probabilistic rainfall thresholds for landslide occurrence using a bayesian approach 1 various methods have been proposed in the literature to predict the rainfall conditions that are likely to trigger landslides in a given area most of these methods however only consider the rainfall events that resulted in landslides and provide deterministic thresholds with a single possible output landslide or no landslide for a given input rainfall conditions such a deterministic view is not always suited to landslides slope stability in fact is not ruled by rainfall alone and failure conditions are commonly achieved with a combination of numerous relevant factors when different outputs landslide or no landslide can be obtained for the same input a probabilistic approach is preferable in this work we propose a new method for evaluating rainfall thresholds based on bayesian probability the method is simple statistically rigorous and returns a value of landslide probability from 0 to 1 for each combination of the selected rainfall variables the proposed approach was applied to the emilia romagna region of italy taking advantage of the historical landslide archive which includes more than 4000 events for which the date of occurrence is known with daily accuracy the results show that landsliding in the study area is strongly related to rainfall event parameters duration intensity total rainfall while antecedent rainfall seems to be less important the distribution of landslide probability in the rainfall duration intensity shows an abrupt increase at certain duration intensity values which indicates a radical change of state of the system and suggests the existence of a real physical threshold

earthquakes in northern europe in 1375 1989 abstract an updated version of the catalogue of earthquakes in northern europe is presented it comprises events inside a region window of about 55 80 n and 10 w 45 e covering a 615 year period from 1375 to 1989 the data have been compiled using all the available historical publications catalogues studies and reports of the region and for events from 1984 to 1989 a regional seismic parameter database maintained by the institute of seismology of the university of helsinki the number of events exceeds 5200 of which more than 40 have been registered since 1980 the huge increase of event reports is the result of the installation of new high frequency networks for microearthquake studies and the upgrade of the seismic instrumentation because of the different degree of accuracy and homogeneity of the parameter data the events were divided into historical 1375 1964 and instrumental 1965 1989 datasets the source parameters are mainly macroseismic for historical events and obtained by iterative location procedure for instrumental data by assuming internal homogeneity between the different regional magnitude scales we estimated the catalogue to be complete for events with magnitude 4 5 since the 1880 s magnitude 4 0 4 4 since the 1940 s and magnitude 3 5 3 9 since the 1970 s although the distribution of seismicity exhibits similar patterns in both datasets the clustering of epicenters and offshore seismicity is more distinct in the instrumental period the occurrence of the greatest events can be seen more clearly in the historical data the earthquake epicenters are concentrated in the geologically younger tectonic provinces in the western part of the region and follow with some exceptions the tectonic fracture and fault zones in the fennoscandian area 80 of the earthquakes occurred in the upper 20 km of the earth s crust the deepest epicenters are in the southwestern corner of the region where the crust is thinnest

probabilistic rainfall thresholds for triggering debris flows in a human modified landscape abstract in the carrara marble basin cmb apuan alps italy quarrying has accumulated widespread and thick quarry waste lying on steep slopes and invading valley bottoms the apuan alps are one of the rainiest areas in italy and rainstorms often cause landslides and debris flows the stability conditions of quarry waste are difficult to assess owing to its textural geotechnical and hydrogeological variability therefore empirical rainfall thresholds may be effective in forecasting the possible occurrence of debris flows in the cmb three types of thresholds were defined for three rain gauges of the cmb and for the whole area rainfall intensity rainfall duration id cumulated event rainfall rainfall duration ed and cumulated event rainfall normalized by the mean annual precipitation rainfall intensity emapi the rainfall events recorded from 1950 to 2005 was analyzed and compared with the occurrence of debris flows involving the quarry waste they were classified in events that triggered one or more debris flows and events that did not trigger debris flows this dataset was fitted using the logistic regression method that allows us to define a set of thresholds corresponding to different probabilities of failure from 10 to 90 and therefore to different warning levels the performance of the logistic regression in defining probabilistic thresholds was evaluated by means of contingency tables skill scores and receiver operating characteristic roc analysis these analyses indicate that the predictive capability of the three types of threshold is acceptable for each rain gauge and for the whole cmb the best compromise between the number of correct debris flow predictions and the number of wrong predictions is obtained for the 40 probability thresholds the results obtained can be tested in an experimental debris flows forecasting system based on rainfall thresholds and could have implications for the debris flow hazard and risk assessment in the cmb

representative rainfall thresholds for landslides in the nepal himalaya measuring some 2400 km in length the himalaya accommodate millions of people in northern india and pakistan nepal bhutan and parts of other asian nations every year especially during monsoon rains landslides and related natural events in these mountains cause tremendous damage to lives property infrastructure and environment in the context of the himalaya however the rainfall thresholds for landslide initiation are not well understood this paper describes regional aspects of rainfall thresholds for landslides in the himalaya some 677 landslides occurring from 1951 to 2006 were studied to analyze rainfall thresholds out of the 677 landslides however only 193 associated with rainfall data were analyzed to yield a threshold relationship between rainfall intensity rainfall duration and landslide initiation the threshold relationship fitted to the lower boundary of the field defined by landslide triggering rainfall events is i 73 90d 0 79 i rainfall intensity in mm h 1 and d duration in hours revealing that when the daily precipitation exceeds 144 mm the risk of landslides on himalayan mountain slopes is high normalized rainfall intensity duration relationships and landslide initiation thresholds were established from the data after normalizing rainfall intensity data with respect to mean annual precipitation map as an index in which ni 1 10d 0 59 ni normalized intensity in h 1 finally the role of antecedent rainfall in causing landslides was also investigated by considering daily rainfall during failure and the cumulative rainfall to discover at what point antecedent rainfall plays an important role in himalayan landslide processes rainfall thresholds presented in this paper are generalized so they can be used in landslide warning systems in the nepal himalaya 2008 elsevier b v all rights reserved

focal mechanisms of three earthquakes in finland and their relation to surface faults abstract focal mechanisms for three recent earthquakes in finland are determined using p wave polarities together with sv p and sh p phase amplitude ratios the events occurred on may 11 2000 in toivakka central finland ml 2 4 on september 15 2000 in kuusamo northeastern finland ml 3 5 and on may 2 2001 in kolari western finnish lapland ml 2 9 in order to obtain reliable estimates of the source parameters one dimensional crust and upper mantle velocity models are derived for the epicenter areas from deep seismic sounding results the starting models are modified by one dimensional ray tracing using the earthquake observations the events are relocated by employing p and s phase arrival times from the nearest seismic stations and the final velocity models synthetic waveforms calculated with the reflectivity method are used to further constrain and verify the source and structural parameters the toivakka earthquake indicates thrust or reverse faulting mechanism at a depth of 5 km after comparison with aeromagnetic and topographic data we suggest the eastward dipping nodal plane 358 42 was the fault plane the best fitting fault plane solution of the kolari earthquake suggests pure thrust faulting at a depth of 5 km the nodal plane striking 035 30 correlates well with surface observations of the postglacial possibly listric fault systems in the source area the kuusamo earthquake focal depth 14 km has a normal faulting mechanism with the nodal planes trending 133 47 or 284 47 preference is given to the sw dipping nodal plane as it seems to coincide with topographic and magnetic lineament directions that have been active after the last ice age the three earthquakes have occurred in old precambrian faults and shear zones which have been reactivated the reactivated faults are favourably oriented in the local stress field

single and joint fault plane solutions for microearthquakes in south iceland abstract we obtain fault plane solutions for a swarm of twelve events and two single events ranging in magnitude between 0 3 and 3 1 the events were recorded by a local network in south iceland consisting of eight three component stations with approximately 30 km between the stations for events larger than m l 1 the solutions are well constrained the non uniqueness of the fault plane solutions increases with diminishing magnitude to enhance the uniqueness of the fault plane solutions for the earthquake swarm we search for mechanisms with a common fault plane but possibly varying slip directions in that plane data for all the events are consistent with faulting on a common plane relative location of the events shows that they all occurred less than 11 m from a single plane fault plane solutions for all the analysed events of the swarm as well as the two single events are consistent with strike slip dominated faulting on faults striking roughly north south the results are in agreement with the strikes of mapped surface fractures and focal mechanisms of larger earthquakes in the area this indicates that the microseismicity is related to the same pattern of regional deformation as the major earthquakes in south iceland

