a tectonic boundary for the southern colorado plateau abstract a tectonic boundary should be defined by changes in tectonic elements tectonic elements would include such parameters as structural style stress orientations volcanism heat flow seismicity and changes in crustal thickness examination of these tectonic elements for the southern colorado plateau suggests that the southwestern part of the physiographic plateau appears to be tectonically part of the basin and range province i therefore propose a boundary at 112 w longitude the locus of seismicity and recent volcanism and also the site of crustal thickening and a change of structural style the tectonic boundary of the southern colorado plateau is suggested to form part of the eastern boundary of the southern basin and range seismotectonic region this seismotectonic region is bounded on the north by the las vegas shear zone nevada seismic zone and has a different stress orientation than the northern basin and range from which it began to evolve separately 13 m y ago the present principal stress orientation of the southern basin and range of arizona appears to be the result of compound movements of the san andreas transform and garlock las vegas shear zone resulting in a shear couple affecting the crust in arizona and an associated ne sw least principal stress orientation

regional scale relief evolution and large landslides insights from geomechanical analyses in the tinee valley southern french alps abstract recurring large rock slope failures of the argentera mercantour massif southern french alps over the past 20 000 years were identified in the field and analyzed using a continuum mechanics approach based on material weakening in a three dimensional finite difference model we compared a mountain slope failure model neglecting the effect of rock strength loss with a model simulating the effect of strength loss and integrating cohesional weakening and frictional strengthening processes the good correspondence between the relative chronology and location of observed and simulated deformations shows that 1 the gradual loss of rock mass strength related to stress release effects following the pleistocene deglaciation can be as long as several thousands of years and 2 the causes and triggering of the present day active landslides are related to this long failure history our study suggests that the episodic nature of massive rock slides can be explained through the gradual development of tensile and shear failure and time dependent strength degradation our numerical model is a good reproduction of large landslides at the regional scale of a mountainous massif

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

post glacial slip history of the sparta fault greece determined by 36cl cosmogenic dating evidence for non periodic earthquakes 1 using 36cl cosmic ray exposure dating we obtained continuous exposure histories for 7 12 m high limestone surfaces at two sites 10 km apart on the sparta normal fault scarp as each major earthquake adds new surface to the cumulative scarp exposing new material to cosmic ray bombardment these exposure histories allow the slip history to be constrained the results show that an earthquake occurred on this fault 2800 300 yr ago we infer that this is the seismic event that destroyed ancient sparta in 464 b c four earlier earthquakes ruptured the sparta fault in the last 13 ka with similar slip amplitudes of about 2 m and with time intervals ranging from 500 yr to 4500 yr the observations also confirm that the sparta scarp is post glacial supporting the hypothesis that similar scarps elsewhere in the mediterranean region have a comparable age the absence of any event since 464 b c could suggest a future event is imminent however the irregularity of earthquake time intervals could also be due to changes of loading with important consequences for the mechanics of continental deformation

do the billecocha normal faults ecuador reveal extension due to lithospheric body forces in the northern andes active compressional and transcurrent structures are widely reported for the entire northern andes whereas there is no clear evidence of extensional tectonics in that region in contrast both active compressional and extensional structures occur extensively in the central andes extensional tectonism in the central andes occurs mainly in high plateaus of large wavelength 100 km and is interpreted to have resulted from the effect of compensated high topography at the lithospheric scale the observation of holocene normal faults on the low wavelength 15 km billecocha high plateau in the northern ecuadorian andes raises a problem could the lithospheric body forces be the cause of the normal faulting in a chain with a mean altitude of 2800 m compared to the central andes where normal faulting is widely distributed across the chain normal faulting on the billecocha plateau is concentrated in a restricted 4 km wide zone in addition normal faulting does not extend further than a few kilometres eastward where compressive structures have been observed considering the local character of the extension body forces at the lithospheric scale cannot be responsible for this normal faulting and thus we can preclude a significant lowering of the magnitude of hmax in the northern andes with respect to the central andes analysis of these normal faults shows that normal faulting occurred between 10 000 yr and 6000 yr b p in addition the relationship between the geometrical parameters vertical throw and rupture length of the major normal fault differs significantly from that given empirically by methods based on scale laws in such a case the billecocha normal faults are unlikely to have a tectonic origin various local processes e g gravity gliding sackung that may be possible are contemplated for triggering the normal faulting in addition a theoretical simple 2 d model is proposed in where local conditions peculiar to the plateau structure glaciation and the surrounding areas are taken into account in this model normal faulting occurs by shearing along the planes of weakness bedding planes in response to the elastic rebound of the fluid saturated plateau which prevailed after the last glaciation

estimating erosion rates and exposure ages with 36cl produced by neutron activation the isotopic composition of water soluble cl extracted from mineral grains in granitic rocks appears to reflect the relative age of debris flow fan surfaces and the erosion rate of bedrock outcrops our data indicate that some granitic landforms are stable landscape elements eroding on the order of meters to tens of meters per million years samples collected from debris flow fan surfaces of three distinct relative ages show the expected increase of model age with time but the 36cl exposure ages for boulders on any particular surface vary by a factor of more than five the method we used for extracting cl was designed to isolate the 35cl n 36cl production pathway and to simplify the chemical preparation of samples such isolation from fluid inclusions allows direct interpretation of measured 36cl cl ratios but requires a model to predict the thermal neutron production and absorption profile below the rock surface using such a model we find good agreement between measured and predicted 36cl cl for eight samples collected below the ground surface as well as consistency between several groups of samples collected near one another using elemental abundance data for 129 granitic rocks we modeled 36cl cl supported by radiogenic neutrons and find that it varies from 4 to 125 10 15 mean 21 18 1 however from the surface to a depth of 10 m thermal neutrons resulting from muon interactions have the potential to generate more 36cl than do radiogenic neutrons the production of 36cl in the subsurface has important implications for surface exposure dating of young low altitude samples collected from moraines and debris flow or alluvial fans especially at ages where erosion of the boulder surface is significant or where the source area for boulders is at altitudes much higher than the landform to be dated

