multi parametric climatological analysis associated with global significant volcanic eruptions during 2002 2017 in this work we search for physical and chemical climatological anomalies preceding major volcanic explosive eruptions mostly vei volcanic explosivity index 4 occurred from 2002 to 2017 by applying two specific algorithms i e capri and means the former algorithm has been already used for a multi climatological analysis of the amatrice norcia 2016 2017 earthquake preparatory phase piscini et al in pure appl geophys 174 3673 3688 2017 here we analyse some climatological parameters for a three month period before each volcanic explosive eruption then we compare the behavior with the typical one of the past the analysis is applied to an area with dimensions comparable to the volcano crater because it is the increase of the magmatic camera activity that in turn can cause a temperature increase whose evidence could be detected at the surface slezin in j volcanol geotherm res 122 1 2 7 50 2003 while the use of a larger area would provide a greater probability of occurrence of other events e g other volcano eruption meteorological storms etcetera therefore a smaller area of study reduces the risk to get false alarms in particular we considered thermal skin temperature skt and total water vapour content tcwv from ecmwf european centre and aerosol optical thickness aot sulphur dioxide so2 and atmospheric dimethylsulphide dms are obtained from nasa merra 2 global modeling and assimilation data archive the latter compound was added in the analysis to check the validity of the method since we did not expect significant anomalies from this parameter the models above described are used for their temporal spatial completeness allowing performing time series analyses and for a real time monitoring on a global scale by simultaneous analysis we found for almost all volcanic eruptions some anomalies in about all analyzed parameters that precede by 75 days to 20 days the explosion these anomalies are not always simultaneous but we find an interesting synchronicity that probably reveals a correlation among the different datasets in addition the agung volcano which has recently started an eruptive activity 25 november 2017 without reaching a vei4 explosion has also been investigated the data related to this volcano present a small number of anomalies much lower than all attributed to the other analyzed explosive volcanoes and this is in high agreement with the low explosive nature of the agung volcano eruption we find that the occurrence of thermal anomalies typically preceding stratovolcano caldera eruptions seems to take place some days after so2 emissions the climatological anomalies that precede eruptions at high latitudes usually surround the volcano in a wider area outside the volcanic edifice we verify that the number of positive anomalies is systematically greater in the year that precedes the investigated eruption with respect to a quiet year of comparison with accuracy from 91 to 100 suggesting that the applied methods detected climatological anomalies likely related to imminent volcanic eruptions

applicability of insar to tropical volcanoes insights from central america measuring volcano deformation is key to understanding the behaviour of erupting vol canoes and detecting those in periods of unrest satellite techniques provide the opportunity to do so on a global scale but with some notable exceptions the deformation of volcanoes in the tropics has been understudied relative to those at higher latitudes largely due to technical difficulties in applying interferometric synthetic aperture radar insar we perform a systematic survey of the central american volcanic arc to investigate the appli cability of interferometric synthetic aperture radar insar to volcanoes in the tropics volcano characteristics that may prevent insar measurement include 1 dense vegetation cover 2 per sistent activity and 3 steep slopes measurements of deformation are further inhibited by atmos pheric artefacts associated with 4 large changes in topographical relief we present a systematic method for distinguishing between water vapour artefacts and true deformation our data show a linear relationship c 2 cm km between the magnitudes of water vapour artefacts and volcano edifice height for high relief volcanoes e g fuego guatemala 3763 m a s l above sea level errors are of the order of 4 5 cm across the volcano s edifice but are less than 2 cm for lower relief e g masaya nicaragua 635 m a s l examples such as arenal atitlan and fuego illustrate that satellite acquisition strategies incorporating ascending and descending tracks are particularly important for studying steep sided volcanoes poor coherence is primarily associated with temporal decorrelation which is typically more rapid in southern central america where evergreen broadleaf vegetation dominates land use classification is a better predictorof decorrelation rate thanvegetationindex comparisonof coher ence for different radar wavelengths match expectations high resolution x band radar is best suited to local studies where high resolution digital elevation models dems exist while l bandwavelengths are necessary for regional surveys however this is the first time that relation ships between phase coherence and time perpendicular baseline radar wavelength and land use have been quantified on the scale of a whole volcanic arc

