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amplitude of a range of expectable tsunami heights the latter combined with complementary data from t wave duration and historical references have been integrated into an automated procedure of tsunami warning by the centre polynesien de prevention des tsunamis cppt in papeete tahiti

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

226ra 230th 238u disequilibria of historical kilauea lavas 1790 1982 and the dynamics of mantle melting within the hawaiian plume abstract the geochemical variations of kilauea s historical summit lavas 1790 1982 document a rapid fluctuation in the mantle source and melting history of this volcano these lavas span nearly the entire known range of source composition for kilauea in only 200 yr and record a factor of 2 change in the degree of partial melting in this study we use high precision measurements of the u series isotope abundances of kilauea s historical summit lavas and two ingrowth models dynamic and equilibrium percolation melting to focus on the process of melt generation at this volcano our results show that the 226 ra 230 th 238 u disequilibria of these lavas have remained relatively small and constant with 12 4 excess 226 ra and 2 5 1 6 excess 230 th both are 2 model calculations based mostly on subtle variations in the 230 th 238 u disequilibria suggest that lavas from the 19th to early 20th centuries formed at significantly higher rates of mantle melting and upwelling up to a factor of 10 compared to lavas from 1790 and the late 20th century the shift to higher values for these parameters correlates with a short term decrease in the size of the melting region sampled by the volcano which is consistent with fluid dynamical models that predict an exponential increase in the upwelling rate and thus the melting rate towards the core of the hawaiian plume the pb sr and nd isotope ratios of lavas derived from the smallest source volumes correspond to the kilauea end member of hawaiian volcanoes whereas lavas derived from the largest source volumes overlap isotopically with recent loihi tholeiitic basalts this behavior probably arises from the more effective blending of small scale source heterogeneities as the melting region sampled by kilauea increases in size the source that was preferentially tapped during the early 20th century when the melt fractions were lowest is more chemically and isotopically depleted than the source of the early 19th and late 20th century lavas which formed by the highest melt fractions this inverse relationship between the magnitude of source depletion and melt fraction suggests that source fertility i e lithology controls the degree of partial melting at kilauea thus rapid changes in the size of the melting region sampled by the volcano in the presence of these small scale heterogeneities may regulate most of the source and melting related geochemical variations observed at kilauea over time scales of decades to centuries

frequency dependent polarization measurements of long period surface waves and their implications for global phase velocity maps abstract surface wave dispersion maps provide important constraints on global models of shear wave velocity structure current surface wave dispersion maps show significant differences from researcher to researcher and it is clear that further work is required in addition to dispersion data polarization measurements obtained from long period 100 s or more three component recordings from the various global networks can also be used to constrain dispersion maps the off great circle propagation of the surface wave packets is relatively easy to interpret within a ray theoretic framework and provides sensitivity to higher order structure the polarization angles as a function of frequency are readily measured using a multi taper technique which also has the benefit of providing an error estimate for the measurements application of the technique to three component seismograms from the global geoscope array reveals large deviations from great circle propagation up to 15 for low orbit love waves and 10 for rayleigh waves in the frequency band 5 12 5 mhz on a more regional scale an analysis of seismograms from the german regional seismic network grsn reveals even larger strongly frequency dependent deviations from great circle propagation in the frequency range 10 50 mhz

global anisotropy in the upper mantle inferred from the regionalization of phase velocities a data set of 2600 paths for rayleigh waves and 2170 paths for love waves was selected in order to resolve azimuthal anisotropy of surface waves in the period range 70 250 s the epicenters were chosen so that the paths provide uniform spatial and azimuthal coverage of earth a synthetic seismogram is computed for each path and compared to the observed seismogram in order to infer the phase velocity along each path to process such a large data set a new tomographic technique is designed a good correlation is found with surface tectonics in the whole period range for love waves and at shorter periods for rayleigh waves the directions of maximum velocities are also well correlated with plate tectonics motions for the 2 azimuthal term of rayleigh waves when the power spectrum of heterogeneities is computed it is found that for love waves the even orders are usually larger than the odd orders for rayleigh waves the degrees 2 and 6 dominate only at long periods suggesting a deep origin for these components

dispersion and attenuation of mantle waves through waveform inversion summary we propose a new approach to the determination of elastic and anelastic parameters of the earth s structure from seismic data instead of measuring such functionals of the medium response as the phase delay or spectral ratios we perturb parameters of the model to satisfy the observed waveforms the advantage of our waveform inversion technique wit is that it uses the properties of the earth as a smoothing filter also because the earth s structure is the common denominator the method allows simultaneous interpretation of different functionals of this structure for example the waveforms of rayleigh and love waves for the same source receiver pair following extensive testing of the method on synthetic and actual data we subject results of our analysis of 37 recordings for various sources and stations to pure path decomposition the period range of analysis extends from 160 to 630s we distinguish four types of regions stable continents areas tectonically active within the last 400myr ocean floors younger than 38 myr and old ocean floors older than 38 myr the results indicate significantly different responses of the oceanic and continental areas at long periods stable continental and tectonic regions have nearly the same dispersion for periods greater than 300 35os and then diverge rapidly with stable continents showing higher velocities the young and old oceans on the other hand become distinct at periods as long as 500 s the old oceans are faster in terms of shear velocity models the data are consistent with a difference of about 4 per cent between the young and old oceans in a depth range from 400 to 670 km while the continental regions are similar and close to the global average at shallower depths our structures are conceptually similar to those inferred from previous pure path analyses and short period surface wave studies while we cannot yet establish statistically significant differences in q for the four regions such differences are obtained if one distinguishes only between continents and oceans the q for the latter is 10 20 per cent lower in the period range of the analysis

the impact of hydrodynamics authigenesis and basin morphology on sediment accumulation in an upwelling environment the miocene monterey formation at shell beach and mussel rock pismo and santa maria basins central california u s a abstract in the sections at shell beach pismo basin and mussel rock santa maria basin both along the central california coast the miocene monterey formation is composed of laminated biosiliceous organic rich and phosphate rich sediments which are intercalated with carbonates and volcanogenic deposits the presence of small and large scale scours conglomerates gravity flow deposits slumps and condensed intervals reveals the importance of sediment reworking which is related to the presence of bottom currents the general morphology of the basins and recurrent high energy events of likely seismic origin the lithologies reflect strong upwelling enhanced primary productivity and the presence of an oxygen minimum zone which is indicated by ubiquitous lamination a general absence of bioturbation with the rare exception of traces related to the gravity flow displacement of trace makers high pyrite mo and u concentrations and molar ratios of total organic carbon and organic phosphorus toc p org of up to 2000 oxygen depletion was particularly severe during the early langhian and the late serravallian and early tortonian and favored the preservation of organic matter episodes of deposition of organic rich sediment were followed by longer phases of subdued sediment accumulation and early diagenetic phosphogenesis which resulted in the formation of a low porosity less permeable lid in the near surface sediments that assisted in preserving organic matter phosphogenesis occurred throughout the time interval considered approximately 17 5 6 5 ma and phosphate rich sediments formed especially during periods of sedimentary condensation in the langhian and earliest serravallian and the latest tortonian and early messinian a comparison of temporal trends in the type and quantity of deposited sediments between the two sections at shell beach and mussel rock and three sections of the santa barbara basin el capitan state beach naples beach and haskell beach confirms that towards the top of the monterey formation sediments become enriched in biosilica in all three basins the transition into this lithology occurred diachronously during the serravallian in the pismo and santa maria basins and tortonian in the santa barbara basin and was probably related to a diachronous shift to more intense upwelling in all three basins a phase of important condensation and phosphogenesis terminated monterey type sedimentation during the latest tortonian and early messinian in both the santa maria and santa barbara basins the uniform expression of this phase is interpreted as the result of improved connections between the two basins

