lithospheric and upper mantle structure of southern tibet from a seismological passive source experiment fifteen seismic stations were operated with about 20 km spacing in southern tibet across the zangbo suture the collision zone between india and asia between may and october 1994 as part of the international deep profiling of tibet and the himalaya project indepth ii for wide angle recording of the controlled source experiment and for passive earthquake recording in addition a dense deployment 4 km spacing of stations within the german depth profiling of tibet and the himalayas gedepth project also recorded a number of teleseismic earthquakes the third data source used in this study is the records of the permanent broadband station at lhasa teleseismic records have been obtained in sufficient quantity and quality to derive an image of the structure of the lithosphere and upper mantle from p to s converted phases important results are as follows the moho at 70 80 km and a second discontinuity at 50 60 km depth are observed over the entire profile south and north of the zangbo suture the data from the gedepth dense array enable the detection of inclined structures penetrating the crust at the zangbo suture a pronounced low velocity zone exists north of the zangbo suture at about 10 20 km depth the locations of the upper mantle discontinuities at 410 and 660 km depth are in agreement with the global reference model iasp91 kennett 1991 over a large region of the himalaya and southern tibet

tomographic low velocity anomalies in the uppermost mantle around the northeastern edge of okinawa trough the backarc of kyushu a simultaneous inversion for three dimensional velocity structure and hypocentral parameters is used to determine the tomographic images of the backarc of kyushu southwestern japan the data used in the imaging are the first arrival times of 2736 local earthquakes recorded at 305 stations in a wide region from western japan to eastern china additional data are provided by including arrival times of 357 teleseismic earthquakes we got the high resolution of the uppermost mantle images for p waves at least in the depth range to 150 km the latitude range of 30 34 n and the longitude range of 128 132 e results of inversion reveal a major zone of strong low velocity under west off kyushu island in the depth from 40 km to 100 km this feature may result from partially melting in relation to the upwelling of hot mantle around the northeastern edge of the extending okinawa trough

rayleigh wave tomography of china and adjacent regions 1 this paper presents a tomographic study on the s wave velocity structure of china and adjacent regions group velocity dispersions of fundamental rayleigh waves along more than 4000 paths were determined with frequency time analysis the study region was divided into a 1 1 grid and velocities in between grid nodes were calculated by bilinear interpolation the occam s inversion scheme was adopted to invert for group velocity distributions this method is robust and allows us to use a fine grid in model parameterization and thus helps to restore a more realistic velocity pattern checkerboard tests were carried out and the lateral resolution was estimated to be 4 6 in china and its eastern continental shelves the resulting group velocity maps from 10 to 184 s showed good correlation with known geological and tectonic features the pure path dispersion curves at each node were inverted for shear wave velocity structures the three dimensional velocity model indicates thick lithospheres in the yangtze and tarim platforms and hot upper mantles in baikal and western mongolia coastal area and continental shelves of eastern china and indochina and south china sea regions the tibetan plateau has a very thick crust with a low velocity zone in its middle beneath the crust a north dipping high velocity zone mimicking a subducting plate reaches to 200 km in depth and reaches to the kunlun mountains northward in northern tibet a low velocity zone immediately below the moho extends eastward then turns southward along the eastern edge of the plateau until it connects to the vast low velocity area in indochina and the south china sea

the motion of crustal blocks driven by flow of the lower lithosphere and implications for slip rates of continental strike slip faults geodetic measurements in actively deforming areas of the continents reveal the pattern of deformation in the lithosphere if the dominant forces acting on crustal blocks are tractions at their bases then the long term motion of each block will be given by the average velocity of the underlying lithosphere slip rates between blocks estimated in this way from recent geodetic measurements across fault zones in the south island of new zealand and southern california are in good agreement with slip rates estimated geologically

