ionospheric gnss imagery of seismic source possibilities difficulties and challenges up to now the possibility to obtain images of seismic source from ionospheric global navigation satellite systems gnss measurements seismo ionospheric imagery has only been demonstrated for giant earthquakes with moment magnitude mw 9 0 in this work we discuss difficulties and restrictions of this method and we apply for the first time the seismo ionospheric imagery for smaller earthquakes the latter is done on the example of the mw7 4 sanriku oki earthquake of 9 march 2011 analysis of 1 hz data of total electron content tec shows that the first coseismic ionospheric disturbances cid occur 470 480 s after the earthquake as tec enhancement on the east northeast from the epicenter the location of these first cid arrivals corresponds to the location of the coseismic uplift that is known as the source of tsunamis our results confirm that despite several difficulties and limitations high rate ionospheric gnss data can be used for determining the seismic source parameters for both giant and smaller moderate earthquakes in addition to these seismo ionospheric applications we raise several fundamental questions on cid nature and evolution namely one of the most challenging queries can moderate earthquake generate shock acoustic waves plain language summary ionosphere is a layer of charged particles of the earth s atmosphere located at altitudes 60 800 km however despite being high above the earth s surface the ionosphere is sensible to numerous near ground geophysical events earthquakes tsunamis volcano eruptions etc acoustic and gravity waves emitted by these events propagate upward and generate atmospheric ionospheric perturbations ionospheric disturbances generated by earthquakes are known as coseismic ionospheric disturbances cid recently it has been suggested that analysis of cid and their first arrivals can provide information on the position and on the structure of seismic fault ruptured in earthquake this method is known as ionospheric imagery of seismic source however so far this method has been only applied to giant earthquakes mw 9 0 in this work for the first time we apply the ionospheric imagery for smaller earthquakes on the example of the m7 4 sanriku oki earthquake that occurred on 9 march 2011 in japan our results show that this method is applicable to smaller earthquakes and despite some difficulties it can indicate the position of coseismic uplift 8 min after the earthquake the uplift generates cid but also tsunamis therefore our method can be used as independent or complementary one for near real time tsunami warning systems

two mode ionospheric response and rayleigh wave group velocity distribution reckoned from gps measurement following mw 7 8 nepal earthquake on 25 april 2015 the coseismic induced ionospheric total electron content tec perturbations were analyzed following the mw 7 8 nepal earthquake 28 147 n 84 708 e depth 15 km that occurred on 25 april 2015 at 06 11 26 utc the ionospheric response is due to both the modes i e shock acoustic waves slow mode and rayleigh wave induced fast mode the continuous global positioning system gps data at about 60 sites from various gps networks have been used in the present study all the sites within epicentral distance of 2400 km and 70 170 azimuth recorded the rayleigh wave induced tec response while the sites within 400 2200 km in the same azimuth recorded the response from both the modes the maximum coseismic induced peak to peak tec amplitude is 1 2 total electron content unit 1 tecu 1016 el m 2 from hodochron plot the apparent rayleigh wave velocity has been determined as 2400 m s on the average and the acoustic wave velocity as 1180 m s both these waves being discernible beyond 1200 km of epicentral distance as also evident from hodochron plot and wavelet spectrographs we reckoned the rayleigh wave group velocities using ionospheric response at selected radial pairs of stations and validated the ionospheric response distribution seen mainly depending on the epicentral distance satellite geometry directivity of radiation pattern and the upper crustal heterogeneity this study highlights the characteristics of ionospheric response consequent to the 2015 nepal earthquake

geomorphometric analysis of the 2014 2015 barðarbunga volcanic eruption iceland abstract topographical information is of fundamental interest for a wide range of disciplines including glaciology agriculture communication network planning or hazard management in volcanology elevation data are of particular importance when assessing material flows throughout a volcanic system to obtain accurate estimates of time varying topography in volcanic active regions high resolution digital elevation models dems are required to monitor and evaluate topographical changes and especially volumetric gains and losses during the 2014 2015 bar arbunga eruption iceland multi temporal tandem x dem sequences were evaluated the 2014 2015 volcanic eruption was associated with the rare event of a caldera collapse visible on the surface of the vatnajokull glacier as well as major lava effusion in the holuhraun plain before investigating topographical change at the two study areas the tandem x dems were analysed for absolute and relative height errors resulting from the radar system parameters the sar processing or the local environment the uncertainty investigation determined that acquisitions over the snow covered bar arbunga caldera were primarily affected by microwave penetration into snow and dems over the holuhraun lava field exhibited increased height errors due to active lava flows and dynamic outwash plain the topographical analysis of the 2014 2015 bar arbunga eruption revealed a maximum vertical displacement of approximately 65 m and 43 m at the study area of the bar arbunga caldera and holuhraun lava field respectively with a total subsidence volume of 1 40 0 13 km3 and a dense rock equivalent dre lava volume of 1 36 0 07 km3 known uncertainties in volume were decreased by approximately 35 and 77 accordingly taking into account the calculation of rates the temporal development of caldera collapse and lava effusion was found to exhibit a near exponential decrease the ratio between subsidence and dre lava volume moreover indicated the coupling between piston collapse and magma drainage

basaltic calderas collapse dynamics edifice deformation and variations of magma withdrawal 1 the incremental caldera collapses of fernandina 1968 miyakejima 2000 and piton de la fournaise 2007 are analyzed in order to understand the collapse dynamics in basaltic setting and the associated edifice deformation for each caldera the collapse dynamics is assessed through the evolution of the 1 time interval t between two successive collapse increments 2 amount of vertical displacement during each collapse increment and 3 magma outflow rate during the whole collapse caldera process we show from the evolution of t that piton de la fournaise and fernandina were characterized by a similar collapse dynamics despite large differences in the caldera geometry and the duration of the whole collapse caldera process this evolution significantly differs from that of miyakejima where t strongly fluctuated throughout the whole collapse process quantification of the piston vertical displacements enables us to determine the magma outflow rates between each collapse increment displacement data tiltmeter and or gps for piton de la fournaise and miyakejima are used to constrain the edifice overall deformation and the edifice deformation rates these data reveal that both volcanoes experienced edifice inflation once the piston collapsed into the magma chamber such a deformation which lasts during the first collapse increments only is interpreted as the result of larger volume of piston intruded in the magma chamber than magma withdrawn before each collapse increment once the effect of the collapsing rock column vanishes edifice deflates we also determine for each caldera the critical amount of magma evacuated before collapse initiation and compare it to analog models the significant differences between models and nature are explained by the occurrence of preexisting weak zones in nature i e the ring faults that are not taken into account in analog models finally we show that t at piton de la fournaise and fernandina was equally controlled by the frictional resistance along the ring faults and the magma outflow rate in addition to these two parameters the collapse dynamics of miyakejima was also influenced by variations of the magma bulk modulus which changed after the influx of deep gas rich magma into the collapse related magma chamber altogether our results show that the dynamics of caldera collapse in basaltic volcanoes proceeds in two phases phase 1 starting with the first collapse is characterized by the largest collapse amplitude an incremental edifice inflation and a step by step increase of the rate of magma outflow phase 2 shows a rapid decrease of the magma discharge rate to a low level concomitant with the continuous edifice deflation if deep magma is injected into the magma chamber as at miyakejima an additional phase occurs phase 3

directivity and apparent velocity of the coseismic ionospheric disturbances observed with a dense gps array abstract coseismic disturbances in ionosphere have been observed after recent thrust earthquakes off the pacific coast of japan with a dense global positioning system array positive pulses in electron content as large as several times 10 15 electrons m 2 and as long as 4 5 min emerge 10 min after earthquakes and propagate horizontally with apparent velocity of 1 km s close to the sound velocity at the ionospheric height they may have been excited by coseismic uplifts of the sea surface initially as upward propagating compressive pulses of atmosphere which were gradually refracted to propagate horizontally in ionosphere the propagation has strong north south asymmetry and interaction between the movements of charged particles in acoustic waves and geomagnetic fields might have selectively attenuated the northward propagating disturbances

static and dynamic angles of repose in loose granular materials under reduced gravity granular materials avalanche when a static angle of repose is exceeded and freeze at a dynamic angle of repose such avalanches occur subaerially on steep hillslopes and wind dunes and subaqueously at the lee side of deltas until now it has been assumed that the angles of repose are independent of gravitational acceleration the objective of this work is to experimentally determine whether the angles of repose depend on gravity in 33 parabolic flights in a well controlled research aircraft we recorded avalanching granular materials in rotating drums at effective gravitational accelerations of 0 1 0 38 and 1 0 times the terrestrial value the granular materials varied in particle size and rounding and had air or water as interstitial fluid materials with angular grains had time averaged angles of about 40 and with rounded grains about 25 for all effective gravitational accelerations except the finest glass beads in air which was explained by static electricity for all materials the static angle of repose increases about 5 with reduced gravity whereas the dynamic angle decreases with about 10 consequently the avalanche size increases with reduced gravity the experimental results suggest that relatively low slopes of granular material on mars may have formed by dry flows without a lubricating fluid on asteroids even lower slopes are expected the dependence on gravity of angle of repose may require reanalysis of models for many phenomena involving sediment also at much lower slope angles

