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

transversal and oblique structures at the serres de llevant thrust belt mallorca island the serres de llevant thrust and fold segment outcrops along the se coast of mallorca balearic isles spain and represents the eastern continuation of the external zones of the alpine betic range the structure of the serres de llevant consists mainly of northwest directed thrusts which involve a sedimentary series ranging in age from upper triassic to middle miocene the thrusts form a thrust system developed both by piggy back and out of sequence thrusting thrust sheets are imbricated to the se and to the sw and in the northern part also to the ne giving rise to a complex 3 d pattern the thrusts and related folds developed during the oligocene and the lower and middle miocene the thrust transport direction has been inferred from the stratigraphic facing directions of all mapped ramps and has been determined with the aid of other transversal structures the resulting transport direction is from se to nw n310e one of the most significant structural features of the serres de llevant thrust segment is the existence of several lateral and oblique structures these structures are ramps which display stratigraphic facing directions both to the ne and sw other lateral structures represented in the northern part of the thrust segment are tear and drop faults in the southern part kilometric scale oblique folds are exposed

extensional vs contractional cenozoic deformation in ibiza balearic promontory spain integration in the west mediterranean back arc setting abstract based on field work and seismic reflection data we investigate the cenozoic tectono sedimentary evolution offshore and onshore ibiza allowing the proposal of a new tectonic agenda for the region and its integration in the geodynamic history of the west mediterranean the late oligocene early miocene rifting event which characterizes the valencia trough and the algerian basin located north and south of the study area respectively is also present in ibiza and particularly well expressed in the northern part of the island among these two rifted basins initiated in the frame of the european cenozoic rift system the valencia trough failed rapidly while the algerian basin evolved after as a back arc basin related to the subduction of the alpine maghrebian tethys the subsequent middle miocene compressional deformation was localized by the previous extensional faults which were either inverted or passively translated depending on their initial orientation despite the lateral continuity between the external betics and the balearic promontory it appears from restored maps that this tectonic event cannot be directly related to the betic orogen but results from compressive stresses transmitted through the algerian basin a still active back arc asthenospheric rise likely explains the stiff behavior of this basin which has remained poorly deformed up to recent time during the late miocene a new extensional episode reworked the southern part of the balearic promontory it is suggested that this extensional deformation developed in a trans tensional context related to the westward translation of the alboran domain and the coeval right lateral strike slip movement along the emile baudot escarpment bounding the algerian basin to the north

seismic evidence for sharp lithosphere asthenosphere boundaries of oceanic plates the mobility of the lithosphere over a weaker asthenosphere constitutes the essential element of plate tectonics and thus the understanding of the processes at the lithosphere asthenosphere boundary lab is fundamental to understand how our planet works it is especially so for oceanic plates because their relatively simple creation and evolution should enable easy elucidation of the lab data from borehole broadband ocean bottom seismometers show that the lab beneath the pacific and philippine sea plates is sharp and age dependent the observed large shear wave velocity reduction at the lab requires a partially molten asthenosphere consisting of horizontal melt rich layers embedded in meltless mantle which accounts for the large viscosity contrast at the lab that facilitates horizontal plate motions

geodetic imaging of plate motions slip rates and partitioning of deformation in japan 1 interseismic deformation in japan results from the combined effects of tectonic processes including rotation of crustal blocks and the earthquake cycle process of elastic strain accumulation about upper plate faults and subduction zone interfaces we use spherical linear block theory constrained by geodetic observations from densely spaced global positioning system gps stations to estimate plate motions fault slip rates and spatially variable interplate coupling on the japan kuril sagami and nankai subduction zones the reference model developed in this paper consists of 20 blocks produces a mean residual velocity magnitude of 1 84 mm yr at 950 stations and accounts for 96 of the observed interseismic deformation signal we estimate fault slip rates in excess of 15 mm yr along the niigata kobe tectonic zone and itoigawa shizuoka tectonic line through central japan confirming their hypothesized roles as major tectonic boundaries oblique convergence across the nankai trough is partitioned with 3 4 of the 30 mm yr of trench parallel motion accommodated by strike slip motion on the subduction interface and the remaining 1 4 accommodated by right lateral slip on the median tectonic line in contrast our models suggest negligible slip partitioning in eastern hokkaido where oblique slip on the japan kuril subduction interface accommodates all of the trench parallel component of relative plate motion inferred spatial variations in the rake and magnitude of slip deficit on subduction zone interfaces reflect the influences of megathrust geometry and earthquake cycle processes such as enhanced elastic strain accumulation about seismic asperities and coseismic sense fault motion indicative of silent slip events or afterslip following large earthquakes

recurring and triggered slow slip events near the trench at the nankai trough subduction megathrust the discovery of slow earthquakes has revolutionized the field of earthquake seismology defining the locations of these events and the conditions that favor their occurrence provides important insights into the slip behavior of tectonic faults we report on a family of recurring slow slip events sses on the plate interface immediately seaward of repeated historical moment magnitude mw 8 earthquake rupture areas offshore of japan the sses continue for days to several weeks include both spontaneous and triggered slip recur every 8 to 15 months and are accompanied by swarms of low frequency tremors we can explain the sses with 1 to 4 centimeters of slip along the megathrust centered 25 to 35 kilometers km from the trench 4 to 10 km depth the sses accommodate 30 to 55 of the plate motion indicating frequent release of accumulated strain near the trench

evidence of viscoelastic deformation following the 2011 tohoku oki earthquake revealed from seafloor geodetic observation the gps acoustic seafloor positioning has detected significant postseismic movements after the 2011 tohoku oki earthquake m9 0 just above the source region off the pacific coast of eastern japan in contrast to the coastal global navigation satellite systems sites where trenchward upward movements were reported the offshore sites above the main rupture zone in the northern part of the source region exhibit landward displacements of tens of centimeters with significant subsidence from almost 3 years of repeated observations at the sites above around the edge of the main rupture zone smaller amount of trench normal movements was found although the terrestrial movements were reasonably interpreted by afterslip beneath the coastal area these offshore results are rather consistent with effects predicted from viscoelastic relaxation in the upper mantle providing definitive evidence of its occurrence on the other hand the results in the southern part of the source region imply superposition of effects from viscoelastic relaxation and afterslip

introduction of covariance components in slip inversion of geodetic data following a non uniform spatial distribution and application to slip deficit rate estimation in the nankai trough subduction zone when spatial distribution of observation stations has bias in geodetic slip inversion modeling errors in the inversion scheme may result in significant unnatural short wave components in estimated slip distribution which overfit to data combined use of both land and seafloor geodetic data in slip inversion often leads to such situations to avoid overfitting i proposed a method to incorporate proper covariance components in the data covariance matrix originated by modeling errors in the geodetic slip inversion because linearity of the inversion problem is retained widely known approaches to introduce prior constraints to the inversion which assumes linear inversion are easily applied to the proposed method synthetic tests showed that the introduction of covariance components allowed for the estimation of slip distributions closer to the true one avoiding overfitting to geodetic data in biasedly distributed observation stations compared to a conventional approach that does not introduce covariance components i applied the proposed method to the estimation of the slip deficit rate in the nankai trough subduction zone using geodetic data of displacement rates provided by land gnss stations and seafloor gnss acoustic stations the proposed method estimated a reasonably smooth distribution of slip deficit rate compared to the conventional approach spatial distribution of residuals in the displacement rates suggested that the proposed method successfully avoids overfitting to the block motion at the south of the median tectonic line which the physical model i assumed here cannot describe

