interannual variation of the late spring early summer monsoon rainfall in the northern part of the south china sea abstractmajor rainfall 60 in the northern part of the south china sea between north vietnam and taiwan during may june the mei yu season the first phase of the southeast east asian monsoon is produced by rainstorms originating over the northern vietnam southwestern china region and the northern part of the south china sea as observed in this study the occurrence frequency of rainstorms and rainfall contribution by these rainstorms undergoes a distinct interannual variation in phase with those of monsoon westerlies in northern indochina and sea surface temperature sst anomalies over the noaa nino 3 4 region sst nino 3 4 this in phase relationship between monsoon westerlies and the sst nino 3 4 anomalies is a result of the filling deepening of the subtropical asian continental thermal low in response to the sst nino 3 4 warm cold anomalies accompanied with this response is a slight southward northward shift of the north pacific convergence zone npcz which extends from southe

role of narrow mountains in large scale organization of asian monsoon convection abstract the asian summer monsoon is organized into distinct convection centers but the mechanism for this organization is not well understood analysis of new satellite observations reveals that narrow mountain ranges are an important organizing agent anchoring monsoon convection centers on the windward side the bay of bengal convection in particular features the heaviest precipitation on its eastern coast because of orographic lifting as the southwest monsoon impinges on the coastal mountains of myanmar also known as burma this is in contrast to the widely held view that this convection is centered over the open ocean as implied by coarse resolution datasets a view that would require an entirely different explanation for its formation narrow in width and modest in height 1 km these mountains are hardly mentioned in conceptual depictions of the large scale monsoon and poorly represented in global climate models the numerical simulations of this study show that orographic rainbands are not a

hydrogeochemistry and stable isotopes of thermal springs earthquake related chemical changes along belice fault western sicily abstract three geothermal systems montevago castellammare alcamo and sciacca are located along the main seismogenetic structures in western sicily concentrations of dissolved species including the gases co 2 n 2 he and the results of stable isotope measurements 18 o d and 13 c tdic in water samples collected from six thermal springs and 28 cold discharges were used to characterise their feeder aquifers and to reveal the relationships between water chemistry and regional seismicity the sciacca thermal springs differ chemically and isotopically from those of montevago and the castellammare alcamo areas the inferred deep end members of the thermal waters of montevago and castellammare alcamo are almost similar suggesting that both systems are fed by carbonate waters and selenite waters a slight contribution 1 3 of seawater during groundwater ascent it is also present the sciacca thermal springs are fed by a deep reservoir comprising a mixture of 50 carbonate water and 50 seawater during ascent towards the surface these waters interact with nacl rich evaporite layers by combination of published and present data significant temporal variations of temperature and some chemical parameters in the thermal waters of western sicily have been recorded these variations were mostly between 1966 and 1969 although the data are discontinuous it is still possible to reveal a direct link between physico chemical changes in the acqua pia and terme selinuntine springs and the 1968 belice valley earthquake within the studied springs two kinds of geochemical behaviour have been recognised the chemistry of the montevago thermal springs was permanently changed in response to changes in the groundwater system water temperature and dissolved so 4 cl na and tds showed minimum values before the earthquake and maximum values after the event almost constant values substantially higher than before were recorded after the seismic event conversely the temporal variations observed in the waters of the terme selinuntine spring from 1965 to 1991 exhibit a transient increase most probably caused by a temporary contribution of deep co 2 rich fluids caused by the strain release during the 1968 earthquake

crustal thicknesses in se brazilian shield by receiver function analysis implications for isostatic compensation hypothesis are proposed to explain the data 1 a lower density by 30 40 kg m 3 i n the lithospheric mantle under the archean block of the sao francisco craton relative to the proterozoic lithosphere is responsible for maintaining the high elevations in the plateau area relatively low density and high p wave velocity are compatible with a depleted low feo composition for the archean lithosphere 2 alternatively if the density contrasts between archean and proterozoic lithospheres are smaller than the values above then the crust beneath the paranabasin must be more dense than that of the craton higher crustal density and high poisson s ratio would be consistent with magmatic underplating in the lower crust beneath the paranabasin as inferred from other studies index terms 7205 seismology continental crust 1242 9360 information related to geographic region south america 7218 seismology lithosphere and upper mantle keywords crust upper mantle brazil parana basin san francisco craton