seismological and sar signature of unrest at nisyros caldera greece abstract nisyros island a quaternary volcanic center located at the se of the aegean volcanic arc has been in the past characterized by periods of intense seismic activity accompanied sometimes by hydrothermal explosions the last one being in 1887 the recent long lasting episode of unrest 1995 1998 in the area is the first instrumentally documented providing information on the behavior of the volcano evidence from seismicity and sar interferometry suggests that the presently active part of the kos nisyros volcano tectonic complex is located at the nw coast of nisyros island defining an area much smaller than the whole volcano tectonic area seismicity patterns vary both temporally and spatially consistently with different rates of vertical ground deformation inferred from sar interferometry these observations help us to discuss the different elements controlling the behavior of the volcanic system such as the existence location and timing of magma chamber inflation the occurrence of tensile failure at the boundaries of the chamber and the possibility of magmatic fluids being expelled to form a shallow magmatic intrusion the seismic failure and migration of hypocenters indicating shallow magma transport

satellite radar interferometry for monitoring ice sheet motion application to an antarctic ice stream satellite radar interferometry sri provides a sensitive means of monitoring the flow velocities and grounding line positions of ice streams which are indicators of response of the ice sheets to climatic change or internal instability the detection limit is about 1 5 millimeters for vertical motions and about 4 millimeters for horizontal motions in the radar beam direction the grounding line detected by tidal motions where the ice goes afloat can be mapped at a resolution of 0 5 kilometer the sri velocities and grounding line of the rutford ice stream antarctica agree fairly well with earlier ground based data the combined use of sri and other satellite methods is expected to provide data that will enhance the understanding of ice stream mechanics and help make possible the prediction of ice sheet behavior

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

permanent scatterers analysis for atmospheric correction in ground based sar interferometry ground based synthetic aperture radar gb sar interferometry has already been recognized as a powerful tool complementary or alternative to spaceborne sar interferometry for terrain monitoring and for detecting structural changes in buildings it has been noted that in spite of the very short range compared with the satellite configuration in gb sar measurement the disturbances due to atmospheric effects cannot be neglected either the analysis of the interferometric phases of very coherent points called permanent scatterers pss allows the evaluation of the atmospheric disturbance and the possibility of removing it in this paper the ps analysis is carried out both on a test site facility and on a real campaign citrin valley italy that provided data with a temporal baseline of about ten months

early detection and in depth analysis of deformation phenomena by radar interferometry the spaceborne differential interferometric sar dinsar technique may play an important role in the measurement of land deformation phenomena especially in urban suburban and industrial areas in order to fully exploit its capabilities and increase its operational use this paper proposes two complementary levels of analysis the first one is a comprehensive low cost screening in order to detect unknown subsidence phenomena over large areas this analysis which provides a first estimation of deformations has to be performed using a limited set of sar images the second level includes an in depth quantitative analysis based on large image stacks which requires more image acquisition and data processing resources this type of analysis can be typically used to study deformation phenomena of special relevance where an effective support to the decision makers requires a fully quantitative estimation of deformations the two levels of analysis were proved over a test area of about 2100 km2 located in catalonia spain without any a priori information seven deformation phenomena were detected using a reduced set of interferograms furthermore the quantitative analysis of a subsidence of small spatial extent which was based on ascending and descending datasets confirmed the capability of dinsar to quantitatively assess deformation phenomena

