paraglacial rock slope stability glaciation and deglaciation along with their associated climatic and non climatic processes modify slope stresses and influence slope stability paraglacial slope failures are those that are a part of or influenced by the transition from glacial conditions to non glacial conditions gravitational failure of rock slopes is a primary and dominant process of slope evolution in mountainous terrain and is the subject of this paper which 1 reviews the approaches taken for researching paraglacial rock slope failure patterns and processes 2 summarises the spatial and temporal patterns of post glacial failures 3 assesses the factors influencing slope stability during glaciation and deglaciation 4 explores some of the applications of paraglacial research and 5 highlights some of the outstanding issues to be resolved and provides recommendations for terminology relating to paraglacial slope processes

seismic site amplification induced by topographic irregularity results of a numerical analysis on 2d synthetic models abstract this study concerns the evaluation of seismic site effects and their relation to the local topographical characteristics of a slope the seismic amplification sa on the free surface is calculated by a numerical model using the finite elements fe method synthetic models by utilized in the fe analysis represent a slope with an inclination ranging from 10 to 41 at the crest and valley of the slope the models were considered horizontal and indefinite the site effects were calculated on the free surface in several nodal points the input motion used in the analysis was a sv seismic wave with variable frequency between 0 5 and 32 hz the seismic site analysis confirmed that in absence of sediments ground motion is more amplified at the upper slope break than in other points of the model in regard to seismic amplification vs the frequency we can affirm that seismic amplification reaches its maxima in the band 4 16 hz and with slope angle value computed at the highest degree it is also clear that a nonlinear seismic amplification response in the crest and valley zone while sa would seem to have a linear response in other zones we propose an empirical method to estimate the sa in the regular slope far from the crest and valley zone

10be exposure ages of a rock avalanche and a late glacial moraine in alta valtellina italian alps abstract a rock avalanche deposit was investigated in order to understand the chronological evolution of geological hazards and to evaluate the interaction of the triggering geodynamic processes in the valley val viola italian alps the deposit is situated west of the alpe dosde in a permafrost area with deep seated gravitational deformations dsgd along a tectonic line based on its geomorphologic context the rock avalanche was first interpreted as a result of slope stress release without exact timing this hypothesis was tested by measuring the 10 be exposure date of quartz from one boulder from the rock avalanche the age of 7430 460 years places the event in the early holocene the timing of the last deglaciation was constrained using the inner late glacial moraine of a moraine doublet in the valley alpe dosde situated at an altitude between 2140 and 2120 m a s l west of the rock avalanche the 10 be concentrations of quartz yield minimum exposure ages of 11 480 670 and 10 850 820 years different proposals for potential triggering factors of the rock avalanche include a melting of the local valley glacier and slope stress release in the val viola likely to play a minor role as trigger because of the time delay between the deglaciation and the rock avalanche event more likely are b enhanced crustal seismicity induced by post glacial regional isostatic glacial rebound coupled with tectonic stress or and c climate conditions with higher temperatures around 7430 460 years resulting in an upwards movement of the permafrost limit and destabilization of the rock walls

thick and fast sedimentation in a pleistocene fiord lake of british columbia canada the central interior plateau of british columbia canada is dissected by numerous elongate glacially overdeepened lake basins akin to coastal fiords an air gun seismic reflection investigation 242 km of trackline of okanagan lake 120 km long 3 5 km wide shows that the pleistocene sediment fill is up to 792 m thick and that bedrock has been excavated by repeated pleistocene glacial erosion to nearly 650 m below sea level the depth of bedrock incision below the surrounding plateau is more than 2000 m exceeding that of the grand canyon in arizona the total volume of sediment infill within the narrow trenchlike basin is more than 90 km 3 and several lines of evidence suggest that this fill accumulated rapidly during a single phase of glaciolacustrine sedimentation during late wisconsin deglaciation of the region after 15 ka similar fiord lake basins up to 100 km long are common in the interior of british columbia if the data from okanagan are representative these basins may represent a major previously unrecognized component of the total glacial sediment flux to the ocean overdeepening below sea level and the focusing of large volumes of glacial sediment and meltwater into such basins are of considerable glaciologic significance and may record the fast unstable flow of ice streams during deglaciation of the cordilleran ice sheet

an exact solution for effects of topography on free rayleigh waves an exact solution for the effects of topography on rayleigh wave amplification is presented the solution is obtained by incorporating conformal mapping into complex variable stress functions developed for free rayleigh wave propagation in an elastic half space with a flat upper surface results are presented for free rayleigh wave propagation across isolated symmetric ridges and valleys it is found for wavelengths that are comparable to ridge widths that horizontal rayleigh wave amplitudes are amplified at ridge crests and that vertical amplitudes are strongly reduced near ridge crests relative to horizontal and vertical amplitudes of free rayleigh waves in the flat case horizontal amplitudes are strongly deamplified at valley bottoms relative to those for the flat case for rayleigh wavelengths comparable to valley widths wave amplitudes in the symmetric ridges and valleys asymptotically approach those for the flat case with increased wavelengths increased ridge and valley widths and with horizontal distance from and depth below the isolated ridges and valleys also prograde particle motion is predicted near crests of narrow ridges and near the bottoms of narrow valleys finally application of the theory at two sites known for topographic wave amplification gives a predicted surface wave amplification ratio of 3 80 at the ridge center for a frequency of 1 0 hz at robinwood ridge in northern california and a predicted surface wave amplification ratio of 1 67 at the ridge center for the same frequency at the cedar hill nursery site at tarzana in southern california