how the development of magma chambers affects collapse calderas insights from an overview here we review the studies of pluton emplacement and caldera collapse proposing a model linking the two processes the shallow rise of magma occurs by dyking and its emplacement occurs along major anisotropies many plutons are emplaced at subhorizontal discontinuities forming sills these will eventually grow forming laccoliths the most common mechanism to store shallow magma calderas are a surface expression of these reservoirs and can be approximated by a piston cylinder which sinks due to 1 underpressure in the reservoir producing outward dipping reverse faults 2 overpressure within a silllike chamber undergoing doming and 3 overpressure within a laccolith generating apical tensile stresses in the latter two cases inward dipping normal faults form we suggest that collapse calderas are the surface expression of pressure variations within laccoliths or tabular intrusions their geometric relationships depend on the shape and aspect ratio of the intrusion and its pressure conditions tabular intrusions generating ring faults mainly at their tips form calderas with a similar width to the intrusion laccoliths may generate ring faults along the intrusion roof forming calderas narrower than the intrusion the outward or inward dip of the caldera faults results from the underpressure or overpressure conditions within the

volcanic and hydrothermal processes in submarine calderas the kulo lasi example sw pacific abstract the study area is located at the transition between the northern end of the tonga trench and the north fiji fracture zone where tectonic movements are reputed to be the fastest in the world to the southeast of futuna island a broad area of volcanism occurs within a region characterized by a change in the tectonic fabric between a ne sw oriented volcanic graben and the n s oriented alofi ridge in 2010 the active volcano kulo lasi which represents the most recent volcanic episode in the futuna area was discovered in the center of this extensive volcanic zone kulo lasi is a 20 km diameter shield volcano that rises 400 m above the seafloor it is composed of basaltic to trachy andesitic lava with no obvious geochemical affinity with the tonga subduction that occurs 500 km to the east the central caldera is 5 km in diameter and 300 m deep and is located at a water depth of 1500 m diving operations with the submersible nautile and high resolution auv mapping have revealed the presence of numerous active and inactive hydrothermal fields on the floor and the walls of the caldera four tectono volcanic stages can be distinguished at kulo lasi caldera in stage 1 the shield volcano is built annular reverse faults develop at the summit and control circulation of water rock dominated hydrothermal fluids and high temperature alteration of rocks along the nascent normal faults mixing of hydrothermal fluids with seawater is favored along normal superficial faults leading to the formation of low temperature fe mn mineralization at the summit of the volcano during stage 2 the caldera collapse gradually revealing outcrops of the altered and mineralized zones formed during stage 1 as the magma chamber cools and collapses less heat is available as a result medium to low temperature

ionospheric response to infrasonic acoustic waves generated by natural hazard events recent measurements of gps derived total electron content tec reveal acoustic wave periods of 1 4 min in the f region ionosphere following natural hazard events such as earthquakes severe weather and volcanoes here we simulate the ionospheric responses to infrasonic acoustic waves generated by vertical accelerations at the earth s surface or within the lower atmosphere using a compressible atmospheric dynamics model to perturb a multifluid ionospheric model response dependencies on wave source geometry and spectrum are investigated at middle low and equatorial latitudes results suggest constraints on wave amplitudes that are consistent with observations and that provide insight on the geographical variability of tec signatures and their dependence on the geometry of wave velocity field perturbations relative to the ambient geomagnetic field asymmetries of responses poleward and equatorward from the wave sources indicate that electron perturbations are enhanced on the equatorward side while field aligned currents are driven principally on the poleward side due to alignments of acoustic wave velocities parallel and perpendicular to field lines respectively acoustic wave driven tec perturbations are shown to have periods of 3 4 min which are consistent with the fraction of the spectrum that remains following strong dissipation throughout the thermosphere furthermore thermospheric acoustic waves couple with ion sound waves throughout the f region and topside ionosphere driving plasma disturbances with similar periods and faster phase speeds the associated magnetic perturbations of the simulated waves are calculated to be observable and may provide new observational insight in addition to that provided by gps tec measurements

scaling and reproducibility of craters produced at the experimental projectile impact chamber epic centro de astrobiologia spain the experimental projectile impact chamber epic is a specially designed facility for the study of processes related to wet target e g marine impacts it consists of a 7 m wide funnel shaped test bed and a 20 5 mm caliber compressed n2 gas gun the target can be unconsolidated or liquid the gas gun can launch 20 mm projectiles of various solid materials under ambient atmospheric pressure and at various angles from the horizontal to test the functionality and quality of obtained results by epic impacts were performed into dry beach sand targets with two different projectile materials ceramic al2o3 max velocity 290 m s 1 and delrin max velocity 410 m s 1 23 shots used a quarter space setting 19 normal 4 at 53 from horizontal and 14 were in a half space setting 13 normal 1 at 53 the experiments were compared with numerical simulations using the isale code differences were seen between the nondisruptive al2o3 ceramic and the disruptive delrin polymer projectiles in transient crater development all final crater dimensions when plotted in scaled form agree reasonably well with the results of other studies of impacts into granular materials we also successfully validated numerical models of vertical and oblique impacts in sand against the experimental results as well as demonstrated that the epic quarter space experiments are a reasonable approximation for half space experiments altogether the combined evaluation of experiments and numerical simulations support the usefulness of the epic in impact cratering studies

stability and instability of quiescently active volcanoes the case of masaya nicaragua quiescently active volcanoes are enigmatic due to their restlessness but lack of eruptive activity i present a model of coupled conduit convection and foam accumulation to explain degassing behavior of masaya an active volcano in nicaragua that is currently emitting large amounts of gas but not erupting gas rich magma is transported through a conduit 2 6 m in radius and then released into a shallow reservoir the magma is degassed in the reservoir and forms a foam 1 3 m thick at the top with bubbles 20 60 m in diameter the foam layer is stable because the input of gas into the foam is balanced by gas release through a vent to the surface if the foam layer is destabilized the volcano can erupt explosively the most likely cause of foam destabilization is a large injection of volatile rich magma from deeper levels into the shallow conduit reservoir system thereby increasing magma fluxes and gas fluxes exsolving large gas bubbles and reducing surface tension of the magma

ionospheric remote sensing of the denali earthquake rayleigh surface waves 1 using the global positioning system we have detected ionospheric disturbances associated with the long period rayleigh waves from the 2002 denali earthquake ms 7 9 the dense california gps networks allowed us to map the ionospheric perturbations and to compute the group velocity with a high spatial resolution above the pacific coasts due to a low sampling rate a large error in the velocity determination remains nonetheless it demonstrates that bi static remote sensing measurements of seismic waves with gps networks can be performed monostatic measurements with a dedicated satellite could possibly be used to record in the ionosphere surface waves originating from large earthquakes such a space based remote sensing of the local group velocity of rayleigh surface waves would effectively complement the seismic networks for high resolution global tomography of the earth s lithosphere

magma chamber volume changes associated with ring fault initiation using a finite sphere model application to the aira caldera japan abstract we have derived an analytical solution expressing the magma chamber volume change required for ring fault caldera initiation in terms of a finite sphere model we consider the conditions by which magma chamber contraction volume reduction could contribute to the initiation of a ring fault at the surface above the chamber using the elastic plastic theory of host rock behaviour the model does not consider underpressure pressure less than lithostatic in the chamber but only magma chamber volume reduction or shrinkage the model is heuristic in the sense that we do not explore the detailed mechanical condition for the volume reduction apart from its being related to magma flow out of the chamber but rather focus on the consequences of the reduction for ring fault initiation and dip the solution obtained for the finite sphere model consists of a leading term that is proportional to the cube of the magma chamber depth and a second term that is proportional to the cube of the magma chamber radius the second term reflects explicitly the effects of a finite source radius whereas the first term corresponds to a solution for a point source model this follows because in a point source model the magma chamber radius is zero so that the second term drops out the equation that plays the key role in obtaining this solution is a linear function relating the radius of the caldera to the magma chamber depth the proportionality coefficient of this equation is dimensionless and depends not only on the elastic constants of the medium but also on the depth d and radius a of the magma chamber given by e a d in addition because this coefficient controls a geometric parameter related to the overall form of the ring fault our results indicate that the ring fault shape and size is decided by the magma chamber depth and size as well as by the host rock elastic properties and angle of internal friction the results indicate that the associated ring fault is inward dipping and that the magma chamber radius can be estimated from the fault radius and dip we applied the analytical solution to the ring fault of the aira caldera in southern kyushu japan the calculations indicate that the aira ring fault could have been initiated at the surface as a result of 2 8 reduction in the volume of a magma chamber with a radius of 4 7 km and at a depth of 9 1 km these results agree with independent information on the aira magma chamber we conclude that the present solution yields useful first order information on magma chambers associated with ring faults

