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 geomorphology of rhea implications for geologic history and surface processes analyses of landforms on rhea are used to define three physiographic provinces cratered terrain 1 undifferentiated cratered terrain 1 lineated cratered terrain 2 for which stratigraphic relationships are derived and examined in relation to major impact basins and tectonic features the formation of multiringed basins may have caused or at least controlled the locations of major resurfacing and mantling events the diameters of central peaks relative to impact crater diameters are significantly larger than those within craters on the moon and mercury rim segments of polygonal craters have preferential orientations both crater and noncrater lineaments show regional orientations that do not fit current global or regional stress models superposition relationships of provinces and associated features imply the following postaccretional sequence for the geological evolution of rhea s surface cratered terrain 1 undifferentiated formed first then linear troughs and chains of coalescing pits developed extensively on cratered terrain 1 lineated a resurfacing event emplaced cratered terrain 2 on which small craters scarps and ridges formed small grooves on cratered terrain 1 undifferentiated are tentatively assigned a young age based on their susceptibility to impact erosion this geologic history is generally consistent with theoretical models for rhea s evolution

large impact features on middle sized icy satellites abstract all of the large impact features of the middle sized icy satellites of saturn and uranus that were clearly observed by the voyager spacecraft are described new image mosaics and stereo and photoclinometrically derived digital elevation models are presented landforms related to large impact features such as secondary craters and possible antipodal effects are examined and evaluated of the large impacts odysseus on tethys appears to have had the most profound effect on its target satellite of any of the impact features we examined our modeling suggests that the odysseus impact may have caused the prompt formation of ithaca chasma a belt of tectonic troughs that roughly follow a great circle normal to the center of odysseus although other hypotheses remain viable we identify probable secondary cratering from tirawa on rhea we attribute a number of converging coalescing crater chains on rhea to a putative possibly relatively fresh 350 km diameter impact feature we examine the antipodes of odysseus the putative 350 km diameter rhean impact feature and tirawa and conclude that evidence from voyager data for damage from seismic focusing is equivocal although our modeling results indicate that such damage may have occurred we propose a number of observations and tests for cassini that offer the opportunity to differentiate among the various explanations and speculations reviewed and evaluated in this study

tsunamis from the 29 march and 5 may 2015 papua new guinea earthquake doublet m w 7 5 and tsunamigenic potential of the new britain trench we characterized tsunamis from the 29 march and 5 may 2015 kokopo papua new guinea mw 7 5 earthquake doublet teleseismic body wave inversions using various rupture velocities vr showed similar source time functions and waveform agreements but the spatial distributions of the slips were different the rupture durations were 45 and 55 s for the march and may events with their peaks at 25 and at 17 s respectively tsunami simulations favored source models with vr 1 75 and 1 50 km s for the march and may earthquakes the largest slip on the fault was similar 2 1 and 1 7 m but the different depths and locations yielded maximum seafloor uplift of 0 4 and 0 2 m tsunami simulation from hypothetical great earthquakes m 8 4 and 8 5 on the new britain trench showed that tsunami amplitudes may reach up to 10 m in rabaul but most tsunami energy was confined within the solomon sea

the effect of rayleigh taylor instabilities on the thickness of undifferentiated crust on kuiper belt objects abstract previous calculations of the internal structure and thermal evolution of kuiper belt objects kbos by desch et al desch s j cook j c doggett t c porter s b 2009 icarus 202 694 714 have predicted that kbos should only partially differentiate with rock and ice separating into a rocky core and icy mantle below an undifferentiated crust of ice and rock this crust is thermally insulating and enhances the ability of subsurface liquid to persist within kbos a dense rock ice layer resting on an icy mantle is gravitationally unstable and prone to rayleigh taylor rt instabilities and may potentially overturn here we calculate the ability of rt instabilities to act in kbos and determine the thickness of undifferentiated crusts we have used previously calculated growth rates of the rt instability to determine the critical viscosity of ice needed for the rt instability to operate we calculate the viscosity of ice at the cold temperatures and long timescales relevant to kbos we find that crustal overturn is only possible where the temperature exceeds about 150 k and that rt instabilities cannot act on geological timescales within about 60 km of the surfaces of a kbo like charon although this crustal thickness is less than the 85 km previously calculated by desch et al desch s j cook j c doggett t c porter s b 2009 icarus 202 694 714 it is still significant representing 25 of the mass of the kbo we conclude that while rt instabilities may act in kbos they do not completely overturn their crusts we calculate that saturn s moon rhea should only partially differentiate resulting in a moment of inertia c mr 2 0 38

ultralong period seismic study of the december 2004 indian ocean earthquake and implications for regional tectonics and the subduction process analysis of the earth s longest period normal modes shows that the december 2004 sumatra andaman earthquake was much larger mw 9 3 than ini tially inferred from surface wave data and involved slip on a much longer fault than initially inferred from body wave data the seismic moment and relative excitation of the normal modes indicate that the entire aftershock zone ruptured consistent with the large tsunami amplitudes in thailand sri lanka and india an apparent increase in seismic moment with period results from interference between parts of the fault the earthquake resulted from subduction of the indian plate beneath the burma microplate a sliver plate between the indian and sunda plates hence the rate and direction of convergence depends on the motion of the burma plate which is not well known convergence would be highly oblique if the rate of motion between burma and sunda is that inferred from spreading in the andaman sea and less if a slower rate is inferred from the sagaing fault the december earthquake was much larger than expected from a previously proposed relation based on the idea of seismic coupling in which such earthquakes occur only when young lithosphere subducts rapidly moreover a global reanalysis finds little support for this correlation hence we suspect that much of the apparent differences between subduction zones such as some trench segments but not others being prone to m w 8 5 events and hence oceanwide tsunamis may reflect the short earthquake history sampled this possi bility is supported by the variability in rupture mode at individual trench segments

