seismic investigations along the european geotraverse and its surroundings in central europe since 1975 several high resolution seismic refraction and reflection surveys have been carried out in western germany to investigate the structure of the earth s crust and uppermost mantle the investigation culminated in the seismic refraction survey along the 825 km long central part of the european geotraverse egt in 1986 this contribution summarizes the main results of the more recent crustal investigations along and around the egt the internal crustal structure throughout the area of the variscides is very complex and changes laterally considerably distinct crustal blocks differing in their internal structure can be assigned to geologically defined units of the variscan and caledonian orogeny in spite of local deviations in general a more or less transparent and low velocity upper crust contrasts with a highly reflective lower crust a subdivision of upper and lower crust by a well defined boundary conrad discontinuity is not always seen towards the alps the average velocity of the lower crust is as low as 6 2 km s 1 in contrast to the area north of the swabian jura where the velocities above moho vary between 6 8 and 7 2 km s 1 in northern germany the elbe line separates the lower crust into two regions with 6 4 km s 1 average velocity in the south and 6 9 km s 1 in the north the total crustal thickness under the variscan part of germany is fairly constant between 28 and 30 km except under the rhine graben area with 25 26 km and beneath the central part of the rhenish massif where an anomalous crustal thickening to 37 km is observed under northern germany the moho rises to about 26 km depth and the data indicate at least one fault like step of 1 km before the crust thickens toward the ringkobing fyn basement high the synthesis of seismic velocity structure and petrological information from xenolith studies allows us to propose a mafic composition for the deeper levels of the crust and uppermost mantle which may be valid at least for the central part of the variscan crust along the european geotraverse in central europe

recovering shear wave anisotropy of the lower crust the influence of systematic errors on travel time inversion studies of seismic anisotropy in situ can help to discriminate between different rock types for the lower crust in this context we investigate the sensitivity of an iterative linearized 3 d travel time inversion scheme for transversely isotropic media with respect to two types of systematic errors wrong velocities and interface topography of the hanging wall of the lower crust the computations simulate realistic field conditions such as found for the variscan crust at the urach geothermal anomaly the study focusses on the possible information content of split s m s arrivals observed along two orthogonal expanding spread profiles it ensues that an imperfect knowledge of the layer geometry is of minor importance compared to errors in the velocities of the hanging wall in particular upper crust anisotropy has to be considered carefully generally the anisotropy of transversely polarized shear waves sh waves was recovered with higher accuracy than the anisotropy of vertically polarized shear waves sv waves

laboratory study of loose saturated and unsaturated decomposed granitic soil weathered soils are used extensively as fill materials in slope construction in tropical and subtropical cities such as hong kong the mechanical behavior of loose decomposed fill materials particularly in the unsaturated state has not often been investigated and is not yet fully understood the objective of this study was to understand the mechanical behavior of loose unsaturated decomposed granitic soil and to study the effects of the stress state the stress path and the soil suction on the stress strain relationship shear strength volume change and dilatancy via three series of stress path triaxial tests on both saturated and unsaturated specimens it was found that loose and saturated decomposed granitic soil behaves like clean sands during undrained shearing strain softening behavior is observed in loose saturated specimens in unsaturated specimens sheared at a constant water content a hardening stress strain relationship and volumetric contractions are observed in the considered range of net mean stresses the suction of the soil contributed little to the apparent cohesion the angle of friction appeared to be independent of the suction in unsaturated specimens subjected to continuous wetting suction reduction at a constant deviator stress the volumetric behavior changed from dilative to contractive with increasing net mean stress and the specimen failed at a degree of saturation far below full saturation it was revealed that the dilatancy of the unsaturated soil depends on the suction the state and the stress path

strength of moist sand controlled by surface tension for tectonic analogue modelling abstract a technique has been developed to control the strength of moistened sand in a quantifiable accurate and reproducible way while other mechanical properties were maintained strength of dry sand was increased through adding a small amount of liquid in order to control the additional cohesion of moist sand the influence of the surface tension of the liquid was investigated direct shear experiments were performed on four granular materials at confining stress levels below 1 kpa it has been found that the surface tension of the added liquid controlled the additional apparent cohesion of sand with high accuracy the mechanical properties of moist sand show dynamic similarity towards natural brittle rock which enables analogue modelling of fault formation fault reactivation and tension fracture formation in the brittle regime with a controlled strength profile furthermore experimental results fit well to shear strength models from this followed the direct proportionality of the unsaturated shear strength parameter b relative to the matrix suction measured at low stress levels moreover shear strength turned out to be also a function of grain size and the grain shape

deep crustal reflections from a vibroseis survey in northern switzerland abstract in 1982 a vibroseis survey comprising 180 km of reflection profiles was run in northern switzerland in order to investigate the suitability of the crystalline basement for the deposition of highly radioactive waste a configuration was chosen with 144 channels 25 m of geophone spacing 20 s sweeps ranging from 11 to 61 hz and stacking of 4 or 8 sweeps of 3 simultaneous vibrators at twice the geophone spacing the listening time was generally 4 s and at 4 sites it was extended to 11s for the detection of deeper crustal reflectors this survey unravelled the complicated fault and thrust system beneath the swiss folded jura mountains the stack from 4 s to 11 s reveals clearly a strong sloping reflector between 3 0 and 3 5 s which is strong evidence for a pronounced differentiation in the upper crust a series of reflections is observed between 5 8 and 7 2 s the top of which can be correlated with the conrad discontinuity a strong layered signal between 9 0 and 9 5 s is interpreted as reflections from the m discontinuity the main features are compatible with results from nearby refraction surveys in the southern rhinegraben rift system which show a distinct velocity increase of about 0 5 km s in the lower crust at a depth ranging from 15 to 20 km followed by an inversion zone or a laminated structure before reaching the moho at about 27 km depth the correlation of the field recordings with the first 10 s of the up sweep only shows some loss of resolution in the uppermost 3 s because of the lower frequency content of the signal however the lower parts of the sections are nearly identical the fact that the deeper reflectors in the sections can consistently be traced laterally is a strong argument for using this processing technique thus high coverage vibroseis surveys utilizing up sweep can be processed for deep crustal reflections even if the recording time is restricted to the standard 4 s provided the surface static corrections are carried out with high precision

a microstructurally based effective stress for unsaturated soils current alternative choices of stress state variables in unsaturated soils are described and compared with a special focus on the use of an effective stress experimental data on stiffness and shear strength evolution with suction suggest that the proportion of suction contributing to the effective stress is often much smaller than predicted by the term suction times degree of saturation generally used in effective stress expressions of the bishop type it is suggested that effective stress in unsaturated soils should be related to soil microstructure an effective degree of saturation is defined as describing the volume of water partially filling the soil macroporosity this effective degree of saturation defines the proportion of the prevailing suction that actually contributes to the effective stress two alternative expressions piecewise linear and non linear are proposed for the effective degree of saturation they offer a similar performance available data on stiffness and shear strength varia

deep structure of the southern ural mountains as derived from wide angle seismic data p and s wave modelling of the data obtained during the seismic refraction wide angle reflection experiment of the urseis95 project demonstrate the presence of a 15 18 km thick crustal root beneath the magnitogorsk tagil zone in the central part of the urals orogen however the centre of this crustal root is displaced by 50 80 km to the east of the present day maximum topography also beneath the magnitogorsk tagil island arc zone an upper crustal body with a high p wave velocity of 6 3 km s 1 at 4 9 km depth can be interpreted as consisting of mafic and or ultramafic rocks this in turn would help to explain the positive bouguer gravity anomaly and the surface heat flow minimum associated with the zone and would also be consistent with the known surface geology of the zone another major feature of the seismic model is the presence of high p and s wave velocities 7 5 and 4 2 km s 1 respectively at the base of the crustal root if the deeper parts of the thickened crust also have high densities small density contrast of about 0 1 g cm 3 with respect to the uppermost mantle then this helps to explain the absence of a pronounced gravity minimum associated with the root these high velocities and densities can be most easily explained by mafic rocks or a mix of mafic and ultramafic rocks within the structural framework of berzin et al 1996 these rocks would belong to the lower russian plate which was being subducted beneath the siberian plate during the uralian orogeny it is possible that the crustal root is formed from the remnants of oceanic crust or a mix of oceanic crust and mantle attached to the russian plate this would mean that little or no continental crust has been subducted or that subduction and hence the uralian orogeny stopped when there was no more oceanic crust or when an attempt was made to subduct lighter continental crust

