topography and self gravitation interaction in elastic gravitational modeling changes in gravity due to volcanic loading of the crust are influenced by topography we investigate the relative importance of topography and self gravitation in the interpretation of gravity changes it is shown that modeling of gravity changes can be more precise with the introduction of topographic relief although it is neglected self gravitation of the medium this paper exploits this result by suggesting a mathematical simplification that could be useful in the future development of a numerical technique to accurately include topographic effects in the modeling of deformation and gravity changes finally we perform an inversion of the gravity changes observed at mayon volcano philippines between december 1992 and december 1996 including topographic effects by varying the depth of the source failure to account for topographic influences can bias estimates of source parameters particularly when the lateral extension of the relief is of the same order of magnitude as the source depth

dislocation modelling of the 1989 dike intrusion into the flank of mount etna sicily we have applied a dislocation model consisting of a dipping tabular body with constant dislocation perpendicular to the plane of the body to surface displacements related to an intrusion in the south flank of etna volcano sicily ground deformation was measured by a trilateration array and automatic tilt measurements during the 1989 eruption of the volcano significant line length changes and tilt were measured associated with an episodic 0 8 km propagation of the intrusion into the measurement array we incorporated the orientation and location of measured surface cracking into a bayesian nonlinear inversion of the data to determine the geometry of the intrusion we suggest the intrusion caused a 1 m wide opening of a vertical crack that extended from a depth of 1 km to within a few hundred meters of the surface we relate the distribution of surface cracking and seismicity associated with the fracture to stresses generated in the slip weakening zone associated with the crack edge

exxon global cycle chart an event for every occasion the basic premise of the recent exxon cycle chart that there exists a globally correlatable suite of third order eustatic cycles remains unproven many of the tests of this premise are based on circular reasoning the implied precision of the exxon global cycle chart is not supportable because it is greater than that of the best available chronostratigraphic techniques such as those used to construct the global standard time scale correlations of new stratigraphic sections with the exxon chart will almost always succeed because there are so many exxon sequence boundary events from which to choose this is demonstrated by the use of four synthetic sections constructed from tables of random numbers a minimum of 77 successful correlations of random events with the exxon chart was achieved the existing cycle chart represents an amalgam of regional and local tectonic events and probably also includes unrecognized miscorrelations it is of questionable value as an independent standard of geologic time

dyke intrusion model for the 1989 seismovolcanic activity off ito central japan in the last 10 years extensive earthquake swarms have occurred intermittently in the region east of izu peninsula central japan in july 1989 an active swarm again took place off ito city and among all past activities it was nearest to land and shallowest this activity eventually became a weak submarine eruption the first of its kind in this region associated with this event a borehole tiltmeter at 92 m depth installed several kilometers from the source area detected distinct continuous tilt change with the following features 1 tilt of 20 rad was observed within 1 week preceding the eruption 2 tilt change showed a good correlation to swarm activity 3 no obvious coeruption tilt change was observed on the basis of the tilt record and swarm distribution we constructed a dislocation model to interpret the seismovolcanic activity the model consists of two tensile faults each of which corresponds to magma intrusions in may and july and a right lateral reverse fault representing the largest earthquake m5 5 at 1109 lt on july 9 this model can simulate not only the above tilt data but also the record of a nearby dilatometer the results from daily laser distance measurements and daily global positioning system monitoring as well as results from other conventional distance surveys and leveling surveys in the surrounding region from this model we conclude that the intersection of the shear fault with the tensile fault caused magma to come up into soft sedimentary layers at the seabottom creating a lava dome later an instability brought about a magma phreatic explosion which did not generate any substantial crustal deformations at deeper levels

age and significance of sequence boundaries on jurassic and early cretaceous rifted continental margins the age and significance of sequence boundaries on jurassic to early cretaceous rifted continental margins in three ocean basins have been documented the margins are the santos basin in the south atlantic the grand banks in the north atlantic and the beaufort sea in the arctic ocean large industry data bases were used for the interpretation of each area megasequence boundaries separate the major phases of basin evolution for example syn rift and post rift boundaries developed with an average periodicity of 49 m y sequence boundaries define the component parts of each megasequence and developed with a modal periodicity of 10 15 m y out of 27 total boundary ages most 16 are developed on just one margin only two possible age ranges overlap on all three margins ighty percent of the megasequence boundaries and 50 of the sequence boundaries show a direct causal connection with coeval faulting and or folding the rest of the boundaries appear as unstructured surfaces separating transgressive and or regressive sedimentary wedges and are interpreted to result from changes in the rate of basin subsidence sediment input and long term eustatic sea level these data do not support theories advocating synchronous worldwide boundary development resulting from periodic short term falls in global eustatic sea level only in like basins of the same age with identical subsidence and sediment input rates are boundaries likely to develop synchronously hence the concept of global synchroneity of sequence boundary development may well be an illusion creat d by the similarity in age of the majority of basins studied as a result of this study it seems wise discard the global approach to basin analysis