fault slip distribution of the 2014 iquique chile earthquake estimated from ocean wide tsunami waveforms and gps data we applied a new method to compute tsunami green s functions for slip inversion of the 1 april 2014 iquique earthquake using both near field and far field tsunami waveforms inclusion of the effects of the elastic loading of seafloor compressibility of seawater and the geopotential variation in the computed green s functions reproduced the tsunami traveltime delay relative to long wave simulation and allowed us to use far field records in tsunami waveform inversion multiple time window inversion was applied to tsunami waveforms iteratively until the result resembles the stable moment rate function from teleseismic inversion we also used gps data for a joint inversion of tsunami waveforms and coseismic crustal deformation the major slip region with a size of 100 km 40 km is located downdip the epicenter at depth 28 km regardless of assumed rupture velocities the total seismic moment estimated from the slip distribution is 1 24 1021 n m mw 8 0

co and postseismic deformation of the 28 march 2005 nias mw 8 7 earthquake from continuous gps data 1 global positioning system gps measurements registered up to 5m of coseismic displacements during the 28 march 2005 mw 8 7 nias earthquake indonesia the vertical offsets put tight constraints on the northern and southern limit of the rupture the inferred coseismic slip distribution indicates high slip patches near the epicenter and near the southern extent of the 26 december 2004 aceh andaman rupture where aftershocks have been abundant six months of postseismic time series are better fit with a logarithmic instead of exponential function suggesting that the postseismic deformation is likely controlled by afterslip our inversion model predicts afterslip to be concentrated both up and down dip from patches of maximum coseismic slip where aftershocks are sparse the shallow afterslip adds further evidence that the earthquake probably did not break the surface with implications for tsunami generation and instead caused aseismic deformation in shallow parts of the subduction zone after the event

saturn s icy satellites thermal and structural models abstract thermal histories of the small icy saturnian satellites mimas tethys dione rhea and iapetus are constructed by assuming that they formed as homogeneous ice silicate mixtures the models include effects of radiogenic and accretional heating conductive and subsolidus convective heat transfer and lithospheric growth accretional heating is unlikely to have melted the water ice in the interiors of these bodies and solid state creep of the predominately ice material precludes melting by radiogenic heating mimas is so small that its thermal evolution is essentially purely conductive at present it is a cold nearly isothermal body any subsolidus convection or thermal activity in mimas would have been confined to a brief period in its early history and would have been due to a warm formation the four largest satellites are big enough and contain sufficient heat producing silicates that solid state convection beneath a rigid lithosphere is inevitable independent of initial conditions dione and rhea have convective interiors for most of their thermal histories while tethys and iapetus have mainly conductive thermal histories with early periods of convective 0activity the thermal histories of the five satellites for the last 4 by are independent of initial conditions at present they have cold conductive interiors the model thermal histories are qualitatively consistent with the appearances of these satellites mimas has an ancient heavily cratered surface tethys and probably iapetus have both heavily cratered and more lightly cratered areas and dione and rhea have extensively modified surfaces because of their similar sizes and densities mimas and enceladus are expected to have similar surfaces and thermal histories but instead enceladus has the most modified surface of all the small icy saturnian satellites our results suggest a heat source for enceladus in addition to radiogenic and accretional heating tidal dissipation is a possibility because the water ice in these bodies does not melt resurfacing must be accomplished by the melting of a low melting temperature minor component such as ammonia hydrate

the 16 april 2016 mw 7 8 ms 7 5 ecuador earthquake a quasi repeat of the 1942 ms 7 5 earthquake and partial re rupture of the 1906 ms 8 6 colombia ecuador earthquake the 2016 ecuador m w 7 8 earthquake ruptured the subduction zone boundary between the nazca and south american plates joint modeling of seismic and tsunami observations indicates an 120 km long rupture area beneath the coastline north of the 1998 m w 7 2 rupture the slip distribution reveals two discrete asperities near the hypocenter and around the equator their locations and the patchy pattern are consistent with the prior interseismic geodetic strain which showed highly locked patches also beneath the coastline aftershocks cluster along two streaks one aligned nearly parallel to the plate convergence direction up dip of the main slip patches and the other on a trench perpendicular lineation south of the 1958 rupture zone comparisons of seismic waveforms and magnitudes show that the 2016 event and 1942 earthquakes have similar surface wave magnitude m s 7 5 overlapping rupture areas and similar main pulses of moment rate the same area ruptured as the southernmost portion of the larger earthquake of 1906 m w 8 6 m s 8 6 the seismic behavior reflects persistent heterogeneous frictional properties of the colombia ecuador megathrust

saturn s satellite rhea is a homogeneous mix of rock and ice 1 a close flyby of saturn s satellite rhea by the cassini spacecraft on 26 november 2005 can be used to infer its mass and quadrupole gravity moments from these data we derive a mean density of 1233 5 kg m 3 for rhea and an axial moment of inertia consistent with an undifferentiated interior the small density implies an interior made up of about 25 rock metal and 75 water ice by mass the moment of inertia implies a homogeneous mix of these constituents with some compression of the ice and the transition from ice i to ice ii at depth

