global distribution of large lunar craters implications for resurfacing and impactor populations by using high resolution altimetric measurements of the moon we produced a catalog of all impact craters 20 kilometers in diameter on the lunar surface and analyzed their distribution and population characteristics the most densely cratered portion of the highlands reached a state of saturation equilibrium large impact events such as orientale basin locally modified the prebasin crater population to 2 basin radii from the basin center basins such as imbrium orientale and nectaris which are important stratigraphic markers in lunar history are temporally distinguishable on the basis of crater statistics the characteristics of pre and postmare crater populations support the hypothesis that there were two populations of impactors in early solar system history and that the transition occurred near the time of the orientale basin event

a new crater near insight implications for seismic impact detectability on mars a new 1 5 m diameter impact crater was discovered on mars only 40 km from the insight lander context camera images constrained its formation between 21 february and 6 april 2019 follow up high resolution imaging science experiment images resolved the crater during this time period three seismic events were identified in insight data we derive expected seismic signal characteristics and use them to evaluate each of the seismic events however none of them can definitively be associated with this source atmospheric perturbations are generally expected to be generated during impacts however in this case no signal could be identified as related to the known impact using scaling relationships based on the terrestrial and lunar analogs and numerical modeling we predict the amplitude peak frequency and duration of the seismic signal that would have emanated from this impact the predicted amplitude falls near the lowest levels of the measured seismometer noise for the predicted frequency hence it is not surprising this impact event was not positively identified in the seismic data finding this crater was a lucky event as its formation this close to insight has a probability of only 0 2 and the odds of capturing it in before and after images are extremely low we revisit impact seismic discriminators in light of real experience with a seismometer on the martian surface using measured noise of the instrument we revise our previous prediction of seismic impact detections downward from a few to tens to just 2 per earth year still with an order of magnitude uncertainty

detection and geometric characterization of rock mass discontinuities using a 3d high resolution digital outcrop model generated from rpas imagery ormea rock slope italy abstract the use of a remotely piloted aircraft system rpas and digital photogrammetry is valuable for the detection of discontinuities in areas where field mapping and terrestrial photogrammetry or laser scanner surveys cannot be employed because the slope is unsafe inaccessible or characterized by a complex geometry with areas not visible from the ground using the structure from motion method the acquired images can be used to create a 3d texturized digital outcrop model tdom and a detailed point cloud representing the rock outcrop discontinuity orientations in a complex rock outcrop in italy were mapped in the field using a geological compass and by manual and automated techniques using a tdom and point cloud generated from rpas imagery there was a good agreement between the field measurements and manual mapping in the tdom semi automated discontinuity mapping using the point cloud was performed using the dse qfacet fm and qfacet kd tree methods applied to the same 3d model significant discrepancies were found between the semi automatic and manual methods in particular the automatic methods did not adequately detect discontinuities that are perpendicular to the slope face bedding planes in the case study these differences in detection of discontinuities can adversely influence the kinematic analysis of potential rock slope failure mechanisms we use the case study to demonstrate a workflow that can accurately map discontinuities with results comparable to field measurements the combined use of tdom and rpas dramatically increases the discontinuity data because rpas can supply a good coverage of inaccessible or hidden portions of the slope and tdom is a powerful representation of the reality that can be used to map discontinuity orientations including those that are oriented perpendicular to the slope

a surface gravity traverse on mars indicates low bedrock density at gale crater gravimetry the precise measurement of gravitational fields can be used to probe the internal structure of earth and other planets the curiosity rover on mars carries accelerometers normally used for navigation and attitude determination we have recalibrated them to isolate the signature of the changing gravitational acceleration as the rover climbs through gale crater the subsurface rock density is inferred from the measured decrease in gravitational field strength with elevation the density of the sedimentary rocks in gale crater is 1680 180 kilograms per cubic meter this value is lower than expected indicating a high porosity and constraining maximum burial depths of the rocks over their history

moon meteoritic seismic hum steady state prediction 1 we use three different statistical models describing the frequency of meteoroid impacts on earth to estimate the seismic background noise due to impacts on the lunar surface because of diffraction seismic events on the moon are typically characterized by long codas lasting 1 h or more we find that the small but frequent impacts generate seismic signals whose codas overlap in time resulting in a permanent seismic noise that we term the lunar hum by analogy with the earth s continuous seismic background seismic hum we find that the apollo era impact detection rates and amplitudes are well explained by a model that parameterizes 1 the net seismic impulse due to the impactor and resulting ejecta and 2 the effects of diffraction and attenuation the formulation permits the calculation of a composite waveform at any point on the moon due to simulated impacts at any epicentral distance the root mean square amplitude of this waveform yields a background noise level that is about 100 times lower than the resolution of the apollo long period seismometers at 2 s periods this noise level is more than 1000 times lower than the low noise model prediction for earth s microseismic noise sufficiently sensitive seismometers will allow the future detection of several impacts per day at body wave frequencies