the younger dryas cold interval as viewed from central greenland abstract greenland ice core records provide an exceptionally clear picture of many aspects of abrupt climate changes and particularly of those associated with the younger dryas event as reviewed here well preserved annual layers can be counted confidently with only 1 errors for the age of the end of the younger dryas 11 500 years before present ice flow corrections allow reconstruction of snow accumulation rates over tens of thousands of years with little additional uncertainty glaciochemical and particulate data record atmospheric loading changes with little uncertainty introduced by changes in snow accumulation confident paleothermometry is provided by site specific calibrations using ice isotopic ratios borehole temperatures and gas isotopic ratios near simultaneous changes in ice core paleoclimatic indicators of local regional and more widespread climate conditions demonstrate that much of the earth experienced abrupt climate changes synchronous with greenland within thirty years or less post younger dryas changes have not duplicated the size extent and rapidity of these paleoclimatic changes

paleomagnetic evidence of tertiary tectonic rotation in west texas paleomagnetic samples obtained from rawls formation 26 9 28 3 ma lava flows of bofecillos volcano in west texas give a paleomagnetic pole at lat 76 5 degree n long 348 0 degree e alpha sub 95 9 4 degree n 20 this pole is displaced significantly from north american reference poles of similar age implying a clockwise rotation of 21 3 degree plus minus 8 8 degree it is also consistent with other paleomagnetic data from west texas the authors argue that the discordance is a result of vertical axis crustal rotation in west texas caused by shear deformation that was probably related to basin and range tectonics

stress tensor orientation derived from fault plane solutions in the southwestern alps gephart and forsyth s method has been applied to estimate stress orientations from earthquake fault plane solutions of the southwestern alps a region where the tectonic stress regime is known to be fairly complex fault plane solutions have been either taken from the literature or computed using data from local and regional networks data refer to seismic events of magnitude in the range 2 5 5 3 which occurred in the last decades at depths between 0 and 25 km two zones with a different stress orientation have been identified in the studied area 44 0 45 5 n 6 5 8 5 e the western zone corresponding to the crest of the alpine belt where a high dip maximum compressive stress is found and the eastern zone alps chain to po plain transition characterized by an almost horizontal e w 1 and a nearly vertical 3 hypocenters of earthquakes used for stress inversion lie in the depth ranges 0 15 km and 5 25 km in the western and eastern zones respectively the transition between the two stress domains is very sharp and this is also indicated by space distribution of earthquake individual misfits to the respective stress models the findings of the present study are a good match for tectonic models which assume e w compression derived from the adria europe interaction and producing 1 major thrusting processes in the eastern side of the chain and 2 secondary tensional effects at very shallow depth beneath the alpine belt crest western zone of the area studied in this work

uphill facing antislope scarps in the coast mountains southwest british columbia uphill facing scarps are examined at affliction creek a glacierized area within the meager creek volcanic complex of southwest british columbia scarps occur directly downslope of tension cracks and are considered to have developed from a combination of 1 antithetic movement between partly toppled slices of rock defined by a master joint set dipping into the slope and 2 erosion of the upslope face of each tension crack leaving the downslope face prominent as an antislope scarp a kinematic test for toppling failure is described glacial erosion and rapid glacial downwasting are probable causes of toppling lichenometric data indicate significant scarp development since affliction glacier attained its maximum neoglacial dimensions about 140 yr ago dilatancy is cited as a possible mechanism for scarp stabilization

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

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

slip accumulation and lateral propagation of active normal faults in afar we investigate fault growth in afar where normal fault systems are known to be currently growing fast and most are propagating to the northwest using digital elevation models we have examined the cumulative slip distribution along 255 faults with lengths ranging from 0 3 to 60 km faults exhibiting the elliptical or bell shaped slip profiles predicted by simple linear elastic fracture mechanics or elastic plastic theories are rare most slip profiles are roughly linear for more than half of their length with overall slopes always 0 035 for the dominant population of nw striking faults and fault systems longer than 2 km the slip profiles are asymmetric with slip being maximum near the eastern ends of the profiles where it drops abruptly to zero whereas slip decreases roughly linearly and tapers in the direction of overall aden rift propagation at a more detailed level most faults appear to be composed of distinct shorter subfaults or segments whose slip profiles while different from one to the next combine to produce the roughly linear overall slip decrease along the entire fault on a larger scale faults cluster into kinematically coupled systems along which the slip on any scale individual fault or fault system complements that of its neighbors so that the total slip of the whole system is roughly linearly related to its length with an average slope again 0 035 we discuss the origin of these quasilinear asymmetric profiles in terms of initiation points where slip starts and barriers where fault propagation is arrested in the absence of a barrier slip apparently extends with a roughly linear profile tapered in the direction of fault propagation

