pancakelike domes on venus the shape of seven large domes on the plains of venus with volumes between 100 and 1000 km3 is compared with that of an axisymmetric gravity current spreading over a rigid horizontal surface both the altimetric profiles and the horizontal projection of the line of intersection of domes on the synthetic aperture radar images agree well with the theoretical similarity solution for a newtonian fluid but not with the shape calculated for a rigid plastic rheology nor with that for a static model with a strong skin as a viscous current spreads it generates an isotropic strain rate tensor whose magnitude is independent of radius such a flow can account for the randomly oriented cracks that are uniformly distributed on the surface of the domes the stress induced by the flow in the plains material below is obtained and is probably large enough to produce the short radial cracks in the surface of the plains beyond the domes the viscosity of the domes can be estimated from their thermal time constants if spreading is possible only when the fluid is hot and lies between 1014 and 1017 pa s laboratory experiments show that such viscosities correspond to temperatures of 610 to 700 c in dry rhyolitic magmas these temperatures agree with laboratory measurements of the solidus temperature of wet rhyolite these results show that the development of the domes can be understood using simple fluid dynamical ideas and that the magmas involved can be produced by wet melting at depths below 10 km followed by eruption and degassing

photometric changes on saturn s titan evidence for active cryovolcanism 1 we report infrared spectrophotometric variability on the surface of saturn s moon titan detected in images returned by the visual and infrared mapping spectrometer vims onboard the cassini saturn orbiter the changes were observed at 7 s 138 w and occurred between october 27 2005 and january 15 2006 after that date the surface was unchanged until the most recent observation march 18 2006 we previously reported spectrophotometric variability at another location 26 s 78 w cassini synthetic aperture radar sar images find that the surface morphology at both locations is consistent with surface flows possibly resulting from cryovolcanic activity wall et al companion paper this issue the vims reported time variability and sar morphology results suggest that titan currently exhibits intermittent surface changes consistent with present ongoing surface processes we suggest that these processes involve material from titan s interior being extruded or effused and deposited on the surface as might be expected from cryovolcanism

steep sided domes on venus characteristics geologic setting and eruption conditions from magellan data a survey of more than 95 percent of the venus surface reveals 145 steep sided domes which can be subdivided into a variety of morphologic forms the most common being shaped like inverted bowls or flat topped domes results of a preliminary analysis of the distribution and geologic setting of the domes are presented the relation of the domes to analogous terrestrial features is examined and possible models for their mode of emplacement are outlined

loess and life out of earth abstract loess is a homogeneous typically nonstratified porous friable slightly coherent often calcareous fine grained silty pale yellow wind blown aeolian and often by water reworked sediment that is distributed on continents world wide recent studies have highlighted the importance of biological loess crusts in trapping and transforming aeolian material into loess and also in prevention from wind and water erosion of deposited material some planets and satellites in our solar system are characterized by conditions comparable to those related to loess formation in terrestrial environments given the requirements for loess deposition on earth this study aims to ask the following questions 1 if loess like sediment formation is possible outside earth what are the mechanisms of sediment deposition and preservation 2 could the possible loess like sediments be stabilized through the activity of extraterrestrial equivalents of biological loess crusts found on earth as loess formation on earth is related to biological activity we propose a new direction in the search for extraterrestrial life evidence about extraterrestrial loess might indicate extraterrestrial life connected to loess formation on the basis of comparative analysis of some astrophysical conditions of seven celestial bodies we propose mars and titan and possibly venus and io to be assessed for evidence of loess deposition and the possible presence of related life forms and their biomarkers following recent advances in our understanding of terrestrial loess deposition we propose new indicators of extraterrestrial life research biomarkers in loess cyanobacterial and other microbial

inversion of complex body waves we have developed a method that inverts seismic body waves to determine the mechanism and rupture pattern of earthquakes the rupture pattern is represented as a sequence of subevents distributed on the fault plane this method is an extension of our earlier method in which the subevent mechanisms were fixed in the new method the subevent mechanisms are determined from the data and are allowed to vary during the sequence when subevent mechanisms are allowed to vary however the inversion often becomes unstable because of the complex trade offs between the mechanism the timing and the location of the subevents many different subevent sequences can explain the same data equally well and it is important to determine the range of allowable solutions some constraints must be imposed on the solution to stabilize the inversion we have developed a procedure to explore the range of allowable solutions and appropriate constraints in this procedure a network of grid points is constructed on the i plane where and i are respectively the onset time and the distance from the epicenter of a subevent the best fit subevent is determined at all grid points then the correlation is computed between the synthetic waveform for each subevent and the observed waveform the correlation as a function of and i and the best fit mechanisms computed at each i grid point depict the character of allowable solutions and facilitate a decision on the appropriate constraints to be imposed on the solution the method is illustrated using the data for the 1976 guatemala earthquake

the 2012 sumatra great earthquake sequence the equatorial indian ocean is a well known place of active intraplate deformation defying the conventional view of rigid plates separated by narrow boundaries where deformation is confined on 11 april 2012 this region was hit in a couple of hours by two of the largest strike slip earthquakes ever recorded moment magnitudes mw 8 6 and 8 2 broadband seismological observations of the mw 8 6 mainshock indicate a large centroid depth 30 km and remarkable rupture complexity detailed study of the surface wave directivity and moment rate functions clearly indicates the partition of the rupture into at least two distinct subevents to account for these observations we developed a procedure to invert for multiple point source parameters the optimum source model at long period consists of two point sources separated by about 209 km with magnitudes mw 8 5 and 8 3 to explain the remaining discrepancies between predicted and observed surface waves we can refine this model by adding directivity along the wnw ese axis however we do not exclude more complicated models to analyze the mw 8 2 aftershock we removed the perturbation due to large surface wave arrivals of the mw 8 6 mainshock by subtracting the corresponding synthetics computed for the two subevent model analysis of the surface wave amplitudes suggests that the mw 8 2 aftershock had a large centroid depth between 30 km and 40 km this major earthquake sequence brings a new perspective to the seismotectonics of the equatorial indian ocean and reveals active deep lithospheric deformation

the april 2012 indian ocean earthquakes seismotectonic context and implications for their mechanisms the 11 april 2012 earthquakes m w 8 6 and m w 8 2 were sourced within the northern wharton basin in the northeastern part of the indo australian diffuse plate boundary this unusually active oceanic intraplate region has generated many large earthquakes in the past most of which are believed to have occurred by strike slip motion triggered by the nw se oriented compressional stresses acting across the indian and australian plates in the aftermath of the 2004 megathrust earthquake along the nearby sunda trench increased seismicity in the northern wharton basin is attributed to the stress transfer from the sumatra andaman plate boundary models proposed for the april 2012 earthquakes differ somewhat in details but partly attribute their complex rupture to the reactivation of pre existing structures these structures include previously mapped n s trending fracture zones within the northern wharton basin and e w lineations across the ninetyeast ridge in this paper we review the regional tectonics and past seismicity on the indo australian plate in order to understand the seismotectonic setting of the april 2012 indian ocean earthquakes c 2014 elsevier b v all rights reserved

the 2002 denali fault and 2001 kunlun fault earthquakes complex rupture processes of two large strike slip events we studied the source processes of two large continental earthquakes the 3 november 2002 denali fault earthquake and the 14 november 2001 kunlun fault earthquake associated with strike slip faulting along ancient sutures we inverted teleseismic p waveforms using a pulse stripping method for multiple time windows with different focal mechanisms and derived composite source models according to our results the 2002 denali fault earthquake began with initial thrusting m w 7 3 along a 40 km long segment of the north northwest dipping susitna glacier fault and later ruptured a 300 km long segment along the denali and totschunda faults with a right lateral strike slip mechanism m w 7 7 in contrast the 2001 kunlun fault earthquake nucleated near an extensional step over with a subevent pair consisting of 30 km long strike slip m w 6 9 event and 40 km long normal m w 6 8 faulting event and later ruptured a 350 km long segment along the kunlun fault with a left lateral strike slip mechanism m w 7 7 both earthquakes propagated primarily unilaterally to the east and released most of their energy along slip patches asperities far from the hypocenter locations we find that both the denali fault and kunlun fault earthquakes had high average rupture velocities of 3 2 km sec and 3 4 km sec respectively we also compared the source properties of these two earthquakes with other strike slip earthquakes for scaling purposes large strike slip earthquakes were classified as interplate oceanic intraplate or continental intraplate events by using this classification the denali fault and kunlun fault earthquakes have an interplate signature that suggests overall weak faulting

