rupture process of the 2011 tohoku oki mega thrust earthquake m9 0 inverted from strong motion data 1 we investigate the rupture process of the m9 0 tohoku oki mega thrust earthquake using the relatively low frequency strong motion records 0 01 0 125 hz observed at 36 k net and kik net stations the epicentral distances of which range from 120 km to 400 km the fault model is a rectangular plane the length and width of which are 510 km along the japan trench and 210 km along subducting direction of the pacific plate respectively we perform the multi time window inversion analysis with a 30 30 km2 subfault the derived slip model has one large slip area this area extends from the region around the hypocenter to the shallow part of the fault plane and further to the north and south along the trench axis located far off southern iwate miyagi and northern fukushima prefectures the seismic moment is 4 42 1022 nm mw 9 0 and the maximum slip is 48 m the slips near the coast are relatively small except off miyagi prefecture which experienced a slip greater than 5 m the shallow large slip area which continuously ruptured from 60 s to 100 s after the initial break radiated seismic waves rich in very low frequency content 0 02 hz the rupture after 100 s propagating to the southern fault area contributes to the distinct phases observed for fukushima and ibaraki prefectures the relationship between the proposed rupture model and the feature of the acceleration waveforms is not straightforward and suggests the frequency dependency of the seismic wave radiation

finite faults and inverse theory with applications to the 1979 imperial valley earthquake abstract using a representation theorem from elastodynamics subsurface slip on a known fault is formulated as the solution to an inverse problem in which recorded surface ground motion is the data two methods of solution are presented the least squares method which minimizes the squared differences between theory and data and the constrained least squares method which simultaneously maintains a set of linear inequalities instabilities in the solution are effectively eliminated in both methods and the sensitivity of the solution to small changes in the data is quantitatively stated the inversion methodology is applied to 77 components of near field ground acceleration recorded during the 15 october 1979 imperial valley earthquake the faulting is constrained to propagate bilaterally away from the epicenter at an average velocity of 90 per cent of the shear wave speed on a vertical fault plane extending from the surface to 10 km depth inequality constraints are used to keep the faulting sequence physically reasonable by maintaining right lateral motion and positive slip velocity the preferred solution is stable and provides a good fit to the data it is also realistic and consistent with observed surface offsets and independent estimates of seismic moment

interpretation of aeromagnetic anomalies over part of southeastern nigeria using three dimensional hilbert transformation we present the results of the application of three dimensional hilbert transformation to the analysis of airborne total field magnetic anomalies over part of southeastern nigeria this study not only substantiates the usefulness of 3 d hilbert transforms in the interpretation of magnetic anomaly maps but also more clearly delineates the structural pattern of the area of study results from the previous study are discussed in relation to the results of previous geological and geophysical studies of the area

a regional gravity study of the west african rift system in nigeria and cameroon and its tectonic interpretation abstract this study brings together existing and new gravity data to investigate the nature and cause of the bouguer gravity field associated with the cretaceous west african rift system in nigeria and cameroon the new gravity measurements include data collected over the basement area between the benue trough and the cameroon border and fill an important gap in the gravity coverage after removal of the long wavelength negative anomaly from the observed gravity field the remaining positive gravity anomaly associated with the rift system is interpreted in terms of two and three dimensional crustal models these models are constrained by crustal thicknesses derived from a seismic refraction study carried out across and to the south of the yola rift the results of simple three dimensional gravity modelling indicate the crust beneath the lower and middle benue is approximately 20 km thick while beneath the gongola rift the crust is approximately 25 km thick relative to a normal crustal thickness of 34 km away from the rift assuming the thinned crust associated with the rift system is the result of simple lithospheric stretching then the maximum possible crustal extensions of 95 65 and 55 km have taken place perpendicular to the benue gongola and yola rifts respectively these crustal extensions do not necessarily reflect the total crustal movement affecting these rifts since the benue and yola rifts have been subjected to varying amounts of shear displacement during the cretaceous and early tertiary times crustal extension estimates across the west african rift system could be as much as four times greater than the published extension estimates across the east african rift system these rift systems have the same plate tectonic setting being the failed third arms of successful triple junctions and are the result of extensional and shear tectonics the differences in crustal extension and the resulting isostatic response of the lithosphere beneath these rifts can explain why the west african rift system has been associated with subsidence processes throughout its development whereas the east african rift system in northeast africa has been strongly affected by uplift

