variability of the north atlantic thermohaline circulation during the last interglacial period studies of natural climate variability are essential for evaluating its future evolution greenland ice cores suggest that the modern warm period the holocene has been relatively stable for the past 9 000 years much less is known about other warm interglacial periods which comprise less than 10 of the climate record during the past 2 5 million years here we present high resolution ocean sediment records of surface and deep water variables from the bermuda rise spanning the last interglacial period about 118 000 127 000 years ago in general deep water chemical changes are coincident with transitions in surface climate at this site the records do not show any substantial fluctuations relative to the much higher variability observed during the preceding and subsequent cool climates the relatively stable interglacial period begins and ends with abrupt changes in deep water flow we estimate using 230 th measurements to constrain the chronology that transitions occur in less than 400 years

three dimensional p and s velocity structure in the coalinga region california the coalinga earthquake sequence of 1983 provided a unique opportunity to perform a three dimensional velocity and hypocenter inversion in an area of complex three dimensional structure dominated by folding and blind thrusts additionally since other varied geological and geophysical studies have been completed in this area the three dimensional inversion solution could be compared to other interpretations inversion of 7696 p and 1511 s first arrivals from earthquakes and 696 p first arrivals from refraction shots produced a three dimensional velocity model with grid spacing of 1 2 km in the hypocentral area the overall shape and location of velocity features correspond well to the mapped surface geology the three dimensional inversion yields details of folds where the resolution is good and the general shape where resolution is lower the amounts of structural relief inferred for the local folds are similar to values inferred from geologic data the three dimensional velocity solution has several distinctive features there is a linear high velocity body 6 1 6 5 km s about 25 km long from 6 to 8 km depth that may represent a fragment of coast range ophiolite a shallow low velocity zone lvz which extends for 20 km along the fold axis at about 6 km depth and correlates with lvzs observed in both the refraction and the reflection data may indicate high pore pressure caused by lateral compressive strain deeper lvzs occur within inferred franciscan material and are characterized by horizontal or southwest dipping zones of varied thickness 4 8 km wide and 5 10 km long these lvzs may represent multiple thrust faults their locations and geometry are consistent with thrust faults inferred with seismic reflection data the three dimensional velocity solution compares well to prior two dimensional seismic reflection and refraction models and observed gravity the shape of the inferred sedimentary section agrees well with the reflections from the cenozoic strata compared to the refraction model the three dimensional solution has similar velocities and similar locations of velocity features but is more detailed in the hypocentral zone where it uses more data the gravity computed from the three dimensional velocities is similar to the observed gravity in both shape and amplitude both a simple one dimensional initial model and a complex initial model derived from the refraction interpretation were tried a simple starting model gave the best results the s velocity solution has different resolution than the p velocity solution because it uses a different set of stations and it has lower resolution because it uses fewer arrival times while the general patterns of velocity variation are similar for both vp and vs the vs solution tends to have more smearing of velocity features and can have somewhat different locations of velocity features

oceanographic dynamics and the end of the last interglacial in the subpolar north atlantic the last interglacial interval was terminated by the inception of a long progressive glaciation that is attributed to astronomically influenced changes in the seasonal distribution of sunlight over the earth however the feedbacks internal dynamics and global teleconnections associated with declining northern summer insolation remain incompletely understood here we show that a crucial early step in glacial inception involves the weakening of the subpolar gyre spg circulation of the north atlantic ocean detailed new records of microfossil foraminifera abundance and stable isotope ratios in deep sea sediments from ocean drilling program site 984 south of iceland reveal repeated progressive cold water mass expansions into subpolar latitudes during the last peak interglacial interval marine isotope substage 5e these movements are expressed as a sequence of progressively extensive southward advances and subsequent retreats of a hydrographic boundary that may have been analogous to the modern arctic front and associated with rapid changes in the strength of the spg this persistent millennial scale oceanographic oscillation accompanied a long term cooling trend at a time of slowly declining northern summer insolation providing an early link in the propagation of those insolation changes globally and resulting in a rapid transition from extensive regional warmth to the dramatic instability of the subsequent 100 ka

north sea rift system abstract the mesozoic north sea rift forms an integral part of the arctic north atlantic rift system rifting activity in the north sea commenced during the earliest triassic during the mid jurassic the central north sea underwent a temporary doming stage crustal extension peaked during the late jurassic earliest cretaceous abated subsequently and terminated altogether during the paleocene the saucer shaped cenozoic post rift basin straddles the axis of the viking and central grabens this speaks for the applicability of a depth dependent pure shear model rather than a simple shear model geophysical data indicate an important discrepancy between upper and lower crustal attenuation across the north sea rift suggesting that during rifting processes the mono discontinuity was seriously destabilized this requires a basic modification of currently favoured crustal stretching models

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

changes in vp vs with depth implications for appropriate velocity models improved earthquake locations and material properties of the upper crust properties associated with the arrival times of shallow microearthquakes are determined for three tectonically different sites soviet central asia the central united states and southern california simple graphical presentations of the earthquake data including wadati and riznichenko diagrams are used to resolve the trade off in origin time and focal depth estimates of the average half space velocities for p and s waves and of the travel time ratio ts tp are also obtained that are relatively free of any model constraints used to initially locate the earthquake in all cases p and s arrivals exhibit a systematic decrease in ts tp with depth in the upper few kilometers this decrease is significant and matches similar variations observed in situ for the velocity ratio vp vs based on laboratory and theoretical studies such observations are consistent with the closing of saturated microcracks with increasing confining pressure independent determinations of velocity structure and rock properties from both refraction studies and borehole experiments show analogous results by specifying separate velocity models for both p and s waves that reflect this variation rather than assuming a constant value of vp vs we find improved stability in hypocenter determination and increased resolution of shallow seismicity patterns

