examination of the repeatability of two ms6 4 menyuan earthquakes in qilian haiyuan fault zone ne tibetan plateau based on source parameters abstract repeating earthquakes are key evidence for understanding earthquake recurrence and help improve long term seismic risk assessment in 1986 and 2016 two ms6 4 earthquakes occurred in menyuan region near the middle segment of qilian haiyuan fault zone ne tibetan plateau long period waveforms of the two events at teleseismic stations show high degree of similarity however previous solutions on earthquake location and focal mechanism show remarkable discrepancies especially for the 1986 event as well the ruptured faults also remain ambiguous in this study we determined the source parameters of these two earthquakes including the relative location focal depth focal mechanism source duration and rupture directivity the results show that two earthquakes are thrust events in shallow crust and are located within 15 km and the 2016 earthquake ruptured down dip for 6 km along the southwest dipping plane combing the source parameters geological data and deep seismic reflection profiles we infer that these two earthquakes occurred on the same secondary fault of lenglong ling fault the middle segment of qilian haiyuan fault but they ruptured on different sections of the fault although the two events are probably not repeating earthquakes of qilian haiyuan fault zone the seismic risk of m6 thrust earthquake on these secondary faults and even larger strike slip earthquake on lenglong ling fault are not negligible based on the source parameters and ten year gps observations

porosity and permeability in volcanic rocks a case study on the serie tobifera south patagonia argentina the middle to late jurassic serie tobifera belongs to the chon aike province and extends all over patagonia and the antarctic peninsula it consists largely of ignimbrites epiclastics and rhyolitic lavas and was considered only a minor reservoir rock for oil with fracture permeability petrographic and petrophysical data in selected core samples from the austral basin were collected to determine the processes controlling the porosity and permeability of these volcanic rocks the sequence of processes occurring during cooling and in the post cooling stages can modify sometimes substantially their original petrophysic characteristics the results show that the highest porosity and permeability occur in rocks with quench fractured glasses and in non welded ignimbrites with gas pipe structures followed by autobrecciated rhyolites welded ignimbrites massive glasses and fresh rhyolites have the lowest permeabilities the new data indicate that tectonic fracturing is not as significant as was considered before and application of these concepts are relevant in the assesment of volcanic reservoir quality

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

petrography and reservoir physics ii relating thin section porosity to capillary pressure the association between pore types and throat size porosity in reservoir rocks is configured into a few types of pores whose size and shape are controlled by depositional fabric and postdepositional processes the size shape and abundance of each pore type can be objectively determined from thin section using image analysis and pattern recognition procedures each pore type tends to be associated with a limited range of throat sizes the association between pore type and throat size can be determined using regression procedures linking pore type data obtained from thin section with capillary pressure data to do so a set of samples is required wherein the association between pore type and throat size is fixed but where pore type proportions vary between samples this condition is met by a sample suite representing res rvoir facies from a single core or in many cases from a single field the relationship between pore type and throat size is an effective means to relate reservoirs in terms of the efficiency of the porous microstructure to multiphase flow parameters derived from the relationship can be used to construct accurate physical models that subdivide physical response in terms of the contributions of each pore type

correction to source processes of the 1978 and 2005 miyagi oki japan earthquakes repeated rupture of asperities over successive large earthquakes 1 highly similar seismograms commonly observed along transform or convergent plate boundaries indicate that repeated small to moderate earthquakes occur within a single area the results of source process inversions for seismic events within the northeastern japan subduction zone suggest that large earthquakes and their component asperities also exhibit this repeating nature under certain conditions however sets of similar seismograms that might provide direct evidence of the repeated rupture of large earthquake asperities have not been observed this paper analyzes two offshore earthquakes near miyagi prefecture japan the most recent occurring in 2005 with a jma magnitude m of 7 2 in the source region of the 1978 earthquake m7 4 we demonstrate the similarity in waveforms from the seismograms recorded during the 1978 and 2005 earthquakes the early portions of the 2005 seismograms resemble the 1978 seismograms suggesting that the asperities located close to the 1978 hypocenter ruptured again during the 2005 event the seismogram similarities provide the first direct evidence for the repeated rupture of asperities during successive large earthquakes the results of our waveform inversions further indicate that the two asperities of the 2005 event largely coincide with the southern two asperities of the 1978 event these repeating asperities are recorded in the early portions of the 2005 seismograms with 60 of the amplitude recorded in the 1978 seismograms the characteristic behavior of the asperities supports the slip predictable recurrence model of earthquake rupture rather than the time predictable recurrence model

volcanic rocks as prolific gas reservoir a case study from the qingshen gas field in the songliao basin ne china abstract the qingshen gas field with over 100 billion cubic meters bcms of proven gas reserves was discovered recently in the upper jurassic lower cretaceous strata of the songliao basin northeastern china the stratigraphic relationships and gas chemical compositions indicate mixed gas sources dominantly from the upper jurassic lower cretaceous coals and associated dark mudstones underlying the gas reservoirs with minor contribution from deep inorganic sources the gas reservoirs consist mainly of volcanic rocks rhyolite and tuff with some production also from the conglomerate gas charge into these largely volcanic rock reservoirs appears to coincide with the peak gas generation in the deep upper jurassic lower cretaceous coal measures the presence of several thick lacustrine mudstone beds in the upper cretaceous strata as regional caprocks and relatively mild structural deformation since the late cretaceous are among the favorable conditions for the preservation of large volume of natural gases in these relatively deep gas reservoirs the gas yields are the highest in the paleomorphological highs where fractures and secondary porosity are well developed in the gas reservoirs

inversion of source parameters for moderate earthquakes using short period teleseismic p waves in this paper we introduce a new method for estimating the source parameters of moderate earthquakes mw 5 0 by modeling short period teleseismic waveforms this method uses a grid search algorithm to minimize misfits between observed data and synthetic seismograms in depth magnitude and mechanism domain in a relative high frequency range of 0 8 2 0 hz similar to the traditional cut and paste method used in regional modeling zhu and helmberger bull sesimol soc am 86 1634 1641 1996 in this frequency range a significant challenge is determining the initial p wave polarity because of a low signal to noise ratio snr therefore we first determine source properties for a master earthquake with a relative strong snr both the travel time and amplitude corrections are developed relative to the reference 1d model along each path used in inverting the master event we then applied these corrections to other earthquakes clustered in the same area to constrain the initial p polarities thus the focal mechanisms can be determined reasonably well we inverted focal mechanisms for a small set of events beneath qeshm island in southern iran and demonstrate the importance of radiation pattern at short periods

preparing to predict the second autonomous ocean sampling network aosn ii experiment in the monterey bay abstract the autonomous ocean sampling network phase two aosn ii experiment was conducted in and offshore from the monterey bay on the central california coast during july 23 september 6 2003 the objective of the experiment was to learn how to apply new tools technologies and analysis techniques to adaptively sample the coastal ocean in a manner demonstrably superior to traditional methodologies and to use the information gathered to improve predictive skill for quantities of interest to end users the scientific goal was to study the upwelling relaxation cycle near an open coastal bay in an eastern boundary current region particularly as it developed and spread from a coastal headland the suite of observational tools used included a low flying aircraft a fleet of underwater gliders including several under adaptive autonomous control and propeller driven auvs in addition to moorings ships and other more traditional hardware the data were delivered in real time and assimilated into the harvard ocean prediction system hops the navy coastal ocean model ncom and the jet propulsion laboratory implementation of the regional ocean modeling system jpl roms two upwelling events and one relaxation event were sampled during the experiment the upwelling in both cases began when a pool of cold water less than 13 c appeared near cape ano nuevo and subsequently spread offshore and southward across the bay as the equatorward wind stress continued the primary difference between the events was that the first event spread offshore and southward while the second event spread only southward and not offshore the difference is attributed to the position and strength of meanders and eddies of the california current system offshore which blocked or steered the cold upwelled water the space and time scales of the mesoscale variability were much shorter than have been previously observed in deep water eddies offshore additional process studies are needed to elucidate the dynamics of the flow

