very short term earthquake precursors from gps signal interference based on the 2013 nantou and rueisuei earthquakes taiwan abstract we set up a gps network with 17 continuous gps cgps stations in southwestern taiwan to monitor real time crustal deformation we found that systematic perturbations in gps signals occurred just a few minutes prior to the 2013 nantou ml 6 5 and rueisuei ml 6 4 earthquakes in taiwan the anomalous pseudorange readings were several millimeters higher or lower than those in the background time period these systematic anomalies were found as a result of interference of gps l band signals by electromagnetic emissions ems prior to the mainshocks the ems may occur in the form of harmonic or ultra wide band radiation and can be generated during the formation of mode i cracks at the final stage of earthquake nucleation we estimated the directivity of the likely em sources by calculating the inner product of the position vector from a gps station to a given satellite and the vector of anomalous ground motions recorded by the gps the results showed that the predominant inner product generally occurred when the satellite was in the direction either toward or away from the epicenter with respect to the gps network our findings suggest that the gps network may serve as a powerful tool to detect very short term earthquake precursors and presumably to locate a large earthquake before it occurs nevertheless a direct measurement of ems at the site of the gps array is required in future studies to confirm this hypothesis

anomalous pre seismic transmission of vhf band radio waves resulting from large earthquakes and its statistical relationship to magnitude of impending earthquakes summary to confirm the relationship between anomalous transmission of vhf band radio waves and impending earthquakes we designed a new data collection system and have documented the anomalous vhf band radio wave propagation beyond the line of sight prior to earthquakes since 2002 december in hokkaido northern japan anomalous vhf band radio waves were recorded before two large earthquakes the tokachi oki earthquake mj 8 0 mj magnitude defined by the japan meteorological agency on 2003 september 26 and the southern rumoi sub prefecture earthquake mj 6 1 on 2004 december 14 radio waves transmitted from a given fm radio station are considered to be scattered such that they could be received by an observation station beyond the line of sight a linear relationship was established between the logarithm of the total duration time of anomalous transmissions te and the magnitude m or maximum seismic intensity i of the impending earthquake for m4 m5 class earthquakes that occurred at depths of 48 54 km beneath the hidaka mountains in hokkaido in 2004 june and 2005 august similar linear relationships are also valid for earthquakes that occurred at different depths the relationship was shifted to longer te for shallower earthquakes and to shorter te for deeper ones numerous parameters seem to affect te including hypocenter depths and surface conditions of epicentral area i e sea or land this relationship is important because it means that pre seismic anomalous transmission of vhf band waves may be useful in predicting the size of an impending earthquake

ageostrophic motions in the stratosphere from satellite observations abstract geopotential height fields based on high vertical resolution radiometer measurements have been used to infer the circulation in the stratosphere from 100 to 1 mb in the northern hemisphere on a daily basis during february and march of 1979 initial calculations were based on geostrophy in the traditional way in addition to demonstrating the benefits of high vertical resolution these calculations show that for the disturbed conditions present at this time many of the terms in the momentum equation which were neglected would have made nonnegligible contributions to the balance of terms in particular the convergence of meridional wave flux can affect the zonally averaged meridional component of the momentum budget ageostrophic terms can affect the zonally varying part of the momentum budgets as well although an accurate assessment of their importance is complicated by nonlinear processes these and other results suggest that studies using diagnostically derived winds should include a scal

multisatellite observations of an intensified equatorial ionization anomaly in relation to the northern sumatra earthquake of march 2005 here we report multisatellite observations of ionospheric disturbances in relation to the occurrence of the m8 7 northern sumatra earthquake of 28 march 2005 the demeter detection of electro magnetic emissions transmitted from earthquake regions and champ challenging minisatellite payload satellite data were investigated to find possible precursory and postevent phenomena it was found that eia equatorial ionization anomaly strength expressed in the apex height derived from the champ plasma density profile was intensified along the orbits whose longitudes were close to the epicenter within about a week before and after occurrence of the earthquake increases in electron and o density along the orbits close to the epicenter were also observed in the demeter measurements the normalized equatorial plasma density derived from the demeter measurements showed intensification about a week before and after the earthquake reaching maximum the day after the shock and afterward disappearing in addition similar behavior of the eia enhancements related to the m8 0 pisco earthquake of 15 august 2007 was observed surveys of space weather and geomagnetic activities excluded the possibility that these fluctuations were caused by changes in space weather or by a geomagnetic storm statistical analyses of the longitudinal variation revealed that the eia was enhanced in the west of the epicenter and reduced in the east of the epicenter and this fits the increased conductivity model based on these observations we proposed a revised view of seismo ionospheric coupling in the region of the geomagnetic equator to explain the eia features observed in this study

