laboratory analogue of the formation of molards cones of rock avalanche debris debris cones or molards occur on the deposits of rockslide avalanches they are a few metres high conical in shape and contain material finer than the surrounding debris previously proposed formation mechanisms of molards were tested against field evidence from the frank slide and are found to be unsatisfactory laboratory experiments indicate that when a mass of cohesion less soil is vibrated particle formed molards therefore may form by vibration of the ground under rockslide avalanches this formation mechanism may bear on the problem of rockslide avalanche mobility

temporal and spatial adjustments of channel migration and planform geometry responses to enso driven climate anomalies on the tropical freely meandering aguapei river sao paulo brazil

dynamics and emplacement mechanisms of the successive baige landslides on the upper reaches of the jinsha river china abstract two successive baige landslides are presented in this study to investigate the dynamics and emplacement mechanisms field survey shows that the deposit characteristics of the first landslide are affected by the extremely fractured rock masses and the complex spatial distribution of lithologies in the source area this deposit consists of abundant angular megablocks on the surface supported by clasts with a relatively abundant content of rubble ranging from micrometre to decimetre sizes and rarely well preserved original stratigraphic sequence diapiric structure and convoluted structure these sedimentological characteristics imply that a simple differential shear process induced by compression is distributed through the entire avalanche masses with low internal disturbance during the emplacement of the first landslide the three dimensional discrete element simulations show that i the first landslide reaches its maximum average velocity of 41 m s in 28 s and eventually is bulldozed to a halt in the river within 80 s ii the second landslide is controlled by entrainment which impedes the avalanche from further accelerating and simultaneously imparts kinematic energy to the substrate eventually becoming entirely mobilized and reaching a maximum average velocity of 35 m s in 36 s in the dynamic process of the second landslide the significant entrainment induced enlarged volume its entrainment ratio reaches 3 3 is associated with the steep concave terrain water bearing substrate and lower roughness substrate basal boundary and overloading impact induced erosion is proposed to be the most significant contribution to this entrainment

seismic attenuation in northeastern sonora mexico we studied the attenuation of local and regional earthquake body waves recorded by the seismic network of northeastern sonora mexico red sismica del noreste de sonora resnes the source station paths of the selected data set cover the epicentral region of the may 1887 m w 7 5 sonora earthquake we used the best located earthquakes recorded by resnes between 2003 and 2004 to analyze the spectral amplitude decay of body waves with hypocentral distance the database consists of 44 earthquakes with magnitudes between 1 8 and 3 2 and hypocentral distances between 25 and 150 km we calculated fourier spectral amplitudes from more than 400 records and defined attenuation functions with a nonparametric model by inverting the observed spectral amplitudes at 23 individual frequencies between 0 4 and 63 1 hz we determined regional attenuation curves based on events located more than 100 km northwest of the center of the network and local curves based on earthquakes located near the fault zone that ruptured in the 1887 earthquake the obtained attenuation curves indicate that the spectral amplitudes decay faster in the area of the 1887 rupture than in the surrounding region to analyze the possible sources of attenuation we parameterized the attenuation functions considering three terms one that accounts for geometrical spreading another one for anelastic attenuation and a third for near surface attenuation we found the s wave quality factor q to be similar in both the general region and near the 1887 rupture however in the region of the 1887 rupture the near surface attenuation exceeds the regional average finally in the region of the 1887 rupture the nonparametric attenuation functions and the estimates of q indicate that at between 0 6 and 63 1 hz p waves attenuate more than s waves q p 20 8 f 1 1 whereas q s 83 8 f 0 9

the angle of reach as a mobility index for small and large landslides the relations between the angle of reach fahrboschung and other indexes expressing the mobility of landslides and vertical drop horizontal reach and volume of landslide mass have been analyzed by means of simplified plots and regression equations results for 204 landslides of all sizes show that whatever the mechanism of motion all kinds of landslides experience a continuous reduction of the angle of reach with volume increase this reduction starts from the smallest sizes scattering in this relation is mostly due to mechanisms of motion and to both obstacles and topographic constraints on the path this synthesis indicates that small landslides less than 0 5 106 m3 in relative terms display excesses of travel distance similar to large landslides since most small landslides are not expected to develop any change in the mechanism of progression while moving the decrease in the reach angle with volume suggests that scale effects should be taken into account the angle of reach is found to be

a slab on slab model for the flims rockslide swiss alps the flims rockslide is the largest landslide in the alps with an estimated volume of 12 km3 it resulted from a prehistoric high speed movement of a large limestone mass several main factors infl