reflectivity characteristics of the crust from modelling refraction wide angle and normal incidence reflection data on babel line 1 marine normal incidence reflection and p and s wave refraction wide angle reflection data from the babel project line 1 in the bothnian sea have been used for investigating the nature of the reflectivity in the area the data are available along the same line and therefore the same piece of crust is probed by two seismic methods we use this favourable circumstance for model calculations concerning both data sets by analysing the waveforms of reflections from normal incidence traveltimes at approximately 4 12 and 16 s twt strong sub horizontal reflections are observed on the normal incidence reflection section at about 4 s twt these reflections have been modelled using the reflectivity method 1 d modelling utilising the water bottom reflection as an estimate of the source wavelet and show a positive polarity thickness and p wave velocity consistent with these reflections are 50 m and 7 km s respectively with a host rock velocity of 6 km s from the polarity velocity and thickness these reflections are attributed to dolerite sills in the upper crust strong lower crustal reflections are observed on the wide angle and normal incidence reflection sections however the corresponding s wave reflections from the lower crust are considerably weaker the implied high positive impedance contrast for the p wave lower crustal reflection and the weak s wave reflectivity suggests the presence of a highly mafic sheet at about 40 km depth the wide angle p and s wave sections show strong reflections at the moho coincident normal incidence data show only weak moho reflectivity indicating a gradient in velocity at the crust mantle boundary dipping events onlap the strong sub horizontal lower crustal and the p wave moho reflections on the wide angle data these are explained by dipping structures above the lower crustal reflector and below the moho with the latter also consisting of a gradient in velocity

the crustal structure of the northwestern basin and range province nevada from wide angle seismic data i present a model of lithospheric p wave velocity structure in the northwestern basin and range province nevada based on wide angle seismic data collected in 1986 under the auspices of the program for array seismic studies of the continental lithosphere passcal the lithosphere in the basin and range consists of 1 2 to 3 km thick low velocity 2 5 4 0 km s sedimentary basins and high velocity 4 5 km s ranges overlying a basement of velocity 5 5 6 1 km s 2 a mid crust 6 1 6 2 km s which consists of rocks of probable granitic to granodioritic composition in greenschist to amphibolite facies and which includes two local low velocity zones 5 5 5 7 km s 3 a laterally varying lower crust which consists of rocks of probable gabbroic composition in upper amphibolite to granulite fades and which comprises layers of 6 6 and 7 0 7 2 km s average velocity 4 a complex crust mantle transition best modeled as a velocity gradient zone 1 2 km thick and 5 an upper mantle with velocities of 7 7 7 9 km s which includes a local low velocity zone 7 5 km s crustal thickness in the region varies laterally from 28 to 37 km significantly thicker than several previous estimates the upper mantle velocities and velocity gradients differ slightly on the two perpendicular profiles suggesting possible azimuthal anisotropy a wedge shaped eastward thickening lower crust of high seismic velocity 7 0 7 2 km s on the eastern pan of the survey may represent the westward edge of rift stage precambrien continental crust or alternatively mafic material underplated and intruded into the crust during cenozoic extension comparison of the velocity model with coincident seismic reflection data shows that the reflection and refraction mohos are coincident across the entire profile thus indicating that deep reflections 4 10 sec two way travel time seen on cocorp and passcal piggyback reflection profiles originate entirely within the crust the top of the reflective zone however lies consistently above the mid crustal increase in average velocity indicating that the reflectivity is not restricted to the mafic part of the crust on passcal piggyback profiles in fact the middle silicic crust appears more reflective than the lower mafic crust this can be explained as the result of either mafic sill like intrusions or ductile strain fabrics both of these processes are likely to have accompanied cenozoic extension in the region

shear strength characteristics of an unsaturated expansive clay the shear strength characteristics of an expansive clay from china were studied by performing suction controlled direct shear tests on both natural and compacted specimens the tested soil was a silty clay with intermedi ate plasticity and medium expansion potential a modified direct shear apparatus with a newly developed water volume indicator was used for this laboratory study the experimental results clearly show that the dilatancy of the expansive clay increases with an increase in the applied suction for both the natural and compacted specimens matric suction contributes to the shear strength of the expansive clay via two different mechanisms the contribution of capillary force to interparticle normal stress and the effect of suction on soil dilatancy as a result of the second mechanism the con tribution of suction to peak shear strength for the clay is more significant than that to post failure shear strength par ticularly at a high suction range the contribution of suction to post failure shear strength for the natural specimen is basically consistent with that for the compacted specimen the higher peak shear strength and dilatancy for the natural specimen are related to the cementation effect of the iron and manganese oxides the contribution of suction to shear strength for the compacted expansive clay is more significant than that for a compacted kaolin at suctions less than 100 kpa

synthetic seismograms for a complex crustal model the algorithm of the original reflectivity method has been vectorized and implemented on a cdc cyber 205 computer calculation times are shortened by a factor of 20 to 30 compared with a general purpose computer with a capacity of several million floating point operations per second mflop the rapid calculation of synthetic seismograms for complex models high frequency sources and all offset ranges is a provision for modeling not only particular phases but the whole observed wavefield as an example we model refraction data of the black forest southwest germany and are able to derive rather tight constraints on the physical properties of the lower crust

relationships between chemical weathering indices and physical and mechanical properties of decomposed granite abstract chemical weathering is one of the dominant mechanisms for weathering of granite in subtropical and tropical regions resulting in modifications of its chemical physical and mechanical properties thus the changes in chemical properties may provide insight about the changes in physical and mechanical properties of weathered granite in this paper three quantitative chemical weathering indices are correlated to the dry density of decomposed granite a linear relationship is found between each chemical weathering index and dry density for granitic saprolites mobiles index i mob gives the highest coefficient of correlation among the three chemical weathering indices further investigations were conducted to establish the relationships between i mob and other physical and mechanical properties of granitic saprolites the test results showed that fines content increases with increasing i mob but peak strength increases with decreasing i mob the peak states of granitic saprolites are consistent with rowe s stress dilatancy relationship dilatancy increases with decreasing i mob that contributes to a higher peak strength based on some test results presented in this study it seems that i mob could be a good indicator to quantify the effects of chemical weathering on physical and mechanical properties of granitic saprolites

properties of the lower crust from modeling refraction and reflection data data of a refraction and a reflection seismic survey in the black forest of southwest germany are used for extensive one and two dimensional modeling the data are available along approximately the same line and therefore the same piece of crust is probed by two seismic methods we utilize this favorable circumstance for detailed model calculations concerning both data sets in this paper we focus on the lower crust its properties vary on the scale of a wavelength and thus full solutions of the elastic equations are required we use the reflectivity method for the evaluation of refraction seismograms and numerical solutions of the acoustic wave equation for the reflection response the lamellae of the lower crust appear as reflecting elements of several hundred meters length randomly distributed in space rocks with extremely low velocities 5 6 km s must be present indicating that anisotropy and or fluids play an important role in the lower crust ideas concerning lower crustal formation evolution and extinction of lamellaetion are developed

crustal evolution of the rhinegraben area 1 exploring the lower crust in the rhinegraben rift by unified geophysical experiments abstract unified geophysical investigations of the lithosphere in the rhinegraben rift system have revealed new details of the lower crust and its role in the rifting process the new findings allow an assessment of the compatibility of four different geophysical notions and properties of the lower crust 1 1 the lower crust as the layer beneath the conrad discontinuity with a p wave velocity of about 6 5 km s or greater refraction seismics 2 2 the laminated band of reflections as seen in the near vertical reflection seismic experiments in many parts of the continents 3 3 the ductile part of the crust below the brittle ductile transition devoid of earthquakes in seismically active regions 4 4 the electrical conductivity of the lower crust indicative of dry or wet conditions or still unknown conduction phenomena in the rhinegraben area the lamination of the lower crust serves as an outstanding marker of deep tectonic activity during the rifting process in which the crust of the rhinegraben rift system has been subjected to three different natural dynamic processes 1 uplift by 2 to 3 km with subsequent erosion of the rhinegraben shoulders black forest and vosges mountains caused decompression possibly leading to the formation of a low velocity high electrical conductivity zone right on top of the laminated lower crust beneath the elevated shoulders of the black forest 2 the brittle crystalline wedge of the graben proper subsided nearly undeformed into the lower crust which became about 5 to 7 km thinner below the graben than below the shoulders 3 the deepest hypocentres in the black forest dinkelberg area if projected onto the neighbouring reflection profile would be located 7 to 8 km within the laminated lower crust beneath the southern black forest indicating a discrepancy between the top of the lower crust as defined by the brittle ductile transition as seen by the deepest earthquakes and by the top of the laminated reflection band the rhinegraben rift system reveals the properties and behaviour of the lower crust under a wide variety of tectonic situations

regional three dimensional gravity investigations in the black forest southwest germany abstract the gravimetric pre surveys of the continental deep drilling project ktb yielded results different to those hoped for at the beginning of the program firstly 2 d calculations based on a refraction seismic interpretation allowed a comparison of gravity effects on a 160 km long profile but despite the fact that in the 2 d model granitic bodies were added at the earth s surface we only obtained a regional gravitational fit with strong deviations on a local scale secondly a gravimetric field survey in the region around haslach yielded rather poor indications of the geological structures in the 5 15 km depth interval which is in the context of the ktb of significant interest therefore all available information derived from geological and tectonic hypotheses and from reflection and refraction seismic interpretation were combined in a regional 3 d density model for the local anomalies the distribution of granite and gneiss bodies known from surface geology was added model bodies from an earlier regional study in southern germany which combined gravimetric and seismic results the moho undulations and the density of the lower crust and upper mantle were taken as additional model parameters in order to discuss regional features the kraichgau anomaly in the north of the black forest is modelled from a 2 d hypothesis as a body with an unusually high density and with a considerable lateral extent this approach demonstrates that evidence concerning the density contrast of anomalous masses can be found if boundary conditions are considered in the construction of the model

