose vegetational and climatic conditions from the present day to the previous interglaciation 120 133 ka the core also contained 15 tephra layers which were characterised by electron microprobe analysis of volcanic glass shards identified tephra include mount st helens ye 3 69 ka mazama ash bed 7 54 ka mount st helens layer c 35 50 ka an unnamed mount st helens tephra 75 150 ka the tephra equivalent of layer e at pringle falls oregon 218 ka and an andesitic tephra layer similar to that at tulelake california 174 ka ten calibrated radiocarbon ages and the ages of mount st helens ye mazama ash and the unnamed mount st helens tephra were used to develop an age depth model this model was refined by also incorporating the age of marine oxygen isotope stage is boundary 4 5 73 9 ka and the age of is 5e 125 ka the justification for this age model is based on an analysis of the pollen record and lithologic data the pollen record is divided into 11 assemblage zones that describe alternations between periods of montane conifer forest pine forest and steppe the previous interglacial period is 5e supported temperate xerothermic forests of pine and oak and a northward and westward expansion of steppe and juniper woodland compared to their present occurrence the period from 83 to 117 ka contains intervals of pine forest and parkland alternating with pine spruce forest suggesting shifts from cold humid to cool temperate conditions between 73 and 83 ka a forest of oak hemlock douglas fir and fir was present that has no modern analogue it suggests warm wet summers and cool wet winters cool humid conditions during the mid wisconsin interval supported mixed conifer forest with douglas fir and spruce the glacial interval featured cold dry steppe with an expansion of spruce in the late glacial xerothermic communities prevailed in the early holocene when temperate steppe was widespread and the lake dried intermittently the middle holocene was characterised by ponderosa pine forest and the modern vegetation was established in the last 3900 yr when ponderosa pine douglas fir fir and oak were part of the local vegetation 2000 elsevier science b v all rights reserved

incision and morphologic evolution of an alluvial channel recovering from hydraulic mining sediment hydraulic gold mining in the sierra nevada california produced such a large volume of sediment from 1853 to 1884 that channels could not carry a substantial proportion of the delivered sediment the lower bear river aggraded as much as 5 m and underwent a major avulsion during the 1870s channel morphology continues to respond to these changes more than 100 years after the cessation of most hydraulic mining textures of mine tailings and older alluvium are contrasted and channel incision and channel shape changes from 1930 to 1985 are documented unlike the yuba and sacramento rivers the lower bear river had not returned to pre mining base levels by 1950 as sediment loads decreased nor were incision rates or morphological change governed by reduced sediment loads below dams built in 1928 and in the mid 1960s channel stability was due to resistance of a cohesive stratum on the channel bed an episode of channel down cutting was instigated by a moderately large flood in december 1955 that pierced the cohesive layer and was sustained through the 1970s by moderate magnitude floods the 1955 flood did not directly erode large volumes of sediment but it destabilized the channel allowing smaller floods to erode the channel at an accelerated rate episodic channel bed incision is contrasted to progressive morphologic changes cross section shape narrowed and deepened steadily from 1930 through the mid 1970s as the channel was superimposed onto cohesive older alluvium progressive deepening set up a positive feedback that ensured the ultimate penetration of the paved bed channel morphologic readjustment from the avulsion thus was both progressive and episodic

beryllium 10 dating of the duration and retreat of the last pinedale glacial sequence accurate terrestrial glacial chronologies are needed for comparison with the marine record to establish the dynamics of global climate change during transitions from glacial to interglacial regimes cosmogenic beryllium 10 measurements in the wind river range indicate that the last glacial maximum marine oxygen isotope stage 2 was achieved there by 21 700 700 beryllium 10 years and lasted 5900 years ages of a sequence of recessional moraines and striated bedrock surfaces show that the initial deglaciation was rapid and that the entire glacial system retreated 33 kilometers to the cirque basin by 12 100 500 beryllium 10 years

