radon earthquake precursor studies in iceland discrete samples of geothermal water have been collected from a network of nine stations for analysis of radon 222 rn content the sampling network consisted of wells that range in wellhead temperature from 48 c to 100 c and the depths range from 38 m to 1338 m the sampling frequency at most stations was about once per week and twice per week at the station fludir the wells are either artesian or pumped more or less continuously the network covered two regions of transform faulting in iceland with seven stations in the southern iceland seismic zone sisz and two stations in northern iceland in the tjornes fracture zone tfz during 1978 and 1979 several anomalous changes in radon content were observed to precede some of the local earthquakes criteria based on tectonic regimes a magnitude distance relationship and time clustering were applied to select a set of 23 earthquakes that could be expected to be preceded by a radon anomaly the magnitude of these earthquakes ranged between 1 0 and 4 3 each of the 23 earthquakes was within the distance range of one or more stations such that altogether 57 potential observations of possible anomalies were available the method of analysis applied to the radon and earthquake data consisted of identifying radon anomalies in retrospect and resulted in nine precursory anomalies 48 cases of failure to observe an anomaly and seven false alarms the probability of observing radon anomalies before earthquakes with magnitudes between 2 0 and 4 3 the largest event observed was found to be approximately 65 based on a weekly sampling rate in the sisz five out of eight earthquakes m 2 were preceded by an anomaly in two cases anomalies were observed at two different stations prior to the same earthquake the anomalies appeared to occur farther away for larger earthquake magnitude an aquiclude that divides the sisz did not seem to affect the occurrence of radon anomalies but the amplitude of anomalies on the east side were larger than the ones on the west side the duration times of the anomalies ranged from 17 to 37 days the large number of failures to observe an anomaly indicated that the occurrence of an anomaly was more strongly dependent on local conditions and earthquake parameters than distance between epicenter and radon station some stations also appeared to be less sensitive than others and three stations never showed an anomaly during periods of bursts in local seismicity some stations reflected distinctively larger background fluctuations which hampered the correlation of the seismicity with the radon data most of the false alarms were related to disturbances caused by changes in well operation in the sisz the high rate of failure to observe an anomaly and the occurrence of false alarms was partly compensated for by operating a dense network of sampling stations wells that are utilized at moderate flow rates are less likely to show false alarms than wells utilized at high flow rates wells situated close to rock formations rich in radioactive minerals may be more likely to show anomalies than others

tectonic setting and source parameters of the september 19 1985 michoacan mexico earthquake analysis of body waves and long period surface waves from the september 1985 earthquake in coastal michoacan mexico shows that the event was an interplate subduction event with a low dip angle fault plane 9 striking parallel to the mid america trench 288 and a small component of left lateral motion 72 with a point source depth of 17 km and a seismic moment in excess of 1 10 28 dyn cm the earthquake was a multiple event with a second source of identical moment fault geometry and depth occurring approximately 26 s after the first directivity in the body wave time function indicates that the second event occurred roughly 100 km to the southeast of the first this suggests that the earthquake first broke the northern portion of the michoacan gap propagated with low moment release through the rupture zone of the 1981 playa azul earthquake and then broke the remaining asperity in the southern section of the gap the seismic moment determined from rayleigh and love waves is between 1 0 1 7 10 28 dyn cm m w 7 9 8 1 the largest moment determined to date for a mexico subduction earthquake comparison of seismograms at pasadena with records of other large mexico events shows that the michoacan earthquake is basically the same size as the 1932 jalisco mexico earthquake and clearly larger than other significant events in mexico since 1932 the seismic moment and the time since the last large earth quake in michoacan in 1911 fit an empirical relation between moment and recurrence time found for the guerrero oaxaca region of the subduction zone the large aftershock on september 21 m s 7 5 has the same geometry as the mainshock a somewhat larger source depth 22 km a simple time function and a seismic moment between 2 9 4 7 10 27 dyn cm m w 7 6 7 7

possible resonance effect in the distribution of earthquake damage in mexico city the destruction caused by the earthquake of 19 september 1985 in mexico city shows three remarkable features1 first a concentration of damage in the former lake bed second a peculiar distribution of high and low damage areas alternating within a few city blocks and third a selectivity for buildings between five and fifteen storeys high while the last point is understood by civil engineers2 and the first confirms the relevance of the soft ground the second feature is the most puzzling to a physicist such a pattern evokes the idea of a standing wave with low and high damage areas corresponding to nodes and antinodes this suggests a resonance phenomenon of the waterlogged ground moving collectively from the navier equations of classical elasticity it is known3 that a transfer of the incoming seismic wave energy to longitudinal waves takes place if a sharp change from hard to soft ground exists solving then the two dimensional poisson equation for the longitudinal waves within the ancient lake boundaries we show that for the observed seismic wave period of 2 s a standing wave solution exists which explains qualitatively the damage distribution pattern

observations of the diurnal tide in the mesosphere and lower thermosphere over christmas island atmospheric tidal variations in the mesosphere wind field have been studied extensively using radars most of the climatological studies of the tide have been done at middle and high latitudes previous tropical observations of the diurnal oscillation derived from campaign studies have shown the dominance of the migrating diurnal tide in the mesosphere and lower thermosphere by using wind measurements obtained with a meteor radar system located at christmas island the diurnal tidal behavior in the upper atmosphere of the equatorial pacific has been characterized over several years the data collected from august 1988 to december 1993 are presented in this paper and compared to various model results our observations show the meridional wind component of the diurnal tide maximizes in april near 94 km the observed meridional vertical wavelengths are large and indicate upward propagating energy even though the vertical wavelengths for the zonal diurnal component are also large the phase progression is upward corresponding to downward propagating energy there is considerable interannual and intraseasonal variation in the diurnal amplitudes throughout the year

the acquisition of source path and site effects from microearthquake recordings using q tomography application to the united kingdom source site and propagation parameters are inverted from a u k database of weak motion events 2 0 m l 4 7 this results in the complete spectral parameterization of over 3200 velocimetric records of 273 events from the year 1992 to 2006 the s wave is extracted from the vertical records and is processed using a multitaper fourier transform we initially use a nonlinear least squares log space optimization to obtain estimates of the attenuation parameter for each spectrum the estimates of t are then used to geometrically constrain a depth dependent q model using a technique adapted from velocity tomography we then invert for the remaining frequency dependent parameters and a collective amplitude parameter from the velocity spectra while fixing the newly computed attenuation parameters based on raytracing through our q model the resultant amplitude parameters are then split into source moments apparent geometrical spreading and site correction factors we find a frequency independent depth dependent q structure a linear relationship proportional to 0 7 m l between moment magnitude m w and local magnitude m l is found in the range of 2 4 7 m l the majority of stress drops are found to range on the order of 0 1 10 mpa a multiple segment apparent geometrical spreading model is found to best describe the amplitude decay with distance accounting for factors such as geometrical spreading and scattering along with multiple phase interference in the analysis window site response functions are found to broadly correlate with regional geology mean amplification occurring in the cenozoic sedimentary rock sites to the southeast of england relative to the harder palaeozoic rock sites of wales and scotland we use a bootstrap analysis technique to analyze the dependence of our results on the data in order to estimate the variance of the results and check the robustness of different inversions synthetic spectra are also computed in order to obtain minimum variance and bias of model parameters associated with the method in applying a geometrical q constraint through the use of q tomography we find that the robustness of the results is significantly increased a thorough analysis of the trade offs involved in the inversion is performed using synthetic datasets we find strong trade offs between the parameters but we are able to show that this covariance is reduced when adopting the q tomography approach

on the signature of the quasi 3 day wave in the thermosphere during the january 2010 ursi world day campaign 1 ultra fast kelvin waves with periods of 3 5 days are important in the coupling of the lower atmosphere to the thermosphere and ionosphere here we focus on the observations and effects of a 3 day wave during january 2010 as this time period coincides with a stratospheric warming event a coordinated set of observations with incoherent scatter radars are available while there is no evidence that the occurrence of this 3 day wave is connected with this event these observations offer an unprecedented glimpse of the thermospheric conditions during this period including the first ever detection of a 3 day wave with an incoherent scatter radar using a combination of ground and space based observations we identify an eastward moving zonal wave number one 3 day equatorial wave that is comprised of a kelvin wave at the lowest latitudes and a rossby gravity wave at higher latitudes in the equatorial region the vertical wavelength is 40 km and the wave peaks in amplitude around 95 100 km altitude the wave observed here is only seen to propagate to around 105 km altitude evidence of an interaction between this wave and the diurnal tide is seen between 82 88 km the resultant 3 day periodicity in the diurnal tide is seen to propagate up to altitudes of 150 km this could have a significant impact on the ionosphere via modulation of the e region dynamo thus carrying the 3 day periodicity to higher altitudes

dislocation model for radon response to distant earthquakes if radon changes associated with earthquakes are caused by changes in strain within the earth reports of radon signals that are measured at considerable distances from the hypocenters of earthquakes can be understood a simple dislocation model leads to estimates of distances that increase to hundreds of kilometers at earthquake magnitudes of 5 and above the essential components of the theory are that the strain from a dislocation loop varies at large distances x as x 3 while the strains increase with the magnitude of the earthquake represented a threshold sensitivity is inferred from radon measurements associated with earthquakes near blue mountain lake new york the usefulness of a global 222rn monitoring network is inferred

horizontal structure of the geomagnetic 2 day variation 1 principal component analysis was applied to 30 year geomagnetic field data of six observatories in low latitudes to extract the longitudinal structure of the geomagnetic 2 day variation it was revealed that characteristics of the 2 day variation agree well with those of the quasi 2 day wave observed in the middle atmosphere it propagates westward with a zonal wave number 3 and the monthly mean amplitude of the variation is largest in january and july in addition an investigation into the latitudinal profile of the variation clarified that the amplitude of the 2 day variation is largest in the equatorial region although it extends to the middle latitudes a previous result of spherical harmonics analysis of geomagnetic field data was reanalyzed to identify the global horizontal pattern of overhead currents responsible for the geomagnetic 2 day variation the results showed that the 2 day variation is attributed to westward propagating current vortices the foci of which are located along the equator all these features can be explained by a scenario in which there exists a 2 day wave in the ionosphere whose horizontal structure and temporal variation resemble those in the middle atmosphere and the wind drives electric fields and currents in the ionosphere through dynamo action

