inertial currents estimated from surface trajectories of argo floats 1 we have developed an analysis method to determine the amplitude of inertial motion from surface trajectory data of argo profiling floats this method gives an estimate of inertial current speed and phase from satellite fixes transmitted while a float drifts at the surface over a time which is typically about one local inertial period the error of this method is about 3 4 cm sec for data records with at least 6 positions with accuracy of 500 m spanning longer than 68 of the inertial period whereas inertial amplitudes are as large as 40 cm sec with a median of about 12 0 cm sec in the japan east sea globally distributed argo floats could provide useful information on the co variability of wind forced inertial currents and mixed layer depths in the ocean

physical links between crustal deformation seismic moment and seismic hazard for regions of varying seismicity summary seismic moment release rates m0 inferred from a weibull frequency magnitude distribution and its extreme value equivalent are compared with observation the seismotectonically diverse regions studied all exhibit the curvature of a log linear frequency magnitude plot associated with applying a maximum magnitude to earthquake recurrence statistics the inferred seismic moment release rates are consistent with available crustal deformation data within uncertainties resulting from the line fit and in magnitude determination the uncertainties for the regions studied southern california the new madrid seismic zone the central and eastern mediterranean and mainland uk vary from at worst an order of magnitude down to a factor of 2 or 3 this agreement can be used to justify the extrapolation of frequency magnitude statistics beyond the historical and instrumental era in seismic hazard studies as a test of the stationarity of short term statistics against long term effects a striking example of a bimodal seismicity distribution is observed in the new madrid zone this can be interpreted as being due to the superposition of two distinct seismogenic source types observed in the area a quantitative analysis of the separate orders of seismicity observed in the frequency magnitude statistics comparing the different maximum magnitudes and inferred seismic moment release rates with those observed supports this hypothesis superposition of many such seismogenic sources can explain the linearity observed in global frequency versus seismic moment magnitude statistics

observations and models of inertial waves in the deep ocean the structure of the inertial peak in deep ocean kinetic energy spectra is studied here records were obtained from polymode arrays deployed in the western north atlantic ocean 40 w to 70 w 15 n to 42 n the results are interpreted both in terms of local sources and of turning point effects on internal waves generated at lower latitudes in most of the data there is a prominent inertial peak slightly above f however the peak height above the background continuum varies with depth and geographical environment three classes of environment and their corresponding spectra emerge from peak height variations class 1 is the 1500 m level near the mid atlantic ridge with the greatest peak height of 18 db class 2 includes a the upper ocean depth less than 2000 m b the deep ocean depth greater than 2000 m over rough topography and c the deep ocean underneath the gulf stream with intermediate peak height of 11 5 db class 3 is the deep ocean over smooth topography with the lowest peak height of 7 5 db near f the horizontal coherence scale is 0 60 km at depths from 200 m to 600 m and the vertical coherence scale is 0 200 m in the lower part of the main thermocline and 0 1000 m in the deep water the phase difference suggests a downward energy propagation in the lower thermocline and standing waves in the deep water a one turning point model is developed to describe inertial waves at mid latitudes based on the assumption that inertial waves are randomly generated at lower latitudes global generation where their frequency wave number spectrum is given by the model of garrett and munk 1972 1975 using the globally valid wave functions obtained by munk and phillips 1968 various frequency spectra near f are calculated numerically the model yields a prominent inertial peak of 7 db in the horizontal velocity spectrum but no peaks in the temperature spectrum the model is latitudinally dependent the frequency shift and bandwidth of the inertial peak decrease with latitude energy level near f is minimum at about 30 and higher at low and high latitudes the observations of class 3 can be well described by the model a low zonal wave number cutoff is required to produce the observed frequency shift of the inertial peak the differences between the global generation model and the observations of class 1 and class 2 are interpreted as the effects of local sources a locally forced model is developed based on the latitudinal modal decomposition of a localized source function asymptotic eigensolutions of laplace s tidal equation are therefore derived and used as a set of expansion functions the forcing is through a vertical velocity field specified at the top or bottom boundaries of the ocean for white noise forcing the horizontal velocity spectrum of the response has an inertial peak which diminishes in the far field with the forcing located at either the surface or the bottom several properties of the class 2 observations can be described qualitatively by a combination of the global and local models the reflection of inertial waves from a turbulent benthic boundary layer is studied by a slab model of given depth frictional effects are confined to the boundary layer and modeled by a quadratic drag law for given incident waves reflection coefficients are found to be greater than 0 9 for the long waves which contain most of the energy this result suggests that energy containing inertial waves can propagate over great distance as is required by the validity of the model of global generation

upper ocean temperature structure inertial currents and richardson numbers observed during strong meteorological forcing abstract upper ocean currents and temperature in the northeastern pacific were measured during a 14 day period in november 1980 as part of strex velocities in the upper ocean are dominated by near inertial frequency oscillations thew oscillations are modified by wind stress variations associated with the passage of a strong cold front the change in the inertial currents both in the mixed layer and below is qualitatively consistent with linear internal wave dynamics if turbulent stresses during the storm are assumed to extend 10 20 m below the mixed layer the ratio of mean squared buoyancy frequency n2 and mean squared shear s2 computed over a 10 m interval defines an average richardson number r0 n2 s2 r0 is approximately 2 5 except in regions of high inertial shear in particular values as low as 0 7 are obtained in a 20 m thick region immediately below the base of the mixed layer the data are consistent with a model of the oecanic shear field consisting of a background shear corresponding to a va

