teleseismic waveform complexities caused by near trench structures and their impacts on earthquake source study application to the 2015 illapel aftershocks central chile

exxon global cycle chart an event for every occasion the basic premise of the recent exxon cycle chart that there exists a globally correlatable suite of third order eustatic cycles remains unproven many of the tests of this premise are based on circular reasoning the implied precision of the exxon global cycle chart is not supportable because it is greater than that of the best available chronostratigraphic techniques such as those used to construct the global standard time scale correlations of new stratigraphic sections with the exxon chart will almost always succeed because there are so many exxon sequence boundary events from which to choose this is demonstrated by the use of four synthetic sections constructed from tables of random numbers a minimum of 77 successful correlations of random events with the exxon chart was achieved the existing cycle chart represents an amalgam of regional and local tectonic events and probably also includes unrecognized miscorrelations it is of questionable value as an independent standard of geologic time

storm time electric fields in the equatorial ionosphere observed near the dusk meridian 1 we compare the dynamics of plasma drifts vp and ionospheric electric fields ei measured near the dusk meridian at the magnetic equator by the defense meteorological satellite program dmsp f13 satellite with those of the dawn to dusk component of the interplanetary electric field ief ey during four large magnetic storms presented data indicate that during the main phase of the magnetic storms when the interplanetary magnetic field imf had a southward component vp had upward and westward components that ranged up to 120 and 210 m s 1 the corresponding eastward and upward components of ei were approximately 5 and 10 of ey the persistence of eastward ei for many hours indicates that electric field shielding of the inner magnetosphere is ineffective during prolonged periods of southward imf during periods of northward imf ey 0 ionospheric responses depended on prior history no ionospheric response is apparent after strong northward imf turnings preceded by geomagnetic quiet if they occurred after a long southward interval ei often had westward and downward components the polarity of the zonal component of ei remained well correlated with that of ey for up to 21 h during periods of slowly varying imf phenomena associated with southward imf periods are consistent with models that allow for prolonged penetration electric field from high latitudes superposed on those of the sq current system however it is not understood why the remarkable correspondence between the polarities of the zonal component of ei and the ief ey occurs during northward imf in some ey 0 periods the vertical component of ei remained upward dmsp detections of upward ei westward vp during periods of ey 0 are not predicted by existing models

global marine gravity from retracked geosat and ers 1 altimetry ridge segmentation versus spreading rate 1 three approaches are used to reduce the error in the satellite derived marine gravity anomalies first we have retracked the raw waveforms from the ers 1 and geosat gm missions resulting in improvements in range precision of 40 and 27 respectively second we have used the recently published egm2008 global gravity model as a reference field to provide a seamless gravity transition from land to ocean third we have used a biharmonic spline interpolation method to construct residual vertical deflection grids comparisons between shipboard gravity and the global gravity grid show errors ranging from 2 0 mgal in the gulf of mexico to 4 0 mgal in areas with rugged seafloor topography the largest errors of up to 20 mgal occur on the crests of narrow large seamounts the global spreading ridges are well resolved and show variations in ridge axis morphology and segmentation with spreading rate for rates less than about 60 mm a the typical ridge segment is 50 80 km long while it increases dramatically at higher rates 100 1000 km this transition spreading rate of 60 mm a also marks the transition from axial valley to axial high we speculate that a single mechanism controls both transitions candidates include both lithospheric and asthenospheric processes

seismic moment catalog of large shallow earthquakes 1900 to 1989 we compile a worldwide catalog of shallow depth 70 km and large ms 7 earthquakes recorded between 1900 and 1989 the catalog is shown to be complete and uniform at the 20 sec surface wave magnitude ms 7 0 we base our catalog on those of abe 1981 1984 and abe and noguchi 1983a b for events with ms 7 0 those catalogs however are not homogeneous in seismicity rates for the entire 90 year period we assume that global rates of seismicity are constant on a time scale of decades and most inhomogeneities arise from changes in instrumentation and or reporting we correct the magnitudes to produce a homogeneous catalog the catalog is accompanied by a reference list for all the events with seismic moment determined at periods longer than 20 sec using these seismic moments for great and giant earthquakes and a moment magnitude relationship for smaller events we produce a seismic moment catalog for large earthquakes from 1900 to 1989 the catalog is used to study the distribution of moment released worldwide although we assumed a constant rate of seismicity on a global basis the rate of moment release has not been constant for the 90 year period because the latter is dominated by the few largest earthquakes we find that the seismic moment released at subduction zones during this century constitutes 90 of all the moment released by large shallow earthquakes on a global basis the seismic moment released in the largest event that occurred during this century the 1960 southern chile earthquake represents about 30 to 45 of the total moment released from 1900 through 1989 a frequency size distribution of earthquakes with seismic moment yields an average slope b value that changes from 1 04 for magnitudes between 7 0 and 7 5 to b 1 51 for magnitudes between 7 6 and 8 0 this change in the b value is attributed to different scaling relationships between bounded large and unbounded small earthquakes thus the earthquake process does have a characteristic length scale that is set by the downdip width over which rupture in earthquakes can occur that width is typically greater for thrust events at subduction zones than for earthquakes along transform faults and other tectonic environments

stresses in the lithosphere and sedimentary basin formation abstract seven fundamental questions on the relationship of lithospheric stresses and sedimentary basin origin and evolution are posed and elaborated these are 1 1 how is the evolution of sedimentary basins tied to lithospheric dynamics 2 2 what are the sources of stress that lead to formation of sedimentary basins 3 3 how does the interaction between internally and externally applied stresses affect the formation and evolution of sedimentary basins 4 4 how do space and time variations of rheology and pore pressure affect stress transmission strain vertical motions and stratigraphy during basin evolution 5 5 what factors influence spatial and temporal variations of rheology in and around different kinds of sedimentary basins 6 6 what is the role of magmatism in basin formation and what deep seated processes does it reflect 7 7 what is the relationship between basin evolution thermal history and fluid flow these fundamental questions can be investigated by developing fully dynamic models of processes at the basin and sub basin scale models must incorporate or honour basin history and plate reconstructions the intregration of structural and sedimentological data direct observations of the physical state and the synthesis of geological and geophysical data including tectono dynamic stratigraphy petrological and geochemical data and geophysical data gravity magnetics heat flow deep and shallow seismics a number of type basins in passive margin foreland rift and strike slip tectonic settings suitable for modelling studies elucidating the fundamental questions are identified