normal modes and long period seismograms in a 3d anelastic elliptical rotating earth 1 we present results of a direct method to compute realistic long period 200 s in this example synthetic seismograms using higher order perturbation theory up to the 3rd order normal modes are computed for the earth taking into account rotation ellipticity 3d elastic lateral heterogeneities saw12d for the whole mantle and anelastic lateral variations in the upper mantle qr19 coupling between different modes and branches is included in the computation we study the sensitivity of the waveform to 3d anelasticity and the biases between 3d elastic and 3d anelastic variations the resulting seismograms can be computed to higher frequency and may then be used to perform whole mantle joint inversions for elastic and anelastic structure

time domain pure state polarization analysis of surface waves traversing california a time domain pure state polarization analysis method is used to characterize surface waves traversing california parallel to the plate boundary the method is applied to data recorded at four broadband stations in california from twenty six large shallow earthquakes which occurred since 1988 yielding polarization parameters such as the ellipticity euler angles instantaneous periods and wave incident azimuths the earthquakes are located along the circum pacific margin and the ray paths cluster into two groups with great circle paths connecting stations mhc and pas or cmb and gsc the first path mhc pas is in the vicinity of the san andreas fault system safs and the second cmb gsc traverses the sierra nevada batholith parallel to and east of the safs both rayleigh and love wave data show refractions due to lateral velocity heterogeneities under the path indicating that accurate phase velocity and attenuation analysis requires array measurements t he rayleigh waves are strongly affected by low velocity anomalies beneath central california with ray paths bending eastward as waves travel toward the south while love waves are less affected providing observables to constrain the depth extent of anomalies strong lateral gradients in the lithospheric structure between the continent and the ocean are the likely cause of the path deflections

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

source process and tectonic implications of the great 1975 north atlantic earthquake summary the atlantic segment of the africa europe plate boundary has usually been interpreted as a transform boundary on the basis of the bathymetric expression of the gloria fault and dextral strike slip first motion mechanisms aligned along the azores gibraltar line of seismicity the 1975 may 26 earthquake ms 7 9 was assumed to fit into this framework because it occurred in the general area of this line and has a similar first motion focal mechanism strike 288 dip 72 slip angle 184 however several anomalies cast doubt on this picture the event is abnormally large for an oceanic transform event a sizeable tsunami was excited the aftershock area is unusually small for such a large event and most significantly the epicentre is 200 km south of the presumed plate boundary the rayleigh wave radiation pattern indicates a change in focal mechanism to one with a significant dip slip component the short duration of the source time history 20 s as deconvolved from long period p waves the lack of directivity in the rayleigh waves and the small one day aftershock area suggest a fault length less than 80 km one nodal plane of the earthquake is approximately aligned with the trace of an ancient fracture zone we have compared the pasadena 1 90 record of the 1975 earthquake to that of the 1941 north atlantic strike slip earthquake 200km to the nnw and confirmed the large size of the 1941 event m 8 2 the non colinear relationship of the 1975 and 1941 events suggests that there is no well defined plate boundary between the azores and gibraltar this interpretation is supported by the intraplate nature of both the 1975 event and the large 1969 thrust event 650 km to the east this study also implies that the largest oceanic strike slip earthquakes occur in old lithosphere in a transitional tectonic regime

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

parasequence types in shelfal mudstone strata quantitative observations of lithofacies and stacking patterns and conceptual link to modern depositional regimes mudstone strata have a vast variety of physical biogenic and chemical attributes at the lamina to bed scale approximately millimeters to decimeters thick our observations of more than 7 km of paleozoic to cenozoic mudstones revealed ordered patterns in this variety i e recurrent associations of lithofacies bedding style sedimentary structures and stratal architecture at bedset to parasequence scales approximately decimeters to meters thick we quantified characteristics of each association and their stacking patterns in vertical succession and linked them to sets of depositional processes most shelf mudstone strata appear to have accumulated in one of three facies association successions fass that can be related to depositional regimes through characteristic modes of sediment transport and accumulation as well as variations in benthic energy and oxygen levels we interpret these three fass as records of mud accumulation on different portions of continental shelves that were dominated by storm waves river floods or tidal currents each fas records a distinct parasequence type this approach can help fully integrate insights from oceanographic studies into more robust interpretations of the rock record and rock property maps

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

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

petrology of lavas from the puu oo eruption of kilauea volcano iii the kupaianaha episode 1986 1992 the puu oo eruption has been remarkable in the historical record of kilauea volcano for its duration over 13 years volume 1 km3 and compositional variation 5 7 10 wt mgo during the summer of 1986 the main vent for lava production moved 3 km down the east rift zone and the eruption style changed from episodic geyser like fountaining at puu oo to virtually continuous relatively quiescent effusion at the kupaianaha vent this paper examines this next chapter in the puu oo eruption episodes 48 and 49 and presents new icp ms trace element and pb sr and nd isotope data for the entire eruption 1983 1994 nearly aphyric to weakly olivine phyric lavas were erupted during episodes 48 and 49 the variation in mgo content of kupaianaha lavas erupted before 1990 correlates with changes in tilt at the summit of kilauea both of which probably were controlled by variations in kilauea s magma supply rate these lavas contain euhedral olivines which generally are in equilibrium with whole rock compositions although some of the more mafic lavas which erupted during 1990 a period of frequent pauses in the eruption accumulated 2 4 vol olivine the highest forsterite content of olivines 85 in kupaianaha lavas indicates that the parental magmas for these lavas had mgo contents of 10 wt which equals the highest observed value for lavas during this eruption the composition of the puu oo lavas has progressively changed during the eruption since early 1985 episode 30 when mixing between an evolved rift zone magma and a more mafic summit reservoir derived magma ended the normalized to 10 wt mgo abundances of highly incompatible elements and cao have systematically decreased with time whereas ratios of these trace elements and pb sr and nd isotopes and the abundances of y and yb have remained relatively unchanged these results indicate that the hawaiian plume source for puu oo magmas must be relatively homogeneous on a scale of 10 20 km3 assuming 5 10 partial melting and that localized melting within the plume has apparently progressively depleted its incompatible elements and clinopyroxene component as the eruption continued the rate of variation of highly incompatible elements in puu oo lavas is much greater than that observed for kilauea historical summit lavas e g ba y 0 09 a 1 vs 0 03 a 1 this rapid change indicates that puu oo magmas did not mix thoroughly with magma in the summit reservoir thus except for variable amounts of olivine fractionation the geochemical variation in these lavas is predominantly controlled by mantle processes

attenuation tomography of the upper mantle we present qsadr17 a global shear wave attenuation model of the upper mantle synthetic tests confirm that large scale shear attenuation anomalies are resolved in the whole upper mantle with limited vertical smearing 50 km qsadr17 shows strong correlation with surface tectonics down to 200 km depth with low attenuation beneath continents and high attenuation beneath oceans the attenuation signal near 250 km depth is dominated by a high quality factor along subduction zones attenuating anomalies are found beneath mid ocean ridges down to 150 km and under most pacific hotspots from the lithosphere down to the transition zone the presence of broad attenuating anomalies at 150 km depth in the pacific ocean suggests that several thermal plumes pond in the asthenosphere evidence for compositional heterogeneities is found in the lithosphere at the base of cratons and in a number of active regions