persistently low asian paleolatitudes implications for the india asia collision history 1 paleomagnetism provides independent paleolatitude constraints on the india asia convergence however implied cenozoic latitudinal convergence within asia thousands of km largely exceeds geologic estimates of tectonic shortening hundreds of km this discrepancy may result from a notoriously low bias in paleomagnetically determined cenozoic paleolatitudes in asia we provide here new paleomagnetic data from cenozoic mongolian volcanic rocks and from chinese paleogene sediments corrected from the depositional bias of inclination shallowing these results combined with similar asian data sets confirm that paleolatitudes are still 5 10 lower than predicted by the paleomagnetic apparent polar wander path apwp for asia between 50 and 20 ma inclination shallowing being excluded from the selected data sets we investigate the likeliness of other proposed mechanisms for this discrepancy 1 more southerly positions of asia than expected by the apwp due to apwp inaccuracies rather than eurasian non rigidity or 2 non dipolar geomagnetic field contributions fully explaining this discrepancy by only one of these mechanisms would imply either unrealistically large 10 apwp inaccuracies or unrealistically large octupolar field contributions up to 16 a combination of these mechanisms is found more likely to have produced the observed latitudinal discrepancy but their respective contributions cannot be quantified given the still relatively low amount and poor quality of cenozoic paleomagnetic data from stable cratons of asia india and europe by allowing for reasonable time dependant non dipolar contributions and a slight 5 apwp bias the latitudinal discrepancy can be resolved and the excessive amounts of intra asian shortening decrease to values in line with tectonic shortening from structural studies

rapid rupture directivity determination of moderate dip slip earthquakes with teleseismic body waves assuming reduced finite source approximation for an earthquake with along dip rupture there is opposite directivity effects on down going direct p wave and up going depth phases pp and sp and this can be exploited for resolving fault plane and rupture direction we propose a method to calculate the reduced finite source synthetics for teleseismic p wave and determine the rupture directivity via waveform fitting we verified the effectiveness of this method with forward tests and investigated its robustness against station selection uncertainties in point source parameters and uncertainties in source finiteness parameters we applied this method to the 2011 mw5 8 virginia earthquake the 2008 mw6 0 nevada earthquake and six other dip slip earthquakes for most cases we obtained rupture directivity results consistent with previous studies but the method could fail for along strike ruptures and very shallow earthquakes our method may help mitigate earthquake hazard by improving shake map with rapid rupture directivity analysis

fast late pleistocene slip rate on the leng long ling segment of the haiyuan fault qinghai china 1 fieldwork along the western haiyuan fault where it cuts young glacial landforms in the leng long ling range qinghai northeastern tibet yields new constraints on its long term left slip rate our mapping near 101 85 e based on aerial photographs 1 50 000 topographic maps and spot images shows glacial valley edges and lateral moraines offset 200 m by the fault quartz rich cobbles were sampled on top of one moraine for in situ 10be and 26al cosmogenic nuclide dating among 12 dated samples the 6 oldest show ages clustering at 10 300 339 years this age probably reflects the time of last reshaping of the moraine before the valley glacier withdrew south of the fault around the end of the younger dryas 11 000 years b p assuming that the 200 40 m moraine offset started to be recorded after glacial retreat across the fault constrains the late pleistocene slip rate on the leng long ling segment of the haiyuan fault to be 19 5 mm yr

genesis of zeolites in the neapolitan yellow tuff geological volcanological and mineralogical evidence the study proposes a model by which a thick succession of volcanic tuffs can be zeolitized by alteration of pyroclastic material in the presence of sufficient eruptive water and at temperatures close to water vapour condensation in the case of phreatomagmatic products the model simplifies interpretation of problematic deposits that exhibit pronounced vertical and lateral variation in lithification grade a major feature of the model is that thick zeolitized tuffs can be formed during emplacement of pyroclastic products in marked contrast to later alteration in an open hydrologic system geological volcanological and mineralogical data for the neapolitan yellow tuff a widespread trachytic pyroclastic deposit outcropping around campi flegrei southern italy have been used to infer the physico chemical conditions that determined mineral genesis this tuff shows a reduction in lithification grade towards the base top and with distance from the vent and very variable zeolitization within the lithified portion we suggest that during initial emplacement the erupted products chilled against the ground inhibiting zeolite crystallization during rapid deposition of the thick wet succession thermal insulation allowed the persistence of elevated temperatures for a time sufficient for enhancement of hydration dissolution processes in the volcanic glass the highly reactive alkali trachytic glass quickly buffered the acid ph of the system favouring phillipsite crystallization followed by chabazite nucleation the variable zeolite content reflects fluctuating emplacement conditions e g changes in water content and temperature cooling of the upper and relatively thin distal deposits inhibited the zeolitization process thereby preserving the primary unlithified deposit

dissipation of fast strike slip faulting within and beyond northeastern tibet structural patterns global positioning system gps velocities and quaternary fault slip rates in northeastern tibet indicate a transfer of left lateral slip from the kunlun fault northeast to the haiyuan fault and minor crustal shortening and rotation within a 200 km wide stepover zone related deformation also continues at least a few hundred kilometers north of the haiyuan fault into a region of diffuse extensional shear or rotation underlain by average thickness crust fast localized slip along the central kunlun fault transforms into distributed deformation across a 500 km wide zone where the lower crust is weak the distribution of fault parallel gps velocities across this region suggests a decrease in fault slip toward eastern fault tips and progressive dissipation of slip to the north rather than east of the tibetan plateau as previously suggested

advancement in source estimation techniques using broadband regional seismograms one important constraint on source retrieval from regional seismograms comes from the amplitude difference between various phases such as pnl surface wave sv sh because the misfit errors used in some waveform inversions are normalized by the data and synthetics the amplitude information in the data has not been fully utilized in this article we modify the cut and paste source estimation technique zhao and helmberger 1994 by removing this type of normalization it is shown that the modified method increases the stability and resolution of inversion when multiple stations at different distance ranges are used a distance scaling factor is introduced to compensate for the amplitude decay with distance by applying the technique to the terrascope data we have determined source mechanisms and depths of 335 southern californian events with m l 3 5 the amplitude decays with distance are r 1 13 for pnl r 0 55 for love waves and r 0 74 for rayleigh waves in contrast to generally shallow source depths reported by the southern california short period network the depth distribution from waveform inversion shows a strong peak around 12 km with few earthquakes occurring above 5 km and below 20 km