significance of geomorphological and subsurface drainage controls on failures of peat covered hillslopes triggered by extreme rainfall on 19 september 2003 40 landslides of 140 18 000 m3 volume occurred within 2 5 km2 on the slopes of dooncarton mountain republic of ireland during a storm that may have exceeded 90 mm within 90 minutes the landslides were investigated to determine the reasons for such a high density of slope failures all of the landslides were surveyed within four months and nine of them were investigated in detail the six largest landslides all peat failures accounted for 57 of the more than 100 000 m3 of material displaced during the event a consistent sequence of superficial materials was found on the failed hillslopes including an extensive iron pan at the base of a buried soil horizon 0 3 m below the base of the peat morphologically almost all of the landslides occurred on steep planar slopes or around sharp convexities with the latter failures developing retrogressively upslope the only significant relationship found from analysis of 371 subsurface pipes and 142 seepage cracks defined here as contiguous fissures conducting concentrated subsurface flow across all the failures was that the thinner the peat cover the deeper the pipes and seepage cracks occurred below the base of peat it is concluded that most of the landslides were probably caused by a combination of excess water pressures in the buried soil horizon and the thinner overburden of peat or peaty soil associated with the steeper slope segments pipes and seepage cracks formed on the iron pan probably existed prior to the failure event and may have contributed to the high water pressures as rainwater inputs exceeded their discharge capacities one large peat slide was probably triggered by excess water pressures developed within and between artificial tine cuts the properties of the blanket peat were generally of little consequence in the occurrence of the landslides but relict desiccation cracks and other structural weaknesses through the peat mass were probably highly significant although several aspects of the peat failures correspond to previously published examples the context of these failures in terms of the topography and upland catena is distinctive copyright 2007 john wiley sons ltd

spatio temporal analysis of a complex landslide in the northern apennines italy by means of dendrochronology dendrochronology is used to determine the spatial and temporal development of movements in a complex landslide located in the northern apennines the analysis of trees growing on the landslide body enabled us to date their colonisation pattern which starts from the 1920s and increases mainly after 1950 since then sampled trees recorded with growth anomalies the movements involving the landslide body in 1956 1957 1982 1983 1990 1995 and 1998 these movements are reactivations of the main landslide that probably occurred in the last decades of the 19th century in 1980 trees on the upper landslide body were involved in a rock fall due to the expansion of the main scarp microsections cut out from selected tree ring sequences allowed seasonal dating of the highlighted movements which mostly occurred in early spring meteorological and seismic time series were analyzed in order to relate them with reactivations and to search for correlations and triggering events the seismic activity although characterized by low magnitudes could be able either to trigger the movements 1990 or to destabilize the ground where rainfalls could have been playing the first role in triggering the reactivation probably in 1982 1983 and 1995 the other reactivations seem to be linked either to long lasting rainfalls or to monthly rainfall peaks mostly following dry periods

crustal structures of eastern fennoscandia the area of the eastern fennoscandian shield is quite well covered by deep seismic sounding profiles most of which were shot in the last ten years in general the velocities of the seismic waves in the crust increase continuously with depth but intense reflections also indicate the presence of distinct velocity boundaries the velocities of the refracted waves in the various profiles resemble each other but the depths to the boundaries vary considerably low velocity zones were found in the uppermost crust along most of the profiles the eastern karelia profiles also exhibited large low velocity zones in the lower part of the crust high velocity bodies found in the uppermost crust in eastern fennoscandia are thought to be associated with mafic intrusions and mafic metavolcanic rocks the depth to the moho shows considerable lateral variation and deep depressions in this boundary are thought to be connected with large fracture zones high pn wave velocities of about 8 5 km s are in many cases associated with these depressions

space geodetic constraints on glacial isostatic adjustment in fennoscandia analysis of global positioning system gps data demonstrates that ongoing three dimensional crustal deformation in fennoscandia is dominated by glacial isostatic adjustment our comparison of these gps observations with numerical predictions yields an earth model that satis es independent geologic constraints and bounds both the average viscosity in the upper mantle 5 x 10 20 to 1 x 10 21 pascal seconds and the elastic thickness of the lithosphere 90 to 170 kilometers we combined gps derived radial motions with fennoscandian tide gauge records to estimate a regional sea surface rise of 2 1 0 3 mm year furthermore ongoing horizontal tectonic motions greater than 1 mm year are ruled out on the basis of the gps derived three dimensional crustal velocity field

the 2003 earthquake swarm in anjalankoski south eastern finland abstract during may 2003 a swarm of 16 earthquakes ml 0 6 2 1 occurred at anjalankoski south eastern finland the activity lasted for three weeks but additional two events were observed at the same location in october 2004 a comparison of the waveforms indicated that the source mechanisms and the hypocentres of the events were nearly identical a relative earthquake location method was applied to better define the geometry of the cluster and to identify the fault plane associated with the earthquakes the relocated earthquakes aligned along an ene wsw trending zone with a lateral extent of about 1 0 km by 0 8 km the relative location and the waveform modelling of depth sensitive surface wave rg and s to p converted body wave sp phases indicated that the events were unusually shallow most likely occurring within the first 2 km of the surface the revised historical earthquake data confirm that shallow swarm type seismicity is characteristic to the area the focal mechanism obtained as a composite solution of the five strongest events corresponds to dip slip motion along a nearly vertical fault plane strike 250 dip 80 rake 90 the dip and strike of this nodal plane as well as the relocated hypocentres coincide with an internal intrusion boundary of the vyborg rapakivi batholith the events occur under a compressive local stress field which is explained by large gravitational potential energy differences and ridge push forces pore pressure changes caused by intrusion of ground water and or radon gas into the fracture zones are suggested to govern the swarm type earthquake activity

critical rainfall for typhoon induced debris flows in the western foothills taiwan abstract typhoon morakot devastated taiwan during august 6 11 2009 with a maximum total rainfall of 2884 mm causing 22 000 cases of slope failures rainfall thresholds for debris flow initiation are investigated using the hourly intensity vs duration i d hourly intensity vs cumulative rainfall i r and daily rainfall vs antecedent daily rainfall adr index methods among the 39 well documented cases 32 sites with known date and time of debris flow initiation were focused results reveal that debris flows and debris avalanches occur under a very wide range of rainfall characteristics with return periods ranging from several years to 200 years indicating that the empirical rainfall threshold alone is insufficient for an effective debris flow prediction system a consistent pattern of all i r paths for the investigated sites shows the combined effect of rainfall characteristics and inherent stability features of the slopes suggesting that the i r path is potentially useful in facilitating debris flow predictions it is also suggested that empirical rainfall thresholds should be calibrated using physical models against specific slope conditions to increase the accuracy of debris flow predictions

rainfall thresholds for landslide activity in portugal a state of the art rainfall is the most important physical process responsible for the landslide triggering in portugal results obtained worldwide have shown that control of rainfall on landslides differs substantially depending upon landslide depth and kinematics and the affected material therefore the critical rainfall conditions for failure are not the same for different types of landslides and may be strongly influenced by regional geologic and geomorphologic conditions rapid debris flows are typically triggered by very intense showers concentrated in just a few hours and shallow translational soil slips are usually triggered by intense precipitation falling within the 1 15 days long range on the contrary activity of deep seated landslides of rotational translational and complex types is related to periods of nearly constant rainfall lasting from several weeks to several months the different rainfall intensity duration conditions are associated with different hydrologic mechanisms for slope failure the generation of surface run off and high peak discharges in first order mountain catchments is a critical triggering mechanism for debris flows the intense rainfall allows the rapid growth of pore water pressure and the drop of capillarity forces that sustain the apparent cohesion of thin soils as a consequence shallow soil slips occur within the soil material or at the contact with the underlying less permeable bedrock long lasting rainfall episodes enable the steady rise of the groundwater table and the development of positive pore water pressures into the soil consequently deep seated failures occur in relation to the reduction of shear strength of affected materials in this work we present the state of the art concerning the proposition of empirical rainfall thresholds in portugal for different types of landslides observed in different zones of the country the lisbon region the douro valley and the nw mountains and the povoacao municipality in sao miguel island azores the empirical thresholds applied in portugal are based on the identification of past landslide events and include i the computation of antecedent rainfall threshold defined by linear regression ii the normalization of rainfall by the mean annual precipitation iii the definition of lower limit and upper limit rainfall thresholds and iv the definition of combined rainfall thresholds which integrates the rainfall event and the antecedent rainfall for different time periods

