is the asthenosphere electrically anisotropic abstract two techniques for resolving the conductance of an electrically conductive asthenosphere are presented the first technique combines observatory electromagnetic data in the period range of the daily variation and longer which provides penetration depths of 400 km and deeper with laboratory data of the conductivity of upper mantle materials the conductance can be estimated by this technique but the geometry e g the exact depth is not resolved the second technique extends the classical magnetotelluric mt tensor estimation and decomposition to the period range 1000 30 000 s if an electrical asthenosphere exists then in this period range the electromagnetic field penetrates into it 1000 s but also through it 30 000 s the concept of regional strike directions which has been successfully used to obtain crustal anisotropy directions is again employed at these long periods the surprising result is that in the depth range of the asthenosphere a strong directional dependence of the conductance again occurs although large arrays will be necessary in order to prove that this is really conductivity anisotropy in the asthenosphere first field results from arrays 100 200 km in extent are encouraging the concept of a superposition of crustal and upper mantle anisotropy explains to some extent why earlier magnetotelluric determinations of the asthenosphere had little success only in the fortunate case where a mt experiment was performed not parallel to the direction of the crustal conductor but parallel to the asthenospheric one is the second structure resolved electrical anisotropy in the uppermost mantle supports the concept of intracrystalline water which allows for a contribution of hydrogen diffusity to the conductivity of olivine this diffusity is highly anisotropic with respect to the crystal axis and if the crystals are partly aligned the conductivity measured with mt is also direction dependent

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

effect of iron content on electrical conductivity of ringwoodite with implications for electrical structure in the transition zone abstract electrical conductivity of ringwoodite with various iron contents fe fe mg 0 09 0 2 and 0 3 was measured at pressure 20 gpa and temperature up to 1900 k conditions of the lower part of the mantle transition zone in a kawai type multi anvil apparatus the conductivity increased with increasing total iron content all electrical conductivity data were fitted to the formula of electrical conductivity 0 xfe exp h kt where 0 is the pre exponential term xfe is the mole fraction of iron content in the mg site h is the activation enthalpy k is the boltzmann constant and t is absolute temperature the activation enthalpy becomes higher at a certain temperature at high temperatures the activation enthalpy decreased from 1 44 to 0 92 ev with increasing total fe content at low temperatures less than 1000 k the activation enthalpy also decreases from 1 15 to 0 74 ev with total fe content dependence of the activation enthalpy on fe content suggests that the dominant mechanism of charge transport is fe2 fe3 hopping small polaron recent electrical conductivity depth profiles of the transition zone beneath the pacific ocean obtained from the electromagnetic induction study shows that the conductivity values between 520 and 660 km depths may be explained by ringwoodite with fe fe mg 0 10 on the other hand assuming a normal geotherm conductivity values beneath the continent or stable craton are considerably lower than those of ringwoodite with fe fe mg 0 10 taking into consideration results from the global seismic tomographic studies relatively low conductivity in these regions can be explained by the existence of a cooler region compared with the surrounding mantle rather than the presence of iron poor ringwoodite or a combination of both

ionospheric current source modeling and global geomagnetic induction using ground geomagnetic observatory data long period global scale electromagnetic induction studies of deep earth conductivity are based almost exclusively on magnetovariational methods and require accurate models of external source spatial structure we describe approaches to inverting for both the external sources and three dimensional 3 d conductivity variations and apply these methods to long period t 1 2 days geomagnetic observatory data our scheme involves three steps 1 observatory data from 60 years only partly overlapping and with many large gaps are reduced and merged into dominant spatial modes using a scheme based on frequency domain principal components 2 resulting modes are inverted for corresponding external source spatial structure using a simplified conductivity model with radial variations overlain by a two dimensional thin sheet the source inversion is regularized using a physically based source covariance generated through superposition of correlated tilted zonal quasi dipole current loops representing ionospheric source complexity smoothed by earth rotation free parameters in the source covariance model are tuned by a leave one out cross validation scheme 3 the estimated data modes are inverted for 3 d earth conductivity assuming the source excitation estimated in step 2 together these developments constitute key components in a practical scheme for simultaneous inversion of the catalogue of historical and modern observatory data for external source spatial structure and 3 d earth conductivity

coastal impacts of the march 11th tohoku japan tsunami in the galapagos islands on march 11 2011 at 5 46 23 utc march 10 11 46 23 pm galapagos local time the mw 9 0 great east japan earthquake occurred near the tohoku region off the east coast of japan spawning a pacific wide tsunami approximately 12 000 km away the galapagos islands experienced moderate tsunami impacts including flooding structural damage and strong currents in this paper we present observations and measurements of the tsunami effects in the galapagos focusing on the four largest islands in the archipelago from west to east isabela santiagio santa cruz and san cristobal access to the tsunami affected areas was one of the largest challenges of the field survey aside from approximately ten sandy beaches open to tourists all other shoreline locations are restricted to anyone without a research permit open cooperation with the galapagos national park provided the survey team complete access to the islands coastlines survey locations were guided by numerical simulations of the tsunami performed prior to the field work this numerical guidance accurately predicted the regions of highest impact as well as regions of relatively low impact tide corrected maximum tsunami heights were generally in the range of 3 4 m with the highest runup of 6 m measured in a small pocket beach on isla isabela puerto ayora on santa cruz island the largest harbor in the galapagos experienced significant flooding and damage to structures located at the shoreline a current meter moored inside the harbor recorded relatively weak tsunami currents of less than 0 3 m s 0 6 knot during the event comparisons with detailed numerical simulations suggest that these low current speed observations are most likely the result of data averaging at 20 min intervals and that maximum instantaneous current speeds were considerably larger currents in the canal de itabaca a natural waterway between santa cruz island and a smaller island offshore were strong enough to displace multiple 5 5 ton navigation buoys numerical simulations indicate that currents in the canal de itabaca exceeded 4 m s 8 knots a very large flow speed for a navigational waterway

lateral variations of the mid mantle conductance beneath europe abstract europe is a region with the largest density of geomagnetic observatories and several authors have used these data to estimate local geomagnetic response functions for various period ranges typically of the width of 1 5 to 2 5 decades by collecting the local response functions from 35 european observatories and by their precise selection and subsequent combination the independent regional geomagnetic induction data set could be extended to a period range of 4 5 decades the initial local responses that were estimated by two magnetovariation methods with two different external source fields employed have been further supplemented by continental and global 11 year data providing thus a data set extending over a period range from the harmonics of the daily variations up to 11 years the combined responses have been inverted individually for each observatory by two techniques by an occam procedure and a stochastic 1d inversion for spherically symmetric earth the integrated mantle conductance has revealed rather regular lateral changes that have been used to design a mantle conductance image down to a depth of about 770 km the presented conductance image can be correlated with major european tectonic units like the baltic shield and the trans european suture zone to examine possible distortions to the inferred mantle conductance models due to large scale near surface heterogeneities specifically those caused by the oceans seas and large sedimentary basins a spherical forward modeling was carried out for a radially symmetric conductor coated by an inhomogeneous thin shell with the variable surface conductance the model responses for the 35 observatory positions were inverted in the same way as previously the experimental data the results for 28 observatories have shown that the depth down to a pre defined conductance level could be retrieved with a high accuracy of a few percents but for seven southernmost observatories the recovery error increased up to 9 with these seven observatories removed from the analysis the effect of the seas and oceans on the upper and mid mantle conductance estimates beneath europe can be considered negligible

can we probe the conductivity of the lithosphere and upper mantle using satellite tidal magnetic signals thesis s m massachusetts institute of technology department of earth atmospheric and planetary sciences 2015

secular variations of the earth s apparent resistivity monitoring carried out by the generalized magnetovariation gmv and geomagnetic depth sounding gds methods has shown a valuable variability of yearly apparent resistivities from the yr 1911 to 2010 for the selected european geomagnetic observatories these deep soundings were carried out by the two methods mentioned above correspondingly for shorter and longer periods in the range from 8 h to a month the possible changes in the source signals through an uncorrelated part of the observed field were mainly suppressed by robust coherence based statistical data processing the detected resistivity variations have periods of more than several yr while inequality of induction arrows obtained by the gmv method may be seen already during a couple of yr the 11 yr variability of the apparent resistivity correlates with wolf numbers with some phase lags the variations with shorter periods have been found to change synchronously with the number of the earthquakes at a region including some seismically active areas in europe the peculiarities and possible origins of the phenomenon are discussed

