piggyback basin development above a thin skinned thrust belt with two detachment levels as a function of interactions between tectonic and superficial mass transfer the case of the subandean zone bolivia abstract the subandean fold and thrust belt of bolivia is characterised by two major detachment levels and large piggyback basins sand box and numerical models have been used to study sedimentation and erosion control on thrust belt evolution and to study the retroactive effects of tectonics on piggyback development in thin skinned thrust belts with two detachment levels analogue models show that surface processes play a dominant role in controlling wedge evolutions erosion promotes fault reactivation and tectonic delamination passive roof duplex while sedimentation promotes forward shifting of the frontal thrust and consequently piggyback basin development numerical models were used to understand the development of the subandean fold and thrust belt of bolivia numerical experiments show that the simultaneity of basement tilting and high sedimentation rates promotes the formation of a stable tectonic wedge outer and inner faults are alternately active during the beginning of deformation a kinematic evolution that favours the development of piggyback basins between the step by step history of the thrust belt predicts that each change in tectonic location is recorded with large unconformities in basins but these unconformities are not well preserved from progressive erosion in the final geometry

topographic expressions of mantle dynamics in the mediterranean abstract the surface of the earth is the ever changing expression of the dynamic processes occurring at depth and at or above its surface however our ability to read landscapes in terms of their underlying tectonic or climatic forcing remains rudimentary during the last decade particular attention has been drawn to the deep dynamic contributions to topography related to the stresses that are produced at the base of the lithosphere by mantle convection and their relevance compared to the iso static component of topography here we use examples from the mediterranean and estimate residual and dynamic topography we then compare those with surface uplift from geology for specific regions to disentangle the dynamic from the static components considering the different topographic signatures of tectonic processes e g actual residual and dynamic topography as well as uplift rates jointly provides a powerful way to distinguish between the contributions of mantle crustal and surface processes such an approach might bring us closer to reading topographic expressions in terms of their geological cause

geophysical geological transect and tectonic evolution of the swiss italian alps a complete alpine cross section integrates numerous seismic reflection and refraction profiles across and along strike with published and new field data the deepest parts of the profile are constrained by geophysical data only while structural features at intermediate levels are largely depicted according to the results of three dimensional models making use of seismic and field geological data the geometry of the highest structural levels is constrained by classical along strike projections of field data parallel to the pronounced easterly axial dip of all tectonic units because the transect is placed close to the western erosional margin of the austroalpine nappes of the eastern alps it contains all the major tectonic units of the alps a model for the tectonic evolution along the transect is proposed in the form of scaled and area balanced profile sketches shortening within the austroalpine nappes is testimony of a separate cretaceous age orogenic event west directed thrusting in these units is related to westward propagation of a thrust wedge resulting from continental collision along the meliata hallstatt ocean further to the east considerable amounts of oceanic and continental crustal material were subducted during tertiary orogeny which involved some 500 km of n s convergence between europe and apulia consequently only a very small percentage of this crustal material is preserved within the nappes depicted in the transect postcollisional shortening is characterized by the simultaneous activity of gently dipping north directed detachments and steeply inclined south directed detachments both detachments nucleating at the interface between lower and upper crust large scale wedging of the adriatic or apulian lower crust into a gap opening between the subduced european lower crust and the pile of thin upper crustal flakes alpine nappes indicates a relatively strong lower crust and detachment between upper and lower crust

vertical averages of rheology of the continental lithosphere relation to thin sheet parameters abstract we calculate vertically averaged rheologies for continental lithosphere subject to biaxial states of stress corresponding to extensional compressional and strike slip regimes we assume that brittle deformation occurs by byerlee s law and that ductile deformation occurs by steady state creep mechanisms under these conditions the vertically averaged rheology may be approximated by a single power law over the range of strain rates from 10 13 to 10 17 s 1 this is true not only when either brittle or ductile behavior dominates the strength of the lithospere but also when the contributions of brittle and ductile behavior are comparable the value of the power law exponent n and the strength of the lithosphere depend on the depth and stress difference at the brittle ductile transition the temperature at the moho and the geothermal gradient in the range of vertically integrated stress between 1012 and 1013 n m 1n reaches a minimum of between 5 and 10 under other circumstancesn increases rapidly as brittle behavior dominates over ductile behavior the strength of the lithosphere depends most strongly on the thermal state of the upper mantle but also is influenced by the stress supported in brittle portions of the lithosphere

coupling surface and mantle dynamics a novel experimental approach recent modeling shows that surface processes such as erosion and deposition may drive the deformation of the earth s surface interfering with deeper crustal and mantle signals to investigate the coupling between the surface and deep process we designed a three dimensional laboratory apparatus to analyze the role of erosion and sedimentation triggered by deep mantle instability the setup is constituted and scaled down to natural gravity field using a thin viscous sheet model with mantle and lithosphere simulated by newtonian viscous glucose syrup and silicon putty respectively the surface process is simulated assuming a simple erosion law producing the downhill flow of a thin viscous material away from high topography the deep mantle upwelling is triggered by the rise of a buoyant sphere the results of these models along with the parametric analysis show how surface processes influence uplift velocity and topography signals

dynamics of retreating slabs 2 insights from three dimensional laboratory experiments 1 a laboratory analogue of a three layer linear viscous slab upper mantle lower mantle system is established in a silicone putty honey and crystallized honey tank experiment the same setup as in the numerical investigation part 1 is used we focus on the interaction of the slab with the induced passive mantle flow by widely varying the mantle volume flux boundary conditions in our numerical experiments the lateral volume flux was set to zero in interpreting the results relative to the real earth the base of the box is taken as the bottom of the mantle convection system while the lateral boundaries may be associated with the presence of other nearby slabs dynamic force equilibrium assessed on the basis of an analytical review of forces is described for four different phases 1 the subduction initiation instability 2 the accelerating dynamic free fall phase of the slab 3 the dynamic interaction with the 660 km discontinuity and 4 a final phase of steady state trench retreat phase 3 is an important feature not observed in the numerical experiments this highly dynamic phase of interrupted trench retreat can therefore be attributed to boundary conditions on mantle volume flux on the basis of integration constants of force equilibrium in phases 2 and 4 we identify two different classes of volume flux one in which the lateral boundary can be considered open and the other class where it is closed closed boundary condition cases are obtained if any of the lateral box boundaries are 600 km away from the slab assuming a one to one relation between trench retreat and back arc spreading enigmatic observations of episodic opening of back arc basins can be explained by our experimental observations

the many surface expressions of mantle dynamics plate tectonic theory suggests that present day topography can be explained by the repeated interactions between the tectonic plates moving along earth s surface however mounting evidence indicates that a significant proportion of earth s topography results from the viscous stresses created by flow within the underlying mantle rather than by the moving plates this dynamic topography is transient varying as mantle flow changes and is characterized by small amplitudes and long wavelengths it is therefore often hidden by or confused with the more obvious topographic anomalies resulting from horizontal tectonic movements however dynamic topography can influence surface processes and thus enter the geological record it has for example played a role in the establishment of amazon drainage patterns in turn surface processes such as the erosion of topographical anomalies could affect mantle flow this emerging view of dynamic topography suggests that the concept of plate tectonics as the driver of surface deformation needs to be extended to include the vertical coupling between the mantle and the surface unravelling this coupling back in time with the help of models and the geological record can potentially provide unprecedented insights into past mantle dynamics

imbricated slip rate processes during slow slip transients imaged by low frequency earthquakes low frequency earthquakes lfes often occur in conjunction with transient strain episodes or slow slip events sses in subduction zones their focal mechanism and location consistent with shear failure on the plate interface argue for a model where lfes are discrete dynamic ruptures in an otherwise slowly slipping interface sses are mostly observed by surface geodetic instruments with limited resolution and it is likely that only the largest ones are detected the time synchronization of lfes and sses suggests that we could use the recorded lfes to constrain the evolution of sses and notably of the geodetically undetected small ones however inferring slow slip rate from the temporal evolution of lfe activity is complicated by the strong temporal clustering of lfes here we apply dedicated statistical tools to retrieve the temporal evolution of sse slip rates from the time history of lfe occurrences in two subduction zones mexico and cascadia and in the deep portion of the san andreas fault at parkfield we find temporal characteristics of lfes that are similar across these three different regions the longer term episodic slip transients present in these datasets show a slip rate decay with time after the passage of the sse front possibly as t 1 4 they are composed of multiple short term transients with steeper slip rate decay as t with between 1 4 and 2 we also find that the maximum slip rate of sses has a continuous distribution our results indicate that creeping faults host intermittent deformation at various scales resulting from the imbricated occurrence of numerous slow slip events of various amplitudes

