the seismic cycle in the area of the 2011 mw9 0 tohoku oki earthquake we model seismic and aseismic slip on the japan megathrust in the area of the m w9 0 2011 tohoku oki earthquake based on daily time series from 400 gps stations of the geonet network and campaign measurements of six sea floor displacements the coseismic and postseismic slip distributions are inverted simultaneously using principal component analysis based inversion method pcaim exploring a wide range of boundary conditions and regularization constraints we found the coseismic slip distribution to be quite compact with a peak slip between 30 and 50 m near the trench our model shows deep afterslip fringing the downdip edge of the coseismic rupture but also a dominant zone of shallow afterslip afterslip over the first 279 days following the main shock represents about 40 of the coseismic moment we compare the coseismic and postseismic models with an interseismic coupling model derived from inland and sea bottom measurements determined in a self consistent manner assuming that seismic and aseismic slip had to match the long term slip rate along the megathrust the recurrence time of m w9 0 earthquakes is estimated to 100 300 years while historical and paleotsunami records suggest a return period more of the order of 1000 years the discrepancy is smaller if the shallower portion of the megathrust is assumed to produce both aseismic slip as the afterslip model suggests and seismic slip during occasional large tsunamigenic earthquakes

late cretaceous palaeocene subduction collision exhumation of a microcontinent along the northern active margin of the southern neotethys evidence from the alanya massif and the adjacent antalya complex s turkey abstract the alanya massif represents a microcontinent that underwent subduction exhumation related to collision with the larger tauride microcontinent to the north during latest cretaceous palaeocene intermediate structural level blueschist melange in the northwest gundogmus area encompasses ductile deformed meta basaltic rocks meta cherts and minor serpentinite in a lower grade meta mudrock matrix the meta basaltic protoliths mainly formed in a subduction influenced setting together with less common oib and e morb late permian platform slope carbonates were intersliced during late stage brittle thrusting and directly over ridden by a lower grade greenschist facies late permian early triassic aged platform unit the blueschist melange is interpreted as an oceanic subduction complex that was obducted southwards related to microcontinental collision intermediate structural level hp lt blueschist ecologites farther south alanya area indicate that the alanya massif represents variably subducted exhumed continental crust both subduction and exhumation took place during the latest cretaceous prior to late palaeocene early eocene marine transgression late precambrian protoliths of eclogitic hp lt rocks and also similar aged amphibolite facies meta basic intrusions farther southeast anamur area are interpreted to have formed in a panafrican cadomian late stage back arc setting late triassic basaltic rocks in the antalya complex structurally beneath and to the north erupted in a rift setting we restore the mesozoic palaeogeography from north to south as tauride microcontinent antalya rift basin alanya micrcontinent s neotethys the subduction exhumation history may serve as a model for similar active margin collisional settings elsewhere

short paper low grade metamorphism of the welsh basin lower palaeozoic succession an example of diastathermal metamorphism the lower palaeozoic succession of the welsh basin has suffered the effects of low grade metamorphism which shows features that do not accord with classical models of regional or burial metamorphism textural evidence demonstrates the development of greenschist facies metamorphism prior to deformation and cleavage development while mineralogical characters indicate a low pressure facies series in order to accommodate these features it is suggested that the area has suffered diastathermal metamorphism in which an enhanced thermal flux develops early in the tectonic cycle in response to an extensional setting temperatures remained relatively high during final closure associated with deformation of the basin sediments and consequent cleavage development such a model adequately resolves previously conflicting interpretations of burial and deformation related metamorphism

highly variable coastal deformation in the 2016 mw7 8 kaikōura earthquake reflects rupture complexity along a transpressional plate boundary abstract coseismic coastal deformation is often used to understand slip on offshore faults in large earthquakes but in the 2016 m w 7 8 kaik ura earthquake multiple faults ruptured across and sub parallel to the coastline along 110 km of coastline a rich dataset of coastal deformation comprising airborne lidar differencing field surveying and satellite geodesy reveals highly variable vertical displacements ranging from 2 5 to 6 5 m these inform a refined slip model for the kaik ura earthquake which incorporates changes to the slip on offshore faults and inclusion of an offshore reverse crustal fault that accounts for broad low amplitude uplift centered on kaik ura peninsula the exceptional detail afforded by differential lidar and the high variability in coastal deformation combine to form the highest resolution and most complex record of coseismic coastal deformation yet documented this should prompt reassessment of coastal paleoseismic records that may not have considered multi fault ruptures and high complexity deformation fields

incipient metamorphism in the lower palaeozoic marginal basin of wales a diagenctic through anchizone to epizone transition is demonstrated in pelitic rocks of the lower palaeozoic marginal basin of wales by examination of variations in phyllo silicate mineralogy illite crystallinity and bo parameter of white micas this transition represents a temperature range from 150 c to 400 c and the metamorphism is of a low pressure facies series type with a geothermal gradient of 40 ckm 1 variations in grade can be correlated largely with the original basin and shelf form suggesting a depth related metamorphism however in areas closer to the site of caledonian plate collision an increasingly syn tectonic metamorphic event is apparent correlation of pelite data with metabasite assemblages is variable the most consistent relationship being between epizone crystallinity values andepidote actinolite greenschist facies assemblages diagenetic clay mineral assemblages are found associated with prehnite pumpellyite assemblages in metabasites and it is suggested that the latter represent non buffered and therefore non diagnostic assemblages

development of slaty cleavage and degree of very low grade metamorphism a review illite crystallinity ic and other indicators of the grade of very low grade metamorphism associated with the appearance of various stages of slaty cleavage in phyllosilicate rich rocks have been compiled from a wide variety of terranes ic values have been converted to a kubler equivalent standard scale but the diverse characterizations of the cleavage fabrics in published descriptions do not always allow an unequivocal identification of equivalent stages of cleavage development nevertheless there exists a distinct relationship between grade and the appearance of various stages of cleavage development 1 indications of incipient slaty cleavage such as s0 s1 pencil structure appearance of primary s1 crenulation cleavage and of closely spaced cleavage without parallel fabric in the microlithons is associated with a wide range of mostly medium and high grade diagenetic ic values 2 the appearance of smooth cleavage with a strong parallel fabric in the microlithons and or quartz mica beards and the chlorite mica stacks shortened at a high angle to 001 and of irregular cleavage in sandy beds is associated with a much narrower range of predominantly low and medium grade anchimetamorphic grades rarely high grade diagenetic the first appearance of these stages of cleavage development with higher grades can often be related to post kinematic magmatic heating polymetamorphism pre cleavage metamorphism or static recrystallization without cleavage formation for example in low strain zones there exists a relationship between finite strain fabric and metamorphic grade in mudstones and slates in coarser clastic rocks the same finite strain fabric relationship occurs at appreciably higher grades a relationship between finite strain in carbonate rocks and ic in the nearby rocks has been reported from the helvetic zone of the swiss alps the earlier stages of cleavage formation are associated with little improvement in ic the narrow range of ic associated with smooth cleavage is concluded to represent recrystallization and grain growth concurrent with cleavage formation

slow slip near the trench at the hikurangi subduction zone new zealand the range of fault slip behaviors near the trench at subduction plate boundaries is critical to know as this is where the world s largest most damaging tsunamis are generated our knowledge of these behaviors has remained largely incomplete partially due to the challenging nature of crustal deformation measurements at offshore plate boundaries here we present detailed seafloor deformation observations made during an offshore slow slip event sse in september and october 2014 using a network of absolute pressure gauges deployed at the hikurangi subduction margin offshore new zealand these data show the distribution of vertical seafloor deformation during the sse and reveal direct evidence for sses occurring close to the trench within 2 kilometers of the seafloor where very low temperatures and pressures exist

tectonics and magmatism in turkey and the surrounding area this volume contains 23 papers from a range of international contributors describing recent research into the tectonics and magmatism of turkey and its surroundings this region is sited at the collision zone between eurasia and afro arabia and as such provides an extraordinarily complete and well exposed record of the staged tectonic evolution of this sector of the alpine himalayan orogen the geological history of this area involves separation of continental fragments from the margin of gondwana their migration across the tethyan oceans the subsequent closure of these oceans and finally the development of the neotectonic regime which continues to evolve to the present day such a comprehensive record is relevant to the understanding of collisional zones worldwide the volume is divided into five sections tethyan evolution neotethyan ophiolites post tethyan basin evolution neotectonics and igneous activity the first two sections deal with tethyan oceans whose growth and subsequent closure dominated the geodynamic framework in the mesozoic and cenozoic the subsequent sections deal with more recent geological developments from the balkan peninsula in the west to the transcaucasus in the east that followed consumption of the tethyan oceans there is a broad mix of papers throughout the volume wide ranging review papers on ocean development and extensional tectonics are followed by detailed descriptions of petrology and geochemistry and geographically focused studies on basin evolution specific aspects of extensional and strike slip tectonics and discussions of the relationship of magmatic activity to the tectonic development of the area tectonics and magmatism in turkey and the surrounding area presents up to date results and ideas from a large number of international contributors on a wide range of current research activity in this region it is essential reading for all geoscientists with an interest in both academic and applied aspects of eastern mediterranean geology

paratethyan mediterranean connectivity in the sea of marmara region nw turkey during the messinian the sea of marmara region is thought to have been a gateway between paratethys and the mediterranean since the middle miocene and is therefore an important control on water mass exchange between the two realms the miocene successions in the northeastern aegean and northwestern marmara regions indicate that the first mediterranean marine transgression to affect these areas occurred during the late serravallian in the northeastern aegean region frequent marine incursions occurred during the tortonian and messinian stages the messinian stage in this area is represented by a package of brackish to fresh water carbonates with some marine sandstone siltstone interbeds alcitepe formation which conformably overlies the tortonian kirazli formation the messinian sequence is overlain with an erosional contact by a shallow marine siliciclastic sequence goztepe formation of zanclean age with its brackish to fresh water carbonates and broadly constrained age the messinian sequence is interpreted as being coeval with the upper evaporite lago mare sequence observed in western mediterranean basins in the western marmara region the pontian messinian alcitepe formation consists of bioclastic and oolitic limestones with basal clastic rocks it conformably overlies the fluvio lacustrine siliciclastic sediments of the middle to upper miocene kirazli formation and is overlain by fluvio lacustrine sediments of the kimmerian 5 5 3 2 ma truva and tevfikiye formations with an erosional contact the bioclastic limestones of the alcitepe formation in the western marmara region contain a molluscan and ostracod fauna that are endemic to paratethys these fauna indicate deposition in a shallow brackish to fresh water environment faunal and paleomagnetic analyses of a section of the alcitepe formation at yenimahalle canakkale confirm that the formation is of pontian age and represents chron c3r 6 04 5 24 ma the ostracod analysis indicates that during deposition of the alcitepe formation salinity increased from brackish in the lower part to more saline conditions in the upper part ostracod valves have low 87sr 86sr values relative to coeval late miocene ocean water this indicates that exchange between the sea of marmara region and the global ocean was restricted throughout this period fossil and sr isotope evidence suggests however that there was a paratethyan marmara connection during the deposition of the lower part of the alcitepe formation with paratethyan influence reaching the north aegean connection via marmara between paratethys and the mediterranean was not re established until the late aktchagylian late pliocene the re connection was caused by both increased activity on the north anatolian fault and global sea level rise