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

an assessment of source parameters of earthquakes in the cordillera of the western united states abstract source parameters for 50 earthquakes occurring between 1915 and 1988 have been used to examine the faulting characteristics of magnitude 5 5 to 7 8 earthquakes within the western u s cordillera an area extending from the eastern sierra nevada to the great plains and from northwestern montana to trans pecos texas source parameters used in this study include seismic information from first motion analyses body and surface waveform modeling geodetic studies and geological studies of surface faulting the principal results of this analysis include 1 all earthquakes occurred on faults dipping 38 or more and no evidence for listric of low angle planar faulting was found 2 all m 7 0 earthquakes occurred at depths 12 km and were composed of multiple subevents 3 most earthquakes 70 per cent had unilateral ruptures and 4 no individual subevent had a rupture length 21 km

drainage systems and the development of normal faults an example from pleasant valley nevada abstract drainage systems in regions of active extension contain information about fault zone structure and development and particularly about the lateral growth of individual fault segments that is difficult to obtain by more conventional means such as the dating of sedimentary material we investigate drainage fault interaction in pleasant valley nevada where a large normal faulting earthquake occurred in 1915 we find geomorphological evidence for a propagation increase in length of several km at both ends of one of the 1915 fault segments at one end we estimate the propagation rate to be about 50 m per earthquake this estimate is uncertain but is within the range predicted by theoretical models of fault growth drainage along the axes of half graben in this region may be influenced by the spacing of tilted fault blocks the highest valleys are also the narrowest whether the axial streams succeed in reaching lower neighbouring sinks depends on whether sedimentation rates are able to keep basins filled to the levels of the basement highs that separate half graben of opposite polarity a knowledge of modern drainage fault interactions may help predict drainage systems and the position of potential syn rift reservoir sediments in older extensional terrains where fault configurations but not facies distributions are known from seismic reflection surveys

signature of rhine valley sturzstrom dam failures in holocene sediments of lake constance germany abstract landslide dammed lakes that form upstream of large scale rockslide avalanches sturzstroms present an enormous potential hazard to downstream areas such failures are recorded in the early holocene sediments of upper lake constance germany by the presence of two clastic layers that were emplaced around 9400 cal ybp the sedimentology of these layers contrasts sharply with the typical late glacial and holocene lacustrine sediments present beneath the floor of the lake sedimentary structures and the magnetic fabric of these clastic deposits strongly suggest that they were emplaced by hyperpycnal underflows related to catastrophic floods that entered the lake from the rhine river from stratigraphic and geologic data it is inferred that the hyperpycnite deposits are directly related to the failure of two sturzstrom dams and the draining of the dammed lakes that developed upstream from them these lakes were dammed by the flims and the tamins sturzstrom deposits respectively sedimentologic data from lake constance indicate that the two successive events occurred within a very short time interval probably not exceeding several years consequently these lacustrine deposits provide essential information about the morphogenic evolution of the rhine river valley during the early holocene and about the sturzstrom events that occurred during the same time interval

structural configuration of the otates fault southern basin and range province and its rupture in the 3 may 1887 mw 7 5 sonora mexico earthquake abstract during the great 3 may 1887 sonoran earthquake surface rupture end to end length 101 8 km m w 7 5 0 3 an array of three north south striking basin and range province faults from north to south pitaycachi teras and otates slipped along the western margin of the sierra madre occidental plateau of northern mexico this detailed field survey of the previously undocumented 1887 earthquake rupture zone along the otates fault includes mapping the rupture scarp and measurements of surface deformation at 25 sites the surface rupture coincides with the mapped trace of the otates fault dips 68 w and has an end point to end point length of 18 2 km the lateral rupture terminations are controlled by cross faults striation measurements and the style of rupture indicate extensional dip slip without significant lateral displacement the average shortening p and extension t kinematic axes inferred from the striations are similar to published composite focal mechanisms of the microseismicity recorded in the epicentral region of the 1887 earthquake based on surface deformation maximum slip along the otates fault in the 1887 earthquake was 270 cm and the average slip was 189 cm a quadratic best fit to the along rupture surface offsets indicates an asymmetric distribution with the maximum offset near the northern end of the rupture segment which can be explained by the mechanical interaction of the teras and otates surface rupture segments through their stress fields the average recurrence interval of 1887 sized earthquakes on the otates fault is 30 42 kyr based on the long term geologic dip slip rate of the fault 0 06 mm yr and its amount of slip in the 1887 earthquake