the jura mountains an active foreland fold and thrust belt abstract recently completed in situ stress measurements using the borehole slotter at 33 new test sites within the swiss and french jura mountains combined with previously published stress data allow a detailed description of the contemporary state of stress in this fold and thrust belt and the adjacent foreland five stress provinces can be recognized with two different general orientations of maximum horizontal stress sh 1 the central and southwest provinces with a nnw sse to nne ssw orientation 2 the east northwest and southeast provinces with an e w to nw se orientation stress magnitudes are in general higher in the southern than in the northern jura mountains characteristic of the northern jura is an e w trending zone of low stress magnitudes which can be traced from the bresse depression south of besancon to the eastern end of the jura northwest of zurich boundaries of stress provinces show poor agreement with boundaries of tectonic units in the jura in addition stress provinces extend beyond the boundaries of the jura mountains into their foreland furthermore palaeo stress orientations show large discrepancies with respect to the contemporary stress orientation these findings are considered to indicate a termination of jura thin skinned foreland tectonics which probably took place some time between 9 and 4 ma according to palaeontological and tectonic evidence it is suggested that a new style of tectonics has commenced in the jura mountains deforming both the basement directly below the jura fold and thrust belt and the cover rocks in a similar mode

intracontinental rift related deposits a review of key models abstract mineral systems associated with extensional fault systems in continental environments and not related to magmatic activity involve various deposit models that can be grouped into a single system which would plausibly explain the source and chemical composition of fluids the formation depth the source of heat and the structural history within a common geologic setting mineral deposits related to this tectonic setting are those described within the detachment related model including massive replacements stockworks and veins of cu and fe oxides with or without au polymetallic sulfide veins barite and or fluorite veins and stratabound and vein mn deposits this paper reviews the abovementioned deposits as well as others related to this tectonic setting such as se rich polymetallic deposits almaden type hg deposits u ni co as ag polymetallic deposits with subordinated bi cu pb zn five element deposits simple polymetallic pb ag zn deposits and the members of the iocg clan including the au ag detachment related deposits involved in the cu fe au model deposits all these mineral deposits are the result of fluid motion unrelated to magmatism in areas of thermal anomalies these fluids collect certain elements producing a district mineralogical specialization with inhomogeneities in the distribution of mineralization types along the region affected by rifting fluid homogenization temperatures and salinities range between 60 and 430 c and 0 and 27 equivalent wt nacl respectively the o s and d isotope composition is consistent with basinal poral fluids derived from meteoric waters under different p t conditions in an active faults environment pb isotopes suggest that pb derives from a mixture of rocks with a long period of residence in the upper crust and rocks deformed along repeated orogenic cycles with a contribution of pb from the lower crust and even the mantle fluid flow along fault planes leads to different types of hydrothermal alterations depending on p t conditions particularly propylitization and low temperature potassium metasomatism all such deposits can be found in two different geotectonic environments of metallogenic interest involving extensional faults associated with detachment zones in depth i e 1 continental extension in a back arc environment and 2 extension with rift development and generation of oceanic crust in a passive continental margin although the economic importance of this group of deposits is mainly related to industrial minerals non magmatic iocg deposits could significantly augment the economic potential of this setting the rift setting itself without relation to detachments is favorable for concentrating metals in stratabound deposits such as sedex ores additionally the development of deposits directly related to magmatic activity contributes to the economic interest of this environment

active normal faulting in the upper rhine graben and paleoseismic identification of the 1356 basel earthquake we have identified an active normal fault in the epicentral area of the basel switzerland earthquake of 18 october 1356 the largest historical seismic event in central europe the event of 1356 and two prehistoric events have been characterized on the fault with geomorphological analysis geophysical prospecting and trenching carbon 14 dating indicates that the youngest event occurred in the interval 610 to 1475 a d and may correspond to the 1356 basel earthquake the occurrence of the three earthquakes induced a total of 1 8 meters of vertical displacement in the past 8500 years for a mean uplift rate of 0 21 millimeters per year these successive ruptures on the normal fault indicate the potential for strong ground movements in the basel region and should be taken into account to refine the seismic hazard estimates along the rhine graben

seismicity wedge beneath the upper rhine graben due to backwards alpine push abstract the distribution of hypocentres in the upper rhine graben area is re examined and discussed with respect to the present day tectonic framework most earthquakes occur within a n60 striking wedge located on top of a moho dome this wedge is limited by the surface and at depth by a plane which in the south of the dome coincides with the se dipping conrad discontinuity in depth the seismicity shows a normal distribution the maximums of which are located on a surface dipping 6 towards se parallel to the south eastward dipping conrad and moho this surface outcrops along the north western edge of the uplifted crystalline vosges and black forest the main shocks in earthquake swarms in the region often occur in the vicinity of this surface and along pre existing n s to ne sw variscan or tertiary faults and show focal mechanisms of strike slip in contrast part of the aftershocks show focal mechanisms of reverse faulting associated with se nw striking compression the seismic wedge and the north westward rising seismic surface suggest initiation of crustal ramp which starts at the south eastern rim of the conrad dome and which may become a thrust plane if se nw compression continues in the south eastern edge of the graben and above the south eastern ridge of the moho dome where evidences for extension have been found we identify clustering of hypocentres along a surface that strikes n150 parallel to the main compression and dipping towards ne dominant normal faulting mechanisms along this surface suggests initiation of a normal probably listric fault at depth the onset of the future fault plane is located on top of the nw se striking ridge of the lower crust and moho which act as a an indenter in addition to thrusting of the whole wedge towards nw increasing of nw se compression would lead to the formation of a half graben at the place of the present sierentz depression

