long period pulses in broadband records of near earthquakes broadband records of weak local earthquakes occasionally exhibit long period pulselike signals appearing exclusively on horizontal components such signals have been recorded at station sergoula in the corinth gulf by guralp cmg 3t 100 sec and wielandt streckeisen sts 2 120 sec instruments the pulses can be perfectly matched by the instrumental responses to a small step of acceleration similar pulses observed during moderate near earthquakes at stations of the greek national network equipped with lennartz le 3d 20s 20 sec sensors can be explained in the same way numerical simulation of the pulses allows their removal thus making the records fully utilizable for waveform inversion in seismic source studies prerequisite for that is precise knowledge of the instrument transfer function we found that poles and zeros of the cmg 3t and sts 2 sensors were consistent with those given by the manufacturer whereas those of the le 3d 20s were not we identified the latter by inversion of spontaneous pulses incidentally appearing in le 3d 20s records without relation to any earthquake what actually generates the earthquake related horizontal acceleration steps remains unclear rapid and permanently lasting tilt is a very likely candidate when we numerically model a coseismic near field static displacement we actually find a tilt step but its amplitude is several orders below the observed values we therefore rather speculate that it is a very local tilt triggered by high frequency ground vibrations

eliassen palm fluxes of the 2 day wave abstract high resolution doppler imager hrdi winds and temperatures are used to diagnose a 2 day wave event detected in the southern hemisphere during january 1994 a novel aspect of this study is the focus upon the wave fluxes throughout the 65 100 km range and their relationship to the background state a wave packet composed of zonal wavenumbers 2 3 and 4 propagates westward with a phase speed near 60 m s 1 the periods associated with zonal wavenumbers 2 3 and 4 are 3 5 2 1 and 1 7 days respectively the morphology of the 2 day temperature and wind fields is consistent with that of a developing baroclinic wave the divergence of the eliassen palm flux of zonal wavenumbers 2 4 is dominated by the vertical convergence of meridional heat flux the wave driving or eliassen palm flux divergence per unit mass is predominantly westward with magnitudes on the order of 5 m s 1 day 1 a steady state quasigeostrophic model of the mean meridionai circulation is used to estimate the mean wind respon

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

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

focal mechanisms of weak earthquakes from amplitude spectra and polarities the aspo method amplitude spectra and polarities for the focal mechanism retrieval from relatively weak events is based on a widely available instrumental setup a few broadband stations within a denser short period network collectively all stations provide the epicenter location complete records are taken from three component broadband stations without selecting a particular wave type or picking amplitudes it makes the method suitable for automated data processing and enables studies of the interference crustal phases only the amplitude spectra are inverted this is a robust feature which makes the method insensitive to any timing problems such as those due to uncertain origin time or due to technical failures the first motion polarities serve as an additional constraint of the amplitude spectra inversion only few clear polarities are taken from the nearest stations wher e they mostly belong to direct p waves the method seeks five parameters the focal depth scalar moment strike dip and rake green s function automatically including possible near field effects and interference e g surface waves is calculated by the discrete wavenumber method aspo works below the corner frequency and the time function is not being retrieved this feature not only minimizes the number of the inverted parameters but also speeds up the calculation because the lower the frequency the faster the discrete wavenumber run instead of an exceedingly slow 5 parameter grid search the inversion is organized in two steps i the depth and moment determination with a coarse grid search of the strike dip and rake and ii a fine grid search of the three source angles uncertainty of the best fitting solution is assessed from the minimum error value and from the scatter of the nodal lines and or p and t axes between min and min 10 the method was tested on the clustered m 3 5 earthquakes recorded by a temporary network of three cmg3 t broadband stations in western corinth gulf a fundamental problem is that the broadband stations suffer systematically from event induced instabilities at horizontal components if earthquakes of the studied magnitudes occur at short distances 10 30 km therefore the aspo method could not be applied below 0 1 hz as such the results are sensitive with respect to unknown crustal structure details and the focal mechanisms remain rather uncertain minimum error higher than 0 34 compared to synthetic tests with perturbed data in which the error is lower than 0 2 it is concluded that the crustal model needs further improvement