dynamic simulation of the motion of fragmenting rock avalanches a mass referenced continuum model for dynamic analysis of rapid mass movement dan is verified by laboratory and field data increased earth pressure coefficients are used in this model to represent the dispersive pressures caused by fragmentation within a translating rock avalanche the numerical model demonstrates that increased runout in large rock avalanches can occur with normal friction coefficients if higher than normal internal pressures such as those believed to be generated by fragmentation are present the extent of the falling mountain rock avalanche deposit in new zealand is reproduced in the model with normal friction and high earth pressure coefficients to represent by analogy the additional internal pressures due to fragmentation it appears that if internal friction is changed by fragmentation it is only by a small amount and may increase rather than decrease to test this and to move beyond the present analogue model requires a better understanding of the rheology of fragmenting ro

the hofðaholar rock avalanche sturzstrom chronological constraint of paraglacial landsliding on an icelandic hillslope the hof aholar rock avalanche in the skagafjor ur area of northern iceland was investigated on the basis of a geomorphological analysis of its landforms and close surrounding environment thanks

from deep seated slope deformation to rock avalanche destabilization and transportation models of the sierre landslide switzerland abstract sackung is a widespread post glacial morphological feature affecting alpine mountains and creating characteristic geomorphological expression that can be detected from topography over long time evolution internal deformation can lead to the formation of rapidly moving phenomena such as a rock slide or rock avalanche in this study a detailed description of the sierre rock avalanche sw switzerland is presented this convex shaped postglacial instability is one of the larger rock avalanche in the alps involving more than 1 5 billion m3 with a run out distance of about 14 km and extremely low fahrboschung angle this study presents comprehensive analyses of the structural and geological characteristics leading to the development of the sierre rock avalanche in particular by combining field observations digital elevation model analyses and numerical modelling the strong influence of both ductile and brittle tectonic structures on the failure mechanism and on the failure surface geometry is highlighted the detection of pre failure deformation indicates that the development of the rock avalanche corresponds to the last evolutionary stage of a pre existing deep seated gravitational slope instability these analyses accompanied by the dating and the characterization of rock avalanche deposits allow the proposal of a destabilization model that clarifies the different phases leading to the development of the sierre rock avalanche

crustal velocity field of mexico from continuous gps measurements 1993 to june 2001 implications for the neotectonics of mexico 1 we combine velocities for 14 continuous gps stations spanning mexico and 173 additional continuous gps sites on the north american and pacific plates to study the large scale deformation of mexico the new station velocities which are derived from more than 6000 days of previously unused gps data provide the first ever view of the crustal velocity field of mexico key results are as follows 1 areas north of the mexican volcanic belt not including baja california move with the north american plate interior within the 1 2 mm yr 1 station velocity uncertainties station velocities for the mexican basin and range are consistent with no present day extension and yield an upper 95 limit of 1 3 mm yr 1 for any regional extension 2 south of the mexican volcanic belt five of the six sites move significantly relative to the north american plate all sites in the yucatan peninsula move toward the east at 3 4 mm yr 1 possibly defining an independent yucatan block 3 site velocities are consistent with limits of 0 4 mm yr 1 for present slip across the mexican volcanic belt 4 tampico on the gulf coast exhibits eastward motion consistent with gravity sliding known to occur in the adjacent mexican ridges fold belt 5 southeastward motion of la paz relative to the pacific plate is consistent with the hypothesis that the baja peninsula is not fully attached to the pacific plate 6 residual velocities for 160 north american plate gps stations outside of mexico exhibit no coherent regional patterns indicative of internal plate deformation

