simple physical model for the probability of a subduction zone earthquake following slow slip events and earthquakes application to the hikurangi megathrust new zealand

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

three dimensional surface displacements during the 2016 m w 7 8 kaikōura earthquake new zealand from photogrammetry derived point clouds

shallow slip deficit due to large strike slip earthquakes in dynamic rupture simulations with elasto plastic off fault response summary slip inversions of geodetic data from several large magnitude 7 strike slip earthquakes point to coseismic slip deficit at shallow depths 3 4 km that is coseismic slip appears to decrease towards the earth surface while the inferred slip distribution may be consistent with laboratory derived rate and state friction laws suggesting that the uppermost brittle crust may be velocity strengthening there remains a question of how the coseismic slip deficit is accommodated throughout the earthquake cycle the consequence of velocity strengthening fault friction at shallow depths is that the deficit of coseismic slip is relieved by post seismic afterslip and interseismic creep however many seismic events with inferred shallow slip deficit were not associated with either resolvable shallow interseismic creep or robust shallow afterslip hence the origin of shallow slip deficit remains uncertain in this study we investigate whether inelastic failure in the shallow crust due to dynamic earthquake rupture can explain the inferred deficit of shallow slip evidence for such failure is emerging from geologic seismic and geodetic observations we find that the amount of shallow slip deficit is proportional to the amount of inelastic deformation near the earth surface such deformation occurs under a wide range of parameters that characterize rock strength in the upper crust however the largest magnitude of slip deficit in models accounting for off fault yielding is 2 4 times smaller than that inferred from kinematic inversions of geodetic data to explain this discrepancy we further explore to what extent assumptions in the kinematic inversions may bias the inferred slip distributions inelastic deformation in the shallow crust reduces coseismic strain near the fault introducing an additional artificial deficit of up to 10 per cent of the maximum slip in inversions of geodetic data that are based on purely elastic models the largest magnitude of slip deficit in our models combined with the bias in inversions accounts for up to 25 per cent of shallow slip deficit which is comparable but still smaller than 30 60 per cent deficit inferred from kinematic inversions we discuss potential mechanisms that may account for the remaining discrepancy between slip deficit predicted by elasto plastic rupture models and that inferred from inversions of space geodetic data

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

a hybrid source mechanism of the 2017 mw 6 5 jiuzhaigou earthquake revealed by the joint inversion of strong motion teleseismic and insar data abstract as occurred during the tourist season the 2017 mw 6 5 jiuzhaigou china earthquake led to destructive damages the seismogenic fault of this event was merely speculated to be the northern extension of the huya fault while no apparent surface ruptures were discovered in the field investigation previous studies and released moment tensor solutions indicated the jiuzhaigou earthquake was dominated by left lateral strike slip with partial normal slip component it seems unintelligible that the normal slip occurred in this event as the epicenter was located near the boundary of convergent blocks hence a reasonable and elaborate source rupture model is necessary to investigate such a blind fault and the role it plays in the complex fault system of this region combining space based geodetic teleseismic or regional seismic observations can provide detailed information about earthquake ruptures we first attempted to determine the fault geometry using the bayesian approach with synthetic aperture radar interferograms insar and then the fault geometry was refined based on the relocated aftershock distribution and a two segment fault model was constructed based on the two segment model we resolved the source rupture process of the 2017 jiuzhaigou earthquake through the joint inversion of strong motion teleseismic body wave and insar data the inversion results reveal a hybrid source mechanism in which normal and thrust slips coexist besides the strike slip component we suggest that the eastward motion with the extrusion of the lower crustal flow in the northeastern margin of the bayan har block is responsible for such a faulting behavior the co seismic coulomb stress changes show a significant stress loading in the western segment of the tazang fault increasing its seismic hazard due to the lack of aftershocks to the southeast of the seismogenic fault the probably enhanced seismicity in the northern segment of the huya fault is also worth further attention

two regions of seafloor deformation generated the tsunami for the 13 november 2016 kaikoura new zealand earthquake the 13 november 2016 kaikoura new zealand m w 7 8 earthquake ruptured multiple crustal faults in the transpressional marlborough and north canterbury tectonic domains of northeastern south island the hikurangi trench and underthrust pacific slab terminate in the region south of kaikoura as the subdution zone transitions to the alpine fault strike slip regime it is difficult to establish whether any coseismic slip occurred on the megathrust from on land observations the rupture generated a tsunami well recorded at tide gauges along the eastern coasts and in chatham islands including a 4 m crest to trough signal at kaikoura where coastal uplift was about 1 m and at multiple gauges in wellington harbor iterative modeling of teleseismic body waves and the regional water level recordings establishes that two regions of seafloor motion produced the tsunami including an m w 7 6 rupture on the megathrust below kaikoura and comparable size transpressional crustal faulting extending offshore near cook strait

back projection imaging of earthquakes back projection analysis of earthquakes is a type of array processing that images the source of seismic waves coherently recorded at stations throughout the seismic network the method was developed following the magnitude 9 2 sumatra andaman earthquake in 2004 although properties of earthquakes have been investigated using array data prior to the introduction of the back projection method this technique differs from other approaches because it makes limited assumptions and allows detailed and complex rupture propagation to be examined these advantages have led several researchers to apply the method to many of the largest earthquakes to occur this century the method has also been effective for the detection of smaller events a critical component of the success of back projection has been the development of large scale dense seismic arrays further improvements and future applications of the method will depend greatly on the continued maintenance and development of these networks

slip weakening distance and energy budget inferred from near fault ground deformation during the 2016 mw7 8 kaikōura earthquake the 2016 m7 8 kaik ura new zealand earthquake struck the east coast of the northern south island resulting in strong ground shaking and large surface fault slip since the earthquake was well recorded by a local strong motion seismic network near fault data may provide direct measurements of dynamic parameters associated with the fault weakening process here we estimate a proxy for slip weakening distance dc defined as double the fault parallel displacement at the time of peak ground velocity from accelerograms recorded at a near fault station three component ground displacements were recovered from the double numerical integration of accelerograms and the corresponding final displacements are validated against coseismic displacement from geodetic data the estimated dc is 4 9 m at seismic station keks located 2 7 km from a segment of the kekerengu fault where large surface fault slip 12 m has been observed the inferred dc is the largest value ever estimated from near fault strong motion data yet it appears to follow the scaling of dc with final slip for several large strike slip earthquakes the energy budget of the m7 8 kaik ura earthquake inferred from the scaling of dc with final slip indicates that a large amount of energy was dissipated by on and off fault inelastic deformation during the propagation of the earthquake rupture resulting in a slower average rupture speed 2 0 km s

