the effect of earth rheology and ice sheet size on fault slip and magnitude of postglacial earthquakes abstract moderate past and present day seismicity is observed in formerly deglaciated regions of north america and europe an understanding of the occurrence of these earthquakes is important for estimating the seismic risk within these areas as well as areas affected by recent ice sheet melting in particular greenland and antarctica we have developed a new finite element approach that allows us to estimate the fault throw for areas once covered by a continental ice sheet the simulation is initialized by loading a two dimensional earth model with an ice sheet the model incorporates a stress field consisting of rebound horizontal background and vertical stresses as well as a fault that can accommodate slip the sensitivity of fault throw and activation time is tested with respect to lithospheric and crustal thickness viscosity structure of upper and lower mantle and ice sheet thickness and width as well as fault location and angle single event seismic displacements of up to 18 5 m are obtained approximately equivalent to an earthquake with a moment magnitude of 8 5 the thickness of the crust and lithosphere are major parameters affecting the total magnitude of fault slip whereas the size of the ice sheet primarily affects the activation time most faults start to move close to the end of deglaciation and movement typically stops for our simulations after one thrusting reverse earthquake however in our simulations faults with a dip of 60 also show several fault movements before and after the end of deglaciation

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

crustal deformation associated with glacial fluctuations in the eastern chugach mountains alaska the changes of the solid earth in south central alaska in response to two major glacial fluctuations on different temporal and spatial scales have been estimated and we evaluated their influence on the stress state and ongoing tectonic deformation of the region during the recent 1993 1995 bering glacier surge a large transfer of ice from the bagley ice field to the bering glacier terminus region occurred we estimated the elastic displacement of the solid earth due to ice mass redistribution from global positioning system gps measurements at sites near the surging glacier we can account for these displacements by transfer of an ice volume of about 14 km3 from the surge reservoir area to the terminus region we examined the background seismicity ml 2 5 before during and after the surge we found that the occurrence of small earthquakes ml 4 0 in the surge reservoir region increased during the surge time interval possibly in response to a decrease in ice mass this suggests that a small decrease in the vertical stress 3 could be enough to modulate the occurrence of small shallow earthquakes in this dominantly thrust fault setting during this century the southern alaska coastal glaciers have been undergoing an overall decrease in volume based on our compilation of changes in the extent and thickness of the coastal glaciers between the malaspina and bering we calculated surface displacements due to the earth s viscoelastic response to annual thinning and to the cumulative retreat over the last 100 years the uplift of the region due to an average annual thinning rate of 1 6 m yr in the ablation region is 1 12 mm yr for our reference model with a viscosity of 5 1019 pa s for depths between 40 and 200 km the total viscoelastic response due to the retreat over the last century may be as much as a couple of meters within the coastal ablation zone near icy bay the maximum decrease in v between 0 and 10 km was 1 0 mpa which is significant in relation to the stress drops in recent earthquakes 2 to 10 mpa but small in relation to the estimated tectonic stress magnitude therefore the occurrence of an earthquake such as the st elias 1979 ms 7 2 may have been advanced in time however most of the ongoing stress accumulation would be primarily due to tectonic forces

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

macropore flow on a reclaimed surface mine infiltration and hillslope hydrology abstract surface coal mining in central pennsylvania alters the physical and hydrological properties of soil from its undisturbed state and changes the surface hydrologic response to precipitation newly reclaimed minesoils exhibit low steady state rates of infiltration 1 2 cm h and produce runoff dominated by infiltration excess overland flow within 4 years after reclamation rates of infiltration on some minesoil surfaces approach pre mined rates 8 cm h as a greater percentage of rainfall infiltrates these reclaimed minesoils little change occurs in the total volume of surface storm runoff on an event basis this indicates that infiltrated water contributes to storm runoff by the processes of throughflow and return flow as the rate of infiltration increases with time the hydrologic response of the minesoil is controlled by rapid macropore throughflow within the unsaturated minesoil application of fluorescent dyes on the reclaimed surface reveals preferred flowpaths through macropores surrounding the numerous large rock fragments in the minesoil development and integration of a macropore network on a reclaimed surface mined watershed has a significant direct effect on the contributions to surface storm runoff from infiltration excess overland flow throughflow and return flow as rates of infiltration increase through time and slightly delayed macropore return flow increases the peak rate of surface storm runoff is reduced therefore reducing the potential for severe gully erosion on the reclaimed site in addition throughflow moves predominantly within the minesoil horizon and has limited contact with potentially acid producing backfill better understanding of the process of macropore flow in reclaimed minesoils will help investigators evaluate past strategies and develop new reclamation techniques that will optimize the long term effluent and ground water quality while minimizing the short term surface erosional effects of mining and reclamation

patterns of accretion of reefs in the sudanese red sea abstract reefs in the north towartit and shambaya groups of the sudanese red sea rest on major blocks which have been defined by large scale fault movements the dominant surface features in these areas have been formed by the sub aerial sculpting of tertiary and later limestones during late pleistocene periods of low sea level stand this has resulted in the formation of large numbers of closed depressions reaching 30 m depth these punctuate a surface lying between 20 and 30 m which is itself probably a residual of an older undulating higher level surface the margins of depressions are submarine cliffs the smooth floors are blanketted with recent sediments while the intervening ridges have become the sites for reef accretion present coral growth began about 6000 years ago and has reached a thickness of 10 to 20 m it has been limited in deeper water but in shallower areas may have been aided by establishment on existing pinnacles steep margins occur on both the windward baraja and leeward towartit harvey margins of reefs these may result from inequalities of growth but cannot be directly related to environmental energy windward and leeward shores are characterised by contrasted coral associations a windward acropora association and a leeward porites association this distribution reflects a depletion of resources downcurrent rather than major differences in water movement reef edges are the most important sediment generating zones and patterns of dispersal point to a dominant westward downwind movement 50 80 of sediments coarser than 1 o are coral and algal fragments mollusc shells are a minor component but reach 26 on the towartit fringe homotrema benthic forams bryozoa crustacean and echinoderm fragments rarely rise above a few percent each mean sizes of sediments range from 2 3167 to 1 2333 o with the coarsest close to the reef edges and the finest in deep water or down current most are poorly sorted and values for standard deviation range between 2 1714 and 0 9512 o skewness values indicate symmetrical or coarse skewed distributions 0 0132 to 0 4982 finally figures for normalised kurtosis range between 0 6023 and 0 4532 these suggest that sediments consist of at least two sub populations 1 a base stock generated in the edge zone with characteristics varying systematically down current and 2 grains formed within the transport system with characters owing more to ecological factors than hydrodynamics the irregular mixing of these two accounts for the variation shown in conclusion the character of the reefs depends both upon present day processes and an inherited morphology

activity along the osning thrust in central europe during the lateglacial ice sheet and lithosphere interactions abstract the osning thrust is one of the major fault systems in central europe with a length of approximately 115 km it underwent a polyphase tectonic evolution in the mesozoic that ranged from extensional movements in the jurassic to reverse faulting and thrusting during inversion in the late cretaceous a series of complex metre scale faults and related fold structures are developed within the upper pleistocene alluvial aeolian complex of the upper senne 1 km away from the thrust the faults dip towards the north and show offsets in a range of several decimetres growth strata indicate a two fold evolution of the structures the faults began as normal faults and were later transformed into reverse faults which resulted in the formation of small scale inversion structures with a typical harpoon shape glaciotectonics can be ruled out as the driving mechanism for these structures because new optically stimulated luminescence osl ages imply that the sedimentary succession was deposited during the late pleistocene between 29 3 2 9 ka and 13 1 1 5 ka at which time the ice margin was much further to the northeast we believe the inversion structures were caused by movement on the osning thrust due to generation of a forebulge of the late pleistocene weichselian ice sheet this led to normal faulting as a consequence of extension in the forebulge area during glaciation the osl ages for the normal fault related growth strata are in a range of 16 13 ka later reverse movements occurred during deglaciation due to the n s directed compressional stress field in northern germany numerical simulations of the deglaciation seismicity point to seismic events with a thrust mechanism in the study area between 15 5 and 12 3 ka bp although normal faulting is also possible in this time period numerous soft sediment deformation structures imply that movement on the osning thrust caused earthquakes with a significant magnitude in the autumn of 1612 an earthquake took place in this area it is very likely that this event is related to background seismicity on this fault although movement due to the influence of the ongoing glacial rebound in fennoscandia is also possible