amplitude phase and period variations of the quasi 2 day wave in the mesosphere and lower thermosphere over london canada 43 n 81 w during 1993 and 1994 because there is as yet no conclusive evidence pointing to the source of the quasi 2 day wave further observations are required in order to resolve questions about the generating mechanism as well as to better understand the role of the wave in the middle atmosphere in this paper we investigate the period amplitude phase and vertical wavelength for the quasi 2 day wave in the mesosphere and lower thermosphere using the university of western ontario 2 mhz radar near london canada and in addition we look at possible coupling with atmospheric tides the results of the present study bring out certain new aspects of the quasi 2 day wave at midlatitude in the northern hemisphere that have not been previously reported in particular we show that the period of the quasi 2 day wave determined from our study is smaller 46 47 hours than the 51 to 52 h period generally suggested by other northern hemisphere results and our periods also showed variability as a function of time we also draw attention to the annual variability and especially highlight the occurrence of the wave in nonsummer months for example a brief occurrence in april is not uncommon our study also contributes additional midlatitude geographical data that should aid in developing a better picture of the quasi 2 day wave

seasonal and longitudinal variations of the solar quiet sq current system during solar minimum determined by champ satellite magnetic field observations 1 vector magnetometer observations from the challenging minisatellite payload champ satellite are used to determine the solar quiet sq current system during the recent solar minimum observations from 2006 to 2008 are combined and after removal of a main field model and accounting for field aligned currents the longitudinal and seasonal variation of the sq currents are determined through the method of spherical harmonic analysis comparison with sq currents derived from ground based magnetometers in the african european longitude sector reveals similar amplitudes and seasonal variations indicating that the champ observations can reliably determine the sq current system the seasonal variation is consistent with prior observations during solar minimum conditions and in the northern hemisphere exhibits a primarily annual variation with peak currents during local summer the seasonal variation in the southern hemisphere is characterized by a semiannual variation with the maxima occurring around the equinoxes significant longitudinal variations are also observed and they display a seasonal variability during northern hemisphere summer the predominant feature at local noon is a wave number 1 variation in longitude during the remainder of the year a wave 3 longitudinal structure is observed at this local time the longitudinal variations are considered to be due to a combination of the orientation and strength of the geomagnetic field as well as the tidal winds in the lower thermosphere variations in tidal winds due to nonmigrating tides may influence the dynamo generated electric fields and currents resulting in the observed longitudinal variations of the sq current function

verification of large scale rapid transport in the lower thermosphere tracking the exhaust plume of sts 107 from launch to the antarctic 1 new analysis of the doppler shift of o2 airglow spectra recorded by the timed doppler interferometer tidi and the high resolution doppler imager hrdi have provided conclusive evidence that the shuttle main engine exhaust plume generated in the lower thermosphere by the launch of sts 107 and imaged by the global ultraviolet imager guvi instrument on timed was transported to the antarctic in 80 h supporting a key inference from the initial study by stevens et al 2005 these new results were aided by improved knowledge of the effects of instrumental and satellite artifacts imposed on the doppler spectra sts 107 launched on 16 january 2003 and the neutral wind near its launch trajectory and nearby volume was sampled within minutes by tidi these initial observations suggested that the northernmost end of the shuttle s exhaust plume would move northeast and that the southern end would move southeast motions that were identified in imagery acquired during the next orbit of timed the direction and magnitude of plume motion inferred from guvi images obtained 12 26 and 50 h after launch were again confirmed by tidi and hrdi the appearance of the plume over the antarctic 80 h after launch inferred from earlier work by the appearance of iron ablated from the shuttle s main engines was consistent with neutral winds measured by the satellite doppler instruments over the antarctic the transport of the plume from the coast of florida to the antarctic was aided by the favorable phase and strong amplitude of a 2 day planetary wave of wave number three in the southern hemisphere on 18 january 2003 the existence of the 2 day wave was deduced from zonally averaged and combined tidi and hrdi neutral wind observations we conclude that the existence of strong and sustained winds in the mlt significantly greater than expected from empirical and theoretical models is indisputable and provides compelling evidence supporting the global scale nature of thermospheric winds with magnitude greater than 100 m s observed by larsen 2002 from 40 years of sounding rocket chemical release experiments

a model for vertical to horizontal response spectral ratios for europe and the middle east in the framework of probabilistic seismic hazard analysis the preferred approach for obtaining the response spectrum of the vertical component of motion is to scale the horizontal spectrum by vertical to horizontal v h spectral ratios in order to apply these ratios to scenario or conditional mean spectra the v h ratios need to be defined as a function of variables such as magnitude distance and site classification a new model for the prediction of v h ratios for peak ground acceleration and spectral accelerations from 0 02 to 3 0 s is developed from the database of strong motion accelerograms from europe and the middle east a simple functional form expres sing the v h ratios as a function of magnitude style of faulting distance and site class is found to be appropriate and the associated aleatory variability is found to be at least as low as that obtained in other studies using more complex models the predicted ratios from the new european model are found to be in broad agreement with recent models derived from predominantly western north america data

first observations of mesospheric dynamics with a partial reflection radar in hawaii 22 n 160 w we present here an overview of the wind measurements made during the first year of operation of a partial reflection radar system in hawaii the system operates at 1 98 mhz and provides wind estimates between 60 and 100 km at 2 km intervals our wind observations reveal a zonal mean motion that has several features in common with the mesopause semiannual oscillation msao seen at more equatorial latitudes but which is influenced as well by the seasonal variations of the mesospheric jet structure at higher latitudes major features of the zonal mean wind structure include a downward progression of strong eastward and westward phases of the msao from january to july coinciding with the period during which the msao and the annual cycle of the zonal mean wind at higher latitudes are in phase this results in an eastward maximum of 60 ms 1 near 80 km during january and february which descends rapidly and a westward maximum of 50 ms near 85 km during march and april which descends much more slowly the second msao cycle is greatly suppressed relative to the first due to the reversal of the correlation between this and the annual cycle at higher latitudes from july to december mean eastward motions occur primarily above 85 km early in this cycle and throughout the height range at later times planetary wave activity is seen to contribute substantial variability during times of eastward mean flow and to have a smaller role when zonal mean motions are westward tidal and 2 day motions are found to be large and variable with the maximum 2 day amplitudes occurring during february and august the largest diurnal tides were observed during october and november march and april and july and august while the semi diurnal amplitudes exhibited a minimum from april to june

sensitivity of mesospheric mean flow planetary waves and tides to strength of gravity wave drag a global circulation model which extends from the surface to 125 km is used to study how the strength of gravity wave drag affects the dynamics of the mesosphere the strength of gravity wave drag has a strong influence on the zonal mean state of the mesosphere in particular the magnitude and variability of the summer mesopause temperature and the shear on the top of the mesospheric jets this change in the zonal mean state strongly affects the susceptibility of the mesosphere to baroclinic and or barotropic instability and hence the formation of the 2 day wave the 2 day wave in turn interacts nonlinearly with the diurnal tide producing secondary waves and a reduction in amplitude of the diurnal tide previous studies with quasi linear mechanistic tidal models have captured some semiannual variation in tidal amplitude through direct interactions between tides and gravity waves our fully nonlinear global circulation model results support an alternative explanation in terms of interactions between planetary waves and tides

the quasi 2 day wave and spatial temporal variability of the oh emission and ionosphere 1 the quasi 2 day wave qtdw during january 2006 is investigated using sounding of the atmosphere using broadband emission radiometry saber observations of oh airglow and temperature in the mesosphere and lower thermosphere mlt and champ in situ electron density observations at an altitude of 360 km the zonal structure of the qtdw during early 2006 in the southern hemisphere mlt and low latitude ionosphere is dominated by westward propagating zonal wave number 3 w3 and eastward propagating zonal wave number 2 e2 components however the observed longitude variability is not fully described by the e2 and w3 components of the qtdw the remaining longitude variability is attributed to the presence of nonmigrating tides and secondary waves generated by the nonlinear interaction of the qtdw with migrating tides the nonmigrating tides are a combination of those that are generated in situ by qtdw tide nonlinear interactions and those of tropospheric origin that propagate upward into the mlt the results presented demonstrate that nonmigrating tides and secondary waves are of considerable importance for determining the total longitude variability during periods of enhanced qtdw activity the general similarity between the qtdw in oh airglow and temperature indicates that variations in atomic oxygen concentrations due to vertical winds during the qtdw are the primary driver of the qtdw in the oh airglow emission however there are some differences in the oh airglow and temperature that we consider to be connected to changes in eddy diffusion due to changes in gravity waves during the qtdw last although similar zonal structure of the qtdw is observed in the ionosphere the observed longitude variations are not well represented by the qtdw components indicating that nonmigrating tides play a critical role in determining longitudinal variability in the ionosphere during the qtdw the importance of nonmigrating tides in the ionosphere may be related to the relative efficiency of the qtdw and different nonmigrating tides in the generation of electric fields

source characteristics of the 1985 michoacan mexico earthquake at periods of 1 to 30 seconds source characteristics of the sept 19 1985 michoacan mexico earthquake and its aftershock on sept 21 were inferred from broadband and short period teleseismic gdsn records we fourier transformed the p waves corrected for instrument response attenuation geometrical spreading and radiation pattern including the depth phases and then averaged to obtain the teleseismic source spectrum from 1 to 30 s the michoacan source spectrum is enriched at 30 s and depleted at 1 to 10 s relative to an average source spectrum of large interplate subduction events source spectra for the sept 21 aftershock 1981 playa azul 1979 petatlan and 1978 oaxaca events follow a trend similar to that of the 1985 michoacan event this spectral trend may characterize the mexican subduction zone a station by station least squares inversion of the michoacan earthquake records for the source time function yielded three source pulses which we interpreted as events on the fault plane the first two are similar in moment and the third contains only 20 of the moment of the first directivity is evident in the timing at each station we measured the time differences between the pulses and performed a least squares nonlinear estimation of the strike distance and time separation between the events to locate them relative to one another the second event occurred 26 s after the first and 82 km southeast of it indicating southeastward rupture along the trench the third event occurred 21 s after the second and about 40 km seaward of it the two large events are also seen in the near field strong motions the mainshock records spectrum and time functions contain less high frequency radiation than those of the 1985 valparaiso chile earthquake apparently the michoacan earthquake ruptured two relatively smooth strong patches which generated large 30 s waves but small 1 to 10 s waves such behavior contrasts with the valparaiso event which had a more complex rupture process and generated more 1 to 5 s energy this difference is consistent with the higher near field accelerations recorded for the valparaiso event