continental scale deep electrical resistivity structure beneath china abstract electrical resistivity structure in the deep earth can provide important information and constraints on regional geodynamics especially in regions with complex tectonics and geodynamical processes in this study we image the electrical resistivity structure in the depth range of 350 1200 km beneath china by inverting the frequency dependent ratios of geomagnetic field components at a relatively dense network of geomagnetic observatories very long time series of hourly mean values of the three component geomagnetic field from 45 geomagnetic observatories are collected and processed to derive robust ratios of the geomagnetic components which are then converted to the apparent resistivities and impedance phases in the period range of 5 3 113 8 days and used in 1 d occam inversion with smoothing constraint and the method to obtain the electrical resistivity profiles and delta function models at individual observatories 1 d electrical resistivity models suggest that low electrical resistivity structure exists in the mantle transition zone beneath eastern china high water content in the mantle minerals due to the subduction of seismically fast pacific slab is proposed as the main reason for the low electrical resistivity beneath eastern china our results provide further evidence that the western front of the subducting pacific slab in the mantle transition zone roughly coincides with the abrupt change in the surface topography in eastern china

recent controversies in predicting post glacial sea level change abstract we compare recent developments in the numerical prediction of post glacial sea level changes and comment on the controversies associated with these developments we conclude that 1 the broad shelf effect discussed by peltier and drummond 2002 in the context of water load modelling at migrating shorelines is incorporated into the sea level algorithms of johnston 1993 and milne et al 1999 and 2 the procedure used by yokoyama et al 2000 to infer an ice equivalent post lgm sea level rise of 130 135 m is technically sound

unraveling middle crust conductive layers in paleozoic orogens through 3d modeling of magnetotelluric data the ossa morena zone case study sw iberian variscides 1 in recent years a number of magnetotelluric mt surveys have been carried out in the southern branch of the iberian variscan massif namely in the ossa morena zone omz and its neighboring areas the south portuguese zone spz and the central iberian zone ciz in order to determine the geoelectrical structure of this transpressive orogen and gain insight into its internal architecture new mt data collected across the omz complete a dense database that covers the whole belt and its boundaries this paper presents an integrative three dimensional model of the available mt data from the apparent resistivities four components impedance phases and geomagnetic transfer functions from 61 stations given the location of the study area near the atlantic ocean coast effect on the data was analyzed as well as the stability of the mesh due to the strong resistivity contrasts a mesh of 80 77 76 cells was finally used with an average cell size of 4 4 km in the horizontal direction and increasing thickness in the vertical direction from 25 m in the shallower layers to 5 km in the deepest ones the most striking feature is in addition to the conductive anomalies associated with the sutures between the spz omz and the omz ciz a conductive layer which spans the whole ossa morena middle to lower crust the top of this conductive layer is interpreted as a major decollement between the granulitic basement and the overlying meta sedimentary pile

3 d modelling and analysis of dst c responses in the north pacific ocean region revisited summary during the last decade a number of one dimensional 1 d conductivity profiles have been constructed for the upper and mid mantle of the north pacific ocean region these profiles differ significantly and from our point of view it is still unclear which profile is the best candidate for the upper and mid mantle conductivity reference model for this region keeping the differences in mind and inspired by recent findings that the ocean effect is a major contributor to the anomalous behaviour of c responses up to the period of 20 days especially at coastal observatories the goal of this paper has been three fold 1 to understand on the basis of systematic model studies using 3 d ocean models which of the published 1 d upper and mid mantle profiles is in best agreement with the available observations 2 to try to reduce the misfit between the observed and modelled responses by using dense grids in modelling by considering 3 d models which include not only an inhomogeneous surface layer but also inhomogeneous deeper structures 3 to derive an alternative 1 d upper and mid mantle section for the north pacific ocean by carefully selecting the data for interpretation and by using 3 d models that are as realistic and detailed as possible in order to perform the simulations using realistic 3 d models on a routine basis a novel 3 d spherical forward solution has been elaborated in this paper the solution combines the modified iterative dissipative method with a conjugate gradient iteration and allows one to compute efficiently the electromagnetic fields in full 3 d spherical models with very high lateral contrasts of conductivity and for very dense grids during the 3 d simulations a systematic shift of observed c responses at honolulu compared with those at other observatories was detected the reason for this shift is still unclear even if a very detailed grid of 0 3 0 3 is used the 3 d simulations using a model of the inhomogeneous surface has no notable ocean effect to c responses at this site an attempt has been made to reduce the misfit between observed and modelled c responses by incorporating a 3 d model with inhomogeneous lithosphere and upper mantle however this has resulted only in a slight change in responses the main conclusion drawn from our 3 d model studies is that there exists a significant disagreement between observed and 3 d modelled c responses if the published 1 d sections with conducting uppermost 400 km are considered as the upper and mid mantle sections our 3 d simulations and reinterpretation of the data also confirm the recent finding that the upper and mid mantle beneath north pacific ocean in the depth range down to 400 km is much more resistive than hitherto assumed

a comprehensive model of the quiet time near earth magnetic field phase 3 summary the near earth magnetic field is caused by sources in the earth s core ionosphere magnetosphere lithosphere and from coupling currents between the ionosphere and the magnetosphere and between hemispheres traditionally the main field low degree internal field and magnetospheric field have been modelled simultaneously with fields from other sources being modelled separately such a scheme however can introduce spurious features especially when the spatial and temporal scales of the fields overlap a new model designated cm3 comprehensive model phase 3 is the third in a series of efforts to coestimate fields from all of these sources this model has been derived from quiet time magsat and pogo satellite and observatory hourly means measurements for the period 1960 1985 it represents a significant advance in the treatment of the aforementioned field sources over previous attempts and includes an accounting for main field influences on the magnetosphere main field and solar activity influences on the ionosphere seasonal influences on the coupling currents a priori characterization of the influence of the ionosphere and the magnetosphere on earth induced fields and an explicit parametrization and estimation of the lithospheric field the result is a model that describes well the 591 432 data with 16 594 parameters implying a data to parameter ratio of 36 which is larger than several popular field models

characteristics of the 2011 great tohoku tsunami on the russian far east coast deep water and coastal observations the source region of the catastrophic tohoku tsunami of 11 march 2011 was not far from the russian far east coast the sakhalin tsunami warning center at yuzhno sakhalinsk issued an alert for threatened coasts of the kuril islands and kamchatka the observed tsunami heights were up to 2 2 5 m along the pacific coast of the kuril islands the tsunami was clearly recorded by a number of coastal tide gauges and by deep ocean bottom pressure stations located in the vicinity of the kuril islands as well as by the russian open ocean dart station 21401 located eastward from the south kuril islands the data from other dart stations in particular those located near japan and the aleutian islands were used for comparison the records from these instruments were used to estimate the major characteristics of the tsunami waves including arrival times maximum heights durations of the signal and main wavelength periods as well as for comparison with the results of numerical modelling in contrast to deep sea stations where the first waves were the highest at russian coastal sites the highest waves occurred several hours after the arrival of the first tsunami wave further analysis indicated significant differences in spectral characteristics of tsunami waves propagating eastward toward north america and those directed in the northeast direction towards the russian far east the main peaks of the eastward propagating tsunami waves were relatively high frequency periods ranging from 6 8 to 15 20 min while those propagating in the northeast direction were mainly low frequency ranging from 25 40 to 60 80 min additionally pronounced spectral peaks with similar long periods were found in the middle field records at hanasaki on the northeastern coast of hokkaido island at yuzhno kurilsk kunashir island and at malokurilsk shikotan island at remote stations the resonant periods associated with local topographic features were predominant in the spectra

