the variation of temperature with time and hydrocarbon maturation in sedimentary basins formed by extension abstract when a sedimentary basin is formed by extension both the subsidence history and the temperature gradient can be calculated hence the time temperature history of any stratum can be obtained three types of behaviour occur the temperature of material which never reaches depths greater than about 4 km increases at all times the time temperature history of material which finally sinks to greater depths reaches a maximum during the subsidence history the time at which this maximum occurs decreases as the depth increases at greater depths the maximum temperature occurs at the time the basin is formed the time temperature history is then used to calculate lopatin s maturation index for each stratum as a function of time and the index plotted as a function of depth and time for different amounts of extension the maximum temperature at a given depth and hence lopatin s index is almost independent of the amount of extension when the age of the basin is greater than about 150 ma similar calculations taking account of sediment compaction show the same behaviour though the maturity of the material at a given depth is increased because both lopatin s index and its calibration are empirical it is important to develop new maturation indices based on individual molecular reactions whose activation energies can be determined in the laboratory

petroleum origin and accumulation in basin evolution a quantitative model basin data geologic geophysical geochemical hydrodynamic and thermodynamic can be combined for quantified hydrocarbon prediction a three dimensional deterministic dynamic basin model can be constructed to calculate all the measurable values with the help of mass and energy transport equations and equations describing the physical and or physicochemical changes in organic matter as a function of temperature input data consist of heat flux initial physical and thermal properties of sediments paleobathymetric estimates sedimentation rate and amount and type of organic matter subsequently the model computes pressure temperature physical and thermal properties of sediments maturity of organic matter and the hydrocarbon potential of any source rock as a func ion of space and time thus the complex dynamic processes of petroleum formation and occurrence in a given sedimentary basin can be quantified for example hydrocarbon potential maps for any given source rock and any geologic time slice of the basin evolution can be provided as computer printouts the computer model can be applied to any stage of an exploration campaign and updated as more information becomes available

finite faults and inverse theory with applications to the 1979 imperial valley earthquake abstract using a representation theorem from elastodynamics subsurface slip on a known fault is formulated as the solution to an inverse problem in which recorded surface ground motion is the data two methods of solution are presented the least squares method which minimizes the squared differences between theory and data and the constrained least squares method which simultaneously maintains a set of linear inequalities instabilities in the solution are effectively eliminated in both methods and the sensitivity of the solution to small changes in the data is quantitatively stated the inversion methodology is applied to 77 components of near field ground acceleration recorded during the 15 october 1979 imperial valley earthquake the faulting is constrained to propagate bilaterally away from the epicenter at an average velocity of 90 per cent of the shear wave speed on a vertical fault plane extending from the surface to 10 km depth inequality constraints are used to keep the faulting sequence physically reasonable by maintaining right lateral motion and positive slip velocity the preferred solution is stable and provides a good fit to the data it is also realistic and consistent with observed surface offsets and independent estimates of seismic moment

botryococcus a planktonic green alga the source of petroleum through the ages transmission electron microscopical studies of oil shales and petroleum source rocks abstract the hydrocarbon secreting alga botryococcus has been identified in organic remains of sediments ranging from precambrian to recent and is believed to have been a major source material for petroleum generation throughout the geological time in some petroleum source rocks of lower palaeozoic and precambrian age identification of the alga is only possible by electron microscopy transmission electron microscopy tem has been used in the present study to identify microstructures of the algal remains in a range of oil shales and petroleum source rocks it has been established that botryococcus is the predominant alga in the kukersite oil shale of estonia similarly the alga has been shown to be a major contributor to petroleum source rocks in cambrian and precambrian sedimentary basins in australia tem has been applied to observations of botryococcus in torbanites and to products from simulated maturation experiments on torbanite a comparison with algal remains from cambrian and precambrian sediments ranging from undermature to overmature enabled the distinction of organic matter in various stages of oil generation maturation thermal effects on alginite have been established by reflectance and fluorescence and compared with experimental results

inversion of complex body waves we have developed a method that inverts seismic body waves to determine the mechanism and rupture pattern of earthquakes the rupture pattern is represented as a sequence of subevents distributed on the fault plane this method is an extension of our earlier method in which the subevent mechanisms were fixed in the new method the subevent mechanisms are determined from the data and are allowed to vary during the sequence when subevent mechanisms are allowed to vary however the inversion often becomes unstable because of the complex trade offs between the mechanism the timing and the location of the subevents many different subevent sequences can explain the same data equally well and it is important to determine the range of allowable solutions some constraints must be imposed on the solution to stabilize the inversion we have developed a procedure to explore the range of allowable solutions and appropriate constraints in this procedure a network of grid points is constructed on the i plane where and i are respectively the onset time and the distance from the epicenter of a subevent the best fit subevent is determined at all grid points then the correlation is computed between the synthetic waveform for each subevent and the observed waveform the correlation as a function of and i and the best fit mechanisms computed at each i grid point depict the character of allowable solutions and facilitate a decision on the appropriate constraints to be imposed on the solution the method is illustrated using the data for the 1976 guatemala earthquake

smooth and rapid slip near the japan trench during the 2011 tohoku oki earthquake revealed by a hybrid back projection method abstract we developed a new back projection method that uses teleseismic p waveforms to integrate the direct p phase with reflected phases from structural discontinuities near the source and used it to estimate the spatiotemporal distribution of the seismic energy release of the 2011 tohoku oki earthquake we projected a normalized cross correlation of observed waveforms with corresponding green s functions onto the seismic source region to obtain a high resolution image of the seismic energy release applying this method to teleseismic p waveform data of the 2011 tohoku oki earthquake we obtained spatiotemporal distributions of seismic energy release for two frequency bands a low frequency dataset and a high frequency dataset we showed that the energy radiated in the dip direction was strongly frequency dependent the area of major high frequency seismic radiation extended only downdip from the hypocenter whereas the area of major low frequency seismic radiation propagated both downdip and updip from the hypocenter we detected a large release of seismic energy near the japan trench in the area of maximum slip which was also the source area of the gigantic tsunami when we used only the low frequency dataset the timing of this large seismic energy release corresponded to an episode of smooth and rapid slip near the japan trench and reflects the strong dependence of the seismic energy distribution obtained on the frequency band of the input waveform dataset the episode of smooth and rapid slip may have been the trigger for a release of roughly all of the accumulated elastic strain in the seismic source region of the 2011 tohoku oki earthquake

oil prospects of the gulf of suez egypt a case study abstract four groups of rocks having more than 0 5 of organic carbon are defined within the subsurface section of rahmi area gulf of suez the deduced types of indigenous kerogen are algal amorphous inertinite woody and herbaceous the algal amorphous kerogen of rudeis nukhul formations lower miocene eocene and pre eocene rocks is recognized as being oil prone that is having high capacity for generating oil the application of hydrocarbon liquid window concept shows that the lom values fall within the range from 8 6 to 10 8 and the thermal alteration index for the different units is not extended into oil generation window where it ranges from immature kareem formation lower miocene to moderately mature paleocene to the beginning of the thermal phase of oil generation senonian the vitrinite reflectance values indicate a low level of thermal maturity the formational temperatures increase towards the depocentral part of the basin and eastwards to the present gulf of suez the thermal maturity index increases towards ancient stratigraphic units the study of organic richness quality and maturity revealed that where the nukhul eocene and senonian rocks are buried deeper in the study area would have been excellent source rocks for oil