the 2015 illapel earthquake central chile a type case for a characteristic earthquake on 16 september 2015 the mw 8 2 illapel megathrust earthquake ruptured the central chilean margin combining inversions of displacement measurements and seismic waveforms with high frequency hf teleseismic backprojection we derive a comprehensive description of the rupture which also predicts deep ocean tsunami wave heights we further determine moment tensors and obtain accurate depth estimates for the aftershock sequence the earthquake nucleated near the coast but then propagated to the north and updip attaining a peak slip of 5 6 m in contrast hf seismic radiation is mostly emitted downdip of the region of intense slip and arrests earlier than the long period rupture indicating smooth slip along the shallow plate interface in the final phase a superficially similar earthquake in 1943 with a similar aftershock zone had a much shorter source time function which matches the duration of hf seismic radiation in the recent event indicating that the 1943 event lacked the shallow slip

offsets of late quaternary morphology rate of slip and recurrence of large earthquakes on the chang ma fault gansu china the chang ma fault in the western qilian shan gansu province shows evidence of consistent left lateral displacements despite a complex en echelon geometry we have measured short and long term offsets on two n70 80 e striking segments of the fault along the southern edge of the ta quen kou basin where it cuts late quaternary terraces transverse ridges and drainage channels to analyze the offsets of such structures at one site in the eastern part of the basin we ran topographic profiles parallel and perpendicular to the fault over a distance of about 5 km spectral analysis and comparison of longitudinal profiles north and south of the fault allowed us to separate horizontal offsets of structures of different wavelengths apparent on air photos and satellite images transverse profiles were used to determine the vertical throw whose variations appear to result from changes in the fault strike small horizontal offsets of ridge crests and valley slopes are about 55 m along the n70 e striking segment of the fault this displacement corresponds to an uplift of the northern block of about 27 m implying that the fault dips about 73 to the south the measurements also constrain horizontal projection of the slip vector to about n78 e a larger horizontal offset 500 m of morphological swells of longer wavelength 1 6 km is visible on the longitudinal profiles assuming that periglacial erosion has reshaped the surface of the lateral slopes and tops of ridges during the wurm glacial period the smallest offsets of adjacent ridge crests may postdate the begining of the holocene yielding an average rate of left lateral slip on the fault of 5 5 2 2 mm yr in the last 10 2 kyr in the western part of the ta quen kou basin a somewhat slower rate of holocene slip 4 6 4 mm yr is obtained measurement of the horizontal displacement due to the 1932 earthquake there 6 2 0 6 m would imply that the recurrence interval for similar earthquakes at this second site is 1350 540 years

cretaceous tertiary structural evolution of the north central lhasa terrane tibet 1 in the north central lhasa terrane of tibet two distinct structural levels of an east west striking thrust system are exposed along the north trending late cenozoic xiagangjiang rift upper paleozoic strata deformed by the south directed langgadong la thrust and cretaceous strata involved in variably north and south directed thrusting characterize these lower and upper structural levels respectively these two structural levels are separated by the tagua ri passive roof thrust balanced cross section restoration suggests that the thrust system accommodated 103 km 53 shortening the 40ar 39ar results together with an interpretation of synthrust deposition of upper cretaceous strata suggest that the majority of shortening occurred during the late cretaceous paleocene cretaceous strata lie unconformable on permian rocks volcanic tuffs directly above the unconformity yield u pb zircon ages of 131 ma upper cretaceous strata record a change from shallow marine to nonmarine deposition indicating uplift above sea level during this time the overall south directed vergence of the thrust belt is consistent with substantial crustal thickening in central tibet by large scale northward underthrusting of lhasa terrane basement beneath the qiantang terrane prior to the indo asian collision the documented decoupling of contractional deformation at shallow crustal levels appears to be a regional characteristic of tibet from at least the bangong suture in the north to the tethyan himalaya to the south this style of deformation explains the absence of basement exposures and major denudation in this region despite substantial crustal shortening

evaluation of pore structures in volcanic reservoirs a case study of the lower cretaceous yingcheng formation in the southern songliao basin ne china different pore types and variable pore structures can determine reservoir potentials of volcanic rocks therefore it is of great importance to understand the pore structures of volcanic reservoirs with the lower cretaceous yingcheng volcanic rocks this study attempts to investigate and evaluate the micro pore structures of a volcanic reservoir through 1 measuring porosity and permeability of core samples 2 identifying pore types within thin sections 3 characterizing pore structures with pressure controlled mercury injection the lower cretaceous yingcheng volcanic rocks exhibits low porosities on average 7 39 and very low permeability on average 0 283 10 6 m2 three major pore types were identified from the lower cretaceous yingcheng volcanic reservoir including primary pores secondary pores and fractures additionally the pore structures of the lower cretaceous yingcheng volcanic reservoir can be classified into three types type i pore structure primarily occurs in the volcanic breccia crystal tuff and tuffites the corresponding pore system is dominated by primary intergranular pores intragranular dissolved pores and devitrified micropores with porosity and permeability higher than 5 4 and 0 05 10 6 m2 respectively corresponding mercury intrusion curves are characterized by low displacement pressure high maximum mercury saturation and mercury withdrawal efficiency type ii pore structure is commonly observed in the tuff and tuffites while primary intergranular pores and secondary micropores dominate pore system with porosity of 2 5 5 4 and permeability of 0 012 0 05 10 6 m2 the mercury intrusion curves are similar to the type i type iii pore structure is also pervasively developed in the crystal tuff and tuffites intragranular dissolved micropores are most important ones with porosity and permeability less than 2 5 and 0 01 10 6 m2 respectively different from type i and ii pore structure the mercury intrusion curves of the type iii have high displacement pressure low maximum mercury saturation and mercury withdrawal efficiency indicating poor reservoir quality

source parameters of the 2016 menyuan earthquake in the northeastern tibetan plateau determined from regional seismic waveforms and insar measurements abstract on january 21st 2016 a ms 6 4 earthquake hit menyuan county qinghai province china the nearest known fault is the leng long ling lll fault which is located approximately 7 km north of the epicenter this fault has mainly shown sinistral strike slip movement since the late quaternary period however the focal mechanism indicates that it is a thrust earthquake which is different from the well known strike slip feature of the lll fault in this study we determined the focal mechanism and primary nodal plane through multi step inversions in the frequency and time domain by using the broadband regional seismic waveforms recorded by the china digital seismic network cdsn our results show that the rupture duration was short within 0 2 s after the earthquake and the rupture expanded upwards along the fault plane based on these fault parameters we then solve for variable slip distribution on the fault plane using the insar data we applied a three segment fault model to simulate the arc shaped structure of the northern lll fault and obtained a detailed slip distribution on the fault plane the inversion results show that the maximum slip is 0 43 m and the average slip angle is 78 8 with a magnitude of mw 6 0 and a focal depth of 9 38 km with the geological structure and the inversion results taken into consideration it can be suggested that this earthquake was caused by the arc shaped secondary fault located at the north side of the lll fault the secondary fault together with the lll fault forms a normal flower structure the main lll fault extends almost vertically into the base rock and the rocks between the two faults form a bulging fault block therefore we infer that this earthquake is the manifestation of a neotectonics movement in which the bulging fault block is lifted further up under the compresso shear action caused by the tibetan plateau pushing towards the northwest direction

