impacts experiments onto heterogeneous targets simulating impact breccia implications for impact strength of asteroids and formation of the asteroid families abstract a series of impact experiments onto solid decimeter sized cylinders made of porous gypsum admixed with approximately 1 cm sized pebbles have been performed the target densities and their heterogeneous structures could be representative of those of the asteroids ida eros and many others because asteroid sub surface could be the consolidated boulders made by self compaction and or by impact compaction impact velocities in the experiments ranged from 2 0 km s to 6 7 km s collision velocity in the asteroid main belt is approximately 5 km s it was found that the slope of the cumulative number distribution of post impact fragments strongly depends on the specific energy of the impact the presence of pebbles strongly influences the impact strength of the target as well as the size distribution of the post impact fragments results of the experiments presented here are aimed at identifying the analogy between the laboratory results and the damage of small asteroids or their catastrophic disruption after impacts

field and seismic images of sharp based shoreface deposits implications for sequence stratigraphic analysis abstract sharp based shoreface sandstones are of considerable interest because of their potential as hydrocarbon reservoirs and because they play an important role in the stratigraphic analysis of basin fills the sharp based shoreface sandstones studied herein are upper jurassic kimmeridgian tithonian and exposed along the coastal cliffs of the dover strait in northwestern france these series consist of tens of meter thick alternations of sandstones bodies and organic rich shales that can be correlated for over 30 km along coastal cliff exposures and tied to high resolution ca 1 m of sediment marine seismic profiles obtained several hundred meters offshore the units described here comprise two sharp based sandstone bodies each is composed of a basal progradational set of shoreface parasequences overlain by a progradational aggradational shoreface succession each sharp based sand body lies on a marine regressive surface of erosion and is truncated by a marine transgressive surface of erosion which in turn is overlain by a thin retrogradational ravinement lag or coarse grained planar laminated bedset the two progradational packages are separated by a third surface a subaerial exposure surface that is interpreted as a sequence boundary two distinct types of seismic units referred to as type a and type b have been identified in the study area seismic unit a has conformable upper and lower boundaries and parallel aggradational configurations seismic unit b is characterized by downlap and toplap boundaries and simple or compound sigmoid and oblique tangential progradational configurations a single sharp based shoreface sandstone body makes up the type b unit and typically consists of two compound superimposed progradational sets b1 b2 the lowermost set b1 corresponds in the field to the progradational set sensu stricto whereas b2 corresponds to a progradational aggradational set b1 and b2 are separated in outcrop by a sequence boundary these observations led us to reevaluate the sequence stratigraphic interpretation of sharp based shoreface sandstones it is proposed here that complete single sharp based shoreface sandstones bodies can be separated into two different systems tracts 1 a progradational set b1 seismic body at the base which corresponds to the forced regressive wedge systems tracts frwst of hunt and tucker 1992 and 2 a progradational aggradational set b2 at the top above the sequence boundary which corresponds to the lowstand systems tract lst of posamentier et al 1992 a complete sharp based shoreface sandstone body is bounded below the frwst by a regressive surface of marine erosion caused by the downward shift of wave base and by a transgressive surface of marine erosion or ravinement surface at the top of the lst

the shape of 433 eros from the near shoemaker laser rangefinder measurements from the near earth asteroid rendezvous near shoemaker laser rangefinder nlr indicate that asteroid 433 eros is a consolidated body with a complex shape dominated by collisions the offset between the asteroid s center of mass and center of figure indicates a small deviation from a homogeneous internal structure that is most simply explained by variations in mechanical structure regional scale relief and slope distributions show evidence for control of topography by a competent substrate impact crater morphology is influenced by both gravity and structural control small scale topography reveals ridges and grooves that may be generated by impact related fracturing

