compositional heterogeneity of central peaks within the south pole aitken basin 1 using high spectral and spatial resolution moon mineralogy mapper data we investigate compositional variations across the central peak structures of four impact craters within the south pole aitken basin spa two distinct causes of spectral diversity are observed spectral variations across the central peaks of bhabha finsen and lyman are dominated by soil development including the effects of space weathering and mixing with local materials for these craters the central peak structure is homogeneous in composition although small compositional differences between the craters are observed this group of craters is located within the estimated transient cavity of spa and their central uplifts exhibit similar mafic abundances therefore it is plausible that they have all uplifted material associated with melts of the lower crust or upper mantle produced during the spa impact compositional differences observed between the peaks of these craters reflect heterogeneities in the spa subsurface although the origin of this heterogeneity is uncertain in contrast to these craters leeuwenhoek exhibits compositional heterogeneity across its central peak structure the peak is areally dominated by feldspathic materials interspersed with several smaller exposures exhibiting a mafic spectral signature leeuwenhoek is the largest crater included in the study and is located in a region of complex stratigraphy involving both crustal feldspathic and spa mafic melt and ejecta materials the compositional diversity observed in leeuwenhoek s central peak indicates that kilometer scale heterogeneities persist to depths of more than 10 km in this region

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

geologic structure generated by large impact basin formation observed at the south pole aitken basin on the moon the south pole aitken spa basin is the largest clearly recognized basin on the lunar surface determining the composition and structure of the spa basin interior provides critical constraints on the deep crustal and or mantle composition of the moon and improves our understanding of large basin forming impact processes here we present a new mineralogical map of the spa basin interior based on high spatial resolution reflectance spectra using the selene kaguya multiband imager which is combined with topographic data in order to interpret the geologic context the derived mineralogical map suggests extensive distribution of ejected low ca pyroxene dominant mantle material with the presence of purest anorthosite crustal materials surrounding a possible melt pool of 0 26 to 0 33 of the basin diameter near the basin center which is significantly smaller than that suggested by the crater scaling law the absence of clear evidence of lower crustal material is consistent with recent impact simulation results

major lunar crustal terranes surface expressions and crust mantle origins in light of global remotely sensed data the igneous crust of the moon can no longer be viewed as a simple globally stratified cumulus structure composed of a flotation upper crust of anorthosite underlain by progressively more mafic rocks and a residual melt kreep sandwich horizon near the base of the lower crust instead global geochemical information derived from clementine multispectral data and lunar prospector gamma ray data reveals at least three distinct provinces whose geochemistry and petrologic history make them geologically unique 1 the procellarum kreep terrane pkt 2 the feldspathic high lands terrane fht and 3 the south pole aitken terrane spat the pkt is a mafic province coincident with the largely resurfaced area in the procellarum imbrium region whose petrogenesis relates to the early differentiation of the moon here some 40 of the th in the moon s crust is concentrated into a region that constitutes only about 10 of the crustal volume this concentration of th average 5 ppm and by implication the other heat producing elements u and k led to a fundamentally different thermal and igneous evolution within this region compared to other parts of the lunar crust lower crustal materials within the pkt likely interacted with underlying mantle materials to produce hybrid magmatism leading to the magnesian suite of lunar rocks and possibly kreep basalt although rare in the apollo sample collection widespread mare volcanic rocks having substantial th enrichment are indicated by the remote data and may reflect further interaction between enriched crustal residues and mantle sources the fht is characterized by a central anorthositic region that constitutes the remnant of an anorthositic craton resulting from early lunar differentiation basin impacts into this region do not excavate significantly more mafic material suggesting a thickness of tens of kilometers of anorthositic crust the feldspathic lunar meteorites may represent samples from the anorthositic central region of the fht ejecta from deep penetrating basin impacts outside of the central anorthositic region however indicate an increasingly mafic composition with depth the spat a mafic anomaly of great magnitude may include material of the upper mantle as well as lower crust thus it is designated a separate terrane whether the spa basin impact simply uncovered lower crust such as we infer for the fht remains to be determined

feo and tio2 concentrations in the south pole aitken basin implications for mantle composition and basin formation we use newly developed spectroscopic methods for determining feo and tio2 abundances to study the huge 2500 km diameter south pole aitken basin the floor of this basin shows iron and titanium values which are weakly correlated and largely range from 7 to 14 wt feo and from 0 5 to 1 5 wt tio2 this composition is consistent with an approximate 1 1 mixture of lower crustal material like that found elsewhere on the moon and mantle rock containing 10 16 wt feo and 0 1 wt tio2 although mantle rock appears to compose about 50 of the floor deposits models of the formation of large impact basins predict that virtually all the floor materials ought to be derived from the mantle