the lobes of lava flows on earth and olympus mons mars the lobate distal margins of lava flows provide a useful source of morphological information on the rheology of the lava if the lobes are assumed to represent the arrest of free flowing isothermal bingham fluids on a slope the widths of lobes are a more useful practical index than lobe thicknesses because they are about an order of magnitude larger and can be more accurately measured from aerial photographs and other remote images lobes do not suffer from the changes in morphology that channels undergo during the course of eruptions a terrestrial data set of flow lobe and ancillary measurements from lavas throughout the range alkali olivine basalt to rhyolite shows some features that are predicted by the isothermal bingham fluid model these are correlation of width and thickness over more than two orders of magnitude and essentially no correlation of aspect ratio with slope there is a positive correlation of lobe width with silica content of the lava from a data set of measurements on lava flow lobes from the martian volcano olympus mons the mean value of aspect ratio 0 07 was found to be significantly less than that for the terrestrial data set 0 19 higher general levels of effusion rate on olympus mons are probably the factor responsible after normalisation lobe widths on olympus mons are found to be largely equivalent to those expected for terrestrial flows with andesitic basaltic silica contents

titan radar mapper observations from cassini s t3 fly by cassini s titan radar mapper imaged the surface of saturn s moon titan on its february 2005 fly by denoted t3 collecting high resolution synthetic aperture radar and larger scale radiometry and scatterometry data these data provide the first definitive identification of impact craters on the surface of titan networks of fluvial channels and surficial dark streaks that may be longitudinal dunes here we describe this great diversity of landforms we conclude that much of the surface thus far imaged by radar of the haze shrouded titan is very young with persistent geologic activity

shapes of venusian pancake domes imply episodic emplacement and silicic composition the main evidence available for constraining the composition of the large circular pancake domes on venus is their gross morphology laboratory simulations using polyethylene glycol show that the height to diameter aspect ratios of domes of a given total volume depend critically on whether their extrusion was continuous or episodic with more episodes leading to greater cooling and taller domes thus without observations of their emplacement the compositions of venusian domes cannot be uniquely constrained by their morphology however by considering a population of 51 venusian domes to represent a sampling of many stages during the growth of domes with comparable histories and by plotting aspect ratio versus total volume we find that the shapes of the domes are most consistent with episodic emplacement on earth this mode of dome growth is found almost exclusively in lavas of dacite to rhyolite composition strengthening earlier inferences about the presence of evolved magmas on venus

effects of three dimensional earth structure on cmt earthquake parameters abstract we investigate errors in centroid earthquake parameters due to unmodeled structural heterogeneity we generate a simulated dataset consisting of synthetic seismograms for 50 earthquakes and 150 stations distributed globally to generate the synthetic seismograms we use a spectral element wave propagation package specfem3d globe that accounts for the earth s three dimensional structure an established centroid moment tensor inversion algorithm from the global cmt project is used to invert the synthetic dataset with and without added noise for earthquake source parameters this algorithm uses a one dimensional earth structure together with approximate corrections for three dimensional structure to model the seismograms we interpret the differences between the estimated source parameters and the parameters used to compute the synthetic dataset as errors due to unmodeled structural heterogeneity and the presence of noise we expect that the errors obtained in this study are representative of the errors in the global cmt catalogue we find that the errors in scalar moment moment tensor elements and location are small on average the depth and centroid time are however biased by a small amount we find that the error in depth can be reduced significantly by applying corrections for the difference in the velocity structure at the source and receiver locations from the earth s average structure in the cmt inversions this modification has a minimal effect on the errors in centroid time we do not find large errors in scalar moments even where the crustal thickness at the source is very different from the earth s average crustal thickness

prerequisites for explosive cryovolcanism on dwarf planet class kuiper belt objects explosive extrusion of cold material from the interior of icy bodies or cryovolcanism has been observed on enceladus and perhaps europa triton and ceres it may explain the observed evidence for a young surface on charon pluto s surface is masked by frosts here we evaluate prerequisites for cryovolcanism on dwarf planet class kuiper belt objects kbos we first review the likely spatial and temporal extent of subsurface liquid proposed mechanisms to overcome the negative buoyancy of liquid water in ice and the volatile inventory of kbos we then present a new geochemical equilibrium model for volatile exsolution and its ability to drive upward crack propagation this novel approach bridges geophysics and geochemistry and extends geochemical modeling to the seldom explored realm of liquid water at subzero temperatures we show that carbon monoxide co is a key volatile for gas driven fluid ascent whereas co 2 and sulfur gases only play a minor role n 2 ch 4 and h 2 exsolution may also drive explosive cryovolcanism if hydrothermal activity produces these species in large amounts a few percent with respect to water another important control on crack propagation is the internal structure a hydrated core makes explosive cryovolcanism easier but an undifferentiated crust does not we briefly discuss other controls on ascent such as fluid freezing on crack walls and outline theoretical advances necessary to better understand cryovolcanic processes finally we make testable predictions for the 2015 new horizons flyby of the pluto charon system

a very broad band inversion method for the recovery of earthquake source parameters abstract waveform studies of the earthquake source have traditionally been performed in narrow bands of the seismic spectrum waveform matching of p and sh waves emphasizes frequencies near and above the corner frequency normal mode and surface wave analyses on the other hand are performed on data which contain information only below the corner frequency a new method is presented which formally includes the result of a long period centroid moment tensor analysis in an inversion of broad band body wave phases a parametrized source model is used which allows for the recovery of a detailed source time function as well as the direction and magnitude of rupture propagation the technical details and the performance of the method are demonstrated in an analysis of the october 28 1983 borah peak idaho earthquake in particular it is shown how the combination of the long period and broad band data sets in the inversion improves the resolution of both the focal mechanism and the scalar moment the very broad band method is applied in an analysis of the september 19 1985 michoacan m w 8 0 earthquake two concentrations of moment release are identified in the source time function separated by 25 30 s in time the spatial distribution of moment is well explained both by a model of unilateral rupture towards the east with a propagation velocity of 2 4 km s 1 and by two point sources separated by 95 km it is shown that the p wave data are largely insensitive to the scalar moment and that source time functions obtained without consideration of the total moment release exaggerate the heterogeneity of slip on the fault plane source time functions which do contain the total moment show that a large fraction of the moment was released smoothly over the whole duration 80 s of the event the results suggest that the fault plane was characterized by two regions of high stress drop but that a large portion of slip occurred on surrounding weak portions of the plane

modeling 3 d wave propagation and finite slip for the 1998 balleny islands earthquake we simulate surface waves in a 3 d earth model using a spectral element method for existing kinematic source models of the m w 8 1 25 march 1998 balleny islands earthquake the 3 d model incorporates lateral variations in the crust and mantle on the basis of models crust2 0 and s20rts our objective is to investigate the fit of the observed and simulated long period surface waves in the hope of improving on the existing source models we modify a body wave model determined by henry et al 2000 to improve the fit of long period surface waveforms we demonstrate that adding a smooth component of slip extending over a fault that connects the two subevents determined by henry et al 2000 without invoking slip on multiple fault planes or on unconnected fault patches provides reasonable fits to long period surface waves as well as body waves