estimation of seismic and aseismic deformation in mexicali valley baja california mexico in the 2006 2009 period using precise leveling dinsar geotechnical instruments data and modeling ground deformation and seismicity in mexicali valley baja california mexico the southern part of the mexicali imperial valley are influenced by active tectonics and human activity in this study data from two successive leveling surveys in 2006 and 2009 2010 are used to estimate the total deformation occurred in mexicali valley during 2006 2009 the leveling data span more than 3 5 years and include deformation from several natural and anthropogenic sources that acted at different temporal and spatial scales during the analyzed period because of its large magnitude the aseismic anthropogenic deformation caused by fluid extraction in the cerro prieto geothermal field obscures the deformation caused by other mechanisms and sources the method of differential interferograms stacking was used to estimate the aseismic interseismic tectonic and anthropogenic components of the observed displacement using sar images taken in 2007 during a period when no significant seismicity occurred in the study area after removing the estimated aseismic signal from the leveling data residual vertical displacement remained and to identify possible sources and mechanisms of this displacement a detailed analysis of records from tiltmeters and creepmeters was performed the results of this analysis suggest that the residual displacement is mainly caused by moderate sized seismicity in the area of study modeling of the vertical ground deformation caused by the coseismic slip on source fault primary mechanism of the two most important earthquakes may 24 2006 mw 5 4 and december 30 2009 mw 5 8 was performed the modeling results together with the analysis of geotechnical instruments data suggests that this moderate sized seismicity influences the deformation in the study area by coseismic slip on the source fault triggered slip on secondary faults and soft sediments deformation

global structure of asteroid 433 eros 1 models of asteroid formation and evolution suggest a variety of internal structures ranging from gravitationally bound accumulations of debris to fully rigid monolithic bodies the near shoemaker spacecraft has provided detailed imaging and gravity data relevant to the characteristics of structural features and global mass properties a long ridge coplanar with a degraded trough ridge system and an approximately parallel surface facet suggest exploitation of a nearly global fabric by both compressive and extensional failure at significantly different times

carboniferous floras in siliciclastic rocks of kashmir himalaya india and the evolutionary history of the tethyan basin the fenestella shale formation of jammu and kashmir himalaya comprises latest visean or serpukhovian siliciclastic deposits formed along the southern margins of the palaeotethys ocean a sequence of shallowing upward and deepening upward units indicates changes from shoreface to offshore and deeper shelf conditions probably controlled by eustatic changes in an otherwise passive depositional system some of the finer grained shallow marine deposits have yielded fossil floras dominated by sub arborescent lycopsids sublepidodendron lepidodendropsis sphenophytes archaeocalamites and pteridophylls nothorhacopteris triphyllopteris the assemblage compares with other gondwanan floras of this age that have been assigned to the paraca floral realm and are taken to indicate relatively warm climatic conditions that existed just prior to the onset of the carboniferous permian ice age

fault slip triggering healing and viscoelastic afterworking in sediments in the mexicali imperial valley crackmeter data from the southern tip of the imperial fault in the mexicali imperial valley in northern baja california mexico show slip events that tend to group in episodes or suites that last over a few days with months of quiescence between them the events in these suites are apparently triggered and stopped by ground strain related to temperature changes a characteristic decrease in peak extension velocities during the slip event suites indicates the presence of viscoelastic afterworking which contributes the strain necessary for succeeding events with diminishing driving stresses and which can be roughly modeled as a series of kelvin voigt viscoelastic solids occurrence of very small events towards the end of the suites plus gaps between suites indicate that for the sediments significant fault healing requires a minimum of several days without slip