electromagnetic induction studies recent developments in electromagnetic induction studies of the lithosphere and the asthenosphere are reviewed attention is given to geoelectrical studies of active tectonic areas in terms of the major zones of crustal extension the basin and range province along western regions of north america and the rio grande rift studies have also been performed of tectonic activity around iceland the salton trough and cerro prieto and the subduction zones of the cascade mountains volcanic belt where magnetotelluric and geomagnetic variation studies have been done geomagnetic variations experiments have been reported in the central appalachians and submarine electromagnetic studies along the juan de fuca ridge controlled source electromagnetic and dc resistivity investigations have been carried out in nevada hawaii and in the adirondacks mountains laboratory examinations on the conductivity of representative materials over a broad range of temperature pressure and chemistry are described

electrical conductivity and crustal deformation from magnetotelluric results in the region of the araguainha impact brazil abstract in order to obtain information about the deep structure of large meteorite craters a series of mt soundings were carried out in the region of the araguainha impact crater located in the northern section of the parana basin mato grosso brazil the mt responses in the short period range from 0 001 to 1 s show one dimensional behaviour in contrast to the longer periods where data are multi dimensional at periods between 1 and 10 s the splitting of the apparent resistivity and phase curves of different polarisations is accompanied by a strong increase of the phase sensitive regional skew parameter to values up to 0 5 the results of two and three dimensional modelling reveal a disk shaped body embedded within a layer of 5000 m the resistivity of the body ranging between 20 m and 500 m lies significantly below the bulk value of the upper crust the anomaly is believed to be caused by impact induced faulting and brecciation of the crust reaching to depths of 3 to 7 km the horizontal extent of this zone is 16 km corresponding to about 40 of the total crater diameter at the surface the long period data t 10s reveal a heterogeneous lower crust of enhanced conductivity at depths between 15 and 30 km which is not related to the impact event it is likely to be a feature typical of the basement in the area of the araguainha structure

regional magnetotelluric surveys in hydrocarbon exploration parana basin brazil the magnetotelluric geophysical method has been used effectively as a hydrocarbon exploration tool in the intracratonic parana basin of south america the parana basin has an area of about 1 200 000 km2 463 000 mi2 extending over portions of brazil paraguay uruguay argentina and bolivia the paleozoic marine sedimentary rocks in the parana basin are covered by the world s most extensive flood basalt complex making geophysical exploration extremely difficult although modern seismic techniques recently applied are achieving good results in some areas the 1 2 km 3 300 6 600 ft thick surface basalts and buried diabase sills pose no problem for the magnetotelluric method because the natural electromagnetic fields used as the energy source pass easily through the basalt data for the regional study were taken on six profiles with soundings spaced 8 to 15 km 5 to 9 mi apart the magnetotelluric sounding data outline a linear uplift known as the ponta grossa arch this major structural feature cuts across the northeast trending intracratonic basin almost perpendicularly and is injected with numerous diabase dikes although its character is reasonably well known in the shallow eastern parts of the basin it is poorly delineated in the deeper parts of the basin where promising natural gas zones have been tested in several wells in the survey area mt interpretations show that basalts have aggregate thickness of as much as 2 km 6 600 ft and basement may be as much as 6 km 20 000 ft below the surface over most of the basin the basalts are covered by upper cretaceous to holocene continental sediments of a few hundred meters thickness and are underlain by 2 to 4 km 6 600 to 13 100 ft thick paleozoic sediments with possible hydrocarbon potential the ponta grossa arch is interpreted to be the failed arm of a triple rift system that formed during the separation of the african and south american continents shales of the devonian ponta grossa formation are important parana basin source rocks for hydrocarbons as are several permian units significant electrical contrasts occur between the permian sediments and older units so that magnetotelluric measurements can give an indication of the regional thickness of the permian and younger sediments to aid in interpreting hydrocarbon migration patterns and possible trap areas

