vertical motion in the gulf stream near 68 w abstract the authors compute and compare vertical motions from three different data sources within a 300 km square domain centered in the gulf stream near 38 n 68 w and show that vertical motions inferred from all three independent data sources and different analysis methods give similar results the time derivatives of rafos float pressures on isopycnal surfaces are used to determine directly observed vertical motion wraf second vertical motions are inferred from the heat equation using measured temperature changes and the backing and veering of currents observed by a stack of current meters to produce wcm third vertical motions are calculated from the quasigeostrophic vorticity equation using geostrophic streamfunctions from inverted echo sounder measurements to produce wies wcm agrees well with wraf from all floats that pass within 10 km of a current meter mooring daily fields of wcm show very good coherence with time series of wcm for periods longer than 16 d but noise domination for periods

the 2006 2007 kuril islands great earthquake sequence the southwestern half of a 500 km long seismic gap in the central kuril island arc subduction zone experienced two great earthquakes with extensive preshock and aftershock sequences in late 2006 to early 2007 the nature of seismic coupling in the gap had been uncertain due to the limited historical record of prior large events and the presence of distinctive upper plate trench and outer rise structures relative to adjacent regions along the arc that have experienced repeated great interplate earthquakes in the last few centuries the intraplate region seaward of the seismic gap had several shallow compressional events during the preceding decades notably an m s 7 2 event on 16 march 1963 leading to speculation that the interplate fault was seismically coupled this issue was partly resolved by failure of the shallow portion of the interplate megathrust in an m w 8 3 thrust event on 15 november 2006 this event ruptured 250 km along the seismic gap just northeast of the great 1963 kuril island m w 8 5 earthquake rupture zone within minutes of the thrust event intense earthquake activity commenced beneath the outer wall of the trench seaward of the interplate rupture with the larger events having normal faulting mechanisms an unusual double band of interplate and intraplate aftershocks developed on 13 january 2007 an m w 8 1 extensional earthquake ruptured within the pacific plate beneath the seaward edge of the kuril trench this event is the third largest normal faulting earthquake seaward of a subduction zone on record and its rupture zone extended to at least 33 km depth and paralleled most of the length of the 2006 rupture the 13 january 2007 event produced stronger shaking in japan than the larger thrust event as a consequence of higher short period energy radiation from the source the great event aftershock sequences were dominated by the expected faulting geometries thrust faulting for the 2006 rupture zone and normal faulting for the 2007 rupture zone a large intraplate compressional event occurred on 15 january 2009 m w 7 4 near 45 km depth below the rupture zone of the 2007 event and in the vicinity of the 16 march 1963 compressional event the fault geometry rupture process and slip distributions of the two great events are estimated using very broadband teleseismic body and surface wave observations the occurrence of the thrust event in the shallowest portion of the interplate fault in a region with a paucity of large thrust events at greater depths suggests that the event removed most of the slip deficit on this portion of the interplate fault this great earthquake doublet demonstrates the heightened seismic hazard posed by induced intraplate faulting following large interplate thrust events future seismic failure of the remainder of the seismic gap appears viable with the northeastern region that has also experienced compressional activity seaward of the megathrust warranting particular attention

influence of maturity on carbazole and benzocarbazole distributions in crude oils and source rocks from the sonda de campeche gulf of mexico abstract carbazole geochemistry has been studied for a petroleum system in which vertical migration is prominent and where reservoirs are locally sourced an essentially uniform organofacies of organicrich tithonian source rocks from the sonda de campeche gulf of mexico covering a well defined maturity sequence 0 36 1 29 rr and associated crude oils 0 49 0 92 rc from palaeocene reservoirs formed the sampling base comparison of the distribution of alkylcarbazoles and benzocarbazoles in rock bitumens and oils revealed that fractionation due to primary expulsion had no effect on the distribution of shielded exposed carbazoles within crude oils perhaps more importantly the benzocarbazole ratio in both rock extracts and crude oils increased with maturity indicating that this parameter cannot be directly used as a migration indicator in petroleum systems where vertical migration through faults and fissures represents the main avenues of oil migration

the oaxaca mexico earthquake of 1931 lithospheric normal faulting in the subducted cocos plate a study of the great earthquake in oaxaca mexico on 15 january 1931 shows that it was a normal fault earthquake striking east west the lack of evidence of surface faulting near the source region1 and the focal depth of 40 km inferred from body wave modelling suggest that the earthquake occurred within the subducted slab the large size of the earthquake ms 8 0 strongly suggests that the rupture broke through the entire lithosphere of the subducted cocos plate other large normal fault earthquakes in the japanese2 aleutian3 peruvian4 and sumba5 arcs show lithospheric faulting seawards of the trench or very close to it the 1931 event however occurred farther down dip in the slab 150 km landward of the trench below the bottom of what appears to be the seismogenic plate interface we speculate here that large although infrequent normal fault earthquakes such as the 1931 oaxaca earthquake may have a role in decoupling at depth the subducted slab from the upper part of the slab and perhaps from the overriding mexican continental plate the epicentral location of the 1858 michoacan earthquake6 ms 7 5 suggests that it may represent another example of lithospheric normal faulting in the middle american arc such earthquakes for which the periods of recurrence are unknown constitute an extremely high seismic risk to population centres of mexico

geochemical characterisation of middle devonian oils in nw alberta canada possible source and maturity effect on pyrrolic nitrogen compounds abstract molecular geochemical compositions of a suite of middle devonian sourced and reservoired oils from the rainbow zama shekilie sub basins in n w alberta canada reveal the presence of at least two oil families in the study area the distribution of each oil family is geographically restricted to a single sub basin consistent with the oils being sourced locally within a series of closed generation migration trapping systems the diversity in the biomarker distributions of the oils indicates the wide range of depositional environments and source materials existing in each sub basin rather than mixing of end member oils across different sub basins clear maturity differences are observed between the oils from the rainbow and zama subbasins pre cretaceous thermal anomalies along the reactivated regional precambrian basement faults are proposed as one of the major causes for the relatively high maturity levels for the middle devonian source rocks in the study area we infer that depositional environment and thermal maturity have had a strong impact on the geochemical characteristics of the saturated and aromatic hydrocarbons in the rainbow shekilie zama oils but may not influence the pyrrolic nitrogen compounds to a significant extent however recognition of possible source and maturity effects on pyrrolic nitrogen compounds in other studies suggests that these factors should be considered before the pyrrolic nitrogen compounds are used to characterize petroleum migration

stress changes and aftershock distribution of the 1994 and 2006 java subduction zone earthquake sequences 1 the mw 7 8 1994 and the mw 7 7 2006 interplate thrust mechanism earthquakes that occurred in the java subduction zone produced dominantly normal faulting aftershocks unusual for large megathrust main shocks various models proposed for these earthquake sequences invoke main shock rupture on an isolated portion of a decoupled plate boundary fault with updip and outer rise extension leading to the normal faulting other models suggest that these aftershocks occurred in a zone of the subduction zone where usually earthquakes cannot propagate or initiate leading to the occurrence of normal faulting aftershocks in the outer rise overriding and subducting plates here we examine a simpler possibility one in which coulomb stress changes cfs imparted by slip during the two large subduction events led to normal faulting events on favorably oriented planes within the slab and near trench region of the subduction zone we compute stress changes resulting from both events and subsequent large aftershocks using both uniform and variable slip models for main shock slip resolved onto both aftershock nodal planes we find that there is not a clear pattern of aftershock occurrence in areas of stress increase due to main shock slip this implies that these aftershocks are not simply triggered by the static stress changes from the main shock and additional complexity should be considered to explain these unusual earthquake sequences

subduction of seamounts at the java trench a view with long range sidescan sonar abstract we describe here a 1300 km by 45 km gloria long range sidescan sonar swath along the eastern java trench the swath images the trench axis a narrow strip of oceanic crust to the south and the toe of the accretionary wedge to the north between 108 and 120 e sonar images of the ocean crust show a pattern of normal faults typical of the outer wall of trenches these result from tension related to the bending of the oceanic lithosphere into the subduction zone a number of sub circular seamounts are also seen some of which are currently being subducted isolated ponds of flat lying sediments occur in the trench axis although along much of its length the trench is devoid of such sediment accumulations on the inner trench wall the accretionary wedge is recognised by its distinctive grainy texture with the grain aligned sub parallel to the deformation front where subducting seamounts are colliding with the wedge large crescentic areas of very high backscattering correlate with re entrants in the deformation front and large indentations in the wedge the high backscattering within these collision scars is interpreted to arise from outcropping strata and talus covered slopes resulting from erosion of an inner trench wall shortened and oversteepened by collision with a seamount all of the sediment ponds in the trench axis occur in close association with collision scars strongly suggesting localised erosion of the accretionary wedge in the scar areas however the volume of the indentations appears to be an order of magnitude greater than the volume of eroded sediments deposited in the trench indicating that erosion cannot be the primary mechanism by which indentations are created most of the missing material must be displaced landward by thrusting and folding ahead of the seamount our observations at the java trench are broadly comparable with those made at the japan trench by french and japanese workers however some differences in the detail of the collision process are evident in particular oversteepening and erosion occur from the earliest stage of collision at the java trench while uplift and understeepening initially dominate at the japan trench differences in the effects of subducting seamounts in the two areas are attributed to contrasts between the relatively unlithified strata of the java trench inner wall and the more lithified strata of the non accreting japan trench inner wall

a new observation of dynamically triggered regional seismicity earthquakes in greece following the august 1999 izmit turkey earthquake the m w 7 4 izmit turkey earthquake triggered widespread regional seismicity in greece over a study region extending from 400 km to nearly 1000 km away from the epicenter small events began immediately after the passage of the mainshock surface waves suggesting that the transient stresses of the seismic waves were the trigger the increase in cataloged earthquakes in ordinary continental crust is a new observation and is statistically significant at the 95 level unlike the previous example of distant triggering during the landers earthquake the activated seismicity occurred entirely in non volcanic areas the greek sites were triggered by waves with amplitudes at least a factor of 3 lower than the observed triggering threshold for imperial valley we speculate that dynamic triggering on a regional scale results in countrywide episodes of increased seismicity or superswarms in regions with low triggering thresholds such as greece

