present day stress field changes along the baikal rift and tectonic implications intraplate extension in a frame of a global compressional stress field seems linked to local lithospheric perturbations lithospheric thinning or thickening able to modify the resulting state of stress zoback 1992 the baikal rift zone brz siberia is located north of the india asia collision zone and exhibits no direct communication with any oceanic domain it can thus be fully considered as an area of continental extension dominated by the global compressional intraplate stress field resulting from plate driving forces in order to address the problem of its dynamics and kinematics and their links with the india asia collision a comprehensive stress tensor analysis is presented based on 319 focal mechanisms of earthquakes located along the whole baikal rift the stress field is varying at different scales of observation when looking at central asia several thousands kilometers the maximum horizontal stress shmax directions remain rather constant with a fan shape geometry when the tectonic regime goes from compressional himalayas to extensional baikal when observing the baikal rift about 1000 km long clear variations of the stress regime are observed from an extensional regime in the central part of the rift to wrench ones in its northern and southern ends finally at the scale of 100 km systematic shmax reorientations occur close to major rift faults we thus infer that the interaction between collisional processes and inherited structures may have a strong influence on rift dynamics we then use computed stress tensors to predict slip vectors on major rift faults deformation patterns show two distinct parts of the rift the south baikal rift sbr is characterized by a constant trending around n100 e slip vector meanwhile the north baikal rift nbr exhibits a complex block rotation behavior involving at least three crustal blocks we propose to interpret these surficial structures and motions as the result of an interaction between the regional compression coming from the india asia collision and the geometry of the hardly deformable siberian platform this particular setting can explain most of the surficial deformation patterns which suggest a large scale cracking of the lithosphere in the baikal region other possible sources of stress could also be considered like deep mantellic upwelling or trench suction linked to the pacific subduction

jers sar interferometry for land subsidence monitoring in this paper the potential of l band repeat pass differential synthetic aperture radar sar interferometry for land subsidence monitoring is evaluated using japanese earth resources satellite jers sar data bologna mexico city and the ruhrgebiet are selected as application sites representing slow to fast deformation velocities the investigation includes feasibility aspects such as data availability the temporal decorrelation over different landcover classes and the range of useful spatial baselines an analysis of the achieved deformation accuracy and considerations on the complementarity to european remote sensing satellite ers sar interferometry and leveling surveys in spite of the rather limited data availability land subsidence maps could be generated for the three selected application sites in contrast to ers c band sar data jers l band interferometry permitted the retrieval of subsidence values over vegetated areas and forest when using interferograms of less than one year acquisition time interval and short baseline in addition the longer l band wavelength was found to be superior in the case of large deformation gradients that lead to phase unwrapping problems in c band interferometry

superimposed brittle structures in the late orogenic extension of the northern apennine results from the carrara area alpi apuane nw tuscany this paper presents data on the geometric and kinematic features of brittle faults in the carrara area alpi apuane nw tuscany italy providing the first paleostress determination in a key region of the northern apennine meso and microfault analyses point out the presence of brittle structures formed during a polyphase deformation and characterized by an older stage ds1 with an interfering system of strike slip and normal faulting followed by the ds2 stage developing normal faults locally showing apenninic trend nw se as a whole the brittle structures are related to the late pliocene middle pleistocene evolution of the thyrrenian side of the northern apennine

a numerical method for determining the state of stress using focal mechanisms of earthquake populations application to tibetan teleseisms and microseismicity of southern peru the numerical method described in this paper enables the study in terms of stress of the kinematics of seismic faults provided by focal mechanisms this method assumes a mean state of stress in the source region and is based on the simple mechanical model used for fault population analysis which supposes slip in the direction of the resolved shear stress acting on the fault plane the proposed algorithm first defines compressional and tensional zones resulting from superimposition of the compressional and tensional quadrants limited by the nodal planes this enables one to test the data homogeneity furthermore this restricts the space where the principal stress axes have to be searched then for each principal stress reference whose location is constrained by above confined zones the r value chosen equal to 2 1 3 1 is computed which fits the slip vector on each nodal plane this permits one to select a set of preferred seismic fault planes from a set of auxiliary planes finally a state of stress is computed from the preferred seismic fault plane set using the non linear simplex method already applied to fault populations this algorithm is constructed so as to avoid two major difficulties misleading estimation of the deviatoric stress tensor which may result from excessive emphasis by minimizing the residuals by a least squares method if some of the data are wrong and a lengthy prospection of the stress references over all the space of directions this calculation does not take into account possible changes of the strike and dip of the nodal planes however we use rotations of nodal planes in agreement with the first arrival data to test the compatibility of these data with the computed state of stress tibetan teleseisms and southern peruvian microseisms are analyzed and results are compared with kinematics of superficial recent and active faults measured in field in the same regions this suggests that major seismic events may give a good evaluation of the regional mean state of stress focal mechanisms of the small events are also modelled by a mean stress deviator but this differs significantly from the regional state of stress in southern peru deduced from quaternary faulting this may be due to imprecise location of the small events however some movements are strongly different from those predicted by the computed mean stress deviator this suggests that small fault kinematics surely depend on the regional state of stress but that local effects may control the small deformations

palaeostress analysis of the northern nijar and southern vera basins constraints for the neogene displacement history of major strike slip faults in the betic cordilleras se spain this paper presents the results of a detailed structural analysis of the northern nijar and southern vera basins with special emphasis on the evolution of the regional stress field and the associated timing of movement of the serrata gafarillos and palomares strike slip fault zones these major fault zones control the neogene deformation of the se internal betic cordilleras in spain detailed stress analysis on neogene sediments of the vera and nijar basins shows a strike slip regime with nw se oriented subhorizontal maximum principal stress 1 during tortonian and earliest messinian times under the influence of this stress field dextral displacement along the n090e trending gafarillos fault zone resulted in deformation of the sediments of the southern sorbas and northeastern nijar basins during the early messinian a clock wise rotation of the stress field occurred stress analysis in rocks with late early messinian up to quaternary ages in the nijar and vera basins indicates a strike slip regime with n s oriented subhorizontal maximum principal stress 1 under the influence of this stress field the main activity along the n010e striking palomares strike slip fault zone took place resulting in deformation of the neogene sediments of the southeastern vera basin and culminating in a maximum sinistral displacement of more than 20 km at the same time the stress field was not suitably oriented to exert a large shear component on the gafarillos fault zone which activity ended after the earliest messinian fault and outcrop patterns of syntectonic neogene sediments in the vera basin show that displacement along the palomares fault zone decreased at the end of the middle miocene although minor displacement phases may still have occurred during the late miocene and possibly even pliocene from the middle miocene onward deformation in the nijar basin was controlled by sinistral displacement along the n040e trending serrata strike slip fault zone

potential of small baseline sar interferometry for monitoring land subsidence related to underground coal fires wuda northern china case study uncontrolled coal fires can result in massive surface displacements due to the change in volume of burning coal and thermal effects in the adjacent rock mass simultaneously the resultant surface breakings provide greater access to air and water that in turn can aggravate the problem of underground coal seam burning in this case study we have investigated the feasibility and potential of detecting the land subsidence accompanying coal fires by means of satellite insar observations three groups of small baseline insar approaches psi stacking and 2 passdinsar were applied to the wuda coalfield northern china to reveal the spatial and temporal signals of the land subsidence in the areas affected by the coal fires the interferometric results agree well with gps observations and coal fire data obtained by field investigation which demonstrates that the small baseline insar techniques have remarkable potential to detect this land subsidence of interest in particular our results show that the development of coal fires can lead to new subsiding areas and also accelerate the ongoing surface subsidence typically within the areas of mature coal fires through a comparison of the interferometric observations and the multi temporal coal fire maps this timely and reliable information on land subsidence will be useful for the detection and mapping of the coal fire affected regions and thereby assist in fighting and controlling coal seam burning

