bayesian source inference of the 1993 1997 deformation at mount etna italy by numerical solutions summary deformation data collected at mount etna from 1993 to 1997 show that the inflation of the volcano edifice is accompanied by instability of the eastern flank we propose a 3 d finite element model including topography and lateral variations of elastic constants source parameters of the inflating source are constrained by a direct search followed by an appraisal stage of the sampled solutions the instability of the eastern flank is addressed using a kinematic approach consisting of a rigid body translation over a prescribed area the aim is to evaluate how source parameters are affected by sliding of the eastern flank when sliding is accounted for the inferred source location shifts 1 km se and its strength decreases by 20 per cent

analytical and 3 d numerical modelling of mt etna italy volcano inflation summary since 1993 geodetic data obtained by different techniques gps edm sar levelling have detected a consistent inflation of the mt etna volcano the inflation culminating with the 1998 2001 strong explosive activity from summit craters and recent 2001 and 2002 flank eruptions is interpreted in terms of magma ascent and refilling of the volcanic plumbing system and reservoirs we have modelled the 1993 1997 edm and gps data by 3 d pressurized sources to infer the position and dimension of the magma reservoir we have performed analytical inversions of the observed deformation using both spheroidal and ellipsoidal sources embedded in a homogeneous elastic half space and by applying different inversion methods solutions for these types of sources show evidence of a vertically elongated magma reservoir located 6 km beneath the summit craters the maximum elevation of topography is comparable to such depth and strong heterogeneities are inferred from seismic tomography in order to assess their importance further 3 d numerical models employing source parameters extracted from analytical models have been developed using the finite element technique the deformation predicted by all the models considered shows a general agreement with the 1993 1997 data suggesting the primary role of a pressure source while the complexities of the medium play a minor role under elastic conditions however major discrepancies between data and models are located in the se sector suggesting that sliding along potential detachment surfaces may contribute to amplify deformation during the inflation for the first time realistic features of mt etna are studied by a 3 d numerical model characterized by the topography and lateral variations of elastic structure providing a framework for a deeper insight into the relationships between internal sources and tectonic structures

coupled magma chamber inflation and sector collapse slip observed with synthetic aperture radar interferometry on mt etna volcano 1 volcanoes deform dynamically due to changes in both their magmatic system and instability of their edifice mt etna features vigorous and almost continuous eruptive activity from its summit craters and periodic flank eruptions even though its shape is that of a large stratovolcano its structure features two rift systems and a flank collapse structure similar to hawaiian shield volcanoes we analyze european remote sensing ers satellite differential interferometric synthetic aperture radar insar data 1993 1996 for mt etna spanning its quiescence from 1993 through the initiation of renewed eruptive activity in late 1995 we use synthetic aperture radar sar data from both ascending and descending ers satellite tracks comparison of independent interferograms covering the first 2 years of the inflationary period shows a pattern consistent with inflation of the volcano calculation of the tropospheric path delay based on meteorological data does not change this interpretation interferograms from late summer 1995 1996 show no significant deformation joint inversion of interferograms from ascending and descending satellite tracks require both inflation from a spheroidal magmatic source located beneath the summit at 5 km below sea level and displacement of the east flank of etna along a basal decollement both sources of deformation were contemporaneous within the resolution of our data and suggest that inflation of the central magma chamber acted to trigger slip of etna s eastern flank these results demonstrate that flank instability and recharge of a volcano s magma system must both be considered toward understanding how volcanoes work and in their hazard evaluation

deformation associated with the 1997 eruption of okmok volcano alaska 1 okmok volcano located on umnak island in the aleutian chain alaska is the most eruptive caldera system in north america in historic time its most recent eruption occurred in 1997 synthetic aperture radar interferometry shows deflation of the caldera center of up to 140 cm during this time preceded and followed by inflation of smaller magnitude the main part of the observed deformation can be modeled using a pressure point source model the inferred source is located between 2 5 and 5 0 km beneath the approximate center of the caldera and 5 km from the eruptive vent we interpret it as a central magma reservoir the preeruptive period features inflation accompanied by shallow localized subsidence between the caldera center and the vent we hypothesize that this is caused by hydrothermal activity or that magma moved away from the central chamber and toward the later vent since all historic eruptions at okmok have originated from the same cone this feature may be a precursor that indicates an upcoming eruption the erupted magma volume is 9 times the volume that can be accounted for by the observed preeruptive inflation this indicates a much longer inflation interval than we were able to observe the observation that reinflation started shortly after the eruption suggests that inflation spans the whole time interval between eruptions extrapolation of the average subsurface volume change rate is in good agreement with the long term eruption frequency and eruption volumes of okmok