simulation of mw 6 0 earthquakes in the upper rhinegraben using empirical green functions summary in low seismicity areas such as southwestern germany quantitative statements on strong ground motion suffer from the lack of instrumental strong motion data although the historic catalogue indicates that events of moment magnitudes up to mw 6 are conceivable this is the situation in the upper rhinegraben area were moderate earthquakes with low probability but high impact caused by the significant aggregation of population infrastructure and industrial facilities are expected to happen we have developed scenarios of crustal earthquakes with moment magnitudes mw 6 0 for a source region southeast of basel switzerland itself being struck by a strong earthquake in 1356 with an intensity of up to ix ems98 intensity in order to synthesize strong ground motion seismograms we are using an empirical green s function egf approach we utilize records in the frequency range of 0 5 25 hz of permanent stations in the rhinegraben and the adjacent black forest in southwestern germany as egfs to be consistent with the local seismicity we model earthquakes with a left lateral strike slip focal mechanism the applied egf approach allows one to define independently a variety of rupture scenarios on the fault plane by varying the hypocentre location rupture velocity fault plane geometry slip distribution and rise time therefore we can create worst case scenarios for the chosen sites we compare peak horizontal acceleration pha and response spectra in terms of spectral accelerations and phas with attenuation laws proposed for europe our results encourage the application of the egf approach as a supplementary tool for site specific strong ground motion prediction in low seismicity regions such as the upper rhinegraben area

relations between sill intrusions and bedding parallel extensional shear zones in the mid continent rift system of the lake superior region abstract the mid continent rift system is a continuous u shaped feature extending from kansas north through the lake superior region and then south through michigan the logan sills on the northwest side of the lake were intruded during the rifting stage 1109 ma deformation features in the country rock adjacent to the logan sills indicate two episodes of shear strain the first consists of minor thrusts and mesoscopic shear bands both suggesting top to the south southwest movement parallel to the bedding the second rotates the previously formed shear bands in the opposite sense top to the north northeast and is localized at the basal contact between the sills and the country rock we attempt to explain the relations observed with a tectonic model in which sill intrusions take advantage of bedding parallel shear zones that are the surface expression of a south dipping detachment plane the detachment plane steps up in the layered proterozoic sedimentary sequence and allows extension during rifting in this scenario the first episode of shear strain might be related to bedding parallel extension and the second to shear stress induced by the intrusion of magma along the detachment from the south the polarity of both events is supported by small scale kinematic indicators such as veins fiber growths and foliation

a new constraint on the composition of the topmost continental mantle anomalously different depth increases of p and s velocity summary compared to clear crustal p and s waves as well as a strong refracted pn wave propagating in the topmost mantle i e 10 to 15 km below the moho an anomalously weak appearance of the corresponding refracted shear wave sn is observed on refraction seismic profiles in sw germany france coastal maine ne united states and fennoscandia it is possible that the observation of pn pmp ratios close to unity combined with small sn sms ratios i e small sn amplitudes is typical for the continental uppermost mantle since this was observed for quite different types of continental crust it is shown that the observed phenomenon is not a source effect several possible causes to explain the observations are studied also with the aid of synthetic seismograms the effects of temperature attentuation and anisotropy have been investigated their influence cannot explain the observations the most likely candidate is a depth increasing vp vs ratio an increase in the order of 0 027 over a depth range of 10 km forcing p and s waves to propagate on different paths in the topmost mantle the observed phenomenon provides new constraints on the change of composition with depth for the crust mantle transition zone with basalt depletion as the most likely explanation

the fine scale structure of upper continental lithosphere from seismic waveform methods insights into phanerozoic crustal formation processes summary studies of the fine scale structure of the continental lithosphere using seismic coda associated with reflections from within the crust and the uppermost mantle have almost solely been based on the compressional wavefield observed at near vertical to wide angle incidence here the results from a full waveform analysis of both p and s wave coda obtained during a crustal scale wide angle refraction experiment from southwest ireland are presented the basic foundation for the study is a 2 d model for the p and s wave structure of the crust and its chemical composition based on traveltime inversion of first arrivals and reflections for the irish caledonides this sector of the caledonian orogenic belt straddles the boundary between the laurentian and avalonian tectonic plates along the iapetus suture zone the excellent quality and relatively broad frequency range e g 1 20 hz of the p and s wave coda permits finer structure in the upper 40 km of lithosphere to be resolved than would be possible using just primary seismic phases a series of 1 d waveform calculations are performed to systematically build a model for the fine scale structure of the 32 km thick crust and the uppermost mantle lithosphere petrophysical and geochemical data from felsic lower crustal xenoliths from central ireland place limits on the permitted velocity fluctuations additional constraints are imposed by vertical p wave reflections observed on contiguous offshore seismic reflection profiles the results indicate that the uppermost mantle to a depth of ca 40 km consists of a vertically stacked sequence of alternating high vp 8 0 km s 1 and low vp 7 25 km s 1 velocity layers each layer is about 500 m thick with a vp vs ratio 1 73 these layers are interpreted as a series of lens shaped mafic sill complexes intruded into the subcrustal lithosphere the fine structure within the lower crust consists of similar seismic velocity fluctuations vp 6 4 and 7 1 km s 1 but on a scale of 200 300 m thickness velocity variations within the lower crust are consistent with the petrophysical properties of metapelitic orthogneissic and psammitic lithologies from lower crustal xenoliths in central ireland and with similar exhumed sections of lower crust in southern europe these results support tectonic theories for the origin of the crust by tectonic accretion of predominantly sedimentary and volcaniclastic material derived from oceanic island arc and continental margin sources during the caledonian orogenic cycle a conceptual model for crustal accretion and growth involves partial melting of the accreted sedimentary wedge producing granites and a chemically differentiated crust during the late caledonian latest silurian early devonian the heat source that drove melting of the accreted sediments may have been provided by the interpreted mafic sills intruded into the uppermost mantle during oblique late caledonian sinistral collision of the laurentian and avalonian plates

seismic images and evolution of the iberian crust in the pyrenees abstract crustal images of the pyrenean range based on coincident wide angle and vertical deep seismic profiles are presented in this study wide angle experiments in the thickened iberian crust along strike lines have provided no evidence for reflections from interfaces between layers of different velocities in the middle or lower crust in contrast reversed sounding on a line across the pyrenean range shows wide angle reflectivity its unusual reflectivity pattern points to widespread impedance contrasts of localized continuity embedded in the crust this observation is consistent with a new image of vertical incidence reflectivity obtained by coherency weighted migration of the coincident ecors traverse this profile shows numerous discontinuous and dipping reflections from the middle to the base of the crust the reflections dip towards the axis of the range the upper limit and the attitude of the reflective zones are so strongly variable that the crust can hardly be envisaged as the simple continuous three layered model previously used for geodynamical reconstructions the reflective zones cannot be brought back to the horizontal image of a layered lower crust of proposed extensional origin by plate unbending to the pre alpine stage the dipping reflections may result from compressional deformation as the south pyrenean deep crustal domain has undergone both hercynian and alpine orogenic deformation if part of the present reflectivity pattern was due to alpine remobilization the corresponding lower crustal deformation would have spread out thereby accomodating convergence by thickening even outside the axial zone where the upper crustal deformation appears to be concentrated

seismic structure of gneissic granitic upper crust geological and petrophysical evidence from the strona ceneri zone northern italy and implications for crustal seismic exploration summary we present a stochastic seismic model of gneissic granitic upper crust by estimating the amplitude probability distribution and the autocorrelation function of the inferred seismic velocity field of the strona ceneri zone northern italy unlike previous investigations of the adjacent ivrea zone and the lewisian gneiss complex scotland the lithologies mapped in the strona ceneri zone cannot be directly correlated with laboratory measured seismic velocities the amplitude probability distribution of the extensive petrophysical database and the relatively uniform mineralogical composition of the lithologies indicate that the velocity distribution in the strona ceneri zone can be approximated as being continuous and gaussian based on this assumption and using the spatial autocorrelation function measured from a digitized geological cross section we have modelled the fine scale structure of the strona ceneri zone as a self affine medium with a fractal dimension of 2 50 0 15 and horizontal and vertical characteristic scales of 2 6 0 4 km and 1 4 0 3 km respectively on near offset shot gather seismic data strona ceneri type upper crustal heterogeneity produces a reflected field with the appearance of incoherent scattered noise characteristic of non reflective transparent upper crust found in extended phanerozoic provinces this type of heterogeneity has a considerable effect on seismic imaging of underlying reflective lower crust individual reflection segments are disrupted and shifted in time by up to several tenths of a second and the boundaries of the reflective zone become distorted and blurred at far offsets seismic scattering from heterogeneity of this type reproduces the commonly observed rapid decay and scattered distribution of pg amplitudes comparable amplitude decay patterns result from layered deterministic upper crustal velocity structures with velocity inversions

