observations of planetary boundary layer structure in the eastern equatorial pacific abstract atmospheric soundings were collected from a research ship in the eastern equatorial pacific to determine the kinematic and thermodynamic structure of the planetary boundary layer pbl in the vicinity of a strong front in sea surface temperature sst these observations have been used to test the hypothesis proposed by wallace et al and hayes et al that the low level wind shear was enhanced on the cold side of the front because of greater static stability the pbl structure was analyzed from a transect along 110 w from 10 n to 5 s with a focus on the 500 m deep atmospheric mixed layer as defined with respect to virtual potential temperature v significant mixed layer variability was found due to diurnal and other effects but there were systematic differences in mean structure as a function of latitude the mixed layer was neutrally stratified over warm water between 6 5 n and 1 5 n and was slightly stably stratified over the cooler water between 1 n and 2 s the mean total vertical wind

seismotectonics at the trench trench trench triple junction off central honshu we study earthquakes in and near the ttt type triple junction off boso peninsula central honshu to elucidate the plate interaction in this area the pacific north america northeast japan and philippine sea plates meet at the junction of the japan and izu bonin trenches and the sagami trough we determine focal mechanisms using wwssn data we also determine accurate focal depths by modeling body waves there is no serious trade off between focal depth and source time function for the events treated in this study

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

idealized simulations of the intertropical convergence zone and its multilevel flows abstract a mesoscale numerical model with an idealized tropical channel environment is used to study the dynamics of intertropical convergence zones itczs and the recently identified shallow return flow srf and midlevel inflow mli four idealized sea surface temperature sst distributions are used a meridionally symmetric sst profile with a sharply peaked sst maximum at the equator a similar profile with the maximum sst shifted off the equator a cosine shaped sst profile with zero gradient at the equator and an idealized sst profile modeled after the observed sst of the eastern pacific the simulations show that both the srf and the mli are robust features of the itcz the prior result that the srf is a sea breeze like response to surface temperature gradients is further supported whereas the mli is caused by the upper level maxima in diabatic heating and vertical motion simulations with the sst maximum at the equator generate long lasting convectively coupled kelvin waves when the sst maxi

large scale characteristics of the atmospheric boundary layer in the eastern pacific cold tongue itcz region abstract observations from the eastern pacific investigation of climate 2001 epic2001 field campaign and a simple mixed layer model are used to study the large scale structure and dynamics of the atmospheric boundary layer abl in the eastern pacific vertical and latitudinal distributions of the meridional pressure gradient winds and other variables are examined and the momentum balance of the mixed layer is explored for a latitudinal range from 0 to 10 n along 95 w including the equatorial cold tongue sea surface temperature sst front and convective region at the latitude of the intertropical convergence zone itcz the surface meridional pressure gradient is partitioned into contributions from the abl largely controlled by the gradient in sst and from the troposphere above the boundary layer mainly controlled by elevated heating and atmospheric wave activity the mean meridional gradient in surface pressure is dominated 90 by the abl contribution however its temporal variability prim

body wave inversion moment tensors and depths of oceanic intraplate bending earthquakes this paper develops a moment tensor inversion technique suited for analysis of long period body waves from distant shallow earthquakes in addition to the moment tensor the procedure resolves precise source depths 5 km and estimates the duration of faulting the technique is applied to digital sro dwwssn recordings of outer rise intraplate earthquakes these earthquakes result from bending of oceanic plates prior to subduction bending induces horizontal tension near the top of the lithosphere and horizontal compression near its base a neutral surface separates compressional from tensional regimes an examination of 11 bending earthquakes in the period january 1981 to july 1982 indicates that the depth to the neutral surface is not geographically uniform although the seismicity sample is very small the depth of the neutral surface appears to correlate with the position of the trench arc in the evolutionary sequence of uyeda and kanamori 1979 in particular neutral surfaces at strongly coupled chilean type plate boundaries are elevated as much as 15 km above those at weakly coupled mariana type boundaries this correlation implies that nonuniformities in neutral surface height are created by variations in regional compressive stress resulting from contrasts in plate plate coupling to account for the observed heights maximum interplate compressive stresses must be comparable with stresses derived from bending

optical characteristics of amorphous kerogens and the hydrocarbon generating potential of source rocks abstract four recurring types of amorphous kerogen are optically identified in petroleum source rock samples and are related to hydrocarbon generating potential defined here as geochemically interpreted oil prone or gas prone at this time a genetic classification is not possible the different amorphous kerogen types are distinguished on the basis of microscopic textural differences type a chunky compact masses with mottled network or weak polygonal textures type b very small dense elongate oval or rounded individual grains type c clumpswith granular fragmented or globular textures type d thin platy or rectangular individual grains geochemistry defined oil prone samples generally contain types a and or d separately or combined geochemically defined gas prone samples rarely contain type a and vary in amounts of types b c and or d the samples in this study contain dominantly one of the four types of amorphous kerogen so the geochemical analyses of the whole rock or bulk concentrated kerogen samples are assumed to be analyses of the dominant amorphous type the samples were chemically analyzed by several techniques to determine the oil or gas generating potential the establishment of relations between specific optical and chemical properties of kerogen types can make visual kerogen analyses more meaningful in predicting the hydrocarbon generation potential of source rocks

depth determination for shallow teleseismic earthquakes methods and results the depths of moderate sized shallow earthquakes can be routinely determined to an accuracy of several kilometers using teleseismic data alone making it possible to determine the vertical positions of earthquakes within the lithosphere this capability provides a valuable tool for plate tectonic studies since earthquake depths can be used to constrain lithospheric thermal and mechanical structure at plate boundaries and in intraplate regions two basic techniques are used for depth analyses surface wave spectra can be used to determine focal depths as mode excitation reflects the behavior of the eigenfunctions with depth the primary limitation on such studies stems from lateral heterogeneity of velocity structure the waveforms of body waves are also diagnostic of focal depth which controls the time separation between the direct arrival and near source surface reflections these studies can be limited by a partial trade off between depth and source time function duration the reliability of the body wave modeling approach now in general use is shown by excellent agreement between depths determined by different investigators using different algorithms the depth determination is robust to typical uncertainties in focal mechanism and near source structure the trade off with source time function duration generally does not produce major difficulties for small events ms 6 5 for larger events the trade off can be resolved using a approach in which for a given depth the time function yielding the best fit to a suite of seismograms is found by deconvolution deconvolution at a series of depths yields a misfit function whose minimum indicates the focal depth tests with synthetic data show that the deconvolution process yields reliable depth estimates even given uncertainties in focal mechanism and near source structure it successfully handles multiple sources moderate sized finite sources and horizontally propagating ruptures good results are obtained for vertically propagating ruptures until the fault area becomes so large that waveforms differ significantly from the point source approximation a number of important tectonic results have emerged from studies using these depth determination methods the maximum depth of oceanic intraplate seismicity increases with lithospheric age and is approximately bounded by the 750 c isotherm this depth roughly equals the flexural thickness of the lithosphere but is much less than the depth to the low velocity zone indicated by surface wave dispersion the maximum depth of continental intraplate seismicity is also temperature limited but by a lower temperature these observations are consistent with the rapid weakening of the appropriate rocks with depth predicted by standard temperature dependent rheologies the maximum depth of oceanic transform seismicity corresponds to an isotherm of about 400 c this temperature is lower than would be predicted from the intraplate results and may indicate that transforms are either hotter or weaker than expected the depths of ridge crest earthquakes large enough for teleseismic analysis are extremely shallow 0 8 km the depth distribution of seismicity in continental normal faulting regions provides constraints on the nature of the extension process at subduction zones precise depth determinations can resolve the upper and lower flexural regions in the bending downgoing plate precisely locate the plate interface and map the vertical extent and position of faulting in large earthquakes