en echelon and orthogonal fault ruptures of the 11 april 2012 great intraplate earthquakes the magnitude 8 7 earthquake that occurred off the coast of the sumatra subduction zone on 11 april 2012 is shown to have had an extraordinarily complex four fault rupture these great ruptures represent large lithospheric deformation that may eventually lead to a localized boundary between the indian and australian plates on 11 april 2012 two of the largest strike slip earthquakes ever recorded at magnitudes of 8 7 and 8 2 occurred in the northeastern indian ocean a few hundred kilometres off the coast of sumatra three groups now report the analysis of seismic data from the days and months before and after these events as well as the events themselves matthias delescluse and co authors show that these earthquakes are part of the ongoing boost of intraplate deformation between india and australia that followed the aceh 2004 and nias 2005 megathrust earthquakes they conclude that the australian plate driven by slab pull forces at the sunda trench is gradually detaching from the indian plate han yue and colleagues show that the 11 april event involved a complex four fault rupture lasting several minutes followed two hours later by a magnitude 8 2 aftershock these great ruptures on a lattice of strike slip faults that extends through the crust and into the upper mantle represent large lithospheric deformation that may eventually create a localized boundary between the indian and australian plates fred pollitz and colleagues show that in the six days following 11 april the global rate of remote earthquakes with magnitudes greater than 5 5 increased nearly fivefold and events up to magnitude 7 seem to have been triggered the unprecedented delayed triggering power of this earthquake may arise from its strike slip source geometry or because it struck at a time of an unusually low global earthquake rate and increased the number of nucleation sites that were very close to failure the indo australian plate is undergoing distributed internal deformation caused by the lateral transition along its northern boundary from an environment of continental collision to an island arc subduction zone1 2 on 11 april 2012 one of the largest strike slip earthquakes ever recorded seismic moment magnitude mw 8 7 occurred about 100 200 kilometres southwest of the sumatra subduction zone occurrence of great intraplate strike slip faulting located seaward of a subduction zone is unusual it results from northwest southeast compression within the plate caused by the india eurasia continental collision to the northwest together with northeast southwest extension associated with slab pull stresses as the plate underthrusts sumatra to the northeast here we use seismic wave analyses to reveal that the 11 april 2012 event had an extraordinarily complex four fault rupture lasting about 160 seconds and was followed approximately two hours later by a great mw 8 2 aftershock the mainshock rupture initially expanded bilaterally with large slip 20 30 metres on a right lateral strike slip fault trending west northwest to east southeast wnw ese and then bilateral rupture was triggered on an orthogonal left lateral strike slip fault trending north northeast to south southwest nne ssw that crosses the first fault this was followed by westward rupture on a second wnw ese strike slip fault offset about 150 kilometres towards the southwest from the first fault finally rupture was triggered on another en echelon wnw ese fault about 330 kilometres west of the epicentre crossing the ninetyeast ridge the great aftershock with an epicentre located 185 kilometres to the ssw of the mainshock epicentre ruptured bilaterally on a nne ssw fault the complex faulting limits our resolution of the slip distribution these great ruptures on a lattice of strike slip faults that extend through the crust and a further 30 40 kilometres into the upper mantle represent large lithospheric deformation that may eventually lead to a localized boundary between the indian and australian plates

rupture process of the 2008 wenchuan china earthquake inferred from teleseismic waveform inversion and forward modeling of broadband seismic waves abstract we investigate the source process of the may 12 2008 wenchuan earthquake using teleseismic waveform data we divide the source area into southwestern and northeastern segments and estimate the probable dip angle for the northeastern fault segment by analyzing the waveform misfit of the inversion the results of the slip distribution indicate a thrust motion around the epicenter while a strike slip motion dominates from about 110 km northeast of the epicenter to the northeastern end of the fault the maximum slip and total seismic moments are estimated as being up to 11 0 m and 1 2 1021 n m mw 8 0 respectively additionally we simulate broadband seismic waves to verify our source model assuming realistic three dimensional earth structures and using the spectral element method the resulting synthetic waveforms agree well with the observed waveforms for both body and surface waves in the frequency range in the period from 20 to 150 s in our model comprising high angle strike slip mechanisms in the northeastern segment the misfits of the surface wave in the range from 60 to 500 s is systematically smaller than the corresponding values in other source models comprising thrust or low angle strike slip mechanisms the coulomb stress distribution in the northeastern segment computed by using our model indicates positive and large changes induced by the rupture in the southwestern segment we consider that the source fault of the 2008 wenchuan earthquake is composed of at least two main fault segments one with a low dip angle and the other with a high dip angle which are dominated by thrust and strike slip motions respectively we further consider that the rupture might transfer between these two faults during the mainshock

mylitta fluctus venus rift related centralized volcanism and the emplacement of large volume flow units mylitta fluctus is a volcanic flow field that covers approximately 300 000 km2 in southern lavinia planitia the flows are typically radar bright with uniform surface textures central channels are common maximum flow lengths range from 400 to 1000 km flow widths range 30 100 km in the medial and distal portions of the flow field the total volume of the flow field based on estimates of flow thickness is of the order of 2 104 km3 the flow field is composed of six smaller flow fields that are interpreted to represent major eruption events in the evolution of mylitta an asymmetric shield volcano 200 km in radius with a central caldera has been identified as the single major source it is located along a possible rift zone at the northern edge of lada terra no evidence for fissure fed eruptions is observed although eruptions may have occurred along fissures within the rift before the main vent centralized mylitta is similar in scale to many terrestrial flood basalt provinces although it is lower in total estimated volume and is distinguished by the presence of a central source edifice the origin of mylitta is proposed to be linked to regional extension and possible hotspot activity in a manner similar to that suggested for the origin of terrestrial flood basalts the lower apparent volume of mylitta relative to terrestrial flood basalts suggests that the amount of material upwelling from the mantle may have been lower in this case or that the formation of the flow field has not yet finished detailed studies of the morphology and distribution of flow fields similar to mylitta should yield insight into the variation and evolution of hotspot related volcanism and the formation of possible flood basalts on venus

the 14 november 2001 kokoxili kunlunshan tibet earthquake rupture transfer through a large extensional step over the 14 november 2001 kokoxili tibet earthquake m w 7 8 ruptured 400 km of the western kunlun fault in northern tibet we apply two inversion methods to p and sh waves recorded by the global seismographic network to recover the spatial and temporal history of the rupture process the observed surface rupture consists of two strike slip segments offset by an extensional step over little surface rupture was observed in the graben system in this step over which is approximately 45 km long and over 10 km wide our results imply that the rupture did not jump this large gap but that the rupture was continuous through the graben the earthquake began with a small strike slip subevent presumably along the westernmost of the two segments this was followed 5 sec later by a subevent of about the same magnitude but having an oblique mechanism with a large normal faulting component the likely location for this subevent is within the graben this oblique slip event probably enabled transfer of the rupture onto the main kunlun fault the main moment release began 18 sec after rupture initiation and propagated over 350 km eastward along the kunlun fault slip on this segment was very heterogeneous averaging 2 m for the first 200 km followed by a sharp increase to a maximum of 7 5 m within the next 50 km and then a rapid decline the average rupture velocity along the main segment was high 3 6 km sec 1 and probably exceeded the local shear wave velocity the m w 7 8 kokoxili earthquake had a longer surface rupture and faster average rupture velocity radiated more energy and probably had a lower average fracture energy than the november 2002 m w 7 9 denali fault alaska earthquake evidence suggests that the velocity of the rupture front dropped significantly after passing the point of maximum slip implying a large difference in frictional strength between the two ends of the fault online material waveform fits to teleseismic body waves

a rare great earthquake on an oceanic fossil fracture zone first motion solution found in this study and has a strike consistent with the fracture zone north of the bend the southern fault plane with strike 178 d ip 54 and rake 65 has a strike consistent with the portion of the fracture zone to the south of the bend and has a dip which can be explained by the style of deformation that the region is undergoing the centroid moment tensor solution of the broad band model is calculated and found to be consistent with the region of low misfit in mantle wave solution space the broad band solution has a moment of 1 53 10 21 nm mw 8 1 again consistent with the mantle wave data slip propagated bilaterally with an approximate rupture velocity of 3k ms 1 80 per cent of local shear wave speed the rupture front is less well resolved to the south of the epicentre than to the north the majority 75 per cent of moment originated from slip on the northern fault the broad band data requires significant slip below the oceanic moho with as much as 70 per cent of moment due to slip in the brittle uppermost mantle in the preferred model

