recovering seismic displacements through combined use of 1 hz gps and strong motion accelerometers retrieving displacement from seismic acceleration records is often difficult because unknown small baseline offsets in the acceleration time series will contaminate the doubly integrated record with large quadratic errors one hertz global positioning system gps position estimates and collocated seismic data are available from the 2003 m w 8 tokachi oki hokkaido earthquake after a process of correcting for possible misorientation of the seismic sensors an inversion method is used to simultaneously solve for ground displacement with both data sets as input constraints this inversion method takes into account the presence of unknown offsets in the acceleration record and the relatively large uncertainties in the estimated 1 hz gps positions in this study 117 channels of seismic data were analyzed only 5 of the time does the static displacement retrieved from traditional baseline correction processing without gps information agree with the absolute displacement measured with 1 hz gps to within the errors of the gps data in solving simultaneously for constrained displacements that agree with both the seismic and gps data sets an optimal solution was found that included only one or two step functions in the acceleration records potential explanations for the offsets are analyzed in terms of tilt of the sensor or electronic noise for nine stations clear misorientations of the seismic sensors of more than 20 deg from the reported orientation were found for this size event the 30 sec sampled gps solutions were also a sufficient constraint for establishing the offset errors and recovering reliable displacements the results significantly extend the frequency band over which accelerometer data are reliable for source inversion studies online material plots of constrained seismograms with metadata

rupture process of the 2011 tohoku oki mega thrust earthquake m9 0 inverted from strong motion data 1 we investigate the rupture process of the m9 0 tohoku oki mega thrust earthquake using the relatively low frequency strong motion records 0 01 0 125 hz observed at 36 k net and kik net stations the epicentral distances of which range from 120 km to 400 km the fault model is a rectangular plane the length and width of which are 510 km along the japan trench and 210 km along subducting direction of the pacific plate respectively we perform the multi time window inversion analysis with a 30 30 km2 subfault the derived slip model has one large slip area this area extends from the region around the hypocenter to the shallow part of the fault plane and further to the north and south along the trench axis located far off southern iwate miyagi and northern fukushima prefectures the seismic moment is 4 42 1022 nm mw 9 0 and the maximum slip is 48 m the slips near the coast are relatively small except off miyagi prefecture which experienced a slip greater than 5 m the shallow large slip area which continuously ruptured from 60 s to 100 s after the initial break radiated seismic waves rich in very low frequency content 0 02 hz the rupture after 100 s propagating to the southern fault area contributes to the distinct phases observed for fukushima and ibaraki prefectures the relationship between the proposed rupture model and the feature of the acceleration waveforms is not straightforward and suggests the frequency dependency of the seismic wave radiation

seismic evidence for an earthquake nucleation phase near source observations show that earthquakes initiate with a distinctive seismic nucleation phase that is characterized by a low rate of moment release relative to the rest of the event this phase was observed for the 30 earthquakes having moment magnitudes 2 6 to 8 1 and the size and duration of this phase scale with the eventual size of the earthquake during the nucleation phase moment release was irregular and appears to have been confined to a limited region of the fault it was characteristically followed by quadratic growth in the moment rate as rupture began to propagate away from the nucleation zone these observations suggest that the nucleation process exerts a strong influence on the size of the eventual earthquake

investigation of low latitude e and valley region irregularities their relationship to equatorial plasma bubble bifurcation 1 the low latitude e valley and f region 3 m scale irregularities are studied with the sanya 18 4 n 109 6 e dip latitude 12 8 n vhf coherent scatter radar the observations show that the e region irregularities eris often weaken or disappear during the development of postsunset equatorial plasma bubbles epbs in equinoctial months however the valley region irregularities vris are found to occur during the epb development and show structures with close relation to those of epbs the interesting aspect is that the eri disruption and vri generation are simultaneously detected in terms of the electric field coupling from the equatorial f region down to low latitude e and valley regions the polarization electric fields pefs associated with the epb bifurcation are suggested to play key roles in the evolution of eris and vris it is shown that the mapping of upward and eastward pefs generated within the equatorial west tilted bubble would inhibit the occurrence of low latitude eris however for the east tilted bubble structure the associated downward pefs might map to the low latitude valley region and play an active role for the development of 3 m scale irregularities through gradient drift instability

operational real time gps enhanced earthquake early warning moment magnitudes for large earthquakes mw 7 0 derived in real time from near field seismic data can be underestimated due to instrument limitations ground tilting and saturation of frequency amplitude magnitude relationships real time high rate gps resolves the buildup of static surface displacements with the s wave arrival assuming nonsupershear rupture thus enabling the estimation of slip on a finite fault and the event s geodetic moment recently a range of high rate gps strategies have been demonstrated on off line data here we present the first operational system for real time gps enhanced earthquake early warning as implemented at the berkeley seismological laboratory bsl and currently analyzing real time data for northern california the bsl generates real time position estimates operationally using data from 62 gps stations in northern california a fully triangulated network defines 170 station pairs processed with the software trackrt the bsl uses g larms the geodetic alarm system to analyze these positioning time series and determine static offsets and preevent quality parameters g larms derives and broadcasts finite fault and magnitude information through least squares inversion of the static offsets for slip based on a priori fault orientation and location information this system tightly integrates seismic alarm systems cisn shakealert elarms 2 as it uses their p wave detections to trigger its processing quality control runs continuously we use a synthetic hayward fault earthquake scenario on real time streams to demonstrate recovery of slip and magnitude reanalysis of the mw7 2 el mayor cucapah earthquake tests the impact of dynamic motions on offset estimation using these test cases we explore sensitivities to disturbances of a priori constraints origin time location and fault strike dip

