distribution and mechanism of neogene to present day vertical axis rotations pacific australian plate boundary zone south island new zealand remarkably little knowledge exists about mechanisms of vertical axis rotation in continental crust steeply dipping basement rocks in south island new zealand provide an opportunity to map the distribution of rotations across the pacific australian plate boundary zone and to delineate boundaries of rotated blocks in unusual detail we synthesize new structural data with new and existing paleomagnetic data with geodetic data and with patterns of neogene quaternary faulting in the strike slip marlborough fault system for the past 20 m y vertical axis rotations have been hinged about two crustal scale boundaries near the east coast the ne hinge accommodated 50 of early middle miocene clockwise rotation which caused deformation of the eastern ends of the alpine wairau and clarence strike slip faults the sw hinge has accommodated a further 30 50 of finite clockwise rotation since 4 ma and deflects active fault traces the locus of rotation has shifted southwestward astride a subduction margin that is lengthening in that direction rotating rocks are pinned to the south against a locked collision zone where the continental chatham rise impinges against the margin slip on inland strike slip faults is transformed seaward across a zone of fault termination into rigid body rotation of a large continental block that has been thrust eastward over the downgoing subducted slab of the pacific plate the rotation mechanism is a migrating hinge which resembles a flexed telephone book strike slip faults are translated through a brecciated hinge region that does not coincide with a fixed material line in the rock

3 d imaging of marlborough new zealand subducted plate and strike slip fault systems summary we present a 3 d seismic velocity model of the northern south island new zealand using several combined passive and active source data sets this area is the transition from hikurangi subduction in the north island to oblique continental collision along the alpine fault and the southern alps and geodetically observed deformation is consistent with plate motion being primarily taken up on a series of rotating strike slip faults we carry out simultaneous inversion for vp and vp vs and hypocentres using earthquake data recorded by the permanent seismic network and three temporary seismic arrays also using active source marine airgun data recorded at onshore stations we image the subducted hikurangi slab as a continuous unbroken feature extending from the active subduction zone to the north beneath the marlborough region the 3 d hypocentres define the subducted slab as a smooth curved feature to over 250 km depth whereas below the junction of the awatere and alpine faults the seismicity abruptly ends at 100 km depth the subducting pacific plate has a thick crust including greywacke upper crust which slows subduction the interaction of the subducted plate with the translating overlying plate forms a 50 km long zone of apparent crustal thickening with vp 7 0 km s 1 observed to 40 km depth the australian plate has a high velocity block to 65 km depth aligned with the separation point pluton and trending oblique to the subducted slab this zone of thicker australian lithosphere may also hinder subduction the marlborough faults trend about 25 to the strike of the underlying subducted slab so that the relation of faults to the slab varies along the fault strikes and the overlying plate ranges in thickness from 20 to 50 km along the faults thus the fault interaction with the subducted slab varies from translating material directly above the subducting plate to bottoming into a thick ductile region the lower crust has high vp vs under the marlborough faults except for a region of haast schist which may indicate excess fluid released by the subducted plate

sahke seismic scatter imaging of subduction beneath wellington north island new zealand scattering reflectivity analysis of onshore seismic data seismic array hikurangi experiment images slab geometry and crustal structure at a geodetically locked subduction boundary a broad seismic scattering zone bsz up to 10 km thick above the subduction interface at depths of 16 30 km has seismic properties vp vp vs and q that imply high fluid pressures probably associated with underplated sediments the listric strike slip wairarapa fault and other splay faults that sole into the bsz imply long term weakness high rates of intraslab seismicity with low rates above the slab imply stress decoupling across the bsz association of high fluid pressures and long term weakness with geodetic locking is in contrast to similar observations at zones of slow slip at the northern hikurangi margin and suggest that either 1 pore fluid pressure or locking behavior may cycle over times longer than two decades or 2 local material properties play a significant role in determining if slow slip or locking occurs