a physically based model for the topographic control on shallow landsliding a model for the topographic influence on shallow landslide initiation is developed by coupling digital terrain data with near surface through flow and slope stability models the hydrologic model topog o loughlin 1986 predicts the degree of soil saturation in response to a steady state rainfall for topographic elements defined by the intersection of contours and flow tube boundaries the slope stability component uses this relative soil saturation to analyze the stability of each topographic element for the case of cohesionless soils of spatially constant thickness and saturated conductivity the steady state rainfall predicted to cause instability in each topographic element provides a measure of the relative potential for shallow landsliding the spatial distribution of critical rainfall values is compared with landslide locations mapped from aerial photographs and in the field for three study basins where high resolution digital elevation data are available tennessee valley in marin county california mettman ridge in the oregon coast range and split creek on the olympic peninsula washington model predictions in each of these areas are consistent with spatial patterns of observed landslide scars although hydrologic complexities not accounted for in the model e g spatial variability of soil properties and bedrock flow control specific sites and timing of debris flow initiation within areas of similar topographic control

the crustal structure along the polar profile from seismic refraction investigations abstract seismic refraction investigations along a 440 km long profije on the northern baltic shield have resolved the crustal structure in this area of archaean to early proterozoic lithosphere formation the profile called the polar profile extends approximately along a sw ne oriented line from the karelian province in northern finland across the lapland granulite belt and the kola peninsula province to the varanger peninsula in northeastern norway at six shotpoints large explosions 200 1680 kg and at three shotpoints small explosions 80 kg were detonated and recorded at an average station spacing of 2 km providing high quality record sections a two dimensional cross section of the crust was obtained by forward modelling using ray tracing techniques high velocity bodies are found in the upper crust related to the karasjok kittila greenstone belt and the lapland granulite belt they extend to a depth of 6 13 km in the karelian province in the southwest a low velocity zone was found between the depths of 8 and 14 km the middle crust shows a slight increase in the average velocities from the southwest to the northeast and a small velocity jump is found along a mid crustal boundary between 18 and 21 km the thickness of the middle crust varies between 16 and 18 km the lower crust and the crust mantle boundary moho show considerable lateral variation the top of the lower crust lies between 26 and 33 km while its thickness decreases from 21 km in the southwest to 10 14 km beneath the lapland granulite belt and the inari terrain reaching 20 km again in the extreme northeast the velocities also change laterally the thin lower crust is characterized by rather low velocities 6 8 6 9 km s whereas in the southwest and northeast the velocities 6 9 7 3 km s resemble more typical shield structures the moho is found at 47 km in the karelian province rises to 40 km beneath the lapland granulite belt and descends to 46 km in the northeastern part of the kola peninsula province the upper mantle velocities at the moho range from 8 1 km s in the region of the thin crust to 8 5 km s and more beneath the karelian province it is tempting to suggest that the anomalous lower crust underlying the lapland granulite belt and the inari terrain may represent the remnants of an early proterozoic back arc basin that was active prior to the 2 0 to 1 9 ga plate convergence event during which the lapland granulite belt was thrust onto the archaean basement of the karelian province another explanation is to assume that the velocity reduction in the anomalous lower crust was caused by a rather pronounced uplift of this region following the 1 9 ga collision event

earthquake source mechanism determination by use of body wave amplitudes an application to swedish earthquakes abstract a method for earthquake source studies based on a combined use of polarity and amplitude observations is proposed it makes use of the impulses of the observed body waves to avoid the introduction of additional source parameters besides the orientation angles and seismic moments a statistical model is proposed and the method is applied to five small earthquakes in sweden recorded by 3 to 5 stations in the distance range of 20 to 100 km the seismic moments of these earthquakes are in the range of 0 6 to 10 10 11 n m 1 n m 10 7 dyne cm the resulting mechanisms are statistically significant and well defined in spite of the fact that for four of the earthquakes only two or less polarities are used furthermore the solutions are close to the mechanism of the major m o 3 5 10 15 n m earthquake in the gulf of finland 1976 they all indicate horizontal principal compressive stresses in the sector e w to sse nnw the successful use of amplitude observations presented in this paper shows that source mechanism inversion can be made based on recordings at only a very few close stations

the 1985 86 western bohemia earthquakes modelling source parameters with synthetic seismograms abstract a major swarm of microearthquakes main shock m l 4 6 occurred in december 1985 and january 1986 in the western bohemia region 50 2 n 12 4 e here we revisit the 1985 86 series by modelling some pronounced features of the observed p waveforms frequently seen in the records of the cll brg and the grf seismograph stations travel times and waveforms can be explained by a simple two layer crustal model consisting of an upper crust with v p 5 9 km s and thickness t 18 km and a lower crust with v p 6 8 km s and t 11 km the crust mantle boundary is at 29 km depth waveforms recorded at distances between about 100 and 120 km consist of a low amplitude first p wave which has travelled through the lower crust this phase is followed about 0 5 to 1 s later by the large amplitude main event about 3 s after the main event another phase stands out with similar amplitude it probably represents the depth phase sp m p which leaves the focus upwards as an s wave is converted at the surface to p and then follows the path of p m p the reflection from the crust mantle boundary to the receiver we used this depth phase to constrain the focal depth of the main shock to 9 km depths of the stronger events m l 3 of the swarm are within the depth range from 7 to 10 km inversion of body wave amplitudes and p wave polarities for the focal mechanism of the main event reveals a strike slip mechanism which agrees well with previously published results

landslides in the central coalfield cantabrian mountains nw spain geomorphological features conditioning factors and methodological implications in susceptibility assessment abstract a geomorphological study focussing on slope instability and landslide susceptibility modelling was performed on a 278 km2 area in the nalon river basin central coalfield nw spain the methodology of the study includes 1 geomorphological mapping at both 1 5000 and 1 25 000 scales based on air photo interpretation and field work 2 digital terrain model dtm creation and overlay of geomorphological and dtm layers in a geographical information system gis and 3 statistical treatment of variables using spss and development of a logistic regression model a total of 603 mass movements including earth flow and debris flow were inventoried and were classified into two groups according to their size this study focuses on the first group with small mass movements 100 to 101 m in size which often cause damage to infrastructures and even victims the detected conditioning factors of these landslides are lithology soils and colluviums vegetation pasture and topography dtm analyses show that high instabilities are linked to slopes with ne and sw orientations curvature values between 6 and 0 7 and slope values from 16 to 30 bedrock lithology carboniferous sandstone and siltstone presence of quaternary soils and sediments vegetation and the topographical factors were used to develop a landslide susceptibility model using the logistic regression method application of zoom method allows us to accurately detect small mass movements using a 5 m grid cell data even if geomorphological mapping is done at a 1 25 000 scale

seismotectonics of the norwegian continental margin the norwegian continental margin and surrounding areas are seismically less active than some other passive margins worldwide indicating a potential earthquake deficit the adjacent oceanic crust is mostly aseismic except for parts of the lofoten and norway basins which have experienced rapid deposition of glacial sediments the excess load has enhanced the local stress field and in turn the seismic activity the marginal highs along the continent ocean transition and the part of the more and voring basins which experienced crustal extension prior to the early tertiary breakup are practically aseismic this region is also underlain by high velocity lower crust emplaced during breakup suggesting crustal strengthening which also may increase the return periods for the largest events farther landward a spatial correlation of seismic activity and the glacial sediment wedge suggests a causal relationship expressed through preferential rejuvenation of late jurassic early cretaceous faults the locally high seismic activity in the coastal region occurs in areas where the continental crust is relatively thick 25 30 km but still thinner than in the shield area farther east 45 50 km although stress relations are complex we suggest that increased stress due to appreciable postglacial rebound gradients in the coastal region may be a contributing factor while the stress field along the margin complies in general with the ridge push force we infer that regional and local stress enhancement factors are not only present in this region but also necessary for explaining the earthquake activity the relative importance of local stress sources is supported by several cases of 90 stress rotations relative to the ridge push direction the superposition of regional and local stress together with the existence of weakness zones and faults yields potentials for earthquakes primarily through structural reactivation

quantification of neotectonic stress orientations and magnitudes from field observations in finnmark northern norway abstract fieldwork was conducted in finnmark northern norway with the purpose of detecting and measuring stress relief features induced by quarrying and road works and to derive from them valuable information on the shallow crustal stress orientations and magnitudes two kinds of stress relief features were considered in this study the first consists of drillhole offsets that were found along blasted road cuts and which were triggered by the sudden rock unloading following the actual blasting vertical axial fractures found in the concave remains of boreholes represent the second kind of stress relief feature the axial fractures are tension fractures produced by gas overpressure inside the drillhole when the blast occurs as such their strike reflects the orientation of the ambient maximum horizontal stress axis the borehole offsets show mostly reverse slip displacements to the e se and the axial fractures trend nw se on average in agreement with nw se compression induced by north atlantic ridge push forces mechanical considerations of the slip planes offsetting some of the drillholes lead to the conclusion that the magnitude of the maximum horizontal stress at the surface is in the range 0 1 1 mpa this range of magnitudes is 1 2 orders less than the horizontal stress magnitudes measured at the surface in other post glacial environments e g canada it is suggested that this difference is related to the marked decline in stress that followed the tremendous post glacial burst of earthquake activity that affected fennoscandia but apparently not the canadian shield