depth resolution of earthquakes in central asia by moment tensor inversion of long period rayleigh waves effects of phase velocity variations across eurasia and their calibration the moment tensor inversion method for long period rayleigh waves is discussed from the point of view of event depth resolution in this method depth is usually determined by finding the minima in appropriate least squares residuals versus depth curves we show that depth cannot be resolved if the data are sampled only at one frequency and a choice of frequencies spanning a wide range of values yields better resolution we also show that the variance reduction at the minimum depends strongly on biases in the data provided they are not simple periodic functions in azimuth from the source since such biases are introduced in particular when the propagation corrections are inaccurate this provides a means by which to study regional trends of phase velocities this method is then applied to obtain an estimate of lateral heterogeneity in central asia starting with a reference point in the pamir mountains and a set of accurately known phase velocities on paths to eurasian wwssn stations we study the rayleigh waves at these stations in the period range 30 to 90 s for eight events located in or near the tibet plateau at stances from the reference point heterogeneity in phase velocity is thus found to be about 1000 to 1500 km in this period range constraining the source parameters of the most distant events by body wave modeling we determine new phase velocities on paths to wwssn stations from the center of the tibet plateau the variation of phase velocity with source location reaches 1 to 2 and the low velocity within tibet clearly has a dominant effect we then discuss the regionalization of phase velocities as a possible way to determine a calibration curve for a given source to receiver path we find that although the regionalized phase velocities in eurasia are stable to first order they do not seem accurate enough to be used for moment tensor inversions with arbitrary source locations this may be due to non ray theoretical effects causing the breakdown of phase velocity additivity when higher order accuracy is needed on the other hand reference phase velocities on source receiver paths can be obtained reasonably fast for events large enough so that body wave modeling is possible to constrain depth and source mechanism we demonstrate that these phase velocity curves are accurate enough for the calibration of propagation effects for another event located as much as 400 to 500 km away this provides an encouraging approach to study both structure and source mechanisms of smaller events within a highly heterogeneous continental region the only constraint is to find several events with the right magnitude of both long period body waves and surface waves

boundary layer cloud and drizzle variability in the southeast pacific stratocumulus regime abstract the southeast pacific stratocumulus regime is an important component of the earth s climate system because of its substantial impact on albedo observational studies of this cloud regime have been limited but during the past 5 yr a series of cruises with research vessels equipped with in situ and remote sensing systems have provided unprecedented observations of boundary layer cloud and drizzle structures these cruises started with the east pacific investigation of climate epic 2001 field experiment followed by cruises in a similar area in 2003 and 2004 pan american climate studies pacs stratus cruises the sampling from these three cruises provides a sufficient dataset to study the variability occurring over this region this study compares observations from the 2004 cruise with those obtained during the previous two cruises observations from the ship provide information about boundary layer structure fractional cloudiness cloud depth and drizzle characteristics this study indicat

determinations of focal depths of earthquakes associated with the bending of oceanic plates at trenches abstract the earthquakes examined in this paper are all within the oceanic lithosphere and are associated with the bending of plates before subduction accurate determinations of the depth of these earthquakes are needed to study the stress pattern within a bending plate routinely determined depths of shallow sub oceanic earthquakes published in bulletins are unreliable the depths can be accurately determined to within a few kilometers if the original seismograms from these events are studied in some cases the reflected phases pp and pwp can be clearly identified there exists the possibility that the wave reflected at the water air interface pwp may be misidentified as pp leading to erroneous estimates of depth additional methods of analysis such as surface wave radiation patterns or the apparent frequency dependence of reflection at the crust water interface can remove this possible source of confusion one of the most powerful techniques for depth analysis is the modelling of long period waveforms the pattern of stresses within the bending oceanic lithosphere revealed by the depths and focal mechanisms of these intraplate earthquakes is one of horizontal deviatoric tension down to a depth of about 25 km with horizontal compression at greater depths

implications of the 26 december 2004 sumatra andaman earthquake on tsunami forecast and assessment models for great subduction zone earthquakes results from different tsunami forecasting and hazard assessment mod els are compared with observed tsunami wave heights from the 26 december 2004 indian ocean tsunami forecast models are based on initial earthquake information and are used to estimate tsunami wave heights during propagation an empirical forecast relationship based only on seismic moment provides a close estimate to the observed mean regional and maximum local tsunami runup heights for the 2004 indian ocean tsunami but underestimates mean regional tsunami heights at azimuths in line with the tsunami beaming pattern e g sri lanka thailand standard forecast models developed from subfault discretization of earthquake rupture in which deep ocean sea level observations are used to constrain slip are also tested forecast models of this type use tsunami time series measurements at points in the deep ocean as a proxy for the 2004 indian ocean tsunami a transect of deep ocean tsunami amplitudes recorded by satellite altimetry is used to constrain slip along four subfaults of the m 9 sumatra andaman earthquake this proxy model performs well in comparison to observed tsunami wave heights travel times and inundation patterns at banda aceh hypothetical tsunami hazard assessments models based on end member estimates for average slip and rupture length m w 9 0 9 3 are compared with tsunami observations using average slip low end member and rupture length high end member m w 9 14 consistent with many seismic geodetic and tsunami inversions adequately estimates tsunami runup in most regions except the extreme runup in the western aceh province the high slip that occurred in the southern part of the rupture zone linked to runup in this location is a larger fluctuation than expected from standard stochastic slip models in addition excess moment release 9 deduced from geodetic studies in comparison to seismic moment estimates may gen erate additional tsunami energy if the exponential time constant of slip is less than approximately 1 hr overall there is significant variation in assessed runup heights caused by quantifiable uncertainty in both first order source parameters e g rupture length slip length scaling and spatiotemporal complexity of earthquake rupture

the influence of sea surface temperature on surface wind in the eastern equatorial pacific weekly to monthly variability abstract temporal correlations between near equatorial surface wind and sea surface temperatures sst at 11 w in the eastern pacific ocean are investigated using data from an array of moored sensors between 5 n and 5 s the signature of tropical instability waves with periods of 20 30 days is apparent in time series of sst and both the meridional and zonal wind components results indicate the existence of a band of pronounced horizontal divergence in the surface wind field associated with the large meridional sst gradient equatorial front normally located just north of the equator perturbations of the equatorial front by the instability waves induce fluctuations in the overlying winds evidence of the air sea coupling is stronger in time series of the meridional gradients of wind and sst than between time series of the variables themselves the meridional differencing serves as a high pass filter in the space domain which removes planetary scale wind fluctuations that are unrelated to the local sst

aspects of palyno organic facies analysis comprehensive evaluation of the source rocks and age of some subsurface lower cretaceous core materials in the north western desert egypt abstract the palyno organic facies aspects of the subsurface lower cretaceous core samples are extensively investigated in three wells in the northern part of the western desert of egypt these wells are burg el arab 1 and mamura 1 mersa matruh 1 bax 1 max 1 and mmx 1 respectively the study is based on the palynofacies and organic geochemical analyses the palynofacies examination includes a statistical analysis of the different classes of organic particles by cluster analysis and principal component analysis pca this analysis leads to identify 4 palynofacies types a b c1 and c2 which are dominated by various levels of terrestrial floral materials the paleoenvironmental settings that are attributed to these palynofacies types are the distal suboxic oxic proximal oxic transitional oxic and highly distal oxic the principal component analysis pca differentiates between these palynofacies types mathematically by the biplot of components 1 and 2 the component 1 corresponds to distance from the terrestrial floral sources the identification of quantity type quality and thermal maturity of organic matter is discussed depending on the palynofacies and organic geochemical analyses the thermal maturity is assessed digitally by measuring the rgb color channels in the spore images and their corresponding thermal alteration index tai incorporated with values of tmax these measures are integrated in burial history models with geothermal gradient and depositional history the study reveals that most of the core samples represent generally fair to good enriched sources of gas prone type iii kerogen and less mixed gas oil type ii iii kerogen additionally some occasional high levels of organic conversions are recorded the burial history models indicate that oil expulsion window initiated in the cretaceous the examinations indicate mature oil sources in the alam el bueib formation in mmx 1 well the organic geochemical parameters are correlated versus the component 1 and sum of all components of pca the correlation coefficients r2 pointed to good correlation between the oxygen index oi toc and s2 and lower correlation with hydrogen index hi

