long period pulses in broadband records of near earthquakes broadband records of weak local earthquakes occasionally exhibit long period pulselike signals appearing exclusively on horizontal components such signals have been recorded at station sergoula in the corinth gulf by guralp cmg 3t 100 sec and wielandt streckeisen sts 2 120 sec instruments the pulses can be perfectly matched by the instrumental responses to a small step of acceleration similar pulses observed during moderate near earthquakes at stations of the greek national network equipped with lennartz le 3d 20s 20 sec sensors can be explained in the same way numerical simulation of the pulses allows their removal thus making the records fully utilizable for waveform inversion in seismic source studies prerequisite for that is precise knowledge of the instrument transfer function we found that poles and zeros of the cmg 3t and sts 2 sensors were consistent with those given by the manufacturer whereas those of the le 3d 20s were not we identified the latter by inversion of spontaneous pulses incidentally appearing in le 3d 20s records without relation to any earthquake what actually generates the earthquake related horizontal acceleration steps remains unclear rapid and permanently lasting tilt is a very likely candidate when we numerically model a coseismic near field static displacement we actually find a tilt step but its amplitude is several orders below the observed values we therefore rather speculate that it is a very local tilt triggered by high frequency ground vibrations

u pb and th pb dating of apatite by la icpms abstract apatite is a common u and th bearing accessory mineral in igneous and metamorphic rocks and a minor but widespread detrital component in clastic sedimentary rocks u pb and th pb dating of apatite has potential application in sedimentary provenance studies as it likely represents first cycle detritus compared to the polycyclic behavior of zircon however low u th and radiogenic pb concentrations elevated common pb and the lack of a u th pb apatite standard remain significant challenges in dating apatite by la icpms and consequently in developing the chronometer as a provenance tool this study has determined u pb and th pb ages for seven well known apatite occurrences durango emerald lake kovdor mineville mud tank otter lake and slyudyanka by la icpms analytical procedures involved rastering a 10 m spot over a 40 40 m square to a depth of 10 m using a geolas 193 nm arf excimer laser coupled to a thermo elementxr single collector icpms these raster conditions minimized laser induced inter element fractionation which was corrected for using the back calculated intercept of the time resolved signal a tl u bi np tracer solution was aspirated with the sample into the plasma to correct for instrument mass bias external standards plesovice and 91500 zircon nist srm 610 and 612 silicate glasses and stdp5 phosphate glass along with kovdor apatite were analyzed to monitor u pb th pb u th and pb pb ratios common pb correction employed the 207pb method and also a 208pb correction method for samples with low th u the 207pb and 208pb corrections employed either the initial pb isotopic composition or the stacey and kramers model and propagated conservative uncertainties in the initial pb isotopic composition common pb correction using the stacey and kramers 1975 model employed an initial pb isotopic composition calculated from either the estimated u pb age of the sample or an iterative approach the age difference between these two methods is typically less than 2 suggesting that the iterative approach works well for samples where there are no constraints on the initial pb composition such as a detrital sample no 204pb correction was undertaken because of low 204pb counts on single collector instruments and 204pb interference by 204hg in the argon gas supply age calculations employed between 11 and 33 analyses per sample and used a weighted average of the common pb corrected ages a tera wasserburg concordia intercept age and a tera wasserburg concordia intercept age anchored through common pb the samples in general yield ages consistent at the 2 level with independent estimates of the u pb apatite age which demonstrates the suitability of the analytical protocol employed weighted mean age uncertainties are as low as 1 2 for u and or th rich palaeozoic neoproterozoic samples the uncertainty on the youngest sample the cenozoic 31 44 ma durango apatite ranges from 3 7 7 6 according to the common pb correction method employed the accurate and relatively precise common pb corrected ages demonstrate the u pb and th pb apatite chronometers are suitable as sedimentary provenance tools the kovdor carbonatite apatite is recommended as a potential u pb and th pb apatite standard as it yields precise and reproducible 207pb corrected 232th 208pb and common pb anchored tera wasserburg concordia intercept ages

asperity break after 12 years the mw6 4 2015 lefkada greece earthquake the mw6 4 earthquake sequence of 2015 in western greece is analyzed using seismic data multiple point source modeling nonlinear slip patch and linear slip inversions reveal a coherent rupture image with directivity toward the southwest and several moment release episodes reflected in the complex aftershock distribution the key feature is that the 2015 earthquake ruptured a strong asperity which was left unbroken in between two large subevents of the mw6 2 lefkada doublet in 2003 this finding and the well analyzed cephalonia earthquake sequence of 2014 provide strong evidence of segmentation of the major dextral cephalonia lefkada transform fault ctf being related to extensional duplex transform zones we propose that the duplexes extend farther to the north and that the ctf runs parallel to the western coast of lefkada and cephalonia islands considerably closer to the inhabited islands than previously thought generally this study demonstrates faulting complexity across short time scales earthquake doublets and long time scales seismic gaps

u pb la icp ms dating of apatite in mafic rocks evidence for a major magmatic event at the devonian carboniferous boundary in the armorican massif france apatite is a ubiquitous accessory mineral found in most magmatic rocks and is often the only u bearing mineral available to date mafic rocks because primary zircon and or baddeleyite are not present in this paper u pb la icp ms dating of apatite was applied to seven different dike and sill samples of dolerite from the variscan belt of brittany armorican massif western france these dolerites which are characterized by a within plate tholeiite geochemical signature are organized in several dense swarms across the belt their geochemical compositions are homogeneous although they intrude a large geographical area subdivided into several domains each characterized by different tectonic metamorphic settings their emplacement ages were so far poorly constrained due to the difficulty to date these mafic rocks using either the 40ar 39ar or the u pb methods on classical minerals like mica plagioclase or zircon although the closure temperature of apatite is lower than the emplacement temperature of the magma physical models show that the time needed to solidify and cool these mafic dikes and sills below the apatite closure temperature is basically of the order of 100 years or less consequently the u pb dates obtained on apatite can be interpreted as the emplacement ages for these mafic intrusions our results demonstrate that in all cases the apatite grains do carry enough radiogenic pb to be dated by in situ u pb analyses and yield a 207pb corrected mean age of 363 4 5 8 ma these results reveal the existence of a major and short lived magmatic event in the variscan belt of brittany during the devonian carboniferous transition a feature further highlighted by field evidence beyond the geological implications of these results u pb la icp ms dating of apatite appears to represent an ideal tool to date small size mafic intrusions

kinematic fault slip evolution source models of the 2008 m7 9 wenchuan earthquake in china from sar interferometry gps and teleseismic analysis and implications for longmen shan tectonics the m w 7 9 2008 wenchuan earthquake ruptured about 280 km of faults in the longmen shan of sichuan province china at the eastern edge of the tibetan plateau we use teleseismic waveforms with geodetic data from global positioning system synthetic aperture radar interferometry and image amplitude correlation to produce a source model of this earthquake the model describes evolution of fault slip during the earthquake the geodetic data constrains the spatial distribution of fault slip and the seismic waveforms constrain mostly the time evolution of slip we find that the earthquake started with largely thrust motion on an imbricate system of faults beneath the central longmen shan including the beichuan fault and pengguan fault with fault slip at depth extending up to 50 km northwest of the mountain front the fault ruptures continued northeast along the beichuan fault with more oblique slip right lateral and thrust and the proportion of lateral motion increasing in the northern longmen shan the northernmost fault segment has a much steeper dip consistent with nearly pure strike slip motion the kinematic source model shows that the rupture propagated to the northeast at about 2 5 3 0 km s 1 producing a cascade of subevents with a total duration of about 110 s the complex fault ruptures caused shortening and uplift of the extremely steep central longmen shan which supports models where the steep edge of the plateau is formed by thrusting over the strong crust of the sichuan basin

testing the application of in situ sm nd isotopic analysis on detrital apatites a provenance tool for constraining the timing of india eurasia collision provenance tools are applicable to many problems in sedimentary geology as they help unravel the tectonic and metamorphic history of the hinterland and provide insights into the erosional pathways and origins of sediments in many cases it is more appropriate to use single grain approaches as opposed to bulk sediment methods in order to discover the precise input of the contributing geological terranes since the input of subordinate sources may not be detectable in bulk rock studies using a selection of modern river sediments we characterise the sm nd isotopic composition of individual detrital apatites from the main himalayan geological terranes our analyses allow us to effectively distinguish between apatites derived from the eurasian plate relatively high end values and low 147sm 144nd ratios from those derived from the indian plate low to high end values and moderate to high 147sm 144nd ratios we then apply this approach to tertiary indus basin sedimentary rocks to attempt to better determine the timing of india eurasia collision we find that detrital apatites in the tertiary indus basin have been sourced solely from eurasia lacking a mixed india eurasia provenance input which would document the india eurasia collision this study illustrates the use of this relatively novel provenance tool and provides a sound framework for similar studies in the future concerning the tectono metamorphic erosional evolution of the himalaya

iterative deconvolution of regional waveforms and a double event interpretation of the 2003 lefkada earthquake greece the moment tensor inversion for multiple point sources based on kikuchi and kanamori 1991 was extended to full waveform data at regional or local distances the new code proved to be efficient for retrieving major source contributions of the 2003 lefkada greece earthquake the source model was derived from five three component regional stations epicentral distances 140 km at periods 10 20 s two main events dominated the rupture process one at the lefkada island comprising three subevents of total moment 0 9 1018 n m and the other at the cephalonia island comprising one subevent of 0 5 1018 n m their spatial and temporal separation is 40 km and 14 s respectively they can be understood as two earthquakes the uncertainty estimate based on reduced data sets repeatedly excluding a station shows that the cephalonia subevent and the major lefkada subevent are very well resolved regarding their position time and focal mechanism the source model explains well the aftershock distribution characterized by two clusters at the lefkada and cephalonia islands respectively the focal mechanisms of the two main subevents are predominantly right lateral strike slip of south southwest north northeast orientation the cephalonia subevent occurred on a less steeply dipping fault with a small thrust component large deviations from pure double couple were found but interpreted as artifacts the new software developed in this article fortran code and matlab graphic user interface is freely available online material color graphics and 3d visualization of the 2003 lefkada earthquake sequence