landslides triggered by the 1994 northridge california earthquake abstract the 17 january 1994 northridge california earthquake m w 6 7 triggered more than 11 000 landslides over an area of about 10 000 km 2 most of the landslides were concentrated in a 1000 km 2 area that included the santa susana mountains and the mountains north of the santa clara river valley we mapped landslides triggered by the earthquake in the field and from 1 60 000 nominal scale aerial photography provided by the u s air force and taken the morning of the earthquake these mapped landslides were subsequently digitized and plotted in a gis based format most of the triggered landslides were shallow 1 to 5 m thick highly disrupted falls and slides within weakly cemented tertiary to pleistocene clastic sediment average volumes of these types of landslides were less than 1000 m 3 but many had volumes exceeding 100 000 m 3 the larger disrupted slides commonly had runout paths of more than 50 m and a few traveled as far as 200 m from the bases of steep parent slopes deeper 5 m thick rotational slumps and block slides numbered in the tens to perhaps hundreds a few of which exceeded 100 000 m 3 in volume most of these were reactivations of previously existing landslides the largest single landslide triggered by the earthquake was a rotational slump block slide having a volume of 8 10 6 m 3 analysis of the mapped landslide distribution with respect to variations in 1 landslide susceptibility and 2 strong shaking recorded by hundreds of instruments will form the basis of a seismic landslide hazard analysis of the los angeles area

structural constraints on deep seated slope deformation kinematics abstract a significant sackung type deep seated slope gravitational deformation dsgsd was recognised for the first time by the authors in the middle part of valfurva east of bormio rhaetian alps italy the reconstruction of its kinematics age and state of activity is presented through a detailed description of its morphological geomechanical and structural features an integrated multi disciplinary approach was performed to achieve a clear comprehension of the phenomenon field surveys and aero photo interpretation were carried out in order to clarify the structural geological and geomorphological setting in which the dsgsd developed a kinematic conceptual model of the slope deformation was developed through the analysis of morpho structures of their significance and relationships with lithological markers and quaternary deposits after a geomechanical characterisation of the rock mass involved in the slope deformation numerical modelling was performed to verify the hypotheses made on kinematics and driving factors of the phenomenon the sackung affects pre permian metapelites metabasites and marbles belonging to the upper austroalpine basement of the campo nappe as well as late pleistocene and holocene glacial and rock glacier deposits the deformation started after the late wurmian age 15 000 11 000 years b p and continued until few centuries ago not excluding a present day low rate activity deformation consists in a large oblique sagging along a deep confined sliding surface associated with gravitational reactivation of pre existing late alpine and recent tectonic brittle structures leading to the formation of n s and wnw ese trending gravitational morpho structures the evolution of the wnw ese trending system resulting in asymmetric trenches led to progressive failure of the lower part of the slope during the last 10 000 years as testified by large paleo landslide accumulations and it is still in progress numerical modelling indicates post glacial unloading as the main triggering factor of the slope deformation the importance of this deep seated slope deformation is enhanced by the occurrence of the 30 mm 3 active ruinon landslide in the lower part of the slope such landslide is subjected to rapid evolution and threatens the valley floor establishing an important risk factor connected to human lives and socio economic activities

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 recent fault scarps of the western alps france tectonic surface ruptures or gravitational sackung scarps a combined mapping geomorphic levelling and 10be dating approach abstract in the western alps some recent scarps were previously interpreted as surface ruptures of tectonic reverse and normal faults that agree with microseismicity and gps measurements our analysis shows that in fact there are hundreds of recent scarps up to 30 m high and 2 1 km long with only pure normal motions they share the same characteristics as typical sackung scarps the scarps are mainly uphill facing parallel to the ridge crests and the contour lines they are relatively short less than 2 1 km with respect to tectonic fault ruptures and organized in swarms they cut screes and relict rock glaciers with a slow commonly 1 mm year average slip rate in the aiguilles grives massif these sackung scarps clearly express the gravitational toppling of sub vertical bedding planes in hard rocks in contrast the belledonne outer crystalline massif exhibits scarps that stem from the gravitational reactivation of conjugate tectonic faults the recent faults extend to about 1600 m beneath the rognier ridge crest but are always above the valley floor the main scarp swarm is 9 2 km long and constitutes the largest sackung ever described in the western alps 10 be dating of a scarp and offset surfaces shows that 4 m slip may have occurred rapidly in less than 3800 years sometimes between the end of the glaciation and 8800 1900 years ago this dating together with the location of some faults far from the deep glacial valleys suggests that sagging might have been triggered by strong earthquakes during a post glacial period of probably enhanced seismicity the belledonne and synclinal median faults just beneath the rognier sackung could have been the sources of this seismicity

widespread extension in the core of the western alps revealed by earthquake analysis the western alps are an active collision belt whose current stress field is inhomogeneous muller et al 1992 we report new seismological data which significantly improve our knowledge of this stress field about 1600 earthquakes which occurred in the western alps during the last 10 years were precisely located and 79 new focal solutions were computed the analysis of this database shows that widespread extension affects all the internal zones of the belt to better constrain the associated stress regime six stress tensors were computed using the gephart and forsyth 1984 method they show that the current tectonics of the western alps are contrasted with close variation in the stress regime transpression to the front of the belt contrasting with extension in the core of the belt the extensional direction is radial to the arcuate geometry of the belt and bounded outboard by the former thrust of the internal zones onto the external zone suggesting extensional reactivation of this inherited crustal discontinuity such widespread extension within the inner part of an actually ongoing collision belt cannot be explained by simple collision related tectonics we propose that intrabelt buoyancy forces such as those produced by a slab retreat or slab break off interfere with the boundary forces driven by the ongoing europe africa convergence

a late holocene deep seated landslide in the northern french pyrenees abstract a very large deep seated landslide dsl in the northern pyrenees with over 1 4 10 9 m 3 was mapped and dated based on sedimentation rates and 10 be terrestrial cosmogenic radionuclide surface exposure cre dating our analysis on the landslide reveals the role of inherited structures in the landslide process and highlighted typical gravitational morpho structures and a small lake trapped at the toe of the landslide head scarp the rate of lake sedimentation 0 86 0 57 mm yr 1 also provided us with the approximate age of the landslide 1106 540 yr the cre dating result highlights two main slope destabilization phases then we discussed the history of dsl activity and its controlling factors information related to historic markers and the absence of particular climate markers and changes during the medieval dark ages point to a single event in ad 1380 due to a major seismic event lavedan earthquake