atmospheric effects on ejecta emplacement laboratory experiments allow the investigation of complex interactions between impacts and an atmosphere although small in scale they can provide essential first order constraints on the processes affecting late stage ballistic ejecta and styles of ejecta emplacement around much larger craters on planetary surfaces the laboratory experiments involved impacting different fine grained particulate targets under varying atmospheric pressure and density different gas compositions during crater formation ballistic ejecta form the classic cone shaped profile observed under vacuum conditions as atmospheric density increases for a given pressure however the ejecta curtain bulges at the base and pinches above this systematic change in the ejecta curtain reflects the combined effects of deceleration of ejecta smaller than a critical size and entrainment of these ejecta within atmospheric vortices created as the outward moving wall of ejecta displaces the atmosphere additionally a systematic change in emplacement style occurs as a function of atmospheric pressure largely independent of density contiguous ejecta rampart superposing ballistically emplaced deposits 0 06 to 0 3 bar ejecta flow lobes 0 3 to 0 7 bar and radial patterns 0 8 bar underlying processes controlling such systematic changes in emplacement style were revealed by observing the evolution of the ejecta curtain by changing target materials including layered targets and low density particulates by varying atmospheric density by changing impact angle and by comparing the ejecta run out distances with first order models of turbidity flows three distinct ejecta emplacement processes can be characterized ejecta ramparts result from coarser clasts sorted and driven outward by vortical winds behind the outward moving ejecta curtain this style of wind modified emplacement represents minimal ejecta entrainment and is enhanced by a bimodal size distribution in the ejecta such eddy supported flows are observed to increase in run out distance scaled to crater size with increasing atmospheric pressure by analogy with turbidity flows this scaled distance should increase as r1 2 for a given atmospheric pressure and degree of entrainment ejecta flows with much greater run out distances develop as the turbulent power in atmospheric response winds increase such flows overrun and scour the inner ejecta facies thereby producing distinct inner and outer facies the degree of ejecta entrainment depends on the dimensionless ratio of drag to gravity forces acting on individual ejecta and the intensity of the winds created by the outward moving curtain entrainment increases with increasing atmospheric density and ejection velocity crater size but decreases with ejecta density and size the intensity of curtain generated winds increases with ejection velocity crater size the dimensionless drag ratio characterizing the laboratory experiments can be applied to mars since the reduced atmospheric density is offset by the increased ejection velocities for kilometer scale events for a given crater size ejection velocity and atmospheric conditions a wide range of nonballistic ejecta emplacement styles could occur simply by varying ejecta sizes even without the presence of water alternatively the onset crater diameter for nonballistic emplacement styles can reflect the range of ejecta sizes possible from the diverse martian geologic history massive basalts to fine grained aeolian deposits scaling considerations further predict that ejecta run out distances scaled to crater size on mars should increase as r1 2 hence long run out flows dependent on crater diameter need not reflect depth to a buried reservoir of water on venus however the dense atmosphere maximizes entrainment and results in ejecta flow densities approaching a constant fraction of the atmospheric density under such conditions ejecta run out distances should decrease as r 1 2

interpretation of aeromagnetic anomalies over the lower and middle benue trough of nigeria summary the results of an interpretation of aeromagnetic anomalies over the lower and middle benue trough of nigeria are presented two dimensional interpretation of the anomalies shows that the anomalies are best interpreted in terms of basic intrusive bodies occurring either within the cretaceous sediments or within the metamorphic basement or both the model suggests that the intrusive bodies are of variable thickness and magnetization polarity and may have been emplaced during different epochs of polarity the model is in good agreement with interpretations of gravity and magnetic anomalies over similar structures elsewhere in the world

transitional morphology in west deuteronilus mensae mars implications for modification of the lowland upland boundary abstract west deuteronilus mensae which lies along the lowland upland boundary of mars at 45 latitude 345 longitude exhibits both gradational l a rossbacher 1985 in models in geomorphology woldenberg ed pp 343 372 allen unwin boston and fretted terrain r p sharp 1973 j geophys res 78 4073 4083 boundary types to the west the boundary is gradational and to the east it is defined by fretted terrain the two types of boundaries do not merge with one another within the west deuteronilus mensae region however the gradational boundary materials appear to overlap the fretted terrain by about 500 km contacts between units associated with the gradational boundary and the fretted terrain boundary can both be recognized in the region of overlap the fretted terrain can be identified as much as 300 km north of the gradational boundary in this region lowland units associated with the gradational boundary embay canyons of the fretted terrain in a topographically conformal fashion changes in the fretted terrain across the gradational boundary from uplands to lowlands include a reduction of canyon wall slopes and depths such that the fretted terrain north of the gradational boundary appears mantled but not obscured there are at least two major classes of processes which might explain the lateral overlap 1 erosion of stratified upland terrain and 2 deposition of plains materials onto the sloping upland margin and fretted terrain erosion of stratified upland terrain does not adequately explain the plainward decrease in crater densities across the gradational boundary nor is it consistent with evidence that lowland plains material appears to onlap the sloping upland margin in several places of the possible plains emplacement mechanisms eolian deposition would not produce the sharp apparently topographically conformal gradational unit contacts volcanics plains emplacement would not preserve the complex geometry of the underlying fretted terrain sediment deposition in either a liquid or ice covered sea could produce the draped appearance of the fretted terrain outflow channels along the lowland upland boundary particularly those of the circum chryse and west elysium regions may have flooded the northern lowlands to depths of tens to hundreds of meters the gradational unit contacts may represent the shorelines of such a sea the scale of characteristic morphologies along these contacts may require an unfrozen condition of sufficient duration to allow lacustrine style wave erosion and redistribution of material along the contacts our limited understanding of the martian paleoclimate and h 2 o inventories allows the possibility of clement periods in the past and other geological evidence e g small valley networks and outflow channels strongly suggests an extensive role of liquid water

coastal geomorphology of the martian northern plains the paper considers the question of the formation of the outflow channels and valley networks discovered on the martian northern plains during the mariner 9 mission parker and saunders 1987 and parker et al 1987 1989 data are used to describe key features common both in the lower reaches of the outflow channels and within and along the margins of the entire northern plains it is suggested that of the geological processes capable of producing similar morphologies on earth lacustrine or marine deposition and subsequent periglacial modification offer the simplest and most consistent explanation for the suit of features found on mars

