an algorithm for automated tsunami warning in french polynesia based on mantle magnitudes we have developed a new magnitude scale mm based on the measurement of mantle rayleigh wave energy in the 50 to 300 sec period range and directly related to the seismic moment through mm log10 m 20 measurements are taken on the first passage of rayleigh waves recorded on scale on broadband instruments with adequate dynamical range this allows estimation of the moment of an event within minutes of the arrival of the rayleigh wave and with a standard deviation of 0 2 magnitude units in turn the knowledge of the seismic moment allows computation of an estimate of the high seas amplitude of a range of expectable tsunami heights the latter combined with complementary data from t wave duration and historical references have been integrated into an automated procedure of tsunami warning by the centre polynesien de prevention des tsunamis cppt in papeete tahiti

importance of on scale observations of first arriving rayleigh wave trains for source studies example of the chilean event of march 3 1985 observed on the geoscope and ida networks a comparative moment tensor inversion study of the chilean event of march 3 1985 is performed using very long period rayleigh wave data from the ida and geoscope networks it is shown that the perturbing effects of lateral heterogeneity on the propagation of the rayleigh waves especially in the amplitudes can be minimized if first arriving trains r1 and r2 only can be used more stable estimates of the main source parameters can then be obtained as well as an estimate of source directivity compatible with the aftershock distribution and body wave results

t phase spectra seismic moments and tsunamigenesis t phase spectrograms and spectra derived from deep ocean hydrophones for tsunamigenic and non tsunamigenic earthquakes in the pacific reveal the following 1 substantial amounts of t phase energy at high frequencies i e 1 hz to at least 35 hz 2 strong correlations of spectral strengths in the 10 hz to 35 hz frequency range to seismic moments and 3 large spectral strengths at high frequencies for tsunamigenic earthquakes these findings are consistent with the low attenuation of the so und fixing and ranging sofar channel which permits efficient propagation of high frequencies to great distances and with the perception that large earthquakes may generate high frequency signals at the water sediment interface which can best be observed by hydroacoustic sensors in the low noise environment of the deep oceans in addition these studies confirm that 1 source bathymetry can strongly influence the character of t phases 2 islands or seamounts near the source area can act as secondary radiators of energy which add to the complexity and duration of the coda 3 there appears to be no significant dependence of t phase strength on earthquake source mechanism and 4 the strength of the t phase is dependent on the purity of its oceanic travel path the strong correlation of t phase spectral strengths to seismic moments suggests that substantial improvements in the reliability of tsunami warnings may be possible by using t phases as an additional independent single station method for estimating seismic moments finally the high frequencies observed in the t phase may be associated with important alternate mechanisms for tsunamigenesis other than faulting i e slumpage compaction or liquefaction

the 2004 sumatra tsunami in the southeastern pacific ocean new global insight from observations and modeling the 2004 sumatra tsunami was an unprecedented global disaster measured throughout the world oceans the present study focused on a region of the southeastern pacific ocean where the westward circumferentially propagating tsunami branch converged with the eastward branch based on data from fortuitously placed chilean dart 32401 and tide gauges along the coast of south america by comparison of the tsunami and background spectra we suppressed the influence of topography and reconstructed coastal spectral ratios that were in close agreement with a ratio at dart 32401 and spectral ratios in other oceans findings indicate that even remote tsunami records carry spectral source signatures birth marks the 2004 tsunami waves were found to occupy the broad frequency band of 0 25 10 cph with the prominent ratio peak at period of 40 min related to the southern fast slip source domain this rupture hot spot of 350 km was responsible for the global impact of the 2004 tsunami data from dart 32401 provided validation of model results the simulated maximum tsunami wave height of 2 25 cm was a conservative approximation to the measured height of 2 05 cm the computed tsunami travel time of 25 h 35 min to dart 32401 although 20 min earlier than the actual travel time provided a favorable result in comparison with 24 h 25 min estimated from classical kinematic theory the numerical simulations consistently reproduced the wave height changes observed along the coast of south america including local amplification of tsunami waves at the northern stations of arica 72 cm and callao 67 cm

ray tracing for dispersive tsunamis and source amplitude estimation based on green s law application to the 2015 volcanic tsunami earthquake near torishima south of japan ray tracing which has been widely used for seismic waves was also applied to tsunamis to examine the bathymetry effects during propagation but it was limited to linear shallow water waves green s law which is based on the conservation of energy flux has been used to estimate tsunami amplitude on ray paths in this study we first propose a new ray tracing method extended to dispersive tsunamis by using an iterative algorithm to map two dimensional tsunami velocity fields at different frequencies ray paths at each frequency can be traced we then show that green s law is valid only outside the source region and that extension of green s law is needed for source amplitude estimation as an application example we analyzed tsunami waves generated by an earthquake that occurred at a submarine volcano smith caldera near torishima japan in 2015 the ray tracing results reveal that the ray paths are very dependent on its frequency particularly at deep oceans the validity of our frequency dependent ray tracing is confirmed by the comparison of arrival angles and travel times with those of observed tsunami waveforms at an array of ocean bottom pressure gauges the tsunami amplitude at the source is nearly twice or more of that just outside the source estimated from the array tsunami data by green s law

t phase data and regional tsunamigenesis in japan abstract good correlations are found between t phase spectral strengths and seismic moments for large earthquakes off the coasts of northern and central honshu japan also earthquakes from these areas which generated regional tsunamis in japan have larger seismic moments and t phase spectral strengths over the frequency range of 10 to 35 hz than nontsunamigenic earthquakes with similar source locations these findings are consistent with earlier observations of t phases from tsunamigenic and nontsunamigenic earthquakes near alaska and the aleutian islands walker et al 1992 and suggest that t phase data may be useful in improving the reliability of tsunami warning systems

equilibrium oxygen hydrogen and carbon isotope fractionation factors applicable to geologic systems as demonstrated by the chapters in this short course stable isotope techniques are an important tool in almost every branch of the earth sciences central to many of these applications is a quantitative understanding of equilibrium isotope partitioning between substances indeed it was harold urey s 1947 thermodynamically based estimate of the temperature dependence of 18o 16o fractionation between calcium carbonate and water and a recognition of how this information might be used to determine the temperatures of ancient oceans that launched the science of stable isotope geochemistry the approach pioneered by urey has since been used to estimate temperatures for a wide range of geological processes e g emiliani 1955 anderson et al 1971 clayton 1986 valley this volume in addition to their geothermometric applications equilibrium fractionation data are also important in the study of fluid rock interactions including those associated with diagenetic hydrothermal and metamorphic processes baumgartner and valley this volume shanks this volume finally a knowledge of equilibrium fractionation is a necessary first step in evaluating isotopic disequilibrium a widespread phenomenon that is increasingly being used to study temporal relationships in geological systems cole and chakraborty this volume in the fifty four years since the publication of urey s paper equilibrium fractionation data have been reported for many minerals and fluids of geological interest these data were derived from 1 theoretical calculations following the methods developed by urey 1947 and bigeleisen and mayer 1947 2 direct laboratory experiments 3 semi empirical bond strength models and 4 measurement of fractionations in natural samples each of these methods has its advantages and disadvantages however the availability of a variety of methods for calibrating fractionation factors has led to a plethora of calibrations not all of which are in agreement in this chapter we evaluate the major methods for determining fractionation factors

effect of variable bathymetry on the amplitude of teleseismic tsunamis a ray tracing experiment we apply surface wave ray tracing techniques to tsunami propagation in an ocean of variable depth because tsunami velocities are proportional to the square root of the depth of the water column the juxtaposition of oceanic plateaux and basins generates strong lateral velocity gradients and bathymetric features can act as lenses focusing or defocusing the tsunami waves we present a reconstruction of the tsunami wave field from the great chilean earthquake of 1960 an order of magnitude computation based on the concept of ray density provides qualitative agreement with observations at several sites in the pacific ocean we also demonstrate the possibility of using reciprocal maps to identify tsunamigenic zones that present particular danger for a given receiving shore

four years of automated measurements of seismic moments at papeete using the mantle magnitude mm 1987 1991 abstract we report on a 4 year experiment of routine automatic determination of seismic moments using the mantle magnitude m m we have developed a system performing automatic detection and location of distant earthquakes on the basis of three component broadband records at a single seismic station this system which has been operational since 1987 at papeete tahiti computes m m from the spectral amplitude of the mantle rayleigh waves based on a dataset of 474 earthquakes we show that m m provides a excellent estimate of the quantity log 10 m 0 20 where m 0 is the seismic moment in dyn cm as published subsequently by the harvard and usgs groups the average residual is 0 07 units of magnitude and the standard deviation 0 22 units this method which necessitates minimal hardware has powerful applications in the field of tsunami warning