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

paraglacial gravitational deformations in the sw alps a review of field investigations 10be cosmogenic dating and physical modelling catastrophic deep seated landslides dsl are generally considered to be the result of large slope deformations also known as deep seated gravitational slope deformation dsgsd this paper aims to build a synthesis of multiple studies made in the tinee valley southern french alps to assess the geometrical kinematical mechanical and chronological relationships between these two gravitational processes at the scale of the valley data issued from geological geomorphological and 10be dating indicate a clear geometrical link between dsgsd and dsl occurring at the base of the slope and suggest that gravitational slope evolution began after the glacial retreat 13 ka bp this is supported by the example of the well documented la clapiere slope a continuous evolution process is characterized geometrically and temporally from geomorphic observations and analogue modelling coupling structural geomorphological physical and chronological studies allowed us to propose a four dimensional 4d deformation model mechanically correlated with progressive failure concept the validity and variability of this reference site are discussed at the valley scale taking isola and le pra slope deformation as examples it allows a rough estimation of the state of slope deformation at the valley scale to be constructed and the slope evolution with time to be considered this 4d model could then be considered as a reference for other deep seated gravitational slope deformations in comparable alpine valleys

recent crustal movements in the alpine mediterrane an region analyzed in the swiss alps abstract the most recent results of uplift rates determined by repeated precise levelling are analyzed in terms of geodynamic processes still going on in the region of the alpine mediterranean plate boundary special emphasis is focused on levelling nets in the swiss alps which have been remeasured for the second time a comparison of these geodetic results with geophysical information such as gravity anomalies and explosion seismic results as well as seismicity provides further evidence that these sets of data are interrelated with each other an attempt is made to estimate the strain energy associated with the crustal deformation by introducing first order stress strain relationships

acquisition of water chemistry in a mobile fissured basement massif its role in the hydrogeological knowledge of the la clapiere landslide mercantour massif southern alps france abstract groundwater flowpaths of the la clapiere landslide are studied by chemical and isotopic water analysis and modeling of the landslide springs in our case it appears that sulfate can be taken as a chemical tracer of the different flowpaths on the gneissic slope of la clapiere geochemical modeling explains sulfate concentrations from 0 to 130 mg l by dissolution of sulfurous minerals present in the gneisses such a variability of the concentrations measured in the springs is due to different infiltration paths direct paths through the basement so 4 2 10 60 mg l or indirect path through superficial deposits like screes or fluvio glacial terrains which cover the basement so 4 2 60 130 mg l the high concentrations 600 800 mg l cannot be explained by thermodynamic geochemical simulations and they reveal triassic gypsum dissolution hidden under the studied slope so two main flowpaths are differentiated in the la clapiere landslide 1 flow through low permeable triassic deposits pinched under the foot of the landslide 2 flow through a more permeable fissured basement with different flow paths and consequently with different transit times due to the anisotropic nature of the top and the central part of the landslide

possible late pleistocene faulting in iar west connacht ireland caledonian and hercynian faults in iar connacht have been examined for evidence of quaternary movements dip slip displacements are detected both through preservation of scarps and in areas of greater denudation through morphological offsets the principle sites of this phenomenon are the maum clifden and gabhla shannaveara faults tectonic scarps are distinguished from those due to differential erosion and glacial scour earthquake risk in iar connacht though slight is not non existent

high resolution seismic stratigraphy of glacial to interglacial fill of a deep glacigenic lake lake le bourget northwestern alps france abstract lake le bourget is a deep peri alpine glacial lake originating from the last glacial the wurm the lake has amassed over 250 m of sediment since the last glacial maximum two seismic sparker surveys on the lake revealed the glacial and post glacial sedimentary infill the depth and the morphology of the wurm erosion surface and penetrated the riss wurm interglacial deposits as deep as the underlying riss erosion surface the density of the seismic grid and the high resolution of the data even at greater depths allowed a detailed study of the sedimentary processes and of their evolution throughout the deglaciation five main seismic facies characterise the basin fill they are interpreted as glacial deposits glacio lacustrine sediments proglacial lacustrine fans alluvial fan deltas and authigenic lacustrine drape these occur as a suite of deposits associated with the major lake tributaries and are the result of major changes in sediment supply and style of discharge into the lake the three dimensional facies associations within the basin fill document the history of the basin and its catchment area since the onset of the deglaciation