shortening of an overriding plate and its implications for slip on a subduction thrust central hikurangi margin new zealand 1 at subduction plate boundaries strains accumulate within the overriding plate in response to motion of the down going plate to a first approximation margin normal interplate slip and shortening in the overriding plate sum to the total plate convergence therefore margin normal interplate slip can be estimated by measuring shortening in the overriding plate and total plate convergence here we quantify margin normal interplate slip by measuring shortening of the upper plate along a profile which extends up to 480 km across and approximately normal to the central hikurangi margin new zealand long term deformation is estimated for periods of millions of years using data from seismic reflection lines and cross sections while contemporary strain rates are derived from global positioning system gps geodetic velocities these data permit comparison of plate convergence rates determined by seafloor spreading data with the rates of contraction over short 7 years and long 2 5 and 5 myr periods of time on this part of the plate boundary total margin normal shortening in the overriding plate over the last 5 myr was 9 28 km and accounts for 6 19 of the total convergence 145 160 km at rates of 2 6 mm yr the remaining 80 or more of plate convergence has been accommodated by slip on the subduction thrust gps contraction along approximately the same profile indicates 14 16 mm yr of contemporary shortening across the terrestrial part of the upper plate which is approximately modeled by 80 interplate coupling on the subduction interface down to depths of 30 km the contrasting proportions of inferred interplate coupling for contemporary and geological data sets are consistent with stick slip behavior on the plate interface and with slip being principally achieved during intermittent large earthquakes the general shapes of short and long term shortening profiles are similar and suggest that the highest strains occur at or immediately east of the mohaka fault these strain profiles are consistent with a model where high strains in the upper plate are concentrated near the down dip end of the contemporary locked zone on the plate interface this model requires that the down dip end of the interseismic locked zone has on average been approximately stable over a period of at least 2 5 5 myr

using centroid time delays to characterize source durations and identify earthquakes with unique characteristics the relationship between m 0 and the rupture duration is often difficult to establish this is particularly true for large earthquakes for which the moment rate functions mrf generally have complicated shapes and the estimated durations can vary considerably depending on the methodology used to evaluate the mrf in this work we show that the centroid time delay c provides an alternative estimate of the source duration inverted mrfs often end gradually making the end of coseismic rupture difficult to detect in such cases when the rupture duration is not well defined the time delay c is a useful quantity to represent the first order temporal characteristics of the rupture process variations in stress parameter can be investigated by assuming a standard scaling relationship between the seismic moment m0m0 and c this simple scaling relationship can also be used to identify unusual earthquakes with unique source properties such as events involving complicated rupture processes or earthquakes characterized by unusual rupture velocities stress drops or aspect ratios

tracking repeated subduction of the hikurangi plateau beneath new zealand abstract the hikurangi plateau has been subducted beneath new zealand twice firstly at ca 100 ma during n s convergence with gondwana and currently during e w convergence between the pacific and australian plates here we use a nationwide 3 d seismic velocity model derived from seismic tomography studies and seismicity relocated with this model to determine the location of the subducted western and southern edges of the plateau in the hikurangi subduction zone in the north island and northern south island we identify the western edge in the 37 140 km depth range based on the distribution of seismic velocities in the top of the subducted pacific plate changes in the thickness of the dipping seismic zone and steepening of the subducted plate downdip of the buoyant plateau in the central south island where the hikurangi plateau is subducting for a second time the plateau dips less steeply its southern edge is well defined by the collision of the delaminated lower crust of the plateau with the northern fiordland subduction zone where it bends the younger subducted australian plate to vertical the hikurangi plateau was originally rifted from the ontong java plateau and the subducted portions of the hikurangi plateau identified here fill a gap in reconstructions of this large igneous province