earthquakes of the holocene geologic studies of earthquakes involve mapping of coseismic surface faulting and secondary deformation from historical events trenching and geomorphic analysis to define the timing and size of past earthquakes and investigations of fault zone structure and geometry in both unconsolidated sediments and bedrock this research is now being referred to as paleoseismology seismic geology and earthquake geology since the mid 1970s it has led to some of the most exciting and important contributions to the understanding of earthquake behavior in space and time hanks 1985 allen 1986 the present report is the first of what is hoped will become a regularly contributed summary of the geologic aspects of the study of earthquakes

near inertial ocean current response to hurricane frederic abstract hurricane frederic passed with 80 to 130 km of the u s naval oceanographic office current meter arrays in water depths ranging from 100 to 470 m near the desoto canyon region and within 150 km of an ocean thermal energy conversion otec mooring in 1050 m of water excitation of near inertial waves by the moving hurricane was observed throughout the water column along the canyon walls and at the otec site the frequencies of the waves were blue shifted between 1 to 6 above the local inertial frequency the horizontal wavelength of 250 km is consistent with an energetic first baroclinic mode response but is considerably below the linear theory prediction of 550 km the inferred vertical wavelengths of the immediate response exceeded 1000 m along the northern and eastern sides of the canyon since the currents throughout the water column increased within hours of the hurricane passage later the vertical wavelengths were about equal to the water depth the vertical group velocities associated

spectral description of oceanic near surface variability this paper provides a spectral description of near surface oceanic velocity variability on a global scale rotary spectra of drifter velocities are estimated in zonal bands of the indian pacific and atlantic oceans the partition of energy between cyclonic and anticyclonic frequencies clearly identifies inertial oscillations at all latitudes the meridional distribution of near inertial energy is described in detail the polarization of super inertial energy is consistent with internal waves dynamics thus the distribution of super inertial energy may be a manifestation of freely propagating near inertial waves on the plane

evaluation of low latitude pi2 pulsations as indicators of substorm onset using polar ultraviolet imagery impulsive pi2 pulsations have long been recognized as one of the key signatures of magnetic activity during substorm periods due to their wide observable range both in latitudes and longitudes it is well documented that there is usually more than one pi2 wave burst associated with a substorm and only one of them corresponds to the onset of the substorm this observational fact poses obstacles to determining substorm onsets with pi2 signals although the pi2 have become one of the most popular indicators for substorm onsets the reliability of using the pi2 in this fashion has not been seriously investigated in this paper we address this question with a statistical approach by using 650 auroral substorm onsets identified with polar ultraviolet images for a time interval from april 1996 to may 1997 a comparison of the low latitude pi2 pulsation onsets from kakioka l 1 07 with the auroral breakups indicates that identifying substorm onset with the pi2 alone is often ambiguous of a total of 119 isolated defined as 10 min of quiet time preceding the onset pi2 bursts seen within 10 min from a magnetic positive bay there were 65 events 55 taking place within 3 min from breakups and 34 events 29 indicating no sign of an auroral breakup within 10 min of the pi2 burst this result suggests that pi2 may not be as a good indicator of the substorm onset as it was thought to be interestingly it is always possible to associate pi2 pulsations with some forms of auroral intensification when compared to auroral breakups pi2 onsets are subject to a small delay of 1 3 min with a peak around l min delays of pi2 onsets are revealed to be a function of location relative to auroral breakup this dependence is found to be consistent with the time of flight for a fast mode wave in a plasmapause cavity mode model propagating in the magnetosphere

on relative timing in substorm onset signatures we investigate the timing of popular substorm onset signatures to understand their temporal relationship proxies for substorm onsets include auroral breakups high latitude magnetic bays low latitude pi2 bursts dispersionless injections at geostationary orbits and auroral kilometric radiation we use the auroral breakup identified with polar uvi images as a common reference time frame to calibrate the others results illustrated by two well defined auroral substorms unambiguously indicate that none of the four frequently used substorm onset proxies can provide a consistent timing of substorm onset this inconsistency in substorm onset timing is attributed as a consequence of temporal and spatial limitations on each observational technique a delay between the proxy identifiers and the auroral breakup is found to be typical it is therefore strongly suggested from this study result that a common reference time frame for substorm onset is necessary and we propose it should be auroral breakups we argue that there is a need for an intercalibration of magnetospheric substorm phenomenology by using a unified definition of the substorm onset

direct measurements of world ocean tidal currents with surface drifters velocities of surface drifters are analyzed to study tidal currents throughout the world ocean the global drifter data set spanning the period 1979 2013 is used to describe the geographical structure of the surface tidal currents at global scale with a resolution of 2 harmonic analysis is performed with two semidiurnal two diurnal and four inferred tidal constituents tidal current characteristics amplitude of semimajor axis rotary coefficient tidal ellipse inclination and greenwich phase are mapped over the world ocean from direct observations the m2 currents dominate on all the shallow continental shelves with magnitude exceeding 60 cm s they are also substantial 4 5 cm s over the main deep topographic features such as the mid atlantic ridge the southwest indian ridge and the mariana ridge the s2 currents have amplitudes typically half the size of the m2 currents with a maximum of about 30 cm s the k1 and o1 currents are important in many shallow seas they are large in the vicinity of the turning latitudes near 30 n s where they merge with inertial motions of the same frequency they are also substantial in the south china sea and philippine sea maps of rotary coefficients indicate that all tidal motions are essentially clockwise anticlockwise in the northern southern hemisphere the rotary coefficient of the tidal currents is compared with the theory of freely and meridionally propagating baroclinic inertia gravity waves the greenwich phase of the m2 constituent has large scale coherent propagation patterns which could be interpreted as the propagation of the barotropic tide

