interactions between sediment production and transport in the geometry of carbonate platforms insights from forward modeling of the great bank of guizhou early to middle triassic south china abstract carbonate platforms grow through the precipitation transport and final deposition of carbonate sediment out of seawater quantifying the relative contributions of initial production versus subsequent transport in determining the growth rates and geometries of platforms remains a significant challenge in this study stratigraphic forward modeling is used to quantify the roles of sediment production transport and deposition during each growth stage of a permian triassic carbonate platform with a complex growth history parameter optimization and sensitivity analysis show that within the range of reasonable values the morphology of the platform is most sensitive to sediment transport moderately sensitive to maximum carbonate production rate and least sensitive to the productivity depth curve the ramp to high relief steep sloped platform transition during early triassic time can be explained by any factor that limits sediment transport from shallow water areas of high production to the slope and basin reefs may play a role in limiting sediment transport on many platforms but other processes such as early marine cementation or carbonate production along the slope may be equally capable of yielding this shift in platform geometry in this particular case early lithification of ooid and skeletal shoals on the platform margin perhaps facilitated by unusually high carbonate saturation state of seawater may have inhibited sediment transport into the basin prior to the development of a reef on the platform margin later anisian progradation of the platform margin can be explained by the development of a slope factory rather than requiring increased sediment transport from the platform top the development of an escarpment margin in the ladinian is mainly influenced by accommodation in the slope profile created by antecedent anisian topography a general implication from the model results is that the growth of steep sloped carbonate platforms lacking slope factories may often be limited by transport of sediment from the platform top to accommodation on the slope rather than by the intrinsic production capacity of the platform top factory

study of the effect of 17 18 march 2015 geomagnetic storm on the indian longitudes using gps and c nofs the largest geomagnetic storm in solar cycle 24 occurred during march 17 18 2015 where the main phase of the storm commenced from 07 00 ut of march 17 2015 and reached the dst negative minimum at 22 00 ut the present paper reports observations of tec amplitude and phase scintillations from different gps stations of india during the storm of march 17 and highlights its effects on gps it also presents the global esf occurrence during the storm using total ion density drift measurements from c nofs satellite tec enhancements were noted from stations along 77oe meridian around 10 00 ut on march 17 compared to march 16 and 18 indicating positive storm effects arising out of equatorward neutral wind in the local morning noon sector of the main phase intense scintillation observations from calcutta were most extensive during 15 00 16 00 ut march 17 and the receiver recorded a longitude deviation of 5 2 m during this time cycle slips of the order of 8 s could be observed during periods of intense phase scintillations on the same night intense scintillation observation from palampur is an exceptional phenomenon attributed to the dramatic enhancement of the electric field due to ppef leading to a very high upward ion velocity over the magnetic equator as recorded by c nofs the total ion density measured globally by c nofs reveals two distinct longitude regions of esf occurrence during the storm i east pacific sector and ii indian longitude during the storm the time and longitude of esf occurrence could be predicted using the time of southward turning of imf bz

mantle phase changes and deep earthquake faulting in subducting lithosphere inclined zones of earthquakes are the primary expression of lithosphere subduction a distinct deep population of subduction zone earthquakes occurs at depths of 350 to 690 kilometers at those depths ordinary brittle fracture and frictional sliding the faulting processes of shallow earthquakes are not expected a fresh understanding of these deep earthquakes comes from developments in several areas of experimental and theoretical geophysics including the discovery and characterization of transformational faulting a shear instability connected with localized phase transformations under nonhydrostatic stress these developments support the hypothesis that deep earthquakes represent transformational faulting in a wedge of olivine rich peridotite that is likely to persist metastably in coldest plate interiors to depths as great as 690 km predictions based on this deep structure of mantle phase changes are consistent with the global depth distribution of deep earthquakes the maximum depths of earthquakes in individual subductions zones and key source characteristics of deep events

rupture characteristics of the deep bolivian earthquake of 9 june 1994 and the mechanism of deep focus earthquakes the m w 8 3 deep 636 kilometers bolivian earthquake of 9 june 1994 was the largest deep focus earthquake ever recorded seismic data from permanent stations plus portable instruments in south america show that rupture occurred on a horizontal plane and extended at least 30 by 50 kilometers rupture proceeded at 1 to 3 kilometers per second along the down dip azimuth of the slab and penetrated through more than a third of the slab thickness this extent is more than three times that expected for a metastable wedge of olivine at the core of the slab and thus appears to be incompatible with an origin by transformational faulting these large events may instead represent slip on preserved zones of weakness established in oceanic lithosphere at the earth s surface

map based uncertainty analysis for exploration using basin modeling and machine learning techniques applied to the levant basin petroleum systems eastern mediterranean abstract the levant basin of the east mediterranean region contains a biogenic petroleum system and possibly an underlying thermogenic system the application of a new map based uncertainty and sensitivity analysis that integrates a large set of geological parameters demonstrates that a connection between an upper cretaceous thermogenic petroleum system and the shallower oligo miocene reservoirs is highly possible in the southern part of the basin offshore israel and southern lebanon where hydrocarbon fluids are generated from the campanian source rock and charge the overlying oligo miocene reservoir interval through faults estimates of volumes of expelled hydrocarbons combined with regional analysis of the eocene top seal integrity indicates that the most prospective zones correspond to the southern offshore lebanon and offshore israel in the northern part of the levant basin offshore central and northern lebanon petroleum fluids potentially generated by the campanian source rocks remain trapped under the eocene seal or they migrate towards the margins of the basin our approach is based on applications of machine learning techniques and robust statistical analyses to petroleum systems modeling focusing on spatial uncertainty analysis it may be used on similar frontier or emerging hydrocarbon provinces to help de risking the petroleum systems

