evaluation of kinetic uncertainty in numerical models of petroleum generation oil prone marine petroleum source rocks contain type i or type ii kerogen having rock eval pyrolysis hydrogen indices greater than 600 or 300 600 mg hydrocarbon g total organic carbon hi mg hc g toc respectively samples from 29 marine source rocks worldwide that contain mainly type ii kerogen hi 230 786 mg hc g toc were subjected to open system programmed pyrolysis to determine the activation energy distributions for petroleum generation assuming a burial heating rate of 1c m y for each measured activation energy distribution the calculated average temperature for 50 fractional conversion of the kerogen in the samples to petroleum is approximately 136 7c but the range spans about 30c 121 151c fifty two outcrop samples of thermally immature jurassic oxford clay formation were collected from five locations in the united kingdom to determine the variations of kinetic response for one source rock unit the samples contain mainly type i or type ii kerogens hi 230 774 mg hc g toc at a heating rate of 1c m y the calculated temperatures for 50 fractional conversion of the oxford clay kerogens to petroleum differ by as much as 23c 127 150c the data indicate that kerogen type as defined by hydrogen index is not systematically linked to kinetic response and that default kinetics for the thermal decomposition of type i or type ii kerogen can introduce unacceptable errors into numerical simulations furthermore custom kinetics based on one or a few samples may be inadequate to account for variations in organofacies within a source rock we propose three methods to evaluate the uncertainty contributed by kerogen kinetics to numerical simulations 1 use the average kinetic distribution for multiple samples of source rock and the standard deviation for each activation energy in that distribution 2 use source rock kinetics determined at several locations to describe different parts of the study area and 3 use a weighted average method that combines kinetics for samples from different locations in the source rock unit by giving the activation energy distribution for each sample a weight proportional to its rock eval pyrolysis s2 yield hydrocarbons generated by pyrolytic degradation of organic matter

three dimensional splay fault geometry and implications for tsunami generation megasplay faults very long thrust faults that rise from the subduction plate boundary megathrust and intersect the sea floor at the landward edge of the accretionary prism are thought to play a role in tsunami genesis we imaged a megasplay thrust system along the nankai trough in three dimensions which allowed us to map the splay fault geometry and its lateral continuity the megasplay is continuous from the main plate interface fault upwards to the sea floor where it cuts older thrust slices of the frontal accretionary prism the thrust geometry and evidence of large scale slumping of surficial sediments show that the fault is active and that the activity has evolved toward the landward direction with time contrary to the usual seaward progression of accretionary thrusts the megasplay fault has progressively steepened substantially increasing the potential for vertical uplift of the sea floor with slip we conclude that slip on the megasplay fault most likely contributed to generating devastating historic tsunamis such as the 1944 moment magnitude 8 1 tonankai event and it is this geometry that makes this margin and others like it particularly prone to tsunami genesis

splay fault activity revealed by aftershocks of the 2010 mw 8 8 maule earthquake central chile splay faults large thrust faults emerging from the plate boundary to the seafloor in subduction zones are considered to enhance tsunami generation by transferring slip from the very shallow dip of the megathrust onto steeper faults thus increasing vertical displacement of the seafloor these structures are predominantly found offshore and are therefore difficult to detect in seismicity studies as most seismometer stations are located onshore the mw moment magnitude 8 8 maule earthquake on 27 february 2010 affected 500 km of the central chilean margin in response to this event a network of 30 ocean bottom seismometers was deployed for a 3 month period north of the main shock where the highest coseismic slip rates were detected and combined with land station data providing onshore as well as offshore coverage of the northern part of the rupture area the aftershock seismicity in the northern part of the survey area reveals for the first time a well resolved seismically active splay fault in the submarine forearc application of critical taper theory analysis suggests that in the northernmost part of the rupture zone coseismic slip likely propagated along the splay fault and not the subduction thrust fault while in the southern part it propagated along the subduction thrust fault and not the splay fault the possibility of splay faults being activated in some segments of the rupture zone but not others should be considered when modeling slip distributions

hydrocarbon generation and expulsion characteristics of the source rocks in the third member of the upper triassic xujiahe formation and its effect on conventional and unconventional hydrocarbon resource potential in the sichuan basin abstract the third member of the upper triassic xujiahe formation t3x3 is a typical source reservoir cap unit for natural gas exploration in the sichuan basin however most previous studies mainly focused on the t3x3 as a source rock ignoring its role as a reservoir as a result the evaluation of hydrocarbon resource potential was not accurate this study established a hydrocarbon generation and expulsion model through analyzing the geological and geochemical characteristics of the t3x3 source rocks and calculated the resource potential of conventional gas tight gas and shale gas systematically with combining the lower boundary of buoyancy dominated accumulation lbba the results indicated that the thickness of the source rocks dominated by mudstone was distributed widely with an average value of more than 45 m the sedimentary environment was salty lacustrine deposits they have a high content of total organic carbon toc with an average value of 4 80 wt the kerogen is mainly type iii with minor type ii and the thermal evolution has entered the high to over mature stage the hydrocarbon generation threshold was determined to be 0 5 ro while the hydrocarbon expulsion threshold and the lbba were determined to be 0 83 ro and 1 12 ro respectively the efficiency of hydrocarbon expulsion was relatively high with an average of about 56 also the maximum hydrocarbon generation and expulsion intensity reached to 110 108 m3 km2 and 53 108 m3 km2 the amounts of hydrocarbon generation expulsion and residual associated with the t3x3 source rocks were 125 68 1012m3 70 38 1012m3 and 55 30 1012m3 respectively under the criterion condition of the lbba the conventional gas resource was 7 21 1010m3 the tight gas resource was 294 34 1010m3 and the shale gas resource was 2488 50 1010m3 it indicated good prospects for exploration

charging time of tight gas in the upper paleozoic of the ordos basin central china abstract the upper paleozoic section contains a tight gas sandstone reservoir of 2 75 10 12 m 3 in the ordos basin central china the measured porosities 13 c 1 were integrated to constrain the timing of gas charge into the tight reservoir the modeling results indicate that the natural gases in the present reservoir are similar to gases liberated from quartz inclusions in both composition and stable carbon isotope values and also similar to gas generated from upper paleozoic coal the similar geochemistry suggests that an important phase of quartz cementation must have occurred after gas emplacement in the reservoirs during regional uplift at the end of the cretaceous the latest carbonate cement postdating quartz cementation consumed most of the late co 2 generated from coal at high maturity r o 1 7 and reduced the reservoir quality dramatically on the contrary tight sandstones from non producing areas have fluid inclusions that were trapped in quartz cements much earlier these data indicate that natural gas migrated into the upper paleozoic reservoir when it still retained high porosity and permeability the reservoir continued to experience porosity and permeability reduction from continued quartz and carbonate cementation after gas charging due to low gas saturation comparison of the relative timing of gas charging with that of sandstone cementation can help to predict areas of risk during tight gas exploration and development

modeling of gas generation from the cameo coal zone in the piceance basin colorado the gas generative potential of the cretaceous cameo coal in the piceance basin northwestern colorado was evaluated quantitatively by sealed gold tube pyrolysis the h c and o c elemental ratios show that pyrolyzed cameo coal samples follow the van krevelen humic coal evolution pathway reasonably simulating natural coal maturation kinetic parameters activation energy and frequency factor for gas generation and vitrinite reflectance ro changes were calculated from pyrolysis data experimental ro results from this study are not adequately predicted by published ro kinetics and indicate the necessity of deriving basin specific kinetic parameters when building predictive basin models using derived kinetics for ro evolution and gas generation basin modeling was completed for 57 wells across the piceance basin which enabled the mapping of coal rank and coalbed gas potential quantities of methane generated at approximately 1 2 ro are about 300 standard cubic feet per ton scf ton and more than 2500 scf ton in situ dry ash free coal at ro values reaching 1 9 gases generated in both low and high maturity coals are less wet whereas the wetter gas is expected where ro is approximately 1 4 1 5 as controlled by regional coal rank and net coal thickness the largest in place coalbed gas resources are located in the central part of the basin where predicted volumes exceed 150 bcf mi 2 excluding gases in tight sands

experimental heating and kinetic models of source rocks comparison of different methods abstract closed system isothermal micro pyrolysis has been carried out for nine upper jurassic source rocks from the norwegian shelf supplemented by hydrous pyrolysis experiments and open system pyromat kinetic determinations in all investigated cases open system kinetics is able to model the residual potential derived from s2 but not the respective low temperature closed system isothermal experiments the relatively detailed micro pyrolysis generation patterns obtained allow us to differentiate between primary generation and secondary cracking of different carbon number classes of hydrocarbons formation of non hydrocarbons or hydrocarbon sinks in residues can be inferred from these patterns comparison of results from low and high temperature experiments suggests that the potential of a source rock may vary according to heating history discrepancies between high and low temperature experiments may be explained in terms of competing reaction pathways these may constitute a main source of uncertainty when extrapolating bulk kinetic models into geological conditions

the hydrogen isotopic characteristics of the upper paleozoic natural gas in ordos basin abstract upper paleozoic natural gas in the ordos basin is typical coal associated gas natural gases in sulige yulin and zizhou gas fields were systematically analyzed in this study based on the hydrogen isotopes of ch 4 c 2 h 6 and c 3 h 8 components in natural gases and combined with the natural gas compositions and carbon isotopes and fluid inclusions homogenization temperature measurement of reservoir rocks we have discussed the source rock depositional environment gas origin and maturity and gas migration and accumulation the results show that methane hydrogen isotope of natural gas not only can indicate the type of precursor organic matter and depositional redox condition but also is closely associated with the maturity of natural gas the difference between d c2h6 and d ch4 values is a good measure of the organic matter input of source rock the value for marine sapropelic gas is normally 10 the hydrogen isotopes of methane in upper palaeozoic natural gas was closely related to the vitrinite reflectance ro of the upper palaeozoic source rocks displaying a short migration and accumulation feature sulige gas field is continually charged with coal derived gas at different thermal maturation stages and the carbon and hydrogen isotopic reversals of alkanes result from the continuous charging and near source migration and accumulation

characteristics of type iii kerogen in coal bearing strata from the pennsylvanian upper carboniferous in the ruhr basin western germany comparison of coals dispersed organic matter kerogen concentrates and coal mineral mixtures abstract quality quantity and maturity of coal and dispersed terrigenous organic matter were studied on six coal bearing intervals in duckmantian strata pennsylvanian upper carboniferous of the ruhr basin western germany between 10 and 40 samples were collected from fresh drill cores of each interval typically consisting of a coal seam as well as clastic roof and floor strata sandstone siltstone claystone coal seams constitute about 8 vol of the succession studied the samples were analysed by organic petrological methods and rock eval pyrolysis maturity expressed in terms of vitrinite reflectance is between 0 75 and 1 0 for the six successions studied the total amount of dispersed organic matter in clastic rocks is about half of that stored in coal seams both containing predominantly vitrinite significant differences between rock eval parameters determined on whole rock samples and kerogen concentrates were observed especially with respect to hydrogen index hi values thus the hi of the coal is about twice as high as that of the dispersed organic matter although the maceral composition is similar the effects of minerals were further examined by rock eval pyrolysis of artificial mixtures of coal lignite powder and different minerals reduced hi values are partly explained by the retention of generated hydrocarbons on mineral surfaces and partly by reactions of generated fluids with pyrite in kerogen concentrates

a comparison of vitrinite reflectance measurements made on whole rock and dispersed organic matter concentrate mounts abstract a comparison of mean random vitrinite reflectance r v r values calculated from measurements on polished whole rock and on concentrates of dispersed organic matter dom mounts of the same samples generally show little difference compared to measurements on dom mounts r v r measurements by the same microscopist on corresponding whole rock samples are up to a few tenths of a percent lower over the range of 0 6 3 2 r v r and have a slightly higher standard deviation whole rock mounts have an advantage over dom mounts in the identification of first cycle vitrinite and differentiation of solid bitumen from vitrinite