two subevents across the japan trench during the 7 december 2012 off tohoku earthquake mw 7 3 inferred from offshore tsunami records a tsunamigenic earthquake with a moment magnitude of 7 3 occurred near the japan trench off tohoku northeast japan on 7 december 2012 operational seismic monitoring inferred that the earthquake was composed of doublet sources of comparable magnitudes the first event was reverse faulting and the second event which occurred 10 20 s later was normal faulting an associated tsunami was observed at offshore stations having an amplitude of 10 1 to 101 cm inverse modeling using the observed tsunami records reveals possible vertical seafloor deformations we can then constrain in terms of the source location that the tsunamigenic earthquake involves two subfaults across the japan trench one is the outer trench reverse faulting as the first event and the second is the inner trench normal faulting the present study shows that tsunami analysis with seismograph analyses effectively constrains the epicenter locations even in the case of complex earthquakes like doublets

rhea s gravitational field and interior structure inferred from archival data files of the 2005 cassini flyby abstract there are three published gravitational fields for rhea and they all differ significantly all three published fields fit the data equally well although not to the noise level there are obvious trends in the doppler residuals however by restricting the data in the fit to a shorter interval surrounding the closest approach to rhea an unbiased estimate for rhea s quadrupole gravitational field is obtained this paper also investigates the effects of thermal emission which are shown to be quite important and may explain part of the discrepancy between this study and previous works with this approach and under the assumption that rhea is in hydrostatic equilibrium he our earlier conclusions about rhea s internal structure are confirmed rhea is an undifferentiated satellite made up of about 25 rock metal and 75 water ice by mass the best fit value of the quadrupole gravitational coefficient c 22 from the present analysis is 267 6 4 9 1 0 6 further any assertions that rhea is not in he are not supported by the data and only an additional highly inclined flyby to rhea s equator could resolve this issue provided rhea were not in he no useful constraint on rhea s interior structure could be imposed non he contributions to the first order deviations from sphericity considered here are not readily available

linear and nonlinear computations of the 1992 nicaragua earthquake tsunami numerical computations of tsunamis are made for the 1992 nicaragua earthquake using different governing equations bottom frictional values and bathymetry data the results are compared with each other as well as with the observations both tide gauge records and runup heights comparison of the observed and computed tsunami waveforms indicates that the use of detailed bathymetry data with a small grid size is more effective than to include nonlinear terms in tsunami computation linear computation overestimates the amplitude for the later phase than the first arrival particularly when the amplitude becomes large the computed amplitudes along the coast from nonlinear computation are much smaller than the observed tsunami runup heights the average ratio or the amplification factor is estimated to be 3 in the present case when the grid size of 1 minute is used the factor however may depend on the grid size for the computation

joint modeling of teleseismic and tsunami wave observations to constrain the 16 september 2015 illapel chile mw 8 3 earthquake rupture process the 16 september 2015 illapel chile m w 8 3 earthquake ruptured 170 km along the plate boundary megathrust fault from 30 0 s to 31 6 s a patch of offshore slip of up to 10 m extended to near the trench and a patch of 3 m slip occurred downdip below the coast aftershocks fringe the large slip zone extending along the coast from 29 5 s to 32 5 s between the 1922 and 1971 1985 ruptures the coseismic slip distribution is determined by iterative modeling of teleseismic body waves as well as tsunami signals recorded at three regional dart stations and tide gauges immediately north and south of the rupture the tsunami observations tightly delimit the rupture length suppressing bilateral southward extension of slip found in unconstrained teleseismic wave inversions the spatially concentrated rupture area with a stress drop of 3 2 mpa is validated by modeling dart and tide gauge observations in hawaii which also prove sensitive to the along strike length of the rupture

variable rupture mode of the subduction zone along the ecuador colombia coast three large earthquakes occurred within the rupture zone of the 1906 colombia ecuador earthquake m w 8 8 in 1942 m s 7 9 1958 ms 7 8 and 1979 m s 7 7 we compared the size and mechanism of these earthquakes by using long period surface waves tsunami data and macroseismic data the 1979 event is a thrust event with a seismic moment of 2 9 10 28 dyne cm and represents subduction of the nazca plate beneath south america the rupture length and direction are 230 km and n40 e respectively examination of old seismograms indicates that the 1906 event is also a thrust event which ruptured in the northeast direction the seismic moment estimated from the tsunami data and the size of the rupture zone is 2 10 29 dyne cm the 1942 and 1958 events are much smaller about 1 5 to 1 10 of the 1979 event in the seismic moment than the 1979 event we conclude that the sum of the seismic moments of the 1942 1958 and 1979 events is only formula of that of the 1906 event despite the fact that the sequence of the 1942 1958 and 1979 events ruptured approximately the same segment as the 1906 event this difference could be explained by an asperity model in which the fault zone is held by a discrete distribution of asperities with weak zones in between the weak zone normally behaves aseismically but slips abruptly only when it is driven by failure of the asperities a small earthquake represents failure of one asperity and the rupture zone is pinned at both ends by adjacent asperities so that the effective width and the amount of slip are relatively small a great earthquake represents failure of more than one asperity and consequently involves much larger width and slip