geometry of the hikurangi subduction thrust and upper plate north island new zealand 1 we use 2800 line km of seismic reflection data to map the offshore character and geometry of the hikurangi subduction thrust and outer forearc wedge to depths of 15 km for 200 km along strike south of hawke bay the subduction thrust is relatively smooth dips less than 8 and the wedge is characterized by accretion of young sediment and topographic slopes of less than 3 in hawke bay and north for 200 km a kink in the subduction thrust is apparent with a downdip increase in dip to angles greater than 8 at depths of 10 15 km there is a corresponding steepening of the topographic slope to greater than 3 outboard of the kink and the wedge is characterized by lithified sedimentary rock and slope failure the kink in the subduction thrust is a locus of inherent weakness in the subducting slab we suggest its occurrence relates to a northward increase in subduction rate that controls initial slab dehydration and fluid release rates and hence intraslab deformation patterns the subduction thrust geometry in combination with a northward increase in subducting plate roughness and decrease in the amount of sediment accreted causes the observed spatial change in character of the subduction thrust and forearc wedge

large scale dynamic triggering of shallow slow slip enhanced by overlying sedimentary wedge seismic waves can trigger further fault slip analysis of seismic and geodetic data shows that seismic waves from the 2016 kaik ura new zealand earthquake were amplified by subduction zone sediments triggering slow fault slip up to 600 km away

quake clamps down on slow slip using continuous gps cgps data from the hikurangi subduction zone in new zealand we show for the first time that stress changes induced by a local earthquake can arrest an ongoing slow slip event sse the cgps data show that the slip rate in the northern portion of the 2013 2014 kapiti sse decreased abruptly following a nearby intraslab earthquake we suggest that deceleration of the kapiti sse in early 2014 occurred due to a tenfold increase in the normal stress relative to shear stress in the sse source induced by the nearby mw 6 3 earthquake consistent with expectations of rate and state friction our observation of an abrupt halting slowing of the sse in response to stress changes imposed by a local earthquake has implications for the strength of fault zones hosting sses and supports the premise that static stress changes are an important ingredient in triggering or delaying fault slip

time dependent modeling of slow slip events and associated seismicity and tremor at the hikurangi subduction zone new zealand we present a time dependent slip model of 12 slow slip events sses occurring in the hikurangi margin of new zealand during 2010 and 2011 this model is obtained by inverting daily gps solutions from geonet s continuous gps network on the north island and northern south island we compare the properties of these sses to observations in japan cascadia and mexico and find that hikurangi sses have comparatively large amounts of slip up to 27 cm high slip rates up to 1 4 cm d and a large range of depths 10 40 km durations 7 270 days and sizes mw 5 9 6 9 we further investigate the relationship between the cape turnagain sse and an associated seismic swarm and find that observations are consistent with stress triggering outside the slowly slipping region however other explanations cannot be ruled out we also compare slip during the long term manawatu sse with the tremor epicenters found by ide 2012 and note that tremor locations are offset in the downdip direction relative to the slipping region similar to observations in the bungo channel of japan and guerrero mexico

role of the tectonic facies concept in orogenic analysis and its application to tethys in the eastern mediterranean region abstract the purpose of this paper is to advocate the use of a tectonic facies concept which aids systematic and objective analysis of orogenic belts the tectonic facies concept as discussed here focuses on the recognition of discrete tectonic settings mainly those exposed at high crustal levels in orogenic belts application of the tectonic facies concept can help field geologists to relate plate scale processes to outcrop geology tectonic facies are recognised based on knowledge of the modern oceans and margins and well constrained land settings tectonic facies analogous to sedimentary facies can be identified from integrated sets of field data and related laboratory studies a number of tectonic facies models can be recognised in this way their identification aids interpretation and comparisons of orogenic belts palinspastic reconstructions require additional information particularly age kinematic and palaeomagnetic data in this paper the tectonic facies concept is tested by application to a well documented mainly high level orogenic segment tethys in the eastern mediterranean area and is found to be an effective way both of the describing and interpreting this region other methods of tectonic analysis e g recognition of tectono stratigraphic terranes may also be found useful in certain settings and can be used in conjunction with the tectonic facies concept

stratigraphic evidence for shear in structural development of the triassic levant margin new borehole data on the epicontinental to deep marine transition in israel abstract triassic tectonic movements that include shear along a significant portion of the levant margin are evidenced from microfacies analysis of material recovered from the asher atlit 1 ga ash 2 meged 2 devora 2 and ramalla 1 onshore boreholes seismic studies showed that structural lineaments attributed to early mesozoic extension underlie coastal and central israel trending ne sw beneath southern israel and sub parallel to the then extensional palmyride basin of syria a more curved trend approximately nnw sse lies to the north beneath central israel coast parallel sedimentary domains formed above these lineaments which constitute the newly formed passive margin of the levant coast in the triassic the sedimentary history of these domains indicates that some were linked to each other and others disconnected the relative vertical movement between one domain and another is explained by activation of transpressional and trans tensional shear movements on the underlying curved faults these subordinate vertical movements also created the discontinuous barriers and small subsiding basins that separate the epicontinental sedimentary domain from the open tethys causing partial restriction necessary for the intermittent development of thick evaporites in the internal domains alternating with a regionally suppressed carbonate system this zone is here named the onshore levant margin shear zone olmsz shear was invoked theoretically in a number of models for the tectonic evolution of the eastern mediterranean as part of a neotethyan opening system this paper provides rock based evidence for such shear applicable to 20 of the eastern levant margin in the triassic

the permian antitropical fusulinoidean genus monodiexodina distribution taxonomy paleobiogeography and paleoecology all the documented occurrences with illustration of specimens of the permian fusulinoidean genus monodiexodina from a total of 33 areas in 11 regions are reviewed and their taxonomic positions are reexamined in this paper among 17 species including two subspecies of monodiexodina in the current taxonomy the following 10 species are recognized as valid m kattaensis m wanneri m caracorumensis m sutchanica m shiptoni m kumensis m wanganensis m neimongolensis m delicata and m rhaphidoformis in addition species once referred to monodiexodina but now should be excluded from the genus are also investigated in terms of their generic positions in reconstructed mid permian paleomap monodiexodina bearing areas can be restored to either northern or southern middle latitudes between high latitudinal cool cold water climatic realm and paleo tropical warm water realm these two middle latitudinal areas each corresponding to the northern and southern transitional zones respectively can be best interpreted climatologically as mesothermal warm temperate belts in both hemispheres thus suggesting the genus to be a paleobiogeographically typical antitropical fusulinoidean taxon moreover the genus is generally found in a monotypic crowded manner in sandy sediments with their shells being often aligned uni directionally this mode of occurrence of monodiexodina strongly suggests that it was adapted to shallow marine high energy environments which would probably be essentially maintained by the acquisition of highly elongated fusiform subcylindrical shells with well developed polar torsion this morphological feature is adapted to increase septal pores per unit area in polar regions thus increasing possibility to develop more pseudopodia on both sides of test it probably has a functional significance for not only locomotion but also anchoring their tests on the surface of bottom sediments in agitated water conditions the genus itself is considered to be a rather long ranging taxon from the late yakhtashian artinskian to the early midian capitanian it is therefore concluded that monodiexodina had an opportunistic character occurring repeatedly only when favorable high energy conditions such as sand shoal appeared in warm temperate climatic belts in both hemispheres monodiexodina originated in the southern transitional zone from an elongated eoparafusulina stock at late early permian around late artinskian time it flourished in southern middle latitudinal areas in latest early and early middle permian time the genus then migrated to the northern hemisphere northern transitional zone by some dispersion mechanism at around the early middle permian and prevailed there during the remaining period of the middle permian

persistent uplift of the lazufre volcanic complex central andes new insights from pcaim inversion of insar time series and gps data we reanalyzed the surface displacements observed at the lazufre volcanic complex in the southern andean central volcanic zone using gps measurements made between 2006 and 2008 and a large insar data set we performed a detailed spatiotemporal analysis of the displacements using a principal component analysis inversion method pcaim the pcaim reveals a source with no significant changes in shape and dimension and with a remarkably linear strength increase over the whole period of observation i e 2003 2010 then we used a three dimensional mixed boundary element method mbem to invert the first component of surface displacement as obtained from pcaim we explored a continuum of geometries from a shallow elliptic crack to a deep massive truncated elliptical cone that could represent a sill or a large magma chamber respectively the best models indicate a large flat topped source with a roof area between 40 and 670 km2 and a depth of between 2 and 14 km below ground surface lastly on the basis of the limited data available for the thermomechanical structure of the crust in the southern andean central volcanic zone we consider some possible scenarios to explain the spatial and temporal pattern of displacements at lazufre

non volcanic tremor associated with the march 2010 gisborne slow slip event at the hikurangi subduction margin new zealand 1 non volcanic tremor accompanies slow slip events at most circum pacific subduction zones previously the hikurangi subduction margin new zealand and the boso peninsula of japan have been noted as exceptions where slow slip which occurs at shallow depth compared to other subduction zones does not generate seismic tremor the lack of tremor observations raises questions whether tremor and slow slip are manifestations of the same process and whether different temperature and pressure conditions influence the physical mechanism of tremor production analysis of seismic data during the march 2010 gisborne slow slip event new zealand reveals that this slow slip event at the northern hikurangi margin is accompanied by tremor with distinctive characteristics compared to local microearthquakes both the gisborne area of new zealand and the boso peninsula of japan are underlain by thick accumulations of sedimentary rocks that likely inhibit the observation of low amplitude tremor due to high attenuation discovery of tremor in new zealand suggests that tremor may always accompany slow slip and that its apparent absence at the boso peninsula the hikurangi margin prior to this study and any future regions discovered to experience slow slip without concurrent tremor may be the effect of highly attenuating sediments

slab detachment beneath eastern anatolia a possible cause for the formation of the north anatolian fault in this paper we discuss the possibility that the north anatolian fault naf results from the deep deformation of the slab beneath the bitlis hellenic subduction zone we described the tectonic evolution of the anatolia aegean area in three main steps before during and after the formation of the naf we remark that the tectonic conditions that are assumed to have triggered the formation of the naf i e collision to the east and extension to the west was already achieved before the onset of that strike slip fault system we also highlight that the formation of the naf was accompanied by the uplift of the turkish iranian plateau and by a surge of volcanism in the eastern anatolia collisional area and probably by the acceleration of the aegean trench retreat we show tomographic images from global p wave model of piromallo and morelli c piromallo a morelli p wave tomography of the mantle under the alpine mediterranean area j geophys res 108 2003 doi 10 1029 2002jb001757 showing that the slab beneath the bitlis collisional belt is not continuous and that its possible rupture pursues to the west at least up to cyprus and possibly up to the eastern end of the hellenic trench all these observations suggest that the plate tectonic re organization occurred in the late miocene early pliocene in the region results from slab break off in the bitlis area and from its lateral propagation to the west this idea is tested in analogue laboratory experiments which confirm that the break of the slab under the collisional belt may trigger 1 the acceleration of slab retreat to the west due to the increase in slab pull force 2 the indentation of the continent in the collisional area and 3 produce the conditions that permit the lateral escape of material towards the west and the formation of the naf

