characteristics of mesospheric gravity waves over the southeastern tibetan plateau region the tibetan plateau tp known as third pole of the earth has important influences on global climates and local weather an important objective in present study is to investigate how orographic features of the tp affect the geographical distributions of gravity wave gw sources three year oh airglow images november 2011 to october 2014 from qujing 25 6 n 103 7 e were used to study the characteristics of gws over the southeastern tp region along with the almost concurrent and collocated meteor radar wind measurements and temperature data from saber timed satellite the propagation conditions of three types of gws freely propagating ducted or evanescent were estimated most of gws exhibited ducted or evanescent characteristics almost all gws propagate southeastward in winter the gw propagation directions in winter are significantly different from other airglow imager observations at northern middle latitudes wind data and convective precipitation fields from the european centre for medium range weather forecasts reanalysis data are used to study the sources of gws on the edge of the tp using backward ray tracing analysis we find that most of the mesospheric freely propagating gws are located in or near the large wind shear intensity region 10 km 17 km on the southeastern edge of the tp in spring and winter the averaged value of momentum flux is 11 6 5 2 m2 s2 in winter and 7 5 3 1 m2 s2 in summer this work will provide valuable information for the gw parameterization schemes in general circulation models in tp region

source parameter inversion of a reservoir induced seismic sequence lake kariba africa 1963 september summary the depth and seismic source parameters of the three largest reservoir induced earthquakes associated with the impoundment of lake kariba africa were determined using a moment tensor formalism of the generalized inverse technique the events characterized by mb 5 5 consisted of the foreshock and main event 0640 and 0901 gmt 1963 september 23 and the principal aftershock 0703 gmt 1963 september 25 from the analysis of analogue rift valley source crustal models a three layer over a half space model were selected for the analysis of the lake kariba events the epicentral proximity and the comparable source parameters of the three large events suggest a common source fault with an approximate strike of s 9 w 4 dip of 62 10 and rake of 266 4 the body wave modelling indicates that the lake kariba events occurred at depths of less than 10 km the inferred source parameters complemented by the structural maps derived from the photo interpretation of landsat imagery of the region indicate a normal fault that uniquely transects the reservoir s deep sanyati basin in a north south heading the active fault seems to correlate with the location of the umi river s submerged river channel the confirmation of shallow depths and the determination of source parameters establishes a basis for addressing the actual triggering mechanisms of these earthquakes

analysis of large amplitude stratospheric mountain wave event observed from the airs and mls sounders over the western himalayan region mountain waves in the stratosphere have been observed over elevated topographies using both nadir looking and limb viewing satellites however the characteristics of mountain waves generated over the himalayan mountain range and the adjacent tibetan plateau are relatively less explored the present study reports on three dimensional 3 d properties of a mountain wave event that occurred over the western himalayan region on 9 december 2008 observations made by the atmospheric infrared sounder on board the aqua and microwave limb sounder on board the aura satellites are used to delineate the wave properties the observed wave properties such as horizontal lambda x lambda y and vertical lambda z wavelengths are 276 km zonal 289 km meridional and 25 km respectively a good agreement is found between the observed and modeled analyzed vertical wavelength for a stationary gravity wave determined using the modern era retrospective analysis for research and applications merra reanalysis winds the analysis of both the national centers for environmental prediction national center for atmospheric research reanalysis and merra winds shows that the waves are primarily forced by strong flow across the topography using the 3 d properties of waves and the corrected temperature amplitudes we estimated wave momentum fluxes of the order of similar to 0 05 pa which is in agreement with large amplitude mountain wave events reported elsewhere in this regard the present study is considered to be very much informative to the gravity wave drag schemes employed in current general circulation models for this region

heat flow on the hawaiian swell and lithospheric reheating most oceanic volcanic centres caused by hotspot activity are surrounded by sea floor that is unusually shallow for its age1 2 there is increasing evidence that swells found on older sea floor like the hawaiian swell have formed from a broad scale reheating and thinning of the lithosphere as it passes over a mantle hotspot3 4 if the formation and subsequent disappearance of these swells are controlled by thermal processes they should have an above normal heat flux we present here the results from 95 new heat flow measurements on the hawaiian swell along the older part of the swell the heat flow is 20 25 higher than the normal heat flow for crust of this age this anomaly is consistent with the observed swell uplift the shape and amplitude of the heat flow anomaly require that the reheating be largely confined to the lower half of the lithosphere