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

analogue models of orogenic wedges controlled by erosion abstract indentation in the upper brittle crust where one plate is stiffer than the other produces vertical extrusion of a doubly vergent orogenic wedge sandbox models of this process show that erosion with or without deposition of the eroded material onto one or both margins significantly changes the internal patterns of orogenic shear and compaction within the orogens erosion decreases the vertical stress and changes the criticality of the orogenic wedge whereas redeposition increases the vertical stress on its margins effective indenters of accreted sand which develop in models without erosion if the rigid indenter face dip is 75 e g 45 or 15 are strongly affected by erosion rapid erosion favors thrusting over compaction and decreases both the size and the relevance of the effective indenters redeposition of eroded material on the margins also expands the lifetime of the active shear as the additional load delays initiation of underlying new shears

experiments on shortening of a 4 layer model of the continental lithosphere davy ph and cobbold p r 1991 experiments on shortening of a 4layer model of the continental lithosphere in p r cobbold editor experimental and numerical modelling of continental deformation tecronophysics 188 l 25 we present an experimental method for modelhng lithospheric deformation the method is based on a simplified profile of lithosphere rheology where only four layers are considered brittle crust ductile crust brittle mantle and ductile mantle the strengths of the four layers calculated from laboratory determined flow laws depend strongly on geothenns and slightly on strain rates and deformation regimes the rheological profiles of the lithosphere have been recreated in experimental models built with analog materials sand silicone putty and golden syrup which flow under their own weight during lithospheric shortening the style of deformation depends on the relative strengths of the four layers especially those in the mantle of special importance is the existence or non existence of a brittle mantle the initial stages of compression often produce flexures or buckles without local isostatic compensation buckling exerts a strong control on the localisation of thrust faults in later stages the thrusts tend to form at the inflexion points of buckles the style of crustal thickening depends on the relative thicknesses and resistances of the lithospheric layers in 2 layer lithospheric models without resistant mantle shortening was concentrated upon a small number of thrusts widely spaced in 3 layer models shortening was concentrated into a large number of reverse faults more closely spaced and more steeply dipping than before in clayer models a single thrust formed in the brittle mantle motion on this thrust dragged the crustal layers down forming an asymmetric crustal root with steep imbricate slices

orogeny and orography the effects of erosion on the structure of mountain belts a numerical model of the coupled processes of tectonic deformation and surface erosion in convergent orogens is developed to investigate the nature of the interaction between these processes crustal deformation is calculated by a two dimensional finite element model of deformation in response to subduction and accretion of continental crust erosion operates on the uplifted surface of this model through fluvial incision which is taken to be proportional to stream power the relative importance of the tectonic and erosion processes is given by a dimensionless erosion number relating convergence velocity rock erodibility and precipitation rate this number determines the time required for a system to reach steady state and the final topographic shape and size of a mountain belt fundamental characteristics of the model orogens include asymmetric topography with shallower slopes facing the subducting plate and an asymmetric pattern of exhumation with the deepest levels of exhumation opposite to subduction these characteristics are modified when the regional climate exhibits a dominant wind direction and orographically enhanced precipitation on one side of the mountain belt the two possible cases are dominant wind in the direction of motion of the subducting plate and dominant wind direction in the opposite direction of the subducting plate velocity models of the former case predict a broad zone of exhumation with maximum exhumation in the orogen interior models of the latter case predict a focused zone of exhumation at the margin of the orogen and at high erosion number a reversal in the topographic asymmetry natural examples of these two cases are presented the southern alps of new zealand exhibits the climate and exhumation asymmetry characteristic of wind in the direction opposite to motion of the subducting plate the asymmetry of topography suggests that erosion is not efficient enough to have reversed the topographic asymmetry the contrasting example of dominant wind in the direction of subduction motion is provided by the olympic mountains of washington state in this case exhumation of deep levels of the cascadia accretionary wedge shows a broad domal pattern consistent with the observed orographic precipitation

the plume head continental lithosphere interaction using a tectonically realistic formulation for the lithosphere summary current debates on the existence of mantle plumes largely originate from interpretations of supposed signatures of plume induced surface topography that are compared with predictions of geodynamic models of plume lithosphere interactions these models often inaccurately predict surface evolution in general they assume a fixed upper surface and consider the lithosphere as a single viscous layer in nature the surface evolution is affected by the elastic brittle ductile deformation by a free upper surface and by the layered structure of the lithosphere we make a step towards reconciling mantle and tectonic scale studies by introducing a tectonically realistic continental plate model in large scale plume lithosphere interaction this model includes i a natural free surface boundary condition ii an explicit elastic viscous ductile plastic brittle rheology and iii a stratified structure of continental lithosphere the numerical experiments demonstrate a number of important differences from predictions of conventional models in particular this relates to plate bending mechanical decoupling of crustal and mantle layers and tension compression instabilities which produce transient topographic signatures such as uplift and subsidence at large 500 km and small scale 300 400 200 300 and 50 100 km the mantle plumes do not necessarily produce detectable large scale topographic highs but often generate only alternating small scale surface features that could otherwise be attributed to regional tectonics a single large wavelength deformation predicted by conventional models develops only for a very cold and thick lithosphere distinct topographic wavelengths or temporarily spaced events observed in the east african rift system as well as over french massif central can be explained by a single plume impinging at the base of the continental lithosphere without evoking complex asthenospheric upwelling

on steady states in mountain belts the dynamic system of tectonics and erosion contains important feedback mechanisms such that orogenic systems tend toward a steady state this concept is often invoked but the nature of the steady state is commonly not specified we identify four types of steady state that characterize the orogenic system and illustrate these cases by using numerical model results and natural examples these types are 1 flux steady state 2 topographic steady state 3 thermal steady state and 4 exhumational steady state they refer to the erosional flux the topography the subsurface temperature field and the spatial pattern of cooling ages respectively models suggest that the topography will reach a steady mean form at the scale of an orogenic belt but perfect topographic steady state is unlikely to be achieved at shorter length scales thermal steady state is a precondition for exhumational steady state and in the case of temperature dependent deformation topographic steady state exhumational steady state is characterized by reset age zones spatially nested according to closure temperature as illustrated in natural systems from new zealand the cascadia accretionary margin and taiwan

sedimentary basins and crustal thickening abstract we consider the development of sedimentary basins in a tectonic context dominated by horizontal shortening and vertical thickening of the crust well known examples are foreland basins others are ramp basins and buckle basins we have reproduced various styles of compressional basins in experiments properly scaled for gravity a multilayered model lithosphere with brittle and ductile layers floats on a model asthenosphere a computer driven piston provides shortening and thickening synchronous with erosion and sedimentation after a first stage of lithospheric buckling thrust faults appear mainly at inflection points slip on an isolated reverse fault is accompanied by flexure footwall flexure results in a foreland basin and becomes accentuated by sedimentation hangingwall flexure is less marked but may become accentuated by erosion motion on a fault leads to hangingwall collapse at the surface either footwall sedimentation or hangingwall erosion tends to prolong the active life of a reverse fault slip on any pair of closely spaced reverse faults of opposite vergence results in a ramp basin simultaneous slip produces a symmetric ramp basin whereas alternating slip results in a butterfly shaped basin with superposed foredeeps some well developed ramp basins become pushed down until bounding faults meet at the surface and the basin disappears from view at this stage the basin depth is equivalent to 15 km or more slip on any pair of widely spaced reverse faults of opposite vergence results in a pronounced central anticline between two distinct foredeeps in central asia and in western europe cenozoic crustal thickening is due to continental collision for central asia western china kyrgyzstan uzbekistan tajikistan we have compiled a regional structure contour map on the base of the tertiary as well as 4 regional sections foreland basins and ramp basins are numerous and associated with cenozoic thrusts large basins tarim junggar fergana tajik occur around and between mountain ranges but smaller basins issyk kul naryn occur within them in western europe the alps and pyrenees are surrounded by foreland basins ramp basins or intermediate styles in the andes and its foreland neogene thrusts and compressional basins are due to subduction of oceanic lithosphere in colombia they account for much of the cordillera oriental in nw argentina for the altiplano in west central argentina for the sierras pampeanas compressional basins are also common in other areas of older crustal thickening

formation of seafloor swells by mantle plumes the prominent oceanic hot spots are located at the crest of broad topographic swells on the seafloor available evidence indicates that swells are supported by anomalously thin or altered lithosphere as might result from the intrusion of a mantle plume into the lithosphere a set of experiments have been made to measure the free surface uplift and subsidence produced by intrusion of a low viscosity buoyant plume into a rheological boundary layer a deep layer of strongly thermoviscous sugar solution with a free surface was cooled from above to simulate the lithosphere asthenosphere system low viscosity low density plumes were released at depth the free surface displacement generated by the ascending plume was recorded as a function of time using a proximity measurement system the plumes ascend through the asthenosphere as nearly spherical diapirs and collapse flatten upon intrusion into the base of the lithosphere evolution of the surface topography can be divided into three phases 1 a low axisymmetric rise supported by the plume deep beneath the lithosphere 2 rapid uplift and steepening as the plume reaches the lithosphere base and 3 slow axial subsidence as the plume stagnates within the lithosphere the measured uplifts are compared with the uplift calculated for buoyant plumes in a uniform viscous half space using morgan s image method the agreement is good for thin lithosphere for thick lithosphere the observed is less than the calculated uplift scaling laws have been derived which relate the measured maximum uplift and maximum uplift rate to diapir parameters extrapolation of these to the scale of ocean floor swells gives uplift rates of approximately 1 km in 5 m y by this mechanism the most significant qualitative results of the experiments are that swells formed by interaction of low viscosity mantle plumes and oceanic lithosphere can be characterized by axial symmetry rapid uplift and shallow compensation

the 1996 peru tsunamigenic earthquake broadband source process we investigate the spatio temporal complexity of moment release of the february 21 1996 peru earthquake mw 7 5 we use a non linear source tomographic technique based on simulated annealing to invert surface wave source spectra for the slip distribution on a gently dipping fault plane the spectra 5 65 mhz are obtained using an empirical green s function egf method applied to first and second orbit fundamental mode rayleigh waves spectra are well fit by a 110 km bilateral rupture subparallel to the trench updip of the hypocenter with a total moment of 2 0 1020 nm the non linear inversion reveals a 30 30 km major slip patch south the onset where rupture velocities attain 1 5 2 0 km s inversions of teleseismic broadband p and sh waves 10 500 mhz indicate little or no directivity consistent with the surface wave data the average source time functions for both the surface and body wave data are similar in shape and in duration 50 s part of the slip during the 1996 peru event occurred in a region of reduced background seismicity as was the case for the 1992 nicaragua slow event suggesting that the seismogenic potential of low seismicity regions near the trench should be globally reassessed

postseismic relaxation driven by brittle creep a possible mechanism to reconcile geodetic measurements and the decay rate of aftershocks application to the chi chi earthquake taiwan we evaluate the effect of coseismic stress changes on the fault slip at midcrustal depth assuming a velocity strengthening brittle creep rheology we show that this model can help reconcile the time evolution of afterslip as measured from geodesy with aftershocks decay we propose an analytical expression for slip of the brittle creeping fault zone bcfz that applies to any dynamic or static stress perturbation including shear stress and normal stress changes the model predicts an initial logarithmic increase of slip with time postseismic slip rate decays over a characteristic time t r a that does not depend on the amplitude of the stress perturbation and it asymptotically joins the long term creep imposed by interseismic stress buildup given that the seismicity rate might be considered proportional to the sliding velocity of the bcfz the model predicts a decay rate of aftershocks that follows omori s law with a mathematical formalism identical to that of dieterich 1994 although based on a different mechanical rationale our model also differs from dieterich s model in that it requires that aftershock sequences and deep afterslip as constrained from geodetic measurements should follow the same temporal evolution we test this for the 1999 chi chi earthquake m w 7 6 and find that both sets of data are consistent with a model of afterslip due to the response of the bcfz the inferred relaxation time t r 8 5 years requires a value for a log v being the coefficient of friction in the range between 1 3 10 3 and 10 2