polar observations and model predictions during may 4 1998 magnetopause magnetosheath and bow shock crossings during the rise to the maximum phase of solar cycle 23 several periods of extreme solar wind conditions have occurred during such an example on may 4 1998 the solar wind monitors observed a period of strong southward interplanetary magnetic field imf accompanied by a solar wind dynamic pressure that was 30 times higher than average during this period the polar spacecraft crossed the magnetopause and bow shock and experienced its first solar wind encounter this case provides a rare opportunity to study the magnetopause low latitude boundary layer magnetosheath and bow shock and to test our ability to model the dynamic behavior of these boundary regions under extreme and highly variable solar wind conditions in this study we use the gas dynamic convected field model to predict the time dependent magnetic field and plasma properties upstream from the magnetopause and the location of the polar spacecraft relative to the magnetopause and bow shock during the event to test the accuracy of the prediction model magnetic field characteristics are compared to the fields observed along the satellite track by the magnetometer on polar the predicted model plasma characteristics density velocity and temperature are compared to moments derived from tide observations extrapolated to account for the higher energy portion of the magnetosheath distributions where ambiguities occur in identifying the satellite location plasma distribution functions from two additional ion detectors timas and hydra are used to resolve the observed location of polar relative to the boundaries with this procedure carried out separately for ace and wind and for two different magnetopause models observed features at polar can be traced back to drivers in the solar wind providing a unique opportunity to assess the evolution of the solar wind and its predictability from the solar wind monitors to the magnetopause when the polar apogee drifts to low latitudes in the future it will provide more and more observations in this region therefore what we learn from this case can be indicative of what we will see in the future in polar operations the high level correlation between the predictions and in situ measurements indicates that the solar wind monitors often provide adequate and useful solar wind conditions near the earth the tests indicate that in this event the vacuum dipole field magnetosphere model predicts a significantly larger magnetosphere than observed while the empirical magnetopause model predictions are more consistent with the observations they overpredict the response of the magnetosphere to transient southward turnings of the imf indicating that the magnetosphere does not respond to the southward imf turnings on small timescales sometimes there are significant differences at relatively small time scales between the measurements from the two solar wind monitors it is possible for the solar wind conditions near the earth to be different from the measurements made by at least one of the solar wind monitors cautions should be taken when interpreting near earth observations if the observations are inconsistent at small timescales with the predictions based on one solar wind monitor

the relation of near inertial motions observed in the mixed layer during the jasin 1978 experiment to the local wind stress and to the quasi geostrophic flow field abstract oscillations with near inertial frequencies were an energetic component of the upper ocean velocity field observed at each of two moorings separated by 44 km during the joint air sea interaction jasin experiment during the late summer of 1978 at each mooring the amplitude of the inertial motion was highest in the mixed layer where it was nearly depth independent previous work pollard and millard 1970 pollard 1980 had found that the amplitude and phase of inertial motion in the mixed layer was related to the local wind stress in this case the loacal winds measured at each mooring were coherent but the time series of mixed layer near inertial motion at one mooring bore little resemblance to that at the other mooring during jasin 1978 the differences in the inertial response at the two moorings coincided with differences in the quasi geostrophic flow field in the vicinity of the two moorings inclusion of the horizontal gradients of the quasi geostrophic flow in model equations prov

the guatemala earthquake of 1816 on the chixoy polochic fault abstract forty historical documents have been found which describe a previously unknown very large earthquake on 22 july 1816 this event occurred along the strike slip boundary between the caribbean and north american plates in guatemala and southern mexico modified mercalli intensities are estimated from these accounts and a rough isoseismal map is constructed the damage pattern indicates that the causative fault was the left lateral chixoy polochic fault for which no damaging earthquake has previously been reported damage of modified mercalli intensity vii or greater covered an area of at least 13 000 km 2 extending over 340 km from alta verapaz province in guatemala westward to san cristobal ias casas in chiapas mexico the area of intensity vii indicates a moment of 1 10 28 dyne cm while the estimated length of the intensity vii isoseismal indicates a more likely figure of 3 5 10 27 dyne cm or an equivalent magnitude m w of 7 1 2 to 7 3 4 the reported aftershock sequence is compatible with an earthquake in this magnitude range these data demonstrate that the chixoy polochic fault is currently an active part of the caribbean north american plate boundary and is capable of producing very large earthquakes

