heat flow strong near fault seismic waves and near fault tectonics on the central san andreas fault the main san andreas fault strikes subparallel to compressional folds and thrust faults its fault normal traction is on average a factor of 1 2 thr 1 thr2 thr where thr is the coefficient of friction for thrust faults times the effective lithostatic pressure a useful upper limit for thr of 0 6 where is 3 12 is obtained from the lack of heat flow anomalies by considering off fault convergence at a rate of 1 mm yr for 10 km across strike if the fault normal traction is in fact this high the well known heat flow constraint of average stresses of 10 20 mpa during strike slip on the main fault becomes more severe only a few percent of the total slip during earthquakes can occur at the peak stress before dynamic mechanisms weaken the fault the spatial dimension of the high stress rupture tip zone is 10 m for 3 12 and for comparison 100 m for 1 high dynamic stresses during shaking occur within these distances of the fault plane in terms of scalars fine scale tectonic stresses cannot exceed the difference between failure stress and dynamic stress plate scale slip causes stresses to build up near geometrical irregularities of the fault plane strong dynamic stresses near the rupture tip facilitate anelastic deformation with the net effects of relaxing the local deviatoric tectonic stress and accommodating deformation around the irregularities there also is a mild tendency for near fault material to extrude upward slip on minor thrust faults causes the normal traction on the main fault to be spatially variable

monitoring volcano slope instability with synthetic aperture radar a review and new data from pacaya guatemala and stromboli italy volcanoes abstract volcano slope instability manifests in many forms ranging from steady state to punctuated movement or shallow erosion to deep seated spreading the interplay of gravity magmatic or hydrothermal fluids and often active tectonics on a volcanic edifice results in complex spatial and temporal variations in deformation kinematics while this makes the recognition assessment and monitoring of volcano slope instability challenging advancements in synthetic aperture radar sar technology have significantly accelerated our knowledge of instability phenomena and our ability to assess their hazards this review discusses the applications and challenges of sar imagery to various slope instabilities at volcanoes around the world sar amplitude images are powerful tools for mapping areas of geomorphological changes these snapshots can be combined using interferometric sar insar to create multi temporal deformation maps that provide unique information on the evolution of slope failures space borne insar has become an economic way to detect changes at volcanoes at very high resolution ground based insar gbinsar can produce frequent sar images on the order of seconds to minutes propelling insar from monitoring to surveillance and early warning applications however interpreting insar derived ground deformation signals related to volcano slope instability is still challenging deformation from magma rise or variations in hydrothermal systems may be inseparable from persistent deep seated flank motion similarly shallow or localized ground motion may occur in overlap with thermal contraction or subsidence of newly emplaced lava or tephra deposits if triggered to failure landslides can vary over several magnitudes from small volume rock falls that pose only a localized hazard to large volume debris avalanches capable of travelling tens of kilometers away from the source these collapses can have cascading hazards if accompanied by directed blasts or tsunamis emphasizing the need for continued advancement of our understanding of these events and their consequences to highlight the utility of sar for measuring and monitoring mass movement two case studies of stromboli italy and pacaya guatemala volcanoes are discussed in detail where recent instability events persistent volcanic activity and ground truth constraints have resulted in excellent case histories in applying sar imagery to understand these potentially hazardous slope instabilities

sentinel 1 observation of the 2017 sangsefid earthquake northeastern iran rupture of a blind reserve slip fault near the eastern kopeh dagh abstract new satellites are now revealing insar based surface deformation within a week after natural hazard events quick hazard responses will be more publically accessible and provide information to responding agencies here we used sentinel 1 interferometric synthetic aperture radar insar data to investigate coseismic deformation associated with the 2017 sangsefid earthquake which occurred in the southeast margin of the kopeh dagh fault system the ascending and descending interferograms indicate thrust dominated slip with the maximum line of sight displacement of 10 5 and 13 7 cm respectively the detailed slip distribution of the 2017 sangsefid mw6 1 earthquake inferred from geodetic data is presented here for the first time although the insar interferograms themselves do not uniquely constrain what the primary slip surface is we infer that the source fault dips to southwest by analyzing the 2 5 d displacement field decomposed from the insar observations the determined uniform slip fault model shows that the dip angle of the seimogenic fault is approximately 40 with a strike of 120 except for a narrower fault width than that predicted by the empirical scaling law we suggest that geometric complexities near the kopeh dagh fault system obstruct the rupture propagation resulting in high slip occurred within a small area and much higher stress drop than global estimates the insar determined moment is 1 71 1018 nm with a shear modulus of 3 32 1010 n m2 equivalent to mw 6 12 which is consistent with seismological results the finite fault model the west dipping fault plane reveals that the peak slip of 0 90 m occurred at a depth of 6 3 km with substantial slip at a depth of 4 10 km and a near uniform slip of 0 1 m at a depth of 0 2 5 km we suggest that the sangsefid earthquake occurred on an unknown blind reverse fault dipping southwest which can also be recognised through observing the long term surface effects due to the existence of the blind fault

temporal changes of shallow seismic velocity around the karadere duzce branch of the north anatolian fault and strong ground motion we analyze temporal variations of seismic velocity along the karadere duzce branch of the north anatolian fault using seismograms generated by repeating earthquake clusters in the aftershock zones of the 1999 mw7 4 izmit and mw7 1 duzce earthquakes the analysis employs 36 sets of highly repeating earthquakes each containing 4 18 events the events in each cluster are relocated by detailed multi step analysis and are likely to rupture approximately the same fault patch at different times the decay rates of the repeating events in individual clusters are compatible with the omori s law for the decay rate of regional aftershocks a sliding window waveform cross correlation technique is used to measure travel time differences and evolving decorrelation in waveforms generated by each set of the repeating events we find clear step like delays in the direct s and early s coda waves sharp seismic velocity reduction immediately after the duzce main shock followed by gradual logarithmic type recoveries a gradual increase of seismic velocities is also observed before the duzce main shock probably reflecting post seismic recovery from the earlier izmit main shock the temporal behavior is similar at each station for clusters at various source locations indicating that the temporal changes of material properties occur in the top most portion of the crust the effects are most prominent at stations situated in the immediate vicinity of the recently ruptured fault zones and generally decrease with normal distance from the fault a strong correlation between the co seismic delays and intensities of the strong ground motion generated by the duzce main shock implies that the radiated seismic waves produced the velocity reductions in the shallow material

seismic guided waves trapped in the fault zone of the landers california earthquake of 1992 a mobile seismic array of seven stations was deployed at 11 sites along the fault trace of the m7 4 landers earthquake of june 28 1992 with a maximum offset of 1 km from the trace we found a distinct wave train with a relatively long period following the s waves that shows up only when both the stations and the events are close to the fault trace this wave train is interpreted as a seismic guided wave trapped in a low velocity fault zone to study the distribution of amplitude of the guided waves with distance from the fault trace and also their attenuation with travel distance along the fault zone we eliminated source and recording site effects by the coda normalization method the normalized amplitudes of guided waves show a spectral peak at 3 4 hz which decays sharply with distance from the fault trace spectral amplitudes at high frequencies 8 15 hz show an opposite trend increasing with distance from the fault trace the normalized amplitudes of guided waves at 3 4 hz also show a systematic decrease with hypocentral distance along the fault zone from which we infer an apparent q of 50 in order to confirm the existence of the guided waves a dense array of 31 stations was deployed at one of the 11 sites the resultant records revealed unequivocal evidence for the existence of guided waves associated with the fault zone by modeling the waveforms as s waves trapped in a low velocity waveguide sandwiched between two homogeneous half spaces with velocity vs 3 0 km s we infer a waveguide width of about 180 m a shear velocity of 2 0 2 2 km s and a q of 50 hypocenters of aftershocks with clear guided waves show a systematic distribution both laterally and with depth delineating the extent of the low velocity fault zone in three dimensions we find that the zone extends to a depth of at least 10 km this zone apparently continues to the south across the pinto mountain fault because guided waves are observed at stations north of the pinto mountain fault for earthquakes with epicenters south of it on the other hand the zone appears to be discontinuous at the fault bend located about 20 km north of the mainshock epicenter guided waves were observed for stations and epicenters which are located on the same sides of the fault bend but not for those on the opposite sides

characterization of the san jacinto fault zone near anza california by fault zone trapped waves we installed three 350 m long seismic arrays each array consisting of 12 three component stations across the coyote creek fault ccf clark valley fault cvf and buck ridge fault brf of the san jacinto fault zone sjfz near anza california to record fault zone trapped waves from microearthquakes we observed trapped waves with relatively large amplitudes and long duration at stations close to the fault traces for earthquakes occurring within the fault zone the coda normalized amplitude spectra of trapped waves showed peaks at 4 7 hz which decreased sharply with the distance from the fault trace observations and three dimensional finite difference simulations of trapped waves revealed low velocity and low q waveguides on these active faults with the width of 75 100 m in which shear velocities are reduced by 25 30 from wall rock velocities and q values are 40 90 at depths between the surface and 18 km the locations of earthquakes for which we observed trapped waves delineate the most seismically active fault strands of the sjfz in a region with complicated slip planes near anza the low velocity waveguides inferred from trapped waves extend 15 to 20 km in the length on these active faults and are segmented by the fault discontinuities the waveguide on the brf dips south westward to connect the waveguide on the cvf which dips northeastward this waveguide extends at the seismogenic depth through anza slip gap to another low velocity waveguide on the casa loma fault clf which has been delineated in our previous study of the sjfz using trapped waves li et al 1997 the waveguide on the ccf in coyote mountain is nearly vertical and disconnected from the clf at the south edge of anza gap we interpret the low velocity waveguides on these active strands to partly result from recent prehistoric significant earthquakes on them and evaluate the future earthquake in the anza region

inelastic response of compliant fault zones to nearby earthquakes 1 using dynamic rupture models we examine the response of compliant fault zones that surround pre existing faults to nearby earthquakes we find that some portions of a compliant fault zone can experience inelastic deformation due to dynamic stress perturbations while the remaining portions deform elastically inelastic response of the fault zone results in sympathetic fault parallel motion i e consistent with long term geologic slip across the fault while elastic response causes retrograde motion i e opposite to long term geologic slip in the static displacement field inelastic deformation signals along fault zones detected geodetically may be used to constrain the stress state in the crust because inelastic response occurs only when the prestress level is close to material strength which can be measured in the laboratory

