hydrocarbon potential and depositional environments of oligo miocene rocks in the eastern carpathians vrancea nappe romania abstract the oligocene to early miocene fine grained succession in the eastern carpathians includes from base to top the lower menilite lmm bituminous marl bmm lower dysodilic shale ldsm and upper dysodilic shale udsm members these stratigraphic units constituting the main hydrocarbon source rocks in the eastern carpathians have been studied in an outcrop section to determine its depositional environment and hydrocarbon potential the lmm contains high amounts of toc but because of low thickness its source potential is limited the organic matter of the overlying bmm is mainly derived from autochthonous marine organisms including bacterial biomass toc contents are moderate because of dilution by carbonate minerals calcareous nannoplankton dates the bmm into nannoplankton zones np21 22 salinity and redox conditions varied from reduced to slightly enhanced and from strictly anoxic to dysoxic the ldsm contains carbonate free black shale and sandstone beds deposited in a depositional lobe under anoxic conditions despite of high hi values land plants form a significant part of the organic matter channel fill sediments form the top of the ldsm the lower part of the early miocene udsm accumulated in a lobe whereas its upper part represents a basin plain setting mttc ratios reflect a trend from slightly enhanced to slightly decreased normal marine salinity the presence of aryl isoprenoids suggests a temporary photic zone anoxia controlled by salinity variations both marine and terrestrial biomass contributed to the organic matter a major change towards oxic conditions occurred at the boundary between the udsm and the overlying gura soimului formation the studied succession can generate 6 t of hydrocarbons per square meter all members are oil prone but yield oil with different biomarker characteristics this allows the identification of oil generated from different lithostratigraphic units

organic matter in oligocene menilite formation rocks of the ukrainian carpathians palaeoenvironment and geochemical evolution abstract the ukrainian carpathians form the middle sector of the carpathian arc the menilite black shale formation oligocene early miocene is the youngest part of the flysch sequence and occurs in a wide depth range the anaerobic bacterial processes during early diagenesis led to formation of 13 c rich carbonate concretions and 13 c depleted organic matter black shales contain type ii kerogen with high source rock potential in the upper 4 km of the sequence the rocks preserved their pre overthrusting level of maturity close to the beginning of the oil window while at greater depths the maturity increases under the influence of present day heat flow

relations between surface deformation fault geometry seismicity and rupture characteristics during the el asnam algeria earthquake of 10 october 1980 abstract the el asnam earthquake of october 10 1980 ms 7 3 produced surface faulting on a northeast trending thrust fault of 30 km length with displacements of up to 6 5 m though average displacements were about 3 m in addition widespread tensional features were formed some in clear association with folding above the thrust and others in an area beyond the exposure of the thrust at the surface which may be related to buried reverse faults the observed thrust fault is split into southern central and northern segments local and teleseismic data are examined to show that the main shock nucleated at the southwest end of the fault and propagated 12 km northeast where a second rupture of approximately equal moment occurred continuing the faulting a further 12 km northeast along the central segment both ruptures nucleated at about 8 10 km depth displacements were largest on the central segment where they were probably enlarged by aftershocks including one of mb 6 1 three hours after the main shock the northern segment was much shorter than the other two and showed smaller displacement the junctions between fault segments are marked by distinct geomorphological characteristics and a change in strike of the faulting as well as a sudden drop in the observed displacement it appears that the rupture development is influenced by the changes in fault geometry between segments and that such junctions or barriers have persisted through much of the late quaternary

stratigraphic and geochemical study of the organic rich black shales in the tarcău nappe of the moldavidian domain carpathian chain romania an integrated stratigraphic analysis has been made of the tarc u nappe moldavidian domain eastern romanian carpathians coupled with a geochemical study of organic rich beds two main sequence boundaries early oligocene and near to the oligocene aquitanian boundary respectively divide the sedimentary record into three depositional sequences the sedimentation occurred in the central area of a basin supplied by different and opposite sources the high amount of siliciclastics at the beginning of the miocene marks the activation of the foredeep stage the successions studied are younger than previously thought and they more accurately date the deformation of the different miocene phases affecting the moldavidian basin the intervals with black shales identified are related to two main separate anoxic episodes with an age not older than late rupelian and not before late chattian the most important organic rich beds correspond to the lower menilites bituminous marls and lower dysodilic shales members interval 2 these constitute a good potential source rock for petroleum with homogeneous type ii oil prone organic matter highly lipidic and thermally immature the deposition of black shales has been interpreted as occurring within a deep periodically isolated and tectonically controlled basin

oil oil and oil source rock correlations in the carpathian foredeep and overthrust south east poland abstract the chemical composition of 35 crude oils and the extracts of potential source rock samples from south east poland were studied in detail by geochemical methods in order to understand their genetic relationships twenty six oils including three seep samples were collected from cretaceous to oligocene reservoirs within the carpathian overthrust nine oils originated from carboniferous to miocene reservoirs within the carpathian foredeep the rock samples studied were selected after rock eval pyrolysis screening of a large suite of samples and consist of one lower cretaceous sample and five oligocene menilite shale samples from three different outcrop locations all within the carpathian overthrust geochemical fingerprinting indicates at least two families of crude oils the first represented only by one oil has no specific characteristics except for a light carbon isotope composition the second family is characterized by the presence of 28 30 dinor hopane oleanane and a highly branched isoprenoid c25 alkane within this latter family four subfamilies were recognized a 19 oils having the aforementioned characteristics b seven oils similar to subfamily a but with a relatively high sulphur content c one oil with high abundance of higher plant derived triterpanes and d seven oils with abundant 28 30 dinor hopane although maturity influences the relative abundance of 28 30 dinor hopane it suggested that subfamilies a b and c had an initial low 28 30 dinor hopane content whereas subfamily d an initial high 28 30 dinor hopane content only one oil of subfamily a could potentially be a high maturity counterpart of subfamily d a palaeozoic source rock is suggested for the first family and the second family including the majority of the pils from the carpathian foredeep is most likely derived from the oligocene menilite shales an oil source rock relationship with the menilite shale is supported by the presence although not in all samples studied of 28 30 dinor hopane oleanane or its precursors and the highly branched isoprenoid alkane the strong facies variations observed within this shale gave rise to the different types of crude oils in the second family

seismicity normal faulting and the geomorphological development of the gulf of corinth greece the corinth earthquakes of february and march 1981 three major destructive earthquakes of m s 6 7 6 4 6 4 occurred in the eastern part of the gulf of corinth in february and march 1981 associated normal faulting was observed on both the north and the south sides of the gulf examination of teleseismic local seismic surface faulting and geomorpbological data suggests that the first and second of these shocks activated major north dipping normal faults these faults control the topography and bathymetry and are related to the recent uplift and subsidence of the coastline it is probable that the first earthquake occurred on a faultwhich outcrops underwater and the second on a fault which is visible on land it appears that the third shock activated an antithetic normal fault dipping southwards on the north side of the gulf and that the overall structure of the gulf of corinth graben is asymmetric the northern antithetic fault clearly demonstrates the geomorphological changes associated with developing young normal faulting in addition we suggest that observations of recent coastline movement provide a powerful tool for identifying major active fault systems and predicting their historical role in the paleogeography of an area

diagenetic and catagenetic products of isorenieratene molecular indicators for photic zone anoxia a wide range of novel diagenetic and catagenetic products of the diaromatic carotenoid isorenieratene a pigment of the photosynthetic green sulphur bacteria chlorobiaceae has been identified in a number of sedimentary rocks ranging from ordovician to miocene compound identification is based on nmr mass spectrometry the presence of atropisomers and stable carbon isotopes atropisomers contain an axially chiral centre which in combination with other chiral centres results in two or more diastereomers that can be separated on a normal gc column chlorobiaceae use the reverse tca cycle to fix carbon so that their biomass is enriched in 13c high 13c contents of isorenieratene derivatives therefore support their inferred origins isorenieratene derivatives include c 40 c 33 and c 32 diaryl isoprenoids and short chain aryl isoprenoids with additional aromatic and or s containing rings c 33 and c 32 compounds are diagenetic products of c 33 and c 32 carotenoids formed from isorenieratene during early diagenesis through expulsion of toluene and m xylene respectively cyclisation of the polyene acyclic isoprenoid chain can proceed via an intramolecular diels alder reaction followed by aromatisation of the newly formed ring sulphurisation is also an important process during early diagenesis competing with expulsion and cyclisation sulphur bound isorenieratane is released during progressive diagenesis due to cleavage of relatively weak ss and cs bonds cleavage of c c bonds during aromatisation of newly formed rings and during catagenesis yields short chain compounds the inherent presence of a conjugated double bond system in carotenoids implies that similar diagenetic and catagenetic reactions can occur with all carotenoids chlorobiaceae live at or below the oxic anoxic boundary layer and require both light and h 2s the presence of isorenieratene or its diagenetic and catagenetic products in ancient sedimentary rocks and crude oils is therefore an excellent indication for photic zone anoxia in the depositional environment diagenetic and catagenetic products of isorenieratene are expected to find applications in reconstruction of palaeoenvironments and in oil oil and oil source rock correlation studies their presence in several petroleum source rocks suggests that anoxia is an important environmental parameter for the preservation of organic matter

a new approach to interpreting rock eval s2 and toc data for kerogen quality assessment abstract a simple method for application in source potential mapping is used to assess the original oil and gas potentials in source rock horizons based upon rock eval potential s 2 and total organic carbon toc values the method assumes that kerogens consist of mixtures of end members with assigned hydrogen index values based on suggested algorithms the average amounts of oil prone gas prone and inert organic material over source rock intervals are determined in toc units the method uses regression lines from plots of remaining hydrocarbon potentials s 2 versus total organic carbon toc and quick look transparent overlays are used to read the appropriate kerogen mixture mineral matrix effects during pyrolysis when strong can cause erroneous results this effect which occurs for oil prone kerogens and adsorptive minerals can cause problems particularly for lean samples s 2 0 3 mg hc g rock whilst the errors for richer samples are less the method is applied on three sections of upper jurassic organic rich rocks from the danish north sea sector which are at different maturity stages one of these sections is dominated by gas prone material one is dominated by oil prone material and the third section contains a mixture of oil and gas prone material the method has been compared with other methods that split kerogens in oil and gas generating potential and has given reasonable results experience using the method and a presented example suggest that sedimentological system tract information may be derived from s 2 to toc cross plots a constructed modelling example suggests that the end member concept used in this approach may be used in forward type source rock prediction models when combined with sedimentological models the resulting s 2 toc plots can be used in order to check the forward modelling results against observed values

the transylvanian basin romania and its relation to the carpathian fold and thrust belt insights in gravitational salt tectonics abstract interpretation of regional seismic profiles stratigraphic and sedimentologic data improved insights in the evolution of the transylvanian basin the basin evolution was coeval with the post mid cretaceous to recent deformation of the carpathian mts four tectonostratigraphic megasequences are differentiated upper cretaceous rift paleogene sag lower miocene flexural basin and middle to upper miocene backarc sequence dominated by gravitational tectonics the mid miocene continental collision in the eastern carpathians is associated with the rising carpathians this uplift enhanced the differential load which together with the high heat flow induced by late miocene to pliocene arc volcanism triggered large scale mio pliocene gravity spreading of the salt overburden this mega slide comprises three structural domains as follows extensional weld upslope contractional folds central and contractional toe thrust downslope the diapirs in the east indicate a pre shortening reactive passive growth stage the central folds are mostly the result of late shortening basement involved thrusting uplifted the toe thrust domain by the late pliocene the late neogene to recent carpathians uplift backarc volcanism and gravity spreading are largely coeval

