suitability of open ocean instrumentation for use in near field tsunami early warning along seismically active subduction zones over the past decade the number of open ocean gauges capable of parsing information about a passing tsunami has steadily increased particularly through national cable networks and international buoyed efforts such as the deep ocean assessment and reporting of tsunami dart this information is analyzed to disseminate tsunami warnings to affected regions however most current warnings that incorporate tsunami are directed at mid and far field localities in this study we analyze the region surrounding four seismically active subduction zones cascadia japan chile and java for their potential to facilitate local tsunami early warning using such systems we assess which locations currently have instrumentation in the right locations for direct tsunami observations with enough time to provide useful warning to the nearest affected coastline and which are poorly suited for such systems our primary findings are that while some regions are ill suited for this type of early warning such as the coastlines of chile other localities like java indonesia could incorporate direct tsunami observations into their hazard forecasts with enough lead time to be effective for coastal community emergency response we take into account the effect of tsunami propagation with regard to shallow bathymetry on the fore arc as well as the effect of earthquake source placement while it is impossible to account for every type of off shore tsunamigenic event in these locales this study aims to characterize a typical large tsunamigenic event occurring in the shallow part of the megathrust as a guide in what is feasible with early tsunami warning

three dimensional splay fault geometry and implications for tsunami generation megasplay faults very long thrust faults that rise from the subduction plate boundary megathrust and intersect the sea floor at the landward edge of the accretionary prism are thought to play a role in tsunami genesis we imaged a megasplay thrust system along the nankai trough in three dimensions which allowed us to map the splay fault geometry and its lateral continuity the megasplay is continuous from the main plate interface fault upwards to the sea floor where it cuts older thrust slices of the frontal accretionary prism the thrust geometry and evidence of large scale slumping of surficial sediments show that the fault is active and that the activity has evolved toward the landward direction with time contrary to the usual seaward progression of accretionary thrusts the megasplay fault has progressively steepened substantially increasing the potential for vertical uplift of the sea floor with slip we conclude that slip on the megasplay fault most likely contributed to generating devastating historic tsunamis such as the 1944 moment magnitude 8 1 tonankai event and it is this geometry that makes this margin and others like it particularly prone to tsunami genesis

time reverse imaging for far field tsunami forecasting 2011 tohoku earthquake case study this paper describes a new method for forecasting far field tsunamis by combining aspects of least squares tsunami source inversion lsq with time reverse imaging tri this method has the same source representation as lsq but uses tri to estimate initial sea surface displacement we apply this method to the 2011 japan tsunami and the results show that the method produces tsunami waveforms of excellent agreement with observed waveforms at both near and far field stations not used in the source estimation the spatial distribution of cumulative sea surface displacement agrees well with other models obtained in more sophisticated inversions but resolve source kinematics are not well resolved the method has potential for application in tsunami warning systems as it is computationally efficient and can be used to estimate the initial source model by applying precomputed green s functions in order to provide more accurate and realistic tsunami predictions

channeling of plume flow beneath mid ocean ridges we investigate the interaction of mantle plumes with mid ocean ridges in 3 d numerical convection models using a finite volume multigrid technique with local grid refinement we are able to incorporate a much stronger temperature dependence of viscosity than was possible in previous models this allows lateral viscosity variations of more than six orders of magnitude which is realistic in a ridge situation in models of ridge centered plumes with constant flux we determine how the shape and the along axis width of the plume head depends on various model parameters the plume material is significantly channeled along the axis of a slow spreading ridge if the plume viscosity is in the order of 1017 pa s the plume material spreads radially below the ridge if the spreading rate is fast or the viscosity contrast between plume and ambient mantle is small in time dependent calculations we investigate the temporal evolution of short term variations of the plume flux at slow spreading ridges these perturbations propagate in the form of pulses along the ridge with a speed much larger than the spreading rate our results support the hypothesis that pulsations of the iceland plume are the cause for v shaped topography and gravity anomalies at the reykjanes ridge

chilean megathrust earthquake recurrence linked to frictional contrast at depth fundamental processes of the seismic cycle in subduction zones including those controlling the recurrence and size of great earthquakes are still poorly understood here by studying the 2016 earthquake in southern chile the first large event within the rupture zone of the 1960 earthquake moment magnitude mw 9 5 we show that the frictional zonation of the plate interface fault at depth mechanically controls the timing of more frequent moderate size deep events mw 8 5 we model the evolution of stress build up for a seismogenic zone with heterogeneous friction to examine the link between the 2016 and 1960 earthquakes our results suggest that the deeper segments of the seismogenic megathrust are weaker and interseismically loaded by a more strongly coupled shallower asperity deeper segments fail earlier 60 yr recurrence producing moderate size events that precede the failure of the shallower region which fails in a great earthquake recurrence 110 yr we interpret the contrasting frictional strength and lag time between deeper and shallower earthquakes to be controlled by variations in pore fluid pressure our integrated analysis strengthens understanding of the mechanics and timing of great megathrust earthquakes and therefore could aid in the seismic hazard assessment of other subduction zones the recurrence time of megathrust earthquakes in chile may be controlled by frictional contrasts at depth according to analyses of stress build up and release related to the december 2016 southern chile earthquake

surface topography as key constraint on thermo rheological structure of stable cratons why some archean cratons survived for billions of years while the rest of the lithosphere has been reworked probably for several times is both enigmatic and fundamental for plate tectonics craton longetivity is mainly explained by their buoyancy and analyzed by testing gravitational stability of hardly detectable cratonic mantle keels as a function of a hypothesized thermo rheological structure destruction of some cratons suggests that buoyancy is not the only factor of their stability and many previous studies show that their mechanical strength is equally important the upper bounds on the integrated strength of cratons are provided by flexural studies demonstrating that te values equivalent elastic thickness in cratons are highest in the world 110 150 km yet the lower bounds on the integrated strength of stable cratons are still a matter of debate as well as the question on how this strength is partitioned between crust and mantle and which set of rheological parameters is most pertinent we show that primary observed cratonic features flat topography and frozen heterogeneous crustal structure represent the missing constraints for understanding of craton longevity the cratonic crust is characterized by isostatically misbalanced density heterogeneities suggesting that the lithosphere has to be strong enough to keep them frozen through time without developing major gravitational instabilities and topographic undulations hence to constrain thermo rheological properties of cratons one should investigate the stability of their topography and internal structure our free surface thermo mechanical numerical models demonstrate that craton stability cannot be warranted even by very high crustal strength so that dry olivine mantle and cold thick lithosphere are indispensable conditions we establish lower bound limits on the thermo rheological structure of cratons in particular we find that minimal te needed for long term stability of continents is approximately 90 110 km of which at least 70 km should be contributed by the lithosphere mantle

lithospheric thinning under the araripe basin ne brazil from a long period magnetotelluric survey constraints for tectonic inversion abstract the lithospheric architecture of the western borborema province and northern sao francisco craton of ne brazil has been investigated through analysis of long period magnetotelluric data acquired along a 700 km long survey using 12 instruments the survey samples several tectonic terrains in the province and penetrates into the adjacent sao francisco craton after crossing the araripe basin an aborted rift basin filled with mesozoic sediments that peak at 1000 m above mean sea level high conductivities are observed at shallow depths under the main precambrian shear zones that pervade the province consistent with tectonic reactivation and as a small patch embedded within the high resistivities that characterize the sao francisco craton high conductivities 25 m are also observed below 120 km depth between the patos and pernambuco lineaments right under the araripe basin flanked by resistive 120 m material immediately to the north and south this deep highly conductive body is found consistent with the presence of melt and aqueous fluids and is interpreted as shallow asthenospheric mantle bounded by thicker lithosphere we propose that extensional stresses in the mesozoic stretched and thinned the lithosphere under the araripe basin causing passive upwelling of asthenospheric material and lateral flow of the overlying lithosphere and resulting in thickening of the lithosphere under the flanks and uplift of the araripe basin we also hypothesize that thermal weakening of the lithospheric mantle perhaps sustained by channeling of asthenospheric flows under the basin would have caused regional stresses to concentrate in the brittle upper crust and contribute to basin inversion we thus propose that a combination of localized horizontal stresses and vertical buoyancy from underlying asthenospheric material are ultimately responsible for the actual topography of the araripe basin

kinematic rupture scenarios and synthetic displacement data an example application to the cascadia subduction zone scenario ruptures and ground motion simulation are important tools for studies of expected earthquake and tsunami hazards during future events this is particularly important for large mw8 and very large mw8 5 events for which observations are still limited in particular synthetic waveforms are important to test the response of earthquake and tsunami warning systems to large events these systems are not often exercised in this manner we will show an application of the karhunen loeve kl expansion to generate stochastic slip distributions of large events with an example application to the cascadia subduction zone we will discuss how to extend the static slip distributions obtained from the k l expansion to produce kinematic rupture models and generate synthetic long period displacement data at the sampling rates of traditional gnss stations we will validate the waveforms produced by this method by comparison to a displacement based ground motion prediction equation gmpe obtained from gnss measurements of large earthquakes worldwide

observation of the 2009 samoa tsunami by the neptune canada cabled observatory test data for an operational regional tsunami forecast model 1 as part of the neptune canada cabled seafloor observatory an array of six high precision bottom pressure recorders was installed in the late summer of 2009 at depths from 100 to 2600 m seaward of the southwest coast of vancouver island in the northeast pacific the instruments transmit 1 sec bottom pressure data at roughly 0 1 mm equivalent sea level height to the data management and archiving system dmas at the university of victoria on september 30 2009 the array recorded waves of 2 5 to 6 cm amplitude associated with the transoceanic tsunami generated by the mw 8 1 samoa earthquake in the south pacific these open ocean observations were uncontaminated by coastal effects demonstrating that neptune records from future tsunami events can be effectively used as realtime input to a regional numerical tsunami forecast model we validate this proposition by showing that wave forms simulated by the regional model using the leading train of waves of the 2009 event are in good agreement with observed tsunami records for both the shelf stations and nearby coastal tide gauges tsunami waves simulated by this model are also significantly more accurate for local regions than those determined by global scale tsunami models this ability to assimilate pristine open ocean data from the cabled observatory into an operational tsunami forecast model makes it possible to provide updated wave information that could help mitigate the impact of future tsunamis approaching the west coast of british columbia and northern washington state