evidence of multiple strain fields beneath the eastern flank of mt etna volcano sicily italy deduced from seismic and geodetic data during 2003 2004 we carried out a study of the seismicity and ground deformation occurring on mt etna volcano after the end of the 2002 2003 eruption and before the onset of the 2004 2005 eruption data were recorded by the permanent local seismic network run by istituto nazionale di geofisica e vulcanologia sezione di catania and by geodetic surveys carried out in july 2003 and july 2004 on the gps network most earthquakes were grouped in two main clusters located in the northeastern and southeastern sectors of the volcano the areal distribution of seismic energy associated with the recorded earthquakes allowed us to highlight the main seismogenic areas of mt etna in order to better understand the kinematic processes of the volcano 3d seismic locations were used to compute fault plane solutions and a selected dataset was inverted to determine stress and strain tensors the focal mechanisms in the northeastern sector show clear left lateral kinematics along an e w fault plane consistent with events occurring along the pernicana fault system the fault plane solutions in the southeastern sector show mainly right lateral kinematics along a nne and ene fault plane and left lateral kinematics along nw fault planes that together suggest roughly e w oriented compression surface ground deformation affecting mt etna measured by gps surveys highlighted a marked inflation during the same period and exceptionally strong seawards motion of its eastern flank the 2d geodetic strain tensor distribution was calculated and the results show mainly ene wsw extension coupled with wnw ese contraction indicating right lateral shear along a nw se oriented fault plane the different deformation of the eastern sector of the volcano as measured by seismicity and ground deformation must be interpreted by considering the different depths of the two signals seismic activity in the southeastern sector of volcano is located between 3 and 8 km b s l and can be associated with a very strong additional e w compression induced by a pressurizing source just westwards and at the same depth located by inverting gps data ground deformation in contrast is mainly affected by the shallower dynamics of the fast moving eastern flank which produces a shallower opposing e w extension the entire dataset shows that two different processes affect the eastern flank at the same time but at different depths the boundary is clearly located at a depth of 3 km b s l and could represent the decollement surface for the mobile flank

the influence of loading by lavas on the siting of volcanic eruption vents on mt etna abstract until now it has been considered that the positioning of magma conduits dykes and eruption sites on mt etna is controlled by stresses set up by regional tectonism it is also likely that gravitational stresses have some influence on the subsurface path taken by etnean magmas prior to eruption an additional effect discussed here is based mainly on convincing field evidence gathered over a number of years it is proposed that fracturing of the surface and changes in the stress pattern due to loading by recent lava flows may strongly influence the siting of eruptions detailed field observations are presented showing that cracks and fumaroles have consistently appeared round the edges of recent lava flows and that these cracks are sometimes later used by erupting lavas eruption statistics indicate that since 1970 50 of new eruptive vents have appeared within 80 m of a recent flow edge and field measurements show that downward flexure is still occurring at the edges of lava flows more than sixteen years old simple theoretical modelling indicates that this effect is strongest at the surface with gravitational and regional tectonic control of eruption sites dominating at progressively deeper levels

phase gradient approach to stacking interferograms the phase gradient approach is used to construct averages and differences of interferograms without phase unwrapping our objectives for change detection are to increase fringe clarity and decrease errors due to tropospheric and ionospheric delay by averaging many interferograms the standard approach requires phase unwrapping scaling the phase according to the ratio of the perpendicular baseline and finally forming the average or difference however unique phase unwrapping is usually not possible since the phase gradient due to topography is proportional to the perpendicular baseline phase unwrapping is unnecessary prior to averaging or differencing phase unwrapping may be needed to interpret the results but it is delayed until all of the largest topographic signals are removed we demonstrate the method by averaging and differencing six interferograms having a suite of perpendicular baselines ranging from 18 to 406 m cross spectral analysis of the difference between two tandem interferograms provides estimates of spatial resolution which are used to design prestack filters a wide range of perpendicular baselines provides the best topographic recovery in terms of accuracy and coverage outside of mountainous areas the topography has a relative accuracy of better than 2 m residual interferograms single interferogram minus stack have tilts across the unwrapped phase that are typically 50 mm in both range and azimuth reflecting both orbit error and atmospheric delay smaller scale waves with amplitudes of 15 mm are interpreted as atmospheric lee waves a few global positioning system gps control points within a frame could increase the precision to 20 mm for a single interferogram further improvements may be achieved by stacking residual interferograms