fault reactivation and structural inversion backarc and intraplate compressive deformations example of the eastern sunda shelf indonesia the tectonic evolution of the eastern sunda platform in indonesia is revealed by the study of seismic profiles and comprises three general tectonic periods during the cenozoic extension with graben infill from the paleogene to the early miocene a tectonically quiet period with only broad subsidence and a middle miocene recent period of folding inversion and thrusting these structures reveal changes in the intraplate stress field which was controlled by the changes in the boundary conditions of the plates collisions on the northern and eastern sides and interplate coupling southward along the java subduction zone inversions often occurred without reactivation of pre existing normal fault planes at the upper levels of these faults the factors controlling these deformations are discussed with special interest placed on the conditions for the potential reactivation of cohesionless normal faults inversion and reactivations were mostly controlled by the orientation of the pre existing fault planes in relation with the regional stress field and by the tectonic stress regime in a strike slip regime effective principal stresses 1 and 3 horizontal with 1 2 3 the optimum conditions for reactivation in isotropic rocks are pre existing faults that strike close to the potential two vertical conjugate failure planes the same mechanical properties as for pre existing fault prevail in such conditions strike slip movements and reverse strike slip movements and associated en echelon folds were generally observed in a compressive regime 1 and 2 horizontal with 1 2 3 typical steeply dipping normal faults are difficult to reactivate by slip movements we suggest that reverse slip movements occurred in the deeper levels of faults and were accommodated by flexure above the pre existing fault planes and the inversion of grabens the strongly inverted grabens are those whose orientation is perpendicular to the regional compression nevertheless with strong regional shortening large uplifts and thrust faults were observed with reactivation in the form of reverse or reverse strike slip movements along pre existing steeply dipping normal fault planes

present day stress orientations adjacent to active strike slip faults california and sumatra present day stress directions interpreted from well bore breakouts adjacent to two crastal scale active strike slip faults the san andreas fault in california and the great sumatran fault in sumatra indicate that the maximum horizontal stress direction sh is oriented at a high angle 70 90 to both faults the regionally defined stress fields spanning these faults show that adjacent young or actively growing folds have formed orthogonal to sh and are therefore in the thrust fault orientation these observations indicate a decoupling of the strike slip and compressional components of the deformation within these broadly transpressive zones borehole breakouts in 118 wells in western california indicate a regionally consistent stress pattern with sh generally oriented ne sw nearly perpendicular 80 90 to the strike of the san andreas fault the orientation of sh nearly perpendicular to the san andreas fault implies low shear stress on the fault and is consistent with geological interpretations of the coast and transverse ranges indicating active compressional deformation fault plane solutions for recent dip slip style earthquakes principal stress directions determined from inversion of earthquake focal mechanisms and induced hydraulic fracture orientations a stress trajectory map for western california is computed using an iterative statistical algorithm in which observed directional data such as breakout directions are used to obtain a model regional stress field analysis of well bore breakouts in 25 wells within the central and southern oil districts of sumatra indicates that the regionally defined sh adjacent to the active great sumatran strike slip fault is oriented at a high angle 70 80 to the fault this orientation of sh is consistent regionally with geologic stress indicators and focal mechanisms of dip slip earthquakes preliminary analysis of the stress field in the vicinity of the philippine and alpine faults suggests sh is also oriented at a high angle to these active strike slip faults similarly the minimum horizontal stress sh is oriented at a high angle to the the kane and dead sea transforms the observation of sh and sh in the vicinity of active strike slip faults being oriented nearly perpendicular and parallel to the faults suggests that large crustal scale strike slip faults may in general be inherently weak surfaces

seismic activity accompanying the outbreak of the 1991 1993 eruption of mt etna italy abstract the character and location of seismic activity accompanying the onset of the 1991 1993 eruption at mt etna are compatible with the surface evidence of the volcanic pile rupture both the epicentral distribution and the focal mechanisms of a swarm that occurred on december 14 1991 agree with magma ascent occurring along the main nnw sse trending structure of the volcano and the consequent opening of a system of effusive fissures with the same trend a typical mainshock aftershock sequence recorded the day after and indicating transcurrent displacement occurring along the second principal structure of etna ne sw depicts the tectonic response of the volcanic pile and the underlying basement to major stresses applied by the magma push