intraseasonal and interannual variability of the quasi 2 day wave in the northern hemisphere summer mesosphere this study uses global synoptic meteorological fields from a high altitude data assimilation system to investigate the quasi 2 day wave q2dw and migrating diurnal tide during the northern hemisphere nh summers of 2007 2009 by applying a two dimensional fast fourier transform to meridional wind and temperature fields we identify q2dw source regions and diagnose propagation of q2dw activity into the upper mesosphere and lower thermosphere we find that the q2dw in nh summer is composed primarily of westward propagating zonal wave number 3 and wave number 4 components that originate within baroclinically unstable regions along the equatorward flank of the summer midlatitude easterly jet the amplitude of the wave number 3 q2dw tends to peak in july while the amplitude of the wave number 4 q2dw tends to peak in late june and again in early august the seasonal mean q2dw amplitudes are largest in 2009 when the amplitude of the migrating diurnal tide in the upper mesosphere near 30 n was relatively weak however there is no evidence of rapid amplification of the q2dw via nonlinear interaction with the diurnal tide instead variations of q2dw amplitudes during nh summer appear to be linked to variations in the strength and location of the mesospheric easterly jet from one summer to the next with a stronger jet producing larger q2dw amplitudes linear instability model calculations based on the assimilated wind fields indicate that the fastest growing modes are zonal wave numbers 3 and 4 with periods near 2 days that originate in the vicinity of the easterly jet

an empirical model of the earth s horizontal wind fields hwm07 1 the new horizontal wind model hwm07 provides a statistical representation of the horizontal wind fields of the earth s atmosphere from the ground to the exosphere 0 500 km it represents over 50 years of satellite rocket and ground based wind measurements via a compact fortran 90 subroutine the computer model is a function of geographic location altitude day of the year solar local time and geomagnetic activity it includes representations of the zonal mean circulation stationary planetary waves migrating tides and the seasonal modulation thereof hwm07 is composed of two components a quiet time component for the background state described in this paper and a geomagnetic storm time component dwm07 described in a companion paper

a deterministic seismic hazard analysis for shallow earthquakes in greece abstract the maximum expected ground motion in greece is estimated for shallow earthquakes using a deterministic seismic hazard analysis dsha in order to accomplish this analysis the input data include an homogeneous catalogue of earthquakes for the period 426 bc 2003 a seismogenic source model with representative focal mechanisms and a set of velocity models because of the discrete character of the earthquake catalogue and of errors in location of single seismic events a smoothing algorithm is applied to the catalogue of the main shocks to get a spatially smoothed distribution of magnitude based on the selected input parameters synthetic seismograms for an upper frequency content of 1 hz are computed on a grid of 0 2 0 2 the resultant horizontal components for displacement velocity acceleration and dga design ground acceleration are mapped the maps which depict these results cannot be compared with previously published maps based on probabilistic methodologies as the latter were compiled for a mean return period of 476 years therefore in order to validate our deterministic analysis the final results are compared with pga estimated from the maximum observed macroseismic intensity in greece during the period 426 bc 2003 since the results are obtained for point sources with the frequency content scaled with moment magnitude some sensitivity tests are performed to assess the influence of the finite extent of fault related to large events sensitivity tests are also performed to investigate the changes in the peak ground motion quantities when varying the crustal velocity models in some seismogenic areas the ratios and the relative differences between the results obtained using different models are mapped and their mean value computed the results highlight the importance in the deterministic approach of using good and reliable velocity models

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

the 23 january 2014 jizan earthquake and its tectonic implications in southwestern saudi arabia abstract a moderate sized earthquake of mw 4 4 occurred in southwestern saudi arabia on 23 january 2014 the event is considered as the largest observed earthquake that has occurred in the epicentral area to examine the seismogenic stress regime and resolve the fault plane ambiguity the hypocenter locations and focal mechanisms were determined using well recorded waveforms of the broadband stations operated by the saudi geological survey the current analysis included dataset consisting of mainshock and a total number of 113 well located aftershocks focal mechanism solutions of the mainshock and fifteen aftershocks were determined the focal mechanism solutions were inverted using stress tensor inversion it indicates that the maximum compressive stress 1 has a nearly shallow plunge 11 8 of ese orientation and minimum compressive stress 3 has a shallow plunge 0 3 toward nne our results obtained from precise earthquake locations focal mechanism solutions and stress tensor inversion reveal dextral strike slip faulting over the ene wsw striking plane the analysis of coulomb failure stress emphasized the causative fault of the 2014 jizan earthquake sequence the active fault implies a reactivation of a high angle fault buried in the precambrian basement which is conjugate to the red sea spreading axis and nnw sse najd fault system the present study provided an impetus toward understanding the seismogenic stress regime in a virgin area