mesozoic igneous activity in the maranha o province northern brazil 40ar 39ar evidence for separate episodes of basaltic magmatism low and high ti basaltic rocks of the maranha o province in northern brazil appear to be related to the opening of the atlantic ocean 40ar 39ar dating was carried out on powdered whole rock basalts both washed and unwashed in dilute nitric acid to document this relationship acid treatment does not alter the argon retention properties of retentive phases but is effective in removing alteration phases high ca k degassed at low laboratory temperatures our results identify that at least two periods of volcanic activity formed the maranha o province low ti basalts from the western sector are 200 190 ma and are related to the opening of the north atlantic high ti basalts from the eastern sector are 129 124 ma slightly younger than compositionally similar rocks in the serra geral flood basalt province of southern brazil and are related to the opening of the south atlantic other flood basalts such as the columbia river deccan rajmahal ferrar and siberian provinces were each predominantly formed in 1 2 ma the maranha o basalts remnants of separate igneous events spanning 70 ma should not be classed as a single flood basalt province the temporal complexities noted in the maranha o basaltic rocks appear to be related to the tracks of hotspots that led to the rifting of the atlantic ocean two sets of mesozoic basaltic rocks occur in southern africa india and south america resulting from events leading to the fragmentation and dispersal of sections of gondwanaland in each sub continent the two provinces were formed by events separated by 50 70 ma of these pairs only the maranha o and serra geral show geochemical similarities indicating compositionally distinct upper mantle source regions under sections of brazil separated by 3000 km

seismic evidence for a fossil mantle plume beneath south america and implications for plate driving forces a teleseismic travel time study reveals the presence of a fossil plume in the deep upper mantle beneath brazil which has apparently remained geographically fixed with respect to the overly ing continent despite thousands of kilometres of plate motion this result implies that the upper mantle and lithosphere beneath south america have remained coupled since the breakup of gondwanaland and may provide an answer to the long standing question of what forces drive continental plates

evolution of the walvis ridge rio grande rise hot spot system implications for african and south american plate motions over plumes crystallization ages of volcanic rocks dredged or drilled from the walvis ridge ten sites and the rio grande rise one site have been determined by the 40ar 39ar incremental heating technique the fundamentally age progressive distribution of these basement ages suggests a common hot spot source for volcanism on the island of tristan da cunha along the walvis ridge and rio grande rise and for the formation of the continental flood basalts located in namibia africa and brazil south america the walvis ridge rio grande rise volcanic system evolved along a section of the south atlantic spreading axis as the african and south american plates migrated apart astride or in close proximity to an upwelling plume reconstructions of the spatial relationship between the spreading axis the tristan hot spot and the evolving walvis ridge rio grande rise volcanic feature show that at about 70 ma the spreading axis began to migrate westward away from the hot spot the resulting transition to intraplate hot spot volcanism along the walvis ridge and associated termination of rio grande rise formation also involved a northward migration of previously formed african seafloor over the hot spot rotation parameters for african motion over fixed hot spots i e absolute motion have been recalculated such that the predicted trail of the tristan hot spot agrees with the distribution of radiometric and fossil basement ages along the walvis ridge african absolute motion has been extended to the south and north american plates by the addition of relative motion reconstruction poles

fault slip distribution of the 2014 iquique chile earthquake estimated from ocean wide tsunami waveforms and gps data we applied a new method to compute tsunami green s functions for slip inversion of the 1 april 2014 iquique earthquake using both near field and far field tsunami waveforms inclusion of the effects of the elastic loading of seafloor compressibility of seawater and the geopotential variation in the computed green s functions reproduced the tsunami traveltime delay relative to long wave simulation and allowed us to use far field records in tsunami waveform inversion multiple time window inversion was applied to tsunami waveforms iteratively until the result resembles the stable moment rate function from teleseismic inversion we also used gps data for a joint inversion of tsunami waveforms and coseismic crustal deformation the major slip region with a size of 100 km 40 km is located downdip the epicenter at depth 28 km regardless of assumed rupture velocities the total seismic moment estimated from the slip distribution is 1 24 1021 n m mw 8 0

lamprophyric volcanism of cenozoic age on the sierra leone rise implications for regional tectonics and the stratigraphic time scale abstract igneous and sedimentary rocks have been recovered by dredging the upper slopes of krause seamount a feature lying on the sierra leone rise near 9 n 20 w in the eastern equatorial atlantic the igneous samples consist of lamprophyres and an ankaramite which are rarely encountered in an oceanic setting associated with these rocks are breccias made up of lamprophyric fragments set in a lithified calcareous matrix containing a rich planktonic foraminiferal assemblage of early eocene ypresian subzone p8a age whole rock k ar dating of the igneous samples proved unsuccessful owing to advanced alteration and consequent argon loss however within the breccias are numerous fresh crystal clasts of ti rich amphibole pyroxene and biotite which have compositions closely similar to phenocrysts observed in the lamprophyric rocks suggesting that they are derived directly from them k ar dating of separates of the three minerals yielded ages in the range 53 3 55 4 ma the concordant results provide a maximum age for the ypresian subzone p8a and are consistent with its position within recently established cenozoic time scales they indicate that krause seamount is appreciably younger than the adjacent gambia and sierra leone basins in common with other occurrences of lamprophyric rocks in the oceans those exposed on krause seamount are located in an area of old oceanic basement close to a large fracture zone which has been reactivated by late stage volcanic activity these relatively rare alkaline rocks may be generated by remelting of a volatile rich metasomatized layer which is present in the upper mantle beneath mesozoic ocean floor

fault slip and seismic moment of the 1700 cascadia earthquake inferred from japanese tsunami descriptions 1 the 1700 cascadia earthquake attained moment magnitude 9 according to new estimates based on effects of its tsunami in japan computed coseismic seafloor deformation for hypothetical ruptures in cascadia and tsunami modeling in the pacific ocean reports of damage and flooding show that the 1700 cascadia tsunami reached 1 5 m heights at seven shoreline sites in japan three sets of estimated heights express uncertainty about location and depth of reported flooding landward decline in tsunami heights from shorelines and post 1700 land level changes we compare each set with tsunami heights computed from six cascadia sources each source is vertical seafloor displacement calculated with a three dimensional elastic dislocation model for three sources the rupture extends the 1100 km length of the subduction zone and differs in width and shallow dip for the other sources ruptures of ordinary width extend 360 670 km to compute tsunami waveforms we use a linear long wave approximation with a finite difference method and we employ modern bathymetry with nearshore grid spacing as small as 0 4 km the various combinations of japanese tsunami heights and cascadia sources give seismic moment of 1 9 1022 n m equivalent to moment magnitude 8 7 9 2 this range excludes several unquantified uncertainties the most likely earthquake of moment magnitude 9 0 has 19 m of coseismic slip on an offshore full slip zone 1100 km long with linearly decreasing slip on a downdip partial slip zone the shorter rupture models require up to 40 m offshore slip and predict land level changes inconsistent with coastal paleoseismological evidence

plumes in a convecting mantle models and observations for individual hotspots the motion of hotspots and the deformation of their underlying plume conduits as calculated within models of global mantle flow are presented a new list of 44 possible hotspots with associated tracks has been compiled for all of them calculations have been performed under consideration of individual age and anomalous mass flux for three different models of plume buoyancy and mantle flow plume source depth has usually been assumed to be the top of d but an alternative source depth at the 670 km discontinuity has also been considered using models of relative plate motions and boundaries hotspot tracks on plates have been calculated and compared with age data ocean floor topography and distribution of volcanics on continents absolute plate motions have been redetermined under consideration of hotspot motion using a new least squares method for the hawaiian and yellowstone hotspots source locations and hotspot motion have been computed for a total of up to 23 different models the results show plume conduits being tilted with source regions at the d moving in the lowermost mantle flow generally toward large scale upwellings under southern africa and the south central pacific hotspot surface motion often represents the horizontal component of midmantle flow which is frequently opposite to plate motion toward ridges and away from subduction zones in particular almost all models tested predict southward motion of the hawaii and kerguelen hotspots and westward motion of the iceland hotspot for models including hotspot motion the agreement between calculated and observed hotspot tracks is frequently about as good as or better than for the fixed hotspot model but sometimes fixed hotspots give the best fit in some cases where the track ends at a subduction zone e g for the bowie hotspot results can give indications about the otherwise unknown age of the hotspot in other cases especially for the tahiti hotspot results suggest an origin shallower than d and in yet other cases particularly east africa the failure of the hotspot models used supports other evidence indicating the presence of comparatively broad upwellings rather than localized plumes

impact of near field deep ocean tsunami observations on forecasting the 7 december 2012 japanese tsunami following the devastating 11 march 2011 tsunami two deep ocean assessment and reporting of tsunamis dart dart and the dart logo are registered trademarks of the national oceanic and atmospheric administration used with permission stations were deployed in japanese waters by the japanese meteorological agency two weeks after deployment on 7 december 2012 a mw 7 3 earthquake off japan s pacific coastline generated a tsunami the tsunami was recorded at the two japanese darts as early as 11 min after the earthquake origin time which set a record as the fastest tsunami detecting time at a dart station these data along with those recorded at other darts were used to derive a tsunami source using the national oceanic and atmospheric administration tsunami forecast system the results of our analysis show that data provided by the two near field japanese darts can not only improve the forecast speed but also the forecast accuracy at the japanese tide gauge stations this study provides important guidelines for early detection and forecasting of local tsunamis