application of geophysical measurements for assessing the role of fissures in water infiltration within a clay landslide trieves area french alps rainfall and its consequences are usually considered as the major factor triggering slope instabilities within clay deposits the link between rainfall water infiltration and landslide activity may be complex and comprehensive sets of data are still necessary to understand how water infiltrates in cohesive material on unstable slopes made of fine grained sediments gravitational deformation generates superficial shear ruptures and tension fissures whose continuous opening could be amplified by shrinkage during dry periods this fissure network at the surface can be very dense and strongly controls the water infiltration process however it remains difficult to assess the fissure evolution at depth and its eventual relationship with shallow slip surfaces this work presents the results of a geophysical study which aimed to characterize the fissures that are observed along the unstable clay slopes of the trieves area french alps the site was first investigated combining geomorphological analysis drilling borehole logging geotechnical tests and geophysical experiments this investigation evidenced the presence of at least three rupture surfaces at 5 10 15 and 42 m with a water flow at the second one in a second step permanent instruments were installed piezometers and soil water content probes results indicate high water infiltration velocities down to the water table located at 2 5 m depth that are likely to be linked with sub vertical preferential paths such as fissures geophysical parameters electrical resistivity s wave velocities and rayleigh waves attenuation were monitored geophysical results suggest that fissures are permanently open that they serve as preferential infiltration paths and that they can reach at least a depth of 2 m the methods employed in this research put forward that the system of imbricated fissures drains water from the surface down to the shallow slip surfaces at 5 and 10 15 m this work highlights the role of fissures network in water infiltration in the numerous clay landslides of the trieves area copyright 2011 john wiley sons ltd

pleistocene incision rates in the western united states calibrated using lava creek b tephra the lava creek b ash bed erupted from the yellowstone caldera ca 0 64 ma provides a datum for measuring long term fluvial incision west of the mississippi river the ash is widely preserved due to its substantial volume broad initial dispersal and the aggrading environment into which the ash fell drainages incised soon after lava creek b deposition isolating the ash from fluvial erosion and preserving it in fill terraces calculated rates of incision since ca 0 60 ma range from 2 to 30 cm k y 1 rates are high in most areas near the rocky mountains and downstream along rivers draining mountainous terrain and are lowest east of the high plains and along the snake river incision rates along many rivers decrease downstream rates of downcutting increased in the late pleistocene along several major rivers indicating that climate change altered sediment budgets regional and temporal data suggest that fluvial incision records increased middle and late pleistocene runoff from the southern rocky mountains rather than epeirogenic uplift but regional rock uplift cannot be excluded as a significant factor

episodic late quaternary slopewash deposition as recorded in colluvial aprons southeastern wyoming abstract colluvial aprons found along fluvial terraces of the laramie river and sybille creek in southeastern wyoming are interpreted as late quaternary slopewash deposits each apron studied contained multiple buried soils interpreted to indicate that slopewash activity was episodic and short lived and was followed by relatively long periods of landscape stability and soil development apron deposits were described and subsequently correlated based on their internal stratigraphy and their relative degree of soil development optical dating was used to chronologically constrain periods of slopewash deposition and based on 17 optical ages taken from five aprons aggradation occurred at 65 56 16 0 12 9 11 8 8 1 7 3 5 0 and 1 7 ka several of these events correspond with climatic transitions such as the termination of heinrich event 1 the onset and termination of the younger dryas and the 8 2 ka event suggesting that apron aggradation was driven by changes in climatic regime although either increased aridity or a change in precipitation regime could result in increased erosion of terrace scarps apron aggradation events do not correlate with regional records of aridity instead periods of increased precipitation intensity and or frequency that occur during climatic transitions most likely drive apron aggradation events

phreatic line calculation and stability analysis of slopes under the combined effect of reservoir water level fluctuations and rainfall rainfall and reservoir water level fluctuations are the main external factors of landslides in the three gorges reservoir area to improve the analysis of slope stability under the combined effect