temporal modulation of the four peaked longitudinal structure of the equatorial ionosphere by the 2 day planetary wave 1 observations of electron densities by the constellation observing system for meteorology ionosphere and climate in august to october 2008 have shown a prominent four peaked longitudinal structure in the height of the f2 layer hmf2 in the equatorial ionosphere the development of this ionospheric structure in daytime is found to be consistent with the forcing by the eastward propagating nonmigrating diurnal tide with zonal wave number 3 de3 it is believed that tidal winds can modify the e region electric fields and subsequently produce variations in the ionosphere through the dynamo effect this study reveals that the amplitude of the hmf2 four peaked longitudinal structure is subject to a 2 day periodic modulation on certain intervals in the two month time period simultaneously wind measurements from the skiymet meteor radar at thumba 8 5 n 77 e india indicate corresponding 2 day planetary wave activity in the mesosphere and lower thermosphere mlt the 2 day planetary wave has both zonal and meridional wind components and it is the variability in the zonal component that most closely corresponds to f2 layer changes the zonal wind observations by the radar also show that the amplitude of the diurnal tide is modulated by the 2 day wave this study suggests that the identified 2 day variation of the hmf2 four peaked longitudinal structure in the equatorial ionosphere is caused by the interaction between the de3 tide and the 2 day planetary wave

magmatic gases in well fluids aid the mapping of the flow pattern in a geothermal system abstract gas composition and silica concentrations of well fluids are used in conjunction with pressure temperature and enthalpy data to obtain a model of the drilled part of the krafla geothermal field northeast iceland a magma chamber is located at 3 8 km depth under the field magmatic gases emanate from the chamber and travel via a channel reaching the surface at the hveragil eruptive fissure the composition of the gases is apparently modified on the way in that sulphur which presumably is in the form of sulphur dioxide to begin with is removed on the way and what remains is in the form of hydrogen sulphide at the end it is suggested that the major removal mechanism is the deposition of pyrite and pyrrhotite during the passage of the gases through the hydrothermal system the hydrothermal system is divided into a lower part whose temperature exceeds 300 c and whose fluids are to a varying extent affected by the magmatic gases and an upper part whose temperature is ca 200 c this upper part is a run off from the lower part but the magmatic effects have mostly disappeared there

zonal wave numbers of the summertime 2 day planetary wave observed in the mesosphere by eos aura microwave limb sounder 1 recent observations and theoretical work suggest that the 2 day planetary wave in the summertime mesosphere is composed of multiple superposed zonal wave numbers here we use eos aura microwave limb sounder mls temperature data to determine the component zonal wave numbers of the 2 day wave in the mesosphere at latitudes of 70 s to 70 n from 2004 to 2009 we consider the effect of aliasing between different wave numbers and note that significant aliasing can occur and result in spurious signals particularly at high latitudes in winter the seasonal evolution of the different wave numbers is investigated and found to be very different between the northern and southern hemispheres in both hemispheres the wave is dominated by westward traveling waves of zonal wave number 3 and 4 w3 and w4 however in the southern hemisphere the wave is dominated by the w3 component but in the northern hemisphere the w3 component is smaller and the w4 component is often of similar or larger amplitude a small amplitude westward traveling zonal wave number 2 w2 wave is also evident in both hemispheres in the northern hemisphere the w2 amplitudes never exceed 3 k the w3 amplitudes can reach 3 5 k and the w4 can be the largest component reaching amplitudes of 4 k in the southern hemisphere the w2 amplitudes can reach up to 3 5 k the w3 amplitudes can be much larger reaching 12 k and the w4 amplitudes are smaller than in the northern hemisphere in 4 out of 5 years not exceeding 3 k the northern hemisphere w4 can reach large amplitudes in august when the w3 is small which means that the late summer northern hemisphere quasi 2 day wave is usually a w4 oscillation rather than the familiar w3 in contrast in the southern hemisphere the w3 is often larger than the w4 around the summer solstice and there are no episodes observed where the wave becomes dominated by the w4 for an extended period of time a high degree of interannual variability is evident particularly in the southern hemisphere where the w3 peak amplitudes vary from 12 k in january 2006 to 3 k in january 2009 the height latitude structure of the w4 suggests that this wave is a 4 0 rossby gravity wave

signatures of the 3 day wave in the low latitude and midlatitude ionosphere during the january 2010 ursi world day campaign 1 recent studies of the equatorial ionosphere have found evidence of forcing by atmospheric ultra fast kelvin ufk waves this study investigates the quasi 3 day ufk wave and its effects on the variations of the ionosphere at low latitudes and midlatitudes using coordinated observations of both the atmosphere and ionosphere during the january 2010 ursi world day campaign the global maps of tec from the igs ground based gps product demonstrate a 3 day periodic variation during january 15 25 this variation has the largest amplitude at 15 magnetic latitude and extends into lower latitudes simultaneously a 3 day wave is observed in the mesosphere in the zonal wind measurements by a meteor radar at the magnetic equator the latitudinal range of the tec variation 20 s 20 n is also consistent with that of the 3 day wave the incoherent scatter radar isr observations show a 3 day signature in vertical ion drifts over jicamarca 11 9 s 76 w and in the electron densities in the top side of ionosphere measured from millstone hill 42 6 n 71 5 w this signature is consistent with the fountain effect in the equatorial region and shows the impact on the topside ionosphere at midlatitudes the ufk wave is trapped within 30 geographic latitude but this study shows that the effects of the wave could reach the ionosphere at the higher latitude even as high as 40 n 50 n magnetic latitude

temporal modulations of the longitudinal structure in f2 peak height in the equatorial ionosphere as observed by cosmic 1 this study investigates the temporal variability of longitudinal structure in f2 layer peak height hmf2 in the equatorial ionosphere for this study electron density profiles retrieved from the radio occultation measurements by the constellation observing system for meteorology ionosphere and climate cosmic are fitted with a two layer chapman function to determine hmf2 the hmf2 values in the magnetic equatorial region display a four peaked longitudinal structure that has been identified in other ionospheric observations the four peaked structure is likely the signature of the forcing by the eastward propagating nonmigrating diurnal tide with zonal wave number 3 de3 further analysis for the period of prominent four peaked structure over august september 2008 finds that this structure exhibits a 5 day periodicity coincidentally the all sky interferometric meteor radar s wind measurements at thumba 8 5 n 77 e in india for the mesosphere and lower thermosphere indicate strong 5 day planetary waves within that time period the observed temporal periodicity of the four peaked longitudinal structure in hmf2 could thus be attributed to the interaction of de3 with a 5 day planetary wave

anomalous hydrogen emissions from the san andreas fault observed at the cienega winery central california we began continuous monitoring of h2 concentration in soil along the san andreas and calaveras faults in central california in december 1980 using small h2 o2 fuel cell sensors ten monitoring stations deployed to date have shown that anomalous h2 emissions take place occasionally in addition to diurnal changes among the ten sites the cienega winery site has produced data that are characterized by very small diurnal changes a stable baseline and remarkably distinct spike like h2 anomalies since its installation in july 1982 a major peak appeared on 1 10 november 1982 and another on 3 april 1983 and a medium peak on 1 november 1983 the occurrences of these peaks coincided with periods of very low seismicity within a radius of 50 km from the site in order to methodically assess how these peaks are related to earthquakes three h2 degassing models were examined a plausible correlational pattern was obtained by using a model that 1 adopts a hemicircular spreading pattern of h2 along an incipient fracture plane from the hypocenter of an earthquake 2 relies on the feo h2o reaction for h2 generation and 3 relates the accumulated amount of h2 to the mass of serpentinization of underlying ophiolitic rocks the mass was tentatively assumed to be proportional to the seismic energy of the earthquake

on fluid reserves and the production of superheated steam from fractured vapor dominated geothermal reservoirs vapor dominated geothermal reservoirs produce saturated or superheated steam and vertical pressure gradients are close to vapor static these observations have been generally accepted as providing conclusive evidence that the liquid saturation must be rather small 50 in order that liquid may be nearly immobile this conclusion ignores the crucial role of conductive heat transfer mechanisms in fractured reservoirs for vaporizing liquid flowing under two phase conditions we have developed a multiple interacting continuum method minc for numerically simulating two phase flow of a homogeneous fluid in a fractured porous medium application of this method to reservoir conditions representative of the geysers california and results from an analytical approximation show that for matrix permeability less than a critical value 2 5 to 5 microdarcies the mass flux of water from the matrix to the fractures will be continuously vaporized by heat transported due to conduction this gives rise to production of superheated steam even when the matrix has nearly full liquid saturation simple estimates also show that heat driven steam water counterflow can maintain a nearly vapor static vertical pressure profile in the presence of mobile liquid water in a reservoir with low vertical matrix permeability the implication of these findings is that the fluid reserves of vapor dominated geothermal reservoirs may be larger by a factor of about 2 than has generally been believed in the past

strong ground motion from the michoacan mexico earthquake the network of strong motion accelerographs in mexico includes instruments that were installed under an international cooperative research program in sites selected for the high potenial of a large earthquake the 19 september 1985 earthquake magnitude 8 1 occurred in a seismic gap where an earthquake was expected as a result there is an excellent descripton of the ground motions that caused the disaster

evidence for a traveling two day wave in the middle atmosphere evidence is presented for the existence of a wave number 3 westward traveling 2 day oscillation in the temperature measurements made by the nimbus 5 scr and nimbus 6 pmr instruments the wave has largest amplitude in the mesosphere at low latitudes of the summer hemisphere and has a markedly asymmetrical meridional structure it is suggested that the wave may be a free wave similar to the 5 day wave identified in nimbus 5 scr data by rodgers 1976 the vertical structure shows little phase tilt and a slight indication of an increase in amplitude with height

ionospheric vertical plasma drift perturbations due to the quasi 2 day wave the thermosphere ionosphere mesosphere electrodynamics general circulation model is utilized to study the vertical e b drift perturbations due to the westward quasi 2 day wave with zonal wave numbers 2 and 3 w2 and w3 the simulations show that both wind components contribute directly and significantly to the vertical drift which is not merely confined to low latitudes the vertical drifts at the equator induced by the total wind perturbations of w2 are comparable with that at middle latitudes while the vertical drifts from w3 are much stronger at middle latitudes than at the equator the ion drift perturbations induced by the zonal and meridional wind perturbations of w2 are nearly in phase with each other whereas the phase discrepancies of the ion drift induced by the individual wind component of w3 are much larger this is because the wind perturbations of w2 and w3 have different latitudinal structures and phases which result in different ionospheric responses through wind dynamo

