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of a range of expectable tsunami heights the latter combined with complementary data from t wave duration and historical references have been integrated into an automated procedure of tsunami warning by the centre polynesien de prevention des tsunamis cppt in papeete tahiti

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

a seismological reassessment of the source of the 1946 aleutian tsunami earthquake summary we present a re evaluation of the seismological properties of the aleutian tsunami earthquake of 1946 april 1 characterized by a deceptively low conventional magnitude 7 4 in view of its catastrophic tsunami both in the near and far fields relocation of 40 aftershocks show that the fault zone extends a minimum of 181 km along the aleutian trench in a geometry requiring a bilateral rupture from the original nucleation at the epicentre their spatial and temporal distribution are typical of the aftershock patterns of a large earthquake and rule out the model of a landslide source exclusive of a dislocation the analysis of the spectra of mantle waves favours the model of a large seismic source with a static moment of 8 5 10 28 dyn cm making the event one of the ten largest earthquakes ever recorded hence the destructive tsunami in the far field and of a slow bilateral rupture at an average velocity of only 1 12 km s 1 hence the destructive interference in all azimuths for all but the longest mantle waves the exceptionally slow character of the earthquake is confirmed by a deficiency in radiated seismic energy expressed by the lowest value measured to date of the energy tomoment ratio the earthquake appears as an end member in the family of tsunami earthquakes resulting from the combination of anomalous but not unprecedented parameters such as low stress drop and rupture velocity

low frequency source characteristics of the great 1960 chilean earthquake the low frequency nature of the great 1960 chilean earthquake the earth s largest recorded event is characterized and a source model composed of three events with a combined seismic moment of 5 5 1023 n m and a duration of 1500 s is presented the results show conclusively that large scale slip which is only observed at low frequencies preceded the main shock complex amplitude measurements of normal mode data in the band 1 0 5 0 mhz recorded at eight vertical component stations comprise the data set in this band the earthquake source is assumed to be described by a line source propagating at a constant rupture velocity the data set is the basis for a sequence of least squares inversions to determine the seismic moment rupture velocity spatial slip distribution and the temporal slip function the data are best explained by a source model that begins 1150 s before the main shock with an event of moment 1 9 1023 n m and rise time of 300 s a main shock with moment of 3 2 1023 n m and for which most of the low frequency energy was released beginning about 50 s after the short period origin time and an event 350 s later with moment of 0 4 1023 n m the uncertainty in the moment estimate of the great 1960 chilean earthquake is about 50 and is due primarily to the probable range of fault plane dip which is not well constrained at this time

mtsu recovering seismic moments from tsunameter records we define a new magnitude scale m tsu allowing the quantification of the seismic moment m0 of an earthquake based on recordings of its tsunami in the far field by ocean bottom pressure sensors tsunameters deployed in ocean basins far from continental or island shores which are known to affect profoundly and in a nonlinear fashion the amplitude of the tsunami wave the formula for m tsu m tsu log10 m o 20 log10 x c d tsu c s tsu c o where x is the spectral amplitude of the tsunami c d tsu a distance correction and c s tsu a source correction is directly adapted from the mantle magnitude m m introduced for seismic surface waves by okal and talandier like m m its corrections are fully justified theoretically based on the representation of a tsunami wave as a branch of the earth s normal modes even the locking constant c 0 which may depend on the nature of the recording surface amplitude of the tsunami or overpressure at the ocean floor and its units is predicted theoretically m tsu combines the power of a theoretically developed algorithm with the robustness of a magnitude measurement that does not take into account such parameters as focal geometry and exact depth which may not be available under operational conditions in the framework of tsunami warning we verify the performance of the concept on simulations of the great 1946 aleutian tsunami at two virtual gauges and then apply the algorithm to 24 records of 7 tsunamis at dart tsunameters during the years 1994 2003 we find that m tsu generally recovers the seismic moment m 0 within 0 2 logarithmic units even under unfavorable conditions such as excessive focal depth and refraction of the tsunami wave around continental masses finally we apply the algorithm to the jason satellite trace obtained over the bay of bengal during the 2004 sumatra tsunami after transforming the trace into a time series through a simple ad hoc procedure results are surprisingly good with most estimates of the moment being over 1029 dyn cm and thus identifying the source as an exceptionally large earthquake