monitoring velocity variations in the crust using earthquake doublets an application to the calaveras fault california we present a technique that greatly improves the precision in measuring temporal variations of crustal velocities using an earthquake doublet or pair of microearthquakes that have nearly identical waveforms and the same hypocenter and magnitude but occur on different dates we compute differences in arrival times between seismograms recorded at the same station in the freqency domain by cross correlation of short windows of signal a moving window analysis of the entire seismograms including the coda gives t the difference in arrival times versus running time along the seismogram the time resolution of the method is an order of magnitude better than the digitization interval the t technique is illustrated with a pair of microearthquakes m 1 7 and 2 0 that occurred before and after the coyote lake california earthquake m 5 9 of august 6 1979 and on the same segment of the calaveras fault that ruptured during the earthquake the coda wave arrivals for some stations are progressively delayed for the second earthquake in the doublet so that its seismogram appears as a stretched version of the earlier event we interpret this systematic variation in t along the coda as a change in the average s velocity in the upper crust in the time interval between the two doublets s wave velocities appear to have decreased by 0 2 in an oblong region 5 10 km in radius at the south end of the aftershock zone

development importance and effect of a ground truth correction for the moon mineralogy mapper reflectance data set 1 we evaluate the effect and importance of a ground truth correction for the moon mineralogy mapper m3 level 2 reflectance data set this correction is derived from extensive laboratory characterizations of mature feldspathic lunar soils and is designed to improve the accuracy of 1 m absorption features in m3 reflectance data to evaluate the correction the band strength across a subset of the feldspathic highlands terrane fht is analyzed with m3 imaging spectroscopy data using m3 reflectance data and derived products we find significant differences in band strength and shape between m3 observations collected over identical terrain but under different observational and operational conditions the ground truth correction minimizes these differences in 1 m band strengths and also brings the 1 m band strengths measured with m3 data into closer agreement with laboratory measurements of lunar soil samples although the fht region studied was found to have very low band strengths the m3 ground truth correction results in overall stronger absorption features for all mature soils relative to uncorrected level 2 reflectance data for the same region these differences between m3 data collected under different operational conditions and the effects of the ground truth correction while minor in appearance can have significant implications for interpretations of any regional soil analyses with m3 data that rely on absolute 1 m absorption feature strength the m3 ground truth correction corrects only wavelengths below 1500 nm and comparisons between corrected and uncorrected wavelengths must be done with caution

ultramafic impact melt sheet beneath the south pole aitken basin on the moon 1 the spectral profiler onboard the japanese lunar explorer kaguya conducted the first hyperspectral survey around the south pole aitken basin spa on the moon that is one of the largest impact structures in the solar system the radiative transfer modeling revealed that fresh crater central peaks inside spa are commonly composed of an ultramafic assemblage dominated by magnesium rich orthopyroxene suggesting a homogeneous layer buried under spa the extensive ultramafic layer could be a relic of a gigantic impact melt pool produced by the spa forming impact the preponderance of orthopyroxene could have resulted from significant fractional crystallization of the lunar magma ocean prior to the onset of plagioclase floatation

near surface stress and displacement in a layered elastic crust in situ stress measurements on the san andreas fault are modeled in terms of a solution to the equations of three dimensional elastic equilibrium in a layered medium crustal stresses are expressed in terms of surface deformations in particular vertical stress gradients are shown to be proportional to horizontal gradients of vertical surface deformation in light of constraints derived by this relation it is proposed to reinterpret the observed near surface in situ vertical stress gradients on the san andreas fault as partly a manifestation of a layered crust with vertically increasing rigidity extrapolation to depth of the revised stress gradients suggests that the san andreas fault can be regarded as a low stress phenomenon compatible with estimates of shear stress obtained from heat flow data

geology of mare deposits in south pole aitken basin as seen by clementine uv vis data a multispectral analysis of 21 discrete lunar mare deposits within the south pole aitken basin was undertaken in order to model the general mineralogical composition of farside mare deposits so that the near and farside may be compared in terms of magma generation and emplacement determination of each deposit s mineralogy was based upon albedo the 0 75 0 95 m ratio indicating the presence of a 1 0 m absorption band and the strength and shape of that band a combination of improved spatial resolution and the availability of the general multispectral signature for each pond allowed deposits to be examined for homogeneity in order to assess the nature and number of flows represented feo and tio 2 abundances were also estimated based upon the resultant data 19 out of 21 ponds were determined to be mare deposits of these 19 15 had spectra well defined enough to classify general mineralogy nine having high ca pyroxene signatures indicative of basalt and six showing low ca signatures suggesting a substantial noritic component we believe these noritic signatures can plausibly be attributed to vertical lateral soil mixing processes for the smallest ponds although a unique lithology cannot be ruled out for the largest pond a majority of ponds in this study region have homogeneous spectral signatures interpreted to represent individual eruptive phases this indicates that very large volumes for these regions may be typical also because such volumes are comparable to the largest terrestrial eruptions they may have formed by a similar mechanism of emplacement the vast majority of mature soils are spectrally redder and thus have a lower estimated feo abundance than the mare serenitatis soil standard ms 2 in particular and nearside basalts in general these soils also average low to medium estimated tio 2 abundance similar to apollo 12 and 15 and luna 24 the observations made here are consistent with a scenario in which basalts with low feo and low to medium tio 2 contents were deposited during the lunar peak volcanic period that occurred in the late imbrian 3 80 3 20 ga and because of their small areal extent were more susceptible to mixing processes than nearside basalts