rupture process of the 2010 mw 7 8 mentawai tsunami earthquake from joint inversion of near field hr gps and teleseismic body wave recordings constrained by tsunami observations the 25 october 2010 mentawai tsunami earthquake mw 7 8 ruptured the shallow portion of the sunda megathrust seaward of the mentawai islands offshore of sumatra indonesia generating a strong tsunami that took 509 lives the rupture zone was updip of those of the 12 september 2007 mw 8 5 and 7 9 underthrusting earthquakes high rate 1 s sampling gps instruments of the sumatra gps array network deployed on the mentawai islands and sumatra mainland recorded time varying and static ground displacements at epicentral distances from 49 to 322 km azimuthally distributed tsunami recordings from two deepwater sensors and two tide gauges that have local high resolution bathymetric information provide additional constraints on the source process finite fault rupture models obtained by joint inversion of the high rate hr gps time series and numerous teleseismic broadband p and s wave seismograms together with iterative forward modeling of the tsunami recordings indicate rupture propagation 50 km up dip and 100 km northwest along strike from the hypocenter with a rupture velocity of 1 8 km s subregions with large slip extend from 7 to 10 km depth 80 km northwest from the hypocenter with a maximum slip of 8 m and from 5 km depth to beneath thin horizontal sedimentary layers beyond the prism deformation front for 100 km along strike with a localized region having 15 m of slip the seismic moment is 7 2 1020 n m the rupture model indicates that local heterogeneities in the shallow megathrust can accumulate strain that allows some regions near the toe of accretionary prisms to fail in tsunami earthquakes

sources of tsunami and tsunamigenic earthquakes in subduction zones we classified tsunamigenic earthquakes in subduction zones into three types earth quakes at the plate interface typical interplate events earthquakes at the outer rise within the subducting slab or overlying crust intraplate events and tsunami earthquakes that generate considerably larger tsunamis than expected from seismic waves the depth range of a typical interplate earthquake source is 10 40km controlled by temperature and other geological parameters the slip distribution varies both with depth and along strike recent examples show very different temporal change of slip distribution in the aleutians and the japan trench the tsunamigenic coseismic slip of the 1957 aleutian earthquake was concentrated on an asperity located in the western half of an aftershock zone 1200km long this asperity ruptured again in the 1986 andreanof islands and 1996 delarof islands earthquakes by contrast the source of the 1994 sanriku oki earthquake corresponds to the low slip region of the previous interplate event the 1968 tokachi oki earthquake tsunamis from intraplate earthquakes within the subducting slab can be at least as large as those from interplate earthquakes tsunami hazard assessments must include such events similarity in macroseismic data from two southern kuril earthquakes illustrates difficulty in distinguishing interplate and slab events on the basis of historical data such as felt reports and tsunami heights most moment release of tsunami earthquakes occurs in a narrow region near the trench and the concentrated slip is responsible for the large tsunami numerical modeling of the 1996 peru earthquake confirms this model which has been proposed for other tsunami earthquakes including 1896 sanriku 1946 aleutian and 1992 nicaragua

correlation and migration studies of north central sumatra oils the central sumatra basin csb is a prolific petroleum producing basin and its petroleum systems have been extensively studied the widely occurring tertiary lacustrine shale brown shale has long been recognized as the main source rock for tens of billions of barrels of oil in place the oils produced from different fields display significant variation in source characteristics that have been attributed to variation in source facies despite this generalized recognition of the oil source the links between major oil accumulations and many possible source kitchens throughout the basin have not been established as detailed oil source correlation and oil migration routes are not well defined for continued exploration in the region detailed genetic grouping and migration routes of the oils were evaluated through geochemical characterization of numerous oils from various fields in the northern part of central sumatra biomarker and carbon isotopic data indicate that the oils are quite similar geochemically but form several genetic groups on the basis of subtle but persistent differences in source facies the groupings appear geographically meaningful and show association of the different oil groups with various troughs carbazole distributions show consistency in suggesting differences in relative migration distance among the oils within each genetic group by combining the oil grouping and carbazole distributions with geological data models of migration directions and pathways for oils in north central sumatra have been constructed

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

influence of maturity on distributions of benzo and dibenzothiophenes in tithonian source rocks and crude oils sonda de campeche mexico abstract the sureste basin is the most prolific oil producing area of mexico extending from the mainland into the sonda de campeche offshore region the tithonian sedimentary sequence is the most important source of hydrocarbons it contains sulphur rich kerogen which progressively cracks to form petroleum beginning at 0 53 rr maturity increases from northeast to southwest across the region sulphur compounds in the tithonian source rocks and in the petroleums they have generated have been studied by gas chromatography alkylbenzothiophenes are present in highest abundance at low maturity whereas the alkyldibenzothiophenes are most abundant at higher stages of maturity the relative abundance of specific c3 benzothiophene isomers are especially sensitive to changes in maturity of sulphur rich type ii organic matter a novel maturity parameter the c3 benzothiophene index c3bti shows a very good correlation to vitrinite reflectance values r2 0 96 n 10 the methyldibenzothiophene ratio mdr also has a wide dynamic range application of c3bti and mdr to the study area strongly supports a model involving localised vertical migration avenues though several possible scenarios may explain the filling history of reservoirs in the southwest part of the sonda de campeche

mesoscale instability and upwelling part 2 testing the diagnostics of vertical motion with a three dimensional ocean front model abstract a three dimensional primitive equation ocean front model is employed to simulate mesoscale instabilities and then to investigate the validity and the contingent differences of three alternative methods used for the diagnosis of mesoscale vertical motion from combined density and horizontal velocity mappings 1 the isopycnic advection equation 2 the vorticity advection equation and 3 the equation the model is integrated for 60 days during which period meanders form along the initially unidirectional jet first preferably at a wavelength of just under 100 km and later also at smaller horizontal scales these growing instabilities are associated with vertical velocities of up to some tens of meters per day the horizontal distribution pattern of vertical velocity can reasonably be estimated by use of method 3 and also method 2 but method 1 may yield a pattern having the wrong phase relationship

carbazole distributions in rocks from non marine depositional environments abstract pyrrolic nitrogen compounds have been studied from extracts of the rocks collected from the tertiary saline lacustrine strata in the qaidam basin and the middle lower jurassic coal bearing strata in the turpan basin nw china biomarker signatures revealed the presence of three sample groups related to saline lacustrine conditions in the qaidam basin and freshwater lake and swamp depositional settings in the turpan basin significant differences in carbazole distributions were observed among the sample groups from different depositional environments generally a strong predominance of 1 4 1 5 dimethylcarbazoles over 1 3 1 6 dimethylcarbazoles was found for the qaidam rocks from the saline lacustrine settings with a ratio of 1 3 1 6 1 4 1 5 dimethylcarbazole ranging from 0 35 to 0 66 while enhanced amounts of 1 3 1 6 dimethylcarbazoles relative to 1 4 1 5 dimethylcarbazoles were detected for the turpan samples from the swamp environments with the 1 3 1 6 1 4 1 5 dimethylcarbazole ratio 0 8 samples from the freshwater lake environments in the turpan basin showed intermediate values for the 1 3 1 6 1 4 1 5 dimethylcarbazole ratio in addition a predominance of 2 4 dimethylcarbazole over 2 6 dimethylcarbazole was observed for the qaidam samples whereas most turpan samples showed elevated amounts of 2 6 dimethylcarbazole relative to 2 4 dimethylcarbazole moreover 3 methylcarbazole occurred as the least abundant c 1 carbazole isomer for most qaidam rocks while the turpan samples from swamp settings often showed an enhanced abundance of 3 methylcarbazole the 1 3 1 6 1 4 1 5 dimethylcarbazole ratio was observed to have a positive correlation with 3 4 methylcarbazole 2 6 2 4 dimethylcarbazole and pr ph respectively these observations may indicate that c 1 and c 2 carbazoles with a methyl group at c 3 c 6 prevailed for swamp settings whereas isomers with a methyl at c 4 c 5 were dominant for the freshwater or saline lacustrine environments although variations in benzocarbazoles were detected in the bitumens an obvious correlation was not observed for the different depositional environments

delayed triggering of the 1999 hector mine earthquake by viscoelastic stress transfer stress changes in the crust due to an earthquake can hasten the failure of neighbouring faults and induce earthquake sequences in some cases1 2 3 4 5 the 1999 hector mine earthquake in southern california magnitude 7 1 occurred only 20 km from and 7 years after the 1992 landers earthquake magnitude 7 3 this suggests that the hector mine earthquake was triggered in some fashion by the earlier event but uncertainties in the slip distribution and rock friction properties associated with the landers earthquake have led to widely varying estimates of both the magnitude and sign of the resulting stress change that would be induced at the location of the hector mine hypocentre with estimates varying from 1 4 bar ref 6 to 0 5 bar ref 7 more importantly coseismic stress changes alone cannot satisfactorily explain the delay of 7 years between the two events here we present the results of a three dimensional viscoelastic model that simulates stress transfer from the ductile lower crust and upper mantle to the brittle upper crust in the 7 years following the landers earthquake using viscoelastic parameters that can reproduce the observed horizontal surface deformation following the landers earthquake our calculations suggest that lower crustal or upper mantle flow can lead to postseismic stress increases of up to 1 2 bar at the location of the hector mine hypocentre during this time period contributing to the eventual occurrence of the 1999 hector mine earthquake these results attest to the importance of considering viscoelastic processes in the assessment of seismic hazard8 9 10 11

fractionation of azaarenes during oil migration abstract a comparative study of alkylbenzoquinolines in crude oils and rock extracts bitumens from japan and sumatra shows that the ratios of nitrogen masked isomers nmis to nitrogen exposed isomers neis and the ratio of higher homologs to lower homologs is higher in crude oils than in corresponding bitumens also a regular increase in the ratios of nmis to neis with increasing migration distance is observed for a series of crude oils from the sarukawa oil field northeastern japan these results are attributed to the preferential migration of nmis caused by their weak adsorption on clay minerals and or their low solubility in interstitial water and the selective removal of lower honologs caused by their irreversible adsorption onto clays during oil migration which are regarded as geochromatographic phenomena it is suggested that those ratios can be used to estimate the degree of fractionation of oils during primary and secondary migration

wedge geometry frictional properties and interseismic coupling of the java megathrust abstract the mechanical interaction between rocks at fault zones is a key element for understanding how earthquakes nucleate and propagate therefore estimating frictional properties along fault planes allows us to infer the degree of elastic strain accumulation throughout the seismic cycle the java subduction zone is an active plate boundary where high seismic activity has long been documented however very little is known about the seismogenic processes of the megathrust especially its shallowest portion where onshore geodetic networks are insensitive to recover the pattern of elastic strain here we use the geometry of the offshore accretionary prism to infer frictional properties along the java subduction zone using coulomb critical taper theory we show that large portions of the inner wedge in the eastern part of the java subduction megathrust are in a critical state where the wedge is on the verge of failure everywhere we identify four clusters with an internal coefficient of friction int of 0 8 and hydrostatic pore pressure within the wedge the average effective coefficient of friction ranges between 0 3 and 0 4 reflecting a strong decollement our results also show that the aftershock sequence of the 1994 mw 7 9 earthquake halted adjacent to a critical segment of the wedge suggesting that critical taper wedge areas in the eastern java subduction interface may behave as a permanent barrier to large earthquake rupture in contrast in western java topographic slope and slab dip profiles suggest that the wedge is mechanically stable i e deformation is restricted to sliding along the decollement and likely to coincide with a seismogenic portion of the megathrust we discuss the seismic hazard implications and highlight the importance of considering the segmentation of the java subduction zone when assessing the seismic hazard of this region