estimation of arctic glacier motion with satellite l band sar data offset fields between pairs of jers 1 satellite sar data acquired in winter with 44 days time interval were employed for the estimation of arctic glacier motion over svalbard novaya zemlya and franz josef land the displacement maps show that the ice caps are divided into a number of clearly defined fast flowing units with displacement larger than about 6 m in 44 days i e 50 m year the estimated error of the jers 1 offset tracking derived displacement is on the order of 20 m year occasionally azimuth streaks related to auroral zone ionospheric disturbances were detected and dedicated processing steps were applied to minimize their influence on the estimated motion pattern our analysis demonstrated that offset tracking of l band sar images is a robust and direct estimation technique of glacier motion the method is particularly useful when differential sar interferometry is limited by loss of coherence i e for rapid and incoherent flow and large acquisition time intervals between the two sar images the jers 1 results obtained using sar data acquired by a satellite operated until 1998 raise expectations of l band sar data from the alos satellite launched in early 2006

nd sr isotopic constraints on the interactions of the intermontane superterrane with the western edge of north america in the southern canadian cordillera sr and nd isotopic compositions of the late paleozoic metavolcanics and late triassic to early tertiary granitoids from four magmatic episodes in the southern canadian cordillera from the kootenay arc to the fraser fault have been used to i identify the sources of these rocks ii constrain the compressive tectonic history from middle jurassic to paleocene and iii constrain the western boundary of the basement in this region the 215 190 ma old primitive granitoids end 3 1 to 8 7 87sr 86sr 0 7028 0 7043 of the late triassic and early jurassic magmatic episode were emplaced in the paleozoic oceanic crust of quesnellia end 2 9 to 9 3 prior to its obduction over the basement in contrast during the younger magmatic episodes middle late jurassic cretaceous and early tertiary the granitoids from western quesnellia show primitive isotopic compositions and those from eastern quesnellia show eastward increasing crust contaminated compositions the contaminated characters of the middle

geochronology and geochemistry of the max porphyry mo deposit and its relationship to pb zn ag mineralization kootenay arc southeastern british columbia canada the max porphyry mo deposit is located at the northern end of the kootenay arc in southeastern british columbia canada molybdenum mineralization is genetically related to the variably altered trout lake granodiorite stock which has lithogeochemical affinities to the low fluorine calc alkaline granodiorite hosted porphyry mo deposit type three molybdenite samples from early and late mo bearing veins yield re os dates that overlap within analytical error with a weighted average age of 80 3 0 2 ma these dates are in close agreement with two 206pb 238u weighted average zircon ages for phases of the trout lake stock at 80 3 1 6 and 79 2 1 0 ma indicating that crystallization of the stock and hydrothermal molybdenite formation were coeval and likely cogenetic 40ar 39ar plateau ages for primary biotite in igneous dikes secondary biotite in early potassic alteration and muscovite in late phyllic alteration range from 80 to 76 ma the younger 40ar 39ar plateau ages may reflect unusually slow cooling of the magmatic hydrothermal system or a late thermal disturbance pb zn ag vein deposits are common throughout the kootenay arc and several such veins are located within and proximal to the max porphyry mo deposit the presence of rare molybdenite associated with sphalerite and argentiferous galena in some of these pb zn ag veins suggests that they represent a late stage event related to the max magmatic hydrothermal system fluid inclusions in quartz from mo and pb zn ag veins are similar and can be divided into two compositional groups type 1 aqueous liquid rich fluid inclusions and type 2 aqueous carbonic liquid rich fluid inclusions pressure corrected 1 4 1 7 kbar trapping temperatures of typical type 1 inclusions from mo bearing veins range from 430 to 460 c and for pb zn ag veins from 335 to 365 c the ranges of salinity 0 12 wt nacl equiv in fluid inclusions from both vein types are almost identical and type 2 inclusions from both vein types contain similar amounts of co2 avg xco2 0 08 with traces of ch4 the similarity of chemistry in the two vein types suggests a genetic link between porphyry mo mineralization and adjacent pb zn ag deposits however muscovite from the alteration halo around a pb zn ag vein within the max deposit yielded a 40ar 39ar plateau age of 72 2 0 5 ma this date is significantly younger than the 80 ma age of porphyry magmatism and mo mineralization suggesting either that this event is in fact unrelated to porphyry mo mineralization at 80 ma or that the k ar isotope system has been disturbed by a later thermal event

analysis of fault slip inversions do they constrain stress or strain rate fault slip data commonly are used to infer the orientations and relative magnitudes of either the principal stresses or the principal strain rates which are not necessarily parallel or equal at the local scale of an individual fault the shear plane and slip direction define the orientations of the local principal strain rate axes but not in general the local principal stress axes at a large scale the orientations of p and t axes maxima for sets of fault slip data do not provide accurate inversion solutions for either strain rate or stress the quantitative inversion of such fault slip data however provides direct constraints on the orientations and relative magnitudes of the global principal strain rates to interpret the inversion solution as constraining the global principal stresses requires that 1 the fault slip pattern must have a characteristic symmetry no lower than orthorhombic 2 the material must be mechanically isotropic and 3 there must be a linear constitutive relationship between the global stress and the global strain rate isotropic linear elastic constitutive equations are appropriate to describe the local deformation surrounding an individual slip discontinuity fault slip inversions however constrain the characteristics of a large scale cataclastic flow which is described by constitutive equations that are probably but to an unknown degree anisotropic and nonlinear such material behavior would not strictly satisfy the requirements for the stress interpretation thus at the present state of knowledge fault slip inversion solutions are most reliably interpreted as constraining the principal strain rates

seismogenic deformation field in the mojave block and implications for tectonics of the eastern california shear zone from the aftershocks of the 1992 landers earthquake we infer the orientation of the principal strain rate axes d 1 d 2 d 3 d 1 lengthening their relative magnitude and the relative spin of fault blocks by using a micropolar continuum model to invert the seismic p and t axes the seismogenic deformation is consistent with the geodetic measurements of the coseismic displacement and with the secular deformation of the central mojave block regionally the aftershock data define two major domains within the central mojave block 1 the western mojave block including the san bernardino mountains and the epicentral area of the big bear earthquake which is characterized by e w d 1 lengthening and n s d 3 shortening and 2 the central mojave block including the landers surface rupture zone which is characterized by nw se d 1 and ne sw d 3 inversion for the principal strain axes of geodetically measured coseismic displacements across the big bear and landers seismogenic zones gives results similar to the aftershock inversions for those areas indicating that the aftershocks accommodate a deformation similar to the main rupture and do not reflect elastic rebound or residual stresses the background seismicity for 1981 to 1991 shows the same characteristic d 1 and d 3 orientations for the two domains indicating that the secular seismogenic strain has the same regional geometry as the 1992 coseismic deformation the micropolar inversion also provides values of the relative vorticity parameter w which reflects a difference between the vorticity of a shearing continuum and the vorticity of fault bounded blocks rotating within tabular seismogenic shear zones the observed fault geometry along the kickapoo fault suggests a pinned block model for the local block rotation that is consistent with the values of w obtained from our inversions we interpret the regional nw se orientation of d 1 in the central mojave block to be characteristic of the dextral eastern california shear zone which transfers approximately 22 of the pacific north american plate motion from the san andreas system to the walker lane belt in eastern california our results and geodetic determinations of the secular shear strain in the central mojave block indicate that the locus of nw dextral shear generally lies between the san bernardino mountains and the pisgah fault

from orientation to magnitudes in paleostress determinations using fault slip data abstract determinations of reduced stress tensors using fault slip data yield the orientation of principal stress axes and the ratio of the differences between principal stress magnitudes the use of rupture and friction laws allows determination of the two remaining unknowns that is the reconstruction of the complete stress tensor taking into account the depth of overburden brings an additional constraint the method is applied and discussed in the case of the hoover dam site western u s a where large data sets and rock mechanics information are available differences between intact sample and rock mass properties account for apparent disagreements between paleostress levels determined in similar tectonic environments pore pressure plays an important role where information about pore pressure is absent zero and hydrostatic pore pressure cases should be considered as limits