regional and residual gravity anomaly separation using singular spectrum based frequency filtering methods a case study of shallow subsurface modeling from nagpur india we present here the application of a single and multichannel singular spectrum analysis ssa based data filtering algorithm for regional and residual gravity field separation initially the single channel ssa method was tested on synthetic gravity profile data generated using gravity and magnetics modelling system gm sys a gravity modeling software for a sedimentary basin structure corrupted with gaussian white noise and compared with the convnetional fast fourier transform fft based wave number non data adaptive and discrete wavelet transform semi data adaptive filtering approaches the comparative results show that the residual filtering of gravity data using the ssa method produces less minimal artifacts compared to fft based wave number filtering and wavelet filtering methods following the synthetic examples we further employed multichannel ssa based frequency filtering on 2d gridded gravity data from umred nagpur district maharashtra india to separate the residual anomaly for modelling the shallow subsurface structures the modelled depth sections of two mutually perpendicular profiles suggest the presence of alluvium lameta kamthi and barakar formations with varying thicknesses the formations identified from the models show a clear match with the local geology and nearby borehole information we suggest that the single and multichannel ssa based frequency filtering are robust approaches for separating regional and residual components from gravity anomalies

an observational study of the south china sea monsoon during the 1979 summer onset and life cycle abstract the onset and life cycle of the 1979 south china sea summer monsoon were examined in the context of the 30 60 and 12 24 day monsoon modes the former intraseasonal mode formed the northward migrating monsoon trough ridge while the latter intraseasonal mode propagated westward in the south china sea the monsoon in this region exhibited three cycles over the summer may august with the onset taking place about one cycle ahead of the onset of the indian and japanese monsoons climatologically a summer trough line radiated out from the indian monsoon trough region across indochina to the northern south china sea the monsoon onset occurred when the 30 60 day monsoon trough and the 12 24 day low center arrived simultaneously at the northern south china sea close to the climatological summer trough line in the middle of may the breaks occurred when the 30 60 day monsoon ridge lines and the 12 24 day high center met near 15 20 n in the northern south china sea the south china sea monsoon wa

audiomagnetotelluric study in northeast region at parana basin south america we conducted natural source audiomagnetotelluric amt soundings at 31 stations along a 215 km profile in the parana basin south america across the previously postulated araxa rio grande alignment our objective was to study the resistive structures of the upper layers of the sedimentary sequence our results made it possible to map the surficial layer of sediments of the bauru group a layer that reaches thicknesses of up to 250 m we concluded that amt soundings have reasonably good potential for groundwater exploration in the region the varying thicknesses of bauru group sediments and the irregularities of their contact surface with resistive volcanic rocks of the serra geral formation along the profile were not known previously our amt profile crossed an important positive gravity anomaly located near the rio grande a natural boundary between the states of sao paulo and minas gerais in brazil which has not been fully interpreted five sites for deeper mt soundings which may throw light on possible causes of the gravity anomaly were selected based on the conclusions from the amt survey

imaging three dimensional crustal conductivity structures reflecting continental flood basalt effects hidden beneath thick intracratonic sedimentary basin a large scale array of long period magnetic data and a deep probing magnetotelluric profile were recorded in the intracratonic parana sedimentary basin in central eastern south america which presents a thick and extensive sedimentary magmatic sequence that allows its basement to be investigated only by indirect methods integration of the results from both methods showed that the crust beneath the basin presents several quasi linear highly conductive channeled zones with limited lateral extent in coincidence with some of the main tectonic structures recognized at the surface and a moderate but pervasive lithosphere conductivity enhancement beneath its central part upward movement of co2 bearing volatiles and magmas precipitating highly conducting mineral phases along discrete subvertical fault zones that served as feeder conduits for early cretaceous voluminous continental flood basalts was a likely process responsible for the localized conductivity enhancements correlation between some of the linear conductive zones and elongated magnetic anomalies and between the maximum depth occurrence of most of these conductive anomalies and the curie depth at which crustal rocks lose their magnetism gives strong support to interconnected iron oxides especially magnetite and iron sulfides such as pyrrhotite as the main conductive sources the moderate bulk conductivity increase in the crust and upper mantle beneath the central part of the basin is unexpected for a postulated cratonic basement and is tentatively associated with impregnation of the lithosphere by conducting minerals related either to widespread tectonic events in the ordovician or late precambrian or to dispersed magmatic residues of an early cretaceous magma differentiation contaminating the entire lithosphere