supercycle at the ecuadorian subduction zone revealed after the 2016 pedernales earthquake large earthquakes are usually assumed to release all of the strain accumulated since the previous event implying a reduced seismic hazard after them however long records of seismic history at several subduction zones suggest supercycle behaviour where centuries long accumulated strain is released through clustered large earthquakes resulting in an extended period of enhanced seismic hazard here we combine historical seismology results present day geodesy data and dense local observations of the recent mw 7 8 2016 pedernales earthquake to reconstruct the strain budget at the ecuador subduction zone since the great 1906 earthquake we show that the pedernales earthquake involved the successive rupture of two patches on the plate interface that were locked prior to the earthquake and most probably overlaps the area already ruptured in 1942 by a similar earthquake however we find that coseismic slip in 2016 exceeds the deficit accumulated since 1942 the seismic moment of every large earthquake during the twentieth century further exceeds the moment deficit accumulated since 1906 these results together with the seismic quiescence before 1906 highlighted by historical records and marine palaeoseismology argue for an earthquake supercycle at the ecuador colombia margin this behaviour which has led to an enhanced seismic hazard for 110 years is possibly still going on and may apply to other subduction zones that recently experienced a great earthquake large earthquakes are often assumed to reset the seismic hazard of a region analysis of recent and historical seismicity in ecuador suggests that this region may experience clusters of large earthquakes and extended periods of high seismic hazard

asthenosphere rheology inferred from observations of the 2012 indian ocean earthquake the concept of a weak asthenospheric layer underlying earth s mobile tectonic plates is fundamental to our understanding of mantle convection and plate tectonics however little is known about the mechanical properties of the asthenosphere the part of the upper mantle below the lithosphere underlying the oceanic crust which covers about 60 per cent of earth s surface great earthquakes cause large coseismic crustal deformation in areas hundreds of kilometres away from and below the rupture area subsequent relaxation of the earthquake induced stresses in the viscoelastic upper mantle leads to prolonged postseismic crustal deformation that may last several decades and can be recorded with geodetic methods the observed postseismic deformation helps us to understand the rheological properties of the upper mantle but so far such measurements have been limited to continental plate boundary zones here we consider the postseismic deformation of the very large moment magnitude 8 6 2012 indian ocean earthquake to provide by far the most direct constraint on the structure of oceanic mantle rheology in the first three years after the indian ocean earthquake 37 continuous global navigation satellite systems stations in the region underwent horizontal northeastward displacements of up to 17 centimetres in a direction similar to that of the coseismic offsets however a few stations close to the rupture area that had experienced subsidence of up to about 4 centimetres during the earthquake rose by nearly 7 centimetres after the earthquake our three dimensional viscoelastic finite element models of the post earthquake deformation show that a thin 30 200 kilometres low viscosity having a steady state maxwell viscosity of 0 5 10 1018 pascal seconds asthenospheric layer beneath the elastic oceanic lithosphere is required to produce the observed postseismic uplift

structural control on the presence and character of calas observations from balearic islands limestone rock coast macroforms abstract calas are characteristic embayed rocky coastline landforms related to steep sided drowned valleys that were deeply incised during low sea level stages into carbonate plateaus this paper studies the factors that control the presence and character of calas in three different islands of the balearic archipelago mallorca menorca and formentera by means of digital elevation model dem reconstructions embayment and catchment morphometric analysis and through the compilation of fault and joint orientations all islands exhibit emerged carbonate platforms upper miocene in age characterised by horizontal or very gently dipping bedding two distinct patterns observed at all study sites are the absence or poor development of calas when carbonate plateaus exhibit strong coast parallel structures and a greater variability of cala embayment size according to stream catchment size lithology or their catchment distance from the coastline furthermore the amount of stream incision and consequently the characteristics of a cala at its mouth depends on the proportion of impermeable rocks exposed in each drainage basin and on the density and spacing of fractures karst collapse dolines and valley infilling associated with quaternary sea level oscillations are also important in determining the shape and size of calas

late pleistocene paleoclimates and sea level change in the mediterranean as inferred from stable isotope and u series studies of overgrowths on speleothems mallorca spain abstract phreatic overgrowths on speleothems form at the surface of brackish pools which are present in many coastal caves of mallorca spain unlike common vadose speleothems formed in subaerial environments their occurrence directly identifies the height of the sea level at the time of the carbonate deposition because such pools are physically connected with the sea these deposits from the late pleistocene have recorded the same global variations in oxygen isotopes as planktonic and benthonic foraminifera corals and cave deposits a number of phreatic overgrowths on speleothems have been dated using the th u method in order to determine the position of the sea level during late quaternary the same samples as well as some subaerial speleothems have been analysed for 18 o 16 o and 13 c 12 c ratios the former samples allow the analysis of variations in sea water component in the brackish pools associated with glacio eustatic mediterranean fluctuations and the latter permit inferences concerning past continental climate changes some high sea stands have been recognized in correspondence with oxygen isotope stages ois 9 or older 7 5e 5c and 5a phreatic overgrowths on speleothems have also been formed during a colder phase ois 4 demonstrating that also in that period there were environmental conditions favourable for this kind of carbonate precipitation vadose crystallizations have recorded a cold period at 36 ka corresponding with the end of ois 3

coseismic slip distribution of the 2011 off the pacific coast of tohoku earthquake m9 0 refined by means of seafloor geodetic data 1 on 11 march 2011 the devastating m9 0 tohoku earthquake occurred on the interface of the subducting pacific plate and was followed by a huge tsunami that killed about 20 000 people several geophysical studies have already suggested that the very shallow portion of the plate interface might have played an important role in producing such a large earthquake and tsunami however the sparsity of seafloor observations leads to insufficient spatial resolution of the fault slip on such a shallow plate interface for this reason the location and degree of the slip has not yet been estimated accurately enough to assess future seismic risks thus we estimated the coseismic slip distribution based on terrestrial gps observations and all available seafloor geodetic data that significantly improve the spatial resolution at the shallow portion of the plate interface the results reveal that an extremely large greater than 50 m slip occurred in a small about 40 km in width and 120 km in length area near the japan trench and generated the huge tsunami the estimated slip distribution and a comparison of it with the coupling coefficient distribution deduced from the analysis of the small repeating earthquakes suggest that the 2011 tohoku earthquake released strain energy that had accumulated over the past 1000 years probably since the jogan earthquake in 869 the accurate assessments of seismic risks on very shallow plate interfaces in subduction zones throughout the world can be obtained by improving the quality and quantity of seafloor geodetic observations

the gulf of valencia continental shelf extensional tectonics in neogene and quaternary sediments abstract seismic reflection profiles obtained with mud penetrator 3 5 khz sparker 3000 j uniboom 300 j and side scan sonar 100 khz enabled us to map recent morphostructural features extensional structures in neogene and quaternary sediments of the gulf of valencia shelf these structures are dominated by a group of normal faults trending subparallel to the coast the faults produced a series of steps in the neogene quaternary depositional series these sedimentary formations are very thick throughout the area decreasing southward in the direction of the betic system this distensive regime is still active today producing structures which affect the morphology of the shelf

near field tsunami models with rapid earthquake source inversions from land and ocean based observations the potential for forecast and warning computation of tsunami models in the region adjacent to large earthquakes immediately after rupture initiation remains a challenging problem limitations of traditional seismological instrumentation in the near field and concern by tsunami modelers regarding the nonuniqueness of source inversions and the use of indirect observations have in the past been hurdles for such efforts employing near field data from the mw 9 0 2011 tohoku oki data we test source models obtained from newly developed algorithms and multisensor data we demonstrate the ability of such source models determined from land based coseismic data from the combination of gps and strong motion sensors to forecast near source tsunamis we also demonstrate that rapid ingestion of offshore shallow water 100 1000 m wave gauge data substantially improves the earthquake source and tsunami forecast to assess the success of such tsunami models we rely on detailed comparisons to 2000 tsunami survey measurements collected after the event we argue that deployments of shallow water wave gauges coupled with land based geophysical sensors can in the future provide enough information to issue timely and accurate forecasts of tsunami intensity immediately or shortly after rupture initiation of large earthquakes