insar imaging of displacement on flexural slip faults triggered by the 2013 mw 6 6 lake grassmere earthquake central new zealand interferometric synthetic aperture radar insar data reveal surface slip on multiple faults triggered by the 2013 mw 6 6 lake grassmere earthquake new zealand surface offsets of 1 2 cm occurred on previously inferred flexural slip faults located 4 km from the epicenter we document dip slip on at least three different northeast striking northwest dipping flexural slip faults located in the western limb of a syncline the along strike extent of the triggered slip is 1 1 5 km for each fault dislocation models suggest that triggered slip is confined to shallow depths 800 m coulomb stress analysis indicates that slip was not triggered by the static stress change of the main shock but was likely caused by dynamic shaking during the passage of seismic waves our finding also provides an important clue on how some slip on shallow flexural slip faults takes place

crustal deformation and stress transfer during a propagating earthquake sequence the 2013 cook strait sequence central new zealand the 2013 cook strait earthquake sequence began on 18 july 2013 with two foreshocks of mw 5 7 and mw 5 8 and culminated in the mw 6 6 cook strait and lake grassmere events on 21 july and 16 august respectively located 50 km south of new zealand s capital wellington the earthquakes generated the most significant ground shaking in the wellington and marlborough regions in recent decades during the first event located under cook strait continuously recording gps instruments across central new zealand recorded up to 5 cm of horizontal displacement modeling suggests that the rupture was 25 km long with up to 90 cm of dextral strike slip the second event located 20 km to the southwest caused displacements of up to 25 cm at gps sites located around the clifford bay area in addition two interferograms from radarsat 2 and terrasar x showed up to 30 cm of line of sight displacement in the vicinity of lake grassmere modeling indicates predominantly dextral strike slip of up to 2 1 m coulomb stress changes induced by the earlier foreshocks suggest that the cook strait event was triggered by the preceding events and that the lake grassmere event was subsequently triggered by the cook strait earthquake

overland flow velocity and roughness properties in peatlands overland flow is an important component of peatland hydrology hydrological models of peatlands are being developed that require estimates of flow velocity and its controls however surprisingly little is known about overland flow velocities in peatlands some peatlands have also been drained using open ditches and these need to be incorporated into flow models this paper presents field data on the velocity of overland flow and drain flow in upland peatlands the relationships between flow velocity vegetation cover slope and water depth are explored sphagnum provided a significantly greater effective hydraulic roughness to overland flow than peatland grasses in all cases a significant break in process occurred for flows with water depths of around 1 cm so that there were two components of the roughness curve this is consistent with partial submergence theory for very shallow flows where resistance increases with depth as the soil surface first becomes fully submerged while each surface cover type should be considered separately the results also suggest that a first order estimate of darcy weisbach roughness and mean velocity can be based on a single parameter for each surface cover this paper presents an empirical overland flow velocity forecasting model that can be applied to peatlands the model combines the partially submerged component for flows with water depths below 1 cm with the fully submerged component for flows with depths up to 5 cm which are representative of the depths of flows that occur across peatlands

the 8 5 magnitude ad365 earthquake in crete coastal uplift topography changes archaeological and historical signature abstract an up to 9 m uplift of western crete a cluster of coastal uplifts in the east mediterranean radiocarbon dated approximately 1500 bp as well as historical and archaeological data are evidence for major although poorly documented seismic destruction on a nearly mediterranean scale in the 4th to 5th c ad including the destruction of the nile delta in egypt by a tsunami in ad365 these data represent parts of a puzzle for historians archaeologists geologists and seismologists detailed analysis of geological historical and archaeological data including precise numismatic evidence permits recognition of a major earthquake in crete responsible for coastal uplift at ad365 elastic dislocation analysis of coastal uplift data reveals that this earthquake was associated with a reverse fault offshore of southwestern crete that its minimum magnitude was 8 5 and that this model is consistent with the available seismological and large scale tectonic data despite its magnitude this earthquake cannot have produced the necessary short period high energy waves which are necessary to explain the seismic damage which occurred circa ad365 in a very broad region from sicily to cyprus and libya hence the ad365 earthquake sequence included at least two other major events with epicentres close to cyprus and sicily although significant changes in the coastal morphology widespread destruction and a high human death toll occurred the ad365 crete earthquake was not responsible for any major cultural change it occurred during the transition from the roman to the christian period characterized by vast luxurious villas and modest dwellings on crete respectively