the earthquake and tsunami of 1865 november 17 evidence for far field tsunami hazard from tonga summary historical reports of an earthquake in tonga in 1865 november identify it as the only event from that subduction zone which generated a far field tsunami observable without instruments run up heights reached 2 m in rarotonga and 80 cm in the marquesas islands hydrodynamic simulations require a moment of 4 1028 dyn cm a value significantly larger than previous estimates of the maximum size of earthquake to be expected at the tonga subduction zone this warrants an upwards re evaluation of the tsunami risk from tonga to the cook islands and the various polynesian chains which had hitherto been regarded as minor

far field simulation of tsunami propagation in the pacific ocean impact on the marquesas islands french polynesia the islands in the marquesas archipelago are most exposed to far field tsunamis in french polynesia four recent earthquakes located at the pacific rim kurile 1994 chile 1995 mexico 1995 and peru 1996 earthquakes generated trans pacific tsunamis and caused contrasting inundations in several inhabited marquesian bays the aim of this study is to better understand the amplification phenomena observed in the marquesas islands and to improve the risk assessment we present here numerical simulations of these four tsunamis by means of a finite difference model solving the equations of tsunami propagation at different scales the water heights computed in the bays are in excellent agreement with the available observations and thus validate our numerical method these numerical results allow us to determine 1 which propagation azimuths are dangerous for the whole marquesas archipelago and 2 the behavior of each studied bay amplitude frequency in response to tsunami waves we observe that the seismogenic subduction zone along south america is likely to define one of the most dangerous tsunami generation areas for the marquesas archipelago owing to the source geometries and to the trapping of the tsunami energy by bathymetric features in the southern pacific ocean fracture zones seamount chains

probabilistic models for estimating lithology abstract the estimation of lithology within a volume of rock from surface mapping and borehole logging has been achieved using probabilistic models the application of two geostatistical techniques indicator kriging and conditional simulation allows the incorporation of observed lithologies taking cognisance of their statistical and spatial distributions the newly developed probabilistic bayes markov method additionally allows for the sequences of lithologies to be modelled by the calculation of transition probabilities and markov chains verification of the estimates produced by these three methods has been enabled using the rocks actually exposed during the driving of an access tunnel into the aspo hard rock laboratory in south east sweden

application of mwp to tsunami earthquake tsunami earthquake produces anomalously strong tsunamis for their surface wave magnitude to issue accurate early tsunami warnings for tsunami earthquakes it is critical to identify them as tsunamigenic events as early as possible here we show that a pulse width of p wave which we use to calculate broadband moment magnitude mwp gives accurate estimates of source duration time we find that we may identify 1992 nicaragua earthquake as a possible tsunamigenic earthquake by using a combination of both mwp and the source duration our result suggests that the combination of mwp and the source duration will provide an effective tool to issue early tsunami warnings even for tsunami earthquakes which have anomalously long source duration

geostatistical simulation to map the spatial heterogeneity of geomechanical parameters a case study with rock mass rating this research was funded by the portuguese foundation for science and technology fct through isise project uid eci 04029 2013 by the chilean economic development agency corfo through project innova chile corfo 11idl2 10630 and by the chilean commission for scientific and technological research conicyt through projects conicyt fondecyt regular n 1130085 and conicyt pia anillo act 1407

the tsunami earthquake of 13 april 1923 in northern kamchatka seismological and hydrodynamic investigations we present a seismological and hydrodynamic investigation of the earthquake of 13 april 1923 at ust kamchatsk northern kamchatka which generated a more powerful and damaging tsunami than the larger event of 03 february 1923 thus qualifying as a so called tsunami earthquake on the basis of modern relocations we suggest that it took place outside the fault area of the mainshock across the oblique pacific north america plate boundary a model confirmed by a limited dataset of mantle waves which also confirms the slow nature of the source characteristic of tsunami earthquakes however numerical simulations for a number of legitimate seismic models fail to reproduce the sharply peaked distribution of tsunami wave amplitudes reported in the literature by contrast we can reproduce the distribution of reported wave amplitudes using an underwater landslide as a source of the tsunami itself triggered by the earthquake inside the kamchatskiy bight

wavelet analysis of the seismograms of the 2004 sumatra andaman earthquake and its application to tsunami early warning we applied the wavelet transform in an attempt to detect long period components early in a seismogram we analyzed the displacement seismograms of the 26 december 2004 sumatra andaman earthquake mw 9 2 and the 28 march 2005 nias earthquake mw 8 7 wavelet analysis is able to clearly distinguish the amplitudes of the long period w phase between the seismograms of the two earthquakes before the s wave reaches the station it shows that the 2004 earthquake generates a w phase of significantly greater amplitude this facility has potential application to the rapid identification of truly great earthquakes with high tsunami potential

modeling tsunamis from earthquake sources near gorringe bank southwest of portugal the azores gibraltar fracture zone with the huge bathymetric reliefs in the area southwest of portugal is believed to have been the source of large historic tsunami events this report describes simulations of tsunami generation and propagation from sources near the gorringe bank the well documented 1969 tsunami event is examined both with a ray tracing technique and with finite difference models based on various shallow water equations both methods show that the most likely source location is southeast of the gorringe bank near the epicenter location determined from seismic data the tsunami source is calculated by formulas given by okada 1985 for surface deformation of an elastic half space caused by faulting observed wave amplitude and travel time and values computed from an initial wave field according to okada 1985 formulas show acceptable agreement for most stations along the coast of portugal and spain however in order to explain a large primary wave with downward displacement observed on the coast of morocco an alternative source model with a larger area of downward displacement has been introduced this also leads to a better overall fit with observed travel time implications for disastrous events as the one in 1755 are also discussed linear hydrostatic shallow water models are used for most of the simulations but the importance of nonlinearity and dispersion is examined with the boussinesq equations the sensitivity of the solution to changes in the location and the strength of the source is discussed and a series of grid refinement studies are performed in order to assess the accuracy of the simulations

seasat geoid anomalies and the macquarie ridge complex abstract the seismically active macquarie ridge complex forms the pacific india plate boundary between new zealand and the pacific antarctic spreading center the late cenozoic deformation of new zealand and focal mechanisms of recent large earthquakes in the macquarie ridge complex appear consistent with the current plate tectonic models these models predict a combination of strike slip and convergent motion in the northern macquarie ridge and strike slip motion in the southern part the hjort trench is the southernmost expression of the macquarie ridge complex regional considerations of the magnetic lineations imply that some oceanic crust may have been consumed at the hjort trench although this arcuate trench seems inconsistent with the predicted strike slip setting a deep trough also occurs in the romanche fracture zone geoid anomalies observed over spreading ridges subduction zones and fracture zones are different therefore geoid anomalies may be diagnostic of plate boundary type we use seasat data to examine the macquarie ridge complex and find that the geoid anomalies for the northern hjort trench region are different from the geoid anomalies for the romanche trough the hjort trench region is characterized by an oblique subduction zone geoid anomaly e g the aleutian komandorski region also limited first motion data for the large 1924 earthquake that occurred in the northern hjort trench suggest a thrust focal mechanism we conclude that subduction is occurring at the hjort trench the existence of active subduction in this area implies that young oceanic lithosphere can subduct beneath older oceanic lithosphere

surface wave amplitude anomalies is reciprocity valid surface wave amplitude anomalies are studied using global digital seismograph network gdsn records of some recent circum pacific events e g 1983 costa rica 1983 akita oki 1982 ometepec and 1983 peru ecuador some event station pairs can be effectively used to interchange the source and receiver on a given path and thus provide information on an approximately reciprocal path at certain stations amplitude asymmetries of r3 to r2 are significant band pass filtered records show that such asymmetries are frequency dependent as these anomalies are primarily caused by focusing and defocusing effects we have done ray tracing experiments using the phase velocity model of tanimoto in an attempt to account for the observed anomalies while anomalies such as those at tato and majo for the costa rica event or at col for the akita oki event are well predicted by the ray tracing others are not at station hon where the ray tracing experiment failed to predict any asymmetry we studied surface wave propagation on nearly reciprocal paths in some detail using records of smaller events the results indicate that actual propagation in the heterogeneous earth considerably varies between closely spaced but not exactly reciprocal paths such sensitivity to source and receiver placement is not predicted by smooth earth structures this suggests that there must be substantial small scale structural variations the length scale of these variations is presumably on the order of the wavelengths of 100 250 s surface waves 400 1000 km there is an unexpectedly large vertical component associated with the overtone phase x3 at some stations in the radial component of these records we identify two group arrivals around the x3 phase the first one directly propagated from the source and the second one which has a prominent vertical component may be due to modal conversion through the path