impact excavation and the search for subsurface life on mars because of the ubiquity of subsurface microbial life on earth examination of the subsurface of mars could provide an answer to the question of whether microorganisms exist or ever existed on that planet impact craters provide a natural mechanism for accessing the deep substrate of mars and exploring its exobiological potential based on equations that relate impact crater diameters to excavation depth we estimate the observed crater diameters that are required to prospect to given depths in the martian subsurface and we relate these depths to observed microbiological phenomena in the terrestrial subsurface simple craters can be used to examine material to a depth of 270 m complex craters can be used to reach greater depths with craters of diameters 300 km required to reach depths of 6 km or greater which represent the limit of the terrestrial deep subsurface biosphere examination of the ejecta blankets of craters between 17 5 and 260 km in diameter would provide insights into whether there is an extant or whether there is evidence of an extinct deep subsurface microbiota between 500 and 5000 m prior to committing to large scale drilling efforts at depths 500 m some crater excavations are likely to be more important than others from an exobiological point of view we discuss examples of impacts into putative intracrater paleolacustrine sediments and regions associated with hydrothermal activity we compare these depths to the characteristics of subsurface life on earth and the fossil microbiological record in terrestrial impact craters

anisotropic shear wave velocity structure of the earth s mantle a global model 1 we combine a new large data set of surface wave phase anomalies long period waveforms and body wave travel times to construct a three dimensional model of the anisotropic shear wave velocity in the earth s mantle our modeling approach is improved and more comprehensive compared to our earlier studies and involves the development and implementation of a new spherically symmetric reference model simultaneous inversion for velocity and anisotropy as well as discontinuity topographies and implementation of nonlinear crustal corrections for waveforms a comparison of our new three dimensional model s362ani with two other models derived from comparable data sets but using different techniques reveals persistent features 1 strong 200 km thick high velocity anomalies beneath cratons likely representing the continental lithosphere underlain by weaker fast anomalies extending below 250 km which may represent continental roots 2 weak velocity heterogeneity between 250 and 400 km depths 3 fast anomalies extending horizontally up to 2000 3000 km in the mantle transition zone beneath subduction zones 4 lack of strong long wavelength heterogeneity below 650 km suggesting inhibiting character of the upper mantle lower mantle boundary and 5 slow velocity superplumes beneath the pacific and africa the shear wave radial anisotropy is strongest at 120 km depth in particular beneath the central pacific lateral anisotropic variations appreciably improve the fit to data that are predominantly sensitive to the uppermost and lowermost mantle but not to the waveforms that control the transition zone and midmantle depths tradeoffs between lateral variations in velocity and anisotropy are negligible in the uppermost mantle but noticeable at the bottom of the mantle

comparing landslides to fluidized crater ejecta on mars 1 we use the mars global surveyor and viking data sets to compare and contrast the geomorphology of four large martian landslides located in valles marineris to fluidized ejecta of seven fresh martian craters located in lunae planum both mass movements have flowed over the martian surface and possess characteristics seen in terrestrial mass movements we combine these comparisons with simple flow models to determine how the planar geometry of landslides and the cylindrical geometry of ejecta can generate different topographic expressions for the same input constraints our purpose is to better understand the emplacement processes of both types of mass movements our geomorphic analyses are consistent with previous views that the large martian landslides resemble large terrestrial long run out flows the planar flow model supports this inference martian landslides probably flowed as a basal glide where motion is limited to a narrow interface at the base of the mass movement geomorphic investigations of fresh multilayered ejecta indicate that their inner portions with their subtle rampart probably flowed like their landslide counterparts as a basal glide distal pronounced contiguous ramparts however resemble features akin to terrestrial debris flows the cylindrical flow model shows that differences in geometry can mask the dynamics of flow emplacement this model suggests as expected a basal glide origin for the inner portions of the ejecta surprisingly basal glide also best explains the topography of the distal ejecta ramparts

a spatial random field model to characterize complexity in earthquake slip 1 finite fault source inversions reveal the spatial complexity of earthquake slip over the fault plane we develop a stochastic characterization of earthquake slip complexity based on published finite source rupture models in which we model the distribution of slip as a spatial random field the model most consistent with the data follows a von karman autocorrelation function acf for which the correlation lengths a increase with source dimension for earthquakes with large fault aspect ratios we observe substantial differences of the correlation length in the along strike a x and downdip a z directions increasing correlation length with increasing magnitude can be understood using concepts of dynamic rupture propagation the power spectrum of the slip distribution can also be well described with a power law decay i e a fractal distribution in which the fractal dimension d remains scale invariant with a median value d 2 29 0 23 while the comer wave number k c which is inversely proportional to source size decreases with earthquake magnitude accounting for larger slip patches for large magnitude events our stochastic slip model can be used to generate realizations of scenario earthquakes for near source ground motion simulations

