t max of asphaltenes a parameter for oil maturity assessment abstract a new maturity parameter determined on both oil and bitumen samples the asphaltene tmax is proposed and discussed this parameter could be very useful to address the maturity of the source rock the asphaltene tmax is measured by programmed rock eval pyrolysis using a modified temperature program some phases of the experimental procedure such as the asphaltene preparation and the rock eval measurement substratum choice are crucial in order to achieve reliable data laboratory simulations were carried out in order to assess the possible effects of both primary and secondary migration on asphaltene tmax in the expelled oil the original value of the asphaltene tmax in the bitumen is not substantially modified and it is very close to that measured on kerogen examples of the determination of asphaltene tmax on many samples collected from different areas and with different organic matter composition are given results show that tmax values from oil asphaltenes are reasonable indicators of source rock maturity

using resourcesat 1 data for determination of snow cover and snowline altitude baspa basin india this paper presents a method for deriving the snowline altitude using a combined analysis of terrain elevation and multispectral advanced wide field sensor awifs data from the resourcesat 1 satellite launched by india on 17 october 2003 awifs is a unique instrument capable of acquiring imagery of the world repeatedly every 5 days with very high radiometric resolution it provides a wide swath width which is very useful for snow cover mapping snowline altitude is a good indicator of snow coverage snowline altitude for the period from october 2004 to june 2005 and from october 2006 to june 2007 is determined for the baspa basin which is located in the kinnaur district of himachal pradesh india it is observed that snowline altitude is generally higher during the year 2006 07 than during 2004 05 except in december 2006 and march 2007 the results obtained with the analysis presented here are validated using available meteorological data and are found to be satisfactory this thus establishes a method that can be applied to other terrains and over longer periods of time within the coverage of the awifs sensor data

detecting seasonal variations in seismic velocities within los angeles basin from correlations of ambient seismic noise summary we analyse 3 yr of continuous seismic records from broad band stations of the caltech regional seismic network ci in vicinity of the los angeles basin using correlations of ambient seismic noise relative velocity variations in the order of 0 1 per cent can be measured between all interstation pairs it is the first time that such an extensive study between 861 interstation pairs over such a large area has been carried out we perform these measurements using the stretching technique assuming that one of the two waveforms is merely a stretched version of the other obviously this assumption is always violated and the two waveforms are generally decorrelated due to temporal changes in the earth crust due to different sources or simply because the cross correlations are not fully converged we investigate the stability of these measurements by repeating each measurement over various time windows of equal length on average between all interstation pairs in the los angeles basin a seasonal signal in the relative velocity variation is observed with peaks and troughs during winter and summer time respectively generally the observed signal decreases with increasing interstation distance and relative traveltime perturbations can only be measured up to an interstation distance of 60 km furthermore the traveltime perturbations do not depend on azimuth of station pairs suggesting that they are not related to seasonal variations of the noise sources performing a simple regionalization by laterally averaging measurements over a subset of stations we found the sedimentary basin showing the most consistent signal and conclude that the observed seasonality might be induced either by changes in the ground water aquifer or thermo elastic strain variations that persist down to a depth of 15 22 km

scaling relations of earthquakes and aseismic deformation in a damage rheology model summary we perform analytical and numerical studies of scaling relations of earthquakes and partition of elastic strain energy between seismic and aseismic components using a thermodynamically based continuum damage model brittle instabilities occur in the model at critical damage level associated with loss of convexity of the strain energy function a new procedure is developed for calculating stress drop and plastic strain in regions sustaining brittle instabilities the formulation connects the damage rheology parameters with dynamic friction of simpler frameworks and the plastic strain accumulation is governed by a procedure that is equivalent to drucker prager plasticity the numerical simulations use variable boundary forces proportional to the slip deficit between the assumed far field plate motion and displacement of the boundary nodes these boundary conditions account for the evolution of elastic properties and plastic strain in the model region 3 d simulations of earthquakes in a model with a large strike slip fault produce scaling relations between the scalar seismic potency rupture area and stress drop values that are in good agreement with observations and other theoretical studies the area and potency of the simulated earthquakes generally follow a linear log log relation with a slope of 2 3 and are associated with stress drop values between 1 and 10 mpa a parameter space study shows that the area potency scaling is shifted to higher stress drops in simulations with parameters corresponding to lower dynamic friction more efficient healing and higher degree of seismic coupling

nonlinear dynamics granular media and dynamic earthquake triggering the landers earthquake of 1992 triggered a series of earthquakes in other parts of california focusing attention on the mechanism of remote triggering laboratory experiments on granular material under pressure suggest that triggering is a result of seismic waves impinging on a fault and inducing elastic nonlinear behaviour of the fault core accompanied by instantaneous weakening and failure the resulting softening to weakening model fits in well with field observations of real earthquakes the 1992 magnitude 7 3 landers earthquake triggered an exceptional number of additional earthquakes within california and as far north as yellowstone and montana1 2 3 since this observation other large earthquakes have been shown to induce dynamic triggering at remote distances for example after the 1999 magnitude 7 1 hector mine1 and the 2002 magnitude 7 9 denali4 earthquakes and in the near field as aftershocks5 the physical origin of dynamic triggering however remains one of the least understood aspects of earthquake nucleation1 2 3 4 5 the dynamic strain amplitudes from a large earthquake are exceedingly small once the waves have propagated more than several fault radii for example a strain wave amplitude of 10 6 and wavelength 1 m corresponds to a displacement amplitude of about 10 7 m here we show that the dynamic elastic nonlinear behaviour of fault gouge perturbed by a seismic wave may trigger earthquakes even with such small strains we base our hypothesis on recent laboratory dynamic experiments conducted in granular media a fault gouge surrogate6 7 from these we infer that if the fault is weak8 9 10 seismic waves cause the fault core modulus to decrease abruptly and weaken further if the fault is already near failure this process could therefore induce fault slip