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

evidence for early warming and cooling in north atlantic surface waters during the last interglacial in depth analysis of planktic foraminiferal census data paired with 18o records of specific indicator species provides new insight into the surface ocean evolution of the northeast atlantic during the previous interglacial warm period oxygen isotope stage ois 5e full interglacial conditions existed at the study site for a maximum of only 8 kyr between 125 and 117 ka highest sea surface temperatures ssts occurred during early ois 5e concomitant with high summer insolation but after the main phase of ice sheet melting of the preceding glaciation saalian this early peak sst interval is marked by the appearance of tropical subtropical species and lasted for 4 kyr until 121 ka as corroborated by a major change in planktic 18o relative stability in global ice volume continued for another 3 4 kyr before ssts dropped further toward the next stadial during early ois 5e the situation of the surface water vertical structure appears to have been different from the early holocene for ois 5e it is therefore suggested that the particular melting history of late saalian ice had a long lasting and profound effect on both postdeglacial surface water mass configuration in the north atlantic and heat moisture transfer into europe

stress tensor determination in france and neighbouring regions abstract the tectonic behaviour of different seismic regions of france is inferred from the properties of the local stress tensor obtained from focal mechanisms of regional earthquakes polarities of p wave arrivals for several earthquakes are used in the inversion of the stress tensor and individual focal mechanisms the principal axes and the shape of the tensor are closely related to the forces which generate seismic ruptures on pre existing faults we analyse 142 earthquakes of magnitude above 3 7 which occurred between 1965 and 1989 good results are obtained for some regions the northern alps and the southern end of the upper rhinegraben show a quasi compressive strike slip tectonic regime with a maximum stress axis oriented nw se the tectonic regime changes to an extensional strike slip type in the rhenish massif and the lower rhinegraben the direction of the minimum stress axis being nne ssw the central and western regions of france central and armorican massifs exhibit an extensional tectonic regime combined with strike slip faulting the minimum stress axis strikes in a ne sw direction a strongly non homogeneous stress field seems to be present in the southwestern alps and no unique stress tensor could be obtained for that region this problem is likely to be related to a rapid variation of the stress field in space which could be expected given the arc like geometry of the mountain range the pyrenean domain is unresolved due to lack of data and moreover existing focal mechanisms are globaly inconsistent nevertheless those mechanisms which are well constrained suggest a nnw sse to nw se direction of maximum stress in the western part of the pyrenees thus the stress field in france is fairly homogeneous at a regional scale for most of the territory except for the highly deformed belts

late eemian warming in the nordic seas as seen in proxy data and climate models 1 we analyze a transient simulation of the last glacial inception in a climate model of intermediate complexity focusing on sea ice ocean circulation dynamics in the north atlantic and nordic seas as northern high latitude summer insolation decreases toward the end of the eemian interglacial arctic sea ice export to the north atlantic increases this surface fresh water transport weakens deep water formation in the north atlantic and the near surface circulation of the subpolar gyre as a consequence the relative contribution of subpolar gyre waters to the atlantic inflow into the nordic seas is reduced giving way to more warm and saline subtropical waters from the north atlantic current we thus find an episode of relatively high heat and salt transport into the nordic seas during the last glacial inception between 119 000 and 115 000 years before present this stabilizes deep ocean convection in the region and warms scandinavia during a phase of low insolation these findings are in good agreement with proxy data from the nordic seas and north atlantic at the end of the warm interval sea surface temperature drops by about 3 c marking the onset of large scale glacier growth over scandinavia

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

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

structure and tertiary tectonic history of the mulhouse high upper rhine graben block faulting modified by changes in the alpine stress regime 1 the mulhouse high horst is situated in the southernmost upper rhine graben and changes in its tectonic history record the interaction with the adjacent alpine front recently released seismic data show that the mulhouse high consists of the sierentz and the altkirch tilted blocks separated by the ferrette fault zone with a throw of several hundred meters during the eocene early rupelian main rifting phase the mulhouse high was the elevated flank of the dannemarie basin with sedimentation affected by the nearby southern boundary of the rhine graben the miocene jura compression extended into the mulhouse high creating a series of semiparallel buried folds with no evidence for thin skin tectonics the change to a nw se regional compressive stress reactivated the main graben faults as wrench faults it also resulted in transpression on the ne sw trending faults particularly the northern segment of the illfurth fault zone consequently the northern part of the mulhouse high was uplifted strike slip motion along the ferrette fault zone is shown to be small

thrust development in the eastern jura mountains related to pre existing extensional structures abstract from tunnel and map data three detailed balanced cross sections of the mesozoic cover of the jura fold and thrust belt in the hauenstein area eastern jura mountains switzerland were constructed viable models of the kinematic evolution of the structures document different stages of thrust development most thrust propagate first from the basal decollement in the middle triassic evaporites to the opalinus shales in some cases they continue for a short distance layer parallel and then break through to the surface in other cases they get stuck in the opalinus shales with further shortening either a delamination occurs where the incompetent layers were wedged under the overlying competent limestones the thrust breaks through the limb of the anticline at a higher level otherwise the thrust steepens and breaks through the hinge of the fold the resulting kinematically viable sections confirm that the miocene thrusts nucleate at inhomogeneities of the sub decollement relief these are possibly related to the borders of an underlying palaeozoic trough system reactivated as faulted flexures during the eocene to early miocene