deep burial of asian continental crust beneath the pamir imaged with local earthquake tomography an inclined zone of intermediate depth seismicity beneath the pamir orogen in central asia has been interpreted as southward subduction of a slab of asian lithosphere however it is not known whether asian lithosphere subducts intact or only partially we used arrival times of shallow and intermediate depth earthquakes recorded with a temporary 2008 2010 seismic network in this region to invert for 3d models of seismic velocities in an attempt to answer this question with local seismicity reaching depths of up to 240 km the deep structure of the pamir could be illuminated with high resolution the resulting velocity models show a north south contrast in crustal seismic velocities in the pamir with very low p velocities 5 7 5 9 km s at 15 30 km depth coupled with relatively low vp vsvp vs 1 70 at mid crustal levels in the southern part of the orogen at sub moho depths we image an arcuate high velocity 8 2 8 6 km s slab dipping south in the eastern pamir and east in the pamir s southwest underlying the intermediate depth earthquakes on top of the high velocity slab and just above the onset of deep seismicity between a depth of 60 to 100 km very low compressional wavespeeds around 7 1 km s and high vp vsvp vs ratios 1 80 attest to subducted crustal rocks additionally we carried out 2d numerical thermomechanical modeling of the continental collision in the pamir focusing on the fate of the crust and mantle lithosphere of the asian and indian plates seismic velocities were computed from the modeling results and the resulting images were compared with the velocity distributions obtained from seismic traveltimes combining tomography and modeling results we infer that a substantial amount of crustal material is pulled down beneath the pamir by cold mantle lithosphere to depths of at least 80 100 km from there on only lower crust and mantle lithosphere continue their subduction and earthquakes occur inside the lower crustal layer probably due to metamorphic reactions the buoyant asian upper and middle crust does not penetrate deeper into the mantle but pools at this depth level from where it might eventually exhume or relaminate

early to middle tertiary foreland basin development and the history of andean crustal shortening in bolivia a 2 5 km thick succession of tertiary strata in the eastern cordillera of southern central bolivia consists of predominantly fluvial and lacustrine deposits the age of the base of the succession is middle paleocene and its upper part which is erosionally truncated is probably late oligocene early miocene the lower 50 130 m of the succession consists of interbedded fluvial sandstone and mudstone including minor paleosols of the santa lucia formation these strata are overlain by up to 50 m of pervasively pedogenically altered mudstone and sandstone in the upper part of the santa lucia formation and lower part of the impora formation that may represent much of late paleocene eocene time above the paleosol zone is a thin zone 10 m of lacustrine carbonate and clastic rocks in the uppermost impora formation and this in turn is overlain by a 2000 m thick upward coarsening succession of clastic fluvial deposits in the cayara camargo and suticollo formations paleocurrent data indicate that fluvial channels that deposited the santa lucia impora and cayara formations flowed mainly westward whereas channels responsible for the camargo and suticollo formations flowed generally eastward modal sandstone petrographic data show a long term evolution from subarkosic during santa lucia deposition to quartz arenitic during impora and cayara deposition to sublitharenitic during camargo and suticollo deposition compositions we argue that the lithofacies and sediment accumulation history of this succession are most consistent with deposition in an eastward migrating foreland basin system e mail decelles geo arizona edu critical to this interpretation is the zone of extreme stratigraphic condensation in the lower impora formation the inferred upper paleocene eocene part of the succession the abrupt decrease in sediment accumulation represented by this zone is difficult to reconcile with the leading alternative model in which continuous postrift thermal subsidence resulted in a gradual continuous decay of early tertiary sediment accumulation rates stratigraphic condensation is however consistent with passage of the forebulge through the region an interpretation that also can be reconciled with the record of foreland basin development in the altiplano to the west and gross sediment accumulation patterns in the subandean zone and modern foreland basin to the east simple flexural modeling and palinspastic reconstruction of the complete cenozoic migration history of the foreland basin system suggest that 1000 km of foreland lithosphere has been underthrust westward beneath the andean orogenic belt at the latitude of southern bolivia the amount of middle and lower crust that would have been added to the andean infrastructure is sufficient to explain the present crustal thicknesses in bolivia

limitations of rupture forecasting exposed by instantaneously triggered earthquake doublet assessments of earthquake risk often assume rupture of a single fault analysis of a 1997 pakistan earthquake reveals that not one but two separate ruptures caused the shaking implying that cascading events should be factored into forecasts

cenozoic stratigraphy and basin tectonics of the andes mountains 20 28 south latitude clastic sedimentary basins have evolved during the past 40 m y in the central andes lat 20 28 s in response to shifting patterns of magmatism and deformation the distribution of these basins and their genetic relations to uplifted areas are analogous to the basins and mountain belts of the north american rocky mountains during the late cretaceous and early cenozoic petroleum exploration has focused on zones underlying the upper cenozoic strata along the eastern margin of the andes mountain belt between about 40 and 25 ma a nonmarine basin extended across the region that is now the andes mountains between about 25 and 10 ma the western part of the former basin became the site of a volcanic arc sediment accumulation continued in the east where marine intercalations demonstrate the low elevation of the basin after 10 ma the volcanic arc remained active and locally widened and crustal shortening caused regionally important thrust and reverse faulted ranges during the past 10 m y up to 4 000 m of coarse clastic debris accumulated in a foreland basin on the eastern flank of the mountains meanwhile in the interior of the mountains over 4 000 m of fine grained strata and evaporites accumulated in local depocenters

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

tectonics and climate of the southern central andes the history of the southern central andes including the world s second largest plateau and adjacent intermontane basins and ranges of the eastern cordillera and the northern sierras pampeanas of argentina and bolivia impressively documents the effects of tectonics and topography on atmospheric circulation patterns the development of orographic barriers and their influence on erosion and landscape evolution at various timescales protracted aridity in the orogen interior has facilitated the creation and maintenance of the puna altiplano plateau contraction and range uplift filling of basins and possibly wholesale uplift of the plateau increased gravitational stresses in the orogen interior which caused the eastward migration of deformation into the foreland and successive aridification the uplift of the andean orogen has also had a far reaching influence on atmospheric and moisture transport patterns in south america this is documented by the onset of humid climate conditions on the eastern side of the andes in late miocene time which was coupled with the establishment of dramatic precipitation gradients perpendicular to the orogen and changes in tectonic processes in the andean orogenic wedge

back propagating super shear rupture in the 2016 mw7 1 romanche transform fault earthquake how an earthquake rupture propagates strongly influences the potentially destructive ground shaking complex ruptures often involve slip along multiple faults which masks information on the frictional behaviour of fault zones geometrically smooth ocean transform fault plate boundaries offer a favourable environment to study fault dynamics because strain is accommodated along a single wide fault zone that offsets the homogeneous geology here we present an analysis of the 2016 mw 7 1 earthquake on the romanche fracture zone in the equatorial atlantic using data from both nearby seafloor seismometers and global seismic networks we show that this rupture had two phases 1 upward and eastward propagation towards a weaker region where the transform fault intersects the mid ocean ridge and then 2 an unusual back propagation westwards at a supershear speed towards the centre of the fault we suggest that deep rupture into weak fault segments facilitated greater seismic slip on shallow locked zones this highlights that even earthquakes along a single distinct fault zone can be highly dynamic observations of back propagating ruptures are sparse and the possibility of reverse propagation is largely absent in rupture simulations and unaccounted for in hazard assessments in one earthquake an oceanic transform fault ruptured in one direction and then backwards at a speed exceeding that of shear wave propagation according to an analysis of data recorded by nearby seafloor and global seismometers

tectonic evolution of the northeastern pamir constraints from the northern portion of the cenozoic kongur shan extensional system western china the late cenozoic kongur shan extensional system lies along the northeastern margin of the pamir at the western end of the himalayan tibetan orogen accommodating east west extension in the pamir at the northern end of the extensional system the kongur shan normal fault juxtaposes medium to high grade metamorphic rocks in both its hanging wall and footwall which record several mesozoic to cenozoic tectonic events schists within the hanging wall preserve a buchan metamorphic sequence dated as late triassic to early jurassic 230 200 ma from monazite inclusions in garnet metamorphic ages overlap with u pb zircon ages from local granite bodies and are interpreted to be the result of regional arc magmatism created by subduction of the paleo tethys ocean the northern portion of the footwall of the extensional system exposes an upper amphibolite facies unit 650 c 8 kbar which structurally overlies a lowgrade metagraywacke unit the high grade unit records late early cretaceous crustal thickening at ca 125 110 ma followed by emplacement over the low grade metagraywacke along a north northeast directed thrust prior to ca 100 ma together these results indicate signifi cant middle cretaceous crustal thickening and shortening in the northern pamir prior to the indo asian collision a third late miocene ca 9 ma amphibolite facies metamorphic event 650 700 c 8 kbar is recorded in footwall gneisses of the kongur shan massif north of the kongur shan massif rapid cooling in the footwall beginning at 7 8 ma is interpreted to date the initiation of exhumation along the kongur shan normal fault a minimum of 34 km of east west extension is inferred along the kongur shan massif based on the magnitude of exhumation since the late miocene 29 km and the present dip of the kongur shan normal fault 40 field observations and interpretation of satellite images along the southernmost segment of the kongur shan extensional system indicate that the magnitude of late cenozoic east west extension decreases signifi cantly toward the south this observation is inconsistent with models in which east west extension in the pamir is driven by northward propagation of the right slip karakoram fault suggesting instead that extension is driven by vertical extrusion due to topographic collapse radial thrusting along the main pamir thrust or oroclinal bending of the entire pamir region

slip distribution of the 2015 lefkada earthquake and its implications for fault segmentation this work was partially supported by the uk natural environmental research council nerc through ne k011006 1 ne p008828 1 and the centre for the observation and modelling of earthquakes volcanoes and tectonics comet ga 13 m 031 http comet nerc ac uk