effect of sedimentary heterogeneities on hydrocarbon accumulations in the permian shanxi formation ordos basin china insight from an integrated stratigraphic forward and petroleum system modelling abstract sedimentary heterogeneities are ubiquitous in nature and occur over a range of scales from core reservoir to basin scales they may thus exert significant influences on hydrocarbon generation migration and accumulation the sedimentary heterogeneities of the permian shanxi formation in the ordos basin china were modelled using sedsim a stratigraphic forward modelling program the simulation results were then used to construct a 3d petroleum system model using petromod the effects of sedimentary heterogeneities on hydrocarbon accumulations were evaluated by comparing the integrated sedsim petromod model with the classic 3d basin model the sedsim simulation shows that considerable sedimentary heterogeneities are present within the shanxi formation as a result of the interplay of the initial topography tectonic subsidence base level change and sediment inputs a variety of lithologies were developed both laterally and vertically within the shanxi formation at kilometre and metre scales respectively with mudstones mainly developed in the depositional centre while sandstones developed in the southern and northern margin areas a typical source ward retrogradation is well developed within the lower shanxi formation a base case classic 3d basin model was constructed to quantify the permian petroleum system in the ordos basin the geological and thermal models were calibrated using vr and borehole temperature data the source rocks of the upper paleozoic became mature r o 0 5 and high mature r o 1 2 in the late triassic and late jurassic respectively in the central and southern areas during the early cretaceous a tectonically induced geothermal event occurred in the southern ordos basin this caused the source rocks to reach over maturity r o 2 0 quite rapidly in the early late cretaceous in the central and southern areas all the source rock transformation ratios tr at present are greater than 70 in the p 1 coal and p 1 mudstone layers with tr values approaching 100 in the central and southern areas the transformation ratios of the p 1 limestone are close to 100 over the entire interval in the base case model a large amount of hydrocarbons appear to have been expelled and migrated into the shanxi formation but only a minor amount was accumulated to form reservoirs in the model the shanxi formation sandstone layer was set to be homogeneous vertically and there was no regional seal rocks present at the top of the shanxi formation therefore hydrocarbons could not be trapped effectively with only minor accumulations in some local structural highs where hydrocarbons are trapped both at the top and in the up dip direction by the adjacent mudstone facies in contrast the integrated sedsim petromod model takes into account of the internal lithological and sedimentary facies heterogeneities within the shanxi formation forming complex contiguous sandstone mudstone stacking patterns hydrocarbons were found to have accumulated in multiple intervals of lithological traps within the shanxi formation the results indicate that lithological distinctions controlled by sedimentary heterogeneities in three dimensions can provide effective sealing in both the top and up dip directions for hydrocarbon accumulations with gas being mainly accumulated near the depocentre where lithological traps usually formed due to frequent oscillations of the lake level

petroleum generation and accumulation in the golfo san jorge basin argentina a basin modeling study abstract the golfo san jorge basin located in patagonia is very important for the oil and gas production of argentina in spite of the long history of exploration and production few geochemical studies were performed until now for this study a set of possible source rocks was analyzed by organic geochemical and petrographical methods the samples of the pozo d 129 fm range from mature to overmature and contain from less than 0 5 to 2 45 toc there is some evidence indicating an algal origin of the more hydrogen rich kerogen present in part of the basin almost all the samples of pozo anticlinal aguada bandera and pozo cerro guadal fm are overmature toc values range from less than 0 5 to 2 5 the maturation of source rocks and generation expulsion and migration of hydrocarbons was evaluated by means of 1d and 2d basin models the 1d models constructed for the western part of the basin and 2d models applied for the eastern part both indicate maximum burial in miocene times the thickness of the tertiary at times of maximum burial ranged from 1000 to 1500 m and the generally small tertiary thickness now present in the fold belt region is assumed to be the result of erosion the main tectonic inversion took place in the late neogene the models strongly suggest that a magmatic event between 20 and 30 ma combined with the maximum burial at miocene times produced a very important pulse in hydrocarbon generation within the major part of the basin dated intrusive and extrusive magmatic rocks extended all over the basin account for this period of elevated heat flow migration pathways are extensively discussed for the 2d model probably major faults acted as important conduits for petroleum

probabilistic earthquake relocation in three dimensional velocity models for the yellowstone national park region wyoming recorded seismicity for the yellowstone national park region comprising 25 267 earthquakes from november 1972 to december 2002 has been relocated using three dimensional velocity models and probabilistic earthquake location in addition new coda magnitudes for earthquakes between 1984 and 2002 were computed by using an improved coda magnitude equation three dimensional velocity models for earthquake location were computed by inverting subsets of high quality data of three different periods 1973 1981 1984 1994 and 1995 2002 for hypocenter locations and seismic velocities earthquakes were relocated by using a nonlinear probabilistic solution to the earthquake location problem fully nonlinear location uncertainties included in the probabilistic solution allow a better and more reliable classification of earthquake locations into four quality classes earthquake locations show an improvement in location accuracy with time which we attribute to improved network geometry and more precise timing of arrival times no large systematic shifts of the relocated earthquake locations are observed except a systematic shift of 2 km to greater depth the new relocated earthquake locations show tighter clustering of epicenters and focal depths when compared with original earthquake locations the most intense seismicity in terms of number of earthquakes and cumulative seismic moment release in the yellowstone national park region occurs northwest of the yellowstone caldera between hebgen lake and the northern rim of the caldera seismicity within the yellowstone caldera is diffuse and shallow individual clusters of earthquakes can be associated with major hydrothermal areas

26th december 2004 great sumatra andaman earthquake co seismic and post seismic motions in northern sumatra trench parallel thrust faults verging both landward and seaward were mapped in the portion of wedge located between northern sumatra and the indian indonesian boundary the spatial aftershocks distribution of the 26th december 2004 earthquake shows that the post seismic motion is partitioned along two thrust faults the lower and median thrust faults the latter being right laterally offset by a n s lower plate fracture zone located along the 93 6 n meridian between february 2005 and august 2005 the upper plate aftershock activity shifted from southeast of this fracture zone to northwest of it suggesting that the lower plate left lateral motion along the fracture zone may have induced a shift of the upper plate post seismic activity along the median thrust fault based on swath bathymetric and 3 5 khz data co seismic deformations were weak close to the trench joint seismic geodetic determination of slip distribution and time arrivals and heights of tsunami waves suggest that the co seismic slip was maximum along a portion of the upper thrust fault located north of the tuba ridge suggesting that the upper thrust fault might be a splay fault originated at the interplate fault plane as the upper thrust fault is steeper than the slab the vertical motion of the adjacent outer arc and overlying water is much larger compared to the one resulting from slip on the megathrust alone increasing tsunamogenic effects

characteristics and genetic types of the lower paleozoic natural gas ordos basin abstract the source of the lower paleozoic natural gas in the ordos basin has been a highly controversial issue using data obtained from newly drilled wells we present the geochemical characteristics of lower paleozoic natural gas in various regions of the ordos basin the lower paleozoic natural gas is dominated by hydrocarbons of which methane accounts for 40 17 97 24 and the heavier gaseous hydrocarbon c 2 ranges from 0 01 to 9 72 non hydrocarbon gases in the lower paleozoic gas reservoir are mainly co 2 and n 2 2 10 for co 2 and 0 04 48 56 for n 2 higher than those in the upper paleozoic gas reservoir this observation showed that the high co 2 and n 2 content was related to the ordovician marine carbonate rock deposits the carbon and hydrogen isotopes of the methane ethane and propane in the lower paleozoic natural gas of the ordos basin showed various degrees of reversal indicating the mixing origin of natural gas in the central eastern ordos basin coal derived gas from the carboniferous permian c p coal measure and oil associated from the lower ordovician majiagou formation marine source rocks gas coexist as well as mixtures of these two gases for the lower paleozoic natural gas from the western margin of the basin coal derived gas coexist with oil associated gas but no mixing gas in which coal derived gas originated mainly from the c p source rocks and oil associated gas from the lower ordovician kelimoli formation and middle ordovician wulalike formation source rocks in the western margin of the basin the lower paleozoic natural gas in the southern part of the ordos basin was mixing gas and the oil associated gas is the dominant one the natural gas was originated from the lower ordovician majiagou formation source rocks in the central eastern ordos basin and the pingliang formation mudstone and argillaceous limestone at the southern margin of the basin

quantifying offshore fore arc deformation and splay fault slip using drowned pleistocene shorelines arauco bay chile most of the deformation associated with the seismic cycle in subduction zones occurs offshore and has been therefore difficult to quantify with direct observations at millennial time scales here we study millennial deformation associated with an active splay fault system in the arauco bay area off south central chile we describe hitherto unrecognized drowned shorelines using high resolution multibeam bathymetry geomorphic sedimentologic and paleontologic observations and quantify uplift rates using a landscape evolution model along a margin normal profile uplift rates are 1 3 m ka near the edge of the continental shelf 1 5 m ka at the emerged santa maria island 0 1 m ka at the center of the arauco bay and 0 3 m ka in the mainland the bathymetry images a complex pattern of folds and faults representing the surface expression of the crustal scale santa maria splay fault system we modeled surface deformation using two different structural scenarios deep reaching normal faults and deep reaching reverse faults with shallow extensional structures our preferred model comprises a blind reverse fault extending from 3 km depth down to the plate interface at 16 km that slips at a rate between 3 0 and 3 7 m ka if all the splay fault slip occurs during every great megathrust earthquake with a recurrence of 150 200 years the fault would slip 0 5 m per event equivalent to a magnitude 6 4 earthquake however if the splay fault slips only with a megathrust earthquake every 1000 years the fault would slip 3 7 m per event equivalent to a magnitude 7 5 earthquake

revealing the deep structure and rupture plane of the 2010 maule chile earthquake mw 8 8 using wide angle seismic data the 27 february 2010 maule earthquake mw 8 8 ruptured 400 km of the nazca south america plate boundary and caused hundreds of fatalities and billions of dollars in material losses here we present constraints on the fore arc structure and subduction zone of the rupture area derived from seismic refraction and wide angle data the results show a wedge shaped body 40 km wide with typical sedimentary velocities interpreted as a frontal accretionary prism fap landward of the imaged fap the velocity model shows an abrupt velocity contrast suggesting a lithological change which is interpreted as the contact between the fap and the paleo accretionary prism backstop the backstop location is coincident with the seaward limit of the aftershocks defining the updip limit of the co seismic rupture and seismogenic zone furthermore the seaward limit of the aftershocks coincides with the location of the shelf break in the entire earthquake rupture area 33 s 38 5 s which is interpreted as the location of the backstop along the margin published seismic profiles at the northern and southern limit of the rupture area also show the presence of a strong horizontal velocity gradient seismic backstop at a distance of 30 km from the deformation front the seismic wide angle reflections from the top of the subducting oceanic crust constrain the location of the plate boundary offshore dipping at 10 the projection of the epicenter of the maule earthquake onto our derived interplate boundary yielded a hypocenter around 20 km depth this implies that this earthquake nucleated somewhere in the middle of the seismogenic zone neither at its updip nor at its downdip limit