dynamics of the shallow meridional circulation around intertropical convergence zones the generally accepted view of the meridional circulation in the tropical east pacific is that of a single deep overturning cell driven by deep convective heating in the intertropical convergence zone itcz similar to the zonal mean hadley circulation however recent observations of the atmosphere from the tropical eastern pacific have called this view into question in several independent datasets significant meridional return flows out of the itcz region were observed not only at high altitudes but also at low altitudes just above the atmospheric boundary layer this paper presents a theory and idealized simulations to understand the causes and dynamics of this shallow meridional circulation smc fundamentally the smc can be seen as a large scale sea breeze circulation driven by sea surface temperature gradients when deep convection is absent in the itcz region a simple model of this circulation is presented using observed values the sea breeze model shows that the pressure gradient above the boundary can indeed reverse leading to the pressure force that drives the shallow return flow out of the itcz the weather research and forecast model wrf is used to simulate an idealized hadley circulation driven by moist convection in a tropical channel the smc is reproduced with reasonable similarity to the circulation observed in the east pacific the simulations confirm that the smc is driven by a reversal of the pressure gradient above the boundary layer and that the return flow is strongest when deep convection is absent in the itcz and weakest when deep convection is active the model also shows that moisture transport out of the itcz region is far greater in the low level shallow return flow than in the high altitude return flow associated with the deep overturning and that a budget for water transport in and out of the itcz region is grossly incomplete without it much of the moisture carried in the shallow return flow is recycled into the boundary layer but does not appear to contribute to enhanced cloudiness in the subtropical stratocumulus poleward of the itcz

observation of the marine atmospheric boundary layer in the gulf of guinea during the 2006 boreal spring in situ satellite and model analyses data in april july 2006 are used to investigate the links between sea surface temperature sst and the marine atmospheric boundary layer mabl in the gulf of guinea the study region between 10 w and 6 e is divided into three areas with different characteristics the north area 4 5 n to 1 n with the wettest atmosphere and the warmest sst the upwelling area 1 n to 4 s with the strongest sst decrease and the south area 4 s to 8 s with a drier atmosphere and a more slowly decreasing sst than in the upwelling area the key zone of the air sea interactions in this region seems to be the sst front between north and upwelling areas on the one hand the study of the mabl on either side of the front shows a well mixed layer between the surface and about 500 m high sensitive to surface variations which gets shallower deeper when the sst decreases increases the mabl height about 1500 m follows the same variations but is not exactly collocated with the sst variations on the other hand the observation of the mabl across the sst front shows a strengthening of southeasterlies in the south area coinciding with a strong sst decrease in the upwelling area in the latter the wind weakens above the colder sst besides in the north area the wind strengthens above the warmer sst however the wind acceleration spans from the equator to 2 n in april and as far as 4 n in june a convergence zone is observed in the vicinity of 2 n in april suggesting a convection activity there favoured by the sst front copyright 2011 royal meteorological society

direct observations of atmospheric boundary layer response to sst variations associated with tropical instability waves over the eastern equatorial pacific tropical instability waves tiws with a typical wavelength of 1000 km and period of 30 days cause the equatorial front to meander and result in sst variations on the order of 18 28c vertical soundings of temperature humidity and wind velocity were obtained on board a japanese research vessel which sailed through three fully developed sst waves from 1408 to 1108w along 28n during 21 28 september 1999 a strong temperature inversion is observed throughout the cruise along 28n capping the planetary boundary layer pbl that is 1 1 5 km deep temperature response to tiw induced sst changes penetrates the whole depth of the pbl in response to an sst increase air temperature rises in the lowest kilometer and shows a strong cooling at the mean inversion height as a result this temperature dipole is associated with little tiw signal in the observed sea level pressure slp the cruise mean vertical profiles show a speed maximum at 400 500 m for both zonal and meridional velocities sst based composite profiles of zonal wind velocity show weakened intensified vertical shear within the pbl that is consistent with enhanced reduced vertical mixing causing surface wind to accelerate decelerate over warm cold ssts taken together the temperature and wind soundings indicate the dominance of the vertical mixing over the slp driving mechanism based on the authors measurements a physical interpretation of the widely used pbl model proposed by lindzen and nigam is presented

an unusual zone of seismic coupling in the bonin arc the 1972 hachijo oki earthquakes and related seismicity the 1972 february and december hachijo oki earthquakes ms 7 3 and 7 4 in the northernmost part of the izu bonin subduction zone are the only major events ms 7 0 in the bonin arc for the past 80 years relocation of the hypocenters using one smaller event having a wellconstrained focal depth as a master event shows that the depth of the february event is 10 km shallower than that of the december event we have determined the rupture process for both events by minimizing the error in waveform between observed and synthetic seismograms although the number of available stations are limited the depth range of the major energy release for the december event extends deeper than for the february one the rupture propagated up dip for both events it is likely that the rupture zone of the two events overlapped and that the december event ruptured the deeper part this suggestion is consistent with the observation that the aftershock zones of both events overlap with that of the december event shifted landward the waveforms of the december event have a smaller high frequency component than those of the february event suggesting that the stress at the thrust zone became more uniform or reduced after the february event

multiyear measurements of the oceanic and atmospheric boundary layers at the brazil malvinas confluence region 1 this study analyzes and discusses data taken from oceanic and atmospheric measurements performed simultaneously at the brazil malvinas confluence bmc region in the southwestern atlantic ocean this area is one of the most dynamical frontal regions of the world ocean data were collected during four research cruises in the region once a year in consecutive years between 2004 and 2007 very few studies have addressed the importance of studying the air sea coupling at the bmc region lateral temperature gradients at the study region were as high as 0 3 c km 1 at the surface and subsurface in the oceanic boundary layer the vertical temperature gradient reached 0 08 c m 1 at 500 m depth our results show that the marine atmospheric boundary layer mabl at the bmc region is modulated by the strong sea surface temperature sst gradients present at the sea surface the mean mabl structure is thicker over the warmside of the bmc where brazil current bc waters predominate the opposite occurs over the coldside of the confluence where waters from the malvinas falkland current mc are found the warmside of the confluence presented systematically higher mabl top height compared to the coldside this type of modulation at the synoptic scale is consistent to what happens in other frontal regions of the world ocean where the mabl adjusts itself to modifications along the sst gradients over warm waters at the bmc region the mabl static instability and turbulence were increased while winds at the lower portion of the mabl were strong over the coldside of the bc mc front an opposite behavior is found the mabl is thinner and more stable our results suggest that the sea level pressure slp was also modulated locally together with static stability vertical mixing mechanism by the surface condition during all cruises sst gradients at the bmc region modulate the synoptic atmospheric pressure gradient postfrontal and prefrontal conditions produce opposite thermal advections in the mabl that lead to different pressure intensification patterns across the confluence

source rock evaluation and nature of hydrocarbons in the khalda concession shushan basin egypt s western desert abstract organic geochemical studies were undertaken on 241 jurassic cretaceous ditch cuttings samples and 9 gases and 10 crude oils from some productive mesozoic pay zone intervals in the khalda concession shushan basin northern western desert egypt we aim to investigate source rock characteristics origin of gases nature of oils and their inferred source rocks and to establish genetic relationships the middle jurassic khatatba formation and older rocks contain organic rich mature coaly and carbonaceous shales which are the main source for hydrocarbons in egypt s western desert including the shushan basin which generally contains kerogen type iii with some contribution of type iii ii kerogen molecular and isotopic composition indicates that the khalda gases are of thermogenic origin a mature 0 6 2 0 ro source rock with terrigenous organic matter kerogen type iii was identified as a precursor of wet thermogenic gases in the shushan basin geochemical results indicate that the oil samples were derived from a source rock deposited mainly under oxic conditions and containing terrigenous organic matter biomarker data indicate that paraffinic oils and condensates from the shushan basin were derived from mature source rocks within the oil window the light hydrocarbon data suggests that the analyzed oils can be classified into two groups as a result of evaporative fractionation and maturation this signal of a secondary reservoir transformation which is not revealed by biomarker analysis emphasizes the importance of integrating biomarker and light hydrocarbon data to understand variations in the chemical composition and origin of oils

palynofacies prediction of distance from sediment source a case study from the upper cretaceous of the pyrenees quantitative variations in the size shape and preservation state of microscopic plant debris assemblages correlate with the actual distance of the sample site from the coastal siliciclastic sediment source a case study from a shelf to basin transect in the upper cretaceous of the spanish pyrenees reveals that 1 the diameter of equant black wood phytoclasts 2 the ratio of equant to lath shaped black wood phytoclasts and 3 several other parameters show predictable changes over a 55 km onshore offshore transect these parameters primarily reflect sedimentological sorting based on particle size and density rather than paleoecological gradients when only samples from the transgressive systems tract are considered multiple regression models predict the distance from the source with a standard error of 5 km r 2 0 84 0 93 these parameters also allow the maximum flooding surface to be more precisely located within mudstone dominated sections by applying the lateral regression relationship to stratigraphic data a quantitative estimate can also be made for the scale of lateral facies shifts through depositional sequences here 10 km

