holocene diatom assemblages and their palaeoenvironmental interpretations in fayoum depression western desert egypt abstract diatom assemblages from the diatomaceous deposits of fayoum depression egypt were analysed to reconstruct the palaeoenvironmental changes during the early to middle holocene a total of 283 diatom species and varieties representing 57 genera were identified the stratigraphic distribution patterns of the recorded diatoms explained eight diatom assemblage zones which revealed an interesting history of shifts in paleosalinity ph and water level of the old fayoum lake as the water body filled in planktonic and benthic epiphytic assemblages alternate throughout the studied sections the alternations reflect paleolimnologic conditions as water levels rose and fell the diatom results have shown four high stands of the freshwater lake level during humid warmer wet climatic phases coinciding with abundance of planktonic stephanodiscus spp and aulacoseira granulata assemblage zones rising lake levels are alternated with phases of lowering freshwater lake level with relatively slight rises in salinity and alkalinity one phase during arid conditions is represented by an abundance of a benthic navicula radiosa assemblage zone the second phase during cold and drier climate is dominated by a staurosira staurosirella spp assemblage zone the third phase is distinguished by predominance of epiphytic epithemia spp encyonema cymbella spp synedra spp and cocconeis placentula assemblage zones during warm arid conditions

detection of a volcanic fracture opening in japan using global positioning system measurements the global positioning system gps is a powerful tool for detecting crustal deformation1 for example the technique has been used to detect plate boundary movements in california2 here we report observations of crustal deformation associated with seismic swarm and sea floor volcanic activity off the east coast of the izu peninsula japan in july 1989 using a fixed point gps network these measurements have enabled us to capture some rarely observed features of seismic and volcanic activity we have for the first time used gps fixed point measurements to follow the evolution with time of the crustal movements such measurements provide a continuous uninterrupted record of deformation our observations were supported by independent data from other sources thus providing further evidence for the utility of the gps

late cenozoic lacustrine and climatic environments at tule lake northern great basin usa cores of lake sediment to a depth of 334 m in the town of tulelake siskiyou county northern california document the late cenozoic paleolimnologic and paleoclimatic history of the northwestern edge of the great basin the cores have been dated by radiometric tephrochronologic and paleomagnetic analyses lacustrine diatoms are abundant throughout the record and document a nearly continuous paleolimnologic history of the tule lake basin for the last 3 myr during most of this time this basin tule lake was a relatively deep extensive lake except for a drier and cooler interval recorded by fragilaria species about 2 4 ma the pliocene is characterized by a dominance of planktonic aulacoseira solida implying a warm monomictic lake under a climatic regime of low seasonality much of the pleistocene is dominated by stephanodiscus and fragilaria species suggesting a cooler often drier and highly variable climate benthic diatoms typical of alkaline enriched saline waters commonly appear after 1 0 ma and tephrochronology indicates slow deposition and possible hiatuses between about 0 6 and 0 2 ma the chronology of even numbered oxygen isotope stages approximately matches fluctuations in the abundance of fragilaria since 800 ka indicating that glacial periods were expressed as drier environments at tule lake glacial and interglacial environments since 150 ka were distinct from and more variable than those occurring earlier the last full glacial period was very dry but shortly thereafter tule lake became a deep cool lacustrine system indicating a substantial increase in precipitation aulacoseira ambigua characterized the latest glacial and holocene record of tule lake its distribution indicates that warmer and wetter climates began about 15 ka in this part of the great basin diatom concentration fluctuates at 41 000 year intervals between 3 0 and 2 5 ma and at approximately 100 000 year intervals after 1 0 ma in the late pliocene and early pleistocene aulacoseira solida percentages wax and wane in an approximately 400 000 year cycle the possible response of tule lake diatom communities to orbitally induced insolation cycles underscores the importance of this record for the study of late cenozoic paleoclimate change