temporal changes in site response associated with the strong ground motion of the 2004 mw 6 6 mid niigata earthquake sequences in japan we analyzed temporal changes in site response associated with the strong ground motion of the 2004 mw 6 6 mid niigata earthquake sequence in japan the seismic data were recorded at a site with accelerometers at the surface and a 100 m deep borehole we computed the empirical surface to borehole spectral ratios and used them to track temporal changes in the top 100 m of the crust we observed that the peak spectral ratio decreases by 40 60 and the peak frequency drops by 30 70 immediately after large earthquakes the coseismic changes are followed by apparent recoveries with the time scale ranging from several tens to more than 100 sec the coseismic peak frequency drop peak spectral ratio drop and the post seismic recovery time roughly scale with the input ground motions when the peak ground velocity is larger than 5 cm sec or the peak ground acceleration is larger than 100 gal our results suggest that at a given site the input ground motion plays an important role in controlling both the coseismic change and the postseismic recov ery in site response

paleoenvironmental reconstruction of the coal and oil shale bearing interval in the lower cretaceous muling formation laoheishan basin northeast china abstract the laoheishan basin in northeast china has been filled with lower cretaceous coal and oil shale bearing sediments the basin fill includes from base to top alluvial conglomerate lower member of muling formation fan delta sediments interbedded with coal and oil prone mudstone denominated as oil shale layers in the upper member of muling formation and volcaniclastic rocks dongshan formation in the present study the maturity of organic matter oil shale quality and paleoenvironment of the coal and oil shale accumulation are investigated based on macro and micropetrographic data proximate and ultimate analyses bulk geochemical parameters biomarkers analysis and stable isotope geochemistry in the laoheishan basin both coal and oil shale layers are derived from land plant organic matter this contrast the oil shale of this basin from oil shale coal intercalations in fault related basins in which oil shale has been found to be of algal origin the coal is sub bituminous in rank hydrogen rich and oil prone the oil shale is of low medium grade and the relatively low oil yield may relate to the abundant resinite and sporinite because of their lower generation potential compared with alginite accumulation of the high ash coal commenced in low lying mire drowned during frequent floodings subsequently high ash low sulfur coal was deposited in a stable low lying mire under oxic conditions and limited bacterial activity afterwards the mire was drowned and formed a freshwater dysoxic to oxic shallow lake in which oil shale layers accumulated finally the depositional environment returned to low lying mire but probably with a brackish influence as indicated by elevated sulfur contents in the uppermost samples petrography and biomarker based proxies indicate that gymnosperms dominated the paleovegetation of the mire accompanied by variable amounts of herbaceous plants such as ferns

rifted margin source rock deposition a carbon isotope and biomarker study of a west african lower cretaceous lacustrine section lower cretaceous passive margin sections penetrated in wells peripheral to the deep basinal development of pre salt sediments of the liawenda ponta vermelha troughs in the lower congo coastal basin revealed sustained source potential kerogen type kinetic ea a and carbon isotopic data plus rock extract biomarker signatures confirmed large systematic organofacies variations within these rift phase sediments an inverse correlation between 25 28 30 trisnorhopane and gammacerane abundances suggested three major depositional regimes reflecting salinity and water depth control 13c depleted basal sediments showing strong gammacerane 4 methyl sterane signatures were segregated by a major isotopic excursion this event represented the transition between saline playa lake to deeper water stratified conditions supporting a high level of anoxia for these intermediate sediments sterane and tricyclic diterpane abundances plus sterane hopane ratios had marine connotations and could be interpreted as the result of intermittent marine incursions fore shadowing irreversible oceanic ingression a resurgence of gammacerane abundance in the uppermost sediments typified littoral shallow marine depositional conditions recognition of a possible non ubiquity in lacustrine depositional conditions during the opening of a rifted margin provides further insight into the complexity and attendant controls on hydrocarbon generation in such habitats

seismic velocity changes in the epicentral region of the 2008 wenchuan earthquake measured from three component ambient noise correlation techniques 1 we investigate temporal changes of seismic velocity in the epicentral region of the 12 may 2008 mw 7 9 wenchuan earthquake using three component continuous waveforms recorded by a seven station small aperture array we use an ambient noise cross correlation technique to compute the empirical green s function between station pairs from august 2004 to september 2011 our results show no obvious precursory change immediately before the main shock clear coseismic reduction of seismic velocity of up to 0 2 and initial postseismic recovery followed by a long lived velocity reduction the coseismic and postseismic velocity changes are most prominent in the period band of 2 4 s approximate depth of 1 4 km and the velocity changes are smaller in other period bands the seismic velocity in the period band of 1 2 s i e top 2 km correlates well with the water level change of the zipingpu reservoir the observed temporal changes likely reflect damage and healing processes with possible permanent deformation in the upper crust associated with the wenchuan main shock