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

shallow megathrust earthquake ruptures betrayed by their outer trench aftershocks signature abstract for some megathrust earthquakes the rupture extends to the solid earth s surface at the ocean floor this unexpected behaviour holds strong implications for the tsunami potential of subduction zones and for the physical conditions governing earthquakes but such ruptures occur in underwater areas which are hard to observe even with current instrumentation and imaging techniques here we evidence that aftershocks occurring ocean ward from the trench are conditioned by near surface rupture of the megathrust fault comparison to well constrained earthquake slip models further reveals that for each event the number of aftershocks is proportional to the amount of shallow slip a link likely related to static stress transfer hence the spatial distribution of these specific aftershock sequences could provide independent constrains on the coseismic shallow slip of future events it also offers the prospect to be able to reassess the rupture of many large subduction earthquakes back to the beginning of the instrumental era

persistent tremor within the northern costa rica seismogenic zone 1 we identify tremor using a spectral detection method and characterize its occurrence over a period of four years 2006 2009 in the vicinity of the nicoya peninsula costa rica although a few major tremor events accompanied by geodetic slow slip occur much of the tremor record consists of minor episodes with short duration and no detectable geodetic slip its persistent occurrence suggests that some portion of the interface is experiencing slow slip nearly continuously driving small patches to fail in accelerated slip locations indicate that much of the tremor occurs at shallow depth in freely slipping regions of the seismogenic zone this result is significant in that locations of slow slip and tremor at other subduction zones are largely limited to the downdip frictional transition tremor locations may help to refine the heterogeneous distribution of locked and freely slipping patches within the costa rica seismogenic zone

earthquake swarms in circum pacific subduction zones abstract we systematically and manually search through clusters of earthquakes along circum pacific subduction zones to identify potential earthquake swarms in total we find 266 potential earthquake swarms 180 we classify as megathrust and 68 we classify as volcanic due to their proximity to the megathrust or to volcanoes we focus on the megathrust swarms and demonstrate that 1 the number of events in a swarm is not a function of the largest earthquake in the swarm 2 swarms exhibit an approximately constant rate of seismicity that lasts until after the mean timing of events in the swarm 3 the timing of the largest earthquake in the sequence is no different than the timing of any other earthquake in the sequence 4 our catalogs of earthquakes comprising swarms 9000 events have high b values 1 5 to 2 and 5 when earthquake swarms are considered as single events using total duration and cumulative moment they appear to be consistent with the slow earthquake magnitude duration scaling law presented by ide et al 2007 the first three observations along with the observation that swarms can span very large areas compared to their cumulative seismic moment argue against static stress triggering as a driving mechanism for earthquake swarms along strike propagation velocities are observed for several swarms showing epicentral propagation of 10 km day similar to other documented slow slip events together this evidence implies that aseismic slip along the megathrust is likely an important mechanism for the generation of megathrust earthquake swarms in circum pacific subduction zones we then conduct a comparison of swarms and large megathrust earthquakes finding evidence that the two are broadly anti correlated megathrust segments with large earthquake swarm gaps are more likely to experience large mw 8 megathrust events we characterize the ubiquity of megathrust swarms at different margins and suggest that fault properties along marianas type margins may allow for earthquake swarms to occur regularly but other margins may rely on other variables such as the subduction of a ridge or seamount to facilitate the generation of megathrust earthquake swarms

rapid aseismic moment release following the 5 december 1997 kronotsky kamchatka earthquake model inversions of displacements of continuously operating gps stations in kamchatka show that aseismic afterslip during 2 months following the mw 7 8 5 december 1997 kronotsky subduction earthquake released as much moment as the earthquake itself the rapidly decaying transient slip on the subduction underthrust occurred near the downdip edge of the coseismic rupture and extended laterally away from it including a region of vigorous foreshock activity a logarithmic decay function fit to the cumulative afterslip curve has a relaxation time of about 3 days rapid afterslip can contribute significantly to the moment release of partially coupled subduction zones

motion of continental slivers and creeping subduction in the northern andes regions of intense continental deformation termed continental slivers have been identified in chile bolivia and ecuador analyses of gps data now identify another large sliver in peru the inca sliver that is moving away from a neighbouring sliver in ecuador implying that moving continental slivers control the deformation of almost the entire andean mountain range

slow slip events and strain accumulation in the guerrero gap mexico 1 global positioning system gps time series in guerrero mexico reveal the existence of large slow slip events sses at the boundary between the cocos and north american plates in this study we examined the last three sses that occurred in 2001 2002 2006 and 2009 2010 and their impact on the strain accumulation along the guerrero subduction margin gps displacements were inverted to retrieve the slip distribution during each sse and the inter sse coupling of the subduction interface the three analyzed sses have equivalent moment magnitudes of between 7 50 and 7 65 their lateral extents are variable and they all show significant slip in the guerrero seismic gap during the inter sse epochs the interplate coupling is high in the area where slow slip subsequently occurs in the guerrero gap the shallow portion of the plate interface from the trench to the coast is weakly coupled the average slip deficit accumulated in the guerrero gap over a period of 12 years which corresponds to three cycles of sse is only 1 4 of the slip deficit accumulated on both sides of the gap moreover the regions of large slip deficit coincide with the rupture areas of recent large earthquakes we conclude that the sses in the guerrero gap release a significant part of the strain accumulated during the inter sse period if large subduction thrust earthquakes occur in the guerrero gap their recurrence time is probably increased compared to adjacent regions

eroding dynamic topography 1 geological observations of mantle flow driven dynamic topography are numerous especially in the stratigraphy of sedimentary basins on the contrary when it leads to subaerial exposure of rocks dynamic topography must be substantially eroded to leave a noticeable trace in the geological record here we demonstrate that despite its low amplitude and long wavelength and thus very low slopes dynamic topography is efficiently eroded by fluvial erosion providing that drainage is strongly perturbed by the mantle flow driven surface uplift using simple scaling arguments as well as a very efficient surface processes model we show that dynamic topography erodes in direct proportion to its wavelength we demonstrate that the recent deep erosion experienced in the colorado plateau and in central patagonia is likely to be related to the passage of a wave of dynamic topography generated by mantle upwelling

a transient subduction zone slip episode in southwest japan observed by the nationwide gps array 1 we investigate the spatiotemporal variation of fault slip on the subduction interface in southwest japan following the two 1996 hyuganada earthquakes m 6 7 using continuous gps observations a silent thrust slip event has been reported by hirose et al 1999 following these earthquakes approximately 100 km to the north beneath the bungo channel we employ the network inversion filter to rigorously invert for the fault slip distribution in space and time the gps time series is modeled as a sum of 1 secular deformation 2 coseismic station displacements 3 transient fault slip 4 random benchmark motion 5 reference frame shifts and 6 observational errors nonnegativity constraints effectively prohibit normal faulting on the subduction interface spatial and temporal smoothing parameters are estimated by the extended kalman filter the estimated fault slip rate images postseismic slip following the two hyuganada earthquakes slip associated with the silent thrust event began roughly 1 month after the second earthquake but initiated 100 km to the northeast of the hyuganada earthquakes the slow event propagated southwest and downdip beneath the bungo channel lasting approximately 1 year with maximum slip rates of 0 6 m yr the equivalent seismic moment was mw 7 2 we can rule out the possibility that slip propagated from the source region of the hyuganada earthquakes to the location of the silent earthquake however the timing of the events suggests a causal connection perhaps due to static stress transfer this kind of transient event or silent earthquake may reflect different fault zone characteristics and may be responsible for accommodating strain that would otherwise be released in large earthquakes

drainage basin responses to climate change recent investigations have shown that the extent of the channel network in some drainage basins is controlled by a threshold for overland flow erosion the sensitivity of such basins to climate change is analyzed using a physically based model of drainage basin evolution the golem model simulates basin evolution under the action of weathering processes hillslope transport and fluvial bedrock erosion and sediment transport results from perturbation analyses reveal that the nature and timescale of basin response depends on the direction of change an increase in runoff intensity or a decrease in vegetation cover will lead to a rapid expansion of the channel network with the resulting increase in sediment supply initially generating aggradation along the main network followed by downcutting as the sediment supply tapers off by contrast a decrease in runoff intensity or an increase in the erosion threshold will lead to a retraction of the active channel network and a much more gradual geomorphic response cyclic changes in runoff intensity are shown to produce aggradational degradational cycles that resemble those observed in the field cyclic variations in runoff also lead to highly punctuated denudation rates with denudation concentrated during periods of increasing runoff intensity and or decreasing vegetation cover the sediment yield from threshold dominated basins may therefore exhibit significant variability in response to relatively subtle environmental changes a finding which underscores the need for caution in interpreting modern sediment yield data

tsunami earthquakes possibly widespread manifestations of frictional conditional stability 1 tsunami earthquakes shallow events that produce larger tsunamis than expected given their surface wave magnitudes ms typically have long durations and a source spectrum depleted in short period energy seven cases of underthrusting tsunami earthquakes provide information on the rupture processes but little constraint on geographic distribution or frequency we compare their rupture characteristics with smaller magnitude earthquakes on circum pacific interplate thrust faults comparable moment release time histories are found for large tsunami earthquakes and for many smaller shallow subduction zone earthquakes with significantly longer durations and additional source complexity than for events deeper than 15 km thus very shallow interplate earthquake ruptures are scale invariant with variable frictional properties on the plate interface controlling the depth dependent rupture process widespread occurrence of small shallow interplate earthquakes with long durations suggests that many subduction faults have frictional properties that may enable large tsunami generating earthquakes to occur fortunately large shallow ruptures are infrequent