processing of regional seismic events using data from small aperture arrays abstract a regional on line array processing package ronapp has been developed and tested on data from a small aperture seismic array noress at norsar consisting of 12 sensors spaced with distances up to about 2 km the processing package automatically detects and locates regional seismic events in the distance range from a few kilometers to the maximum propagation range of regional s type waves sn or lg the package contains a conventional sta lta detector which works on a set of filtered beams deployed at typical phase velocities of pn and lg sn 8 0 and 4 5 km sec when a detection is found data within a certain time window around the detection time are used for estimates of refined arrival time and signal frequency and a wavenumber analysis is then performed following a proper prefiltering this gives in addition to arrival time and frequency estimates of phase velocity azimuth and signal to noise ratio for each detection following each processed detection an event location based on azimuth and s p travel times is performed if the last detection is identified as an s type wave phase velocity below 6 km sec and a preceding p wave phase velocity above 6 km sec has been detected with about the same direction of approach appropriate procedures are developed to allow for several detections within the p and s coda to keep track of used and unused detections and to identify epicenter locations that override preliminary ones as the analysis progresses through the s wave train of the event the processing package has been tested off line and on line on a number of data intervals for various experimental noress array configurations the automatic processing package provides detection results for regional events that compare favorably with those from the full norsar array and location results that deviate from locations by the fennoscandian network of seismological stations by typically 30 km which is of the order of the location uncertainty of the network

modelling of stresses in the fennoscandian lithosphere induced by pleistocene glaciations the seismicity observed in fennoscandia is usually explained by tectonic stresses the question of the contribution of stresses induced by glacial isostatic adjustment to the seismicity has not finally been settled yet in order to quantify the isostatic stress field generated by the fennoscandian glacial load we consider layered maxwell viscoelastic half spaces loaded by axisymmetric discs in particular we calculate the maximum shear stress distribution induced by the load model and the associated stress regimes in the lithosphere emphasis is placed on a discussion of the sensitivity of the calculated isostatic stresses to variations in load cross section lithosphere thickness and asthenosphere viscosity we also examine the effects produced by the viscous relaxation of the lithosphere whose viscosity is parameterized according to the stratification expected for temperature activated diffusion creep our results show that the isostatic shear stresses typically reach 2 mpa near the surface at the present time but that their distribution may be modified strongly by the details of the earth and load models investigated the viscous relaxation of the lithosphere becomes particularly important if more than one glaciation is considered since the last ice age in fennoscandia consisted of several glaciations the model of a perfectly elastic lithosphere conventionally employed in models of glacial isostatic adjustment therefore may not be justified when calculating the isostatic stresses

postglacial seismicity offshore mid norway with emphasis on spatio temporal magnitudal variations abstract norway and its continental margin in spite of being located in an intraplate environment is of great interest from a neotectonic perspective influence on neotectonics stems both from the fact that this is a recently deglaciated region in which significant rebound is still occurring and from its proximity both to a rifted continental margin and to failed rift zones passive continental margins and rift related structures are the most seismically active ones within stable continental regions with a number of well documented earthquakes of magnitude 7 and higher as observed around the globe indeed the disparity in seismicity between such regions and plate boundary regions is greater in terms of return times than in terms of maximum magnitude a recent detailed assessment of neotectonics in fennoscandia has shown strong bedrock related evidence for several large magnitude m 7 earthquakes in the northern areas lapland while few if any similar observations have been made farther south a possible explanation for this is that postglacial earthquakes have been occurring on hidden thrusts in the south in fact several major structures have recently been mapped and shown to have capabilities to accommodate m 6 5 7 earthquakes without breaking the surface given that the largest historically known earthquake in fennoscandia is only of the order of m 5 8 it is likely therefore that the potentially largest magnitude in this region may be well above this

induced seismicity in the khibiny massif kola peninsula the topic of this paper is to review recent processes of increasing seismic activity in the khibiny massif in the kcla peninsula it is a typical example of induced seismicity caused by rock deformation due to the extraction of more than 2 109 tons of rock mass since the mid 1960s the dependence of seismic activity on the amount of extracted ore is demonstrated some of the induced earthquakes coincide with large mining explosions thus indicating a trigger mechanism the largest earthquake which occurred on 16 april 1989 ml 4 1 could be traced along the surface for 1200 m and observed to a depth of at least 220 m the maximum measured displacement was 15 20 cm

seismic activity inferred crustal stresses and seismotectonics in the rana region northern norway abstract the seismotectonic significance of the rana region is known both from the fact that this was the location of the largest known earthquake in fennoscandia in recent times the m s 5 8 6 2 earthquake of august 31 1819 and from its relatively high constant seismic activity also in the 20th century in order to study this region in more detail a local seismic network has been in operation there since july 1997 as part of the neonor neotectonics in norway project the network was primarily designed to detect possible activity on the basmoen fault which runs 50 km subparallel to the rana fjord and which shows signs of likely post glacial activity the results have revealed a quite complex spatio temporal distribution of seismic activity and has also shown no activity on the basmoen fault itself during the first 18 months of operation july 1997 january 1999 the network has detected 373 locatable seismic events of which 267 were local earthquakes most of these earthquakes occurred in five groups in the western parts of the network all five groups had similar nnw esw trends in epicenter locations and all have shallow foci 2 12 km similar to what has also been found earlier for other concentrated earthquake zones in northern norway and the magnitude range is between m l 0 1 and 2 8 earthquake focal mechanism solutions within the network reveal a predominance for normal faulting with the tensional stress axis perpendicular do the coastline implying an unusual coast parallel orientation of the principal horizontal compressive stress the earthquakes occur in a region of maximum post glacial uplift gradients which supports deglaciation flexure as a viable explanation for these earthquakes a certain influence from more local factors however tied in general to crustal in homogeneities cannot be ruled out

late cretaceous to recent tectonic evolution of the north german basin and the transition zone to the baltic shield southwest baltic sea abstract in this study we investigate the late cretaceous to recent tectonic evolution of the southwestern baltic sea based on a dense grid of seismic reflection profiles this area covers the baltic sea sector of the salt influenced north german basin and its transition to the salt free baltic shield across the tornquist zone the upper cretaceous to recent structural evolution is discussed by means of individual seismic sections and derived high resolution time structure maps of the main horizons i e the upper cretaceous tertiary and pleistocene the upper cretaceous and tertiary layers reveal numerous significant faults throughout the study area several of these faults propagate upwards across the unconsolidated pleistocene sediments and occasionally penetrate the surface the salt influenced north german basin reveals three major fault trends nw se n s and nne ssw several of these faults are located directly above basement sub salt faults and salt pillows the majority of these faults are trending n s to nne ssw and parallel the direction of the gluckstadt graben faults in the salt free tornquist zone we identify two major shallow fault trends which are nw se and ne sw the majority of these faults are located above basement faults following the direction of the tornquist zone we conclude that generally basement tectonics controls activation and trends of shallow faults if salt is present the ductile salt layer causes a lateral shift between the sub and supra salt faults major plate reorganisation related to the africa iberia europe convergence and the subsequent alpine orogeny caused reactivation of pre existing faults and vertical salt movement in the late cretaceous the change of stress orientation from ne sw to a nw se during neogene caused another phase of fault and salt tectonic reactivation we explain that the ice sheet loading and or present day stress field may have acted in combination causing the recent tectonics and upward extension of the faults

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

microearthquakes illuminate the deep structure of the endglacial parvie fault northern sweden at 155 km the parvie fault is the world s longest known endglacial fault egf it is located in northernmost sweden in a region where several kilometre scale egfs have been identified based on s

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

comparison of the hydrological role of two reclaimed slopes of different ages in the athabasca oil sands region alberta canada establishing hydrological connectivity in reconstructed landscapes and understanding how this connectivity evolves over time is critical for the development of effective water management strategi