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

space clustering properties of the betic alboran earthquakes in the period 1962 1989 abstract in order to obtain a way to quantify the spatial dependence between earthquakes in the betic alboran south spain region the single link clustering slc method has been applied to a catalogue of earthquakes with magnitude greater or equal to 4 0 that occurred in this region from 1962 to 1989 the significant distances of links obtained which show alignments whose direction is similar to the direction of some surface faults are 15 30 and 40 km and the limit of inconsistency appears at distances greater than or equal to 70 km most of the historical destructive earthquakes have taken place within the clusters obtained and the majority within the dc 30 km cluster this implies that the most relevant seismic activity occurs in some source areas where there is a strong nesting of activity

the upper rhenish shield basement vosges upper rhinegraben and schwarzwald main structural features deduced from magnetic gravimetric and geological data abstract interpretation of magnetic and gravimetric data and correlations with geological observations on outcrops and in boreholes have enabled the construction of a geological sketch map of the pre westphalian basement in the area of the upper rhenish shield the map demonstrates the contrast between the heavy and magnetic saxothuringian characterized by palaeozoic units metamorphosed to varying degrees and intruded by early carboniferous basites and the lighter moldanubian consisting mainly of gneisses and granites geological structures and tectonic features are recorded beneath the mesozoic and cenozoic cover the present picture of the basement is mainly the result of late visean early namurian structural features represented by a linear arrangement of magmatic bodies and the distribution of strike slip and thrust faults the major structural features are the e w vittel lalaye lubine baden baden fault that marks the border between saxothuringian and moldanubian the n35 left lateral wrench fault system running along the present rhinegraben the n60 grain of the northern vosges and the saar basin and the s verging crustal thrusts of moldanubian

three dimensional vp vs variations for the coso region california recent seismological studies of the coso region of southeastern california document both low p wave velocities and abnormal sv attenuation in indian wells valley south of the pleistocene volcanics of the coso range in order to learn more about the physical nature of these colocated anomalies a tomographic inversion for the three dimensional variations of vp vs the ratio of compressional to shear velocity was performed iterative back projection of 2966 shear and compressional wave travel time residuals from local earthquakes recorded on vertical instruments reveals that vp vs is generally high at the surface and decreases systematically to 10 km depth superimposed on this trend are several large anomalies near devil s kitchen in the coso geothermal area vp vs values are very low near the surface consistent with measured values for steam dominated geothermal systems abnormally high values of vp vs are observed in portions of indian wells valley and also below the cactus peak rhyolite dome from 2 to 5 km in depth in indian wells valley the co occurrence of low p velocities low s velocities high vp vs and anomalous sv attenuation are indicative of subsurface partial melt because the inversion is based on vertical data only however the results cannot be considered conclusive only suggestive

evolution of the northeast labrador sea during the last interglaciation 1 boreal summer insolation during the last interglaciation lig generally warmed the subpolar to polar northern hemisphere more than during the early holocene yet regional climate variations between the two periods remain we investigate northeast labrador sea subsurface temperature and hydrography across terminations t i and ii and during the lig to assess the impact of two different magnitudes of boreal summer insolation increase on the northeast labrador sea we use mg ca ratios in neogloboquadrina pachyderma sinistral as a proxy of calcification temperature to document changes in subsurface temperatures over eirik drift our corresponding record of d 18 o of seawater documents changes in water mass salinity mg ca calcification temperatures peak early in the holocene coincident with peak boreal summer insolation in contrast lig temperatures are relatively constant through the interglaciation and are no warmer than peak holocene temperatures during the first half of the lig d 18 o of seawater remains depleted likely from southern greenland ice sheet retreat and enhanced arctic freshwater and sea ice export to the labrador sea the consequent stratification of the labrador sea and attendant suppressed convection explains delayed deep ocean ventilation and a cooler subsurface in the northeast labrador sea during the lig

new insight in the tectonics of the southern rhine graben jura region using local earthquake seismology 1 a new seismic data set was acquired using a dense temporary network of mobile seismic stations it is combined with existing seismological data for the southern rhine graben the data yielded some new focal mechanisms and allowed for a detailed local earthquake tomography these methods give new insight in the structure of the crust and stress conditions in the area by combining the tomography with the earthquake hypocenter locations and focal mechanisms some of the structures in the p wave velocity model are interpreted as active faults the eastern boundary fault zone of the graben is found to be activated in a left lateral strike slip sense the southern continuation of these faults is formed by variscan structures in the basement a change in orientation of the graben axis between the main graben and its southern end have played a role during the development of the system this difference in orientation caused the development of the dannemarie and allschwil subbasins during a late stage of the opening of the rhine graben this study shows evidence for active faulting in the basement underneath the detachment of the jura mountains these faults which are interpreted as reactivated permo carboniferous troughs coincide with the frontal thrusts of the jura mountains it might be that these structures in the basement have influence on the detachment tectonics in the region

evidence for northward expansion of antarctic bottom water mass in the southern ocean during the last glacial inception 1 we investigated deep water changes in the southern ocean during the last glacial inception in relationship to surface hydrology and global climatology to better understand the mechanisms of the establishment of a glacial ocean circulation changes in benthic foraminiferal 13c from three high resolution cores are compared and indicate decoupled intermediate and deep water changes in the southern ocean from the comparison with records from the north atlantic south atlantic and the southern ocean we show that the early southern deep water 13c drop observed at the mis 5 5 5 4 transition occurred before any significant reduction of north atlantic deep water ventilation we propose that this drop is linked to the northward expansion of poorly ventilated antarctic bottom water aabw mass in the southern ocean associated with an early cooling in the high southern latitudes the westerly winds and surface oceanic fronts would migrate equatorward thus weakening the upwelling of circumpolar deep waters reduced heat brought to antarctic surface waters would enhance sea ice formation during winters and the deep convection of cold and poorly ventilated aabw

