growth and deformation of the ladakh batholith northwest himalayas implications for timing of continental collision and origin of calc alkaline batholiths abstract the calc alkaline ladakh batholith nw himalayas was dated to constrain the timing of continental collision and subsequent deformation batholith growth ended when collision disrupted subduction of the tethyan oceanic lithosphere and thus the youngest magmatic pulse indirectly dates the collision both u pb ages on zircons from three samples of the ladakh batholith and k ar from one subvolcanic dike sample were determined magmatic activity near leh the capital of ladakh occurred between 70 and 50 ma with the last major magmatic pulse crystallizing at ca documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand tex

solar and lunar tidal variabilities in gps tec and geomagnetic field variations seasonal as well as during the sudden stratospheric warming of 2010 the global positioning system gps deduced total electron content tec data at 15 n geomagnetic which is the northern crest region of equatorial ionization anomaly are used to study solar and lunar tidal variabilities during the years 2008 and 2009 and also during the 2009 2010 winter when a major sudden stratospheric warming ssw event has occurred the diurnal and semidiurnal tidal amplitudes show semiannual variation with maximum amplitudes during february march and september november whereas terdiurnal tide is larger during april september they show significant longitudinal variability with larger smaller amplitudes over 250 e 150 e 200 e 250 e lunar semidiurnal tidal amplitudes show sporadic enhancements during northern winter months and negligible amplitudes during northern summer months they also show notable longitudinal variabilities the solar migrating tides dw1 and sw2 show semiannual variation with larger amplitudes during spring equinox months whereas tw3 maximizes during northern summer dw2 shows larger amplitudes during summer months during the ssw except tw3 the migrating tides dw1 and sw2 show considerable enhancements among solar nonmigrating tides sw1 tw2 and ds0 show larger enhancements solar tides in tec and equatorial electrojet strength over tirunelveli vary with the time scale of 60 days during october 2009 march 2010 similar to ozone mass mixing ratio at 10 hpa and this confirms the vital role of ozone in tidal variabilities in ionospheric parameters lunar tidal amplitudes in changes in horizontal component of geomagnetic field h are larger over tirunelveli a station near dip equator solar semidiurnal tides in h have larger amplitudes than lunar tides over polar stations mawson and godhavn

paleomagnetic evidence for block rotations in central hokkaido south sakhalin northeast asia abstract the eocene to lower miocene strata in the bykov region of south sakhalin island far east russia show a mean paleomagnetic direction of dec 28 7 inc 55 7 95 6 7 and n 22 and a paleomagnetic pole at 66 3 n 245 7 e and a95 8 8 which shows that south sakhalin rotated 25 15 clockwise with respect to northeast asia since the early miocene this pole agrees with that of the eocene to middle miocene sedimentary rocks in central hokkaido japan it suggests that both south sakhalin and central hokkaido have rotated clockwise with respect to northeast asia since the early miocene these clockwise rotations can be interpreted as a vertical axis rotation of the blocks distributed in the north south direction more than 1000 km along the dextral hokkaido sakhalin shear zone considering the development of an en echelon structure of the basins in the shear zone we recognized five blocks each of which had rotated since the early miocene we conclude that this dextral shear is responsible not only for these block rotations but also for the opening of the kuril basin and the japan sea and that the shear motion was caused by oblique convergence between the eurasian and the okhotsk plates since the early miocene

observations of global ionospheric responses to the 2009 stratospheric sudden warming event by formosat 3 cosmic 1 the global ionospheric response to a stratospheric sudden warming ssw is studied using three dimensional electron density maps derived from radio occultation observations of formosat 3 cosmic during the 2009 ssw periods results show that the ionospheric electron density at eia crests exhibit a morning early afternoon increase followed by an afternoon decrease and an evening increase indicative of a semidiurnal component during the ssw period which is consistent with recent studies the latitude altitude electron density slice maps show that the ssw related modifications of the equatorial plasma fountain interact with the existing summer to winter neutral winds and resulting in a north south asymmetry the global ionospheric response shows a clear longitudinal dependence in the equatorial plasma fountain enhancement during morning early afternoon inferred from the duration of the equatorial ionization anomaly eia enhancement following the enhancement prominent global eia reductions resulting from the equatorial plasma fountain weakening in the afternoon sector are seen the ionospheric response to the 2009 ssw event is also compared with the usual seasonal variation during january february 2007 instead of showing the electron density increase in the northern hemisphere and decrease in the southern hemisphere as the usual seasonal variation does the ssw period ionosphere shows prominent global electron density reductions in the afternoon period during the 2009 ssw event

kinematics of cenozoic extension on the south china sea continental margin and its implications for the tectonic evolution of the region abstract in the northern south china sea several large sedimentary basins developed during the cenozoic characterized by episodic rifting clockwise rotation of the rifts an eastward aging breakup unconformity and intensifying crustal extension to the east these features may be summarized by a scissors model the maximum rifting occurred north of the maximum thermal subsidence which was in turn north of the seafloor opening in contrast the nansha microcontinent south of the south china sea basin was dominated by compressional deformation during the cenozoic extension was of subordinate significance and manifested mainly by block faulting and tilting in the late early oligocene maximum tilting occurred in the southern part of the nansha microcontinent at distance from the deep sea basin of the south china sea the asymmetric development of extensional structures around the south china sea basin may be explained by the simple shear model proposed by wernicke 1981 the tectonic development of the south china sea was the consequence of various interactions of three major plates and may be summarized into three stages with dominating influences of respectively the retreat of the west pacific subduction zone in the late cretaceous the hard collision and impinging of india to tibet since the late eocene and the fast northward subduction of the indian ocean australian plate since the late early miocene

new insights on 3 d plates interaction near taiwan from tomography and tectonic implications abstract recent tomographic results are used to trace the south china sea and philippine sea subducting slabs south and northeast of taiwan along the manila and ryukyu trenches respectively in particular the 3 d plates interaction beneath taiwan is discussed based on a close up view of the tomographic sections together with earthquake hypocenters distribution our study indicates that 1 the east dipping south china sea slab can be followed to the north up to the latitude of hualien 2 the eurasian plate subducts beneath most part of the taiwan island down to the 670 km depth discontinuity 3 the north dipping philippine sea slab can be followed slightly west of the longitude of hualien both plates thus interact beneath northern taiwan where the arc continent collision is paroxysmal 4 slab detachment is envisaged at the northern edge of the subducted eurasian plate beneath the coastal range of taiwan which may facilitate the northwestward motion of the philippine sea plate with respect to eurasia slabs geometries obtained from tomographic sections allow us to reconstruct the late neogene plate kinematics and dynamics in this region our main conclusions are 1 the size of the original south china sea was about twice its present size 2 the subducted part of the west philippine basin i e the largest oceanic basin of the philippine sea plate extends only 400 km north of the ryukyu trench 3 slab detachment might have occurred 3 5 my ago beneath the central and northern ryukyu arc along a weak zone that is aligned with the gagua ridge an ancient plate boundary 4 the ryukyu trench has propagated westward from 126 e of longitude southeast of miyako island to the locus of the present arc continent collision along a major lithospheric tear that cut through the continent ocean boundary first and then through the continental lithosphere as a consequence the southern ryukyu margin developed progressively from east to west as a subduction zone during the last 8 my it has been elaborated onto a passive margin which corresponded to the edge of the eurasian continental shelf bordering the south china sea prior to pliocene 5 the southern okinawa trough rifted during the last 2 1 ma following the propagation of the subduction zone 6 subduction of the eurasian margin probably stopped recently beneath northern taiwan and a flip of subduction from west to east is being initiated near hualien