eocene exhumation and basin development in the puna of northwestern argentina 1 the puna is part of the larger puna altiplano plateau also known as the central andean plateau characterized by high elevation low relief and aridity located in the central andes of bolivia and argentina tertiary sedimentary rocks preserved within the puna contain a unique archive of information regarding the paleogeography depositional environments and timing of sediment source exhumation during the early stages of andean mountain building the eocene geste formation in the salar de pastos grandes area within the central puna of northwestern argentina consists of deposits that are the result of confined to unconfined flows in a sandy to gravelly braided fluvial system and alluvial fans proximal to the source terrane paleocurrent data document an overall eastward flow direction up section coarsening of the geste formation suggests that topographic relief in the source area increased through time possibly owing to enhanced tectonic activity and source terrane unroofing sandstone petrography and conglomerate clast count data document quartzose and phyllitic compositions typical of ordovician rocks preserved just west of the salar de pastos grandes area paleocene eocene detrital apatite fission track age populations p1 35 52 ma p2 52 65 ma of the geste formation and their consistent trends up section suggest moderate to rapid 0 4 mm a to 1 mm a exhumation of western sediment sources during the early to mid tertiary stages of andean mountain building sedimentation rates increase up section from 0 1 mm a to 1 mm a our data when combined with other structural stratigraphic and seismic evidence from surrounding regions suggest that the geste formation was deposited in response to crustal shortening and resulting erosion and sedimentation which started as early as cretaceous in the chilean cordillera de domeyko and in the salar de pastos grandes area by eocene time the geste formation could be interpreted either as a local wedge top accumulation on the eastward propagating central andean orogenic wedge or as a local intermontane basin the similarities between wedge top deposits preserved in bolivia and eocene deposits in northwestern argentina south of 25 s lead us to favor the wedge top scenario for the geste formation if correct this implies that the deformation front of the andean orogenic wedge incorporated both thin and thick skinned structures as it migrated possibly unsteadily from the cordillera de domeyko during the cretaceous paleocene to areas within the puna and eastern cordillera by mid late eocene time contemporaneously a regional scale foreland basin system developed over an along strike distance of at least 650 km

coseismic and postseismic deformation of the 2016 m w 6 6 aketao earthquake from insar observations and modelling on november 25 2016 the mw 6 6 aketao earthquake occurred in xinjiang western china we used the combination of ascending sentinel 1a descending sentinel 1b and ascending alos 2 palsar data to measure the coseismic deformation the line of sight los coseismic deformation implies that the earthquake was dominated by right lateral strike slip ignoring the fault perpendicular deformation the fault parallel and up down deformation was extracted based on the combination of sentinel 1a and 1b observations results show that the maximum fault parallel deformation is 13 7 cm at the north wall and the minimum is 16 5 cm at the south wall of the muji fault then coseismic slip distribution was derived using the steepest descent method sdm based on a single segment fault model using the three insar los observations as constraints the slip distribution reveals two slip centers the maximum slip of the eastern center is 0 5 m at a depth of 8 8 km where the rake angle is 181 2 the maximum slip of the western center is 0 6 m at a depth of 10 8 km where the rake angle is 181 1 the derived seismic moment obtained equals the mw 6 6 earthquake in this study postseismic deformation time series in 1 5 years after the earthquake were retrieved from 26 multi temporal sentinel 1 descending scenes the postseismic los deformation at the north and south walls of muji fault both increases with time but in opposite directions the cumulative deformation is 60 80 mm at the north wall and 30 to 20 mm at the south wall the postseismic deformation shows similar patterns with the coseismic deformation and has the same mechanism there is no obvious lock at the unbroken gap

thermal and exhumation history of the coastal cordillera arc of northern chile revealed by thermochronological dating abstract the thermal and erosional history of convergent plate boundaries is important for understanding the links between subduction arc magmatism genesis of ore deposits topography and climate of orogenic belts unlike the continent continent collision that formed many of the largest orogenic belts known today the central andes of south america is a unique case where an oceanic continent collision has given rise to the earth s longest and second tallest orogenic belt over the last thirty years a plethora of models have been suggested in an attempt to explain how a plateau type orogen formed at the leading edge of western south america in the central andes most research have focussed attention on the study of the evolution of the arc and backarc since continuous subduction erosion of the forearc has left little trace of the interplate dynamics that initiated the orogenic belt in this article we present a new insight into the thermal and exhumation history of the forearc along the coastal cordillera of northern chile based on biotite k ar apatite fission track and apatite zircon u th he dating we collected diorite samples in a 2 km thick crustal section at the coastal cliff 22 s and a sea level isoelevation profile between 21 and 27 s results from all three dating methods show that the cooling of coastal cordillera took place shortly after emplacement during a period of rifting in jurassic times cooling took place in two episodes mainly in late jurassic early cretaceous 118 152 ma but also during late cretaceous 60 80 ma due to the resumption of compression rift closure arc uplift exhumation eastward migration of magmatic arc activity and thermal relaxation the youngest apatite u th he ages reveal a cooling event never reported previously between 40 and 50 ma eocene this thermal event affected a 500 km long and 1 km thick section of the coastal cordillera in northern chile rock cooling recorded in the eocene cannot be explained by the thermal effect of the magmatic arc we explore two scenarios that can provide an explanation for the observed cooling 1 forearc uplift and exhumation and 2 changes in plate subduction dynamics erosion rates of 0 24 to 0 36 km myr for a period of 10 myr are necessary to explain the cooling event alternatively the subduction of a ridge could explain significant cooling by flat slab dewatering based on recent sea floor spreading reconstruction we suggest the subduction of the farallon phoenix ridge as a possible candidate the subduction of this ridge can account for the cooling event at 40 50 ma but also for some important aspects of the eocene development of the central andes notably the onset of uplift an abrupt decrease in magmatic activity and porphyry copper mineralization

two go together near simultaneous moment release of two asperities during the 2016 mw 6 6 muji china earthquake abstract on 25 november 2016 a mw 6 6 earthquake ruptured the muji fault in western xinjiang china we investigate the earthquake rupture independently using geodetic observations from interferometric synthetic aperture radar insar and regional seismic recordings to constrain the fault geometry and slip distribution we test different combinations of fault dip and slip direction to reproduce insar observations both insar observations and optimal distributed slip model suggest buried rupture of two asperities separated by a gap of greater than 5 km additional seismic gaps exist at the end of both asperities that failed in the 2016 earthquake to reveal the dynamic history of asperity failure we inverted regional seismic waveforms for multiple centroid moment tensors and construct a moment rate function the results show a small centroid time gap of 2 6 s between the two sub events considering the 5 km gap between the two asperities and short time interval we propose that the two asperities failed near simultaneously rather than in a cascading rupture propagation style the second sub event locates 39 km to the east of the epicenter and the centroid time is at 10 7 s it leads to an estimate of average velocity of 3 7 km s as an upper bound consistent with upper crust shear wave velocity in this region we interpret that the rupture front is propagating at sub shear wave velocities but that the second sub event has a reduced or asymmetric rupture time leading to the apparent near simultaneous moment release of the two asperities

apatite triple dating and white mica 40ar 39ar thermochronology of syntectonic detritus in the central andes a multiphase tectonothermal history we applied apatite u pb fission track and u th he triple dating and white mica 40 ar 39 ar thermochronology to syntectonic sedimentary rocks from the central andean puna plateau in order to determine the source area geochronology and source sedimentary basin thermal histories and ultimately the timing of multiple tectonothermal events in the central andes apatite triple dating of samples from the eocene geste formation in the salar de pastos grandes basin shows late precambrian devonian apatite u pb crystallization ages eocene apatite fission track aft and eocene miocene u th he ca 8 47 ma cooling ages double dating of cobbles from equivalent strata in the arizaro basin documents early eocene 46 2 3 9 ma and cretaceous 107 6 7 6 109 5 7 7 ma aft and eocene oligocene ca 55 30 ma u th he ages thermal modeling suggests relatively rapid cooling between ca 80 and 50 ma and reheating and subsequent diachronous basin exhumation between ca 30 ma and 5 ma the 40 ar 39 ar white mica ages from the same samples in the salar de pastos grandes area are mainly 400 350 ma younger than apatite u pb ages suggesting source terrane cooling and exhumation during the devonian early carboniferous together these data reveal multiple phases of mountain building in the paleozoic and cenozoic basin burial temperatures within the plateau were limited to

estimating source parameters from deformation data with an application to the march 1997 earthquake swarm off the izu peninsula japan we have applied two monte carlo optimization techniques simulated annealing and random cost to the inversion of deformation data for fault and magma chamber geometry these techniques involve an element of randomness that permits them to escape local minima and ultimately converge to the global minimum of misfit space we have tested the monte carlo algorithms on two synthetic data sets we have also compared them to one another in terms of their efficiency and reliability we have applied the bootstrap method to estimate confidence intervals for the source parameters including the correlations inherent in the data additionally we present methods that use the information from the bootstrapping procedure to visualize the correlations between the different model parameters we have applied these techniques to gps tilt and leveling data from the march 1997 earthquake swarm off of the izu peninsula japan using the two monte carlo algorithms we have inferred two sources a dike and a fault that fit the deformation data and the patterns of seismicity and that are consistent with the regional stress field

episodic exhumation in the western alps oligocene to miocene clastic sediments of the tertiary piedmont basin northwest italy were derived from erosion of western alps source rocks detrital white micas from dif ferent stratigraphic units and from sands of three present day rivers draining the internal western alps have been analyzed by 40 ar 39 ar geochronology our data suggest a wide spread fast cooling and exhumation event prior to ca 38 ma followed by a 30 m y period of slower cooling and exhumation combined with erosion of crustal rocks with uniform 40 ar 39 ar signatures these processes have resulted in a pattern of regularly increasing lag time up section

uplift of the central andean plateau and bending of the bolivian orocline the topography of the central andes can be considered the primary tectonic signal of late cenozoic mountain building in an arid region where the effects of uplift and magmatism are little obscured by denudation the spatial coverage of the topographic signal is more complete than that for sparsely sampled geological and geophysical data a color coded image of digitized topography between 12 s and 37 s highlights the altiplano puna one of the world s most remarkable plateaus and reveals important physiographic clues about the formation of that major feature the topographic data combined with information on structure magmatism seismicity and paleomagnetism support a simple kinematical model for the late cenozoic evolution of the central andes the model does not require collisional effects or enormous volumes of intrusive additions to the crust but instead calls upon plausible amounts of crustal shortening and lithospheric thinning the model interrelates andean uplift a changing geometry of the subducted nazca plate and a changing outline in map view of the leading edge of the south american plate crustal shortening has accommodated convergence between the chilean peruvian forearc and the south american foreland the altiplano puna plateau can be constructed by a combination of crustal shortening and thickening and lithospheric thinning above a shallow dipping 20 30 subducted plate the seawardly concave bend of western south america the bolivian orocline was enhanced but not completely produced by an along strike variation in the amount of late cenozoic shortening maximum shortening in bolivia both produced the widest part of the plateau and increased the seaward concavity of the bolivian orocline the along strike variations of shortening are hypothesized to result from corresponding along strike variations in the width of a weakened zone in the overriding plate weakening occurs above the wedge of asthenosphere located between the subducted and overriding plates hence the width of the zone of weakening depends upon the dip of the subducted plate two types of shortening are recognized 1 a widespread basin and range laramide like shortening that characterizes modem activity in the sierras pampeanas and late miocene deformation of the altiplano puna and 2 on the eastern side of the cordilleras and plateau an east verging foreland fold thrust belt in which the underthrust foreland compresses and thickens the ductile lower crust and produces a plateau uplift of the upper crust the second type of shortening can be applied to plio quaternary deformations throughout the central andes but with a substantial narrowing of the region of plateau uplift in peru and south of 28 s a proposed monoclinal flexure of the upper crust on the western side of the plateau uplift explains the remarkably simple and regular morphology of the main western slope of the central andes the monocline is located above the tip of the asthenospheric wedge between the converging plates it is postulated to occur above the western limit of lower crustal thickening in the regions of horizontal subduction the monocline can be associated with a late miocene asthenospheric wedge tip