the influence of facies and depositional environment on the occurrence and distribution of carbazoles and benzocarbazoles in crude oils a case study from the gulf of suez egypt abstract two major hinge zones separate the gulf of suez gos of egypt into three tectonic sub provinces namely the northern central and southern sectors based on bulk and molecular parameters the crude oils from the gos can be subdivided into three groups according to their geographical origin from the three sectors the geochemical characteristics of the oils are consistent with inferred depositional environments of anoxic marine carbonate facies in the central sector compared to a more oxic environment that has received an increased proportion of clastic input in the southern sector while the northern is intermediate in character most of the oils cover a relatively narrow maturity range 0 86 0 98 r c in the peak oil window the biomarker parameter ts ts tm is controlled by variations of facies and depositional environment but not by maturity concentrations of pyrrolic nitrogen compounds in the gos crude oils are in general relatively low but show a large range of variability in crude oils of the northern sector a strong predominance of c 4 and c 5 carbazoles over the lower homologues is observed towards the south the relative abundance of carbazole and the methylcarbazoles increases successively variations within the methylcarbazoles and c 2 carbazoles are rather small and therefore are not useful for a straightforward classification of oil families however atypical patterns in some of the oils particularly from the northern sector give evidence for contributions from yet unidentified local sources which might not be of general importance in the gos petroleum province benzo b carbazole is near or even below detection limit in the gos crude oils the benzocarbazole a a c ratio shows a consistently positive correlation with api gravity pr ph and ts ts tm and a negative correlation with the sulphur content based on these observations it is inferred that facies and depositional environment of the relevant source rocks are the major factors influencing the benzocarbazole distributions in the central sector of the gos in which oils are predominantly sourced from carbonates deposited under strongly reducing conditions a a c values are mainly below 0 5 in the southern sector where source rocks were deposited under less reducing conditions and received significant clastic input as well as in the northern sector the a a c values are mainly above 0 5

a new statistical test for static stress triggering application to the 1987 superstition hills earthquake sequence over the past several years many investigators have argued that static stress changes caused by large earthquakes influence the spatial and temporal distributions of subsequent regional seismicity with earthquakes occurring preferentially in areas of stress increase and reduced seismicity where stress decreases some workers have developed quantitative methods to test for the existence of such static stress triggering but no firm consensus has yet been reached as to the significance of these effects we have developed a new test for static stress triggering in which we compute the change in coulomb stress on the focal mechanism nodal planes of a set of events spanning the occurrence of a large earthquake we compare the statistical distributions of these stress changes for events before and after the mainshock to decide if we can reject the hypothesis that these distributions are the same such rejection would be evidence for stress triggering we have applied this test to the november 24 1987 elmore ranch superstition hills earthquake sequence and find that those post mainshock events that experienced stress increases of at least 0 01 0 03 mpa 0 1 0 3 bar or that occurred from 1 4 to 2 8 years after the mainshocks are consistent with having been triggered by mainshock generated static stress changes

net primary production in the gulf stream sustained by quasi geostrophic vertical exchanges we analyze 12 years of mesoscale vertical motion derived from an observation based product in the top 1000 m of the north west atlantic ocean vertical velocities o 10 m d 1 associated with gulf stream instabilities consist of alternating cells of upwelling and downwelling here we show that the magnitude of the vertical motions decays exponentially southward with an e folding length scale that is informative on the dynamics of the system we further investigate the impact of the vertical supply of nutrients about phytoplankton growth with a conceptual model incorporating the mean effect of nutrient distribution quasi geostrophic dynamics and ekman suction pumping results confirm that the mean effect of mesoscale vertical velocity variability alone can sustain observed levels of net primary production in the immediate vicinity of the gulf stream while other mechanisms including horizontal advection and submesoscale dynamics need to be considered when moving toward the subtropical gyre

mesoscale dynamics and vertical motion in the alboran sea abstract the inflow of atlantic water through the strait of gilbraltar usually exhibits a stationary wavelike pattern in the alboran sea we use an objective analysis technique for quantitative scale separation to investigate the interaction of scales in the region the large scale is clearly dominated by an anticyclonic gyre smaller scale analysis shows the existence of several mesoscale cyclonic eddies along the northern boundary of the western alboran sea anticyclonic gyre the relationship between the large scale mesoscale variability and the induced ageostrophic vertical motion is established using the q vector formulation we find that on the macroscale upward motion occurs upstream of the anticyclonic gyre upstream of a wave crest while downward motion takes place downstream upstream of a trough we also show that the vertical motion associated with the mesoscale eddies is an order of magnitude higher than the large scale vertical motion these patterns of large scale and mesoscale vertical m

upper plate stressing and seismicity in the subduction earthquake cycle we investigate upper plate stressing during the earthquake cycle in a subduction segment using three dimensional 3 d elastic models to address the effects of strongly heterogeneous coupling along strike of the interplate interface we show how heterogeneity controls the locations and mechanisms of seismicity in the upper plate oblique subduction segments two from the aleutians andreanof islands 1986 and rat islands 1965 and one from indonesia biak 1996 are studied all examples of upper plate seismicity from the aleutians represent events occurring toward the beginning of a new cycle while in biak indonesia the examined events occur both toward the end of one cycle and the beginning of the next in the majority of cases studied the location and mode of the upper plate seismicity are consistent with space and time dependent stressing as predicted by modeling this confirms earlier observations that seismicity in the vicinity of large great subduction earthquakes toward the outer rise at intermediate depth and now in the upper plate depends in an interpretable manner on the stage in the earthquake cycle as well as on distribution of coupling along the interplate interface

a possible stress interaction between large thrust and normal faulting earthquakes in the mexican subduction zone abstract a large nearly vertical normal faulting earthquake mw 7 1 took place in 1997 in the subducting cocos plate just beneath the ruptured fault zone of the 1985 michoacan mexico earthquake mw 8 1 we investigate the possibility of stress interaction between the two large events through a 3d analysis of coseismic stress change that was due to the first event taking into consideration the postseismic change and the dynamic rupture process of the second event in the middle portion of the subducting plate at depths below 30 km the calculated coseismic increase in the vertical shear stress and in the coulomb failure stress beneath the high stress drop zones of the 1985 earthquake is in the order of 0 4 to 0 8 mpa it was also found that the 1997 earthquake took place in the zone of maximum coseismic stress increase possible postseismic stress changes due to the subduction process or to the loading of the overriding continental lithosphere and from aseismic slip would enhance the coseismic stress change and hence the possibility of occurrence of a normal faulting earthquake in the subducting plate the dynamic rupture pattern of the 1997 event seems to be consistent with the inferred stress interactions introduction a large nearly vertical normal faulting earthquake mw 7 1 occurred on 11 january 1997 beneath the mi choacan segment of the mexican subduction zone santoyo

effect of artificial maturation on carbazole distributions as revealed by the hydrous pyrolysis of an organic sulphur rich source rock ghareb formation jordan abstract hydrous pyrolysis experiments were performed on the ghareb formation upper cretaceous jordan a carbonate and organic rich toc 19 6 source rock using a temperature range of 200 to 360 c 72 h the original sediment contains only low amounts of carbazoles maximum 2 2 g g bitumen for 1 methylcarbazole with increasing thermal maturation intense generation begins at temperatures only in excess of 300 c reaching a maximum at 360 c likewise during natural maturation generation occurs at later stages of maturity e g for tithonian source rocks at 0 81 rr and for posidonia shale at 0 88 rr some isomeric changes during hydrous pyrolysis do not resemble those in nature whereas others do the relative abundances of selected c1 and c2 alkylcarbazoles on ternary diagrams reveal differences whereas the benzo a carbazole benzo a carbazole benzo c carbazole ratio is closely similar the latter result supports the contention that maturation plays a key role in controlling carbazole distributions in source rocks however the results for alkylcarbazoles especially the c2 carbazoles are not easy to interpret

stress triggering in thrust and subduction earthquakes and stress interaction between the southern san andreas and nearby thrust and strike slip faults 1 we argue that key features of thrust earthquake triggering inhibition and clustering can be explained by coulomb stress changes which we illustrate by a suite of representative models and by detailed examples whereas slip on surface cutting thrust faults drops the stress in most of the adjacent crust slip on blind thrust faults increases the stress on some nearby zones particularly above the source fault blind thrusts can thus trigger slip on secondary faults at shallow depth and typically produce broadly distributed aftershocks short thrust ruptures are particularly efficient at triggering earthquakes of similar size on adjacent thrust faults we calculate that during a progressive thrust sequence in central california the 1983 mw 6 7 coalinga earthquake brought the subsequent 1983 mw 6 0 nunez and 1985 mw 6 0 kettleman hills ruptures 10 bars and 1 bar closer to coulomb failure the idealized stress change calculations also reconcile the distribution of seismicity accompanying large subduction events in agreement with findings of prior investigations subduction zone ruptures are calculated to promote normal faulting events in the outer rise and to promote thrust faulting events on the periphery of the seismic rupture and its downdip extension these features are evident in aftershocks of the 1957 mw 9 1 aleutian and other large subduction earthquakes we further examine stress changes on the rupture surface imparted by the 1960 mw 9 5 and 1995 mw 8 1 chile earthquakes for which detailed slip models are available calculated coulomb stress increases of 2 20 bars correspond closely to sites of aftershocks and postseismic slip whereas aftershocks are absent where the stress drops by more than 10 bars we also argue that slip on major strike slip systems modulates the stress acting on nearby thrust and strike slip faults we calculate that the 1857 mw 7 9 fort tejon earthquake on the san andreas fault and subsequent interseismic slip brought the coalinga fault 1 bar closer to failure but inhibited failure elsewhere on the coast ranges thrust faults the 1857 earthquake also promoted failure on the white wolf reverse fault by 8 bars which ruptured in the 1952 mw 7 3 kern county shock but inhibited slip on the left lateral garlock fault which has not ruptured since 1857 we thus contend that stress transfer exerts a control on the seismicity of thrust faults across a broad spectrum of spatial and temporal scales