geological observations of damage asymmetry in the structure of the san jacinto san andreas and punchbowl faults in southern california a possible indicator for preferred rupture propagation direction we present new in situ observations of systematic asymmetry in the pattern of damage expressed by fault zone rocks along sections of the san andreas san jacinto and punchbowl faults in southern california the observed structural asymmetry has consistent manifestations at a fault core scale of millimeters to meters a fault zone scale of meters to tens of meters and related geomorphologic features the observed asymmetric signals are in agreement with other geological and geophysical observations of structural asymmetry in a damage zone scale of tens to hundreds of meters in all of those scales more damage is found on the side of the fault with faster seismic velocities at seismogenic depths the observed correlation between the damage asymmetry and local seismic velocity structure is compatible with theoretical predictions associated with preferred propagation direction of earthquake ruptures along faults that separate different crustal blocks the data are consistent with a preferred northwestward propagation direction for ruptures on all three faults if our results are supported by additional observations asymmetry of structural properties determined in field studies can be utilized to infer preferred propagation direction of large earthquake ruptures along a given fault section the property of a preferred rupture direction can explain anomalous behavior of historic rupture events and may have profound implications for many aspects of earthquake physics on large faults

fault plane determination of the 18 april 2008 mount carmel illinois earthquake by detecting and relocating aftershocks we developed a sliding window cross correlation scc detection technique and applied the technique to continuous waveforms recorded by the cooperative new madrid seismic network stations following the 18 april 2008 illinois earthquake the technique detected more than 120 aftershocks down to m l 1 0 in the 2 week time window following the mainshock which is three times more than the number of aftershocks reported by the seismic network most aftershocks happened within 24 hrs of the mainshock we then relocated all events by the double difference relocation algorithm accurate p and s wave differential arrival times between events were obtained by waveform cross correlation after relocation we used the l1 norm to fit all located events by a plane to determine the mainshock fault plane the best fit plane has a strike of 292 11 and dips 81 7 to the northeast this plane agrees well with the focal mechanism solutions of the mainshock and four largest aftershocks by combining the aftershock locations and focal mechanism solutions we conclude that the 18 april earthquake occurred on a nearly vertical left lateral strike slip fault orienting in the west northwest east southeast direction the fault coincides with the proposed left stepping divide accommodation zone in the la salle deformation belt and indicates reactivation of old deformation zone by contemporary stresses in the midcontinent

high resolution imaging of the bear valley section of the san andreas fault at seismogenic depths with fault zone head waves and relocated seismicity summary detailed imaging of fault zone fz material properties at seismogenic depths is a difficult seismological problem owing to the short length scales of the structural features seismic energy trapped within a low velocity damage zone has been utilized to image the fault core at shallow depths but these phases appear to lack sensitivity to structure in the depth range where earthquakes nucleate major faults that juxtapose rocks of significantly different elastic properties generate a related phase termed a fault zone head wave fzhw that spends the majority of its path refracting along the fault we utilize data from a dense temporary array of seismometers in the bear valley region of the san andreas fault to demonstrate that head waves have sensitivity to fz structure throughout the seismogenic zone measured differential arrival times between the head waves and direct p arrivals and waveform modelling of these phases provide high resolution information on the velocity contrast across the fault the obtained values document along strike fault normal and downdip variations in the strength of the velocity contrast ranging from 20 to 50 per cent depending on the regions being averaged by the ray paths the complexity of the fz waveforms increases dramatically in a region of the fault that has two active strands producing two separate bands of seismicity synthetic waveform calculations indicate that geological observations of the thickness and rock type of the layer between the two strands are valid also for the subsurface structure of the fault the results show that joint analysis of fzhws and direct p arrivals can resolve important smallscale elements of the fz structure at seismogenic depths detailed characterization of material contrasts across faults and their relation to earthquake ruptures is necessary for evaluating theoretical predictions of the effects that these structures have on rupture propagation

joint inversion for vp vs and vp vs at safod parkfield california we refined the three dimensional 3 d vp vs and vp vs models around the san andreas fault observatory at depth safod site using a new double difference dd seismic tomography code tomoddps that simultaneously solves for earthquake locations and all three velocity models using both absolute and differential p s and s p times this new method is able to provide a more robust vp vs model than that from the original dd tomography code tomodd obtained simply by dividing vp by vs for the new inversion waveform cross correlation times for earthquakes from 2001 to 2002 were also used in addition to arrival times from earthquakes and explosions in the region the vp values extracted from the model along the safod trajectory match well with the borehole log data providing in situ confirmation of our results similar to previous tomographic studies the 3 d structure around parkfield is dominated by the velocity contrast across the san andreas fault saf in both the vp and vs models there is a clear low velocity zone as deep as 7 km along the saf trace compatible with the findings from fault zone guided waves there is a high vp vs anomaly zone on the southwest side of the saf trace that is about 1 2 km wide and extends as deep as 4 km which is interpreted to be due to fluids and fractures in the package of sedimentary rocks abutting the salinian basement rock to the southwest the relocated earthquakes align beneath the northeast edge of this high vp vs zone we carried out a 2 d correlation analysis for an existing resistivity model and the corresponding profiles through our model yielding a classification that distinguishes several major lithologies

slip rate of the calico fault implications for geologic versus geodetic rate discrepancy in the eastern california shear zone 1 long term 10 5 years fault slip rates test the scale of discrepancy between infrequent paleoseismicity and relatively rapid geodetic rates of dextral shear in the eastern california shear zone ecsz the calico fault is one of a family of dextral faults that traverse the mojave desert portion of the ecsz its slip rate is determined from matching and dating incised pleistocene alluvial fan deposits and surfaces displaced by fault slip a high resolution topographic base acquired via airborne laser swath mapping aids in identification and mapping of deformed geomorphic features the oldest geomorphically preserved alluvial fan unit b is displaced 900 200 m from its source at sheep springs wash in the northern rodman mountains this fan deposit contains the first preserved occurrence of basalt clasts derived from the pipkin lava field and overlies quaternary conglomerate deposits lacking these clasts the 40 ar 39 ar dating of two flows from this field yields consistent ages of 770 40 ka and 735 9 ka an age of 650 100 ka is assigned to this fan deposit based on these ages and on the oldest cosmogenic 3 he exposure date of 653 20 ka on a basalt boulder from the surface of unit b this assigned age and offset together yield a mid pleistocene to present average slip rate of 1 4 0 4 mm yr ayounger fan surface unit k records 100 10 m of dextral displacement and preserves original depositional morphology of its surface granitic boulders and pavement samples from this surface yield an average age of 56 4 7 7 ka after taking into account minimal cosmogenic inheritance of granitic clasts the displaced and dated k fans yield a slip rate of 1 8 0 3 mm yr distributed deformation of the region surrounding the fault trace if active could increase the overall displacement rate to 2 1 0 5 mm yr acceleration of slip rate from an average of 1 4 mm yr prior to 50 ka to 1 8 mm yr since 50 ka is possible though a single time averaged slip rate of 1 6 0 2 mm yr satisfies the data these rates are faster than any other paleoseismic or long term slip rate yet determined for other dextral faults in the mojave desert and imply that fault slip rates and earthquake productivity are heterogeneous across this portion of the ecsz total displacement across the calico fault diminishes northward as shear is distributed into folding and sinistral faults in the calico mountains this pattern is consistent with an approximately threefold drop in geologic slip rate as the calico fault steps over onto the blackwater fault and demonstrates the significance of fault interaction for understanding the pattern of present day strain accumulation in the ecsz

diel behavior of rare earth elements in a mountain stream with acidic to neutral ph abstract diel 24 h changes in concentrations of rare earth elements ree were investigated in fisher creek a mountain stream in montana that receives acid mine drainage in its headwaters three simultaneous 24 h samplings were conducted at an upstream station ph 3 3 an intermediate station ph 5 5 and a downstream station ph 6 8 the ree were found to behave conservatively at the two upstream stations at the downstream station ree partitioned into suspended particles to a degree that varied with the time of day and concentrations of dissolved ree were 2 9 to 9 4 fold 190 to 830 higher in the early morning vs the late afternoon the decrease in dissolved ree concentrations during the day coincided with a corresponding increase in the concentration of ree in suspended particles such that diel changes in the total ree concentrations were relatively minor 27 to 55 increase at night across the lanthanide series the heavy ree partitioned into the suspended solid phase to a greater extent than the light ree filtered samples from the downstream station showed a decrease in shale normalized ree concentration across the lanthanide series with positive anomalies at la and gd and a negative eu anomaly as the temperature of the creek increased in the afternoon the slope of the ree profile steepened and the magnitude of the anomalies increased the above observations are explained by cyclic adsorption of ree onto suspended particles of hydrous ferric and aluminum oxides hfo hao conditional partition coefficients for each ree between the suspended solids and the aqueous phase reached a maximum at 1700 hours and a minimum at 0700 hours this pattern is attributed to diel variations in stream temperature possibly reinforced by kinetic factors i e slower rates of reaction at night than during the day estimates of the enthalpy of adsorption of each ree onto suspended particles based on the field results averaged 82 kj mol and are similar in magnitude to estimates in the literature for adsorption of divalent metal cations onto clays and hydrous metal oxides the results of this study have important implications to the use of ree as hydrogeochemical tracers in streams