structure of the southern rhine graben from gravity and reflection seismic data ecors dekorp program the southern rhine graben was investigated by the seismic reflection ecors dekorp program gravity data available in this region have been reprocessed in order to develop a coherent map along the seismic line the new map has been corrected for the gravity effects of tertiary sediment and crust mantle discontinuity the strong negative gradient towards the alps may be explained by a density contrast of 300 500 kg m3 at the crust mantle interface the residual map shows a negative long wavelength anomaly superimposed on the moldanubian domain of the variscan belt along a vosges black forest swabian jura axis this anomaly cannot be explained by the properties of the variscan crust but may result from a low density body within the upper mantle however its ene wsw direction rules out any connection with the formation of the tertiary grabens which trend north south the recent uplift of topography and the volcanic activity 20 ma of the southern rhine graben may partly be a consequence of an asthenospheric upwelling beneath this area the analysis of the residual short wavelength anomalies shows a fundamental difference between the light variscan terranes of the moldanubian zone and the dense barrandian saverne kraighau structures of the saxothuringian domain a density cross section along the ecors dekorp line confirms that the moho uplift extends beyond the graben whereas thinning of the lower crust affects the graben area only we interpret this crustal structure as an initially thin hercynian crust later deformed by asymmetric extension during oligocene rifting

volumetric behavior of unsaturated soils an elastoplastic framework to account for the volumetric behavior of unsaturated soils is proposed herein the proposed equation is based on the effective stress principle and results in a unifying framework for the volumetric behavior for both saturated and unsaturated soils the results of the proposed equation are compared with experimental results published by different researchers these comparisons show that the equation is adequate to account for wetting drying and net stress loading unloading paths in addition the collapse upon wetting phenomenon can be simulated and the critical state for unsaturated soils coincides with the proposed volumetric framework this analysis confirms that the effective stress principle can be applied to the volumetric behavior of unsaturated soils

3 d structure of the lithosphere beneath the southern rhine graben area abstract the 3 d velocity structure of the lithosphere asthenosphere system beneath the southern rhine graben area is imaged by inverting p wave traveltime residuals of teleseismic events recorded by a dense network of short period stations the upper part of the lithosphere marked by velocity anomalies orientated along the graben strike can be related to the development of the graben these upper 50 km display stronger lateral heterogeneities than the weak anomalies observed at deeper levels which show roughly an e w orientation the teleseismic inversion models yield no indications for significantly reduced seismic p wave velocities in the upper mantle as could be expected from an actively upwelling mantle diapir located beneath the southern rhine graben area the observation of generally weak p wave velocity variations at greater depth indicates a rather smooth transition from the lower lithosphere to the upper asthenosphere the observed heterogeneities in the 25 50 km depth range may be related to partial melts which intruded the mantle lithosphere during the middle and late miocene these melts cooled and solidified since that intrusion the rifting and thermal doming stage of the rhine graben ceased at the end of the miocene

simultaneous inversion for 3 d crustal structure and hypocentres including direct refracted and reflected phases iii application to the southern rhine graben seismic region germany summary the new technique of simultaneous inversion for hypocentres and crustal structure ssh is applied to the southern rhine graben p and s wave first and later arrival times of direct refracted and reflected phases of 350 seismic events are used in the study substantial improvements of over 100 per cent in the non linear residual fit are obtained for the 3 d and less for the 1 d models many of the structural results of the 3 d ssh models are consistent with major findings from other seismic refraction experiments and fit into the general geological petrological and geodynamica1 frame of this area thus the thick sedimentary layer in the rhine graben proper manifests itself by large negative seismic velocity anomalies for the middle crust the ssh models show a strong seismic differentiation between sections of the graben proper and the areas under its western and eastern shoulders of the vosges and the black forest respectively using a new a priori bayesian inversion technique it has been attempted to substantiate the refraction seismic low velocity zone of gajewski prodehl 1987 in the middle crust under the black forest the results demonstrate that such a velocity low is compatible with the observed traveltimes only if one assumes it as a more local crustal phenomenon in this area in the lower crust the ssh models are able to clarify some controversies from earlier refraction experiments in the region the models reveal many seismic features which are typical for continental rift zones such as high transitional velocity anomalies 7 4 km s l under parts of the graben proper rift cushion in the upper mantle the models show a ring like high velocity structure of 8 30 8 40 km s l centred around a low velocity area 7 9 km s l beneath the kaiserstuhl i conjecture this to be a thermal fingerprint of a partially molten upwelling asthenospheric diapir bulging under the moho the simultaneously relocated hypocentres for the 1 d models show some systematic downward movements for the events in the lower crust of the southern black forest area but otherwise do not differ too much from the initial ones to alter the present seismotectonic picture of the southern rhine graben thus the hypothesized phenomenon of the seismic gap along the southern section of the graben black forest wedge can both structurally and seismically be substantiated the relocated hypocentres suggest optically even a widening of this seismic gap the later has thus to be accepted as a possibly more general characteristic of a graben formation

experimental investigation of both the disturbed and undisturbed granitic saprolite soil granitic saprolites are abundant in many regions around the world and they are widely employed in various engineering projects behavior of such kinds of soils is not sufficiently understood and our knowledge about the fundamental behavior of saprolites is to a far less extent than the sedimentary soils owing to the limited knowledge many problems occurred in the engineering applications that used saprolites as a construction material this study presents results of a set of conventional drained and undrained triaxial compression shearing tests on the granitic saprolites in both the disturbed and undisturbed conditions this study showed that the soil fabric was the paramount factor governing on the soil stress strain response rather than the soil bonds under the drained shearing condition the undisturbed soil revealed a strain softening behavior with a dilative response at the low consolidation stress level while a contractive response was present at the high consolidation stress levels however the disturbed soil showed a strain hardening behavior with a contractive response regardless of the consolidation stress levels during the drained shearing the undrained response was complicated as the soil showed both the contractive and dilative responses with phase transformation points regardless of the soil condition i e disturbed or undisturbed and the consolidation stress levels the bond effect of the intact soil persisted during the consolidation stage however its effect did not extend to the large strain controlled shearing stage where the tangential stiffness suddenly decreased at the axial strain of 1 5

a numerical study of steady state evaporative conditions applied to mine tailings the suction profile of a desiccating soil is dependent on the water table depth the soil water retention characteristics and the climatic conditions in this paper an unsaturated flow model whi

coincident seismic reflection refraction studies of the continental lithosphere a global review nearly 50 coincident seismic reflection refraction studies to depths of at least the moho provide an improved understanding of the continental lithosphere some conclusions include the following 1 a transparent upper crust a common observation on vertical reflection profiles cannot generally be correlated with velocity gradients or low velocity zones rather a commonly transparent upper crust may be explained by short wavelength steeply dipping features in the brittle upper crust and to a lesser degree by signal contamination from source generated noise 2 the reflective lower crust in extensional terranes appears to be characterized by a high average seismic velocity 6 6 7 3 km s and to consist of laminated high and low velocity layers with typical thicknesses of 100 200 m 3 landward dipping reflectors observed in the middle to lower crusts of convergent zones have been identified as paired high and low velocity slabs which represent oceanic crust and mantle accreted via underplating to the continental margin 4 the crust mantle boundary may differ sufficiently when imaged with vertical incidence and wide angle data to justify the retention for the present of the concept of separate reflection and refraction mohos while there is good evidence that these features are coincident within measurement uncertainties in most regions recently recorded data from the basin and range admit the possibility for noncoincidence in that area 5 upper mantle reflections which cannot be migrated into the lower crust remain rare despite isolated unequivocal examples thus the upper mantle appears to be relatively homogeneous at seismic reflection wavelengths and to lack the laminations inferred for the lower crust the wide angle method will likely provide the most reliable information on the velocity structure and physical state of this portion of the lithosphere for some years to come 6 there appear to be clear and consistent basic differences between convergent and extensional terranes which have been identified from coincident experiments these differences may be sufficiently universal to infer the tectonic history of poorly exposed terranes 7 no truly three dimensional coincident experiment i e including three dimensional migration has been conducted but some three dimensional data have been collected using both methods measurements of attenuation poisson s ratio and anisotropy within the crust using coincident data sets remain frontiers

