refractory inclusions in the murchison meteorite mineralogical and petrographic studies of a wide variety of refractory objects from the murchison c2 chondrite have revealed for the first time melilite rich and feldspathoid bearing inclusions in this meteorite but none of these is identical to any inclusion yet found in allende blue spinel hibonite spherules have textures indicating that they were once molten and thus their sio2 poor bulk composition requires that they were exposed to higher temperatures 1550 c than those deduced so far from any allende inclusion melilite rich inclusions are similar to allende compact type a s but are more al ti rich one inclusion much 1 consists of a delicate radial aggregate of hibonite crystals surrounded by alteration products and probably originated by direct condensation of hibonite from the solar nebular vapor the sinuous nodular and layered structures of another group of inclusions spinel pyroxene aggregates suggest that these also originated by direct condensation from the solar nebular gas each type of inclusion is characterized by a different suite of alteration products and or rim layers from all the other types indicating modification of the inclusions in a wide range of different physico chemical environments after their primary crystallization all of these inclusions contain some iron free rim phases these could not have formed by reaction of the inclusions with fluids in the murchison parent body because the latter would presumably have been very rich in oxidized iron other rim phases and alteration products could have formed at relatively low temperatures in the parent body but some inclusions were not in the locations in which they were discovered when this took place some of these inclusions are too fragile to have been transported from one region to another in the parent body indicating that low temperature alteration of these may have occurred in the solar nebula

seismotectonics of western anatolia regional stress orientation from geophysical and geological data abstract available fault plane solutions of shallow earthquakes occurring in the central part of western anatolia were reviewed in order to determine the stress directions active in this region data on 66 shocks were used for numerical analysis with the p and t dihedra method some of these data being used in further determination of stress tensors through numerical methods despite uncertainties on depth determinations results were found consistent and in agreement with those of geological analyses independently carried out on recent and active faults selections from the data were adopted on the basis of areal distribution magnitude and depth of earthquakes variations in stress axes orientation with depth seem significant and related to increasing influence of crustal anisotropy near the surface the dominant trend of the present day extension in this region as indicated by the analysis of available earthquake mechanisms is nne ssw with a corresponding azimuth of the 3 axis n25 e the stress regime is extensional with dominant normal fault motions and increasing importance of strike slip faults from south to north this pattern of stress in western turkey is consistent with kinematic reconstructions indicating a westward and southwestward motion of anatolia and aegea relative to eurasia

how do asperities fracture an experimental study of unbroken asperities abstract the fracture of a shear fault containing several unbroken asperities in a granitic porphyry is examined in detail via acoustic emission ae data collected by a high speed multi channel waveform recording system the experimental results reveal that a quasi static nucleation of the shear faulting corresponds to the fracture of coupled asperities on the fault plan aes caused by the fracture of individual asperities exhibit similar characteristics to the sequence for natural earthquakes including foreshock mainshock and aftershock events foreshocks initiated at the edge of the asperity occur with an event rate that increases according to a power law of the temporal distance to the mainshock and with a decreasing b value from 1 1 to 0 5 one or a few mainshocks then initiate at the edge of the asperity or the front of the foreshocks the aftershock period is characterized by a remarkable increase and subsequent gradual decrease in b value and a decreasing event rate obeying the modified omori law which has been well established for earthquakes the fracture of neighboring asperities is then initiated after the mainshock of a particular asperity presumably due to redistribution of the strain energy accumulated within an asperity which is released by the mainshock resulting in enhancement of the stress concentration around the nearest neighboring intact asperities the progressive fracturing of multiple coupled asperities during the nucleation of shear faulting results in short term precursory fluctuations in both b value and event rate which may prove useful information in the prediction of failure of the main fault plane of seismic earthquakes

inversion of complex body waves we have developed a method that inverts seismic body waves to determine the mechanism and rupture pattern of earthquakes the rupture pattern is represented as a sequence of subevents distributed on the fault plane this method is an extension of our earlier method in which the subevent mechanisms were fixed in the new method the subevent mechanisms are determined from the data and are allowed to vary during the sequence when subevent mechanisms are allowed to vary however the inversion often becomes unstable because of the complex trade offs between the mechanism the timing and the location of the subevents many different subevent sequences can explain the same data equally well and it is important to determine the range of allowable solutions some constraints must be imposed on the solution to stabilize the inversion we have developed a procedure to explore the range of allowable solutions and appropriate constraints in this procedure a network of grid points is constructed on the i plane where and i are respectively the onset time and the distance from the epicenter of a subevent the best fit subevent is determined at all grid points then the correlation is computed between the synthetic waveform for each subevent and the observed waveform the correlation as a function of and i and the best fit mechanisms computed at each i grid point depict the character of allowable solutions and facilitate a decision on the appropriate constraints to be imposed on the solution the method is illustrated using the data for the 1976 guatemala earthquake

fault reactivation and pseudotachylite generation in the semi brittle and brittle regimes examples from the gavilgarh tan shear zone central india in the sheared and foliated granitoids of the proterozoic gavilgarh tan shear zone gtsz in central india two types of pseudotachylite pt m and pt c are recognized pt m layers are interbanded with mylonite and ultramylonite show strong internal plastic deformation and buckle folding concurrent with the host rocks and appear to have formed within the greenschist facies 300 400 c in the brittle plastic transitional semi brittle regime pt c layers show sharp contacts with the host rock exhibit abundant coeval cataclasis preserve no evidence of subsequent plastic deformation and formed at shallower depths at temperature

dislocation creep regimes in quartz aggregates abstract using optical and tem microscopy we have determined that three regimes of dislocation creep occur in experimentally deformed quartz aggregates depending on the relative rates of grain boundary migration dislocation climb and dislocation production within each regime a distinctive microstructure is produced due primarily to the operation of different mechanisms of dynamic recrystallization at lower temperatures and faster strain rates the rate of dislocation production is too great for diffusion controlled dislocation climb to be an effective recovery mechanism in this regime recovery is accommodated by strain induced grain boundary migration recrystallization with an increase in temperature or decrease in strain rate the rate of dislocation climb becomes sufficiently rapid to accommodate recovery in this regime dynamic recrystallization occurs by progressive subgrain rotation with a further increase in temperature or decrease in strain rate dislocation climb remains sufficiently rapid to accommodate recovery however in this regime grain boundary migration is rapid thus recrystallization occurs by both grain boundary migration and progressive subgrain rotation the identification of the three regimes of dislocation creep may have important implications for the determination of flow law parameters and the calibration of recrystallized grain size piezometers in addition the identification of a particular dislocation creep regime could be useful in helping to constrain the conditions at which a given natural deformation has occurred

upper crust response to geodynamic processes beneath isparta angle sw turkey revealed by cmt solutions of earthquakes abstract the isparta angle is an important area of sw anatolia where extensions in all directions n s ne sw nw se and e w meet these extensions were determined by normal faulting structures as well as by shallow earthquakes all extensions except the e w one were attributed to the deviatoric stresses in relation to slab forces and or extrusion of anatolia the moment tensor inversion of 40 shallow earthquakes which occurred in the inner part of the isparta angle give focal mechanisms mostly indicating normal faulting inversion of all focal mechanisms of the earthquakes obtained from the moment tensor inversion yields normal faulting characterized by an approximately e w n268 e 3 axis the calculated stress ratio r is 0 6944 indicating a triaxial stress state commonly accepted geodynamic models for the eastern mediterranean region do not include plate boundary forces acting in the east or west direction our hypothesis is that the cause of the e w extension is the combined forces of gravitational potential energy and the hot asthenosphere upwelling through a tear fault in the subducted african plate between the hellenic and cyprus arcs beneath the isparta angle

tectonothermal events in central indian tectonic zone citz and its implications in rodinian crustal assembly abstract the precambrian crust of central india comprising bundelkhand craton bkc in the north and bastar craton bc in the south were accreted along a ene wsw trending proterozoic central indian tectonic zone citz the citz is an ensemble of several low to medium grade supracrustal belts gneisses granitoids and a few linear tracts of granulite belts a number of crustal scale shear zones define the boundaries of the supracrustal belts and discrete terrains available data suggest polyphase tectonothermal events in citz spanning from palaeoproterozoic to early neoproterozoic each event is characterized by contractional tectonic regime and attendant metamorphism and magmatism a new plate tectonic model in contrast to the earlier one of yedekar et al geol surv india spec publ 28 1990 is proposed according to the present model a northward dipping subduction system leading to continent continent collision explains the growth and assembly of the citz the continent continent collision is tentatively placed at ca 1 5 ga which is comparable to similar tectonothermal event in chotanagpur gneissic complex further east while the suturing event predates the global grenvillian orogeny ca 1 3 1 0 ga the sausar tectonothermal event ca 1 1 0 9 ga of citz is correlatable with the latter

the 1 october 1995 dinar earthquake sw turkey the dinar earthquake ms 6 1 usgs pde of 1 october 1995 occurred on the nwse trending dinar fault the earthquake is associated with a 10 km long surface rupture with predominantly normal faulting the mainshock was preceded by a series of foreshocks that started 6 days before the mainshock and included two md 4 5 events the mainshock source mechanism derived from the inversion of broad band p waves revealed that two sub events occurred on a nw se trending normal fault with a small strike slip component according to the source model estimated in this study the first rupture started at a depth of about 8 km and reached to a depth of about 12 km propagating north west the total seismic moment found from the inversion of p waveforms is 2 0 times 10 18 nm the seismic moment of the second sub event was about four times larger than the first one field observations gps measurements and slip vector obtained from the inversion of broad band p waveforms suggest that the nw se trending dinar fault is due to the internal deformation of sw anatolia moving south westwards

surface rupture and rupture mechanism of the october 1 1995 m w 6 2 dinar earthquake sw turkey abstract a moderate earthquake m w 6 2 caused substantial damage in the town of dinar at 17 57 ut on october 1 1995 surface rupture has been observed to be discontinuous for 10 km along the nw trending dinar fault segments the surface rupture has consisted of nearly vertical cracks up to several tens of meters long and a meter wide that display linear sigmoidal and anastomosing geometries indicating the mechanism of displacement on the fault plane most of these cracks display a dip slip component of displacement 0 05 0 6 m those with anastomosing geometries indicate a large dip slip 0 25 m sigmoidal crack patterns show both right and left strike slip rotational component of displacement and a small dip slip