differential analysis of coda q using similar microearthquakes in seismic gaps part 1 techniques and application to seismograms recorded in the anza seismic gap abstract a large but conflicting literature exists that suggests that the scattering properties of the earth in seismogenic areas may be temporally variable and that this variability could be correlated with the nucleation times of moderate to large earthquakes to search for temporal variations in coda q in the vicinity of an expected moderate earthquake nucleation region along the san jacinto fault zone pairs and clusters of earthquakes recorded by the anza seismic network between 1982 and 1992 are examined to minimize differences arising from path and source variability only the most similar examples of microearthquake wave fields are intercompared to assess coda q differences between similar microearthquake signals we search for systematic temporal changes in moving window spectral amplitude ratios for a single scattering coda model with an envelope decay function of the form t m e ft qc the relationship between the natural log amplitude spectral ratio and q 1 q 1 c 2 q 1 c 1 is linear i e ln r f t ft q 1 f w f where w f is a time independent relative source term to obtain robust uncertainty estimates of q 1 f and w f we utilize multi taper spectral analysis coupled with a nonparametric monte carlo confidence interval estimation procedure for the most similar events in the anza region coda cross correlation values of approximately 0 7 for 16 sec of coda we find that coda q as a function of time is stable at a typical 1 resolution of only between 25 and 50 of the reference coda q value for the area even in the best constrained frequency bands comparison of similar microearthquake coda signals with both short and long temporal separations indicates that all of this variability can be reasonably attributed to random fluctuations in the coda that are driven by source variability and is not indicative of any systematic temporal variability in coda q to obtain estimates of relative coda q that are more precise than this level the spectral ratio analysis technique requires significantly more similar earthquakes than are produced by seismogenic processes in the anza region such earthquakes have been observed to occur in other regions of the san andreas fault system and are analyzed in antolik et al 1996

observation and modelling of fault zone fracture seismic anisotropy i p sv and sh travel times summary three component vsp borehole seismograms taken in the vicinity of an active normal fault in california show strong systematic shear wave splitting that increases with proximity to the fault using cerven s method of characteristics for ray tracing in anisotropic heterogeneous media and hudson s formulation of elastic constants for media bearing aligned fractures we have fitted a suite of p sv and sh hanging wall and foot wall travel times with a simple model of aligned fractures flanking the fault zone the dominant fracture set is best modelled as parallel to the fault plane and increasing in density with approach to the fault the increase in fracture density is non uniform power law or gaussian with respect to distance to the fault although the hanging wall and the foot wall rock are petrologically the same unit the fracture halo is more intense and extensive in the hanging wall than in the foot wall upon approach to the fault plane the fracture density or fracture density gradient becomes too great for the seismic response to be computed by hudson cerven procedures the maximum fracture density that can be modelled is about 0 08 within this 25 m fracture domain it appears more useful to model the fault and near field fractures as a low velocity waveguide we observe production of trapped waves within the confines of the intense fracture interval

space weathering on airless bodies resolving a mystery with lunar samples using new techniques to examine the products of space weathering of lunar soils we demonstrate that nanophase reduced iron npfe0 is produced on the surface of grains by a combination of vapor deposition and irradiation effects the optical properties of soils both measured and modeled are shown to be highly dependent on the cumulative amount of npfe0 which varies with different starting materials and the energetics of different parts of the solar system the measured properties of intermediate albedo asteroids the abundant s type asteroids in particular are shown to directly mimic the effects predicted for small amounts of npfe0 on grains of an ordinary chondrite regolith this measurement and characterization of space weathering products seems to remove a final obstacle hindering a link between the abundant ordinary chondrite meteorites and common asteroids

strain accumulation in southern california 1973 1980 frequent surveys of seven trilateration networks in southern california over the interval 1973 1980 suggest that a regional increment in strain may have occurred in 1978 1979 prior to 1978 and after late 1979 the strain accumulation has been predominantly a uniaxial north south compression this secular trend was interrupted sometime in 1978 1979 by an increment in both north south and east west extension in five of the seven networks the onset of this change appears to have occurred first in the networks farthest south the changes occurred without any unusual seismicity within the networks but the overall seismicity in southern california was unusually low prior to and has been unusually high since the occurrence the average principal strain rates for the seven networks in the 1973 1980 interval are 0 17 mu strain yr north south contraction and 0 08 mu strain yr east west extension although the observed increment in strain could be related to unidentifed systematic error in the measuring system a careful review of the measurements and comparison with three other measuring systems reveal no appreciable cumulative systematic error

pyroxene spectroscopy revisited spectral compositional correlations and relationship to geothermometry the authors wish to thank the various agencies which have provided the necessary support for this project including grants in aid of research from sigma xi the scientific research society to e a c the geological society of america grant 3741 87 to e a c and nasa planetary geology and geophysics grant nagw 642 to m j g

the impact of refraction correction on leveling interpretations in southern california recent investigations show that the refraction corrections in leveling are large but can be adequately modeled the corrections are proportional to the temperature differences and the square of the sight lengths changes in sight length with time have resulted in apparent crustal movements when non refraction corrected data were used applying refraction corrections to leveling data in southern california significantly alters the size and configuration of the southern california uplift uplift at palmdale and gorman lebec relative to los angeles bm v32 during the 1953 1978 time period is no greater than 10 cm the bulk of the motion about 6 cm occurs as localized motion along the san gabriel fault during the 1953 1964 time period this motion along the san gabriel fault and uplift of 8 cm directly north of the san fernando fault between 1955 and 1968 may represent precursors to the 1971 san fernando earthquake