gravity waves generated by a tropical cyclone during the step tropical field program a case study overflights of a tropical cyclone during the australian winter monsoon field experiment of the stratosphere troposphere exchange project step show the presence of two mesoscale phenomena a vertically propagating gravity wave with a horizontal wavelength of about 110 km and a feature with a horizontal scale comparable to that of the cyclone s entire cloud shield wavelength of 250 km or greater the larger feature is fairly steady though its physical interpretation is ambiguous the 110 km gravity wave is transient having maximum amplitude early in the flight and decreasing in amplitude thereafter its scale is comparable to that of 100 to 150 km diameter cells of low satellite brightness temperatures within the overall cyclone cloud shield these cells have lifetimes of 4 5 to 6 hours aircraft flights through the anvil show that these cells correspond to regions of enhanced convection higher cloud altitude and upwardly displaced potential temperature surfaces a three dimensional transient linear gravity wave simulation shows that the temporal and spatial distribution of meteorological variables associated with the 110 km gravity wave can be simulated by a slowly moving transient forcing at the anvil top having an amplitude of 400 600 m a lifetime of 4 5 6 hours and a size comparable to the cells of low brightness temperature the forcing amplitudes indicate that the zonal drag due to breaking mesoscale transient convective gravity waves is definitely important to the westerly phase of the stratopause semiannual oscillation and possibly important to the easterly phase of the quasi biennial oscillation there is strong evidence that some of the mesoscale gravity waves break below 20 km as well the effect of this wave breaking on the diabatic circulation below 20 km may be comparable to that of above cloud diabatic cooling

kinematic rupture scenarios and synthetic displacement data an example application to the cascadia subduction zone scenario ruptures and ground motion simulation are important tools for studies of expected earthquake and tsunami hazards during future events this is particularly important for large mw8 and very large mw8 5 events for which observations are still limited in particular synthetic waveforms are important to test the response of earthquake and tsunami warning systems to large events these systems are not often exercised in this manner we will show an application of the karhunen loeve kl expansion to generate stochastic slip distributions of large events with an example application to the cascadia subduction zone we will discuss how to extend the static slip distributions obtained from the k l expansion to produce kinematic rupture models and generate synthetic long period displacement data at the sampling rates of traditional gnss stations we will validate the waveforms produced by this method by comparison to a displacement based ground motion prediction equation gmpe obtained from gnss measurements of large earthquakes worldwide

localization of lacustrine groundwater discharge lgd by airborne measurement of thermal infrared radiation abstract although lacustrine groundwater discharge lgd might be important in water and nutrient budgets it has often been neglected due to the required effort to measure lgd and due to intense spatial heterogeneity of lgd limiting the validity of measurements therefore fast easy applicable methods for a first snapshot of the lgd pattern are required and might be the basis for choosing relevant and representative sampling sites in the present case study which is actually the first application of an airborne measurement of thermal infrared radiation tir to identify lgd pattern for entire deep freshwater lakes the measurement was substantiated with thermal profiles in sediments and a water table map we found that measurement of tir is a powerful tool to identify lgd pattern in lake related studies provided that there is a lack of warm surface inflows a tir image taken in march 2012 shows that warm groundwater entering the relatively colder lake water in some near shore areas is visible as a plume floating on top of the lake water prerequisites for the application of tir to detect lgd pattern are the positive buoyancy of the groundwater relative to lake water and weak mixing in the water column we propose a dimensionless scale for identifying groundwater floating conditions based on weather conditions attributing a surface thermal anomaly to lgd depends on careful consideration of other factors that could produce similar patterns and careful consideration of lake physics

factors influencing groundwater seepage in a large mesotrophic lake in new york abstract groundwater seepage is gaining recognition as a critical feature of lake shoreline environments yet our understanding of this process is complicated by the considerable spatial heterogeneity observed in flow rates within and among lakes this research investigated spatial patterns in groundwater seepage around the shoreline of oneida lake a 207 km2 lake located in central new york usa replicated shielded seepage meters with associated controls were used to quantify rates and directions of groundwater flow along a 120 m stretch of shoreline throughout the summers of 1997 1999 these reference meters exhibited an average flow rate of 72 ml m 2 h 1 n 840 se 5 with individual flow rates as high as 1200 ml m 2 h 1 additional meters monitored in 1998 indicated that seepage patterns were highly synchronous but increased in magnitude of flow rate with increasing distances offshore up to 100 m from shore in 1999 private landowners assisted in weekly monitoring of seepage meters at 28 additional sites distributed around the 88 km perimeter of oneida lake the highest groundwater flow rates averaging 100 ml m 2 h 1 consistently occurred along the northern and eastern shorelines lowest flow rates including areas of groundwater recharge occurred along the western and southwestern shorelines proximal to the lake s outlet spatial patterns in groundwater flow were surprisingly unrelated to substrate texture despite wide variability observed around the lake edge from silty clays to sands gravels and boulders broad scale factors of underlying bedrock geology and regional precipitation patterns appear to be driving the observed spatial patterns in oneida lake s groundwater contributions

dynamic temporal patterns of nearshore seepage flux in a headwater adirondack lake abstract although seepage in lakes is known to vary as a function of precipitation and watershed characteristics temporal patterns of seepage flux over daily and weekly time scales have not been extensively studied with a concentrated effort of direct measurement of seepage in nearshore areas in this study seepage was intensively measured with seepage meters over two summers and during snowmelt in lower sylvan pond a small lake in the adirondack mountains region of new york state usa a consistent pattern of slight discharge never exceeding 105 ml m 2 h 1 was observed at three stations along a segment of the shoreline near the inlet stream a distinct temporal pattern of seepage was observed at three stations along another portion of the shoreline seepage discharged 400 ml m 2 h 1 for a portion of the summer in 1998 and then shifted to recharge 2 h 1 for the remainder of the summer a similar temporal pattern was observed again in 1999 but the transition to recharge occurred earlier and higher rates of discharge 610 ml m 2 h 1 and recharge 608 ml m 2 h 1 were recorded additionally seepage at these three stations increased after large rainfall events and a pronounced episodic increase of seepage was measured during snowmelt distinct seepage patterns along portions of the shoreline show that seepage can vary considerably within seasons and suggests a need to consider changes of seepage over time periods of days to weeks as well as among seasons and years this study demonstrates that the resolution of temporal seepage data can be important to the understanding of water fluxes to aquatic ecosystems

near field tsunami models with rapid earthquake source inversions from land and ocean based observations the potential for forecast and warning computation of tsunami models in the region adjacent to large earthquakes immediately after rupture initiation remains a challenging problem limitations of traditional seismological instrumentation in the near field and concern by tsunami modelers regarding the nonuniqueness of source inversions and the use of indirect observations have in the past been hurdles for such efforts employing near field data from the mw 9 0 2011 tohoku oki data we test source models obtained from newly developed algorithms and multisensor data we demonstrate the ability of such source models determined from land based coseismic data from the combination of gps and strong motion sensors to forecast near source tsunamis we also demonstrate that rapid ingestion of offshore shallow water 100 1000 m wave gauge data substantially improves the earthquake source and tsunami forecast to assess the success of such tsunami models we rely on detailed comparisons to 2000 tsunami survey measurements collected after the event we argue that deployments of shallow water wave gauges coupled with land based geophysical sensors can in the future provide enough information to issue timely and accurate forecasts of tsunami intensity immediately or shortly after rupture initiation of large earthquakes