the brittle plastic transition and the depth of seismic faulting a simple rheological model of shearing of the lithosphere that has gained wide acceptance is a two layer model with an upper brittle zone in which deformation takes place by frictional sliding on discrete fault surfaces and a lower plastic zone in which deformation takes place by bulk plastic flow the two are separated by an abrupt brittle plastic transition which is assumed to be indicated by the lower limit of seismicity experimental studies however as well as the deformation structures of mylonites indicate that a broad transitional field of semi brittle behavior lies between these extremes this is a field of mixed mode deformation with a strength that can be expected to be considerably higher than that predicted from the extrapolation of high temperature flow laws for quartzofeldspathic rocks the semi brittle field lies between t1 the onset of quartz plasticity at about 300 c and t2 feldspar plasticity at about 450 c a model is presented in which the transition t1 does not correspond to a transition to bulk flow but to a change from unstable velocity weakening friction to stable velocity strengthening friction t1 thus marks the depth limit of earthquake nucleation but large earthquakes can propagate to a greater depth t3 t3 t2 which corresponds to the lower limit of dynamic frictional behavior in the semi brittle field and approximately to the peak in strength the zone between t1 and t3 is one of alternating behavior with flow occurring m the interseismic period and with co seismic dynamic slip occurring during large earthquakes this zone is characterized by mylonites interlaced by pseudotachylytes and other signs of dynamic faulting the transition t1 is also marked by a change in the generation mechanism of fault rocks from abrasive wear above which produces cataclastites to adhesive wear below which is proposed as an important generation mechanism of mylonites in the upper part of the semi brittle field

active tectonics of the north and central aegean sea summary in this paper we examine the connection between the westward motion of turkey relative to europe and the extension in and around the aegean sea the principal new data available since the last attempt to synthesize the tectonics of this region by mckenzie 1978 are much improved focal mechanisms of earthquakes constrained by p and sh body wave modelling as well as by first motions these mechanisms show that the faulting in the western part of the aegean region is mostly extensional in nature on normal faults with a nw to wnw strike and with slip vectors directed nnw to nne there is evidence from palaeomagnetism that this western region rotates clockwise relative to stable europe in the central and eastern aegean and in nw turkey distributed right lateral strike slip is more prevalent on faults trending ne to ene and with slip vectors directed ne palaeomagnetic data in this eastern region is more ambiguous but consistent with very small or no rotations in the northern part and possibly anticlockwise rotations relative to europe in the south the strike slip faulting that enters the central aegean from the east appears to end abruptly in the sw against the nw trending normal faults of greece the kinematics of the deformation is controlled by three factors the westward motion of turkey relative to europe the continental collision between nw greece albania and the apulia adriatic platform in the west and the presence of the hellenic subduction zone to the south as the right lateral slip on the north anatolian fault enters the aegean region it splays out becoming distributed on several parallel faults the continental shortening in nw greece and albania does not allow the rotation of the western margin of the region to be rapid enough to accommodate this distributed e w right lateral shear and thus leads to e w shortening in the northern aegean which is compensated by n s extension as the southern aegean margin can move easily over the hellenic subduction zone the dynamics of the system once initiated is self sustaining being driven by the high topography in eastern turkey and by the roll back of the subducted slab beneath the southern aegean the geometry of the deformation resembles the behaviour of a system of broken slats attached to margins that rotate in spite of its extreme simplicity a simple model of such broken slats is able to reproduce quantitatively most of the features of the instantaneous velocity field in the aegean region including the slip vectors and nature of the faulting in the eastern and western parts the senses and approximate rates of rotation the overall extensional velocity across the aegean and the distribution of strain rates as seen in the seismicity and topography or bathymetry and using geodetic measurements as part of this study we re examined the relation between the surface faulting and the focal parameters determined seismologically for the three large 1981 gulf of corinth earthquakes and reassessed the evidence for associating particular earthquakes in the sequence with observed surface faulting an important result is that in one of the events there is a resolvable discrepancy between the slip vector measured at the surface and that determined from the seismic body waves

zirconolite and baddeleyite in an ultramafic suite from southern india early ordovician carbonatite type melts associated with extensional collapse of the gondwana crust abstract we report here the occurrence of rare zirconium bearing minerals zirconolite cazrti2o7 and baddeleyite zro2 from an unusual ultramafic suite within the achankovil shear zone acsz in southern india zirconolite occurs as inclusions within spinel in phlogopite graphite spinellite and shows characteristic development of radial cracks baddeleyite is commonly observed as an included phase within phlogopite from phlogopite dunite and graphite spinel glimmerite the mineral also occurs less commonly within spinel and graphite from graphite spinel glimmerite the composition of zirconolite is characterized by an enrichment of u and th over rare earth elements baddeleyite shows abundance of zr with minor hf ti and u the mode of occurrence along with the chemical composition of these minerals implies their formation as early stage crystallization products from a silica undersaturated melt that was enriched in carbonatite phile elements such as ca zr ti and volatiles co2 and h2o we report

rb sr and sm nd dating of different metamorphic events from the sausar mobile belt central india implications for proterozoic crustal evolution abstract sr and nd isotopic studies of various rock suites and their mineral separates in and around the sausar mobile belt central india have revealed that 1 the last amphibolite facies metamorphism main sausar metamorphism occurred during 800 900 ma and has more or less reset the rb sr isotopic clock in this whole terrain whereas older sm nd isotopic signatures were mostly unaffected 2 the main sausar group of rocks is bounded both in the north and the south by two granulite belts of different crustal histories at least up to 1100 ma 3 the northern granulite belt experienced peak metamorphism during pre 1100 ma followed by steep decompression and subsequent cooling around 1100 ma 4 peak metamorphism in the southern granulite belt occurred at 2672 ma this was followed by emplacement of a vast basic igneous body represented as metagabbro and subsequent cooling around 1400 ma these two granulite belts were juxtaposed with each other during the neo mesoproterozoic which is correlatable with high pressure metamorphism in the northern granulite belt this tectonic movement might have been triggered by mesoproterozoic rifting of the southern bastar craton resulting in basic magmatism in the southern granulite belt mafic dykes were emplaced during subsequent readjustment of the crust and amphibolite facies reactivation main sausar event of granulites in the whole terrain lithological and tectonic arrangements metamorphic history along with the present geochronological data from citz point towards an evolutionary history similar to the grenville province of canada

failure stress change caused by the 1992 erzincan earthquake ms 6 8 we calculated coulomb failure stress change caused by the march 13 1992 erzincan turkey earthquake and explored the relationship between failure stress and the aftershock distribution which includes the pulumur earthquake ms 5 8 that occurred two days later one of the most significant features of the erzincan earthquake was the location of aftershocks which did not correspond with either the eastern segment of the north anatolian fault zone or the ovacik fault this feature can be explained by mapping the failure stress due to the erzincan earthquake the map revealed that there is a significant correlation between the aftershock distribution and the areas where static stress was raised by 0 3 bar the 1992 erzincan earthquake raised the coulomb failure stress about 1 4 bar at the site of the pulumur event this stress rise and optimum orientation of the pulumur fault favoured its occurrence

hydrothermal experiments on alteration of ca al rich inclusions cais in carbonaceous chondrites implication for aqueous alteration in parent asteroids carbonaceous chondrites contain ca al rich inclusions cais which consist mainly of refractory minerals including gehlenite spinel perovskite and hibonite which are predicted to be the first phases formed from early solar nebula on the basis of thermodynamic calculations however many cais contain secondary minerals such as nepheline calcite and phyllosilicates the formation process of secondary minerals in cais is still controversial whether they were produced by the reaction with solar nebula or by aqueous alteration in parent asteroids we performed hydrothermal experiments on gehlenite spinel and diopside which are common in cais in carbonaceous chondrites to study aqueous alteration in parent asteroids mixtures of gehlenite with sio2 and or al2o3 and those of sio2 with al2o3 were also employed to study products of these systems which have a close relationship to crystallization of secondary minerals in cais in fluid in parent asteroids hydrogrossular calcite and amorphous al si were obtained from gehlenite by hydrothermal experiments whereas both spinel and diopside escaped alteration suggesting that gehlenite is the weakest mineral among these refractory minerals against alteration this result is consistent with observation of cais analcime nepheline hydrate and tobermorite were obtained from the runs for mixtures of gehlenite with sio2 whereas the products from mixtures of al2o3 with sio2 were analcime nepheline hydrate and hydrosodalite these results suggest that the alteration process of gehlenite is as follows 1 gehlenite was dissolved by fluid in chondrite parent asteroids to release ca al and si from the surface 2 co32 in fluid reacted with ca to crystallize calcite 3 na al and si in fluid crystallized nepheline hydrate hydrosodalite and or analcime 4 ca al and si in fluid crystallized hydrogrossular without co32 and excess ca and si crystallized ca si hydrate such as tobermorite heating experiments on several minerals obtained through hydrothermal experiments were also performed to study thermal metamorphism in parent asteroids hydrogrossular was converted into hydrogrossular with a lower h2o content and analcime and nepheline hydrate were converted into nepheline tobermorite is known to be converted into wollastonite with increasing temperature the results of experimental studies suggest that most secondary minerals found in cais in carbonaceous chondrites were produced from gehlenite by aqueous alteration and the subsequent thermal metamorphism in parent asteroids

shear criteria in granite and migmatite deformed in the magmatic and solid states microstructural criteria for the determination of the sense of shear in rocks homogeneously deformed in the partially melted state are similar to those which apply to solid state deformation sense of shear determination is either direct deduced from the sense of rotation of markers or indirect involving the obliquity between the shear and foliation planes or between the successive foliations imprinted at different stages of progressive deformation this study is a by product of the detailed structural and microstructural investigation of a high grade metamorphic rock pile variscan vosges massif france which underwent subhorizontal shearing during partial melting and further solidification depending on the rock chemistry on the position in the pile and the relative timing of progressive deformation layered migmatites and homogeneous granites were variously deformed in the partially melted and solid states the sense of shear obtained from these rock types using the criteria presented here consistently gives a top to sw direction