the erosion of a thermocline abstract measurements of winds currents and temperature are used to describe the response of the baltic sea to the passage of a sequence of severe storms during the bosex experiment in september 1977 before the onset of the storms the thermocline was at a depth of 25 m the storms deepened the mixed surface layer and redistributed the heat content the storms generated strong inertial waves and vertical current shears which reduced the richardson number within the thermocline to values of 0 25 the non linearity of the inertial waves in this area of variable depth is demonstrated the response of the baltic sea to the meteorological conditions has been modeled numerically by means of a semispectral model the theoretical results are compared to the observations and lead to the same conclusion that the erosion of the thermocline is due to the strong shears of the inertial waves

eddy mean flow decomposition and eddy diffusivity estimates in the tropical pacific ocean 1 methodology 1 eddy diffusivity of the surface velocity field in the tropical pacific ocean was estimated using satellite tracked drifting buoys 1979 through mid 1996 the tropical pacific surface current system is characterized by nonstationarity strong meridional shear and an energetic mesoscale velocity field eddy diffusivity may be defined as the integral of the autocovariance of lagrangian eddy velocities requiring both stationary and homogeneous statistics of the eddy field eddy velocities were obtained by removing a splined mean field to eliminate mean shear from observations binned 1 spatially to group data that have similar dispersion characteristics and 2 temporally to create stationary eddy statistics zonal diffusivity estimates are up to 7 times larger than meridional diffusivity estimates in the high eddy energy regions this anisotropy is associated with the meridional mesoscale wave motion i e by equatorial and tropical instability waves that increases eddy variance but does not lead to a proportional increase in water parcel diffusion because of the coherent character of the trajectory motion at least for initial time lags simple autoregressive models of first and second order are used to describe and classify the resulting eddy statistics an independent confirmation of the diffusivity estimate in the central eastern pacific was obtained by comparing tracer flux divergence computed from a parameterization using diffusivity estimates of our analysis with that from direct eddy reynolds stress flux divergence our results show that diffusivity can be estimated for regions not considered previously either because of sparse data or the complexities of the velocity field

basin formation along the bocono moron el pilar fault system venezuela within the boundary zone between the caribbean south america plates which includes the bocono moron el pilar right lateral fault system that has been active since the late tertiary there are several sedimentary basins in the venezuelan andes and the caribbean mountains these were formed in zones of crustal depression where faults diverge and as pull apart basins in zones of en echelon stepovers or along releasing bends in the faults in addition there are pull apart basins along the avila and la victoria faultzones in the caribbean mountains which are associated with the plate boundary the basins are filled with alluvial lacustrine fluvial and marine sediments mainly of quaternary age on the basis of model studies dimensions of the basins and age of their sedimentary fill it is estimated that right lateral offset necessary to form them along the bocono moron el pilar fault system varies from 2 to 125 km along the avila and la victoria fault zones this right lateral offset is estimated to range from 2 to 30 km on this basis the maximum right lateral offset along the southern caribbean plate boundary that can be documented along the bocono moron el pilar fault system has not exceeded 100 125 km if there has been larger offset it has to be documented by other means or it has taken place along other fault zones within the system

near surface velocity variability at inertial and subinertial frequencies in the vicinity of the california current abstract observations of the horizontal velocity field in the upper 150 m made from the research platform flip as it drifted of the coast of baja california were used to examine the velocity of the velocity field and its relation to local wind forcing at subinertial frequencies a spatially varying flow field associated with the california current system was encountered in addition there was low frequency near surface flow to the right of the wind stress that decayed with depth at near inertial frequencies victory motion with an amplitude of up to 40 cm s 1 was observed most of the energy in the near inertial frequency band was associated with modes with vertical wavelengths large compared to the thickness of the mixed layer the local wind alone had neither the strength nor the variability needed to directly produce the observed inertial period variability it is suggested that flip encountered regions in which the shear of the quasi geostrophic flow resulted in localized intensifications of near i

a comparison of magnetic signatures and dmsp auroral images at substorm onset three case studies the authors explore the relationship between mid latitude and synchronous orbit magnetic signatures and the location of the auroral surge at the onset of three isolated magnetospheric substorms mid latitude data come from the air force geophysics laboratory magnetometer network synchronous orbit data form the satellites goes 2 and 3 and auroral data from defense meteorological satellite program auroral images and auroral magnetograms they find that the surge forms with its western edge approximately 1 hour west of the longitude where the major axis of the mid latitude pi 2 polarization ellipse is along magnetic north and where the d component perturbation of the magnetic bay is near zero these observations are in qualitative agreement with a current wedge consisting of a localized upward current in the west and a longitudinally distributed current in the east at synchronous orbit the longitude of the surge head appears to separate a region to the west where the magnetic field becomes more taillike from one to the east where the magnetic field becomes more dipolar

modulation of near inertial oscillations by low frequency current variations on the inner scotian shelf abstractnear inertial oscillations nios on the inner scotian shelf are studied using observations a simple slab model and two operational shelf circulation models high frequency radar and adcp

estimates of wind energy input to the ekman layer in the southern ocean from surface drifter data 1 the energy input to the upper ocean ekman layer is assessed for the southern ocean by examining the rotary cross spectrum between wind stress and surface velocity for frequencies between 0 and 2 cpd the wind stress is taken from european center for medium range weather forecasts era 40 reanalysis and drifter measurements from 15 m depth are used to represent surface velocities with an adjustment to account for the vertical structure of the upper ocean the energy input occurs mostly through the nonzero frequencies rather than the mean phenomenologically the combination of a stronger anticyclonic wind stress forcing associated with a greater anticyclonic response makes the contribution from the anticyclonic frequencies dominate the wind energy input the latitudinal and seasonal variations of the wind energy input to the ekman layer are closely related to the variations of the wind stress both for the mean and for the time varying components the contribution from the near inertial band follows a different trend increasing from 30 s to about 45 s and decreasing further south possibly a consequence of the lack of variance in this band in the drifter and wind stress data