mass accumulation rates in asia during the cenozoic summary this work establishes estimates of mass accumulation rates in 18 mostly offshore sedimentary basins in asia since the beginning of the cenozoic 66 ma the estimates were derived from isopach maps cross sections and drill holes or stratigraphic columns assuming regional similarity of the strata average solid phase volumes and accumulation rates were calculated for nine epochs approximately corresponding to geological periods palaeocene 66 58 ma eocene 58 37 ma oligocene 37 30 and 30 24 ma miocene 24 17 17 11 and 11 5 ma pliocene 5 2 ma and quaternary 2 0 ma these rates shed new light on the geological history of asia since the onset of the collision of india with asia 50 ma the overall average accumulation rates curve for asian sedimentary basins since the beginning of the tertiary shows an exponential form with slow accumulation rates less than 0 5 106 km3 myr 1 until the beginning of the oligocene more than 15 myr after the onset of the collision from the oligocene onwards rates increase quickly in an exponential manner reaching their maximum values in the quaternary more than 1 5 106 km3 myr 1 from these observations we suggest that extrusion and crustal shortening are complementary processes that have been successively dominant throughout the india eurasia collision history at smaller scales one may distinguish between independent histories at the subcontinental and basin scales this permits a comparison of the relative importance of tectonic and climatic erosion processes affecting the different mountain belts of asia during the cenozoic

implications of crustal property variations for models of tibetan plateau evolution shear coupled teleseismic p waves sampling the interior of the tibetan plateau provide evidence of systematic variations in crustal structure the crust thins by up to 20 km from south to north with a concomitant increase in poisson s ratio from normal values in the south to unusually high values in the north this suggests that the crust of the northern plateau is partially melted due to high temperatures these changes imply spatial and perhaps temporal variations in the way the elevation of the high plateau is created and maintained

mongolian plateau evidence for a late cenozoic mantle plume under central asia the 2500 x 700 km mongolian plateau average elevation 2000 m is situated between the altai orogen and the siberian craton and occupies much of mongolia and transbaikalia in russia the plateau is characterized by 1 basin and range topography and two major domes hentai 600 x 300 km and hangai 800 x 550 km where altitudes reach 3905 m 2 lithosphere that is thinner than adjacent areas minimum 50 km 3 elevated heat flow up to 120 mw m2 4 dominantly alkaline basaltic volcanism in the form of cones lava fields and volcanic plateaus mostly of miocene quaternary age and 5 rifts including baikal main evolution in the pliocene quaternary tunka oligocene early miocene and hobsogol pliocene quaternary existing models explain these features in terms of diapiric upwelling of a mantle asthenolith below the main rifts and or as a long distance effect of the india asia collision we propose that the late cenozoic uplift of the whole mongolian plateau and associated rifting magmatism high heat flow and lithospherec thinning are not externally driven by the india asia collision but are the expression of the interaction of a mantle plume with overlying lithosphere some rifts link and interact with major strike slip faults such as the bolnai such faults may be the major expression of the india asia collision in this region

a no lid zone in the central chang thang platform of tibet evidence from pure path phase velocity measurements of long period rayleigh waves pure path phase velocities of fundamental mode rayleigh waves in the period range 30 80s are obtained for different paths across the tibet plateau using a two event method with events located in tibet and aligned with world wide standard seismograph network stations at teleseismic distance evidence is found for significant lateral variations of structure of the crust and uppermost mantle in tibet in particular phase velocities obtained on paths contained in the chang thang platform are higher than average in tibet at periods shorter than 60s while remaining very low at longer periods when interpreting these phase velocities in terms of simple layered s velocity models it is found that contrary to other areas in tibet they are incompatible with the existence of a high velocity lid s velocities of 4 4 4 5 km s are found immediately beneath the moho and the crust is somewhat thinner 50 60 km than average in tibet this indicates a possible upwelling of hot asthenospheric material compatible with landsat evidence for subrecent basaltic volcanism and independent seismic evidence such as inefficient transmission of sn waves on the other hand a 70 km thick crust and very high upper mantle s velocities are found on the western border of tibet karakorum hindu kush compatible with previous finer scale results concerning the associated zone of intermediate depth seismicity

surface wave dispersion and earth structure in south eastern china summary a reconnaissance study of crust and mantle structure in southeastern china was made using surface waves confined to that region from recent earthquakes data from the wwssn stations anp arid seo and from the digital stations tato and mat were used to measure fundamental mode group velocities of love and rayleigh waves over nine paths in south eastern china an area which has been technically quiet since the early cenozoic crustal structure in this region is typical of stable continents but shear wave velocities in the uppermost mantle are low for a continent 4 45 km s 1 or less other seismological data support this observation