variations of lateral bedrock erosion rates control planation of uplifting folds in the foreland of the tian shan nw china fluvial planation surfaces such as straths commonly serve as recorders of climatic and tectonic changes and are formed by the lateral erosion of rivers a process that remains poorly understood here we present a study of kilometer wide fluvially eroded low relief surfaces on rapidly uplifting folds in the foreland of the southwestern tian shan a combination of field work digital elevation model analysis and dating of fluvial deposits reveals that despite an arid climate and rapid average rock uplift rates of 1 3 mm yr rivers cut extensive 1 2 km wide surfaces with typical height variations of 2 6 kyr the extent of this beveling varies in space and time such that different beveling episodes affect individual structures between times of planation beveled surfaces are abandoned incised and deformed across the folds in a challenge to models that link strath cutting and abandonment primarily to changes in river incision rates we demonstrate that lateral erosion rates of antecedent streams crossing the folds have to vary by more than 1 order of magnitude to explain the creation of beveled platforms in the past and their incision at the present day these variations do not appear to covary with climate variability and might be caused by relatively small much less than an order of magnitude changes in sediment or water fluxes it remains uncertain in which settings variations in lateral bedrock erosion rates predominate over changes in vertical erosion rates therefore when studying fluvial planation and strath terraces variability of both lateral and vertical erosion rates should be considered

recent seismicity and crustal stress field in the lucanian apennines and surrounding areas southern italy seismotectonic implications abstract we analyzed the instrumental seismicity of southern italy in the area including the lucanian apennines and bradano foredeep making use of the most recent seismological data base available so far p and s wave arrival times recorded by the italian national seismic network rsnc operated by the istituto nazionale di geofisica e vulcanologia ingv were re picked along with those of the saptex temporary array deployed in the region in the period 2001 2004 for some events located in the upper val d agri we also used data from the eni agip oil company seismic network we examined the seismicity occurred during the period between 2001 and 2006 considering 514 events with magnitudes m 2 0 we computed the v p v s ratio obtaining a value of 1 83 and we carried out an analysis for the one dimensional 1d velocity model that approximates the seismic structure of the study area earthquakes were relocated and for well recorded events we also computed 108 fault plane solutions finally using 58 solutions the most constrained we computed regional stress field in the study area earthquake distribution shows three main seismic regions the westernmost lucanian apennines characterized by high background seismicity mostly with shallow hypocenters the easternmost below the bradano foredeep and the murge with deeper and more scattered seismicity and finally the more isolated and sparse seismicity localized in the sila range and in the offshore area along the northeastern calabrian coast focal mechanisms computed in this work are in large part normal and strike slip solutions and their tensional axes t axes have a generalized ne sw orientation the denser station coverage allowed us to improve hypocenters determination compared to those obtained by using only rsnc data for a better characterization of the crustal and subcrustal seismicity in the study area

dating fluvial terraces by 230th u on pedogenic carbonate wind river basin wyoming abstract reliable and precise ages of quaternary pedogenic carbonate can be obtained with 230th u dating by thermal ionization mass spectrometry applied to carefully selected milligram size samples datable carbonate can form within a few thousand years of surface stabilization allowing ages of quaternary deposits and surfaces to be closely estimated pedogenic carbonate clast rinds from gravels of glacio fluvial terraces in the wind river basin have median concentrations of 14 ppm u and 0 07 ppm 232th with median 230th 232th 270 making them well suited for 230th u dating horizons as thin as 0 5 mm were sampled from polished slabs to reduce averaging of long 105 yr and sometimes visibly discontinuous depositional histories dense translucent samples with finite 230th u ages preserve within rind stratigraphic order in all cases ages for terraces wr4 167 000 6 400 yr and wr2 55 000 8600 yr indicate a mean incision rate of 0 26 0 05 m per thousand years for the wind river over the past glacial cycle slower than inferred from cosmogenic nuclide dating terrace wr3 which formed penecontemporaneously with the final maximum glacial advance of the penultimate rocky mountain bull lake glaciation has an age of 150 000 8300 yr indicating that it is broadly synchronous with the penultimate global ice volume maximum