processes controlling porosity and permeability in volcanic reservoirs from the austral and neuquen basins argentina volcanic rocks develop primary and secondary porosity and permeability depending on both their lithology and the sequence of processes involved in their formation primary processes welding deuteric crystal dissolution gas release flow fragmentation and crystal shattering may lead to high porosity and permeability the best example of which is a nonwelded ignimbrite with well developed gas pipe zones secondary processes different types of alteration however tend to decrease primary porosity however certain secondary processes such as dissolution and hydraulic fracturing may contribute to enhance total porosity and permeability these conclusions were developed through a systematic review of reservoir quality in volcanic rocks integrating lithology and process interpretation with petrophysical data the said information was taken from selected cores of volcanic rocks from the serie tobfera unit in the austral basin and the precuyano unit in the neuqun basin argentina a clear understanding of both primary and secondary processes may serve to predict the quality of volcanic reservoirs and could be used as a guide for oil and gas exploration and development in many parts of the world

comparisons of upwelling and relaxation events in the monterey bay area 1 observations show significant differences in circulation patterns of upwelling and relaxation events that occurred in the monterey bay during two autonomous ocean sampling network field experiments in august 2003 and 2006 during the 2003 experiment circulation exhibited more typical patterns associated with upwelling relaxation the development of the southward flowing jet and pair of cyclonic inside of the bay and anticyclonic outside of the bay circulations during upwelling and the development of the northward flow along the coast during relaxation of winds during the upwelling event of 2006 the southward flow was weaker and shallower than in 2003 the second relaxation event of 2006 was significantly different from the first relaxation event of 2006 and the relaxation event of 2003 a southward flow was present along the entrance to the bay and this southward flow penetrated into the subsurface up to around 50 m at the mooring location two reasons for the observed differences in upwelling and relaxation events of 2003 and 2006 are identified in the paper weaker winds in august 2006 than in august 2003 and strong positive sea surface height anomalies propagating poleward along the coast during 2006 the 2003 field program included an extensive sampling of the bay and surrounding areas with a fleet of underwater gliders while during 2006 program the extensive sampling was conducted in the area of upwelling center to the north of the monterey bay during the 2003 field program the monterey bay model was able to reproduce observed surface and subsurface features with assimilation of glider observations however during the 2006 field program the assimilation of glider data from the upwelling center to the north of the monterey bay had minimal impact on model simulations of observed features to the south of the upwelling center

extension in the graben systems around the ordos china and its contribution to the extrusion tectonics of south china with respect to gobi mongolia the graben basins around the ordos block are major tectonic features of late cenozoic extension in north china this paper gives a synthetic view of the basic characteristics of the graben basins and of the kinematics of the graben bounding faults this view is based on the available geological data spot imagery analysis field observations and focal mechanisms of earthquakes from this region these graben basins have been grouped into two major systems the yinchuan hetao graben system along the northern and northwestern margins of the ordos and the weihe shanxi graben system along the southern and eastern margins of the ordos crustal deformation along these graben systems involves normal slip on ne sw striking graben bounding faults normal right lateral and normal left lateral slip on nne ssw and wnw ese striking faults respectively this fault pattern is consistent with nw se trending extension the amount and rate of deformation resulting from this extension have been estimated from geological data using a cross sectional area balance and the extensional factor method deduced from the tilt of faulted blocks the results of these estimates show that the uppermost pliocene quaternary extension rate in a nw se direction is in the order of 1 6 mm yr 1 across the weihe graben 0 5 mm yr 1 across the central shanxi graben on the southeastern margin of the ordos block and 3 1 mm yr 1 across the linhe graben on the northwestern margin of the ordos block the extension across these graben systems is accompanied with counterclockwise rotation of continental blocks in north china ordos taihang shan north china plain a kinematic model is proposed in which the late cenozoic extension and block rotation in north china are interpreted as the effect of the eastward termination of the left lateral slip haiyuan fault and kunlun taibai fault system the ordos block rotates counterclockwise as a result of the push of tibet through the left lateral strike slip haiyuan fault and the liupan shan thrust and fold belt the extension along the weihe shanxi graben system may represent the effect of the left lateral slip on the kunlun taibai qinling fault system the rough estimates of the extensional deformation around the ordos block indicate that this contributes to about 5 2 mm yr 1 of left lateral movement in a n125 e direction between south china and gobi mongolia this motion adds to the left lateral slip on the qinling fault zone about 7 2 mm yr 1 in a n90 e direction between the qinling shan and the hua shan north china thus the eastward motion of south china with respect to gobi mongolia is partitioned between normal faulting around the ordos and strike slip faulting in the qinling shan it is estimated to be in the order of 12 4 mm yr 1 in a n105 e direction during the quaternary

volcanic settings and their reservoir potential an outcrop analog study on the miocene tepoztlan formation central mexico abstract the reservoir potential of volcanic and associated sedimentary rocks is less documented in regard to groundwater resources and oil and gas storage compared to siliciclastic and carbonate systems outcrop analog studies within a volcanic setting enable to identify spatio temporal architectural elements and geometric features of different rock units and their petrophysical properties such as porosity and permeability which are important information for reservoir characterization despite the wide distribution of volcanic rocks in mexico their reservoir potential has been little studied in the past in the valley of mexico situated 4000 m above the neogene volcanic rocks groundwater is a matter of major importance as more than 20 million people and 42 of the industrial capacity of the mexican nation depend on it for most of their water supply here we present porosity and permeability data of 108 rock samples representing five different lithofacies types of the miocene tepoztlan formation this 800 m thick formation mainly consists of pyroclastic rocks mass flow and fluvial deposits and is part of the southern transmexican volcanic belt cropping out south of the valley of mexico and within the two states of morelos and mexico state porosities range from 1 4 to 56 7 average porosity is 24 8 generally permeabilities are low to median 0 2 933 3 md with an average permeability of 88 5 md the lavas are characterized by the highest porosity values followed by tuffs conglomerates sandstones and tuffaceous breccias on the contrary the highest permeabilities can be found in the conglomerates followed by tuffs tuffaceous breccias sandstones and lavas the knowledge of these petrophysical rock properties provides important information on the reservoir potential of volcanic settings to be integrated to 3d subsurface models

oblique stepwise rise and growth of the tibet plateau two end member models of how the high elevations in tibet formed are i continuous thickening and widespread viscous flow of the crust and mantle of the entire plateau and ii time dependent localized shear between coherent lithospheric blocks recent studies of cenozoic deformation magmatism and seismic structure lend support to the latter since india collided with asia 55 million years ago the rise of the high tibetan plateau likely occurred in three main steps by successive growth and uplift of 300 to 500 kilometer wide crustal thrust wedges the crust thickened while the mantle decoupled beneath gently dipping shear zones did not sediment infilling bathtub like of dammed intermontane basins formed flat high plains at each step the existence of magmatic belts younging northward implies that slabs of asian mantle subducted one after another under ranges north of the himalayas subduction was oblique and accompanied by extrusion along the left lateral strike slip faults that slice tibet s east side these mechanisms akin to plate tectonics hidden by thickening crust with slip partitioning account for the dominant growth of the tibet plateau toward the east and northeast