the composition of 433 eros a mineralogical chemical synthesis abstract the near earth asteroid rendezvous near mission carried x ray gamma ray spectrometers and multi spectral imager near infrared spectrometer instrument packages which gave complementary information on the chemistry and mineralogy respectively of the target asteroid 433 eros synthesis of these two data sets provides information not available from either alone including the abundance of non mafic silicates metal and sulfide minerals we have utilized four techniques to synthesize these data sets venn diagrams which examine overlapping features in two data sets suggest that the best match for 433 eros is an ordinary chondrite altered at the surface of the asteroid or perhaps a primitive achondrite derived from material mineralogically similar to these chondrites normalized element distributions preclude feo rich pyroxenes and suggest that the x ray and gamma ray data can be reconciled with a common silicate mineralogy by inclusion of varying amounts of metal normative mineralogy cannot be applied to these data sets owing to uncertainties in oxygen abundance and lack of any constraints on the abundance of sodium matrix inversion for simultaneous solution of mineral abundances yields reasonable results for the x ray derived bulk composition but seems to confirm the inconsistency between mineral compositions and orthopyroxene clinopyroxene ratios a unique solution does not seem possible in synthesizing these multiple data sets future missions including a lander to fully characterize regolith distribution and sample return would resolve the types of problems faced in synthesizing the near data

near at eros imaging and spectral results eros is a very elongated 34 kilometers by 11 kilometers by 11 kilometers asteroid most of the surface of which is saturated with craters smaller than 1 kilometer in diameter the largest crater is 5 5 kilometers across but there is a 10 kilometer saddle like depression with attributes of a large degraded crater surface lineations both grooves and ridges are prominent on eros some probably exploit planes of weakness produced by collisions on eros and or its parent body ejecta blocks 30 to 100 meters across are abundant but not uniformly distributed over the surface albedo variations are restricted to the inner walls of certain craters and may be related to downslope movement of regolith on scales of 200 meters to 1 kilometer eros is more bland in terms of color variations than gaspra or ida spectra 800 to 2500 nanometers are consistent with an ordinary chondrite composition for which the measured mean density of 2 67 0 1 grams per cubic centimeter implies internal porosities ranging from about 10 to 30 percent

modeling the structure of high porosity asteroids abstract a number of asteroids have been observed to have extremely low bulk densities in the 1 3 g cm 3 range given reasonable compositions based on meteorite analogues this bulk density implies bulk porosities of 40 60 suggesting that many asteroids are rubble piles held together by self gravity and containing significant empty space perhaps more empty space than solid material simple energy balance calculations and accretional models of disrupted asteroids suggest that materials in porous asteroids may be sorted by particle size the large irregular pieces and larger voids fractures are probably located deeper inside the asteroid and the fine particle size fractions that are observed on their surfaces are restricted to the surface regolith zone the large interior voids fractures are preserved from infilling by the effects of friction on the smaller size fractions friction tends to dominate the downward pull of gravity and prevents the fine fractions from filtering into the interior of the asteroid and infilling the large fractures and voids friction may also play a role in allowing shattered asteroids to maintain their relief features and shape by resisting the movements of pieces within the object in effect providing strength to non coherent objects

model for asteroid regolith to guide simulant development abstract when creating asteroid regolith simulant it is necessary to have a model of asteroid regolith to guide and to evaluate the simulant we created a model through evaluation and synthesis of the available data sets including 1 the returned sample from itokawa by the hayabusa spacecraft 2 imagery from the hayabusa and near spacecraft visiting itokawa and eros respectively 3 thermal infrared observations from asteroids 4 the texture of meteorite regolith breccias and 5 observations and modeling of the ejecta clouds from disrupted asteroids comparison of the hayabusa returned sample with other data sets suggest the surficial material in the smooth regions of asteroids is dissimilar to the bulk regolith probably due to removal of fines by photoionization and solar wind interaction or by preferential migration of mid sized particles into the smooth terrain we found deep challenges interpreting and applying the thermal infrared data so we were unable to use those observations in the model texture of regolith breccias do not agree with other data sets suggesting the source regolith on vesta was coarser than typical asteroid regolith the observations of disrupted asteroids present a coherent picture of asteroid bulk regolith in collisional equilibrium unlike lunar regolith hed textures and the itokawa returned sample the model we adopt consists of power laws for the bulk regolith in unspecified terrain differential power index 3 5 representing equilibrium and the surficial regolith in smooth terrain differential power index 2 5 representing disequilibrium available data do not provide adequate constraints on maximum and minimum particle sizes for these power laws so the model treats them as user selectable parameters for the simulant