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

scaling factors for the rates of production of cosmogenic nuclides for geometric shielding and attenuation at depth on sloped surfaces abstract the decrease in rates of production of cosmogenic nuclides occurs because of shielding of cosmic rays by mountains sloped surfaces and local rock formations that block them when a large part of the sky is blocked this correction is large and requires detailed model calculations this paper considers three geometries a rectangular obstruction a triangular obstruction and a sloped surface other geometries can be considered as a combination of these the results are presented in terms of formulas and graphs so that the reader can easily apply them to common field situations any use of cosmogenic nuclides in the study of geomorphic processes or forms must consider factors that introduce variations in the production of nuclides

tectonic geomorphology of the triglav lakes valley easternmost southern alps nw slovenia abstract we present a study on the impact of litho structural setting and neotectonic activity on meso and macro scale relief production in alpine areas the topography of the high alpine triglav lakes valley nw slovenia was studied by means of detailed mapping and stratigraphic study of the valley the triglav lakes valley is characterised by a generally asymmetric transverse e w profile a very steep eastern slope a relatively flat valley and a relatively gentle western slope on the transverse profile the valley floor is essentially flat gently dipping towards the east in the longitudinal cross section however the valley floor is marked by sharply defined fault blocks extending in a w e to nw se direction additionally the highest block elevations 2100 m is in the northern part of the valley the lowest elevations 1600 m in the southern part of the valley our research shows that the triglav lakes valley directly represents the topographic expression of paleogene neogene thrusting and faulting having recorded the following geomorphologic evolutionary stages 1 an oligocene to early miocene w vergent thrusting phase with steep w facing slopes of the eastern part of the valley directly representing the thrusting front and 2 a neogene to present strike slip faulting in nne ssw direction with two bifurcating right lateral strike slip systems we show that the triglav lakes valley almost perfectly mimics the wedge shaped damage zone located between these faults

postglacial tectonics of the scottish glacio isostatic uplift centre new evidence combined with a detailed re evaluation of postglacial fault movements seismic activity and shoreline sequences suggests that the period of deglaciation and the early holocene was more seismically active than the mid to late holocene it is proposed that the large scale lateral displacements formerly proposed can not be justified rather all postglacial fault movements appear to be limited to metre scale vertical movements along pre existing fault lines in addition it is argued that the younger dryas ice advance may have produced localised crustal redepression but not the more widespread impact formerly proposed both tectonic and postglacial rebound stresses however may be needed to explain the contemporary seismotectonics of the scottish highlands

are icelandic rock slope failures paraglacial age evaluation of seventeen rock slope failures in the skagafjorður area based on geomorphological stacking radiocarbon dating and tephrochronology in iceland there are numerous rock slope failures especially in the tertiary basaltic formations of the northern eastern and northwestern regions the temporal pattern of rock slope failures is fundamental for understanding post glacial events in the skagafjor ur district central northern iceland 17 rock slope failures were investigated to determine the age of their occurrence a geomorphic survey was carried out to identify and characterize landform units both on the rock slope failures and in their immediate vicinity in this coastal area we used geomorphological stacking which included the relationship between rock slope failures and raised beaches caused by glacial isostatic rebounds the chronology of which was established in previous studies we searched for depressions on the rock slope failures to then excavate a series of pits and map the stratigraphy the resulting stratigraphic framework was then validated using i radiocarbon dating of wood remains and ii tephrochronology both of which were complemented by age depth model calibration the results confirm that all the rock slope failures potentially occurred before the boreal 8 ka while 94 occurred before the preboreal 10 ka they all potentially occurred after the glacial retreat following the maximal ice extent and the preboreal more precisely 11 of them potentially occurred between the preboreal and the first half of the holocene this study demonstrates the relationship between the deglaciation and destabilization of slopes during the paraglacial phase debuttressing decompression glacial isostatic rebound seismic activity etc which are also controlling factors favouring landsliding but are difficult to identify for each individual rock slope failure

cosmic ray exposure cre dating in a wet tropical domain late quaternary fan emplacements in central sulawesi indonesia accurate chronological records are critical for studying the alluvial fan sequences emplaced during local global climatic changes but in general there are no satisfactory quantitative dating methods available in situ produced be 10 concentrations have been measured in quartz boulders exposed on sulawesian late quaternary fan surfaces these concentrations suggest that the two fan units evidenced by geomorphic study were emplaced during two distinct major climatic events the calculated minimum exposure ages imply abandonment ages of 11 kyr and 120 kyr for the younger and older units respectively this study demonstrates that using both the neutron and muon components implicated in the in situ be 10 production surficial erosion rates can be estimated and alluvial fans dated ln particular it shows that in situ be 10 may be used to date fan emplacement during the last 120 kyr under humid tropical conditions significantly helping to constrain continental palaeoclimatology

giant non catastrophic landslides and the long term exhumation of the european alps landslides influence local slope morphology affect sediment flux from hillslopes to rivers and mass wasting in response to tectonics and climate forcing however the links between giant non catastrophic landslides known as deep seated gravitational slope deformations dsgsds and the long term evolution of orogenic landscapes are almost unknown we explore these links in the european alps using the first orogen scale inventory of dsgsds 900 over an area 105 km2 and a dataset of published apatite fission track ages 1000 that provides an estimate of the long term exhumation patterns of the orogen we show that dsgsds are more widespread than previously considered and exhibit an orogen scale distribution not explained by well known local lithological and structural controls we test the hypothesis that this orogen scale distribution correlates to the long term evolution of the alps by subdividing the study area into 37 square sub areas 50 50 km classified according to combinations of long term exhumation and mean annual rainfall on each sub area we perform a morphometric analysis of topography hypsometry relief slope excluding local and regional controls due to rock type and structure dsgsds tend to cluster in areas with intermediate exhumation rates fission track age between 10 and 40 ma where large scale topography is less dissected and incision is localised along major valleys here dsgsd abundance correlates positively with the degree of valley incision and related relief instead dsgsds lack in areas which underwent either low exhumation rates resulting in insufficient relief production or high exhumation rates associated to rapid uplift or higher erosional dissection of topography negative correlation between dsgsd abundance and mean annual rainfall suggests that effective hydrological surface processes contribute on the long term timescale to the development of large scale topography unfavourable to dsgsds especially in areas of high exhumation rates where dsgsds are abundant long lasting slope deformations effectively adjust post glacial relief by reducing slope inclination values and are thus expected to significantly contribute to the long term denudation of active orogens