analysis of the geological evolution and vertical movements in the valencia trough area western mediterranean abstract the valencia trough located between the iberian peninsula and the balearic islands corresponds to the south west prolongation of the provencal basin the analysis of recently released seismic lines shows that the present day tectonics of the valencia trough are the result of the coeval development of 1 a system of horsts and grabens in the north west part of the basin during the late oligocene early miocene catalan valencian domain and 2 a thrust and fold system which lasted up to the middle miocene and which was followed by extensional tectonics during the late miocene betic balearic domain in an attempt to characterize the evolution of the valencia trough subsidence curves have been calculated for 18 wells and three regional cross sections distributed across the basin backstripping of these data shows two major stages of tectonic subsidence history 1 a first stage coeval with basin formation 30 15 my characterized by a rapid and strong tectonic subsidence which attains its maximum values in the central basin areas and close to the balearic islands and 2 a second stage 15 0 my in which the tectonic subsidence decreases gradually the amount of crustal thinning estimated from a comparison of the observed and modelled tectonic subsidence ranges between 1 5 iberian margin areas and 4 5 central and south western basin areas these values agree with the crustal thicknesses inferred from seismic refraction data and gravimetric modelling nevertheless such a degree of thinning cannot be explained by the neogene extensional structure the presence of thick mesozoic deposits suggests that the present crustal thinning is partly due to previous mesozoic extension

the neogene structure of the eastern iberian margin structural constraints on the crustal evolution of the valencia trough western mediterranean abstract the presence of a thinned crust beneath the valencia trough has been recognized for a long time however to date no attempt to link this thinning inferred from geophysical data with the superficial structures has been made a quantification of the neogene extensional processes in the crustal evolution of the valencia trough is presented as a consequence of the complexity of the betic balearic domain the analysis has been done for the catalan valencian domain northwestern areas of the trough crustal and superficial data in this area show that neogene extension was accommodated by a listric normal fault system detached in a deep upper crustal level 13 15 km in the marginal zone of the domain quantitative analysis of the neogene structure shows the incoherence between the upper crustal thinning inferred from the geometric analysis of the superficial structures factor 1 4 1 5 and from geophysical data 1 8 although the latter value agrees with that deduced from the analysis of neogene subsidence this incoherence suggests that the present thinned crust would be partially inherited from the mesozoic extension in this way mesozoic subsidence analysts and the recognized mesozoic structure show that the mesozoic extension was almost as important as the neogene one

a structural outline of the serra de tramuntana of mallorca balearic islands abstract the structural and stratigraphic aspects of the balearic islands are described by outlining the geology of the serra de tramuntana this range is part of the southeastern margin of the valencia trough and has the typical features of thrust tectonic areas a stratigraphic column a structural map and three cross sections show the main features of this range thrusts dip to the southeast and are arranged in an imbricate system with a transport direction to the nw the thrusts recorded involve upper paleozoic to middle miocene rocks imbricates bearing thin slices and duplexes developed where thin sequences with pronounced competency contrasts exist folds are also present they usually trend ne sw except in local areas where they are interpreted as being associated with oblique ramps fold axes plunge sub horizontally and folds face the northwest thrust displacements of up to 10 km are deduced from the existence of klippes and windows and shortening of around 50 is deduced from a comparison of deformed and restored cross sections the onset of the main contractional event is pre miocene probably late oligocene in age but major thrust emplacement occurred during the middle miocene the widespread occurrence of compression structures in the balearic islands developed from late oligocene to middle miocene put strong constraints on the models explaining the origin of both the valencia trough and the algerian basin the first must be considered at least in part as the balearic foreland basin and the second could be superimposed on the internal zone of the western mediterranean orogenic belt

numerical modeling of long term earthquake sequences on the ne japan megathrust comparison with observations and implications for fault friction we use numerical modeling to investigate fault properties that explain key features of the 2011 mw 9 0 tohoku oki earthquake as well as the overall regional behavior of the ne japan megathrust in particular we study the possibility that slip near the trench resulted from thermal pressurization on a shallow patch of the megathrust and investigate whether low velocity friction on that patch is rate strengthening or rate weakening our models also contain a deeper rate weakening patch not prone to efficient thermal pressurization to account for the moderate sized interplate seismicity we produce earthquake sequences and aseismic slip in our models using 2d dynamic simulations that incorporate shear induced temperature variations and the associated change in pore fluid pressure to capture thermal pressurization we find that all our models can reproduce more frequent deeper moderate mw 7 5 events and less frequent larger events with substantial slip at shallow depth as observed along the fukushima miyagi segment of the japan megathrust however only the scenario with a sufficiently rate strengthening patch can match the thousand year recurrence time of tohoku oki like earthquakes suggested by the historical and geological record due to co existence of seismic and aseismic slip at the shallow depths this scenario also reproduces other characteristics of the tohoku oki earthquake the trenchward skewed distribution of slip the backward re rupture of the deeper patch as well as the weaker radiation at high frequency of the shallower portion of the rupture in spite of its larger slip

two dimensional simulations of surface deformation caused by slab detachment detachment of the deeper part of subducted lithosphere causes changes in a subduction zone system which may be observed on the earth s surface constraints on the expected magnitudes of these surface effects can aid in the interpretation of geological observations near convergent plate margins where detachment is expected in this study we quantify surface deformation caused by detachment of subducted lithosphere we determine the range of displacement magnitudes which can be associated with slab detachment using numerical models the lithospheric plates in our models have an effective elastic thickness which provides an upper bound for rapid processes like slab detachment to the surface deformation of lithosphere with a more realistic rheology the surface topography which develops during subduction is compared with the topography shortly after detachment is imposed subduction with a non migrating trench system followed by detachment leads to a maximum surface uplift of 2 6 km while this may be higher for the case of roll back preceding detachment in the latter situation the back arc basin may experience a phase of compression after detachment within the context of our elastic model the surface uplift resulting from slab detachment is sensitive to the depth of detachment a change in friction on the subduction fault during detachment and viscous stresses generated by sinking of the detached part of the slab overall surface uplift of these magnitudes is not diagnostic of slab detachment since variations during ongoing subduction may result in similar vertical surface displacements d 2002 elsevier science b v all rights reserved

prevalence of viscoelastic relaxation after the 2011 tohoku oki earthquake seafloor global positioning system observations immediately after the great 2011 tohoku oki earthquake provide unambiguous evidence for the dominant role of viscoelastic relaxation in short term postseismic deformation rather than just afterslip on the fault as is commonly assumed this paper presents revised estimates of the afterslip following the 2011 tohoku oki earthquake based on seafloor gps observations made immediately after the earthquake tianhaozhe sun et al obtain unambiguous evidence for the dominant role of viscoelastic relaxation in short term postseismic deformation rather than elastic afterslip on the fault as is commonly assumed they conclude that models which erroneously assume an elastic earth substantially overestimate afterslip downdip of the rupture zone and underestimate afterslip updip after a large subduction earthquake crustal deformation continues to occur with a complex pattern of evolution1 this postseismic deformation is due primarily to viscoelastic relaxation of stresses induced by the earthquake rupture and continuing slip afterslip or relocking of different parts of the fault2 3 4 5 6 when postseismic geodetic observations are used to study earth s rheology and fault behaviour it is commonly assumed that short term a few years deformation near the rupture zone is caused mainly by afterslip and that viscoelasticity is important only for longer term deformation6 7 however it is difficult to test the validity of this assumption against conventional geodetic data here we show that new seafloor gps global positioning system observations immediately after the great tohoku oki earthquake provide unambiguous evidence for the dominant role of viscoelastic relaxation in short term postseismic deformation these data reveal fast landward motion of the trench area opposing the seaward motion of gps sites on land using numerical models of transient viscoelastic mantle rheology we demonstrate that the landward motion is a consequence of relaxation of stresses induced by the asymmetric rupture of the thrust earthquake a process previously unknown because of the lack of near field observations our findings indicate that previous models assuming an elastic earth will have substantially overestimated afterslip downdip of the rupture zone and underestimated afterslip updip of the rupture zone our knowledge of fault friction based on these estimates therefore needs to be revised