the displacement field of the landers earthquake mapped by radar interferometry geodetic data obtained by ground or space based techniques can be used to infer the distribution of slip on a fault that has ruptured in an earthquake although most geodetic techniques require a surveyed network to be in place before the earthquake1 3 satellite images when collected at regular intervals can capture co seismic displacements without advance knowledge of the earthquake s location synthetic aperture radar sar interferometry first introduced4 in 1974 for topographic mapping5 8 can also be used to detect changes in the ground surface by removing the signal from the topography9 10 here we use sar interferometry to capture the movements produced by the 1992 earthquake in landers california11 we construct an interferogram by combining topographic information with sar images obtained by the ers 1 satellite before and after the earthquake the observed changes in range from the ground surface to the satellite agree well with the slip measured in the field with the displacements measured by surveying and with the results of an elastic dislocation model as a geodetic tool the sar interferogram provides a denser spatial sampling 100 m per pixel than surveying methods1 3 and a better precision 3 cm than previous space imaging techniques12 13

atmospheric effects in interferometric synthetic aperture radar surface deformation and topographic maps interferogram images derived from repeat pass spaceborne synthetic aperture radar systems exhibit artifacts due to the time and space variations of atmospheric water vapor other tropospheric variations such as pressure and temperature also induce distortions but the effects are smaller in magnitude and more evenly distributed throughout the interferogram than the wet troposphere term spatial and temporal changes of 20 in relative humidity lead to 10 cm errors in deformation products and perhaps 100 m of error in derived topographic maps for those pass pairs with unfavorable baseline geometries in wet regions such as hawaii these are by far the dominant errors in the spaceborne imaging radar c and x band synthetic aperature radar sir c x sar interferometric products the unknown time delay from tropospheric distortion is independent of frequency and thus multiwavelength measurements such as those commonly used to correct radar altimeter and global positioning system gps ionospheric biases cannot be used to rectify the error in the topographic case the errors may be mitigated by choosing interferometric pairs with relatively long baselines as the error amplitude is inversely proportional to the perpendicular component of the interferometer baseline for the sir c x sar hawaii data we found that the best longest baseline pair produced a map supporting 100 m contouring whereas the poorest baseline choice yielded an extremely noisy topographic map even at this coarse contour interval in the case of deformation map errors the result is either independent of baseline parameters or else very nearly so here the only solution is averaging of independent interferograms so in order to create accurate deformation products in wet regions many multiple passes may be required rules for designing optimal data acquisition and processing sequences for interferometric analyses in nondesert parts of the world are 1 to use the longest radar wavelengths possible within ionospheric scintillation and faraday rotation limits 2 for topography maximize interferometer baseline within decorrelation limits and 3 for surface deformation use multiple observations and average the derived products following the above recipe yields accuracies of 10 m for digital elevation models and 1 cm for deformation maps even in very wet regions such as hawaii

a new approach to the monitoring of deformation on lanzarote canary islands an 8 year radar perspective there was significant eruptive activity on lanzarote canary islands in the 18th and 19th centuries and future activity is a clear likelihood today the fact that not all of the island is covered by geodetic monitoring prompted the authors to assess the possibility of using sar interferometry for routine volcanic activity monitoring of the island this paper presents the results obtained after testing this technique using six radar images acquired by the ers 1 and ers 2 satellites during the period 1992 2000 the analysis of these images has confirmed the existence of long term stability coherence across most of the island a prerequisite for using sar interferometry in volcano monitoring the analysis of 15 redundant interferograms allowed us to study both the impact of atmospheric artifacts on lanzarote and any possible displacements and to conclude that there has been no displacement greater than 3 cm on the island during the period in question this result matches those obtained with the geodetic equipment installed on the island our results show that the inclusion of sar interferometry in routine geodetic monitoring supplementing terrestrial techniques will clearly improve the chances of detecting any possible deformation and its broad coverage will enhance the interpretation of any observed anomalies

deflation of mount etna monitored by spaceborne radar interferometry ground based measurements of volcano deformation can be used to assess eruptive hazard but require the costly and often hazardous installation and maintenance of an instrument network here we show that spaceborne radar interferometry which has already shown its utility in mapping earthquake related deformation1 can be used to monitor long term volcano deformation two families of synthetic aperture radar images acquired from ascending and descending orbits by the satellite ers 1 and looking at mount etna from opposite sides cover the time period from 17 may 1992 to 24 october 1993 and include the second half of etna s most recent eruption despite artefacts of the interferometric technique we can observe a volcano wide deflation which is an expected consequence of the eruption but which had not previously been appreciated we quantify it using a simple model based on the change of pressure in a sphere located in an elastic half space the modelled deformation increases linearly with time until the end of the eruption our results show that it will be possible to use this technique to detect the inflation of volcanic edifices that usually precedes eruptions

