the 1994 sefidabeh earthquakes in eastern iran blind thrusting and bedding plane slip on a growing anticline and active tectonics of the sistan suture zone summary in 1994 a sequence of five earthquakes with mw 5 5 6 2 occurred in the sistan belt of eastern iran all of them involving motion on blind thrusts with centroid depths of 5 10 km coseismic ruptures at the surface involved bedding plane slip on a growing hanging wall anticline displaying geomorphological evidence of uplift and lateral propagation the 1994 earthquakes were associated with a nw trending thrust system that splays off the northern termination of a major n s right lateral strike slip fault elevation changes along the anticline ridge suggest that displacement on the underlying thrust dies out to the nw away from its intersection with the strike slip fault this is a common fault configuration in eastern iran and accommodates oblique ne sw shortening across the n s deforming zone probably by anticlockwise rotations about a vertical axis this style of fault kinematics may be transitional to a more evolved state that involves partitioning of the strike slip and convergent motion onto separate subparallel faults

geophysical geological transect and tectonic evolution of the swiss italian alps a complete alpine cross section integrates numerous seismic reflection and refraction profiles across and along strike with published and new field data the deepest parts of the profile are constrained by geophysical data only while structural features at intermediate levels are largely depicted according to the results of three dimensional models making use of seismic and field geological data the geometry of the highest structural levels is constrained by classical along strike projections of field data parallel to the pronounced easterly axial dip of all tectonic units because the transect is placed close to the western erosional margin of the austroalpine nappes of the eastern alps it contains all the major tectonic units of the alps a model for the tectonic evolution along the transect is proposed in the form of scaled and area balanced profile sketches shortening within the austroalpine nappes is testimony of a separate cretaceous age orogenic event west directed thrusting in these units is related to westward propagation of a thrust wedge resulting from continental collision along the meliata hallstatt ocean further to the east considerable amounts of oceanic and continental crustal material were subducted during tertiary orogeny which involved some 500 km of n s convergence between europe and apulia consequently only a very small percentage of this crustal material is preserved within the nappes depicted in the transect postcollisional shortening is characterized by the simultaneous activity of gently dipping north directed detachments and steeply inclined south directed detachments both detachments nucleating at the interface between lower and upper crust large scale wedging of the adriatic or apulian lower crust into a gap opening between the subduced european lower crust and the pile of thin upper crustal flakes alpine nappes indicates a relatively strong lower crust and detachment between upper and lower crust

morphology of the casper mountain uplift and related subsidiary structures central wyoming implications for laramide kinematics dynamics and crustal inheritance the general east west trend of the regional scale fault related cas per mountain uplift in central wyoming reflects a preexisting pre cambrian fabric along which there was laramide compressional re activation initial fault displacement on the south dipping casper mountain fault zone probably predates displacement on the inter secting northwest trending northeast dipping casper arch thrust that forms the northeastern border of the wind river basin later phase incremental laramide displacements occurred along both fault zones left oblique slip on the casper mountain fault zone dip slip on the crosscutting casper arch thrust basement involved thrust generation of the subsidiary laramide northwest trending iron creek and emigrant gap anticlines along the north footwall side of the casper mountain fault zone also occurred during this later phase laramide deformation perturbation of far field northeast southwest laramide max imum horizontal paleostress trajectories s1 to local nearly fault normal orientation at casper mountain together with strain par titioning is proposed to explain the apparent coeval development of divergent hanging wall and footwall basement involved fault related structures this kinematic and dynamic interpretation may be applied conditionally to other east west trending laramide up lifts in the central rocky mountain foreland province

storm generated depositional types and associated trace fossils in lower carboniferous shallow marine carbonates of three cliffs bay and ogmore by sea south wales abstract four distinct storm generated or induced depositional types have been recorded in lower carboniferous shallow marine limestones of ogmore by sea and three cliffs bay south wales type a deposits have whole and oriented horn coral lag deposits and graded limestones with large regular zoophycos they are interpreted as storm generated turbidite deposits in an area below storm wave base type b deposits are characterized by graded limestones and short wavelength hummocky cross bedding with rhizocorallium and small arcuate zoophycos small planolites like burrows and were probably formed by storm currents at depths just above storm wave base type c deposits consist of crinoidal lag deposits and long wavelength hummocky cross bedding with escape burrows and were probably deposited just below fair weather wave base type d deposits contain skeletal sandstone lag deposits and large scale low angle cross bedding generally without bioturbation apart from borings indicating a shore face or beach environment the depositional types belong to the courceyan limestone zaphrentis zone and arundian limestone caninia zone it appears that the pattern of trace fossils and bioturbation as well as sedimentary structure and texture change characteristically with changing wave effect depth in this area

structural architecture of the southern and middle urals foreland from reflection seismic profiles structural architecture of the southern and middle urals foreland from reflection seismic profiles

transpressional deformation strain partitioning and fold superimposition in the southern chinese altai central asian orogenic belt transpressional deformation has played an important role in the late paleozoic evolution of the western central asian orogenic belt caob and understanding the structural evolution of such transpressional zones is crucial for tectonic reconstructions here we focus on the transpressional irtysh shear zone with an aim at understanding amalgamation processes between the chinese altai and the west east junggar we mapped macroscopic fold structures in the southern chinese altai and analyzed their relationships with the development of the adjacent irtysh shear zone structural observations from these macroscopic folds show evidence for four generations of folding and associated fabrics the earlier fabric s 1 is locally recognized in low strain areas and is commonly isoclinally folded by f 2 folds that have an axial plane orientation parallel to the dominant fabric s 2 s 2 is associated with a shallowly plunging stretching lineation l 2 and defines similar to nw se tight close upright macroscopic folds f 3 with the doubly plunging geometry f 3 folds are superimposed by similar to nnw sse gentle f 4 folds the f 3 and f 4 folds are kinematically compatible with sinistral transpressional deformation along the irtysh shear zone and may represent strain partitioning during deformation the sub parallelism of f 3 fold axis with the irtysh shear zone may have resulted from strain partitioning associated with simple shear deformation along narrow mylonite zones and pure shear dominant deformation f 3 in fold zones the strain partitioning may have become less efficient in the later stage of transpressional deformation so that a fraction of trans current components was partitioned into f 4 folds c 2016 elsevier ltd all rights reserved

deep electrical resistivity tomography for the prospection of low to medium enthalpy geothermal resources summary the growth of the geothermal industry sector requires innovative methods to reduce explo ration costs whilst minimizing uncertainty during subsurface exploration until now geoelec trical prospection had to trade between logistically complex cabled technologies reaching a few hundreds meters deep versus shallow reaching prospecting methods commonly used in hydro geophysical studies we present a recent technology for geoelectrical prospection and show how geoelectrical methods may allow the investigation of medium enthalpy geothermal resources until about 1 km depth the use of the new acquisition system which is made of a distributed set of independent electrical potential recorders enabled us to tackle logistics and noise data issues typical of urbanized areas we acquired a 4 5 km long 2 d geoelectrical survey in an industrial area to investigate the subsurface structure of a sedimentary sequence that was the target of a 700 m geothermal exploration well geo 01 satigny in the greater geneva basin western switzerland to show the reliability of this new method we compared the acquired resistivity data against reflection seismic and gravimetric data and well logs the processed resistivity model is consistent with the interpretation of the active seismic data and density variations computed from the inversion of the residual bouguer anomaly the combination of the resistivity and gravity models suggest the presence of a low resistivity and low density body crossing mesozoic geological units up to palaeogene neogene units that can be used for medium enthalpy geothermal exploitation our work points out how new geoelectrical methods may be used to identify thermal groundwater at depth this new cost efficient technology may become an effective and reliable exploration method for the imaging of shallow geothermal resources

late stage tectonic evolution of the al hajar mountains oman new constraints from palaeogene sedimentary units and low temperature thermochronometry mountain building in the al hajar mountains ne oman occurred during two major shortening stages related to the convergence between africa arabia and eurasia separated by nearly 30 ma of tectonic quiescence most of the shortening was accommodated during the late cretaceous when northward subduction of the neo tethys ocean was followed by the ophiolites obduction on top of the former mesozoic margin this shortening event lasted until the latest santonian early campanian maastrichtian to eocene carbonates unconformably overlie the eroded nappes and seal the cretaceous foredeep these neo autochthonous post nappe sedimentary rocks were deformed along with the underlying cretaceous tectonic pile during the second shortening event itself including two main exhumation stages in this study we combine remotely sensed structural data seismic interpretation field based structural investigations and apatite u th he ahe cooling ages to obtain new insights into the cenozoic deformation stage seismic interpretation indicates the occurrence of a late eocene flexural basin later deformed by an oligocene thrusting event during which the post nappe succession and the underlying cretaceous nappes of the internal foredeep were uplifted this stage was followed by folding of the post nappe succession during the miocene ahe data from detrital siliciclastic deposits in the frontal area of the mountain chain provide cooling ages spanning from 17 3 to 42 ma consistent with available data for the structural culminations of oman our work points out how renewal of flexural subsidence in the foredeep and uplift of the mountain belt were coeval processes followed by layer parallel shortening preceding final fold amplification

stratigraphic record of pliocene pleistocene basin evolution and deformation within the southern san andreas fault zone mecca hills california abstract a thick section of pliocene pleistocene nonmarine sedimentary rocks exposed in the mecca hills california provides a record of fault zone evolution along the coachella valley segment of the san andreas fault saf geologic mapping measured sections detailed sedimentology and paleomagnetic data document a 3 5 myr history of deformation and sedimentation in this area sw side down offset on the painted canyon fault pcf starting 3 7 ma resulted in deposition of the mecca conglomerate southwest of the fault the lower member of the palm spring formation accumulated across the pcf from 3 0 to 2 6 ma during regional subsidence sw side up slip on the pcf and related transpressive deformation from 2 6 to 2 3 ma created a time transgressive angular unconformity between the lower and upper members of the palm spring formation the upper member accumulated in discrete fault bounded depocenters until initiation of modern deformation uplift and basin inversion starting at 0 7 ma some spatially restricted deposits can be attributed to the evolution of fault zone geometric complexities however the deformation events at ca 2 6 ma and 0 7 ma are recorded regionally along 80 km of the saf through coachella valley covering an area much larger than mapped fault zone irregularities and thus require regional explanations we therefore conclude that late cenozoic deformation and sedimentation along the saf in coachella valley has been controlled by a combination of regional tectonic drivers and local deformation due to dextral slip through fault zone complexities we further propose a kinematic link between the 2 6 2 3 ma angular unconformity and a previously documented but poorly dated reorganization of plate boundary faults in the northern gulf of california at 3 3 2 0 ma this analysis highlights the potential for high precision chronologies in deformed terrestrial deposits to provide improved understanding of local to regional scale structural controls on basin formation and deformation along an active transform margin

seismotectonics and 1 d velocity model of the greater geneva basin france switzerland the greater geneva basin located in south western switzerland and neighboring france is enclosed by the rotating north western edge of the alpine front and the jura mountains chain recently this basin has received increasing attention as a target for geothermal exploration historical and instrumental seismicity suggest that faults affecting the basin may still be active moderate magnitude earthquakes have been located along the vuache fault a major strike slip structure crossing the basin before geothermal exploration starts it is key to evaluate the seismic rate in the region and identify possible seismogenic areas in this context we deployed a temporary seismic network of 20 broadband stations from september 2016 to january 2018 to investigate the ongoing seismic activity its relationship with local tectonic structures and the large scale kinematics of the area our network lowered the magnitude of completeness of the permanent swiss and french networks from 2 0 to a theoretical value of 0 5 using a new coherence based detector lassie particularly effective to detect microseismicity in noisy environments we recorded scarce seismicity in the basin with local magnitudes ranging from 0 7 to 2 1ml no earthquakes were found in the canton of geneva where geothermal activities will take place we constructed a local minimum 1d p wave velocity model adapted to the greater geneva basin using earthquakes from surrounding regions we relocated the events of our catalogue obtaining deeper hypocenters compared to the locations obtained using the available regional velocity models we also retrieved 8 new focal mechanisms using a combination of polarities and waveform inversion techniques csps the stress inversion shows a pure strike slip stress regime which is in agreement with structural and geological data combining the background seismicity with our catalogue we identified seismogenic areas offsetting the basin