discontinuities in the shallow martian crust at lunae syria and sinai plana detailed photoclinometric profiles across 125 erosional features and 141 grabens in the western equatorial region of mars indicate the presence of three discontinuities within the shallow crust pits troughs and wall valleys tributary canyons within noctis labyrinthus and valles marineris and escarpments within the fretted terrain of sacra fossae and kasei valles show distinct erosional base levels at depths of 0 3 0 6 km 1 km and 2 3 km the shallowest discontinuity corresponds to thickness estimates for the ridged plains unit in this region and thus the discontinuity probably is the contact between a sequence of layered rock making up this unit and the underlying megaregolith the 1 km discontinuity is reflected in the base levels of erosion of all the features studied and it may correspond to the base of the proposed layer of ground ice model calculations using photoclinometric profiles of simple grabens corrected for the effects of mass wasting and the 60 dip of bounding faults measured from the exposed traces of faults on trough walls show that graben bounding faults consistently intersect at the mechanical discontinuity at about 1 km depth this discontinuity may represent an interface between ice laden and dry regolith ice laden and water laden regolith or pristine and cemented regolith a correlation between wall valley head depth and local thickness of the faulted layer suggests that the 1 km discontinuity also controlled the depth of the heads of sapping canyons there is no apparent relation between the pit and trough depths and the local thickness of the faulted layer which can be explained if pits and troughs developed by subsidence into underlying tension cracks that disrupted the 1 km discontinuity the data do suggest however that erosion of shallow pits and troughs was influenced by the 1 km discontinuity the third discontinuity at a depth of 2 3 km corresponds to the proposed base of the martian megaregolith and is probably the interface between overlying ejected breccia and in situ fractured basement rocks

a model for the tectonic evolution of the benue trough of nigeria based on the results of a detailed magnetic study of the lower and middle benue trough of nigeria carried out by the author and results of previous geophysical studies of the benue trough and of similar structures elsewhere in the world a possible model for the tectonic evolution of the benue trough has been developed it is here suggested that the tectonic evolution of the benue trough of nigeria involved the rise of a mantle plume or mantle upwelling emplacement of intrusive igneous material in the crust crustal stretching and thinning and consequently rifting it is thought that this sequence of events may have been repeated in a cyclic manner with intercyclic structural deformations the basic ideas of the model is shown to be in agreement with acceptable ideas on riftogenesis

rupture process of the 2004 sumatra andaman earthquake the 26 december 2004 sumatra andaman earthquake initiated slowly with small slip and a slow rupture speed for the first 40 to 60 seconds then the rupture expanded at a speed of about 2 5 kilometers per second toward the north northwest extending 1200 to 1300 kilometers along the andaman trough peak displacements reached 15 meters along a 600 kilometer segment of the plate boundary offshore of northwestern sumatra and the southern nicobar islands slip was less in the northern 400 to 500 kilometers of the aftershock zone and at least some slip in that region may have occurred on a time scale beyond the seismic band

the origin and peculiarities of the nigerian benue trough another look from recent gravity data obtained from the middle benue abstract the origin of the benue trough has been a controversial subject previous workers in the area have evolved several theories ranging from a rift with or without plate tectonic concepts king 1950 wright 1968 1970 burke et al 1970 grant 1971 olade 1975 to a geosyncline lees 1952 and a combination of both cratchley and jones 1965 offodile 1976 to explain the origin of the trough one of the aims of the gravity survey carried out in the middle benue and discussed in this paper was to attempt to resolve some of the problems associated with the origin of the trough as proposed by previous workers and in so doing to explain the geological peculiarities associated with the trough interpretations of the gravity data along two north south profiles in the survey area indicated the existence of a rift of normal width about 40 km buried under the cretaceous cover and located between the central axis ridge of the trough and the northern boundary of the trough the gravity minimum which occurs south of the central axis of the trough was also ascribed to another rift thus the benue trough is considered to consist of two parallel rifts separated by the axial ridge which partly explains the abnormal width of the trough the interpreted models also indicate a low angle thrust fault with a small displacement which may be related to the folding of the sediments in the trough and also to the asymmetry of the trough furthermore the gravity data suggest that oceanic crust might not have reached the ground surface in the benue trough as in the red sea before rifting ceased

teleseismic inversion for rupture process of the 27 february 2010 chile mw 8 8 earthquake the 27 february 2010 chile m w 8 8 earthquake is the fifth largest earthquake to strike during the age of seismological instrumentation the faulting geometry slip distribution seismic moment and moment rate function are estimated from broadband teleseismic p sh and rayleigh wave signals we explore some of the trade offs in the rupture process estimation due to model parameterizations limited teleseismic sampling of seismic phase velocities and uncertainty in fault geometry the average slip over the 81 500 km 2 rupture area is about 5 m with slip concentrations down dip up dip and southwest and up dip and north of the hypocenter relatively little slip occurred up dip offshore of the hypocenter the average rupture velocity is 2 0 2 5 km s

the great sumatra andaman earthquake of 26 december 2004 the two largest earthquakes of the past 40 years ruptured a 1600 kilometer long portion of the fault boundary between the indo australian and southeastern eurasian plates on 26 december 2004 seismic moment magnitude mw 9 1 to 9 3 and 28 march 2005 mw 8 6 the first event generated a tsunami that caused more than 283 000 deaths fault slip of up to 15 meters occurred near banda aceh sumatra but to the north along the nicobar and andaman islands rapid slip was much smaller tsunami and geodetic observations indicate that additional slow slip occurred in the north over a time scale of 50 minutes or longer

possible ancient oceans on mars evidence from mars orbiter laser altimeter data high resolution altimetric data define the detailed topography of the northern lowlands of mars and a range of data is consistent with the hypothesis that a lowland encircling geologic contact represents the ancient shoreline of a large standing body of water present in middle mars history the contact altitude is close to an equipotential line the topography is smoother at all scales below the contact than above it the volume enclosed by this contact is within the range of estimates of available water on mars and a series of extensive terraces parallel the contact in many places