very long period magnetotellurics at tucson observatory estimation of impedances eleven years 1932 1942 of electric potential and magnetic measurements at the tucson observatory represent a unique very long period magnetotelluric mt data set we report here on a careful reanalysis of this data using modern processing techniques we have developed and used novel methods for separating out the quasi periodic daily variation fields and for cleaning up outliers and filling in missing data in the time domain mt impedance tensors estimated using the cleaned and filled data and using robust frequency domain methods are well determined and smoothly varying for periods between 4 hours and 10 days at longer periods the electric field data are swamped by large amplitude incoherent noise particularly after the third year of the experiment although we find no evidence for contamination of any field components by oceanic motional induction at tidal periods the mt impedance estimates do show evidence of small systematic biases due to finite spatial scale geomagnetic sources at harmonies of the daily variation period these periods are thus removed from the time series and not used in further analysis we show that the resulting impedance tensor is well modeled by a real frequency independent distortion of a scalar impedance which is consistent with non inductive distortion of the electric fields by local surface geology to estimate the undetermined static shift of the mt impedance we compare the long period mt results to equivalent mt impedances determined from 46 years of geomagnetic data combining the geomagnetic and undistorted mt impedances results in scalar impedance estimates for periods 0 17 t 91 days of unprecedented precision however for periods less than one day the phase and amplitude of this impedance while individually consistent are not mutually consistent with any one dimensional conductivity distribution the inconsistency probably results from a combination of subtle multidimensional effects and systematic biases

a comparison of electromagnetic distortion and resolution of upper mantle conductivities beneath continental europe and the mediterranean using islands as windows abstract to investigate the potential of utilising islands as windows through which oceanic mantle conductivities might be imaged simultaneous magnetotelluric mt measurements were carried out continuously over a 3 month duration at two continental stations one in the swabian alps southern germany the other in the bourgogne central france and on the mediterranean islands of montecristo mchr and mallorca mall the mt transfer functions to 1 5 cycles per day cpd and single site z h transfer functions for the first four harmonics of the solar quiet sq daily field variations are presented the transfer functions derived at the island sites are corrected for the distortive and inductive effects arising from the mediterranean bathymetry relative to the transfer functions calculated at the continental stations using three dimensional thin sheet modelling the corrections are formulated in terms of the magnetic perturbation tensor w static shifts in the mt transfer functions are corrected using the z h transfer functions and by comparison with hypothesised resistivity jumps at the transition zones models are derived jointly from the residual mt and z h transfer functions constraints on the resistivities of the upper mantle are investigated despite the widely different tectonic settings no significant differences in the conductivities of the upper mantle below 100 km are detected the disadvantages of utilising widely spaced islands as windows to the mantle are highlighted by departures from one dimensionality in the complex tectonic setting of the mediterranean region

cm5 a pre swarm comprehensive geomagnetic field model derived from over 12 yr of champ orsted sac c and observatory data a comprehensive magnetic field model named cm5 has been derived from champ rsted and sac c satellite and observatory hourly means data from 2000 august to 2013 january using the swarm level 2 comprehensive inversion ci algorithm swarm is a recently launched constellation of three satellites to map the earth s magnetic field the ci technique includes several interesting features such as the bias mitigation scheme known as selective infinite variance weighting sivw a new treatment for attitude error in satellite vector measurements and the inclusion of 3 d conductivity for ionospheric induction sivw has allowed for a much improved lithospheric field recovery over cm4 by exploiting champ along track difference data yielding resolution levels up to spherical harmonic degree 107 and has allowed for the successful extraction of the oceanic m2 tidal magnetic field from quiet nightside data the 3 d induction now captures anomalous solar quiet features in coastal observatory daily records cm5 provides a satisfactory continuous description of the major magnetic fields in the near earth region over this time span and its lithospheric ionospheric and oceanic m2 tidal constituents may be used as validation tools for future swarm level 2 products coming from the ci algorithm and other dedicated product algorithms

imaging the continental upper mantle using electromagnetic methods abstract the internal structure of the continental lithosphere holds the key to its creation and development and this internal structure can be determined using appropriate seismic and electromagnetic methods these two are complementary in that the seismic parameters usually represent bulk properties of the rock whereas electrical conductivity is primarily a function of the connectivity of a minor constituent of the rock matrix such as the presence of a conducting mineral phase e g carbon in graphite form or of a fluid phase e g partial melt or volatiles in particular conductivity is especially sensitive to the top of the asthenosphere generally considered to be a region of interconnected partial melt knowledge of the geometry of the lithosphere asthenosphere boundary is important as this boundary partially controls the geodynamic processes that create modify and destroy the lithosphere accordingly collocated seismic and electromagnetic experiments result in superior knowledge than would be obtained from using each on its own this paper describes the state of knowledge of the continental upper mantle obtained primarily from the natural source magnetotelluric technique and outlines how hypotheses and models regarding the development of cratonic lithosphere can be tested using deep probing electromagnetic surveying the resolution properties of the method show the difficulties that can be encountered if there is conducting material in the crust examples of data and interpretations from various regions around the globe are discussed to demonstrate the correlation of electromagnetic and seismic observations of the lithosphere asthenosphere boundary also the observations from laboratory measurements on candidate mineralogies representative of the mantle such as olivine are presented

the 2010 and 2011 tsunamis in french polynesia operational aspects and field surveys we present a detailed timeline of the warning procedures as they unfolded at the laboratoire de geophysique in papeete tahiti during the nights of 26 27 february 2010 maule chile tsunami and 10 11 march 2011 tohoku tsunami in particular we discuss how the flow of information available to the warning center including seismic evaluations obtained both locally and from other warning centers as well as maregraph and dart buoy data built up and eventually led to red alerts which the local authorities used in both cases to impose an evacuation of low lying areas on 68 islands while the alerts were successful in polynesia a difficulty arose in 2011 when the alert had to be reinstated immediately as the all clear was being declared since the maximum amplitude was carried by the fourth wave packet we also present a complete dataset of 119 values of run up and inundation surveyed in the aftermath of the two tsunamis principally in the marquesas islands where their effects were maximal and on tahiti and moorea for the 2011 event the highest run up 4 45 m was observed in 2011 in the bay of taipivai on nuku hiva where seven houses were flooded we find no clear correlation between run up values at the same locations in 2010 and 2011 suggesting that local responses are controlled by details specific to each tsunami in 2010 in the village of puamau on hiva oa marquesas a delayed harbor response probably due to resonance of the bay upon arrival of short period components dispersed outside the shallow water approximation flung a launch onto a wharf 7 h after the first arrivals and 2 5 h after issuance of the all clear

model of the geoelectrical structure of the mid and lower mantle in the europe asia region summary the conductivity structure of the earth s mantle was estimated using the induction method down to 2100 km depth for the europe asia region for this purpose the responses obtained at seven geomagnetic observatories irt kiv mos nvs hlp wit and ngk were analysed together with reliable published results for 11 yr variations 1 d spherical modelling has shown that beneath the mid mantle conductive layer 600 800 km the conductivity increases slowly from about 1 s m 1 at 1000 km depth to 10 s m 1 at 1900 km while further down 1900 2100 km this increase is faster published models of the lower mantle conductivity obtained using the secular 30 60 yr variations were also considered in order to estimate the conductivity at depths down to the core the new regional model of the lower mantle conductivity does not contradict most modern geoelectrical sounding results this model supports the idea that the mantle base situated below 2100 km depth has a very high conductivity

estimating past continental ice volume from sea level data we predict sea level change since the last glacial maximum lgm at four far field sites barbados bonaparte gulf huon peninsula and tahiti using a revised theoretical formalism this formalism includes a time varying shoreline geometry an accurate treatment of sea level variations near regions of ice retreat and the influence of glacial cycle perturbations in earth rotation we elucidate the physics of far field sea level change by de constructing the predicted signal into spatially uniform versus spatially varying components as well as isolating contributions due to the ice load the ocean load and the rotational potential we demonstrate that the sum of these three contributions plus the spatially uniform sea level fall associated the with retreat of grounded marine ice sheets can produce a significant difference between predictions of sea level change at far field sites and the eustatic or meltwater curve associated with the adopted ice model this difference is site and time dependent for example the total sea level rise since the lgm predicted using our ice earth model can be either smaller e g barbados or larger e g tahiti than the eustatic sea level change finally we review procedures that have been applied to estimate continental ice volume from far field sea level observations and apply these procedures to data from barbados and bonaparte gulf applying an ice earth model that is tuned to fit the barbados data we estimate a change in grounded ice volume from the lgm to the present of 43 5 51 106 km3 based on barbados data and an lgm ice volume estimate of 51 106 km3 based on bonaparte gulf data our results for the bonaparte gulf data are consistent with the recent study by yokoyama et al nature 406 2000 713 these lgm ice volume estimates map into a eustatic or meltwater sea level rise of 115 135 m taking into account plausible variations in the adopted radial earth model introduces uncertainties in the range of 1 5 106 km3 for ice volume estimates based on the barbados data