rayleigh wave group velocity tomography of siberia china and the vicinity rayleigh waves are used in a tomographic inversion to obtain group velocity maps of east asia 40 e 160 e and 20 n 70 n the period range studied is 30 to 70 seconds seismograms used for this study were recorded at cdsn stations at a temporary broadband seismic array in tibet at several sro stations and kirnos equipped stations established in asia by the former soviet union in siberia in the sakhalin and in mongolia altogether more than 1200 paths were available in the tomographic inversion the study area includes the angara craton the geologically ancient core of asia and the subsequently accreted units the altaids a paleozoic collision complex the sino korean platform a chain of archaen terranes separated by belts of active structures the south china platform a collage of precambrian paleozoic and mesozoic metamorphic and igneous terranes as well as the tibetan plateau an active tectonic feature created in late cenozoic through collision of the indian subcontinent and the asian continent many of these main units are recognizable in the tomographic images as distinctive units tibet appears as a prominent low velocity about 15 from the average structure with western and central tibet often appearing as the areas with the lowest velocities the central asian fold belt and the angara craton are consistently high group velocity areas some lesser tectonic features are also recognizable for example lake baikal is seen as a high velocity feature at periods greater than 40 seconds however the high group velocity feature does not stop near the southern end of lake baikal it extends south southwestward across mongolia the north china plain a part of the platform where extensional tectonics dominate is an area of high velocities as a result of relatively thin crust the south china block the least tectonically active region of china is generally an area of high velocity for periods longer than 40 seconds a nne trending high group velocity gradient clearly exists in eastern china the velocities are noticeably higher in the east from the group velocity maps average dispersion curves at twelve locations were determined and inverted to obtain velocity structures main results of group velocity inversion include 1 a tibetan crust of around 60 km thick with low crustal and upper mantle shear velocities at 3 3 km s and 4 2 km s respectively 2 with the moho constrained at 40 43 km the angara craton and the central asian foldbelt have a v s in excess of 4 6 km s 3 relatively low shear velocities are obtained for tectonically active areas in many parts of the study area where precambrian basement is exposed the process in the crust and upper mantle due to recent tectonic activities have modified the crust and upper mantle velocity structures under the precambrian terranes they are no longer underlain by high velocity crust and mantle

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

cenozoic plate reconstruction of the south china sea region abstract reconstructions of the south china sea region at 60 ma 40 ma 30 ma 20 ma 10 ma and 5 ma are presented we have attempted to place the south china sea basin in a regional tectonic framework the tectonic evolution of the major blocks surrounding the south china sea were analyzed as well as the relative motions of the indian and australian plates we have tried to correct the tectonic models available in this region a 3 d graphics terminal was used to derive rotation poles for the different tectonic blocks and our model was then tested to determine its self consistency when the model conflicted with previous interpretations the input data were evaluated for alternative explanations at least two and possibly three stages of extension can be recognized in this region the earliest one active in the late cretaceous to eocene involved nw se extension the second one active from the late eocene to early miocene involved north south extension the third stage of extension which probably trended nw se can be dated as post oligocene the first extensional event produced the ne sw trending proto south china sea and a series of sedimentary basins along the south china margin following the southeastward extrusion of indochina the proto south china sea was mostly consumed at the palawan trough renewed north south extension in the south china continental margin started the present day south china sea spreading in the oligocene the southeastward extrusion of indochina blocked by sundaland resulted in the nw se trending opening of the south china sea basin in the early miocene collision of the north palawan microcontinental block with the west philippines block stopped the opening of the south china sea at the end of early miocene spreading activity switched to the sulu sea basin in the middle miocene but collision between the sulu ridge and the west philippines at mindanao halted the opening of the sulu sea at the end of the middle miocene in the late miocene greater india continued its northward path and seems to have ripped open the andaman sea in the pliocene subduction along the northern manila trench placed the north luzon arc on a collision path with the east asia continental margin at taiwan our reconstructions along with detailed geological and geophysical information may be used as a predictive tool for basin evolution models and block interactions in this region the development of the south china sea basin the gulf of thailand the malay basin and the central thailand basins are the result of collision induced extensional forces the sulu celebes and sumatra basins were formed as a consequence of prolonged subduction the opening of the pearl river mouth west natuna south china sea sulu and possibly celebes basins were terminated by various plate collisions during the course of plate reorganizations major boundary faults have changed their slip senses during different stages of evolution