tsunami forecast by joint inversion of real time tsunami waveforms and seismic or gps data application to the tohoku 2011 tsunami correctly characterizing tsunami source generation is the most critical component of modern tsunami forecasting although difficult to quantify directly a tsunami source can be modeled via different methods using a variety of measurements from deep ocean tsunameters seismometers gps and other advanced instruments some of which in or near real time here we assess the performance of different source models for the destructive 11 march 2011 japan tsunami using model data comparison for the generation propagation and inundation in the near field of japan this comparative study of tsunami source models addresses the advantages and limitations of different real time measurements with potential use in early tsunami warning in the near and far field the study highlights the critical role of deep ocean tsunami measurements and rapid validation of the approximate tsunami source for high quality forecasting we show that these tsunami measurements are compatible with other real time geodetic data and may provide more insightful understanding of tsunami generation from earthquakes as well as from nonseismic processes such as submarine landslide failures

variations in the onset diameter for martian layered ejecta morphologies and their implications for subsurface volatile reservoirs we investigated regional variations in the onset diameter of craters displaying a single layer ejecta morphology within 30 latitude using viking imagery our results generally agree with those of previous studies which show onset diameters of 5 to 6 km in the equatorial region but we have identified localized regions with unusually small onset diameters the largest region is located in solis and thaumasia planae the 3 5 km onset diameter range in this area indicates a near surface ice rich reservoir depth 110 m this unusual concentration of near surface ice may have resulted from magmatic driven uplifts associated with the tharsis rise which modified parts of a regional aquifer drainage basin system and resulted in the transfer and concentration of subsurface volatiles in this region

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

determination of megathrust rupture processes using plate interface based fault models and 3d green s functions an application to the 2011 mw 9 1 tohoku earthquake in order to understand physical processes of megathrust earthquakes and thus to analyze hazards of the regions proper information of the rupture processes is essential in this study we develop a technique for determination of large spatial scale rupture processes on megathrust faults in subduction zones as soon as possible based on teleseismic broadband full waveform inversions using realistic models of finite fault geometries and 3d global velocity structures finite fault geometry models are constructed for eleven subduction zones of the circum pacific area utilizing the 3d plate interface model slab 1 0 of usgs green s functions for available pairs of subfaults and globally distributed stations to be used in the inversions are computed in the global 3d velocity model using spectral element method rather than in a 1d velocity model this scheme accommodates synthetic waves with lateral velocity variations especially for surface waves which is useful in estimations of large spatial scale slip distributions the data utilized are teleseismic broadband full waveform records including body waves and surface waves at the epicentral distance of 30o 80o the observed data are inverted for fault rupture processes based on the non negative least square technique with a multiple source time window scheme for each subfault the applicability of the method is tested for the 2011 mw 9 0 tohoku oki earthquake and the result shows that the proposed scheme of the finite fault inversion produces reasonable results of slip distributions

a unified source model for the 2011 tohoku earthquake abstract the devastating 2011 tohoku earthquake was observed by dense networks of geophysical instruments a unified source model was constructed through joint inversion of teleseismic strong motion and geodetic datasets the result indicates that the earthquake consists of three main ruptures after small rupture in the initial 50 s the first rupture expanded at a slow speed of 1 8 km s to the northeast and east the second rupture began 20 s later at the slowest speed of 1 5 km s and became dominant with the largest slip of 36 m the third rupture then played the leading role propagating southward at a speed of 2 5 km s only the tsunami inversion requires an extension of the source fault to a shallow part between the first rupture area and the japan trench recovering tsunamigenic slips larger than 40 m the slow rupture speed and tsunamigenic slips can explain the features of the disaster by the earthquake

slip of the 2004 sumatra andaman earthquake from joint inversion of long period global seismic waveforms and gps static offsets the 26 december 2004 great sumatra andaman earthquake opened a new era for seismologists to understand the complex source process of a great earth quake this is the first event with moment magnitude greater than 9 since the de ployment of high dynamic range broadband seismic and global positioning system gps sensors around the globe this study presents an analysis of the ruptured fault plane geometry and slip distribution using long period teleseismic data and gps measured static surface displacements near the fault plane we employ a rupture geometry with six along strike segments with and without a steeper down dip ex tension the fault segments are further subdivided into a total of 201 30 30 km fault patches sensitivity tests of fault plane geometry and the variation in rupture velocity indicate that the dip and curvature of the fault plane are not well resolved from the given data set and the rupture velocity is constrained to be between 1 8 and 2 6 km sec error estimations of the slip distribution using a random selection of seismic and gps station subsets 50 of all stations illustrate that slip is well re solved along the whole rupture and the mean slip uncertainty is less than 1 5 m about 11 although it is possible that near field gps data include contributions from additional postseismic transient deformation our preferred model suggests that the sumatra andaman earthquake had a magnitude of mw 9 20 0 05 0 06 online material comparison of slip models gps modeling waveform fit fault geometry and inversion parameters