application of pattern recognition techniques to earthquake catalogs generated by model of segmented fault systems in three dimensional elastic solids techniques and seismicity parameters described by eneva and ben zion 1997 are used to examine synthetic earthquake catalogs generated by ben zion 1996 for precursory patterns of large model events different model realizations represent various levels of fault zone disorder these include models with uniform properties u a parkfield type asperity a fractal brittle properties f and multi size scale heterogeneities m the seismicity parameters used are based on information contained in typical earthquake catalogs reflecting earthquake distribution in space time and size the analysis highlights the complexity of the information content of the synthetic earthquake catalogs simple repetitive precursory signals have not been found however local extrema in the examined parameters are found to have significant association in time with large events thus our techniques and parameters may be useful for intermediate term earthquake prediction especially when parameters are used in combinations some analysis results are the same for all model realizations and some depend on the model features characterizing all catalogs are as follows 1 large model events are statistically predictable on the basis of patterns in the distribution of smaller events 2 for a given parameter the type of precursory extrema maxima or minima is the same for all models 3 the interparameter correlation for any parameter pair has the same sign positive or negative in all models 4 the large events are neither slip nor time predictable based on previous large events results that differ from model to model include the following 1 the degree of predictability of large events correlates with the degree of regularity in the assumed fault properties following the order u f a and m 2 there is no one to one correlation between type of precursory extrema maxima or minima and type of precursory trends increase or decrease this produces great variations in observable trends for any given parameter both from model to model and for different events in the same model 3 the interparameter correlations vary among models with the highest correlations in model f most discussed patterns are in agreement with observations from seismically active zones laboratory models and mining induced seismicity

compositional variations of the lunar crust results from radiative transfer modeling of central peak spectra 1 we present model mineralogy of impact crater central peaks combined with crustal thickness and crater central peak depth of origin models to report multiple perspectives of lunar crustal composition with depth here we report the analyses of 55 impact crater central peaks and how their compositions directly relate to the lunar highlands sample suite a radiative transfer model is used to analyze clementine visible plus near infrared spectra to place compositional constraints on these central peak materials central peaks analyzed are dominantly magnesian and plagioclase poor strong compositional similarities to lunar mg suite materials are evident relative to crustal thickness estimates central peak mineralogy becomes more plagioclase rich as the crust thickens relative to the crust mantle boundary the origin of peaks with dominantly mafic mineralogy are confined to the lower crust and primarily within the south pole aitken and procellarum kreep terranes pkt additionally central peaks with anorthositic mineralogy 60 vol plagioclase are transported to the surface from all depths in the crustal column and confined to the feldspathic highlands terrane fht the discovery of mafic and magnesian materials consistent with mg suite rocks of the sample collection in all lunar terranes suggests that the process and sources that give rise to these types of rocks is not unique to the pkt and not necessarily dependent on incompatible elements for formation the identification of ferroan and magnesian anorthositic material near the crust mantle boundary of the fht is also inconsistent with an increasing mafic feldspar ratio and mg with depth in the crust

ancient multiring basins on the moon revealed by clementine laser altimetry analysis of laser altimetry data from clementine has confirmed and extended our knowledge of nearly obliterated multiring basins on the moon these basins were formed during the early bombardment phase of lunar history have been filled to varying degrees by mare lavas and regional ejecta blankets and have been degraded by the superposition of large impact craters the mendel rydberg basin a degraded three ring feature over 600 kilometers in diameter on the lunar western limb is about 6 kilometers deep from rim to floor only slightly less deep than the nearby younger and much better preserved orientale basin 8 kilometers deep the south pole aitken basin the oldest discernible impact feature on the moon is revealed as a basin 2500 kilometers in diameter with an average depth of more than 13 kilometers rim crest to floor this feature is the largest deepest impact crater yet discovered in the solar system several additional depressions seen in the data may represent previously unmapped ancient impact basins

mineralogical and chemical characterization of lunar highland soils insights into the space weathering of soils on airless bodies 1 with reflectance spectroscopy one is measuring only properties of the fine grained regolith most affected by space weathering the lunar soil characterization consortium has undertaken the task of coordinated characterization of lunar soils with respect to their mineralogical and chemical makeup it is these lunar soils that are being used as ground truth for all airless bodies modal abundances and chemistries of minerals and glasses in the finest size fractions 20 45 10 20 and 10 m of four apollo 14 and six apollo 16 highland soils have been determined as well as their bulk chemistry and is feo values bidirectional reflectance measurements 0 3 2 6 m of all samples were performed in the reflectance experiment laboratory a significant fraction of nanophase fe0 np fe0 appears to reside in agglutinitic glasses however as grain size of a soil decreases the percentage of total iron present as np fe0 increases significantly whereas the agglutinitic glass content rises only slightly this is evidence for a large contribution to the is feo values from the surface correlated nanophase fe0 particularly in the 10 m size fraction the compositions of the agglutinitic glasses in these fine fractions of the highland soils are different from the bulk chemistry of that size however compositional trends of the glasses are not the same as those observed for mare soils it is apparent that the glasses in the highland soils contain chemical components from outside their terrains it is proposed that the apollo 16 soils have been adulterated by the addition of impact transported soil components from surrounding maria