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

ice ages and nuclear waste isolation abstract the greatest natural threats to the integrity of the geological barriers to nuclear wastes isolated in cavities mined at depths between 400 and 800 m are likely during rapid retreats of future ice sheets the next major glacial retreat is expected at ca 70 ka well within the lifetime of high grade nuclear waste but it is not yet clear how long man s greenhouse effect may delay it this contribution discusses the potential problems posed to european waste isolation sites during erosion by ice and over pressurizing of meltwater and gasses in a lithosphere flexed by major ice sheets these depend on the target rocks and the location of the site with respect to the ice streams and margins of future ice sheets of particular size no sites are planned under the centres of future ice sheets in europe where end glacial earthquakes can be expected to reactivate major faults nor where ice can be expected to deepen and lengthen fjords along the atlantic coast sites in the alps may be vulnerable to radical changes in the patterns of glacial troughs the stability and geohydrology of sites in coastal areas beyond future ice margins are threatened by river gorges when sea level falls ca 125 m or in enclosed basins like the mediterranean ever lower the greatest problems are likely in lowland regions exposed by the rapid retreat of thick ice fronts where large lakes on or under thick warm based ice are dammed by more distal cold based ice groundwater in subhorizontal fractures dilated by glacial unloading may reach over pressures capable of hydraulically lifting megablocks of bedrock with fracture permeability and or the ice damming them so that less permeable substrates are susceptible to incisions eroded to depths of ca 360 at locations controlled mainly by ice topography kinematics and history

seismicity and seismotectonics of norway and nearby continental shelf areas the earthquake activity of norway and nearby offshore areas is low to intermediate with few events above magnitude 5 recent significant improvements in instrumental coverage in parallel with a better utilization of older including historical data have shown that the seismicity in the south is predominantly confined to the coastal areas and to the viking graben while from the northern north sea to svalbard the earthquakes in a broad sense follow the continental margin fifty one focal mechanism solutions from these areas about half of them new reveal stress directions that clearly indicate a connection to the plate tectonic ridge push force at least for the areas at a minimum distance from the continental margin along the margin stress directions also indicate a possible connection to postglacial uplift as well as to lithospheric loading effects a dominance of normal faulting on the landward side and reverse faulting on the oceanic side agrees with this interpretation on a regional level the seismicity in these areas correlate quite well with geologic features such as grabens fault zones fault complexes fracture zones and the margin itself indicating that these structures act in a general sense as weakness zones in the presence of a regionally more stable stress field in the northern north sea however an area with quite anomalous stress orientations with strike slip faulting is found in a region transitional between normal and reverse faulting most of the earthquake foci are confined to the presumably brittle parts of the crust but many events are also located quite close to and on both sides of the moho discontinuity

waveform modeling of the 17 august 1999 kola peninsula earthquake on the kola peninsula one of the strongest seismic events m s 4 2 in recent years occurred on 17 august 1999 the event was located in the lovozero massif close to the city of revda and the umbozero mining site the revda event was recorded with a temporary broadband network in finnmark masi region northern norway based on high quality three component seismic data from this network we analyzed the event by full waveform modeling using a frequency wavenumber method we systematically varied the source depth the size and orientation of the fault plane and the crustal velocity model and compared the resulting synthetic seismograms with the observed data the spectra could be matched quite well with synthetics for a circular fault plane of radius 1 6 km an effective stress drop of 4 5 mpa and a seismic moment of 6 0 10 15 n m the source depth was estimated to be about 5 km the fault plane solution is mainly characterized by a reverse focal mechanism with strike 240 dip 60 and rake 70 consistent with first motions observed at 28 fennoscandian stations the distinct dispersion of the observed data could be explained by introducing a relatively strong shear wave velocity gradient in the uppermost crust we think that the revda event may have been influenced possibly even triggered by the presence of the mine the lovozero massif has a distinct block structure with a northeast southwest oriented fault system and a conjugated system in the north west southeast direction associated and consistent with the regional north northwest compressional tectonic stress field long term mining can redistribute stress and initiate ruptures along favorably oriented faults and to this end our fault plane solution is in agreement with an event on the major alluaiv fault of the northeast southwest oriented system local inspections revealed that a rockburst occurred in a part of the mine that was abandoned 10 20 years ago this rockburst has also a reverse fault mechanism but with a shear plane striking perpendicular to our solution we therefore consider the observed rockburst as a secondary effect

stress transfer in the storegga area offshore mid norway abstract the recently discovered large gas field ormen lange within the storegga submarine slide area offshore mid norway poses important questions as to the origin of these large submarine slides and their possible implications in terms of the safety of the development and the production in this respect the present study was initiated with the main objective of investigating the possibility of stress transfer as triggering mechanism for multiple earthquake occurrence and hence for the storegga submarine slide ca 8200 years before present bp stress changes following different scenario earthquakes along the selected faults in the area are modeled and computed for a number of cases using the coulomb failure criterion we demonstrate the possibility of large earthquakes triggering multiple ruptures along neighbouring fault segments the combined effect of the co seismic slip and strong ground shaking due to a large earthquake m 7 accompanied by the stress transfer on the optimally oriented normal fault planes which are analogous to the slide scar may have played an important role for the triggering of the storegga submarine slide

interaction of groundwater and shallow lakes on outwash sediments in the sub humid boreal plains of canada abstract the hydrologic controls on the interaction between a shallow lake and a groundwater flow system have been determined for a coarse textured landscape on the boreal plains of canada lake groundwater interactions were studied to provide an understanding of the near surface hydrologic processes in a sub humid climate where annual precipitation is equal to or less than potential evapotranspiration this study was initiated to assess potential landscape impact from forestry and energy industrial activity and future scenarios of climate change expected in the western boreal forest a 39 ha lake on outwash sediments was studied for two consecutive years hydrometric measurements and stable isotopic analyses indicated that evaporation was the dominant hydrologic flux during ice free months and was primarily responsible for a 0 2 m decline in lake level during this study a combination of summer rain and consistent supply of groundwater discharge throughout each year were the dominant sources of water the near equivalence of precipitation and evaporation and relative dominance of each of these processes during the hydrologic year resulted in the formation of a water table mound downgradient of the lake and its disappearance each year the presence of these humid mound and arid complete disappearance phenomena at one location within the same year reveal the sensitivity of hydrologic systems in this sub humid region to small variations in climate the onset and duration of evaporation from the lake surface was a major controlling factor on groundwater exchange to such a degree that the shallow lakes are thought to be evaporation windows in this landscape creating sub surface capture zones that depend on lake size and landscape position these findings indicate a very dynamic relationship between atmospheric water fluxes and groundwater interaction which could potentially conceal anthropogenic impacts within natural variability

response of normal faults to glacial interglacial fluctuations of ice and water masses on earth s surface 1 changes in surface loads during glacial interglacial cycles and the associated flexure and rebound of the lithosphere alter the stress field in actively extending regions and may lead to slip rate variations on normal faults in particular loading may cause a period of seismic quiescence that is followed by temporal clustering of earthquakes during and after unloading here we present a suite of finite element experiments to evaluate how the magnitude distribution and temporal evolution of the load as well as rheological parameters of the lithosphere and asthenosphere influence the response of a normal fault the results show that the duration of the seismically quiet period during loading and the intensity of the slip rate increase during unloading are primarily controlled by the magnitude of the load the time lag between the changes in loading and the reaction of the fault is mainly determined by the viscosity of the asthenosphere parameters that play only a minor role for the fault s response include the rate of load removal fault strength and the thickness of the lithosphere our results imply that earthquake recurrence models derived from holocene slip histories may not be representative for the long term evolution of seismogenic faults

carbonate cements in a modern red sea reef north of jeddah saudi arabia abstract subsea carbonate cements vary in their types and distribution in a modern coral reef formation north of jeddah saudi arabia the petrographic characteristics of cemented reefs were studied by scanning electron microscope and x ray diffraction methods the cements consist basically of acicular aragonite and magnesium calcite containing 17 mole mgco3 the predominant cement in the red sea reefs is aragonite which is generally restricted to the intraskeletal cavities of coral whereas the mg calcite develops as a cryptocrystalline cement filling and coating the reef components

implications of a ductile crustal layer for the deformation caused by the fennoscandian ice sheet summary previous studies of glacial isostatic adjustment have usually considered earth models with a purely elastic lithosphere a possibly significant deviation from this assumption is the presence of a ductile crustal layer embedded in an otherwise elastic lithosphere such a layer has been suggested for various continental regions on the basis of seismic and tectonic evidence the present study investigates the implications of a ductile crustal layer for the interpretation of glacial isostatic adjustment using a layered incompressible maxwell viscoelastic earth model and a simplified representation of the fennoscandian glaciation the relaxation time and amplitude spectra show that besides the conventional buoyancy mode m0 also present in earth models with a purely elastic lithosphere the ductile layer supports a slowly decaying mode mc which is capable of modifying the deformation markedly thus measures of the absolute deformation such as the stress clearly reflect the presence of the ductile layer in contrast to this are measures of the relative deformation such as the vertical displacement rate and the rate of gravity change to a good approximation these rates are inversely proportional to the relaxation time of the more quickly decaying mode m0 and are therefore less affected by the ductile layer taken together the present study suggests that provided a ductile crustal layer exists its presence should be accounted for in interpretations of the glacial isostatic adjustment following the fennoscandian or smaller glaciations

