an experiment to detect and locate lightning associated with eruptions of redoubt volcano abstract a commercially available lightning detection system was temporarily deployed near cook inlet alaska in an attempt to remotely monitor volcanogenic lightning associated with eruptions of redoubt volcano the system became operational on february 14 1990 lightning was detected in 11 and located in 9 of the 13 subsequent eruptions the lightning was generated by ash clouds rising from pyroclastic density currents produced by collapse of a lava dome emplaced near redoubt s summit lightning discharge flash location was controlled by topography which channeled the density currents and by wind direction in individual eruptions early flashes tended to have a negative polarity negative charge is lowered to ground while late flashes tended to have a positive polarity positive charge is lowered to ground perhaps because the charge separation process caused coarse rapid settling particles to be negatively charged and fine slow settling particles to be positively charged results indicate that lightning detection and location is a useful adjunct to seismic volcano monitoring particularly when poor weather or darkness prevents visual observation the simultaneity of seismicity and lightning near a volcano provides the virtual certainty that an ash cloud is present this information is crucial for aircraft safety and to warn threatened communities of impending tephra falls the alaska volcano observatory has now deployed a permanent lightning detection network around cook inlet

character mass distribution and origin of tephra fall deposits of the 1989 1990 eruption of redoubt volcano south central alaska abstract the 1989 1990 eruption of redoubt volcano spawned about 20 areally significant tephra fall deposits between december 14 1989 and april 26 1990 tephra plumes rose to altitudes of 7 to more than 10 km and were carried mainly northward and eastward by prevailing winds where they substantially impacted air travel commerce and other activities in comparison to notable eruptions of the recent past the redoubt events produced a modest amount of tephra fall deposits 6 10 7 to 5 10 10 kg for individual events and a total volume dense rock equivalent of about 3 5 10 7 m 3 of andesite and dacite two contrasting tephra types were generated by these events pumiceous tephra fall deposits of december 14 and 15 were followed on december 16 and all later events by fine grained lithic crystal tephra deposits much of which fell as particle aggregates the change in the character of the tephra fall deposits reflects their fundamentally different modes of origin the pumiceous deposits were produced by magmatically driven explosions the finegrained lithic crystal deposits were generated by two processes hydrovolcanic vent explosions generated tephrafall deposits of december 16 and 19 such explosions continued as a tephra source but apparently with diminishing importance during events of january and february ash clouds of lithic pyroclastic flows generated by collapse of actively growing lava domes probably contributed to tephra fall deposits of all events from january 2 to april 26 and were the sole source of tephra fall for at least the last 4 deposits

aquifer heterogeneity characterization with oscillatory pumping sensitivity analysis and imaging potential 1 periodic pumping tests in which a fluid is extracted during half a period then reinjected have been used historically to estimate effective aquifer properties in this work we suggest a modified approach to periodic pumping test analysis in which one uses several periodic pumping signals of different frequencies as stimulation and responses are analyzed through inverse modeling using a steady periodic model formulation we refer to this strategy as multifrequency oscillatory hydraulic imaging oscillating pumping tests have several advantages that have been noted including no net water extraction during testing and robust signal measurement through signal processing through numerical experiments we demonstrate additional distinct advantages that multifrequency stimulations have including 1 drastically reduced computational cost through use of a steady periodic numerical model and 2 full utilization of the aquifer heterogeneity information provided by responses at different frequencies we first perform fully transient numerical modeling for heterogeneous aquifers and show that equivalent results are obtained using a faster steady periodic heterogeneous numerical model of the wave phasor the sensitivities of observed signal response to aquifer heterogeneities are derived using an adjoint state based approach which shows that different frequency stimulations provide complementary information finally we present an example 2 d application in which sinusoidal signals at multiple frequencies are used as a data source and are inverted to obtain estimates of aquifer heterogeneity these analyses show the different heterogeneity information that can be obtained from different stimulation frequencies and that data from several sinusoidal pumping tests can be rapidly inverted using the steady periodic framework

statistical forecasting of repetitious dome failures during the waning eruption of redoubt volcano alaska february april 1990 abstract the waning phase of the 1989 1990 eruption of redoubt volcano in the cook inlet region of south central alaska comprised a quasi regular pattern of repetitious dome growth and destruction that lasted from february 15 to late april 1990 the dome failures produced ash plumes hazardous to airline traffic in response to this hazard the alaska volcano observatory sought to forecast these ash producing events using two approaches one approach built on early successes in issuing warnings before major eruptions on december 14 1989 and january 2 1990 these warnings were based largely on changes in seismic activity related to the occurrence of precursory swarms of long period seismic events the search for precursory swarms of long period seismicity was continued through the waning phase of the eruption and led to warnings before tephra eruptions on march 23 and april 6 the observed regularity of dome failures after february 15 suggested that a statistical forecasting method based on a constant rate failure model might also be successful the first statistical forecast was issued on march 16 after seven events had occurred at an average interval of 4 5 days at this time the interval between dome failures abruptly lengthened accordingly the forecast was unsuccessful and further forecasting was suspended until the regularity of subsequent failures could be confirmed statistical forecasting resumed on april 12 after four dome failure episodes separated by an average of 7 8 days one dome failure april 15 was successfully forecast using a 70 confidence window and a second event april 21 was narrowly missed before the end of the activity the cessation of dome failures after april 21 resulted in a concluding false alarm although forecasting success during the eruption was limited retrospective analysis shows that early and consistent application of the statistical method using a constant rate failure model and a 90 confidence window could have yielded five successful forecasts and two false alarms no events would have been missed on closer examination the intervals between successive dome failures are not uniform but tend to increase with time this increase attests to the continuous slowly decreasing supply of magma to the surface vent during the waning phase of the eruption the domes formed in a precarious position in a breach in the summit crater rim where they were susceptible to gravitational collapse the instability of the february 15 april 21 domes relative to the earlier domes is attributed to reaming the lip of the vent by a laterally directed explosion during the major dome destroying eruption of february 15 a process which would leave a less secure foundation for subsequent domes

the dynamics and thermodynamics of volcanic clouds theory and observations from the april 15 and april 21 1990 eruptions of redoubt volcano alaska on april 15 1990 and april 21 1990 two relatively small explosive eruptions occurred at redoubt volcano alaska lasting about 4 and 8 minutes respectively on both occasions the erupted material travelled as a pyroclastic flow down an ice canyon on the north flank of the volcano using slow scan television recordings of the eruption and the seismic record in both the near and far field we deduce that after a few minutes the upper parts of these pyroclastic flows became buoyant and a large and hot ash cloud ascended off the flow these thermals rose to a height of about 12 km at which point they began to spread laterally as umbrella clouds using a simple thermodynamic model we estimate that the clouds had a temperature in the approximate range 600 700 k as they rose buoyantly from the flow after entraining and heating air and melting and vaporizing ice we also estimate that in each eruption approximately 109 kg of fine ash was injected into the atmosphere during the april 15 eruption a slow scan television camera recorded the ascent of the cloud these observations are described analysed and compared with the predictions of a new model for the dynamics governing the ascent of such clouds in accord with the observations our model predicts that the cloud initially ascended rather sluggishly since it is only just buoyant on rising from the pyroclastic flow as it ascends it entrains and heats up more air and hence generates more buoyancy therefore it accelerates upwards only much higher in the cloud does the velocity decrease again as the thermal energy of the cloud becomes exhausted the model also predicts that the height of rise of such coignimbrite thermals is a function of the initial mass and temperature of the cloud but is almost independent of the initial velocity during the april 21 eruption a sequence of photographs recorded the lateral spreading of the umbrella cloud during an interval of about 10 minutes after the eruption these photographs are analysed and successfully compared with a simple model for the spreading of the umbrella cloud as a gravity current in a stratified environment using an avhrr satellite image of the air fall deposit from the april 15 eruption combined with a simple model we suggest that the primary mechanism of ash dispersal was transport by the ambient wind