global geologic history and distribution of hydrocarbon reserves a review of global geologic history during seven major periods between the cambrian and the holocene reveals the principal factors influencing the distribution of world hydrocarbon reserves the paleozoic reserves located mainly in north america and europe are mostly related to stable platform environments the mesozoic and tertiary reserves are found in more diverse tectonic environments represented mainly by the mesogean tethyan realm passive margins and the western american mobile belts the mesogea tethys formed a latitudinal feature separating gondwana and laurasia the mesogean realm contains 69 of the world oil and gas reserves divided almost equally between the gondwana and laurasia areas the voluminous reserves in the mesogean realm reflect the history of repeated opening and closing of the mesogea ocean that resulted in several phases of basin development the comparative isolation of the basins from the global ocean circulation favored preservation f organic matter because of diagenesis the thermal history and migration the ultimate hydrocarbon reserves generally decrease as the ages of the reservoir and source rocks increase migration is usually directed toward the higher parts of the stratigraphic section concentrations of reserves within particular age ranges apparently reflect development of two major categories of basins 1 marine platform basins which were dominant in the devonian jurassic and cretaceous periods and 2 rapidly subsiding basins which were dominant in the late tertiary and probably during the late carboniferous pennsylvanian the middle east has an exceptional volume of sediments prolific source rocks and well preserved hydrocarbons and it is not likely that another hydrocarbon province of comparable importance will be found moreover these middle east reserves do not give any anomalous weight to the total reserves of the gondwanian areas when compared to those in the laurasian areas

petroleum potential of the adriatic offshore croatia the adriatic offshore of croatia extends from the istrian peninsula in the northwest to the dubrovnik offshore area to the southeast and from the croatian coast line to the offshore boundary with italy geochemical prospecting comprised analyses of permian through pliocene quaternary sediments integrated results of geochemical analyses indicate the presence of source rocks in triassic ladinian carnian and lower to upper cretaceous units triassic source rock sequences within the thin limestone streaks from the lithologically mixed sabkha facies are evidenced in the southeastern portion of the adriatic carbonate platform complex algal bacterial organic matter of the predominantly marine origin is in the early stage of thermal maturation properties of analysed bitumen and oil samples imply a direct relationship with the associated source rocks cretaceous source rock sequences with good generating potential were determined in the central part of the adratic offshore layers of micritic limestone and bituminous laminated limestone contain mixtures of oil prone types i and ii high sulfur kerogen all the maturity parameters indicate immature to marginally mature stage of thermal transformation resulting from extremely low geothermal gradients in the area coupled with the observed burial history in addition to oil biogenic gases with a predominance of inorganic compounds co2 and h2s were recovered from the cretaceous carbonates the results of oil and gas analyses define the depositional environment during source rock accumulation and the subsequent thermal conditions it can be concluded that the biogenic gas accumulations in the pliocene quaternary sandstones in the northern adriatic area are the most prospective accumulations in the area

geochemical characteristics and origin of natural gas from wufeng longmaxi shales of the fuling gas field sichuan basin china abstract as the first giant shale gas field in china the fuling gas field has recently been regarded as one of the most important regions for natural gas exploration and production in the sichuan basin however the origin of natural gas from upper ordovician wufeng and the bottom of lower silurian longmaxi wl shales in the fuling gas field is poorly understood to limit a comprehensive understanding of gas generation accumulation and exploration in this work based on molecular and stable carbon isotopic composition of a total of 24 gas samples from five shale gas wells in the fuling field we analyzed the geochemical characteristics and gas origin and discussed the cause for the geochemical anomalies carbon isotopic reversals molecular composition results show that gases from the fuling gas field are dry and mainly composed of methane 97 9 98 9 with a very low level of ethane c2h6 propane c3h8 and non hydrocarbon gases mainly co2 and n2 these dry gases are classified as oil associated gas and mainly derived from secondary cracking due to the lack of gas samples across a maturation gradient from immature to late mature the wl gases in the fuling field show an unclear evolution trend between the 13c2 and wetness values however all these samples are located in the isotopic reversal zone carbon isotopes of gaseous alkanes clearly display full isotopic reversals 13c1 13c2 13c3 which is indicative of a relatively high thermal maturity and consistent with the measured vitrinite reflectance and modeled values 3 0 ro the observed complete carbon isotopic reversals in the wl gases are caused by a combination of several mechanisms in which isotope exchange at high temperature is the primary controlling factor other secondary factors include rayleigh type fractionation of c2h6 and c3h8 secondary cracking and gas diffusion mixing of gases at different thermal maturity levels

time reversal imaging of seismic sources and application to the great sumatra earthquake the increasing power of computers and numerical methods like spectral element methods allows continuously improving modelization of the propagation of seismic waves in heterogeneous media and the development of new applications in particular time reversal in the three dimensional earth the concept of time reversal hereafter referred to as tr was previously successfully applied for acoustic waves in many fields like medical imaging underwater acoustics and non destructive testing we present here the first application at the global scale of tr with associated reverse movies of seismic waves propagation by sending back long period time reversed seismograms we show that seismic wave energy is refocused at the right location and the right time of the earthquake when tr is applied to the sumatra andaman earthquake 26 dec 2004 the migration of the rupture from the south towards the north is retrieved therefore tr is potentially interesting for constraining the spatio temporal history of complex earthquakes

mapping and geochemical characterization of the toarcian organic matter in the mediterranean tethys and middle east organic matter from toarcian outcrops and boreholes in several basins around the mediterranean sea and middle east has been studied rock eval pyrolysis elemental analyses of kerogens and gas chromatography of chloroform extracts within these different basins have been used to determine the amount petroleum potential and type of the organic matter the results have been used to compile a mapping of the organic matter for the toarcian stage which shows heterogeneities in the distribution and type of organic matter 1 1 marine organic matter type ii occurs in different environments of deposition whereas high contents 5 total organic carbon correspond to thick deposits within the west european realm great britain north sea paris basin and germany the organic matter is less abundant in the mediterranean area where lower concentrations 1 2 toc preserved in lower toarcian thin levels are limited only to restricted basins northern italy greece 2 2 the predominance of continental organic matter type iii along the northern margin of the tethys corresponds to a deltaic environment 3 3 there is a predominance of altered organic matter within the carbonated platforms around the mediterranean tethys these results supplemented with the data issuing from the literature add a geochemical dimension to the paleogeography of the tethys

a common source rock for egyptian and saudi hydrocarbons in the red sea the northern red sea area hosts a classic triple junction of the red sea gulf of aqaba and gulf of suez rifted basins the sedimentary succession here can be divided into prerift pre miocene and synrift miocene and post miocene megasequences the prerift section has been penetrated in only a few wells drilled on the western egyptian side of the red sea whereas the synrift section is known on both the egyptian and the saudi sides of the red sea although the synrift units on both sides of the water are similar in facies thicknesses and depositional environments they have different stratigraphic nomenclatures the northern red sea consists of elongated troughs separated by elongated structural highs both of which trend northwest southeast gulf of suez trend these highs are dissected by cross elements trending northeast southwest gulf of aqaba trend and east northeast west southwest and are looked upon as strike slip faults dislocating these highs identified rich source rocks are present in the upper senonian carbonates the sudr and duwi formations on the western side of the sea the early miocene rudeis formation burqan group and the middle miocene kareem and belayim formations maqna group the pre miocene and the early miocene source rocks host oil prone kerogen whereas the middle and late miocene source rocks contain oil and gas prone kerogen all of these source rocks are sufficiently mature copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received january 18 1996 revised manuscript received october 11 1996 final acceptance march 21 1997 2faculty of science uae university p o box 17551 al ain united arab emirates we are especially grateful to the egyptian general petroleum corporation for supplying the materials and the necessary data on which the present work is based and the permission to publish it we also thank c g st c kendall and a e m nairn who read the early draft of this paper and offered valuable comments thanks to aapg reviewers d waples r j murris w maze and an anonymous reviewer for their constructive comments which we have used to improve our paper we acknowledge g cole bhp petroleum for granting permission to use some of his previous work