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

chemistry of modern sediments in a hypersaline lagoon north of jeddah red sea abstract previous studies of modern peritidal sedimentary environments of the red sea such as hypersaline lagoons and sea marginal flats have concentrated on its northern part particularly in the gulf of aqaba however little is known about lagoon sediments in other localities along the red sea coastal stretches this paper deals with the chemical characteristics of the sediments of a hypersaline ras hatiba lagoon north of jeddah saudi arabia the chemistry of hypersaline lagoon sediments is considerably changed following the modifications to the water chemistry by evaporation and precipitation ras hatiba lagoon is a hypersaline elongated water body connected to the red sea by a narrow and shallow opening the total area of the lagoon is c 30 km 2 coarse bioclastic sands are dominant in the lagoon and mostly surround lithified calcareous grounds however fine silt and clay sediments are present in separate patches the sediments are rich in carbonates average 78 5 and organic carbon average 7 3 although they are negatively correlated calcium average 25 1 and magnesium average 10 8 show a similar distribution pattern in the lagoon sediments strontium average 5 2 is positively correlated with calcium sodium and potassium are relatively highly concentrated in the sediments average 118 ppm and 173 ppm respectively magnesium and strontium are of prime importance in the process of mineralization and diagenesis the sabkha formation surrounding the lagoon is of low carbonate and organic carbon content compared with the lagoon sediments whilst it is characterized by high magnesium sodium and potassium concentrations ras hatiba lagoon sediments and sabkha resemble those of the northern red sea in the gulfs of aqaba and suez and the arabian gulf in their major sedimentological and chemical characteristics

neotectonic faulting in northern norway the stuoragurra and nordmannvikdalen postglacial faults abstract a systematic compilation and characterisation of many reports of neotectonic crustal deformation in norway both on local and regional scales has identified two neotectonic faults in northern norway the stuoragurra fault is a large reverse fault in finnmark county the nordmannvikdalen fault is a much smaller normal fault in troms county the stuoragurra postglacial fault can be followed in several discontinuous sections for 80 km in a ne sw direction the fault has up to 10 m of displacement during 1998 two trenches were made across the fault the hanging wall was seen to be thrust upwards over the footwall with 7 m vertical displacement evident from displaced glacial contacts the fault did not penetrate the overlying glacial materials but rather folded them forming a blind thrust large liquefaction and other deformation structures were found in the glaciofluvial sediments in both trenches veins of angular and subangular pebbles from the local bedrock penetrate more than 10 m laterally from the thrust plane and into the sediments in the footwall it is thought that these veins were injected during the fault activity the major deformation of the sediments has a decollement plane that continues laterally in the e b horizon contact of the modern soil on top of the footwall this may indicate that an initial pedogenesis had taken place before the fault activity occurred however no macro plant fossils to support this were found in the possible buried soil deformational structures seen in the trench can be explained as a result of one major fault event the nordmannvikdalen postglacial fault is a nw se trending normal fault dipping to the ne the fault offsets till on the nw slope of nordmannvikdalen the escarpment varies in height from 0 5 to 1 5 m with a trench often present between the hanging wall and the footwall the fault locally splits into two subparallel branches however this is probably only in the glacial overburden ground penetrating radar gpr profiles show two prominent bedrock reflectors dipping approximately 40 to the ne an upward extrapolation of the northernmost reflector through the overburden coincides with the position of the surface scarp the bedrock is well exposed along a streamed parallel to the gpr profiles bedding and foliation cannot be responsible for the reflectors visible in the gpr profiles gravitational forces have been ruled out as the origin of the fault although both faults probably formed shortly after weichselian deglaciation there is evidence that isostatic uplift was not the only force acting quaternary tilting of fennoscandia due to ridge push or mantle convection may also play a role in neotectonic activity in norway

constraints on the geometry of the suasselka post glacial fault northern finland based on reflection seismic imaging abstract unloading of the ice during the last glacial period in northern fennoscandia is believed to have generated major faulting these faults often referred to as post glacial faults typically have clear surface exposures but their geometry at depth is poorly known in order to better understand the geometry at depth of the suasselka post glacial fault in finland three high resolution 2d reflection seismic profiles over the fault were reprocessed their total profile length is about 60 km and they were acquired as part of a major effort in finland to map the uppermost crust in mining areas the reprocessing led to significantly improved images that could be used to map the fault at depth two approximately n s striking profiles and one e w striking profile were reprocessed the different azimuths and the crooked nature of the profiles allowed the fault geometry to be relatively well constrained clear reflections from the fault dipping towards the se can be traced from the shallow subsurface down to about 3 km the strike and dip of two sets of dipping reflections in the stacked data along with geometrical constraints and cross dip analysis give a consistent dip of about 35 45 towards the se for the fault the strike and dip vary from n55e with a dip of 35 in the east to a strike of n48e with a dip of 45 in the west existence of the two sets of reflections indicates that the fault surface is non planar aside from allowing the geometry of the fault to be determined the seismic data show a complex reflectivity pattern in the area and indications of both reverse and normal movement along fault planes with similar orientation to the suasselka post glacial fault these images can be used as a basis for better characterizing the 3d geology of the area

late ordovician ashgillian glacial deposits in southern jordan the late ordovician ashgillian glacial deposits in southern jordan comprise a lower and upper glacially incised palaeovalley system occupying reactivated basement and pan african fault controlled depressions the lower palaeovalley incised into shoreface sandstones of the pre glacial tubeiliyat formation is filled with thin glaciofluvial sandstones at the base overlain by up to 50 m of shoreface sandstone a prominent glaciated surface near the top of this palaeovalley fill contains intersecting glacial striations aligned e w and nw se the upper palaeovalley fill comprises glaciofluvial and marine sandstones incised into the lower palaeovalley or where this is absent into the tubeiliyat formation southern jordan lay close to the margin of a late ordovician terrestrial ice sheet in northwest saudi arabia characterised by two major ice advances these are correlated with the lower and upper palaeovalleys in southern jordan interrupted by two subsidiary glacial advances during late stage filling of the lower palaeovalley when ice advanced from the west and northwest thus four ice advances are now recorded from the late ordovician glacial record of southern jordan disturbed and deformed green sandstones beneath the upper palaeovalley fill in the jebel ammar area are confined to the margins of the hutayya graben and have been interpreted as structureless glacial loessite or glacial rock flour petrographic and textural analyses of the deformed sandstones their mapped lateral transition into undeformed tubeiliyat marine sandstones away from the fault zone and the presence of similar sedimentary structures to those in the pre glacial marine tubeiliyat formation suggest that they are a locally deformed facies equivalent of the tubeiliyat not part of the younger glacial deposits deformation is attributed to glacially induced crustal stresses and seismic reactivation of pre existing faults previously weakened by epeirogenesis triggering sediment liquefaction and deformation typical of earthquake generated seismites deformation confined to an area of not more than 4 km wide adjacent to the major fault zone implies earthquake magnitudes of at least 6 mo the high authigenic chlorite content of deformed tubeiliyat sandstones compared to undeformed ones is attributed to a post seismic hydrothermal system driven by compactional dewatering and hydrofracturing of the bedrock which acted as a groundwater recharge area supplied by subglacial meltwater from beneath the ice sheet fluid movement along glacial seismotectonically reactivated faults infiltrated the adjacent tubeiliyat sandstones under pressure and elevated geothermal gradient where chlorite was precipitated from solution d 2005 elsevier b v all rights reserved

slip rate variations on faults during glacial loading and post glacial unloading implications for the viscosity structure of the lithosphere abstract many active faults in extensional and contractional tectonic settings experienced a slip rate increase after the last glacial period when the volume of nearby glaciers and lakes decreased this post glacial slip rate increase is caused by transient stresses that are generated by the unloading induced rebound and superimposed on the tectonic background stress field as the latter is different for normal and thrust faults the response to loading and unloading should depend on the fault type here we use finite element models including a fault in rheologically layered lithosphere to explore the conditions under which both normal and thrust faults experience a post glacial slip rate increase the results show that a post glacial slip rate increase occurs on normal faults if the lower crust is stronger than the lithospheric mantle whereas thrust faults accelerate if the lower crust is weaker than the lithospheric mantle these findings imply that the response of faults to mass fluctuations on the earth9s surface may provide constraints on the rheological stratification of the lithosphere we use our results to make predictions on the viscosity structure of the basin and range province and northern scandinavia where palaeoseismological data document a pronounced increase in seismicity as a result of post glacial unloading and rebound