seismodynamics of sweden deduced from earthquake focal mechanisms summary focal mechanisms from 18 major swedish earthquakes ml upp 3 reveal that 1 several of the studied earthquakes have focal mechanisms with significant extensional stresses which fit well to the idea of postglacial rebound as an important stress generator 2 in areas like south western sweden the north westerly trending compressional axes indicate that ridge push from the north atlantic ridge is also a considerable stress contributor 3 some local tectonic features like the skalderviken depression in kattegat are momentous for seismotectonic interpretations in addition to first p polarities full waveform modelling for frequencies up to 3 hz and epicentral distances up to 225 km provides rather robust focal mechanism determinations focal depths of seven events ranging from 11 to 37 km are well resolved within a few km by waveform modelling

hydrometeorological triggers of periglacial debris flows in the zermatt valley switzerland since 1864 1 the triggering of debris flows depends on a critical combination of available unconsolidated material and water supply in periglacial environments debris flows are generally triggered by liquefaction of loose material in a channel or by progressive erosion during a large release of water here we link an unusually dense and highly resolved database on periglacial debris flows with meteorological records dating back to ad 1864 to reconstruct 150 yr of rainstorms that triggered debris flows at high elevation sites source area elevations ranging from 2000 to 4545 m a s l in the swiss alps analysis is based on a tree ring derived frequency series of debris flows from eight torrents as well as on daily records from three meteorological stations and runoff data from four river gauging stations results show that the debris flow season at these high altitude sites now is much longer may to october than it used to be in the late nineteenth century when activity was limited to june september debris flows early in the season are generally triggered by lower rainstorm totals 20 mm day than those occurring later in the season because early season snowmelt adds considerable amounts of water to the system and therefore facilitates debris flow formation debris flows in may june july and august are triggered primarily by short duration high intensity rainstorms local thunderstorms whereas late season september october debris flows are commonly related to longer lasting advective rainstorms

the determination of statistical and deterministic hydrological landslide triggering thresholds hydrological landslide triggering thresholds separate combinations of daily and antecedent rainfall or of rainfall intensity and duration that triggered landslides from those that failed to trigger landslides they are required for the development of landslide early warning systems when a large data set on rainfall and landslide occurrence is available hydrological triggering thresholds are determined in a statistical way when the data on landslide occurrence is limited deterministic models have to be used for shallow landslides directly triggered by percolating rainfall triggering thresholds can be established by means of one dimensional hydrological models linked to the infinite slope model in the case of relatively deep landslides located in topographic hollows and triggered by a slow accumulation of water at the soil bedrock contact simple correlations between landslide occurrence and rainfall can no longer be established therefore real time failure probabilities have to be determined using hydrological catchment models in combination with the infinite slope model

postglacial rebound and fault instability in fennoscandia summary the best available rebound model is used to investigate the role that postglacial rebound plays in triggering seismicity in fennoscandia the salient features of the model include tectonic stress due to spreading at the north atlantic ridge overburden pressure gravitationally self consistent ocean loading and the realistic deglaciation history and compressible earth model which best fits the sea level and ice data in fennoscandia the model predicts the spatio temporal evolution of the state of stress the magnitude of fault instability the timing of the onset of this instability and the mode of failure of lateglacial and postglacial seismicity the consistency of the predictions with the observations suggests that postglacial rebound is probably the cause of the large postglacial thrust faults observed in fennoscandia the model also predicts a uniform stress field and instability in central fennoscandia for the present with thrust faulting as the predicted mode of failure however the lack of spatial correlation of the present seismicity with the region of uplift and the existence of strike slip and normal modes of current seismicity are inconsistent with this model further unmodelled factors such as the presence of high angle faults in the central region of uplift along the baltic coast would be required in order to explain the pattern of seismicity today in terms of postglacial rebound stress the sensitivity of the model predictions to the evects of compressibility tectonic stress viscosity and ice model is also investigated for sites outside the ice margin it is found that the mode of failure is sensitive to the presence of tectonic stress and that the onset timing is also dependent on compressibility for sites within the ice margin the evect of earth rheology is shown to be small however ice load history is shown to have larger evects on the onset time of earthquakes and the magnitude of fault instability

kinematics of a landslide derived from archival photogrammetry and gps data abstract the evolution of the patigno landslide a deep seated gravitational slope deformation in the northern apennine range italy was investigated using archival photogrammetry and gps observations from a permanent station located inside the landslide historical aerial photographs of the area taken in 1975 scale 1 13 000 1987 1 13 000 and 2004 1 30 000 were co registered into the same reference frame using an unconventional method based on the detection of homologous points in multi temporal models three dtms were produced using a digital photogrammetric workstation and compared the displacement vectors of 293 points in the landslide were determined the average movement velocity of the gps station since 2004 about 3 5 cm yr 1 agrees with the mean displacement rate obtained from photogrammetry furthermore the estimated velocity varies seasonally between 3 and 6 cm yr 1 this variability correlated with rainfall suggests that the creep of the landslide is influenced by hydrological factors

rainfall induced debris flows in pyroclastic deposits campania southern italy abstract a combination of empirical and physically based hydrological models has been used to analyze historical data on rainfall and debris flow occurrence in western campania to examine the correlation between rainfall and debris flow events rainfall data from major storms recorded in recent decades in western campania were compiled including daily series from several rain gauges located inside landslide areas supplemented by hourly rainfall data from some of the principal storms a two phase approach is proposed during phase 1 soil moisture levels have been modelled as the hydrological balance between precipitation and evapotranspiration on a daily scale using the method of thornthwaite geograph rev 38 1948 55 phase 2 is related to the accumulation of surplus moisture from intense rainfall leading to the development of positive pore pressures these interactions take place on an hourly time scale by the leaky barrel lb model described by wilson and wiezoreck env eng geoscience 1 1995 11 in combination with hourly rainfall records the lb model has been used to compare hydrological effects of different storms the critical level of retained rain water has been fixed by the timing of debris flow activity related to recorded storm events new rainfall intensity duration thresholds for debris flow initiation in western campania are proposed these thresholds are related to individual rain gauge and assume a previously satisfied field capacity condition the new thresholds are somewhat higher than those plotted by previous authors but are thought to be more accurate and thus need less conservatism

major palaeoproterozoic shear zones of the central fennoscandian shield abstract employing two recently studied crustal scale shear zones as type examples this paper summarizes the major palaeoproterozoic svecokarelian shear tectonics of the central fennoscandian shield and demonstrates that this part of the shield was not as stable during the svecokarelian orogeny as commonly assumed the collision of the svecofennian island arc with the karelian continent first created numerous nw se trending folds and thrusts of stages d1 and d2 which were then modified by successive shearing during stages d3 and d4 stage d3 built up a system of n s trending shear zones here named the savolappishearsystem the type example of which is the hirvaskoski shear zone this is a dextral strike slip shear zone at least 150 km long and 10 30 km wide characterized by blastomylonitic fault rocks and various structures such as hook folds z folds and sheath folds associated with the principal displacement zone synthetic riedel shears and pinnate shears the traces of the axial planes of f3 en echelon folds deviate 15 30 anticlockwise from the plane of the principal displacement zone other members of the savolappi shear system are the pajala shear zone in northern sweden and the russian north karelia shear zone in the east stage d4 created a conjugate shear system called the finlandia shear system the type example of which is the oulujarvi shear zone this is a ne sw trending sinistral strike slip shear zone more than 250 km long and 20 30 km wide across its southwestern end it is composed of a ne sw trending principal displacement zone synthetic riedel shears and pinnate shears with antithetic riedel shears in a nw se direction typical fault rocks within these shears are s c mylonites the axial plane traces of f4 folds of all scales diverge by 20 40 clockwise from the plane of the principal displacement zone the kuopio shear zone is a conjugate nw se trending counterpart of the oulujarvi shear zone as a whole the finlandia shear system forms a conjugate network of nw se and ne sw trending shear zones which occupies most of the northern and central fennoscandian shield