characterization of various types of deformation and their corresponding deviatoric stress tensors using microfault analysis abstract considering an ideally prefractured material based on mohr s representation and bott s model we define the geometry and the peculiarities of the different theoretical fault domains which are likely to be reactivated under different tectonic regimes the theoretical striations associated with the different types of deformation are also calculated the compressive strike slip extensive strike slip radial extensive and constrictive types of deformation are specified in the second part of this paper using etchecopar s computer aided method a quantitative structural analysis of various types of superficial deformation has been carried out in different study areas southern france greece spain tunisia and nigeria the geometry of the microfault domains as well as the nature of the associated tensors are determined for each type of regional deformation the problem of the spatial homogeneity of the tensors deduced by the microtectonic analysis within the framework of a particular tectonic phase is also discussed

paleostress reconstructions and geodynamics of the baikal region central asia part 2 cenozoic rifting abstract investigations on the kinematics of rift opening and the associated stress field present a renewed interest since it has recently been shown that the control of the origin and evolution of sedimentary basins depends to a large extent on the interplay between lithospheric strength and applied stresses it appears that changes of stress field with time are an important factor that either controls or results from the rifting process the object of this paper is to study the changes of fault kinematics and paleostress field with time in the baikal rift system during the cenozoic reduced paleostress tensors were determined by inversion from fault slip data measured in the central part of the rift and its southwestern termination between 1991 and 1995 results show that the stress field varies as well in time as in space two major paleostress stages are determined corresponding broadly to the classical stages of rift evolution late oligocene early pliocene and late pliocene quaternary the first paleostress stage is related to the rift initiation and the second to the major stage of rift development similarities between the recent paleostress field and the present day stress field inverted from focal mechanisms indicate that the second paleostress stage is still active therefore we propose to use proto rift for the late oligocene early pliocene stage and active rift for the late pliocene quaternary stage of rift development during the proto rift stage the stress field was characterized by a compressional to strike slip regime a progressive change from transpression to transtension is suspected for the central part of the rift baikal and barguzin basins during this period in the western termination of the rift sayan massif tunka depression a strongly compressional stress field with oblique thrusting kinematics is well constrained in the late miocene early pliocene interval the active rift stage was initiated by a marked change in fault kinematics and stress regime in the late pliocene in the central part of the rift the stress regime changed into pure extension while in the southwestern extremity it changed into pure strike slip fault kinematics suggests that rifting was initiated by an extrusion mechanism due to the interaction of far field compressional stress on a mechanically heterogeneous crust with the southwards pointing wedge of the siberian craton acting as a passive indentor the cenozoic time space evolution of the stress field is believed to reflect the increasing influence of locally generated buoyancy extensional stresses associated with density anomalies of the lithosphere on intraplate stresses generated by the india eurasia convergence and the west pacific subduction

episodic exhumation and related tectonic controlling during mesozoic in the eastern tian shan xinjiang northwestern china abstract the eastern tian shan ets which is located in the southern margin of the central asian orogenic belt experienced multiple cooling episodes during the mesozoic however the topography and cooling pattern of the region have been extensively affected by complex structural deformations here we combined a detailed structural analysis with new and existing low temperature thermochronological data from the eastern ets moqingwula range to constrain the process of deformation and exhumation during the mesozoic our results indicate that two phases deformation occurred in the late jurassic and the late cretaceous to the paleocene that transformed the landscape of the moqingwula range the first phase tilted the northern moqingwula range coinciding with folding and thrusting the second phase of deformation disrupted planation surfaces which dominantly formed in the early cretaceous and were preserved on the summit of the ranges our new data reveals three prominent cooling episodes during the 222 ma 138 113 ma and 68 57 ma as well as another subdued cooling phase during 113 92 ma in addition through integration of the regional cooling history and topographic evolution we discuss the geodynamics of the deformations and exhumations associated with tectonism within the central asian orogenic belt

land subsidence in central mexico detected by alos insar time series abstract massive groundwater extraction is common throughout mexico and is well known to result in land subsidence however most land subsidence surveys focus on one single city mainly mexico city and thus fail to reveal the regional extent of the problem here we use 2007 2011 interferometric synthetic aperture radar insar time series analysis of alos data to resolve land subsidence in the entire central mexico region we identify land subsidence in 21 areas including 17 cities linear vertical rates over 30 cm yr are observed in mexico city while in the other locations rates of 5 10 cm yr are detected we define 3 main categories of subsidence using the averaged velocity maps in conjunction with previously published structural surface geology and land use mapping 1 rapid large scale subsidence 2 rapid local scale subsidence and 3 slow patchy subsidence the correlation between subsidence and land use confirms that groundwater extraction mainly for agricultural and urban activities is the main cause of land subsidence we observe that the boundaries of the subsiding areas are typically characterized by high velocity gradients often coinciding with pre existing faults motion on these faults being driven by water extraction rather than by tectonic activity regional surveys of this type are necessary to understand the spatial and temporal evolution of land subsidence to constrain the distribution and connectivity of water bearing units and ultimately to reach better hazard mitigation plans

an inverse problem in microtectonics for the determination of stress tensors from fault striation analysis abstract a method is proposed to compute some characteristics of a possible stress tensor related to striations measured in a given faulted area if several tectonic phases are responsible for the striations the method separates and determines the successive stress tensors the iterative algorithm consists of alternatively a sorting the data attributed to a tectonic phase and b computing the characteristics of the stress tensor of this phase the method is tested using an application to synthetic and actual data

relict landscape resistance to dissection by upstream migrating knickpoints expanses of subdued topographies are common at high elevation in mountain ranges they are often interpreted as relict landscapes and are expected to be replaced by steeper topography as erosion proceeds preservation of such relict fragments can merely reflect the fact that it takes time to remove any preexisting topography however relict fragments could also possess intrinsic characteristics that make them resilient to dissection we document here the propagation of a wave of dissection across an uplifted relict landscape in puerto rico using 10be 26al burial dating on cave sediments we show that uplift started 4 ma and that river knickpoints have since migrated very slowly across the landscape modern detrital 10be erosion rates are consistent with these long term rates of knickpoint retreat analysis of knickpoint distribution combined with visual observations along the streambeds indicates that incision by abrasion and plucking is so slow that bedrock weathering becomes a competing process of knickpoint retreat the studied rivers flow over a massive stock of quartz diorite surrounded by an aureole of metavolcanic rocks earlier studies have shown that vegetation over the relict topography efficiently limits erosion allowing for the formation of a thick saprolite underneath such slow erosion reduces streambed load fluxes delivered to the knickpoints as well as bed load grain size both processes limit abrasion compounding the effect of slow abrasion wide joint spacing in the bedrock makes plucking infrequent thus the characteristics of the relict upstream landscape have a direct effect on stream incision farther downstream reducing the celerity at which the relict subdued landscape is dissected we conclude that similar top down controls on river incision rate may help many relict landscapes to persist amidst highly dissected topographies

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

a km scale triaxial experiment reveals the extreme mechanical weakness and anisotropy of mica schists grandes rousses massif france abstract the development of andersonian faults is predicted according to theory and experiments for brittle frictional deformation occurring in a homogeneous medium in contrast in an anisotropic medium it is possible to observe fault nucleation and propagation that is non andersonian in geometry and kinematics here we consider post metamorphic brittle frictional deformation in the mechanically anisotropic mylonitic mica schists of the grandes rousse massif france the role of the mylonitic foliation and of any other source of mechanical anisotropy in brittle frictional deformation is a function of orientation and friction angle according to the relative orientation of principal stress axes and foliation a foliation characterized by a certain coefficient of friction will be utilized or not for the nucleation and propagation of brittle frictional fractures and faults if the foliation is not utilized the rock behaves as if it was isotropic and andersonian geometry and kinematics can be observed if the foliation is utilized the deviatoric stress magnitude is buffered and andersonian faults fractures cannot develop in a narrow transition regime both andersonian and non andersonian structures can be observed we apply stress inversion and slip tendency analysis to determine the critical angle for failure of the metamorphic foliation of the grandes rousses schists defined as the limit angle between the foliation and principal stress axes for which the foliation was brittlely reactivated this approach allows defining the ratio of the coefficient of internal friction for failure along the mylonitic foliation to the isotropic coefficient of friction thus the study area can be seen as a km scale triaxial experiment that allows measuring the degree of mechanical anisotropy of the mylonitic mica schists in this way we infer a coefficient of friction w e a k 0 14 for brittle frictional failure of the foliation or 20 of the isotropic coefficient of internal friction