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

rupture of a seismic gap in southeastern alaska the 1972 sitka earthquake ms 7 6 abstract the sitka alaska earthquake of july 30 1972 m s 7 6 is one of the largest strike slip events since 1963 this earthquake is thought to have ruptured the pacific north america plate boundary segment between the large strike slip events in 1949 and 1958 and the sitka earthquake was heralded as one of the first successful forecasts of an earthquake based on the seismic gap hypothesis another motivation to study this event is the availability of a strong ground motion recording 50 km from the epicenter which is near the middle of the 180 km long plate boundary segment the teleseismically located aftershocks occur only in the southern half of this segment we have analyzed rayleigh waves and p waves recorded by wwssn long period vertical instruments a total of 25 very long period rayleigh phases r2 r5 define a symmetric four lobed radiation pattern from which we can infer a nearly pure right lateral strike slip fault striking 340 n20 w and a bilateral rupture comparison of synthetic and observed rayleigh waves yields a seismic moment of 3 10 27 dyn cm m w 7 6 the p waves are characterized by a dominant complex pulse in the first 40 s and a succession of smaller pulses after that the source time functions are deconvolved from 32 p waves with good azimuthal distribution to obtain the moment depth extent and rupture history the mean moment of the source time functions is 5 0 2 4 10 27 dyn cm and the depth extent is 0 10 km tomographic inversion of the source time functions produces an image of the earthquake rupture process this procedure maps the moment release of the complex pulse into two high displacement regions i e asperities 1 the epicentral area to 40 km north and 2 between 60 and 90 km south of the epicenter the main asperity just north of the epicenter coincides with a quiescent zone of microaftershocks while the overall average seismic displacement is 6 m the displacement at the main asperity is 7 m the same value as the tectonic displacement accumulated since the previous earthquake in 1848 the fault averaged stress drop is 100 bars while the asperity stress drop is 130 bars tomographic imaging of the source time functions thus resolves several features of the rupture process notably the bilateral propagation and rupture initiation at the largest asperity this is in contrast to the large 1976 guatemala strike slip earthquake where the largest displacements occurred away from rupture initiation

chemical and isotopic variations in mauna loa tholeiites abstract a suite of basaltic lavas of known eruption age from mauna loa hawaii has provided the basis for a detailed investigation of the evolution of the melting process beneath hawaii high precision 238 u 230 th 226 ra measurements by mass spectrometry reveal that 230 th 238 u ratios are close to 1 02 in all samples younger than 7 ka and that age corrected 226 ra 230 th ratios for three samples less than 2 ka are 1 15 1 20 these results are indistinguishable from the disequilibria reported previously for young kilauea lavas and are consistent with dynamic mantle melting within the garnet stability field at high melting rates 0 001 kg m 3 a 1 and low porosities 230 th 238 u ratios of up to 1 16 are found in some older mauna loa lavas but these are likely to have resulted from post eruptive loss of u by weathering as 230 th 238 u ratios correlate positively with th u ratios and inversely with k and rb abundances sr and nd isotopes define an excellent inverse correlation even though the total range in 143 nd 144 nd is only 1 nd however changes in the sr and nd isotopic compositions over the last 30 ka have not been progressive but have occurred rapidly and with an apparent cyclicity of 4 5 ka moreover these isotopic changes are mirrored by cyclical changes in certain trace element abundance ratios if the melts were produced within a single melting column then all elements must have travelled at similar velocities because the isotopic and abundance ratios of elements of widely differing compatibilities 143 nd 144 nd 87 sr 86 sr ba th la yb vary coherently in the lavas in this scenario chromatographic exchange between melt and matrix must have been minimal however it is more likely that the lava compositions record the mixing of melts from two or more source regions of different compositions 226 ra 230 th ratios in excess of unity in the lavas indicate that the transport of melt was rapid after leaving the melt column and suggest that melt movement through the lithosphere took place in cracks or fractures

sequence stratigraphy of the monterey formation santa barbara county integration of physical chemical and biofacies data from outcrop and subsurface deep basinal rocks of the monterey formation can be allocated to different depositional environments based on an integration of bedding stacking patterns of facies lithology biofacies and inorganic and organic chemistry these rocks show evidence of systematic changes in depositional environments that can be related to eustatic sea level changes and basin evolution even deep basinal environments are affected by changing sea level through changes in circulation patterns and intensities nutrient budgets and dispersal patterns and location and intensity of the oceanic oxygen minimum the sequence stratigraphic framework was constructed based on the physical expression of the outcrop strata and confirmed by typing the outcrop sections to an integrated will log seismic grid through outcrop gamma ray spectral profiles interpretation of a sequence boundary was based on increased proportions of hemipelagic facies and evidence of increased bottom energy levels above the boundary and local erosion and relief on the surface the proportion of shallower water and reworked dinoflagellates increased to a local maximum above the boundary downlap surfaces exhibited increased proportions of pelagic facies around the surface a secular change in the dominant lithology across the surface evidence of decreased bottom energy levels and terrigenous sedimentation rates and little or not significant erosion on the surface themore proportion of deeper water dinoflagellates increased to a local maximum at or near the downlap surface there was no evidence of reworked individuals the detailed sequence stratigraphic framework makes it possible to tie rock properties to genetic processes for construction of predictive models less

aspherical earth structure from fundamental spheroidal mode data free oscillation data reveal heterogeneity in the earth s mantle whose geographical pattern is dominated by spherical harmonics of angular degree two and correlates well with the hydrostatically referenced geoid the heterogeneity can be modelled as localized in the transition zone 420 670 km depth and may be related to a large scale component of mantle convection

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

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

measurement of mantle wave velocities and inversion for lateral heterogeneity and anisotropy 1 analysis of great circle phase velocities long period 100 330 s fundamental mode love and rayleigh waves have been processed to measure the great circle phase velocities for about 200 and 250 paths respectively the observations are inverted for regionalized phase velocities and for an even order harmonic expansion of the lateral velocity heterogeneity the regionalized inversions achieve a maximum variance reduction of about 65 and 85 for the love and the rayleigh wave data respectively the l max 2 inversions give a maximum variance reduction of about 60 and 90 for love and rayleigh waves respectively the l max 8 inversion does not make a large improvement in the fit the love wave phase velocities have more power in l 4 and 6 relative to l 2 than the rayleigh waves for both love and rayleigh wave data the sectoral component dominates the l 2 harmonics and this component is stable if we increase l max from 2 to 6 heat flow also has strong sectoral components lm 22 which are approximately in phase with those of the phase velocities the l 2 harmonics of the nonhydrostatic geoid are dominated by large zonal lm 20 and moderate sectoral components the sectoral components are in phase with those of the phase velocities the sectoral pattern of heat flow and phase velocity is controlled by high heat flow low velocity of the east pacific rise and western north america which is reinforced by low velocities in the antipodal region red sea gulf of aden east african rift by contrast the geoid l 2 pattern is dominated by geoid highs over the western pacific subduction zones a spherical harmonic expansion of regionalized phase velocities shows that they have l 2 variations similar to those of the l max 2 nonregionalized inversions this means that the regionalization approach is appropriate as a first step for studying lateral heterogeneity of the earth however the great circle phase velocities are not sufficient by themselves to uniquely locate the lateral heterogeneity the same is true for free oscillation data regions of convergence have the interesting property of being slow for short period waves and fast faster than shields for long period waves