10be and 9be in marine sediments and their potential for dating using sequential leaching experiments we have measured the fraction of the cosmogenic isotope 10be half life 1 5 my and its stable isotope 9be co extracted with the following phases in marine sediments exchangeable calcium carbonate fe and mn oxyhydroxides organic opal and detrital the extraction of the authigenic phases typically release 70 of the 10be but only 40 of the 9be in order to test its potential for dating marine sediments we have measured the authigeniccally associated 10be 9be in 17 surface sediment samples from different ocean basins the observed spatial variability which appears to be influenced by proximity to continental input of 9be precludes the general and precise applications of leached 10be 9be for dating however the relatively constant value observed in surface sediments over large areas of the pacific indian and southern atlantic oceans shows considerable promise for approximate dating of open oceans sediments in order to test temporal variability a profile of the authigenically associated 10be 9be ratio has been measured in the independently dated central pacific core rc12 65 the observed variation in 10be 9be over the past nine my is approximately twice that expected on the basis of 10be decay alone several possible explanations for such behavior and their potential consequences for the use of leached 10be 9be for dating are discussed

deep seated gravitational slope deformations along the active bocono fault in the central portion of the merida andes western venezuela abstract two very large deep seated gravitational slope deformations in the highlands of the merida andes venezuela are herein described the mucubaji pass and cerro la camacha these slope movements have slid in post last glacial maximum times in addition both landslides are in very close association with the active bocono fault trace the cerro la camacha camacha range landslide is fault bounded along its northwest flank whereas the mucubaji pass mass movement is even cut by the active fault trace the almost 10 km long mucubaji slide mobilizes lgm moraine deposits along the unconformable basement contact la camacha slope movement is a sackung type landslide involving two huge masses that affect the entire northwestern slope of the la camacha range this sackung is at least 20 km long paralleling the active bocono fault trace combination of high relief energy gravitational forces and seismic shaking related to an on site active fault could be responsible for the destabilization of the slopes or massif in both cases although the seismically induced re activation of the la camacha landslide is very likely there is no proof for that yet conversely the mucubaji slide shows geomorphic geodetic and sedimentary evidence of episodic activity in recent times which could be ascribed to seismic triggering in the particular case of the la camacha sackung the combination of dextral slip along the bocono fault and a se dipping fault plane could additionally favor the destabilization of the nw slope of the la camacha range

mid pleistocene cosmogenic minimum age limits for pre wisconsinan glacial surfaces in southwestern minnesota and southern baffin island a multiple nuclide approach abstract paired 10 be and 26 al analyses n 14 indicate that pre wisconsinan glaciated bedrock surfaces near the northern baffin island and southern minnesota paleo margins of the laurentide ice sheet have long and complex histories of cosmic ray exposure including significant periods of partial or complete shielding from cosmic rays using the ratio 26 al 10 be we calculate that striated outcrops of sioux quartzite in southwestern minnesota southern margin were last overrun by ice at least 500 000 years ago weathered bedrock tors on the once glaciated uplands of baffin island northern margin are eroding no faster than 1 1 m myr 1 the equivalent of at least 450 000 years of surface and near surface exposure our data demonstrate that exposure ages and erosion rates calculated from single nuclides can underestimate surface stability dramatically because any intermittent burial and the resultant lowering of nuclide production rates and nuclide abundances will remain undetected

neogene kinematics of the central and western alps evidence from fission track dating zircon and apatite fission track analysis has established the continuation of a zone of rapid change in mineral ages extending from the simplon fault zone in the simplon alps through the rhone valley and along the southeastern side of the mont blanc and belledonne massifs apatite fission track ages to the northwest of this zone generally range from 1 4 to 6 ma whereas those to the southeast range from 6 to 13 ma corresponding values for zircon are 11 13 and 16 26 ma respectively the zone corresponds to the position of the frontal pennine thrust in the mont blanc belledonne region this structure a prominent feature on recent deep seismic profiles may have been reactivated in the neogene with an important normal fault component this is suggested by apatite and zircon fission track ages in the footwall that are younger than those in the hanging wall and by the observed elimination of the lower pennine or simplon nappes along this fault zone in the rhone valley mont blanc belledonne region resulting in the juxtaposition of north penninic and helvetic ultra helvetic nappes at the current erosion level the distribution of fission track ages reflects this movement and the related neogene exhumation of the mont blanc and belledonne external massifs which has continued until less than 1 4 m y ago i e it is almost certainly still active and has tilted the overlying nappe sequence

temporal behavior of deep seated gravitational slope deformations a review abstract deep seated gravitational slope deformations dsgsds are slow moving hillslope scale mass movements featuring characteristic landforms such as double crested ridges and upslope facing scarps that occur in diverse landscapes throughout the world although these deformations have been studied since the 1960s significant insights to the rates of dsgsds have only been gained within the last two decades owing to progress in geochronology remote sensing and instrumental monitoring absolute age and monitoring data indicate that dsgsd movements are observable over long term 102 years and short term future research directions include constraining the lifespan of dsgsds with absolute age dating and precise high resolution monitoring of spatio temporal displacement across dsgsd bodies it is of great importance to include absolute time scales in the numerical models of dsgsds furthermore combining remote sensing techniques such as synthetic aperture radar interferometry with high resolution lidar scanning and near surface geophysics offers a promising toolkit for collecting very detailed and accurate data on the short term deformation rates of dsgsds