nonlinear ionospheric responses to large amplitude infrasonic acoustic waves generated by undersea earthquakes numerical models of ionospheric coupling with the neutral atmosphere are used to investigate perturbations of plasma density vertically integrated total electron content tec neutral velocity and neutral temperature associated with large amplitude acoustic waves generated by the initial ocean surface displacements from strong undersea earthquakes a simplified source model for the 2011 tohoku earthquake is constructed from estimates of initial ocean surface responses to approximate the vertical motions over realistic spatial and temporal scales resulting tec perturbations from modeling case studies appear consistent with observational data reproducing pronounced tec depletions which are shown to be a consequence of the impacts of nonlinear dissipating acoustic waves thermospheric acoustic compressional velocities are 250 300 m s superposed with downward flows of similar amplitudes and temperature perturbations are 300 k while the dominant wave periodicity in the thermosphere is 3 4 min results capture acoustic wave processes including reflection onset of resonance and nonlinear steepening and dissipation ultimately leading to the formation of ionospheric tec depletions holes that are consistent with reported observations three additional simulations illustrate the dependence of atmospheric acoustic wave and subsequent ionospheric responses on the surface displacement amplitude which is varied from the tohoku case study by factors of 1 100 1 10 and 2 collectively results suggest that tec depletions may only accompany very large amplitude thermospheric acoustic waves necessary to induce a nonlinear response here with saturated compressional velocities 200 250 m s generated by sea surface displacements exceeding 1 m occurring over a 3 min time period

conceptual and numerical models of ring fault formation abstract most ring faults of collapse calderas are primarily shear fractures the initiation and development of which depends on the state of stress in the host rock the state of stress in a volcano is controlled by the loading conditions such as magma chamber geometry and pressure but also by the mechanical properties of its rock units and structures such as existing contacts faults and joints ring fault formation is thus essentially a problem in rock physics field observations show that some ring faults are dip slip whereas others are partly faults shear fractures and partly ring dykes extension fractures although slip on existing ring faults is much more common in basaltic edifices shield volcanoes than in true composite volcanoes in both types of volcanoes most caldera unrest periods do not result in ring fault slip here i present new conceptual and numerical models of caldera formation in volcanoes with shallow spherical circular or oblate ellipsoidal sill like magma chambers in the layered models the host rock above the chamber is composed of 30 comparatively thin layers with stiffnesses young s moduli alternating between 1 gpa and 100 gpa the chamber itself is located in a single thick layer the crustal segment hosting the chamber is either 20 km or 40 km wide but has a constant thickness of 20 km the loading conditions considered are 1 a crustal segment subject to 5 mpa tension 2 crustal segment subject to excess magmatic pressure of 10 mpa at the bottom doming of the volcanic field containing the chamber 3 a combination of tension and doming and 4 chamber subject to underpressure negative excess pressure of 5 mpa the main results are as follows 1 excess pressure and underpressure in a chamber normally favour dyke injection rather than ring fault formation 2 for doming or tension a spherical magma chamber favours dyke injection except when the layer hosting the chamber is very soft 10 gpa or one with recent dyke injections in which case the surface stress field favours ring fault formation 3 for a sill like chamber in a 20 km wide crustal segment a ring fault can be generated by either tension or tension and doming for a 40 km wide segment doming alone is sufficient to generate a ring fault 4 since individual layers in a volcano may develop different local stresses stress field homogenisation through all the layers between the chamber and the surface is a necessary condition for ring fault formation 5 because the mechanical properties of the layers that constitute basaltic edifices are more uniform than those that constitute true composite volcanoes it follows that stress field homogenisation and thus ring fault formation or slip is more commonly reached in basaltic edifices than in composite volcanoes 6 both for basaltic edifices and composite volcanoes the stress fields most likely to initiate ring faults are those generated around sill like chambers subject to tension doming or both

the new worldwide collapse caldera database ccdb a tool for studying and understanding caldera processes collapse calderas are one of the most important volcanic structures not only because of their hazard implications but also because of their high geothermal energy potential and their association with mineral deposits of economic interest the objective of this work is to describe a new general worldwide collapse caldera database ccdb in order to provide a useful and accessible tool for studying and understanding caldera collapse processes the principal aim of the ccdb is to update the current field based knowledge on calderas merging together the existing databases and complementing them with new examples found in the bibliography and leaving it open for the incorporation of new data from future studies this database does not include all the calderas of the world but it tries to be representative enough to promote further studies and analyses we have performed a comprehensive compilation of published field studies of collapse calderas including more than 200 references and their information has been summarized in a database linked to a geographical information system gis application thus it is possible to visualize the selected calderas on a world map and to filter them according to different features recorded in the database e g age structure the information recorded in the ccdb can be grouped in seven main information classes caldera features properties of the caldera forming deposits magmatic system geodynamic setting pre caldera volcanism caldera forming eruption sequence and post caldera activity additionally we have added two extra classes the first records the references consulted for each caldera the second allows users to introduce comments on the caldera sample such as possible controversies concerning the caldera origin a further purpose of this work is to construct the ccdb web page in this web page where registered users can acquire the current database version as well as to propose corrections or updates and to exchange information with other registered members also involved in the study of caldera collapse processes additionally the ccdb includes a formulary that will facilitate the incorporation of new calderas into the database

subaqueous calderas in the archean abitibi greenstone belt an overview and new ideas abstract the 300 700 km abitibi greenstone belt in canada contains numerous world class archean volcanogenic massive sulfide vms deposits yet documentation of archean subaqueous calderas hosting such deposits is lacking the modern sunrise deposit in the myojin knoll caldera of the izu bonin arc shows that submarine calderas are first order sites for vms the hunter mine and normetal calderas as well as the blake river megacaldera complex are reviewed with respect to geometry regional geology physical volcanology dyke emplacement and hydrothermal carbonate alteration these subaqueous calderas are placed into the geodynamic context of the abitibi greenstone belt the abitibi belt displays a complex history of oceanic arc formation evolution collision and fragmentation with numerous types of volcanic edifices and sedimentary basins controlled by oblique subduction and mantle plumes analogue models yielding new insights into the sequence of caldera forming events and their synvolcanic fault patterns are applied to explain archean examples underpressure experiments develop a consistent sequence of fault patterns that compare favourably with natural caldera events during subsidence two sets of faults propagate from the magma chamber margin 1 early reverse outward dipping faults and 2 normal inward dipping faults the largest massive sulfide deposits form preferentially at the caldera margin based on experimental studies and detailed facies mapping the hunter mine caldera is of the segmented piecemeal variety and the normetal caldera is akin to a piston structure the blake river megacaldera contains 1 the e w trending misema 2 the nw trending new senator and 3 the ne trending noranda calderas with the latter two being nested graben type calderas consistent with oblique archean subduction the poorly documented hydrothermal carbonate alteration is discussed and a new exploration model for calderas is presented the alteration study was evaluated at three levels microprobe analysis geochemical staining of drill core and whole rock analyses there were two principal stages of alteration related to vms formation an early silicification phase developed either at depth and or at the seawater interface whereby silicification was bedding parallel in fine grained volcaniclastic deposits near the water surface a pervasive and extensive semi conformable carbonate alteration zone with a discordant focused root zone along faults evolved subsequently three distinct carbonate pairings were observed 1 proximal siderite sideroplesite fe ankerite next to the vms deposit 2 an intermediate ankerite fe dolomite zone and 3 a distal calcite dolomite zone the carbonate phase is associated with the mineralizing event transitions between carbonate species are subtle and changes are indicated by mineral assemblage overlap the silica carbonate hydrothermal alteration pattern is a replacement product and is far more widespread than has been documented this alteration can be easily confused with primary carbonates and chemical precipitation deposits e g banded iron formation if detailed volcano sedimentary facies mapping with alteration has not been conducted and if outcrop is insufficient

sounding the plume of the 18 august 2000 eruption of miyakejima volcano japan using gps 1 we processed 79 days of gps data collected at four stations on miyakejima volcano japan before and during its eruption in 2000 this period includes a strong seismic swarm 27 june to 8 july followed by five eruptions 8 and 14 15 july 10 18 and 29 august surface motion is strong during the seismic swarm then remains almost steady during eruptions however during each eruption we found anomalous values of the lc ionosphere free double differences especially on 18 august with a peak of 0 6 cycles i e an apparent 290 mm increase of the satellite station range we cannot explain these anomalies by temporary ground displacements during the events instead we propose that they are due to path delay effects in the hot volcanic plume by adapting a seismic tomography algorithm the refractivity anomaly and the inferred temperature in the plume is mapped in time and space