electrical conductivity in the earth s mantle inferred from champ satellite measurements i data processing and 1 d inversion summary a novel time domain approach to the global electromagnetic induction problem is applied to vector magnetometer data observed by the champ satellite data recorded during 11 storm events in 2001 2003 are processed track by track yielding time series of spherical harmonic coefficients the data are then interpreted in terms of 1 d layered electrical conductivity models the inversion is performed by full search of model parametric space which yields sensitivity of misfit with respect to conductivities of layers and positions of interfaces in the upper 50 km the inversion solidly recovers a conductive layer corresponding to averaged surface conductance the conductivity of the lower mantle is established at 6 s m 1 assuming the upper lower mantle interface is fixed at the seismic based 670 km boundary however the satellite data favour the models with a large jump around 1000 km to unrealistic conductivity values exceeding 10 3 sm 1 the resolution of the method in the resistive upper mantle sandwiched between conductive crust and lower mantle is poor nevertheless an upper bound of 0 01 s m 1 is suggested by the data a conductivity increase in the transition zone is not

comments on the paper of yokoyama et al 2000 entitled timing of the last glacial maximum from observed sea level minima abstract in their analysis of relative sea level observations from the j bonaparte gulf of northern australia the authors interpret the raw observations of the last glacial maximum lgm lowstand of the sea by invoking the notion that there is a significant difference between the spatially averaged change in sea level at any time and what is referred to as ice equivalent eustatic sea level in peltier on eustatic sea level history last glacial maximum to holocene quaternary science review 21 2002 in press companion paper this notion is incorrect as it violates the principle of mass conservation the implications of this error of interpretation to the primary conclusion of the yokoyama et al nature 406 2000 713 716 analysis that the ice volume equivalent sea level at lgm lies between 135 and 130 m is discussed herein it is concluded on the basis of this discussion that although the argument presented in this paper for such a deep lgm depression of sea level relies upon this invalid notion it may nevertheless be true that the lgm low stand was greater than the 120 m conventionally assumed

lower mantle conductivity anomalies estimated from geomagnetic jerks 1 the occurrence epochs and duration periods of the 1969 1978 and 1991 geomagnetic jerks are estimated for 65 geomagnetic observatories by applying a statistical time series model to monthly means of the geomagnetic eastward component it is found for every jerk that the occurrence epochs around south africa and south pacific ocean are delayed several years from those in other regions moreover it is found for the 1969 and 1978 jerks that the duration times around south africa which are defined as the lengths of the duration periods are longer than those in other regions the distribution of these anomalous regions of the jerks i e south africa and south pacific ocean may imply the existence of higher conductivities in the lower mantle beneath these regions which possibly relates to the fact that the velocity of a seismic s wave in the d layer beneath these regions is slower than that in other regions the mantle conductivities beneath south africa south pacific ocean and other regions are estimated through a numerical simulation the magnetic diffusion equation in the mantle is solved for an abrupt magnetic change generated at the core mantle boundary comparing the results obtained by the simulation with those obtained by the data analysis it is plausible that the mantle conductivities beneath south africa and south pacific ocean are higher than that beneath other regions although there is an ambiguity in the estimated magnitudes of the mantle conductivity

far field tsunami hazard in new zealand ports we present the results of a numerical modeling study investigating the effects of far field tsunamis in new zealand ports four sites marsden point tauranga harbor port taranaki and lyttelton harbor were selected based on a combination of factors such as economic importance and the availability of historical and or instrumental data numerical models were created using the commit tsunami modeling tool and the method of splitting tsunami most hydrodynamic model comparison of model results to measured data from recent historical events showed that for particular sites and events the model correlated well with the timing and amplitude of the observed tsunami and in most cases there was generally good agreement between the and modeled tsunami heights and current speeds a sensitivity analysis for tsunami heights and current speeds was conducted using a suite of large m w 9 tsunamigenic earthquake sources situated at regular 15 intervals in azimuth along the pacific rim while another set of scenarios focused on regional tsunami sources in the southwest pacific model results were analyzed for tsunami heights and current speeds as a function of the source region in terms of currents the analysis identified where speeds were greatest and which source was responsible results suggested that tsunamis originating from central america produced the strongest response in new zealand the modeling was also used to determine the timing and duration of potentially dangerous current speeds as well as minimum safe depths for vessel evacuation offshore this study was motivated by the desire to reduce damage and operational losses via improved forecasting of far field tsunamis at new zealand ports it is important that forecasts are accurate since tsunami damage to ships and facilities is expensive and can be mitigated given timely warnings and because preventable false alarms are also costly in terms of lost productivity the modeling presented here will underpin efforts to produce port specific guidance and information in the event of future pacific tsunamis

on the electrical conductivity of the mid mantle i calculation of equivalent scalar magnetotelluric response functions summary the problem of global conductivity sounding has been re posed in order to investigate the possible existence of large scale lateral heterogeneities in mid mantle conductivity a response function z h is robustly estimated and scaled into an equivalent scalar magnetotelluric impedance by assuming the geomagnetic field spatial variations are adequately described by a p10 spherical harmonic data found to be inconsistent with this representation in either the time frequency or spatial domain are excluded from the analysis making use of this relationship robust statistical techniques and careful data handling procedures have been applied to a new global magnetic database containing well in excess of 106 daily mean values 1358 observatory years spanning the period 1883 1980 a set of spatially distributed scalar frequency domain impedance functions for a variety of tectonic provinces result from this analysis response functions consistent with both the p10 assumption and local 1 d earth structure were found for 22 of the 79 observatories examined the set of acceptable response functions is presented along with a summary of data quality for the observatories represented in the database

constraining the composition and thermal state of the mantle beneath europe from inversion of long period electromagnetic sounding data 1 we reexamine the problem of inverting c responses covering periods between 1 month and 1 year collected from 42 european observatories to constrain the internal structure of the earth earlier studies used the c responses which connect the magnetic vertical component and the horizontal gradient of the horizontal components of electromagnetic variations to obtain the conductivity profile of the earth s mantle here we go beyond this approach by inverting directly for chemical composition and thermal state of the earth rather than subsurface electrical conductivity structure the primary inversion parameters are the composition of the earth s mantle within the system cao feo mgo al2o3 sio2 and geotherm given these parameters we calculate mineral modes at the prevailing physical conditions and combine these with laboratory based models for the conductivity of individual minerals to estimate the bulk earth electrical conductivity structure from which c responses are calculated to further constrain the radial density profile we also invert for mass and moment of inertia the results agree with earlier geophysically derived conductivity and seismic velocity models and confirm that inversion of geophysical data for compositional parameters planetary composition and thermal state is feasible the inversion indicates most probable lower mantle geothermal gradients of 0 58 k km core mantle boundary temperatures of 2900 c bulk earth molar mg si ratios of 1 1 intermediate between the chondrite and pyrolite models and no significant change in mantle composition across the 670 km seismic discontinuity

water in the mantle results from electrical conductivity beneath the french alps 1 a deep magnetotelluric sounding in the french alps provided a vertical electrical conductivity profile between 200 1000 km two prominent features are observed first the conductivity in the depth range 400 800 km is smaller than the conductivity of a pyrolite mantle obtained from laboratory results for a normal geotherm second the data do not require the conductivity to change throughout the transition zone 410 660 km in this part of the mantle a temperature of 350 450 c less than normal explains the magnetotelluric conductivity profile at 200 400 km our model favors a cold mantle with 1000 1500 ppm of water dissolved in olivine if correct this model suggests that the subducted slab is dehydrated before reaching the transition zone