electrical conductivity imaging of the philippine sea upper mantle using seafloor magnetotelluric data abstract we performed a three year seafloor electromagnetic survey in the philippine sea including the western edge of the pacific ocean to image electrical features of a deep mantle slab stagnating in the transition zone and the surrounding mantle in three dimensions 3 d the project iterated one year deployment of ocean bottom electromagnetometers obems using a total of 37 instruments installed at 18 sites the data obtained have been analyzed in the order of their recovery based on a magnetotelluric mt method in this study we attempt to obtain a one dimensional 1 d electrical conductivity model beneath the philippine sea and the pacific region separately that can be used as a reference model in the first step toward the 3 d analysis the resultant 1 d models show three main features 1 the conductivity in the shallower 200 km of the upper mantle depths of the two regions contrasts sharply which is qualitatively consistent with the large difference in lithospheric age 2 the conductivity at 200 300 km depth in both regions is more or less the same at approximately 0 3 s m 1 3 the conductivity just below 400 km depth is higher for the philippine sea mantle than for the pacific mantle the conductivity structure can be interpreted in terms of the thermal structure mantle hydration and existence of partial melt using experimental results for the conductivity of mantle minerals if the conductivity is interpreted simply as the effect of temperature the mantle beneath the philippine sea could be hotter than the dry solidus of mantle peridotite and thus partially molten however beneath the pacific region the present analysis suggests that the partial melting is not required under the assumed peridotitic composition even if we consider mantle hydration

crustal deformation caused by magma migration in the northern izu islands japan intense crustal activity including earthquake swarms eruptions and a caldera formation in the northern izu islands started on june 26 2000 accompanied with large crustal deformation permanent gps data reveals the spatial pattern and time evolution of ground deformation the observations reveal shrinking and subsidence of miyakejima and extension between kouzushima and niijima we constructed a source model to explain the observed displacements during the period between june 26 and the end of august the model consists of a deflation source 0 12km beneath miyakejima tensile faults 1 04km located between miyakejima and kouzushima and several shear faults mass balance considerations suggest that a large amount of magma migrated 30km from miyakejima toward kouzushima

interseismic seafloor crustal deformation immediately above the source region of anticipated megathrust earthquake along the nankai trough japan 1 we monitored seafloor crustal deformation using the gps acoustic seafloor geodetic observation technique at three sites on the kumano basin off southwestern japan which is located immediately above the source region of the anticipated tonankai megathrust earthquake we directly measured landward crustal movements of 40 mm y in the n80 w direction with respect to the amurian plate on the seafloor the directions were found to be the same as those measured at the on land gps stations the magnitudes of the velocity vectors indicated significant crustal shortenings of approximately 10 20 mm y between the kumano basin and the southeastern coast of the kii peninsula of the japanese islands the present observational results show strong and direct evidence for interplate locking during the interseismic period coupling ratios were roughly estimated at 0 6 0 8 on the plate interface up to at least 10 km in depth

geological framework of the ebro continental margin and surrounding areas abstract the eastern and southeastern margins of iberia were affected during neogene time by a rifting tectonic process superimposed on the alpine structures the valencia trough situated off the northeastern coast of iberia has been defined as a rift system that began its activity in late oligocene early miocene time the opening of the valencia trough produced a series of tectonic grabens created by fractures which strike parallel to the coastline as a consequence of the rifting subsidence occurred and depositional sequences of miocene age were subsequently deposited over the triassic and mesozoic basement some of the mesozoic faults were reactivated and affected the tertiary deposits the depositional history was controlled mainly by extensional faulting during the late paleocene early miocene and by rapid subsidence during the late pliocene a second extensional period occurred in the iberian chain resulting in the present configuration of the continental margin in the study area the pliocene quaternary evolution of the margin was largely controlled by fluctuation of the ebro river sediment supply and sea level oscillations

geological structure and evolution of majorca implications for the origin of the western mediterranean abstract the island of majorca forms part of the ne sw continental balearic promontory which is surrounded by continental and oceanic extensional basins majorca has a basin and range physiography mainly resulting from late neogene extension the basins and ranges strike ne sw the structure of the ranges consists of thrust faults and associated folds involving mesozoic series paleogene series are also involved in the compressional structures located in the southeast whereas a stratigraphic hiatus embracing late cretaceous and paleogene is present in the rest of the island the age of syncompressive rocks and sediments is chattian to aquitanian in the se llevant ranges aquitanian to burdigalian in the central ranges and burdigalian to langhian in the nw tramuntana range thus compressive deformation progressed from southeast to northwest the thrust fault hangingwall displacement is to the northwest and shortening is large 44 seismic reflection sections reveal the presence of compressive structures in the substratum of the basins moreover normal faults due to wnw ese extension occurred during the serravallian and tortonian producing additional subsidence in the basins minor compression could have occurred since the onset of the pleistocene majorca was shortened when the extensional basins surrounding the island originated available models for the origin and evolution of extensional basins of the western mediterranean do not consider the structure observed in majorca

sinkholes related to discontinuous pumping susceptibility mapping based on geophysical studies the case of crestatx majorca spain the crestatx aquifer is the main source of water supply to the bay of alcudia one of the largest resorts on the island of majorca spain this water has been used since the 1970s using several pumping wells which draw an annual volume of 1 5 hm3 the seasonal exploitation of this karstic aquifer causes a substantial cone of depression with great variations in the piezometric level up to 120 m and dynamic water levels of down to 87 m below sea level at the end of the 1990s several sinkholes and subsidence depressions started being detected in a highly karstified area twenty subsidence and sinkhole morphologies have been inventoried in an area measuring 70 000 m2 with diameters up to 23 m and depth more than 15 m the intense and continuous rainfall during recent years 2008 2010 has considerably accelerated the process increasing the dimensions of existing sinkholes and the appearance of new morphologies by means of electrical tomography techniques a ground study was carried out numerous cavities have been identified in the upper 30 m using a map of the surface morphologies and the geophysical profiles we can determine that the propagation and orientation of the sinkholes lie along three main directions n30 e n130 e and n60 e the first is the most relevant which is parallel to the main tectonic structures in the area the interpretation of the electrical profiles has enabled us to identify the potentially most unstable areas which is an effective tool to assess risk in the area as there are roads and a housing development nearby the high but discontinuous exploitation of the aquifer is considered the main trigger for these sinkholes and subsidence depressions as it causes large variations of pressure and accelerates the dissolution process in the underlying rock