tracking magma volume recovery at okmok volcano using gps and an unscented kalman filter 1 changes beneath a volcano can be observed through position changes in a gps network but distinguishing the source of site motion is not always straightforward the records of continuous gps sites provide a favorable data set for tracking magma migration dense campaign observations usually provide a better spatial picture of the overall deformation field at the expense of an episodic temporal record combining these observations provides the best of both worlds a kalman filter provides a means for integrating discrete and continuous measurements and for interpreting subtle signals the unscented kalman filter ukf is a nonlinear method for time dependent observations we demonstrate the application of this technique to deformation data by applying it to gps data collected at okmok volcano seven years of gps observations at okmok are analyzed using a mogi source model and the ukf the deformation source at okmok is relatively stable at 2 5 km depth below sea level located beneath the center of the caldera which means the surface deformation is caused by changes in the strength of the source during the 7 years of gps observations more than 0 5 m of uplift has occurred a majority of that during the time period january 2003 to july 2004 the total volume recovery at okmok since the last eruption in 1997 is 60 80 the ukf allows us to solve simultaneously for the time dependence of the source strength and for the location without a priori information about the source

abrupt post glacial climate events in west asia and north africa monsoon domains regions beyond the present or past penetration of the indian and african monsoons have experienced several large and abrupt climatic fluctuations over the past 13 14c kyr pollen and lake records from west asia western tibet and rajasthan east africa ethiopia and west africa western sahara sahel and subequatorial africa were selected on the basis of chronological control sensitivity of both site and environmental indicators to climate change the continuity of the record and interdisciplinary control of the palaeoclimatic interpretation conditions wetter than those of today prevailed during the early mid holocene period but major dry spells are recorded at all sites during the intervals 11 0 9 5 kyr bp 8 7 kyr bp and 3 4 kyr bp several records also suggest dry events of minor amplitude around 6 kyr bp potential boundary forcings of insolation and sea surface and tropical land surface conditions are discussed the solar radiation accounts for the general envelop of the post glacial monsoon fluctuations but explains neither the timing nor the amplitude of the short term changes in spite of apparent covariation between fluctuations in sea surface conditions in the north atlantic and the monsoon record no direct mechanism could be found relating the intensity of the oceanic thermohaline conveyor belt to the monsoon strength changes in tropical land surface conditions soil moisture negative feedback and changes in ch4 production from wetlands provide a more satisfactory hypothesis for explaining abrupt reversal events

mid to late holocene paleoclimatic changes and paleoenvironmental shifts inferred from pollen and diatom assemblages at lake hamra wadi el natrun western nile delta north western desert egypt abstract four palynological and three diatom zones of mid to late holocene are identified along a 370 cm long radiocarbon dated sediment core collected in lake hamra at wadi el natrun western nile delta egypt the mid late holocene between the predynastic to old kingdom was terrestrial wetland habitat with high seasonal rainfall and or nile flood as revealed by the dominance of cyperaceae pollen therefore people gathered in and around the nile valley and the agricultural activities increased during the early stage of late holocene coincident with the old kingdom to middle kingdom the paleoclimate became more arid with low seasonal precipitation and or nile flood as reflected by the increasing abundance of poaceae pollen and the absence of diatoms in addition to low values of toc tn ts c s and high values of c n these drought conditions possibly played a role in the old kingdom collapsing the late stage of the late holocene showed terrestrial wetland habitat with brackish conditions coupled with aquatic contribution under oxic conditions as inferred by the dominance of typha sp and amaranthaceae pollens as well as the diatom assemblages the relatively high values of toc c n c s coupled with low values of ts and tn reveal terrestrial origin of organic matter the late holocene recent has turned into a terrestrial wetland habitat with more brackish conditions and increasing in the seasonal rainfall as supported by the marked increasing of cyperaceae pollen the overall increase of the diatom inferred salinity dis as well as the marked increasing of c s tn and decreasing of toc c n and ts values towards the recent point to higher saline brackish wetland paleoenvironment and a terrestrial origin of the organic matter with more aquatic contribution under oxic conditions