eurasian fundamental mode surface wave phase velocities and their relationship with tectonic structures we automatically analyzed 32 000 fundamental mode love and rayleigh wave signals with earthquake station paths traversing eurasia and indonesia and obtained robust average phase velocity measurements between 20 s and 170 s periods along 4389 love and 4020 rayleigh paths these were inverted to give phase velocity maps at 14 fixed periods resolution tests suggest that features with diameter 750 km and 500 km are resolved over most of eurasia and central se asia respectively low period love waves image areas with thick sedimentary cover as low velocity zones and almost all periods image mountainous regions since these have thick crust and hence low average lithospheric shear velocity at long periods both love and rayleigh waves define high phase velocity zones across shield and cratonic areas reflecting their deep lithospheric roots we observe significant along strike heterogeneity in the zagros fold belt and tien shan altai system taking sections across eurasian phase velocity space allows us to make approximate interpretations in terms of shear velocity structure directly for example the red river and east vietnam boundary faults are traced on their eastern side by low velocities which extend at depth into indonesia we relate this to mantle upwelling associated with early eocene rotation of indochina and reversal of the sense of shear across the red river fault post 20 ma we observe dipping subduction of the mediterranean beneath the aegean of the philippine sea beneath indonesia and of the indian shield beneath tibet we also image a fossil subducted plate beneath ne borneo which we associate with subduction of the proto south china sea between 50 ma and 15 ma

crust and upper mantle tomography in tibet using surface waves we have obtained maps of lateral variations of structure in the crust and lithosphere in tibet and surrounding regions by inversion of single station measurements of fundamental mode rayleigh wave phase velocities in the period range 25 100 sec for earthquakes located in central asia and observed at teleseismic digital stations in eurasia phase velocity maps are obtained using a tomographic method without a priori constraints on region boundaries the lateral variations of s velocity reveal a symmetric pattern on each side of crustal low velocity zone centered on the chang tang region north central tibet this zone is bounded by rather steep velocity gradients to the south and east about 250 and 400 km north and west of the frontal thrusts of the himalayas and lungmen shan respectively the northern boundary of the zone crosses the northern limit of the tibet plateau altyn tagh and kunlun extending into the southwest tarim and qaidam basins the low crustal velocities are consistent with a thick hot crust in the central part of tibet consistent with quaternary volcanism in chang tang the steep gradients towards higher velocities in the south and in the north are compatible with the documented continental subduction in the south and suggest that a similar situation might exist in the north

okinawa trough backarc basin early tectonic and magmatic evolution the okinawa trough lying between japan and taiwan is a backarc basin formed by extension within the continental lithosphere behind the ryukyu trench arc system stress directions associated with the two last extensional phases in the southwestern okinawa trough have been deduced from a comparison with analog modeling the direction of extension is n 150 o for the pleistocene phase of extension 2 0 1 ma and n 170 o for the late pleistocene holocene phase of extension 0 1 0 ma the present day ryukyu volcanic arc a narrow continuous feature extending from japan to taiwan is located on the eastern side of the okinawa trough 80 100 km above the wadati benioff zone the minimum depth for emplacement of arc magmatism scarce present day backarc volcanism appears in the middle and southern okinawa trough within linear en echelon bathymetric depressions a n045 o oriented seamount volcanic chain cuts across obliquely the southwestern okinawa trough and lies in the direct line of extension of the gagua ridge a n s linear volcanic feature of the philippine sea plate associated with this extension of the gagua ridge a large reentrant located at the base of the ryukyu prism the uplift of part of the nanao forearc basin and the deformation of the sedimentary arc suggest that the voluminous cross backarc volcanism could be tied to the subduction of the gagua ridge located there at a depth of 80 100 km beneath the backarc basin a second area of anomalous volcanism has been identified in the middle okinawa trough in the ene extension of the daito ridge a wnw ese 400 km long volcanic feature of the philippine sea plate we suggest that the gagua and daito ridges initially induced stress at the base of the arc which is still brittle and cracks propagated through the overlying brittle lithosphere allowing magmas with arc affinities to erupt at the seafloor this excessive magmatism reaches the seafloor through conduits which preferentially follow in their shallowest portion the crustal normal faults of the backarc rifts the okinawa trough is consequently still in an early stage of evolving from arc type to backarc activity