equatorial vertical drift modulation by the lunar and solar semidiurnal tides during the 2013 sudden stratospheric warming during the 2013 stratospheric sudden warming ssw period the jicamarca unattended long term investigations of the ionosphere and atmosphere julia radar at jicarmarca peru observed low latitude vertical drift modulation with lows of 0 12 m s daytime maximum drifts between 6 13 and 22 25 january and enhanced drifts up to 43 m s between 15 snd 19 january the ncar thermosphere ionosphere mesosphere electrodynamics general circulation model reproduces the prevailing vertical drift feature and is used to examine possible causes the simulations indicate that the modulation of the vertical drift is generated by the beating of the semidiurnal solar sw2 and lunar m2 tides during the ssw period the beating is observable since the magnitudes of lunar and solar semidiurnal tidal amplitudes are comparable the theoretical beating frequency between sw2 and m2 is 1 15 13 day which may be modified due to phase changes this study highlights the importance of the lunar tide during ssw periods and indicates that the equatorial vertical drift modulation should be observable at other longitudes as well

estimating daytime vertical exb drift velocities in the equatorial f region using ground based magnetometer observations 1 the daytime equatorial electrojet is a narrow band of enhanced eastward current flowing in the 100 to 120 km altitude region within 2 latitude of the dip equator a unique way of determining the daytime strength of the electrojet is to observe the difference in the magnitudes of the horizontal h component between a magnetometer placed directly on the magnetic equator and one displaced 6 to 9 degrees away the difference between these measured h values provides a direct measure of the daytime electrojet current and in turn the magnitude of the vertical exb drift velocity in the f region ionosphere this paper discusses a recent study that has established the quantitative relationship between the vertical exb drift velocity in the ionospheric f region and the daytime strength of the equatorial electrojet in the south american west coast longitude sector

crustal extension in the baikal rift zone analysis of the gravity field along four profiles crossing the baikal rift zone permits an estimate of the amount of anomalous mass produced by 1 1 graben fill sediments 2 2 moho uplift and intrusion of mantle sills and dikes 3 3 an asthenospheric bulge crustal extension is evaluated based on the idea of mass and volume balance of material introduced into and removed from the initial volume of the crust extension in the baikal rift increases southwestward from 0 9 km in the chara depression to 19 3 km in the south baikal depression these values generally agree with the position of the euler pole determined from seismic data fault plane solutions average rotation velocity for the lithospheric plates separated by the rift zone is estimated to be 5 93 10 4 rad m y over about 30 m y

the 2004 2008 dome building eruption at mount st helens washington epilogue the 2004 2008 dome building eruption at mount st helens ended during winter 2007 2008 at a time when field observations were hampered by persistent bad weather as a result recognizing the end of the eruption was challenging but important for scientists trying to understand how and why long lived eruptions end and for public officials and land managers responsible for hazards mitigation and access restrictions in hindsight the end of the eruption was presaged by a slight increase in seismicity in december 2007 that culminated on january 12 13 2008 with a burst of more than 500 events most of which occurred in association with several tremor like signals and a spasmodic burst of long period earthquakes at about the same time a series of regular localized small amplitude tilt events thousands of which had been recorded during earlier phases of the eruption came to an end thereafter seismicity declined to 10 20 events per day until january 27 28 when a spasmodic burst of about 50 volcano tectonic earthquakes occurred over a span of 3 h this was followed by a brief return of repetitive drumbeat earthquakes that characterized much of the eruption by january 31 however seismicity had declined to 1 2 earthquakes per day a rate similar to pre eruption levels we attribute the tilt and seismic observations to convulsive stagnation of a semisolid magma plug in the upper part of the conduit the upward movement of the plug ceased when the excess driving pressure which had gradually decreased throughout the eruption as a result of reservoir deflation and increasing overburden from the growing dome was overcome by increasing friction as a result of cooling and crystallization of the plug

evolution of retreating subduction boundaries formed during continental collision retreating subduction boundaries formed where the rate of subduction exceeds the rate of overall plate convergence appear to be commonly developed features within regions of early or incomplete continent continent collision they are characterized by regional extension within the overriding plate and at their leading edge by thin skinned arcuate thrust belts that are concave towards the overriding plate as is illustrated by examples from the mediterranean region the formation of retreating subduction boundaries is intimately related to the process of continental collision during the early stages of collision retreating subduction boundaries are commonly formed by lateral ejection from zones of crustal shortening along the main collision boundary retreating plate boundaries can also form before the main collision and the associated thrust belts emplaced as precollisional accretionary assemblages because the driving mechanism for retreating subduction boundaries appears to be gravity acting on a dense subducted slab slab pull subduction usually ceases when and only when thick buoyant continental crust enters the subduction zone thus differences in the evolution and duration of retreating subduction systems can be largely attributed to the size and configuration of the deep water regions available to be subducted in some cases retreating subduction boundaries may escape into the open ocean where they form nearly isolated local tectonic systems in these systems the rate of subduction is approximately compensated by the rate of upper plate extension and migration of the system across the oceanic region may be very rapid for example the horseshoe seamounts located about 800 km offshore in the eastern north atlantic may be the active expression of an east dipping westwardly migrating retreating subduction boundary that has evolved from the betic cordillera rif system active in miocene time and may now be progressing across the atlantic at approximately 50 mm yr an analogous situation may be represented by the scotia arc system a westward dipping retreating subduction system located between the south american and antarctic plates which may have escaped into the south atlantic ocean from a zone of crustal shortening in the andes and is now progressing across the atlantic at a rate of about 80 mm yr

modes of continental lithospheric extension experimental verification of strain localization processes abstract three modes of continental lithospheric extension narrow rift wide rift and core complex were studied by means of analogue experiments the experimental method is based on models which simulate an idealized lithospheric strength profile and are scaled for gravity various styles of lithospheric extension were induced by systematic variation of brittle upper crustal thicknesses narrow rifting occurs during stable lithospheric extension when the resistance of the brittle upper crust dominates the deformation process wide rifting results from unstable lithospheric extension when the brittle upper crust is thin and ductile flow in the lower crust allows expansion of the deformation zone periodic instabilities with two wavelengths dominate wide rifting core complex mode extension is transitional between unstable and stable lithospheric extension it begins as a distributed zone of unstable extension due to thin upper brittle crust but lower crustal flow induced by the gravity force causes a relocalization of strain into narrow zones transitions between the three modes of extension are characterized in terms of competition between the strength of lithosphere and gravity forces as well as between stable and unstable deformation processes