ground deformation associated with the precursory unrest and early phases of the january 2006 eruption of augustine volcano alaska 1 on january 11 2006 augustine volcano erupted after nearly 20 years of quiescence global positioning system gps instrumentation at augustine consisting of six continuously recording telemetered receivers measured clear precursory deformation consistent with a source of inflation or pressurization beneath the volcano s summit at a depth of around sea level deformation began in early summer 2005 and was preceded by a subtle but distinct increase in seismicity which began in may 2005 after remaining more or less constant deformation rates accelerated on at least three stations beginning in late november 2005 after this date gps data suggest the upward propagation of a small dike into the edifice which based on the style of deformation and high levels of gas emission appears to have ascended to shallow levels by mid december 2005 about four weeks before the eruption began

constraints on dike propagation from continuous gps measurements the january 1997 east rift zone eruption on kilauea volcano hawaii occurred within a network of continuous global positioning system gps receivers the gps measurements reveal the temporal history of deformation during dike intrusion beginning 8 hours prior to the onset of the eruption the dike volume as a function of time estimated from the gps data using elastic green s functions for a homogeneous half space shows that only two thirds of the final dike volume accumulated prior to the eruption and the rate of volume change decreased with time these observations are inconsistent with simple models of dike propagation which predict accelerating dike volume up to the time of the eruption and little or no change thereafter deflationary tilt changes at kilauea summit mirror the inferred dike volume history suggesting that the rate of dike propagation is limited by flow of magma into the dike a simple lumped parameter model of a coupled dike magma chamber system shows that the tendency for a dike to end in an eruption rather than intrusion is favored by high initial dike pressures compressional stress states large compressible magma reservoirs and highly conductive conduits linking the dike and source reservoirs comparison of model predictions to the observed dike volume history the ratio of erupted to intruded magma and the deflationary history of the summit magma chamber suggest that most of the magma supplied to the growing dike came from sources near to the eruption through highly conductive conduits interpretation is complicated by the presence of multiple source reservoirs magma vesiculation and cooling as well as spatial variations in dike normal stress reinflation of the summit magma chamber following the eruption was measured by gps and accompanied a rise in the level of the pu u o o lava lake for a spheroidal chamber these data imply a summit magma chamber volume of 20 km3 consistent with recent estimates from seismic tomography continuous deformation measurements can be used to image the spatiotemporal evolution of propagating dikes and to reveal quantitative information about the volcanic plumbing systems

rapid deformation of kilauea volcano global positioning system measurements between 1990 and 1996 campaign global positioning system gps measurements from 1990 to 1996 are used to calculate surface displacement rates on kilauea volcano hawaii the gps data show that the south flank of the volcano which has generated several large earthquakes in the past 3 decades is displacing at up to 8 cm yr to the south southeast the summit and rift zones are subsiding with maximum subsidence rates of 8 cm yr observed a few kilometers south of the summit caldera elastic dislocation modeling of the gps data suggests that the active sources of deformation include deep rift opening along the upper east and east rift zone fault slip along a subhorizontal fault near the base of the volcano and deflation near the summit caldera a nonlinear optimization algorithm was used to explore the parameter space and to find the best fitting source geometry there is a broad range of model geometries that fit the data reasonably well however certain models can be ruled out including those that have shallow rift opening or shallow fault slip some offshore aseismic slip on a fault plane that dips between 258 north northwest and 88 south southeast is required best fitting slip and rift opening rates are 23 28 cm yr although rates as low as 10 cm yr are permitted by the data