detrital apatite u pb and trace element analysis as a provenance tool insights from the yenisey ridge siberia abstract the use of zircon u pb geochronology to study the provenance of sediment is well established yet there are fundamental biases that are hard to avoid these biases are due in part to the limited range of magmatic compositions from which zircon will crystallise this can manifest as the over under representation of particular age populations i e sediment sources in the data the analysis of apatite a mineral found in a wide variety of igneous rocks can help to address this bias in detrital geochronology in this study we combine geochemical and u pb la icp ms analysis of individual apatite grains to characterise the potential source rocks this information is integrated with zircon u pb data from the same samples in order to demonstrate the complementary provenance information that can be derived from apatite and zircon archives the analysis of detrital apatite from sedimentary rocks in the yenisey ridge siberia found two main u pb age populations an apatite u pb population at 880 720 ma corresponds to neoproterozoic magmatism in the yenisey ridge and a second at 1800 ma to magmatism related to the assembly of the siberian craton abundant neoproterozoic apatites many of which have chemistries indicative of crystallising from a mafic magma are considerably more common than the relatively rare zircons of the same age the ability of apatite analysis to detect mafic magmatic sources is one of the strengths of this approach that makes it particularly useful when used in combination with zircon u pb geochronology this study shows that multi method analysis of detrital apatite has the potential to be an important tool in conjunction with detrital zircon analysis in future efforts to understand the provenance of sedimentary rocks

uniform california earthquake rupture forecast version 2 ucerf 2 the 2007 working group on california earthquake probabilities wgcep 2007 presents the uniform california earthquake rupture forecast version 2 ucerf 2 this model comprises a time independent poisson process earthquake rate model developed jointly with the national seismic hazard mapping program and a time dependent earthquake probability model based on recent earthquake rates and stress renewal statistics conditioned on the date of last event the models were developed from updated statewide earthquake catalogs and fault deformation databases using a uniform methodology across all regions and implemented in the modular extensible open seismic hazard analysis framework the rate model satisfies integrating measures of deformation across the plate boundary zone and is consistent with historical seismicity data an overprediction of earthquake rates found at intermediate magnitudes 6 5 m 7 0 in previous models has been reduced to within the 95 confidence bounds of the historical earthquake catalog a logic tree with 480 branches represents the epistemic uncertainties of the full time dependent model the mean ucerf 2 time dependent probability of one or more m 6 7 earthquakes in the california region during the next 30 yr is 99 7 this probability decreases to 46 for m 7 5 and to 4 5 for m 8 0 these probabilities do not include the cascadia subduction zone largely north of california for which the estimated 30 yr m 8 0 time dependent probability is 10 the m 6 7 probabilities on major strike slip faults are consistent with the wgcep 2003 study in the san francisco bay area and the wgcep 1995 study in southern california except for significantly lower estimates along the san jacinto and elsinore faults owing to provisions for larger multisegment ruptures important model limitations are discussed

the 2011 mw 7 1 van eastern turkey earthquake 1 we use interferometric synthetic aperture radar insar body wave seismology satellite imagery and field observations to constrain the fault parameters of the mw 7 1 2011 van eastern turkey reverse slip earthquake in the turkish iranian plateau distributed slip models from elastic dislocation modeling of the insar surface displacements from envisat and cosmo skymed interferograms indicate up to 9 m of reverse and oblique slip on a pair of en echelon nw 40 54 dipping fault planes which have surface extensions projecting to just 10 km north of the city of van the slip remained buried and is relatively deep with a centroid depth of 14 km and the rupture reaching only within 8 9 km of the surface consistent with the lack of significant ground rupture the up dip extension of this modeled wsw striking fault plane coincides with field observations of weak ground deformation seen on the western of the two fault segments and has a dip consistent with that seen at the surface in fault gouge exposed in quaternary sediments no significant coseismic slip is found in the upper 8 km of the crust above the main slip patches except for a small region on the eastern segment potentially resulting from the mw 5 9 aftershock on the same day we perform extensive resolution tests on the data to confirm the robustness of the observed slip deficit in the shallow crust we resolve a steep gradient in displacement at the point where the planes of the two fault segments ends are inferred to abut at depth possibly exerting some structural control on rupture extent

the 2012 mw 8 6 wharton basin sequence a cascade of great earthquakes generated by near orthogonal young oceanic mantle faults we improve constraints on the slip distribution and geometry of faults involved in the complex multisegment mw 8 6 april 2012 wharton basin earthquake sequence by joint inversion of high rate gps data from the sumatran gps array sugar teleseismic observations source time functions from broadband surface waves and far field static gps displacements this sequence occurred under the indian ocean 400 km offshore sumatra the events are extraordinary for their unprecedented rupture of multiple cross faults deep slip large strike slip magnitude and potential role in the formation of a discrete plate boundary between the indian and australian plates the sugar recorded static displacements of up to 22 cm along with time varying arrivals from the complex faulting which indicate that the majority of moment release was on young wnw trending right lateral faults counter to initial expectations that an old lithospheric nne trending fracture zone played the primary role the new faults are optimally oriented to accommodate the present day stress field not only was the greatest moment released on the younger faults but it was these that sustained very deep slip and high stress drop 20 mpa the rupture may have extended to depths of up to 60 km suggesting that the oceanic lithosphere in the northern wharton basin may be cold and strong enough to sustain brittle failure at such depths alternatively the rupture may have occurred with an alternative weakening mechanism such as thermal runaway

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

tectonothermal history of the schwarzwald ore district germany an apatite triple dating approach abstract exceptionally large u rich apatite from the schwarzwald ore district germany was triple dated using id tims u pb fission track ft and u th he dating methods the aim of adopting the multi dating approach on a single sample was to i further constrain thermo tectonic evolution of the schwarzwald from the formation of crystalline basement through to cooling and exhumation and ii test potential and limitations of in situ ft u th he double dating the apatite u pb age of 289 5 4 5 ma records the cooling of the basement through the 550 c during the early permian and brackets the age of the apatite hosting rhyolite between 289 5 4 5 ma and 314 6 ma which is the age of rhyolite hosting granite this is in excellent agreement with radiometric ages of related rhyolites and fits with the magmatic evolution of the schwarzwald during variscan orogeny in the eocene between 50 and 40 ma the basement resided at 100 c and then cooled to surface temperatures as revealed by the ft age 37 6 1 3 ma and thermal modelling results based on track lengths during the cooling event the basement was likely exhumed as a rift shoulder of newly formed upper rhine graben rift nine apatite grains yielded u th he ages from 30 7 1 5 to 65 0 2 6 ma mean age 45 7 1 3 ma three possible reasons for the lack of reproducibility are i non homogeneous distribution of parent isotopes evidenced by strong u zoning ii bad neighbourhood causing implantation of extraneous he and iii radiation damage leading to increased he retentivity implied by the high 250 ppm u concentration these problems could not be circumvented by mechanical abrasion of outermost rim of dated crystals which yielded u th he ages from 26 0 1 0 to 56 2 2 2 ma mean age 37 2 1 4 ma in situ ft and traditional u th he double dating of single apatite crystals revealed that the vast majority of u th he ages were younger than indistinguishable from or overlap within error with corresponding ft ages proving the robustness of this approach the results also show that apparent discrepancies between ft and u th he ages reported in the literature may arise simply as a result of statistical misconceptions and conventional data treatment considering the range of single grain ft ages and the oldest single grain ft age in addition to the central ft age may provide an effective basis on which to evaluate the viability of u th he data

oligocene range uplift and development of plateau morphology in the southern central andes 1 the puna altiplano plateau in south america is a high elevation low internal relief landform that is characterized by internal drainage and hyperaridity thermochronologic and sedimentologic observations from the sierra de calalaste region in the southwestern puna plateau argentina place new constraints on early plateau evolution by resolving the timing of uplift of mountain ranges that bound present day basins and the filling pattern of these basins during late eocene miocene time paleocurrent indicators sedimentary provenance analyses and apatite fission track thermochronology indicate that the original paleodrainage setting was disrupted by exhumation and uplift of the sierra de calalaste range between 24 and 29 ma this event was responsible for basin reorganization and the disruption of the regional fluvial system that has ultimately led to the formation of internal drainage conditions which in the salar de antofalla were established not later than late miocene upper eocene oligocene sedimentary rocks flanking the range contain features that suggest an arid environment existed prior to and during its uplift provenance data indicate a common similar source located to the west for both the southern puna and the altiplano of bolivia during the late eoceneoligocene with sporadic local sources this suggests the existence of an extensive longitudinally oriented foreland basin along the central andes during this time citation carrapa b d adelmann g e hilley e mortimer e r sobel and m r strecker 2005 oligocene range uplift and development of plateau morphology in the southern central andes tectonics 24 tc4011 doi 10 1029 2004tc001762