the kinematics of northern south island new zealand determined from geologic strain rates relative motions within the distributed plate boundary zone of northern south island new zealand are determined through an inversion of geologic strain rate estimates the quaternary fault slip rate estimates define the shear strain rates and rock uplift rates provide information on the horizontal divergence rates an erosion rate to rock uplift rate ratio along with a crustal compensation factor is estimated in order to convert rock uplift rates to horizontal divergence rates because of the uncertainty in erosion rates horizontal divergence rates are given a large standard error of the three horizontal strain rate components obtained from these data completely define the horizontal velocity gradient tensor strain rate distributions are matched with spline polynomial functions which can be constrained to behave rigidly within specified regions such as the pacific or australian plates inversion of the strain rate distribution assuming uniform erosion rates across the northern south island yields a velocity field that has small differences in both magnitude 10 larger and direction with the nuvel 1a plate motion model between pacific and australian plates a revised strain rate data set obtained from a variable erosion model in which erosion rates are a linear function of the log of the average annual rainfall magnitudes yields a velocity field with expected directions that are indistinguishable from the nuvel 1a plate motion model between pacific and australian plates but velocity magnitudes are still 10 15 higher than the plate motion model therefore the average values of slip rate on strike slip faults in marlborough required by the nuvel 1a plate motion model are typically close to the low end of the published range of slip values for those structures the major strike slip structures within the marlborough region are accommodating 80 100 of the total plate motion between australia and pacific plates on northern south island as much as 20 of the relative motion could be accommodated by shear generated by folding or thrust faulting with a single orientation between the major structures the magnitude of plate motion contributed by the major faults indicates that the distributed geodetic shear strains measured across northern south island and discussed by bibby 1981 and walcott 1984 are not a form of irrecoverable strain but rather a feature of the strain field that will eventually be released primarily as concentrated slip on the strike slip structures within the region strain modeling indicates that the earthquake moment release over the last 150 years within the northwest nelson province which is west of the marlborough region is at least half an order of magnitude higher than the long term rate of moment release overall the northwest nelson region is playing only a minor role in taking up the long term plate motion

sahke geophysical transect reveals crustal and subduction zone structure at the southern hikurangi margin new zealand 1 the seismic array hikurangi experiment sahke investigated the structure of the forearc and subduction plate boundary beneath the southern north island along a 350 km transect tomographic inversion of first arrival travel times was used to derive a well resolved 15 20 km deep p wave image of the crust the refracted phases and migrated reflection events image subducting slab geometry and crustal structure in the west australian plate moho depth decreases westward across the taranaki fault system from 35 to 28 30 km in the east subducted pacific plate oceanic crust is recognized to have a positive velocity gradient but becomes less distinct beneath the tararua ranges where the interface increases in dip at about 15 km depth from 15 this bend in the subducted plate is associated with vertical clusters in seismicity splay fault branching and low velocity high attenuation material that we interpret to be an underplated subduction sedimentary channel we infer that a step down in the decollement transfers slip on the plate interface at the top of a subduction channel to the oceanic crust and drives local uplift of the tararua ranges reflections from the wairarapa fault show that it is listric and soles into the top of underplated sediments which in turn abut the moho of the overriding plate at 32 km depth near the downdip end of the strongly locked zone the change in dip of the hikurangi subduction interface is spatially correlated with the transition from geodetically determined locked to unlocked areas of the plate interface