comparison of t phase spectra and tsunami amplitudes for tsunamigenic and other earthquakes t phase spectral strengths and seismic moments from earlier studies for tsunamigenic and nontsunamigenic earthquakes off alaska the aleutians northern honshu and central honshu are compared to tsunami height recordings from coastal tide gauges and deep ocean pressure recorders tsunamigenic earthquakes have larger seismic moments and t phase spectral strengths than nontsunamigenic earthquakes pacific wide tsunamigenic earthquakes had well recorded water waves on the deep ocean pressure gauges while water waves for the regional tsunamis could be found only on coastal tide gauges in close proximity to the earthquake epicenters thresholds of t phase spectral strengths required for tsunamigenesis are estimated for each of the areas investigated on comparing tsunami heights seismic moments and spectral strengths for two pacific wide tsunamis generated by earthquakes with similar source locations we note that the earthquake with the larger tsunami has the larger t phase spectral strength but smaller seismic moment we conclude that t phase spectral strengths may be useful in estimating tsunami energy

tsunami earthquakes the quest for a regional signal using the technique developed by newman and okal j geophys res 103 1998 26885 a dataset of digital records from 84 earthquakes is analyzed to investigate their source slowness in the quest for a possible regional signal in three subduction zones which experienced recent tsunami earthquakes nicaragua 1992 java 1994 peru 1996 the dataset is augmented by analog seismograms from historical events including major tsunamigenic earthquakes of the past 65 years we fail to detect a regional trend for slowness which suggests that the latter may be controlled on a more local scale by morphological structures of the subducting plate no correlation is found between slowness and either depth focal mechanism or seismic moment in nicaragua we document two slow historical earthquakes located on the slab down dip from the 1992 shock the most interesting results are in peru where a local area of slowness is tentatively defined around the source of the 1960 tsunami earthquake and where both the 1996 and 1960 tsunami earthquakes occur at the intersection of the trench with major topographic features on the nazca plate the mendana fracture zone and the trujillo trough respectively 2001 elsevier science b v all rights reserved

the deficient t waves of tsunami earthquakes summary we develop an algorithm quantifying the energy flux of t phases recorded at island stations following major teleseismic events which we further scale by the seismic moment m0 of the earthquake to define a t phase efficiency we apply this concept to a set of six recognized tsunami earthquakes which generated tsunamis larger than expected from their conventional seismic waves through comparison with nearby reference events the t waves of which were recorded at the same sites we find that the tsunami earthquakes exhibit a deficiency in ranging from 1 5 to 2 5 orders of magnitude this result settles a 50 yr old controversy on the possible correlation between t wave generation and tsunami genesis the deficient character of the t waves from tsunami earthquakes readily supports the proposed model of an exceedingly slow rupture velocity for this class of events and the close examination of t wave trains supports the concept of a jerky rupture in at least two cases the computation of is straightforward in real time and could become a valuable contribution to real time tsunami warning in the far field

far field tsunami hazard from mega thrust earthquakes in the indian ocean summary we evaluate far field tsunami hazard in the indian ocean basin based on hydrodynamic simulations of ten case studies of possible mega earthquakes at the major seismic zones surrounding the basin they represent worst case scenarios of seismic rupture along the full extent of seismogenic faults having supported large earthquakes in the historical record in a series of numerical experiments in which the source parameters of the 2004 sumatra tsunami are allowed to vary one by one while keeping the seismic moment and the fault orientation unchanged we document that the main patterns of far field tsunami amplitudes are remarkably robust with respect to nominal variations in such parameters as hypocentral depth exact centroid location and slip distribution on the fault plane these results validate the concept of modelling case scenarios of potential future earthquakes whose source is by definition imprecise we consider seismic sources located at the extremities of the 2004 sumatra andaman rupture namely along the southern coast of sumatra and in the andaman myanmar province along the makran coast of pakistan and iran and also along the southern coast of java where the possibility of a large interplate thrust earthquake cannot be entirely dismissed the results of our hydrodynamic simulations indicate that the distribution of maximum amplitudes in the indian ocean basin is primarily controlled by the classical effect of source directivity and additionally by refraction and focusing along bathymetric features as a result many provinces in the basin could be threatened by higher tsunami amplitudes than in 2004 this pattern is particularly important along the coast of east africa from somalia to and including south africa in madagascar and the mascarene islands especially under a south sumatra scenario involving an earthquake comparable to or even possibly larger than the 1833 event whose epicentral area is widely believed to be under enhanced seismic risk as a result of stress transfer from the 2004 and 2005 ruptures to the northwest possibly even in the wake of the 2007 bengkulu earthquakes

terrestrial oxygen isotope variations and their implications for planetary lithospheres oxygen isotopes provide key data on the formation and evolution of the solar system particularly for earth and other rocky bodies that are principally constituted of oxygen rich phases the dynamic interactions between earth s lithosphere hydrosphere biosphere and atmosphere are elucidated by a wealth of oxygen isotope data that in turn provide a template for predicting the types of variations that occur on other planets these isotopic variations are basically controlled by two master effects first isotopic fractionations among coexisting phases tend to be greatest at low temperatures and are also large when they involve interactions between solids or liquids and gaseous phases second material balance effects require the 18 o contents of the most abundant phases to be close to the planetary average and restrict extreme isotopic enrichments or depletions to minor phases these dual controls of fractionation and material balance work in concert with practically any other dynamic process to foster the upward enrichment and increased heterogeneity of 18 o contents on earth and by implication in planetary lithospheres in general upward 18 o enrichment in planetary lithospheres is promoted by the tendency for the least dense silicate and oxide minerals to concentrate 18 o relative to more dense minerals and also by convective transfer fractional crystallization hydrothermal alteration and other processes earth s continents and the uppermost parts of its ocean floor consequently have higher 18 o contents than average upper mantle material and normal sediments carbon dioxide and oxygen gas are all very rich in 18 o heterogeneity is evident in the large ranges of 18 o values observed in sediments at least 8 to 38 and terrestrial igneous rocks at least 10 5 to 16 and in the even larger ranges in natural waters and atmospheric gases all representing materials that constitute or interacted with oxygen reservoirs near earth s surface key identified processes include weathering precipitation from water phase changes exchange with infiltrating hydrothermal fluids and assimilation of wallrocks having disparate compositions all such processes that promote the upward enrichment and heterogeneity of 18 o complicate the deduction of the bulk planetary contents of this isotope

one station estimates of seismic moments from the mantle magnitudemm the case of the regional field 1 5 δ 15 we extend to the regional field of distances the procedure of one station estimation of seismic moments using the mantle magnitudemm as introduced earlier in the case of teleseismic events a theoretical analysis of the validity of the asymptotic expansion of normal modes in terms of surface waves which was used in the development ofmm upholds the validity of the algorithm for distances as short as 1 5 this is confirmed by the analysis of a dataset of 149 geoscope records obtained at distances ranging from 1 5 to 15 from earthquakes with moments between 1024 and 2 5 1027 dyn cm the performance ofmm as measured in terms of average residual with respect to published values ofm0 and standard deviation of the residuals is not degraded in this distance range with respect to the teleseismic case this indicates that the mantle magnitudemmcan be reliably used at regional distances notably for tsunami warning applications

an indian ocean tsunami triggered remotely by an onshore earthquake in balochistan pakistan this paper describes and documents instrumentally recorded tsunami waves that are interpreted as secondary effects of a 7 7 magnitude earthquake in southern pakistan on 24 september 2013 the tsunami waves were almost unnoticed because the wave heights were low and the tsunami occurred at low tide the historical record of tsunami events within the arabian sea northern indian ocean is fragmentary large tsunamigenic earthquakes are known to be generated in the makran subduction zone the area that forms the boundary of the arabian and eurasian plates submarine sliding is reported along the owen fracture zone which marks the boundary between the arabian and indian plates hence the tsunami hazard potential within the arabian sea is enigmatic our analysis is based on sea level oscillations recorded at various tide gauge stations along the coastlines of oman pakistan and iran as well as eyewitness accounts of the event in oman our results indicate that the waves were in the range of 1 m or less in height they were first recorded along the eastern coast of oman and propagated toward the west we suggest that the waves must have been triggered by a submarine slide on the makran margin cascading effects resulting in large submarine slope failures within the arabian sea are more frequent than postulated the hazard potential is underestimated as such secondary effects of distant ruptures onshore were previously not taken into account