radar interferometry and its application to changes in the earth s surface geophysical applications of radar interferometry to measure changes in the earth s surface have exploded in the early 1990s this new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times the resulting interferogram is a contour map of the change in distance between the ground and the radar instrument these maps provide an unsurpassed spatial sampling density 100 pixels km 2 a competitive precision 1 cm and a useful observation cadence 1 pass month 1 they record movements in the crust perturbations in the atmosphere dielectric modifications in the soil and relief in the topography they are also sensitive to technical effects such as relative variations in the radar s trajectory or variations in its frequency standard we describe how all these phenomena contribute to an interferogram then a practical summary explains the techniques for calculating and manipulating interferograms from various radar instruments including the four satellites currently in orbit ers 1 ers 2 jers 1 and radarsat the next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement respecting the limits of the technique assessing its uncertainty recognizing artifacts and discriminating different types of signal we then review the geophysical applications published to date most of which study deformation related to earthquakes volcanoes and glaciers using ers 1 data we also show examples of monitoring natural hazards and environmental alterations related to landslides subsidence and agriculture in addition we consider subtler geophysical signals such as postseismic relaxation tidal loading of coastal areas and interseismic strain accumulation we conclude with our perspectives on the future of radar interferometry the objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it

ground deformation patterns at mt etna from 1993 to 2000 from joint use of insar and gps techniques abstract combined gps measurements and radar interferometry insar have been applied at mt etna to study the ground deformation affecting the volcano both over the long 1993 2000 and short term 1997 1998 and 1998 2000 the aim was to better understand the dynamics of the volcano during the magma recharging phase following the 1991 93 eruption since 1993 insar and gps data indicate that mt etna has undergone an inflation a deep intrusion was detected by insar on the western flank of the volcano between march and may 1997 in the following months this intrusion rose up leading to a seismic swarm occurring in january 1998 in the western sector this now shallow intrusion is confirmed by gps data from 1998 to 2000 a general deflation affecting the upper part of the volcano was detected over the whole study period a continuous eastward to south eastward motion of the eastern sector of the volcano was also evidenced the analytical inversions of gps data inferred a plane dipping about 12 ese located beneath the eastern flank of the volcano at a depth of 1 4 km b s l the movement along this plane is able to reproduce the observed south eastward motion of a sector bounded northward by the pernicana fault westward by the north east rift and the south rift and southward by the mascalucia tremestieri trecastagni fault system insar data have validated this model

the global positioning system as a useful technique for measuring ground deformations in volcanic areas abstract in this paper the global positioning system technique for measuring ground deformations in volcanic areas is presented after an outline of the mathematical background the results of three years experience regarding the use of this technique on mt etna are reported the ground deformation patterns recorded between 1989 and 1991 are shown and discussed in the geodynamic framework which characterized mt etna in the time interval considered attention is focused on modeling a ground deformation episode which occurred on mt etna between 1990 and 1991 which contributed to characterizing the dynamic framework where the 1991 1992 eruptive event took place the deformation pattern mentioned has been interpreted by using a dislocation model the optimal solution for the inversion problem has been found by using an optimization approach based on the simplex method this solution agrees with the regional stress field whose compressive direction is nne ssw oriented

source model for the 2001 flank eruption of mt etna volcano 1 using interferometric synthetic aperture radar insar we constrain the deformation sources for the july august 2001 flank eruption of mt etna volcano italy insar data from ascending and descending passes of the ers2 satellite reveal a pattern of deformation that cannot be explained by a dike intrusion alone in addition to a vertical dike beneath the south rift zone the spatially large 10 km scale 15 20 cm in range negative range displacement lobes across the western descending data and eastern ascending data flanks require a nearly symmetric set of shallowly dipping normal faults to each side of the central dike complexity in the observed insar surface displacements constrains an additional dike intrusion beneath its ne flank long term deformation of etna s eastern and southern flanks is well established through field and insar observations therefore the relative symmetry of motion beneath both the western and eastern flanks during the 2001 eruption is surprising our model of symmetric flank motion suggests that on the short time scales of a large dike intrusion volcanoes can deform differently from their long term deformation