long term monitoring of ulf electromagnetic fields at parkfield california 1 electric and magnetic fields in the 10 4 1 0 hz band were monitored at two sites adjacent to the san andreas fault near parkfield and hollister california from 1995 to 2007 a data window 2002 2005 enclosing the 28 september 2004 m6 parkfield earthquake was analyzed to determine if anomalous electric or magnetic fields or changes in ground conductivity occurred before the earthquake the data were edited removing intervals of instrument malfunction leaving 875 days in the 4 year period frequent spikelike disturbances were common but were not more frequent around the time of the earthquake these were removed before subsequent processing signal to noise amplitude spectra estimated via magnetotelluric processing showed the behavior of the ultralow frequency fields to be remarkably constant over the period of analysis these first order plots make clear that most of the recorded energy is coherent over the spatial extent of the array three main statistical techniques were employed to separate local anomalous electrical or magnetic fields from the dominant coherent natural fields transfer function estimates between components at each site were employed to subtract the dominant field and look deeper at the residual fields the data were decomposed into principal components to identify the dominant coherent array modes and the technique of canonical coherences was employed to distinguish anomalous fields which are spatially broad from anomalies which occur at a single site only and furthermore to distinguish anomalies present in both the electric and magnetic fields from those present in only one field type standard remote reference apparent resistivity estimates were generated daily at parkfield a significant seasonal component of variability was observed suggesting local distortion due to variations in near surface resistance in all cases high levels of sensitivity to subtle electromagnetic effects were demonstrated but no effects were found that can be reasonably characterized as precursors to the parkfield earthquake

fluvial terrace formation in the eastern fenwei basin china during the past 1 2 ma as a combined archive of tectonics and climate change abstract the key to understanding the fluvial response to climate change and surface uplift is a thorough distinguishing between their roles in terrace formation previous studies have tended to attribute the fluvial behavior of deposit incision alternation to climate cyclicity a preliminary explanation is proposed here for terrace formation in the eastern part of the fenwei basin china the observed fluvial terrace sequence was developed by the yellow river deeply downcutting into the emei platform which was uplifted within the eastern fenwei basin and therefore it probably records the tectonic history of this platform on the basis of the magnetostratigraphy and optically stimulated luminescence osl dating a ca 1 2 ma chronology was established for this terrace sequence pedostratigraphic analysis of the loess deposits accumulated on each tread reveals that the terrace deposits are overlain immediately by a paleosol bed suggesting that the abandonment of these terraces due to fluvial incision occurred at the transitions from glacial to interglacial climates the glacial interglacial climate cycle probably has a temporal control on the fluvial behavior of deposit incision alternation even though the yellow river develops in the subsiding fenwei basin the terrace generation may be sporadic and in the form of unusual stacked pattern before the emei platform was uplifted within the eastern fenwei basin the terrace staircases however formed in synchrony with glacial interglacial climate cycles since this platform began to uplift in the late middle pleistocene this result indicates that uplift may be necessary in large terrace staircase genesis it can force the river system to downcut deeply enough during climatic transitions to separate terrace levels adequately favoring the generation and subsequent preservation of the terrace treads the terrace sequence of the yellow river in the eastern fenwei basin therefore can be considered as a combined archive of climate change and local tectonic activity

upper crustal structure seismicity and pore pressure variations in an extensional seismic belt through 3 d and 4 d vp and vp vs models the example of the val d agri area southern italy 1 we use local earthquake tomography and background seismicity to investigate static and transient features of the crustal velocity structure in the val d agri southern apennines italy one of the regions in central mediterranean with the highest seismogenic potential the upper crust is dominated by two broad high velocity anticlines of the buried apulia carbonate platform ramping on two parallel high angle thrusts interpreted as preexisting inverted normal faults the deep core of the anticlines consists of very high vp up to 6 9 km s and low vp vs rocks suggesting the involvement of the apulian crystalline basement in the apennine belt these results provide valuable constraints on the apennine belt tectonic evolution supporting a thick skinned interpretation for the pliocene terminal phase of the compressional tectonics the geometry of the val d agri quaternary basin is controlled by these inherited compressive features whereas the presently active extensional tectonics barely reworked the structure we find inconsistency between the structure of the apulia carbonate platform and the location and geometry of the quaternary normal faults mapped at the surface this suggests either the immaturity of the normal faults or their secondary role in accommodating the extension we observe spatiotemporal 4 d changes of vp and vp vs models defining transient variations of pore fluid pressure in the upper crust a strong change in the vp vs ratio heralds a raise in the seismicity rate that can be related to large water level changes in a nearby artificial lake this evidence is consistent with a mechanism of reservoir induced seismicity by fluid pressure increase and pore pressure diffusion the 4 d velocity variations are confined in the shallow portion of the upper crust 3 6 km depth where fluids are stored in a highly fractured medium pore pressure fluctuations can affect the strength of fault segments favoring seismicity rate changes along the active faults and possibly promoting large future earthquakes