river transport effects on compressional belts first results from an integrated analogue numerical model 1 erosion deposition and tectonic processes interact to define the style of deformation in compressional belts this paper introduces a method of integrating a numerical model for surface transport with analogue sandbox models of compressional belts to further improve our understanding of this interplay the analogue model provides the numerical model with the rising topography whereas the numerical model calculates the river network and the resulting amount of erosion and sediment transport compared to previous analogue models with uniform two dimensional erosion this method provides a tool to incorporate process based rates of erosion and deposition with spatial distributions that depend on the river network developed on the evolving topography rivers running parallel to the evolving mountain belt induce along strike changes in erosion and deposition that in turn result in asymmetric tectonic deformation the additional load of sediments controls the propagation of thrust as well as the direction of vergence of the main thrust high erosion rates do not always lead to fewer thrusts within the compressional belts but generally steepen and lengthen the lifetime of the affected faults

estimating seismic moment magnitude mw of tremor bursts in northern cascadia implications for the seismic efficiency of episodic tremor and slip 1 we develop a method to estimate the seismic moments of deep non volcanic tremor bursts observed in northern cascadia for each tremor burst the maximum amplitudes at individual stations within a time window 5 s around the predicted arrivals of the s phase are measured and compared to the maximum s amplitudes measured from synthetic seismograms the proposed method is thoroughly calibrated using 464 local earthquakes and the results show excellent consistency between the reported ml and the estimated mw we apply the method to northern cascadia tremors and infer that most bursts have mw 1 0 1 7 the corresponding b value appears to be 1 consistent with that of ordinary earthquakes but over a narrower mw range comparison of cumulative tremor mw and the mw estimated from the accompanying slow slip suggests that the seismic efficiency of the episodic tremor and slip ets is of the order of 0 1 or less

a mixed seismic aseismic stress release episode in the andean subduction zone in subduction zones stress is released by earthquakes and transient aseismic slip the latter falls into two categories slow slip and afterslip slow slip events emerge spontaneously during the interseismic phase and show a progressive acceleration of slip with a negligible contribution of synchronous tremors or microseismicity to the energy or moment release1 2 3 4 5 6 7 8 9 10 11 12 in contrast afterslip occurs immediately after large and moderate earthquakes decelerates over time and releases between 20 and 400 of the moment released by the preceding earthquake13 14 15 16 17 18 here we use seismic and gps data to identify transient aseismic slip that does not fit into either of these categories we document a seismic aseismic slip sequence which occurred at shallow depths along a weakly coupled part of the andean subduction zone19 in northern peru and lasted seven months the sequence generated several moderate earthquakes that together account for about 25 of the total moment released during the full sequence equivalent to magnitude 6 7 transient slip immediately followed two of the earthquakes with slip slowing at a logarithmic rate considered separately the moment released by transient slip following the second earthquake was more than 1 000 of the moment released during the earthquake itself a value incompatible with classical models of afterslip synchronous seismic swarms and aseismic slip may therefore define a stress release process that is distinct from slow slip events and afterslip

intraplate lithosphere deformation and the strength of the lithosphere summary the intraplate deformation of continental lithosphere in response to applied stress has been investigated using a mathematical model which incorporates the elastic ductile and brittle response of lithosphere material ductile deformation is assumed to be controlled in the crust by dislocation creep in quartz and in the mantle by dislocation creep and plasticity in olivine brittle failure is predicted using modified griffith theory a fundamental feature of the model is the redistribution of stress within the lithosphere following stress release by both ductile and brittle deformation this redistribution produces high levels of stress in the middle or lower crust immediately above the elastic ductile or brittle ductile transition lithosphere deformation is shown to be critically dependent on the temperature structure of which surface heat flow is a convenient indicator for higher geothermal gradients the release of stress in the lower lithosphere by ductile deformation is more rapid and complete and results in large stress levels in the upper lithosphere for sufficiently large applied stresses or steep geothermal gradients the stress levels in the upper and middle crust will cause complete fracture of the upper lithosphere whole lithosphere failure wlf then results by continued brittle and ductile deformation causing geologically significant strains the critical value of applied stress required to give wlf has been calculated for both tensional and compressional deformation as a function of surface heat flow the predicted lithosphere bulk strength is then compared with expected levels of intraplate stress arising from plate boundary forces and isostatically compensated loads which are thought to give net stress levels in the continental lithosphere in the range 0 25 to 0 25 kb using these expected maximum stress levels the model predicts significant extensional deformation in regions of moderate heat flow with q c 60mwm e g central europe as well as for areas of high heat flow like the basinand range province significant compressional deformation is predicted for areas of high heat flow with q c 75 mwm 2 but only for restricted conditions of stress combination these results are in good agreement with

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

shortening of recurrence interval of boso slow slip events in japan a slow slip event occurred off the coast of the boso peninsula japan from approximately 28 december 2013 to 10 january 2014 the estimated aseismic slip expanded slightly southward and westward over time with a moment magnitude of 6 5 which was the smallest value since 1996 the recurrence interval has decreased from approximately 6 4 to 2 2 years from 1996 to 2014 one explanation of this shortening is the change in coulomb failure stress due to the 2011 mw9 0 tohoku earthquake and its afterslip another interpretation is related to a scenario observed in several numerical simulation studies in which the recurrence interval of slow slip becomes shorter as the time nears a large earthquake this case will constrain the physical processes of a slip cycle the boso slow slip events together with the tohoku earthquake and its afterslip changed the stress state for the anticipated interplate earthquake near the sagami trough

global review of human induced earthquakes the human induced earthquake database hiquake is a comprehensive record of earthquake sequences postulated to be induced by anthropogenic activity it contains over 700 cases spanning the period 1868 2016 activities that have been proposed to induce earthquakes include the impoundment of water reservoirs erecting tall buildings coastal engineering quarrying extraction of groundwater coal minerals gas oil and geothermal fluids excavation of tunnels and adding material to the subsurface by allowing abandoned mines to flood and injecting fluid for waste disposal enhanced oil recovery hydrofracturing gas storage and carbon sequestration nuclear explosions induce earthquakes but evidence for chemical explosions doing so is weak because it is currently impossible to determine with 100 certainty which earthquakes are induced and which not hiquake includes all earthquake sequences proposed on scientific grounds to have been human induced regardless of credibility challenges to constructing hiquake include under reporting which is 30 of m 4 events 60 of m 3 events and 90 of m 2 events the amount of stress released in an induced earthquake is not necessarily the same as the anthropogenic stress added because pre existing tectonic stress may also be released thus earthquakes disproportionately large compared with the associated industrial activity may be induced knowledge of the magnitude of the largest earthquake that might be induced by a project mmax is important for hazard reduction observed mmax correlates positively with the scale of associated industrial projects fluid injection pressure and rate and the yield of nuclear devices it correlates negatively with calculated inducing stress change likely because the latter correlates inversely with project scale the largest earthquake reported to date to be induced by fluid injection is the 2016 m 5 8 pawnee oklahoma earthquake by water reservoir impoundment the 2008 m 8 wenchuan people s republic of china earthquake and by mass removal the 1976 m 7 3 gazli uzbekistan earthquake the minimum amount of anthropogenic stress needed to induce an earthquake is an unsound concept since earthquakes occur in the absence of industrial activity the minimum amount of stress observed to modulate earthquake activity is a few hundredths of a megapascal and possibly as little as a few thousandths equivalent to a few tens of centimeters of water table depth faults near to failure are pervasive in the continental crust and induced earthquakes may thus occur essentially anywhere in intraplate regions neither infrastructure nor populations may be prepared for earthquakes human induced earthquakes that cause nuisance are rare but in some cases may be a significant problem e g in the hydrocarbon producing areas of oklahoma usa as the size of projects and density of populations increase the potential nuisance of induced earthquakes is also increasing and effective management strategies are needed

scaling and spatial complementarity of tectonic earthquake swarms abstract tectonic earthquake swarms tes often coincide with aseismic slip and sometimes precede damaging earthquakes in spite of recent progress in understanding the significance and properties of tes at plate boundaries their mechanics and scaling are still largely uncertain here we evaluate several tes that occurred during the past 20 years on a transform plate boundary in north iceland we show that the swarms complement each other spatially with later swarms discouraged from fault segments activated by earlier swarms which suggests efficient strain release and aseismic slip the fault area illuminated by earthquakes during swarms may be more representative of the total moment release than the cumulative moment of the swarm earthquakes we use these findings and other published results from a variety of tectonic settings to discuss general scaling properties for tes the results indicate that the importance of tes in releasing tectonic strain at plate boundaries may have been underestimated

slow slip slow earthquakes period two cycles full and partial ruptures and deterministic chaos in a single asperity fault abstract the assimilation of geological geophysical and laboratory data in physics based models of fault dynamics promises increasingly realistic simulations of the seismic cycle to assist this effort i explore the dynamics of a single velocity weakening asperity to delineate the relationship between a fault physical properties and the style of faulting during the seismic cycle based on a micro physical model of rate and state friction from a dimensional analysis four non dimensional parameters control the characteristics of slip events and the behavior during the interseismic period including the dieterich ruina rice number ru which is proportional to the ratio of asperity to critical nucleation size w h and rb b a b where a and b control the direct and local evolutionary effects respectively for sufficiently large rb the ru number controls the spectrum of fault slip from periodic slow slip events to aperiodic fast ruptures in finite faults but not in semi infinite faults the transition between these end members includes a bifurcation that involves period two period four period six cycles and deterministic chaos with increasing ru macroscopic fault slip is stabilized as rb vanishes even as ru 1 for finite faults but not for semi infinite faults the transition between slow and fast ruptures for increasing rb includes another type of bifurcation with period two and period four cycles of slow and fast ruptures for 0