depth distribution of coseismic slip along the nankai trough japan from joint inversion of geodetic and tsunami data coseismic slip distribution on the fault plane particularly in the downdip direction associated with large subduction earthquakes can be estimated by joint inversion of geodetic and tsunami data two large earthquakes the 1944 tonankai earthquake mw 8 1 and the 1946 nankaido earthquake mw 8 3 occurred on the nankai trough southwestern japan where the philippine sea plate is subducting beneath the eurasian plate the source areas of these events extended over both land and ocean coseismic crustal movements on land were measured by leveling while those in ocean were recorded as tsunami waveforms on tide gauges the coseismic slip distribution inverted from these data shows that the slip on the shallower part of the fault plane is comparable to that on the deeper parts this indicates that large coseismic slip can occur beneath an accretionary wedge where current seismicity is low the result has implications for other subduction zones having a similar tectonic environment such as for the pacific northwest region of the united states although the possibility of a large earthquake there is still debated should a large subduction earthquake occur in this region coseismic slip on the shallow part could be large and the potential for large tsunamis is high

atmospheric boundary layer adjustment to the synoptic cycle at the brazil malvinas confluence south atlantic ocean 1 this study analyzes and discusses atmospheric boundary layer vertical profiles of potential temperature specific humidity and wind speed at each of the sides of the brazil malvinas confluence in the southwestern atlantic ocean such confluence is characterized by the meeting of water masses with very different characteristics the southern waters of the malvinas current can be several degrees colder and appreciably less salty than the northern brazil current waters at the same time a synoptic cycle can be identified at the region marked by the successive passages of frontal systems and extratropical cyclones the different phases of the synoptic cycle lead to different thermal advections at the confluence causing respective different patterns of atmospheric boundary layer adjustment to the surface heterogeneity induced by the confluence in the present study this adjustment along the synoptic cycle is analyzed using data from five experiments performed across the confluence from 2003 to 2008 in each of the campaigns a number of soundings were launched from a ship at both sides of the confluence a climatological analysis with respect to the closest frontal passage is presented and it suggests that the observations collected at each of the years analyzed are referent to a different day of the synoptic cycle the average profiles at each side of the confluence are in agreement with previous modeling studies of warm and cold thermal advection patterns over an oceanic front furthermore our study shows that peculiar transitional characteristics are also observed between the conditions of well established warm and cold advection at many phases of the synoptic cycle a strongly stratified boundary layer occurs at one or both sides of the confluence some of the observed characteristics such as a large moisture accumulation near the surface suggest that existing sensible and latent heat fluxes parameterizations fail under very strong stratifications and the consequences of this deficiency are analyzed

digital quantification of the miospore coloration to assess the thermal maturity novel rgb based measuring technique abstract the post depositional thermal maturity and its related chemical changes induce the sporomorphs color alteration which is a common useful tool in the optical microscopy of the organic matters om and their pre geochemical studies the present contribution uses the modern available opportunity of digital technology to achieve a quantifying system technique which includes color measurements and their possible graphic presentation the normal digital images of sporomorphs from several ages and geological settings are used to obtain color measurements in the form of digital red green and blue triple color system rgb these measurements were accomplished using some software programs such as photoshop or imagej with employing average microscope setup the triple rgb color readings are plotted on a ternary diagram which is divided into three fields these fields express the maturity levels the presented new rgb based quantifying technique is economic and provides a simple examination for maturity which is linked to the hydrocarbon generation this can partially replace or walk side by side with the vitrinite reflectance microscopy

linear moment tensor inversion for shallow thrust earthquakes combining first motion and surface wave data we derive a linear moment tensor inversion method which we call second nodal plane inversion for obtaining a double couple focal mechanism when only one nodal plane is known this typically is the case for shallow thrust events for which only the steeply dipping nodal plane can be determined from teleseismic first motions conventional moment tensor inversion methods are known to fail for these events because the portion of the moment tensor corresponding to vertical dip slip faulting is extremely inefficient in exciting surface waves in this paper we invert long period 256 s fundamental mode rayleigh waves from the ida network the inversion technique can also be applied to body wave amplitude data or to entire records as a sum of normal modes given the appropriate normal equations we study several shallow h 35 km thrust earthquakes for which the steeply dipping nodal plane can easily be found from body wave first motions in contrast to standard surface wave moment tensor inversion techniques which have serious stability problems for such shallow events our technique successfully finds the scalar moment and second nodal plane

inversion of long period p waves from great earthquakes along subduction zones abstract long period p waves from subduction zone earthquakes in the moment range from 7 1027to 8 1029dyn cm are analyzed using an iterative deconvolution method in addition to discrete subevents which effectively contribute to the observed seismograms the long period component of the moment rate function is derived with the constraint that the total seismic moment is equal to the moment determined from long period surface waves it is shown that great earthquakes can be described by several subevents with a duration of about 10 s which changes little from earthquake to earthquake in the above moment range the long period component of the moment rate function becomes larger for a greater earthquake the greatest earthquakes of mw 9 additionally involve subevents with another duration scale much longer than 10 s it is also shown that the local stress drop is 1 order of magnitude larger than the stress drop averaged over the entire fault plane the constancy of the local stress drop as well as the average stress drop holds among various magnitudes of earthquakes these observations suggest an essential similarity in the mode of dislocation distribution

source rock evaluation by pyrolysis gas chromatography a pyrolysis gas chromatography system has been developed for the rapid evaluation of potential source rocks for the determination of organic richness and maturation this system uses the pyrolysis methods previously described however the determination of hydrocarbon production type and the identification of contamination by migrated hydrocarbons or drilling additives are accomplished by gas chromatographic gc analysis of the thermal extracts and pyrolysis products of rock samples or isolated kerogens the production type is recognized either qualitatively by gc fingerprint traces or quantitatively by hydrocarbon composition c1 to c6 c6 to c11 c11 from the kerogen peak ii pyrolysate oil prone erogens are recognized by gc traces with a full spectrum of c1 to c28 hydrocarbons or by high concentrations of c11 compounds in contrast gas prone kerogens are characterized by the predominance of light hydrocarbons from c1 to c4 and higher contributions of aromatic compounds mixed type production is intermediate in character between the two contaminants are identified from the gc analysis of the thermally extractable material in peak i possible mineral organic matter reactions during sample heating make interpreting data from whole rock samples more difficult

spatial variability of atmospheric boundary layer structure over the eastern equatorial pacific abstract variations in the atmospheric boundary layer structure over the eastern equatorial pacific are analyzed using 916 soundings collected during the first global atmospheric research program global experiment unstable boundary layer structures are observed much more frequently in soundings north of the ocean front located near 2 5 n in the eastern equatorial pacific than in soundings south of the front an objective criterion is applied to identify the presence of the transition layer a weak stable layer near cloud base in the soundings the transition is observed in about 45 of the soundings in both the unstable and the inversion categories a comparison of soundings over the cold tongue with those over the itcz indicates that differences in static stability between these regions are limited to the layer from the surface to about 850 mb which is the mean height of the inversions capping the cloud layer over the cold tongue the cold tongue soundings on average are found to be drier from the sur

palynology and chronostratigraphy of the upper cretaceous in the subsurface of the barinas area western venezuela palynological and well log analyses of cretaceous strata from southeastern venezuela allow the recognition of third order eustatic cycles and are the basis for a chronostratigraphic framework with a datum approximately every 0 8 m y this definition permits the correlation of events in the local geologic evolution with regionally important sedimentological and tectonic events an early cretaceous marine transgression reached areas north of the andes before 113 ma however according to our framework the transgression extended into the barinas area shortly after 98 ma an interval of relatively low sea level from 95 5 ma to 91 5 ma is represented by oil bearing sandstones and dolomitic limestones a second marine transgression reached the area at approximately 91 5 ma and resulted in the deposition of organic rich clastics that are correlatable with source rocks from areas to the north a major hiatus santonian campanian encompasses approximately 11 m y and probably is related to the emplacement of oceanic rocks in western colombia a younger major hiatus maastrichtian eocene encompasses approximately 26 m y and probably is related to the emplacement of the lara nappes in northern venezuela two other minor intra turonian and intra maastrichtian hiatuses are recognized and encompass approximately 1 5 m y each