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

oil origin and secondary migration pathway in the bonan sag bohai bay basin china abstract the oil origin and secondary migration pathways were investigated in the bonan sag using basin modeling and petroleum geochemical data including biomarker assemblages of saturated hydrocarbons and pyrrolic nitrogen compounds the modeling of secondary oil migration pathway was performed based on the reconstruction of burial thermal maturity and oil generation histories modeling results are calibrated by the distribution of oil wells and oil fields as well as traced secondary oil migration pathways inferred from pyrrolic nitrogen compounds carbazole parameters were selected to trace the secondary oil migration pathway based on the investigation of oil origin three groups of oils sourced from source rocks of the third and fourth members of shahejie formation es3 and es4 have been identified in this study group oils from es3 source rocks mainly occurred in the center of sag group oils from es4 source rocks occurred in the margin regions group oils were interpreted to be the mixed sources from es3 and es4 source rocks three oil migration pathways can be traced by pyrrolic nitrogen compounds based on varied carbazole parameters the major stages of oil generation of es3 and es4 source rocks occurred at about 30 20 ma and 5 0 ma which coincided with oil charge periods secondary oil migration pathways have been predicted successfully by the oil migration modeling in the bonan sag based on the calibration with oil wells oil fields and the traced oil migration pathways by pyrrolic nitrogen compounds favorable zones located on the primary secondary oil migration pathways at the periods of oil charge may be the prospective regions for oil exploration in the bonan sag

some features of the algerian current an analysis of infrared images leads to a new conception of the dynamics of the atlantic water in the algerian basin in situ current measurements are not yet available but coherent hypotheses are presented with the aim to initiate further experimental and theoretical works the algerian current flows steadily along the coast near 0 and becomes unstable near 1 2 e eddies of both signs are generated that are advected by the mean current but only the anticyclonic eddies increase in size diameter about 100 km as they extract more energy from the mean current they are advected more slowly and they may detach from the coast and drift for several weeks in the algerian basin they grow as deep as 1000m at least and they are able to pull lenses of intermediate water seaward from the sardinian continental slope coastal upwelling cells are generated near 1 2 e between the cyclonic and the anticyclonic eddies they are also advected by the mean current and are definitively not wind induced these turbulent structures create intense mixing between the atlantic and mediterranean waters which account for the large eastward gradient of salinity encountered in the surface layer therefore the algerian basin is characterized by a large mesoscale variability mainly due to the instability of the algerian current it appears to be a reservoir in which the water of atlantic origin is amassed and it forms a buffer zone which disconnects the flow of atlantic water coming in at gibraltar from the flow of hygly modified atlantic water exiting the basin through the strait of sardinia and into the ligurian sea

the origin and characteristics of the algerian current satellite and ship data collected between may 1 and 22 1986 show that the algerian current originates in the almeria oran front and remains within 30 km of the algerian coast for over 300 km between oran and algiers the differences between the water masses of the current and the resident regional waters are clearly observed in the chlorophyll concentrations and optical characteristics thus permitting the resulting patterns to be used as tracers of the circulation during this field period the algerian current begins as an extension of the almeria oran front which is found at the western periphery of the eastern alboran gyre this major oceanographic salinity front s 1 km delineates the boundary of the algerian current which has average surface velocities of 40 cm s and maximum speeds reaching 80 cm s the current which has a volume transport between 0 4 and 0 5 sv is confined to the upper 150 m and is in geostrophic balance a sequence of coastal zone color scanner czcs and advanced very high resolution radiometer avhrr satellite imagery showing the rapidly evolving surface circulation features is augmented with in situ ship data of current and water mass characteristics rapid undulations and frontal movements of the current were observed during the study period however the flow remained unbroken between 1 and 3 e current instability increased eastward as the undulations were sharper and the current appeared to depart from the coast near algiers

effect of maturity and petroleum expulsion on pyrrolic nitrogen compound yields and distributions in duvernay formation petroleum source rocks in central alberta canada abstract a quantitative study of pyrrolic nitrogen compounds was conducted on a series of marine carbonate petroleum source rock extracts taken from the upper devonian duvernay formation in the central alberta portion of the western canada sedimentary basin with increasing thermal maturity concentrations of various pyrrolic nitrogen compounds in the rock extracts increase drastically together with significant compositional variations related to alkyl substitution position the study provides circumstantial evidence for adsorptive interactions operating between organic nitrogen compounds and solid organic mineral phases in subsurface sedimentary rocks during petroleum generation and expulsion the absolute concentrations and relative distributions of pyrrolic nitrogen compounds in the extracts of different maturity ranges provide background information for the calibration of such data in migrated petroleums as an independent measurement of secondary oil migration range of duvernaysourced oils in the basin

vertical motion in the upper ocean from glider and altimetry data 1 this study represents a first attempt to combine new glider technology data with altimetry measurements to understand the upper ocean dynamics and vertical exchanges in areas with intense horizontal density gradients in july 2008 just two weeks after jason 2 altimeter was launched a glider mission took place along a satellite track in the alboran sea western mediterranean the mission was designed to be almost simultaneous with the satellite passage dynamic height from glider reveals a sharp gradient 15 cm and corresponds very well with the absolute dynamic topography from jason 1 jason 2 tandem mission r 0 97 rms differences 1 6 cm we blend both data sets glider and altimetry to obtain a consistent and reliable 3d dynamic height field using quasi geostrophic dynamics we diagnose large scale vertical motions 1 m day 1 which may provide a local mechanism for the subduction of the chlorophyll tongue observed by the glider

the 1998 earthquake sequence south of long valley caldera california hints of magmatic involvement a significant episode of seismic and geodetic unrest took place at long valley caldera california beginning in the summer of 1997 activity through late may of 1998 was concentrated in and around the south moat and the south margin of the resurgent dome the sierran nevada block snb region to the south southeast remained relatively quiet until a m 5 1 event occurred there on 9 june 1998 ut a second m 5 1 event followed on 15 july ut both events were followed by appreciable aftershock sequences an additional distinct burst of activity began on 1 august 1998 the number of events in the august sequence over the first week or two was similar to the aftershock sequence of the 15 july 1998 m 5 1 event but the later sequence was not associated with any events larger than m 4 3 all of the summer 1998 snb activity was considered tectonic rather than magmatic in general the snb is considered an unlikely location for future eruptions however the august sequence an aftershock sequence without a mainshock is suggestive of a strain event larger than the cumulative seismotectonic strain release moreover a careful examination of waveforms from the august sequence reveals a small handful of events whose spectral signature is strikingly harmonic we investigate the waveforms of these events using spectral autocorrelation and empirical green s function techniques and conclude that they were most likely associated with a fluid controlled source our observations suggest that there may have been some degree of magma or magma derived fluid involvement in the 1998 snb sequence

geochemical effects of petroleum migration and expulsion from toarcian source rocks in the hils syncline area nw germany for mature oil prone source rocks of toarcian age in the hils syncline area nw germany the geochemical effects of primary migration of petroleum are shown expulsion has occurred at high efficiencies primarily via a network of macro and micro fractures the effects of this fracture controlled expulsion with respect to gross and molecular composition of c15 soluble organic matter are documented samples from fractured intervals have expelled total c15 soluble organic matter more efficiently than adjacent unfractured intervals a systematic comparison of samples taken at cm intervals away from macro fractures reveals compositional gradients which are interpreted to reflect preferential depletion of saturated and aromatic hydrocarbons from the source rock shale into the fractures extracts of shale samples directly at fracture walls are enriched in nso compounds and highly polar asphaltene like fractions the composition of residual petroleum fluids extracted from the fracture fill materials is variable in some cases there is a close match with that of the shale at some distance away from the fractures in other cases there is geochemical evidence to suggest that petroleum fluids were chemically altered during lateral flow along the fractures based on available geological and geochemical evidence a conceptual model is proposed to explain fracture development and fluid flow processes rapid heating by a nearby intrusive body at shallow depths when the toarcian sediments still contained about 15 20 pore water has played an important role overpressuring of aqueous pore fluids with abundant dissolved carbonate caused intense fracturing of the rich intervals in the mature toarcian sections finally the closely interdependent relationships between petroleum generation and petroleum migration processes are documented especially the evolution of these relationships with maturity progress from immature 0 48 rm to mature 0 68 and 0 88 rm and overmature 1 45 rm stages is shown for example in the maturity interval from 0 68 to 0 88 rm most of the measured shale compaction and porosity decrease is achieved by expulsion of petroleum for some samples there is an inverse relationship between kerogen quality and extractable hydrocarbon yields suggesting that expulsion efficiencies were higher from the better quality intervals because the petroleum achieved higher saturations and hence higher relative permeabilities

maturity effect on carbazole distributions in source rocks from the saline lacustrine settings the western qaidam basin nw china abstract carbazole distributions and biomarker compositions have been investigated in a series of source rocks from the tertiary strata in the western qaidam basin nw china typical biomarker signatures high gammacerane high c 35 hopane and low pr ph indicate a saline lacustrine environment maturity parameter c 29 sterane s s r ranges from 0 06 to 0 58 indicating immature ca 0 35 stages significant variations were observed for carbazole distributions with maturation as for c 1 carbazoles the relative amounts of 1 mc methylcarbazole show a decrease trend in the immature stage and an increase trend in the mature stage while the other three isomers 2 3 and 4 mcs show a generally opposite change indicating a two stage variation as for c 2 carbazole isomers complex variations were observed for their relative amounts an overall increase for 1 7 dmc dimethylcarbazole a slight two stage change for 1 8 and 1 3 dmcs and a marked two stage variation for 2 4 2 5 and 2 6 dmcs comparison of the distributions of carbazole and benzocarbazoles revealed a preferential generation for benzocarbazoles at high maturity levels benzocarbazole ratio a a c varies only in a narrow range 0 52 0 61 in the entire maturity range suggesting limited maturity dependence the results here support the idea that carbazole distributions have strong maturity effect in a wide maturity range and the two stage variations for some pyrrolic nitrogen isomers may indicate their different geochemical controls between the immature and mature stages

coastal and mesoscale dynamics characterization using altimetry and gliders a case study in the balearic sea 1 dynamics along the continental slopes are difficult to observe given the wide spectrum of temporal and spatial variability of physical processes which occur coastal currents meanders eddies etc studying such complex dynamics requires the development of synergic approaches that use integrated observing systems in this context we present the results of an observational program conducted in the balearic sea combining coastal gliders and altimetry the objectives of this experiment are to study regional dynamics using new technologies such as gliders in synergy with satellite altimetry and to investigate the limitations and potential improvement to altimetric data sets in the coastal zone in this regard new methodologies have been developed to compute consistent altimetric and glider velocities and a novel technique to estimate absolute glider velocities combining surface glider geostrophic velocities with integrated currents estimated from the glider gps positioning has been applied in addition the altimetric velocity computation has been improved especially in the coastal zone using high frequency along track sampling associated with new filtering and editing techniques this approach proves efficient for homogenizing the physical contents of altimetry and glider surface currents percentage of standard deviation explained is 40 and characterizing regional dynamics in the balearic sea through a combined analysis of a high resolution observing system such as the appearance of anomalous intense mesoscale features missing in the classical circulation scheme of the balearic sea