mechanism of backarc opening in the japan sea role of asthenospheric injection abstract the process of backarc extension in the japan sea includes two modes of spreading the parallel and rotational or fan shape opening data from paleomagnetism for rocks on the northeast japan arc radiometric age determination for dredged volcanic rocks and heat flow in the basin have suggested that the parallel opening of the japan sea took place earlier than the rotational opening at 21 14 ma the mechanism of opening of the japan sea has been examined based on the secular change in the geometry of the subducted slab and in the volcanic activity on the northeast japan arc mechanisms of backarc rifting including mantle diapirism mantle flow induced by the slab subduction or interaction of the over and the underriding plates cannot reasonably explain the process of opening of the japan sea the most plausible mechanism operating in the spreading process of the japan sea is injection of the asthenosphere into the mantle wedge that forcefully pushed the subducted slab to cause both steepening of the slab and the backarc extension the asthenospheric current towards the northeast japan arc trench system may have been associated with the large scale upwelling of the asthenosphere beneath the northeastern china region that caused intra plate volcanism and produced continental rift systems in the region the present mechanism can also explain the active backarc rifting in the okinawa trough in the western pacific and the taupo depression in north island new zealand

thermodynamic analysis and simulation of coal metamorphism in the fushun basin china abstract taking the fushun basin as an example this paper analyses the relation of coal metamorphism to the normal geothermal field and additional geothermal field and establishes the thermodynamical model for the paleogeothermal field and corresponding coal metamorphism of the basin the 2 d simulation of the superimposition of coal geothermal metamorphism and telemagmatic thermal metamorphism has also been preliminarily accomplished the computer simulation results have shown that the coal formed in the paleogene in the fushun basin had an ro m value of only 0 3 and the intrusion of diabase sills in the later oligocene increased the coal rank to the low metamorphism stage ro m 0 5 1 0 it has been found in the simulation that the way in which the thermal flow in basement rock is controlled using the results from paleogeothermal structural analysis is obviously better than the method in which a value is artificially selected for the thermal flow according to the basin basement in addition the former can be used to study the variation of ro m itself so it is also better than the method to perform back confining analysis using ro m values

towards a mechanical model for the formation of the pannonian basin abstract new maps showing crustal and lithospheric thickness variations in the pannonian basin and the surrounding east alpine carpathian and dinaric mountains have been prepared on the basis of recent seismic seismologic and electromagnetic data a map presenting miocene faults of regional significance has been also constructed for the same region by using a wealth of recently available national and or more local studies it is suggested that observed crustal and lithospheric structural contrasts have been controlled primarily by neogene kinematic history of the region kinematic history is characterized by the following main patterns 1 1 indentation by adria and large scale backthrusting in the southern alps 2 2 eastward escape and extension of the eastern alps 3 3 extensional collapse in the pannonian basin area 4 4 formation of broad wrench fault systems along strike in the dinarides and southern carpathians and the western carpathians with dextral and sinistral shear respectively 5 5 compression and accretion of the external thrust and fold belt in the eastern carpathians these kinematic patterns are thought to be interrelated and all are manifestations of the late stage evolution of an overthickened orogenic wedge in order to arrive at a better understanding of the mechanism of extension which formed the pannonian basin deep crustal seismic profiles hydrocarbon exploration reflection lines and borehole data have been analyzed in the little hungarian plain this plain represents the transition zone between the alps and the pannonian lowlands and the results are illustrated by eight interpreted cross sections one result of regional importance is the clear recognition that the transdanubian central range at the southeastern flank of the little hungarian plain is composed of alpine pre senonian thrust sheets this finding marks the end of a century of debate the allochthony of the substrata of the pannonian basin can be now considered proven another result of more general interest is that these cross sections document the mode of lithospheric extension preexisting compressional detachment planes reactivate as low angle normal faults and lead to tectonic unroofing of deeply buried metamorphic terranes characterized by ductile flow along subhorizontal lineation

impact of sudden stratospheric warming of 2009 on the equatorial and low latitude ionosphere of the indian longitudes a case study using the equatorial electrojet eej induced surface magnetic field and total electron content tec measurements we investigated the impact of the sudden stratospheric warming ssw of january 2009 on the equatorial electrodynamics and low latitude ionosphere over the indian longitudes results indicate that the intensity of eej and the tec over low latitudes extending up to 30 n exhibit significant perturbations during and after the ssw peak one of the interesting features is the deviation of eej and tec from the normal quiet time behaviour well before the onset of the ssw this is found to be coincided with the beginning of enhanced planetary wave pw activity over high latitudes the substantial amplification of the semidiurnal perturbation after the ssw peak is seen to be coinciding with the onset of new and full moon the response of tec to ssw is found to be latitude dependent as the near equatorial ne stations show the semidiurnal perturbation only after the ssw peak another notable feature is the presence of reduced ionization in the night sector over the ne and low latitude regions appearing as an ionization hole well after the ssw peak the investigation revealed the existence of a quasi 16 day wave in the tec over low latitudes similar to the one present in the eej strength these results have been discussed in the light of changes in the dynamical background because of enhanced pw activity during ssw which creates favourable conditions for the amplification of lunar tides and their subsequent interaction with the lower thermospheric tidal fields

influence of the subducting plate velocity on the geometry of the slab and migration of the subduction hinge abstract geological observations indicate that along two active continental margins east asia and mediterranean major phases of overriding plate extension resulting from subduction hinge retreat occurred synchronously with a reduction in subducting plate velocity in this paper results of fluid dynamical experiments are presented to test the influence of the velocity of the subducting plate on the hinge migration velocity and on the geometry of the slab results show that hinge retreat decreases with increasing subducting plate velocity in addition phases of hinge retreat alternate with phases of hinge advance for relatively high subducting plate velocities due to interaction of the slab with the bottom of the box simulating the upper lower mantle discontinuity such slab kinematics could explain the episodic behaviour of back arc opening observed in convergent settings the geometry of the slab and the kinematics of subduction are significantly affected by the velocity of the subducting plate three subduction modes with accompanying slab geometry can be recognized a relatively low subducting plate velocity is accompanied by relatively fast hinge retreat with backward sinking of the slab and a backward draping slab geometry with increasing subducting plate velocity hinge migration is relatively small resulting in subvertical sinking of the slab and a folded slab piling geometry for a very high velocity the hinge migrates forward resulting in forward oriented subduction vectors and a forward draping slab geometry