a shallow fault zone structure illuminated by trapped waves in the karadere duzce branch of the north anatolian fault western turkey summary we discuss the subsurface structure of the karadere duzce branch of the north anatolian fault based on analysis of a large seismic data set recorded by a local passcal network in the 6 months following the mw 7 4 1999 izmit earthquake seismograms observed at stations located in the immediate vicinity of the rupture zone show motion amplification and long period oscillations in both p and s wave trains that do not exist in nearby off fault stations examination of thousands of waveforms reveals that these characteristics are commonly generated by events that are well outside the fault zone the anomalous features in fault zone seismograms produced by events not necessarily in the fault may be referred to generally as fault zone related site effects the oscillatory shear wave trains after the direct s arrival in these seismograms are analysed as trapped waves propagating in a low velocity fault zone layer the time difference between the s arrival and trapped waves group does not grow systematically with increasing source receiver separation along the fault these observations imply that the trapping of seismic energy in the karadere duzce rupture zone is generated by a shallow fault zone layer traveltime analysis and synthetic waveform modelling indicate that the depth of the trapping structure is approximately 3 4 km the synthetic waveform modelling indicates further that the shallow trapping structure has effective waveguide properties consisting of thickness of the order of 100 m a velocity decrease relative to the surrounding rock of approximately 50 per cent and an s wave quality factor of 10 15 the results are supported by large 2 d and 3 d parameter space studies and are compatible with recent analyses of trapped waves in a number of other faults and rupture zones the inferred shallow trapping structure is likely to be a common structural element of fault zones and may correspond to the top part of a flower type structure the motion amplification associated with fault zone related site effects increases the seismic shaking hazard near fault zone structures the effect may be significant since the volume of sources capable of generating motion amplification in shallow trapping structures is large

slip distribution of the 2015 lefkada earthquake and its implications for fault segmentation this work was partially supported by the uk natural environmental research council nerc through ne k011006 1 ne p008828 1 and the centre for the observation and modelling of earthquakes volcanoes and tectonics comet ga 13 m 031 http comet nerc ac uk

inversion of surface deformation data for rapid estimates of source parameters and uncertainties a bayesian approach new satellite missions e g the european space agency s sentinel 1 constellation advances in data downlinking and rapid product generation now provide us with the ability to access space geodetic data within hours of their acquisition to truly take advantage of this opportunity we need to be able to interpret geodetic data in a prompt and robust manner here we present a bayesian approach for the inversion of multiple geodetic data sets that allows a rapid characterization of posterior probability density functions pdfs of source model parameters the inversion algorithm efficiently samples posterior pdfs through a markov chain monte carlo method incorporating the metropolis hastings algorithm with automatic step size selection we apply our approach to synthetic geodetic data simulating deformation of magmatic origin and demonstrate its ability to retrieve known source parameters we also apply the inversion algorithm to interferometric synthetic aperture radar data measuring co seismic displacements for a thrust faulting earthquake 2015 mw 6 4 pishan earthquake china and retrieve optimal source parameters and associated uncertainties given its robustness and rapidity in estimating deformation source parameters and uncertainties our bayesian framework is capable of taking advantage of real time geodetic measurements thus our approach can be applied to geodetic data to study magmatic tectonic and other geophysical processes especially in rapid response operational settings e g volcano observatories our algorithm is fully implemented in a matlab based software package geodetic bayesian inversion software that we make freely available to the scientific community

three dimensional displacement field of the 2015 mw8 3 illapel earthquake chile from across and along track sentinel 1 tops interferometry wide swath imaging has become a standard acquisition mode for radar missions aiming at applying synthetic aperture radar interferometry insar at global scale with enhanced revisit frequency increased swath width compared to classical stripmap imaging mode is achieved at the expense of azimuthal resolution this makes along track displacements and subsequently north south displacements difficult to measure using conventional split beam multiple aperture insar or cross correlation techniques alternatively we show here that the along track component of ground motion can be deduced from the double difference between backward and forward looking interferograms within regions of burst overlap burst overlap interferometry takes advantage of the large squint angle diversity of sentinel 1 1 to achieve subdecimetric accuracy on the along track component of ground motion we demonstrate the efficiency of this method using sentinel 1 data covering the 2015 mw8 3 illapel earthquake chile for which we retrieve the full 3 d displacement field and validate it against observations from a dense network of gps sensors

deformation on nearby faults induced by the 1999 hector mine earthquake interferometric synthetic aperture radar observations of surface deformation due to the 1999 hector mine earthquake reveal motion on several nearby faults of the eastern california shear zone we document both vertical and horizontal displacements of several millimeters to several centimeters across kilometer wide zones centered on pre existing faults portions of some faults experienced retrograde that is opposite to their long term geologic slip motion during or shortly after the earthquake the observed deformation likely represents elastic response of compliant fault zones to the permanent co seismic stress changes the induced fault displacements imply decreases in the effective shear modulus within the kilometer wide fault zones indicating that the latter are mechanically distinct from the ambient crustal rocks

seismic and geodetic evidence for extensive long lived fault damage zones during earthquakes slip is often localized on preexisting faults but it is not well understood how the structure of crustal faults may contribute to slip localization and energetics growing evidence suggests that the crust along active faults undergoes anomalous strain and damage during large earthquakes seismic and geodetic data from the calico fault in the eastern california shear zone reveal a wide zone of reduced seismic velocities and effective elastic moduli using seismic traveltimes trapped waves and interferometric synthetic aperture radar observations we document seismic velocities reduced by 40 50 and shear moduli reduced by 65 compared to wall rock in a 1 5 km wide zone along the calico fault observed velocity reductions likely represent the cumulative mechanical damage from past earthquake ruptures no large earthquake has broken the calico fault in historic time implying that fault damage persists for hundreds or perhaps thousands of years these fi ndings indicate that faults can affect rock properties at substantial distances from primary fault slip surfaces and throughout much of the seismogenic zone a result with implications for the amount of energy expended during rupture to drive cracking and yielding of rock and development of fault systems

dynamic rupture on a material interface with spontaneous generation of plastic strain in the bulk abstract we discuss 2d simulations of in plane ruptures on a fault between different solids in a model that includes dynamic generation of plastic strain off the fault the fault is governed by a regularized friction with a gradual response to abrupt changes of normal stress while plastic strain in the bulk is governed by a coulomb yielding criterion the occurrence of off fault damage stabilizes the slip velocity on the fault stable self sustaining ruptures propagate on the material interface as narrow unidirectional pulses in the direction of slip on the more compliant side of the fault plastic strain is generated only on the stiffer side of the fault the tensional quadrant in the direction of rupture propagation in a strip of approximately constant width that is correlated with the slip velocity on the fault simulations for various values of confining normal stress material contrast and cohesion in the bulk suggest that significant generation of off fault damage is limited to conditions that correspond to the top few kilometers of the crust the results are compatible with field observations of shallow asymmetric damage patterns in the structure of several large faults

multiple fault rupture of the m7 1 hector mine california earthquake from fault zone trapped waves 1 we studied the complex multiple faulting pattern of the 40 km long rupture zone of the 1999 m7 1 hector mine california earthquake with fault zone trapped waves generated by near surface explosions and aftershocks and recorded by linear seismic arrays deployed across the surface rupture the explosion excited trapped waves with relatively large amplitudes at 3 5 hz and a long duration of s coda waves are similar to those observed for aftershocks but have lower frequencies and travel more slowly three dimensional finite difference simulations of fault zone trapped waves indicate a 75 to 100 m wide low velocity and low q zone waveguide along the rupture surface on the lavic lake fault llf in the bullion mountains the s velocity within the waveguide varies from 1 0 to 2 5 km s at depths of 0 8 km reduced by 35 45 from the wall rock velocity and q is 10 60 the pattern of aftershocks for which we observed trapped waves shows that this low velocity waveguide has two branches in the northern and southern portions of the rupture zone indicating a multiple fault rupture at seismogenic depth north of the bullion mountains although only the rupture segment on the northwest llf broke to the surface a rupture segment on a buried fault also extended 15 km in the more northerly direction from the main shock epicenter to the south the rupture on the llf intersected the bullion fault bf and bifurcated the rupture on the south llf extended 10 km from the intersection and diminished while there was minor rupture on the southeast bf which dips to the northeast and disconnects from the llf at depth thus the analysis of fault zone trapped waves helps delineate a more complex set of rupture planes than the surface breakage in accord with the complex pattern of aftershock distribution and geodetic evidence that the hector mine event involved several faults which may also rupture individually our simulations of dynamic rupture using a finite element code show that generic models are able to produce the general features of the northern part of the rupture including slips on subparallel fault segments the models indicate that such a faulting pattern is physically plausible and consistent with observations

depth dependent structure of the landers fault zone from trapped waves generated by aftershocks we delineate the internal structure of the johnson valley and kickapoo faults landers southern rupture at seismogenic depth using fault zone trapped waves generated by aftershocks trapped waves recorded at the dense linear seismic arrays deployed across and along the surface breaks of the 1992 m7 5 landers earthquake show large amplitudes and dispersive wave trains following the s waves group velocities of trapped waves measured from multiple band pass filtered seismograms for aftershocks occurring at different depths between 1 8 km and 8 2 km show an increase in velocity with depth velocities range from 1 9 km s at 4 hz to 2 6 km s at 1 hz for shallow events while for deep events velocities range from 2 3 km s at 4 hz to 3 1 km s at 1 hz coda normalized amplitude spectra of trapped waves peak in amplitudes at 3 4 hz for stations located close to the fault trace the amplitude decays rapidly with the station offset from the fault zone normalized amplitudes also decrease with distance along the fault giving an apparent q of 30 for shallow events and 50 for deep events we evaluated depth dependent fault zone structure and its uncertainty from these measurements plus our previous results from near surface explosion excited trapped waves li et al 1999 in a systematic model parameter searching procedure using a three dimensional 3 d finite difference computer code graves 1996 our best model of the landers fault zone is 250 m wide at the surface tapering to 100 150 m at 8 2 km depth the shear velocity within the fault zone increases from 1 0 to 2 5 km s and q increases from 20 to 60 in this depth range fault zone shear velocities are reduced by 35 to 45 from those of the surrounding rock and also vary along the fault zone with an increase of 10 near ends of the southern rupture zone

seismic radiation from an sh line source in a laterally heterogeneous planar fault zone a solution to the class of problems in which an sh line source is operating in a medium consisting of two quarter spaces with an arbitrary number of semi infinite vertical layers in between is given in a frequency wavenumber domain the general result is applied to a model with a single vertical layer and synthetic seismograms are calculated for a source specified as an sh line dislocation at the interface between the vertical layer and the faster quarter space the numerical examples demonstrate that moderate fault normal material heterogeneity can have significant effects on the seismic response of a medium the overall distribution of travel times amplitudes and motion polarities in the presence of fault zone material heterogeneity is different from a corresponding distribution in a homogeneous half space the effects are most prominent near the fault zone where head waves surface waves and trapped modes result in waveform complexities large amplifications over an order of magnitude in the fault zone itself and first motion polarities which are reversed from homogeneous medium predictions the results imply that material heterogeneity should be included in fault zone models which are used for the interpretation of observed seismic data and theoretical calculations of near fault responses such models can be utilized to obtain important fault zone and earthquake source parameters