analytical and 3 d numerical modelling of mt etna italy volcano inflation summary since 1993 geodetic data obtained by different techniques gps edm sar levelling have detected a consistent inflation of the mt etna volcano the inflation culminating with the 1998 2001 strong explosive activity from summit craters and recent 2001 and 2002 flank eruptions is interpreted in terms of magma ascent and refilling of the volcanic plumbing system and reservoirs we have modelled the 1993 1997 edm and gps data by 3 d pressurized sources to infer the position and dimension of the magma reservoir we have performed analytical inversions of the observed deformation using both spheroidal and ellipsoidal sources embedded in a homogeneous elastic half space and by applying different inversion methods solutions for these types of sources show evidence of a vertically elongated magma reservoir located 6 km beneath the summit craters the maximum elevation of topography is comparable to such depth and strong heterogeneities are inferred from seismic tomography in order to assess their importance further 3 d numerical models employing source parameters extracted from analytical models have been developed using the finite element technique the deformation predicted by all the models considered shows a general agreement with the 1993 1997 data suggesting the primary role of a pressure source while the complexities of the medium play a minor role under elastic conditions however major discrepancies between data and models are located in the se sector suggesting that sliding along potential detachment surfaces may contribute to amplify deformation during the inflation for the first time realistic features of mt etna are studied by a 3 d numerical model characterized by the topography and lateral variations of elastic structure providing a framework for a deeper insight into the relationships between internal sources and tectonic structures

intrusive mechanisms at mt etna forerunning the july august 2001 eruption from seismic and ground deformation data in this work we present seismological and ground deformation evidence for the phase preparing the july 18 to august 9 2001 flank eruption at etna the analysis performed through data from the permanent seismic and ground deformation networks highlighted a strong relationship between seismic strain release at depth and surface deformation this joint analysis provided strong constraints on the magma rising mechanisms we show that in the last ten years after the 1991 1993 eruption an overall accumulation of tension has affected the volcano then we investigate the months preceding the 2001 eruption in particular we analyse the strong seismic swarm on april 20 24 2001 comprising more than 200 events mmax 3 6 with prevalent dextral shear fault mechanisms in the western flank the swarm showed a ca ne sw earthquake alignment which in agreement with previous cases can be interpreted as the response of the medium to an intrusive process along the approximately nnw sse volcano genetic trend these mechanisms leading to the july 18 to august 9 2001 flank eruption are analogous to ones observed some months before the 1991 1993 flank eruption and more recently in january 1998 before the february november 1999 summit eruption

a multidisciplinary approach to detect active pathways for magma migration and eruption at mt etna sicily italy before the 2001 and 2002 2003 eruptions two strong flank eruptions occurred in july august 2001 and from late october 2002 to late january 2003 at mt etna volcano the two eruptions mainly involved the upper southern flank of the volcano a particularly active area during the last 30 years damaging several tourist facilities and threatening some villages the composite eruptive activity on the upper southern flank of mt etna during 2001 2003 has confirmed a posteriori the results of a multidisciplinary study started well before its occurrence by combining geological seismic and geochemical data gathered in this part of the volcano we were able in fact to highlight fractured zones likely to be re activated in the near future in this area where the largest majority of eruptive fissures in the recent past opened along n120 to n180 ranging directions the spatial distribution of earthquake epicentres during the period june 30th 2000 june 30th 2001 showed the greatest frequency in a sector compatible with both the direction of the main fissures of the pre 2001 period and that of the 2001 and 2002 lateral eruptions soil co2 and soil temperature surveys carried out in the studied area during the last 3 years have revealed anomalous release of magmatic fluids mainly co2 and water vapour along some nnw sse trending volcano tectonic structures of the area even during inter eruptive periods indicating persistent convective hydrothermal systems at shallow depth connected with the main feeder conduits of etna the temporal changes in both seismic and geochemical data from june 30th 2000 to june 30th 2001 were compared with the evolution of volcanic activity the comparison allowed to recognize at least two sequences of anomalous signals august to december 2000 and april to june 2001 likely related to episodes of step like magma ascent towards the surface as indicated by the following eruptive episodes the n120 to n180 structural directions are in accord with one of the main structural lines affecting eastern sicily they would be important pathways for magma uprise to the surface that will keep on feeding the eruptive activity of etna in the near future this study also pointed out the high instability of the southern slope of etna a sector where the potential hazard by lava flow invasion will remain high also in the near future