sensitivity of static stress calculations to the earthquake slip distribution 1 the apparent strong correlation between coulomb stress changes and the spatial distribution of aftershocks suggests the possibility of making near real time estimations of areas at risk of experiencing off fault aftershocks in order to do this in practice a number of issues must first be addressed including the extent to which the main shock slip must be known in detail before a meaningful stress map can be constructed here we investigate this issue by constructing a time ordered sequence of slip solutions for the landers earthquake computing coulomb stress changes for each solution and quantitatively comparing the stress field with the observed aftershocks by 1 resolving the coulomb stress change onto the aftershock nodal planes and calculating the percentage of events consistent with triggering and 2 constructing a two dimensional map of coulomb stress and computing the correlation coefficient between the positive and negative areas and the locations of the aftershocks we find that slip solutions based on empirical relations and either focal mechanism or moment tensor data produce stress fields inconsistent with the observed spatial distribution of aftershocks whereas slip solutions incorporating the correct rupture geometry but greatly simplified slip produce stress fields consistent with the aftershock distribution when very near fault events are excluded we further find that resolving stress perturbations onto earthquake nodal planes and computing the percentage of events experiencing positive coulomb stress provides a poor measure of success because of the limited range of structures on which events occur and the compatibility of the main shock stress field with these structures our results support the hypothesis that coulomb stress changes affect the spatial distribution of aftershocks and suggest that meaningful calculations of coulomb stress can be made as soon as an earthquake s rupture geometry is well constrained

features of earthquake occurrence in a complex normal fault network results from a synthetic seismicity model of the taupo rift new zealand 1 the taupo rift in the central north island of new zealand is a region of active extension of up to 15 mm yr in the back arc of the hikurangi subduction system mapping and trenching has defined a network of active normal faults because the paleoseismic and historical earthquake catalogs are short and inhomogeneous a deterministic computer model of seismicity has been constructed to better understand the earthquake history the model consists of 26 primary normal fault segments corresponding to mapped faults with vertical displacement rates of 0 1 1 6 mm yr and 4700 randomly distributed small normal faults in a 40 25 km area all of the model faults interact elastically parameters of the model are adjusted to reproduce the geologically observed displacement rates a regional b value of 1 0 and average slip event of 1 m the result is a long catalog of 500 000 events magnitude 3 82 to 6 62 which simulates a time period of 2 myr characteristic slip events on each segment are mostly well defined and their recurrence times can usually be described by a three parameter weibull distribution the coefficient of variation cv for recurrence intervals ranges from 0 12 to 1 22 with an average of 0 66 these reduce by about half if fault interactions are turned off the time series of characteristic earthquakes shows clear evidence of triggered slip up to about 3 years after large magnitude events followed by relative seismic quiescence on all segments the moment release rate is relatively stable over time periods of more than about five recurrence intervals 2 20 kyr but can vary on time scales less than that

sub surface small scale eddy dynamics from multi sensor observations and modeling the study of mesoscale and submesoscale hereafter sub mesoscale hydrodynamic features is essential for understanding thermal and biogeochemical exchanges between coastal areas and the open ocean in this context a glider mission was conducted in august 2008 closely co located and almost simultaneously launched with a jason 2 altimetric pass to fully characterize the currents associated with regional sub mesoscale processes regularly observed to the north of mallorca mediterranean sea a synoptic view from satellite remote sensing fields before and during the glider mission provided a descriptive picture of the main surface dynamics at the balearic basin scale to quantify the absolute surface geostrophic currents the coastal altimetry derived current computation was improved and cross compared with its equivalent derived from glider measurements model simulations were then validated both qualitatively and statistically with the multi sensor observations the combined use of modeling and multi sensor observational data reveals the baroclinic structure of the balearic current and the northern current and a small scale anticyclonic eddy observed northeast of the mallorca coast current 15 cm s 180 m deep this mesoscale structure partially intercepted by the glider and along track altimetric measurements is marked by relatively strong salinity gradients and not as is more typical temperature gradients finally the use of the validated model simulation also shows that the geostrophic component of this small scale eddy is controlled by sub surface salinity gradients we hypothesize that this structure contains recently modified atlantic water arriving from the strait of ibiza due to a northerly wind which strengthens the northward geostrophic circulation

a great earthquake doublet and seismic stress transfer cycle in the central kuril islands temporal variations of the frictional resistance on subduction zone plate boundary faults associated with the stick slip cycle of large interplate earthquakes are thought to modulate the stress regime and earthquake activity within the subducting oceanic plate here we report on two great earthquakes that occurred near the kuril islands which shed light on this process and demonstrate the enhanced seismic hazard accompanying triggered faulting on 15 november 2006 an event of moment magnitude 8 3 ruptured the shallow dipping plate boundary along which the pacific plate descends beneath the central kuril arc the thrust ruptured a seismic gap that previously had uncertain seismogenic potential although the earlier occurrence of outer rise compressional events had suggested the presence of frictional resistance within minutes of this large underthrusting event intraplate extensional earthquakes commenced in the outer rise region seaward of the kuril trench and on 13 january 2007 an event of moment magnitude 8 1 ruptured a normal fault extending through the upper portion of the pacific plate producing one of the largest recorded shallow extensional earthquakes this energetic earthquake sequence demonstrates the stress transfer process within the subducting lithosphere and the distinct rupture characteristics of these great earthquakes illuminate differences in seismogenic properties and seismic hazard of such interplate and intraplate faults

the ms 8 tensional earthquake of 9 december 1950 of northern chile and its relation to the seismic potential of the region abstract the only known great m s 8 intermediate depth earthquake localized downdip of the main thrust zone of the chilean subduction zone occurred landward of antofagasta on 9 december 1950 in this paper we determine the source parameters and rupture process of this shock by modeling long period body waves the source mechanism corresponds to a downdip tensional intraplate event rupturing along a nearly vertical plane with a seismic moment of m 0 1 10 28 dyn cm of strike 350 dip 88 slip 270 m w 7 9 and a stress drop of about 100 bar the source time function consists of two subevents the second being responsible for 70 of the total moment release the unusually large magnitude m s 8 of this intermediate depth event suggests a rupture through the entire lithosphere the spatial and temporal stress regime in this region is discussed the simplest interpretation suggests that a large thrust earthquake should follow the 1950 tensional shock considering that the historical record of the region does not show large earthquakes a slow earthquake can be postulated as an alternative mechanism to unload the thrust zone a weakly coupled subduction zone within an otherwise strongly coupled region as evidenced by great earthquakes to the north and south or the existence of creep are not consistent with the occurrence of a large tensional earthquake in the subducting lithosphere downdip of the thrust zone the study of focal mechanisms of the outer rise earthquakes would add more information which would help us to infer the present state of stress in the thrust region

fractionation of benzocarbazoles between source rocks and petroleums the concentrations of the a and c isomers of benzocarbazoles in a number of crude oils and source rock bitumens were obtained by in house methods and from reported published data the changes in benzocarbazole concentrations and the benzocarbazole a a c ratio relating to source maturity facies and migration are described with increasing source maturity in north sea oils and source rocks up to 0 85 vitrinite reflectance equivalent benzocarbazole concentrations increase due to generation followed by a decrease above 0 85 vitrinite reflectance equivalent due to expulsion dilution by newly generated hydrocarbons comparison of benzocarbazole concentrations between reservoired petroleum and related source petroleum revealed a concentration bias in favour of source petroleum where concentrations of benzocarbazoles reached up to 10 times that found in equivalent reservoired petroleum the differences in benzocarbazole concentrations between related oils and source rocks indicate that the major fractionation is introduced during primary migration and expulsion because when secondary migration is limited as in the miller field we see extensive benzocarbazole fractionation between reservoired petroleum and associated source petroleum the relationships between source rock toc content and petroleum benzocarbazole concentrations and a a c ratios indicate that source organic matter exerts a strong influence on benzocarbazole distributions the introduction of a reservoir source fractionation parameter rsfp defined as the ratio between the concentrations of benzo a benzo c carbazole in reservoired petroleum versus the concentration of benzo a benzo c carbazole in source petroleum enables description of the relationship between reservoired petroleum and source petroleum from different petroleum systems petroleum deriving from clastic source rocks demonstrated high levels of benzocarbazole fractionation between reservoired petroleum and source petroleum during primary and secondary migration compared to petroleum deriving from carbonate systems the rsfp parameter may also be used to examine fractionation effects during migration between different compound types the more polar benzocarbazoles are fractionated more strongly than dibenzothiophene and phenanthrene between reservoired petroleum and source petroleum whereas sometimes source maturity signals do dominate the benzocarbazole signals in migrated oils in other circumstances often associated with clastic source rocks no clear maturity signal is transferred to migrated oils

vorticity and vertical circulation at an ocean front abstract density and velocity data with 4 km horizontal resolution from a survey of a front during fasinex frontal air sea interaction experiment are combined to describe the structure of the top 300 m of the ocean the geostrophic velocity field is derived and is used to examine the relative importance of stratification relative vorticity and twisting terms in ertel s potential vorticity q tenfold isopycnic changes in q are found across a horizontal scale of only 10 km these changes are confined to isopycnals that outcrop from the seasonal thermocline into the mixed layer the ageostrophic velocity field is quantified by solution of the omega equation and vertical velocities of up to 40 m day 1 are found small 40 km surface trapped top 200 m eddies are found to play a crucial role in the transport and effective diffusion of properties across the thermocline out of the mixed layer

evaluating the use of high frequency radar coastal currents to correct satellite altimetry 1 coastal altimeter waveforms may differ from the ones in the open ocean either from rapid changes in the sea state or the presence of land within the satellite altimeter footprint the optimal retracking method for an individual track may turn out to be a combination of several retrackers and may depend on the sea state the coastal high frequency radar hfr ocean surface currents hourly interpolated with a resolution up to 2 km and an offshore range up to 150 km are evaluated to validate the altimeter sea surface height ssh measurements a method to derive hfr ssh mapped with a varying spatial scale optimal interpolation from the hfr velocities has been implemented evaluated mainly in the regions farther than 25 km off the u s west coast the hfr ssh shows good agreement with jason 1 2 altimetry products over the years 2008 and 2009 three jason 2 pistach retrackers and one generic open ocean retracker have been analyzed using the traditional 1 hz sampling rate nearshore an experimental reprocessing of the 20 hz range measurements is also tested to check for a gain in along track spatial resolution referencing to the hfr ssh indicate the need to have several retrackers available even over the continental shelf with ice3 fitting better during bloom events and mle 4 or red3 for high sea states these studies demonstrate the value of hfr as a potential tool to correct coastal altimeter ssh refine their spatial resolution and provide some insight into the altimeter behavior as a function of ocean conditions