seismic structures of the calico fault zone inferred from local earthquake travel time modelling author posting the authors 2011 this article is posted here by permission of john wiley sons for personal use not for redistribution the definitive version was published in geophysical journal international 186 2011 760 770 doi 10 1111 j 1365 246x 2011 05055 x

shallow seismic trapping structure in the san jacinto fault zone near anza california summary we analyse fault zone trapped waves generated by 500 small earthquakes for high resolution imaging of the subsurface structure of the coyote creek clark valley and buck ridge branches of the san jacinto fault zone near anza california based on a small number of selected trapped waves within this data set a previous study concluded on the existence of a lowvelocity waveguide that is continuous to a depth of 15 20 km in contrast our systematic analysis of the larger data set indicates a shallow trapping structure that extends only to a depth of 3 5 km this is based on the following lines of evidence 1 earthquakes clearly outside these fault branches generate fault zone trapped waves that are recorded by stations within the fault zones 2 a traveltime analysis of the difference between the direct s arrivals and trapped wave groups shows no systematic increase moveout with increasing hypocentral distance or event depth estimates based on the observed average moveout values indicate that the propagation distances within the low velocity fault zone layers are 3 5 km 3 quantitative waveform inversions of trapped wave data indicate similar short propagation distances within the low velocity fault zone layers the results are compatible with recent inferences on shallow trapping structures along several other faults and rupture zones the waveform inversions also indicate that the shallow trapping structures are offset to the northeast from the surface trace of each fault branch this may result from a preferred propagation direction of large earthquake ruptures on the san jacinto fault

grounding line retreat of pope smith and kohler glaciers west antarctica measured with sentinel 1a radar interferometry data we employ sentinel 1a c band satellite radar interferometry data in terrain observation with progressive scans mode to map the grounding line and ice velocity of pope smith and kohler glaciers in west antarctica for the years 2014 2016 and compare the results with those obtained using earth remote sensing satellites ers 1 2 in 1992 1996 and 2011 we observe an ongoing rapid grounding line retreat of smith at 2 km yr 40 km since 1996 an 11 km retreat of pope 0 5 km yr and a 2 km readvance of kohler since 2011 the variability in glacier retreat is consistent with the distribution of basal slopes i e fast along retrograde beds and slow along prograde beds we find that several pinning points holding dotson and crosson ice shelves disappeared since 1996 due to ice shelf thinning which signal the ongoing weakening of these ice shelves overall the results indicate that ice shelf and glacier retreat in this sector remain unabated

present day kinematics of the eastern california shear zone from a geodetically constrained block model we use global positioning system gps data from 1993 2000 to determine horizontal velocities of 65 stations in eastern california and western nevada between 35 and 37 n we relate the geodetic velocities to fault slip rates using a block model that enforces path integral constraints over geologic and geodetic time scales and that includes the effects of elastic strain accumulation on faults locked to a depth of 15 km the velocity of the sierra nevada block with respect to nevada is 11 1 0 3 mm yr with slip partitioned across the death valley 2 8 0 5 mm yr panamint valley 2 5 0 8 mm yr and airport lake owens valley 5 3 0 7 4 6 0 5 mm yr faults the western mojave block rotates at 2 1 0 8 my clockwise with 3 7 0 7 mm yr of left lateral motion across the western garlock fault we infer 11 2 mm yr of right lateral motion across the mojave region of the eastern california shear zone

the 2008 eruptive unrest at cerro azul volcano galapagos revealed by insar data and a novel method for geodetic modelling

quantitative analysis of seismic fault zone waves in the rupture zone of the 1992 landers california earthquake evidence for a shallow trapping structure summary we analyse quantitatively a waveform data set of 238 earthquakes recorded by a dense seismic array across and along the rupture zone of the 1992 landers earthquake a grid search method with station delay corrections is used to locate events that do not have catalogue locations the quality of fault zone trapped waves generated by each event is determined from the ratios of seismic energy in time windows corresponding to trapped waves and direct s waves at stations close to and off the fault zone approximately 70 per cent of the events with s p times of less than 2 s including many clearly off the fault produce considerable trapped wave energy this distribution is in marked contrast with previous claims that trapped waves are generated only by sources close to or inside the landers rupture zone the time difference between the s arrival and trapped waves group does not grow systematically with increasing hypocentral distance and depth the dispersion measured from the trapped waves is weak these results imply that the seismic trapping structure at the landers rupture zone is shallow and does not extend continuously along strike by more than a few kilometres synthetic waveform modelling indicates that the fault zone waveguide has depth of approximately 2 4 km a width of approximately 200 m an s wave velocity reduction relative to the host rock of approximately 30 40 per cent and an s wave attenuation coefficient of approximately 20 30 the fault zone waveguide north of the array appears to be shallower and weaker than that south of the array the waveform modelling also indicates that the seismic trapping structure below the array is centred approximately 100 m east of the surface break

characterization of fault zones there are currently three major competing views on the essential geometrical mechanical and mathematical nature of faults the standard view is that faults are possibly segmented and heterogeneous euclidean zones in a continuum solid the continuum euclidean view is supported by seismic gravity and electromagnetic imaging studies by successful modeling of observed seismic radiation geodetic data and changes in seismicity patterns by detailed field studies of earthquake rupture zones and exhumed faults and by recent high resolution hypocenter distributions along several faults the second view focuses on granular aspects of fault structures and deformation fields the granular view is supported by observations of rock particles in fault zone gouge by studies of block rotations and the mosaic structure of the lithosphere which includes the overall geometry of plate tectonics by concentration of deformation signals along block boundaries by correlation of seismicity patterns on scales several times larger than those compatible with a continuum framework and by strongly heterogeneous wave propagation effects on the earth s surface the third view is that faults are fractal objects with rough surfaces and branching geometry the fractal view is supported by some statistical analysis of regional hypocenter locations by long range correlation of various measurements in geophysical boreholes by the fact that observed power law statistics of earthquakes are compatible with an underlying scale invariant geometrical structure by geometrical analysis of fault traces at the earth s surface and by measurements of joint and fault surfaces topography

seismic trapped modes in the oroville and san andreas fault zones three component borehole seismic profiling of the recently active oroville california normal fault and microearthquake event recording with a near fault three component borehole seismometer on the san andreas fault at parkfield california have shown numerous instances of pronounced dispersive wave trains following the shear wave arrivals these wave trains are interpreted as fault zone trapped seismic modes parkfield earthquakes exciting trapped modes have been located as deep as 10 kilometers as shallow as 4 kilometers and extend 12 kilometers along the fault on either side of the recording station selected oroville and parkfield wave forms are modeled as the fundamental and first higher trapped sh modes of a narrow low velocity layer at the fault modeling results suggest that the oroville fault zone is 18 meters wide at depth and has a shear wave velocity of 1 kilometer per second whereas at parkfield the fault gouge is 100 to 150 meters wide and has a shear wave velocity of 1 1 to 1 8 kilometers per second these low velocity layers are probably the rupture planes on which earthquakes occur

san jacinto fault zone guided waves a discrimination for recently active fault strands near anza california we deployed three 350 m long eight element linear seismic arrays in the san jacinto fault zone sjfz near anza california to record microearthquakes starting in august through december 1995 two arrays were deployed 18 km northwest of anza across the casa loma fault clf and the hot springs fault hsf strands of the sjfz the third array was deployed across the san jacinto fault sjf in the anza slip gap we observed fault zone guided waves characterized by low frequency large amplitudes following s waves at the clf array and the sjf array for earthquakes occurring within the fault zone however we did not observe guided waves at the hsf array for any events the amplitude spectra of these guided waves showed peaks at 4 hz at the clf and 6 hz at the sjf which decreased sharply with the distance from the fault trace in contrast no spectral peaks at frequency lower than 6 hz were registered at the hsf array we used a finite difference method to simulate these guided modes as 5 waves trapped in a low velocity waveguide sandwiched between high velocity wall rocks the guided mode data are adequately fit by a waveguide on the clf with the average width of 120 m and s velocity of 2 5 km s about 25 reduced from the s velocity of the surrounding rock this waveguide becomes 40 to 60 m wide with the 5 velocity of 2 8 km s in the anza slip gap on the other hand there is not a continuous waveguide on the hsf at depth locations of the events with guided modes suggest that the fault plane waveguide extends along the clf between the towns of san jacinto and anza dipping northeastward at 75 80 to a depth of about 18 km it becomes nearly vertical in the anza gap we speculate that the existence of a continuous low velocity waveguide on the clf can be caused by the rupture of the magnitude 6 9 earthquake on april 21 1918 occurring near the towns of san jacinto and hemet further the lack of a clear waveguide on the hsf suggests that it was not ruptured in this event

multiparameter monitoring of fogo island cape verde for volcanic risk mitigation fogo island in the cape verde archipelago north atlantic is a stratovolcano of nearly conical shape that rises 2829 m above sea level and v6000 m above the surrounding seafloor with a population of 40 000 the island has known intense historical volcanic activity since ad 1500 with an average interval between eruptions of the order of 20 years twentieth century rates were more subdued with only two flank eruptions in 1951 and 1995 following the 1995 eruption increased awareness of the volcanic hazard affecting the population of the island led to the deployment of the permanent vigil network seismographic stations both broadband and short period tiltmeters and a co2 sensor where installed in fogo together with a telemetry infrastructure to allow remote real time monitoring a broadband seismographic station was installed in neighbour brava island the operation of the network was complemented by the introduction of routine geodetic and microgravity surveying and the operation of an automatic meteorological station in this paper we describe the methodology adopted to monitor the volcanic activity combining real time data analysis volcanotectonic and volcanic earthquakes volcanic tremor and tilt with repeated surveying at intervals of several months gps microgravity examples of data from the first years of operation are presented in particular the data pertaining to a period of anomalous activity in september october 2000 are discussed in the context of the risk mitigation strategy currently being developed