an experimental study on the influence of surface finishing on the weathering of a building low porous limestone in coastal environments limestones used as building material are especially prone to weathering in coastal environments due to interactions between sea mist and the carbonate stone subtle variations of the commercial surface finishing may lead to differences in decay patterns and aesthetic properties due to salt crystallization to explore this potentially contrasting behavior tablets of rough and polished low porous limestone were aged in a sea salt spray corrosion chamber to simulate their exposure in a coastal environment different crystallization morphologies and relative proportions of soluble halite and less soluble gypsum salts were observed in the aged rough and polished surface samples these morphologies are ascribed to the microtextural characteristics and the surface pore systems of the diverse rough and polished substrates that in turn influence fluid saline solution transport toward their interior as well as the different salt solubilities interacting with the substrates polished surfaces exhibit little evidence of damage after the ageing test in contrast to the rough samples but do have conspicuous gypsum on the surface together with halite the scarcity of gypsum on the rough surfaces in addition to a more severe change in the porosity system suggests that salts penetrate deeper when the stone surface is not polished potential decay induced by salt crystallization pressure is therefore minimized when the stone surface is polished however polished surfaces show more significant changes in luminosity and chroma after the ageing test and so are less attractive from an aesthetic point of view surface finishing is thus an important feature that needs to be characterized for a better understanding of the weathering behavior of building stones used in coastal environments

evidence of gravity wave ducting in the mesopause region from airglow network observations 1 we present observational evidence of gravity wave ducting and show for the first time that the ducting occurs over large horizontal distances in the mesopause region an optical network of four all sky imagers in japan identified two dimensional patterns of small scale gravity wave bands in oh airglow images on 13 june 2004 the wave signatures clearly showed northward propagation of more than 1800 km over a wide range of latitudes the horizontal wavelength horizontal phase speed and wave period were estimated from the airglow data as 33 4 km 42 8 m s 1 and 13 4 min respectively the wave structure lasted for the whole 5 h airglow observation period simultaneous mf radar wind data and timed saber measurements suggested that the wave was trapped and ducted at the airglow height the ducting likely contributed to the remarkable coherence of the wave as it propagated northward

statistical characteristics of polar cap mesospheric gravity waves observed by an all sky airglow imager at resolute bay canada 1 an airglow imager at resolute bay canada 74 7 n 265 1 e has been used for the observation of gravity waves in the polar cap mesosphere since january 2005 on the basis of the long term imaging observations obtained over 137 nights during the winter seasons of 2005 and 2006 we extracted 143 events of small scale 100 km gravity waves using airglow keograms which represent a time series of the horizontal cross sections of the airglow images the horizontal wavelengths and phase speeds of the large scale waves were typically 100 400 km and 60 100 ms 1 respectively the propagation directions of these large scale waves also showed a westward preference the wave parameters appeared to have no relation with the geomagnetic activities represented by the kp index on the other hand the propagation directions of the observed waves were consistent with the prevailing eastward winds in the mesosphere and the updraft associated with a low pressure area that generally appears to the east of resolute bay at tropospheric altitudes these results suggest that the main source of the gravity waves in the polar cap mesosphere is tropospheric dynamics rather than auroral activities

mesospheric gravity waves over a tropical convective region observed by oh airglow imaging in indonesia 1 from oh airglow imaging observation carried out over one year in indonesia 74 events of gravity waves in the mlt mesosphere and lower thermosphere region were extracted observed period horizontal wavelength and observed horizontal phase speeds of gravity waves were typically 5 13 min 13 45 km and 37 75 m s respectively propagation directions were mostly southward except for the period between december and february when eastward propagation was preferential spatial distributions of tropospheric clouds estimated with gms geostationary meteorological satellite were consistent with the propagation direction of gravity waves i e these clouds mainly existed in the opposite direction to the propagation direction of waves this suggests that horizontal propagation characteristics of the short period gravity waves in the low latitude mlt region are mainly affected by the distribution of the wave sources in the troposphere and the effect of the background mean wind in the middle atmosphere is smaller as it is weaker 20 m s in the equatorial region

an investigation of gravity wave activity in the low latitude upper mesosphere propagation direction and wind filtering horizontal phase speeds of up to 80 m s 1 the large scale band wave patterns horizontal wavelength between 10 and 60 km exhibited a clear seasonal dependence on the horizontal propagation direction propagating toward the southeast during the summer months and toward the northwest during the winter the direction of propagation was observed to change abruptly around the equinox period in mid march and at the end of september using a numerical simulation of gravity wave propagation in a seasonally variable climatological wind field we have determined that the observed anisotropy in the wave propagation directions can be attributed to a strong filtering of the waves in the middle atmosphere by stratospheric winds index terms 0310 atmospheric composition and structure airglow and aurora 3332 meteorology and atmospheric dynamics mesospheric dynamics 3360 meteorology and atmospheric dynamics remote sensing keywords airglow winds gravity waves wind filtering imager

