3 d inhomogeneities in the upper mantle abstract the method developed by aki christofferson and husebye for determining a 3 d seismic image of the earth s interior from the travel time data obtained at a 2 d array has been applied to seventeen arrays around the world by various authors the most outstanding results from these works are that small scale lateral velocity anomalies exist in the lower crust and upper mantle everywhere studied the reality of these deep seated anomalies is supported by 1 1 significant reduction of residual variance 2 2 resolution analysis for decoupling from shallower anomalies and 3 3 error analysis for the significance of anomalies in this paper we try to strengthen the credibility of these deep seated anomalies by drawing attention to those found where they were expected namely low velocity bodies under several geothermal areas and high velocity anomalies associated with the subducting plate

abrupt mid holocene decline in the indian summer monsoon caused by tropical indian ocean cooling the evolution of the indian summer monsoon ism has been widely investigated and traditionally interpreted as consequences of orbital forcing change and the migration of the intertropical convergent zone itcz the potential influence of sea surface temperature sst on ism variation at millennial time scales has been progressively proposed in recent studies towards a better understanding of holocene evolution of ism especially the potential response to variations in sst a 643 cm continuous sediment sequence covering the past 11 1 ka was recovered from beihai wetland in western yunnan plateau fossil pollen analysis revealed that evergreen broadleaved forest dominated the regional vegetation in the early holocene which represented a warm and humid period associated with strong ism expansions of deciduous broadleaved forest and grassland from 5 2 cal ka bp to the present together with the appearance of abundant plant remains indicate the formation of the wetland system ordination analysis of the pollen assemblages further confirmed the abrupt vegetation turnover at ca 5 2 cal ka bp which is consistent with the abrupt decline in reconstructed mean annual precipitation pann from ca 1400 to 1100 mm and indicates an abrupt decline in the summer monsoon we performed a climate regime shift test on various records from the ism domain and eastern africa and found this phenomenon as well which could not be explained by changes in solar insolation or the migration of the itcz a mid holocene cooling was detected from the indian ocean especially a decreased sst in the tropical indian ocean ca 5 5 cal ka bp cooling of the tropical indian ocean possibly caused the abrupt retreat of the summer monsoon by restraining the duration of the monsoonal season and the convergent process which was supported by an abrupt monsoon decline based on results from a minimal concept model

discovery of a powerful transient explosive thermal event at marduk fluctus io in galileo nims data analysis of galileo near infrared mapping spectrometer nims observations of marduk fluctus a volcano on the jovian moon io reveals a style of volcanic activity not previously seen there a powerful thermal event lasting only a few minutes in 1997 the thermal emission rapidly fades suggesting extremely rapid cooling of small clasts the duration and evolution of the explosive eruption is akin to what might be expected from a strombolian or vulcanian explosion the presence of such events provides an additional volcanic process that can be imaged by future missions with the intent of determining lava composition from eruption temperature an important constraint on the internal composition of io these data promise to be of particular use in understanding the mechanics of explosive volcanic processes on io

partitioning of india eurasia convergence in the pamir hindu kush from gps measurements 1 convergence of 29 1 mm yr between the nw corner of the indian plate and asia is accommodated by a combination of thrust and strike slip faulting on prominent faults and apparent distributed deformation within the hindu kush pamir south tien shan and kohistan ranges an upper bound to the slip rate of known faults is obtained by ignoring distributed strain and rotation convergence occurs on thrust faults north of the peshawar basin 13 1 mm yr and in the alai south tien shan 12 2 mm yr and shear on the northeast trending northern chaman gardiz konar system 18 1mm yr and the darvaz karakul fault zone 11 2 mm yr slip rates on the herat and talas ferghana faults are small 2 mm yr shortening not attributable to known active faults occurs within the hindu kush and central pamir 16 2 mm yr with concomitant east west extension in the latter of 9 2 mm yr this diversity of strain styles confirms the importance of mechanical heterogeneity to continental tectonics and shows that the pamir although less than half the size behaves more like tibet than like a linear belt of localized deformation