fault slip directions in central and southern greece measured from striated and corrugated fault planes comparison with focal mechanism and geodetic data fault slip directions recorded by outcropping striated and corrugated fault planes in central and southern greece have been measured for comparison with extension directions derived from focal mechanism and global positioning system gps data for the last 100 years to test how far back in time velocity fields and deformation dynamics derived from the latter data sets can be extrapolated the fault slip data have been collected from the basin bounding faults to plio pleistocene to recent extensional basins and include data from arrays of footwall faults formed during the early stages of fault growth we show that the orientation of the inferred stress field varies along faults and earthquake ruptures so we use only slip directions from the centers of faults where dip slip motion occurs to constrain regionally significant extension directions the fault slip directions for the peloponnese and gulfs of evia and corinth are statistically different at the 99 confidence level but statistically the same as those implied by earthquake focal mechanisms for each region at the 99 confidence level they are also qualitatively similar to the principal strain axes derived from gps studies extension directions derived from fault slip data are 043 047 for the southern peloponnese 353 for the gulf of corinth and 015 014 for the gulf of evia extension on active normal faults in the two latter areas appears to grade into strike slip along the north anatolian fault through a gradual change in fault slip directions and fault strikes to reconcile the above with 5 myr 1 clockwise rotations suggested for the area we suggest that the faults considered formed during a single phase of extension the deformation and formation of the normal fault systems examined must have been sufficiently rapid and recent for rotations about vertical axes to have been unable to disperse the fault slip directions from the extension directions implied by focal mechanisms and gps data thus in central and southern greece the velocity fields derived from focal mechanism and gps data may help explain the dynamics of the deformation over longer time periods than the 100 years over which they were measured this may include the entire deformation history of the fault systems considered a time period that may exceed 1 2 myr

alteration paragenesis and the timing of mineralised quartz veins at the world class geita hill gold deposit geita greenstone belt tanzania abstract the world class geita hill deposit is one of the largest gold deposits located within the geita greenstone belt in nw tanzania the deposit is hosted within a complexly deformed sedimentary package dominated by ironstone and intruded by diorite dykes the gold mineralisation is spatially associated with the geita hill shear zone which is a ne trending moderately nw dipping deformation zone consisting of a network of discontinuous shear fractures that record early thrusting overprinted by later strike slip and normal events the regional metamorphic assemblage in the meta sediments is characterised by biotite chlorite actinolite k feldspar magnetite pyrrhotite pyrite indicating upper greenschist facies conditions the gold related alteration overprints the regional metamorphic assemblage and is characterised by silicification and sulfidation fronts that generally extend out from the mineralised zone by no more than one meter the alteration assemblage includes sub vertical mineralised quartz veins that trend approximately e w the mineralised quartz veins are accompanied by alteration halos of quartz biotite k feldspar pyrite which overprints the peak metamorphic assemblage gold is closely associated with secondary pyrite and occurs as free gold and gold tellurides sylvanite calaverite and nagyagite it occurs mainly as inclusions in pyrite and as invisible gold in pyrite but also as gold inclusions in biotite and along quartz grain boundaries two distinct textural styles of auriferous pyrite can be distinguished inclusion rich subhedral pyrite hosting invisible gold and inclusion free euhedral pyrite hosting visible gold grains it is common for the inclusions rich pyrite to have thick rims of inclusion free pyrite the mineralising alteration is overprinted by barren multiphase quartz carbonate and carbonate chlorite veins this alteration is characterised by the assemblage calcite siderite chlorite quartz pyrite barite palaeostress analysis of mineralised shear fractures along the geita hill shear zone are indicative of sigma 1 being vertical and sigma 3 trending n s indicating n s extension which is consistent with the orientation of the mineralised quartz veins

stress and the direction of slip on fault planes the shear stress direction on a fault plane depends only on four of the six components of the stress tensor assuming only that the slip direction marks the shear stress direction on any fault plane and that stress is homogeneous it is possible to estimate these four stress parameters from populations of fault planes with known slip directions as several workers have observed different formulations of the problem may yield varying best fitting stresses and estimates of uncertainty in the simplest case no assumptions are made regarding the orientations of fault planes relative to the stress tensor thus the technique allows for the possibility that the fault planes may be very weak here we present simple analytical and graphical descriptions of the field of admissible fault geometries relative to any four parameter stress model which can be used to illustrate the significance of various inverse strategies in particular this paper explores the effects of using two alternative measures of misfit between an observed fault datum and stress model 1 the pole rotation the angle between the observed and predicted slip direction on the observed fault plane and 2 the minimum rotation the smallest angle between the observed fault geometry and any fault geometry which is consistent with the model by allowing for variation of the fault plane as well as the slip vector the minimum rotation procedure generally achieves a more stable and presumably realistic estimate of the actual discrepancy between a fault observation and stress model than the pole rotation procedure in a test case using 17 earthquake focal mechanisms from the yuii region of eastern taiwan separate inversions based on the two misfit criteria yield different optimum stress models and uncertainty estimates additional constraints on the stress tensor such as the effect of friction can be superimposed on the ones used here

strain rate and stress fields in the west and south lut block iran insights from the inversion of focal mechanism and geodetic data abstract the active tectonic deformation and hazardous earthquakes in the south and west of the lut block have been investigated for a long time in this study we compute the geodetic and seismic strain rates using focal mechanism data from the harvard cmt catalogue and various other sources including the published gps velocities moreover we also perform focal mechanism stress inversion fmsi to deduce a stress model for the region our study shows an expected correlation between the stress orientations seismic and geodetic strain rates our results show that the south and west of the lut block is generally exposed as a compressional strike slip tectonic regime the tectonic convergence in this area is taken up not only by motions along and across the faults but also by the rotation of those blocks which bounded by these faults the maximum amount of rotation rate is observed where there are the main right lateral strike slip fault systems such as sabzevaran gowk nayband bam kuhbanan and kahurak the orientation of the mean stress direction obtained from the fmsi results in the west and south of the lut block is approximated n19 e in this area faults are almost oblique relative to the tectonic motion direction moreover there are right lateral and left lateral shears in addition to the dip movements in different parts of the south and west of the lut block our analyses show three main categories of the stress regimes including strike slip faulting 43 2 thrust faulting 38 6 and unknown or oblique faulting 18 2 we also calculated seismic and geodetic moment rates for this area which indicate the seismic moment rate is relatively high between bam and shahdad where there are some segments of the gowk fault

crustal scale rheological transitions during late orogenic collapse abstract orogeny involves crustal thickening followed by thermal relaxation and radiogenic heat production in the thickened crust culminating in crustal melting and magma intrusion which decrease the crustal viscosity by several orders of magnitude and cause late orogenic collapse collapse of the canadian cordillera is expressed in the early tertiary shuswap metamorphic core complex british columbia which displays a three layer crustal section separated by two fundamental rheological discontinuities 1 the brittle ductile transition across which high angle normal faults in the upper crust control basin formation merge into a low angle detachment zone where leucogranite laccoliths ponded and deformed progressively under submagmatic to low temperature conditions and 2 the metatexite diatexite transition across which the rocks lose their solid framework and behave like a viscous magma this transition has the potential to mechanically decouple the upper crust from the rest of the lithosphere during a late orogenic gravitational collapse

active tectonics in the central apennines and possible implications for seismic hazard analysis in peninsular italy abstract the central apennines fault system cafs of peninsular italy overprints earlier structures of a neogene fold and thrust belt and includes segments characterized by diffuse seismicity distributed within a nnw sse trending zone 50 60 km wide the system has been analysed by means of morphotectonic and structural analysis of exposed active fault segments the resulting fault structure consists of an interconnecting network of roughly n s trending left lateral strike slip segments and mostly nw se oriented transtensional to normal faults evidence for recent activity of cafs structures is provided by faulted middle pleistocene holocene deposits including 30 40 ka old pyroclastites and 40 ka old palustrine sediments fresh scarps in both bedrock and late quaternary continental deposits and decametric lateral offsets locally affecting the post wurmian drainage pattern of the area the regional stress field responsible for the development and evolution of the cafs as inferred from fault slip data is characterized by a nw se compression and by a ne sw extension the cafs pattern and its present day kinematics have been related to left lateral strike slip motion on north south trending crustal faults the existence of deep seated strike slip faults in the central apennines has implications for seismic hazard analysis motion along these structures suggests in fact that coseismic surface faulting is distributed and that cumulative displacements include normal transtensional and strike slip components the seismogenic potential of cafs structures can therefore be best described by multiple rupture models and be better analysed in terms of partial contributions of lower rank features constituting congruent structural associations within the system