structural assessment of mount etna volcano from permanent scatterers analysis a study of the deformation pattern of mount etna volcano based on the results from the permanent scatterers ps technique is reported ground motion data provided by the interferometric synthetic aperture radar insar ps technique from 1995 to 2000 are compared and validated by gps data an analysis of the ascending and descending line of sight los components of ground velocities has yielded detailed ground deformation maps and cross sections this analysis allows detection and constraint of discontinuities in the surface velocity field los velocities have then been combined to calculate the vertical and horizontal e w ground velocities a wide inflation of the edifice has been detected on the western and northern flanks over an area of about 350 km2 a seaward motion of the eastern and southern flanks has also been measured ps data allows the geometry and kinematics of the several blocks composing the unstable flanks to be defined even in the highly urbanized areas and their displacement rates have been measured with millimeter precision this analysis reveals the extension of some features beyond their field evidences and defines new important features the results of this work depict a new comprehensive kinematic model of the volcano highlighting the gravitational reorganization of the unbuttressed volcanic pile on its slippery clay basement on the southern flank but an additional drag force due to a strong subsidence of the continental margin facing the etna volcano is necessary to explain the ps velocity field observed on the eastern flank

on the application of sar interferometry to geomorphological studies estimation of landform attributes and mass movements this paper presents two examples of application of synthetic aperture radar sar interferometry insar to typical geomorphological problems the principles of insar are introduced taking care to clarify the limits and the potential of this technique for geomorphological studies the application of insar to the quantification of landform attributes such as the slope and to the estimation of landform variations is investigated two case studies are presented a first case study focuses on the problem of measuring landform attributes by interferometric sar data the interferometric result is compared with the corresponding one obtained by a digital elevation model dem in the second case study the use of insar for the estimation of landform variations caused by a landslide is detailed

a shallow dipping dike fed the 1995 flank eruption at fernandina volcano galapagos observed by satellite radar interferometry satellite radar interferometry data reveal strong localized uplift in a semi circular pattern on the southwest flank of fernandina volcano galapagos where an eruption took place in january to april 1995 the observations show a maximum decrease in radar range of 0 75 m and they are consistent with a model of a shallow dipping dike intrusion feeding this fissure eruption we solve for the best fit single rectangular dislocation dike source using non linear inver sion techniques where simulated annealing searching algo rithm is used to avoid local minima the best fit dike is 3 8 km long 2 3 km high 0 86 m thick and with a 34 dip the total dike volume 7 5 x 10 3 km 3 is 40 of the vol ume of extrusive materials estimated to have been produced during the eruption the data do not permit a sub vertical dike implying that the least principal stress direction is not horizontal as is usually assumed

ground deformation monitoring at mt etna evidence for dyke emplacement and slope instability ground deformation monitoring at mount etna has successfully enabled the sub surface paths of two shallow feeder dykes to be traced and their dimensional parameters depths and departures from the vertical to be constrained determinations of horizontal movement have recorded the displacement by 3 6 m maximum of a rim segment of the valle del bove flank caldera due to dilation associated with dyke emplacement adjacent to the rim over the period 1981 to 1989 small scale collapse along this rim segment associated with the opening of the 1989 fissure points to increasing slope instability and highlights the potential for major failure and debris avalanche generation

dynamic deformation of etna volcano observed by satellite radar interferometry satellite radar interferometry of mt etna volcano sicily italy reveals a sequence of deformation characterized by deflation during the end of the 1993 eruption inflation from 1993 1995 with an increase in the inflation rate immediately before its resumed eruptive activity in late 1995 this was followed by very low deformation levels during the following year the source of the deformation changed from a depth of 9 km during deflation to more than 11 14 km during the subsequent inflation consistent with a model in which deflation at shallower levels is followed by inflation at greater depth as the volcano system recharges from below before its next eruption this study demonstrates that radar interferometry provides an important contribution towards understanding the dynamic deformation of volcanoes by revealing large scale changes in their pre eruption deformation rates radar interferometry could play an important role in volcano eruption monitoring

on the derivation of coseismic displacement fields using differential radar interferometry the landers earthquake we present a map of the coseismic displacement field resulting from the landers california june 28 1992 earthquake derived using data acquired from an orbiting high resolution radar system we achieve results more accurate than previous space studies and similar in accuracy to those obtained by conventional field survey techniques data from the ers 1 synthetic aperture radar instrument acquired in april july and august 1992 are used to generate a high resolution wide area map of the displacements the data represent the motion in the direction of the radar line of sight to centimeter level precision of each 30 m resolution element in a 113 km by 90 km image our coseismic displacement contour map gives a lobed pattern consistent with theoretical models of the displacement field from the earthquake fine structure observed as displacement tiling in regions several kilometers from the fault appears to be the result of local surface fracturing comparison of these data with global positioning system and electronic distance measurement survey data yield a correlation of 0 96 thus the radar measurements are a means to extend the point measurements acquired by traditional techniques to an area map format the technique we use is 1 more automatic 2 more precise and 3 better validated than previous similar applications of differential radar interferometry since we require only remotely sensed satellite data with no additional requirements for ancillary information the technique is well suited for global seismic monitoring and analysis