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

anomalously large near field rayleight waves excited by the 1992 landers california earthquake abstract the epicenter of the landers california earthquake 28 june 1992 m w 7 3 was located near the terrascope network of broadband seismic stations the direct rayleigh wave arrivals r1 were clipped and the first two later arrivals r2 and r3 were contaminated by the waves from a large aftershock but as reported by kanamori et al 1992a the amplitudes of r4 and later great circle rayleigh wave arrivals fundamental mode spheroidal free oscillations are about 10 times larger than predicted by synthetic seismograms for a spherically symmetric earth model we show that for the moment tensor of the landers event predominantly vertical strike slip the amplitudes of synthetics at the terrascope stations for a laterally heterogeneous rotating elliptical model are about 10 times greater than those for a spherically symmetric model because the anomaly ratio is sensitive to both the source model and the three dimensional 3d earth model we do not attempt to reproduce the exact anomaly ratios recorded by the various stations to explain the existence of near field amplitude anomalies in general we use the first order born approximation to find the perturbation to the synthetic seismogram resulting from lateral heterogeneity ellipticity and the earth9s rotation in a coordinate system with the source on the z axis a point source strike slip earthquake on a vertical fault plane in a spherically symmetric medium excites rayleigh waves with azimuthal order 2 only these waves have a near field vertical displacement of zero at the source the displacement increases with the square of epicentral distance for any given azimuth coupling as a result of asphericity allows such a source to excite rayleigh waves with azimuthal order zero whose near field amplitude is independent of epicentral distance thereby generating large near field amplitude anomalies we conduct numerical experiments to study the influence of various parameters on near field amplitude anomalies

multiscale petrographic heterogeneity and their implications for the nanoporous system of the wufeng longmaxi shales in jiaoshiba area southeast china response to depositional diagenetic process

evolution of mauna kea volcano inferences from lava compositions recovered in the hawaii scientific drilling project the lower 776 m of core recovered during the initial phase of the hawaii scientific drilling project hsdp contains lavas erupted from mauna kea volcano tholeiitic and alkalic basalts including an fe ti rich flow are intercalated in the upper 58 m of mauna kea lavas similar basaltic sections are subaerially exposed on the lower east flank of mauna kea the fe ti rich lavas reflect large amounts of clinopyroxene plagioclase and olivine fractionation within the crust and upper mantle but the range from tholeiitic to alkalic compositions reflects variable extents of melting of a garnet bearing source based on abundances of incompatible elements the extent of melting for a basanitoid was a factor of 2 less than that for nearly coeval tholeiitic lavas all flow units in the lower 718 m of the hsdp core are tholeiitic lavas their variability in major element compositions reflect variable accumulation of olivine incompatible element abundance ratios in these lavas reflect a complex temporal variation in extent of melting within the tholeiitic part of the core lavas from 800 m to 950 m formed by the largest extent of melting whereas tholeiitic lavas from the bottom of the core and from just below the tholeiitic to alkalic transition formed by lower degrees of melting inferred melt compositions at 16 mgo show that the 200 to 400 ka mauna kea lavas from the hsdp core and the 250 ka subaerial exposures define an inverse correlation between sio2 and feo contents based on experimental studies this correlation is caused by differing pressures of melt segregation furthermore abundances of nb and sio2 are also inversely correlated in these calculated melts in general the younger lavas are relatively enriched in feo and incompatible elements but are depleted in sio2 these trends are interpreted to reflect an overall trend of increasing pressure of melt segregation and decreasing extent of melting with decreasing eruption age there are however geochemical variations which indicate short term reversals in this long term trend previously the geochemical trends accompanying the transition from tholeiitic to alkalic volcanism at hawaiian volcanoes have been interpreted as reflecting the effects of increasing distance from the plume axis the long term geochemical trends of tholeiitic lavas in the hsdp core also reflect migration of mauna kea away from the hawaiian plume

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

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

body wave and surface wave analysis of large and great earthquakes along the eastern aleutian arc 1923 1993 implications for future events the 500 km long alaska peninsula and shumagin islands segments of the aleutian arc have a moderate to high probability of rupturing in one or more large or great earthquakes in the next few decades to understand the likely modes of rupture in the next sequence of large and great events and to delineate the current geometry of the plate interface we determine focal mechanisms depths and source time functions from seismic records for the largest events since 1917 the great earthquake of november 10 1938 and seven events with surface wave magnitude ms of 6 9 to 7 5 teleseismic body waves and surface waves are used to estimate the seismic moment and gross rupture characteristics of the great earthquake of november 10 1938 along the alaska peninsula body wave inversion of five p and four sh waves gives a duration of about 110 s in which moment was released in two episodes each of about 50 s duration with the second being larger than the first the first source was located in the general vicinity of the epicenter of the mainshock and the second which occurred about 60 s later was centered about 180 km to the northeast the body wave derived seismic moment is 3 7 1021 n m mw 8 3 we corroborate the body wave results by calculating surface waves by normal mode summation and comparing them with data at periods greater than 50 s an adequate fit to observed seismograms is obtained for either a single point source or two point sources with one located about 180 km northeast of the mainshock epicenter rupture in 1938 appears to have been confined to the alaska peninsula segment uniform rupture into the shumagin region is not supported by the data the ms 6 9 earthquake of may 13 1993 ruptured a small portion of the shumagin gap the earthquake of may 14 1948 ms 7 5 occurred on a shallow dipping thrust fault with a depth of about 31 km not 60 km as originally suggested five ms 7 events in the 1938 rupture zone have locations depths and mechanisms that define a shallow dipping 16 19 plate interface which shallows to 8 under kodiak island subduction of seamounts of the gulf of alaska seamount province may explain the location moment focal mechanism and depth of the five ms 7 events the plate interface dips nearly uniformly between the alaska peninsula and shumagin segments indicating that segmentation if any is not controlled by the orientation of the plate interface a slight warp of the plate interface may form the boundary between rupture zones of great earthquakes along the kodiak and alaska peninsula segments of the arc and may explain why rupture zones of large to great earthquakes rarely cross this tectonic boundary