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

groundwater lake interactions ii nearshore seepage patterns and the contribution of ground water to lakes in central alberta abstract seepage flux was measured with seepage meters placed along transects from the lake shore to 30 110m offshore in 10 lakes in central alberta during may august 1986 in the study area the predominant surficial deposit is glacial till which is underlain by sedimentary bedrock seepage flux into the lakes ranged from 3 10 10 to 2 10 7 ms 1 seepage out of the lakes was recorded at only one of 92 seepage meter sites at one lake seepage was measured fortnightly along transects at two locations from may to august 1986 seepage patterns were consistent throughout that period in the nearshore region of six of 10 lakes seepage flux to the lakes decreased with distance from shore deviations from that pattern were probably a result of 1 spatial variability of seepage flux within a small area of lakebed 2 intertill sand and gravel lenses near the lake 3 preglacial bedrock channels of sand and gravel underlying some of the lakes ground water was the major source of water 49 of total inflow to one lake at the other lakes ground water was a relatively small component 10 of total inflow

numerical investigation of lake bed seepage patterns effects of porous medium and lake properties abstract three dimensional steady state numerical models were used to investigate the relative significance of several factors controlling lake bed seepage patterns lake depth lake bed slope orientation of an asymmetric lake with respect to a regional hydraulic gradient lake bed sediments and heterogeneity and anisotropy of the porous medium we considered both inflow and flow through lakes and our focus was on the details of seepage flux at the lake bed not on the surrounding porous medium while porous medium factors anisotropy and heterogeneity are important we found several conditions where lake bed factors were nearly as important in controlling the distribution of seepage varying lake bed slope from 0 013 to 0 04 in different simulations had a significant effect on shoreline seepage rates were 10 40 higher for lakes of low slope than lakes of steep slope also significantly elevated seepage in some cases a local maximum was observed offshore at the break in bed slope between the sloping side and flat central portions of the lake bed whenever the surrounding porous medium had a high anisotropy 1000 or 100 for flow through lakes in media of high anisotropy the annual volume of groundwater inseepage was significantly higher about 20 in lakes with steep bed slope compared to those with low slope this effect of slope was smaller at lower anisotropy for an asymmetric flow through lake a lake with a steep bed slope on one side moderate slope on the other the percentage of lake bed experiencing inseepage was greatest when the steep side was downgradient and the effect was larger at higher anisotropy these effects illustrate the complex interaction between lake bed slope and the anisotropy of the surrounding porous medium in controlling lake groundwater exchange adding low conductivity lake sediments and decreasing their conductivity shifted groundwater seepage further offshore in inflow lakes increasing the anisotropy of the surrounding porous medium had the same effect adding sediments and increasing anisotropy also decreased nearshore seepage in flow through lakes but without increasing offshore seepage in this case the net effect was a smaller annual volume of lake groundwater exchange at the same time the percentage of the lake bed experiencing inseepage increased in flow through lakes even as the annual volume of inseepage was decreasing thus for flow through lakes a larger area of inseepage may not be a good indicator of a greater volume of inseepage lake depth did not have a significant effect on the quantity or distribution of seepage to inflow or flow through lakes many of the physical factors investigated here influence the amount of lake groundwater exchange and the proportions of nearshore and offshore seepage therefore they are potentially significant to lake water quality and ecology in addition to hydrology

a new seismogeodetic approach applied to gps and accelerometer observations of the 2012 brawley seismic swarm implications for earthquake early warning 1 the 26 august 2012 brawley seismic swarm of hundreds of events ranging from m1 4 to m5 5 in the salton trough california provides a unique data set to investigate a new seismogeodetic approach that combines global positioning system gps and accelerometer observations to estimate displacement and velocity waveforms first in simulated real time mode we analyzed 1 5 hz gps data collected by 17 stations fully encircling the swarm zone at near source distances up to about 40 km using precise point positioning with ambiguity resolution ppp ar we used a reference network of north american gps stations well outside the region of deformation to estimate fractional cycle biases and satellite clock parameters which were then combined with ultrarapid orbits from the international gnss service to estimate positions during the brawley seismic swarm next we estimated seismogeodetic displacements and velocities from gps phase and pseudorange observations and 100 200 hz accelerations collected at three pairs of gps and seismic stations in close proximity using a new tightly coupled kalman filter approach as an extension of the ppp ar process we can clearly discern body waves in the velocity waveforms including p wave arrivals not detectable with the gps only approach for earthquake magnitudes as low as mw 4 6 and significant static offsets for magnitudes as low as mw 5 4 our study shows that gps networks upgraded with strong motion accelerometers can provide new information for improved understanding of the earthquake rupture process and be of critical value in creating a robust early warning system for any earthquake of societal significance

hypothetical real time gnss modeling of the 2016 mw 7 8 kaikōura earthquake perspectives from ground motion and tsunami inundation predictionhypothetical real time gnss modeling of the 2016 mw 7 8 kaikōura earthquake

geometry of depleted plasma regions in the equatorial ionosphere an image intensified all sky 6300 a airglow imaging system operating on ascension island is early 1981 has been used to assemble a photographic data base of several hundred airglow depletion patterns by mapping the airglow depletion features along geomagnetic field lines to the equatorial plane the geometrical characteristics of plasma depleted regions may be described over the 400 to 1200 km altitude region above the equator such an analysis revealed that single or linear depletions tilted toward the west with an average skewness of 0 6 longitude west 100 km altitude corresponding to a zenith angle tilt of 40 at a height of 800 km the tilts increased with local time during the evening hours showing that an effective velocity shear of 0 05 m s km is required to account for the observed evolution in several cases the depletion geometry showed a wishbone or bifurcated pattern such features had a mean height of bifurcation of 740 km and tilt factors very similar to those found for linear depletions observed during the same local time periods