rupture characterization and aftershock relocations for the 1994 and 2006 tsunami earthquakes in the java subduction zone 1 two tsunami earthquakes occurred in the java subduction zone within the last 12 years providing multiple well recorded tsunami events for analysis the june 2 1994 mw 7 8 and july 17 2006 mw 7 7 reverse mechanism earthquakes produced tsunami with locally large 8 m runups were deficient in high frequency energy relative to long period radiation had primarily normal faulting aftershocks and occurred near subducting seamounts previous models of the 1994 event and aftershocks suggested extension in the outer rise due to slip at depth at a subducted seamount here we relocate aftershocks for the 1994 and 2006 events and compare to slip distributions and bathymetry most 1994 aftershocks occurred within the slab updip of the mainshock consistent with the extensional hypothesis but the 2006 aftershocks have a more complex pattern regional subducting features as asperities and barriers may influence both events but in different ways

forecasting the evolution of seismicity in southern california animations built on earthquake stress transfer 1 we develop a forecast model to reproduce the distribution of main shocks aftershocks and surrounding seismicity observed during 1986 2003 in a 300 310 km area centered on the 1992 m 7 3 landers earthquake to parse the catalog into frames with equal numbers of aftershocks we animate seismicity in log time increments that lengthen after each main shock this reveals aftershock zone migration expansion and densification we implement a rate state algorithm that incorporates the static stress transferred by each m 6 shock and then evolves coulomb stress changes amplify the background seismicity so small stress changes produce large changes in seismicity rate in areas of high background seismicity similarly seismicity rate declines in the stress shadows are evident only in areas with previously high seismicity rates thus a key constituent of the model is the background seismicity rate which we smooth from 1981 to 1986 seismicity the mean correlation coefficient between observed and predicted m 1 4 shocks the minimum magnitude of completeness is 0 52 for 1986 2003 and 0 63 for 1992 2003 a control standard aftershock model yields 0 54 and 0 52 for the same periods four m 6 0 shocks struck during the test period three are located at sites where the expected seismicity rate falls above the 92 percentile and one is located above the 75 percentile the model thus reproduces much but certainly not all of the observed spatial and temporal seismicity from which we infer that the decaying effect of stress transferred by successive main shocks influences seismicity for decades finally we offer a m 5 earthquake forecast for 2005 2015 assigning probabilities to 324 10 10 km cells

influence of migration distance maturity and facies on the stable isotopic composition of alkanes and on carbazole distributions in oils and source rocks of the alpine foreland basin of austria abstract the austrian part of the alpine foreland basin has been studied previously by organic geochemical methods to establish oil oil and oil source rock correlations the lateral distance of oil fields to the position of mature source rocks lower oligocene schoneck and eggerding formations beneath the alpine nappes in the south suggests long distance migration up to 50 km minor compositional trends in w e direction were obtained reflecting differences in depositional environment facies and maturity of potential source rocks therefore the oil and source rock samples are thought to provide valuable insights into carbazole distributions in relation to migration distance maturity and facies compound specific carbon isotope analyses on n alkanes and isoprenoids reflect the w e trend already seen within the total hydrocarbon fractions the observed trend toward lighter 13 c values of alkanes from oil fields in a w e direction are consistent with lower 13 c values of organic matter in unit c and similar differences obtained from sediments of the schoneck formation at wells oberhofen 1 w and molln 1 e the 13 c patterns of n alkanes and isoprenoids are in agreement with data obtained from the potential marine source rocks schoneck formation of the oils the hydrogen isotopic composition of short chain n alkanes c 15 19 of most oil samples are lower than the data obtained from the extracts of the marine permian kupferschiefer of the polish zechstein basin at similar maturation stages only the oils from the western oil fields yield d values of n alkanes comparable to those obtained from marine source rocks the data imply brackish water conditions during deposition of unit c of the schoneck formation differences in the position of d of isoprenoids in relation to the respective maturation trend line are most probably related to calibration errors alkylated carbazoles and benzocarbazoles are only present in sufficient amounts for quantification in oils sampled from the eastern fields rock extracts of the schoneck formation from drill cores molln 1 5200 m depth 0 92 rr and from the marginally mature ca 0 6 rr samples from well oberhofen 1 4300 m depth obtained sufficient amounts of carbazoles the significantly different concentrations of benzocarbazoles in the extracts around 10 g g at oberhofen 1 50 g g at molln 1 are related to maturity differences whereas the predominance of 1 methylcarbazole in the oberhofen samples is inferred to reflect differences in source rock facies in the oils from the eastern deposits neither the concentration ratios of methylcarbazoles nor the benzocarbazole ratio show indications for the influence of facies differences maturity of oil expulsion is estimated on the basis of mpi 1 rc 0 76 0 88 confirmed by sterane isomerization parameters the results argue for a minor influence of maturity differences on the benzocarbazole ratios of the oil samples the obtained ratios and the reservoir source fractionation parameters calculated from the data of molln 1 source rocks and the respective oils show a systematic decrease with the estimated migration distance the results argue for the applicability of benzocarbazoles for the assessment of relative differences in migration distances in oil plays characterized by minor differences in source rock facies and maturity during oil expulsion

hydrocarbon migration in the multiple sourced petroleum system in the northwestern junggar basin northwestern china constraint from geochemical and phase fractionation analysis oil mixing and absence of source rock samples make it difficult to identify the hydrocarbon migration routes in a petroleum system we provide a case study in the northwestern junggar basin to show that combined geochemical and phase fractionation analyses are robust tools to unravel the complex hydrocarbon migration processes the study rebuilds a migration history that multiple sourced hydrocarbons migrated mixed accumulated and fractionated along the evolution of regional tectonics in detail the shawan and mahu sags expelled the early stage hydrocarbons during the late triassic and late jurassic respectively because of their variable subsidence these hydrocarbons charged the entire area based on the evidence from bitumen and oil inclusions during the early cretaceous both sags subsided rapidly and expelled their late stage hydrocarbons these hydrocarbons first mixed along unconformities in the sags which generated mixed source oils and induced gas washing subsequently they further mixed with or displaced the encountered early stage oils during migration along the basal unconformity of the upper permian into the area causing a horizontal distribution of oil maturity zones in addition gases flowing through the early stage oils induced gas washing again creating heavy oils condensate oils and mixed gases after the late stage oils finally accumulated in fractured volcanics migration fractionation caused the remigration of light end compositions this study also shows the strong control of structures on hydrocarbon migration the unconformity network provided opportunities for long distance migration and widespread mixing of multiple sourced hydrocarbons whereas the paleoridge line of the zhongguai high defined the boundary of regional migration

similar power laws for foreshock and aftershock sequences in a spring block model for earthquakes we introduce a crust relaxation process in a continuous cellular automaton version of the burridge and knopoff 1967 model the most important model parameters are the level of conservation and the ratio of the crust relaxation time to the tectonic reloading time in correspondence with the original spring block model the modified model displays a robust power law distribution of event sizes the principal new result obtained with our model is the spatiotemporal clustering of events exhibiting several characteristics of earthquakes in nature large events are followed by aftershock sequences obeying the omori 1894 law and preceded by localized foreshocks which are initiated after a time period of seismic quiescence while we observe a considerable variability of precursory seismicity we find that the rate of foreshocks increases on average according to a power law with an exponent q which is in good agreement with the exponent p of the omori law in contrast to other events the distribution of foreshock sizes is characterized by a significantly smaller richter b value our model reproduces simultaneously the empirically observed values of the power law exponents the richter b p and q and their variability

the java margin revisited evidence for subduction erosion off java the eastern sunda margin off indonesia from central java to sumba island remains a little investigated subduction zone contrary to its well studied northwestern segment whereas large portions of the sunda margin are considered a classical accretionary zone subduction characteristics along the central java sector indicate erosive processes as the dominant mode of mass transfer the tectonic framework of the central java margin with a convergence rate of 6 7 cm yr insignificant sediment input and a pronounced seafloor roughness where the oceanic roo rise is subducting underneath java facilitates subduction erosion evidence for erosion comes from newly acquired geophysical data off central java local erosive processes in the wake of seamount subduction are documented by a high resolution bathymetric survey and result in an irregular trend of the deformation front sculpted by seamount collision scars subduction of oceanic basement relief leads to large scale uplift of the forearc as recorded on a reflection seismic profile and to a dismemberment of the previous outer forearc high giving way to isolated topographic elevations the broad retreat of the java trench and deformation front above the leading edge of the roo rise has exposed an area of approximately 25 000 km2 of deeper seafloor formerly covered by the previous frontal prism frontal erosion coincides with a steepening of the lower slope angle in the central java sector compared to the neighbouring segments in global compilations the key geological parameters of the central java margin lie in the erosive regime reflecting the interplay of basement relief subduction negligible sediment supply and a high convergence rate on the evolution of the margin

the 1994 java tsunami earthquake slip over a subducting seamount on june 2 1994 a large subduction thrust earthquake ms 7 2 produced a devastating tsunami on the island of java this earthquake had a number of unusual characteristics it was the first recorded large thrust earthquake on the java subduction zone all of the aftershock mechanisms exhibit normal faulting no mechanisms are similar to the main shock also the large tsunami and the relatively low energy radiated by the main shock have led to suggestions that this earthquake might have involved slow shallow rupture near the trench similar to the 1992 nicaragua earthquake we first relocate the main shock and the aftershocks we then invert long period surface waves and broadband body waves to determine the depth and spatial distribution of the main shock slip a dip of 12 hypocenter depth of 16 km and moment of 3 5 l020 n m mw 7 6 give the best fit to the combined seismic data and are consistent with the plate interface geometry the source spectrum obtained from both body and surface waves has a single corner frequency between 10 and 20 mhz implying a stress drop of 0 3 mpa the main energy release was preceded by a small subevent lasting 12 s the main slip occurred at 20 km depth downdip and to the nw of the hypocenter this area of slip is collocated with a prominent high in the bathymetry that has been identified as a subducting seamount we interpret the java earthquake as slip over this subducting seamount which is a locked patch in an otherwise decoupled subduction zone we find no evidence for slow shallow rupture no thrust aftershocks are expected if the entire locked zone slipped during the main shock but extension of the subducting plate behind the seamount would promote normal faulting as observed it seems probable that such a source model could also explain the size and timing of the observed tsunami