development of the southern eastern cordillera nw argentina constrained by apatite fission track thermochronology from early cretaceous extension to middle miocene shortening 1 for the puna plateau and eastern cordillera of nw argentina the temporal and spatial pattern of deformation and surface uplift remain poorly constrained analysis of completely and partially reset apatite fission track samples collected from vertical profiles along an ese trending transect extending from the plateau interior across the southern eastern cordillera at 25 s reveals important constraints on the deformation and exhumation history of this part of the andes the data constrain the neogene andean development of the eastern cordillera as well as rift related exhumation for some of the sampled locations in the late jurassic early cretaceous an intervening eocene oligocene exhumation episode in the southern eastern cordillera was probably related to crustal shortening subsequent reburial of the area by andean foreland basin strata commenced between 30 and 25 myr magnitude and duration of sedimentation revealed by thermal modeling differ between the sample locations pointing to an eastward propagating basin system in the southern eastern cordillera andean deformation commenced at 22 5 21 myr predating both the inferred formation of significant topography by 5 7 5 myr and preservation of sediments in the adjacent cenozoic basins by 6 5 8 myr comparing the calculated structural depth of partially reset samples suggests that newly formed west dipping reverse faults along the former salta rift margin accommodated most of the neogene tectonic movement late cenozoic deformation at the southern eastern cordillera began earlier in the west and subsequently propagated eastward the lateral growth of the orogen is coupled with a foreland basin system developing in front of the range and then becomes subsequently compartmentalized by later emergent topography

detrital zircon u pb ages provide provenance and chronostratigraphic information from eocene synorogenic deposits in northwestern argentina paleogene clastic sedimentary rocks in the puna plateau of northwestern argentina contain valuable information about the timing and location of early mountain building in the central andes because these rocks generally lack tuffaceous facies only paleontological ages have been available we present u pb ages from detrital zircons in the conglomeratic eocene geste formation of the central puna plateau the zircon ages indicate that the geste formation was derived from nearby high relief ranges composed of ordovician metasedimentary rocks a small population of ca 37 35 ma grains also confirms the late eocene stratigraphic age of the geste formation and suggests that u pb detrital zircon ages may provide a new tool for determining depositional ages and provenance of widespread paleogene deposits in the central andes

seismic slip on an upper plate normal fault during a large subduction megathrust rupture slip during subduction zone earthquakes is often assumed to occur on a single fault analysis of a 2011 chilean earthquake shows that the event was composed of two quakes with megathrust rupture triggering slip in the overriding plate quantification of stress accumulation and release during subduction zone seismic cycles requires an understanding of the distribution of fault slip during earthquakes reconstructions of slip are typically constrained to a single known fault plane yet slip has been shown to occur on multiple faults within the subducting plate1 owing to stress triggering2 resulting in phenomena such as earthquake doublets3 however rapid stress triggering from the plate interface to faults in the overriding plate has not been documented here we analyse seismic data from the magnitude 7 1 araucania earthquake that occurred in the chilean subduction zone in 2011 we find that the earthquake which was reported as a single event in global moment tensor solutions4 5 was instead composed of two ruptures on two separate faults within 12 s a thrust earthquake on the plate interface triggered a second large rupture on a normal fault 30 km away in the overriding plate this configuration of partitioned rupture is consistent with normal faulting mechanisms in the ensuing aftershock sequence we conclude that plate interface rupture can trigger almost instantaneous slip in the overriding plate of a subduction zone this shallow upper plate rupture may be masked from teleseismic data posing a challenge for real time tsunami warning systems

oceanic style subduction controls late cenozoic deformation of the northern pamir orogen abstract the northern part of the pamir orogen is the preeminent example of an active intracontinental subduction zone in the early stages of continent continent collision such zones are the least understood type of plate boundaries because modern examples are few and of limited access and ancient analogs have been extensively overprinted by subsequent tectonic and erosion processes in the pamir it has been assumed that most of the plate convergence was accommodated by overthrusting along the plate bounding main pamir thrust mpt which forms the principal northern mountain and deformation front of the pamir however the synopsis of our new and previously published thermochronologic data from this region shows that the hanging wall of the mpt experienced relatively minor amounts of late cenozoic exhumation the pamir orogen as a whole is an integral part of the overriding plate in a subduction system while the remnant basin to the north constitutes the downgoing plate with the bulk of the convergence accommodated by underthrusting herein we demonstrate that the observed deformation of the upper and lower plates within the pamir alai convergence zone resembles highly arcuate oceanic subduction systems characterized by slab rollback subduction erosion subduction accretion and marginal slab tear faults we suggest that the curvature of the north pamir is genetically linked to the short width and rollback of the south dipping alai slab northward motion indentation of the pamir is accommodated by crustal processes related to this rollback the onset of south dipping subduction is tentatively linked to intense pamir contraction following break off of the north dipping indian slab beneath the karakoram

fault slip distribution of the 1999 mw 7 1 hector mine california earthquake estimated from satellite radar and gps measurements we use a combination of satellite radar and gps data to estimate the slip distribution of the 1999 m w 7 1 hector mine earthquake a right lateral strikeslip earthquake that occurred on a northwest southeast striking fault in the southern california mojave desert the data include synthetic aperture radar interferograms insar from both ascending and descending orbits radar amplitude image offset fields sario for both ascending and descending azimuth directions and campaign gps observations from 55 stations provided by agnew et al 2002 we model the fault with nine segments derived from the field mapped fault rupture the sario data and aftershock locations we first estimate the dip of each fault segment as well as a single constant strike slip component across each segment resulting in an average dip of 83 to the northeast and slip of up to 5 6 m then we fix the optimal fault segment dip discretize the fault segments into 1 5 km 1 5 km patches and solve for the variable slip distribution using a nonnegative least squares method that includes an appropriate degree of smoothing our preferred solution has both right lateral strike slip and reverse faulting the estimated geodetic moment is 5 93 10 19 n m m w 7 1 similar to seismological estimates indicating that there are insignificant interseismic and postseismic deformation signals in the data we find strike slip displacements of up to 6 0 m and reverse faulting of up to 1 6 m with the maximum slip located just northwest of the epicenter most of the slip is concentrated northwest and south of the epicenter little slip is found on the northeastern branch of the fault the sario data and our modeling indicate that the amount and extent of surface fault rupture were underestimated in the field

apatite u th he thermochronometry using a radiation damage accumulation and annealing model helium diffusion from apatite is a sensitive function of the volume fraction of radiation damage to the crystal a quantity that varies over the lifetime of the apatite using recently published laboratory data we develop and investigate a new kinetic model the radiation damage accumulation and annealing model rdaam that adopts the effective fission track density as a proxy for accumulated radiation damage this proxy incorporates creation of crystal damage proportional to production from u and th decay and the elimination of that damage governed by the kinetics of fission track annealing the rdaam is a version of the helium trapping model hetm shuster d l flowers r m and farley k a 2006 the influence of natural radiation damage on helium diffusion kinetics in apatite earth planet sci lett 249 148 161 calibrated by helium diffusion data in natural and partially annealed apatites the chief limitation of the hetm now addressed by rdaam is its use of he concentration as the radiation damage proxy for circumstances in which radiation damage and he are not accumulated and lost proportionately from the crystal by incorporating the rdaam into the hefty computer program we explore its implications for apatite u th he thermochronometry we show how u th he dates predicted from the model are sensitive to both effective u concentration eu and details of the temperature history the rdaam predicts an effective he closure temperature of 62 c for a 28 ppm eu apatite of 60 m radius that experienced a 10 c ma monotonic cooling rate this is 8 c lower than the 70 c effective closure temperature predicted using commonly assumed durango diffusion kinetics use of the rdaam is most important for accurate interpretation of u th he data for apatite suites that experienced moderate to slow monotonic cooling 1 0 1 c ma prolonged residence in the helium partial retention zone or a duration at temperatures appropriate for radiation damage accumulation followed by reheating and partial helium loss under common circumstances the rdaam predicts u th he dates that are older sometimes much older than corresponding fission track dates nonlinear positive correlations between apatite u th he date and eu in apatites subjected to the same temperature history are a diagnostic signature of the rdaam for many but not all thermal histories observed date eu correlations in four different localities can be explained with the rdaam using geologically reasonable thermal histories consistent with independent fission track datasets the existence of date eu correlations not only supports a radiation damage based kinetic model but can significantly limit the range of acceptable time temperature paths that account for the data in contrast these datasets are inexplicable using the durango diffusion model the rdaam helps reconcile enigmatic data in which apatite u th he dates are older than expected using the durango model when compared with thermal histories based on apatite fission track data or other geological constraints it also has the potential to explain at least some cases in which u th he dates are actually older than the corresponding fission track dates

fault slip in the 1997 manyi tibet earthquake from linear elastic modelling of insar displacements summary the mw 7 6 1997 manyi earthquake occurred in an area of central northern tibet where sparse vegetation coverage and a lack of human habitation provide excellent conditions for interferometric synthetic aperture radar insar studies we use coseismic pairs of radar images acquired by the esa ers 2 satellite to construct interferograms of the surface displacement field due to the earthquake the location and extent of the coseismic fault rupture are mapped using a combination of optical satellite imagery high resolution digital topography interferometric correlation and azimuth offset measurements in so doing we are able to relate prominent geomorphic features in the fault zone to bends in the fault using elastic dislocation models consistent with this mapped fault trace we then test a range of fault geometries and slip conditions to find the combination which best explains the insar displacements our favoured model contains a reversal in fault dip approximately halfway along its length occurring at the location of a restraining bend slip on this model fault is heterogeneous with two areas of peak slip of 7 m or greater and components of dip slip displacement which vary significantly along strike the success of this model in fitting the data implies that an observed asymmetry in the coseismic interferograms can be explained in terms of the local fault geometry rather than by using non linear elastic rheologies as suggested by earlier authors

u pb and u th sm he double dating of detrital apatite by laser ablation a critical evaluation abstract paired u pb and u th sm he dating of individual detrital apatite crystals has potential as a valuable tool for constraining the high and low temperature thermal evolution of sediment source terrains here we present the results of exploratory applications of the laser ablation double dating ladd method originally developed for detrital zircon research to the widely available durango fluorapatite standard in order to evaluate the practicality of the method sixty two laser ablation analyses of a single large crystal of durango fluorapatite yielded an inverse variance weighted mean 206pb 238u date of 31 46 0 48 ma and an inverse variance weighted mean u th sm he date of 31 75 0 60 ma both of which are in good agreement with previously published conventional dates while these results are encouraging several factors suggest that ladd may be less useful for detrital apatites than for detrital zircons given widely available analytical instrumentation these principally reflect the propensity for apatites to have comparatively lower u th concentrations and thus lower radiogenic he and pb concentrations as well as high concentrations of common pb these factors contribute to substantially higher analytical imprecision for most ladd u pb dates for apatite occasionally too high for the dates to be geologically useful reasonably precise laser ablation u th sm he dating of detrital apatites requires relatively large crystal sizes 100 m in the shortest dimension with the minimum useful size increasing with decreasing u th sm he apparent age in contrast to the geological interpretation of ladd datasets for detrital zircons the interpretation of datasets for detrital apatites is less straightforward in particular researchers should consider carefully the possibility that u th sm he apparent age distributions are biased by the need to analyze only larger apatites