determination of critical parameters for evaluating coal measure shale gas in china abstract coal measure shale is one of the most abundant types of marine continental shales in china two sets of typical coal measure shales in china are developed in the shanxi formation ordos basin and in the longtan formation guizhou province in this study thermal simulation rock pyrolysis and x ray diffraction experiments were used to analyze four coal measure shale samples collected from typical areas of china based on the study of hydrocarbon generation process of the samples the lower limits of thermal maturity ro of favorable and target areas for coal measure shale were 1 8 and 2 5 respectively the threshold ro value of oil generation in coal measure shale was preliminarily inferred to be 0 6 the gaseous hydrocarbon production per unit of s1 s2 after the gas generation threshold was linearly and positively correlated with ro the lower limits of total organic carbon toc corresponding to the favorable and target areas were 2 45 wt and 2 84 wt respectively combined with x ray diffraction experiments the diagenetic stage and the hydrocarbon generation model of coal measure shale were established and could be divided into four evolutionary stages the results of this study have direct scientific and practical significance for the evaluation of gas content and selection of areas in china for the extraction of coal measure shale

generation of topographic waves over the continental margin abstract numerical experiments were carried out to simulate the generation of topographic waves by a gulf stream ring over the continental margin in a stratified ocean on an f plane the study was aimed at understanding the combined effect of density advection and bottom topography on the flow field the momentum equation is linear and nonlinearity is introduced in the density equation the mechanism of wave generation was investigated by turning on and off the nonlinear density advection and by changing the strength of the ring and bottom topography the results show that topographic waves are generated by advection of density in a ring over a sloping bottom the vorticity associated with the swirl velocity of a ring is less important during wave generation the strength of a ring affects the wave amplitude in the case of a strong ring self advection of density may be induced at the surface however the generation and propagation of topographic waves are independent of the strength of the ring waves

expulsion of petroleum hydrocarbons from shale source rocks there is compelling evidence that movement of petroleum from organic rich shales into sandstones and limestones occurs in the subsurface1 this expulsion of material must occur if crude oil accumulations are to form and it is termed primary migration2 earlier studies3 4 suggested that this movement occurs with chemical fractionation some components are more mobile than others one of the agents of expulsion at early maturity stages is compaction which is not only capable of forcing water but also organic components out of the pore network of a source rock2 5 6 because the fractionation effects associated with expulsion provide clues to the transport mechanisms involved we have made detailed quantitative comparisons of the hydrocarbons of shales of different thicknesses the centre and edges of thick shales and sandstones adjacent to shales from two cored interbedded shale and sandstone sequences from spitsbergen island svalbard norway these observations confirm considerable movement of hydrocarbons in the subsurface with lower molecular weight components being more mobile up to 90 the original amount of n pentadecane may be lost from very thin shales sandwiched between sandstone horizons and from shales close to a lithological boundary with sandstone

integrated seismic source model of the 2015 gorkha nepal earthquake we compared spatiotemporal slip rate and high frequency around 1 hz radiation distributions from teleseismic p wave data to infer the seismic rupture process of the 2015 gorkha nepal earthquake for these estimates we applied a novel waveform inversion formulation that mitigates the effect of green s functions uncertainty and a hybrid backprojection method that mitigates contamination by depth phases our model showed that the dynamic rupture front propagated eastward from the hypocenter at 3 0 km s and triggered a large slip event centered about 50 km to the east it also showed that the large slip event included a rapid rupture acceleration event and an irregular deceleration of rupture propagation before the rupture termination heterogeneity of the stress drop or fracture energy in the eastern part of the rupture area where aftershock activity was high inhibited rupture growth high frequency radiation sources tended to be in the deeper part of the large slip area which suggests that heterogeneity of the stress drop or fracture energy there may have contributed to the damage in and around kathmandu

13c nuclear magnetic resonance studies of kerogen from cretaceous black shales thermally altered by basaltic intrusions and laboratory simulations cretaceous black shales from dsdp leg 41 site 368 in the eastern atlantic ocean were thermally altered during the miocene by an intrusive basalt the sediments overlying and underlying the intrusive body were subjected to high temperatures up to 500 c and as a result their kerogen was significantly altered the extent of this alteration has been determined by examination by means of 13c nuclear magnetic resonance using cross polarization magic angle spinning cp mas results indicate that the kerogen becomes progressively more aromatic in the vicinity of the intrusive body laboratory heating experiments simulating the thermal effects of the basaltic intrusion produced similar results on unaltered shale from the drill core the 13c cp mas results appear to provide a good measure of thermal alteration

time and temperature in petroleum formation application of lopatin s method to petroleum exploration n v lopatin in the soviet union has developed a method for taking both time and temperature into account as factors in thermal maturation of kerogen lopatin s time temperature index of maturity tti values correlate with the thermal regimes corresponding to generation and preservation of hydrocarbons because such information is potentially of great interest for oil exploration a calibration and evaluation have been made of lopatin s method within the limitations of the data presently available the following statements can be made 1 the rate of the chemical reactions involved in thermal maturation of organic material appears to double with every 10 c 18 f rise in temperature 2 threshold values of lopatin s time temperature index of maturity tti are 15 onset of oil generation 75 peak oil generation 160 end oil generation 500 40 oil preservation deadline 1 000 50 oil preservation deadline 1 500 wet gas preservation deadline 65 000 dry gas preservation deadline 3 tti values calculated from lopatin reconstructions consistently agree with other maturation parameters commonly used by petroleum geochemists potential applications of lopatin s method for oil exploration include timing of oil generation calculation of volume of hydrocarbons generated within a basin and determination of economic deadlines

the 2010 mw 8 8 chile earthquake triggering on multiple segments and frequency dependent rupture behavior 1 multi frequency back projection results of the february 27 2010 mw 8 8 chile earthquake reveal that this earthquake consists of distinct subevents with different slip characteristics the subevent south of the epicenter releases its energy at low frequencies 0 05 0 1 hz implying slow slip and has a rupture speed around 0 8 km s two subevents north of the epicenter are characterized by high frequency energy 1 5 hz release the first of these subevents appears to trigger slip on the second segment to the north which has higher amplitude energy release and a fast propagation speed of about 2 9 km s in addition to these rupture details high frequency energy release is observed at the rupture front followed by lower frequency energy release this observation suggests that the rupture of large earthquakes involves dynamic weakening of faults and hence their rupture properties may not be related easily to those of small earthquakes these distinct slip behaviors point out the need to consider data from a wide range of frequencies to fully assess the rupture process and associated hazards of giant earthquakes

