geodynamics of the ogcheon belt south korea abstract the ogcheon belt is a stack of synmetamorphic southeastward verging nappes resulting from the deformation of a volcanosedimentary sequence deposited in an early palaeozoic rift which was affected by polyphase tectonics its pre cretaceous structure results from three main orogenic events the ogcheon late silurian devonian indosinian late permian triassic and yenshanian middle jurassic early cretaceous tectonic phases the external autochthonous or para autochthonous units represent platform zones with shallow water deposits whereas rift facies characterize the internal domain the yeongweol sequence forming an outer shelf on the southeastern margin of the rift displays affinities with the jiangnan basin of south china it is in wrench fault contact with the easternmost duwibong sequence correlated with the north china north korea platform in the internal metamorphic units post cambrian early ordovician pelitic and turbiditic rift metasediments overlie a thin cambrian or cambrian ordovician early platform sequence two subdomains are distinguished the upper units chung ju and pibaryeong units representing the deep axial part of the basin contain distal flyshoids and large olistoliths derived from the northwestern narrow margin the lower units turung san poeun and iwharyeong are related to the wide margin located between the deep rift domain and the stable southeastern platform the latter transitional domain is characterized by thick submarine debris flows and volcanics of alkali or transitional tholeiitic affinity the volcanic activity and mass gravity flow sedimentation are closely related to the crustal thinning and subsequent rifting and tilting lithostratigraphic evidence allows the correlation of the unfossiliferous rift metasediments with the cambrian ordovician platform sequence in one single basin the post middle silurian pre mid carboniferous ogcheon ensialic orogeny resulted in the closure of the rift with relatively minor effects in the platform area it gave rise to an intracontinental fold thrust belt without ophiolites this tectonic event may have been contemporaneous with early palaeozoic tectonism in the quinling belt in central china and in the southeast china fold belt the definitive constitution of the sino korean craton took place before the mid carboniferous and molasse sedimentation was initiated on a single platform located on the western edge of the yakuno oceanic basin of southwest japan in late permian and early triassic times the closure of the oceanic area and the subsequent westward collision of the honshu block are marked in korea by the intracratonic indosinian tectonism since late triassic times predominantly transcurrent movements have occurred along nne ssw faults associated with syntectonic intermontane troughs and important granitization

pre neogene controls on present day fault activity in the west netherlands basin and roer valley rift system southern netherlands role of variations in fault orientation in a uniform low stress regime the west netherlands basin wnb and the neighbouring roer valley rift system rvrs form the most prominent tectonic features of the onshore netherlands the two basins have a common tectonic origin and similar mesozoic evolution their neogene quaternary evolution however is markedly different while the wnb is tectonically seismically inactive and is characterised by uniform neogene quaternary subsidence in the rvrs fault controlled intra plate deformation has taken place since late oligocene times with pronounced seismic activity considering the present day ne sw regional extension as well as the similar basin orientation and mesozoic evolutions one would not expect strikingly different neotectonic activity in the two basins detailed analysis of mesozoic tertiary and quaternary fault patterns revealed that 1 the palaeozoic mesozoic tectonic fabric has great influence on the cenozoic deformation style of the basin system 2 present day faulting in the rvrs is related to the reactivation of pre existing faults and 3 the mesozoic fault pattern is slightly different in the two basins using a novel technique three dimensional 3 d slip tendency analysis we aim to determine whether these differences in fault orientation are substantial enough to produce significantly different resolved stresses along the faults this modelling not only tests a common geological phenomena but indirectly also delivers important constraints regarding the origin of faulting in the study area during the analysis 3 d geometric models of 84 mapped faults were investigated the results of this recently developed modelling technique reveal that the faults in both basins should behave similarly under the condition of a laterally homogeneous regional stress field which is in disagreement with the present day tectonic activity of the region on the other hand the modelling also reveals that the predicted tendency of slip is very sensitive to the ratio of the minimum horizontal and the vertical stress s as an explanation for the pronounced fault activity in the rvrs and the tectonic quietness of the wnb it is proposed that either the regional extension in the wnb is weaker in term of higher s ratio than that in the rvrs or the slip thresholds in the two basins are different the study emphasised that differentiation in the tectonic evolution has already started in the tertiary therefore it is reasonable to assume that the different tectonic stress field and or slip threshold between the two areas is directly related to the origin of the cenozoic rifting in the rvrs several hypotheses are discussed to account for these two possibilities taking into account the lithospheric structure and the cenozoic tectonic evolution of the two basins as well as surrounding areas 2004 elsevier ltd all rights reserved

a full coverage high resolution topographic model of greenland computed from a variety of digital elevation data in this paper a new high resolution elevation model of greenland including the ice sheet as well as the ice free regions is presented it is the first published full coverage model computed with an average resolution of 2 km and providing an unprecedented degree of detail the topography is modeled from a wide selection of data sources including satellite radar altimetry from geosat and ers 1 airborne radar altimetry and airborne laser altimetry over the ice sheet and photogrammetric and manual map scannings in the ice free region the ice sheet model accuracy is evaluated by omitting airborne laser data from the analysis and treating them as ground truth observations the mean accuracy of the ice sheet elevations is estimated to be 12 13 m and it is found that on surfaces of a slope between 0 2 and 0 8 corresponding to approximately 50 of the ice sheet the model presents a 40 improvement over models based on satellite altimetry alone on coastal bedrock the model is compared with stereo triangulated reference points and it is found that the model accuracy is of the order of 25 35 m in areas covered by stereo photogrammetry scannings and between 200 and 250 m elsewhere

the cenozoic evolution of the roer valley rift system integrated at a european scale the roer valley rift system rvrs is located between the west european rift and the north sea rift system during the cenozoic the rvrs was characterized by several periods of subsidence and inversion which are linked to the evolution of the adjacent rift systems combination of subsidence analysis and results from the analysis of thickness distributions and fault systems allows the determination of the cenozoic evolution and quantification of the subsidence during the early paleocene the rvrs was inverted laramide phase the backstripping method shows that the rvrs was subsequently mainly affected by two periods of subsidence during the late paleocene and the oligocene quaternary time intervals separated by an inversion phase during the late eocene during the oligocene and miocene periods the thickness of the sediments and the distribution of the active faults reveal a radical rotation of the direction of extension by about 70 80j counter clockwise integration of these results at a european scale indicates that the late paleocene subsidence was related to the evolution of the north sea basins whereas the oligocene quaternary subsidence is connected to the west european rift evolution the distribution of the inverted provinces also shows that the early paleocene inversion laramide phase has affected the whole european crust whereas the late eocene inversion was restricted to the southern north sea basins and the channel area finally comparison of these deformations in the european crust with the evolution of the alpine chain suggests that the formation of the alps has controlled the evolution of the european crust since the beginning of the cenozoic

slip tendency analysis as a tool to constrain fault reactivation a numerical approach applied to three dimensional fault models in the roer valley rift system southeast netherlands we describe a new numerical approach to constrain the three dimensional 3 d pattern of fault reactivation taking advantage of the knowledge of the tectonic stress field the ratio of the resolved shear and normal stresses slip tendency as well as the direction of the shear stress is calculated at every location on the faults modelled by triangulated surfaces although the calculated contact stresses represent only a first order approximation of the real stresses comparison of the 3 d pattern of slip tendency with the frictional resistance of the fault can provide useful constraints on the probability of fault reactivation the method was applied to 3 d geometrical fault models in the roer valley rift system southeast netherlands which is presently characterized by pronounced tectonic activity the input stress tensors were constrained by published stress indicators the analysis demonstrated that the observed fault activity could be explained within a reasonable range of frictional parameters and input stress magnitudes in addition a fairly good correlation was found between the predicted slip directions and the focal mechanisms of local earthquakes this suggests that in the study area fault models being valid in the uppermost part of the crust are suitable to constrain fault reactivation even in the deeper part of the seismogenic layer the analysis further demonstrated that fault hierarchy and the regional tectonic contexts of the fault system are important factors in fault reactivation therefore they always should be taken into account during evaluation of the calculated slip tendency and slip direction patterns

over winter persistence of supraglacial lakes on the greenland ice sheet results and insights from a new model we present a newly developed 1 d numerical energy balance and phase transition supraglacial lake model glacierlake glacierlake incorporates snowfall in situ snow and ice melt incoming water from the surrounding catchment ice lid formation basal freeze up and thermal stratification snow cover and temperature are varied to test lake development through winter and the maximum lid thickness is recorded average wintertime temperatures of 2 to 30 circ rm c and total snowfall of 0 to 3 45 m lead to a range of the maximum lid thickness from 1 2 to 2 8 m after sim 250 days with snow cover exerting the dominant control an initial ice temperature of 15 circ rm c with simulated advection of cold ice from upstream results in 0 6 m of basal freeze up this suggests that lakes with water depths above 1 3 to 3 4 m dependent on winter snowfall and temperature upon lid formation will persist through winter these buried lakes can provide a sizeable water store at the start of the melt season expedite future lake formation and warm underlying ice even in winter