the petroleum potential of tertiary coals from western indonesia relationship to mire type and sequence stratigraphic setting abstract more than 500 deltaic sediments from 14 basins in western indonesia were subjected to detailed geochemical petrographic and palynological analysis the resultant data represent each of the main peat forming tectonostratigraphic episodes paleogene syn rift transgressive paleogene neogene post rift transgressive and neogene syn tectonic regressive of the indonesian tertiary the coals are hydrogen rich with average hydrogen index hi of 250 300 and atomic h c ratios of 1 0 1 3 where immature paleogene coals from syn rift transgressive systems tracts are more hydrogen rich than neogene coals from syn tectonic regressive systems tracts and upon pyrolysis yield lower gas oil ratios implying they are more oil prone pliocene coals from a strongly regressive sequence in the sumatran fore arc are very hydrogen poor with average hi of 138 indonesian coals display a systematic increase in hi with increasing rank peaking at a tmax of c 430 c suggesting that rock eval pyrolysis underestimates petroleum potential in low rank coals the increase in hi is accompanied by a decrease in s1 toc ratio and the disappearance of suberinite and resinite reflecting the assimilation of these macerals into the coal matrix with increasing diagenesis petrographic analyses reveal a very poor correlation between liptinite content and hi the term detrovitrinite index di is coined to describe the ratio of detrovitrinite total vitrinite a better relationship between hi and di suggests that vitrinite type is a more important control on petroleum potential than liptinite content the coals are classified into four sub types i iv on the basis of their pyrolysis potential and petrographic composition sub types i ii and iii are low ash coals and are likely to have been deposited in raised mires sub type i is hydrogen rich and primarily represents middle to late miocene coals deposited in a regressive megasequence sub type ii coals are hydrogen poor and occur in multiple tectonostratigraphic settings sub type iii consists of very hydrogen poor pliocene coals from the rapidly subsiding west sumatran fore arc sub type iv is hydrogen rich and consists of high ash eocene coals deposited in submerged mires in a transgressive syn rift setting a close relationship between hi and tissue preservation index tpi suggests that the degree of degradation of the peat is an important factor in determining petroleum potential highly degraded peats result in hydrogen rich coals with a higher proportion of vitrinite of detrital or allochthonous origin the degree of degradation is most likely related to the amount of time the peat spends within the zone of influence of the water table and is unlikely to be directly related to tectonostratigraphic setting

origin of contrasting features and preservation pathways in kerogens from the kashpir oil shales upper jurassic russian platform abstract a kerogen termed abs base from the gorodische section russian platform was studied using a combination of microscopic spectroscopic and pyrolytic methods in order to determine its chemical structure source organisms and formation pathway s this kerogen was mainly formed via degradation recondensation of phytoplanktonic material selective preservation and natural sulphurisation pathways only played a minor role whereas a substantial contribution of ether linked lipids was noticed revealing large oxygen cross linking such observations allowed us to put forward for the first time to the best of our knowledge a substantial role for the oxidative reticulation pathway in the formation of a kerogen comparision with a previously studied sample from the same outcrop revealed contrasting features which reflect differences in preservation pathways triggered by different depositional conditions

stratigraphy and tectonic setting of the cretaceous and paleogene volcanic sedimentary successions in northwest sulawesi indonesia implications for the cenozoic evolution of western and northern sulawesi abstract new field and laboratory data from nw sulawesi indonesia integrated with existing information provide a tectonostratigraphic framework for the cretaceous and paleogene of this region the study area straddles two distinct provinces referred to as western and northern sulawesi western sulawesi forms the rifted continental margin of eastern sundaland it consists of a metamorphic basement partly of australian origin overlain by late cretaceous turbidites that were deposited in a fore arc setting latimojong formation these are in turn covered by volcanic sedimentary successions that were deposited during the early middle eocene to earliest miocene they represent a transgressive cycle from syn rift siliciclastics through nummulitic limestone and associated shelf sediments to deeper marine mudstones and turbidites budungbudung and tinombo formations during the same period northern sulawesi developed as an oceanic island arc characterized by bimodal volcanism papayato volcanics founded on back arc oceanic crust the cretaceous and paleogene volcanic and sedimentary suites show lithological and geochemical characteristics that reflect the contrasting tectonic setting of the two provinces the tectonic relationship between the two domains is not clear they probably formed a more or less continuous belt throughout the cenozoic but were definitely connected not later than the early miocene strong deformation in the paleogene formations in the northern part of nw sulawesi and their unconformable relationship with the overlying formations may be the result of the collision of the north arm of sulawesi with a continental fragment of australian derivation during the early miocene or it may be related to the formation of a metamorphic core complex in a mid miocene extensional tectonic setting a second major tectonic event which commenced in the pliocene and is still ongoing affected the entire region