magnetic dipolarization with substorm expansion onset 1 we compare the timing and spatial extent of dipolarization with auroral breakup by using magnetic field data 1 min time resolution from goes 8 and goes 9 and global auroral images 37 s frame rate from the polar ultraviolet imager we survey the entire year of 1997 data and obtain 32 unambiguous dipolarization events that had ionospheric footprints within 2 hours in magnetic local time mlt from their associated auroral breakups it is found that the auroral breakup preceded the arrival of dipolarization at goes by an average of 1 7 2 7 min 1 0 2 1 min for events 1 hour from the auroral breakup the delay of geosynchronous dipolarization represents a propagation time as the substorms rarely initiated at the goes location propagation velocities derived from the propagation time are 60 km s 1 eastward 75 km s 1 westward and 270 km s 1 earthward at geosynchronous orbit we also show for the first time that auroral bulge and dipolarization region closely map the bulge is the region of currents out of the ionosphere the eastern edge of the dipolarization region where field aligned currents are flowing into the ionosphere is based on the t89 magnetic field model located at 0 5 hour in mlt eastward of the eastern edge of the auroral bulge within the initiation site meridian the dipolarization onset was observed 1 min prior to the auroral breakup at the goes altitude this time is associated with alfven transit time and therefore depends on the radial location of the onset the azimuthal scale of the initiation site is found to be 0 5 hour in mlt in the ionosphere or less than 1 earth s radius at 6 6 re these results support current diversion into the ionosphere as a critical part of substorms finally a simple timing analysis of specific substorm onset time features suggests that near earth reconnection cannot occur before current disruption and therefore cannot be the cause of substorm

distinction between auroral substorm onset and traditional ground magnetic onset signatures 1 to evaluate whether ground magnetic responses traditionally viewed as signatures of substorm onset may be related to postonset auroral streamers rather than to substorm onset seen in aurora we have analyzed ground magnetic and all sky image responses for 14 substorm onsets selected solely on imager coverage we find evidence supporting this possibility the response being approximately coincident for midlatitude positive bay and pi2 pulsation enhancements and for abrupt auroral zone h decreases at stations near a streamer these are all signatures of current wedge formation indicating that substorm current wedge formation may be more of a response to plasma sheet flow channels associated with postonset streamers than to the process leading to auroral onset and that the current wedge may develop via a series of distinctly narrower wedge like structures we also find evidence that periods of streamers can occur more than once during a substorm expansion phase and can give magnetic signatures of multiple onsets even if there are no additional auroral onsets furthermore the peak auroral zone h decreases are seen in association with streamers and at times varying from just a few minutes to well over a half hour after substorm auroral onset if there is a prolonged period of streamers this indicates that peak substorm ae and al values are likely related to features of postonset streamers and their locations relative to observing stations and are not a measure of the strength of the substorm auroral onset processes we discuss possible additional implications on substorm expansion phase development

perceptible earthquakes in the central and eastern united states examined using gumbel s third distribution of extreme values abstract earthquake perceptibility p l m in the central and eastern united states is defined as the joint probability that a point site perceives ground motion at least at intensity i in conjunction with an earthquake occurrence specifically of magnitude m regional seismicity expressed in the catalogs of meyers and von hake 1976 and nuttli 1979 is examined in terms of magnitude frequency using gumbel9s asymptotic extreme value distribution with an upper bound to magnitude gumbel iii the large rogue earthquakes associated particularly with the new madrid seismic zone lead to upper bounded macroseismic body wave magnitudes with large uncertainties around m b 7 3 4 but this approximate value is not contradicted by deterministic arguments examination of the regional earthquake perceptibility curves then shows a maximum perceptibility at several intensity levels for earthquakes in a relatively narrow band of magnitudes around m b 6 1 2 for the central and eastern united states this most perceptible magnitude is the earthquake which is most likely to be felt at any site and this might be used in aseismic engineering design of noncritical structures extension of the analysis to integrated perceptibility then facilitates calculation of intensity expectation at any site

an information theory approach to the storm substorm relationship 1 one of the most interesting aspects of the global magnetospheric response to solar wind changes is the relationship between storms and substorms here we present new results on the relationship between these two different classes of magnetospheric phenomena by approaching the problem on the side of information theory using the auroral electrojet al and sym h indices as representative proxies of magnetic substorms and storms we investigate the transfer of information by means of transfer entropy analysis schreiber 2000 the obtained results seem on average to indicate the presence of a net transfer of information from al to sym h on time scales shorter than 10 h on the basis of this result geomagnetic substorms may act as a driver for the occurrence of geomagnetic storms however carrying out a more careful analysis which takes into account the global geomagnetic daily activity we suggest that the direction of information flow between substorms and storms depends on the global activity level indeed if it is true that a sequence of magnetospheric substorms may drive a moderate storm it is also true that very large storms may dominate and drive the occurrence of magnetospheric substorms