alkaline volcano of paleocene age on the southern guinean margin mapping petrology 40ar 39ar laser probe dating and implications for the evolution of the eastern equatorial atlantic abstract a segment of the southern guinea plateau margin s g p m was surveyed during the 1988 equamarge ii cruise of the r v jean charcot detailed seabeam mapping reveals a huge 3000 m high volcano which was called the nadir seamount culminating at 840 m below sea level and 6 adventive cones volcanics dredged between 2100 and 1300 m of water depth consist of hyaloclastite breccias and subaerial alkali basalts recovered as both massive blocks and eolian pebbles with a desert varnish the data are consistent with the growth of a volcano up to emergence and thereafter its dismembering and subsidence volcanological petrographic and geochemical features ree of the volcanics present similarities with those observed 1 in early basalts from fuerteventura canary islands and maio cape verde islands 2 in lamprophyric volcanism from the sierra leone rise and 3 in volcanics from the gorringe bank 40ar 39ar laser probe dating was performed on two biotite phenocrysts from a massive basalt using step heating and spot fusion procedures both experiments concordantly display a plateau age of 58 6 0 3 ma and an integrated age of 58 6 0 7 ma respectively the nadir seamount provides the third evidence of paleocene alkaline volcanism in the eastern atlantic after the gorringe bank and the northern sierra leone rise krause seamount these volcanoes are presumed to have been controlled by fractures zones the ages and compositions of the nadir and krause seamounts respectively suggest a connection between the volcanic chains of both the sierra leone rise and guinea f z which may have recorded the same hotspot track

a latest cretaceous hotspot and the southeasterly tilt of britain the southeasterly regional dip of england and wales is usually ascribed to miocene movements loss of up to 2 km of cover from northern england shown by apatite fission track analysis has been related to uplift and erosion induced by a mantle hotspot but its effects were far more widespread than considered hitherto outcrop patterns throughout much of england wales and eastern ireland can be related to a hotspot beneath the irish sea uplift occurred within the late maastrichtian and erosion continued into the late palaeogene after post oligocene down faulting of the irish sea the modern drainage was initiated on the eroded surface unconformities provide the best means of dating orogenic movements in some localities the time interval between the youngest rocks preserved beneath the unconformity and the oldest preserved above may be small enough to enable the dating of fold movements to be determined with some precision thus in southeastern britain the major e w structures of the hampshire basin the weald and the london basin can be dated as miocene as rocks of oligocene age are involved in the folding in the hampshire basin and pliocene sands rest in erosional pockets of the chalk of se england because fold movements tend to affect large areas of the crust at discrete intervals of time the southeasterly tilt of britain evident from the fact that a nw se transect from anglesey to london crosses outcrops of rocks getting progressively younger from the precambrian of anglesey to the tertiary of the london basin has

reawakening of large earthquakes in south central chile the 2016 mw 7 6 chiloe event on 25 december 2016 the mw 7 6 chiloe earthquake broke a plate boundary asperity in south central chile near the center of the rupture zone of the mw 9 5 valdivia earthquake of 1960 to gain insight on decadal scale deformation trends and their relation with the chiloe earthquake we combine geodetic teleseismic and regional seismological data gps velocities increased at continental scale after the 2010 maule earthquake probably due to a readjustment in the mantle flow and an apparently abrupt end of the viscoelastic mantle relaxation following the 1960 valdivia earthquake it also produced an increase in the degree of plate locking the chiloe earthquake occurred within the region of increased locking breaking a circular patch of 15 km radius at 30 km depth located near the bottom of the seismogenic zone we propose that the chiloe earthquake is a first sign of the seismic reawakening of the valdivia segment in response to the interaction between postseismic viscoelastic relaxation and changes of interseismic locking between nazca and south america

understanding cratonic flood basalts the origin of continental flood basalts has been debated for decades these eruptions often produce millions of cubic kilometers of basalt on timescales of only a million years although flood basalts are found in a variety of settings no locale is more puzzling than cratonic areas such as southern africa or the siberian craton where strong thick lithosphere is breached by these large basaltic outpourings conventionally flood basalts have been interpreted as melting events produced by one of two processes 1 elevated temperatures associated with mantle plumes and or 2 adiabatic decompression melting associated with lithospheric thinning in southern africa however there are severe problems with both of these mechanisms first the rifting circumstances of several wellknown basaltic outpourings clearly reflect lithospheric control rather than the influence of a deep seated plume specifically rift timing and magmatism are correlated with stress perturbations to the lithosphere associated with the formation of collisional rifts second the substantial lithospheric thinning required for adiabatic decompression melting is inconsistent with xenolith evidence for the continued survival of thick lithosphere beneath flood basalt domains as an alternative to these models we propose a new two stage model that interprets cratonic flood basalts not as melting events but as short duration drainage events that tap previously created sublithospheric reservoirs of molten basalt formed over a longer time scale reservoir creation existence stage i requires long term e g 1 ma supersolidus conditions in the sublithospheric mantle that could be maintained by an elevated equilibrium geotherm appropriate for the archean a slow thermal perturbation e g thermal blanketing or large scale mantle upwelling or a subduction related increase in volatile content the drainage event stage ii occurs in response to an abrupt stress change in the lithosphere which leads to the initiation and propagation of lithospheric dikes such a model accounts for the short eruption time of flood basalts the evidence for lithospheric control of the eruptions and the continued survival of cratonic lithosphere following these magmatic events the most notable consequence of this model is that it implies the existence of large reservoirs of magma comparable to the eruption volume of flood basalts that have been and are still likely present beneath stable continental lithopshere

localized fault slip to the trench in the 2010 maule chile mw 8 8 earthquake from joint inversion of high rate gps teleseismic body waves insar campaign gps and tsunami observations the 27 february 2010 mw 8 8 maule earthquake ruptured 500 km along the plate boundary offshore central chile between 34 s and 38 5 s establishing whether coseismic fault offset extended to the trench is important for interpreting both shallow frictional behavior and potential for tsunami earthquakes in the region joint inversion of high rate gps teleseismic body waves interferometric synthetic aperture radar insar campaign gps and tsunami observations yields a kinematic rupture model with improved resolution of slip near the trench bilateral rupture expansion is resolved in our model with relatively uniform slip of 5 10 m downdip beneath the coast and two near trench high slip patches with 12 m displacements the peak slip is 17 m at a depth of 15 km on the central megathrust located 200 km north from the hypocenter and overlapping the rupture zone of the 1928 m 8 event the updip slip is 16 m near the trench another shallow near trench patch is located 150 km southwest of the hypocenter with a peak slip of 12 m checkerboard resolution tests demonstrate that correctly modeled tsunami data are critical to resolution of slip near the trench with other data sets allowing but not requiring slip far offshore large interplate aftershocks have a complementary distribution to the coseismic slip pattern filling in gaps or outlining edges of large slip zones two clusters of normal faulting events locate seaward along the plate motion direction from the localized regions of large near trench slip suggesting that proximity of slip to the trench enhanced extensional faulting in the underthrusting plate

the denudation history of the onshore continental margin of se brazil inferred from apatite fission track data a suite of 68 new apatite fission track analysis results from the onshore rift margin in southeast brazil are presented some of the results reflect resetting related to the eruption of the parana continental flood basalt 130 ma and four others are directly related to late cretaceous magmatism 80 ma the majority of the results were obtained from precambrian basement rocks and sediments from the parana basin the fission track ages broadly increase inland from 60 90 ma on the coastal plain to 300 ma in the continental hinterland the track length distributions show a characteristic trend being negatively skewed at the coast and showing increasing bimodality inland except for the oldest samples which are more unimodal these trends do not reflect rift related heating and resetting but are the result of protracted denudation since the opening of the south atlantic the results are consistent with more than 3 km of exhumation on the coastal plain but little more than 1 km in the hinterland the topographic morphology in the northern region of the study area is complex and is clearly influenced by structure and bedrock lithology for the region further south model calculations of the isostatic response to the denudation suggest that isostatic rebound makes a minor contribution to the long wavelength topography unless the flexural rigidity is more than 1025 n m in this case the initial elevation of the rift margin would need to be 2 5 km in order to accommodate the amount of denudation inferred from the fission track data however it is possible that the effective flexural rigidity varies across the margin becoming greater in the continental interior alternatively the broad scale wavelength topography may be the result of magmatic underplating related to the parana continental flood basalt event if so estimates of the volume of magma generated would need to be revised upward by as much as a factor of 5

three dimensional simulations of plume lithosphere interaction at the hawaiian swell rapid lithospheric thinning by mantle plumes has not been achieved in numerical experiments performed to date efficient thinning depends on small scale instabilities that convectively remove lithospheric material these instabilities are favored by hotter plumes or stronger temperature dependence of viscosity and a simple scaling independent of rheology controls their onset this scaling allows extrapolation of the results of numerical experiments to the earth s mantle mantle plumes between 100 and 150 kelvins hotter than the background mantle should exhibit small scale convective rolls aligned with the plate motion the unusual variation in heat flow across the hawaiian swell may be due to such instabilities it was found that the spreading of the plume creates a downwelling curtain of material that isolates it from the rest of the mantle for distances of at least 1000 kilometers from the plume origin this isolation has important consequences for the geochemical heterogeneity of the lithosphere and upper mantle

a new plumbing system framework for mantle plume related continental large igneous provinces and their mafic ultramafic intrusions abstract the magmatic components of continental large igneous provinces lips include flood basalts and their plumbing system of giant mafic dyke swarms radiating linear and the recently discovered circumferential type mafic sill provinces a lower crustal magmatic underplate mafic ultramafic m um intrusions associated silicic magmatism and associated carbonatites and kimberlites this paper proposes a new plumbing system framework for mantle plume related continental lips that incorporates all of these components and provides a context for addressing key thematic aspects such as tracking magma batches upstream and downstream and their geochemical evolution assessing the setting of m um intrusions and their economic potential interpreting deep magmatic component identified by geophysical signatures and estimating magnitudes of extrusive and intrusive components with climate change implications this plumbing system model and its associated implications needs to be tested against the rapidly improving lip record