the 2 day wave in the middle atmosphere observations and theory a recurrent global scale 2 day oscillation in the middle atmosphere is well documented in a variety of data sources meteor wind partial reflection satellite and rocketsonde the observed period is almost invariably near 2 1 days and the zonal structure has been established as a westward propagating wave number 3 mode observations also indicate that the meridional wind component maximizes near the equator and dominates the wind field at low latitudes these features suggest the disturbance s identification with the wave number 3 rossby gravity normal mode of a windless isothermal atmosphere such modes are found to exist largely independent of the mean fields the eigenperiods are only modestly altered by mean wind variations on the lowest three scale heights and the influence on the mode structure is local the vertical growth of amplitude is enhanced in regions of weak westerly wind relative to the wave and equatorward temperature gradient while the vertical growth rate is retarded and amplitudes may even decay in regions of strong westerlies or poleward temperature gradient in realistic mean fields the third rossby gravity mode has magnified responses very near 2 25 days in both equinox and solstice conditions the horizontal structure remains largely intact in the lowest levels however considerable asymmetry is introduced in the solstice upper stratosphere and mesosphere by the magnified vertical growth of amplitude in the summer hemisphere the latter results from the moderate easterlies and equatorward temperature gradient characteristic of the region as for the simple eigenstructure the meridional wind component in this region maximizes near the equator and dominates the wind field up to mid latitudes

coordinated global radar observations of tidal and planetary waves in the mesosphere and lower thermosphere during january 20 30 1993 a multi instrument global campaign involving incoherent scatter medium frequency and meteor wind radars was conducted during the period of january 20 30 1993 to study the dynamics of the mesosphere and lower thermosphere data obtained from 15 radar stations covering a wide latitude range have been used to determine the global distribution of planetary and tidal waves during this 10 day campaign spectral analysis of the neutral winds measured by the radars in the altitude range from 80 to 130 km indicates the existence of a strong 48 hour wave near 90 km at latitudes between 40 n and 40 s that is present up to 108 km at 18 n the semidiurnal tide is large at middle and high latitudes near 90 km and is predominant above 110 km while the diurnal tide is observed to be particularly important in the upper mesosphere near 40 latitude a least squares fit to the radar data is performed to obtain the amplitudes and phases of the tidal and 48 hour waves comparison with national center for atmospheric research thermosphere ionosphere mesosphere general circulation model shows that the predictions from the model agree reasonably well with the observed global morphology of tidal wave amplitudes

observations of the quasi two day wave in the middle and lower atmosphere over christmas island we present analyses of data collected at christmas island in the mesosphere and lower thermosphere using a meteor echo detection and collection system medac in addition to data collected in the troposphere and lower stratosphere using a clear air stratosphere troposphere st radar these data which provide 5 years of semicontinuous horizontal wind velocity estimates are analyzed to determine the temporal structure of the quasi two day wave in the middle and lower atmosphere our results show the presence of strong wave activity in the middle atmosphere during late january and early february as well as a secondary maxima in june august for each of the years we have data however the magnitude and duration of the wave events observed in late january and early february exhibit interannual variability

mesospheric planetary wave signatures in the equatorial electrojet 1 using five years 1994 1998 of simultaneous and collocated measurements of horizontal winds associated with mesosphere and lower thermosphere mlt region and geomagnetic field measurements in the indian geomagnetic dip equatorial region an extensive experimental study has been made on the influences of mesospheric planetary waves on the equatorial electrojet eej the winds are measured using medium frequency mf radar 1 98 mhz located at tirunelveli the eej strength is determined by measuring the geomagnetic field strength at both the geomagnetic dip and off dip equatorial stations trivandrum and alibag india by noting the simultaneous time evolution of spectral signal morlet wavelet analysis in both the eej strength and mesospheric winds at 88 km it is found that mesospheric planetary waves with periodicities of 2 25 days often do propagate up to the ionospheric dynamo region and have their influences on eej strength sometimes only one of the parameters shows strong spectral signal in this periodicity range it is also observed that often the diurnal oscillation in eej strength and mesospheric winds exhibits coherent variations in amplitude when the signature of mesospheric planetary scale oscillations is found in the eej strength also it is found that variations in high energy solar radiations f10 7 is used as a proxy can influence the eej strength at planetary timescales this leads to an interesting question what actually causes the vertical coupling between ionosphere and atmosphere through upward propagating planetary waves to be operative only during some and not all of the episodes

two day wave traveling westward with wave number 1 during the sudden stratospheric warming in january 2017 quasi two day wave qtdw propagating westward with wavenumber number 1 w1 in january 2017 is studied using global temperature observed by saber and wind observed by a meteor radar at fuke china 19 0on 109 8oe the amplitude of w1 significantly enhances during january 2017 when two stratospheric warming events occur the temperature perturbation of w1 reaches maximum amplitude of more than 6k at latitude 15o around 84 km and 95 km the structure of temperature w1 is symmetric with regard to the equator the temporal variation of w1 is consistent with the stationary planetary wave with wavenumber 2 spw2 but contrary to the qtdw propagating westward with wavenumber 3 w3 when spw2 is large during two sudden stratospheric warming events energy transfers from w3 to w1 two bursts of the two day wave in meridional wind observed by the meteor radar are just corresponding to the local maxima of w3 and w1 respectively we conclude that during january 2017 w1 is generated by the nonlinear interaction between spw2 and w3 spw2 which is modulated by the quasi 16 day perturbation in the stratosphere plays a key role in the energy transmission from w3 to w1 and it is responsible for the 16 day variation of w1

southern argentina agile meteor radar system design and initial measurements of large scale winds and tides 1 the southern argentina agile meteor radar saamer was installed at rio grande on tierra del fuego 53 8 s 67 8 w in may 2008 and has been operational for 24 months this paper describes the motivations for the radar design and its placement at the southern tip of south america its operating modes and capabilities and observations of the mean winds planetary waves and tides during its first 20 months of operation saamer was specifically designed to provide very high resolution of large scale motions and hopefully enable direct measurements of the vertical momentum flux by gravity waves which have only been possible previously with dual or multiple beam radars and lidars or in situ measurements saamer was placed on tierra del fuego because it was a region devoid of similar measurements the latitude was anticipated to provide high sensitivity to an expected large semidiurnal tide and the region is now recognized to be a hot spot of small scale gravity wave activity extending from the troposphere into the mesosphere and lower thermosphere perhaps the most dynamically active location on earth saamer was also intended to permit simultaneous enhanced meteor studies including head echo and nonspecular measurements which were previously possible only with high power large aperture radars initial measurements have defined the mean circulation and structure exhibited planetary waves at various periods and revealed large semidiurnal tide amplitudes and variability with maximum amplitudes at higher altitudes often exceeding 60 m s 1 and amplitude modulations at periods from a few to 30 days

origin of hydrogen and carbon dioxide in fault gases and its relation to fault activity gases occluded in fracture zones of active faults are characterized by a high concentration of h 2 and or co 2 a predominant gas species h 2 or co 2 is related to the lithofacies which the fault cuts carbon dioxide concentration in sediments fluctuates with temperature this evidence and sigma 13 c of co 2 about 20 suggests that co 2 originates from organic materials carbon dioxide with sigma 13 c of 5 to 17 in brecciated gneiss containing marble may have been produced by interaction between organically derived co 2 and the marble or alternatively may have been magmatically derived hydrogen usually occurs in sheared silicate rocks and its concentration fluctuates a great deal the concentration of h 2 from active faults associated with historical earthquakes usually amounts to as high as several percent in maximum whereas the concentration of h 2 from quaternary faults not associated with historical earthquakes is at most 1

first observations of intraseasonal oscillations in the equatorial mesosphere and lower thermosphere we present the first evidence of strong intraseasonal 10 100 day variability of the equatorial mesosphere and lower thermosphere drawn from spectral analysis of three years of radar wind measurements of the region at christmas island 2 n 157 w oscillations in the zonal wind as large as 20 m s 1 are observed with periods 60 days at 85 95 km amplitudes attenuate near 80 km then reintensify near 75 km where they are usually of longer period and are out of phase with the upper level oscillations oscillations with periods 35 40 days are also observed at 85 95 km these oscillations are transient and usually appear when the background flow is westward similar signals are not observed in the meridional winds these facts suggest that they could be kelvin waves similar to intraseasonal variability in the equatorial lower atmosphere associated with the madden julian oscillation somewhat different time height activity at 20 days could be related to the 1 3 rossby normal mode or the 20 25 day tropospheric oscillation as it is unlikely that any of these oscillations could propagate to these heights from the lower atmosphere we postulate that they arise due to variations in gravity wave activity and transmissivity induced by intraseasonal oscillations lower down which is transferred into the mean flow when these gravity waves dissipate in the mesosphere this may mean that this intraseasonal activity is a time varying mean wind rather than a forced planetary wave

a spreading episode at the southern end of the san andreas fault system the cerro prieto region of baja california mexico is one of the few locations in the world where on land spreading is indicated1 and represents a transition between the east pacific rise and the strike slip san andreas fault system fig 1 it is characterized by high heat flow and volcanic activity and contains one of the world s most closely monitored geothermal fields whose heat source is thought to be a magmatic body emplaced at 5 6 km depth2 cerro prieto is thus an excellent area in which to examine the spatial and temporal properties of the spreading process in detail here we present four lines of evidence that an on land spreading episode occurred at cerro prieto between 1979 and 1981 the occurrence of the imperial valley earthquake of 15 october 1979 and the victoria earthquake of 9 june 1980 both of which produced slip near cerro prieto extension in the expected nw se spreading direction both from direct measurements of areal strain and from the combined slip on the two faults subsidence of up to 25cm near the cerro prieto geothermal field from levelling and gravity data and an abrupt rise in temperature and hco3 concentration in the cerro prieto geothermal reservoir both of which indicate the presence of magma at depth3

