seismic evidence for an earthquake nucleation phase near source observations show that earthquakes initiate with a distinctive seismic nucleation phase that is characterized by a low rate of moment release relative to the rest of the event this phase was observed for the 30 earthquakes having moment magnitudes 2 6 to 8 1 and the size and duration of this phase scale with the eventual size of the earthquake during the nucleation phase moment release was irregular and appears to have been confined to a limited region of the fault it was characteristically followed by quadratic growth in the moment rate as rupture began to propagate away from the nucleation zone these observations suggest that the nucleation process exerts a strong influence on the size of the eventual earthquake

observation of the seismic nucleation phase in the ridgecrest california earthquake sequence near source observations of five m 3 8 5 2 earthquakes near ridgecrest california are consistent with the presence of a seismic nucleation phase these earthquakes start abruptly but then slow or stop before rapidly growing again toward their maximum rate of moment release deconvolution of instrument and path effects by empirical green s functions demonstrates that the initial complexity at the start of the earthquake is a source effect the rapid growth of the p wave arrival at the start of the seismic nucleation phase supports the conclusion of mori and kanamori 1996 that these earthquakes begin without a magnitude scaled slow initial phase of the type observed by iio 1992 1995

thorium abundances on the aristarchus plateau insights into the composition of the aristarchus pyroclastic glass deposits 1 thorium th data from the lunar prospector gamma ray spectrometer lp grs are used to constrain the composition of lunar pyroclastic glass deposits on top of the aristarchus plateau our goal is to use forward modeling of lp grs th data to measure the th abundances on the plateau and then to determine if the elevated th abundances on the plateau are associated with the pyroclastic deposits or with thorium rich ejecta from aristarchus crater we use a variety of remote sensing data to show that there is a large homogenous portion of the pyroclastics on the plateau that has seen little or no contamination from the th rich ejecta of aristarchus crater our results show that the uncontaminated pyroclastic glasses on aristarchus plateau have an average th content of 6 7 ppm and 7 wt tio2 these th and ti values are consistent with th rich intermediate ti yellow glasses from the lunar sample suite on the basis of this information we use petrologic equations and interelement correlations for the moon to estimate the composition of the source region from which the aristarchus glasses were derived we find that the source region for the aristarchus glasses contained high abundances of heat producing elements which most likely served as a thermal driver for the prolonged volcanic activity in this region of the moon

characteristic features of local breakdown near a crack tip in the transition zone from nucleation to unstable rupture during stick slip shear failure abstract characteristic features of local breakdown near a propagating crack tip during slip failure nucleation and its transition process to unstable rupture under mode ii conditions are experimentally studied using a rock sample with a simulated fault the size of which is large compared with the size of the breakdown zone in addition distinctive features in the nucleation zone are compared with those in the zone of steady dynamic rupture propagation it is found that the local breakdown stress drop the local dynamic stress drop the local stress increase immediately before the slip weakening process the dimensionless parameter s defined by das and aki and the shear fracture energy are functions of crack length in the transition zone from nucleation to unstable rupture i e they all increase with crack growth in the nucleation zone this is contrasted with the observations in the zone of steady dynamic rupture propagation where these physical parameters do not depend on crack length an increase in the magnitudes of these parameters with crack growth in the nucleation zone results in increasing resistance to crack extension with crack growth in the nucleation zone the reason for the increase in crack growth resistance in this zone is that a slip failure nucleus is formed at a point or zone where the local strength and the shear fracture energy are at a minimum this basic physical information can provide the key to earthquake prediction since the nucleation itself is a precursory phenomenon the ratio of the size of the breakdown zone to the crack length decreases abruptly beyond the critical crack length rupture velocity v accelerates with crack growth and reaches the shear wave velocity or super shear and v is found to be expressed empirically as a function of crack length in the nucleation zone a positive correlation is found between s and v in the nucleation zone v increases with increasing s however no such correlation was observed in the zone of steady dynamic rupture propagation where v seems to have reached the shear wave velocity of super shear for s 0 5 this is consistent with das and aki s numerical result the interrelationships between shear stress slip displacement slip velocity and acceleration near the crack tip during the breakdown in the nucleation zone are revealed and they are compared with those in the zone of dynamic rupture propagation the present experiments suggest that the relationship between shear stress and slip displacement is more fundamental during the breakdown process than the relationship between shear stress and slip velocity a model is presented to describe the breakdown process in the nucleation zone