can compliant fault zones be used to measure absolute stresses in the upper crust 1 geodetic and seismic observations reveal long lived zones with reduced elastic moduli along active crustal faults these fault zones localize strain from nearby earthquakes consistent with the response of a compliant elastic layer fault zone trapped wave studies documented a small reduction in p and s wave velocities along the johnson valley fault caused by the 1999 hector mine earthquake this reduction presumably perturbed a permanent compliant structure associated with the fault the inferred changes in the fault zone compliance may produce a measurable deformation in response to background tectonic stresses this deformation should have the same sense as the background stress rather than the coseismic stress change here we investigate how the observed deformation of compliant zones in the mojave desert can be used to constrain the fault zone structure and stresses in the upper crust we find that gravitational contraction of the coseismically softened zones should cause centimeters of coseismic subsidence of both the compliant zones and the surrounding region unless the compliant fault zones are shallow and narrow or essentially incompressible we prefer the latter interpretation because profiles of line of sight displacements across compliant zones cannot be fit by a narrow shallow compliant zone strain of the camp rock and pinto mountain fault zones during the hector mine and landers earthquakes suggests that background deviatoric stresses are broadly consistent with mohr coulomb theory in the mojave upper crust with 0 7 large uncertainties in mojave compliant zone properties and geometry preclude more precise estimates of crustal stresses in this region with improved imaging of the geometry and elastic properties of compliant zones and with precise measurements of their strain in response to future earthquakes the modeling approach we describe here may eventually provide robust estimates of absolute crustal stress

damage to the shallow landers fault from the nearby hector mine earthquake crustal faults have long been identified as sites where localized sliding motion occurs during earthquakes which allows for the relative motion between adjacent crustal blocks although there is a growing awareness that we must understand the evolution of fault systems on many timescales to relate present day crustal stresses and fault motions to geological structures formed in the past fault zone damage and healing have been documented quantitatively in only a few cases we have been monitoring the healing of damage on the shallow johnson valley fault after its rupture in the 1992 magnitude 7 3 landers earthquake and here we report that this healing was interrupted in 1999 by the magnitude 7 1 hector mine earthquake rupture which occurred 20 30 km away the hector mine earthquake both strongly shook and permanently strained the johnson valley fault adding damage discernible as a temporary reversal of the healing process the fault has since resumed the trend of strength recovery that it showed after the landers earthquake these observations lead us to speculate that fault damage caused by strong seismic waves may help to explain earthquake clustering and seismicity triggering by shaking and may be involved in friction reduction during faulting

ground deformation due to steam cap processes at reykjanes sw iceland effects of geothermal exploitation inferred from interferometric analysis of sentinel 1 images 2015 2017

spatial variability in microscopic deformation and composition of the punchbowl fault southern california implications for mechanisms fluid rock interaction and fault morphology abstract we examine the distribution and nature of microstructures geochemistry and mineralogy along two traverses across the punchbowl fault southern california to determine the morphology and deformation mechanisms of the fault zone in schistose rocks the punchbowl fault is an exhumed fault that has two main strands of slip localization and has a total of 44 km of right slip protolith in the study area consists of the pelona schist which is primarily a quartz albite muscovite actinolite schist with thin to medium banding and rare metabasalts the traverses are 1 3 km apart and were conducted at a site with a single fault strand and a site where both principal strands of the fault are exposed the fault zone thickness is a function of the type of measurement that is used to define it for the single strand site analysis of the distribution of microfractures shows that the fault zone consists of a roughly 40 m thick damaged zone adjacent to the fault core the damaged zone is marked by an increase in veins thin cataclasite bands inter and intragranular fracturing and alteration relative to the country rock brittle grain size reduction occurs in a zone 10 m thick as measured from the fault core which consists of a continuous 10 cm thick very fine grained cataclasite that experienced repeated alteration vein injection and grain size reduction whole rock geochemical analyses of the fault related rocks suggest that the geochemically defined fault zone is less than 10 m thick volume loss at the site with one fault strand appears to have been small the dominant alteration reactions associated with the fault core are the hydration of hornblende and actinolite accompanied by the alteration of muscovite to produce a quartz chlorite albite epidote ultracataclasite the composition of the fault core is variable and locally influenced by one of the adjacent protoliths the examination of the two fault strand sites shows that two damaged zone fault core structures are present the region between the two strands experienced a greater degree of deformation than the protolith but the total deformation is much less than immediately adjacent to the fault cores the total thickness of the damaged zone around the two strands is less than 200 m the fault core enveloped by a damaged zone morphology as well as the textures of the fault core rocks are similar to rocks associated with the north branch san gabriel fault which formed in crystalline rocks with a total displacement of 22 km fault thickness is less in the pelona schist than in the crystalline rocks perhaps owing to more efficient strain localization in the schists thus the faults of the san andreas system may be thinner in regions where schists or franciscan rocks are the protolith but the main fault core may be a constant feature of the fault zone transformation induced weakening is less important in this part of the punchbowl fault since the protolith has a large amount of mica the structure of the fault zone with two principal slip surfaces is marked by both chemical changes and microstructures and indicates that some parts of the san andreas fault system may consist of multiple slip surfaces each with a damaged zone that together may create a fault zone 100 m thick and in which slip is localized to zones meters to decimeters thick

velocity contrast along the calaveras fault from analysis of fault zone head waves generated by repeating earthquakes 1 we systematically investigate the velocity contrast along the calaveras fault that ruptured during the 1984 morgan hill earthquake using fault zone head waves fzhw that refract along the fault interface we stack waveforms in 353 sets of repeating clusters and align the peaks or troughs of the direct p waves assuming rightlateral strike slip focal mechanisms the obtained velocity contrasts are 2 3 and 12 14 nw and se of station cco respectively the fzhw and the fault plane outlined by the relocated seismicity se of cco are more complicated than those nw of cco the results can be explained by a relatively simple and sharp fault interface in the nw and a complicated fault structure with a presence of a low velocity zone in the se the along strike variations in the strength of the velocity contrast are consistent with surface geological mapping and recent 3d tomography studies in this region citation zhao p and z peng 2008 velocity contrast along the calaveras fault from analysis of fault zone head waves generated by repeating earthquakes geophys res lett 35 l01303 doi 10 1029 2007gl031810

toward full exploitation of coherent and incoherent information in sentinel 1 tops data for retrieving surface displacement application to the 2016 kumamoto japan earthquake sentinel 1 s continuous observation program over all major plate boundary regions makes it well suited for earthquake studies however decorrelation due to large displacement gradients and limited azimuth resolution of the terrain observation by progressive scan tops data challenge acquiring measurements in the near field of many earthquake ruptures and prevent measurements of displacements in the along track direction here we propose to fully exploit the coherent and incoherent information of tops data by using standard interferometric synthetic aperture radar insar split bandwidth interferometry in range and azimuth swath burst overlap interferometry and amplitude cross correlation to map displacements in both the line of sight and the along track directions application to the 2016 kumamoto earthquake sequence reveals the coseismic displacements from the far field to the near field by adding near field constraints the derived slip model reveals more shallow slip than obtained when only using far field data from insar highlighting the importance of exploiting all coherent and incoherent information in tops data

the 2015 wolf volcano galapagos eruption studied using sentinel 1 and alos 2 data an energetic eruption started on 25 may 2015 from a circumferential fissure at the summit of wolf volcano on isabela island western galapagos further eruptive activity within the wolf caldera followed in mid june 2015 as no geodetic observations of earlier eruptions at wolf exist this eruption provides an opportunity to study the volcano s magmatic plumbing system for the first time here we use interferometric synthetic aperture radar insar data from both the sentinel 1a and alos 2 satellites to map and analyze the surface deformation at four time periods during the activity these data allow us to identify the two eruption phases and reveal strong co eruptive subsidence within the wolf caldera that is superimposed on a larger volcano wide subsidence signal modeling of the surface displacements shows that two shallow magma reservoirs located under wolf at 1 km and 5 km below sea level explain the subsidence and that these reservoirs appear to be hydraulically connected we also suggest that the transition from the circumferential to the intra caldera eruption may have involved ring fault activity

importance of horizontal seafloor motion on tsunami height for the 2011 mw 9 0 tohoku oki earthquake abstract it is now clear that the 2011 tohoku oki earthquake ruptured the subduction interface all the way to the japan trench however there is significant disagreement about just how much slip occurred at the trench with most geodetic studies locating only a small fraction of the maximum slip there whereas broadband seismic studies put the majority of the slip near the trench measurements of seafloor displacement near the trench also imply more slip there than is estimated by the geodetic studies here by means of a joint inversion of displacement measurements and seafloor pressure data we show that it is possible to reconcile geodetic and seismic studies and that a considerable amount of slip indeed occurred at the trench with slip magnitudes reaching 57 74 of the maximum slip the seafloor displacement predicted by our model agrees very well with independent measurements made close to the trench we also find good agreement between our tsunami model and independent measurements of tsunami height in the ocean and on land re running of the inversion without the near field pressure gauge data however leads to underprediction of the flooding on land even when the seafloor geodetic data are still included thus even if the seafloor geodetic measurements had been available in real time they would still not have allowed reliable prediction of near field tsunami inundation close to the trench the dip of the plate interface is shallow which serves to decrease the vertical motion of the sea floor for any given slip however the horizontal motion is conversely larger because the ocean floor slopes steeply near the trench it acted like a giant wedge converting the horizontal motion of the ground into an uplift of the water column and causing the peak initial tsunami wave height to be twice as high as it would have been from vertical displacement alone

high resolution digital elevation model from tri stereo pleiades 1 satellite imagery for lava flow volume estimates at fogo volcano resolving changes in topography through time using accurate high resolution digital elevation models dems is key to understanding active volcanic processes for the first time in a volcanic environment we utilize very high resolution tri stereo optical imagery acquired by the pleiades 1 satellite constellation and generate a 1 m resolution dem of fogo volcano cape verde the most active volcano in the eastern atlantic region point cloud density is increased by a factor of 6 5 compared to conventional stereo imagery and the number of 1 m2 pixels with no height measurements is reduced by 43 we use the dem to quantify topographic changes associated with the 2014 2015 eruption at fogo height differences between the posteruptive pleiades 1 dem and the preeruptive topography from tandem x give a lava flow volume of 45 83 0 02 106 m3 emplaced over an area of 4 8 km2 at a mean rate of 6 8 m3 s 1