upper crustal structure of the northeast parana basin brazil determined from integrated magnetotelluric and gravity measurements eight magnetotelluric mt soundings were performed as a continuation of an earlier audiomagnetotelluric amt survey conducted in the northeastern border of the parana basin a large intracratonic basin located in central eastern south america and constituted by silurian to jurassic sedimentary rocks with lower cretaceous sill type magmatic intrusions and overlying volcanics two of the mt stations were carried out near two deep petroleum wells the remaining mt soundings were done on a profile traversing two important gravity features a positive anomaly near the border of the states of sao paulo and minas gerais and a strong trending nw se linear gradient major findings of an integrated interpretation of the mt survey and of available gravity data are as follows 1 inhomogeneities and or strong magnetization of the superficial volcanics and diabase intrusions in the paleozoic sedimentary rocks appearing to distort the mt results and 2 identification of important structural discontinuities including a possible different crustal structure beneath the parana basin compared to the region on the north a thickening of the crust toward the ne and the probable existence of a trough graben within the basin characterized by a thick accumulation of sediments and basalts

columbia river basalt plateau an integrated approach to interpretation of basalt covered areas an interpretation is presented of a 219 km regional profile which traverses the eastern columbia river plateau in washington state aeromagnetic magnetotelluric mt and gravity data were first interpreted separately all three data sets then were satisfied by a single geologic model the objective of this case study is to illustrate the individual contributions derived from these three geophysical data sets to a final integrated interpretation the aeromagnetic interpretation has produced regional structural information and data from which rock compositions can be inferred the mt interpretation shows that the basalt sediment interface can be determined and thus a relative sediment thickness can be inferred the gravity interpretation is dependent upon an additional method to determine either the basalt or basement horizon in order for the gravity interpretation to approximate depth to basement or sedimentary thickness the base of the basalt must be determined from another scientific method from co

an interpretive analysis of magnetotelluric data a simple analysis to determine the dimensionality of magnetotelluric resistivity variations to separate the near surface resistivity variation from the variations at depth and to find the relative resistivity variations with depth is described parameters derived from the magnetotelluric impedance tensor are mapped in pseudosection and planar view for two dimensional 2 d model data and for survey data from montana these data illustrate procedures that can qualitatively map complex resistivity structures in the lateral distance frequency domain or equivalently the lateral distance scaled vertical distance domain phase dependent parameters have better vertical resolution than parameters related to scalar apparent resistivity but the latter allow estimates of the resistivities encountered phase parameters for the montana data provide a semiquantitatively accurate cross section of a geologically known anticlinal structure this suggests a means of subsurface structural mapping with magnetotelluric data the use of these parameters with sufficiently dense and accurate data provides a first order indication of structure for subsequent quantitative modeling

geoelectric crustal structures off the sw border of the sao francisco craton central brazil as inferred from a magnetotelluric survey summary a magnetotelluric mt survey of the crust beneath sedimentary basins and thrust sheets along the southwestern edge of the sao francisco craton central brazil reveals intricate electrical characteristics that are interpreted in the context of proterozoic collision tectonics and horizontal transport of allochthonous rock units emplacement of cretaceous hypabyssals lavas and diatremes of ultrapotassic mafic composition and occurrence of induced seismicity the data exhibit strong distortions represented by 3 d induction effects and galvanic disturbances resulting from shallow structures frequency and site dependence of electrical strike and inhomogeneous anisotropic layers with smoothly varying phase split conductance and azimuth of the highly conductive direction geoelectrical and orthogonal phase difference directions 2 d inversion and forward modelling characterize three distinct subhorizontal sections showing two anisotropic conductors within a highly resistive crust laterally segmented into unique blocks the model for the uppermost crust section has e w geoelectric directions and a 15 30 s anisotropic zone at a depth of approximately 1 2 km along the entire profile this conducting layer is interpreted to represent a brine filled fracture layer possibly controlled by the present day state of crustal stresses as disclosed from reservoir triggered quakes the mid crust section presents a deeper conducting zone located at depths below 10 km it is defined by stronger mt responses having phase split directions oscillating from wnw ese to e w beneath sites in the central western area parana basin and allochthonous cover units and nne ssw in the northeastern region autochthonous platform units and sanfranciscana basin anisotropy is greater than an order of magnitude in the highly conductive direction with conductance in the range of 250 400 s conjecturally the source of this anomalous feature would come from interconnected grain boundary phases and hypersaline fluids exsolved and precipitated from upwelling cretaceous magma in the central western area favourable trapping of conductors was constrained along a nearly e w direction feasibly associated with relic structures inherited from brasiliano pan african continental collisions along the northeast however the coincidence with superficial nne ssw structural directions suggests a localized direct causal relationship with the trend of extension related to magma emplacement the lower crust has a highly resistive quasi 1 d section along the entire profile that prevails also at uppermost mantle depths thus whereas the brittle crust would have reconciled subhorizontal strain with fluid percolation related to uplift and magma emplacement a mechanically coupled and stronger lower crust upper mantle would have controlled the deep magma generation during cretaceous distention pulses