the march 1981 mount etna eruption inferred through ground deformation modelling abstract the march 1981 eruption of mt etna was characterised by the fast propagation of a long eruptive fissure approximately 7 km and by an unusually high eruption rate the continuous tilt recorded by a bore hole station located on the southern flank showed a small inflation 3 4 months before the eruption followed by a rapid deflation during the fissure opening the discrete deformation measurements electroptical distance measurements edm and levelling showed large horizontal changes in the volcano flanks and smaller vertical ones close to the eruptive fissure we modelled the deformation pattern associated with the 1981 eruption using horizontal 57 data and vertical 50 data measurements two geometric constraints were considered for the eruptive fissure the dislocation theory was used to model the intrusion by characterising it in two parts as a double tensile crack which represents the initial deeper intrusion first crack and then the final shallower part associated with the eruptive fissure second crack an analytic inversion was performed obtaining a very good solution and then the robustness of this result was verified through an accurate trial and error search the first deeper crack extends vertically from about 300 to 1700 m above sea level a s l it was widely opened opening 5 m dipping w and radiating from the summit of the volcanic edifice in the nnw direction for approximately 3 km in the shallowest part last 500 m the intrusion propagated radially in the northern sector along the nnw direction second crack matching the surface location of the observed eruptive fissure we interpret that the deeper crack formed during the 3 4 months preceding the eruption

dispersion of gaseous volcanogenic fluoride island of hawaii abstract fluoride was measured in samples of lichen collected in 1990 from 68 sites on the island of hawaii in addition fluoride levels were measured in 8 rainfall samples collected at the same time the levels of fluoride in the lichens range from 6 to 332 g g 1 which are similar to the levels measured on etna the highest levels of fluoride were detected close to kilauea and the concentration generally decreases with increasing distance from this volcano this overall pattern of distribution is modified by local variations in wind direction which relate to the topographic features of the island close to kilauea there are more localised controls on the fluoride levels caused by circulating groundwaters and degassing lavas

petrologic isotopic and radiometric age constraints on the origin and tectonic history of the malino metamorphic complex nw sulawesi indonesia the malino metamorphic complex mmc is located at the western end of the north arm of sulawesi it consists of mica schists and gneisses derived from proximal turbidite and granitoid protoliths with intercalations of greenschist amphibolite marble and quartzite forming an e w elongated dome like structure bounded on all sides by faults the age of the mmc is constrained between devonian and early carboniferous this paleozoic age the presence of archean and proterozoic inherited zircons and the isotopic signature of the mica schists and gneisses indicate that the terrane was derived from the new guinea australian margin of gondwana similarities with basement rocks in the bird s head suggests a common origin greenschists forming a discontinuous selvage metamorphic carapace around the complex were derived from adjacent autochthonous paleogene formations the rocks of the mmc show a barrovian type progression from greenschist through epidote amphibolite to amphibolite facies p t estimations suggest a depth of burial of up to 27 30 km k ar and 40ar 39ar cooling ages of 23 11 ma and a 7 ma age for unconformably overlying volcanic rocks indicate that the complex was exhumed during the miocene two tectonic scenarios are considered 1 the continental fragment docked with sulawesi during the mesozoic and was exhumed as a metamorphic core complex during the miocene 2 it was subducted beneath the north arm during the late oligocene and then rapidly returned back to the surface

dynamic dyke propagation deduced from tilt variations preceding the march 9 1998 eruption of the piton de la fournaise volcano during the hour preceding the march 9 1998 eruption of the piton de la fournaise volcano the deformation network of the observatory recorded some large deformations in the summit area a broadband seismic station of the geoscope global network rer is located about 8 km away from the summit of the volcano signals from that station may be interpreted as tilt changes the combination of the above two kinds of signals allows by using a tensile fault model to constrain the geometry as well as some characteristics volume propagation velocity of the dyke that intruded the summit area during the hour preceding the beginning of eruptive activity