historical 1942 ecuador and 1942 peru subduction earthquakes and earthquake cycles along colombia ecuador and peru subduction segments two large shallow earthquakes occurred in 1942 along the south american subduction zone inclose proximity to subducting oceanic ridges the 14 may event occurred near the subducting carnegie ridge off the coast of ecuador and the 24 august event occurred off the coast of southwestern peru near the southern flank of the subducting nazca ridge source parameters for these for these two historic events have been determined using long periodp waveforms p wave first motions intensities and local tsunami data we have analyzed thep waves for these two earthquakes to constrain the focal mechanism depth source complexity and seismic moment modeling of thep waveform for both events yields a range of acceptable focal mechanisms and depths all of which are consistent with underthrusting of the nazca plate beneath the south american plate the source time function for the 1942 ecuador event has one simple pulse of moment release with a duration of 22 suconds suggesting that most of the moment release occurred near the epicenter the seismic moment determined from thep waves is 6 8 1020n m corresponding ot a moment magnitude of 7 8 7 9 the reported location of the maximum intensities ix for this event is south of the main shock epicenter the relocated aftershcks are in an area that is approximately 200 km by 90 km elongated parallel to the trench with the majority of aftershocks north of the epicenter in contrast the 1942 peru event has a much longer duration and higher degree of complexity than the ecuador earthquake suggesting a heterogeneous rupture seismic moment is released in three distinct pulses over approximately 74 seconds the largest moment release occurs 32 seconds after rupture initiation the seismic moment as determined from thep waves for the 1942 peru event is 10 25 1020n m corresponding to a moment magnitude of 7 9 8 2 aftershock locations reported by the iss occur over a broad area surrounding the main shock the reported locations of the maximum intensities ix are concentrated south of the epicenter suggesting that at least part of the rupture was to the south we have also examined great historic earthquakes along the colombia ecuador and peru segments of the south american subduction zone we find that the size and rupture length of the underthrusting earthquakes vary between successive earthquake cycles this suggests that the segmentation of the plate boundary as defined by earthquakes this century is not constant

rupture of the indian slab in the 2011 mw 6 9 sikkim himalaya earthquake and its tectonic implications unlike the other himalayan plate boundary segments the eastern nepal to bhutan himalayan region is not known to have generated prominent shallow thrust faulting earthquakes typical of the ongoing convergence this region features strike slip earthquakes over the depth ranges of 40 120 km indicating intraslab deformation here we present for the first time a slip distribution model for the largest recorded intraslab strike slip earthquake in this region the mw 6 9 sikkim event that occurred on 18 september 2011 relying on kinematic source process modeling our results indicate a ne sw trending steeply dipping sinistral source zone within the underthrusting indian slab the rupture propagated radially with a low rupture velocity of 1 7 km s breaking a large asperity of 20 a 20 km 2 with a maximum slip of 1 6 m the rupture nucleated at a depth of 45 km and reached upper mantle depths the computed coseismic stress drop value is 13 6 mpa we suggest that most of the aftershocks occurred on the conjugate plane possibly due to stress triggering stress inversion of focal mechanisms indicates a transpressive stress regime throughout the crust and pure strike slip regime in the upper mantle we observed a unimodal distribution of earthquakes beneath the higher himalaya this indicates a strong brittle indian slab and unravels a scenario of an eventual breakup of the lithosphere the key trigger might be variation in the convergence rates along the himalayan arc 2019 american geophysical union all rights reserved

comparative study of two tsunamigenic earthquakes in the solomon islands 2015 mw 7 0 normal fault and 2013 santa cruz mw 8 0 megathrust earthquakes the july 2015 mw 7 0 solomon islands tsunamigenic earthquake occurred 40 km north of the february 2013 mw 8 0 santa cruz earthquake the proximity of the two epicenters provided unique opportunities for a comparative study of their source mechanisms and tsunami generation the 2013 earthquake was an interplate event having a thrust focal mechanism at a depth of 30 km while the 2015 event was a normal fault earthquake occurring at a shallow depth of 10 km in the overriding pacific plate a combined use of tsunami and teleseismic data from the 2015 event revealed the north dipping fault plane and a rupture velocity of 3 6 km s stress transfer analysis revealed that the 2015 earthquake occurred in a region with increased coulomb stress following the 2013 earthquake spectral deconvolution assuming the 2015 tsunami as empirical green s function indicated the source periods of the 2013 santa cruz tsunami as 10 and 22 min

fault size and depth extent of the ecuador earthquake m w 7 8 of 16 april 2016 from teleseismic and tsunami data the april 2016 ecuador mw 7 8 earthquake was the first megathrust tsunamigenic earthquake along the ecuador colombia subduction zone since 1979 mw 8 2 with 200 deaths from tsunami while there was no tsunami damage from the 2016 earthquake small tsunamis were recorded at deep ocean assessment and reporting of tsunami and tide gauges here we designed various fault models with and without shallow slip area and compared the computed teleseismic and tsunami waveforms with the observations while teleseismic inversions were indifferent about inclusion or exclusion of the shallow slip tsunami waveforms strongly favored the slip model without shallow slip our final slip model has a depth range of 15 44 km and its western shallowest limit is located at the distance of 60 km from the trench maximum and average slips were 2 5 and 0 7 m respectively the large slip area was 80 km along strike 60 km along dip in the depth range of 15 35 km