ridge forces absolute plate motions and the intraplate stress field torque poles are calculated for a variety of possible forces acting on the plates including ridge push slab pull and collisional resistance these torque poles are then compared to the directions of absolute plate motions there is a strong correlation between ridge torque poles and the azimuth of absolute plate motions for the north american south american pacific cocos and eurasian plates simple slab pull torques correlate well with absolute motion azimuths for the pacific nazca and cocos plates and moderately well with the absolute motion azimuth of the indoaustralian plate collisional resistance torque poles correlate with the absolute motion azimuth of the eurasian plate only the correlations are presented as further evidence that the absolute reference frame for plate motion is determined by the surface plates themselves torque poles for various forces are also compared with several long wavelength features of the global intraplate stress field that also tend to be aligned with absolute motion directions in general ridge torque directions agree well with the orientations of maximum horizontal stresses for stable north america western europe and south america and provide an alternative explanation for the alignment in terms of ridge push forces rather than basal drag collisional resistance forces can also explain the alignment of stresses in western europe for the indoaustralian plate the torque pole for collisional resistance forces is consistent with the general pattern of stresses in at least the western half of the plate but is not a good predictor of the entire data set for the plate other processes in addition to collisional resistance must be important for the indo australian plate ridge push forces may account for a significant portion of the long wavelength features of the intraplate stress field especially away from continental collisions such a conclusion is consistent with negative buoyancy of the slab being an important component of the driving mechanism as previously suggested slab forces may be largely balanced within the subducted slab itself and thus have limited effect on deformation of the surface plates

travel times and attenuation relations for regional phases in the barents sea region a database containing 45 events in the barents sea region has been compiled and analyzed with the aim of evaluating crustal models travel times and attenuation relations in the context of performing regional detection threshold monitoring of this region the 45 events are mostly located around the circumference of the study area due to the virtually aseismic nature of the barents sea itself regional p n and s n phases were observable for most events in the database while p g and l g phases were only observable for events with raypaths that do not cross the tectonic structures in the barents sea this corroborates a number of previous observations of l g wave blockage within the barents sea three existing velocity models were evaluated with a model having slightly lower s velocities than earlier assumed in the upper mantle giving the overall best fit to the observed arrivals in order to estimate magnitudes short term average sta and spectral amplitude values were calculated in several frequency bands for all phase arrivals in the database there were no significant differences between spectral and sta amplitudes so the latter were used as this parameter is more efficient to calculate in real time processing an inversion was performed in order to determine an attenuation relation specific for this region the resulting magnitudes based on p n p g s n and l g phases gave an internally consistent reasonably stable set of values which can be calibrated towards any existing global or regional scale

some seismological and geometric features of intraplate earthquakes to understand the nature and cause of intraplate earthquakes we carried out a systematic search for common features associated with them various geological geophysical and seismic data were analyzed and geometric and seismic parameters were compared for 29 intraplate events m 4 5 occurring worldwide the results suggest that intraplate earthquakes occur by the reactivation of pre existing zones of weakness in a compressional stress regime which is generally oriented parallel to the absolute direction of plate motion two styles of faulting were observed for type a earthquakes observed in the eastern united states eastern china western europe and west africa deformation occurs by strike slip motion on steeply dipping faults type b events are usually associated with thrust or normal faulting and were observed in eastern canada fennoscandia australia and peninsular india focal depths did not explain the differences between type a and type b earthquakes rather the differences are due to the perturbation of a regional stress field by a local stress field the regional stress field for type a events is primarily due to ridge push forces the method of stress perturbation varied from region to region the earthquakes in the type b category were further divided into three subcategories type b1 occurring in eastern canada and fennoscandia type b2 occurring in australia peninsular india and central brazil and type b3 occurring in the gulf coast of the u s the inferred causes of the perturbing stresses are deglaciation intracontinental resistive forces resulting from the collision of plates and the deposition of a large thickness of sediments respectively type a events were found to be associated with intersecting faults and generally supported the intersection model of talwani 1988 and had analogs in plate boundary events

the post glacial landscape evolution of the north german basin morphology neotectonics and crustal deformation the recent evolution of the north german basin ngb which is presently a low seismic area was partly affected by glacial loading and unloading of the ice masses major stresses acting within the ngb are induced by the north atlantic ridge push the ongoing alpine collision and the post glacial rebound of fennoscandia present day horizontal stresses within the ngb are directed generally nw se but fan and bend north of 52 n towards nne major basement faults are directed nw se minor faults ne sw and nne ssw and are clearly detectable in geomorphological and satellite lineaments furthermore the drainage pattern and the distribution of lakes in northern germany follow exactly block boundaries and hence mark zones of present day subsidence the understanding of the post glacial morphology and reactivation of faults requires a view into the very heterogeneous crust and upper mantle below the ngb the re adjustment of the individual fault blocks during post glacial relaxation of the lithosphere leads to differential crust dependent uplift and probably to the formation of urstrom valleys the urstrom valleys and terminal moraines in northern germany appear to parallel the major tectonic lineaments and lithospheric block boundaries the lithospheric memory is expressed in the post glacial landscape evolution of the ngb

probabilistic and deterministic seismic hazard results and influence of the sedimentary more basin ne atlantic abstract seismic hazard assessments have been conducted for the ormen lange gas field in the norwegian sea on the flank of the more basin the study used logic tree based probabilistic methods combined with semi deterministic methods for hazard contributions from mapped faults and the hazard was computed in terms of peak ground acceleration pga and spectral acceleration the probabilistic seismic hazard results were complemented by deterministic modelling in 1d wave number integration and 2d finite difference crustal models the deterministic modelling first of all elucidated the shaking duration problem indicating that thick offshore sediment structures like the ones in the more basin may significantly extend the shaking duration of an earthquake the presence of sedimentary layers with large velocity contrasts are responsible for this observation and a conventional soil amplification analysis would not have revealed this phenomenon a modelling along similar lines as indicated in the present paper may be recommended in certain vulnerable situations and in geologic provinces with thick sedimentary layers with significant internal velocity contrasts even though large earthquakes most likely have occurred in the region during the postglacial period the study could not resolve if the huge storegga slide which occurred about 8100 yb was triggered by an earthquake

three dimensional numerical modeling of slip rate variations on normal and thrust fault arrays during ice cap growth and melting 1 changes in the volumes of ice caps considerably alter the stress state of the lithosphere by generating a transient signal that is added to the tectonic background stress field these stress field changes in turn affect crustal deformation and in particular the slip behavior of existing faults here we use three dimensional finite element models to investigate how arrays of normal and thrust faults near a growing and subsequently melting ice cap are influenced in their slip evolution the results show that regardless of fault dip both types of faults experience a decrease in their slip rate during ice cap advance and an increase in their slip rate during ice cap retreat if they are located beneath the ice cap in contrast faults outside the ice cap that are loaded on their footwall or hanging wall only show the opposite pattern their slip rate increases during glacial loading and decreases during subsequent unloading if the load is located along strike of the fault that is at one of its tips the slip behavior of normal and thrust faults is different the normal fault shows a slip rate increase during unloading the thrust fault during loading our results explain the location and timing of deglaciation induced paleoearthquakes in scandinavia and the contrasting slip histories reported from normal faults in the basin and range province which are located at different positions relative to the former yellowstone ice cap more generally our findings imply that a uniform slip behavior of faults in formerly glaciated regions should not be expected

can deglaciation trigger earthquakes in n america a spherical self gravitating viscoelastic earth model is used to calculate the spatial and temporal evolution of the glacially induced lithospheric stress and fault stability in north america the predicted onset time of a pulse of earthquake activities the mode of failure and the magnitude of instability are investigated for three sites with different distance from the former ice margin it is found that glacial unloading is able to trigger paleo earthquakes within the ice margin near charlevoix 47 5 n 70 1 w and in wabash valley 38 5 n 87 w outside the ice margin however rebound stress decays away from the former ice margin thus glacial unloading is unlikely to have triggered the large m8 earthquakes in new madrid 36 6 n 89 5 w