geology and mineralogy of the auki crater tyrrhena terra mars a possible post impact induced hydrothermal system abstract a variety of hydrothermal environments have been documented in terrestrial impact structures due to both past water interactions and meteoritic bombardment on the surface of mars several authors have predicted various scenarios that include the formation of hydrothermal systems geological and mineralogical evidence of past hydrothermal activity have only recently been found on mars here we present a geological and mineralogical study of the auki crater using the spectral and visible imagery data acquired by the crism compact reconnaissance imaging spectrometer for mars ctx context camera and hirise high resolution imaging science experiment instruments on board the nasa mro mission the auki crater is a complex crater that is 38 km in diameter located in tyrrhena terra 96 8 e and 15 7 s and shows a correlation between its mineralogy and morphology the presence of minerals such as smectite silica zeolite serpentine carbonate and chlorite associated with morphological structures such as mounds polygonal terrains fractures and veins suggests that the auki crater may have hosted a post impact induced hydrothermal system although the distribution of hydrated minerals in and around the central uplift and the stratigraphic relationships of some morphological units could also be explained by the excavation and exhumation of carbonate rich bedrock units as a consequence of crater formation we favor the hypothesis of impact induced hydrothermal circulation within fractures and subsequent mineral deposition the hydrothermal system could have been active for a relatively long period of time after the impact thus producing a potential transient habitable environment

evaluation of flowmeter head loss effects in the flowmeter test in this study we develop an axisymmetric groundwater flow model to numerically simulate the hydraulic head loss across the flowmeter during a flowmeter test using it we investigate the influence of flowmeter induced hydraulic head losses and filter pack effects on the calculated drawdown distributions in the vicinity of the pumping well and on the flowmeter test estimates of layer horizontal hydraulic conductivity ki in three different aquifer well systems a homogeneous aquifer a homogeneous aquifer with a filter pack surrounding the well and a two layer aquifer with a filter pack surrounding the well we confirm that the ki estimates can be significantly biased due to the head loss across the flowmeter this head loss induces a non uniform flow pattern in the vicinity of the well which violates the horizontal flow assumption invoked by flowmeter test interpretation methodologies the effect of the hydraulic head losses alone i e no cross flow through the filter pack can lead to ki estimation errors as great as a factor of three even in a homogeneous aquifer the coupled effect of hydraulic head losses and cross flow through the filter pack can lead toki estimation errors of up to a factor of 10 or greater in actual flowmeter tests these head losses can be reduced by increasing the annulus of the flowmeter by operating the flowmeter without a packer or by choosing a small enough pumping rate q 1999 elsevier science b v all rights reserved

reactive facies an approach for parameterizing field scale reactive transport models using geophysical methods 1 developing a predictive understanding of subsurface contaminant plume evolution and natural attenuation capacity is hindered by the inability to tractably characterize controlling reactive transport properties over field relevant scales here we explore a concept of reactive facies which is based on the hypothesis that subsurface units exist that have unique distributions of properties that influence reactive transport we further hypothesize that geophysical methods can be used to identify and spatially distribute reactive facies and their associated parameters we test the reactive facies concept at a u s department of energy uranium contaminated groundwater site where we have analyzed the relationships between laboratory and field including radar and seismic tomographic data sets our analysis suggests that there are two reactive facies that have unique distributions of mineralogy texture hydraulic conductivity and geophysical attributes we use these correlations within a bayesian framework to integrate the dense geophysical data sets with the sparse core based measurements this yields high resolution 0 25 m 0 25 m estimates of reactive facies and their associated properties and uncertainties along the 2 d tomographic transects comparison with colocated samples shows that the estimated properties fall within 95 uncertainty bounds to illustrate the value of reactive facies characterization approach we used the geophysically estimated properties to parameterize reactive transport models which were then used to simulate migration of an acidic u plume through the domain modeling results suggest that each identified reactive facies exerts a unique control on plume evolution highlighting the usefulness of the reactive facies concept for spatially distributing properties that control reactive transport over field relevant scales

syneruptive mixing degassing and crystallization at redoubt volcano eruption of december 1989 to may 1990 abstract the 1989 1990 eruption of redoubt volcano included initial energetic vertical venting of pumiceous tephra followed by shedding of dense pyroclastic flows from successive unstable domes the suite of quenched magmatic materials thus produced coupled with detailed seismic observations provides a record of establishment and subsequent evolution of an active magma column in the upper crust the initial eruptive event involved a dacite magma with rhyolite melt and an andesite magma with dacite melt the dacite magma contains reaction rim free hornblende high cl concentrations 0 12 0 02 wt of melt and is microlite free all evidence for rapid ascent from depth in contrast the andesite component is microlite rich though this characteristic may have arisen by mixing between the two magmas rather than by slow ascent abundant dense juvenile lava like clasts with low h2o 0 1 0 3 wt were ejected in the initial eruption event implying that the magma column had reached the near surface and its upper portion had undergone degassing and bubble collapse prior to explosive disruption later eruptive events contain evidence of progressive blending of the two magmatic components as well as mixing between fresh reservoir derived and old conduit resident magma magma apparently ascended to the surface from the 6 10 km deep source chamber in a series of pulses rather than by steady flow or gradual emptying of a shallowly intruded body increased shallow long period seismicity which may indicate subsurface degassing from the flowing magma column occurred 5 days before each major eruptive event petrologic evidence indicates that each eruption contained some magma that ascended quickly from the chamber with time the proportion of new magma in eruptive batches may have decreased however even the final dome contains magma that left the chamber no more than a few days before extrusion together the pulses apparently record passage of an andesite plume through redoubt s dacite magma reservoir

seismic character and progression of explosive activity during the 2016 2017 eruption of bogoslof volcano alaska bogoslof volcano in the central aleutian arc experienced a major eruption between december 2016 and august 2017 that was characterized by explosive activity volcanic explosivity index 2 to 3 and the extrusion of lava domes the alaska volcano observatory tracked the activity in real time using seismicity observed on distant stations as well as infrasound lightning satellite data and occasional visual observations in this study we measure the duration of seismic signals associated with individual explosive events to track their progression during the two explosive phases of the eruption seismic recordings of bogoslof explosions show complex waveforms that suggest both individual explosive events and sequences of several explosions separated by lower amplitude tremor the lack of local seismic monitoring stations at distances of 1 km to 15 km distance unfortunately limits our ability to closely observe seismicity and to interpret changing conditions at the vent such as position the presence of a lava dome or plug and the role of seawater associated with the eruption we use the rate of explosive activity seismic waveform character and repose time between explosions to infer the conditions within the conduit