geochemical evidence for the trindade hotspot trace columbia seamount ankaramite abstract the columbia seamount 825 km offshore from brazil at 20 s lies on the east west trace of the trindade hotspot continental and oceanic magmatism believed to have originated with this hotspot is alkalic and sio2 undersaturated and dates from 85 ma in southern brazil to

joint modeling of teleseismic and tsunami wave observations to constrain the 16 september 2015 illapel chile mw 8 3 earthquake rupture process the 16 september 2015 illapel chile m w 8 3 earthquake ruptured 170 km along the plate boundary megathrust fault from 30 0 s to 31 6 s a patch of offshore slip of up to 10 m extended to near the trench and a patch of 3 m slip occurred downdip below the coast aftershocks fringe the large slip zone extending along the coast from 29 5 s to 32 5 s between the 1922 and 1971 1985 ruptures the coseismic slip distribution is determined by iterative modeling of teleseismic body waves as well as tsunami signals recorded at three regional dart stations and tide gauges immediately north and south of the rupture the tsunami observations tightly delimit the rupture length suppressing bilateral southward extension of slip found in unconstrained teleseismic wave inversions the spatially concentrated rupture area with a stress drop of 3 2 mpa is validated by modeling dart and tide gauge observations in hawaii which also prove sensitive to the along strike length of the rupture

fate of mantle plume material trapped within a lithospheric catchment with reference to brazil 1 local regions of thin lithosphere act as catchments of hot buoyant plume material unless replenished the trapped plume material cools by convection to the mantle adiabat by several tens of million years in particular currently hot material from the 130 ma parana starting plume head is unlikely to supply 85 ma to recent volcanism on the mainland of brazil and the martin vaz and fernando hot spots rather a plume tail may now underlie southern brazil where tomographic studies detect conduit shaped velocity anomaly through the upper mantle if the tomographic study in fact found a plume tail the track crossed the amazon rift at 85 ma and since then lateral flow along thin regions of the lithosphere from the tail fed widespread feeble volcanism including the flow line hot spots of martin vaz and fernando

lateral flow and ponding of starting plume material many mantle plumes started with voluminous heads of hot material that ascended as diapirs through the mantle flood basalts radial dike swarms and frequently continental breakup are associated with the impingement of starting plume heads on the base of the lithosphere the buoyant plume head material ponds at the base of the lithosphere and then flows laterally relief on the base of the lithosphere acts as an upside down drainage pattern with enclosed catchments for this flow that is plume material preferentially collects beneath regions where the lithosphere is locally thin such as thermally subsiding sedimentary basins an example is uplift associated with the iceland starting plume which inverted the mesozoic irish sea basin additional relief at the base of the lithosphere is associated with rifting and seafloor spreading in the case of the northern north sea material from the iceland starting plume ponded beneath a basin with locally thin lithosphere rifting breached the enclosed catchment allowing the ponded plume material to drain across the new passive margin toward very thin lithosphere produced by seafloor spreading rifting also creates a conduit for the flow of plume material away from the region underlain by the starting plume head an example is the volcanic passive margin off nova scotia which is 2000 km from the center of the bahama starting plume head numerical and analytical calculations indicate that lateral flow of plume material consistent with this observation is expected if its viscosity is around 1018 pa s

consistent estimates of tsunami energy show promise for improved early warning early tsunami warning critically hinges on rapid determination of the tsunami hazard potential in real time before waves inundate critical coastlines tsunami energy can quickly characterize the destructive potential of generated waves traditional seismic analysis is inadequate to accurately predict a tsunami s energy recently two independent approaches have been proposed to determine tsunami source energy one inverted from the deep ocean assessment and reporting of tsunamis dart data during the tsunami propagation and the other derived from the land based coastal global positioning system gps during tsunami generation here we focus on assessing these two approaches with data from the march 11 2011 japanese tsunami while the gps approach takes into consideration the dynamic earthquake process the dart inversion approach provides the actual tsunami energy estimation of the propagating tsunami waves both approaches lead to consistent energy scales for previously studied tsunamis encouraged by these promising results we examined a real time approach to determine tsunami source energy by combining these two methods first determine the tsunami source from the globally expanding gps network immediately after an earthquake for near field early warnings and then to refine the tsunami energy estimate from nearby dart measurements for improving forecast accuracy and early cancelations the combination of these two real time networks may offer an appealing opportunity for early determination of the tsunami threat for the purpose of saving more lives and early cancelation of tsunami warnings to avoid unnecessary false alarms

analysis of the 23 june 2001 mw 8 4 peru underthrusting earthquake and its aftershocks on 23 june 2001 a m w 8 4 underthrusting earthquake occurred in the southern peru subduction zone followed by several large aftershocks including 26 june m w 6 7 and 7 july m w 7 5 broadband analyses of seismic data for the largest of these earthquakes show southeastward rupture of 180 km along the portion of the subduction zone previously ruptured in 1868 m w 8 8 9 moment release distributions determined are consistent with aftershock location patterns earthquake rupture mode varies along southern peru from larger multi segment rupture in 1868 to several smaller segment ruptures in 2001 similar to rupture variation observed in northern peru and other subduction zones based on models of subduction zone segment interaction the 2001 earthquake sequence may suggest a shorter recurrence time for future earthquakes along this portion of the peru chile subduction zone

channeling at the base of the lithosphere during the lateral flow of plume material beneath flow line hot spots chains of volcanic edifices lie along flow lines between plume fed hot spots and the thin lithosphere at ridge axes discovery and euterpe musicians seamounts are two examples an attractive hypothesis is that buoyant plume material flows along the base of the lithosphere perpendicular to isochrons the plume material may conceivably flow in a broad front or flow within channels convectively eroded into the base to the lithosphere a necessary but not sufficient condition for convective channeling is that the expected stagnant lid heat flow for the maximum temperature of the plume material is comparable to the half space surface heat flow of the oceanic lithosphere two dimensional and three dimensional numerical calculations confirm this inference a second criterion for significant convective erosion is that it needs to occur before the plume material thins by lateral spreading scaling relationships indicate spreading and convection are closely related mathematically the nusselt number ratio of convective to conductive heat flow in the plume material scales with the flux volume per time per length of flow front of the plume material a blob of unconfined plume material thus spreads before the lithosphere thins much and evolves to a slowly spreading and slowly convecting warm region in equilibrium with conduction into the base of the overlying lithosphere three dimensional calculations illustrate this long lasting and hence observable state of plume material away from its plume source a different flow domain occurs around a stationary hot plume that continuously supplies hot material the plume convectively erodes the overlying lithosphere trapping the plume material near its orifice the region of lithosphere underlain by plume material grows toward the ridge axis and laterally by convective thinning of the lithosphere at its edges the hottest plume material channels along flow lines geologically the regions of lithosphere underlain by either warm or hot plume material are likely to extend laterally away from the volcanic edifices whether or not channeling occurs

extreme runup from the 17 july 2006 java tsunami 1 the 17 july 2006 magnitude mw 7 8 earthquake off the south coast of western java indonesia generated a tsunami that effected over 300 km of coastline and killed more than 600 people with locally focused runup heights exceeding 20 m this slow earthquake was hardly felt on java and wind waves breaking masked any preceding withdrawal of the water from the shoreline making this tsunami difficult to detect before impact an international tsunami survey team was deployed within one week and the investigation covered more than 600 km of coastline measured tsunami heights and run up distributions were uniform at 5 to 7 m along 200 km of coast however there was a pronounced peak on the south coast of nusa kambangan where the tsunami impact carved a sharp trimline in a forest at elevations up to 21 m and 1 km inland local flow depth exceeded 8 m along the elevated coastal plain between the beach and the hill slope we infer that the focused tsunami and runup heights on the island suggest a possible local submarine slump or mass movement

tsunami sources of the november 2006 and january 2007 great kuril earthquakes abstract along the northern kuril trench a great interplate earthquake occurred in november 2006 followed by an outer rise normal fault event in january 2007 surface wave magnitudes m s 7 8 and 8 2 indicate that the 2007 event was larger while the global cmt solutions m w 8 3 and 8 1 indicate that the 2006 event was larger tsunamis from both events were recorded at tide gauge stations in japan russia and the united states as well as deep ocean assessment and reporting of tsunamis dart systems and cabled tsunami sensors installed on deep ocean bottom inversion of 52 tsunami waveforms indicates that the 2006 tsunami source was about 200 km long extending from the epicenter to northeast the largest slips of 4 7 m are estimated on the northeastern subfaults for the 2007 event inversion of 32 waveforms shows that the tsunami source was about 120 km long with the largest slip of 3 5 m on the northeastern subfault the agreements between the observed and synthetic tsunami waveforms are generally good for both events not only within the inversion time windows but also for the later phases which were not used in inversions the slip distributions yield the seismic moment of m w 8 1 for the 2006 event and m w 7 9 for the 2007 event the seismic moment of the 2006 event was larger than the 2007 event from comparison of tsunami data regardless of fault model

teleseismic estimates of radiated seismic energy the e m 0 discriminant for tsunami earthquakes we adapt the formalism of boatwright and choy for the computation of radiated seismic energy from broadband records at teleseismic distances to the real time situation when neither the depth nor the focal geometry of the source is known accurately the analysis of a large data set of more than 500 records from 52 large recent earthquakes shows that this procedure yields values of the estimated energy ee in good agreement with values computed from available source parameters for example as published by the national earthquake information center neic the average logarithmic residual being only 0 26 units we analyze the energy to moment ratio by defining log10 ee m0 for regular earthquakes this parameter agrees well with values expected from theoretical models and from the worldwide neic catalogue there is a one to one correspondence between values of that are deficient by one full unit or more and the so called tsunami earthquakes previously identified in the literature as having exceedingly slow sources and believed due to the presence of sedimentary structures in the fault zone our formalism can be applied to single station measurements and its coupling to automated real time measurements of the seismic moment using the mantle magnitude mm should significantly improve real time tsunami warning