characteristics of penetration electric fields to the equatorial ionosphere during southward and northward imf turnings 1 the signatures of abrupt turnings of the vertical component of the interplanetary magnetic field imf bz can be seen at equatorial latitudes through the prompt transmission of high latitude electric fields to the lower latitudes called as prompt penetration electric field ppe the present work studies the signatures of ppe in daytime equatorial electrojet eej index derived in the indian sector during 2001 2005 the signatures are observed in polar pcn index and equatorial eej index ionosphere almost instantaneously 1 min the communication time of 12 6 min is observed between bow shock nose and the equatorial ionosphere and it is found to have inverse relationship with radial component of solar wind velocity during southward and northward bz turnings which might indicate magnetosphere crossing time scale by solar wind ionospheric reconfiguration time during southward turnings shows inverse relationship with solar wind flow in contrast to northward turnings with no relationship indicating differences in underlying physical mechanisms during both turnings we observe no local time dependence within 06 18 h in conductivity corrected eej signatures associated with bz turnings regression analysis between conductivity corrected eej and interplanetary electric field shows higher efficiency during northward turnings however further analysis investigating the effect of actual orientation of bz indicates that the magnitude of northward bz does not have influence on the ionospheric signatures it is noticed that the response signatures are mainly controlled by the magnitudes of southward bz thus the present study signifies the role of inner magnetospheric shielding electric field in addition to ceasing of convection during northward turnings

middle and low latitude ionosphere response to 2015 st patrick s day geomagnetic storm this paper presents a study of the st patrick s day storm of 2015 with its ionospheric response at middle and low latitudes the effects of the storm in each longitudinal sector asian african american and pacific are characterized using global and regional electron content at the beginning of the storm one or two ionospheric positive storm effects are observed depending on the longitudinal zones after the main phase of the storm a strong decrease in ionization is observed at all longitudes lasting several days the american region exhibits the most remarkable increase in vertical total electron content vtec while in the asian sector the largest decrease in vtec is observed at low latitudes using spectral analysis we were able to separate the effects of the prompt penetration of the magnetospheric convection electric field ppef and of the disturbance dynamo electric field ddef on the basis of ground magnetic data concerning the ppef earth s magnetic field oscillations occur simultaneously in the asian african and american sectors during southward magnetization of the b z component of the interplanetary magnetic field concerning the ddef diurnal magnetic oscillations in the horizontal component h of the earth s magnetic field exhibit a behavior that is opposed to the regular one these diurnal oscillations are recognized to last several days in all longitudinal sectors the observational data obtained by all sensors used in the present paper can be interpreted on the basis of existing theoretical models

understanding the gravity response variability of sedimentary basins using forward stratigraphic modelling abstract it is accepted that gravity inversions are non unique and that multiple models will fit the data equally well over sedimentary basins this implies that gravity anomalies can be equally well explained by sedimentary strata with constant densities over a highly heterogeneous basement or by highly heterogeneous sedimentary strata over a constant density basement while both scenarios minimise the difference between the predicted and observed gravity signal neither are geologically plausible in this work we explore stratigraphic modelling as a new parameterisation for gravity models by using a process based numerical simulation to generate the sedimentary basins density models we seek to focus only on geologically plausible models we then study the variability of the sedimentary strata s gravity response i e the range of possible geophysical signatures to stratigraphic parameter changes results from a study of a 2d section in the northern carnarvon basin the northwest shelf of australia emphasize that even when the stratigraphic models are trialled using a wide range of input parameters the simulated gravity response still has a limited variability when compared to model results generated using other parameterisations lastly our results provide insights into the global sensitivity of the gravity response highlighting the sedimentary and stratigraphic parameters that most affect the geophysical signal allowing for a discussion of the geologic and stratigraphic controls of the sedimentary basin s gravity response

a regionalized upper mantle rum seismic model seismic velocity heterogeneity in the earth s mantle is strongly concentrated near its top the shallow heterogeneity of the mantle correlates strongly with surface tectonics we use these observations as constraints of a tomographic experiment aimed at building a regionalized upper mantle rum reference model we use a select set of teleseismic travel times to minimize the mapping of mislocation into structure the data selection emphasizes the robustness of individual picks the form of the rum model is a set of velocity profiles as functions of depth through the upper mantle for each of the different tectonic provinces of earth together the profiles constitute a three dimensional model which incorporates considerable structural detail but is described by only 90 parameters and has only about 22 degrees of freedom this is achieved by irregularly sampling a detailed regionalization of the globe by detailed mapping of subducted lithosphere in the mantle as defined by seismicity and by combining these structures in an irregular grid in which bookkeeping is efficiently handled the resulting rum model includes subducting slabs as sharp fast features in the upper mantle old continents are fast young oceans are slow models have been derived for both compressional and shear velocity the rum model is designed to represent as much of upper mantle heterogeneity as seen by body wave travel times as possible with a simple model it can be useful as a reference model for individual tectonic regions travel times are efficiently generated for the rum model mislocations of explosions of known location are significantly reduced when corrections for the rum model are applied to travel time residuals for a spherically symmetrical earth model