inversion of long period p waves from great earthquakes along subduction zones abstract long period p waves from subduction zone earthquakes in the moment range from 7 1027to 8 1029dyn cm are analyzed using an iterative deconvolution method in addition to discrete subevents which effectively contribute to the observed seismograms the long period component of the moment rate function is derived with the constraint that the total seismic moment is equal to the moment determined from long period surface waves it is shown that great earthquakes can be described by several subevents with a duration of about 10 s which changes little from earthquake to earthquake in the above moment range the long period component of the moment rate function becomes larger for a greater earthquake the greatest earthquakes of mw 9 additionally involve subevents with another duration scale much longer than 10 s it is also shown that the local stress drop is 1 order of magnitude larger than the stress drop averaged over the entire fault plane the constancy of the local stress drop as well as the average stress drop holds among various magnitudes of earthquakes these observations suggest an essential similarity in the mode of dislocation distribution

the 2012 mw 8 6 wharton basin sequence a cascade of great earthquakes generated by near orthogonal young oceanic mantle faults we improve constraints on the slip distribution and geometry of faults involved in the complex multisegment mw 8 6 april 2012 wharton basin earthquake sequence by joint inversion of high rate gps data from the sumatran gps array sugar teleseismic observations source time functions from broadband surface waves and far field static gps displacements this sequence occurred under the indian ocean 400 km offshore sumatra the events are extraordinary for their unprecedented rupture of multiple cross faults deep slip large strike slip magnitude and potential role in the formation of a discrete plate boundary between the indian and australian plates the sugar recorded static displacements of up to 22 cm along with time varying arrivals from the complex faulting which indicate that the majority of moment release was on young wnw trending right lateral faults counter to initial expectations that an old lithospheric nne trending fracture zone played the primary role the new faults are optimally oriented to accommodate the present day stress field not only was the greatest moment released on the younger faults but it was these that sustained very deep slip and high stress drop 20 mpa the rupture may have extended to depths of up to 60 km suggesting that the oceanic lithosphere in the northern wharton basin may be cold and strong enough to sustain brittle failure at such depths alternatively the rupture may have occurred with an alternative weakening mechanism such as thermal runaway

the 2016 kaikōura earthquake revealed by kinematic source inversion and seismic wavefield simulations slow rupture propagation on a geometrically complex crustal fault network the 2016 kaik ura new zealand earthquake generated large ground motions and resulted in multiple onshore and offshore fault ruptures a profusion of triggered landslides and a regional tsunami here we examine the rupture evolution using two kinematic modelling techniques based on analysis of local strong motion and high rate gps data our kinematic models capture a complex pattern of slowly vr 2km s propagating rupture from the south to north with over half of the moment release occurring in the northern source region mostly on the kekerengu fault 60 seconds after the origin time both models indicate rupture re activation on the kekerengu fault with the time separation of 11 seconds between the start of the original failure and start of the subsequent one we further conclude that most near source waveforms can be explained by slip on the crustal faults with little 8 or no contribution from the subduction interface

cassini radar views the surface of titan the cassini titan radar mapper imaged about 1 of titan s surface at a resolution of 0 5 kilometer and larger areas of the globe in lower resolution modes the images reveal a complex surface with areas of low relief and a variety of geologic features suggestive of dome like volcanic constructs flows and sinuous channels the surface appears to be young with few impact craters scattering and dielectric properties are consistent with porous ice or organics dark patches in the radar images show high brightness temperatures and high emissivity and are consistent with frozen hydrocarbons

geomorphologic mapping of the menrva region of titan using cassini radar data abstract we made a detailed geomorphologic map of the menrva region of titan using cassini radar data as our map base using similar techniques and approaches that were applied to mapping magellan radar images of venus and earlier more generalized titan maps we were able to define and characterize 10 radar morphologic units along with inferred dunes and fluvial channels from the radar data structural features such as scarps ridges and lineaments were also identified using principles of superposition cross cutting and embayment relations we created a sequence of map units for this region we interpret menrva to be a 440 km wide degraded impact basin in agreement with earlier studies by elachi et al elachi c et al 2006 nature 441 709 713 and wood et al wood c a lorenz r kirk r lopes r mitchell k stofan e and the cassini radar team 2010 icarus 206 334 344 and identify it as the oldest feature in the map region exogenic processes including hydrocarbon fluid channelization forming the elivagar flumina channel network and dune fields resulting from aeolian activity are the current geologic processes dominating our map area and these processes have contributed to the erosion of the crater s ejecta field there is evidence of multiple episodes of channel formation erosion and burial by aeolian deposits as observed elsewhere on titan by e g barnes et al barnes j w et al 2005 icarus 195 400 414 channel outflow regions have morphologies suggestive of streams formed by flash floods and dune fields are small and restricted rather than forming large dune seas consistent with a desert like environment for this region with low supply of hydrocarbon particles also consistent with other studies by e g lorenz et al lorenz r d et al 2008a planet space sci 56 1132 1144 there is no evidence of cryovolcanism or non impact related tectonic activity in the menrva region although this region is too small to infer anything about the roles of these processes elsewhere on titan this work suggests detailed geomorphologic mapping can confidently be applied to cassini radar data and we suggest that more extensive mapping should be done using radar iss and vims data geographically distributed across titan to assess its usefulness for a future combined radar iss vims based global geologic map

the 2015 mw 7 1 earthquake on the charlie gibbs transform fault repeating earthquakes and multimodal slip on a slow oceanic transform the 2015 mw 7 1 earthquake on the charlie gibbs transform fault along the mid atlantic ridge is the latest in a series of seven large earthquakes since 1923 we propose that these earthquakes form a pair of quasi repeating sequences with the largest magnitudes and longest repeat times for such sequences observed to date we model teleseismic body waves and find that the 2015 earthquake ruptured a distinct segment of the transform from the previous 1998 earthquake the two events display similarities to earthquakes in 1974 and 1967 respectively we observe large oceanic transform earthquakes to exhibit characteristic slip behavior initiating with small slip near the ridge and propagating unilaterally to significant slip asperities nearer the center of the transform these slip distributions combined with apparent segmentation support multimode slip behavior with fault slip accommodated both seismically during large earthquakes and aseismically in between

on convection in ice i shells of outer solar system bodies with detailed application to callisto it has been argued that the dominant non newtonian creep mechanisms of water ice make the ice shell above callisto s ocean and by inference all radiogenically heated ice i shells in the outer solar system stable against solid state convective overturn conductive heat transport and internal melting oceans are therefore predicted to be or have been widespread among midsize and larger icy satellites and kuiper belt objects alternatively at low stresses where non newtonian viscosities can be arbitrarily large convective instabilities may arise in the diffusional creep regime for arbitrarily small temperature perturbations for callisto ice viscosities are low enough that convection is expected over most of geologic time above the internal liquid layer for plausible ice grain sizes a few mm the alternative for early callisto a conducting shell over a very deep ocean 450 km is not compatible with callisto s present partially differentiated state moreover if convection is occurring today the stagnant lid would be quite thick 100 km and compatible with the lack of active geology nevertheless callisto s steady state heat flow may have fallen below the convective minimum for its ice i shell late in solar system history in this case convection ends the ice shell melts back at its base and the internal ocean widens considerably the presence of such an ocean of order 200 km thick is compatible with callisto s moment of inertia but its formation would have caused an 0 25 radial expansion the tectonic effects of such a late slow expansion are not observed so convection likely persists in callisto possibly subcritically ganymede due to its greater size rock fraction and full differentiation has a substantially higher heat flow than callisto and has not reached this tectonic end state titan if differentiated and triton should be more similar to ganymede in this regard pluto like callisto may be near the tipping point for convective shutdown but uncertainties in its size and rock fraction prevent a more definitive assessment

modeling cryogenic mud volcanism on pluto abstract subsurface ice cryofluids and ice interactions with ammonia for cryovolcanic materials give the potential ingredients for the formation of mud volcanoes on pluto in order to constrain the possible morphology from images acquired by the new horizons spacecraft we have modeled the formation of mud volcanoes isostatic layers of ice overlain by denser material from a series of possible solid liquid mud compositions methane and ammonia as well as accounting for the full range of eruption variables e g mud viscosity conduit diameter and eruption duration we categorize them into nine specific scenarios based on the composition of the top ice layer and mud composition from these scenarios the maximum height of the potential mud volcano can be calculated we find that ammonia mud sources produce smaller edifice heights and wider flow profiles compared to methane dominant mud cryovolcanoes assuming certain preliminary parameters we also propose the evolution and development of the edifice of wright mons in as little as 3 8 million years given a 10 wt ammonia subsurface mud composition if characterized on pluto s surface mud volcanoes would provide an interesting insight on the subsurface dynamics of solids and cryofluids on pluto

europa tidal heating of upwelling thermal plumes and the origin of lenticulae and chaos melting europa we show that tidal energy can be preferentially focused in rising plumes for viscosities in agreement with laboratory experiments when the plume cores reach the base of the outer cold brittle layer they spread laterally causing shallow melting disruption and formation of terrain similar to lenticulae and chaos we show that this mechanism can readily explain the major characteristics of chaos and lenticulae even if the average outer solid ice layer thickness is larger than 20 km