empirical ground motion relations for subduction zone earthquakes and their application to cascadia and other regions ground motion relations for earthquakes that occur in subduction zones are an important input to seismic hazard analyses in many parts of the world in the cascadia region washington oregon northern california and british columbia for example there is a significant hazard from megathrust earthquakes along the subduction interface and from large events within the subducting slab these hazards are in addition to the hazard from shallow earthquakes in the overlying crust we have compiled a response spectra database from thousands of strong motion record ings from events of moment magnitude m 5 8 3 occurring in subduction zones around the world including both interface and in slab events the 2001 m 6 8 nis qually and 1999 m 5 9 satsop earthquakes are included in the database as are many records from subduction zones in japan kyoshin net data mexico guerrero data and central america the size of the database is four times larger than that available for previous empirical regressions to determine ground motion relations for subduc tion zone earthquakes the large dataset enables improved determination of attenu ation parameters and magnitude scaling for both interface and in slab events soil response parameters are also better determined by the data we use the database to develop global ground motion relations for interface and in slab earthquakes using a maximum likelihood regression method we analyze regional variability of ground motion amplitudes across the global database and find that there are significant regional differences in particular amplitudes in cascadia differ by more than a factor of 2 from those in japan for the same magnitude distance event type and national earthquake hazards reduction program nehrp soil class this is believed to be due to regional differences in the depth of the soil profile which are not captured by the nehrp site classification scheme regional correction factors to account for these differences are proposed for cascadia and japan the results of this study differ significantly from previous analyses based on more limited data and have important implications for seismic hazard analysis the ground motion relations predict that a great megathrust earthquake m 8 at a fault distance of about 100 km would produce pseudoacceleration psa 5 damped horizontal component on soil sites of about 110 cm sec 2 at 0 5 hz 660 cm sec 2 at 2 5 hz and 410 cm sec 2 at 5 hz with a peak ground acceleration of about 180 cm sec 2 these damaging levels of motion would be experienced over a very large area corresponding to a rectangular area about 300 km wide by 500 km long large in slab events m 7 5 would produce even higher psa values within 100 km of the fault but the in slab motions attenuate much more rapidly with distance thus the hazard posed by moderate to large in slab events such as the 2001 nisqually earth quake is modest compared to that of a cascadia megathrust earthquake of m 8 in terms of the area that would experience damaging levels of ground motion

volcanic eruptions on io nine eruption plumes were observed over a period of 6 1 2 days during the voyager 1 encounter with io during the voyager 2 encounter 4 months later eight of these eruptions were still active the largest plume viewed by voyager 1 became inactive sometime between the two encounters however a major eruption occurred at surt sometime between the two encounters and deposited an ejecta blanket comparable in size to those associated with the largest plumes the plumes range in height from about 60 to over 300 km with corresponding ejection velocities of about 0 5 to 1 0 km s where topographic information exists plumes 1 and 8 the plume source is located on level plains rather than topographic highs and consists of either fissures or calderas with the exception of plume 1 pele the brightness distribution monotonically decreases from the core to the top of the plume the shape and brightness distribution together with the pattern of the surface deposit of at least plume 3 prometheus can be simulated by a ballistic model in which the ejection velocity is constant 0 5 km s and ejection angles vary from vertical 0 to 55 the brightness distribution of plume 1 is probably better explained by a shock front near the top of the plume numerous surface deposits similar to those associated with active plumes probably mark the sites of recent eruptions the distribution of active and recent eruptions appears to be concentrated in the equatorial regions and indicates the volcanic activity is more frequent and intense in the equatorial regions than the polar regions this suggests that the depositional rate is greater and the surface age younger in the equatorial regions which may account for the darker polar regions the geologic setting of certain plume sources and the very large reservoirs of volatiles required for the active eruptions suggests that sulphur volcanism rather than silicate volcanism is the most likely driving mechanism for the eruption plumes

charting thermal emission variability at amirani with the galileo nims io thermal emission database nited abstract we have examined the variability of thermal emission from lava flows at amirani on io using measurements of radiant flux from detections by the galileo near infrared mapping spectrometer nims between 1996 and 2001 amirani is the longest currently active lava flow field in the solar system and a persistent thermal source in every galileo nims observation that covers its location we have quantified the thermal emission from hot spots correlated with discrete areas of new lava flow emplacement at points along the length of the amirani flow field in high spatial resolution nims observations in 2000 and 2001 where discernible the position of some effusive activity changes from orbit to orbit we find the implied style of emplacement of lava at amirani is consistent with pahoehoe like flows there is an estimated 50 decrease in discharge rate between 1997 and late 2001 perhaps linked to an outburst eruption in the amirani vicinity in february 2001 the variability of thermal emission from amirani is less than that seen at a number of other persistently active ionian volcanoes such as prometheus culann and loki patera all of these volcanoes exhibit large increases and decreases in the absolute magnitude of thermal emission see matson et al 2006 loki patera davies a g et al 2006 icarus 184 460 477 prometheus and davies a g ennis m e 2011 icarus 215 401 416 culann at amirani as at these volcanoes the thermal emission measured between 1996 and 2001 indicates a persistent although variable supply of magma to the surface in high spatial resolution nims observations of hot spots obtained in 2000 and 2001 we estimate the emitted power from active lava flows associated with amirani to be 170 30 gw which corresponds to total effusion rates assuming a basaltic composition from multiple points along the amirani flow of 34 56 m 3 s