seismicity of the garlock fault california the garlock fault is a 265 km long left slip fault striking northeastward from the san andreas fault in southern california relocations of earthquakes that occurred from 1932 to 1981 on and near this major fault were made using the master event technique the spatial distribution of seismicity along the fault is different west and east of its midpoint near rand where the largest en echelon offset and a marked change in strike occur these two segments also display distinct geologic features and different seismic and aseismic behavior the 150 km long segment west of rand has shown continuous low seismic activity during the past 50 yr well documented aseismic creep and has a relatively complex fault trace in contrast the 155 km long segment east of rand has very few small earthquakes no demonstrable creep and a simpler fault trace p wave first motion studies substantiate predominantly left slip motion along the garlock fault overall energy release during this 50 yr period gives a seismic moment rate of 2 75 10 21 dyne cm yr much lower than that inferred from holocene geologic offsets thus indicating that the garlock fault currently represents a temporal seismic gap and that the potential exists for large earthquakes if behavior of the garlock fault is similar to that of the san andreas the western segment of the fault can be compared with the central creeping segment of the san andreas and the eastern segment with those segments broken by the 1857 and 1906 earthquakes thus larger events might be expected on the eastern segment than on the western segment or if the entire fault breaks during a single event larger displacements toward the east

deriving inertial wave characteristics from surface drifter velocities frequency variability in the tropical pacific two techniques have been developed for estimating statistics of inertial oscillations from satellite tracked drifters these techniques overcome the difficulties inherent in estimating such statistics from data dependent upon space coordinates that are a function of time application of these techniques to tropical surface drifter data collected during the norpax epocs and toga programs reveals a latitude dependent statistically significant blue shift of inertial wave frequency the latitudinal dependence of the blue shift is similar to predictions based on global internal wave spectral models with a superposition of frequency shifting due to modification of the effective local inertial frequency by the presence of strongly sheared zonal mean currents within 12 of the equator

regional relationships among earthquake magnitude scales various magnitude scales commonly used and the interrelationships among them are reviewed it is shown that problems exist with all of the magnitude scales being used in the united states when using regional catalogs for example it is often necessary to determine how the reported magnitudes were determined often such information is not available although the potential errors are quite large both the ms and the mb scales were designed to be universal scales however both ms and mb magnitudes are often determined beyond the applicable range of the equations used to define the two scales furthermore the ms magnitudes are not generally available for moderate to small earthquakes in most earthquake catalogs the mb magnitudes are more generally available than ms values however there is also much greater variation in the way mb is determined in particular a significant change in the mb scale occurred in the early 1960 s when the world wide standard seismograph network wwssn was established this change in instrumentation used to determine mb values had a significant effect on estimated magnitudes post 1960 values are lower and the saturation level of the mb scale the older longer period instruments recorded larger mb magnitudes than can be recorded with the wwssn instruments in addition great care must be taken when selecting the mb magnitudes of western u s earthquakes because the values are often in considerable error owing to the fact that they were determined at distances less than 25 and were not properly corrected for attenuation in the upper mantle or asthenosphere the seismic body wave magnitude mb of an earthquake is strongly affected by regional variations in the q structure composition and physical state within the earth therefore because of differences in attenuation of p waves between the western and eastern united states a problem arises when comparing mb values for the two regions a regional mb magnitude bias exists which depending on where the earthquake occurs and where the p waves are recorded can lead to magnitude errors as large as unit there is also a significant difference between mb and ml values for earthquakes in the western united states an empirical link between the mb of an eastern u s earthquake and the ml of an equivalent western earthquake is given by ml 0 57 0 92 mb east this result is important when comparing ground motion between the two regions and for choosing a set of real western u s earthquake records to represent eastern earthquakes

detailed analysis of a substorm event on 6 and 7 june 1989 2 stepwise auroral bulge evolution during expansion phase 1 we have analyzed in detail the auroral bulge evolution during the expansion phase of an isolated substorm which was observed by the uv imager aboard the akebono satellite it was found that there were three distinct stages in the evolution stage 1 was characterized by rapid poleward and azimuthal predominantly westward expansions in a short time about 2 min stage 2 was characterized by a very slow poleward and slower and continuous azimuthal expansions there was a certain period for transition between stage 1 and stage 2 and it was characterized by a very slow poleward and rapid eastward expansions stage 3 started about 11 min after the onset and was characterized by a sudden reactivation of the rapid poleward and azimuthal expansions the reactivation started around the initial onset meridian and then spread both eastward and westward at the azimuthal front the expansion first occurred at the lowest latitudes spread poleward to around the highest latitudes of stage 1 and then spread further poleward after a brief interval hence the local expansion also had three distinct stages similar to the global one the ground based observations showed that the highest latitude of the local first stage was very close to the latitude of auroral activity that appeared near the ionospheric plasma sheet boundary layer psbl region a few minutes before the onset the further poleward expansion during the local third stage started with a significant intensification of the poleward most auroral activity during the local third stage the bright electron auroral region was bifurcated into a poleward expanding part and an equatorward moving part the proton auroral emission coexisted in the bulge during the local first and second stages and almost disappeared soon after the bifurcation during the local third stage based on these observations we discuss the evolution in the magnetosphere during the expansion phase