coseismic radiation and stress drop during the 2015 mw 8 3 illapel chile megathrust earthquake on 16 september 2015 an mw 8 3 earthquake struck middle chile due to the subduction of the nazca plate beneath the south america plate this earthquake is the consequence of 72 years of strain accumulation in the region since the 1943 m 8 3 event in this study we apply the compressive sensing method cs to invert for the spatiotemporal distribution of the coseismic radiation at different frequencies of this event the results show clear frequency dependent feature of earthquake rupture with low frequency lf radiation located in the updip region while high frequency hf radiation concentrated in the downdip region of the megathrust we also compare the cs results with three coseismic slip models as well as the stress drop distributions inferred from these slip models the comparison confirms our understanding of coseismic radiation that energy sources are mostly located in the margin of large coseismic slip regions furthermore we find that the lf radiation sources are mainly within the stress decreasing releasing regions while the hf radiation sources are mainly located in the stress increasing loading regions due to rupturing of relatively large asperities nearby stress decreasing and releasing these results help to better understand the physics of the rupture process during megathrust earthquakes moreover our results do not show radiation sources south of the epicenter suggesting that the subducting juan fernandez ridge probably stopped the rupture of this earthquake toward the south

the continental margin of the mesozoic tethys in the western alps abstract most of the structural units of the western alps were derived from the european continental margin of the ligurian ocean a segment of the mesozoic tethys ocean their mesozoic palaeotectonic and stratigraphic evolution bears witness of the following main stages 1 deposition of the triassic platform carbonates essentially prerift but nevertheless bearing the imprint of some extensional movements 2 the liassic middle jurassic rifting corresponds to the creation of a horst and graben system with especially tilted blocks and hence a shoal and basin palaeogeography but without a preliminary doming event 3 the late jurassic early cretaceous opening and spreading of the ligurian ocean began with a general collapse of the continental margin thermal subsidence latest middle jurassic and earliest late jurassic in this paper emphasis is given to the refting derived structures more especially to the major tilted crustal blocks a few tens of kilometres wide which can be either reconstructed or directly observed the rifting stage lasted roughly 40 m y with the alternation of extensional tectonic phases and of relatively quiet periods during the extensional phases movements along fault planes and related episodes of tilting were followed by sudden and rapid episodes of subsidence the latter may be interpreted as resulting from the isostatic and thermal readjustment that follows a phase of stretching of the crust and of the lithosphere the tectonic evolution of the margin continued but decreased during the late jurassic early cretaceous oceanspreading stage tectonic activity resumed in the late cretaceous this probably resulting from the beginning of contraction of both the ocean and the continental margin leading progressively to the continental collision in the tertiary

modeling tsunami observations to evaluate a proposed late tsunami earthquake stage for the 16 september 2015 illapel chile mw 8 3 earthquake resolving seaward extent of slip during great subduction zone interplate ruptures using land based seismological and geodetic observations is challenging modeling of tsunami recordings from ocean bottom pressure sensors of the deep ocean assessment and reporting of tsunami dart network has added valuable constraints on near trench slip for recent events we use dart and tide gauge recordings to evaluate a proposed seismological scenario involving a late mw 8 08 tsunami earthquake following the 95 s long main rupture stage of the 16 september 2015 illapel chile mw 8 3 earthquake tsunami observations constrain the spatial extent of any late tsunami earthquake slip to locate north of the mainshock hypocenter the proposed late shallow slip predicts tsunami signals with considerable amplitudes but shorter wavelengths compared to those of the main stage slip constrained by joint seismic and tsunami modeling yielding over prediction of first arrival amplitudes at dart and tide gauge stations when the two stages are combined

a 3 d spectral element and frequency wave number hybrid method for high resolution seismic array imaging we present a three dimensional 3 d hybrid method that interfaces the spectral element method sem with the frequency wave number fk technique to model the propagation of teleseismic plane waves beneath seismic arrays the accuracy of the resulting 3 d sem fk hybrid method is benchmarked against semianalytical fk solutions for 1 d models the accuracy of 2 5 d modeling based on 2 d sem fk hybrid method is also investigated through comparisons to this 3 d hybrid method synthetic examples for structural models of the alaska subduction zone and the central tibet crust show that this method is capable of accurately capturing interactions between incident plane waves and local heterogeneities this hybrid method presents an essential tool for the receiver function and scattering imaging community to verify and further improve their techniques these numerical examples also show the promising future of the 3 d sem fk hybrid method in high resolution regional seismic imaging based on waveform inversions of converted scattered waves recorded by seismic array

effects of sedimentary structure and bathymetry near the source on teleseismic p waveforms from shallow subduction zone earthquakes summary the effects of sedimentary layers and non flat bathymetry on teleseismic p waveforms from shallow subduction zone earthquakes are examined by calculating synthetic seismograms the actual bathymetry and shallow sedimentary layers revealed by the seismic refraction studies are incorporated in 2 d velocity models of the oceanic trench region 2 d finite difference calculation is employed to get a complete response of the assumed non flat model structures the result of the modelling of wwssn long period seismograms shows that not only the non flat bathymetry but also thick sedimentary layers are essential to model the synthetic seismograms the lack of non flat bathymetry or sedimentary structure in the structural model often results in unrealistic synthetics in general the paths going across the trench axis are most affected this is caused by the steeply dipping ocean bottom and the thick sedimentary layers at the trench slope observed seismograms of the 1968 kurile thrust event mb 5 5 and the 1967 java normal event mb 6 0 show remarkable large amplitude later arrivals despite their moderate magnitudes a realistic model of the trench structure however reproduces remarkably well this character of later arrivals which shows that it is essential to incorporate the structure our results also indicate that we need precise knowledge on the trench structure to model the structural effects in detail on the gdsn long period seismograms the effect of the sedimentary layers is negligible because the rather narrow band response of the gdsn seismograph lies in a frequency range lower than the affected band however the effect of the non flat bathymetry is significant and can not be neglected

slip segmentation and slow rupture to the trench during the 2015 mw8 3 illapel chile earthquake the 2015 mw8 3 illapel chile earthquake is the latest megathrust event on the central segment of that subduction zone it generated strong ground motions and a large up to 11 m runup tsunami which prompted the evacuation of more than 1 million people in the first hours following the event observations during recent earthquakes suggest that these phenomena can be associated with rupture on different parts of the megathrust the deep portion generates strong shaking while slow large slip on the shallow fault is responsible for the tsunami it is unclear whether all megathrusts can have shallow slip during coseismic rupture and what physical properties regulate this here we show that the illapel event ruptured both deep and shallow segments with substantial slip we resolve a kinematic slip model using regional geophysical observations and analyze it jointly with teleseismic backprojection we find that the shallow and deep portions of the megathrust are segmented and have fundamentally different behavior we forward calculate local tsunami propagation from the resolved slip and find good agreement with field measurements independently validating the slip model these results show that the central portion of the chilean subduction zone has accumulated a significant shallow slip deficit and indicates that given enough time shallow slip might be possible everywhere along the subduction zone