inducing in situ nonlinear soil response applying an active source 1 it is well known that soil sites have a profound effect on ground motion during large earthquakes the complex structure of soil deposits and the highly nonlinear constitutive behavior of soils largely control nonlinear site response at soil sites measurements of nonlinear soil response under natural conditions are critical to advancing our understanding of soil behavior during earthquakes many factors limit the use of earthquake observations to estimate nonlinear site response such that quantitative characterization of nonlinear behavior relies almost exclusively on laboratory experiments and modeling of wave propagation here we introduce a new method for in situ characterization of the nonlinear behavior of a natural soil formation using measurements obtained immediately adjacent to a large vibrator source to our knowledge we are the first group to propose and test such an approach employing a large surface vibrator as a source we measure the nonlinear behavior of the soil by incrementally increasing the source amplitude over a range of frequencies and monitoring changes in the output spectra we apply a homodyne algorithm for measuring spectral amplitudes which provides robust signal to noise ratios at the frequencies of interest spectral ratios are computed between the receivers and the source as well as receiver pairs located in an array adjacent to the source providing the means to separate source and near source nonlinearity from pervasive nonlinearity in the soil column we find clear evidence of nonlinearity in significant decreases in the frequency of peak spectral ratios corresponding to material softening with amplitude observed across the array as the source amplitude is increased the observed peak shifts are consistent with laboratory measurements of soil nonlinearity our results provide constraints for future numerical modeling studies of strong ground motion during earthquakes

monitoring a temporal change of seismic velocity in a volcano application to the 1992 eruption of mt merapi indonesia multiplets i e events with similar waveforms are selected from shallow earthquakes recorded on merapi volcano indonesia before the eruption of february 2nd 1992 two multiplet families are found with their sources close to the summit their seismograms are analyzed using the moving window cross spectrum technique which measures the precise time delay between seismic phases in the entire seismogram for both families of multiplets a gradual decrease in the arrival times of coda waves is observed as a function of the date prior to the eruption coda waves are becoming progressively faster up to 1 2 per cent as the time interval to the eruption shortens this observation is interpreted as the consequence of an increase in the seismic velocity inside the volcano the increase in velocity started in may 1991 and was observed until september 1991 4 months before the eruption this velocity increase may be related to an increase in pressure in the magma chamber or in the conduits and to the resulting closure of the surrounding cracks

guidelines for evaluating petroleum source rock using programmed pyrolysis rock eval pyrolysis is used to rapidly evaluate the petroleum generative potential and thermal maturity of rocks accurate conclusions require programs every 30 60 ft 9 18 m understanding of interpretive pitfalls and supporting data such as visual kerogen vitrinite reflectance and elemental analyses the generative potential of coals is commonly overestimated by pyrolysis and is best determined by elemental analysis and organic petrography most coals show high s2 s3 5 and low hi values 300 mg hc g toc migrated oil and mud additives which alter rock eval data can sometimes be removed by special processing for immature rocks bimodal s2 peaks and pi values over 0 2 indicate contamination pyrolysis downgrades organic poor clay rich rocks which show lower hi and higher tmax values than isolated kerogen because of adsorption of pyrolyzate on the clays tmax values for small s2 peaks 0 2 mg hc g toc are unreliable tmax is affected by maturation organic matter type contamination and the mineral matrix s3 is sensitive to inorganic and adsorbed carbon dioxide and to instrumentation problems acidification of carbonate rich samples and proper maintenance improves s3 measurement constant sample weights 100 mg are recommended below a threshold weight tmax increases by up to 10 c and other parameters decrease organic rich samples which overload the detector can be diluted with carbonate detector linearity is determined by pyrolyzing various weights of an organic rich rock

seismic evidence of nonlinear crustal deformation during a large slow slip event in mexico repeated cross correlations of ambient seismic noise indicate a long term seismic velocity change associated with the 2006 m7 5 slow slip event sse in the guerrero region mexico because the sse does not radiate seismic waves the measured velocity change cannot be associated with the response of superficial soil layers to strong shaking as observed for regular earthquakes the perturbation observed maximized at periods between 7 s and 17 s which correspond to surface waves with sensitivity to the upper and middle crust the amplitude of the relative velocity change 10 3 was much larger than the volumetric deformation 10 6 at the depths probed 5 20 km moreover the time dependence of the velocity perturbation indicated that it was related to the strain rate rather than the strain itself this suggests that during strong slow slip events the deformation of the overlying crust shows significant nonlinear elastic behavior

expulsion of oil from petroleum source rocks inferences from pyrolysis of samples of unconventional grain size oil expulsion efficiencies from different lithologies have been investigated and compared employing pyrolyses of samples of unconventional grain size from 300 mg hc g corg show that liquid range hydrocarbons are expelled from coal when the generated oil exceeds the coal sorption capacity this suggests that expulsion of oil from liptinite poor or in general h poor humic coals is primarily limited by the release of generated liquid hydrocarbons from kerogen because such coals generally do not generate sufficient amounts of liquid hydrocarbons to overcome the coal sorption capacity