large scale waves in the mesosphere and lower thermosphere observed by saber observations made by the sounding of the atmosphere using broadband emission radiometry saber instrument on board nasa s thermosphere ionosphere mesosphere energetics and dynamics timed satellite have been processed using salby s fast fourier synoptic mapping ffsm algorithm the mapped data provide a first synoptic look at the mean structure and traveling waves of the mesosphere and lower thermosphere mlt since the launch of the timed satellite in december 2001 the results show the presence of various wave modes in the mlt which reach largest amplitude above the mesopause and include kelvin and rossby gravity waves eastward propagating diurnal oscillations non sunsynchronous tides and a set of quasi normal modes associated with the so called 2 day wave the latter exhibits marked seasonal variability attaining large amplitudes during the solstices and all but disappearing at the equinoxes saber data also show a strong quasi stationary rossby wave signal throughout the middle atmosphere of the winter hemisphere the signal extends into the tropics and even into the summer hemisphere in the mlt suggesting ducting by westerly background zonal winds at certain times of the year the 5 day rossby normal mode and the 4 day wave associated with instability of the polar night jet are also prominent in saber data

observations of the quasi 2 day wave from the high resolution doppler imager on uars a strong westward traveling oscillation with a period of 2 days and zonal wave number 3 is observed in the mesospheric and lower thermospheric winds from the high resolution doppler imager on the upper atmosphere research satellite the important events happen in january july and september october of which the occurrence in january is the strongest with an amplitude over 60ms 1 detailed analyses for the periods of january 1992 and january 1993 reveal a cause and effect relationship in the wave developing process at 95km the global structures of the wave amplitude and phase are also presented

observations of the 2 day wave in nmc stratospheric analyses abstract observational characteristics of the 2 day wave a westward propagating zonal wave 3 oscillation in the summer subtropical upper stratosphere and mesosphere are studied based on five years of national meteorological center nmc operational stratospheric analyses these data show episodic occurrence of the 2 day wave in the upper stratosphere in january centered near 20 s and july august centered near 20 n these episodes are strongly correlated with observed reversals of the zonal mean potential vorticity gradient near the core of the summer easterly jet consistent with previous suggestions that the 2 day wave is generated by an in situ instability of this jet on the other hand the horizontal and vertical structure of the waves is very similar to that calculated by salby for a global normal mode rossby wave the combination of normal mode structure and instability signature suggests that the 2 day wave is a near resonant mode forced by dynamical instability

short term variability in the migrating diurnal tide caused by interactions with the quasi 2 day wave 1 the migrating diurnal tide is one of the dominant dynamical features in the low latitudes of the earth s mesosphere and lower thermosphere mlt region representing the atmospheric response to the largest component of solar forcing ground based observations of the tide have resolved short term variations attributed to nonlinear interactions between the tide and planetary waves that are also in the region using the ncar thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm we simulate a quasi 2 day wave qtdw event under late january conditions in this case sideband sum and difference child waves are resolved indicating that a nonlinear interaction is occurring between the qtdw and the tide the migrating diurnal tide in the mlt displays local amplitude decreases of 20 40 as well as a shortening of vertical wavelength by roughly 4 km examining the physical mechanisms driving the interaction nonlinear advection is found to result in amplification of the tide in some regions and damping in others manifesting as increased smoothing of the tidal structure when the qtdw is present in the mlt additionally the qtdw also enhances the easterly summer mean wind jet that can also account for changes in tidal amplitude and vertical wavelength we find that qtdw induced background atmosphere changes in time gcm can drive tidal variability at levels greater than nonlinear advection a possibility not previously considered