scaling relationships between sizes of nucleation regions and eventual sizes of microearthquakes abstract we investigate the initial rupture process of microearthquakes to reveal relationships between nucleation region sizes and eventual earthquake sizes in order to obtain high quality waveform data we installed a trigger recording system with a sampling frequency of 10 khz at the base of a deep borehole at the nojima fault japan we analyze waveform data of 31 events around the borehole with seismic moment ranging from 4 2 10 9 nm to 7 1 10 11 nm we use both a circular crack model with an accelerating rupture velocity sk model sato t kanamori h 1999 beginning of earthquakes modeled with the griffith s fracture criterion bull seism soc am 89 80 93 which generates a slow initial phase of velocity pulse and a circular crack model with a constant rupture velocity sh model sato t hirasawa t 1973 body wave spectra from propagating shear cracks j phys earth 21 415 431 which generates a ramp like velocity pulse source parameters of these two models are estimated by waveform inversion of the first half cycle of the observed velocity pulse applying both a grid search and a non linear least squares method 14 of 31 events are never reproduced by the sh model with a constant q operator but sk model with a constant q operator provides a size of the pre existing crack corresponding to the size of the nucleation regions and a size of the eventual crack we recognize that i the eventual seismic moment is approximately scaled as the cube of the size of pre existing cracks ii the eventual seismic moment is scaled as the cube of the size of eventual cracks and iii the size of eventual cracks is roughly proportional to the size of pre existing cracks we thus conclude that the size of eventual earthquakes is controlled by the size of the nucleation regions

concentrations of radioactive elements in lunar materials as an aid to interpreting data obtained remotely on the distribution of radioactive elements on the lunar surface average concentrations of k u and th as well as al fe and ti in different types of lunar rocks and soils are tabulated the u th ratio in representative samples of lunar rocks and regolith is constant at 0 27 k th ratios are more variable because k and th are carried by different mineral phases in nonmare regoliths at the apollo sites the main carriers of radioactive elements are mafic i e 6 8 fe impact melt breccias created at the time of basin formation and products derived therefrom

processes involved in the formation of magnesian suite plutonic rocks from the highlands of the earth s moon the earliest evolution of the moon likely included the formation of a magma ocean and the subsequent development of anorthositic flotation cumulates this primary anorthositic crust was then intruded by mafic magmas which crystallized to form the lunar highlands magnesian suite the present study is a compilation of petrologic mineral chemical and geochemical information on all pristine magnesian suite plutonic rocks and the interpretation of this data in light of 18 new samples of these 18 clasts taken from apollo 14 breccias 12 are probably pristine and include four dunites two norites four troctolites and two anorthosites radiogenic isotopic whole rock data also are reported for one of the probably pristine anorthositic troctolites sample 14303 347 the relatively low rb content and high sm and nd abundances of 14303 347 suggest that this cumulate rock was derived from a parental magma which had these chemical characteristics trace element isotopic and mineral chemical data are used to interpret the total highlands magnesian suite as crustal precipitates of a primitive kreep possessing a k rare earth element ree and p enriched chemical signature basalt magma this kreep basalt was created by the mixing of ascending ultramafic melts from the lunar interior with urkreep the late k ree and p enriched residuum of the lunar magma ocean the trace and major element compositions of nearly all magnesian suite cumulates can be generated by 0 55 fractional crystallization of a primitive kreep basalt combined with the trapping of varied proportions generally 20 of instantaneous residual kreep basalt liquid a few samples of the magnesian suite with extremely elevated large ion lithophile elements 5 10 other magnesian suite rocks cannot be explained by this model or any other model of autometasomatism equilibrium crystallization or local melt pocket equilibrium without recourse to an extremely large ion lithophile element enriched parent liquid it is difficult to generate parental liquids which are 2 4 higher in the ree than average lunar kreep unless the liquids are the basic complement of a liquid liquid pair i e the so called reep fraction from the silicate liquid immiscibility of urkreep scarce age information on lunar rocks suggests that magnesian suite magmatism was initiated at progressively more recent time from the northeast to the southwest on the lunar nearside from 4 45 to 4 25 ga this magmatic event could be due to melting of the lunar mantle beneath these regions and could have been generated either by latent heat during crystallization of the final kreep rich and thus th and u rich residual lunar magma ocean liquid or heating due to radioactive decay of k th and u

major factors controlling lamina induced fractures in the upper triassic yanchang formation tight oil reservoir ordos basin china abstract lamina induced fractures lf are abundant in lacustrine formations playing an important role for the tight oil resource exploration studies of controlling factors of the lf are still lacking especially for the heterogeneous formations characterized with complex combinations of the lamina and surrounding rock therefore 28 long column samples for triaxial compression tests 37 short column samples for brazil split tests and 12 powder samples for mineral component analysis and isotopes analysis carbon and oxygen are made from 6 cores in 4 petrophysical faces the experiments are designed to study the lf propagation process considering the controlling factors in terms of mineral component the lamina angle and the petrophysical faces our results show that clay content and dolomite cement degree more significantly control the lf propagation than the other minerals the lf propagation is not only dependent on the mineral component in the lamina but even more on the mineral component difference between the lamina and the surrounding rock i e the l s values where l represents the lamina and s represents the surrounding rock adjacent to the lamina the lf tended to propagate in a middle lamina angle range approximately 10 60 in shear properties and characterized with lower compression strength values all the lf observed in the thin sections were associated with oil although there was no obvious oil shown in the study cores the 13c and 18o values of lamina samples varied with the lamina mineral component for the complex organic matter oxidation and degradation reactions additionally the hydrocarbon flow parameter phf has been proposed on the carbon and oxidation isotope trace lines to indicate the oil rock reactions during the lf open period