exhaustion and steady state models for predicting landslide hazards in the canadian rocky mountains abstract the temporal distribution of landslides can be evaluated by steady state and exhaustion models the probability of landsliding remains constant through time in the steady state model but the probability decreases in the exhaustion model as more slopes fail rock sliding down bedding surfaces on overdip slopes exhausts hazardous sites to leave stable dipslope landforms in kananaskis country in the canadian rocky mountains the distribution of rock slides in this area can be better explained by the exhaustion model than by the steady state model

the role of fluvial and glacial erosion in landscape evolution the ben ohau range new zealand a morphometric comparison of valleys has been made for the ben ohau range in the central southern alps of new zealand the range is undergoing rapid tectonic transport and uplift the humid north of the range is a glacial trough and arete landscape with a temperate glacial climate the dry south has rounded divides and plateau remnants dissected by fluvial valleys assuming that space time substitution allows today s spatial valley form transition to represent evolutionary stages in valley development the tectonic history allows time constraints to be placed on the rate of transition to an alpine glacial landscape morphometric change has been quantified using hypsometric curves and distance elevation plots of cirque and valley floor altitudes ancestral fluvial valleys have less concave long profiles but are stepped at altitude owing to the presence of high level cirques and remnant plateau surfaces and possess a low proportion of land area at low elevation increasing glacial influence is manifest as smoother more deeply concave long profiles and u shaped cross profiles associated with a higher proportion of the land area at lower elevation the full morphological transition has involved up to 2 4 km of vertical denudation over the 4 ma lifetime of the mountain range of which 80 per cent would have occurred by preglacial fluvial erosion combining the trajectory of tectonic transport with reconstructed glaciation limits and climatic history it is indicated that about 200 ka of temperate glacial erosion produces recognizable trough and areete topography mean and modal relief increase where glacial activity is confined to cirques but decrease when trough incision by ice becomes established as a dominant process in the landscape 1997 by john wiley sons ltd

a search for direct hydrocarbon indicators in the formby area it has been proposed that the high frequency low amplitude magnetic anomalies found over some hydrocarbon deposits are due to long term microseepage of hydrocarbons into iron rich sedimentary roof rocks with subsequent precipitation of diagenetic magnetite or pyrrhotite at or near the water table aerogeophysical data sets comprising both magnetic and gamma ray spectrometer measurements over the formby oil field lancashire u k have been analysed for hydrocarbon related anomalies detailed ground magnetic traverses were also made to investigate some of the aeromagnetic anomalies no hydrocarbon induced magnetic anomalies were detected the majority of the high frequency events occurring in the aeromagnetic data correlated with cultural features others were attributed to artefacts of the data processing in particular there were no extensive areas of high frequency low amplitude anomalies as might be expected from authigenic magnetic minerals borehole chippings from inside and outside the oil field were examined high magnetic susceptibilities were due to contamination during drilling magnetite which was identified by mineralogical analysis was found to be of detrital origin if any diagenetic magnetic material was present it was in such small quantities as to be insignificant the oil field did not possess a characteristic gamma ray spectrometric signature anomalies were found to be related to hydrological conditions and to the distribution of surficial deposits attempts to suppress the influence of the drift geology had only limited success it is concluded that the effectiveness of high resolution aeromagnetic onshore surveys for direct hydrocarbon detection has yet to be established in particular the anomaly found over the formby oil field was caused by the cumulative effect of borehole casing similar cultural contamination by oil field equipment may explain some of the anomalies discovered over hydrocarbon deposits in north america it is also unlikely that the spectrometric method can be applied diagnostically in any but the most simple and drift free geological environments

effects of the vertical component of ground shaking on earthquake induced landslide displacements using generalized newmark analysis abstract the popular newmark method calculates the cumulative permanent displacement of a landslide having a known critical acceleration as it is subjected to the effects of an earthquake acceleration time history for an infinite slope this method considers ground acceleration as parallel to the slope and downslope which results in two important limitations 1 vertical downslope acceleration only is considered 2 the ratio of vertical to horizontal acceleration only depends on the inclination of the slope surface in the model developed herein the ground acceleration is not parallel to the slope the ratio of vertical to horizontal acceleration called the vertical accelerometric parameter depends on the seismic situation of the slope magnitude earthquake source distance style of faulting and the vertical acceleration acts alternately upslope and downslope application of the principles of classical mechanics leads to the pseudo static factor of safety and hence to the seismic horizontal critical acceleration of a potential landslide which depends not only on its static factor of safety geometry geotechnical properties and hydrogeologic conditions but also on its seismic situation it is shown that newmark s model is in fact a particular case of the general model and in most cases the seismic horizontal critical acceleration results from vertical upslope acceleration and is lower than newmark s critical acceleration as a consequence the displacements d resulting from the model developed herein will be greater than the displacements dn calculated from newmark s approach for some potential landslides the difference d dn is considerable and results in significant consequences in the seismic stability analysis of the affected slopes which justifies the importance of the effects of vertical ground shaking