cretaceous and tertiary sedimentary magmatic and tectonic evolution of north central sonora arizpe and bacanuchi quadrangles northwest mexico the arizpe and bacanuchi quadrangles provide a geologic history representative of the north central part of sonora where lithologies are dominated by late mesozoic and cenozoic igneous rocks in this study new geologic mapping 40ar 39ar dating and geochemical analyses have been combined to provide a stratigraphic framework for this area ten lithostratigraphic units and several igneous and tectonic events can be recognized the oldest outcropping rocks are lower cretaceous strata of the bisbee group which along with the picacho conglomerate record a middle cretaceous compressive tectonic event and associated sedimentation laramide igneous activity is widespread and represented by 1 highly altered andesitic flows and volcaniclastic rocks arroyo alcaparros andesitic rocks of late campanian to maastrichtian age 2 less altered andesitic and dacitic flows cerro las jarillas volcanic rocks of late paleocene age and the intrusive bodies of 3 sierra el manzanal granodiorite and 4 rancho vaqueria quartz monzonite the sierra el manzanal granodiorite was emplaced at ca 68 ma on the basis of a 40ar 39ar biotite age 67 97 0 19 ma and cooled relatively rapidly according to less precise 40ar 39ar hornblende and k feldspar ages from the same sample 64 8 1 0 ma and 62 8 0 3 ma respectively the cerro las jarillas volcanic rocks are slightly younger 40ar 39ar biotite age of 58 67 0 17 ma the rancho vaqueria quartz monzonite was emplaced at ca 57 ma 40ar 39ar biotite age of 56 73 0 14 ma and a less precise 40ar 39ar hornblende age of 55 0 0 7 ma a protracted cooling history of this pluton is indicated by the age spectrum of k feldspar from the same sample a probable magmatic lull and denudation seem to have occurred between middle and late eocene time and probably until the early oligocene subsequently rhyolitic to mafic volcanism began close to late oligocene time and lasted until the early miocene felsic volcanism is represented by the cerro cebadehuachi volcanic rocks from which 40ar 39ar hornblende ages of 27 25 0 09 and 27 32 0 06 ma and a biotite age of 26 97 0 06 ma were obtained at three different localities the mesa pedregosa volcanic rocks represent the transition to younger mafic volcanic activity that occurred during the late oligocene as indicated by a sanidine 40ar 39ar age of 25 48 0 05 ma this late oligocene and early miocene magmatism was paired by two episodes of extensional deformation the first phase is characterized by northwest striking normal faults and folds which expose the deepest structural levels of the area and by the related basin fill the bacanuchi conglomerate the second phase is represented by north striking normal faults and by the syntectonic basin fill the arizpe conglomerate basaltic andesite volcanic flows at the base of the arizpe conglomerate yielded 40ar 39ar whole rock ages of 23 52 0 17 and 21 0 20 ma the extensional deformation 27 to 23 ma in the study area is coeval with the development of metamorphic core complexes in neighboring areas of sonora and with the onset of extension in southern sonora the mafic volcanic rocks and clastic sedimentary units associated with this extension resemble the basin fills that in other parts of sonora are assigned to the baucarit formation geochemical information from samples representing each of the igneous events displayed high k calc alkalic and mostly metaluminous compositions the older units including the arroyo alcaparros andesitic rocks the cerro las jarillas volcanic rocks the sierra el manzanal granodiorite and the rancho vaqueria quartz monzonite are characterized by steep chondrite normalized ree rare earth element slopes and generally well developed negative eu anomalies suggesting garnet and plagioclase removal in the source the younger igneous events including the cerro cebadehuachi and mesa pedregosa volcanic rocks and the basaltic flows associated with the arizpe conglomerate showed basin shaped ree slopes with no eu anomalies suggesting clinopyroxene or amphibole fractionation

the formation and impact of landslide dams state of the art abstract the blocking of river courses by mass movements is very common in mountainous areas with deep and narrow valleys landslide dams may pose serious threats to people and their livelihoods downstream in the case of abrupt dam failure since the publication of benchmark reviews of costa and schuster 1988 and korup 2002 there is a growing number of studies focusing on the formation stability and short term impacts of landslide dams this review combines the insights of all these studies builds on current concepts of landslide dams and suggests ways to unify terminologies and classifications we furthermore present a new worldwide database compiled from literature data it contains 410 landslide dams 1 million m3 in volume that were formed since 1900 since these have the most complete data entries these data show that dam longevity is among other factors correlated with the type of landslide forming the dam those formed by rock debris avalanches and rockslides have longest lifespans however the influence of landslide type or material on dam longevity decreases with time after dam formation to ensure consistency in the next database generation we suggest guidelines for data collection to provide a solid basis for evaluating dam stability and governing factors a preliminary classification matrix for landslide dam stability that combines topographic setting and the internal structure of the dam body is another outcome of our review furthermore an evaluation of the various geomorphic stability indices proposed in the literature regarding their suitability and limitations in assessing dam formation and stability shows that they predict the probability of dam formation reasonably well but that their application to longevity estimates requires further assessment the geomorphic impacts of landslide dams in the short medium and long term are summarized and illustrated with key examples finally for a better understanding of the factors controlling dam stability we recommend to 1 include dam composition and sedimentary structures in future case studies 2 maintain and update the worldwide database for sound statistical analyses 3 refine landslide dam stability indices and test them for different landslide types and 4 study hazard cascades related to multiple dams in one watershed for long term landscape evolution studies we suggest to 5 quantify terrestrial sediment flux related to landslide dams 6 detect ancient landslide dams in river profiles and 7 further exploit the sediment archives in former impoundment areas