inner core translation and the hemispheric balance of the geomagnetic field bulk translation of the earth s inner core has been proposed as an explanation of observed quasi hemispheric seismic structure an important consequence of inner core translation would be the generation of a spherical harmonic degree one heat flow anomaly at the inner core boundary icb that would provide an inhomogeneous forcing for outer core convection we use geodynamo simulations to investigate the geomagnetic signature of such heterogeneity strong hemispheric heterogeneity at the icb is found to produce a hemispheric signature in both the morphology of the magnetic field and its secular variation in particular we note the formation of high intensity flux patches at high latitudes and american longitudes in our model with strong icb heterogeneity in our simulations this model provides the best match to the earth s field over the past 400 years according to previously proposed measures of field structure however these criteria do not include the hemispheric balance of the field we propose new criteria to measure this balance and find that our model with strong icb heterogeneity produces the poorest match to the hemispheric balance of the historical geomagnetic field resolution of the hemispheric balance of the magnetic field throughout the holocene would provide a strong test of any proposal of rapid inner core translation

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

integrated satellite interferometry tropospheric noise gps estimates and implications for interferometric synthetic aperture radar products interferometric synthetic aperture radar insar like other astronomic and space geodetic techniques is limited by the spatially and temporally variable delay of electromagnetic waves propagating through the neutral atmosphere statistical analysis of these variations from a wide variety of instruments reveals a power law dependence on frequency that is characteristic of elementary kolmogorov turbulence a statistical model for a major component of the delay fluctuations the wet component has previously been developed by treuhaft and lanyi 1987 for very long baseline interferometry a continuous global positioning system gps network is now in place in southern california that allows estimation of along with geodetic parameters the total delay due to the atmosphere above each site on a subhourly basis these measurements are shown to conform to the treuhaft and lanyi tl statistical model both temporally and spatially the tl statistical model is applied to the problem of insar and used to produce the covariance between two points separated in time and or space the error due to the atmospheric variations for sar products such as topography and surface deformation is calculated via propagation of errors there are two methods commonly cited to reduce the effect of atmospheric distortion in products from sar interferometry stacking and calibration stacking involves averaging independent interferograms to reduce the noise calibration involves removing part or all of the delay using data from an independent source such as total zenith delay estimates from continuous gps networks despite the relatively poor spatial density of surface measurements calibration can be used to reduce noise if the measurements are sufficiently accurate reduction in tropospheric noise increases with increasing number of measurement points and increasing accuracy up to a maximum of n where n is the number of points stacking and calibration are shown to be complementary and can be used simultaneously to reduce the noise to below that achievable by either method alone

interferometric synthetic aperture radar study of okmok volcano alaska 1992 2003 magma supply dynamics and postemplacement lava flow deformation 1 okmok volcano located in the central aleutian arc alaska is a dominantly basaltic complex topped with a 10 km wide caldera that formed circa 2 05 ka okmok erupted several times during the 20th century most recently in 1997 eruptions in 1945 1958 and 1997 produced lava flows within the caldera we used 80 interferometric synthetic aperture radar insar images interferograms to study transient deformation of the volcano before during and after the 1997 eruption point source models suggest that a magma reservoir at a depth of 3 2 km below sea level located beneath the center of the caldera and about 5 km northeast of the 1997 vent is responsible for observed volcano wide deformation the preeruption uplift rate decreased from about 10 cm yr 1 during 1992 1993 to 2 3 cm yr 1 during 1993 1995 and then to about 1 2 cm yr 1 during 1995 1996 the posteruption inflation rate generally decreased with time during 1997 2001 but increased significantly during 2001 2003 by the summer of 2003 30 60 of the magma volume lost from the reservoir in the 1997 eruption had been replenished interferograms for periods before the 1997 eruption indicate consistent subsidence of the surface of the 1958 lava flows most likely due to thermal contraction interferograms for periods after the eruption suggest at least four distinct deformation processes 1 volcano wide inflation due to replenishment of the shallow magma reservoir 2 subsidence of the 1997 lava flows most likely due to thermal contraction 3 deformation of the 1958 lava flows due to loading by the 1997 flows and 4 continuing subsidence of 1958 lava flows buried beneath 1997 flows our results provide insights into the postemplacement behavior of lava flows and have cautionary implications for the interpretation of inflation patterns at active volcanoes