an eastward propagating two day wave evidence for nonlinear planetary wave and tidal coupling in the mesosphere and lower thermosphere 1 temperature observations from the saber instrument on the timed spacecraft are used to investigate the structure and evolution of an eastward propagating zonal wavenumber 2 disturbance with a period near two days this oscillation obtains a maximum amplitude of nearly 10 k in the southern hemisphere mid latitudes during late january the timing and location of this planetary wave is coincident with the regular quasi two day wave intensification that occurs annually in late january the period wavenumber and spatial structure of the eastward propagating two day wave are consistent with a wave that results from a nonlinear interaction between the quasi two day wave and the migrating diurnal tide the existence of an eastward propagating wave with a period near two days coincident with the westward propagating two day wave will have an impact on the interpretation of ground based observations analysis of the saber temperature observations are utilized to determine the structure and evolution of both this eastward propagating two day wave and the classic westward propagating zonal wavenumber 3 quasi two day wave during january 2005

state of tectonic stress in northeast india and adjoining south asia region an appraisal an attempt is made to map the spatial variation of the tectonic stress pattern in northeast india and its adjoining south asia region using stress tensor inversion of some 516 fault plane solutions the bhutan himalaya and the arunachal himalaya are mapped with north south to north northwest south southeast compression the eastern himalaya syntaxis zone on the other hand shows a clockwise rotation a north northeast compression is dominant to the south in the intraplate part of the region the shillong plateau assam valley bengal basin bangladesh and tripura fold belt exhibit north northwest to north northeast compression orthogonal horizontal extension is dominant in southern tibet bhutan and partly in the syntaxis zone and the same is also observed in the shillong plateau and assam valley area of the intraplate region the indo burma ranges and the sagaing fault in the myanmar region show a northeast southwest compression an orthogonal horizontal northwest southeast extension is also observed in the sagaing fault zone a depth variation of the tectonic stress is observed below the indo burma ranges it changes from north south to northeast southwest in the southern part and from northeast southwest to north northeast south southwest in the northern part in the deeper seismogenic zone the stress inversion results of clusters of events in individual zones though mostly conformable with the average observations indicate a variation in the shillong plateau due to heterogeneity and tectonic complexity

the 6 5 day wave and its seasonal variability in the middle and upper atmosphere 1 the zonal wave number 1 planetary wave of period near 6 5 days is a robust feature in the mesosphere and lower thermosphere mlt region with prominent seasonal variability as revealed by ground based and satellite observations this wave and its seasonal variability are well reproduced in a recent one model year run of the national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm with its lower boundary specified according to the national centers for environmental prediction analysis year 1993 wavelet analysis of the model output shows that in the mlt region the wave maximizes before and after the equinoxes and minimizes at solstices the wave amplitudes at the equinoxes are smaller than the peaks before and after but are still larger than the wave amplitudes at solstices however at the lower boundary near 30 km the wave peaks are predominantly between fall and the following spring by examining the episodes of maximum and minimum wave amplitude and by conducting additional control experiments using the time gcm the structure of this planetary wave and the factors determining the wave characteristics and seasonal variability are studied in detail it is found that the wave source mean wind structure instability and the critical layers of the wave can all affect the wave response in the mlt region and can have a strong seasonal dependence before and after equinox the wave follows the waveguide and propagates from the stratosphere to the summer mesosphere mesopause where it may amplify due to baroclinic barotropic instability such instability is usually absent from the equinoctial atmosphere so that there is no wave amplification at equinox at solstice the wave decays significantly when propagating away from its winter source due to the strong eastward winter stratospheric jet in the summer side the westward jet is also strong and the meridional and vertical extension of the critical layer of the wave is large enough to enclose the instability in the summer mesosphere mesopause at middle to high latitudes the wave is thus reflected away and prevented from reaching and amplifying at the unstable region the seasonal variation of the quasi two day wave which has zonal phase speed similar to the 6 5 day wave is also studied using similar diagnostics it is further shown that within certain seasonal window periods the variability in the mlt especially the summer mlt may closely track the lower atmospheric variability associated with these waves