3 d modelling of plate interfaces and numerical simulation of long term crustal deformation in and around japan we developed a 3 d simulation model for long term crustal deformation due to steady plate subduction in and around japan by incorporating viscoelastic slip response functions into a realistic 3 d plate interface model constructed on the basis of the topography of ocean floors and hypocenter distributions of earthquakes the lithosphere asthenosphere system is modelled by an elastic surface layer overlying a maxwellian viscoelastic half space kinematic interaction at plate interfaces is rationally represented by the increase of tangential displacement discontinuity fault slip across the interfaces with this model giving the steady slip rates at plate interfaces calculated from nuvel 1a we simulated long term crustal deformation due to steady plate subduction in and around japan the simulated crustal deformation pattern is characterized by steep uplift at island arcs sharp subsidence at ocean trenches and gentle uplift at outer rises the numerical results show the strong dependence of the deformation pattern on the 3 d geometry of plate interfaces

synchronous changes in the seismicity rate and ocean bottom hydrostatic pressures along the nankai trough a possible slow slip event detected by the dense oceanfloor network system for earthquakes and tsunamis donet abstract we detected long term hydrostatic pressure changes at ocean bottom stations of the dense oceanfloor network system for earthquakes and tsunamis donet along the nankai trough off southwestern japan we detected these changes after removing the contributions of ocean mass variations and sensor drift from the records in addition we detected a decrease in the background seismicity rate of a nearby earthquake cluster that was synchronous with the hydrostatic pressure changes we interpreted these observed hydrostatic pressure changes to reflect vertical deformation of the ocean floor of 3 8 cm and we consider the cause of the seafloor crustal deformation to be a slow slip event sse beneath the stations because the pressure changes were observed at stations with distances less than 20 km to each other we inferred that the sse occurred in the shallow part of the sedimentary wedge such as on a splay fault system the synchronous observation of an sse and a seismicity rate change suggests that both were triggered by a change in the regional stress that may be associated with stress accumulation and release processes occurring along the nankai trough these data show that continuous and careful monitoring of crustal activities by donet stations provides an effective way to detect seismic and geodetic signals related to the occurrence of megathrust or other types of large earthquakes

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

structural architecture and active deformation of the nankai accretionary prism japan submersible survey results from the tenryu submarine canyon two research cruises that deployed submersible surveys were undertaken along the tenryu submarine canyon to directly observe the structural architecture of the eastern nankai accretionary prism off the coast of southern japan the surveys have demonstrated that the accreted sediments are strongly deformed turbidite sequences that occur in repeated thrust anticline structures from the leading edge of the prism near the trench toward the arc the following deformation zones have been identified within the prism frontal thrust zone prism toe zone imbricate thrust zone and tokai thrust zone or out of sequence thrust or oost zone the frontal thrust zone is characterized by debris deposits within the hanging wall that have an age of 0 0 43 ma as determined from radiolarian biostratigraphy the prism toe zone is characterized by unconsolidated turbidite sequences that are 1 98 3 4 ma these sequences are cut by normal and thrust faults the imbricate thrust zone includes consolidated muddy layers and unconsolidated sandy layers that contain numerous fracture cleavages the oost zone consists of highly deformed consolidated sediments ranging in age from 0 18 to 1 03 ma from the prism toe zone to the imbricate thrust zone the uniaxial compressive strength increases gradually from 0 5 3 0 to 1 0 6 0 mpa while the anisotropy of magnetic susceptibility changes from oblate to prolate shapes and porosity decreases from 40 50 to 30 50 these data indicate that the eastern nankai accretionary prism appears to have been deformed toward the imbricate thrust zone just south of the oost stable isotope analyses of calcite veins and calcite cement of the sandstone samples from the tokai thrust zone have shown that fluid temperatures for calcite precipitation were 24 63 c in the oost zone the occurrence of highly deformed and consolidated rocks within the nankai accretionary prism likely resulted from tectonic transportation of deeply buried rocks along major out of sequence thrust faults such as the tokai oost we infer therefore that out of sequence thrust faults play a major role in transporting deeply buried deformed rocks in accretionary prisms to the shallower depths and even to the seafloor during ongoing subduction

the 2011 magnitude 9 0 tohoku oki earthquake mosaicking the megathrust from seconds to centuries geophysical observations from the 2011 moment magnitude m w 9 0 tohoku oki japan earthquake allow exploration of a rare large event along a subduction megathrust models for this event indicate that the distribution of coseismic fault slip exceeded 50 meters in places sources of high frequency seismic waves delineate the edges of the deepest portions of coseismic slip and do not simply correlate with the locations of peak slip relative to the m w 8 8 2010 maule chile earthquake the tohoku oki earthquake was deficient in high frequency seismic radiation a difference that we attribute to its relatively shallow depth estimates of total fault slip and surface secular strain accumulation on millennial time scales suggest the need to consider the potential for a future large earthquake just south of this event

geodynamics of the emile baudot escarpment and the balearic promontory western mediterranean abstract the 348 km long 105 155 km wide and 1000 2000 m high northeast trending balearic promontory separates the valencia trough to the northwest from the south balearic algerian basin to the southeast it consists of three blocks ibiza at the southwest end mallorca in the center and menorca at the northeast end of the promontory the ibiza and mallorca blocks were thrust faulted and folded in the miocene the menorca block appears to be undisturbed but strata within the transform separating the mallorca and menorca blocks are folded and faulted miocene and younger volcanic pinnacles also are extensive along the transform separating the ibiza and mallorca blocks we infer that the tectonic features on the balearic promontory are the creations of the late oligocene miocene southeast migration of the blocks making up the promontory way from the spanish margin leading to the opening of the valencia trough behind them the westward displacement of the alboran microplate along the emile baudot escarpment on the southeast side of the promontory and the opening of the south baleric algeria basin behind it and the clockwise rotation of the ibiza and mallorca blocks produced by the passing alboran microplate

the 2004 earthquakes offshore of the kii peninsula japan hypocentral relocation source process and tectonic implication on 5 september 2004 two major earthquakes of mw 7 2 and mw 7 3 referred to as the foreshock and the mainshock hereafter occurred close to the nankai trough in southwest japan this earthquake sequence is located within the subducting philippine sea plate phs with an aftershock distribution that overlapped a portion of the source region of the 1944 tonankai earthquake mw 7 9 we relocate 53 events with magnitudes greater than 4 2 by combining a single event location method for depth and a multiple event location method for epicenter and origin time source mechanisms and rupture histories of the foreshock and the mainshock are investigated by using a waveform modeling method which allows for mechanism changes during the rupture process the mw 7 2 foreshock and the mw 7 3 mainshock are relocated in the uppermost mantle of the phs on primary high angle reverse faults focal mechanisms are consistent with the horizontal and vertical projects of the distribution of aftershocks we speculate that this earthquake sequence was due to the collision reaction between the phs and the zenisu ridge

observation of coseismic seafloor crustal deformation due to m7 class offshore earthquakes 1 we have developed an observation system for seafloor crustal deformation measurement combining the two following techniques the precise acoustic ranging and kinematic gps global positioning system positioning on july 14 2003 we installed the units for this observation system at the seafloor of the kumano basin japan 33 58 n 136 60 e we performed repeated observation six times on 1 july 15 16 and 21 2004 2 november 9 10 2004 3 may 18 and 20 2005 4 july 19 20 2005 5 august 18 19 2005 and 6 august 29 30 2005 the present observation system can stably determine the seafloor position with an rms repeatability of 3 cm in both horizontal components two m7 class offshore intraplate earthquakes occurred only 60 km from the kumano basin site on september 5 2004 we observed the coseismic horizontal displacement of 18 cm at the kumano basin site using the presently developed seafloor observation system our observation system can provide seafloor crustal deformation associated with crustal activities in offshore areas