fundamentally distinct outcomes of asteroid collisional evolution itokawa and eros 1 the outcomes of asteroid collisional evolution are presently unclear are most asteroids larger than 1 km size gravitational aggregates reaccreted from fragments of a parent body that was collisionally disrupted while much smaller asteroids are collisional shards that were never completely disrupted the 16 km mean diameter s type asteroid 433 eros visited by the near mission has surface geology consistent with being a fractured shard the hayabusa spacecraft visited an s asteroid smaller than 1 km namely 25143 itokawa here we report the first comparative analyses of itokawa and eros geology itokawa lacks a global lineament fabric and its blocks craters and regolith are inconsistent with formation and evolution as a fractured shard unlike eros itokawa is not a scaled down eros but formed by a distinct process of catastrophic disruption and reaccumulation

near s flyby of 253 mathilde images of a c asteroid on 27 june 1997 the near earth asteroid rendezvous near spacecraft flew within 1212 kilometers of asteroid 253 mathilde mathilde is an irregular heavily cratered body measuring 66 kilometers by 48 kilometers by 46 kilometers the asteroid s surface is dark estimated albedo between 0 035 and 0 050 and similar in color to some cm carbonaceous chondrites no albedo or color variations were detected the volume derived from the images and the mass from doppler tracking of the spacecraft yield a mean density of 1 3 0 2 grams per cubic centimeter about half that of cm chondrites indicating a porous interior structure

fault slip seismicity and deformation in mexicali valley baja california mexico after the m 7 1 1999 hector mine earthquake a local small deformation network in mexicali valley baja california mexico recorded fault slip seismicity and deformation produced by the 16 october 1999 m 7 1 hector mine earthquake 260 km away the network consists of two crackmeters two biaxial surface tiltmeters and one broadband seismograph all recording continuously these instruments are complemented by other seismological instruments within the valley local microearthquakes with clear p and s phases began 2 hours after arrival of the hector mine p wave and earthquakes with m 2 5 large enough to be located started about 33 hours after the earthquake local seismicity continued with decreasing frequency for about 2 weeks after the hector mine earthquake vertical and horizontal slip and tilt began on the imperial fault simultaneously with the hector mine earthquake seismic wave arrival which is clearly recorded by the tiltmeters deformation recorded by a tiltmeter on the cerro prieto geothermal field began about 30 hours after the main event and ended 13 hours later after the occurrence of the largest local earthquake m 4 1 in this episode the temporal pattern of seismicity and deformation suggests that deformation is the main process triggered by the hector mine earthquake waves in the study area and the transient local seismicity increase is a response to the triggered deformation

collisional evolution of the asteroid belt abstract a new synthesis of asteroid collisional evolution is motivated by the question of whether most asteroids larger than 1 km size are strengthless gravitational aggregates rubble piles near found eros not to be a rubble pile but a shattered collisional fragment with a through going fracture system and an average of about 20 m regolith cover of four asteroids visited by spacecraft none appears likely to be a rubble pile except perhaps mathilde nevertheless current understanding of asteroid collisions and size dependent strength and the observed distribution of rotation rates versus size have led to a theoretical consensus that many or most asteroids larger than 1 km should be rubble piles is eros the best observed asteroid highly unusual because it is not a rubble pile is mathilde if it is a rubble pile like most asteroids what would be expected for the small asteroid itokawa the muses c sample return target an asteroid size distribution is synthesized from the minor planet center listing and results of the sloan digital sky survey an infrared space observatory survey the small main belt asteroid spectroscopic survey and the infrared astronomical satellite survey a new picture emerges of asteroid collisional evolution in which the well known dohnanyi result that the size distribution tends toward a self similar form with a 2 5 index power law is overturned because of scale dependent collision physics survival of a basaltic crust on vesta can be accommodated together with formation of many exposed metal cores the lifetimes against destruction are estimated as 3 gyr at the size of eros 10 gyr at ten times that size and 40 gyr at the size of vesta eros as a shattered collisional fragment is not highly unusual the new picture reveals the new possibility of a transition size in the collisional state where asteroids below 5 km size would be primarily collisional breakup fragments whereas much larger asteroids are mostly eroded or shattered survivors of collisions in this case well defined families would be found in asteroids larger than about 5 km size but for smaller asteroids families may no longer be readily separated from a background population moreover the measured boulder size distribution on eros is re interpreted as a sample of impactor size distributions in the asteroid belt the regolith on eros may result largely from the last giant impact and the same may be true of itokawa in which case about a meter of regolith would be expected there even a small asteroid like itokawa may be a shattered object with regolith cover