geophysical geotechnical and hydrological investigations of a small landslide in the french alps abstract geophysical geotechnical and hydrological surveys were conducted in the french alps on a small landslide in black marl material to assess the stability the geophysical survey consisting of electromagnetic geo electric and relative differences in water content the data on the basal slip surface together with geotechnical parameters cohesion and angle of internal friction were used to make a stability analysis this analysis revealed that a groundwater level of 4 m below the ground surface is the critical threshold for reactivating the landslide the hydrological investigation which entailed measurements of saturated permeability and pressure heads indicated that instability depended on long term wet conditions with little evapotranspiration

forecasting landslide hazard by the 3d discrete element method a case study of the unstable slope in the lushan hot spring district central taiwan abstract catastrophic landslides and related phenomena are commonly facilitated by the subtropical climate with frequent typhoons and recurrent earthquakes in taiwan s mountainous areas one area susceptible to potentially catastrophic landslides is located at lushan in central taiwan which is famous for its hot springs and tourism the northern slope above the hot spring district slips gradually and frequently due to heavy rainfall for safety reasons the slip affected area has been under constant borehole monitoring by government agencies and a controversial public debate has arisen over permanent evacuation of the hot spring district in this study we attempt to simulate possible scenarios of catastrophic slope failure using slip geometries derived from the monitoring data and assess potential landslide impact areas by a discrete element method using the pfc3d code in the worst case scenario the lushan hot spring district is predicted to be destroyed by debris in 20 s besides the planned regional emergency refuge is rapidly jeopardized by flooding resulted from landslide dammed lakes this study addresses catastrophic slope failure under heavy rainfall conditions given a range of friction coefficients and varied continuity of the failure surfaces it is noted that the pfc3d code has limitations in modeling all complex mechanisms of landslide particularly in modeling loss of material shear strength due to increases in pore pressure nevertheless the numerical simulation results by the 3d discrete element method provide scenario based runout paths particle velocities and landslide affected areas which are useful information for decision support and future landslide hazard assessment

crust and upper mantle structure along the dss baltic profile in se finland summary the 430 km long dss baltic profile in se finland runs through the rapakivi intrusion the svecokarelian geosynclinal complex including the ladoga bothnian bay zone and the archean basement complex a brief description of field operations in 1982 is presented record sections of p and s waves were used for the interpretations a starting model was constructed by inverse methods and improved by dynamic ray tracing modelling three blocks are indentified on the cross section from sw to ne these are the southern associated with the rapakivi massif depth to moho m about 40 km the central ladoga bothnian bay zone with m of approximately 55 60 km and the northern archean crystalline basement with m about 40 45 km the average crustal velocity is 6 6 6 7 kms the crustal structure along the baltic profile is compared with the surrounding dss profiles finnish sveka and soviet kern tulos and ladoga profiles the eastern border of the ladoga bothnian bay zone was located and specific features of the crust and uppermost mantle along the profile area are discussed

fennoscandian earthquakes whole crustal rupturing related to postglacial rebound local and regional earthquake locations provide seismic evidence that large shield earthquakes have occurred in northern fennoscandia these paleoearthquakes with fault lengths of up to 160 kilometers and average displacements of up to 15 meters were triggered by nonisostatic compressive stresses caused by the removal of the ice at the end of the last deglaciation the fennoscandian faults were probably formed by single events that ruptured through most of the crust the largest event moment magnitude mw 8 2 was larger than other known stable continent earthquakes outside failed rifts or extended crust

the analysis of rainfall induced slope failures at iva valley area of enugu state nigeria this paper analyses the dominant mechanisms of slope failures and identifies potential obstacles to landslide hazard reduction at the iva valley area enugu nigeria the landscape is replete with landslide scars and gullies of varied sizes and the slope deposits comprise unconsolidated friable sands inter bedded with thin units of montmorillonitic claystone forty three landslide events were identified in the study area with most being shallow short run out movements with slip surface depth 2 m the study found the landslides mainly occur in the beginning of rainy season characterized by short duration high intensity rainfall an integrated approach comprising field mapping laboratory tests and numerical analyses reveals that the barren nature of the slopes prior to the outset of rainy season high rainfall intensity erosion overgrazing soil characteristics and the site s unique lithologic sequence are the main causes of instability shearing tests under several conditions showed that the soils strongly strain soften until low steady state strength is achieved a computer code based on this strength reduction technique used input parameters obtained from the field and laboratory studies to simulate a landslide with similar structure travel distance and distribution area it is noted that urbanization has gradually increased the vulnerability of the society s poor to landslide hazards as they now erect unplanned residence tents and blocks on the slopes this work is part of a regional study aimed at finding ways of protecting the vulnerable by generating data that could be used to build future landslide susceptibility map

effects of hydromechanical loading history and antecedent soil mechanical damage on shallow landslide triggering evidence suggests that the sudden triggering of rainfall induced shallow landslides is preceded by accumulation of local internal failures in the soil mantle before their abrupt coalescence into a landslide failure plane the mechanical status of a hillslope at any given time reflects competition between local damage accumulated during antecedent rainfall events and rates of mechanical healing e g rebonding of microcracks and root regrowth this dynamic interplay between damage accumulation and healing rates determines the initial mechanical state for landslide modeling we evaluated the roles of these dynamic processes on landslide characteristics and patterns using a hydromechanical landslide triggering model for a sequence of rainfall scenarios the progressive nature of soil failure was represented by the fiber bundle model formalism that considers threshold strength of mechanical bonds linking adjacent soil columns and bedrock the antecedent damage induced by prior rainfall events was expressed by the fraction of broken fibers that gradually regain strength or mechanically heal at rates specific to soil and roots results indicate that antecedent damage accelerates landslide initiation relative to pristine undamaged hillslopes the volumes of first triggered landslides increase with increasing antecedent damage however for heavily damaged hillslopes landslide volumes tend to decrease elapsed time between rainfall events allows mechanical healing that reduces the effects of antecedent damage this study proposed a quantitative framework for systematically incorporating hydromechanical loading history and information on precursor events e g such as recorded by acoustic emissions into shallow landslide hazard assessment

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

fiber bundle model for multiscale modeling of hydromechanical triggering of shallow landslides 1 sudden and rapid mass movements associated with landslides and snow avalanches present a hazard to life and infrastructure yet their predictions and triggering mechanisms remain poorly understood statistical methods and correlative studies have been used to produce landslide or avalanche susceptibility maps often with limited physical basis mechanistic approaches based on factor of safety computation seldom represent the progressive transition from local failure events to a landslide and in general do not include heterogeneities associated with land cover or with subsurface material properties and hydrologic pathways focusing on rainfall induced shallow landslides we propose the use of the fiber bundle model fbm a generic yet powerful and adaptable model used in modeling fatigue and fracture of complex and disordered materials the primary strength of the fbm is its ability to represent the progressive failure of cracks and shear zones and the ruptures of highly heterogeneous bonding elements that are present in soils at all scales the model also provides a natural framework for interpretation of acoustic emission signatures from failing slopes which may form the basis of a monitoring and warning system

comparison of satellite and air photo based landslide susceptibility maps landslide susceptibility maps can be prepared in a variety of ways many geoscientists favour the use of an overlay model approach in which several map layers are combined by some arithmetic rules to determine the potential for sliding in an area or region the resulting susceptibility maps although based on a subjective weighting of relevant factors can often be of high accuracy and utility in order to obtain the relevant input data for this type of analysis remotely sensed data are often used to date susceptibility mapping just as the mapping of historic and individual landslides has tended to require higher resolution imagery this has somewhat limited the application of landslide susceptibility mapping while high resolution air photo or satellite imagery is superior to lower resolution imagery for the purpose of mapping of historic and individual landslides such higher levels of resolution may not be required for the development of landslide susceptibility maps in order to determine if medium resolution satellite imagery such as spot or aster could provide the needed data for landslide susceptibility mapping a comparison was undertaken of landslide susceptibility model output resulting from the use of stereo napp aerial photography versus the use of data obtained from stereo spot imagery the test area selected for this study consisted of two watersheds pena canyon and big rock canyon situated west of santa monica california usa along the pacific coast highway both watersheds have a long and well documented history of landslide activity and sufficient geologic variability and complexity to provide a good test site the specific overlay model used in this evaluation required input data consistent with the needs of many other models of this type the model output derived from the two different data sources and presented here in the form of susceptibility maps were virtually identical statistical and difference analysis confirmed that both methods of obtaining input data provide similar results and successfully identified landslide prone areas these results suggest that satellite imagery in this instance spot images could potentially be used in lieu of conventional air photos to evaluate landslide susceptibility in many situations especially in the case of remote locations and or developing countries this capability should result in substantial savings in terms of time financial resources and overall viability