the 1978 earthquake sequence near thessaloniki northern greece summary this paper presents a detailed study of teleseismically and locally recorded foreshocks and aftershocks of the 1978 thessaloniki earthquake sequence and discusses the relations between the locations and mechanisms of these shocks and the three dimensional geometry of faulting in the source region sixteen teleseismically recorded events were relocated using a relative relocation method and positioned geographically using the accurate locally determined location of the largest aftershock all these shocks had depths shallower than 15 km the spatial distribution of the foreshocks showed that the activity was initiated at the central part of the epicentral region progressed westwards and for about 20 days clustered in the region of the imminent mainshock no teleseismically recorded foreshock was located west of the mainshock location in less than 1 hr after the mainshock large aftershocks occurred west of it and in later stages spanned the entire western part of the epicentral region no teleseismically recorded aftershocks were located east of the mainshock locally recorded aftershocks were accurately located and provided a more detailed picture of the seismic deformation they occurred at depths between 3 and 12 km and in three distinct clusters separated by well defined gaps the largest foreshock on may 23 had a moment of 5 6 1024dyne cm and a mean displacement of 31cm the mainshock on june 20 had a moment of 5 2 1025dyne cm a strain drop of 4 0 10 5 static stress drop of 12 bar and a mean displacement of 64 cm these values are for one of the two possible interpretations of the aftershock distribution which suggests that the largest earthquakes of the sequence occurred on two different but adjacent fault segments the first event 1 on may 23 occurred along the central fault segment and was followed 28 days later by the second event 2 on june 20 along a western fault segment finally 61 days later another smaller earthquake event 3 occurred along another fault east of event 1

regional state of stress and characteristic fault kinematics instabilities shown by aftershock sequences the aftershock sequences of the 1978 thessaloniki greece and 1980 campania lucania italia earthquakes as examples abstract usual analysis of fault kinematics in terms of stress supposes that the slip occurs in the direction of the shear stress resolved on the fault plane due to an homogeneous state of stress however as a block moves this yields perturbations of the static stress conditions the resulting displacement may produce interactions of blocks and may induce complex fault motions such as those demonstrated by the aftershock sequences of the thessaloniki and campania lucania earthquakes each of which shows a main group of focal mechanisms whose normal fault motions are modelled using a stress deviator tm in agreement both with the motion of the main seismic fault and with the regional stress pattern deduced from quarternary and recent faults it is therefore considered as representative of the mean state of stress acting in the epicentral area but two other families of fault motions are also demonstrated one shows reverse motions explained by a compressional stress deviator tc the other involving normal motions is explained by a tensional stress deviator te these deviators are not representative of the mean regional state of stress the compressional 1 axis of tc and the tensional 3 axis of te are roughly orthogonal to the 3 axis of the mean state of stress tm these tc and te deviators may be deduced from the mean state of stress tm by adding respectively td1 and td2 deviators to this latter this means that on each fault plane having a reverse c or a normal e motion this motion may be deduced from the normal kinematics m it should have occurred in the mean regional state of stress tm by adding local pushes d1 and d2 respectively the deviator td2 being nearly axisymmetric around a vertical 3 axis the local reverse pushes d1 are nearly dip slip and td2 having a high angle dipping 2 axis the local pushes d2 are essentially strike slip approximated solutions of these td1 and td2 deviators have been calculated by taking tm td1 tc and tm td2 te the mean state of stress tm being divided into two parts tv and ts which respectively produce the dip slip and essentially strike slip components of the stress resolved on the fault plane a first approximation of the data shows that td1 kv tv and td2 ks ts with kv and ks equal to 2 this approximation supposes that tm tc and te are coaxial and that td1 and td2 are respectively axisymmetric around the vertical 3 axis and planar in the horizontal plane actually the data give kv 2 and ks in the order of 4 5 it is suggested that the local reverse and strike slip pushes are induced by the reaction of the rocky body surrounding small blocks moving as a consequence of a motion on a major fault particularly as there are incompatibilities of motion of adjacent small blocks however data are not sufficient to demonstrate the mechanical and geometric conditions which control the observed different behaviors of the small seismic faults numerical simulations or experiments could probably precise these conditions whatever under certain conditions the stable solution m is replaced by kinematics instabilities e and c however it is usually observed that faults studied in the field in a simple way often yield a single stress deviator this is probably due to the nature of the measured striations which are often growth fibers and oblique stylolithes resulting from creep fault motions in this case incompatibilities of block motions are probably accommodated by a pressure dissolution phenomena therefore it is suggested that the bifurcation parameter which controls the occurrence of the characteristic instabilities possibly depends on a ratio of the deformation rate versus the pressure dissolution rate of the material a question remains unanswered are these instabilities scale invariant or is there a changeover in the behavior between minor and major faults

organofacies and paleoenvironment of the oligocene maikop series of angeharan eastern azerbaijan the maikop formation deposited in eastern azerbaijan during oligocene and early miocene times contains prolific source rocks with primarily type ii organic matter paleontological analyses of dinoflagellate cysts revealed a lower to upper oligocene age for the investigated succession near angeharan a major contribution of aquatic organisms diatoms green algae dinoflagellates chrysophyte algae and minor inputs from macrophytes and land plants to organic matter accumulation is indicated by n alkane distribution patterns composition of steroids and 13c of hydrocarbon biomarkers microbial communities included heterotrophic bacteria cyanobacteria chemoautotrophic bacteria as well as green sulfur bacteria higher inputs of terrigenous organic matter occurred during deposition of the upper oligocene units of the maikop formation from angeharan mountains the terpenoid hydrocarbon composition argues for angiosperm dominated vegetation in the shamakhy gobustan area high primary bioproductivity resulted in a stratified water column and the accumulation of organic matter rich sediments in the lower oligocene units of the maikop formation organic carbon accumulation during this period occurred in a permanently salinity stratified mesohaline environment with free h2s in the water column this is indicated by low pristane phytane ratios of all sediments varying from 0 37 0 69 lower methylated trimethyltridecyl chromans ratio in the lower units and their higher contents of aryl isoprenoids and highly branched isoprenoid thiophenes subsequently the depositional environment changed to normal marine conditions with oxygen deficient bottom water the retreat of the chemocline towards the sediment water interface and enhanced oxic respiration of om during deposition of the upper oligocene maikop sediments is proposed parallel depth trends in 13c of total om n alkanes isoprenoids and steranes argue for changes in the regional carbon cycle associated with the changing environmental conditions increased remineralisation of om in a more oxygenated water column is suggested to result in low toc and hydrocarbon contents as well as 15n enriched total nitrogen of the upper oligocene units

irpinia italy 1980 earthquake waveform modelling of strong motion data summary several strong motion records of the irpinia southern italy 1980 earthquake have been modelled for a total time duration of about 180 s with the use of the rnultimode summation of waves of p sv and sh type if waveform modelling is applied to unfiltered accelerations the best that can be done at present is amplitude envelope matching in time and frequency domain the early phase of the studied event can be synthesized by 12 main episodes of different sizes modelling the rupturing process the space time distribution of such episodes suggests that the rupturing process did propagate in a bilateral fashion this model of the seismic source gives rise to synthetic velocity records which match quite well the experimental ones to avoid the problems connected with the large instability of displacements obtained from direct numerical integration of observed accelerograms the synthetic signals can be first used to perform acceleration or velocity fitting of experimental data an estimate of the ground displacement above 1 hz can then be obtained by analytical integration of the synthetic velocities

seismotectonics of the calabrian arc abstract relocation of intermediate and deep earthquakes of tyrrhenian sea area through joint hypocenter determination for the period 1962 1979 has allowed a more detailed definition of the geometry of this peculiar benioff zone earthquakes dip along a quasi vertical plane to 250 km depth there is a 50 dip in the 250 340 km depth range and a low dip angle to 480 km depth the structure sketched from the hypocenters is almost continuous but most energy has been released in the 230 340 km depth interval an evaluation of fault plane solutions of intermediate earthquakes in this area indicates predominance of down dip compressions in the central part of the slab at the border strike slip motion occurs independent of depth some earthquakes that occurred at intermediate depth less than 100 km along the ionian margin of calabria show predominance of reverse faulting with the p axis oriented se nw however shallow earthquakes in the calabria sicily region indicate a more complex motion with predominance of normal faulting a possible interpretation of these features according to the available geological history which involves subduction of continental lithosphere is discussed

elemental and major biochemical changes across an oxidation front in a relict turbidite an oxygen effect abstract the elemental and major biochemical compositions of the relict f turbidite sampled in two cores from the madeira abyssal plain were determined this fine grained distal sequence occurs at ca 9 m core depth and includes a surficial oxidized horizon defined by a distinct color change oxygen diffused downward through sediments above this interface and in ca 10 kyr destroyed 80 of the organic substances that below the front had survived degradation in the presence of porewater sulfate for ca 140 kyr these deposits provide an opportunity to establish the extent and selectivity of oxic sedimentary degradation under natural conditions without the usual complications of bioturbation and varying sources or sedimentation rates in both cores a sample from the upper oxidized layer was compared to two samples from the underlying unoxidized layers the unoxidized sequences of both turbidities contained 0 93 1 02 wt organic carbon oc and 0 10 0 11 wt total nitrogen tn approximately 20 of the initial oc and 40 of the initial tn remained in the oxidized horizons with a consequent decrease in atomic c n ratio from ca 11 to ca 5 all samples gave very low yields of lignin phenols and comparable oc normalized yields of total aldoses and amino acids and indicated predominantly marine organic matter om and nonselective oxic degradation of these biochemical classes compositions of individual aldoses and amino acids generally were also similar in surface and deep sediments except that the oxidized horizons yielded markedly elevated 3 5x percentages of nonprotein amino acids this study clearly demonstrates that prolonged exposure to oz can lead to organic matter alteration which is far more extensive than that obtained with sulfate alone in comparison to early diagenesis however alteration of the measured biochemicals was largely nonselective such oxidation reactions could control the distribution and composition of organic matter in slowly accumulating continental rise and deep ocean environments

correlation alteration and origin of hydrocarbons in the gca bahar and gum adasi fields western south caspian basin geochemical and multivariate statistical assessments abstract geochemical as well as multivariate statistical analyses pca were carried out on 20 crude oil samples from middle pliocene production series mpps of guneshli chirag azeri gca bahar and gum adasi fields in the western south caspian basin scb pca analysis employed to source specific biomarkers distinguishes the oils into two types one being divided into two sub types type 1 gca oils type 2a bahar field oils and type 2b gum adasi field oils indirect oil to source rock correlations to available source rock data from previous studies suggest that type 1 oils located in the apsheron balkhans uplift area are derived from basinal shales of the oligocene lower miocene middle maikop formation type 2a and 2b oils located in the gum deniz bahar shakh deniz trend area are more likely derived from shelf edge shales of the upper maikop formation and the middle upper miocene diatom suite respectively biomarker maturity study reveals that type 1 oils mean rc 0 78 are more mature than type 2 oils mean rc 0 71 source rocks which generated these oils were at generation depth interval between 5200 m 112 c and 7500 m 153 c at the time of expulsion this indicates that the western scb oils experienced significant long range vertical migration along the deep seated faults to accumulate in the mpps reservoirs post accumulation biodegradation process was only observed in the guneshli field where bacterial alteration level 4 began between 4 2 and 2 6 mybp and stopped with the deposition of the overlying impermeable upper pliocene akchagyl formation subsequent light hydrocarbon c1 c16 charge into the guneshli fields caused precipitation of asphaltenes which is evidenced by high resin to asphaltene ratios for the present day guneshli oils evaporative fractionation examined using the scheme of thompson 1987 showed high correlations of the aromaticity b parameter toluene n c7 and parafinicity f parameter n c7 mch with the rc maturity and c27 c29 sterane ratio organic matter type this implies that thompson s approach should be used with caution in the scb among the several mechanisms rapid and thick deposition of pliocene sediments and subsequent high heating rate on the maikop formation and diatom suite is probably the most plausible way of explaining the origin of light hydrocarbons in the guneshli and bahar fields