measuring ground displacements from sar amplitude images application to the landers earthquake ers sar amplitude images are utilized to map ground displacements from a sub pixel correlation method it yields a ground two dimensional displacement field with independent measurements about every 128m in azimuth and 250m in range the accuracy depends on the characteristics of the images for the landers test case the 1 uncertainty is 0 8m in range and 0 4m in azimuth we show that this measurement provides a map of major surface fault ruptures accurate to better than 1km and information on coseismic deformation comparable to the 92 gps measurements available although less accurate this technique is more robust than sar interferometry and provides complementary information since interferograms are only sensitive to the displacement in range

logarithmic model joint inversion method for coseismic and postseismic slip application to the 2017 mw 7 3 sarpol zahāb earthquake iran

the 2016 kaikōura earthquake simultaneous rupture of the subduction interface and overlying faults abstract the distribution of slip during an earthquake and how it propagates among faults in the subduction system play a major role in seismic and tsunami hazards yet they are poorly understood because offshore observations are often lacking here we derive the slip distribution and rupture evolution during the 2016 mw 7 9 kaik ura new zealand earthquake that reconcile the surface rupture space geodetic measurements seismological and tsunami waveform records we use twelve fault segments with eleven in the crust and one on the megathrust interface to model the geodetic data and match the major features of the complex surface ruptures our modeling result indicates that a large portion of the moment is distributed on the subduction interface making a significant contribution to the far field surface deformation and teleseismic body waves the inclusion of local strong motion and teleseismic waveform data in the joint inversion reveals a unilateral rupture towards northeast with a relatively low averaged rupture speed of 1 5 km s the first 30 s of the rupture took place on the crustal faults with oblique slip motion and jumped between fault segments that have large differences in strike and dip the peak moment release occurred at 65 s corresponding to simultaneous rupture of both plate interface and the overlying splay faults with rake angle changes progressively from thrust to strike slip the slip on the papatea fault produced more than 2 m of offshore uplift making a major contribution to the tsunami at the kaik ura station while the northeastern end of the rupture can explain the main features at the wellington station our inversions and simulations illuminate complex up dip rupture behavior that should be taken into consideration in both seismic and tsunami hazard assessment the extreme complex rupture behavior also brings new challenges to the earthquake dynamic simulations and understanding the physics of earthquakes

transpressional rupture cascade of the 2016 mw 7 8 kaikoura earthquake new zealand large earthquakes often do not occur on a simple planar fault but involve rupture of multiple geometrically complex faults the 2016 m w 7 8 kaikoura earthquake new zealand involved the rupture of at least 21 faults propagating from southwest to northeast for about 180 km here we combine space geodesy and seismology techniques to study subsurface fault geometry slip distribution and the kinematics of the rupture our finite fault slip model indicates that the fault motion changes from predominantly right lateral slip near the epicenter to transpressional slip in the northeast with a maximum coseismic surface displacement of about 10 m near the intersection between the kekerengu and papatea faults teleseismic back projection imaging shows that rupture speed was overall slow 1 4 km s but faster on individual fault segments approximately 2 km s and that the conjugate oblique reverse north striking faults released the largest high frequency energy we show that the linking conway charwell faults aided in propagation of rupture across the step over from the humps fault zone to the hope fault fault slip cascaded along the jordan thrust kekerengu and needles faults causing stress perturbations that activated two major conjugate faults the hundalee and papatea faults our results shed important light on the study of earthquakes and seismic hazard evaluation in geometrically complex fault systems

climatic and ecologic changes during miocene surface uplift in the southern patagonian andes abstract the up to 4 km high southern patagonian andes form a pronounced topographic barrier to atmospheric circulation in the southern hemisphere westerlies and cause one of the most drastic orographic rain shadows on earth geologic data imply that this climatic pattern has been established or significantly enhanced during miocene surface uplift of this andean segment we report evidence for important climatic and ecologic changes in the eastern foreland of the patagonian andes that appear to be the result of this uplift to provide constraints on miocene plant ecosystems and precipitation in the eastern leeward foreland of the patagonian andes we determined carbon and oxygen isotope values of pedogenic carbonate nodules from a 500 m thick section of the continental santa cruz formation the age of these deposits was constrained by ar ar dating of intercalated tuffs which range from 22 to 14 ma at 16 5 ma the 13 c values increase by 3 the 18 o values decrease by 2 and the scatter in the oxygen isotope data increases significantly we interpret these changes as the consequence of 1 km surface uplift in this andean segment from the 18 o values and increased aridity to its east from the 13 c values and the increased scatter in the 18 o values sediments overlying the santa cruz formation are very limited in extent and volume and dominated by coarse conglomerates related to pleistocene and older glaciations it thus seems that by 14 ma deposition in the eastern foreland of the southern patagonian andes had essentially ceased as the result of rain shadow formation

major earthquakes occur regularly on an isolated plate boundary fault the scarcity of long geological records of major earthquakes on different types of faults makes testing hypotheses of regular versus random or clustered earthquake recurrence behavior difficult we provide a fault proximal major earthquake record spanning 8000 years on the strike slip alpine fault in new zealand cyclic stratigraphy at hokuri creek suggests that the fault ruptured to the surface 24 times and event ages yield a 0 33 coefficient of variation in recurrence interval we associate this near regular earthquake recurrence with a geometrically simple strike slip fault with high slip rate accommodating a high proportion of plate boundary motion that works in isolation from other faults we propose that it is valid to apply time dependent earthquake recurrence models for seismic hazard estimation to similar faults worldwide

geodetic model of the 2015 april 25 mw 7 8 gorkha nepal earthquake and mw 7 3 aftershock estimated from insar and gps data