analysis of long period events recorded at mount etna italy in 1992 and their relationship to eruptive activity seismic activity recorded at mount etna during 1992 was characterized by long period lp events and tremor with fluctuating amplitudes these signals were associated with the evolution of the eruptive activity that began on december 14 1991 following the occurrence of numerous volcano tectonic earthquakes at the onset of the eruption lp events dominated the overall seismicity starting in january 1992 the lp activity occurred primarily in swarms which were temporally correlated with episodic collapses of the crater floor in the northeast crater source depths determined for selected lp events suggest a source region located slightly east of northeast crater and extending from the surface to a depth of 2000 m based on the characteristic signatures of the time series four families of lp events are identified each family shares common spectral peaks independent of azimuth and distance to the source these spectral features are used to develop a fluid filled crack model of the source we hypothesize that the locus of the lp events represents a segment of the magma feeding system connecting a depressurizing magma body with a dike extending in the sse direction along the western wall of valle del bove toward the site of the mount etna eruption we surmise that magma withdrawal from the source volume beneath northeast crater may have caused repeated collapses of the crater floor some collapse events may have produced pressure transients in the subjacent dike which acted as seismic wave sources for lp events

the 1989 1990 eruptions of redoubt volcano an introduction abstract redoubt volcano located on the west side of cook inlet in south central alaska erupted explosively on over 20 separate occasions between december 14 1989 and april 21 1990 fourteen lava domes were emplaced in the summit area thirteen of which were subsequently destroyed the eruption caused economic losses estimated at over 160 000 000 making this the second most costly eruption in u s history this economic impact provided the impetus for a integrated comprehensive account of an erupting volcano using both modern and classical research and modern techniques which in turn led to advances in eruption monitoring and interpretation research on such topics as dome formation and collapse and the resulting pyroclastic flows elutriated ash lightning tephra and flooding was blended with the rapid communication of associated hazards to a large user group the seismology successes in predicting and monitoring eruption dynamics were due in part to 1 the recognition of long period seismic events as indicators of the readiness of the volcano to erupt and 2 to the development of new tools that allowed the seismicity to be assessed instantaneously integrated studies of the petrology of erupted products and volatile content over time gave clues as to the progress of the eruption towards completion

large scale natural gradient tracer test in sand and gravel cape cod massachusetts 1 experimental design and observed tracer movement a large scale natural gradient tracer experiment was conducted on cape cod massachusetts to examine the transport and dispersion of solutes in a sand and gravel aquifer the nonreactive tracer bromide and the reactive tracers lithium and molybdate were injected as a pulse in july 1985 and monitored in three dimensions as they moved as far as 280 m down gradient through an array of multilevel samplers the bromide cloud moved horizontally at a rate of 0 42 m per day it also moved downward about 4 m because of density induced sinking early in the test and accretion of areal recharge from precipitation after 200 m of transport the bromide cloud had spread more than 80 m in the direction of flow but was only 14 m wide and 4 6 m thick the lithium and molybdate clouds followed the same path as the bromide cloud but their rates of movement were retarded about 50 relative to bromide movement because of sorption onto the sediments

development of a joint hydrogeophysical inversion approach and application to a contaminated fractured aquifer this paper presents a joint inversion approach for combining crosshole seismic travel time and borehole flowmeter test data to estimate hydrogeological zonation the approach is applied to a complex fractured department of energy field site located at the oak ridge national laboratory in tennessee united states we consider seismic slowness the inverse of seismic velocity and hydrogeological zonation indicators as unknown variables and use a physically based model with unknown parameters to relate the seismic slowness to the zonation indicators we jointly estimate all the unknown parameters in the model by conditioning them to the crosshole seismic travel times as well as the borehole flowmeter data using a bayesian model and a markov chain monte carlo sampling method the fracture zonation estimates are qualitatively compared to bromide tracer breakthrough data and to uranium biostimulation experiment results the comparison suggests that the joint inversion approach adequately estimated the fractured zonation and that the fracture zonation influenced biostimulation efficacy our study suggests that the new joint hydrogeophysical inversion approach is flexible and effective for integrating various types of data sets within complex subsurface environments and that seismic travel time data have the potential to provide valuable information about fracture zonation

structure coupled joint inversion of geophysical and hydrological data abstractin groundwater hydrology geophysical imaging holds considerable promise for improving parameter estimation due to the generally high resolution and spatial coverage of geophysical data however inversion of geophysical data alone cannot unveil the distribution of hydraulic conductivity jointly inverting geophysical and hydrological data allows us to benefit from the advantages of geophysical imaging and at the same time recover the hydrological parameters of interest we have applied a coupling strategy between geophysical and hydrological models that is based on structural similarity constraints model combinations for which the spatial gradients of the inferred parameter fields are not aligned in parallel are penalized in the inversion this structural coupling does not require introducing a potentially weak unknown and nonstationary petrophysical relation to link the models the method was first tested on synthetic data sets and then applied to two combinations of geophysical hydrolog

a borehole flowmeter investigation of small scale hydraulic conductivity variation in the biscayne aquifer florida geostatistical analysis of closely spaced borehole flowmeter measurements was used to estimate the variance 2 53 and vertical and horizontal correlation lengths of ln k 0 57 and 7 3 m in the biscayne aquifer a limestone aquifer critical for florida s water supply and for everglades restoration efforts the variance and correlation lengths of the biscayne aquifer are similar to some of the values for unconsolidated siliciclastic sediments especially those at columbus mississippi the larger h for the biscayne aquifer 7 3 m is thought to be due at least in part to the lower lateral variability of the carbonate platform depositional environment compared to the fluvial environments in which the siliciclastic sediments were deposited an improved down hole packer would allow for data with finer vertical resolution the current system is adequate for work inside well screens but cannot adequately seal many spots in open irregular rock boreholes research in rock presents additional logistical difficulties but is important for addressing fundamental questions about solute transport in a wider range of geological media beyond unconsolidated siliciclastic deposits

identifying hydraulically conductive fractures with a slow velocity borehole flowmeter the u s geological survey used a recently developed heat pulse flowmeter to measure very slow borehole axial water velocities in granitic rock at a site near lac du bonnet manitoba canada the flowmeter was used with other geophysical measurements to locate and identify hydraulically conducting fractures contributing to the very slow vertical water flow in the two boreholes selected for study the heat pulse flowmeter has no moving parts and operates on the tag trace principle it is an improved version of the flowmeter developed by the water research centre in england in 1975 the u s geological survey s heat pulse flowmeter has a flow measuring range in water of 0 06 6 m min and can resolve velocity differences as slow as 0 01 m min this is an order of magnitude slower than the stall speed of spinner flowmeters the flowmeter is 1 16 m long and 44 mm in diameter it was calibrated in columns of 76 and 152 mm diameter to correspond to the boreholes studied the heat pulse flowmeter system is evalu

field laboratory and modeling investigation of the skin effect at wells with slotted casing boise hydrogeophysical research site understanding and quantification of wellbore skin improves our ability to accurately measure or estimate hydrologic parameters with tests at wells such as pumping tests flowmeter tests and slug tests this paper presents observations and results from a series of field laboratory and modeling tests which together explain the source of wellbore skin at wells at a research wellfield and which support estimation of skin thickness ds and skin hydraulic conductivity ks positive wellbore skin effects were recognized at wells in the shallow unconfined coarse grained fluvial aquifer at the boise hydrogeophysical research site bhrs well development efforts at the bhrs removed residual drilling fines but only marginally reduced the skin effect likely causes for the remaining wellbore skin effect were examined partial clogging of screen slots with sand is consistent with field observations and can account for the magnitude of wellbore skin effect observed we then use the wtaq code barlow and moench 1999 with a redefinition of the term for delayed observation well response to include skin effects at observation wells in addition to pumping wells in order to analyze aquifer tests at the bhrs for average ks values at individual wells systematic differences in ks values are recognized in results at pumping ks q and observation ks obs wells larger values are seen at observation wells average ks obsz0 0023 cm s than pumping wells two possible causes are recognized for the occurrence of higher ks values at observation wells than pumping wells 1 flow diversion between aquifer layers on approach to a pumping well with positive skin and 2 larger portion offlow passing through lower k zones in the heterogeneous aquifer near the pumping well than the observation wells due to strongly radially convergent flow near the pumping well for the wellaquifer system at the bhrs modeling analyses of drawdown vs time at observation wells provide better ks estimates than those from pumping wells q 2005 elsevier b v all rights reserved