alleviation of a systematic westerly bias in general circulation and numerical weather prediction models through an orographic gravity wave drag parametrization systematic westerly biases in the northern hemisphere wintertime flow of the meteorological office 15 layer operational model and 11 layer general circulation model are described evidence that the failure to parametrize subgrid scale orographic gravity wave drag may account for such biases is presented this evidence is taken from aircraft studies surface pressure drag measurements and studies of the zonally averaged momentum budget a parametrization scheme is described in which the surface stress is proportional to the near surface wind speed and static stability and to the variance of subgrid scale orography the stress is absorbed in the vertical by considering the influence of such gravity wave activity on static stability and vertical wind shear a richardson number dependent wave breaking formulation is devised and the vertical stress profile determined by a saturation hypothesis whereby the breaking waves are maintained at marginal stability it is shown that wave breaking preferentially occurs in the boundary layer and in the lower stratosphere results from a simple zonally symmetric model show how the adjustment to thermal wind balance with a wave drag in the stratosphere warms polar regions by adiabatic descent and decelerates the mean westerlies in the troposphere the influence of the parametrization scheme on integrations of the 11 layer model is described and found to be generally beneficial in a discussion of the reasons why this problem has only recently emerged it is suggested that the satisfactory northern hemisphere winter circulations of previous coarser general circulation models were due to a compensation implied by underestimating both the surface drag and the horizontal flux of momentum by explicitly resolved large scale eddies

first seismic record for intra arc strike slip tectonics along the liquine ofqui fault zone at the obliquely convergent plate margin of the southern andes a temporal seismic network recorded local seismicity along a 130 km long segment of the transpressional dextral strike slip liquine ofqui fault zone lofz in southern chile seventy five shallow crustal events with magnitudes up to m tief w 3 8 and depths shallower than 25 km were observed in an 11 month period mainly occurring in different clusters those clusters are spatially related to the lofz to the volcanoes chaiten michinmahuida and corcovado and to active faulting on secondary faults further activity along the lofz is indicated by individual events located in direct vicinity of the surface expression of the lofz focal mechanisms were calculated using deviatoric moment tensor inversion of body wave amplitude spectra which mostly yield strike slip mechanisms indicating a ne sw direction of the p axis for the lofz at this latitude the seismic activity reveals the present day activity of the fault zone the recent m tief w 6 2 event near puerto aysen southern chile at 45 4 s on april 21 2007 shows that the lofz is also capable of producing large magnitude earthquakes and therefore imposing significant seismic hazard to this region

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

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

causes of the longitudinal differences in the equatorial vertical e b drift during the 2013 ssw period as simulated by the time gcm during stratospheric sudden warming ssw periods large changes in the low latitude vertical drift have been observed at jicamarca as well as in other longitudinal sectors in general a strengthening of the daytime maximum vertical drift with a shift from prenoon to the afternoon is observed during the january 2013 stratospheric warming significant longitudinal differences in the equatorial vertical drift were observed at jicamarca the previously reported ssw behavior prevails however no shift of the daytime maximum drift was exhibited in the african sector using the national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm the possible causes for the longitudinal difference are examined the timing of the strong ssw effect in the vertical drift 15 20 january coincides with moderate geomagnetic activity the simulation indicates that approximately half of the daytime vertical drift increase in the american sector may be related to the moderate geophysical conditions kp 4 with the effect being negligible in the african sector the simulation suggests that the wind dynamo accounts for approximately 50 of the daytime vertical drift in the american sector and almost 100 in the african sector the simulation agrees with previous findings that the migrating solar tides and the semidiurnal westward propagating tide with zonal wave number 1 sw1 mainly contribute to the daytime wind dynamo and vertical drift numerical experiments suggest that the neutral wind and the geomagnetic main field contribute to the presence absence of a local time shift in the daytime maximum drift in the american african sector

source process and tectonic implication of the january 20 2007 odaesan earthquake south korea abstract the source process for the 20th of january 2007 mw 4 5 odaesan earthquake in south korea is investigated in the low and high frequency bands using velocity and acceleration waveform data recorded by the korea meteorological administration seismographic network at distances less than 70 km from the epicenter synthetic green functions are adopted for the low frequency band of 0 1 0 3 hz by using the wave number integration technique and the one dimensional velocity model beneath the epicentral area an iterative technique was performed by a grid search across the strike dip rake and focal depth of rupture nucleation parameters to find the best fit double couple mechanism to resolve the nodal plane ambiguity the spatiotemporal slip distribution on the fault surface was recovered using a non negative least square algorithm for each set of the grid searched parameters the focal depth of 10 km was determined through the grid search for depths in the range of 6 14 km the best fit double couple mechanism obtained from the finite source model indicates a vertical strike slip faulting mechanism the nw faulting plane gives comparatively smaller root mean squares rms error than its auxiliary plane slip pattern event provides simple source process due to the effect of low frequency that acted as a point source model three empirical green functions are adopted to investigate the source process in the high frequency band a set of slip models was recovered on both nodal planes of the focal mechanism with various rupture velocities in the range of 2 0 4 0 km s although there is a small difference between the rms errors produced by the two orthogonal nodal planes the sw dipping plane gives a smaller rms error than its auxiliary plane the slip distribution is relatively assessable by the oblique pattern recovered around the hypocenter in the high frequency analysis indicating a complex rupture scenario for such moderate sized earthquake similar to those reported for large earthquakes