statistical study of short period gravity waves in oh and oi nightglow images at two separated sites 1 using airglow images of the near infrared oh band 720 910 nm and oi 557 7 nm line we investigated seasonal latitudinal and local time variations of short period gravity waves the images were obtained at two locations in japan that are 1200 km apart rikubetsu 43 5 n 143 8 e and shigaraki 34 9 n 136 1 e between october 1998 and october 1999 our analysis has focused on small scale gravity waves with wavelengths less than 40 km and dominant phase speeds of 20 50 m s wave occurrences for both oh and oi at rikubetsu and shigaraki are significantly higher than 60 with a slightly larger value in summer the occurrences increase from evening to midnight there are no obvious local time dependencies in horizontal wavelength propagation direction and phase speed the propagation directions in summer are either northward or northeastward at both locations however in winter the propagation directions at rikubetsu are generally westward nw w and sw whereas those at shigaraki are only southwestward from simultaneous wind observation by the mf radars at wakkanai 45 4 n 141 7 e and yamagawa 31 2 n 130 6 e we discuss possible influences of doppler and thermal ducting wind filtering and source distribution of gravity waves propagating from the lower atmosphere to the airglow heights in the mesopause region

concentric gravity waves over northern china observed by an airglow imager network and satellites the first no gap oh airglow all sky imager network was established in northern china in february 2012 the network is composed of six all sky airglow imagers that make observations of oh airglow gravity waves and cover an area of about 2000 km east and west and about 1400 km south and north an unusual outbreak of concentric gravity wave cgw events were observed by the network nearly every night during the first half of august 2013 these events were coincidentally observed by satellite sensors from fengyun 2 fy 2 atmospheric infrared sounder airs aqua and visible infrared imaging radiometer suite viirs suomi national polar orbiting partnership npp combination of the ground imager network with satellites provides multilevel observations of the cgws from the stratosphere to the mesopause region in this paper two representative cgw events in august 2013 are studied in detail first is the cgw on the night of 13 august 2013 likely launched by a single thunderstorm the temporal and spatial analyses indicate that the cgw horizontal wavelengths follow freely propagating waves based on a gw dispersion relation within 300 km from the storm center in contrast the more distant observed gravity wave field exhibits a smaller horizontal wavelength of 20 km and our analysis strongly suggest this wave field represents a ducted wave a second event exhibiting multiple cgws was induced by two very strong thunderstorms on 9 august 2013 multiscale waves with horizontal wavelengths ranging from less than 10 km to 200 km were observed

on the nature of short period mesospheric gravity wave propagation over halley antarctica 1 as part of a collaborative program between british antarctic survey and utah state university measurements were made using an all sky airglow imager located at the u k halley station 76 s 27 w during the 2000 and 2001 austral winter seasons from april through to early september a co located imaging doppler interferometer was utilized to obtain coincident wind measurements for a total of 171 wave events this study comprises the first detailed climatological investigation of the propagation nature freely propagating doppler ducted or evanescent of individual quasi monochromatic short period wave events at a high southern latitude distributions of the derived vertical wavelength exhibit an interquartile range from 16 48 km with a median vertical wavelength of 21 km the majority of the wave events were found to be freely propagating waves with only 5 exhibiting a clear doppler ducted signature while 15 of the waves were found to be evanescent in nature although no coincident temperature measurements were available subsequent saber temperature measurements suggest that up to 28 of the measured temperature profiles are capable of providing a ducted environment for the observed wave field this is in sharp contrast to findings at mid and low latitudes where these waves have been shown to be prone to doppler ducted motion it is suggested that the relatively weak wind field and associated tidal wind amplitudes over halley are not capable of forming a significant doppler ducted region to sustain a substantial amount of ducted waves belonging to the detectable spectrum of the airglow imager as these wind fields are comparable to wind fields found at other polar latitudes we hypothesize that the majority of short period gravity waves observed in the polar mesosphere are freely propagating and thus an important source of energy transfer into the mlt region

a procedure for modelling shallow dislocation sources summary expressions for displacements on the surface of a layered half space due to an arbitrary oriented shear dislocation are given in terms of generalized ray expansions useful approximations of these expressions for shallow events as recorded at teleseismic distances for realistic earth models are presented the results of this procedure are used to generate synthetic p sv and sh waveforms for various assumptions of stress drop

gravity wave characteristics in the mesopause region revealed from oh airglow imager observations over northern colorado using 5 years of all sky oh airglow imager data over yucca ridge field station co 40 7 n 104 9 w from september 2003 to september 2008 we extract and deduce quasi monochromatic gravity wave gw characteristics in the mesopause region the intrinsic periods are clustered between approximately 4 and 10 min and many of them are unstable and evanescent gw occurrence frequency exhibits a clear semiannual variation with equinoctial minima which is likely related to the seasonal variation of background wind the anomalous propagation direction in january 2006 with strong southward before major warming starting in 21 january and weak southward propagation afterward was most likely affected by stratospheric sudden warming the momentum fluxes show strongly anticorrelated with the tides with 180 out of phase in the zonal component while in the meridional component the easterly maximum occurred approximately 2 6 h after maximum easterly tidal wind however the anticorrelations are both weakest during the summer the dissipating and breaking of small scale and high frequency gw s components could have a potential impact on the general circulation in the mesopause region