body wave inversion of the 1970 and 1963 south american large deep focus earthquakes a comprehensive set of teleseismic waveforms from two south american deep focus earthquakes of the predigital era the 1970 colombia mw 8 1 and 1963 peru bolivia mw 7 7 events are inverted for source mechanism seismic moment rupture history and centroid depth the p and sh wave inversion of the colombia event confirms previous work indicating that rupture occurred on a plane that dips steeply west rupture direction paralleled the trend of the wadati benioff zone we decompose the source into subevents based on a source time function which shows two major moment release pulses separated by 20 s the first subevent is located near the initiation point at a depth of 630 km the main moment release was located 70 km to the southeast and 20 km shallower rupture subsequently propagated farther southeast the source time function has an initial subevent accounting for 30 of the moment release of the entire event whereas the long period centroid moment tensor cmt analysis russakoff et al 1997 has the initial subevent yielding 50 the high angle nodal plane rotated 15 clockwise during the rupture explaining the large compensated linear vector dipole clvd component inferred from cmt solutions individual subevents have large clvd and compressive isotropic components a full moment tensor inversion of the colombia and 1994 bolivia events suggests that the initial subevents might contain a large non double couple ndc component for the 1963 peru bolivia event using p waves rupture propagated nnw for a distance of 70 km parallel to the high angle nodal plane and the trend of the wadati benioff zone the focal mechanism changed dramatically after the second subevent causing a very large ndc component both events together with the 1994 bolivia earthquake have a precursor separated in space and time from the main rupture and show rupture velocities varying between 3 and 4 km s between subevents with 2 0 km s on average for the entire event low seismic efficiencies and rupture velocities support a highly dissipative temperature dependent rupture mechanism for large deep focus south american earthquakes compared with events in cold subducting slabs

deep earthquakes in the southwest pacific a tectonic interpretation this paper examines the spatial distribution of deep earthquakes in the tonga fiji new hebrides region of the southwest pacific our interpretation emphasizes the complex cenozoic tectonics of the pacific indo australian plate boundary as a primary control on the distribution and deformation of subducted lithosphere most deep earthquakes in the interarc region are associated with the contorted pacific plate lithosphere subducted at the tonga trench however anomalous groups of deep earthquakes located west of the tonga zone are unrelated to the present plate configuration tectonic reconstructions of the region to 8 m y b p provide circumstantial evidence that 1 the anomalous events west of the tonga zone occur in two pieces of detached lithosphere subducted at the vitiaz and proto new hebrides trenches during the late miocene 2 the flattening of the inclined seismic zone in northernmost tonga is related to the rapid opening of the lau basin since 4 m y b p and 3 the sharp westward curvature of the tonga seismic zone in this area coincides with a preexisting bend in the late miocene vitiaz arc the sharpness of its present curvature appears to be a secondary effect of shear flow in the lower mantle and compression between detached vitiaz and attached tonga lithosphere thus much of the contortion of the subducted lithosphere beneath tonga fiji may be produced by local tectonic interactions rather than collision of the slab with an impenetrable boundary in the midmantle

rupture history of the great bolivian earthquake slab interaction with the 660 km discontinuity teleseismic body waves of the great bolivian earthquake of june 9 1994 are analyzed to determine the focal parameters and rupture history broadband seismograms reveal a complex rupture process a small initial event mw 7 2 was followed about 10 s later by a large moment release pulse of about 40 s duration focal mechanisms determined for the mainshock indicate normal faulting with one very shallow ne dipping plane azimuthal variation in body wave displacement pulse widths suggest northward rupture from master event and body wave inversion the main moment release is located 25 50 km ne of the initiation point at about 650 km depth with only small depth variations between the initial and main event this suggests that rupture was n directed on the near horizontal plane because the slab along other parts of the andean arc at about 600 km depth dips steeply a sub horizontal plane may imply shearing perpendicular to slab dip downdip compression on a sub horizontal plane would then imply that the slab does not penetrate the 660 km seismic discontinuity but rather is being sheared out to the ne this interpretation is not unique as other scenarios are also possible such an event immediately above the 660 km discontinuity suggests massive deformation above the discontinuity with no smooth slab penetration into the lower mantle

high resolution image of the oceanic moho in the subducting nazca plate from p s converted waves short period p s converted waves outline the oceanic moho of the descending nazca plate in northern chile at 24 s comparison with hypocentral locations obtained with temporary local seismic networks show that earthquakes inside the subducting oceanic lithosphere of the nazca plate are located predominantly in the oceanic crust at depths between 70 and 120 km and probably in the upper mantle at depths below 120 km the results suggest that dehydration embrittlement as mechanism for intermediate depth earthquakes is active both in the former oceanic crust and upper mantle of subducting lithosphere

impact of the perturbation zonal velocity variation on the spatio temporal occurrence pattern of l band scintillation a case study the earlier evolved method for the forecast of the spatiotemporal variation of l band scintillation based on the expected variation of the perturbations under favorable ionospheric thermospheric conditions has been refined by duly accounting for the local time variation of the zonal velocity of the perturbations the unique combination of the two geostationary satellites gsat 8 and gsat 10 over the indian zone has been used to estimate the typical local time dependence of the perturbation velocities by closely following identifiable features in the scintillation pattern the measured velocities that registered a steady decrease with the progression of night had been shown to significantly alter the forecast pattern of the scintillations with respect to longitude and local time the significant improvement in the forecast pattern has been demonstrated through a case study putting the forecast method on a firmer footing

storm time dependence of equatorial disturbance dynamo zonal electric fields we use jicamarca radar observations of f region vertical plasma drifts and auroral electrojet indices during 1968 1988 to study the characteristics and temporal evolution of equatorial disturbance dynamo zonal electric fields these electric fields result from the dynamo action of storm time winds and or thermospheric composition changes driven by enhanced energy deposition into the high latitude ionosphere during geomagnetically active conditions the equatorial vertical drift perturbations last for periods of up to 30 hours after large increases in the high latitude currents on the average this process can be described by two basic components with time delays of about 1 12 hours and 22 28 hours between the high latitude current enhancements and the equatorial velocity perturbations our data indicate strong coupling between dynamo processes with different timescales the short term disturbance dynamo drives upward equatorial drifts eastward electric fields at night with largest amplitudes near sunrise and small downward drifts during the day these perturbation drifts are in good agreement with results from the blanc richmond disturbance dynamo theory the dynamo process with time delays of about a day drives upward drift velocities at night with largest values near midnight and downward drifts in the sunrise noon sector in this case the amplitudes of the disturbance drifts maximize during geomagnetically quiet times preceded by strongly disturbed conditions we also present results of a new equatorial storm time dependent empirical model which illustrate the characteristics of the vertical disturbance dynamo drifts