study of physical and chemical properties of vitrinites inferences on depositional and coalification controls abstract a detailed study of petrological geochemical textural and coking properties was carried out on vitrains from the puertollano blanzy montceau asturias and teruel the objective was to determine in depth the physical and chemical properties of a series of natural and pure vitrinites of different rank and the influence that the sedimentary and post sedimentary conditions had on them it is demonstrated that although vitrains are almost entirely made up of the huminite vitrinite maceral group they have a different composition thermal behaviour and physical properties thus geochemical and textural properties of blanzy montceau vitrains can be considered to be representative of the telinite the major component in both samples 75 vol at the beginning of the bituminization stage subbituminous high volatile c bituminous coals the characteristics of the puertollano vitrains described here can also be attributed to the telocollinite 80 vol for the high volatile c bituminous coal variations in physico chemical properties between puertollano and blanzy montceau vitrains are due to the differences in the initial composition of organic matter slight differences i e bed moisture content or porosity between vitrains from the two coal seams in the same basin can be attributed to their stratigraphic position several parameters such as s 2 hi oil and extraction yield and fluorescent properties suggest that the puertollano and blanzy montceau vitrains have a lower hydrocarbon potential the relationships between geochemical and textural properties make it possible to distinguish between normal and perhydrous vitrains the two different hydrogen enrichment processes that occur in vitrains from the teruel and asturias basins can be distinguished from the extraction yield data

seismotectonics of the el asnam earthquake the mechanism of the el asnam earthquake of 10 october 1980 ms 7 2 the strongest recorded in northwestern africa is compatible with a convergence between the african and european plates the thrust is also consistent with field observations and with long period data from the global network aftershocks cluster around the fault trace with a maximum depth of 12 km maximum vertical displacement is 6 m and there is some left lateral motion the fault trace of the 1954 earthquake at beni rached was also reactivated

methane and sulfide fluxes in permanent anoxia in situ studies at the dvurechenskii mud volcano sorokin trough black sea the dvurechenskii mud volcano dmv is located in permanently anoxic waters at 2060 m depth sorokin trough black sea the dmv was studied during the rv meteor expedition m72 2 as an example of an active mud volcano system to investigate the significance of submarine mud volcanism for the methane and sulfide budget of the anoxic black sea hydrosphere our studies included benthic fluxes of methane and sulfide as well as the factors controlling transport consumption and production of both compounds within the sediment the pie shaped mud volcano showed temperature anomalies as well as solute and gas fluxes indicating high fluid flow at its summit north of the geographical center the anaerobic oxidation of methane aom coupled to sulfate reduction sr was repressed in this zone due to the upward flow of sulfate depleted fluids through recently deposited subsurface muds apparently limiting microbial methanotrophic activity consequently the emission of dissolved methane into the water column was high with an estimated rate of 0 46 mol m 2 d 1 on the wide plateau and edge of the mud volcano surrounding the summit fluid flow and total methane flux were lower allowing higher sr and aom rates correlated with an increase in sulfate penetration into the sediment here between 50 and 70 of the methane flux 0 07 0 1 mol m 2 d 1 was consumed within the upper 10 cm of the sediment the overall amount of dissolved methane released from the entire mud volcano structure into the water column was significant with a discharge of 1 3 107 mol yr 1 the dmv maintains also high areal rates of methane fueled sulfide production and emission of on average 0 05 mol m 2 d 1 this is a difference to mud volcanoes in oxic waters which emit similar amounts of methane but not sulfide however based on a comparison of this and other mud volcanoes of the black sea we conclude that sulfide and methane emission into the hydrosphere from deep water mud volcanoes does not significantly contribute to the sulfide and methane inventory of the black sea

source rock habitat and hydrocarbon potential of oligocene menilite formation flysch carpathians southeast poland an organic geochemical and isotope approach geochemical and isotope methods have been used to analyse the hydrocarbon potential and petroleum generation characteristics of the oligocene menilite formation the most important petroleum source rock in the overthrust part of the carpathian foreland basin in se poland the data show a large variability in quantity up to 18 toc quality type ii and ii iii and carbon isotope composition of the organic matter in samples of different lithology and from different stratigraphic and tectonic settings these differences reflect distinct sedimentary and tectonic histories of individual sub basins the maturity in the outer tectonic units is very low tmax 420 c ro 0 35 but increases towards the inner nappes and also laterally to the se the variability of the kinetic parameters indicates the likely occurrence of multiphase hydrocarbon generation the menilite formation forms a very good source rock in the complex petroleum system of the carpathian overthrust belt

a procedure for modelling shallow dislocation sources summary expressions for displacements on the surface of a layered half space due to an arbitrary oriented shear dislocation are given in terms of generalized ray expansions useful approximations of these expressions for shallow events as recorded at teleseismic distances for realistic earth models are presented the results of this procedure are used to generate synthetic p sv and sh waveforms for various assumptions of stress drop

normal faulting in the upper continental crust observations from regions of active extension abstract observations of present day normal faulting in regions of active continental extension may be helpful when interpreting the geological record in older extensional basins the most obvious manifestation of active extension is normal faulting in earthquakes earthquake foci are mostly confined to the upper seismogenic continental crust whose thickness imposes a scale on the observed deformation large earthquakes move faults with lengths similar or large compared with the thickness of the seismogenic layer large seismogenic normal faults on the continents appear to be restricted to a dip range of around 30 60 dips significantly gentler than 20 have not been observed in fault plane solutions of large earthquakes large seismographic normal faults are approximately planar in cross section and cut through the base of the upper seismogenic layer rotating about a horizontal axis as they move a reasonable estimate of the regional extension can often be made from the dip of the large normal faults and the tilt of the blocks they bound the domino model such faults are rarely continuous for more than 15 20 km but commonly change strike or step in an en echelon fashion this segmentation may occur on a scale controlled by the thickness of the seismogenic layer and is an important influence on sedimentation and drainage these observations are common to large seismogenic normal faults from a variety of tectonic settings and suggest that the kinematics of normal faulting may not be strongly influenced by the forces responsible for the extension which can vary widely in nature and magnitude small earthquakes which move faults that are small compared with the seismogenic layer thickness show no simple pattern and often can be interpreted as internal deformation of blocks bounded by large faults in some places the seismogenic basement faults do not reach the surface but are decoupled from the sedimentary cover by layers of weak lithology faults in the sedimentary cover may be strongly curved in cross section requiring their hangingwalls to deform internally estimating extension from such faults is not straightforward and requires a knowledge of the hangingwall deformation estimates made in this way are often very non unique and prone to large errors we postulate that the thickness of the seismogenic upper crust controls both the maximum length of large normal fault segments along strike and the maximum size of blocks that can rotate coherently about a horizontal axis

oil source rock correlations in the polish flysch carpathians and mesozoic basement and organic facies of the oligocene menilite shales insights from hydrous pyrolysis experiments the oligocene menilite shales in the study area in the polish flysch carpathians are organic rich and contain varying mixtures of type ii type iis and type iii kerogen the kerogens are thermally immature to marginally mature based on atomic h c ratios and rock eval data this study defined three organic facies i e sedimentary strata with differing hydrocarbon generation potentials due to varying types and concentrations of organic matter these facies correspond to the silesian unit and the eastern and western portions of the skole unit analysis of oils generated by hydrous pyrolysis of outcrop samples of menilite shales demonstrates that natural crude oils reservoired in the flysch sediments appear to have been generated from the menilite shales natural oils reservoired in the mesozoic basement of the carpathian foredeep appear to be predominantly derived and migrated from menilite shales with a minor contribution from at least one other source rock most probably within middle jurassic strata definition of organic facies may have been influenced by the heterogeneous distribution of suitable menilite shales outcrops and producing wells and subsequent sample selection during the analytical phases of the study

extractable organic material in fault zones as a tool to investigate frictional stress abstract the detection of a frictional heating signature is an attractive but elusive way to measure frictional stress on exhumed faults with no evidence of melting we present a new paleothermometer for fault zones that utilizes the thermal maturity of extractable organic material to determine the maximum frictional heating experienced by the fault because there are no retrograde reactions in these organic systems maximum heating is preserved we investigate the punchbowl fault an ancient strand of the san andreas fault in southern california according to the methylphenanthrene index for thermal maturity there is no differential heating between the fault and off fault samples indicating that the fault did not get hotter than the surrounding rock during slip additionally the thermal maturity of the rocks falls within the range of heating expected from the bounds on burial depth and time and adds some constraint to the burial depth range simple heating models indicate that the fault must have had either 1 an extremely low shear stress during slip 2 an active slipping zone thicker than 1 mm or 3 earthquakes smaller than m6 to lack a differential heating signature after 44 km slip

the oligocene maikop series of lahich eastern azerbaijan paleoenvironment and oil source rock correlation abstract the maikop formation deposited in eastern azerbaijan during oligocene and early miocene represents a prolific source unit for the oils found within the southern gobustan area and the kura depression based on biomarker characteristics the oils are believed to have originated from a clastic source rock deposited in an anoxic to suboxic transitional marine environment with low to moderate input of terrigenous organic matter however due to the thermal immaturity of accessible maikop rocks oil source rock correlation based on biomarker fingerprints is hampered the results from a sedimentary succession sampled in the shemakha gobustan area near the village of lahich revealed the presence of marginally mature rr 0 6 0 7 maikop rocks based on lithology geochemical data and paleontological analyses the sampled section contains upper eocene and lower oligocene sediments palynological analyses of dinoflagellate cysts indicate an early rupelian to early chattian oligocene age for the upper part of the investigated maikop succession however the stratigraphic position of the middle and lower part of the succession remains unclear maceral composition as well as biomarker and stable isotope c n data indicate a major contribution of aquatic organisms and variable inputs from macrophytes and land plants to organic matter deposition during the oligocene microbial communities most probably included heterotrophic bacteria and cyanobacteria as well as green sulfur bacteria higher inputs of terrigenous organic matter occurred during deposition of the lower part of the succession increased remineralisation of organic matter in the water column is suggested to result in low toc and hydrocarbon contents as well as 15n enriched total nitrogen of the eocene to earliest oligocene sediments organic carbon accumulation during the oligocene occurred in a stratified episodically euxinic environment this is indicated by low toc s ratios and higher contents of aryl isoprenoids in several samples from the upper units a moderate to good oil source rock correlation with oils from the kura depression is indicated by sterane and triterpane fingerprints as well as carbon isotopic composition of hydrocarbon fractions