lower crustal thinning in the rhinegraben implications for recent rifting seismic near vertical and undershooting experiments carried out in the southern upper rhinegraben area between 1984 and 1991 show pronounced lateral variations of deep crustal properties significant differences in the apparent thickness of the reflective lower crust and the transparent upper crust appear to be related to different structural settings a 12 to 14 km thick reflective lower crust beneath a 15 km thick transparent upper crust of the eastern graben shoulder black forest probably originated during permo carboniferous reequilibration of thickened variscan orogenic crust thinning of this lower crust by about 5 km beneath the graben and rifted domains transitional between graben and shoulder the dinkelberg block is interpreted to be related to cenozoic extensional faulting a discrepancy between moderate extension of upper crust and lower crustal geometry indicates mechanical decoupling at depth during extension congruent modification of other physical properties is suggested by strong single reflective elements in the topmost parts of the thinned lower crust in the transitional dinkelberg block such an anomalously strong reflector occurs at a depth of 20 km below a pronounced local maximum of earthquake activity it is interpreted to be the presently active zone of decoupling which in time shifted from the rift axis to the eastern transition area

an interpretation of wide angle compressional and shear wave data in southwest germany poisson s ratio and petrological implications shear wave velocity especially when used with compressional wave velocity is an important constraint on estimates of the composition and physical state of the continental lithosphere we present shear velocity s models derived from high quality s wave data along three profiles in southwest germany which combine with existing p wave velocity p models to give poisson s ratio in the crust and uppermost mantle we then construct a laterally varying petrological model of the crust by comparing our p and s models with published laboratory measured rock velocities in general poisson s ratio is 0 25 in the uppermost crust 0 22 0 23 in the mid crust but reaching a low of 0 15 in the black forest low p zone and varies laterally from 0 24 to 0 30 in the lower crust the average poisson s ratio of the whole crust is everywhere about 0 25 the laminated signature of the lower crust prominent on reflection and p wave refraction data is absent on the s wave refraction data implying a strong high low alternation of poisson s ratio in the lower crust this suggests that the lower crustal laminae represent mafic silicic compositional layering for example basic sills in an originally more quartz rich lower crust rather than alternating zones of high and low pore pressure there is no evidence for a shear wave low velocity zone lvz in the black forest mid crust despite the presence of a strong p wave lvz this suggests high quartz content and the presence of pore fluids at low not high pore pressure a clear p to s converted moho reflection pm s is visible on several shots indicating that the moho is at least locally a first order discontinuity no shear wave refractions from the upper mantle are present even where strong p wave refractions are observed possibly indicating an increase of poisson s ratio with depth in the upper mantle the petrological modeling indicates that the upper and middle crust are probably of granitic composition that the mid crustal low p zones have high quartz content and that the lower crust probably consists of granulites of laterally varying bulk composition from granodioritic to gabbroic the lower crust is more mafic in areas of high reflection density on seismic reflection profiles suggesting that the laminations are caused by mafic intrusions into the lower crust either prior to the variscan orogeny or during tertiary volcanic activity

behavior of a compacted completely decomposed granite soil from suction controlled direct shear tests a series of single staged consolidated drained direct shear tests are carried out on recompacted completely decomposed granite cdg soil a typical residual soil in hong kong under different matric suctions and net normal stresses matric suction is controlled by applying air pressure in the pressure chamber and water pressure at the bottom of the high air entry ceramic disk the experimental results show that the contribution of suction to shear strength is significant shear strength of cdg soil increases with the increase of matric suction net normal stress has a remarkable influence on the shear strength of unsaturated cdg soil the increase in shear strength due to an increase in matric suction suction envelope is observed as nonlinear i e b value varies with matric suction no soil dilatancy is observed for zero matric suction saturated case but as the suction value is increased higher soil dilatancy is obvious in lower net normal stresses the rate of increase of soil dilatancy is greater

crustal structure beneath the eastern margin of the tibetan plateau and its tectonic implications 1 two crustal cross sections through the eastern margin of the tibetan plateau are jointly determined from deep seismic sounding the e w trending line aa passes through the western sichuan plateau including the songpan garze terrane and the longmenshan fault belt and ends in the sichuan basin a part of the yangtze craton line bb has a trend of nne and crosses the songpan garze terrane two dimensional crustal structures along the profiles were jointly determined by the additional use of existing deep seismic sounding data our seismic velocity models indicate that the western sichuan plateau and the sichuan basin have crustal thicknesses of 62 and 43 km average crustal p wave velocities of 6 27 and 6 45 km s and lower crustal vp 6 5 km s thicknesses of 27 and 15 km respectively density models constructed from the seismic velocity models are consistent with observed bouguer gravity anomalies we infer that collision between the tibetan plateau and the yangtze craton has caused thickening of the lower crust and uplift of the western sichuan plateau we detect a low velocity layer in the upper crust of the western sichuan plateau but observe no equivalence in the sichuan basin west dipping thrusts may detach into this low velocity layer the seismic phase pmp in the western sichuan plateau has low amplitude suggesting high attenuation in the lower crust qp of 100 300 we suggest that the high attenuation is a consequence of lower crustal flow caused by the large lower crustal thickness beneath the western sichuan plateau

the krisp 90 seismic experiment a technical review abstract on the basis of a preliminary experiment in 1985 krisp 85 a seismic refraction wide angle reflection survey and a teleseismic tomography experiment were jointly undertaken to study the lithospheric structure of the kenya rift down to depths of greater than 200 km this report serves as an introduction to a series of subsequent papers and will focus on the technical description of the seismic surveys of the main krisp 90 effort the seismic refraction wide angle reflection survey was carried out in a 4 week period in january and february 1990 it consisted of three profiles one extending along the rift valley from lake turkana to lake magadi one crossing the rift at lake baringo and one located on the eastern flank of the rift proper a total of 206 mobile vertical component seismographs with an average station interval of about 2 km recorded the energy of underwater and borehole explosions to distances of up to about 550 km during the teleseismic survey an array of 65 seismographs was deployed to record teleseismic regional and local events for a period of about 7 months from october 1989 to april 1990 the elliptical array spanned the central portion of the rift with nakuru at its center and covered an area about 300 200 km with an average station spacing of 10 30 km major scientific goals of the project were to reveal the detailed crustal and upper mantle structure under the kenya rift to study the relationship between deep crustal and mantle structure and the development of sedimentary basins and volcanic features within the rift to understand the role of the kenya rift within the afro arabian rift system and to answer fundamental questions such as the mode and mechanism of continental rifting

crustal structure along the central segment of the egt from seismic refraction studies abstract the seismic refraction line between the gulf of genova and the baltic sea was carried out in 1986 as part of the european geotraverse egt 86 the central segment of the egt also known as eugemi european geotraverse middle part has a total length of 825 km and runs from the northern margin of the alps to the baltic sea traversing mainly the variscan mountain area of western germany the p wave data of nine shotpoints were interpreted in detail and a two dimensional p velocity model of the crust was developed between the molasse basin and the southern end of the north german basin for the north german basin the data quality justifies only the construction of a simplified model the internal crustal structure is quite complex in the upper crust of the moldanubian and saxothuringian zones of the variscan orogen the velocities are lower than in the rhenohercynian area the velocity of 6 0 km s representing consolidated seismic basement is reached at depths of as much as 10 12 km northern margin of alps and north german basin and of only 3 km under the mid german crystalline rise mid crustal velocities range from 5 8 to 6 1 km s forming weak velocity reversals in some parts in the lower crust velocities as low as 6 2 km s are seen near the alps in contrast to velocities between 6 8 and 7 2 km s in the exposed variscan orogen north of shotpoint e between hannover and the river elbe the velocity of the lower crust is about 6 4 km s north of the elbe line it increases abruptly to 6 9 km s the crust mantle boundary rises from 34 km depth under the northern margin of the alps to 29 km under the swabian jura under the variscan orogen to the north the crustal thickness varies only slightly around an average depth of about 29 1 k but drops to about 30 km under the north german basin between the elbe line and the ringkobing fyn high the moho rises to a depth of about 26 km and the data indicate at least one fault like step of 1 km before the crust thickens toward the basement high the velocities in the uppermost mantle show considerable variation the highest velocity of 8 4 km s is observed beneath the saxothuringian zone and the lowest values of 7 8 7 9 km s are recorded under the hessen depression

a relationship describing the shear strength of unsaturated soils a relationship describing the shear strength profile of a desiccating soil deposit is essential for the purpose of analysis especially when a numerical method is adopted where each zone in a discretised grid is assigned an elevation dependent shear strength value the matric suction profile of a desiccating soil deposit is nonlinear up to the air entry value an increase in matric suction is associated with a linear increase in shear strength beyond air entry as the soil starts to desaturate a nonlinear increase in shear strength occurs the soil water characteristic curve is stress dependent as is the shear strength gain as matric suction increases in this paper a three dimensional nonlinear regression analysis showed that a power additive function is suitable to describe the variation of the shear strength of unsaturated soils with matric suction the proposed function incorporates the effect of normal stress on the contribution of matric suction to the shear strength