imaging the hikurangi subduction zone new zealand using teleseismic receiver functions crustal fluids above the forearc mantle wedge summary we image the hikurangi subduction zone using receiver functions derived from teleseismic earthquakes migrated receiver functions show a northwest dipping low shear wave feature down to 60 km depth which we associate with the crust of the subducted pacific plate receiver functions rf at several stations also show a pair of negative and positive polarity phases with associated conversion depths of 20 26 km where the subducted pacific plate is at a depth of 40 50 km beneath the overlying australian plate rf inversion solutions model these phases with a thin low s wave velocity zone less than 4 km thick and an s wave velocity contrast of more than 0 5 km s 1 with the overlying crust we interpret this phase pair as representing fluids near the base of the lower crust of the australian plate directly overlying the forearc mantle wedge

godene zone antalya complex volcanism and sedimentation along a mesozoic continental margin s w turkey the godene zone antalya complex is an assemblage of ophiolitic and associated sedimentary rocks formed on a passive margin during and after the rifting of a mesozoic ocean basin the zone comprises late triassic alkaline mafic submarine lavas and sediments mostly pelagic which are tectonically intercalated with mafic ultramafic plutonic rocks taken to be remnants of an original ophiolitic substratum the godene zone also includes major limestone massifs and tectonised remnants of former carbonate margin facies early triassic rifting initiated a horst graben terrain with localised evaporite and clastic deposition by late triassic time continued extension allowed substantial extrusion of submarine mafic volcanics these were often erupted close to tectonically active fault scarps generating both epiclastic and pyroclastic volcanic breccias several large slivers of continental basement were rifted off to form major offshore massifs which remained as topographic highs throughout the mesozoic during late triassic time exposed parts of the continent bey daglari and the offshore massifs shed siliciclastics mostly turbidites above the mafic lavas offshore reefs also shed material ranging from substantial detached blocks to finer grainedhalobia limestone facies during jurassic to late cretaceous time the whole area underwent passive margin deposition radiolarian pelagic sediments were deposited in deep water above the ophiolitic basement and around the offshore massifs the reef complexes persisted until mid cretaceous time when calcareous pelagic deposition was initiated passive margin conditions were terminated with deposition of ophiolitic clastics and olistostrome melange in the maastrichtian followed by major tectonism

first u pb shrimp zircon and 40ar 39ar ages of metarhyolites from the afyon bolkardag zone sw turkey implications for the rifting and closure of the neo tethys abstract the afyon bolkardag zone abz is one of the most important metamorphic zones in turkey this zone consists of metasedimentary and metavolcanic rocks which have undergone regional greenschist facies metamorphism the metavolcanic rocks are dominated by rhyolite dacite and trachyandesite in the ilgin konya area the low grade metavolcanics were originally rhyolitic lavas and tuffs we present new precise sensitive high resolution ion microprobe shrimp 206 pb 238 u age analyses of zircons and 40 ar 39 ar age data of phengite from metarhyolites that enable a more precise reconstruction of the abz shrimp analyses of euhedral or sub euhedral magmatic zircons from two metarhyolite samples yield weighted means 230 2 ma and 229 2 ma these ages are interpreted as formation age of rhyolitic volcanics implying they were formed in the late triassic time carnian we suggest that these upper triassic magmatic rocks were formed in an extensional tectonic setting on the northern active margin of gondwana which led to the development of the northern branch of the neo tethys 40 ar 39 ar dating of two phengite samples from metarhyolites gave plateau ages of between 63 7 0 1 ma and 62 6 0 1 ma these dates are interpreted as the metamorphic age of these volcanic rocks and as the age of metamorphism that affected the abz consequently these earliest tertiary ages also constrain the timing of the closure of the neo tethys

optimal interpolation of spatially discretized geodetic data abstract we present an algorithm to calculate horizontal strains or strain rates through interpolation of geodetically derived displacements or velocities this is an underdetermined inverse problem to derive smoothly distributed strains or strain rates using spatially discretized geodetic observations a priori information in the form of weighted smoothing is critical to facilitate the solution at a given site the horizontal displacement or velocity field in its vicinity is approximated by a bilinear function and represented by rigid block translation rotation and strains or their rates the weighted displacement or velocity data in the neighborhood are used to estimate the field parameters through a least squares inversion procedure optimal weightings are prescribed for the neighboring data based on their distances to the interpolation site and their spatial coverage nonelastic strains resulted from surface fault rupture and creep may also be excluded from the solution we apply this method to the southern california earthquake center crustal motion map version 4 0 velocity field and derive the strain rate field in southern california our result shows that 1 distance dependent weighting can be optimally achieved by employing either a gaussian or quadratic decay function with the former offering a slightly sharper result than the latter 2 spatially dependent weighting is important to improve the interpolation and can be done by invoking either an azimuthal weighting or a voronoi cell areal weighting function 3 the strain rate pattern in southern california is dominated by dextral shear of the san andreas fault saf system and the secondary faults surrounding the big bend of the saf strike at oblique angles with respect to the maximum shear direction suggesting that tectonic deformation field on and off the saf is dominated by mechanic processes of the saf

the 2016 kaikōura earthquake revealed by kinematic source inversion and seismic wavefield simulations slow rupture propagation on a geometrically complex crustal fault network the 2016 kaik ura new zealand earthquake generated large ground motions and resulted in multiple onshore and offshore fault ruptures a profusion of triggered landslides and a regional tsunami here we examine the rupture evolution using two kinematic modelling techniques based on analysis of local strong motion and high rate gps data our kinematic models capture a complex pattern of slowly vr 2km s propagating rupture from the south to north with over half of the moment release occurring in the northern source region mostly on the kekerengu fault 60 seconds after the origin time both models indicate rupture re activation on the kekerengu fault with the time separation of 11 seconds between the start of the original failure and start of the subsequent one we further conclude that most near source waveforms can be explained by slip on the crustal faults with little 8 or no contribution from the subduction interface

complex multifault rupture during the 2016 mw 7 8 kaikōura earthquake new zealand the 2016 moment magnitude m w 7 8 kaik ura earthquake was one of the largest ever to hit new zealand hamling et al show with a new slip model that it was an incredibly complex event unlike most earthquakes multiple faults ruptured to generate the ground shaking a remarkable 12 faults ruptured overall with the rupture jumping between faults located up to 15 km away from each other the earthquake should motivate rethinking of certain seismic hazard models which do not presently allow for this unusual complex rupture pattern science this issue p eaam7194 1 1 lookup doi 10 1126 science aam7194

from palaeotectonics to neotectonics in the neotethys realm the importance of kinematic decoupling and inherited structural grain in sw anatolia turkey abstract in order to asses young i e neotectonic fault kinematics and the relation with plate tectonic processes in sw turkey we focused on the questions 1 what produced the structural grain i e how and when are faults generated 2 what was is the kinematic behaviour of these faults and 3 during which period s were these faults active firstly the distribution of faults has been investigated using a lineament analysis performed on satellite imagery and digital elevation models we define five main tectonic domains in sw turkey 1 and 2 the northern and southern western anatolian extensional provinces 3 the eastern hellenic arc including rhodes island and the submarine anaximander mountains 4 the lycian taurides and 5 the western limb of the isparta angle lineament analysis reveals dominance of three lineament groups i e nne ene and wnw trending in all identified domains variations in the relative importance of lineament groups exist and are attributed to the specific tectonic evolution of each domain a synthesis of recently published field data shows that the onset of activity of related fault groups is neither synchronous nor uniform the structural grain for the neotectonic deformation in sw turkey is formed during the last stage of palaeotectonic deformation stage 1 which is dominated by the onset of the menderes massif exhumation along a top n major detachment the datca break away fault seyitoglu g isik v and cemen i 2004 complete tertiary exhumation history of the menderes massif western turkey an alternative working hypothesis terra nova 16 358 364 and related se ward sliding of the lycian nappes in the footwall of this fault this stage is characterized by spatially variable types of deformation that are delineated by from nw to se the datca fault around the menderes lycian contact zone and the lycian frontal thrust zone respectively the kinematic decoupling along these structures explains the co existence of top n detachment type extension in the western anatolian extensional province and ongoing nappe emplacement and piggy back development in the lycian taurides the decoupling also explains the lateral complexity of deformation associated with later neotectonic deformation from late miocene onward stage 2 nne ssw extension dominated the western anatolian extensional province influenced by combined anatolian extrusion and hellenic subduction roll back contemporaneously bidirectional ese wnw and nne ssw extension controls the lycian taurides due to the effects of hellenic arc expansion superposed on extrusion roll back extension the zone of kinematic decoupling is characterized by structural complexity with local transpressional features during stage 3 post late pliocene the same types of extension prevail in the western anatolian extensional province and the lycian taurides although a third tectonic regime becomes gradually more important this regime is associated with a tectonic escape in the hellenic arc that induced forearc slivers to be sheared of the expanding arc along mostly sinistrally displacing ene trending strike slip zones several of these zones have been identified in the coastal zones of sw turkey either through recent seismicity or field observations and are especially focused in the lycian taurides domain here they form what is classically referred to as the fethiye burdur fault zone which becomes gradually penetrated from the sw by oblique or strike slip zones exemplifying the time transgressive nature of the tectonic escape mechanism zones of kinematic decoupling remain persistent throughout the entire early miocene recent tectonic evolution of sw turkey and explain the existence of differently deforming tectonic domains

slow slip on the northern hikurangi subduction interface new zealand 1 in october 2002 a surface displacement episode of 20 30 mm magnitude was observed over a 10 day period on two continuous global positioning system gps instruments near gisborne north island new zealand we interpret this to result from slow slip on the northern hikurangi subduction interface using ten years of regional campaign gps 1995 2004 and recent continuous gps data we estimate the recurrence interval for similar events to be 2 3 yrs in november 2004 a similar slow slip event occurred within this recurrence period the 2002 event can be modeled by 18 cm of slow slip near the down dip end of the seismogenic zone on the subduction interface offshore of gisborne the campaign gps data show that the 2002 slow slip event had little effect on regional strain patterns