gravity map of brazil 2 regional and residual isostatic anomalies and their correlation with major tectonic provinces an isostatic residual gravity map of brazil has been computed by removing from a 0 5 0 5 bouguer anomaly grid a regional gravity field calculated for compensating masses of surface topography the coherence function a statistical measure of the correlation between bouguer anomaly and topography was first computed in order to constrain the compensation mechanism within brazil similar to results for north america and australia the coherence function of south america has a broad transition between high and low coherence values suggesting a combination of tectonic provinces with different flexural rigidities and or loading processes in view of this result we have considered as a first approximation a model in which the surface topography is the only load acting on a nonrigid lithosphere a regional gravity field has been computed assuming airy heiskanen isostasy with compensation at the crust mantle boundary the residual gravity map which was obtained by removing the computed regional gravity field from the observed bouguer anomaly shows a long wavelength n s trending negative anomaly over most of brazil this gravity feature of approximately 3000 km width is the southern continuation of the western north atlantic negative geoid gravity anomaly and reaches at least 15 mgal in the northern portion of brazil using the upward continued isostatic residual gravity field at 300 km this long wavelength component which may be dynamically induced has been removed to first approximation the final isostatic residual gravity anomaly map depicts anomalies with wavelengths between 100 and 1000 km which correlate with major tectonic provinces negative anomalies occur mainly over paleozoic intracratonic and cretaceous rift type sedimentary basins and granitic intrusions and along proterozoic thrust belts positive residual anomalies are generally observed over regions affected by igneous activity and volcanism such as in the amazon basin and the parana flood basalt province positive anomalies are also associated with overthrust crustal plates which define a suture zone in central brazil and over sub andean tertiary foreland basins

signification structurale des anomalies gravimetriques de la partie sud du craton de sao francisco bresil abstract the relationships between the cratonic area and orogenic belts of the southern part of the state of minas gerais brazil are analyzed using data from a recent bouguer anomaly map the interpretation was carried out using inverse anomaly approach and statistical analysis the stable area is characterized by elongate anomalies trending nne ssw which correspond to a higher level of the basement under the upper precambrian sedimentary cover bambui and macaubas groups they can be related to rejuvenated nne ssw trending fractures the gravity trends are either deformed or interrupted over the brasilian fold belt where an important negative linear anomaly is present this anomaly is produced by a thick sequence of folded sedimentary or metasedimentary terrains which can be interrupted as miogeoclinal units the alfenas mobile belt is characterized by a strong positive anomaly probably associated with heavy infracrustal rock complexes granulites charnockites a crustal thickening probably associated with a pre brazilian continental collision can be inferred from a long wavelength linear negative anomaly

electrical conductivity temperatures and fluids in the lower crust we have compiled both laboratory and worldwide field data on electrical conductivity to help understand the physical implications of deep crustal electrical profiles regional heat flow was used to assign temperatures to each layer in regional electrical conductivity models we avoided those data where purely conductive heat flow suggested temperatures more than about 1000 sup 0 c substantially higher than solidus temperatures and outside the range of validity of heat flow models the resulting plots of log conductivity sigma versus 1 t demonstrate that even low conductivity layers lcl have conductivities several orders of magnitude higher than dry laboratory samples and that the data can be represented by straight line fits in addition tectonically active regions show systematically higher conductivities than do shield areas because volatiles are usually lost in laboratory measurements and their absence is a principal difference between laboratory and field conditions these materials probably account for the relatively higher conductivities of rocks in situ in the crust free water in amounts of 0 01 0 1 in fracture porosity could explain crustal conductivities other possibilities are graphite hydrated minerals in rare instances and sulfur in combination with other volatiles as most of the temperatures are less than 700 sup 0 c partial melting seems likely onlymore in regions of highest heat flow where the conductive temperature profiles are inappropriate another result is that at a given temperature crustal high conductivity layes hcl are more conductive by another order of magnitude and show more scatter than do lcl s less