plate interactions control middle late miocene proto gulf and basin and range extension in the southern basin and range middle late miocene proto gulf 12 6 ma extension around the gulf of california gulf extensional province is commonly interpreted as resulting from partitioning of oblique pacific north american plate motion into strike slip displacement along the margin and east northeast extension perpendicular to the margin within the north american plate we propose that this mechanism also applies to kinematically similar predominantly east northeast extension that occurred at the same time throughout the southern basin and range province from southern arizona and new mexico to the trans mexican volcanic belt new field and 40ar 39ar data in sinaloa and durango confirm that this episode of extension occurred on the mainland side of the gulf and in the basin and range east of the sierra madre occidental which is generally considered the eastern margin of the gulf extensional province published data indicate the middle late miocene episode also occurred across the northern and southern ends of the sierra madre where the gulf extensional province connects with the basin and range 1 from central sonora into southern arizona and new mexico and 2 from nayarit into central mexico north of the trans mexican volcanic belt this episode appears to have avected an area that continues to the eastern edge of the basin and range province in texas and san luis potosi recognition that this episode of extension avected the entire southern basin and range resolves the discrepancy between the amount of extension calculated based on plate reconstructions and that based on field data within the gulf extensional province alone published plate reconstructions require 160 to 110 km of east northeast extension between 12 and 6 ma if taken up solely within the gulf extensional province this would have generated 66 to 78 extension which is much greater than observed spread across the entire southern basin and range it requires only 20 total extension which is more consistent with observations of cumulative extension between 12 and 6 ma extension was partitioned into the gulf extensional province because 1 it lies between two stable batholith belts mesozoic peninsular ranges on the west and mid tertiary sierra madre occidental on the east that resisted extension and 2 the gulf was thermally weakened by immediately preceding arc magmatism extension in the main basin and range province in part probably avoided the relatively strong batholithic crust of the sierra madre occidental 2000 elsevier science b v all rights reserved

transport and emplacement mechanisms of large volcanic debris avalanches evidence from the northwest sector of cantal volcano france abstract large volcanic debris avalanche vda deposits of miocene age occur within the stratigraphic sequence of cantal stratovolcano central france the vda of cantal volcano were initiated by sector collapse of a cone of high elevation up to 4500 m a s l two distinct superimposed vda deposit units breccias i and ii resulted from at least two successive large scale collapse events during the evolution of the volcanic complex breccia i the oldest one is very thick up to 200 m and heterolithologic it is overlain by breccia ii which is thinner up to 50 m and contains more heterometric clasts ranging from hectometer to millimeter size the vda deposits are poorly sorted clasts are angular and highly fractured at different scales often with jigsaw fit in breccia ii jigsaw megaclasts have usually subspheric shapes with size decreasing distally basal deposits commonly display thin inversely graded layers reorientated clasts along ramp structures and cataclasis of the substratum some units have a distal fabric in the form of a poorly developed clast imbrication the clasts are commonly sub rounded thereby indicating abrasion during viscous flow anisotropy of magnetic susceptibility a m s measurements indicate absence of a preferentially oriented matrix fabric magnetic foliation parallel to the bedding suggests that the depositional process is dominated by particle settling the magnetic fabric is better organized in distal deposits where magnetic carriers are imbricated moreover the fragmented clasts and megaclasts are not abraded rather inflation led to isotropic spherical dispersion of clastic material isotropic dispersive inflation which fed the interclast matrix this is also confirmed by the lack of rotation at the individual crystal level all these data strongly suggest transport of vda by liquified non turbulent granular flows distally imbricated deposits suggest more turbulent flow emplacement of the vda results from progressive upward aggradation of the particles by volume reduction and deflation loss the non turbulent liquified stage of the vda disappears the vda behaves as a sliding rigid mass plug flow that exerts strong friction on the basement leading to gouge formation