induced seismicity around the tous new dam spain summary induced seismicity around the tous new dam located 45 km southwest of valencia spain is studied from a detailed analysis of seismic data from a 16 month period starting in 1999 january recorded by the tous new dam seismic network tdsn which comprises a threecomponent station located in the dam and six vertical component outstations within 25 km of the dam on the basis of the spatial 2d 3d and temporal distribution of this seismicity we have found 24 microearthquakes of magnitudes 0 4 3 8 most of which appear correlated in time and space with changes in the water level in the tous new dam reservoir an initial group of earthquakes all within 12 km or less of the reservoir occurred over roughly 1 yr starting in mid 1999 while the water level was at its maximum continuing during draining in late 1999 and subsequent refilling in early 2000 thereafter seismicity was more widespread reaching up to 40 km from the dam and with the greatest frequency of occurrence coinciding with the rapid draining of the reservoir in mid 2000 the few focal mechanisms able to be found are normal or strike slip in general it is clear that a relationship exists between reservoir water level which probably modifies the pre existing tectonic stress field and pore fluid pressures but no specific mechanism for the induced seismicity has yet been identified

measuring the onset of locking in the peru chile trench with gps and acoustic measurements the subduction zone off the west coast of south america marks the convergence of the oceanic nazca plate and the continental south america plate nazca south america convergence over the past 23 million years has created the 6 km deep peru chile trench 150 km offshore high pressure between the plates creates a locked zone leading to deformation of the overriding plate the surface area of this locked zone is thought to control the magnitude of co seismic release and is limited by pressure temperature sediment type and fluid content1 here we present seafloor deformation data from the submerged south america plate obtained from a combination of global positioning system gps receivers and acoustic transponders we estimate that the measured horizontal surface motion perpendicular to the trench is consistent with a model having no slip along the thrust fault between 2 and 40 km depth a tsunami in 1996 200 km north of our site was interpreted as being the result of an anomalously shallow interplate earthquake2 seismic coupling at shallow depths such as we observe may explain why co seismic events in the peruvian subduction zone create large tsunamis

tsunami scenarios based on interseismic models along the nankai trough japan from seafloor and onshore geodesy the recent availability of global positioning system acoustic seafloor geodetic observations enables us to resolve the spatial distribution of the slip deficit rate near the nankai trough southwestern japan considering a tectonic block model and the transient deformation due to the major earthquakes in this area the slip deficit rate between the two relevant blocks can be estimated in this study we remove the time dependent postseismic deformation of the 2004 southeastern off the kii peninsula earthquakes mjma 7 1 7 4 which had led to the underestimation of the slip deficit rate in earlier studies we model the postearthquake viscoelastic relaxation using the 3d finite element model with bi viscous burgers rheology as well as the afterslip on the finite faults the corrected global positioning system acoustic and land based global navigation satellite systems data are aligned to the existing tectonic model and used to estimate the slip deficit rate on the plate boundary we then calculate the coseismic displacements and tsunami wave propagation with the simple assumption that a hundred years of constant slip deficit accumulation was released instantaneously to evaluate the influence of uncertainties in the plate interface geometry on a tsunami model for the nankai trough we investigated two different geometries and performed checkerboard inversion simulations although the two models indicate roughly similar results the peak height of the tsunami wave and its arrival time at several points are significantly different in terms of the expected hazard

evolution of the central catalan margin of the valencia trough western mediterranean abstract the evolution of the central catalan margin was conditioned by major fault activity and thermal processes generated by crustal thinning the continental margin structure is characterised by major ne sw striking southeast dipping basement faults which have given rise to a graben half graben and horst system these faults acted essentially as normal faults no major neogene strike slip activity has affected the continental margin although minor episodic variations from the dominant extensional regime to strike slip tectonics cannot be discounted two major structural evolutionary stages took place at the margin the transition from one stage to the other being gradual 1 rifting stage late oligocene to early burdigalian related to the opening of the valencia trough and from which originated both the barcelona and valles penedes half grabens 2 thermal subsidence stage late burdigalian to present generated by the subsequent crustal cooling and thinning fault activity during this stage was essentially concentrated in the major half graben bounding faults the sedimentary evolution of the central sector of the catalan margin was controlled by the tectonic and crustal evolution as well as by the successive sea level and paleoclimatic changes which affected the region drastic changes in the depositional systems took place during the transition from the rifting stage into the thermal subsidence stage during aquitanian langhian time characterized by an overall trend of pulsating encroachment of marine conditions over the continental margin a noticeable diversity of depositional systems alluvial lacustrine coastal evaporitic fan delta bay shelf carbonate platform systems developed from the latest serravallian up to the present the depositional framework was less varied due to a general lowering of sea level and to the final onlapping of most of older structural highs which are now buried below the miocene sediments two progradational terrigenous shelf talus systems separated by the messinian erosive surface developed during the latest serravallian tortonian and pliocene quaternary

depth extent of the long term slow slip event in the tokai district central japan a new insight 1 temporal changes to interplate coupling and long term aseismic slip in the tokai region of central japan from july 1996 to june 2009 are statically inverted using continuous global positioning system gps data and leveling observations and examined using a new interpretation of aseismic slip in this interpretation the interplate coupling and the aseismic slip should be inferred and compared with reference to a state of no coupling on the plate interface rather than assuming steady state interplate coupling before the occurrence of the aseismic event as previous works have done for this purpose we used original time series data without subtracting any linear trends the inferred distribution shows that the entire period can be divided into three subperiods based on the existence of the aseismic slip area from 2000 to 2005 the strength of the interplate coupling does not change throughout the observed period even though the distribution narrows along the dip direction after the aseismic slip terminates the aseismic slip area inferred in this study based on the no coupling reference was determined to be deeper than the area where the long term slow slip event sse defined as the slip corresponding to the residual displacement from the steady state was hypothesized to have occurred in numerous previous studies the total seismic moment released by the aseismic slip is equivalent to a mw 6 6 earthquake while the sse in previous works was considered to be equivalent to a mw 7 0 to 7 1 earthquake this difference can be attributed primarily to the effects on the interplate coupling which previous studies did not take into account when defining the sse the aseismic slip area coincides well with the distribution of other types of plate interactions such as short term slow slip events and low frequency earthquakes

tsunami waveform inversion including dispersive waves the 2004 earthquake off kii peninsula japan 1 long waves are often assumed to model tsunamis but the wavelength of the initial water height distribution produced by a large submarine earthquake particularly in the direction perpendicular to the fault strike is sometimes not much greater than the water depth the resulting tsunami may have a dispersive character that cannot be simulated based on a conventional long wave approximation the 2004 earthquake off kii peninsula m 7 4 on the southern coast of japan indeed produced a dispersive tsunami that was recorded at two stations located off shikoku for the foreshock m 7 1 on the contrary a dominant dispersive tsunami was not recognized at these stations because dispersive waves show strong directional dependence with respect to the fault strike the above difference indicates that the strikes of the main shock and the foreshock were different we conducted a tsunami waveform inversion analysis based on the dispersive tsunami equations to estimate the initial water height distribution of the main shock the estimated initial water height distribution overlapped with the aftershock region suggesting that the fault strike was perpendicular to the trough axis and the total displaced water volume was 1 7 2 0 109 m3 when we used the conventional long wave approximation the estimated initial water height distribution extended considerably from the aftershock area because artificial sources were needed outside the aftershock area to reproduce the observed dispersive waves