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

the mantle magnitude mm and the slowness parameter θ five years of real time use in the context of tsunami warning we study a database of more than 119 000 measurements of the mantle magnitude mm introduced by okal and talandier 1989 obtained since 1999 as part of the operational procedures at the pacific tsunami warning center the perfor mance of this method is significantly affected by the seismic instrumentation at the recording station with the very broadband sts 1 and ks54000 systems offering the lowest residuals between measured values of mm and those predicted from the har vard centroid moment tensor cmt catalog and also by the period at which spec tral amplitudes are measured with the best results between 70 and 250 sec with such mild restrictions estimates of seismic moments can be obtained in real time by retaining either the maximum value of mm measured on each record or its average over the various mantle frequencies with the resulting residuals on the order of 0 1 0 2 moment magnitude units mm deficiencies in the case of the two large earthquakes of peru 2001 and hokkaido 2003 are attributed to azimuthal bias from an excess of stations principally in north america in directions nodal for the focal mechanism and directivity patterns we further study a group of more than 3000 measurements of the energy to moment ratio h introduced by newman and okal 1998 which allows the real time identification of teleseismic sources violating scaling laws and in particular of so called tsunami earthquakes the use of a sliding window of analysis in the computation of h allows the separation of late earthquakes characterized by a delayed but fast moment release from truly slow earthquakes many such events are recognized notably on major oceanic and con tinental strike slip faults introduction and background we present detailed analyses of a large dataset resulting from implementation as part of the operational procedures of the pacific tsunami warning center ptwc of the real time calculation of the mantle magnitude mm and of the slowness parameter h as defined and introduced by okal and talandier 1989 and newman and okal 1998 re spectively during the past five years more than 119 000 individual measurements of mm and 3000 values of h have been computed through automated algorithms these values contribute to the estimation of the source characteristic of distant earthquakes in the framework of the real time as sessment of their tsunamigenic potential this study offers a progress report on the performance of the algorithms and in particular discusses the influence of instrumentation at the various reporting stations as the final revision of this article was being prepared the occurrence of the great sumatra earthquake on 26 de cember 2004 provided an opportunity to extend the concepts of mm and h to a range of magnitudes unexplored for the

estimation of tsunami hazard in new zealand due to south american earthquakes we develop a probabilistic model for estimating the tsunami hazard along the coast of new zealand due to plate interface earthquakes along the south american subduction zone to do this we develop statistical and physical models for several stages in the process of tsunami generation and propagation and develop a method for combining these models to produce hazard estimates using a monte carlo technique this process is largely analogous to that used for seismic hazard modelling but is distinguished from it by the use of a physical model to represent the tsunami propagation as opposed to the use of empirical attenuation models for probabilistic seismic hazard analysis

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

intraplate tectonics in asia a precise age for large scale miocene movement along the ailao shan red river shear zone china tertiary left lateral movement along the 1000 km long ailao shan red river shear zone appears to have played an important role in absorbing post collisional northward penetration of india into asia crustal strike slip shear along this zone caused the formation of a gneiss belt metamorphosed to amphibolite grade including anatectic melting both metamorphism and melting were induced by ductile deformation yielding the possibility to date the major tectonometamorphic event that shaped the ailao shan red river belt 17 u pb isotope analyses were performed on small size fractions of zircon monazite and xenotime extracted from two different leucogranitic layers the two samples are located about 50 km apart in the central segment of ailao shan in structurally well controlled settings where the melts crystallized within the strongly foliated gneisses during late stages of deformation all mineral u pb analyses had to be corrected for excess or deficit amounts of radiogenic 206 pb originating from initial 230 th disequilibrium in the 238 u decay series in monazite such disequilibrium 206 pb reaches 20 of total radiogenic 206 pb the corrected u pb ages of monazite and xenotime lie between 22 1 and 23 9 ma whereas zircon yields significantly discordant u pb ages between 30 5 and 33 9 ma pointing to precambrian material in the magma source region inherited components could also be detected in monazite the set of u pb data shows that monazite and xenotime formed simultaneously in both localities substantiating an early miocene age of 23 0 0 2ma for late kinematic crystallization of anatectic melts in the metamorphic belt of the ailao shan red river shear zone