kinetic modelling of petroleum formation and cracking implications from the high pressure high temperature elgin field uk north sea in this paper we use a case study to test the simulation of generation migration and cracking of petroleum fluids by a 2d compositional basin simulator using kinetic models based on chemical classes of compounds the selected area is the high pressure 1100 bar high temperature 190 c elgin field in the north sea this study is mainly focused on kinetic modelling of secondary cracking because in this zone paraffinic condensates with almost 50 c6 alkanes were recently discovered whereas only gas c5 was expected given the high temperature conditions the detailed hydrocarbon composition observed today in the fulmar sands reservoir of the elgin field is compared with the results of several simulations aimed at testing the influence of jurassic source rocks retention properties kinetic parameters and temperature variations on the predicted composition of fluids the influence of pressure was neglected in the modelling on the basis of results published in the literature results show that in this north sea area primary cracking of the kerogen into oil is completed whichever source rock is considered and that secondary cracking of accumulated petroleum compounds in the reservoir is presently in progress under these conditions source rock type and retention during primary and secondary migration have little influence on the present oil composition the occurrence of a monophasic paraffinic fluid in the elgin reservoir despite the high temperature is due to its very recent increase from 160 c to over 180 c in the last million years the fluid composition evolves rapidly and our compositional kinetic scheme accounts correctly for the presence of c6 hydrocarbons in these geological conditions first results using the compositional kinetic scheme of behar et al behar f kressman s rudkiewicz j l vandenbroucke m 1991 experimental simulation in a confined system and kinetic modelling of kerogen and oil cracking organic geochemistry 19 1 3 173 189 for secondary cracking showed a reasonably good fit between calculated and observed detailed fluid composition except for methylated aromatics which are overestimated and methane which is underestimated a recent comparison of kinetic parameters obtained from pyrolysis experiments on model compounds showed that it is not realistic to assume as done previously the same frequency factor for all chemical classes of compounds the higher stability of methylated aromatics relative to saturates observed under laboratory conditions would be extended to geological conditions a second set of simulations using frequency factors and activation energies obtained on these model compounds gave a better fit for methylated aromatics however methane is still strongly underestimated and reasons which could explain this discrepancy are discussed

thermal cracking of kerogen in open and closed systems determination of kinetic parameters and stoichiometric coefficients for oil and gas generation abstract the purpose of the study is to compare artificial maturation of kerogens representative of the main types of organic matter kerogen types i ii ii s and iii in open and anhydrous closed pyrolysis systems the generated compounds are fractionated according to their thermal stability into six chemical classes c 1 c 2 c 5 c 6 c 14 c 15 saturates c 15 aromatics and nsos which include resins and asphaltenes in both systems primary cracking of kerogen can be described by two main reactions oil generation together with early gas generation followed by late gas production mass balances obtained in the two pyrolysis systems are reasonably similar although some secondary cracking of the nsos and underestimation of methane potential due to incomplete pyrolysis may occur in the open system kinetic parameters of thermal cracking are derived from experiments in the open system using an optimization procedure which determines a unique frequency factor and a weight distribution of chemical classes for a discrete series of activation energies the resultant frequency factors are checked with those obtained for specific molecular tracers such as n c 12 and n c 24 alkanes generated from kerogens in open and closed systems under isothermal conditions the results show that using a unique frequency factor as determined by optimization is correct for type i ii and ii s kerogens this factor is more questionable however when the distribution of activation energies is very broad such as for type iii coals based on this study a strategy for determination of kinetic parameters on any new source rock sample is proposed

critical taper model of fold and thrust belts and accretionary wedges the fold and thrust belts and submarine accretionary wedges that lie along compressive plate boundaries are one of the best understood deformational features of the earth s upper crust although there is considerable natural variation among the many fold and thrust belts and accretionary wedges that have been recognized and explored several features appear to be universal in cross section fold and thrust belts and accretionary wedges occupy a wedge shaped deformed region overlying a basal detachment or decollement fault the rocks or sediments beneath this fault show very little deformation the decollement fault characteristically dips toward the interior of the mountain belt or in the case of a submarine wedge toward the island arc the topography in contrast slopes toward the toe or deformation front of the wedge deformation within the wedge is generally dominated by imbricate thrust faults verging toward the toe and related fault bend folding two north american fold and thrust belts that exhibit these features are shown in figure 1 neither of these two examples is tectonically active today the southern canadian fold and thrust belt was active during the late jurassic and cretaceous 150 100 ma whereas the southern appa lachians were deformed during the late carboniferous to permian alle ghenian orogeny 300 250 ma figure 2 shows two examples that are currently active the taiwan fold and thrust belt produced by the sub duction of the eurasian plate beneath the philippine sea plate suppe 1981 1987 and the barbados accretionary wedge produced by the sub

origin of natural gas from the ordovician paleo weathering crust and gas filling model in jingbian gas field ordos basin china abstract the ordos basin the second largest natural gas producing basin in china is one of the most tectonically stable sedimentary basins favorable to natural gas generation and preservation the origin and potential source of the jingbian gas field one of the five giant gas fields in the basin containing the ordovician paleo weathering crust as reservoir strata remains unclear the question is whether gas is generated from carboniferous permian coal measures or ordovician carbonates this study provides abundant gas geochemical evidence which clarifies its origin and source among 82 natural gas samples collected from the ordovician paleo weathering crust in the jingbian gas field c1 c4 gaseous hydrocarbons are dominant with low amounts of non hydrocarbons co2 h2s and n2 the content of c1 c4 ranges from 79 26 to 99 93 with a gas dryness c1 c1 4 of 0 981 0 999 suggesting that natural gases are dry and possibly originate from a high to over mature source the carbon isotopic compositions of methane and its homologues in natural gases from the ordovician paleo weathering crust vary widely with 13c1 13c2 and 13c3 values of 38 9 to 29 1 37 5 to 22 2 and 30 0 to 20 9 respectively the 13c2 and 13c3 values in the jingbian gas field are much more negative than those of typical coal type gas in sulige wushenqi yulin daniudi and kela2 gas fields the carbon isotopic signature suggests that the natural gas in the ordovician paleo weathering crust in the jingbian gas field most likely originates from ordovician carbonates containing sapropelic organic matter the measured d values of methane range from 177 to 155 and support our hypothesis of the natural gases originating from marine sapropelic organic matter the thermal maturity of the natural gases in the ordovician paleo weathering crust is at a high to over mature stage suggesting that the gases originated from secondary cracking of oil and gas at high temperature and pressure thermochemical sulfate reduction tsr might partially play a role in the alteration of gas dryness and 13c1 in those areas where gypsum is present as an effective cap rock mixing of high to over mature secondary cracking gas from the ordovician source and coal type gas from carboniferous permian coal in the jingbian gas field is minor

tectonic and stratigraphic controls of hydrocarbon systems in the ordos basin a multicycle cratonic basin in central china the ordos basin is the oldest and still an important hydrocarbon province in central china it is a typical cratonic basin developed on the archean granulites and lower proterozoic greenschists of the north china block the development of the ordos basin during the paleozoic mesozoic can be divided into three evolutionary stages cambrian early ordovician cratonic basin with divergent margins middle ordovician middle triassic cratonic basin with convergent margins and late triassic early cretaceous intraplate remnant cratonic basin two hydrocarbon systems are present in the basin the paleozoic gas and mesozoic oil systems in the paleozoic gas system the lower ordovician marine carbonates and pennsylvanian lower permian coal measures serve as source rocks the lower ordovician karst modified dolomites and pennsylvanian bauxitic mudstones form a significant reservoir seal association and the pennsylvanian lower permian deltaic sandstones and upper permian lacustrine mudstones form another effective reservoir seal association in the mesozoic oil system the upper triassic lacustrine mudstones are mature source rocks the upper triassic deltaic sandstones and overlying shallow lacustrine and swamp mudstones form a reservoir seal association and the lower jurassic fluvial sandstones and overlying shallow lacustrine and swamp mudstones form another reservoir seal association in both hydrocarbon systems the stratigraphic variations provide the principal traps the ordos basin is characterized by a stable tectonic setting that controlled the distribution of depositional systems and the development of erosional surfaces and ultimately governed the distribution of oil and gas fields and trap types

active tectonics of the south chilean marine fore arc 35 s 40 s the south chilean marine fore arc 35 s 40 s is separated into four tectonic segments concepcion north concepcion south nahuelbuta and tolten from north to south these are each characterized by their individual tectonic geomorphology and reflect different ways of mechanical and kinematic interaction of the convergent nazca and south american plates splay faults that cut through continental framework rock are seismically imaged in both concepcion segments and the tolten segment additionally the concepcion south segment exhibits prominent upper plate normal faults normal faults apparently relate to uplift caused by sediment underthrusting at depth this has led to oversteepening and gravitational collapse of the marine fore arc there is also evidence for sediment underthrusting and basal accretion to the overriding plate in the tolten segment there uplift of the continental slope has created a landward inclined seafloor over a latitudinal distance of 50 km in the nahuelbuta segment transpressive upper plate faults aligned oblique to the direction of plate motion control the seafloor morphology based on a unique acoustic data set including 90 of bathymetric coverage of the continental slope we are able to reveal an along strike heterogeneity of a complexly deformed marine fore arc which had escaped attention in previous studies that only considered the structure along transects normal to the plate margin

on the relationship between structure morphology and large coseismic slip a case study of the m w 8 8 maule chile 2010 earthquake abstract subduction megathrust earthquakes show complex rupture behaviour and large lateral variations of slip however the factors controlling seismic slip are still under debate here we present 2 d velocity depth tomographic models across four trench perpendicular wide angle seismic profiles complemented with high resolution bathymetric data in the area of maximum coseismic slip of the m w 8 8 maule 2010 megathrust earthquake central chile 34 36 s results show an abrupt lateral velocity gradient in the trench perpendicular direction from 5 0 to 6 0 km s interpreted as the contact between the accretionary prism and continental framework rock whose superficial expression spatially correlates with the slope shelf break the accretionary prism is composed of two bodies 1 an outer accretionary wedge 5 10 km wide characterized by low seismic velocities of 1 8 3 0 km s interpreted as an outer frontal prism of poorly compacted and hydrated sediment and 2 the middle wedge 50 km wide with velocities of 3 0 5 0 km s interpreted as a middle prism composed by compacted and lithified sediment in addition the maximum average coseismic slip of the 2010 megathrust event is fairly coincident with the region where the accretionary prism and continental slope are widest 50 60 km wide and the continental slope angle is low m w 9 5 megathrust earthquake for the case of the maule event published differential multibeam bathymetric data confirms that coseismic slip must have propagated up to 6 km landwards of the deformation front and hence practically the entire base of the middle prism sediment dewatering and compaction processes might explain the competent rheology of the middle prism allowing shallow earthquake rupture in contrast the outer frontal prism made of poorly consolidated sediment has impeded the rupture up to the deformation front as high resolution seismic reflection and multibeam bathymetric data have not showed evidence for new deformation in the trench region

tectonic control on sediment accretion and subduction off south central chile implications for coseismic rupture processes of the 1960 and 2010 megathrust earthquakes based on a compilation of published and new seismic refraction and multichannel seismic reflection data along the south central chile margin 33 46 s we study the processes of sediment accretion and subduction and their implications on megathrust seismicity in terms of the frontal accretionary prism fap size the marine south central chile fore arc can be divided in two main segments 1 the maule segment south of the juan fernandez ridge and north of the mocha block characterized by a relative large fap 20 40 km wide and 2 the chiloe segment south of the mocha block and north of the nazca antarctic south america plates junction characterized by a small fap 10 km wide in addition the maule and chiloe segments correlate with a thin 1 km thick and thick 1 5 km thick subduction channel respectively the mocha block lies between 37 5 and 40 s and is configured by the chile trench mocha and valdivia fracture zones this region separates young 0 25 ma oceanic lithosphere in the south from old 30 35 ma oceanic lithosphere in the north and it represents a fundamental tectonic boundary separating two different styles of sediment accretion and subduction respectively a process responsible for this segmentation could be related to differences in initial angles of subduction which in turn depend on the amplitude of the down deflected oceanic lithosphere under trench sediment loading on the other hand a small fap along the chiloe segment is coincident with the rupture area of the trans pacific tsunamigenic 1960 earthquake mw 9 5 while a relatively large fap along the maule segment is coincident with the rupture area of the 2010 earthquake mw 8 8 differences in earthquake and tsunami magnitudes between these events can be explained in terms of the fap size along the chiloe and maule segments that control the location of the updip limit of the seismogenic zone the rupture area of the 1960 event also correlates with a thick subduction channel chiloe segment that may provide enough smoothness at the subduction interface allowing long lateral earthquake rupture propagation