seismicity and structural complexity of the dinkelberg block southern rhine graben summary a detailed analysis of the dinkelberg seismicity is presented the seismic activity of the central dinkelberg block starts at about 10 km and increases with depth to a maximum between 18 and 20 km joint hypocentre determinations clearly prove that no hypocentres are located within the lower crust which starts at a depth of about 20 km according to results from recent reflection seismic surveys the seismic activity is concentrated just above the top of the lower crust fault plane solutions of the dinkelberg events show that the strike of the nodal planes is parallel to the directions of near surface tectonic features a correlation also exists between the main fault directions and the spatial distribution of the hypocentres in the pratteln earthquake cluster at the southern end of the dinkelberg block the occurrence of negative p residuals from local earthquakes for special propagation directions of waves crossing the dinkelberg block is modelled by a westward dipping layer this postulated upper crustal structure together with observations of preferred s wave polarizations are discussed in regard to recent tectonic models and geological findings

behavior of a loosely compacted unsaturated volcanic soil in this paper the stress strain relationsihp and volumetric behavior of a loosely compacted unsaturated decomposed volcanic soil fill were studied by conducting three series of triaxial stress path tests 1 consolidated undrained on the saturated fill 2 constant water content and 3 a reducing suction under constant deviator stress on the unsaturated fill the last two series of tests were designed to simulate the effects of undrained response and rainfall infiltration in initially unsaturated slopes respectively it was found that the saturated loose volcanic soil behaves like clay under isotropic compression but it resembles sand behavior when it was subjected to undrained shear for isotropically consolidated unsaturated specimens sheared under a constant water content a hardening stress strain and a nonlinear shear strength suction relationship are observed at relatively high suctions both angle of friction and apparent cohesion appear to be independent of suction volumetric contraction during shear is observed in this series of tests on the other hand anisotropically consolidated loose unsaturated specimens subjected to a reducing suction change from contractive to dilative behavior as the net mean stress increases this observed volumetric behavior unlike the shear strength is stress path dependent and cannot be explained by using the existing elastoplastic critical state theoretical framework extended for unsaturated soils

european cenozoic rift system abstract the european cenozoic rift system extends from the coast of the north sea to the mediterranean over a distance of some 1100 km it finds its southern prolongation in the valencia trough and a plio pleistocene volcanic chain crossing the atlas ranges development of this mega rift was paralleled by orogenic activity in the alps and pyrenees major rift domes accompanied by subsidence reversal of their axial grabens developed 20 40 ma after beginning of rifting uplift of the rhenish shield is related to progressive thermal lithospheric thinning the vosges black forest and the massif central domes are probably underlain by asthenoliths emplaced at the crust mantle boundary evolution of this rift system is thought to be governed by the interaction of the eurasian and african plates and by early phases of a plate boundary reorganization that may lead to the break up of the present continent assembly

seismic refraction investigation of the black forest abstract within the framework of site surveys of the deep continental drilling program ktb deep seismic sounding experiments were carried out in the black forest southwest germany in august 1984 these site surveys comprised seismic refraction as well as seismic reflection measurements this paper will concentrate on the interpretation of the refraction data which were observed along a 240 km long line approximately following the morphological axis of the black forest in a n s direction and extending in the south into the swiss molasse basin from the available seismic refraction data a detailed velocity depth model of the crust and uppermost mantle was derived a clear phase refracted in the basement with a velocity of 5 9 km s is observed for all shots this phase is followed by a reflection from the upper boundary of a low velocity zone this zone is very accentuated under the northern and central black forest and is characterized by a velocity decrease from 6 2 to 5 4 km s between depths of about 8 and 14 km towards the south the velocity inversion gradually loses its intensity under the center of the southern black forest velocities of about 6 km s prevail throughout the upper crust the lower crust which starts at the lower boundary of the low velocity zone shows a very complicated response in the record sections due to long reverberations between travel times of 1 5 3 5 s reduced by 6 0 km s at an epicentral distance of approximately 30 70 km a classical phase correlation is not possible based on a combined interpretation of near angle and wide angle reflection data the lower crust is characterized by a stack of thin layers with alternating high and low velocities the average velocity of the laminated zone is 6 7 km s the reflection from the moho at a depth of 25 26 km is the most prominent phase at epicentral distances greater than 60 km

the refraction seismic experiment granu95 in the saxothuringian belt southeastern germany summary in this paper we present newly acquired high quality wide angle seismic data of the granu95 project and first models of the crustal structure along two profiles 95 a and 95 b beneath the saxonian granulites a major ellipse shaped exposure of lower crustal material within the mid european variscan belt in southeastern germany saxony the crust is subdivided into four layers the crystalline basement with velocities higher than 6 0 km s 1 is generally reached at shallow depths with three major sedimentary structures as prominent exceptions where velocities considerably lower than 6 0 km s 1 as low as 5 1 km s 1 reach as deep as 4 km the highest upper crustal velocities up to 6 5 km s 1 are not seen below the exposed granulites themselves but at shallow depths 4 km sw of the exposure these shallow high velocities correlate well in depth with highly reflective zones observed on three seismic reflection lines of dekorp 85 4n 95 01 95 02 at their intersection with the seismic refraction line 95 b where they appear as a set of nw se trending dome shaped reflections on profile 95 a this high velocity uppercrustal layer 6 3 km s 1 dips from 5 to 9 km beneath the se margin of the exposed granulites these results suggest that the granulite dome and its western continuation are widely underlain by a ne trending antiformal structure probably a sheet of metabasic rocks where the exposed felsic granulites form just a local cap on top below the upper crustal high velocities a layer with decreased velocity 6 2 6 25 km s 1 extends down to an average depth of 15 km along the variscan strike 95 b and to 11 16 km depth slightly dipping towards the se perpendicular to the terrane boundaries 95 a at mid crustal levels a weak reflection from a layer with a velocity of 6 4 6 6 km s 1 may indicate the classical conrad discontinuity at the depth range 22 24 km the velocity jumps to an average value of 7 0 km s 1 thus defining a prominent high velocity layer in the lower crust which may be viewed as the well known laminated lower crust typical of variscan structures but with higher average velocity than usually detected the crust mantle boundary at about 30 31 km is typical for western europe and confirms the extensional signature of the west european crust below the moho poorly constrained upper mantle velocities of about 7 9 8 0 km s 1 are derived the high velocities observed in the lower crustal layer would not exclude the possibility of mantlederived intrusions but the lack of any sign of an updoming moho favours the interpretation of a more passively driven extension

seismic profiling the continental lithosphere deep seismic reflection profiling is successfully being used worldwide to study the structure of the continental crust1 7 the moist8 profile recorded by birps british institutions reflection profiling syndicate was the first to show that the structure of the upper mantle could also be imaged given a powerful source and long recording times birps has recently acquired an ultra deep seismic reflection line drum deep reflections from the upper mantle the drum line was designed specifically to investigate the reflectivity of the lower continental lithosphere and was therefore recorded to a two way time twt of 30 s giving a depth of penetration into the lithosphere of 110 km this profile has now revealed strong reflections which are unequivocally from the lower lithosphere well below the base of the crust and which are as far as we are aware the deepest and most continuous structures imaged in the upper mantle by multi channel seismic reflection profiling

a three dimensional crustal model of southwest germany derived from seismic refraction data abstract from densely covered seismic refraction data obtained in 1978 urach experiment and 1984 schwarzer zollern wald experiment and from seismic reflection data and results from previous refraction investigations a three dimensional crustal model of southwest germany was derived travel time and amplitude information of seismic refraction data were interpreted with two dimensional forward modeling ray tracing to calculate two crustal cross sections in southwest germany these results fill a gap in the existing data and enabled the construction of a detailed three dimensional crustal model while seismically the upper crust is laterally homogeneous 5 9 6 0 km s throughout the area the middle and lower crust show pronounced lateral variations in thickness velocity and reflectivity the moho is a flat surface at a relatively shallow depth 25 26 km we classify the middle and lower crust of southwest germany into two characteristic crustal types type i consists of a mid crustal low velocity zone 5 4 5 8 km s overlying a thick 10 km high velocity 6 6 6 8 km s lower crust type ii has no prominent mid crustal low velocity zone and a thin

analysis of self boring pressuremeter sbpm and marchetti dilatometer dmt tests in granite saprolites this paper presents the analyses of the results of the site investigation programme carried out at the kowloon bay site in hong kong the tests consisted of self boring pressuremeter sbpm marchetti dilatometer dmt and laboratory tests carried out in a granite saprolite which can be described as a lightly cemented sand the purpose of this research project is to stimulate the development of methods to interpret data obtained from tests in residual soils in particular the work aims to evaluate the analyses of the sbpm data through a curve fitting technique both the loading and unloading portions of the sbpm curve were analysed and the results compared with those from other tests the advantage of this analysis technique is the possibility of constructing a theoretical curve that reproduces a pressuremeter test from which a set of fundamental parameters can be derived namely the friction angle cohesion intercept lateral stress and shear modulus the dmt proved to be a reliable tool that yielded