sea water circulation on an oolite dominated carbonate system in an epeiric sea middle jurassic switzerland the middle jurassic burgundy carbonate platform occupied a central part of the central european epeiric sea during the middle jurassic the facies architecture of the oolitic calcarenite bodies was affected by tidal currents on the platform and relative sea level changes the 13c values of inorganic carbonates sampled in biostratigraphic defined intervals do not match very well between closely spaced sections and hence are of restricted use for stratigraphic purposes it appears that the platform interior might have been decoupled from the global carbon pool although deposited in a rapidly accumulating setting the recorded isotope signatures might be affected by some local stratigraphic gaps nonetheless the carbon isotope data imply lateral changes of the platform waters these appear to be related to the position on the platform and to the sediment dispersal pattern as evidenced by clay minerals adjacent to the eastern margin of the platform detrital chlorite and illite occur in considerable proportions both ascribed to a boreal source to the east and the north east in contrast smectite rich mixed layer clay mineral content increases significantly towards the platform interior pointing to a delivery from the north west all these data are suggestive of an overall clockwise current pattern in the central european epeiric sea during the middle jurassic

reactivated basement structures affecting the sedimentary facies in a tectonically quiescent epicontinental basin an example from nw switzerland abstract the jurassic deposits in the southern part of central europe accumulated in a shallow epicontinental sea and their deposition has usually been believed to have corresponded to a phase of tectonic quiescence neither on conventional seismic records nor in outcrops obvious indications of synsedimentary tectonics were found nonetheless subtle variations in lithofacies and thickness occur above faults in the crystalline basement in fact preexisting structures became reactivated in the jurassic during major extensional phases when the tethys and the north atlantic opened this reactivation led to differential subsidence and or to rotation of fault bounded blocks but the sediments were deformed mainly flexurally as vertical movements in the basement were dissipated by triassic salt thus the depositional area was morphologically differentiated into swells and depressions in siliciclastic muddy environments swells were characterized by hardbottoms and hiatus beds depressions were filled by distal tempestites and gravity deposits in carbonate settings reefs nucleated on swells marls and muds were deposited in depressions many of them gravity deposits reactivation of faults occurred only during short episodes and was not synchronous throughout the study area and reactivation of individual faults was episodic and probably controlled by the palaeostress field and the faults orientation reactivation of deep rooted faults is also documented by hydrothermal activity which led to vein mineralization and alteration of minerals today exposed in nearby basement units the chronostratigraphic ages of the hydrothermal processes coincide with phases of enhanced subsidence during the sinemurian aalenian bajocian bathonian and oxfordian in turn facies changes of the sedimentary cover should be useful to predict basement structures when no seismic records are available

episodic development of a convergent margin inferred from structures and processes along the southern chile margin seismic reflection data acquired in the vicinity of isla mocha across the southern coast of chile image structures formed along the continental margin and reveal an episodic history of accretion nonaccretion and possibly erosion structures formed at the toe of the continental slope suggest frontal accretion of to 1 km of trench fill seismic images also reveal that a small accretionary wedge 20 30 km wide abuts the truncated continental metamorphic basement that extends seaward from beneath the shelf the small size of the accretionary wedge on three profiles examined here is not consistent with a long history of accretion with the current deformational style as current rates of frontal accretion could have accumulated all of the existing accretionary wedge in less than 1 2 m y this is a small fraction of convergence history along this margin and the current accretionary mode has not been consistently maintained in the past the isla mocha region is located between the temperate climate of central chile and the glacial climate of southern chile and climatic conditions in this region have likely fluctuated sufficiently to cause significant variation in trench sediment supply accretionary and nonaccretionary or erosional episodes are probably linked to temporal variations in trench sediment thickness as suggested by observations along the chile margin currently thick trench sediment correlates with accretion along the southern chile margin and thin trench sediment correlates with nonaccretion tectonic erosion as near the chile ridge and from the juan fernandez ridge to northern chile the isla mocha region also lies 900 1000 km north of the chile triple junction and the chile ridge lies approximately 2000 km to the west and has not yet collided and affected the margin near isla mocha this part of the precollision zone provides an excellent reference to examine the effects of chile ridge collision in the development of the chile margin the most apparent effect of subduction of the buoyant young crust of the chile ridge is a shallow trench that is nearly devoid of sediment consequently the triple junction is undergoing nonaccretion or erosion and the accretionary complex near the triple junction remains smaller than to the north or south because the current phase of rapid accretion elsewhere in the trench has bypassed the triple junction region the interplay of subduction zone processes such as trench sedimentation and ridge collision has resulted in an episodic development of the margin and produced a discontinuous record of convergence history within the accretionary wedge

subsidence of the paris basin we discuss the main results of a systematic quantitative analysis of the subsidence of the paris basin made on 100 wells backstripping techniques with decompaction as well as sea level and water depth corrections are used to derive tectonic subsidence curves in the absence of water and sediment loading assuming local as well as regional compensation a best fitting sea level variations curve is derived for the deepest central part on the basis of the resulting tectonic subsidence curve the adopted amplitude of the regression since upper cretaceous is 330 m the spatial and temporal distribution of tectonic subsidence is reconstructed and discussed it is shown that rigidity of the lithosphere with an adopted 50 km flexural parameter plays a significant role these results are then quantitatively interpreted in terms of the lithospheric stretching model this interpretation is reasonable provided it is made in terms of volumetric subsidence over the whole basin because of the thermal conduction and the rigidity low pass filtering effects the subsidence can be explained if the axial zone was thinned during permo triassic by a factor of about 1 3 with respect to the adjacent lithosphere it is shown that either the initial altitude was more than 500 m above sea level or the lower part of the lithosphere was lost at the beginning of the permo triassic phase of extension resulting in a rapid uplift of several hundreds of meters the similarity of the permo triassic initiating extensional phase with active continental rifting is shown

determination of earthquake focal depths and source time functions in central asia using teleseismic p waveforms we developed a new method to determine earthquake source time functions and focal depths it uses theoretical green s function and a time domain deconvolution with positivity constraint to estimate the source time function from the teleseismic p waveforms the earthquake focal depth is also determined in the process by using the time separations of the direct p and depth phases we applied this method to 606 earthquakes between 1990 and 2005 in central asia the results show that the centroid moment tensor solutions which are routinely computed for earthquake larger than m5 0 globally using very long period body and surface waves systematically over estimated the source depths and durations especially for shallow events away from the subduction zone most of the 606 earthquakes occurred within the top 20 km of crust this shallow distribution of earthquakes suggests a high geotherm and a weak ductile lower crust in the region