complex multifault rupture during the 2016 mw 7 8 kaikōura earthquake new zealand the 2016 moment magnitude m w 7 8 kaik ura earthquake was one of the largest ever to hit new zealand hamling et al show with a new slip model that it was an incredibly complex event unlike most earthquakes multiple faults ruptured to generate the ground shaking a remarkable 12 faults ruptured overall with the rupture jumping between faults located up to 15 km away from each other the earthquake should motivate rethinking of certain seismic hazard models which do not presently allow for this unusual complex rupture pattern science this issue p eaam7194 1 1 lookup doi 10 1126 science aam7194

superficial simplicity of the 2010 el mayor cucapah earthquake of baja california in mexico the geometry of faults is usually thought to be more complicated at the surface than at depth and to control the initiation propagation and arrest of seismic ruptures the fault system that runs from southern california into mexico is a simple strike slip boundary the west side of california and mexico moves northwards with respect to the east however the m w 7 2 2010 el mayor cucapah earthquake on this fault system produced a pattern of seismic waves that indicates a far more complex source than slip on a planar strike slip fault here we use geodetic remote sensing and seismological data to reconstruct the fault geometry and history of slip during this earthquake we find that the earthquake produced a straight 120 km long fault trace that cut through the cucapah mountain range and across the colorado river delta however at depth the fault is made up of two different segments connected by a small extensional fault both segments strike n130 e but dip in opposite directions the earthquake was initiated on the connecting extensional fault and 15 s later ruptured the two main segments with dominantly strike slip motion we show that complexities in the fault geometry at depth explain well the complex pattern of radiated seismic waves we conclude that the location and detailed characteristics of the earthquake could not have been anticipated on the basis of observations of surface geology alone

local tsunami warnings perspectives from recent large events we demonstrate a flexible strategy for local tsunami warning that relies on regional geodetic and seismic stations through retrospective analysis of four recent tsunamigenic events in japan and chile we show that rapid earthquake source information provided by methodologies developed for earthquake early warning can be used to generate timely estimates of maximum expected tsunami amplitude with enough accuracy for tsunami warning we validate the technique by comparing to detailed models of earthquake source and tsunami propagation as well as field surveys of tsunami inundation our approach does not require deployment of new geodetic and seismic instrumentation in many subduction zones and could be implemented rapidly by national monitoring and warning agencies we illustrate the potential impact of our method with a detailed comparison to the actual timeline of events during the recent 2015 mw8 3 illapel chile earthquake and tsunami that prompted the evacuation of 1 million people

scaling relations of earthquake source parameter estimates with special focus on subduction environment abstract earthquake rupture length and width estimates are in demand in many seismological applications earthquake magnitude estimates are often available whereas the geometrical extensions of the rupture fault mostly are lacking therefore scaling relations are needed to derive length and width from magnitude most frequently used are the relationships of wells and coppersmith 1994 derived on the basis of a large dataset including all slip types with the exception of thrust faulting events in subduction environments however there are many applications dealing with earthquakes in subduction zones because of their high seismic and tsunamigenic potential there are no well established scaling relations for moment magnitude and length width for subduction events within this study we compiled a large database of source parameter estimates of 283 earthquakes all focal mechanisms are represented but special focus is set on large subduction zone events in particular scaling relations were fitted with linear least square as well as orthogonal regression and analyzed regarding the difference between continental and subduction zone oceanic relationships additionally the effect of technical progress in earthquake parameter estimation on scaling relations was tested as well as the influence of different fault mechanisms for a given moment magnitude we found shorter but wider rupture areas of thrust events compared to wells and coppersmith 1994 the thrust event relationships for pure continental and pure subduction zone rupture areas were found to be almost identical the scaling relations differ significantly for slip types the exclusion of events prior to 1964 when the worldwide standard seismic network was established resulted in a remarkable effect on strike slip scaling relations the data do not show any saturation of rupture width of strike slip earthquakes generally rupture area seems to scale with mean slip independent of magnitude the aspect ratio l w however depends on moment and differs for each slip type

water pathways and chemistry at the groundwater surface water interface to lake skjervatjern norway water pathways and chemistry at the groundwater surface waterinterface to lake skjervatjern norway

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

earthquake magnitude calculation without saturation from the scaling of peak ground displacement gps instruments are noninertial and directly measure displacements with respect to a global reference frame while inertial sensors are affected by systematic offsets primarily tilting that adversely impact integration to displacement we study the magnitude scaling properties of peak ground displacement pgd from high rate gps networks at near source to regional distances 10 1000 km from earthquakes between mw6 and 9 we conclude that real time gps seismic waveforms can be used to rapidly determine magnitude typically within the first minute of rupture initiation and in many cases before the rupture is complete while slower than earthquake early warning methods that rely on the first few seconds of p wave arrival our approach does not suffer from the saturation effects experienced with seismic sensors at large magnitudes rapid magnitude estimation is useful for generating rapid earthquake source models tsunami prediction and ground motion studies that require accurate information on long period displacements

real time magnitude characterization of large earthquakes using the predominant period derived from 1 hz gps data earthquake early warning eew systems performance is driven by the trade off between the need for a rapid alert and the accuracy of each solution a challenge for many eew systems has been the magnitude saturation for large events mw 7 and the resulting underestimation of seismic moment magnitude in this study we test the performance of high rate 1hz gps based on seven seismic events to evaluate whether long period ground motions can be measured well enough to infer reliably earthquake predominant periods we show that high rate gps data allow the computation of a gps based predominant period g to estimate lower bounds for the magnitude of earthquakes and distinguish between large mw 7 and great mw 8 events and thus extend the capability of eew systems for larger events it is also identified the impact of the different value of the smoothing factor on the g results and how the sampling rate and the computation process differentiates g from the commonly used p