complex rupture process of the mw 7 8 2016 kaikoura earthquake new zealand and its aftershock sequence abstract the m7 8 kaikoura earthquake that struck the northeastern south island new zealand on november 14 2016 local time is one of the largest ever instrumentally recorded earthquakes in new zealand it occurred at the southern termination of the hikurangi subduction margin where the subducting pacific plate transitions into the dextral alpine transform fault the earthquake produced significant distributed uplift along the north eastern part of the south island reaching a peak amplitude of 8 m which was accompanied by large 10 m horizontal coseismic displacements at the ground surface along discrete active faults the seismic waveforms expression of the main shock indicate a complex rupture process early automated centroid moment tensor solutions indicated a strong non double couple term which supports a complex rupture involving multiple faults the hypocentral distribution of aftershocks which appears diffuse over a broad region clusters spatially along lineaments with different orientations a key question of global interest is to shed light on the mechanism with which such a complex rupture occurred and whether the underlying plate interface was involved in the rupture the consequences for seismic hazard of such a distributed shallow faulting is important to be assessed we perform a broad seismological analysis combining regional and teleseismic seismograms gps and insar to determine the rupture process of the main shock and moment tensors of 118 aftershocks down to mw 4 2 the joint interpretation of the main rupture and aftershock sequence allow reconstruction of the geometry and suggests sequential activation and slip distribution on at least three major active fault domains we find that the rupture nucleated as a weak strike slip event along the humps fault which progressively propagated northward onto a shallow reverse fault where most of the seismic moment was released before it triggered slip on a second set of strike slip faults at the northern end of the rupture the northern and southern strike slip fault domains have the same orientation but are spatially separated by 15 km in our model the low angle splay thrust fault is located above the slab and connects the strike slip faults kinematically during the aftershock phase the entire fault system remained active

late cenozoic evolution and earthquake potential of an active listric thrust complex above the hikurangi subduction zone new zealand in the center of the frontal wedge of the hikurangi subduction zone new zealand mahia peninsula and its submarine continuation lachlan ridge are being uplifted and folded above an active landward dipping thrust fault complex that is 80 km long high quality marine seismic reflection profiles reveal complex deformation of a cretaceous to holocene sedimentary section and enable a detailed analysis of the stratigraphy structural evolution deformation rates and future earthquake potential the structural analysis is facilitated by uplifted marine terraces on mahia peninsula and by 14 submarine unconformities in the hanging wall sequence five of which are correlated across the eroded crest of lachlan ridge and into the footwall basin the ages of the unconformities are determined by seismic ties to an offshore exploration well onshore outcrops on the peninsula and seabed samples dated by pollen coccolith nannoflora and foraminifera biostratigraphy nine regional quaternary unconformities which developed in response to eustatic fluctuations in sea level and are not older than ca 1 ma are correlated with oxygen isotope stages in equatorial pacific ocean drilling project core 677 the ages of fault growth strata and progressive restorations of deformed stratigraphy indicate that lachlan ridge developed during three phases of deformation since subduction of the pacific plate commenced beneath the australian plate in the early miocene these include an initial phase of thrust faulting a subsequent phase dominated by extensional faulting and the current mainly pleistocene to holocene phase of structural inversion reactivated listric thrust faulting and folding early to middle miocene thrusts in the deeper core of the complex developed out of sequence by sequentially stepping up into the hanging wall section creating an imbricate fan with emerging thrust tips now buried within the forelimb basin in the middle miocene early pliocene listric extensional faults developed in the active thrust wedge possibly as a result of substantial relief on the subducted pacific plate and controlled the development of lachlan basin to the west of the ridge the principal active thrust is the lachlan fault a listric extensional detachment reactivated to accommodate thrust movement and consisting of at least three right stepping segments depth converted seismic profiles indicate that the fault dips westward at 15 20 6 8 km beneath the western flank of lachlan ridge and steepens to 55 70 or even steeper in the upper 1 2 km of section beneath the eastern flank syninversion pleistocene fault growth strata on both flanks of the associated anticline provide an exceptional record of progressive fold limb rotation resulting from the listric fault geometry a geometric analysis of the fault growth strata and deformed terraces was used to derive a maximum dip slip displacement rate of as fast as 3 0 6 5 mm yr the implied shortening rate of 2 6 6 3 mm yr represents 8 20 of the total 31 mm yr of orthogonal plate convergence across this part of the upper plate of the hikurangi subduction zone the top of the pre fault growth paleogene section reveals as much as 5 8 1 5 km of vertical separation in the north decreasing to 30 50 of this value in the south temporal 10 3 10 6 yr and spatial 10 3 10 4 m of strike length variations in vertical deformation rate have occurred during the past 1 m y maximum rates occurred in the holocene and middle quaternary a long term increase in vertical separation rate on all segments during the pleistocene largely reflects a change in thrust kinematics associated with structural inversion the relatively greater increase in uplift rate on the northern part of the fault during the past 1 m y could be related to the possibility that a subducted seamount lies 10 km beneath the peninsula estimates of earthquake source parameters incorporating paleoseismic uplift data from mahia peninsula indicate a potential moment magnitude of up to m w 7 6 8 0 for an earthquake that ruptures all three segments of the lachlan fault the average recurrence interval for such events is estimated to be 615 2333 yr which is consistent with a mean recurrence interval of 1062 yr for four late holocene earthquakes thus the uplift and folding of mahia peninsula and lachlan ridge results from coseismic displacements on a major listric thrust fault that ruptures the upper plate frequently in association with large magnitude earthquakes