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

a possible normal fault rupture for the 464 bc sparta earthquake surface ruptures have been identified for some normal faulting earthquakes in the aegean region1 3 but for most historical earthquakes the associated faults are unknown this hampers the evaluation of the rates and styles of present day deformation and the assessment of seismic hazard in the region4 here we examine the famous earthquake that destroyed sparta in 464 bc using spot satellite images and fieldwork we have mapped a 20 km long normal fault scarp trending approximately north south a few kilometres east of the ancient city our observations combined with an examination of historical descriptions of the earthquake damage suggest that the sparta earthquake ruptured this fault scarp in an event of magnitude ms 7 2 the holocene slip rate and the recurrence time for such large events on the sparta fault would be 1 mm yr 1 and 3 000 yr respectively

physical model of aftershock temporal behaviour abstract the aim of the model is to describe the temporal behaviour of cumulative seismic moment released in aftershock sequences it therefore constitutes an alternative approach with respect to the omori and utsu laws which model the number of events against time static fatigue is assumed to be the principal explanation of the aftershock temporal behaviour as a result aftershocks can originate at a stress intensity factor lower than the fracture toughness under the condition that the mainshock causes a redistribution of stress the initial stress condition of the aftershock sequence at mainshock origin time t0 can be considered as the superposition of the stress before the mainshock and of the stress step d caused by the dynamic rupture of the mainshock the model can be written in the form s t d rt ln t where s t is the cumulative stress drop at time t after the mainshock t the temperature r the universal gas constant and a constant dependent on material type the model is derived from the empirical static fatigue law t s exp u rt widely applied in fracture mechanics is the stress s a constant and the other parameters as above the fit of the model to five aftershock sequences obtained by linear regression analysis is quite good with the r2 greater than 0 85 for all the sequences but the imperial valley sequence where r2 0 7 the results seem to favour the hypothesis that the decay of the rate of seismic moment release depends on temperature in agreement with other evidences based on the evaluation of the decay rate of omori law but in contrast to some static fatigue results obtained in laboratory tests on granite rocks the scarcity of field data on underground temperature does not allow any definitive conclusion about this subject

artificial generation of pseudotachylyte using friction welding apparatus simulation of melting on a fault plane a 150 m thick fused layer of rock has been produced by rotating two metadolerite core faces against each other at 3000 r p m under an axial load of 330 kg for 11 s using friction welding apparatus scanning electron microscopy and electron microprobe analysis reveal that the melt layer comprises sub angular to rounded porphyroclasts of clinopyroxene feldspar and ilmenite 20 m diameter derived from the host metadolerite set within a silicate glass matrix thermal calculations confirm that melting occurred at the rock interface and that mean surface temperatures in excess of 1400 c were attained the fused layer shows many textural similarities with pseudotachylyte described from fault zones morphologically the fused layer consists of a series of stacks of porphyroclasts welded together by melt to form build ups oriented at right angles to the friction surface there is also evidence of gouging ploughing and plucking as well as transfer and adhesion of material having occurred between the rock faces the mean surface velocity attained by the metadolerite 0 24 m s 1 and duration of the experiment are comparable with velocities and rise times of typical single jerk earthquakes occurring during stick slip seismic faulting within brittle crust i e slip rates of 0 1 0 5 m s 1 for say 1 10s in these respects the experiment successfully simulated frictional fusion on a fault plane in the absence of an intergranular fluid power dissipation during the experiment was about mw m 2 comparable only to very low values for earthquakes e g 1 100 mw m 2 for displacement rates of 0 1 0 5 m s 1 at shear stresses of 100 1000 bars this indicates that melting on fault planes during earthquakes should be commonplace field evidence however does not support this contention either pseudotachylyte is not being recognized in exhumed ancient seismic fault zones or melting only occurs under very special circumstances

interrelation between fault zone structures and earthquake processes in order to develop capabilities for predicting earthquake processes on the basis of known fault zone structures and stress conditions we need to find relations between seismogenic structures and processes in the present paper we search for the scale dependence in various earthquake phenomena with the hope to find some structures in the earth that may control the earthquake processes among these phenomena we shall focus on 1 geologic structures which play some role in nucleation and stopping of earthquake fault rupture 2 depth ranges of the brittle seismogenic zone 3 asperities and barriers distributed over a fault plane 4 source controlled f max effect 5 nonfractal behavior of creep events and 6 temporal correlation between coda q 1 and seismicity of earthquakes with magnitude characteristic to a given area our review of various scale dependent phenomena leads us to propose a working hypothesis that the temporal change in coda q 1 may reflect the activity of creep fractures near the brittle ductile transition zone

higher plant biomarkers reflect palaeovegetation changes during jurassic times abstract the relative abundances of three higher plant derived biomarkers retene cadalene and ip ihmn have been measured in marine sedimentary rocks from the northwest margin of australia it is thought that each biomarker represents input from a different plant type the distributions of these three compounds form a fingerprint representing higher plant input hpf variations in hpf in oxfordian sediments were nearly identical in all three locations with retene becoming very abundant relative to the other two compounds with decreasing age of the sediment this finding strongly suggests that the composition of terrestrial input during deposition largely determines hpf and that the possible effects of diagenesis and catagenesis on the distribution of the three biomarkers are relatively unimportant the marked increase in the abundance of retene relative to that of cadalene during the oxfordian is interpreted to reflect an increase in the contribution of plants that produced precursors for retene i e conifers brought about by a significant change in climate this was exemplified by measuring the distributions of retene and cadalene expressed in the higher plant parameter hpp for a suite of sediments from the carnarvon basin western australia covering the complete jurassic period the hpp profile displays three major cycles each covering a period of at least 10 million years this profile not only compared well with published palaeoclimate data but also showed a remarkable similarity with second order cycles in the global sea level curve thus strongly supporting the proposal that variations in hpf and hpp are indications of changes in palaeoclimate the relation with global sea level further suggests that global factors e g the atmospheric carbon dioxide concentration may play a major role in determining the observed variations in the distributions of these higher plant derived biomarkers

growth processes and melange formation in the southern apennines accretionary wedge abstract the southern apennines owe their present geometry to the subduction of an apulian continental lithospheric slab and are thus best interpreted as an accretionary wedge southward the apenninic thrust front branches on to the still active ionian wedge which is related to the present calabro sicilian subduction the interpretation of conventional seismic reflection profiles and exploration wells combined with geologic field studies biostratigraphy and structural geology provide constraints for a geodynamic model for the post messinian growth of the apenninic prism our model for the apennines is a good analogy for submerged oceanic accretionary prisms in both instances features such as out of sequence thrusts underplating and duplexes are viewed as processes to explain the thickening of accretionary wedges syntectonic terrigenous deposits have accumulated in the synclines developed above the flats of pliocene thrust faults these depocenters represent piggy back basins younger accretion at the eastern border of the accretionary wedge has led to a progressive uplifting and tilting of the already emplaced thrust sheets including a continous westward migration of the depocenters in the piggy back basins during pliocene and early quaternary times a contrary west to east migration of the depocenters locally occurred where preexisting flats of pliocene thrust faults have been refolded rather than only being rotated dewatering processes and effects of overpressures on undercompacted sediment deformations can also be studied in the southern apennines melanges and broken formations form an important component of the trench apparently restricted to the base of tectonic nappes listric normal faults are a major structural element which preserves in combination with the erosion of topographic highs and resedimentation in the piggy back basins a uniform geometric shape critical taper for the prism the age and location of these distensive or gravitational effects are also discussed

the campania lucania southern italy earthquake of 23 november 1980 abstract we present the main seismological results of our study of the campania lucania earthquake of 23 november 1980 a complete set of far field and local data has been analysed from long period body waves data we determine the fault plane solution 1 140 1 60 2 75 2 54 a depth of 15 km and calculate a seismic moment of 6 1025 dyne cm and a source duration of 6 s from data of a local network deployed immediately after the event we determine aftershock locations they are aligned in a direction nw se that fit extremely well with the focal solution determined above we can choose as fault plane the plane striking 140 and dipping at 60 and the event is a normal event with a large component of left lateral strike slip the source area evaluated from this aftershock distribution 14 km 40 km is quite suitable for an earthquake of a seismic moment of 6 1025 dyne cm

characteristics of collisional orogens with low topographic build up an example from the carpathians sequence stratigraphy in the hinterland kinematic analysis of thin skinned thrusting in the foreland and thermochronological tracking of exhumation in the orogenic core are combined to quantify the mechanics of an orogen with low topographic build up the carpathian system demonstrates that collisional deformation can couple and thicken the lower orogenic plate along reverse faults that dip more steeply than the subduction zone defining a foreland coupling type of collision near the surface this is expressed by wide antiforms in the upper plate and the thin skinned orogenic wedge a sequence stratigraphic analysis of the back arc transylvanian basin demonstrates that the sedimentary architecture records orogenic uplift pulses with both short and long wavelengths these correspond to the activation of individual thrust sheets in the thin skinned wedge and to lower plate coupling events respectively

aftershocks of the campania lucania italy earthquake of 23 november 1980 abstract the result of a study of 1130 aftershocks of the 1980 campania lucania earthquake are presented the data were collected primarily with a dense array of portable smoked drum seismographs deployed in the epicentral region a few days after the main shock tests performed on subsets of the data to establish the location accuracy are described in detail and epicentral maps and cross sections are presented and discussed one hundred and sixty well constrained fault plane solutions using upward traveling rays are presented the distribution of aftershocks forms an elongate cloud which does not define a plane this is not because the events are poorly located a subset of events located with epicentral errors of less than 1 km and depth errors less than 2 km forms a similar cloud to the complete aftershock set the aftershock mechanisms are very varied some are similar to the main event but many differ profoundly these include events on shallow or vertical planes and thrust events the latter include some events which require contraction in the direction in which the main event indicates extension the aftershocks of all mechanisms are intermixed in space in such a way that no simple system of faults can explain them a model to explain the aftershocks and the lack of surface ruptures in the main event is offered it is proposed that the main shock cuts between two aseismic detachment surfaces and that the aftershocks are a consequence of the complicated deformation that such a geometry demands whatever interpretation is adopted the results are a challenge to the commonly accepted view that aftershocks even approximately define simple fault planes or that aftershock mechanisms replicate the mechanism of the main shock defects in interpretations of the main shock and aftershocks process arise largely from a lack of information about the geometry of structures at depth in the epicentral region suitable deep reflection profiles could help to resolve this problem

source modelling of the m5 6 emilia romagna italy earthquakes 2012 may 20 29 on 2012 may 20 and 29 two damaging earthquakes with magnitudes mw 6 1 and 5 9 respectively struck the emilia romagna region in the sedimentary po plain northern italy causing 26 fatalities significant damage to historical buildings and substantial impact to the economy of the region the earthquake sequence included four more aftershocks with mw 5 0 all at shallow depths about 7 9 km with similar wnw ese striking reverse mechanism the timeline of the sequence suggests significant static stress interaction between the largest events we perform here a detailed source inversion first adopting a point source approximation and considering pure double couple and full moment tensor source models we compare different extended source inversion approaches for the two largest events and find that the rupture occurred in both cases along a subhorizontal plane dipping towards ssw directivity is well detected for the may 20 main shock indicating that the rupture propagated unilaterally towards se based on the focal mechanism solution we further estimate the co seismic static stress change induced by the may 20 event by using the rate and state model and a poissonian earthquake occurrence we infer that the second largest event of may 29 was induced with a probability in the range 0 2 0 4 this suggests that the segment of fault was already prone to rupture finally we estimate peak ground accelerations for the two main events as occurred separately or simultaneously for the scenario involving hypothetical rupture areas of both main events we estimate mw 6 3 and an increase of ground acceleration by 50 per cent the approach we propose may help to quantify rapidly which regions are invested by a significant increase of the hazard bearing the potential for large aftershocks or even a second main shock