quantitative models of sedimentary basin filling summary quantitative modelling of the filling of sedimentary basins was begun in earnest in the 1960s dozens of themes and variations have been proposed since then and have yielded an abundance of idealized stratigraphic patterns as functions of both imposed changes and basin properties post plate tectonic modelling began with rigid lid models which show the stratigraphic signature of subsidence variation this work introduced the connection between stratigraphy and the rheology of the lithosphere rigid lid models are the simplest type of geometric model in which the sediment surface is assigned prescribed geometries usually corresponding to different depositional environments these can reproduce many aspects of overall stratal geometry but are formally restricted to relatively long timescales for which quasi steady surface topography can be assumed so called dynamic models attempt to represent the morphodynamics of the sediment surface by abstracting and averaging short term transport processes most of the dynamic models proposed to date can be seen as special cases of a single general morpho dynamic equation the most important result of the first wave of quantitative basin filling models is that even relatively simple models can produce reasonable stratal patterns we now have a wide array of tools for exploring scenarios searching for general behaviours and effects and making initial quantitative predictions we have also learned that basin response to external forcing as recorded in stratigraphy can be as sensitive to the characteristics of the basin as to the forcing the main brake on the development of basin modelling is not computing power but lack of methods and data for testing the models we have already developed physical experiments which are only just beginning are one means of doing this experimental stratigraphy is a bridge to quantitative field tests which will require collaboration among academic researchers from a wide range of areas and between academia and industry on projects of greater scale and degree of integration than we have seen so far the advancement of quantitative sedimentary geology will also require significant changes in the way the subject is taught at all levels

equatorial ionospheric electric fields during the november 2004 magnetic storm 1 we use radar measurements from the jicamarca radio observatory magnetometer observations from the pacific sector and ionosonde data from brazil to study equatorial ionospheric electric fields during the november 2004 geomagnetic storm our data show very large eastward and westward daytime electrojet current perturbations with lifetimes of about an hour indicative of undershielding and overshielding prompt penetration electric fields in the pacific equatorial region during the november 7 main phase of the storm when the southward imf the solar wind and reconnection electric fields and the polar cap potential drops had very large and nearly steady values this result is inconsistent with the recent suggestion that solar wind electric fields penetrate without attenuation into the equatorial ionosphere for several hours during storm main phase the largest daytime prompt penetration electric fields about 3 mv m ever observed over jicamarca occurred during the november 9 storm main phase when large equatorial electrojet current and drift perturbations were also present in the pacific and brazilian equatorial regions the rise and decay times of these equatorial electric fields were about 20 min longer than of the corresponding solar wind electric fields the ratios of prompt penetration electric fields and corresponding solar wind electric field changes were highly variable even during the day and had largest values near dawn also the prompt penetration electric fields did not show polar cap potential drop saturation effects our results clearly highlight that the relationships of prompt penetration and solar wind electric fields and polar cap potentials are far more complex than implied by simple proportionality factors

impact of environmental parameters on coral reef development and drowning forward modelling of the last deglacial reefs from tahiti french polynesia iodp expedition 310 the sedimentological and chronological analysis of the last deglacial reef sequences of tahiti french polynesia drilled during the integrated ocean drilling program expedition 310 provide a high resolution data set allowing a well constrained forward modelling study this study represents the first attempt to model in three dimensions the coral reef development of tahiti during the last deglacial sea level rise 23 000 to 6000 cal yr bp using the software dionisos developed by ifp energies nouvelles it allows the testing of the reconstructed last deglacial sea level curve and the different environmental parameters for example wave energy and sediment fluxes that could have influenced the reef development these last deglacial reef sequences form two prominent ridges occurring seaward of the living barrier reef that consist of successive submerged reefs these reefs have been prone to drowning because the window of maximum carbonate production rate is inhibited by high water turbidity sediment supply from a nearby river shallow depth of wave action and substrate availability these factors combined with rapid sea level rise have driven the growth of retrograding reef pinnacles local factors substratum nature sediment supply and wave energy were the main processes that induced the drowning of the inner ridge whereas interplay of local and global factors acceleration of the sea level rise was responsible for the drowning of the outer ridge this particular acceleration of sea level rise of 16 m between 14 6 ka and 14 ka bp corresponds to meltwater pulse 1a