late quaternary slip rates and slip partitioning on the alpine fault new zealand abstract published geological data on late quaternary offsets on the alpine fault new zealand have been assembled into a common format and analysed with respect to uncertainties uncertainties arise mainly from measurement of offset features relating apparent offsets to actual fault slip and dating the offset features despite the considerable uncertainties the data form a coherent set consistent with a relatively constant rate of strike slip of 27 5 mm year between milford sound and hokitika this rate represents 70 75 of the fault parallel interplate motion north of the confluence with the hope fault the rate drops substantially dip slip rates on the other hand show considerable variation along strike rising to a maximum of more than 10 mm year in the central section and decreasing to zero at the southern end partitioning of c 25 of the interplate slip on to structures east of the alpine fault occurs in the central section consistent with predictions from critical wedge models the partitioning of all the fault normal component of displacement on to other structures in the south may be related in part to a doubling in width of the deforming wedge to the east most probably however the fault normal displacement is mainly accommodated by underthrusting of the australian plate offshore due to a change in the nature of the crust from continental to oceanic

paleoseismology of the 2010 mw 7 1 darfield canterbury earthquake source greendale fault new zealand abstract the previously unknown greendale fault ruptured in the september 2010 moment magnitude mw 7 1 darfield earthquake surface rupture fracture patterns and displacements along the fault were measured with high precision using real time kinematic rtk gps tape and compass airborne light detection and ranging lidar and aerial photos no geomorphic evidence of a penultimate surface rupture was revealed from pre 2010 imagery the fault zone is up to 300 m wide and comprises both distributed folding and discrete faulting deformation dominated by right lateral displacement surface fracturing accommodates 30 of the total right lateral displacement in the central fault zone the remainder is accommodated by distributed deformation ground penetrating radar and trenching investigations conducted across the central greendale fault reveal that most surface fractures are undetectable at depths exceeding 1 m however large discrete riedel shears continue to depths exceeding 3 m and displace interbedded gravels and sand filled paleochannels at one trench site a riedel shear displaces surface agricultural markers e g fences and plow lines and a subsurface 0 6 m deep paleo channel by 60 cm right laterally and 10 cm vertically indicating the paleochannel has been displaced only in the darfield earthquake optically stimulated luminescence osl dating of the displaced paleochannel yields an age of 21 6 1 5 ka two additional paleochannels at 2 5 m depth with osl ages of 28 4 2 4 ka and 33 2 ka have been displaced 120 cm right laterally and 20 cm vertically the doubling of displacement at depth is interpreted to indicate that in the central section of the greendale fault the penultimate surface rupturing event occurred between ca 20 and 30 ka the greendale fault remained undetected prior to the darfield earthquake because the penultimate fault scarp was eroded and buried during late pleistocene alluvial activity similar active faults with low slip rates i e lower than sedimentation erosion rates are likely to be concealed in alluvial settings globally