three dimensional numerical experiments of strain partitioning at oblique plate boundaries implications for contrasting tectonic styles in the southern coast ranges california and central south island new zealand a three dimensional numerical model is used to investigate the nature and distribution of crustal scale deformation and strain partitioning across obliquely convergent transpressive plate boundaries a uniform elastic plastic crustal layer obeying murrell s extension to three dimensions of the griffith failure criterion was deformed under basal kinematic boundary conditions that correspond to the oblique convergence between two mantle lithospheres one of which detaches and subducts beneath the other the results show deformation concentrated in relatively narrow shear zones the character planar versus curved and dip of these shear zones or crustal scale faults depend on the relative amount of convergence versus transcurrent motion imposed across the plate boundary in models dominated by transcurrent boundary conditions two separate sets of coexisting structures develop 1 a pair of planar relatively shallow dipping thrust zones arranged in a v structure that accommodate convergent motion and 2 a set of curved near vertical strike slip zones arranged in a flower structure that accommodates the transcurrent motion in models dominated by convergence both contractional and transcurrent deformations are accommodated by oblique slip across a single pair of structures that have the same geometry as the thrust shear zones there is a gradational behavior between these end member partitioned and nonpartitioned modes for intermediate boundary conditions in all cases the dip of the shear zones predicted by the numerical model is in good agreement with the dip of ideal faults predicted by mohr s incipient faulting hypothesis the two basic modes are interpreted to underlie the contrasting tectonic styles of the southern coast ranges california and central south island new zealand factors other than obliquity of convergence which play a role in strain partitioning are discussed

oroclinal bending of the southern sierra nevada batholith structural magmatic and isotopic features of the southern sierra nevada batholith are deflected clockwise with respect to its central and northern parts directions of magnetization at three localities in the southern sierra nevada are progressively deflected this is consistent with the hypothesis that the region was tectonically rotated in an orocline no paleomagnetic deflection was observed northwest of the white wolf kern canyon fault system oroclinal bending ofa block bounded by the san andreas garlock and white wolf kern canyon faults may have occurred before about 16 x l06 years ago the deformation may have been a response to shear at the western boundary of the north american plate caused by oblique subduction

strain partitioning of active transpression within the lebanese restraining bend of the dead sea fault lebanon and sw syria this material has been published in the journal of the geological society of london the only definitive repository of the content that has been certified and accepted after peer review copyright and all rights therein are retained by the geological society of london copyright 2001 the geological society of london see also http atlas geo cornell edu deadsea publications gomez2007 gsl htm

thirty five year creep rates for the creeping segment of the san andreas fault and the effects of the 2004 parkfield earthquake constraints from alignment arrays continuous global positioning system and creepmeters we present results from differential global positioning system gps surveys of seven alignment arrays and four continuous gps sites along the creeping segment of the san andreas fault surveys of four alignment arrays from the central creeping segment yield 33 to 36 year average minimum slip rates of 21 26 mm yr these rates are consistent with previous alignment array surveys spanning a 10 year period and with rates determined by creepmeters indicating approximate steady state creep along the central creeping segment for at least 35 years motion between continuous gps sites that span the central creeping segment is 28 2 0 5 mm yr for two sites that are 1 km apart and 33 6 1 mm yr for two sites that are 70 km apart slip rates therefore increase with distance from the creeping segment of the san andreas fault all rates reported here are significantly slower than the 39 2 mm yr rate predicted for motion between the sierra nevada great valley block and the pacific plate repeat surveys of three alignment arrays following the 2004 parkfield earthquake demonstrate that its coseismic and short term postseismic offsets decrease rapidly with distance from the epicenter from 150 mm to 15 mm to 5 mm at respective distances of 9 36 and 54 km to the northwest continuous gps data confirm that little coseismic and postseismic slip occurred along the central creeping segment geodetic and geologic slip rates are compared and different models for the accommodation of transcurrent deformation across the creeping segment are discussed

formation burial and exhumation of basement nappes at crustal scale a geometric model based on the western swiss italian alps abstract information from geological and reflection seismic data from the western swiss italian alps and from numerical models is used to build a geometrical model that can explain some of the major tectonic metamorphic features of alpine type basement nappes the model gives a geometrical and mechanical explanation for the initiation burial and subsequent uplift and partial exhumation of basement nappes at a crustal scale three main tectonic stages during convergence are distinguished and each correlated with the formation of specific nappe structures the first two stages are single vergent nw and correspond to the subduction of continental margin crust and the formation and uplift of high pressure rocks simple shear flow and superimposed wedge shaped pure shear flow is proposed for the creation and intrusion of high pressure nappes of the monte rosa type the third stage is characterized by a doubly vergent style with both pro and retro movements the former created nw vergent nappes as seen in the external alpine massifs and the latter caused backfolding and thrusting typical of the internal alps this third stage corresponds to the neoalpine movements in the western swiss italian alps and is accompanied by a generalized uplift mountain building and molasse sedimentation

decollement tectonics in the jura forelandfold and thrust belt abstract interpretation of more than 1500 km of industry seismic reflection lines from theswiss and french jura mountains and the western swiss molasse basin demonstrates that themesozoic and cenozoic cover of the jura fold and thrust belt has been deformed over a veryweak basal decollement and displaced for many kilometers toward the nw and that thebasement is not involved a depth to the basement map derived from depth conversion of theseismic lines shows a rather smooth flat basement dipping 1 3 to the s se the low amplitudebroad folds of the molasse basin and the external plateau jura are controlled by evaporitepillows or anticlines of middle triassic age the high amplitude folds of the haute chaine jura however are related to nw or se vergent thrusts with at least kilometric dipslip displacementthat has doubled the entire jurassic sequence the plateau jura evaporite related folds located in the foreland are interpreted as early stage buckle folds with further deformation afault ramp nucleates and develops into thrust related folds as observed in the haute chaine thus within the fold and thrust belt deformation increases toward the hinterland in the molassebasin however low amplitude folds represent an early deformation stage which could notdevelop further owing to the load of the overlying thick tertiary clastic wedge

mechanical model for subduction collision tectonics of alpine type compressional orogens alpine type orogens are characterized by three distinct convergent tectonic phases subduction with deformation that has primarily single vergence a transition from subduction to collision and continental collision with double vergence although the cenozoic history of the european alps has additional complexities a mechanical explanation for these three phases would provide the necessary crustal scale framework in which to develop an understanding of the smaller scale processes we present results from a simple numerical model which explain the mechanics of these three phases as a consequence of the changing buoyancy of the lithosphere subducted beneath the orogen the development and exhumation of a subduction complex suture zone and basement nappe stack piemont suture penninic nappes the presence of a crustal scale back fold and thrust insubric line and uplift of basement on the pro european side of the orogen external basement massifs may be explained as a simple consequence of changing dynamics during the transition from subduction to collision

structural and rheological implications of lower crustal earthquakes below northern switzerland abstract a detailed study of the recent seismicity in the northern alpine foreland of switzerland reveals that earthquakes with magnitudes between 0 9 and 4 2 occur not only in the upper part of the crust but contrary to observations in most other intracontinental settings seismicity extends down to depths of about 30 km in the lower crust observed p wave velocities in the focal region of even the deepest earthquakes are less than 6 3 km s 1 the average value of poisson s ratio for the entire focal depth range 6 30 km lies between 0 23 and 0 24 focal mechanisms are mostly a combination of strike slip and normal faults with consistent orientations of p and t axes but without any systematic dependence on focal depth from geological observations regional strain rates are of the order of 10 13 s 1 two dimensional temperature modelling indicates that temperatures in the lower crustal seismogenic zone are well above 450 c under the assumption of a dry environment the observed p wave velocities and poisson s ratios imply either a granitic or quartz rich gneissic composition or possibly a gabbroic quartz free granulite the deformation would be governed either by the rheology of quartz or of plagioclase the onset of ductility observed in laboratory studies lies around 300 c for quartz and around 450 c for plagioclase thus conditions in the lower crust beneath northern switzerland appear to be incompatible with the occurrence of either brittle failure or plastic instabilities as is implied by the existence of earthquakes alternatively lower crustal earthquakes could be a manifestation of the presence of fluids in the lower crust fluids under near lithostatic pressure either evolved in situ from metamorphic reactions or from infiltration from the mantle would tend to decrease the effective stress on pre existing faults and thus allow brittle friction failure to occur at depths where under dry conditions or low fluid pressures only ductile deformation would be expected

southern continuation of the coast shear zone and paleocene strain partitioning in british columbia southeast alaska this paper documents the newly recognized southern continuation of the early tertiary coast shear zone extending its known length by 350 km to more than 1200 km three sites along the shear zone in british columbia douglas channel bella coola and machmell river have similar histories during the period ca 65 55 ma the shear zone is 2 11 km thick and is defined by well developed mylonite zones that strike northwest and dip steeply northeast motion on the shear zone was predominantly reverse with the northeast side up synkinematic plutons are common in the shear zone lower plate rocks high grade gneiss derived from an ancient continental margin assemblage show little evidence of the extensive deformation and plutonism in the shear zone north of bella coola high grade gneiss forms the upper plate but to the south weakly metamorphosed rocks of stikinia compose the upper plate geochronologic data show that the shear zone was active between ca 60 and 55 ma at douglas channel ca 62 and 56 ma at bella coola and after 66 and before 56 ma near the machmell river these features match those of the coast shear zone in southeast alaska and adjacent british columbia together the shear zones formed a continental scale reverse ductile fault in paleocene time plate reconstructions show an oblique component to the dominantly dextral transcurrent paleocene margin partitioning of this motion across the continental margin produced a regional system of strike slip faults and contraction on the coast shear zone

geologic versus geodetic deformation adjacent to the san andreas fault central california we combine geologic and global positioning system gps data to characterize the style and magnitude of off fault deformation across the san andreas fault system in central california geologic structures record 12 km of both fault parallel and fault perpendicular displacements across creeping and locked portions of the san andreas fault analysis of 150 gps site velocities suggests that the borderlands record 4 6 mm yr of fault parallel and 3 5 mm yr of fault perpendicular motion alongside the creeping segment where elastic strain is minimized the distribution of both long term geologic and short term geodetic deformation is affected by basement type where more deformation is concentrated northeast of the san andreas fault on franciscan basement we suggest that at least half the fault parallel gps deformation measured by gps bordering the creeping segment must be accommodated by geologic structures this permanent deformation needs to be incorporated into dynamic models of the fault system elastic modeling of the san andreas fault in central california which incorporates its well known transition from locked to creeping behavior near parkfield predicts first order variations in the gps velocity field along the fault and corresponding variations in dilatational strain rates the strain rate pattern is dominated by a large contractional region northeast of the transition from locked to creeping behavior and a large extensional region southwest of the transition the former coincides with the coalinga and kettleman hills anticlines the growth and development of which seem to have occurred under at least two kinematic conditions we suggest that the onset of fault creep in central california promoted the growth of these folds by implication fault creep has been active over geologic time scales

using vertical axis rotations to characterize off fault deformation across the san andreas fault system central california we use vertical axis rotations from new paleomagnetic data to constrain off fault deformation within the san andreas fault system in central california samples were collected from 177 sites in the miocene monterey formation adjacent to the rinconada fault reliable means from 57 sites have 3 prominent patterns 1 the largest clockwise rotations are close to the rinconada and nacimiento faults 2 no significant rotation is observed near the san andreas fault and 3 counterclockwise rotations are observed at several sites northwest of paso robles these paleomagnetic results are compared to two other measures of off fault deformation where rotation can be calculated results from a fold based kinematic model show increasing clockwise rotations toward the rinconada fault consistent with pattern 1 few folds are observed in rocks on salinian basement near the san andreas fault suggesting that little deformation has occurred and providing an explanation for the negligible paleomagnetic rotations in pattern 2 rotations calculated from the global positioning system velocity field predict counterclockwise rotations that coincide with those observed from paleomagnetic data in pattern 3 broad patterns in the velocity field appear to be controlled by the transition from creeping to locked behavior along the san andreas fault and the region of counterclockwise rotation is linked to this transition thus we suggest that the creeping segment has been aseismic over geologic time scales in order to produce the observed paleomagnetic rotations the integration of all three data sets demonstrates that the san andreas fault borderlands record an important portion of fault parallel plate motion over geologic and geodetic time scales