excitation mechanism of atmospheric pressure waves from the 1980 mount st helens eruption summary atmospheric pressure waves from the mount st helens eruption 1980 may 18 have been clearly recorded by a sensitive microbarograph at berkeley california the record shows three types of waves with different group velocities the pressure waves can be interpreted in terms of direct waves a1 antipodean travelling waves a2 and circumnavigating waves a3 all of which are composed of several acoustic gravity modes propagated in the lower atmosphere synthetic barograms appropriate to the berkeley station have been calculated on the basis of the dynamic response of the lower atmospheric structure together with various assumptions of source properties comparisons between synthetic and observed barograms provide estimates for ranges of the time history of upward particle velocity at the source source dimensions and the velocity of the source spreading over the blast zone as well as for the average dissipation effects over the circumferential path the results suggest that two major compression pulses on the a1 record correlate with the arrival of pressure waves from the first lateral blast and second vertical blast although the inferred interblast time interval is not consistent with that estimated from seismic observations

deep structure of the longling ruili fault underneath ruili basin near the eastern himalayan syntaxis insights from magnetotelluric imaging magnetotelluric mt geophysical profiling has been applied to the determination of the deep structure of the longling ruili fault lrf part of a convergent strike slip fault system underneath thick caenozoic cover in ruili basin in southwestern yunnan china the recorded mt data have been inverted using a two dimensional 2 d nonlinear conjugate gradients scheme with a variety of smooth starting models and the resulting models show common subsurface conductivity structures that are deemed geological significant the models show the presence of a conductive 5 60 m cover sequence that is thickest 1 1 5 km in the centre of the basin and rapidly pinches out towards the margins a half graben structure is interpreted for the ruili basin this is underlain by about 7 10 km thick upper crustal layer of high resistivity 200 4000 m that is dissected by steep faults which we interpret to flatten at depth and root into an underlying mid crustal conductive layer at about 10 km depth the mid crustal layer does not appear to have been severely affected by faulting we interpret it as a zone of partial melt or intracrustal detachment the mt models suggest se directed thrusting of basement rocks in the area the longling ruili fault is interpreted as a nw dipping feature bounding one of the identified upper crustal fragments underneath ruili city we suggest that mt imaging is a potent tool for deep subsurface mapping in this terrain

high resolution electromagnetic imaging of the san andreas fault in central california although there is increasing evidence that fluids may play a significant role in the earthquake rupture process direct observation of fluids in active fault zones remains difficult since the presence of an electrically conducting fluid such as saline pore water strongly influences the overall conductivity of crustal rocks electrical and electromagnetic methods offer great potential for overcoming this difficulty here we present and compare results from high resolution magnetotelluric mt profiles across two segments of the san andreas fault saf which exhibit very different patterns of seismicity parkfield which has regular small earthquakes and creep events and in the carrizo plain where the fault is seismically quiescent and apparently locked in both surveys electric fields were sampled continuously with 100 m long dipoles laid end to end across the fault from 100 to 0 1 hz the data from both profiles are consistent with a two dimensional 2 d fault parallel resistivity model when both transverse electric and magnetic te and tm mode data are included in the interpretation narrow approximately 300 endash 600 m wide zones of low resistivity extending to depths of 2 endash 4 km in the core of the fault are required at both locations however at parkfield the conductance conductivity thickness product of the anomalous region ismore an order of magnitude larger than at carrizo plain suggesting much higher concentrations of fluids for the more seismically active parkfield segment we also image structural differences between the two segments at carrizo plain resistive presumably crystalline rocks are present on both sides of the fault at depths below 3 endash 4 km in particular we clearly image resistive basement extending approximately 10 km or more east of the saf beneath the elkhorn hills and temblor range at parkfield the situation is quite different with a resistive block of salinian granite west of the fault and an electrically conductive presumably fluid rich franciscan complex to the east it is possible that these structural differences control the difference in mechanical behavior of the fault either directly by affecting fault strength or indirectly by controlling fluid supply copyright 1999 american geophysical union less