volcano seismology hazards assessment the last few years have seen several impressive examples of seismic monitoring at volcanoes to provide warnings that have saved lives and property changes in the rates and character of volcanic earthquakes provided precursory signs to explosive eruptions of moderate size at redoubt volcano alaska mount unzen japan mount spurr alaska and rabaul caldera papua new guinea as well as the large eruption at mount pinatubo philippines in all these cases information was successfully communicated and put to practical use through broadcasts of public warnings prior to the eruptions and evacuations were initiated for the volcanoes located in populated areas at mount pinatubo probably thousands and possibly tens of thousands of lives were saved

high resolution aquifer characterization using crosshole gpr full waveform tomography comparison with direct push and tracer test data limited knowledge about the spatial distribution of aquifer properties typically constrains our ability to predict subsurface flow and transport here we investigate the value of using high resolution full waveform inversion of cross borehole ground penetrating radar gpr data for aquifer characterization by stitching together gpr tomograms from multiple adjacent crosshole planes we are able to image with a decimeter scale resolution the dielectric permittivity and electrical conductivity of an alluvial aquifer along cross sections of 50 m length and 10 m depth a logistic regression model is employed to predict the spatial distribution of lithological facies on the basis of the gpr results vertical profiles of porosity and hydraulic conductivity from direct push flowmeter and grain size data suggest that the gpr predicted facies classification is meaningful with regard to porosity and hydraulic conductivity even though the distributions of individual facies show some overlap and the absolute hydraulic conductivities from the different methods direct push flowmeter grain size differ up to approximately one order of magnitude comparison of the gpr predicted facies architecture with tracer test data suggests that the plume splitting observed in a tracer experiment was caused by a hydraulically low conductive sand layer with a thickness of only a few decimeters because this sand layer is identified by gpr full waveform inversion but not by conventional gpr ray based inversion we conclude that the improvement in spatial resolution due to full waveform inversion is crucial to detect small scale aquifer structures that are highly relevant for solute transport

borehole flowmeters field application and data analysis abstract this paper reviews application of borehole flowmeters in granular and fractured rocks basic data obtained in the field are the ambient flow log and the pumping induced flow log these basic logs may then be used to calculate other quantities of interest the paper describes the applications of the tennessee valley authority tva electromagnetic em flowmeter in a granular medium in an attempt to ascertain the effect of formation disturbance on flowmeter readings test wells were subjected to repeated periods of development using air lifting between the development periods flowmeter tests were run the results indicated that flowmeter data are not highly sensitive to formation disturbance in the near vicinity of a test well evidence of changes in the natural ambient flow in the test well was attributed to high variable rates of pumping by nearby chemical plants in fractured media flowmeters may be used to detect flow to or from individual fractures or fracture zones in these applications additional information in the form of caliper televiewer and resistivity logs are useful further studies of the type described herein are warranted

relationship between tremor and volcanic activity during the southeast crater eruption on mount etna in early 2000 1 the southeast crater of mount etna italy was characterized by a violent eruptive activity between 26 january and 24 june 2000 this activity produced 64 lava fountain episodes with repose periods from 3 hours to 10 days we estimated a volume of about 15 20 106 m3 lava and at least 2 3 106 m3 of tephra we compared the paroxysmal volcanic activity to its associated seismic signature the high number of events highlighted a strict correlation between tremor and volcanic activity seismic and volcanic characteristics such as the frequency of occurrence the duration of lava fountains and the associated tremor energy suggested the subdivision of the studied period into two stages separated by the 20 february event combining volcanic with seismic data we observed some useful relationships among lava fountain height sustained column height and reduced displacement in addition we found that the entire episode was well correlated with the duration of the amplitude increase computing the tremor energy linked to each event the total energy associated with lava fountains episodes results in 76 of the energy released during the whole period finally the different ratios among the overall spectral amplitude of the seismic signals of the stations located at different altitudes suggested to us the elaboration of a simple qualitative model to explain the dynamic behavior of the tremor source during the whole episode

temporal change of upper crustal vp vs ratios with volcanic evolution in redoubt volcano abstract volcanic activities accompany changes in the physical and chemical properties of the medium the ratio between p and s wave velocities v p v s is sensitive to the medium property changes we investigate temporal variations of the v p v s ratios in the upper crust around redoubt volcano in the 1989 2014 time period using the traveltimes of local earthquakes the v p v s ratios reached 2 0 immediately prior to the 1989 1990 and 2009 eruptions these high v p v s ratios may be associated with partial melts in the edifice the v p v s ratios rapidly decreased to 1 7 during the 1989 1990 and 2009 eruptions due to decreasing temperatures fluids and pore pressures and increasing effective stresses after melt eruptions and gas emission the change rates of the v p v s ratios showed evident spatial distributions the v p v s ratios increased at a rate of 0 025 0 003 yr 1 below the 2009 vent during the inter eruption period between the 1989 1990 and 2009 eruptions due to an increase in the temperature which may be associated with the recharge of the magma in the lower crust the increase rate of the v p v s ratios was as low as 0 005 0 001 yr 1 in the regions located away from the eruption site the v p v s ratios appear to have increased consistently at a rate of 0 017 0 004 yr 1 since the 2009 eruption

three dimensional bayesian geostatistical aquifer characterization at the hanford 300 area using tracer test data 1 tracer tests performed under natural or forced gradient flow conditions can provide useful information for characterizing subsurface properties through monitoring modeling and interpretation of the tracer plume migration in an aquifer nonreactive tracer experiments were conducted at the hanford 300 area along with constant rate injection tests and electromagnetic borehole flowmeter tests a bayesian data assimilation technique the method of anchored distributions mad rubin et al 2010 was applied to assimilate the experimental tracer test data with the other types of data and to infer the three dimensional heterogeneous structure of the hydraulic conductivity in the saturated zone of the hanford formation in this study the bayesian prior information on the underlying random hydraulic conductivity field was obtained from previous field characterization efforts using constant rate injection and borehole flowmeter test data the posterior distribution of the conductivity field was obtained by further conditioning the field on the temporal moments of tracer breakthrough curves at various observation wells mad was implemented with the massively parallel three dimensional flow and transport code pflotran to cope with the highly transient flow boundary conditions at the site and to meet the computational demands of mad a synthetic study proved that the proposed method could effectively invert tracer test data to capture the essential spatial heterogeneity of the three dimensional hydraulic conductivity field application of mad to actual field tracer data at the hanford 300 area demonstrates that inverting for spatial heterogeneity of hydraulic conductivity under transient flow conditions is challenging and more work is needed