is stoping a volumetrically significant pluton emplacement process magmatic stoping is widely called upon to explain discordant pluton contacts but several lines of evidence indicate that stoping is not volumetrically significant in the emplacement of most plutons first xenoliths rarely make up more than a few percent of most plutons this sparseness even on well exposed pluton floors argues that few xenoliths make it into plutons second piles of rock fragments have sufficiently high porosities 50 that a significant accumulation of stoped blocks on the floor of a magma chamber would trap much if not all of the available magma producing pluton scale magmatic breccias that are not observed third although settling calculations show that large meter scale or larger xenoliths could sink rapidly in magma natural fragmentation processes are likely to produce a fractal distribution of particle sizes with small particles far more abundant than large ones the absence of small xenoliths at pluton contacts where magma cools most rapidly thus argues against stoping fourth although contamination of magmas by anatectic liquids derived from wall rocks and xenoliths is common geochemical data from many plutons clearly rule out significant bulk assimilation of local wall rocks finally there is growing evidence that at least some large plutons never were large molten bodies of magma but grew incrementally stoping cannot be volumetrically important in incrementally emplaced plutons because blocks can only fall through the volume that is molten at any given time where xenoliths are abundant in plutons they may commonly represent isolation of wall rock bodies between successive intrusive increments rather than wall rock fragments that were engulfed by magma however even xenoliths that were engulfed by magma did not necessarily sink from the roof of a magma chamber although stoping undoubtedly occurs during the emplacement of some plutons it is unlikely to be a volumetrically significant process

crystallinity and b0 spacing of k white micas in a paleozoic accretionary complex eastern australia metamorphism paleogeotherms and structural style of an underplated sequence white micas in slates and meta sandstones from deformed and imbricated chert basalt turbidite sequences of the narooma accretionary complex of the eastern lachlan fold belt australia show b0 cell values indicative of intermediate p metamorphic facies conditions documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes 10 9 7 6 begin document landscape x 9 025 n 73 end document illite crystallinity ic values indicate middle to upper anchi zonal metamorphic conditions and are constant throughout the area they are in general agreement with the infe

tectonic transport directions of the lycian nappes in southwest turkey constrained by kinematic indicators abstract the orientation asymmetry and cross cutting relationships of the structures along the contact zone between the lycian nappes and the menderes massif suggest the presence of three deformation phases in the milas region of southwest turkey the first deformation phase d1 is characterized by a ductile deformation with top to the ne sense of shear structural data of the first deformation measured along the uppermost part of the menderes massif and the base of the lycian nappes suggest that the lowermost unit of the lycian nappes was emplaced initially from southwest to northeast onto the menderes massif during the early eocene the second deformation phase d2 is also ductile in nature and is characterized by an e w trending stretching lineation with a bivergent sense of shear which is probably related to the load of the overlying nappes a third deformation phase d3 is characterized by south dipping normal faults with top to the s sense of movement this third deformation phase can be related to southward movement of the lycian nappes along a low angle decollement zone the tectonic contact between the menderes massif and the lycian nappes and their strongly deformed rocks are unconformably covered by approximately flat lying coal bearing early middle miocene sedimentary rocks which constrains the upper time limit for all three deformation phases

earthquakes triggered by slow slip at the plate interface in the hikurangi subduction zone new zealand 1 an earthquake swarm in the crust of the subducted plate in the southern hikurangi subduction zone in aprilmay 2004 was most likely triggered by slow slip at the plate interface directly downdip during the previous year double difference relocation indicates that the swarm represents incremental slip on adjacent patches of the same fault a subsequent ml 5 5 earthquake in january 2005 occurred on a separate deeper fault sub parallel to that of the 2004 swarm but separated from it by about 1 km this suggests a rapid decrease in mechanical damage in the slab with depth below the plate interface the normal faulting observed in both earthquake sequences represents unbending of the subducted plate such unbending may be diagnostic of deformation on the deeper edge of a strongly coupled region of the plate interface resulting from adjacent slow slip citation reyners m and s bannister 2007 earthquakes triggered by slow slip at the plate interface in the hikurangi subduction zone new zealand geophys res lett 34 l14305 doi 10 1029 2007gl030511

gondwana derived microcontinents the constituents of the variscan and alpine collisional orogens abstract the european variscan and alpine mountain chains are collisional orogens and are built up of pre variscan building blocks which in most cases originated at the gondwana margin such pre variscan elements were part of a pre ordovician archipelago like continental ribbon in the former eastern prolongation of avalonia and their present day distribution resulted from juxtaposition through variscan and or alpine tectonic evolution the well known nomenclatures applied to these mountain chains are the mirror of variscan resp alpine organization it is the aim of this paper to present a terminology taking into account their pre variscan evolution at the gondwana margin they may contain relics of volcanic islands with pieces of cadomian crust relics of volcanic arc settings and accretionary wedges which were separated from gondwana by initial stages of rheic ocean opening after a short lived ordovician orogenic event and amalgamation of these elements at the gondwanan margin the still continuing gondwana directed subduction triggered the formation of ordovician al rich granitoids and the latest ordovician opening of palaeo tethys an example from the alps external massifs illustrates the gradual reworking of gondwana derived pre variscan elements during the variscan and alpine tertiary orogenic cycles

biochronology of jurassic and early cretaceous radiolarites from the lycian melange sw turkey and implications for the evolution of the northern neotethyan ocean new radiolarian ages for blocks of radiolarian cherts associated with other blocks of distal pelagic facies and ophiolitic lithologies within the lycian melange sw turkey indicate deposition during mid jurassic to early cretaceous time radiolarites overlying pink pelagic limestones of an allochthonous carbonate unit accumulated during the midto late jurassic on the basis of structural evidence the lycian melange is inferred to have been rooted within the northern neotethys to the north of the tauride anatolide microcontinent the lycian radiolarites can be compared with other dated radiolarites from the izmir ankara suture the root zone of the northern neotethyan ocean based on all the available radiolarian data it is inferred that radiolarites accumulated within the northern neotethys in western turkey from late triassic mid carnian to late norian to midcretaceous cenomanian time the radiolarites were later detached from their inferred oceanic basement and accreted within a subduction complex during the late cretaceous turonian maastrichtian and emplaced over the northern margin of the tauride anatolide continent together with slices of continental margin and ophiolitic lithologies following the development of mesozoic radiolarian biostratigraphical schemes during the last 25 years radiolarian biochronology has become invaluable for reconstructing the palaeogeography palaeoceanography and tectonic evolution of tethyan oceanic basins and margins de wever 1989 robertson et al 1991 de wever et al 1994 danelian robertson 1997 2001 radiolarites in the tethyan realm commonly occur within melanges that are interpreted as parts of accretionary prisms related to subduction of ocean crust robertson 2002 2004 radiolarian ages from such melanges provide valuable age constraints on related geological processes including spreading intra plate volcanism and tectonic accretion e g al riyami et al 2001 beccaletto et al 2005 here we will present the first radiolarian evidence from the lycian melange an east west trending late mesozoic accretionary complex in sw turkey collins robertson 1997 fig 1 this melange forms part of the wellknown lycian nappes in sw turkey de graciancky 1972 poisson 1977 1984 collins robertson 1998 the root zone of the melange is considered to lie to the north of the regional basement represented by the tauride anatolide platform collins robertson 1998 2003 and is inferred to lie within the izmir ankara suture zone to the north of the menderes massif robertson pickett 2000 robertson et al 2004 we will also review the limited available data for radiolarites from comparable tectonic units within the izmir ankara suture zone and the bey daglari we conclude by considering the implications of the available radiolarian evidence for the evolution of the mesozoic tethyan ocean

oxygen and sulfur isotope geochemistry revealing a significant crustal signature in the genesis of the post collisional granitoids in central anatolia turkey abstract late cretaceous granitoid rocks from central anatolia comprise s i a type plutons derived from the collisional stages of the neo tethyan convergence system in central turkey these granitoids intrude the tectonic imbrication zone consisting of blocks of supra subduction zone type ssz type central anatolian ophiolite and crustal metasediments which are present in the izmir ankara erzincan suture zone the plutons are overlain by late palaeocene early eocene or younger detrital sediments granitoid formation is thought to be related to magma generation processes occurring in a post collisional lithospheric detachment related geodynamic setting that resulted from slab break off or lithospheric delamination whole rock s and quartz feldspar o isotope data from these plutons yields a broad range of values and both parameters indicate a nearly exclusively supracrustal origin for the s type granites as well as a significant crustal contribution in the genesis of the hybrid i type and a type granitoids the more mafic i type and a type granitoid rocks of any given suite have lower s and o values indicative of their larger degree of mantle component the combined stable isotope geochemical compositions when coupled with major trace and ree geochemistry and regional geology provide evidence that the significant crustal contribution originated from a metasomatized mantle layer which was affected by earlier ssz derived fluids and then accreted into the subcontinental lithosphere as collision occurred the partial melting of such a metasomatized mantle layer in a post collisional extensional geodynamic setting supplied either by the slab break off or lithospheric delamination mechanisms provided the significant crustal signature in the hybrid magmas of the late cretaceous i type and a type granitoids in central anatolia turkey

coseismic and early postseismic deformation of the 2016 m w 7 8 kaikōura earthquake new zealand from continuous gps observations the mw 7 8 kaik ura north canterbury new zealand earthquake which occurred on 14 november 2016 local time was one of the most complex continental earthquakes ever documented and among the largest instrumentally recorded events in new zealand history the epicenter was located at the southern termination of the hikurangi margin where the subducting pacific plate transfers into the dextral alpine transform fault in this work we precisely estimate three dimensional coseismic and postseismic displacements caused by this event from continuous global navigation satellite systems gnss stations in new zealand the kaik ura earthquake activated significant and diverse coseismic and postseismic deformation on a large spatial scale located mainly in the southern part of the north island and the northern part of the south island station cmbl had the largest coseismic offsets and the most remarkable postseismic displacements the accumulated postseismic displacements at this station reached 13 7 and 29 of the coseismic values on the east north and vertical components respectively in the first 1 5 years after the mainshock integrating our estimated coseismic displacements with previously published coseismic displacements we inverted for the spatial distribution of coseismic slip and spatiotemporal evolution of postseismic slip our optimal coseismic model suggests that rupture occurred both on shallow crustal faults and to some extent at the southern hikurangi subduction interface the gps inverted coseismic moment release is equivalent to an mw 7 9 event the postseismic slip was not only significantly extended at the subduction interface but also appeared on the needles fault the cumulative moment magnitude is mw 7 35 in the first 1 5 years after the event and mw 7 35 mw 6 95 and mw 6 80 during the periods 0 0 0 5 0 5 1 0 and 1 0 1 5 years respectively indicating rapid decay of the postseismic deformation comparing the spatial distribution of the postseismic to the coseismic slip although their direction is similar the discrepancy between their location is significant the slip located along the shallow crustal faults activated the coseismic deformation while the slip located on the deep subduction interface controlled the postseismic deformation