deep earthquakes beneath the fiji basin sw pacific earth s most intense deep seismicity in stagnant slabs abstract previous work has suggested that many of the deep earthquakes beneath the fiji basin occur in slab material that has been detached and foundered to the bottom of the transition zone or has been laid down by trench migration in a similar recumbent position since nowhere else in the earth do so many earthquakes occur in slabs stagnated in the transition zone these earthquakes merit closer study accordingly we have assembled from historical and modern data a comprehensive catalogue of the relocated hypocenters and focal mechanisms of well located deep events in the geographic area between the bottoms of the main vanuatu and tonga wadati benioff zones two regions of deep seismogenesis are recognized there i 163 deep shocks have occurred north of 15 s in the vityaz group from 1949 to 1996 these seismological observations and the absence of other features characteristic of active subduction suggest that the vityaz group represents deep failure in a detached slab that has foundered to a horizontal orientation near the bottom of the transition zone ii another group of nearly 50 outboard deep shocks occur between about 450 and 660 km depth west of the complexly buckled and offset western edge of the tonga wadati benioff zone their geometry is in the form of two or possibly three small circle arcs that roughly parallel the inferred motion of tonga trench migration earthquakes in the southernmost of these arcs occur in a recumbent high seismic wavespeed slab anomaly that connects both to the main inclined tonga anomaly to the east and a lower mantle anomaly to the west van der hilst r 1995 complex morphology of subducted lithosphere in the mantle beneath the tonga trench nature vol 374 pp 154 157 both groups show complexity in their focal mechanisms the major question raised by these observations is the cause of this apparent temporary arrest in the descent of the tonga slab into the lower mantle we approach these questions by considering the effects of buoyant metastable peridotite in cold slab material that was detached and rapidly foundered or was buckled segmented and laid out in the transition zone

automatic calibration of stratigraphic forward models for predicting reservoir presence in exploration understanding and predicting reservoir presence and characteristics at regional to basin scales is important for evaluating risk and uncertainty in hydrocarbon exploration simulating reservoir distribution within a basin by a stratigraphic forward model enables the integration of available prior information with fundamental geologic processes embedded in the numerical model stratigraphic forward model predictions can be significantly improved by calibrating the models to independent constraints such as thicknesses from seismic or well data a three dimensional basin scale stratigraphic forward modeling tool is coupled with an inversion algorithm the inversion algorithm is a modification of the neighborhood algorithm a type of genetic algorithm which is designed to sample complex multimodal objective functions and is parallelized on computer clusters to accelerate convergence the process generates a set of representative geological models that are consistent with prior ranges for uncertain parameters calibration constraints and associated tolerance thresholds the workflow is first demonstrated on two data sets a synthetic example based on a clastic passive margin and a real hydrocarbon exploration example for slope and basin floor stratigraphic traps in the neocomian lower cretaceous of the west siberian basin the analysis of calibrated models provides constraints on stratigraphic controls and allows prediction of locations with higher potential to develop stratigraphic traps these locations are related to complex interactions between paleobathymetry subsidence eustatic fluctuations characteristics of sediment input sources and sediment transport parameters results show the potential of stratigraphic forward modeling combined with inverse methods as an additional tool to support conventional play based exploration and reservoir presence prediction

role of imf b y in the prompt electric field disturbances over equatorial ionosphere during a space weather event on 7 january 2005 a p 40 prompt penetration electric field perturbations of opposite polarities were observed over thumba and jicamarca on a few occasions during 13 45 16 30 ut however the electric field was found to be eastward during 14 45 15 30 ut over both thumba and jicamarca contrary to the general expectation wherein opposite polarities are expected at nearly antipodal points on closer scrutiny three important observational features are noticed during 14 10 15 15 ut first during 14 10 14 45 ut despite increasing southward interplanetary magnetic field imf b z condition the already westward electric field over thumba weakened less westward while the eastward electric field over jicamarca intensified more eastward second the electric field not only became anomalously eastward over thumba but also got intensified further during 14 45 15 00 ut similar to jicamarca third during 15 00 15 15 ut despite imf b z remaining steadily southward the eastward electric field continued to intensify over thumba but weakened over jicamarca it is suggested that the changes in imf b y component under southward imf b z condition are responsible for skewing the ionospheric equipotential patterns over the dip equator in such a way that thumba came into the same dp2 cell as that of jicamarca leading to anomalous electric field variations magnetic field measurements along the indian and jicamarca longitude sectors and changes in high latitude ionospheric convection patterns provide credence to this proposition thus the present investigation shows that the variations in imf b y are fundamentally important to understand the prompt penetration effects over low latitudes

low latitude ionospheric thermospheric response to storm time electrodynamical coupling between high and low latitudes 1 using multi instrumental and multistation data we present low latitude ionospheric thermospheric behavior during the geomagnetic storm of 15 may 2005 the diurnal pattern of total electron content tec at a chain of equatorial to low latitude stations shows strong positive ionospheric storm on 15 may latitudinal variation of tec shows development of strong equatorial ionization anomaly eia on the same day evidence in terms of equatorial electrojet eej and magnetogram signatures is presented for the prompt penetration of interplanetary electric field ief as the cause of the positive ionospheric storm consequent to the storm time circulation resulting from the extra energy deposition via joule heating over high latitudes compositional changes occur in the global thermosphere tec enhancements on 16 may are attributed to enhancement of atomic oxygen at equatorial and low latitudes and the negative ionospheric storm on 17 may observed beyond certain low latitudes is explained in terms of enhancement of molecular species because of the storm time neutral composition changes strong esf plume structures on range time intensity rti map and l band scintillation and tec depletions in gps measurements are observed in the longitude sectors where the local time of sudden storm commencement ssc falls after the post sunset hours the ionospheric zonal electric fields are altered by the combined effects of eastward disturbance dynamo electric fields and direct prompt penetration of eastward electric fields associated with the northward turning of interplanetary magnetic field imf bz leading to subsequent development of esf after midnight