global 3 d imaging of mantle conductivity based on inversion of observatory c responses ii data analysis and results summary the global 3 d electrical conductivity distribution in the mantle in the depth range between 400 and 1600 km is imaged by inverting c responses estimated on a global net of geomagnetic observatories very long time series up to 51 years 1957 2007 of hourly means of three components of the geomagnetic field from 281 geomagnetic observatories are collected and analysed special attention is given to data processing in order to obtain unbiased c responses with trustworthy estimates of experimental errors in the period range from 2 9 to 104 2 d after careful inspection of the obtained c responses the data from 119 observatories are chosen for the further analysis squared coherency is used as a main quality indicator to detect and then to exclude from consideration observatories with a large noise to signal ratio during this analysis we found that along with the c responses from high latitude observatories geomagnetic latitudes higher than 58 the c responses from all low latitude observatories geomagnetic latitudes below 11 also have very low squared coherencies and thus cannot be used for global induction studies we found that the c responses from the selected 119 mid latitude observatories show a huge variability both in real and imaginary parts and we investigated to what extent the ocean effect can explain such a scatter by performing the systematic model calculations we conclude that 1 the variability due to the ocean effect is substantial especially at shorter periods and it is seen for periods up to 40 d or so 2 the imaginary part of the c responses is to a larger extent influenced by the oceans 3 two types of anomalous c response behaviour associated with the ocean effect can be distinguished 4 to accurately reproduce the ocean effect a lateral resolution of 1 1 of the conductance distribution is needed and 5 the ocean effect alone does not explain the whole variability of the observed c responses we also detected that part of the variability in the real part of the c responses is due to the auroral effect in addition we discovered that the auroral effect in the c responses reveals strong longitudinal variability at least in the northern hemisphere europe appears to be the region with smallest degree of distortion compared with north america and northern asia we found that the imaginary part of the c responses is weakly affected by the auroral source thus confirming the fact that in the considered period range the electromagnetic em induction from the auroral electrojet is small assuming weak dependence of the auroral signals on the earth s conductivity at considered periods and longitudinal variability of the auroral effect we developed a scheme to correct the experimental c responses for this effect with these developments and findings in mind we performed a number of regularized 3 d inversions of our experimental data in order to detect robust features in the recovered 3 d conductivity images although differing in details all our 3 d inversions reveal a substantial level of lateral heterogeneity in the mantle at the depths between 410 and 1600 km conductivity values vary laterally by more than one order of magnitude between resistive and conductive regions the maximum lateral variations of the conductivity have been detected in the layer at depths between 670 and 900 km by comparing our global 3 d results with the results of independent global and semi global 3 d conductivity studies we conclude that 3 d conductivity mantle models produced so far are preliminary as different groups obtain disparate results thus complicating quantitative comparison with seismic tomography or and geodynamic models in spite of this our 3 d em study and most other 3 d em studies reveal at least two robust features reduced conductivity beneath southern europe and northern africa and enhanced conductivity in northeastern china

on reduction of long period horizontal seismic noise using local barometric pressure summary tilt from atmospheric loading has long been known to be the major source of long period horizontal seismic noise we try to quantify these effects for seismic data from the black forest observatory bfo which is known to be a very quiet station experimental transfer functions between local barometric pressure and horizontal seismic noise are estimated for two long time series by standard methods two simple analytical physical models are developed the local deformation model ldm and the acoustic gravity wave model twm subsequently these models with only two free parameters are fit using least squares to the observed seismic noise for time series of widely differing lengths the results are variable sometimes rather dramatic variance reductions are obtained and sometimes the reduction is hardly significant the method produces the best results when barometrically induced noise is high the resulting admittances for the ldm are compared to finite element calculations since the methods are simple and can result in conspicuous reductions in noise we provide one more reason for installing barometers at even the best broad band seismic stations

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

corrigendum to global ice volumes at the last glacial maximum and early lateglacial earth planet sci lett 181 2000 513 527 in the above article an erroneous distinction was made between the ice volume equivalent sea level vje t de ned by eq 3 and eustatic sea level vjeus t in the absence of other factors contributing to sea level change thermal expansion melting of mountain glaciers not included in the ice models or changes in groundand surfacewater storage vje t corresponds to eustatic sea level eqs 4 and 5 state that the two are diierent but this is incorrect since the averages of the terms over the oceans must vanish in order to conserve mass as has been repeatedly stated in earlier papers by the authors the error was a result of a programming error introduced in the output of the sea level code whereby at the end of each iteration the mean sea level change is computed in our formulation sea level change is non zero over land so as to permit the calculation of change along narrow waterways the tilting of inland lakes and the changing elevations of inland barriers or sills of lakes thus the appropriate areal integral is over the ocean surface whereas the erroneous quantity calculated at this stage was the average over the entire globe because this was found to be diierent from that estimated from the ice volumes directly and because of the similarity in magnitude it was seen as an explanation for the distinction sometimes made between sea level equivalent and eustatic sea level e g denton and hughes 13 p 74 rather than as being incompatible with the condition of conservation of mass the integration of the sea level change over the oceans requires a knowledge of the location of the shoreline at each time step of the grounding line of the ice and of the part of the shelf ice that oats or grounds as a result of sea level change and shelf ice thickness change the mistake was introduced in 1998 modi cations to the code when this treatment of the shelf ice was improved fortunately this erroneous estimate of the mean sea level change at no stage feeds back into the main part of the sea level calculation because there the correct estimate based on the ice volume change is used thus the relative sea level predictions are unaiected and the relation between vje t and ice volume eq 3 below remains correct none of the conclusions about ice volume change are aiected in the paper it was noted that some inconsistency has crept into the usage of the term eustatic sea level to which the senior author has contributed unfortunately the senior author contributed further to this confusion by allowing himself to be convinced that the wrong argument to explain the diierence was correct hopefully that was a temporary lapse we thank w r peltier for drawing this lapse to our attention

comparison of the 2010 chile and 2011 japan tsunamis in the far field in this study we analyze water level data from coastal tide gauges and deep ocean tsunameters to explore the far field characteristics of two major trans pacific tsunamis the 2010 chile and the 2011 japan tohoku oki events we focused our attention on data recorded in california 14 stations and new zealand 31 stations as well as on tsunameters situated along the tsunami path and proximal to the study sites our analysis considers statistical analyses of the time series to determine arrival times of the tsunami as well as the timing of the largest waves and the highest absolute sea levels fourier and wavelet analysis were used to describe the spectral content of the tsunami signal these characteristics were then compared between the two events to highlight similarities and differences between the signals as a function of the receiving environment and the tsunami source this study provides a comprehensive analysis of far field tsunami characteristics in the pacific ocean which has not experienced a major tsunami in nearly 50 years as such it systematically describes the tsunami response characteristics of modern maritime infrastructure in new zealand and california and will be of value for future tsunami hazard assessments in both countries

tsunami hazard assessment and risk in aotearoa new zealand a systematic review ad 1868 2012 abstract this paper presents a systematic review of peer reviewed journal articles scientific reports books and research theses covering tsunami hazard assessment and risk in aotearoa new zealand a nz fifteen electronic databases were examined using an array of keyword search strings to comprehensively gather all available sources of information spanning 1868 2012 ad 222 references were identified as directly relevant to tsunami hazard assessment and risk in a nz with a further 51 references identified by scrutinising the original 222 references the amount of information as well as the emphasis of the science contained in these 273 references differs greatly between documents a meta analysis of this collective scholarship shows six principal areas of scientific endeavour i observation and cataloguing of modern and historical tsunami impacts caused by earthquakes and landslides ii modelling and evaluation of near and far field generated tsunamis iii detailed mapping and assessment of offshore seismic and other geological structures responsible for near field tsunami generation iv investigation and cross referencing of holocene palaeo records of tsunami deposits preserved in wetlands dunes and other coastal landforms v survey and reconnaissance of modern and historical tsunami impacts and vi guidance for tsunami hazard mitigation preparedness and land use planning synthesising all of these references it is clear that a nz has been affected by remote regional and locally generated tsunami during the historic pre written and pre human periods further scientific knowledge of tsunami risk and the forces responsible for tsunami generation has greatly improved however in spite of the many scientific advances detailed in this review much more remains to be done to better understand and deal with the diverse tsunami hazard and risk facing a nz

long period 30 days 1 year electromagnetic sounding and the electrical conductivity of the lower mantle beneath europe the c response connects the magnetic vertical component and the horizontal gradient of the horizontal components of electromagnetic variations and forms the basis for deriving the conductivity depth profile of the earth time series of daily mean values at 42 observatories typically with 50 years of data are used to estimate c responses for periods between 1 month and 1 yr the z y method is applied which means that the vertical component is taken locally whereas the horizontal components are used globally by expansion in a series of spherical harmonics in combination with results from previous analyses the method yields consistent results for european observatories in the entire period range from a few hours to 1 yr corresponding to penetration depths between 300 and 1800 km 1 d conductivity models derived from these results show an increase in conductivity with depth z to about 2 s m 1 at z 800 km and almost constant conductivity between z 800 and z 2000 km with values of 3 10 s m 1 in good agreement with laboratory measurements of mantle material below 2000 km the conductivity is poorly resolved however the best fitting models indicate a further increase in conductivity to values between 50 and 150 s m 1