long term dynamics of piton de la fournaise volcano from 13 years of seismic velocity change measurements and gps observations we study the piton de la fournaise pdf volcano dynamics through the observation of continuous seismic velocity changes from 2000 to 2013 we compute the cross correlations of ambient seismic noise recorded at more than 30 short period and broadband stations of the undervolc temporary seismic experiment and of the pdf volcano observatory network the velocity changes are estimated from the travel time delay measured on the cross correlations computed between pairs of stations we average the relative velocity changes for all pairs of stations and obtain a time series of the velocity change of piton de la fournaise volcano over 13 years from the period 0 5 to 4 s the depth sensitivity of the velocity change is ranging from approximately 100 m to 2500 m a slow decrease of velocity is measured from 2000 and ends with a major eruption that occurred in april 2007 this eruptive episode is followed by an increase of the velocity these long term changes are compared to the deformation of the piton de la fournaise edifice estimated from geodetic measurements an analysis of baseline change between gps stations indicates an inflation of the volcanic edifice prior to april 2007 followed by a deflation since then this deflation predominantly affects the terminal cone seismic velocity changes and deformation have similar long term trends with velocity decrease observed during inflation and velocity increase during deflation however the velocity change magnitude is about 2 orders of magnitude greater than the deformation this suggests nonlinear relation between velocity changes and deformation

upper ocean water mass characteristics of the california current summer 1993 abstract two large high resolution upper ocean surveys of the california current region were conducted in the summer of 1993 temperature and salinity were measured from a seasoar vehicle and velocity was measured by a ship borne acoustic doppler current profiler both surveys extended from the continental margin to 128 w and consisted of zonal sections 28 km apart the first survey 7 28 june extended from 39 5 n to 36 25 n and the second 16 august to 1 september extended from 39 0 n to 37 0 n the current field was fairly simple in june showing an equatorward surface jet with only one gentle meander a nearly continuous poleward california undercurrent near the continental margin and two anticyclonic subsurface eddies offshore of the jet by august meanders in the surface jet had strengthened and eddies dominated the flow field large scale trends in the water mass characteristics spiciness along three isopycnal surfaces 26 4 26 0 and 25 6 kg m 3 show that temperature and salinity tend to increase towards the equator and towards shore consistent with poleward advection along the continental margin local minima in spiciness tend to coincide with the equatorward surface jet local maxima in spiciness are associated with subsurface anticyclonic eddies which have a core depth of about 150 m and seem to originate in the california undercurrent over the continental slope at local latitudes we identified several different anticyclonic eddies each with different water mass characteristics all of the eddies we observed had diameters larger than the baroclinic radius of deformation water mass characteristics and migration rates are consistent with formation over the continental margin within the preceding 6 8 months

potential volcanological applications of the doris system a geodetic study of the socorro island mexico coordinate time series summary we analysed doris data from socorro island mexico providing weekly coordinates in itrf2000 from 1900 to 2006 careful analysis of this time series shows horizontal and vertical movements related to recent activity of the mt evermannn volcano a deflation of the volcano between 1993 and 1996 94 mm yr 1 in the n23 w direction directly pointing in the direction of the crater summit is observed we identify also a clear horizontal discontinuity of 81 mm and a significant change in velocity on 2002 october 3 we use a mogi formalism to provide constraints from our geodetic results on the successive locations and size of the depletion and inflation sources our model is consistent with a deflation source for the period 1993 1996 located beneath mt evermannn at a depth of about 6 2 km below sea level however our data constrain only the azimuth and dip angles of the source which could be located elsewhere along the azimuth of the summit depth and volume varying linearly with the distance