bunte breccia of the ries continuous deposits of large impact craters the ries crater an impact structure of 26 km diameter in south germany is the largest terrestrial crater where substantial amounts of ejecta are preserved on occasion 100 m deep further the target stratigraphy is well known and it is possible to relate specific clasts and breccia lithologies to initial target depth as a consequence the continuous deposits of the ries also known as bunte breccia may be studied with exceptional field control we report field observations and laboratory analyses obtained from 560 m core materials taken at nine different locations that range from 16 to 37 km in radial distance from the impact center the objective is to relate the ries observations to ejection and to emplacement processes of large scale planetary crater deposits the observations regarding the modal stratigraphic characteristics of the bunte breccia may be summarized as follows only 600 m some 0 7 is composed of triassic clasts originating from 300 to 600 m depths lower and middle jurassic horizons approximately 300 150 m constitute some 2 3 and upper jurassic 0 150 m makes up some 31 5 in addition the bunte breccia contains tertiary materials in the form of 1 cm clasts 29 1 and as highly comminuted fine grained matrix 10 gpa constitute 0 1 weight of the entire deposit which indicates that bunte breccia was emplaced at essentially ambient temperatures when possible the above observations are quantified via linear regressions throughout the text all of these observations are consistent with if not predicted by a ballistic emplacement scenario as postulated by oberbeck and co workers primary crater ejecta are expelled ballistically and will form secondary craters in the local substrate a mixture of primary and secondary ejecta results and combines into a highly turbulent ground hugging debris surge as the final phase of ejecta emplacement total emplacement time for the bunte breccia 200 km is estimated to be of the order of 5 min only these findings are compared with cratering theory relating to a number of ejecta thickness decay models and with the so called z model addressing material flow during various stages of crater formation qualitative to fair agreement of observations and predictions results an initial crater radius of 6 5 km an excavation depth of 1650 m an excavation volume of 136 km and an associated transient cavity volume of aproximately 230 km appear to be reasonable estimates approximately 170 km of material was involved in slumping and restoration of the transient cavity for the above radius and z 2 7 the modal composition of ries ejecta with regard to preimpact target stratigraphy indicates that materials contained in the continuous deposits of large complex planetary craters are predominantly derived from depths as small as one hundredth the apparent crater diameter a number of implications are addressed regarding remote sensing of planetary surfaces and investigation of lunar and meteoritic impact breccias

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

ages of rampart craters in equatorial regions on mars implications for the past and present distribution of ground ice we are testing the idea of squyres et al 1992 that rampart craters on mars may have formed over a significant time period and therefore the onset diameter minimum diameter of a rampart crater only reflects the ground ice depth at a given time we measured crater size frequencies on the layered ejecta of rampart craters in three equatorial regions to derive absolute model ages and to constrain the regional volatile history nearly all rampart craters in the xanthe terra region are 3 8 gyr old this corresponds to the noachian fluvial activity that region rampart crater formation declines in the hesperian whereas onset diameters minimum diameter increase no new rampart craters formed after the end of the hesperian 3 gyr this indicates a lowering of the ground ice table with time in the xanthe terra region most rampart craters in the valles marineris region are around 3 6 gyr old only one large probably amazonian aged 2 5 gyr rampart crater exists these ages indicate a volatile rich period in the early hesperian and a lowering of the ground ice table with time in the valles marineris study region rampart craters in southern chryse planitia which are partly eroded by fluvial activity show ages around 3 9 gyr rampart craters superposed on channels have ages between 1 5 and 0 6 gyr the onset diameter 3 km at 1 5 gyr in this region may indicate a relatively shallow ground ice table loss of volatiles due to diffusion and sublimation might have lowered the ground ice table even in the southern chryse planitia region afterwards in general our study implies a formation of the smallest rampart craters within and or shortly after periods of fluvial activity and a subsequent lowering of the ground ice table indicated by increasing onset diameter to the present these results question the method to derive present equatorial ground ice depths from the onset diameter of rampart craters without information about their formation time

rapid estimation of first order rupture characteristics for large earthquakes using surface waves 2004 sumatra andaman earthquake 1 broadband surface waves from large earthquakes can be rapidly processed to estimate seismic moment faulting duration and general slip distribution supplying important information for hazard response efforts including tsunami warnings deconvolution of surface wave green s functions removes propagation effects yielding azimuthally varying effective source time functions even a single faultperpendicular time function can provide robust first order estimates of the temporal history of seismic radiation and associated slip distribution simplified two dimensional finite fault modeling using a few surface wave time functions can reliably characterize the smooth component of the overall rupture process these procedures are demonstrated using 13 rayleigh wave observations for the 26 december 2004 sumatra andaman earthquake yielding satisfactory agreement with models based on more complete seismic data sets depending on source and station locations stable slip estimates can be obtained within 15 60 minutes of the onset of a large earthquake citation ammon c j a a velasco and t lay 2006 rapid estimation of first order rupture characteristics for large earthquakes using surface waves 2004 sumatra andaman earthquake geophys res lett 33 l14314 doi 10 1029 2006gl026303

geothermal energy reconnaissance of southeastern nigeria from analysis of aeromagnetic and gravity data given the daunting energy challenges currently bedeviling nigeria with demand for electrical power exceeding availability alternative energy sources preferentially renewable are vigorously considered this is the first study to examine geothermal energy prospects in southeastern nigeria with the ultimate aim of locating and mapping regions of shallow curie point depths cpds crustal thickness and geologic structures supportive of a geothermal system we estimated cpd using the spectral analysis technique on magnetic field anomalies gravity anomalies were subjected to a series of procedures to assess geological structures result reveals deeper cpds within central and southern regions of okposi afikpo and biase towns in an approximate range of 18 4 to 19 3 km shallow cpds 9 8 17 4 km have also been obtained within obubra and abakaliki regions estimated crustal thickness moho ranges between 26 5 and 35 8 km part of the region with shallow cpd correlates with regions of shallow moho depths particularly in abakaliki and deeper moho depths coincide with deeper cpd estimates at the afikpo location the estimated geothermal gradient and heat flow values range between 29 0 and 45 0 oc and 52 2 101 5 mw m2 respectively and fall within values evaluated from deep wells drilled for oil exploration within the adjoining anambra basin region this study recommends the regions with shallow depths for possible geothermal power plant location gravity data evaluations also reveal significant subsurface intrusions within ugbodo obubra and abakaliki locations overall this study is a step forward toward a better evaluation of the geothermal energy resources potential of southeastern nigeria