re os isotope and geochemical study of the vredefort granophyre clues to the origin of the vredefort structure south africa the origin of granophyric rock dikes the vredefort granophyre at the 2 ga vredefort structure in south africa has been controversial they have been interpreted as either impact melt or igneous intrusions most vredefort granophyre samples have considerably higher os contents than the country rocks and 187re 188os and 187os 188os ratios that scatter about a 2 ga isochron their initial 187os 188os ratios at 2 ga overlap the meteoritic data range indicating that all the granophyre samples contain some meteoritic os the re os isotopic composition of the granophyre is significantly different from that of local precursor rocks and indicates that up to 0 2 of a chondritic component could be contained in the granophyre our results confirm the interpretation that the vredefort granophyre represents an impact melt rock

crustal scale thrusting and extension in the hercynian schwarzwald and vosges central europe the hercynian outcrop areas in the schwarzwald of sw germany and vosges of easternmost france consist from north to south of three major lithotectonic complexes very low to medium grade metamorphics of the saxothuringian belt the polymetamorphic central gneiss complex and the tectonic melange of the southern complex juxtaposition of these three complexes occurred by oblique convergent motions in early carboniferous time the saxothuringian belt is part of a major se dipping accretionary wedge that consists of lower paleozoic meta sedimentary and metaigneous rocks and superimposed upper devonian to lower carboniferous synorogenic volcanics and elastics the central gneiss complex consists of polymetamorphic paragneisses orthogneisses metabasites and meta ultramafics dipping to the nw the southern complex consists of an imbricated melange of north to nw dipping synorogenic elastics volcanics and blocks of ultramafics and gneissic basement the central gneiss complex cgc experienced pervasive hercynian low pressure high temperature metamorphisrn before it was emplaced against and thrust over the sedimentary and volcanic fill of the adjacent synorogenic basins this convergence 340 330 ma produced mylonitic cataclastic shear zones in the cgc the most significant shear zones are the se verging todtnau fault zone between the cgc and the southern complex and the nw verging lubine fault zone between the central gneiss complex and the rocks of the saxothuringian belt these two fault zones enclose a bivergent pop up of the polymetamorphic basement the todtnau fault zone probably extends for more than 100 km along strike and can be traced to a depth of 10 km by deep seismic reflection studies detachment probably occurred along a mid crustal zone of anatexis expressed by a domain of low seismic reflectivity between about 10 and 15 km crustal thickening during early carboniferous convergence led to an extensional phase of crustal reordering between about 330 and 280 ma that was accompanied by the massive rise of posttectonic granitic plutons from middle to high crustal levels simultaneous creation of a structural lamination in the refractory lower crust neglected the main convergent tectonic boundaries it produced a basin and range type lower crust and mantle crust transition in early permian time and involved a major advective input of heat

crustal structure of the northwestern basin and range province from the 1986 program for array seismic studies of the continental lithosphere seismic experiment the basin and range province of the western united states is characterized by active east west extension at strain rates of 1 cm yr 1 high regional heat flow of 90 mw m 2 and widespread late cenozoic bimodal rhyolitic basaltic magmatism the 1986 program for array seismic studies of the continental lithosphere basin and range seismic experiment imaged a portion of northwestern nevada to determine the crustal structure and to assess reported differences between refraction versus reflection determinations of moho depth and how the crustal composition and structure has been influenced by volcanic and extension mechanisms our interpretation of the refraction wide angle reflection data suggests that the crust is fairly uniform in thickness and varies by less than 5 km over the 280 km east west profile and 3 km over its 220 km north south length we characterize the velocity structure by five layers 1 an upper most crust composed of sedimentary rocks and basement that has an average velocity of 5 7 km s i 2 a middle crust that extends to a depth of 18 22 with an average velocity of 6 1 km s 1 3 a 10 12 km thick lower crust with an average velocity of 6 6 km s 1 4 a 2 5 km thick transitional crust mantle boundary defined by a 7 6 km s l velocity and 5 an upper mantle with an average pn velocity of 7 9 8 0 km s 1 these data show a uniformily thick crust of 28 km 5 km beneath northwestern nevada and a lack of evidence for significant low velocity crustal layers in general the entire crustal column exhibits uniform positive velocity gradients of 0 02 0 04 s the midcrustal discontinuity is interpreted as a small velocity increase of 0 2 km s l at 18 km depth the absence of a significant midcrustal reflection and the presence of large velocity gradients throughout the crust arises either from 1 a systematic increase in mafic composition with depth or 2 possibly high lower crustal pore pressure that acts to decrease the velocity contrast across the midcrustal boundary our interpreted seismic velocity structure is consistent with a broad range of bulk compositions for the crust upper crustal velocities are consistent with bulk compositions that range from metasediments and granites at shallow depth to diorites at midcrustal levels while lower crustal velocities suggest bulk compositions that range from diorites and amphibolities at midcrustal depths to mafic granulites and gabbros at the base of the crust the uniform crustal thickness of 30 34 km in northwestern nevada is close to the crustal average for the basin and range province but is thin when compared to surrounding regions such as the sierra nevada and colorado plateau where crustal thickness is greater than 40 kin similarily northwestern nevada pn velocities of 7 9 8 0 km s 1 are near the province wide average of 7 9 km s l temperature corrected pn velocities from a 90 mw m 2 geotherm for the basin and range to 60 mw m 2 for the stable interior of the united states are within one standard deviation of the continental average of 8 05 km s i and suggest a uniform upper mantle composition across the basin and range in addition to these observations the homogeneity of the velocity structure beneath the western basin and range argues for a youthful moho and crust that has been reworked by province wide late cenozoic extension episodic magmatism and underplating

shear wave evidence for an anisotropic lower crust beneath the black forest southwest germany abstract controlled shear wave sources a horizontal vibrator and dynamite were used in near vertical reflection studies to explore the nature of the reflective laminated lower crust in southwest germany the data reveal strong s wave reflections from the lower crust these lower crustal s reflections were not observed by previous wide angle surveys in the same region a laminated crustal model with isotropic layers and changing poisson s ratio cannot explain the differing near and far offset s response by introducing alternating anisotropic and isotropic lamellae this discrepancy may be resolved this seismic model is consistent with a petrological model of deformed amphibolites containing 10 30 of preferentially orientated hornblende observed amplitude differences in p and s wave reflections from the same depth in the lower crust suggest regions with a changing poisson s ratio

the deep crust of the southern rhine graben reflectivity and seismicity as images of dynamic processes abstract the rhine graben part of the european cenozoic rift system deserves special attention because of its location in the foreland of the alpine orogen the phanerozoic evolution of the lithosphere in this region is defined by a set of major geodynamic events ranging from the variscan orogeny late orogenic crustal re equilibration to the interference of rifting and alpine orogeny in tertiary times the rhine graben is one of the most detailedly studied continental grabens prospecting for hydrocarbons in its sedimentary fill and intensive pre site studies for the continental deep drilling program ktb on its eastern crystalline flank black forest provided a comprehensive set of geoscience data seismic investigations ranging from a deep seismic network of near vertical reflection to concurrent wide angle refraction experiments were accompanied by seismological and geological surveys therefore a direct observational comparison between the two depth definitions of crustal subdivisions elastic vs strength rheological was possible in large parts of western europe deep seismic sounding dss investigation distinguishes between a crystalline upper crust of comparatively low p wave velocities 5 9 6 0 km s with little and discrete reflectivity and a strongly reflective lower crust with higher p wave velocities about 6 4 6 8 km s both are separated by the conrad discontinuity in contrast strength and rheological considerations define a brittle upper crust and a ductile lower crust the boundary between these two realms is usually referred to as the brittle ductile transition zone which in seismically active regions is imaged by the deepest crustal hypocentres the present brittle ductile transition in the rhine graben region as defined by the deepest hypocentres does not necessarily coincide with the structural separation in an upper and lower crust as seen in deep seismic studies this suggests that the laminated lower crust developed during the crustal re equilibration phase at the end of the variscan orogeny the second part of this paper concentrates on evidence of recent tectonic activities related to rifting processes impacting on the variscan lower crust a remarkable concentration of deep crustal earthquakes reaching to the top of an asymmetrical thinned lower crust is observed at or near the eastern border fault of the southern rhine graben and is possibly induced by the young rifting process we suggest that this asymmetry could be a consequence of the uppermost mantle detaching from the upper crust in collision with the alpine orogen this allows us to propose the distinction between the influence of compression extension continental subduction and intra crustal detachment during graben formation the dynamic interference of rifting and foreland compression shown by structural and seismological observations leads to the notion of small scale collisional escape tectonics associated with an intra continental transform fault at the southern end of the rhine graben the rhine sao ne transform zone

shear strength characteristics of two saprolitic soils the saturated and unsaturated shear strength behavior of an undisturbed completely decomposed fine ash tuff and an undisturbed completely decomposed granite from hong kong were studied using direct shear and triaxial tests the completely decomposed fine ash tuff is a fine to medium grained saprolite the completely decomposed granite is a coarse grained saprolite results show that matric suction increases the shear strength of both soils the extent of the increase is the shear strength with matric suction is related to the soil water characteristic curve for the soil and to the amount of dilation during shear the effect of matric suction on the shear strength was more pronounced for the fine to medium grained completely decomposed fine ash tuff than for the coarse grained completely decomposed granite these studies on the saprolitic soils provide insight into the understanding of the shear strength of unsaturated coarse grained soils key words saprolites shear strength matric suction triaxi