seismicity and time lagged lava output at mount etna a new method of long term forecasting at a destructive volcano time averaged seismic moments m0 of earthquakes in the etna region between 1874 and 1998 show good inverse correlations with functions of time lagged volumetric lava output rates at mount etna the highest correlation coefficients are for a time lag of 25 yr because earthquake activity precedes lava emission the relationship can be used to forecast lava output years in advance the method has valuable potential for forward planning at a destructive volcano and applying it to the immediate future it is predicted that 170 50 106 m3 of lava will be erupted from mount etna between the years 2007 and 2015 this is about half the volume of lava erupted between 1987 and 1995

remote sensing of active volcanoes the synoptic coverage offered by satellites provides unparalleled opportunities for monitoring active volcanoes and opens new avenues of scientific inquiry thermal infrared radiation can be used to monitor levels of activity which is useful for automated eruption detection and for studying the emplacement of lava flows satellite radars can observe volcanoes through clouds or at night and provide high resolution topographic data in favorable conditions radar inteferometery can be used to measure ground deformation associated with eruptive activity on a centimetric scale clouds from explosive eruptions present a pressing hazard to aviation therefore techniques are being developed to assess eruption cloud height and to discriminate between ash and meterological clouds the multitude of sensors to be launched on future generations of space platforms promises to greatly enhance volcanological studies but a satellite dedicated to volcanology is needed to meet requirements of aviation safety and volca

spatial changes of inter plate coupling inferred from sequences of small repeating earthquakes in japan 1 we extract sequences of small repeating earthquakes to clarify inter plate coupling of subducting plates over a large area of the japanese islands as a result many sequences arc detected at the philippine sea plate subducting from the ryukyu trench and pacific plate subducting from the kuril japan trench the average slip rates and standard deviations estimated from the sequences show substantial spatial changes of inter plate coupling the large deviations of slip rates correspond to the occurrence of episodic slips such as after slips following large earthquakes constant slip rates approaching the relative plate motion indicate weak coupling areas slip deficits and sparse distributions of repeating groups suggest locked areas in the nankai trough deep low frequency earthquakes in the transition zone and burst type repeating sequences within plates have not been located in the downdip direction of groups with slow slip rates this suggests that the space time characteristics of inter plate coupling affected these seismic events

evidence of deep magma degassing and ascent by geochemistry of peripheral gas emissions at mount etna italy assessment of the magmatic reservoir pressure 1 five gas discharges in the area of mount etna volcano italy and in the near hyblean plateau have been monitored since 1996 all the emissions displayed low contributions from crustal fluids whereas magmatic gases were the main component selective dissolution of these gases into hydrothermal aquifers has been recognized and modeled allowing us to calculate the original composition of the magma released gases the inferred composition of the magmatic gases exhibits synchronous variations of he ne and he co2 ratios which are coherent with the magma degassing process on the basis of numerical simulations of volatile degassing from etnean basalts we have computed the initial and final pressures of the magma batches feeding the emissions we thus can define the levels of the etna plumbing system where magmas are stored pressure values were around 360 and 160 mpa for initial and final stages respectively meaning related depths of about 10 and 3 km below sea level matching those obtained by geophysical investigations for the deep and shallow magma reservoirs in addition we have been able to recognize episodes of magma migration from the deeper reservoir toward the shallow one an important magma injection into the shallow storage volume was detected during the onset of the 2001 eruption 17 july no further injection had taken place during this period until september 2001 providing a possible reason for the quick exhaustion of the eruption in view of this we suggest that the sampled emissions are a powerful geochemical tool to investigate the etna s plumbing system and its magma dynamics as well as the development of eruptive events

slope movement crisis on the east flank of mt etna volcano models for eruption triggering and forecasting abstract benchmarks installed on the upper eastern flank of mt etna in 1982 have subsided continually since then with the rate of subsidence twice accelerating prior to eruptions the first of these eruptions was in december 1985 and the second in september 1989 this pattern of accelerating downslope movement has also been observed prior to landslides and recent work applying knowledge of the failure of materials has shown that analysis of the inverse rate of these movements can be used to predict the time of failure post eruption analyses of geodetic or seismic data from volcanoes has shown that in several cases this approach could have been used to forecast eruptions weeks in advance applying the same principles to the accelerating subsidence on mt etna s eastern flank prior to the eruptions of 1985 and 1989 shows that rough estimates of eruption dates could have been obtained several months in advance these observations also suggest a speculative eruption triggering mechanism involving an interplay between slope creep deformation and extensional weakening over the zone of intrusion