experimentally based water budgets for dehydrating slabs and consequences for arc magma generation phase diagrams of hydrous mid ocean ridge mor basalts to 330 km depth and of hydrous peridotites to 250 km depth are compiled for conditions characteristic for subduction zones a synthesis of our experimentally determined phase relations of chlorite lawsonite epidote zoisite amphibole paragonite chloritoid talc and phengite in basalts and of phase relations from the literature of serpentine talc chlorite amphibole and phase a in ultramafics permits calculation of h2o contents in hydrous phase assemblages that occur in natural compositions this yields the information necessary to calculate water budgets for descending slabs starting from low grade blueschist conditions 10 20 km depth with h2o contents between 5 and 6 wt for hydrated oceanic crust complete dehydration is achieved between 70 and 300 km depth as a function of individual slab geotherms hydrous phases which decompose at depth below volcanic arcs are lawsonite zoisite chloritoid and talc phengite in mafic compositions and chlorite and serpentine in peridotite approximately 15 35 of the initially subducted h2o are released below volcanic arcs the contribution of amphibole dehydration to the water budget is small 5 20 and occurs at relatively shallow depth 65 90 km in any predicted thermal structure dehydration is a combination of a stepwise and a continuous process through many different reactions which occur simultaneously in the different portions of the descending slab such a dehydration characteristic is incompatible with single phase dehydration models which focus fluid flow through a unique major dehydration event in order to explain volcanic fronts as a consequence of continuously progressing dehydration water ascending from the slab will be generally available to depth of ca 150 200 km the fluid rising from the subducting lithosphere will cause partial melting in the hot portion of the mantle wedge we propose that the volcanic front simply forms above the mantle wedge isotherm where the extent of melting is sufficient to allow for the mechanical extraction of parental arc magmas thermal models show that such an isotherm ca 1300oc locates below volcanic fronts slab surface depths below such an isotherm are compatible with the observed depths of the slab surface below volcanic fronts 1998 elsevier science b v all rights reserved

seismic body wave constraint on mechanisms of intermediate depth earthquakes 1 source parameters of six large earthquakes 7 1 mw 7 7 in the depth range between 112 and 277 km from five different subduction zones are derived from teleseismic body waves recorded by global seismic networks except for the 21 october 1995 mexican event which is consistent with the model of simple rupture on a planar surface the investigated earthquakes show complex rupture processes that can be explained by irregularities in the focal region as is the case of shallow events the inferred velocity of the moment release varies between 2 5 and 4 km s corresponding to 40 90 of the shear velocity at the focus four of the six earthquakes show stress drops in the range observed for shallow events 1 10 mpa ruptures extend mainly parallel to the strike of subducting slabs with dimensions reaching up to 50 km the extent of rupture perpendicular to slab dip of generally less than 15 km is comparatively small this suggests that the rupture during large intermediate depth earthquakes propagates predominantly parallel to the strike of the subducting plate and that the seismogenic zone perpendicular to the dip direction is limited to a narrow width the relatively small rupture size perpendicular to slab dip suggests that the rupture process does not extend into regions of significantly different temperatures the spatial extent of the investigated earthquakes is consistent with the orientation of trench parallel faults that are generally observed in near trench outer rise regions suggesting that these events may result from reactivation of such preexisting faults at intermediate depths through dehydration of hydrous minerals concentrated in these zones of weakness depths of most of the earthquakes are consistent with the dehydration embrittlement of serpentine the bolivian earthquake of 23 january 1997 seems to be too deep 277 km for such an explanation

are the lower planes of double seismic zones caused by serpentine dehydration in subducting oceanic mantle in a number of subduction zones earthquakes at 50 200 km depth define two dipping planes separated by 20 40 km that appear to merge downdip upper plane earthquakes are inferred to occur within the subducting oceanic crust whereas lower plane earthquakes occur in the subducting oceanic mantle beneath northeast japan the results of a new finite element heat transfer model suggest that the lower seismic plane cuts across isotherms at a shallow angle lower plane earthquakes occur at 550 800 c at 100 km depth and at 350 600 c at 160 km depth these conditions coincide with the dehydration reaction antigorite serpentine forsterite enstatite h 2 o which suggests that lower plane earthquakes may be triggered by dehydration embrittlement which in turn suggests that the subducting oceanic mantle is partially hydrated serpentinization may occur in the trench outer rise region where faulting may promote infiltration of seawater several tens of kilometers into the oceanic lithosphere if this hypothesis is correct current subduction zone h 2 o budgets may significantly underestimate the amount of bound h 2 o entering the subduction factory

global equatorial plasma bubble occurrence during the 2015 st patrick s day storm an analysis of the occurrence of equatorial plasma bubbles epbs around the world during the 2015 st patrick s day geomagnetic storm is presented a network of 12 global positioning system receivers spanning from south america to southeast asia was used in addition to colocated vhf receivers at three stations and four nearby ionosondes the suppression of postsunset epbs was observed across most longitudes over 2 days the epb observations were compared to calculations of the linear rayleigh taylor growth rate using coupled thermosphere ionosphere modeling which successfully modeled the transition of favorable epb growth from postsunset to postmidnight hours during the storm the mechanisms behind the growth of postmidnight epbs during this storm were investigated while the latter stages of postmidnight epb growth were found to be dominated by disturbance dynamo effects the initial stages of postmidnight epb growth close to local midnight were found to be controlled by the higher altitudes of the plasma i e the gravity term modeling and observations revealed that during the storm the ionospheric plasma was redistributed to higher altitudes in the low latitude region which made the plasma more susceptible to rayleigh taylor growth prior to the dominance of the disturbance dynamo in the eventual generation of postmidnight epbs