climatology and modeling of quasi monochromatic atmospheric gravity waves observed over urbana illinois from analyzing nine months of airglow imaging observations of atmospheric gravity waves agws over adelaide australia 35 s walterscheid et al 1999 have proposed that many of the quasi monochromatic waves seen in the images were primarily thermally ducted here are presented 15 months of observations from february 1996 to may 1997 for agw frequency and propagation direction from a northern latitude site urbana illinois 40 n as adelaide urbana is geographically distant from large orographic features similar to what was found in adelaide the agws seem to originate from a preferred location during the time period around summer solstice in conjunction with these airglow data there exists mf radar data to provide winds in the 90 km region and near simultaneous lidar data which provide a temperature climatology the temperature data have previously been analyzed by states and gardner 2000 the temperature and wind data are used here in a full wave model analysis to determine the characteristics of the wave ducting and wave reflection during the 15 month observation period this model analysis is applied to this and another existing data set recently described by nakamura et al 1999 it is shown that the existence of a thermal duct around summer solstice can plausibly account for our observations however the characteristics of the thermal duct and the ability of waves to be ducted is also greatly dependent on the characteristics of the background wind a simple model is constructed to simulate the trapping of these waves by such a duct it is suggested that the waves seen over urbana originate no more than a few thousand kilometers from the observation site

statistical characteristics of gravity waves observed by an all sky imager at darwin australia 1 an all sky airglow imager with a cooled charge coupled device camera in place at darwin 12 4 s 131 0 e australia since october 2001 has been used to obtain two dimensional gravity wave images in the mesopause region using airglow images of the oi 557 7 nm emission altitude 96 km and oh band 720 910 nm 86 km emissions obtained for october 2001 to august 2002 we investigated the wavelengths phase velocities and propagation directions of gravity waves wave occurrence in oh images 60 90 is higher than in oi images 30 70 for all seasons the waves have wavelengths of less than 90 km peak 30 50 km and phase velocities of less than 90 m s peak 30 60 m s most of the waves propagate in the meridional direction and the directionality strongly depends on the season in winter waves propagate both poleward and equatorward while in summer almost all waves propagate poleward an examination of airglow imaging statistics at adelaide 35 s 138 e australia obtained by walterscheid et al 1999 leads us to conclude that this clear directionality is caused by the location of the wave sources and by the wave ducting processes that is poleward waves in summer come from an equatorial convective source through a thermal duct structure the effect of wind filtering on the waves is also discussed for zonal wave propagation

dominant control of the south asian monsoon by orographic insulation versus plateau heating heat emitted from the tibetan plateau as dry heat and water vapour has long been assumed to be the main driver of the south asian summer monsoon but new work suggests that in fact it is the neighbouring mountains that are the major influence william boos and zhiming kuang use an atmospheric model to show that flattening the tibetan plateau has little effect on the monsoon so long as the himalayas and surrounding mountain ranges remain the plateau does boost rainfall locally along its southern edge but it is the build up of hot moist air over india insulated from colder drier air by the himalayas that drives large scale monsoon circulation the elevation of the tibetan plateau is thought to cause its surface to serve as a heat source that drives the south asian summer monsoon potentially coupling uplift of the plateau to climate changes on geologic timescales here however an atmospheric model is used to show that flattening of the tibetan plateau has little effect on the monsoon provided that the narrow orography of the himalayas and adjacent mountain ranges is preserved the tibetan plateau like any landmass emits energy into the atmosphere in the form of dry heat and water vapour but its mean surface elevation is more than 5 km above sea level this elevation is widely held to cause the plateau to serve as a heat source that drives the south asian summer monsoon potentially coupling uplift of the plateau to climate changes on geologic timescales1 2 3 4 5 observations of the present climate however do not clearly establish the tibetan plateau as the dominant thermal forcing in the region peak upper tropospheric temperatures during boreal summer are located over continental india south of the plateau here we show that although tibetan plateau heating locally enhances rainfall along its southern edge in an atmospheric model the large scale south asian summer monsoon circulation is otherwise unaffected by removal of the plateau provided that the narrow orography of the himalayas and adjacent mountain ranges is preserved additional observational and model results suggest that these mountains produce a strong monsoon by insulating warm moist air over continental india from the cold and dry extratropics these results call for both a reinterpretation of how south asian climate may have responded to orographic uplift and a re evaluation of how this climate may respond to modified land surface and radiative forcings in coming decades