northwestern turkey earthquakes and the crustal structure inferred from surface waves observed in western greece records of several earthquakes occurring in turkey in 1999 obtained at broadband seismic stations in western greece have been used to study the dispersion of surface waves mainly love waves the observed group velocity dispersion curves have been inverted into horizontally layered models of the earth s crust by a modified method of the single parameter variation as compared with a previous model for the territory of greece the dispersion data require significantly lower velocities in the uppermost crust and smaller crustal thickness in particular the resulting model displays s wave velocities between 1 3 and 2 4 km sec in the upper 2 km and a crustal thickness of about 33 km manuscript received 31 july 2000

combined inversion of broadband and short period waveform data for regional moment tensors a case study in the alborz mountains iran abstract in this study we suggest a novel approach for the retrieval of regional moment tensors for earthquakes with small to moderate magnitudes the first modification is the combined inversion of broadband and short period waveform data the broadband waveforms are inverted in a frequency range suitable for surface waves whereas for the short period data a frequency range suitable for body waves is applied the second modification is the use of first motion body wave polarities to select the most probable solution out of all solutions from inversion to combine three different criteria for selecting the most probable solution i e residual from inversion double couple content of solution number of nonmatching first motion body wave polarities the l2 norm is applied to the normalized parameters we chose five earthquakes within the alborz mountains iran as a case study 3 1 m w 4 1 in this area several factors exacerbate the difficulty of performing inversion for moment tensors for example a heterogeneous station network and large azimuthal gaps we have demonstrated that our approach supplies reliable moment tensors when inversion from broadband data alone fails in one case we successfully retrieved a stable solution from short period waveform data alone thus our approach enables successful determination of seismic moment tensors wherever a sparse network of broadband stations has thus far prevented it

amplification of the quasi two day wave through nonlinear interaction with the migrating diurnal tide 1 we present a case study of the non linear interaction between the quasi two day wave q2dw and the migrating diurnal tide based on global synoptic meridional wind fields for january 2006 and january 2008 from a high altitude data assimilation forecast system we find large quasi two day wave amplitudes small diurnal tide amplitudes and phase locking of the q2dw with the diurnal cycle during january 2006 in january 2008 the amplitudes of the q2dw were much smaller with no evidence of phase locking while the tidal amplitudes were larger than in the 2006 case space time spectral analysis reveals an enhancement in a diurnal zonal wavenumber 6 feature in the january 2006 case which can be attributed to a non linear interaction between the q2dw and migrating diurnal tide the relatively strong summer easterly jet in the extratropical upper mesosphere during early january 2006 appears to have created conditions favoring this interaction

genetic waveform modeling for the crustal structure in northeast japan we propose a genetic algorithm ga search procedure for waveform modeling of local crustal earthquakes for optimal one dimensional 1 d crustal velocity model both waveforms and travel time data are used for the structure determination the use of travel times in model evaluation improves the waveform modeling performance in the sense of computation speed and accuracy we applied this method to broadband waveforms of a local crustal earthquake m 4 2 in northeast japan p wave velocities of the crustal model are found to be 4 95 0 30 5 9 0 02 and 6 51 0 20 km s for a surface layer upper crust and lower crust respectively the surface layer thickness and the conrad and moho depths are found to be 3 01 0 8 17 77 0 4 and 34 59 1 0 km respectively for epicentral distances 200 km our synthetic waveforms match the observed ones generally well early arrivals are mainly observed at stations near the pacific coast in the forearc area having a thinner crust in contrast delayed arrivals appear at stations near the volcanic front and back arc areas where low velocity anomalies exist due to the effect of the pacific slab dehydration and the hot upwelling flows in the mantle wedge in general our results agree well with the main tectonic setting of the study area which confirms the reliability of the proposed approach despite a 1 d velocity model is too simple to represent the complex crustal structure it is still required for the conventional routine analysis of seismology such as earthquake location and source parameter studies the current approach is considered as a step toward the genetic full waveform modeling for the 3 d velocity model estimation