vs30 mapping and soil classification for seismic site effect evaluation in dinar region sw turkey summary the dinar earthquake m s 6 1 of 1995 october 1 killed 90 people and destroyed more than 4000 buildings despite the moderate size of the earthquake the level of damage was extremely high which led to many studies that were carried out in the region the majority of these studies concluded that the main reasons for the damage were the construction errors and the poor soil conditions however at that time no appropriate soil condition map based on extended high density measurements was available shear wave velocity is an important parameter for evaluating the dynamic behaviour of soil in the shallow subsurface thus site characterization in calculating seismic hazards is usually based on the near surface shear wave velocity values the average shear wave velocity for the top 30 m of soil is referred to as v s 30 for earthquake engineering design purposes both the uniform building code ubc and eurocode 8 ec8 codes use v s 30 to classify sites according to the soil type the v s 30 values calculated by using multichannel analysis of surface waves masw were used to create a new soil classification map of the dinar region surface seismic measurements were carried out at 50 locations mostly in dinar city and its surroundings the dispersion data of the recorded rayleigh waves were inverted using a genetic algorithm ga method to obtain shear wave velocity profiles of the investigated sites thus the derived v s 30 map of the dinar region was transformed to the ubc and ec8 standards soil classification results show that most parts of the region located in alluvial basin have low shear wave velocity values these values are within the range of 160 240 m s 1 and thus fall into the s d and s e categories according to the ubc and the c and d categories according to ec8 within the region some parts located on the hill zone and the transition zone have better soil conditions corresponding to s c ubc and b ec8 categories and have comparatively high shear wave velocities in the range of 500 740 m s 1 and 350 450 m s 1 respectively v s 30 and soil classification maps were compared with the damage distribution associated with the earthquake in possession of a detailed shear wave velocity map of dinar city in general the results show that there is a correlation between the v s 30 values and the damage distribution of the region in addition to the low v s 30 values the likely causes of the damage were investigated and it is observed that one of the major factors for high levels of damage is 3 d variations of geological structures

geomorphic evidences and chronology of multiple neotectonic events in a cratonic area results from the gavilgarh fault zone central india abstract the ene wsw trending gavilgarh fault zone gfz is an important tectonic lineament within the central indian shield geomorphological mapping and spatial analyses of rivers were carried out to elucidate the imprints of active tectonics on the fluvial systems of this region the sinuosity index width depth ratio of river valleys longitudinal profile s l index and hypsometric index of the rivers flowing from north to south across the gfz lineament suggest that the northern side of gfz was tectonically uplifted luminescence dating of sediments from river terraces and calculation of knickpoint migration rates in the rivers indicate occurrence of multiple neotectonic events in gfz at ca 65 80 ka ca 50 ka ca 30 40 ka and ca 14 ka evidences of neotectonic activity presence of active geothermal springs and occurrence of recent earthquakes along gfz suggest that this lineament is tectonically active and there is a need for proper seismic monitoring of this fault zone

repeated reactivation of the gavilgarh tan shear zone central india implications for the tectonic survival of deep seated intra continental fault zones abstract continental crust accommodates crustal deformation through repeated reactivation of old shear fault zones that constitute domains of long term structural weakness reactivation is often triggered by mechanical and chemical fluid assisted changes of the host rocks within the fault core region however faults can also reactivate in fluid poor condition if they are oriented favourably with respect to the prevalent stress regime an example comes from the gavilgarh tan shear fault zone gtsz in the central indian craton which shows clear evidences of repeated fault reactivation movements widely separated in time in neoproterozoic ordovician permo triassic late cretaceous and holocene presence of pseudotachylyte along some reactivated fault strands indicates seismogenic fault movements in the past kinematic signatures of the shear zone with contrasting slip senses indicate repeated geometric reactivation of the gtsz in the pre quaternary as well as one episode of kinematic reactivation in the quaternary period under the present nne ssw directed compressive stress regime of the indian craton the gtsz is prone to further seismogenic fault movements

when is a fault extinct existing regulatory definitions of time periods over which evidence should be searched to demonstrate whether a fault is or is not active may be unconservative in slowly deforming continental regions where recurrence intervals of surface faulting are in excess of 100 000 years self evidently no definition of an active fault can be satisfactory when founded on some extrinsic time period instead it must be derived from the properties of the system itself preferably through knowledge of fault movement recurrence intervals or alternatively and conservatively from an understanding of the time period over which the present conditions of regional stress and strain the current tectonic regime have prevailed borrowing from volcanological terminology out of the definition of the active fault emerges an antithesis the extinct fault time periods by which directly dated faults are designated as active or extinct have to be locally derived

the blue angel i the mineralogy and petrogenesis of a hibonite inclusion from the murchison meteorite a detailed mineralogie chemical and petrologic study of the blue angel a relatively large 1 5 mm hibonite containing inclusion from the murchison meteorite was performed in an attempt to understand the mechanisms of formation and modification of hibonite rich inclusions the blue angel inclusion is composed of roughly equal amounts of hibonite and calcite with minor amounts of spinel perovskite diopside and an fe rich silicate the inclusion can be divided into three roughly concentric zones a hibonite rich core a calcite rich mantle and a spinel rich layered rim the mineral chemistry and petrography of the blue angel are consistent with a three stage formation history 1 an early stage of nebular condensation which produced the hibonite perovskite and spinel 2 a moderate temperature stage of aqueous alteration and metamorphism occurring on a small planetary body containing co 2 and h 2o during which calcite was formed in the inclusion and 3 the final emplacement of the blue angel into its present position in murchison the study of the blue angel indicates that extensive alteration of ca al rich inclusions cai may have occurred by aqueous alteration and thermal metamorphism followed by explosive mixing processes on a parent body such metamorphic reactions may involve formation and destruction of phases such as melilite and diopside which have been previously thought to be primary condensates the mechanisms proposed for the formation and modification of the blue angel help to explain the secondary phases and oxygen isotope anomalies found in many cai and eliminate the need for invoking kinetically complicated back reactions at very low pressures with a cool part of the solar nebula the contribution of planetary metamorphism in the formation and alteration of cai must be considered along with nebular processes in order to understand the formation of carbonaceous chondrites

the recognition of reactivation during continental deformation reactivation involves the accommodation of geologically separable displacement events intervals 1 ma along pre existing structures the definition of a significant period of quiescence is central to this phenomenological definition and the duration of the interval chosen represents the resolution limit of reactivation criteria found in most ancient settings in neotectonic environments reactivation can be further defined as the accommodation of displacements along structures that formed prior to the onset of the current tectonic regime this mechanistic definition cannot always be applied to ancient settings due to the uncertainties in constraining relative plate motion vectors four sets of criteria may be used to recognize reactivation in the geological record stratigraphic structural geochronological and neotectonic some structural criteria may not be reliable if used in isolation to identify reactivated structures much of the previously published evidence cited to invoke structural inheritance is equivocal as it uses similarities in trend dip or three dimensional shape of structures numerous fault and shear zone processes can cause significant weakening both synchronously with deformation and in the long term and may be invoked to explain reactivation the collage of fault bounded blocks forming most continents therefore carries a long term architecture of inheritance which can explain much of the observed complexity of continental deformation zones

a detailed slip model for the 1995 october 1 dinar turkey earthquake ms 6 1 determined from inversion of teleseismic p and sh waveforms summary teleseismically recorded p and sh waveforms of the 1995 october 1 dinar turkey earthquake are inverted to find detailed coseismic slip distribution on the ruptured part of the dinar civril fault for this purpose a linear finite fault inversion procedure with time window approach is used to allow variable rise time and rupture velocity on the model fault the source is represented by a 24 21 km rectangle fault plane which is divided into 56 equal size subfaults the strike and the dip of the fault plane are assumed as determined by a previous study the amount of slip and the rake angle on each subfault is retrieved through fitting the observed and synthetic seismograms in a least squares sense the previous inversion studies indicated that the earthquake was associated with two subevents with a 6 s time lag of the nw subevent therefore the model fault plane is also divided into two separate equal area segments the se and the nw segments to delay the rupture propagation over the nw segment we tried several models to fix the delay time and hypocentral depth and to explain the waveforms the smallest misfit error resulted from a model with 5 s delay time and 7 5 km hypocentral depth the preferred solution suggests that the earthquake is associated with breaking of two asperities and the coseismic slip occurred mostly above the depth of 10 km the smaller asperity is located to the se just beneath dinar town with peak slip of 26 cm while the larger one is located to the nw with peak slip of 41 cm the observed surface rupture coincides with the location of the smaller asperity the seismic moment for our slip model is 2 8 1018 n m the modelling yields an average rake angle of 102 and almost no difference between the average rake angles of the two asperities

fault zone reactivation kinematics and mechanisms the kinematics and mechanisms of fault zone reactivation are reviewed reactivation is dependent upon fault zone orientation and the existence of weak mylonites along these zones the recognition of reactivation within mylonite zones and the softening processes that first concentrate deformation into these and secondly provide a weak medium for reactivation are discussed attention is given to the darling mobile zone western australia and the redbank zone see obee white this symposium as examples of reactivated zones