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

large scale geomorphology classical concepts reconciled and integrated with contemporary ideas via a surface processes model linear systems analysis is used to investigate the response of a surface processes model spm to tectonic forcing the spm calculates subcontinental scale denudational landscape evolution on geological timescales 1 to hundreds of million years as the result of simultaneous hillslope transport modeled by diffusion and fluvial transport modeled by advection and reaction the tectonically forced spm accommodates the large scale behavior envisaged in classical and contemporary conceptual geomorphic models and provides a framework for their integration and unification the following three model scales are considered micro meso and macroscale the concepts of dynamic equilibrium and grade are quantified at the microscale for segments of uniform gradient subject to tectonic uplift at the larger meso and macroscales which represent individual interfluves and landscapes including a number of drainage basins respectively the system response to tectonic forcing is linear for uplift geometries that are symmetric with respect to baselevel and which impose a fully integrated drainage to baselevel for these linear models the response time and the transfer function as a function of scale characterize the model behavior numerical experiments show that the styles of landscape evolution depend critically on the timescales of the tectonic processes in relation to the response time of the landscape when tectonic timescales are much longer than the landscape response time the resulting dynamic equilibrium landscapes correspond to those envisaged by hack 1960 when tectonic timescales are of the same order as the landscape response time and when tectonic variations take the form of pulses much shorter than the response time evolving landscapes conform to the penck type 1972 and to the davis 1889 1899 and king 1953 1962 type frameworks respectively the behavior of the spm highlights the importance of phase shifts or delays of the landform response and sediment yield in relation to the tectonic forcing finally nonlinear behavior resulting from more general uplift geometries is discussed a number of model experiments illustrate the importance of fundamental form which is an expression of the conformity of antecedent topography with the current tectonic regime lack of conformity leads to models that exhibit internal thresholds and a complex response

microseismicity but no tremor accompanying slow slip in the hikurangi subduction zone new zealand abstract geodetically detected episodes of slow slip appear in several subduction zones to be accompanied by bursts of low frequency coherent noise known as seismic tremor but whether a single physical process governs this association or even whether slow slip is invariably accompanied by tremor remains unresolved detailed analysis of broadband seismic data spanning a slow slip episode in the hikurangi subduction zone new zealand reveals that slow slip was accompanied by distinct reverse faulting microearthquakes rather than tremor the timing location and faulting style of these earthquakes are consistent with stress triggering down dip of the slow slip patch either on the subduction interface or just below it these results indicate that tremor is not ubiquitous during subduction zone slow slip and that slow slip in subduction zone environments is capable of triggering high frequency earthquakes near the base of the locked subduction thrust in this and other locations hawaii boso peninsula where slow slip is accompanied by triggered microseismicity the estimated upper extent of the slow slip is shallower less than 20 km than in those locations from which tremor has been reported this suggests that ambient temperature or pressure dependent factors govern the character of the seismic response to slow slip on subduction thrusts and other large faults with rheological or lithological conditions at shallow depths triggering high frequency microearthquakes and those at greater depths triggering seismic tremor

a nonplanar slow rupture episode during the 2000 miyakejima dike intrusion magmatic intrusions release extensional strain in the earth s crust upon availability of magma intrusions are typically accompanied by earthquake swarms and by surface faulting that is often larger than what is expected from the magnitude of the induced earthquakes the 2000 miyakejima dike intrusion triggered the largest volcanic earthquake swarm monitored so far with five ml 6 earthquakes we analyze the seismicity and deformation induced by the miyakejima dike with the aim of constraining the timescale and mechanisms of slow strain release during the episode in six earthquake bursts lasting few hours and migrating at 1 km h 1 we find candidates for slow earthquakes each burst nucleated at the tips of previous bursts suggesting stress interaction the variability of fault plane solutions indicates that the bursts occurred on a complex system of fractures consistent with weakly consolidated surface layers strained by spatially inhomogneous stresses that change in time such as those induced by a dike based on dislocation models we find that deformation is best explained by aseismic slip in addition to the seismic burst with a moment 1 3 to 2 3 times larger than the earthquakes seismic moment and opening of 0 20 0 07 m on the dike the aseismic slip occurred over a few hours with moment duration and migration velocity consistent with that of previously observed slow slip events we argue that the seismic bursts are likely driven by slow slip sharing most properties with tectonic slow slip events and swarms but occurring on a set of nonaligned faults

collision tectonics in the swiss alps insight from geodynamic modeling this paper compares results from two dimensional finite element dynamic modeling with the kinematic evolution of the swiss alps during the collision phase in particular we investigate the role of inherited lateral strength heterogeneities on orogenesis a number of first order characteristics are directly comparable at crustal scales in the models the entry of continental crust into the convergent margin marks the end of near perfect subduction accretion of material of the subducting plate to the upper plate creates an orogenic wedge on the incoming pro side and initiates a retroshear zone or model backthrust the addition of material to the upper plate builds a bivergent orogen heterogeneities in the pro crust focus shear and lead to the development of nappe structures the combined action of pro shear nappe stacking and retroshear backthrusting uplifts a plug between the two shear zones subsequent focusing of shear along the retroshear zone results in rotation of the plug and overlying units leading to crustal scale backfolds as observed in the swiss alps the model experiments predict features relevant to alpine dynamics including 1 similar crustal thicknesses and exhumation patterns to those observed in the swiss alps today for erosion rates comparable to natural ones 1 mm yr 1 2 continued accretion and subduction of upper crustal fragments allowing high pressure metamorphic conditions 3 tilting and exhumation of lower crust when a midcrustal weak zone is present and 4 shunting of material across the strong lower crustal wedge of the upper plate

the november 20 1960 peru tsunami earthquake source mechanism of a slow event the november 20 1960 peru earthquake excited a tsunami that was anomalously large for an earthquake of moderate magnitude m 6 75 pas body wave first motions combined with observed love to rayleigh wave spectral ratios indicate slip along a shallowly dipping thrust fault rather than a single force mechanism suggestive of a landslide deconvolution of sh waveforms shows a time function consisting of 4 subevents with a total duration of 110 s using this time function body waveform inversion yields a very shallowly dipping thrust faulting mechanism strike 0 dip 6 slip 100 and a seismic moment of 1 9 1027 dyn cm however the time function obtained from the band limited body waveforms cannot fit the surface wave data which show a large increase in amplitude with period and a moment of 3 4 1027 dyn cm both types of data can be modeled by combining the body wave time function and a 130 s cosine time function representing a longer period component this event represents the largest earthquake to occur along this relatively aseismic portion of the peruvian coast the tsunami excitation is not anomalous relative to the measured seismic moment and moment magnitude mw 7 6 the disparity between tsunami height and surface wave magnitude results from underestimation of the earthquake size by conventional magnitude scales due to the long source duration

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

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

slab1 0 a three dimensional model of global subduction zone geometries 1 we describe and present a new model of global subduction zone geometries called slab1 0 an extension of previous efforts to constrain the two dimensional non planar geometry of subduction zones around the focus of large earthquakes slab1 0 describes the detailed non planar three dimensional geometry of approximately 85 of subduction zones worldwide while the model focuses on the detailed form of each slab from their trenches through the seismogenic zone where it combines data sets from active source and passive seismology it also continues to the limits of their seismic extent in the upper mid mantle providing a uniform approach to the definition of the entire seismically active slab geometry examples are shown for two well constrained global locations models for many other regions are available and can be freely downloaded in several formats from our new slab1 0 website http on doi gov d9arbs we describe improvements in our two dimensional geometry constraint inversion including the use of average active source seismic data profiles in the shallow trench regions where data are otherwise lacking derived from the interpolation between other active source seismic data along strike in the same subduction zone we include several analyses of the uncertainty and robustness of our three dimensional interpolation methods in addition we use the filtered subduction related earthquake data sets compiled to build slab1 0 in a reassessment of previous analyses of the deep limit of the thrust interface seismogenic zone for all subduction zones included in our global model thus far concluding that the width of these seismogenic zones is on average 30 larger than previous studies have suggested

modulation of fault strength during the seismic cycle by grain size evolution around contact junctions abstract earthquake prediction is fundamentally hampered by insufficient knowledge of the constitutive behavior of faults laboratory and theoretical work by dieterich 1978 and ruina 1983 formed the basis of rate and state friction a constitutive framework that captures the healing and weakening of frictional contacts the rate and state law successfully explains the frictional behavior of a wide range of rocks and many phenomena associated with fault slip the physics underlying the rate and state friction law is not fully understood but it is generally accepted that several micro mechanisms operate depending on the texture maturity fluid content and other physical and kinematic conditions of the fault here i formulate a constitutive framework that unifies a number of laboratory experiments on silicate rocks and the gouges derived from these rocks that describe the effect of grain size temperature real area of contact gouge thickness and fault roughness fundamental to the model is that fault strength is controlled by the area of the interfacial contact junctions that support the shear and normal loads the curvature of asperities weakly controls the area of their contact junction and the resulting fault strength as a result the dynamics of grain size evolution around micro asperities enables the seismic cycle the model quantitatively explains the correlation between the characteristic weakening distance and the gouge thickness marone and kilgore 1993 the correlation of the static friction coefficient with the rate dependence parameters ikari et al 2011 the dependence of frictional resistance to sub solidus temperatures chester 1994 and predicts a range of grain sizes that is compatible with observations at exposed fault zones however the dynamics of grain size evolution is still challenging to verify experimentally the model features a regularization at vanishing slip speeds that implies distinct dynamics at low strength for friction coefficients lower than 0 1 seismic cycle simulations predict the emergence of frictional instabilities with complex source time functions this is a significant departure from the predictions of rate and state friction that is most relevant to the dynamics of decollements serpentinized shear zones and other low strength faults

nonvolcanic tremor evolution and the san simeon and parkfield california earthquakes nonvolcanic tremors occur adjacent to locked faults and may be closely related to the generation of earthquakes monitoring of the san andreas fault in the parkfield california region revealed that after two strong earthquakes tremor activity increased in a nearly dormant tremor zone increased and became periodic in a previously active zone and has remained elevated and periodic for over 4 years static shear and coulomb stress increases of 6 to 14 kilopascals from these two earthquakes are coincident with sudden increases in tremor rates the persistent changes in tremor suggest that stress is now accumulating more rapidly beneath this part of the san andreas fault which ruptured in the moment magnitude 7 8 ft tejon earthquake of 1857