time gcm study of the ionospheric equatorial vertical drift changes during the 2006 stratospheric sudden warming this modeling study quantifies the daytime low latitude vertical e b drift changes in the longitudinal wave number 1 wn1 to wn4 during the major extended january 2006 stratospheric sudden warming ssw period as simulated by the national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm and attributes the drift changes to specific tides and planetary waves pws the largest drift amplitude change approximately 5 m s is seen in wn1 with a strong temporal correlation to the ssw the wn1 drift is primarily caused by the semidiurnal westward propagating tide with zonal wave number 1 sw1 and secondarily by a stationary planetary wave with zonal wave number 1 pw1 sw1 is generated by the nonlinear interaction of pw1 and the migrating semidiurnal tide sw2 at high latitude around 90 100 km the simulations suggest that the e region pw1 around 100 130 km at the different latitudes has different origins at high latitudes the pw1 is related to the original stratospheric pw1 at midlatitudes the model indicates pw1 is due to the nonlinear interaction of sw1 and sw2 around 95 105 km and at low latitudes the pw1 might be caused by the nonlinear interaction between de2 and de3 the time evolution of the simulated wn4 in the vertical e b drift amplitude shows no temporal correlation with the ssw the wn4 in the low latitude vertical drift is attributed to the diurnal eastward propagating tide with zonal wave number 3 de3 and the contributions from se2 te1 and pw4 are negligible

ionospheric variability over indian low latitude linked with the 2009 sudden stratospheric warming in this paper we analyze radar observations of e b drift and plasma irregularities ionosonde observations of e and f layer parameters including spread f and magnetic field observations made from indian low latitudes linked with the 2009 sudden stratospheric warming ssw event e b drift variations presented here are the first of their kind from the indian sector as far as the effect of ssw is concerned difference of magnetic fields observed from the equator and low latitude h and e b drift show linear relation and both show remarkably large positive values in the morning and negative values in the afternoon exhibiting semidiurnal behavior remarkable changing patterns in the critical frequency of f2 layer fof2 and f3 layer fof3 were observed after the occurrence of ssw large variations with quasi 16 day periodicity were observed in h fof2 and fof3 both semidiurnal and quasi 16 day wave modulation observed after the 2009 ssw event are consistent with those reported earlier we also noted quasi 6 day variations in h and fof2 soon after the ssw commencement not much reported before during the counterelectrojet events linked with the ssw event while equatorial es esq disappeared as expected there were no blanketing es esb a finding not reported and discussed earlier esb was also not formed at the off equatorial location indicating the absence of required vertical wind shear but e region plasma irregularities were observed by the ionosonde and radar with a close relationship between the two weak f region irregularities were observed in the postmidnight hours and case studies suggest the possible role of ssw related background electric field in the manifestation of postmidnight f region irregularities

observational evidence of ionospheric migrating tide modification during the 2009 stratospheric sudden warming 1 in this paper modifications of the ionospheric tidal signatures during the 2009 stratospheric sudden warming ssw event are studied by applying atmospheric tidal analysis to ionospheric electron densities observed using radio occultation soundings of formosat 3 cosmic the tidal analysis indicates that the zonal mean and major migrating tidal components dw1 sw2 and tw3 decrease around the time of the ssw with 1 5 4 hour time shifts in the daily time of maximum around eia and middle latitudes the typical ionospheric ssw signature a semi diurnal variation of the ionospheric electron density featuring an earlier commencement and subsidence of eia can be reproduced by differencing the migrating tides before and during the ssw period our results also indicate that the migrating tides represent 80 of the ionospheric tidal components at specific longitudes suggesting that modifications of the migrating tides may be the major driver for producing ionospheric changes observed during ssw events accounting for greater variability than the nonmigrating tides that have been the focus of previous studies

asymmetric deformation in the backarc region of the kuril arc northwest pacific new insights from analogue modeling 1 the eocene to middle late miocene tectonic evolution of the kuril arc and backarc region has been simulated with analogue experiments the experiments simulate asymmetric deformation in the overriding plate due to anticlockwise rollback of the subducting pacific plate the results show the formation of a n s to ne sw oriented dextral shear zone near the far edge of the retreating boundary analogous to the sakhalin hokkaido dextral shear zone contemporaneously normal faults and grabens form striking parallel to the retreating boundary near the far edge but striking more oblique near the hinge point and away from the retreating boundary this is similar to extensional structures observed in the kuril basin and the sea of okhotsk furthermore the model shows that the amount of extension progressively decreases away from the retreating boundary this appears to have also happened in the kuril okhotsk region as evidenced by crustal thickness variation in the region finally the model results show that extension is increasingly accommodated by the region close to the retreating boundary with progressive deformation this can account for the eocene early miocene extension in the sea of okhotsk followed by miocene spreading in the kuril basin

global ionospheric response to the 2009 sudden stratospheric warming event using ionospheric data assimilation four dimensional ida4d algorithm a data assimilation algorithm is used to delineate the time dependent three dimensional ionospheric response to the 2009 sudden stratospheric warming ssw event we use the ionospheric data assimilation four dimensional ida4d algorithm to study the global ionospheric response to the 2009 ssw this is the first study to utilize global ionospheric measurements in a data assimilation framework to unambiguously characterize atmosphere ionosphere coupling via tidal modifications during the 2009 ssw event model results reveal that the dominant mode of ionospheric variability during the 2009 ssw is driven by the enhancements in westward propagating semidiurnal tide with zonal wave number 1 the ida4d results completely characterize the tidal perturbation during the 2009 ssw for the first time and show the global 3 d structure of the tide in total electron content tec and electron density the largest ionospheric responses were seen at low latitudes where ionospheric plasma is extremely sensitive to the zonal electric field and susceptible to modifications by tidal winds in the lower thermosphere the ionospheric response to the warming was characterized by an increase in tec in the morning early afternoon sector and a decrease during the late afternoon evening period the effects of coupling between the stratosphere and ionosphere were strongest between 220 km and 380 km the ida4d results also show a reversal of asymmetry in the equatorial ionization anomaly crests occurring several days after the peak of the 2009 ssw event we suggest that this could be a result of the equatorial fountain effect being further modified by the summer to winter meridional neutral winds

lunar and solar tidal variabilities in mesospheric winds and eej strength over tirunelveli 8 7 n 77 8 e during the 2009 major stratospheric warming 1 mesospheric wind observations by the medium frequency radar and geomagnetic field observations at tirunelveli 8 7 n 77 8 e 1 75 n dip angle are used to study the relative importance of solar and lunar influences in the variabilities of mesospheric tides and equatorial electrojet eej strength during the unprecedented major stratospheric sudden warming ssw of 2009 it is observed that the afternoon reversal in the eej popularly known as counter electrojet occurs consecutively for several days during the ssw event when there is an enhancement of solar semidiurnal tide in both zonal wind at 90 km and eej strength over tirunelveli although the amplitude of lunar tides also shows enhancement it is much less than that of solar the diurnal tidal amplitude in zonal wind and eej strength also shows large enhancement just before the onset of ssw however solar semidiurnal tide dominates diurnal tide during the ssw the diurnal tidal phase in zonal wind shifts to a few hours earlier during the ssw the lunar semidiurnal tidal phase shifts to later hours in both zonal wind and eej strength the main observation of the present study is that the large semidiurnal tide observed during the ssw 2009 is mostly solar driven and only partly lunar driven although tidal planetary wave interaction also may play a vital role although a similar behavior is noticed during the ssw 2006 also the large lunar semidiurnal tide observed in the eej strength without having large lunar semidiurnal tide in the underlying mesospheric winds needs further investigation