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

evidence for a large strike slip component during the 1960 chilean earthquake the strainmeter record observed at isabella isa california for the 1960 chilean earthquake m w 9 5 is one of the most important historical records in seismology because it was one of the three records that provided the opportunity for the first definitive observations of free oscillations of the earth because of the orientation of the strainmeter rod with respect to the back azimuth to chile the isa strainmeter is relatively insensitive to g love waves and higher order order 6 toroidal modes yet long period g waves and toroidal modes were recorded with large amplitude on this record this observation cannot be explained with the conventional low angle thrust mechanism typical of great subduction zone earthquakes and requires an oblique mechanism with half strike slip and half thrust the strain record at ogdenburg new jersey the press ewing seismograms at berkeley california and the ultra long period displacement record at pasadena california also support the oblique mechanism we tested the performance of the isa strainmeter using other events including the 1964 alaskan earthquake and found no instrumental problems thus the isa observation of large g r and toroidal spheroidal ratios most likely reflects the real characteristics of the 1960 chilean earthquake rather than an observational artefact the interpretation of the large strike slip component is not unique but it may represent release of the strike slip strain that has accumulated along the plate boundary as a result of oblique convergence at the nazca south american plate boundary the slip direction of the 2010 chilean maule earthquake m w 8 8 is rotated by about 10 clockwise from the plate convergence direction suggesting that right lateral strain comparable to that of an m w 8 3 earthquake remained unreleased and accumulates near the plate boundary one possible scenario is that the strike slip strain accumulated over several great earthquakes like the 2010 maule earthquake was released during the 1960 chilean earthquake if this is the case we cannot always expect a similar behaviour for all the great earthquakes occurring in the same subduction zone and such variability needs to be considered in long term hazard assessment of subduction zone earthquakes

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

the active tectonics of the eastern himalayan syntaxis and surrounding regions source parameters of 53 moderate sized earthquakes obtained from the joint inversion of regional and teleseismic distance long period body waves provide the data set for an analysis of the style of deformation and kinematics in the region of the eastern himalayan syntaxis focal mechanisms of eastern himalayan events show oblique thrust consistent with the n ne directed movement of the indian plate as it underthrusts a boundary that strikes at an oblique angle to the direction of convergence earthquakes near the sagaing fault show strike slip mechanisms with right lateral slip earthquakes on its northern splays however indicate predominant thrusting evidence that the dextral motion on the sagaing fault which accommodates a portion of the lateral motion between india and southeast asia terminates in a zone of thrust faulting at the eastern himalayan syntaxis remaining motion between india and southeast asia is accommodated in a zone of distributed shear in east burma and yunnan manifested by strike slip and oblique normal faulting east west extension crustal thinning and clockwise rotation of crustal blocks we determined strain rates throughout the region with a moment tensor summation using 25 years modern and 85 years modern and historic of earthquake data we matched the observed strains with a fifth order polynomial function and from this we determined both the velocity field and rotations with respect to a specified region velocities calculated relative to south china stationary show that the entire area extending from 20 n 36 n within deforming asia yunnan western sichuan and east tibet constitutes a distributed dextral shear zone with clockwise rotations up to 1 7 m y maximum in the region of the eastern syntaxis proper integrated strains across this zone relative to south china stationary show 38 mm yr 12mm yr of north directed motion at the himalaya remaining plate motion relative to south china fixed must be taken up by the underthrusting of india beneath the lesser himalaya strike slip motion on the sagaing fault and intraplate ne directed shortening within ne india as well as ne directed shortening within the eastern syntaxis proper 10 mm yr 2 mm yr of relative right lateral motion between india and southeast asia is absorbed in the region between the sagaing and red river faults 94 e 100 e it is the clockwise vorticity relative to south china associated with the deformation in yunnan east tibet and western sichuan that provides the relative north directed motion of 38 12 mm yr at the himalaya not all of the deformation is accommodated in right lateral shear between india and south china and between east tibet and south china velocity gradients exist that are parallel to the trend of the shear zone relative to a point within western sichuan 32 n 100 e the velocity field shows that the yunnan crust is moving s se at rates of 8 10 mm yr relative to south china there is no eastward expulsion of crustal material beyond the eastern margin of the tibetan plateau