a compositional study of the aristarchus region of the moon using near infrared reflectance spectroscopy newly obtained near infrared reflectance spectra for features on or near the aristarchus plateau demonstrate the diversity of compositions in the region highland units are of three probable compositions a feldspar and clinopyroxene assemblage a probable clinopyroxene olivine and possibly feldspar assemblage and an assemblage composed of olivine or olivine and feldspar the feldspar clinopyroxene assemblage is tentatively correlated with the major th anomaly centered on aristarchus crater the regional pyroclastic deposits on the plateau are composed of greater than 90 fe2 bearing glass the aristarchus cratering event fully penetrated any mare or pyroclastics in the target evidence for mare related material is found in the ejecta on the mare side of the mare plateau contact

initial rupture of earthquakes in the 1995 ridgecrest california sequence close examination of the p waves from earthquakes ranging in size across several orders of magnitude shows that the shape of the initiation of the velocity waveforms is independent of the magnitude of the earthquake a model in which earthquakes of all sizes have similar rupture initiation can explain the data this suggests that it is difficult to estimate the eventual size of an earthquake from the initial portion of the waveform previously reported curvature seen in the beginning of some velocity waveforms can be largely explained as the effect of anelastic attenuation thus there is little evidence for a departure from models of simple rupture initiation that grow dynamically from a small region the results of this study indicate that any precursory radiation at seismic frequencies must emanate from a source region no larger than the equivalent of a m0 5 event i e a characteristic length of 10 m the size of the nucleation region for magnitude 0 to 5 earthquakes thus is not resolvable with the standard seismic instrumentation deployed in california

semi automated detection of annual laminae varves in lake sediments using a fuzzy logic algorithm abstract annual laminae varves in lake sediments are typically visually identified measured and counted although numerous attempts have been made to automate this process the reason for the failure of most of these automated algorithms for varve counting is the complexity of the seasonal laminations typically rich in lateral facies variations and internal heterogeneities in the manual counting of varves the investigator acquired and interpreted flexible numbers of complex decision criteria to understand whether a particular simple lamination is a varve or not fuzzy systems simulate the flexible decision making process in a computer by introducing a smooth transition between true varve and false varve in our investigation we use an adaptive neuro fuzzy inference system anfis to detect varves on the basis of a digital image of the sediment the results of the application of the anfis to laminated sediments from the meerfelder maar eifel germany and from a landslide dammed lake in the quebrada de cafayate of argentina are compared with manual varve counts and possible reasons for the differences are discussed

relationship between rupture process complexity and earthquake size 1 we studied the complexity of waveforms for two shallow crustal earthquake sequences in japan using 47 earthquakes of the 2003 northern miyagi sequence and 95 events of the 2004 mid niigata sequence we estimated the number of complex and simple p waveforms for events with magnitudes from m3 1 to m6 6 data were recorded at borehole and surface stations with minimal site responses for close hypocentral distances of less than 30 km the determination of complexity was done by counting the zero crossings of the accelerations waveforms our results show that for the smaller earthquakes there are both simple and complex events but that all of the larger earthquakes are complex there appears to be a threshold size over which the earthquakes always become complex for both data sets this threshold is m4 0 to m4 5 we attribute this difference in complexity with earthquake size as an indication that larger earthquake grow with a complex ruptures that may be indicative of stochastic processes there do not appear to be large earthquakes that grow smoothly to their final size

thorium concentrations in the lunar surface iv deconvolution of the mare imbrium aristarchus and adjacent regions the distribution of th over the mare imbrium and northern oceanus procellarum portions of the apollo 15 lunar ground track has been modeled by deconvolving several fields of orbital gamma ray spectroscopy data including a prior study of the apenninus region a continuous swath from 10 e to 60 w in the northwest quadrant has now been analyzed in the aristarchus region the crater dominates the th distribution with a concentration of 20 ppm other enhancements are seen on the aristarchus plateau and south of the plateau the concentration across the aristarchus plateau is not uniform the average th concentration in oceanus procellarum is less to the west than to the east of the aristarchus plateau substantial enhancements are found in mare regions around brayley and at the ejecta blankets of timocharis and lambert th in the eratosthenian mare regions is generally low with one notable exception lying roughly between the craters euler and carlini the existence of enhanced th concentrations in mare basalt regions suggests that reservoirs of some late stage mare basalts incorporated kreep rich material during formation or transit