tectonic and climate control of oil shale deposition in the upper cretaceous qingshankou formation songliao basin ne china oil shales were deposited in the songliao basin ne china during the upper cretaceous period representing excellent hydrocarbon source rocks high organic matter om contents a predominance of type i kerogen and a low maturity of om in the oil shales are indicated by bulk geochemical parameters and biomarker data a major contribution of aquatic organisms and minor inputs from terrigenous land plants to om input are indicated by n alkane distribution patterns composition of steroids and organic macerals strongly reducing bottom water conditions during the deposition of the oil shale sequences are indicated by low pristane phytane ratios high c14 aryl isoprenoid contents homohopane distribution patterns and high v ni ratios enhanced salinity stratification with mesosaline and alkaline bottom waters during deposition of the oil shales are indicated by high gammacerane index values low mttc ratios high carotene contents low toc s ratios and high sr ba ratios the stratified water column with anoxic conditions in the bottom water enhanced preservation of om moderate input of detrital minerals during the deposition of the oil shale sequences is reflected by titanium concentrations in this study environmental conditions in the paleo lake leading to om accumulation in the sediments are related to sequence stratigraphy governed by climate and tectonics the first member of the qingshankou formation k2qn1 in the songliao basin containing the oil shale sequence encompasses a third order sequence that can be divided into three system tracts transgressive system tract tst highstand system tract hst and regressive system tract rst enrichment of om changed from low values during tst i to high moderate values during tst ii iii and hst i ii low om enrichment occurs during rst i and rst ii therefore the highest enrichment of om in the sediments is related to stages of mid late tst and early hst

extension rates across the northern shanxi grabens china from quaternary geology seismicity and geodesy discrepancies between geological seismic and geodetic rates of strain can indicate that rates of crustal deformation and hence seismic hazard are varying through time previous studies in the northern shanxi grabens at the northeastern corner of the ordos plateau in northern china have found extension rates of anywhere between 0 and 6 mm a at an azimuth of between 95 and 180 in this paper we determine extension rates across the northern shanxi grabens from offset geomorphological features and a variety of quaternary dating techniques including new irsl and ar ar ages a kostrov summation using a 700 year catalogue of historical earthquakes and recent campaign gps measurements we observe good agreement between quaternary seismic and geodetic rates of strain and we find that the northern shanxi grabens are extending at around 1 to 2 mm a at an azimuth of 151 the azimuth of extension is particularly well constrained and can be reliably inferred from catalogues of small earthquakes we do not find evidence for any substantial variations in extension rate through time though there is a notable seismic moment rate deficit since 1750 this deficit could indicate complex fault interactions across large regions aseismic accommodation of deformation or that we are quite late in the earthquake cycle with the potential for larger earthquakes in the relatively near future

source estimation from broadband regional seismograms recently developed source inversion techniques do not take full advantage of the broadband nature of regional seismograms the reason is that green s functions generated from flat layered models are not correct for the complicated propagational phenomena associated with realistic crustal structure the inversion is usually performed by removing short periods and inverting only selected portions of the records in this article we introduce a source estimation technique that allows for better use of the entire broadband record when only imperfect green s function are available the procedure desensitizes the timing between the principal crustal arrivals by fitting portions of the green s functions independently the preferred source is the orientation that minimizes the average l1 and l2 norms in term of the four parameters m 0 strike dip and rake the l2 error emphasizes the longer period surface waves while the l1 error weights the shorter period body waves we obtain estimates of duration by modeling long period and broadband signals the depth determination can be obtained directly from the surface reflected phases sp mp or ss ms or by cycling through the depth dependent green s functions in addition to the source parameters we obtain t phase alignments shifts that can be used as green s function corrections for relocating other events or as a guide to deriving new crustal models

cenozoic shortening budget for the northeastern edge of the tibetan plateau is lower crustal flow necessary 1 two of the most popular mechanisms for thickening the crust beneath the tibetan plateau are 1 pure shear with faulting and folding in the upper crust and horizontal shortening below and 2 flow of lower or middle crust without significant shortening of the upper crust to help discriminate between the relative contributions of these two mechanisms well constrained estimates of upper crustal shortening are needed here we document the cenozoic shortening budget across the northeastern tibetan plateau margin with several balanced cross sections that exploit thermochronological and magnetostratigraphic constraints these sections indicate 11 2 1 east west shortening since middle miocene time and 9 2 3 nne ssw shortening between middle eocene and middle miocene times with little subsequent shortening of this orientation shortening rates accelerate fivefold after middle miocene time given the present day crustal thickness of 56 4 km in northeastern tibet crustal restorations that remove cenozoic shortening suggest that the northeastern tibetan crust was 45 5 km thick prior to the india asia continental collision this precollision thickness estimate is equivalent to average continental crustal thicknesses both adjacent to the tibetan plateau 44 4 km and globally 41 6 km and suggests that pure shear alone may account for cenozoic crustal thickening in northeastern tibet in contrast to eastern tibet where in the absence of significant shortening structures crustal flow has been invoked to explain the addition of crustal material since middle miocene time our results may obviate lower crustal flow as a necessary crustal thickening agent in northeastern tibet

three types of flower structures in a divergent wrench fault zone flower structures are typical features of wrench fault zones in conventional studies two distinct kinds of flower structures have been identified based on differences in their internal structural architecture 1 negative flower structures characterized by synforms and normal separations and 2 positive flower structures characterized by antiforms and reverse separations in addition to negative and positive flower structures in this study a third kind of flower structure was identified in a divergent wrench fault zone a hybrid characterized by both antiforms and normal separations negative flower structures widely occur in divergent wrench fault zones and their presence indicates the combined effects of extensional and strike slip motion in contrast positive and hybrid flower structures occur only in fault restraining bends and step overs a hybrid flower structure can be considered as product of a kind of structural deformation typical of divergent wrench zones it is the result of the combined effects of extensional compressional and strike slip strains under a locally appropriate compressional environment the strain situation in it represents the transition stage that in between positive and negative flower structures kinematic and dynamic characteristics of the hybrid flower structures indicate the salient features of structural deformation in restraining bends and step overs along divergent wrench faults including the coexistence of three kinds of strains i e compression extension and strike slip and synchronous presence of compressional i e typical fault bend fold and extensional normal faults deformation in the same place hybrid flower structures are also favorable for the accumulation of hydrocarbons because of their special structural configuration in divergent wrench fault zones

a creeping intracontinental thrust fault past and present slip rates on the northern edge of the tien shan kazakhstan we demonstrate that a continental interior reverse fault is deforming by aseismic creep presently and likely also in the long term the karkara rangefront fault part of the larger main terskey front forms the northern boundary of the high terskey tien shan in southeastern kazakhstan and is a mature structure with evidence for high slip rates throughout the late cenozoic combining field studies with a satellite stereo image derived digital elevation model 2 m resolution we map a series of fluvial terraces along the rangefront which are uplifted by up to 300 m above the present river level radiocarbon ages from one catchment constrain the ages of the lowermost two terraces to be 4 5 ka and 10 15 ka consistent with prominent regionally extensive terraces observed elsewhere in the tien shan based on conservative estimates for the fault dip under the displaced terraces we estimate a slip rate along the fault plane of 3 5 1 7 0 4 mm yr 1 on the karkara rangefront fault and a further 0 8 mm yr 1 on a fold structure in the kegen basin that we infer is driven by a detachment from the main rangefront we therefore estimate a minimum shortening rate across the rangefront of 1 1 3 3 mm yr 1 elastic modelling of the regional gps velocity field suggests that the fault is presently creeping at 3 mm yr 1 horizontal shortening consistent with the upper limit of our late quaternary slip rate estimate this is the fastest known slip rate in the northern tien shan and the only individual structure resolved in the regional velocity field at present the fault is accumulating minimal strain and there is evidence in the geomorphology that this creep is sustained in the long term but whether or not it is also capable of generating earthquakes requires further study