bootstrap inversion for vertical and lateral variations of the s wave structure and the υp υs ratio from shallow earthquakes in the rhinegraben seismic zone germany using s wave arrival times of 400 earthquakes in the southern rhinegraben 1 d and 3 d inversions for the shear s wave crustal structure of that region are performed these models are then combined with previously obtained 1 d and 3 d p wave models to compute vertical and lateral variations of the p s poisson s ratio such an independent p and s wave inversion approach circumvents many of the limitations of the classical wadati diagram method usually used for the determination of crustal p s ratios for the statistical evaluation of the 1 d models we have used a new monte carlo bootstrap resampling technique which has been found useful in many statistical estimation problems where the underlying statistics of the data is poorly known the 1 d bootstrap p s crustal models exhibit significant vertical variations whereas the upper sedimentary and crystalline layer of the crust is characterized by a significant increase of p s over the reference value p s in the upper and middle crust is lowered this correlates well with several findings from wadati diagrams for p s in other seismically active zones and might be explained through the gradual closing of saturated microcracks in that depth range however the p s reduction can also be interpreted in terms of a particular petrological composition such as orthoclase feldspar without the indispensable need for fluids a lowering of p gus is also observed for the lower crust which might reflect the strong lamination found here from previous deep seismic sounding experiments for the upper mantle a strong increase of p s is observed which is primarily triggered by a decrease of s and is best explained by an eclogite petrological assemblage for the 3 d s wave models significant reductions of more than 100 were obtained for the unexplained travel time residuals variations of p s in the upper and middle crust are mostly induced by changes in p rather than s for the upper crust slight decreases of p s are observed for the rhinegraben but increases are detected for the adjacent vosges and black forest areas in the middle crust the refraction seismic deduced reduction of p s under parts of the black forest can neither be corroborated nor rejected however because of some experimental ambiguity on the effects of petrological composition and interstitial pore fluids this does not rule out the presence of the latter in the lower crust a local reduction of p s is observed under the kaiserstuhl and graben black forest shoulder and has been explained in terms of a metamorphic dehydrating phase change of the hydrous amphibolite facies to the anhydrous granulite facies depending on the pore pressure of the dehydrated water and the fractional amount of interstitial co2 granulite facies metamorphism occurs in the 650 800 c temperature range temperatures at the upper end of this interval can be generated by the mechanism of accretionary magmatic underplating as it has been proposed for some extensional rift zones where asthenospheric upwelling as in the rhinegraben occurs

scales of structure in the lithosphere images of processes advances in deep seismic sounding observations of the lithosphere on continents allow to identify various scales of heterogeneities in the crust mantle transition in this paper a fresh look is taken at the dynamic properties of seismic waves propagating through this zone ranging from the lower crust well into the lithospheric mantle as observed in near vertical reflection and wide angle refraction experiments the abrupt termination of near vertical reflections at the moho and the coincident presence of a strong coda accompanying the supercritical pmp reflection phase in record sections of continental seismic wide angle refraction experiments reveal a new property of the crust mantle boundary the moho forms a sandwiched mix of crust mantle material between lower crust and topmost mantle in combination with a step in mean velocity a significant change in scale of the structural dimensions and of velocity variance this view is strongly supported by the recognition of the subcrustal lithosphere as a high frequency 5 10 hz scattering wave guide for long distance propagation of the pn phase over more than 3000 km detected during seismic experiments in russia using peaceful nuclear explosions evidence is brought forward that this high frequency wave guide is likely to be present also in the phanerozoic upper mantle of western europe it is furthermore hypothesized that the global propagation of teleseismic sn or corresponding pn waves observed on continents and oceans combined with the recording of strong pmp codas for wave paths on continents points to a world wide change of scale of structure and velocities near the moho a change in scale of heterogeneities under almost all physical and chemical conditions indicates possibly a differential horizontal movement or decoupling of crust and upper mantle at the level of the moho the global presence of the scattering pn wave guide with a preferred horizontal elongation is hypothetically described as a seismic image of processes in the lithospheric mantle locations of present day tectonic activity where horizontal decoupling between crust and mantle are likely to occur e g subduction at continent continent collision zones change of tectonic regimes and continental transform faults are discussed

lateral structural variation across a collision zone in central hokkaido japan as revealed by wide angle seismic experiments the crustal evolution in the central part of hokkaido island japan has been dominated by a series of accretion and collision processes from the late jurassic to the present this region is divided into three main tectonic belts the sorachi yezo hidaka and tokoro belts from west to east formed in different cretaceous subduction systems since the miocene the sorachi yezo belt and the western part of the hidaka belt the hidaka metamorphic belt hmb have suffered severe deformation during two tectonic events the dextral oblique collision between the north american okhotsk and eurasian plates and the arc arc collision of the kuril forearc sliver with the western part of hokkaido the ne japan arc a thrust belt along the western margin of the sorachi yezo belt is considered to represent the miocene to pliocene eastward subduction of the ne japan arc due to the compressional stress regime this subduction jumped to the eastern margin of the japan sea in pleistocene time the reanalysis of wide angle seismic data collected in central hokkaido has provided a new image of crustal scale structural variation and deformation in the tectonic environments mentioned above the western part of the sorachi yezo belt is characterized by a 2 4 5 km thick forearc sedimentary layer with a velocity of 3 0 3 9 km s 1 beneath which a 3 9 5 8 km s 1 body forms an eastward dipping boundary to the upper unit this boundary may be the eastward extension of the thrust belt representing the miocene to pliocene plate boundary a 5 3 5 7 km s 1 body almost crops out beneath the eastern part of the sorachi yezo belt where ophiolite sequences and high p metamorphic rocks are exposed our rather low velocity of 5 3 5 7 km s 1 may suggest that the original oceanic crustal rocks or the metamorphics were fragmented and merged with low velocity accretionary prism rocks plausible tectonic events responsible for this process are fast uplift of a large amount of underplated materials in the cretaceous subduction system of this region and or severe deformation by collision tectonics since the miocene the hmb is characterized by high t metamorphic rocks almost equivalent to those of continental or arc crust the seismic velocity in the upper 5 7 km of crust in this part increases westwards from 5 6 to 5 85 km s 1 showing a good correlation with the change in metamorphic grade of the exposed rocks the velocity structure in the eastern part of the hidaka belt is composed of 15 20 km thick upper crust overlying 6 6 6 7 km s 1 lower crust the crystalline part of the upper crust is divided into a 6 7 km thick 5 6 6 0 km s 1 layer and an 8 5 11 km thick 6 2 6 35 km s 1 layer in the depth range 25 45 km there exist crustal laminations probably forming a ductile and sheared zone good agreement of this velocity structure with physical properties of the metamorphics exposed in the hmb indicates that a 25 26 km thick brittle part of the hidaka crust was obducted towards the west to form the hmb under the collision framework in this region major layer boundaries east of the hmb show a gentle eastward dip which might have acted as a decollement at the time of the obduction the tokoro belt which is composed of accreted jurassic seamounts is marked by a high upper crustal velocity 6 1 km s 1 in our model this velocity represents relatively mafic rock compositions of the seamounts and or oceanic crust trapped in this belt

lower crustal petrology from wide angle p and s wave measurements in the black forest abstract the lower crust of the black forest in southwest germany is strongly reflective for compressional waves but almost non reflective for shear waves if the reflectivity for p waves is caused by alternating high and low velocity rocks the s wave observations require that the low velocity rocks have a low poisson s ratio and vice versa a purely compositional petrological model for lower crustal rocks can fit the observed p and s wave velocity data provided a rather high quartz content 50 is acceptable for the lower crust

seismic anisotropy within the uppermost mantle of southern germany summary this paper presents an updated interpretation of seismic anisotropy within the uppermost mantle of southern germany the dense network of reversed and crossing refraction profiles in this area made it possible to observe almost 900 traveltimes of the p phase that could be effectively used in a time term analysis to determine horizontal velocity distribution immediately below the moho for 12 crossing profiles amplitude ratios of the p phase compared to the dominant crustal phase were utilized to resolve azimuthally dependent velocity gradients with depth a p wave anisotropy of 3 4 per cent in a horizontal plane immediately below the moho at a depth of 30 km increasing to 11 per cent at a depth of 40 km was determined for the axis of the highest velocity of about 8 03 kms at a depth of 30 km a direction of n31 e was obtained the azimuthal dependence of the observed p amplitude is explained by an azimuth dependent sub moho velocity gradient decreasing from 0 06 s in the fast direction to 0 s in the slow direction of horizontal p wave velocity from the seismic results in this study a petrological model suggesting a change of modal composition and percentage of oriented olivine with depth was derived