landslides triggered in weathered crystalline rocks of moderate latitudes a case study in mediterranean environment the maures massif france abstract the main purpose of this study is to characterize shallow and moderately deep landslide prone materials in crystalline rocks at moderate latitudes the procedure is based by a four step approach coupling the geomorphological approach the geotechnical approach and slope stability analyses based on limit equilibrium equations firstly different weathering horizons were identified with different thicknesses and characteristics depending on the original lithology these observations led to the development of a weathering model with two steps a regional paleo weathering step and a geomorphological weathering step secondly conceptual models of weathered horizon thicknesses were created according to the lithological context these models led to the identification of three major weathering types thirdly slope stability models were computed for three types of weathered lithology favourable theoretically to slope failure granit micaschists gneiss for each case the different models properly computed landslide occurrences and their locations for highly saturated weathered materials that corresponded to field observations to finalize the study a first analysis of precipitation data was carried out to define some triggering trends for slope failures in this environment therefore based on this simple approach it is possible to define some trends for shallow and moderately deep landslides in weathered crystalline environment located in moderate latitudes with mediterranean climate finally the information can be used by end users and practitioners for public works management on these slopes

rainfall thresholds for shallow landsliding derived from pressure head monitoring cases with permeable and impermeable bedrocks in boso peninsula japan rainfall thresholds for shallow landslide initiation were determined for hillslopes with two types of bedrock permeable sandstone and impermeable mudstone in the boso peninsula japan the pressure head response to rainfall was monitored above a slip scarp due to earlier landslides multiple regression analysis estimated the rainfall thresholds for landsliding from the relation between the magnitude of the rainfall event and slope instability caused by the increased pressure heads the thresholds were expressed as critical combinations of rainfall intensity and duration incorporating the geotechnical properties of the hillslope materials and also the slope hydrological processes the permeable sandstone hillslope has a greater critical rainfall and hence a longer recurrence interval than the impermeable mudstone hillslope this implies a lower potential for landsliding in sandstone hillslopes corresponding to lower landslide activity copyright 2007 john wiley sons ltd

landslide triggering scenarios in homogeneous geological contexts the area surrounding acri calabria italy abstract the paper describes a methodology to detect landslide triggering scenarios in geological homogeneous areas and for some specific landslide categories in these scenarios the rainfall landslide relationship as well as the pluviometric load conditions influencing slope instability have to be investigated the methodology is applied to an area located in northern calabria italy and affected by widespread and different slope instability phenomena outcropped fractured and deeply weathered crystalline rock masses determining geologic homogeneous conditions are present in the same area suitable and homogeneous climatic features have also been found according to the methodology adopted the hydrologic analysis of rainfall time series is initially carried out notwithstanding historical data concerning landslide mobilization but using simple models to determine critical pluviometric scenarios for the three landslide categories shallow medium deep and deep landslide triggering scenarios individualized according to this procedure are less significant as compared to the landslide mobilization detected in the study area by means of historical research and ascribed to the three landslide categories according to geomorphologic analysis subsequently the possible landslide triggering scenarios are outlined by carefully investigating the hydrologic analysis limited to the periods identified according to the historical data in the study area and approximately for all the areas characterized by the outcrop of fractured and deeply weathered crystalline rocks significant triggering scenarios can be outlined in particular shallow landslide triggers could be activated by rainfall events with intensities exceeding 90 mm day and or with amounts exceeding 160 mm as for medium deep and deep landslides triggering mechanisms are more complicated and effective rainfall contribution must be taken into account compared to groundwater storage moreover a more complex link between deep landslides and precipitation is confirmed the results obtained to date highlight the potential of this methodology which enables us to define and progressively improve the knowledge framework by means of a work sequence integrating different disciplinary tools and results

the polar profile revisited combined p and s wave interpretation abstract the polar profile project studied the crustal structure in a 440 km long swath extending across the northern baltic shield in a southwest northeasterly direction the obtained seismic data comprise p waves and very clear s waves the results of forward modelling using the raytracing technique together with synthetic seismograms for the s waves necessitated slight modification of a previously published velocity model obtained from p waves only the profile crosses the lapland granulite belt with granulite facies rocks at the surface the lapland granulite belt and a part of the karasjok kittila greenstone belt are recognized as high velocity bodies in the upper crust both for p and s waves the v p v s ratio and poisson ratio respectively seems to be slightly lower than that in the surrounding archaean gneisses which also prevail in the middle crust down to a depth of about 30 km the lower crust 30 45 km is marked by a pronounced velocity contrast of the p waves in respect to the middle crust but only a small velocity contrast for the s waves is seen in the southwestern part of the profile unusually high velocities 8 6 8 7 km s are found in the upper mantle at depths of 46 to 50 km

moment tensors state of stress and their relation to post glacial rebound in northeastern canada summary in the stable craton of northeastern canada moderate seismicity as well as glacial isostatic adjustment gia has been observed we investigate five earthquakes with moment magnitudes between 3 6 and 4 1 that have occurred in northern hudson bay since 2007 which may be triggered by gia focal mechanisms of the earthquakes are determined using a waveform fitting procedure for surface waves in which the best double couple mechanism is obtained through a grid search over strike dip and rake all events exhibit a thrust fault mechanism in general agreement with mechanisms of previously analysed earthquakes in that area stress inversion results incorporating our new mechanisms as well as previously published results exhibit significant differences from previously calculated stresses from gia models for the first time maximum horizontal stress direction shmax is compared to the modelled stress values for northeastern canada we find that the maximum horizontal stress direction strikes roughly nnw sse in contrast to previously inferred ne sw orientation of shmax our results indicate that the local stress field in northern hudson bay deviates from regional stresses resulting from the existence of a roughly e w oriented zone of faulting which is not included in existing gia models

failure characteristics of rainfall induced shallow landslides in granitic terrains of shikoku island of japan soil slips debris slides and flow occurrences on hill slopes of particular areas are closely related to the mode of rainfall because of geological geomorphological and climatic settings japan is highly prone to rainfall induced landslides in 2004 shikoku the smallest island of japan faced extreme events of typhoon rainfalls and suffered huge losses of life and property because of floods and landslides this paper deals with the synoptic descriptions of failures that occurred in the granitic terrain of northeast shikoku island japan along with rainfall and failure relationships during the typhoon 0423 tokage of 2004 examples of typical failures that occurred in moriyuki and monnyu of northeast shikoku are taken into consideration in this study data from laboratory and field were used to perform sensitivity and stability analyses with respect to varying slope angles strength parameters and thicknesses of saturated residual soil this study attempts to employ a standard method of stability analysis of translational slides which are very common in masa soil weathered granite during extreme rainfall average rainfall intensities and duration during typhoon tokage were also used to interpret landslide triggering thresholds for the study area

evaluation of landslide reactivation a modified rainfall threshold model based on historical records of rainfall and landslides abstract this study proposes a modification of the conventional threshold model for assessing the probability of rainfall induced landslide reactivation the modification is based on the consideration that exceedance of a pre determined rainfall threshold is a necessary but not sufficient condition to reactivate a landslide the proposed method calculates the probability of reactivation as a function of the probability of exceedance of a pre determined rainfall threshold as well as the probability of occurrence of a landslide after such exceedance the data for the calculation were obtained from historical records of landslides and rainfall the method was applied to two complex landslides san donato and la salsa involving fine grained debris in the southern section of the apennine foredeep the minimum rainfall threshold triggering landslide reactivation on the two slopes was determined by examining rainfall patterns during the 180 days preceding the slide events for the san donato and la salsa landslides the minimum triggering threshold consists of rainfall events lasting 15 days with cumulated rainfall exceeding 150 and 180 mm respectively based on hydrological and statistical analyses the annual probabilities of exceeding the thresholds were estimated to be 0 38 and 0 25 respectively during the period from 1950 to 1987 the minimum threshold was exceeded 14 times and four reactivations occurred at san donato whereas the threshold was exceeded 10 times and three reactivations occurred at la salsa hence the probabilities of landsliding after exceedance of the minimum rainfall threshold are 4 14 and 3 10 respectively finally annual reactivation probabilities were calculated to be 0 11 and 0 08 respectively the reliability of the minimum rainfall threshold was tested by i simulating variations in the stress strain behavior of the slopes as a result of fluctuations in the water table from normal to extreme values and ii analyzing the results of continuous multi year monitoring of pore pressure and rainfall variations on a slope composed of dominantly fine grained debris

modelling morphological processes in the vicinity of shore parallel breakwaters abstract a coastal area morphological modelling system is used to investigate the planform development tombolo or salient behind a single surface piercing detached breakwater a quasi three dimensional q3d description of the flow and the sediment transport together with a revised bed level update scheme were incorporated recently in the morphological modelling suite applied in the present investigation the q3d sediment transport formulation used allows simulating beach profile evolution and planform development simultaneously several breakwater layouts were investigated in a series of tests in which the incident wave condition was taken as constant in time the investigation was done for surface piercing shore parallel breakwaters in a non tidal environment the morphological simulation results for the planform shape agree qualitatively with field observations and predictions from empirical rules using the simulation results simple design curves for surface piercing breakwaters are derived the importance of properly accounting for the influence of wave diffraction when modelling sediment transport and morphology in the vicinity of shore parallel structures is also investigated the present paper summarises much of the work performed at dhi water environment over the past 10 years within the field of coastal area morphological modelling