the depth of the october 1981 off chile outer rise earthquake ms 7 2 estimated by a comparison of several waveform inversion methods the determination of source depth of the october 1981 ms 7 2 outer rise earthquake off the chilean coast has important implications for the stress state of the subducting plate we analyze the chile earthquake using three different waveform inversion methods in order to check the consistency of these methods and to estimate the source depth the methods we used are 1 1 honda and seno s 1989 inversion method in which we incorporate both long period p waves and surface waves 2 2 nab lek s 1984 body wave inversion methods for long period p and sh waves 3 3 seno and honda s 1988 deconvolution method in which we assume vertically distributed point sources and use long period p waves these methods give consistent results which suggest that the centroid depth and depth extent of the chile earthquake lies between 20 to 45 km measured from the sea surface this conclusion is contradictory to those obtained by the previous workers who prefer a shallow 25 km source depth we found that the gdsn long period data alone cannot constrain the source depth well the shape of deconvolved source time function is found to be strongly dependent on the assumption of point and distributed sources and the crustal structure used in the deconvolution the source depth obtained in this study shows that the 1981 chile outer rise earthquake possibly occurred because of the compression associated with the bending of the subducting plate

analysis of the trade off between hypocentral depth and source time function focal depth determination for shallow 60 km intermediate size ms 6 5 to 7 5 earthquakes continues to be problematic for these events the depth phases i e pp and sp are not distinctly separated in time and thus synthetic modeling of wave shapes becomes necessary unfortunately the uniqueness of the solution is not easily determined because of the trade off between various focal parameters we have investigated the trade off between depth and source function both theoretically and experimentally the changes in the green s function caused by an incorrect assumed depth can almost always be compensated by changes in the source function producing the same observed seismogram thus there is considerable trade off between depth and the source function perturbing the depth from the true depth leads to a more complicated source function the simplest source function then pinpoints the true depth we have used two different measures of simplicity the varimax norm v max and the half absolute moment time t 1 2 both measures successfully characterize the complications that appear in the source functions for incorrect assumed depths the true depth of an event can be interpreted from the resultant v max versus depth and t 1 2 versus depth curves thus we have a technique that determines the depth range of faulting in a systematic quantitative fashion our observations from the synthetic study have been applied to an outer rise event off the coast of central chile 16 october 1981 ms 7 2 to an event in southern mexico 24 october 1980 ms 7 0 and to the borrego mountain event in southern california 9 april 1968 ms 6 4 resulting in faulting depth ranges of 0 to 20 5 km 60 to 70 5 km and 10 to 14 5 km respectively

shallow meridional circulation in the tropical eastern pacific abstract based on four independent datasets this study presents observational evidence of a shallow meridional circulation cell in the eastern tropical pacific in this shallow meridional circulation cell the northerly cross equatorial return flow from the itcz into the southern hemisphere is found immediately above the atmospheric boundary layer in contrast to the classic concept of the hadley type deep meridional circulation whose northerly return flow resides in the upper troposphere the strength and depth of this shallow meridional circulation undergo a distinct annual cycle possible causes and climatic implications of this shallow meridional circulation are discussed

regional 3 d heterogeneities by waveform inversion application to the atlantic area the waveform inversion method described in woodhouse dziewonski 1984 was modified to retrieve regional scale 3 d heterogeneities by using the minor arc part of seismograms the lateral heterogeneities are expanded horizontally into blocks 10 10 and radially into legendre polynomials up to order 3 0 670 km and thus the results show much fine details of lateral variation than previous global scale studies we assumed that the heterogeneities produce the perturbation of eigenfrequencies which are the minor arc average of local eigenfrequency shift we applied the method to the upper mantle beneath the atlantic ocean and its environments care was taken about the weighting of the data set we found that the fit of each seismogram became better when the weighting of each seismogram is proportional to the inverse of initial data residuals resolution is good in the triangular region surrounded by south america europe and north america resolution is not good in the south atlantic because of the poor path coverage depth resolution is not clear because of the use of legendre polynomials though the results suggest a broad half width of the order of 200 km or more we found some similarities between previous global studies and our results for example low velocities beneath the east pacific rise chile rise and azores triple junction and a high velocity canadian shield are obtained however there are also differences the high velocity zone beneath the brazilian shield at shallow depth is not a prominent feature in this study instead we found a somewhat unexpected feature near the romanche and vema fracture zones where shallow positive anomalies exist smoothed results calculated by the spherical harmonic expansion are also shown for the purpose of comparison with global studies

source mechanisms of twenty six large shallow earthquake ms 6 5 during 1980 from p wave first motion and long period rayleigh wave data source mechanisms of 26 large shallow earthquakes are determined in terms of a double couple point source with a correction for the nondirectional part of source finiteness by using p wave first motions and long period rayleigh wave spectra recorded on wwssn ida and gdsn networks the combined use of both data sets allows us to determine the double couple mechanism uniquely in most cases constrained linear moment tensor inversion m xz m yz 0 correctly determines the strike of the fault but fails to estimate the dip and underestimates the scalar moment all thrust events along the deep sea trenches analyzed in this study show nodal planes which dip perpendicular to the trench axis at an angle shallower than 45 the fit to data of the double couple inversion is comparable to that of the constrained moment tensor inversion using the phase spectra of surface waves we can detect a slow source process with an accuracy of about 10 to 20 sec

low level inversions over the tropical pacific thermodynamic structure of the boundary layer and the above inversion moisture structure abstract the structure of the boundary layer over a broad region of the equatorial pacific is studied using dropwinsonde measurements made in january february may and june of 1979 low level inversions of sufficient strength to inhibit deep convection are found to be present in more than 50 of the soundings these inversions appear to play a critical role in regulating convective activity over the central and eastern pacific the tops of the inversions have an average pressure level of approximately 300 mb and show little latitudinal or longitudinal variation the majority of the inversion soundings approximately 70 have a reversal in the mixing ratio profile qreversal above the inversion that appears as a dry layer at the top of the inversion layer capped by a relatively moist layer this moist layer is on the average 2 g kg 1 more moist than the corresponding soundings that have no qreversal no systematic regional or temporal variations in the frequency of occurrence of the qreversal or the str

seismic moment tensors and source depths determined by the simultaneous inversion of body and surface waves we present a linear moment tensor inversion method that incorporates both body and surface wave data the source coordinates are fixed during the inversion and the source depth is determined by applying the inversion at several depths and taking the depth that produces the minimum residual the inversion is carried out in the time domain for body wave data and in the frequency domain for surface wave data the fundamental rayleigh waves at the period of 256 s from ida stations and the long period p waves from wwssn and gdsn stations whose angular distances are from 30 to 90 are used as the data the simultaneous inversion of both body and surface wave data sets has several merits because of the body wave constraints the present method gives reasonable solutions at shallow depths 30 km where long period surface wave inversions become unstable although the inversion using only body wave data is unstable in the sense that it allows for a variety of solutions with a slight change in the assumed depth probably because of the noise present and poor coverage of body wave data to determine the source mechanisms the inclusion of surface wave data makes the solution stable this is because the surface wave data constrain nodal plane strikes we may also expect better resolution in source depth by including the body wave data because the local crustal structure above the source can be taken into account to generate the green s function we applied our method to two large earthquakes one occurring at the triple junction off boso peninsula central honshu on 18 september 1984 and another at the outer rise area off the chile trench on 16 october 1981 the scalar moments of the boso oki and chile earthquakes are estimated to be 3 2 1026 dyn cm and 6 3 1026 dyn cm respectively the ratio of the minimum absolute eigenvalue of the moment tensor to the maximum which may measure the non double couple component is less than 10 for both earthquakes this suggests that their sources are essentially a double couple the source depths of both events are determined as 30 km the boso oki event is indicative of hinge faulting within the pacific slab at the triple junction the chile event is consistent with compressional bending stress in the deeper part of the lithosphere at the trench outer rise area off chile