evolution of the pannonian basin system 1 tectonics the carpathian arc formed during cretaceous to miocene time by continental collision between europe and smaller continental fragments following southward and westward subduction of ocean floor during the last stages of thrusting in the outer carpathians a set of discrete basins formed behind the carpathian loop these basins are regions of middle to late miocene extension and are connected to each other and to areas of coeval shortening in the outer carpathian thrust belt by a system of strike slip faults sinistral northeast trending and dextral northwest trending sets of conjugate shears reflect overall east west extension of the intra carpathian region during middle to late miocene time palinspastic reconstruction of the basins indicates about 100 50 km of east west extension across the intra carpathian region during this time we interpret the vienna basin which is superimposed partly on the flysch nappes of the outer west carpathians as the result of thin skinned extensional tectonics above a shallow detachment surface within the crust extension of upper crustal rocks above this detachment was probably accomodated by thrusting of the outermost nappes of the west carpathians over the european platform extension of basins farther inside the carpathian loop probably involved rocks at deeper crustal levels and within the upper mantle the most internally situated basins formed by extensional processes that involved the entire lithosphere thus the depth to which extension occurred seems to be closely related to the proximity of each basin to the active thrust front in the carpathians this can be related to the geometry of the subduction zone extension within the intra carpathian basins began first in the northernmost basins and migrated southward and eastward over a ten million year period palinspastic reconstruction of the basins at three different times during the miocene 17 5 16 5 and 13 0 ma predicts eastward migration of the zone of thrusting and shortening within the carpathian mountains to accomodate the synchronous eastward and southward migration of areas of extension from these reconstructions about 120 60 km of east west shortening is predicted across the outer east carpathians from about 17 5 ma until present both predictions are in good agreement with the timing and magnitude of shortening in the carpathian thrust belt as determined directly from rocks within the belt from this we infer a close relationship for middle to late miocene extension of the intra carpathian region and middle to late miocene crustal shortening within the outer carpathians during middle and late miocene time deformation of the pannonian fragment was dominated by extensional and wrench tectonics except along a narrow zone in the outer carpathian thrust belt middle and late miocene thrusting in the carpathians is interpreted as the result of simple shear caused by relative motion between europe and the overriding pannonian fragment at the subduction boundary rather than of regional compression of lithospheric rocks at depth the initiation of extensional tectonics within the intra carpathian region in middle miocene time can be related to reorganization of major fragment boundaries of the eastern european alpine system

lunar tide in the equatorial electrojet in relation to stratospheric warmings 1 the relationship between sudden stratospheric warmings ssws and large amplitude lunar tides in the equatorial electrojet eej is studied analysis of ground magnetometer data shows that the lunar tide in the eej is maximum during the northern winter season except in the pacific ocean region since ssws are also a northern winter phenomenon it is suggested that the relation between the large lunar tide in the eej and the ssw may possibly be coincidental the lunar tide in the geomagnetic variations at huancayo is anomalously large compared with other eej stations an examination of geomagnetic variations at eej stations during ssw events shows that afternoon counter electrojets are frequently present at new moon and full moon though the relationship is sometimes broken the observation of large lunar eejs when no ssw is present and of various different delay times suggests that other atmospheric processes are likely to be in play

neotectonic activity along the shanxi rift system china abstract the shanxi rift system is one of the most outstanding pliocene quaternary continental rift systems and strong earthquake belts in china it extends as a series of en echelon left stepping asymmetrical half graben basins on the shanxi highlands over a distance of more than 1200 km it describes a sinous s shaped curve with a nne trending transtensional segment in the middle and ne ene trending extensional domains on both terminal segments the latter are characterized by apparently synchronous high angle normal faulting accommodating large vertical and relatively smaller lateral strains 3 5 8 5 which produces the modern basin and range structure the rift system has been intermittently active since the pliocene geomorphological neotectonic and seismic studies indicate that the rift system is at present still developing as demonstrated by the occurrence of strong destructive historical earthquakes of magnitudes 7 8 and the large slip rates on the nne trending transtensional faults in the middle segment the slip rates of these faults reached 4 9 6 4 mm per year during the holocene geophysical studies show that the rifting occurred in a thickened crust and no compelling evidence exists for the major thermal event in the mantle uniquely associated with the rifting the development of the shanxi rift system is consistent with the regional brittle strain pattern of a right lateral shear belt and a regional stress field of ene wsw compression and nnw sse extension of the north china subplate this structural setting corroborates the hypothesis that the deformation is in response to the escape tectonics caused by the himalayan indenter from the southwest and at the same time by the counter clockwise rotation of the intervening crustal blocks this provides the mode of formation of the shanxi rift system

quiet variability of equatorial e b drifts during a sudden stratospheric warming event 1 we present strong evidence that during the january 2008 minor sudden stratospheric warming ssw event the equatorial vertical e b drifts exhibit a unique and distinctive daytime pattern we do not think one event causes the other however both events might be related through the global effects of planetary waves the drifts were measured by the jicamarca incoherent scatter radar located under the magnetic equator we have observed an anomalous temporal variation of the vertical e b drifts during the minor ssw event showing a semidiurnal variation with very large amplitudes lasting for several days large differences in the e b drifts were observed during a period of large increase of temperature and a large decrease of mean zonal wind in the high latitude stratosphere 60 90 n this high correlation is an unexpected finding which might shed new light on sources and mechanisms of quiet time ionospheric variability

the cenozoic tectonic evolution of the great north china two types of rifting and crustal necking in the great north china and their tectonic implications abstract the great north china underwent widespread continental rifting during cenozoic time that caused extension and necking of the crust in this area and formed four major rift systems in this paper we provide geological and geophysical evidence that rifting and extension in the western part of the great north china differs from that in its eastern part in age and nature the space time relationships show that the origins of the western rift group of the great north china are probably related to the tibet plateau tectonics whereas those of the eastern rift group are related to the subduction events in the western margin of the pacific plate furthermore the quaternary tectonic regime in the eastern part of the great north china differs from the neogene tectonic pattern and shows relations with western rifts we speculate that during the quaternary the processes that caused rifting in the west have spread further east and now affect the eastern part of the great north china