implications of continuous structural inversion in the west netherlands basin for understanding controls on palaeogene deformation in nw europe a detailed analysis of high quality 3d seismic and borehole data provides new insights into the palaeogene tectonic history and inversion of the west netherlands basin the inversion characteristics are compared with those of other basins in the region to provide constraints on the palaeogene compressional tectonic movements in nw europe the inversion of the west netherlands basin which is characterized by the doming of the basin centre and by the reactivation of pre existing faults in a reverse mode was found to be the result of a continuous inversion process rather than a distinct tectonic pulse the intensity of the tectonic movements was not uniform throughout the eocene and was strongest during the latest eocene these characteristics are similar to those of other basins in the southern north sea region and in the english channel area in addition a good correlation exists between alpine tectonic events and the palaeogene inversion phases in light of these observations the latest eocene inversion pulse in the southern north sea region can be considered as the culmination of a long term inversion process that originated from the alpine collision

neotectonics of the netherlands a review abstract earthquakes and vertical land movements inferred from geodetic levelling results demonstrate that the netherlands is situated on a tectonically active part of the earth s surface tectonic subsidence analyses of the sedimentary records in the basins and the history of tectonic uplift inferred from meuse river terraces show that the current tectonic activity is part of a deformation phase which began in the late early miocene which we take as the start of the neotectonic period the neotectonic faulting mode is normal slip this is in accordance with the present day orientation of the maximum horizontal stress and the vertical orientation of the maximum stress however the neotectonic fault zones are reactivated variscan or older wrench faults these faults have been reactivated repeatedly during the mesozoic and cenozoic in normal and wrenching modes and therefore represent fundamental crustal weakness zones as a result the surficial neotectonic fault pattern resembles the inherited wrenching fault pattern although the faulting mode is normal slip this is illustrated for the area where normal faults have displaced the meuse fluvial terrace system in the southeastern part of the netherlands the neotectonic vertical motions in and around the roer valley rift system have affected the courses of the rhine and meuse rivers from pliocene times until the present in addition a fluvial terrace staircase developed along the meuse river in response to the uplift of the ardennes rhenish massif and its foreland for example near maastricht furthermore small fault scarps are present along segments of the bounding fault zones of the roer valley graben the peel boundary fault zone and the feldbiss fault zone in other parts of the netherlands the neotectonic vertical motions have no direct expression in the morphology examples of possible indirect control on the morphology in these areas occur in glacial landscapes the zuiderzee basin and the coastal zone

a comparison of extended and quasigeostrophic dynamics for a case of small rossby number extratropical cyclone development abstract this note compares the extended ext and quasigeostrophic qg dynamics of a small rossby number extratropical cyclone using the zwack okossi zo equation applied to a cyclone that occurred on 8 9 november 1985 over the north atlantic ocean results show that although differences exist both the ext and qg forms of the zo equation provide very adequate estimates of the large scale forcing processes associated with this case

reactivation tendency analysis a theory for predicting the temporal evolution of preexisting weakness under uniform stress state abstract understanding the mechanical controls on reactivation of preexisting weakness is a fundamental problem in tectonic studies in this study we develop a theoretical framework for evaluating the likelihood of seismicity on active faults and the sequence of reactivation of multiple sets of preexisting weakness our analysis overcomes the restrictions of the early work that assumes uniform coefficient of friction across all preexisting planes with negligible cohesive strength and vertical or horizontal orientations of principal stresses using a coordinate system transformation we developed a new graphical technique that can express the reactivation problem in the mohr space with the principal stresses oriented neither vertically nor horizontally we verified the predicted sequence of reactivation on preexisting weakness and initiation of new fractures according to the byerlee law and the coulomb fracture criterion by conducting a simple sandbox experiment our proposed reactivation tendency analysis can be expanded to evaluate the likelihood of seismicity on a single fault with curvi planar geometry e g listric normal faults ramp flat thrusts and strike slip faults with restraining and releasing bend geometry our analysis also provides a new insight into the mechanical cause of temporal evolution of pre existing weakness in geologic records finally our work implies that the sequence of faulting reactivated from preexisting weakness provides critical information on the mechanical properties of the deforming lithosphere

positive degree day factors for ablation on the greenland ice sheet studied by energy balance modelling ice ablation is related to air temperature by the positive degree day factor variations of the positive degree day factor in west greenland are studied using an energy balance model to simulate ablation under different conditions degree day factors for simulated and measured ice ablation at nordbogletscher and qaman rssup sermia agree well with values around 8 mm d 1 c 1 degree day factors for snow are less than half those for ice energy balance modelling shows that degree day factors vary with summer mean temperature surface albedo and turbulence but there is only evidence of large positive degree day factors at lower temperatures and with low albedo 0 3 the greatest effect of albedo variations 0 3 0 7 is at lower temperatures while variations in turbulence have greater effect at higher temperatures current models may underestimate runoff from the greenland ice sheet by several tenths because they use a degree day factor for melting ice that is too small for the colder parts of the ice sheet i e the upper ablation area and the northerly margin

diagnosing summertime mesoscale vertical motion implications for atmospheric data assimilation abstract balance omega equations have recently been used to try to improve the characterization of balance in variational data assimilation schemes for numerical weather prediction nwp results from fisher and fillion et al indicate that a quasigeostrophic omega equation can be used adequately in the definition of the control variable to represent synoptic scale balanced vertical motion for high resolution limited area data assimilation and forecasting 1 10 km horizontal resolution such a diagnostic equation for vertical motion needs to be revisited using a state of the art nwp forecast model at 2 5 km horizontal resolution these issues are examined starting from a complete diagnostic partial differential equation for omega the rhs forcing terms were computed from model generated fields these include the streamfunction temperature and physical time tendencies of temperature in gridpoint space to accurately compute one term of second order importance i e the ageostrophic vorticity tendenc

mass balance of the greenland ice sheet at high elevations comparison of ice discharge from higher elevation areas of the entire greenland ice sheet with total snow accumulation gives estimates of ice thickening rates over the past few decades on average the region has been in balance but with thickening of 21 centimeters per year in the southwest and thinning of 30 centimeters per year in the southeast the north of the ice sheet shows less variability with average thickening of 2 centimeters per year in the northeast and thinning of about 5 centimeters per year in the northwest these results agree well with those from repeated altimeter surveys except in the extreme south where we find substantially higher rates of both thickening and thinning

investigating the local atmospheric response to a realistic shift in the oyashio sea surface temperature front abstractthe local atmospheric response to a realistic shift of the oyashio extension sst front in the western north pacific is analyzed using a high resolution hr 0 25 version of the global community atmosphere model version 5 cam5 a northward shift in the sst front causes an atmospheric response consisting of a weak surface wind anomaly but a strong vertical circulation extending throughout the troposphere in the lower troposphere most of the sst anomaly induced diabatic heating is balanced by poleward transient eddy heat and moisture fluxes collectively this response differs from the circulation suggested by linear dynamics where extratropical sst forcing produces shallow anomalous heating balanced by strong equatorward cold air advection driven by an anomalous stationary surface low to the east this latter response however is obtained by repeating the same experiment except using a relatively low resolution lr 1 version of cam5 comparison to observations suggests that the hr respo

episodic activity of a dormant fault in tectonically stable europe the rauw fault ne belgium abstract our knowledge about large earthquakes in stable continental regions comes from studies of faults that generated historical surface rupturing earthquakes or were identified by their recent imprint in the morphology here we evaluate the co seismic character and movement history of the rauw fault in belgium which lacks geomorphological expression and historical present seismicity this 55 km long normal fault with known neogene and possibly early pleistocene activity is the largest offset fault west of the active roer valley graben its trace was identified in the shallow subsurface based on high resolution geophysics all the layers within the late pliocene mol formation 3 6 to 2 59 ma are displaced 7 m vertically without growth faulting but deeper deposits show increasing offset a paleoseismic trench study revealed cryoturbated but unfaulted late glacial coversands overlying faulted layers of mol formation in between those deposits the fault tip was eroded along with evidence for individual displacement events fragmented clay gouge observed in a micromorphology sample of the main fault evidences co seismic faulting as opposed to fault creep based on optical and electron spin resonance dating and trench stratigraphy the 7 m combined displacement is bracketed to have occurred between 2 59 ma and 45 ka the regional presence of the sterksel formation alluvial terrace deposits limited to the hanging wall of the rauw fault indicates a deflection of the meuse rhine confluence 1 0 to 0 5 ma by the fault s activity suggesting that most of the offset occurred prior to at this time interval in the trench sterksel formation is eroded but reworked gravel testifies for its former presence hence the rauw fault appears as typical of plate interior context with an episodic seismic activity concentrated between 1 0 and 0 5 ma or at least between 2 59 ma to 45 ka possibly related to activity variations in the adjacent continuously active roer valley graben