tsunami forecast by joint inversion of real time tsunami waveforms and seismic or gps data application to the tohoku 2011 tsunami correctly characterizing tsunami source generation is the most critical component of modern tsunami forecasting although difficult to quantify directly a tsunami source can be modeled via different methods using a variety of measurements from deep ocean tsunameters seismometers gps and other advanced instruments some of which in or near real time here we assess the performance of different source models for the destructive 11 march 2011 japan tsunami using model data comparison for the generation propagation and inundation in the near field of japan this comparative study of tsunami source models addresses the advantages and limitations of different real time measurements with potential use in early tsunami warning in the near and far field the study highlights the critical role of deep ocean tsunami measurements and rapid validation of the approximate tsunami source for high quality forecasting we show that these tsunami measurements are compatible with other real time geodetic data and may provide more insightful understanding of tsunami generation from earthquakes as well as from nonseismic processes such as submarine landslide failures

intraplate seismicity in se brazil stress concentration in lithospheric thin spots summary intraplate seismicity has generally poor correlation with surface geological patterns except for major extensional features such as aborted continental rifts which may act as weak zones it is usually difficult to find simple geology based models to explain differences in seismic activity in stable continental regions seismicity in brazil is clearly not uniform and a few areas of higher activity have been identified however the seismic areas show almost no correlation with the main geological provinces which is typical of other intraplate settings a recent uppermantle tomography study in se and central brazil using approximately 8500 p wave and 2000 pkp wave arrivals recorded in 59 sites since 1992 has mapped p wave velocity anomalies from lithospheric depths down to 1300 km in this region higher seismic activity occurs preferentially in areas with low p wave velocities at 150 250 km depth the low p wave velocities are interpreted as shallower asthenosphere in such areas a hotter geotherm will reduce the strength of the lithospheric upper mantle causing most of the intraplate forces to be concentrated in the brittle upper crust the low velocity anomalies coincide with late cretaceous provinces of alkaline intrusions the proposed ponding of the trindade plume head beneath lithospheric thin spots is consistent with our tomography results suggesting that plume effects may have helped to preserve lithosphere asthenosphere topography although other factors are also important the present data show that stress concentrations resulting from lithosphere asthenosphere topography should play an important role in explaining the intraplate seismicity in the brazilian platform

fault parameters of the 1896 sanriku tsunami earthquake estimated from tsunami numerical modeling the june 15 1896 sanriku earthquake generated devastating tsunamis with the maximum run up of 25 m and caused the worst tsunami disaster in the history of japan despite its moderate surface wave magnitude ms 7 2 and weak seismic intensity this is a typical tsunami earthquake which generates anomalously larger tsunamis than expected from its seismic waves previously proposed mechanisms of tsunami earthquakes include submarine slumping and slow rupture in the accretionary wedge or in the subducted sediments in this paper we estimate the fault parameters of the 1896 tsunami earthquake by numerically computing the tsunami and comparing the waveforms with those recorded at three tide gauge stations in japan the result indicates that the tsunami source is very close to the japan trench and the fault strike is parallel to the trench axis the fault width is about 50 km suggesting that the tsunami earthquake is a slow rupture in the subducted sediments beneath the accretionary wedge

the bahia seamounts test of a hotspot model and a preliminary south american late cretaceous to tertiary apparent polar wander path abstract detailed bathymetric and magnetic data collected over the bahia seamounts in the western south atlantic brazil basin are analyzed six paleomagnetic poles are determined one from three seamounts sharing a ridge and five from isolated seamounts two poles fall near a continental late cretaceous south american pole and are assumed to be of late cretaceous age another seamount has a preliminary 40 ar 39 ar age of 62 4 ma we check this age and estimate the ages of other seamounts by rotating their poles into north american coordinates and comparing them with north american paleomagnetic reference poles these ages and the characteristic magnetic polarities of all bahia seamounts are used to test hotspot models of formation of the seamount group the northern and central bahia seamount chains could have formed from a single hotspot the southern bahia chain may require a second hotspot the two postulated hotspots were probably concurrent and separated by 150 to 200 km the paleomagnetic poles trace out a smooth curve from the late cretaceous poles to a pole that is indistinguishable from the spin axis which we estimate as having an early eocene age the pole ages remain preliminary until better age dates are found and rocks are recovered from more seamounts

upper mantle structure of the borborema province ne brazil from p wave tomography implications for rheology and volcanism data were collected with support of the instituto nacional de ciencia e tecnologia em estudos tectonicos inct et of the centro nacional de desenvolvimento cientifico e tecnologico cnpq grant number 57 3713 2008 01 and the borborema deep electromagnetic and seismic experiment bodes cnpq grant number 400743 2014 0 flsn acknowledges support from the coordenacao de aperfeicoamento de pessoal de nivel superior capes through a 4 yr scholarship to complete his phd at the universidade federal do rio grande do norte ufrn jj thanks cnpq for his research fellowship cnpq grant number 304421 2015 4 ms acknowledges support by brazilian science without border program grant number 40 2174 2012 7

geologic evidence for earthquakes during the past 2000 years along the copalis river southern coastal washington evidence for several prehistoric earthquakes is present in deposits less than 2000 years old that crop out at the copalis river estuary 47 07 2 n 124 09 7 w the deposits show that land subsided decimeters into the intertidal zone on as many as three occasions and that sand vented while the land underwent little or no subsidence on another occasion the evidence for earthquake induced subsidence consists of buried marsh and forest soils that evince sudden estuarine submergence attended on at least one occasion by a landward directed surge of sandy water this combination of submergence and surge implies subsidence and tsunami exposed evidence for subsidence and tsunami along the copalis river is strong for a time within a few decades of 300 years ago moderate for a time 1400 1900 years ago and weak subsidence or lacking tsunami for an intermediate time also about 1400 1900 years ago the history of sudden submergence and tsunami in the past 2000 years at the copalis river estuary resembles that shown by buried soils farther south in coastal washington at grays harbor and willapa bay the history can be explained most simply by great mw of 8 or 9 thrust earthquakes at the boundary between the juan de fuca and north america plates with one or two earthquakes occurring 1400 1900 years ago and another close to 300 years ago the evidence for earthquake induced venting along the copalis river consists of sand intrusions and vented sand volcanoes the sand rose through muddy estuarine deposits at least 3 m thick entraining these deposits in fragments as much as 0 3 m long intrusion occurred at one or more times in the past 2000 years and at least some of the venting occurred 900 1300 years ago the sand bodies do not imply artesian flow of flood pressured groundwater because the sand vented forcefully and infrequently through a lowland that probably lacked natural levees the earthquake implied by the venting of sand 900 1300 years ago could have come from a source below above or at the boundary between the juan de fuca and north america plates if from the subducted juan de fuca plate the implied earthquake was farther west or larger than the largest earthquakes within that plate during the past 100 years evidence permitting a source within the north america plate includes a fault scarp an uplifted tideflat and landslides near puget sound dating from the interval 700 1700 years ago a plate boundary source would explain buried soils whose estuarine submergence and burial imply coseismic subsidence for parts of coastal washington in the interval 600 1300 years ago however stratigraphy shows that little or no coseismic subsidence occurred along the copalis river during the venting 900 1300 years ago if a plate boundary earthquake struck coastal washington 900 1300 years ago the earthquake produced a different distribution of land level change than did the plate boundary earthquakes inferred for 1400 1900 and 300 years ago

numerical modeling of flexural stresses in the upper crust of ne brazil implications for stress regimes in intraplate settings abstract we model the contribution of the stresses generated by the topography and density heterogeneities in the stress field of ne brazil and the interplay between these and regional stresses our model consists of a horizontally layered elastic slab the lithosphere that floats above an inviscid fluid the asthenosphere where the surface load is generated by the topography and bathymetry and the internal loads are calculated from the bouguer anomalies the deviatoric flexural stresses are calculated in the fourier domain our results showed local flexural stresses with magnitudes comparable to those of the plate wide stresses and mainly controlled by the long wavelength bouguer anomalies scenarios for the total stress field were calculated by superposing different values for an e w oriented regional compression we predict the stress axes orientations and stress regimes for the equatorial margin and the pernambuco shear zone pesz region however we highlight the importance of spreading stresses not considered here in rotating the maximum horizontal compression shmax predictions the prediction of stress regime and stress axes orientation in pesz using low to zero regional compression suggest that a decoupling of the shallow stresses from the plate wide stresses might occur in this region another possible explanation found was that the spreading stresses might counterbalance the regional stresses we conclude that the superposition of principally flexural and plate wide stresses explains reasonably the observed stress regimes and shmax orientations in a great part of ne brazil furthermore flexural stresses are playing an important role in the reactivation of the pesz possibly controlling the stress field