an abrupt transition in the mechanical response of the upper crust to transpression along the queen charlotte fault the queen charlotte fault qcf is a major strike slip fault that forms the boundary between the pacific and north american plates from 51 to 58 n near 53 2 n the angle of oblique convergence predicted by the mid ocean ridge velocity morvel interplate pole of rotation decreases from 15 in the south to 15 in the north south of 53 2 n the convergent component of plate motion results in the formation of a 40 km wide terrace on the pacific plate west of qcf and earthquakes with thrust mechanisms including the 2012 haida gwaii earthquake sequence are observed north of 53 2 n in the primary rupture zone of the m 8 1 strike slip earthquake of 1949 the linear terrace disappears and topography of the continental slope west of the qcf is characterized by a complex pattern of ridges and basins that trend obliquely to the primary trace of the qcf deformation within the pacific plate appears to occur primarily through strike slip faulting with a minor thrust component on secondary synthetic faults the orientations of these secondary faults as determined from seismic reflection and bathymetric data are consistent with the reactivation of faults originally formed as ridge parallel normal faults and as thrust faults formed parallel to the qcf south of the bend at 53 2 n and subsequently translated to the north we suggest that an oblique convergence angle of 15 represents a critical threshold separating distinct crustal responses to transpression this result is consistent with theoretical and analog strain models of transpressive plate boundaries the sharpness of this transition along the qcf in contrast to purely continental transform boundaries may be facilitated by the relatively simple structure of oceanic crust and the presence of pre existing optimally oriented faults in the young pacific plate

present day vertical displacements in the north western alps and southern jura mountains data from leveling comparisons two high precision leveling networks were successively surveyed in france the ngf measured during the 1886 1907 period and the ign69 measured from 1965 to 1979 the accuracy of these levelings standard deviation of 1 8mm km to 3 8mm km allows us to compute the vertical displacements of the benchmarks between two different eras the results indicate the occurrence of discrete zones of uplift and subsidence 1 a regional uplift up to 1 4 mm yr of the subalpine massifs 2 an important uplift of the internal jura up to 2 mm yr 3 a relative subsidence of the southern part of the jura 0 8 mm yr and 4 a relative subsidence of the bresse basin with respect to the external jura comparing the spatial distribution of zones of uplift and their respective vertical displacement rates with a regional structural cross section leads to the conclusion that present day uplift of the belledonne and bornes massifs and of the internal parts of the jura mountains can be explained by crustal shortening along a major basement involving thrust fault this fault ramps up under the bornes massif from a depth of 12 km to 7 km turns into a flat under the molasse basin ramps up to the top of the basement at the north eastern margin of the internal jura mountains and reaches the surface in the external jura the saleve ramp anticline is carried by a bifurcation of this thrust horizontal displacement rates of 6 mm yr at the bornes ramp 2 mm yr at the saleve ramp and 4 mm yr at the internal jura ramp have been determined by inversion of profiles of uplift rates whether this basement involving thrust fault was already active during the miocene main folding phase of the jura mountains or whether it was activated only during pliocene pleistocene times is subject to debate

tectonic and sedimentary evolution of the korean peninsula a review and new view abstract this review focuses on the tectonics and sedimentation of major sedimentary basins and orogenic belts late proterozoic neogene in the korean peninsula the korean peninsula is part of the amuria plate and represents an important link between continental blocks of north and south china and the island arcs of japan the basement rocks exposed in the kyonggi and yongnam massifs consist of 2 7 to 1 1 ga high grade gneiss and schist these massifs are separated by the okchon fold belt which comprises metasedimentary rocks and bimodal meta volcanic rocks the stratigraphy of the okchon group is unclear at present the okchon basin was probably initiated as an intraplate rift prior to the late proterozoic the hwanggangri formation clast bearing phyllite most likely represents deposition by subaqueous debris flows in slope environments of an enclosed basin the stratigraphic relationship between the okchon group and the choson supergroup cambro ordovician of the taebaeksan basin is poorly constrained the choson supergroup unconformably overlies the yongnam massif and consists mainly of carbonate sequence that formed mostly in shallow marine and tidal environments reflecting numerous sea level fluctuations the sequence is disconformably overlain by siliciclastic sequence of pyongan supergroup carboniferous triassic which formed most likely in shallow marine deltaic and fluvial environments the imjingang belt is an east trending fold and thrust zone and consists of metasedimentary rocks and volcaniclastics devonian carboniferous underlain unconformably by proterozoic basement rocks late proterozoic amphibolites of oceanic affinity were metamorphosed at about 8 13 kbar and 630 740 c during the late permian to the early triassic the south vergent contraction and top down to the north normal faulting are suggestive of a suture belt between the north china block sino korea craton and the south china block yangtze craton an extension of sulu belt across the yellow sea entire peninsula experienced strong deformation and metamorphism during the suturing event namely songrim orogeny during this orogenic event the kyonggi massif and the okchon basin accreted to the yongnam massif and taebaeksan basin along the south korean tectonic line running northeast southwest a series of northward trending thrust formed along the boundary zone to the east kaktong and kongsuwon thrusts and others piggyback basins locally developed along the thrust faults forming the taedong group the crustal deformation resumed in the early to late jurassic daebo event under contractional setting dextral ductile shearing associated with thrusting and folding continued in the mid southern part of the peninsula it was due to orthogonal northwestward subduction of the izanagi plate under the asian continent the yongnam massif experienced continuous dextral offset along the honam shear zone in the early cretaceous the izanagi plate began to subduct northward and caused formation of strike slip basins in retroarc setting i e kyongsang basin in the southeastern part and a number of small scale basins in the mid southwestern part of the peninsula small scale alluvial fans and fluvial channel networks formed in the basin margin and were transitional to ephemeral lacustrine systems under semiarid to arid conditions extensive intrusion of granitoids occurred from triassic to early tertiary with a gap between 160 and 100 ma representing continental magmatic arc in the tertiary the southeastern margin of the korean peninsula experienced back arc opening pull apart basins formed in the miocene bounded by the yangsan and hupo faults the yonil group sedimentary fill of the pohang basin comprises more than 1 km thick siliciclastic sequence which represents deposition in fan delta systems on the hanging wall of the yangsan fault thick more than 10 km thick sediments in the ulleung basin margin were deformed in the late miocene due to the northward movement of kyushu block quarternary volcanic events in cheju island represent intraplate hot spots

slab breakoff a model for syncollisional magmatism and tectonics in the alps slab breakoff is the buoyancy driven detachment of subducted oceanic lithosphere from the light continental lithosphere that follows it during continental collision in a recent paper davies and von blanckenburg 1994 have assessed the physical conditions leading to breakoff by quantitative thermomechanical modeling and have predicted various consequences in the evolution of mountain belts breakoff will lead to heating of the overriding lithospheric mantle by upwelling asthenosphere melting of its enriched layers and thus to bimodal magmatism breakoff will also lead to thermal weakening of the subducted crustal lithosphere thereby allowing buoyant rise of released crustal slices from mantle depths in this paper we present a test of this model in the tertiary evolution of the european alps in the alps both basaltic and granitoid magmatism occur between 42 and 25 ma following the closure of oceanic basins by subduction and continental collision the granitoids are now well established to result from mixing of basalt with assimilated continental crust to identify the tectonically crucial origin of the partial mantle melts we have compiled all published geochemical and isotopic data of numerous mafic dykes occurring throughout the whole alpine arc their trace element and isotopic composition suggests that they have been formed by low degree melting of the mechanically stable lithospheric mantle we see no evidence for melting of asthenospheric mantle it was thus not decompressed to depths shallower than 50 km once initiated rapid lateral migration of slab breakoff will result in a linear trace of magmatism in locally thermal weakened crust this explains why all alpine magmatic rocks intruded almost synchronously along a strike slip fault the periadriatic lineament a compilation of ages from penninic high pressure rocks subducted to depths of up to 100 km shows that subduction took place at circa 55 40 ma followed by uplift at 40 35 ma from the short time interval between their uplift and the onset of magmatism we infer that both processes have been induced by the breakoff the slab breakoff model fulfills its predictions in the case of the alps and therefore supports the assumptions made in the theoretical model on a geological basis we believe that the characteristic association of magmatic activity with the return of high pressure rocks to the surface allows the identification of this process in the earth s mountain belts

pretectonic and posttectonic emplacements of the granitoids in the south central okchon belt south korea implications for the timing of strike slip shearing and thrusting structural analyses of three granitic plutons in the south central okchon belt of the korean peninsula reveal that the baegnok and cheongsan plutons are pretectonic with respect to right lateral strike slip ductile shearing along the cheongsan shear zone and later top to the ese thrusting whereas the boeun pluton is posttectonic with respect to these two deformation events u pb sphene age data from the three plutons indicate that the intrusion ages of the baegnok cheongsan and boeun plutons are 222 7 2 1 ma 216 9 2 2 ma and 171 7 1 4 ma respectively microstructural evidence preserved in deformed rocks from the ne striking cheongsan shear zone and adjacent nne striking thrusts suggests that the right lateral ductile shearing event along the shear zone occurred before the ese directed thrusting since these thrusts crosscut the late triassic early jurassic taedong group we estimate that the thrusts developed at 180 ma during the daebo tectonic event just prior to the intrusion of the boeun pluton we also constrain the age of the cheongsan shear zone at middle late triassic time corresponding to the songrim orogeny so that the shear zone is not related to deformation along the middle jurassic honam shear zone 176 ma the honam shear zone is not a simple tectonic boundary between the okchon belt and the yongnam massif but an anastomosing ductile shear zone not only affecting the okchon belt and the yongnam massif but also crosscutting the boundary between them at a low angle we suggest that the right lateral cheongsan shear zone is a major boundary between the okchon zone and the yongnam massif with paleozoic cover rocks the kyonggi massif and the okchon zone south china block were juxtaposed against the yongnam massif and taebaeksan basin north china block along the cheongsan shear zone during a late stage of the middle triassic songrim orogeny probably related to the late paleozoic early mesozoic collision between the north and south china blocks

the ml 5 3 epagny french alps earthquake of 1996 july 15 a long awaited event on the vuache fault the ml 5 3 epagny earthquake that occurred on 1996 july 15 in the vicinity of annecy french alps was the strongest event to shake southeastern france in the last 34 years moderate to serious damage in the annecy area is consistent with msk intensities of vii viii this earthquake occurred on the vuache fault a geologically well known morphologically clear nw se trending strike slip fault that links the southern jura mountains with the northern subalpine chains the hypocentre was located in mesozoic limestones at shallow depths 1 3 km the focal mechanism indicates left lateral strike slip motion on a n136 e striking plane dipping 70 to the ne abundant field evidence was gathered in the days following the main shock several hundred aftershocks were recorded thanks to the rapid installation of a 16 station seismic network all aftershocks occurred along the southernmost segment of the vuache fault defining a 5 km long 3 5 km deep n130 e striking rupture zone dipping 73 to the ne the fault plane solutions of 60 aftershocks were found to be consistent with left lateral slip on nw se striking planes at the se tip of the aftershock zone we found ground cracks parallel to the fault close to the annecy meythet airport runway at the nw tip near bromines we observed left lateral displacement of concrete walls in a building we also noticed flow changes in two springs close to that locality geodetic levelling across the fault revealed about 1 cm of uplift for the region north of the fault the recording of aftershocks with a six station accelerometric network showed that lacustrine deposits locally amplified the ground motion up to eight times which explains how this moderate magnitude shock could cause such heavy damage historical records draw attention to the central segment of the vuache fault which has been locked for at least 200 years situated nw of the 1996 aftershock zone between the mandallaz and vuache mountains this segment forms a 12 km long potential seismic gap where other m5 events or one single m6 event might occur