western extension of the iberian european plate boundary during the early cenozoic pyrenean convergence a new model abstract a dense seismic net work allows of drawing the western prolongation of the northern boundary of the iberian plate this early cenozoic deformed boundary is disrupted by two prominent nw se transform faults a kinematic reconstruction with a nw late cretaceous lower eocene motion of the iberian plate is proposed the azores biscay rise is interpreted as a short lived subduction zone whereas king s trough could be a transform fault

porosity and mineralogy evolution during the decay process involved in the chellah monument stones the objective of this work is to study the decay process involved in the historical roman chellah located in the rabat city morocco this monument is made up of porous calcarenite stone several samples taken from altered and unaltered blocks were analyzed by the water saturation the mercury intrusion porosimetry techniques and using the scanning electron microscopy coupled to energy dispersive x ray spectrometer sem edx to perform a reliable chemical analysis some samples were also analyzed by inductively coupled plasma atomic emission spectroscopy icp aes the mercury porosimetry results show a bimodal porous network for this porous material the deterioration process of these stones involved an increase in porous volume of about 2 the lowest porosity observed in the unaltered block is connected to the presence of sparitic cement which causes a partial inter granular porosity clogging the highest porosity of the deteriorated block without crust is due to the increase in inter granular space sem photographs of the unaltered sample show the presence of the porous primary grains of ovoid forms and millimeter length sizes and of the secondary grains of rhombohedric forms and micro size porosity is essentially located between the primary grains and can be completely clogged by secondary precipitations various forms of deterioration are observed on the altered samples such as the dissolution of the secondary grains edges wells of dissolution and also the presence of argillaceous residues on the surface this last was also detected by the icp aes and edx analysis which show an increase of the silicon and aluminum contents toward the surface

source inversion of seismic waveforms the koyna india earthquakes of 13 september 1967 abstract the treatment of the seismic source inverse problem when diverse forms of waveform data are available is simple and elegant using a moment tensor formalism if earth structure is known and its effects predictable in terms of vertically inhomogeneous elastic layered models then all types of wave phenomena e g surface waves body waves leaky modes etc for a purely deviatoric moment tensor point source may be represented by at most a sum of three green9s functions for an arbitrary symmetric moment tensor point source one additional green9s function is needed for the p sv system however elegant this formalism may be for posing the linear inverse problem the major difficulties lie in earth structure unknowns and resultant nonlinearities in the green9s functions which can cause significant trade offs with source parameters a hybrid inversion procedure is set up to gain insight into the probable unknowns in particular problems by incorporating both a linearized least squares gradient method for the moment tensor or double couple and smoothed time function parameters and a nonlinear systematic trial and error search for moment tensor or double couple parameters for several assumptions of green9s function the inversion technique is applied to near regional waveform data from a small earthquake associated with the koyna reservoir which occurred 13 september 1967 as the second in a group of three events with very similar waveshapes but differing amplitudes the magnitudes of the second and third events are smaller by 0 2 and 0 8 units respectively compared to the first the absolute magnitude for the first event is poorly constrained but is estimated to be 4 0 to 4 5 rather than the previously published value of 5 5 to 6 0 from the similarity of waveshapes all three events are inferred to have the same mechanism and occurred within about 2 km of the same hypocenter the results from moment tensor and double couple inversions for event 2 data indicate that source depth was 5 km and that left lateral faulting occurred on a plane with a strike of n20 e 5 dip of 90 15 and a rake of 0 35 the inferred far field time function is approximately 3 sec in duration unusually long for the seismic moment of 9 10 22 dyne cm yielding a possible stress drop of about 0 05 bars a fault map was constructed from landsat image interpretation and shows a predominance of nnw to nne striking faults in the koyna area which is used to infer the appropriate nodal plane in the inversion results these faults tend to define a broad en echelon zone which parallels the western ghats in this area

new statistical analysis of the horizontal phase velocity distribution of gravity waves observed by airglow imaging we have developed a new analysis method for obtaining the power spectrum in the horizontal phase velocity domain from airglow intensity image data to study atmospheric gravity waves this method can deal with extensive amounts of imaging data obtained on different years and at various observation sites without bias caused by different event extraction criteria for the person processing the data the new method was applied to sodium airglow data obtained in 2011 at syowa station 69 s 40 e antarctica the results were compared with those obtained from a conventional event analysis in which the phase fronts were traced manually in order to estimate horizontal characteristics such as wavelengths phase velocities and wave periods the horizontal phase velocity of each wave event in the airglow images corresponded closely to a peak in the spectrum the statistical results of spectral analysis showed an eastward offset of the horizontal phase velocity distribution this could be interpreted as the existence of wave sources around the stratospheric eastward jet similar zonal anisotropy was also seen in the horizontal phase velocity distribution of the gravity waves by the event analysis both methods produce similar statistical results about directionality of atmospheric gravity waves galactic contamination of the spectrum was examined by calculating the apparent velocity of the stars and found to be limited for phase speeds lower than 30 m s in conclusion our new method is suitable for deriving the horizontal phase velocity characteristics of atmospheric gravity waves from an extensive amount of imaging data