dynamics of submarine groundwater discharge and freshwater seawater interface 1 relationships between submarine groundwater discharge sgd and the freshwater saltwater interface are evaluated by continuous measurements of sgd rates conductivity and temperature of sgd and resistivity measurements across the coastal aquifer our measurements show that the processes of sgd differ between the offshore and nearshore environments sgd and submarine fresh groundwater discharge sfgd rates were largest just landward of the saltwater freshwater interface sgd variations landward the saltwater freshwater interface had negative correlations with tidal variations because of the connections of terrestrial groundwater in the land and the ocean sgd in the nearshore can be explained mainly by connections of terrestrial groundwater while offshore sgd rate is controlled mostly by oceanic process such as recirculated saline groundwater discharge

comparing source inversion techniques for gps based local tsunami forecasting a case study for the april 2014 m8 1 iquique chile earthquake

real time centroid moment tensor determination for large earthquakes from local and regional displacement records summary we present an algorithm to rapidly determine the moment tensor and centroid location for large earthquakes employing local and regional real time high rate displacement records from gps the algorithm extracts the coseismic offset from the displacement waveforms and uses the information to invert for the moment tensor the green s functions for a layered earth are obtained numerically from open source code edgrn to determine the centroid multiple inversions are simultaneously performed within a grid of inversion nodes and the node with the smallest misfit is then assigned the centroid location we show results for two large earthquakes replayed in simulated real time mode using recorded 1 hz gps displacements the 2003 mw 8 3 tokachi oki and the 2010 mw 7 2 el mayor cucapah earthquakes we demonstrate that it is feasible to obtain accurate cmt solutions within the first 2 3 min after rupture initiation without any prior assumptions on fault characteristics demonstrating an order of magnitude improvement in latency compared to existing seismic methods for the two earthquakes studied this methodology is useful for rapid earthquake response tsunami prediction and as a starting point for rapid finite fault modelling

the 2011 magnitude 9 0 tohoku oki earthquake mosaicking the megathrust from seconds to centuries geophysical observations from the 2011 moment magnitude m w 9 0 tohoku oki japan earthquake allow exploration of a rare large event along a subduction megathrust models for this event indicate that the distribution of coseismic fault slip exceeded 50 meters in places sources of high frequency seismic waves delineate the edges of the deepest portions of coseismic slip and do not simply correlate with the locations of peak slip relative to the m w 8 8 2010 maule chile earthquake the tohoku oki earthquake was deficient in high frequency seismic radiation a difference that we attribute to its relatively shallow depth estimates of total fault slip and surface secular strain accumulation on millennial time scales suggest the need to consider the potential for a future large earthquake just south of this event

effect of ground water recharge on configuration of the water table beneath sand dunes and on seepage in lakes in the sandhills of nebraska u s a abstract analysis of water level fluctuations in about 30 observation wells and 5 lakes in the crescent lake national wildlife refuge in the sandhills of nebraska indicates water table configuration beneath sand dunes in this area varies considerably depending on the configuration of the topography of the dunes if the topography of an interlake dunal area is hummocky ground water recharge is focused at topographic lows causing formation of water table mounds these mounds prevent ground water movement from topographically high lakes to adjacent lower lakes if a dune ridge is sharp the opportunity for focused recharge does not exist resulting in water table troughs between lakes lakes aligned in descending altitudes parallel to the principal direction of regional ground water movement generally have seepage from higher lakes toward lower lakes

earthquake magnitude scaling using seismogeodetic data 1 the combination of gps and strong motion data to estimate seismogeodetic waveforms creates a data set that is sensitive to the entire spectrum of ground displacement and the full extent of coseismic slip in this study we derive earthquake magnitude scaling relationships using seismogeodetic observations of either p wave amplitude or peak ground displacements from five earthquakes in japan and california ranging in magnitude from 5 3 to 9 0 the addition of the low frequency component allows rapid distinction of earthquake size for large magnitude events with high precision unlike accelerometer data that saturate for earthquakes greater than m 7 to 8 and is available well before the coseismic displacements are emplaced these results though based on a limited seismogeodetic data set support earlier studies that propose it may be possible to estimate the final magnitude of an earthquake well before the rupture is complete

factors contributing to the salinity of lakes riske creek region south central british columbia canada abstract the objective of this study was to determine the primary factors that contribute to the salinity of lakes located within the riske creek region of south central british columbia canada the riske creek region contains numerous lakes with a salinity range of 0 10 8 ppt with high and low salinity lakes co existing in close proximity to one another the region is of extreme ecological importance because it is located on the pacific flyway and serves as a major breeding ground for a number of waterfowl species water budgets lake water chemistry and cation ca 2 mg 2 na and k interstitial water composition were determine for 9 lakes 3 oligosaline 0 ppt 3 mesosaline 0 4 1 0 ppt and 3 euryhaline 2 7 5 3 ppt to determine if evapo precipitive or saline groundwater inputs were the primary determinants of lake salinity lake water budgets indicated that meso and euryhaline lakes were in a close to zero or negative water balance whereas the 3 oligosaline lakes were in a positive water balance groundwater saline inputs as measured by lake sediment interstitial water cation concentrations indicated that groundwater made only minor contributions to lake salinity water budget calculations and sediment interstitial water chemistry suggest that lakes are saline largely due to evaporative processes

magnitude estimation using the first three seconds p wave amplitude in earthquake early warning 1 pd is the peak amplitude of displacement in the first three seconds after the arrival of the p wave we investigated the attenuation of pd with the hypocentral distance r in southern california as a function of magnitude m and obtained the following relationship log pd 3 463 0 729 m 1 374 log r 0 305 given an earthquake location determined by the p wave arrival times at stations close to the epicenter this relationship can be used to define a so called pd magnitude of earthquakes our result shows that for earthquakes in southern california the pd magnitudes agree with the catalog magnitudes with a standard deviation of 0 18 for events less than magnitude 6 5 therefore pd is a robust measurement for estimating the magnitudes of earthquakes and has practical application in earthquake early warning systems citation wu y m and l zhao 2006 magnitude estimation using the first three seconds p wave amplitude in earthquake early warning geophys res lett 33 l16312 doi 10 1029 2006gl026871