linear wavetrains in models of the stratosphere experiments with a primitive equation model of the stratosphere and mesosphere are described which investigate the effect on the stratosphere of the growth of localized stationary forcing in the troposphere two basic states are used which are representative of stratospheric flow in early and late winter in the southern hemisphere simple mechanistic models are then introduced to examine the wave phenomena which occur during the first 10 days of the experiments when the dynamics are known to be linear the localized forcing grows to a peak amplitude of 600 gpm and half width of 15 of latitude values typical of the mid latitude upper troposphere stratospheric travelling waves are excited with phase velocities which are sensitive to the zonal mean winds and to the speed of the switch on of the forcing and wave activity spreads quickly from the localized forcing with a typical vertical group velocity of 10 km d 1 strong horizontal curvature in the basic states can profoundly affect the vertical and horizontal structures of the wavetrains mid latitude regions of negative northward potential vorticity gradient in the stratosphere as seen in the southern hemisphere in late winter lead to the confinement and amplification of waves in high latitudes three dimensional diagnostics of wave activity propagation reveal wave reflections missed by zonally averaged ep flux diagnostics significant wave reflection and trapping occur on the flow from late winter eventually producing a steady linear wavetrain with an intense local centre of circulation in the upper stratosphere the maximum anomaly being 1000gpm at 1mb it is argued that such wavetrains are unrealistic because nonlinear ageostrophic winds drive the dynamics away from any linear steady state

an observational study of traveling planetary waves in the southern hemisphere abstract southern hemisphere analyses from the surface to 2 mb and from 20 to 80 s for the period may september 1979 have been used to study the structure of traveling planetary waves space time cross spectral analysis of the height field has been employed to define the amplitude and phase for both the eastward and westward moving components of particular combinations of zonal wavenumber and frequency band latitude height contour plots of power phase and coherence squared show that westward moving waves have structure characteristic of barotropic external modes and are coherent across a broad range of latitudes and from the surface to 2 mb the highest level analyzed eastward moving waves on the other hand have more rapid phase variations especially in the troposphere and appear more baroclinic the tropospheric structure of the moving components of wavenumbers 1 4 is as one would expect for baroclinically unstable modes of the charney type wavenumbers 1 and 2 both have double amplitude maxima i

observations of wave mean flow interaction in the southern hemisphere abstract variations of zonal mean and eddy properties in the southern hemisphere during the winter of 1979 are studied several periods of enhanced wave activity and rapid zonal mean changes are observed during these periods of rapid change both the actual zonal wind tendency and the eliassen palm flux divergence have a dipole pattern in the upper stratosphere with positive values in high latitudes and negative values in middle and low latitudes the positive values of e p flux divergence near the pole are particularly interesting since they suggest a possible source of wave activity in this region the stationary component of wavenumber 1 and the eastward traveling component of wavenumber 2 contribute most to the dipole pattern of wave driving in the stratosphere a nearly uniform deceleration of the mean flow in the troposphere is contributed to by all zonal wavenumbers from 1 to 10 the lower wavenumbers contribute most to the driving in high latitudes while the driving in lower latitudes is contri

climatology and interannual variability of wave mean flow interaction in the southern hemisphere abstract the climatology and interannual variability of wave mean flow interaction in the southern hemisphere 20 80 s 0 55 km is described for the winter months of june september based on a sample of four years 1979 82 the stratospheric jet stream shifts downward and poleward over the course of the winter in response to seasonal variations in thermal forcing the shift occurs at different times in different years however so that the months of july and august show substantial interannual variability of monthly mean zonal winds the poleward and downward shift of the jet axis in an individual year is usually abrupt and occurs in association with a burst of upwardly propagating planetary waves the driving of the mean flow in the stratosphere generally has a dipolar structure with easterly accelerations near 40 s and westerly accelerations in polar latitudes the structure of the wave driving is consistent with the structure of the observed mean flow accelerations

atmospheric anomalies observed during earthquake occurrences 1 appearance of anomalies in the atmosphere before earthquakes eqs has been verified through observation of anomalous transmission of vhf electromagnetic em waves beyond line of sight anomalous increase of the received intensity for a few minutes several hours on a day was identified by the previous 15 day running median and its inter quartile range the cross correlation between the eq occurrences and the anomalies shows that the appearance of anomalies was significantly enhanced within 5 days before m 4 8 eqs the one day average number of the anomaly appearance within 5 days was found 2 4 times larger than that of other days through the polarization measurement of the received em waves the anomalies were found to occur in the atmosphere index terms 6904 radio science atmospheric propagation 6964 radio science radio wave propagation 7223 seismology seismic hazard assessment and prediction citation fujiwara h m kamogawa m ikeda j y liu h sakata y i chen h ofuruton s muramatsu y j chuo and y h ohtsuki 2004 atmospheric anomalies observed during earthquake occurrences geophys res lett 31 l17110