tropical cyclone track characteristics as a function of large scale circulation anomalies abstract factors that contribute to intraseasonal variability in western north pacific tropical cyclone track types are investigated it is hypothesized that the 700 mb large scale circulation can affect tropical cyclone track characteristics by enhancing or excluding genesis in certain regions and concurrently prohibiting or favoring recurving versus straight tracks a track type climatology indicates that genesis location alone may explain some of the variability in track type although some genesis regions have no preference for straight moving or recurving tracks a formation north of 20 n or east of 150 e and north of 10 n favors a recurvature track these recurving storms are classified as recurving north and recurving storms that form in regions with nearly equal probability of straight or recurving tracks are classified as recurving south a compositing technique is used to define anomalous 700 mb large scale circulations that exist during the formation of tropical cyclones that subsequently fol

uranium series dating uranium decays through a number of radioactive daughter isotopes some of which have half lives comparable to the time scale of prehistoric archaeology the growth of these isotopes in naturally occurring materials at archaeological sites can be used to determine the age of sites the growth of 230th from its parent 234u can be used over a time range from a few hundred to half a million years calcite precipitated from running or dripping water in springs and caves as well as marls and soil deposited calcretes may be spatio temporally associated with archaeological materials they can be dated by 230th 234u and 234u 238u measurements with a precision of 5 10 of the age by alpha counting or 1 by mass spectrometry bones teeth mollusk and egg shells are also datable but present problems due to migration of parent u in and out of the samples during their burial history

interannual variation of the cold season rainfall center in the south china sea abstractduring 15 november 31 december a cold season rainfall center appears in the southern part of the south china sea scs north of northwestern borneo and juxtaposed along the southwest northeast direction with rainfall centers for the malay peninsula and the philippines this scs rainfall center also coincides geographically with the scs surface trough an effort is made to explore the formation mechanism of this rainfall center it is primarily formed by the second intensification of heavy rainfall flood cold surge vortex csv hrf through its interaction with a cold surge flow over the scs trough both the scs rainfall center and the scs surface trough are located at the easterly flow north of the near equator trough modulated by the interannual variation of the cyclonic shear flow along the near equator trough in concert with the el nino southern oscillation enso cycle the scs rainfall center undergoes an interannual variation the impact of this enso cycle is accomplished through the regul

maintenance of summer monsoon circulations a planetary scale perspective abstract the monsoon circulation which is generally considered to be driven by the landmass ocean thermal contrast like a gigantic land sea breeze circulation exhibits a phase reversal in its vertical structure a monsoon high aloft over a continental thermal low is juxtaposed with a midoceanic trough underlaid by an oceanic anticyclone this classic monsoon circulation model is well matched by the monsoon circulation depicted with the observational data prior to the first global atmospheric research program garp global experiment fgge however synthesizing findings of the global circulation portrayed with the post fgge data it was found that some basic features of major monsoon circulations in asia north america south america and australia differ from those of the classic monsoon circulation model therefore a revision of the classic monsoon theory is suggested with four different wave regimes selected to fit the horizontal dimensions of these monsoon circulations basic features common to

electron spin resonance esr dating abstract esr dating has been systematically applied in earth sciences and archaeology since 1975 when ikeya dated a stalactite from the akiyoshi cave in japan in the meantime this new technique has been successfully applied to the dating of materials such as speleothems spring deposited travertines mollusc shells corals and tooth enamel the present research focuses on the dating of quartz which allows the age assessment of heated ceramics volcanic rocks intrafault material or windblown sediments esr dating is based on the measurement of the number of paramagnetic centers in a mineral these centers are generated by alpha beta and gamma radiation of the matural radioelements such as u th and k and have accumulated over time two parameters have to be determined the accumulated dose ad and the dose rate d to which the sample was exposed this review comprises three major parts a introduction into esr dating b application of the method and c appendices giving detailed description of dose rate calculation physical basis of electron spin resonance the esr spectrometer and esr lines the major emphasis lies on the outline of the application of esr dating this includes the discussion of the esr signals of the various materials sampling sample preparation and measurement techniques