on the absence of insar detected volcano deformation spanning the 1995 1996 and 1999 eruptions of shishaldin volcano alaska shishaldin volcano a large frequently active basaltic andesite volcano located on unimak island in the aleutian arc of alaska had a minor eruption in 1995 1996 and a vei 3 sub plinian basaltic eruption in 1999 we used 21 synthetic aperture radar images acquired by ers 1 ers 2 jers 1 and radarsat 1 satellites to construct 12 coherent interferograms that span most of the 1993 2003 time interval all interferograms lack coherence within 5 km of the summit primarily due to persistent snow and ice cover on the edifice remarkably in the 5 15 km distance range where interferograms are coherent the insar images show no intrusion or withdrawal related deformation at shishaldin during this entire time period however several insar images do show deformation associated with a shallow ml 5 2 earthquake located 14 km west of shishaldin that occurred 6 weeks before the 1999 eruption we use a theoretical model to predict deformation magnitudes due to a volumetric expansion source having a volume equivalent to the 1999 erupted volume and find that deformation magnitudes for sources shallower than 10 km are within the expected detection capabilities for interferograms generated from c band ers 1 2 and radarsat 1 synthetic aperture radar images we also find that insar images cannot resolve relatively shallow deformation sources 1 2 km below sea level due to spatial gaps in the insar images caused by lost coherence the lack of any deformation particularly for the 1999 eruption leads us to speculate that magma feeding eruptions at the summit moves rapidly at least 80m day from n10 km depth and that the intrusion eruption cycle at shishaldin does not produce significant permanent deformation at the surface published by elsevier b v

actively growing anticlines beneath catania from the distal motion of mount etna s decollement measured by sar interferometry and gps we used sar interferometry and gps to measure the rise of an anticline beneath the urban area of catania italy which originates from outward thrusting above the basal decollement of etna volcano the anticline grows at a rate of over 0 015 m a 1 of se thrusting and about 0 007 m a 1 of relative uplift by relating this growth to the simultaneous extension measured at the summit of the volcano we demonstrate the occurrence of active volcanic spreading this process may exert a control on eruptions earthquakes sector collapses and landslides

gravity and magma induced spreading of mount etna volcano revealed by satellite radar interferometry 1 mount etna underwent a cycle of eruptive activity over the past ten years here we compute ground displacement maps and deformation time series from more than 400 radar interferograms to reveal mount etna s average and time varying surface deformation from 1992 to 2001 we find that during this time interval it experienced magmatic inflation and radial spreading to the west south and east steady relative motion between the west and south flanks and between the east and north flanks during this time interval suggests they are related to gravitational spreading of the volcanic edifice time series analysis shows that growth of a southeastern basal anticline began with the end of magma recharge in 1995 thus showing a direct link between deep seated magma intrusions and edifice spreading these observations support a complex mode of radial gravitational collapse underlain by deeper magma driven basal spreading although ultimately the two must be related

fast deformation processes and eruptive activity at mount etna italy the seismic and deformation patterns observed on mount etna before and during the 1991 1993 eruption the third largest since the seventeenth century in terms of lava volume are consistent with the regional tectonic framework of eastern sicily the pattern of the stress field acting on the intermediate and lower crust was defined at the local scale by focal mechanisms of microearthquakes occurring at depths between 10 and 25 km beneath the volcano they provide evidence for a strike slip compressional stress regime with the maximum compressive component acting approximately n s the fault plane solutions and the spatial and temporal distribution of seismicity indicate that usually sinistral shear ruptures occur along approximately ne sw trending fault zones while dip slip ruptures affect approximately nnw sse trending fault zones the latter include the avenues along which magma ascended during the 1991 1993 eruption seismic observations indicate a local inversion of the stress field acting on the upper crust depth 10 km underlying mount etna which was initiated less than 2 months before the eruptive event and disappeared with its end this is consistent with a local tensile regime that favored the magma ascent through the shallow crust the events preceding the eruption and accompanying its onset tilt anomalies and seismic swarms and those occurring shortly after its beginning a mainshock aftershock seismic sequence and associated coseismic tilts provide important evidence for understanding the dynamics of the two main volcano tectonic structures ne sw and nnw sse trending fault zones and associated intrusive mechanisms on etna the shape and location of the eruption feeding dike have been modeled from ground deformation data this approximately nnw sse modeled dike the seismicity and the position of the fractures are consistent with the regional stress field characterized by 1 oriented approximately n s the geophysical data presented and analyzed in the present paper strongly suggest an overall regional tectonic control as well as an active role for the intruding magma in the dynamics of the volcano