1 9 1 8 ga old strike slip megashears in the baltic shield and their plate tectonic implications abstract the tectonic evolution of the ca 2 0 1 75 ga old svecokarelian fold belt is reviewed and evidence is presented for large scale intraplate strike slip movements along ductile megashears after the formation of the kola collision suture and the neighbouring granulite tanaelv thrust belt around 1 9 ga ago dextral shearing was initiated along n s trending megashears subsequent anticlockwise rotation of the initially nne ssw oriented principal compressive stress caused dextral shearing along a nw se trending megashear and reversal in the sense of shearing in the n s trending ones further anticlockwise stress rotation to a total of about 120 brought an end to sinistral shearing along the n s megashears around 1 8 ga ago and caused reversal to sinistral slip along the nw se megashear both the older 1 9 1 85 ga and younger 1 84 1 8 ga parts of this evolution are recorded within the karelian province and its southwestern margin where consolidation of the lithosphere took place shortly after 1 9 ga ago in the svecofennian province where crustal accretion did not start until around 1 9 ga ago the older movements may have caused synaccretional crustal folding but with increasing consolidation the deformation was concentrated along megashears although it is still not possible to interrelate the function of active subduction zones and intraplate megashears the evolution traced so far provides support for plate tectonic interpretations of the early proterozoic geodynamics of the baltic shield

seismo and neotectonics in finnmark kola and the southern barents sea part 2 seismological analysis and seismotectonics abstract a detailed review and analysis of seismological data acquired since 1979 from finnmark kola and the southern barents sea has provided a much improved delineation of the earthquake activity in that region in the barents sea the seismicity is confined only to the western areas while the finnmark kola coastal areas show some seismicity only north and east of murmansk in the rybachi cape tereberski region further inland there are several clear seismicity lineations that to some extent can be correlated with postglacial faults including the ne sw striking stuoragurra fault in finnmark the spatial correlation between seismicity and mapped faults is interpreted in general as a reflection of broad zones of weakness that respond to the present day stress field a detailed analysis of the earthquakes in this area has also shown a dynamic consistency in that they reveal a reverse faulting pattern that is consistent with a detailed geological study that includes a core drilling the dominant horizontal stress direction in this region is nnw sse consistent with the ridge push effect

focal depth determination for moderate and small earthquakes by modeling regional depth phases spg spmp and spn there are three usable regional depth phases spg spmp and spn and their corresponding reference phases pg pmp and pn the differential time between each depth phase and its reference phase can be used to estimate earthquake focal depth we have developed a method to determine focal depth for moderate and small earthquakes by using a regional depth phase modeling rdpm method we used a default focal mechanism to generate the differential times for all earthquakes to estimate the reliability of the modeled focal depths we compared our solutions with those obtained by other methods and found the consistency is good because the focal depths estimated by rdpm are model dependent we tested the extent of the dependency and found that a 10 error in the crustal model may generate a 10 15 error in the modeled depth the absolute error is determined by the error in the crustal model and the focal depth itself we found that earthquake location errors have only a small effect on the modeled focal depths by analyzing synthetic and observed waveforms we found a distance window within which spmp and pmp are well developed and within the window the p portion of the waveform is relatively simple and spmp and pmp are easy to identify we also demonstrated that the assumptions of spmp and pmp are correct that regional depth phases are not developed or not discernible in some regions and that regional depth phases have special features that can be used to identify those phases

a warning system for rainfall induced shallow failures abstract it is widely recognised that soil slips and debris flows are triggered by short intense storms owing its geologic geomorphologic and climatic settings the piedmont region nw italy is highly prone to the occurrence of this kind of landslides in the last two centuries in fact a total of 105 severe meteoric events which triggered shallow failures occurred and of these 18 events took place from 1990 to 2002 a fair number of rainfall thresholds have been proposed in the literature defined both on empirical or on physical bases empirical thresholds are defined collecting rainfall data for landslide meteoric events and for events without landslides while physical thresholds are based on numerical models that consider the relation between rainfall pore pressure and slope stability the main objective of this paper is the identification of the empirical triggering thresholds for the piedmont region four meteoric events were selected and analysed november 4 5 1994 july 7 8 1996 april 27 30 2000 october 13 16 2000 because they supply a wide range of variation for both rainfall parameters duration intensity cumulative rainfalls and the number of induced landslides in the intensity duration plot the critical limit is described by the equation i 19d 0 50 where i rainfall intensity expressed in mm h and d rainfall duration expressed in hours such a limit is traced to envelop 90 of the points on the graph in the ni d diagram the triggering thresholds are given by the equations ni 0 76d 0 33 and ni 4 62d 0 79 where ni normalised intensity with respect to the annual precipitation map expressed in mm h pma 100 in the article the different meaning of these thresholds is discussed finally the diagram ni ncr is proposed the triggering threshold is given by the expression ni 0 09ln ncr 0 54 where ncr is the normalised cumulative critical rainfall mm pma 100 the application of the triggering thresholds as a fundamental element in a warning system dedicated to the safeguarding of population in landslide prone areas is discussed in detail an operating procedure which is presently being verified and tested in the studied area is described

landslide databases for climate change detection and attribution abstract a systematic inventory of landslide events over regional spatial scales and through time is required for investigating changes in landslide frequency along side changes in landslide triggers this paper describes the methods used to compile a european wide landslide inventory and some of the methodological and practical obstacles that inhibit better use and development of such inventories we argue that these methods can be used more widely to provide a comprehensive picture of landslide populations and to further enrich our understanding of the impact of climate change and other drivers on landslide frequency and magnitude

image enhancements of landsat 8 oli and sar data for preliminary landslide identification and mapping applied to the central region of kenya image enhancements lead to improved performance and increased accuracy of feature extraction recognition identification classification and hence change detection this increases the utility of remote sensing to suit environmental applications and aid disaster monitoring of geohazards involving large areas the main aim of this study was to compare the effect of image enhancement applied to synthetic aperture radar sar data and landsat 8 imagery in landslide identification and mapping the methodology involved pre processing landsat 8 imagery image co registration despeckling of the sar data after which landsat 8 imagery was enhanced by principal and independent component analysis pca and ica a spectral index involving bands 7 and 4 and using a false colour composite fcc with the components bearing the most geologic information the sar data were processed using textural and edge filters and computation of sar incoherence the enhanced spatial textural and edge information from the sar data was incorporated to the spectral information from landsat 8 imagery during the knowledge based classification the methodology was tested in the central highlands of kenya characterized by rugged terrain and frequent rainfall induced landslides the results showed that the sar data complemented landsat 8 data which had enriched spectral information afforded by the fcc with enhanced geologic information the sar classification depicted landslides along the ridges and lineaments important information lacking in the landsat 8 image classification the success of landslide identification and classification was attributed to the enhanced geologic features by spectral textural and roughness properties

seismo and neotectonics in finnmark kola peninsula and the southern barents sea part 1 geological and neotectonic framework abstract as a background for assessing the seismo and neotectonics of the finnmark kola peninsula region emphasis has been directed towards the lineament framework involving a careful examination of digital landsat tm imagery integrated with a variety of data sets ranging from geophysics and digital elevation models to microtectonics based on a detailed field structural control of many of the multiphase lineaments in this 70 000 km2 area of the northeastern part of the fennoscandian shield as well as microscopic investigation of the fault mylonites and breccias five principal lineament sets were distinguished of the nw se polyphasal megafractures the murmansk shear zone carries geological and isotopic evidence of an archaean tectonothermal history and demarcates an important terrane boundary lineaments irrespective of their trends were classified according to their significance in the regional geological framework some lineaments are clearly associated with gravity and aeromagnetic anomalies and probably extend to deep crustal levels quite a few of the prominent faults within lineament zones were reactivated in post glacial times in one area in finnmark core drilling through a se dipping post glacial reverse fault has confirmed its listric shape at depth earthquake focal mechanisms for this same fault are presented in the second part of this dual contribution