inversion of surface wave spectra for source parameters of large earthquakes using aspherical earth models abstract amplitude and phase spectra of rayleigh and love waves of periods of 150 to 300 s from eight large earthquakes which occurred between 1990 and 1993 are corrected for wave propagation and then inverted for the source duration rupture directivity and moment tensor of the earthquake source for various propagation anomalies predicted by models of the earth s aspherical elastic and anelastic structure the application of corrections for the focusing and take off azimuth anomaly in addition to conventional corrections for the phase anomaly improves inversions of surface waves rayleigh waves provide better constraints than love waves in the determination of source parameters the data consist of either only rayleigh waves or both love and rayleigh waves whenever the full moment tensor is involved for several earthquakes there is clear discrepancy between source parameters determined from different data sets particularly from rayleigh or love waves the moment tensor solution tends to underpredict observed amplitude spectra for data sets with large amplitude anomalies especially for love waves this study shows that 1 the 1990 sudan earthquake is anomalous for its unusually large non double couple component of the moment tensor 2 the 1990 iran earthquake has a strike slip mechanism with a subvertical nw striking nodal plane which is the fault plane inferred from surface ruptures 3 the 1991 costa rica earthquake may have a seismic moment larger than previously determined from long period surface waves 4 the 1992 nicaragua earthquake involves a predominant rupture parallel to the trench and a large centroid offset up dip to the trench axis and the latter process may be responsible for large tsunami generation 5 the 1993 hokkaido earthquake has a shallow dipping and west plunging nodal plane which is consistent with the p wave first motions but differs from the centroid moment tensor solutions

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

use of long period surface waves for rapid determination of earthquake source parameters 2 preliminary determination of source mechanisms of large earthquakes ms 6 5 in 1980 an inversion method for fast retrieval of earthquake source parameters developed earlier has been applied to 28 large m s 6 5 shallow earthquakes which occurred in 1980 rayleigh waves recorded by the ida international deployment of accelerographs network were used for the analysis for very shallow events the inversion is ill conditioned and two of the moment tensor elements m zx and m zy are unresolvable of the 28 events a solution is obtained for 25 with the constraints m zx m zy 0 although these constraints limit the solution to be either vertical strike slip or 45 dip slip the method provides a useful first approximation to the mechanism solution for deeper events all of the elements of the moment tensor can be determined after the seismograms have been retrieved the solution can be obtained in 10 min for most events the method would be adequate for preliminary cataloging purposes

tectonic and climate control of oil shale deposition in the upper cretaceous qingshankou formation songliao basin ne china oil shales were deposited in the songliao basin ne china during the upper cretaceous period representing excellent hydrocarbon source rocks high organic matter om contents a predominance of type i kerogen and a low maturity of om in the oil shales are indicated by bulk geochemical parameters and biomarker data a major contribution of aquatic organisms and minor inputs from terrigenous land plants to om input are indicated by n alkane distribution patterns composition of steroids and organic macerals strongly reducing bottom water conditions during the deposition of the oil shale sequences are indicated by low pristane phytane ratios high c14 aryl isoprenoid contents homohopane distribution patterns and high v ni ratios enhanced salinity stratification with mesosaline and alkaline bottom waters during deposition of the oil shales are indicated by high gammacerane index values low mttc ratios high carotene contents low toc s ratios and high sr ba ratios the stratified water column with anoxic conditions in the bottom water enhanced preservation of om moderate input of detrital minerals during the deposition of the oil shale sequences is reflected by titanium concentrations in this study environmental conditions in the paleo lake leading to om accumulation in the sediments are related to sequence stratigraphy governed by climate and tectonics the first member of the qingshankou formation k2qn1 in the songliao basin containing the oil shale sequence encompasses a third order sequence that can be divided into three system tracts transgressive system tract tst highstand system tract hst and regressive system tract rst enrichment of om changed from low values during tst i to high moderate values during tst ii iii and hst i ii low om enrichment occurs during rst i and rst ii therefore the highest enrichment of om in the sediments is related to stages of mid late tst and early hst

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

geochemical evolution of the tertiary mull volcano western scotland the early tertiary mull volcano western scotland is one of the most dissected and best exposed igneous complexes of the north atlantic province the new and published geochemical data enable us to chart the magmatic evolution of the mull volcano from the oldest lavas through the intrusive rocks of three overlapping igneous centres to the youngest dykes in this study we identify four successive magma types within the remnant volcano the earliest type the mull plateau group comprises mildly alkaline basaltic rocks with steep chondrite normalized rare earth element ree patterns this type is succeeded within the lava succession and dyke swarm by the coire gorm magma type with essentially flat chondrite normalized ree patterns a third magma type represented within the lava and dykes the central mull tholeiites is more depleted in incompatible trace elements than the preceding types and has flat to lree depleted chondrite normalized patterns the major intrusions and cone sheets of mull centre 1 and early centre 2 belong to this magma type midway through the igneous activity associated with centre 2 the magma type changed to become more alkalic and more enriched in incompatible trace elements this magma type the late mull type is found to persist through the cone sheets and major intrusions of centre 3 to the youngest dykes these changes in magma composition were related to variations in the mantle source and depth of partial melting beneath mull and or differences in the efficiency of melt pooling before ascent through the lithosphere with the exception of the early staffa magma sub type part of the mull plateau group the location of magma chambers in which the bulk of contamination occurred changed with time from deep lower crustal lewisian gneiss to shallow upper crustal moine schist intermediate members of the plateau group and the late mull magma type are enriched in fe ti and p relative to the central mull tholeiites we attribute this difference to the more alkalic nature of these suites lower fo2 and the formation of fe3 p complexes in the magma the intermediate rocks were important in magma mixing processes with two types of mixing identified on mull 1 cryptic mixing between basalts and low fe intermediate magmas typified by lavas and early basic cone sheets of the central mull tholeiite magma type 2 observable mingling between rhyolitic magmas and high fe intermediate magmas of the late mull type shown by the mixed magma bodies of the glen more and loch ba ring dykes the main factor in determining which type of mixing occurred appears to have been the density contrast between the various magmas it may safely be maintained that mull includes the most complicated igneous centre as yet accorded detailed examination anywhere in the world bailey et al 1924 memoir of the geological survey of great britain scotland hmso edinburgh 1924

worldwide distribution of group velocity of mantle rayleigh waves as determined by spherical harmonic inversion we have determined the worldwide distribution of group velocity of mantle rayleigh waves for periods between 100 and 300 sec without assuming any regionalization group slowness 1 u is expressed by spherical harmonics and the coefficients up to angular order 7 have been determined from travel times of rayleigh waves by a least squares method from these u has been synthesized since we cannot obtain information about the odd terms of the expansion from one circuit measurements around the world we have used group velocities of mainly r 2 and r 3 the overall pattern of u for periods between 100 and 200 sec is consistent with results of previous pure path and regional studies group velocities for tectonically active regions are low and those of the shields and the northwestern pacific are high