3 d seismic velocity structure of the crust and the uppermost mantle in the northeastern japan arc 3 d seismic velocity structure of the crust and the uppermost mantle beneath the northeastern japan arc is investigated by using arrival time data from local earthquakes we use a velocity model composed of three layers corresponding to the upper crust the lower crust and the uppermost mantle respectively taking into account the observed regional variation of pn velocity the uppermost mantle is further divided into three parts by two pn velocity boundaries near the coasts of the japan sea and the pacific ocean the velocities within the upper crust the lower crust and the three parts of the uppermost mantle are assumed to be constant locations of two pn velocity boundaries and depth distributions of the conrad and the moho discontinuities are expressed by continuous functions of unknown parameters station corrections and hypocenters are also introduced to be unknowns these unknown parameters are determined by inverting arrival time data of p and s wave first arrivals and clear later arrivals of pg and p waves the pn velocity boundary between the land and the pacific ocean is located approximately along the pacific coastline and that between the land and the japan sea is nearly along the japan sea coastline the conrad and the moho discontinuities are at depths ranging from 14 to 20 km and from 27 to 36 km respectively the conrad and the moho depths have similar spatial distributions they are deep beneath the land and become shallower toward the western and the eastern coastlines beneath the land they are shallow in the central part of the tohoku district and become deeper toward both the north and the south directions in the north they become shallow again

c nofs observations of the equatorial ionospheric electric field response to the 2009 major sudden stratospheric warming event 1 we present new observations made by the coupled ion neutral dynamics investigation cindi ion velocity meter ivm instrument onboard the communication navigation outage forecasting system c nofs satellite that show the effects of the january 2009 sudden stratospheric warming ssw event on equatorial electric fields we have used ivm observations to construct composite curves of mean equatorial vertical plasma drifts as a function of local time and longitude sector these curves show large upward vertical drifts during morning hours and downward drifts during afternoon our analysis indicates that this pattern could be observed over the range of longitudes where adequate ivm measurements were available from approximately 165 e to about 315 e longitude a clear day to day quasi deterministic variability in the drifts is also observed with the transition from upward to downward drifts occurring at increasing local times from 25 to 30 january 2009 the analysis also suggests some level of longitudinal variability in the magnitude of the drifts these in situ observations are in good agreement with previous ground based measurements of the response of equatorial electric fields to ssw events in particular we found that ivm drift measurements centered around 285 e depart significantly from climatological values but agree exceptionally well with ground based measurements of vertical drifts made by the jicamarca incoherent backscatter radar overall the results agree well with previous studies of ssw events demonstrate the usefulness of the ivm observations and motivate further studies of the variability of the equatorial ionosphere using c nofs

a neogene back arc origin for the banda sea basins geochemical and geochronological constraints from the banda ridges east indonesia abstract dredgings conducted during the french indonesian cruises banda sea ii and iii collected volcanic rocks from several ridges of the banda sea area tukang besi ridge site 218 lucipara ridge sites 214 and 305 nieuwerkerk emperor of china sites 219 and 220 with the exception of one 46 ma old n morb type basalt thought to belong to an ophiolitic complex k ar and ar ar datings indicate that all the dredged volcanics are neogene they range in age from ca 10 ma tukang besi back arc basalts to 8 7 ma nieuwerkerk emperor of china calc alkaline andesites and to 7 3 ma lucipara oib type transitional basalts and cordierite bearing andesites radiogenic isotopic signatures of andesites are consistent with an afc assimilation coupled with fractional crystallization process involving assimilation of continental crust 8 3 ma old calc alkaline volcanic activity is also recorded on the wetar segment an inactive part of the east sunda arc and corresponding isotopic compositions are also consistent with an afc process involving continental crust these features suggest that lucipara nieuwerkerk emperor of china ridges and the wetar segment were representing a single volcanic arc 8 7 ma ago the corresponding calc alkaline activity was related to the subduction of the indian oceanic lithosphere beneath continental blocks of australian origin back arc opening processes occurred from 6 to 3 ma as a multi rift opening for the wetar basin and as a single rift opening for the damar basin while subduction related magmatism was still active in the wetar segment volcanic activity stopped at 7 ma in the nieuwerkerk emperor of china ridge on lucipara ridge 6 3 ma volcanic activity emplaced concomitantly transitional basalts and cordierite bearing andesites the mineralogical and chemical features of the latter are consistent with an afc process involving assimilation of continental crust by mantle derived basaltic magmas the end of magmatic activity on both volcanic segments at 3 ma is thought to result from the collision of timor with the wetar segment of the sunda arc

coupling between mesosphere and ionosphere over beijing through semidiurnal tides during the 2009 sudden stratospheric warming 1 sudden stratospheric warming ssw in the winter of 2008 2009 is the strongest recorded ssw event the enhancement in semidiurnal variation of ionospheric tec total electron content with phase shift forward is shown during 22 to 27 january 2009 based on the tec observations in beijing 40 30 n 116 19 e geographic 39 73 n dip latitude we focus on finding the reason for the tec variation winds observed by an all sky meteor radar in the same observatory are used to study mesospheric variation the semidiurnal solar tide in the mesosphere starts to increase before the ssw and maintains oscillation with period 16 20 days during the ssw the semidiurnal lunar tides in tec and wind start to increase on 17 and 15 january respectively although the semidiurnal lunar tide in tec over beijing almost dies out on 1 february that over equatorial ionospheric anomaly crest does not vanish until 15 february when lunar tide in wind tends to be very weak the maximum of lunar tide in wind appears on 2 february at 96 km with amplitudes of 15 m s and 21 m s for zonal and meridional winds the phase comparison shows that lunar tides in tec and zonal wind reach their maxima at almost the same time which is 2 4 h lag behind the meridional wind the coupling between the mesosphere and ionosphere contributes to the semidiurnal variation of tec through both solar and semidiurnal lunar tides the enhancement in semidiurnal lunar tide is responsible for the tec peak shift forward during the ssw

longitudinal differences of ionospheric vertical density distribution and equatorial electrodynamics 1 accurate estimation of global vertical distribution of ionospheric and plasmaspheric density as a function of local time season and magnetic activity is required to improve the operation of space based navigation and communication systems the vertical density distribution especially at low and equatorial latitudes is governed by the equatorial electrodynamics that produces a vertical driving force the vertical structure of the equatorial density distribution can be observed by using tomographic reconstruction techniques on ground based global positioning system gps total electron content tec similarly the vertical drift which is one of the driving mechanisms that govern equatorial electrodynamics and strongly affect the structure and dynamics of the ionosphere in the low midlatitude region can be estimated using ground magnetometer observations we present tomographically reconstructed density distribution and the corresponding vertical drifts at two different longitudes the east african and west south american sectors chains of gps stations in the east african and west south american longitudinal sectors covering the equatorial anomaly region of meridian 37 e and 290 e respectively are used to reconstruct the vertical density distribution similarly magnetometer sites of african meridian b field education and research amber and intermagnet for the east african sector and south american meridional b field array samba and low latitude ionospheric sensor network lisn are used to estimate the vertical drift velocity at two distinct longitudes the comparison between the reconstructed and jicamarca incoherent scatter radar isr measured density profiles shows excellent agreement demonstrating the usefulness of tomographic reconstruction technique in providing the vertical density distribution at different longitudes similarly the comparison between magnetometer estimated vertical drift and other independent drift observation such as from vefi onboard communication navigation outage forecasting system c nofs satellite and julia radar is equally promising the observations at different longitudes suggest that the vertical drift velocities and the vertical density distribution have significant longitudinal differences especially the equatorial anomaly peaks expand to higher latitudes more in american sector than the african sector indicating that the vertical drift in the american sector is stronger than the african sector