the importance of earthquake induced landslides to long term slope erosion and slope failure hazards in seismically active regions abstract this paper describes a general method for determining the amount of earthquake induced landsliding that occurs in a seismically active region over time this determination can be used as a quantitative measure of the long term hazard from seismically triggered landslides as well as a measure of the importance of this process to regional slope erosion rates and landscape evolution the method uses data from historical earthquakes to relate total volume of landslide material dislodged by an earthquake to the magnitude m and seismic moment m0 of the earthquake from worldwide data a linear regression relation between landslide volume v and m0 is determined as v m0 1018 9 0 13 where v is measured in m3 and m0 is in dyn cm to determine the amount of earthquake generated landsliding over time this relation is combined with data on seismic moment release for a particular region which may be derived from either earthquake history or fault slip data the form of the m0 v relation allows the rate of production of earthquake induced landslides over time to be determined from total rate of seismic moment release without regard to the distribution of individual events thus simplifying and generalizing the determination application of the method to twelve seismically active regions with areas ranging from 13 275 to 2 308 000 km2 shows that erosion rates from earthquake induced landslides vary significantly from region to region of the regions studied the highest rates were determined for the island of hawaii new zealand western new guinea and the san francisco bay region of california significantly lower rates were determined for iran tibet the sierra nevada great basin region of california and central japan for the time period from 715 ad to the present intermediate rates were determined for peru southern california onshore california turkey and central japan for the time period from 1586 ad to the present to determine the relative long term importance of seismically triggered landslides these erosion rates are compared to erosion rates calculated for other slope processes and to rates calculated from fluvial sediment discharge comparisons with other slope processes indicate that earthquake induced landslides are the predominant agents of slope erosion on the island of hawaii in the san francisco bay region and in western new guinea for hawaii the san francisco bay region and sierra nevada great basin region of california the erosion rates calculated for earthquake induced landslides also exceed the regional erosion rates calculated from fluvial sediment discharge

the effect of glaciation on the intensity of seismic ground motion seismicity is known to contribute to landscape denudation through its role in earthquake triggered slope failure but little is known about how the intensity of seismic ground motions and therefore triggering of slope failures may change through time topography influences the intensity of seismic shaking generally steep slopes amplify shaking more than flatter slopes and because glacial erosion typically steepens and enlarges slopes glaciation may increase the intensity of seismic shaking of some landforms however the effect of this may be limited until after glaciers retreat because valley ice or ice caps may damp seismic ground motions two dimensional numerical models flac 6 0 were used to explore how edifice shape rock stiffness and various levels of ice inundation affect edifice shaking intensity the modelling confirmed that earthquake shaking is enhanced with steeper topography and at ridge crests but it showed for the first time that total inundation by ice may reduce shaking intensity at hill crests to about 20 50 of that experienced when no ice is present the effect is diminished to about 80 95 if glacier ice level reduces to half of the mountain slope height in general ice cover reduced shaking most for the steepest sided edifices for wave frequencies higher than 3 hz and when ice was thickest and the rock had shear stiffness well in excess of the stiffness of ice if rock stiffness is low and shear wave velocity is similar to that of ice the presence of ice may amplify the shaking of rock protruding above the ice surface the modelling supports the idea that topographic amplification of earthquake shaking increases as a result of glacial erosion and deglaciation it is possible that the effect of this is sufficient to have influenced the distribution of post glacial slope failures in glaciated seismically active areas copyright 2012 john wiley sons ltd

seismically induced rock slope failures resulting from topographic amplification of strong ground motions the case of pacoima canyon california abstract the 1994 northridge earthquake mw 6 7 triggered extensive rock slope failures in pacoima canyon immediately north of los angeles california pacoima canyon is a narrow and steep canyon incised in gneissic and granitic rocks peak accelerations of nearly 1 6 g were recorded at a ridge that forms the left abutment of pacoima dam peak accelerations at the bottom of the canyon were less than 0 5 g suggesting the occurrence of topographic amplification topographic effects have been previously suggested to explain similarly high ground motions at the site during the 1971 mw 6 7 san fernando earthquake furthermore high landslide concentrations observed in the area have been attributed to unusually strong ground motions rather than higher susceptibility to sliding compared with nearby zones we conducted field investigations and slope stability back analyses to confirm the impact of topographic amplification on the triggering of landslides during the 1994 earthquake our results suggest that the observed extensive rock sliding and falling would have not been possible under unamplified seismic conditions which would have generated a significantly lower number of areas affected by landslides in contrast modelling slope stability using amplified ground shaking predicts slope failure distributions matching what occurred in 1994 this observation confirms a significant role for topographic amplification on the triggering of landslides at the site and emphasises the need to select carefully the inputs for seismic slope stability analyses