coseismic and postseismic velocity changes measured by repeating earthquakes 1 repeating earthquakes that rupture approximately the same fault patch and have nearly identical waveforms are a useful tool for measuring temporal changes in wave propagation in the earth s crust since source and path effects are common to all earthquakes in a repeating earthquake sequence multiplet differences in their waveforms can be attributed to changes in the characteristics of the medium we have identified over 20 multiplets containing between 5 and 40 repeating events in the aftershock zones of the 1989 loma prieta and 1984 morgan hill california earthquakes postmain shock events reveal delays of phases in the early s wave coda of as much as 0 2 s relative to premain shock events the delay amounts to a path averaged coseismic velocity decrease of about 1 5 for p waves and 3 5 for s waves since most of the multiplets are aftershocks and follow omori s law we have excellent temporal sampling in the immediate postmain shock period we find that the amplitude of the velocity decrease decays logarithmically in time following the main shock in some cases it returns to the premain shock values while in others it does not similar results are obtained for the morgan hill main shock because the fractional change in s wave velocity is greater than the fractional change in p wave velocity it suggests that the opening or connection of fluid filled fractures is the underlying cause the magnitude of the velocity change implies that low effective pressures are present in the source region of the velocity change our results suggest that the changes are predominantly near the stations and shallow but we cannot exclude the possibility that changes occur at greater depth as well if the variations are shallow we may be detecting the lingering effects of nonlinearity during main shock strong ground motion if the variations are deep it suggests that pore pressures at seismogenic depths are high which would likely play a key role in the earthquake process

distribution of seismic wave speed changes associated with the 12 may 2008 mw 7 9 wenchuan earthquake 1 we used continuous recordings in sichuan china to track the temporal change of the seismic wave speed at a regional scale for 2 years including the wenchuan mw 7 9 earthquake the data are recorded by a temporary network of 156 broad band seismographs in a region that covers the southern 2 3 of the fault activated during the earthquake a doublet analysis applied on the codas of seismic noise cross correlation functions is used to detect temporal velocity changes we found clear evidence that the seismic velocity drops by up to 0 08 in the fault region just after the earthquake with fluctuations within 0 02 before the earthquake we compared the measurements in different sub arrays to get a spatial distribution of the velocity changes this distribution is consistent with the volumetric strain change during the wenchuan earthquake and shows that the co seismic velocity change is not controlled by the response of sediments

seismic evidence for rock damage and healing on the san andreas fault associated with the 2004 m 6 0 parkfield earthquake we deployed a dense linear array of 45 seismometers across and along the san andreas fault near parkfield a week after the m 6 0 parkfield earthquake on 28 september 2004 to record fault zone seismic waves generated by aftershocks and explosions seismic stations and explosions were co sited with our previous exper iment conducted in 2002 the data from repeated shots detonated in the fall of 2002 and 3 months after the 2004 m 6 0 mainshock show 1 0 1 5 decreases in seismic wave velocity within an 200 m wide zone along the fault strike and smaller changes 0 2 0 5 beyond this zone most likely due to the coseismic damage of rocks during dynamic rupture in the 2004 m 6 0 earthquake the width of the damage zone characterized by larger velocity changes is consistent with the low velocity waveguide model on the san andreas fault near parkfield that we derived from fault zone trapped waves li et al 2004 the damage zone is not symmetric but extends farther on the southwest side of the main fault trace waveform cross correlations for repeated aftershocks in 21 clusters with a total of 130 events located at different depths and distances from the array site show 0 7 1 1 increases in s wave velocity within the fault zone in 3 months starting a week after the earthquake the velocity recovery indicates that the damaged rock has been healing and regaining the strength through rigidity recovery with time most likely due to the closure of cracks opened during the mainshock we estimate that the net decrease in seismic velocities within the fault zone was at least 2 5 caused by the 2004 m 6 0 parkfield earthquake the healing rate was largest in the earlier stage of the postmainshock healing process the magnitude of fault healing varies along the rupture zone being slightly larger for the healing beneath middle mountain correlating well with an area of large mapped slip the fault healing is most promi nent at depths above 7 km

constraining depth range of s wave velocity decrease after large earthquakes near parkfield california we use noise correlation and surface wave inversion to measure the s wave velocity changes at different depths near parkfield california after the 2003 san simeon and 2004 parkfield earthquakes we process continuous seismic recordings from 13 stations to obtain the noise cross correlation functions and measure the rayleigh wave phase velocity changes over six frequency bands we then invert the rayleigh wave phase velocity changes using a series of sensitivity kernels to obtain the s wave velocity changes at different depths our results indicate that the s wave velocity decreases caused by the san simeon earthquake are relatively small similar to 0 02 and access depths of at least 2 3 km the s wave velocity decreases caused by the parkfield earthquake are larger similar to 0 2 and access depths of at least 1 2 km our observations can be best explained by material damage and healing resulting mainly from the dynamic stress perturbations of the two large earthquakes