interannual variation of the summer rainfall center in the south china sea abstracta northwest southeast oriented summer monsoon trough exists between northern indochina and northwestern borneo ahead of this the south china sea scs trough is located at a convergent center west of the philippines which provides an environment favorable for rain producing synoptic systems to produce rainfall over this center and form the scs summer rainfall center revealed from the x t diagram for rainfall this rainfall center is developed by multiple scale processes involved with the scs trough tr tropical depression ty interaction of the scs trough with the easterly wave tropical depression ei and easterly wave ew it is found that 56 of this rainfall center is produced by the scs trough while 41 is generated by the other three synoptic systems combined apparently the formation of the scs summer monsoon rainfall center is contributed to by these four rain producing synoptic systems from the scs and the philippines sea the southeast asian summer monsoon undergoes an interan

the quaternary travertine deposits of europe and asia minor abstract a summary is provided of the published information relating to all aspects of quaternary travertine formation in europe west of the ural mountains the deposits have been divided into two broad groups the meteogene travertines which result primarily from the degassing of soil borne aqueous co 2 and thermogene deposits resulting from the degassing of thermally generated co 2 meteogene deposits are rare above latitude 58 n and in regions where the mean annual air temperature is below 5 c a significant positive correlation exists between mean air temperature and travertine deposit thickness the combined effects of temperature and rainfall are used to provide a zoned map showing the travertine forming potential of limestones within the region information from 14 c dating indicates that deposition reached a maximum in the period 5 10 ka bp and is currently limited by land and water management practices in the populated areas thermogene deposits occur in regions of high co 2 discharge resulting from tectonic activity such as italy and turkey where there is much vulcanism these travertines are frequently more massive and less readily weathered than meteogene deposits fully referenced information is provided for 320 important mostly well studied sites 227 meteogene 93 thermogene of which 156 are currently active

some effects of the intraseasonal oscillation on the equatorial waves over the western tropical pacific south china sea region during the northern summer abstract previous studies have shown that the life cycle of the asian summer monsoon is modulated by the 30 60 day oscillation the arrival of the 30 60 day monsoon trough ridge at 15 20 n intensifies weakens the monsoon flow over the south china sea western tropical pacific region and in turn extends eastward west ward the monsoon westerlies trade easterlies over this region since equatorial waves are important synoptic disturbances to the weather of this region an effort was made in this study to explore the possible impact of the 30 60 day mode an the occurrence frequency and westward propagation of these waves the major findings of this study are as follows 1 the westward intrusion of trade easterlies during the break monsoon facilitates the occurrence and westward propagation of equatorial waves along trade easterlies in the southern flank of the north pacific anticyclone and 2 the eastward expansion of monsoon westerlies during the active monsoon varies relative to the activity of

the impact of hydrological changes on travertine deposits related to thermal springs in the pamukkale area sw turkey pamukkale thermal waters 35 c exhibiting calcium bicarbonate sulfate composition and high carbon dioxide concentration are of a predominantly meteoric origin the meteoric fluid circulating through faults and fractures is heated by magmatic intrusions at great depth and ascends from deep reservoirs to the surface mixing with relatively cold groundwater in the near surface zone promotes different saturation conditions with respect to calcium carbonate that later precipitates at depth and or the surface dissolution deposition processes of calcium carbonate both at surface and depth environments may help to reconstruct past climate direction in the field during wet climate conditions a high rate of calcium carbonate accumulation would be expected to occur at the surface because thermal fluid would be under saturated with respect to calcium carbonate at depth because of a relatively higher mixing ratio with cold groundwater during dry climate conditions the thermal fluid would be super saturated at depth because of the highly acidic environment hydrometeorological studies reveal that the annual precipitation at the pamukkale hydrothermal field tends to decrease with time this climatic change in the area was also detected from geological records while humid climate conditions prevailed during the late quaternary the area has recently been affected by arid semi arid climate conditions followed by some episodic transitions this study has shown how the system has possibly reacted to different climate conditions since antiquity