the impeller meter for measuring aquifer permeability variations evaluation and comparison with other tests a knowledge of the variation of horizontal hydraulic conductivity with vertical position k z is important in understanding the transport and dispersive properties of aquifers using an impeller meter to measure the discharge distribution in a screened well while pumping at a constant rate is a promising technique for obtaining the k z function such an application is described herein and the resulting k z functions are compared with those obtained previously using tracer tests and multilevel slug tests impeller meter data were the most convenient to obtain and tracer data the most difficult the k z functions obtained by the three methods were not identical but quite similar overall this similarity between both borehole tests and the larger scale tracer test showed that nonstationary hydraulic conductivity trends in a stochastic hydrologic sense exist in the test aquifer the impeller meter method was better able to detect the higher k layers than was the multilevel slug approach overall the results suggest that a practical strategy for fitting impeller meter tracer or multilevel slug test data to a given aquifer is to use the selected testing procedure to obtain a dimensionless distribution and then a standard pumping test to measure combining both types of information enables dimensional values for k z to be calculated in low permeability aquifers or near the bottom of a test well the fluid velocity due to pumping may be below the stall velocity of an impeller thus there is a definite need for the commercial development of more sensitive flow measuring devices such as heat pulse flowmeters hess 1986 which will extend the resolution of this field method

volumetric estimates of ancient water on mount sharp based on boxwork deposits gale crater mars while the presence of water on the surface of early mars is now well known the volume distribution duration and timing of the liquid water have proven difficult to determine this study makes use of a distinctive boxwork rich sedimentary layer on mount sharp to map fluid based cementation from orbital imagery and estimate the minimum volume of water present when this sedimentary interval was formed the boxwork structures on mount sharp are decameter scale light toned polygonal ridges that are unique compared to previous observations of martian fractured terrain because they are parallel sided ridges with dark central linear depressions this texture and the sedimentary setting strongly imply that the ridges are early diagenetic features formed in the subsurface phreatic groundwater zone high resolution orbital imagery was used to map the volume of light toned cemented ridges based on the cemented volume a minimum of 5 25 105 m 3 of cement was deposited within the fractures using a brine composition based on observations of other martian cements and modeling the degree of evaporation each volume of cement requires 800 6700 pore volumes of water so the mapped boxwork ridge cements require a minimum of 0 43 km 3 of water this is a significant amount of groundwater that must have been present at the 3620 m level 1050 m above the current floor of gale crater providing both a new constraint on the possible origins of mount sharp and a possible future science target for the curiosity rover where large volumes of water were present and early mineralization could have preserved a once habitable environment

precursory swarms of long period events at redoubt volcano 1989 1990 alaska their origin and use as a forecasting tool abstract during the eruption of redoubt volcano from december 1989 through april 1990 the alaska volcano observatory issued advance warnings of several tephra eruptions based on changes in seismic activity related to the occurrence of precursory swarms of long period lp seismic events dominant period of about 0 5 s the initial eruption on december 14 occurred after 23 years of quiescence and was heralded by a 23 hour swarm of lp events that ended abruptly with the eruption after a series of vent clearing explosions over the next few days dome growth began on december 21 another swarm with lp events similar to those of the first began on the 26th and ended in a major tephra eruption on january 2 eruptions continued over the next two weeks and then ceased until february 15 when a large eruption initiated a long phase of repetitive dome building and dome destroying episodes that continued into april warnings were issued before the major events on december 14 and january 2 but as the eruptive sequence continued after january 2 the energy of the swarms decreased and forecasting became more difficult a significant but less intense swarm preceded the february 15 eruption which was not forecast this eruption destroyed the only seismograph on the volcanic edifice and stymied forecasting until march 4 when the first of three new stations was installed within 3 km of the active vent from march 4 to the end of the sequence on april 21 there were eight eruptions six of which were preceded by detectable swarms of lp events although weak these swarms provided the basis for warnings issued before the eruptions on march 23 and april 6 the initial swarm on december 13 had the following features 1 short duration 23 hours 2 a rapidly accelerating rate of seismic energy release over the first 18 hours of the swarm followed by a decline of activity during the 5 hours preceding the eruption 3 a magnitude range from 0 4 to 1 6 4 nearly identical lp signatures with a dominant period near 0 5 s 5 dilatational first motions everywhere and 6 a stationary source location at a depth of 1 4 km beneath the crater this occurrence of long period events suggests a model involving the interaction of magma with groundwater in which magmatic gases steam and water drive a fixed conduit at a stationary point throughout the swarm the initiation of that sequence of events is analogous to the failure of a pressure relief valve connecting a lower supercharged magma dominated reservoir to a shallow hydrothermal system a three dimensional model of a vibrating fluid filled crack recently developed by chouet is found to be compatible with the seismic data and yields the following parameters for the lp source crack length 280 380 m crack width 140 190 m crack thickness 0 05 0 20 m crack stiffness 100 200 sound speed of fluid 0 8 1 3 km s compressional wave speed of rock 5 1 km s density ratio of fluid to rock 0 4 and ratio of bulk modulus of fluid to rigidity of rock 0 03 0 07 the fluid filled crack is excited intermittently by an impulsive pressure drop that varies in magnitude within the range of 0 4 to 40 bar such disturbance appears to be consistent with a triggering mechanism associated with choked flow conditions in the crack

seismological aspects of the 1989 1990 eruptions at redoubt volcano alaska the ssam perspective abstract ssam is a simple and inexpensive tool for continuous monitoring of average seismic amplitudes within selected frequency bands in near real time on a pc based data acquisition system during the 1989 1990 eruption sequence at redoubt volcano the potential of ssam to aid in rapid identification of precursory long period lp event swarms was realized and since this time ssam has been incorporated in routine monitoring efforts of the alaska volcano observatory in particular an eruption that occurred on april 6 was successfully forecast primarily on the basis of recognizing the precursory lp activity on ssam of twenty two significant eruptions that occurred between december 14 and april 21 eleven had precursory swarms longer than one hour in duration that could be detected on ssam for individual swarms the patterns of relative spectral amplitudes are distinct at each station and remain largely stationary through time thus indicating that one source may have been preferentially and repeatedly activated throughout the swarm typically a single spectral band dominates the signal at each seismic station for the vigorous one day swarm that preceded the first eruption on december 14 signals were sharply peaked in the 1 9 2 7 hz band at the closest station located 4 km from the vent but were dominated by 1 3 1 9 hz energy at three more distant stations located 7 5 22 km from the vent the tendency for the signals from different swarms recorded at the same station to be peaked in the same frequency band suggests that all of the sources are characterized by a predominant length scale signals from the precursory lp swarms became weaker as the eruption sequence progressed and swarms that occurred in march and april could only be detected at seismographs on the volcanic edifice onset times of precursory lp swarms prior to eruptions ranged from a few hours to about one week but after the initial vent clearing phase that ended december 19 these intervals tended to become progressively shorter for successive swarms these trends in the relative onset times and intensities of successive precursory lp swarms are consistent with an overall depressurization of the magmatic system through time in general each of the swarms had an emergent onset but the intensities did not always increase steadily until the eruptions instead as the time of an eruption approached the intensity usually increased more rapidly before peaking and then declining prior to the eruption for three of the swarms two distinct peaks in intensity were apparent the time intervals between final peaks in swarm intensity and ensuing eruptions ranged from about 2 hours to almost 2 days but the peaks always occurred closer to the eruptions than to the swarm onsets both the onset of lp swarm activity and a decline in intensity prior to an eruption may represent critical points in the process of pressurization that drives the flow of fluids and gas in a sealed magmatic system a notable exception to this pattern is the eruption of march 9 which lacked a detectable precursory lp swarm but was followed by an unusually long period of strong lp seismicity that may have been stimulated by a depressurization of the magmatic system resulting from dome failure on both december 14 and january 2 the spectra of early syn eruptive signals have peaked signatures much like those of the spectra of precursory lp activity from shortly before the eruptions these similarities may indicate that the source of precursory seismicity continued to be active during at least the early part of each eruption in syn eruptive signals from march and april recorded at stations on the volcanic edifice the dominant spectral energy progressively shifts with time during the eruption to lower frequencies at least part of the energy in these signals may have been generated by the debris flows associated with dome failures