seismic and ground deformation monitoring in the seismogenetic region of the southern apennines italy abstract the 23 november 1980 magnitude m s 6 9 southern italy earthquake has been associated by crosson et al 1986 with a faulting system consisting predominantly of two high angle sub perpendicular normal faults forming the corner of down dropped crustal block this model was inferred from a detailed analysis of the space time distribution of aftershocks and their focal mechanisms some features of the acceleration field the focal mechanism of the main shock and the observed displacements along two leveling profiles quantitative modelling of ground displacements which amounted to up to 70 cm was performed through a forward analysis with a dislocation source consisting of several fault segments and by inverse methods with a priori information allowing the parameters of a multiple rectangular fault system to be retrieved quantitative modeling of vertical displacements observed in a nearby seismic region showed a similar mechanism with coseismic movements of up to 12 cm which are consistent with uniform dislocation on two rectangular faults coinciding with the focal mechanism location and magnitude of the earthquakes which occurred in august 1962 m s 5 7 6 1 and 5 4 a system for monitoring ground displacements and related seismic activities has been in place since 1982 in this region and has recently been improved on the basis of our knowledge of the seismic source mechanisms the aim is to study the stress regime during interseismic phases to gain a better understanding of the physics of earthquake processes and to discover any patterns in earthquake occurrences in the seismogenetic regions of the apennines

detailed study of the potentino seismic zone in the southern apennines italy abstract most relevant macroseismic and instrumental data concerning past and current seismic activity of the potentino southern italy have been collected in order to study the seismic behaviour of this area ten among the most important recent and historical earthquakes occurred in the area from 1826 to 1990 have been studied by means of macroseismic methodologies macroseismic fields for all the events indicate a general isoseismal lengthening in the direction of the apennines chain northwest southeast a rapid attenuation of intensity westward of the studied area and a strong propagation eastwards this configuration is strongly dependent on the source mechanisms of the seismic events and the geological dishomogeneities of the concerned areas as regards earthquakes which have been instrumentally recorded in the campania basilicata area from 1980 to 1991 more than 1300 accurate hypocentral locations have been computed for events with m d 2 5 using data from osservatorio vesuviano o v and istituto nazionale di geofisica i n g seismic networks special emphasis is put on the potenza may 5 1990 earthquake m s 5 4 neic national earthquake information center i vii msk which was the strongest recent event in the area and was felt in a large sector of southern italy as regards the seismic sequence following this event about 110 aftershocks with m d 1 9 have been located very close to the town of potenza northeast of it with a clustering type space distribution the occurrence of the events is strongly time concentrated in so defining a main shock aftershocks typical sequence moreover the macroseismic investigation of the main event has allowed to map out isoseismal lines bounding vii vi v and iv msk areas the isoseismals pattern shows that attenuation and amplification of intensity are observed in the same areas as for the previous events beginning from may 26 1991 an increase of seismicity initiated by an earthquake of m l 4 7 neic and i vi vii msk was observed nearly in the same area as the 1990 sequence accurate locations of 84 events with m d 1 9 have been computed however this sequence seems to have a slightly different character from the 1990 one in that events are scattered in time and seismic energy release is comparable to a swarm type seismic sequence as regards the previous sequences fault plane solutions for the highest magnitude events and for appropriate groups of events have been worked out the mechanisms indicate normal faulting motion with t axes oriented orthogonal to the apenninic chain in conclusion detailed analyses on the historical and recent seismicity of the potentino area and adjacent ones have allowed to identify at least four seismogenic zones which show activity with different features such zoning represents a contribution to the seismic hazard assessment in the southern apennines on a regional scale

a case of the influence of radiation pattern on peak accelerations abstract the strong ground shaking of the 23 november 1980 earthquake in southern italy seems to have been conditioned by the dimension of the source its focal mechanism and by the distance from the shallow portion of the source there was only a low and doubtful directivity effect these results come from a comparison of the azimuthal distribution of the recorded peak ground horizontal accelerations with that of the total dimensionless radiation pattern of s waves in the horizontal plane at each site radiation from the closest point of the fault and appropriate azimuth and take off angles were considered the recorded maxima were obtained from hodogram plots of each couple of automatically digitized horizontal components in 13 stations with negligible local site effects at a distance of up to 78 km from the epicenter the analysis indicates the strong influence of the strike slip component on the azimuthal distribution of motion the fault mechanism best fitting the recorded maxima is as follows strike 318 dip 64 rake 317 this picture does not change if acceleration maxima in the frequency bands 0 1 to 5 hz 1 to 5 hz or 1 to 2 hz are used in a segment of the southern apennines where the strong motion energy radiation in the near intermediate field of a repetitive series of shocks from the seventeenth century up to 1980 seems to be controlled by the gross features of the source it could be useful to include radiation patterns into algorithms for regional seismic hazard calculations conversely because of the fact that drawing isoseismal lines results in a smoothing of at least the very local site effects it might be possible to infer information about the gross features of the sources of historical earthquakes from macroseismic data

focal mechanism of an earthquake of baroque age in the regno delle due sicilie southern italy abstract a new kinematic function kf which incorporates fault dimension mean variation in velocity of rupture v r radiation pattern and mean depth from which the majority of the damaging energy is radiated is able to model the shape of isoseismals of the 1694 earthquake the focal mechanism of this earthquake is estimated to be a normal fault of apenninic direction dipping 60 70 towards the ne with a left lateral strike slip component due to the similarity with isoseismals of other earthquakes in the southern apennines it is argued that similar mechanisms could be responsible for other earthquakes in the region

regional state of stress fault kinematics and adjustments of blocks in a fractured body of rock application to the microseismicity of the rhine graben a simple mechanical model of a homogeneous state of stress and independent fault motions is generally used to interpret fault kinematics in terms of stress however analysis of focal mechanisms of microearthquakes shows that as a result of incompatibilities of block motions in an assemblage of rigid or elastic blocks deformation of a fractured body of rocks is in general heterogeneous analyses of focal mechanism sets show that they are in general composed of a main group whose fault motions result from a mean state of stress tm in good agreement with the regional state of stress the remaining complex fault motions are explained by a compressional tc and or a tensional deviator te an important observation is that within the computed uncertainties these tc and te deviators are co axial with the mean state of stress tm these deviators statistically model the local fault slips probably due to the incompatibilities of block motions and cannot be considered as other mean states of stress thus if the regional state of stress is known for a fault plane whose strike and dip are given its kinematics cannot be surely predicted two types tc and te of motions different from that tm predicted by the regional state of stress may exist they are the kinematic instabilities as a consequence all the motions shown by focal mechanisms or by striated faults are not significant of the regional tectonic regime this is well illustrated by the microseismicity of the rhine graben where it is shown that the compressional fault motions are kinematic instabilities and the extensional fault motions are representative of a regional state of stress 1 vertical with a n45 trending 3 axis hence the simple mechanical model of homogeneous state of stress and independant fault motions is valid only if there are no incompatibilities of block motions possibly these incompatibilities may be accommodated by a pressure solution crystallization process for creep faulting or by internal cataclastic deformation of large blocks separated by major stick slip faults

a comprehensive approach for evaluating network performance in surface and borehole seismic monitoring t a stabile 1 2 g iannaccone 3 a zollo 1 a lomax 4 m f ferulano 5 m l v vetri5 and l p barzaghi5 1dipartimento di scienze fisiche universita di napoli federico ii naples italy e mail tony stabile imaa cnr it 2istituto di metodologie per l analisi ambientale cnr imaa tito pz italy 3istituto nazionale di geofisica e vulcanologia osservatorio vesuviano naples italy 4alomax scientific mouans sartoux france 5eni s p a e p division san donato milanese mi italy

conifer and angiosperm biomarkers in clay sediments and fossil plants from the miocene clarkia formation idaho usa the aliphatic lipids and terpenoids of conifer and angiosperm macrofossils and the clay sediment from a new site p 37 of the miocene clarkia formation idaho usa were analyzed to evaluate the preservation of characteristic conifer and angiosperm biomarkers in the sediment series of aliphatic lipids terpenoids and steroids similar to the biomarkers found in type locality clarkia p 33 were the predominant compounds in the sediment and in the fossils long chain aliphatic lipids were major compounds in the fossil plants and the sediment but a differentiation of angiosperm and conifer sources is not possible due to their common distribution among all vascular plants in addition to previously reported terpenoids diterpenoids of a conifer origin and several angiosperm derived polar triterpenoids of the oleanane lupane ursane and friedelane classes are reported here for the first time from the clarkia sediments the conifer shoots taxodium glyptostrobus calocedrus contained characteristic conifer biomarkers such as abietane type diterpenoids while characteristic angiosperm triterpenoids were predominant in the angiosperm leaves betula quercus lithocarpus the biomarker compositions of the taxodium and glyptostrobus shoots match the terpenoid patterns previously reported from fossil seed cones of the same genera although conifer macrofossils contribute about 45 to the flora of site p 37 characteristic conifer biomarkers occurred in the sediment in only low amounts while the angiosperm derived triterpenoids were present in comparatively higher abundances the results indicate that the conifers are under represented compared to the angiosperms according to the terpenoid composition of the sediment extract this may be due to the presence of small angiosperm derived particles leaf detritus wax in the sediment and or migration of leaf waxes from the angiosperm leaves into the sediment in contrast the diterpenoids are trapped in the resinous woody tissue of the conifers and are thus disseminated less into the sediment

an example of stress tensor distribution deduced from the aftershocks of the november 23 1980 southern italy earthquake abstract the total inversion algorithm tarantola and valette 1982 is applied to a set of focal mechanisms corresponding to the aftershocks of the southern italy november 23 1980 earthquake m s 6 9 and the elements of several stress tensors are computed the obtained complex distribution of stress for this region is analyzed and two zones around the main event corresponding to areas of tension and compression distributed at different depths are delimited a stress tensor was sought for a third region corresponding to events which occurred along the strike of the main event and with magnitudes greater than 2 2 but with ambiguous results

the southern italy earthquake of 23 november 1980 an unusual pattern of faulting abstract a complex rupture history for the 23 november 1980 magnitude 6 9 italian earthquake resulted in an unusual pattern of two high angle subperpendicular normal faults forming the corner of a down dropped crustal block evidence for this interpretation is from aftershocks the pattern of strong ground motion focal mechanism of the mainshock and two critically placed leveling profiles quantitative modeling of leveling profiles using smoothly varying dislocation segments provides confirmation of the fault pattern and specific verification of the existence of a secondary fault which is suborthogonal to the primary fault rupture began on the nw trending main fault with downward motion of the northeast block about 40 sec after initial motion began rupture initiated on an orthogonal ne trending subsidiary fault propagating away from the main fault this fault pattern is consistent with tectonic extension in a northeasterly direction

intensity based source inversion of the destructive earthquake of 1694 in the southern apennines italy 1 we inverted the regional pattern of intensities of the catastrophic earthquake of 1694 in the southern apennines and determined the geometrical and kinematic characteristics of its source including the double couple orientation strike angle 299 10 dip 54 12 and rake 309 11 pure dip slip solution not precluded the objective nonlinear inversion was performed using the simple 11 parameter kinematic function model kf with a niching genetic algorithm technique the similarity between the pattern of the field intensities of the 1694 earthquake and the synthetic pattern is striking this result is supported by the fact that our inversion technique was verified in the study area where it was able to again find the source of the ms 6 9 irpinia 1980 earthquake known from instruments and from field surveys of the rupture this type of inversion enables researchers to exploit the extensive intensity data from italy and other countries to extend the knowledge of seismotectonic activity to preinstrumental times new paleoseismological evidence and even published descriptions of the fault rupture by witnesses of the 1694 earthquake were found confirming our results we also present and apply a new algorithm of general interest to calculate disorientations between double couples via standard linear algebra the 3 d rotations that bring the pairwise orthogonal unit vectors that were estimated by our intensity inversion into the instrumental triples of the 1980 irpinia earthquake assumed as benchmarks provide verification of our algorithm