long duration penetration of the interplanetary electric field to the low latitude ionosphere during the main phase of magnetic storms 1 it is well known that the interplanetary electric field can penetrate to the low latitude ionosphere it is generally believed that the penetration of electric fields can last only for 30 min because of the shielding effect in the ring current in this paper we present the observations of the dayside ionospheric electric field enhancements at middle and low latitudes in association with reorientations of the interplanetary magnetic field imf in six cases the eastward electric field in the dayside equatorial ionosphere measured by the jicamarca incoherent scatter radar was enhanced for 2 3 hours after the imf turned southward and remained continuously southward in one case the eastward electric field in the dayside midlatitude ionosphere measured by the millstone hill incoherent scatter radar was continuously enhanced for 10 hours during southward imf since millstone hill is close to the equatorward boundary of the auroral zone during magnetic storms the penetration electric field there may be different from that at the equatorial ionosphere the most striking feature of the measurements is that the enhancements of the ionospheric electric field can last for many hours without significant decay the electric field enhancements in the middle and low latitude ionosphere are closely related to magnetic activity and occur during the main phase of magnetic storms the observations show that the interplanetary electric field can continuously penetrate to the low latitude ionosphere without shielding for many hours as long as the strengthening of the magnetic activity is going on under storm conditions

advancement in source estimation techniques using broadband regional seismograms one important constraint on source retrieval from regional seismograms comes from the amplitude difference between various phases such as pnl surface wave sv sh because the misfit errors used in some waveform inversions are normalized by the data and synthetics the amplitude information in the data has not been fully utilized in this article we modify the cut and paste source estimation technique zhao and helmberger 1994 by removing this type of normalization it is shown that the modified method increases the stability and resolution of inversion when multiple stations at different distance ranges are used a distance scaling factor is introduced to compensate for the amplitude decay with distance by applying the technique to the terrascope data we have determined source mechanisms and depths of 335 southern californian events with m l 3 5 the amplitude decays with distance are r 1 13 for pnl r 0 55 for love waves and r 0 74 for rayleigh waves in contrast to generally shallow source depths reported by the southern california short period network the depth distribution from waveform inversion shows a strong peak around 12 km with few earthquakes occurring above 5 km and below 20 km

sea level variations global sedimentation rates and the hypsographic curve sea level changes during the neozoic have been estimated by two different methods the first involves measuring the amount of present day land area which was flooded during the past and using the present day hypsographic curve to estimate the amount of sea level rise necessary to produce this flooding the second involves the estimation of the changing volume of mid oceanic ridges through time and estimating sea level changes after having allowed for isostatic adjustment a difference in sea level of 170 m is obtained from the two methods for the cretaceous 80 100 m y b p this is equivalent to a difference in continental flooding of 24 mm 2 using the present day hypsographic curve we attempt to explain this difference firstly by allowing for the fact that the present day ocean basins have more sediment in them than did the cretaceous ocean basins this produces a sea level change in the opposite direction to that produced by the reduction in mid ocean ridge volume since the cretaceous secondly we suggest another large factor in producing the difference is that the present day hypsographic curve is not the correct one to use when studying sea level stands in the cretaceous present day average continental heights are closely related to continental areas accepting this principle if continents are joined together in the past their average height must be greater and so their hypsographic curve must be steeper a given sea level rise would produce less continental flooding during times of continental aggregation than it would today

fault interactions and triggering during the 10 january 2012 mw 7 2 sumatra earthquake the 10 january 2012 mw 7 2 sumatra earthquake in the wharton basin occurred 3 months before the great mw 8 6 and mw 8 2 earthquakes in the same region which had complex ruptures and are the largest strike slip earthquakes ever recorded teleseismic p wave back projection of the mw 7 2 earthquake images a unilateral rupture lasting 40 s without observable frequency dependency low frequency 0 05 0 3 hz high frequency 0 3 1 hz in addition to radiation bursts during the mw 7 2 main shock coherent energy releases from 50 to 75 s and from 100 to 125 s are observed about 143 km northeast of the main shock rupture and landward of the trench analysis of globally recorded p waves in both 0 02 0 05 hz velocity records and 1 5 hz stacked envelope functions confirms the presence of coherent sources during the time windows the observed energy bursts are likely to be large early aftershocks occurring on or near the subduction interface both dynamic and static triggering could have induced these early aftershocks as they initiated after the surface wave passed by and the coulomb stress perturbations from the mw 7 2 main shock promote earthquakes in the observed locations the earthquake sequence is a clear example of a seaward intraplate strike slip earthquake triggering landward intraplate earthquakes in the same region in contrast to previously reported normal reverse or reverse normal interactions at subduction zones

intraplate stresses a new tectonic mechanism for fluctuations of relative sea level stress variations in the lithosphere of a few hundred bars can explain the major part of the seismostratigraphic record at passive margins and intracratonic basins however to induce apparent sea level fluctuations with magnitudes greater than 50 m changes in stress level of more than 1 kbar are required these must be related to major reorganizations at convergent plate boundaries fragmentation of plates or collision processes specific rapid falls in the vail et al curves can be associated quantitatively with particular plate tectonic reorganizations of lithospheric stress fields the seismostratigraphic record may provide a new source of information on paleo stress fields to be correlated with results of independent numerical modeling of intraplate stresses

haq et al eustatic sea level curve implications for sequestered water volumes the eustatic sea level curve of haq and co workers differentiates a long and a short term signal the mechanism that controls the long term curve is primarily variation in the volume of the ocean basins while the short term curve reflects changes in ocean water volume only glacial eustasy operates at the frequency and with sufficient magnitude to control the short term curve at each increment of time the volume of water sequestered from the ocean basins to account for the difference between the long and short term curves is computed incorporating both hypsometric and water loading factors an amount equivalent to that of present day antarctica was sequestered at an approximately 5 ma frequency since 145 ma but direct geological evidence of late jurassic to early tertiary continental ice of this equivalent magnitude is lacking because the existing ice coverage of antarctica inhibits direct observation we use the known fractionation affects of sequestration of water on the oxygen isotopic composition

discriminating between tectonic and eustatic controls on the stratigraphic record in the paris basin the quantification of tectonic and eustatic factors in the control of the sedimentary record is one of the main questions in sedimentary basin dynamics we propose two methods allowing i 3d measurement of accommodation at basin scale and ii to decipher between local 10 100 km wavelength and basin scale accommodation the local signal is necessarily of tectonic origin the basin scale signal is of both eustatic and large tectonic origin the measurement of accommodation requires a high resolution time lines calibrated in ages sequence stratigraphy on well logs and biostratigraphy on cores b decompacted lithologies well logs and c palaeodepth palaeoaltitude sedimentology and well logs application of these methods to the intracratonic paris basin during the lias early jurassic suggests a tectonic origin for the 1 5 myr stratigraphic cycles with basin scale flexure during transgressive half cycles and 10 100 km uplift of basement units during regressive half cycles