middle miocene palaeoenvironments of the niger delta abstract in order to recognize the palaeoenvironments of the deltaic sequence of the middle miocene oil bearing e2 0 reservoir in the kolo creek field investigations of sediment grain size textures structures trace fossils mineralogical composition diagenetic imprints palynodebris types palynomorphs and foraminifera have been carried out on materials from two boreholes using this multidisciplinary approach the following have been identified in the reservoir ten lithofacies two palynofacies associations a total of 103 palynomorph taxa and a low diversity assemblage of benthic foraminifera these criteria have provided information on the positions of the deposits relative to the palaeocoastline as well as the physical and ecological conditions within the delta the overall depositional conditions were found to be broadly similar to those in the present day niger delta although the climatic conditions were somewhat drier in the middle miocene as reflected in the abundance of the grass pollen graminidites seven or possibly eight deltaic sub environments of deposition have been recognized based on an interpretation of gamma ray and resistivity log profiles as well as sedimentological and microfossil data from cores of two boreholes in the field these depositional settings are the distributary channel fill tidal channel fill lagoon tidal flat lagoonal delta flood tidal delta in the lower delta plain the coastal barrier and the delta fringe and prodelta in the outer delta the two palynofacies associations a c and b d which emerged from average linkage cluster analysis of the palynodebris are environmentally significant

effects of centroid location on determination of earthquake mechanisms using long period surface waves determination of shallow earthquake source mechanisms by inversion of longperiod 150 to 300 sec rayleigh waves requires epicentral locations with greater accuracy than that provided by routine source locations of the national earthquake information center neic and international seismological centre isc the effects of epicentral mislocation on such inversions are examined using synthetic calculations as well as actual data for three large mexican earthquakes for rayleigh waves of 150 sec period an epicentral mislocation of 30 km introduces observed source spectra phase errors of 0 6 radian for stations at opposing azimuths along the source mislocation vector this is larger than the 0 5 radian azimuthal variation of the phase spectra at the same period for a thrust fault with 15 dip and 24 km depth the typical landward mislocation of routinely determined epicenters of shallow subduction zone earthquakes causes source moment tensor inversions of long period rayleigh waves to predict larger fault dip than indicated by teleseismic p wave first motion data for dip slip earthquakes inversions of long period rayleigh waves that use an erroneous source location in the down dip or along strike directions of a nodal plane overestimate the strike dip and slip of that nodal plane inversions of strike slip earthquakes that utilize an erroneous location along the strike of a nodal plane overestimate the slip of that nodal plane causing the second nodal plane to dip incorrectly in the direction opposite to the mislocation vector the effects of epicentral mislocation for earthquakes with 45 dip slip fault mechanisms are more severe than for events with other fault mechanisms existing earth model propagation corrections do not appear to be sufficiently accurate to routinely determine the optimal surface wave source location without constraints from body wave information unless extensive direct path r1 data are available or empirical path calibrations are performed however independent surface wave and body wave solutions can be remarkably consistent when the effects of epicentral mislocation are accounted for this will allow simultaneous unconstrained body wave and surface wave inversions to be performed despite the well known difficulties of extracting the complete moment tensor of shallow sources from fundamental modes

depth extent of rupture of the 1981 chilean outer rise earthquake as inferred from long period body waves we have investigated how well the depth extent of rupture can be determined for a shallow dip slip earthquake from long period wwssn body waves the 16 october 1981 chilean outer rise earthquake mw 7 2 is analyzed as an example calculation of the resolution matrix for the vertical distribution of displacement rate on the fault plane shows that the depth extent of rupture cannot be resolved better than 20 km even when the data set consists of both p and s waves although the depth extent of rupture of the 1981 earthquake is too small to be resolved it is possible to infer some constraints from the point source depth in combination with the source duration while inversion for the depth extent of rupture can be formulated as a linear problem determination of the point source depth is nonlinear and a formal resolution study cannot be conducted the point source depth estimate for the 1981 earthquake is 28 to 32 km 80 confidence interval the source duration is 8 sec assuming a rupture velocity of 3 km sec we have explored several rupture models in a synthetic experiment to shed light on the relation between point source depth and centroid depth the experiments show that point source depths agree with the centroid depth given that there is poor resolution of the depth extent of rupture of the 1981 earthquake we conclude from the synthetic experiments that the earthquake may have ruptured updip to a depth as shallow as 17 km or downdip to a depth as deep as 43 km

the influence of sea surface temperature gradients on stratiform cloudiness along the equatorial front in the pacific ocean abstract satellite observations of visible cloudiness and sea surface temperature sst are used to test the hypothesis that the configuration of cool low level winds blowing across a sharp sst front in the equatorial eastern pacific gives rise to stratiform clouds on the warm downstream side of the front the results show that there is a maximum in low clouds over the equatorial front during the cold season of 1988 when the front and cross isotherm winds were strong the low cloud maximum was reduced in the warm el nino year of 1987 consistent with the weakening of the front instability waves along the equatorial front were pronounced during the summer and autumn of 1988 the results show a strong association between visible cloud and the sst waves with enhanced reduced cloudiness in the warm troughs cold crests of the waves

joint inversion of observed gravity and gps baseline changes for the detection of the active fault segment at the red river fault zone summary methods for the determination of active fault segments by inversion of temporal gravity and gps global positioning system baseline changes are presented in this paper a numerical test is performed for estimating four types of fault movement models from simulated gravity changes with random noise results of the numerical test show clearly the possibility of detecting fault movement from observed gravity changes based on this work active segments of the red river fault zone rrfz are investigated by inversion of observed gravity changes from 1985 november to 1988 november and gps baseline changes from 1988 august to 1991 october both separately and jointly the results from the joint inversion indicate an active segment of the red river fault characterized by right lateral strike slip 1 0 0 2 m with a length of 232 3 km a width of 6 3 km a dip angle of 100 5 80 5 ne a depth of 10 1 km and a strike direction of 169 2 se these characteristics of the detected active segment at the rrfz agree with those of geological investigations and seismic activity in the area estimated horizontal displacements at the rrfz indicate that drastic movements are concentrated on the northern segment whereas the southern segment of the fault is relatively stable the estimated fault slip rate along strike at the red river fault is 8 11 mm yr 1 larger than the geological estimate of 6 mm yr 1 which implies that the rrfz is presently active the results obtained in this research support previous interpretations that the fault movements at the rrfz are mainly a result of the collision of the indian and the eurasian plates

regional source rock mapping using a source potential rating index a method has been developed to combine sediment thickness organic carbon content and thermal maturity data from potential source rock units into a single mappable parameter that can be used to indicate areas of potential hydrocarbon generation this parameter is computed by multiplying the average percent organic carbon by the effective source rock thickness of a formation this yields a richness factor that is then multiplied by maturity scaling factors to give source potential ratings for oil and or gas generation the rating values can be combined with kerogen type data if available to refine these assessments of generating potential the rating index can also be used with burial history curves and thermal maturation modeling to look at source potential during geol gic time an example is given of the rating index mapping applied to the bakken formation in the williston basin the source potential rating index provides objective semiquantitative measures by which the source potential of a single formation can be compared within an area or by which the source potential of two or more formations can be compared in the same or different basins in conjunction with structural analysis of a basin the resulting maps can help the explorer explain known hydrocarbon accumulations trace migration pathways and point toward new areas for exploration

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

on the atmospheric boundary layer over the equatorial front abstract this paper presents surface meteorological data and boundary layer profiles from a single meridional transect across the equator along 125 w collected during the pan american climate study mooring cruise in september of 1998 these observations are unique because they occurred at the start of a cold event in the eastern tropical pacific when the sst gradients along the equatorial front were near their climatological maximum in addition to the anomalous cold conditions encountered near the equator an added benefit of this limited study is the relatively high station resolution across the front the meridional minimum in sst and center of the cold tongue was 20 9 c and occurred at 0 4 n an equatorial front was located to the north where sst increased linearly to 25 5 c at 2 0 n the atmospheric boundary layer abl was stable over the cold tongue an unstable abl developed over the warm side of the front in less than 55 km the unstable abl was found at two more stations over the warm side of

the influence of sea surface temperature on surface wind in the eastern equatorial pacific seasonal and interannual variability abstract the climate of the eastern pacific exhibits a pronounced equatorial asymmetry boundary layer air originating in the southern hemisphere trades crosses the equator and flows into the intertropical convergence zone itcz whose southern limit is nearly always located at least 4 to the north of the equator the sea surface temperature sst distribution is characterized by a prominent cold tongue centered 1 s a strong frontal zone centered 2 n and a warm eastward current centered near 5 n the surface wind field exhibits a pronounced horizontal divergence as the air flows northward across the oceanic frontal zone these features vary in strength in response to the annual cycle and the el nino southern oscillation phenomenon the northward cross equatorial surface winds the cold tongue and the frontal zone all tend to be strongest during the cold season july through november during the cold season of the coldest years when the cold tongue is most prominent the cross equatorial flow t