pore structure characteristics of tight sandstones in the northern songliao basin china abstract understanding the pore structure characteristics of tight gas sandstones is the primary purpose of reservoir evaluation and efforts to characterize tight gas transport and storage mechanisms and their controls due to the various pore types and multi scale pore sizes in tight reservoirs it is essential to combine several techniques to characterize pore structure scanning electron microscopy sem nitrogen gas adsorption n2ga mercury intrusion porosimetry mip and nuclear magnetic resonance nmr were conducted on tight sandstones from the lower cretaceous shahezi formation in the northern songliao basin to investigate pore structure characteristics systematically e g type and size distribution of pores and to establish how significant porosity and permeability are for different pore types the studied tight sandstones are composed of intergranular pores dissolution pores and intercrystalline pores the integration of n2ga and nmr can be used as an efficient method to uncover full pore size distribution psd of tight sandstones with pore sizes ranging from 2 nm to dozens of microns the full psds indicate that the pore sizes of tight sandstones are primarily distributed within 1 0 m with an increase in porosity and permeability pores with larger sizes contribute more to porosity intercrystalline pores and intergranular dissolution pores can be clearly distinguished on the basis of mercury intrusion and surface fractal the relative contribution of intercrystalline pores to porosity ranges from 58 43 to 91 74 with an average of 79 74 the intercrystalline pores are the primary contributor to pore space whereas intergranular dissolution pores make a considerably greater contribution to permeability a specific quantity of intergranular dissolution pores is the key to producing high porosity and permeability in tight sandstone reservoirs the new two permeability estimation models show an applicable estimation of permeability with r2 values of 0 955 and 0 962 for models using dmax pore diameter corresponding to displacement pressure and df pore diameter at inflection point respectively these results indicate that both dmax and df are key factors in determining permeability

the geological evolution of the tibetan plateau the geological evolution of the tibetan plateau is best viewed in a context broader than the india eurasia collision zone after collision about 50 million years ago crust was shortened in western and central tibet while large fragments of lithosphere moved from the collision zone toward areas of trench rollback in the western pacific and indonesia cessation of rapid pacific trench migration 15 to 20 million years ago coincided with a slowing of fragment extrusion beyond the plateau and probably contributed to the onset of rapid surface uplift and crustal thickening in eastern tibet the latter appear to result from rapid eastward flow of the deep crust probably within crustal channels imaged seismically beneath eastern tibet these events mark a transition to the modern structural system that currently accommodates deformation within tibet

can vertical migrations of dinoflagellates explain observed bioluminescence patterns during an upwelling event in monterey bay california 1 extensive auvs surveys showed that during the development of upwelling bioluminescent dinoflagellates from the northern part of the monterey bay california called the upwelling shadow area were able to avoid advection by southward flowing currents along the entrance to the bay while non bioluminescent phytoplankton were advected by currents it is known that vertical swimming of dinoflagellates to deeper layers helps them avoid losses due to advection in the present paper we investigate if modeling dinoflagellates vertical swimming can explain the observed dinoflagellates ability to avoid advection during the upwelling development the dynamics of a dinoflagellate population is modeled with the tracer model with introduced vertical swimming velocity three swimming behaviors are considered sinking swimming to the target depth and diel vertical migration velocities in all swimming cases are considered in the ranges of documented velocities for the observed dinoflagellates species during the upwelling development in the monterey bay our modeling confirmed that observed bioluminescent dinoflagellates avoidance of advection during the upwelling development can be explained by their vertical swimming ability in the case of swimming with 20 m day which is half of observed maximum swimming velocity around 40 of dinoflagellates population from the northern part of the bay were advected along the entrance to the bay in comparison to the case without swimming this is in agreement with the ratio of around 45 of observed mean bioluminescence intensity at the entrance to the bay to the observed mean intensity in the northern part of the bay this mechanism also helps explain the general persistence of dinoflagellates in this part of the coastline

modeling of upwelling relaxation events with the navy coastal ocean model prediction system coamps tm coamps is a registered trademark of the naval research laboratory issues investigated in this study are ncom based model simulations of upwelling and relaxation events coupling to coamps use of sigma versus hybrid sigma z vertical grids and coupling with a larger scale model on the open boundaries the ncom simulations were able to reproduce the observed sequence of the upwelling and relaxation events which can be attributed in part to the good agreement between the observed and coamps winds comparisons with the mooring observations show that coamps overestimates shortwave radiation values which makes the ncom modeled ssts too warm in comparison with observations the ncom runs forced with different resolution atmospheric forcing 3 versus 9 km do not show significant differences in the predicted ssts and mixed layer depths at the mooring locations at the same time during the extended upwelling event the model runs forced with 3 and 9 km resolution coamps fields show differences in the surface circulation patterns which are the most distinct in the southern portion of the model domain the model run with 9 km forcing develops a northward flow along the coast which is not present in the run with 3 km forcing and in observations for example hf radar derived radials comparison of the wind patterns of the 3 and 9 km products shows a weakening of the 9 km wind stress along the southern coast of the ncom model domain which is responsible for the development of the artificial northward flow in the ncom run with 9 km forcing

the growth of northeastern tibet and its relevance to large scale continental geodynamics a review of recent studies recent studies of the northeastern part of the tibetan plateau have called attention to two emerging views of how the tibetan plateau has grown first deformation in northern tibet began essentially at the time of collision with india not 10 20 myr later as might be expected if the locus of activity migrated northward as india penetrated the rest of eurasia thus the north south dimensions of the tibetan plateau were set mainly by differences in lithospheric strength with strong lithosphere beneath india and the tarim and qaidam basins steadily encroaching on one another as the region between them the present day tibetan plateau deformed and its north south dimension became narrower second abundant evidence calls for acceleration of deformation including the formation of new faults in northeastern tibet since 15 ma and a less precisely dated change in orientation of crustal shortening since 20 ma this reorientation of crustal shortening and roughly concurrent outward growth of high terrain which swings from nne ssw in northern tibet to more ne sw and even ene wsw in the easternmost part of northeastern tibet are likely to be in part a consequence of crustal thickening within the high tibetan plateau reaching a limit and the locus of continued shortening then migrating to the northeastern and eastern flanks these changes in rates and orientation also could result from removal of some or all mantle lithosphere and increased gravitational potential energy per unit area and from a weakening of crustal material so that it could flow in response to pressure gradients set by evolving differences in elevation