discriminating the tectonic and non tectonic contributions in the ionospheric signature of the 2011 mw7 1 dip slip van earthquake eastern turkey 1 it has previously been suggested that ionospheric perturbations triggered by large dip slip earthquakes might offer additional source parameter information compared to the information gathered from land observations based on 3d modeling of gps and glonass derived total electron content signals recorded during the 2011 van earthquake thrust intra plate event mw 7 1 turkey we confirm that coseismic ionospheric signals do contain important information about the earthquake source namely its slip mode moreover we show that part of the ionospheric signal initial polarity and amplitude distribution is not related to the earthquake source but is instead controlled by the geomagnetic field and the geometry of the global navigation satellite system satellites constellation ignoring these non tectonic effects would lead to an incorrect description of the earthquake source thus our work emphasizes the added caution that should be used when analyzing ionospheric signals for earthquake source studies

efficiency of coseismic ionospheric perturbations in identifying crustal deformation pattern case study based on mw 7 3 may nepal 2015 earthquake the amplitude asymmetry and initial polarity of seismic induced ionospheric perturbations around the epicenter are considered to be important in providing information about the rupture propagation and related vertical surface deformation to comprehend this we study ionospheric perturbations related to the 12 may 2015 mw 7 3 nepal earthquake we model the coseismic slip associated with the event using the interferometric synthetic aperture radar derived surface deformation data the ionospheric perturbations associated with the obtained surface deformation are explained in terms of rupture propagation favorable geomagnetic field wave coupling and satellite geometry effects we discuss the effects of phase cancelation on the perturbation evolution for various receiver satellite line of sight configurations invoking an elementary version of satellite geometry factor the present study thus elucidates further the role of nontectonic forcing mechanisms while identifying ground source pattern using the associated ionospheric perturbations

coseismic contortion and coupled nocturnal ionospheric perturbations during 2016 kaikoura mw 7 8 new zealand earthquake

the spectrum of basaltic feeder systems from effusive lava eruption to explosive eruption at miyakejima volcano japan basaltic feeder systems exposed in the caldera wall of miyakejima volcano are classified into three groups 1 effusive feeders 2 moderately explosive feeders and 3 highly explosive feeders the surface deposits and feeder systems reveal a wide variation in the explosivity of the eruptions that produced them ranging from non explosive lava effusions to violent explosive eruptions despite the apparent lack of influence of external water effusive feeders are filled with coherent non fragmented intrusive rock indicating no significant fragmentation in the feeder system the other two types of feeder systems consist of a coherent dike in their deeper part and a pyroclastic fill in their uppermost part their uppermost parts show an upward flaring shape the transition from coherent intrusion to pyroclastic fill in the feeder systems suggests underground fragmentation of the rising magma the depth of the coherent pyroclastic transition is deeper 20 150 m in highly explosive feeders than in the moderately explosive feeders 20 m and coincides with the depth at which the system flares upwards presence of lithic fragments derived from the host rock in the products of the highly explosive feeder systems indicates the removal of the wall rock by explosive activity this observation suggests that the fragmentation of rising magma promoted the enlargement of the feeder systems to form their upward flaring shapes by mechanical erosion and wall collapse

mach number scaling of impact craters in unconsolidated granular materials abstract the formation of impact craters in unconsolidated granular materials is a topic of enduring interest in solid earth geophysics planetary science and several branches of engineering science in particular a general relationship between crater size impact parameters and target material properties is often sought this paper presents a new empirical relationship based on dimensional analysis and inspired by gas dynamic shock physics for the diameters of low and high speed impact craters in dry granular materials based on the hypothesis that surface gravity and shock wave phenomena primarily set crater size the final relationship involves the impacting object s kinetic energy and speed the target material s density angle of repose and sound speed and the gravitational acceleration at the impact location it is formulated in terms of a dimensionless crater diameter an algebraic combination of froude number mach number and the tangent of the target material s angle of repose using an analogy to gas dynamics and an empirical power law for the dependence of granular material sound speed on gravitational acceleration the coefficient of determination for the final fit is 0 969 based on experimental impact data from 325 individual impacts spanning parametric ranges of 400 in crater diameter 1010 in impact energy 500 in gravitational acceleration and 40 in target material density for two different angles of repose the final formula provides insight into how impact energy conversion depends on mach number and may be useful for predictive and forensic analysis of planetary impact craters and for granular flow code validation

ionospheric disturbances triggered by the 11 march 2011 m9 0 tohoku earthquake 1 an earthquake of magnitude 9 0 occurred near the east coast of honshu tohoku area japan producing overwhelming earth surface motions and inducing devastating tsunamis which then traveled into the ionosphere and significantly disturbed the electron density within it hereafter referred to as seismotraveling ionospheric disturbances stids the total electron content tec derived from nationwide gps receiving networks in japan and taiwan is employed to monitor stids triggered by seismic and tsunami waves of the tohoku earthquake the stids first appear as a disk shaped tec increase about 7 min after the earthquake occurrence centered at about 200 km east of the epicenter near the west edge of the japan trench fast propagating disturbances related to rayleigh waves quickly travel away from the epicenter along the main island of japan with a speed of 2 3 3 3 km s accompanied by sequences of concentric circular tec wavefronts and followed by circular ripples close to a tsunami speed of about 720 800 km h that travel away from the stid center these are the most remarkable stids ever observed where signatures of rayleigh waves tsunami waves etc simultaneously appear in the ionosphere

subsurface cyclic magma sill expansions in the 2000 miyakejima volcano eruption possibility of two phase flow oscillation 1 step like tilt changes were observed at intervals of dozens of hours during the caldera formation stage occurred during the 2000 miyakejima volcano eruption our analysis suggests that these tilt steps were caused by the cyclic expansion of a subsurface sill like magma plumbing system trending from se to nw of the volcano in the same period a caldera gradually grew at the summit area to a very large 1 6 km in diameter and 450 m in depth the source mechanism of these tilt steps is fairly well explained by a two phase flow instability called a pressure drop oscillation this model indicates that the gas phase capacity in the upper part of the conduit acts as a pump that controls the flux of two phase magma in the sill like reservoir caldera formation as well as magma uplift and descent in the conduit may reflect temporal changes in the intervals between tilt steps which are themselves proportional to the volume of this gas capacity

caldera faults capture and deflect inclined sheets an alternative mechanism of ring dike formation the subsurface structures of caldera ring faults are often inferred from numerical and analog models as well as from geophysical studies all of these inferred structures need to be compared with actual ring faults so as to test the model implications here we present field evidence of magma channeling into a caldera ring fault as exhibited at hafnarfjall a deeply eroded and well exposed 5 ma extinct volcano in western iceland at the time of collapse caldera formation over 200 m of vertical displacement was accommodated along a ring fault which is exceptionally well exposed at a depth of approximately 1 2 km below the original surface of the volcano there are abrupt changes in the ring fault attitude with depth but its overall dip is steeply inward several inclined sheets within the caldera became arrested at the ring fault other sheets became deflected up along the fault to form a multiple ring dike we present numerical models showing stress fields that encourage sheet deflection into the subvertical ring fault our findings provide an alternative mechanical explanation for magma channeling along caldera ring faults which is a process likely to be fundamental in controlling the location of post caldera volcanism

ionospheric response to earthquakes of different magnitudes larger quakes perturb the ionosphere stronger and longer recently it has been shown that the ionosphere is capable of showing images of seismic fault shortly after an earthquake this gives rise to the idea of retrieval of seismic information from ionospheric observations as the first step toward such inversion here we study distinctive features of ionospheric response to shallow earthquakes both submarine and inland of moment magnitudes mw7 2 9 1 using gps measurements of the ionospheric total electron content we show that 1 the amplitude of coseismic total electron content variations in the near field is larger after more powerful earthquakes and 2 stronger earthquakes m 7 9 are in general characterized by a longer negative phase in coseismic perturbations

gps detection of ionospheric perturbations following the january 17 1994 northridge earthquake sources such as atmospheric or buried explosions and shallow earthquakes producing strong vertical ground displacements are known to produce pressure waves that propagate at infrasonic speeds in the atmosphere at ionospheric altitudes low frequency acoustic waves are coupled to ionospheric gravity waves and induce variations in the ionospheric electron density using global positioning system gps data recorded by the permanent gps network operating in southern california we computed ionospheric electron content time series for several days preceding and following the january 17 1994 mw 6 7 northridge earthquake we observe an anomalous signal beginning several minutes after the earthquake with time delays that increase with distance from the epicenter the signal frequency and phase velocity are consistent with results from numerical models of atmospheric ionospheric acoustic gravity waves excited by seismic sources as well as previous electromagnetic sounding results we believe that these perturbations are caused by the ionospheric response to the strong ground displacement associated with the northridge earthquake