erosion driven uplift of the modern central alps abstract we present a compilation of data of modern tectono geomorphic processes in the central european alps which suggest that observed rock uplift is a response to climate driven denudation this interpretation is predominantly based on the recent quantification of basin averaged late holocene denudation rates that are so similar to the pattern and rates of rock uplift rates as determined by geodetic leveling furthermore a gps data based synthesis of adriatic microplate kinematics suggests that the central alps are currently not in a state of active convergence finally we illustrate that the central alps have acted as a closed system for holocene redistribution of sediment in which the peri alpine lakes have operated as a sink for the erosional products of the inner central alps while various hypotheses have been put forward to explain central alpine rock uplift e g lithospheric forcing by convergence mantle processes or ice melting we show with an elastic model of lithospheric deformation that the correlation between erosion and rock uplift rates reflects a positive feedback between denudation and the associated isostatic response to unloading thus erosion does not passively respond to advection of crustal material as might be the case in actively converging orogens rather we suggest that the geomorphic response of the alpine topography to glacial and fluvial erosion and the resulting disequilibrium for modern channelized and associated hillslope processes explains much of the pattern of modern denudation and hence rock uplift therefore in a non convergent orogen such as the central european alps the observed vertical rock uplift is primarily a consequence of passive unloading due to erosion

the diffuse transition between the zagros continental collision and the makran oceanic subduction iran microearthquake seismicity and crustal structure summary the nature of the transition between the zagros intra continental collision and the makran oceanic subduction is a matter of debate either a major fault cutting the whole lithosphere or a more progressive transition associated with a shallow gently dipping fault restricted to the crust microearthquake seismicity located around the transition between the transition zone is restricted to the west of the jaz murian depression and the jiroft fault no shallow micro earthquakes seem to be related to the nnw sse trending zendan minab palami active fault system most of the shallow seismicity is related either to the zagros mountain belt located in the west or to the ns trending sabzevaran jiroft fault system located in the north the depth of microearthquakes increases northeastwards to an unusually deep value for the zagros of 40 km two dominant types of focal mechanisms are observed in this region low angle thrust faulting mostly restricted to the lower crust and strike slip at shallow depths both consistent with ns shortening the 3 d inversion of p traveltimes suggests a high velocity body dipping northeastwards to a depth of 25 km this high velocity body probably related to the lower crust is associated with the deepest earthquakes showing reverse faulting we propose that the transition between the zagros collision and the makran subduction is not a sharp lithospheric scale transform fault associated with the zendan minab palami fault system instead it is a progressive transition located in the lower crust the oblique collision results in partial partitioning between strike slip and shortening components within the shallow brittle crust because of the weakness of the pre existing zendan minab palami faults

reappraisal of hypothetical franciscan thrust wedging at coalinga implications for tectonic relations along the great valley flank of the california coast ranges 1 correlation of the character and orientation of seismic reflectors imaged on profiles across the coalinga anticline with known surface geology indicates that local franciscan thrust wedging favored for past geodynamic interpretations of the 1983 coalinga earthquake is an untenable hypothesis the inference that a subhorizontal detachment surface of simple shear is present beneath the anticline is consequently unnecessary and unlikely in view of the coherent areal pattern of wrench folding within the southern diablo range elsewhere along the structural front of the california coast ranges at the western flank of the great valley interpretations of similar thrust wedging based in part on analogy with supposed structural relations at coalinga are equally questionable in a wider context the seismogenic behavior of blind thrust and reverse faults in california cannot be interpreted with the invalid concept of thrust wedging at coalinga as a guiding template for geotectonic interpretations

dating incipient metamorphism using 40 ar 39 ar geochronology and xrd modeling a case study from the swiss alps six samples of a single carbonate rich unit of the swiss prealpes progressively metamorphosed from diagenesis to deep anchizone yield 40ar 39ar spectra with variably developed staircase patterns consistent with mixtures of detrital mica and neocrystallized mixed layer illite smectite the lowest temperature heating steps for different size fractions 2 6 m and 6 20 m converge to 40 ma providing an imprecise maximum age of regional metamorphism a method is described for distinguishing and quantifying the amount of pre existing detrital mica versus neoformed illite layer in the illite smectite formed during tertiary alpine metamorphism by comparison of x ray diffraction patterns with newmod simulations in the least metamorphosed samples the illite smectite contains 65 neoformed illite and this illite accounts for approximately 17 of all dioctahedral phyllosilicate minerals in the rock e g detrital mica and illite smectite in contrast the illite smectite from the more strongly metamorphosed samples contains 97 neoformed illite which accounts for 70 to 90 of all dioctahedral phyllosilicate minerals phyllosilicate morphologies viewed by scanning electron microscopy are consistent with these estimates a process of dissolution reprecipitation is inferred as a mechanism for the growth of the neoformed phyllosilicates a plot of neoformed illite content versus 40ar 39ar total fusion age yields a near linear curve with an extrapolated age of 27 ma for 100 neoformed dioctahedral phyllosilicates this age is interpreted as the time of incipient metamorphism and is consistent with independent biostratigraphic constraints model 40ar 39ar age spectra constructed with the xrd simulation results correspond well to the experimental data and illustrate the changes in degassing properties of progressively metamorphosed mixtures of detrital mica and neoformed illite

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

syntectonic fluid flow and deformation mechanisms within the frontal thrust of a foreland fold and thrust belt example from the internal jura eastern france abstract structural mapping and microstructural analyses are combined with stable clumped and radiogenic isotopes to unravel deformation mechanisms and syntectonic fluid flow during upward propagation along the frontal thrust fuans thrust of the internal part of the jura fold and thrust belt the fuans thrust cuts through upper jurassic lower cretaceous carbonate deposits branches into two splays and generates a system of fault propagation folds folding was accomodated by layer parallel shortening and layer parallel shear which generated flexural slip along bedding surfaces stylolites and foliated fabric in marly limestone interbeds thrusting was characterized by cycles of mutually overprinting pressure solution and brittle processes such as frictional sliding and fracturing veining this generated foliated tectonites in marls and limestones without significant cataclasis of the host rock pressure solution and micrometer slip along slickenfibers are evidence of aseismic slip in agreement with the ongoing aseismic growth of anticlines in the jura fold and thrust while crackle like vein texture may account for episodic seismic fracturing geochemical data show that fuans thrust acted as a conduit for the downward infiltration of meteoric derived fluids which channeled along foliated tectonites during syntectonic fluid flow calcite mineralizations precipitated at temperatures between 54 c and 10 c showing an increased contribution of organic carbon from soils in colder paleofluids this indicates a progressive opening of the system characterized by a more efficient and extensive meteoric fluids circulation considering the highest recorded temperature of 54 c and assuming the modern geothermal gradient of 30 c km thrusting in the study outcrop initiated at a burial depth of at least 1 4 km

subduction of continental crust in the western alps as a result of recent deep reflection and refraction seismology the crustal structure of the western alps is now quite well defined however this raises the question of what is present below the moho such as a crustal eclogitic root this study attempts to estimate the volume of this eclogitic root on the basis of palinspastic reconstructions even with a minimum estimate of the crustal material involved in the subduction processes which took place during the alpine orogeny a significant eclogitized crustal root must be present down to depths of around 100 km below the po plain a maximum estimate suggests that a large part of this root could now be recycled in the asthenosphere

3d effects of strain vs velocity weakening on deformation patterns in accretionary wedges abstract shear zones are weaker than surrounding rocks whether weakening depends on accumulated strain or strain rate is debated we used a three dimensional numerical code with a visco plastic brittle rheology to investigate the influence of strain and strain rate weakening often referred to as velocity weakening on the evolution of thin skinned fold and thrust belts two model setups are used i a uniform setup to recognize the effects of each weakening mode on the structural evolution and dynamics of fold and thrust belts and ii a dual setup with two adjacent domains of decollement strength to investigate the structural response of laterally varying systems strain weakening and velocity weakening lead to remarkably different structural patterns in particular strain weakening favours out of sequence shear zones whilst some amount of finite plastic strain has to be achieved before the structural development initiates weakening in contrast velocity weakening starts with the onset of high strain rate bands and does not favour out of sequence deformation we also tested separately the influences of shortening velocity cover sequence thickness and weakening style and amount on the structural evolution of the dual systems the shortening velocity has a minor effect in strain weakened models velocity weakening and a thinner cover sequence enhance the occurrence of strike slip shear zones we conclude that the weakening mode strongly influences the fault patterns and the dynamics of thrust wedges inversely natural fault patterns are keys to discriminate weakening processes

active tectonism in the central alps contrasting stress regimes north and south of the rhone valley an integrated interpretation of seismicity fault plane solutions and deep seismic reflection data suggests that the ne sw to nw se trending rhone simplon fault zone and the gently s dipping basal penninic thrust separate fundamentally different stress regimes in the western swiss alps north of the rhone simplon fault zone strike slip earthquakes on steep dipping faults within the helvetic nappes are a consequence of regional nw se compression and ne sw extension to the south vertical maximum stress and n s extension are responsible for normal mechanism earthquakes that occur entirely within the penninic nappes above the basal penninic thrust such normal faulting likely results from extension associated with southward movements collapse of the penninic nappes and or continued uplift and relative northward displacements of the underlying alpine massifs geological mapping and fission track dating suggest that the two distinct stress regimes have controlled tectonism in the western swiss alps since at least the neogene

interactions between tectonics erosion and sedimentation during the recent evolution of the alpine orogen analogue modeling insights 1 on the basis of a section across the northwestern alpine wedge and foreland basin analogue modeling is used to investigate the impact of surface processes on the orogenic evolution the basis model takes into account both structural and lithological heritages of the wedge during shortening erosion and sedimentation are performed to maintain a critical wedge frontal accretion leads to the development of a foreland thrust belt underplating leads to the formation of an antiformal nappe stack in the internal zones important volumes of analogue materials are eroded out of the geological record which in the case of the alps suggests that the original lengths and volumes may be underestimated the foreland basin evolves differently depending on the amounts of erosion sedimentation its evolution and internal structuring is governed by the wedge mechanics thought to be the main controlling mechanism in the development of the molasse basin in a feedback interaction with surface processes

three dimensional interface modelling with two dimensional seismic data the alpine crust mantle boundary summary we present a new approach to determine the 3 d topography and lateral continuity of seismic interfaces using 2 d derived controlled source seismic reflector data the aim of the approach is to give the simplest possible structure consistent with all reflector data and error estimates we define simplicity of seismic interfaces by the degree of interface continuity i e shortest length of ovsets and by the degree of interface roughness least surface roughness the method is applied to structural information of the crust mantle boundary moho obtained from over 250 controlled source seismic reflection and refraction profiles in the greater alpine region the reflected and refracted phases from the moho interface and their interpretation regarding crustal thickness are reviewed and their reliability weighted weights assigned to each reflector element are transformed to depth errors considering fresnel volumes the 2 d derived reflector elements are relocated in space 3 d migration and interpolation is performed between the observed reflector elements to obtain continuity of model parameters interface ovsets are introduced only where required according to the principle of simplicity the resulting 3 d model of the alpine crust mantle boundary shows two ovsets that divide the interface into a european an adriatic and a ligurian moho with the european moho subducting below the adriatic moho and with the adriatic moho underthrusting the ligurian moho each sub interface depicts the smoothest possible i e simplest surface fitting the reflector data within their assigned errors the results are consistent with previous studies for those regions with dense and reliable controlledsource seismic data the newly derived alpine moho interface however surpasses earlier studies by its lateral extent over an area of about 600 km by 600 km by quantifying reliability estimates along the interface and by obeying the principle of being consistently as simple as possible