the palliser rockslide canadian rocky mountains characterization and modeling of a stepped failure surface abstract this paper presents the results of an investigation of the prehistoric palliser rockslide rocky mountains canada conventional aerial photograph interpretation and field mapping are complemented by terrestrial digital photogrammetry these techniques allow quantification of the rockslide debris volume and reconstruction of the pre slide topography it has been estimated that the volume of rock involved in the most recent large rockslide is 8 mm 3 terrestrial digital photogrammetry is used in the characterization of the failure surface morphology which is subdivided into four types of step path geometry comprising both pre existing discontinuities and intact rock fractures incorporation of these data into various rock slope stability numerical modeling methods highlights a complex failure mechanism which includes sliding along a large scale curved failure surface intact rock bridge fracturing and lateral confinement a preliminary quantification of the contribution of intact rock bridges to the shear strength of the failure surface is presented in terms of the apparent cohesion apparent tensile strength and cumulative length of the intact rock segments

changes in blast zone albedo patterns around new martian impact craters abstract blast zones bzs around new martian craters comprise various albedo features caused by the initial impact including diffuse halos extended linear and arcuate rays secondary craters ejecta patterns and dust avalanches we examined these features for changes in repeat images separated by up to four mars years here we present the first comprehensive survey of the qualitative and quantitative changes observed in impact blast zones over time such changes are most likely due to airfall of high albedo dust restoring darkened areas to their original albedo the albedo of adjacent non impacted surfaces although some sites show drastic changes over short timescales nearly half of the sites show no obvious changes over several mars years albedo changes are more likely to occur at higher latitude sites lower elevation sites and at sites with smaller central craters no correlation was seen between amount of change and dust cover index relative halo size or historical regional albedo changes quantitative albedo measurements of the diffuse dark halos relative to their surroundings yielded estimates of fading lifetimes for these features the average lifetime among sites with measurable fading is 15 mars years the median is 8 mars years for a linear brightening however at approximately half of sites with three or more repeat images a nonlinear function with rapid initial fading followed by a slow increase in albedo provides a better fit to the fading behavior this would predict even longer lifetimes the predicted lifetimes of bzs are comparable to those of slope streaks and considered representative of fading by global atmospheric dust deposition they last significantly longer than dust devil or rover tracks albedo features that are erased by different processes these relatively long lifetimes indicate that the measurement of the current impact rate by daubar et al daubar i j et al 2013 icarus 225 506 516 http dx doi org 10 1016 j icarus 2013 04 009 does not suffer significantly from overall under sampling due to blast zones fading before new impact sites can be initially discovered however the prevalence of changes seen around smaller craters may explain in part their shallower size frequency distribution

overview of the mars science laboratory mission bradbury landing to yellowknife bay and beyond the mars science laboratory mission reached bradbury landing in august 2012 in its first 500 sols the rover curiosity was commissioned and began its investigation of the habitability of past and present environments within gale crater curiosity traversed eastward toward glenelg investigating a boulder with a highly alkaline basaltic composition encountering numerous exposures of outcropping pebble conglomerate and sampling aeolian sediment at rocknest and lacustrine mudstones at yellowknife bay on sol 324 the mission turned its focus southwest beginning a year long journey to the lower reaches of mt sharp with brief stops at the darwin and cooperstown waypoints the unprecedented complexity of the rover and payload systems posed challenges to science operations as did a number of anomalies operational processes were revised to include additional opportunities for advance planning by the science and engineering teams

identifying and mapping potentially adverse discontinuities in underground excavations using thermal and multispectral uav imagery abstract geotechnical mapping rock mass characterization and inspections of underground excavations are critical to ensuring that excavation geometry and ground support design are appropriate for stable conditions a lack of access poor timing or hazardous conditions are all factors that can prohibit engineering personnel from collecting high quality data in the field advances in unmanned aerial vehicles uav and portable sensor technology now allow engineering personnel to remotely capture data from underground workings that can be used for developing designs generating inputs for analyses and making more informed decisions ground falls are a source of many accidents in the underground environment and they are the focus of many geotechnical investigations and analyses in this study the authors investigated how portable uav mounted thermal and multispectral imagers could be used to detect and quantify adverse geological discontinuities in hard rock masses that are structurally controlled multiple thermal multispectral rgb red green and blue and lidar light detection and ranging data sets were captured from 5 flights in sub level open stopes at the barrick golden sunlight mine in the state of montana in the western united states of america using off the shelf software the thermal rgb and multispectral images were processed to create individual three dimensional point clouds and meshes which were georeferenced using the lidar data discontinuities identified in the three dimensional point clouds and meshes were mapped using tools found in the freeware cloudcompare one of the thermal models identified wedges that had developed in the crown pillar of an open stope and 4 of the multispectral models contained enough detail for mapping individual discontinuities the results of this investigation indicate that these portable imagers are viable tools that can be used to aid engineering personnel in identifying and mapping adverse geological discontinuities and unique rock mass composition the techniques for capturing processing and interpreting thermal and multispectral imagery captured in underground excavations are described in this paper and can be used as the basis for future investigations at individual underground sites