splay fault slip during the mw 8 8 2010 maule chile earthquake splay faults are thrusts that emerge from the plate boundaries of subduction zones such structures have been mapped at several convergent margins and their activity commonly ascribed to large megathrust earthquakes however the behavior of splay faults during the earthquake cycle is poorly constrained because typically these structures are located offshore and are difficult to access here we use geologic mapping combined with space and land geodesy as well as offshore sonar data to document surface fault ruptures and coastal uplift at isla santa maria in south central chile 37 s caused by the 27 february 2010 maule earthquake m w 8 8 during the earthquake the island was tilted parallel to the margin and normal faults ruptured the surface and adjacent ocean bottom we associate tilt and crestal normal faulting with growth of an anticline above a blind reverse fault rooted in the nazca south america plate boundary which slipped during the maule earthquake the splay fault system has formed in an area of reduced coseismic plate boundary slip suggesting that anelastic deformation in the upper plate may have restrained the 2010 megathrust rupture surface fault breaks were accompanied by prominent discharge of fluids our field observations support the notion that splay faulting may frequently complement and influence the rupture of subduction zone earthquakes

stable carbon isotope compositions and source rock geochemistry of the giant gas accumulations in the ordos basin china ordos basin the second largest sedimentary basin in china contains enormous natural gas resources each of the four giant gas fields discovered so far in this basin i e sulige yulin wushenqi and jingbian has over 100 billion cubic meters bcm or 3 53 trillion cubic feet tcf of proven gas reserves this study examines the stable carbon isotope data of 125 gas samples collected from the four giant gas fields in the ordos basin source rocks in the upper paleozoic coal measures are suggested by the generally high 13c values of c1 c4 gaseous hydrocarbons in the gases from the sulige yulin and wushenqi gas fields while the 13cic4 value is higher than that of the 13cnc4 the dominant ranges for the 13c1 13c2 and 13c3 values in these upper paleozoic reservoired gases are 34 to 32 27 to 23 and 25 to 24 respectively the 13c values of methane benzene and toluene in gases from the lower paleozoic reservoirs of the jingbian field indicate a significant contribution from humic source rocks as they are similar to those in the upper paleozoic reservoirs of the sulige yulin and wushenqi gas fields however the wide variation and reversal in the 13c1 13c2 and 13c3 values in the jinbian gases cannot be explained using a single source scenario thus the gases were likely derived dominantly from the carboniferous permian coal measures with some contribution from the carbonates in the lower permian taiyuan formation the gas isotope data and extremely low total organic carbon contents 0 2 toc suggest that the ordovician majiagou formation carbonates are unlikely to be a significant gas source rock thus almost all of the economic gas accumulations in the ordos basin were derived from upper paleozoic source rocks

toward understanding tectonic control on the mw 8 8 2010 maule chile earthquake the maule earthquake of 27th february 2010 m w 8 8 affected similar to 500 km of the nazca south america plate boundary in south central chile producing spectacular crustal deformation here we present a detailed estimate of static coseismic surface offsets as measured by survey and continuous gps both in near and far field regions earthquake slip along the megathrust has been inferred from a joint inversion of our new data together with published gps insar and land level changes data using green s functions generated by a spherical finite element model with realistic subduction zone geometry the combination of the data sets provided a good resolution indicating that most of the slip was well resolved coseismic slip was concentrated north of the epicenter with up to 16 m of slip whereas to the south it reached over 10 m within two minor patches a comparison of coseismic slip with the slip deficit accumulated since the last great earthquake in 1835 suggests that the 2010 event closed a mature seismic gap slip deficit distribution shows an apparent local overshoot that highlight cycle to cycle variability which has to be taken into account when anticipating future events from interseismic observations rupture propagation was obviously not affected by bathymetric features of the incoming plate instead splay faults in the upper plate seem to have limited rupture propagation in the updip and along strike directions additionally we found that along strike gradients in slip are spatially correlated with geometrical inflections of the megathrust our study suggests that persistent tectonic features may control strain accumulation and release along subduction megathrusts c 2012 elsevier b v all rights reserved

comparison of petroleum generation kinetics by isothermal hydrous and nonisothermal open system pyrolysis this study compares kinetic parameters determined by open system pyrolysis and hydrous pyrolysis using aliquots of source rocks containing different kerogen types kinetic parameters derived from these two pyrolysis methods not only differ in the conditions employed and products generated but also in the derivation of the kinetic parameters i e isothermal linear regression and non isothermal nonlinear regression results of this comparative study show that there is no correlation between kinetic parameters derived from hydrous pyrolysis and open system pyrolysis hydrous pyrolysis kinetic parameters determine narrow oil windows that occur over a wide range of temperatures and depths depending in part on the organic sulfur content of the original kerogen conversely open system kinetic parameters determine broad oil windows that show no significant differences with kerogen types or their organic sulfur contents comparisons of the kinetic parameters in a hypothetical thermal burial history 2 5 c my show open system kinetic parameters significantly underestimate the extent and timing of oil generation for type iis kerogen and significantly overestimate the extent and timing of petroleum formation for type i kerogen compared to hydrous pyrolysis kinetic parameters these hypothetical differences determined by the kinetic parameters are supported by natural thermal burial histories for the naokelekan source rock type iis kerogen in the zagros basin of iraq and for the green river formation type i kerogen in the uinta basin of utah differences in extent and timing of oil generation determined by open system pyrolysis and hydrous pyrolysis can be attributed to the former not adequately simulating natural oil generation conditions products and mechanisms

aftershock seismicity of the 27 february 2010 mw 8 8 maule earthquake rupture zone on 27 february 2010 the mw 8 8 maule earthquake in central chile ruptured a seismic gap where significant strain had accumulated since 1835 shortly after the mainshock a dense network of temporary seismic stations was installed along the whole rupture zone in order to capture the aftershock activity here we present the aftershock distribution and first motion polarity focal mechanisms based on automatic detection algorithms and picking engines by processing the seismic data between 15 march and 30 september 2010 from stations from iris ipgp gfz and university of liverpool we determined 20 205 hypocentres with magnitudes mw between 1 and 5 5 seismic activity occurs in six groups 1 normal faulting outer rise events 2 a shallow group of plate interface seismicity apparent at 25 35 km depth and 50 120 km distance to the trench with some variations between profiles along strike the aftershocks occur largely within the zone of coseismic slip but extend 50 km further north and with predominantly shallowly dipping thrust mechanisms along dip the events are either within the zone of coseismic slip or downdip from it depending on the coseismic slip model used 3 a third band of seismicity is observed further downdip at 40 50 km depth and further inland at 150 160 km trench perpendicular distance with mostly shallow dipping 28 thrust focal mechanisms indicating rupture of the plate interface significantly downdip of the coseismic rupture and presumably above the intersection of the continental moho with the plate interface 4 a deep group of intermediate depth events between 80 and 120 km depth is present north of 36 s within the maule segment a large portion of events during the inter seismic phase originated from this depth range 5 the magmatic arc exhibits a small amount of crustal seismicity but does not appear to show significantly enhanced activity after the mw 8 8 maule 2010 earthquake 6 pronounced crustal aftershock activity with mainly normal faulting mechanisms is found in the region of pichilemu 34 5 s these crustal events occur in a 30 km wide region with sharp inclined boundaries and oriented oblique to the trench the best located events describe a plane dipping to the southwest consistent with one of the focal planes of the large normal faulting aftershock mw 6 9 on 11 march 2010

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

space geodetic estimation of the nazca south america euler vector abstract gps data from four sites in the nazca plate easter island galapagos robinson crusoe and san felix islands and from five sites in the stable core of the south american plate enabled us to estimate the euler vector of the nazca plate with respect to south america the observed velocities of easter island 6 6 cm yr at 102 3 galapagos 5 1 cm yr at 90 0 robinson crusoe 6 6 cm yr at 80 1 and san felix 6 0 cm yr at 82 1 are significantly slower than the global plate model nuvel 1a velocites for those four sites our estimated euler pole is located at 48 8 n 91 7 w with a rate of 0 59 m y the nuvel 1a and earlier space geodetic studies give rotation rates that are 20 faster

aftershock seismicity of the 2010 maule mw 8 8 chile earthquake correlation between co seismic slip models and aftershock distribution 1 the 27 february 2010 maule chile mw 8 8 earthquake is one of the best instrumentally observed subduction zone megathrust events here we present locations magnitudes and cumulative equivalent moment of the first 2 months of aftershocks recorded on a temporary network deployed within 2 weeks of the occurrence of the mainshock using automatically determined onset times and a back projection approach for event association we are able to detect over 30 000 events in the time period analyzed to further increase the location accuracy we systematically searched for potential s wave arrivals and events were located in a regional 2d velocity model additionally we calculated regional moment tensors to gain insight into the deformation history of the aftershock sequence we find that the aftershock seismicity is concentrated between 40 and 140 km distance from the trench over a depth range of 10 to 35 km focal mechanisms indicate a predominance of thrust faulting with occasional normal faulting events increased activity is seen in the outer rise region of the nazca plate predominantly in the northern part of the rupture area further down dip a second band of clustered seismicity showing mainly thrust motion is located at depths of 40 45 km by comparing recent published mainshock source inversions with our aftershock distribution we discriminate slip models based on the assumption that aftershocks occur in areas of rapid transition between high and low slip surrounding high slip regions of the mainshock

paleoenvironment and stratigraphy during the last glacial in the belgian dutch border region the weichselian deposits of the flat dutch belgian coversand area are characterized by highly varying facies types the geomorphological location and the role of water during the deposition and the transportation of the original eolian sediments may fully explain the texture and sedimentary structures of the lithostratigraphic units directly deposited eolian loams and sands on the dry interfluves contrast with the same but reworked sediments in wet valleys and depressions the formation of periglacial phenomena is also dependent on the geomorphologic lithologic and hydrologic conditions the occurrence of peaty beds is restricted to wet environments without precise climatic significance the pleniglacial sequence is subdivided into early and late pleniglacial stades both characterized by partial permafrost conditions interrupted by a middle pleniglacial interstadial complex with clearly milder conditions

noncohesive critical coulomb wedges an exact solution active fold and thrust belts or submarine accretionary complexes can be modeled as critically tapered wedges of material on the verge of coulomb failure everywhere overlying a basal decollement where frictional sliding is occurring ignoring cohesion the four strength parameters needed to describe a critical coulomb wedge are its internal and basal coefficients of friction and b and its internal and basal hubbert rubey fluid pressure ratios and b an exact relation between surface slope and basal dip of a noncohesive critical wedge with uniform properties is derived the state of stress within such a wedge has the same orientation everywhere and is constant if is and vice versa a coefficient of internal friction 1 1 is consistent with the known surface slope basal dip and pore fluid pressures in the active fold and thrust belt of western taiwan assuming that byerlee s law b 0 85 is valid on the base the wide variety of tectonic styles observed to occur along convergent margins including subduction erosion active accretion subduction without accretion and even extension and normal faulting may be controlled by relatively small spatial or temporal variations in either b or b

accretionary prisms in subduction earthquake cycles the theory of dynamic coulomb wedge 1 we expand the theory of critically tapered coulomb wedge for accretionary prisms by considering stress changes in subduction earthquake cycles building on the coulomb plasticity of the classical theory we assume an elastic perfectly coulomb plastic rheology and derive exact stress solutions for stable and critical wedges the new theory postulates that the actively deforming most seaward part of an accretionary prism the outer wedge overlies the updip velocity strengthening part of the subduction fault and the less deformed inner wedge overlies the velocity weakening part the seismogenic zone during great earthquakes the outer wedge is pushed into a compressively critical state with an increase in basal and internal stresses and pore fluid pressure after the earthquake the outer wedge returns to a stable state the outer wedge geometry is controlled by the peak stress of the updip velocity strengthening part of the subduction fault achieved in largest earthquakes the inner wedge generally stays in the stable regime throughout earthquake cycles acting as an apparent backstop and providing a stable environment for the formation of forearc basins the new theory has important implications for the studies of the updip limit of the seismogenic zone the evolution of accretionary prisms and forearc basins activation of splay faults and tsunami generation evolution of the fluid regime and mechanics of frontal prisms at margins dominated by tectonic erosion