interaction of folding and thrusting during fold and thrust belt evolution insights from numerical simulations and application to the swiss jura and the canadian foothills abstract we use two dimensional numerical simulations to investigate the interaction of folding buckling and thrusting localized shearing during the structural evolution of fold and thrust belts ftb we model layer parallel shortening of mechanically strong layers resting above a weaker layer referred to as detachment we consider a viscoplastic rheology with linear viscosity and frictional plastic drucker prager yield criterion the detachment thickness is larger in one model half and only this geometrical thickness perturbation triggers folding and thrusting in the simulations we conduct a systematic analysis to quantify the impact of model parameters such as magnitude of the thickness perturbation or detachment rheology frictional or viscous on the ftb evolution the magnitude of the perturbation determines whether or not folding is favoured over thrusting and hence controls the progressive interaction of folding and thrusting during ftb evolution the asymmetry of modelled anticlines is proportional to the relative height of the initial perturbation we also adapt the model configuration to specific mechanical stratigraphies of two regions in natural ftb namely the haute chaine of the jura mountains switzerland and the foothills of alberta canada the modelled fold and thrust geometries agree with different types of observed anticlinal structures such as symmetric detachments folds and asymmetric thrust folds our results suggest that an initial stage of low amplitude buckling likely occurred prior to the main folding and thrusting phase we argue that folding and thrusting are equally important and interacting processes during the structural evolution of many natural ftb

late quaternary folding in the jura mountains evidence from syn erosional deformation of fluvial meanders the present tectonic activity of the jura fold and thrust belt is a matter of scientific debate at its north western front differentially uplifted palaeo meanders of the doubs river record late quaternary growth of the citadelle anticline associated with a minimum rock uplift of 13 m local rock uplift rates estimated from optical stimulated luminescence dating of oxbow lake deposits measure 0 17 0 05 mm per annum reconstruction of the deformation history reveals that buckling took place simultaneously with focused pleistocene river incision the structural geomorphic and temporal setting suggests that active deformation could possibly be sustained by incision related erosion these observations shed new light on the modes of recent deformation in the jura mountains and on the present day dynamics of the alpine orogenic front

arcuate thrust systems in sandbox experiments a comparison to the external arcs of the western alps in the external western alps two regional structural arcs were generated during tertiary northwest directed collision between the apulian indenter and the european passive margin these arcs distinguished by their geographic position and their age are examined by using a new compilation of structural data and comparing these to the results of sandbox analogue experiments the principal western alpine arc comprises two orthogonal synchronous thrust systems in the late eocene early miocene major shortening 105 km was toward the northwest to west northwest and minor shortening 11 km was toward the southwest shortening in each branch decreased toward the core of the arc during the late miocene and pliocene the jura arc accommodated 35 km of northwest directed shortening while 10 5 km of southwest to south southwest directed shortening was accommodated on the digne thrust system sandbox experiments were used to investigate the role of the motion vector of a rigid rectangular indenter orthogonal diagonal curved or rotational paths and the mechanical stratigraphy of the foreland in the evolution of upper crustal arcuate systems e g presence of a basal easy slip silicone horizon comparison of experimental results with the external alpine arc suggests that the indenter followed a slightly diagonal path with respect to the european margin from the eocene to the early miocene and curved counterclockwise by 10 15 in the middle miocene mechanical stratigraphy experiments support the hypothesis that thick triassic evaporites played a primary role in the evolution of the jura arc the influence of mechanical stratigraphy was most prominent during weak deformation at the external boundaries of the alpine orogen jura fold and thrust belt digne thrust

near field transpressive deformation along the san andreas fault zone in southern california based on exhumation constrained by u th he dating low temperature thermochronometry reveals that a narrow crustal sliver trapped within strands of the san andreas fault zone in southern california has experienced recent rapid exhumation eight apatite u th he ages from a 1 km relief section along yucaipa ridge in the san bernardino mountains range from 1 4 to 1 7 ma the minimal change in age with elevation implies exhumation of 5 7 mm yr 1 sustained for at least several hundred thousand years three titanite helium ages from the ridge are much older ranging from 57 to 82 ma these show a steep gradient with elevation representing either an exhumed partial retention zone or slow cooling through much of the tertiary these data imply that a total exhumation of 3 to 6 km has occurred since 1 8 ma it is uncertain whether this exhumation terminated as early as 1 ma or has continued up to the present at a decelerated rate we surmise that this exhumation represents rock uplift in the absence of major surface uplift in that it kept pace with tectonic uplift as the narrow fault block maintained steady state relief the record of sedimentation in adjacent basins is consistent with the implied magnitude of erosion such rapid large magnitude exhumation within the strands of the san andreas fault zone is important for models of transpressional tectonics it is consistent with a strain partitioning model which predicts that pure shear dominated fault zones experience significant vertical strain however it is inconsistent with a stress partitioning model which predicts that fault zone weakness limits pure shear deformation to the borderlands of the master strike slip fault in addition a concentration of secondary contraction within the fault zone may require modification of coupling models between strong upper mantle and brittle upper crust via the weak lower crust these models predict that transpressional deformation will either be uniformly distributed across the plate boundary or be limited to the far field borderlands rather than concentrated in the near field alternatively the exhumation of yucaipa ridge may have been driven by the nearby restraining bend in the san andreas fault at san gorgonio pass in which case it represents local fault geometry rather than accommodation of far field plate motion

style and magnitude of tectonic shortening normal to the san andreas fault across pyramid hills and kettleman hills south dome california a blind thrust zone and the overlying fold forming the kettleman hills south dome were produced by late cenozoic shortening normal to the san andreas fault west of kettleman hills toward the san andreas fault the region of pyramid hills experienced structural growth as early as late cretaceous time and growth accelerated in pliocene to holocene time these structures were imaged to a depth of 7 km by reprocessing a seismic reflection record section restored structural cross sections indicate a three stage growth history for kettleman hills south dome 1 late miocene reverse faulting 2 pliocene fault propagation type folding and 3 late pliocene to holocene tectonic wedge emplacement late pliocene to holocene structural growth at pyramid hills probably resulted from thrust emplacement of the franciscan complex a forward model demonstrates that tectonic wedging could account for post 2 5 ma deformation of pyramid hills and kettleman hills south dome horizontal shortening across pyramid hills and kettle man hills south dome normal to the san andreas fault since the cretaceous period is 3 7 km this figure does not include shortening within the basement adding shortening of our tectonic wedge model yields 7 9 km of shortening since cretaceous time post 2 5 ma shortening determined by our tectonic wedge model is 6 3 km the rate of post 2 5 ma shortening 2 5 mm yr when added to that on the west side of the san andreas fault is consistent with the values derived from plate motion models that describe the san andreas discrepancy

structure deformation and strength of the loma prieta fault northern california usa as inferred from the 1989 1990 loma prieta aftershock sequence analysis of aftershock focal mechanisms of the october 1989 m 7 1 loma prieta earthquake reveals details of structure and deformation aftershocks below 4 6 km define an alignment plane oriented 131 65 this alignment includes three planar segments defining a restraining bend in a blind strike slip fault dextral strike slip dominates in the south and reverse dextral slip dominates in the north a distribution similar to slip during the main shock above this fault dominantly reverse faults striking roughly 110 lie en echelon along the main fault trend in the 17 sets of spatially clustered aftershocks a more complex substructure is defined by local planar hypocenter alignments and by preferred orientations of aftershock shear planes the maximum shortening axes make angles with the normal to these planes that average 46 and 53 respectively these angles are incompatible with a weak fault for which 0 20 orientations of preferred aftershock shear planes resemble riedel shears relative to local hypocenter alignment planes the similarity of slip distributions inferred from the aftershock inversions and from the main shock implies that the stress drop during the main shock was incomplete and thus that the loma prieta fault is not unusually weak triaxial brittle deformation is partitioned into a pair of plane strains rotated relative to each other about a common principal axis the shape of the triaxial strain ellipsoid determines the angle of rotation evidence supports our micropolar model of brittle deformation which predicts that the antisymmetric part of the seismic moment tensor records effects of block rotations

mesozoic episodic magmatism in south korea and its tectonic implication 1 ne trending granitoid batholiths in south korea are part of the huge phanerozoic granitoid belt in east asia the crystallization ages of granitoid plutons show three episodes of mesozoic magmatism in south korea triassic 248 210 ma jurassic 197 158 ma and late cretaceous early tertiary 110 50 ma with a late jurassic early cretaceous 50 m y hiatus the granitoid ages and kinematic analyses of the mesozoic structures in south korea suggest that the middle jurassic 180 170 ma dextral strike slip ductile shear zones formed by the northwest orthogonal subduction of the izanagi plate whereas the cretaceous sinistral faults formed by the northward oblique subduction of the same plate which generally agree with proposed reconstruction of plate motions albeit uncertain around east asia among the models proposed to explain magmatic lull in a continental arc shallow angle subduction associated with high convergence rate and subduction of oceanic plateaus might be the probable cause for the magmatic hiatus in south korea and japan the huge width 500 km of the east asian granitoid belt may be explained by oceanward retreat of subduction zone in the cretaceous in association with change in the movement direction of the subducting plate

subsurface geometry of the san andreas calaveras fault junction influence of serpentinite and the coast range ophiolite while an enormous amount of research has been focused on trying to understand the geologic history and neotectonics of the san andreas calaveras fault saf cf junction fundamental questions concerning fault geometry and mechanisms for slip transfer through the junction remain we use potential field geologic geodetic and seismicity data to investigate the 3 d geologic framework of the saf cf junction and identify potential slip transferring structures within the junction geophysical evidence suggests that the san andreas and calaveras fault zones dip away from each other within the northern portion of the junction bounding a triangular shaped wedge of crust in cross section this wedge changes shape to the south as fault geometries change and fault activity shifts between fault strands particularly along the calaveras fault zone cfz potential field modeling and relocated seismicity suggest that the paicines and san benito strands of the cfz dip 65 to 70 ne and form the southwest boundary of a folded 1 to 3 km thick tabular body of coast range ophiolite cro within the vallecitos syncline we identify and characterize two steeply dipping seismically active cross structures within the junction that are associated with serpentinite in the subsurface the architecture of the saf cf junction presented in this study may help explain fault normal motions currently observed in geodetic data and help constrain the seismic hazard the abundance of serpentinite and related cro in the subsurface is a significant discovery that not only helps constrain the geometry of structures but may also help explain fault behavior and the tectonic evolution of the saf cf junction

impact of erosion and decollements on large scale faulting and folding in orogenic wedges analogue models and case studies deformation mechanisms long term kinematics and evolution of fold and thrust belts subjected to erosion are studied through 2d analogue experiments involving large convergence first order parameters tested include 1 decollements and or plastic layers interbedded at different locations within analogue materials and 2 synconvergence surface erosion weak layers depending on their location in the model favour deformation partitioning characterized by the simultaneous development of underplating domains in the inner part of the wedge basal accretion and frontal accretion where the wedge grows forward interaction between tectonics and surface processes influences this behaviour development of antiformal thrust stacks controlled by underplating shows small and large scale cyclicity thin plastic layers induce folding processes which are studied at wedge scale recumbent and overturned folds with large inverted limbs develop in a shear induced asymmetric deformation regime via progressive unrolling of synclinal hinges surface erosion and underplating at depth induce further rotation passive tilting and horizontalization of fold limbs model results give insights to discuss the mechanisms responsible for the large scale structures i e antiformal nappe stacks klippen and kilometre scale recumbent fold nappes encountered in several mountain belts such as the montagne noire french massif central the galicia variscan belt spain and the northern apennines italy supplementary material raw data of the experiments are available at www geolsoc org uk sup18658

fault strength and transpressional tectonics along the castle mountain strike slip fault southern alaska analyses of structures along the castle mountain fault reveal the mechanical relations and relative timing of orogen parallel strike slip faulting to distributed wrenching and shortening and to plate motion in the southern alaskan transpressive margin the castle mountain fault is a 200 km long orogen parallel right lateral seismogenic fault in the southern alaskan plate margin exposures of the fault in the study area have been exhumed from 3 4 km depth and 80 c moment tensor summations and stress inversions of slip data from fault networks within 400 m of the castle mountain fault and analyses of structures in forearc deposits 2 4 km from the fault yield maximum incremental shortening and maximum compressive stress 1 axes that are subhorizontal and trend 325 this trend is close to the 340 north american pacific plate convergence direction the inferred 1 makes a 70 80 angle with the 070 striking castle mountain fault indicating that the fault slips at a lower shear stress than predicted by laboratory rock friction experiments if hydrostatic pore pressure exists in the fault i e coefficient of friction 0 85 byerlee9s law the forearc structures record coaxial strain and apparently remain in their formative orientations showing that previously documented distributed shearing in the form of vertical axis block rotations in the forearc ceased prior to formation of the structures in late oligocene time the mechanical weakness of the castle mountain fault probably results in part from its clay rich gouge which averages about 43 wt clay phases however the gouge composition does not account for slip in response to 1 at 70 80 to the fault another mechanism such as elevated pore pressure further weakens the fault and enables it to slip right laterally in response to the small component of oblique motion across the plate boundary upon its inception in early tertiary time the fault could not have formed a 200 km long planar zone of low friction clay rich gouge or elevated pore pressure thus the mechanisms that weaken it must have developed over time the distributed shearing in the forearc may have ended in response to the weakening and localization of dextral slip onto the castle mountain fault