ionospheric signature of surface mine blasts from global positioning system measurements sources such as atmospheric or buried explosions and shallow earthquakes are known to produce infrasonic pressure waves in the atmosphere because of the coupling between neutral particles and electrons at ionospheric altitudes these acoustic and gravity waves induce variations of the ionospheric electron density the global positioning system gps provides a way of directly measuring the total electron content in the ionosphere and therefore of detecting such perturbations in the upper atmosphere in july and august 1996 three large surface mine blasts 1 5 kt each were detonated at the black thunder coal mine in eastern wyoming as part of a seismic and acoustic monitoring experiment we deployed five dual frequency gps receivers at distances ranging from 50 to 200 km from the mine and were able to detect the ionospheric perturbation caused by the blasts the perturbation starts 10 to 15 min after the blast lasts for about 30 min and propagates with an apparent horizontal velocity of 1200 meters per second its amplitude reaches 3 x 10 exp 14 el per square meters in the 7 3 min period band a value close to the ionospheric perturbation caused by the m 6 7 northridge earthquake the small signal to noise ratio of the perturbation can be improved by slant stacking the electron content time series recorded by the different gps receivers taking into account the horizontal propagation of the perturbation the energy of the perturbation is concentrated in the 200 to 300 second period band a result consistent with previous observations and numerical model predictions the 300 second band probably corresponds to gravity modes and shorter periods to acoustic modes respectively using a 1 d stratified velocity model of the atmosphere we show that linear acoustic ray tracing fits arrival times at all gps receivers we interpret the perturbation as a direct acoustic wave caused by the explosion itself this study shows that even relatively small subsurface events can produce ionospheric perturbations that are above the detection threshold of the gps technique by sensing derivative signals which can be detected over a relatively broad region it appears that gps might be particularly useful for source characterization within the first acoustic quiet zone where infrasound would probably be ineffective this suggests that dual frequency gps monitoring could contribute to comprehensive nuclear test ban treaty verification

cyclonic activity over northeastern africa at 8 5 6 7 cal kyr b p based on lacustrine records in the faiyum oasis egypt abstract during african humid period in the holocene when the summer intertropical convergence zone migrated to its northernmost position the qarun lake in the faiyum oasis in egypt was fed with regular inflows from the nile river and rainfall brought by the mediterranean winter circulation finely laminated lake sediments dated at 8 5 6 7 cal kyr b p were examined in terms of lithology geochemistry microfossils diatom pollen and magnetic susceptibility based on the inferred geographical derivation of pollen the environmental affiliation of diatom taxa and geochemistry of lake sediments wind trajectories were distinguished related to two main atmospheric circulation phases during the earlier phase 8 50 7 83 cal kyr b p there were northwestern wind trajectories followed by southern ones and during the later phase 7 83 6 70 cal kyr b p the northern winds were followed by northwestern and southern ones northwestern and northern winds brought winter rainfall and caused water turbulence in the lake and the southern winds were associated with regional aridification this scenario of atmospheric circulation in northeastern africa extends significantly our understanding of key modes of climatic variability and wind trajectories in the early to middle holocene greenlandian to northgrippian transition

dynamics of active magmatic and hydrothermal systems at taal volcano philippines from continuous gps measurements 1 a dense network of continuous single and dual frequency gps receivers at taal volcano philippines reveals four major stages of volcanogenic deformation deflation from installation in june 1998 to december 1998 inflation from january to march 1999 deflation from april 1999 to february 2000 and inflation from february to november 2000 the largest displacements occurred during the february november 2000 period of inflation which was characterized by 120 mm of uplift of the center of volcano island relative to the northern caldera rim at average rates up to 216 mm yr deformation sources were modeled using a constrained least squares inversion algorithm the source of 1999 deflation and inflation in 2000 were modeled as contractional and dilatational mogi point sources centered at 4 2 and 5 2 km depth respectively beneath volcano island the locations of the inflationary and deflationary sources are indistinguishable within the 95 confidence estimates modeling using a running 4 month time window from june 1999 to march 2001 reveals little evidence for source migration we suggest that the two periods of inflation observed at taal result from episodic intrusions of magma into a shallow reservoir centered beneath volcano island subsequent deflation may result from exsolution of magmatic fluids and or gases into an overlying unconfined hydrothermal system