erosion as a driving mechanism of intracontinental mountain growth in nature mountains can grow and remain as localized tectonic features over long periods of time 10 m y by contrast according to current knowledge of lithospheric rheology and neglecting surface processes any intracontinental range with a width that exceeds that which can be supported by the strength of the lithosphere should collapse within a few tens of millions of years for example assuming a quartz dominated crustal rheology the relief of a range initially 3 km high and 300 400 km wide is reduced by half in about 15 m y as a result of lateral spreading of its crustal root we suggest that surface processes might actually prevent such a subsurface collapse removal of material from topographic heights and deposition in the foreland oppose spreading of the crustal root and could eventually drive a net influx of material toward the orogeny we performed a set of numerical experiments in order to validate this hypothesis a section of a lithosphere with a brittle elasto ductile rheology initially loaded by a mountain range is submitted to horizontal shortening and to surface processes if erosion is intense material is removed more rapidly than it can be supplied by crustal thickening below the range and the topography is rapidly smoothed for example a feature 3 km high and 300 400 km wide is halved in height in about 15 m y for an erosion coefficient k 10 3 m 2 yr the erosion rate is of the order of a few 0 1 mm yr this regime might be called erosional collapse if erosion is not active enough the crustal root spreads out laterally and subsurface collapse occurs in the third intermediate regime removal of the material by erosion is dynamically compensated by isostatic rebound and inward flow in the lower crust so that the range can grow in this mountain growth regime the range evolves toward a characteristic graded shape that primarily depends on the erosion law the erosion rate may be high e g 0 5 0 9 mm yr close to the rate of tectonic uplift e g 0 7 1 1 mm yr and few times higher than the rate of topographic uplift 0 15 0 2 mm yr these experiments show that surface processes can favor localized crustal shortening and participate in the development of an intracontinental mountain surface processes must therefore be taken into account in the interpretation and modeling of long term deformation of continental lithosphere conversely the mechanical response of the lithosphere must be accounted for when large scale topographic features are interpreted and modeled in terms of geomorphologic processes

seismic and aseismic slip on the central peru megathrust slip on a subduction megathrust can be seismic or aseismic with the two modes of slip complementing each other in time and space to accommodate the long term plate motions although slip is almost purely aseismic at depths greater than about 40 km heterogeneous surface strain suggests that both modes of slip occur at shallower depths with aseismic slip resulting from steady or transient creep in the interseismic and postseismic periods thus active faults seem to comprise areas that slip mostly during earthquakes and areas that mostly slip aseismically the size location and frequency of earthquakes that a megathrust can generate thus depend on where and when aseismic creep is taking place and what fraction of the long term slip rate it accounts for here we address this issue by focusing on the central peru megathrust we show that the pisco earthquake with moment magnitude m w 8 0 ruptured two asperities within a patch that had remained locked in the interseismic period and triggered aseismic frictional afterslip on two adjacent patches the most prominent patch of afterslip coincides with the subducting nazca ridge an area also characterized by low interseismic coupling which seems to have repeatedly acted as a barrier to seismic rupture propagation in the past the seismogenic portion of the megathrust thus appears to be composed of interfingering rate weakening and rate strengthening patches the rate strengthening patches contribute to a high proportion of aseismic slip and determine the extent and frequency of large interplate earthquakes aseismic slip accounts for as much as 50 70 of the slip budget on the seismogenic portion of the megathrust in central peru and the return period of earthquakes with m w 8 0 in the pisco area is estimated to be 250 years

dominant controls of downdip afterslip and viscous relaxation on the postseismic displacements following the mw7 9 gorkha nepal earthquake author s zhao b burgmann r wang d tan k du r zhang r abstract 2017 american geophysical union all rights reserved we analyze three dimensional gps coordinate time series from continuously operating stations in nepal and south tibet and calculate the initial 1 year postseismic displacements we first investigate models of poroelastic rebound afterslip and viscoelastic relaxation individually and then attempt to resolve the trade offs between their contributions by evaluating the misfit between observed and simulated displacements we compare kinematic inversions for distributed afterslip with stress driven afterslip models the modeling results show that no single mechanism satisfactorily explains near and far field postseismic deformation following the gorkha earthquake when considering contributions from all three mechanisms we favor a combination of viscoelastic relaxation and afterslip alone as poroelastic rebound always worsens the misfit the combined model does not improve the data misfit significantly but the inverted afterslip distribution is more physically plausible the inverted afterslip favors slip within the brittle ductile transition zone downdip of the coseismic rupture and fills the small gap between the mainshock and largest aftershock slip zone releasing only 7 of the coseismic moment our preferred model also illuminates the laterally heterogeneous rheological structure between india and the south tibet the transient and steady state viscosities of the upper mantle beneath tibet are constrained to be greater than 1018 pa s and 1019 pa s whereas the indian upper mantle has a high viscosity 1020 pa s the viscosity in the lower crust of southern tibet shows a clear trade off with its southward extent and thickness suggesting an upper bound value of 8 1019 pa s for its steady state viscosity

lithospheric folding in iberia integration of stress indicator data gravity data crustal kinematics data and analysis of topography and recent vertical motions demonstrates the occurrence of consistently oriented spatial patterns of large scale alpine to recent intraplate deformation in iberia the inferred upper crustal and lithospheric deformation patterns and the timing of the associated expressions at or near the surface support the existence of a close coupling with plate boundary processes operating at the margins of iberia patterns of lithosphere and upper crustal folds are oriented perpendicular to the main axis of present day intraplate compression in iberia inferred from structural analysis of stress indicator data and focal mechanism solutions these findings suggest the presence of lithospheric folds with wavelengths compatible with theoretical predictions of folding wavelengths of variscan lithosphere stress induced intraplate deformation set up by plate interactions is compatible with indications for the absence of present day deep mantle lithosphere interactions inferred from seismic tomography

aftershocks driven by afterslip and fluid pressure sweeping through a fault fracture mesh a variety of physical mechanisms are thought to be responsible for the triggering and spatiotemporal evolution of aftershocks here we analyze a vigorous aftershock sequence and postseismic geodetic strain that occurred in the yuha desert following the 2010 m w 7 2 el mayor cucapah earthquake about 155 000 detected aftershocks occurred in a network of orthogonal faults and exhibit features of two distinct mechanisms for aftershock triggering the earliest aftershocks were likely driven by afterslip that spread away from the main shock with the logarithm of time a later pulse of aftershocks swept again across the yuha desert with square root time dependence and swarm like behavior together with local geological evidence for hydrothermalism these features suggest that the events were driven by fluid diffusion the observations illustrate how multiple driving mechanisms and the underlying fault structure jointly control the evolution of an aftershock sequence

the strength of intraplate lithosphere abstract the deformation of intraplate lithosphere in response to laterally applied stress has been investigated using a mathematical model of the elastic brittle and viscous response of the lithosphere fundamental to the model is the conservation of the horizontal force associated with the applied stress and the redistribution of stress within the lithosphere after stress release by ductile or brittle failure ductile deformation is assumed to be controlled by dislocation creep in quartz in the crust and by dislocation and dorn law creep in olivine in the mantle brittle failure is predicted using griffith theory the redistribution of stress after brittle and ductile deformation results in large levels of stress in the middle and lower crust immediately above the elastic ductile or brittle ductile transition lithosphere deformation is controlled critically by the lithosphere thermal structure of which surface heat flow q is taken as a convenient indicator for hotter lithosphere stress release by ductile deformation in the middle and lower lithosphere is more extensive and rapidly leads to larger levels of stress in the upper lithosphere for sufficiently large levels of applied stress or sufficiently hot lithosphere complete failure whole lithosphere failure of the lithosphere occurs by ductile and brittle deformation resulting in geologically significant strains critical levels of applied stress required to produce whole lithosphere failure have been computed as a function of the lithosphere surface heat flow the predicted strength of the lithosphere has been compared with expected levels of intraplate stress arising from plate boundary forces and isostatically compensated loads the model predicts significant extensional intraplate deformation in regions of moderate heat flow with q 60 m w m 2 for compressional deformation however a hotter lithosphere is required with q c 75 m w m 2 the model predictions are in general agreement with the comparatively widespread occurrence of extensional intraplate deformation and the restricted occurrence of compressional deformation the model has also been used to investigate the relationship between the depth of the brittle ductile transition and lithosphere temperature structure the brittle ductile transition depth is shown to become shallower with increasing heat flow in good agreement with seismic evidence

himalayan tectonics explained by extrusion of a low viscosity crustal channel coupled to focused surface denudation recent interpretations of himalayan tibetan tectonics have proposed that channel flow in the middle to lower crust can explain outward growth of the tibetan plateau1 2 3 and that ductile extrusion of high grade metamorphic rocks between coeval normal and thrust sense shear zones can explain exhumation of the greater himalayan sequence4 5 6 7 here we use coupled thermal mechanical numerical models to show that these two processes channel flow and ductile extrusion may be dynamically linked through the effects of surface denudation focused at the edge of a plateau that is underlain by low viscosity material our models provide an internally self consistent explanation for many observed features of the himalayan tibetan system8 9 10

unraveling topography around subduction zones from laboratory models the relief around subduction zones results from the interplay of dynamic processes that may locally exceed the iso static contributions the viscous dissipation of the energy in and around subduction zones is capable of generating kilometer scale vertical ground movements in order to evaluate dynamic topography in a selfconsistent subduction system we carried out a set of laboratory experiments wherein the lithosphere and mantle are simulated by means of newtonian viscous materials namely silicone putty and glucose syrup models are kept in their most simple form and are made of negative buoyancy plates of variable width and thickness freely plunging into the syrup the surface of the model and the top of the slab are scanned in three dimensions a forebulge systematically emerges from the bending of the viscous plate adjacent to the trench with a large wavelength dynamic pressure offsets the foreside and backside of the slab by 500 m on average the suction that accompanies the vertical descent of the slab depresses the surface on both sides at a distance equal to the half width of the slab the topographic depression amounts to 500 m on average and becomes negligible at a distance that equals the width of the slab in order to explore the impact of slab rollback on the topography the trailing edge of the plates is alternatively fixed to fixed mode and freed from free mode the end wall of the tank both the pressure and suction components of the topography are 30 lower in the free mode indicating that slab rollback fosters the dynamic subsidence of upper plates our models are compatible with first order observations of the topography around the east scotia tonga kermadec and banda subduction zones which exhibit anomalous depths of nearly 1 km as compared to adjacent sea floor of comparable age