observed relation of soil magnetic susceptibility and soil gas hydrocarbon analyses to subsurface hydrocarbon accumulations magnetic susceptibility ms studies on soils over 19 oil and gas fields showed anomalously large amounts of diagenetic magnetic minerals in shallow depth samples in about 89 of the cases tested soil ms anomalies were compared with soil gas hydrocarbon ghc anomalies over 12 oil and gas fields including several stratigraphic traps and one gas storage reservoir samples were collected along the same profiles six examples are presented with detailed data listings our goal is to test the utility of soil magnetic susceptibility and soil gas hydrocarbons as petroleum prospecting methods we emphasize statistical evaluation of anomalies and their empirical correlation with producing areas and leads identified by other geochemical geological or geophysical data for direct comparison of anomaly strengths data are expressed statistically in terms of the appropriate background mean and standard deviation soil ms and soil ghc data complement each other providing better guidance to productive areas than either data set alone when used in an integrated exploration program their combined positive evidence of hydrocarbon presence under prospects could result in fewer dry holes than when drilling with structural information only

integration of geologic geochemical and geophysical data of the cement oil field oklahoma using spatial array processing geologic geochemical and geophysical measurements were made at the cement oil field oklahoma test site using airborne and spaceborne sensors coupled with ground based data collection the data collected include 1 airborne gamma ray spectrometry 214bi 208tl 40k and total intensity channels 2 low altitude aeromagnetic profiles 3 precision gravity measurements 4 images from the landsat multispectral scanner mss systems and u 2 photography and 5 geologic and topographic maps in order to reduce analyze display and correlate the information it was necessary to transform the data from vector space to raster space a two dimensional image array with fixed resolution and array dimension with the data in array form spatial array processing techniques were applied to 1 correct geometrically the data for proper registration 2 perform areal interpolation and smoothing 3 display the data as images and 4 perform integration and correlation studies each data set was transforme

a seismologically consistent expression for the total area and volume of earthquake triggered landsliding we present a new seismologically consistent expression for the total area and volume of populations of earthquake triggered landslides this model builds on a set of scaling relationships between key parameters such as landslide spatial density seismic ground acceleration fault length earthquake source depth and seismic moment to assess the model we have assembled and normalized a catalog of landslide inventories for 40 shallow continental earthquakes low landscape steepness causes systematic overprediction of the total area and volume of landslides when this effect is accounted for the model predicts the total landslide volume of 63 of 40 cases to within a factor 2 of the volume estimated from observations r2 0 76 the prediction of total landslide area is also sensitive to the landscape steepness but less so than the total volume and it appears to be sensitive to controls on the landslide size frequency distribution and possibly the shaking duration some outliers are likely associated with exceptionally strong rock mass in the epicentral area while others may be related to seismic source complexities ignored by the model however the close match between prediction and estimate for about two thirds of cases in our database suggests that rock mass strength is similar in many cases and that our simple seismic model is often adequate despite the variety of lithologies and tectonic settings covered this makes our expression suitable for integration into landscape evolution models and application to the anticipation or rapid assessment of secondary hazards associated with earthquakes

differential glacio isostatic uplift of crustal blocks at glen roy scotland abstract detailed measurements of the altitudes of the shorelines of former ice dammed lakes in glen roy and vicinity in the scottish highlands prove erroneous the conventional view that former shorelines in areas affected by glacio isostatic uplift are uniformly tilted and or gently warped the measurements demonstrate differential uplift of blocks of the earth s crust the surfaces of some blocks have no detectable tilt whereas others have gradients up to at least 4 6 m km and are tilted in different directions in three areas 0 7 2 0 km long shorelines are distorted by crustal movements all these areas have landslides attributed to earthquakes that accompanied the release of stress in the area of greatest local distortion three shorelines rose about 3 m above their average altitudes for the immediately surrounding area and a fault scarp was produced possibly these local distortions accompanied catastrophic lake drainage by jokulhlaup analogous to crustal movements associated with man made lakes a relationship between crustal movement and the limit of a glacial advance is demonstrated these findings have implications for other parts of the world affected by glacioisostatic uplift

the little red hill seismic experimental study topographic effects on ground motion at a bedrock dominated mountain edifice the kinematic response of a bedrock dominated mountain edifice to seismic shaking near lake coleridge in the southern alps of new zealand was examined a small elongated and bedrock dominated mountain ridge little red hill was equipped with a seismic array seven earss instruments mark l 4 3d seismometers were installed along the ridge crest the flank and at the base of the 210 m high 500 m wide and 800 m long mountain edifice from february to july 2006 seismic records of local and regional earthquakes were used to provide information on amplification and deamplification effects as well as on the frequency response at different parts on the edifice the ground motion records were analyzed using three different methods comparisons of peak ground accelerations power spectral density analysis and standard spectral ratio analysis time and frequency domain analyses show that site amplification is concentrated along the elongated crest of the edifice where amplifications of up to 1100 were measured relative to the motion at the flat base the field experiment also highlighted the extreme variations in amplification with regard to closely located sites but at contrasting topographic locations theoretical calculations and frequency analyses of field data indicate a maximum response along the ridge crest of little red hill for frequencies of about 5 hz which correlate to wavelengths approximately equal to the half width or height of the edifice the consequence of amplification effects on the stability and degradation of rock masses can be seen areas showing high amplification effects overlap with the spatial distribution of seismically generated block fields at little red hill it is concluded that topography geometry and distance to the seismic source play key roles in causing amplification effects of seismic ground motion and supporting dilation and degradation of rock mass across bedrock dominated mountain edifices