seismic hazard in greece i magnitude recurrence two different methods are applied to the earthquake catalogue for greece makropoulos and burton 1981 mb catalogue to evaluate greek seismic hazard in terms of magnitude earthquake strain energy release and gumbel s third asymptotic distribution of extreme values it is found that there is a close relationship between results from the two methods in places where the cumulative strain energy release graphs include at least one well defined cycle of periodicity of strain release then the parameters of the third type asymptote are well defined with small uncertainties in almost all cases the magnitude distribution shows a remarkably good third type asymptotic behaviour the results are presented in the form of graphs and contour maps of annual and 80 year modes and magnitudes with 70 probability of not being exceeded in the next 50 and 100 years for six of the most heavily industrial and highly populated centres of greece magnitude hazard parameters are also derived and examined in more detail thereby illustrating the direct applicability of the methods in terms of zoning the close agreement between observed and predicted extreme magnitudes shows that the sample period considered 1900 1978 is long enough to obtain statistically stable estimates for athens the upper bound magnitude is found to be 6 7 0 3 within 100 km and 6 8 0 4 100 km from the two methods respectively whereas for corinth an earthquake of magnitude 6 5 has a mean return period of 43 years greece as a whole has an upper bound magnitude 8 7 0 6 and earthquakes of a size similar to the 1903 kithira event m 8 0 have a mean return period of about 200 years the significantly different maps contouring magnitudes of the annual and 80 year modes result from the fact that each place has its own distribution curvature for magnitude occurrence and thus they are not a linear extrapolation of each other however as longer return periods are considered these differences become small because the expected magnitudes approach the regional upper bound a feature common to all these maps is the existence of three well defined aseismic blocks 1 a the attikocycladic block 2 b the ptolemais basin and 3 c the block formed by the northeastern part of greece well defined areas of high seismic hazard which correlate with the most tectonically active areas are 1 a along the hellenic arc the greek albania border leukas cephalonia islands and the southeastern end of the arc 2 b the western end of the north anatolian fault and 3 c the chalkidiki peninsula and the northern sporadhes islands

detailed analysis of a substorm event on 6 and 7 june 1989 1 growth phase evolution of nightside auroral activities and ionospheric convection toward expansion phase onset 1 we have analyzed in detail the evolution of nightside auroral activities and ionospheric convection during the growth phase of an isolated substorm the following three characteristic auroral activities were identified by meridian scanning photometers msp at ground stations 1 proton main oval 2 fast equatorward moving fem arc and 3 near plasma sheet boundary layer npsbl aurora the proton main oval corresponds to the main part of the proton auroral region and was located at the equatorward most region of the electron auroral emissions and gradually moved equatorward during the growth phase the fem arc was a discrete auroral arc having a clear longitudinally elongated form it appeared about 20 min before the onset on the high latitude side of the auroral region and moved equatorward toward the proton main oval its equatorward motion gradually slowed as it approached the proton main oval as the fem arc moved equatorward the location of the peak velocity in the nightside return flow of the two cell convection also moved equatorward the auroral breakup occurred in a localized area around the demarcation region between the two return flows close to the latitude of the fem arc this was observed by the uv imager aboard the akebono satellite the npsbl aurora appeared a few minutes before the onset around the poleward most region of the aurora and continued even after the onset our detailed analysis of these phenomena can give us important clues as to how the growth phase proceeds toward the expansion phase onset

polar ultraviolet imager observation of auroral breakup 1 the nasa s polar satellite completed its mission in march 2008 during its 12 year operation the ultraviolet imager uvi on board polar acquired a large number of auroral images in fuv bands with unprecedented spatial and temporal resolutions the purpose of this brief report is to provide a list of auroral substorm onset identified with uvi to the community for full use a total of 2003 auroral substorm onsets are identified in the northern hemisphere between 1996 and 2000 and 536 onsets in southern hemisphere in 2007 distributions of the onset locations are near gaussian with a population mean of 65 9 standard deviation 2 2 in magnetic latitude mlat and 22 6 1 1 in magnetic local time mlt for the northern hemispheric events and 68 0 2 3 in mlat and 22 6 1 1 in mlt for the southern hemispheric events a comparison with previously published image onset results suggests that substorms occur more frequently and intensely in the descending than in the ascending phase of solar cycle the list of onset events includes the onset times and locations and is provided as a supplement

substorm onset timing via traveltime magnetoseismology 1 this letter introduces a traveltime magnetoseismic technique that can estimate the substorm onset time in the magnetotail from multi point observations of pi 2 pulsations the arrival time of pi 2 which is defined as the first peak in pi 2 amplitude observed by ground magnetometers presents a strong function of latitude using the tamao traveltime as the forward model the magnetoseismic inversion from the observed pi 2 arrival time infers that the onset of the 22 july 1998 substorm in the magnetotail started at x 20 re at 6 53 10 ut or 1 3 minutes earlier than the pi 2 onset time conventionally identified in ground records the magnetoseismic result is further compared with the observations of auroral brightening revealing a clear sequence of events during this substorm