the current martian cratering rate abstract the discovery of 248 dated impact sites known to have formed within the last few decades allows us to refine the current cratering rate and slope of the production function at mars we use a subset of 44 of these new craters that were imaged before and after impact by mars reconnaissance orbiter s context camera a thoroughly searched data set that minimizes biases from variable image resolutions we find the current impact rate is 1 65 10 6 craters with an effective diameter 3 9 m km2 yr with a differential slope power law exponent of 2 45 0 36 this results in model ages that are factors of three to five below the hartmann hartmann w k 2005 icarus 174 294 320 and neukum et al neukum g ivanov b a hartmann w k 2001 space sci rev 96 55 86 ivanov ivanov b a 2001 space sci rev 96 87 104 model production functions where they overlap in diameter the best fit production function we measure has a shallower slope than model functions at these sizes but model function slopes are within the statistical errors more than half of the impacts in this size range form clusters which is another reason to use caution when estimating surface ages using craters smaller than 50 m in diameter

experimental ejection angles for oblique impacts implications for the subsurface flow field a simple analytical solution for subsurface particle motions during impact cratering is useful for tracking the evolution of the transient crater shape at late times a specific example of such an analytical solution is maxwells z model which is based on a point source assumption here the parameters for this model are constrained using measured ejection angles from both vertical and oblique experimental impacts at the nasa ames vertical gun range data from experiments reveal that impacts at angles as high as 45 to the targets surface generate subsurface flow fields that are significantly different from those created by vertical impacts the initial momentum of the projectile induces a subsurface momentum driven flow field that evolves in three dimensions of space and in time to an excavation flow field during both vertical and oblique impacts a single stationary pointsource model specifically maxwells z model however is found inadequate to explain this detailed evolution of the subsurface flow field during oblique impacts because 45 is the most likely impact angle on planetary surfaces a new analytical model based on a migrating point source could prove quite useful such a model must address the effects of the subsurface flow field evolution on crater excavation ejecta deposition and transient crater morphometry

quantitative three dimensional description of a rough surface and parameter evolution with shearing note roches reference lmr article 2002 005view record in web of science record created on 2006 11 09 modified on 2016 08 08

multimodal internal waves generated over a subcritical ridge impact of the upper ocean stratification abstractinteraction of barotropic tides with subsurface topography is vital to ocean mixing yet the behavior of large amplitude nonlinear internal solitary waves isws that can cause strong mixing remains poorly understood especially that of higher mode and multimodal internal waves therefore a 2 5 dimensional nonhydrostatic model with adjustable vertical resolution was developed to investigate effects of upper ocean stratification on tidally induced multimodal internal waves and to show how they are generated by the subcritical ridge where only upward propagating internal wave beams iwbs are present the effects of the stratification on properties and characteristics of the excited iwbs and on the energy partition of the radiated mode 1 and mode 2 internal waves were investigated based on the model results higher modes of internal waves can also be effectively generated in the iwbs by the subcritical topography and the contribution to iwbs from higher modes increases with the upper ocean stra

global characteristics of porosity and density stratification within the lunar crust from grail gravity and lunar orbiter laser altimeter topography data the gravity recovery and interior laboratory grail mission is providing unprecedentedly high resolution gravity data the gravity signal in relation to topography decreases from 100 km to 30 km wavelength equivalent to a uniform crustal density of 2450 kg m3 that is 100 kg m3 smaller than the density required at 100 km to explain such frequency dependent behavior we introduce rock compaction models under lithostatic pressure that yield radially stratified porosity and thus density and examine the depth extent of porosity our modeling and analysis support the assertion that the crustal density must vary from surface to deep crust by up to 500 kg m3 we found that the surface density of megaregolith is around 2400 kg m3 with an initial porosity of 10 20 and this porosity is eliminated at 10 20 km depth due to lithostatic overburden pressure our stratified density models provide improved fits to both grail primary and extended mission data

geodesy constraints on the interior structure and composition of mars abstract knowledge of the interior structure of mars is of fundamental importance to the understanding of its past and present state as well as its future evolution the most prominent interior structure properties are the state of the core solid or liquid its radius and its composition in terms of light elements the thickness of the mantle its composition the presence of a lower mantle and the density of the crust in the absence of seismic sounding only geodesy data allow reliably constraining the deep interior of mars those data are the mass moment of inertia and tides they are related to mars composition to its internal mass distribution and to its deformational response to principally the tidal forcing of the sun here we use the most recent estimates of the moment of inertia and tidal love number k2 in order to infer knowledge about the interior structure of the mars we have built precise models of the interior structure of mars that are parameterized by the crust density and thickness the volume fractions of upper mantle mineral phases the bulk mantle iron concentration and the size and the sulfur concentration of the core from the bulk mantle iron concentration and from the volume fractions of the upper mantle mineral phases the depth dependent mineralogy is deduced by using experimentally determined phase diagrams the thermoelastic properties at each depth inside the mantle are calculated by using equations of state since it is difficult to determine the temperature inside the mantle of mars we here use two end member temperature profiles that have been deduced from studies dedicated to the thermal evolution of mars we calculate the pressure and temperature dependent thermoelastic properties of the core constituents by using equations state and recent data about reference thermoelastic properties of liquid iron liquid iron sulfur and solid iron to determine the size of a possible inner core we use recent data on the melting temperature of iron sulfur within our model assumptions the geodesy data imply that mars has no solid inner core and that the liquid core contains a large fraction of sulfur the absence of a solid inner is in agreement with the absence of a global magnetic field we estimate the radius of the core to be 1794 65 km and its core sulfur concentration to be 16 2 wt we also show that it is possible for mars to have a thin layer of perovskite at the bottom of the mantle if it has a hot mantle temperature moreover a chondritic fe si ratio is shown to be consistent with the geodesy data although significantly different value are also possible our results demonstrate that geodesy data alone even if a mantle temperature is assumed can almost not constrain the mineralogy of the mantle and the crust in order to obtain stronger constraints on the mantle mineralogy bulk properties like a fixed fe si ratio have to be assumed