2010 maule earthquake slip correlates with pre seismic locking of andean subduction zone analysis of seismic data and global positioning system gps observations from the region around the site of the recent magnitude 8 8 maule earthquake in chile have been combined with modelling of the andean subduction zone to build up a detailed image of the event the earthquake occurred at a seismic gap part of the fault that has not experienced a major earthquake since 1835 and it seems to have released most of the stress accumulated since that time the observations suggest that coseismic slip heterogeneity at the scale of single asperities and therefore the seismic potential of future great earthquakes might be anticipated by geodetic observations these authors show evidence for a high coherence between the slip distribution inferred from the 2010 maule earthquake chile and the patchwork of interseismic locking distribution derived from global positioning system observations during the previous decade their work suggests that coseismic slip heterogeneity at the scale of single asperities should indicate the seismic potential of future earthquakes which thus might be anticipated by geodetic observations the magnitude 8 8 maule chile earthquake of 27 february 2010 ruptured a segment of the andean subduction zone megathrust that has been suspected to be of high seismic potential1 2 3 4 5 6 it is the largest earthquake to rupture a mature seismic gap in a subduction zone that has been monitored with a dense space geodetic network before the event this provides an image of the pre seismically locked state of the plate interface of unprecedentedly high resolution allowing for an assessment of the spatial correlation of interseismic locking with coseismic slip pre seismic locking might be used to anticipate future ruptures in many seismic gaps6 7 8 9 10 11 12 given the fundamental assumption that locking and slip are similar this hypothesis however could not be tested without the occurrence of the first gap filling earthquake here we show evidence that the 2010 maule earthquake slip distribution correlates closely with the patchwork of interseismic locking distribution as derived by inversion of global positioning system gps observations during the previous decade the earthquake nucleated in a region of high locking gradient and released most of the stresses accumulated in the area since the last major event in 1835 two regions of high seismic slip asperities appeared to be nearly fully locked before the earthquake between these asperities the rupture bridged a zone that was creeping interseismically with consistently low coseismic slip the rupture stopped in areas that were highly locked before the earthquake but where pre stress had been significantly reduced by overlapping twentieth century earthquakes our work suggests that coseismic slip heterogeneity at the scale of single asperities should indicate the seismic potential of future great earthquakes which thus might be anticipated by geodetic observations

the 25 october 2010 mentawai tsunami earthquake from real time discriminants finite fault rupture and tsunami excitation 1 the moment magnitude 7 8 earthquake that struck offshore the mentawai islands in western indonesia on 25 october 2010 created a locally large tsunami that caused more than 400 human causalities we identify this earthquake as a rare slow source tsunami earthquake based on 1 disproportionately large tsunami waves 2 excessive rupture duration near 125 s 3 predominantly shallow near trench slip determined through finite fault modeling and 4 deficiencies in energy to moment and energy to duration cubed ratios the latter in near real time we detail the real time solutions that identified the slow nature of this event and evaluate how regional reductions in crustal rigidity along the shallow trench as determined by reduced rupture velocity contributed to increased slip causing the 5 9 m local tsunami runup and observed transoceanic wave heights observed 1600 km to the southeast

fibrous calcite veins overpressures and primary oil migration the fibrous calcite veins found parallel to the bedding of certain shales may have been formed during burial as a consequence of overpressuring their presence could even be indicative of former overpressures this suggestion if it can be upheld carries implications for theories of primary oil migration

controls of mantle plumes and lithospheric folding on modes of intraplate continental tectonics differences and similarities summary mantle plume activity and lithospheric folding by far field stresses exerted from plate boundaries are two important end members as mechanisms for continental intraplate deformation the topographic expression of mantle plume impingement on continental lithosphere and lithospheric folding has some striking similarities observations from a number of areas in europe s intraplate lithosphere demonstrate that these mechanisms commonly interact in space and time we present the results of thermomechanical modelling addressing the role of factors such as the presence of a hot upper mantle the spatial dimensions of the plume and the time constants involved in the temporal succession of plume activity and lithospheric folding by stress accumulation in intraplate continental lithosphere the results demonstrate that both the processes plume lithosphere interactions and folding may interact resulting either in strong amplification attenuation or modification of their surface expression these inferences are compatible with a number of key observations on the nature and the temporal succession of topography evolution in the alpine foreland the pannonian basin the scandinavian continental margin and the iberian peninsula

lithosphere structure beneath the phanerozoic intracratonic basins of north america four intracratonic basins of north america the hudson bay michigan illinois and williston basins have similar ages and are close to one another yet they exhibit different subsidence histories characterised by different time scales and sediment thicknesses they can be explained by local lithosphere thinning and by the cooling of the induced thermal anomaly within the framework of 1d thermal models for vertical heat transport each basin requires a different lithosphere thickness or a different boundary condition at the base of the lithosphere heat flow and seismic studies show that beneath the north american craton the lithosphere is too thick for the assumption of purely vertical heat transfer to be valid thermal models are developed to account for finite thermal anomaly width and for two types of basal boundary conditions fixed temperature or fixed heat flux different subsidence histories are explained by deep lithospheric anomalies of different sizes the stability of thick continental roots requires the mantle part of the lithosphere to be compositionally buoyant with respect to normal convecting mantle localised lithospheric thinning due for example to plume penetration results in the emplacement of compositionally denser mantle into the lithosphere this represents a load which drives permanent flexure the cooling time and the characteristics of flexure allow constraints on the dimensions of these deep lithospheric anomalies there are no solutions for lithosphere thicknesses less than 170 km the williston and illinois basins are associated with wide v200 km and thin anomalies v100 km whereas the michigan and hudson bay are located on top of narrow v100 km and tall v200 km anomalies fl 2000 elsevier science b v all rights reserved

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

survey of 2011 tohoku earthquake tsunami inundation and run up 1 at 14 46 local time on march 11 2011 a magnitude 9 0 earthquake occurred off the coast of northeast japan this earthquake generated a tsunami that struck japan as well as various locations around the pacific ocean with the participation of researchers from throughout japan joint research groups conducted a tsunami survey along a 2000 km stretch of the japanese coast more than 5300 locations have been surveyed to date generating the largest tsunami survey dataset in the world on the sendai plain the maximum inundation height was 19 5 m and the tsunami bore propagated more than 5 km inland along the ria coast from about 50 to 200 km north of sendai the narrow bays focused the tsunami waves generating the largest inundation heights and run ups the survey data clearly show a regional dependence of tsunami characteristics

the 1992 nicaragua earthquake a slow tsunami earthquake associated with subducted sediments the 1992 nicaragua earthquake was a tsunami earthquake that is it generated tsunamis disproportionately large for its surface wave magnitude m s the moment magnitude m w determined from long period 250 s surface waves was 7 6 significantly larger than the 20 s m s of 7 this m s m w disparity is also characteristic of tsunami earthquakes the nicaragua earthquake is the first tsunami earthquake to be captured by modern broadband seismic networks allowing us to present here seismograms of sufficiently high quality to make inferences about the rupture mechanisms we conclude that the nicaragua earthquake was a slow thrust earthquake which occurred on the subduction interface between the cocos and north american plates and because of the absence of sediments on the trench floor offshore of nicaragua the slip propagated up dip all the way to the ocean bottom exciting large tsunamis the occurrence of slip on a plate interface filled with soft subducted sediments caused the rupture process to be slower than in ordinary subduction zone thrust earthquakes our results reinforce the idea that tsunami warning systems using long period 100 s waves are necessary to reduce the hazard from this type of earthquake

the global reach of the 26 december 2004 sumatra tsunami numerical model simulations combined with tide gauge and satellite altimetry data reveal that wave amplitudes directionality and global propagation patterns of the 26 december 2004 sumatra tsunami were primarily determined by the orientation and intensity of the offshore seismic line source and subsequently by the trapping effect of mid ocean ridge topographic waveguides

migrating cretaceous eocene magmatismin the serra do mar alkaline province se brazil melts from the deflected trindade mantle plume department of geological sciences university of durham south road durham dh1 3le uk department of earth sciences university of cambridge downing street cambridge cb2 3eq uk department of physics the university newcastle upon tyne ne1 7ru uk department of geology mcmaster university 1280 main street west hamilton ont canada l8s 4m1 departmento de geoquimica e recursos minerais instituto de geociencias universidade de brasilia

the 1994 java tsunami earthquake slip over a subducting seamount on june 2 1994 a large subduction thrust earthquake ms 7 2 produced a devastating tsunami on the island of java this earthquake had a number of unusual characteristics it was the first recorded large thrust earthquake on the java subduction zone all of the aftershock mechanisms exhibit normal faulting no mechanisms are similar to the main shock also the large tsunami and the relatively low energy radiated by the main shock have led to suggestions that this earthquake might have involved slow shallow rupture near the trench similar to the 1992 nicaragua earthquake we first relocate the main shock and the aftershocks we then invert long period surface waves and broadband body waves to determine the depth and spatial distribution of the main shock slip a dip of 12 hypocenter depth of 16 km and moment of 3 5 l020 n m mw 7 6 give the best fit to the combined seismic data and are consistent with the plate interface geometry the source spectrum obtained from both body and surface waves has a single corner frequency between 10 and 20 mhz implying a stress drop of 0 3 mpa the main energy release was preceded by a small subevent lasting 12 s the main slip occurred at 20 km depth downdip and to the nw of the hypocenter this area of slip is collocated with a prominent high in the bathymetry that has been identified as a subducting seamount we interpret the java earthquake as slip over this subducting seamount which is a locked patch in an otherwise decoupled subduction zone we find no evidence for slow shallow rupture no thrust aftershocks are expected if the entire locked zone slipped during the main shock but extension of the subducting plate behind the seamount would promote normal faulting as observed it seems probable that such a source model could also explain the size and timing of the observed tsunami

the guinea continental margin an example of a structurally complex transform margin abstract the guinean continental margin corresponds to a wide hinge zone which developed between the jurassic central atlantic and the cretaceous equatorial atlantic the guinea marginal plateau that characterizes the southern border of this margin is a wide triangular morphological feature bounded to the west by a typical rifted margin slope segment while its southern edge corresponds to a narrow and morphologically complex continental slope probably resulting from intracontinental transcurrent motion during the early cretaceous on the basis of seismic profiles recorded in two selected areas located along the southern guinea margin a seismic stratigraphy is established at depth the plateau is underlain by a thick mesozoic and cenozoic sedimentary wedge made of two main ensembles a lower ensemble or sequence 1 consists of early cretaceous clastics an upper ensemble includes a series of four distinct sequences attributed to albian to tertiary deposits eastward the sedimentary cover of the southern plateau edge is locally pierced by volcanic bodies of paleocene age beneath the southern margin of the guinea plateau the sedimentary sequences appear deformed by faults and folds resulting from at least two main tectonic episodes a first event only affected sequence 1 which is cut by a set of extensional faults a second tectonic phase including folding reverse faulting and transcurrent faulting is responsible for the deformation of sequences 1 and 2 during this tectonic episode former normal faults have been reactivated as reverse faults resulting in a structural inversion a third tectonic phase was responsible for structures transverse to the general e w trend of the southern guinea margin and consisting of n s trending normal faults and associated volcanoes the spatial distribution of the tectonic trends clearly substantiates a polyphase tectonic activity that can be related to plate motion changes during early stages of the continental separation a first stage is characterized by a divergent rifting leading to n s trending synsedimentary normal faults during the cretaceous the tectonic activity increased as a general transform motion occurred between the guinea plateau and its american conjugate margin the demerara plateau local tensional stresses were responsible for a splay fault system active near the tip of the guinea plateau in late albian times a slight adjustment of the africa plate with respect to the south american one resulted in local squeezing of the whole sedimentary wedge after this short compressive event final continental separation occurred in an extensional regime characterized by a general collapse along two major scarps and volcanic activity