sedimentology of rock avalanche deposits case study and review abstract detailed sedimentological studies concerning different facies types and the factors influencing their development such as lithology topography substrates etc were carried out at the carbonate tschirgant rockslide rock avalanche deposit in the eastern alps of austria several depositional facies and sub facies have been identified at this and other sites by many researchers these facies are found throughout the debris regardless of depth or travel distance and result from highly heterogeneous stress distributions in time and space during emplacement one of the most important recent observations in terms of emplacement dynamics is that shear is not confined to the base but is distributed throughout the debris except the coarse carapace due to the preservation of source stratigraphy in these non turbulent mass movements any horizontal facies or grain size variations need to be regarded in context since they strongly depend on source stratigraphy and hence the spatial distribution of lithologies i e geological units of different mechanical properties for example some lithologies do not form a boulder carapace due to absence of large in situ blocks in the source rock mass however at tschirgant slight facies maturation with distance within the same lithology is observed i e clast fragmentation progresses to create the distinct facies characteristic grain size distribution only after some distance travelled these details are revealed through facies based sampling and analysis studies based on bulk sampling in some cases observed progressively reduced grain sizes with distance and depth which might be a function of added variations within different facies sampled together in this paper the wealth of observations on rockslide and rock avalanche sedimentology of the past decades is combined with a detailed case study of a lithologically relatively simple deposit to outline global and site specific depositional structures and facies with the aim to summarize review and refine the current state of knowledge on rock avalanche and rockslide emplacement processes

geochemical evidence for the nature of the crust beneath the eastern north penninic basin of the mesozoic tethys ocean the north penninic basin was a subbasin in the northern part of the mesozoic tethys ocean its significance within the framework of this ocean is controversial because it is not clear whether it was underlain by thinned continental or oceanic crust remnants of the eastern north penninic basin are preserved in the alps of eastern switzerland grisons as low metamorphic bundnerschiefer sediments and associated basaltic rocks which formed approximately 140 170 ma ago misox bundnerschiefer zone middle jurassic to early cretaceous nb u zr nb and y nb ratios as well as nd sr isotopic and ree data of most of the metabasalts point to a depleted morb type mantle origin they have been contaminated by magmatic assimilation of bundnerschiefer sediments and by exchange with seawater but do not prove the existence of a subcontinental lithospheric mantle or continental crust beneath the north penninic basin this suggests that the studied part of the north penninic realm was underlain by oceanic crust only the metabasalts from two melange zones vals and grava melanges show a more important contamination by crustal material since this type of contamination cannot be observed in the other tectonic units we suggest that its occurrence is related to melange formation during the subduction of the north penninic basin in the tertiary the north penninic basin was probably despite the occurrence of oceanic crust smaller than the south penninic ocean where the presence of oceanic crust is well established modern analogues for the north penninic basin could be the transitional zone of the red sea or the pull apart basins of the southernmost gulf of california where local patches of oceanic crust with effusive volcanism have been described

lake sediments deposited on the flims rockslide mass the key to date the largest mass movement of the alps long piston cores taken from the subsurface of two mountain lakes of the eastern swiss alps recovered sediments which overlie the flims rockslide deposits these sediments provide new information on the chronology of the largest known alpine rockslide and can be used to reconstruct the post landslide environmental evolution the oldest 14 c date of the lake sediments yields a minimum age of the rockslide at 9660 9430 cal yr bp in addition the dating of a wood fragment contained in the rockslide deposits directly below the lake sediments shows a maximum age of 9480 9120 cal yr bp the overlap of the maximum and minimum ages 9480 9430 cal yr bp approximates the age of the flims rockslide this early holocene range coincides with a period of higher frequency of large mass movements observed in the alps which could be related to climatic changes

dynamic disintegration processes accompanying transport of the holocene flims sturzstrom swiss alps abstract a sturzstrom is a large scale landslide that evolves during transport into a rapid granular flow rock avalanche by a dynamic disintegration process numerous theoretical hypotheses have been proposed to explain the excessive mobility of these catastrophic mass movements but the role of disintegration processes remains poorly understood exceptional outcrop conditions at the giant 12 km3 flims sturzstrom swiss alps permit the analysis of disintegration processes that result from shearing during transport in confined zones of the rock mass shearing is concentrated along preferred surfaces originating as bedding planes which evolve into shear band layers differential velocities of slabs separated by these shear layers induce oblique fractures in the slabs by accommodation contacts between grains are maintained in the shear layers in unconfined zones near the top and the lateral margins shearing generates dilatancy the rock mass is affected by anisotropic dispersion without mixing and disintegrated material is preferentially produced to the top due to inflation the rock slide then evolves to a granular flow the consequence of these processes is the formation of two distinct depositional facies in the sturzstrom the structured facies exhibits a stratified aspect close to the base reflecting confined slab on slab shearing motion towards the top and distally it evolves into a chaotic facies with some isolated pockets of the structured facies reduction of confining forces on the moving sturzstrom allows transformation of the structured facies into the chaotic facies this characteristic transition observable in many sturzstrom deposits seems to be necessary for the rock avalanche process to occur and offers insights into the long runout characteristics of these catastrophic mass movements