punctual and continuous estimation of transit time from dissolved organic matter fluorescence properties in karst aquifers application to groundwaters of fontaine de vaucluse experimental basin se france for about 10 years environmental tracing development using dissolved organic matter dom has been the subject of several studies particularly the use of characterization techniques like fluorescence emission excitation matrices has enabled the identification of dom sources and monitoring them within mainland or marine hydrosystems moreover hydrogeologists have shown the significance of total organic carbon content used as a fast seepage tracer in karstic aquifers the aim of this study consists in using dom fluorescence signals to develop a transit time semi quantitative tracer in heterogeneous hydrosystems the low noise underground laboratory vaucluse france cuts the network of fontaine de vaucluse fv karstic vadose zone randomly and offers a special access to different unstructured dripwaters with different hydrodynamic behaviour inside its galleries i e not hierarchical as in natural caves previous long term hydrodynamic and hydrochemical studies allowed the understanding of their hydrogeological behaviour and the estimation of mean transit times that is why this site is adequate to develop new transit time tracers after identification of the different dom sources i e lithic and rendzic leptosols fluorescence intensities monitoring from soil leachates and dripwaters for certain excitation emission wavelength pairs allowed the development of punctual transit time tracing by spotting infiltration periods of fluorescent compounds and monitoring their transfer within a hydrosystem a fluorescence index humification index and the mean transit time of each gallery groundwater stemmed from previous hydrodynamic and hydrochemical studies allowed the calibration of a logarithmic relationship this one allows the development of a continuous transit time tracing method that estimates transit times without long term studies it has been tested on two springs of fv catchment basin providing transit time estimations for karstic hydrosystems that do not present a mixture between recent and pluriannual waters

using 1 hz gps data to measure deformations caused by the denali fault earthquake the 3 november 2002 moment magnitude 7 9 denali fault earthquake generated large permanent surface displacements in alaska and large amplitude surface waves throughout western north america we find good agreement between strong ground motion records integrated to displacement and 1 hertz global positioning system gps position estimates collected 140 kilometers from the earthquake epicenter one hertz gps receivers also detected seismic surface waves 750 to 3800 kilometers from the epicenter whereas these waves saturated many of the seismicinstruments in the same region high frequency gps increases the dynamic range and frequency bandwidth of ground motion observations providing another tool for studying earthquake processes

tracing groundwater flow and sources of organic carbon in sandstone aquifers using fluorescence properties of dissolved organic matter dom abstract the fluorescence properties of groundwaters from sites in two uk aquifers the penrith sandstone of cumbria and the sherwood sandstone of south yorkshire were investigated using excitation emission matrix eem fluorescence spectroscopy both aquifers are regionally important sources of public supply water and are locally impacted by pollution the penrith sandstone site is in a rural setting while the sherwood sandstone site is in suburban doncaster fluorescence analysis of samples from discrete sample depths in the penrith sandstone shows decreasing fulvic like intensities with depth and also shows a good correlation with cfc 12 an anthropogenic groundwater tracer tryptophan like fluorescence centres in the depth profile may also provide evidence of rapid routing of relatively recent applications of organic slurry along fractures fluorescence analysis of groundwater sampled from multi level piezometers installed within the sherwood sandstone aquifer also shows regions of tryptophan like and relatively higher fulvic like signatures the fluorescence intensity profile in the piezometers shows tryptophan like peaks at depths in excess of 50 m and mirrors the pattern exhibited by microbial species and cfcs highlighting the deep and rapid penetration of modern recharge due to rapid fracture flow fluorescence analysis has allowed the rapid assessment of different types and relative abundances of dissolved organic matter dom and the fingerprinting of different sources of organic c within the groundwater system the tryptophan fulvic ratios found in the penrith sandstone were found to be between 0 5 and 3 0 and are characteristic of ratios from sheep waste sources the sherwood sandstone has the lowest ratios 0 2 0 4 indicating a different source of dom most likely a mixture of terrestrial and microbial sources although there is little evidence of pollution from leaking urban sewage systems results from these two studies suggest that intrinsic fluorescence may be used as a proxy for or complementary tool to other groundwater investigation methods in helping provide a conceptual model of groundwater flow and identifying different sources of dom within the groundwater system