detecting tsunami genesis and scales directly from coastal gps stations 1 different from the conventional approach to tsunami warnings that rely on earthquake magnitude estimates we have found that coastal gps stations are able to detect continental slope displacements of faulting due to big earthquakes and that the detected seafloor displacements are able to determine tsunami source energy and scales instantaneously this method has successfully replicated three historical tsunamis caused by the 2004 sumatra earthquake the 2005 nias earthquake and the 1964 alaska earthquake respectively and has been compared favorably with the conventional seismic solutions that usually take hours or days to get through inverting seismographs because many coastal gps stations are already in operation for measuring ground motions in real time as often as once every few seconds this study suggests a practical way of identifying tsunamigenic earthquakes for early warnings and reducing false alarms

shallow subduction zone earthquakes and their tsunamigenic potential summary we have examined the source spectra of all shallow subduction zone earthquakes from 1992 to 1996 with moment magnitude 7 0 or greater as well as some other interesting events in the period range 1 20 s by computing moment rate functions of teleseismic p waves after comparing the source spectral characteristics of tsunami earthquakes earthquakes that are followed by tsunamis greater than would be expected from their moment magnitude with regular events we identified a subclass of this group slow tsunami earthquakes this subclass consists of the 1992 nicaragua the 1994 java and the february 1996 peru earthquakes we found that these events have an anomalously low energy release in the 1 20 s frequency band with respect to their moment magnitude although their spectral drop ov is comparable to those of the other earthquakes from an investigation of the centroid and body wave locations it appears that most earthquakes in this study conformed to a simple model in which the earthquake nucleates in a zone of compacted and dehydrated sediments and ruptures up dip until the stable sliding friction regime of unconsolidated sediments stops the propagation sedimentstarved trenches e g near jalisco can produce very shallow slip because the fault material supports unstable sliding the slow tsunami earthquakes also ruptured up dip however their centroid is located unusually close to the trench axis the subduction zones in which these events occurred all have a small accretionary prism and a thin layer of subducting sediment ocean surveys show that in these regions the ocean floor close to the trench is highly faulted we suggest that the horst and graben structure of a rough subducting oceanic plate will cause contact zones with the overriding plate making shallow earthquake nucleation and up dip propagation to the ocean floor possible the rupture partly propagates in sediments making the earthquake source process slow two factors have to be considered in the high tsunami generating potential of these events first the slip propagates to shallow depths in low rigidity material causing great deformation and displacement of a large volume of water second the measured seismic moment may not represent the true earthquake displacement because the elastic constants of the source region are not taken into account in the standard cmt determination

the 17 july 2006 java tsunami earthquake the 17 july 2006 java earthquake involved thrust faulting in the java trench and excited a deadly tsunami 5 8 m that inundated the southern coast of java the earthquake s size estimates vary significantly with seismic wave period very long period signals 300 500 s indicate a seismic moment of 6 7 10 20 nm m w 7 8 m s 20 s 7 2 m b 1 s 6 2 while shaking intensities 3 10 hz were mmiv the large tsunami relative to ms characterizes this event as a tsunami earthquake like previous tsunami earthquakes the java event had an unusually low rupture speed of 1 0 1 5 km s and occurred near the up dip edge of the subduction zone thrust fault most large aftershocks involved normal faulting the rupture propagated 200 km along the trench with several pulses of shorter period seismic radiation superimposed on a smooth background rupture with an overall duration of 185 s

field survey of the march 28 2005 nias simeulue earthquake and tsunami on the evening of march 28 2005 at 11 09 p m local time 16 09 utc a large earthquake occurred offshore of west sumatra indonesia with a moment magnitude mw of 8 6 the event caused substantial shaking damage and land level changes between simeulue island in the north and the batu islands in the south the earthquake also generated a tsunami which was observed throughout the source region as well as on distant tide gauges while the tsunami was not as extreme as the tsunami of december 26th 2004 it did cause significant flooding and damage at some locations the spatial and temporal proximity of the two events led to a unique set of observational data from the earthquake and tsunami as well as insights relevant to tsunami hazard planning and education efforts

global upper mantle tomography with the automated multimode inversion of surface and s wave forms summary we apply the automated multimode inversion of surface and s wave forms to a large global data set verify the accuracy of the method and assumptions behind it and compute an s vvelocity model of the upper mantle crust 660 km the model is constrained with 51 000 seismograms recorded at 368 permanent and temporary broadband seismic stations structure of the mantle and crust is constrained by waveform information both from the fundamentalmode rayleigh waves periods from 20 to 400 s and from s and multiple s waves higher modes in order to enhance the validity of the path average approximation we implement the automated inversion of surface and s wave forms with a three dimensional 3 d reference model linear equations obtained from the processing of all the seismograms of the data set are inverted for seismic velocity variations also relative to a 3 d reference in this study composed of a 3 d model of the crust and a one dimensional 1 d global average depth profile in the mantle below waveform information is related to shear and compressional velocity structure within approximate waveform sensitivity areas we use two global triangular grids of knots with approximately equal interknot spacing within each a finely spaced grid for integration over sensitivity areas and a rougher spaced one for the model parametrization for the tomographic inversion we use lsqr with horizontal and vertical smoothing and norm damping we invert for isotropic variations in s and p wave velocities but also allow for s wave azimuthal anisotropy in order to minimize errors due to possible mapping of anisotropy into isotropic heterogeneity the lateral resolution of the resulting isotropic upper mantle images is a few hundred kilometres varying with data sampling we validate the imaging technique with a spectral element resolution test inverting a published global synthetic data set computed with the spectral element method using a laterally heterogeneous mantle model we are able to reconstruct the synthetic model accurately this test confirms both the accuracy of the implementation of the method and the validity of the jwkb and path average approximations as applied in it reviewing the tomographic model we observe that low s v velocity anomalies beneath mid ocean ridges and backarc basins extend down to 100 km depth only shallower than according to some previous tomographic models this presents a close match to published estimates of primary melt production depth ranges there in the seismic lithosphere beneath cratons unambiguous high velocity anomalies extend to 200 km pronounced low velocity zones beneath cratonic lithosphere are rare where present south america tanzania they are neighboured by volcanic areas near cratonic boundaries the images of these low velocity zones may indicate hot material possibly of mantle plume origin trapped or spreading beneath the thick cratonic lithosphere

time and size of a giant earthquake in cascadia inferred from japanese tsunami records of january 1700 geological evidence shows that great earthquakes have occurred in the recent prehistoric past in the cascadia subduction zone off the pacific coast of north america the most recent event or series of events is dated at about 300 years ago1 4 but the precise date and magnitude have not been determined geological investigations have not been able to distinguish a single giant earthquake from a series of great earthquakes occurring over a timespan of a decade or two4 although this information is important for the assessment of future hazard5 we have found several tsunami records in japan from ad 1700 with no indication of a local cause historical earthquake records and palaeoseismic evidence indicate the absence of a large earthquake in 1700 in south america alaska or kamchatka leaving cascadia as the most likely source of this tsunami the estimated time of the earthquake is the evening about 21 00 local time of 26 january 1700 the magnitude is estimated as 9 from the tsunami heights in which case the earthquake ruptured the entire length of the cascadia subduction zone2 these estimates are consistent with native american legends that an earthquake occurred on a winter night6

source model of the 16 september 2015 illapel chile m w 8 4 earthquake based on teleseismic and tsunami data teleseismic data were provided by the incorporated research institutions for seismology http www iris edu wilber3 find event tide gauge data can be found at the intergovernmental oceanographic commission website http www ioc sealevelmonitoring org dart records were provided by noaa http nctr pmel noaa gov dart earthquake catalogs by the usgs national earthquake information center http earthquake usgs gov earthquakes search and global instrumental earthquake catalogue 1900 2009 of international seismological centre global earthquake model http www globalquakemodel org what seismic hazard instrumental catalogue were used in this study we used the gmt software for drawing the figures wessel and smith 1998 this article benefited from constructive review comments by costas e synolakis university of southern california usa and yuichiro tanioka hokkaido university japan for which we are grateful we acknowledge financial supports from the japan society for the promotion of science

petrographic evidence for emplacement of carbon into witwatersrand conglomerates under high fluid pressure abstract much gold in the witwatersrand conglomerates is directly associated with seams of carbon that are generally parallel with bedding some seams locally crosscut bedding and form anastomosing fracture patterns showing that emplacement of liquid hydrocarbons in those seams was postdepositional and infilled fractures that are generally parallel to bedding seams that are not observed to crosscut bedding are nonetheless petrographically identical and are believed to have a common postdepositional origin carbon also occurs along sets of bedding parallel microfractures through individual quartz pebbles in mineralized conglomerates planes of fluid inclusions parallel to the microfractures in pebbles show further evidence for the importance of bedding parallel fluid flow the occurrence of carbon seams on sedimentary discontinuity surfaces may reflect preferential emplacement of carbon along planes of weakness brittle extensional fracturing in pebbles indicates high fluid pressures which may relate to hydrocarbon generation bedding parallel minealization by quartz clays metamorphic chlorite pyrophyllite and gold which reflect a complex multistage paragenesis indicate repeated reactivation of bedding plane permeability previous arguments against a hydrocarbon origin for the carbon seams have been based upon the low intergranular permeability of the rocks however the present study shows that this condition actually caused focusing of hydrocarbon fluid flow along discontinuity surfaces and facies boundaries interaction with uranium could have caused fixation of fluid hydrocarbon by radiolytic polymerization the columnar nature of carbon in many of the seams interpreted by others as a biogenic structure could instead reflect polymer swelling normal to bedding in the direction of least confining stress