synextensional pliocene pleistocene eruptive activity in the camargo volcanic field chihuahua mexico the camargo volcanic field is the largest mafic alkalic volcanic field in the mexican basin and range province and the relationship between volcanism and normal faulting is especially strong the camargo volcanic field lies in the northern part of the province midway between the sierra madre occidental and trans pecos texas it is formed by pliocene pleistocene 4 7 0 09 ma intraplate mafic alkalic volcanic rocks some of which contain peridotite pyroxenite and granulite xenoliths the volcanic field covers 3000 km2 and has an estimated volume of 120 km3 erupted from 300 recognized vents twenty six new 40ar 39ar age determinations for the camargo volcanic field and its environs show that volcanic activity began in the southwest part of the field and shifted toward the northeast at 15 mm yr the average magmatic eruption rate during growth of the field was 0 026 km3 k y the camargo volcanic field lies within an accommodation zone with west dipping faults and east tilted blocks to the north and east dipping faults and west tilted blocks to the south these faults are expressed in the volcanic field by a n30 w trending graben with scarps up to 100 m high through its central part volcanism and faulting were at least in part coeval and younger volcanic products commonly drape fault scarps that cut earlier lavas normal faulting is bracketed between 4 7 and 2 1 ma and may have also migrated northeastward estimated vertical slip rates on four pliocene faults range from 0 03 mm yr a likely long term rate to 1 67 mm yr interpreted as a short term rate operative during periods of active faulting northwest striking normal faults that cut alluvial fan deposits and pleistocene lavas in the northern camargo volcanic field and geomorphic evidence for recent uplift to the south of the volcanic field suggest that the region is still extending

the sanfandila earthquake sequence of 1998 queretaro mexico activation of an undocumented fault in the northern edge of central trans mexican volcanic belt abstract a sequence of small earthquakes occurred in central mexico at the northern edge of the trans mexican volcanic belt tmvb in the state of queretaro during the first 3 months of 1998 medium to large events in the continental regime of central mexico are not common but the seismic history of the region demonstrates that faults there are capable of generating destructive events the sequence was analyzed using data from a temporary network with the goals of identifying the causative fault and its relation to regional tectonics employing a waveform inversion scheme adapted from a method used for regional studies we found that the source mechanisms conform to the style of faulting i e extension in the e w direction representative of the taxco san miguel allende fault system this system has been proposed as the southernmost extension of the basin and range br province the spatial distribution of hypocenters and source mechanisms indicate that the seismogenic segment was a fault with an azimuth of approximately 334 with almost pure dip slip since events which occurred just south from this region show features which are consistent with tmvb tectonics i e extension in an n s direction the sequence may mark the boundary between the tmvb and br stress domains

seismicity in the epicentral region of the 1887 northeastern sonoran earthquake mexico the 1887 sonoran earthquake in northeastern sonora mexico has an 80 km rupture length with an average 3 m displacement and an assumed 16 km depth of rupture this corresponds to a seismic moment of 1 27 x 1027 dyne cm and an ms of 7 4 seven to ten portable seismographs with an average spacing of 10 km were operated in a 2800 km 2 region surrounding the 1887 fault scarp thirtythree earthquakes were detected during 30 days of usable recording for all events 1 3 m 2 the most accurate locations horizontal error 5 km define a west dipping normal range bounding fault all events occurred within 15 km of the surface the name pitaycachi fault after the most prominent peak of the horst block is proposed for this zone of active faulting seismicity along the zone terminates abruptly 13 km north of the fault scarp and extends to the south for at least 32 km beyond the southern a composite focal mechanism from events at the southern end of the 1887 scarp indicates a normal fault striking n35 e and dipping 72 to the northwest