the structure and rheological evolution of reactivated continental fault zones a review and case study abstract repeated reactivation of structures and reworking of crustal volumes are characteristic though not ubiquitous features of continental deformation reactivated faults and shear zones exposed in the deeply exhumed parts of ancient orogenic belts present opportunities to study processes that influence the mechanical properties of long lived fault zones at different palaeo depths ancient basement fault systems typically comprise heterogeneous superimposed assemblages of fault rocks formed at different times and depths for which down temperature thermal histories are most common several lithological and environmental factors influence the evolution of fault rock fabrics and rheology but most fault shear zone arrays appear to develop as self organized deformation systems once mature the kinematic and mechanical evolution of the system is strongly influenced by the rheological behaviour of the interconnected fault shear zone network a case study from the crustal scale great glen fault zone ggfz scotland reveals a complex evolution of mid to upper crustal deformation textures formed adjacent to the frictional viscous transition fluid influx in the mid crust has led to reaction softening of the rock aggregate as strong pre existing phases such as feldspar are replaced by fine grained strongly aligned aggregates of weak phyllosilicates in addition a grainsize controlled switch to fluid assisted diffusional creep occurs in the highest strain regions of the fault zone it is proposed that this led to a shallowing and narrowing of the frictional viscous transition and to long term overall weakening of the fault zone relative to the surrounding wall rocks cataclasis is particularly important in the deeper part of the frictional regime as it helps to promote retrograde metamorphism and changes in deformation regime by both reducing grainsize and promoting pervasive fluid influx along fault strands due to grain scale dilatancy equivalent processes are likely to occur along many other long lived crustal scale fault zones

active fault segmentation of the civril graben system and surface rupture of the 1 october 1995 dinar earthquake mw 6 2 southwestern anatolia turkey abstract the civril graben system cgs is one of the important tectonic structures developed within the western anatolia extensional tectonic regime the cgs has an arcuate geometry looking south and comprises two main geometric sections of the nw striking dinar graben and the ne striking baklan graben with a total length of 100 km the main faults limit the north edge of the cgs while the south edge is bounded by their antithetic structures the northern boundary structures of the graben comprise two main fault segments of dinar and civril graben fill is plio quaternary lacustrine fluvial sediments with late pleistocene holocene flood plain lacustrine marsh and alluvial fan sediments historical records and destructive earthquakes occurred in the last century indicate the region is one of the significant seismogenic zones the last destructive earthquake in the graben was the 1995 dinar earthquake mw 6 2 which caused approximately 10 km long surface rupture on the kizilli segment of the dinar fault field based geological mapping and structural geology in this study and available seismic and paleoseismological data reveal that the other sub segments of the dinar and civril faults which have not ruptured in the last 150 years have the potential to produce earthquakes with mw 6 0 and larger the paleoseismic rate is assessed to be 1 mm year for the kizilli segment while the geologically long term slip rate range is calculated to be 0 27 0 05 mm year

precambrian continental crust of india and its evolution the indian precambrian continental crust exhibits a variety of geological features fashioned at different times by different geotectonic processes the bulk of this crust was formed prior to 2600 m y ago and remobilized at least twice between 2600 2000 m y ago early proterozoic mobile belt epmb and 2000 1500 m y ago middle proterozoic mobile belt mpmb three early precambrian nucleii karnataka kn jeypore bastar jbn and singhbhum sn appear to have survived in the craton and are characterized by low grade supracrustals and tonalitic trondhjemite gneisses formed 3800 2600 m y ago the epmb event involved sedimentation amphibolite granulite facies metamorphism and co 2 k metasomatism and produced amphibolite facies rocks and k granites in the north and charnockite and other granulite facies rocks in the south gold sporadically distributed in the supracrustal rocks of the craton was remobilized during the epmb event k granites form a garland around the central dharwar craton sugg

stress field and seismicity in the indian shield effects of the collision between india and eurasia intraplate stresses and intraplate seismicity in the indian subcontinent are strongly affected by the continued convergence between india and eurasia the mean orientation of the maximum horizontal compression in the indian subcontinent is subparallel to the direction of the ridge push at the plate boundary as well as to the direction of compression expected to arise from the net resistive forces at the himalayan collision zone indicating that the intraplate stresses in the subcontinent including the shield area are caused by plate tectonic processes spatial distribution of historic and instrumentally recorded earthquakes indicate that the seismic activity is mostly confined to linear belts while the remaining large area of the shield is stable the available conventional heat flow data and other indicators of heat flow suggest hotter geotherms in the linear belts leading to amplification of stresses in the upper brittle crust many of the faults in these linear belts which happen to be 200 80 m y old are being reactivated either in a strike slip or thrust faulting mode the reactivation mechanisms have been analyzed by taking into consideration the amplification of stresses pore pressures geological history of the faults and their orientation with respect to the contemporaneous stress field the seismicity of the indian shield is explained in terms of these reactivation mechanisms

asperities barriers characteristic earthquakes and strong motion prediction recent results from paleoseismology suggest that earthquakes recurrent on a given fault may often have the same characteristic length and amount of slip stable asperities and barriers which survive many earthquakes can explain these results the activity of volcano usu japan since 1977 which produced a dacite dome with a total upheaval of 180 m offered a great opportunity to study the recurrence behavior of a fault seismologists at hokkaido university revealed a family of repeated earthquakes with nearly the same amount of slip generated from the same fault plane on the crater wall along which the dome moved upward this family can be explained by the existence of a stable asperity on the crater wall and is called the asperity type family they found however another type of family of earthquakes which share the same fault plane but show a great range of variation in the amount of slip the behavior of the latter family can be explained by the presence of weak barriers over a fault plane defined by strong stable barriers and this family is referred to as the barrier type family this type of earthquake model has been used successfully in the interpretation of observed strong motion acceleration spectra from california and the results reveal the stability of local stress drop among different earthquakes the agreement found between local stress drops estimated from strong motion data and those inferred from geological observation supports the possibility for predicting earthquake strong motion directly from geological observation of the causative fault

magnitude versus faults surface parameters quantitative relationships from the aegean region historical and seismotectonic data from the broader aegean region have been collected and all possible information relative to ground deformation associated to earthquakes that hit the area have been re evaluated all events associated to co seismic surface faulting have been selected and further investigated while geomorphologic and geological criteria have been used to recognise and characterise the seismogenic faults associated to these morphogenic earthquakes sensu bull inqua 16 1993 24 in particular in order to perform seismic hazard analyses we compiled a list of all earthquakes where the surface rupture length srl the maximum vertical displacement mvd or the average displacement ad is available we thus obtained reliable values of these source parameters for 36 earthquakes of which 26 occurred during the 20th century 6 in the 19th century and the 3 remaining earlier magnitude versus srl and mvd has been compiled for estimating empirical relationships the calculated regression equations are ms 0 90 log srl 5 48 and ms 0 5 9log mvd 6 75 showing good correlation coefficients equal to 0 84 and 0 82 respectively co seismic fault rupture lengths and especially maximum displacements in the aegean region have systematically lower values than the same parameters worldwide but are similar to those of the eastern mediterranean middle east region the envelopes of our diagrams are also calculated and discussed for estimating the worst case scenario furthermore for all investigated seismogenic structures based on several geological criteria we measured the geological fault length gfl which is the total length of the neotectonic faults showing cumulative recent activity we then compared srl with gfl and their ratio shows a clear bimodal distribution with a major peak at 0 8 1 0 indicating that about 50 of the investigated earthquakes ruptured almost the entire fault length while a second peak around the value of 0 5 is clearly related to a segmentation process of longer neotectonic structures further implications of this distribution are also discussed eventually from the distribution of gfl versus magnitude we also infer an important geological threshold for the occurrence of morphogenic earthquakes at about 5 5 degrees

the horizontal velocity field in the deforming aegean sea region determined from the moment tensors of earthquakes we use the spatial distribution of seismic moment tensors of earthquakes in the aegean region over the time interval 1909 1983 to recover a continuous horizontal velocity field that describes the overall deformation of the lithosphere at large length scales the calculated velocity field is dominated by two effects 1 an e w right lateral shear of the eastern aegean related to motion on the north anatolian fault becoming distributed as it enters the aegean and 2 a n s extension probably related to the sinking of the slab in the hellenic trench the southern part of the central aegean is found to be moving in a sw direction relative to europe at a rate of about 30 mm yr probably a lower bound with an error of around 10 mm yr and rotating clockwise in the seismogenic upper crust this velocity field is accommodated by right lateral strike slip faults in the eastern aegean and by normal faults that rotate clockwise in central greece a comparison of paleomagnetic declination data with the expected rotation of rigid elongate inclusions in the velocity field shows in most places an agreement in sense and approximate agreement in rate of rotation expected rotation rates of line elements are sometimes too low probably because our derived velocity field is smoothed and unable to match locally high strain rates there is only one part of the region where line elements are predicted to rotate in either clockwise or counterclockwise directions depending on their orientation this is in western turkey which coincident ally is the only place where paleomagnetic rotations in both directions have been observed this coincidence in particular suggests to us that the analogy of rigid elongate inclusions in the velocity field responding to forces on their bases may be useful in predicting the senses and approximate rates of rotation of crustal blocks in deforming continental regions the velocity field we obtain preserves the strike directions of the major faults as directions of zero length change in spite of considerable smoothing we use this observation to speculate that the interaction between the upper crust and the rest of the lithosphere beneath it may involve an interplay of effects on one hand the variation of strength with direction in the crust may control the strike directions of faults that form or become reactivated and may also limit the velocity fields that are allowable on the other hand the fault bounded blocks may rotate in the velocity field in response to forces on their bases which would require the velocity field to change with time if the directions of zero length change are fixed to the blocks

evolution of caal rich bodies in the earliest solar system growth by incorporation abstract many type b ca al rich inclusions cai s in the allende carbonaceous chondrite contain two types of spinel structures framboids and palisades framboids are clumps of spinel grains generally in situ by solid state growth processes palisades are texturally different and consist of ovoid shells of spinel grains that appear in thin sections as long arcs or rings with diameters ranging from 50 m up to 2 cm no in situ formation process seems able to explain the variety of sizes and morphologies of palisades nor the different compositions and textures of the enclosed and enclosing materials we therefore suggest that palisades are the spinel rims of smaller earlier formed type b cai s that were incorporated into other cai material in various ways by capture into liquid drops by solid condensate overgrowths and by the partial melting or welding of agglomerates containing the bodies as some type b bodies have been found inside type a host material it appears that in at least some regions and probably generally type a cai s formed after type b we propose that type b cai s are residues from the heating and incomplete evaporation of interstellar dust during the accretion of the protosolar nebula and that type a cai s are later condensates from completely evaporated dust whose exotic 16 o rich component became more diluted in the gas phase