high rate gps data on active volcanoes an application to the 2005 2006 mt augustine alaska usa eruption volcanic eruptions are usually preceded by measurable signals of growing unrest the most evident of which are the increase in seismicity and ground deformation it is also important to identify precursors of a possible renewal of the volcanic activity and to distinguish between an eruptive activity characterized by an intrusion with the related destructive power and a migration of magma stored in the main conduits the 2005 2006 eruption at mt augustine alaska usa is a good example of a massive migration of magmatic fluids from depth about 1 km b s l under the effect of gas overpressure the movements recorded by high rate gps hrgps data 15 s of sampling and processing rate from the stations deployed on the volcano define the dimensions and the characteristics of the shallow plumbing system in this study we propose a model of the different stages preceding the effusive phase the precursory phase where gas overpressure in the body of the volcano opens the terminal conduit

an exploratory early and middle holocene sedimentary record with palynoforms and diatoms from faiyum lake egypt abstract we report on the sedimentology pollen and diatom records in a 26 m long core of holocene sediments from the tersa area near the centre of the faiyum depression egypt two radiocarbon and one osl dates have been obtained for the core dates range from 9545 60 cal bp to c 4040 bp these correspond respectively with the terminal palaeolithic qarunian and neolithic faiyum a faiyumian cultures the core is subdivided into 3 sedimentological units unit 1 21 26 m is very thinly laminated calcareous silt deposited in a deep water lake unit 2 9 5 21 m is finely laminated sand silt and carbonates formed as a lacustrine fan delta unit 3 9 5 m to the core top is formed of massive silt sandy silt and very fine grained flood plain sands planktonic diatom taxa mainly cyclostephanos aulacoseira cyclotella and stephanodiscus spp were abundant in units 1 2 a indicating deep open lake conditions magnetic minerals increased from the base of unit 2 indicating an increasing contribution of nile alluvium benthic taxa such as fragilaria cocconeis amphora and navicula tended to increase towards the core top from unit 2 b 3 a to 3 b indicative of lake shallowing and periods of low nile floods unit 3 c is barren of diatoms and is compatible with terrestrial flood plain conditions vegetation was mainly represented by herbaceous pollen throughout most of the core and in the topmost sediment pollen was scarce but pteridophyte osmundaceae spores increased arboreal vegetation had low percentages in most of the record but increased in the middle section of the core unit 2 a depositional deltaic environment was indicated throughout most of the core sub units 2 a 3 a where high abundances of poaceae cyperaceae chenopodiaceae amaranthaceae polypodiaceae and osmundaceae were recorded indicating high nile floods and fluctuating rainfall

stepwise holocene aridification in ne africa deduced from dust borne radiogenic isotope records abstract transfer of tropical heat to higher latitudes is the major driving force of the earth s climate consequently sediments in regions to the north and south of the tropics potentially retain an archive of past major climate reconfigurations the climate of one such region around the arabian sea sensitively depends on the coupled asian and african monsoons that also control the dust transport here we use the sr nd isotope ratios of the dust fraction from core 905 arabian sea off somalia as a novel tool to deduce the holocene weathering history of the horn of africa with emphasis on the climate transition that took place from a wet early to a dry late holocene the highly variable sr isotope ratios are interpreted to reflect mainly changes in the evaporation precipitation balance over ne africa whilst the nd isotope measurements record no significant variations and point to a prevailing ne african dust source the sr isotope record shows that the first aridification step occurred at 8 5 kyr bp followed by an unstable transitional period up to 6 kyr bp characterized by decadal scale high amplitude variations in the evaporation precipitation balance a second aridification step began at 6 kyr bp and ceased at 3 8 kyr bp when modern day dry climate was established the combined sr and nd isotope records probably reflect north south shifts of the intertropical convergence zone controlling the evaporation precipitation balance over ne africa