characteristics of the equatorial plasma drifts as obtained by using canadian doppler ionosonde over southern tip of india we present here characteristics of the doppler drift measurements over tirunelveli 8 73 n 77 70 e dip 0 5 n an equatorial site over southern india using doppler interferometry technique of canadian ionosonde three dimensional bulk motions of the scatterers as reflected from the ionosphere are derived by using doppler interferometry technique at selected frequencies using spaced receivers arranged in magnetic e w and n s directions after having compared with lowell s digisonde drifts at trivandrum we studied the temporal and seasonal variabilities of quiet time drifts for the year 2012 the observations showed higher vertical drifts during post sunset in the equinox followed by winter and summer seasons the comparison of doppler vertical drifts with the drifts obtained from a virtual height and b fejer drift model suggests that doppler vertical drifts are relatively higher as compared to the drifts obtained from model and virtual height methods further it is seen that vertical drifts exhibited equinoctial asymmetry in prereversal enhancement quite similar to such asymmetry observed in the spread f in the ionograms and gps l band scintillations the zonal drifts on the other hand showed westward during daytime with mean drifts of 150 200 m s and correlated well with equatorial electrojet strength indicating the role of e region dynamo during daytime while they are eastward during nighttime with mean drifts of 100 m s resembling f region dynamo process also zonal drifts showed large westward prior to the spread f onset during autumn equinox than vernal equinox suggesting strong zonal shears which might cause equinoctial asymmetry in spread f

equatorial disturbance dynamo electric fields f region vertical drift data from jicamarca peru show that equatorial east west electric fields are sometimes perturbed 16 24 hours after the onset of geomagnetic storms these disturbance dynamo electric fields which must be caused primarily by the action of neutral winds at low and middle latitudes decrease and sometimes even reverse the quiet time electric field pattern during both daytime and nighttime the long delay excludes the possibility that gravity waves are responsible and suggests that the thermospheric circulation is disturbed the data also show that after some storms there are no such delayed disturbances a fact which may be due to the longitudinal structure of the disturbances at high latitudes and or that only very strong storms can produce major thermospheric perturbations that extend to middle and low latitudes

millennial scale sequence stratigraphy numerical simulation with dionisos abstract we investigate whether depositional sequences can form on 1000 y or millennial scale and what stratal architecture can develop as the result of these short term variations abrupt climate changes are caused by a complex interplay between atmospheric oceanic and cryospheric processes dansgaard oeschger d o cycles of 1000 y and bond cycles of 7000 y have been identified in climate studies since the early 1990s a 3d forward stratigraphic model dionisos was used in this study to analyze the possible stratigraphic architecture that may evolve in response to the millennial scale climatic cycles according to current knowledge no detectable eustatic changes occur in a d o cycle but sea level may change slightly through several d o cycles an abrupt 20 m fall and subsequent rise characterize the heinrich events between bond cycles our modeling included three experiments i stable sea level ii slightly rising sea level and iii slightly falling sea level between heinrich events the applied fluvial water discharge and sediment supply varied according to the millennial climatic variations in each experiment the modeling experiments lead to the formulation of a conceptual model for millennial scale stratigraphy relevant to glacial periods the millennial scale sequences belong to a two fold hierarchy defined by a series of short d o cycles nested within longer bond cycles which in turn are separated by the sharp heinrich events the stacking patterns predicted between heinrich events include i alternating thicker and thinner bedsets of normal regressive highstand progradation hst on d o scale if sea level is stable ii highstand systems tract transgressive systems tract hst tst sequences on d o scale if the sea level is rising and iii thickening and thinning forced regressive bedsets on d o scale if the sea level is falling in case iii the bond scale falling stage systems tract fst has two distinct parts a proximal slightly and gradually downstepping unit followed by a strongly offlapping unit deposited offshore the intra fst surface that separates the two units corresponds to the heinrich sea level drop and is referred to in this paper as the heinrich discontinuity this type of sequence consists of fst lst tst and no hst may form

effect of slab temperature on deep earthquake aftershock productivity and magnitude frequency relations deep earthquakes generally show fewer aftershocks and a larger variability in magnitude frequency relations than shallow earthquakes1 5 these characteristics and the factors that control them may place constraints on the mechanism of deep earthquakes which is still uncertain6 8 here we show that systematic variations in aftershock productivity and magnitude frequency relations are related to the temperature of the downgoing slab as inferred from the vertical velocity and age of the subducting lithosphere deep earthquakes with substantial aftershock sequences are found only in colder slabs and earthquakes in warmer slabs consistently show few aftershocks magnitude frequency relations for deep earthquakes also show systematic variations as a function of slab thermal structure with warmer slabs showing fewer small earthquakes lower b values the statistical properties of deep earthquakes thus appear to be temperature sensitive to an extent not observed for shallow earthquakes and not adequately explained by simple geometrical limitations on fault width

low latitude ionospheric disturbance electric field effects during the recovery phase of the 19 21 october 1998 magnetic storm 1 low latitude ionospheric electric fields and currents are often strongly disturbed during periods of enhanced geomagnetic activity these perturbations can last for several hours after geomagnetic quieting we use incoherent scatter radar measurements from jicamarca and arecibo during 19 21 october 1998 to study for the first time the low latitude disturbance electric fields during the recovery phase of a large magnetic storm on 19 october the jicamarca data showed initially large and short lived time scale of about 10 20 min upward and westward drift perturbations in the early afternoon sector due to the penetration of strong magnetospheric electric fields probably driven by an increase in the solar wind dynamic pressure following the decrease of auroral activity very strong afternoon and nighttime zonal and vertical disturbance dynamo drifts were observed over jicamarca but surprisingly only small and sporadic perturbation drifts were present over arecibo the latitudinal variation of the daytime zonal disturbance dynamo drifts during this day is in good agreement with that previously observed for thermospheric disturbance winds the disturbance dynamo drifts also indicate significantly different local storm time and possibly latitudinal dependences for their vertical perpendicular and zonal drift components suggesting large variations in both the amplitude and direction of the disturbance dynamo electric field vector in the next day during moderately disturbed conditions the daytime perturbation drifts were small but following transient increases in geomagnetic activity large upward perpendicular drifts were observed near dusk over jicamarca and arecibo where simultaneous westward perturbation drifts were also seen these perturbations are consistent with the occurrence of strong prompt penetration electric fields reaching the magnetic equator the measured prompt penetration drift patterns are generally in good agreement with predictions from global convection models later at night under moderately disturbed conditions relatively large zonal and meridional disturbance dynamo electric fields were observed by the two radars our results illustrate the large variability of the low latitude perturbation electric fields relative to their climatological values after large storms probably due to the importance of additional disturbance processes they also indicate that a much deeper understanding of solar wind magnetospheric ionospheric processes is required for accurate predictions of these electric fields