late cretaceous transition from subduction to collision along the bangong nujiang tethys new volcanic constraints from central tibet abstract this study deals with arc type and subsequent bimodal volcanic rocks interbedded with late cretaceous sedimentary formations near gaize central tibet that shed new light on the tethyan evolution along the bangong nujiang suture unit i consists of trachyandesites interbedded with fine grained sandstone slate and limestone zircon dating on a trachyandesite sample yields a 206pb 238u age of 99 1 ma the trachyandesites are characterized by strong enrichment in lile but depletion in hfse low zircon saturation temperatures tzr 642 727 c and high oxygen fugacity fmq 0 67 0 73 indicating their arc affinities unit ii comprises a bimodal basalt rhyolite suite interbedded with coarse grained sandstone and conglomerate zircon dating on two rhyolitic samples yield 206pb 238u ages of 97 1 87 0 ma in contrast with unit i trachyandesites unit ii basalts and rhyolites exhibit oib like trace element patterns high temperatures t 1298 1379 c for basalts tzr 855 930 c for rhyolites and low oxygen fugacity fmq 3 37 0 43 suggesting that unit ii bimodal volcanic rocks probably formed in an extensional setting the sr nd isotopes of both unit i 87sr 86sri 0 7052 0 7074 end t 2 21 1 02 and unit ii 87sr 86sri 0 7057 0 7098 end t 3 22 0 88 rocks are similar to mantle wedge derived volcanic rocks within the southern qiangtang block the parental magma of unit i trachyandesites was formed by fluid induced melting of the mantle wedge above the subducted bangong nujiang tethyan slab and contaminated by crustal materials during mash process within a deep crustal hot zone and unit ii bimodal volcanic rocks were derived by melting of upwelling asthenosphere and a mildly metasomatized mantle wedge during the lhasa qiangtang collision we propose that the transition from the bangong nujiang tethyan subduction to the lhasa qiangtang collision occurred during the late cretaceous in central tibet

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

three dimensional seismic models of the earth s mantle accurate models of the distribution of elastic heterogeneity in the earth s mantle are important in many areas of geophysics the purpose of this paper is to characterize and compare quantitatively a set of recent three dimensional models of the elastic structure of the earth to assess their similarities and differences and to analyze their fit to one class of data in order to highlight fruitful directions for future research the aspherical models considered are the following m84c woodhouse and dziewonski 1984 lo2 56 dziewonski 1984 mdlsh tanimoto 1990a sh 10c 17 masters et al 1992 and s12 wm13 su et al 1994 through much of the discussion m84c and lo2 56 are combined into a single whole mantle model m84c lo2 56 the fit of each model to previously tabulated even degree normal mode structure coefficients taken from smith and masters 1989a and ritzwoller et al 1988 for multiplets along the normal mode fundamental and first second and fifth overtone branches is also presented rather than concentrating on detailed comparisons of specific features of the models analyses of these models are general and statistical in nature in particular we focus on a comparison of the amplitude and the radial and geographical distribution of heterogeneity in each model and how variations in each affect the fit to the normal mode observations in general the results of the comparisons between the models are encouraging especially with respect to the geographical distribution of heterogeneity and in the fit to the normal mode data sensitive to the upper mantle and lowermost lower mantle there remain however significant discrepancies in amplitude and in the radial distribution of heterogeneity especially near the top of the upper mantle and near the top of the lower mantle the confident use of these models to constrain compositional and dynamical information about the mantle will await the resolution of these discrepancies the factors that may be responsible for the differences in the models and or for the misfit between the observed and predicted normal mode data are divided into two types intrinsic or procedural and extrinsic or structural we discuss only three extrinsic factors at length here including errors in the reference crustal models unmodeled topography on discontinuities in the interior of the mantle and errors in the assumed relationships between shear s and compressional p heterogeneity

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

three dimensional structure of the upper mantle beneath the atlantic ocean inferred from long period rayleigh waves 1 group and phase velocity distributions group and phase velocity distributions of rayleigh wave fundamental modes are determined in the atlantic ocean using a method of regionalization without a priori constraints for a period range from 50 to 200 s eighty six direct source station paths are studied and 38 out of the best data from weidner s 1974 phase velocities are added to our data set for periods lower than 100 s the importance of shallow layer corrections is described in detail the general features of the distributions agree with global models and smaller scale heterogeneities are revealed a spatial resolution of 1500 km is needed to detect fine lateral heterogeneities in the atlantic the small lateral extent of young oceanic regions and strong lateral velocity gradients do not allow to quantify velocity versus age relationships using our data set on the other hand the regionalization without a priori constraints of phase velocities confirms the presence of a high velocity anomaly beneath the central part of the atlantic for periods greater than 100 s

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

high frequency isotopic variations in the mauna kea tholeiitic basalt sequence melt zone dispersivity and chromatography a stratigraphically controlled sequence of sr nd pb and he isotope ratio measurements on tholeiitic basalt cored by the hawaii scientific drilling project is analyzed to constrain the dispersivity and chromatographic efficiency of the melt producing zone under hawaii the data are interpreted using a simplified model for the transport of isotopic signals through the melt zone as magma separates from the upwelling solid by buoyancy driven porous flow a constant lava accumulation rate is assumed for the 620 m thick section of analyzed basalt a total duration of lava accumulation of 120 kyr is based on ar ar dating the amplitude period spectrum of the isotopic variations in the lava sequence is determined by fourier analysis and compared with a predicted amplitude period spectrum for the mantle magma sources based on an assumed amplitude wavelength spectrum for the mantle and a plume upwelling velocity of 20 cm yr the isotopic variations in the mantle appear to be substantially attenuated in the lava record if the attenuation is due to hydrodynamic dispersion in the melting zone then the melt zone dispersivity is estimated to be in the range 100 1000 m depending mainly on the value assumed for the melt matrix velocity contrast dispersivity is a crude measure of effective grain size in the melt zone the large values although strictly only upper limits suggest that permeability in the melt zone is inhomogeneous and some amount of channel development is present the ratios 3he 4he and 206pb 204pb in the mauna kea section describe convoluted loops when plotted against one another consistent with significant chromatographic separation of he and pb in the melt zone the evidence for chromatography of isotopic signals is consistent with the porous flow model predictions and indicates that the melt is maintained moderately close to chemical equilibrium with the solid as it separates the modeling suggests that generally chromatography in the melting zone causes isotope ratio ratio relationships observed in the lava record to be severely out of phase with those present in the mantle source if the period of the variability is of order 105 years for periods greater than 106 years the ratios are close to being in phase whereas for periods less than 104 years the lava record is hopelessly scrambled

source geometry and mechanism of 1978 tabas iran earthquake from well located aftershocks abstract aftershocks of the september 16 1978 tabas earthquake located from close in observations made during a four week fielding of temporary stations have been analyzed for the purpose of delineating detailed source geometry of the 1978 earthquake spatial distribution of aftershocks and their composite focal mechanism suggest that the geometry of faulting is far from planar aftershocks define two prominent alignment the southern alignment strikes e w to wnw ese whereas the northern alignment strikes in a n s to nnw sse direction with an abrupt change of nearly 55 60 degrees near 33 4 n latitude both field observations of surface faulting pattern and systematic variation of principal directions of stress axes computed from aftershock focal mechanisms are consistent with the upthrusting and imbrication of a wedge shaped crustal block with the wedge angle of about 120 degrees both geological and seismological evidence suggest that the deformed zone is truncated at the southern edge by preexisting e w fault structures new observations may provide a partial answer to the unexplained farfield asymmetry of the long period rayleigh wave radiation pattern recently observed for the mainshock across ida network