upper rhine graben role of preexisting structures during rift evolution 1 the evolution of the cenozoic upper rhine graben was controlled by a repeatedly changing stress field and the reactivation of a complex set of crustal discontinuities that had come into evidence during permo carboniferous times a comparison of the spatial and temporal thickness distribution of synrift deposits with preexisting fault patterns permits to infer a sequence of distinct basin subsidence phases that can be related to changes in the ambient stress field reactivation of a system of late palaeozoic fault systems outlining troughs and highs controlled the nucleation of initially separated middle and late eocene basins the depocenters of which coincided with a preexisting wsw ene trend during oligocene crustal extension the individual basins coalesced resulting in the development of the ssw nne striking upper rhine graben during the late oligocene chattian change in stress field the upper rhine graben was probably reactivated as a dextral strike slip system with the central graben segment forming a releasing bend during the early miocene aquitanian a major reorientation of the regional stress field is held responsible for the main subsidence phase of the northern parts of the upper rhine graben this is reflected by a counterclockwise rotation and northeastward shift of the depocenter axis and later by the middle miocene uplift and erosion of the southern parts of the upper rhine graben during the plio quaternary the upper rhine graben was reactivated as a sinistral strike slip system with the central graben segment forming a restraining bend

local earthquake tomography of the altiplano and the eastern cordillera of northern bolivia the velocity structure in the crest beneath the central andes of northern bolivia is obtained by the simultaneous inversion of local earthquake arrival time data for velocity and hypocentral parameters the data were recorded between october 1990 and february 1991 by the french lithoscope network the 34 vertical short period seismic stations were installed along a 320 km long profile crossing two main morphological units of the andean chain the altiplano and the eastern cordillera the arrival times of seismic waves generated by earthquakes located in the subduction zone of the nazca plate underneath the south american plate were inverted using a modified version of thurber s 3 d iterative simultaneous inversion code the results are consistent with the inversion of teleseismic travel time residuals from the same network and closely correlate with the mapped surface geological features the altiplano basin is characterized by a low velocity zone down to 20 km enclosed by the san andres and laurani faults at the surface the cordillera real fault zone crfz bounds to the west the high p wave velocity anomaly lying under the axial zone of the eastern cordillera the velocity discontinuity dips steeply to the southwest to the bottom of the crust from the velocity model the depth of the moho is estimated to be 66 km under the altiplano moreover the different behaviour of p and s waves found below the western cordillera and above the slab is consistent with the presence of partially melted asthenosphere that may be responsible for the magmatic activity finally the seismicity defines between 90 and 225 kin a part of the slab dipping to the north northeast with a low angle of about 30

the climate influence on the mid depth northeast atlantic gyres viewed by cold water corals 1 the neodymium nd isotopic composition expressed in epsilon units nd of reef framework forming cold water corals provides unique measures of water mass provenance and mixing within the northeast atlantic today and in the past a reconstruction of near thermocline water nd from cold water corals of the gulf of cadiz and porcupine seabight spanning over the past 300 000 years now revealed that climate cooling during marine isotope stages mis 7 2 and mis 8 9 led to a retraction of the mid depth subpolar gyre mspg to the west conversely northern hemisphere warming and increasing fresh water fluxes to the northwest labrador sea favor a stronger eastward extension of the mspg blocking the northward flow of temperate atlantic water as observed during the early mis 1 and the early stage mis 5 5 these changes are likely the result of large scale south north displacement of the westerlies similar to present day observations that the north atlantic oscillation nao is linked with mid depth ocean circulation based on these observations we hypothesize that further climate warming will also strengthen the mspg leading to a salt and temperature decrease in the northeast atlantic whereas salinity and temperature will increase in the temperate atlantic however the amplitude of such changes on north atlantic overturning remains to be tested

lithospheric memory state of stress and rheology neotectonic controls on europe s intraplate continental topography abstract to date research on neotectonics and related continental topography development has mostly focused on active plate boundaries characterized by generally high deformation rates the intraplate sedimentary basins and rifts of the northern alpine foreland are associated with a much higher level of neotectonic activity than hitherto assumed seismicity and stress indicator data combined with geodetic and geomorphologic observations demonstrate that europe s intraplate lithosphere is being actively deformed this has major implications for the assessment of its natural hazards and environmental degradation the lithosphere of the northern alpine foreland has undergone a polyphase evolution with an intense interplay between upper mantle thermal perturbations and stress induced intraplate deformation that points to the importance of lithospheric folding of the thermally weakened lithosphere in this paper we address relationships between deeper lithospheric processes neotectonics and surface processes in the northern alpine foreland with special emphasis on tectonically induced topography the objectives are to quantify the effects of ongoing alpine collision and atlantic ridge push on the intraplate deformation in europe and its impact on topography evolution and related natural hazards this paper reviews the four dimensional topographic evolution of the european lithosphere through a multi disciplinary approach linking geology geophysics and geotechnology until now research on neotectonics and related topography development of intraplate regions has received little attention our study examines a number of selected natural laboratories in continental europe from orogen through platform to continental margin these natural laboratories include the carpathians pannonian system the northwest european platform iberia and the atlantic continental margin we focus on lithosphere memory and neotectonics with special attention to the thermo mechanical structure of the lithosphere mechanisms of large scale intraplate deformation late neogene anomalies in subsidence and uplift and links with surface processes and topography evolution