seismic noise correlations to image structural and mechanical changes associated with the mw 7 9 2008 wenchuan earthquake we locate temporal changes of seismic wave speed and scattering properties of the crust associated with the 2008 mw7 9 wenchuan earthquake to that end we analyze ambient seismic noise records from 2007 until the end of 2008 in the 1 3 s period band and in the 12 20 s period band measured in a region that covers the southern two thirds of the fault activated during the earthquake to locate the changes we use a refined imaging procedure based on the sensitivity of scattered waves to weak perturbations this inverse method uses the radiative transfer approximation to describe the intensity of the noise correlation coda our results show that the largest structural changes are observed northeast of the wenchuan epicenter around the fault zone where aftershocks are distributed the spatial and temporal characteristics of the behavior of the crust at depth around the wenchuan earthquake suggest a postseismic and geology dependent signature of the middle crust we also observe a clear seasonal signature within the sichuan basin at depth that we relate to the heavy rainfalls during the monsoon season this seasonality can also be observed at the surface in form of a waveform decoherence our study highlights that seismic velocity changes and waveform decoherence are independent measurements that are sensitive to different parameters and can thus give complementary information in our study we also point out the value of studying the evolution of the changes at different times in the coda

simple kinetic models of petroleum formation part i oil and gas generation from kerogen modern basin analysis uses kinetic models to predict the extent of petroleum generation within potential source rocks the global kinetic model presented here assigns kinetic parameters based on gross depositional environment and stratigraphic age this is useful in areas of low geochemical knowledge including exploration frontiers five kerogen kinetic organofacies each characterized by a specific organic matter input and early diagenetic overprint can broadly be related to sedimentary facies age associations even using seismic sequence stratigraphy alone a aquatic marine siliceous or carbonate evaporite any age b aquatic marine siliciclastic any age c aquatic non marine lacustrine phanerozoic d e terrigenous non marine ever wet coastal mesozoic and younger and f terrigenous non marine coastal late palaeozoic and younger routine pyrolysis data allow partitioning of organic carbon in the immature source rock into four initial components oil oil generative gas generative and inert separate kinetic parameters for the oil and gas generative fractions allow computation of the evolving concentration and composition of the products it was assumed that the activation energy distributions for each fraction were normally distributed non linear regression of large combined laboratory and field data sets varying by up to 12 orders of magnitude in heating rate established optimum values for the required ten 5 2 kinetic parameter sets a emean e differences in kinetic parameters can be reconciled with known chemical properties although our knowledge base is still inadequate to construct kinetic models from first principles mean activation energies governing oil generation increase systematically in the order a f causing a corresponding increase in generation temperature at a reference heating rate 2 c ma 1 the oil generation window 10 90 oil generative kerogen degraded increases from ca 95 135 c to 145 175 c organofacies c has the tightest energy distribution and narrowest oil generation window the gas generation window ranges from ca 105 155 c to 175 220 c thermal stress results from a combination of temperature and time an order of magnitude increase decrease in heating rate elevates depresses reaction temperatures by ca 15 c heating rates in subsiding sedimentary basins can vary by two orders of magnitude dramatic differences in generation temperature can result if the heating rate and organofacies effects compound thus global oil and gas generation temperature thresholds constitute blunt instruments with which to screen the petroleum potential of sedimentary basins because unexpelled oil provides a potential feedstock for oil to gas cracking in the source rock quantitative models of petroleum generation become really useful only when coupled with models of oil gas cracking and expulsion for example the frequently observed association between gas provinces and coals cannot be explained solely by their generation behaviour

aftershock distribution as a constraint on the geodetic model of coseismic slip for the 2004 parkfield earthquake several studies of the 2004 parkfield earthquake have linked the spatial distribution of the event s aftershocks to the mainshock slip distribution on the fault using geodetic data we find a model of coseismic slip for the 2004 parkfield earthquake with the constraint that the edges of coseismic slip patches align with aftershocks the constraint is applied by encouraging the curvature of coseismic slip in each model cell to be equal to the negative of the curvature of seismicity density the large patch of peak slip about 15 km northwest of the 2004 hypocenter found in the curvature constrained model is in good agreement in location and amplitude with previous geodetic studies and the majority of strong motion studies the curvature constrained solution shows slip primarily between aftershock streaks with the continuation of moderate levels of slip to the southeast these observations are in good agreement with strong motion studies but inconsistent with the majority of published geodetic slip models southeast of the 2004 hypocenter a patch of peak slip observed in strong motion studies is absent from our curvature constrained model but the available gps data do not resolve slip in this region we conclude that the geodetic slip model constrained by the aftershock distribution fits the geodetic data quite well and that inconsistencies between models derived from seismic and geodetic data can be attributed largely to resolution issues