cenozoic evolution of the mojave block of southern california the recorded cenozoic history of the mojave desert region of southern california began in the latest oligocene when intense volcanism and tectonism interrupted a long early tertiary silence volcanism commenced across the region in an east west band ca 24 22 ma northwest of barstow volcanism was accompanied by intense crustal extension and development of a metamorphic core complex outside of this relatively restricted area extension was minor or absent after extension ceased ca 18 ma volcanism shifted to small volume eruptions of basalt post extensional deformation has largely been by strike slip faulting along northwest striking dextral faults and west striking sinistral faults and total dextral slip across the mojave desert region since the early miocene is 45 60 km strike slip deformation has been overprinted locally by intense north south contraction that is the dominant style of deformation in the western mojave block paleomagnetic data indicate that parts of the mojave block were rotated clockwise although the magnitude and timing of this rotation are poorly determined the best evidence for large 45 rotation comes from the area east of barstow where large clockwise declination anomalies and mesozoic and cenozoic dikes with anomalous strikes may reflect early miocene clockwise deflection along the mojave river fault volcanism and tectonism in the mojave block resulted from interactions among the north american pacific and various oceanic plates patterns of volcanism and tectonism do not correlate with growth of slab windows beneath the continent but do correlate with the position of the subducted mendocino fracture zone plate circuit reconstructions suggest that the driving force for extension was divergence between the pacific and north american plates along the transform margin that separated the two this hypothesis accounts for the direction magnitude and rate of extension in the mojave block

uncertainties and implications of the late cretaceous and tertiary position of north america relative to the farallon kula and pacific plates we present updated global plate reconstructions and calculated uncertainties of the pacific kula and farallon vancouver plates relative to north america for selected times since 68 ma improved magnetic data from the indian ocean decrease the uncertainties in the global plate circuit approach these uncertainties are now considerably smaller than those inherent in equivalent reconstructions based on the assumption of fixed hotspots major differences between these results and those of others are due to our use of more detailed africa north america reconstructions separate vancouver and farallon plate reconstructions and the assumption of a rigid antarctica plate during cenozoic time the uncertainties in the relative positions of the pacific and north america plates since the time of anomaly 7 26 ma range up to 100 km in position or from 1 to 3 m y in time if the mendocino triple junction initiated at about 28 5 ma its position would have been at 31 3 n 130 km relative to fixed north america unacceptable overlap of oceanic crust of the pacific plate with continental crust of western north america in the anomaly 10 30 ma reconstruction is a minimum of 340 200 km along an azimuth of n60 e and may be accounted for by basin and range extension pacific north america displacement in the past 20 ma is found to be considerably less than that calculated by fixed hotspot reconstructions farallon vancouver north america convergence velocity decreased greatly between the times of anomalies 24 and 21 56 to 50 ma prior to the 43 ma age of the hawaiian emperor bend and the often quoted 40 ma end of the laramide orogeny a change in direction of farallon north america convergence occurred sometime between 50 and 42 ma and also may not correlate with the time of the hawaiian emperor bend the lack of data from subducted parts of the farallon and kula plates permits many possibilities regarding the position of the kula farallon ridge the age of subducted crust or the position of oceanic plateaus during the laramide orogeny leaving open the question of the relationship between plate tectonic scenarios and tectonic style during laramide time displacements of points on the various oceanic plates along the west coast of an arbitrarily fixed north america during the interval between anomalies 30 31 and 18 68 to 42 ma are found to be pacific plate 1700 200 km northward farallon plate 3200 400 km northeastward vancouver plate 3000 400 km northeastward kula plate if attached to the pacific plate after a24 time 2500 400 km northward

linking the northern alps with their foreland the latest exhumation history resolved by low temperature thermochronology the evolution of the central alpine deformation front subalpine molasse and its undeformed foreland is recently debated because of their role for deciphering the late orogenic evolution of the alps its latest exhumation history is poorly understood due to the lack of late miocene to pliocene sediments we constrain the late miocene to pliocene history of this transitional zone with apatite fission track and u th he data we used laser ablation inductively coupled mass spectrometry for apatite fission track dating and compare this method with previously published and unpublished external detector method fission track data two investigated sections across tectonic slices show that the subalpine molasse was tectonically active after the onset of folding of the jura mountains this is much younger than hitherto assumed thrusting occurred at 10 8 6 5 ma and potentially thereafter this is contemporaneous with reported exhumation of the external crystalline massifs in the central alps the jura mountains and the subalpine molasse used the same detachments as the external crystalline massifs and are therefore kinematically coupled estimates on the amount of shortening and thrust displacement corroborate this idea we argue that the tectonic signal is related to active shortening during the late stage of orogenesis

architecture and kinematics of the constance frick trough northern switzerland implications for the formation of post variscan basins in the foreland of the alps and scenarios of their neogene reactivation post variscan basins are commonly inferred to represent important precursor structures of later extensional and contractional tectonic events in the foreland of the european alps nevertheless their structural characteristics are typically poorly constrained our investigation sheds new light on the architecture and kinematics of the constance frick trough cft in northern switzerland according to our analysis of an extensive and revised 2 d reflection seismic data set the ene wsw striking cft is divided into an eastern segment and a western segment characterized by opposing half graben geometries the transition between the two segments coincides with the prolongation of a preexisting wnw ese trending strike slip fault zone exposed in the adjacent black forest massif to the north field based analysis of outcrop scale faults in the latter area implies that the minimum horizontal stress during the formation of the cft was roughly oriented ne sw which is oblique to the trough axis while previously published analogue models imply that some characteristics of the cft could be explained by lateral linkage of graben segments under oblique extension the pronounced half graben geometry of the cft suggests that low angle normal faulting may also have contributed to trough formation the observed structural complexities of the cft and uncertainties regarding its deep structure must be taken into account for interpretations of similar late paleozoic basins inferred in the subsurface of the northern alpine foreland basin in particular concerning scenarios of their neogene reactivation during alpine orogeny

ontong java plateau and late neogene changes in pacific plate motion aided by a new geometrical technique called hot spotting we recently proposed a new model for the absolute motion of the pacific plate this model called wk97 assumed the hawaiian hotspot is under loihi and that there was a change in plate motion at 3 6 ma the model located the louisville hotspot close to the hollister ridge a shallow volcanic ridge associated with a geoid high seismicity and recent volcanism most of the tectonic implications of wk97 however were not addressed furthermore although several recent studies suggest that the geochemistry of hollister lavas may indicate a mixture between louisville melt material and pacific antarctic ridge mid ocean ridge basalt these studies strongly disagree with wk97 and consider it seriously flawed here we discuss numerous tectonic predictions of wk97 and present a large amount of observational evidence in support of it we find that a late neogene collision between the ontong java plateau and the northern margin of the australia plate appears to have altered the motion of the pacific plate as inferred from hotspot volcanism by forcing it to rotate counter clockwise this rotation about a low latitude pole appears to have induced right lateral shear stress along the entire pacific plate divergent boundary which resulted in the formation of extensional transform faults microplates and propagating ridges this change in motion also appears to have triggered concomitant circum pacific tectonism including trench migration and back arc rifting the wk97 suggests that long lived plume fed volcanism on the pacific plate appears very limited perhaps only to five to six hotspots hawaii louisville cobb caroline and perhaps marquesas and bowie the geometry of these chains are consistent with our model despite some evidence for volcanic age progressions most other pacific neogene hotspots are most likely crack spots i e sites of extensional volcanism at preexisting zones of weakness reactivated by plate stresses indeed several volcanic ridges such as hollister ridge near the louisville hotspot appear to have formed in response to stresses following the change in absolute plate motion wk97 also obviates the need for simultaneous different directions of mantle flow in the south central pacific transpression at the san andreas and alpine strike slip faults and aleutian arc explosivity since 6 ma also appear to be consequences of the changes in pacific plate motion furthermore both the wk97 model and observed relative plate motions suggest that adjoining plates have changed their absolute motions as well and that large changes in absolute plate motion do not necessarily imply large changes in relative plate motion our findings support slab pull as the dominant plate tectonic driving force highlight the rheological difference between strong oceanic lithosphere and weak continental crust and suggest that wk97 presently provides a unifying albeit preliminary framework for relating both intraplate and circum pacific tectonism and volcanism in the late neogene

fault slip analysis of quaternary faults in southeastern korea abstract the quaternary stress field has been reconstructed for southeast korea using sets of fault data the subhorizontal direction of the maximum principal stress 1 trended ene and the direction of the minimum principal stress 3 was nearly vertical the stress ratio 2 3 1 3 value was 0 65 two possible interpretations for the stress field can be made in the framework of eastern asian tectonics 1 the hmax trajectory for southeast korea fits well with the fan shaped radial pattern of maximum principal stress induced by the india eurasia collision thus we suggest that the main source for this recent stress field in southeast korea is related to the remote india eurasia continental collision 2 the stress field in korea shows a pattern similar to that in southwestern japan the origin for the e w trending hmax in japan is known to be related to the mantle upwelling in the east china sea thus it is possible that quaternary stress field in korea has evolved synchronously with that in japan we suggest further studies gps and in situ stress measurement to test these hypotheses

lower cretaceous to eocene sedimentary transverse ridge at the romanche fracture zone and the opening of the equatorial atlantic abstract a transform parallel transverse ridge runs for several hundred kilometers along the northern side of the romanche fracture zone rfz being most prominent opposite to the eastern mid atlantic ridge transform intersection rti seismic reflection profiles and rock sampling indicate that the western part of the transverse ridge is made of uplifted slivers of oceanic lithosphere in contrast the eastern part east of the rti consists of a thick 4 km sedimentary succession affected by faulting and thrusting we call it the romanche sedimentary sequence rss if this sedimentary sequence were underlain by oceanic crust its predicted age should be not more than 60 ma however dolomitized maiolica type pelagic limestones containing calpionellids of early cretaceous age 140 ma were sampled from the rss in addition to paleocene eocene quartzs and stones siltstones claystones diatomites and limestones we present a description of the rock samples and a reconstruction of their environment of deposition and of their age the rss may represent material deposited during initial continent continent transform motion in a narrow deep e w elongated basin that communicated with the central atlantic the rss was later subjected to transpression and uplift due to transform related tectonics gabbros but not basalts were sampled from the igneous basement underlying the rss it is not clear whether the rss overlies oceanic crust or some sort of pre oceanic northern red sea type crust the presence of lower cretaceous pelagic deposits near the romanche eastern rti implies an age for the initial stage of the opening of the equatorial atlantic older than the generally assumed aptian albian

thick skinned tectonics and basement involved fold thrust belts insights from selected cenozoic orogens defining the structural style of fold thrust belts and understanding the controlling factors are necessary steps towards prediction of their long term and short term dynamics including seismic hazard and to assess their potential in terms of hydrocarbon exploration while the thin skinned structural style has long been a fashionable view for outer parts of orogens worldwide a wealth of new geological and geophysical studies has pointed out that a description in terms of thick skinned deformation is in many cases more appropriate this paper aims at providing a review of what we know about basement involved shortening in foreland fold thrust belts on the basis of the examination of selected cenozoic orogens after describing how structural interpretations of fold thrust belts have evolved through time this paper addresses how and the extent to which basement tectonics influence their geometry and their kinematics and emphasizes the key control exerted by lithosphere rheology including structural and thermal inheritance and local regional boundary conditions on the occurrence of thick skinned tectonics in the outer parts of orogens