the effects of topography on magma chamber deformation models application to mt etna and radar interferometry we have used a three dimensional elastic finite element model to examine the effects of topography on the surface deformation predicted by models of magma chamber deflation we used the topography of mt etna to control the geometry of our model and compared the finite element results to those predicted by an analytical solution for a pressurized sphere in an elastic half space topography has a significant effect on the predicted surface deformation for both displacement profiles and synthetic interferograms not only are the predicted displacement magnitudes significantly different but also the map view patterns of displacement it is possible to match the predicted displacement magnitudes fairly well by adjusting the elevation of a reference surface however the horizontal pattern of deformation is still significantly different thus inversions based on constant elevation reference surfaces may not properly estimate the horizontal position of a magma chamber we have investigated an approach where the elevation of the reference surface varies for each computation point corresponding to topography for vertical displacements and tilts this method provides a good fit to the finite element results and thus may form the basis for an inversion scheme for radial displacements a constant reference elevation provides a better fit to the numerical results

models of ground deformation from vertical volcanic conduits with application to eruptions of mount st helens and mount etna we present simple analytical models of ground deformation from inflation of vertical volcanic conduits or pipes we compare three cases corresponding to 1 a pressurized pipe with closed end at the top that resists the internal pressure 2 a pressurized pipe with top open for which the internal deformation is mainly dislocation of the cylindrical walls and 3 a pipe shaped region that dilates for the closed pipe we use eshelby s inclusion theory to model deformation from a thin pressurized elongated prolate ellipsoid in a full space which we express in terms of double forces to satisfy surface boundary conditions we superimpose image solutions by using double forces derived from mindlin s half space solution for the point force for the open pipe we apply the volterra integral to dislocation across a cylindrical surface and generalize it to the half space using mindlin s point force solution these two solutions show marked differences from the line of dilatation solution ratios of maximum horizontal deformation to maximum vertical deformation for the pipe models are significantly greater than values for the center or line of dilatation models this and the more gradual fall off of the deformation with distance may be used as diagnostics for discriminating between pipe like sources and dilatational sources on volcanoes where both components of the deformation field are available as examples we compare the closed pipe model with deformation associated with dome building on mount st helens volcano and tilt predicted by the open pipe model with tilt measured during a period of explosive eruptive activity on mount etna sicily in 1995 comparison between model values and the measurements suggests that the effective elastic moduli of the volcanic cones are very low

the banda celebes sulu basin a trapped piece of cretaceous eocene oceanic crust the banda celebes and sulu basins are poorly understood marginal seas located at the junction of the eurasian indian australian and pacific philippine sea plates the incompleteness of the data sets the complex geology of the surrounding islands and the late cenozoic evolution involving subduction rifting transform faulting and island arc collision have complicated tectonic interpretation of the region the banda basin is underlain by oceanic crust1 3 bowin et al 2 and lapouille et al 3 have suggested that it is a trapped oceanic basin which was once continuous with the late jurassic argo abyssal plain off north west australia similarly the celebes and sulu basins are also underlain by oceanic crust4 6 on the basis of newly identified magnetic reversal ages fig 1 heat flow data and on land geological studies we suggest that the celebes and sulu seas may have been continuous with the banda basin this cretaceous eocene basin has been dissected into its present configuration by tertiary tectonic processes

structural evolution of malay basin its link to sunda block tectonics abstract the malay basin is located offshore west malaysia in the south china sea within north central region of 1st order sunda block the basin developed partly as a result of tectonic collisions and strike slip shear of the southeast asia continental slabs as the indian plate collided into eurasia and subsequent extrusion of lithospheric blocks towards indochina the sunda block epicontinental earliest rift margins were manifested by the palaeogene w e rift valleys which formed during nw se sinistral shear of the region later eocene nw se dextral shear of 2nd order indochina block against east malaya block rifted open a 3rd order malay basin developed within it is a series of 4th order n s en echelon ridges and grabens the grabens and some ridges sequentially host w e trending 5th order folds of later compressional episodes the malay basin ridge and graben model explains the multi phased structural deformation which started with the a pre rift palaeo mesozoic crystalline metamorphic basement b synrift phase during paleogene c fast subsidence from late oligocene to middle miocene d compressional inversion of first sunda fold during late miocene and e basin sag during plio pleistocene with mild compressional episodes the subsequent mio pliocene folding history of malay basin is connected to the collision of sunda block against subducting indian australian plate this neogene sunda tectonics to some degree after the cessation of south china sea spreading is due to the diachronous collision along the 1st order plate margins between se asia and australia