analysis of activity intensity for landslides triggered by the wenchuan earthquake sichuan province china activity intensity for swarms of landslides is a key issue in geohazard predictions and assessment at a regional scale from reviewed literatures little work has been carried out on the description of activity intensity and its evaluation indicator system on may 12 2008 the great wenchuan earthquake triggered numerous landslides and debris flows to evaluate the activity intensity of coseismic landslides a variety of regional slides debris flows and rock falls was investigated concerning the geological characteristics damage to property and life loss after the interpretation using high resolution imagery to map landslide inventories they were statistically analyzed within the scope of geographical information systems noting areal density the maximum areal density was thus obtained for seismically triggered landslides combined analyses in these areas show that the maximum value of areal density can be described as the activity intensity of regional landslides the activity intensity can be categorized into eight levels from zero to seven in terms of areal density of landslides it was noted that the activity intensity for landslides in the area hit by wenchuan earthquake was classified into level 7 illustrating that this area was extremely damaged by these coseismic geohazards following this classification the center of the highest intensity was located on the banks of the minjiang river near the epicenter of the earthquake and in the vicinity of a seismic fault at hanwang town of mianzhu city meanwhile the banks of the jian river and the northeast river at nanba town in pingwu county were classified into level 6 it was significantly shown that the activity intensity obviously weakens from the boundary of a coseismic fault zone to its interior finally causes of triggering large numbers of landslides were interpreted and their regional distribution was analyzed for the earthquake event

a novel series of benzohopanes widespread in sediments abstract a novel series c 31 c 35 of benzohopanes cyclized at the c 16 position has been characterized by gas chromatography mass spectrometry and nmr structural elucidation of the usually predominant c 31 member the 4 methylbenzo 16 17 21 22 29 30 trinorhop 16 ene isolated from the messel shale germany these biological markers of bacterial origin seem to be widely distributed in sediments and to show low specificity with regard to the depositional environment although they are well represented in evaporites up to now they have been detected only in thermally immature samples which could reflect either a relative fragility or other possibilities of transformation as compared to the regular benzohopanes cyclised at c 20

three common source rock evaluation errors made by geologists during prospect or play appraisals geologists are frequently called on to evaluate the source rocks associated with their exploration prospects or plays the three most common questions asked and answered about the source rock during project reviews are what s the total organic carbon toc what kerogen type does rock eval indicate and what maturity level does the vitrinite reflectance data point to the answers to these seemingly innocuous questions may in fact be providing a false sense of security about the source rock in question understanding how this line of questioning can lead you astray and make you the victim of the toc myth if i have high toc i have a good source rock the rock eval fallacy the rock eval data tell me what kind of kerogen is in my source rock and the vitrinite reflectance deficiency vitrinite reflectance will tell me if my source rock is generating is important some of the solutions to these problems include fully integrating toc and rock eval data supplementing rock eval data with pyrolysis gas chromatography and using burial history diagrams to help interpret vitrinite reflectance harry dembicki jr is a senior geological advisor for geochemistry in the geological technology group at anadarko petroleum corporation where he provides technical support to both exploration and development teams he holds a b s degree 1973 in geology from the state university college of new york at new paltz and a ph d 1977 in geology with emphasis in organic geochemistry from indiana university he previously worked as an organic geochemist for conoco and marathon

radiogenic helium degassing and rock fracturing a case study of the southern apennines active tectonic region gas from mud volcanoes dry mofettes springs and wells were sampled in a region of active tectonics and high seismicity in the southern apennines italy where there is a long history of disastrous earthquakes with the latest ms 6 9 occurring in 1980 the fluids consist of a mixture of mantle derived and crust derived volatiles with a low atmosphere derived contribution as identified by the he isotope signature and he ne ratio measurements one year of monthly monitoring of the he concentrations and he isotopes revealed no seasonal modifications or variations induced by low seismicity there are extraordinary high outputs of 4he produced in the crust in the area up to 2 5 1028 atoms yr 1 these outputs cannot be solely due to the whole rock production rate and a long lasting diffusion degassing through the crust of the produced 4he this study explored the relation between the volume of fractured rock and the related release of he the results support that crustal degassing can be controlled by tectonic events resulting in earthquakes the high seismicity in this sector of the apennines provides the conditions necessary for a massive release of he that has accumulated in the rock over a long time period we identified that the assessed high crustal 4he output can be attributed to an intense fracturing of a calculable volume of rock which gives new constraints on the volume of rock involved in high magnitude earthquakes in the region

organic geochemical study and genetic correlation of natural gas oil and menilite source rocks in the area between san and stryi rivers polish and ukrainian carpathians abstract we studied the source rocks and petroleum accumulations in the carpathian mountains of the polish ukrainian border area between the san and stryi rivers a total of 108 oligocene menilite formation rock samples 12 oil and 15 gas samples accumulated in the oligocene reservoirs and one oil and gas sample from an upper cretaceous reservoir were analysed the aim of this study was to evaluate the petroleum potential of the menilite formation in this area and to evaluate potential genetic correlations between source rock and petroleum the menilite formation represents a prolific source rock with toc content ranging from 2 to 7 wt locally exceeding 20 wt algal type ii and mixed type ii iii kerogens dominate but sometimes type iii kerogen and rarely type i kerogen occur thermal maturity of the oligocene menilite formation increases from outer to inner tectonic units from the immature in the boryslav pokuttya and skole units to the overmature in the southern parts of silesian and dukla units as a consequence petroleum potential decreases in the same order geochemical analyses reveal that oil and gas generation and migration processes within the carpathian flysch succession are complicated all analysed oils were generated from the menilite formation during early and peak stages of the oil window associated gas is of low temperature thermogenic origin sometimes containing an admixture of microbial gas high temperature thermogenic gas occurs only in the polish part of the silesian unit

the rupture process of the 1980 irpinia italy earthquake from the inversion of strong motion waveforms abstract the distribution of slip and the behaviour of rupture propagation during the 23rd november 1980 irpinia earthquake ms 6 9 was investigated by analysing strong motion accelerograms the rupture was assumed to develop on a two dimensional purely normal fault whose geometry was constrained by geologic and geodetic data and by the aftershock space distribution theoretical seismograms have been computed using the isochron approach with a spatially variable slip intensity the asymptotic ray theory is used to evaluate the far field green functions the rupture model was updated following a trial and error approach the fit of observed waveforms with synthetic seismograms allowed several peculiarities in the rupture history to be pointed out the source model resulting from the solution of the forward waveform modelling was then used as starting model for the inversion of ground velocities therefore we performed a linearized inversion for slip velocity and rupture times on the fault by iteratively perturbing the assumed starting model the inverse problem is solved by means of a tomographic back projection technique the inferred source model shows a bilateral rupture which does not propagate uniformly away from the hypocentre the rupture velocity and the slip distribution on the fault plane are rather variable the solution confirms the shallow dislocation gap in the central part of the fault suggested by the behaviour of the surface rupture the results indicate that the rupture propagated northwestward along a further fault fragment for which no surface evidence is observed the aftershocks occurred mostly inside of or near to the edges of the source areas of maximum co seismic slip

depositional environment and hydrocarbon source potential of the oligocene ruslar formation kamchia depression western black sea abstract the oligocene ruslar formation is a hydrocarbon source rock in the kamchia depression located in the western black sea area depositional environment and source potential of the predominantly pelitic rocks were investigated using core and cuttings samples from four offshore wells in these wells the ruslar formation is up to 500 m thick based on lithology and well logs the ruslar formation is subdivided from base to top into units i vi dysoxic to anoxic conditions and mesohaline to euhaline salinities prevailed during deposition of the ruslar formation relatively high oxygen contents occurred during early solenovian times lower part of unit ii when brackish surface water favoured nannoplankton blooms and the deposition of bright marls solenovian event anoxic conditions with photic zone anoxia were established during late oligocene times units iii and iv and probably reflect a basin wide anoxic event in the eastern paratethys during kalmykian times organic carbon content in the ruslar formation is up to 3 autochthonous aquatic and allochthonous terrigenous biomass contribute to the organic matter relatively high amounts of aquatic organic matter occur in the lower part of the ruslar formation units i and ii and in its upper part unit vi diatoms are especially abundant in the lower part of unit vi the kerogen is of type iii and ii with hi values ranging from 50 to 400 mghc gtoc units i and ii pshekian lower solenovian are characterized by a fair to good potential to produce gas and oil but potential sources for gas and oil also occur in the upper oligocene units iv vi

effective petroleum source rocks of the world stratigraphic distribution and controlling depositional factors six stratigraphic intervals representing one third of phanerozoic time contain petroleum source rocks that have provided more than 90 of the world s discovered original reserves of oil and gas in barrels of oil equivalent the six intervals are 1 silurian generated 9 of the world s reserves 2 upper devonian tournaisian 8 of reserves 3 pennsylvanian lower permian 8 of reserves 4 upper jurassic 25 of reserves 5 middle cretaceous 29 of reserves and 6 oligocene miocene 12 5 of reserves this uneven distribution of source rocks in time displays no obvious cyclicity and the factors that controlled the formation of source rocks vary from interval to interval maps that show facies structural forms and petroleum source rocks were prepared for this study analysis of the maps indicates that several primary factors controlled the areal distribution of source rocks their geochemical type and their effectiveness i e the amounts of discovered original conventionally recoverable reserves of oil and gas generated by these rocks these factors are geologic age paleolatitude of the depositional areas structural forms in which the deposition of source rocks occurred and the evolution of biota the maturation time of these source rocks demonstrates that the majority of discovered oil and gas is very young almost 70 of the world s original reserves of oil and gas has been generated since the coniacian and nearly 50 of the world s petrole m has been generated and trapped since the oligocene the term petroleum as used in this study includes oil gas condensate and gas but does not include bitumen and other solid and semisolid oil derivatives

the irpinia italy 1980 earthquake detailed analysis of a complex normal faulting a detailed analysis of near source strong motion and leveling data together with the results of teleseismic waveform modeling by westaway and jackson 1987 and aftershock studies by deschamps and king 1984 allows a satisfactory kinematic description of the complex normal faulting associated with the magnitude ms 6 9 november 23 1980 irpinia earthquake southern italy the three main rupture episodes starting at about 0 20 and 40 s are here associated with better constrained source parameters than in previous studies we first evaluated the triggering time for the 11 closest accelerometers by using the well recorded 40 s strong motion phases this gave the absolute time and location of the dominant episodes of faulting the first rupture propagated mainly toward the northwest on a ne dipping normal fault at a mean velocity close to 3 km s for about 20 km and continued 15 km further on smaller subfaults it was associated with surface breakage in the southeastern part the second rupture started from the southeastern end of the first rupture about 18 s after it and propagated about 20 km toward the southeast on a low angle normal fault dipping 20 ne it was associated with secondary faulting on steeper planes reaching the surface the third and last episode at 39 s nucleated near the first hypocenter at shallower depth and the rupture possibly propagated on a 10 to 15 km long normal fault striking se antithetic to the first activated fault a clear correlation appears between the strength of the geological formations and the existence of surface breakage and shallow aftershock activity