off fault ground ruptures in the santa cruz mountains california ridge top spreading versus tectonic extension during the 1989 loma prieta earthquake the ms 7 1 loma prieta earthquake of 18 october 1989 produced abundant ground ruptures in an 8 by 4 km area along summit road and skyland ridge in the santa cruz mountains predominantly extensional fissures formed a left stepping crudely en echelon pattern along ridges of the hanging wall block southwest of the san andreas fault about 12 km northwest of the epicenter the fissures are subparallel to the san andreas fault and appear to be controlled by bedding planes faults joints and other weak zones in the underlying tertiary sedimentary strata of the hanging wall block the pattern of extensional fissures is generally consistent with tectonic extension across the crest of the uplifted hanging wall block also many displacements in laurel creek canyon and along the san andreas and sargent faults are consistent with right lateral reverse faulting inferred for the mainshock additional small tensile failures along the axis of the laurel anticline may reflect growth of the fold during deep seated compression however the larger ridge top fissures commonly have displacements that are parallel to the north northeast regional slope directions and appear inconsistent with east northeast extension expected from this earthquake measured cumulative displacements across the ridge crests are at least 35 times larger than that predicted by the geodetically determined surface deformation these fissures also occur in association with ubiquitous landslide complexes that were reactivated by the earthquake to produce the largest concentration of co seismic slope failures in the epicentral region the anomalously large displacements and the apparent slope control of the geometry and displacement of many co seismic surface ruptures lead us to conclude that gravity is an important driving force in the formation of the ridge top fissures shaking induced gravitational spreading of ridges and downslope movement may account for 90 or more of the observed displacements on the linear fissures similar fissures occurred in the same area and elsewhere near the san andreas fault during the predominantly right lateral 1906 san francisco earthquake and suggest that the loma prieta ground ruptures may in large part be independent of fault kinematics

rock slope movements along the mount currie fault scarp southern coast mountains british columbia rock slope movements are reported from mount currie ridge near pemberton in the southern coast mountains of british columbia the site displays linear trenches antislope scarps and tension cracks typical of mountain ridges undergoing slow deformation however the most prominent linear scarp on the ridge has been previously interpreted as a fault scarp kinematic tests on rock discontinuities demonstrate the feasibility of both toppling and plane sliding at this site ground motion vectors based on a 4 year laser electronic distance measurement edm record of slope movements are generally compatible with the results of the kinematic tests these results cast doubt on a strictly seismic interpretation of the mount currie scarp

current strain regime in the western alps from continuous global positioning system measurements 1996 2001 four to six years of continuous measurements at 10 permanent global positioning system sites in the western alps show horizontal residual velocities of 2 mm yr with respect to stable europe uncertainties range from 0 3 to 1 4 mm yr these velocities and the associated strain rate field indicate that the central part of the range is currently dominated by east west extension whereas the southern part shows north south to northwest southeast compression the geodetic and seismotectonic data are consistent with a model where strain is essentially controlled by the counterclockwise rotation of the adriatic microplate with respect to eurasia this rotation together with the arcuate shape of the contact between the adriatic microplate and the alps induces dextral shear kinematic boundary conditions across the western alps with an additional divergence component in their central part and in switzerland and a convergence component in their southern part

chronological constraints on processes leading to large active landslides abstract cosmic ray exposure dating of gravitational scarps along a slope nesting a presently active landslide la clapiere landslide tinee valley argentera massif se france reveal successive periods of gravitational destabilization an initial gravitational destabilization at 10 3 0 5 10 be ka occurs more than 3000 yr after the end of the last deglaciation of the tinee valley dated in the studied area from stoss and lee topography sampled along the tinee and its tributary rabuons valleys a second gravitational destabilization is well constrained at 7 1 0 5 10 be ka through the dating of two gravitational scarps although coincidental with the so called climatic optimum other local or regional triggering factors may be invoked a third evidenced gravitational destabilization occurred 2 3 0 5 10 be ka ago this study thus demonstrates that in situ produced cosmogenic 10 be allows establishing the chronology of gravitational destabilization leading to present major active landslides however in the present case deciphering between the various possible triggering factors will necessitate similar studies on other landslides inside the alpine arc

widespread post nappe normal faulting in the internal western alps a new constraint on arc dynamics abstract field data collected in the brianconnais and piemont zones at the centre of the western alpine arc demonstrate a high density of normal faults normal displacements are pervasive from the millimetric to the kilometric scales they occur both parallel and at high angles to the arc overprinting all the alpine folds and thrusts and the associated schistosities the orientation of fault striae implies that the pile of metamorphic nappes se of the pelvoux massif has undergone a general extension extension tends to be multidirectional in the brianconnais zone orogen parallel extension prevails in most of the piemont schistes lustres to the west in brianconnais zone brittle extension is associated with a reversal of movement along the brianconnais frontal thrust that started before the end of the oligocene in the piemont schistes lustres the onset of normal faulting occurred early in the miocene and continued the ductile extension that accompanied the exhumation of hp lt metamorphic thrust sheets during the palaeogene in both zones extension remains currently active resulting in the regional seismicity since more than 20 ma ago this normal faulting in the internal arc coexists with an outward propagation of folds and thrusts in the external arc we discuss its possible significance in the context to the dynamic evolution of the alps