concepts for estimating hydrocarbon accumulation and dispersion the present volume and composition of trapped hydrocarbons are temporary events controlled by the interacting volumes of trap oil and gas all of which change through time thus both the volume and type of trapped hydrocarbon result from the interacting effects of kerogen amount type and maturity gas and oil migration efficiencies trap growth and the possibility that free gas may displace trapped liquids by estimating the historical evolving effects of each factor we can estimate trapped hydrocarbon volume as well as trap content i e only oil oil leg and gas cap or only gas the procedures that lead to such estimates are 1 estimate the quantities of oil and gas provided by the source within the drainage area 2 estimate the quantities of gas lost by dissolution and diffusion 3 estimate the trap volume and 4 compare hydrocarbon volumes with trap volume to find the limiting volume

paleoreconstruction by biological markers abstract during diagenesis and conversion of the original lipid fraction of biological systems to petroleum hydrocarbons the following four basic events needed for paleoreconstruction can be monitored by biological markets 1 sourcing 2 maturation 3 migration and 4 biodegradation actual cases of applying biological markers to petroleum exploration problems in different parts of the world are demonstrated cretaceous and phosphoria sourced oils in the wyoming thrust belt can clearly be distinguished from one another by high quality source fingerprinting of biomarker terpanes using gas chromatography mass spectrometry identification of recently discovered biological markers head to head isoprenoids allows subtle source differentiation between oils from sumatra the degree of crude oil maturation in basins from california alaska russia wyoming and louisiana can be assessed by specific novel biomarker ratios 20s 20r sterane epimers field evidence from such interpretation is confirmed by laboratory pyrolysis of the rock an example of immature sumatra rock is given extensive migration is documented by biomarkers in several oils the effect of biodegradation on biomarker steranes and terpanes is exemlified in a california basin all biological marker results are consistent with the geological setting and add a new dimension in assisting the petroleum explorationist toward paleo reconstruction

geodetic data inversion based on bayesian formulation with direct and indirect prior information summary mechanical interaction between adjacent plates which causes crustal deformation in plate boundary zones is rationally represented by tangential displacement discontinuity fault slip at plate interfaces given fault slip distribution we can compute surface displacements on the basis of elastic dislocation theory thus we can determine the functional form of a stochastic model to extract information about unknown fault slip distribution from observed surface displacement data in addition to observed data we usually have prior information for example plate tectonics postulates that primary fault slip is parallel to relative plate motion this is direct prior information that bounds the values of model parameters within certain ranges from physical consideration we may impose prior constraint on the roughness of fault slip distribution this is indirect prior information that regulates the structure of stochastic models by combining the direct and indirect prior information with observed data in a proper way we constructed a bayesian model for geodetic data inversion which has a hierarchic flexible structure controlled by hyper parameters the optimum values of hyper parameters are objectively determined from observed data by using akaike s bayesian information criterion abic the inversion formula derived from the bayesian model unifies the jackson matsu ura formula with direct prior information and the yabuki matsu ura formula with indirect prior information in a rational way we demonstrated the effectiveness of the unified inversion formula through the analysis of the surface displacement data associated with the 1923 kanto earthquake in the analysis with direct and indirect prior information we obtained the bimodal distribution of fault slip almost parallel to plate convergence on the north american philippine sea plate interface if we ignore the direct prior information in the analysis additional significant distribution of fault slip perpendicular to plate convergence appears to the east which is incomprehensible from plate tectonics

supershear rupture on multiple faults for the mw 8 6 off northern sumatra indonesia earthquake of april 11 2012 1 we perform a back projection method to image the rupture propagation and short period energy release of the 2012 off northern sumatra earthquake mw8 6 using hi net data recorded in japan the results show a complex pattern of four conjugate faults over about 180 sec there is a striking correspondence between the lengths and orientations of our rupture pattern with the distribution of aftershocks each of the first three stages of the rupture corresponds to a clear lineation in the aftershocks with lengths of 200 to 400 km rupture speeds for several of the fault segments were very high about 5 km s and exceed the local s wave velocity this is the first example of an oceanic earthquake with supershear rupture speed

submesoscale cyclones in the agulhas current gliders were deployed for the first time in the agulhas current region to investigate processes of interactions between western boundary currents and shelf waters continuous observations from the gliders in water depths of 100 1000 m and over a period of 1 month provide the first high resolution observations of the agulhas current s inshore front the observations collected in a nonmeandering agulhas current show the presence of submesoscale cyclonic eddies generated at the inshore boundary of the agulhas current the submesoscale cyclones are often associated with warm water plumes which extend from their western edge and exhibit strong northeastward currents these features are a result of shear instabilities and extract their energy from the mean agulhas current jet

relationships between thermal maturity indices calculated using arrhenius equation and lopatin method implications for petroleum exploration thermal maturity can be calculated with time temperature indices tti based on the arrhenius equation using kinetics applicable to a range of types ii and iii kerogens these ttis are compared with tti calculations based on the lopatin method and are related theoretically and empirically via vitrinite reflectance to the petroleum generation window the ttis for both methods are expressed mathematically as integrals of temperature combined with variable linear heating rates for selected temperature intervals heating rates control the thermal maturation trends of buried sediments relative to arrhenius ttis lopatin ttis tend to underestimate thermal maturity at high heating rates and overestimate it as low heating rates complex burial histories applicable to a range of tectonic environments illustrate the different exploration decisions that might be made on the basis of independent results of these two thermal maturation models

subevent location and rupture imaging using iterative backprojection for the 2011 tohoku mw 9 0 earthquake summary knowledge of the rupture speed and spatial temporal distribution of energy radiation of earthquakes is important for earthquake physics backprojection of teleseismic waves is commonly used to image the rupture process of large events the conventional backprojection method typically performs temporal and spatial averaging to obtain reliable rupture features we present an iterative backprojection method with subevent signal stripping to determine the distribution of subevents large energy bursts during the earthquake rupture we also relocate the subevents initially determined by iterative backprojection using the traveltime shifts from subevent waveform cross correlation which provides more accurate subevent locations and source times a bootstrap approach is used to assess the reliability of the identified subevents we apply this method to the mw 9 0 tohoku earthquake in japan using array data in the united states we identify 16 reliable subevents in the frequency band 0 2 1 hz which mostly occurred around or west of the hypocentre in the downdip region analysis of tohoku aftershocks shows that depth phases can often produce artefacts in the backprojection image but the position and timing of our main shock subevents are inconsistent with depth phase artefacts our results suggest a complicated rupture with a component of bilateral rupture along strike the dominant energy radiation between 0 2 and 1 hz is confined to a region close to the hypocentre during the first 90 s a number of subevents occurred around the hypocentre in the first 90 s suggesting a low initial rupture speed and repeated rupture or slip near thehypocentre therupturereachedthecoastalregionabout106kmnorthwestofthehypocentreat43sandtheregionabout110kmnorthofthehypocentreat105swithanorthwardrupture speed 2 0 kms 1 at 60 110 s after 110 s a series of subevents occurred about 120 220 km southwest of the hypocentre consistent wit ha3k ms 1 along strike rupture speed the abundant high frequency radiation in the downdip region close to the coast suggests intermittent rupture probably in the brittle ductile transition zone the lack of high frequency radiation in the updip region suggests the rupture near the trench was more continuous probably due to more homogeneous frictional properties of the shallow slab interface the lack of early aftershocks in the updip region indicates that most of the accumulated slip in the updip region during the interseismic period was probably released during the main shock