on the shear failure of incipient rock discontinuities under cnl and cns boundary conditions insights from dem modelling abstract this paper presents a numerical investigation of the effects of boundary conditions i e constant normal load cnl and constant normal stiffness cns on the failure mechanism of incipient rock discontinuities in direct shear a series of numerical simulations were performed using the particle based discrete element method dem in which rock matrix and rock bridges on incipient joint planes were modeled as an assembly of rigid particles that were bonded together at their contacts smooth joint model was assigned to particles of the persistent portions of incipient rock joints input micro parameters of particles bonds and smooth joint were calibrated against a series of laboratory experiments the study reveals that cnl and cns boundary conditions significantly affect shear characteristics of incipient rock discontinuities peak shear stress increased significantly up to three times in the cns direct shear in comparison with that measured in the cnl direct shear under the same initially applied normal stresses the significant increase of shear stress in the cns direct shear tests conducted in this study was related to the opening of newly created micro cracks and creation of the rupture zones within the rock bridges leading to a dramatic increase in the normal stresses in the meanwhile yield behavior was observed in the cns direct shear while brittle failure was noticed in the cnl direct shear it is also found that micro cracks initiated at the vicinity of rock bridges in both cnl and cns shear tests while they propagated differently due to the gradual increase of normal stress under cns boundary conditions

seismic observations of meteors coupling theory and observations to date coupling of acoustic waves directly with the earth s surface represents the bulk of the observed meteor related seismic signals while precursory and impact related seismic waves remain an observational rarity with proliferation of infrasound and seismic monitoring systems new opportunities exist to explore the relationship between earth s atmosphere andsurface continued studyofmeteorseismologywillleadto new methods to constrain energies sizes and fluxes for moderately cm to m sized meteoroids on earth and potentially on mars

reflecting tidal wave beams and local generation of solitary waves in the ocean thermocline it is generally accepted that ocean internal solitary waves can arise from the interaction of the barotropic tide with the continental shelf which generates an internal tide that in turn steepens and forms solitary waves as it propagates shorewards some field observations however reveal large amplitude internal solitary waves in deep water hundreds of kilometres away from the continental shelf suggesting an alternative generation mechanism tidal flow over steep topography forces a propagating beam of internal tidal wave energy which impacts the thermocline at a considerable distance from the forcing site and gives rise to internal solitary waves there motivated by this possibility a simple nonlinear long wave model is proposed for the interaction of a tidal wave beam with the thermocline and the ensuing local generation of solitary waves the thermocline is modelled as a density jump across the interface of a shallow homogeneous fluid layer on top of a deep uniformly stratified fluid and a finite amplitude propagating internal wave beam of tidal frequency in the lower fluid is assumed to be incident and reflected at the interface the induced weakly nonlinear long wave disturbance on the interface is governed in the far field by an integral differential equation which accounts for nonlinear and dispersive effects as well as energy loss owing to radiation into the lower fluid depending on the strength of the thermocline and the intensity of the incident beam nonlinear wave steepening can overcome radiation damping so a series of solitary waves may arise in the thermocline sample numerical solutions of the governing evolution equation suggest that this mechanism is quite robust for typical oceanic conditions

quantifying crater production and regolith overturn on the moon with temporal imaging random bombardment by comets asteroids and associated fragments form and alter the lunar regolith and other rocky surfaces the accumulation of impact craters over time is of fundamental use in evaluating the relative ages of geologic units crater counts and radiometric ages from returned samples provide constraints with which to derive absolute model ages for unsampled units on the moon and other solar system objects however although studies of existing craters and returned samples offer insight into the process of crater formation and the past cratering rate questions still remain about the present rate of crater production the effect of early stage jetting during impacts and the influence that distal ejecta have on the regolith here we use lunar reconnaissance orbiter camera lroc narrow angle camera nac temporal before and after image pairs to quantify the contemporary rate of crater production on the moon to reveal previously unknown details of impact induced jetting and to identify a secondary impact process that is rapidly churning the regolith from this temporal dataset we detected 222 new impact craters and found 33 per cent more craters with diameters of at least ten metres than predicted by the standard neukum production and chronology functions for the moon we identified broad reflectance zones associated with the new craters that we interpret as evidence of a surface bound jetting process we also observe a secondary cratering process that we estimate churns the top two centimetres of regolith on a timescale of 81 000 years more than a hundred times faster than previous models estimated from meteoritic impacts ten million years