active tectonics of northeastern sonora mexico southern basin and range province and the 3 may 1887 mw 7 4 earthquake north south striking and west dipping basin and range province normal faults form the western edge of the sierra madre occidental plateau in northeastern sonora these faults and associated half grabens extend over a distance of more than 300 km between the san bernardino basin in the north and the sahuaripa basin in the south an earthquake in 1887 ruptured three neighboring segments of this major fault zone our field mapping in this region indicates that the surface rupture of the 1887 earthquake extends farther to the south and is considerably longer 101 4 km end to end length than previously reported a compilation of the seismicity in the epicentral region of the 1887 earthquake shows the epicenters to be distributed in well defined clusters at the northern end of the 1887 surface rupture in the step overs between the three rupture segments on a neighboring fault in the west fronteras fault and on fault segments farther south along the same fault zone granados region the distribution of seismicity correlates well with calculated changes in coulomb failure stress resulting from the 1887 earthquake

gis based landslide susceptibility mapping for the 2005 kashmir earthquake region abstract the m w 7 6 october 8 2005 kashmir earthquake triggered several thousand landslides throughout the himalaya of northern pakistan and india these were concentrated in six different geomorphic geologic anthropogenic settings a spatial database which included 2252 landslides was developed and analyzed using aster satellite imagery and geographical information system gis technology a multi criterion evaluation was applied to determine the significance of event controlling parameters in triggering the landslides the parameters included lithology faults slope gradient slope aspect elevation land cover rivers and roads the results showed four classes of landslide susceptibility furthermore they indicated that lithology had the strongest influence on landsliding particularly when the rock is highly fractured such as in shale slate clastic sediments and limestone and dolomite moreover the proximity of the landslides to faults rivers and roads was also an important factor in helping to initiate failures in addition landslides occurred particularly in moderate elevations on south facing slopes shrub land grassland and also agricultural land were highly susceptible to failures while forested slopes had few landslides one third of the study area was highly or very highly susceptible to future landsliding and requires immediate mitigation action the rest of the region had a low or moderate susceptibility to landsliding and remains relatively stable this study supports the view that 1 earthquake triggered landslides are concentrated in specific zones associated with event controlling parameters and 2 in the western himalaya deforestation and road construction contributed significantly to landsliding during and shortly after earthquakes

the seismicity of chihuahua mexico and the 1928 parral earthquake abstract studies of the seismicity of chihuahua mexico and determination of source parameters for the 1928 parral earthquake suggest that the eastern portion of chihuahua is currently undergoing extension the parral earthquake has similar source parameters to other southern basin and range rio grande rift events the focal mechanism for the parral event however indicates northeast southwest oriented extension a direction that is parallel to neither the east west oriented extension seen near the us mexican bordern nor to the physiographic province boundary between the sierra madre occidental and the southern basin and range where the earthquake occurred intensity information for the parral event and the 1931 valentine texas earthquake suggests that attenuation within the region lies somewhere between relationships developed for the eastern and cordilleran portions of the usa

late holocene catastrophic slope collapse affected by deep seated gravitational deformation in flysch ropice mountain czech republic the region of the flysch western carpathians is characterized by abundant deep seated gravitational slope deformations dsgsds this study deals with a detailed analysis of late holocene catastrophic collapse of a fault created slope of mountain ropice in the moravskoslezske beskydy mountains eastern czech republic the catastrophic collapse was initialized by huge compound rotational slide toppling deformation which occurs on the upper part of the studied slope and affects tectonically weakened subhorizontally inclined sandstone beds detailed geomorphological mapping accompanied by morphotectonic analysis and geophysical sounding revealed at least two historic flowslides the older event f1 affected 0 5 0 8 mm3 of bedrock and created a 1000 m long and up to 150 m wide accumulation with abundant transverse steps and a carapace like surface the landslide toe blocked an adjacent valley which led to the development of a small impoundment with 4 m thick deposits containing lacustrine peat bog floodplain and alluvial fan facies radiocarbon dating and pollen analysis indicate the valley blockage at 1 5 ka bp the other flowslide f2 of much smaller dimensions 10 000 12 000 m3 overlaid the main landslide body and according to the dating of minerogenic horizon in the impoundment may have taken place 0 3 ka bp the organisation of landforms character of slope failures and dynamic back modelling point to a likely rock avalanche or combined rock slide debris avalanche mechanism of movement this case study shows that rapid rock avalanches can operate also in mountainous terrain with moderate relief if toppling together with deep seated gravitational deformation of slopes modifies the original stable position of bedding planes