plate interactions at the southern end of the rhine graben abstract the southern end of the rhine graben in the basel area originated in the early tertiary as an extensional structure it is the site of a transfer zone that connected the rhine graben with the bresse rhone grabens this transfer zone is located in an area into which a late paleozic trough projects which apparently was reactivated from the beginning of miocene to recent times three distinct phases of slight compression were superimposed on the southern end of the rhine graben the first one in the aquitanian early burdigalian is coeval with the development of the helvetic nappes and the insubric fault zone in the alps the second one in the langhian tortonian interval occurred when the external massifs and an important part of the lombardic fold thrust belt in the southern alps developed and the third pliocene to recent one is contemporaneous with the inactivation of this belt and its incorporation into the foredeep of the northern apennines in the aquitanian the forebulge of the alpine orogen is recognizable as a system of flexures that developed preferably on the margin of the late paleozoic trough the middle late miocene one gave rise to uplift of the black forest vosges domain and a river system flowing from this high to the south in the pliocene to recent one alpine rivers made their appearance flowing first to the west into the rhone system and then as the rhine to the north the pliocene to recent phase seems to be decoupled from the body of the central and southern alps

three dimensional velocity structure in northern california coast ranges from inversion of local earthquake arrival times abstract the three dimensional p wave velocity structure in the upper crust in the northern california coast ranges from santa rosa to ukiah is obtained by simultaneous inversion of local earthquake and refraction travel time data for velocity and hypocentral parameters in this region where there are lateral heterogeneities the three dimensional inversion provides important results not found in two dimensional refraction studies the medium is parameterized with velocities at the intersections gridpoints of a nonuniform three dimensional grid travel times are calculated with approximate ray tracing along arcuate paths which are reasonable for lateral distances less than 45 km inversions with 5 to 10 and 2 to 3 km gridspacing achieved 80 per cent decreases in data variance the inversion with 2 to 3 km gridspacing reduced the rms residual level to approximately the level of timing error anomalously low velocities to at least 6 km depth are found along the maacama and healdsburg rodgers creek hrc fault zones the low velocity region is widest at the en echelon junction of the maacama and hrc fault zones low velocities are associated with the clear lake basin where there is a thick sequence of volcanics interbedded with sedimentary deposits there is a high velocity body located southeast of the geysers between the maacama and collayomi fault zones which may be associated with igneous intrusives or high grade metamorphism related to an underlying inferred partial melt body modeled in previous teleseismic travel time studies there is some indication in the vapor dominated geothermal reservoir of lower velocities relative to surrounding water saturated rock as has been shown in some laboratory experiments hypocenter locations obtained in the inversion show little variation from hypocenters obtained through inversion for one dimensional velocity model and station corrections for the inversion with 2 to 3 km gridspacing however some groups of events become more tightly clustered

the variscan tectonic inheritance of the upper rhine graben evidence of reactivations in the lias late eocene oligocene up to the recent processing of gravity and magnetic maps shows that the basement of the upper rhine graben area is characterized by a series of ne sw trending discontinuities and elongated structures identified in outcrops in the vosges black forest and the odenwald mountains they form a 40 km wide n30 40 striking sinistral wrench zone that in the visean shifted the variscan and pre variscan structures by at least 43 km to the ne wrenching was associated with emplacement of several generations of plutonic bodies emplaced in the time range 340 325 ma the sub vertical ne sw trending discontinuities in the basement acted as zones of weakness susceptible to reactivation by subsequent tectonism the first reactivation marked by mineralizations and palaeomagnetic overprinting along ne sw faults of the vosges mountains results from the liassic nw se extension contemporaneous with the break up of pangea the major reactivation occurred during the late eocene n s compression and the early middle oligocene e w extension the ne sw striking basement discontinuities were successively reactivated as sinistral strike slip faults and as oblique normal faults elongated depocenters appear to form in association with reactivated variscan wrench faults some of the recent earthquakes are located on ne sw striking variscan fault zones and show sinistral strike slip focal mechanisms with the same direction suggesting also present reactivation

a multi scale approach to study the lithospheric structure of the southern upper rhine graben from seismic tomography through reflection seismics to surface geology this paper integrates the results of different techniques local and regional travel time tomography reflection seismics and surface geology with this integration of different techniques working on different scales it is possible to derive a comprehensive picture of the present day structures in the lithosphere of the upper rhine graben it is shown that the stucture of the lithosphere is dominated by structures related to the variscan orogeny late stage strike slip reactivation of the internal faults of the rhine graben is observed in the field this reactivation is of dominant influence on the geomorphology in the southern end of the upper rhine graben

southern rhine graben small wavelength tomographic study and implications for the dynamic evolution of the graben summary inversion of p wave traveltime residuals of teleseismic events recorded by a dense network of short period stations yielded a detailed image of the 3 d velocity structure of the lithosphere asthenosphere system beneath the southern rhine graben area 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 roughtly an e w orientation the teleseismic inversion models yield no indications for significantly reduced seismic 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 velocity variations at greater depth indicates a rather smooth transition from the lower lithosphere to the upper asthenosphere deeper parts of the lithosphere were probably altered by metasomatic processes as a consequence of the intrusion of melts during middle and late miocene times these melts cooled and solidified from the end of the miocene when rifting and thermal doming ceased in the southern rhine graben area

stress tensor and fault plane solutions for a population of earthquakes an algorithm for the simultaneous estimation of the orientation and shape of the stress tensor and the individual fault plane solutions for a population of earthquakes is studied it corresponds to a synthesis of the methods used by brillinger et al 1980 to obtain focal mechanisms and by armijo and cisternas 1978 for stress tensor analysis in microtectonics the input data are the polarities of the p arrival and take off angles for the set of source station pairs the method distinguishes in general which one of the nodal planes corresponds to the fault and gives the direction of the slip the application to the aftershock sequence of the 1980 arudy earthquake western pyrenees shows that the observations may be explained by a single stress tensor producing a n32 e extension with a likelihood of 95 per cent