plate tectonics and island arcs the plate tectonic concepts that developed rapidly in the late l960s made possible the understanding of island arcs before that time mobilistic concepts evolved slowly hindered particularly in the united states by an obstructionist geoscience establishment the volcanic belts of island arcs form about 100 km above subducting plates convergent plate boundaries evolve complexly with time and at any one time vary greatly along their lengths seismicity defines positions but not trajectories of descending slabs which sink more steeply than they dip and are overridden by advancing upper plates subduction occurs beneath only one side at a time of an internally rigid plate and the common regime in an overriding plate behind a surficial accretionary wedge is extensional except where a collision is underway back arc basin lithosphere is built behind or by migrating island arcs which lengthen and increase their curvatures a collision can involve two active arcs in which case intervening lithosphere sinks beneath both of them or an active margin and a passive one either type of collision generally is followed by the breaking through of new subduction beneath the composite mass of light crust from a new trench on the outside of the aggregate conversely a new subduction system commonly is a by product of collision a strip of back arc basin crust is in many cases left attached to the aggregate in front of the new trench and becomes the basement for a fore arc basin the leading edge of which is raised as melange is stuffed under it sedimentation in trenches is predominantly longitudinal and can be from distant sources accretionary wedges are dynamic being thickened at both toes and bottoms by tectonic accretion and thinned by gravitational forward flow melange is largely a product of tectonic imbrication and flowage driven by these conflicting processes not of submarine sliding high pressure metamorphic rocks form beneath overriding plates not within wedges in front of them arc magmas incorporate much material from the lithosphere through which they rise and vary correspondingly with the evolving composition of that lithosphere arc crust is inflated into geanticlines by intrusive rocks and thermal expansion submarine island arc volcanic rocks are widely spilitized with na enrichment and ca depletion by hydrothermal reaction with sea water the lower crust of mature island arcs consists of granulite facies rocks of mafic intermediate and felsic intermediate compositions the mohorovicic discontinuity may be primarily a constructional boundary representing the shallow limit off crystallization of voluminous rocks of ultramafic composition or plagioclase free mineralogy

neogene structures and sedimentation history along the sunda forearc basins off southwest sumatra and southwest java abstract twenty multi channel seismic lines in the southwest sunda arc margin between manna and west java have been studied this study depicts the structures and stratigraphy of the fore arc basin since late paleogene in relation to the regional tectonic events the paleomorphology of the cretaceous continental margin persisted until the oligocene and the paleoshelf margin of the continent extended north westward off sumatra a residual basin filled with turbidite deposits developed just offshore of this margin subsequent fore arc basin evolution was related to the slow down of subduction rate due to the collision of the indian and eurasian plates in the eocene the rising himalayan orogenic zone shed large amounts of sediment to the indian ocean and sunda trench beginning in the late paleogene which led to the growth of the accretionary prisms and the development of the neogene fore arc basin at least two major structural events can be recognized in the fore arc basin between late oligocene and pliocene back thrust faulting along the southern border of the fore arc basin and initiation of the cimandiri fault zone occurred in late oligocene whereas the development of the sumatra and mentawai fault zones was initiated in pliocene four neogene sedimentary units can be recognized representing three main transgressive regressive cycles and basin fill deposits the cycles resulted from a complex interplay of tectonically induced basin subsidence eustatic sea level change and sediment supply related to volcanic activity that became abundant since late middle miocene turbidite deposition was common along and seaward of the basin slope during sea level lows in late middle miocene and late miocene sediment aggradation and progradation occurred during high sea level still stand and fall respectively basin fills occurred mainly during the pleistocene

india eurasia collision chronology has implications for crustal shortening and driving mechanism of plates the motion of the indian plate is determined in an absolute frame of reference and compared with the position of the southern margin of eurasia deduced from palaeomagnetic data in tibet the 2 600 900 km of continental crust shortening observed is shown to have occurred in three different episodes subduction of continental crust intracontinental thrusting and internal deformation and lateral extrusion the detailed chronology of the collision and plate reorganizations in the indian and pacific oceans supports the hypothesis that slab pull is a dominant driving mechanism of plate tectonics