faulting associated with large earthquakes and the average rate of deformation in central and eastern asia we determine approximate average rates of deformation in portions of eastern and central asia for the last 80 years these rates are based on estimates of source dimensions average displacements seismic moments and orientations of faults of all large earthquakes m 7 5 and as many other major earthquakes m 7 0 as possible in asia since 1900 a major part of this study is the compilation of these data for separate parts of asia we combine seismic moment tensors to estimate the average rotational strain or deformation tensors for these regions for the last 80 years we estimate that shortening across the tien shan has occurred at 11 mm yr between 5 and 19 mm yr left lateral shear on easterly trending planes in mongolia in northwestern tibet gansu and ningxia and on the xianshuihe fault in western sichuan has been very rapid more than 10 mm yr in each region and apparently as rapid as 40 mm yr in northwestern tibet gansu and ningxia slower rates of a few to 10 mm yr appear to characterize east west extension and conjugate north south shortening of tibet the earthquake history of the himalaya is consistent with rates of underthrusting of more than 10 mm yr but is probably less than the convergence rate of india with eurasia of about 50 mm yr the overall strain field is consistent with a large part of india s penetration into eurasia being absorbed by the extrusion of material out of india s way as a result southeast china moved at about 21 mm yr east southeast with respect to eurasia in the last 80 years with an uncertainty of about a factor of 2 in this estimated rate

seismic strain rates in the central and eastern united states seismic strain rates for the entire central and eastern united states are estimated from historical seismicity and from several seismicity models typical strain rates are estimated to be the on the order of 10 12 to 10 11 per year except near historical sites of large earthquakes where higher rates pertain uncertainties in strain rates are large deformation caused by strain rates less than 10 10 yr 1 is very small compared to average denudation rates denudation and deposition may control the rate of earthquake occurrence in some parts of the central and eastern united states by modifying the vertical stress due to load a simple quantitative model predicts the earthquake occurrence rate in the appalachian mountains from an estimate of the regional denudation rate

satellite tracked drifter measurement of inertial and semidiurnal currents in the northeast pacific we examine current variability in the open northeast pacific using 3 hourly sampled trajectories from satellite tracked drifters drogued at depths of 15 and 120 m within the wind mixed layer and permanent pycnocline respectively findings show the following 1 motions were dominated by inertial currents which accounted for 58 35 of the total variance measured by the shallow deep drifters semidiurnal motions accounted for roughly 10 of the variance at both depths there were detectable currents at twice the inertial frequency 2f 3 cpd and negligible diurnal currents 2 inertial currents attained root mean square rms speeds of around 50 cm s in the mixed layer and 10 cm s in the pycnocline speeds in the semidiurnal band were similar 10 cm s at both depths 3 inertial and semidiurnal currents were strongly clockwise rotary while low frequency currents 0 95 occurred for drifter separations r 500 km semidiurnal currents were uncorrelated beyond several tens of kilometers 6 inertial currents appear to be linked to the passage of atmospheric lows and semidiurnal currents to the passage of remotely generated baroclinic tides the spectral peak near 2f is indicative of nonlinear inertial wave interactions

quaternary faulting near arco and howe idaho abstract well defined high angle faults were exposed in 1969 by trenching across scarps in alluvial fans along mountain ranges north of arco and howe idaho faulting along both the arco and howe scarps disrupts well developed calcic soils that are considered to be about 30 000 yr old on the other hand both scarps are interrupted by gaps occupied by unfaulted alluvial fans that probably are younger than 15 000 yr old the arco scarp coincides with a zone of closely spaced faults in alluvial fans along the western foot of the lost river range from arco the scarp extends northward about 16 km 10 miles where it merges into an unstudied scarp in bedrock at a trench across the scarp 10 km 6 miles north of arco multiple movements in the fault zone have resulted in aggregate vertical displacement of at least 12 m 40 ft measured offsets of stratigraphic units exposed in the trench indicate at least two episodes of vertical movement on individual faults one episode of movement caused a minimum offset of 4 6 to 6 1 m 15 to 20 ft and another offset was more than 3 m 10 ft the howe scarp coincides with a zone of closely spaced faults in alluvial fans along the western foot of the lemhi range a southern part of the scarp trends northwest along the southern part of the range a distance of 15 km 9 miles and a northern part trends north at least another 6 km 4 miles these parts of the scarp are separated by a bedrock ridge 3 km 2 miles wide in which the scarp is indistinct at a trench aross the scarp about 11 km 7 miles north of howe multiple movements in the fault zone have resulted in aggregate vertical displacement of at least 15 m 50 ft measured offsets of stratigraphic units exposed in the trench indicate five or more episodes of vertical movement on individual faults ranging from 0 3 m 1 ft to more than 3 m 10 ft

on the variation of seismic hazard along the san andreas fault recurrence probabilities of earthquakes were evaluated at 33 locations along the san andreas fault using gumbel s method two minima in the mode of the largest annual earthquakes occur one north of san francisco centered around 38 75 n latitude and the other centered in the carizzo plain area at 35 25 n latitude the latter is offset by an unusually large ratio of large to small earthquakes so that only one minimum around 38 75 n is observed in the expected 100 yr earthquake size this broad minimum closely coincides with where the san andreas fault broke in 1906 and may be only temporary there appears to be a slight systematic tendency for the observed largest 50 year earthquake to become larger than the expected 50 yr earthquake as the size of the area being studied is reduced the preferred explanation for this is that the pattern of size as a function of frequency becomes nonlinear when the size of the area studied is less than the focal area of the largest earthquakes