beyond debuttressing mechanics of paraglacial rock slope damage during repeat glacial cycles cycles of glaciation impose mechanical stresses on underlying bedrock as glaciers advance erode and retreat fracture initiation and propagation constitute rock mass damage and act as preparatory factors for slope failures however the mechanics of paraglacial rock slope damage remain poorly characterized using conceptual numerical models closely based on the aletsch glacier region of switzerland we explore how in situ stress changes associated with fluctuating ice thickness can drive progressive rock mass failure preparing future slope instabilities our simulations reveal that glacial cycles as purely mechanical loading and unloading phenomena produce relatively limited new damage however ice fluctuations can increase the criticality of fractures in adjacent slopes which may in turn increase the efficacy of fatigue processes bedrock erosion during glaciation promotes significant new damage during first deglaciation an already weakened rock slope is more susceptible to damage from glacier loading and unloading and may fail completely we find that damage kinematics are controlled by discontinuity geometry and the relative position of the glacier ice advance and retreat both generate damage we correlate model results with mapped landslides around the great aletsch glacier our result that most damage occurs during first deglaciation agrees with the relative age of the majority of identified landslides the kinematics and dimensions of a slope failure produced in our models are also in good agreement with characteristics of instabilities observed in the field our results extend simplified assumptions of glacial debuttressing demonstrating in detail how cycles of ice loading erosion and unloading drive paraglacial rock slope damage

glacio seismotectonics ice sheets crustal deformation and seismicity abstract the last decade has witnessed a significant growth in our understanding of the past and continuing effects of ice sheets and glaciers on contemporary crustal deformation and seismicity this growth has been driven largely by the emergence of postglacial rebound models pgm constrained by new field observations that incorporate increasingly realistic rheological mechanical and glacial parameters in this paper we highlight some of these recent field based investigations and new pgms and examine their implications for understanding crustal deformation and seismicity during glaciation and following deglaciation the emerging glacial rebound models outlined in the paper support the view that both tectonic stresses and glacial rebound stresses are needed to explain the distribution and style of contemporary earthquake activity in former glaciated shields of eastern canada and fennoscandia however many of these models neglect important parameters such as topography lateral variations in lithospheric strength and tectonic strain built up during glaciation in glaciated mountainous terrains glacial erosion may directly modulate tectonic deformation by resetting the orogenic topography and thereby providing an additional compensatory uplift mechanism such effects are likely to be important both in tectonically active orogens and in the mountainous regions of glaciated shields in general the short term response to ice fluctuations is similar to the earth s response to fluctuations in water reservoirs with the subsequent increase or decrease in seismicity which depends on the pre existing stress state when the ice fluctuations occur on the spatial scale and magnitude of the late pleistocene glaciation and deglaciation however the viscoelastic response of the earth especially the mantle causes significant changes in crustal deformation and earthquake activity that is spatially extensive and temporally complex the regions of greatest ice thickness and the regions marginal to the late pleistocene ice sheets indicate the most dramatic evidence of earthquake faulting the mantle response to these large ice mass fluctuations and the change in mass between the oceans and land caused and continues to cause measureable crustal deformation at hundreds of kilometres from the ice margins for both tectonically active and cratonic regions palaeoseismic investigations of late pleistocene and holocene faults are an important tool in evaluating earthquake hazard the predicted response of the earth over this time however is very dependent on the model assumed for most regions far more carefully designed field observations are needed to constrain the existing rheological and ice models

investigating the effect of earthquakes on open pit mine slopes abstract this paper develops a database for studying the circumstances under which dynamic loading of earthquake can cause slope failure in deep open pit mines with a long lifetime the database includes 177 open pit mines hit by earthquake and 95 natural slopes and 37 tailing dams which have been failed by earthquakes both earthquake parameters and geomechanical characteristics involved in each case study are investigated from this information the elements playing role in the earthquake triggered failures in natural slopes and tailing dams are identified and used to indicate conditions that may result in earthquake induced failures in open pit mines the result shows that even though the valley shape geometry and absence of the top weathered layer make open pit mines less prone to earthquake induced failures excessive pore pressure in pit slopes still carries the risk of earthquake triggered failures in open pit slopes only limited numbers of open pit mines have been so far exposed to earthquakes with the same parameters as those causing failure in natural slopes and tailing dams that is the response of open pit mines to higher magnitude shallower and closer earthquakes is still unknown studying the earthquakes that have caused failure in other slopes it is concluded that open pit mines may still experience reportable failures if struck by earthquakes with local depth of less than 40 km epicentral distance of less than 100 km and magnitude of greater than 6 0 the necessity of accounting for seismic loading in slope stability analyses and active dewatering for open pit mines located in seismically active areas are also discussed