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

the unique radar properties of silicic lava domes 1 silicic lava domes exhibit distinct morphologic characteristics at scales of centimeters to kilometers multiparameter radar observations capture the unique geometric signatures of silicic domes in a set of radar scattering properties that are unlike any other natural geologic surfaces backscatter cross section values are among the highest observed on terrestrial lava flows and show only a weak decrease with incidence angle cross polarization backscatter hv shows a unique behavior increasing with increasing wavelength circular polarization ratios are relatively high in the 0 3 0 95 range and increase with increasing wavelength field measurements of boulder size frequency distributions and microtopography indicate that silicic dome surfaces are among the roughest ever measured rms heights at a 1 m lateral scale range from 13 cm to 50 cm rms slopes at 1 m spacing range from 12 to 43 degrees modeling of the scattering behavior suggests it results from a combination of rough surface facet scattering and scattering from block edges that act as a random collection of dipoles the unusual wavelength dependence of the radar parameters appears to result from a higher component of edge scattering at large wavelengths producing for example higher cross polarized backscatter at p band 68 cm steep sided volcanic domes on venus superficially resemble terrestrial silicic domes in plan view gross morphology but few similarities remain when the radar scattering and three dimensional shapes of the features are compared the unique radar scattering properties suggest that such volcanic surfaces can be identified with multiparameter radar observations in future planetary radar missions and in active terrestrial volcanoes where dome development can represent serious hazards

centroid moment tensor solutions for january to march 1998 abstract centroid moment tensor cmt solutions are presented for 204 earthquakes that occurred during the first quarter of 1998 the solutions are obtained using corrections for aspherical earth structure represented by a whole mantle shear velocity model sh8 u4l8 of dziewonski and woodward dziewonski a m woodward r l 1992 acoustic imaging at the planetary scale in emert h harjes h p eds acoustical imaging vol 19 plenum press new york pp 785 797 a model of anelastic attenuation of durek and ekstrom bull seism soc am 86 1996 144 is used to predict the decay of the waveforms

the great march 25 1998 antarctic plate earthquake moment tensor and rupture history we use broadband body and mantle wave data to study the 1998 antarctic intraplate earthquake the centroid moment tensor cmt has a large non double couple component there exist two pure double couple constrained solutions that fit the data almost equally well the frequent practice of taking the best double couple gives a far from optimal solution we use p and sh body waves to determine the rupture parameters of the first and larger of the two observed subevents the best rupture plane with strike 96 dip 69 and rake 18 is compatible with only one of the two cmt solutions strike 96 dip 64 rake 23 centroid location 63 1 s 148 4 e 10 km depth centroid time 0313 02 ut and m0 1 3 1021 n m mw 8 0 the first subevent is a simple primarily westward propagating 140 km rupture of 45 s duration with average velocity 3 km s 1 it has a seismic moment of 1 2 1021 n m mw 8 0 with 75 of its moment released between 10 and 27 s and a stress drop of 240 bars the rupture is physically bounded by two fracture zones at 147 5 e and 150 e the second subevent lasted from 70 to 90 s on a fault extending from 210 to 270 km west of the epicenter with a moment of 0 3 0 6 1021 n m mw 7 6 7 8 this is a spectacular example of dynamic stress triggering over a 100 km separation distance with a time delay of 40 s the complex pattern of aftershocks is primarily controlled by preexisting fracture zones on the ocean floor

resurfacing of titan by ammonia water cryomagma the cassini titan radar mapper observed on titan several large features interpreted as cryovolcanic during the october 26 2004 pass at high northern latitudes lopes r m c and 43 colleagues 2007 icarus 186 395 412 to date models of ammonia water resurfacing have not been tied to specific events or evolutionary stages of titan we propose a model of cryovolcanism that involves cracking at the base of the ice shell and formation of ammonia water pockets in the ice as these ammonia water pockets undergo partial freezing in the cold ice shell the ammonia concentration in the pockets increases decreasing the negative buoyancy of the ammonia water mixture if the ice shell is contaminated by silicates delivered in impacts the liquid solid density difference would be even less while the liquid cannot easily become buoyant relative to the surrounding ice these concentrated ammonia water pockets are sufficiently close to the neutral buoyancy point that large scale tectonic stress patterns tides non synchronous rotation satellite volume changes solid state convection or subsurface pressure gradients associated with topography would enable the ammonia to erupt effusively onto the surface rather than suggesting steady state volcanism over the history of the solar system we favor a scenario where the cryovolcanic features could have been associated with episodic potentially late geological activity

the march 25 1998 antarctic plate earthquake the march 25 1998 antarctic plate earthquake mw 8 1 occurred 250 km from the nearest plate boundary in oceanic lithosphere with an age of 35 55 my analysis of aftershock patterns shows that the earthquake ruptured a fault or series of strike slip fault segments nearly 300 km long the strike of the fault s is nearly perpendicular to the north south trending fossil fracture zones which are the most marked bathymetric features of this region moment release during the mainshock was concentrated in two large subevents clearly visible in the teleseismic body wave waveforms modeling of these body waves using a finite fault source places the first of the two subevents near the point of rupture initiation on the eastern end of the fault with the second large subevent occurring 220 280 km to the west the two pulses of moment release are found to be separated in time by 65 s comparison of the relative s wave amplitudes of the first and second pulses suggests that a rotation of the focal mechanism by 10 occurred between the two subevents

the geology of hotei regio titan correlation of cassini vims and radar abstract joint cassini vims and radar sar data of 700 km wide hotei regio reveal a rich collection of geological features that correlate between the two sets of images the degree of correlation is greater than anywhere else seen on titan central to hotei regio is a basin filled with cryovolcanic flows that are anomalously bright in vims data in particular at 5 m and quite variable in roughness in sar the edges of the flows are dark in sar data and appear to overrun a vims bright substrate sar stereo topography shows the flows to be viscous 100 200 m thick on its southern edge the basin is ringed by higher 1 km mountainous terrain the mountains show mixed texture in sar data some regions are extremely rough exhibit low and spectrally neutral albedo in vims data and may be partly coated with darker hydrocarbons around the southern margin of hotei regio the sar image shows several large dendritic radar bright channels that flow down from the mountainous terrain and terminate in dark blue patches seen in vims images whose infrared color is consistent with enrichment in water ice the patches are in depressions that we interpret to be filled with fluvial deposits eroded and transported by liquid methane in the channels in the vims images the dark blue patches are encased in a latticework of lighter bands that we suggest to demark a set of circumferential and radial fault systems bounding structural depressions conceivably the circular features are tectonic structures that are remnant from an ancient impact structure we suggest that impact generated structures may have simply served as zones of weakness no direct causal connection such as impact induced volcanism is implied we also speculate that two large dark features lying on the northern margin of hotei regio could be calderas in summary the preservation of such a broad suite of vims infrared color variations and the detailed correlation with features in the sar image and sar topography evidence a complex set of geological processes pluvial fluvial tectonic cryovolcanic impact that have likely remained active up to very recent geological time