an egf technique to infer the rupture velocity history of a small magnitude earthquake 1 an empirical green s function egf technique has been developed to detect the rupture velocity history of a small earthquake the assumed source model is a circular crack that is characterized by a single and unipolar moment rate function mrf the deconvolution is treated as an inverse problem in the time domain which involves an assumed form of the moment rate function mrf the source parameters of the mrf are determined by adopting a global nonlinear inversion scheme a thorough synthetic study on both synthetic and real seismograms allowed us to evaluate the degree of reliability of the retrieved model parameters the technique was applied to four small events that occurred in the umbria marche region italy in 1997 to test the hypothesis of a single rupture process the inversion results were compared with those arising from another egf technique which assumes a multiple rupture process for each event the best fit model was selected using the corrected akaike information criterion for all the considered events the most interesting result is that the selected best fit model favors the hypothesis of a single faulting process with a clear variability of the rupture velocity during the process for the studied events the maximum rupture speed can even approach the p wave velocity at the source as theoretically foreseen in studies of the physics of the rupture and recently observed for high magnitude earthquakes

transport processes on the lunar surface comparison of model calculations with radionuclides data the most useful radionuclides for deciphering the recent history of the lunar surface are 53mn t1 2 3 7 m y and 26al t 1 2 0 72 m y on the time scales of 0 1 to 10 m y on which these species give information the lunar surface seems to be disturbed to depths of 1 to 50 g cm2 the most likely agent of such disturbances is meteoritic mixing since both large scale and small scale events are important the use of monte carlo methods was indicated experimental evidence is now available for seven lunar cores representing a significant statistical sample it thus seems timely to consider the evidence for disturbance recorded in these cores on the time scales of 26al and 53mn and to match it against the predictions of a meteoritic mixing model we show that if secondary processes of meteoritic impacts such as the down slope movement of ejecta are taken into account such a model is consistent with the experimental results except for the anomalous core 70009 which however exhibit a tendency for deeper depth disturbances

crustal diversity of the moon compositional analyses of galileo solid state imaging data the multispectral images of the lunar limb and farside obtained by the solid state imaging ssi system on board the galileo spacecraft provide the first new pulse of compositional data of the moon by a spacecraft in well over a decade the wavelength range covered by ssi filters 0 4 1 0 m is particularly sensitive to the composition of mare basalts the abundance of mafic ferrous minerals and the maturity of the regolith to a first order the limb and farside material is consistent with previous characterization of nearside lunar spectral types for mare and highland soils and craters most basalts are of an intermediate tio 2 composition and most of the highland crust is feldspathic with local variations in mafic content identified principally at impact craters dark manfling material on the farside can be interpreted in terms of known properties of lunar pyroclastic glass regions of cryptornate are shown to have spectral properties intermediate between those of highland and mare soils as would be expected from a mixture of the two there are several important exceptions and surprises however unlike the basalt types identified on the nearside limb and farside basalts exhibit an exceptionally weak 1 xm ferrous absorption band this may indicate a compositionally distinct lunar basalt group that for example is more mg rich than most basalts of the nearside some of the most notable compositional anomalies are associated with south pole aitken basin this large region has a much lower albedo than surrounding highlands the inner darkest portion of the basin exhibits optical properties indistinguishable low ti basalts deposits to the south exhibit unique properties with a strong and broad ferrous 1 xrn absorption most consistent with abundant olivine the unusual compositions associated with south pole aitken and their spatial e3tent suggests the impact creating this huge lunar basin excavated mafic rich lower crust or perhaps mantle material 1 intro oucri ion

a delineation of the nojima fault ruptured in the m7 2 kobe japan earthquake of 1995 using fault zone trapped waves we used four linear seismic arrays of portable seismometers at the northern awaji island japan to record fault zone trapped waves from aftershocks of the 1995 m7 2 hyogoken nanbu kobe earthquake from april to june 1996 three arrays were deployed across the nojima fault which ruptured during the mainshock while one array was deployed across the higashiura fault which did not break recently we observed significant fault zone trapped waves with relatively large amplitudes and the long wave train following s waves only when both the stations and aftershocks were located close to the nojima fault the coda normalized spectral amplitudes of trapped waves show a maximum peak at 4 7 hz which decreases rapidly with distance from the fault trace the normalized amplitudes of trapped waves also show a decrease with hypocentral distance along the fault giving an apparent q of approximately 25 at 4 7 hz in comparison the array across the higashiura fault recorded much shorter wave trains with higher frequencies after s arrivals for the same events we simulate these trapped waves as s waves guided in a low velocity waveguide sandwiched between high velocity wall rocks we find an adequate fit by using a waveguide 60 m wide at the northern site and 30 40 m wide elsewhere along the nojima fault a waveguide s velocity of 1 5 1 7 km s and a q value of 25 for the higashiura fault the s velocity is 2 5 km s and the q value is 80 the locations of aftershocks for which we observed fault zone trapped waves show that the nojima waveguide is 9 km long and dips southeastward at 80 85 to a depth of 16 km it extends 6 km farther south westward along the asano fault though there are no obvious surface breaks along it however the waveguide is disconnected from the suma fault on the main island which was also ruptured during the kobe earthquake possibly because of the existence of an offset between the nojima fault and the suma fault