comparison of different digital elevation models and satellite imagery for lineament analysis implications for identification and spatial arrangement of fault zones in crystalline basement rocks of the southern black forest germany abstract gis based remote sensing techniques and lineament mapping provide additional information on the spatial arrangement of faults and fractures in large areas with variable outcrop conditions due to inherent censoring and truncation bias mapping of lineaments is still a challenging task in this study we show how statistical evaluations help to improve the reliability of lineament mappings by comparing two digital elevation models aster lidar and satellite imagery data sets in the seismically active southern black forest a statistical assessment of the orientation average length and the total length of mapped lineaments reveals an impact of the different resolutions of the data sets that allow to define maximum censoring bias and minimum truncation bias observable lineament length for each data set the increase of the spatial resolution of the digital elevation model from 30 m 30 m to 5 m 5 m results in a decrease of total lineament length by about 40 whereby the average lineament lengths decrease by about 60 lineament length distributions of both data sets follow a power law distribution as documented elsewhere for fault and fracture systems predominant ne n nnw and nw directions of the lineaments are observed in all data sets and correlate with well known mappable large scale structures in the southern black forest therefore mapped lineaments can be correlated with faults and hence display geological significance lineament density in the granite dominated areas is apparently higher than in the gneiss dominated areas application of a slip and dilation tendency analysis on the fault pattern reveals largest reactivation potentials for wnw ese and n s striking faults as strike slip faults whereas normal faulting may occur along nw striking faults within the ambient stress field remote sensing techniques in combination with highly resolved digital elevation models and a slip and dilation tendency analysis thus can be used to quickly get first order results of the spatial arrangement of critically stressed faults in crystalline basement rocks

near surface strong winds in a marine extratropical cyclone acceleration of the winds and the importance of surface fluxes a rapidly developing extratropical cyclone named tini brought strong winds to ireland and the united kingdom on 12 february 2014 a mesoscale model simulation is used to analyze the development of the strong winds through the terms in the horizontal momentum equation the maximum of near surface wind speed equatorward of the cyclone was composed of two different airstreams that underwent different paths to acceleration first horizontally moving air in the cold conveyor belt was accelerated by the along flow pressure gradient force but was decelerated by friction second descending air accelerated into the eastern end of the maximum of near surface wind speed and was associated in part with a sting jet caused by the increasing along flow horizontal pressure gradient force at lower levels when this descending air entered the boundary layer it too was decelerated by surface friction surface fluxes of heat and moisture were necessary to destabilize and deepen the boundary layer allowing mixing of the strongest winds from the free troposphere down to the surface a simulation with the surface fluxes turned off during cyclogenesis showed a more stable boundary layer around the bent back front which inhibited the strongest winds from reaching the surface the descent of the sting jet air was associated with a maximum in quasigeostrophic omega which consisted of both synoptic scale and mesoscale descent the latter associated with frontolysis occurring at the end of the bent back front thus the near surface wind maximum was created by the synoptic scale and mesoscale dynamics whereas localized moist processes were negligible

precipitation over greenland retrieved by a dynamic method and its relation to cyclonic activity abstract in order to calculate the vertical motion over some high mountain regions such as greenland an equation without the quasigeostrophic approximation in coordinates has been developed a dynamic method for retrieving precipitation over greenland is based on this equation the retrieved annual mean precipitation distribution for 1987 and 1988 is in very good agreement with the observed annual accumulation pattern over the greenland ice sheet the major weather system producing precipitation over greenland is the frontal cyclone based on the precipitation characteristics greenland can be divided into five subregions precipitation over the north coastal and central interior regions primarily occurs in summer for the three other subregions if the composite monthly mean sea level pressure charts for high and low monthly precipitation amounts are constructed a clear relationship between precipitation and cyclonic activity emerges if a mean cyclone exists in the labrador sea heavy precipita

the roer valley graben earthquake of 13 april 1992 and its seismotectonic setting a moderately sized pure normal dip slip earthquake occurred in the roer valley graben rvg near roermond the netherlands on 13 april 1992 at 1h 20m utc this contribution presents an overview of the locations fault plane solutions and magnitudes obtained for the mainshock and the aftershocks by the different scientific groups involved in their analysis the observed maximum intensity of vii is compared with that of other earthquakes in the region to illustrate the relatively low level of damage caused by the mainshock using sh and lg waves recorded at seven local and regional broadband stations we determine a seismic moment of 1 4 1017 nm a static stress drop of 9 7 mpa and an average displacement of 33 cm over a rupture surface of approximately 11 km2 the seismotectonics of the region extending from the rvg to the city of liege including the western part of the rhenish massif wrm and the eastern part of the brabant massif ebm is analysed based on the roermond earthquake studies and data collected since 1985 by the belgian seismic network the geographical distribution of focal mechanism reveals four different seismotectonic regimes in this area from stress tensor inversion we find that s3 coincides with the minimum horizontal stress component in the rvg the wrm and possibly in the ebm while in the liege region s3 is approximately vertical the minimum horizontal stress component shows a 30 rotation to the north in the wrm and the liege region and possibly 50 in the ebm when compared with the minimum horizontal stress component in the rvg

precipitation over greenland and its relation to the north atlantic oscillation the equation method based on an equivalent isobaric geopotential height in coordinates has been used to retrieve the precipitation over greenland this approach is designed to accurately represent the topographic effects of the greenland ice sheet on atmospheric motion and precipitation the 11 year mean precipitation from 1985 to 1996 over all of greenland is 376 mm yr 1 which is close to the long term mean precipitation of 346 mm yr 1 estimated from glaciological data the precipitation over all of greenland shows that the largest value in 1986 is 472 mm yr 1 and the smallest value in 1995 is 309 mm yr 1 the major interannual variability of the atmospheric circulation in the north atlantic can be represented by the variation of the north atlantic oscillation nao index which is most pronounced during winter it is found that if the nao index increases the total precipitation over greenland decreases and vice versa the correlation coefficient between these two series for 1985 1995 is 0 75 the mean precipitation over southern greenland where the majority of precipitation falls is more closely related to the nao index in winter and their correlation coefficient is 0 80 this relationship can be understood from the composite maps of sea level pressure and greenland precipitation for the high and low index months during months of high nao index values the icelandic low is strong during months of low nao index values the monthly mean low is located to the southwest of greenland over the labrador sea precipitation amounts over the southeast coast of greenland are about 100 mm larger during the low nao index months than the high nao index months precipitation over all of greenland during the low nao index months is higher there are significant downward trends in annual precipitation from 1985 1995 for all of greenland and its southern and central west coastal regions amounting to about 3 per year

lithospheric cross sections of the european cenozoic rift system abstract the lithospheric structure of the european cenozoic rift system ecris is presented in transects through the southern rhine graben and the rhenish massif hessen depression emphasizing the geophysical structure of the lithosphere based on seismic refraction reflection investigations teleseismic tomography electromagnetic depth sounding models and gravity aeromagnetic earthquake uplift subsidence and heat flow data the rift is clearly expressed in the rhine graben but is not evident at the surface in the area of the rhenish massif where its existence is indicated by seismicity it is characterized by abnormal crustal and upper mantle structures which vary considerably in horizontal direction for example under the rhine graben the crust is thinned to 25 km but at 40 km depth anomalously high velocities are observed in contrast beneath the rhenish massif the crust is thickened to 35 37 km and under its eastern part a high velocity thin upper mantle slice is seen at 30 km depth within the lower crust which towards the hessen depression is gradually replaced by normal variscan mantle with the moho near 30 km depth under the western part of the rhenish massif p and s wave velocities are reduced below 50 km depth which is not seen east of the rhine river under the rhine graben the existence of a low velocity upper mantle above 100 km cannot be generalized but is restricted to confined regions

crack seal microstructure evolution in bi mineralic quartz chlorite veins in shales and siltstones from the rwth 1 well aachen germany abstract in core samples from the deep geothermal well rwth 1 we studied variscan quartz chlorite veins formed by crack seal processes in siliciclastics at the brittle to ductile transition these sheared veins are common in sections of the well which are interpreted as variscan thrust zones based on image logs and seismic data microstructures interpreted to reflect different stages in the evolution of such crack seal veins suggest the veins started in microcracks sealed by quartz and chlorite to veinlets crossing multiple grains and bundles of veinlets evolving by progressive localization into low angle extensional shear veins and high angle dilational jog veins in the sheared veins chlorite and quartz ribbons show evidence for crack seal and simultaneous ductile shearing during vein evolution forming peculiar fin shaped microstructures in quartz ribbons in high angle dilational jogs fibrous crystals of quartz and chlorite point to multiple crack seal events with simultaneous growth of two different mineral phases this is interpreted to be the basic microstructural process in the veins we extend earlier models of polycrystal growth in fractures and present a series of 2d simulations of the kinematics of crystal growth in these bi mineralic veins for both localized and non localized cracking results are compared with the observed microstructures we show that when the relative growth rates of the two mineral phases are different serrated grain boundaries evolve the similarities between observation and model suggest that the assumption of our model is valid although many second order processes require a more detailed study we propose that the principles observed here can be applied to other bi mineralic crack seal veins