geophysical applications of electrokinetic conversion in volume 1 of geophysics 1936 r r thompson of humble oil and refining company proposed that the coupling of seismic and electrical energy can be used as an exploration tool subsequent efforts were directed toward using electric field antennas as geophones small scale studies concluded that antennas are not as sensitive as conventional geophones and their response is highly variable depending on the local soil conditions by 1959 martner and sparks of pan american petroleum reported in geophysics a systematic study of seismoelectric coupling using explosives at various depths their results were the first to show that the conversion of seismic to electromagnetic energy at the water table could be detected using surface antennas no studies have systematically explored the full potential of electroseismic methods using the same level of experimental sophistication used in seismic exploration

seismomagnetic effects from the long awaited 28 september 2004 m 6 0 parkfield earthquake precise measurements of local magnetic fields have been obtained with a differentially connected array of seven synchronized proton magnetometers located along 60 km of the locked to creeping transition region of the san andreas fault at parkfield california since 1976 the m 6 0 parkfield earthquake on 28 september 2004 occurred within this array and generated coseismic magnetic field changes of between 0 2 and 0 5 nt at five sites in the network no preseismic magnetic field changes exceeding background noise levels are apparent in the magnetic data during the month week and days before the earthquake or expected in light of the absence of measurable precursive deformation seismicity or pore pressure changes obser vations of electric and magnetic fields from 0 01 to 20 hz are also made at one site near the end of the earthquake rupture and corrected for common mode signals from the ionosphere magnetosphere using a second site some 115 km to the northwest along the fault these magnetic data show no indications of unusual noise before the earthquake in the ulf band 0 01 20 hz as suggested may have preceded the 1989 ml 7 1 loma prieta earthquake nor do we see electric field changes similar to those suggested to occur before earthquakes of this magnitude from data in greece uni form and variable slip piezomagnetic models of the earthquake derived from strain displacement and seismic data generate magnetic field perturbations that are con sistent with those observed by the magnetometer array a higher rate of longer term magnetic field change consistent with increased loading in the region is apparent since 1993 this accompanied an increased rate of secular shear strain observed on a two color edm network and a small network of borehole tensor strainmeters and increased seismicity dominated by three m 4 5 5 earthquakes roughly a year apart in 1992 1993 and 1994 models incorporating all of these data indicate increased slip at depth in the region and this may have played a role in the final occurrence of the 28 september 2004 m 6 0 parkfield earthquake the absence of electric and magnetic field precursors for this and other earthquakes with m 5 7 3 elsewhere in the san andreas fault system indicates useful prediction of damaging earthquakes seems unlikely using these electromagnetic data

a major seismogenic fault in a silent area the castrovillari fault southern apennines italy summary large historical earthquakes in italy define a prominent gap in the pollino region of the southern apennines geomorphic and palaeoseismological investigations in this region show that the castrovillari fault cf is a major seismogenic source that could potentially fill the southern part of this gap the surface expression of the cf is a complex 10 13 km long set of prominent scarps trenches across one scarp indicate that at least four surface faulting earthquakes have occurred along the cf since late pleistocene time each producing at least 1 m of vertical displacement the length of the fault and the slip per event suggest m 6 5 7 0 for the palaeoearthquakes preliminary radiocarbon dating coupled with historical considerations imply that the most recent of these earthquakes occurred between 380 bc and 1200 ad and probably soon after 760 ad no evidence for this event has been found in the historical record we estimate a minimum recurrence interval of 1170 years and a vertical slip rate of 0 2 0 5 mm yr for the cf which indicates that the seismic behaviour of this fault is comparable to other major seismogenic faults of the central southern apennines the lack of mention or the mislocation of the most recent event in the historical seismic memory of the pollino region clearly shows that even in italy which has one of the longest historical records of seismicity a seismic hazard assessment based solely on the historical record may not be completely reliable and shows that geological investigations are critical for filling possible information gaps