beginning of earthquakes modeled with the griffith s fracture criterion we present a source model for the beginning of earthquakes based on the griffith s fracture criterion the initial state is a critical state of pre existing circular fault which is on the verge of instability after the onset of instability the fault grows with a progressively increasing rupture speed satisfying the condition of fracture energy balance at the crack tip we investigate the difference in rupture growth patterns in two classes of models that are considered to represent end member cases in the first model spontaneous model we assume that the surface energy varies smoothly as a function of position in the crust in this model faults with small initial dimensions grow in regions with small surface energy and those with large initial dimensions in large surface energy the rupture velocity increases progressively until it reaches its limiting value the synthetic velocity seismogram at far field shows a weak initial phase during the transitional stage to limiting velocity the time taken to reach the limiting velocity is proportional to the initial length of pre existing fault therefore the duration of the weak initial phase scales with the initial length of fault in the second model trigger model we envisage that there are many pre existing faults in the crust with various lengths these faults are stable because they encounter some obstacle at their ends e g fault segmentation strong asperity etc this situation is modeled with a local increase of surface energy near the ends of fault an earthquake is triggered when the obstacle is suddenly removed i e sudden weakening or the stress is suddenly increased locally to overcome the obstacle once an earthquake is triggered the fault growth is governed by the ambient surface energy in this model the rupture speed attains its limiting velocity almost instantly the synthetic velocity seismogram at far field shows an abrupt linear increase in amplitude without the weak initial phase that appears in the spontaneous model both models can be unified using a trigger factor defined as a fractional perturbation of the surface energy at the ends of fault relative to the ambient surface energy the spontaneous model is characterized by a small trigger factor and the trigger model by a large trigger factor thus the seismic initiation phase with and without the slow initial phase can both occur depending on the trigger factor the variability in the observed seismic initiation phase may represent a variation surface energy strength distribution surrounding the pre existing cracks a theoretical consideration of rupture arrest by barriers using the griffith s fracture criterion does not support the scaling relation between the nucleation moment and the eventual size of earthquake

lignite cleat studies from the first middle polish first lusatian lignite seam in central poland abstract some miocene lignite seams are characterized by the presence of natural discontinuities so called cleats most often they are opening mode fractures consisting of two orthogonal sets face and butt both almost perpendicular to the bedding this paper determines distributions of cleat orientation spacing and aperture from the first group of the middle polish first lusatian lignite seams mpls 1 which has been exploited inter alia in the jo win iib and kazimierz n opencast mines in central poland all observations and measurements were conducted at macroscopic scale the cleats mean orientations are ne sw and nw se dipping at a high angle 75 the first set of fractures refers to the face cleats and the second one to the butt cleats the spacing of face cleats is from 10 0 to 17 2 cm averaging 12 65 cm and the spacing of butt cleats is from 9 3 to 24 3 cm averaging 13 75 cm on the other hand aperture measurements of these cleats range from 0 2 to 1 9 cm averaging 0 68 cm and from 0 1 to 1 5 cm averaging 0 42 cm respectively the obtained results clearly indicate that face cleat orientations nw se are strictly parallel to the elongation of the main tectonic structures in the study area their origin may be explained in at least two ways that is by tectonic folding the maximum principal stress 1 was horizontal or by salt diapirism the maximum principal stress 1 was vertical in both cases the intermediate principal stress 2 was parallel to the face cleat strikes namely nw se although the well developed butt cleats in the context of regional geology provide additional evidence for the creation of an orthogonal system of fractures cleats in the cover of salt structures thus the nw se direction is characteristic of both the extent of the main tectonic units in central poland and the face cleat orientation in mpls 1

slow initial phase generated by microearthquakes occurring in the western nagano prefecture japan the source effect near source observations of microearthquakes occurring in the western nagano prefecture show that durations of recorded slows initial phases were almost constant independently of focal distance although a closer inspection revealed that the durations of the slow initial phases slightly increased with focal distance they were not proportional to focal distance thus it is concluded that the slow initial phases do not mainly reflect the whole path q if the slow initial phases were attributed to the strong anelastic attenuation in the surface layer combined with that of the whole path q the rise time of the p wave velocity pulse at the source for a m2 4 event would be estimated as about 3 ms and the source radius of the m2 4 event would be estimated as about 10 m this value of the source radius is too small for m2 4 this suggests that the slow initial phase does not arise from the strong anelastic attenuation in the surface layer it is likely that the slow initial phase does not mainly reflect a path effect but a source effect

properties of the seismic nucleation phase abstract near source observations show that earthquakes begin abruptly at the p wave arrival but that this beginning is weak with a low moment rate relative to the rest of the main shock we term this initial phase of low moment rate the seismic nucleation phase we have observed the seismic nucleation phase for a set of 48 earthquakes ranging in magnitude from 1 1 8 1 the size and duration of the seismic nucleation phase scale with the total seismic moment of the earthquake suggesting that the process responsible for the seismic nucleation phase carries information about the eventual size of the earthquake the seismic nucleation phase is characteristically followed by quadratic growth in the moment rate consistent with self similar rupture at constant stress drop in this paper we quantify the properties of the seismic nucleation phase and offer several possible explanations for it