a statistical study on the correlation between lower ionospheric perturbations as seen by subionospheric vlf lf propagation and earthquakes 1 the subionospheric vlf lf propagation is extensively used to investigate the lower ionospheric perturbation in possible association with earthquakes an extensive period of data over 7 yr from january 2001 to december 2007 and a combination of different propagation paths in and around japan are used to examine the statistical correlation between the vlf lf propagation anomaly average nighttime amplitude dispersion and nighttime fluctuation and earthquakes with magnitude 6 0 it is then found that the propagation anomaly exceeding the 2 standard deviation criterion indicating the presence of ionospheric perturbation is significantly correlated with earthquakes with shallow depth 40 km finally the mechanism of seismoionospheric perturbations is discussed

on the three dimensional propagation of stationary waves abstract a locally applicable nonzonally averaged conservation relation is derived for quasi geostrophic stationary waves on a zonal flow a generalization of the eliassen palm relation the flux which appears in this relation constitutes it is argued a useful diagnostic of the three dimensional propagation of stationary wave activity this is illustrated by application to a simple theoretical model of a forced rossby wave train and to a northern hemisphere winter climatology results of the latter procedure suggest that the major forcing of the stationary wave field derives from the orographic effects of the tibetan plateau and from nonorographic effects diabatic heating and or interaction with transient eddies in the western north atlantic and north pacific oceans and siberia no evidence is found in the data for wave trains of tropical origin forcing by the orographic effects of the rocky mountains seems to be of secondary importance

planetary wave mean flow interaction in the stratosphere a comparison between northern and southern hemispheres by the use of stratospheric height and temperature field data obtained from the tiros satellite dynamical interaction between planetary waves and mean zonal winds in the stratosphere is investigated special attention is paid to differences between northern and southern hemispheres an analysis is made for pressure levels from 70 to 0 4 mb during the period from june 1981 to may 1982 eliassen palm e p flux diagnostics are used as a powerful and useful tool to investigate the wave mean flow interaction from winter to summer the seasonal marches of wave activity measured by the e p flux and of mean zonal wind are different between the two hemispheres in the nh wave activity varies intermittently with a characteristic timescale of about two weeks once the core of the stratospheric westerly jet shifts poleward due to a minor warming the subsequent wave activity breaks the westerlies dramatically to replace them by the easterlies in association with the sudden warming whilst in the sh wave activity in mid winter is quiet corresponding to small time variations of the maximum westerly speed in late winter the core of the stratospheric westerly jet suddenly shifts poleward and downward due to a wavenumber 2 minor warming after the shifting of the westerly jet the wave activity of wavenumber 1 is enhanced and continues until early summer on the basis of this observational evidence we discuss i the seasonal evolutions of wave activity and the mean zonal wind ii the interannual variability of the stratospheric circulations and iii the time variation of wave activity

subionospheric vlf signal perturbations possibly related to earthquakes a likely vlf subionospheric signal effect related to seismic activity was first reported by hayakawa et al 1996a b in association with the great kobe earthquake we have analyzed similar data during periods around 10 other great earthquakes magnitude m 6 in order to understand the main features of such an effect the following characteristics emerged from our analysis the effect appears as a transient oscillation with a 5 to 10 day period which is initiated a few days before a large earthquake and decays over a few days to weeks after it it is mainly related to crustal earthquakes it appears when resonant atmospheric oscillations with periods in a range of 5 11 days exist before the earthquake the seismic influence on the vlf signal is probably explained by the generation of long period gravity waves during the earthquake process and their intensification at heights of 70 90 km

a systematic compilation of earthquake precursors article a survey of published scientific literature was undertaken to identify and catalog observed earthquake pre cursors the earthquake precursors selected for analysis included electric and magnetic fields gas emissions groundwater level changes temperature changes surface deformations and seismicity for each of these precursors the published scientific literature was searched to document the statistics of each reported earth quake precursor spatial extent time duration amplitude signal noise ratio to analyze dependence of the observable for each precursor on earthquake magnitude and to explore proposed physical models to explain eachearthquakeprecursor somegeneralcharacteristics wereobservedfortheseprecursoryphenomena first the largest amplitude precursory anomalies tend to occur before the largest magnitude earthquakes also the number of precursory anomalies tends to increase the closer in time to the occurrence of the earthquake finally theprecursoryanomaliestendtooccurclosetotheeventualepicenterof theearthquake ingeneral the physical models indicate that all of the precursory phenomena are related to deformation that occurs near the fault prior to the main earthquake while the models provide plausible physical explanations for the pre cursors there are many free parameters in the models that are poorly resolved