localized versus distributed shear in transform plate boundary zones the case of the dead sea transform in the jericho valley 1 continental transform plate boundaries are typically either localized along a single usually segmented major fault or distributed over a broad deformation zone in the latter shear is partitioned between major strike slip faults and intervening often rotating fault systems analog and numerical simulations suggest that such internal fault systems evolve and may be localized or delocalized depending on strain and fault zone strength this paper examines the degree and evolution of shear localization in the jericho valley section of the dead sea transform dst which is part of the africa arabia plate boundary in this section the current breadth of the transform valley and its penetrative strain field are difficult to reconcile with localized shear we integrate newly acquired high resolution reflection data reprocessed exploration reflection data both focused to 2 5 3 5 km depth relatively relocated earthquake epicenters and fault plane solutions based on p wave first arrivals and suggest reinterpretations for previously published structural and seismic data in the jericho valley and the northern dead sea basin it is found that shear in this section of the dst evolved from an early probably miocene pliocene stage of localized strike slip motion primarily along the jericho fault to a late stage pliocene recent when shear has been distributed over internal fault sets that apparently lean against a major eastern dst segment in the early stage the jericho fault formed the western boundary of a deep narrow probably pull apart basin filled by fluvial clastics and evaporites this is overlain by the late stage broad basin characterized by low energy deposition of lacustrine and fluvial sediments pliocene rock salt has apparently utilized the jericho fault zone as a conduit for diapirism causing the uplift normal faulting and surface deformation of late pleistocene and holocene sediments currently observed along the 15 km long jericho lineament on the basis of the currently observed dextral normal motion across the internal nne ne trending fault system counterclockwise rotation is expected to have occurred within the transform zone these tectonic and depositional changes were probably associated with onset of transtension across the dst related to the previously postulated shift of the africa arabia euler pole of rotation in the pliocene

systematic variations in stress state in the southern san joaquin valley inferences based on well bore data and contemporary seismicity analysis of stress induced well bore breakouts in 35 wells from 10 production fields in the southern san joaquin valley ssjv indicates systematic spatial variations in the direction of the maximum horizontal stresses at three different scales first the regional northeast southwest compressional stress direction seen along the western margin of the san joaquin valley in the elk hills kettleman hills and coalinga areas gradually changes to approximately north south compression over a distance of 10 20 km in the ssjv this major excursion in the stress field seen in the yowlumne yowlumne north paloma and rio viejo production fields represents an approximately 40 counterclockwise rotation in the direction of the maximum horizontal stress shmax th s systematic reorientation is consistent with approximately north south convergence as seen in the local fold axes and reverse faults of pliocene age and younger second at the extreme southern reaches of the ssjv in the san emidio los lobos pleito wheeler ridge and north tejon fields another systematic but localized reorientation in the stress field indicates an abrupt change to an approximately east northeast west southwest compression over a distance of a few kilometers this latter reorientation of shmax stress direction which is inconsistent with the local east west trending fold axes and thrust faults represents a 40 50 clockwise rotation in the stresses this reorientation appears to be limited to production fields located within the inferred hanging w ll of the white wolf fault that ruptured during the 1952 ms 7 8 kern county earthquake inversion of earthquake focal mechanisms of events located below the perturbed stress field indicates approximately north south compression the stress drop associated with the 1952 earthquake may have been responsible for rotating the shmax stress direction from the regional approximately north south to approximately east northeast west southwest in the southernmost ssjv implying that the remote horizontal stresses are comparable in magnitude finally localized stress perturbations observed at the scale of a few meters in several wells may reflect local perturbations in the stress field resulting from slip along small faults penetrated by the borehole knowledge of the nonun formity in the ssjv stress field is important for designing development programs for production fields in terms of borehole stability propagation of hydraulic fractures and fluid transport properties

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

accommodation of transpressional strain in the arabia eurasia collision zone new constraints from u th he thermochronology in the alborz mountains north iran the alborz range of n iran provides key information on the spatiotemporal evolution and characteristics of the arabia eurasia continental collision zone the southwestern alborz range constitutes a transpressional duplex which accommodates oblique shortening between central iran and the south caspian basin the duplex comprises nw striking frontal ramps that are kinematically linked to inherited e w striking right stepping lateral to obliquely oriented ramps new zircon and apatite u th he data provide a high resolution framework to unravel the evolution of collisional tectonics in this region our data record two pulses of fast cooling associated with sw directed thrusting across the frontal ramps at 18 14 and 9 5 7 5 ma resulting in the tectonic repetition of a fossil zircon partial retention zone and a cooling pattern with a half u shaped geometry uniform cooling ages of 7 6 ma along the southernmost e w striking oblique ramp and across its associated nw striking frontal ramps suggests that the ramp was reactivated as a master throughgoing n dipping thrust we interpret this major change in fault kinematics and deformation style to be related to a change in the shortening direction from ne to n nne the reduction in the obliquity of thrusting may indicate the termination of strike slip faulting and possibly thrusting across the iranian plateau which could have been triggered by an increase in elevation furthermore we suggest that 7 6 m y old s directed thrusting predated inception of the westward motion of the south caspian basin

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

dynamics of orogenic wedges and the uplift of high pressure metamorphic rocks subduction accretion complexes can be approximated as wedge shaped continua with a rigid buttress behind and a subducting litho spheric slab beneath thick wedges undergoing prograde metamorphism have a negligible long term yield strength and are likely to exhibit a complex nonlinear viscous rheology such a wedge will tend to deform internally until it reaches a stable configuration in which the gravitational forces generated by the wedge geometry balance the traction exerted on its underside by the subducting slab accretion of material at the wedge front will lengthen the wedge and cause it to shorten internally to regain the stable geometry this shortening will be expressed as late out of sequence thrusting backthrusting and folding conversely underplating of sediment or crustal slices will thicken the wedge which may need to extend internally to regain stability extension will cause listric normal faults that may merge downward into zones of ductile extension continued underplating at depth and compensating extension above provides a mechanism for bringing high p low t metamorphic rocks to upper levels in the rear of the wedge where they are commonly observed many major tectonic boundaries in convergent orogens such as the coast range thrust in the franciscan complex major nappe contacts in the alps and the contact between the nevado filabride and higher betic nappe complexes in the betic cordillera show abrupt increases in metamorphic grade downward across them this is consistent with their origin or reactivation as uplift related extensional structures

a basin modeling and organic geochemistry study in the vallecitos syncline san joaquin basin california abstract the vallecitos syncline is a westerly structural extension of the san joaquin basin the vallecitos oil field comprised of eight separate areas that produce from cretaceous and paleogene reservoirs accounted for 5 4 mmb of oil and 5 6 bcf associated of gas through 2010 however exploration for oil and gas in the vallecitos area is challenging due to structural complexity and limited data the purpose of this study is to evaluate whether source rocks are actively generating petroleum in the vallecitos syncline and to improve our understanding of burial history and timing of hydrocarbon generation we conducted biomarker analysis on twenty two oil samples from the vallecitos syncline source related biomarkers show two genetic groups of oil which originated from two different source rocks these results differ from earlier published interpretations in which the kreyenhagen formation is the only source rock in the vallecitos syncline and suggest that the cretaceous moreno formation in the syncline also is an active source rock stratigraphic evidence and modeling suggest that late cenozoic episodes of erosion due to folding and uplift removed significant overburden on the flanks of the syncline to better understand the petroleum systems and clarify the total active source rocks in the area 2d burial histories were generated through the vallecitos syncline a published cross section through the deepest part of the syncline was selected to conduct thermal history basin evolution and migration analyses the 2d model results indicate that the lower kreyenhagen formation has various maturities within the formation at different locations in the present day syncline the basal part of the kreyenhagen formation is in the dry gas window and maturity decreases away from the central part to the flanks it remains immature along shallow portions of the present day flanks in contrast the basal part of the moreno formation achieved extremely high maturity past the gas generation zone but is in the oil generation zone on the flanks of the syncline at shallow depth all of our geochemical and 2d model results suggest that there are two active source rocks in the vallecitos syncline accordingly we propose that there are two active petroleum systems in the vallecitos syncline

distributed shear rotation and partitioned strain along the san andreas fault central california folds commonly form along transform fault systems in the san andreas strike slip fault two mechanisms of folding have been described that are regarded as incompatible 1 wrench tectonics or distributed shear and 2 strain partitioning shortening being perpendicular to the fault the compatibility and relative importance of these two mechanisms are not well understood in part because folds are the result of lengthy deformation this paper synthesizes paleomagnetic data sedimentary thickness maps fault patterns and seismic reflection profiling data along the san andreas transform fault system that indicate a 20 30 clockwise map view reorientation of pliocene en echelon folds to their present position subparallel to the san andreas fault the folds continue to develop today as a result of shortening perpendicular to the fault folds apparently rotated with continuing strain in the wrench zone and with increasing shortening across the shear zone rotation likely occurred when changing pacific plate motions increased the component of convergence across the fault system this field example documents deformation by these two different mechanisms in the same fold belt which has broad implications for interpreting other fold belts formed in similar settings the geologic record suggests that the opposing theories of wrench deformation and strain partitioned shortening perpendicular to the fault are both important and compatible processes that act at different times and places

present day and future tectonic underplating in the western swiss alps reconciliation of basement wrench faulting and decollement folding of the jura and molasse basin in the alpine foreland abstract the western alps form a geodynamically active mountain belt showing the typical features of an evolving orogenic wedge with its pro wedge geometry to the nnw and its retro wedge structures to the sse renewed tectonic underplating of european continental crust occurred after the orogenic wedge underwent major dynamic disequilibrium following the break off of the southward subducting slab of the european passive margin the most important of these basement imbricates are the mont blanc aiguilles rouges and gastern aar crystalline massifs also forming the alps highest mountains the upper plate present day orogenic wedge of the western alps includes the molasse basin and the jura fold and thrust belt both decoupled from the basement over a basal decollement surface the overall geometry of this wedge appears to be strongly unstable according to simple wedge models in its attempt to regain stability out of sequence thrusts form in the existing basement nappes but also new basement nappes should develop beneath the southern portion of the molasse basin new out of sequence thrusts in the cover trigger higher than average uplift rates concentrated around the newly forming structures and are accompanied by a concentration of earthquakes tectonic underplating is further corroborated by neotectonics and the tectonic structures observed in the prealpes molasse basin and jura similarly uplift rates and earthquakes along the southern edge of the jura mountains seem to witness the development of a new incipient basement nappe at depth partial inversion of former permo carboniferous grabens in the basement a possible spatial coincidence of areas with strong earthquake activity and zones with uplift rates above surrounding values suggest a common mechanism for their origin in the western swiss alpine foreland combined with information from basement geometry and wedge dynamics it is proposed that the common mechanism is the development of basement imbricates by tectonic underplating the proposed model for ongoing and possible future tectonic underplating beneath an active alpine orogenic wedge also allows to reconcile the models of basement wrench faulting in the molasse basin and jura with the distant push theory where the molasse basin and jura develop over a basal decollement horizon

the moroccan anti atlas the west african craton passive margin with limited pan african activity implications for the northern limit of the craton abstract the moroccan anti atlas region located south of the south atlas fault has been viewed traditionally as containing two segments separated by the anti atlas major fault these two segments are said to consist of a 600 700 ma pan african segment located in the northeast and b 2 ga eburnian segment situated to the southwest on the basis of observations in the zenaga and saghro inliers and of a recent literature review we suggest that this subdivision is inappropriate in that eburnian and pan african materials occur throughout the anti atlas region the entire anti atlas is underlain by eburnian crust unconformably overlain by a lower neoproterozoic passive margin allochthonous pan african ocean crustal slices were thrust onto the west african craton wac passive margin sequence 685 ma ago as a result of pan african accretion tectonics high level high k calc alkaline and alkaline granitoids locally intruded the anti atlas sequence as a whole at the end of the pan african orogeny at 585 560 ma the intervening 100 m y interval was marked by quiescence this succession of events can be related to the behaviour of one single rigid cratonic passive margin during an orogeny and correlated to the pan african events that occurred to the east in the tuareg shield and to the north in avalonian terranes this model implies that the actual northern limit of the wac is located at the south atlas fault saf and not at the anti atlas major fault aamf we propose that the aamf corresponds to the southwestern boundary of an aulacogen that formed along the northern margin of the wac during early neoproterozoic times this is consistent with the development of the gourma aulacogen on the eastern side of the wac this model further suggests that the northeastern boundary of the wac occurs north and not south of ougarta algeria support for this model is provided by geological and geophysical evidence