modeled variations of precipitation over the greenland ice sheet abstract a parameterization of the synoptic activity at 500 hpa and a simple orographic scheme are used to model the spatial and temporal variations of precipitation over the greenland ice sheet for 1963 88 from analyzed geopotential height fields produced by the national meteorological center nmc model coefficients are fitted to observed accumulation data primarily from the summit area of the ice sheet all major spatial characteristics of the observed accumulation distribution are reproduced apart from the orographic accumulation maximum over the northwestern coastal slopes the modeled time averaged total precipitation amount over greenland is within the range of values determined by other investigators from surface based observations a realistic degree of interannual variability in precipitation is also simulated a downward trend in simulated ice sheet precipitation over the 26 years is found this is supported by a number of lines of evidence it matches the accumulation trends during this peri

multiyear accumulation and temperature history near the north greenland ice core project site north central greenland this paper presents a comparison of two independent methods of estimating subseasonal accumulation across the interior of greenland these methods high resolution snow pit studies and atmospheric modeling have differing spatial and temporal resolution but both can estimate net accumulation for subseasonal and shorter periods the snow pit approach is based on a documented relationship between high resolution snow pit profiles of oxygen stable isotope ratio 18o and multiyear special sensor microwave imager ssm i 37 ghz brightness temperature records comparison of ssm i data to profiles obtained during the 1995 alfred wegener institut north greenland traverse field season shows that 18o data from snow in north central greenland are a reliable high resolution temperature proxy this enables determination of accumulation amount rate and timing from approximately july 1991 through june 1995 across this 220 km long transect of the ice sheet precipitation estimates derived from early modeling based on european centre for medium range weather forecasts data show a similar average seasonal pattern but a diminished magnitude of accumulation 56 for these sites the slope of the multiyear t versus correlation was evaluated for each site on the basis of the observed and calculated temperature history from the nearby north greenland ice core project ngrip site automatic weather station these data should assist interpretation of the paleoclimatic record in the ngrip deep core

greenland ice sheet surface mass balance variability 1991 2003 the polar mm5 mesoscale atmospheric model was run for 13 years 1991 2003 over greenland at 24 km horizontal resolution box and others 2004 the model physics were driven by satellite station and weather balloon observational data assimilation i e european centre for medium range weather forecasts ecmwf operational analysis the analysis in this study focuses on the response of the surface mass balance to its primary controls temperature and precipitation the results indicate coherent spatial patterns of variability and statistically significant links with temperature and precipitation and the north atlantic oscillation precipitation trends have the same spatial pattern and sign as temperature suggesting an association of precipitation and temperature variability increasing temperatures contribute to an increasing ablation trend and expansion of the ablation zone despite increasing accumulation trends the pinatubo philippines volcanic cooling in the early 1990s enhances this apparent warming trend only in the northeast does precipitation appear to dominate the surface mass balance where both temperature and precipitation have decreased there is little evidence for a total ice sheet surface mass balance trend although the meltwater runoff has a positive trend and combined with iceberg discharge and basal melting estimates suggests the ice sheet as a whole is in a state of net mass loss over this period

rapid thinning of parts of the southern greenland ice sheet aircraft laser altimeter surveys over southern greenland in 1993 and 1998 show three areas of thickening by more than 10 centimeters per year in the southern part of the region and large areas of thinning particularly in the east above 2000 meters elevation the ice sheet is in balance but thinning predominates at lower elevations with rates exceeding 1 meter per year on east coast outlet glaciers these high thinning rates occur at different latitudes and at elevations up to 1500 meters which suggests that they are caused by increased rates of creep thinning rather than by excessive melting taken as a whole the surveyed region is in negative balance

developing a structural and conceptual model of a tectonically limited karst aquifer a hydrogeological study of the hastenrather graben near aachen germany interdisciplinary and comprehensive field work combining hydraulic and geophysical experiments yielded an improved understanding of the fractured and partly karstified kohlenkalk aquifer in the hastenrather graben near aachen germany the aquifer is used for drinking water production and located in a geologically and tectonically complex area shaped by various tectonic events a workflow which combines implicit 3d structural modeling with hydrogeological conceptual model building enabled determining hydrogeological boundary conditions at specific boundary cross sections calculating the aquifer volume and analyzing the hydraulic influence of faults on the aquifer system electrical resistivity tomography seismic refraction tomography well logging and a coring campaign combined with available maps and additional literature research served as basis for the setup of the 3d structural model this 3d model comprises all important structural elements including the fault system deep folded structures and thrusts in the graben center integration of geological structure and hydraulic studies yielded a conceptual model of the hydrogeology describing the kohlenkalk aquifer and neighboring layers hydraulic conductivity of the aquifer system varies between 6 0 10 7 and 6 4 10 4 m s 1 with a decreasing trend from the ne graben shoulder to the graben center analysis of piezometric heads and resulting groundwater contour maps indicated four hydrogeological units which are partly limited by faults data on groundwater recharge as well as anthropogenic influences on the groundwater resources are part of the conceptual model

asiras airborne radar resolves internal annual layers in the dry snow zone of greenland 1 we present data from the european space agency s airborne sar interferometric radar altimeter system asiras flown during the cryovex 2004 field calibration validation campaign and new high resolution depth profiles of snow density measured in the field by neutron scattering we combine these data to calculate the depth of internal reflecting horizons in the asiras data the high resolution density data allow us to identify annual layers in the snow density profile and correlate their peaks with the reflecting horizons we use the thickness of the annual layers combined with the density profile to determine the spatial and temporal pattern of snow accumulation along the radar track for a period of 6 years from 1995 2002 our mean annual accumulation rate is 0 47 0 09 ma 1 water equivalent in agreement with the value determined from a core taken in this location in 1992 similarly our inter annual variability shows the same trends as recent model estimates over the entire ice sheet because asiras was designed to mimic as closely as possible the characteristics of the sar interferometric radar altimeter siral the principal payload of cryosat the detection of internal layering with asiras illuminates the possibility of detecting internal layers with a space borne radar and thus the possible application of this technique to the dry snow zones of antarctica greenland and smaller ice bodies

neotectonics and intraplate continental topography of the northern alpine foreland research on neotectonics and related seismicity has hitherto been mostly focused on active plate boundaries that are characterized by generally high levels of earthquake activity current seismic hazard estimates for intraplate domains are mainly based on probabilistic analyses of historical and instrumental earthquake catalogues the accuracy of such hazard estimates is limited by the fact that available catalogues are restricted to a few hundred years which on geological time scales is insignificant and not suitable for the assessment of tectonic processes controlling the observed earthquake activity more reliable hazard prediction requires access to high quality data sets covering a geologically significant time span in order to obtain a better understanding of processes controlling on going intraplate deformation the alpine orogen and the intraplate sedimentary basins and rifts in its northern foreland are associated with a much higher level of neotectonic activity than hitherto assumed seismicity and stress indicator data combined with geodetic and geomorphologic observations demonstrate that deformation of the northern alpine foreland is still on going and will continue in the future this has major implications for the assessment of natural hazards and the environmental degradation potential of this densely populated area we examine relationships between deeper lithospheric processes neotectonics and surface processes in the northern alpine foreland and their implications for tectonically induced topography for the environmental tectonics project entec the upper and lower rhine graben urg and lrg and the vienna basin vb were selected as natural laboratories the vienna basin developed during the middle miocene as a sinistral pull apart structure on top of the east alpine nappe stack whereas the upper and lower rhine grabens are typical intracontinental rifts the upper rhine graben opened during its late eocene and oligocene initial rifting phase by nearly orthogonal crustal extension whereas its neogene evolution was controlled by oblique extension seismic tomography suggests that during extension the mantle lithosphere was partially decoupled from the upper crust at the level of the lower crust however whole lithospheric folding controlled the mid miocene to pliocene uplift of the vosges black forest arch whereas thermal thinning of the mantle lithosphere above a mantle plume contributed substantially to the past and present uplift of the rhenish massif by contrast oblique crustal extension controlling the late oligocene initial subsidence stage of the lower rhine graben gave way to orthogonal extension at the transition to the neogene the entec project integrated geological geophysical geomorphologic geodetic and seismological data and developed dynamic models to quantify the societal impact of neotectonics in areas hosting major urban and industrial activity concentrations the response of europe s intraplate lithosphere to late neogene compressional stresses depends largely on its thermo mechanical structure which in turn controls vertical motions topography evolution and related surface processes