differential impact cratering of saturn s satellites by heliocentric impactors saturnian satellites are thought to have been struck by two different types of impactors those with heliocentric origins and those with planetocentric origins many of the impacts are suggested to come from planetocentric debris while many crater count studies assume an ecliptic comet origin when determining the ages of the surfaces to assess the contribution of planetocentric impactors this study examines the global distribution and apex antapex asymmetry of impact craters on rhea and iapetus the results demonstrate that the craters of rhea more than 20 km in diameter and iapetus more than 30 km in diameter show an apex antapex asymmetry this suggests that most of the large craters are formed from heliocentric impacts in contrast the craters less than 20 km in diameter seem to show no asymmetry possible explanations for this are either planetocentric impactor origins or saturation with impact craters

scaling relations of seismic moment rupture area average slip and asperity size for m 9 subduction zone earthquakes 1 scaling relations for seismic moment m0 rupture area s average slip d and asperity size sa were obtained for large great and giant mw 6 7 9 2 subduction zone earthquakes we compiled the source parameters for seven giant mw 9 earthquakes globally for which the heterogeneous slip distributions were estimated from tsunami and geodetic data we defined sa for subfaults exhibiting slip greater than 1 5 times d adding 25 slip models of 10 great earthquakes around japan we recalculated regression relations for 32 slip models s 1 34 10 10 m02 3 d 1 66 10 7 m01 3 sa 2 81 10 11 m02 3 and sa s 0 2 where s and sa are in square kilometers m0 is in newton meters and d is in meters these scaling relations are very similar to those obtained by murotani et al 2008 for large and great earthquakes thus both scaling relations can be used for future tsunami hazard assessment associated with a giant earthquake

impact basin relaxation on rhea and iapetus and relation to past heat flow abstract evidence for relaxation of impact crater topography has been observed on many icy satellites including those of saturn and the magnitude of relaxation can be related to past heat flow e g moore j m schenk p m bruesch l s asphaug e mckinnon w b 2004 icarus 171 421 443 dombard a j mckinnon w b 2006 j geophys res 111 e01001 http dx doi org 10 1029 2005je002445 we use new global digital elevation models of the surfaces of rhea and iapetus generated from cassini data to obtain crater depth diameter data for both satellites and topographic profiles of large basins on each in addition to the factor of three lower amplitude of global topography on rhea compared to iapetus we show that basins on iapetus 100 km in diameter show little relaxation compared to similar sized basins on rhea because of the similar gravities of rhea and iapetus we show that iapetus basin morphologies can be used to represent the initial unrelaxed morphologies of the rhea basins and we use topographic profiles taken across selected basins to model heat flow on both satellites we find that iapetus has only experienced radiogenic heat flow since formation whereas rhea must have experienced heat flow reaching a few tens of mw m 2 although this heat flow need only be sustained for as little as several million years in order to achieve the observed relaxation magnitudes rhea experienced a different thermal history from iapetus which we consider to be primarily related to their different formation mechanisms and locations within the saturnian system a recent model for the formation of saturn s mid sized icy satellites interior to and including rhea charnoz s et al 2011 icarus 216 535 550 describes how rhea s orbit would have expanded outwards after its accretion from a giant primordial ring which would have instigated early heating through rapid despinning and tidal interaction with saturn and other satellites rhea s basins would therefore be required to have formed within the first few tens of myr of rhea s formation in order to relax due of this heating and if so may provide an important anchor point for saturn system chronology none of these heating mechanisms are viable for iapetus in its isolated position far from saturn and as such it has remained dynamically inert since formation confirming conclusions based on thermal modeling of iapetus interior rapid and complete relaxation and subsequent erosion by bombardment of a first generation of large basins on rhea is regarded as an explanation for the lower counts of large basins on rhea relative to iapetus and the overall lower amplitude of topography on rhea compared to iapetus

seismicity associated with the great colombia ecuador earthquakes of 1942 1958 and 1979 implications for barrier models of earthquake rupture abstract we have relocated earthquakes along the colombia ecuador coast with the method of joint hypocenter determination in order to examine the nature of fault heterogeneities that controlled northward propagation of plate boundary rupture from the source region of the earthquake of 14 may 1942 to the source region of the 19 january 1958 earthquake and eventually to the source region of the earthquake of 12 december 1979 the entire region of the 1942 1958 and 1979 shocks had previously ruptured in the single great earthquake of 31 january 1906 the relocated hypocenters lie on the same plane to within the approximately 20 km uncertainty of the focal depths also the main shocks nucleated at nearly the same distance from the colombia trench these observations suggest that the heterogeneities between the 1942 and 1958 ruptures and between the 1958 and 1979 ruptures do not correspond to a major distortion of the downgoing slab but rather to either minor distortions of the slab or to regions of high friction or low available strain energy on a continuous fault surface in particular the heterogeneity between the 1958 and 1979 rupture zones seems to have been a high strength barrier with dimensions much smaller than the dimensions of either of the rupture zones the 1942 and 1958 earthquakes had source dimensions no larger than the 1979 main shock but they had stronger aftershock sequences than the 1979 earthquake this observation suggests that the arrest of earthquake rupture in 1979 left the plate boundary segment that had ruptured in 1906 in a state of lower stress than it had been following the 1942 and 1958 earthquakes long term seismicity in the decades preceding the 1979 earthquake occurred mostly outside or on the boundaries of the rupture area defined by the distribution of 1979 aftershocks the intense aftershock activity that followed the 1958 main shock within tens of kilometers of the eventual 1979 hypocenter may correspond to a long term precursory seismic swarm for the 1979 earthquake