role of diffusion in primary migration of hydrocarbons the following effective diffusion coefficients d cm2 sec were determined for the diffusion of light hydrocarbons through the water saturated pore space of shales methane 2 12 10 6 ethane 1 11 10 6 propane 5 55 10 7 iso butane 3 75 10 7 n butane 3 01 10 7 n pentane 1 57 10 7 n hexane 8 20 10 8 n heptane 4 31 10 8 and n decane 6 08 10 9 on the basis of these new data a deterministic dynamic model was set up to simulate the diffusive transport of light hydrocarbons c1 to c10 from source rocks for eight documented source rock units representing a wid range of geologic conditions maturities of 0 40 to 1 35 mean vitrinite reflectance oil to gas prone kerogens the cumulative amounts of hydrocarbons escaping with time were calculated thus it was shown that diffusion represents an effective process for primary migration of gas but not for oil the rate of mass transport for gas from source rocks with geologic time can be sufficiently high to account for the origin of commercial size gas fields for example a cumulative amount of 109 kg of methane 1 5 109 std m3 or 5 3 1010 scf has escaped by diffusion in 540 000 years from a certain volume 1 000 km2 by 200 m thick of a high mature gas prone mesozoic source rock in western canada the origin of hydrocarbon accumulations with high gas to oil ratios in low mature sediments in geologically young basins early gases and condensates can be explained by an early phase of primary migration predominantly based on diffusion during the initial stages of the accumulation history of those fields extending up to millions of years under certain conditions the reservoir gas changes with geologic time from a methane rich to a wet gas composition at low maturity levels below about 0 6 rm even oil prone source rocks yield methane rich light hydrocarbon mixtures by migration through diffusion compositional trends among reservoir gases of several multiple pay gas fields in louisiana represent evidence for diffusive transport of hydrocarbons the variation in gas composition between the individual pay zones is controlled by increasing distances of diffusive transport of the hydrocarbons from a uniform source rock at depth to their present accumulation sites in the shallow pay zones compounds of high diffusivity are enriched for example in the sligo gas field of louisiana the methane ethane and the iso butane n butane ratios increase from 10 2 to 36 0 and from 0 86 to 1 13 respectively from the deepest to the shallowest of the five productive reservoir sands which are spread over a a depth interval of 5 500 ft 1 676 m diffusion of light hydrocarbons in the subsurface can also have economically adverse effects for example existing gas accumulations can be destroyed by dissipation the rate of this destruction was calculated for the harlingen gas field holland by diffusive loss through 400 m of shale cap rock the initial amount of methane in place of 1 93 109 std m3 6 8 1010 scf is reduced by one half over a period of 4 5 million years this leads us to propose the concept that large gas accumulations can persist through extended periods of geologic time only as dynamic systems reaching some kind of steady state equilibrium between diffusive loss through the cap rock and continuous replenishment from the source rock

geochemical characterization of organic facies in the dugi otok basin the adriatic sea yugoslavia sediments in the dugi otok basin are predominantly of upper and lower cretaceous age to characterize the organic facies we used geochemical analyses of core samples from different wells and a few outcrop samples geochemical data indicate that the carbonate sequences of the lower cretaceous represent a good source rock section with a high potential for petroleum the source rocks consist both of dark grey uniform micritic limestones and highly bituminous laminated limestones they are associated with oil stains and bitumen impregnations the organic matter is predominantly of marine origin algal sapropelic with a minor input of terrestrial components the extract contents of the samples are anomalously high but contain variable amounts of hydrocarbons and low saturated aromatic hydrocarbon ratios the maturation stage is immature to marginally mature as characterized by a high proportion of resins and asphaltenes with high sulphur content an even predominance of n alkanes a high ratio of acyclic isoprenoids to n alkanes pr ph 1 and a tmax around 430 c the organic facies in the dugi otok basin varies as it is possible to find both organic rich and oxidized organic lean sediments differences in organic facies have been caused by many changes in the depositional environment with tectonic processes contributing to the heterogeneity of the organic facies

petrographic and geochemical characterization of microfacies in a lacustrine shale oil system in the dongying sag jiyang depression bohai bay basin eastern china abstract petrology and rock eval analyses have been conducted in the lower third and upper fourth members lower es3 and upper es4 of the shahejie fm source rock intervals in well fanye1 in the dongying sag jiyang depression bohai bay basin eastern china the organic matter in rocks intersected by this well is dominated by lamalginite and bituminite and most samples contain type i or ii kerogen microfacies a h has been identified according to their organic mineral composition and structure using polished thin sections under microscopy the form and location of hydrocarbon residue occurrences mainly as solid bitumen with fluorescence are different in those microfacies microfacies a which is dominant in well fanye 1 is calcareous mudstone without lamination and the hydrocarbon residue is dispersed through the rock with some being present in subtle microfractures microfacies b and f are mostly composed of shale with adsorbed hydrocarbon indicated by fluorescence along mineral grains microfacies c is laminated argillaceous carbonate with hydrocarbon residue mainly occurring in thin microfractures along the bedding plane microfacies d and e are mainly carbonate and microfacies d is laminated with micrite and sparite and hydrocarbon residue occurrence is not only in the microfractures along the bedding but also in the micropores among the grains in the sparite layers which is the main place for hydrocarbon residue occurrence in microfacies type e without lamination microfacies g and h are both micrite microfacies g shows bioturbation and hydrocarbon residue occurs within small irregular microfractures along the bedding planes and pores only a little solid bitumen without fluorescence has been observed in microfacies h the rock eval oil saturation index osi s1 100 toc value is variable because of the different characteristics of these hydrocarbon residue occurrences osi values in microfacies a are normally high 74 8 242 8 mg hc g toc average of 117 2 mg hc g toc and likely much higher if microfractures develop 200 mg hc g toc osi values averaging 43 7 mg hc g toc are lowest in microfacies f because of adsorption on the shales and osi values are the highest in microfacies d 371 3 mg hc g toc and e 199 9 mg hc g toc since the hydrocarbon residues are stored both in microfractures and pores between the grains both osi values are high in microfacies g and h because of low toc content the combination of petrographic and osi analysis appear to be a promising tool for characterizing shale oil systems

rupture evolution of the 2006 java tsunami earthquake and the possible role of splay faults abstract the 2006 mw 7 8 java earthquake was a tsunami earthquake exhibiting frequency dependent seismic radiation along strike high frequency global back projection results suggest two distinct rupture stages the first stage lasted 65 s with a rupture speed of 1 2 km s while the second stage lasted from 65 to 150 s with a rupture speed of 2 7 km s high frequency radiators resolved with back projection during the second stage spatially correlate with splay fault traces mapped from residual free air gravity anomalies these splay faults also colocate with a major tsunami source associated with the earthquake inferred from tsunami first crest back propagation simulation these correlations suggest that the splay faults may have been reactivated during the java earthquake as has been proposed for other tsunamigenic earthquakes such as the 1944 mw 8 1 tonankai earthquake in the nankai trough