three dimensional simulation of gas and dust in io s pele plume abstract io s giant pele plume rises high above the moon s surface and produces a complex deposition pattern we use the direct simulation monte carlo dsmc method to model the flow of so2 gas and silicate ash from the surface of the lava lake into the umbrella shaped canopy of the plume and eventually onto the surface where the flow leaves black butterfly wings surrounded by a large red ring we show how the geometry of the lava lake from which the gas is emitted is responsible for significant asymmetry in the plume and for the shape of the red deposition ring by way of complicated gas dynamic interactions between parts of the gas flow arising from different areas in the lava lake we develop a model for gas flow in the immediate vicinity of the lava lake and use it to show that the behavior of ash particles of less than about 2 m in diameter in the plume is insensitive to the details of how they are introduced into the flow because they are coupled to the gas at low altitudes we simulate dust particles in the plume to show how particle size determines the distance from the lava lake at which particles deposit on the surface and we use this dependence to find a size distribution of black dust particles in the plume that provides the best explanation for the observed black fans to the east and west of the lava lake this best fit particle size distribution suggests that there may be two distinct mechanisms of black dust creation at pele and when two log normal distributions are fit to our results we obtain a mean particle diameter of 88 nm we also propose a mechanism by which the condensible plume gas might overlay black dust in areas where black coloration is not observed and compare this to the observed overlaying of pillanian dust by pele s red ring

kinematics of the pamir and hindu kush regions from gps geodesy 1 gps velocities measured in the pamir and surrounding regions show a total of 30 mm yr of northward relative motion between stable pakistan and eurasia the convergence budget is partitioned into 10 15 mm yr of localized shortening across the trans alai thrust which bounds the pamir on the north consistent with southward subduction of intact lithosphere another 10 15 mm yr of shortening is distributed across the chitral himalaya and hindu kush suggesting that hindu kush seismicity might be related to northward subduction of indian lithosphere modest shortening at 5 mm yr occurs north of the trans alai thrust across the south tien shan and between the ferghana valley and eurasia negligible north south shortening occurs within the high pamir but as much as 5 mm yr and perhaps 10 mm yr of east west extension occurs within this region this extension is matched by a comparable amount of east west shortening in the tajik depression the localization of shortening to the margins of the pamir combined with observations of distributed internal extension implies that the east west vertically averaged horizontal compressive normal stress is smaller than the north south compressive stress

imaging of volcanic activity on jupiter s moon io by galileo during the galileo europa mission and the galileo millennium mission the solid state imaging ssi instrument provided the first high and medium resolution views of io as the galileo spacecraft closed in on the volcanic body in late 1999 and early 2000 while each volcanic center has many unique features the majority can be placed into one of two broad categories the promethean eruptions typified by the volcanic center prometheus are characterized by long lived steady eruptions producing a compound flow field emplaced in an insulating manner over a period of years of decades in contrast pillanian eruptions are characterized by large pyroclastic deposits and short lived but high effusion rate eruptions from fissures feeding open channel or open sheet flows both types of eruptions commonly have 100 km tall bright so2 rich plumes forming near the flow fronts and smaller deposits of red material that mark the vent for the silicate lavas

volcanic activity at tvashtar catena io abstract galileo s solid state imager ssi observed tvashtar catena four times between november 1999 and october 2001 providing a unique look at a distinctive high latitude volcanic complex on io the first observation orbit i25 november 1999 resolved for the first time an active extraterrestrial fissure eruption the brightness temperature was at least 1300 k the second observation orbit i27 february 2000 showed a large 500 km 2 region with many small hot regions of active lava the third observation was taken in conjunction with cassini imaging in december 2000 and showed a pele like annular plume deposit the cassini images revealed an 400 km high pele type plume above tvashtar catena the final galileo ssi observation of tvashtar orbit i32 october 2001 revealed that obvious to ssi activity had ceased although data from galileo s near infrared mapping spectrometer nims indicated that there was still significant thermal emission from the tvashtar region in this paper we primarily analyze the style of eruption during orbit i27 february 2000 comparison with a lava flow cooling model indicates that the behavior of the tvashtar eruption during i27 does not match that of simple advancing lava flows instead it may be an active lava lake or a complex set of lava flows with episodic overlapping eruptions the highest reliable color temperature is 1300 k although higher temperatures cannot be ruled out they do not need to be invoked to fit the observed data the total power output from the active lavas in february 2000 was at least 10 11 w

a survey of io s volcanism by adaptive optics observations in the 3 8 μm thermal band 1996 1999 in this study we analyze a series of images of io obtained with the european southern observatory adaptive optics system adaptive optics near infrared system adonis at 3 8 m from 1996 to 1999 with particular emphasis on the observations carried out in late 1999 in support of the galileo flybys of io use of a new myopic deconvolution method myopic iterative step preserving algorithm mistral especially designed for planetary objects significantly improves the quality and the reliability of the reconstructed images using a simulation of artificial images of io we estimate the extent to which this algorithm is able to prevent noise amplification to better restore sharp edges and to preserve the initial photometry once this algorithm has been applied to our data and the solar reflected background has been subtracted we have 89 images of io available for search and temporal survey of the hot spots over 4 years in most cases the data acquired during two consecutive nights provide an almost global view of the surface of io we identify 20 hot spots for which we determine the coordinates and the brightness at 3 8 m as a function of time more than half of the hot spots were detected on all the images and were considered as persistent particular emphasis has been put on the brightest two hot spots loki and pele for which we obtain a center to limb variation curve a cosine curve for loki and a curve decreasing slightly faster than a cosine law for pele with possible physical interpretations the temporal variations of their activity have been derived over these 4 years and for loki compared with the results of other ground based surveys the variability of the other fainter sources has also been derived but with less accuracy we have also identified a few new hot spots some of which are transient such as a diffuse emission seen in september and november 1999 at the location of the upcoming tvashtar outburst the data are based on observations 58 f 1003 63 s 0260 and 64 s 0661 collected at the european southern observatory in la silla chile