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

rapid forecast of tsunami wave heights from a database of pre computed simulations and application during the 2011 tohoku tsunami in french polynesia 1 we present a method for the rapid estimation of tsunami wave heights either in the deep pacific basin or at specific shore locations it uses a database of 260 pre computed scenarios of generic sources distributed along the pacific trenches and can provide an estimate of wave heights within minutes of the location of the earthquake and the estimation of its moment the method is tested against a set of dart data and of 51 maregraph records in tahiti and the marquesas islands it was used in real time to successfully predict tsunami amplitudes in polynesia during the 2011 tohoku alert

quartz crystal size distribution of the ordovician millbrig k bentonite abstract crystal size distribution csd analysis has been applied to quartz crystals of the ordovician millbrig k bentonite which represents one of the largest known fallout ash deposits in the phanerozoic era to establish crystal growth histories and conditions in the magma chamber prior to eruption specific csds were examined for crystal growth conditions all millbrig samples exhibit lognormal concave down shapes in agreement with previously reported csds on large silicic systems but in contrast to more mafic systems characterized by linear csds concave down csds are possibly an intrinsic property of phenocryst growth in large volume silicic magmas as documented in the literature bindeman i n 2003 crystal sizes in evolving silicic magma chambers geology 31 367 370 quartz crystals of the millbrig must have been produced by surface controlled size dependent growth with a minor ostwald ripening component which could have easily changed to supply controlled growth due to a limited supply of nutrients as the crystals grew larger csds were also used to examine the possible origin of multiple ash beds in the millbrig these ash beds appear to be a product of a series of separate eruptions that represent separate magma layers or batches each with slightly different crystal growth conditions

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

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

intracrustal detachment within zones of continental deformation geologic mapping of active to recently active geologic structures in panamint valley western united states and in the haiyuan region and northern tibetan plateau china suggests detachment in the middle and lower crust on a scale of tens of kilometres to at least several hundred kilometres detachment occurs similarly in predominantly extensional panamint valley and in predominantly compressional china environments it involves structures with displacements of more than 10 km and displacement rates of more than 3 mm yr perhaps more than 10 mm yr the steeply dipping strike slip faults present in all three areas hunter mountain fault haiyuan fault and altyn tagh fault zone terminate in zones of extension or compression and geometric relations indicate that all structures including strike slip faults are thin skinned and restricted to the upper crust in panamint valley and in the haiyuan region deformation within these systems can be reconstructed in three dimensions displacement on the strike slip faults is absorbed by extension or compression occurring at the termination of the faults so strike slip displacement is roughly equal to and in the same direction as shortening or extension we propose that left slip on the altyn tagh fault zone in northern tibet is similarly absorbed by shortening southeast of the fault zone within the qaidam basin and the nan shan

mode wave equivalence and other asymptotic problems in tsunami theory abstract a study is conducted of the asymptotic behavior of the gravity modes of an incompressible spherical oceanic layer surrounding a rigid earth as its radius goes to infinity the flat layered earth dispersion relation c gh for the phase velocity of the tsunami wave is derived and the existence of only one branch of tsunami modes is proved a result fundamental for the use of mode theory in marigram synthesis studied further are the influence of such parameters as finite incompressibility in the ocean and finite rigidity of the ocean floor on the dispersion of tsunami modes both theoretically and numerically for a number of models it is concluded that for all physically acceptable models of both the ocean and its floor tsunami dispersion is not significantly affected by either this includes in particular the case of a sedimentary layer which is found to have no effect on tsunami propagation the maximum and extremely small rigidity allowed in the fluid before the tsunami modes disappear is also derived