limitations of use of organic petrographic techniques for identification of petroleum source rocks organic petrographic and organic geochemical studies have been conducted on 58 sediment samples of differing ages and depositional environments in this study interpretations of petroleum source rock potential based on data from transmitted light microscopy show a poor correlation with those derived from chemical data this lack of correlation arises from the failure to distinguish consistently between hydrogen poor and hydrogen rich amorphous organic matter and inability to detect hydrogen rich components exinite and resinite in coal fragments interpretations based on data from reflected light microscopy show a better correlation with those derived from chemical studies but difficulties still remain these difficulties arise from inability except on the basis of luorescence intensity to distinguish hydrogen rich from hydrogen poor organic matter in a finely dispersed state

rupture details of the 28 march 2005 sumatra mw 8 6 earthquake imaged with teleseismic p waves 1 we image the rupture of the 28 march 2005 sumatra mw 8 6 earthquake by back projecting teleseismic p waves recorded by the global seismic network and the japanese hi net to their source the back projected energy suggests that the rupture started slowly had a total duration of about 120 s and propagated at 2 9 to 3 3 km s from the hypocenter in two different directions first toward the north for 100 km and then after a 40 s delay toward the southeast for 200 km our images are consistent with a rupture area of 40 000 km2 the locations of the first day of aftershocks and the harvard cmt mw of 8 6 which implies an average slip of 6 m the earthquake is similar in its location size and geometry to a mw 8 5 event in 1861 our estimated average slip is consistent with a partially coupled subduction interface gps forearc velocities and the 59 mm yr convergence rate if the 2005 earthquake released elastic strain that accumulated over many hundreds of years rather than just since the last 1861 event

rupture process of the 2011 tohoku oki earthquake and absolute elastic strain release 1 on 11 march 2011 the tohoku oki earthquake in eastern japan and the devastating tsunami that followed it caused severe damage and numerous deaths to clarify the rupture process of the earthquake we inverted teleseismic p wave data applying a novel formulation that takes into account the uncertainty of green s function which has been a major error source in waveform inversion the estimated seismic moment is 5 7 1022 nm mw 9 1 associated with a fault rupture 440 km long and 180 km wide along the plate interface the source process is characterized by asymmetric bilateral rupture propagation but we also found continuous slips up dip from the hypocenter which led to a large maximum slip 50 m long slip duration 90 s and a large stress drop 20 mpa the long slip duration large stress drop extensional normal faulting aftershocks in a previously compressional stress regime and low angle normal slips at approximately the depth of the plate interface suggest that the earthquake released roughly all of the accumulated elastic strain on the plate interface owing to exceptional weakening of the fault the stress accumulated on the plate interface was about 20 mpa near the trench and 0 10 mpa in the down dip source region

a novel approach for recognition and quantification of hydrocarbon migration effects in shale sandstone sequences a detailed organic geochemical study of over 150 samples from two cores with a total combined length of 320 m 1 050 ft through sequences of interbedded source rock type shales 0 84 rm maturity and reservoir sandstones allowed recognition and quantitation of a number of migration effects detailed gas chromatography mass spectrometry of steranes and triterpanes was used to insure that samples being compared to investigate migration effects contain organic matter of a similar type thin shales interbedded in sands and the edges of thick shale units are depleted in petroleum range hydrocarbons to a much higher degree than the centers of thick shale units for the alkanes expulsion occurs with pronounced compositional fractionation effects shorter chain length n alkanes are expelled preferentially and isoprenoid alkanes are expelled to a lesser degree than their straight chain isomers based on material balance calculations expulsion efficiencies were determined and found to be very high in certain instances for thin interbedded shales they decrease from about 80 around c15 to near zero in the c25 region there is no evidence for significant redistribution of steranes and triterpanes in the two sequences compared to c15 to c25 n alkanes they appear relatively immobile the composition of the hydrocarbons impregnating parts of the reservoir sandstones is in agreement with expulsion occurring with pronounced fractionation based on molecular chain length hence consideration of bulk expulsion efficiencies gives an unrealistic picture furthermore the impregnation of a siltstone cap rock from an underlying hydrocarbon accumulation seems to have occurred by bulk oil migration and without significant fractionation the degree of hydrocarbon depletion of some of the shales of both sequences appears to be controlled by compaction and the primary migration process appears to have occurred with chromatographic separation the migration phenomena observed in both sequences lead us to propose that the main phase of expulsion can be preceded by an earlier sta e during which the edges of thick shales and thin interbedded shales appear to be slowly and continuously depleted by the chromatographic processes the composition of the hydrocarbon product accumulating in the reservoirs at this stage appears to be controlled primarily by physical processes rather than by the type and maturity of the organic matter in the generating source rock by this mechanism the origin of accumulations of light oils and gas condensates in low mature sequences bearing predominantly terrestrial derived organic matter can be explained finally the migration effects documented in this study have some consequences for interpretation of geochemical data e g the pristane n c17 ratio a commonly accepted maturity parameter has been shown to be also controlled by the degree of hydrocarbon expulsion

depth dependence of rupture velocity in deep earthquakes 1 explaining deep seismicity is a long standing challenge in earth science between 300 and 700 km depth earthquakes are scarce except between 530 and 600 km where the majority of events occur by imaging the seismic rupture process for a set of recent deep earthquakes using the back projection of teleseismic p waves we found that the rupture velocities are less than 60 of the shear wave velocity except in the depth range of 530 to 610 km we propose that large fracture surface energy gc values for deep earthquakes generally prevent the acceleration of dynamic rupture propagation and generation of earthquakes between 300 and 700 km depth whereas small gc value in the exceptional depth range promote dynamic rupture propagation and explain the seismicity peak near 600 km

kerogen origin evolution and structure kerogen commonly defined as the insoluble macromolecular organic matter om dispersed in sedimentary rocks is by far the most abundant form of om on earth this fossil material is of prime importance as the source of oil and natural gas moreover kerogen can provide essential information on major topics such as past environments climates and biota this review reports the main advances in kerogen studies since the comprehensive synthesis edited by durand durand b ed kerogen insoluble organic matter from sedimentary rocks editions technip paris 1980 it is organized into eight sections the first two are concerned with the successive definitions of kerogen and the definition used here the different techniques used for kerogen isolation without loss or degradation and basic kerogen analysis the third and fourth focus on sedimentary om sources and preservation processes in relation to depositional environment including sedimentation conditions favourable for kerogen accumulation and extrapolation to past geological time great strides have been made in the latter topics over the last 25 years owing to a combination of classical studies in organic geochemistry and studies in other domains such as biogeochemistry oceanography hydrology and soil science along with the development of powerful analytical tools the next two sections deal with the different kerogen classifications by type and kerogen evolution and maturation upon burial in sediments structural modelling of coal and kerogen based on physical and or chemical structural analysis is described in the following section although only statistical the models thus derived provide a synthetic view of the main structural resemblances and differences among various samples in relation to source maturity or physicochemical properties finally the last section explores some of the advances in kerogen understanding expected for the near future the review includes a list containing about 500 references