small area thorium features on the lunar surface 1 using an improved understanding of the lunar prospector gamma ray spectrometer lp grs spatial footprint we have derived a new map of global thorium abundances on the lunar surface this map has a full width half maximum spatial resolution of 80 km 2 and is mapped on the lunar surface using 0 5 0 5 pixels this map has allowed the identification and classification of 42 small area 3 g g in southwestern mare tranquillitatis near the apollo 11 landing site with our better understanding of the lp grs spatial footprint we have been able to constrain the surface thorium abundance at the compton belkovich thorium anomaly to 40 55 g g which is higher than any other measured location on the lunar surface and higher than most samples finally using 1 km pixel feo abundances from clementine and lp grs spatial footprint information we have been able to obtain plausible thorium distributions around kepler crater at a resolution of 1 km pixel the materials around kepler crater appear to be a relatively simple mixing of thorium rich mib compositions and high thorium mare basalts

quartz cement and its origin in tight sandstone reservoirs of the cretaceous quantou formation in the southern songliao basin china abstract the tight sandstones of the cretaceous quantou formation are the main exploration target for hydrocarbons in the southern songliao basin authigenic quartz is a significant cementing material in these sandstones significantly reducing porosity and permeability for efficient predicting and extrapolating the petrophysical properties within these tight sandstones the quartz cement and its origin need to be better understood the tight sandstones have been examined by a variety of methods the sandstones are mostly lithic arkoses and feldspathic litharenites compositionally immature with an average framework composition of q43f26l31 which are characterized by abundant volcanic rock fragments mixed layer illite smectite i s ordered interstratified with r 1 and r 3 is the dominating clay mineral in the studied sandstone reservoirs two different types of quartz cementation modes namely quartz grain overgrowth and pore filling authigenic quartz have been identified through petrographic observations cl and sem analysis homogenization temperatures of the aqueous fluid inclusions indicate that both quartz overgrowths and pore filling authigenic quartz formed with a continuous process from about 70 c to 130 c sources for quartz cement produced are the conversion of volcanic fragments smectite to illite reaction and pressure solution at micro stylolites potassium for the illitization of smectite has been sourced from k feldspar dissolution and albitization silica sourced from k feldspars dissolution and kaolinite to illite conversion is probably only minor amount and volumetrically insignificant the internal supplied silica precipitate within a closed system where the transport mechanism is diffusion the quartz cementation can destroy both porosity and permeability but strengthen the rock framework and increase the rock brittleness effectively at the same time

the imbrium impact event and the thorium distribution at the lunar highlands surface late in the moon s heavy bombardment period the impact that formed the imbrium basin excavated and melted a tremendous volume of material that was subsequently distributed over most of the moon s surface the apollo orbiting ray experiments metzger et al 1977 show that the imbrium projectile struck in a th rich area called the high th oval region here and regarded as a unique lunar geochemical province imbrium primary ejecta were thus probably rich in th it is shown here using ejecta deposit modeling that the distribution of th in the highlands surface along the ground tracks of the ray spectrometers is consistent with the distribution expected for imbrium ejecta deposits deep basins other than imbrium appear to have excavated regions of lower crust that were mafic and fe bearing but not th rich the possibility that the surface th distribution arises mainly from imbrium ejecta has implications for the nature of the moon s igneous differentiation and the nature of the proposed cataclysm or late bombardment with large meteoroids

the geochemistry of carbonate diagenesis the past present and future stable carbon and oxygen isotopes 18o and 13c values and trace elements have been applied to the study of diagenesis of carbonate rocks for over 50 years as valuable as these insights have been many problems regarding the interpretation of geochemical signals within mature rocks remain for example while the 18o values of carbonate rocks are dependent both upon the temperature and the 18o value of the fluid and additional information including trace element composition aids in interpreting such signals direct evidence of either the temperature or the composition of the fluids is required such information can be obtained by analysing the 18o value of any fluid inclusions or by measuring the temperature using a method such as the clumped isotope technique such data speak directly to a large number of problems in interpreting the oxygen isotope record including the well known tendency for 18o values of carbonate rocks to decrease with increasing age unlike the 18o 13c values of carbonates are considered to be less influenced by diagenesis and more a reflection of primary changes in the global carbon cycle through time however many studies have not sufficiently emphasized the effects of diagenesis and other post depositional influences on the eventual carbon isotopic composition of the rock with the classic paradigm that the present is the key to the past being frequently ignored finally many additional proxies are poised to contribute to the interpretation of carbonate diagenesis although the study of carbonate diagenesis is at an exciting point with an explosion of new proxies and methods care should be taken to understand both old and new proxies before applying them to the ancient record