geotechnical characterization of the upper pleistocene holocene alluvial deposits of roma italy by means of multivariate geostatistics cross validation results abstract we are presenting an attempt to evaluate the spatial variability of geotechnical parameters in the upper pleistocene holocene alluvial deposits of roma italy by means of multivariate geostatistics the upper pleistocene holocene alluvial deposits of roma are sensitive to high levels of geohazard they occupy a sizable and significant part of the city being the foundation for many monuments historical neighborhoods and archaeological areas and the main host of the present and future subway lines we have stored information from more than 2000 geotechnical boreholes crossing the alluvial deposits into a relational database for the present study only the boreholes with lithologic textural interpretation and geotechnical information were selected the set includes 283 boreholes and 719 samples which have a set of geotechnical information comprising physical properties and mechanical parameters techniques of multivariate statistics and geostatistics were combined and compared to evaluate the estimation methods of the mechanical parameters with special reference to the drained friction angle from direct shear test principal component analysis was applied to the dataset to highlight the relationships between the geotechnical parameters through cross validation analysis multiple linear regression kriging and cokriging were tested as estimators of cross validation demonstrates that the cokriging with granulometries as auxiliary variables is the most suitable method to estimate in addition to proving that cokriging is a good estimator of cross validation demonstrates that input data are coherent and this allows us to use them for estimation of geotechnical parameters although they come from different laboratories and different vintages nevertheless to get the same good results of cross validation in estimation it is necessary for granulometries to be available at grid points since this information being not available at all grid points it is expected that in the future textural information can be derived in an indirect way i e from lithologic textural spatial reconstructions

elevator tectonics and orogenic collapse of a tibetan style plateau in the european variscides the role of the bohemian shear zone variscan collision of peri gondwanan terranes led to a doubly vergent crustal wedge that was thicker than 55 km in the area of the bohemian massif this crustal thickness resulted in a highly elevated bohemian plateau with a topographic height 3 4 km the bohemian plateau was covered with unmetamorphic paleozoic strata all of which are today well preserved in the tepla barrandian unit because of crustal scale vertical slip along the bohemian shear zone bsz the bsz forms a subvertical ca 500 km long and up to 2 km wide belt of dip slip mylonites which show several 90 deflections in map view tepla barrandian down movements were active under retrograde metamorphic conditions starting with granulite and ceasing with greenschist facies conditions as slip along the bsz was largely vertical and led to a minimum throw of 10 km this type of crustal scale deformation is referred to as elevator tectonics the elevator style movements caused the juxtaposition of the supracrustal tepla barrandian lid the elevator against high grade rocks of the extruding orogenic root the bsz has further governed the foci of mantle derived plutonism new u pb zircon and monazite tims dating of six plutons suggest that emplacement of mantle derived melts along the bsz lasted for at least 20 m y starting with the emplacement of the klatovy granodiorite at 347 4 3 ma and ceasing with the emplacement of the drahotin pluton at 328 1 ma when taking into account the new ages of synkinematic plutons the simultaneous vertical slip along the individual segments of the bsz north west and central bohemian shear zone is bracketed to the period 343 337 ma elevator tectonics was probably controlled by delamination of thickened mantle lithosphere that caused a dramatic thermal turnover and heating up of the orogenic root the overheated lower crust was thermally softened by anatexis and diffusion creep resulting in channel flow vertical extrusion fast uplift and exhumation of the orogenic root

tsunamigenic earthquakes past and present milestones we review a number of events which taken individually have significantly affected our understanding of the generation of tsunamis by earthquake sources and our efforts at mitigating their hazards notably through the development of warning algorithms starting with the 1700 cascadia earthquake we examine how significant tsunamis have changed our views in fields as diverse as seismotectonics the diversity of earthquake cycles the development of warning algorithms the response of communities at risk to warnings and their education the latter being either formal or rooted in ancestral heritage we discuss in detail lessons from the 2004 sumatra disasters and review the performance of warning centers and the response of affected populations during the nine significant tsunamis which have taken place since 2004

symmetry of flow in the comstock lode hydrothermal system evidence for longitudinal convective rolls in geologic systems 1 hydrothermal fluid flow can be visualized by three dimensional 3 d kriging and computer contouring of oxygen isotope data on propylitized andesites in the comstock lode mining district this data set consists of 18o results for 327 samples from surface outcrops drill cores and mine workings in a 3 5 km 1 7 km 1 0 km block in the hanging wall of the comstock fault encompassing the region where the most important ore bodies were discovered the 18o contours deep in the hanging wall are not simply parallel to the comstock fault or to the boundary of the davidson granodiorite stock as would be expected for a hydrothermal convection system dominated by unicellular flow instead the subsurface 18o values exhibit a high degree of symmetry about a vertical plane directed radially toward the stock with isotopic contours being predominantly perpendicular to the comstock fault and the eastern contact of the davidson granodiorite a vertical cross section along the comstock lode shows a low 18o core with two symmetrical zones of higher 18o values to either side where the contours are steeply inclined which we infer reflects downwelling of fluids shifted by water rock exchange or steam loss this 3 d visualization of 18o values provides the first evidence that longitudinal convective rolls can be significant in geologic environments in this case within a zone of high temperature gradients and permeability near the comstock fault and the davidson granodiorite stock

reexamination of the magnitudes for the 1906 and 1922 chilean earthquakes using japanese tsunami amplitudes implications for source depth constraints far field tsunami records from the japanese tide gauge network allow the reexamination of the moment magnitudes mw for the 1906 and 1922 chilean earthquakes which to date rely on limited information mainly from seismological observations alone tide gauges along the japanese coast provide extensive records of tsunamis triggered by six great mw 8 chilean earthquakes with instrumentally determined moment magnitudes these tsunami records are used to explore the dependence of tsunami amplitudes in japan on the parent earthquake magnitude of chilean origin using the resulting regression parameters together with tide gauge amplitudes measured in japan we estimate apparent moment magnitudes of mw 8 0 8 2 and mw 8 5 8 6 for the 1906 central and 1922 north central chile earthquakes the large discrepancy of the 1906 magnitude estimated from the tsunami observed in japan as compared with those previously determined from seismic waves ms 8 4 suggests a deeper than average source with reduced tsunami excitation a deep dislocation along the chilean megathrust would favor uplift of the coast rather than beneath the sea giving rise to a smaller tsunami and producing effects consistent with those observed in 1906 the 1922 magnitude inferred from far field tsunami amplitudes appear to better explain the large extent of damage and the destructive tsunami that were locally observed following the earthquake than the lower seismic magnitudes ms 8 3 that were likely affected by the well known saturation effects thus a repeat of the large 1922 earthquake poses seismic and tsunami hazards in a region identified as a mature seismic gap

mapping the upper mantle three dimensional modeling of earth structure by inversion of seismic waveforms a method is presented for the inversion of waveform data for the three dimensional distribution of seismic wave velocities the method is applied to data from the global digital networks international deployment of accelerometers global digital seismograph network the selected data set consists of some 2000 seismograms corresponding to 53 events and 870 paths the moment tensors of the earthquakes are determined through an iterative procedure which minimizes the corrupting influence of lateral heterogeneity a global model is constructed for shear wave velocity expanded up to degree and order 8 in spherical harmonics and described by a cubic polynomial in depth for the upper 670 km of the earth s mantle although no a priori information is incorporated the model predictions reproduce much of what is known about the dispersion of mantle waves for example high phase velocities for shields low velocities at ridges and a strong degree 2 pattern for rayleigh waves since the method makes use of complete waveforms overtone data are also included it is shown that the model is reproducible in that substantially the same model can be constructed from each half of the total data set considered independently the model shows that shields and ridges are major features in the depth interval 25 250 km the ridges of the southern pacific and the larger shields persist to 350 km but the southeast indian rise is underlain by a high velocity anomaly at this depth as is much of the mid atlantic ridge at 450 650 km the major features are a broad region of high velocities incorporating south america much of the south atlantic and parts of west africa a broad region of low velocities in the central and eastern pacific high velocities in the western pacific and a low velocity anomaly beneath the red sea and the gulf of aden in the absence of a crustal correction degrees 2 and 3 show a high positive correlation with the geoid paradoxically this is largely destroyed when the distribution in crustal thickness is taken into account spherical harmonic degrees 4 7 show a significant negative correlation