assessment of site effects in alpine regions through systematic site characterization of seismic stations abstract in the framework of the renewal project of the swiss strong motion network ssmnet a procedure for site characterization has been established the aim of the procedure was to systematically derive realistic 1d velocity profiles at each station it is mainly based on the analysis of surface waves particularly from passive experiments and includes cross checks of the derived amplification functions with those obtained through spectral modeling of recorded earthquakes the systematic use of three component surface wave analysis allowing the derivation of both rayleigh and love dispersion curves also contributes to the improvement of the quality of the retrieved profiles the procedure is applied to the 30 ssmnet stations installed on various site types within the project covering different aspects of seismic risk the characterization of these 30 sites gives an overview of the variety of possible effects of surface geology on ground motion in the alpine area such effects ranged from deamplification at hard rock sites to amplification up to a factor of 15 in lacustrine sediments with respect to the swiss reference rock velocity model the derived velocity profiles are shown to reproduce observed amplification functions from empirical spectral modeling although many sites are found to exhibit 1d behavior the procedure allows the detection and qualification of 2d and 3d effects the sites are therefore classified with respect to the occurrence of 2d 3d resonance and edge generated surface waves in addition to the large and deeply incised alpine valleys of the rhone the rhine and the aar smaller structures such as local alpine valleys and alluvial fans are shown to exhibit 2d 3d behavior

s wave velocity measurements applied to the seismic microzonation of basel upper rhine graben summary an extensive s wave velocity survey had been carried out in the frame of a recent seismic microzonation study of basel and the border areas between switzerland france and germany the aim was to better constrain the seismic amplification potential of the surface layers the survey included single station h v spectral ratios and ambient vibration array measurements carried out by the swiss team as well as active s wave velocity measurements performed by the german and french partners this paper is focused on the application of the array technique which consists in recording ambient vibrations with a number of seismological stations several practical aspects related to the field measurements are outlined the signal processing aims to determine the dispersion curves of surface waves contained in the ambient vibrations the inversion of the dispersion curve provides a 1 d s wave velocity model for the investigated site down to a depth related to the size of the array since the size of arrays is theoretically not limited arrays are known to be well adapted for investigations in deep sediment basins such as the upper rhine graben including the area of the city of basel in this region 27 array measurements with varying station configurations have been carried out to determine the s wave velocity properties of the geological layers down to a depth of 100 250 m for eight sites the outputs of the array measurements have been compared with the results of the other investigations using active sources the spectral analysis of surface waves sasw and s wave reflection seismics borehole information available for a few sites could be used to calibrate the geophysical measurements by this comparison the advantages and disadvantages of the array method and the other techniques are outlined with regard to the effectiveness of the methods and the required investigation depth the dispersion curves measured with the arrays and the sasw technique were also combined and inverted simultaneously to use the advantages of both methods finally the paper outlines and discusses the contribution of the s wave velocity survey to the new seismic microzonation of the basel region in this regard one major outcome of the survey is the quantification of vertical and lateral changes of the s wave velocity due to changing lithology or changing compaction and degree of weathering of the layers

volcanic stratigraphy of the los azufres geothermal area mexico abstract the los azufres volcanic center located 200 km northwest of mexico city is one of a number of pleistocene silicic volcanic centers with active geothermal systems that lie north of the axis of the mexican neovolcanic belt silicic volcanism began approximately 1 m y ago with eruption of the agua fria rhyodacite to high silica rhyolite lava domes and flows they are covered by rhyodacite and dacite lava domes and flows of the san andres volcano dated at 0 3 m y a north to northeast trending set of high angle normal faults is offset by a younger and more prominent east trending set that parallels the principal regional structural trend these faults cut all but the youngest volcanic rocks of the center the yerbabuena rhyodacites to high silica rhyolites these morphologically well preserved lava domes are approximately 0 15 m y old and are probably associated with air fall tuffs that blanket the western portion of the volcanic center two episodes of high heat flow suggested by studies of drill core samples and fluids from the los azufres geothermal field may correspond to two different episodes of magma injection to high levels the most recent one resulting in eruption of the yerbabuena lavas

testing the depths to 1 0 and 2 5 km s velocity isosurfaces in a velocity model for japan and implications for ground motion modeling

seismic gaps and recurrence periods of large earthquakes along the mexican subduction zone a reexamination abstract seismic gaps and recurrence periods of large shallow interplate earthquakes along the mexican subduction zone are reexamined after combining information from a catalog of nineteenth century9s earthquakes some relocated epicenters of the early part of this century source parameters of recent large earthquakes and redetermined magnitudes of great shallow earthquakes of this century tehuantepec and michoacan gaps have not experienced a large shock in this century and perhaps none in the past century they are either aseismic or have anomalously large repeat times guerrero jalisco and ometepec regions presently appear to have a high seismic potential observed average repeat times of large earthquakes m s 7 4 in six regions east central and west oaxaca san marcos petatlan and colima are between 32 to 56 yr data of this century indicate that the strain is released mostly in large events m s 7 4 a simple dislocation model with parameters obtained from the studies of recent earthquakes explains the observed recurrence periods quite well the b value for this zone is not meaningful an observation which is of significance for seismic risk estimation most of seismic moment or equivalently seismic energy release since 1800 appears to occur for 15 yr followed by relative quiescence in the next 15 yr

analysis of three component ambient vibration array measurements summary both synthetic and observed ambient vibration array data are analysed using high resolution beam forming in addition to a classical analysis of the vertical component this paper presents results derived from processing horizontal components we analyse phase velocities of fundamental and higher mode rayleigh and love waves and particle motions ellipticity retrieved from h v spectral ratios a combined inversion with a genetic algorithm and a strategy for selecting possible model parameters allow us to define structural models explaining the data the results from synthetic data for simple models with one or two layers of sediments suggest that in most cases the number of layers has to be reduced to a few sediment strata to find the original structure generally reducing the number of soft sediment layers in the inversion process with genetic algorithms leads to a class of models that are less smooth they have a stronger impedance contrast between sediments and bedrock combining love and rayleigh wave dispersion curves with the ellipticity of the fundamental mode rayleigh waves has some advantages scatter is reduced when compared to using structural models obtained only from rayleigh wave phase velocity curves by adding information from love waves some structures can be excluded another possibility for constraining inversion results is to include supplementary geological or borehole information analysing radial components also can provide segments of rayleigh wave dispersion curves for modes not seen on the vertical component finally using ellipticity information allows us to confine the total depth of the soft sediments for real sites considerable variability in the measured phase velocity curves is observed this comes from lateral changes in the structure or seismic sources within the array constraining the inversion by combining love and rayleigh wave information can help reduce such problems frequency bands in which the rayleigh wave dispersion curves show considerable scatter are often better resolved by love waves information from the horizontal component can be used to correctly assign the mode number to the different phase velocity curve segments especially when two modes seem to merge at osculation points such merging of modes is usually observed for rayleigh waves and thus can be partly solved if additional information from the love waves and the horizontal component of rayleigh waves is considered whenever a site presents a velocity inversion below the top layer love wave data clearly helps to better constrain the solution

the quasi two day wave observed in the equatorial middle atmosphere an oscillation with a period near 2 days is found in radar wind measurements made in the upper mesosphere and lower thermosphere at christmas island 2 n 157 w in the central pacific the oscillation is particularly strong in the meridional wind component and seems to be present almost continuously ir the 80 100 km height region although some intermittency is evident wave amplitudes are especially large about one month after the solstices in july august and in january february at times coincident with large 2 day wave events in the summer mesosphere at extratropical latitudes power spectral and complex demodulation techniques are used to study the amplitude and frequency variations of the oscillation as a function of height and time downward phase propagation is found consistent with upward energy propagation and with a vertical wavelength of about 70 km an unusual feature is a shift in wave period from near 50 hours in july august to 48 hours in january february when the largest amplitudes up to 45 m s 1 are observed a 16 hour oscillation is also found at times when the 2 day wave amplitudes are largest the observations are consistent with the 2 day wave being a manifestation of the 3 0 rossby gravity normal mode another weaker oscillation is also found in the meridional wind field at a period near 44 hours this oscillation may be due to the 2 0 normal mode

a predictive equation for the vertical to horizontal ratio of ground motion at rock sites based on shear wave velocity profiles from japan and switzerland abstract ratios of vertical to horizontal v h ground motion are important for the computation of scenario compatible vertical design spectra they are therefore a crucial aspect of seismic hazard analysis we characterize the v h ratio at rock sites in terms of the recording site s average quarter wavelength velocity a predictive equation is presented which can be used for reconstructing the expected v h ratio of the 5 damped response and fourier spectra for rock sites given a known shear wave velocity profile the equation is based on the regression analysis of two datasets one from switzerland and one from japan the two datasets allow us to analyze well characterized hard rock sites in switzerland using small earthquakes m w 2 while the magnitude range is increased up to events of m w 7 3 using strong motion recordings from japan s kik net seismic network it is shown that a correlation exists between the quarter wavelength velocity at a given frequency and the v h ground motion ratio small differences possibly due to velocity measurement bias or topographical and basin effects existed when analyzing the individual regional datasets apart from near source distances r v h no clear magnitude or distance dependence of the v h ratios is present in either of the datasets of earthquake recordings we show that the same correlation exists for response spectra and fourier spectra of recorded ground motion a similar correlation was derived for ambient vibrations recorded at swiss station sites resulting in larger values of v h at a given frequency and thereby indicating that v h is sensitive to the composition of the wave field finally uncertainties in the v h models are presented we separate the sources of uncertainty into source and site specific components and present the single site sigma uncertainty measure for site specific hazard analyses

ground motion characterization for vertical ground motions in turkey part 1 v h ratio ground motion models two approaches are used to develop the vertical design spectra in probabilistic seismic hazard assessment psha i performing psha for the vertical component using vertical ground motion models gmms and ii utilizing the v h ratio gmms to scale the horizontal spectrum during or after the hazard calculations for the horizontal component this study intends to develop a new framework for building a vertical ground motion logic tree that combines both vertical and v h ratio gmms in the psha analysis for this purpose the turkish strong motion database tsmd akkar et al in journal of seismology 14 3 457 479 2010 is updated with recordings from earthquakes that occurred between 2008 and 2015 including the mw 6 1 elazig and mw 7 2 van earthquakes the updated tsmd contains 2698 recordings with the earthquake metadata source to site distance metrics for the recordings measured shear wave velocity profiles for the recording stations and spectral accelerations for horizontal and vertical components four candidate v h ratio gmms proposed by gulerce and abrahamson in earthquake spectra 27 4 1023 1047 2011 gulerce and akyuz in seismological research letters 84 4 678 687 2013 akkar et al in bulletin of earthquake engineering 12 1 517 547 2014a bozorgnia and campbell in earthquake spectra 32 2 951 978 2016 are selected and the model predictions are compared with the actual data in the updated tsmd using the analysis of the residuals and data driven techniques analysis results showed that the median predictions of the v h ratio gmms proposed by gulerce and akyuz 2013 akkar et al 2014a and bozorgnia and campbell 2016 are compatible with the v h ratios in the turkish strong motion dataset the findings of this study and the compatibility analysis of the vertical gmms with the updated tsmd are combined in the accompanying manuscript gulerce et al in pure and applied geopyhsics 2019 submitted to provide the complete framework of ground motion characterization for vertical ground motion component