slip rate variations on normal faults during glacial interglacial changes in surface loads geologic and palaeoseismological data document a marked increase in the slip rates of the wasatch fault and three adjacent normal faults in the basin and range province during the late pleistocene early holocene epochs the cause of this synchronous acceleration of fault slip and the subsequent clustering of earthquakes during the holocene has remained enigmatic although it has been suggested that the coincidence between the acceleration of slip and the shrinkage of lake bonneville after the last glacial maximum may indicate a causal relationship here we use finite element models of a discrete normal fault within a rheologically layered lithosphere to evaluate the relative importance of two competing processes that affect fault slip postglacial unloading the removal of mass which decreases the slip rate and lithospheric rebound which promotes faster slip we show that lithospheric rebound caused by regression of lake bonneville and deglaciation of adjacent mountain ranges provides a feasible mechanism for the high holocene rates of faulting in the wasatch region our analysis implies that climate controlled changes in loads applied to earth s surface may exert a fundamental control on the slip history of individual normal faults

rock slope failure following late pleistocene deglaciation on tectonically stable mountainous terrain the ages of 31 postglacial rock slope failures rsfs in scotland and nw ireland derived from 89 cosmogenic isotope exposure ages are employed to analyse the temporal pattern of failure and its relationship to the timing of deglaciation rates of glacio isostatic crustal uplift and periods of rapid climate change rsf ages span almost the whole period since ice sheet retreat from 18 2 1 2 ka to 1 7 0 2 ka or from 17 1 1 0 ka to 1 5 0 1 ka depending on the production rate used in 10 be age calculation but catastrophic failure of rock slopes was w4 6 times more frequent prior to w11 7 ka than during the holocene 95 of dated rsfs at sites deglaciated during retreat of the last ice sheet occurred within w5400 years after deglaciation with peak rsf activity 1600e1700 years after deglaciation this time lag is inferred to represent 1 stress release initiated by deglacial unloading leading to 2 time dependent rock mass strength degradation through progressive failure plane development and ultimately 3 to either spontaneous kinematic release or failure triggered by some extrinsic mechanism by contrast 11 dated rsfs at sites reoccupied by glacier ice during the younger dryas stade yds of w12 9e11 7 ka exhibit no clear temporal pattern suggesting that glacial reoccupance during the yds was ineffective in preconditioning a renewed cycle of enhanced rsf activity comparison of timing of individual rsfs with that of deglaciation and rapid warming events at w14 7 ka and w11 7 ka suggests that glacial debuttressing enhanced joint waterpressuresduringdeglaciationandthawofpermafrosticeinrockjointscouldhavetriggeredfailurein only a small number of cases conversely the timing of maximum rsf activity following ice sheet deglaciation corresponds broadly with maximum rates of glacio isostatic crustal uplift suggesting that the two are linked by enhanced seismic activity a seismic failure trigger is consistent with full slope failure at all sites where failure planes are clearly defined our results indicate that numerous rsfs must have occurred in areas that were reoccupied by glacier ice during the yds but have not been identified because runout debris was removed by yds glaciers more generally they provide the first reliably dated body of evidence to support the view that retreat of the last ice sheets in tectonically stable mountainous terrain initiated a period of enhanced rock slope failure due to deglacial unloading and probably lateglacial seismic activity implying that most undated rsfs in such areas are probably of lateglacial or veryearly holocene age they also demonstrate however that a low frequency of rsf activity extended throughout the holocene

impacts of post glacial rebound on landslide spatial distribution at a regional scale in northern iceland skagafjorður in de glaciated areas para glaciation i e the conditioning of landscapes by prior glaciation has often been considered a major predisposing factor in landslide occurrence its consequences have been particularly well identified at a fine scale especially on bedrock jointing hitherto the relative impacts of para glaciation on hillslope dynamics at a regional scale had nevertheless not been quantified statistically we examine skagafjor ur area northern iceland where landslides are widespread at least 108 were mapped in an area of c 3000km2 we compare the role of para glaciation debuttressing influence of post glacial rebound with that of classic factors topography lithology etc in landslide occurrence and location using a spatial analysis based on a chi square test on the one hand the results highlight that landslides are over represented in areas where post glacial rebound was at its maximum with a stronger concentration of landslides in the northern part of the fjord on the other hand the distribution of landslides did not show any clear relationship with the pattern of glacial debuttressing tschuprow coefficient highlights that the influence of post glacial rebound on landslide location is higher than the combined influence of slope gradient curvature or geological structure this result is supported by our initial evidence for the timing of landslides in the area most landslides occurred during the first half of the holocene and a period of hillslope instability was initiated when the post glacial uplift was at its maximum finally the mechanisms that link post glacial rebound and landsliding as well as the geomorphic impacts of landslides are discussed