late cenozoic and modern stress fields in the western fars iran implications for the tectonic and kinematic evolution of central zagros 1 the zagros iran developed during mio pliocene times in response to arabia eurasia convergence the western fars highlights a major bend of the deformation front and displays a remarkable set of nearly n s right lateral strike slip faults the kazerun borazjan karebass sabz pushan sarvestan faults oblique at high angle to the belt the region likely plays a major kinematic role by accommodating the change in shortening modes from partitioned in the western central zagros to nonpartitioned in the eastern zagros the inversion of focal mechanisms from small and moderate earthquakes shows a consistent n020 030 compression with a low ratio between differential stresses this regime accounts for the combination of strike slip and thrust type mechanisms through likely 2 3 permutations fault slip analysis reveals two successive late cenozoic regional compressional trends ne sw then n020 the latter is in good agreement with the present day stress the significance of the ne sw compression is discussed alternatively in terms of stress deviations or block rotations in relation to the strike slip fault system fieldwork and satellite imagery suggest that these faults behave first as transfer faults during folding of the cover and later as strike slip faults in agreement with the succession of stress regimes and the evolution of the dominant deformation style from thin skinned to thick skinned the first order stability of the collision related state of stress since 5 ma supports that the arabia eurasia convergence did not give rise to partitioning in the western fars but rather was and is still accommodated by distributed deformation involving both shortening and strike slip motion throughout the cover and the basement

cenozoic foreland basin system in the central andes of northwestern argentina implications for andean geodynamics and modes of deformation 1 cenozoic strata in the central andes of northwestern argentina record the development and migration of a regional foreland basin system analogous to the modern chaco parana alluvial plain paleocene lower eocene fluvial and lacustrine deposits are overlain by middle upper eocene hypermature paleosols or an erosional disconformity representing 10 15 myr this supersol disconformity zone is traceable over a 200 000 km2 area in the andean thrust belt and is overlain by 2 6 km of upward coarsening eastward thinning upper eocene through lower miocene fluvial and eolian deposits middle miocene pliocene fluvial lacustrine and alluvial fan deposits occupy local depocenters with contractional growth structures paleocurrent and petrographic data demonstrate westerly provenance of quartzolithic and feldspatholithic sediments detrital zircon ages from cenozoic sandstones cluster at 470 491 522 544 555 994 and 1024 1096 ma proterozoic mesozoic clastic and igneous rocks in the puna and cordillera oriental yield similar age clusters and served as sources of the zircons in the cenozoic deposits arc derived zircons become prominent in oligo miocene deposits and provide new chronostratigraphic constraints sediment accumulation rate increased from 20 m myr during paleocene eocene time to 200 600 m myr during the middle to late miocene the new data suggest that a flexural foreland basin formed during paleocene time and migrated at least 600 km eastward at an unsteady pace dictated by periods of abrupt eastward propagation of the orogenic strain front despite differences in deformation style between bolivia and northwestern argentina lithosphere in these two regions flexed similarly in response to eastward encroachment of a comparable orogenic load beginning during late paleocene time

early evolution of the proto andean margin of south america from a detailed study of a 500 km transect in the sierras pampeanas central west argentina two pre silurian tectono magmatic episodes are recognized and defined each culminating in micro continental collisions against the proto andean margin of gondwana the pampean orogeny started in early cambrian time with short lived subduction indicated by ca 535 ma calc alkaline granitoids following pampean terrane collision burial to granulite facies conditions ca 9 kbar generated widespread migmatites and ca 520 ma highly peraluminous granites in the eastern sierras pampeanas after brief quiescence a second major episode the famatinian orogeny started with subduction ca 490 ma forming a wide continental arc and ensialic backarc basin this heralded the approach of laurentia to gondwana during which the precordillera terrane separated from the southern appalachian region finally colliding with gondwana in silurian devonian time

routine low damage apatite u pb dating using laser ablation multicollector icpms 1 apatite is a common u bearing accessory mineral with a u pb closure temperature of 500 c making u pb dating of apatite a potentially valuable thermochronometer however its low u concentration and tendency to incorporate common lead has limited widespread application to destructive isotope dilution methods we overcome previous limitations by using a nu plasma multicollector icpms with an attached short pulse excimer laser and by identifying two new matrix matched reference apatites to correct for elemental fractionation gem quality 485 myr old apatite from madagascar which we independently characterized by id tims analysis and 523 5 ma apatite from the mcclure mountain syenite source of the40ar 39ar reference mmhb common pb is corrected using measured 204pb isobarically corrected for hg interference and a five step iterative process using stacey and kramers common pb model we accurately reproduce ages of numerous independently characterized apatites regularly achieving precision of 2 2 by pooling as few as five 30 m spot analyses data quality in apatite with low u concentrations low 206pb 204pb values 30 and young ages 75 ma is compromised by the goal of avoiding significant grain damage such limitations can be overcome by using spot sizes 65 m or greater but at the expense of substantial grain damage for single detrital apatite grains with ages of 500 ma precision of 4 2 was achieved by pooling 2 to 3 spots per grain the accuracy of our detrital results is supported by a good age match with similar closure temperature 40ar 39ar detrital hornblende ages from the same sediment

the aftershock signature of supershear earthquakes recent studies show that earthquake faults may rupture at speeds exceeding the shear wave velocity of rocks this supershear rupture produces in the ground a seismic shock wave similar to the sonic boom produced by a supersonic airplane this shock wave may increase the destruction caused by the earthquake we report that supershear earthquakes are characterized by a specific pattern of aftershocks the fault plane itself is remarkably quiet whereas aftershocks cluster off the fault on secondary structures that are activated by the supershear rupture the post earthquake quiescence of the fault shows that friction is relatively uniform over supershear segments whereas the activation of off fault structures is explained by the shock wave radiation which produces high stresses over a wide zone surrounding the fault

cretaceous to middle cenozoic exhumation history of the cordillera de domeyko and salar de atacama basin northern chile

displacement and geometrical characteristics of earthquake surface ruptures issues and implications for seismic hazard analysis and the process of earthquake rupture there now exist about three dozen historical earthquakes for which in vestigators have constructed maps of earthquake rupture traces accompanied by de scriptions of the coseismic slip observed along the fault strike the maps and slip distributions are compiled here to place observational bounds on aspects of seismic hazard analysis and fault mechanics analysis leads to an initial statistical basis to predict the end points of rupture and the amount of surface slip expected at sites along the strike during earthquakes on mapped faults the observations also give support to the ideas that there exists a process zone or volume of about 3 4 km in dimension at the fronts of large laterally propagating earthquake ruptures within which stress changes may be sufficient to trigger slip on adjacent faults and that the ultimate length of earthquake ruptures is controlled primarily by the geometrical complexity of fault traces and variations in accumulated stress levels along faults that arise due to the location of past earthquakes to this may be added the observation that the form of earthquake surface slip distributions is better described by asymmetric rather than symmetric curve forms and that earthquake epicenters do not appear to correlate in any systematic manner to regions of maximum surface slip observed along strike online material maps of surface ruptures digitized values and curve fits to surface slip distributions and notes and references for tables 1 and 2

fault scarp features and cascading rupture model for the mw 7 9 wenchuan earthquake eastern tibetan plateau china on 12 may 2008 the m w 7 9 wenchuan earthquake ruptured two northeast striking imbricated reverse faults and one northwest striking reverse fault along the middle longmen shan thrust belt at the eastern margin of the tibetan plateau the morphology of the coseismic scarp varies drastically along strike we distinguish eight different categories 1 simple thrust scarp 2 hanging wall collapse scarp 3 simple pressure ridge 4 dextral pressure ridge 5 fault related fold scarp 6 backthrust pressure ridge 7 local normal fault scarp and 8 pavement suprathrust scarp the coseismic surface ruptures confirm that the wenchuan earthquake is dominated by reverse faulting with some right lateral component that varies from site to site the surface rupture can be divided into two parts the yingxiu segment and the beichuan segment when the earthquake is split into two subevents accordingly they correspond to an m w 7 8 event and an m w 7 6 event respectively these two segments can in turn be divided into four second order subsegments which are equivalent to four subevents of m w 7 5 m w 7 7 m w 7 0 and m w 7 5 respectively the segmentation of the rupture is consistent with a cascading rupture pattern responsible for the total 110 s of the earthquake rupture in addition to surface ruptures the focal mechanisms determined for the aftershocks recorded by the local seismic network are used to constrain the fault geometry of the subsegments they show that the dip of the fault responsible for the earthquake varies along strike and the fault tends to flatten at depth in addition the fault plane gets steeper northward enabling the fault to accommodate a larger strike slip component along a lateral ramp this major earthquake confirms that crustal shortening could be the main driving force for the growth of high topography along the eastern margin of the tibetan plateau and that lower crustal flow is not required

cumulative and coseismic during the 2016 m w 6 6 aketao earthquake deformation of the dextral slip muji fault northeastern pamir orogen

detrital zircon u th he thermochronometry of the mesozoic daba shan foreland basin central china evidence for timing of post orogenic denudation abstract the timing of the transition of a peripheral foreland basin from underfilled to overfilled provides important insights into the post orogenic dynamics of its coupled orogenic wedge such information is lacking in the mesozoic foreland basins surrounding the qinling orogen central china such as the daba shan foreland basin dsfb the northeastern part of the sichuan basin in an effort to constrain the timing of maximum burial and onset of denudation we report detrital zircon u th he zhe data from four deep boreholes in the dsfb results show that zhe ages from the oldest foreland basin formations upper triassic lower middle jurassic are mostly younger than their depositional age whereas non reset zhe ages characterize younger strata this suggests that the oldest strata attained maximum temperatures between 130 c and 200 c zhe partial retention zone which is consistent with previous independent paleotemperatures organic matter reflectance and illite crystallinity reported in two of the boreholes and another nearby the fully reset ages apparently show the youngest peaks at 80 ma and 100 ma which are interpreted as the minimum constraints on the timing of maximum basinal burial and subsequent denudation considering that the regional deposition has lasted to aptian time it is proposed that the onset of the basin exhumation in the dsfb started at aptian albian time 100 125 ma heralding the termination of regional tectonic shortening in the hinterland southern qinling