30 years in the life of an active submarine volcano a time lapse bathymetry study of the kick em jenny volcano lesser antilles effective monitoring is an essential part of identifying and mitigating volcanic hazards in the submarine environment this is more difficult than onshore because observations are typically limited to land based seismic networks and infrequent shipboard surveys since the first recorded eruption in 1939 the kick em jenny kej volcano located 8km off northern grenada has been the source of 13 episodes of t phase signals these distinctive seismic signals often coincident with heightened body wave seismicity are interpreted as extrusive eruptions they have occurred with a recurrence interval of around a decade yet direct confirmation of volcanism has been rare by conducting new bathymetric surveys in 2016 and 2017 and reprocessing 4 legacy datasets spanning 30 years we present a clearer picture of the development of kej through time processed grids with a cell size of 5m and vertical precision on the order of 1 4m allow us to correlate t phase episodes with morphological changes at the volcano s edifice in the time period of observation 7 09x106 m3 of material has been added through constructive volcanism yet 5 times this amount has been lost through landslides limited recent magma production suggests that kej may be susceptible to larger eruptions with longer repeat times than have occurred during the study interval behavior more similar to sub aerial volcanism in the arc than previously thought t phase signals at kej have a varied origin and are unlikely to be solely the result of extrusive submarine eruptions our results confirm the value of repeat swath bathymetry surveys in assessing submarine volcanic hazards

insar monitoring using radarsat 2 data at piton de la fournaise la reunion and karthala grande comore volcanoes piton de la fournaise la reunion and karthala grande comore are the two active volcanoes of the southwestern indian ocean a 14 month april 2013 to june 2014 monitoring period was carried out at both volcanoes using synthetic aperture radar interferometry insar techniques on radarsat 2 data thanks to the seas oi survey of environment assisted by satellite in the indian ocean station 21 sar scenes were acquired over this period and insar results revealed the slow subsidence of the dolomieu caldera floor at piton de la fournaise following the 2009 and 2010 eruptions and the subsidence of the whole cone between april and july 2013 at karthala no evidence of any volcanic activity was found for the period april 2013 to june 2014 the use of systematic insar for volcano monitoring is an efficient tool to study effusive eruptions we showed that during periods of unrest insar is able to pick up early signs of a future eruption and monitor secondary phenomena that require no real time data during an effusive crisis it is still difficult to carry out fully operational insar monitoring but using the example of the june 2014 eruption at piton de la fournaise we show that sar data can help with the detection and tracking of lava flows and active flow paths during effusive eruptions based on sar coherence and sar amplitude these preliminary results are very promising for the future of insar monitoring of active volcanoes and highlight the need for near real time access to sar data in the mapping of active lava flows during effusive eruptions this study also revealed the major role of ground stations like seas oi in the efficiency of this monitoring supplying free near real time remote sensing data to the scientific and institutional communities

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

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

deformation time series generation in areas characterized by large displacement dynamics the sar amplitude pixel offset sbas technique we exploit the amplitude information of a sequence of synthetic aperture radar sar images acquired at different times in order to generate displacement time series in areas characterized by large and or rapid deformation the size of which is on the order of the image s pixel dimensions we follow the same rationale of the small baseline subset sbas differential sar interferometry dinsar approach by coupling the available sar images into pairs characterized by a small separation between the acquisition orbits we exploit the amplitudes of the selected image pairs in order to calculate the relative across track range and along track azimuth pixel offsets po finally we apply the sbas inversion strategy to retrieve the range and azimuth displacement time series this approach referred to as pixel offset po sbas technique has been applied to a set of 25 envisat sar observations of the sierra negra caldera galapagos islands spanning the 2003 2007 time interval the retrieved deformation time series show the capability of the technique to detect and measure the large displacements affecting the inner part of the caldera that in correspondence to the october 2005 eruption reached several meters moreover by comparing the po sbas results to continuous gps measurements we estimate that the accuracy of the po sbas time series is on the order of 1 30th of a pixel for both range and azimuth directions

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