a semi global reference model for electrical conductivity in the mid mantle beneath the north pacific region 1 one dimensional electrical conductivity structure in the mid mantle of the one fourth of the earth beneath the north pacific ocean was obtained by a semi global electromagnetic induction study electromagnetic response functions estimated from electric field variations measured by submarine cables and geomagnetic field variations obtained by magnetic observatories and long term observations sites were inverted into radially symmetric conductivity distribution by taking the distribution of land and ocean at the surface into account as a most preferred model a smooth conductivity depth profile was obtained with two abrupt increases that possibly correspond to the seismic discontinuities at 410 and 660 km

deep array electromagnetic sounding on the baltic shield external excitation model and implications for upper mantle conductivity studies abstract the bear array of simultaneous electromagnetic em observations probes the deep crustal and upper mantle conductivity structure of the baltic shield searching for the lithosphere asthenosphere boundary beneath the adequate interpretation of the results of this unique high latitude natural field em sounding requires proper understanding of the actual external excitation conditions because conventionally used plane wave model assumptions may be substantially violated in the vicinity of inhomogeneous polar sources the paper presents an overview of the morphology and statistics of source distortions in the bear em field transfer functions tf and the ways of their suppression the stability of the final tf estimates obtained with the exclusion of intensive non stationary auroral effects is further justified the external excitation model effective for the whole bear observation period is inferred from the array distribution of the inter station geomagnetic transfer functions the model is supported by the results of polar ionosphere magnetosphere current system studies based on the simultaneous ground and satellite geomagnetic observations and sets bounds for the plane wave approach in the bear data interpretation to avoid unfounded inferences on the upper mantle electrical properties the signatures of the lithosphere asthenospere boundary under fennoscandia derived from the bear data are summarized and its resolution within the traditional plane wave interpretational paradigm is analysed assuming the presented external source pattern and estimated tf uncertainties caused by the source inhomogeneity

compatibility of induction methods for mantle soundings 1 formulations that form the basis of experimental impedances in induction soundings result from the impedance boundary conditions or from the simplified theoretical models the formulations are essentially different for the magnetotelluric and magnetovariation sounding methods in order to increase reliability of mantle investigations studies of the mantle s electrical properties are often carried out by the joint inversion of impedances obtained by both sounding methods a forward modeling approach is used to verify the accuracy of merging the long period impedances obtained by the magnetotelluric and magnetovariation methods the spherical modeling of the responses above 2 d and 3 d mantle inhomogeneities has shown that the different induction methods can give mutually inconsistent results and the combination of their responses can be problematic in practice for this reason much attention is given to the generalized horizontal spatial gradient sounding method which results in impedance functions that in space and frequency domains closely resemble the magnetotelluric impedances in this study some interesting properties of the induction arrows above a spherical inhomogeneity excited by an inhomogeneous external field are estimated for long periods a final comprehensive model assuming a shell of realistic conductance at the earth s surface is evidence that the generalized horizontal spatial gradient method is promising for the study of mantle inhomogeneities and can be reliably used in combination with the magnetotelluric method in a specific way

the electrical conductivity of the mantle beneath europe derived from c responses from 3 to 720 hr summary the c response which connects the magnetic vertical component and the horizontal gradient of the horizontal components of electromagnetic fluctuations forms the basis for estimating the conductivity depth profile of the earth this paper describes new estimates of the c response obtained from observatory hourly mean values the z y method is applied which means that the vertical component is used locally whereas the horizontal components are used globally by expansion into terms of spherical harmonics a special evort is made to obtain unbiased estimates of c when applied to 90 months of hourly mean values from about 90 observatories the method yields consistent results for european observatories in the entire period range from 3 to 720 hr and for two diverent source mechanisms s and d st a good description of the source structure for individual time segments is essential this was achieved by a separate spherical harmonic analysis of the data for each month for d st or each day for s and by estimating a large number 120 of expansion coeycients the results are interpreted by means of 1 d conductivity models which show that the upper mantle has remarkably little structure with a monotonic decrease of resistivity from 100 v m near z 200 km to 0 7 v m below z 1000 km

electrical conductivities of pyrolitic mantle and morb materials up to the lowermost mantle conditions abstract the electrical conductivities of natural pyrolitic mantle and morb materials were measured at high pressure and temperature covering the entire lower mantle conditions up to 133 gpa and 2650 k in contrast to the previous laboratory based models our data demonstrate that the conductivity of pyrolite does not increase monotonically but varies dramatically with depth in the lower mantle it drops due to high spin to low spin transition of iron in both perovskite and ferropericlase in the mid lower mantle and increases sharply across the perovskite to post perovskite phase transition at the d layer we also found that the morb exhibits much higher conductivity than pyrolite the depth conductivity profile measured for pyrolite does not match the geomagnetic field data below about 1500 km depth possibly suggesting the existence of large quantities of subducted morb crust in the deep lower mantle the observations of geomagnetic jerks suggest that the electrical conductivity may be laterally heterogeneous in the lowermost mantle with high anomaly underneath africa and the pacific the same regions as large low shear wave velocity provinces such conductivity and shear wave speed anomalies are also possibly caused by the deep subduction and accumulation of dense morb crust above the core mantle boundary

observed and modeled currents from the tohoku oki japan and other recent tsunamis in northern california we investigate the currents produced by recent tsunamis in humboldt bay and crescent city california the region is susceptible to both near field and far field tsunamis and has a historic record of damaging events crescent city harbor located approximately 100 kms north of humboldt bay suffered us 28 million in damages from strong currents produced by the 2006 kuril islands tsunami and an additional us 26 million from the 2011 japan tsunami in order to better evaluate these currents in northern california we deployed a nortek aquadopp 600 khz 2d acoustic doppler current profiler adcp with a 1 min sampling interval in humboldt bay near the existing national oceanic and atmospheric administration noaa national ocean service nos tide gauge station the instrument recorded the tsunamis produced by the mw 8 8 chile earthquake on february 27 2010 and the mw 9 0 japan earthquake on march 11 2011 one other tsunami was recorded on the humboldt bay tide gauge during the period of adcp operation but was not visible on the adcp suggesting a threshold water level value of about 0 2 m to produce an observable adcp record the 2010 tsunami currents persisted in humboldt bay for approximately 30 h with peak amplitudes of about 0 35 m s the 2011 tsunami signal lasted for over 40 h with peak amplitude of 0 84 m s the strongest currents corresponded to the maximum change in water level approximately 67 min after the initial wave arrival no damage was observed in humboldt bay for either event in crescent city currents for the first three and one half hours of the 2011 japan tsunami were estimated using security camera video footage from the harbor master approximately 70 m away from the noaa nos tide gauge station the largest amplitude tide gauge water level oscillations and most of the damage occurred within this time window the currents reached a velocity of approximately 4 5 m s and six cycles exceeded 3 m s during this period measured current velocities both in humboldt bay and in crescent city were compared to calculated velocities from the method of splitting tsunamis most numerical model the frequency and pattern of current amplification and decay at both locations are replicated by the most model for the first several hours after the tsunami onset most generally underestimates 2011 peak current velocities by about 10 30 with a few peaks by as much as 50 at humboldt bay most predicted attenuation of the signal after 4 h but the actual signal persisted at a nearly constant level for at least twice as long the results from this project demonstrate that adcps can effectively record tsunami currents for small to moderate events and can be used to calibrate and validate models i e most in order to better understand hazardous tsunami conditions within harbors

the long period electromagnetic response of the earth summary the techniques of complex demodulation and spherical harmonic analysis have been used to examine the time frequency and location dependent properties of the long period electromagnetic response of the earth fourteen years of daily three component magnetic field data recorded by 18 permanent geomagnetic observatories were used to estimate the response in the period range 2 200 day it is found that lateral conductivity inhomogeneities within the earth notably the oceans have a considerable effect on the observed response even at these long periods