high spatial resolution 40ar 39ar dating of pseudotachylites geochronological evidence for multiple phases of faulting within basement gneisses of the outer hebrides uk abstract pseudotachylites within the neoarchaean to palaeoproterozoic basement of the lewisian gneiss complex have been analysed using the high spatial resolution 40 ar 39 ar uv laserprobe technique it has been possible to measure 40 ar 39 ar age and apparent9 age variations that would be beyond resolution by lower spatial resolution or bulk 40 ar 39 ar dating methods we report a range of complexities including significantly younger narrow 40 ar 39 ar ages for pseudotachylite forming events in lewis the c 1900 ma event may relate to early stages of laxfordian reworking in barra and south uist a 1300 1200 ma event is recorded whereas in barra south and north uist a second event is recorded at c 700 ma which is likely to be associated with nw and west directed thrusting and could represent far field effects of tectonic events recorded at this time east of the moine thrust in nw scotland supplementary material 40 ar 39 ar data are available at http www geolsoc org uk sup18372

regional variation of the ω upper bound magnitude of giii distribution in and around turkey tectonic implications for earthquake hazards complete data set of earthquakes in turkey and the adjacent areas has been used in order to compute the values in 24 seismic regions of turkey the parameter is obtained through gumbel s third asymptotic distribution of extreme values and is well known as upper bound magnitude this is an interpretation that no earthquake magnitude greater than can occur in a region the results also estimate the most probable magnitude for a time period of 100 years the estimates of exceed the value of 7 00 in 20 of the 24 seismic regions an effort is also made to find a relation between the magnitude and the length of a fault in the complicated tectonics of turkey and the surrounding area earthquake hazard revealed as tables and maps are also considered for turkey and the surrounding area

active faulting in apparently stable peninsular india rift inversion and a holocene age great earthquake on the tapti fault we present observations of active faulting within peninsular india far from the surrounding plate boundaries offset alluvial fan surfaces indicate one or more magnitude 7 6 8 4 thrust faulting earthquakes on the tapti fault maharashtra western india during the holocene the high ratio of fault displacement to length on the alluvial fan offsets implies high stress drop faulting as has been observed elsewhere in the peninsula the along strike extent of the fan offsets is similar to the thickness of the seismogenic layer suggesting a roughly equidimensional fault rupture the subsiding footwall of the fault is likely to have been responsible for altering the continental scale drainage pattern in central india and creating the large west flowing catchment of the tapti river a preexisting sedimentary basin in the uplifting hanging wall implies that the tapti fault was active as a normal fault during the mesozoic and has been reactivated as a thrust highlighting the role of preexisting structures in determining the rheology and deformation of the lithosphere the slip sense of faults and earthquakes in india suggests that deformation south of the ganges foreland basin is driven by the compressive force transmitted between india and the tibetan plateau the along strike continuation of faulting to the east of the holocene ruptures we have studied represents a significant seismic hazard in central india

a calcium aluminum rich inclusion from the essebi cm2 chondrite evidence for captured spinel hibonite spherules and for an ultra refractory rimming sequence abstract an unusual refractory inclusion was discovered in the essebi cm2 chondrite the inclusion has high concentrations of refractory lithophile and siderophile elements with strong enrichments of the most refractory elements lu sc hf in one part of the inclusion the inclusion consists of a melilite rich core partially surrounded by a very refractory rim which in turn is covered by a mantle enriched in si al fe mn cl and s melilite compositions vary from ak 10 26 in the core to ak 0 12 in the rim the core contains several complex framboids consisting of spinel fassaite or spinel hibonite these framboids are probably spherules of the types reported from murchison and were possibly captured by the molten inclusion before it solidified these findings may indicate a genetic link between framboids in cai s and the spinel rich spherules in murchison the rim sequence consists of the following five layers from inside to outside 1 1 hibonite spinel melilite 2 2 hibonite perovskite spinel melilite melilite in this layer is altered to sodalite nepheline calcite 3 3 a hibonite corundum solid solution 4 4 a spinel corundum solid solution as much as 0 1 mole fraction al 2 67 o 4 5 5 sc rich fassaite as much as 6 2 wt sc 2 o 3 spinel al 2 o 3 solid solution al rich diopside pt rich metal crystals occur only in the rim some of these metal crystals contain minor amounts of zr and hf indicating that they formed under reducing conditions the bulk mineral chemistry and texture of the essebi inclusion indicates a complex history involving capture of solid spinel and spinel hibonite spherules similar to the murchison type by a refractory melt droplet solidification of the droplet without obliteration of the spherule textures transportation of the composite object to hotter regions of the solar nebula where the very refractory rim condensed alteration of melilite to sodalite nepheline minor calcite and finally burial in the essebi parent body the cl s bearing mantle probably formed by reactions between the inclusion and liquid and gaseous phases in the parent body

architecture of the continental lithosphere the continental lithospheric plates are traversed by numerous large scale disclocations many of which date back to late archean or proterozoic times these major dislocations often extending for 1000 km or more are commonly characterized not only by the presence of fault rocks and by significant misfits between the adjacent crustal blocks but also by the presence of localized basins of deposition or by anomalous igneous suites or mineral deposits although to a first approximation they may be regarded as narrow linear features most consist of complex arrays of faults ductile shear zones and fractures some with associated deformation spread over tens and hundreds of kilometres lineaments that originated as whithin plate transcurrent shear zones or rift systems are generally steep and many of these probably extend down through the base of the crust into lithospheric mantle lineaments that iriginated as sutures along which formerly separated crustal blocks have been welded together are on the other hand sometimes expressions of low angle dislocations not continuous with mantle structures directly beneath the lineament observed at the surface geological records show that displacements or magmatic activity or both along many lineaments were repeated over long periods spanning successive changes in the global tectonic regime modern lineament movements can be fitted to plate tectonic hypotheses however pre phanerozoic movements are more conjectural for example early proterozoic lineaments appear to be associated with more extensive internal deformation within large crustal blocks the siting of fracture systems activated in response to regional plate motions has on occasion been determined by the occurrence of pre existing deep dislocations the scale and longevity of the deep dislocations raise many interesting general questions with respect to the coordination of mantle and crustal activities and to the evolution of the continental lithosphere

superimposed basin formation during neogene quaternary extensional tectonics in sw anatolia turkey insights from the kinematics of the dinar fault zone abstract in the extensional province of sw anatolia the cross cutting relationship between the nw and ne oriented neogene and quaternary basins is an ongoing debate in the understanding of the tectonic evolution of this area in order to contribute to this issue we carried out a structural and kinematic study along the seismogenic nw trending dinar fault zone dfz this structure was initially controlled by the sedimentary and tectonic evolution of the ne oriented neogene baklan acigol and burdur basins and later by the nw oriented quaternary dinar basin on the basis of 1000 structural and kinematic data in conjunction with basin stratigraphy the dfz can be divided into three almost parallel and continuous bands that are a the hangingwall where quaternary sediments are deformed by normal faults with mechanical striations b the inner zone corresponding to the present dinar fault scarp where nw trending normal faults with mechanical striations are dominant and c the outer zone located in the footwall of the structure comprising the area between the fault scarp and undeformed bedrock where faults exhibit variable orientation and kinematics from strike slip to normal dip slip these kinematics are mainly indicated by calcite shear veins and superimposed mechanical striations respectively this suggests that the dfz changed kinematics over time i e the dfz initiated as dominant dextral strike slip to oblique slip fault system and continued with a dominant normal movement therefore we hypothesize that the nw trending dfz was initially a transfer zone during the late miocene pliocene coeval to the sedimentary and structural evolution of the ne trending baklan acigol and burdur basins during the quaternary the dfz representing an already weakened crustal sector played the role of a normal fault system providing the accommodation space for the quaternary dinar basin hydrothermal circulation and volcanism at ne nw trending faults intersection implies structurally driven conduits channeling fluids from depth to surface

replacement textures in cai and implications regarding planetary metamorphism textural and chemical features of five coarse grained calcium aluminum rich inclusions from the allende meteorite indicate that some of the melilite in these inclusions was formed by a secondary metamorphic event and not by primary crystallization from a melt or by a sequential nebular condensation process these inclusions contain embayed pyroxene surrounded by melilite physically separated pyroxene crystals are often in optical continuity indicating that they were once part of larger single crystals that have been partly replaced by melilite other evidences of metamorphism include reaction textures between melilite and spinel and metamorphic textures such as kink band like features lobate sutured grain boundaries and 120 triple points this type of metamorphic process requires the addition of ca which we propose came from calcite or by introduction of a fluid phase we believe that the most likely environment for this metamorphic process is on a small planetary body and not in the solar nebula the results of this study are compatible with oxygen isotopic heterogeneities within cai and provide a mechanism for producing lower temperature alteration phases and the rim phases found in these inclusions we conclude that planetary processes must thus be considered in the formation history of cai and that it is necessary to reconsider the classification system of these objects in light of the replacement process proposed here