subsidence monitoring using sar interferometry reduction of the atmospheric effects using stochastic filtering 1 the atmospheric effects represent one of the major limits of sar interferometry as a quantitative technique to monitor subsidences in this work which focuses on subsidences of small spatial extent a procedure to reduce these effects is described the atmospheric component of the interferometric phase is estimated adopting a filtering and prediction procedure which exploits the phase over stable areas identified in the vicinity of the analysed subsidence area the procedure was validated on a suitable test site located in north eastern spain furthermore it was employed in the study of a small scale subsidence where the interferometric results were validated using precise geodetic observations

monitoring land subsidence in the southern part of the lower liaohe plain china with a multi track ps insar technique abstract the lower liaohe plain is one of the most important industrial zones in liaoning province china and activities here include oil and gas exploration aquaculture and salt production heavy land use may have contributed to the different magnitudes of land deformation in this region and this has been detrimental to the environment and economic construction projects in this zone in this paper we employ the permanent scatterer interferometry psi technique with l band alos palsar imagery data to monitor the annual land subsidence and produce accumulative time series maps for the years of 2007 to 2011 the unwrapped grid size was tested in order to recover the maximum deformation insar results from two adjacent tracks were merged by considering the offset over the overlapped area a ps standard deviation of 0 91 cm year was achieved in the vertical direction according to calculation from two independent ps results three kinds of land subsidence were analyzed quantitatively over the oil fields coastal zones and salt production areas some severe land subsidence regions were verified by field investigations

petrogenesis of the cretaceous cassiar batholith yukon british columbia canada implications for magmatism in the north american cordilleran interior the ca 100 ma cassiar batholith is the single largest plutonic body in the hinterland of the canadian cordillera and is part of widespread middle cretaceous to eocene magmatism that occurred in the omineca crystalline belt the cassiar batholith is dominated by muscovite biotite granite and biotite muscovite granodiorite along with subordinate biotite hornblende granodiorite quartz monzodiorite and quartz monzonite the batholith has a wide range of strontium neodymium and oxygen isotope compositions 87 sr 86 sr i 0 706 to 0 734 nd 2 7 to 17 1 t dm 2000 to 980 ma 18 o 7 6 to 11 6 but the batholith9s lead isotope compositions are limited 206 pb 204 pb 19 14 to 19 24 207 pb 204 pb 15 70 to 15 72 208 pb 204 pb 39 14 to 39 26 these data require that the cassiar magmas have been generated from at least two distinct sources an isotopically evolved felsic source and an isotopically more primitive source of mafic to intermediate composition we propose that the felsic source comprised mesoproterozoic to neoproterozoic metasedimentary rocks and paleoproterozoic basement rocks of the north american cratonic margin determining the mafic source is more problematic but most likely it was proterozoic basement rocks of mafic to intermediate composition such as have been reported from various parts of the omineca crystalline belt the cassiar batholith is lithologically geochemically and isotopically similar to other major batholiths in the cordilleran interior including the batholiths of southeastern british columbia and the idaho batholith we interpret these similarities to reflect melting of common crustal source materials namely proterozoic basement and cover rocks of western laurentia the cassiar batholith and other cordilleran interior granitoids are distinct from granitoids generated in known subduction zone environments in terms of their mineralogical geochemical and isotopic characteristics these differences reflect a predominantly or exclusively crustal source region for the cordilleran interior granitoids in contrast subduction zone magmatism contains a significant mantle input even in cases where subduction takes place beneath thick continental crust these results strongly suggest that cordilleran interior granitoids did not form directly from a subduction setting rather an intracontinental collisional setting seems more appropriate in which magma generation occurred in response to crustal thickening followed in some cases by extension

origin and tectonic interpretation of multiple fault patterns abstract it is shown that in two dimensional and three dimensional deformation accommodated by fracture the symmetry of the fault patterns is an intrinsic attribute because it reflects the symmetry of either stress or strain tensors the deformation accommodated by sliding along pre existing planes when there is kinematic interaction between that planes forms multiple fault pattern and multiple slickenline sets during a single deformation event these fault patterns have no restrictions with respect to symmetry number of fault sets or fault orientation the kinematic analysis developed here shows that an interacting system is formed by two cross cutting faults and three slickenlines one slickenline must be parallel to the intersection line between the planes also it is demonstrated that the slickenlines generally do not correspond to the shear stress solution on the planes thus the interaction between planes does not satisfy the assumption of parallelism between shear stress and slip vector we conclude that the inversion methods to calculate paleostress tensors can lead to erroneous interpretations in structurally complex zones with many pre existing planes of weakness we propose four possibilities to form multiple fault patterns 1 two or more events of faulting obeying coulomb s law with a change of orientation of the principal stresses in each event 2 reactivation of non interacting planes according to the bott 1959 model 3 one three dimensional strain event that obeys the slip model this mechanism will form an orthorhombic four fault pattern and two slickenline sets in a single strain event and 4 one or more events obeying the interacting block model proposed here with or without rotation of the principal stresses we propose the last origin as the most common in continental regions

tectonostratigraphic evolution of the basins on the southern branch of the north anatolian fault system in the se marmara region turkey the lithostratigraphy of the mekece iznik corridor the geyve pamukova and the iznik basins on the southern branch of the north anatolian fault system nafs sb was investigated in detail the intra basin deposits carried by sakarya river and the drainage systems in the northern and southern elevated blocks of the iznik and geyve pamukova basins have been classified based on their lithofacies characteristics the geyve pamukova basin which has developed with a nne ssw trending transtensional strain was formed as a lazy z shaped and releasing bend or pure strike slip pull apart basin that is related to simple shear right lateral strike slip faulting the iznik basin was formed by a right lateral strike slip faulting kinematics and nne ssw trending transtension as a result of the step over of the northeast trending dirazali fault from the southern edge to the nw trending gurle fault and the western step over of this fault to the e w trending umurbey fault this strike slip setting is also supported by the nw se trending right lateral oblique normal orhangazi fault on the northern edge of the basin according to this the iznik basin can be described as a more advanced stage of a large scale pull apart basin compared with a lazy z shaped and releasing bend or transtensional strain furthermore it is defined as the former stage of an extreme or rhomboid type transtensional pull apart basin

complex fault patterns transtension and structural segmentation of the lofoten ridge norwegian margin using digital mapping to link onshore and offshore geology an integrated onshore offshore study involving regional to outcrop scale fault analysis is used to develop a self consistent structural model for transtension along the lofoten ridge the lofoten vesteralen archipelago lva is a segmented basement high showing distinct lateral variations in trend deformational style and structural complexity this study investigates whether segmentation can be linked to differences in the obliquity of preexisting structures relative to plate movement vectors regional analysis of fault lineament patterns using geographic information systems gis reveals that the lva can be subdivided into a series of distinct lineament domains these domains are closely coincident with changes in ridge trend and variations in structure within offshore models derived from seismic reflection studies digital field mapping and spatial analysis of faulting in the north lofoten reveal that multimodal faulting is dominated by transtensional dip slip and oblique slip movements which are comparable to analogue models where the ridge axis is 30 oblique to regional extension the overall change in fault orientation fault geometry and deformation style are consistent with models for transtension where the ridge bounding structure becomes increasingly oblique to regional extension previously identified transfer zones simply reflect segment domain boundaries and are not reactivating basement structures this model is a possible analogue for other orthogonal and oblique rift structures on the norwegian and other margins