layered ejecta craters and the early water ice aquifer on mars a model for emplacement of deposits of impact craters is presented that explains the size range of martian layered ejecta craters between 5 km and 60 km in diameter in the low and middle latitudes the impact model provides estimates of the water content of crater deposits relative to volatile content in the aquifer of mars these estimates together with the amount of water required to initiate fluid flow in terrestrial debris flows provide an estimate of 21 by volume 7 6 x 10 7 km 3 of water ice that was stored between 0 27 and 2 5 km depth in the crust of mars during hesperian and amazonian time this would have been sufficient to supply the water for an ocean in the northern lowlands of mars the existence of fluidized craters smaller than 5 km diameter in some places on mars suggests that volatiles were present locally at depths less than 0 27 km deposits of martian craters may be ideal sites for searches for fossils of early organisms that may have existed in the water table if life originated on mars

slip distribution of the february 27 2010 mw 8 8 maule earthquake central chile from static and high rate gps insar and broadband teleseismic data 1 the shallow depth underthrust earthquake of february 27 2010 mw 8 8 ruptured the subduction plate interface in central chile between 34 s and 38 s we retrieve the spatial and temporal distribution of slip during this mega earthquake through a joint inversion of teleseismic records insar and high rate gps hrgps data additionally our model is shown to agree with broadband surface waves rupture initiated at about 32 km depth and propagated bilaterally resulting in two main slip zones located ssw and nne of the hypocenter nucleation did not take place within or at the edge of one of these main asperities but in between during the first 30s slip propagated predominantly southwards later on the rupture evolved more slowly and more symmetrically eventually the northern asperity became predominant with maximum slip reaching about 20 m most of the seismic moment was released within 110s a relatively short time explained by the bilateral propagation the overall average rupture velocity is 2 6 km s but propagation occurred initially faster towards the south 3 2 km s large slip did not reach the trench a result consistent with the moderate size of the tsunami down dip rupture stopped at about 50 km depth in agreement with the lower limit of the locked zone inferred by ruegg et al 2009 from pre seismic gps data

martian impact craters correlations of ejecta and interior morphologies with diameter latitude and terrain abstract the premise of this study is that global analysis of crater morphologies can discriminate between the effects of impact energy atmosphere and subsurface volatiles based on the correlation between morphology and latitude diameter and terrain this study focuses on seven ejecta and nine interior morphologies associated with 3819 craters 8 km in diameter distributed across the entire martian surface this data set is sufficiently large to provide statistically viable results on a global scale the results of the analyses indicate that changes in ejecta and interior morphology correlate with increases in crater diameter excavation depths corresponding to these diameters are calculated from depth diameter relationships and are compared to the theoretical distribution of subsurface volatiles the different ejecta morphologies can be described by impact into material with varying proportions of volatiles and the latidudinal variations seen for rampart crater morphologies correlate well with the proposed latitude depth relationship for ice and brines across the planet many of the interior structres show distributions indicative of terrain dependent influences for example the concentrations of central pit craters around ancient impact basins and on alba patera suggest that volatiles preferentially collect in these areas however central peak and peak ring interior morphologies show little relationship to planetary properties and probably result from changes in impact energy thus many of the unique morphologies associated with martian impact craters result from the presence of subsurface volatiles

constraints on early events in martian history as derived from the cratering record the shapes and densities of crater size frequency distribution curves are used to constrain two major events early in martian history termination of high obliteration rates and viability of the multiple impact origin of the crustal dichotomy distribution curves of fresh craters superposed on uplands intercrater plains and ridged plains display shapes and densities indicative of formation prior to the end of heavy bombardment this observation correlates with other geologic evidence suggesting a major change in the erosional regime following the last major basin size impact i e argrye in addition the multisloped nature of the curves supports the idea that the downturn in the crater size frequency distribution curves reflects the size frequency distribution of the impactors rather than being the result of erosion the crustal dichotomy formed prior to the heavy bombardment intermediate epoch based on distribution curves of knobby terrain if the dichotomy resulted from a single gigantic impact this observation places constraints on when this event happened an alternate theory for dichotomy formation the multiple impact basin idea is questioned since distribution curves of large basins as well as heavy bombardment era units are not represented by a 3 differential power law function this study finds fewer basins missing on mars compare to the moon and mercury than previously reported the area covered by these missing basins is less than that covered the northern plains

evidence of large scale repeating slip during the 2011 tohoku oki earthquake 1 the repetition of slip during rupture process of earthquake is a debate issue which had never been confirmed clearly in the past big events due to the lack of dense near field observations and limited resolution in time of source model the 2011 m9 0 tohoku oki earthquake generated a wealth seismic records which provided us an unprecedented opportunity to study the rupture evolution of giant earthquake at a high spatio temporal resolution here we use teleseismic local strong motion and near field coseismic geodetic data to investigate the source rupture process of this event based on the parallel inversion technique the results reveal a broad slip zone with remarkable large scale repeating slip during the earthquake the inverted source model shows several time periods of energy release with three main peaks these energy bursts and temporal rupture snapshots suggest repetition of a large scale slip on the biggest asperity this rupture behavior resulted in 50 m slips on the slip zone and prolonged the entire rupture process for a long duration of 160 seconds the proposed source model is in a good agreement with the aftershock distribution and can interpret the characteristics of local strong motions further investigations of repeating slip during this event are crucial which will deeply transform earthquake science from dynamic point of view

gravity study of lower benue trough nigeria about 300 gravity stations were established at 2 4 km intervals along an e w profile across the lower benue trough from gboko nsukka auchi with the main objectives of investigating the nature and configuration of the basement complex underlying the trough and estimating the thickness of the sedimentary cover rocks the resulting bouguer anomaly profile shows a series of alternating positives and negatives for a preliminary interpretation the positive anomalies are attributed to shallow basement and the negative anomalies to sediment fill of maximum thickness 4250 m