measurements of mantle wave velocities and inversion for lateral heterogeneities and anisotropy 3 inversion lateral heterogeneity in the earth s upper mantle is investigated by inverting dispersion curves of long period surface waves 100 330 s models for seven different tectonic regions are derived by inversion of regionalized great circle phase velocity measurements from our previous studies we also obtain a representation of upper mantle heterogeneities with no a priori regionalization from the inversion of the degree 6 spherical harmonic expansion of phase and group velocities the data are from the observation of about 200 paths for love waves and 250 paths for rayleigh waves for both the regionalized and the spherical harmonic inversions corrections are applied to take into account lateral variations in crustal thickness and other shallow parameters these corrections are found to be important especially at low spherical harmonic order the trench region and fast velocities down to 250 km under shields below 200 km under the oceans both s velocity and s anisotropy support a model of small scale convection in which cold blobs detach from the bottom of the lithosphere when its age is large enough the spherical harmonic models clearly demonstrate a posteriori the relation between surface tectonics and s velocity heterogeneities in the first 250 km all shields are fast most ridges are slow below 300 km a belt of fast mantle follows the pacific subduction zones however at greater depths large scale heterogeneities that seem to bear no relationship to surface tectonics are observed the most prominent feature at 450 km is a fast velocity region under the south atlantic ocean smaller scale heterogeneities that are not related to surface tectonics are also mapped at shallower depths an anomalously slow region centered in the south central pacific is possibly linked to intense hot spot activity a very fast region southeast of south america may be related to subduction of old pacific plate between 200 and 400 km a belt of sv sh anisotropy follows part of the ridge and subduction systems indicating vertical mantle flow in these regions the spherical harmonic results open new horizons for the understanding of convection in the mantle perspectives for the improvement of the models presented are discussed

a mantle wave magnitude for the st elias alaska earthquake of 28 february 1979 abstract we have investigated surface and mantle waves from the st elias earthquake 28 february 1979 21 27 06 1 utc using standard time domain techniques and highly automated procedure for frequency domain analysis mantle wave spectral densities at periods of 100 150 200 and 250 sec were determined from r 1 through r 5 and g 1 through g 6 recorded by 10 stations of the global digital seismograph network using a method similar to one developed by brune and engen 1969 for 100 sec love waves for comparison we have generated synthetic seismograms by normal mode summation using two published fault plane solutions lahr et al 1979 hasegawa et al 1980 and assuming a point source for the st elias event we find that the precise orientation of the focal mechanism has a significant impact on the efficiency of mantle wave generation and hence on moment inference further source finiteness effects expressed as distortion of the radiation pattern and a disparity between moment estimates made using love and rayleigh waves are clearly visible at all periods we examined however these effects decrease dramatically with increasing periods and are gratifyingly small by 250 sec allowing us to make a moment estimate we have made the following measurements of the size of the st elias earthquake

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

long period mechanism of the 8 november 1980 eureka california earthquake the seismic moment and source orientation of the 8 november 1980 eureka california earthquake m s 7 2 are determined using long period surface and body wave data obtained from the sro asro and ida networks the favorable azimuthal distribution of the recording stations allows a well constrained mechanism to be determined by a simultaneous moment tensor inversion of the love and rayleigh wave observations the shallow depth of the event precludes determination of the full moment tensor but constraining m zx m zy 0 and using a point source at 16 km depth gives a major double couple for period t 256 sec with scalar moment m 0 1 1 10 27 dyne cm and a left lateral vertical strike slip orientation trending n48 2 e the choice of fault planes is made on the basis of the aftershock distribution this solution is insensitive to the depth of the point source for depths less than 33 km using the moment tensor solution as a starting model the rayleigh and love wave amplitude data alone are inverted in order to fine tune the solution this results in a slightly larger scalar moment of 1 28 10 27 dyne cm but insignificant 5 changes in strike and dip the rake is not well enough resolved to indicate significant variation from the pure strike slip solution additional amplitude inversions of the surface waves at periods ranging from 75 to 512 sec yield a moment estimate of 1 3 0 2 10 27 dyne cm and a similar strike slip fault orientation the long period p and sh waves recorded at sro and asro stations are utilized to determine the seismic moment for 15 to 30 sec periods a deconvolution algorithm developed by kikuchi and kanamori 1982 is used to determine the time function for the first 180 sec of the p and sh signals the sh data are more stable and indicate a complex bilateral rupture with at least four subevents the dominant first subevent has a moment of 6 4 10 26 dyne cm summing the moment of this and the next three subevents all of which occur in the first 80 sec of rupture yields a moment of 1 3 10 27 dyne cm thus when the multiple source character of the body waves is taken into account the seismic moment for the eureka event throughout the period range 15 to 500 sec is 1 3 0 2 10 27 dyne cm

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

isotopic composition and speciation of sulfur in the miocene monterey formation reevaluation of sulfur reactions during early diagenesis in marine environments the timing and pathways of early diagenetic sulfur transfer from dissolved species in pore waters to solid inorganic and organic compounds in sediments have been studied in the miocene monterey formation santa maria basin onshore california correlation between concentrations of total organic carbon toc and total sulfur ts in addition to concentrations of titanium aluminum total iron and reactive iron have been used to infer organic matter reactivity redox conditions and relative rates of clastic and biogenic input for each lithofacies isotopic compositions of six sulfur species acid volatile disulfide kerogen bitumen sulfate and elemental have provided information regarding relative timing of sulfur incorporation sulfate diffusivity in the upper centimeters of the sediments and the sources of sulfur for individual species isotopically the disulfide species expresses the greatest fractionation relative to estimated values of miocene seawater sulfate 22 cdt on average disulfide is depleted in 34s by 10 4 relative to kerogen and by 9 9 relative to acid volatile sulfide the 34s of bitumen shows no systematic change relative to 34skeregon suggesting the presence of migrated bitumen isotopic similarity of sulfate and elemental sulfur to sulfides and bitumen indicates that sulfate and elemental sulfur are chemical and or biological oxidation products derived from sulfides and bitumen consistent ordering of isotopic values for sulfur species disulfide acid volatile sulfide kerogen indicates that pyrite precipitated nearest to the sediment water interface under mildly reducing conditions and with little or no decrease in sulfate concentration relative to seawater enrichment of 34s in acid volatile sulfide and kerogen sulfur resulted from formation of these species at greater depths or in restricted micro environments under more reducing conditions and with low concentrations of porewater sulfate the formation of acid volatile sulfide after pyrite but during early diagenesis is significant because it implies more strongly reducing conditions than are generally recognized in deep water marine sediments

source parameters of 1978 tabas and 1979 qainat iran earthquakes from long period surface waves the teleseismic records of three strong earthquakes which inflicted heavy damage and loss of many thousands of lives in northeastern iran during 1978 and 1979 are analyzed the observed r 2 and r 3 phases of the 16 september 1978 tabas earthquake across the ida network are inverted to derive the gross source parameters of the main shock the synthetic seismograms computed for the inferred source model are compared with observations the agreement is generally good at most of the stations however unexpected asymmetrical observations at esk cmo kip and pfo stations cannot be explained by directivity alone possible factors responsible for these observations may include regional heterogeneities or the departure of fault plane from simple planar geometry the resulting focal mechanism agrees with nearly pure reverse mechanism with a nw se strike the seismic moment estimate for this earthquake is about 1 5 10 27 dyne cm m w 7 4 the seismic moment of the same earthquake obtained from long period p wave observations at six wwssn stations is smaller than the above estimate by a factor of 2 starting with the geologic field data of the qainat earthquakes of 14 and 27 november 1979 the r 2 and g 2 phases on the ultra long period instruments at pasadena and berkeley are analyzed to estimate their seismic source moments the estimated values are 1 0 10 26 dyne cm for the 14 november and 8 0 10 26 dyne cm for the 27 november 1979 events their corresponding moment magnitudes are 6 6 and 7 2 respectively