galileo observations of volcanic plumes on io abstract io s volcanic plumes erupt in a dazzling variety of sizes shapes colors and opacities in general the plumes fall into two classes representing distinct source gas temperatures most of the galileo imaging observations were of the smaller more numerous prometheus type plumes that are produced when hot flows of silicate lava impinge on volatile surface ices of so2 few detections were made of the giant pele type plumes that vent high temperature sulfur rich gases from the interior of io this was partly because of the insensitivity of galileo s camera to ultraviolet wavelengths both gas and dust spout from plumes of each class favorably located gas plumes were detected during eclipse when io was in jupiter s shadow dense dust columns were imaged in daylight above several prometheus type eruptions reaching heights typically less than 100 km comparisons between eclipse observations sunlit images and the record of surface changes show that these optically thick dust columns are much smaller in stature than the corresponding gas plumes but are adequate to produce the observed surface deposits mie scattering calculations suggest that these conspicuous dust plumes are made up of coarse grained ash particles with radii on the order of 100 nm and total masses on the order of 106 kg per plume long exposure images of thor in sunlight show a faint outer envelope apparently populated by particles small enough to be carried along with the gas flow perhaps formed by condensation of sulfurous snowflakes as suggested by the plasma instrumentation aboard galileo as it flew through thor s plume frank l a paterson w r 2002 j geophys res space phys 107 doi 10 1029 2002ja009240 31 1 if so the total mass of these fine nearly invisible particles may be comparable to the mass of the gas and could account for much of io s rapid resurfacing

silicate cooling model fits to galileo nims data of volcanism on io abstract the near infrared mapping spectrometer nims has obtained spectra of volcanoes on the surface of the jovian satellite io fits to data using a silicate cooling model allow us to constrain lava eruption rates and eruption age the thermal signatures of the hot spots are indicative of active and cooling silicate lava flows for large active hot spots maximum ages of flow surfaces detected by nims typically range from days to months although in one case it is nearly 30 years mass eruption rates for the main hot spots are in the range 7 m3 s 1 to 79 m3 s 1 using an average flow thickness of 1 m these mass eruption rates are orders of magnitude less than those implied for large thermal outbursts on io the eruptions observed during june 1996 are most likely of a different eruption style on a much smaller scale the observation analyzed here may be representative of the current background level of volcanic activity on the anti jove hemisphere of io the global mass eruption rate from these non outburst hot spots is calculated to be 43 km3 year equivalent to a global resurfacing rate of about 1 mm year about 10 of the minimum required global resurfacing volume the total observed energy output from the 14 hot spots analyzed is 3 6 1012 w normalized globally these hot spots contribute approximately 10 of io s radiometric heat flux

observations and initial modeling of lava so2 interactions at prometheus io we present observations and initial modeling of the lava so2 interactions at the flow fronts in the prometheus region of io recent high resolution observations of prometheus reveal a compound flow field with many active flow lobes many of the flow lobes are associated with bright streaks of what is interpreted to be volatilized and recondensed so2 radiating away from the hot lava lower resolution color data show diffuse blue to violet areas also near the active flow front perhaps from active venting of so2 not clearly visible in any of the images is a single source vent for the active plume while the size of the proposed vent is probably near the limit of the resolution we expected to see radial or concentric albedo patterns or other evidence for gas and entrained particles above the flow field the lack of an obvious plume vent earlier suggestions that the prometheus type plumes may originate from the advancing flow lobes and the high resolution images showing evidence for large scale volatilization of the so2 rich substrate at prometheus encouraged us to develop a model to quantify the heat transfer between a basaltic lava flow and a substrate of so2 snow we calculate that the vaporization rate of so2 snow is 2 5 10 6 m s 1 per unit area using an estimated 5 m2 s 1 lava coverage rate from change detection images we show that the gas production rate of so2 at the flow fronts is enough to produce a resurfacing rate of 0 24 cm yr 1 at the annulus of prometheus this is much less than other estimates of resurfacing by the prometheus plume while not easily explaining the main prometheus plume our model readily accounts for the bright streaks