break of slope in earthquake size distribution and creep rate along the san andreas fault system crustal faults accommodate slip either by a succession of earthquakes or continuous slip and in most instances both these seismic and aseismic processes coexist recorded seismicity and geodetic measurements are therefore two complementary data sets that together document ongoing deformation along active tectonic structures here we study the influence of stable sliding on earthquake statistics we show that creep along the san andreas fault is responsible for a break of slope in the earthquake size distribution this slope increases with an increasing creep rate for larger magnitude ranges whereas it shows no systematic dependence on creep rate for smaller magnitude ranges this is interpreted as a deficit of large events under conditions of faster creep where seismic ruptures are less likely to propagate these results suggest that the earthquake size distribution does not only depend on the level of stress but also on the type of deformation

holographic measurements of surface topography in laboratory models of mantle hotspots summary the evolution of surface topography produced by the rise of a buoyant droplet or diapir towards the free surface of a very viscous fluid in laboratory experiments is monitored using holographic interferometry such experiments enable us to investigate implications for surface topography of one possible unsteady model for intraplate hotspots the arrival of mantle thermals or diapirs near the base of the earth s lithosphere our model is possibly of most direct relevance to the interaction with the earth s surface and lithosphere of large spherical caps that are expected to rise at the head of new mantle plumes to previous experimental results for the axial height of topography olson nam we add further information on the height shape and width of the surface swell and on the evolution of the diapir itself when the ambient fluid has uniform density and viscosity no lithosphere surface topography is determined by the diameter density anomaly and depth of the droplet as the diapir approaches the surface a broad axisymmetric surface swell appears and initially increases in height while decreasing in width when the leading edge of the diapir is 0 2 diapir diameters below the surface the height passes through a maximum and the width through a minimum the swell then proceeds to subside and increase in width as the diapir spreads beneath the surface in separate experiments the lithosphere is modelled by a discrete surface layer of more viscous fluid whose thickness and viscosity contrast with the mantle are treated as independent parameters effects of lithosphere buoyancy relative to the mantle a property which may influence continental hotspot swells are also studied within the parameter range used the maximum swell height is independent of the lithosphere viscosity contrast but decreases with increasing lithosphere thickness and with decreasing lithosphere density surface uplift produced by the rise of two consecutive diapirs is shown to be more complex comparison of results with the characteristics of hotspot swells is attempted and should assist in determining the nature of hotspot plumes

erosional control on the structural evolution of a transpressional thrust complex on the alpine fault new zealand abstract the waikukupa thrust is a 4 km long oblique thrust segment of the new zealand alpine fault that has developed over the last 65 000 years emplacing mylonite and cataclasite over fluvioglacial gravel during the last 20 000 years or so a 2 km long out of sequence imbricate the hare mare thrust has formed on the east side of the waikukupa river valley the average rate of slip on the two thrusts is estimated at 22 30 mm year analysis of the fault structure in terms of critical wedge theory is consistent with imbrication resulting from a reduction in wedge taper below the critical value due to rapid river erosion the internal structure of the waikukupa thrust sheet consists of reverse faults and angular folds forming duplex like systems associated with minor strike slip faults within the limits of uncertainty the structures are consistent with strain accumulating during internal transpressional shear of the thrust sheet while the taper of the latter was subcritical prior to the transfer of fault displacement to the hare mare imbricate the thrust complex forms part of a serrated range front fault system consisting of oblique thrust sections linked by strike slip faults we introduce the term serial partitioning for this type of partitioned transpressional fault system its development is linked to the erosional processes at the range front an alternative system consisting of parallel thrust and strike slip faults we here term parallel partitioning while angle of obliquity is an important parameter in determining which partitioning model develops we suggest that erosion rate is also an influential factor

impact of the lithosphere on dynamic topography insights from analogue modeling density anomalies beneath the lithosphere are expected to generate dynamic topography at the earth s surface due to the induced mantle flow stresses which scale linearly with density anomalies while the viscosity of the upper mantle is expected to control uplift rates however limited attention has been given to the role of the lithosphere here we present results from analogue modeling of the interactions between a density anomaly rising in the mantle and the lithosphere in a newtonian system we find that for instabilities with wavelengths of the same order of magnitude as lithosphere thickness the uplift rate and the geometry of the surface bulge are inversely correlated to the lithosphere thickness we also show that a layered lithosphere may modulate the topographic signal with respect to previous approaches our models represent a novel attempt to unravel the way normal stresses generated by mantle flow are transmitted through a rheologically stratified lithosphere and the resulting topographic signal

two sided orogen collision and erosion from the sandbox to the southern alps new zealand in continental collision zones the indentor is of approximately the same vertical dimension as the material being deformed thereby allowing material to move over the indentor and out of the deforming orogen this simple constraint on the height of the indentor differs from that imposed by the bulldozer model of wedge deformation and results in the formation of an orogen with two opposite dipping topographic slopes these two wedges are mechanically coupled and the mechanics are strongly influenced by the erosion conditions imposed on the wedge where the growing mountains perturb prevailing moisture laden winds the erosion pattern is highly asymmetric erosional work being concentrated at the toe of the steep wedge facing the indentor the inboard wedge concentration of erosional energy results in concentration of mechanical energy in the same region and produces the distinctive geological and geophysical patterns associated with continental collision these include rapid uplift and exposure of deep crustal assemblages adjacent to the indentor accompanied by high crustal heat flow and anomalously low seismicity the outcrop pattern along the inboard wedge evolves from that of a crustal cross section currently exposed in the southern alps to one dominated by repetitive nappe structures consisting predominantly of lower crustal units as in the western alps of europe the other wedge the outboard wedge undergoes relatively little erosion is broad with a more gentle surface slope and maintains an outcrop pattern consisting of upper crustal material

time dependent inversion study of the slow thrust event in the nankai trough subduction zone southwestern japan we estimate time variation of interplate coupling between the subducting philippine sea and the overriding continental plates along the western part of the nankai trough japan during the period between 1996 and 1999 after subtracting annual components and average annual velocities deviation from steady crustal deformation in the shikoku and kyushu islands is examined around 15 gps stations facing the bungo channel detected the following three stage ground displacements of up to 3 cm in 1997 with a duration of 1 year 1 increased displacement rate associated with the 1996 hyuga nada earthquakes 2 an increasingly rapid anomalous period of deformation from june 1997 to the end of 1997 and 3 a slowdown period and return to normal rates of deformation after the end of 1997 linearized least squares locate the slip area of this slow event near the plate boundary beneath the bungo channel the estimated slip is opposite the motion of the philippine sea plate these results support the hypothesis that the observed anomalous caistal deformation is due to a rebound process of the philippine sea plate time dependent inversion analysis shows the following slip history during the initial period of increased displacement rate a visible slip area is resolved beneath the coastal area of southwestern shikoku in the next stage of accelerated displacements the slip area expanded southwestward to the bungo channel beginning around june 1997 when postseismic slip of the 1996 hyuga nada earthquakes almost ended after this accelerated period the estimated thrust slip ends with time

thrust geometry controlled by erosion and sedimentation a view from analogue models analogue sandbox models have been set up to study thrust systems formed above two decollements and affected by erosion and sedimentation the deformation was imaged by x ray scanner three erosion sedimentation conditions were tested for all the experiments a duplex develops between the two decollement levels for the experiment without erosion and without sedimentation ramp anticlines form in the upper series for the model with syntectonic sedimentation and without erosion the shortening in the upper series is first characterized by fault related folds and then by a forward propagation of the decollement that induces the development of a piggy back basin for the experiment with erosion and sedimentation a passive roof duplex is formed relationships between structural style and syntectonic superficial conditions in classical thin skinned thrust belts are similar to those found in the analogue models the ramp anticlines of the jura developed with low erosion and low sedimentation and the large sub andean thrust belt is controlled by syntectonic sedimentation whereas the passive roof duplex of pakistan is synchronized with intense erosion this study outlines the crucial effect of the superficial mass transport phenomena in the tectonic style of thrust belts

intense interface seismicity triggered by a shallow slow slip event in the central ecuador subduction zone we document a 1 week long slow slip event sse with an equivalent moment magnitude of 6 0 6 3 which occurred in august 2010 below la plata island ecuador south of the rupture area of the 1906 mw 8 8 megathrust earthquake gps data reveal that the sse occurred at a depth of about 10 km within the downdip part of a shallow 15 km isolated locked patch along the subduction interface the availability of both broadband seismometer and continuous geodetic station located at the la plata island 10 km above the sse enables a careful analysis of the relationships between slow and rapid processes of stress release along the subduction interface during the slow slip sequence the seismic data show a sharp increase of the local seismicity with more than 650 earthquakes detected among which 50 have a moment magnitude between 1 8 and 4 1 however the cumulative moment released through earthquakes accounts at most for 0 2 of the total moment release estimated from gps displacements most of the largest earthquakes are located along or very close to the subduction interface with focal mechanism consistent with the relative plate motion while the earthquake sizes show a classical distribution gutenberg richter law with a b value close to 1 the space time occurrence presents a specific pattern first the largest earthquakes appear to occur randomly during the slow slip sequence which further evidence that the seismicity is driven by the stress fluctuations related to aseismic slip moreover the seismicity observed during the sse consists in individual events and families of repeating earthquakes these observations indicate that the stress increment induced by the episodic aseismic slip may lead both to sudden seismic moment release and to progressive rupture within small locked patches this study offers an a posteriori interpretation of the seismogenesis in the central ecuador subduction zone where intense seismic swarms have been regularly observed 1977 1998 2002 and 2005 these swarms have likely been triggered by large magnitude slow slip events