equatorial electrodynamics and neutral background in the asian sector during the 2009 stratospheric sudden warming using ground observations of total electron content tec and equatorial electrojet eej in the asian sector along with plasma and neutral densities obtained from the champ satellite we investigate the ionospheric electrodynamics and neutral background in this longitude sector during the major stratospheric sudden warming ssw in january 2009 our analysis reveals the following prominent features first the tec response in tropical regions is strongly latitude dependent with monotonic depletion at the dip equator but a semidiurnal perturbation at low latitudes second the tec semidiurnal perturbation possesses a significant hemispheric asymmetry in terms of onset date and magnitude it starts on the same day as the ssw peak in the northern hemisphere but 2 days later in the southern hemisphere its magnitude is twice as strong in the north than in the south third strong counter electrojet occurs in the afternoon following the strengthening of the eastward eej in the morning fourth semidiurnal perturbation in both tec and eej possesses a phase shift at a rate of about 0 7 h day comparisons with results reported in the peruvian sector reveal clear longitude dependence in the amplitude and hemispheric asymmetry of the semidiurnal perturbation finally thermospheric density undergoes 25 decrease at low latitudes in the afternoon local time sector during the ssw indicating significant cooling effects in the tropical upper thermosphere

simultaneous observations of the phase locked 2 day wave at adelaide cerro pachon and darwin the southern hemisphere summer 2 day wave tdw is the most dramatic large scale event of the upper mesosphere the winds accelerate over 1 week may attain 70 m s and are often accompanied by a near disappearance of the diurnal tide and stabilization of the period close to 48 h we denote this as the phase locked 2 day wave pl tdw we have examined airglow and meteor radar mr wind data from the andes lidar observatory cerro pachon chile 30 s 289 3 e mr data from darwin 12 5 s 131 e and airglow and medium frequency radar data from the university of adelaide 34 7 s 138 6 e for the behavior of the tdw during the austral summers of 2010 2012 and 2013 the cerro pachon and adelaide sites are located at similar latitudes separated in longitude by about 120 we find a remarkable coincidence between the tdw oscillations at chile and adelaide for the period january february 2010 the oscillations are nearly in phase in terms of local time and the minima and maxima repeat at nearly the same local time from cycle to cycle consistent with a phase locked wave number 3 tdw data for this and other years including darwin show that the amplitude of the diurnal tide decreases when the tdw is largest and that this occurs when the period is close to 48 h these observations support the proposal that the pl tdw is a subharmonic parametric instability wherein the diurnal tide transfers energy to a tdw that is resonant at nearly 48 h

boiling and depth calculations in active and fossil hydrothermal systems a comparative approach based on fluid inclusion case studies from mexico abstract a boiling model that considers the increase of salinity due to the steam loss and uses a combined density of the coexisting vapor and liquid phases was applied to fluid inclusion data from los azufres geothermal zone and from an eocene epithermal vein of taxco these case studies are taken as examples of active and fossil hydrothermal systems respectively in los azufres high temperatures of homogenization 300 c are commonly attained at depths between 1500 and 2000 m whereas salinity values above 2 0 wt nacl eq occur within the upper 500 m of the system suggesting that the geothermal zone is largely affected by boiling the depths calculated with the boiling model are close to real depths with accuracy greater than 99 for one case however considerably large error 30 was obtained to the top of the geothermal system due to enhanced co2 concentrations contrastingly the depths estimated by plotting microthermometric data on boiling point curves of constant salinity and discarding the effect of vapor on hydrostatic pressure were systematically shallower than real ones implying an underestimation of depth of up to 50 for the application case of the taxco epithermal deposit microthermometric data describe a boiling evolution path in the temperature salinity space although some values deviate from it thus likely reflecting local mixing with fluids of contrasting salinity according to our model boiling occurred from a paleo depth of 360 m which corresponds to a current sampling depth of about 200 m this level in the hydrothermal system coincides with the boundary between a lower base metal zone and an upper silver rich zone these results suggest that the descriptive models for epithermal deposits could be incorrectly calibrated in terms of depth therefore they could be revised and corrected by applying the boiling model used in this paper

global distribution and variability of quasi 2 day waves based on the nogaps alpha reanalysis model this study presents the analysis of 14 months january 2009 february 2010 of continuous hourly nogaps alpha reanalysis data used for examining the quasi 2 day wave otdw the global structure and seasonal variability of the eastward and westward traveling qtdws in all meteorological fields geopotential height zonal and meridional wind and temperature have been studied the use of hourly reanalysis data allows a comprehensive understanding of the global spatial temporal qtdw distribution by simultaneous separations of all tides and planetary waves the wave characteristics amplitudes and phases are presented in latitude range 80 and altitudes from 15 to 95 km two different types of eastward traveling waves are identified i waves at middle and high latitudes with zonal wave numbers 2 and 3 which are observed in the local winters and ii waves observed predominantly over the equator with zonal wave number 2 which do not have a well defined seasonal variability but show some enhancement between june and august while the first type waves are seen in all meteorological fields the second ones are not seen in the meridional wind and belong to the ultra fast kelvin waves two different types of westward traveling waves have been identified as well i waves at middle and high latitudes with zonal wave numbers 2 3 and 4 which are observed mainly in summer hemisphere and ii waves observed predominantly over the equator with zonal wave numbers 1 2 and 3 enhanced predominantly at both solstices but are seen in other seasons as well while the first type waves are seen in all meteorological fields the second ones are observed in the meridional wind and are rossby gravity normal modes

a comprehensive survey of atmospheric quasi 3 day planetary scale waves and their impacts on the day to day variations of the equatorial ionosphere this study reports a comprehensive survey of quasi 3 day 2 5 4 5 day period planetary scale waves in the low latitude mesosphere and lower thermosphere using the temperature observations from thermosphere ionosphere and mesosphere electric dynamics sounding of the atmosphere using broadband emission radiometry throughout 2002 2012 occurrences and properties of the waves including the eastward propagating zonal wave numbers of 1 3 e1 e3 and vertical wavelengths are determined for each case the impacts of these waves on the equatorial ionosphere are investigated by searching for the corresponding variations with the same periods and wave numbers in total electron content tec from the concurrent observations of the ground based gps network for a threshold amplitude o f4ki n temperature a total of 300 waves are identified of which there are 186 e1 6 3e2 and 51 e3 events the mean amplitudes and vertical wavelengths of these waves are calculated to be about 7 9 k and 34 km for the e1 5 7 k and 29 km for the e2 and 5 1 k and 27 km for the e3 having the standard deviations of 1 5 k and 6 5 km 0 6 k and 5 6 km and 0 5 k and 6 7 km occurrences of the e1 cases are not observed to depend on season but the large amplitude 8 k cases occur more often during solstices than at equinoxes similarly the e2 and e3 cases are observed to occur most often in january february and may august among these waves 199 cases 66 are found to have the corresponding variations in the equatorial ionosphere with amplitudes 4 2 relative to the mean tec values corresponding to 90th percentile most of these waves have long vertical wavelengths and large amplitudes 3 times more than short vertical wavelength and small amplitude waves because no seasonal or solar cycle dependence on the frequency at which these waves have corresponding variations in the ionosphere at this tec perturbation threshold is observed we conclude that there is no seasonal and solar cycle dependence on the propagation of such waves from the mesopause region to higher altitudes we also identify that only 28 cases 19 of the e1 tec variations do not correspond to any e1 waves which is consistent with the hypothesis that e1 waves are the primary cause of e1 tec variations conditions that are favorable for 3 day waves to create ionospheric variations are present approximately two thirds of the time this study quantifies the importance and frequency of atmospheric quasi 3 day planetary scale waves on the day to day variations of the equatorial ionosphere using a statistical rather than case study approach

attribution of ionospheric vertical plasma drift perturbations to large scale waves and the dependence on solar activity 1 in this study we quantify the contribution of individual large scale waves to ionospheric electrodynamics and examine the dependence of the ionospheric perturbations on solar activity we focus on migrating diurnal tide dw1 plus mean winds migrating semidiurnal tide sw2 quasi stationary planetary wave one qspw1 and nonmigrating semidiurnal westward wave one sw1 under northern winter conditions when qspw1 and sw1 are climatologically strong from thermosphere ionosphere mesosphere electrodynamics general circulation model simulations under solar minimum conditions it is found that the mean winds and dw1 produce a wave two pattern in equatorial vertical e bdrift that is upward in the morning and around dusk the modeled sw2 also produces a wave two pattern in the ionospheric vertical drift that is nearly a half wave cycle out of phase with that due to mean winds and dw1 sw1 can cause large vertical drifts around dawn while qspw1 does not have any direct impact on the vertical drift wind components of both sw2 and sw1 become large at middle to high latitudes in the e region and kernel functions obtained from numerical experiments reveal that they can significantly affect the equatorial ion drift likely through modulating the e region wind dynamo the most evident changes of total ionospheric vertical drift when solar activity is increased are seen around dawn and dusk reflecting the more dominant role of large f region pedersen conductivity and of the f region dynamo under high solar activity therefore the lower atmosphere driving of the ionospheric variability is more evident under solar minimum conditions not only because variability is more identifiable in a quieter background but also because the e region wind dynamo is more significant these numerical experiments also demonstrate that the amplitudes phases and latitudinal and vertical structures of large scale waves are important in quantifying the ionospheric responses

two day wave coupling of the low latitude atmosphere ionosphere system 1 vertical coupling in the low latitude atmosphere ionosphere system driven by the 2 day wave in the tropical mlt region has been investigated the problem is studied from an observational point of view three different types of data were analyzed in order to detect and extract the 2 day wave signals the 2 day wave event during the period from 1 december 2002 to 28 february 2003 was identified in the neutral winds by radar measurements located at four tropical stations the 2 day variations in the ionospheric electric currents registered by perturbations in the geomagnetic field and in the f region electron densities were detected in the data from 23 magnetometer and seven ionosonde stations situated at low latitudes two features for each kind of wave were investigated in detail the variation with time of the wave amplitude and the zonal wave number the results show that the westward propagating global 2 day wave with zonal wave number 2 seen in the ionospheric currents and in f region plasma is forced by the simultaneous 2 day wave activity in the mlt region the main forcing agent in this atmosphere ionosphere coupling seems to be the modulated tides particularly the semidiurnal tide this tide has a larger vertical wavelength than the diurnal tide and propagates well into the thermosphere the parameter that appears to be affected and thus drives the observed 2 day wave response of the ionosphere is the dynamo electric field