moment tensor inversion of complex earthquakes summary moment tensor inversion methods can be applied with success in the determination of source properties of simple earthquakes however these methods utilize the assumption of a point source which is inadequate for modelling many complicated shallow earthquakes for complex earthquakes an inversion using finite faulting models is desirable but the number of parameters involved requires that a good starting model be found or that independent constraints be placed on some of the parameters a method is presented for low pass filtering both the data and green s functions passing only signals with wavelengths greater than the dimension of the entire fault the filter tends to smooth complications in the waveforms and allows application of the point source moment tensor inversion this method is applied to body waves from the 1978 thessaloniki greece earthquake the 1971 san fernando earthquake and to a multiple point source synthetic model of the san fernando event for the thessaloniki event although a multiple source mechanism has been suggested inversion results before and after filtering were essentially identical indicating that a point source mechanism is sufficient in modelling the long period teleseismic body waves in the case of the san fernando earthquake the point source green s functions were incapable of simultaneously modelling the p and sh waves inversion of p waves alone resulted in extreme parameter resolution problems but allowed constraint in one axis of the moment tensor and suggested an overall source time function inversion of a synthetic san fernando data set yielded similar results but allowed an investigation of the shortcomings of the method under controlled circumstances although the results may require substantial interpretation the method presented represents a simple first step in the analysis of complex earthquakes

a study of the source parameters of some large earthquakes of northeastern north america waveforms of body and surface waves for six moderately large north eastern north american earthquakes are analyzed for source information the earthquakes studied are the 1925 charlevoix quebec earthquake ms 6 4 the 1935 timiskaming quebec earthquake ms 6 0 the 1939 charlevoix quebec earthquake mb 5 4 the 1940 ossipee new hampshire earthquakes ml 5 3 and 5 1 and the 1944 cornwall ontario massena new york earthquake m 5 1 the focal depths for all of the earthquakes for which determinations could be made 1925 1935 1939 and december 20 1940 were about 8 to 10 km the waveforms of the 1925 1935 1939 and 1940 events are consistent with thrust mechanisms although there is some ambiguity in the strike direction for each of the events the favored focal mechanism for the 1925 and 1939 events had northeast southwest nodal planes for the 1935 event the available data suggest that the earthquake occurred on a northwest southeast oriented fault plane the strike of the nodal planes for the december 20 1940 event is quite uncertain but a north south orientation is preferred no body waves that could be modeled were collected for the december 24 1940 or 1944 events the stress drops for the events scatter widely but are comparable to those from other intraplate earthquakes there is a difference in source complexity from event to event with the december 20 1940 event having had one simple source while the 1935 shock had three separate energy releases the source time functions found for the 1935 1939 and december 20 1940 earthquakes from the short period teleseismic body waves resemble those for some shocks from california the focal mechanisms found here suggest that the minimum principal deviatoric stress is vertical and that the horizontal principal deviatoric stresses both compressional are controlled primarily by plate driving forces

observational investigations of gravity wave momentum flux with spectroscopic imaging 1 we apply a newly developed gravity wave momentum flux estimation method to the mesospheric measurements obtained with colocated airglow imager and meteor radar at maui hawaii 20 7 n 156 3 w during the maui mesosphere and lower thermosphere maui malt campaign the method identifies individual quasi monochromatic gravity waves with periods between 6 and 40 min estimates the intrinsic wave parameters and calculates the momentum fluxes carried by vertically propagating waves data taken on 28 october 2003 are analyzed in detail to reveal the relationship between momentum flux and wave parameters the january april july and october 2003 data are divided into summer and winter categories and nightly average momentum fluxes are calculated for comparison of the seasonal wave propagation directions average wave momentum flux is directed to the northeast during most of the summer nights while a southwest preference exists for the winter nights the results extracted from maui hawaii combined with the earlier results from starfire optical range new mexico 35 n 107 w and other observations support the notion that the seasonal trend in meridional flux is a global phenomenon