surface fault breaks aftershock distribution and rupture process of the 17 august 1999 izmit turkey earthquake the results obtained from field studies of surface fault breaks on land aftershock studies and analysis of complex teleseismic body waves of the 17 august 1999 izmit earthquake m w 7 4 indicate that the northern strand of the north anatolian fault zone had been ruptured between 29 1 e and 31 1 e with a maximum total fault rupture length of about 200 km the 12 november 1999 duzce earthquake m w 7 2 extended the surface fault break an additional 41 km to the east alignment of the aftershocks delineates the fault rupture on land and extends it to the west of the hersek delta well into the marmara sea to 29 1 e longitude we have identified six fault rupture segments two of them are located to the west of the hersek delta and four are located to the east rupture process analysis suggests two stages of rupture separated in space and time with an estimated total scalar seismic moment of 2 42 1020 n m the first stage initiated at the epicenter near izmit and propagated asymmetrically first eastward and then westward with a total scalar moment of 1 6 1020 n m showing predominantly right lateral strike slip faulting followed by a minor subevent extending the rupture further east the second stage took place at the western and eastern ends of the source area rupturing two segments within the marmara sea west of the hersek delta and two segments between akyazi and golyaka the rupture process analysis indicates that six fault segments were ruptured during the mainshock four of them on land and two within the marmara sea the major moment release of 1 2 1020 n m is found on the 64 km long sapanca segments located between the easternmost tip of the gulf of izmit and akyazi with an estimated maximum slip of 5 3 m the moment release on the golcuk segment with a length of 30 km is about 3 7 1019 n m and the estimated slip on this segment is 4 1 m rupture process analysis suggests two 20 km long segments between akyazi and golyaka striking n70 e the scalar moment releases on these segments are 2 7 1019 and 1 9 1019 n m with estimated offsets of 2 2 and 1 6 m respectively the last two subevents took place to the west of the hersek delta on the yalova segment and within the marmara sea with estimated offsets of 1 3 and 1 0 m respectively manuscript received 20 august 2000

magnitude distribution of linear morphogenic earthquakes in the mediterranean region insights from palaeoseismological and historical data we analyse the earthquake magnitude distribution of linear morphogenic earthquakes that reactivated dip slip normal faults within the mediterranean region information on past events is obtained following two distinct methodological approaches the geological one morphotectonic investigations and palaeoseismological excavations and the historical one contemporaneous descriptions and surveys of coseismic ruptures in order to homogenize the different data sets and therefore enabling a comparison we calculate moment magnitudes m w starting from seismic moments m 0 estimates the cumulative distributions thus obtained for the two data sets show differences that a series of non parametric tests suggests to be statistically significant coseismic displacements are systematically overestimated for strong m w 6 5 historically based earthquakes and for moderate 5 0 6 0 palaeoseismologically observed events also concerning the rupture length the geological information generally provides larger values for moderate earthquakes the possible causes of this discrepancy and the consequences in using the two data sets for seismic hazard assessment analyses are also discussed

seismic activity triggered by the 1999 izmit earthquake and its implications for the assessment of future seismic risk summary a serious question has remained as to the location of the western end of the main rupture zone associated with the 1999 izmit turkey earthquake a clear answer to this question is extremely important for the assessment of future seismic risk in the eastern marmara sea region turkey in this paper we show an effective approach to answering this important question unifying different kinds of information such as seismic activity focal mechanism solutions and stress changes caused by the main shock into a clear image we first point out that the major moment release is 1 6r10 20 n m and covered the area between 29 7ue and 30 5ue and we then claim that the enhanced seismic activity after the main shock in the eastern marmara sea region should be regarded as activity triggered by the increase of stress rather than as aftershock activity along the ruptured zone we propose three fault segments with an average stress increase on each in the western extension of the main shock rupture zone as potential sites for future large earthquakes namely i the 50 km long yalova hersek segment 0 45 mpa ii the nw setrending right lateral strike slip fault known as the princes islands segment 0 18 mpa

source inversion of the october 1 1995 dinar earthquake ms 6 1 a rupture model with implications for seismotectonics in sw turkey abstract an earthquake of ms 6 1 devastated the town of dinar sw turkey population 35 000 on october 1 1995 killing 90 people and destroying 30 of the town the earthquake generated complex body waveforms varying with azimuth at teleseismic distances the method of complex body waveform inversion developed by kikuchi and kanamori 1991 was used to infer a source process for the earthquake two subevents were necessary to explain the observed seismic records the inversion result suggests that the dinar earthquake initiated at the se end of the dinar fault with a subevent of seismic moment mo 0 5 1018 n m six seconds later the second subevent took place about 10 km to the northwest of the first subevent with a seismic moment a few times larger than the first the cmt depths of the first and second subevents were found to be 10 and 15 km respectively both subevents had a predominantly normal faulting mechanism with slip vectors oriented ne sw showing good agreement with the velocity vectors obtained from the recent slr and gps studies as well as with the regional stress orientation obtained from geological data the main shock was preceded by foreshock activity concentrated at the se end of the dinar fault where the first subevent took place while the aftershock activity was concentrated in the vicinity of the second subevent the spatial distribution of the foreshock and the aftershock activities and the locations of the subevents suggest that the first subevent broke an asperity and the second subevent broke a barrier on the fault following the definition by aki 1984 of an asperity and barrier earthquake model about 10 km of surface ruptures were associated with the earthquake while the estimates yield a rupture length of 25 km the calculated source parameters of the subevents and their locations suggest that the surface ruptures were probably associated with the first subevent the estimates also show that the rupture zones of the two subevents overlapped where the maximum vertical displacement was observed

origin of spinel rich chondrules and inclusions in carbonaceous and ordinary chondrites our evaluation of three models of the origin of spinel rich chondrules and inclusions includes new calculations of the major element refractory mineral condensation sequence from a gas of solar composition over a wide pressure interval our condensation calculations show that spinel rich chondrules did not crystallize from metastable liquid condensates and that spinel rich inclusions are not aggregates of refractory nebular condensates we propose that spinel rich objects are fractionated distillation residues of small aggregates of primitive dust that lost ca si rich partial melts by evaporation ablation or splashing during collisions this model also explains why spinel rich chondrules and inclusions 1 are usually smaller than melilite rich chondrules and inclusions 2 often have highly fractionated trace element compositions and 3 usually do not contain pt metal nuggets even when they are more enriched in the pt group metals than nugget bearing melilite rich objects

stress tensor inversions along the westernmost north anatolian fault zone and its continuation into the north aegean sea summary gephart forsyth s method has been applied to estimate stress orientations from earthquake fault plane solutions of the westernmost north anatolian fault zone nafz its westward continuation in the northern aegean sea where it interacts with the normal faulting of central greece and of the western coastal parts of anatolia in total 163 fault plane solutions were used to invert for the stress tensor of 9 seismotectonic subregions magnitudes range from 1 1 to 7 4 all events have shallow focal depths most occurred in the uppermost 15 km and very few in the 15 to 40 km depth range the region studied is characterized by strike slip nafz by transtension central greece and western anatolia and by a strong signature of transpression in the marmara area from nafz to central greece the 3 axis changes continuously and smoothly its orientation from n35 e in the westernmost nafz to nearly north south in continental central greece and the maximum horizontal stress hmax changes from wnw ese to e w the total angle of lateral variation in the direction of either hmax or 3 is 40 in central western anatolia the orientation of 3 is nne ssw n10 e while in southern western anatolia it is nnw sse n33 w in both cases the development of the major grabens simav gediz menderes is in agreement with the resolved stress tensor at the termination of the nafz against central greece the regime is complex the dextral shear motion transferred from the east crosses the pilion peninsula and northern evia island where it interacts with the major normal faults of continental greece these faults have variable orientations the e w trending quaternary fault system and the nw se trending fault system which is inherited from the past the latter faults under the presently acting stress field are reactivated either as strike slip faults with sinistral strike slip component when oriented at small angle in respect to 3 or as normal faults with small sinistral strike slip component when oriented at high angle in respect to 3 the occurrence of the recent 2001 july 26 skyros event which was clearly connected to a nnw sse fault with sinistral strike slip motion provides strong seismological evidence that the old structures can equally well be reactivated under the presently active stress field

crystallization sequences of ca al rich inclusions from allende an experimental study the equilibrium crystallization sequence at 1 atmosphere in air of a melt corresponding in composition to the average composition of type b ca al rich inclusions from the allende meteorite is spinel 1550 c melilite 1400 c ak22 anorthite 1260 c ti al rich clinopyroxene 1230 c ti fassaite the melilite becomes increasingly akermanitic with decreasing temperature the pyroxene is similar in composition to fassaites from type b inclusions preliminary results suggest that the crystallization sequence is similar at oxygen fugacities near the iron wustite buffer the results of these experiments have been integrated with available phase equilibrium data in the system cao mgo al 2o 3 sio 2tio 2 and a phase diagram for predicting the crystallization sequences of liquids with compositions of coarse grained ca al rich inclusions has been developed available bulk compositions of coarse grained inclusions form a well defined trend in terms of major elements extending from type a and bl inclusions near the spinel melilite join to more pyroxene rich type b2 inclusions the trend deviates from the expected sequence of solid condensates from a nebular gas at p 10 3 atm if pure diopside is assumed to be the clinopyroxene that condenses the type a b1 end of the trend is similar in composition to calculated equilibrium condensates at 1202 1227 c and the trend as a whole parallels the sequence of condensates expected from diopside condensation at 1170 c the trend is consistent to first order with the condensation of solid ti rich fassaite in place of pure diopside at higher temperatures than those at which pure diopside is predicted to condense partially molten condensates may be likely in this case or if the nebular pressure is higher than 10 3 atm

empirical relationships between aftershock area dimensions and magnitude for earthquakes in the mediterranean sea region fault dimension estimates derived from the aftershock area extent of 36 shallow depth v31 km earthquakes that occurred in the mediterranean sea region have been used in order to establish empirical relationships between length width area and surface wave moment magnitude this dataset consists of events whose aftershock sequence was recorded by a dense local or regional network and the reported location errors did not exceed on average 3 5 km surface wave magnitudes for these events were obtained from the neic database and or published reports while moment magnitudes as well as focal mechanisms were available from the harvard usgs catalogues contrary to the results of some previously published studies we found no evidence in our dataset that faulting type may have an effect on the fault dimension estimates and therefore we derived relationships for the whole of the dataset comparisons by means of statistical f tests of our relationships with other previously published regional and global relationships were performed in order to check possible similarities or differences most such comparisons showed relatively low significance levels b95 since the differences in source dimension estimates were large mainly for magnitudes lower than 6 5 becoming smaller with increasing magnitude some degree of similarity however could be observed between our fault length relationship and the one derived from aftershock area lengths of events in greece while a difference was found between our regional and global fault length relationships a calculation of the ratio defined as the fault length derived from our relationships to the length estimated from regional empirical relationships involving surface ruptures showed that it can take a maximum value of about 7 for small magnitudes while it approaches unity at ms 7 2 when calculating the same ratio using instead global empirical relationships we see the maximum value not exceeding 1 8 while unity is reached at mw 7 8 indicating the existence of a strong regional variation in the fault lengths of earthquakes occurring in the mediterranean sea region also a relationship between the logarithms of the rupture area and seismic moment is established and it is inferred that there is some variation of stress drop as a function of seismic moment in particular it is observed that for magnitudes