spatial color variations in the volcanic plume at loki on io multicolor voyager 1 photographs of the loki volcanic plume on io have been analyzed to determine the nature and quantity of the scattering material within the plume this work indicates that there are two particle populations the first population consists of particles with radius of 0 001 0 01 microns while the second population which is concentrated near the source comprises particles with radius greater than 1 micron the population of smaller particles includes most of the particulate mass in the plume this work increases the previously estimated particulate mass johnson et al 1979 and suggests that the so2 gas spectroscopically identified by pearl et al 1979 may represent transient flow from the volcano instead of an atmosphere in stable equilibrium with the local surface

surface changes on io during the galileo mission abstract a careful survey of galileo ssi global monitoring images revealed more than 80 apparent surface changes that took place on io during the 5 year period of observation ranging from giant plume deposits to subtle changes in the color or albedo of patera surfaces explosive volcanic activity was discovered at four previously unrecognized centers an unnamed patera to the south of karei that produced a pele sized red ring a patera to the west of zal that produced a small circular bright deposit a large orange ring detected near the north pole of io and a small bright ring near io s south pole only a handful of io s many active volcanoes produced large scale explosive eruptions and several of these erupted repeatedly leaving at least 83 of io s surface unaltered throughout the galileo mission most of the hot spots detected from ssi nims and ground based thermal observations caused no noticeable surface changes greater than 10 km in extent over the five year period surface changes were found at every location where active plumes were identified including acala which was never seen in sunlight and was only detected through auroral emissions during eclipse two types of plumes are distinguished on the basis of the size and color of their deposits confirming post voyager suggestions by mcewen and soderblom icarus 55 1983 191 smaller plumes produce near circular rings typically 150 200 km in radius that are white or yellow in color unless contaminated with silicates and frequently coat their surroundings with frosts of fine grained so2 the larger plumes are much less numerous limited to a half dozen examples and produce oval orange or red sulfur rich rings with maximum radii in the north south direction that are typically in the range from 500 to 550 km both types of plumes can be either episodic or quasi continuous over a five year period repeated eruptions of the smaller so2 rich plumes likely contribute significantly to io s resurfacing rate whereas dust ejection is likely dominated by the tenuous giant plumes both types of plume deposits fade on time scales of months to years through burial and alteration episodic seepages of so2 at haemus montes zal montes dorian montes and the plateau to the north of pillan patera may have been triggered by activity at nearby volcanic centers

a possible brine reservoir beneath occator crater thermal and compositional evolution and formation of the cerealia dome and vinalia faculae abstract the dawn spacecraft has imaged several putative cryovolcanic features on ceres and several lines of evidence point to past cryovolcanic activity at occator crater it is therefore possible that cryovolcanism played a key role in delivering sodium carbonate and chloride enriched brines to ceres surface in recent geological times the detection of a 200 km 200 km negative bouguer anomaly beneath occator suggests the presence of a low density region beneath the crater if this region is a residual partially crystallized cryomagma chamber excess pressures caused by its gradual freezing or stresses produced by the occator forming impact could have facilitated the delivery of cryolavas to the surface in the geologically recent past here the progressive solidification of a cryomagma chamber beneath occator and implications for the delivery of cryolavas to the surface has been explored models for the behavior of cryolavas at ceres surface and for the formation of the cerealia dome and vinalia faculae are also presented minimal crystallization of a subsurface fluid reservoir located at the crust mantle boundary could have driven cryolavas enriched in chloride salts and nh3 to ceres surface however cryolavas enriched in sodium carbonates would have had to have existed at shallower levels in the crust in order to be delivered to the surface via pressure driven ascent depending on the size of the reservoir cryolavas could have been driven to ceres surface for tens to hundreds of millions of years after cooling of the cryomagma chamber commenced the mineralogy at occator is suggestive of subsurface cryomagma reservoirs enriched in sodium carbonate and chloride salts aqueous solutions enriched in chloride salts and or ammonia would have arrived at the surface at warm enough temperatures to erupt if transported in propagating fractures that traveled at least 10 5 m s additionally if the cerealia dome was formed from viscous cryolava extrusions bulk kinematic lava viscosities may have been between 106 108 m2 s at the onset of relaxation plausible relaxation times to form the dome which are linked to bulk cryolava rheology are found to have ranged from 2 5 to 273 days moreover the low volatile content necessary to drive explosive eruptions on ceres supports the possibility that cerealia and vinalia faculae were emplaced as a consequence of ballistic eruptions the enigmatic geology of occator crater is consistent with a diversity of exchange processes operating on ceres in the geologically recent past further the processes that have occurred at occator could shed light on the changing geology associated with a relic ocean world future studies of occator and ceres should be undertaken with these results in mind