ionospheric detection of the 25 may 2009 north korean underground nuclear test 1 the total electron content tec measurements of the global navigation satellite system gnss revealed traveling ionospheric disturbances tid that locate north korea s underground nuclear explosion une of 25 may 2009 to within about 3 5 km of its seismically determined epicenter the random chance for this pattern of tids to register across the eleven gnss stations is roughly 1 in 19 billion monte carlo analysis of nearly 1 300 tids from a 7 station subset of the 11 gnss stations supports the statistical strength of the array s signature the une was also detected by seismic stations and possibly a local infrasound network of the international monitoring system ims of the comprehensive nuclear test ban treaty organization ctbto but no radionuclide evidence was found thus global gnss infrastructure enables mapping spatial and temporal variations of tec that augment and complement other methods of detecting and locating clandestine unes

holocene lakes and prehistoric settlements of the western faiyum egypt abstract holocene lake stages in the faiyum depression commenced with a high lake stand during the 10th millennium bp followed by an early holocene lake from 8500 to 7000 bp a pronounced recession and the development of a palaeosol preceded another rise to a mid holocene high lake level from 6500 to 5100 bp a major drop in level coincided with the late neolithic and early dynastic the moeris lake witnessed by herodotus is also documented the drop in lake level during early ptolemaic times marked the end of the freshwater lake and was apparently in part a result of declining nile floods terminal palaeolithic sites are associated with the early holocene lake and neolithic sites with the mid holocene phase prehistoric settlements were placed near lake margin marshes and ponds the richness of the lake margin in aquatic resources and its susceptibility to short and long term fluctuations influenced both subsistence and settlements and is believed to have encouraged a para agricultural economy

volcano monitoring using gps developing data analysis strategies based on the june 2007 kīlauea volcano intrusion and eruption 1 the global positioning system gps is one of the most common techniques and the current state of the art used to monitor volcano deformation in addition to slow several centimeters per year displacement rates gps can be used to study eruptions and intrusions that result in much larger tens of centimeters over hours days displacements it is challenging to resolve precise positions using gps at subdaily time intervals because of error sources such as multipath and atmospheric refraction in this paper the impact of errors due to multipath and atmospheric refraction at subdaily periods is examined using data from the gps network on k lauea volcano hawai i methods for filtering position estimates to enhance precision are both simulated and tested on data collected during the june 2007 intrusion and eruption comparisons with tiltmeter records show that gps instruments can precisely recover the timing of the activity

explosion energy of the 2004 eruption of the asama volcano central japan inferred from ionospheric disturbances 1 the japanese dense array of global positioning system recorded ionospheric disturbances as changes in total electron content 12 minutes after the september 1 2004 eruption of the asama volcano central japan the disturbance had a period of one and a quarter minutes and propagated as fast as 1 1 km s suggesting its origin as the acoustic wave generated by the explosion by comparing the disturbance amplitudes with those by a surface mine blast with a known energy the overall asama explosion energy is inferred to be about 2 1014 j

accuracy of high rate gps for seismology 1 we built a device for translating a gps antenna on a positioning table to simulate the ground motions caused by an earthquake the earthquake simulator is accurate to better than 0 1 mm in position and provides the ground truth displacements for assessing the technique of high rate gps we found that the root mean square error of the 1 hz gps position estimates over the 15 min duration of the simulated seismic event was 2 5 mm with approximately 96 of the observations in error by less than 5 mm and is independent of gps antenna motion the error spectrum of the gps estimates is approximately flicker noise with a 50 decorrelation time for the position error of 1 6 s we find that for the particular event simulated the spectrum of surface deformations exceeds the gps error spectrum within a finite band more studies are required to determine whether a generally optimal bandwidth exists for a target group of seismic events

january 30 1997 eruptive event on kilauea volcano hawaii as monitored by continuous gps a continuous global positioning system gps network on kilauea volcano captured the most recent fissure eruption in kilauea s east rift zone erz in unprecedented spatial and temporal detail the short eruption drained the lava pond at pueu oeo leading to a two month long pause in its on going eruption models of the gps data indicate that the intrusion s bottom edge extended to only 2 4 km continuous gps data reveal rift opening 8 hours prior to the eruption absence of precursory summit inflation rules out magma storage overpressurization as the eruption s cause we infer that stresses in the shallow rift created by the continued deep rift dilation and slip on the south flank decollement caused the rift intrusion