detection of active crustal structures in the upper rhine graben using local earthquake tomography gravimetry and reflection seismics abstract this paper presents a case study in which three different geophysical methods are combined to link the large scale seismically active deformation of the basement to the deformation of the sedimentary cover in the seismically active southern end of the upper rhine graben local earthquake tomography shows velocity contrasts related to large scale faulting in the basement the observed faults coincide with the discontinuities in the bouguer anomaly map for the upper part of the basement and the sedimentary cover reflection seismic profiles show distinct faulting in the sedimentary cover at the position of the structures observed in the local earthquake tomography and the bouguer anomaly maps they provide the link of the seismogenic structures at depth and the near surface geology it is shown that the structure of the southern end of the rhine graben is dominated by faults that have a nne ssw trend slightly oblique to the graben axis the presence of earthquake hypocenters nearby the faults indicate their present day activity

control of preexisting faults on geometry and kinematics in the northernmost part of the jura fold and thrust belt 1 this study investigates the formation of the northernmost anticlines of the late miocene to early pliocene thin skinned jura fold and thrust belt and provides evidence that a transition to thick skinned tectonics did occur in this particular area during the late pliocene the northernmost anticlines of the jura fold and thrust belt are characterized by pronounced along strike asymmetries that were predetermined by a fault pattern inherited from paleogene upper rhine graben rifting this fault pattern had disrupted the triassic basal decollement of the jura mountains and controlled the nucleation of thrusts and folds as well as transfer zones during the generally n nw directed transport of the detached sedimentary cover sinistral transpressive oblique ramps nucleated along paleogene nne trending basement normal faults and led to a northward protrusion of the jura front encroaching onto the southernmost upper rhine graben shortening across the frontal anticlines is greatest along the oblique ramps and decreases along strike toward the east necessitating a gentle clockwise rotation of the detached sediments despite the fact that the stress field in the sedimentary cover remained unchanged thin skinned folding and thrusting came to a halt in the early pliocene giving way to thick skinned tectonics very probably governing neotectonic activity in the area this transition might represent a geodynamic reorganization of the northwestern alpine foreland

interactions between thin and thick skinned tectonics at the northwestern front of the jura fold and thrust belt eastern france 1 this study investigates spatial and temporal interactions of thin and thick skinned tectonics in a classical foreland setting located at the front of the jura fold and thrust belt in eastern france the working area coincides with the intracontinental rhine bresse transfer zone and represents the most external front of the deformed alpine foreland the investigation combines analyses of largely unpublished and newly available subsurface information with our own structural data including an exhaustive paleostress analysis and geomorphologic observations results are provided in the form of a new tectonic map and a series of regional cross sections through the study area the besancon zone forming the most external part of the thin skinned fold and thrust belt encroached onto the eo oligocene rhine bresse transfer fault system until early pliocene times thrust propagation was largely controlled by the late paleozoic to paleogene preexisting fault pattern that characterizes the rhine bresse transfer zone thick skinned deformation dominant throughout the avant monts zone located farther to the west was associated with compressional to transpressional reactivation of such faults overprinting and crosscutting criteria of fault slip data allow distinguishing between systematically fanning maximum horizontal stress axes that define the front of the thin skinned jura fold and thrust belt and consistently nw se directed maximum horizontal stress axes that characterize deformation of the autochthonous cover of the foreland which is affected by thick skinned tectonics tectonic and geomorphic analyses indicate that thick skinned tectonics started at a very late stage of foreland deformation post early pliocene geomorphic observations imply that deformation between mesozoic cover and basement is locally still decoupled however overprinting relationships and recent seismicity suggest that present day tectonic activity is thick skinned which probably reflects ongoing tectonic underplating in the alpine foreland

deep crustal structure of the rhine graben from dekorp ecors seismic reflection data a summary abstract results of two deep reflection seismic lines crossing the northern and southern part of the rhine graben which were recorded in 1988 by the french ecors and the german dekorp teams indicate that the asymmetry of this rift persists to the base of the crust the brittle ductile transition zone approximately coincides with the top of the lower crust ductile shear zones appear to affect the crust mantle boundary upper crustal extension by faulting accounts for a divergence of the graben flanks by 5 7 km whereas the crustal configuration of the rhine graben suggest an extension value of some 17 km

kinematic analysis of the upper rhine graben boundary fault system this paper presents a new set of kinematic data for the central part of the upper rhine graben fault slip measurements were gathered covering the near field of a 200 km long segment of the graben boundary faults on both sides the resulting kinematic analysis shows a strong predominance of strike slip faulting and some oblique slip and pure normal faulting overall there is a regional coherence in the orientations of the extensional and shortening axes associated with both types of faulting throughout the entire study area the data set is best interpreted as the result of more or less continuous sinistrally transtensive kinematics with a nw se to nnw sse oriented or subvertical shortening and a ne sw to e w oriented extensional direction local transpressive overprints are not reflected in the pattern of brittle deformation in the near field of the boundary fault system we conclude that the opening history of the rhine graben may be less complex than hitherto assumed