seismo ionospheric signatures prior to m 6 0 taiwan earthquakes this paper examines variations of the greatest plasma frequency in the ionosphere fof2 recorded by the chung li ionosonde 25 0 n 121 1 e before m 6 0 earthquakes during 1994 1999 the 15 day running median and the associated inter quartile range are utilized as the reference and the upper or lower bounds to monitor the ionospheric fof2 variations for finding seismo ionospheric signatures precursors of the earthquakes it is found that precursors in the form of the recorded fof2 falling below its associated lower bound around 1200 1700 lt appear 1 6 days prior to these earthquakes on september 20 1999 ut september 21 taiwan local time a large mw 7 7 earthquake struck central taiwan near the small town of chi chi we analyzed the fof2 and found three clear precursors 1 3 and 4 days prior to the chi chi earthquake

short term earthquake prediction current status of seismo electromagnetics abstract loss of human lives as a result of earthquakes is caused overwhelmingly by the collapse of buildings within less than a few minutes of main shocks the most urgent countermeasure consists of two key elements one is strengthening of weak structures and the other is short term earthquake prediction short term prediction needs precursors although some promising precursors are reported the prevailing views in japan and elsewhere are overly pessimistic the pessimism largely roots in the fact that short term precursors are generally non seismic and tools developed for seismology are not designed to detect them nonetheless nationally funded large scale earthquake prediction programs always emphasize the need to reinforce seismometer networks they do not take into account the views of those in the science community who point to the importance of non seismic precursors while there are well founded causes to be skeptical the situation needs to be improved one reason for skepticism is that the observations of precursors have not yet been perfect enough and another is that some important fundamental aspects of non seismic precursors are still unresolved we review some of these problems

vertical zonal propagation of a stationary planetary wave packet abstract in order to explain why the aleutian high stands out in the winter stratosphere a complex fourier analysis is made of simulated and observed stationary waves it is found that in the troposphere the envelope of the time mean geopotential height consisting of wavenumbers 1 3 attains its major and minor maxima in the pacific and atlantic respectively the major maximum is dominated by wavenumbers 1 2 and shifts eastward with height in the stratosphere in the approximate direction of the group velocity and strengthens the aleutian high the minor maximum is dominated by wavenumber 3 and is confined in the troposphere

the importance of nonlinear wave processes in a quiescent winter stratosphere linear wave modelling about a zonally symmetric state is often assumed to be able to simulate accurately time averaged planetary wave geopotential heights in the stratosphere during quiescent winter periods we test this linear assumption by using a time dependent three dimensional primitive equation model of the stratosphere and mesosphere to simulate the quiescent winter stratospheric circulation during december 1980 the results from this simulation together with two other idealized integrations indicate that nonlinear wave interactions were crucial in accounting for the observed monthly mean wavenumber 1 planetary wave amplitude particularly in the upper stratosphere our results suggest that in general such interactions cannot be ignored for quantitatively accurate simulations of the middle atmosphere

investigation of ionospheric electron content variations before earthquakes in southern california 2003 2004 1 it has been proposed that earthquakes are preceded by electromagnetic signals detectable from ground and space based measurements ionospheric anomalies such as variations in the electron density a few days before earthquakes are one of the precursory signals proposed since global positioning system gps data can be used to measure the ionospheric total electron content tec the technique has received attention as a potential tool to detect ionospheric perturbations related to earthquakes here we analyze 2 years 2003 2004 of data from the southern california integrated gps network scign a dense network of 265 continuous gps stations centered on the los angeles basin for possible precursors this time period encompasses the december 2003 m6 6 san simeon and september 2004 m6 0 parkfield earthquakes we produce tec time series at all scign sites and apply three different statistical tests to detect anomalous tec signals preceding earthquakes we find anomalous tec signals but no statistically significant correlation in time or in space between these tec anomalies and the occurrence of earthquakes in southern california for the 2003 2004 period this result does not disprove the possibility of precursory phenomena but show the signal to noise ratio of a hypothetical tec precursor signature is too low to be detected by the analysis techniques employed here precursors may still be revealed for future large earthquakes in well instrumented areas such as california and japan if the tests can be developed into techniques that can better separate external influences from the actual tec signal

suspected seismo ionospheric coupling observed by satellite measurements and gps tec related to the m7 9 wenchuan earthquake of 12 may 2008 anomalous changes in the ionospheric conditions related to the wenchuan earthquake of 12 may 2008 are investigated using electron density ne from detection of electro magnetic emissions transmitted from earthquake regions demeter and champ satellites electric field from demeter and gps total electron content tec maps the normalized ne from the demeter satellite reveal that the previously reported tec increments before the earthquake can be considered as fragments of the gradual equatorial ionization anomaly eia enhancements near the epicenter longitude that began approximately 1 month before the earthquake and reached its maximum with an exceptionally large strength index 8 days prior to the main shock this feature is indirectly confirmed through the champ ne and gps tec data following the eia intensity peak disturbances in the ne and o density were observed in the nightside based on the concurrent electric field and ne changes it is suggested that eia intensification could be triggered by the e field disturbances over the epicenter