the comoros archipelago a right lateral transform boundary between the somalia and lwandle plates abstract the origin of the comoros archipelago in the mozambique channel is the subject of a longstanding controversy this volcanic chain has been successively interpreted as a hotspot track as built on an intraplate fracture zone or a passive margin or as the northern limit of a diffuse deformation zone in the nubia somalia plate system none of these interpretations being entirely satisfactory it is also possible that the volcanism of the comoros is a branch of the east african rift system and delineates the still poorly constrained northern boundary between the lwandle and somalia plates to better understand the origin of the comoros archipelago we combined a formal stress inversion of earthquake focal mechanisms and deformation structures faults and dykes observed on three islands mayotte anjouan and moheli with a morphologic study of the repartition of onshore and offshore volcanic vents in the area earthquake focal mechanisms and field observed deformation structures both yield a generalized strike slip regime with a maximum horizontal stress oriented nw se in tandem the study of topographic and bathymetric features shows that volcanic vents follow a preferential repartition along two trends n105 10 lineaments up to 100 km long and n145 10 less than 60 km long lineaments organized in an en echelon fashion earthquakes deformation structures and volcanic vents all consistently designate the comoros archipelago as an e w elongated 150 km wide zone of right lateral tear in the lithosphere because the clockwise rotation of somalia relative to lwandle requires the existence of such a right lateral shear zone we interpret the comoros archipelago as the northern boundary between the two plates this plate boundary is still in an immature state which is why it remained undetected until now

neogene evolution of the sorbas basin se spain determined by paleostress analysis abstract the neogene subsidence history of the sorbas basin situated in the internal zone of the betic cordilleras of southeastern spain is strongly controlled by strike slip deformation the sedimentary sequence of the basin offers a good control on the timing of separate phases of fault activation the southern border of the sorbas basin is formed by a major east west trending fault zone the gafarillos fault zone which consists of intermixed slivers of pre neogene basement blocks and neogene basin sediments fault patterns and paleostress analysis both indicate that major displacement along this fault zone was dextral with a n310e oriented maximum principal stress axis strike slip movement along the east west oriented faults ended during the earliest messinian after a minimum of 6 ma of activation paleostress analysis indicates a subsequent phase of strike slip fault movement present in sites of up to early pliocene age the maximum principal stress axis orientation is n350e for this phase this deformation is synchronous with sinistral displacement along the palomares fault zone situated directly to the east of the study area subsequently our paleostress analysis indicates an extensional regime during the late pliocene to quaternary however extensional tensors were calculated at a number of sites possibly representing local stress regimes coexisting with the main strike slip deformation and sorbas basin subsidence folding of tortonian sediments points out that local compressional deformation took place as well during the neogene basin history observed wide ranges for the ellipsoid shapes of the calculated tensors support the existence of lateral stress variations

slip tendency analysis as a tool to constrain the mechanical properties of anisotropic rocks abstract the mechanical strength of foliated rocks is typically anisotropic because it varies with the orientation of the foliation relative to the applied principal stresses and commonly depends on phyllosicate content and phyllosicate physical interconnectivity we constrain the degree of mechanical anisotropy associated with pre existing planar discontinuities such as metamorphic foliations and inherited faults by combining paleostress analysis and meso and microscale characterization of brittle failure modes in different phyllosilicate bearing rocks outcropping in the sierras de cordoba sdc of central argentina the sdc show evidence of a long brittle deformation history from early triassic present with three distinct brittle deformational events each phase caused new strain increments accommodated by the formation of newly formed faults or by the reactivation of inherited discontinuities structural investigations reveal that gneisses and phyllites deformed by different failure modes during the different events therefore we were able to use a conceptual field scale triaxial experiment by applying a stress model based on normalised slip tendency analysis we constrained the friction coefficient for slip along the foliations s and along pre existing faults f to 0 2 to 0 3 and 0 4 respectively these values fit independent estimates for similar rocks confirming the potential of our approach for other case studies

the origin of mineralized fractures at the bluebell mine site riondel british columbia the bluebell pb zn deposit is located on the east side of kootenay lake in southeastern british columbia it is a fracture controlled replacement deposit hosted in lower cambrian marble of the badshot and mohican formations the orebodies trend west northwest parallel to a prominent set of fractures that controlled mineralization these fractures are interpreted to have formed as part of a conjugate set contrary to some earlier suggestions folding played no role in fracture formation the youngest generation of folds are reinterpreted as having formed through development of shear bands during extension of the layering prior to fracture development formation of the fractures also postdated motion on a number of early tertiary normal faults that are associated with regional extension and alkaline magmatism west northwest trending fractures which formed as part of a conjugate set were reactivated and controlled the intrusion of mafic dikes mineralizing fluids and minor late faulting fracturing faulting mafic dike intrusion and mineralization may be associated with a long lived basement structure that runs below the area which could have facilitated the ascent of deep crustal or mantle derived magma and mineralizing fluids the results of this study provide a new perspective on exploration strategies for hydrothermal ore deposits in this part of southeastern british columbia

geochemical and nd pb o isotope systematics of granites from the taltson magmatic zone ne alberta implications for early proterozoic tectonics in western laurentia the early proterozoic taltson magmatic zone tmz comprises the southern part of the taltson thelon orogenic belt of northwestern canada the tmz is dominated by 1 96 1 99 ga i type and 1 93 1 95 ga s type suites of granitoids previous workers attributed the formation of the i type granitoids to subduction of oceanic crust beneath the churchill craton in an andean type setting and generation of the s type granitoids to subsequent collision between the churchill craton and the buffalo head terrane to test this hypothesis we carried out a geochemical and isotopic nd pb and o study of granitoids and associated metasedimentary rocks and basement gneisses from the southern part of the tmz both i and s type suites of granitoids are characterized by relatively high sio2 content with the great majority of samples containing more than 64 wt sio2 the two suites also have strongly crustal end t values of 3 8 to 9 8 and an average tdm of 2 8 ga the initial pb isotope composition of the granitoids as determined from leached feldspar mineral separates forms a linear array that is bracketed by the isotopic compositions of basement orthogneisses and metasediments similarly 18o values of the granitoids overlap those of the orthogneisses and metasediments these isotopic data are consistent with derivation of the granitoids from a mixture of metaigneous and metasedimentary source rocks similar to those presently exposed in the tmz importantly the data suggest that both i and s type granitoids of the southern tmz had an exclusively intra crustal origin unlike phanerozoic examples of subduction related magmatism where a significant mantle contribution is easily recognized therefore we argue that the existing andean type model for early tmz magmatism is not viable the tmz granitoids show geochemical and isotopic similarities to the cordilleran interior granitoids of western north america which formed in response to crustal thickening in the distant hinterland of a convergent plate margin we propose that these hinterland granitoids are a more appropriate analogue for tmz magmatism than are the granitoids of plate margins the tectonic implication of this proposal is that the taltson thelon orogenic belt does not mark the location of the plate boundary in western laurentia at 1 9 2 0 ga rather the tectonic setting of the tmz at that time may have been more akin to the present day intra continental mountain belts of central asia e g tian shan mountains where compressional tectonism and crustal thickening are occurring well inboard from a convergent plate margin

palaeostress reconstructions and geodynamics of the baikal region central asia part i palaeozoic and mesozoic pre rift evolution abstract this paper presents the first palaeostress results obtained for the basement of the baikal rift system in southern siberia russia large scale structural analysis and palaeostress reconstructions show that the palaeozoic mesozoic kinematic history precursor of the baikal cenozoic rifting is characterized by the succession of six regional palaeostress stages stress inversion of fault slip data and earthquake focal mechanisms is performed using an improved right dieder method followed by rotational optimization d delvaux tensor program the results are interpreted in the light of recent developments in the investigation of regional intraplate stress field and used as additional constraints for palaeogeodynamic reconstruction of central asia after the final palaeozoic closure of the palaeo asian ocean on the southern margin of the siberian platform the marginal suture with the sayan baikal caledonian belt was repeatedly and preferentially reactivated during the subsequent palaeozoic and mesozoic history this suture zone also controlled the opening of the baikal rift system in the cenozoic the progressive closure of the palaeo asian and mongol okhotsk oceans generated successive continental collisions which were recorded in the baikal area by brittle ductile and brittle deformations the first two palaeostress stages correspond to the successive collage of precambrian microcontinents and caledonian terranes along the southern margin of the siberian platform 1 late cambrian early ordovician n s compression and 2 late silurian early devonian nw se compression the next two stages are related to the remote effects of the complex evolution of the western palaeo asian ocean southwest of the siberian continent 3 late devonian early carboniferous n s compression recorded only in the altai region and 4 late carboniferous early permian e w compression recorded both in the altai and baikal regions the last stages are the consequences of the mongol okhotsk oceanic closure 5 late permian triassic nw se extension with development of cordilleran type metamorphic core complexes and volcanism along the active margin of the mongol okhotsk ocean 6 initial development of early middle jurassic 10 15 km wide molassic basins in trans baikal and large foredeeps along the southern margin of the siberian platform in probable extensional context but for which no palaeostress data are available and 7 final closure of the mongol okhotsk ocean in the cretaceous this last event results from the collision between the mongol china and the siberian plates and is evidenced by the inversion of the middle mesozoic basins and by late jurassic early cretaceous coal bearing sedimentation in trans baikal this long tectonic history yielded a highly heterogeneous basement in the baikal area precursor of the cenozoic rifting