uplift of the central andes of nw argentina associated with upper crustal shortening revealed by multiproxy isotopic analyses this study contributes to the uplift history of the andes which has received increasing attention in recent years because of its implications for geodynamic models and climate feedbacks shortening resulting in crustal thickening and removal of gravitationally unstable mantle lithosphere has been proposed to control deformation and uplift of cordillera type orogenic systems such as the puna plateau of the central andes and its eastern margin the eastern cordillera we present new clumped isotope 47 18o and 2 data from carbonate nodules marlstone spring deposits and volcanic ashes from the puna plateau and eastern cordillera of nw argentina when combined with other geological evidence our data indicate that the puna plateau was near its present elevation since at least 10 ma whereas the eastern cordillera rose 1 5 km between 14 and 7 ma this history of uplift correlates with active shortening in the eastern cordillera and with incorporation of a regional foreland into the propagating orogenic wedge our study suggests that the elevation of the puna plateau changed little during the miocene pliocene whereas the margin experienced significant uplift associated with active deformation and crustal thickening

mainshocks aftershocks study of the august 2012 earthquake doublet on ahar varzaghan complex fault system nw iran abstract seismotectonic features of the ahar varzaghan complex fault system are reviewed by the mainshocks aftershocks study of the 2012 ahar varzaghan earthquake doublet mw 6 5 mw 6 3 the early aftershocks were accurately monitored by a dense local seismological network the mainshocks hypocenters were relocated using a new velocity model for the area the regional displacement waveforms of the mainshocks and large aftershocks were jointly inverted for their moment tensors and centroids precisely located aftershocks are mostly distributed in three distinct clusters these e w trending clusters are situated to the north of the surface rupture over a 30 km long and 10 km wide zone extending from the ground surface down to the depth of 15 km based on our results the first mainshock m1 with mw 6 5 nucleated 3 km east of the surface rupture at a depth of 10 km the rupture evolved toward the west and shallower depths on an almost e w striking right lateral strike slip vertical fault plane and produced 12 km surface rupture its main energy was released at about 5 km west of the hypocenter at an average depth of 5 km about 11 min later the second mainshock m2 with mw 6 3 nucleated 5 km northwest of the m1 hypocenter and at a depth of 15 km it occurred on an ene wsw striking north dipping 65 to 70 fault plane with a dominant reverse mechanism and strike slip component the m2 related rupture also expanded to the west and to shallower depths and released most of its energy 5 km west of the respective hypocenter at an average depth of 11 km the eastern aftershocks mainly show the right lateral strike slip mechanism on almost e w trending fault close to the location of the first main centroid m1 the northern aftershocks mostly include reverse mechanisms with strike slip component near the m2 centroid a big gap of aftershock activity is observed close to the m1 centroid location most likely associated with the area of maximum slip we do not observe any n s lineament of aftershocks neither near the m2 hypocenter and nor its centroid thus making the suggestion of some previous investigators that m2 ruptured an n s trending fault unlikely

late miocene pliocene deceleration of dextral slip between pamir and tarim implications for pamir orogenesis abstract the timing of the late cenozoic collision between the pamir salient and the tien shan as well as changes in the relative motion between the pamir and tarim are poorly constrained the northern margin of the pamir salient indented northward by 300 km during the late cenozoic accommodated by south dipping intracontinental subduction along the main pamir thrust mpt coupled to strike slip faults on the eastern flank of the orogen and both strike slip and thrust faults on the western margin the kashgar yecheng transfer system kyts is the main dextral slip shear zone separating tarim from the eastern pamir with an estimated cumulative offset of 280 km at an average late cenozoic dextral slip rate of 11 15 mm a cowgill 2010 in order to better constrain the slip history of the kyts we collected thermochronologic samples along the eastward flowing deeply incised antecedent tashkorgan yarkand river which crosses the fault system on the eastern flank of the orogen we present 29 new biotite 40 ar 39 ar ages apatite and zircon u th sm he ages and apatite fission track aft analysis combined with published muscovite and biotite 40 ar 39 ar and aft data to create a unique thermochronologic dataset in this poorly studied and remote region we constrain the timing of four major n trending faults the latter three are strands of the kyts the westernmost the kuke fault experienced significant dip slip west side up displacement between 12 and 6 ma to the east within the kyts our new thermochronologic data and geomorphic observations suggest that the kumtag and kusilaf dextral slip faults have been inactive since at least 3 5 ma long term incision rates across the aertashi dextral slip fault the easternmost strand of the kyts are compatible with slow horizontal slip rates of 1 7 5 3 mm a over the past 3 to 5 ma in summary these data show that the slip rate of the kyts decreased substantially during the late miocene or pliocene furthermore miocene present regional kinematic reconstructions suggest that this deceleration reflects the substantial increase of northward motion of tarim rather than a significant decrease of the northward velocity of the pamir

tracking the growth of the himalayan fold and thrust belt from lower miocene foreland basin strata dumri formation western nepal u s national science foundation nsf tectonics ear 1140068 conoco fellowship scholarship 2016 chevron texaco geology fellowship 2016 university of arizona galileo circle scholarship 2017 u s national science foundation nsf nsf ear 1338583 ear1649254

seismotectonic range front segmentation and mountain belt growth in the pamir alai region kyrgyzstan india eurasia collision zone the trans alai range along the northern perimeter of the pamir region of kyrgyzstan is at the northern edge of the india eurasia collision zone the range defines a section of main pamir thrust which is divided into eastern central and western segments that record differential absorption of plate convergence the 50 km long east west striking central fault segment of the main pamir thrust has dip slip thrust fault offsets with a minimum holocene dip slip rate of 6 mm yr and is linked to the other segments via northwest striking dextral transfer the western transfer faults are well characterized geomorphically and the westernmost records the predominant transition to north vergent thrusting along the western segment via north vergent low angle thrust faults rooted in a steeply south dipping dextral shear zone in contrast the eastern segment deformation is widely distributed and geomorphically less evident but the transfer also takes place in a structurally complex zone asymmetric offset of a regionally correlated terrace geomorphic zonation and the distribution of historic earthquakes suggest that the central segment is mechanically linked with the western segment but not with the eastern segment the progressive closure of the alai valley by the northward advance of thrusting exemplifies the annihilation of an intramontane basin if the high surface uplift rates implied by these geologic observations have been maintained for the last few million years they attest to the high level of tectonic activity and the recency of construction of the trans alai range

detecting magma poor orogens in the detrital record the clastic record is commonly interrogated by analysis of detrital heavy mineral assemblages with the bulk of modern detrital geochronological studies employing u pb dating of detrital zircon however the bias of zircon toward felsic igneous sources and the limited ability of the u pb system in zircon to record low to medium grade metamorphic events means that the u pb detrital zircon record is largely insensitive to magma poor orogens in this study u pb ages were obtained by laser ablation inductively coupled plasma mass spectrometry for apatite and rutile extracted from alluvium of the french broad river fbr in the southern appalachians southeastern united states in contrast to previously published fbr u pb zircon data sets which yield essentially no record of the most recent appalachian metamorphic events ca 320 ma associated with assembly of pangea the u pb detrital rutile and especially the u pb apatite systems together provide a complete record of complex polyphase appalachian orogenesis it is unexpected that the apatite and rutile u pb appalachian age populations differ significantly with probable low temperature breakdown of rutile biasing the rutile data set toward the most recent alleghanian metamorphic event these data make the fbr one of the most intensely studied river systems globally for multiproxy single grain u pb analysis clearly demonstrate dependence of provenance information on mineral proxy choice and emphasize the resolving power of multiproxy provenance studies

fast slip rate along the northern end of the karakorum fault system western tibet 1 the exact location of the northern karakorum fault kf in western tibet is unclear and its current activity is debated here we investigate the possible northern extension of the kf the muji fault located in the chinese pamir which belongs to the kongur shan extensional system and provide the first quantitative estimate of its holocene slip rate the fault cuts and offsets a series of 6 fluvial terraces yielding a minimum slip rate of 4 5 0 2 mm yr by matching the largest terrace riser offset with its upper surface age 10be n 24 field evidences of right lateral movement along the kongur shan fault as well as geometry and kinematic similarities with the southern half of the kf attest that the muji fault belongs to the kf system therefore its fast slip rate combined with the slow slip rates along minor splays of the northern kf maybe up to 4 mm yr southwest of the tashkorgan basin agrees with the late pleistocene southern kf slip rate 8 mm yr

radiation damage control on apatite u th he dates from the grand canyon region colorado plateau individual detrital apatite grains from the esplanade coconino and moenkopi formations in the grand canyon region of the colorado plateau yield u th he dates from 104 to 5 ma the range of dates within each unit far exceeds analytical uncertainty but correlates with both he concentration he and effective u concentration eu these dates are all signifi cantly younger than the sandstone units indicating partial to complete he loss following deposition recently published laboratory diffusion data suggest that he retentivity in apatite increases with radiation damage forward models predict that the consequences of this effect will be manifested most clearly as a correlation between u th he dates and the he and eu in suites of apatites that 1 are characterized by a large span of eu and 2 had thermal histories in which suffi cient time elapsed for the apatite he diffusion kinetics to diverge prior to reheating and partial resetting apatites in the sedimentary units investigated fi t these cri teria using geologically reasonable deposition burial and unroofi ng histories simulations that include the effect of radiation damage on apatite he retentivity can reproduce the observed distributions of apatite dates and correlations with parent and daughter concentrations these results suggest that a span of u th he dates positively correlated with eu may provide important information regarding a sample s thermal history