cyclic stressing and seismicity at strongly coupled subduction zones we use the finite element method to analyze stress variations in and near a strongly coupled subduction zone during an earthquake cycle deformation is assumed to be uniform along strike plane strain on a cross section normal to the trench axis and periodic earthquake slip is imposed consistent with the long term rate of plate convergence and degree of coupling simulations of stress and displacement rate fields represent periodic fluctuations in time superimposed on an average field the oceanic plate descending slab and continental lithosphere are assumed here to respond elastically to these fluctuations and the remaining mantle under and between plates is assumed to respond as maxwell viscoelastic in the first part of the analysis we find that computed stress fluctuations in space and time are generally consistent with observed earthquake mechanism variations with time since a great thrust event in particular trench normal extensional earthquakes tend to occur early in the earthquake cycle toward the outer rise but occur more abundantly late in the cycle in the subducting slab downdip of the main thrust zone compressional earthquakes when they occur at all have the opposite pattern our results suggest also that the actual timing of extensional outer rise events is controlled by the rheology of the shallow aseismic portion of the thrust interface the second part of the analysis shows the effects of mantle relaxation on the rate of ground surface deformation during the earthquake cycle models without relaxation predict a strong overall compressional strain rate in the continental plate above the main thrust zone with the strain rate constant between mainshocks however with significant relaxation present a localized region of unusually low compressional or even slightly extensional strain rate develops along the surface of the continental plate above and somewhat inland from the downdip edge of the locked main thrust zone the low strain rate starts in the middle or late part of the cycle depending on position this result suggests that the negligible or small contraction measured on the shumagin islands alaska during 1980 to 1991 may not invalidate an interpretation of that region as being a moderately coupled subduction zone in contrast mantle relaxation causes only modest temporal nonuniformity of uplift rates in the overriding plate and of extensional stress rates in the subducting plate even when the maxwell time is an order of magnitude less than the recurrence interval

shallow subduction zone earthquakes and their tsunamigenic potential summary we have examined the source spectra of all shallow subduction zone earthquakes from 1992 to 1996 with moment magnitude 7 0 or greater as well as some other interesting events in the period range 1 20 s by computing moment rate functions of teleseismic p waves after comparing the source spectral characteristics of tsunami earthquakes earthquakes that are followed by tsunamis greater than would be expected from their moment magnitude with regular events we identified a subclass of this group slow tsunami earthquakes this subclass consists of the 1992 nicaragua the 1994 java and the february 1996 peru earthquakes we found that these events have an anomalously low energy release in the 1 20 s frequency band with respect to their moment magnitude although their spectral drop ov is comparable to those of the other earthquakes from an investigation of the centroid and body wave locations it appears that most earthquakes in this study conformed to a simple model in which the earthquake nucleates in a zone of compacted and dehydrated sediments and ruptures up dip until the stable sliding friction regime of unconsolidated sediments stops the propagation sedimentstarved trenches e g near jalisco can produce very shallow slip because the fault material supports unstable sliding the slow tsunami earthquakes also ruptured up dip however their centroid is located unusually close to the trench axis the subduction zones in which these events occurred all have a small accretionary prism and a thin layer of subducting sediment ocean surveys show that in these regions the ocean floor close to the trench is highly faulted we suggest that the horst and graben structure of a rough subducting oceanic plate will cause contact zones with the overriding plate making shallow earthquake nucleation and up dip propagation to the ocean floor possible the rupture partly propagates in sediments making the earthquake source process slow two factors have to be considered in the high tsunami generating potential of these events first the slip propagates to shallow depths in low rigidity material causing great deformation and displacement of a large volume of water second the measured seismic moment may not represent the true earthquake displacement because the elastic constants of the source region are not taken into account in the standard cmt determination

the 17 july 2006 java tsunami earthquake the 17 july 2006 java earthquake involved thrust faulting in the java trench and excited a deadly tsunami 5 8 m that inundated the southern coast of java the earthquake s size estimates vary significantly with seismic wave period very long period signals 300 500 s indicate a seismic moment of 6 7 10 20 nm m w 7 8 m s 20 s 7 2 m b 1 s 6 2 while shaking intensities 3 10 hz were mmiv the large tsunami relative to ms characterizes this event as a tsunami earthquake like previous tsunami earthquakes the java event had an unusually low rupture speed of 1 0 1 5 km s and occurred near the up dip edge of the subduction zone thrust fault most large aftershocks involved normal faulting the rupture propagated 200 km along the trench with several pulses of shorter period seismic radiation superimposed on a smooth background rupture with an overall duration of 185 s

seismic history and seismotectonics of the sunda arc historic records of the last 300 years reveal two great interplate earthquakes 1833 mw 8 1861 mw 8 8 which ruptured major segments of the sumatra fore arc in western indonesia a significant percentage of interplate slip along this portion of the plate boundary appears to occur seismically the ends of these rupture zones are coincident with clusters of large ms 7 and moderate 6 ms 7 shocks and with heterogeneities in the plate interface as inferred from geologic and geophysical data the northern extent of the 1833 rupture zone is coincident with a group of moderate and large earthquakes a structural arch in the fore arc and a fracture zone on the subducted plate the southern portion is coincident with a very prominent cluster and the along strike extension of a sediment filled trough on the subducted plate prior to this study sumatra was characterized as relatively aseismic as inferred from the lack of great earthquakes in the instrumental record of this century java and the lesser sunda islands had major ms 6 earthquakes in the historic record but none are of the same magnitude as the great events near sumatra there is no clear evidence that shocks in the java fore arc were interplate events yet geophysical data indicate recent uplift of the trench slope break and a change in strike of the trench axis where the northernmost flank of the roo rise a prominent bathymetrie high appears to be interacting with the fore arc this feature was formed at a ridge crest and is more buoyant and thus more difficult to subduct than the surrounding seafloor there is no increase in seismicity associated with this tectonism however that may indicate a lack of contact between the crystalline portions of the plates at this time we infer that a majority of slip on the plate interface near java occurs aseismically the variation in occurrence of great interplate earthquakes along the sunda arc may be interpreted in terms of a model that attributes variation in interplate coupling to the age of the subducted lithosphere great interplate earthquakes occur near sumatra where the age of the youngest crust is 46 ma the characteristics of the sunda arc and analogies with pacific arcs imply that the entire length of sumatra has the potential to produce great thrust earthquakes its seismic potential should be considered high as there has been no recurrence of the great events of 1833 and 1861 in contrast no such events have been reported off java and the lesser sunda islands where the oldest crust is 152 ma the plate interface near java and the lesser sunda islands should be considered to have low seismic potential

diagnosis of the three dimensional circulation associated with mesoscale motion in the california current a high resolution upper ocean survey of a cyclonic jet meander and an adjacent cyclonic eddy in the california current region near 388n 1268w was conducted as part of the summer of 1993 eastern boundary currents program temperature and salinity were measured from a seasoar vehicle and velocity was measured by shipboard acoustic doppler current profiler adcp seasoar data show a density front at a depth of 70 100 m with strong cyclonic curvature the geostrophic velocity fields referenced to the adcp data at 200 m show a strong surface intensified jet maximum speed of 0 9 m s 21 that follows the density front along a cyclonic meander relative vorticities within the jet are large ranging from 20 8 f to 11 2 f where f is the local coriolis parameter the seasoar density and adcp velocity data are used to diagnose the vertical velocity via the q vector form of the quasigeostrophic omega equation the diagnosed vertical velocity field shows a maximum speed of 40 45 m d21 the lateral distribution of vertical velocity is characterized by two length scales a large 75 km pattern where there is downwelling upstream and upwelling downstream of the cyclonic bend and smaller patches arrayed along the jet core with diameters of 20 30 km geostrophic streamline analysis of vertical velocity indicates that water parcels make net vertical excursions of 20 30 m over 2 3 days resulting in net vertical velocities of 7 15 m d21 water parcels moving along geostrophic streamlines experience maximum vertical velocities in the regions of maximum alongstream change in relative vorticity an indication of potential vorticity conservation

molecular distributions and geochemical implications of pyrrolic nitrogen compounds in the permian phosphoria formation derived oils of wyoming abstract crude oils from the laramide structures of wyoming were studied with respect to their geochemical compositions the sampling areas include the greater green river wind river and big horn basins and the casper arch region based on pristane phytane ratio and various hopane and sterane parameters the permian phosphoria formation derived oils can be readily differentiated from oils with different origins within the phosphoria formation derived oils three subgroups can be identified using ts ts tm and diasterane regular sterane ratios corresponding to sources with subtle variation in organic facies and or thermal maturity of the phosphoria formation differences in source organic input depositional environments and thermal maturity were observed to greatly influence the saturated hydrocarbon compositions of the permian phosphoria formation derived oils however the distributions of pyrrolic nitrogen compounds in these oils do not appear as diagnostic as the conventional hydrocarbon parameters commonly used as indicators of these geological factors this fact may be related to the more significant role of oil migration in the modification of pyrrolic nitrogen compound distributions in foreland basins as compared to that in rift basins the recognition of possible source and maturity effects on pyrrolic nitrogen compounds suggests that all of these factors should be taken into proper consideration before the pyrrolic nitrogen compounds are used as indicators for any specific geological process

seismic coupling and outer rise earthquakes variation of interplate seismic coupling at subduction zones is a major factor controlling the size of the largest underthrusting events this variation also has a profound effect on the regional intraplate stresses in the vicinity of the subduction zone outer rise seismicity is strongly correlated with variations in interplate coupling reflecting the stress state of the interplate coupled zone over 200 outer rise earthquakes with known focal mechanisms are used to investigate the relationship between stresses in the outer rise and interplate seismic coupling these events occur within the downgoing i e oceanic plate near the bathymetric trench axes and generally fall into the categories of tensional normal or compressional thrust with their tensional or compressional stress axes oriented approximately horizontal and perpendicular to the trench in uncoupled subduction zones only tensional outer rise earthquakes occur which indicates that the outer rise is dominated by tensional stresses associated with plate bending and or slab pull forces in strongly coupled subduction zones both tensional and compressional outer rise events are found these events are related both spatially and temporally to the distribution of large underthrusting earthquakes and are thus an integral part of the earthquake cycle in the strongly coupled regions tensional outer rise events follow large underthrusting events as the outer rise is temporarily in tension due to the underthrusting motion compressional outer rise events take place as compressional stress slowly accumulates oceanward of locked sections of the interplate zone in four instances compressional outer rise earthquakes have been followed by large underthrusting events which have occurred 2 4 7 and 19 years after the associated outer rise event the remaining compressional outer rise events are located in regions that are either known seismic gaps or in regions where the seismic potential is unknown the occurrence of compressional outer rise earthquakes suggests that compressional stress is accumulating in the adjacent interplate region and that there is the potential for a future large underthrusting event in the region thirty compressional outer rise events have been located in trench segments of middle and south america the kurile islands the tonga and kermadec islands the new hebrides arc and the solomon islands regions in both the southern kamchatka and northern new hebrides regions the outer rise seismicity indicates that the stress regimes in the outer rise have changed with time from tensional following a previous large underthrusting event to compressional at present thus three stages of the cycle from underthrusting to tensional outer rise regime to compressional outer rise regime are present requiring only the occurrence of the next underthrusting event to complete the cycle the occurrence of compressional outer rise events is useful for assessing the seismic potential of a region on an intermediate time scale