internal solitary waves in the mozambique channel observations and interpretation this paper presents new results showing that the sofala shelf in the mozambique channel 20 s 36 e is a previously unknown hot spot for the generation of internal tides and internal waves we investigate available envisat advanced synthetic aperture radar imagery of the region which is capable of showing the surface signatures of the internal waves this is complemented by modeling of the ray pathways of internal tidal energy propagation and of the p g baines 1982 barotropic body force which drives the generation of internal tides near the shelf break the hot spot region is localized between 20 and 21 s because of the particular nature of the bathymetry there farther north and south the forcing is reduced and insufficient to generate internal solitary waves in the synthetic aperture radar images the analysis reveals two distinct types of internal wave trains that are observed traveling oceanward away from the shelf break and we suggest that these result from direct generation at the shelf break and from local generation at about 80 km from the shelf break respectively because of the surfacing of internal tidal rays at the thermocline finally we have investigated seasonal differences in the wave patterns which penetrate more extensively into the channel during the southern summer and appear slightly farther to the south during the southern winter we also conclude that the local generation process is more likely to occur during the winter when the stratification is reduced

detailed dem analysis of a rockslide scar to characterize the basal sliding surface of active rockslides 1 the basal sliding surfaces in large rockslides are often composed of several surfaces and possess a complex geometry the exact morphology and location in three dimensions of the sliding surface remains generally unknown in spite of extensive field and subsurface investigations such as those at the aknes rockslide western norway this knowledge is crucial for volume estimations failure mechanisms and numerical slope stability modeling this paper focuses on the geomorphologic characterization of the basal sliding surface of a postglacial rockslide scar in the vicinity of aknes this scar displays a stepped basal sliding surface formed by dip slopes of the gneiss foliation linked together by steeply dipping fractures a detailed characterization of the rockslide scar by means of high resolution digital elevation models permits statistical parameters of dip angle spacing persistence and roughness of foliation surfaces and step fractures to be obtained the characteristics are used for stochastic simulations of stepped basal sliding surfaces at the aknes rockslide these findings are compared with previous models based on geophysical investigations this study discusses the investigation of rockslide scars and rock outcrops for a better understanding of potential rockslides this work identifies possible basal sliding surface locations which is a valuable input for volume estimates design and location of monitoring instrumentation and numerical slope stability modeling

quantitative analysis of impact induced seismic signals by numerical modeling we quantify the seismicity of impact events using a combined numerical and experimental approach the objectives of this work are 1 the calibration of the numerical model by utilizing real time measurements of the elastic wave velocity and pressure amplitudes in laboratory impact experiments 2 the determination of seismic parameters such as quality factor q and seismic efficiency k for materials of different porosity and water saturation by a systematic parameter study employing the calibrated numerical model by means of numerical experiments we found that the seismic efficiency k decreases slightly with porosity from k 3 4 10 3 for nonporous quartzite to k 2 6 10 3 for 25 porous sandstone if pores are completely or partly filled with water we determined a seismic efficiency of k 8 2 10 5 which is approximately two orders of magnitude lower than in the nonporous case by measuring the attenuation of the seismic wave with distance in our numerical experiments we determined the seismic quality factor q to range between 35 for the solid quartzite and 80 for the porous dry targets for water saturated target materials q is much lower 10 the obtained values are in the range of literature values translating the seismic efficiency into seismic magnitudes we show that the seismic magnitude of an impact event is about one order of magnitude smaller considering a water saturated target in comparison to a solid or porous target obtained seismic magnitudes decrease linearly with distance to the point of impact and are consistent with empirical data for distances closer to the point of impact the seismic magnitude decreases more rapidly with distance for a water saturated material compared to a dry material

the production of small primary craters on mars and the moon abstract we model the primary crater production of small d d 10 20 cm well below the downturn observed in the distribution of fresh craters detected by the mars global surveyor mgs mars orbiter camera moc or the mars reconnaissance orbiter mro context camera ctx crater counts are conducted on the ejecta blanket of zunil crater and the interior of pangboche crater on mars and north ray and cone craters on the moon our model isochrons produce a similar slope and age estimate for the formation of zunil crater as the hartmann production function 1 ma we derive an age of 35 1 ma for pangboche when accounting for the higher elevation 20 km higher than zunil a factor 2 younger than estimated using the hartmann production function which assumes 6 mbar surface pressure we estimate ages of 52 3 ma and 23 9 ma for north ray and cone crater respectively consistent with cosmic ray exposure ages from apollo samples our results indicate that the average cratering rate has been constant on these bodies over these time periods since our monte carlo simulations demonstrate that the existing crater chronology systems can be applied to date young surfaces using small craters on the moon and mars we conclude that the signal from secondary craters in the isochrons must be relatively small at these locations as our monte carlo model only generates primary craters