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

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

some thoughts on measuring earthquake deformation using optical imagery optical imagery has been proven to be an effective tool for measuring earthquake deformation in continental regions since its first application in the 1999 izmit earthquake in this article we compile and analyze all the earthquakes that have been investigated with optical image matching by 2019 based on which we comment on various issues regarding measuring earthquake deformation with optical imagery new generations of very high resolution vhr data are effective for earthquake studies but orthorectification of the vhr images is the major source of error which is often ignored we found that the displacements derived from the worldview images strongly correlate with the errors in the shuttle radar topography mission srtm digital elevation model dem that was used in orthorectification based on the observed correlation between displacements and topography we propose a new dem based method using the advanced land observing satellite alos world 3 d dem to reduce the orthorectification errors combining the published optical data of earthquake deformation we re analyze the coseismic slip distribution and shallow slip deficit ssd the ssd model states that the coseismic slip in many strike slip earthquakes decreases in magnitude toward the surface but this model remains arguable because the interferometric synthetic aperture radar insar derived slip is usually not well constrained at shallow depths due to decorrelation because optical matching directly measures the surface slip we re examine the slip distribution of 11 strike slip earthquakes and find that the ssd model may primarily be artifacts in the insar measurements it is therefore of great importance to include the optical data in earthquake studies to constrain coseismic slip inversions

complete three dimensional coseismic deformation field of the 2016 central tottori earthquake by integrating left and right looking insar observations with the improved sm vce method

melting of a subducting oceanic crust from u th disequilibria in austral andean lavas understanding crustal genesis at convergent plate boundaries is important for determining mass transfer between different geochemical reservoirs in the earth s mantle and for deciphering the long term growth of the continental crust most arc magmas are thought to be generated from fluid induced melting of the mantle wedge above slabs of subducting oceanic crust1 such magmas frequently display 238u enrichments or radioactive equilibrium2 3 between 238u and its radiogenic product 230th but where a young and hot oceanic crust is being subducted it may itself partially melt and produce calc alkaline andesites and dacites termed adakites4 here we report a uniform excess of 230th over 238u but variable th isotope ratios in young adakites from the andean austral volcanic zone south of the triple junction where the chile ridge subducts beneath south america we show that these results are compatible with the adakites having been formed by approximately 20 equilibrium melting due to amphibole decomposition in a heterogeneous5 oceanic crust moreover both the degree of melting of the oceanic crust and its thermal structure appear to be uniform under most of the andean austral volcanic zone such partial melting of subducted oceanic slabs may have occurred throughout the earth s history where young oceanic plates were subducted

stress triggering in thrust and subduction earthquakes and stress interaction between the southern san andreas and nearby thrust and strike slip faults 1 we argue that key features of thrust earthquake triggering inhibition and clustering can be explained by coulomb stress changes which we illustrate by a suite of representative models and by detailed examples whereas slip on surface cutting thrust faults drops the stress in most of the adjacent crust slip on blind thrust faults increases the stress on some nearby zones particularly above the source fault blind thrusts can thus trigger slip on secondary faults at shallow depth and typically produce broadly distributed aftershocks short thrust ruptures are particularly efficient at triggering earthquakes of similar size on adjacent thrust faults we calculate that during a progressive thrust sequence in central california the 1983 mw 6 7 coalinga earthquake brought the subsequent 1983 mw 6 0 nunez and 1985 mw 6 0 kettleman hills ruptures 10 bars and 1 bar closer to coulomb failure the idealized stress change calculations also reconcile the distribution of seismicity accompanying large subduction events in agreement with findings of prior investigations subduction zone ruptures are calculated to promote normal faulting events in the outer rise and to promote thrust faulting events on the periphery of the seismic rupture and its downdip extension these features are evident in aftershocks of the 1957 mw 9 1 aleutian and other large subduction earthquakes we further examine stress changes on the rupture surface imparted by the 1960 mw 9 5 and 1995 mw 8 1 chile earthquakes for which detailed slip models are available calculated coulomb stress increases of 2 20 bars correspond closely to sites of aftershocks and postseismic slip whereas aftershocks are absent where the stress drops by more than 10 bars we also argue that slip on major strike slip systems modulates the stress acting on nearby thrust and strike slip faults we calculate that the 1857 mw 7 9 fort tejon earthquake on the san andreas fault and subsequent interseismic slip brought the coalinga fault 1 bar closer to failure but inhibited failure elsewhere on the coast ranges thrust faults the 1857 earthquake also promoted failure on the white wolf reverse fault by 8 bars which ruptured in the 1952 mw 7 3 kern county shock but inhibited slip on the left lateral garlock fault which has not ruptured since 1857 we thus contend that stress transfer exerts a control on the seismicity of thrust faults across a broad spectrum of spatial and temporal scales

three dimensional dynamic rupture simulations across interacting faults the m w 7 0 2010 haiti earthquake the mechanisms controlling rupture propagation between fault segments during a large earthquake are key to the hazard posed by fault systems rupture initiation on a smaller fault sometimes transfers to a larger fault resulting in a significant event e g 2002 m7 9 denali usa and 2010 m7 1 darfield new zealand earthquakes in other cases rupture is constrained to the initial fault and does not transfer to nearby faults resulting in events of more moderate magnitude this was the case of the 1989 m6 9 loma prieta and 2010 m7 0 haiti earthquakes which initiated on reverse faults abutting against a major strike slip plate boundary fault but did not propagate onto it here we investigate the rupture dynamics of the haiti earthquake seeking to understand why rupture propagated across two segments of the leog ne fault but did not propagate to the adjacent enriquillo plantain garden fault the major 200 km long plate boundary fault cutting through southern haiti we use a finite element model to simulate propagation of rupture on the leog ne fault varying friction and background stress to determine the parameter set that best explains the observed earthquake sequence in particular the ground displacement the two slip patches inferred from finite fault inversions are explained by the successive rupture of two fault segments oriented favorably with respect to the rupture propagation while the geometry of the enriquillo fault did not allow shear stress to reach failure