postseismic deformation associated with the 2015 mw 7 8 gorkha earthquake nepal investigating ongoing afterslip and constraining crustal rheology abstract the 2015 mw 7 8 gorkha earthquake has not only imposed effective constraints on the geometrical structures friction behaviours and seismogenic patterns of the nepal himalaya thrust systems but has also provided valuable insights into the uplift mechanism and lithosphere rheology of the tibetan plateau here 1 6 year gps observations are used to reveal the postseismic deformation characteristics following the gorkha earthquake investigate the ongoing aseismic afterslip on the main himalayan thrust mht fault and constrain the crustal rheology of the southern tibetan plateau first afterslip is considered to be solely responsible for the postseismic deformation afterslip only model the results show that afterslip is anticorrelated with peak coseismic slip areas one high afterslip concentration area with a peak of 24 cm is distributed downdip of the coseismic rupture as well as in two other regions one partially overlapping the mainshock rupture and the other next to the mw 7 3 aftershock area second the gps postseismic observations are inverted to jointly investigate afterslip and viscoelastic deformation multiple mechanism model the afterslip inversion results of the above two models are highly consistent indicating the dominant contribution of afterslip to surface deformation during the 1 6 year postseismic period considering the interseismic fault coupling and historical seismicity no appreciable fault slip associated with the gorkha earthquake is found to occur both updip and west of the mainshock rupture areas this reveals that the gorkha earthquake only unzipped the lower edge of the locked portion of the mht leaving the shallow portion and western segment of the seismogenic zone still locked and the nepal region under high seismic risk the viscoelastic mechanism contributes minorly to surface deformation during the 1 6 year postseismic period the middle lower crust is assumed to comprise maxwell material beneath an elastic 25 km thick upper crust and the optimal viscosity is conservatively estimated to be 1 6 1019 pa s beneath the southern tibetan plateau which should be robustly constrained with more long term observations more effective spatial constraints and more detailed crustal models

the influence of strain lithology and stratigraphical depth on white mica illite crystallinity in mudrocks from the vicinity of the corris slate belt wales implications for the timing of metamorphism in the welsh basin low and very low grade metamorphism in a mudrock dominated succession ranging from upper cambrian to wenlock is characterized by the white mica illite crystallinity technique kubler indices indicate that grade ranges from late diagenetic to low epizonal the prograde reaction most easily observed by xrd study is the progressive ordering of k na micas diagnostic 2m 1 polytypic reflections become recognizable at 0 4 2 and strengthen as grade advances grade generally correlates with thickness of overburden in the 9 km thick succession however strain exercises additionally a profound influence on grade and the distribution of strain was related to decollement resulting from inhomogeneities and ductility contrasts within the succession strain energy is seen as an additional and important variable in the development of white mica crystallinity in slates the distribution of metamorphic grade implies that the lower palaeozoic succession was augmented by several kilometres of lower devonian old red sandstone strata at the metamorphic culmination the culmination was syntectonic and represents an acadian rather than an early diastathermal event subsequent dextral movement on the bala fault displaced the regional isocryst pattern by c 4 km retrogressive smectite appears to be localized to the vicinity of the bala fault and is probably of variscan age

diverse slow slip behavior at the hikurangi subduction margin new zealand 1 the installation of a continuous gps cgps network in new zealand since 2002 has enabled the discovery of 15 slow slip events at the hikurangi subduction margin our analysis and interpretation of the cgps data reveal a marked diversity in characteristics of slow slip events sses in the north island with durations varying from 6 days to 1 5 years equivalent moment release between mw 6 3 7 2 and recurrence intervals of repeating sses on the order of 2 years to more than 5 years the duration and magnitude characteristics of hikurangi sses appear to be related to the depth where they occur the deepest longest duration and largest sses occur at the southern hikurangi margin near the downdip limit of deep down to 40 km depth strong interseismic coupling the shallowest shortest duration smallest and most frequent sses occur at the northern and central hikurangi margin near the downdip limit of unusually shallow 10 15 km depth interseismic coupling the direction of slip on the interface in the hikurangi sses is consistent with slip partitioning at the hikurangi subduction margin we also show that moment accumulation rates on the interface for the time periods between sses are 40 higher than for the period of more than a decade averaging through the sses indicating that sses compose a major portion of the overall moment release budget of the hikurangi subduction interface

small earthquakes provide insight into plate coupling and fluid distribution in the hikurangi subduction zone new zealand abstract to better understand the nature of interplate coupling in the southern north island of new zealand we compare the distribution of relocated small earthquakes with interseismic geodetic locking of the plate interface from gps and structure within the overlying plate from tomographic inversions relocated seismicity shows a good correlation with both the distribution of strong geodetic locking and geological terranes in the overlying plate it appears that the strong permian triassic rakaia geological terrane controls coupling at the plate interface this relatively impermeable terrane also modulates the small earthquake distribution within the underlying slab promoting clustered seismicity in the slab crust and suppressing lower plane seismicity in the mantle the seismicity and structural data suggest a model where plate coupling is controlled by the ability of fluid to cross the plate interface when an impermeable terrane in the overlying plate prevents such fluid flow plate coupling appears to be strong

petrology and geochemistry of augite trachytes and porphyritic trachytes from the golcuk volcanic region isparta sw turkey a case study abstract the plio quaternary alkaline volcanic rocks at golcuk isparta sw turkey include older porphyritic trachytes augite trachytes and younger trachyandesitic and tephriphonolitic dikes in order to better understand their pre eruptive evolution the geochemical variations of porphyritic trachytes and augite trachytes have been modeled quantitatively using the melts algorithm ghiorso and sack 1995 their geochemical variations are also compared with those of the younger series results show that two distinct magma series trachyte trachyandesite and tephriphonolite governed the petrogenesis of golcuk volcanic rocks geochemistry of the trachytic trachyandesitic series is controlled predominantly by clinopyroxene and plagioclase fractionation at a shallow depth under oxygen fugacity conditions two units above the qfm buffer melts calculations also show that the crystallisation of trachytic trachyandesitic magma produces clinopyroxene plagioclase alkali feldspar biotite apatite and magnetite quartz consistent with the mineralogy of the augite trachyte porphyritic trachyte and trachyandesitic dikes

coseismic slip and afterslip of the 2015 mw 8 3 illapel chile earthquake determined from continuous gps data we analyzed the coseismic and early postseismic deformation of the 2015 mw 8 3 illapel earthquake by inverting 13 continuous gps time series the seismic rupture concentrated in a shallow 20 km depth and 100 km long asperity which slipped up to 8 m releasing a seismic moment of 3 6 1021 nm mw 8 3 after 43 days postseismic afterslip encompassed the coseismic rupture afterslip concentrated in two main patches of 0 50 m between 20 and 40 km depth along the northern and southern ends of the rupture partially overlapping the coseismic slip afterslip and aftershocks confined to region of positive coulomb stress change promoted by the coseismic slip the early postseismic afterslip was accommodated 53 aseismically and 47 seismically by aftershocks the illapel earthquake rupture is confined by two low interseismic coupling zones which coincide with two major features of the subducting nazca plate the challenger fault zone and juan fernandez ridge

the temporal evolution of the active margin along the southeast anatolian orogenic belt se turkey evidence from u pb ar ar and fission track chronology abstract the southeast anatolian orogenic belt saob resulted from the north dipping subduction of the southern neotethyan oceanic lithosphere in late mesozoic and early cenozoic however the timing and the rate of the continental collision are still under debate here we present new u pb ar ar and fission track ages from the i type calc alkaline granitoids esence dogansehir and baskil cutting the goksun ispendere and komurhan ophiolites and also the malatya keban metamorphics representing the tauride active continental margin along the saob in this study high to low temperature thermochronological methods applied to the granitoids are used to understand the temporal and geodynamic evolution of the tauride active continental margin and continental collision between tauride and arabian platforms in the frame of the neotethyan convergence during cretaceous and miocene the u pb zircon ages range from 83 to 88 ma for the baskil and from 81 to 83 ma for the esence granitoids the 39 ar 40 ar ages indicate that these late cretaceous granitoids cooled below 300 c in 6 10 ma the formation ages and the timing of the gradual cooling of the late cretaceous granitoids are similar to metamorphism age and the timing of the exhumation of the hp lt bitlis metamorphics during this stage the combined field geochemistry and geo thermochronological data suggest that the first continental collision event occurred between bitlis puturge micro continents to the south and tauride platform to the north in an oblique subduction zone between 84 and 74 ma the granitoids continued uplifting during early middle eocene together with the exhumation of hp uht berit metaophiolite in an extensional regime related to the opening of the maden back arc basin this period also let the intrusion of the dogansehir arc magmatism intruding the puturge and malatya keban metamorphics berit metaophiolite and maden complex the eocene dogansehir granitoid has similar u pb and 39 ar 40 ar ages suggesting a fast cooling the apatite fission track aft ages for all granitoid bodies suggest that they were mainly cooled or uplifted in two episodes where the first one is in the eocene in an extensional setting the aft data marked the final continental collision between the taurides and the arabian platform first in oligocene and the break off of the subducted slab and the delamination process caused fast uplift of the eastern anatolia during middle to late miocene

pcaim joint inversion of insar and ground based geodetic time series application to monitoring magmatic inflation beneath the long valley caldera this study demonstrates the interest of using a principal component analysis based inversion method pcaim to analyze jointly insar and ground based geodetic time series of crustal deformation a major advantage of this approach is that the insar tropospheric biases are naturally filtered out provided they do not introduce correlated or high amplitude noise in the input times series this approach yields source models which are well constrained both in time and space due to the temporal resolution of the ground based geodetic data and the spatial resolution of the insar data the technique is computationally inexpensive allowing for the inversion of large datasets to demonstrate the performance of this approach we apply it to the 1997 98 magmatic inflation event in the long valley caldera california

slow slip events and the 2016 te araroa mw 7 1 earthquake interaction northern hikurangi subduction new zealand following a sequence of three slow slip events sses on the northern hikurangi margin between june 2015 and august 2016 a mw 7 1 earthquake struck 30 km offshore of the east cape region in the north island of new zealand on the 2nd september 2016 nz local time the earthquake was also followed by a transient deformation event sse or afterslip northeast of the north island closer to the earthquake source area we use data from new zealand s continuous global positioning system cgps networks to invert for the sse slip distribution and evolution on the hikurangi subduction interface our slip inversion results show an increasing amplitude of the slow slip towards the te araroa earthquake foreshock and mainshock area suggesting a possible triggering of the mw 7 1 earthquake by the later stage of the slow slip sequence we also show that the transient deformation following the te araroa earthquake ruptured a portion of the hikurangi trench northeast of the north island further north than any previously observed hikurangi margin sses our slip inversion and the coulomb stress calculation suggest that this transient may have been induced as a response to the increase in the static coulomb stress change downdip of the rupture plane on the megathrust these observations show the importance of considering the interaction between slow slip events seismic and aseismic events not only on the same megathrust interface but also on faults within the surrounding crust

silent triggering aseismic crustal faulting induced by a subduction slow slip event abstract slow slip events sses are a form of fault slip behaviour whose importance has only been recognised in the last decade at subduction zone plate boundaries worldwide here we show one of the first examples of the use of interferometric synthetic aperture radar insar data to document deformation during an sse on the hikurangi subduction interface in new zealand although much of the deformation that we observe is attributable to slow slip on the subduction interface the insar data also reveals surface offsets of up to 1 2 cm across a major crustal fault during the period of the slow slip event in order to fit the observations we find that reverse aseismic slip is required along a portion of the wellington fault where the coulomb failure stress changes cfs due to the sse are in excess of 0 01 mpa this is the first ever documented example of a subduction interface sse triggering a transient slip event on a major upper plate fault and it has wide ranging implications for the role that sses can play in time dependent seismic hazard