an active ring fault detected at tendurek volcano by using insar 1 although ring faults are present at many ancient deeply eroded volcanoes they have been detected at only very few modern volcanic centers at the so far little studied tendurek volcano in eastern turkey we generated an ascending and a descending insar time series of its surface displacement field for the period from 2003 to 2010 we detected a large 105 km2 region that underwent subsidence at the rate of 1 cm yr during this period source modeling results show that the observed signal fits best to simulations of a near horizontal contracting sill located at around 4 5 km below the volcano summit intriguingly the residual displacement velocity field contains a steep gradient that systematically follows a system of arcuate fractures visible on the volcano s midflanks rapideye satellite optical images show that this fracture system has deflected holocene lava flows thus indicating its presence for at least several millennia we interpret the arcuate fracture system as the surface expression of an inherited ring fault that has been slowly reactivated during the detected recent subsidence these results show that volcano ring faults may not only slip rapidly during eruptive or intrusive phases but also slowly during dormant phases

two mode long distance propagation of coseismic ionosphere disturbances 1 using gps total electron content tec measurements we analyzed ionosphere response to the great kurile earthquake of 4 october 1994 high spatial resolution of the japanese dense array of gps receivers geonet provided us the unique opportunity to observe the evolution of coseismic ionospheric disturbances cid which propagated for more than 1800 km away from the epicenter plotting a traveltime diagram for the cid and using an array processing technique within the approximation of a spherical cid wavefront we observed a phenomenon of cid separation into two modes and we found that characteristics of the cid depend on the distance from the epicenter the maximum of the cid amplitude was observed at 500 km from the epicenter within the first 600 700 km the cid propagation velocity was about 1 km s which is equal to the sound speed at the height of the ionospheric f layer starting from 600 to 700 km out from the epicenter the disturbance seems to divide into two separate perturbations with each propagating at a different velocity about 3 km s for the one and about 600 m s for the other apparently the tec response in the far field of the cid source is a mixture of signals that further splits into two modes because of the difference in their velocities our observations are in good agreement with the results of space time data processing in the approximation of a spherical wavefront of cid propagation

the november 2002 eruption at piton de la fournaise volcano la reunion island ground deformation seismicity and pit crater collapse an eruption on the eastern flank of piton de la fournaise volcano started on 16 november 2002 after 10 months of quiescence after a relatively constant level of activity during the first 13 days of the eruption lava discharge volcanic tremor and seismicity increased from 29 november to 3 december lava effusion suddenly ceased on 3 december while shallow earthquakes beneath the dolomieu summit crater were still recorded at a rate of about one per minute this unusual activity continued and increased in intensity over the next three weeks ending with the formation of a pit crater within dolomieu based on ground deformation measured by rapid static and continuous gps and an extensometer seismic data and lava effusion patterns the eruptive period is divided into five stages 1 slow summit inflation and sporadic seismicity 2 rapid summit inflation and a short seismic crisis 3 rapid flank inflation onset of summit deflation sporadic seismicity accompanied by stable effusion 4 flank inflation coupled with summit deflation intense seismicity and increased lava effusion and finally 5 little deflation intense shallow seismicity and the end of lava effusion we propose a model in which the pre intrusive inflation of stage 1 in the months preceding the eruption was caused by a magma body located near sea level the magma reservoir was the source of an intrusion rising under the summit during stage 2 in stage 3 the magma ponded at a shallow level in the edifice while the lateral injection of a radial dike reached the surface on the eastern flank of the basaltic volcano causing lava effusion pressure decrease in the magmatic plumbing system followed resulting in upward migration of a collapse front forming a subterranean column of debris by faulting and stoping this caused intense shallow seismicity increase in discharge of lava and volcanic tremor at the lateral vent in stage 4 and eventually the formation of a pit crater in stage 5

seismo ionospheric observations modeling and backprojection of the 2016 kaikōura earthquake we processed global navigation satellite system gnss time series data to extract total electron content tec perturbations of the ionosphere caused by the kaik ura earthquake we used ray based modeling to infer which part of the earth s surface coupled significant energy from the solid earth into the atmosphere we compared modeled tec data with the observed time series data and determined that significant coupling occurred north northeast of the initial slip this work corroborates existing analysis made with geodetic and interferometric synthetic aperture radar insar data the tec data suggested that the initial rupture coupled some energy into the atmosphere but later surface displacements 60 s after the initiation caused more significant ionospheric perturbations using an array of gnss stations we were able to track the moveout of the acoustic wave through the ionosphere we used a method commonly used in seismological studies called backprojection to estimate the location of the source of the tec perturbation on earth s surface this is the first time that this method has been applied to tec data and the results are promising the backprojection results are slightly shifted in space from the known area of maximum uplift and we attribute this small discrepancy to the fact that we did not account for horizontal winds in the atmosphere nor the 3d heterogeneity of the real atmosphere in the travel time modeling

searching for patterns in caldera unrest the ultimate goal of volcanology is forecasting eruptions this task is particularly challenging at calderas where unrest is frequent affects wider areas and its evidence is often masked by the activity of hydrothermal systems a recent study has compiled a database on caldera unrest derived from seismicity geodetic gravity and geochemical monitoring data at calderas worldwide from 1988 to 2014 here we exploit this database searching for the most recurring features of unrest and in turn its possible dynamics in particular we focus on a the duration of unrest at calderas b recurring patterns in unrest c unrest episodes culminating in eruptions including time or size predictability and a multivariate regression analysis our analysis indicates that pre eruptive unrest is shorter than non eruptive unrest particularly with open or semi open calderas calderas with mafic or mixed composition of past eruptive products or unrest driven by mafic magma conversely lack of data on pre eruptive unrest driven by felsic magma and or at felsic or plugged calderas prevents an analysis of these specific subsets in addition 72 of pre eruptive unrest lasts 10 months and shows high seismicity and degassing the remaining 28 a is essentially aseismic in calderas with open conduit 17 or b lasts between 10 and 18 months with seismicity and degassing constituting a longer duration tail of the pre eruptive unrest with seismicity and degassing 11 surface deformation is not always reliable to characterize pre eruptive unrest our analysis suggests that magma may withstand only a limited period of eruptability before becoming stored in the upper crust

surface displacements resulting from magma chamber roof subsidence with application to the 2014 2015 bardarbunga holuhraun volcanotectonic episode in iceland abstract the conditions which lead to caldera collapse are still poorly constrained as there have only been four possibly five well documented caldera forming events in the past century the geodetic signals produced during chamber roof subsidence or chamber volume reduction shrinkage in general are not well documented or understood in particular when two or more geodetic sources are operating and providing signals at the same time it is important to be able to estimate the likely contribution of each simultaneous activities of different geodetic sources are common and include pressure changes in magma chambers reservoirs occurring at the same time as dyke emplacement here we present results from numerical models designed to simulate the subsidence of a magma chamber roof either directly chamber shrinkage or through ring fault displacement and the induced surface deformation and crustal stresses we consider chamber depths at 3 km 5 km and 7 km below the crustal surface using both non layered isotropic and layered anisotropic crustal models we also model the effects of a caldera lake and of a thick ice cover ice sheet on top of the caldera the results suggest that magma chamber roof subsidences between 20 m and 100 m generate large tens of centimetres vertical and in particular horizontal displacements at the surfaces of the ice and the crust out to distances of up to tens of kilometres from the caldera chamber centre crustal layering tends to reduce but increasing chamber depth to enlarge the horizontal and vertical surface displacements applying the results to the ice subsidence in the bardarbunga caldera during the 2014 2015 bardarbunga holuhraun volcanotectonic episode indicates that the modelled ice displacements are less than those geodetically measured also the geodetically measured crustal displacements are less than expected for a 60 m chamber roof subsidence the modelling results thus suggest that only part of the ice subsidence is due to chamber roof subsidence the other part being related to flow in and down bending of the ice we show that such a flow is likely within the caldera as a result of the stress induced by the 45 km long regional dyke emplaced primarily in vertical magma flow during the episode this conclusion is further supported by the model results suggesting that the ring fault piston like displacements must have been much less than the total 60 m ice subsidence or else faults with tens of metres displacements would have cut through the ice these are not observed we suggest that the ring fault subsidence was triggered by small doming of the volcanic field and system hosting the bardarbunga caldera and that this doming occurred as a result of magma inflow and pressure increase in a deep seated reservoir the doming is confirmed by gps measurements and supported by the seismicity results the magmatic pressure increase in the reservoir was in terms of the present model responsible for the regional dyke emplacement the holuhraun eruption and part of the stress concentration around and displacement of the bardarbunga caldera