a statistical analysis of equatorial plasma bubble structures based on an all sky airglow imager network in china this paper investigates the statistical features of equatorial plasma bubbles epbs using airglow images from 2012 to 2014 from a ground based network of four imagers in the equatorial region of china it is found that 1 epbs mainly occur during 21 00 00 00 local time lt in equinoxes there is an asymmetry in occurrence rates between march june and september equinoxes december solstices 2 most epbs occur in groups of two to six depletions the distance between adjacent epb depletions is 100 700 km and the average is 200 300 km the zonal extension of an epb group is usually less than 1500 km but can reach 3000 km 3 epbs usually have a maximum drift velocity near 100 m s at 21 00 22 00 lt in 9 5 1 5 geomagnetic latitude and then decrease to 50 70 m s toward sunrise 4 the averaged westward tilt angle of most epbs with respect to the geographic north south increased from 5 10 to 23 30 with lt between 20 00 and 03 00 lt then decreasing to 10 20 toward sunrise 5 when 90 140 the maximum pmle increases by 3 4 5 5 when f10 7 changes from 90 to 190 6 the epb occurrence patterns and zonal drift velocities are significantly different from those at kolhapur india which locates west to our stations by 20 0 32 0 in longitude

seismic moment assessment of earthquakes in stable continental regions ii historical seismicity summary this part i study in conjunction with part 11 develops a method to determine within specified uncertainty bounds the seismic moment and thus moment magnitude of all earthquakes of stable continental regions scr for which instrumental or intensity data exist its basis is polynomial regression analysis using a database of scr earthquakes with direct seismic moment determination the independent variables include modern teleseismic magnitudes and regional magnitudes part i and isoseismal areas or number of recording stations part 11 part i11 is an application of the methodology of parts i and i1 to several major historical earthquakes all data used in the regressions are assigned individual uncertainties estimated from the literature or from experience formal confidence limits 68 per cent or 95 per cent on both the regression formulas and the predicted seismic moment values are then possible via error propagation analysis the most complete development is for the teleseismic magnitudes m and mb for both the final regression for log m is a quadratic formula that closely emulates the relationship between amplitude magnitudes and log m expected from dislocation theory and source scaling arguments regressions are also derived for the regional magnitudes mlg and m because there are many scr events mainly pre 1964 that have no teleseismic magnitudes prediction uncertainties from teleseismic magnitudes in moment magnitude units are in the ao 18 0 28 range and from regional magnitudes in the ko 23 0 38 range over a wide magnitude band finally the methodology developed here is generic even though the database is specific application to plate boundary oceanic intraplate or active continental intraplate regions should be straightforward

gravity wave radiation and mean responses to local body forces in the atmosphere the authors determine the spectral linear solutions that arise in response to local 3d body forces and heatings in an idealized environment that turn on and off smoothly but not necessarily slowly over a finite interval in time the solutions include impulsive through slowly varying body forcings the forcings result in both a mean response which is typically significantly broadened spatially in one direction and a gravity wave response which allows the fluid to reach this state the gravity wave field depends on both the spatial attributes of the source and the forcing duration the frequency of the wave response is the characteristic source frequency formed from the source dimensions if the forcing frequency is greater than the characteristic frequency and is the forcing frequency otherwise the radiated gravity waves from zonal forcings have vertical wavelengths which are approximately twice the vertical extent of the forcing and horizontal wavelengths which are at least twice the horizontal extent of the forcing wave excitation is increasingly inefficient when the forcing frequency is smaller than the characteristic source frequency in addition the mean responses are not confined to the source region in general significant spatial broadening of the mean responses occurs if the source s frequency is high and low the responses are broadened horizontally and vertically respectively with the amount depending on the characteristic scales of the source if the body forcing is in the eastward direction then much or all of the ensuing zonal mean wind is eastward however for many realistic forcing scenarios a large percentage of the ensuing zonal wind flows westward these countersigned jets are displaced meridionally about the source thus spatially confined body forcings create both gravity wave and mean responses if the forcings are fast enough very slowly varying forcings create only mean responses

source depth determination using multi modal rayleigh spectral ratios and linear discriminant analysis a study of the reservoir induced seismic sequence at lake kariba africa september 1963 to august 1974 abstract the source depths of 12 reservoir induced seismic events at lake kariba were determined using the short to long period spectral ratios of multi modal rayleigh data recorded at two african stations source depths of less than 10 km were confirmed through the analysis of short period pp p time differentials two separate source to receiver crustal path models were employed in the analysis an african shield model with low velocity surficial layers and a low shear velocity zone between 7 and 18 km was utilized to reproduce the observed multi modal rayleigh waves acquired from the kariba to nairobi path the model is consistent with published evidence that the east african rift system extends south to lake kariba a conventional south african shield model was utilized for the kariba to pretoria path synthetic multi modal rayleigh waveforms were computed for a range of source depths for the two crustal models the spectral ratios obtained from these waveforms provided the synthetic data base to which the observed rayleigh wave spectral ratios were compared using linear discriminant analysis due to the limitations in the available data the source depths could not be determined at a statistical level of confidence however the demonstration of the feasibility of the procedure should stimulate its application to many other problems associated with source parameter inversion