sand injectites at the base of the coconino sandstone grand canyon arizona usa abstract in the grand canyon large tabular and wedge shaped sand filled cracks commonly occur at the base of the coconino sandstone penetrating downward into the coarse siltstones of the hermit formation all previous workers have casually identified the vertical sand filled cracks as desiccation cracks until now they have never been studied cracks and their associated features were found and examined at thirty locations and it was found that they have characteristics difficult to explain using desiccation mud cracks or large playa cracks as a model instead it was found the cracks have features commonly found in clastic dikes and sand injectites some lateral sand bodies associated with the cracks have clastic sill like characteristics liquefaction and injection of the basal coconino into the hermit is indicated by 1 macroscopic and microscopic banding flow structures within the cracks 2 bedded sandstone clast breccias in structureless sandstone lenses at the base of the coconino 3 lateral sand bodies which are connected to the vertical cracks 4 a zoned depth distribution of cracks about the bright angel fault zone 5 insufficient clay mineralogy and particle size for the hermit to crack by desiccation 6 preferred orientation of the cracks roughly perpendicular to the bright angel fault zone and several other features caution should be exercised when interpreting sand filled cracks as desiccation features i e mud cracks even if the interpretation fits well with accepted paleoenvironmental models

comments on near surface stress and displacement in a layered elastic crust and stress in a stratified crust overlying a buried screw dislocation by p c leary

quantitative measurements of shear wave polarizations at the anza seismic network southern california implications for shear wave splitting and earthquake prediction we analyze shear wave polarizations from local earthquakes recorded by the anza network in southern california using an automated method which provides unbiased and quantitative measurements of the polarization and the duration of linear motion following the shear wave arrival the linearity interval initial shear wave particle motions are strongly aligned at four stations a feature that is not predicted by focal mechanisms the particle motion alignment is most likely caused by shear wave splitting due to anisotropy beneath these stations a result supported by the clear shear wave splitting seen in a borehole recording near one of the anza stations these results are consistent with an earlier analysis of these data by peacock et al 1988 however our analysis does not support claims by crampin et al 1990 that shear wave splitting delay times at station knw exhibit temporal variations which can be correlated with the occurrence of the north palm springs earthquake ml 5 6 of july 8 1986 automatically determined linearity intervals scatter widely from 0 02 to 0 15 s and exhibit no clear temporal trends we find a correlation between earthquake moment and the linearity interval possibly a result of longer effective source time functions for the larger events the inability to identify a distinct slow quasi shear wave pulse for the vast majority of these events indicates that scattering strongly affects the particle motion even in the very early shear wave coda analysis of earthquake clusters with similar waveforms recorded at knw shows that seismic green functions are stable throughout the observational period and that most linearity interval variation is due to source and ray path differences between events if shear wave splitting is causing the observed delay times between horizontal components the waveform stability for events in these clusters restricts any temporal changes in shear wave splitting delay times to less than 5 10

stress in a stratified crust overlying a buried screw dislocation a haskell matrix solution to the equation of stress equilibrium is used to describe the crustal response to a screw dislocation source lying beneath a uniform elastic crust capped by a region of layered rigidity the solution is used to illustrate the effect a stratified crustal rigidity has on the near surface in situ stress field without accounting for this effect it is possible to overestimate the deep tectonic stress levels inferred from in situ vertical gradients measured in the uppermost crust

constraints on temporal variations in velocity near anza california from analysis of similar event pairs similar earthquake pairs recorded by the anza seismic network in southern california are used as repeatable sources to place an upper limit on temporal changes in seismic velocity which occurred in the vicinity of the anza seismic gap in the last 9 yr relative arrival times for each pair of events are found using a cross correlation method and relative locations are calculated to verify that the pairs have nearly identical hypocenters the time separation between events in these pairs varies from less than a day to almost 7 yr the long term changes in seismic travel times as measured from the pairs with the longest time separation are not significantly greater than the noise level estimated from the short time separation event pairs almost all p wave paths show less than 0 06 0 007 sec change in travel time and all s wave paths have less than 0 03 0 004 sec change sensitivity tests place an upper bound on travel time changes that could be compensated by hypocenter mislocation at 0 2 there is no evidence that localized stress accumulation causes measurable changes in seismic velocity in the anza region

earthquake prediction a critical review summary earthquake prediction research has been conducted for over 100 years with no obvious successes claims of breakthroughs have failed to withstand scrutiny extensive searches have failed to find reliable precursors theoretical work suggests that faulting is a non linear process which is highly sensitive to unmeasurably fine details of the state of the earth in a large volume not just in the immediate vicinity of the hypocentre any small earthquake thus has some probability of cascading into a large event reliable issuing of alarms of imminent large earthquakes appears to be effectively impossible key word earthquake prediction