very long period seismic signals observed before the caldera formation with the 2000 miyake jima volcanic activity japan 1 very long period seismic signals whose waveform consists of an initial impulsive signal and a later oscillatory wave with 0 2 or 0 4 hz in dominant frequency were observed before the caldera formation in the 2000 activity of miyake jima volcano japan the results of waveform inversion show that the initial and later parts can be explained by a northward single force of 1 5 108 n working at a depth of 2 km beneath the summit and a moment tensor solution at a depth of 5 km below and 2 km southwest of the summit with 1012 nm respectively a clear positive correlation of the amplitudes between the two sources strongly suggests that the shallow single force triggers the deeper moment source in spite of the several km distance between the two sources to analyze the source time functions of the moment tensor that do not always oscillate in phase we introduce a new method of moment tensor diagonalization which is performed in the frequency domain according to the analysis the two principal components have similar amplitudes and are greater than the third principal component suggesting an axially symmetric oscillation one of the possible systems is a combination of two cracks intersecting perpendicularly our interpretation is that the single force was generated when magma containing rock blocks suddenly began to move in a choked subsurface magma path and the resultant pressure waves propagated and excited a resonance oscillation of the two cracks

the 2011 magnitude 9 0 tohoku oki earthquake mosaicking the megathrust from seconds to centuries geophysical observations from the 2011 moment magnitude m w 9 0 tohoku oki japan earthquake allow exploration of a rare large event along a subduction megathrust models for this event indicate that the distribution of coseismic fault slip exceeded 50 meters in places sources of high frequency seismic waves delineate the edges of the deepest portions of coseismic slip and do not simply correlate with the locations of peak slip relative to the m w 8 8 2010 maule chile earthquake the tohoku oki earthquake was deficient in high frequency seismic radiation a difference that we attribute to its relatively shallow depth estimates of total fault slip and surface secular strain accumulation on millennial time scales suggest the need to consider the potential for a future large earthquake just south of this event

evolution of the quaternary silicic volcanic complex of shiribetsu hokkaido japan an example of ignimbrite shield volcanoes in an island arc setting this paper describes the geology and eruptive history of a quaternary silicic volcanic complex at shiribetsu hokkaido japan with a focus on volcanic landforms produced by silicic explosive eruptions that were not associated with caldera collapse the shiribetsu volcanic complex comprises a dacitic pyroclastic plateau and an overlying dacitic central dome complex the pyroclastic plateau is 22 25 km in size 200 m high and consists of two ignimbrite units the km 1 and km 2 deposits sio2 67 68 wt total volume 10 km3 the central dome complex is 4 5 km wide rises to 650 m above the pyroclastic plateau and comprises two adjoining edifices which are east and west shiribetsu sio2 62 64 wt total volume 1 6 km3 east shiribetsu has a conical morphology whereas west shiribetsu comprises lava flows and a dome and has a large amphitheater a debris avalanche deposit volume 1 km3 extends from the amphitheater to the western foot of west shiribetsu a dacitic lava dome volume 0 2 km3 occurs within the amphitheater according to the stratigraphic relationships and new fission track dating the shiribetsu volcanic complex evolved as follows 1 dacitic explosive eruptions at ca 130 ka km 2 and 70 ka km 1 produced the pyroclastic plateau 2 effusive dacitic eruptions at 70 ka east shiribetsu and 60 ka west shiribetsu produced the central dome complex 3 sector collapse occurred at west shiribetsu at 50 60 ka and 4 lava dome formation within the amphitheater at 50 ka the evolution of the shiribetsu volcanic complex resembles that of ignimbrite shield volcanoes in the central andes shiribetsu may be the first identified example of ignimbrite shield volcanoes in an island arc setting we suggest that these are an independent class of explosive silicic volcanoes distinct from calderas and form above small magma chambers

h2o emission rate by the volcanic plume during the 2000 2002 miyakejima volcanic activity 1 extremely intense degassing at miyakejima volcano japan was observed after the 2000 eruption the h2o emission rate was estimated using a record of infrared thermal images at 400 kton day in november 2000 by april 2002 h2o emission rate had decreased exponentially to 100 kton day the h2o emission rate varied in parallel with the so2 emission rate except for the early stage in september 2000 the ratio of h2o to so2 emission rate after november 2000 remained constant at about 10 which is consistent with the h2o so2 ratio in the magma the large rate of h2o and so2 emission requires efficient degassing at shallow depth the agreement between the gas composition of the plume and that of dissolved volatiles in melt inclusions indicates h2o discharged from the vent was mostly magmatic in origin after november 2000

coseismic ionospheric disturbances triggered by the chi chi earthquake 1 at 17 47 ut on 20 september 1999 a large earthquake of magnitude mw 7 6 struck the central taiwan near a small town of chi chi the ground based receivers of the global positioning system gps in the taiwan area detected coseismic ionospheric disturbances cids in the total electron content tec triggered by the chi chi earthquake when the cids travel away from the origin on the earth surface and then propagate into the ionosphere their amplitudes and periods generally become smaller and longer respectively moreover two global grid searches adapting the ray tracing and the beam forming techniques have been used to analyze the observed gps tec we have not only estimated the average speed of the cids propagating in the atmosphere and ionosphere but also determined the location of cid origin on the earth surface by using the two techniques the results show that the observed cids result from shock acoustic waves triggered by sudden and large vertical motions of the chi chi earthquake

insights into the 3d architecture of an active caldera ring fault at tendurek volcano through modeling of geodetic data abstract the three dimensional assessment of ring fault geometries and kinematics at active caldera volcanoes is typically limited by sparse field geodetic or seismological data or by only partial ring fault rupture or slip here we use a novel combination of spatially dense insar time series data numerical models and sand box experiments to determine the three dimensional geometry and kinematics of a sub surface ring fault at tendurek volcano in turkey the insar data reveal that the area within the ring fault not only subsides but also shows substantial westward directed lateral movement the models and experiments explain this as a consequence of a sliding trapdoor ring fault architecture that is mostly composed of outward inclined reverse segments most markedly so on the volcano s western flanks but includes inward inclined normal segments on its eastern flanks furthermore the model ring fault exhibits dextral and sinistral strike slip components that are roughly bilaterally distributed onto its northern and southern segments respectively our more complex numerical model describes the deformation at tendurek better than an analytical solution for a single rectangular dislocation in a half space comparison to ring faults defined at glen coe fernandina and bar arbunga calderas suggests that sliding trapdoor ring fault geometries may be common in nature and should therefore be considered in geological and geophysical interpretations of ring faults at different scales worldwide

propagation linkage and interaction of caldera ring faults comparison between analogue experiments and caldera collapse at miyakejima japan in 2000 the formation of ring faults yields important implications for understanding the structural and dynamic evolution of collapse calderas and potentially associated ash flow eruptions caldera collapse occurred in 2000 at miyakejima island japan in response to a lateral intrusion based on geophysical data it is inferred that a set of caldera ring faults was propagating upward to understand the kinematics of ring fault propagation linkage and interac tion we describe new laboratory sand box experiments that were analyzed through digital image correlation dic and post processed using 2d strain analysis the results help us gain a better understanding of the processes occurring during caldera subsidence at miyakejima we show that magma chamber evacuation induces strain localization at the lateral chamber margin in the form of a set of reverse faults that sequentially develops and propagates upwards then a set of normal faults initiates from tension fractures at the surface propagating downwards to link with the reverse faults at depth with increasing amounts of subsidence interaction between the reverse and normal fault segments results in a deactivation of the reverse faults while displacement becomes focused on the outer normal faults modeling results show that the area of faulting and collapse migrates successively outward as peak displace ment transfers from the inner ring faults to later developed outer ring faults the final structural architecture of the faults bounding the subsiding piston like block is hence a consequence of the amount of subsidence in agreement with other caldera structures observed in nature the experimental simulations provide an analogy to the obser vations and seismic records of caldera collapse at miyake jima volcano but are also applicable to caldera collapse in general

understanding oblique impacts from experiments observations and modeling natural impacts in which the projectile strikes the target vertically are virtually nonexistent nevertheless our inherent drive to simplify nature often causes us to suppose most impacts are nearly vertical recent theoretical observational and experimental work is improving this situation but even with the current wealth of studies on impact cratering the effect of impact angle on the final crater is not well understood although craters rims may appear circular down to low impact angles the distribution of ejecta around the crater is more sensitive to the angle of impact and currently serves as the best guide to obliquity of impacts experimental studies established that crater dimensions depend only on the vertical component of the impact velocity the shock wave generated by the impact weakens with decreasing impact angle as a result melting and vaporization depend on impact angle however these processes do not seem to depend on the vertical component of the velocity alone finally obliquity influences the fate of the projectile in particular the amount and velocity of ricochet are a strong function of impact angle