from a mountain belt collapse to a sedimentary basin development 2 d thermal model based on inversion of stratigraphic data in the paris basin abstract the thermal mineralogical and mechanical behaviour of the lithosphere determines the genesis and evolution of sedimentary basins subsidence amplitude geometry of sediment bodies sedimentary processes using the large stratigraphic database available for the paris basin we constrain the lithosphere thermal evolution thickness and rigidity as well as the mechanism that gave birth to this wide intracontinental basin the thermal subsidence calculated with a two dimensional thermal model is adjusted to the estimated tectonic subsidence by optimization of three parameters extension profile crustal thickness profile and average mantle heat flow the best fits for the paris basin lithosphere are obtained for a mantle heat flow of 23 mw m 2 and for an elastic thickness lower than 20 km preferred value te 5 km two mechanisms for the origin of the basin subsidence have been tested a pure extensional collapse of the variscan belt and a delamination of the mantle lithosphere at the end of carboniferous it appears that in both cases inverted extension factors are large in the range 1 2 1 85 in the first case and in the range 1 0 1 85 in the second case both cases involve the presence of a thick variscan crustal wedge and a mountain belt elevation of 1500 3500 m located in the paris basin centre the maximum extensional rates are obtained in the centre part of the basin in addition lithospheric delamination at around 300 ma allows for both crustal and mantle melting in agreement with the widespread existence of permian bimodal magmatism in france at the end of extension the basin centre kept a high elevation of about 1000 m before subsiding around 40 my later below sea level

growth and demise of the jurassic carbonate platform in the intracratonic paris basin france interplay of climate change eustasy and tectonics it is usually very difficult to identify and quantify the relative influence of tectonics eustasy and climateon carbonate system evolution from sedimentary records in order to improve our understanding of these mechanisms we have traced for the first time the evolution of the eastern paris basin platform throughout the entire jurassic period this carbonate platform underwent eight successive growth and demise phases with different depositional profiles ranging from ramps to flat topped geometries the eight carbonate growth periods are compared with the standard sea level curves local tectonic regimes and recently published oxygen isotope and or clay mineralogy databases prograding heterozoan facies along ramp profiles mark periods dominated by second order eustatic sea level rise relatively cool sea surface temperatures and mesotrophic and humid conditions hettangian pliensbachian late oxfordian tithonian during these periods variable detrital contents in the sedimentary succession hampered the efficiency of shallow marine carbonate factories higher sea surface temperatures oligotrophic and humid conditions associated with either eustatic sea level rise or very high local subsidence occurred during the early bajocian and the mid oxfordian these seawater properties seem to have favoured the aggradation of scleractinian corals forming dome shaped bioherm buildups an oolitic and lime mud carbonate system deposited during the bathonian second order eustatic sea level fall is characterised by miliolid rich micritic facies on a rimmed ramp under stable cooler and drier conditions the secondorder maximum flooding associated with a sea surface temperature decline and or a seawater eutrophication caused at least five carbonate demise periods i e toarcian earliest late bajocian callovian oxfordian transition earliest late oxfordian and kimmeridgian

three dimensional full waveform inversion of short period teleseismic wavefields based upon the sem dsm hybrid method we present a method for high resolution imaging of lithospheric structures based on full waveform inversion of teleseismic waveforms we model the propagation of seismic waves using our recently developed direct solution method spectral element method hybrid technique which allows us to simulate the propagation of short period teleseismic waves through a regional 3 d model we implement an iterative quasi newton method based upon the l bfgs algorithm where the gradient of the misfit function is computed using the adjoint state method compared to gradient or conjugate gradient methods the l bfgs algorithm has a much faster convergence rate we illustrate the potential of this method on a synthetic test case that consists of a crustal model with a crustal discontinuity at 25 km depth and a sharp moho jump this model contains short and long wavelength heterogeneities along the lateral and vertical directions the iterative inversion starts from a smooth 1 d model derived from the iasp91 reference earth model we invert both radial and vertical component waveforms starting from long period signals filtered at 10 s and gradually decreasing the cut off period down to 1 25 s this multiscale algorithm quickly converges towards a model that is very close to the true model in contrast to inversions involving short period waveforms only which always get trapped into a local minimum of the cost function

temperate carbonates on a modern low energy isolated ramp the balearic platform spain abstract this paper presents a depositional model for a temperate low energy carbonate ramp based on descriptive studies of five areas around the balearic islands of mallorca and menorca this low energy ramp differs significantly from other present day temperate carbonate platforms that are primarily high energy open shelves it is characterized by the following lithofacies from shore to basin 1 lagoon 2 barrier island 3 shallow subtidal 4 inner ramp 5 middle ramp and 6 distal ramp subaqueous carbonate dunes are present near slope breaks off menorca and cabrera but they are not representative of the entire ramp balearic ramp sediments differ in composition texture biology and degree of cementation from those on modern low energy tropical ramps balearic ramp carbon tes lack ooids and peloids hermatypic coral buildups and calcareous green algae except in one restricted bay where halimeda is relatively common red algal sands and gravels extend to depths of up to 90 m and are coarser than their strandplain equivalent lime sands skeletal allochems consist of the bryomol rhodalgal association marine cementation is rare and the carbonate fraction of deep water muds is mainly mg calcitic and calcitic in composition aragonite is rare except for the red alga peyssonnelia which is composed of aragonite it is neither a dominant skeletal constituent nor common as a cement the mediterranean sea off mallorca and menorca is a low energy temperate oligotrophic clear water environment the depositional model for the region is an isolated platform configured as a homoclinal ramp ancient counterparts of the balearic ramp are present in the neogene of the mediterranean tethys and the paratethys and though the constituents of fossil assemblages vary with time the biota of the balearic ramp such as bryozoans red algae echinoderms and mollusks ranges from the paleozoic era to the present echinodermal bryomols passing to basinal muds on carbonate ramps are particularly characteristic of the early carboniferous in north america and europe this suggests that the balearic islands temperate ramp may be more representative of some ancient carbonate sequenc s than either temperate high energy open shelves or tropical ramps in the present oceans

three dimensional accommodation analysis of the keuper of the paris basin discrimination between tectonics eustasy and sediment supply in the stratigraphic record abstract during the keuper the paris basin was an intracratonic sedimentary basin filled by continental deposits using paleo environmental isopach and paleo altitude maps we estimate the variations of accommodation rate at the scale of stratigraphic minor hemi cycle 1 3 ma an analysis of the short and long wavelength accommodation variations allows us to assess the relative influence of tectonics eustasy and sediment supply on the stratigraphic record our data suggest a pattern of subsidence along three trends e w in the carnian e w to nne ssw in the norian and ne sw in the norian rhaetian during the keuper the paris basin accurately records the different phases of the opening of the tethys ocean associated with a rotation of the extension direction the norian cycle could thus reflect the intraplate stresses in a transitional period between the triassic and the liassic

spike like change of the vertical e b drift in the equatorial region during very large geomagnetic storms 1 we investigate the characteristics of the storm time disturbance electric fields in the equatorial region using the measurements of the vertical ion velocity from the defense meteorological satellite program f13 and the first republic of china satellite during the selected 43 geomagnetic storms of dst 100 nt in 2000 2004 the distinguishing feature in both observations is the occurrence of the spike like vertical e b drift during the main phase of very large storms dst 150 nt the spikes occur simultaneously at different local times but the direction of the spikes shows a dependence on the local time the spikes are upward on the dayside and downward on the nightside the observed characteristics of the spikes can be explained by the penetration of the dawn to dusk polar cap electric field to low latitude