verifying single station seismic approaches using earth based data preparation for data return from the insight mission to mars abstract the planned insight mission will deliver a single seismic station containing 3 component broadband and short period sensors to the surface of mars in 2016 while much of the progress in understanding the earth and moon s interior has relied on the use of seismic networks for accurate location of sources single station approaches can be applied to data returned from mars in order to locate events and determine interior structure in preparation for the data return from insight we use a terrestrial dataset recorded at the global seismic network station bfo located at the black forest observatory in germany to verify an approach for event location and structure determination based on recordings of multiple orbit surface waves which will be more favorable to record on mars than earth due to smaller planetary radius and potentially lower background noise with this approach applied to events near the threshold of observability on earth we are able to determine epicentral distance within approximately 1 corresponding to 60 km on mars and origin time within 30 s with back azimuth determined from rayleigh wave polarization absolute locations are determined generally within an aperture of 10 allowing for localization within large tectonic regions on mars with these locations we are able to recover earth mantle structure within 5 the insight mission requirements for martian mantle structure using 1d travel time inversions of p and s travel times for datasets of only 7 events the location algorithm also allows for the measurement of great circle averaged group velocity dispersion which we measure between 40 and 200 s to scale the expected reliable frequency range of the insight data from earth to mars data using the terrestrial data we are able to resolve structure down to 200 km but synthetic tests demonstrate we should be able to resolve martian structure to 400 km with the same frequency content given the smaller planetary size

a crater and its ejecta an interpretation of deep impact we apply recently updated scaling laws for impact cratering and ejecta to interpret observations of the deep impact event an important question is whether the cratering event was gravity or strength dominated the answer gives important clues about the properties of the surface material of tempel 1 gravity scaling was assumed in pre event calculations and has been asserted in initial studies of the mission results because the gravity field of tempel 1 is extremely weak a gravity dominated event necessarily implies a surface with essentially zero strength the conclusion of gravity scaling was based mainly on the interpretation that the impact ejecta plume remained attached to the comet during its evolution we address that feature here and conclude that even strength dominated craters would result in a plume that appeared to remain attached to the surface we then calculate the plume characteristics from scaling laws for a variety of material types and for gravity and strength dominated cases we find that no model of cratering alone can match the reported observation of plume mass and brightness history instead comet like acceleration mechanisms such as expanding vapor clouds are required to move the ejected mass to the far field in a few hour time frame with such mechanisms and to within the large uncertainties either gravity or strength craters can provide the levels of estimated observed mass thus the observations are unlikely to answer the questions about the mechanical nature of the tempel 1 surface

predicted detection rates of regional scale meteorite impacts on mars with the insight short period seismometer abstract in 2016 nasa will launch the insight discovery class mission which aims to study the detailed internal structure of mars for the first time short and long period seismometers form a major component of insight s payload and have the potential to detect seismic waves generated by meteorite impacts large globally detectable impact events producing craters with diameters of 100 m have been investigated previously and are likely to be rare teanby n a wookey j 2011 phys earth planet int 186 70 80 but smaller impacts producing craters in the 0 5 20 m range are more numerous and potentially occur sufficiently often to be detectable on regional scales 1000 km at these distances seismic waves will have significant high frequency content and will be suited to detection with insight s short period seismometer seis sp in this paper i estimate the current martian crater production function from observations of new craters malin m c et al 2006 science 314 1573 1577 daubar i j et al 2013 icarus 225 506 516 model results williams j p pathare a v aharonson o 2014 icarus 235 23 36 and standard isochrons hartmann w k 2005 icarus 174 294 320 these impact rates are combined with an empirical relation between impact energy source receiver distance and peak seismogram amplitude derived from a compilation of seismic recordings of terrestrial and lunar impacts chemical explosions and nuclear tests the resulting peak seismogram amplitude scaling law contains significant uncertainty but can be used to predict impact detection rates i estimate that for a short period instrument with a noise spectral density of 10 8 ms 2 hz 1 2 in the 1 16 hz frequency band approximately 0 1 30 regional impacts per year should be detectable with a nominal value of 1 3 impacts per year therefore small regional impacts are likely to be a viable source of seismic energy for probing mars crustal and upper mantle structure this is particularly appealing as such impacts should be easily located with orbital imagery increasing their scientific value compared to other types of events with unknown origins finally comparison of the empirical results presented here with the modelling study of teanby and wookey teanby n a wookey j 2011 phys earth planet int 186 70 80 provides constraints on the seismic efficiency suggesting that values of 5 10 4 may be appropriate for impact generated seismic waves comparing explosion and impact datasets indicate that buried explosions are 10 times more efficient at generating seismic waves than impacts

apollo lunar seismic experiment final summary processing and initial analysis of the entire set of apollo lunar seismic data collected continuously from 1969 through 1977 have now been completed recent results include 1 better defined deep moonquake locations which appear to be bounded rather sharply between about 800 km and 1000 km depths with concentrations near both boundaries and 2 middle mantle 500 to 1000 km depth seismic velocities of vp 8 3 0 4 km sec and vs 4 6 0 2 km sec which are significantly higher than previous estimates and represent an increase of velocities from the upper mantle as opposed to a decrease in previous estimates

internal wave reflection on shelf slopes with depth varying stratification abstractreflection of internal waves from sloping topography is simple to predict for uniform stratification and linear slope gradients however depth varying stratification presents the complication that regions of the slope may be subcritical and other regions supercritical here a numerical model is used to simulate a mode 1 m2 internal tide approaching a shelf slope with both uniform and depth varying stratifications the fractions of incident internal wave energy reflected back offshore and transmitted onto the shelf are diagnosed by calculating the energy flux at the base of slope with and without topography and at the shelf break for the stratifications topographies considered in this study the fraction of energy reflected for a given slope criticality is similar for both uniform and depth varying stratifications this suggests the fraction reflected is dependent only on maximum slope criticality and independent of the depth of the pycnocline the majority of the reflected energy flux is in