repeat times of large earthquakes implications for earthquake mechanics and long term prediction information on the time intervals between large earthquakes is now available for several fault segments along plate boundaries in japan alaska california cascadia and turkey when dates in a sequence are known historically as along much of the nankai trough they provide information on the natural intrinsic variability of the rupture process most sets of repeat times however are dominated by paleoseismic determinations of dates of older large earthquakes which contain measurement uncertainties in addition to intrinsic variability a bayesian technique along with prior information on measurement uncertainties is used to make maximum likelihood estimates of intrinsic repeat time and its normalized standard deviation the coefficient of variation cv it is these intrinsic parameters and their uncertainties that are most useful for understanding the mechanics of earthquakes and for prediction for timescales of a few decades our estimates of intrinsic cv are small 0 to 0 25 for several very active fault segments where deformation is relatively simple large events do not appear to be missing in historic and paleoseismic records and data are available at or near major asperities and away from the ends of rupture zones cv is larger for regions of multibranched faulting overlapping slip near the ends of rupture zones and for data from uplifted terraces at subduction zones a poisson process is an inferior characterization of all of the 11 segments we examined scenarios used by recent working groups that assume either poissonian behavior or renewal processes with cv of 0 5 0 2 for the most active fault segments in the san francisco bay area likely lead to incorrect 30 year probability estimates the hayward fault and perhaps the peninsular segment of the san andreas fault in the san francisco bay area appear to be advanced in their buildup of stress that will be released in future large earthquakes multibranched faulting may account for why the predicted tokai earthquake in japan has not occurred as of 2006 parkfield earthquakes from 1857 to 2004 were characterized by the largest uncertainty of the sequences we studied cv 0 37 which may account for the failure of past predictions the large cv for parkfield fits our hypothesis that relatively weak fault segments are characterized by more irregular earthquake recurrence paleoseismic data from coastal sites along the cascadia subduction zone are characterized by cvs of about 0 3

variability in magnitude of paleoearthquakes revealed by trenching and historical records along the haiyuan fault china paleoseismology provides fundamental data for generalizing earthquake recurrence behavior by revealing past surface rupturing events determining the size of paleoseismic events is notoriously more challenging than their timing paleoearthquakes exposed in trenches are vaguely defined as large enough to break to the surface and often assumed to be similar in size here we show an example where the paleoseismic record includes events of both moderate and large magnitudes at the salt lake site on the active left lateral haiyuan fault northern tibetan plateau a high resolution stratigraphic sequence recorded three and possibly four events since a d 1500 constrained by accelerator mass spectrometry 14 c dating historical accounts of earthquake damage in the study region suggest that several earthquakes exposed in the trenches markedly differ in magnitude with the exception of the most recent m 8 earthquake that occurred in a d 1920 two earlier events which occurred in a d 1760 or 1709 and 1638 respectively are considerably smaller with magnitude m 7 and more likely m 6 or less thus this section of the haiyuan fault that broke during moderate magnitude events failed again after a short interval during a large m w 7 8 8 3 earthquake as part of a larger multisegment rupture our study shows that moderate magnitude events can be preserved in the stratigraphy and exposed by paleoseismic trenching under ideal conditions for instance if sedimentation is fast enough and there is no hiatus in deposition eventually the data presented add to the growing body of paleoseismic records containing events of different magnitudes with a large variability in rupture length and coseismic slip

faulting associated with large earthquakes and the average rate of deformation in central and eastern asia we determine approximate average rates of deformation in portions of eastern and central asia for the last 80 years these rates are based on estimates of source dimensions average displacements seismic moments and orientations of faults of all large earthquakes m 7 5 and as many other major earthquakes m 7 0 as possible in asia since 1900 a major part of this study is the compilation of these data for separate parts of asia we combine seismic moment tensors to estimate the average rotational strain or deformation tensors for these regions for the last 80 years we estimate that shortening across the tien shan has occurred at 11 mm yr between 5 and 19 mm yr left lateral shear on easterly trending planes in mongolia in northwestern tibet gansu and ningxia and on the xianshuihe fault in western sichuan has been very rapid more than 10 mm yr in each region and apparently as rapid as 40 mm yr in northwestern tibet gansu and ningxia slower rates of a few to 10 mm yr appear to characterize east west extension and conjugate north south shortening of tibet the earthquake history of the himalaya is consistent with rates of underthrusting of more than 10 mm yr but is probably less than the convergence rate of india with eurasia of about 50 mm yr the overall strain field is consistent with a large part of india s penetration into eurasia being absorbed by the extrusion of material out of india s way as a result southeast china moved at about 21 mm yr east southeast with respect to eurasia in the last 80 years with an uncertainty of about a factor of 2 in this estimated rate

magnetotelluric survey for exploration of a volcanic rock reservoir in the yurihara oil and gas field japan the yurihara oil and gas field is located on the southern edge of akita prefecture northeastern japan in this area drilling surface geological surveys and many seismic surveys have been used to investigate the geological structure wells drilled into the nishikurosawa basalt group nbg of miocene age found oil and gas reservoirs at depths of 1 5 2km oil and gas are now being produced commercially and further exploration is required in the surrounding areas however since the neighbouring areas are covered with young volcanic products from the chokai volcano and have a rough topography the subsurface distribution of the nbg must be investigated using other methods in addition to seismic reflection according to the well data the resistivity of the nbg is comparatively higher than that of the overlying sedimentary formations and therefore the magnetotelluric mt method is expected to be useful for the estimation of the distribution of the nbg an mt survey was conducted along three survey lines in this area each line trended east west perpendicular to the regional geological strike and was composed of about 25 measurement sites induction vectors evaluated from the magnetic field show that this area has a two dimensional structure the evaluated resistivity sections are in agreement with the log data in conclusion we were able to detect resistive layers the nbg below conductive layers the results indicate that the nbg becomes gradually less resistive from north to south in the centre of the northern line an uplifted resistive area is interpreted as corresponding to the reservoir by comparison with a seismic section we prove the effectiveness of the integration of seismic and mt surveys for the investigation of the morphology and internal structure of the nbg on other survey lines the resistive uplifted zones are interpreted as possible prospective areas

quantitative modelling of hydrocarbon expulsion and quality grading of tight oil lacustrine source rocks case study of qingshankou 1 member central depression southern songliao basin china the quality of source rocks plays an important role in the distribution of tight and conventional oil and gas resources despite voluminous studies on source rock hydrocarbon generation expulsion and overpressure a quality grading system based on hydrocarbon expulsion capacity is yet to be explored such a grading system is expected to be instrumental for tight oil and gas exploration and sweet spot prediction this study tackles the problem by examining late cretaceous lacustrine source rocks of the qingshankou 1 member in the southern songliao basin china by evaluating generated and residual hydrocarbon amounts of the source rock the extent of hydrocarbon expulsion is modelled through a mass balance method the overpressure is estimated using petromod software through correlation between the hydrocarbon expulsion and source rock evaluation parameters total organic carbon toc kerogen type vitrinite reflectance ro and overpressure three classes of high quality effective and ineffective source rocks are established high quality class contains toc 2 type i kerogen ro 1 0 overpressure 7mpa sharp increase of hydrocarbon expulsion along with increasing toc and overpressure and high expulsion value at ro 1 source rocks with toc and ro 0 8 type ii2 iii kerogen overpressure 3mpa and low hydrocarbon expulsion volume are considered ineffective rocks with parameters between the two are considered effective the high quality class shows a strong empirical control on the distribution of tight oil in the songliao basin this is followed by the effective source rock class the ineffective class has no measurable contribution to the tight oil reserves because the hydrocarbon expulsion efficiency of source rocks is controlled by many factors the lower limits of the evaluation parameters in different basins may vary however the classification method of tight source rocks proposed in this paper should be widely applicable