crustal extensional faulting triggered by the 2010 chilean earthquake the pichilemu seismic sequence 1 we report a sequence of crustal quakes that began after the mw 8 8 thrust subduction maule earthquake that affected the central chile margin on 27 february 2010 this activity lasted by several months having the most important events on 11 march 2010 mw 6 9 and mw 7 0 with normal focal mechanisms seismicity shows a rupture oriented along a nw striking and sw dipping normal fault from the surface down to the interplate contact seismicity can be correlated with neotectonics extensional structures similarly oriented in the region which have coexisted with nne ssw reverse faults since the late pliocene even though both have older periods of activity since the paleozoic this crustal rupture would have been triggered by the high coulomb stress change produced by the maule earthquake enhanced by likely fluid presence along weakened zones of the forearc crust as evidenced by high vp vs ratio the occurrence of relevant neotectonic activity in coincidence with short term deformation suggests a relationship with long term tectonic features of this region which would have been acting as a barrier during the interseismic period increasing the strain accumulation and triggering contractional faulting in the crust as well as producing high slip patches during great subduction ruptures favoring triggering of crustal extensional faulting crustal faulting in pichilemu suggests that this kind of events should be considered in seismic hazard analysis despite the absence of historical crustal seismic activity before the maule earthquake

geochemical characteristics and hydrocarbon generation modeling of the kazhdumi early cretaceous gurpi late cretaceous and pabdeh paleogene formations iranian sector of the persian gulf abstract the marls and argillaceous limestones of the early cretaceous kazhdumi late cretaceous gurpi and paleogene pabdeh formations are considered as potential source rock candidates in this area the present study characterizes hydrocarbon potential type of organic matter and thermal maturity of these three formations in the iranian sector of the persian gulf also 1d basin modeling was used to analyse the burial history and timing of hydrocarbon generation in these formations a total of 179 cutting samples from 25 wells were evaluated through rock eval pyrolysis and organic petrography average total organic carbon toc content for the samples of the kazhdumi gurpi and pabdeh formations that were analyzed for the current study is 1 2 0 9 and 1 wt respectively all three formations show lower toc contents in central part relative to eastern and western parts of the study area rock eval pyrolysis and organic petrography show that the organic matter in all three formations is mainly composed of type ii and mixed type ii iii kerogen this study shows that the kazhdumi gurpi and pabdeh formations in iranian offshore areas are not as rich as onshore areas and specifically in the dezful embayment in terms of organic matter quantity and quality thermal history modeling indicates that constant heat flow values in the range of 64 73 mw m 2 gives the best fit between measured and calculated vitrinite reflectance and bottom hole temperature the rock eval t max vitrinite reflectance and the generated models suggested that in the eastern parts of the study area the kazhdumi formation is at the last stage of oil generation and the gurpi and pabdeh formations are within the main oil generation window hydrocarbon generation began in the early eocene middle eocene and early miocene in the kazhdumi gurpi and pabdeh formations respectively in the western parts of the persian gulf the kazhdumi formation is within the main oil window with hydrocarbon generation took place during the oligocene and the gurpi and pabdeh formations are early mature and immature respectively all three formations are thermally immature in the central part of the persian gulf the kazhdumi formation shows positive correlation with the crude oils of the cretaceous and tertiary reservoirs taken from the northwestern persian gulf the pabdeh and gurpi formations show no correlation with crude oils produced in the northwestern and southeastern persian gulf

migration features of crude oil in fluvial deposits of maling oilfield in ordos basin china abstract oils in the maling oil field ordos basin are produced from fluvial deposits within the yan 9 and yan 10 subsections of the yanan formation through the analysis of pyrrolic nitrogen compounds and fluid inclusions the oil charging site migration direction and pathway and timing were interpreted in relationship with the sedimentary features and the high pressure observed in the mesozoic sequence the spatial distribution pattern of the fractionation of neutral nitrogen compounds in the crude oils suggested two possible charging positions in the studied area the ratios of the isomeric nitrogen compounds increase toward the center of the study area from both northwest and southeast directions of the region indicating that the lateral charging directions were likely from both the southeast and the northwest toward the center of the oil field the isomeric ratios of pyrrolic nitrogen compounds in the oils from different area of the maling oilfield increase with the decrease of depth from yan 10 to yan 4 5 subsections showing vertical migration of oil to the reservoirs the homogenization temperature of fluid inclusions in the reservoir rocks exhibited two peaks reflecting the two stages of oil migration and accumulation the migration pathways include fluvial sand bodies and unconformity surfaces the migration driving force was likely the capillary pressure and the abnormally high strata pressure in the mesozoic sequences

megathrust friction determined from mechanical analysis of the forearc in the maule earthquake area the seismogenic potential of a given fault depends essentially on its frictional properties and on the mechanical properties of the medium determining the spatio temporal variations of frictional properties is therefore a key issue in seismotectonics this study aims to characterize the friction on the south america megathrust in the 2010 mw 8 8 maule earthquake area from mechanical analysis of the forearc structure and morphology based on the critical taper theory we first show that the rupture area of the maule earthquake also shown to be locked in the interseismic period coincides with the stable part of the wedge in the surrounding area the wedge is critical a finding consistent with various evidence for active deformation there this is in particular true for the arauco peninsula area which seems to have arrested the maule earthquake s rupture to the south this observation lends support to the view that the seismic rupture is inhibited when propagating beneath a critical area the geometry of the critical portion of the wedge suggests a standard internal friction int 0 7 0 13 and a hydrostatic pore pressure within the wedge the effective friction beneath the critical outer wedge is estimated to be eff b 0 27 0 03 this could be related to intrinsically low friction minerals clay or high pore pressure along the megathrust we next use the limit analysis approach to constrain the variation of the effective friction along the megathrust based on the location and geometry of internal faulting within the forearc a low effective friction is found within the rupture area eff b 0 14 to explain the reactivation of thrust fault such as the santa maria updip of the coseismic rupture or the activation of normal splay faults downdip of the rupture area the low effective friction found there could reflect strong dynamic weakening

origin of a crustal splay fault and its relation to the seismogenic zone and underplating at the erosional north ecuador south colombia oceanic margin 1 splay faults within accretionary complexes are commonly associated with the updip limit of the seismogenic zone prestack depth migration of a multichannel seismic line across the north ecuador south colombia oceanic margin images a crustal splay fault that correlates with the seaward limit of the rupture zone of the 1958 mw 7 7 tsunamogenic subduction earthquake the splay fault separates 5 6 6 km s velocity inner wedge basement rocks which belong to the accreted gorgona oceanic terrane from 4 to 5 km s velocity outer wedge rocks the outer wedge is dominated by basal tectonic erosion despite a 3 km thick trench fill subduction of 2 km high seamount prevented tectonic accretion and promotes basal tectonic erosion the low velocity and poorly reflective subduction channel that underlies the outer wedge is associated with the aseismic decollement thrust subduction channel fluids are expected to migrate upward along splay faults and alter outer wedge rocks conversely duplexes are interpreted to form from and above subducting sediment at 14 to 15 km depths between the overlapping seismogenic part of the splay fault and the underlying aseismic decollement coeval basal erosion of the outer wedge and underplating beneath the apex of inner wedge control the margin mass budget which comes out negative intraoceanic basement fossil listric normal faults and a rift zone inverted in a flower structure reflect the evolution of the gorgona terrane from cretaceous extension to likely eocene oblique compression the splay faults could have resulted from tectonic inversion of listric normal faults thus showing how inherited structures may promote fluid flow across margin basement and control seismogenesis

modelling petroleum formation from heterogeneous source rocks the influence of frequency factors on activation energy distribution and geological prediction abstract the application of basin modelling programs permits the prediction of organic matter transformation to oil and gas under variable geological conditions simplified kinetic models are commonly applied with a distribution of activation energies and a single average frequency factor here it will be shown that such simplified kinetic models are not sufficient to correctly predict organic matter transformation in heterogeneous kerogens under geological conditions in the present paper individual pairs of frequency factors and activation energies were calculated from the temperature shift of nine different levels of organic matter transformation ranging from 0 1 to 0 9 tr at different heating rates 0 1 0 7 and 5 0 k min this type of extended kinetic evaluation has been applied on samples from the green river shale the toarcian shale the duvernay formation the draupne formation a type ii s source rock petroleum asphaltenes and a tertiary coal from the mackenzie delta respectively for terrestrial and heterogeneous marine source rocks the frequency factors systematically increase with increasing level of transformation while such an increase was insignificant or absent when homogeneous source rocks were studied by applying geological heating rates it was possible to illustrate the significance of the extended calculation of individual frequency factors the predicted onset temperature of petroleum formation was displaced to 60 70 c in case of lignites coals and type ii s source rocks which was up to 30 40 c lower than predicted by the use of a conventional single frequency factor model to a lesser extend such a shift was also documented for some marine shales e g draupne formation and the duvernay formation the reason for this phenomenon is that an average single frequency factor suppresses the initial formation of petroleum at geological heating rates because high activation energies are needed to maintain the kinetic equation at low generation temperatures in contrast correct activation energies derive from individual frequency factors which keep the activation energies low at low levels of organic matter transformation and result in a more reliable description of the low energy bonds in the heterogeneous organic matter types

constraining the strength of megathrusts from fault geometries and application to the alpine collision zone abstract using coulomb wedge solutions we show that the effective strength of megathrusts b can be determined from the geometry of out of sequence thrusts cutting through an accretionary or orogenic wedge the method is first tested on central chilean margin for which it yields a frictional strength of b 0 053 0 043 0 024 the inferred value agrees well with previous strength estimates and with the tectonic response of the central chilean wedge to 2010 m w 8 8 maule earthquake we then use the approach to constrain the strength of the collision megathrust of the central european alps 30 20 million years ago we find that the collision megathrust had a strength of b 0 065 0 035 0 026 which is similarly low than the strength of subduction megathrusts the result is integrated into a static force balance model to examine potential implications of a weak megathrust for the alpine orogeny the model results suggest that the alpine megathrust supported a mean maximum elevation of 2 000 m and that growth of the wedge up to this elevation supported a switch from contractional to extensional tectonics in the interior of the alps around 20 ma finally using the example of the himalayas we show how the strength of megathrusts may be also derived from the geometry of crustal ramps which provides a valuable alternative if details on out of sequence thrusts are missing

natural gas genesis and sources in the zizhou gas field ordos basin china abstract the zizhou gas field is a large tight sandstone gas field in the ordos basin china based on the analysis of the geological background gas components light hydrocarbon composition carbon and hydrogen isotope values of alkane gases and the geochemical correlation between gases of the zizhou gas field and analogs from other fields in the basin we conclude that a most natural gases in the zizhou gas field are dry with a small content of wet gas b the gases have similar carbon isotopic and light hydrocarbon compositions to the analogs from other fields as well as much more positive 13c values and high contents of c5 7 i alkanes and methylcyclohexanes indicating typical coal derived gas c carbon isotopic reversal in some gas samples is due to mixing of coal derived gases of different maturities d the gases are sourced from mature to high mature carboniferous permian coal measures and e the gas reservoirs represent continuous accumulations