subsidence analysis and modelling of the roer valley graben se netherlands abstract the roer valley graben southeastern netherlands forms the most northern branch of the european cenozoic rift system sedimentary backstripping of exploration wells provides control on vertical tectonic motions during the complex post paleozoic geodynamic evolution of the area the roer valley graben evolved by repeated reactivation of permo carboniferous fracture systems at least three episodes of extension related subsidence are recorded these occurred during the late permian early triassic 255 240 ma the middle jurassic 168 165 ma and the late cenozoic 36 0 ma a late jurassic early cretaceous stretching phase is weakly inferred from incomplete data crustal stretching values calculated from the tectonic subsidence curves can account for the reflection seismic controlled crustal configuration of the roer valley graben area results demonstrate a close relationship between the roer valley graben and the basins in the north sea during the mesozoic in contrast the cenozoic evolution of the roer valley graben is independent from that of the north sea and is related to the development of the rhine graben

evolution of strength recovery and permeability during fluid rock reaction in experimental fault zones abstract physical and chemical fluid rock interactions are implicated in controlling earthquake nucleation and recurrence in particular interseismic compaction sealing and healing of fractured fault rocks can lead to strength recovery and stabilisation of fault zones in contrast these same processes can also assist increases in pore fluid pressures and consequent destabilisation of faults here we present high temperature hydrothermal experiments designed to assess the evolution of strength of fault zones in previously intact rock and also characterise the associated changes to porosity and permeability cores of fontainebleau sandstone were initially loaded to failure in a high pressure gas medium apparatus the failed specimens were then hydrothermally reacted at 927 c for variable duration under isostatic conditions and subsequently re fractured to determine the interseismic strength recovery in the most extreme case hydrothermally induced gouge compaction cementation and crack healing resulted in 75 strength recovery after reaction for 6 h isostatic hydrothermal treatment also resulted in dramatic reduction in porosity and permeability strength of the fault zone following hydrothermal reaction appears to be closely correlated to porosity consistent with previous studies on brittle failure of porous aggregates the experimental results show how hydrothermal reactions in fault zones may lead to two competing time dependent effects fault strengthening due to increased cohesion in the fault zone and fault weakening arising from elevated pore pressures within a well cemented low permeability gouge layer

modeled precipitation variability over the greenland ice sheet on the basis of the evaluation of recent greenland precipitation studies some of the deficiencies in the modeled precipitation are probably related to the topographic data employed in modeling in this paper the modern digital elevation data of ekholm 1996 is used if the horizontal pressure gradient force in coordinates is separated into its irrotational and rotational parts which are expressed by the equivalent geopotential and geo stream function respectively the topographic effect on the precipitation can be accurately modeled the equivalent geopotential and geo stream function are implemented in a fully consistent manner in the generalized equation in this paper a simplified large scale condensation without evaporation of condensate is also used these improvements are combined to yield an improved dynamic method two aspects of the precipitation distribution are refined by the improved dynamic method one is the 10 cm yr 1 contour near summit greenland and the other is a relative large precipitation area centered near the point 70 n 49 w extensive comparisons are made between the retrieved precipitation and the observed annual accumulation time series from 11 ice core sites on the ice sheet the modeled precipitation from the original method must use sealers to have a high degree of interannual correspondence between the measured accumulation and the retrieved precipitation but the retrieved precipitation from the improved method increases at all ice core sites and a good correspondence is obtained without any sealer being required the spatial average of multiyear mean error e j is 11 5 cm yr 1 for the modeled precipitation from the improved method while that for p from era 15 is 14 5 cm yr 1 the total mean error em is 3 0 cm yr 1 for the improved method while em for the p from era 15 is 4 0 cm yr 1 these two errors show that the precipitation modeled by the improved method is better than the p from era 15 thus the distribution of precipitation over the 11 sites retrieved by the improved dynamic method is considerably refined large downward trends in annual amounts are present in the precipitation retrieved by the improved dynamic method for all of greenland and its southern and central west coastal regions the modeled precipitation from the improved dynamic method and observed accumulation from ice cores are all in agreement with the thomas et al 1999 result that the southern greenland ice sheet above 2000 m is approximately in balance it also shows that local thickening and thinning areas of the ice sheet derived by airborne laser altimetry from 1993 to 1999 over the entire greenland above 2000 m krabill et al 2000 are approximately consistent with precipitation change retrieved by the improved dynamic method

lithospheric dynamics and the rapid pliocene quaternary subsidence phase in the southern north sea basin abstract we present stratigraphic modeling and quantitative analysis of the pliocene and quaternary subsidence of the southern north sea basin during the late pliocene well before the onset of quaternary glaciation the subsidence rate in the southern part of the north sea basin showed a ten fold increase relative to previous tertiary rates the high pliocene quaternary subsidence rate is consistent with the direction and state of the present intraplate stress field in northwest europe one possible consequence of the modern compressional stress field in northwest europe is reactivation of faulting in the central graben resulting in localized stretching and the development of pull apart basins alternatively the acceleration in late pliocene subsidence rates could be due to localized flexural downwarping of the lithosphere in the central graben caused by an increase in the level of intraplate compression both mechanisms succesfully predict the major characteristics of the overall quaternary subsidence history and stratigraphy gravity modeling suggests that the mechanism of localized stretching dominates the recent tectonostratigraphic evolution of the southern north sea

greenland ice sheet high elevation balance and peripheral thinning aircraft laser altimeter surveys over northern greenland in 1994 and 1999 have been coupled with previously reported data from southern greenland to analyze the recent mass balance of the greenland ice sheet above 2000 meters elevation the ice sheet is in balance on average but has some regions of local thickening or thinning thinning predominates at lower elevations with rates exceeding 1 meter per year close to the coast interpolation of our results between flight lines indicates a net loss of about 51 cubic kilometers of ice per year from the entire ice sheet sufficient to raise sea level by 0 13 millimeter per year approximately 7 of the observed rise

changes in greenland ice sheet elevation attributed primarily to snow accumulation variability the response of grounded ice sheets to a changing climate critically influences possible future changes in sea level recent satellite surveys over southern greenland show little overall elevation change at higher elevations but large spatial variability using satellite studies alone it is not possible to determine the geophysical processes responsible for the observed elevation changes and to decide if recent rates of change exceed the natural variability here we derive changes in ice sheet elevation in southern greenland for the years 1978 88 using a physically based model of firn densification and records of annual snow accumulation reconstructed from 12 ice cores at high elevation our patterns of accumulation driven elevation change agree closely with contemporaneous satellite measurements of ice sheet elevation change and we therefore attribute the changes observed in 1978 88 to variability in snow accumulation similar analyses of longer ice core records show that in this decade the greenland ice sheet exhibited typical variability at high elevations well within the long term natural variability our results indicate that a better understanding of ice sheet mass changes will require long term measurements of both surface elevation and snow accumulation

modeled antarctic precipitation part ii enso modulation over west antarctica the impacts of the el nino southern oscillation enso on the antarctic region are of special importance in evaluating the variability and change of the climate system in high southern latitudes in this study the enso signal in modeled precipitation over west antarctica since 1979 is evaluated using forecast precipitation from several meteorological analyses and reanalyses additionally a dynamical retrieval method drm for precip itation is applied over the last two decades the southern oscillation index soi has an overall anticorrelation with precipitation over the west antarctic sector bounded by 758 908s 1208w 1808 while it is positively correlated with precipitation over the south atlantic sector bounded by 658 758s 308 608w decadal variations are found as the relationship between the soi and west antarctic precipitation is stronger in the 1990s than that in the 1980s the polar front jet stream west antarctic precipitation and the soi show a well ordered correspondence during the 1990s as the jet zonal speed is negatively correlated to the soi and positively correlated to west antarctic precipitation these relationships are weaker during the 1980s consistent with the change in sign of the correlation between the soi and west antarctic precipitation the decadal variations are apparently related to changes in the quasi stationary eddies that determine the local onshore and offshore flow over west antarctica

an early autumn polar low formation over the norwegian sea around october 15 1993 an unusual polar low formation took place over the norwegian sea the evolution is studied by means of the hirlam forecasting model at the danish meteorological institute satellite imagery and observations the investigation to some extent based on generalized forms of the equations for omega and geopotential tendency reveals that the disturbance forms initially by baroclinic instability along a frontal zone within a maritime polar air mass and in close proximity of an intense extratropical cyclone during its growth to a polar low air sea interaction seems to work in conjunction with the baroclinic process a parallel forecast with the latent heat set to zero shows that heating of the atmosphere associated with precipitation is necessary for the polar low formation