geophysical implications of the long wavelength topography of rhea 1 we use limb profiles to investigate the long wavelength topography and topographic variance spectrum of rhea one dimensional variance spectra show a break in slope at a wavelength of 300 km a similar effect is seen on the moon and may be a signature of an elastic lithosphere having a thickness te 10 km the implied heat flux is 15 mw m 2 much higher than can be explained by radiogenic heating we use the 1 d spectral behavior to constrain our solution for the long wavelength global topography of rhea the degree 3 topography is large enough if uncompensated to contaminate estimates of the degree 2 gravity using existing flyby data current models of rhea internal structures which rely on these degree 2 estimates may thus be inaccurate illustrating the need to acquire further rhea gravity data

are rupture zone limits of great subduction earthquakes controlled by upper plate structures evidence from multichannel seismic reflection data acquired across the northern ecuador southwest colombia margin 1 subduction of the nazca plate beneath the ecuador colombia margin has produced four megathrust earthquakes during the last century the 500 km long rupture zone of the 1906 mw 8 8 event was partially reactivated by three thrust events in 1942 mw 7 8 1958 mw 7 7 and 1979 mw 8 2 whose rupture zones abut one another multichannel seismic reflection and bathymetric data acquired during the sisteur cruise show evidence that the margin wedge is segmented by transverse crustal faults that potentially correlate with the limits of the earthquake coseismic slip zones the paleogene neogene jama quininde and esmeraldas crustal faults define a 200 km long margin crustal block that coincides with the 1942 earthquake rupture zone subduction of the buoyant carnegie ridge is inferred to partially lock the plate interface along central ecuador however coseismic slip during the 1942 and 1906 earthquakes may have terminated against the subducted northern flank of the ridge we report on a newly identified manglares crustal fault that cuts transversally through the margin wedge and correlates with the limit between the 1958 and 1979 rupture zones during the earthquake cycle the fault is associated with high stress concentration on the plate interface an outer basement high which bounds the margin seaward of the 1958 rupture zone may act as a deformable buttress to seaward propagation of coseismic slip along a megathrust splay fault coseismic uplift of the basement high is interpreted as the cause for the 1958 tsunami we propose a model of weak transverse faults which reduce coupling between adjacent margin segments together with a splay fault and an asperity along the plate interface as controlling the seismogenic rupture of the 1958 earthquake

the tectonic and volcanic history of rhea as inferred from studies of scarps ridges troughs and other lineaments abstract analyses of landforms on rhea are used to define 13 types of geomorphic features interpreted to be of tectonic and volcano tectonic origin all types except one seem to be extensional in origin they occurred after the formation of population i craters and are contemporaneous with a major resurfacing event the troughs grabens grooves pit chains scarps and other lineaments vare pure extensional features while the ridges are volcanic features formed in an extensional stress field this global surface extension was followed by an era of global compression which produced megaridges and megascarps these compressional features are not numerous enough to fit the theoretical stresses predicted by the typical thermal models of rhea all the extensional landforms appear to form a global grid pattern this planetary wide grid is similar in direction to the theoretical pattern of a tidally distorted planet that suggests either an orbital variation very early in the history of rhea or the existence of an unknown process which has oriented the stress field during the extensional period

storm induced sediment gravity flows at the head of the eel submarine canyon northern california margin 1 as part of the strataform program a bottom boundary layer bbl tripod was deployed at 120 m depth in the northern thalweg of the eel canyon during winter 2000 increases of the near bottom suspended sediment concentrations ssc recorded at the canyon head were not directly related to the eel river discharge but were clearly linked to the occurrence of storms bbl measurements revealed that during intensifications of the wave orbital velocity sediment transport at the head of the canyon occurred as sediment gravity flows directed down canyon observational evidence for near bed sediment gravity flow transport included an increase toward the bed of the down canyon component of wave averaged velocity and high estimated ssc at higher sampling frequencies 1 hz the current components during these events fluctuated at the same periodicity as the pressure reflecting a clear influence of the surface wave activity on the generation and maintenance of the sediment gravity flows the origin of such flows is not related to the formation of fluid muds on the shelf or to intense wave current sediment resuspension around the canyon head region rather liquefaction of sediment deposited at the head of the canyon induced by wave load excess pore water pressures during storms combined with elevated slopes around the canyon head appear to be the mechanisms initiating sediment transport the resulting fluidized sediment layer can easily be eroded entrained into the water column and transported down canyon as a sediment gravity flow results from this study reveal that storm induced sediment gravity flows occur periodically in the eel canyon head and suggest that this kind of sediment transport process can occur in other submarine canyons more frequently than previously expected

cassini observes the active south pole of enceladus cassini has identified a geologically active province at the south pole of saturn s moon enceladus in images acquired by the imaging science subsystem iss this region is circumscribed by a chain of folded ridges and troughs at 55 s latitude the terrain southward of this boundary is distinguished by its albedo and color contrasts elevated temperatures extreme geologic youth and narrow tectonic rifts that exhibit coarse grained ice and coincide with the hottest temperatures measured in the region jets of fine icy particles that supply saturn s e ring emanate from this province carried aloft by water vapor probably venting from subsurface reservoirs of liquid water the shape of enceladus suggests a possible intense heating epoch in the past by capture into a 1 4 secondary spin orbit resonance