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

a gravity interpretation of the benue trough nigeria abstract reconnaissance gravity surveys carried out in the benue trough from 1975 to 1977 have revealed a broad positive regional anomaly over the whole trough attributable to moho uplift superimposed on this regional gravity high in the lower benue trough is an axial positive anomaly this positive anomaly with a maximum width of 100 km and an amplitude of 20 mgal seems to disappear around latitude 9 n and is associated with a basic body of density 2 90 gcm 3 that decreases in width and thickness from the south to the north an axial negative anomaly observed in the upper benue is attributed to sedimentary fill 6000 m thick in the middle and lower benue flanking negative anomalies are attributable to the accumulation in the marginal basins of post deformational sediments up to 5000 m thick

direct energy estimation of the 2011 japan tsunami using deep ocean pressure measurements 1 we have developed a method to compute the total energy transmitted by tsunami waves to the case where the earthquake source is unknown by using deep ocean pressure measurements and numerical models tsunami source functions based on the first wave recorded at the two closest tsunameters deep ocean assessment and reporting of tsunamis dart our analysis suggests that the march 11 2011 tohoku oki tsunami generated off japan originated from a 300 400 km long and 100 km wide area and the total propagated energy is 3 1015j with 6 uncertainty measurements from 30 tsunameters and 32 coastal tide stations show excellent agreement with the forecasts obtained in real time our study indicates that the propagated energy and the source location are the most important source characteristics for predicting tsunami impacts interactions of tsunami waves with seafloor topography delay and redirect the energy flux posing hazards from delayed and amplified waves with long duration seafloor topography also gives its spectral imprint to tsunami waves travel time forecast errors are path specific and correlated to the major wave scatterers in the pacific numerical dissipation in the propagation modeling highlights the need of high resolution inundation models for accurate coastal predictions on the other hand it also can be used to account for physical dissipation to achieve efficiency our results provide guidelines for the earliest reliable tsunami forecast warnings of long duration tsunami waves signals and enhancement of the experimental tsunami forecast system we apply the method to quantify the energy of 15 past tsunamis independently from earthquake magnitudes the small tsunami to seismic radiation energy ratios and their variability 0 01 0 8 reinforce the importance of using deep ocean tsunami data the direct measures of tsunamis for estimates of tsunami energy and accurate forecasting

source description of the 1999 hector mine california earthquake part ii complexity of slip history we present a rupture model of the hector mine earthquake m 7 1 determined from the joint inversion of strong motion records p and sh teleseismic body waves global positioning system gps displacement vectors and measured surface offset we solve for variable local slip rake angle rise time and rupture velocity of a finite fault model involving multiple segments the inversion methodology developed in a companion article ji et al 2002 combines a wavelet transform approach with a nonlinear simulated annealing algorithm the final model is checked by forward simulating the interferometric synthetic aperture radar insar data our estimation to the seismic moment is 6 28 10 19 n m which is distributed along three segments from north to south releasing 37 41 and 22 of the total moment respectively the average slip is 1 5 m with peak amplitudes as high as 7 m the fault rupture has an average rise time of 3 5 sec and a relatively slow average rupture velocity 1 9 km sec resulting in a 14 sec rupture propagation history our approach permits large variation in rupture velocity and rise time and indicates that rise time appears to be roughly proportional to slip and shorter rise times are associated with the initiation of asperity rupture we also find evidence for nearly simultaneous rupture of the two northern branches

effect of volatiles and target lithology on the generation and emplacement of impact crater fill and ejecta deposits on mars impact cratering is an important geological process on mars and the nature of martian impact craters may provide important information as to the volatile content of the martian crust terrestrial impact structures currently provide the only ground truth data as to the role of volatiles and an atmosphere on the impact cratering process recent advancements based on studies of several well preserved terrestrial craters have been made regarding the role and effect of volatiles on the impact cratering process combined field and laboratory studies reveal that impact melting is much more common in volatile rich targets than previously thought so impact melt rocks melt bearing breccias and glasses should be common on mars consideration of the terrestrial impact cratering record suggests that it is the presence or absence of subsurface volatiles and not the presence of an atmosphere that largely controls ejecta emplacement on mars furthermore recent studies at the haughton and ries impact structures reveal that there are two discrete episodes of ejecta deposition during the formation of complex impact craters that provide a mechanism for generating multiple layers of ejecta it is apparent that the relative abundance of volatiles in the near surface region outside a transient cavity and in the target rocks within the transient cavity play a key role in controlling the amount of fluidization of martian ejecta deposits this study shows the value of using terrestrial analogues in addition to observational data from robotic orbiters and landers laboratory experiments and numerical modeling to explore the martian impact cratering record