snowmelt on the greenland ice sheet as derived from passive microwave satellite data abstract the melt extent of the snow on the greenland ice sheet is of considerable importance to the ice sheet s mass and energy balance as well as arctic and global climates by comparing passive microwave satellite data to field observations variations in melt extent have been detected by establishing melt thresholds in the cross polarized gradient ratio xpgr the xpgr defined as the normalized difference between the 19 ghz horizontal channel and the 37 ghz vertical channel of the special sensor microwave imager ssm i exploits the different effects of snow wetness on different frequencies and polarizations and establishes a distinct melt signal using this xpgr melt signal seasonal and interannual variations in snowmelt extent of the ice sheet are studied the melt is found to be most extensive on the western side of the ice sheet and peaks in late july moreover there is a notable increasing trend in melt area between the years 1979 and 1991 of 4 4 per year which came to an abrupt halt in 1

an improved method for determining the regional stress tensor using earthquake focal mechanism data application to the san fernando earthquake sequence the orientations of fault planes and slip directions indicated by a population of earthquake focal mechanisms can be used to determine best fit regional principal stress directions and r 2 1 3 1 a measure of relative stress magnitudes under the assumption of uniform stress in the source region this analysis allows for the possibility that failure occurs on preexisting zones of weakness of any orientation in the inversion we perform a grid search of stress models to find the one which requires the smallest total rotation of all the fault planes that is needed to match the observed and predicted slip directions the method allows for errors in orientations of both the fault planes and slip directions we have an objective means for identifying the more likely of the two possible fault planes from each focal mechanism relative to a given stress model thus we do not face the problem of ambiguity of nodal planes which plagues other analyses of this kind by using a grid search of stress models rather than a linearization scheme we are able to perform a realistic error analysis and thus establish confidence limits for the preferred regional stresses the method can be used to investigate possible stress inhomogeneities during earthquake sequences by analyzing subsets of the data population the technique has been applied to 76 events from the san fernando earthquake sequence for which we have found best fit stresses plunge and azimuth 1 7 187 2 27 281 3 62 84 and r 0 65 the average misfit between this stress model and all the data is about 8 and all but eight of the aftershocks have misfits of less than 20 these values are considerably less than the uncertainty of the focal mechanism determinations therefore significant stress inhomogeneities are not required by the data our analysis does not support the suggestion of a change in stresses during the aftershock sequence as proposed by others on the basis of an apparent change in focal mechanisms

interannual variations of snow accumulation on the greenland ice sheet 1985 1996 new observations versus model predictions newly measured time series of net water equivalent accumulation from ice cores are reported for 11 sites located near the 2000 m contour of the greenland ice sheet many of these sites are located in regions where accumulation has not been previously measured we compared these new time series of annual accumulation with previously reported modeled precipitation covering the same time range because ice core accumulation records include both regional and local accumulation components we used adjacent ice core records at six multiple core sites to estimate the local component and extrapolated these results to the five single core sites we investigated the impact of this short scale spatial variability in accumulation on statistical comparisons between the observed accumulation and model precipitation although sealers were required to match the 12 year mean modeled precipitation to the mean observed accumulation a high degree of correspondence between observed interannual accumulation and scaled modeled precipitation was found at 7 of 11 locations the need for scaling and the low correspondence between model simulations and observations at some sites clearly indicate that model improvements are needed although very encouraging a more spatially distributed array of ice core accumulation measurements spanning the same time period as the precipitation modeling is necessary for continued model improvement and validation in agreement with earlier studies the large temporal variability in snow accumulation predicted by modeling and confirmed by ice cores indicates that the ice sheet elevation varies by tens of centimeters from year to year simply because of changing accumulation

structural evolution of inverted basins in the dutch offshore abstract the structural evolution of the dutch central north sea graben and the fault bounded broad fourteens basin is discussed graben formation started during the early triassic and culminated in strong differential subsidence during the late jurassic early cretaceous narrow fault bounded grabens and troughs and broad intervening highs were formed as a result of crustal distension and associated transtensional deformations the thickness of the late jurassic to early cretaceous fill of these basins may have exceeded 3000 m concurrent with the filling of these basins the bordering highs became deeply truncated during the late cretaceous and early tertiary compressive stresses resulted in inversion of these basins whereby movements along their bounding normal faults were reversed giving rise locally to overthrusting as for instance in the broad fourteens and west netherlands basins the timing of these compressional deformations has been palaeontologically dated and coincides with major orogenic events in the alps

measurements of friction coefficients and cohesion for faulting and fault reactivation in laboratory models using sand and sand mixtures abstract simple laboratory tests have been made on dry quartz sand and on mixtures of sand and clay and sand and cement tests were made on both low and high density specimens of each mixture as determined by physical handling techniques the tests included measurements of density estimates of the coefficient of internal friction based on fault orientation and estimates of the friction coefficients and cohesion values for fault initiation and reactivation in a shear frame apparatus which was also used to test artificial fault zones made from pure clay glass microspheres and wheat flour the results suggest that density is determined more by handling technique than by composition and that friction coefficients and perhaps cohesion both increase with increasing density the shear testing revealed a consistent drop in cohesion for fault reactivation in all densely packed mixtures tested although small this drop may be significant for some types of laboratory models

geological causes of recent 100 yr vertical land movement in the netherlands abstract geodetic levelling data record differential vertical movements of the top of the pleistocene sands of up to 1 5 mm year in the netherlands over the last century we compare these movements to a mean tectonic isostatic and compaction movements at time scales of millions of years obtained by backstripping of cenozoic stratigraphy and b estimates of recent 100 yr movements from process modelling of isostasy glacio and hydro isostasy and compaction the process rates at time scales of millions of years are insufficient to account for the geodetic observations by an order of magnitude the isostasy and compaction rates inferred for the last century are also insufficient they explain less than half of the observed movements this suggests that the residual observed rates less isostasy and compaction estimates which is interpreted to represent tectonic crustal deformation constitutes an important contribution to present day movements the surprisingly high rates of short term tectonic vertical movements in a region which is relatively inactive seismically indicate that correction of tide gauge records for the glacio isostatic signal alone does not yield an appropriate measure of eustatic sea level rise along the dutch coast

cenozoic block rotation according to a conjugate shear system in central europe indications from palaeomagnetic measurements abstract results of palaeomagnetic measurements in the middle tertiary volcanic provinces of siebengebirge and westerwald northeastern rhenish massif germany indicate that block rotation of the northeastern rhenish massif of the order of 10 to 16 has occurred since the late oligocene contemporaneous subsidence in the upper rhine graben neuwied basin and lower rhine basin and intensive faulting in the hessian depression document a new period of intraplate tectonism in central europe in the tertiary presumably from the eocene to the miocene the axis of maximum horizontal stress rotated from the nne ssw to the nnw sse and the nw se direction respectively the new stress conditions may be responsible for the development of a conjugate shear system in central europe north of the alps a model of a conjugate shear system is presented a sinistral divergent strike slip fault extends ssw nne from the upper rhine graben to the north the fault splits up into two branches in the area of the hessian depression a conjugate dextral wrench fault system develops from the bavarian pfahl zone southeastern germany to the rhenish massif about 200 km to the northeast a parallel dextral strike slip fault is known from the southern lower saxony basin to the north of the osning zone and harz mountains the northeastern block of the rhenish massif was created between dextral strike slip faults the block began clockwise rotation presumably in the late oligocene due to small changes in direction of the maximum horizontal compressive stress from nnw to nw and contemporaneous extension of the western european crust to the southwest it is assumed that the block rotation is responsible for the v shaped opening of the lower rhenish basin and anticlockwise micro block rotation within the hessian depression opening between the rotating and nonrotating crust along the recent rhine river in the central part of the rhenish massif formed triangular transrotational basins basin of neuwied due to movements of crustal blocks in the western rhenish massif bounded by wnw ese dextral faults fault plane solutions from recent earthquakes in the rhine system support the model of block rotation and related crustal movements due to rotation of the northeastern rhenish massif the continuation of the upper rhine graben development to the north is prevented

a comparison of quasigeostrophic and nonquasigeostrophic vertical motions for a model simulated rapidly intensifying marine extratropical cyclone abstract large scale departures from quasigeostrophic vertical motions are diagnosed for a model simulation of the qe ii storm 9 11 september 1978 the simulation was performed by the limited area mesoscale prediction system lamps initialized at 1200 utc 9 september 1978 the model cyclone intensified from a central pressure of 1003 mb to 976 mb in 24 h considerably short of the 59 mb 24 h 1 observed deepening but reasonable in comparison to other model simulations of this storm this diagnosis centers on a hydrostatic generalized omega equation which scales to the quasigeostiophic omega equation for small rossby number vertical motions were computed both from this generalized omega equation and the quasigeostrophic omega equation in order to examine the importance of nonquasigeostrophic effects the high correlation of vertical motions from a control experiment using most of the terms in the generalized omega equation with the vertical motions predicted by the model establishes the validity o