deformation and seismicity in the coso geothermal area inyo county california observations and modeling using satellite radar interferometry interferometric synthetic aperture radar insar data collected in the coso geothermal area eastern california during 1993 1999 indicate ground subsidence over a 50 km 2 region that approximately coincides with the production area of the coso geothermal plant the maximum subsidence rate in the peak of the anomaly is 3 5 cm yr 1 and the average volumetric rate of subsidence is of the order of 10 6 m 3 yr 1 the radar interferograms reveal a complex deformation pattern with at least two irregular subsidence peaks in the northern part of the anomaly and a region of relative uplift on the south we invert the insar displacement data for the positions geometry and relative strengths of the deformation sources at depth using a nonlinear least squares minimization algorithm we use elastic solutions for a prolate uniformly pressurized spheroidal cavity in a semi infinite body as basis functions for our inversions source depths inferred from our simulations range from 1 to 3 km which corresponds to the production depths of the coso geothermal plant underpressures in the geothermal reservoir inferred from the inversion are of the order of 0 1 1 mpa except a few abnormally high underpressures that are apparently biased toward the small source dimensions analysis of the insar data covering consecutive time intervals indicates that the depths and or horizontal extent of the deformation sources may increase with time this increase presumably reflects increasing volumes of the subsurface reservoir affected by the geothermal exploitation we show that clusters of microearthquakes associated with the geothermal power operation may result from perturbations in the pore fluid pressure as well as normal and shear stresses caused by the deflation of the geothermal reservoir

supergene sulphate minerals from the burning coal mining dumps in the upper silesian coal basin south poland abstract sulphate minerals of various chemical compositions form subtle mixtures of small aggregated crystals on some burning coal mining dumps in the upper silesian coal basin poland they include na and mg sulphates blodite and konyaite magnesium sulphates belong to the second group and hexahydrite is its most common representative aluminium sulphates include tamarugite pickeringite and alunogen iron sulphates are copiapite group minerals metavoltine butlerite and voltaite group minerals calcium sulphates are almost exclusively represented by gypsum eds proved to be in general a better tool than wds for the chemical analysis of the sulphates both the rietveld and pawley methods were found to be useful in the calculation of unit cell parameters the analysed sulphates contain some rare and interesting elements the most important being tl ga in cd se and as the sulphates formed as a result of the mutual action of various supergene processes including the oxidation of s rich coal fire gases metal leaching from waste rocks by h2so4 solutions and evaporation the complexity of the sulphate efflorescence composition is explained by the chaotic nature of settings involving a variety of waste rocks hydration dehydration reactions and access of both ground and rain water and atmospheric oxygen

mt etna volcano modelling of ground deformation patterns of recent eruptions and considerations on the associated precursors abstract the study of the ground deformation associated with the recent eruptions of the etna volcano 1981 1989 1991 93 furnished the opportunity to observe different behaviour relating to the eruptive activity and suggested different feeding and penetration mechanisms inside the volcano edifice in particular the analytical modelling of geodetic data was applied to study the strain sources of these eruptions by the application of single and multiple source models i e composed of two single sources in particular a single tensile dislocation was used to model the se fracture associated with the 1989 eruption a double tensile dislocation was adopted to interpret and model the deformation pattern of the 1981 eruption a double source composed of a tensile dislocation for the final eruptive fracture and a depressuring body for the deflation during the eruption course was considered for the 1991 93 eruption the results of this modelling show that however the final uprising system i e the tensile mechanisms inside the volcano edifice involved the same structure oriented approximately nnw sse this structure was activated by different eruption mechanisms with associated different deformation patterns during these three recent eruptions a review of the methodologies applied and main results obtained in modelling of different sources and mechanisms is presented here the analysis of the deformation data and the performed modelling evidence that the associated precursors can strongly change for the different eruptions in addition the implications both in terms of how the volcano works and in terms of ground deformation precursors are discussed