macrofracturing of oceanic lithosphere in complex large earthquake sequences major earthquakes in oceanic lithosphere seaward of the subduction zone outer trench slope are relatively uncommon but several recent occurrences have involved very complex sequences rupturing multiple nonaligned faults and or having high aftershock productivity with diffuse distribution this includes the 21 december 2010 m w 7 4 ogasawara bonin 11 april 2012 m w 8 6 indo australia 23 january 2018 m w 7 9 off kodiak island and 20 december 2018 m w 7 3 nikol skoye northwest pacific earthquakes major oceanic intraplate event sequences farther from plate boundaries do not tend to be as complex in faulting or aftershocks outer trench slope extensional faulting can involve complex distributed sequences particularly when activated by great megathrust ruptures such as 11 march 2011 m w 9 1 tohoku and 15 november 2006 m w 8 3 kuril islands intense faulting sequences also occur near subduction zone corners with many fault geometries being activated including some in nearby oceanic lithosphere as for the 29 september 2009 m w 8 1 samoa 6 february 2013 m w 8 0 santa cruz islands and 16 november 2000 m w 8 0 new ireland earthquakes the laterally varying plate boundary stresses from heterogeneous locking recent earthquakes or boundary geometry influence the specific faulting geometries activated in nearby major intraplate ruptures in oceanic lithosphere preexisting lithospheric structures and fabrics exert secondary influences on the faulting intraplate stress release in oceanic lithosphere near subduction zones favors distributed macrofracturing of near critical fault systems rather than localized single fault failures both under transient loading induced by plate boundary ruptures and under slow loading by tectonic motions and slab pull

titan s inventory of organic surface materials 1 cassini radar observations now permit an initial assessment of the inventory of two classes presumed to be organic of titan surface materials polar lake liquids and equatorial dune sands several hundred lakes or seas have been observed of which dozens are each estimated to contain more hydrocarbon liquid than the entire known oil and gas reserves on earth dark dunes cover some 20 of titan s surface and comprise a volume of material several hundred times larger than earth s coal reserves overall however the identified surface inventories 3 104 km3 of liquid and 2 105 km3 of dune sands are small compared with estimated photochemical production on titan over the age of the solar system the sand volume is too large to be accounted for simply by erosion in observed river channels or ejecta from observed impact craters the lakes are adequate in extent to buffer atmospheric methane against photolysis in the short term but do not contain enough methane to sustain the atmosphere over geologic time unless frequent resupply from the interior buffers this greenhouse gas at exactly the right rate dramatic climate change on titan is likely in its past present and future

distribution and interplay of geologic processes on titan from cassini radar data abstract the cassini titan radar mapper is providing an unprecedented view of titan s surface geology here we use synthetic aperture radar sar image swaths ta t30 obtained from october 2004 to december 2007 to infer the geologic processes that have shaped titan s surface these sar swaths cover about 20 of the surface at a spatial resolution ranging from 350 m to 2 km the sar data are distributed over a wide latitudinal and longitudinal range enabling some conclusions to be drawn about the global distribution of processes they reveal a geologically complex surface that has been modified by all the major geologic processes seen on earth volcanism tectonism impact cratering and erosion and deposition by fluvial and aeolian activity in this paper we map geomorphological units from sar data and analyze their areal distribution and relative ages of modification in order to infer the geologic evolution of titan s surface we find that dunes and hummocky and mountainous terrains are more widespread than lakes putative cryovolcanic features mottled plains and craters and crateriform structures that may be due to impact undifferentiated plains are the largest areal unit their origin is uncertain in terms of latitudinal distribution dunes and hummocky and mountainous terrains are located mostly at low latitudes less than 30 with no dunes being present above 60 channels formed by fluvial activity are present at all latitudes but lakes are at high latitudes only crateriform structures that may have been formed by impact appear to be uniformly distributed with latitude but the well preserved impact craters are all located at low latitudes possibly indicating that more resurfacing has occurred at higher latitudes cryovolcanic features are not ubiquitous and are mostly located between 30 and 60 north we examine temporal relationships between units wherever possible and conclude that aeolian and fluvial pluvial lacustrine processes are the most recent while tectonic processes that led to the formation of mountains and xanadu are likely the most ancient

tracking high frequency seismic source evolution 2004 mw 8 1 macquarie event the 2004 mw 8 1 event on 23 december 2004 near the macquarie ridge is a very large intraplate event that has been overshadowed by the mw 9 3 sumatra andaman event only 3 days later we are able to track the progress of source evolution by estimating the progression of the points of energy emission exploiting the good azimuthal distribution of available stations the results indicate that this event ruptured on two nearby fault systems reactivating fossil fracture zones with the second subevent to the west triggered by the first the total duration of high frequency radiation is quite short about 60 s for such a large event much of the high frequency radiation occurs on a fault subparallel to that inferred from long period studies this composite fault behavior with displaced triggered failure appears to be a characteristic of large intraplate events beneath the oceans

fluvial erosion and post erosional processes on titan the surface of titan has been revealed by cassini observations in the infrared and radar wavelength ranges as well as locally by the huygens lander instruments sand seas recently discovered lakes distinct landscapes and dendritic erosion patterns indicate dynamic surface processes this study focus on erosional and depositional features that can be used to constrain the amount of liquids involved in the erosional process as well as on the compositional characteristics of depositional areas fluvial erosion channels on titan as identified at the huygens landing site and in radar and visible and infrared mapping spectrometer vims observations have been compared to analogous channel widths on earth yielding average discharges of up to 1600 m3 s for short recurrence intervals that are sufficient to move centimeter sized sediment and significantly higher discharges for long intervals with respect to the associated drainage areas this roughly translates to 1 150 cm day runoff production rates with 10 years recurrence intervals and by assuming precipitation this implies 0 6 60 mm h rainfall rates thus the observed surface erosion fits with the methane convective storm models as well as with the rates needed to transport sediment during cassini s t20 fly by the vims observed an extremely eroded area at 30 w 7 s with resolutions of up to 500 m pixel that extends over thousands of square kilometers the spectral characteristics of this area change systematically reflecting continuous compositional and or particle size variations indicative of transported sediment settling out while flow capacities cease to account for the estimated runoff production and widespread alluvial deposits of fine grained material release of area dependent large fluid volumes are required only frequent storms with heavy rainfall or cryovolcanic induced melting can explain these erosional features

mathematical modelling of anisotropy of illite rich shale summary the estimation of illite rich shale anisotropy to account for the alignment of clays and gas or brine filled cracks is presented via mathematical modelling such estimation requires analysis to interpret the dominance of one effect over another this knowledge can help to evaluate the permeability in the unconventional reservoir stress orientation and the seal capacity for the conventional reservoir effective media modelling is used to predict the elastic properties of the illite rich shale and to identify the dominant contributions to the shale anisotropy we consider two principal reasons of the shale anisotropy orientation of clay platelets and orientation of fluid filled cracks in reality both of these two factors affect the shale anisotropy the goal of this study is first to separately analyse the effect of these two factors to reveal the specific features in p and s wave velocity behaviour typical of each of the factors and then consider a combined effect of the factors when the cracks are horizontally or vertically aligned to do this we construct four models of shale the behaviour of p and s wave velocities is analysed when gas and water filled cracks embedded in a host matrix are randomly oriented or horizontally or vertically aligned the host matrix can be either isotropic or anisotropic of vti symmetry in such a modelling we use published data on mineralogy and clay platelet alignment along with other micromechanical measurements in the model where the host matrix is isotropic the presence of a singularity point when the difference changes its sign in shear wave velocities is an indicator of brine filled aligned cracks in the model with the vti host matrix and horizontally aligned cracks filled with gas an increase in their volume concentration leads to that the azimuth at which the singularity is observed moves toward the symmetry axis in this case if the clay content is small around 20 per cent the singularity point may even vanish the thomsen parameters are helpful in fluid type indication in shale an indicator of gas filled aligned cracks is if aligned cracks in illite rich shale are brine filled negative value of indicates brine filled cracks in illite rich shale a shale with brine filled cracks exhibits higher vp vs ratio in the vertical direction as compared to the gas filled shale a disorientation of clay platelets and brine filled cracks may lead to that the singularity point is absent for brine saturated shale as well in this case one can also observe and decreased values of vp vs in the vertical direction as in the case of gas filled cracks in the presence of vertically aligned cracks shales exhibit distinctly revealed features of orthorhombic symmetry the results have important applications where seismic measurements are applied to predict the maturity state of the shale