evaluation of recent precipitation studies for greenland ice sheet the retrieval of an accurate spatial and temporal record of contemporary greenland precipitation is a uniquely challenging task because of the extreme variability in both atmospheric processes and the resulting precipitation distribution over relatively small spatial scales a comparison of precipitation data sets composed of monthly mean values from recent studies shows a convergence on the general features of the long term spatial patterns but substantial disagreement on the temporal variability both regionally and for all of greenland there is general agreement on a long term greenland average of about 35 cm yr 1 and on long term values for regional scales although differences for outlying data sets exceed 50 of the observed glaciological estimate for particular regions a fundamental problem is the inadequate topographic representation of greenland in the numerical analyses nearly all of the data sets are overly dry for high elevation areas as seen from comparisons with glaciological observations from summit the east central region of greenland is found to be particularly susceptible to the temporal discontinuities in data sets which employ operational analyses in contrast there is strong agreement among all methods on the temporal variability for the west central region over a 15 year period from the comparison it is concluded that none of the data sets is able to capture all of the regional scale features in general however the deficiencies of each data set are readily identifiable from comparison and evaluation in the context of circulation features agreement among the methods on particular regions and timescales gives increased confidence in drawing conclusions related to aspects of greenland s precipitation climatology in particular an enhanced precipitation retrieval method is found to be less susceptible to data artifacts than other methods using operational analyses in the north anomalously high precipitation is associated with cyclonic development near the fram strait for west central greenland the close agreement among methods is related to the dominant contribution of the mean circulation

the tectonic evolution of the southern dutch north sea during the palaeogene basin inversion in distinct pulses abstract in this paper we discuss the response of a sedimentary basin to compressional reactivation of extensional faults in distinct pulses the inversion of the broad fourteens basin in the southern dutch north sea is used as a case study the first pulse of inversion occurred during the late mesozoic as a result of the sub hercynean phase a second pulse occurred during the mid palaeocene laramide phase a final inversion pulse occurred around the eocene oligocene boundary coinciding with the pyrenean tectonic event we reconstructed the stratigraphic and structural development of the area during the palaeogene in detail basic data are two 2d seismic surveys supported by 74 geophysical wireline logs on which newly constructed depth and thickness maps are based the reconstruction is aided by a quantitative subsidence analysis cessation of compression resulted in relaxation and tensional reactivation of faults caused differential subsidence inheritance of geological structures is a key element in the tectonic activity in the broad fourteens basin during the palaeogene tectonic movement during the palaeogene was always accommodated by reactivation of palaeozoic mesozoic faults the intensity of inversion in the southern north sea basin during the pyrenean phase appears much larger than previously noticed moreover the area affected by the inversion is much wider than during previous phases minor differences in the direction of the local stress field between the tectonic phases and by the deposition of a thick sedimentary succession during the periods of tectonic quiescence between the inversion phases can account for this

origin of gem corundum in calcite marble the revelstoke occurrence in the canadian cordillera of british columbia abstract the calcite marble hosted gem corundum ruby sapphire occurrence near revelstoke british columbia canada occurs in the monashee complex of the omineca belt of the canadian cordillera corundum occurs in thin folded and stretched layers with green muscovite ba bearing k feldspar anorthite an0 85 1 phlogopite na poor scapolite other silicate layers within the marble are composed of 1 diopside tremolite quartz and 2 garnet alm0 7 0 5grs0 2 0 4 na rich scapolite diopside tremolite na k amphiboles non silicate layers in the marble are either magnetite or graphite bearing predominantly pink locally red or purple opaque to transparent corundum crystals have elevated cr2o3 0 21 wt and variable amounts of tio2 rare blue rims on the corundum crystals contain higher amounts of tio2 0 53 wt and fe2o3 0 07 wt the associated micas have elevated cr v ti and ba contents petrography of the silicate layers show that corundum formed from muscovite at the peak of metamorphism 650 700 c at 8 5 9 kbar because the marble is almost pure calcite dolomite is very rare the corundum was preserved because it did not react with dolomite to spinel calcite during decompression the scapolite bearing assemblages formed during or after decompression of the rock at 650 c and 4 6 kbar gem quality corundum crystals formed especially on borders of the mica feldspar layers in an assemblage with calcite whole rock geochemistry data show that the corundum bearing silicate mica feldspar layers formed by mechanical mixing of carbonate with the host gneiss protolith the bulk composition of the silicate layers was modified by si and fe depletion during prograde metamorphism high element mobility is supported by the homogenization of 18o and 13c values in carbonates and silicates for the marble and silicate layers the silicate layers and the gneiss contain elevated contents of cr and v due to the volcanoclastic component of their protolith

tectonic analysis of fault slip data sets using data that include the direction and the sense of motion on individual fault surfaces determined by slickenside lineations it is possible to reconstruct reduced stress tensors that correspond to the orientation of stress axes and to the ratio 2 3 1 3 between principal stress values 1 2 3 compression being positive no assumption is made concerning the orientation of fault planes relative to stress axes so that reactived faults are taken into account as well as newly created ones qualitative and quantitative methods for analysis of fault slip data were developed during the last 10 years the practical limitation of the methods and the necessity for critical field observations are emphasized these methods can be applied to focal mechanisms of earthquakes a more complex analysis of heterogeneous data sets involving an iterative separation of different stress systems is also discussed this analysis enables one to distinguish successive faulting events careful qualitative study in the field is in all cases essential

diagnosing mesoscale vertical motion from horizontal velocity and density data the mesoscale vertical velocity is obtained by solving a generalized omega equation equation using density and horizontal velocity data from three consecutive quasi synoptic high resolution surveys in the alboran sea the atlantic jet aj and the northern part of the western alboran gyre wag were observed as a large density anticyclonic front extending down to 200 230 m the horizontal velocity uh in the aj reached maxima of 1 2 m s 1 for the three surveys with extreme rossby numbers of f 0 9 in

crustal observations beneath the southern north sea and their tectonic and geological implications abstract in 1991 a deep seismic reflection line mpni 9101 was acquired in the southern north sea from the mesozoic broad fourteens basin across the west netherlands basin onto the london brabant massif lbm the resultant section shows a strongly reflective lower crust beneath the area of mesozoic basin development this lower crustal reflectivity continues to be strong beneath the lbm the travel time to the base of the reflective zone increases from approximately 11 0 s beneath the mesozoic basins to 12 5 s beneath the lbm suggesting a southward thickening of the crust rijkers et al 1993 based on these travel times and information from deep wells and refraction surveys moho depth is estimated to increase from about 31 km beneath the mesozoic basins to about 38 km beneath the lbm this difference in depth to the moho can partly be explained by coaxial stretching of the crust beneath the mesozoic basins in comparison with the mesozoic basins the crust beneath the lbm was thickened during the caledonian and variscan orogenies

elevation change of the southern greenland ice sheet seasat and geosat satellite altimeter measurements for the greenland ice sheet south of 72 degreesn latitude show that surface elevations above 2000 meters increased at an average rate of only 1 5 0 5 centimeters per year from 1978 to 1988 in contrast elevation changes varied regionally from 15 to 18 centimeters per year seasonally by 15 centimeters and interannually by 8 centimeters the average growth rate is too small to determine if the greenland ice sheet is undergoing a long term change due to a warmer polar climate

structural control of geothermal reservoirs in extensional tectonic settings an example from the upper rhine graben abstract in extensional tectonic settings major structural elements such as graben boundary faults are typically oriented subparallel to the maximum horizontal stress component shmax they are often structurally accompanied by transfer zones that trend subparallel to the extension direction in the upper rhine graben such transfer faults are typically characterized by strike slip or oblique slip kinematics a major re orientation of the regional stress field by up to 90 of the upper rhine graben in the early miocene led to the present day normal and strike slip faulting regimes in the north and south of the upper rhine graben respectively and a transition zone in between consequently conditions for fault frictional failure changed significantly moreover it has been observed during tracer and stimulation experiments that such transfer faults may be of major importance for the hydraulic field of geothermal reservoirs under the present stress condition especially when located between production and injection well in this context we have investigated slip and dilation tendencies ts and td of major structural elements at reservoir scale for two representative geothermal sites bruchsal germany and riehen switzerland located close to the eastern main boundary fault of the upper rhine graben we have evaluated the quality and uncertainty range of both tendencies with respect to potential variation in shmax orientation despite significant differences in orientation of the structures and the stress regimes the resulting variation of ts and td reveal major similarities concerning the reactivation potential of both the graben parallel structures and the transfer faults the conditions of criticality for tensile failure and non criticality for shear failure suggest that transfer faults are most likely naturally permeable structures with low stimulation potential this is in agreement with the absence of both immediate tracer recovery and seismicity in the studied geothermal sites