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

mid holocene cluster of large scale landslides revealed in the southwestern alps by 36cl dating insight on an alpine scale landslide activity abstract although it is generally assumed that the internal structure of a slope e g lithology and rock mass properties inherited faults and heterogeneities etc is preponderant for the progressive development of large scale landslides the ability to identify triggering factors responsible for final slope failures such as glacial debuttressing seismic activities or climatic changes especially when considering landslide cluster at an orogen scale is still debated highlighting in this study the spatial and temporal concordant clustering of deep seated slope failures in the external southwestern alps we discuss and review the possible causes for such wide spread slope instabilities at both local and larger alpine scale high resolution field mapping coupled with electrical resistivity tomography first allows establishing an inventory of large landslides in the southwestern alps determining their structural model precising their depth limit 100 200 m as well as the involved rock volumes 10 7 m 3 we show that they developed in the same geostructural context of thick mudstone layers overlain by faulted limestone and followed a block spread model of deformation that could evolve in rock collapse events cosmic ray exposure dating cre using both 36 cl and 10 be in coexisting limestone and chert respectively has been carried out from the main scarps of six deep seated landslides dsl and leads to landslide failure cre ages ranging from 3 7 to 4 7 ka they highlighted i mainly single and fast ruptures and ii a possible concomitant initiation with a main peak of activity between 3 3 and 5 1 ka centered at ca 4 2 ka because this region was not affected by historical glaciations events landslide triggering by glacial unloading can be excluded the presented data combined with field observations preferentially suggest that these failures were climatically driven and were most likely controlled by high pressure changes in the karstic medium in effect the chronicle of failure ages is concomitant to a well known climatic pulse the 4 2 ka climate event characterized by intense hydrological perturbations associated to the heaviest rainfall period of the entire holocene despite requiring further investigations and discussions the dating of numerous events across the entire alps during the middle holocene period suggests a potential synchronous triggering of several large scale gravitational failures induced by the mid holocene climatic transition

gravitational spreading of mountain ridges coeval with late weichselian deglaciation impact on glacial landscapes in trollaskagi northern iceland abstract during the late weichselian deglaciation the coastal mountains of northern central iceland have experienced significant paraglacial readjustment processes in the form of conspicuous rock slope failures and deep seated gravitational slope deformation dsgsd local topographic slopes and ridges were deeply reshaped by these large scale paraglacial processes located on the eastern side of skagafjor ur one of the largest fjords of northern iceland the oslandshli arfjoll and hnjukar ridges 65 49n 19 14w exhibit geomorphic evidence of spectacular dsgds several series of dsgsd induced landforms such as crestal graben and troughs initiated by ridge top splitting were investigated over a 30 km 2 area on the basis of geomorphological mapping we recognized i a ridge top splitting event mainly controlled by glacial debuttressing induced by a minimal 300 m lowering of the glacier surface in the deildardalur valley ii a rapid late weichselian deglaciation of the deildardalur valley spanning a few thousands of years ice free stage probably reached around 14 000 years cal bp iii ridge top splitting having an influence on large scale glacial patterns by guiding and facilitating glacial erosion along ridge top grabens resulting in accelerated trough widening based on these interpretations we propose an evolutionary sequence of both the kinematic stages of the dsgsd and the late weichselian deglaciation at the valley scale this work provides new insights into i the patterns of the late weichselian deglaciation in the skagafjor ur area especially in tributary valleys of the fjord ii the timing of large scale paraglacial ridge top deformations in relation to the post lgm deglaciation and iii the influence of paraglacial dsgsd features on large scale glacial erosional patterns

geological evidence for neotectonic activity during deglaciation of the southern sperrin mountains northern ireland in the southern sperrin mountains northern ireland stacked glacigenic sequences that accumulated during deglaciation ca 17000 13000 yr bp overlie a basement of jointed and mascerated bedrock the glacigenic sequences comprise interbedded glaciotectonic shears diamictic breccias and rock rafts at one site a normal fault with a metre scale vertical displacement cuts through part of the sequence and is overlain by a glacial diamict sediments at an adjacent site show that faulting and associated hydrothermal activity was related to neotectonic reactivation of pre existing caledonian lineaments caused by ice unloading from stratigraphical and directional evidence fault reactivation occurred early in the deglaciation after north central ireland ice had retreated southwards into lowland areas but before sperrin mountain ice readvanced from the north this relationship provides evidence for the relative timing of neotectonic activity in northern ireland and demonstrates the effects of glacio isostatic unloading near ice sheet centres copyright 1999 john wiley sons ltd

the belledonne border fault identification of an active seismic strike slip fault in the western alps summary in the french western alps east of grenoble we identify the belledonne border fault as an active seismic fault this identification is based on the seismic monitoring of the grenoble area by the sismalp seismic network over the past 12 yr 1989 2000 we located a set of earthquakes with magnitudes ranging from 0 to 3 5 along a 50 km long alignment which runs in a n30 e direction on the western flank of the belledonne crystalline massif available focal solutions for these events are consistent with this direction n36 e strike slip fault with right lateral displacement these events along the belledonne border fault have a mean focal depth of 7 km in the crystalline basement with a probably very low slip rate the belledonne border fault has never been mapped at the surface where the otherwise heavily folded and faulted mesozoic cover makes this identification difficult historical seismicity also shows that over the past two and a half centuries a few events located mainly along the southern part of the belledonne border fault caused damage with the magnitude 4 9 1963 monteynard earthquake reaching intensity vii the most recent damaging event in the study area is the magnitude 3 5 1999 laffrey earthquake intensity v vi although its epicentre lies at the southern tip of the belledonne border fault there is clear evidence that aftershocks were activated by the left lateral slip of a n122 e striking fault the length of the belledonne border fault which could easily accommodate a magnitude 6 event as well as the proximity to the isere valley with its unlithified quaternary deposits up to 500 m thick known to generate marked site effects make the identification of the belledonne border fault an important step in the evaluation of seismic risk in the grenoble area besides the activity observed on the fault will now have to be taken into account in future geodynamic models of the western alps