stress changes in the costa rica subduction zone due to the 1999 mw 6 9 quepos earthquake abstract stress changes after large earthquakes can trigger substantial seismicity along many fault systems as subduction zones produce the majority of large earthquakes it is essential to understand how significant earthquakes may affect stress conditions and aftershock locations calculations of stress changes due to large underthrusting earthquakes can be used to examine likely zones of triggered seismicity in subduction environments however associations between stress changes and locations of small aftershocks are typically difficult because of large errors on offshore aftershock locations based on land based seismic observations after the 1999 quepos earthquake m w 6 9 in the subduction zone offshore costa rica small magnitude earthquakes were located using a local onshore offshore temporary seismic network providing a data set of high quality aftershock locations in light of these well located aftershocks we compute coulomb stress changes for the 1999 quepos earthquake for comparison our calculations show lobes of increased stress in regions coinciding with most of the small magnitude seismicity following the mainshock as seen in many cases of large strike slip earthquakes few small earthquakes occur in regions of decreased stress within three years a large m w 6 4 earthquake occurred in this region however based on this modeling it does not appear that the 2002 earthquake occurred in a zone of stress increase from the 1999 event

evaluating southern ocean carbon eddy pump from biogeochemical argo floats the vertical transport of surface water and carbon into ocean s interior known as subduction is one of the main mechanisms through which the ocean influences earth s climate new instrumental approaches have shown the occurrence of localized and intermittent subduction episodes associated with small scale ocean circulation features these studies also revealed the importance of such events for the export of organic matter the so called eddy pump however the transient and localized nature of episodic subduction hindered its large scale evaluation to date in this work we present an approach to detect subduction events at the scale of the southern ocean using measurements collected by biogeochemical autonomous floats bgcargo we show how subduction events can be automatically identified as anomalies of spiciness and apparent oxygen utilization aou below the mixed layer using this methodology over more than 4 000 profiles we detected 40 subduction events unevenly distributed across the sothern ocean events were more likely found in hot spots of eddy kinetic energy eke downstream major bathymetric features moreover the bio optical measurements provided by bgcargo allowed measuring the amount of particulate organic carbon poc being subducted and assessing the contribution of these events to the total downward carbon flux at 100 m ep100 we estimated that the eddy pump represents less than 19 to the ep100 in the southern ocean although we observed particularly strong events able to locally duplicate the ep100 this approach provides a novel perspective on where episodic subduction occurs that will be naturally improved as bgcargo observations continue to increase

a study of an intense density front in the eastern alboran sea the almeria oran front abstract studies of satellite imagery and space shuttle photographs of the western mediterranean have indicated that the main path of inflowing atlantic water is around two large anticyclonic gyres in the alboran sea and along the algerian coast these studies have also shown that a strong ocean front is present between almeria spain and oran algeria which is part of the easternmost segment of the eastern alboran gyre based on these satellite studies the first in situ investigation of the front called here the almeria oran front was conducted in march 1986 as part of the winter campaign of the western mediterranean circulation experiment wmce analyses of the resulting data show that the almeria oran front is a large scale density front formed by the convergence of two distinct water masses and controlled by the geographic position and strength of the eastern alboran gyre physical and biochemical data indicate that the front is limited to the upper 300 m with a strong southward baroclinic jet

carbazole distributions in carbonate and clastic source rocks abstract carbazole the benzocarbazoles and their alkyl derivatives have been studied from rock extracts to assess the contribution of facies and maturity in controlling their distribution carbonates from the keg river formation elk point group middle devonian western canada consisting of two different facies reflecting deposition under trangressive and regressive events were used to assess facies influences to study maturation a uniform organo facies of organic rich posidonia shale lower toarcian jurassic northern germany from 0 48 to 1 45 r r was used the organic rich lower keg member deposited under photic zone anoxia contained predominantly c 4 c 5 carbazoles by contrast the upper keg river member deposited under regressive higher salinity environment contains predominantly carbazole itself 1 methylcarbazole and a high abundance of benzo c carbazole relative to benzo a carbazole the distribution of the c 1 to c 3 carbazoles was seen to vary with facies an examination of the carbazole derivatives within the posidonia shale reveals that maturation strongly influences the distribution of carbazole methylcarbazoles 1 8 dimethylcarbazole 1 ethylcarbazole benzo a carbazole and benzo c carbazole quantitative determination of these compounds indicates a maximum yield at 0 88 r r for all derivatives with the exception of carbazole which displays as a maximum at 0 53 r r a systematic variation of compound ratios with maturity to 0 88 r r suggests that selective isomerisation destruction generation of carbazole derivatives may occur in contrast to earlier publications which stress the importance of carbazoles as migration markers in migrated oils the results presented here indicate that facies and maturation do play a significant role in controlling the distribution of carbazole derivatives in source rocks and other sediments

aromatic biomarkers as indicators of source depositional environment maturity and secondary migration in the oils of cambay basin india abstract aromatic biomarkers have been analysed for source depositional environment maturity and secondary migration in crude oils from different formations of paleocene to eocene age in the ahmedabad mehsana block of north cambay basin and the broach block of south cambay basin north cambay basin oils are characterized by a high abundance of 1 2 5 and 1 2 7 trimethylnaphthalenes tmn and low to medium ratio of dibenzothiophene phenanthrene and low ratio of pristane phytane indicates that these oils have been derived from a source containing predominantly higher plants and that the organic matter was deposited in restricted marine or lacustrine environments in anoxic to suboxic conditions the relative abundance of 1 2 7 tmn suggests that it was derived from the structural degradation of oleanane type triterpenoids present in angiosperms south cambay basin oils are less abundant in 1 2 5 and 1 2 7 tmns and low ratio of dibenzothiophene phenanthrene and high ratio of pristane phytane indicating that the oils were derived from higher plant source organic matter deposited under marine or fluvial deltaic environment in oxic conditions maturity sensitive ratios based on phenanthrene naphthalene dibenzothiophene and their alkyl substituted isomers have been used to calculate the equivalent vitrinite reflectance these parameters indicate a wide range of thermal maturity of the oils ranging from 0 60 to 0 93 vrc methylphenanthrene index and methyldibenzothiophene ratios indicate that the maturity of north and south cambay basin oils are different the north cambay basin oils are less mature than south cambay basin oils pyrrolic nitrogen distribution indicates that the alkylated carbazoles and benzocarbazoles are more abundant in south cambay basin oils as compared to north cambay basin oils these data indicate that north cambay basin oils are less migrated compared to south cambay basin oils this systematic investigation of the aromatic biomarkers in oils of cambay basin has resulted in a new generation migration and entrapment model that has led to the development of new exploration leads

migration and accumulation of crude oils from permian lacustrine source rocks to triassic reservoirs in the mahu depression of junggar basin nw china constraints from pyrrolic nitrogen compounds and fluid inclusion analysis abstract the geochemical compositions of crude oils and permian source rocks from the mahu depression of the junggar basin were analyzed in this study based on tricyclic terpanes and isoprenoid biomarkers three oil groups i ii and iii can be identified that correspond to different source rock formations and organic facies after examination of the influence of source facies and thermal maturity and selected biomarker ratios based on carbazole isomers such as 1 mc 4 mc 1 8 dmc 2 7 dmc and a a c bc ratios in different oil groups allowed us to determine the direction of hydrocarbon migration in different reservoirs in addition abundant oil inclusions are present with fluorescence colors ranging from yellow to blue white these were analyzed by ftir to distinguish between different sources for the oils fluid inclusion petrography and microthermometry were also used to prove two stages of oil migration and their different sources taking into consideration possible migration pathways and likely driving forces we conclude that abnormally high pressure in the permian sequence acted as the main driving force for oil migration the major migration pathways were vertical faults in the fault belts and slope areas and sand bodies in the deeper areas group i1 oils from p1f carbonate source rocks in the fault belts mainly migrated vertically through the faults and accumulated in t1b reservoirs in the late triassic and were driven by excess formation pressure and buoyancy group i2 oils in the slope areas first migrated vertically within thrust faults from p1f mudstone source rock in the late triassic after which they migrated laterally over short distances to accumulate in t1b sand bodies group ii oils from adjacent p2w source rocks in the center of the depression migrated mainly in the late jurassic due to abnormally high pressure and accumulated in nearby t1b traps some reservoir rocks in the slope area contain two generations of fluid inclusions implying oil mixing from early stage p1f oils and late stage p2w oils resulting in the group iii oils combining these data from biomarkers pyrrolic nitrogen compounds and fluid inclusions allowed us to construct models of migration and accumulation for oils in the mahu depression

sentinel 3a views ocean variability more accurately at finer resolution this is the first multiplatform evaluation involving data from the new sentinel 3a altimeter an experiment was undertaken in the algerian basin employing an ocean glider and a ship mission along the same track and synchronous with an overpass of the sentinel 3a mission this provided three independent views of the ocean velocity field along a section that encompassed three different oceanographic regimes the results demonstrate the capacity of sentinel 3a to retrieve fine scale oceanographic features 20 km the intercomparison with in situ platforms showed a significant improvement order 30 in resolution and 42 in velocity accuracy using a synthetic aperture radar mode with respect to lower resolution mode of conventional altimetry in addition the three platform view provided valuable insight into the variability of evolving oceanographic features in an area of the mediterranean that remains chronically under sampled

triggered seismicity associated with the 1990 nicoya costa rica mw 7 0 earthquake 1 the 25 march 1990 mw 7 0 subduction megathrust earthquake that occurred offshore the nicoya peninsula costa rica produced a large number of aftershocks on the subduction plate interface as expected and preceded an unusual sequence of earthquakes 75 km inland that had two periods of significant increase one at 60 90 days and one near 270 days following the main shock this inland sequence of events would not typically fall within the classification of aftershocks given their spatial and temporal distance and we show here that this sequence was likely triggered by the 25 march main shock we compute stress changes on representative faults within this inland region using both a simple half space model as well as with a 2 d finite element model that incorporates variable rheologic properties the half space model predicts a minor increase in coulomb stress changes and a large amount of unclamping in this region likely enough to cause triggering on the inland right lateral strike slip faults models that include a viscoelastic response also indicate stress increases that may link to triggering particularly related to the time delay earthquakes on the subduction zone thrust along costa rica should be considered in hazard assessments for the inland populated region as several sets of strike slip faults have been mapped in the fore arc region