failure of peat covered hillslopes at dooncarton mountain co mayo ireland analysis of topographic and geotechnical factors abstract shallow landslides involving loss of blanket peat are relatively uncommon but can nevertheless be environmentally and geomorphologically significant this paper describes a cluster of 40 shallow landslides including significant peat failures which occurred within 2 5 km 2 on dooncarton mountain republic of ireland in the evening of 19 september 2003 during an exceptional rainfall event it examines two hypotheses i that the combination of topography and local soil catena characteristics were the primary site factors that led to the occurrence of most of the failures and ii that anthropogenic disturbance to the slopes in the form of boundary ditches or peat cutting activities may have contributed to three of the largest peat failures all of the landslides were mapped and sampled within 4 months of the event physical hydrological and geotechnical properties of the slope materials were determined from samples obtained from nine representative failures possible controls on the stability of the slopes were investigated by modelling seven of the landslides and a series of hypothetical slopes using standard limit equilibrium methods the humified blanket peat was underlain by a dominantly sandy mineral material including a buried soil horizon derived from weathering of the mainly schist bedrock direct shear tests established the respective shear strengths to be 50 c 0 buried soil and 21 25 c 8 11 kpa basal peat although back analyses suggested that the average peat cohesion was lower than this on the failed slopes analyses of separate slope segments of the landslides showed that the main slope convexity where the peat cover gives way to thin peaty soil defined the zone of minimum stability failure of the slope segment immediately above the convexity was controlled by the depth of peat and the hydrostatic or possibly artesian water pressures within the slopes thus catena characteristics coupled with local topography gradient and peat depth were important determinants of slope instability two of the failed slopes were crossed by boundary ditches but contrary to accounts from elsewhere stability analyses suggested that these ditches did not contribute significantly to the landslides stability analysis of a slope affected by peat extraction also suggested no direct causal association but the hydrological conditions developed in the vertical tine cuts did probably contribute to a large peat slide at other locations therefore similar anthropogenic factors should be incorporated in landslide hazard assessments

evolution of the large landslide induced by typhoon morakot a case study in the butangbunasi river southern taiwan using the discrete element method abstract in 2009 typhoon morakot delivered high intensity rainfall and triggered many sites of large landslide which projected areas were larger than 10 000 m 2 from the satellite image especially in southern taiwan according to dtm analysis the material volume of the large landslide in butangbunasi river was more than four times larger than that of the nearly famous landslide disaster in hsiaolin village nevertheless the different movement of these two large landslides led to different disaster impacts based on literatures and field works the large hsiaolin landslide was a catastrophic landslide which had high velocity and less energy loss in the kinematic process the source area of the large landslide in the butangbunasi river on the other hand was composed of several landslide events and the kinetic energy dissipated when the landslide materials attained to riverbed in sequence in this study we divided the butangbunasi river large landslide into five slope units namely a b c d and e landslide events to recognize the mechanism of the large landslide and the simulation by using the particle flow code 3d pfc3d which is based on the discrete element method provided the kinematic process of the large landslide in the butangbunasi river it is noticed that most of the initial energy dissipated during the movement which the fist happening landslide event counteracted the crash of the follow up events and the residual energy gradually declined by the collision interaction of landslide blocks until the end of the large landslide the result helps to reconstruct the evolution of the large landslide from small scale landslide events and contributes to predict the affected region of the disaster it also reveals that even though the impact of the large landslide is reduced by sequent small scale landslide events there still remain secondary disasters such as landslide dam which show a high potential risk in the river valley and midstream

geotechnical aspects of soil slips in alpine regions abstract slope movements are due to many different causes numerous investigations carried out during the last ten years have led to the supposition that almost all slope movements and particularly those occurring in soils are conditioned by a significant combination of factors for the alpine regions quantity duration and kind of precipitation have to be considered as direct mechanical causes combined with such contributing factors as geological and soil mechanical properties aspect vegetation slope inclination and slope morphology they will determine the type dimensions and process of slope movements the detailed investigation of 140 slope movements in slightly cohesive soils show that the process of movement is represented by sliding and flow events in particular it was found out that shallow scars with planar slides predominate so that the supposition of an infinite slope model for slope stability appears to be justified in many cases debris flows and debris avalanches continued downslope of the source area of the scars

postglacial reactivation of the suasselka pgf complex in sw finnish lapland the suasselka fault complex is recognized from high resolution digital elevation models lidar dems as a complex of 37 surface ruptures striking sw ne and cutting through weichselian glacial sediments confirming the postglacial nature of the rupturing event the analysis of lidar dems geophysical profiles and trenching of glacial sediments at two sites along the suasselka postglacial fault pgf system has provided evidence of earthquakes that post and predate the late weichselian deglaciation at the suaspalo trenching site at least two different rupture events are observed the first one predates the deposition of the lowermost till unit and potentially dates to the early or even pre weichselian the second rupture event on the other hand deforms overlying tills and is thus a post weichselian event our results indicate that multiple rupturing events can take place within postglacial fault complexes which is the second time such a characteristic has been proven for pgfs in northern fennoscandia furthermore the present results provide the first evidence of either early or even pre weichselian faulting in finland suggesting that the same fault complexes were also active after glacial phases that predated the last glacial maximum of the late weichselian these results warrant re evaluation of the long term seismic risk associated with the faults as the assumption of single rupture events is erroneous considering that the suasselka pgf complex is composed of four pgf systems and 37 isolated 150 7500 m long segments we calculated the potential moment magnitudes based on the rupture length and mean maximum vertical displacement for each individual segment and system taken that they potentially ruptured independently and finally for the entire suasselka pgf complex for the entire complex rupturing in a single event the observed displacement and length of the complex yields a moment magnitude estimate of mw 6 7 8 1 however based on geomorphological and sedimentological evidence we believe that this is a conservative estimate of the moment magnitude of the paleoearthquake if isolated pgf systems are considered to have ruptured individually the moment magnitudes estimated based on surface rupture lengths range from mw 5 5 6 7 and based on mean and maximum cumulative displacement values the estimated values range from mw 6 2 7 3 and mw 6 7 8 0 respectively as we cannot with the available data distinguish the exact number of events the age of events or which segments potentially ruptured at the same time we conclude that the events that took place in the complex ranged in moment magnitude from c mw 5 5 to 8 1 the mw 8 1 estimate representing conservative upper bound for the maximum moment magnitude

infiltration analysis to evaluate the surficial stability of two layered slopes considering rainfall characteristics abstract shallow slope failures in residual soil during periods of prolonged infiltration are common throughout the world using a one dimensional infiltration model and an infinite slope analysis this study examines an approximate method of determining how infiltration influences the surficial stability of two layered slopes the method extends moore s infiltration model which is based on the green ampt model to cover more general situations including those where water moves upward from a perched water table in decreasingly permeable soil the method has also been used to evaluate the likelihood of a shallow slope failure being induced by a particular rainfall event in making this evaluation the method takes into accounts the rainfall intensity and duration of various return periods in a two layered soil profile a comparison of the results of the infiltration model with the results of numerical analyses shows that with the use of properly estimated input parameters the proposed model compares reasonably well with other model that rely on more rigorous finite element method

estimating temporal probability for landslide initiation along transportation routes based on rainfall thresholds abstract the estimation of the temporal probability of landslide initiation is an essential component in landslide hazard assessment in this paper a temporal probability model is presented for the initiation of shallow translational debris slides and debris flows along cut slopes of a railroad sector in southern india for which an extensive landslide database was available covering a time span of 15 years the model is based on rainfall thresholds and gives the likelihood of occurrence of rainfall that can trigger landslides with a certain density the temporal probability was calculated as the joint probability of annual exceedance probability of the rainfall threshold determined using a poisson probability model and the probability of landslide occurrence once the threshold had been exceeded the model was tested for a 19 km long railroad alignment in the nilgiri hills which was divided into a number of sections on the basis of terrain characteristics a landslide inventory containing dates of occurrence was prepared from historical records for the period 1987 to 2007 daily rainfall for the same period was collected from 15 rain gauges rainfall thresholds were established for the sections based on the relationship between daily and antecedent rainfalls four thresholds were defined for rainfall events that can trigger one or more landslides within each section and one threshold that can trigger 15 or more landslides along the entire route the annual temporal probability varies from 0 27 to 0 49 the model was also found useful in predicting landslides in a nearby road with similar characteristics the result indicates that more than 60 of the recorded landslides along the road occurred within the sections with high temporal probability values 0 40 the temporal probability derived from the model forms the basis for future landslide risk analysis along the transportation routes