synthetic source inversion tests with the full complexity of earthquake source processes including both supershear rupture and slip reactivation recent studies in dynamic source modeling and kinematic source inversion show that earthquake rupture may contain greater complexity than we previously anticipated including multiple slipping at a given point on a fault finite source inversion methods suffer from the nonuniqueness of solutions and it may become more serious if we aim to resolve more complex rupture models in this study we perform synthetic inversion tests with dynamically generated complex rupture models including both supershear rupture and slip reactivation to understand the possibility of resolving complex rupture processes by inverting seismic waveform data we adopt a linear source inversion method with multiple windows allowing for slipping from the nucleation of rupture to the termination at all locations along a fault we regularize the model space effectively in the bayesian framework and perform multiple inversion tests by considering the effect of inaccurate green s functions and station distributions we also perform a spectral stability analysis our results show that it may be possible to resolve both a supershear rupture front and reactivated secondary slipping using the linear inversion method if those complex features are well separated from the main rupture and produce a fair amount of seismic energy it may be desirable to assume the full complexity of an earthquake rupture when we first develop finite source models after a major event occurs and then assume a simple rupture model for stability if the estimated models do not show a clear pattern of complex rupture processes

teleseismic p wave imaging of the 26 december 2004 sumatra andaman and 28 march 2005 sumatra earthquake ruptures using the hi net array 1 seismograms from a dense high quality seismic network in japan are used to investigate the characteristics of the 26 december 2004 sumatra andaman and the 28 march 2005 sumatran earthquakes the onset of the p waveforms are aligned through cross correlation and a simple concept of back projecting seismic energy to a grid of potential source locations is applied the waveform alignment removes the effects due to lateral variations in wave speed between the hypocenter and each station to better approximate the effects of three dimensional heterogeneity for paths originating from grid points away from the hypocenter cross correlation results of the p waveforms from aftershocks are introduced this additional information leads to improved resolution of smaller scale features near many of the aftershocks by reducing wavefront distortion the back projection analysis provides a quick assessment of the spatiotemporal extent and variability of relative high frequency energy release which can be translated into an estimate of the moment magnitude as well as an unparalleled view of high frequency rupture propagation the results are in general consistent with those obtained from more involved source inversion methods the 2004 sumatra andaman earthquake released most energy in a region northwest of the sumatra island and the rupture extended to the northern andaman islands about 1300 km from the epicenter this northern portion of the rupture radiated a considerable amount of energy but there is little evidence of slow slip the 2005 event is imaged to have bilateral rupture with northwestern slip occurring for about 50 s before it moved to the southeast of the epicenter

insights into the mechanism of intermediate depth earthquakes from source properties as imaged by back projection of multiple seismic phases 1 this study investigates the spatial and temporal distribution of energy release of large intermediate depth earthquakes using a modified back projection technique first used to study the 2004 sumatra andaman megathrust event multiple seismic phases are included in the back projection analysis which provides the capability to determine the energy distribution with respect to depth and time a total of 22 intermediate depth earthquakes with moment magnitudes greater than or equal to 6 5 are investigated with hypocentral depths between 100 and 300 km for most of these events the vertical extent of energy release is either below the resolution of this study 5 km or slightly above 15 km this observation agrees with previous studies that find large intermediate depth earthquakes have subhorizontal rupture planes the results also show a significant portion of the events have multiple rupture planes that are well separated in depth the closeness in time of the ruptures on separate planes and the distance between the planes suggest dynamic triggering where the p waves from the first rupture initiate rupture on the second plane we propose that a dehydration embrittlement mechanism combined with preferentially hydrated subhorizontal faults can explain the observations of dominant subhorizontal rupture planes and the frequent occurrence of rupture complexity involving multiple subevents

a global search inversion for earthquake kinematic rupture history application to the 2000 western tottori japan earthquake 1 we present a two stage nonlinear technique to invert strong motions records and geodetic data to retrieve the rupture history of an earthquake on a finite fault to account for the actual rupture complexity the fault parameters are spatially variable peak slip velocity slip direction rupture time and risetime the unknown parameters are given at the nodes of the subfaults whereas the parameters within a subfault are allowed to vary through a bilinear interpolation of the nodal values the forward modeling is performed with a discrete wave number technique whose green s functions include the complete response of the vertically varying earth structure during the first stage an algorithm based on the heat bath simulated annealing generates an ensemble of models that efficiently sample the good data fitting regions of parameter space in the second stage appraisal the algorithm performs a statistical analysis of the model ensemble and computes a weighted mean model and its standard deviation this technique rather than simply looking at the best model extracts the most stable features of the earthquake rupture that are consistent with the data and gives an estimate of the variability of each model parameter we present some synthetic tests to show the effectiveness of the method and its robustness to uncertainty of the adopted crustal model finally we apply this inverse technique to the well recorded 2000 western tottori japan earthquake mw 6 6 we confirm that the rupture process is characterized by large slip 3 4 m at very shallow depths but differently from previous studies we imaged a new slip patch 2 2 5 m located deeper between 14 and 18 km depth

origin migration and entrapment of natural gas in alberta deep basin part 1 abstract the alberta deep basin situated along the northeastern front of the rocky mountain belt is the deepest part of the alberta synclinal sedimentary basin this trough shaped deep basin extending across northwestern alberta and into northeastern british columbia covers an area of 65 000 km2 25 000 mi2 enormous volumes of natural gas have been found in recent years within the thick clastic mesozoic sediments which partly fill the deep basin these sediments exceed 3 100 m 10 200 ft in total thickness based on detailed geochemical analyses of more than 300 rock samples mainly cutting samples from several wells in the elmworth gas field information was obtained on the hydrocarbon source strata and the generation and redistribution of hydrocarbons the clastic mesozoic rock section contains numerous shaly zones which are very rich in organic matter and also a suite of coal strata this section containing mainly type iii kerogen is the ideal gas generator maturity ranges from about 0 5 vitrinite reflectance to about 2 0 in the deeper part of the section maturity has also been defined in terms of the methylphenanthrene index which is based on aromatic hydrocarbons apparently the mature section is still in an active phase of hydrocarbon generation due to the tightness of the rocks hydrocarbon transport mechanisms seem to be dominated by diffusion processes the light hydrocarbon distribution patterns observed throughout the wells suggest a dynamic trapping mechanism light hydrocarbons are lost at the top of the mature ydrocarbon generating zone and are replenished in the middle part of the section where rich source rocks are found end of article last page 642

upper cretaceous organic rich laminated limestones of the adriatic carbonate platform island of hvar croatia several organic rich samples taken from upper santonian late campanian laminated limestones of hvar island croatia were investigated to characterize palynofacies macerals type of organic matter and organic geochemistry these characterizations as well as the reconstruction of the depositional environment are interpreted in terms of a source rock perspective the results suggest that the laminated limestones were formed within shallow depressions of the carbonate platform in an anoxic restricted marine environment with increased salinity the hvar island laminated limestones contain type ii s kerogen and they are found to be marginally mature and oil prone

rupture imaging of the mw 7 9 12 may 2008 wenchuan earthquake from back projection of teleseismic p waves 1 the mw 7 9 wenchuan earthquake of 12 may 2008 was the most destructive chinese earthquake since the 1976 tangshan event tens of thousands of people were killed hundreds of thousands were injured and millions were left homeless here we infer the detailed rupture process of the wenchuan earthquake by back projecting teleseismic p energy from several arrays of seismometers this technique has only recently become feasible and is potentially faster than traditional finite fault inversion of teleseismic body waves therefore it may reduce the notification time to emergency response agencies using the iris dmc we collected 255 vertical component broadband p waves at 30 95 from the epicenter we found that at periods of 5 s and greater nearly all of these p waves were coherent enough to be used in a global array we applied a simple down sampling heuristic to define a global subarray of 70 stations that reduced the asymmetry and sidelobes of the array response function arf we also considered three regional subarrays of seismometers in alaska australia and europe that had apertures less than 30 and p waves that were coherent to periods as short as 1 s individual arfs for these subarrays were skewed toward the subarrays however the linear sum of the regional subarray beams at 1 s produced a symmetric arf similar to that of the groomed global subarray at 5 s for both configurations we obtained the same rupture direction rupture length and rupture time we found that the wenchuan earthquake had three distinct pulses of high beam power at 0 23 and 57 s after the origin time with the pulse at 23 s being highest and that it ruptured unilaterally to the northeast for about 300 km and 110 s with an average speed of 2 8 km s it is possible that similar results can be determined for future large dip slip earthquakes within 20 30 min of the origin time using relatively sparse global networks of seismometers such as those the usgs uses to locate earthquakes in near real time