present day impact cratering rate and contemporary gully activity on mars the mars global surveyor mars orbiter camera has acquired data that establish the present day impact cratering rate and document new deposits formed by downslope movement of material in mid latitude gullies on mars twenty impacts created craters 2 to 150 meters in diameter within an area of 21 5 106 square kilometers between may 1999 and march 2006 the values predicted by models that scale the lunar cratering rate to mars are close to the observed rate implying that surfaces devoid of craters are truly young and that as yet unrecognized processes of denudation must be operating the new gully deposits formed since august 1999 are light toned and exhibit attributes expected from emplacement aided by a fluid with the properties of liquid water relatively long extended digitate distal and marginal branches diversion around obstacles and low relief the observations suggest that liquid water flowed on the surface of mars during the past decade

characterization and analysis of a translational rockslide on a stepped planar slip surface abstract in 2014 a small stepped planar rockslide blocked a road near the town of san germano chisone in northwest italy photographs of the rock cut that failed above the road were taken before and after the rockslide occurred some photos were acquired with the assistance of a uav these photos were used to conduct a forensic analysis of the rockslide with the aid of photogrammetry software it was possible to characterize the slope geometry and the larger geological structures that influenced the slope behaviour a stepped planar slip surface and the shape of the slabs of rock that failed were defined by discontinuities and these were well documented in the 3d photogrammetry models the effective dilation angle was estimated from an assessment of the roughness of the discontinuity surfaces forming the slip surface the stability of the rockslide was analysed as a stepped translational failure mechanism a two block force equilibrium model of the rockslide was developed with this analytic model both deterministic and probabilistic methods were used to study the influence of water pressure as well as time dependent shear strength degradation along the discontinuities and corrosion of rockbolts the analysis suggests that the rockslide was caused by a combination of inadequate rock support time dependent shear strength degradation and water pressure in the joints resulting from above average rainfall

large impacts detected by the apollo seismometers impactor mass and source cutoff frequency estimations abstract meteoroid impacts are important seismic sources on the moon as they continuously impact the moon they are a significant contribution to the lunar micro seismic background noise they also were associated with the most powerful seismic sources recorded by the apollo seismic network we study in this paper the largest impacts we show that their masses can be estimated with a rather simple modeling technique and that high frequency seismic signals have reduced amplitudes due to a relatively low about 1 s corner frequency resulting from the duration of the impact process and the crater formation if synthetic seismograms computed for a spherical model of the moon are unable to match the waveforms of the observations they nevertheless provide an approximate measure of the energy of seismic waves in the coda the latter can then be used for an estimation of the mass of the impactors when the velocity of the impactor is known this method for the artificial impacts of the lm and sivb apollo upper stages allows us to retrieve the mass within 20 of relative error the estimated mass of the largest impacts observed during the 7 years of activity of the apollo seismic network provides an explanation for the non detection of surface waves on the seismograms the specifications of future moon seismometers in order to provide the detection of surface waves are given in conclusion

the seismic signatures of recently formed impact craters on mars we investigated the seismic signatures of recent impact crater clusters on mars that would be recorded by the interior exploration using seismic investigations geodesy and heat transport insight seismometers we used a database of 77 measured and dated impact sites with craters with diameters between 2 1 and 33 8 m along with inferred impact angle bolide trajectory and varying target material properties to empirically scale for the momentum expected seismic source function and radiation pattern of impacts the impact source is simulated in a local 3 d finite difference wave propagation code and coupled to teleseismic distances by scaling the spectra of 1 d global synthetic seismograms we use the insight seismometer noise floors to estimate detectability of impact s across azimuth and distance our experiments reveal that impact clusters have a higher peak corner frequency resulting from energy contributed by smaller craters to the power spectrum we also find that the time separation between individual impacts in a cluster is small 100 hz to resolve individual impacts within the cluster two of the clusters in our database 20 m effective diameter would have been detectable by insight with the assumptions that the martian background noise and seismic attenuation are both low joint detection of surface changes from newly formed crater s in images and by insight will provide precise source locations that are crucial for constraining the internal structure of mars

seismic detection of meteorite impacts on mars abstract meteorite impacts provide a potentially important seismic source for probing mars interior it has recently been shown that new craters can be detected from orbit using high resolution imaging which means the location of any impact related seismic event could be accurately determined thus improving the constraints that could be placed on internal structure using a single seismic station this is not true of other seismic sources on mars such as sub surface faulting which require location using multiple seismic stations this study aims to determine the seismic detectability of meteorite impacts and assess whether they are a viable means of probing deep internal structure first we derive a relation between crater diameter and equivalent seismic moment based on observational data compiled from impact tests controlled explosions and earthquake seismology second this relation was combined with updated cratering rates based on newly observed craters to derive the impact induced seismicity on mars which we estimate to total 10 13 10 14 n m per year finally seismic waveform modelling was used to determine the detectability of these impacts based on reasonable assumptions about likely seismometer performance and background noise levels for our nominal noise instrument case we find that detectable impacts at teleseismic distances source receiver offsets greater than 60 are very rare and occur approximately once every 10 years for our most optimistic noise instrument case approximately one such event occurs each year this suggests that using solely meteorite impacts is not a reliable way of probing the martian interior although local impacts are more frequently detectable and could provide important constraints on near surface seismic properties