seismological aspects of the 1989 1990 eruption at redoubt volcano alaska the materials failure forecast method ffm with rsam and ssam seismic data abstract seismic activity during the december 1989 to april 1990 eruption of redoubt volcano alaska has been tracked by the alaska volcano observatory using real time seismic amplitude measurement rsam and seismic spectral amplitude measurement ssam systems with up to five stations data consist of 10 minute averages of the absolute amplitudes of seismometer output these data have been used to test in hindsight the materials failure forecast method ffm which attempts to define the time of eruption with a time series for precursory phenomena whose rate of change accelerates measurably before events practical application of the method emphasizes inverse rate plots both for early detection of signal emergent from background and for event forecasting eruption windows are determined by graphical or numerical extrapolation of the inverse rate trend and by intersection of a data envelope reflecting data scatter and consistency with an empirical critical rate near the time of eruption prior to the dome destroying eruption of january 2 rate changes were of sufficient consistency duration and intensity for a qualitative or quantitative ffm predictive analysis using either rsam or ssam signal to noise ratio was high for both rsam or ssam data sets and ffm analyses could have provided useful support for decision making following january 2 in association with a rapid succession of dome collapse eruptions signal strength diminished and rsam signal to noise ratio declined the most distinct patterns on rsam reflected noise rather than signal and forecasting exclusively based for rsam would have been misleading by eliminating the noise in excluded frequencies an enhanced signal to noise ratio was generally produced by ssam for banded frequencies near 2 hz after january 2 only ssam exhibited signal to noise ratios suitable for ffm analysis inverse ssam plots could have been informative for early detection of precursory long period seismicity the prospect of combining the ffm approach with spectral amplitudes in selected frequencies offers considerable promise

seismic evolution of the 1989 1990 eruption sequence of redoubt volcano alaska abstract redoubt volcano in south central alaska erupted between december 1989 and june 1990 in a sequence of events characterized by large tephra eruptions pyroclastic flows lahars and debris flows and episodes of dome growth the eruption was monitored by a network of five to nine seismic stations located 1 to 22 km from the summit crater notable features of the eruption seismicity include 1 small long period events beginning in september 1989 which increased slowly in number during november and early december 2 an intense swarm of long period events which preceded the initial eruptions on december 14 by 23 hours 3 shallow swarms 0 to 3 km of volcano tectonic events following each eruption on december 15 4 a persistent cluster of deep 6 to 10 km volcano tectonic earthquakes initiated by the eruptions on december 15 which continued throughout and beyond the eruption 5 an intense swarm of long period events which preceded the eruptions on january 2 and 6 nine additional intervals of increased long period seismicity each of which preceded a tephra eruption hypocenters of volcano tectonic earthquakes suggest the presence of a magma source region at 6 10 km depth earthquakes at these depths were initiated by the tephra eruptions on december 15 and likely represent the readjustment of stresses in the country rock associated with the removal of magma from these depths the locations and time history of these earthquakes coupled with the eruptive behavior of the volcano suggest this region was the source of most of the erupted material during the 1989 1990 eruption this source region appears to be connected to the surface by a narrow pipe like conduit as inferred from the hypocenters of volcano tectonic earthquakes concentrations of shallow volcano tectonic earthquakes followed each of the tephra eruptions on december 15 these shocks may represent stress readjustment in the wall rock related to the removal of magma and volatiles at these depths this shallow zone was the source area of the majority of long period seismicity through the remainder of the eruption the long period seismicity likely reflects the pressurization of the shallow portions of the magmatic system

proximal pyroclastic deposits from the 1989 1990 eruption of redoubt volcano alaska stratigraphy distribution and physical characteristics abstract more than 20 eruptive events during the 1989 1990 eruption of redoubt volcano emplaced a complex sequence of lithic pyroclastic flow surge fall ice diamict and lahar deposits mainly on the north side of the volcano the deposits record the changing eruption dynamics from initial gas rich vent clearing explosions to episodic gas poor lava dome extrusions and failures the repeated dome failures produced lithic pyroclastic flows that mixed with snow and glacial ice to generate lahars that were channelled off drift glacier into the drift river valley some of the dome failures occurred without precursory seismic warning and appeared to result solely from gravitational instability material from the disrupted lava domes avalanched down a steep partly ice filled canyon incised on the north flank of the volcano and came to rest on the heavily crevassed surface of the piedmont lobe of drift glacier most dome collapse events resulted in single monolithologic massive to reversely graded medium to coarse grained sandy pyroclastic flow deposits containing abundant dense dome clasts these deposits vary in thickness grain size and texture depending on distance from the vent and local topography deposits are finer and better sorted down flow thinner and finer on hummocks and thicker and coarser where ponded in channels cut through the glacial ice the initial vent clearing explosions emplaced unusual deposits of glacial ice snow and rock in a frozen matrix on the north and south flanks of the volcano similar deposits were described at nevado del ruiz columbia and have probably been emplaced at other snow and ice clad volcanoes but poor preservation makes them difficult to recognize in the geologic record in a like fashion most deposits from the 1989 1990 eruption of redoubt volcano may be difficult to recognize and interpret in the future because they were emplaced in an environment where glacio fluvial processes dominate and quickly obscure the primary depositional record

advanced aquifer characterization for optimization of managed aquifer recharge managed aquifer recharge mar will play an increasingly important role in solving water scarcity the performance of mar systems depends primarily upon local hydrogeology greatest opportunities for improvement in the implementation of mar systems lie in the targeted application of conventional and advanced technologies to improve aquifer characterization surface geophysics e g ves tdem and seismic reflection and refraction generally provide low resolution but areal extensive data on subsurface hydrogeology times series of relative microgravity measurements have been used to map changes in both vadose and phreatic zone storage and to augment monitoring well systems surface nuclear magnetic resonance nmr has the potential to provide quantitative data on water filled porosity and pore size distribution and in turn an estimate of hydraulic conductivity standard borehole geophysical logging techniques can provide coarse scale data on aquifer heterogeneity advanced borehole logging techniques such as nmr microresistivity imaging and gamma ray spectroscopy have been used in mar projects in the usa and uae to provide fine scale petrophysical data e g porosity porosity types and pore size distribution groundwater modeling is used in mar investigations to evaluate system feasibility and to optimize system design and operation opportunities to improve groundwater modeling exist through the application of advanced reservoir simulation platforms that allow for the processing and integration of available lithological geophysical and aquifer testing data and their subsequent incorporation into groundwater flow models advanced groundwater modeling programs are available that allow for the simulation of complex aquifers such as dual porosity systems and variable density