a possible source mechanism of the 1946 unimak alaska far field tsunami uplift of the mid slope terrace above a splay fault zone in 1946 megathrust seismicity along the unimak segment of the alaska subduction zone generated the largest ever recorded alaska aleutian tsunami the tsunami severely damaged pacific islands and coastal areas from alaska to antarctica it is the charter member of tsunami earthquakes that produce outsized far field tsunamis for the recorded magnitude its source mechanisms were unconstrained by observations because geophysical data for the unimak segment were sparse and of low resolution reprocessing of legacy geophysical data reveals a deep water high angle reverse or splay thrust fault zone that leads megathrust slip upward to the mid slope terrace seafloor rather than along the plate boundary toward the trench axis splay fault uplift elevates the outer mid slope terrace and its inner area subsides multibeam bathymetry along the splay fault zone shows recent but undated seafloor disruption the structural configuration of the nearby semidi segment is similar to that of the unimak segment portending generation of a future large tsunami directed toward the us west coast

upper plate splay fault earthquakes along the arakan subduction belt recorded by uplifted coral microatolls on northern ramree island western myanmar burma abstract upper plate structures that splay out from the megathrusts are common features along major convergent plate boundaries however their earthquake and tsunami hazard potentials have not yet received significant attention in this study we identified at least one earthquake event that may have been produced by an upper plate splay fault offshore western myanmar based on u th ages of uplifted coral microatolls this event is likely an earthquake that was documented historically in c e 1848 with an estimated magnitude between 6 8 and 7 2 based on regional structural characteristics such magnitude is consistent with the observed co seismic uplift amount of 0 5 m although these events are smaller in magnitude than events produced by megathrusts they may produce higher earthquake and tsunami hazards for local coastal communities due to their proximity our results also indicate that earthquake events with co seismic uplift along the coast may not necessarily produce a flight of marine terraces therefore using only records of uplifted marine terraces as megathrust earthquake proxies may overlook the importance of upper plate splay fault ruptures and underestimate the overall earthquake frequency for future seismic and tsunami hazards along major subduction zones of the world

modelling the petroleum generation and migration of the third member of the shahejie formation es3 in the banqiao depression of bohai bay basin eastern china abstract the mudstones in the third member of the shahejie formation es3 are the primary source rocks in the banqiao depression of bohai bay basin they are rich in organic matter with total organic carbon toc content up to 3 5 the sandstones in the es3 member are the deepest proven hydrocarbon reservoir rocks with measured porosity and permeability values ranging from 3 6 to 32 4 and from 0 01 md to 3283 7 md respectively one two and three dimensional basin modelling studies were performed to analyse the petroleum generation and migration history of the es3 member in the banqiao depression based on the reconstruction of the burial thermal and maturity history in order to evaluate the remaining potential of this petroleum province the modelling results are calibrated with measured vitrinite reflectance ro borehole temperatures and some drilling results of 63 wells in the study area calibration of the model with thermal maturity and borehole temperature data indicates that the present day heat flow in the banqiao depression varies from 59 8 mw m2 to 61 7 mw m2 and the paleo heat flow increased from 65 ma to 50 4 ma reached a peak heat flow values of approximately 75 mw m2 at 50 4 ma and then decreased exponentially from 50 4 ma to present day the source rocks of the es3 member are presently in a stage of oil and condensate generation with maturity from 0 5 to 1 8 ro and had maturity from 0 5 to 1 25 ro at the end of the dongying formation ed deposition 26 ma oil generation 0 5 ro in the es3 member began from about 37 ma to 34 ma and the peak hydrocarbon generation 1 0 ro occurred approximately from 30 ma to 15 ma the modelled hydrocarbon expulsion evolution suggested that the timing of hydrocarbon expulsion from the es3 member source rocks began from 31 ma to 10 ma with the peak hydrocarbon expulsion shortly after 26 ma secondary petroleum migration pathways in the es3 member of the banqiao depression are modelled based on the structure surfaces at 26 ma and present day respectively the migration history modelling results have accurately predicted the petroleum occurrences within the es3 member of the banqiao depression based on the calibration with drilling results of 10 oil producing wells one well with oil shows and 52 dry holes six favorable zones of oil accumulations in the es3 member of the banqiao depression are identified especially oil accumulation zones i and ii due to their proximity to the generative kitchens short oil migration distances and the presence of a powerful drive force

comparison of postseismic afterslip models with aftershock seismicity for three subduction zone earthquakes nias 2005 maule 2010 and tohoku 2011 we focus on the relation between seismic and total postseismic afterslip following the maule mw 8 8 earthquake on 2010 february 27 in central chile first we calculate the cumulative slip released by aftershock seismicity we do this by summing up the aftershock regions and slip estimated from scaling relations comparing the cumulative seismic slip with afterslip models we show that seismic slip of individual aftershocks exceeds locally the inverted afterslip model from geodetic constraints as the afterslip model implicitly contains the displacements from the aftershocks this reflects the tendency of afterslip models to smear out the actual slip pattern however it also suggests that locally slip for a number of the larger aftershocks exceeds the aseismic slip in spite of the fact that the total equivalent moment of the afterslip exceeds the cumulative moment of aftershocks by a large factor this effect seen weakly for the maule 2010 and also for the tohoku 2011 earthquake can be explained by taking into account the uncertainties of the seismicity and afterslip models in spite of uncertainties the hypocentral region of the nias 2005 earthquake is suggested to release a large fraction of moment almost purely seismically therefore these aftershocks are not driven solely by the afterslip but instead their slip areas have probably been stressed by interseismic loading and the mainshock rupture in a second step we divide the megathrust of the maule 2010 rupture into discrete cells and count the number of aftershocks that occur within 50 km of the centre of each cell as a function of time we then compare this number to a time dependent afterslip model by defining the afterslip to aftershock ratio asar for each cell as the slope of the best fitting line when the afterslip at time t is plotted against aftershock count although we find a linear relation between afterslip and aftershocks for most cells there is significant variability in asar in both the downdip and along strike directions of the megathrust we compare the spatial distribution of asar with the spatial distribution of seismic coupling coseismic slip and bouguer gravity anomaly and in each case we find no significant correlation

the accretion of foreland basin sediments during early stages of continental collision in the european alps and similarities to accretionary wedge tectonics we present structural observations from foreland basin sediments that were incorporated into the orogenic wedge of the central european alps during early stages of continental collision our analysis focuses on the prograde evolution and considers the full history of the sediments ranging from their deposition in the basin to deep burial and metamorphism at temperatures of 320 c the tectonic evolution is matched with constraints on the diagenetic alteration of the sediments for this purpose we calculate the temperatures and depths of sediment compaction and illitization as well as the associated fluid liberation the data set highlights that the tectonic incorporation of the sediments into the orogenic wedge was strongly controlled by their diagenetic state earliest deformation took place during imbrication and frontal accretion of unconsolidated and fluid saturated sediments ductile folding of the sediments occurred already at this stage and was assisted by particulate flow with the progressive consolidation of the sediments the elastic strength increased which resulted in an overall embrittlement this rheological change is recorded by the onset of out of sequence thrusting brittle faulting and the formation of massive quartz calcite veins which took place in the approximate temperature range of the seismogenic zone i e 150 350 c moreover widespread pressure solution resulted in the formation of a penetrative cleavage and records slow but long lasting deformation at low background strain rates in summary the prograde tectonic evolution of the frontal alpine wedge exhibits many similarities with the structural and mechanical evolution of accretionary wedges at active subduction zones

the reconstruction of past climates using multi proxy evidence an example of the weichselian pleniglacial in northwest and central europe abstract different lines of terrestrial biotic and abiotic evidence are used for large scale climate reconstructions to transform proxy data into climate parameter values standardisation procedures are defined and described as each type of biotic and abiotic proxy provides its own climate parameter a detailed climate reconstruction may be obtained the multi proxy database for palaeoclimate reconstruction is a specially designed computer database that facilitates data processing and management of weichselian climate proxies this paper describes the application of multi proxy evidence to reconstruct the climate across lowland northwest and central europe during the interval 41 38 bp for this period the mean temperature of the warmest month is estimated at 10 to 11 c and the mean temperature of the coldest month ranges from 27 to 20 c the annual range suggests a cold continental setting with an estimated mean annual temperature between 9 and 4 c a north to south transition from dis continuous permafrost to seasonally frozen ground is suggested by periglacial evidence

systematic changes of earthquake rupture with depth a case study from the 2010mw 8 8 maule chile earthquake aftershock sequence the very shallow part of subduction megathrusts occasionally hosts tsunami earthquakes with unusually slow rupture propagation the aftershock sequence of the 2010 mw 8 8 maule earthquake offshore chile provides us with the opportunity to study systematic changes in source properties for smaller earthquakes within a single segment of a subduction zone we invert amplitude spectra for double couple moment tensors and centroid depths of 71 aftershocks of the maule earthquake down to magnitudes mw 4 0 in addition we also derive average source durations we find that shallower earthquakes tend to have longer normalized source durations on average similar to the pattern observed previously for larger magnitude events this depth dependence is observable for thrust and normal earthquakes the normalized source durations of normal faulting earthquakes are at the lower end of those for thrust earthquakes probably because of the higher stress drops of intraplate earthquakes compared to interplate earthquakes we suggest from the similarity of the depth dependence of normal and thrust events and between smaller and larger magnitude earthquakes that the depth dependent variation of rigidity rather than frictional conditional stability at the plate interface is primarily responsible for the observed pattern tsunami earthquakes probably require both low rigidity and conditionally stable frictional conditions the presence of longduration moderate magnitude events is therefore a helpful but not sufficient indicator for areas at risk of tsunami earthquakes

upper paleozoic petroleum system ordos basin china abstract the ordos basin is a typical lapped basin including three sequences of strata early paleozoic late paleozoic and mesozoic with a total thickness of 4000 6000 m impermeable sealing beds are well developed at the top and base of the upper paleozoic sequence separating it from the mesozoic and the lower paleozoic strata to form an independent petroleum system in this petroleum system the source rocks are widely distributed coals and dark mudstones occurring in the carboniferous lower permian coal measures with a thickness of 10 15 and 40 60 m respectively the reservoirs are mainly early permian tight sandstones mostly with a porosity of 4 8 and a permeability of 0 1 1 0 10 3 m2 the regional cap rock is a 100 150 m thick mudstone in the upper permian strata the structural framework of the basin is a huge asymmetric syncline dipping gently toward the east and north and steeply toward the south and west well data show that gas saturated gas water transition and water saturated zones are developed from the depositional center to the basin edges the gas saturated zone mainly lies in the gently dipping slope area of the shanbei slope toward eastern and northern up dip directions the water gas transitional zone occurs and finally the water saturated zone presenting a reverse relation of water on top of gas an abnormal negative strata pressure is developed in the gas bearing area with a pressure coefficient cp ranging from 0 83 to 0 95 fluid inclusion data indicate that the upper paleozoic gas pool began to develop around the wuqi area at about 150 ma and it extended toward the north and was largely formed at about 120 ma showing there was a regional migration of the gas water interface from south to north during the gas pool formation these characteristics appear to show that the northern and eastern margins of the petroleum system are defined by a regional hydrodynamic regime the critical moment of the petroleum system occurred during the early cretaceous the basin experienced a rapid subsidence and a significant geothermal event resulting in the source rocks being matured into the main stage of gas generation to form a huge amount of gas the gas migrated into the tight sandstone reservoirs and displaced the rock pore water to form the gas pools and developing the regional hydrodynamic trap