polycrystal anelasticity at near solidus temperatures elasticity anelasticity and viscosity of polycrystalline aggregates were measured at the near solidus temperatures ranging from below to above the solidus temperature tm the result shows that the mechanical effects of the partial melting are twofold changes just below the solidus temperature in the absence of melt and changes at the solidus temperature due to the onset of partial melting as homologous temperature t tm increases from about 0 92 to 1 high frequency part of the attenuation spectrum significantly grows viscosity of the grain boundary diffusion creep is also reduced in this temperature range these changes are caused by a solid state mechanism and have a large amplitude even for the samples which can generate very small amounts of melt at the solidus temperature at the onset of melting further increases in the elastic anelastic and viscous compliances occur these changes are caused by the direct effects of the melt phase and are very small for the samples with very small melt fractions mechanical properties of a partially molten aggregate are determined by these twofold changes and when melt fraction is small the former changes are dominant we performed a parameterization of the present experimental results and applied the obtained empirical formula to the seismic tomographic data in the upper mantle the present model explains well the steep reduction of the seismic shear wave velocity in the oceanic lithosphere just below the solidus temperature

trench normal variation in observed seafloor displacements associated with the 2011 tohoku oki earthquake 1 seafloor geodetic measurements using the gps acoustic technique just above the rupture area of the 2011 tohoku oki earthquake revealed strong trench normal variation in the horizontal crustal displacement associated with the earthquake one set of observations at a site only 50 km away from the trench yielded the most trench ward data ever reported with an accuracy better than 1 m it showed a coseismic displacement of up to 31 m whereas another set of observations 100 km away from the trench showed a 15 m displacement these horizontal data as well as vertical data from pressure gauges and tsunami observations strongly indicate that the seismic slip reached the trench they are also likely to contribute quantitatively to further investigations that reveal the coseismic behavior of the frontal wedge of the overriding plate in the source region along the japan trench

transient crustal movement in the northern izu bonin arc starting in 2004 a large slow slip event or a slow back arc rifting event abstract the izu bonin arc lies along the convergent boundary where the pacific plate subducts beneath the philippine sea plate horizontal velocities of continuous global navigation satellite system stations on the izu islands move eastward by up to 1 cm year relative to the stable part of the philippine sea plate suggesting active back arc rifting behind the northern part of the arc here we report that such eastward movements transiently accelerated in the middle of 2004 resulting in 3 cm extra movements in 3 years we compare three different mechanisms possibly responsible for this transient movement i e 1 postseismic movement of the 2004 september earthquake sequence off the kii peninsula far to the west 2 a temporary activation of the back arc rifting to the west dynamically triggered by seismic waves from a nearby earthquake and 3 a large slow slip event in the izu bonin trench to the east by comparing crustal movements in different regions the first possibility can be shown unlikely it is difficult to rule out the second possibility but current evidence support the third possibility i e a large slow slip event with moment magnitude of 7 5 may have occurred there

seafloor geodetic constraints on interplate coupling of the nankai trough megathrust zone seafloor geodetic data from the nankai trough off southwestern japan show that most offshore sites in this earthquake prone region have high slip deficit rates revealing previously unknown locations that could be important for the mitigation of future earthquake and tsunami associated disasters yusuke yokota et al have used seafloor geodetic observations to visualize the seismogenic zone along the nankai trough off southwestern japan which is thought to be one of the most dangerous megathrust zones in the world they suggest that most offshore sites in this region have positive slip deficit rates revealing previously unknown locations that could be potential sources of future earthquakes and tsunamis low slip deficit rates are observed in other regions consistent with distributions of shallow slow earthquakes and subducting seamounts interplate megathrust earthquakes have inflicted catastrophic damage on human society such an earthquake is predicted to occur in the near future along the nankai trough off southwestern japan an economically active and densely populated area in which megathrust earthquakes have already occurred1 2 3 4 5 megathrust earthquakes are the result of a plate subduction mechanism and occur at slip deficit regions also known as coupling regions 6 7 where friction prevents plates from slipping against each other and the accumulated energy is eventually released forcefully many studies have attempted to capture distributions of slip deficit rates sdrs in order to predict earthquakes8 9 10 however these studies could not obtain a complete view of the earthquake source region because they had no seafloor geodetic data the hydrographic and oceanographic department of the japan coast guard jhod has been developing a precise and sustainable seafloor geodetic observation network11 in this subduction zone to obtain information related to offshore sdrs here we present seafloor geodetic observation data and an offshore interplate sdr distribution model our data suggest that most offshore regions in this subduction zone have positive sdrs specifically our observations indicate previously unknown regions of high sdr that will be important for tsunami disaster mitigation and regions of low sdr that are consistent with distributions of shallow slow earthquakes and subducting seamounts this is the first direct evidence that coupling conditions might be related to these seismological and geological phenomena our findings provide information for inferring megathrust earthquake scenarios and interpreting research on the nankai trough subduction zone

subduction of the philippine sea plate beneath southwestern japan slab geometry and its relationship to arc magmatism 1 we carry out high resolution three dimensional seismic tomography of the crust and upper mantle beneath southwestern sw japan using arrival time data obtained from the nationwide seismograph network the tomographic images provide new insights into the configuration of the philippine sea slab and arc magmatism the results confirm the existence of an aseismic portion of the philippine sea slab at greater depths beyond the seismic portion the philippine sea slab is subducting aseismically down to at least a depth of 200 km in chubu 60 80 km in kinki and 60 km in chugoku and is subducting seismically to depths of 150 200 km in kyushu in the chubu district it is subducting seismically at a shallow dip and then bends downward beneath the volcanic area whereas in the kinki district it is subducting subhorizontally as far as the japan sea the differences in the slab geometry between adjacent regions correlate with the differences in volcanic activity suggesting the importance of the geometry of the philippine sea slab on arc magmatism our tomographic images further imply subduction of the philippine sea slab down to a depth of around 70 km northwest of the izu peninsula the philippine sea slab in that region might have split into western and eastern parts separated by a slab tear and collided with the pacific slab at depths of 150 200 km

large scale boudinage of late miocene platform series triggered by margin collapse during the messinian salinity crisis ibiza island spain abstract in ibiza island we show for the first time that the post tectonic late miocene deposits are locally deformed in synsedimentary large scale boudinage structures the late miocene series is composed of a carbonate rich unit 1 that is overlaid by a clastic unit 2 and a unit 3 in which a basal oolite rich deposit is distinguished from an upper stromatolite rich part the oolite rich and competent layers of unit 3 are dissected into large rectangular to barrel shape boudins that indicate a multidirectional extension the separation of the blocks develops significantly northward revealing a stretching increase in a seaward direction that could have been favored by sliding of the distal part of the underlying marly unit over the clays along and in between the boudins the laminated layers form soft sediment syncline folds the progressive bending of these laminated layers created spaces that were filled with calcite crystal wedges providing evidence for large fluid circulation during deformation microthermometry on fluid inclusions in these calcite crystals revealed growth temperatures ranging from 190 to 260 c this high recrystallization rate is an indication of important fluid circulation during deformation processes besides the progressive infill of paleosols over some of the synsedimentary synclines indicates that deformation was a slow process during the emersion of the series and the subaerial messinian channels location in the topographic depressions formed by the boudinage of the late miocene series confirms that the deformation and sliding occurred during the relative emersion associated with the messinian salinity crisis we thus interpret the boudinage as resulting from the destabilization of a still soft carbonate platform whose sliding has been helped substantially by the injection of relatively hot fluids this work provides an onland evidence for extensional collapse during the messinian sea level drawdown

displacement above the hypocenter of the 2011 tohoku oki earthquake the moment magnitude m w 9 0 2011 tohoku oki mega thrust earthquake occurred off the coast of northeastern japan combining global positioning system gps and acoustic data we detected very large sea floor movements associated with this event directly above the focal region an area with more than 20 meters of horizontal displacement that is four times larger than those detected on land stretches several tens of kilometers long along the trench the largest amount reaches about 24 meters toward east southeast just above the hypocenter furthermore nearly 3 meters of vertical uplift occurred contrary to observed terrestrial subsidence