effects of near source bathymetry on teleseismic p waveforms teleseismic p waveforms from submarine earthquakes show water reverberations that are often poorly modeled by synthetic seismograms this study suggests that considerable misfit results from the non horizontal nature of the seafloor in the epicentral region and examines this effect for a planar dipping water crust interface geometric ray theory synthetics calculated for a double couple source show that p waveforms are extremely sensitive to seafloor orientation because of the large impedance contrast across the boundary seafloor dips as small as 0 5 significantly modify the ray paths affecting the take off angle at the source reflection and transmission coefficients at the interface geometric spreading and travel time to test the applicability of such modeling p waveforms from the march 29 1976 cocos ridge intraplate earthquake were studied the waveforms many of which show prominent water multiples poorly modeled with flat lying bathymetry were inverted for the best fitting planar ocean bottom orientation using a grid search technique synthetics computed for the best fitting seafloor orientation match the data much better than synthetics for a flat lying structure and reproduce the observed azimuthal dependence of water multiple amplitudes the derived ocean bottom dip angle and direction are in agreement with bathymetric charts suggesting p waveforms provide constraints on the seafloor orientation in the epicentral region green s functions incorporating the effects of bathymetry should provide better resolution of the source parameters of submarine earthquakes

source rock evaluation and sequence stratigraphic model based on the palynofacies and geochemical analysis of the subsurface devonian rocks in the western desert egypt abstract the paleozoic rocks are the least explored among the subsurface successions in the western desert of egypt this contribution submits a significant record for the palynofacies and geochemical analysis for an important division of the subsurface paleozoic rocks from faghur 1 and nw d302 1 boreholes the palynofacies of the devonian sediments of zeitoun formation extensively verified and classified the palynofacies classification depended on the statistical techniques of cluster and correspondence analysis the cluster analysis discriminated four classes of palynofacies in r mode which are brown wood palynofacies class r1 spore palynofacies class r2 aom opaque phytoclasts palynofacies class r3 and marine phytoplankton palynofacies class r4 in the q mode the cluster analysis revealed three palynofacies types which are palynofacies type c palynofacies type b palynofacies type a the combination of cluster and correspondence analysis is employed to interpret the evolution of basin dynamics and the mechanisms that controlled the deposition of the devonian rocks three basic environmental settings were recognized and they include 1 oxic highly proximal shelf setting 2 oxic proximal shelf setting and 3 oxic distal shelf the high oxygenation levels are confirmed by the inorganic geochemical analysis of fe ts fe and ts toc in the samples from faghur 1 borehole the paleoenvironmental reconstruction is used to identify four 2nd order stratigraphic sequences in the studied sections which are devseq1 devseq2 devseq3 and devseq4 these sequences are systematically described and correlated with their equivalent global devonian sequences the palynofacies investigation is integrated with the inorganic and organic geochemical analysis to evaluate the potentially of hydrocarbon generation from the probable source rocks in the studied sections and its onset timing the identified kerogen types are mostly mature tai range between 2 and 3 and tmax range between 427 and 439 c gas prone type iii with poor organic enrichment toc

a practical model for organic richness from porosity and resistivity logs a practical method the delta log r technique for identifying and calculating total organic carbon in organic rich rocks has been developed using well logs the method employs the overlaying of a properly scaled porosity log generally the sonic transit time curve on a resistivity curve preferably from a deep reading tool in water saturated organic lean rocks the two curves parallel each other and can be overlain since both curves respond to variations in formation porosity however in either hydrocarbon reservoir rocks or organic rich non reservoir rocks a separation between the curves occurs using the gamma ray curve reservoir intervals can be identified and eliminated from the analysis the separation in organic rich intervals results from two effects the orosity curve responds to the presence of low density low velocity kerogen and the resistivity curve responds to the formation fluid in an immature organic rich rock where no hydrocarbons have been generated the observed curve separation is due solely to the porosity curve response in mature source rocks in addition to the porosity curve response the resistivity increases because of the presence of generated hydrocarbons the magnitude of the curve separation in non reservoirs is calibrated to total organic carbon and maturity and allows for depth profiling of organic richness in the absence of sample data this method allows organic richness to be accurately assessed in a wide variety of lithologies and maturities using common well logs

recurring patterns of total organic carbon and source rock quality within a sequence stratigraphic framework sequence stratigraphy has been combined with total organic carbon toc analysis from well logs core and cuttings to develop a model of toc accumulation in marine source rocks routine well profiling of toc in marine source rocks has revealed that recurrent patterns in the vertical distribution of toc occur that can be explained with sequence stratigraphic concepts the model assumes that the principle controls on organic carbon accumulation are 1 the presence of low oxygen conditions at the sediment water interface and 2 sedimentation rate under these circumstances toc will vary inversely with terrigenous clastic influx if accommodation is high clastic influx is low in distal locations and the resulting weight percent toc in basinal sediments is increased th maximum toc in a vertical profile through a single marine sequence probably correlates to the maximum flooding surface toc decreases above this surface due to increasing sediment dilution during highstand progradation and decreases below it with the higher sedimentation rate of the older transgressive systems tract commensurate with toc increase towards the maximum flooding surface the organic matter type becomes more marine and therefore increasingly oil prone several marine source rock examples are presented as well as a lacustrine example which also conforms to the marine model

buoyancy reversal decoupling and the transition from stratocumulus to shallow cumulus topped marine boundary layers the transition in a marine boundary layer mbl from stratocumulus topped to shallow cumulus topped is investigated by using a large eddy simulation les model the experiments performed aim to examine the influence on the transition of 1 the probability of buoyancy reversal at the mbl top i e situations in which the mixture of two air parcels becomes denser than either of the original parcels due to phase change or other nonlinear processes involved in the mixing and 2 the degree of decoupling in the mbl i e the strength of a shallow stably stratified layer near cloud base our results suggest that a stratocumulus topped mbl is most likely to transit to a cumulus topped one when 1 there exists high probability of buoyancy reversal at the mbl top and 2 the mbl is decoupled due to large surface evaporation we argue that a parameterization that includes representation of those two effects combined has the potential to provide a simple way of predicting the mbl transition in climate models

neogene sequence stratigraphic architecture of the nile delta egypt a micropaleontological perspective abstract the sequence stratigraphic architecture of the neogene section from the subsurface nile delta is resolved based on exceptionally well preserved microfossils from the offshore ndob 1 borehole the architecture is configured on bathymetry variations and statistical parameters as deduced from the relative abundance of foraminiferal associations the statistical parameters include ratios of planktic versus benthic foraminifera and cluster and correspondence analysis of the twelve most commonly used benthic foraminiferal genera as proxies of water depths the combination of cluster and correspondence analysis was employed to decipher the evolution and dynamics of the basin and the mechanisms that controlled the deposition of neogene sequences in the nile delta region four basic environmental settings were recognized 1 a middle to outer neritic eutrophic setting 2 a middle to outer neritic mesotrophic setting 3 an outer neritic to upper bathyal mesotrophic setting and 4 an upper bathyal mesotrophic setting eight stratigraphic sequences were identified in the neogene nile delta section three sequence in the miocene mseq1 mseq2 and mseq3 three in the pliocene pseq1 pseq2 and pseq3 and two in the pleistocene ptseq1 and ptseq2 these sequences are systematically measured and described in terms of time space and water bathymetry the sequence boundaries and flooding surfaces were dated using high resolution microfossil biochronology and stratigraphic index markers individual sequences and boundaries were correlated with international and local sequence stratigraphic models the new sequence stratigraphic model established here provides age calibrated surfaces for inter basinal correlations and opens new avenues for hydrocarbon reservoir exploration

waveform inversion for three dimensional density and s wave structure long period seismic data longer than about 100 s are sensitive to density as well as p wave and s wave structure in the earth seismograms containing overtone and fundamental mode signals are inverted directly for density and s wave velocity structure a simple relation between p wave and s wave velocity perturbations is assumed in order to reduce the number of unknowns a model is parameterized by spherical harmonics up to degree and order 8 and by five knots in depth at 30 220 450 670 and 882 km with linear interpolation between adjacent knots density resolution is good only at shallow depths in fact only the average in the upper 200 km is marginally resolved s wave resolution is generally good throughout the depth range s wave results show good correlation to surface geological features and are similar to previous studies density results show quite different patterns from s wave maps high density regions appear along the subduction zones surrounding the pacific ocean and low density regions appear in most major continents most continents have low density and high s wave velocity which suggests that continental mantle consists of compositionally different materials since thermal effects can never produce such perturbations high s wave velocity also suggests a relatively cold geotherm for continents and thus continents should consist of significantly low density material such as depleted mantle rocks as proposed by many researchers before the density map also correlates well with a geoid map for spherical harmonic components l 4 6 but not for l 2 3 it suggests that sources for these geoid undulations l 4 6 are in the upper mantle probably in the upper 300 400 km but those for l 2 3 are in deeper regions