mountains on io high resolution galileo observations initial interpretations and formation models during three close flybys in late 1999 and early 2000 the galileo spacecraft acquired new observations of the mountains that tower above io s surface these images have revealed surprising variety in the mountains morphologies they range from jagged peaks several kilometers high to lower rounded structures some are very smooth others are covered by numerous parallel ridges many mountains have margins that are collapsing outward in large landslides or series of slump blocks but a few have steep scalloped scarps from these observations we can gain insight into the structure and material properties of io s crust as well as into the erosional processes acting on io we have also investigated formation mechanisms proposed for these structures using finite element analysis mountain formation might be initiated by global compression due to the high rate of global subsidence associated with io s high resurfacing rate however our models demonstrate that this hypothesis lacks a mechanism for isolating the mountains the large fraction 40 of mountains that are associated with paterae suggests that in some cases these features are tectonically related therefore we have also simulated the stresses induced in io s crust by a combination of a thermal upwelling in the mantle with global lithospheric compression and have shown that this can focus compressional stresses if this mechanism is responsible for some of io s mountains it could also explain the common association of mountains with paterae

kernel estimation methods for seismic hazard area source modeling in probabilistic seismic hazard analysis the representation of seismic sources by area zones is a standard means of data reduction however where the association between seismicity and geology is complex as it is in many tectonic regimes the construction of zone geometry may become contentiously subjective and ambiguities may end up being resolved through appeal to the nonscientific rule of conservatism or pragmatism although consideration of alternative zonations within a logic tree framework provides a channel for some of the uncertainty it does not address the fundamental validity of the zonation procedure itself in particular neither the minimal assumption of uniform seismicity within a zone nor the euclidean geometry of a zone accord with the fractal spatial distribution of seismicity and the magnitude insensitivity of zonation ignores the spatial extent and correlations of different sized earthquakes an alternative procedure for area source modeling avoids euclidean zones and is based statistically on kernel estimation of the activity rate density inferred from the regional earthquake catalog the form of kernel is governed by the concepts of fractal geometry and self organized criticality with the bandwidth scaling according to magnitude in contrast with zonal models for intraplate regions the kernel estimation methodology makes provision for moderate earthquakes to cluster spatially while larger events may migrate over sizeable distances

cryomagmatic mechanisms for the formation of rhadamanthys linea triple band margins and other low albedo features on europa we investigate cryomagmatic mechanisms for the formation of the diffuse low albedo margins of triple bands and haloes associated with elliptical lenticulae on europa one mechanism involves explosive venting of a gas particle spray derived from a subsurface body of volatile bearing water assuming the dark features represent cryoclastic deposits erupted from a medial or central vent modeling the dynamics of the eruptive plumes indicates that eruption velocities of 30 to 250 m s 1 and volatile contents of 0 1 to 20 wt are required to produce deposits having the observed dimensions calculated heights for ballistic plumes range from 1 to 25 km as an alternative mechanism we consider conductive heating of lithospheric ice by a subsurface heat source e g a warm ice diapir or cryomagmatic intrusion which promotes enhanced sublimation of surface ice producing local enrichment of nonice material an analytical model describing a constant temperature infinite heat source places lower bounds on the time scales required to produce a detectable feature a numerical treatment of more realistic geometries and boundary conditions allows cooling of the heat source to be modeled we find that the thermal model satisfactorily explains features with the dimensions of minor lineaments and lenticulae haloes a few kilometers over time intervals of 104 to 105 years the formation of a sublimation lag deposit proceeds rapidly once the ice temperature exceeds a threshold of 130 k however for triple bands measuring up to 25 km in width additional heat sources such as repeated or multiple intrusions are necessary to reproduce the observed dimensions this is consistent with the observation that well developed triple bands typically have multiple medial ridge sets each of which may represent a discrete tabular heat source although neither the volcanic nor intrusive thermal model can be ruled out at this stage the latter is a more satisfactory explanation for some characteristics of the low albedo features analyzed in this study

continuous deformation of the tibetan plateau from global positioning system data global positioning system velocities from 553 control points within the tibetan plateau and on its margins show that the present day tectonics in the plateau is best described as deformation of a continuous medium at least when averaged over distances of 100 km deformation occurs throughout the plateau interior by ese wnw extension and slightly slower nne ssw shortening relative to eurasia material within the plateau interior moves roughly eastward with speeds that increase toward the east and then flows southward around the eastern end of the himalaya crustal thickening on the northeast ern and eastern margins of the plateau occurs over a zone 400 km wide and cannot be the result of elastic strain on a single major thrust fault shortening there accommodates much of india s penetration into eurasia a description in terms of movements of rigid blocks with elastic strain associated with slip on faults between them cannot match the velocity field