stratigraphic simulation of sedimentary basins concepts and calibration a two dimensional stratigraphic simulation program based on semiempirical algorithms has been successfully applied to clastic carbonate and mixed clastic carbonate depositional regimes the program may be used to predict reservoir distribution to constrain interpretations of well and seismic data to test exploration scenarios in frontier basins and to evaluate the fundamental controls on basin stratigraphy applications to seismic and well log data sets from main pass u s gulf coast offshore sarawak malaysia and the baltimore canyon u s east coast demonstrate that the program simulates stratigraphy on a basin wide scale as well as on the scale of individual prospects the main pass section is an offlapping sequence of neogene clastics the model simulates 17 m y of geologic history at a 200 000 yr resolution and reproduces gross basin geometry major sequence boundaries depth and location of nearshore marine sands intervals of sediment bypass into deep water shelf margin positions and paleobathymetry three neogene carbonate buildups of central luconia offshore sarawak malaysia were simulated using a sea level history optimized to reproduce the carbonate growth anatomy the model reproduced observed seismic reflection geometries and transgressive aggradational progradational retrogradational and subaerial exposure phases the program has also simulated jurassic pleistocene basin and stratigraphic sequence geometries and mixed clastic carbonate facies distribution along a 300 km regional dip line of the baltimore canyon trough modeled features of interest include a progradational middle jurassic carbonate margin punctuated by clastic deposition during sea level lowstands and a late jurassic early cretaceous aggradational carbonate margin culminating in the development and subsequent drowning of isolated carbonate buildups simulated bathymetries facies relations and subaerial exposure surfaces for the early cretaceous aggradation margin are consistent with detailed petrographic paleontologic and seismic stratigraphic interpretations

probability maps of reservoir presence and sensitivity analysis in stratigraphic forward modeling one of the main objectives of petroleum exploration consists of predicting reservoir location data collected in the basin are used to better understand the sedimentary architecture but are usually insufficient to accurately characterize this architecture three dimensional stratigraphic forward modeling has brought new insights in the understanding of sediment distribution it gives the opportunity to investigate several geological models and to tackle reservoir presence probability however simulation time is a strong limitation to properly taking the uncertainties into account during operational studies here we propose a methodology based on metamodels or surrogate models to perform sensitivity and risk analyses the objective is to reduce the simulation time necessary to quantify the regional impact of the input parameters and to estimate probability maps of reservoir presence the approach consists of building functions that approximate the spatial outputs of the simulator such as sediment thickness or net to gross distributions in the basin and that are fast to evaluate these functions are then called instead of the stratigraphic forward simulator for uncertainty quantification the proposed methodology is applied to a three dimensional synthetic case study considering uncertainty on input parameters related to sediment transport accommodation space and sediment supply the sensitivity analysis quantifies in each location the influence of the parameters on the sediment distribution which can help to better understand the influence of each uncertain process on the basin architecture in addition probability maps of reservoir presence are estimated the proposed approach is a promising trade off between simulation time and information that can be inferred

first observation of interhemispheric asymmetry in the epbs during the st patrick s day geomagnetic storm of 2015 in this work we have studied the characteristics of epbs such as their zonal drift and tilt from the low latitude and dip equatorial region in the indian longitude sector during the main phase of the 17 march 2015 storm all sky airglow imaging observations from tirunelveli 8 7on 77 8oe geographic 1 7on dip latitude and kolhapur 16 7on 74 3oe geographic 11 5on dip latitude are utilized here on 17 march 2015 epbs were observed to drift eastward during 14 30 16 30 ut between 3os and 15on dip latitudes a westward drift presumably under the influence of the disturbance dynamo electric field ddef initially appeared at higher dip latitudes almost 10 hours after the storm onset and subsequently the same was observed at lower dip latitudes the epbs attained a peak westward drift at 17 00 ut followed by a gradual decrease in their speed till 18 30 ut after regaining their westward speed the epbs continued to drift westward till 22 00 ut moreover a latitudinal gradient in the drift motion of the epbs was also observed on this night another interesting observation made from the images obtained from tirunelveli was the presence of a large westward tilt of the epbs the most intriguing finding of this study however was the asymmetry in the tilt of the epbs at conjugate points during the pre midnight hours on 17 march 2015 in this study the possible mechanisms that can explain these observations are discussed in the light of the current understanding of the equatorial electrodynamics and epbs

seismic consequences of warm versus cool subduction metamorphism examples from southwest and northeast japan warm and cool subduction zones exhibit differences in seismicity seismic structure and arc magmatism which reflect differences in metamorphic reactions occurring in subducting oceanic crust in southwest japan arc volcanism is sparse and intraslab earthquakes extend to 65 kilometers depth in northeast japan arc volcanism is more common and intraslab earthquakes reach 200 kilometers depth thermal petrologic models predict that oceanic crust subducting beneath southwest japan is 300 to 500 c warmer than beneath northeast japan resulting in shallower eclogite transformation and slab dehydration reactions and possible slab melting