sensitivity of biomarker properties to depositional environment and or source input in the lower toarcian of sw germany abstract a sequence of lower toarcian sediments which are highly contrasting in their depositional environment over a 5 m depth interval has been investigated in detail for the variability of geochemical properties which are used for source characterization and oil to source correlation lower liassic marls are representative of a well aerated shallow water environment in contrast to the immediately overlying bituminous shales which are deposited under extremely reducing conditions various properties have been found to vary considerably within these two units amongst the most important are carbon isotopic composition of the kerogen the pristane phytane ratios nickel as opposed to vanadyl porphyrins and the c27 dia regular steranes although maturation within the profile does not change some of the maturation dependent biomarker properties such as the monoaromatic steroid side chain cracking and the tm ts ratio exhibit large changes which can be assigned to diagenetic processes another maturation dependent property the 20s 20r epimerization of c29 steranes exhibits smaller changes which could also be due to early diagenetic processes the study suggests that reducing and oxidizing conditions i e eh and ph in the sediment exert an influence on several biomarker precursor product pathways in maturation studies initial variations due to depositional conditions have therefore to be taken into account

source complexity of the 1980 southern italian earthquake from the analysis of strong motion s wave polarization strong motion records from 23 november 1980 earthquake in irpinia basilicata southern italy recorded less than 59 km to the source show strong s wave phases coherent up to 10 hz at more distant stations the signal is only coherent up to 5 hz even when recordings contain signal up to 10 hz hodogram plots of the coherent signal in the 5 to 10 hz range show lissajous figures of sh and sv waves radiated by the nearest point with strong seismic radiation by the terminations of the rupture or by other relatively compact features the largest acceleration recorded at the sturno station is due to high frequency pulses radiated by a source south of the station and 25 km from the epicenter hodogram plots of low frequencies show polarizations due to the propagation of the large scale rupture along the fault lissajous figures help to discriminate p and s arrivals and reveal their direction of propagation on the basis of this kind of analysis it is confirmed that the 1980 irpinia basilicata earthquake ml 6 5 was composed of three main sub events at 0 sec 19 sec and 39 sec in relative time the first and second events broke the same structure striking nw there is also evidence of bilateral propagation the third event broke a second smaller structure also striking nw and placed very close to the alignment of the previous ones

modern tectonic stress field in the mediterranean region evidence for variation in stress directions at different scales summary a compilation of more than one thousand stress indicators which include in situ stress measurements focal mechanisms microtectonic and other geological data allowed us to reconstruct the modern stress field in the mediterranean region and the surrounding area average stress directions at different scales have been reconstructed by means of a linear interpolation method this method takes into account the distribution scale and quality of stress data the results of the interpolation at plate scale allow us to recognize slightly deformed regions such as the northwestern european platform where average maximum horizontal stress direction is oriented roughly nnw sse subparallel to absolute and relative plate velocity directions other regions such as the caucasus alps and pyrenees where recent tectonic deformation and seismicity are present display important variations of stress directions the reconstruction of the average stress directions at different scales within the french alps pointed out that the average stress field pattern may vary from one scale to another nevertheless variations of stress directions at a given scale are consistent with the kinematics of faults of the same scale

ray tracing for earthquake location in laterally heterogeneous media we propose a technique for the fast solution of ray tracing in three dimensional laterally heterogeneous media analytical solutions for both ray tracing and paraxial ray tracing for a medium with an arbitrary gradient of the square of slowness are used to develop a systematic procedure to construct exact solutions complex heterogeneous media are divided into tetrahedral finite elements inside which the square of the slowness has a simple linear distribution arbitrarily complex media may be studied by judicious choice of the elements we develop appropriate boundary conditions for interfaces with zeroth or first order velocity discontinuities two point ray tracing is performed by a newton method based on paraxial ray theory with a few iterations the ray trajectories through the source and the observer are calculated with the same overall speed as with ray bending the paraxial method has the additional advantage that it can be used to identify caustics and to separate travel time branches we used the previously described method to replace the ray tracing algorithm of the hypo71 program probably the most commonly used earthquake location program the ray tracing routine may be easily modified to adapt it to other earthquake location environments with the modified hypo71 program we relocated the aftershock sequence of the november 23 1980 irpinia italy earthquake the introduction of a low velocity zone proposed by different authors shifts aftershock locations to the ne this horizontal displacement of hypocenters is not very sensitive to the thickness of the low velocity zone

empirical relationships between aftershock area dimensions and magnitude for earthquakes in the mediterranean sea region fault dimension estimates derived from the aftershock area extent of 36 shallow depth v31 km earthquakes that occurred in the mediterranean sea region have been used in order to establish empirical relationships between length width area and surface wave moment magnitude this dataset consists of events whose aftershock sequence was recorded by a dense local or regional network and the reported location errors did not exceed on average 3 5 km surface wave magnitudes for these events were obtained from the neic database and or published reports while moment magnitudes as well as focal mechanisms were available from the harvard usgs catalogues contrary to the results of some previously published studies we found no evidence in our dataset that faulting type may have an effect on the fault dimension estimates and therefore we derived relationships for the whole of the dataset comparisons by means of statistical f tests of our relationships with other previously published regional and global relationships were performed in order to check possible similarities or differences most such comparisons showed relatively low significance levels b95 since the differences in source dimension estimates were large mainly for magnitudes lower than 6 5 becoming smaller with increasing magnitude some degree of similarity however could be observed between our fault length relationship and the one derived from aftershock area lengths of events in greece while a difference was found between our regional and global fault length relationships a calculation of the ratio defined as the fault length derived from our relationships to the length estimated from regional empirical relationships involving surface ruptures showed that it can take a maximum value of about 7 for small magnitudes while it approaches unity at ms 7 2 when calculating the same ratio using instead global empirical relationships we see the maximum value not exceeding 1 8 while unity is reached at mw 7 8 indicating the existence of a strong regional variation in the fault lengths of earthquakes occurring in the mediterranean sea region also a relationship between the logarithms of the rupture area and seismic moment is established and it is inferred that there is some variation of stress drop as a function of seismic moment in particular it is observed that for magnitudes

local lithospheric stress distribution deduced by means of the total inversion algorithm and an objective classification method classification of populations of focal mechanisms are commonly used as a step in retrieving states of stress in the lithosphere although such classifications are usually made according to subjective criteria an objective one based on a classification algorithm is presented the procedure is based on two steps first each mechanism is characterized by the components of its principal tensional and compressional axes and then objectively classified accordingly second each mechanism is characterized by its geographic coordinates latitude and longitude after which each group obtained in the first step is divided into new groups according to geographic coordinates the classification algorithm together with a standard inversion algorithm is applied to data from aftershocks belonging to the irpinia southern italy earthquake of november 23 1980 a few incompatible groups of focal mechanisms obtained by the classification algorithm show a spatial overlap nevertheless the new methodology allows us to present a more accurate description of a local state of stress for an aftershock area than the stress pattern obtained from subjective classifications the new stress pattern is compared with principal stress axes deduced from the main event and two local states of stress deduced previously from the aftershock mechanisms

the werra cyclotheme upper permian fore sudetic monocline poland insights into fluctuations of the sedimentary environment from organic geochemical studies abstract a study of the extracts of samples recording a transgressive regressive succession of the werra cyclothem zechstein upper permian from the southern margin of the european permian basin the fore sudetic monocline poland provides an insight into major sources of organic matter and diagenetic processes the studied cross section comprises all lithologies representative for the european basin including transgressive sandstones weissliegend and organic rich shales kupferschiefer followed by carbonates as well as regressive anhydrites with intercalations of rock salt due to the variable influence of overlapping diagenetic processes that affected the organic matter i e maturation and late diagenetic oxidation related to base metal mineralisation a reliable comparison of the biomarker results is only possible for the major upper part of the section ca 38 m including carbonates and evaporites but not for the oxidised first 2 3 m from the base of the kupferschiefer the transition from carbonate to evaporate sedimentation is associated with a shift to predominant even c numbered n alkanes increased abundance of carotanes and high homohopane index reflecting enhanced reducing conditions the presence of the c25 regular isoprenoid squalane biphytane and the rapid decrease in the pristane phytane ratio in the evaporites are mainly controlled by the important contribution from both halophilic and methanogenic archaea the occurrence of gammacerane in the anhydrites suggests development of water column stratification at some stages of the sea regression this is associated with appearance of specific aryl isoprenoids with a lycopane carbon skeleton most likely related to botrycoccus braunii race l algae lycopane derivative occurrence suggests that such an algal race could have occurred since permian currently known recent eocene the presence of the abundant freshwater brackish algal biomarkers in evaporititic deposits can be envisaged in the costal part of the zechstein basin with temporary salt wedge estuary water stratification the algae bloomed in the top fertile fresh brackish water layer fed by rivers and the algal biomass was deposited on the sea floor covered with evaporitic brine the stratification periodically broke down during precipitation of the rock salt presumably due to a decrease in riverine water input as revealed by characteristic disappearance of gammacerane and hopane distributions similar to those observed for the carbonate rocks the methylphenanthrenes phenanthrene ratio was used together with methyldibenzothiophenes dibenzothiophene ratio to assess maturity these maturity estimations indicate that the peak of oil window has been reached which is confirmed by other biomarker maturity parameters based on sterane and hopane distributions the maturity stage of oil generation and expulsion was further confirmed by the presence of solid bitumen as cements in the sandstone underlying kupferschiefer and bitumen veins and lenses in the carbonates

dynamical influences of anvil shading on simulated supercell thunderstorms abstractnumerical simulations of supercell thunderstorms including parameterized radiative transfer and surface fluxes are performed using the advanced regional prediction system arps model to investigate how low level air temperature deficits within anvil shadows affect the simulated storms the maximum temperature deficits within the modeled cloud shadows are 1 5 2 0 k which is only about half that previously observed within the shadows the loss of strong solar heating cools and stabilizes the near surface layer which suppresses vertical mixing and modifies the near surface vertical wind shear in a case of a stationary storm the enhanced easterly shear present beneath the anvil leads to a thinning of the outflow layer and corresponding acceleration of the rear flank gust front far ahead of the overlying updraft weakening the low level mesocyclone it is further shown that the direct absorption and emission of radiation by clouds does not significantly affect the simulated supercells varying th

interpreting rock eval pyrolysis data using graphs of pyrolizable hydrocarbons vs total organic carbon kerogen the major organic component of sedimentary rocks is commonly analyzed by rock eval pyrolysis plotting the data on a graph of s 2 vs total organic carbon toc and determining the regression equation is the best method for determining the true average hydrogen index and measuring the adsorption of hydrocarbon by the rock matrix such a plot also indicates the type of kerogen present and avoids the problem of increasing hydrogen index with total organic carbon content with the s 2 vs toc diagram the organic component of different suites of samples may be compared and their petroleum generation potentials established as an example the diagrams are used to evaluate the sedimentary environments and petroleum potential of the paleogene evaporitic sediments of the mulhouse basin alsace france