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

potential earthquake triggering in a complex fault network the northern south island new zealand summary a synthetic seismicity computer model of multiple interacting faults has been used to investigate potential earthquake triggering in the alpine marlborough buller fault network northern south island new zealand of particular interest is whether large characteristic earthquakes on the central 300 km long segment of the alpine fault average recurrence time of 240 yr might trigger events to the north and northeast possible temporal clustering of other large events and stress shadows the synthetic seismicity model generates long homogeneous catalogues that sample a wide range of possible stress interactions and stress states allowing statistical analysis the catalogues used here include 1500 central alpine fault events of m 7 8 and approximately 2 000 000 other events of magnitudes down to 4 8 these other events occur on four additional segments of the alpine fault on 30 segments of the major marlborough and buller faults and on 4650 randomly distributed smaller faults the synthetic seismicity model is of the quasi static type governed by the coulomb failure criterion with extensions to better account for rupture propagation and fault healing true rate and state friction and viscoelastic relaxation are not yet included mechanical properties are adjusted so that most events rupture an entire fault segment i e the faults behave characteristically the regional b value of 1 thus arises mainly from the fault size distribution the driving mechanism and fault properties are iteratively adjusted so that the resulting long term slip rates single event displacements and recurrence times match the observed real world values the major results are as follows i large alpine fault earthquakes m 7 8 on the central segment have recurrence times with a broad distribution from 81 to 601 yr average 234 yr ii the regional moment release rate is constant over periods of 1000 yr but is quite variable on scales of a few hundred years iii large events on the central alpine fault will usually propagate at least part way along strike to the northeast past the junctures with the marlborough faults that splay off to the east iv thirty seven per cent of such large alpine fault events lafes will also instantaneously trigger significant activity m 6 5 on one or another of the other major faults here instantaneous means with a 0 to approximately 3 yr delay v characteristic events initiating on other major faults also have a high chance of triggering activity elsewhere vi following the short period of increased risk of triggered events a stress shadow effect predominates probably reflecting the mutually inhibitory nature of parallel strike slip faults and the need for a constant long term moment release rate

the 2009 l aquila mw 6 3 earthquake a new technique to locate the hypocentre in the joint inversion of earthquake rupture process summary a new technique is presented to jointly invert the teleseismic and interferometric synthetic aperture radar insar data by simultaneously searching for the hypocentre and the relative weight of insar data in this technique the parameters of causative fault is determined by using insar data first and then the hypocentre is searched for by jointly inverting teleseismic and insar data with the assumption that each subfault on the fault is a potential hypocentre with this technique we investigated the source rupture process of the 2009 april 6 l aquila mw 6 3 earthquake without the use of the existing hypocentre locations our estimated hypocentre is 42 366 n 13 385 e depth 6 9 km with an uncertainty of 1 2 km similar to the hypocentre 42 348 n 13 380 e depth 9 5 km determined by national institute of geophysics and volcanology ingv using arrival time data within the epicentral distance of 50 km our joint inversion suggests a scalar moment of 3 5 1018 nm equivalent to a moment magnitude of mw 6 3 the source process consists of two subevents with a total duration of 7 7 s the first event 0 3 s corresponds to the slip patch near the hypocentre and the second in the next 4 7 s ruptured the other slip patch at 4 16 km along the strike direction these unilateral rupture characteristics of the l aquila earthquake are confirmed by the apparent source time functions astfs analysis in addition two resolution tests are performed to check the reliability of this work clarifying the differences between the inversion results with teleseismic data only insar data only and joint inversion indicating that a higher resolution can be achieved through the joint inversion