first order control of syntectonic sedimentation on crustal scale structure of mountain belts the first order characteristics of collisional mountain belts and the potential feedback with surface processes are predicted by critical taper theory while the feedback between erosion and mountain belt structure has been fairly extensively studied less attention has been given to the potential role of synorogenic deposition for thin skinned fold and thrust belts recent studies indicate a strong control of syntectonic deposition on structure as sedimentation tends to stabilize the thin skinned wedge however the factors controlling basement deformation below fold and thrust belts as evident for example in the zagros mountains or in the swiss alps remain largely unknown previous work has suggested that such variations in orogenic structure may be explained by the thermotectonic age of the deforming lithosphere and hence its rheology here we demonstrate that sediment loading of the foreland basin area provides an additional control and may explain the variable basement involvement in orogenic belts when examining the role of sedimentation we identify two end members 1 sediment starved orogenic systems with thick skinned basement deformation in an axial orogenic core and thin skinned deformation in the bordering forelands and 2 sediment loaded orogens with thick packages of synorogenic deposits derived from the axial basement zone deposited on the surrounding foreland fold and thrust belts and characterized by basement deformation below the foreland using high resolution thermomechanical models we demonstrate a strong feedback between deposition and crustal scale thick skinned deformation our results show that the loading effects of syntectonic sediments lead to long crustal scale thrust sheets beneath the orogenic foreland and explain the contrasting characteristics of sediment starved and sediment loaded orogens showing for the first time how both thin and thick skinned crustal deformations are linked to sediment deposition in these orogenic systems we show that the observed model behavior is consistent with observations from a number of natural orogenic systems

tectonics controls on fluvial landscapes and drainage development in the westernmost part of switzerland insights from dem derived geomorphic indices abstract this work focuses particularly on the geomorphological evidence for the tectonic controls on the development of the present day fluvial landscapes in the westernmost part of switzerland the tectonic deformation was evaluated on the basis of a combined analysis of several classical geomorphic indices hypsometric curves and integrals transverse topographic symmetry index and channel s bottom gradients through high precision dem processing a new optimization strategy was applied for defining geomorphic anomalies related to tectonic activity along the channels of three rivers based on a combined investigation of topographic swath longitudinal profiles geological and geophysical observations the results show that the abnormally high values of hypsometric integral are spatially occurred on the hanging walls of thrust faults while abnormally low ones are spatially observed in the same locations of paleo ice stream pathways observations obtained from transverse topographic symmetry index display asymmetries in the most of the studied drainage basins with a predominant se direction of lateral migration this direction is in agreement with the dominant dip direction of the bedding planes within the study area abnormal changes in the channel s bottom gradients which almost coincide in space with pronounced change in the depth of the subsurface geologic layers and in the geophysical properties are marked by distinct topographic relief in areas where rivers flow above blind and emergent faults our analysis not only confirms that there is a significant tectonic control on the evolution of drainage systems but also revealed a possible evidence for the reactivation of some inherited faults

are the alps collapsing abstract orogenic collapse is a process that transfers gravitational potential energy from regions of high potential energy to regions of lower potential energy this transfer is classically considered to be accomplished by extension in the orogenic core and by synchronous shortening in foreland regions of the orogen not all extensional features in collisional mountain belts need however reflect orogenic collapse normal faulting thrust faulting and strike slip faulting are all active in different parts of the alps today and reflect complex local responses to ongoing europe adria convergence the western alps is the only area today where extension and shortening radial to orogen trend occur synchronously and where orogenic collapse may be an important process elsewhere in the alps normal faults are oriented at a high angle to orogen trend and were primarily active in oligocene and miocene time most present day activity in the central and eastern alps is on strike slip faults that are accommodati

strain partitioning along the western margin of north america abstract this paper describes an elastic block model for the interseismic horizontal crustal velocity field occurring in that part of the united states located west of longitude 100 w and between latitudes 31 n and 49 n we developed the model by simultaneously inverting 6873 gps derived velocity vectors and 166 geological fault slip rates for the angular velocities i e the euler poles relative to the north america plate of 46 elastic blocks horizontal strain rate tensors for 38 of these blocks and the spatially variable elastic coupling coefficients on faults that bound adjacent blocks while the model covers all of the western united states located between canada and mexico this paper focuses on the region residing south of cape mendocino where plate boundary deformation is accommodated predominantly by slip on the san andreas fault system block strain rates which account for deformation associated with distributed faults within blocks are systematically higher in blocks located in the western part of the model and adjacent to the plate boundary strain rate magnitudes range from over 10 7 yr for some blocks adjacent to the san andreas fault system to values of about 10 9 yr for blocks located in eastern nevada and western utah blocks adjacent to the san andreas fault system are characterized by strain rate tensors that correspond to uniaxial contraction perpendicular to the local strike of the san andreas the highest rates of fault normal contraction are associated with the northern end of the fault north of san francisco and in the southern end south of los angeles the central san andreas including the creeping segment of the fault is characterized by strain rate tensors more consistent with dextral shear thus the northern and southern ends of the fault are consistent with a transpressional strain partitioning model with strike slip occurring on the san andreas fault system and distributed shortening occurring within the blocks adjacent to this fault system there is no evidence of strain partitioning in the central san andreas

age and origin of base and precious metal veins of the coeur d alene mining district idaho ore bearing quartz carbonate veins of the coeur d alene mining district yield 87sr 86sr ratios of 0 74 to 1 60 for low rb sr carbonate gangue minerals similar to current ranges measured in middle proterozoic high rb sr rocks of the belt supergroup stable isotope and fluid inclusion studies establish a genetic relationship between vein formation and metamorphic hydrothermal systems of the region these extraordinary 87sr 86sr ratios require accumulation of radiogenic 87sr in a high rb sr system over an extended period prior to incorporation of sr into the hydrothermal veins evaluation of the age and composition of potential sources of highly radiogenic sr indicates that the ore bearing veins of the coeur d alene district formed during the cretaceous from components scavenged from rocks of the belt supergroup the primary host rocks of the district proterozoic pb isotope ratios observed in galena from many coeur d alene veins were established when pb separated from uranium during deposition or diagenesis of the belt supergroup at 1400 to 1500 ma possibly as disseminated syngenetic deposits k ar and rb sr apparent ages and 18o values of belt supergroup rocks decrease from the coeur d alene district toward the idaho and kaniksu batholiths approximately normal to the trends of metamorphic isograds fold axes foliation and the major reverse faults of the district isoclinal folding thrust faulting high temperature metamorphism granitic plutonism and regional scale metamorphic hydrothermal activity is documented in the region between 140 and 45 ma representing the only such combination of events in the coeur d alene region subsequent to about 1300 ma the sr and oxygen results and geologic evidence favor formation of the ore bearing carbonate veins by fluids related to a complex metamorphic hydrothermal system during the cretaceous pb with proterozoic isotopic compositions was probably mobilized and incorporated like other metals into the hydrothermal veins during this event the ore bearing veins were sheared and displaced during early tertiary northwest trending dextral strike slip faulting along the osburn fault and related structures of the lewis and clark line

the akato tagh bend along the altyn tagh fault northwest tibet 2 active deformation and the importance of transpression and strain hardening within the altyn tagh system we investigated active deformation within the akato tagh restraining double bend to determine the age of the active altyn tagh fault relative to the altyn tagh system and thereby evaluate the extent to which this system evolved by net strain hardening or softening active structures were mapped based on their geomorphology and disruption of quaternary deposits surfaces the style of active faulting is strongly correlated with fault strike 065 070 striking segments show pure left slip whereas faults with more northward or eastward strikes are transtensional or transpressional respectively our mapping further suggests that the 065 to 070 striking western and eastern segments of the akato tagh bend are characterized by pure strike slip motion with partitioned transpression along the 090 striking central segment of the double bend it remains unclear how this active bend perpendicular shortening is absorbed in conjunction with previous work the present study fails to support the commonly held idea that tarim tibet motion is strongly oblique to the altyn tagh system estimates for the age of the akato tagh bend derived in a companion study suggest the bend is only a few million years old the current principal trace is probably similarly young because formation of the bend by recent deformation of an old trace should result in transpression along the western and eastern segments contrary to the pure left slip shown here the altyn tagh system comprises multiple fault strands in a zone 100 km wide across strike because the main trace appears to be much younger than the system in which it is embedded we speculate that this system evolved by the sequential formation and death of short lived fault strands in particular we suggest that geometrically complex strike slip fault systems such as the altyn tagh may form via system strain hardening where this net response reflects a dynamic competition between hardening and softening processes that are active simultaneously within the fault zone hardening mechanisms may include growth of restraining bend topography or material hardening of phyllosilicate rich gouge whereas softening processes might include r p shear linkage or reduction in bend angle by vertical axis rotation our analysis suggests that net strain hardening of a fault system can produce continental deformation that is spatially localized over the 1 5 m y during which an individual strand is active but distributed over the 10 100 m y corresponding to the life span of the whole fault system and the collision zone in which it is contained thus time scale is critically important in determining whether or not continental deformation is spatially distributed or localized

a kinematic model for the rinconada fault system in central california based on structural analysis of en echelon folds and paleomagnetism deformation associated with the rinconada fault one of the major strands of the san andreas fault system in central california is accommodated by both discrete fault offset w18 km and distributed off fault deformation en echelon folds adjacent to the rinconada fault were studied in detail at two locations near williams hill and lake san antonio to characterize the magnitude and style of distributed deformation the obliquity between fold hinges and the local strike of the fault was 27 and 14 at these two sites respectively systematic outcrop scale fault displacement measurements along roadcuts indicate that the maximum horizontal elongation occurs parallel to local fold hinges and ranges from 4 to 9 we used the orientation and stretch of fold hinges to construct a transpressional kinematic model for distributed deformation this modeling suggests a 20e50 angle of oblique convergence 5 km of fault parallel wrench deformation and 2e4 km of fault perpendicular shortening between 3 and 16 of clockwise rotation is also predicted by our model this rotation is independently confirmed by a 14 7 vertical

localised and distributed deformation in the lithosphere modelling the dead sea region in 3 dimensions article i nfo the earth s lithosphere behaves as a strain softening elasto plastic material in the laboratory such materials are known to deform in a brittle or a ductile manner depending on the applied geometric boundary conditions in the lithosphere however the importance of boundary conditions in controlling the deformation style has been largely ignored under general boundary conditions both laboratory and field scale observations show that only part of the deformation can localise on through going faults while the rest must remain distributed in process zones where spatially varying shear directions inhibit localisation conventional modelling methods finite difference finite or discrete elements use rheologies deduced from laboratory experiments that are not constrained as a function of the geometry of the applied boundary conditions in this paper we propose an alternative modelling method that is based on the use of an appropriate distribution of dislocation sources to create the deformation field this approach because it does not rely on integrating differential equations from more or less well constrained boundary conditions does not require making assumptions on the parameters controlling the level and distribution of stresses within the lithosphere it only supposes that strain accumulates linearly away from the dislocation singularities satisfying the compatibility equations we verify that this model explains important and hitherto unexplained features of the topography of the dead sea region following the idea that strain can only localise under specific conditions as inferred from laboratory and field scale observations we use our model of deformation to predict where deformation can localise and where it has to remain distributed we find that 65 of the deformation in the dead sea region can localise on kinematically stable through going strike slip faults while the remaining 35 has to remain distributed observations suggest that distributed deformation occurs at stress levels that can be ten times greater than that associated with motion on well localised faults thus although only representing a minor part of the total deformation distributed deformation should provide the greatest source of resistance to motion along this part of the levant plate these results can change dramatically our view of the behaviour of this and other plate boundaries if the lithosphere can be regarded as a strain softening elasto plastic material then similar behaviour should occur throughout with important implications not only for its mechanical behaviour but also for heat generation and related issues like metamorphism or magma genesis