constraints on rates of granitic magma transport from epidote dissolution kinetics epidote is stable only at high pressure in granitic magmas but is found in magmas crystallized at shallow crustal levels this observation suggests qualitatively that magma transport is sufficiently rapid to prevent complete epidote resorption experimental measurements of epidote dissolution showed that the presence of epidote implies that magma transport from the deep crust in these systems was rapid and that the transport was by dikes rather than diapirs

monitoring surface elevation changes in jharia coalfield india using synthetic aperture radar interferometry this paper investigates surface elevation changes that occurred during 1996 2004 in the jharia coalfield through the digital elevation model dem generated using synthetic aperture radar interferometry insar using ers 1 2 european remote sensing satellite tandem and radarsat 1 data the comparison of elevation values derived from the insar dem and topographic height data shows a bias of 23 08 m with root mean square error of 2 31 m 5 8 the accuracy of the dem was investigated by comparing the elevation profiles with the digitized elevation contour data at four different locations the profile comparison shows a mean bias of 22 68 m local topography shows changes in elevation up to 40 00 m due to mining activities on the 8 year time period the results of insar derived heights and topographic heights were comparable and well matched except at a few locations where topographic data were unavailable dem generated using insar due to its high spatial details is ideal for the detection and estimation of surface elevation changes in mining areas

erratum to paleostress reconstruction from kinematic indicators in the oslo graben southern norway new constraints on the mode of rifting tectonophysics 266 1996 55 79

spatial variation of present day stress field and tectonic regime in tunisia and surroundings from formal inversion of focal mechanisms geodynamic implications for central mediterranean we compiled 123 focal mechanisms from various sources for tunisia and adjacent regions up to sicily to image the current stress field in the maghrebides chain from tunisia to sicily and its foreland stress inversion of all the available data provides a first order stress field with a n150 e horizontal compression shmax and a transpressional tectonic regime but the obtained stress tensor poorly fit to the data set we separated them into regional subsets boxes in function of their geographical proximity kinematic regime homogeneity of kinematic orientations and tectonic setting their respective inversion evidences second and third order spatial variations in tectonic regime and horizontal stress directions the stress field gradually changes from compression in the maghrebides thrust belt to transpression and strike slip in the atlassic and pelagian foreland respectively where preexisting nw se to e w deep faults system are reactivated this spatial variation of the sismotectonic stress field and tectonic regime is consistent with the neotectonic stress field determined by others from fault slip data the major slab transfer edge propagator faults i e north south axis hammamet relay and malte escarpment which laterally delimit the subducting slabs play an active role in second and third order lateral variations of the tectonic regime and stress field orientations over the tunisian sicilian domain the past and current tectonic deformations and kinematics of the central mediterranean are subordinately guided by the plate convergence i e africa eurasia controlled or influenced by lateral slab migration segmentation and by deep dynamics such as lithosphere mantle interaction

a quasi elastic aquifer deformational behavior madrid aquifer case study summary the purpose of this paper is to analyze the quasi elastic deformational behavior that has been induced by groundwater withdrawal of the tertiary detrital aquifer of madrid spain the spatial and temporal evolution of ground surface displacement was estimated by processing two datasets of radar satellite images sar using persistent scatterer interferometry psi the first sar dataset was acquired between april 1992 and november 2000 by ers 1 and ers 2 satellites and the second one by the envisat satellite between august 2002 and september 2010 the spatial distribution of psi measurements reveals that the magnitude of the displacement increases gradually towards the center of the well field area where approximately 80 mm of maximum cumulated displacement is registered the correlation analysis made between displacement and piezometric time series provides a correlation coefficient greater than 85 for all the wells the elastic and inelastic components of measured displacements were separated observing that the elastic component is on average more than 4 times the inelastic component for the studied period moreover the hysteresis loops on the stress strain plots indicate that the response is in the elastic range these results demonstrate the quasi elastic behavior of the aquifer during the aquifer recovery phase ground surface uplift almost recovers from the subsidence experienced during the preceding extraction phase taking into account this unique aquifer system a one dimensional elastic model was calibrated in the period 1997 2000 subsequently the model was used to predict the ground surface movements during the period 1992 2010 modeled displacements were validated with psi displacement measurements exhibiting an error of 13 on average related with the inelastic component of deformation occurring as a long term trend in low permeability fine grained units this result further demonstrates the quasi elastic deformational behavior of this unique aquifer system

mid cretaceous transtension in the canadian cordillera evidence from the rocky ridge volcanics of the skeena group the age relations geochemistry and sedimentology of the rocky ridge formation of the skeena group are used to test competing tectonic reconstructions for the mid cretaceous canadian cordillera as well as the timing and location of the accretion of the insular superterrane pollen and macrofossil assemblages indicate that these intrabasinal basalts were erupted along the southern margin of the bowser basin in the early albian to early cenomanian single crystal fusion and step heating 40ar 39ar dating of hornblendes in one basalt flow from the uppermost part of the formation yielded middle cenomanian ages of 94 3 0 4 95 6 1 6 and 95 0 1 6 ma vesicular basalt flows interbedded with crystal rich tuff breccias contain evidence for hot emplacement as pyroclastic flows individual eruptive centers are identified by their proximal facies paleoflow indicators within the lava flows paleoflow indicators within interbedded volcaniclastic fluvial deposits geochemical differences and geographic isolation of volcanic deposits major and trace element geochemistry from 20 sampled lava flows indicates an alkali basalt composition for the volcanics the basalts of the northern rocky ridge volcanic center show enrichment of light rare earth and large ion lithophile elements with strong negative nb ta anomalies whereas the basalts of the southern tahtsa lake volcanic center show depletion to slight enrichment of light rare earth elements slight enrichment of large ion lithophile elements with minimal negative nb ta anomalies the geochemistry combined with paleogeographic and regional tectonic reconstruction suggests a continental arc setting with intraarc extension the presence of deeper marine facies to the west and the lack of a western sediment source in the skeena group indicate that the technically active insular superterrane was not west of the study area during mid cretaceous time thus we reconsider the omineca belt as the main axis of a mid cretaceous continental arc placing the intermontane superterrane in the intraarc to forearc position with the rocky ridge volcanics erupted along the forearc side of the omineca arc coeval regional strike slip faulting and reconstructed oblique plate convergence suggest a transtensional setting for rocky ridge intraarc extension an electronic supplement of tables a1 a2 may be obtained on a diskette or anonymous ftp from kosmos agu org login to agu s ftp account using anonymous as the username and guest as the password go to the right directory by typing cd apend type ls to see what files are available type get and the name of the file to get it finally type exit to leave the system paper 95tc03496 mid cretaceous transtension in the canadian cordillera evidence from the rocky ridge volcanics of the skeena group kari n bassett and karen l kleinspehn diskette may be ordered from american geophysical union 2000 florida avenue n w washington dc 20009 15 00 payment must accompany order