interlaboratory standardization and calibration of day mineral crystallinity and crystallite size data clay mineral crystallinity and crystallite domain size data determined by x ray diffraction xrd are methods extensively used in the characterization of very low grade metamorphic conditions however the lack of sufficient interlaboratory standardization has made comparisons between different research groups unreliable due to significant variations in numerical results obtained a consequence of the different machine conditions measurement methods and sample preparations used during analysis a calibration approach to the standardization of data using rock chip standards is presented which allows data sets produced by different research groups to be directly and quantitatively compared a standardized scale the crystallinity index standard cis is proposed with illite crystallinity anchizonal boundary limits of 0 25d 2 and 0 42d 2 and equivalent illite crystallite sizes of 52 and 23 nm respectively determined by the warren averbach method calibrating both old and new data will enable more reliable comparisons between similar and contrasting geological environments and should improve the accuracy and reliability of correlations made between xrd data and other indicators of very low grade metamorphism hence increasing the value of such clay mineral studies

inverting geodetic time series with a principal component analysis based inversion method 1 the global positioning system gps system now makes it possible to monitor deformation of the earth s surface along plate boundaries with unprecedented accuracy in theory the spatiotemporal evolution of slip on the plate boundary at depth associated with either seismic or aseismic slip can be inferred from these measurements through some inversion procedure based on the theory of dislocations in an elastic half space we describe and test a principal component analysis based inversion method pcaim an inversion strategy that relies on principal component analysis of the surface displacement time series we prove that the fault slip history can be recovered from the inversion of each principal component because pcaim does not require externally imposed temporal filtering it can deal with any kind of time variation of fault slip we test the approach by applying the technique to synthetic geodetic time series to show that a complicated slip history combining coseismic postseismic and nonstationary interseismic slip can be retrieved from this approach pcaim produces slip models comparable to those obtained from standard inversion techniques with less computational complexity we also compare an afterslip model derived from the pcaim inversion of postseismic displacements following the 2005 8 6 nias earthquake with another solution obtained from the extended network inversion filter enif we introduce several extensions of the algorithm to allow statistically rigorous integration of multiple data sources e g both gps and interferometric synthetic aperture radar time series over multiple timescales pcaim can be generalized to any linear inversion algorithm

the beysehir hoyran hadim nappes genesis and emplacement of mesozoic marginal and oceanic units of the northern neotethys in southern turkey the beysehir hoyran hadim nappes crop out over 700 km from nw to se above a regionally autochthonous tauride carbonate platform the beysehir hoyran nappes begin with a thrust sheet c 400 m of mainly redeposited carbonates quartzose sandstones and mudstones of mid late triassic age interpreted as a proximal slope base of slope succession above is a thrust sheet c 1 km of middle upper triassic intermediate acidic extrusive rocks volcaniclastic rocks and minor pelagic carbonates interpreted as a continental rift thin

afterslip following the 2007 mw 8 4 bengkulu earthquake in sumatra loaded the 2010 mw 7 8 mentawai tsunami earthquake rupture zone the 12 september 2007 mw 8 4 bengkulu earthquake in sumatra marked the first in a modern series of large earthquakes along the mentawai section of the sunda megathrust understanding the spatial distribution of coseismic slip and ensuing afterslip is important for assessing seismic hazard in neighboring unruptured regions of the megathrust we re estimate the spatial distribution of coseismic slip during this earthquake with improved coseismic offsets from the sumatran gps array sugar and estimate afterslip following this earthquake with sugar postseismic time series spanning 6 3 years after the earthquake we invert for the spatio temporal distribution of afterslip with the principal component analysis based inversion method pcaim and we take into account viscoelastic deformation by incorporating into the inversion the estimation of strain within ductile deforming blocks located at asthenospheric depths our results suggest cumulative afterslip concentrated within updip and downdip of the 2007 coseismic rupture area and shallow afterslip that borders and overlaps the 2010 mw 7 8 mentawai earthquake rupture zone the cumulative contribution of stress changes due to the coseismic event and the ensuing afterslip likely increased strain rates in the shallow portion of the megathrust adjacent to the mentawai earthquake rupture area potentially promoting its rupture in 2010

burial and exhumation history of the daday unit central pontides turkey implications for the closure of the intra pontide oceanic basin in northern turkey the intra pontide suture zone represents one of the first order tectonic structures located between the istanbul zonguldak and the sakarya continental terranes it consists of an e w trending assemblage of deformed and variably metamorphosed tectonic units including sedimentary rocks and ophiolites derived from a neo tethyan oceanic basin known as the intra pontide oceanic basin one of these units is represented by the daday unit that consists of a block in matrix assemblage derived from supra subduction oceanic crust and related deep sea sedimentary cover of middle jurassic age this setting was acquired during late jurassic time by tectonic underplating at a depth of 35 42 km associated with blueschist facies metamorphism d1 phase the following d2 d3 and d4 phases produced the exhumation of the daday unit up to shallower structural levels in a time span running from the albian to late paleocene the high geothermal gradient detected during the d2 phase indicates that the daday unit was exhumed during a continent arc collisional setting the tectonic structures of the intra pontide suture zone resulting from the previously described tectonic history are unconformably sealed by the upper paleocene eocene deposits this tectonic setting was intensely reworked by the activity of the north anatolian fault zone producing the present day geometrical relationships of the intra pontide suture zone of the central pontides

slow slip events and seismic tremor at circum pacific subduction zones 1 it has been known for a long time that slip accompanying earthquakes accounts for only a fraction of plate tectonic displacements however only recently has a fuller spectrum of strain release processes including normal slow and silent earthquakes or slow slip events and continuous and episodic slip been observed and generated by numerical simulations of the earthquake cycle despite a profusion of observations and modeling studies the physical mechanism of slow slip events remains elusive the concurrence of seismic tremor with slow slip episodes in cascadia and southwestern japan provides insight into the process of slow slip a perceived similarity between subduction zone and volcanic tremor has led to suggestions that slow slip involves fluid migration on or near the plate interface alternatively evidence is accumulating to support the notion that tremor results from shear failure during slow slip global observations of the location spatial extent magnitude duration slip rate and periodicity of these aseismic slip transients indicate significant variation that may be exploited to better understand their generation most slow slip events occur just downdip of the seismogenic zone consistent with rate and state dependent frictional modeling that requires unstable to stable transitional properties for slow slip generation at a few convergent margins the occurrence of slow slip events within the seismogenic zone makes it highly likely that transitions in frictional properties exist there and are the loci of slow slip nucleation slow slip events perturb the surrounding stress field and may either increase or relieve stress on a fault bringing it closer to or farther from earthquake failure respectively this paper presents a review of slow slip events and related seismic tremor observed at plate boundaries worldwide with a focus on circum pacific subduction zones trends in global observations of slow slip events suggest that 1 slow slip is a common phenomena observed at almost all subduction zones with instrumentation capable of recording it 2 different frictional properties likely control fast versus slow slip 3 the depth range of slow slip may be related to the thermal properties of the plate interface and 4 the equivalent seismic moment of slow slip events is proportional to their duration mo different from the mo 3 scaling observed for earthquakes

multi phased uplift of the southern margin of the central anatolian plateau turkey a record of tectonic and upper mantle processes abstract uplifted neogene marine sediments and quaternary fluvial terraces in the mut basin southern turkey reveal a detailed history of surface uplift along the southern margin of the central anatolian plateau from the late miocene to the present new surface exposure ages 10be 26al and 21ne of gravels capping fluvial strath terraces located between 28 and 135 m above the goksu river in the mut basin yield ages ranging from ca 25 to 130 ka corresponding to an average incision rate of 0 52 to 0 67 mm yr published biostratigraphic data combined with new interpretations of the fossil assemblages from uplifted marine sediments reveal average uplift rates of 0 25 to 0 37 mm yr since late miocene time starting between 8 and 5 45 ma and 0 72 to 0 74 mm yr after 1 66 to 1 62 ma together with the terrace abandonment ages the data imply 0 6 to 0 7 mm yr uplift rates from 1 6 ma to the present the different post late miocene and post 1 6 ma uplift rates can imply increasing uplift rates through time or multi phased uplift with slow uplift or subsidence in between longitudinal profiles of rivers in the upper catchment of the mut and ermenek basins show no apparent lithologic or fault control on some knickpoints that occur at 1 2 to 1 5 km elevation implying a transient response to a change in uplift rates projections of graded upper relict channel segments to the modern outlet together with constraints from uplifted marine sediments show that a slower incision uplift rate of 0 1 to 0 2 mm yr preceded the 0 7 mm yr uplift rate the river morphology and profile projections therefore reflect multi phased uplift of the plateau margin rather than steadily increasing uplift rates multi phased uplift can be explained by lithospheric slab break off and possibly also the arrival of the eratosthenes seamount at the collision zone south of cyprus

a large slow slip event on the central hikurangi subduction interface beneath the manawatu region north island new zealand 1 we present continuous gps observations of a surface deformation episode in the manawatu region of the north island new zealand lasting 18 months from january 2004 to june 2005 we invert vertical and horizontal displacements of gps sites during the event for slow slip on the hikurangi subduction thrust we find that up to 350 mm of slip occurred on the thrust in the transition zone between strong interseismic coupling and aseismic creep if the entire slip in the manawatu slow slip event had occurred instantaneously it would have resulted in an mw 7 0 earthquake given the large amount of slip we expect that the recurrence interval for similar slow slip events may be ten years or more

transition from diagenesis to metamorphism near the front of the variscan regional metamorphism cantabrian zone northwestern spain abstract distribution of paleotemperatures has been studied in paleozoic rocks of the variscan fold and thrust belt of the nw cantabrian zone spain by a combined application of illite crystallinity ic and conodont color alteration index cai results show that the diagenetic metamorphic grade increases with the increase in rock age as marked by decreasing ic values and increasing cai values moreover the cai isogrades roughly reflect the structural traits of the area indicating that maximum temperatures were attained during sedimentary burial previous to folding the geothermal paleogradient obtained suggests conditions near the boundary between low and middle p t conditions there is evidence of at least two thermal events during the tectonothermal development of the belt the main stage is interpreted as the result of the burial of the rocks characterized by late diagenesis conditions that occurred under a geothermal gradient of 35 c km 1 the narrow zone with low anchizonal conditions in the w