the cenozoic growth of the qilian shan in the northeastern tibetan plateau a sedimentary archive from the jiuxi basin sedimentary deposits in tibetan basins archive the spatial temporal patterns of the deformation and surface uplift processes that created the area s high topography during the cenozoic india asia collision in this study new stratigraphic investigation of the caogou section from the jiuxi basin in the northeasternmost part of tibetan plateau provides chronologic constraints on the deformation and northward growth of the plateau magnetostratigraphic analysis results suggest that the age of the studied 1000 m thick section spans from 24 2 ma to 2 8 ma detailed sedimentology and apatite fission track aft analyses reveal that variations in the clast provenance lithofacies sediment accumulation rates and aft lag times occurred at 13 5 10 5 ma we interpret these changes as in response to the initial uplift of the north qilian shan in addition paleomagnetic declination results from the section indicate a clockwise rotation of the jiuxi basin before 13 5 ma which was followed by a subsequent counterclockwise rotation during 13 5 9 ma this reversal in rotation direction may be directly related to left lateral strike slip activity along the easternmost segment of the altyn tagh fault combined with previous studies we suggest that movement on the western part of the altyn tagh fault was probably initiated during the oligocene 30 ma and that fault propagation to its eastern tip occurred during the middle late miocene

paleomagnetic age of the tangxian planation surface northwestern zhongtiao shan of the shanxi graben system north china abstract a numerical formation age for the tangxian planation surface txps in north china is still controversial the txps beveled across paleoarchean basement rocks is overlain by late cenozoic conglomerate aeolian red clay and loess the magnetostratigraphy of two late cenozoic deposition sections is established and two other sections are recorded and measured in this work the magnetostratigraphy indicates six normal magnetozones n1 to n6 and six reverse magnetozones r1 to r6 these magnetozones are correlated to chron c1n through c2an 1r indicating that the txps was formed at 3 12 3 03 ma the characteristics of the zhongtiao shan tectonic uplift and its relationship with the tibetan plateau and ordos block are discussed in terms of tectonic uplift the txps formation and accumulation of the late cenozoic sediments are mainly controlled by tectonic activities the formation and uplift of the txps with a lag in the shanxi graben system is consistent with the activities of the tibetan plateau and ordos block implying that the ne extension of the tibetan plateau epeirogenic uplift advances successively

lithospheric velocity structure of the northeast margin of the tibetan plateau relevance to continental geodynamics and seismicity abstract we provide teleseismic constraints on the continental collision zone along the sw ne profile from the tibetan plateau to the alxa block traversing lenglong ling a topographic boundary of the northeastern tibetan plateau our seismic profile crosses the qilian shan thrust belt a zone of intense earthquake activity that includes a pair of mw 5 9 earthquakes in 1986 and 2016 with a 30 year time interval occurring at the city of menyuan near lenglong ling a high degree of similarity between the two waveforms and their similar hypocenters indicate that the two events are repeating earthquakes both p and s wave receiver functions show contrasting lithospheric structure and crustal seismic properties across the repeating earthquake region suggesting that lenglong ling can be the crustal boundary between the tibetan plateau and the alxa block high frequency p receiver functions clearly show a sw dipping underthrusted upper crust beneath the foreland of the qilian shan thrust belt a strong low velocity feature above the intracrustal underthrust beneath southwest lenglong ling indicates a mechanically weak zone developed coeval with the main compressional deformation during the last major tectonic event our observed localized upper crustal deformation beneath lenglong ling can be direct evidence of the lateral growth of the northeastern tibetan plateau and can control the seismicity of the qilian shan thrust belt including the menyuan repeating earthquakes

transformation of displacement between strike slip and crustal shortening in the northern margin of the tibetan plateau evidence from decadal gps measurements and late quaternary slip rates on faults abstract studies of late quaternary geological slip rates and the gps decadal slip rates along the major strike slip faults in the northern margin of the tibetan plateau show that slip rates remain relatively constant along the middle sections of each fault and decrease rapidly toward the ends our recent studies suggest that the slip rates are low

high resolution real time modeling of the marine atmospheric boundary layer in support of the aosn ii field campaign abstract the navy s coamps atmospheric model has been used to provide twice daily real time forecasts of 72 h duration in support of the aosn ii field campaign during august 2003 the model was configured with four grid meshes with a minimum horizontal grid increment of 3 km a statistical analysis of the model forecasts using available buoy observations demonstrates the skill of the atmospheric model predictions with characteristic wind speed rms and bias errors of 1 3 m s 1 and less than 0 5 1 0 m s 1 respectively and temperature rms errors of 1 2 c and biases typically less than 1 0 c the highest resolution mesh provides more accurate wind speed variances during the upwelling periods in the nearshore region where the wind speed gradients and diurnal variations are the largest persistent and strong low level winds from a northwesterly direction were associated with a mid tropospheric trough and jet stream that was substantially stronger than the overall mean monthly conditions during the relaxation periods which were relatively infrequent during august 2003 the trough was weaker than the mean conditions with a closed low west of the coast that resulted in southerlies near the coast during upwelling favorable conditions the mean marine inversion was substantially stronger than during the relaxation periods with the surface stress field exhibiting maxima in the lee of prominent coastal capes and topography particularly during the periods of strong larger scale low level flow the persistent mean stress pattern that is topographically locked yields maxima in the stress curl pattern that induce favorable regions of coastal upwelling near and downwind of the coastal promontories and headlands

normal faulting in central tibet since at least 13 5 myr ago tectonic models for the evolution of the tibetan plateau interpret observed east west thinning of the upper crust to be the result of either increased potential energy of elevated crust1 or geodynamic processes that may be unrelated to plateau formation2 3 4 5 6 a key piece of information needed to evaluate these models is the timing of deformation within the plateau the onset of normal faulting has been estimated to have commenced in southern tibet between about 14 myr ago7 and about 8 myr ago8 and in central tibet about 4 myr ago9 here however we report a minimum age of approximately 13 5 myr for the onset of graben formation in central tibet based on mineralization ages determined with rb sr and 40ar 39ar data that post date a major graben bounding normal fault these data along with evidence for prolonged activity of normal faulting in this and other tibetan grabens support models that relate normal faulting to processes occurring beneath the plateau thinning of the upper crust is most plausibly the result of potential energy increases resulting from spatially and temporally heterogeneous changes in thermal structure and density distribution within the crust and upper mantle beneath tibet this is supported by recent geophysical and geological data10 11 12 13 14 15 16 17 which indicate that spatial heterogeneity exists in both the tibetan crust and lithospheric mantle

origin of light hydrocarbons from volcanic rocks in the green tuff region of northeast japan biogenic versus magmatic abstract geochemical analyses were carried out to assess the origin of light hydrocarbons in natural gases derived from volcanic rocks in the green tuff region of northeast japan whose high he isotope ratios have suggested a possible magma gas component biogenic steroid hydrocarbons were detected unambiguously in the oils associated with the natural gases and they showed similar molecular distributions from c 27 to c 29 as those of the oils accumulated in the adjacent sedimentary rocks correlation of c 1 c 2 c 3 vs 13 c ch 4 for the light hydrocarbons indicated that they are thermocatalytic products from sedimentary organic matter on the assumption that the magmatic ch 4 3 he ratio is 10 6 no more than 0 1 of the total methane can be attributed to a magmatic origin the remaining methane is likely to have migrated from the adjacent sedimentary layers