response of salt structures to ice sheet loading implications for ice marginal and subglacial processes abstract during the past decades the effect of glacioisostatic adjustment has received much attention however the response of salt structures to ice sheet loading and unloading is poorly understood our study aims to test conceptual models of the interaction between ice sheet loading and salt structures by finite element modelling the results are discussed with regard to their implications for ice marginal and subglacial processes our models consist of 2d plane strain cross sections which represent simplified geological cross sections from the central european basin system the model layers represent i sedimentary rocks of elastoplastic rheology ii a viscoelastic diapir and layer of salt and iii an elastoplastic basement on top of the model a temporarily variable pressure simulates the advance and retreat of an ice sheet the durations of the individual loading phases were defined to resemble the durations of the pleistocene ice advances in northern central europe the geometry and rheology of the model layers and the magnitude spatial distribution and timing of ice sheet loading were systematically varied to detect the controlling factors all simulations indicate that salt structures respond to ice sheet loading an ice advance towards the diapir causes salt flow from the source layer below the ice sheet towards the diapir resulting in an uplift of up to 4 m the diapir continues to rise as long as the load is applied to the source layer but not to the crest of the diapir when the diapir is transgressed by the ice sheet the diapir is pushed down up to 36 m as long as load is applied to the crest of the diapir during and after ice unloading large parts of the displacement are compensated by a reversal of the salt flow plastic deformation of the overburden is restricted to the area immediately above the salt diapir the displacements after unloading range between 3 1 and 2 7 m larger displacements are observed in models with deep rooted diapirs thicker ice sheets longer duration of the loading phase thicker salt source layers and lower viscosity of the salt the rise or fall of diapirs triggered or amplified by ice sheet loading are likely to affect glacigenic deformation erosion and deposition above the diapir and within the rim synclines ice load induced uplift in front of an ice sheet will provide favourable conditions for the formation of push moraines for example by creating a topographic obstacle and inclining potential detachments subglacial subsidence of salt structures will enhance erosion by providing a preferential drainage pathway and fracturing of the overburden of the salt structure and thereby contribute to the incision of tunnel valleys however the resulting displacements are probably too low to have a marked effect on the advance or retreat pattern of the ice sheets

reverse slip offsets and axial fractures in road cut boreholes from the caledonides in finnmark northern norway neotectonic stress orientation indicators abstract reverse slip offsets of road cut drillholes and axial fractures developed in the walls of many such holes have been recorded from areas in the porsangerfjord and laksefjord districts of the caledonides of finnmark northern norway displacement vectors of the offset boreholes indicate movement towards 120 136 in phyllites of the laksefjord nappe at the base of the kalak nappe and in the gaissa nappe in western porsanger reverse slip offset is directed almost due east observations of the extensional axial fractures which are considered to have developed normal to the least principal in situ stress 3 at the time of blasting support a c ese wnw orientation of shmax at or close to the surface in these parts of finnmark possibly with a slightly more e w trend in western areas the consistency of orientation of these structural features is considered to reflect a regional stress pattern and is not merely a manifestation of the local geology or topography

unconsolidated reefal sediments in the jubal strait region red sea egypt abstract the strait of jubal lies in a geologically active zone forming the junction between the old gulf of suez and the comparatively younger red sea the western side of the strait is bordered by a series of high islands and extensive coral reef formations the coast of the mainland is characterized by a developing fringing reef and intense sedimentation of terrigenous clastics this area is under the influence of an arid climate and strong tidal currents the beach and bottom sediments have different origins the beach sediments are siliciclastics of terrigenous origin whereas the bottom sediments comprise carbonate reef products both sediment types are poorly sorted reflecting the instability of the hydrodynamic conditions and the high rate of sedimentation it appears that lime mud originates in the northern agitated part of the area and drifts southeastwards to become trapped in the deep water areas the mineral assemblage of the reefal sands comprises high mg calcite aragonite and low mg calcite in decreasing order of abundance while the lime mud is composed of low mg calcite calcite and aragonite the terrigenous mineral association of the beach sands includes quartz and feldspars magnetite and ilmenite are the most common heavy minerals

the impact of reclamation cover depth on the performance of reclaimed shale overburden at an oil sands mine in northern alberta canada multilayer covers are widely accepted reclamation designs in the oil sands region of northern alberta canada with an ultimate goal of revegetating to species characteristic of predisturbance native plant communities to determine the optimal depth of reclamation material required to reclaim overburden shale from an oil sands mine an evaluation was made of the long term performance of six reclamation soil cover depths all placed over overburden the measured soil water contents from different cover thicknesses at south bison hills located at the syncrude mine site north of fort mcmurray alberta were used to calibrate and validate a dual porosity model in hydrus 1d the calibrated and validated model was then used to evaluate the influence of cover thickness and climatic variability on plant available water for forest growth the frequency distributions of actual transpiration tr for six cover treatments with a range of leaf area index lai cases were developed these tr frequency distributions were then modified by coupling tr and lai the modified frequency distributions for annual tr for the six simulated cover thickness highlight the strong nonlinearity between the distributions of tr over a long term 60 years climate cycle in that incremental increases in cover thickness do not produce proportional increases in tr the results indicated that once the cover thickness exceeds 100 cm there is little incremental increase in the median value of tr over the 60 year climate cycle copyright 2014 john wiley sons ltd

induced stresses and fault potential in eastern canada due to a realistic load a preliminary analysis summary in order to understand the causal relation between postglacial rebound and earthquakes a simple disc load model is used to 1 calculate stresses induced in the lithosphere and mantle by glacial loading melting and postglacial rebound and 2 evaluate the effect of glacial loading rebound on the failure potential for earthquakes in the upper crust the dependence of the failure potential and the actual mode of failure on the coefficient of friction the ambient tectonic stress magnitude direction the stress due to the overlying rocks and lithospheric thickness are investigated prominent features of this paper are the inclusion of 1 a viscoelastic mantle and thus the migration of stress and 2 the ambient tectonic stress and overburden stress contributions in the calculation of the total stress field it is assumed that throughout the earth there are optimally oriented pre existing virtual faults that are initially close to but not at failure thus a time dependent quantity called dfsm related to the coulomb mohr failure criterion can be defined such that a negative value of dfsm would advocate faulting or earthquake activities whereas a positive value of dfsm would promote stability the results indicate that under all combinations of tectonic stress magnitude and overburden stress crustal loading promotes fault stability directly underneath the load upon the removal of the load thrust faulting is predicted within the ice margin if the horizontal stress s induced by the overburden is greater than or equal to the vertical component s of the overburden stress 121 where sjs under this condition theory predicts that faulting or earthquake activity should have reached a maximum immediately after deglaciation if the horizontal stress induced by the overburden is less than the vertical component of the overburden stress 1 l then theory predicts fault stability within the ice margin the theory predicts fault instability both north and south of the ice margin the mode of failure however is completely determined by the value of i the trade off between the tectonic stress magnitude and the overburden stress parameter 1 is also investigated it is shown that a larger tectonic stress magnitude can be used to compensate a smaller value of 1 the results of this analysis show that variations in the coefficient of friction lithospheric thickness and a ductile zone below the upper crust do not significantly affect the above conclusions

will earthquake activity in eastern canada increase in the next few thousand years knowledge of whether earthquake activity will increase in the next few thousand years is important for the planning of nuclear waste repositories assuming that fault instability portends earthquak