source parameters and slip distribution of the 2018 mw 7 5 palu indonesia earthquake estimated from space based geodesy abstract the 2018 mw 7 5 palu earthquake is one of the most geometrically complex events ever recorded on central sulawesi island it caused devastating tsunamis and landslides after the mainshock resulting in great casualties and damages to the infrastructures in palu city and surrounding areas in this study we combined far field insar near field sar and optical sub pixel correlation data to determine the fault geometry source parameters and fault slip distribution of this event along the palu koro fault zone our best fitting fault model contains three fault segments with variable strike angles showing that the coseismic rupture is dominated by a left lateral strike slip motion accompanied by minor normal slip and reverse slip components on the onshore segments the maximum slip is up to 8 4 m with a left lateral strike slip component of 6 8 m at a depth of 4 km on the central segment near palu city a normal slip component of 4 3 m in the left releasing step over and a reverse slip component of 3 2 m in the offshore area near the palu bay on the offshore segment the maximum slip is up to 4 2 m with a normal slip component of 1 8 m we argue that the offshore reverse slip motion might have played a key role in the generation of the palu tsunami we also suggest that the linking normal segment contributed to the rupture propagation across the left releasing step over from the central segment to the southern segment while the linking reverse segment arrested the rupture propagation across the right restraining step over to north the coulomb stress change reveals that there is possibility of future great earthquakes occurring on several major faults in the northeast of palu city our results have great significance to qualitatively assess the risk of future seismic hazards in such a geometrically complex fault system

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

integration of coseismic deformation into webgis for near real time disaster evaluation and emergency response earthquakes are one of the destructive natural disasters immediate emergency response in the first few hours is important for life rescue the near real time ground deformation maps generated after earthquakes are crucial for hazard assessments which normally take a couple of hours or longer to be generated using conventional ways in this study we propose a near real time coseismic ground deformation map generation system with the aim of assisting rapid seismic hazard evaluations and emergency responses this framework adopts the source parameters published by seismological agencies and uses the empirical equations to generate the near real time coseismic ground deformation maps the source parameters of an earthquake such as the focal mechanism are programmatically accessed from the united states geological survey national earthquake information center usgs neic in a nearly real time manner the ground deformation estimated using empirical equations is integrated as self adapting spatial data fusion and visualized on an interactive webgis platform we develop the webgis platform namely quickdeform at https www insar com cn and successfully applied the system to several recent large magnitude earthquakes we find that the proposed framework functions robustly and proficiently to automatically generate the seismic deformation map within several minutes after the occurrence of an earthquake the generated deformation map shows good agreement when compared to the data from real earthquakes quickdeform can be used as a volunteered geographic information platform for crowdsourcing disaster data for rescue and model validation

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

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

refining the shallow slip deficit geodetic slip inversions for three major m w 7 strike slip earthquakes 1992 landers 1999 hector mine and 2010 el mayor cucapah show a 15 60 per cent reduction in slip near the surface depth 2 km relative to the slip at deeper depths 4 6 km this significant difference between surface coseismic slip and slip at depth has been termed the shallow slip deficit ssd the large magnitude of this deficit has been an enigma since it cannot be explained by shallow creep during the interseismic period or by triggered slip from nearby earthquakes one potential explanation for the ssd is that the previous geodetic inversions lack data coverage close to surface rupture such that the shallow portions of the slip models are poorly resolved and generally underestimated in this study we improve the static coseismic slip inversion for these three earthquakes especially at shallow depths by 1 including data capturing the near fault deformation from optical imagery and sar azimuth offsets 2 refining the interferometric synthetic aperture radar processing with non boxcar phase filtering model dependent range corrections more complete phase unwrapping by snaphu statistical non linear approach for phase unwrapping assuming a maximum discontinuity and an on fault correlation mask 3 using more detailed geologically constrained fault geometries and 4 incorporating additional campaign global positioning system gps data the refined slip models result in much smaller ssds of 3 19 per cent we suspect that the remaining minor ssd for these earthquakes likely reflects a combination of our elastic model s inability to fully account for near surface deformation which will render our estimates of shallow slip minima and potentially small amounts of interseismic fault creep or triggered slip which could make up a small percentages of the coseismic ssd during the interseismic period our results indicate that it is imperative that slip inversions include accurate measurements of near fault surface deformation to reliably constrain spatial patterns of slip during major strike slip earthquakes

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

the 2018 mw6 4 hualien earthquake dynamic slip partitioning reveals the spatial transition from mountain building to subduction abstract the hualien earthquake of 6 february 2018 occurred on the east coast of taiwan in the collision zone between the eurasia and philippine sea plates even though an event with a moderate magnitude of mw6 4 it caused widespread surface rupture in and around the city of hualien leading to significant loss of life and property damages in this study we investigate the rupture process of this earthquake using teleseismic strong motion gps and sar observations we first employ the geodetic data to search for the geometry of multiple fault planes followed by a multi point source inversion using teleseismic and strong motion waveforms to determine the possible change in mechanism during the rupture process we parameterize the fault model with three curved segments to represent the complicated fault system involved in the rupture process an offshore fault was ruptured by the hualien earthquake showing a curved geometry with the dip angle changing from shallow 45 in the north to sub vertical 80 in the south evidence from tomographic velocity model indicates that the offshore fault is the boundary between the subducted coastal range and meilun tableland which is also a plate interface finally a joint inversion is carried out to constrain the complete rupture process the inversion result reveals that the rupture initiated on the offshore fault interface and propagated unilaterally towards south southwest the rupture then jumped on to the sub vertical meilun fault and reached the ground surface significant dynamic slip partitioning occurred during the rupture process near the meilun fault with the majority of thrust and strike slip motions occurring on the off shore fault and the meilun fault respectively the afterslip model is inverted with sar timeseries spanning 6 months after the mainshock the afterslip model shows a strong complementary pattern with co seismic slips the comparison between the 1951 and 2018 hualien earthquake shows that the rupture behavior of the meilun fault does not follow a repeating earthquake pattern thrust motion may occur on the two side walls of the meilun tableland with a teeterboard uplift pattern in different earthquake cycles the change in geometry and slip on the inter plate fault appears to be related to the transition of the coastal range from mountain building to subduction