impact cutoff frequency momentum scaling law inverted from apollo seismic data abstract we perform the analysis of both long and short period data for 40 large meteoroid impacts event gathered by the apollo lunar seismic network we extract the linear momentum released by the impact and the cutoff frequency of the recorded seismic spectrum related to the radiation process of the shock wave generated by the impact by using a proxy to the local porosity based on the density of surface craters and well correlated to the most recent grail observations we demonstrate that the seismic cutoff frequencies for 40 selected impacts correlate with this proxy and therefore likely with the porosity at the impacted areas our finding shows that lunar seismic records of meteoroid impacts represent unique geophysical data documenting medium to high energy 0 1 1 kt tnt yield impact processes including the interaction of shock waves with porous media this work can be applied to the analysis of the seismic data to be obtained by the insight mission in 2016 and the investigation of the lateral variations in the martian regolith

the morphology of small fresh craters on mars and the moon the depth diameter ratio for new meter to decameter scale martian craters formed in the last 20 years averages 0 23 only slightly deeper than that expected for simple primary craters on rocky surfaces large variations in depth diameter d d between impact sites indicate that differences between the sites such as target material properties impact velocity angle and physical state of the bolide s are important in determining the depth of small craters in the strength regime on the moon the d d of random fresh small craters with similar diameters averages only 0 10 indicating that either the majority of them are unrecognized secondaries or some proportion are degraded primaries older craters such as these may be shallower due to erosional infilling which is probably not linear over time but more effective over recently disturbed and steeper surfaces processes that are not yet acting on the new martian craters brand new meter to decameter scale craters such as the martian ones studied here are statistically easily distinguishable as primaries but the origins of older craters of the same size such as the lunar ones in this study are ambiguous

cratering asymmetry on the moon new insight from the apollo passive seismic experiment 1 the synchronous rotation of the moon can lead to an asymmetry in the cratering rate between the leading and trailing sides of lunar orbital motion the observation of the apollo passive seismic experiment can be viewed as a continuous seismic observation of lunar impacts it provides information of the current bombardments and small impact events of meter sized craters to evaluate the current leading trailing cratering asymmetry on the moon we investigated the spatial distribution of impact sites determined by apollo seismic observation we determined that the number density of impacts on the leading side is substantially higher than that on the trailing side in addition we discovered a possible enhancement of the number density of 1 4 0 4 to 1 9 0 5 on the leading side relative to that of the trailing side this indicated that the cratering asymmetry predicted from historical cratering records also exists in the current low magnitude impacts

remote sensing and seismic data integration for the characterization of a rock slide and an artificially triggered rock fall abstract on may 5th 2013 a planar rock slide 450 m3 occurred in the village of la riba ne spain which forced the closure of the road c 240z for 6 months this slide left a hanging block 130 m3 suspended on the slope forcing a controlled blasting followed by rock slope stabilization works the volume of rock displaced during the both events was deduced from lidar and photogrammetry data following two approaches subtracting pre and post event data and reconstructing the volume by fitting planes on the structural surfaces after a structural analysis of the slope information about the natural rock slide was obtained from the records of two permanent broadband seismic stations located 10 km from the site from these seismic records the existence of a rock slide was confirmed and its time of occurrence was determined information that would be otherwise unknown in addition despite the small volume displaced during the event its location was deduced from a single seismic station analysis the blasting process was recorded with two high definition hd video cameras and by two temporary seismic stations deployed close to the site 10 km partially because only a part of the released energy is transmitted into the ground as seismic energy and partially because the recorded seismic signal is highly dependent on the event characteristics and the geotechnical conditions of the ground materials nevertheless seismic data is very well suited to detect and characterize in detail both rockfall events of different nature and size merging and integrating remote sensing techniques such as lidar or photogrammetry with seismic measurements should allow the implementation of rockfall early warning systems

internal solitary waves induced by flow over a ridge with applications to the northern south china sea 1 the generation of internal solitary waves by barotropic tides over a ridge is studied in a nonhydrostatic numerical model under idealized oceanographic settings the experiments examine the effects of ridge width barotropic tidal strength and stratification on wave generation the barotropic tidal flow produces internal wave beams emitting from the ridge top if the slope of the ridge exceeds a critical value equal to the slope of the wave beam reflection and refraction of a wave beam in an upper ocean waveguide associated with a strong shallow thermocline produce horizontally propagating internal tides when the local froude number over a ridge is not small lee waves generated on the ridge convert enough energy from the barotropic tides to the internal tides to form tidal bores and solitary waves increasing stratification at ridge depths enhances the generation of internal waves particularly at the diurnal periods in the luzon strait the slope of the wave beam decreases in spring and summer as stratification at the ridge depths increases favoring the generation of internal tides without the presence of a strong shallow thermocline internal solitary waves are not observed east of the luzon strait in the northern south china sea internal solitary waves are likely observed from april to july when a strong shallow thermocline is present a deep mixed layer in winter suppresses the production of internal solitary waves