glacier shrinkage and modeled uplift of the alps 1 present day glacier reduction in the alps estimated from glacier inventories and induced viscoelastic response of a stratified earth s model is responsible for sizable uplift rates patches of 0 4 0 5 mm yr due to ice mass loss of largest ice complexes overprint a characteristic area of slower uplift of 0 1 0 2 mm yr signature of the phenomenon in the whole alpine chain viscous stress relaxation in the lower crust due to glacier mass loss after the end of the little ice age is expected to produce uplift rates of 0 32 mm yr leading to a total viscoelastic response up to 0 8 mm yr our predictions in the western alps show that viscoelastic response to present day glacier shrinkage forms a substantial fraction half of the observed uplift data attempts to constrain the contributions arising from active alpine tectonics and drainage must account for this uplift signal citation barletta v r c ferrari g diolaiuti t carnielli r sabadini and c smiraglia 2006 glacier shrinkage and modeled uplift of the alps geophys res lett 33 l14307 doi 10 1029 2006gl026490

a rugose coral bryozoan association from the lower devonian of nw spain abstract a new rugose coral cystoporate bryozoan association is here described from the devonian of nw spain this is the first evidence of intergrowths between devonian rugose corals and bryozoans in this case bryozoans provided a suitable substrate for the settlement of corals which were subsequently encrusted by the bryozoans the hypothesis of intergrowth between living organisms is supported by the absence of encrustation of the rugose coral calices by the cystoporates we suggest that the association was specific and developed through chemical mediation this symbiosis was facultative for the bryozoans but likely not for the corals the association provided the bryozoan host with additional substrate for encrustation as well as protection from various predators and it allowed the rugose corals to grow in a muddy environment and benefit from the feeding currents of the bryozoans

magnetic forward models of cement oil field oklahoma based on rock magnetic geochemical and petrologic constraints magnetic forward models of the cement oil field oklahoma were generated to assess the possibility that ferrimagnetic pyrrhotite related to hydrocarbon seepage in the upper 1 km of permian strata contributes to aeromagnetic anomalies at cement six bodies having different magnetizations were constructed for the magnetic models based on geology and on petrologic and geochemical results supplemented by rock magnetic measurements of shallow core and outcrop samples the column of rock through which hydrocarbons have passed is divided into three sulfide zones on the basis of pyrrhotite content and the column is capped by a 30 m thick zone that contains ferric oxide minerals formed mainly from oxidized pyrite red beds unaffected by sulfidization as well as a zone of rock depleted in hematite but lacking sulfide surround sulfidic zones the synthetic magnetic profiles are controlled mainly by pyrrhotite bearing strata at depths of 200 500 m the magnetizations of these bodies are calculated from 1 pet

active deformation in the eastern swiss alps post glacial faults seismicity and surface uplift abstract post glacial tectonic faults in the eastern swiss alps occur as single lineaments clusters of faults or extensive fault zones consisting of several individual faults aligned along the same trend the orientation of the faults reflects the underlying lithology and the pre existing structures joints pervasive foliations within these lithologies most post glacially formed faults in the area around chur which undergoes active surface uplift of 1 6 mm year trend e w and cut across alpine and glacial features such as active screes and moraines additionally there are nnw and ene striking faults reactivating pervasive alpine foliations and shear zones based on a comparison with the nodal planes of recent earthquakes e w striking faults are interpreted as active faults because of very short rupture lengths and mismatches of fault location with earthquake distribution magnitude and abundance the faults are considered to be secondary faults due to earthquake shaking cumulative deformation in post or interseismic periods or creep and not primary earthquake related faults the maximum of recent surface uplift rates coincides with the youngest cooling of the rocks according to apatite fission track data and is therefore a long lived feature that extends well into pre glacial times isostatic rebound owing to overthickened crust or to melting of glacial overburden cannot explain the observed surface uplift pattern rather the faults earthquakes and surface uplift patterns suggest that the alps are deforming under active compression and that the aar massif basement uplift is still active in response to ongoing collision

regional patterns of earthquake triggered landslides and their relation to ground motion 1 we have documented patterns of landsliding associated with large earthquakes on three thrust faults the northridge earthquake in california chi chi earthquake in taiwan and two earthquakes on the ramu markham fault bounding the finisterre mountains of papua new guinea in each case landslide densities are shown to be greatest in the area of strongest ground acceleration and to decay with distance from the epicenter in california and taiwan the density of co seismic landslides is linearly and highly correlated with both the vertical and horizontal components of measured peak ground acceleration based on this observation we derive an expression for the spatial variation of landslide density analogous with regional seismic attenuation laws in its general form this expression applies to our three examples and we determine best fit values for individual cases our findings open a window on the construction of shake maps from geomorphic observations for earthquakes in non instrumented regions