sedimentary and volcano tectonic processes in the british paleocene igneous province a review research on the british paleocene igneous province bpip has historically focused on the emplacement chemistry and chronology of its elaborate central intrusive complexes and lava fields however the bpip has also been dramatically shaped by numerous erosion sedimentation and volcano tectonic events the significance of which becomes ever clearer as localities in the bpip are re investigated and our understanding of volcano sedimentary processes advances the resultant deposits provide important palaeo environmental palaeo geographical and stratigraphical information and highlight the wide range of processes and events that occur in ancient volcanic settings such as the bpip in this paper we review the sedimentary and volcano tectonic processes that can be distinguished in the bpip and conceptualize them within a generalized framework model we identify and describe the sedimentary responses to four broadly chronological stages in the history of the bpip volcanoes 1 the development of the lava fields 2 early intrusion induced uplift 3 caldera collapse and 4 post volcano denudation and exhumation of central complexes we highlight and illustrate the range of sedimentary processes that were active in the bpip these operated on and helped shape a dynamic landscape of uplands and lowlands of alluvial fans braided rivers lakes and swamps and of volcanoes torn apart by catastrophic mass wasting events and or caldera collapse

detection of ruptures of andaman fault segments in the 2004 great sumatra earthquake with coseismic ionospheric disturbances 1 near field coseismic perturbations of ionospheric total electron content tec caused by direct acoustic waves from focal regions can be observed with global positioning system gps they appear 10 15 min after the earthquake with typical periods of 4 5 min and propagate as fast as 1 km s toward directions allowed by ambient geomagnetic fields ionospheric disturbance associated with the 2004 december 26 great sumatra andaman earthquake was recorded with nine continuous gps receiving stations in indonesia and thailand here we explore the possibility to constrain the rupture process of the earthquake with the observed ionospheric disturbances we assumed linearly distributed point sources along the zone of coseismic uplift extending 1300 km from sumatra to the andaman islands that excited acoustic waves sequentially as the rupture propagate northward by 2 5 km s tec variations for several satellite receiver pairs were synthesized by simulating the propagation of acoustic waves from the ground to the ionosphere and by integrating the tec perturbations at intersections of line of sights and the ray paths the tec perturbations from individual point sources were combined using realistic ratios and the total disturbances were compared with the observed signals prescribed ratios based on geodetically inferred coseismic uplifts reproduced the observed signals fairly well similar calculation using a rupture propagation speed of 1 7 km s degraded the fit suppression of acoustic waves from the segments north of the nicobar islands also resulted in a poor fit which suggests that ruptures in the northern half of the fault were slow enough to be overlooked in short period seismograms but fast enough to excite atmospheric acoustic waves coseismic ionospheric disturbance could serve as a new indicator of faulting sensitive to ruptures with timescale up to 4 5 min

cratering experiments in sands and a trial for general scaling law we report results of vertical impacts of aluminum projectiles into quartz sand the impacts were performed at velocities of 35 to 830 m sec with a single stage powder gun morphology of craters formed in loose sands is generally conical whereas morphology of craters formed in self compacted sands varies from a flat floor type to a double ring type with increasing impact velocity the present data together with previous experimental data and dienes and walsh s late stage equivalence indicate that crater diameter is expressed by a function of the late stage effective energy but not of the impact kinetic energy the diameter of a crater formed in a noncohesive sand was found to be proportional to one fourth the power of the late stage effective energy for a general impact cratering in a target with a finite strength the diameter d versus impact velocity v relation is written as follows vv vv 2 k dd 4 dd 5 2 where v and d are normalizing values of the impact velocity and diameter and k is a constant related to target and projectile properties the relation suggests that there are four regimes in crater diameter versus the kinetic energy relation

a volcanotectonic survey of ascraeus mons mars 1 ascraeus mons is one of the largest volcanoes on mars it is replete with well preserved features that can be used to understand its volcanotectonic evolution previous studies of this volcano focused on specific features and were limited by the quality and coverage of contemporary data our objective is to review and enhance the existing developmental model for ascraeus by considering all endogenic surface features on the volcano we surveyed the volcano s caldera complex flank terraces pit structures sinuous rilles arcuate grabens and small vents we report the spatial and temporal distributions of these features appraise their proposed formation mechanisms in light of our mapping results and propose a detailed geological history for ascraeus mons an initial shield building phase was followed by the formation of a summit caldera complex and small parasitic cones while compression due to flexure of the supporting basement led to extensive terracing of the shield flanks an eruptive hiatus followed ending with the construction of expansive rift aprons to the northeast and southwest against later extensive flank resurfacing in the late amazonian continued flexure formed arcuate grabens concentric to the edifice localized eruption and surface flow of a fluid agent lava and or water from within the volcano then produced a population of rilles on the lower flanks finally in a change of flank tectonic regime from compression to extension pit crater chains and troughs developed on the main shield and rift aprons eventually coalescing to form large embayments at the northeast and southwest base of the volcano

first ionospheric images of the seismic fault slip on the example of the tohoku oki earthquake 1 1hz gps measurements from the japanese gps network geonet allowed to retrieve information on the seismic fault of the great m9 0 tohoku oki earthquake from the ionosphere total electron content tec measurements the first arrival of the tec perturbation was registered 464 seconds after the earthquake 140 km on the east from the epicenter within next 45 seconds the distribution of ionospheric points imaged a rectangular area 37 39 39 28 n 142 8 143 73 e which coincides with the area of the coseismic crustal uplift from this source region the coseismic ionospheric perturbation further propagated at 1 3 1 5 km s such velocity values are 30 40 higher than previously reported for acoustic waves it is likely that we observed shock acoustic waves propagating at supersonic speed and having blown all the electrons available between the ground and the height of detection this fact is coherent with registration of the first arrival of perturbation 464 sec after the earthquake that is generally speaking too short time for a regular acoustic wave to reach the ionosphere our findings show that the real time gps monitoring of seismo active areas could inform about the parameters of coseismic crustal displacements and can be subsequently used for short term tsunami warnings in the case of the 03 11 2011 earthquake the first ionosphere perturbations were registered 17 minutes before the tsunami arrived on the east coast of honshu

silicic magmas in the izu bonin oceanic arc and implications for crustal evolution abundant rhyolitehaseruptedfromthe izu bonin marianavolca nic arc ibm arc from its earliest stage eocene to the present geochemically three types of quaternary rhyolites exist in the izu bonin arcfront and theyare closely related tovolcanotypeand crus tal structure the dominantly basaltic islands of the volcanic frontproduce small volumes of rhyolites that we call r1 the submarinecalderas of the volcanic front erupt mostly rhyolite that we call r2 seamounts knolls and pillow ridges in thebackarcextensionalzoneare mostly basaltic but also contain rhyolites that we call r3 thethickest total crust and the thickest intermediate compositionmiddle crust occurs below the dominantly basaltic volcanoes whereas the intermediate composition middle crust tends to be thin nerbeneaththesubmarinecalderas r1rhyolitesmaybederivedfromquaternary andesitic sources whereas r2 and r3 rhyolites may bederivedfromoligoceneones thehighercao al

parameters of seismic source as deduced from 1 hz ionospheric gps data case study of the 2011 tohoku oki event following the first time ionospheric imaging of a seismic fault here we perform a case study on retrieval of parameters of the extended seismic source ruptured during the great m9 0 tohoku oki earthquake using 1 hz ionospheric gps data from the japanese network of gps receivers geonet and several gps satellites we analyze spatiotemporal characteristics of coseismic ionospheric perturbations and we obtain information on the dimensions and location of the sea surface uplift seismic source we further assess the criterion for the successful determination of seismic parameters from the ionosphere the detection is possible when the line of sights from satellites to receivers cross the ionosphere above the seismic fault region besides we demonstrate that the multisegment structure of the seismic fault of the tohoku oki earthquake can be seen in high rate ionospheric gps data overall our results show that under certain conditions ionospheric gps derived tec measurements could complement the currently working systems or independent ionospherically based system might be developed in the future

tsunamigenic ionospheric hole 1 traveling ionospheric disturbances generated by an epicentral ground sea surface motion ionospheric disturbances associated with rayleigh waves as well as post seismic 4 minute monoperiodic atmospheric resonances and other period atmospheric oscillations have been observed in large earthquakes in addition a giant tsunami after the subduction earthquake produces an ionospheric hole which is widely a sudden depletion of ionospheric total electron content tec in the hundred kilometer scale and lasts for a few tens of minutes over the tsunami source area the tsunamigenic ionospheric hole detected by the tec measurement with global position system gps was found in the 2011 m9 0 off the pacific coast of tohoku the 2010 m8 8 chile and the 2004 m9 1 sumatra earthquakes this occurs because plasma is descending at the lower thermosphere where the recombination of ions and electrons is high through the meter scale downwelling of sea surface at the tsunami source area and is highly depleted due to the chemical processes