carbonate platform drowning in a foreland setting the mid carboniferous platform in western urals russia abstract the stratigraphic evolution through time of the mid carboniferous russian platform deposited on the distal margin of the west uralian prograding foredeep basin can be observed in the approximately 3000 m thick sedimentary cover that constitutes the upper paleozoic foreland mid carboniferous permian of the uralian fold belt it is composed of wave dominated low angle carbonate ramps of late visean to early moscovian age and carbonate platforms bordered by slope reef mounds from the kasimovian to the late artinskian early kungurian eastward in the foredeep the carbonate platforms pass into terrigenous deposits a complete transgressive progradational section at the transition between carbonate ramp and terrigenous deposits exhibits from base to top 1 deepening upward carbonate ramp deposits 2 a shaly condensed section with volcaniclastics glauconite and phosphorites of late moscovian to early asselian age the transgressive part and 3 a shallowing upward section of turbidites ending in coarse grained fan deltas evaporites and meandering river redbeds by the earliest triassic the progradational section this paper focuses on the uppermost part of the carbonate ramp deposits serpukhovian to early moscovian these ramp facies comprise peritidal channels and mud flats wave to storm dominated shoals and patch reefs that are overlain by channel attached sand lobes of turbidites black shales and radiolarites of the condensed section this large scale deepening upward trend from inner ramp to outer ramp environments reflects a change in the depositional profile from a tide and wave dominated flat ramp to a wave and storm dominated steepened ramp margin and then to foreslope turbidites correlation of sections dated by fusulinid faunas in southern urals shows that the ramp evolved from emergent in the north perm solikamsk area as evidenced by karstification and deepened to the south belaya area with emplacement of carbonaceous foreslope debris flows and turbidites capped by deep marine black shales and radiolarites the time gap increases northward and reaches a span including the siuransky pro parte the akavassky the askynbashky and the asatausky pro parte biohorizons the mapping of these facies belts across all the urals shows that carbonate ramps wedge out in the middle urals and give rise to widely distributed diversified and deeper marine facies belts not only to the south towards the precaspian depression but also to the north towards the polar urals the drowning of these carbonate ramps and the cutoff in carbonate production on the russian platform during the mid carboniferous is explained by a succession of low frequency flexure relaxation cycles in the foreland associated with dilution by siliciclastics outpouring of volcaniclastics and changes in the nature and direction of the sediment input and high frequency cycles mainly controlled by eustasy

observed spectral properties of near earth objects results for population distribution source regions and space weathering processes abstract we present new visible and near infrared spectroscopic measurements for 252 near earth neo and mars crossing mc objects observed from 1994 through 2002 as a complement to the small main belt asteroid spectroscopic survey smass http smass mit edu combined with previously published smass results we have an internally consistent data set of more than 400 of these objects for investigating trends related to size orbits and dynamical history these data also provide the basis for producing a bias corrected estimate for the total neo population stuart and binzel 2004 icarus 170 295 311 we find 25 of the 26 bus 1999 phd thesis taxonomic types are represented with nearly 90 of the objects falling within the broad s q x and c complexes rare a and e types are more common in the mc than neo population about 5 compared to 3 orbits in terms of possible space weathering effects we see a size dependent transition from ordinary chondrite like q type objects to s type asteroids over the size range of 0 1 to 5 km where the transition is effectively complete at 5 km a match between the average surface age of 5 km asteroids and the rate of space weathering could constrain models for both processes however space weathering may proceed at a very rapid rate compared with collisional timescales in this case the presence or absence of a regolith may be the determining factor for whether or not an object appears space weathered thus 0 1 to 5 km appears to be a critical size range for understanding the processes timescales and conditions under which a regolith conducive to space weathering is generated retained and refreshed