organofacies variation control on hydrocarbon generation a lower congo coastal basin angola case history abstract a group of lower congo coastal basin angola carbonate platform petroleums all determined to be of lower cretaceous pre salt bucomazi fm neocomian aptian rift phase provenance showed considerable internal diversity recognised in terms of biomarker abundances and waxiness this variation was particularly evident in their carbon isotopic compositions which ranged from 26 4 to 29 7 ppt although not exclusive to all oils many contained an abundance of an unusual triterpane tentatively characterised as 25 30 bisnorhopane using a combination of kerogen type i ii iii and kinetic data ea and a plus kerogen pyrolysate isotopic signatures a conspicuous variation in organofacies was observed over the vertical and lateral development of this lacustrine source unit in a series of control wells three oil prone organofacies were recognised two of which could be individually characterised as type i 13c depleted and type ii 13 c enriched assemblages a third assemblage of type ii iisuperior character and intermediate isotopic signature not dependent upon mixing of the above end members was similarly recognised significantly the 25 30 bisnorhopane marker observed in many of the oils was found to be exclusively associated with the type ii 13c enriched organofacies on this basis rationalisation of crrde oil character and genera was possible in terms of phased co generation from these limiting organofacies with subsequent co mingling of the resultant oils although dissimilar end member oils could be isotopically matched to source facies representative of the more labile type ii lower ea to the less labile type i higher ea candidates most oils showed a mixed character reflecting their aggregate compostion definition of organofacies make up and variation is crucial to the fine tuning of contemporary modelling practises in their application to the study of hydrocarbon productive habitats

warm humid paleoclimate control of salinized lacustrine organic rich shale deposition in the oligocene hetaoyuan formation of the biyang depression east china abstract lacustrine organic rich shales are widely developed within the oligocene biyang depression in the nanxiang basin in east china and across southeast asia these shales have been proven as hydrocarbon source rocks of crude oil as well as sources and reservoirs of shale oil understanding the deposition of these shales is essential to reconstruct the paleoenvironment and paleoclimate during the oligocene in east china as well as target the potential shale oil resources based on x ray diffraction organic and inorganic petrologic organic and inorganic geochemical and stable isotopic analyses paleoenvironment paleoclimate and hydrocarbon potential of the lacustrine organic rich shales in the oligocene hetaoyuan formation were investigated the mineral composition of hetaoyuan formation organic rich shales is dominated by clay minerals followed by quartz plagioclase calcite dolomite pyrite and gypsum six lithotypes are identified including siltstone silty shale clay shale calcareous shale dolomite shale and massive mudstone the organic matter om of the organic rich shales is dominated by type i kerogen lamalginite maturity parameters tmax biomarker ratios and calculated vitrinite reflectance suggest that the om enters the oil window maturity high toc and generative potential together with high contents of brittle minerals including quartz plagioclase and carbonates reveal the oligocene hetaoyuan formation hold good to very good potential of shale oil exploitation six organic rich shale layers have been identified in the hetaoyuan formation shale layer 1 to 6 from top to bottom among them shale layers 5 and 3 hold the best shale oil potential and therefore be investigated in the present paper shale layer 5 was deposited in a semi deep lacustrine environment under the moderately warm humid paleoclimate further dividing into lower middle and upper units relatively low toc contents av 2 6 wt in the lower unit are probably caused by high sedimentation rate high bioproductivity under favorable preservation conditions led to relatively high toc contents av 3 6 wt in the middle unit less reducing conditions together with moderate low bioproductivity resulted in relatively low toc contents av 2 6 wt in the upper unit warm humid paleoclimate prevailed during deposition of shale layer 3 deepened water depth and formed a deep lacustrine environment the stratified water column led to stable anoxic condition and photic zone euxinia in the saline deep lacustrine environment which enabled the accumulation of high amounts of om av 4 9 wt toc under excellent preservation av hi 710 mg hc g toc the results of core scanning analysis indicate that formation of the laminated shales probably controlled by seasonal fluctuations of paleoclimate

mapping pressurized volcanic fluids from induced crustal seismic velocity drops volcanic eruptions are caused by the release of pressure that has accumulated due to hot volcanic fluids at depth here we show that the extent of the regions affected by pressurized fluids can be imaged through the measurement of their response to transient stress perturbations we used records of seismic noise from the japanese hi net seismic network to measure the crustal seismic velocity changes below volcanic regions caused by the 2011 moment magnitude m w 9 0 tohoku oki earthquake we interpret coseismic crustal seismic velocity reductions as related to the mechanical weakening of the pressurized crust by the dynamic stress associated with the seismic waves we suggest therefore that mapping seismic velocity susceptibility to dynamic stress perturbations can be used for the imaging and characterization of volcanic systems

sudden drop of seismic velocity after the 2004 mw 6 6 mid niigata earthquake japan observed with passive image interferometry 1 passive image interferometry pii is a seismological method employing ambient seismic noise to monitor the temporal evolution of mean shear wave velocity within the earth first the elastic green s tensor between two seismometers is computed from the cross correlation of seismic noise recorded during a certain period second the constructed seismograms of different time periods are treated as earthquake multiplets and small time shifts in their coda are used to invert a relative change in mean shear wave velocity when applied to the source region of the 2004 mw 6 6 mid niigata earthquake japan centroid depth 5 km we used noise recorded at six seismometers located at a distance of less than 25 km from the epicenter daily inversions during the 2 months before and after the earthquake show a sudden drop of mean shear wave velocity of some tenths of a percent at the time of the mid niigata earthquake using noise in two frequency bands 0 1 0 5 hz and 2 8 hz we find similar amplitudes for the velocity drop which indicates that changes are not restricted to the shallow subsurface possible interpretations of this velocity decrease are a decrease of crustal stress after the earthquake a nonlinear site response in the shallow subsurface layer due to strong ground motion or structural weakening due to the creation of new fractures in the source area of the earthquake