caldera collapse during the 2000 eruption of miyakejima volcano japan a collapsed caldera 1 6 km in diameter and 450 m in depth was formed at the summit of miyakejima volcano during the 2000 eruption the collapsed caldera appeared on 8 july with a minor phreatic eruption 12 days after seismic activity and magma intrusion occurred northwest of the volcano growth of the caldera took from 8 july to the middle of august with seismic swarms associated with the continuous intrusion of magma northwest of the volcano the growth rate of the caldera was about 1 4 107 m3 day and the final volume of the collapsed caldera was about 6 108 m3 major phreatomagmatic eruptions produced a total of about 1 6 1010 kg 1 1 107 m3 of volcanic ash after caldera growth the caldera structure and the nature of the eruptive materials of the first collapse on 8 july suggest that the surface subsidence was caused by the upward migration of a steam filled cavity with stoping of the roof rock above the magma reservoir the diameter of the stoping column was estimated to be 600 700 m from circumferential faults that developed in the caldera floor and the collapse of the caldera wall enlarged the diameter of the caldera to 1 6 km the total volume of the caldera and the horizontal diameter of the stoping column gave a subsidence of the caldera floor of 1 6 2 1 km

growth of phreatomagmatic explosion craters a model inferred from suoana crater in miyakejima volcano japan abstract a subvertical cross section of a maar diatreme volcano is exposed in the wall of the a d 2000 caldera on miyakejima volcano the maar suoana is one of the lateral vents of this volcano and it was inferred to be formed in the 7th century the subvertical wall of the a d 2000 caldera truncated the suoana maar crater at its center revealing the near comlete cross section of this small maar diatreme volcano exposed in the cross section are a 400 m wide maar crater an associated tuff ring with a maximum thickness of 20 m a diatreme extending vertically to a depth of about 220 m from the floor of the maar crater and a feeder dike connected to the base of the diatreme the depth of the diatreme structure is about 260 m from the original ground surface the outline of the diatreme resembles an upward opening funnel with an almost vertical wall below 560 m asl and an upward flaring wall above 560 m asl coarse grained volcanic breccia fills the diatreme the deposits of which can be divided into 6 units based on lithological and structural characteristics the upper half of the diatreme is filled with landslide deposits mainly derived from the surrounding crater wall the bottom of the diatreme is occupied by massive explosion breccia some coherent blocks were detached from the wall of the diatreme and preserved in the diatreme fill the y shaped cross sectional geometry of the suoana diatreme is the result of a combination of an underground subsidence in the lower part of the diatreme and the surface landslide in its upper part the inwardly inclined stratification of pyroclastic rock units and development of many small faults in the diatreme filling breccia indicate successive collapse and deformation of these materials within the diatreme during the eruption the upper part of the diatreme was formed by the landslides of the crater wall induced by the subsidence of the crater floor discharge of tephra from the bottom of the diatreme caused infill subsidence which induced sliding of the inner wall of the crater as a result the topographic diameter of the crater became much larger than that of the diatreme itself the tephra ring surrounding the crater consists mainly of pyroclastic fall deposits

the magmatic plumbing of the submarine hachijo nw volcanic chain hachijojima japan long distance magma transport 1 recent geophysical observations on basaltic composite volcanoes in izu bonin arc reveal the process of long distance lateral magma transport within arc crust to clarify a long distance magma transport system of the basaltic arc volcano from geological and petrological aspects we investigated 20 km long submarine volcanic chains hachijo nw chain and hachijo kojima chain and cones on the northeastern slope ne edifices as well as subaerial satellite cones nested hachijo nishiyama volcano in the northern izu arc front basalts from hachijo nw chain have more primitive composition than those from other edifices the composition of the hachijo nw chain basalts is controlled by fractional crystallization while plagioclase accumulation occurred in ne edifices and subaerial satellite cones trace element and isotopic characteristics indicate that the same basaltic primary magma is involved in all sections of the volcano this leads us to consider that magma was transported long distances between the nishiyama volcano and the hachijo nw chain primitive magma was laterally transported nnw for at least 20 km in the middle to lower crust 10 20 km deep from nishiyama volcano with only minimal crustal level modifications and formed hachijo nw chain on the other hand magmas experienced crystal fractionation and accumulation at shallow magma chamber beneath nishiyama volcano seems to have been transported in a short distance 5 km and formed ne trending edifices and subaerial satellite cones the long distance magma transport seems to be controlled by a regional extensional stress regime while short distance transport may be controlled by local stress regime affected by load of main volcanic edifice

ionospheric detection and localization of volcano eruptions on the example of the april 2015 calbuco events using data from ground based gnss receivers located in southern chile we study the ionospheric total electron content tec response to two eruptions of the calbuco volcano that occurred on 22 23 april 2015 in both cases the tec response showed quasi periodic signals with several consecutive wave trains the averaged amplitude of the observed co volcanic tec perturbations amounted 0 45 tecu for the first eruption and 0 16 tecu for the second one we compare amplitudes of the tec response to volcano eruptions of different intensity from our and previously published data and we show that both the intensity and the background ionospheric conditions define the amplitude of ionospheric co volcanic disturbances cvid the relative contribution however scales with the eruption intensity the travel time diagrams allowed to estimate the propagation speed of the observed co volcanic tec perturbations as 900 1200 m s which is close to the acoustic or shock acoustic waves speed at the ionospheric height the spectrograms are consistent with the conclusion on the acoustic nature of the observed tec perturbations finally we use the approximation of a spherical wave propagating at a constant velocity from a point source and for the first time we calculate the location of the volcanic source and the onset time of the volcano eruption from ionospheric measurements we show that even from 30 sec ionospheric gps data it is possible to localize the eruptive source within several degrees of latitude longitude

localized deformation at miyakejima volcano based on jers 1 radar interferometry 1992 1998 1 stacked radar interferograms at miyakejima volcano japan between 1992 and 1998 showed two localized significantly deforming areas with a magnitude of 4 6 mm yr in the radar line of sight one area is close to the 1983 eruption vent and using a simple closed analytical formulation the deformation is interpreted as due to a thermoelastic contraction of a formerly intruded magma the other one detected in the previous caldera is explained by a depressurization source whose depth 500 m coincides with that of a low resistivity zone interpreted as a hydrothermal reservoir also our computed co2 flux is consistent with in situ measurement data the reservoir volume is significantly less than the collapsed volume in 2000 and its depth is much shallower than the void detected prior to the collapse hence the depressurization would not directly induce the caldera collapse in 2000

strike slip earthquakes can also be detected in the ionosphere it is generally assumed that co seismic ionospheric disturbances are generated by large vertical static displacements of the ground during an earthquake consequently it is expected that co seismic ionospheric disturbances are only observable after earthquakes with a significant dip slip component therefore earthquakes dominated by strike slip motion i e with very little vertical co seismic component are not expected to generate ionospheric perturbations in this work we use total electron content tec measurements from ground based gnss receivers to study ionospheric response to six recent largest strike slip earthquakes the mw7 8 kunlun earthquake of 14 november 2001 the mw8 1 macquarie earthquake of 23 december 2004 the sumatra earthquake doublet mw8 6 and mw8 2 of 11 april 2012 the mw7 7 balochistan earthquake of 24 september 2013 and the mw 7 7 scotia sea earthquake of 17 november 2013 we show that large strike slip earthquakes generate large ionospheric perturbations of amplitude comparable with those induced by dip slip earthquakes of equivalent magnitude we consider that in the absence of significant vertical static co seismic displacements of the ground other seismological parameters primarily the magnitude of co seismic horizontal displacements seismic fault dimensions seismic slip may contribute in generation of large amplitude ionospheric perturbations

impact experiments i ejecta velocity distributions and related results from regolith targets velocity distributions are determined for ejecta from 14 experimental impacts into regolithlike powders in near vacuum conditions at velocities from 5 to 2321 m sec of the two powders the finer produces slower ejecta ejecta include conical sheets with ray producing jets and in the fastest impacts at vimp 700 m sec high speed vertical plumes of uncertain nature velocities in the conical sheets and jets increase with impact velocity sect 6 ejecta velocities also increase as impact energy and crater size increase a suggested method of estimating ejecta velocity distributions in large scale impacts involves homologous scaling according to r rcrater where r is radial distances from the crater sect 7 the data are consistent with holsapple schmidt scaling relationships sect 8 the fraction of initial total impact energy partitioned into ejecta kinetic energy increases from around 0 1 for the slow impacts to around 10 for the fast impacts with the main increase probably at the onset of the hypervelocity impact regime sect 9 crater shapes are discussed including an example of a possible frozen transient cavity sect 10 ejecta blanket thickness distributions as a function of r vary with target material and impact speed but the results measured for hypervelocity impacts agree with published experimental and theoretical values sect 11 the low ejecta velocities for powder targets relative to rock targets together with the paucity of powder ejecta in low speed impacts 1 projectile mass for vimp 10 m sec enhance early planetary accretion effeciency beyond that in some earlier theoretical models 100 efficient accretion is found for certain primordial conditions sect 12