albedos and diameters of three mars trojan asteroids abstract we observed the mars trojan asteroids 5261 eureka and 101429 1998 vf 31 and the candidate mars trojan 2001 fr 127 at 11 2 and 18 1 microns using michelle on the gemini north telescope we derive diameters of 1 28 0 78 and 0 14 the albedos for eureka and 1998 vf 31 are consistent with the taxonomic classes and compositions s i angritic and s vii achondritic respectively and implied histories presented in a companion paper by rivkin et al eureka s surface likely has a relatively high thermal inertia implying a thin regolith that is consistent with predictions and the small size that we derive

surface expressions of structural features on eros abstract near shoemaker imaging of the asteroid eros has revealed a variety of surface forms that probably reflect underlying structures they range from global to local in scale the most prominent positive topographic feature is a long ridge rahe dorsum which extends over 18 km and has the morphology of a thrust fault two large ancient trough systems are also present grooves are ubiquitous commonly occur in suborthogonal sets and have linear or scalloped outlines the grooves on eros are similar in morphology and scale to those on other small bodies such as gaspra ida and phobos and are likely to have a similar mode of origin namely drainage of regolith into underlying fractures models that use groove dimensions as indicators of regolith thickness imply depths of up to several tens of meters many craters have been subjected to structural control resulting in squared outlines we find no evidence that specific groove sets are associated with individual impact events however evidence exists that preexisting structures have been reactivated by later impact activity the large scale of rahe dorsum and many grooves on eros s surface suggests that the asteroid is a largely coherent but fractured body

ponded deposits on asteroid 433 eros in late january 2001 the near shoemaker spacecraft performed low altitude passes over the surface of 433 eros coordinated observations of the asteroid surface were obtained at submeter resolution by the near laser rangefinder and the multispectral imager this paper presents three independent coordinated observations of a 90 m pond adjacent to a granular debris flow including the highest resolution altimetric measurements of ponded deposits on eros the ponded deposits appear to have been emplaced by fluid like motion of dry asteroidal regolith a simple model of seismic agitation from impacts is developed to account for pond formation on eros the model predicts that ponds should form readily on eros but not on the moon where ponds are not observed the model also suggests that the absence of observable ponds in the largest craters of eros as well as on phobos and deimos may be related to regolith depth

an estimate of eros s porosity and implications for internal structure abstract earth based spectral measurements and near shoemaker magnetometer x ray and near infrared spectrometer data are all consistent with eros having a bulk composition and mineralogy similar to ordinary chondrite meteorites oc by comparing the bulk density of 433 eros 2 67 0 03 g cm 3 with that of ocs 3 40 g cm 3 we estimate the total porosity of the asteroid to be 21 33 macro or structural porosity best estimated to be 20 is constrained to be between 6 and 33 we conclude that eros is a heavily fractured body but we find no evidence that it was ever catastrophically disrupted and reaccumulated into a rubble pile

co seismic displacements of the 1992 landers earthquake sequence we present co seismic displacement vectors derived from global positioning system gps measurements of 92 stations in southern california these gps results are combined with five well determined gps displacement vectors from continuously tracking stations of the permanent gps geodetic array as well as line length changes from usgs geodolite and two color laser trilateration observations to determine a self consistent set of geodetic data for the earthquake these combined displacements are modeled by an elastic dislocation representation of the primary fault rupture planes on average the model residuals are about twice the estimated measurement errors