shocks in a box an analogue model of subduction earthquake cycles with application to seismotectonic forearc evolution 1 we introduce and test an experimental approach to simulate elastoplastic megathrust earthquake cycles using an analogue model and apply it to study the seismotectonic evolution of subduction zones the quasi two dimensional analogue model features rate and state dependent elastic frictional plastic and viscoelastic material properties and is scaled for gravity inertia elasticity friction and viscosity the experiments are monitored with a high resolution strain analysis tool based on digital image correlation particle imaging velocimetry piv providing deformation time series comparable to seismologic geodetic and geologic observations in order to separate elastic and nonelastic effects inherent the experimental deformation patterns we integrate elastic dislocation modeling edm into a hybrid approach we use the analogue earthquake slip and interseismic locking distribution as edm dislocation input and forward model the coseismic and interseismic elastic response the residual which remains when the edm prediction is subtracted from the experimental deformation pattern highlights the accumulation of permanent deformation in the model the setup generates analogue earthquake sequences with realistic source mechanisms and elastic forearc response and recurrence patterns and reproduces principal earthquake scaling relations by applying the model to an accretionary type plate margin we demonstrate how strain localization at the rupture peripheries may lead to a seismotectonically segmented forearc including a tectonically stable shelf and coastal high 20 plate convergence accommodated by internal shortening overlying the area of large megathrust earthquake slip fifty to 75 of plate convergence is accommodated by internal shortening in the slope region where earthquake slip tapers out toward the trench the inner forearc region remains undeformed and represents a basin

slab1 0 a three dimensional model of global subduction zone geometries 1 we describe and present a new model of global subduction zone geometries called slab1 0 an extension of previous efforts to constrain the two dimensional non planar geometry of subduction zones around the focus of large earthquakes slab1 0 describes the detailed non planar three dimensional geometry of approximately 85 of subduction zones worldwide while the model focuses on the detailed form of each slab from their trenches through the seismogenic zone where it combines data sets from active source and passive seismology it also continues to the limits of their seismic extent in the upper mid mantle providing a uniform approach to the definition of the entire seismically active slab geometry examples are shown for two well constrained global locations models for many other regions are available and can be freely downloaded in several formats from our new slab1 0 website http on doi gov d9arbs we describe improvements in our two dimensional geometry constraint inversion including the use of average active source seismic data profiles in the shallow trench regions where data are otherwise lacking derived from the interpolation between other active source seismic data along strike in the same subduction zone we include several analyses of the uncertainty and robustness of our three dimensional interpolation methods in addition we use the filtered subduction related earthquake data sets compiled to build slab1 0 in a reassessment of previous analyses of the deep limit of the thrust interface seismogenic zone for all subduction zones included in our global model thus far concluding that the width of these seismogenic zones is on average 30 larger than previous studies have suggested

petroleum generation kinetics single versus multiple heating ramp open system pyrolysis some recent publications promote one run open system pyrolysis experiments using a single heating rate ramp and fixed frequency factor to determine the petroleum generation kinetics of source rock samples because compared to multiple ramp experiments the method is faster less expensive and presumably yields similar results some one ramp pyrolysis experiments yield kinetic results similar to those from multiple ramp experiments however our data for 52 worldwide source rocks containing types i ii iis ii iii and iii kerogen illustrate that one ramp kinetics introduce the potential for significant error that can be avoided by using high quality kinetic measurements and multiple ramp experiments in which the frequency factor is optimized by the kinetic software rather than fixed at some universal value the data show that kinetic modeling based on a discrete activation energy distribution and three different pyrolysis temperature ramps closely approximates that determined from additional runs provided the three ramps span an appropriate range of heating rates for some source rocks containing well preserved kerogen and having narrow activation energy distributions both single and multiple ramp discrete models are insufficient and nucleation growth models are necessary instrument design thermocouple size or orientation and sample weight likely influence the acceptable upper limit of pyrolysis heating rate caution is needed for ramps of 30 50 c min which can cause temperature errors due to impaired heat transfer between the oven sample and thermocouple compound volatility may inhibit pyrolyzate yield at the lowest heating rates depending on the effectiveness of the gas sweep we recommend at least three pyrolysis ramps that span at least a 20 fold variation of comparatively lower rates such as 1 5 and 25 c min the product of heating rate and sample size should not exceed 100 mg c min our results do not address the more fundamental questions of whether kinetic models based on multiple ramp open system pyrolysis are mechanistically appropriate for use in basin simulators or whether petroleum migration through the kerogen network rather than cracking of organic matter represents the rate limiting step in expulsion

preliminary evaluation of the coalbed methane production potential and its geological controls in the weibei coalfield southeastern ordos basin china article i nfo the coalbed methane cbm geology resource and production potential in the weibei coalfield southeastern ordos basin are studied based on geological surveys and laboratory measurements the results showed that coal rank varies both laterally and vertically and changes from volatile bituminous coals in the margin to anthracites towards the basin 1 6 2 5 ro coals are composed of 60 85 vitrinite 15 40 inertinite and a trace amount of minerals methane isothermal adsorption measurements of 20 coal samples revealed that the maximum adsorption capacity on a dry and ash free basis of coals which are affected by coal rank coal maceral coal lithotype and especially to the moisture content varies from 13 91 to 29 54 m 3 t estimated gas contents range from 0 to 15 m

tsunamis and splay fault dynamics 1 the geometry of a fault system can have significant effects on tsunami generation but most tsunami models to date have not investigated the dynamic processes that determine which path rupture will take in a complex fault system to gain insight into this problem we use the 3d finite element method to model the dynamics of a plate boundary splay fault system we use the resulting ground deformation as a time dependent boundary condition for a 2d shallow water hydrodynamic tsunami calculation we find that if the stress distribution is homogeneous rupture remains on the plate boundary thrust when a barrier is introduced along the strike of the plate boundary thrust rupture propagates to the splay faults and produces a significantly larger tsunami than in the homogeneous case the results have implications for the dynamics of megathrust earthquakes and also suggest that dynamic earthquake modeling may be a useful tool in tsunami research

large extensional aftershocks in the continental forearc triggered by the 2010 maule earthquake chile summary the mw 8 8 maule earthquake occurred off the coast of central chile on 2010 february 27 and was the sixth largest earthquake to be recorded instrumentally this subduction zone event was followed by thousands of aftershocks both near the plate interface and in the overriding continental crust here we report on a pair of large shallow crustal earthquakes that occurred on 2010 march 11 within 15 min of each other near the town of pichilemu on the coast of the o higgins region of chile field and aerial reconnaissance following the events revealed no distinct surface rupture we infer from geodetic data spanning both events that the ruptures occurred on synthetic sw dipping normal faults the first larger rupture was followed by buried slip on a steeper fault in the hangingwall the fault locations and geometry of the two events are additionally constrained by locations of aftershock seismicity based on the international maule aftershock data set the maximum slip on the main fault is about 3 m and consistent with field results the onshore slip is close to zero near the surface satellite radar data also reveal that significant aseismic afterslip occurred following the two earthquakes coulomb stress modelling indicates that the faults were positively stressed by up to 40 bars as a result of slip on the subduction interface in the preceding megathrust event in other words the pichilemu earthquakes should be considered aftershocks of the maule earthquake the occurrence of these extensional events suggests that regional interseismic compressive stresses are small several recent large shallow crustal earthquakes in the overriding plate following the 2011 mw 9 0 tohoku oki earthquake in japan may be an analogue for the triggering process at pichilemu

vegetation and climate in the early and pleni weichselian in northern central europe analysis of numerous pollen diagrams from north and central germany and from the adjacent lowlands of the netherlands denmark poland and belarus have facilitated a regional comparison of the vegetation and climatic evolution from the beginning of the early weichselian glaciation to the weichselian pleniglacial data from geological studies and analysis of fossil beetles and plant macroremains have been used to supplement the palaeoclimatic reconstruction up to the end of the oerel interstadial the palaeoclimate was characterised by increasing continentality the winter temperatures in particular tended to fall continuously during the stadials and the interstadials of the early weichselian and early pleniglacial in the brorup and odderade interstadials summer temperatures where sufficiently high to enable boreal forests to grow whereas in the oerel interstadial summer temperatures were such that tree growth was inhibited it is probable that falling sea level and the consequent extension northwards of the north sea coast were the main causes of increasing continentality in the latter part of the pleniglacial peat accumulation frequently took place and humic silts were deposited under lacustrine conditions correlation between various sites is extraordinarily difficult pollen diagrams from the so called interstadials of the glinde moershoofd complex hengelo and denekamp are similar to those of the known early weichselian stadials it is proposed therefore that these interstadials should be called intervals and that the term interstadial be reserved for climatic variations that result in distinctive pollen assemblages and which in turn reflect distinctive vegetation dynamics interstadials should be capable of being characterised on a biostratigraphical basis and it should be possible to establish correlations over considerable distances according to this definition the first three warm oscillations of the weichselian glaciation in the central european lowlands are the brorup odderade and oerel interstadials all other pleniglacial peat layers should be assigned the rank of interval copyright 2001 john wiley sons ltd

a possible transoceanic tsunami directed toward the u s west coast from the semidi segment alaska convergent margin the semidi segment of the alaska convergent margin appears capable of generating a giant tsunami like the one produced along the nearby unimak segment in 1946 reprocessed legacy seismic reflection data and a compilation of multibeam bathymetric surveys reveal structures that could generate such a tsunami a 200 km long ridge or escarpment with crests 1 km high is the surface expression of an active out of sequence fault zone recently referred to as a splay fault such faults are potentially tsunamigenic this type of fault zone separates the relatively rigid rock of the margin framework from the anelastic accreted sediment prism seafloor relief of the ridge exceeds that of similar age accretionary prism ridges indicating preferential slip along the splay fault zone the greater slip may derive from quaternary subduction of the patton murray hot spot ridge that extends 200 km toward the east across the north pacific estimates of tsunami repeat times from paleotsunami studies indicate that the semidi segment could be near the end of its current inter seismic cycle gps records from chirikof island at the shelf edge indicate 90 locking of plate interface faults an earthquake in the shallow semidi subduction zone could generate a tsunami that will inundate the us west coast more than the 1946 and 1964 earthquakes because the semidi continental slope azimuth directs a tsunami southeastward this article is protected by copyright all rights reserved

the micro scale simulation of maturation outline of a new technique and its potential applications a micro analytical technique has been developed for artifically maturing sedimentary organic matter and then quantifying the major components generated during this process in a single analytical step such a capability is well suited for examining the compositional relationships between kerogens and petroleums determining reaction kinetics and making precursor product mass balances according to this technique simulations are made using sealed glass capillary tubes heated here for three days at 300 c 330 c and 350 c pyrolysis products are then released directly into a combined thermovaporisation pyrolysis gc instrument and the major components of the entire c1 yto c35 range can be quantified in a single step using gas chromatography alkene yields are very low and pyrolysates are oil like this is exemplified by the fact that then c9 c19 alkane distribution range of simulated whole petroleum chromatograms from originally immaturegloeocapsamorpha typz alginite a resembles that seen in crude oils generated from this same kerogen type in nature sealed tube experiments usingbotryococcus type alginite a generated a high wax pyrolysate the relative abundance ofn alkanes in the c2 c32 range of many kerogen pyrolysates does not appear to change significantly despite an approximately fifteen fold difference inn alkane yield between the 300 c and 350 c experiments kerogens which are paraffinic oil prone and whose pyrolysates are very rich inn alkanes might therefore generate petroleums in nature with a fixed wet gas c2 c4 to oil c5 ratio alginite b in a greenland shale is much more thermally labile than eitherbotryococcus type alginite a orgloeocapsamorpha type alginite a the mass balance capabilities of the technique have been tested using alum shale kerogen two gas chromatograms were obtained one for the free compounds generated during simulation and one for the high temperature pyrolysate of the kerogen residue for each heating experiment precursor product relationships were qualitatively assessed and dead carbon formation was quantified in this exercise