epeirogeny and eustatic sea level changes as inferred from cretaceous shoreline deposits applications to the central and western united states uplift and subsidence histories of continental margins are by now reasonably well understood in the context of plate tectonics but the epeirogenic movements of continental interiors have been neither well documented nor properly understood epeirogenic movements are important to recognize when reconstructing paleogeography and may yield information regarding mantle dynamics and the amplitudes wavelengths and rates of lithospheric flexure sediments deposited at or near sea level can be used as a worldwide datum against which to measure postdepositional epeirogenic movements the present elevations of shoreline sediments of epicontinental seas deposited during sea level highstands at particular times in the past define a warped surface documenting subsequent epeirogeny of continental interiors when the amplitude of sea level rise during transgression is small relative to the observed epeirogenic motions the diachronous shoreline deposits represented in the entire transgressive surface can be used as a datum in the analysis thus greatly augmenting the available data and areal coverage if a stable frame of reference can be defined a eustatic sea level correction can be applied to every continent the elevation of the upper cenomanian mid cretaceous shoreline gives little evidence of warping tilting or uplift in central cratonic north america but indicates that a large area of the western united states including the colorado plateau has undergone more than 2 km of post cenomanian epeirogenic uplift

gps derived interseismic coupling on the subduction and seismic hazards in the atacama region chile the atacama region between 29 s and 25 s is located in the north central area of chile a tectonically complex transition area between north and central chile deformation in atacama is due mainly to elastic loading on the subduction interface but also to diffuse shortening in the sierras pampeanas argentina the seismicity of the subduction is complex in this region seismic swarms often occur moderate mw 6 to large mw 7 earthquakes occur repeatedly and finally megathrust earthquakes of magnitudes significantly larger than 8 occur once in a while the last one being in 1922 almost a century ago we use new gps data we collected in the atacama region between 2008 and 2012 to complete and densify existing data we acquired since 2004 in north central chile these new data allow to quantify the motion of the andean sliver and assess the kinematic coupling on the subduction interface at these latitudes we find that only 7 per cent of the whole convergence motion is taken up by an eastward rotation of the rigid sliver a large part of the remaining 93 per cent approximately 6 cm yr gives way to accumulation of elastic deformation in the upper plate due to locking on the plate interface this accumulation shows important along strike and along dip variations interpreted in terms of variable coupling which we correlate with seismicity we identify two areas of low coupling near the la serena 30 s and baranquilla 27 5 s bays both are correlated with the subduction of singular bathymetric features and seem to stop the propagation of large seismic ruptures these zones are also seismic swarm prone areas which seem to occur rather on their edges these low coupling areas separate two seismic segments where coupling is high the atacama segment 100 km long between 29 s and 28 s and the cha naral segment 200 km long between 27 s and 25 s should they rupture alone these segments are sufficiently coupled and apparently since long enough to produce mw 8 events however a collective failure of both segments could generate a megathrust earthquake of magnitude close to 8 5 similar to the 1819 and 1922 complex events which produced important tsunamis such giant events may occur in the area once a century

high resolution seismic array imaging based on an sem fk hybrid method we demonstrate the feasibility of high resolution seismic array imaging based on teleseismic recordings using full numerical wave simulations we develop a hybrid method that interfaces a frequency wavenumber fk calculation which provides analytical solutions to 1 d layered background models with a spectral element sem numerical solver to calculate synthetic responses of local media to plane wave incidence this hybrid method accurately deals with local heterogeneities and discontinuity undulations and represents an efficient tool for the forward modelling of teleseismic coda including converted and scattered waves we benchmark the accuracy of the sem fk hybrid method against fk solutions for 1 d media we then compute sensitivity kernels for teleseismic coda waves by interacting the forward teleseismic waves with an adjoint wavefield produced by injecting coda waves as adjoint sources based on adjoint techniques these sensitivity kernels provide the basis for mapping variations in subsurface discontinuities density and velocity structures through non linear conjugate gradient methods we illustrate various synthetic imaging experiments including discontinuity characterization volumetric structural inversion for the crust or subduction zones these tests show that using pre conditioners based upon the scaled product of sensitivity kernels for different phases combining finite frequency traveltime and waveform inversion and or adopting hierarchical inversions from longto short period waveforms could reduce the non linearity of the seismic inverse problem and speed up its convergence the encouraging results of these synthetic examples suggest that inversion of teleseismic coda phases based on the sem fk hybrid method and adjoint techniques is a promising tool for structural imaging beneath dense seismic arrays

effects of near source seafloor topography on long period teleseismic p waveforms in the study of the shallow earthquakes in the subduction zones reverberations inside the water layer near the source are known to affect very significantly the far field body waveforms the usual correction is to take a horizontally layered model as the near source structure but it is not realistic for the trench geometry therefore finite difference simulation combined with far field ray theory is employed in order to examine the effects of the realistic non flat seafloor topography as a realistic trench model the japan trench is selected the response of the structure near the source is calculated by two dimensional finite difference simulation then teleseismic p waveforms are calculated by using reciprocal theorem our results suggest that 1 around the trench bottom effects of non planar structure are remarkable and the realistic seafloor cannot be approximated by any model of planar structure however 2 effects of the continental slope are well approximated by a model of planar dipping seafloor of appropriate dip therefore the near source structure must include the realistic seafloor topography or the waveform analyses may lead to spurious subevents in a later stage of rupture process and mislocation of events our results also show that present knowledge about the seafloor topography is enough to incorporate the complicated geometry

global synthetic seismograms using a 2 d finite difference method two dimensional 2 d finite difference fd synthetics which fill the gap between fast 1 d analytic synthetics and time consuming full 3 d synthetics in our ability to model seismograms have been used in many studies we address several issues involving 2 d fd methods in generating global synthetic seismograms these include 1 interfacing point source excitation for earthquakes with 2 d fd methods 2 out of plane spreading corrections and 3 reducing the spherical earth to the flattened models the first issue is tackled using two methods a transparent source box approach and a moment tensor excitation approach where each has its own advantages moreover our source box excitation does not have the late time drift problem that occurred in previous studies the out of plane geometric spreading correction is accounted for by estimating the ray parameter and applying a post simulation filter to 2 d synthetics finally parameters of the earth flattening transformation are discussed and validated the effectiveness of this method is demonstrated by comparing our synthetics with frequency wavenumber summation normal mode and 3 d spectral element synthetics