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

a fast and simple diagnostic method for identifying tsunamigenic earthquakes an analysis of regional broadband seismograms of moderate and large subduction zone earthquakes in mexico shows that earthquakes which occur near the trench are abnormally depleted in high frequency radiation this observation leads to a simple and fast method to assess regional tsunami potential from earthquakes which occur along the pacific coast of mexico a significant advantage of the method is that a single broadband seismograph is sufficient for the purpose the method is based on the ratio of the total energy to the high frequency energy between 1 and 5 hz er computed from the seismograms for earthquakes with the same seismic moment er is an order of magnitude greater for a source area near the trench as compared to those near the coast the same seismograms are used to compute energy magnitude me which is tied to the moment magnitude mw a regional tsunami may be expected along the coast if me 6 5 and er corresponds to a source near the trench if however er corresponds to a near coast source then me may have to be greater than about 7 3 for a tsunami of similar size to occur along the coast the method holds promise for a fast regional tsunami warning in many pacific basin countries which lack an adequate seismic network

tsunami early warning using earthquake rupture duration and p wave dominant period the importance of length and depth of faulting summary after an earthquake rapid real time assessment of hazards such as ground shaking and tsunami potential is important for early warning and emergency response tsunami potential depends on seafloor displacement which is related to the length l width w mean slip d and depth z of earthquake rupture currently the primary discriminant for tsunami potential is the centroid moment tensor magnitude mcmtw representing the seismic potency lwd and estimated through an indirect inversion procedure the obtained mcmtw and the implied lwd value vary with the depth of faulting assumed earth model and other factors and is only available 30 min or more after an earthquake the use of more direct procedures for hazard assessment when available could avoid these problems and aid in effective early warning here we present a direct procedure for rapid assessment of earthquake tsunami potential using two simple measures on p wave seismograms the dominant period on the velocity records td and the likelihood that the high frequency apparent rupture duration t0 exceeds 50 55 s t0 can be related to the critical parameters l and z while td may be related to w d or z for a set of recent large earthquakes we show that the period duration product tdt0 gives more information on tsunami impact and size than mcmtw and other currently used discriminants all discriminants have difficulty in assessing the tsunami potential for oceanic strike slip and backarc or upper plate intraplate earthquake types our analysis and results suggest that tsunami potential is not directly related to the potency lwd from the seismic faulting model as is assumed with the use of the mcmtw discriminant instead knowledge of rupture length l and depth z alone can constrain well the tsunami potential of an earthquake with explicit determination of fault width w and slip d being of secondary importance with available real time seismogram data rapid calculation of the direct period duration discriminant can be completed within 6 10 min after an earthquake occurs and thus can aid in effective and reliable tsunami early warning

solfataric alteration in the san juan mountains colorado oxygen isotope variations in a boiling hydrothermal environment an oxygen isotope study was made on hydrothermal quartz and altered volcanic rocks from six areas of advanced argillic alteration in the san juan volcanic field southwest colorado these include the historically productive mining districts at summitville delta 18 o quartz 13 0 15 5ppm and the national belle pipe at red mountain pass delta 18 o quartz 10 0 12 3ppm other areas studied are engineer pass delta 18 o quartz 6 4ppm delta 18 o sub whole rock 1 9 3 4ppm carson camp delta 18 o quartz 11 9 13 6ppm and calico peak near rico delta 18 o quartz 6 9 9 0ppm delta 18 o sub whole rock 4 7 6 9ppm samples were also analyzed from surface outcrops delta 18 o quartz 4 9 11 2ppm and from an 837 m cored drill hole in the red mountain quartz latite lava dome on the eastern edge of the 23 m y old lake city caldera at this locality the altered volcanic rocks delta 18 o sub whole rock 1 7 8 2ppm and the hydrothermal quartz delta 18 o quartz 1 4 11 2ppm exhibit a distinct vertical 18 o 16 o gradient of about 0 8 per mil 100 m with the highest delta 18 o values at the highest elevations these data are incorporated into a general model for solfataric alteration in these mid to late tertiary hot spring systems this involves a convecting meteoric hydrothermal fluid which at shallow depths rises along the hydrostatic boiling curve the delta 18 o variation in solfataric quartz in the uppermost 300 m of the hot spring system from 5 11ppm is mainly a function of a temperature variation from about 225 degrees to 125 degrees c along the boiling curve and to a lesser extent a result of the delta 18 o effects that accompany vapor phase separating during boiling

oxygen isotope constraints on the origin and differentiation of the moon we report new high precision laser fluorination three isotope oxygen data for lunar materials terrestrial silicates with a range of 18 o values 0 5 to 22 9 were analyzed to independently determine the slope of the terrestrial fractionation line tfl 0 5259 0 0008 95 confidence level this new tfl determination allows direct comparison of lunar oxygen isotope systematics with those of earth values of 17 o for apollo 12 15 and 17 basalts and luna 24 soil samples average 0 01 and are indistinguishable from the tfl the 18 o values of high and low ti lunar basalts are distinct average whole rock 18 o values for low ti lunar basalts from the apollo 12 5 72 0 06 and apollo 15 landing sites 5 65 0 12 are identical within error and are markedly higher than apollo 17 high ti basalts 5 46 0 11 evolved low ti lapaz mare basalt meteorite 18 o values 5 67 0 05 are in close agreement with more primitive low ti apollo 12 and 15 mare basalts modeling of lunar mare basalt source composition indicates that the high and low ti mare basalt mantle reservoirs were in oxygen isotope equilibrium and that variations in 18 o do not result from fractional crystallization instead these differences are consistent with mineralogically heterogeneous mantle sources for mare basalts and with lunar magma ocean differentiation models that result in a thick feldspathic crust an olivine pyroxene rich mantle and late stage ilmenite rich zones that were convectively mixed into deeper portions of the lunar mantle higher average 18 o wr values of low ti basalts compared to terrestrial mid ocean ridge basalts 0 18 suggest a possible oxygen isotopic difference between the terrestrial and lunar mantles however calculations of the 18 o of lunar mantle olivine in this study are only 0 05 higher than terrestrial mantle olivine these observations may have important implications for understanding the formation of the earth moon system 2006 elsevier b v all rights reserved

mm a variable period mantle magnitude this paper lays the theoretical groundwork for a variable period mantle magnitude mm based on the measurement of the spectral amplitude x of very long period rayleigh waves we retain the concept of magnitude by restricting ourselves to single station measurements ignoring the focal mechanism and the exact depth of the shallow earthquakes considered our measurements are made at a series of periods in all cases greater than 40 s and the largest value is retained this procedure effectively avoids the well known interference effects leading to saturation of magnitude scales defined at a fixed period two corrections are used a period dependent distance correction cd and a source correction cs also period dependent compensating for the variation of the excitation of rayleigh waves with period both of these corrections are fully predictable on the basis of standard surface wave excitation and dispersion theory the result is a formula of the type mm log10 x cd cs c0 in which all coefficients including the constant c0 are justifiable on sound theoretical grounds the analysis of a data set of 256 records from the broadband seismograph at papeete tahiti the ultra long period system at pasadena and stations of the geoscope network shows that the mean error in the estimation of the seismic moment is on the order of 0 1 0 2 units of magnitude with the standard deviation at each station also on the order of 0 2 units of magnitude no significant trend with either distance period or station can be identified the method can also be transposed to the time domain under some simple assumptions which are justifiable theoretically for typical teleseismic distances across the pacific basin both versions of the method lend themselves well to automation thus by providing a real time estimate of the seismic moment of distant earthquakes mm has considerable potential for tsunami warning purposes its concept can easily be extended to love waves and also to intermediate and deep earthquakes

the 15 august 2007 peru earthquake and tsunami influence of the source characteristics on the tsunami heights the tsunami caused by the 2007 peru earthquake mw 8 0 provoked less damage than by the seismic shaking itself numerous casualties due to the earthquake in the vicinity of pisco however it propagated across the pacific ocean and small waves were observed on one tide gauge in taiohae bay nuku hiva marquesas french polynesia we invert seismological data to recover the rupture pattern in two steps the first step uses surface waves to find a solution for the moment tensor and the second step uses body waves to compute the slip distribution in the source area we find the slip distribution to consist of two main slip patches in the source area the inversion of surface waves yields a scalar moment of 8 9 1020 nm and body wave inversion gives 1 4 1021 nm the inversion of tsunami data recorded on a single deep ocean sensor also can be used to compute a fault slip pattern yielding a scalar moment of 1 1 1021 nm we then use these different sources to model the tsunami propagation across the pacific ocean especially towards nuku hiva while the source model taken from the body wave inversion yields computed tsunami waves systematically too low with respect to observations on the central pacific ocean dart buoy as on the polynesian tide gauge the source model established from the surface wave inversion is more efficient to fit the observations confirming that the tsunami is sensitive to the low frequency component of the source finally we also discuss the modeling of the late tsunami arrivals in taiohae bay using several friction coefficients for the sea bottom