millisecond accurate monitoring of seismic travel times over 13 and 18 kilometer baselines using a repeatable airgun source we have monitored the travel times of several seismic phases along 13 and 18 km baselines from bouquet reservoir to boreholes on the san andreas fault near palmdale california the first arriving phases refract at a depth of 2 3 km while one later arrival is possibly a reflection from 10 km the majority of some 200 travel time determinations for the most prominent phases were made between august 1979 and march 1980 isolated measurements were made in november 1978 and march 1981 there exists ample geodetic and other evidence for significant strain changes during this period allowing for source variation due to fluctuating reservoir water levels we observed no travel time changes to the limit of our precision of 1 2 ms for the first arrivals and 3 5 ms for secondary arrivals or about 0 1 of the total travel time an earlier study which monitored rays penetrating only 500 m into the crust found that travel times varied by up to 0 3 over a period of several days the variations showed some correlation with strain changes due to local seismic activity and were not permanent to understand this different behavior of crustal rocks between 500 and 2000 m we investigate the depth dependence of their velocity strain sensitivity using measured p and s velocity profiles to gauge the rate at which confining pressure increases velocity we find that 1 bar of overpressure at 500 m can vary the p velocity by 0 1 while 1 bar at 2000 m will vary the velocity by only 0 01 applying the o connell budiansky physical model for cracked rock to the velocity depth profiles we can further characterize the local crust as having a high crack density a mobile fluid component and an average crack aspect ratio of 2 5 10 3 the combination of a mobile fluid content and high crack density suggests that fluids play a role in the transient velocity anomalies observed at a depth of 500 m and argues against significant undersaturation phenomena at seismogenic depths on the san andreas fault

an assessment of the accuracy of the geodetic measurements that define the southern california uplift examination of the charge that the geodetic measurements which define the southern california uplift are seriously flawed by height dependent systematic errors indicates that this charge is unfounded our review of those factors designed to minimize the effects of rod error shows that systematic errors attributable to rod miscalibration are trivial and would tend to cancel during the particularly pertinent period 1955 1965 comparisons between the results of measurements in which the correlation between topography and signal is generally poor reveal large aseismic tilts in a number of places within and around the margins of the uplift especially significant in this context are the results of preuplift and postuplift levelings over routes characterized by diverse length topography and atmospheric conditions that produce closely matching temporally equivalent heights for a representative bench mark within the uplift statistical analyses of the short wavelength components of uplift signal and elevation along a frequently repeated survey line indicate variable correlations between the two however the spatial and temporal patterns of these correlations are inconsistent with their attribution to height dependent systematic errors statistically significant short wavelength correlations along this survey line are reasonably explained in part as due to real movement associated with differentially subsiding bench marks and there is a strong likelihood that this movement tends to dominate many of the correlations

possible tilt phenomena observed as water level anomalies along the los angeles aqueduct water levels in the los angeles aqueduct in southern california fluctuate in a manner that are not easily attributable to normal aqueduct operations simple hydraulics suggests that large scale earth tilt can register as water level anomalies with a sensitivity of about 01 ft microradian two aqueduct anomalies which coincide spatially and temporally with independently observed deformational phenomena are used to explore this suggestion

initial observations from the lunar orbiter laser altimeter lola as of june 19 2010 the lunar orbiter laser altimeter an instrument on the lunar reconnaissance orbiter has collected over 2 0 10 9 measurements of elevation that collectively represent the highest resolution global model of lunar topography yet produced these altimetric observations have been used to improve the lunar geodetic grid to 10 m radial and 100 m spatial accuracy with respect to the moon s center of mass lola has also provided the highest resolution global maps yet produced of slopes roughness and the 1064 nm reflectance of the lunar surface regional topography of the lunar polar regions allows precise characterization of present and past illumination conditions lola s initial global data sets as well as the first high resolution digital elevation models dems of polar topography are described herein

systematic global mixing and melting in lunar soil evolution 1 we present a revised model of soil evolution constrained by the recent lscc data for lunar soils in addition to an observed universal increase in feldspathic components in the finer fractions of soils taylor et al 2001 2003a 2003b both differential melting and lateral mixing processes appear to be required during the evolution of lunar soils we propose mare highland mixing of a significant glass component along with a preferential melting sequence for agglutinitic glass formation of glass plagioclase pyroxene ilmenite

measuring moonlight an overview of the spatial properties lunar coverage selenolocation and related level 1b products of the moon mineralogy mapper 1 the moon mineralogy mapper m3 a high resolution high precision imaging spectrometer flew on board india s chandrayaan 1 mission from october 2008 through august 2009 this paper describes some of the spatial sampling aspects of the instrument the planned mission and the mission as flown we also outline the content and context of the resulting level 1b spatial products that form part of the m3 archive while designed and planned to operate for 2 years in a 100 km lunar orbit m3 was able to meet its lunar coverage requirements despite the shortened mission an increase of the orbit altitude to 200 km and several relevant problems with spacecraft attitude timing and ephemeris the unexpected spacecraft issues required us to invent a novel two step approach for selenolocation leveraging newly available lunar reconnaissance orbiter lunar orbiter laser altimeter lola topography and an improved spacecraft ephemeris we have created a method that permits us to bootstrap spacecraft attitude estimates from the image data themselves this process performs a nonlinear optimization to honor a set of data derived image to image tie points and image to lola control points error analysis of the final results suggests we have converged to a selenolocation result that has image to image root mean square rms errors less than 200 m and image to lola rms errors less than 450 m despite using data derived spacecraft attitude results the level 1b products include the lunar coordinates resulting from this inversion process and 10 relevant observational geometry parameters that fully characterize the ray tracing geometry on a pixel by pixel basis