compaction as the origin of the unusual craters on the asteroid mathilde the asteroid mathilde has suffered at least five giant impacts previous studies suggest that mathilde s giant craters should be surrounded by blankets of ejecta that are kilometres deep1 2 yet the craters show no evidence of filling by material excavated during later nearby impacts1 3 computer simulations of impacts have been used to suggest that the absence of ejecta arises because the impact energy is deposited in a small volume due to mathilde s unusually high porosity4 which produces ejecta velocities so high that nearly all of the material escapes mathilde s gravitational field5 here we report laboratory measurements of high velocity impacts into porous material which support an alternative explanation3 the crater is formed mainly by compaction not excavation the small amount of ejecta lofted in our experiments have velocities sufficiently low that nearly all of the material is redeposited within the crater bowl the crater itself results from material being compressed rather than ejected this type of cratering implies that highly porous asteroids are minor contributors of meteorites because essentially no material escapes the asteroids

40ar 39ar age of material returned from asteroid 25143 itokawa the hayabusa mission to asteroid 25143 itokawa brought back 2000 small particles which most closely resemble material found in ll4 6 chondrites we report an 40ar 39ar age of 1 3 0 3 ga for a sample of itokawa consisting of three grains with a total mass of 2 g this age is lower than the 4 0 ga ages measured for 75 of ll chondrites but close to one for y 790964 and its pairs the flat 40ar 39ar release spectrum of the sample suggests complete degassing 1 3 ga ago recent solar heating in itokawa s current orbit does not appear likely to have reset that age solar or impact heating 1 3 ga ago could have done so if impact heating was responsible then the 1 3 ga age sets an upper bound on the time at which the itokawa rubble pile was assembled and suggests that rubble pile creation was an ongoing process in the inner solar system for at least the first 3 billion years of solar system history

surface displacement and groundwater level changes associated with the 24 may 2006 mw 5 4 morelia fault earthquake mexicali valley baja california mexico on 24 may 2006 a moderate size m w 5 4 earthquake occurred in the mexicali valley mexico the event created 5 km of surface rupture associated deformation was recorded by geotechnical instruments leveling profile and synthetic aperture radar interferometry a coseismic steplike groundwater level change was detected at seven wells the surface rupture consisted of up to 30 cm of primarily normal displacement 20 25 cm of vertical offset was recorded by a crackmeter and 20 cm on leveling line we created envisat c band interferograms spanning the 24 may 2006 earthquake to image the coseismic displacement although the coherence of the interferometric images is low the images clearly show a spatial displacement field centered on the known surface rupture that is consistent with the expected sense of motion the interferograms and leveling line also include subsidence related to geothermal production this anthropogenic subsidence component was estimated using a pre event interferogram source parameters for the earthquake were estimated using forward modeling of both surface deformation data and static volume strain change inferred from coseismic changes in groundwater level modeling was based on finite rectangular fault embedded in an elastic media the preferred fault model has a strike rake and dip of 48 89 45 and has a length of 5 2 km width of 6 7 km and 34 cm of uniform slip the geodetic moment based on the modeled fault parameters is graphic 1 the model matched the observed surface deformation expected groundwater changes and teleseismic moment reasonably well 1 embed inline graphic 1 gif

global positioning system constraints on fault slip rates in southern california and northern baja mexico we use global positioning system gps estimates of horizontal site velocity to constrain slip rates on faults comprising the pacific north america plate boundary in southern california and northern mexico we enlist a simple elastic block model to parameterize the distribution and sum of deformation within and across the plate boundary we estimate a pacific north america relative plate motion rate of 49 3 mm yr one standard deviation consistent with nuvel 1a estimates we are able to resolve robust slip rate estimates for the southernmost san andreas san jacinto and elsinore faults 26 2 9 2 and 6 2 mm yr respectively and for the imperial and cerro prieto faults 35 2 and 42 1 mm yr respectively accounting for about 86 of the total plate motion the remaining 14 appears to be accommodated to the west of these fault systems probably via slip along the san clemente fault and or the san miguel vallecitos rose canyon and newport inglewood fault systems these results are highly consistent with paleoseismic estimates for slip rates implying that off fault strain accumulation within the deforming zone of the plate boundary is largely elastic we estimate that the seismically quiescent southernmost san andreas fault has incurred about 8 2 m of slip deficit over the last few hundred years presumably to be recovered during a future large earthquake