an analog experiment for the aegean to describe the contribution of gravitational potential energy the southern aegean seafloor exhibits clear evidence of internal deformation stretching as shown by tectonics seismology and space geodesy we use an analog three layer laboratory experiment of sand silicone putty and honey to investigate the deformation of the southern aegean lithosphere the model is installed in a box and confined by a vertical wall we open a gate in the wall and observe the deformation of the two upper layers due to buoyancy forces the general pattern of the deformation of the southern aegean is found in the analog model we observe the formation of an arc spreading outward with time the extension is radial in the inner part but parallel to the arc in the external part and of comparable importance at both ends of the gate we observe strike slip motion dextral in the western part sinistral in the eastern part rotation clockwise in the western part counterclockwise in the eastern part of up to 40 is seen on both sides of the gate but is also present with a smaller amplitude far in the internal region partially due to distributed shear the spreading is associated with the thinning of the two upper layers and affects a region of dimensions comparable to the length of the free boundary this spreading does not propagate inward with time some pieces of material located near the active boundary remain undeformed during the experiment

causes of the longitudinal differences in the equatorial vertical e b drift during the 2013 ssw period as simulated by the time gcm during stratospheric sudden warming ssw periods large changes in the low latitude vertical drift have been observed at jicamarca as well as in other longitudinal sectors in general a strengthening of the daytime maximum vertical drift with a shift from prenoon to the afternoon is observed during the january 2013 stratospheric warming significant longitudinal differences in the equatorial vertical drift were observed at jicamarca the previously reported ssw behavior prevails however no shift of the daytime maximum drift was exhibited in the african sector using the national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm the possible causes for the longitudinal difference are examined the timing of the strong ssw effect in the vertical drift 15 20 january coincides with moderate geomagnetic activity the simulation indicates that approximately half of the daytime vertical drift increase in the american sector may be related to the moderate geophysical conditions kp 4 with the effect being negligible in the african sector the simulation suggests that the wind dynamo accounts for approximately 50 of the daytime vertical drift in the american sector and almost 100 in the african sector the simulation agrees with previous findings that the migrating solar tides and the semidiurnal westward propagating tide with zonal wave number 1 sw1 mainly contribute to the daytime wind dynamo and vertical drift numerical experiments suggest that the neutral wind and the geomagnetic main field contribute to the presence absence of a local time shift in the daytime maximum drift in the american african sector

quantifying the net slab pull force as a driving mechanism for plate tectonics 1 it has remained unclear how much of the negative buoyancy force of the slab fb is used to pull the trailing plate at the surface into the mantle here i present three dimensional laboratory experiments to quantify the net slab pull force fnsp with respect to fb during subduction results show that fnsp increases with increasing slab length and dip up to 8 12 of fb making fnsp up to twice as large as the ridge push force the remainder of fb is primarily used to drive rollback induced mantle flow 70 to bend the subducting plate at the trench 15 30 and to overcome shear resistance between slab and mantle 0 8

late cretaceous and cenozoic tectono stratigraphic development of the east java sea basin indonesia abstract the east java sea basin is underlain by a metamorphic basement complex subsidence of this basement during the late cretaceous resulted in accumulation of up to 3 km of marine upper cretaceous sediments megasequence 1 contraction and near peneplanation of the upper cretaceous sediments and underlying basement occurred before the middle early eocene producing a regional unconformity which defines the base of megasequence 2 the cenozoic east java sea basin started to form during the early eocene by crustal extension on both planar normal faults and extensionally reactivated cretaceous thrusts normal faulting was pulsed from the early eocene to early oligocene and affected a progressively larger area with time complex structural geometries evolved in response to local extensional reactivation of obliquely orientated pre existing structures the resultant palaeogene fault controlled sub basins were filled with fluvial coastal plain and shelf clastic and carbonate sediments recording an overall transgressive evolution regional subsidence became dominant over fault controlled subsidence during the early oligocene basin fill during this time was dominated by deep marine fine grained clastic sediments a regional unconformity of intra oligocene age is recognized and is overlain by oligocene to lowermost miocene deep water calcareous mudrocks and limestones which locally onlap erosionally truncated eocene rocks the lower eocene to lowermost miocene sediment package comprises megasequence 2 regional inversion of palaeogene sub basins commenced in the early miocene and continues to the present day the syn inversion lower miocene to recent sediments comprise megasequence 3 inversion has resulted from regional contraction and resultant reverse reactivation of palaeogene normal faults and cretaceous thrusts regional subsidence has been continuous during the inversion history resulting in a gradual reversal of depocentre location palaeogene depocentres became neogene highs whereas palaeogene platforms became neogene depocentres miocene deposition during inversion was dominated by the alternation of fine grained carbonate dominated and clastic dominated cycles subsequent pliocene sandstone deposition followed fluvial incision during an early pliocene lowstand the depositional history during the pleistocene to recent records rapid relative sea level changes progradation of clastic and carbonate sediments erosional truncation channelling and slumping the tertiary structural geometrical evolution and preserved sediment distribution can be explained by dominantly dip slip fault movement during the extensional and contractional phases of basin development and deformation basin scale cross sectional geometries similar to classical positive flower structures have evolved by the reverse reactivation of a geometrically complex extensional fault system

tertiary tectonics of the sea of okhotsk russia far field effects of the india eurasia collision a new structural map of the western sea of okhotsk based on grids of multichannel seismic data provides several new insights into the tertiary deformation of asia especially in regard to the extension of extrusion tectonics linked to the india eurasia collision into northeastern asia the sedimentary basins in this offshore region are the result of two regional shear systems in the west the north trending sakhalin hokkaido dextral fault system transects sakhalin island accessory structures closely related to its dextral shear include northeast trending normal faults as well as northwest trending en echelon folds and thrusts the accessory normal faults are predominantly eocene to lower miocene and indicate transtensional shear whereas the folds and thrusts are mostly younger and indicate late miocene and pliocene transpression in the north an east west trending sinistral shear zone enters the sea at its northwest corner this sinistral shear system links farther west to extensional faults of the early tertiary baikal rift extending northeastward from the terminus of this sinistral shear zone are a series of long predominantly northwest dipping listric normal faults that form a large lazy s shaped pull apart basin the shantar liziansky basin slb normal faults in this 500 140 km basin accommodate 15 to 20 extension extension and related sinistral shear appear to be largely eocene to oligocene in age with lesser later activity to the northeast of slb a further extension of the sinistral shear zone appears to bend northeastward transecting pustorets and penzhina basins and following the course of the older mesozoic mongol okhotsk chukotsk active margin and suture it possibly reaches as far as the arctic as suggested by previous workers the baikal rift and its associated sinistral shear zone may be interpreted as by products of the india eurasia collision in eocene time mapping results included here show that this diffuse sinistral shear system extends much farther to the northeast the sinistral shear zone is transected by the dextral sakhalin hokkaido fault zone in the kashevarov region of central slb where a fan of north to northwest striking late tertiary transpressional fault splays marks the northern termination of the dextral fault zone older slb normal faults are locally deformed and half grabens are partly inverted by the slightly younger dextral splays the two regional fault systems are essentially conjugate and the pattern of intersection closely resembles that predicted by recent modelling studies of india eurasia collision tectonics