segmentation of megathrust rupture zones from fore arc deformation patterns over hundreds to millions of years arauco peninsula chile 1 this work explores the control of fore arc structure on segmentation of megathrust earthquake ruptures using coastal geomorphic markers the arauco nahuelbuta region at the south central chile margin constitutes an anomalous fore arc sector in terms of topography geology and exhumation located within the overlap between the concepcion and valdivia megathrust segments this boundary however is only based on 500 years of historical records we integrate deformed marine terraces dated by cosmogenic nuclides syntectonic sediments published fission track data seismic reflection profiles and microseismicity to analyze this earthquake boundary over 10 2 10 6 years rapid exhumation of nahuelbuta s dome like core started at 4 1 2 ma coeval with inversion of the adjacent arauco basin resulting in emergence of the arauco peninsula here similarities between topography spatiotemporal trends in fission track ages pliocene pleistocene growth strata and folded marine terraces suggest that margin parallel shortening has dominated since pliocene time this shortening likely results from translation of a fore arc sliver or microplate decoupled from south america by an intra arc strike slip fault microplate collision against a buttress leads to localized uplift at arauco accrued by deep seated reverse faults as well as incipient oroclinal bending the extent of the valdivia segment which ruptured last in 1960 with an mw 9 5 event equals the inferred microplate we propose that mechanical homogeneity of the fore arc microplate delimits the valdivia segment and that a marked discontinuity in the continental basement at arauco acts as an inhomogeneous barrier controlling nucleation and propagation of 1960 type ruptures as microplate related deformation occurs since the pliocene we propose that this earthquake boundary and the extent of the valdivia segment are spatially stable seismotectonic features at million year scale

strike slip fault geometry in turkey and its influence on earthquake activity the geometry of turkish strike slip faults has been reviewed and described from this data set it appears that fault geometry the distribution of discontinuities such as bends and stepovers along the main fault trace plays an important role in controlling the location of large earthquake rupture segments along the fault zones large earthquake ruptures generally do not propagate past individual stepovers that are wider than 5 km or bends that have angles greater than about 30 more important than the size of each discontinuity however is the total geometric pattern i e the distribution of adjacent bends and stepovers based not only on distance from one another but also on relative discontinuity size certain geometric patterns restraining single or double bends are particularly common and can be viewed as responsible for strain accumulation along portions of the fault zone fault geometry not only plays a role in the extent of earthquake rupture but also in characteristics of earthquake behavior for example large earthquake epicenters often occur near restraining bends or double bends furthermore aftershocks and swarm activity can often be associated with releasing areas areas along the strike slip fault that are undergoing a relatively large amount of extension

controls on uranium and thorium behaviour in ocean floor hydrothermal systems examples from the pindos ophiolite greece abstract a suite of hydrothermally altered basaltic rocks from the jurassic pindos ophiolite of greece was analysed for its u and th content samples taken from different levels within the ophiolite display variable degrees of hydrothermal alteration ranging from low water rock ratio recharge zone alteration to high water rock ratio discharge zone alteration most samples analysed exhibit constant u th ratios regardless of the degree of alteration however neither of these two elements correlate with any other immobile element zr y ti ree these results suggest that both u and th have been mobile during high temperature ocean floor hydrothermal alteration and indicate a common probably mineralogical control for both elements the chemical composition of hydrothermal fluids from modern tectonic settings equivalent to that of the pindos ophiolite east pacific rise guaymas basin was used to predict theoretical aqueous speciation and solubility of u and th during water rock interaction in these environments the results of this treatment agree with the above conclusions drawn from rock studies and indicate that oxide mineral phases uraninite thorianite control u and th solubility during hydrothermal alteration at oceanic spreading environments