a uniform isotopic and chemical signature of dust exported from patagonia rock sources and occurrence in southern environments patagonia is considered to be the most important source of dust from south america that is deposited in surrounding areas and we present here a systematic sr and nd isotopic study of sediment currently being exported eolian and suspended riverine sediments from patagonia have a homogeneous chemical and isotopic composition that results from the mixing of by products from explosive andean volcanism derived from the extensive jurassic silicic province of chon aike and pyroclastic materials from the basic to intermediate southern andean quaternary arc which are easily denudated and dispersed the main andean uplift and the glaciations that began in the late tertiary account for the extensive distribution of these sediments in the extra andean region the present geochemical signature of patagonian sediments was produced during the pleistocene along with the onset of the southern andean explosive arc volcanism previously published compositions of sediments from other southern south american source regions assumed to be representative of patagonia are distinct from our data considering the alleged importance of patagonia as a dust source for different depositional environments in southern latitudes it is surprising to verify that the chemical and isotopic signatures of patagonian sourced sediments are different from those of sediments from the southern ocean the pampean region or the antarctic ice sediments from these areas have a crustal like geochemical signature reflecting a mixed origin with sediment from other southern south american sources whereas patagonian sediments likely represent the basic to intermediate end member composition

slip in the 2010 2011 canterbury earthquakes new zealand the 3rd september 2010 mw 7 1 darfield and 21st february 2011 mw 6 3 christchurch new zealand earthquakes occurred on previously unknown faults we use insar ground displacements sar amplitude offsets field mapping aerial photographs satellite optical imagery a lidar dem and teleseismic body wave modeling to constrain the pattern of faulting in these earthquakes the insar measurements reveal slip on multiple strike slip segments and secondary reverse faults associated with the darfield main shock fault orientations are consistent with those expected from the gps derived strain field the insar line of sight displacement field indicates the main fault rupture is about 45 km long and is confined largely to the upper 10 km of the crust slip on the individual fault segments of up to 8 m at 4 km depth indicate stress drops of 6 10 mpa in each event rupture initiated on a reverse fault segment before continuing onto a strike slip segment the non double couple seismological moment tensors for each event are matched well by the sum of double couple equivalent moment tensors for fault slip determined by insar the slip distributions derived from insar observations of both the darfield and christchurch events show a 15 km long gap in fault slip south west of christchurch which may present a continuing seismic hazard if a further unknown fault structure of significant size should exist there

dynamic transfer of rupture across differently oriented segments in a complex 3 d fault system 1 we simulate spontaneous dynamic propagation of rupture across two adjacent fault segments subject to a triaxial compressive stress regime these segments have different orientations and hence different focal mechanisms vertical strike slip and dipping thrust numerical simulations using a biem boundary integral equation method have revealed that under a typical triaxial homogeneous compressive stress regime where the magnitude of the intermediate principal stress lies halfway between those of the maximum and minimum ones ruptures of different focal mechanisms are not likely to occur simultaneously in a single rupture event propagation of rupture from a vertical strike slip fault segment to a pure dip slip normal reverse fault segment is possible only when the stress field is close to uniaxial compression or when the intermediate stress magnitude is close either to the minimum or the maximum one these findings are useful for evaluating possible earthquake scenarios along fault systems with complex 3d geometries

the complete 3 d surface displacement field in the epicentral area of the 1999 mw7 1 hector mine earthquake california from space geodetic observations we use interferometric synthetic aperture radar insar data to derive continuous maps for three orthogonal components of the co seismic surface displacement field due to the 1999 m w7 1 hector mine earthquake in southern california vertical and horizontal displacements are both predominantly antisymmetric with respect to the fault plane consistent with predictions of linear elastic models of deformation for a strike slip fault some deviations from symmetry apparent in the surface displacement data may result from complexity in the fault geometry

triggered afterslip on the southern hikurangi subduction interface following the 2016 kaikōura earthquake from insar time series with atmospheric corrections abstract the 2016 mw 7 8 kaik ura earthquake represents an extremely complex event involving over ten major crustal faults altering conventional understanding of multi fault ruptures although evidence for coseismic slip on the hikurangi subduction interface is controversial we present afterslip on the subduction zone beneath marlborough using 13 months of interferometric synthetic aperture radar insar and global positioning system gps observations the spatially and temporally correlated atmospheric errors in sar interferograms are problematic and hence a new insar time series approach combining the generic atmospheric correction online service gacos with a spatial temporal atmospheric phase screen aps filter to facilitate the insar time series analysis is developed for interferograms with over 250 km spatial extent we achieve a 0 77 cm displacement rms difference against gps improving 61 from the conventional insar time series method ts comparisons between the overlapping region of two independent tracks show an rms difference of 1 1 cm for the ts gacos aps combined method improving 54 from the ts method and 27 from using ts with an aps filter only the aps filter reduces the short wavelength residuals substantially but fails to remove the long wavelength error even after the ramp removal revealing that the gacos correction has played a key role in mitigating long wavelength atmospheric effects the resultant insar displacements together with the gps displacements are used to recover the time dependent afterslip distribution on the hikurangi subduction interface which provides insights for reviewing the co seismic slip sources the present status of the subduction plate boundary and future seismic hazards

imaging the 2016 mw 7 8 kaikoura new zealand earthquake with teleseismic p waves a cascading rupture across multiple faults the 13 november 2016 mw 7 8 kaikoura new zealand earthquake was investigated using teleseismic p waves backprojection of high frequency p waves from two regional arrays shows unilateral rupture of at least two southwest northeast striking faults with an average rupture speed of 1 4 1 6 km s and total duration of 100 s guided by these backprojection results 33 globally distributed low frequency p waves were inverted for a finite fault model ffm of slip the ffm showed evidence of several subevents however it lacked significant moment release near the epicenter where a large burst of high frequency energy was observed a local strong motion network recorded strong shaking near the epicenter hence for this earthquake the distribution of backprojection energy is superior to the ffm as a guide of strong shaking for future large earthquakes that occur in regions without strong motion networks initial shaking estimates could benefit from backprojection constraints