assessment of resolution and accuracy of the moving window cross spectral technique for monitoring crustal temporal variations using ambient seismic noise summary temporal variations in the elastic behaviour of the earth s crust can be monitored through the analysis of the earth s seismic response and its evolution with time this kind of analysis is particularly interesting when combined with the reconstruction of seismic green s functions from the cross correlation of ambient seismic noise which circumvents the limitations imposed by a dependence on the occurrence of seismic events in fact because seismic noise is recorded continuously and does not depend on earthquake sources these cross correlation functions can be considered analogously to records from continuously repeating doublet sources placed at each station and can be used to extract observations of variations in seismic velocities these variations however are typically very small of the order of 0 1 per cent such accuracy can be only achieved through the analysis of the full reconstructed waveforms including later scattered arrivals we focus on the method known as moving window cross spectral analysis that has the advantage of operating in the frequency domain where the bandwidth of coherent signal in the correlation function can be clearly defined we investigate the sensitivity of this method by applying it to microseismic noise cross correlations which have been perturbed by small synthetic velocity variations and which have been randomly contaminated we propose threshold signal to noise ratios above which these perturbations can be reliably observed such values are a proxy for cross correlation convergence and so can be used as a guideline when determining the length of microseismic noise records that are required before they can be used for monitoring with the moving window cross spectral technique

slip history of the 2003 san simeon earthquake constrained by combining 1 hz gps strong motion and teleseismic data 1 the slip history of the 2003 san simeon earthquake is constrained by combining strong motion and teleseismic data along with gps static offsets and 1 hz gps observations comparisons of a 1 hz gps time series and a co located strong motion data are in very good agreement demonstrating a new application of gps the inversion results for this event indicate that the rupture initiated at a depth of 8 5 km and propagated southeastwards with a speed 3 0 km sec with rake vectors forming a fan structure around the hypocenter we obtained a peak slip of 2 8 m and total seismic moment of 6 2 10 18 nm we interpret the slip distribution as indicating that the hanging wall rotates relative to the footwall around the hypocenter in a sense that appears consistent with the shape of the mapped fault trace index terms 1242 geodesy and gravity seismic deformations 7205 7212 seismology earthquake ground motions and engineering 8123 tectonophysics dynamics seismotectonics citation ji c k m larson y tan k w hudnut and k choi 2004 slip history of the 2003 san simeon earthquake constrained by combining 1 hz gps strong motion and teleseismic data geophys res lett 31 l17608 doi 10 1029 2004gl020448

depth sensitivity of seismic coda waves to velocity perturbations in an elastic heterogeneous medium summary numerous monitoring applications make use of seismic coda waves to evaluate velocity changes in the earth this raises the question of the spatial sensitivity of coda wave based measurements here we investigate the depth sensitivity of coda waves to local velocity perturbations using 2 d numerical wavefield simulations we calculate the impulse response at the surface before and after a slight perturbation of the velocity within a thin layer at depth is introduced we perform a parametric analysis of the observed apparent relative velocity changes e obs versus the depth of the thin perturbed layer through the analysis of the decay of e obs we can discriminate two different regimes one for a shallow perturbation and the other for a deep perturbation we interpret the first regime as the footprint of the 1 d depth sensitivity of the fundamental surface wave mode to interpret the second regime we need to model the sensitivity of the multiply scattered body waves in the bulk we show that the depth sensitivity of coda waves can be modelled as a combination of bulk wave sensitivity and surface wave sensitivity the transition between these two regimes is governed by mode conversions due to scattering we indicate the importance of surface waves for the sensitivity of coda waves at shallow depths and at early times in the coda at later times bulk waves clearly dominate the depth sensitivity and offer the possibility of monitoring changes at depths below the sensitivity of the surface waves based on the transition between the two regimes we can discriminate a change that occurs at the surface from a change that occurs at depth this is illustrated for shallow depth perturbations through an example from lunar data

depositional environment of the lower cretaceous muling formation of the laoheishan basin ne china implications from geochemical and petrological analyses abstract the laoheishan basin located in northeastern china is filled with non marine coal and oil shale oil prone mudstone sediments of the lower cretaceous muling formation based on petrological mineralogical and geochemical methods the depositional environment during organic matter om accumulation is investigated for the first time the coal is subbituminous in rank petrological and bulk geochemical data indicate sapropelic coal deposited in low lying mire under freshwater conditions high pristane phytane ratios provide evidence for a land plant origin of om and oxic conditions during deposition a neutral to slightly alkaline ph is reflected by the presence of carbonate high liptinite contents and terpenoid biomarker composition indicate high amounts of resinous om during oil shale deposition a raised water table was favorable for om preservation under oxic to dysoxic conditions the oil shales in the lower unit of the succession not associated with coal are characterized by high hydrogen index and resinite contents interpreted to reflect deposition at elevated water depths in contrast to the findings of previous studies on oil shales in china indicating its origin from algal om a predominance of terrigenous om rich in waxy and resinous lipids is implied from biomarker and maceral composition the lower cretaceous oil shale and coal in the laoheishan basin contain high amounts of land plant derived terpenoid biomarkers derived from coniferales e g pinaceae cupressaceae taxodiaceae araucariaceae podocarpaceae and ferns the results are in agreement with palynological data the data highlight the potential of resinous and waxy om to form excellent hydrocarbon source rocks