inflation of long valley caldera california basin and range strain and possible mono craters dike opening from 1990 94 gps surveys five years of annual global positioning system gps surveys of a network centered on long valley california constrain displacement rates for these stations relative to a central station in the network these observations are consistent with recent models of resurgent dome inflation in long valley langbein et al 1995 and have sufficient signal to detect the presence of basin and range strain in the long valley region the data also allow for the possibility of dike inflation beneath the mono craters dike intrusion is consistent with the mono craters recent geologic history of ash eruptions with seismic tomography leveling data and geologic studies of these volcanic domes and flows

detection of arbitrarily large dynamic ground motions with a dense high rate gps network 1 we describe the detection of teleseismic surface waves from the 3 november 2002 mw 7 9 denali fault earthquake in alaska with a dense network of 1 hz gps stations in southern california about 3900 km from the event relative horizontal displacements with amplitudes in excess of 15 mm and duration of 700 seconds agree with integrated velocities recorded by nearby broadband seismometers with an rms difference of 2 3 mm the displacements are derived from independent 1 hz instantaneous positions demonstrating that a gps network can provide direct measurements of arbitrarily large dynamic and static ground horizontal displacements at periods longer than 1 s and amplitudes above 2 mm with an inherent precision signal to noise that improves indefinitely with amplitude without clipping and in real time high rate real time gps networks can enhance earthquake detection and seismic risk mitigation and support other applications such as intelligent transportation and civil infrastructure monitoring

gps applications for geodynamics and earthquake studies geodetic measurements obtained with the global positioning system gps are increasingly more widely applied in geophysical studies in this paper we review the changes to the technology of gps geodesy over the last five years that are responsible for this increased applicability we survey geophysical investigations employing gps to measure coseismic postseismic and interseismic deformation plate motion and crustal deformation at plate boundaries volcano deformation and the deformation associated with glacial isostatic adjustment and its application to sea level studies we emphasize the use of gps determinations for the modeling of this wide variety of geophysical phenomena we also discuss the recent advent of permanent gps networks for regional geophysical studies as well as the possible future of gps surveying in light of the recent advances

geodetic evidence for en echelon dike emplacement and concurrent slow slip during the june 2007 intrusion and eruption at kīlauea volcano hawaii 1 a series of complex events at k lauea volcano hawaii 17 june to 19 june 2007 began with an intrusion in the upper east rift zone erz and culminated with a small eruption 1500 m3 surface deformation due to the intrusion was recorded in unprecedented detail by global positioning system gps and tilt networks as well as interferometric synthetic aperture radar insar data acquired by the envisat and alos satellites a joint nonlinear inversion of gps tilt and insar data yields a deflationary source beneath the summit caldera and an ene striking uniform opening dislocation with 2 m opening a dip of 80 to the south and extending from the surface to 2 km depth this simple model reasonably fits the overall pattern of deformation but significantly misfits data near the western end of an inferred dike like source three more complex dike models are tested that allow for distributed opening including 1 a dike that follows the surface trace of the active rift zone 2 a dike that follows the symmetry axis of insar deformation and 3 two en echelon dike segments beneath mapped surface cracks and newly formed steaming areas the en echelon dike model best fits near field gps and tilt data maximum opening of 2 4 m occurred on the eastern segment beneath the eruptive vent although this model represents the best fit to the erz data it still fails to explain data from a coastal tiltmeter and gps sites on k lauea s southwestern flank the southwest flank gps sites and the coastal tiltmeter exhibit deformation consistent with observations of previous slow slip events beneath k lauea s south flank but inconsistent with observations of previous intrusions slow slip events at k lauea and elsewhere are thought to occur in a transition zone between locked and stably sliding zones of a fault an inversion including slip on a basal decollement improves fit to these data and suggests a maximum of 15 cm of seaward fault motion comparable to previous slow slip events