dynamically triggered slip on a splay fault in the mw 7 8 2016 kaikoura new zealand earthquake we investigate the mw 7 8 2016 kaikoura new zealand earthquake using optical satellite imagery and seismology to reveal the main features of the rupture process correlation of landsat8 images reveals a 30 40 km surface rupture on the kekerengu fault and jordan thrust with up to 12 m of right lateral slip a previously unrecognized conjugate strike slip fault the papatea fault also slipped co seismically 3 4 m the global cmt centroid indicates both thrust and right lateral slip and is located 100 km ne of the mainshock epicenter the significant non double couple component of the gcmt 25 suggests the mainshock is not well represented by a single planar fault back projection of teleseismic p waves reveals two main bursts of seismic radiation 1 at 10 20 s near the mainshock epicenter and 2 at 70 s close to the observed surface ruptures we determine a finite source kinematic model of the rupture from the inversion of seismic waveforms we use two faults in our model defined to match the observed slip on the kekerengu fault and a deeper offshore fault with a lower dip angle to satisfy the long period seismological observations we compute the equivalent moment tensor from our finite source model and find it to be remarkably consistent with the gcmt solution although little is known about the geometry of these faults at depth if the kekerengu fault splays from the deeper thrust it provides a rare example where the contribution of slip on a splay fault can be clearly isolated in the seismological waveforms

reconciling the deformational dichotomy of the 2016 mw 7 8 kaikoura new zealand earthquake following the 2016 mw 7 8 kaikoura earthquake uncertainty over the nature of the coseismic rupture developed seismological evidence pointed to significant involvement of the subduction megathrust while geodetic and field observations pointed to a shallow set of intracrustal faults as the main participants during the earthquake the addition of tsunami observations and modeling as reported in bai et al 2017 places additional constraints on the specific location of coseismic slip which when combined with other observations indicates the simultaneous occurrence of shallow slip on the subduction interface and slip on overlying upper crustal fault structures this kaikoura style earthquake involving synchronous ruptures on multiple components of the plate boundary is an important mode of plate boundary deformation affecting seismic hazard along subduction zones

diverse volumetric faulting patterns in the san jacinto fault zone we examine locations magnitudes and faulting types of post 2000 earthquakes in the trifurcation area of san jacinto fault zone to clarify basic aspects of failure processes in the area most m 3 5 events have strike slip mechanisms occur within 1 km of the main faults clark buck ridge and coyote creek and have hypocenter depths of 10 13 km in contrast many smaller events have normal source mechanisms and hypocenters in intrafault areas deeper than 13 km additional small events with hypocenter depth 13 km occur in off fault regions and have complex geometries including lineations normal to the main faults five moderate earthquakes with m 4 7 5 4 have high aftershock rates 150 m 1 5 events within 1 day from the mainshock to obtain more details on aftershock sequences of these earthquakes we detect and locate additional events with the matched filter method there are almost no aftershocks within 1 km from the mainshocks consistent with large mainshock stress drops and low residual stress the five aftershock sequences have almost no spatial overlap while the mainshocks are on the main faults most aftershocks are located in intrafault and off fault regions their locations and spatial distribution reflect the mainshock rupture directions and many also follow structures normal to the main faults the significant diversity of observed features highlights the essential volumetric character of failure patterns in the area the increasing rate of moderate events productive aftershock sequences and large inferred stress drops may reflect processes near the end of a large earthquake cycle

long period analysis of the 2016 kaikoura earthquake abstract the recent m w 7 8 kaikoura new zealand earthquake involved a remarkably complex rupture propagating in an intricate network of faults at the transition between the alpine fault in the south island and the kermadec tonga subduction zone we investigate the main features of this complicated rupture process using long period seismological observations apparent rayleigh wave moment rate functions reveal a clear northeastward directivity with an unusually weak rupture initiation during 60 s followed by a major 20 s burst of moment rate to further explore the rupture process we perform a bayesian exploration of multiple point source parameters in a 3 d earth model the results show that the rupture initiated as a small strike slip rupture and propagated to the northeast triggering large slip on both strike slip and thrust faults the kaikoura earthquake is thus a rare instance in which slip on intraplate faults trigger extensive interplate thrust faulting this clearly outlines the importance of accounting for secondary faults when assessing seismic and tsunami hazard in subduction zones

which fault segments ruptured in the 2008 wenchuan earthquake and which did not new evidence from near fault 3d surface displacements derived from sar image offsets the 2008 m w 7 9 wenchuan earthquake ruptured a complex thrust faulting system at the eastern edge of the tibetan plateau and west of sichuan basin though the earthquake has been extensively studied several details about the earthquake such as which fault segments were activated in the earthquake are still not clear this is in part due to difficult field access to the fault zone and in part due to limited near fault observations in interferometric synthetic aperture radar insar observations because of decorrelation in this study we address this problem by estimating sar image offsets that provide near fault ground displacement information and exhibit clear displacement discontinuities across activated fault segments we begin by reanalyzing the coseismic insar observations of the earthquake and then mostly eliminate the strong ionospheric signals that were plaguing previous studies by using additional postevent images we also estimate the sar image offsets and use their results to retrieve the full 3d coseismic surface displacement field the coseismic deformation from the insar and image offset measurements are compared with both global positioning system and field observations the results indicate that our observations provide significantly better information than previous insar studies that were affected by ionospheric disturbances we use the results to present details of the surface faulting offsets along the beichuan fault from the southwest to the northeast and find that there is an obvious right lateral strike slip component as well as thrust faulting along the southern beichuan fault in yingxiu county which was strongly underestimated in earlier studies based on the results we provide new evidence to show that the qingchuan fault was not ruptured in the 2008 wenchuan earthquake a topic debated in field observation studies but show instead that surface faulting occurred on a northward extension of the beichuan fault during or immediately following the mainshock electronic supplement 1 parallel ascending orbit track coseismic deformation 1 http www bssaonline org lookup suppl doi 10 1785 0120160126 dc1