oxygen isotope exchange kinetics of mineral pairs in closed and open systems applications to problems of hydrothermal alteration of igneous rocks and precambrian iron formations the systematics of stable isotope exchange between minerals and fluids are examined in the context of modal mineralogical variations and mass balance considerations both in closed and in open systems on mineral pair 18 o plots samples from terranes that have exchanged with large amounts of fluid typically map out steep positively sloped non equilibrium arrays analytical models are derived to explain these effects these models allow for different exchange rates between the various minerals and the external fluids as well as different fluid fluxes the steep arrays are adequately modelled by calculated isochron lines that involve the whole family of possible exchange trajectories these isochrons have initially steep near vertical positive slopes that rotate toward a 45 equilibrium slope as the exchange process proceeds to completion the actual data point array is thus analogous to the hand of an isotopic clock that measures the duration of the hydrothermal episode the dimensionless ratio of the volumetric fluid flux to the kinetic rate parameter u k determines the shape of each individual exchange trajectory in a fluid buffered system u k 1 the solutions to the equations 1 are independent of the mole fractions of the solid phases 2 correspond to taylor s open system water rock equation and 3 yield straight line isochrons that have slopes that approach 1 f where f is the fraction reacted of the more sluggishly exchanging mineral the isochrons for this simple exchange model are closely congruent with the isochrons calculated for all of the more complex models thereby simplifying the application of theory to actual hydrothermal systems in nature in all of the models an order of magnitude of time in units of kt separates steep non equilibrium arrays e g slope 10 from arrays approaching an equilibrium slope of unity on a diagram because we know the approximate lifetimes of many hydrothermal systems from geologic and heat balance constraints we can utilize the 18 o 16 o data on natural mineral assemblages to calculate the kinetic rate constants k s and the effective diffusion constants d s for mineral h 2o exchange these calculated values k qtz 10 14 k feld 10 13 10 12 agree with experimental determinations of such constants in nature once the driving force or energy source for the external infiltrating fluid phase is removed the disequilibrium mineral pair arrays will either 1 remain frozen in their existing state if the temperatures are low enough or 2 re equilibrate along specific closed system exchange vectors determined solely by the temperature path and the mineral modal proportions thus modal mineralogical information is a particularly important parameter in both the open and closed system scenarios and should in general always be reported in stable isotopic studies of mineral assemblages these concepts are applied to an analysis of 18 o 16 o systematics of gabbros plagioclase clinopyroxene and plagioclase amphibole pairs granitic plutons quartz feldspar pairs and precambrian siliceous iron formations quartz magnetite pairs in all these examples striking regularities are observed on and plots but we point out that plots have many advantages over their equivalent diagrams as the latter are more susceptible to misinterpretation using the equations developed in this study these regularities can be interpreted to give semiquantitative information on the exchange histories of these rocks subsequent to their formation in particular we present a new interpretation indicating that precambrian cherty iron formations have in general undergone a complex fluid exchange history in which the iron oxide magnetite precursor has exchanged much faster with low temperature 400 c fluids than has the relatively inert quartz

amplitude and phase data inversions for phase velocity anomalies in the pacific ocean basin summary rayleigh wave phase velocities at periods 30 80 s in the pacific ocean are calculated by inverting phase and amplitude anomaly data using the paraxial ray approximation and the gaussian beam method the region is divided into 5 x 5 blocks and approximately 200 source receiver pairs from 18 well studied events around the pacific ocean are used first we assume phase anomalies for the lithospheric age dependent model next conventional phase data inversions are conducted assuming great circle paths so that the phase discrepancies are reduced to less than t this procedure is essential for later inversions using amplitude data we then determine the residuals of both amplitude and phase terms by calculating ray synthetic seismograms using the born approximation for a 2 d wave equation a nonlinear iterative inversion for phase velocities is performed with both residuals frbchet derivatives for the inversion consist primarily of two wavefields 1 the wavefield at the model point from the source and 2 the green s function from the model point to the receiver these wavefields are also calculated by the paraxial ray approximation and gaussian beam methods in the inverse formulations the simple use of the conventional backus gilbert approach yields undesirable results in the non linear iterative case and an extra term is necessary to control the model perturbations in order to minimize departures from the a priori model the use of this additional term guarantees that we are able to obtain a fairly reliable phase velocity model even in the present non linear problem in most cases residual variances are significantly reduced after two or three iterations as far as the starting model is fairly correct compared with the phase data inversions this inverse scheme gives more reliable resolution and most of the inverted features in phase velocities are significantly larger than the uncertainty level while some features obtained by the great circle phase data

single station estimates of the seismic moment of the 1960 chilean and 1964 alaskan earthquakes using the mantle magnitudem m measurements are taken of the mantle magnitudem m developed and introduced in previous papers in the case of the 1960 chilean and 1964 alaskan earthquakes by far the largest events ever recorded instrumentally we show that them m algorithm recovers the seismic moment of these gigantic earthquakes with an accuracy typically 0 2 to 0 3 units of magnitude or a factor of 1 5 to 2 on the seismic moment comparable to that achieved on modern digital datasets in particular this study proves that the mantle magnitudem m does not saturate for large events as do standard magnitude scales but rather keeps growing with seismic moment even for the very largest earthquakes we further prove that the algorithm can be applied in unfavorable experimental conditions such as instruments with poor response at mantle periods seismograms clipped due to limited recording dynamics or even on microbarograph records of air coupled rayleigh waves

an effective bayesian model for lithofacies estimation using geophysical data 1 a bayesian model coupled with a fuzzy neural network bfnn is developed to enhance the use of geophysical data in lithofacies estimation prior estimates are inferred from borehole lithofacies measurements using indicator kriging and posterior estimates are obtained by updating the prior using geophysical data the novelty of this study lies in the use of the fuzzy neural network for the inference of the likelihood function this allows spatial correlation of lithofacies as well as nonlinear cross correlation between lithofacies and geophysical attributes to be incorporated into lithofacies estimation the effectiveness of bfnn is demonstrated using synthetic data emulating measurements at the lawrence livermore national laboratory llnl site

mm use of a variable period mantle magnitude for the rapid one station estimation of teleseismic moments broadband records of the first passage of rayleigh waves at papeete tahiti from large circum pacific earthquakes are used to recover in real time their seismic moments the magnitude concept is used at periods varying from 50 to 300 s adequate corrections are made for distance and period typical standard deviations are 0 2 orders of magnitude on mo this mantle scale mm can be extended continuously with no additional corrections over 4 orders of magnitude it can be measured in the frequency or time domains and we describe briefly the automation of the method with obvious applications in tsunami warning

global seismicity of 1981 centroid moment tensor solutions for 542 earthquakes abstract centroid moment tensor solutions are presented for 542 earthquakes that occurred during 1981

tsunami detection by satellite altimetry we present what is to our knowledge the first direct observation of the deformation of the surface of the ocean upon passage of a tsunami wave on the high seas far from the influence of shorelines and continental shelves we use satellite altimetry data from the ers 1 and topex poseidon programs complemented by spectrogram techniques and synthetic maregrams to examine the case of seven recent tsunamigenic earthquakes we make a positive identification of the tsunami wave field in the case of the 1992 nicaraguan tsunami which we detect at 15 s 106 w five hours after origin time we model the observed spectrogram by injecting a synthetic of variable amplitude into the signal of a repetitive cycle of the satellite along the same track concluding that the nicaraguan tsunami had a zero to peak amplitude of 8 cm in that region in the case of the 1995 chilean tsunami a large scatter in the spectral properties of the reference tracks renders the detection tentative we fail to detect the tsunamis of five other large events including the 1996 biak and 1996 peru earthquakes primarily on account of unfavorable source directivity in the geometry of existing satellite tracks and of the strong and incoherent noise produced by large current systems such as the kuroshio in the northwest pacific

m m a variable period mantle magnitude for intermediate and deep earthquakes we extend to the case of intermediate and deep earthquakes the mantle magnitude developed for shallow shocks byokal andtalandier 1989 specifically from the measurement of the spectral amplitude of rayleigh waves at a single station we obtain a mantle magnitude mm theoretically related to the seismic moment of the event through m m log 10 m 0 20 the computation ofmminvolves two corrections the distance correction is the same as for shallow shocks for the purpose of computing the frequency dependent source correction we define three depth windows intermediate a 75 to 200 km intermediate b 200 400 km and deep over 400 km in each window the source correctioncs is modeled by a cubic spline of log10t

merging tsunamis of the 2011 tohoku oki earthquake detected over the open ocean 1 tsunamis often travel long distances without losing power and severely devastate some coastal areas while leaving others with little damage this unpredictable situation has been a major challenge for accurate and timely tsunami forecasting to facilitate early warning and possible evacuations of affected coastal communities without disturbing the lives of others here we show evidence from satellite altimetry observations of the 2011 tohoku oki earthquake induced tsunami that sheds light on this issue three satellites observed the same tsunami front and for the first time one of them recorded a tsunami height about twice as high as that of the other two model simulations based on the gps derived earthquake source and constrained by measurements of seafloor motions near the hypocenter confirm that the amplified tsunami is one of several jets formed through topographic refraction when tsunamis travel along ocean ridges and seamount chains in the pacific ocean this process caused the tsunami front to merge as it propagates resulting in the doubling of the wave height and destructive potential in certain directions we conclude that the potential of merging tsunamis should be emphasized in mapping tsunami hazards and assessing risk levels at key coastal facilities