weathered spheroids in a cretaceous tertiary boundary shale at woodside creek new zealand three types of spheroids are found in the iridium rich shale layer at the cretaceous tertiary boundary at woodside creek south island new zealand two of the types a and b consist mainly of microcrystalline goethite whereas the third type f contains an appreciable quantity of hematite there is a strong correlation between the iridium content of the spheroids and their matrices and the concentrations of other siderophiles such as chromium cobalt iron and nickel a similar pattern was observed for the chalcophiles arsenic copper and zinc it is suggested that spheroids of types a and b are weathering products derived from diagenetic pyrite clumps and that type f which contains hematite represents a further stage in the weathering process and was derived from goethite the original pyritic material could have readily scavenged arsenic and other siderophiles from the sea water column under organic rich reducing conditions at the end of the cretaceous and the siderophiles including iridium could have been incorporated into the original meteoritic material it was concluded therefore that types a b and f spheroids are weathering products and do not represent original meteoritic material

the quasi 2 day wave observed in the polar mesosphere comparison of the characteristics observed at tromso and poker flat 1 a comparison of the quasi 2 day wave q2dw observed at tromso 69 6 n 19 2 e and poker flat 65 2 147 6 w is presented at four heights of 70 76 82 and 88 km using wind data taken for 4 years from 1 november 1998 to 7 november 2002 the characteristics of the q2dw such as seasonal variation occurrence of period of maximum amplitude ratio of meridional to zonal amplitudes shape of altitude profile of phase and modulation of amplitude at a 4 10 days rate found at poker flat are very similar to those found at tromso reported by nozawa et al 2003 the activity of the q2dw is higher in winter than in summer for meridional and zonal components at the two sites long term variation i e seasonal variation of the q2dw is found to be similar between the two sites while short term variations i e over several days do not synchronize well with each other the ratio of amplitudes of the q2dw between the two sites varies mainly between 0 5 and 2 and there is no significant preference toward either site phase differences of q2dws between the two sites are examined and it is found that in phase like events are more frequently seen than out of phase like events at 76 82 and 88 km in winter and at 88 km in summer this can be interpreted to mean that the zonal wave number of the q2dw appears to be 2 or 4 more often than 3 in the polar upper mesosphere these results suggest that observed q2dws have features consistent with the rossby gravity wave mode but the amplitude and phase of the q2dw are affected significantly by local sources a possibility that the observed q2dw is an eastward moving wave is also discussed

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

moment magnitude m w and local magnitude m l relationship for earthquakes in northeast india an attempt has been made to examine an empirical relationship between moment magnitude mw and local magnitude ml for the earthquakes in the northeast indian region some 364 earthquakes that were recorded during 1950 2009 are used in this study focal mechanism solutions of these earthquakes include 189 harvard cmt solutions mw 4 0 for the period 1976 2009 61 published solutions and 114 solutions obtained for the local earthquakes 2 0 ml 5 0 recorded by a 27 station permanent broadband network during 2001 2009 in the region the mw ml relationships in seven selected zones of the region are determined by linear regression analysis a significant variation in the mw ml relationship and its zone specific dependence are reported here it is found that mw is equivalent to ml with an average uncertainty of about 0 13 magnitude units a single relationship is however not adequate to scale the entire northeast indian region because of heterogeneous geologic and geotectonic environments where earthquakes occur due to collisions subduction and complex intra plate tectonics

the two day wave in eos mls temperature and wind measurements during 2004 2005 winter 1 two day wave observations during january march 2005 are reported using the recently launched microwave limb sounder mls aboard nasa s earth observing system aura mission wave induced disturbances in temperature water vapor carbon monoxide and mls line of sight wind appear in early january peak near the end of january and persist until late february temperature and wind amplitudes as large as 9 k and 50 m s are observed near 90 km the wave disturbance is initially confined in the mid to low summer latitudes where the climatological summer easterly jet exhibits strong shear the wave then develops features akin to the third rossby gravity global normal mode with a weak temperature disturbance in the winter hemisphere anti symmetric about the equator and wind disturbance over the equator strong wind perturbation episode around 17 23 january 2005 in the mid latitude southern hemisphere coincides with a particularly intense solar proton event