shoemaker crater as the source of most ejecta blocks on the asteroid 433 eros the loose material regolith on the surfaces of asteroids is thought to represent ballistically emplaced ejecta from impacts but the identification of source craters and the detailed study of the regolith modification have been hampered by the limited spatial resolution and area coverage of the few asteroids imaged by spacecraft here we report the results of global mapping of the asteroid 433 eros from high resolution images obtained by the near shoemaker spacecraft based on the images and ejecta emplacement models we suggest that most large ejecta blocks on eros originate from a relatively young 7 6 km diameter crater a large fraction of the ejecta from impacts pre dating that crater has apparently been buried or eroded the images also show evidence for the action of a variety of sorting environments for regolith particles after they are deposited on the surface

a survey of karin cluster asteroids with the spitzer space telescope abstract the karin cluster is one of the youngest known families of main belt asteroids dating back to a collisional event only 5 8 0 2 myr ago using the spitzer space telescope we have photometrically sampled the thermal continua 3 5 22 m of 17 karin cluster asteroids of different sizes down to the smallest members discovered so far in order to make the first direct measurements of their sizes and albedos and study the physical properties of their surfaces our targets are also amongst the smallest main belt asteroids observed to date in the mid infrared the derived diameters range from 17 3 km for 832 karin to 1 5 km for 75176 with typical uncertainties of 10 the mean albedo is p v 0 215 0 015 compared to 0 20 0 07 for 832 karin itself for h 11 2 0 3 consistent with the view that the karin asteroids are closely related physically as well as dynamically the albedo distribution 0 12 p v 0 32 is consistent with the range associated with s type asteroids but the variation from one object to another appears to be significant contrary to the case for near earth asteroids our data show no evidence of an albedo dependence on size however the mean albedo is lower than expected for young fresh s type surfaces suggesting that space weathering can darken main belt asteroid surfaces on very short timescales our data are also suggestive of a connection between surface roughness and albedo which may reflect rejuvenation of weathered surfaces by impact gardening while the available data allow only estimates of lower limits for thermal inertia we find no evidence for the relatively high values of thermal inertia reported for some similarly sized near earth asteroids our results constitute the first observational confirmation of the legitimacy of assumptions made in recent modeling of the formation of the karin cluster via a single catastrophic collision 5 8 0 2 myr ago

secondary craters of tycho size frequency distributions and estimated fragment size velocity relationships 1 we examined the size frequency distribution and the spatial distribution of secondary craters around the lunar crater tycho secondary crater diameters were found to range from 0 55 to 4 0 km and their distance from tycho to range from 130 to 370 km the diameter and ejection velocity of the secondary forming fragments were also estimated from the crater size and the distance from the primary using the scaling relationships for cratering the power law index of the size frequency distribution of the tycho secondary craters ranges from 3 3 to 4 0 the same as the steep slope of the typical size frequency distribution for lunar craters of less than 4 km diameter the decay index of secondary crater densities with distance from the primary craters is not constant and is small at large distances less than 2 5 for r 2 5r the total number of secondaries forming ejecta fragments is more than twice larger than for other lunar primaries previously studied these results imply that there are many small secondary craters in fields far from the primary crater a dominant contribution of secondaries to the size frequency distribution of all lunar craters is thus strongly suggested the index range of 2 6 to 3 0 for estimated fragment size distributions is not only close to other natural and experimental craters but also to those of blocks on asteroids the relative fragment size distributions are independent of the ejection velocity this result is the first observational confirmation of the theoretical assumption and agrees with a recent result from laboratory experiments