comparison of long period surface wave amplitude and phase anomalies for two models of global lateral heterogeneity surface wave raytracing calculations for periods of 150 to 250 s were performed using the two models of global phase velocity heterogeneity produced by harvard and cit pro viding a comparison of predicted amplitude and phase anomalies theoretical r3 r and g3 g amplitude asymmetries resulting from focussing and defocussing have similar azimuthal distribu tions of the more pronounced anomalies for the two structures the azimuthal patterns of long period rayleigh and love wave phase anomalies about a given source region also resemble one another for the two models travel time errors as large as 12 s are accumulated for 200 s period rarrivals by neglecting the raypath deviations from great circles such errors may be significant when inverting for earth structure or when applying corrections for lateral heterogeneity in source studies

geometric effects of global lateral heterogeneity on long period surface wave propagation long period rayleigh waves from iranian earthquakes have large amplitude asymmetries between minor arc and major arc arrivals e g r 2 and r 3 at digital stations in the azimuth range n20 w to n60 e these asymmetries are as large as a factor of 2 at a period of 256 s and persist to periods greater than 300 s in some cases the entire rayleigh wave group arrival spanning periods from 100 to 300 s is either uniformly enhanced in amplitude or diminished to such a degree that the group arrival appears to be missing the amplitude anomalies are generally not accompanied by significant phase anomalies the irregular azimuthal distribution of the amplitude asymmetries and their occurrence for events with different focal mechanisms and epicentral separations of several hundred kilometers preclude an explanation of these observations by source complexity events in the mediterranean and nepal do not produce similar amplitude asymmetries at the same stations the anomalies are thus most likely due to focusing and defocusing propagation effects as a preliminary investigation of the effects of lateral heterogeneity of upper mantle velocity structure on long period surface wave amplitudes surface wave ray tracing calculations are performed using recently proposed global phase velocity distributions dramatic deviations from great circle paths are predicted for long propagation paths e g r 3 the particular spatial distribution of lateral velocity gradients around a given source location determines whether substantial amplitude asymmetries will be observed between minor arc and major arc arrivals and whether these will persist for sequential great circle orbits the 200 s period amplitude asymmetry observed at kip for the iranian source region r 2 4 r 3 is well predicted by the ray tracing results the absence of this anomaly for the other source regions is also predicted other observed anomalies are not all well predicted but it is clear that geometric effects can contribute significantly to the observed variations of rayleigh and love wave amplitudes this is the probable explanation for the instability of q estimates made from surface waves other source regions producing large surface wave amplitude anomalies include japan and southeastern alaska

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

the tsunami earthquake of 1932 june 22 in manzanillo mexico seismological study and tsunami simulations summary we conduct a detailed seismological study of the large colima mexico earthquake of 1932 june 3 and of its aftershocks of june 18 and 22 the latter event iii generated a tsunami more devastating than that of the main shock despite much smaller seismic magnitudes thus qualifying as a so called tsunami earthquake relocation based on published arrival times shows that event iii took place up dip of the main shock the analysis of the spectral amplitude of mantle surface waves yields low frequency moments of 24 5 2 and 4 times 1027 dyn cm respectively with event iii featuring a moment growing with period which expresses the source slowness characteristic of tsunami earthquakes this is confirmed by a deficient energy to moment ratio as derived from high frequency p waves recorded at pasadena near field hydrodynamic simulations show that the effects of the main shock s tsunami are well modelled by a standard seismic source whereas the stronger tsunami from event iii can be modelled by rupture along a splay fault in a mechanically deficient material all our results then fit the model for tsunami earthquake aftershocks proposed for the kuril islands by fukao in 1979

rupture process of the march 3 1985 chilean earthquake the march 3 1985 central chile earthquake ms 7 8 ruptured a well studied seismic gap along the chilean subduction zone the epicenter of this event is located near the center of an approximately 300 km long region which ruptured in a great event in 1906 mw 8 2 the northern portion of the 1906 zone has since ruptured in 1971 ms 7 5 and 1973 ms 6 7 we have determined the rupture history of the 1985 central chile earthquake from the deconvolved source functions of body waves both p and pp the source functions show one major pulse of moment release the onset of which occurs about 16 seconds after an initial small pulse the azimuthal directivity in the p waves indicates that the rupture front propagated from the epicenter southward and that the moment release of the major pulse is concentrated in a region between the epicenter and approximately 75 km south of the epicenter we conclude that the region of high moment release is the dominant asperity and was loaded by slip in the relatively weaker northern region

seismic records of the 2004 sumatra and other tsunamis a quantitative study following the recent reports by yuan et al 2005 of recordings of the 2004 sumatra tsunami on the horizontal components of coastal seismometers in the indian ocean basin we build a much enhanced dataset extending into the atlantic and pacific oceans as far away as bermuda and hawaii and also expanded to five additional events in the years 1995 2006 in order to interpret these records quantitatively we propose that the instruments are responding to the combination of horizontal displacement tilt and perturbation in gravity described by gilbert 1980 and induced by the passage of the progressive tsunami wave over the ocean basin in this crude approximation we simply ignore the island or continent structure and assume that the seismometer functions de facto as an ocean bottom instrument the records can then be interpreted in the framework of tsunami normal mode theory and lead to acceptable estimates of the seismic moment of the parent earthquakes we further demonstrate the feasibility of deconvolving the response of the ocean floor in order to reconstruct the time series of the tsunami wave height at the surface of the ocean suggesting that island or coastal continental seismometers could complement the function of tsunameters

an experiment in systematic study of global seismicity centroid moment tensor solutions for 201 moderate and large earthquakes of 1981 data from the global digital seismograph network were used to obtain centroid moment tensor solutions using the method of dziewonski et al 1981 results were obtained for 201 earthquakes ranging in seismic moment from 7 1023 to 3 1027 dyne cm the wide dynamic range of the sro asro stations allows us to investigate using the same algorithm series of events among which the smallest and the largest may differ in moment by a factor as large as 1000 among the events studied is a particularly interesting series in january 1981 off the island of honshu the main shock was preceded by three foreshocks and followed by four aftershocks all falling within the range of our analysis there is an indication that the source mechanism changes with the size of the event statistical analysis of the results for all earthquakes reveals that the half duration of shallow and intermediate events is approximated by 1 6 10 8 m01 3 the shifts in origin time for deep focus earthquakes are indicative of the general complexity of these events which depends only weakly on the seismic moment the extreme departures from a double couple mechanism seem to depend both on the moment and on the focal depth while for shallow earthquakes these departures decrease from a maximum at about 1025 dyne cm with increasing moment the reverse appears to be true with respect to deep focus earthquakes shallow earthquakes north of new guinea and along the solomon islands show systematic and substantial departures from the double couple mechanism

use of the mantle magnitude m m for the reassessment of the moment of historical earthquakes the mantle magnitudemm is used on a dataset of more than 180 wavetrains from 44 large shallow historical earthquakes to reassess their moments which in many cases had been previously estimated only on the basis of the earthquake s rupture area we provide 27 new or revised values ofmo based on the spectral amplitudes of surface waves recorded at a number of stations principally uppsala and pasadena among them and most significantly we document a large low frequency component to the source of the 1923 kanto earthquake the low frequency seismic moment is 2 9 1028 dyn cm in accord with geodetic observations on the other hand we revise downwards the seismic moment of the 1906 ecuador event which did not exceed 6 1028 dyn cm

shear velocities qβ and the frequency dependence of qβ in stable and tectonically active regions from surface wave observations summary velocities and attenuation coefficient values of rayleigh waves within the south american continent and indian subcontinent have been determined in order to study velocity structure and qp structure as well as their lateral variation in those regions single station and two station data are combined to yield dispersion and attenuation data from periods of a few seconds to periods between 60 s and 100 s for each region both types of data are inverted using differential inversion schemes this inversion process is found to sometimes allow the location of velocity discontinuities in the models directly from the dispersion data qp models obtained from the inversion process are not constrained to have high values at large depths a problem with earlier methods used to invert surface wave attenuation data the shear velocity models for the indian shield and eastern south america are similar to one another and have somewhat slower velocities than those reported for shield regions of north america the shear velocity models for the himalaya and andes are similar to one another in crustal thickness but the velocities in the andes are lower than those in the himalayas in the uppermost mantle a low velocity zone can marginally be resolved in the upper mantle beneath the himalaya but not beneath the other regions in this study qp models obtained for the stable regions of eastern north america and eastern south america exhibit similar qp values at mantle depths the indian shield however has much lower qp values in both the crust and upper mantle a result which may be related to the unusually high heat flow observed for that stable region for the tectonically active regions of western north america western south america and the himalaya is considerably lower than qp for the stable regions throughout most of the crust and upper mantle minimum mantle values appear to be about 120 for stable regions and 40 or less for tectonically active regions thus qp values in the upper mantle appear to vary regionally by a factor of 3 or more whereas shear velocities in the same regions vary by no more than 13 per cent