recent advances in petroleum geochemistry applied to hydrocarbon exploration this paper presents a critical review of recent advances in the study of generation maturation and migration of petroleum the different source potentials for generating hydrocarbons depend on the type of kerogen in addition to the classic types i ii and iii a residual oxidized organic matter is also observed which has no potential for hydrocarbon generation coal is widely considered as a potential source for gas but some coals may generate sizeable amounts of oil as well the development of routine analytical tools particularly pyrolysis makes possible the preparation of geochemical logs that are the basis for screening samples and for interpreting other analyses among optical techniques the major subjects of discussion concern the nature of amorphous organ c matter which may encompass different chemical types of kerogen and the applicability of vitrinite reflectance techniques to type i and ii kerogens following important advances in identification of biological markers in sediments and crude oils these markers are used for oil source rock correlation and proposed for reconstruction of depositional environment and subsequent thermal evolution migration of hydrocarbons is now better understood and the importance of a hydrocarbon phase migration is widely recognized overpressuring of pore fluids is mainly responsible for expulsion of petroleum geologic models of basin evolution subsidence compaction thermal history and geochemical models hydrocarbon generation and migration become progressively available their integration int a comprehensive model should be one of the major developments in future petroleum exploration

impact of cretaceous sea level rise and anoxic events on the mesozoic carbonate platform of yugoslavia the adriatic dinaric carbonate platform of yugoslavia was influenced by rapid sea level rise and an oceanic anoxic event during the cenomanian turonian open marine biota such as planktonic foraminifera radiolarians and locally even ammonites associated with and bracketed by successions of typical shallow water carbonates indicate partial drowning of substantial areas of the platform during this time suggestive furthermore that the rate of increase of water depth was locally great enough to outpace carbonate production the presence of carbon rich and fish bearing platy limestones commonly cherty as an associated coeval facies indicates the development of anoxic or euxinic environments and the stromatolitic laminations in such rocks are attributed to the action of bacterial mats it is suggested that an extensive column of deoxygenated water developed in the neighboring marche umbrian adriatic deep water basin and was carried on to the carbonate platform during the cenomanian turonian transgression

inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 imperial valley california earthquake a least squares point by point inversion of strong ground motion and teleseismic body waves is used to infer the fault rupture history of the 1979 imperial valley california earthquake the imperial fault is represented by a plane embedded in a half space where the elastic properties vary with depth the inversion yields both the spatial and temporal variations in dislocation on the fault plane for both right lateral strike slip and normal dip slip components of motion inversions are run for different fault dips and for both constant and variable rupture velocity models effects of different data sets are also investigated inversions are compared which use the strong ground motions alone the teleseismic body waves alone and simultaneously the strong ground motion and teleseismic records the inversions are stabilized by adding both smoothing and positivity constraints the moment is estimated to be 5 0 10 25 dyne cm and the fault dip 90 5 dislocation in the hypocentral region south of the united states mexican border is relatively small and almost dies out near the border dislocation then increases sharply north of the border to a maximum of about 2 m under interstate 8 dipslip motion is minor compared to strike slip motion and is concentrated in the sediments the best fitting constant rupture velocity is 80 per cent of the local shear wave velocity however there is a suggestion that the rupture front accelerated from the hypocenter northward the 1979 imperial valley earthquake can be characterized as a magnitude 5 earthquake at the hypocenter which then grew into or triggered a magnitude 6 earthquake north of the border

a geostrophic vortex over a slope abstract nonlinear quasigeostrophic f plane vortices in two layers over a topographic slope are considered scaling arguments suggest two parameters that dictate the effective strength of the slope the first indicates the likelihood of dispersion at depth and the second relates to baroclinic stability if the deep flow is only weakly dispersive weak slopes an initially barotropic vortex can translate barotropically across the isobaths provided the vortex scale exceeds the deformation scale over stronger slopes the vortex separates into topographic waves and a stationary surface trapped vortex an initially surface trapped vortex larger than deformation scale becomes unstable over a weak slope as it does over a flat bottom however a strong slope can stabilize the vortex to small perturbations despite the large vortex scale the effective slope parameters depend not only on topographic grade but on vortex strength and size and on the ambient stratification parameters obtained with represen

organic microfacies and basinal tectonic control on source rock accumulation a microscopic approach with examples from an intracratonic and extensional basin abstract relationships among organic petrographic maceral assemblages and hydrocarbon source rock depositional environments distinguish broad marine terrestrial and mixed kerogen accumulation settings organic microfacies from paleozoic and mesozoic source rock intervals in the intracratonic williston basin and the extensional sverdrup basin have been studied using incident white and fluorescent light microscopy distinct anoxic organic microfacies are defined in upper ordovician bighorn group subtidal platformal kukersites and middle devonian upper elk point group carbonate lithologies that preserve a progression of depositional environments from platformal to starved basinal paleozoic carbonate platform microfacies are characterized by well preserved cyanophyceae alginite stromatolitic mats displaying upper surface textural features such as pustules pinnacles endolithic algal borings and interlaminated vertical and horizontal alginite resulting from phototactic growth potential source intervals in middle and upper triassic shelf shales from the sverdrup basin and middle devonian carbonate platform marginal mudstones in the williston basin are both characterized by high concentrations of sapropelic bituminite kerogen hosting unicellular marine alginite similar bituminite rich organic microfacies occur in middle devonian basinal settings associated with larger more abundant alginite and significant amounts of dasycladacean calcareous algae the main controls on source rock accumulation are water depth and chemistry as controlled by depositional setting and basin restriction

source description of the 1999 hector mine california earthquake part ii complexity of slip history we present a rupture model of the hector mine earthquake m 7 1 determined from the joint inversion of strong motion records p and sh teleseismic body waves global positioning system gps displacement vectors and measured surface offset we solve for variable local slip rake angle rise time and rupture velocity of a finite fault model involving multiple segments the inversion methodology developed in a companion article ji et al 2002 combines a wavelet transform approach with a nonlinear simulated annealing algorithm the final model is checked by forward simulating the interferometric synthetic aperture radar insar data our estimation to the seismic moment is 6 28 10 19 n m which is distributed along three segments from north to south releasing 37 41 and 22 of the total moment respectively the average slip is 1 5 m with peak amplitudes as high as 7 m the fault rupture has an average rise time of 3 5 sec and a relatively slow average rupture velocity 1 9 km sec resulting in a 14 sec rupture propagation history our approach permits large variation in rupture velocity and rise time and indicates that rise time appears to be roughly proportional to slip and shorter rise times are associated with the initiation of asperity rupture we also find evidence for nearly simultaneous rupture of the two northern branches