surface seismic and electrical methods to detect fluids related to faulting in the absence of drilling surface based geophysical methods are necessary to observe fault zones and fault zone physical properties at seismogenic depths these in situ physical properties can then be used to infer the presence and distribution of fluids along faults although such observations are by nature indirect and become less exact with greater depth multiple observations of a range of such geophysical properties as compressional and shear seismic velocity vp and vs vp v5 ratio related to poisson s ratio resistivity and attenuation in and adjacent to fault zones offer the greatest hope of making inferences of the fault zone geometry fluids in the fault zone and fluid reservoirs in the surrounding crust for simple geometries fault zone guided waves can provide information on fault zone width and velocities for faults of the order of 200 m wide to address the question of whether a narrow fault zone can be imaged well enough at depths of seismic rupture to infer the presence of anomalously high fluid rock ratios we present synthetic seismic tomography and magnetotelluric examples for an ideal case of a narrow fault zone with a simple geometry large changes in material properties and numerous earthquakes within the fault zone a synthetic 0 5 km wide fault zone with 20 velocity reduction is well imaged using local earthquake tomography when sequential velocity inversions are done the true fault width is found even to 9 km depth although the calculated amplitude of the velocity reduction is lower than the actual amplitude vp vs is as well determined as vp magnetotelluric imaging of a synthetic fault zone shows that a conductive fault zone can be well imaged within the upper 10 km further a narrow 1 km very low resistivity 3 ohm m fault core can be imaged within a broad 5 km low resistivity 10 ohm m fault zone illustrating that regions of a fault containing large quantities of interconnected fluids within a broader conductive fault zone should be detectable thus variations in fluid content and fluid pressure can be inferred from electrical and seismic methods but there will always be uncertainty in these inferences due to the trade off with other factors such as intrinsic variations in porosity mineralogy and pore geometry the best approach is combined modeling of varied seismic and electrical data

low velocity damaged structure of the san andreas fault at parkfield from fault zone trapped waves 1 we used dense linear seismic arrays across and along the san andreas fault saf at parkfield california to record fault zone trapped waves generated by explosions and microearthquakes in 2002 prominent trapped waves appeared at stations close to the saf main fault trace while some energy was trapped in the north strand at the array site observations and 3 d finite difference simulations of trapped waves at 2 5 hz show evidence of a damaged core zone on the main saf the zone from the surface to seismogenic depths is marked by a low velocity waveguide 150 m wide in which q is 10 50 and shear velocities are reduced by 30 40 from wall rock velocities with the greatest velocity reduction at shallow depth we interpret that this distinct low velocity zone on the main saf is a remanent of damage due to past large earthquakes on the principal fault plane at parkfield a less developed low velocity zone may be evident on the north strand that experienced minor breaks in the 1966 m6 event

a past giant lateral collapse and present day flank instability of fogo cape verde islands fogo island is a large and extremely steepsided oceanic island volcano in the cape verde archipelago it has a large ca 9 km across east facing summit collapse structure the monte amarelo collapse with a probable volume of at least 150 200 km3 for most of its history the monte amarelo volcano had a small but productive central vent complex and radial rift zones fed by laterally propagating dykes shortly before the collapse the latter were replaced by north south trending arrays of en echelon vertically propagating dykes since the monte amarelo collapse the scar has partly filled with a new volcano the cha das caldeiras volcano the summit cone of this volcano the pico do fogo is a very young feature but has been abandoned in the most recent phase of activity from the 18th century onwards the same period has also seen the abandonment of earlier radial rift zones with laterally propagating dykes and their replacement with en echelon arrays of vents fed by vertically propagating dykes these form an n s trending array within the older collapse structure and are associated with seaward displacement of the eastern flank of the volcano within the old collapse structure the most recent eruptions those of 1951 and 1995 appear to be associated with episodes of flank instability manifested in n s surface fissuring and east facing normal faults these recent structural changes in the volcano parallel those which took place in the monte amarelo volcano prior to its collapse

study of the 1999 m 7 1 hector mine california earthquake fault plane by trapped waves we recorded fault zone trapped waves from aftershocks on portable seismometers in a tight linear array across the lavic lake fault which was one of several faults that ruptured in the m 7 1 hector mine california earthquake on 16 october 1999 trapped waves with large amplitudes and long duration at 4 to 7 hz produced by aftershocks occurring within the rupture zone were recorded at stations close to the fault trace however the s waves registered at stations farther from the rupture zone for the same events were much briefer trapped waves recorded at the hector mine rupture zone are similar to those observed in the landers rupture zone li et al 1994a b but show higher frequencies simulations of these trapped waves indicate a 75 to 100 m wide low velocity and low q waveguide along the hector mine rupture zone in which the s velocity is reduced by about 40 to 50 from wall rock velocities and q is 10 to 60 in the depth range from the surface to 10 km we interpret this low velocity waveguide as being a remnant of the process zone formed by inelastic deformation around the propagating crack tip during dynamic rupture in the 1999 hector mine earthquake the reductions of velocities and q within the hector mine rupture zone are similar to those within the landers rupture zone suggesting that the fault zone rock was damaged to the same degree in the two earthquakes the wave guide width 75 100 m on the hector mine rupture zone 40 km in the total length is half that 150 250 m of the landers rupture zone 80 km in the total length consistent with the scaling of process zone size to rupture length as predicted in some published dynamic rupture models locations of aftershocks for which we observed trapped waves show bifurcation of the northern hector mine rupture at depth although only the west rupture branch broke to the surface

spatial and temporal patterns of deformation at the tendaho geothermal prospect ethiopia abstract observations of ground deformation in east africa have been fundamental for unveiling the tectonics of continental rifting assessing the seismic and volcanic hazard to development and identifying geothermal resources here we investigate the active natural and anthropogenic processes in the tendaho graben afar using interferometric synthetic aperture radar insar collected by the envisat satellite in 2004 2010 we used the poly interferometric rate and time series estimation rate method to calculate displacement in satellite line of sight and a least square inversion to decompose the line of sight displacement into vertical and rift perpendicular components we observe two zones of deformation a 20 km wide circular region of subsidence located 10 km northeast of the town of semera with a maximum displacement rate of 5 cm yr and elongated zone 50 km of subsidence in the area of the geothermal prospect maximum rate of 4 cm yr the temporal characteristics of subsidence varies between these zones with an increase in subsidence rate observed in the circular region in august 2008 we used a bayesian inversion to find the best fitting source models and compared this to locations of seismicity and other geophysical observations the pattern of deformation is consistent with a combination of magmatic and geothermal processes but there does not appear to be a direct link to a sequence of dyke intrusions during 2005 2010 at manda hararo graben 60 km away but dynamic stress changes or deep crustal flow could account for the observations

fault zone structure at depth from differential dispersion of seismic guided waves evidence for a deep waveguide on the san andreas fault summary seismic guided wave dispersion can be used to image fault zone structure at seismogenic depth a two station differential group velocity technique previously used for surface waves was adapted to solve for local fault zone structure between two stations this method was extended to solve for fault zone structure between two earthquakes using differential group arrival times at a single station the method was tested with finite difference synthetic data for an inhomogeneous fault as well as with a pair of shallow earthquakes recorded in the san andreas fault observatory at depth safod borehole station results from a pair of deep earthquakes recorded in the safod borehole station indicate that the low velocity waveguide of the san andreas fault extends to 10 km depth the waveguide at 10 12 km depth is 120 190 m wide and the velocity contrast is 20 per cent similar to the values in the shallow subsurface multiple earthquakes and receivers could be used to map fault zone structure at seismogenic depth as a function of depth and strike

diversity of fault zone damage and trapping structures in the parkfield section of the san andreas fault from comprehensive analysis of near fault seismograms summary we perform comprehensive analyses of trapped waves and signals of damaged fault zone rocks associated with time delays of body waves along the parkfield section of the san andreas fault saf waveforms generated by thousands of earthquakes and recorded by near fault stations in several permanent and temporary deployments are examined with attention to the possible influence of a lithology contrast across the fault on signals of the low velocity damage zone clear candidate trapped waves are identified at only three stations mmnb and two of the other near fault stations flip and pies further to the nw clear candidate trapped waves are not seen at any of the near fault stations to the se of mmnb the locations of the events generating good candidate trapped waves at mmnb and the other two stations are not distributed broadly in space but clustered in a small number of locations moreover events that generate clear candidate trapped waves at one station do not typically generate trapped waves at the other two stations these observations imply that the damage zone is highly variable along strike and that a coherent connected waveguide does not exist for distances along strike larger than at most 3 5 km the distance between stations synthetic waveform fits for observed trapped waves at stations mmnb and flip indicate that the most likely parameters of the trapping structures at these locations are widths of about 150 m depths of about 3 km velocity reductions of 30 40 per cent and q values of 10 40 synthetic calculations of trapped waves demonstrate that if there is a contrast of seismic velocity across the fault the trapped waves are delayed relative to the s wave arrival trapped waves at station mmnb and to a lesser extent also at stations flip and pies in the nw section show this characteristic this suggests a lithology contrast in the top few km at these locations in agreement with results from tomography and studies of head waves in the parkfield area at several mini across fault arrays where trapped waves are not observed a low velocity damage zone is detected from the delay in the arrival time of body wave phases relative to a nearby off fault station the observed delay of the s wave is greater than the p wave delay consistent with the existence of a damage zone with poisson ratio of about 0 33 the observations of time delays without trapped waves indicate that parts of the damage zone are insufficiently coherent to generate trapped waves a broader damage zone may exist in the region between the saf and the south west fracture zone the results highlight the diversity of damage structures along the 40 km of the saf examined in this study and imply that fault imaging based on data at single sites does not necessarily apply to a larger section