dating fluvial terraces with and profiles application to the wind river wyoming abstract fluvial strath terraces provide a record of river incision and the timing of climatic perturbations to the fluvial system dating depositional surfaces like terraces that are older than the range of 14 c however is difficult we employ a cosmogenic radionuclide crn profile technique that addresses a major problem of crn dating on such surfaces nuclide inheritance by measuring 10 be and 26 al profiles we constrain the exposure age and the mean crn inheritance for the deposit the crn profile also yields a self check on the assumptions underlying the method we report our attempts to date terraces along the wind river wy like many sequences of western north american fluvial terraces these are inferred to reflect oscillation between glacial and interglacial conditions in the headwaters previous dating of some of these terraces and the associated terraces and glacial deposits makes this a unique location to compare dating methods dates from five sites along the bull lake glacial correlative terrace wr 3 are 118 125 ka which agrees with dates on bull lake age moraines and independent age estimates on the terrace and is consistent with the model of terrace glacial relationship crn inheritance is significant and highly variable requiring it be considered despite the additional sampling complexity assuming all inheritance in wr 3 deposits arises during exhumation in the headwaters we obtain minimum mean rates of exhumation of 13 130 m my for the source rocks alternatively assuming the crns are inherited during clast transport the time of fluvial transport from source to terrace is 10 ka it increases downstream and is lower for sand than cobbles the crn ages for older terraces wr 7 300 ka and wr 15 510 ka are lower by 50 than previous estimates based on tephrochronology the most plausible explanation is eolian deflation of a once thicker loess cover on the terrace surfaces mean thicknesses of loess of 0 5 1 5 m are required to reconcile these concentrations of crn with the previous estimates of age difficulty in dating the older terraces emphasizes that geologic caution independent estimates of age and multiple sample sites should still be part of dating depositional surfaces with crns even when employing the inheritance correction technique

26al and10be dating of late pleistocene and holocene fill terraces a record of fluvial deposition and incision colorado front range cosmogenic 26al 10be and 14c dating of fluvial fill terraces in steep canyons of the colorado front range provides a temporal framework for analysing episodic aggradation and incision results from boulder canyon show that terrace heights above the modern channel grade can be divided into 1 bull lake 100 ka 20 15 m above grade 2 pinedale 32 10 ka 15 4 m above grade and 3 holocene age 15 m above grade record bull lake deposition well preserved terraces of pinedale age suggest that the range of terrace height above grade reflects short term fluctuations in the river profile during periods of rapidly changing stream load and power net river incision apparently occurred during transitions to interglacial periods soil development and stratigraphic position along with limited cosmogenic and 14c dating suggest that 130 ka terraces in boulder canyon correlate with the louviers alluvium and that 32 to 10 ka fills in the canyon correlate with the broadway alluvium on the adjacent high plains late pleistocene incision rates 0 15 m ka 1 along boulder canyon exceed pre late pleistocene incision rates and are higher than middle to late pleistocene incision rates 0 04 m ka 1 on the high plains this study provides an example of how modern geochronologic techniques allow us to understand better rivers that drain glaciated catchments copyright 2002 john wiley sons ltd

application of a two step cluster analysis and the apriori algorithm to classify the deformation states of two typical colluvial landslides in the three gorges china several extensive landslides have occurred in the vicinity of the three gorges reservoir since its initial impoundment in june 2003 a reduction of the landslide risk is essential for the safety and security of lives and property in the region this study analyses the deformation states of two typical colluvial landslides the baijiabao and laoshewo landslides using 6 years of monitoring data a two step cluster analysis and the apriori algorithm the landslide displacement versus time curves exhibit step like patterns and the landslide deformation is highly correlated with fluctuations in the reservoir level and seasonal precipitation to determine different types of landslide deformation the monthly displacement curves of the colluvial landslides are classified into three types using a two step cluster analysis initial deformation constant deformation and rapid deformation five driving factors were selected as the antecedents for the apriori algorithm to obtain rules that describe the relationships between the landslide deformation and the influential parameters these factors include the cumulative precipitation over the previous month the maximum daily precipitation during the current month changes in the reservoir level over the previous month cumulative increases in the reservoir level and the average reservoir level during the current month the analytical results were validated by comparing them with observed landslide deformation characteristics using three measurement standards support confidence and lift the results show that the combined method of a two step cluster analysis with the apriori algorithm can effectively model the landslide deformation states that are associated with the baijiabao and laoshewo landslides moreover this method may serve as a potential reference for deformation analyses of colluvial landslides in the three gorges