subsidence structures associated with subaerial desiccation crack piping and their role in drainage evolution on a drained proglacial lake bed hagavatn iceland abstract a range of subsidence structures associated with desiccation crack piping are described from the drained proglacial lake bed of hagavatn iceland subsurface drainage along desiccation cracks leads to the formation of small scale subsidence structures these subsidence structures include linear fissures located along the limbs of desiccation cracks and crater like depressions that form at crack intersections the controls on subsurface piping are discussed and the role of these subsidence structures in determining the pattern of surface drainage on the former lake bed is identified preservation potential of these sedimentary structure is considered to be high given renewed lacustrine sedimentation the potential for similar structures to be found in the geological record is considered likely and consequently these structures may be of importance in the interpretation of crack networks in the geological record as being of subaerial as opposed to subaqueous origin

lunar cryptomaria physical characteristics distribution and implications for ancient volcanism cryptomaria lunar volcanic deposits obscured by crater and basin impact ejecta can provide important information about the thermal and volcanic history of the moon the timing of cryptomare deposition has implications for the duration and flux of mare basalt volcanism in addition knowing the distribution of cryptomaria can provide information about mantle convection and lunar magma ocean solidification here we use multiple datasets e g m3 lola lroc diviner to undertake a global analysis to identify the general characteristics e g topography surface roughness rock abundance albedo etc of lunar light plains in order to better distinguish between ancient volcanic deposits cryptomaria and impact basin and crater ejecta deposits we find 20 discrete regions of cryptomaria covering approximately 2 of the moon which increase the total area covered by mare volcanism to 18 of the lunar surface comparisons of light plains deposits indicate that the two deposit types volcanic and impact produced are best distinguished by mineralogic data on the basis of cryptomaria locations the distribution of mare volcanism does not appear to have changed in the time prior to its exposed mare basalt distribution there are several hypotheses explaining the distribution of mare basalts which include the influence of crustal thickness mantle convection patterns asymmetric distribution of source regions kreep distribution and the influence of a proposed procellarum impact basin the paucity of farside mare basalts means that multiple factors such as crustal thickness variations and mantle convection are likely to play a role in mare basalt emplacement

fr waves a second fault guided mode with implications for fault property studies previous work has shown that earthquake s waves can become fault zone guided waves we present observational evidence for a second type of earthquake generated fault guided seismic wave apparently involving coupled p and s waves our data are from a fault located in igneous rocks in owens valley california in analogy to standard love and rayleigh waves we suggest that purely s type modes be indicated on seismograms by f l and the new coupled p and s type by f r since f r waves are sensitive to both the local p and s wave velocities their presence implies unique conditions in and near the fault modeling of our seismograms suggests a differential reduction in these velocities with a larger change in bulk modulus than in shear modulus we propose that this reduction is due to unsaturated fractures within the core of the fault we view f r waves as a new tool for detecting and characterizing highly fractured fault zones providing important information on the relation of earthquakes and subsurface fluid conduits

rock types of south pole aitken basin and extent of basaltic volcanism the enormous pre nectarian south pole aitken spa basin represents a geophysically and compositionally unique region on the moon we present and analyze the mineralogical diversity across this basin and discuss the implications for basin evolution rock types are derived from clementine multispectral data based on diagnostic characteristics of ferrous absorptions in fresh materials individual areas are characterized as noritic dominated by low ca pyroxene gabbroic basaltic dominated by high ca pyroxene feldspathic 3 6 feo and olivine gabbro dominated by high ca pyroxene and olivine the anorthositic crust has effectively been removed from the interior of the basin the style of volcanism within the basin extends over several 100 myr and includes mare basalt and pyroclastic deposits several areas of ancient pre orientale volcanism or cryptomaria have also been identified the nonmare mafic lithology that occurs across the basin is shown to be noritic in composition and is pervasive laterally and vertically we interpret this to represent impact melt breccia deposits derived from the lower crust a few localized areas are identified within the basin that contain more diverse lithologies gabbro olivine gabbro some of which may represent material from the deepest part of the lower crust and perhaps uppermost mantle involved in the spa event

the character of south pole aitken basin patterns of surface and subsurface composition using moon mineralogy mapper data we characterize surface diversity across the enormous south pole aitken basin spa by evaluating the abundance and composition of pyroxenes which are overwhelmingly the most abundant mafic mineral in the region although spa exhibits significant complexity due to billions of years of geologic processes subsequent to formation the basin has retained regular patterns of compositional heterogeneity across its structure four distinct roughly concentric zones are defined 1 a central spa compositional anomaly spaca which exhibits a pervasive elevated ca fe rich pyroxene abundance 2 a mg pyroxene annulus which is dominated by abundant mg rich pyroxenes 3 a heterogeneous annulus which exhibits localized pyroxene rich areas spatially mixed with feldspathic materials and 4 the spa exterior which is primarily feldspathic pyroxene compositions in the heterogeneous annulus are similar to those in the mg pyroxene annulus and mg rich pyroxenes also underlie the more ca fe rich pyroxene surface material across spaca the establishment of these four distinct compositional zones across spa constrains future basin evolution models serves to guide potential sample return and other science targets