a new seismic hazard model for new zealand we present a new probabilistic seismic hazard analysis psha for new zealand an important feature of the analysis is the application of a new method for the treatment of historical distributed seismicity data in psha the psha uses the seismicity recorded across and beneath the country to define a three dimensional grid of a values i e parameter a of a gutenberg richter distribution log n yr a bm in which n yr is the number of earthquakes per year recorded inside each grid cell equal to or greater than magnitude m parameter b and the limiting maximum cutoff magnitude of the gutenberg richter distribution are defined from the surrounding region 14 crustal and 23 subcrustal seismotectonic zones are defined for the country and then smoothed across the boundaries of the zones the methodology therefore combines the modern method of defining continuous distributions of seismicity parameters frankel 1995 frankel et al 1996 with the traditional method of defining large area sources and the associated seismicity parameters e g algermissen et al 1990 the methodology provides a means of including deep subduction zone seismicity in a psha preserves the finer scale spatial variations of seismicity rates across a region avoids the undesirable edge effects produced in the traditional method when adjacent area sources enclose areas of significantly different seismicity rates and also enables parameters most reliably defined at a regional scale parameter b and maximum cutoff magnitude of a gutenberg richter distribution and slip type to be incorporated into the psha the psha combines the modeled seismicity data with geological data describing the location and earthquake recurrence behavior of 305 active faults and new attenuation relationships for peak ground acceleration and spectral acceleration developed specifically for new zealand different attenuation expressions are used for crustal and subduction zone earthquakes the resulting psh maps for a 150 year return period show the highest hazard to occur in the center and southwest of the country in the areas of highest historical crustal and deep subduction zone seismicity in contrast the longer return period maps 475 and 1000 year return period show the highest hazard to occur from the southwest to northeast ends of the country along the faults that accommodate the majority of the motion between the pacific and australian plates the maps are currently being used to revise new zealand s building code which has previously been based on pshas that did not explicitly include individual faults as earthquake sources manuscript received 10 april 2001

timing and periodicity of paraglacial rock slope failures in the scottish highlands abstract many formerly glaciated mountains exhibit a high density of postglacial rock slope failures rsfs in the form of rockslides rock avalanches or deep seated gravitational slope deformations such rsfs are often termed paraglacial as they reflect pre conditioning by glaciation and deglaciation the temporal pattern of paraglacial rsfs is unknown we employ 47 cosmogenic isotope exposure ages obtained for 17 catastrophic rsfs in the scottish highlands to test models of changes in rsf frequency since deglaciation our results show that rsf activity spans almost the entire postglacial period from 17 ka until 1 5 ka and that the periodicity of sampled postglacial rsfs is statistically indistinguishable from a pattern of uniform periodicity 1 ka 1 our data do not conform to proposed models of declining rsf frequency with time elapsed since deglaciation but suggest that the temporal distribution of postglacial rsfs is best described by a combination of rapid response enhanced rsf frequency during or immediately after deglaciation followed by approximately constant periodicity our findings are consistent with near surface fracturing of rock when glacially induced confining stresses are removed causing some failures during or immediately after deglaciation and reducing other slopes to critical conditional stability so that failure is triggered by progressive rock mass weakening or by transient triggering mechanisms neither permafrost degradation thaw of ice in joints nor seismic activity offers a general explanation for triggering scottish rsfs but could be contributory in some cases the quasi constant periodicity inferred for holocene rsfs implies that the probability of rsfs in this seismically quiescent intraplate area has not changed in the past 10 ka and that further though infrequent catastrophic rsfs are likely to occur in the future

the effect of topography on earthquake ground motion a review and new results a brief review of experimental and theoretical results about the effect of topography on seismic motion shows that they are consistent only on a qualitative basis amplification at mountain tops for wavelengths comparable with mountain widths is predicted and observed but the numerical simulations often underestimate the actual observed effects we propose that this disagreement is because current models are not complex enough we therefore computed the response to incident sh waves of a set of different complex configurations that include two dimensional surface topography with or without periodic ridges and subsurface layering the results show that 1 the topographic effect in itself is difficult to isolate from other effects like surface layering and therefore the amplification on top of geomorphologically complex sites cannot be predicted by a priori estimations based solely on topography and 2 the high crest base amplification ratio observed in the field cannot usually be matched even with complex two dimensional structures with incident plane sh waves which suggests that more complex models are needed to incorporate more complex wave fields e g sv surface and three dimensional geologic configurations

influence of surface normal ground acceleration on the initiation of the jih feng erh shan landslide during the 1999 chi chi taiwan earthquake the 1999 chi chi taiwan earthquake triggered numerous landslides throughout a large area in the central range to the east southeast and south of the fault rupture among them are two large rock avalanches at tsaoling and at jih feng erh shan at jih feng erh shan the entire thickness 30 50 m of the mio cene changhukeng shale over an area of 1 km 2 slid down its bedding plane for a distance of about 1 km initial movement of the landslide was nearly purely trans lational we investigate the effect of surface normal acceleration on the initiation of the jih feng erh shan landslide using a block slide model we show that this ac celeration currently not considered by dynamic slope stability analysis methods significantly influences the initiation of the landslide