the valencia trough western mediterranean an overview abstract the valencia trough located between the spanish mainland and the balearic islands corresponds to a late oligocene to recent sedimentary basin that is characterized by a highly attenuated continental crust its northwestern part evolved in response to a late oligocene to early miocene rifting phase that was followed by a period of post rift subsidence and a late miocene pleistocene phase of renewed crustal extension and magmatism its southeastern part is characterized by late oligocene to mid miocene compressional deformation and subsequent extension in the axial parts of the basin the crust has been thinned by a factor of 3 whereby the lower crust is either absent or very thin upper crustal extension appears to be considerably smaller than indicated by the crustal configuration of the basin a major problem in understanding the evolution of the valencia trough is the lack of knowledge about the physical state and structure of the lithosphere before late oligocene extension evolution of the northwestern part of the basin appears to be linked with the development of the oceanic provencal basin middle miocene compressional deformation of the balearic fold belt forming the southeastern margin of the valencia trough appears to have interfered with the tensional evolution of the latter which only resumed after crustal shortening in the balearic domain had given way to extensional tectonics during the late miocene

the slip distribution of the 1946 nankai earthquake estimated from tsunami inversion using a new plate model abstract a new model for the shape of the philippine sea plate psp subducting beneath southwest japan was constructed by combining marine seismic survey results and seismicity data this resulted in a plate model that is generally 3 5 km shallower than previous estimates and contains new details of plate boundary structure near the nankai trough axis we estimated the slip distribution of the 1946 nankai earthquake by inverting tsunami waveforms using the new plate boundary model and found that the large slip off cape muroto and seismic moment were reduced by about 10 from the previous estimate of tanioka and satake 2001a however we also found reason to suspect the tide gauge closest to the epicenter at shimotsu and this resulted in a much more substantial reduction in the amount of slip in the eastern segment of the rupture area we also find that our new rupture model correlates well with features of the subducting plate boundary such as a large subducting seamount off cape muroto kodaira et al 2000a this suggests that such features have an important effect on either earthquake rupture propagation or the interseismic accumulation of elastic strain energy or both

three dimensional seismic velocity structure and configuration of the philippine sea slab in southwestern japan estimated by double difference tomography 1 three dimensional seismic velocity structure in and around the philippine sea plate subducting beneath southwestern sw japan is determined by applying double difference tomography method to arrival time data for earthquakes obtained by a dense nationwide seismic network in japan a region of low s wave velocity and high vp vs of several kilometers in thickness is recognized immediately above the region of intraslab seismicity in a wide area from tokai to kyushu this characteristic layer dips shallowly in the direction of slab subduction compared with the upper surface of the philippine sea slab based on seismic reflection and refraction surveys on seven survey lines we interpret that the low vs and high vp vs layer corresponds to the oceanic crust of the philippine sea slab on the basis of the position of the low vs and high vp vs layer and the precisely relocated hypocenter distribution of intraslab earthquakes the upper surface of the philippine sea slab is reliably determined for the entire area of sw japan nonvolcanic deep low frequency earthquakes that occurred associated with the subduction of the philippine sea slab are distributed along the isodepth contour of 30 km in sw japan except for the tokai district where the depth of deep low frequency earthquakes becomes gradually deeper toward northeast

interplate locking condition derived from seafloor geodetic observation in the shallowest subduction segment at the central nankai trough japan we monitored seafloor crustal deformation at two observation stations on opposite sides of the nankai trough from 2013 to 2016 in order to investigate the interplate locking condition along the central nankai trough we estimated the seafloor crustal deformation with respect to the amurian plate based on five observations the results for two stations tca and toa were 38 25 mm yr toward n78 w and 57 21 mm yr toward n69 w 1 respectively the displacement rate at toa is consistent with the motion of the philippine sea plate with respect to the amurian plate using the euler vector of the revel model the displacement rate at tca is similar to that at other seafloor geodetic stations e g 48 10 mm yr at kum2 station on the kumano basin the interplate coupling rate was estimated to be roughly 70 40 1 in the shallowest segment of the nankai trough

morphodynamic classification of sandy beaches in low energetic marine environment abstract morphodynamic classification of beaches has achieved widespread acceptance in both geological and geomorphological literature in this sense the present work classifies twelve mediterranean low energetic beaches according to the dimensionless fall parameter parameter in the island of mallorca propagation of 44 yr of wave data as well as a detailed sediment study allows to provide probabilities for morphodynamical beach state on an annual and seasonal basis consequently beaches in mallorca fall between three major categories which are a truly reflective b reflective skewed to intermediate and c intermediate beaches the mallorcan beach position in the morphodynamical scheme is close related to the physiographical and geological framework comparison of observed values with those obtained in the analysis leads that for gross beach classification there is agreement between predicted and real state however on a seasonal classification mainly during summer there is no agreement between the predicted state and the real one as the model does not incorporate the role of summer sea breezes beach reflective states are highlighted real beach configurations correspond to more energetic wave dynamic conditions and to intermediate state scenarios

geomorphological characteristics and slope processes associated with different basins mallorca western mediterranean abstract we compare the different geomorphological processes which occurred in pliocene quaternary times on two very similar slopes in mallorca one located at the tramuntana range and the other in the llevant ranges both slopes have the same geological structure the same stratigraphic and lithological levels and the same altitude and orientation the different slope processes are due to the relationship between the accommodation space and the sedimentation rate in the adjacent basins in the valencia trough located n of the tramuntana range the sedimentation rate has not been sufficient to fill the accommodation space whereas in the alcudia basin adjacent to the llevant ranges the sedimentation rate has been sufficient to fill the accommodation space this difference has resulted in major landslides on the tramuntana slope whereas the llevant slope is characterized mainly by alluvial fans and debris screes

on the post 25 ma geodynamic evolution of the western mediterranean during the neogene and quaternary western mediterranean geodynamics were dominated by the eastward migration of the apenninic arc and associated back arc basins the migration was controlled by retreat of the apenninic slab and was associated with boudinage of the lithosphere in the back arc area palaeo reconstruction of the kinematics of the arc suggests about 775 km of migration from the late oligocene to present along a transect from the gulf of lions to calabria a maximum of 135 km of n s converge occurred between africa and europe during the same time span the western mediterranean was thus mainly shaped by the migration of the slab related to west directed subduction it is hypothesized that minor n s convergence deformed the arc but was not the cause of its formation 1998 elsevier science b v all rights reserved

interplate coupling off northeastern japan before the 2011 tohoku oki earthquake inferred from seafloor geodetic data 1 seafloor crustal movements off miyagi and fukushima prefectures northeastern japan observed for about 9 years before the 2011 tohoku oki earthquake m9 0 with the gps acoustic geodetic technique revealed the spatiotemporal variation of interplate coupling in this region off miyagi prefecture temporal variations of the crustal movements are characterized as a strain accumulation release process in relation to the 2005 miyagi oki earthquake m7 2 the intraplate velocity since december 2006 when the strain accumulation seemed to have restarted is 4 5 cm yr relative to the north american plate which is significantly lower than that before the 2005 event 6 7 cm yr this suggests that interplate coupling off miyagi prefecture since around 2007 is weaker than that before the 2005 event on the other hand off fukushima prefecture a westward crustal movement at a constant rate of about 2 cm yr relative to the north american plate has been observed for the interseismic period from 2002 to 2008 the interplate coupling off fukushima prefecture is significantly weak compared with that off miyagi prefecture this is consistent with the observed coseismic displacements associated with the 2011 event which are much smaller off fukushima prefecture than off miyagi prefecture