breaking a subduction termination from top to bottom the large 2016 kaikōura earthquake new zealand abstract subduction systems globally terminate allowing plate motion to be transferred from the oceanic megathrust onto continental and or oceanic transform faults the mechanism of this kinematic transition over earthquake timescales is however poorly understood due to a lack of relevant data here we study the 2016 mw 7 8 kaik ura earthquake in new zealand the first large instrumentally recorded earthquake across a subduction termination to investigate this transfer mechanism in detail we find that the kaik ura earthquake unlike standard subduction earthquakes globally involved a predominance 80 of coseismic slip on upper plate faults and minor triggered slip on the underlying oceanic subduction thrust in the months following the earthquake the subduction thrust accommodated most of the earthquake s afterslip down dip of its co seismic rupture zone this top down strain release mechanism is in accord with local geological geodetic and historical seismicity data which suggest that the bulk of plate convergence 75 is accommodated in the upper plate we suggest therefore that this alternative strain release mechanism which is distinct from standard plate boundary earthquakes is characteristic of subduction terminations and results in the majority of seismic tsunami hazard being on steep near surface faults

possible dual earthquake landslide source of the 13 november 2016 kaikoura new zealand tsunami a complicated earthquake m w 7 8 in terms of rupture mechanism occurred in the ne coast of south island new zealand on 13 november 2016 utc in a complex tectonic setting comprising a transition strike slip zone between two subduction zones the earthquake generated a moderate tsunami with zero to crest amplitude of 257 cm at the near field tide gauge station of kaikoura spectral analysis of the tsunami observations showed dual peaks at 3 6 5 7 and 5 7 56 min which we attribute to the potential landslide and earthquake sources of the tsunami respectively tsunami simulations showed that a source model with slip on an offshore plate interface fault reproduces the near field tsunami observation in terms of amplitude but fails in terms of tsunami period on the other hand a source model without offshore slip fails to reproduce the first peak but the later phases are reproduced well in terms of both amplitude and period it can be inferred that an offshore source is necessary to be involved but it needs to be smaller in size than the plate interface slip which most likely points to a confined submarine landslide source consistent with the dual peak tsunami spectrum we estimated the dimension of the potential submarine landslide at 8 10 km

effect of seismogenic depth and background stress on physical limits of earthquake rupture across fault step overs earthquakes can rupture geometrically complex fault systems by breaching fault step overs quantifying the likelihood of rupture jump across step overs is important to evaluate earthquake hazard and to understand the interactions between dynamic rupture and fault growth processes here we investigate the role of seismogenic depth and background stress on physical limits of earthquake rupture across fault step overs our computational and theoretical study is focused on the canonical case of two parallel strike slip faults with large aspect ratio uniform prestress and friction properties we conduct a systematic set of 3 d dynamic rupture simulations with different seismogenic depth step over distance and initial stresses we find that the maximum step over distance h c that a rupture can jump depends on seismogenic depth w and strength excess to stress drop ratio s commonly used to evaluate probable rupture velocity as h c w s n where n 2 when h c w 1 5 and n 1 otherwise the critical nucleation size largely controlled by frictional properties has a second order effect on h c rupture on the secondary fault is mainly triggered by the stopping phase emanated from the rupture end on the primary fault asymptotic analysis of the peak amplitude of stopping phases sheds light on the mechanical origin of the relations between h c w and s and leads to the scaling regime with n 1 in far field and n 2 in near field the results suggest that strike slip earthquakes on faults with large seismogenic depth or operating at high shear stresses can jump wider step overs than observed so far in continental interplate earthquakes

dynamic shear rupture interactions with fault bends and off axis secondary faulting 1 on the basis of elastodynamic stress fields for singular crack and nonsingular slip weakening models of propagating rupture we develop preliminary answers to such questions as follows if a rupturing fault is intersected by another providing a possible bend in the failure path when will stressing be consistent with rupture along the bend what secondary fault locations and orientations in a damaged region bordering a major fault will be stressed to failure by the main rupture stresses that could initiate rupture on a bend are shown to increase dramatically with crack speed especially near the limiting speed rayleigh for mode ii shear for mode iii whether a bend path once begun can be continued to larger scales depends on principal stress directions and ratios in the prestress field conditions should often be met in mode ii for which bend paths encouraged by stressing very near the rupture tip are discouraged by the larger scale stressing a basis for intermittent rupture propagation and spontaneous arrest secondary failure in the damage zone likewise increases markedly as the limiting speed is approached such may make the fracture energy much greater than for slip on a single surface the extent of secondary faulting is strongly affected by prestress directions and the ratio of residual to peak strength for mode ii prestress controls whether activation occurs primarily on the extensional side which we show to be the typical case or on the compressional side too natural examples are consistent with the concepts developed

a window into the complexity of the dynamic rupture of the 2011 mw 9 tohoku oki earthquake the 2011 mw 9 tohoku oki earthquake recorded by over 1000 near field stations and multiple large aperture arrays is by far the best recorded earthquake in the history of seismology and provides unique opportunities to address fundamental issues in earthquake source dynamics here we conduct a high resolution array analysis based on recordings from the usarray and the european network the mutually consistent results from both arrays reveal rupture complexity with unprecedented resolution involving phases of diverse rupture speed and intermittent high frequency bursts within slow speed phases which suggests spatially heterogeneous material properties the earthquake initially propagates down dip with a slow initiation phase followed by sustained propagation at speeds of 3 km s the rupture then slows down to 1 5 km s for 60 seconds a rich sequence of bursts is generated along the down dip rim of this slow and roughly circular rupture front before the end of the slow phase an extremely fast rupture front detaches at about 5 km s towards the north finally a rupture front propagates towards the south running at about 2 5 km s for over 100 km key features of the rupture process are confirmed by the strong motion data recorded by k net and kik net the energetic high frequency radiation episodes within a slow rupture phase suggests a patchy image of the brittle ductile transition zone composed of discrete brittle asperities within a ductile matrix the high frequency is generated mainly at the down dip edge of the principal slip regions constrained by geodesy suggesting a variation along dip of the mechanical properties of the mega thrust fault or their spatial heterogeneity that affects rise time