shallow low velocity zone of the san jacinto fault from local earthquake waveform modelling summary we developed a method to determine the depth extent of low velocity zone lvz associated with a fault zone fz using s wave precursors from local earthquakes the precursors are diffracted s waves around the edges of lvz and their relative amplitudes to the direct s waves are sensitive to the lvz depth we applied the method to data recorded by three temporary arrays across three branches of the san jacinto fz the fz dip was constrained by differential traveltimes of p waves between stations at two side of the fz other fz parameters width and velocity contrast were determined by modelling waveforms of direct and fz reflected p and s waves we found that the lvz of the buck ridge fault branch has a width of 150 m with a 30 40 per cent reduction in vp and a 50 60 per cent reduction in vs the fault dips 70 5 to southwest and its lvz extends only to 2 1 km in depth the lvz of the clark valley fault branch has a width of 200 m with 40 per cent reduction in vp and 50 per cent reduction in vs the coyote creek branch is nearly vertical and has a lvz of 150 m in width and of 25 per cent reduction in vp and 50 per cent reduction in vs the lvzs of these three branches are not centred at the surface fault trace but are located to their northeast indicating asymmetric damage during earthquakes

applicability of sentinel 1 terrain observation by progressive scans multitemporal interferometry for monitoring slow ground motions in the san francisco bay area 2017 american geophysical union all rights reserved data from the sentinel 1 satellite have already proven useful for investigating seismic and volcanic events since its launch in april 2014 the requirement of ultrahigh coregistration accuracy and the current relatively short time of sentinel 1 acquisitions make its application challenging for studying slow deformation processes such as fault creep and land subsidence here we analyze a set of 14 sar images over the san francisco bay area spanning 1 year from early 2015 to 2016 we show that implementing an existing enhanced spectral diversity algorithm or using precise orbits together with a reference digital elevation model both yield the required coregistration accuracy for making use of the phase measurements in time series analysis of ground deformation following a thorough validation test we update our estimates of hayward fault creep rate and confirm uplift due to recharge of the santa clara valley aquifer system during the final summer of 4 year drought

application of independent component analysis to multi temporal insar data with volcanic case studies a challenge in the analysis of multi temporal interferometric synthetic aperture radar insar data is distinguishing and separating volcanic tectonic and anthropogenic displacements from each other and from atmospheric or orbital noise independent component analysis ica is a method for decomposing a mixed signal based on the assumption that the component sources are non gaussian and statistically independent ica has potential as a tool for exploratory analysis of insar data and in particular for testing whether geophysical signals are related or independent this article presents tests of the applicability of ica to insar using synthetic data and application to sentinel 1a archive images from two contrasting examples of volcano deformation co eruptive subsidence associated with the april 2015 eruption of calbuco chile was identified in spatial patterns found by maximising both spatial and temporal independence spatial patterns and rates of lava subsidence were retrieved using ica analysis of interferograms from paricutin lava fields mexico and found to be consistent with previous observations i demonstrate that ica is an appropriate method for the analysis of volcanic signals in the presence of atmospheric noise and propose a strategy for the automatic identification of geophysical displacements using cluster analysis of the spatial patterns of independent components this approach allows the detection of geophysical processes on a range of scales and provides a test of signal independence where multiple displacement sources are active

tracking morphological changes and slope instability using spaceborne and ground based sar data abstract stromboli aeolian archipelago italy is an active volcano that is frequently affected by moderate to large mass wasting which has occasionally triggered tsunamis with the aim of understanding the relationship between the geomorphologic evolution and slope instability of stromboli remote sensing information from space born synthetic aperture radar sar change detection and interferometry insar and ground based insar gbinsar was compared with field observations and morphological analyses ground reflectivity and squeesar an insar algorithm for surface deformation monitoring displacement measurements from x band cosmo skymed satellites csk were analysed together with displacement measurements from a permanent sited ku band gbinsar system remote sensing results were compared with a preliminary morphological analysis of the sciara del fuoco sdf steep volcanic flank which was carried out using a high resolution digital elevation model dem finally field observations supported by infrared thermographic surveys irt allowed the interpretation and validation of remote sensing data the analysis of the entire dataset collected between january 2010 and december 2014 covers a period characterized by a low intensity of strombolian activity this period was punctuated by the occurrence of lava overflows occurring from the crater terrace evolving downslope toward sdf and flank eruptions such as the 2014 event the amplitude of the csk images collected between february 22nd 2010 and december 18th 2014 highlights that during periods characterized by low intensity strombolian activity the production of materials ejected from the crater terrace towards the sdf is generally low and erosion is the prevailing process mainly affecting the central sector of the sdf csk squeesar and gbinsar data allowed the identification of low displacements in the sdf except for high displacement rates up to 1 5 mm h that were measured following both lava delta formation after the 2007 eruption and the lava overflows of 2010 and 2011 after the emplacement of the 2014 lava field high displacements in the central and northern portions of the sdf were recorded by the gbinsar device whereas the spaceborne data were unable to detect these rapid movements a comparison between irt images and gbinsar derived displacement maps acquired during the same time interval revealed that the observed displacements along the sdf were related to the crumbling of newly emplaced 2014 lava and of its external breccia detected slope instability after the 2014 flank eruption was related to lava accumulation on the sdf and to the difference in the material underlying the 2014 lava flow i lava flows and breccia layers related to the 2002 03 and 2007 lava flow fields in the northern sdf sector and ii loose volcaniclastic deposits in the central part of the sdf this work emphasizes the importance of smart integration of spaceborne sar derived hazard information with permanent sited operational monitoring by gbinsar devices to detect areas impacted by mass wasting and volcanic activity

implications for mechanical properties of brittle faults from observations of the punchbowl fault zone california field observations of the punchbowl fault zone an inactive trace of the san andreas are integrated with results from experimental deformation of naturally deformed punchbowl fault rocks for a qualitative description of the mechanical properties of the fault and additional information for conceptual models of crustal faulting the punchbowl fault zone consists of a single continuous gouge layer bounded by zones of extensively damaged host rock fault displacements were not only localized to the gouge layer but also to discrete shear surfaces within the gouge deformation in the exposure studied probably occurred at depths of 2 to 4 km and was dominated by cataclastic mechanisms textural data also suggest that significant amounts of pore fluids were present during faulting and that fluid assisted mechanisms such as dissolution diffusion and precipitation were operative the experimental data on specimens collected from the fault zone suggest that there is a gradual decrease in strength and elastic modulus and an increase in relative ductility and permeability toward the main gouge zone the gouge layer has fairly uniform mechanical properites and it has significantly lower strength elastic modulus and permeability than both the damaged and the undeformed host rock for the punchbowl fault and possibly other brittle faults the variations in loading of the gouge zone with time are primarily governed by the morphology of the fault and the mechanical properties of the damaged host rock in addition the damaged zone acts as the permeable unit of the fault zone and surrounding rock it appears that the gouge primarily governs whether displacements are localized and it therefore may have a significant influence on the mode of slip

deformation of compliant fault zones induced by nearby earthquakes theoretical investigations in two dimensions 1 using spontaneous rupture models with off fault elastoplastic material response we investigate the deformation of compliant fault zones induced by nearby earthquake ruptures in a two dimensional plane strain framework we find that dynamic stresses from nearby ruptures can produce inelastic strain along some portions of a fault zone that experience dilatational stress changes if the fault zone rock is close to failure in the prestress field accumulation of inelastic strain causes dramatic variations in particle velocity across the fault zone reversing the sense of fault parallel relative motion from retrograde opposite to the long term geologic slip to sympathetic consistent with the long term slip during the dynamic process in the static displacement field of a roughly parallel strike slip fault system the inelastic response of a fault zone results in sympathetic motion while the elastic response generally gives rise to retrograde motion our theoretical investigations reveal that some deficiencies may exist in applying an elastic inhomogeneity model to infer fault zone properties in previous studies including the assumption of negligible fault normal motion and ignorance of changes in some components of the stress tensor these deficiencies and possible constraints on the in situ stress state by inelastic strain signals in the static displacement field call for a reexamination of existing observations of fault zone deformation induced by recent large earthquakes

the 2014 2015 eruption of fogo volcano geodetic modeling of sentinel 1 tops interferometry after 20 years of quiescence fogo volcano erupted in november 2014 the eruption produced fast moving lava flows that traveled for several kilometers and destroyed two villages this event represents the first episode of significant surface deformation imaged by the new european space agency s sentinel 1 satellite in its standard acquisition mode terrain observation by progressive scans tops which differs from that of previous synthetic aperture radar sar missions we perform a bayesian inversion of sentinel 1 tops sar interferograms spanning the eruption and accurately account for variations in the tops line of sight vector when modeling displacements our results show that magma ascended beneath the pico do fogo cone and then moved laterally toward its southwestern flank where the eruptive fissure opened this study provides important insights into the inner workings of fogo volcano and shows the potential of sentinel 1 tops interferometry for geophysical e g volcano monitoring applications

investigating collapse structures in oceanic islands using magnetotelluric surveys the case of fogo island in cape verde abstract one of the most remarkable natural events on earth are the large lateral flank collapses of oceanic volcanoes involving volumes of rock exceeding tens of km3 these collapses are relatively frequent in recent geological times as supported by evidence found in the geomorphology of volcanic island edifices and associated debris flows deposited on the proximal ocean floor the island of fogo in the cape verde archipelago is one of the most active and prominent oceanic volcanoes on earth the island has an average diameter of 25 km and reaches a maximum elevation of 2829 m above sea level m a s l at pico do fogo a young stratovolcano located within a summit depression open eastward due to a large lateral flank collapse the sudden collapse of the eastern flank of fogo island produced a megatsunami 73 ky ago the limits of the flank collapse were deduced as well from geomorphologic markers within the island the headwall of the collapse scar is interpreted as either being located beneath the post collapse volcanic infill of the summit depression or located further west corresponding to the bordeira wall that partially surrounds it the magnetotelluric mt method provides a depth distribution of the ground resistivity obtained by the simultaneous measurement of the natural variations of the electric and magnetic field of the earth two n s magnetotelluric profiles were acquired across the collapsed area to determine its geometry and boundaries the acquired mt data allowed the determination of the limits of the collapsed area more accurately as well as its morphology at depth and thickness of the post collapse infill according to the newly obtained mt data and the bathymetry of the eastern submarine flank of fogo the volume involved in the flank collapse is estimated in 110 km3 this volume the first calculated onshore stands between the previously published more conservative and excessive calculations offshore that were exclusively based in geomorphic evidence the model for the summit depression proposing two caldera collapses preceding the collapse of the eastern flank of fogo is supported by the mt data