teleseismic synthetics obtained from 3 d calculations in 2 d media summary at subduction zones the laterally heterogeneous medium such as the steeply dipping sea bottom and thick sedimentary layers causes large effects on the teleseismic body waveforms from the shallow events occurred in this region we develop a new method to incorporate these effects from near source structure in calculating the teleseismic body waveforms to incorporate the structural effects we simulate 3 d elastic wave propagation in a two dimensionally heterogeneous structure although the simulated wavefield is 3 d our method does not require huge computer storage this is because we assume a 2 d structure to reduce the dimension of the equations of motion by spatial fourier transform because of the strong laterally heterogeneous features such as steeply dipping sea bottom and thick sedimentary layers and because of the 2 d geometry of the oceanic trench our method is particularly applicable to the shallow subduction zone earthquakes in our formulation we assume a 2 d model structure in which the physical properties are constants in the direction parallel to the trench axis then we apply the spatial fourier transform to the equations of motion in that direction the resultant wavenumber domain equations can be solved as independent sets of 2 d equations on a computer with a moderate sized storage we solve these wavenumber domain equations by the staggered grid finite difference method finally the inverse fourier transform provides the 3 d displacement field the reciprocal principle is used to obtain the teleseismic displacement first the response of the near source structure to an input plane p wave is calculated by the 3 d method introduced here then based on the reciprocal principle convolution of the response strain at the source position with the moment tensor is calculated to get far field p wave displacement as an example of the application of the present method we calculated the waveforms from a shallow thrust event that occurred at the kurile trench 1964 october 16 ms 6 5 the synthetics calculated by the new method reproduce the large amplitude later arrivals in the observed seismograms furthermore a reasonable source position is obtained from the waveform analysis

bathymetric effects on body waveforms from shallow subduction zone earthquakes and application to seismic processes in the kurile trench resolution of earthquake source characteristics is limited by structural complexities in the source region this study explores the effects of dipping near source bathymetry and structure on long period teleseismic body waveforms from shallow subduction zone earthquakes ray theory synthetics calculated for shallow double couple sources and velocity structures incorporating planar dipping interfaces suggest that p waveforms are most sensitive to water depth and sea bottom orientation for sources beneath a substantial water layer the seafloor dip of the inner trench slope can give rise to prominent later arrivals and waveform complexity not found on synthetics calculated for horizontal bathymetry sediment thickness and the dip of the sediment crust and crust mantle interfaces generally have lesser effects the high amplitude arrivals result largely from changes in the source takeoff angles of the reverberations these arrivals present difficulties for source depth and time function determination from p waveforms and may cause spurious complexity in the derived pattern of earthquake moment release sh waveforms show little effect of sea bottom orientation or local structure for shallowly dipping thrust faulting events suggesting that sh waveform analysis can stabilize source parameter studies with respect to unknown or incompletely parameterized bathymetry and structure effects of nonhorizontal structure are observed in the p waveforms from shallow kurile trench events ms 5 8 7 2 which show prominent later arrivals not observed on sh waveforms synthetics calculated for a dipping water crust interface provide a better fit to these arrivals than those calculated for a horizontal interface suggesting that the p waveforms show systematic effects of seafloor dip the synthetics are highly sensitive to the assumed orientation of the seafloor the data are fit best for seafloor orientations consistent with the dip of the inner trench slope the distorting effect of the water layer gives rise to systematic differences in p wave complexity between shallow events near the seismic front which occur beneath a thick water layer and show numerous later arrivals and deeper arcward events which occur beneath a thin water layer and show simple waveforms large reverberations in the p waveforms of the october 20 1963 and june 10 1975 kurile tsunami earthquakes have previously been used as evidence for a long source duration and a change in focal mechanism during rupture however sh waveforms suggest simple source time functions with durations of 25 and 43 s inversion of p and sh waveforms and amplitudes yields shallowly dipping thrust mechanisms with no conclusive evidence for a previously proposed steepening of the fault dip during rupture the large p wave reverberations cannot be fit using a point source and a horizontal seafloor detailed modeling of the 1963 event as an upward propagating rupture extending through low velocity sediments to the ocean bottom combined with the effects of the dipping seafloor allow the reverberation amplitudes to be matched the anomalous tsunami excitation appears to be related to the location of the sources at shallow depths within low velocity sediments

effects of near source bathymetry on teleseismic p waveforms teleseismic p waveforms from submarine earthquakes show water reverberations that are often poorly modeled by synthetic seismograms this study suggests that considerable misfit results from the non horizontal nature of the seafloor in the epicentral region and examines this effect for a planar dipping water crust interface geometric ray theory synthetics calculated for a double couple source show that p waveforms are extremely sensitive to seafloor orientation because of the large impedance contrast across the boundary seafloor dips as small as 0 5 significantly modify the ray paths affecting the take off angle at the source reflection and transmission coefficients at the interface geometric spreading and travel time to test the applicability of such modeling p waveforms from the march 29 1976 cocos ridge intraplate earthquake were studied the waveforms many of which show prominent water multiples poorly modeled with flat lying bathymetry were inverted for the best fitting planar ocean bottom orientation using a grid search technique synthetics computed for the best fitting seafloor orientation match the data much better than synthetics for a flat lying structure and reproduce the observed azimuthal dependence of water multiple amplitudes the derived ocean bottom dip angle and direction are in agreement with bathymetric charts suggesting p waveforms provide constraints on the seafloor orientation in the epicentral region green s functions incorporating the effects of bathymetry should provide better resolution of the source parameters of submarine earthquakes

sediment routing system and sink preservation during the post orogenic evolution of a retro foreland basin the case example of the north pyrenean aquitaine bay of biscay basins abstract we investigated here the evolution of the sediment routing system i e the sediment transport and deposition evolution along successive depositional topographies and environments and the sink i e deposited sediments preservation in a foreland basin from the period of mountain belt shortening to its post orogenic stage the studied system is the north pyrenean retro foreland basin from 50 ma to today which is composed of a subsiding platform the aquitaine basin fed by the erosion of the pyrenees passing laterally to a slope and a deep sea plain the bay of biscay deep basin the ultimate area of deposition this study is based on a double seismic stratigraphic and structural analysis of an extensive seismic dataset and on an age model of the sediments combining biostratigraphy orbitostratigraphy and sequence stratigraphy with a time resolution of 0 1 ma four major periods of deformation corresponding to a single or a set of stratigraphic sequence boundaries were characterized the pyrenean shortening decrease may be recorded by a basin scale uplift at 49 8 ma late ypresian the paroxysm of the piggy back shortening and related uplift is dated at 35 8 ma priabonian the end of the pyrenees shortening transition to post orogenic conditions is well dated between 27 1 and 25 2 ma chattian a major west european scale deformation of possible mantle origin uplifted the basin from 16 4 to 10 6 ma late burdigalian to early tortonian these major periods of deformations controlled the sink preservation at the first order through the ratio between the accommodation space created by subsidence on the aquitaine platform asub and the siliciclastic sediment supply coming from the erosion of the pyrenees ssc a general model is proposed at the time of the foreland basin when asub ssc most of the sediments are preserved on the platform as a progradational aggradational wedge up to 25 2 ma here at the time of the post foreland evolution when asub the continental sediment routing system is mainly provided along nearly flat alluvial plains with extensive lakes and or humid zones i e the local base levels of the alluvial fans the aquitaine retro foreland was never overfilled