ridge push and associated plate interior stress in normal and hot spot regions abstract the stress distribution and plate boundary force produced by ridge push are modelled by elastic viscoelastic finite element analysis in oceanic lithosphere and in an adjacent continent separated by a passive margin models are presented for both a normal slow spreading ridge and for one underlain by an anomalously low density upper mantle associated with a hot spot which gives rise to 1 km extra elevation of the sea floor the weak zone at the ridge crest is simulated by the viscoelastic elements extending up to the surface beneath the immediate crest using a standard thermal and rheological model of the oceanic lithosphere a normal ridge gives rise to horizontal deviatoric compression of about 40 mpa in the 25 30 km elastic layer beneath older ocean floor a much smaller modelled compression of 9 mpa occurs in the 20 km thick elastic layer of the adjacent upper continental crust as a result of the superimposed tension produced by the thick low density continental crust in reality this compression may be up to 30 mpa higher if the sub continental mantle is denser than that beneath old ocean floor as the geoid anomalies possibly suggest a fourfold increase in spreading rate has an insignificant effect on the stresses much larger compressions develop adjacent to the modelled hot spot ridge in normal oceanic and especially continental lithosphere these reaching 100 mpa beneath the old ocean floor and 90 mpa in the adjacent continent the stresses determined by the modelling are comparable in magnitude but generally slightly lower than values estimated using the density moment function the ridge push force referenced to 90 ma old oceanic lithosphere is estimated to be 2 5 1012 n m for the modelled normal ridge and 6 2 1012 for the modelled hot spot ridge the modelling shows that the ridge push is produced by the high pressure and shear drag exerted by the asthenosphere on the lithosphere the high pressure effect predominates at normal ridges where the plates are forced apart by gravitational wedging the shear drag effect contributes substantially at hot spot ridges the modelling helps to explain the prominent compressional stress in the continents bordering the north atlantic in terms of the hot spot activity beneath the mid atlantic ridge

to what extent is the present seismicity of norway driven by post glacial rebound abstract the seismicity of scandinavia is low to intermediate in intensity and with magnitudes that rarely exceed 5 5 even so the seismicity is characterized by a great diversity in space and time related to the fact that its driving forces or sources of stress are multiple and also diverse in nature the dominant driving forces range from plate related such as ridge push through regional to local ones such as topography all however are somehow related to lateral inhomogeneities in lithospheric structure whereas it was earlier assumed that the post glacial uplift was the main cause for the seismicity of scandinavia we now conclude that the uplift may at most be playing a minor role along the coastal stretch of northern norway there are still some indications that the seismicity which is often shallow normal faulting and swarm related may be related to the still remaining glacial isostatic adjustment the flexuring that is needed to explain such behaviour could however also be related to erosion and sedimentation processes it will take more work to separate these potential driving forces

submarine landslides along the malacca strait mergui basin shelf margin insights from sequence stratigraphic analysis the enormously destructive tsunami of december 2004 caused by sudden motion of the sunda megathrust beneath the indian ocean raised concerns about tectonically induced tsunami worldwide submarine landslides may also trigger dangerous tsunami however the potential and repeat time for such events is in most places poorly known due to inadequate exploration of the sea floor and age constraints the high sediment flux and tectonic subsidence rate of the malacca strait mergui basin shelf margin ne of northernmost sumatra provide a favorable environment to generate and preserve submarine landslides from ten seismic reflection profiles acquired in 2006 we identify three sediment packages that exhibit sliding characteristics such as headscarps distorted beds and debris toe structures we assign lowstand marine isotope stages to the paleo shoreline indicators observed in the profiles we then determine the ages of these submarine landslides as 20 30 ka 342 364 ka and 435 480 ka by the paleo shoreline indicators that bound the top and bottom of the slide bodies this sequence stratigraphic approach shows that these events occurred near times of sea level lowstands which implies that a large amount of direct sediment influx during glacial periods is an essential precondition for basin margin submarine landsliding spatiotemporal variations of sediment input due to lobe switching or asian monsoon intensity changes also control basin margin instability because we are currently at a highstand stage and sediment flux to the continental margin is relatively small so the chance of having a repeat submarine landslide and landslide tsunami along this basin margin is low

earthquake of 4 november 1898 in northern europe new insights 1 the earthquake of 4 november 1898 utc is a rare event in terms of the size of the area of perceptibility that extended to finland and sweden located in the intraplate northern europe previously unknown macroseismic reports were discovered in a thorough search of the contemporary press in this study the comprehensive collection of written documentary records is used to prepare an intensity data point map the slightly damaging intensities 5 5 6 and 6 on the european macroseismic scale are distributed over a larger area than outlined earlier this is attributed to the amplification of ground shaking by the soil characteristics in the river valleys where habitation concentrated at that time the new epicenter is located within a north south oriented seismicity trend that shows frequent microearthquakes and runs parallel to a mapped shear zone the magnitude of the main shock is inferred to be within the range from 4 4 to 4 7 and the magnitude of the immediate aftershock is inferred to be between 3 7 and 4 1 a theoretical relationship of intensity attenuation is employed in the inference of the magnitude the macroseismic reports show that earthquakes of this size posed an indirect hazard of fire to the dwellings in a region where earthquake related problems have previously been considered absent

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

evolution of the hydraulic conductivity of reclamation covers over sodic saline mining overburden the evolution of the field saturated hydraulic conductivity of four covers located on a reclaimed saline sodic shale overburden from oil sands mining is presented three covers consisted of a surface layer of peat glacial topsoil over a mineral soil and one cover was a single layer of mixed peat and mineral soil measurements of the field saturated hydraulic conductivity of the cover and shale materials were made with a guelph permeameter between 2000 and 2004 the hydraulic conductivity of the cover materials in the multilayered covers increased by one to two orders of magnitude over the first few monitoring seasons the hydraulic conductivity of the single layer cover system which was placed three years before the multilayered covers marginally increased from 2000 to 2002 and then remained relatively unchanged the hydraulic conductivity of the shale underlying all four covers increased approximately one order of magnitude soil temperature measurements indicated that one freeze thaw cycle occurred

transport of stable isotopes of water and sulphate within reclaimed oil sands saline sodic mine overburden summary the reclamation of shale overburden dumps from oil sands mining requires the placement of reclamation covers comprised of salvaged organic and mineral soils the primary issues associated with the long term performance of these covers are their ability to store sufficient water to meet transpiration demands and the potential threat of salt ingress into the cover from the underlying shale the first issue has been addressed in previous studies so the objective of this study was to evaluate controls on salt ingress through observations and modelling of the transport of the stable isotopes of water and salt within reclaimed profiles at the south bison hills overburden dump located north of fort mcmurray alberta the water flow model was based on a dual porosity soil vegetation atmosphere model calibrated to observed field data this model was then used to simulate deuterium and sulphate transport within the soil profiles the optimized transport model for deuterium was used to estimate net percolation rates through the cover soil into the underlying shale this model was then used to assess the controls on sulphate migration including the rate of sulphate generation as a result of ongoing oxidation of the pyritic shale the model results indicate that the average net percolation rate is a function of topographic location ranging from 2 2 10 5 m d at slope locations to 20 8 10 5 m d at plateau locations during the unfrozen days these rates of net percolation should have produced observable patterns of salt flushing from the cover and upper shale however the observed sulphate levels could only be simulated by including a production term related to pyrite oxidation of the shale the simulated oxidation rates ranged from 0 4 to 5 65 mg l d similar to those estimated from previous laboratory and field investigations

reefal sediments of al ghardaqa northern red sea egypt abstract reefal sediments are abundant along the red sea samples of such sediments were studied in the al ghardaqa area along the red sea coast of egypt twenty samples were collected from the beach intertidal zone and lagoon in the study area geochemical analyses were carried out by atomic absorption spectrophotometer and flamephotometer while mineralogical compositions of the sediments were studied by x ray diffraction the average concentrations of the different chemical constituents were as follows sio 2 21 4 al 2 o 3 8 5 tio 2 0 12 fe 2 o 3 0 38 mno 0 021 cao 21 7 mgo 5 01 sro 0 82 na 2 o 0 23 k 2 o 0 11 zn 31 ppm and cu 21 ppm the chemical constituents are categorized into four groups regarding their possible sources aragonite and high mg calcite are the major carbonate minerals characterizing the reefal sediments on the other hand quartz and feldspar are the common minerals of terrigenous origin