superficial alteration and soluble salts in the calcarenite weathering case study of almohade monuments in rabat morocco this work analyzes the stone superficial deterioration of some monuments in rabat city the rock is a calcarenite with porous texture rich in calcium carbonates and fossils the techniques used to study the surfaces altered by blackening or black crusts are the sem equipped with edx microprobe the x ray diffraction and the analysis of the soluble salts by ionic chromatography for anions and flame spectrometer for cations they reveal significant contents of calcium sulphates mainly gypsum often associated with sodium chlorides these salts known to have a destructive effect on the calcareous stones seem to be originated from the contamination by atmospheric pollutants particularly sulfur dioxide and by the marine sprays

observational evidence of wave ducting and evanescence in the mesosphere a collaborative radar and imaging study of gravity waves over the hawaiian islands was performed during october 1993 as part of the airborne lidar and observations of hawaiian airglow 1993 coupling and dynamics of regions equatorial aloha 93 cadre campaign to investigate the propagation characteristics of short period 1 hour waves at nightglow altitudes the horizontal wavelengths and apparent phase speeds of quasi monochromatic wave events were measured in four separate nightglow emissions using data obtained by a high resolution ccd imager this information was correlated with simultaneous mf radar wind measurements over the same height interval 80 100 km to infer intrinsic wave parameters in each case correlating the two data sets allowed the determination of the local vertical wavenumber for each event in particular whether it be real indicative of freely propagating waves or imaginary indicative of ducted or evanescent waves the results of this study indicate a preponderance of ducted or evanescent waves at 80 100 km during the time of the observations with up to 75 of the events recorded exhibiting ducted or evanescent behavior also noted was a tendency for ducted behavior to be more prevalent among waves with shorter horizontal wavelengths in agreement with doppler ducting theory these results suggest that ducted waves are relatively common in the upper mesosphere and lower thermosphere region at least over the mid pacific ocean as small scale waves which are ducted have the potential to travel much longer horizontal distances than freely propagating waves the frequency of their occurrence should be taken into account in efforts to quantify gravity wave effects at these altitudes

inversion of teleseismic body waves for the moment tensor of the 1978 thessaloniki greece earthquake seismograms from wwssn and canadian network stations were modeled to determine the source parameters of the 20 june 1978 thessaloniki greece earthquake m s 6 4 the depth of the initial rupture was constrained to 11 1 km by comparison of the arrival times of surface reflections with synthetic short period seismograms a focal sphere plot of first motion polarities provided little constraint on other focal parameters except to indicate that predominantly normal faulting was involved a generalized inverse technique utilizing the moment tensor formalism was applied to teleseismic p and sh waves for six increments of depth the moment tensor obtained indicated a nearly horizontal n trending tension axis and a nearly vertical compression axis and yielded the following double couple source parameters strike 280 7 dip 55 3 rake 65 5 seismic moment 5 7 1025 dyne cm and a skewed triangular source time function with a rise time of about 1 sec and duration of 6 to 8 sec due to indications of multiple or finite source effects for this event and the assumption in the moment tensor formalism of a point source a low pass filter was applied to the data and the inversions were repeated the results were nearly identical with those of the original inversion suggesting that any individual sources had similar mechanisms or that the point source model is sufficient for this earthquake

the geology and formation of king s trough northeast atlantic ocean king s trough comprises a 450 km long chain of roughly parallel basins and flanking ridges situated 700 km northeast of the azores its formation has been variously described as a short lived plate boundary a compressional boundary or a re orientated former bend in the mid atlantic ridge recent studies of seismic and gravity data concluded that the flanking ridges result from hot spot activity which began around 55 m y b p while the trough could have been produced by contemporaneous or later rifting or shearing the geological sampling described in this paper was planned to resolve the mode of formation of the trough a long range sidescan sonar survey of the region was used as control for new bathymetric and geologic maps of the area and for transponder navigated dredging and coring operations on the flanks of the trough the samples recovered show that basalt volcanism dated at over 52 m y b p was followed by the deposition of a chalk sequence until miocene times trachyte volcanism at 32 2 m y b p was followed by a period of tuff and ash volcanism near sea level in the late oligocene and miocene a middle miocene chalk sequence is at present exposed on the trough walls the detailed morphology and geological sequence at king s trough agrees best with a hypothesis which involves uplift by around 2 km of an aseismic ridge hot spot trace at about 32 m y ago which was followed by intra plate rifting at around 16 20 m y b p a number of interpretations are possible for the amounts of vertical displacement during this rifting we favour total vertical fault movements of the order of 2 5 to 3 5 km