an ultra refractory inclusion from the ornans carbonaceous chondrite a small refractory inclusion 1 g was found in the ornans carbonaceous chondrite the inclusion is extremely enriched in the most refractory ree lu er ho the more volatile light ree having more than two orders of magnitude lower concentrations refractory metals are fractionated in a similar way high abundances of the most refractory metals os re low content of more volatile metals such as ru and pt gas solid equilibrium at high temperatures can easily account for the observed relative abundances of refractory elements independent temperature estimates from ree abundances and refractory metal contents suggest an equilibrium temperature of about 1670 k at 10 3 atm the trace element pattern of the inclusion is complementary to the pattern of fine grained allende inclusions the inclusion may either represent a first condensate from a cooling gas of approximately solar composition or the very last residue from an evaporation process only the low contents of w and mo do not fit the pattern of refractory elements predicted from condensation calculations both elements however readily form volatile oxides therefore this depletion could be taken as indication of an evaporative origin of the inclusion the metal phase consists of small os rich grains in a comparatively os poor matrix grains and matrix appear to be a mechanical mixture this textural evidence cannot be easily reconciled with an evaporative origin a condensation origin of the inclusion would require that w and mo were lost at a later time in a more oxidising environment without affecting the metallic ta found in some of the metal grains

the role of basement reactivation in continental deformation the papers in this thematic set arise from a discussion meeting sponsored by the tectonic studies group and held at burlington house on 6 7 march 1996 about 170 people heard 19 formal oral presentations and studied 17 posters of which 15 were briefly introduced with five minute talks sixteen of these contributions are published in this thematic set pre existing heterogeneities in the continental lithosphere are thought to influence markedly its response to subsequent deformation a major reason for this thinking is the long held view e g hills 1956 that fault zones are inherently weak virtually all regions of continental lithosphere are riddled with faults and shear zones thus any subsequent deformation might be expected to utilize these pre existing weak zones as reviewed by white et al 1986 this type of reactivation where faulting activity is localized onto pre existing faults can be contrasted with more general cases of deformation reworking broader volumes of lithosphere there need not be complete reactivation of individual faults and shear zones the distinc tion is nicely illustrated by the concepts of basin inversion a topic that has been well aired in recent years e g cooper williams 1989 coward 1994 in many sedimentary basins there is evidence of contractional reactivation of segments of originally extensional faults e g letouzey 1990 yet for the contrasting tectonic setting of collisional mountain belts recent work has emphasized that in general thrusts do not reactivate pre existing extensional faults e g gillchrist et al 1987 however the sites of almost all the shortened continental

a non linear geodetic data inversion using abic for slip distribution on a fault with an unknown dip angle summary we have developed a method of geodetic data inversion for slip distribution on a fault with an unknown dip angle a common strategy for obtaining slip distribution in previous studies is to first determine the fault geometry by minimizing the square misfit under the assumption of a uniform slip on a rectangular fault and then apply the usual linear inversion technique to estimate a slip distribution on the determined fault it is not guaranteed however that the fault determined under the assumption of a uniform slip gives the best fault geometry for a spatially variable slip distribution the inverse problem is non linear for cases with unknown fault geometries but the non linearity of the problems is actually weak when we can assume the fault surface to be a flat plane in particular when a clear trace of coseismic faults is observed on the earth s surface only the dip angle is an unknown parameter to determine the fault geometry then we regarded the dip angle as an hyperparameter that prescribed the structure of parametric models and obtained the best estimate of the dip angle using akaike s bayesian information criterion abic with the best estimate of the dip angle we can obtain the slip distribution on the fault based on the maximum likelihood principle we applied the method to the insar data of the 1995 dinar turkey earthquake and obtained a much lower dip angle than the previous analyses

40ar 39ar geochronolgy and neoproterozoic tectonics along the northern margin of the eastern ghats belt in north orissa india abstract the post 1100 950 ma cooling history of the northern margin of the high grade eastern ghats belt is determined from 40ar 39ar data collected from schist and gneiss samples the data define two groups of dates with distinct cooling histories between ca 700 and 420 ma the oldest group of ages define a slow apparent cooling path whereas a younger group of 40ar 39ar dates from the west and north margin of the eastern ghats belt and along the southern margin of the rengali province define a more rapid cooling path the younger 40ar 39ar dates are interpreted to reflect a variable and locally intense thermal event at ca 550 500 ma associated with reactivation of major shear zones final exhumation to current exposed levels occurred by ca 300 ma as constrained by unconformable permo triassic coal bearing sediments overlying the northern eastern ghats belt and northwestern rengali province dextral reverse reactivation after ca 950 ma and possibly prior to ca 700 ma along the kerajang and barakot fault zones was associated with regional shortening within the eastern ghats belt and rengali province further reactivation of major shear zones within the same shortening regime at ca 550 500 ma is indicated by the 40ar 39ar data resetting of the k ar system was locally more intense along the eastern ghats boundary fault and kerajang fault zones and was associated with ingress of high temperature fluids the resulting post grenvillian tectonic framework for northern orissa provides insight into the character of intra cratonic pan african tectonism within east gondwanaland

structure of pseudotachylyte vein systems as a key to co seismic rupture dynamics the case of gavilgarh tan shear zone central india the secondary fractures associated with a major pseudotachylyte bearing fault vein in the sheared aplitic granitoid of the proterozoic gavilgarh tan shear zone in central india are mapped at the outcrop scale the fracture maps help to identify at least three different types of co seismic ruptures e g x x t1 and t2 which characterize sinistral sense shearing of rocks confined between two sinistral strike slip faults slipping at seismic rate from the asymmetric distribution of tensile fractures around the sinistral sense fault vein the direction of seismic rupture propagation is predicted to have occurred from west southwest to east northeast during an ancient ordovician earthquake calculations of approximate co seismic displacement on the faults and seismic moment m 0 of the earthquake are attempted following the methods proposed by earlier workers these estimates broadly agree to the findings from other studied fault zones e g gole larghe fault zone italian alps this study supports the proposition by some researchers that important seismological information can be extracted from tectonic pseudotachylytes of all ages provided they are not reworked by subsequent tectonic activity

source parameters of the 1 october 1995 dinar turkey earthquake from sar interferometry and seismic bodywave modelling abstract the 1 october 1995 m s 6 1 dinar earthquake ruptured a 10 km section of the nw se dinar civril fault there are discrepancies between the published source parameters from seismic data with seismic moments in disagreement by over a factor of two we use both sar interferometry and seismic bodywave modelling to determine earthquake source parameters an interferogram generated from ers 1 2 sar imagery spanning the event and separated by 5 months is used to derive source parameters by a downhill simplex inversion with multiple monte carlo restarts we model the displacements in the satellite line of sight initially using uniform slip on a rectangular dislocation in an elastic half space the resultant model fault plane agrees in strike and location with the observed surface break but systematic residuals exist in the line of sight deformation field resulting in a r m s residual of 20 mm in the interferogram the residuals are reduced if the depth distribution of slip is allowed to vary spatially in four segments along a continuous fault plane our best fitting solution with a r m s misfit of 8 mm reveals two distinct areas of slip on the fault plane strike 145 dip 49 rake 270 a main rupture slipping by 1 44 m between depths of 1 and 8 km becoming deeper to the se and matching the observed surface rupture and an along strike continuation to the nw of the same fault plane but between depths of 8 and 13 km and not associated with a surface break the total geodetic moment 4 5 0 1 10 18 nm is more than twice as large as published seismic moments based on the inversion of p waveforms alone but close to the harvard cmt moment 4 7 10 18 nm we use sh waveforms in addition to the p waves used previously to determine an alternative seismic source mechanism sh waves constrain the depth to be shallower than solutions based on p waves alone agreeing with the depths from the interferometric inversion and resulting in a larger moment 3 1 0 4 10 18 nm than the previous bodywave estimates 2 2 1 10 18 nm the cmt moment reduces in magnitude to a similar size 3 3 10 18 nm if the centroid depth and fault dip are constrained to the values determined from bodywave modelling and interferometry thus the geodetic moment is 40 bigger than the moment determined from seismology

intraplate deformation of the indian subcontinent 1 while deformation at the earth s surface primarily occurs along tectonic plate boundaries major earthquakes have shaken regions deep within continental interiors three of the largest m 7 5 historic intraplate earthquakes occurred within the indian subcontinent suggesting the possibility of significant intraplate deformation we consider surface velocities determined from new gps data collected at 29 continuous gps stations and 41 survey mode gps stations in india between 1995 and 2007 to find a north south shortening rate of 0 3 0 05 nanostrain yr 1 which may be accommodated by 2 1 mm yr of more localized convergence across central india southward motions at 4 7 mm yr of sites on the shillong plateau in northeast india reflect rapid shortening and high earthquake hazard associated with active thrust faults bounding the plateau the width and magnitude of the elastic strain accumulation field across the himalaya varies little from 76 90 longitude but the strain is more broadly distributed and convergence rates are higher along the eastern 200 km of the range

spectral characteristics and source parameters of microearthquakes from the mt cameroon volcanic region west africa summary estimates of source parameters seismic moment source radius and stress drop for a representative sample of 33 mt cameroon region microearthquakes with magnitudes in the range md 0 8 2 8 have been obtained from the analysis of their far field displacement amplitude spectra the spectral character of these events seems to be characterized by a lack of high frequencies the computed seismic moments lie between 10 and 10l6 nm and vary linearly with magnitude albeit with some scatter source radii are relatively large in the range 135 703m the stress drops are small 0 4 19 bar and roughly constant independent of seismic moment thus suggesting that the property of self similarity seems to hold over this moment range for this area