water column structure during deposition of middle devonian lower mississippian black and green gray shales of the illinois and michigan basins a biomarker approach abstract the extractable organic matter of organic rich black shales and associated organic poor bioturbated green gray shales of the illinois and michigan basins of north america is analyzed to constrain the water column structure during their deposition all black shale samples contain derivatives of the biomarker isorenieratene a diaromatic carotenoid pigment produced exclusively by the brown strain of the green sulfur bacteria chlorobiaceae chlorobiaceae are phototrophic organisms requiring euxinic anoxic and sulfidic conditions to survive and the presence of isorenieratene derivatives indicates that the middle devonian early mississippian epeiric seas of north america experienced bottom water euxinic conditions during black shale deposition analysis of green gray shales also reveals the presence of isorenieratene derivatives and in some cases isorenieratane the highly bioturbated fabric of these sediments indicates the presence of oxygen in bottom waters during their deposition thus we suggest that short term shoaling of the oxycline across the basin slope may have occurred during their deposition though they were deposited predominantly under an oxygenated water column i e above the chemocline most green gray shales contain three pseudohomologous series of branched alkanes with quaternary substituted carbon atoms baqcs which are absent in black shale samples recent studies suggest that baqcs are produced by benthic chemoautotrophs dwelling at the redox boundary separating anoxic sediments from moderately oxygenated waters comparison of the biomarker content i e regular isoprenoid baqcs between black and green gray shales indicates different sources of organic matter and suggests that phytoplanktonic productivity in the upper water column was enhanced during black shale deposition the results of this study indicate that the alternation of green gray and black shales in these basins results from the vertical fluctuations of the chemocline these fluctuations seem to be driven by changes in phytoplanktonic productivity our data when associated to previous studies of other black shales from canada and europe confirm that photic zone euxinia was a widespread feature of low latitude epeiric seas during the middle devonian lower mississippian

new data on the vrancea nappe moldavidian basin outer carpathian domain romania paleogeographic and geodynamic reconstructions a study has been performed on the cretaceous to early miocene succession of the vrancea nappe outer carpathians romania based on field reconstruction of the stratigraphic record mineralogical petrographic and geochemical analyses extra basinal clastic supply and intra basinal autochthonous deposits have been differentiated appearing laterally inter fingered and or interbedded the main clastic petrofacies consist of calcarenites sub litharenites quartzarenites sub arkoses and polygenic conglomerates derived from extra basinal margins an alternate internal and external provenance of the different supplies is the result of the paleogeographic re organization of the basin margins system due to tectonic activation and exhumation of rising areas the intra basinal deposits consist of black shales and siliceous sediments silexites and cherty beds evidencing major environmental changes in the moldavidian basin organic matter rich black shales were deposited during anoxic episodes related to sediment starvation and high nutrient influx due to paleogeographic isolation of the basin caused by plate drifting the black shales display relatively high contents in sub mature to mature type ii lipidic organic matter good oil and gas prone source rocks constituting a potentially active petroleum system the intra basinal siliceous sediments are related to oxic pelagic or hemipelagic environments under tectonic quiescence conditions although its increase in the oligocene part of the succession can be correlated with volcanic supplies the integration of all the data in the progressive reorientation of convergence direction carpathian model and their consideration in the framework of a foreland basin led to propose some constrains on the paleogeographic geodynamic evolutionary model of the moldavidian basin from the late cretaceous to the burdigalian

biomarker geochemistry of a foreland basin the oligocene menilite formation in the flysch carpathians of southeast poland black shales of the menilite formation the source rock for oils in the carpathian overthrust belt display a large variability in their bulk and molecular geochemical parameters biomarker and stable carbon isotope analyses indicate a variable contribution from different algae particularly dinoflagellates and diatoms and cyanobacteria this is reflected by specific predominantly sulfurised biomarkers e g c35 homohopanoids c25 highly branched isoprenoids and marine n alkanes and by particular distributions of steranes and 4 methylsteranes comprising 24 nor and 24 methyl 27 norcholestanes and related novel steranes with a methylation at c 23 the presence of hopanoids of methanotrophic origin 13c up to 57 implies a temporarily enhanced full methane cycle in a marine environment which affected the isotopic composition of organisms dwelling in the upper photic zone the presence of isorenieratene derivatives indicate periods of euxinic conditions within the photic zone in all investigated sub basins

organic matter maturity and hydrocarbon potential of the lower oligocene menilite facies in the eastern flysch carpathians tarcău and vrancea nappes romania abstract bulk organic geochemical and molecular composition data have been used to analyse the hydrocarbon potential and organic matter maturity of the lower oligocene menilite facies from two adjacent tectonic units of the eastern flysch carpathians tarc u and vrancea nappes romania due to the importance of these source rocks in hydrocarbon exploration in entire paratethys realm the data show strong variability in organic matter quantity and quality organic carbon content reaches peak values in the siliceous facies of the lower menilite member up to 8 6 wt toc which contains type ii kerogen with increasing contribution of flysch sedimentation mixed type ii iii kerogen gains importance the biomarker distribution reveals strong variation in the supplied organic matter common for flysch influenced sedimentary environments terrigenous input is marked by epicuticular wax imprint in n alkane distribution and occurrence of conifer biomarkers while marine organic matter origin is expressed by the occurrence of short chain n alkanes and hopanes especially in the siliceous facies thus these source rocks can be classified as oil prone and subordinately mixed oil gas prone the maturity in the outer tectonic unit vrancea is low t max 425 c r o 0 4 but increases towards the inner tarc u nappe t max 430 c r o 0 5 reaching onset of hydrocarbon generation the studied rocks have good petroleum potential but hydrocarbons were generated only in more mature tarc u nappe where solid bitumen veins were observed bitumen impregnation of numerous vitrinite grains possibly suppressed vitrinite reflectance thus leading to more accurate maturity assessment based on molecular proxies biomarker maturity indices the observed difference in maturity levels between the nappes results from the more inner position of the sampled tarc u nappe succession within the orogen relative to the vrancea unit this is related to different burial histories as well as variation in subsequent erosion and exhumation levels the actual hydrocarbon potential in the studied area varies due to local interplay of these critical factors

surface faulting in the southern italian campania basilicata earthquake of 23 november 1980 the campania basilicata earthquake of 23 november 1980 was the largest ms 6 9 and most destructive earthquake that has occurred in this region of southern italy for over 100 years killing more than 3 000 people the consensus among seismologists geologists and earthquake engineers who have studied1 10 this event is in keeping with previous italian earthquakes that it did not produce faulting at the surface this has led to the establishment of a number of models2 3 11 13 requiring an unusual tectonic setting for the southern apennines however on a recent visit to the epicentral region of the earthquake may 1984 we discovered more than 10 km of surface faulting that is consistent with focal mechanisms for this event based on first motion polarities2 4 5 12 and long period waveform studies14 16 which show that it involved normal faulting with one nodal plane dipping at 60 towards the north east our observations of this the first well documented earthquake fault break to be reported in italy suggest that the deformation associated with earthquakes in the southern apennines takes place in the upper 10 15 km of the earth s crust on steep planar normal faults which break the surface as is widely observed in other areas of active extension outside italy

novel families of tetra and hexacyclic aromatic hopanoids predominant in carbonate rocks and crude oils two novel families of monoaromatic geomarkers related to hopanoids have been separated and characterized in sediments and crude oils the benzohopanes c32 c35 1 and the ring d aromatized 8 14 secohopanoids c27 c35 4 and 5 both series are particularly abundant in many carbonate samples where they amount to approximately 100 p p m per component in some crude oils but can also be detected in other environments the benzohopanes have been separated as pure compounds by high performance liquid chromatography and identified by x ray diffraction the structure of the 8 14 secohopanoids mostly relies on spectroscopic data nmr and ms and comparison with synthetic analogs both families must be formed in the subsurface from bacterial c35 hopanoid precursors but the benzohopanes seem to occur at an earlier stage of sedimentation the two series appear in varying distributions in the different samples and may therefore be potentially useful as geochemical correlation parameters

effects of source thermal maturity and biodegradation on the distribution and isomerization of homohopanes in petroleum abstract the distributions of c31 c35 17 21 h homohopanes in marine petroleums can be used to describe redox conditions in the source rock depositional environment for example high c35 homohopane indices c35 c31 c35 are typical of petroleums generated from source rocks deposited under anoxic marine conditions where the c35 backbone of the precursor bacteriohopanetetrol is preferentially preserved homohopane distributions have been used to distinguish petroleums from different organic facies of the same source rock homohopane distributions are altered by secondary processes for example the c35 homohopane index decreases with increasing api gravity and thermal maturity of related oils from the monterey formation offshore california similar decreases in the homohopane index are observed for expelled oils from monterey source rock during hydrous pyrolysis biodegradation can result in selective loss of high or low molecular weight homologs apparently depending on the bacterial population in the reservoir bacterial demethylation of homohopanes appears necessary to explain 25 norhopanes in at least one biodegraded oil hydrous pyrolysis studies of the phosphatic and siliceous members in the monterey formation show that identical heating conditions result in different homohopane c 22 epimer ratios furthermore a reversal in the trend of the epimer ratio at high experimental temperatures is observed for the phosphatic but not for the siliceous lithology this could be caused by the combined effects of isomerization and differential thermal destruction of epimers at high temperatures possibly mediated by rock mineralogy

organic geochemistry and petrology of oil source rocks carpathian overthrust region southeastern poland implications for petroleum generation abstract the organic matter rich oligocene menilite black shales and mudstones are widely distributed in the carpathian overthrust region of southeastern poland and have excellent hydrocarbon generation potential according to toc rock eval and petrographic data extractable organic matter was characterized by an equable distribution of steranes by carbon number by varying amounts of 28 30 dinor hopane 18 h oleanane and by a distinctive group of c24 ring a degraded triterpanes the menilite samples ranged in maturity from pre generative to mid oil window levels with the most mature in the southeastern portion of the study area carpathian petroleum samples from campanian oligocene sandstone reservoirs were similar in biomarker composition to the menilite rock extracts similarities in aliphatic and aromatic hydrocarbon distributions between petroleum asphaltene and source rock pyrolyzates provided further evidence genetically linking menilite kerogens with carpathian oils

facies evolution and stratigraphic correlation in the early oligocene tard clay of hungary as revealed by maceral biomarker and stable isotope composition abstract hydrocarbon source rocks i e tard clay formation containing type ii organic matter were deposited in the hungarian paleogene basin during lower oligocene a major contribution of aquatic organisms green algae dinoflagellates chrysophyte algae and minor inputs from macrophytes and land plants to organic matter accumulation is indicated by n alkane distribution patterns composition of steroids and 13c of hydrocarbon biomarkers microbial communities included heterotrophic bacteria cyanobacteria chemoautotrophic bacteria as well as green sulphur bacteria the presence of methanotrophic bacteria is indicated by 13c depleted hop 17 21 ene higher inputs of terrestrial organic matter occurred during deposition of the lower and uppermost units of the tard clay formation the terpenoid hydrocarbon composition argues for angiosperm dominated vegetation in the area of the hungarian paleogene basin diterpenoid hydrocarbons derived from the resins of conifers are about 2 3 enriched in 13c compared to the angiosperm biomarkers environmental conditions changed from marine to brackish accompanied by oxygen depletion in the lower parts of the water column organic carbon accumulation during this period was a consequence of stagnant bottom water conditions in the hungarian paleogene basin due to salinity stratification this is indicated by low pristane phytane ratios varying from 0 27 to 1 44 enhanced ratios of dimethylated versus trimethylated mttcs 0 14 0 59 and the presence of aryl isoprenoids from 0 4 to 14 1 g g toc a major marine incursion is evidenced by stable isotope ratios of organic matter and carbonates in the uppermost member of the tard clay a transition from brackish towards normal marine conditions is proposed up to 3 anoxic cycles are recognized in the drill core sections separated by minima in pristane phytane ratios and maxima in the depth trends of di tri methylated mttcs and aryl isoprenoid concentrations in combination with the position of maxima of 13c of carbonate and organic matter and an abrupt decrease in perylene concentrations the cycles can be used for intra formational correlation of the tard clay