on the presence of intermediate scale heterogeneity in the upper mantle summary power spectra of tomographic models of the entire earth and of models of europe and the mediterranean area are compared this comparison reveals a discrepancy a factor 15 30 between the power of both kinds of models at intermediate spherical harmonic degrees around l 30 two possible explanations for this discrepancy are given first the fact that europe is more complex than the global average and second the lack of resolution in the inversions another approach to the problem of the power spectrum of heterogeneities of intermediate length scale is the study of multipathing of long period surface waves the multipathing observed in the recordings of these waves which manifests itself as an increasing complexity of their amplitude spectra due to increasing interference of spectral components with increasing epicentral distance cannot be explained by present day global earth models the gradients in the models are simply not strong enough however random models with more power at intermediate scales and consequently stronger gradients are able to explain the observed multipathing it is concluded that the global models underestimate the power in the heterogeneities of intermediate scale structure in the earth finally an explanation is given why current global models although they do not contain sufficient power at shorter scales do explain the traveltime and dispersion data used for the construction of the models

structure of the earth mantle and core the deep interior structure of the earth has been extensively analyzed using a wide variety of seismic phases and techniques during the last four years most studies have emphasized quantitative three dimensional mapping of the lateral velocity heterogeneity of the mantle and core these aspherical velocity variations are believed to be direct manifestations of thermal and compositional heterogeneity associated with convective processes a first generation of global models for the lateral velocity variations in the deep earth has been produced providing tantalizing images of large scale structures suggestive of a non steady state thermal convection system the upper 400 km of the mantle has the strongest lateral velocity variations of up to 10 for shear velocity surface wave analyses that do not require a priori regionalizations have demonstrated that there is a strong association between surface tectonic provinces and the uppermost mantle velocity variations thus the thermal and convective state of the upper 200 km of the mantle can be reliably interpreted in the context of plate tectonics the upper mantle models support the contention that continents have deep roots with differences in velocity structure from oceanic and active tectonic regions extending as deep as 400 km very long wavelength lateral velocity variations of a few percent have been detected in the transition zone at depths from 400 to 670 km as well as throughout the lower mantle these deep seated variations have little correspondence to surface tectonics and efforts to interpret their nature are just beginning the lowermost 200 km of the mantle d region has lateral velocity fluctuations comparable to those in the upper mantle and evidence has been presented for the presence of a sizable velocity discontinuity at the top of the d layer a combined thermal and compositional boundary layer roughly mirroring the lithosphere is a likely explanation for this anomalous zone the core mantle boundary appears to have significant 10 km long wavelength topography presumably sustained by dynamic stresses from deep mantle convection the inner core may have strong lateral heterogeneity or axially symmetric anisotropy suggesting a complex thermal and compositional state significant progress has been made in characterizing the frequency dependence of anelastic attenuation in the mantle in the short period body wave band models for teleseismic p wave attenuation operators have converged with t values of 0 7 1 0 s appropriate at 1 hz and t values of 0 4 0 6 s appropriate at 4 hz regional variations of attenuation are slowly being mapped out as well

global love wave phase velocity variation and its significance to plate tectonics abstract global love wave phase velocity variation was constructed for periods between 80 and 200 s by using approximately 9000 paths from 971 earthquakes with m 5 5 the data set was from gdsn and geoscope networks between 1980 and 1987 we examined both the spherical harmonic expansion method and the block parameterization method with a simple constant damping parameter approach synthetic tests showed that more accurate results were obtained by the block parameterization method than by the spherical harmonic expansion method we adopted the block inversion method with a nearly equal area block 5 5 near the equator discretization the general pattern of the resulting maps were consistent with previous global and local studies with a discretization of 5 by 5 the maps were detailed enough to test some plate tectonic models for the pacific atlantic and indian oceans surface wave velocities increased smoothly to plate ages older than 100 ma simple forward modeling showed that seismic phase velocity variation with a continuous thickening of lithosphere up to about 150 ma fits the present observation disagreeing with the model deduced from the heat flow and ocean depth data which change variations at about 60 80 ma the seismic phase velocity variations in different oceans showed systematic differences at younger ages and convergence beyond 100 ma the difference at younger ages implies a failure of scaling derived from a simple thermal boundary layer model for oceanic plates age seismic phase velocity relationships on each side of ridges were also examined and asymmetric velocity variations were found which suggests differences in thermal states from one side of the ridge to the other in order to further examine the thermal state of the lithosphere average age phase velocity relations were established for each ocean and subtracted from phase velocity variation maps the results indicated broad low velocity regions in the south pacific super swell region the south and west indian ocean and high velocity regions east of the east pacific rise and in the north to northeast indian ocean the results reflect the asymmetry of phase velocity variation about ridges there is some correlation between hot spot locations and low velocity anomalies but additional large scale thermal anomalies exist under old oceanic plate

arrival angle anomalies across the usarray transportable array abstract we construct composite maps of surface wave arrival angle anomalies using clustered earthquakes and an array method for measuring wave front geometry this results in observations of arrival angles covering the entire footprint of the usarray transportable array during 2006 2010 bands of arrival angle deviations in the propagation direction indicate the presence of heterogeneous velocity structure both inside and outside of the array we compare the observed patterns to arrival angles predicted using two global tomographic models the mantle model s362ani and the surface wave dispersion model gdm52 we use both ray theory based prediction methods and measurements on synthetic data calculated using a spectral element method both models and all prediction methods produce similar mean arrival angles and long wavelength patterns of anomalies which are similar to the observations predicted short wavelength features generally do not agree with the observations the spectral element method produces some complexity that is not obtained using the ray theory based methods this predicted complexity is similar in character to the observed patterns but does not match them

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

water and partial melting in mantle plumes inferences from the dissolved h2o concentrations of hawaiian basaltic magmas knowledge of dissolved h2o in primary kilauean magmas provides a constraint on h2o abundance in the deep mantle region that feeds the upwelling plume beneath hawaii given an h2o k2o mass ratio of 1 3 for basaltic glasses and melt inclusions from kilauea the mantle source is estimated to contain 450 190 ppm h2o this value is 3 times greater than that estimated for the mantle source for mid ocean ridge basalts consideration of oh solubility in olivine suggests that water undersaturated melting of the upwelling hawaiian plume probably begins at a depth of 250 km thus during plume ascent through most of the upper mantle water is partitioned between nominally anhydrous silicates and a small mass fraction of entrained hydrous silicate melt because water strongly influences the viscosity of olivine aggregates partial melting and melt extraction will have important effects on the rheology of the upwelling plume beneath hawaii