scaling law between corner frequency and seismic moment of microearthquakes is the breakdown of the cube law a nature of earthquakes 1 the corner frequency fc and the seismic moment m0 of microearthquakes local magnitude from 1 3 to 1 3 are estimated from the records of sensors located at an 1800 m deep borehole at the nojima fault central japan the digital waveforms of each event are recorded with two different sampling rates 10 khz and 100 hz the source parameters estimated from high sampling data satisfy a relationship of m0 fc 3 corresponding to a constant stress drop law while those calculated from low sampling data follow a relationship of m0 fc 4 a lack of high frequency components in the 100 hz sampling data seem to be obvious indicating that the value of fc and m0 are incorrectly estimated and the relationship of m0 fc 4 is an artifact caused by the limited frequency band of these data the scaling relationship of m0 fc 3 is thus also valid for microearthquakes and the breakdown of the constant stress drop law reported in the literature is not well founded

shale oil occurring between salt intervals in the dongpu depression bohai bay basin china abstract the saline mudstone sequence of the paleogene shahejie formation in the dongpu depression of bohai bay basin is a major source rock for conventional hydrocarbons however shale oil having a density of 0 9 g cm 3 and a viscosity of 21 mpa s has also been discovered and is being produced from these mudstones to better understand the occurrence of such shale oil geochemical petrological and mineralogical investigations were carried out on a suite of saline mudstone samples by using rock eval x ray diffraction and sem the shahejie formation samples analyzed in the current study are characterized by type ii kerogen with lesser amounts of types i and iii such that petroleum generation ranges from fair to excellent in general terms with the exception of es1 uppermost member which is immature to marginally mature for oil generation the sequence studied ranges from mature for oil generation to mature for wet gas generation on the basis of vitrinite reflectance data the most prospective depths for shale oil condensate generation are between 2300 and 4000 m depth in area studied the saline mudstones comprise mainly clay minerals followed by carbonates quartz and feldspar based solely on the brittle mineral index the amounts of carbonate and quartz in many of the samples lead to a similar or greater suitability for hydraulic fracturing than for many haynesville woodford and upper bakken shales sem studies show that abundant micro fractures commonly occur in the mudstones and these include tectonic fractures bedding plane fractures shrinkage fractures and over pressured fractures for the es3 m middle third member unit shale oil prospectivity is likely to be enhanced around the towns of wl wenliu lt liutun and hbz hubuzhai due to the increased frequency of tectonic fractures which would contribute to oil storage and flow mineral interparticle mineral intraparticle and organic matter pores are well developed in the rocks studied mineral dissolution has created secondary pores in some areas such that reservoir capacity is increased the increased concentration of organic acids between 2800 and 3500 m is likely to lead to enhanced shale oil prospectivity the micro fractures and dissolution pores are probably the main reservoirs for shale oil accumulation the association of these features with saline facies potentially offers an exploration tool for further shale oil occurrences in the studied area as well as in other areas containing similar lithologies

scaling of the shear rupture process from nucleation to dynamic propagation implications of geometric irregularity of the rupturing surfaces a series of systematic high resolution laboratory experiments have been performed on the nucleation of propagating slip failure on preexisting faults having different surface roughnesses to demonstrate how the size scale and duration of shear rupture nucleation are affected by geometric irregularity of the rupturing surfaces on the basis of the experimental results it has been discussed theoretically how consistently scale dependent physical quantities inherent in shear rupture are scaled the experiments led to conclusive results that the nucleation process consists of two phases phase i an initial quasi static phase and phase ii a subsequent accelerating phase and that the nucleation process is greatly affected by geometric irregularities on the rupturing surfaces in phase i the rupture grows at a slow steady speed which is independent of the rupture growth length l in contrast during phase ii the rupture develops at accelerating speeds v which increase with an increase in l obeying a power law v vs l c n where vs is the shear wave velocity c is the characteristic length representing the geometric irregularity of the fault surfaces and and n are constants 8 87 10 29 and n 7 31 scale dependency of scale dependent physical quantities including the nucleation zone size and its duration is commonly ascribed to scale dependency of the slip dependent constitutive law parameter dc which is in turn governed by c it has been discussed that a unified comprehension can be provided for shear rupture of any size scale if the constitutive law for shear rupture is formulated as a slip dependent law

scaling relationship of initiations for moderate to large earthquakes 1 we investigate the initiation sizes of earthquakes over a wide range of moderate to large events using the model of sato and kanamori which is based on griffith crack theory for a circular fault we estimate the initial crack sizes of earthquakes using high quality data recorded at close hypocentral distances taking into account the local attenuation and the dynamic stress drop of the earthquakes we estimate trigger factors and initial crack radii for 35 events in japan and taiwan with magnitudes of 3 5 to 7 9 our results show that all of the earthquakes can be explained with a small trigger factor and initial crack sizes of 12 96 m for the large range of earthquake sizes this is a small range of initial crack sizes there does not appear to be a clear scaling relationship between initial crack size and final earthquake size instead our results show that all the moderate to large earthquakes initiate with initial crack radii on the order of tens of meters