longitudinal variation of ionospheric vertical drifts during the 2009 sudden stratospheric warming 1 the whole atmospheric model wam initialized with a data assimilation scheme is capable of simulating real sudden stratospheric warming ssw events the electrodynamics in the coupled thermosphere ionosphere and plasmasphere with electrodynamics model ctipe was driven by the wam thermospheric winds in january 2009 to study the response of ionospheric drifts during the ssw simulation results are compared with observations of the vertical drift at jicamarca and the equatorial electrojet eej in the asian sectors early morning upward drift and afternoon downward drift are reproduced in all longitudes in the simulations and are consistent with the available observations results also show that the occurrence time of the early morning upward drift and afternoon downward drift have significant phase differences between different longitudes simulations suggest that during the ssw the longitude dependence of the amplitude and phase of the equatorial vertical plasma drift is caused by the changing magnitudes of the migrating tides modulated by the geometry of the geomagnetic field some additional day to day variability and modulation of the phase structures at different longitudes in ionospheric vertical drifts during the ssw are possibly produced by the short term changes in the non migrating tides and by planetary waves

longitudinal and interhemispheric ionospheric response to 2009 and 2013 ssw events in the african european and indian east asian sectors

radar and satellite global equatorial f region vertical drift model we present the first global empirical model for the quiet time f region equatorial vertical drifts based on combined incoherent scatter radar observations at jicamarca and ion drift meter observations on board the atmospheric explorer e satellite this analytical model based on products of cubic b splines and with nearly conservative electric fields describes the diurnal and seasonal variations of the equatorial vertical drifts for a continuous range of all longitudes and solar flux values our results indicate that during solar minimum the evening prereversal velocity enhancement exhibits only small longitudinal variations during equinox with amplitudes of about 15 20 m s is observed only in the american sector during december solstice with amplitudes of about 5 10 m s and is absent at all longitudes during june solstice the solar minimum evening reversal times are fairly independent of longitude except during december solstice during solar maximum the evening upward vertical drifts and reversal times exhibit large longitudinal variations particularly during the solstices in this case for a solar flux index of 180 the june solstice evening peak drifts maximize in the pacific region with drift amplitudes of up to 35 m s whereas the december solstice velocities maximize in the american sector with comparable magnitudes the equinoctial peak velocities vary between about 35 and 45 m s the morning reversal times and the daytime drifts exhibit only small variations with the phase of the solar cycle the daytime drifts have largest amplitudes between about 0900 and 1100 lt with typical values of 25 30 m s we also show that our model results are in good agreement with other equatorial ground based observations over india brazil and kwajalein

age of initiation of collision between india and asia a review of stratigraphic data abstract the collision of india with asia is perhaps the most profound tectonic event to have occurred in past 100 ma it is responsible for the uplift of the himalayas and tibetan plateau and has been argued to have been responsible for geological geochemical and climatological consequences of global extent yet the age of initiation of this collision remains poorly constrained the literature is replete with estimates that range from the late cretaceous 65 ma to latest eocene

sudden stratospheric warming event signatures in daytime exb drift velocities in the peruvian and philippine longitude sectors for january 2003 and 2004 1 this paper first describes the technique that has been developed to obtain realistic daytime vertical exb drift velocities in the equatorial ionosphere using two ground based magnetometers one on the magnetic equator and the other located 6 9 away in latitude this technique is then employed to study the unique exb drift signatures associated with sudden stratospheric warming events ssw in both the peruvian and philippine longitude sectors occurring in january 2003 and january 2004 it is found that the semidiurnal shaped signature first appears in the peruvian sector and 3 days later appears in the philippine sector in both sectors the exb drift signature lasts for approximately 5 days

the role of the east asian active margin in widespread extensional and strike slip deformation in east asia east asia is a region of widespread deformation dominated by normal and strike slip faults deformation has been interpreted to result from extrusion tectonics related to the india eurasia collision which started in the early eocene in east and se china however deformation started earlier than the collision latest cretaceous to palaeocene suggesting that extrusion tectonics is not the only driving mechanism for east asia deformation it is suggested that the east asian active margin has influenced deformation in east asia significantly along the margin cenozoic back arc extension took place behind several adjoining arcs implying eastward rollback of the subducting slab and collapse of the overriding plate towards the retreating hinge line we show that extension took place along a c 7400 km long stretch of the east asian margin during most of the cenozoic physical models are presented simulating overriding plate collapse and back arc extension the models reproduce important aspects of the strain field in east asia for geometrical and rheological conditions scaled to represent east asia modelling shows that the active margin can be held responsible for deformation in east asia as far west as the baikal rift zone located c 3300 km from the margin

the stratigraphy structure and evolution of zengmu basin abstract the zengmu basin is a large tertiary marine sedimentary basin in the southern region of the south china sea it is considered to have multiple combinations of source rocks reservoirs and caprock making it a favourable prospect for oil and gas seismic investigations have shown that this has three tectonic sequences separated by two unconformities the upper sequence consists of oligocene to recent marine sediments the middle sequence is thought to be composed of paleogene to eocene shelf neritic clastic deposits and the lower sequence is interpreted as being pre tertiary metamorphic or igneous rocks the development of the basin has been controlled by faults especially by northwest trending faults leading to gradual stepped block subsidence to the northeast three fault systems trending nw ne and s n separate the basin into ten secondary tectonic units with five depressions and five highs taking into account the seismic reflection data collected during the 1987 survey by the shiyan ii and the geological information available from earlier work this paper elucidates our understanding of the sequences division and tectonic subdivision and of the formation evolution and oil and gas prospects of the zengmu basin

effect of sudden stratospheric warming on lunar tidal modulation of the equatorial electrojet 1 using the equatorial electrojet eej peak current intensity as deduced from champ magnetic observations from the years 2001 through 2009 we investigated the relationship between sudden stratospheric warming ssw and lunitidal signatures in the tropical ionosphere there is a practically one to one correspondence between midwinter ssw periods and the strongest 13 day modulation of the eej strength as observed by champ that is all the midwinter ssw periods from december 2001 to august 2009 were accompanied by an enhanced 13 day modulation of the eej strength no other geophysical phenomenon brought about as strong a 13 day modulation as those of the midwinter ssw periods during each midwinter ssw period the amplified 13 day modulation of the eej strengths starts roughly within 1 week around the first peak in stratospheric temperature difference an oscillation with a period of 13 26 days is predicted by the lunitidal equation when considering the precession of the champ orbit when fitting the lunitidal equation to the eej modulations during the midwinter ssw periods consistent phase delays of 4 4 0 3 days of the tidal signal emerge for all the cases the results suggest that the pronounced 13 day modulation of the eej strength is related to an enhancement of the lunar tide in the ionosphere by the ssw effect