day to day migrating and nonmigrating tidal variability due to the six day planetary wave 1 to investigate day to day variability in the mesosphere and lower thermosphere mlt an idealized simulation of a six day westward propagating zonal wave number 1 planetary wave is performed using the national center for atmospheric research ncar thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm the six day planetary wave introduces a six day periodicity in the zonal mean atmosphere migrating and nonmigrating tides as well as in secondary waves that are produced by nonlinear planetary wave tide interactions we have further used the linear global scale wave model gswm to isolate the effect of how the day to day changes in zonal mean zonal winds may influence tides in the mlt the most significant changes are observed in the migrating diurnal tide dw1 eastward propagating nonmigrating tides with zonal wave numbers 2 and 3 de2 and de3 and a 20 hr eastward propagating wave with zonal wave number 2 20e2 because we have included the lower atmospheric source of nonmigrating tides de2 and de3 are present with relatively large amplitudes in the mlt even in the absence of planetary wave forcing the 20e2 wave is produced by the nonlinear interaction between the de3 and the six day planetary wave and its large amplitude indicates the importance of including the realistic spectra of nonmigrating tides in numerical simulations of planetary waves the gswm simulations reveal that the dw1 is not significantly influenced by the changes in the zonal mean winds we thus conclude that the dw1 changes are driven by a combination of changes due to nonlinear interaction with the six day planetary wave as well as changes due to zonal asymmetries that result from the six day planetary wave the six day planetary wave induced changes in zonal mean zonal winds lead to a general reduction in the amplitude of de2 and de3 and introduce a slight periodic behavior in these tides the effect of changing zonal mean zonal winds appears to be the primary driver of the changes in the de2 however for de3 although the changes that can be attributed to zonal mean zonal wind variability are not insignificant the primary driver of the de3 perturbations appears to be the nonlinear interaction with the six day planetary wave last we demonstrate that the day to day changes in the de3 introduce similar day to day changes in the daytime wave number 4 longitude structure in the low latitude ionosphere these results indicate that short term variability in the low latitude ionosphere is likely to be driven by similar short term variability in nonmigrating tides in the mlt

fine structure of a postfailure wadati benioff zone the hypocentral distribution of locally recorded aftershocks of the great ms 8 1 michoacan mexico earthquake of september 19 1985 defines a narrow wadati benioff zone structure roughly 10 km thick dipping 14 at n23 e this is in good agreement with the source geometry obtained by waveform modeling of the 1985 michoacan mainshock and the large 1979 petatlan earthquake in the adjoining region we inverted for the crustal velocity structure in the epicentral region by applying the levenberg marquardt non linear least squares algorithm to our local aftershock data the velocity model consists of a layer with linearly increasing velocity in depth overlying a dipping constant velocity halfspace our hypocentral location program uses a velocity model of the same form together with ray tracing the earthquake hypocentral resolution obtained with this program is significantly better than that from conventional approaches hypo and looks very promising for use in velocity structures with an important dipping interface like subduction zones

derivation of a reference shear wave velocity model from empirical site amplification abstract the definition of a reference bedrock condition representative of a region of interest is of great significance in seismic hazard assessment it is highly beneficial when ground motion prediction equations are referenced to a specific site condition particularly in the case of site specific seismic hazard analyses when known the effect of any given site with respect to the reference can then be applied to the predicted ground motion however the choice of a reference velocity profile is not straightforward mainly due to the high variability of the velocity structure in the shallower layers a new method to define the regional reference rock profile is proposed the method relates quarter wavelength average velocity at a site to frequency dependent amplification a reference bedrock velocity profile can then be directly defined in relation to expected amplification characteristics over a number of sites we compare 27 quarter wavelength velocity profiles from seismic station locations in switzerland with empirical amplification functions derived from spectral modeling from this comparison a set of frequency dependent calibration relationships is established assuming that the reference profile is defined by a lack of any relative amplification the quarter wavelength velocity profile that corresponds to unitary spectral amplification can be extracted the reference velocity profile can then be obtained through an inversion procedure and defines the reference for the ground motion prediction equation gmpe the proposed reference velocity profile is compared with previous reference velocity profiles a good agreement is found between the different methods additionally an estimation of the transfer function for the swiss reference rock condition is provided this can be used to correct recorded or estimated spectral amplitudes for the local response of the reference site finally it is shown that the coefficients from the aforementioned correlations can be used to estimate a generic amplification function at any site with a known quarter wavelength velocity profile

gas geochemistry applied to earthquake prediction an overview terrestrial gases in groundwater and soil air have been extensively studied in recent years in seismically active areas especially in ussr china japan and united states in search of premonitory changes that might be useful for earthquake prediction concentrations of radon helium hydrogen mercury carbon dioxide and several other volatiles have been found generally to be anomalously high along active faults suggesting that the faults may be paths of least resistance for the terrestrial gases generated or stored in the earth to escape to the atmosphere temporal gas concentration changes with durations of a few hours to many months have been observed before many large earthquakes at a relatively small number of favorably situated stations at epicentral distances of up to several hundreds of kilometers these sensitive stations are generally located along active faults especially at intersections or bends of faults or some other structurally weak zones possibly because of tectonic strain concentration at such places however gas concentrations especially those measured at or near the ground surface may also be significantly affected by meteorological hydrological and other nontectonic changes in the environment the nontectonically induced variations must be carefully eliminated or recognized in the search of true earthquake related anomalies

dynamics of the equatorial mesosphere first results with a new generation partial reflection radar the first observations of mesospheric winds made between january august 1990 with an mf partial reflection radar located on christmas island 2 n 157 w in the central pacific are described the mean zonal winds are in general westward but show clear evidence for a wave driven circulation power spectral studies indicate that waves are present over a wide range of periods ultra fast kelvin waves are especially evident in january march with peak amplitudes 20 ms 1 and intrinsic phase speeds of 150 ms 1 indicated the kelvin waves are estimated to contribute an eastward acceleration of up to 10 ms 1 day 1 gravity wave amplitudes are also found to be almost as large as those observed at mid latitude sites which suggests that convection is a major source of gravity wave activity

two day wave structure and mean flow interactions observed by radar and high resolution doppler imager data obtained with four mf and meteor radars at equatorial and subtropical sites and with the high resolution doppler imager hrdi instrument aboard the uars satellite were used to examine the structure wave mean flow interactions and potential sources of the 2 day wave in the middle atmosphere during three southern hemisphere summers the three wave events were highly transient having typical durations of 20 to 30 days and exhibiting modulation at shorter periods temporal variations were found to exhibit good correlations between radar and hrdi data radar and hrdi data were used to estimate those components of the eliassen palm flux that could be assessed with these data meridional fluxes of momentum and heat were computed using hrdi data and agree reasonably with the momentum fluxes computed from radar data at discrete locations these fluxes were found to exhibit consistent latitudinal structures each year suggesting systematic wave excitation and wave mean flow interactions meridional momentum flux gradients were seen to be anticorrelated with zonal wind accelerations in a manner consistent with wave forcing of the large scale circulation the apparent wave mean flow interactions suggest that the 2 day wave could be a transient response to baroclinic instability of the summer hemisphere mesospheric jet a calculation of the meridional gradient of quasi geostrophic potential vorticity using hrdi winds and the cospar international reference atmosphere cira 1986 temperatures exhibits a region of instability in the lower and middle mesosphere extending into subtropical latitudes and provides additional evidence of a possible source of this motion via baroclinic instability of the summer hemisphere jet structure

some seasonal hemispheric similarities in ƒ o f2 quasi 2 day oscillations the annual variations of the amplitude period and probability of existence of of2 quasi 2 day oscillations at middle latitudes in both northern and southern hemispheres are investigated the of2 hourly data for the period 1977 1982 for stations kiev 50 5 n 30 5 e and wakkanai 45 39 n 141 69 e for the northern hemisphere and kerguelen 49 35 s 70 24 e and campbell island 52 6 s 169 1 e for the southern hemisphere are used for analysis it is found that there is a strong tendency for hemispheric similarities in the seasonal variations of oscillation amplitude period and probability of existence the annual variations of the oscillation amplitude are modulated by the 12 month hemispheric and semiannual geomagnetic waves the dominant period of oscillation is maximum in summer 50 51 hours and minimum in winter 47 49 hours and the probability of existence has a maximum in the summer half year and minimum in the winter half year the seasonal similarities in the annual variations of the oscillation period and the probability of existence show the possible influence of the planetary 2 day wave in the middle neutral atmosphere on the electron density variations in the f region

a comparison of observed and simulated site response in the rhone valley summary site effects in the city of sion in the rhone valley are analysed from weak motion signals recorded on a dense temporary array we simulate the recorded events with a 3 d finite differ ence method for frequencies up to 4 hz using a recently developed velocity model of the sion basin site to reference fourier spectral ratios are computed from 16 local and regional events all sites exhibit amplification factors of up to 12 between 0 5 and 0 6 hz which can be reproduced by the numerical simulations by rotating the weak motion to directions parallel and perpendicular to the valley axis we show that this low frequency amplification is caused by the sh00 and sv0 fundamental modes of 2 d resonance additional peaks of amplification can be observed at higher frequencies with amplification factors of up to 20 at some sites application of the high resolution frequency wavenumber and the multiple signal char acterization method to the vertical component of recorded and simulated signals show that edge generated surface waves arriving from almost all directions dominate the wavefield at 1 25 and 2 50 hz peak ground velocities computed from the simulated ground motion show interference patterns that depend strongly on the incidence direction and the computed amplification of peak ground velocities are generally in agreement with the observations we conclude that the complex 3 d geometry of the basin needs to be considered to evaluate site effects up to at least 2 5 hz