new insights into lunar petrology distribution and composition of prominent low ca pyroxene exposures as observed by the moon mineralogy mapper m3 1 lunar geochemical groups such as mg suite ferroan anorthosite and alkali suite rocks are difficult to distinguish from orbit because they are defined by both modal mineralogy and elemental composition of their constituent minerals while modal mineralogy can be modeled only specific minerals or elements can be directly detected at near infrared nir wavelengths pyroxenes are among the most spectrally distinctive minerals and their absorption bands are sensitive to structure and composition pyroxenes thus provide important clues to distinguish these geochemical groups and to understand lunar crustal evolution using moon mineralogy mapper data we search for lithologies dominated by strong low calcium pyroxene lcp signatures we compare the nir absorptions of 20 lcps to a suite of synthetic pyroxenes to determine which lunar pyroxenes appear magnesian enough to be candidate mg suite norites we detail three prominent regions of lcp 1 in south pole aitken basin spa 2 south of mare frigoris and 3 north of mare frigoris the absorption band positions suggest that the lcps north of mare frigoris and those in spa are compositionally similar to one another and of mg50 75 implying that the mafic material excavated by the spa impact was relatively iron rich modified gaussian modeling results suggest that the apollo basin may have tapped different composition material than is exposed in much of spa the lcps located in the highlands south of mare frigoris exhibit absorption bands at short wavelengths consistent with mg 80 the coincidence of these mg rich lcps with the thorium measured by lunar prospector make them good candidates for kreep related mg suite pyroxenes

precise measurement of seismic travel times from an air gun source summary seismic travel times for extrema zero crossings or entire body waves need to be determined precisely to one part in lo3 or better in several varieties of seismic studies employing an impulsive artificial source examples are crosshole surveys which delineate rock crack distribution separating the holes and monitoring of crustal seismic travel times in earthquake precursor studies a timing resolution of one part in lo3 has been achieved previously using digitally recorded seismic data these methods however do not use interpolation between digitized data points as a method to increase the timing resolution we report travel time determinations based on interpolation between digitized points which achieve a precision of two parts in lo4 a five fold improvement over the existing methods in addition the effects of seismic noise on travel time measurement have been compared for the extremum location the unnormalized correlation and the normalized correlation method the following conclusions are drawn from this comparison 1 the normalized correlation method provides an 18 55 per cent improvement in the standard deviation of the mean over the extremum location method and 2 results as accurate as those by the normalized correlation can be obtained by the unnormalized correlation if a complete up and down swing of the waveform is used as the master trace and if the master trace is close to being sinusoidal the advantage of the unnormalized correlation over the normalized correlation is speed the unnormalized correlation is faster by a factor of 28 in computing time

crustal structure near palmdale california from borehole determined ray parameters abstract seismic refraction profiles across and along the san andreas fault zone near palmadale california were used to establish propagation paths for several phases whose travel times are being monitored for earthquake precursors the profiles were generated using an airgun submerged in bouquet reservoir together with surface and borehole geophone receivers source signal stacking coupled with the noise reduction provided by the downhole receivers provided data of sufficient quality to measure the ray parameters of the phases using the ray parameters and surface travel time curves velocity structures parallel and transverse to the fault zone have been constructed two of the observed phases are confined to the upper portions of the crustal structure which was found to differ across the fault a third phase is consistent with a reflection from a depth of approximately 10 km two later arrivals are suggestive of reflections from depths of 21 and 27 km

olivine rich exposures in the south pole aitken basin abstract the distribution and the geological context of the olivine rich exposures in the south pole aitken spa basin on the moon were investigated based on the spectral data obtained from the spectral profiler sp and multiband imager mi onboard the japanese lunar explorer kaguya selene the olivine rich exposures are found only in the peak rings or central peaks of the schrodinger basin and zeeman crater which are located in the outer region of the spa basin and not in the center region on a localized scale the olivine rich materials are exposed on landslide features on the crater walls or sloped wall of the central peaks or the peak rings another observational finding is the co existence of olivine rich and plagioclase rich materials on a kilometer scale spanning most of the olivine rich sites in the schrodinger basin pyroxene rich materials are found in fresh craters outside the peak rings or the central peaks with olivine rich materials based on these results the following scenario are proposed 1 the impact to form the spa basin melted a large amount of the lunar upper mantle and crust and distributed the melted materials to the outer region 2 local differentiation of melted materials hid the olivine rich materials in the center region of the spa basin 3 later impacts that formed the schrodinger and zeeman craters excavated and exposed the olivine rich materials to the surface again and 4 space weathering and regolith gardening obscured the olivine rich spectra at the exposure sites but recent small scale impacts or landslides on the sloped wall exposed fresh olivine rich materials allowing the identification of the olivine rich exposures by spectral remote sensing this suggests that several different scale events play an important role in forming the surface distributions of originally deep seated materials on the moon as well as on other planetary bodies