coseismic and postseismic elastic wave velocity variations caused by the 2008 iwate miyagi nairiku earthquake japan 1 we analyze coseismic and postseismic velocity variations caused by the june 13 2008 iwate miyagi nairiku earthquake mw 6 9 using passive image interferometry pii seismic noise is correlated in order to reconstruct the green s function between two sensors shear wave velocity changes are determined by relating the coda parts of the daily green s functions to a long term reference green s function our study extends from january 2008 to august 2010 and includes the correlations for 190 station pairs in three different frequency ranges from 0 125 to 1 0 hz we show that combining the 9 different component cross correlation functions stabilizes the velocity change estimation and increases analysis resolution the observed velocity change curves can be fitted by model time series consisting of a coseismic velocity drop followed by logarithmic postseismic recovery and seasonal velocity variations the coseismic velocity drops are stronger at higher frequencies and are concentrated in the southern part of the fault zone a tomography algorithm was developed to reproject the observed velocity variations of the different sensor pairs onto the single sensors the depth distribution of coseismic changes was modeled for the three stations with the largest velocity drops at two stations the coseismic velocity changes are located in the upper several hundred meters the third station shows indications for deeper changes in the order of kilometers postseismic recovery takes significantly longer than the analyzed two year period seasonal velocity variations with periods of one year are observed at all analyzed frequencies for most station pairs

variations of crustal elastic properties during the 2009 l aquila earthquake inferred from cross correlations of ambient seismic noise 1 we retrieve seismic velocity variations within the earth s crust in the region of l aquila central italy by analyzing cross correlations of more than two years of continuous seismic records the studied period includes the april 6 2009 mw 6 1 l aquila earthquake we observe a decrease of seismic velocities as a result of the earthquake s main shock after performing the analysis in different frequency bands between 0 1 and 1 hz we conclude that the velocity variations are strongest at relatively high frequencies 0 5 1h z suggesting that they are mostly related to the damage in the shallow soft layers resulting from the co seismic shaking citation zaccarelli l n m shapiro l faenza g soldati and a michelini 2011 variations of crustal elastic properties during the 2009 l aquila earthquakeinferred from cross correlations of ambient seismic noise geophys res lett 38 l24304 doi 10 1029 2011gl049750

tremor reveals stress shadowing deep postseismic creep and depth dependent slip recurrence on the lower crustal san andreas fault near parkfield 1 the 2003 magnitude 6 5 san simeon and the 2004 magnitude 6 0 parkfield earthquakes induced small but significant static stress changes in the lower crust on the central san andreas fault where recently detected tectonic tremor sources provide new constraints on deep fault creep processes we find that these earthquakes affect tremor rates very differently consistent with their differing transferred static shear stresses the san simeon event appears to have cast a stress shadow north of parkfield where tremor activity was stifled for 3 6 weeks in contrast the 2004 parkfield earthquake dramatically increased tremor activity rates both north and south of parkfield allowing us to track deep postseismic slip following this event rates initially increased by up to two orders of magnitude for the relatively shallow tremor sources closest to the rupture with activity in some sources persisting above background rates for more than a year we also observe strong depth dependence in tremor recurrence patterns with shallower sources generally exhibiting larger less frequent bursts possibly signaling a transition toward steady creep with increasing temperature and depth

surface wave tomography of the upper mantle beneath the reykjanes ridge with implications for ridge hot spot interaction 1 we modeled fundamental mode love and rayleigh waves to study the seismic properties of the upper mantle beneath the reykjanes ridge these waves were generated by regional earthquakes occurring in the north atlantic to the south of iceland and were recorded by stations located on iceland over 12 000 measurements of the phase group arrival time and amplitude of narrow pass filtered waveforms over the period range of 9 5 100 s were used to solve for mantle shear wave velocity structure and anisotropy in a vertical plane oriented normal to the ridge axis the velocity structure contains a broad and deep low velocity zone in the upper mantle beneath the ridge a joint analysis of the seismic structure with gravity data reveals that the low velocities are consistent with elevated temperatures 75 our study shows that plume material spreads broadly outward beneath the reykjanes ridge from iceland and is not confined to a narrow lithospheric channel at distances 200 km from the ridge shear wave anisotropy indicates a predominant horizontal alignment of the fast axes of anisotropic crystals mainly above 50 km depth which can be interpreted as past horizontal ridge perpendicular flow within 200 km of the ridge the anisotropy indicates a general vertical alignment of the fast axes or an alignment such that the fast axes point along the ridge the transition to this type of anisotropy coincides with the appearance of increased hot spot ridge interaction 20 myr ago indicating that plume flow has largely disrupted mantle flow beneath the ridge since that time