marshall islands fringing reef and atoll lagoon observations of the tohoku tsunami the magnitude 9 0 tohoku earthquake on 11 march 2011 generated a tsunami which caused significant impacts throughout the pacific ocean a description of the tsunami within the lagoons and on the surrounding fringing reefs of two mid ocean atoll islands is presented using bottom pressure observations from the majuro and kwajalein atolls in the marshall islands supplemented by tide gauge data in the lagoons and by numerical model simulations in the deep ocean although the initial wave arrival was not captured by the pressure sensors subsequent oscillations on the reef face resemble the deep ocean tsunami signal simulated by two numerical models suggesting that the tsunami amplitudes over the atoll outer reefs are similar to that in deep water in contrast tsunami oscillations in the lagoon are more energetic and long lasting than observed on the reefs or modelled in the deep ocean the tsunami energy in the majuro lagoon exhibits persistent peaks in the 30 and 60 min period bands that suggest the excitation of closed and open basin normal modes while energy in the kwajalein lagoon spans a broader range of frequencies with weaker multiple peaks than observed at majuro which may be associated with the tsunami behavior within the more irregular geometry of the kwajalein lagoon the propagation of the tsunami across the reef flats is shown to be tidally dependent with amplitudes increasing decreasing shoreward at high low tide the impact of the tsunami on the marshall islands was reduced due to the coincidence of peak wave amplitudes with low tide however the observed wave amplitudes particularly in the atoll lagoon would have led to inundation at different tidal phases

spatiotemporal sampling of sq induced geomagnetic responses at leo satellite altitude for a radially conductive earth summary a new simulation tool is introduced for extracting earth conductivity information from geomagnetic satellites in low earth orbit leo such as champ swarm and potential follow on missions theoretical reconstruction of spherical harmonic spectra of global universal time ut geomagnetic field maps is analysed an idealized regular solar daily variation field is assumed along with its induced counterpart from a radially stratified earth solar quiet sq spectra can be reliably reconstructed from discrete time series of measurements sampled daily within a fixed ut window a single leo satellite should be in orbit for at least 1 yr under quiet time conditions to ensure accurate spectral reconstruction of an sq geomagnetic spectrum the length of the daily sampling window and random day to day variability in the sq source strength have only minor effects on spectral reconstruction the shape of the spectra and spectral ratios are independent of radial mantle conductivity further research employing 3 d forward modelling of induction in a laterally heterogeneous earth with more realistic and complete external source descriptions is advocated the new simulation tool should prove valuable to planners of future multisatellite geomagnetic missions as well as scientists interested in analysing and interpreting satellite induction signals

electromagnetic induction in the oceans and the anomalous behaviour of coastal c responses for periods up to 20 days 1 electromagnetic transfer functions at coastal sites are known to be strongly distorted by the conductivity of the seawater this ocean effect is generally considered to be small for periods greater than a few days we revise this statement by detailed and systematic model studies in the period range from 1 to 64 days with subsequent comparison of the modelled and observed electromagnetic responses the conductivity model consists of a radial symmetric 1 d section that is overlaid by a thin spherical surface shell the conductance of which is compiled using the noaa etopo topography bathymetry and map of sediment thicknesses the simulations were performed for spatial resolutions of the surface shell of 5 5 2 2 and 1 1 respectively and for two continental and oceanic underlying 1 d conductivity models the inducing source is described by the spherical harmonic p10 in dipole coordinates comparisons are made for the coastal geomagnetic observatories apia hermanus kakioka kanoya and simosato where an anomalous behaviour of the local response has been previously detected from the comparison of observed and modelled responses we conclude that peculiarities in the observed coastal responses in the period range from 1 to 20 days can be explained to a large amount by induction in the oceans we show that correction for the ocean effect results in responses that are much better interpretable by 1 d conductivity models compared to the uncorrected responses

pressure effect on electrical conductivity of mantle olivine abstract we report new measurements of electrical conductivity of olivine that were made in a multi anvil press using solid buffers mo moo2 to stabilize oxygen partial pressure the temperature range was 1000 c 1400 c and the pressure range was 4 10 gpa when pressure effects are interpreted as activation volumes in the arrhenius equation they yield values of order 0 6 0 6 cm3 mole values of the pre exponential factor 0 are of the order of hundreds of s m and the zero pressure activation energy is about 1 5 ev in agreement with laboratory measurements at lower pressure conditions in addition we analyzed older literature data which produced a similar result but with larger variation the common practice of assuming that the pressure effect on electrical conductivity of olivine in the earth s upper mantle depends weakly on pressure has rested on uncertain grounds these new observations suggest that for upper mantle conditions depths of 80 200 km neglecting pressure effects on olivine conductivity is justified a weak pressure effect also supports the small polaron fe3 model as the dominant conduction mechanism although the mainly positive activation volumes argue for a component of lattice deformation when applied to the depth range 200 400 km in the earth the laboratory data yield conductivities of order 10 2 s m slightly lower than the range of geophysical conductivity profiles but well within this range after allowing for probable effects of oxygen activity and temperature uncertainty

the 2011 tohoku tsunami on the coast of mexico a case study the tohoku east japan earthquake of 11 march 2011 m w 9 0 generated a great trans oceanic tsunami that spread throughout the pacific ocean where it was measured by numerous coastal tide gauges and open ocean dart deep ocean assessment and reporting of tsunamis stations statistical and spectral analyses of the tsunami waves recorded along the pacific coast of mexico have enabled us to estimate the principal parameters of the waves along the coast and to compare statistical features of the tsunami with other tsunamis recorded on this coast we identify coastal hot spots manzanillo zihuatanejo acapulco and ensenada corresponding to sites having highest tsunami hazard potential where wave heights during the 2011 event exceeded 1 5 2 m and tsunami induced currents were strong enough to close port operations based on a joint spectral analysis of the tsunamis and background noise we reconstructed the spectra of tsunami waves in the deep ocean and found that with the exception of the high frequency spectral band 5 cph the spectra are in close agreement with the true tsunami spectra determined from dart bottom pressure records the departure of the high frequency spectra in the coastal region from the deep sea spectra is shown to be related to background infragravity waves generated in the coastal zone the total energy and frequency content of the tohoku tsunami is compared with the corresponding results for the 2010 chilean tsunami our findings show that the integral open ocean tsunami energy i 0 was 2 30 cm2 or approximately 1 7 times larger than for the 2010 event comparison of this parameter with the mean coastal tsunami variance 451 cm2 indicates that tsunami waves propagating onshore from the open ocean amplified by 14 times the same was observed for the 2010 tsunami the tsunami colour frequency content for the 2011 tohoku tsunami was red with about 65 of the total energy associated with low frequency waves at frequencies 35 min the red colour i e the prevalence of low frequency waves in the 2011 tohoku as well as in the 2010 chile tsunamis is explained by the large extension of the source areas in contrast the 2014 and 2015 chilean earthquakes had much smaller source areas and consequently induced bluish high frequency tsunamis

on the electrical conductivity of the mid mantle ii delineation of heterogeneity by application of extremal inverse solutions summary long period equivalent scalar magnetotelluric impedance functions from 22 magnetic observatories distributed over the earth s surface are inverted to test the hypothesis that there exists significant lateral heterogeneity in the electrical conductivity structure of the mid mantle limited spaces of extremal models are examined and strict bounds are placed on the range of permissible models joint d inversion of combined response functions from observatory pairs proves the requirement for global heterogeneity while exploration of h layered earth model space suggests systematic regional heterogeneity indicating that enhanced upper mantle conductivity is found within the pacific basin and baikal rift zone and is absent elsewhere the results of these extremal inverse solutions are compared with the backus gilbert like schmucker inversion and a heuristic inversion

lithosphere conductivity structure using the cam 1 lisbon madeira submarine cable summary voltage measurements made in the cam 1 submarine cable located between sesimbra lisbon and madeira island have been used in combination with magnetic observations carried out in the geomagnetic observatory of guimar canary islands to estimate the deep geoelectrical structure beneath the ocean apparent resistivities and phases were calculated from those data sets published geomagnetic deep sounding results were used to correct the cam 1 response for static shift distortion magnetic transfer function tipper and invariant apparent resistivity and phase obtained from the determinant of the impedance tensor z det on shore in sw iberia were used in the modelling in order to better constrain some model parameters the results obtained by 1 d occam s inversion and 2 d trial and error modelling reveals a resistive zone 300 1200 m between 10 and 200 km depth followed by a decreasing in resistivity with depth the order of the integral resistivity of the lithosphere beneath the ocean was found lying in the 9 10 7 6 10 8 m 2 range the estimated depth conductivity profile was compared with those obtained from studies in the pacific ocean indicating that the atlantic lithosphere between lisbon and madeira is more resistive than that in the pacific the most probable explanation for such observation is the long term stability or very low activity of the sampled atlantic region a comparison of the depth conductivity profile with published theoretical results based on olivine properties shows that our result is compatible with an isotropic and undersaturated mantle