source area and rupture parameters of the 31 december 1881 mw 7 9 car nicobar earthquake estimated from tsunamis recorded in the bay of bengal 1 on the morning of 31 december 1881 a submarine earthquake beneath the andaman islands generated a tsunami with a maximum crest height of 0 8 m that was recorded by eight tide gauges surrounding the bay of bengal since the earthquake occurred 8 years before the construction of the world s first teleseismic recording seismometer little has been known about its rupture parameters or location waveform and amplitude modeling of the tsunami indicate that it was generated by a mw 7 9 0 1 rupture on the india andaman plate boundary resulting in 10 60 cm of uplift of the island of car nicobar the rupture consisted of two segments the northern 40 km long segment is separated from the southern 150 km long segment by a 100 km region corresponding to the westward projection of the west andaman spreading center the main rupture occurred between 8 5 n and 10 n with a total area of 150 km 60 km dipping 20 e with a mean slip of 2 7 m the recurrence time for 1881 type events is estimated to be 114 200 years on the basis of inferred gps convergence rates and inferred plate closure vectors although slip partitioning in the region may extend this estimate by as much as 30

seismic potential for large and great interplate earthquakes along the chilean and southern peruvian margins of south america a quantitative reappraisal the seismic potential of the chilean and southern peruvian margins of south america is reevaluated to delineate those areas or segments of the margin that may be expected to experience large or great interplate earthquakes within the next 20 years 1984 2004 long term estimates of seismic potential or the conditional probability of recurrence within a specified period of time are based on 1 statistical analysis of historic repeat time data using weibull distributions and 2 deterministic estimates of recurrence times based on the time predictable model of earthquake recurrence both methods emphasize the periodic nature of large and great earthquake recurrence and are compared with estimates of probability based on the assumption of poisson type behavior the estimates of seismic potential presented in this study are long term forecasts only as the temporal resolution or standard deviation of both methods is taken to range from 15 to 25 of the average or estimated repeat time at present the valparaiso region of central chile 32 35 s has a high potential or probability of recurrence in the next 20 years coseismic uplift data associated with previous shocks in 1822 and 1906 suggest that this area may have already started to rerupture in 1971 1973 average repeat times also suggest this area is due for a great shock within the next 20 years flanking segments of the chilean margin coquimbo illapel 30 32 s and talca concepcion 35 38 s presently have poorly constrained but possibly quite high potentials for a series of large or great shocks within the next 20 years in contrast the rupture zone of the great 1960 earthquake 37 46 s has the lowest potential along the margin and is not expected to rerupture in a great earthquake within the next 100 years in the north the seismic potentials of the mollendo arica 17 18 s and arica antofagasta 18 24 s segments which last ruptured during great earthquakes in 1868 and 1877 are also high but poorly constrained

automatic detection location and quantification of earthquakes application to tsunami warning we describe a fully automated seismic event detection and location system providing for real time estimates of the epicentral parameters of both local and distant earthquakes the system uses 12 telemetered short period stations with a regional aperture of 350 km as well as two 3 component broad band stations detection and location of teleseismic events is achieved independently and concurrently on the short period and long period channels the long period data is then used to obtain an estimate of the seismic momentm0 of the earthquake through the mantle magnitudemm as introduced byokal andtalandier 1989 in turn this estimate ofm0 is used to infer the expected tsunami amplitude at papeete within 15 minutes of the recording of rayleigh waves the performance of the method is discussed in terms of the accuracy of the epicentral parameters and seismic moment obtained in real time as compared to the values later published by the reporting agencies our estimates are usually within 3 degrees of the reported epicenter and the standard deviation on the seismic moment only 0 19 unit of magnitude for a population of 154 teleseismic events

shear velocity and shear attenuation models inverted from the world wide and pure path average data of mantle rayleigh waves 0s25 to 0s80 and fundamental spheroidal modes 0s2 to 0s24 summary global and regional structures of the earth s mantle are studied original phase velocities and q 1 of rayleigh waves are converted to equivalent free oscillation periods and q 1 global average upper mantle shear velocity models are derived from the inversions of the world wide average eigenperiods corrected for attenuative dispersion resolution analysis shows that the thickness and velocity of the lithosphere cannot be determined from our data set inverted models have a well developed low velocity zone in the depth range between 70 and 280 km global average q 1 models for the whole mantle are derived from the world wide average q 1 of mantle rayleigh waves and fundamental spheroidal modes the resolution analysis indicates that q 1 at depths shallower than about 100 km cannot be determined by our data set and that the depth resolution for q 1 of the lower mantle is poor all inverted q 1 models are characterized by a well developed high q 1 zone in the depth range between about 100 and 300 km in the upper mantle q has a minimum value of about 90 at depths around 200 km begins to increase at a depth of about 300 km rapidly increases in the depth range from 300 to 400 km and gradually increases at depths between 400 and 800 km q of the lower mantle is about 330 the boundary between the high q 1 upper mantle and low q 1 lower mantle is sharper than has been suggested in the past inverted q 1 models predict qscs 226 to 250 the earth s surface is divided into mountainous oceanic ridge shield and trench and marginal sea regions and a regionalized shear velocity model of the upper mantle is derived the inversions of the pure path eigenperiods without correction for attenuative dispersion show that strong lateral variations in shear velocity exist at depths shallower than 250 km in the upper mantle a low velocity zone for shear waves exists in the upper mantle beneath all the tectonic regions except perhaps the shield region if the sn velocity of the starting model is equal to or higher than 4 7 km s 1 the shield data require a moderate low velocity zone data from the mountainous region require a much lower shear velocity than the shield region at depths shallower than 250 km the oceanic ridge and trench and marginal sea models have a well developed low velocity zone the shear velocity model for the trench and marginal sea region is characterized by a velocity increase at depths between 250 and 400 km this increase in velocity is interpreted as a consequence of the subducted lithospheric slabs beneath many of our trench and marginal sea regions regional differences in rayleigh wave q 1 are found for modes from 0s25 to 0s45 since the resolving power of this data set is limited we could not locate the depths at which regional variations of q 1 exist since the oceanic q 1 for modes from 0s45 to 0s78 appear to be stable the oceanic q 1 model is derived this model has a well developed high q 1 zone q has a minimum value of about 110 at depths between 200 and 300 km and rapidly increases to a high value of about 250 at a depth of about 400 km

rupture characteristics of the 1982 tonga and 1986 kermadec earthquakes source time functions are obtained for the december 19 1982 tonga and october 20 1986 kermadec earthquakes from deconvolution of p waves using a model including a significant dip of the ocean bottom in such a geometry the amplitudes of subsequent water multiples are large and irregular as a result we can model these two events as consisting of a single pulse of short duration 23 s in the case of the 1982 event and 19 s for the 1986 one despite complex teleseismic waveshapes this is in contrast to inversions using flat layered models which required very complex source time functions which were mutually inconsistent at different stations the anomalously large tsunami generated by the 1982 event is modeled as the result of propagation of the rupture into the sedimentary wedge at the trench rather than due to a long lived complex source time function the latter being also incompatible with the total lack of excitation of the earth s normal modes in the low frequency limit for the 1986 event we derive a source duration 19 s very short in relation to its moment 8 1027 dyn cm this earthquake a high stress drop rupture featuring a unique combination of strike slip and thrust motion on a plane dipping oceanwards of the trench is interpreted as expressing internal deformation of the subducting pacific slab at a depth of 40 km under the compressional stresses resulting from the collision

an experiment in the retrieval of depth and source mechanism of large earthquakes using very long period rayleigh wave data abstract the possibility of obtaining an estimate of depth for large earthquakes from low frequency mantle wave data alone is investigated using moment tensor formalism after illustrating the sensitivity to depth of the eigenfunctions in the period range of 160 to 350 sec we give several examples of application of the two step inversion procedure proposed earlier for shorter period rayleigh wave data romanowicz 1982 we find that for earthquakes below a depth of about 50 km we are able to resolve depth even when a spherically symmetric average earth model is used for propagation corrections this is particularly interesting in the case of large subduction zone earthquakes for which an estimate of the vertical extent of faulting can thus be obtained independently of aftershock studies in a very fast and simple manner which does not involve any synthetic seismogram calculations or lateral heterogeneity modeling for shallower earthquakes especially those with one steeply dipping nodal plane the resolution of depth is less precise taking lateral heterogeneity into account by using available regionalized phase velocities improves the results marginally we anticipate that accounting more accurately for the low order harmonics in the worldwide phase velocity distribution should prove most helpful since these interfere the most with the theoretical radiation patterns of earthquakes the determination of depth depends more critically on the source process time which has to be accounted for especially for horizontally propagating faults