two stage composite megathrust rupture of the 2015 mw8 4 illapel chile earthquake identified by spectral element inversion of teleseismic waves the mw8 4 illapel earthquake occurred on 16 september was the largest global event in 2015 this earthquake was not unexpected because the hypocenter was located in a seismic gap of the peru chile subduction zone however the source model derived from 3 d spectral element inversion of teleseismic waves reveals a distinct two stage rupture process with completely different slip characteristics as a composite megathrust event the two stages were temporally separated rupture in the first stage with a moment magnitude of mw8 32 built up energetically from the deeper locked zone and propagated in the updip direction toward the trench subsequently the rupture of the second stage with a magnitude of mw8 08 mainly occurred in the shallow subduction zone with atypical repeating slip behavior the unique spatial temporal rupture evolution presented in this source model is key to further in depth studies of earthquake physics and source dynamics in subduction systems

a hybrid method to compute short period synthetic seismograms of teleseismic body waves in a 3 d regional model we present a hybrid method to simulate the propagation of short period teleseismic body waves through 3 d regional models the incident wavefield is computed in an spherically symmetric reference earth model based on the direct solution method the global and regional wavefields are matched at the boundaries of the regional mesh in the regional domain we implement a spectral element method with absorbing boundaries to cancel the outgoing scattered wavefield the hybrid method is successfully benchmarked against the direct solution method in the reference earth model iasp91 the potential of the method is illustrated by computing short period p wave synthetic seismograms in a 3 d model with a 20 km moho offset and or topography on the free surface focusing on the actual example of the pyrenees

rapidly estimated seismic source parameters for the 16 september 2015 illapel chile m w 8 3 earthquake on 16 september 2015 a great m w 8 3 interplate thrust earthquake ruptured offshore illapel chile producing a 4 7 m local tsunami the last major rupture in the region was a 1943m s 7 9 event seismic methods for rapidly characterizing the source process of value for tsunami warning were applied the source moment tensor could be obtained robustly by w phase inversion both within minutes chilean researchers had a good solution using regional data within 5 min and within an hour using broadband seismic data short period teleseismic p wave back projections indicate northward rupture expansion from the hypocenter at a modest rupture expansion velocity of 1 5 2 0 km s finite fault inversions of teleseismic p and sh waves using that range of rupture velocities and a range of dips from 16 consistent with the local slab geometry and some moment tensor solutions to 22 consistent with long period moment tensor inversions indicate a 180 to 240 km bilateral along strike rupture zone with larger slip northwest to north of the epicenter with peak slip of 7 10 m using a shallower fault model dip shifts slip seaward toward the trench while a steeper dip moves it closer to the coastline slip separates into two patches as assumed rupture velocity increases in all cases localized 5 m slip extends down dip below the coast north of the epicenter the seismic moment estimates for the range of faulting parameters considered vary from 3 7 1021nm dip 16 to 2 7 1021 nm dip 22 the static stress drop estimates range from 2 6 to 3 5 mpa and the radiated seismic energy up to 1 hz is about 2 2 3 15 1016 j

localized water reverberation phases and its impact on backprojection images coherent radiators imaged by back projections bp are commonly interpreted as part of the rupture process nevertheless artifacts introduced by structure related phases are rarely discriminated from the rupture process in this study we use a calibration event to discriminate between rupture and structure effects we re examine the waveforms and bp images of the 2012 mw 7 2 indian ocean earthquake and a calibration event mw 6 2 the p wave codas of both events present similar shape with characteristic period of approximately 10 s which are back projected as coherent radiators near the trench s wave bp doesn t image energy radiation near the trench we interpret those coda waves as localized water reverberation phases excited near the trench we perform a 2d waveform modeling using realistic bathymetry model and find that the steep near trench bathymetry traps the acoustic water waves forming localized reverberation phases these waves can be imaged as coherent near trench radiators with similar features as that in the observations we present a set of methodologies to discriminate between the rupture and propagation effects in bp images which can serve as a criterion of subevent identification

tectonic control of the subducting juan fernandez ridge on the andean margin near valparaiso chile near the latitude of valparaiso chile a fundamental change in configuration of the benioff zone volcanic arc activity and the structure of the continental margin occurs opposite the subducting juan fernandez ridge upper plate tectonics related to subduction of the ridge were studied by an international group of geoscientists in the two degree segment offshore valparaiso extending from the shelf edge seaward across the eastern end of juan fernandez ridge near the o higgins group of seamounts the juan fernandez ridge strikes northeast rather than continuing its east west trend across the pacific basin the ridge uplifts the upper plate and sediments of the valparaiso basin are deformed against its southern flank this deformation is consistent with the southward migration required by an oblique trending ridge and the nearly trench normal vector of plate convergence in the trench axis the ridge forms a basement barrier behind which sediments 2 5 km deep have ponded the lower slope over the ridge appears eroded whereas the margin not yet affected by ridge subduction is fronted by an accretionary prism about 25 km wide nazca plate relief clearly influences tectonism of the margin where it subducts beneath thin continental crust its relation to deeper processes segmenting the andean orogen appears to involve prior tectonic events

coherent seismic arrivals in the p wave coda of the 2012 m w 7 2 sumatra earthquake water reverberations or an early aftershock

rapid erosion of the southern african plateau as it climbs over a mantle superswell we present new sedimentary flux data confirming that a large pulse of erosion affected the southern african plateau in the late cretaceous and is likely to be related to a major uplift episode of the plateau this short phase of erosion i e less than 30 myr in duration has commonly been difficult to reconcile with a mantle origin for the plateau anomalous uplift given its size the rise of the african superplume is likely to have lasted much longer here we demonstrate by using a simple model for fluvial erosion that tilting of the continent as it rides over a wide dynamic topography high cannot only cause rapid uplift of the plateau but also trigger continent wide drainage reorganization leading to substantial denudation in a relatively short amount of time the amplitude and short duration of the sedimentary pulse are best reproduced by assuming a strong erodibility contrast between the karoo sedimentary and volcanic rocks and the underlying basement we also present a new compilation of paleoclimate indicators that shows a transition from arid to very humid conditions approximately at the onset of the documented erosional pulse suggesting that climate may have also played a role in triggering the denudation the diachronism of the sedimentary flux between the eastern and western margins of the plateau and the temporal and geographic coincidence between the uplift and kimberlite eruptions are however better explained by our tilt hypothesis driven by the migration of the continent over a fixed source of mantle upwelling