an experiment in systematic study of global seismicity centroid moment tensor solutions for 201 moderate and large earthquakes of 1981 data from the global digital seismograph network were used to obtain centroid moment tensor solutions using the method of dziewonski et al 1981 results were obtained for 201 earthquakes ranging in seismic moment from 7 1023 to 3 1027 dyne cm the wide dynamic range of the sro asro stations allows us to investigate using the same algorithm series of events among which the smallest and the largest may differ in moment by a factor as large as 1000 among the events studied is a particularly interesting series in january 1981 off the island of honshu the main shock was preceded by three foreshocks and followed by four aftershocks all falling within the range of our analysis there is an indication that the source mechanism changes with the size of the event statistical analysis of the results for all earthquakes reveals that the half duration of shallow and intermediate events is approximated by 1 6 10 8 m01 3 the shifts in origin time for deep focus earthquakes are indicative of the general complexity of these events which depends only weakly on the seismic moment the extreme departures from a double couple mechanism seem to depend both on the moment and on the focal depth while for shallow earthquakes these departures decrease from a maximum at about 1025 dyne cm with increasing moment the reverse appears to be true with respect to deep focus earthquakes shallow earthquakes north of new guinea and along the solomon islands show systematic and substantial departures from the double couple mechanism

petroleum play of the lower cretaceous alam el bueib formation in the el noor 1x well in the north western desert egypt a sequence stratigraphic framework abstract the north umbaraka concession in umbaraka basin in the northern the western desert of egypt has been the subject of continuous exploration efforts in the recent years despite many oil discoveries gave evidence of a working petroleum system however there is little economic production the petroleum plays of the alam el bueib formation are in the central focus of the exploration in this region because of their high economic reservoir potentiality in other areas of the western desert in the present study three powerful tools are used to delineate the sequence stratigraphic frame that considers the occurrences of the petroleum play chances of alam el bueib formation in el noor 1 well these tools are palynofacies electric log and organic geochemistry the palynofacies analysis revealed three biotopes that cover deposition in wave dominated to fluvial wave dominated deltas with energetic oxic and active reworking conditions these environmental settings are only suitable for deposition of organic lean hydrocarbon source however there are abundant organic materials that fluoresce under the uv v blue incident light especially in proximal delta front prodelta slope biotope a and these materials can generate oil as indicated also by pyrolysis gas chromatography in addition analysis of electric logs is used to assess reservoir capacities and effective porosities in the studied rocks eight sequences are identified based on these trends including e4 e3 e2 e1 d1 c1 c2 and b1 four petroleum plays are determined in the studied succession within the frame of the stratigraphic sequences e d c and b there are six reservoirs identified in the sandy bodies of the lowstand systems tracts and the carbonates of the transgressive and highstand systems tracts the critical moment of hydrocarbon generation occurred during the campanian 76 ma the entire succession of the alam el bueib formation is in the oil window and the source rocks in this formation initiated petroleum expulsion during the eocene time 32 myr

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

regional geothermal exploration in egypt although egypt is not characterized by abundant cenozoic igneous activity its location in the northeastern corner of the african plate suggests that it may possess geothermal resources especially along its eastern margin regional geothermal exploration has been carried out in egypt using the thermal gradient heat flow technique and groundwater temperature chemistry technique in the thermal gradient heat flow study existing oil well bottom hole temperature data as well as subsurface temperature measurements in existing boreholes were utilized before special thermal gradient holes were drilled groundwater temperature and chemistry data were used to extend the geographic range of the direct subsurface thermal measurements on a very modest budget a regional thermal high has been discovered along the eastern margin of egypt and a local thermal anomaly has been discovered in this zone published geological information suggests that the sandstones of the nubian formation may be a suitable reservoir for geothermal fluids the new data indicate that temperatures of 150 sup 0 c or higher may be found in this reservoir in the gulf of suez and red sea coastal zone where it lies at a depth of 4 km and deeper

evolution of marine atmospheric boundary layer structure across the cold tongue itcz complex the structure of the marine atmospheric boundary layer mabl over the tropical eastern pacific ocean is influenced by spatial variations of sea surface temperature sst in the region as the mabl air is advected across a strong sst gradient associated with the cold tongue itcz complex ctic substantial changes occur in the thermodynamic structure surface fluxes and cloud properties this study attempts to define and explain the variability in the mabl structure and clouds over the ctic using data collected on research cruises from the fall seasons of 1999 2001 composite soundings were created for both the cold and warm sides of the sst front to describe the mean atmospheric boundary layer abl structure and its evolution across this front the average difference in sst across this front was 6 c much of this difference was concentrated in a band only 50 km wide during the fall seasons on the cold side of the gradient a well defined inversion exists in all years below this inversion both fair weather cumulus and stratiform clouds are observed as the mabl air moves over the sst front to warmer waters the inversion weakens and increases in height the mabl also moistens and eventually supports deeper convection over the itcz both the latent and sensible heat fluxes increase dramatically across the sst front because of both an increase in sst and surface wind speed cloudiness is variable on the cold side of the sst front ranging from 0 2 to 0 9 coverage on the warm side cloud fraction was quite constant in time with values generally greater than 0 8 the highest cloud top heights 3 km are found well north of the sst front indicating areas of deeper convection an analysis using energy and moisture budgets identifies the roles of various physical processes in the mabl evolution

the controls on the composition of biodegraded oils in the deep subsurface part ii geological controls on subsurface biodegradation fluxes and constraints on reservoir fluid property prediction the principal controls on the fluid properties of biodegraded oil systems have been determined by a combination of petroleum geochemistry numerical modeling of oil biodegradation in reservoirs and analysis of oil property data sets from a variety of geological settings petroleum biodegradation proceeds under anaerobic conditions in any reservoir that has a water leg and has not been heated to temperatures more than 80c in most reservoirs with low concentrations of aqueous sulfate methanogenic degradation is a primary mechanism of petroleum degradation whereas in waters containing abundant sulfate sulfate reduction and sulfide production may dominate net degradation of petroleum fractions in reservoirs is primarily controlled by the reservoir temperature the chemical compounds being degraded and relationships between the oil water contact owc area and oil volume the relative volumes of water leg to oil leg prior level of oil biodegradation and reservoir water salinity act as second order controls on the process typically degradation fluxes kilograms of petroleum destroyed per square meter of oil water contact area per year or kg petroleum m2 owc yr1 for fresh petroleum in clastic reservoirs are in the range of 103 104 kg petroleum m2 owc yr1 and increase with decreasing reservoir temperature from zero near 80c to a maximum flux at the owc of less than 103 kg petroleum m2 owc yr1 at a temperature less than 40c at very low reservoir temperatures and with severely degraded oils such as are seen in the near surface canadian tar sands at the present day the net degradation fluxes are much less than maximum values nutrient supply from the aquifer and adjacent shales mostly buffered by mineral dissolution probably provides the ultimate control on the range of degradation flux values oil compositional gradients and resulting oil viscosity variations are common on both reservoir thickness and field scales in biodegraded oil reservoirs and are a defining characteristic of heavy oil fields produced by crude oil biodegradation continuous vertical gradients in the oil columns document episodic degradation for many millions of years suggesting that the time scales of oil field degradation and petroleum charging are similar the flux temperature relationship we have derived coupled with typical reservoir charge histories defines the range of variation of fluid properties seen in many biodegraded oil provinces and identifies oil charge mixing of biodegraded and fresh oils and reservoir temperature history as the primary controls on fluid properties these flux temperature relationships are easily integrated into prospect charge modeling procedures sensitivity analyses show that the limiting factor in fluid property predictions using even this first level approach are ultimately constrained by the accuracy of current oil charge modeling estimates the absence today of any functional geochemical proxies for assessing oil residence time in oil fields and the substantial uncertainty in petroleum charging times estimated by forward basin modeling is a major obstacle to more accurate fluid property predictions that needs to be addressed