interpretation of transient borehole flow metering data in a fissured granite formation summary heat pulse flowmeter hpf data obtained in a fractured granite formation under transient pumping conditions are interpreted using a borehole flow model the phraeatic formation is modeled using cylindrically symmetric layers composed of thick low permeability intervals between thin layers of much higher permeability corresponding to fracture zones the inflow to the borehole at fracture zones generates sharp increases in the flow profiles obtained during pumping heat pulse flowmeter measurements are given as a function of depth and time drawdown and pumping rate are also recorded during the measurement period the numerical flow model is used to calculate the drawdown and evolving profile of borehole flow as a function of time during the pumping period the model allows for vertical flow across the horizontal interfaces between layers and accounts for borehole storage effects the model is also designed to allow for changes in fracture zone permeability with distance from the borehole bi zonal flow by allowing for changes in permeability with radial distance the model uses a finite difference technique to compute borehole flow and drawdown during pumping the accuracy of the finite difference code was checked against available analytical and semi analytical solutions derived by integral transform techniques the model was calibrated using estimates of formation properties and distance to lateral boundaries derived from short medium and long term packer tests results of two borehole flow experiments are evaluated for experiments in boreholes with 7 and 4 discrete fracture zones distributed over 59 50 and 121 16 m of open borehole interval

imaging and characterization of facies heterogeneity in an alluvial aquifer using gpr full waveform inversion and cone penetration tests summary spatially highly resolved mapping of aquifer heterogeneities is critical for the accurate prediction of groundwater flow and contaminant transport here we demonstrate the value of using full waveform inversion of crosshole ground penetrating radar gpr data for aquifer characterization we analyze field data from the krauthausen test site where crosshole gpr data were acquired along a transect of 20 m length and 10 m depth densely spaced cone penetration tests cpt located close to the gpr transect were used to validate and interpret the tomographic images obtained from gpr a strong correlation was observed between cpt porosity logs and porosity estimates derived from gpr using the complex refractive index model crim a less pronounced correlation was observed between electrical conductivity data derived from gpr and cpt cluster analysis of the gpr data defined three different subsurface facies which were found to correspond to sediments with different grain size and porosity in conclusion our study suggests that full waveform inversion of crosshole gpr data followed by cluster analysis is an applicable approach to identify hydrogeological facies in alluvial aquifers and to map their architecture and connectivity such facies maps provide valuable information about the subsurface heterogeneity and can be used to construct geologically realistic subsurface models for numerical flow and transport prediction

interpretation of flowmeter data in heterogeneous layered aquifers summary we analyze numerically the impact of key assumptions which are usually adopted to interpret borehole flowmeter test data we base our work on a set of detailed numerical simulations of transient and pseudo steady state convergent flow to a fully penetrating well that pumps at a constant total flow rate in a confined three dimensional system formed by well demarcated facies our results allow identifying the effects of i the presence of a skin zone around the well ii the contrast of hydraulic conductivities of the aquifer facies and the gravel pack and iii the dynamics of the flow regime on the ability to characterize the local aquifer conductivities of a stratified system through the typical interpretation of downhole flowmeter tests vertical intervals along the wellbore where reliable estimates of the aquifer conductivities can be obtained through classical formulations are identified in terms of a set of dimensionless parameters these parameters involve the thickness of the facies constituting the stratified aquifer and the contrast of conductivities amongst different facies and between them and the skin zone

large scale natural gradient tracer test in sand and gravel cape cod massachusetts 3 hydraulic conductivity variability and calculated macrodispersivities hydraulic conductivity k variability in a sand and gravel aquifer on cape cod massachusetts was measured and subsequently used in stochastic transport theories to estimate macrodispersivities nearly 1500 k measurements were obtained by borehole flowmeter tests and permeameter analyses of cores the geometric mean for the flowmeter tests 0 11 cm s is similar to that estimated from other field tests the mean for the permeameter tests 0 035 cm s is significantly lower possibly because of compaction of the cores the variance for the flowmeter 0 24 is also greater than that for the permeameter 0 14 geostatistical analyses applying negative exponential models with and without nuggets reveal similar spatial correlation structures for the two data sets estimated correlation scales range from 2 9 to 8 m in the horizontal and from 0 18 to 0 38 m in the vertical estimates of asymptotic longitudinal dispersivity b 35 0 78 m are similar in magnitude to that observed in the natural gradient tracer test 0 96 m previously conducted at this site

deep confined karst detection analysis and paleo hydrology reconstruction at a basin wide scale using new geophysical interpretation of borehole logs summary deep karst voids can be identified by a new method of geophysical interpretation of commonly used borehole logs in deeply confined carbonate aquifers we show that deep buried karst voids can be characterized by combining this geophysical interpretation together with geological and hydrological data and with known speleological constraints we demonstrate how this characterization can reveal past hydrological regimes and allow mapping of karst distribution on a basin wide scale a combined analysis of geophysical geological hydrological and speleological data in the confined yarkon taninim aquifer israel led us to reconstruct past groundwater levels at different relief and sea levels with the karst voids as a marker for long term flow close to the water table paleo canyons along the mediterranean sea shoreline strongly affected the region s paleo hydrology by serving as major outlets of the aquifer during most of the cenozoic we conclude that intensive karstification was promoted by flow periods of longer duration and or higher flux and flow velocities close to the aquifer s past and present outlets in addition we suggest that karst voids found under shallow confinement were developed by renewed aggressivity due to hypogene water rising in cross formational flow becoming mixed with fresh lateral water flow from the east

dome growth and destruction during the 1989 1990 eruption of redoubt volcano abstract much of the six month long 1989 1990 eruption of redoubt volcano consisted of a dome growth and destructive phase in which 14 short lived viscous silicic andesite domes were emplaced and 13 subsequently destroyed the life span of an individual dome ranged from 3 to 21 days and volumes are estimated at 1 10 6 to 30 10 6 m 3 magma supply rates to the vent area averaged about 5 10 5 m 3 day for most of the dome building phase and ranged from a high of 2 2 10 6 m 3 per day initially to a low of 1 8 10 5 m 3 per day at the waning stages of the eruption the total volume of all domes is estimated to be about 90 10 6 m 3 and may represent as much as 60 70 of the volume for the entire eruption the site of 1989 1990 dome emplacement like that in 1966 was on the margin of a north facing amphitheatre like summit crater the domes were confined on the east and west by steep cliffs of pre eruption cone building volcanic rocks and thus were constrained to grow vertically rapid upward growth in a precarious site caused each dome to spread preferentially to the north resulting in eventual gravitational collapse as long as the present conduit remains active at redoubt volcano any dome formed in a new eruption will be confined to a narrow steeply sloping gorge leading to rapid vertical growth and a tendency to collapse gravitationally repetitive cycles of dome formation and failure similar to those seen in 1989 1990 are probably the norm and must be considered in future hazard analyses of redoubt volcano