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

the basel 1356 earthquake which fault produced it the 1356 basel earthquake was the strongest event to have shaken nw europe in the last thousand years the peculiar location of this historical event makes it possible to relate it to normal faulting along the edges of the rhine graben as well as to reverse faulting along the jura frontal thrust or to fault reactivation within the hercynian basement alternate hypotheses are discussed and their implications compared taking into account available structural data and results of the morphotectonic study performed in the epicentral area this study combines field observations with the analysis of spot satellite imagery aerial photographs and detailed topography it is concluded that the basel earthquake most probably reactivated a basement fault reverse or wrench fault beneath the shallow depth aseismic detachment that underlies the jura mountains

3d crustal structure from local earthquake tomography around the gulf of arta ionian region nw greece during summer of 1995 local seismicity was recorded in the area around the gulf of arta in northwestern greece by a dense temporary seismic network of the 441 local events observed at 37 stations 232 well locatable events with a total of 2776 p phase readings were selected applying the criteria of a minimum of 6 p observations and an azimuthal gap less than 180 this data set is used to compute a minimum 1d velocity model for the region several tests are conducted to estimate model stability and hypocenter uncertainties leading to the conclusion that relative hypocenter location accuracy is about 500 m in latitude and longitude and 1 km in depth the minimum 1d velocity model serves as initial model in the non linear inversion for three dimensional p velocity crustal structure by iteratively solving the coupled hypocenter velocity problem in a least squares sense careful analysis of the resolution capability of our data set outlines the well resolved features for interpretation the resulting 3d velocity model shows generally higher average crustal velocities in the east and the well resolved area of the eastern gulf of arta exhibits a homogeneous velocity around 6 km s for the whole upper crust a pronounced north south trending zone of low velocities in the upper 5 10 km is observed in the area of the katouna fault zone kfz at greater depths below 10 km the kfz is underlain by high velocity material e w profiles suggest a horst graben structure associated with the kfz

intraplate deformation and 3d rheological structure of the rhine rift system and adjacent areas of the northern alpine foreland the lithosphere of the northern alpine foreland has undergone a polyphase evolution during which interacting stress induced intraplate deformation and upper mantle thermal perturbations controlled folding of the thermally weakened lithosphere in this paper we address relationships among deeper lithospheric processes neotectonics and surface processes in the northern alpine foreland with special emphasis on tectonically induced topography we focus on lithosphere memory and neotectonics paying special attention to the thermo mechanical structure of the rhine graben system and adjacent areas of the northern alpine foreland lithosphere we discuss implications for mechanisms of large scale intraplate deformation and links with surface processes and topography evolution

earthquake locations and three dimensional crustal structure in the coyote lake area central california previous work on the simultaneous inversion method has been improved and extended to incorporate iterative solution for earthquake locations and laterally heterogeneous structure approximate ray tracing and parameter separation are important elements of the improved method application of the method to p wave arrival time data recorded by stations of the u s geological survey central california network yields a three dimensional model for the velocity structure of the upper crust in an area encompassing the rupture zone of the coyote lake earthquake of august 1979 very strong correlations between the velocity model and the geology and gravity and magnetic anomalies are observed improved estimates of the locations of earthquakes in the study area are also determined the relocation of explosions indicates epicentral accuracies of the order of a kilometer or better based on the revised hypocentral locations it is concluded that the san andreas fault is vertical in this area with no actual offset between the epicenters and the fault trace in contrast the calaveras has two or more active fault surfaces one nearly vertical and another dipping 75 to the northeast

the west european stress field new data and interpretation abstract the mapped stress field of western europe reflects the tectonic process active there a traverse of stress measurements from the alps and through their northern foreland to the southern border of the lower rhine embayment identifies three distinct stress sub provinces the western alps the blocks on both flanks of the rhinegraben and the rhenish shield the alps have high magnitude stresses up to 35 mpa in the direction of maximum compression here called 1 h the general direction of 1 h is about 140 the foreland has the same directional trend of 1 h with a magnitude reduced to about 2 0 mpa local anomalies in magnitude and direction occur along the course of the rhinegraben which is a site of active sinistral shear the rhenish shield shows an internal zonation of the stress field the magnitudes of the stresses are low usually negative along the axis connecting the northern end of the rhinegraben with the rifting of the lower rhine embayment the direction there is about 150 on the eastern and western flanks of the shield the stress directions are essentially the same as in the southern blocks these zones are distant from the belt of active strain release consequently stresses of up to 4 0 mpa have accumulated

monazite trumps zircon applying shrimp u pb geochronology to systematically evaluate emplacement ages of leucocratic low temperature granites in a complex precambrian orogen although zircon is the most widely used geochronometer to determine the crystallisation ages of granites it can be unreliable for low temperature melts because they may not crystallise new zircon for leucocratic granites u pb zircon dates therefore may reflect the ages of the source rocks rather than the igneous crystallisation age in the proterozoic capricorn orogen of western australia leucocratic granites are associated with several pulses of intracontinental magmatism spanning 800 million years in several instances shrimp u pb zircon dating of these leucocratic granites either yielded ages that were inconclusive e g multiple concordant ages or incompatible with other geochronological data to overcome this we used shrimp u th pb monazite geochronology to obtain igneous crystallisation ages that are consistent with the geological and geochronological framework of the orogen the u th pb monazite geochronology has resolved the time interval over which two granitic supersuites were emplaced a paleoproterozoic supersuite thought to span 80 million years was emplaced in less than half that time 1688 1659 ma and a small meso to neoproterozoic supersuite considered to have been intruded over 70 million years was instead assembled over 130 million years and outlasted associated regional metamorphism by 100 million years both findings have consequences for the duration of associated orogenic events and any estimates for magma generation rates the monazite geochronology has contributed to a more reliable tectonic history for a complex long lived orogen our results emphasise the benefit of monazite as a geochronometer for leucocratic granites derived by low temperature crustal melting and are relevant to other orogens worldwide