groundwater lake interactions i accuracy of seepage meter estimates of lake seepage abstract the use of seepage meters to identify nearshore seepage patterns and to quantify seepage in lakes was evaluated with a monte carlo simulation model the model simulated seepage flux as would be derived from seepage meter measurements along a transect extending from the shore of a hypothetical lake to 40 or 100m offshore along the transect simulated seepage velocities decreased exponentially with distance from shore according to patterns measured at narrow lake alta and lake sallie mn to determine statistical parameters needed in the model seepage flux was measured in situ with closely spaced seepage meters at four different sites in narrow lake seepage velocities within a small area of lakebed were log normally distributed and the variance was positively correlated with mean seepage flux the modeling indicated that the most sensitive parameter affecting the accuracy of seepage meter estimates of seepage patterns and average seepage flux along the transect was the variability in the spatial distribution of seepage flux within a small area of lakebed there was little improvement in the accuracy of estimates of seepage patterns or transect flux when more than ten seepage meters were simulated along the transect when the transect was sampled more than twice or when seepage meters along the transect were simulated to follow a stratified rather than a systematic design

interesting equatorial plasma bubbles observed by all sky imagers in the equatorial region of china this paper reports some interesting equatorial plasma bubbles epbs on 04 05 october 2013 and 29 30 september 2013 observed by two all sky imagers located in the magnetically equatorial region of hainan 19 5 n 9 5 geomagnetic latitude and guiping 23 8 n 13 9 geomagnetic latitude china the case of 04 05 october 2013 shows that 1 epbs had planar wave like structures and their wavefronts were parallel to each other before midnight 2 the angle between the wavefronts of those epbs and the geomagnetic meridian were 30 3 near midnight the higher latitude part of one epb suddenly began to rotate with a large eastward zonal drift resulting in an unusual c shaped epb that was observed for the first time by an all sky imager 4 after midnight one epb merged into another epb and formed an integrated epb the other epb case on 29 30 sept 2013 shows that 1 the images captured the full evolution processes of an i shaped epb with an angle of 30 with respect to the geomagnetic meridian the imagers also observed s and y shaped epbs 2 the change of epbs shape was directly related to the change of epbs zonal drift velocities 3 the angle between the i shaped epbs and the geomagnetic meridian was likely caused by the change of the latitudinal gradient of zonal neutral wind velocities and ionospheric conductivity 4 the zonal velocity of each branch of the y shape epb was different which could be related to the polarization electric fields within each branch

effects of water table configuration on seepage through lakebeds the interaction of lakes and groundwater is controlled in part by the configuration of the water table near a lake seepage from lakes does not occur if the water table mound between the lake and a regional groundwater discharge arca is sufficiently high and the water table gradient between the mound and the discharge area sufficiently small water table configurations associated with two grountlwatcr systems of different geometry were examined by digital simulation for the first setting there is no seepage from the lake if the water table gradient from the mound to the regional discharge area is 0 011 for the second the critical gradient is about 0 009 seepage from the lake occurs if water table gradients are greater than these two values for various glacial terrains in which most natural lakes occur water table gradients of 0 010 or greater are most common in the more rugged end moraines consisting of silty till and gradients of 40 010 are common in arcas of ground moraine outwash plains

observations of dc electric fields in the low latitude ionosphere and their variations with local time longitude and plasma density during extreme solar minimum 1 dc electric fields and associated e b plasma drifts detected with the double probe experiment on the c nofs satellite during extreme solar minimum conditions near the june 2008 solstice are shown to be highly variable with weak to moderate ambient amplitudes of 1 2 mv m 25 50 m s average field or drift patterns show similarities to those reported for more active solar conditions i e eastward and outward during day and westward and inward at night however these patterns vary significantly with longitude and are not always present daytime vertical drifts near the magnetic equator are largest in the prenoon sector observations of weak to nonexistent prereversal enhancements in the vertical drifts near sunset are attributable to reduced dynamo activity during solar minimum as well as seasonal effects enhanced meridional drifts are observed near sunrise in certain longitude regions precisely where the enhanced eastward flow that persisted from earlier local times terminates the nightside ionosphere is characterized by larger amplitude structured electric fields dominated by horizontal scales of 500 1500 km even where local plasma densities appear relatively undisturbed data acquired during successive orbits indicate that plasma drifts and densities are persistently organized by longitude the high duty cycle of the c nofs observations and its unique orbit promise to expose new physics of the low latitude ionosphere

imaging the 2016 mw 7 8 kaikoura new zealand earthquake with teleseismic p waves a cascading rupture across multiple faults the 13 november 2016 mw 7 8 kaikoura new zealand earthquake was investigated using teleseismic p waves backprojection of high frequency p waves from two regional arrays shows unilateral rupture of at least two southwest northeast striking faults with an average rupture speed of 1 4 1 6 km s and total duration of 100 s guided by these backprojection results 33 globally distributed low frequency p waves were inverted for a finite fault model ffm of slip the ffm showed evidence of several subevents however it lacked significant moment release near the epicenter where a large burst of high frequency energy was observed a local strong motion network recorded strong shaking near the epicenter hence for this earthquake the distribution of backprojection energy is superior to the ffm as a guide of strong shaking for future large earthquakes that occur in regions without strong motion networks initial shaking estimates could benefit from backprojection constraints

the condor equatorial spread f campaign overview and results of the large scale measurements during the condor campaign a number of instruments were set up in peru to support the rocket experiments in this series of papers we report on the results of the experiments designed to study the equatorial f region in this overview paper we summarize the main results as well as report upon the macroscopic developments of spread f as evidenced by data from backscatter radas from scintillation observations and from digital ionosonde meaurements in this latter regard we argue here that at least two factors other than the classical gravitational rayleigh taylor plasma instability process must operate to yield the longest scale horizontal organization of spread f structures the horizontal scale typical of plume separation distances can be explained by invoking the effect of a shear in the plasma flow although detailed comparison with theory seems to require shear frequencies a bit higher than observa tions indicate on the other hand the largest scale organization or modulation of the scattering layer cannot be explained by the shear theory and must be due to local time variations in the ionospheric drift or to gravity wave induced vertical motions using simultaneous rocket and radar data we were also able to confirm the oft quoted hypothesis that rapid overhead height variations in the scattering region over jicamarca are primarily spatial structures advecting overhead the detailed rocket radar compari son verified several other earlier results and speculations particularly those made in the plumex experiments in particular companion papers discuss and extend some of the plumex results to include the role of anomalous diffusion labelle et al this issue in the theory of equatorial spread f and to shed light upon the shallow spectral form often observed in the intermediate scale regime labelle and kelley this issue