hope fault jordan thrust and uplift of the seaward kaikoura range new zealand in the northern south island of new zealand displacement at the pacific indian plate boundary is accommodated by the east north east striking right lateral strike slip marlborough fault system the southernmost marlborough fault is the hope fault the late pleistocene holocene horizontal slip rate on this fault is 20 25 mm yr about half of the rate of pacific australian plate motion near the eastern end of the hope fault most displacement is transferred to the north northeast striking jordan thrust but the average dip slip rate at the surface trace of this thrust is less than 4 mm yr we propose that most slip takes place on a blind thrust expressed at the surface by the fault propagation folding of the seaward kaikoura range and that the rate of uplift of this range is as high as that of the southern alps 6 to 10 mm yr the major restraining bend of the alpine fault has the same average slip rate as the wairau fault 4 6 mm yr even though the alpine fault is an east dipping reverse separation fault at the restraining bend this low slip rate results in uplift of the spenser mountains east of the bend at a rate lower than that of the southern alps and seaward kaikoura range

production of jurassic rhyolite by anatexis of the lower crust of patagonia abstract the mid jurassic marifil and chon aike volcanic rocks of eastern patagonia are part of one of the largest silicic igneous provinces known rb sr geochronology indicates eruptive ages of 175 190 ma for the marifil complex mostly toarcian aalenian the majority of the rocks are isotopically uniform with initial 87sr 86sr 0 7067 0 0003 and endt 4 2 primary magmas of andesitic composition were generated by partial melting of mafic grenvillian lower crust indentified by depleted mantle model ages of 1150 1600 ma lower crustal pyroxene granulite xenoliths can be modelled as residual jurassic source although they may alternatively be co genetic cumulates the dacite rhyolite suite formed by crystal liquid fractionation processes from the primary andesites involving multistage crystallization and re melting during magma ascent with the later stages of evolution being explicable by fractional crystallization of plagioclase amphibole and accessory minerals the province represents large scale lower crustal reworking associated with the unique tectonic and igneous environment of gondwana break up

earthquake in a maze compressional rupture branching during the 2012 mw 8 6 sumatra earthquake seismological observations of the 2012 moment magnitude 8 6 sumatra earthquake reveal unprecedented complexity of dynamic rupture the surprisingly large magnitude results from the combination of deep extent high stress drop and rupture of multiple faults back projection source imaging indicates that the rupture occurred on distinct planes in an orthogonal conjugate fault system with relatively slow rupture speed the east southeast west northwest ruptures add a new dimension to the seismotectonics of the wharton basin which was previously thought to be controlled by north south strike slip faulting the rupture turned twice into the compressive quadrant against the preferred branching direction predicted by dynamic coulomb stress calculations orthogonal faulting and compressional branching indicate that rupture was controlled by a pressure insensitive strength of the deep oceanic lithosphere

paleoearthquakes and rupture behavior of the lenglongling fault implications for seismic hazards of the northeastern margin of the tibetan plateau

aftershocks are well aligned with the background stress field contradicting the hypothesis of highly heterogeneous crustal stress 1 it has been proposed that the crustal stress field contains small length scale heterogeneity of much larger amplitude than the uniform background stress this model predicts that earthquake focal mechanisms should reflect the loading stress rather than the uniform background stress so if the heterogeneous stress hypothesis is correct focal mechanisms before and after a large earthquake should align with the tectonic loading and the earthquake induced static stress perturbation respectively however i show that the off fault triggered aftershocks of the 1992 m7 3 landers california earthquake align with the same stress field as the pre landers mechanisms the aftershocks occurred on faults that were well oriented for failure in the pre landers stress field and then loaded by the landers induced static stress change aftershocks in regions experiencing a 0 05 to 5 mpa coseismic differential stress change align with the modeled landers induced static stress change implying that they were triggered by the stress perturbation contrary to the heterogeneous stress hypothesis these triggered aftershocks are also well aligned with the pre landers stress field obtained from inverting the pre landers focal mechanisms therefore the inverted pre landers stress must represent the persistent background stress field earthquake focal mechanisms provide an unbiased sample of the spatially coherent background stress field which is large relative to any small scale stress heterogeneity the counterexample provided by the landers earthquake is strong evidence that the heterogeneous stress model is not widely applicable

space imaging geodesy reveals near circular coseismic block rotation during the 2016 mw 7 8 kaikōura earthquake new zealand

coseismic and postseismic stress rotations due to great subduction zone earthquakes 1 the three largest recent great subduction zone earthquakes 2011 m9 0 tohoku japan 2010 m8 8 maule chile and 2004 m9 2 sumatra andaman exhibit similar coseismic rotations of the principal stress axes prior to each mainshock the maximum compressive stress axis was shallowly plunging while immediately after the mainshock both the maximum and minimum compressive stress axes plunge at 45 dipping faults can be oriented for either reverse or normal faulting in this post mainshock stress field depending on their dip explaining the observed normal faulting aftershocks without requiring a complete reversal of the stress field the significant stress rotations imply near complete stress drop in the mainshocks with 80 of the pre mainshock stress relieved in the tohoku and maule earthquakes and in the northern part of the sumatra andaman rupture the southern part of the sumatra andaman rupture relieved 60 of the pre mainshock stress the stress axes rotated back rapidly in the months following the tohoku and maule mainshocks and similarly in the southern part of the sumatra andaman rupture a rapid postseismic rotation is possible because the near complete stress drop leaves very little background stress at the beginning of the postseismic reloading in contrast there has been little or no postseismic rotation in the northern part of the sumatra andaman rupture over the 7 years since the mainshock all m 8 0 subduction earthquakes since 1990 with an adequate number of pre and post mainshock events were evaluated and not all show similar coseismic stress rotations deeper earthquakes exhibit smaller coseismic stress rotations likely due to increasing deviatoric stress with depth

near field investigations of the landers earthquake sequence april to july 1992 the landers earthquake which had a moment magnitude m w of 7 3 was the largest earthquake to strike the contiguous united states in 40 years this earthquake resulted from the rupture of five major and many minor right lateral faults near the southern end of the eastern california shear zone just north of the san andreas fault its m w 6 1 preshock and m w 6 2 aftershock had their own aftershocks and foreshocks surficial geological observations are consistent with local and far field seismologic observations of the earthquake large surficial offsets as great as 6 meters and a relatively short rupture length 85 kilometers are consistent with seismological calculations of a high stress drop 200 bars which is in turn consistent with an apparently long recurrence interval for these faults