geochemical monitoring system ii prototype gms ii installation at the acqua difesa well within the etna region first data during the 1999 volcanic crisis abstract the geochemical monitoring system ii gms ii prototype was designed assembled tested and installed at the acqua difesa test site near belpasso ct within the etna region in the frame of an ec funded program named automatic geochemical monitoring of volcanoes the easily changeable and versatile configuration of the remote station provides actual data every 10 min recording groundwater temperature electrical conductivity ph redox potential dissolved co 2 he atmospheric pressure and air temperature the radon sensor was assembled despite no jet added to the remote station an automatic sampler collects every 72 h 3 days two bottles of water acidified and not for further laboratory analyses the choice of the acqua difesa test site arises from preliminary volcanological studies deserving special interest i e for the high co 2 degassing for the high he isotopic values exhibiting a direct mantle signature of the volcanic gases and for the peculiar sensitivity to volcanic activity as tested by discrete monitoring in the past and confirmed by the present study during the discussed monitoring period october 1998 june 1999 an enhanced volcanic activity of etna was observed it started on july 1998 with enhanced plume degassing and since september 1998 with periodical lava fountains as well as with episodic low energy earthquakes and seismic swarms m max 3 1 till june 1999 the activity culminated with a summit crater fracture involving a sub terminal eruption on 04 02 1999 the summit crater fracture was not accompanied by enhanced seismicity despite moderate seismic energy release occurring in the succeeding months in that monitoring period the acqua difesa gms ii station recorded a few geochemical anomalies mostly in temperature ph co 2 electrical conductivity and eh as well as in the concentration of some major elements trend mostly in mg and hco 3 the geochemical continuous and discrete data set is discussed in comparison with the available information on the ongoing volcanic and seismic activity tentatively enhancing the comprehension of the aquifers mass heat transport properties of the volcano during crises the experimental observations may be defined at present the forerunners of the etna eruptions affecting the single out acqua difesa well it is nowadays a self consistent site with its own response to the pre eruptive processes defined sensitive to the etna aquifer modifications induced by the volcanic activity in a recurrent way thus we defined the typical answer of this specific test site to the pre eruptive processes and to the associated seismicity further data may modify this statement the station prototype configuration and the results may give hints for future volcanic eruption and seismic activity forecasting

ground deformation associated with the march 1996 earthquake swarm at akutan volcano alaska revealed by satellite radar interferometry in march 1996 an intense swarm of volcano tectonic earthquakes 3000 felt by local residents mmax 5 1 cumulative moment of 2 7 1018 n m beneath akutan island in the aleutian volcanic arc alaska produced extensive ground cracks but no eruption of akutan volcano synthetic aperture radar interferograms that span the time of the swarm reveal complex island wide deformation the western part of the island including akutan volcano moved upward while the eastern part moved downward the axis of the deformation approximately aligns with new ground cracks on the western part of the island and with holocene normal faults that were reactivated during the swarm on the eastern part of the island the axis is also roughly parallel to the direction of greatest compressional stress in the region no ground movements greater than 2 83 cm were observed outside the volcano s summit caldera for periods of 4 years before or 2 years after the swarm we modeled the deformation primarily as the emplacement of a shallow east west trending north dipping dike plus inflation of a deep mogi type magma body beneath the volcano the pattern of subsidence on the eastern part of the island is poorly constrained it might have been produced by extensional tectonic strain that both reactivated preexisting faults on the eastern part of the island and facilitated magma movement beneath the western part alternatively magma intrusion beneath the volcano might have been the cause of extension and subsidence in the eastern part of the island we attribute localized subsidence in an area of active fumaroles within the akutan caldera by as much as 10 cm during 1992 1993 and 1996 1998 to fluid withdrawal or depressurization of the shallow hydrothermal system

surface movements of emplaced lava flows measured by synthetic aperture radar interferometry lava flows continue to move after they have been emplaced by flow mechanisms this movement is largely vertical and can be detected using differential synthetic aperture radar sar interferometry there are three main components to this motion 1 movement of surface scatterers resulting in radar phase decorrelation 2 measurable subsidence of the flow surface due to thermal contraction and clast repacking and 3 time dependent depression of the flow substrate these effects act in proportion to the thickness of the lava flow and decay with time although there is a time lag before the third component becomes significant we explore these effects using sar data from the ers satellites over the etna volcano sicily phase decorrelation on young thick a a lava flows persists for a few years and probably results from surface block rotations during flow contraction maximum measured subsidence rates of the 1991 1993 lava flow over a period of 70 days are about 0 7 mm day 1 but are potentially greater in areas of data decorrelation these rates fall to 2 7 10 2 mm day 1 after about 20 years in flows about 50 m thick sooner for thinner flows comparison with measured subsidence rates on kilauean lava lakes suggests that thermal contraction only accounts for about one third of the observed subsidence the remaining motion is thought to come from surface clast repacking during cooling and from creep mechanisms in the flow substrate measurements of postemplacement surface movement provide new constraints on the thermomechanical properties of lava flows and have cautionary implications for the interpretation of interferometric sar data of volcanoes 2001 american geophysical union