global distribution of density irregularities in the equatorial ionosphere we analyzed measurements of ion number density made by the retarding potential analyzer aboard the atmosphere explorer e ae e satellite which was in an approximately circular orbit at an altitude near 300 km in 1977 and later at an altitude near 400 km large scale 60 km density measurements in the high altitude regions show large depletions of bubble like structures which are confined to narrow local time longitude and magnetic latitude ranges while those in the low altitude regions show relatively small depletions which are broadly distributed in space for this reason we considered the altitude regions below 300 km and above 350 km and investigated the global distribution of irregularities using the rms deviation n n over a path length of 18 km as an indicator of overall irregularity intensity seasonal variations of irregularity occurrence probability are significant in the pacific regions while the occurrence probability is always high in the atlantic african regions and is always low in the indian regions we find that the high occurrence probability in the pacific regions is associated with isolated bubble structures while that near 0 longitude is produced by large depletions with bubble structures which are superimposed on a large scale wave like background considerations of longitude variations due to seeding mechanisms and due to f region winds and drifts are necessary to adequately explain the observations at low and high altitudes seeding effects are most obvious near 0 longitude while the most easily observed effect of the f region is the suppression of irregularity growth by interhemispheric neutral winds

real time inversion of gps data for finite fault modeling and rapid hazard assessment 1 responses to recent great earthquakes and ensuing tsunamis in sumatra chile and japan with the resulting loss of life and damage to infrastructure demonstrate that our ability to ascertain the full extent of slip of catastrophic earthquakes and their tsunamigenic potential in the first minutes after the initiation of rupture is problematic regional gps networks such as those in western north america and japan are complementary to seismic networks by being able to directly measure displacements close to the source during large earthquakes in real time we report on rapid modeling of two large earthquakes the 2003 mw 8 3 tokachi oki earthquake 100 km offshore hokkaido island using 356 geonet stations and the 2010 mw 7 2 el mayor cucapah earthquake in northern baja california using 95 crtn stations in southern california about 75 km northwest of the epicenter working in a simulated real time mode we invert for finite fault slip in a homogeneous elastic half space using green s functions obtained from okada s formulation we compare two approaches the first starts with a catalog of pre defined faults while the second uses a rapid centroid moment tensor solution to provide an initial estimate of the ruptured fault plane in either case we are able to characterize both earthquakes in less than two minutes reducing the time necessary to obtain finite fault slip and moment magnitude for medium and greater earthquakes compared to traditional methods by an order of magnitude

rapid modeling of the 2011 mw 9 0 tohoku oki earthquake with seismogeodesy 1 rapid characterization of finite fault geometry and slip for large earthquakes is important for mitigation of seismic and tsunamigenic hazards saturation of near source weak motion and problematic integration of strong motion data into displacements make this difficult in real time combining gps and accelerometer data to estimate seismogeodetic displacement waveforms overcomes these limitations by providing mm level three dimensional accuracy and improved estimation of coseismic deformation compared to gps only methods we leverage collocated gps and accelerometer data from the 2011 mw 9 0 tohoku oki japan earthquake by replaying them in simulated real time mode using a novel approach to account for fault finiteness we generate an accurate centroid moment tensor solution independently of any constraint on the slab geometry followed by a finite fault slip model the replay of gps and seismic data demonstrates that robust models could have been made available within 3 min of earthquake initiation

calibration and use of continuous heat type automated seepage meters for submarine groundwater discharge measurements abstract submarine groundwater discharge sgd assessments were conducted both in the laboratory and at a field site in the northeastern gulf of mexico using a continuous heat type automated seepage meter seepmeter the functioning of the seepmeter is based on measurements of a temperature gradient in the water between downstream and upstream positions in its flow pipe the device has the potential of providing long term high resolution measurements of sgd using a simple inexpensive laboratory set up we have shown that connecting an extension cable to the seepmeter has a negligible effect on its measuring capability similarly the observed influence of very low temperature 3 c on seepmeter measurements can be accounted for by conducting calibrations at such temperatures prior to field deployments compared to manual volumetric measurements calibration experiments showed that at higher water flow rates 28 cm day 1 or cm 3 cm 2 day 1 an analog flowmeter overestimated flow rates by 7 this was apparently due to flow resistance turbulence and formation of air bubbles in the seepmeter water flow tubes salinity had no significant effect on the performance of the seepmeter calibration results from fresh water and sea water showed close agreement at a 95 confidence level significance between the data sets from the two media r 2 0 98 comparatively the seepmeter sgd measurements provided data that are comparable to manually operated seepage meters the radon geochemical tracer approach and an electromagnetic em seepage meter

airglow characteristics of equatorial plasma depletions a new low light level all sky 6300 a airglow imaging system has been developed for ground based studies of the optical signatures of equatorial plasma depletions the system was designed for narrowband interference filters 6 a full width at half power with interchangeable all sky 180 and narrow field 60 lenses and records images photographically by using a standard 35 mm camera a field test of the apparatus was conducted on ascension island 8 0 s 14 4 w from january 24 to february 10 1981 the photographs were analyzed for broad morphological characteristics by using simple overlay techniques augmented by digital image processing methods to extract more quantitative detail the initial results to come from these observations show that airglow depletions occur most often during the 2030 2330 lt period often covering one fourth of the visible sky they extend from the magnetic equator to beyond the crest of the equatorial anomaly with east west cross sections of 100 km to several hundred kilometers they are usually not aligned with magnetic meridians showing a progressive skewness to the west at further distances from the equator several cases of apparently twisting overlapping and bifurcating depletions were observed the depletions drifted to the east with speeds that decreased from 190 m s at 2100 lt to 80 m s at 0100 lt the airglow intensities within depletions were typically 40 50 of the background levels and the western walls of the depletions usually had a steeper gradient than the corresponding eastern walls