hydrogeological characterization of the south oyster bacterial transport site using geophysical data a multidisciplinary research team has conducted a field scale bacterial transport study within an uncontaminated sandy pleistocene aquifer near oyster virginia the overall goal of the project was to evaluate the importance of heterogeneities in controlling the field scale transport of bacteria that are injected into the ground for remediation purposes geochemical hydrological geological and geophysical data were collected to characterize the site prior to conducting chemical and bacterial injection experiments in this paper we focus on results of a hydrogeological characterization effort using geophysical data collected across a range of spatial scales the geophysical data employed include surface ground penetrating radar radar cross hole tomography seismic cross hole tomography cone penetrometer and borehole electromagnetic flowmeter these data were used to interpret the subregional and local stratigraphy to provide high resolution hydraulic conductivity estimates and to provide information about the log conductivity spatial correlation function the information from geophysical data was used to guide and assist the field operations and to constrain the numerical bacterial transport model although more field work of this nature is necessary to validate the usefulness and cost effectiveness of including geophysical data in the characterization effort qualitative and quantitative comparisons between tomographically obtained flow and transport parameter estimates with hydraulic well bore and bromide breakthrough measurements suggest that geophysical data can provide valuable high resolution information this information traditionally only partially obtainable by performing extensive and intrusive well bore sampling may help to reduce the ambiguity associated with hydrogeological heterogeneity that is often encountered when interpreting field scale bacterial transport data

statistical analysis of intermittent volcanic tremor associated with the september 1989 summit explosive eruptions at mount etna sicily the pattern of volcanic tremor accompanyingthe 1989 september eruption at the south east summit crater of mount etna is studied in specific sixteen episodes of lava fountaining which occurred in the first phase of the eruption are analysed their periodic behaviour also evidenced by autocorrelation allows us to define the related tremor amplitude increases as intermittent volcanic tremor episodes focusingon the reg ular intermittent behaviour found for both lava fountains and intermittent volcanic tremors we tried an a posteriori forecast usingsimple statistical methods based on linear regression and the student t test we performed the retrospective statistical forecast and found that several eruptions would have been successfully forecast in order to focus on the source mechanism of tremor linked to lava fountains we investigated the relationship between volcanic and seismic parameters a mechanism based on a shallow magma batch regularly refilled from depth is suggested 1 2002 elsevier science b v all rights reserved

flow modeling and permeability estimation using borehole flow logs in heterogeneous fractured formations a numerical model of flow in the vicinity of a borehole is used to analyze flowmeter data obtained with high resolution flowmeters the model is designed to 1 precisely compute flow in a borehole 2 approximate the effects of flow in surrounding aquifers on the measured borehole flow 3 allow for an arbitrary number n of entry exit points connected to m n far field aquifers and 4 be consistent with the practical limitations of flowmeter measurements such as limits of resolution typical measurement error and finite measurement periods the model is used in three modes 1 a quasi steady pumping mode where there is no ambient flow 2 a steady flow mode where ambient differences in far field water levels drive flow between fracture zones in the borehole and 3 a cross borehole test mode where pumping in an adjacent borehole drives flow in the observation borehole the model gives estimates of transmissivity for any number of fractures in steady or quasi steady flow experiments that agree with straddle packer test data field examples show how these cross borehole type curves can be used to estimate the storage coefficient of fractures and bedding planes and to determine whether fractures intersecting a borehole at different locations are hydraulically connected in the surrounding rock mass

using flowmeter pulse tests to define hydraulic connections in the subsurface a fractured shale example cross borehole flowmeter pulse tests define subsurface connections between discrete fractures using short stress periods to monitor the propagation of the pulse through the flow system this technique is an improvement over other cross borehole techniques because measurements can be made in open boreholes without packers or previous identification of water producing intervals the method is based on the concept of monitoring the propagation of pulses rather than steady flow through the fracture network in this method a hydraulic stress is applied to a borehole connected to a single permeable fracture and the distribution of flow induced by that stress monitored in adjacent boreholes the transient flow responses are compared to type curves computed for several different types of fracture connections the shape of the transient flow response indicates the type of fracture connection and the fit of the data to the type curve yields an estimate of its transmissivity and storage coefficient the flowmeter pulse test technique was applied in fractured shale at a volatile organic contaminant plume in watervliet new york flowmeter and other geophysical logs were used to identify permeable fractures in eight boreholes in and near the contaminant plume using single borehole flow measurements flowmeter cross hole pulse tests were used to identify connections between fractures detected in the boreholes the results indicated a permeable fracture network connecting many of the individual boreholes and demonstrated the presence of an ambient upward hydraulic head gradient throughout the site

observations of particle movement in a monitoring well using the colloidal borescope abstract the colloidal borescope consists of a set of lenses and miniature video cameras capable of observing natural particles in monitoring wells based on field observations of these particles it appears possible to measure in situ groundwater velocity in a well bore field observations have shown that directional measurements using the colloidal borescope are generally in good agreement with expected flow directions however the magnitude of flow velocity is higher compared with values based on conventional test methods high relative flow velocities even after correction factors have been applied to compensate for well bore effects are believed to be due to preferential flow zones in the surrounding aquifer low flow zones exhibit swirling multidirectional flow that does not allow for a linear velocity measurement consequently groundwater flow velocities measured by the colloidal borescope in heterogeneous aquifers will be biased toward the maximum velocity values present in the aquifer a series of laboratory experiments was conducted to assess the reliability of the instrument based on this work a seepage velocity correction factor of 1 4 was found for quantifying groundwater seepage velocity in the adjacent aquifer from observations in a well bore laboratory measurements also indicate that preferential flow in the surrounding aquifer dominates flow in the well results of this work suggest the possibility of quantifying higher flow velocities associated with preferential flow zones in the subsurface

seismic observations of redoubt volcano alaska 1989 2010 and a conceptual model of the redoubt magmatic system abstract seismic activity at redoubt volcano alaska has been closely monitored since 1989 by a network of five to ten seismometers within 22 km of the volcano s summit major eruptions occurred in 1989 1990 and 2009 and were characterized by large volcanic explosions episodes of lava dome growth and failure pyroclastic flows and lahars seismic features of the 1989 1990 eruption were 1 weak precursory tremor and a short 23 hour long intense swarm of repetitive shallow long period lp events centered 1 4 km below the crater floor 2 shallow volcano tectonic vt and hybrid earthquakes that separated early episodes of dome growth 3 13 additional swarms of lp events at shallow depths precursory to many of the 25 explosions that occurred over the more than 128 day duration of eruptive activity and 4 a persistent cluster of vt earthquakes at 6 to 9 km depth in contrast the 2009 eruption was preceded by a pronounced increase in deep lp dlp events at lower crustal depths 25 to 38 km that began in mid december 2008 two months of discontinuous shallow volcanic tremor that started on january 23 2009 a strong phreatic explosion on march 15 and a 58 hour long swarm of repetitive shallow lp events the 2009 eruption consisted of at least 23 major explosions between march 23 and april 5 again accompanied by shallow vt earthquakes several episodes of shallow repetitive lp events and dome growth continuing until mid july increased vt earthquakes at 4 to 9 km depth began slowly in early april possibly defining a mid crustal magma source zone magmatic processes associated with the 2009 eruption seismically activated the same portions of the redoubt magmatic system as the 1989 1990 eruption although the time scales and intensity vary considerably among the two eruptions the occurrence of precursory dlp events suggests that the 2009 eruption may have involved the rise of magma from lower crustal depths based on the evolution of seismicity during the 1989 1990 and 2009 eruptions the redoubt magmatic system is envisioned to consist of a shallow system of cracks extending 1 to 2 km below the crater floor a magma storage or source region at roughly 3 to 9 km depth and a diffuse magma source region at 25 to 38 km depth close tracking of seismic activity allowed the alaska volcano observatory to successfully issue warnings prior to many of the hazardous explosive events that occurred in 2009