andean type active margin formation in the eastern taurides geochemical and geochronogical evidence from the baskil granitoid elazig se turkey abstract the southeast anatolian orogen resulted from collision of the afro arabian and the eurasian plates following the cretaceous to miocene closure of the southern neotethyan oceanic basin in this orogenic belt there are number of tectonomagmatic stratigraphic units in the kahramanmaras malatya elazig region that are important to understand the geological evolution of southeast anatolia during the late cretaceous these are a metamorphic massifs i e malatya keban platform b ophiolites i e goksun ispendere komurhan c ophiolite related metamorphics i e berit metaophiolite and d granitoids i e goksun dogansehir and baskil the baskil granitoid crops out to the northwest of elazig and is a large magmatic body 170 km2 that intruded all of the above mentioned units during late cretaceous time the baskil granitoid comprises both mafic and felsic plutonic sub plutonic rock associations the felsic plutonic phase includes granite granodiorite tonalite and quartz monzonite whereas the felsic sub plutonic phase is characterized by aplite granophyre granite porphyry and granodiorite porphyry the granite and granodiorite contain mafic microgranular enclaves mme the mafic plutonic phase comprises gabbro diorite quartz diorite whereas the mafic sub plutonic phase is represented by diabase microdiorite quartz microdiorite diorite porphyry quartz diorite porphyry and dykes of orbicular gabbro dyke geochemically the baskil granitoid rocks have i type metaluminous peraluminous calc alkaline characteristics the ree and ocean ridge granite normalized multi element patterns and tectonomagmatic discrimination diagrams together with biotite geochemistry suggest that the granitoids were formed in a volcanic arc setting the40ar 39ar geochronology of the granitoid rocks yielded biotite ages of 81 9 0 7 ma and 81 5 0 8 ma 95 confidence level coexisting hornblende and hornblende from additional samples yielded ages ranging from 84 0 0 7 ma to 81 5 1 1 ma the ophiolites are believed to have formed in a suprasubduction zone tectonic setting whereas the ophiolite related metamorphic rocks formed either during the initiation of intraoceanic subduction or later stage thrusting 90 ma these units were then thrust beneath the malatya keban platform during the progressive closure of the southern neotethys this was followed by intrusion of the granitoids 85 82 ma along the tauride active continental margin of the southern neotethys

geochronology of the karadere basement nw turkey and implications for the geological evolution of the istanbul zone earlier geological work in the istanbul zone western pontide tectonic belt has revealed the presence of extensive basement outcrops exposed underneath palaeozoic and mesozoic to tertiary cover sequences the basement of suspected neoproterozoic age plays an important role in understanding the crustal accretion process in nw turkey we report the first results of a detailed pb pb and u pb zircon study complemented by nd sr whole rock and mineral data from basement rocks exposed in the karadere valley safranbolu area five samples were selected for this study comprising three metagranitoids and two metasediments zircon geochronology indicates that the metagranitoids were formed during late proterozoic pan african magmatic events between 590 and 560 ma the rocks are of tonalitic and granitic composition and have low nb y ratios and ti contents consistent with those of arc rocks a continental arc setting is supported by their sr and nd isotope data that indicate a contribution of a mantle source as well as crustal assimilation during magma genesis the metasediments can clearly be distinguished from the metagranitoids by their higher 87sr 86sr ratios and lower end values at 580 ma which supports the suggestion that the arc was underlain by mature continental crust zircons from the metasediments yield a range of pb pb ages between 1 860 and 710 ma thirty per cent of them fall between 890 and 710 ma possibly suggesting a derivation from gondwana afro arabian regions a sm nd garnet whole rock analysis obtained on a metagranite gives an age of 559 8 ma which either reflects pre metamorphic magmatic growth of garnet in a felsic melt or a syntectonic high temperature metamorphic event uplift and cooling of the basement is further constrained by rb sr biotite ages of 548 545 ma these lower cambrian mineral ages demonstrate that the istanbul zone was not thermally reactivated during the hercynian cimmerian or alpine orogeny in contrast to its neighbouring tectonic zones confirming its role as a suspect terrane in the modern western pontide tectonic belt

spatial temporal evolution of slow slip movements triggered by the 2016 mw 7 8 kaikoura earthquake new zealand abstract the 2016 mw 7 8 kaikoura earthquake involved complex rupture across multiple faults and triggered large scale slow slip movements on the hikurangi subduction zone the complex seismically triggered slow slip events sses contribute to the understanding of triggering mechanisms of sses in new zealand here we invert the continuous global positioning system cgps observations to investigate the temporal evolution of the seismically triggered slow slip behaviour on the hikurangi subduction interface similar to previous studies our optimal geodetic inversion model reproduces deep 30 50 km marlborough afterslip of over 60 cm deep kapiti slow slip of up to 31 cm and shallow 10 cm east coast slow slip on the hikurangi subduction interface the slow accumulated seismic moment over the past eight months from the large scale slow slip motion is 3 12 1020 nm which is equivalent to a magnitude 7 6 earthquake both the marlborough afterslip and kapiti slow slip were considerably active during the first week after the mainshock and gradually slowed down in the following months these deep ongoing fault motions may continue for at least several months and are expected to decay logarithmically with time in agreement with previous studies the east coast slow slip motion occurred rapidly within 2 3 weeks which stretched from the central to northern hikurangi subduction margin the coseismic coulomb failure stress change investigation suggests that large scale stress increase over 1 2 mpa appears on the southern hikurangi subduction interface which encourages afterslip underlying the marlborough fault system and slow slip beneath the kapiti coast consistent with previous studies the long distance slow slip motion offshore the east coast was likely dynamically triggered by the kaikoura earthquake where the static coulomb stress increase is insignificant

simultaneous long term and short term slow slip events at the hikurangi subduction margin new zealand implications for processes that control slow slip event occurrence duration and migration 1 we document a sequence of simultaneous short term and long term slow slip events sses at the hikurangi subduction zone during the 2010 2011 period the sequence of short term events each 2 3 weeks in duration ruptured much of the shallow plate interface 15 km at central and northern hikurangi over a 6 month period was accompanied by microseismicity and involved patchy irregular migration of sse slip we suggest that the patchy migration of the short term sse is due to large scale 100 3500 km heterogeneities on the plate interface related to seamount subduction and sediment subduction and or underplating this is in contrast to a 2010 2011 long term sse at the central hikurangi margin which evolved steadily over 1 5 years and ruptured much of the plate interface between 20 and 70 km depth we suggest that the occurrence of long term versus short term sses at hikurangi is related to differences in effective normal stresses and relative heterogeneity of the subduction interface the long term sse sequence began 1 year before the short term sequence coulomb stress change models suggest that the long term sse may have triggered initiation of the subsequent short term sse sequence initiation of the short term sequence occurred in a region just updip of or within an interseismically locked portion of the plate interface and may be located within the updip transition from seismic to aseismic behavior alternatively it could be characteristic of a region undergoing partial interseismic coupling this is in contrast to sses observed elsewhere in the world that typically occur within the downdip transition from seismic to aseismic behavior

newly observed deep slow slip events at the central hikurangi margin new zealand implications for downdip variability of slow slip and tremor and relationship to seismic structure 1 we present previously undocumented deep 25 45 km depth moderate duration 2 3 months slow slip events sses directly downdip of known shallow 15 km depth short term 2 3 weeks sses at the central hikurangi margin new zealand the moderate duration sses produce 2 6 mm of horizontal displacement at continuous global positioning system stations in 2006 and 2008 similar to cascadia sses they involve 2 5 cm of slip over 5000 km2 of the subduction interface tremor occurs just downdip of the deep sse source area we also present results from a large shallow 12 km sse in 2013 just updip of the 2006 2008 sses the location of deep sses between shallow short term sses and tremor indicates strong downdip variation of subduction interface slip behavior at central hikurangi the deep sses occur where qp and vp vs data suggest an accumulation of fluid rich underplated sediment at the interface consistent with the idea that sses occur under high fluid pressure

variscan very low grade metamorphism in southwest england a diastathermal and thrust related origin abstract regional metamorphism in the external variscides of southwest england varied from diagenetic level to greenschist facies there is a fundamental difference in the metamorphic character between the northern and southern regions of the area in the north m1 metamorphism is of a sedimentary burial character associated with high heat flow whilst to the south it is related to tectonic burial during thrust thickening processes with lower geothermal gradients this pattern appears to be related to the character of basin development and its subsequent tectonic evolution the northern region has features that accord with a diastathermal extensional origin for the very low grade metamorphism whilst in the southern region the very low grade metamorphism is linked to thrusting as a consequence of variscan compression the tintagel high strain zone presents an anomaly in this regional pattern where an m2 metamorphic phase is attributed to localized d2 thrust stacking along the southern margin of the culm basin there is no extensive overprint of the regional metamorphic pattern by the contact aureoles surrounding the granite plutons of the region however there is a noticeable coincidence between the areas of regional epizone grade and the extent of the geophysically defined subsurface limit of the granite batholith excluding the north devon area this link is attributed largely to the late stage structural up doming of the higher grade areas over the roof of the batholith

transition from diagenesis to metamorphism in extensional and collision settings areas in which there is a transition from diagenesis to metamorphism occur in a variety of tectonic settings some of which are of an extensional character rather than the collision setting normally associated with regional metamorphism in collision settings the diagenetic to metamorphic transition is typically followed by a continuum into the highest grades of metamorphism the baric type is usually of an intermediate pressure variety and metamorphism occurs at a late stage in the tectonic cycle in extensional settings such as marginal basins a restricted facies series is developed that ranges from diagenetic levels up to a low greenschist facies maximum the metamorphism is normally of a low pressure type and develops early in the tectonic cycle these characteristics suggest that it is possible to subdivide broadly the field of low grade regional metamorphism into compressional orogenic and extensional settings

oxygen isotope geochemistry of the lassen volcanic center california resolving crustal and mantle contributions to continental arc magmatism this study reports oxygen isotope ratios determined by laser fluorination of mineral separates mainly plagioclase from basaltic andesitic to rhyolitic composition volcanic rocks erupted from the lassen volcanic center lvc northern california plagioclase separates from nearly all rocks have o values 6 1 8 4o higher than expected for production of the magmas by partial melting of little evolved basaltic lavas erupted in the arc front and back arc regions of the southernmost cascades during the late cenozoic most lvc magmas must therefore contain high o crustal material in this regard the o values of the volcanic rocks show strong spatial patterns particularly for young rhyodacitic rocks that best represent unmodified partial melts of the continental crust rhyodacitic magmas erupted from vents located within 3 5 km of the inferred center of the lvc have consistently lower o values average 6 3o 0 1o at given sio2 contents relative to rocks erupted from distal vents 47 0 km average 7 1o 0 1o further magmas erupted from vents situated at transitional distances have intermediate values and span a larger range average 6 8o 0 2o basaltic andesitic to andesitic composition rocks show similar spatial variations although as a group the o values of these rocks are more variable and extend to higher values than the rhyodacitic rocks these features are interpreted to reflect assimilation of heterogeneous lower continental crust by mafic magmas followed by mixing or mingling with silicic magmas formed by partial melting of initially high o continental crust 9 0o increasingly hybridized by lower o 6 0o mantle derived basaltic magmas toward the center of the system mixing calculations using estimated endmember source o values imply that lvc magmas contain on a molar oxygen basis approximately 42 to 4 isotopically heavy continental crust with proportions declining in a broadly regular fashion toward the center of the lvc conversely the o values of the rhyodacitic rocks suggest that the continental crust in the melt generation zones beneath the lvc has been substantially modified by intrusion of mantlederived basaltic magmas with the degree of hybridization ranging on a molar oxygen basis from approximately 60 at distances up to 12 km from the center of the system to 97 directly beneath the focus region these results demonstrate on a relatively small scale the strong influence that intrusion of mantle derived mafic magmas can have on modifying the composition of pre existing continental crust in regions of melt production given this result similar but larger scale regional trends in magma compositions may reflect an analogous but more extensive process wherein the continental crust becomes progressively hybridized beneath frontal arc localities as a result of protracted intrusion of subduction related basaltic magmas