upper mantle beneath southeast asia from s velocity tomography 1 we present a three dimensional s velocity model of the se asian western pacific upper mantle with 400 km lateral resolution using the novel automated multimode inversion technique we processed 4038 vertical component seismograms and extracted 22 708 linear equations with uncorrelated uncertainties that constrain upper mantle structure we used time frequency windows to select signal with negligible proportion of scattered energy the windows included the fundamental rayleigh mode and s and multiple s waves the observed range of s velocity variations is the widest 17 18 in the upper 150 km of the mantle high velocity continental roots can reach beyond the present extent of the overlying archean proterozoic crust by 500 km beneath some precambrian units the roots are absent which can be attributed to deformation and gradual destruction of the ancient lithosphere at 120 150 km s velocity beneath some cratons reaches 4 8 km s this can be accounted for by thermal and compositional effects beneath the hainan island area a low velocity anomaly is observed from near the surface to the bottom of our model the hot spot type volcanism here may be caused by the deep mantle hainan plume a low velocity mantle domain underlies the south central sea of japan surrounded on the surface by intraplate volcanoes a deep seismicity gap is present near 40 n in the pacific slab subducting below and may result from a plume slab interaction a high velocity anomaly is present in the transition zone beneath the northern boundary of the yangtze craton we propose that the anomaly corresponds to subducted continental lithosphere stagnant atop the 660 km discontinuity

baikal rift zone structure and geodynamics abstract the cenozoic baikal rift zone is superimposed on the caledonian baikal fold belt representing the suture between the precambrian siberian craton and several microcontinents the baikal rift zone consists of a system of disconnected fault bounded basins and extensional and wrench faults that straddles a major arch having a topographic relief of 2 3 km rifting activity commenced during the oligocene and is still active as evident from high seismicity of the baikal rift zone across the baikal rift zone upper crustal extension is considerably smaller than would be expected from its crustal thickness which decreases by 8 11 km across the baikal basins as compared to the adjacent unextended areas the discrepancy between upper and lower crustal attenuation could be attributed to intrusion of a major diapir indeed geophysical data indicate that the sayan baikal dome coincides with such a diapir the top of which is located at the crust mantle boundary this intrusion is held responsible for oligocene and quaternary doming of the rift zone development of the intra continental baikal rift system is thought to be related to asthenospheric diapirism active rifting however intra plate stresses in conjunction with the himalayan collision may have played some role

constraints on the structure of the tibet plateau from pure path phase velocities of love and rayleigh waves pure path phase velocities of love and rayleigh waves across the tibet plateau are determined for the period range 30 90 s and for two opposite directions of propagation along the length of the plateau the method used is a two event method similar in principle to the classical two station method where the roles of stations and events are interchanged the success of this method is due to a favorable geometry whereby events located at each end of the plateau align to within 1 of a great circle path with one wwssn station at teleseismic distance to the east and one to the west body wave modeling is used to constrain depth and source mechanism of the events in order to calculate the corresponding source phases for surface waves phase velocities are determined to within 0 02 km s or better for rayleigh waves and 0 007 km s for love waves the constraints added by these data to the crust and upper mantle structure beneath tibet are discussed in the light of previous studies the best fitting model has a 65 km thick crust with low average crustal velocities and an sn velocity of 4 65 km s the low velocity zone is limited to the depth range 100 150 km the interesting result of this study is that both love and rayleigh wave data can be matched to within 1 in phase velocity by a unique isotropic model this points to a similarity with a stable region upper mantle structure such as that of the canadian shield finally additional rayleigh wave phase velocity data are used to compare propagation on different paths in the vicinity of tibet the tarim basin to the north of tibet stands out as having a distinct crustal structure more similar to an average tectonic region structure moreover evidence is presented for the existence of a very low velocity region at the western end of tibet which correlates well with a pronounced gravity low observed in that area