high resolution structures of the landers fault zone inferred from aftershock waveform data summary high frequency body waves recorded by a temporary seismic array across the surface rupture trace of the 1992 landers california earthquake were used to determine fault zone structures down to the seismogenic depth we first developed a technique to use generalized ray theory to compute synthetic seismograms for arbitrarily oriented tabular low velocity fault zone models we then generated synthetic waveform record sections of a linear array across a vertical fault zone they show that both arrival times and waveforms of p and s waves vary systematically across the fault due to transmissions and reflections from boundaries of the low velocity fault zone the waveform characteristics and arrival time patterns in the record sections allow us to locate the boundaries of the fault zone and to determine its p and s wave velocities independently as well as its depth extent therefore the trade off between the fault zone width and velocities can be avoided applying the method to the landers waveform data reveals a low velocity zone with a width of 270 360 m and a 35 60 per cent reduction in p and s velocities relative to the host rock the analysis suggests that the low velocity zone extends to a depth of 7 km the western boundary of the low velocity zone coincides with the observed main surface rupture trace

a network based enhanced spectral diversity approach for tops time series analysis for multitemporal analysis of synthetic aperture radar sar images acquired with a terrain observation by progressive scan tops mode all acquisitions from a given satellite track must be coregistered to a reference coordinate system with accuracies better than 0 001 of a pixel assuming full sar resolution in the azimuth direction such a high accuracy can be achieved through geometric coregistration using precise satellite orbits and a digital elevation model followed by a refinement step using a time series analysis of coregistration errors these errors represent the misregistration between all tops acquisitions relative to the reference coordinate system we develop a workflow to estimate the time series of azimuth misregistration using a network based enhanced spectral diversity nesd approach in order to reduce the impact of temporal decorrelation on coregistration example time series of misregistration inferred for five tracks of sentinel 1 tops acquisitions indicates a maximum relative azimuth misregistration of less than 0 01 of the full azimuth resolution between the tops acquisitions in the studied areas standard deviation of the estimated misregistration time series for different stacks varies from 1 1e 3 to 2e 3 of the azimuth resolution equivalent to 1 6 2 8 cm orbital uncertainty in the azimuth direction these values fall within the 1 sigma orbital uncertainty of the sentinel 1 orbits and imply that orbital uncertainty is most likely the main source of the constant azimuth misregistration between different tops acquisitions we propagate the uncertainty of individual misregistration estimated with esd to the misregistration time series estimated with nesd and investigate the different challenges for operationalizing nesd

tectonic and anthropogenic deformation at the cerro prieto geothermal step over revealed by sentinel 1a insar the cerro prieto geothermal field cpgf lies at the step over between the imperial and the cerro prieto faults in northern baja california mexico while tectonically this is the most active section of the southern san andreas fault system the spatial and temporal deformation in the area is poorly resolved by the sparse global positioning system gps network coverage moreover interferograms from satellite observations spanning more than a few months are decorrelated due to the extensive agricultural activity in this region here we investigate the use of frequent short temporal baseline interferograms offered by the new sentinel 1a satellite to recover two components of deformation time series across these faults following previous studies we developed a purely geometric approach for image alignment that achieves better than 1 200 pixel alignment needed for accurate phase recovery we construct interferometric synthetic aperture radar time series using a coherence based small baseline subset method with atmospheric corrections by means of common point stacking we did not apply enhanced spectral diversity because the burst discontinuities are generally small 1 4 mm and can be effectively captured during the atmospheric corrections with these algorithms the subsidence at cpgf is clearly resolved the maximum subsidence rate of 160 mm yr due to extraction of geothermal fluids and heat dominates the 40 mm yr deformation across the proximal ends of the imperial the cerro prieto and the indiviso faults

the spectrum of persistent volcanic flank instability a review and proposed framework based on kīlauea piton de la fournaise and etna abstract persistent motion of the south flank of k lauea volcano hawai i has been known for several decades but has only recently been identified at other large basaltic volcanoes namely piton de la fournaise la reunion and etna sicily thanks to the advent of space geodetic techniques nevertheless understanding of long term flank instability is based largely on the example of k lauea despite the large differences in the manifestations and mechanisms of the process when viewed through a comparative lens for example the rate of flank motion at k lauea is several times that of etna and piton de la fournaise and is accommodated on a slip plane several km deeper than is probably present at the other two volcanoes gravitational spreading also appears to be the dominant driving force at k lauea given the long term steady motion of the volcano s south flank regardless of eruptive intrusive activity whereas magmatic activity plays a larger role in flank deformation at etna and piton de la fournaise k lauea and etna however are both characterized by heavily faulted flanks while piton de la fournaise shows little evidence for flank faulting a helpful means of understanding the spectrum of persistent flank motion at large basaltic edifices may be through a framework defined on one hand by magmatic activity which encompasses both magma supply and edifice size and on the other hand by the structural setting of the volcano especially the characteristics of the subvolcanic basement or subhorizontal intravolcanic weak zones a volcano s size and magmatic activity will dictate the extent to which gravitational and magmatic forces can drive motion of an unstable flank and possibly the level of faulting of that flank while the volcano s structural setting governs whether or not a plane of weakness exists beneath or within the edifice and can facilitate flank slip considering persistent flank instability using this conceptual model is an alternative to using a single volcano as a type example especially given that the example is usually k lauea which defines an extreme end of the spectrum and can provide a basis for understanding why flank motion may or may not exist on other large basaltic volcanoes worldwide

coseismic deformation from the 1999 mw 7 1 hector mine california earthquake as inferred from insar and gps observations we use interferometric synthetic aperture radar insar and global positioning system gps observations to investigate static deformation due to the 1999 m w 7 1 hector mine earthquake that occurred in the eastern california shear zone interferometric decorrelation phase and azimuth offset measurements indicate regions of surface and near surface slip which we use to constrain the geometry of surface rupture the inferred geometry is spatially complex with multiple strands the southern third of the rupture zone consists of three subparallel segments extending about 20 km in length in a n45 w direction the central segment is the simplest with a single strand crossing the bullion mountains and a strike of n10 w the northern third of the rupture zone is characterized by multiple splays with directions subparallel to strikes in the southern and central the average strike for the entire rupture is about n30 w the interferograms indicate significant along strike variations in strain which are consistent with variations in the ground based slip measurements using a variable resolution data sampling routine to reduce the computational burden we invert the insar and gps data for the fault geometry and distribution of slip we compare results from assuming an elastic half space and a layered elastic space results from these two elastic models are similar although the layered space model predicts more slip at depth than does the half space model the layered model predicts a maximum coseismic slip of more than 5 m at a depth of 3 to 6 km contrary to preliminary reports the northern part of the hector mine rupture accommodates the maximum slip our model predictions for the surface fault offset and total seismic moment agree with both field mapping results and recent seismic models the inferred shallow slip deficit is enigmatic and may suggest that distributed inelastic yielding occurred in the uppermost few kilometers of the crust during or soon after the earthquake

insar observations of the 1995 fogo cape verde eruption implications for the effects of collapse events upon island volcanoes 1 fogo volcano cape verde islands erupted in april 1995 after 43 years of dormancy about 46 106 m3 of lava erupted during 7 5 weeks from vents on the sw flank of pico do fogo into cha das caldeiras interferograms obtained from 1993 1998 ers sar data show ground deformation due to the feeder dike but lack evidence for any volcano wide deformation related to volume changes of a shallow magma reservoir this suggests that fogo is fed from a relatively deep mantle lithospheric source 16 5 km depth consistent with petrological data this supports the concept that cha das caldeiras is the fill of a collapse scar created by a giant landslide and not a collapse caldera overlying a central shallow magma chamber the disturbance of the magmatic system by giant landslides may explain why some oceanic island volcanoes with high magma supply rates currently lack well developed shallow reservoirs

can seismic waves be trapped inside an inactive fault zone the case study of nocera umbra central italy in march 1998 a small aperture 350 m linear array of five broadband stations was installed across a pliocene strike slip fault crossing the town of nocera umbra central italy three component seismograms of local earthquakes recorded during the umbria marche seismic sequence have shown that the degradation of mechanical properties in damaged rock causes a significant amplification of ground motion within the fault zone marra et al 2000 during the operation of the array an m w 5 3 subcrustal earthquake occurred at a depth of 48 km and an epicentral distance of 10 km from nocera umbra the near vertical incidence of this event offers a unique opportunity for constraining the 2d geometry of the laterally heterogeneous low velocity structure responsible for the large amplification across the fault based on the observed symmetry of the amplification pattern a 2d wedge shaped model of the fault zone is used for the computation of antiplane sh synthetic waveforms to be compared with observations along the array two parameters of the wedge model can be constrained by independent geophysical and geological data 1 shear wave velocity in pristine rock outside the fault zone v s 2200 m sec and 2 the lateral extent of the damaged rock zone l 160 m the other two model parameters namely the wedge depth h and shear wave velocity of the fault zone v f s are varied computer simulations show that trapped waves which have been observed so far for earthquakes occurring inside the fault zone can develop inside a 2d wedge model when struck by external vertically incident seismic radiation results of numerical modeling indicate that in spite of its extreme simplicity such an idealized model is successful in reproducing many of the essential characters of ground motion within the fault zone of nocera umbra even though the best fit solution is not unique and the model parameters trade off each other a study of parameter sensitivity comparing synthetics with recorded data indicates that the variability of h and v f s can be restricted to a limited range of values the quality of fit is optimal when the shear velocity reduction lies in the range of 40 50 and the depth of the trapping zone is comprised between 1 and 2 km

high resolution surface velocities and strain for anatolia from sentinel 1 insar and gnss data measurements of present day surface deformation are essential for the assessment of long term seismic hazard the european space agency s sentinel 1 satellites enable global high resolution observation of crustal motion from interferometric synthetic aperture radar insar we have developed automated insar processing systems that exploit the first 5 years of sentinel 1 data to measure surface motions for the 800 000 km2 anatolian region our new 3d velocity and strain rate fields illuminate deformation patterns dominated by westward motion of anatolia relative to eurasia localized strain accumulation along the north and east anatolian faults and rapid vertical signals associated with anthropogenic activities and to a lesser extent extension across the grabens of western anatolia we show that automatically processed sentinel 1 insar data can characterize details of the velocity and strain rate fields with high resolution and accuracy over large regions these results are important for assessing the relationship between strain accumulation and release in earthquakes