diagenetic and low grade metamorphic terranes of gaspe peninsula related to the geological structure of the taconian and acadian orogenic belts quebec appalachians illite crystallinity ic measurements determination of the proportion of 2m mica polytypes and organic matter reflectance measurements establish regional diagenetic low grade metamorphic trends for the taconian and acadian belts of gaspe peninsula ic varies as a function of many factors besides maximum burial temperature and heating time correlation between ic and 2m illite polytypes for the fortin group and temiscouata formation suggests i that the amount of high grade detrital mica in the samples is low and ii that ic can be used with some confidence as an estimator of regional thermal maturation levels correlation of these parameters with available organic reflectance values further supports this assumption the illites of the temiscouata and western fortin groups are mostly phengitic in composition whereas in the eastern outcrop belt they are more mg and fe rich celadonitic but generally also of lower grade and lower 2m content the d 060 values for illites measured on the unorientated 2 m fraction of samples fall between 1 502 and 1 503 a range 1 500 1 504 a indicating relatively low octahedral occupancy by mg and fe between one fifth and one third of the available spaces pyrophyllite and paragonite were not detected chlorites are fe rich and ripidolitic the ic map for the acadian belt of the peninsula displays general congruence between ic contours 2200 sample points and structural trends for the 27 000 km2 area the highest grades anchimetamorphic are associated with the oldest rocks honorat and matapedia groups exposed in the cores of major anticlines anchimetamorphic grades associated with the western outcrop belt of the lower devonian fortin group require 7 8 km of subsidence to accommodate sufficient thickness of overlying younger rocks on top of 4 5 km of fortin group deep water clastics to explain the grades in terms of burial metamorphism assuming a geothermal gradient of 30 c km 1 the lowest grade diagenetic rocks occupy a large area in the northeastern part of the peninsula smaller areas in the northwestern part of the acadian belt in the centre of chaleurs bay synclinorium and in the ordovician mictaw group the contact between the taconian and acadian belt is marked by a distinct maturation discontinuity the grand pabos fault juxtaposes rocks of contrasting maturation levels matapedia group against fortin group in the west but shows no maturation offset further east in the honorat group the fault zone limiting the fortin group in the north is also associated with a major ic jump

coulomb stress evolution along xianshuihe xiaojiang fault system since 1713 and its interaction with wenchuan earthquake may 12 2008 abstract the curved left lateral strike slip xianshuihe xiaojiang fault system xxfs in southwestern china extends at least 1400 km in the eastern margin of the tibetan plateau fieldworks confirm that the xxfs is one of the longest and most seismically active faults in china the strain released by the slip motion on the xxfs is related to the convergence between the indian and eurasian plates the entire fault system has experienced at least 35 earthquakes of m 6 in the recent 300 years and almost all segments of the system have been the locus of major historical earthquakes since the xxfs region is heavily populated over 50 million people understanding the migration of the large earthquakes in space and time is of crucial importance for the seismic hazard assessment in this region we analyze a sequence of 25 earthquakes m 6 5 that occurred along the xxfs since 1713 and investigate their influence on the 2008 mw7 9 wenchuan earthquake occurred on the adjacent longmenshan fault in our analysis the relevant parameters for the earth crust are constrained by seismic studies the locations and geometries of the earthquake faults as well as the rupture distributions are taken from field observations and seismological studies results from the coulomb failure stress modeling indicate significant interactions among the earthquakes after the 1713 earthquake 19 out of 24 earthquakes occurred in the positive stress zone of the preceding earthquakes the other 5 earthquakes located in the area without significant stress changes induced by the preceding events in particular we can identify 4 visible earthquake gaps with increasing seismic hazard along the xxfs consistent with the findings from the paleo seismological studies the seismic activity and tectonic motion on the xxfs reduced the coulomb stress accumulation at the hypocenter of 2008 mw7 9 wenchuan earthquake implying that the wenchuan earthquake might not be triggered directly by the seismic activities on the xxfs on the other hand the coulomb failure stress induced by the wenchuan earthquake has increased in a region of 125 km long segment of the xxfs northwest of kangding city

palaeomagnetism and magnetic properties of the cappadocian ignimbrite succession central turkey and neogene tectonics of the anatolian collage abstract the cappadocian ignimbrite succession of central southern anatolia comprises at least nine major and two minor calc alkaline rhyolitic sheets emplaced at 1 2 ma intervals between 11 2 and 1 1 ma it records the last phase of neotethyan subduction during final emplacement of the tauride orogen in southern turkey this study reports magnetostratigraphy and describes associated rock magnetic properties remanence resides in ti poor titanomagnetites haematisation is locally produced by post emplacement oxidation but does not contribute significantly to the palaeomagnetic signature although secondary processes within the ignimbrite sheets have produced composite isothermal remanent magnetisation spectra and variable intensities of magnetisation weak anisotropy of magnetic susceptibility describes tensors with maximum axes close to bedding and minimum axes perpendicular to this plane directions of kmax with weak imbrication mostly suggest flow away from centres of eruption located by gravity and remote sensing older ignimbrites upper and lower goreme akdag zelve from the cardak centre are all of normal polarity later ignimbrites partly erupted from the derinkuyu centre comprise the sarimaden r cemilkoy r tahar r kizilkaya r incesu n and valibaba sofular r ignimbrites the overall reversed group mean is d i 174 51 n 10 units r 9 84 95 6 6 k 55 and all magnetisation directions from the upper goreme 9 0 ma onwards are rotated anticlockwise with respect to eurasian and african palaeofields this sense of rotation characterises most of central anatolia and averages 9 5 in this sector the rotation rate from 8 to 1 ma bp was 1 25 ma but it appears to have accelerated during the latter part of the quaternary to about an order higher than rates determined from gps rotation has resulted from extrusion of fault blocks during tectonic escape of the anatolian collage to the southwest and followed crustal thickening as the afro arabia plate has continued to impinge differentially into eurasia cenozoic magnetic inclinations are systematically shallower across anatolia than inclinations expected from the geocentric dipole model and the apparent polar wander of bordering major plates only part of this difference 400 km can be accommodated by northward movement and crustal thickening in central anatolia since mid miocene times shallow inclinations observed in the aegean region extend into turkey they are observed in young volcanics and appear to reflect a regional geomagnetic anomaly the pattern of neotectonic declinations across anatolia shows rotations that are strongly anticlockwise rotated in the east near the arabian pincer but diminish towards the west to become zero or slightly clockwise at the western extremity of the collage rotations also seem to become generally younger towards the south crustal deformation has therefore been distributed and the net effect of terrane extrusion to the west and south has been to expand the curvature of the tauride arc and by inference the cyprus arc

diagenesis and very low grade metamorphism of the antalya unit mineralogical evidence of triassic rifting alanya gazipasa central taurus belt turkey the paleozoic lower mesozoic formations of the antalya unit in southern turkey comprise diagenetic sediments shale mudstone shale siltstone sandstone and scarce spiculite together with very low grade metamorphic lithologies slate metamudstone metasiltstone metasandstone and metalimestone these diagenetic and metamorphic lithologies are dominant in the northern demirtas alanya and southern gazipasa parts of the unit respectively the main minerals of the meta sedimentary rocks are phyllosilicates 2m1 1md 1m illite ia chlorite c v c s i s quartz plagioclase calcite and dolomite the cambrian cretaceous units of the antalya unit differ from the devonian cretaceous northern bolkardagi and aladag units with respect to age lithology and phyllosilicate assemblage but show a considerable similarity to the metamorphic permian triassic mahmutlar nappe of the alanya unit in their phyllosilicate paragenesis although the antalya and precambrian tertiary geyikdagi units seem to have similar lithologies and phyllosilicate associations there are some distinct mineralogical differences such as phyllosilicate polytypes and degree of diagenetic metamorphic alteration ophiolitic fragments olistostromal lithologies phyllosilicate parageneses illite polytype variations anchi epimetamorphic illite crystallinity and relatively low b values suggest that the paleozoic lower mesozoic parts of the antalya unit were metamorphosed in anticlockwise p t t paths in a rifting associated extensional basin the grade of diagenetic metamorphic alteration increases from north to south in the antalya unit related to the higher heat flow due to the southward deepening of the basin vertical diagenetic metamorphic inversion between the lower paleozoic and triassic units is related to higher the heat flux which affected the triassic sediments rather than to thrust tectonics

eopolydiexodina middle permian giant fusulinids from afghanistan biometry morphometry paleobiogeography and end guadalupian events abstract the most spectacular macroevolutionary trend presented by the genera of schwagerinoid fusulinids during the pennsylvanian permian is an enormous increase in size which culminated in the middle permian with eopolydiexodina however this potential major biogeographic marker during the kubergandian early midian time interval is as yet hampered by its poor taxonomic characterization hence eopolydiexodina is revised here using biometric and morphometric methods applied to large collections from afghanistan and selected taxa in the literature these multivariate analyses consist of classical linear test parameters as well as new area parameters acquired by computer image analysis the afghan species are re defined and some other species occasionally described as cimmerian are re discussed these methods combined with classical morphological analyses also permit to conclude that the largest eopolydiexodina of afghanistan are microspheric specimens probably agamonts of e afghanensis and e bithynica two megalospheric groups of individuals probably gamonts and schizonts are represented in both species as well as in e persica and e darvasica due to this presence of gamonts agamonts and schizonts in several species eopolydiexodina is probably the oldest identified trimorphic genus among the large benthic foraminifers biostratigraphically eopolydiexodina appears restricted to the late kubergandian to early midian the associated afghan fusulinids dunbarula kahlerina afghanella yangchienia sumatrina and codonofusiella allow proposing an accurate biostratigraphy of the eopolydiexodina species in the murgabian midian boundary interval paleobiogeographically eopolydiexodina was essentially located in the laurentian and perigondwanan borders of the tethys the possible presence of eopolydiexodina in the cimmerian continent and in some regions of china has never been irrefutably demonstrated this paleobiological revision of eopolydiexodina and the biostratigraphic revision of other large capitanian fusulinids permit to suggest that the end guadalupian event is most probably a protracted succession of last appearance data of giant genera rather than an instantaneous lilliput effect at the capitanian wuchiapingian boundary

an integrated perspective of the continuum between earthquakes and slow slip phenomena slow slip a mechanism by which faults can relieve stress was thought to be distinct from earthquakes however a global review of slow slip phenomena suggests that instead there is a continuum between the two types of event