a new zealand specific pseudospectral acceleration ground motion prediction equation for active shallow crustal earthquakes based on foreign models abstract the applicability of foreign ground motion prediction equations gmpes for predicting geometric mean pseudospectral acceleration amplitudes from active shallow crustal earthquakes in new zealand nz is examined four different foreign gmpes were considered as well as the nz based mcverry et al 2006 mcv06 model it was found that the mcv06 model exhibited the lowest applicability with a database of 2437 recorded ground motions and that the chiou et al 2010 c10 modification of the chiou and youngs 2008b cy08 model was the most applicable discrepancies between the c10 model and the nz database which were empirically identified and theoretically justified were used to modify the c10 model for 1 small magnitude scaling 2 scaling of short period ground motion from normal faulting events in volcanic crust 3 scaling of ground motions on very hard rock sites 4 anelastic attenuation in the nz crust and 5 consideration of the increased anelastic attenuation in the taupo volcanic zone the developed nz specific model therefore contains features as evident from recorded ground motions in nz and consistent scaling for parameters not well constrained by nz data comparisons with ground motions from the 4 september 2010 darfield and 22 february 2011 christchurch earthquakes which occurred following completion of the nz specific model illustrate that it provides an empirical prediction with sufficient accuracy and precision

earthquake in a maze compressional rupture branching during the 2012 mw 8 6 sumatra earthquake seismological observations of the 2012 moment magnitude 8 6 sumatra earthquake reveal unprecedented complexity of dynamic rupture the surprisingly large magnitude results from the combination of deep extent high stress drop and rupture of multiple faults back projection source imaging indicates that the rupture occurred on distinct planes in an orthogonal conjugate fault system with relatively slow rupture speed the east southeast west northwest ruptures add a new dimension to the seismotectonics of the wharton basin which was previously thought to be controlled by north south strike slip faulting the rupture turned twice into the compressive quadrant against the preferred branching direction predicted by dynamic coulomb stress calculations orthogonal faulting and compressional branching indicate that rupture was controlled by a pressure insensitive strength of the deep oceanic lithosphere

an integrated approach to quantify groundwater transport of phosphorus to narrow lake alberta an integrated approach was used to quantify groundwater phosphorus flux to narrow lake a smallglacial terrain lake in central alberta data from a drilling program major ion concentrations environmental isotopes and computer simulations indicated that the lake gains water through the nearshore region from a small shallow groundwater flow system at deep offshore regions water moves from the lake to the groundwater flow system seepage flux was quantified by water budget darcy s equation with data from wells near the lake darcy s equation with data from minipiezometers in the lake and seepage meters whole lake seepage flux determined from minipiezometer data 30 mm yr i was only lo 25 of the other estimates mean 221 mm yr i range 133 332 mm yr l from seepage meter and water budget data respectively groundwater contributed 30 of the annual water load to the lake the p concentration pi in pore water from lake sediments mean 175 mg m was 8 times higher than groundwater from wells near the lake mean 2 1 mg m 3 thus if well water was used to estimate the p of the seepage water the rate of groundwater p loading to the lake would be underestimated the rate of groundwater p loading to the lake computed from average seepage flux and average pore water p was 39 mg m 2 yr i and groundwater may be the largest single source of p to epilimnetic water in the lake

rapid determination of earthquake magnitude using gps for tsunami warning systems 1 the 26 december 2004 sumatra earthquake mw 9 2 9 3 generated the most deadly tsunami in history yet within the first hour the true danger of a major oceanwide tsunami was not indicated by seismic magnitude estimates which were far too low mw 8 0 8 5 this problem relates to the inherent saturation of early seismic wave methods here we show that the earthquake s true size and tsunami potential can be determined using global positioning system gps data up to only 15 min after earthquake initiation by tracking the mean displacement of the earth s surface associated with the arrival of seismic waves within minutes displacements of 10 mm are detectable as far away as india consistent with results using weeks of data after the event these displacements imply mw 9 0 0 1 indicating a high tsunami potential this suggests existing gps infrastructure could be developed into an effective component of tsunami warning systems

earthquake magnitude estimation from peak amplitudes of very early seismic signals on strong motion records 1 we show that the low pass filtered peak amplitudes of initial p and s wave seismic signals recorded in the vicinity of an occurring earthquake source correlates with the earthquake magnitude and may be used for real time estimation of the event size in seismic early warning applications the earthquake size can be therefore estimated using only a couple of seconds of signal from the p or s wave onsets i e while the rupture itself is still propagating and rupture dimension is far from complete we argue that dynamic stress release and or slip duration on the fault in the very early stage of seismic fracture scales both with the observed peak amplitude and with the elastic energy available for fracture propagation the probability that a fracture grows to a larger size should scale with the energy initially available citation zollo a m lancieri and s nielsen 2006 earthquake magnitude estimation from peak amplitudes of very early seismic signals on strong motion records geophys res lett 33 l23312 doi 10 1029 2006gl027795

gravity wave generation in the lower stratosphere due to passage of the typhoon 9426 orchid observed by the mu radar at shigaraki 34 85 n 136 10 e 1 intense gravity wave activities were investigated in the lower stratosphere during the typhoon 9426 strong vertical winds were observed just a few hours before the arrival of the typhoon center at the mu radar site about 30 min to 1 hour after the typhooncenter had passed a considerable reduction in vertical wind amplitude was detected dominant gravity waves showed time period in the range of 7 8 min 15 min and 40 60 min in the upper troposphere and lower stratosphere in the vicinity of the central region of the typhoon a gravity wave was observed which was monochromatic in nature with a vertical wavelength 3 km between 1 5 km and 23 km height in the lower stratosphere the horizontal wavelength for the prominent period was detected in the range of 10 15 km for 15 min wave period and 25 50 km for 40 60 min wave period the vertical wavelength of these waves was examined from 2 5 km to 4 0 km in the horizontal direction the intrinsic group velocity was estimated between 9 2 and 11 2 m s near the tropopause the average direction of group velocity was assessed at about 20 3 from the horizontal the generation of gravity wave like features in the lower stratosphere is believed induced by convection as the low temperature of the clouds indicates a deep penetration over the radar region as seen in the satellite gms images index terms 3314 meteorology and atmospheric dynamics convective processes 3334 meteorology and atmospheric dynamics middle atmosphere dynamics 0341 0342 3329 meteorology and atmospheric dynamics mesoscale meteorology 3384 meteorology and atmospheric dynamics waves and tides 6952 radio science radar atmospheric physics keywords convective updrafts gravity waves troposphere lower stratosphere