an engineering site investigation using non invasive geophysical approach subsurface geological formation is essential to validate design assumptions for the construction of deep engineering structures especially in the weathered terrains the geological formation can be delineated using resistivity values through an electrical survey however the subsurface resistivity alone is ambiguous to interpret the subsurface geological units as part of an ongoing investigation to select the key methods towards this end an integrated geophysical survey through a combination of electrical resistivity tomography ert induced polarization ip magnetic method and joint profile method jpm was carried out in a weathered terrain of south huizhou china resistivity ip and magnetic data were obtained using a variety of survey parameters subsurface resistivity was calibrated with upfront boreholes lithology to constrain geological formation into four discrete layers such as topsoil cover with resistivity 2 3257 m highly weathered layer having resistivity 2 636 m partly weathered layer with resistivity range 448 1204 m and unweathered bedrock having resistivity 791 116 497 m the integration of ert with ip magnetic and jpm delineated four faults namely f1 f2 f3 and f4 and several localized fractures the weathered layer fractures and faults were marked as the weakest zones for engineering projects whereas the unweathered fresh bedrocks were identified as the most appropriate locations for the construction of deep structures in the study area the weakest zones unsuitable for engineering structures were delineated as the most appropriate places of groundwater occurrence in the studied area revealed by low resistivity ranging from 2 to 1204 m and overlapped by low chargeability less than 14 8 ms this non invasive geophysical approach suggests the most suitable locations highly significant not only for the future construction of engineering structures but also the exploitation of groundwater resources in the investigated area

mechanical and electrical response due to fluid pressure equilibration following an earthquake 1 the mechanical and electrical response in a uniform porous crust are determined following a shear dislocation earthquake on an internal slip surface a uniform crust is studied because many exact analytical relations hold between the various response fields in this case the initial stress field that is created immediately following the earthquake subsequently relaxes through time as the fluid pressure equilibrates by fluid flow maps of the electric field generated due to the fluid flow electrokinetic coupling are presented using conservative estimates of the various parameters involved electric fields significantly larger than the diurnal magnetotelluric fields are generated quantitative results for how various components of the stress tensor change due to the fluid equilibration are also presented the coulomb stress can easily change by 100 and more in the months following an earthquake due to the fluid pressure equilibration

aseismic transient driving the swarm like seismic sequence in the pollino range southern italy tectonic earthquake swarms challenge our understanding of earthquake processes since it is difficult to link observations to the underlying physical mechanisms and to assess the hazard they pose transient forcing is thought to initiate and drive the spatio temporal release of energy during swarms the nature of the transient forcing may vary across sequences and range from aseismic creeping or transient slip to diffusion of pore pressure pulses to fluid redistribution and migration within the seismogenic crust distinguishing between such forcing mechanisms may be critical to reduce epistemic uncertainties in the assessment of hazard due to seismic swarms because it can provide information on the frequency magnitude distribution of the earthquakes often deviating from the assumed gutenberg richter relation and on the expected source parameters influencing the ground motion for example the stress drop here we study the ongoing pollino range southern italy seismic swarm a long lasting seismic sequence with more than five thousand events recorded and located since october 2010 the two largest shocks magnitude m w 4 2 and m w 5 1 are among the largest earthquakes ever recorded in an area which represents a seismic gap in the italian historical earthquake catalogue we investigate the geometrical mechanical and statistical characteristics of the largest earthquakes and of the entire swarm we calculate the focal mechanisms of the m l 3 events in the sequence and the transfer of coulomb stress on nearby known faults and analyse the statistics of the earthquake catalogue we find that only 25 per cent of the earthquakes in the sequence can be explained as aftershocks and the remaining 75 per cent may be attributed to a transient forcing the b values change in time throughout the sequence with low b values correlated with the period of highest rate of activity and with the occurrence of the largest shock in the light of recent studies on the palaeoseismic and historical activity in the pollino area we identify two scenarios consistent with the observations and our analysis this and past seismic swarms may have been passive features with small fault patches failing on largely locked faults or may have been accompanied by an active largely aseismic release of a large portion of the accumulated tectonic strain those scenarios have very different implications for the seismic hazard of the area