from petroleum type organofacies to hydrocarbon phase prediction the organic facies concept states that kerogen abundance and composition are relatable to depositional settings this link has been extended using open system pyrolysis methods to include major petroleum types whose gross compositions are inherently defined by source rock kerogens and hence to petroleum composition which directly controls the physical response of fluids to changing pressure and temperature conditions during secondary migration the possibility to model petroleum composition during hydrocarbon generation as well as the phase behavior of the fluids during migration is now available in modern basin modeling software however whereas pyrolysis methods can accurately reconstruct hydrocarbon gas oil ratios and liquid compositions they are inherently incapable of correctly reproducing the gas composition of natural fluids and because the gas composition dominantly controls the phase behavior of petroleums multicompound compositional kinetic predictions based on pyrolysis results alone are inappropriate for the prediction of phase behavior the new phasekinetics approach described here combines open and closed system pyrolysis techniques to characterize the compositional evolution of the fluids generated as a function of increasing thermal stress as well as correcting experimentally determined gas compositions and therefore overcomes these deficiencies it has been used to develop compositional kinetic schemes capable of predicting natural petroleum phase behavior for different organofacies types the methodology uses a compositional description of the generated fluids similar to that used in pressure volume temperature pvt simulation selected studies in the norwegian north sea brazil and mexico demonstrate the quality of the tuned compositional predictions for different organic facies types

constructing forearc architecture over megathrust seismic cycles geological snapshots from the maule earthquake region chile we present new field structural data from the chilean coastal cordillera located above the northern and central parts of the interplate contact ruptured by the a d 2010 m w 8 8 maule earthquake the northern study area contains the northwest striking pichilemu normal fault an intraplate structure reactivated after the megathrust event by crustal earthquakes up to m w 7 0 the structural style of this region is dominated by kilometer scale normal faults that have been active at least throughout the quaternary the orientations of these main faults define three structural systems 1 northeast and 2 northwest striking margin oblique faults and 3 north to north northeast striking margin parallel faults from north to south these three systems vary in their predominant occurrence starting with bimodal orientations of groups 1 and 2 followed by predominantly single north to north northeast orientations of group 3 reverse faults coexist in time and space with the normal structures but are scarce and display variable apparently random orientations the shallow crustal normal faults including the pichilemu fault show a persistent kinematic history probably spanning thousands of subduction seismic cycles though historically smaller in magnitude than those of the triggered normal faults interseismic forearc thrust events were recorded above the rupture area prior to the maule earthquake the quaternary reverse faults identified in our study regions may be preserving interseismic slow strain rate permanent deformation signature in the structural grain analogous observations along the a d 2011 tohoku earthquake rupture in japan imply that such a link between the short and long term deformation patterns of the forearc is not exclusive of the maule earthquake region

modeling of gas generation from the barnett shale fort worth basin texas the generative gas potential of the mississippian barnett shale in the fort worth basin texas was quantitatively evaluated by sealed gold tube pyrolysis kinetic parameters for gas generation and vitrinite reflectance ro changes were calculated from pyrolysis data and the results used to estimate the amount of gas generated from the barnett shale at geologic heating rates using derived kinetics for ro evolution and gas generation quantities of hydrocarbon gas generated at ro 1 1 are about 230 l t 7 4 scf t and increase to more that 5800 l t 186 scf t at ro 2 0 for a sample with an initial total organic carbon content of 5 5 and ro 0 44 the volume of shale gas generated will depend on the organic richness thickness and thermal maturity of the shale and also the amount of petroleum that is retained in the shale during migration gas that is reservoired in shales appears to be generated from the cracking of kerogen and petroleum that is retained in shales and that cracking of the retained petroleum starts by ro 1 1 this result suggests that the cracking of petroleum retained in source rocks occurs at rates that are faster than what is predicted for conventional siliciclastic and carbonate reservoirs and that contact of retained petroleum with kerogen and shale mineralogy may be a critical factor in shale gas generation shale gas systems together with overburden can be considered complete petroleum systems although the processes of petroleum migration accumulation and trap formation are different from what is defined for conventional petroleum systems

spatial variations of aftershock parameters and their relation to geodetic slip models for the 2010 mw8 8 maule and the 2011 mw9 0 tohoku oki earthquakes recent development in analysis tools and deployments of the geodetic and seismic instruments give an opportunity to investigate aftershock sequences at local scales which is important for the seismic hazard assessment in particular we study the dependencies between aftershock sequences properties and deformational geological data on a scale of the rupture extension of megathrust earthquakes for this goal we use on one hand published models of inter co and postseismic slip and geological information and on the other hand aftershock parameters obtained by fitting a modified epidemic type aftershock sequence etas model the altered etas model takes into account the mainshock rupture extension and it distinguishes between primary and the secondary aftershock triggering involved in the total seismicity rate we estimate the spearman correlation coefficients between the spatially distributed aftershock parameters estimated by the modified etas model and crustal physical properties for the maule 2010 mw8 8 and the tohoku oki 2011 mw9 0 aftershock sequences we find that 1 modified etas model outperforms the classical one when the mainshock rupture extension cannot be neglected and represented as a point source 2 anomalous aftershock parameters occur in the areas of the reactivated fault systems 3 aftershocks regardless of their generation tend to occur in the areas of high coseismic slip gradient afterslip and interseismic coupling 4 aftershock seismic moment releases preferentially in regions of large coseismic slip coseismic slip gradient and interseismically locked areas 5 b value tends to be smaller in interseismically locked regions

contrasting amount of fluids along the megathrust ruptured by the 2010 maule earthquake as revealed by a combined analysis of aftershocks and afterslip abstract we present a novel approach combining time variable computations of b value and afterslip to study the postseismic activity following the mw 8 8 maule 2010 earthquake we subdivided the first 392 days after the mainshock into overlapping windows for which we compared maps of b value computed from neic seismicity and afterslip computed from continuous gps stations the correlation between both parameters is weak during the first 2 months when the aftershocks magnitude of completeness decreases and the number of gps stations increased after this early stage a correlation between both parameters emerges we interpret this correlated spatiotemporal pattern combining factors proposed to control each parameter separately this exercise suggests a segmentation of the maule megathrust the northern segment is characterized by an increase of afterslip and b value during the early postseismic phase and then a simultaneous decrease of both parameters which we interpret as the effect of an ingression of fluids into the megathrust and its subsequent consumption during fault healing in contrast the southern segment is characterized by a central region with minimum afterslip and low b value surrounded by areas that experience mostly seismic afterslip as a consequence of large static stress loaded by the mainshock suggesting a drier and stronger megathrust where healing was active earlier interpreted along with features of the pre and coseismic phases our results allow us to propose the existence of two contrasting types of seismic asperities classical strong stick slip patches that we link with dry regions of the megathrust versus weak wet and conditionally stable frictional patches that could have a range of seismogenic behaviors from creeping and or locking during the interseismic period largely contributing with coseismic slip and concentrating afterslip at their borders the application of our novel method to other great earthquakes could reveal whether this is a common or anomalous feature of megathrusts

genesis of tight sand gas in the ordos basin china abstract based on molecular and stable carbon isotope composition of a large collection of gas samples and integrated with the geological context this article discusses the genesis and migrational characteristics of natural gases from the giant tight sand gas fields of the upper paleozoic strata ordos basin upob our results show that the upob gas is mostly derived from coaly source rocks with a minor contribution of oil associated gas probably from the interbedded carbonate source rocks gas isotope data suggest that the yulin zizhou gas field was likely formed from a single gas charge with no significant alteration whereas the sulige field contains a mixture of gases from successive charges with multiple maturity levels the geographical variation in the observed gas composition is attributed primarily to the effect of source rock maturity with no explicit geochemical fractionation caused by long distance lateral migration

characterising and dating weichselian organogenic sediments a case study from the lusatian ice marginal valley scheibe opencast mine eastern germany abstract dates determined with three absolute dating methods 14c luminescence and 230th u supported the findings of the paleobotanical investigations of the weichselian upper fluvial sequence of the scheibe opencast mine in the niederlausitz lower lusatia eastern germany they allowed to identify three units of organogenic sediments organogenic complexes oc developed as peaty and or humic silts samples from the uppermost oc i unit displayed 14c age ranges from 32 to 28 and 26 to 24 ka respectively for the latest phase an open landscape was identified although high arboreal values point to locally extended sparse forests the lithologically and paleobotanically heterogeneous oc ii unit 37 ka represents at least two periods during which organic matter accumulated in an open landscape the uppermost subunit represents an unforested interstadial of the middle pleniglacial the lowermost oc iii unit has an age of about 56 ka or higher according to the 230th u or tl dates respectively it represents a forested interstadial assigned to the early weichselian

crustal thickness and mantle wedge structure from receiver functions in the chilean maule region at 35 s a temporary passive seismic network of 21 broad band stations was deployed in central chile between 35 s to 36 s the network recorded data prior to the magnitude mw 8 8 2010 maule earthquake at a latitude of the major slip and surface deformation the experiment was conducted to survey crustal and mantle structures and to assess the state of hydration of the mantle wedge we present results of a teleseismic p receiver function study supporting a continental moho at approx 38 km depth phase conversion at this boundary could be observed continuously from the intersection of the subducting slab with the continental moho towards the andes the character of receiver functions indicated little evidence for infiltration of water from the subducting plate into the overlying mantle wedge suggesting that only a small amount of water is released from the subducting plate aftershocks of the maule earthquake and post seismic slip reached depths of 50 km and hence slip spread down dip of the continental moho in the post seismic phase co seismic rupture however occurred updip of the continental moho spare aftershock seismicity is observed at the intersection of the continental moho with the subducting slab

the art of maturity modeling part 2 alternative models and sensitivity analysis the sensitivity of exploration decisions to variations in several input parameters for maturity modeling was examined for the miti rumoi well hokkaido japan decisions were almost completely insensitive to uncertainties about formation age and erosional removal across some unconformities but were more sensitive to changes in removal during unconformities which occurred near maximum paleotemperatures exploration decisions were not very sensitive to the choice of a particular kinetic model for hydrocarbon generation uncertainties in kerogen type and the kinetics of different kerogen types are more serious than differences among the various kinetic models results of modeling using the tti method were unsatisfactory thermal history and timing and amount of hydrocarbon generation estimated or calculated using the tti method were greatly different from those obtained using a purely kinetic model we strongly recommend use of the kinetic r o method instead of the tti method if we had lacked measured r o data subsurface temperature data or both our confidence in the modeling results would have been sharply reduced conceptual models for predicting heat flow and thermal conductivity are simply too weak at present to allow us to carry out highly meaningful modeling unless our input is constrained by measured data maturity modeling therefore requires the use of more not fewer measured temperature and maturity data the use of sensitivity analysis in maturity modeling is very important for understanding the geologic system for knowing what level of confidence to place on the results and for determining what new types of data would be most necessary to improve our confidence sensitivity analysis can be carried out easily using a rapid interactive maturity modeling program

quantitative evaluation of gas generation from the upper paleozoic coal mudstone and limestone source rocks in the ordos basin china abstract significant quantities of tight gas resources have been discovered in the upper paleozoic interval in the ordos basin central china the gas is believed to have been derived primarily from the upper paleozoic coal mudstone and limestone source rocks an integrated organic geochemistry and basin modeling approach was applied to quantitatively evaluate gas generation from the three types of source rocks source specific gas generation kinetics were first established on the basis of sealed gold tube pyrolysis experiments gas generation was then modeled in 1d and 3d using the source specific kinetics obtained the results show that 1 near the depositional and thermal center e g well zt 1 gas generation occurred much earlier and was greater than that of the sh 360 well which is away from the depositional and thermal center 2 c2 c5 gases in the zt 1 well underwent thermal cracking while gases in the sh 360 well did not experience any secondary thermal alteration 3 hydrocarbon gases were mainly generated during the early cretaceous 135 96 ma and the late jurassic 161 135 ma 4 the cumulative amounts of gas generation from the coal mudstone and limestone source rocks are 147 23 1012 57 85 1012 and 12 73 1012 m3 respectively with coal seams being a major contributor about 67 6 to the upper paleozoic gas system followed by the mudstone about 26 6 and limestone about 5 8 by comparing with previous work and a default kinetics basin model our source specific kinetics basin model is more suitable for simulating gas generation in the upper paleozoic source rocks within the ordos basin