volcanic resurfacing of io post repair hst imaging abstract in march 1994 we used the newly refurbished hubble space telescope hst to obtain global imaging of io at five wavelengths between 0 34 and 1 02 m with a spatial resolution of 160 km the images provided the clearest view of io since voyager and the first systematic observations in the wavelength range 0 7 1 0 m we have produced absolutely calibrated global mosaics of io s reflectance in all our five wavelengths the near infrared images reveal that the 0 55 to 0 7 m absorption edge seen in io s disk integrated spectrum has a very different spatial distribution from the better known 0 40 to 0 50 m absorption edge studied by voyager and must be generated by a different chemical species the 0 55 to 0 7 m absorption edge is strongly concentrated in the pyroclastic ejecta blanket of the volcano pele at a few much smaller discrete spots and probably also in the polar regions the pele ejecta spectrum is consistent with the idea that s 2 o partially decomposed to s 4 and probably s 3 may be the species responsible for the 0 55 to 0 7 m absorption edge at pele and elsewhere on io though s 4 generated by other processes may also be a possibility s 2 o can be produced by high temperature decomposition of so 2 gas and the high temperature of the pele volcano may account for its concentration there spectral anomalies of comparable size and prominence are not seen around the other pele type volcanos surt and aten a s mcewen and l a soderblom 1983 icarus 55 191 217 suggesting that these volcanos if chemically similar to pele are much less active the spectrum of high latitude regions is similar to that of quenched red sulfur glass and if this similarity is not coincidental the glass may be preserved here by the low polar surface temperatures alternatively the low polar temperatures may preserve sulfur that has been reddened by radiation there are many changes in albedo patterns in the 15 years between voyager and these hst observations but these are generally subtle at hst resolution and are not strongly concentrated in longitude however there was a major brightening of a 400 km diameter region centered on ra patera between march 1994 and repeat hst observations in july 1995 which was a larger albedo change than any seen in the previous 15 years this was presumably due to a large eruption at ra patera as confirmed by galileo images long exposure eclipse images of io at 1 02 m on march 6 1994 place strong limits on the area of exposed silicate magma on io at the time of the observations

probabilistic seismic hazard assessment for the area of kyrgyzstan tajikistan and eastern uzbekistan central asiaprobabilistic seismic hazard assessment for the area of kyrgyzstan tajikistan and eastern uzbekistan

volcanic plume heights on mars limits of validity for convective models 1 previous studies have overestimated volcanic plume heights on mars in this work we demonstrate that volcanic plume rise models as currently formulated have only limited validity in any environment these limits are easily violated in the current mars environment and may also be violated for terrestrial and early mars conditions we indicate some of the shortcomings of the model with emphasis on the limited applicability to current mars conditions specifically basic model assumptions are violated when 1 vertical velocities exceed the speed of sound 2 radial expansion rates exceed the speed of sound 3 radial expansion rates approach or exceed the vertical velocity or 4 plume radius grossly exceeds plume height all of these criteria are violated for the typical mars example given here solutions imply that the convective rise model is only valid to a height of 10 km the reason for the model breakdown is that the current mars atmosphere is not of sufficient density to satisfy the conservation equations it is likely that diffusion and other effects governed by higher order differential equations are important within the first few kilometers of rise when the same criteria are applied to eruptions into a higher density early mars atmosphere we find that eruption rates higher than 1 4 109 kg s also violate model assumptions this implies a maximum extent of 65 km for convective plumes on early mars the estimated plume heights for both current and early mars are significantly lower than those previously predicted in the literature therefore global scale distribution of ash seems implausible

characterizing deposits emplaced by cryovolcanic plumes on europa abstract in the absence of direct observations of europa s particle plumes deposits left behind during eruptive events would provide the best evidence for recent geological activity and would serve as indicators of the best places to search for ongoing activity on the icy moon here we model the morphological and spectral signatures of europan plume deposits utilizing constraints from recent hubble space telescope observations as model inputs we consider deposits emplaced by plumes that are 1 km to 300 km tall and find that in the time between the galileo mission and the arrival of the europa clipper spacecraft plumes that are

volcanic history geologic analysis and map of the prometheus patera region on io data from jupiter s moon io returned by the galileo spacecraft have been used to create a geologic map of prometheus patera its associated flow field and nearby features we have identified the location of the vent that fed the prometheus flow field during the galileo epoch in the north eastern portion of the main prometheus flow field this vent is the probable source of a small sulphur rich plume previous studies suggested that the vent may be atop a tectonic fault but we find that the vent is offset from the putative fault it is plausible that in the past magma exploited the fault to reach the surface at prometheus patera but subsequent magma cooling in the conduit could have caused an obstruction preventing further eruptions from providing significant contributions to the prometheus flow field we also speculate on how a new prometheus plumbing system may be fed by mafic magmas after melt stalls in magma reservoirs during its ascent through the lithosphere from the mantle