the influence of natural radiation damage on helium diffusion kinetics in apatite abstract stepwise degassing diffusion experiments on 39 different apatite samples using radiogenic 4he and proton induced 3he reveal a range in closure temperature tc from 50 to 115 c for a cooling rate of 10 c myr there is no correlation between helium diffusion and apatite chemistry including f cl ratio but the closure temperature is positively correlated with the radiogenic 4he concentration 4he in each sample we argue that 4he is a proxy for a sample s natural exposure to actinide radioactivity below the closure temperature and that helium diffusion in apatite is impeded by radiation induced damage to the apatite structure the kinetics must therefore be an evolving function of time measured diffusivities thus reflect a snapshot in time and cannot alone be applied to the thermochronometric interpretation of a given sample the effect of radiation damage on helium diffusion appears to far exceed other known controls on helium diffusivity including grain size our diffusion data are well described by a previously proposed quantitative model that consists of two arrhenius relations one for volume diffusion through undamaged mineral structure and one for release of helium from radiation damage traps the unknown parameters in this trapping model were determined from the diffusion experiments and allow us to develop a tentative mathematical function that relates diffusivity to temperature and 4he by inserting this function into a 4he production diffusion model we have explored how these results affect the interpretation of apatite u th he thermochronometry the model predicts that the effective 4he closure temperature of apatite will vary with cooling rate and effective u concentration eu and may differ from the commonly assumed tc of 70 c by up to 15 c the 4he partial retention zone will look similar to previous expectations but its depth will depend on accumulation time and on eu most notably samples subjected to reheating after accumulation of substantial radiation damage will be more retentive than previously expected these predictions are consistent with recent observations of unexpected apatite u th he ages in some settings

quaternary deformation in the eastern pamirs tadzhikistan and kyrgyzstan active deformation in the eastern pamir of central asia is concentrated on the margins of the orogen with minor deformation within the high terrain along the trans alai mountain front at the northern perimeter of the orogen quaternary thrusting is documented by uplifted pediments now at 500 m above the piedmont holocene fault scarps and large earthquakes with n to nw oriented p axes seismicity in the interior of the orogen outlines a n s belt that includes normal faulting events with e w oriented t axes n s striking active normal faults in the interior lake karakul region are compatible with these earthquakes they define an asymmetric graben with a master fault at the western basin margin in the southern pamirs dextral strike slip faults root in the dextral karakorum fault which bounds the pamirs to the east a mixture of dextral and reverse offsets totalling 135 m in pleistocene terraces and 8 m in late pleistocene holocene deposits demonstrates contemporary transpression indicating average displacement rates of 1 mm yr the concentration of young thrusts along the trans alai the northward migration of thrusting and the scarcity of other large scale shortening features within the eastern pamirs suggest that this part of the orogen moves northward en bloc and causes the progressive annihilation of the intermontane alai valley widespread dextral shear in the eastern pamirs both to the south and north of the extensional karakul depression and combined dextral strike slip and normal faulting in the muji tashgorgan graben of the chinese pamirs are interpreted as localized space accommodation phenomena formed during progressive transfer of compressional deformation along a dextral strike slip deformation zone with extensional stepovers

scardec a new technique for the rapid determination of seismic moment magnitude focal mechanism and source time functions for large earthquakes using body wave deconvolution accurate and fast magnitude determination for large shallow earthquakes is of key importance for post seismic response and tsumami alert purposes when no local real time data are available which is today the case for most subduction earthquakes the first information comes from teleseismic body waves standard body wave methods give accurate magnitudes for earthquakes up to mw 7 7 5 for larger earthquakes the analysis is more complex because of the non validity of the point source approximation and of the interaction between direct and surface reflected phases the latter effect acts as a strong high pass filter which complicates the magnitude determination we here propose an automated deconvolutive approach which does not impose any simplifying assumptions about the rupture process thus being well adapted to large earthquakes we first determine the source duration based on the length of the high frequency 1 3 hz signal content the deconvolution of synthetic double couple point source signals depending on the four earthquake parameters strike dip rake and depth from the windowed real data body wave signals including p pcp pp sh and scs waves gives the apparent source time function stf we search the optimal combination of these four parameters that respects the physical features of any stf causality positivity and stability of the seismic moment at all stations once this combination is retrieved the integration of the stfs gives directly the moment magnitude we apply this new approach referred as the scardec method to most of the major subduction earthquakes in the period 1990 2010 magnitude differences between the global centroid moment tensor cmt and the scardec method may reach 0 2 but values are found consistent if we take into account that the global cmt solutions for large shallow earthquakes suffer from a known trade off between dip and seismic moment we show by modelling long period surface waves of these events that the source parameters retrieved using the scardec method explain the observed surface waves as well as the global cmt parameters thus confirming the existing trade off for some well instrumented earthquakes our results are also supported by independent studies based on local geodetic or strong motion data this study is mainly focused on moment determination however the scardec method also informs us about the focal mechanism and source depth and can be a starting point to study systematically the complexity of the stf

geometry of the pamir hindu kush intermediate depth earthquake zone from local seismic data 1 we present new seismicity images based on a two year seismic deployment in the pamir and sw tien shan a total of 9532 earthquakes were detected located and rigorously assessed in a multistage automatic procedure utilizing state of the art picking algorithms waveform cross correlation and multi event relocation the obtained catalog provides new information on crustal seismicity and reveals the geometry and internal structure of the pamir hindu kush intermediate depth seismic zone with improved detail and resolution the relocated seismicity clearly defines at least two distinct planes one beneath the pamir and the other beneath the hindu kush separated by a gap across which strike and dip directions change abruptly the pamir seismic zone forms a thin approximately 10 km width curviplanar arc that strikes east west and dips south at its eastern end and then progressively turns by 90 to reach a north south strike and a due eastward dip at its southwestern termination pamir deep seismicity outlines several streaks at depths between 70 and 240 km with the deepest events occurring at its southwestern end intermediate depth earthquakes are clearly separated from shallow crustal seismicity which is confined to the uppermost 20 25 km the hindu kush seismic zone extends from 40 to 250 km depth and generally strikes east west yet bends northeast toward the pamir at its eastern end it may be divided vertically into upper and lower parts separated by a gap at approximately 150 km depth in the upper part events form a plane that is 15 25 km thick in cross section and dips sub vertically north to northwest seismic activity is more virile in the lower part where several distinct clusters form a complex pattern of sub parallel planes the observed geometry could be reconciled either with a model of two sided subduction of eurasian and previously underthrusted indian continental lithosphere or by a purely eurasian origin of both pamir and hindu kush seismic zones which necessitates a contortion and oversteepening of the latter

cenozoic orogenic growth in the central andes evidence from sedimentary rock provenance and apatite fission track thermochronology in the fiambala basin southernmost puna plateau margin nw argentina abstract intramontane sedimentary basins along the margin of continental plateaus often preserve strata that contain fundamental information regarding the pattern of orogenic growth the sedimentary record of the clastic miocene pliocene sequence deposited in the fiambala basin at the southern margin of the puna plateau nw argentina documents the late miocene paleodrainage evolution from headwaters to the west towards headwaters in the ranges that constitute the border of the puna plateau to the north apatite fission track aft thermochronology of sedimentary and basement rocks show that the southern puna plateau was the source for the youngest middle miocene detrital population detected in late miocene rocks and that the margin of the puna plateau expressed a high relief possibly similar to or higher than at present by late miocene time cooling ages obtained from basement rocks at the southern puna margin suggest that exhumation started in the oligocene and continued until the middle miocene we interpret the basin reorganization and the creation of a high relief plateau margin to be the direct response of the source basin system to a wholesale surface uplift event that may have occurred during the late cenozoic in the puna altiplano region at this time coeval paleodrainage reorganization is observed not only in the fiambala basin but also in different basins along the southern and eastern puna margin suggesting a genetic link between the last stage of plateau formation and basin response however this event did not cause sufficient exhumation of basin bounding ranges to be recorded by aft thermochronology our new data thus document a decoupling between late cenozoic surface uplift and exhumation in the southern puna plateau high relief achieved at the puna margin by late miocene time is linked to oligocene miocene exhumation no significant erosion

deformation history of the puna plateau central andes of northwestern argentina abstract two tectonic shortening events created the first order structural characteristics of the puna plateau one in the paleozoic and a second during the andean orogeny in the cenozoic to constrain the structural characteristics and timing of andean deformation in the puna plateau we focus on differentiating these two shortening events and provide cooling ages apatite fission track and apatite u th he to determine the amount of andean exhumation on the hanging wall of major cenozoic faults two contrasting expressions of shortening are documented in ordovician strata strain requires four stages folding flattening through cleavage formation low angle faulting and local distributed shear in the mesozoic and cenozoic strata shortening is expressed as reverse faults fault propagation folds and dipping panels dissimilarities reflect different p t conditions and amount of strain as structures in the ordovician rocks require higher temperatures and strain than andean structures in the mesozoic and cenozoic strata furthermore local cretaceous aft cooling ages in pervasively cleaved ordovician rocks reveal these rocks did not reach temperatures compatible with cleavage formation during the andean event lastly our data show a middle eocene to oligocene exhumation history that supports an overall continuous development of the andean thrust belt in the puna plateau since the early cenozoic

end member models for andean plateau uplift abstract diverse techniques have been applied over the past decade to quantify the uplift history of the central andean plateau ap in this study opposing models for surface uplift are evaluated including a rapid rise of 2 5 km 10 6 ma and a slow and steady rise since 40 ma these end member models are evaluated by synthesizing observations of the ap lithosphere and the history of deformation sedimentation exhumation magmatism uplift and fluvial incision structural and geophysical studies estimate variable shortening magnitudes 530 150 km involving cover to basement rocks an isostatically compensated thick crust 80 65 km high heat flow and zones of variable velocity and attenuation in the crust and mantle these observations have invoked interpretations such as a hot weak lithosphere partial melt crustal flow and perhaps current localized delamination but do not provide strong support for massive delamination required by the rapid uplift model deformation and associated exhumation began 60 40 ma and generally migrated eastward with consistent long term average shortening rates 12 8 mm yr in bolivia favoring the slow uplift model volcanic and helium isotope evidence show an ap wide zone of shallow mantle melting and thin lithosphere that has existed since 25 ma which is inconsistent with the rapid rise model that suggests lithospheric thinning occurred 10 6 ma paleoaltimetry data suggest a rapid 2 5 km elevation gain 10 to 6 ma but are equally consistent within error with a linear rise since 25 ma widespread fluvial incision 2 5 1 km occurred along the western flank since 11 8 ma and may be associated with surface uplift as proposed by the rapid rise model however the paleoaltimetry and incision data can also be explained by regional climate change associated with plateau uplift implications of these results for reconstructions of ap evolution are that 1 substantial deformation of a weak lithosphere is essential 2 ap growth has taken significantly longer 40 myr and was more uniform along strike 1500 km than previously appreciated and 3 the slow and steady uplift model is most consistent with available constraints we conclude that the rapid uplift model may be an overestimate and that a more protracted cenozoic uplift history is tenable