slab1 0 a three dimensional model of global subduction zone geometries 1 we describe and present a new model of global subduction zone geometries called slab1 0 an extension of previous efforts to constrain the two dimensional non planar geometry of subduction zones around the focus of large earthquakes slab1 0 describes the detailed non planar three dimensional geometry of approximately 85 of subduction zones worldwide while the model focuses on the detailed form of each slab from their trenches through the seismogenic zone where it combines data sets from active source and passive seismology it also continues to the limits of their seismic extent in the upper mid mantle providing a uniform approach to the definition of the entire seismically active slab geometry examples are shown for two well constrained global locations models for many other regions are available and can be freely downloaded in several formats from our new slab1 0 website http on doi gov d9arbs we describe improvements in our two dimensional geometry constraint inversion including the use of average active source seismic data profiles in the shallow trench regions where data are otherwise lacking derived from the interpolation between other active source seismic data along strike in the same subduction zone we include several analyses of the uncertainty and robustness of our three dimensional interpolation methods in addition we use the filtered subduction related earthquake data sets compiled to build slab1 0 in a reassessment of previous analyses of the deep limit of the thrust interface seismogenic zone for all subduction zones included in our global model thus far concluding that the width of these seismogenic zones is on average 30 larger than previous studies have suggested

three dimensional tsunami generation simulation due to sea bottom deformation and its interpretation based on the linear theory summary the present study investigates the tsunami generation process by using 3 d numerical simulations and the linear potential theory first we evaluate the relation between sea bottom elevation and sea surface elevation as function of source size l sea depth h and source duration t based on 3 d numerical simulations the surface elevation decreases with increasing sea depth and source duration the difference between the sea bottom and the sea surface elevation appears when the source size is smaller than approximately 10 times the sea depth for a short source duration the linear potential theory can precisely predict the numerical simulation results based on the theory we can consider the tsunami generation as two spatial lowpass filter processes in which the cut off wavenumbers are given by the sea depth and the source duration the criteria for small source size and short source duration are given as l 13h and t l 8c respectively where c is the phase velocity of the tsunami we then simulate the tsunami generation of the 1896 sanriku tsunami earthquake japan the simulated sea surface elevation is significantly different from the sea bottom elevation which suggests the need for correction of the sea depth and source duration for the precise evaluation of the initial water height distribution to include these effects in 2 d simulations we can use the impulse response function and add the fractional sea surface uplift within the time step to the sea surface for each time step

long term perspectives on giant earthquakes and tsunamis at subduction histories of earthquakes and tsunamis inferred from geological evidence aid in anticipating future catastrophes this natural warning system now influences building codes and tsunami planning in the united states canada and japan particularly where geology demonstrates the past occurrence of earthquakes and tsunamis larger than those known from written and instrumental records under favorable circumstances paleoseismology can thus provide long term advisories of unusually large tsunamis the extraordinary indian ocean tsunami of 2004 resulted from a fault rupture more than 1000 km in length that included and dwarfed fault patches that had broken historically during lesser shocks such variation in rupture mode known from written history at a few subduction zones is also characteristic of earthquake histories inferred from geology on the pacific rim

indonesian earthquake earthquake risk from co seismic stress last year s indonesian earthquake has increased seismic hazard in the region the scale of death and destruction caused by the recent sumatra andaman islands earthquake and its tsunami has raised concerns that another earthquake might be triggered on the contiguous sunda trench subduction zone a new calculation of stress distribution here and on the neighbouring sumatra fault reveals stress build up on both structures severe enough to increase the already high earthquake hazard this finding makes the need for an indian ocean tsunami warning system all the more pressing following the massive loss of life caused by the sumatra andaman earthquake in indonesia and its tsunami the possibility of a triggered earthquake on the contiguous sunda trench subduction zone is a real concern we have calculated the distributions of co seismic stress on this zone as well as on the neighbouring vertical strike slip sumatra fault and find an increase in stress on both structures that significantly boosts the already considerable earthquake hazard posed by them in particular the increased potential for a large subduction zone event in this region with the concomitant risk of another tsunami makes the need for a tsunami warning system in the indian ocean all the more urgent

stability of ice rock mixtures with application to a partially differentiated titan titan s moment of inertia calculated assuming hydrostatic equilibrium from gravity field data obtained during the cassini huygens mission implies an internal mass distribution that may be incompatible with complete differentiation this suggests that titan may have a mixed ice rock core possibly consistent with slow accretion in a gas starved disk which may initially spare titan from widespread ice melting and subsequent differentiation a partially differentiated titan however must still efficiently remove radiogenic heat over geologic time we argue that compositional heterogeneity in the major saturnian satellites indicates that titan formed from planetesimals with disparate densities the resulting compositional anomalies would quickly redistribute to form a vertical density gradient that would oppose thermal convection we use elements of the theory of double diffusive convection to create a parameterized model for the thermal evolution of ice rock mixtures with a stabilizing compositional gradient to account for large uncertainties in material properties and accretionary processes we perform simulations for a wide range of initial conditions ultimately for realistic density gradients double diffusive convection in the ice rock interior can delay but not prevent ice melting and differentiation even if a substantial fraction of potassium is leached from the rock component consequently titan is not partially differentiated