a once molten coarse grained ca rich inclusion in allende a compact spheroidal type b inclusion in allende contains melilite laths that project radially inward from the inclusion edge which show interference growth textures the combined textural and chemical features of this object cannot be explained by independent vapor solid condensation of grains in space followed by random aggregation of these grains into an inclusion rather it probably formed from a once molten droplet that crystallized in response to radiative cooling from its outer surface the crystallization sequence in this and another similar inclusion in which oxygen isotopes have been measured is melilite spinel anorthite fassaite this sequence supports the idea that oxygen isotopic heterogeneities in coarse grained inclusions were formed after complete solidification of these objects by partial exchange with a less16o rich gas and not during or before a melting event

microearthquake spectra from the anza california seismic network site response and source scaling abstract we analyzed spectra of local microearthquakes recorded by the anza california seismic network to isolate the effects of site response and to investigate the scaling of source parameters for small earthquakes spectra of microearthquakes m m o 19 dyne cm at anza have shapes characteristic of the receiver sites and are generally independent of the source region thus the site response is a major conditioner of the observed spectral shape to remove the effects of site response from the spectra of a m 3 event and isolate its source spectrum we divided by the spectra of an adjacent aftershock used as an empirical green9s function event the spectral ratios indicate that the apparent corner frequencies of small earthquakes m o 19 dyne cm observed at even the high f max stations on hard rock are much lower than the source corner frequencies the spectral ratios are consistent with stress drop remaining constant with decreasing seismic moment for events with moments as small as 10 18 dyne cm the spectral ratios display remarkable agreement between sites which showed vast differences in their original spectra indicating that the spectral division effectively removed the site response the source spectrum of the m 3 event has a high frequency spectral fall off of about 2 an apparent dependence of high frequency fall off with seismic moment in the original spectra can also be explained by the effects of site response the difference between the p and s wave corner frequencies and high frequency roll offs in the observed spectra for these events is the result of the site response and is not a source property the shapes of the spectra of microearthquakes at anza can largely be explained by attenuation at shallow depth with a frequency independent q for some sites near surface resonances are also apparent in the spectra of microearthquakes it is indicated by t values determined for each site that q p q s for the shallow low q layer further evidence of low near surface q is observed in the anomalous spectra of an unusually shallow earthquake source depth 1 km in the network the spectra from this shallow event are depleted in high frequency energy at most stations relative to those of deeper events this observation can be explained by a low q surficial zone for stations of the network situated on alluvium this low q layer has a maximum thickness of about 3 km and maximum p and s wave q values of 30 to 50

seismic anisotropy beneath the continents probing the depths of geology seismic anisotropy beneath continents is analyzed from shear wave splitting recorded at more than 300 continental seismic stations anisotropy is found to be a ubiquitous property that is due to mantle deformation from past and present orogenic activity the observed coherence with crustal deformation implies that the mantle plays a major if not dominant role in orogenies no evidence is found for a continental asthenospheric decoupling zone suggesting that continents are coupled to general mantle circulation

a reappraisal of the sibson scholz fault zone model the nature of the frictional to viscous brittle ductile transition along a long lived crustal scale fault outer hebrides scotland the widely cited sibson scholz conceptual fault zone model suggests that seismically active upper crustal brittle faults pass downward across a predominantly thermally controlled transition at 10 15 km depth into ductile shear zones in which deformation occurs by aseimic viscous creep the crustal scale outer hebrides fault zone ohfz in nw scotland has been described as the type example of such a continental fault zone it cuts precambrian basement gneisses and is deeply exhumed allowing direct study of the deformation products and processes that occur across a wide range of crustal depths a number of fault rock assemblages are recognized to have formed during a long lived displacement history lasting in excess of 1000 myr during caledonian movements that are recognized along much of the 190 km onshore fault trace brittle cataclasite bearing faults in the west of the ohfz are unequivocally overprinted to the east by a younger fabric related to a network of ductile shear zones field observations and regional geochronological data demonstrate that there is no evidence for reheating of the fault zone due to thrust related crustal thickening or shear heating microstructural observations show that the onset of viscous deformation was related to a major influx of hydrous fluids this led to retrogression with the widespread development of new finegrained phyllosilicate bearing fault rocks phyllonites and the onset of fluid assisted grain size sensitive diffusional creep in the most highly deformed and altered parts of the fault zone phyllonitic fault rocks also occur in older more deeply exhumed parts of the fault zone implying that phyllonitization had previously occurred at an earlier stage and that this process is possible over a wide temperature depth range within crustal scale faults our data provide an observational basis for recent theoretical and experimental studies which suggest that crustal scale faults containing interconnected networks of phyllosilicate bearing fault rocks will be characterized by long term relative weakness and shallow 5 km frictional viscous transition zones similar processes acting at depth may provide an explanation for the apparent weakness of presently active structures such as the san andreas fault

a unique ultrarefractory inclusion from the murchison meteorite through freeze thaw disaggregation of the murchison meteorite we have recovered a refractory inclusion hib 11 that is unique in terms of its texture mineral compositions and bulk composition it consists of anhedral y rich 1 6 wt y2o3 perovskite and lathlike spinel grains enclosed in a matrix of fine grained sc rich 10 5 wt sc2o3 avg ti rich 12 6 wt tio2 avg reporting all ti as tio2 clinopyroxene the chondrite normalized rare earth element ree pattern is complex with light ree lree at 10 c1 abundances increasing from gd through ho the latter at 104 c1 decreasing through yb at 200 c1 and lu at 400 c1 the pattern reflects several stages of high temperature volatility fractionation removal of lu and er from the source gas in the first condensation event was followed by partial to complete removal of the somewhat less refractory heavy ree gd through ho in the hib 11 precursors by condensation from the fractionated residual gas in a second event both of these events probably reflect condensation of ree into zro2 or a mixed zr sc ti y oxide at temperatures too high for hibonite stability a second lower temperature component which was subsequently added had fractionated nd poor ce rich lree abundances that resulted from condensation from a gas that had undergone prior removal of the more refractory lree resulting in enrichment in ce and the most volatile ree eu and yb the aggregate was then melted and quickly cooled forming a fine grained spherule this is the first reported inclusion in which the two most refractory ree lu and er are strongly fractionated from the other ree an absence of mass fractionation among the ti isotopes indicates that hib 11 is not an evaporative residue implying that volatility fractionation of trace elements took place during condensation the fact that the two most refractory heavy ree could be separated from the other only slightly less refractory heavy ree suggests that a wide variety of ree patterns is possible and that ultrarefractory inclusions with other unusual ree patterns important recorders of nebular condensation may yet be discovered

relation of alkaline volcanism and active tectonism within the evolution of the isparta angle sw turkey the isparta angle ia is formed along the boundary of the african and eurasian plates by ne and nw striking faults north of the antalya gulf in sw turkey the ne striking strike slip burdur fault bounds the ia to the west and is probably the continuation of the pliny system of the hellenic arc the nw striking aksehir fault bounds it to the east platform type parautochthonous mesozoic carbonate sequences such as the beydag and anamas akseki occur in the western and eastern parts of the ia respectively whereas allochthonous ophiolite nappes include the antalya beysehir hoyran and lycian nappes the ia and adjacent areas are divided into three areas the teke the antalya and the akseki fragments by ne nw and n striking active strike slip faults with normal components ia region volcanics are alkaline and hyperkaline in character potassic ultrapotassic and locally occur as subvolcanic stocks and dikes they can be traced between the afyon and isparta regions these volcanics consist mainly of

structural evolution of gavilgarh tan shear zone central india a possible case of partitioned transpression during mesoproterozoic oblique collision within central indian tectonic zone abstract gavilgarh tan shear zone gtsz a map scale ductile shear zone occurring in the southern part of the central indian tectonic zone citz contains many important clues to the tectonics of this important proterozoic mobile belt of central india which is yet controversial and hotly debated data from structural mapping microstructural study and kinematic analyses of the gtsz have been presented in this paper which clearly implies that gtsz is mainly represented by a wrench dominated transpressional shear zone with sinistral shear sense analysis of lineation patterns shows that while horizontal stretching dominated within the ductile shear zone rocks on either side north and south of it stretched vertically with a transition zone of simultaneous horizontal and vertical stretching in between these two domains a general transpressional strain has thus been partitioned into wrench and pure shear dominated domains at large scale further strain partitioning also took place at the outcrop scale geochemistry of the granitoids occupying the shear zone and its surrounding area indicates continental collision set up which supports the structural model on the basis of earlier proposed tectonic models and limited geochronological data available of the southern part of citz it is suggested here that an oblique collision and final suturing between the northern bundelkhand craton and southern bastar craton terrains within the citz around 1100 ma have been partly accommodated by partitioned transpression along gtsz and its surrounding gneiss granitoid terrain more intensive geochronological constraint of the collision event from both northern and southern side are however lacking at present

geodetic determination of the kinematics of central greece with respect to europe implications for eastern mediterranean tectonics we use a new satellite laser ranging global positioning system slr gps solution at seven sites in anatolia and aegea to obtain a better definition of the extrusion motion of the anatolian aegean block with respect to europe we show that this motion can be described in a first approximation by a counterclockwise rotation which transfers most of the motion of arabia to anatolia we combine 78 displacement vectors obtained at common points of two triangulation nets measured in central greece in 1895 and 1975 with the slr gps measurements to compute the velocity field over greece with respect to europe these measurements indicate that central greece is a zone of extension between the anatolian aegean counterclockwise rotation to the south and the northern greece clockwise rotation to the north this extension is principally localized within the gulf of corinth to the east but is distributed to the west we then extrapolate this velocity field to the whole aegea and western anatolia using recently published gps results as well as the slr results the narrow dextral north anatolian fault which limits the velocity field to the north progressively gives way to a much wider boundary zone where extension becomes dominant we show that the collision between the mediterranean ridge and africa began 3 6 ma and we describe the modifications that this collision has produced on the kinematic pattern both in aegea and on the mediterranean ridge