sulfur volcanism on io abstract in february 2003 march 2003 and january 2004 pele plume transmission spectra were obtained during jupiter transit with hubble s space telescope imaging spectrograph stis using the 0 1 wide slit and the g230lb grating the stis spectra covered the 2100 3100 a wavelength regions and extended spatially along io s limb encompassing the region directly above and northward of the vent of the pele volcano the s2 and so2 absorption signatures evident in these data indicate that the gas signature at pele was temporally variable and that an s2 absorption signature was present 12 from the pele vent near 6 5 s and 264 15 w suggesting the presence of another s2 bearing plume on io contemporaneous with the spectral data uv and visible wavelength images of the plume were obtained in reflected sunlight with the advanced camera for surveys acs prior to jupiter transit the dust scattering recorded in these data provide an additional qualitative measure of plume activity on io indicating that the degree of dust scattering over pele varied as a function of the date of observation and that there were several other dust bearing plumes active during the observations we present constraints on the composition and variability of the gas abundances of the pele plume as well as the plumes detected by acs and recorded within the stis data as a function of time

analysis of seismic activity in the crust from earthquake relocation in the central tien shan using p and s wave arrivals from local earthquakes recorded by a temporary broadband seismic network ghengis and a kyrgyzstan broadband seismic network knet we determined the source parameters of 1938 earthquakes occurring from 1997 to 1998 in the central tien shan and adjacent areas based on one dimensional and three dimensional velocity models the results indicate that seismic activity is not restricted to only central tien shan but also penetrates into the edges of the kazakh platform and the tarim basin to the north and south respectively it implies that most range bounding faults in the central tien shan are active and they play a significant role in the tectonic activity of the mountain belt however seismic activity of the talas fergana fault in the study area is different its central segment seems more active than its eastern segment we infer that this part of the fault may be activated by neighboring faults whereas its eastern segment could be temporally locked the earthquakes at the depths of 30 40 km beneath the east central tien shan reveal an interaction between the upper and mid lower crust this suggests that brittle failure is possible to greater depth within the crust another possibility is that the seismic activity in the mid lower crust is affected by a positive buoyancy force created by mantle upwelling of this area these observations indicate that dynamic processes such as small scale mantle convection or mantle upwelling which resulted in lithospheric thinning or removal still occur beneath the central tien shan

speckle imaging of volcanic hotspots on io with the keck telescope abstract using speckle imaging techniques on the 10 m w m keck i telescope we observed near infrared emission at 2 2 m from volcanic hotspots on io in july august 1998 using several hundreds of short exposure images we reconstructed diffraction limited images of io on each of three nights we measured the positions of individual hotspots to 0 004 or better corresponding to a relative positional error of 20 km on io s surface the sensitivity of normal ground based images of io is limited by confusion between overlapping sources by resolving these multiple points we detected up to 17 distinct hotspots the largest number ever seen in a single image during the month long span of our 1998 observations several events occurred loki was at the end of a long brightening and we observed it to fade in flux by a factor of 2 8 over the course of one month at the 3 sigma level we see evidence that loki s position shifts by 100 km this suggests that the brightening may not have been located at the primary loki emission center but at a different source within the loki caldera we also see a bright transient source near loki among many other sources we detect a dim source on the limb of io at the latitude of pele this source is consistent with 2 7 of the thermal emission from the pele volcano complex being scattered by the pele plume which would be the first detection of a plume through scattered infrared hotspot emission

high temperature silicate volcanism on jupiter s moon io infrared wavelength observations of io by the galileo spacecraft show that at least 12 different vents are erupting lavas that are probably hotter than the highest temperature basaltic eruptions on earth today in at least one case the eruption near pillan patera two independent instruments on galileo show that the lava temperature must have exceeded 1700 kelvin and may have reached 2000 kelvin the most likely explanation is that these lavas are ultramafic magnesium rich silicates and this idea is supported by the tentative identification of magnesium rich orthopyroxene in lava flows associated with these high temperature hot spots

density structure of io and the migration of magma through its lithosphere we model the density structure of the outer several tens of kilometers of io on the basis of the assumption that condensed volatiles mainly so2 exist at shallow depths in a mafic to ultramafic lithosphere which has a finite porosity due to its accumulation as a mixture of pyroclastic and effusive volcanic deposits which include condensed volatiles the porosity decreases with increasing depth due to pressure driven compaction and temperature driven melting of the volatiles and this controls the bulk density structure of the lithosphere we also model the densities of ascending magmas as a function the types and amounts of volatiles that are available in their source regions the relative densities of the accumulated volcanic deposits and of the magmas rising through them control whether the magmas will erupt at the surface or will stall to form intrusions which can grow into magma reservoirs we find that the depths at which magma reservoirs may exist are strongly influenced by the void space fraction in surface deposits and only weakly controlled by the mass fraction of so2 in the deposits and the mass fraction of so2 in the magmas once nucleated a reservoir has the potential to grow to a very large vertical extent 15 km total height before the magma immediately beneath its roof is again buoyant relative to the surrounding rocks the presence of large volume reservoirs may explain the great extent of the larger lava flow fields seen on io and the longevity of some eruptions the presence of very soluble volatiles such as water in magmas would have virtually no effect on these findings because these volatiles would influence the densities of magmas only very near the surface though they would even in very small amounts then have a dramatic effect on the explosivities of eruptions