tectonics of the qinling belt build up and evolution of eastern asia the structure and history of the qinling range which separates the north and south china cratons are a key to the tectonic evolution of eastern asia the mountain range is composed of a northern palaeozoic belt and a southern mesozoic belt the palaeozoic orogeny probably involved the closure of an oceanic basin along a north dipping subduction zone followed by south vergent obduction of ophiolites and intracontinental thrusting during the devonian the mesozoic belt appears to be the product of purely intracontinental shallow crustal deformation over a large decollement with at least 100 km of horizontal transport since the devonian both belts have been sliced by huge east west sinistral strike slip faults

phase velocity structure from rayleigh and love waves in tibet and its neighboring regions deep geodynamic processes involved in the continental collision between india and asia are still controversial to address this issue phase velocities of 619 rayleigh waves and 254 love waves have been inverted by using an anisotropic tomographic technique such a technique enables us not only to retrieve phase velocity distributions but also to map azimuthal anisotropy on a large scale only phase velocity anomalies in the period range 50 200 s are dealt with here but the azimuthal anisotropy has been taken into account in the inversion process moreover because of the important influence of shallow layers on the inversion results an inversion of phase velocities corrected for shallow layers has been performed to correct raw phase velocities the 3smac crust heterogeneous reference earth model has been used the comparison of phase velocity distributions for love and rayleigh waves with and without corrections of surficial layers implies that much of the low velocity zone visible at short periods in central tibet can be explained by unusually thick crust at periods longer than 100 s tibet is overall characterized by high velocity anomalies such anomalies seem to converge toward the center of the plateau as period increases we conclude that the phase velocity structure beneath tibet results at short periods from thick crust and possible partial melting in the uppermost lithosphere and at long periods from the inward plunge of the cold lithospheric mantle surrounding the high plateau

velocities and propagation characteristics of pn and sn beneath the himalayan arc and tibetan plateau possible evidence for underthrusting of indian continental lithosphere beneath tibet new seismological observations on velocities and propagation characteristics of pn and sn waves beneath tibet can be interpreted although not uniquely to indicate the shallow angle underthrusting of the greater indian continental lithosphere beneath the tibetan plateau this is inferred from available geological and geophysical data and is now supported by new seismological observations the most significant observation is that high frequency sn waves shear waves that travel in the mantle lithosphere propagate efficiently in the uppermost mantle beneath the tibetan plateau except beneath the north central part of tibet the chang thang terrane furthermore sn propagates efficiently across the stable block of the tarim basin along the tien shan and himalayan mountains and across the indian shield apparent velocities of pn and sn waves that traverse the uppermost mantle beneath the tibetan plateau are 8 42 and 4 73 km s respectively these velocities are very similar to those beneath the himalayan mountains and the indian shield the efficient propagation and the velocities of pn and sn waves beneath tibet are also similar to those commonly observed beneath shield and stable continental regions these results are consistent with the underthrusting model and do not favor the class of alternative models in which the tibetan plateau is formed by shortening and thickening of hot crustal and uppermost mantle material in response to the convergence of india and asia

the unusual midwinter warming in the southern hemisphere stratosphere 2002 a comparison to northern hemisphere phenomena a strong midwinter warming occurred in the southern hemisphere sh stratosphere in september 2002 based on experiences from the northern hemisphere nh this event can be defined as a major warming with a breakdown of the polar vortex in midwinter which has never been detected so far in the sh since observations began at the earliest in the 1940s minor midwinter warmings occasionally occurred in the sh but a strong interannual variability as is present in winter and spring in the nh has been explicitly associated with the spring reversals a detailed analysis of this winter reveals the dominant role of eastward traveling waves and their interaction with quasi stationary planetary waves forced in the troposphere such wave forcing finally leading to the sudden breakdown of the vortex is a familiar feature of the northern winter stratosphere therefore the unusual development of this antarctic winter is described in the context of more than 50 arctic winters concentrating on winters with similar wave perturbations the relevance of preconditioning of major warmings by traveling and quasi stationary planetary waves is discussed for both hemispheres