surface albedo spectral properties of geologically interesting areas on titan we investigate the nature and possible formation processes of three areas on titan s surface which have been suggested as geologically interesting hotei regio tui regio and sotra patera we also reanalyze the spectral characteristics of the huygens landing site we apply a statistical principal component analysis pca and a radiative transfer rt method on the visual and infrared mapping spectrometer datacubes in order to retrieve the surface albedo of distinct spectral units in the near infrared we have been able to exploit only a subset of the currently available hotei regio data which are in general not optimal in terms of geometry for an analysis with a plane parallel rt code our inferred surface albedos present generally higher values from 1 to 2 m and lower ones at 0 94 and in the 2 6 5 m region the regions of interest rois within hotei regio tui regio and sotra patera are always significantly brighter than the surrounding areas the largest variations are found longward of 2 m and mainly at 5 m this higher surface albedo with respect to the surrounding area and in general the fact that the spectral behavior is different for each of these areas is probably indicative of diverse chemical compositions and origins we compare the spectral albedos with some suggested surface candidates on titan such as h2o co2 and ch4 ices as well as tholin and discuss possible chemical composition variations as well as other interpretations

compound rupture of the great 1998 antarctic plate earthquake the march 25 1998 antarctic plate earthquake ruptured a portion of the antarctic plate more than 200 km west of its boundary with the australian plate the harvard centroid moment tensor solution indicates that the earthquake was primarily a strike slip event but the large non double couple component of the moment tensor suggests considerable complexity in the rupture process we use a finite fault inversion method to determine details of the rupture process from teleseismic body waves recorded by the global seismic network the p waves are poorly fit by one or more subevents having only a strike slip mechanism we find that the presence of a large oblique normal faulting subevent located to the east of the hypocenter is necessary to improve the fit this subevent combines with a larger strike slip subevent to the west to comprise the main moment release in the earthquake and is the cause of the large non double couple component in the long period focal mechanism the earthquake exhibited very high slip and high stress drop compared with most interplate strike slip events and the rupture was largely confined to the upper 15 20 km of the lithosphere both constituent focal mechanisms indicate that this part of the antarctic plate is under nw se oriented tension although the origin of these stresses is unknown

the 2012 mw 8 6 sumatra earthquake evidence of westward sequential seismic ruptures associated to the reactivation of a n s ocean fabric 1 the 11 april 2012 mw 8 6 earthquake offshore sumatra is the largest of the rare great intraplate earthquakes of the instrumental era this major strike slip event occurred in the diffuse zone of deformation that accommodates differential rotation between indian and australian plates we perform a back projection analysis calibrated with well located aftershocks of short period teleseismic p waves recorded by the european array to image the rupture process during the mainshock in complement a love wave analysis is conducted for tracking azimuthal change in the apparent global source duration due to the source spatio temporal extent the combined analysis reveals a complex rupture pattern characterized by three main episodes of energy release the latest being located 370 km west of the epicenter on the ninety east ridge with a delay of 120 s we interpret the 11 april 2012 mw 8 6 offshore sumatra earthquake as a complex westward propagating sequence of dynamically triggered strike slip fault ruptures associated to the reactivation of the inherited nne striking sea floor fabric the dynamic triggering mechanism could result from the interaction between transient surface wave stress perturbations and fluids

microwave dielectric constant of liquid hydrocarbons application to the depth estimation of titan s lakes 1 cassini radar reveals the surface of titan since flyby ta acquired on october 2004 the radar instrument discovered volcanic structures craters dunes channels lakes and seas in particular flyby t16 realized in july 2006 imaged tens of radar dark features close to titan s north pole they are interpreted as lakes filled with liquid hydrocarbons mainly methane a key material in the geologic and climatic history of titan in order to perform quantitative analysis and modeling of the radar response of titan s lakes the dielectric constant of liquid hydrocarbons is a crucial parameter in particular to estimate the radar wave attenuation we present here first measurements of the dielectric constant of lng liquefied natural gas mainly composed of methane at ku band 10 13 ghz we obtained a value 1 75 0 002j this value is used to model the radar backscattering of lakes observed during t16 flyby using a two layer scattering model we derive a relationship that is used to estimate a minimum depth for titan s lakes the proposed relationship is also coherent with the observation that the larger and then the deeper lakes are also the darker in radar images

analysis and interpretation of cassini titan radar altimeter echoes abstract the cassini spacecraft has acquired 25 radar altimeter elevation profiles along titan s surface as of april 2008 and we have analyzed 18 of these for which there are currently reconstructed ephemeris data altimeter measurements were collected at spatial footprint sizes from 6 60 km along ground tracks of length 400 3600 km the elevation profiles yield topographic information at this resolution with a statistical height accuracy of 35 50 m and kilometer scale errors several times greater the data exhibit significant variations in terrain from flat regions with little topographic expression to very rugged titanscapes the bandwidth of the transmitted waveform admits vertical resolution of the terrain height to 35 m at each observed location on the surface variations in antenna pointing and changes in surface statistics cause the range compressed radar echoes to exhibit strong systematic and time variable biases of hundreds of meters in delay it is necessary to correct the received echoes for these changes and we have derived correction algorithms such that the derived echo profiles are accurate at the 100 m level for off nadir pointing errors of 0 3 and 0 6 for leading edge and echo centroid estimators respectively the leading edge of the echo yields the elevation of the highest points on the surface which we take to be the peaks of any terrain variation the mean value of the echo delay is more representative of the mean elevation so that the difference of these values gives an estimate of any local mountain heights finding locations where these values diverge indicates higher relief terrain elevation features are readily seen in the height profiles several of the passes show mountains of several hundred m altitude spread over 10 s or even 100 s of km in spatial extent so that slopes are very small large expanses of sub 100 m topography are commonplace on titan so it is rather smooth in many locations other areas exhibit more relief although the overall observed variation in surface height on any pass is less than about 1 km some elevation features correspond to observed changes in brightness in cassini infrared images but many do not correspondence between the imaging sar ground tracks and the altimeter paths is limited so that identifying elevation changes with higher resolution sar features is premature at present

a rigid and weathered ice shell on titan a strong inverse correlation between gravity and topography leads to the conclusion that saturn s largest moon titan must have a rigid ice shell with an elastic thickness exceeding 40 kilometres titan saturn s largest moon may have a stronger ice shell than previously thought several lines of evidence suggest that titan has a global subsurface ocean beneath an outer ice shell 50 200 km thick with a rigid portion that is thin and weak here hemingway et al report a strong inverse correlation between gravity and topography at long wavelengths that are not dominated by tides and rotation this finding is not compatible with a geologically active low rigidity ice shell suggesting that titan s ice shell must be substantially rigid with an elastic thickness of greater than 40 km several lines of evidence suggest that saturn s largest moon titan has a global subsurface ocean beneath an outer ice shell 50 to 200 kilometres thick1 2 3 4 if convection5 6 is occurring the rigid portion of the shell is expected to be thin similarly a weak isostatically compensated shell has been proposed7 8 to explain the observed topography here we report a strong inverse correlation between gravity3 and topography9 at long wavelengths that are not dominated by tides and rotation we argue that negative gravity anomalies mass deficits produced by crustal thickening at the base of the ice shell overwhelm positive gravity anomalies mass excesses produced by the small surface topography giving rise to this inverse correlation we show that this situation requires a substantially rigid ice shell with an elastic thickness exceeding 40 kilometres and hundreds of metres of surface erosion and deposition consistent with recent estimates from local features10 11 our results are therefore not compatible with a geologically active low rigidity ice shell after extrapolating to wavelengths that are controlled by tides and rotation we suggest that titan s moment of inertia may be even higher that is titan may be even less centrally condensed than is currently thought12

modelling of possible mud volcanism on titan possible sedimentary basins on titan are potential sites for the formation of mud volcanoes in order to constrain the appearance of such features in remotely sensed imagery being acquired by the cassini spacecraft we have modelled the formation of mud volcanoes on titan for a series of plausible mud compositions climatic conditions and geological settings as well as addressing the full range of eruption variables mud viscosity conduit diameter and eruption duration we find that for an acetylene mud source containing 20 wt liquid methane in pore spaces overlain by a sheet of water ice 500 m thick a mud volcano can grow as high as 140 m assuming reasonable eruption parameters such an edifice may develop into a pancake like dome several kilometres in diameter if observed and properly characterised mud volcanoes would provide an important window on the subsurface distribution and dynamics of solids and liquids in sedimentary basins on titan

inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 imperial valley california earthquake a least squares point by point inversion of strong ground motion and teleseismic body waves is used to infer the fault rupture history of the 1979 imperial valley california earthquake the imperial fault is represented by a plane embedded in a half space where the elastic properties vary with depth the inversion yields both the spatial and temporal variations in dislocation on the fault plane for both right lateral strike slip and normal dip slip components of motion inversions are run for different fault dips and for both constant and variable rupture velocity models effects of different data sets are also investigated inversions are compared which use the strong ground motions alone the teleseismic body waves alone and simultaneously the strong ground motion and teleseismic records the inversions are stabilized by adding both smoothing and positivity constraints the moment is estimated to be 5 0 10 25 dyne cm and the fault dip 90 5 dislocation in the hypocentral region south of the united states mexican border is relatively small and almost dies out near the border dislocation then increases sharply north of the border to a maximum of about 2 m under interstate 8 dipslip motion is minor compared to strike slip motion and is concentrated in the sediments the best fitting constant rupture velocity is 80 per cent of the local shear wave velocity however there is a suggestion that the rupture front accelerated from the hypocenter northward the 1979 imperial valley earthquake can be characterized as a magnitude 5 earthquake at the hypocenter which then grew into or triggered a magnitude 6 earthquake north of the border

the tectonics of titan global structural mapping from cassini radar abstract the cassini radar mapper has imaged elevated mountain ridge belts on titan with a linear to arcuate morphology indicative of a tectonic origin systematic geomorphologic mapping of the ridges in synthetic aperture radar sar images reveals that the orientation of ridges is globally e w and the ridges are more common near the equator than the poles comparison with a global topographic map reveals the equatorial ridges are found to lie preferentially at higher than average elevations we conclude the most reasonable formation scenario for titan s ridges is that contractional tectonism built the ridges and thickened the icy lithosphere near the equator causing regional uplift the combination of global and regional tectonic events likely contractional in nature followed by erosion aeolian activity and enhanced sedimentation at mid to high latitudes would have led to regional infilling and perhaps covering of some mountain features thus shaping titan s tectonic landforms and surface morphology into what we see today

geomorphological map of the afekan crater region titan terrain relationships in the equatorial and mid latitude regions we carried out geomorphological mapping in a mid latitude area surrounding the afekan crater region on titan we used cassini radar synthetic aperture radar mode data as the basemap supplemented by cassini radar microwave emissivity imaging science subsystem iss infrared data visual and infrared mapping spectrometer vims spectral images and topography derived from synthetic aperture radar sar mapping was done at a spatial scale of 300 m pixel which corresponds to a map scale of 1 800 000 we describe multiple terrain units and their spatial relations we describe five broad classes of units that are in agreement with previous mapping efforts crater labyrinth hummocky mountainous plains and dune terrain classes we subdivide these into seven crater units four hummocky mountainous units six plains units and three dunes units our results show that plains are the dominant unit in titan s mid latitudes of the plains units the undifferentiated plains are the largest by total areal extent in the mapped region accounting for over 45 of the mapped area we developed a stratigraphic sequence that has the hummocky mountainous and labyrinth terrains as the oldest units the observed properties of the hummocky mountainous terrain are consistent with fractured water ice materials while the labyrinth terrains are consistent with organic materials the youngest units are the dune units and streak like plains units with the undifferentiated plains units being of intermediate age the microwave emissivity of the undifferentiated plains and dune units are consistent with organic materials given their properties and stratigraphic placement we conclude that the hummocky mountainous terrains are most consistent with the presumed crustal materials of titan the plains materials are consistent with deposits resulting from the transport and emplacement of organic rich materials predominantly by aeolian mechanisms our geomorphological mapping results are consistent with the equatorial and mid latitudes of titan being dominated by organic materials that have been deposited and emplaced by aeolian activity

the vanishing cryovolcanoes of ceres ahuna mons is a 4 km tall mountain on ceres interpreted as a geologically young cryovolcanic dome other possible cryovolcanic features are more ambiguous implying that cryovolcanism is only a recent phenomenon or that other cryovolcanic structures have been modified beyond easy identification we test the hypothesis that cerean cryovolcanic domes viscously relax precluding ancient domes from recognition we use numerical models to predict flow velocities of ahuna mons to be 10 500 m myr depending upon assumptions about ice content rheology grain size and thermal parameters slower flow rates in this range are sufficiently fast to induce extensive relaxation of cryovolcanic structures over 108 109 years but gradual enough for ahuna mons to remain identifiable today positive topographic features including a tholus underlying ahuna mons may represent relaxed cryovolcanic structures a composition for ahuna mons of 40 ice explains the observed distribution of cryovolcanic structures because viscous relaxation renders old cryovolcanoes unrecognizable

titan s surface from cassini radar sar and high resolution radiometry data of the first five flybys abstract the first five titan flybys with cassini s synthetic aperture radar sar and radiometer are examined with emphasis on the calibration and interpretation of the high resolution radiometry data acquired during the sar mode sar radiometry maps of the 2 cm wavelength brightness temperature are obtained coincident with the sar swath imaging with spatial resolution approaching 6 km a preliminary calibration shows that brightness temperature in these maps varies from 64 to 89 k surface features and physical properties derived from the sar radiometry maps and sar imaging are strongly correlated in general we find that surface features with high radar reflectivity are associated with radiometrically cold regions while surface features with low radar reflectivity correlate with radiometrically warm regions we examined scatterplots of the normalized radar cross section 0 versus brightness temperature finding differing signatures that characterize various terrains and surface features implications for the physical and compositional properties of these features are discussed the results indicate that volume scattering is important in many areas of titan s surface particularly xanadu while other areas exhibit complex brightness temperature variations consistent with variable slopes or surface material and compositional properties

cryovolcanic features on titan s surface as revealed by the cassini titan radar mapper abstract the cassini titan radar mapper obtained synthetic aperture radar images of titan s surface during four fly bys during the mission s first year these images show that titan s surface is very complex geologically showing evidence of major planetary geologic processes including cryovolcanism this paper discusses the variety of cryovolcanic features identified from sar images their possible origin and their geologic context the features which we identify as cryovolcanic in origin include a large 180 km diameter volcanic construct dome or shield several extensive flows and three calderas which appear to be the source of flows the composition of the cryomagma on titan is still unknown but constraints on rheological properties can be estimated using flow thickness rheological properties of one flow were estimated and appear inconsistent with ammonia water slurries and possibly more consistent with ammonia water methanol slurries the extent of cryovolcanism on titan is still not known as only a small fraction of the surface has been imaged at sufficient resolution energetic considerations suggest that cryovolcanism may have been a dominant process in the resurfacing of titan

cassini radar images at hotei arcus and western xanadu titan evidence for geologically recent cryovolcanic activity 1 images obtained by the cassini titan radar mapper radar reveal lobate flowlike features in the hotei arcus region that embay and cover surrounding terrains and channels we conclude that they are cryovolcanic lava flows younger than surrounding terrain although we cannot reject the sedimentary alternative their appearance is grossly similar to another region in western xanadu and unlike most of the other volcanic regions on titan both regions correspond to those identified by cassini s visual and infrared mapping spectrometer vims as having variable infrared brightness strengthening the case that these are recent cryovolcanoes citation wall s d et al 2009 cassini radar images at hotei arcus and western xanadu titan evidence for geologically recent cryovolcanic activity geophys res lett 36 l04203 doi 10 1029 2008gl036415

non double couple moment tensor of the march 25 1998 antarctic earthquake composite rupture of strike slip and normal faults the 1998 antarctic intraplate earthquake mw 8 1 has a significant non double couple component in the moment tensor solution as determined from long period surface waves in the teleseismic p and sh wave forms there are two distinctive wave packets that can be explained by multiple strike slip subevents we propose a composite rupture model comprising two different episodes two predominant clusters of en echelon strike slip segments 16 1020 nm and normal faulting with a long duration of approximately 100 s 4 1020 nm this model agrees with observations of both teleseismic body waves and long period surface waves including the large non double couple component the normal faulting with as long a duration as the main strike slip rupture might be secondarily induced by the en echelon segments of strike slip faulting