the 3d electromagnetic response of the earth to ring current and auroral oval excitation summary we report on a new compilation of functions representing the geoelectromagnetic response of the earth s mantle the c response functions and newly defined d response functions the latter of which constitutes a sensitive indicator of lateral heterogeneities in conductivity were estimated for periods from 5 to 106 7 days the spatial coverage and statistical quality of these response function estimates were improved over previous compilations in part by making use of a newly assembled global catalogue of magnetic observatory hourly mean values and by applying a statistically robust form of empirical orthogonal function eof analysis the eof results suggest that for periods longer than 5 days the geomagnetic field variation can be represented predominantly by a single eigenmode we have identified that the primarysource fields of the dominant mode consist of two current systems in the same direction an equatorial ring current in the magnetosphere and two conjugate auroral oval ring currents in the ionosphere the influence of the auroral current system is seen at surprisingly low latitudes 40 and 50 for the vertical and northern components respectively which results in non negligible bias on the conventional c response at high latitudes a preliminary correction of the auroral current effect has been made on the c and d responses obtained for data from 55 and 52 observatories respectively at latitudes from 60 to 60 we also present a set of approximate equivalent internal mantle electrical current distributions that prove a useful indicator of the presence of deep earth heterogeneities these new sets of electromagnetic information will increase the resolving power of 3d distribution of electrical conductivity in the earth s mantle

extending comprehensive models of the earth s magnetic field with orsted and champ data summary a new model of the quiet time near earth magnetic field has been derived using a comprehensive approach which includes not only pogo and magsat satellite data but also data from the orsted and champ satellites the resulting model shows great improvement over its predecessors in terms of completeness of sources time span and noise reduction in parameters with its well separated fields and extended time domain of 1960 to mid 2002 the model is able to detect the known sequence of geomagnetic jerks within this frame and gives evidence for an event of interest around 1997 because all sources are coestimated in a comprehensive approach intriguing north south features typically filtered out with other methods are being discovered in the lithospheric representation of the model such as the s atlantic spreading ridge and andean subduction zone lineations in addition this lithospheric field exhibits significantly less noise than previous models as a result of improved data selection the f region currents through which the satellites pass are now treated as lying within meridional planes as opposed to being purely radial results are consistent with those found previously for magsat but an analysis at orsted altitude shows exciting evidence that the meridional currents associated with the equatorial electrojet likely close beneath the satellite besides the model a new analysis technique has been developed to infer the portion of a model parameter state resolved by a particular data subset this has proven very useful in diagnosing the cause of peculiar artefacts in the magsat vector data which seem to suggest the presence of a small misalignment bias in the vector magnetometer

effects of the march 2011 japanese tsunami in bays and estuaries of se australia on 11 march 2011 a subsea earthquake off the north eastern coast of honshu island japan generated a huge tsunami which was felt throughout the pacific at the opposite end of the pacific ocean on the south east coast of australia multiple reflections scatterings and alternate pathways lead to a prolonged and complicated response this response was largely unaltered in crossing the continental shelf but was then transformed by bay resonances and admittances these effects are described using data from tide recorders sparsely spread over 1 000 km of the coast some new adaptations and applications of time series analysis are applied to separate tsunami waves that have followed different pathways but contain the same spectral components the possible types of harbour response are classified and illustrated despite its small height in this region the tsunami put several swimmers at serious risk and generated strong harbour oscillations which should be considered when generating future warnings

electrical conductivity of majorite garnet and its implications for electrical structure in the mantle transition zone abstract electrical conductivities of majorite garnet with compositions of pyrolite minus olivine pyrolite majorite and mid ocean ridge basalt morb majorite were measured under physical conditions of the mantle transition zone 18 and 23 gpa and temperatures up to 2000 k in a kawai type multi anvil apparatus the samples with morb composition are mainly composed of majorite which has higher fe and al contents and contain a small amount of stishovite the conductivity of the morb majorite is more than twice higher than those of the pyrolite majorite at the same temperature the activation energies of these majorites are both 1 4 ev at temperature of 1000 1600 k suggesting that the dominant mechanism of charge transportation is fe 2 fe 3 hopping small polaron conduction at higher temperatures 1600 k corresponding to temperature conditions of the transition zone conduction mechanism of the pyrolite majorite would change from small polaron to ionic conduction the pyrolite majorite has only slightly higher and lower conductivity than dry wadsleyite and ringwoodite respectively and will not largely change the conductivity depth profile predicted for the dry mantle transition zone the laboratory based conductivity profile of the mantle transition zone with pyrolitic composition can explain well the current semi global conductivity depth profile obtained from electromagnetic study beneath pacific on the other hand the garnetite originating from the oceanic crust has remarkably higher conductivity than the surrounding mantle because the conductivity of morb majorite is significantly higher than those of wadsleyite and ringwoodite conductivity values of morb majorite agree with those of the stagnant slab beneath the northeastern china

evidence of a large deep conductive body within the basement of the guadalquivir foreland basin betic cordillera s spain from tipper vector modelling tectonic implications abstract the betic cordillera is an alpine belt formed by the interaction of the eurasian and african plates and the westward motion of the alboran domain long period magnetotelluric observations at 26 sites in its westernmost part provide induction arrows that have been compared with 3d forward models including bathymetry and major geological bodies the results highlight the presence of a major conductive body 0 05 m unknown to date and located within the basement of the guadalquivir foreland basin aeromagnetic and field magnetic measurements further support the occurrence of magnetic anomalies related to the top of this anomalous body this major structure is interpreted as an intermediate or basic igneous rock with a high proportion of metallic mineralization its origin is discussed in the framework of the regional geological setting possibly produced in the southern iberian variscan massif by a huge concentration of volcanogenic massive sulphide vms in the prolongation of the iberian pyrite belt during devonian early carboniferous times another possibility is that the conductive anomaly is due to magmatic intrusions associated with the mesozoic fragmentation of southern iberia and the opening of the tethys

observations effects and real time assessment of the march 11 2011 tohoku oki tsunami in new zealand the great tohoku oki earthquake of march 11 2011 generated a devastating tsunami in the near field as well as substantial far field effects throughout the pacific ocean in new zealand the tsunami was widely observed and instrumentally recorded on an extensive array of coastal tidal gauges and supplemented by current velocity data from two sites while the tsunami s first arrival was on the morning of march 12 in new zealand the strongest effects occurred throughout that afternoon and into the following day tsunami effects consisted primarily of rapid changes in water level and associated strong currents that affected numerous bays harbors tidal inlets and marine facilities particularly on the northern and eastern shores of the north island the tsunami caused moderate damage and significant overland flooding at one location the tsunami signal was clearly evident on tide gauge recordings for well over 2 days clearly illustrating the extended duration of far field tsunami hazards real time analysis and modelling of the tsunami through the night of march 11 as the tsunami crossed the pacific was used as a basis for escalating the predicted threat level for the northern region of new zealand a comparison to recorded data following the tsunami shows that these real time prediction models were accurate despite the coarse near shore bathymetry used in the assessment suggesting the efficacy of such techniques for future events from far field sources

waves and currents in hawaiian waters induced by the dispersive 2011 tohoku tsunami this study focuses on the effects of frequency dispersion on tsunami induced coastal water waves and currents exemplified by the 2011 tohoku tsunami event the investigation relies on numerical simulations we start from a tsunami source constrained through the inversion algorithm of noaa s tsunami inundation forecast system the trans pacific propagation and the hydrodynamic processes in the hawaiian islands region are simulated with a weakly dispersive boussinesq model and a shallow water model that neglects dispersion effects from these modeling results boundary conditions are derived to force the high resolution simulations in the coastal waters in the hawaiian islands region through most a tsunami simulating code based on the shallow water theory we note that the dispersion effects generally lower the amplitudes of leading waves trailing waves of short wavelengths and high amplitudes can develop in coastal waters a model neglecting dispersion effects could under predict the wave heights and current speeds at the trailing waves