the rupture process of the great 1979 colombia earthquake evidence for the asperity model we have determined the asperity distribution in the segment of the ecuador colombia subduction zone that was ruptured by the 1979 mw 8 2 and 1958 mw 7 7 earthquakes for the 1979 earthquake we are able to document directivity in the p wave source time functions and consequently have spatially located the moment release by combining results from both p wave and surface wave directivity we have defined three regions 1 from 0 to 56 km northeast of the epicenter with low moment release and a small seismic displacement 2 the asperity from 56 to 116 km northeast of the epicenter with most of the moment release and a displacement of 6 m and 3 a small displacement region from 116 to 180 240 km northeast of the epicenter thus the 1979 rupture zone is composed of an asperity 60 km in length bounded by two weak small displacement regions the displacement at the asperity is equal to the cumulative tectonic displacement between 1979 and 1906 the year of the previous great earthquake in this segment the 1958 earthquake is characterized by the rupture of a small asperity length scale approximately 25 km in the epicentral region the 1958 event continued to rupture past this small epicentral asperity and stopped near the epicenter of the following 1979 event this detailed study of the spatial variation in moment release offers strong support for the asperity model of large earthquake occurrence

geometry and petrophysical parameters of a calcarenitic turbidite lobe barremian aptian pas de la cluse france abstract several bioclastic resedimentation systems late barremian to early aptian in age outcrop in southeastern france the upslope portion of a calcarenitic turbidite lobe outcrops as a cliff 2 3 km wide and up to 45 m high oriented roughly perpendicular to the direction of palaeoflow it has been studied through 31 sections the studied body is point sourced and corresponds to a channel lobe transition located at the toe of slope of a urgonian carbonate platform on the western edge of the vocontian trough french subalpine chains the internal geometry of the lobe is the result of repeated erosion and filling of channels creating well defined stacked units filling phases result in lobe shaped morphology units evolve from base to top in an ordered way first the sediments exported from the platform and deposited in the basin are represented by decimetre thick sheet like and fine grained bouma a e and ab e sequences in this first unit erosion is limited and represented by shallow and symmetrical channels this initial phase of deposition corresponds to the formation of a lobe with a positive morphology the next phase of system development is more erosional and this is dominated by migrating sinuous channels several metres deep filled with coarse grained poorly graded turbidites these channels are first filled through lateral accretion and then sediment spills over to create a sub lobe the mixture of channel and lobe features could be considered as a carbonate equivalent of the channel levee system of siliciclastic deposits finally the system ends with the deposition of a flat based unit this unit extends for more than 2 km and is composed of the southwards lateral accretion of hundreds of metres wide sequences each composed of a debris flow deposit capped by a coarse grained calcarenite bed these sigmoidal bodies could be the ultimate forms of a spreading out phenomenon of the lobe overall the pas de la cluse system is a coarsening upward body as the grain size is related to the nature of the material this coarsening upward implies either an evolution in the nature of the carbonate material produced on the platform from grainy to bioconstructed a displacement of the source sediment from inner platform to margin or a displacement of the channel head through time from distal to proximal the upward evolution from classic turbidites to debris flow deposits can be explained either by the way the platform facies evolved with time in a depositional sequence or through retrogressive erosion by successive slope failures that cut deeper and deeper into the platform slope although its present day porosity is low the size of the system and the fact that it is encased in marls make it an interesting outcrop analogue for hydrocarbon exploration

source model of the 16 september 2015 illapel chile m w 8 4 earthquake based on teleseismic and tsunami data teleseismic data were provided by the incorporated research institutions for seismology http www iris edu wilber3 find event tide gauge data can be found at the intergovernmental oceanographic commission website http www ioc sealevelmonitoring org dart records were provided by noaa http nctr pmel noaa gov dart earthquake catalogs by the usgs national earthquake information center http earthquake usgs gov earthquakes search and global instrumental earthquake catalogue 1900 2009 of international seismological centre global earthquake model http www globalquakemodel org what seismic hazard instrumental catalogue were used in this study we used the gmt software for drawing the figures wessel and smith 1998 this article benefited from constructive review comments by costas e synolakis university of southern california usa and yuichiro tanioka hokkaido university japan for which we are grateful we acknowledge financial supports from the japan society for the promotion of science

constraints on gas giant satellite formation from the interior states of partially differentiated satellites an icy satellite whose interior is composed of a homogeneous ice rock mixture must avoid melting during its entire history including during its formation when it was heated by deposition of accretional energy and short lived radioisotopes estimates of the temperature rise associated with radiogenic and accretional heating coupled with limits on satellite melting can be used to constrain the timing of formation of a partially differentiated satellite relative to the origin of the calcium aluminum rich inclusions cai s as a function of its accretion timescale and the protosatellite disk temperature td geological characterization and spacecraft radio tracking data suggest that callisto the outermost regular satellite of jupiter and saturn s mid sized satellite rhea are partially differentiated if their interiors are in hydrostatic equilibrium because the specific conditions during the satellites formation are uncertain we determine accretional temperature profiles for a range of values for td and accretion time scales with the limiting assumption that impactors deposit all their energy close to the surface leading to maximally effective radiative cooling we find that callisto can remain unmelted during formation if it accreted on a time scale longer than 0 6 myr considering both radiogenic and accretional heating callisto must have finished accreting no earlier than 4 myr after formation of cai s for td 100 k warmer disks or larger impactors that deposit their energy at depth in the satellite would require longer and or later formation times if rhea accreted slowly in 10 5