evidence for nonlinear coupling of planetary waves and tides in the antarctic mesopause analyses of hourly mean meridional and zonal winds near 95 km observed with the meteor radar system at molodezhnaya station 68 s 45 e during 1990 reveal the presence of long period 2 18 day waves with dominant periods corresponding to those of rossby normal modes modified by mean zonal winds time varying analyses indicate that although significant contributions at planetary wave periods persist with nearly constant periods for intervals of days to weeks temporal variability of these periods is observed over longer intervals tidal motions which mainly consist of the semidiurnal and the diurnal periods demonstrate considerable modulation of their amplitudes that vary with time the observed tidal amplitude modulations are investigated through bispectral analyses the results of these analyses suggest nonlinear interactions of quadratic form between oscillations with periods in the range of 2 to 19 days and the diurnal and semidiurnal tides at various intervals during 1990

coordinated observations of 8 and 6 hr tides in the mesosphere and lower thermosphere by three meteor radars near 60 s latitude

ground motion prediction model for vertical response spectra from mexican interplate earthquakes abstract we present ground motion prediction equations gmpes for vertical response spectra from mexican interplate earthquakes at rock sites national earthquake hazards reduction program b class two options to obtain the vertical response spectrum are presented 1 directly from the vertical attenuation model and 2 by multiplying the horizontal spectral ordinates by the vertical to horizontal ratios the equations were built as functions of magnitude and distance to the fault surface of the earthquake using 40 interplate earthquakes we compared our results with previous attenuation models for inslab and interplate earthquakes in mexico and other vertical attenuation models in the world the predicted intensities from the model were found to be in broad agreement with models derived with other models worldwide not many vertical and or vertical to horizontal attenuation models were found in the literature although the vertical response of structures is used in practice and included in design codes nevertheless it seems to be a trend to pay more attention to this model there was also found to be a lack of gmpes for vertical response spectra applicable to subduction interplate earthquakes for a large range of distances and the region under study therefore an attenuation model for interplate earthquakes was developed for distances up to around 400 km and m w from 5 to 8 the model could be useful for probabilistic seismic hazard assessment and as an aid for code writers

the quasi two day wave event of january 1984 and its impact on the mean mesospheric circulation abstract studies of the quasi two day wave show that it is a summertime phenomenon in the summer of 1983 84 at adelaide 35 s 138 e the main phase of the wave appeared as a pulse in mid january which lasted about seven cycles 14 days coincident with the onset of the pulse a temporary but substantial change occured in the prevailing circulation throughout a deep layer of the upper mesosphere a perturbation of more than 10 m s 1 occurred in the northward flow whereas the change in the zonal flow about 30 m s 1 westward actually caused a reversal of the prevailing eastward simulation above 84 km it is suggested that these changes in the prevailing circulation were a response to the wave pulse a simple calculation is performed to estimate the anticipated response to the observed wave event under plausible assumptions about the magnitude of mean and eddy dissipation processes predicted circulation changes agree reasonably well with those observed it is concluded that such events have a substan

reference s wave velocity profile and attenuation models for ground motion prediction equations application to japan defining the reference rock or soil condition related to ground motion prediction is an important aspect of seismic hazard analysis in a previous study by the authors a method was proposed to establish a reference rock profile for switzerland through the comparison of empirical amplification functions with shear wave velocity profiles at 27 selected sites of the swiss national seismic network the retrieved velocity profile served as reference for a regional ground motion prediction equation however a lacking piece of information remained the anelastic attenuation for such a reference profile reference attenuation is essential to correctly model and interpret amplification at high frequencies in the present study we extended our approach to simultaneously model both the reference shear wave velocity profile and the corresponding attenuation for japan we compared site specific attenuation measurements with quarter wavelength average velocities at 36 soil and rock sites from the japanese kik net strong motion network the selected sites are characterized by a lack of observed resonance phenomena in order to avoid trade off between amplification and attenuation effects we establish a parametric model through regression analysis the resulting model gives us the possibility to estimate anelastic attenuation of a rock site with a given velocity profile and provides the base for host to target adjustments of real or modeled ground motion

the effect of quaternary alluvium on strong ground motion in the coyote lake california earthquake of 1979 abstract the effect of alluvium on strong ground motion can be seen by comparing two strong motion records of the coyote lake california earthquake of 6 august 1979 m l 5 9 one record at a site on franciscan bedrock had a peak horizontal acceleration of 0 13 g and a peak horizontal velocity of 10 cm sec the other at a site 2 km distant on 180 meters of quaternary alluvium overlying franciscan had values of 0 26 g and 32 cm sec amplifications by factors of 2 and 3 horizontal motions computed at the alluvial site for a linear plane layered model based on measured p and s velocities show reasonably good agreement in shape with the observed motions but the observed peak amplitudes are greater by a factor of about 1 25 in acceleration and 1 8 in velocity about 15 per cent of the discrepancy in acceleration and 20 per cent in velocity can be attributed to the difference in source distance the remainder may represent focusing by refraction at a bedrock surface concave upward there is no clear evidence of nonlinear soil response fourier spectral ratios between motions observed on bedrock and alluvium show good agreement with ratios predicted from the linear model in particular the observed frequency of the fundamental peak in the amplification spectrum agrees with the computed value indicating that no significant nonlinearity occurs in the secant shear modulus computations show that nonlinear models are compatible with the data if values of the coefficient of dynamic shear strength in terms of vertical effective stress are in the range of 0 5 to 1 0 or greater the data illustrate that site amplification may be less a matter of resonance involving reinforcing multiple reflections and more the simple effect of the low near surface velocity application of traditional seismological theory leads to the conclusion that the site amplification for peak horizontal velocity is approximately proportional to the reciprocal of the square root of the product of density and shear wave velocity

determination of shallow shear wave velocity profiles in the cologne germany area using ambient vibrations summary we have used both single station and array methods to determine shallow shear velocity site profiles in the vicinity of the city of cologne germany from ambient vibration records based on fk analysis we assume that fundamental mode rayleigh waves dominate the analysed wavefield in the frequency range of 0 7 2 2 hz according to this view a close relation exists between h v spectral ratios and the ellipticity of the contributing rayleigh waves the inversion of the shape of h v spectral ratios then provides quantitative information concerning the local shear wave velocity structure however based on tests with synthetic data believed to represent a typical situation in the lower rhine embayment dispersion curves were found to provide stronger constraints on the absolute values of the velocity depth model than the ellipticities the shape of the ellipticities was found to be subject to a strong trade off between the layer thickness and the average layer velocity we have made use of this observation by combining the inversion schemes for dispersion curves and ellipticities such that the velocity depth dependence is essentially constrained by the dispersion curves while the layer thickness is constrained by the ellipticities in order to test this method in practice we have used array recordings of ambient vibrations from three sites where the subsurface geology is fairly well known and geotechnical information is at least partially available in order to keep the parameter space as simple as possible we attempted to fit only a single layer over a half space model however owing to earlier studies from the region we assume a power law depth dependence for sediment velocities for all three sites investigated the inversion resulted in models for which the shear wave velocity within the sediment layer both in absolute value at the surface and in depth dependence are found to be remarkably similar to the results obtained by budny from downhole measurements this is strong support for the interpretation of h v spectral ratios as rayleigh wave ellipticities for all three sites the predicted sh wave site amplification factors at the fundamental frequency are of the order of 5 6 with a slightly smaller value south of cologne

characterizing the vertical to horizontal ratio of ground motion at soft sediment sites a predictive equation to obtain the vertical to horizontal ratio v h of ground motion for rock sites has been established in a previous article the method was based on the comparison between v h of fourier and response spectra of earthquakes with the quarter wavelength average velocity at discrete frequencies we extend this approach to account for resonance phenomena at soft sediment sites in order to do so a new parameter is defined and included in the comparison with the v h spectra the new parameter is directly derived from the quarter wavelength velocity and represents the frequency dependent seismic impedance contrast at the site we show that extending the correlation in this three dimensional space is beneficial to reconstruct v h of the 5 damped response spectra at soft sediment sites v s 30 800 m s for which a shear wave velocity profile is available in this study we analyze 220 sites of the japanese kik net strong motion network these sites were selected from the entire network through comparison of the fundamental frequencies estimated from the recordings and by indirect modeling methods from the analysis two types of predictive equations are then established the first based on frequency dependent and the second on frequency independent correlations these can subsequently be used to reconstruct the v h spectrum at any site with a known shear wave velocity profile for both equations uncertainties of the v h models are provided and a sensitivity study to magnitude distance dependence is presented finally we show an example of the application of the model at four selected soft sediment sites of the swiss seismic network

observations of the phase locked 2 day wave over the australian sector using medium frequency radar and airglow data 1 the quasi 2 day wave with a nominal mean period just above 50 h is a significant feature of the 80 100 km altitude region in both hemispheres it becomes particularly prominent in the southern hemisphere summer at midlatitudes where a short time after summer solstice its amplitude rapidly increases and its mean period is found to be approximately 48 h producing an oscillation phase locked in local time this lasts for a few weeks presented here are observations of the meridional winds and airglow over two sites in australia for 4 years during the austral summers of 2003 2006 we show that during those times when the large amplitude phase locked 2 day wave pl tdw is present the diurnal tide greatly decreases this is consistent with the walterscheid and vincent 1996 model in which the pl tdw derives its energy from a parametric excitation by the diurnal tide these data also show that the diurnal tide is more suppressed and the pl tdw amplitude is larger in odd numbered years suggesting a biannual effect the airglow data indicated that for the pl tdw the winds and temperature are nearly out of phase when the pl tdw is present airglow amplitudes can become quite large a result dependent on the local time of the pl tdw maximum the airglow intensity response was in general much larger than what would be expected from the airglow temperature response suggesting that the pl tdw is causing a significant composition change possibly due to minor constituent transport

variability in the gas phase composition of fluids discharged from los azufres geothermal field mexico abstract studies related to hydrological structure of the los azufres geothermal field and its effects on the exploitation of the field for generation of electrical energy have included a program of sampling and chemical analysis of fluids discharged by a number of deep wells in continuous production chemical analysis of the gaseous phase includes monitoring of co 2 h 2 s nh 3 h 2 he n 2 ch 4 and 222 rn five wells in los azufres field were periodically sampled during 1983 1988 the monitoring program has shown considerable variability in the gas concentrations of fluids before mid 1985 the base line concentrations of the gases showed standard deviations between 8 and 28 during the later period the average concentrations of different gases ranged from 37 to much higher values above the base line the largest variations are observed in he co 2 and 222 rn this variability is interpreted in terms of 1 addition of excess steam 2 a possible relationship with earthquake events that occurred in mexico during september 19 21 1985 and early may to early june of 1987 and 3 more recent variations after mid 1987 increased exploitation of the field