variation in slip on intersecting normal faults implications for paleostress inversion numerical models based on linear elasticity theory predict asymmetric slip distribution with a steep slip gradient near the line of intersection of intersecting normal faults they also predict a discrepancy between the direction of slip on the fault plane and the direction of resolved shear stress both variations in slip magnitude and direction are due to mechanical interaction between the faults with intersecting patterns these interactions cause local perturbations of the shear stress field acting on the plane of the adjacent fault field observations from the chimney rock area of central utah show that slickensides on normal faults cutting the navajo sandstone change rake away from the expected downdip direction as the intersection line with adjacent faults is approached the sense and magnitude of this change in orientation are similar to those computed by using the numerical models the good correspondence between field observations and theoretical results from this paper not only provides insight into the mechanics of intersecting faults but suggests that care is required when using standard inverse methods to compute paleostresses from slickenside data the slickenside orientation near intersection lines will generally not be in the direction of the remote maximum shear stress as resolved on the fault plane a parameter study of this change in orientation provides helpful results for evaluating field data prior to a paleostress analysis

tectonic evolution of the intra uplift vigodi gugriana khirasra netra fault system in the seismically active kachchh rift basin india implications for the western continental margin of the indian plate abstract the e w striking kachchh rift basin krb at the western continental margin of indian plate is located in the northern part of gujarat state india krb has undergone polyphase deformation owing to changing stress field since late triassic we establish the kinematic framework along the nw striking intra uplift vigodi gugriana khirasra netra fault system vgknfs located at the western part of the krb the vgknfs consists of 0 25 50 km long sub parallel striated reactivated dip slip faults a total of 1150 fault slip data consisting of fault planes and striations attitude were recorded from 66 sites including a single site with systematic joints slip sense of faults was determined by documenting kinematic indicators paleostress analysis was carried out using win tensor t tecto faultkin and sg2ps to compare and validate the results the chi square statistical analysis was undertaken to evaluate how relevant are paleostress analysis results to the present day compressional stress field geophysical investigations were conducted at selected sites using ground penetrating radar gpr to understand the shallow subsurface geometry and trace the continuity of faults buried below patchy alluvial cover 15 17 m long 2d gpr cross sections were recorded across faults using monostatic antenna of 200 mhz frequency two major deformation events d1 and d2 are determined in the present study the extension event d1 shows w and nw nnw extension during late triassic to late cretaceous it occurred during the rift phase of krb in response of the break up of gondwanaland the latest event d2 shows nne ne compression from late cretaceous up to the present it is interpreted to have developed during post rift inversion phase induced by collision of the indian plate with the eurasian plate at 55 ma

the nature and significance of rift related near surface fissure fill networks in fractured carbonates below regional unconformities fissure fill networks are a widely recognized but relatively little described near surface phenomenon supplementary material appendix a is available at https doi org 10 6084 m9 figshare c 5023103

u pb geochronology of jurassic to early tertiary granitic intrusives from the nelson castlegar area southeastern british columbia canada eleven u pb zircon dates from seven intrusives in the nelson castlegar area provide new age constraints on the granitoid magmatism in southeastern british columbia four samples from the nelson batholith date three distinct intrusive phases spanning ca 10 ma one sample from the eastern porphyritic phase coffee creek yields the oldest age at 172 5 5 0 ma two samples from the central k feldspar megacrystic phase crescent bay give precise ages at 162 0 1 0 and 161 5 1 5 ma and possibly date the youngest phase of the batholith an intermediate age of emplacement at 166 0 3 0 ma is suggested for the southern tail of the batholith the new and published data suggest that the nelson batholith was emplaced in roughly concentric zones in contrast the southern quartz diorite phase and the northwestern granodiorite phase of the bonnington pluton were emplaced coevally during the middle jurassic at 167 4 2 0 and 165 0 3 0 ma respectively middle jurassic ages were also obtained for a sample of

tectonic setting of the taltson magmatic zone at 1 92 0 ga a granitoid based perspective the paleoproterozoic taltson magmatic zone is one of the key tectonic features of western laurentia the existing tectonic model for the belt envisions its formation by subduction of oceanic crust beneath a continental margin followed by direct collision between formerly separate crustal blocks we tested this model by comparing the large geochemical and isotopic database available for taltson magmatic zone granitoids with similar databases for phanerozoic granitoid suites from different tectonic environments the comparison reveals that the early granitoid suite of the taltson magmatic zone which had been ascribed to the subduction phase of orogenesis lacks the mantle signature apparent in granitoids of phanerozoic continental margin arc settings instead both early and late suites appear to have an intracrustal origin similar to mesozoic and cenozoic granitoids of the cordilleran interior of western north america which formed in the distant hinterland of a convergent plate margin in light of thes

subsidence of kolkata calcutta city india during the 1990s as observed from space by differential synthetic aperture radar interferometry d insar technique abstract in kolkata city india potential land subsidence due to over drafting of groundwater under confined condition has been reported by a number of previous workers and by the local media the presence of a thick surface clay layer with an average thickness of more than 40 m over the aquifer sand layer raises questions on the possibility and doubtfulness of land subsidence in kolkata city in this work d insar based study has been undertaken to detect and measure land subsidence phenomenon in kolkata city for detecting slow land subsidence phenomenon in kolkata city occurring primarily due to piezometric fall consequent to groundwater over drafting we have chosen the insar data pairs acquired during post monsoon t 1 pre monsoon t 2 periods when the lowering of piezometric head was the maximum and therefore land subsidence would be more prominent than that of pre monsoon t 1 pre monsoon t 2 and post monsoon t 1 post monsoon t 2 periods of similar time intervals for detecting slow land subsidence phenomenon essentially from long temporal baseline data pairs usually in years temporal decorrelation and atmospheric artefacts have been found to pose serious difficulties adaptive filtering of the noisy interferograms followed by summing of the independent interferograms was performed in complex domain in order to suppress noise from the fringes and highlight the deformation fringes over atmospheric artefacts respectively results indicate that an area in kolkata city surrounded by machhua bazar calcutta university and raja bazar science college had been undergoing subsidence during the observation period i e 1992 1998 with an estimated rate of 5 to 6 5 mm year

extension driven brittle exhumation of the lower middle crustal rocks a paleostress reconstruction of the neoproterozoic ambaji granulite nw india abstract the exhumation of the deep crustal rocks through brittle crust by extensional tectonics is recognized in orogens of all ages paleostress analysis are generally used to understand the brittle exhumation process in this study we reconstructed the paleostress of faults of the neoproterozoic ambaji granulite south delhi terrane of the aravalli delhi mobile belt nw india by analyzing the fault slip data in win tensor program several ne sw and wnw ese faults have been mapped in the area and found to be normal faults with a few strike slip faults the strike slip faults are pre kinematic to normal faults tensor solutions for 237 fault slip data points estimate wnw ese extension for strike slip faults and nw se direction extension for normal faults from these results we interpret that the ne sw striking orogen parallel normal faults were produced from a nw se directed extensional stress and are primarily responsible for brittle exhumation of the granulite through crustal extension and thinning at 764 650 ma this is comparable to earlier studies on brittle exhumation along the southern tibet detachment in the higher himalayas on a more regional scale our results are in agreement with the extensional tectonics that affected the entire aravalli delhi mobile belt and adjoining continents of the neoproterozoic cambrian gondwanaland supercontinent

geochemical characterization of mid cretaceous granitoids of the kootenay arc in the southern canadian cordillera within southeast british columbia mid cretaceous granitoid batholiths are exposed in the omineca belt a north south trending metamorphic and plutonic orogenic belt the bugaboo horsethief creek and fry creek batholiths are post kinematic with respect to regional metamorphism that affected their host rocks and are composed of hornblende and biotite granodiorites and granites in all three batholiths and two mica granites in fry creek the biotite granites are weakly peraluminous have initial esr ranging from 36 to 56 and initial end ranging from 4 8 to 7 5 and overlap the range of nd sr isotopic compositions for precambrian basement gneisses and proterozoic metasediments found in southeast british columbia the initial 206pb 204pb versus 208pb 204pb and 207pb 204pb for these granitoids lie in bands between model lower and upper crustal pb isotopic compositions above the northern hemisphere reference line for oceanic basalts these granitoids have high nb and rb and low ba abundances relative t