global petrologic variations on the moon a ternary diagram approach ltrbil kreep rich rocks 5j portions of the east limb and 4 highlands have considerable amounts of a mafic chondritic th ti component like mare basalt whose occurrences coincide with mapped concentrations of light plains that display dark halo craters the presence of this component supports the hypothesis that mare volcanism had occurred within this highland region before the end of final heavy bombardment

initial rupture process of microearthquakes recorded by high sampling borehole seismographs at the nojima fault central japan abstract we analyze high sampling waveforms of the initial part of p wave recorded at the 1800 m deep borehole seismographs at the nojima fault from december 1999 to may 2000 to clarify the initial rupture process of microearthquakes we select 12 events with high s n whose magnitudes range from 0 3 to 2 2 and hypocentral distances from 1 to 11 km we adopt the two different source models by sato and hirasawa 1973 and by sato and kanamori 1999 the former model by sato and hirasawa sh model generates only a ramp like onset of velocity pulse the later model by sato and kanamori sk model is able to generate a weak initial phase that is controlled by a trigger factor and the length of pre existing crack we perform the waveform inversion to estimate the optimum source parameters of each model waveforms of 5 of the 12 events are clearly reproduced by both sh model and sk model with a large trigger factor and a small length of pre existing crack the others are explained by not sh model but only sk model with a small trigger factor and a large length of the pre existing crack indicating that the weak initial phase is a nucleation phase and reflects the source process these seven events satisfy roughly a relation that a large event has a large length of the pre existing crack the final crack length is proportional to the length of the pre existing crack

reservoir characterization of a tight oil reservoir the middle jurassic upper shaunavon member in the whitemud and eastbrook pools sw saskatchewan abstract new horizontal drilling and multi stage fracture completion technology have proven successful in unlocking hydrocarbons from previously uneconomic reservoirs in this paper we investigate the application of this new technology to a medium gravity oil sandstone reservoir to enhance the poor oil recovery within the pool but also to evaluate if the pool boundaries can be expanded petrophysical well logs were integrated with detailed core descriptions thin sections and core analysis data to provide insight to the reservoir characteristics and factors controlling production reservoir distribution depositional environments and lateral extent of depositional fairways for the reservoirs the middle jurassic upper shaunavon b sandstone is the main reservoir in the studied whitemud and eastbrook pools in southwest saskatchewan the reservoirs are composed of mixed siliciclastic carbonate shallow marine shoreface deposits which have a strike trend northeast southwest although the pools were discovered in 1953 and 1966 and have cumulative production of 3 3 mmbbls of medium gravity 22 api oil estimated oil recovery is less than 4 the upper shaunavon b sandstone has two main reservoir facies shoreface sandstones with permeabilities in the 0 1 10 md range and relatively thin but high permeability 10 1000 md coquina beds until recently wells targeted mainly the high permeability coquina for its higher production rates and as a means to drain the associated thick lower permeability shoreface sandstone reservoir this study evaluates the upper shaunavon b shoreface sandstone reservoir quality by examining the reservoir properties heterogeneity connectivity and pore volume of the flow units based on core and petrophysical data comparison of production data from wells intersecting both facies of the upper shaunavon b versus wells where the underlying high permeability coquina facies is absent allows a perspective on the impact that the coquina has on the recovery factor in both reservoir types integration of petrophysical well logs detailed core descriptions thin sections and core analysis data provide insight to the facies interpretation reservoir distribution and lateral extent of depositional fairways for both units reservoir characterization of the lower permeability siliciclastic facies at the whitemud and eastbrook pools coupled with recent advances in horizontal drilling and completion technology show that additional drilling opportunities exist within the pools to improve oil recovery but also that oil saturated sandstone reservoirs exist outside the boundaries of the pools recent successes with multi stage fracturing of horizontal wells have confirmed the findings of this study

the aristarchus impact event and the effects of target material the relatively well preserved 42 km diameter lunar impact crater aristarchus was excavated across the boundary between the aristarchus plateau and the mare plains previous geological mapping of the different ejecta facies associated with aristarchus has shown that there are distinct morphological differences between ejecta emplaced on either side of the fault scarp that separates the plateau from the mare one explanation of this observation is that ejecta behaved in different ways on emplacement depending on the original lithology of the excavated material to test this proposal we examine the pre aristarchus regional stratigraphy and identify the spectral signatures of each of the material s units by comparing these data with analysis of the geology and spectral characteristics of the ejecta units we are able to show the provenance of each of the mappable ejecta facies the conclusions are consistent with the concept of the crater ejecta asymmetry being related to bedrock characteristics using geological mapping spectral interpretation and present understanding of the impact cratering process we reconstruct the impact event and suggest how such techniques could be used further to interpret the moon s composition and history