thermo mechanical controls on intra plate deformation and the role of plume folding interactions in continental topography thermo tectonic age and inherited structure exert the main controls on the bulk strength of the lithosphere in intraplate settings mechanical decoupling within the lithosphere strongly affects the interaction between deep earth and surface processes thermo mechanical models demonstrate the particular importance of the rheological stratification of the lithosphere in the preservation of ancient cratonic blocks in the surface expression of plume and mantle lithosphere interactions and their impact on the dynamic topography in general the same is true for the effect of large scale lithospheric folding on intraplate basin formation and associated differential vertical motions initiation of continental lithosphere subduction crucial for linking orogenic deformation to intraplate deformation appears to be facilitated by plume lithosphere interactions we present a discussion of these aspects focusing on better process understanding of continental deformation in the context of a number of well documented cases of intraplate deformation

direct energy estimation of the 2011 japan tsunami using deep ocean pressure measurements 1 we have developed a method to compute the total energy transmitted by tsunami waves to the case where the earthquake source is unknown by using deep ocean pressure measurements and numerical models tsunami source functions based on the first wave recorded at the two closest tsunameters deep ocean assessment and reporting of tsunamis dart our analysis suggests that the march 11 2011 tohoku oki tsunami generated off japan originated from a 300 400 km long and 100 km wide area and the total propagated energy is 3 1015j with 6 uncertainty measurements from 30 tsunameters and 32 coastal tide stations show excellent agreement with the forecasts obtained in real time our study indicates that the propagated energy and the source location are the most important source characteristics for predicting tsunami impacts interactions of tsunami waves with seafloor topography delay and redirect the energy flux posing hazards from delayed and amplified waves with long duration seafloor topography also gives its spectral imprint to tsunami waves travel time forecast errors are path specific and correlated to the major wave scatterers in the pacific numerical dissipation in the propagation modeling highlights the need of high resolution inundation models for accurate coastal predictions on the other hand it also can be used to account for physical dissipation to achieve efficiency our results provide guidelines for the earliest reliable tsunami forecast warnings of long duration tsunami waves signals and enhancement of the experimental tsunami forecast system we apply the method to quantify the energy of 15 past tsunamis independently from earthquake magnitudes the small tsunami to seismic radiation energy ratios and their variability 0 01 0 8 reinforce the importance of using deep ocean tsunami data the direct measures of tsunamis for estimates of tsunami energy and accurate forecasting

local lithospheric relief associated with fracture zones and ponded plume material 1 buoyant plume material ponds at the base of oceanic lithosphere it is a natural probe for the relief on the base of the lithosphere owing to plate age because it flows laterally along an upside down drainage pattern geomorphic and geochemical studies of near ridge and on ridge hot spots indicate as expected that the oceanic lithosphere thickens as it ages corridors of thin lithosphere channel plume material along the axis while the thick lithosphere at the end of ridge segments dams this along axis flow channel hot spots extend from plumes toward ridge axes however a good correlation between local lithospheric thickness and local age is not evident at fracture zones within the old ocean basins such a correlation would be expected if the lithosphere cooled only by conduction then pressure release melting and volcanoes would occur preferentially near fracture zones where plume material cascades from thick old to thin young lithosphere this concentration of volcanic edifices does not occur this lack of correlation between lithosphere thickness and plate age is an expected consequence of small scale convection at the base of the lithosphere scaling relationships and numerical models indicate that modestly vigorous convection of several milliwatt per meter squared is sufficient to perturb local lithospheric relief beneath fracture zones without changing the gross correlation of lithospheric thickness with plate age typically the step in lithospheric thickness moves toward the old side of the fracture zone

bulk crustal properties of the borborema province ne brazil from p wave receiver functions implications for models of intraplate cenozoic uplift abstract we investigate variations in crustal thickness and bulk vp vs ratio across the borborema province of ne brazil by analyzing teleseismic p to s conversions recorded at 52 seismic stations in the province the borborema province represents the western portion of a larger neoproterozoic mobile belt that resulted from the assembly of gondwanaland and that split from the african continent during mesozoic times the evolution of the province after continental breakup was marked by episodes of diffuse intraplate magmatism perhaps leading to uplift of the borborema plateau in the cenozoic a number of geodynamic models have been proposed to explain coeval cenozoic magmatism and uplift in the province which invoke either thermal anomalies under the plateau and related mantle upwellings channeling along lithospheric thin spots from a distant mantle plume and small scale convection at the continental edge alternatively plateau uplift might have resulted from thickening of the crust after depth dependent stretching of the continental lithosphere in the mesozoic most of the models imply mafic underplating of the plateau s crust in order to fully explain its elevated topography but the volume of such mafic underplate varies among them our results show that i the crust is 32 40 km thick under the borborema plateau ii the crust is generally thinner about 30 33 km under the lower topographies surrounding the plateau and iii vp vs ratios are in the 1 68 1 80 range for both regions of higher and lower topography no apparent correlation is observed between vp vs ratio and crustal thickness our results suggest that compositional differences between thick and thin crust across the borborema province are minimal and that models of plateau uplift involving a small volume of mafic underplate provide a more plausible explanation for the observed topography of the borborema plateau

source model of the great 2011 tohoku earthquake estimated from tsunami waveforms and crustal deformation data the slip distribution of the 11 march 2011 tohoku earthquake is inferred from tsunami waveforms gps data and seafloor crustal deformation data the major slip region extends all the way to the trench and the large slip area extends 300 km long and 160 km wide the largest slip of 44 m is located up dip of the hypocenter the large slip amount about 41 m ruptured the plate interface near the trench the seismic moment calculated from the estimated slip distribution is 5 5 10 22 n m mw 9 1 the large tsunami due to the 2011 tohoku earthquake is generated from those large slip areas near the trench the additional uplift at the sedimentary wedge as suggested for the 1896 sanriku earthquake may have occurred during the 2011 tohoku earthquake too

real time assessment of the 16 september 2015 chile tsunami and implications for near field forecast the magnitude 8 3 earthquake in central chile on 16 september 2015 and the resulting tsunami severely affected the region with 15 deaths onemi in monitoreo por sismo de mayor intensidad in spanish available at http www onemi cl alerta se declara alerta roja por sismo de mayor intensidad y alarma de tsunami 2015 over one million evacuated and flooding in nearby coastal cities we present our real time assessment of the 2015 chile tsunami using the short term inundation forecasting for tsunamis system and post event analyses with local community models in chile we evaluate three real time tsunami sources which were inverted at the time that the first quarter half and full wave passed the first tsunameter dart 32402 located approximately 580 km north northwest of the epicenter respectively measurement comparisons from 26 deep ocean tsunameters and 38 coastal tide stations show that good model accuracies are achieved for all three sources particularly for the local sites that recorded the most destructive waves the study highlights the forecast speed time and accuracy dependence and their implications for the local forecast capability our analyses suggest that the tsunami s main origination area is about 100 200 km long and 100 km wide to the north of the earthquake epicenter along the trench and the total estimated tsunami wave energy is 7 9 1013 j with 13 uncertainty the study provides important guidelines for the earliest reliable estimate of tsunami energy and local forecasts they can be obtained with the first quarter wave of tsunameter recording these results are also confirmed by a forecast analysis of the 2011 japan tsunami furthermore we find that the first half wave tsunameter data are sufficient to accurately forecast the 2015 chile tsunami due to the specific orientation between the nearest tsunameter and the source the study also suggests expanding the operational use of the local community models in real time and demonstrates the applicability of the model results for all clear evaluations search and rescue operations and near real time mitigation planning in both near and far fields

seismic velocity anomalies beneath se brazil from p and s wave travel time inversions 1 we present the result from teleseismic travel time inversions for p and s wave data mainly recorded at portable broadband stations in se brazil the stations were deployed at 45 sites within an area 1000 1700 km during the years 1992 1999 more than 10 000 relative p and s wave arrival times including core phases were obtained from the waveforms using a new coherence functional these p and s relative phase times are independently inverted for slowness perturbations earthquake relocations and station corrections the final models represent the least amount of structure required to explain the residuals within a defined standard error the robust and consistent features in the velocity anomaly models are interpreted and their resolution is tested with synthetic case inversions we confirm the existence of a cylindrical low velocity anomaly beneath the parana basin which has been interpreted by vandecar et al 1995 as the fossil conduit through which the initial tristan da cunha plume head traveled to generate the parana etendeka flood basalts about 130 ma we now show that this low velocity cylindrical structure seems to be confined to the upper mantle beneath the upper mantle the velocity anomalies show a n s oriented pattern which we interpret as due to the nazca plate subducted slab at lithospheric depths the archean southern part of the sao francisco craton shows high velocities down to 200 300 km all areas with late cretaceous postrift alkaline intrusions are characterized by low velocities at lithospheric depths

rupture characterization and aftershock relocations for the 1994 and 2006 tsunami earthquakes in the java subduction zone 1 two tsunami earthquakes occurred in the java subduction zone within the last 12 years providing multiple well recorded tsunami events for analysis the june 2 1994 mw 7 8 and july 17 2006 mw 7 7 reverse mechanism earthquakes produced tsunami with locally large 8 m runups were deficient in high frequency energy relative to long period radiation had primarily normal faulting aftershocks and occurred near subducting seamounts previous models of the 1994 event and aftershocks suggested extension in the outer rise due to slip at depth at a subducted seamount here we relocate aftershocks for the 1994 and 2006 events and compare to slip distributions and bathymetry most 1994 aftershocks occurred within the slab updip of the mainshock consistent with the extensional hypothesis but the 2006 aftershocks have a more complex pattern regional subducting features as asperities and barriers may influence both events but in different ways