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

how and when did the yellow river develop its square bend the current course of the yellow river china involves an unusual 1500 km long angular bend around the ordos tectonic block although sedimentary evidence suggests that the river once followed a more direct path eastward into the bohai sea geologic evidence reveals that the yellow river formed in the eocene as an eastward draining river and developed its square bend around the ordos block in late miocene early pliocene time as a result of folding and uplift that are most probably related to the collision and penetration of india into eurasia as well as rifting around the ordos block the change in course of the yellow river predates flat lying pliocene pleistocene sediment deposits that unconformably overlie folded eocene miocene strata the yellow river provides a typical example of tectonic controls on the size morphology and longevity of rivers

interplay between tectonics climate and fluvial transport during the cenozoic evolution of the ebro basin ne iberia 1 three dimensional modeling that integrates fluvial sediment transport crustal scale tectonic deformation and lithospheric flexural subsidence is carried out to simulate the landscape and drainage evolution of the ebro sedimentary basin ne iberia the ebro basin underwent a long period of closed intramountain drainage as a result of tectonic topography generation at the pyrenees the iberian range and the catalan coastal range in the late oligocene the catalan coastal range underwent extension leading to the formation of the valencia trough nw mediterranean but the ebro basin remained closed for nearly 15 myr more before the ebro river cut through the remnants of the topographic barrier this drainage opening caused widespread basin incision that shaped spectacular outcrops of the syntectonic and posttectonic infill here we investigate the processes controlling these major drainage changes the modeling results constrained by a large data set on the tectonic and transport evolution of the area predict a closed phase characterized by a large lake in the central eastern ebro basin dry climatic conditions probably lowered the lake level and contributed together with rift flank uplift to prolong this endorheic basin stage the age and amount of reworked sediment after the opening are consistent with an onset of basin incision between 13 and 8 5 ma as a result of lake capture by escarpment erosion and lake level rise associated with sediment accumulation and wetter climatic conditions sea level changes in the mediterranean had no major impact in the large scale drainage evolution of the ebro basin index terms 1625 global change geomorphology and weathering 1824 1886 1815 hydrology erosion and sedimentation 3210 mathematical geophysics modeling 3344 meteorology and atmospheric dynamics paleoclimatology 8102 tectonophysics continental contractional orogenic belts keywords pyrenees drainage evolution lake sediment budget erosion flexure

tidal modulation of slow slip in cascadia 1 several studies have shown that the seismic tremor in episodic tremor and slip is tidally modulated suggesting a sensitivity to the rather small tidal stresses we address whether the slip rate in slow slip events is also tidally modulated by examining data from six borehole strainmeters in northwest washington and southern vancouver island we simultaneously fit data from multiple stations and from slow slip events occurring over a 3 year interval from january 2007 to june 2009 as we are unable to extract a meaningful signal from a single record we find modulation of the strain rate with a 12 4 h period that of the tide with the largest amplitude that is significant at the 99 level the amplitude of this modulation suggests that the slip rate during slow slip events oscillates on average 25 above and below its mean value during a tidal cycle tidal modulation estimates at three other periods are significant with more than 70 probability the phase of maximum strain rate in the 12 4 h m2 period coincides with the phase of the maximum tremor rate taken from a catalog in an overlapping region comparison with a simple tidal loading model shows that the phase of maximum strain rate in the m2 period may occur at the maximum shear stress or up to 90 before it depending on the location of slip in the subduction zone

orogeny and metamorphism a model for deformation and pressure temperature time paths with applications to the central and southern appalachians a model is presented for deformation uplift and exhumation in convergent orogens based on the following premises 1 foreland basin subsidence monitors the distribution in time and space of overthrust loads added to an orogen 2 the presence of an inherited rifted margin plays an important role in the subsequent history of an orogen by forming a basement ramp or buttress that must be surmounted in order for thrusts to advance on the craton on the seaward side of this transition up to 20 km of overthrusts can be accumulated without creating topography 3 critical shape theory can be applied to orogens as a whole allowing predictions to be made concerning dynamic balance between mass addition and loss uplift exhumation and growth of topography and 4 pressure temperature time p t t data can be used to reconstruct particle paths within the deforming orogen three states of overthrust orogens can be defined based on the relative rates of mass loss and mass addition as monitored by the foreland rapid exhumation of metamorphic terranes is most likely in the steady state where erosion balances accretion a constructive state where mass addition is greater than mass loss results in crustal thickening and initially little exhumation a destructive state where mass loss outweighs mass addition results in slow exhumation or subsidence of metamorphic rocks in the orogen depending on whether mass is removed by erosion or by extension p t t data on peak metamorphism pluton emplacement uplift exhumation and cooling can be used in conjunction with data from the foreland to distinguish among these various states the topography and strength of the inherited rifted margin play an important role in localizing zones of exhumation and uplift within the orogen application of this model to the central and southern appalachians suggests that during the constructive phases of the taconian and acadian orogenies overthrust loads accumulated mainly on the seaward side of the ocean continent transition as marked by the bouguer gravity gradient between the acadian and alleghanian orogenies the appalachian orogen was probably in a steady state with uplift and exhumation of rocks in the orogen but little subsidence of the foreland or advance of thrusts toward the craton the constructive stage of the alleghanian orogeny achieved the critical topography necessary to drive crystalline thrust sheets over the craton this resulted in widespread uplift and westward transport of older metamorphic rocks post orogenic unroofing of the southern appalachians is compatible with the predictions of flexural models the post orogenic unroofing history of the central appalachians and ouachitas probably reflects mesozoic extension in these areas

active tectonics of peru heterogeneous interseismic coupling along the nazca megathrust rigid motion of the peruvian sliver and subandean shortening accommodation over 100 gps sites measured in 2008 2013 in peru provide new insights into the present day crustal deformation of the 2200 km long peruvian margin this margin is squeezed between the eastward subduction of the oceanic nazca plate at the south america trench axis and the westward continental subduction of the south american plate beneath the eastern cordillera and subandean orogenic wedge continental active faults and gps data reveal the rigid motion of a peruvian forearc sliver that extends from the oceanic trench axis to the western eastern cordilleras boundary and moves southeastward at 4 5 mm yr relative to a stable south america reference frame gps data indicate that the subandean shortening increases southward by 2 to 4 mm yr in a peruvian sliver reference frame the residual gps data indicate that the interseismic coupling along the nazca megathrust is highly heterogeneous coupling in northern peru is shallow and coincides with the site of previous moderate sized and shallow tsunami earthquakes deep coupling occurs in central and southern peru where repeated large and great megathrust earthquakes have occurred the strong correlation between highly coupled areas and large ruptures suggests that seismic asperities are persistent features of the megathrust creeping segments appear at the extremities of great ruptures and where oceanic fracture zones and ridges enter the subduction zone suggesting that these subducting structures play a major role in the seismic segmentation of the peruvian margin in central peru we estimate a recurrence time of 305 40 years to reproduce the great 1746 mw 8 8 lima callao earthquake

climate exposed source rock lithologies crustal uplift and surface erosion a theoretical analysis calibrated with data from the alps north alpine foreland basin system paleofloristic data imply that paleoclimate changed in the swiss alps at the oligocene miocene boundary from humid and hot conditions toward a climate with high temperature and low humidity the aridization is associated with a change in depositional pattern from alluvial fans to lakes and floodplains suggesting decreasing sediment discharge a further 25 40 decrease of sediment discharge occurred at ca 20 ma when the orogenic core of the alps became exposed to the surface we applied a surface processes model to explore potential controls on the pattern of sediment discharge and on the evolution of the alpine drainage basin the model is based on the presumption that the rates of fluvial incision into bedrock are proportional to shear stress exerted by the flowing water the model results imply that the paleoclimate change resulted in an instantaneous decrease of sediment discharge and a vertical topographic growth until steady state conditions between erosional and crustal mass flux are established however exposure of the crystalline core of the alps at ca 20 ma is likely to have resulted in the 25 40 decrease of sediment discharge and the reorganization of the drainage pattern from an orogen normal to an orogen parallel orientation of dispersion

a silent slip event on the deeper cascadia subduction interface continuous global positioning system sites in southwestern british columbia canada and northwestern washington state usa have been moving landward as a result of the locked state of the cascadia subduction fault offshore in the summer of 1999 a cluster of seven sites briefly reversed their direction of motion no seismicity was associated with this event the sudden displacements are best explained by 2 centimeters of aseismic slip over a 50 kilometer by 300 kilometer area on the subduction interface downdip from the seismogenic zone a rupture equivalent to an earthquake of moment magnitude 6 7 this provides evidence that slip of the hotter plastic part of the subduction interface and hence stress loading of the megathrust earthquake zone can occur in discrete pulses

indenter growth in analogue models of alpine type deformation a series of analogue experiments were carried out to simulate continental convergence as seen in a profile through the central alps a rigid indenter representing the adriatic plate was driven laterally into a sand pack representing the brittle upper crust of europe detached and thickening above its subducting ductile lower crust the rigid indenter advanced at the same steady rate in each experiment but the dip of its front face was steepened in 15 increments from 15 to 90 where the rigid indenter face dipped at 45 or less a sand wedge rose and was bound by a series of forekinks that nucleated at the toe of the indenter where the face of the rigid indenter dipped 60 or more the wedge was defined by a single forekink and one or more backkinks that nucleated from a point advancing in front of the indenter toe we interpret these results as indicating that slices of the sand pack and rising wedge are transferred across kink bands to build an effective indenter with a frontal dip closer to that dictated by the changing shear strength of the sand pile which thickens vertically as it shortens laterally one of our models with a rigid indenter dipping 75 simulates most of the major structures shown in recent syntheses of surface geology and deep seismic data in the central alps without the isostatic lithospheric depression this model accounts for the late collisional stage oligocene to present complex strain and metamorphic histories in the core of the orogenic wedge the rapid rise and extrusion of small pips of alpine eclogites and the current passivity of the insubric line it also emphasizes that lateral extension along gently dipping thrusts orogen normal horizontal escape is confined to the extruded portion of the rising wedge