vanadium and barium bearing green mica within coaly metapelite from the ogcheon supergroup republic of korea abstract vanadium and barium bearing green mica first reported in korea has been found within the coaly metapelite from the ogcheon supergroup at the deokpyeong and hoenam area the occurrence optical property chemical composition crystal structure and formation environment of the green mica were systematically investigated concentrations of the v2o3 and bao in green mica bearing coaly metapelite range from 0 15 to 1 88 wt and 0 55 to 6 66 wt respectively the mode of occurrence and grain size of this mica are variable most of the green mica ranging from 50 to 100 m in length and from 5 to 10 m in width occur along foliation boundaries between graphite and quartz grains the green mica predominantly occur as pseudo hexagonal forms pale to deep green in colour with flakes of crystals based on 2m structure unit cell parameters of the mica are a 5 213 5 249 a b 8 936 8 990 a c 20 524 20 924 a and 95 89 95 98 which are higher than the normal 2m1 muscovite representative chemical formula of the mica is na0 1k1 4ba0 5 al2 8ti0 1v0 5fe0 1mg0 5 si6 0al2 0 o22 the v and ba possibly substitute for octahedral alvi and k respectively the compositional ranges of v and ba on the basis of o 22 are from 0 31 to 0 68 and from 0 37 to 0 57 respectively we suggest that the genesis of this green mica within the coaly metapelite could be interpreted as due to apparently related metamorphism the ba and v enriched during diagenesis at the interface between the basinal brine and organic matter possibly substituted for the k and alvi in smectite and or illite respectively

late quaternary activity of the feldbiss fault zone roer valley rift system the netherlands based on displaced fluvial terrace fragments abstract the meuse river crosses the feldbiss fault zone one of the main border fault zones of the roer valley graben in the southern part of the netherlands uplift of the area south of the feldbiss fault zone forced the meuse river to incise and as a result a flight of terraces was formed faults of the feldbiss fault zone have displaced the middle and late pleistocene terrace deposits in this study an extensive geomorphological survey was carried out to locate the faults of the feldbiss fault zone and to determine the displacement history of terrace deposits the feldbiss fault zone is characterized by an average displacement rate of 0 041 0 047 mm a 1 during the late pleistocene individual faults show an average displacement rate ranging between 0 010 and 0 034 mm a 1 the spatial variation in displacement rates along the individual faults reveals a system of overstepping faults these normal faults developed by reactivation of paleozoic strike slip faults as fault displacements at the bases of the younger terrace deposits are apparently similar to the tops of the adjacent older terrace the age of these horizons is the same within thousands of years this implies that the model of terrace development by rapid fluvial incision followed by slow aggradation does apply for this area

a model of composite seismic sources for the lower rhine graben northwest europe abstract the lower rhine graben lrg straddling the border zone of belgium the netherlands and germany is an active tectonic structure in continental northwest europe it is characterized by northwest southeast oriented normal faults and moderate but rather continuous seismic activity many faults have been mapped in the lrg but so far a model of fault hierarchy or fault segmentation has been lacking in the frame of a european database of seismogenic sources we have devised a seismic source model for the lrg consisting of so called composite seismic sources each composite seismic source may encompass one or more segments but it is unlikely that a segment would extend across more than one source we distinguish 15 seismic sources based on major stepovers bifurcations gaps and important changes in strike dip direction or slip rate the sources are partitioned into one or more informal fault sections each with an associated surface trace for each source we describe the limits and the composing fault sections and present the geological arguments for their existence we have compiled all relevant data concerning the seismic source parameters required for the database putting lower and upper bounds on strike dip rake slip rate and depth and an upper bound on earthquake magnitude this source model should provide a new basis for modeling seismic hazard as well as for guiding further paleoseismic studies in the lrg online material detailed maps of the composite sources in the lower rhine graben 3d views of the fault model and a table with parameters of earthquake focal mechanisms and detailed information sheets for each composite seismic source

regional patterns of tectonic stress in europe nearly 1500 stress orientation determinations are now available for europe the data come from earthquake focal mechanisms overcoring measurements well bore breakouts hydraulic fracturing measurements and young fault slip studies and sample the stress field from the surface to seismogenic depths three distinct regional patterns of maximum compressive horizontal stress shmax orientation can be defined from these data a consistent nw to nnw shmax stress orientation in western europe a wnw ese shmax orientation in scandinavia similar to western europe but with a larger variability of shmax orientations and a consistent e w shmax orientation and n s extension in the aegean sea and western anatolia the different stress fields can be attributed to plate driving forces acting on the boundaries of the eurasian plate locally modified by lithospheric properties in different regions on average the orientation of maximum stress in western europe is subparallel to the direction of relative plate motion between africa and europe and is rotated 17 clockwise from the direction of absolute plate motion the uniformly oriented stress field in western europe coincides with thin to medium lithospheric thickness approximately 50 90 km and high heat flow values 80 m w m2 in western europe a predominance of strike slip focal mechanisms implies that the intermediate principal stress is vertical the more irregular horizontal stress orientations in scandinavia coincide with thick continental lithosphere 110 170 km and low heat flow 50 m w m2 the cold thick lithosphere in this region may result in lower mean stresses associated with far field tectonic forces and allow the stress field to be more easily perturbed by local effects such as deglaciation flexure and topography the stress field of the aegean sea and western anatolia is consistent with n s extension in a back arc setting behind the hellenic trench subduction zone the stress field is influenced in places by regional geologic structures e g in the western alps where shmax directions show a slight tendency toward a radial stress pattern not all major geologic structures however appear to affect the shmax orientation e g in the vicinity of the rhine rift system horizontal stress orientations are continuous

mass changes of the greenland and antarctic ice sheets and shelves and contributions to sea level rise 1992 2002 changes in ice mass are estimated from elevation changes derived from 10 5 years greenland and 9 years antarctica of satellite radar altimetry data from the european remote sensing satellites ers 1 and 2 for the first time the dh dt values are adjusted for changes in surface elevation resulting from temperature driven variations in the rate of firn compaction the greenland ice sheet is thinning at the margins 42 2g t a 1 below the equilibrium line altitude ela and growing inland 53 2g t a 1 above the ela with a small overall mass gain 11 3g t a 1 0 03 mm a 1 sle sea level equivalent the ice sheet in west antarctica wa is losing mass 47 4g t a 1 and the ice sheet in east antarctica ea shows a small mass gain 16 11 gt a 1 for a combined net change of 31 12 gt a 1 0 08 mm a 1 sle the contribution of the three ice sheets to sea level is 0 05 0 03 mm a 1 t he antarctic ice shelves show corresponding mass changes of 95 11 gt a 1 in wa and 142 10 gt a 1 in ea thinning at the margins of the greenland ice sheet and growth at higher elevations is an expected response to increasing temperatures and precipitation in a warming climate the marked thinnings in the pine island and thwaites glacier basins of wa and the totten glacier basin in ea are probably ice dynamic responses to long term climate change and perhaps past removal of their adjacent ice shelves the ice growth in the southern antarctic peninsula and parts of ea may be due to increasing precipitation during the last century

characterization and quantification of active faulting in the roer valley rift system based on high precision digital elevation models the roer valley rift system rvrs is located in the northern prolongation of the upper rhine graben during the cenozoic the evolution of the rvrs was influenced by two different rift systems situated in the north and in the south the north sea rift system and the west european rift system respectively during the last decades moderate seismicity revealed the continuous activity of the graben border faults the peel boundary fault zone pbfz and the feldbiss fault zone ffz we use a high precision digital elevation model dem to characterize and quantify the present day deformation along these faults the fault pattern shows similarity to a strike slip structure however analysis of the dem reveals that the recent to quaternary formations and landforms affected by the fault activity are only vertically offset this suggests a pure normal faulting mode for the main border faults and a direction of extension perpendicular to the graben i e ne sw quantification of the offset dated markers allows the determination of the displacement rates along the fault segments in the southeastern part of the rvrs the vertical displacement rates inferred for the ffz and the southeastern pbfz range between 55 and 65 mm ky and around 65 mm ky respectively in contrast the displacement rates determined for the northwestern segment of the pbfz are around 200 mm ky we explain these differences between the northwestern and southeastern parts of the rvrs by the large scale geometry of the graben the rvrs being symmetric in the south east and asymmetric half graben in the north west the deformation is accommodated by two border faults ffz and the south eastern part of the pbfz in the south east and by only one fault in the north west the north western segment of the pbfz in addition the thickness of the neogene main depocentre in the northwestern half of the rvrs indicates a larger amount of extension in this part of the graben than in the south east the combination of the graben geometry and the amount of extension can explain the differences in the displacement rate