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

dispersal of mediterranean and suez bay sediments in the suez canal abstract this study determines the extent to which sediments of mediterranean suez bay and in situ authigenic eroded channel derivation have been displaced along the suez canal sediment transport is largely a response to hydrodynamics controlled by markedly different oceanographic conditions at both ends of the channeled byway petrology of sand silt and clay fractions determine distributions of diagnostic tracer minerals these are used to identify five sediment provinces in the canal which indicate long term dispersal patterns sediments of mediterranean origin largely terrigenous from the nile river are transported southward to ballah bypass while those of suez bay southern canal derivation mixed carbonate and terrigenous are transported northward to the northern edge of great bitter lake in situ derived bitter lakes sediments mostly carbonates are not transported extensively from the lakes area similarly derived lake timsah sediment is transported into the short stretches of the canal to the north and south of the lake the canal south of little bitter lake is a zone of erosion while the bitter lakes are sinks for sediments from several sources

preferential flow in a reclamation cover hydrological and geochemical response evapotranspirative covers used for waste containment or land reclamation strategies are intended to function in perpetuity pedogenesis of the cover materials caused by biophysical processes may lead to the development of macroporosity i e preferential flow paths which will alter the hydrological response from the intended design function hydrometric and geochemical data were used in this study to examine the contribution of preferential flow to the hydrological response of a reclamation cover on saline sodic shale mine overburden in a cold semiarid environment the hydrometric data suggest that infiltration occurs along preferential flow paths when the ground is frozen or when wet antecedent soil moisture conditions develop prior to precipitation events interflow is initiated during the spring snowmelt when the cover thaws and water migrates from the preferential flow paths into the soil matrix causing a perched water table to form on the cover shale interface the cessation of interflow coincides with a recession of the perched water table and an increase in matric suction within the cover in response to elevated evapotranspiration demands the chemistry and stable isotope signature of the interflow demonstrates that these waters are initially composed of fresher snowmelt water flowing along preferential flow paths which then transition to pre event water dominated by higher concentration water from within the soil matrix a numerical simulation demonstrates that macroporosity imposes a significant control on the discharge rate and cumulative volume of interflow

suppression of earthquakes by large continental ice sheets the interior regions of antarctica and greenland are aseismic no earthquake larger than body wave magnitude 4 5 5 0 is known for either except along coastal zones or continental shelves here i advance an explanation for this lack of seismic activity in terms of pressure effects produced by the continental ice sheets that mantle both continents

on a possible connection between three major earthquakes in california and oil production abstract the 1983 coalinga m 6 5 the 1985 kettleman north dome m 6 1 and the 1987 whittier narrows m 5 9 earthquake sequences each occurred beneath major producing oil fields and caused an aftershock sequence whose epicentral extent coincides approximately with that of the overlying oil field despite this coincidence a causal relationship between these sequences and oil production has been discounted because the earthquakes were located at depths of the order of 10 km whereas oil production is confined to the topmost several km moreover because all three oil fields coalinga kettleman north dome and montebello are situated on anticlines that have undergone recent uplift as a consequence of horizontal tectonic compression of the crust natural earthquakes are not unexpected a mechanical connection between oil production and the earthquake sequence is suggested however by the observation that in each case the total seismic deformation was just that required to offset the force imbalance caused by oil production specifically for each of the three sequences m 0 2 m c where m 0 is the sum of the seismic moments is the modulus of rigidity m is the mass of the fluid removed due to oil production is the fraction of the upper crust that is seismogenic and c is the average upper crustal density in essence net extraction of oil and water reduces slightly the average density of the upper crust causing an isostatic imbalance the ductile lower crust deforms in response to this imbalance thus increasing the load on the seismogenic layer which fails seismically to thicken the crust so as to restore static equilibrium locally accordingly earthquakes near the base of the upper crust may be an expected outcome of major oil production from growing anticlines irrespective of the depths of the producing formations

crustal stress in the northern north sea as inferred from borehole breakouts and earthquake focal mechanisms the regional stress field in the northern north sea offshore western norway has been studied through the acquisition and analysis of directions of maximum horizontal compression sh as extracted from borehole breakouts and from earthquake focal mechanism solutions the results indicate that the regional stress field is dominated by nw se compression with good consistency between shallow borehole breakouts 2 5 km depth and deeper earthquakes 10 25 km depth the broad spatial consistency in stress direction indicates that the main stress field is related to factors of primarily plate tectonic origin and the results are in good agreement with the western europe trend found in earlier investigations the tampen spur region in the northern north sea has been subjected to particularly complex deformation with two dominating fault directions trending nw se and ne sw from tampen spur in the west to the sogn graben in the east an anomalous stress field is indicated with ne sw oriented maximum horizontal compressions this anomaly is clearly seen both in the borehole breakout data and in the earthquake data possible sources for this anomaly are discussed and include postglacial uplift and or lateral variations in the physical properties of the crust

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

aspect influences on soil water retention and storage abstract many catchment hydrologic and ecologic processes are impacted by the storage capacity of soil water which is dictated by the profile thickness and water retention properties of soil soil water retention properties are primarily controlled by soil texture which in turn varies spatially in response to microclimate induced differences in insolation wetness and temperature all of these variables can be strongly differentiated by slope aspect in this study we compare quantitative measures of soil water retention capacity for two opposing slopes in a semi arid catchment in southwest idaho usa undisturbed soil cores from north and south aspects were subjected to a progressive drainage experiment to estimate the soil water retention curve for each sample location the relatively large sample size 35 supported statistical analysis of slope scale differences in soil water retention between opposing aspects soils on the north aspect retain as much as 25 more water at any given soil water pressure than samples from the south aspect slope soil porosity soil organic matter and silt content were all greater on the north aspect and each contributed to greater soil water retention these results along with the observation that soils on north aspect slopes tend to be deeper indicate that north aspect slopes can store more water from the wet winter months into the dry summer in this region an observation with potential implications for ecological function and landscape evolution

hydrology of two slopes in subarctic yukon canada two subarctic forested slopes in central wolf creek basin yukon were studied in 1996 1997 to determine the seasonal pattern of the hydrologic processes a south facing slope has a dense aspen forest on silty soils with seasonal frost only and a north facing slope has open stands of black spruce and an organic layer on top of clay sediments with permafrost snowmelt is advanced by approximately one month on the south facing slope due to greater radiation receipt meltwater infiltrates its seasonally frozen soil with low ice content recharging the soil moisture reservoir but yielding no lateral surface or subsurface flow summer evaporation depletes this recharged moisture and any additional rainfall input at the expense of surface or subsurface flow the north facing slope with an ice rich substrate hinders deep percolation snow meltwater is impounded within the organic layer to produce surface runoff in rills and gullies and subsurface flow along pipes and within the matrix of the organic soil during the summer most subsurface flows are confined to the organic layer which has hydraulic conductivities orders of magnitudes larger than the underlying boulder clay evaporation on the north facing slope declines as both the frost table and the water table descend in the summer a water balance of the two slopes demonstrates that vertical processes of infiltration and evaporation dominate moisture exchanges on the south facing slope whereas the retardation of deep drainage by frost and by clayey soil on the permafrost slope promotes a strong lateral flow component principally within the organic layer these results have the important implication that permafrost slopes and organic horizons are the principal controls on streamflow generation in subarctic catchments copyright 1999 john wiley sons ltd

soft sediment deformation of late pleistocene sediments along the southwestern coast of the baltic sea ne germany a 1 460 m long profile of a late glacial subglacial glacio fluvial glacio limnic and glacio deltaic sequence exposed at a cliff section on usedom island sw baltic sea coast is described the sequence is up to 31 m thick and shows sedimentary structures typical of a glacial setting soft sediment deformation is encountered and is associated with changes in lithology these deformations include liquefaction slumping and faulting as the most plausible cause earthquake induced shaking is discussed the associated neotectonic activity is seen as a consequence of the postglacial isostatic crustal rebound as the deglaciation earthquake ratio diminishes with time and as the rebound is phasing out no large earthquakes are anticipated for northern germany although in conclusion the lithosphere of the north german basin has to be regarded as weakened by repeated ice loading and deloading

effect of ice sheet growth and melting on the slip evolution of thrust faults abstract field investigations suggest that postglacial unloading and rebound led to the formation or re activation of reverse faults even in continental shields like scandinavia here we use finite element models including a thrust fault embedded in a rheologically layered lithosphere to investigate its slip evolution during glacial loading and subsequent postglacial unloading the model results show that the rate of thrusting decreases during the presence of an ice sheet and strongly increases during deglaciation the magnitude of the slip acceleration is primarily controlled by the thickness of the ice sheet the viscosity of the lithospheric layers and the long term shortening rate in contrast the width of the ice sheet the rate of deglaciation or the fault dip have an only minor influence on the slip evolution in all experiments the slip rate variations are caused by changes in the differential stress the modelled deglaciation induced slip acceleration agrees well with the occurrence of large earthquakes soon after the melting of the fennoscandian ice sheet which led to the formation of spectacular fault scarps in particular in the lapland fault province furthermore our model results support the idea that the low level of seismicity in currently glaciated regions like greenland and antarctica is caused by the presence of the ice sheets based on our models we expect that the decay of the greenland and antarctica ice sheets in the course of global warming will ultimately lead to an increase in earthquake frequency in these regions