neogene evolution of the denizli region of western turkey the denizli region contains one of the easternmost neogene sedimentary basins in the part of western turkey that takes up ssw extension this isolated active normal fault zone which contains closely spaced en echelon normal fault branches is investigated using field measurements of fault exposures and tilted sediments and seismological observations as a case study to address its style of extension the denizli basin is no more than 1 km thick and has accommodated up to 4 km of extension substantial 20 sediment dips are readily explicable assuming extension is accompanied by distributed vertical simple shear with initial and present day dips of the main normal faults that control extension most likely 54 57 and 45 50 other aspects of the form of this basin require regional uplift at 0 1 mm yr 1 providing the first indication of major tectonic elevation changes in this actively extending region that are not directly related to throw on normal faults

the 30 50 day mode at 850 mb during monex abstract the analyzed wind field at 850 mb during the summer monsoon experiment monex is subjected to a time series analysis to confirm the existence of a peak in the time range of 30 50 days having established that this study presents a mapping of the motion field for this time scale in this short paper we illustrate the steady meridional propagation of a train of troughs and ridges that seem to form near the equator and dissipate near the himalayas the meridional scale of this mode is around 300 km and its meridional speed of propagation is 0 75 latitude per day the amplitude of the wind for this mode is around 3 6 m s 1 the salient contributions here are the mapping and the demonstration of a very regular behavior of this mode its existence is here noted from a period well before the onset of monsoon i e from early may to late july three major storms during monex were noted to form within the trough line of this system and the period of major cessation of rains over the indian subconti

earthquake induced variations in the composition of the water in the geothermal reservoir at vulcano island italy abstract during 1979 1989 variations were observed in the oxygen composition of the water contained in the geothermal reservoir at vulcano island italy the reservoir water that has a magmatic origin showed an oxygen composition of 1 0 0 5 18o during periods without local tectonic earthquakes and an oxygen composition of 3 4 0 5 18o after the highest energy seismic activity that occurred recently near the island a slight increase of the 18o value in the reservoir water was also observed after a low energy sequence of tectonic earthquakes that occurred at very shallow depth just beneath vulcano island these 18o variations in the reservoir water are consistent with earthquake induced increases in the contribution from high temperature 18o rich magmatic condensate to the geothermal reservoir and with subsequent decreases in the 18o value due to 18o exchanges at the temporarily increased reservoir temperature during reactions between the highly reactive magmatic condensate and the local rocks only minor changes in the deuterium composition of the reservoir water occurred with time as the d value in the magmatic condensate released from the magma after major local earthquakes quickly approached the d value of the water contained in the geothermal reservoir also the chloride concentration in the reservoir water appears to be linked to the contribution from the magmatic fluid this chloride content seems not to have undergone major changes with time as it may be buffered by temporary increases in the reservoir temperature up to values 300 c induced by major local earthquakes this mechanism may possibly occur also in other magmatic hydrothermal systems

helium isotope variations in turkey relationship to tectonics volcanism and recent seismic activities the distribution of helium isotope ratios in the various tectonic provinces of turkey is examined through a synthesis of previously published data and the results of a recent survey along the north anatolian fault zone nafz following the catastrophic 1999 earthquakes the r ra values where r sample 3he 4he and ra air 3he 4he cover a wide range from 0 05 to 7 87 and the mantle derived helium is clearly identified in most locations the mantle derived component is high 50 of total he in a regions of central and eastern anatolia both of which are associated with historically active volcanoes and b the seismically active west to central segment of nafz while the mantle contribution reaches a maximum at nemrut volcano in eastern anatolia a region of dominantly compressional tectonics and with moderate enthalpy geothermal fields it is relatively low 50 in the western anatolian extensional province even though this region has the highest geothermal potential the average 3he enthalpy ratios estimated for the different provinces suggest lithospheric stretching and rise of the geotherm as the major mechanism of high heat flow yet limited intrusive activity in western anatolia is suggested as the reason for the comparatively low he additions and consequently low 1 7 106 atoms j 3he enthalpy ratios a more extensive magmatic activity appears to be responsible for the greater input of both heat and helium in eastern and central anatolia with intra province 3he enthalpy variations from 3 1 106 atoms j in eastern to 0 25 106 atoms j in central anatolia reflecting the ageing of hydro magmatic systems the relatively high 3he concentrations in low enthalpy waters of northern anatolia 2 8 106 atoms j are particularly significant since there is no evidence of volcanic activity associated with the strike slip motion along the seismically active segment of nafz continuous monitoring of he isotope compositions along nafz should lead to a better understanding of this apparent anomaly as well as the relationship if any between he isotope variations and seismic activities in this region