the origin of the east java sea basins deduced from sequence stratigraphy abstract a study of facies distribution through time shows there are at least six different basinal areas which are usually described as a single entity called the east java basin each of these different depositional lows plus the transgressed platforms between them have a unique stratigraphic history and distinct sets of petroleum systems with different exploration risks the development of the main phases of sedimentation indicate that the east java basinal system was formed as a continuation of extension around the makassar straits and not as a back arc basin this interpretation is based on a tectonically pulsed east to west trend in crustal thinning subsidence and transgression in addition there were elongate and anastomosing faults along the southern edge of this extending crust creating a unique stratigraphic zone south of the rembang line fault periodic changes in strain strongly affected this faulted southern margin including a mid oligocene tectonic event that also created a new depocentre the sibaru trough a poorly defined lithostratigraphic term the ngimbang formation is recommended to be abandoned its historical usage for a series of highly diverse lithofacies spanning four or five major unconformity bounded sequences renders it meaningless its long standing and inconsistent use is one of the factors that has prevented a clearer stratigraphic history from emerging an alternative nomenclature based on facies and natural sequences of deposition is recommended instead

neogene subsidence and stratigraphy of the simeulue forearc basin northwest sumatra abstract interpretation of new multi channel seismic data reveals the neogene subsidence history of the simeulue forearc basin located off northwestern sumatra the trench parallel elongated basin extends over 260 km in nw se direction and 100 km in sw ne direction maximum water depth is about 1300 m and the neogene sedimentary fill shows a thickness of up to 5 s two way traveltime we identified three stages of subsidence evolution after the formation of a regional basal neogene unconformity which are characterized by changing accumulation space sedimentation rates source areas and tectonic phases an early mid miocene stage is marked by occurrence of subsidence in several half grabens forming along the western border of the basin during the late miocene pliocene this small scale subsidence changed to a steadily subsiding trench parallel trough the present setup of the forearc region under the influence of strike slip faults due to oblique subduction is active at least since this time as evidenced by wrench faulting at the end of this stage subsidence expanded significantly eastwards drowning a large carbonate platform that evolved in the then shallow southern and eastern parts of the basin presently the central part of the simeulue basin is subject to inversion probably related to reactivation of early mid miocene half grabens

long term record of co2 degassing along mt etna s flanks and its relationship with magma dynamics and eastern flank instability a record of soil co2 flux data on the lower flanks of mt etna measured from 1989 to 2008 is discussed in the framework of multidisciplinary observations including seismicity ground deformations and flank instability a huge increase in soil co2 fluxes appears to be related to the dynamics of magma ascent in the upper portions of the volcano 0 3 km and the intrusion of dykes along the southern rift as mainly observed before the 1991 93 eruption even after the 1991 93 eruption the recharge of the shallow central reservoir was accompanied by a long term increase in soil co2 degassing mainly in the southwestern area the 2001 eruption marked dramatic changes in the areal distribution of seismicity the deformation pattern and the soil co2 degassing indeed while the soil co2 degassing showed background values in the southwestern area it progressively increased in the eastern sector and along the pernicana fault this has been related to the marked sliding of the eastern flank since the 2002 03 eruption and the associated seismicity this study provides evidence that the extent of soil co2 degassing on the lower flanks of mt etna is controlled by 1 the volume of involved magma 2 the intrusion of dykes in the upper parts of the volcano and 3 fault movement and seismicity this implies that different degassing structures must be monitored simultaneously when attempting to understand the behavior of the volcano as a whole

deflation of mount etna monitored by spaceborne radar interferometry ground based measurements of volcano deformation can be used to assess eruptive hazard but require the costly and often hazardous installation and maintenance of an instrument network here we show that spaceborne radar interferometry which has already shown its utility in mapping earthquake related deformation1 can be used to monitor long term volcano deformation two families of synthetic aperture radar images acquired from ascending and descending orbits by the satellite ers 1 and looking at mount etna from opposite sides cover the time period from 17 may 1992 to 24 october 1993 and include the second half of etna s most recent eruption despite artefacts of the interferometric technique we can observe a volcano wide deflation which is an expected consequence of the eruption but which had not previously been appreciated we quantify it using a simple model based on the change of pressure in a sphere located in an elastic half space the modelled deformation increases linearly with time until the end of the eruption our results show that it will be possible to use this technique to detect the inflation of volcanic edifices that usually precedes eruptions

ground deformation patterns at mt etna from 1993 to 2000 from joint use of insar and gps techniques abstract combined gps measurements and radar interferometry insar have been applied at mt etna to study the ground deformation affecting the volcano both over the long 1993 2000 and short term 1997 1998 and 1998 2000 the aim was to better understand the dynamics of the volcano during the magma recharging phase following the 1991 93 eruption since 1993 insar and gps data indicate that mt etna has undergone an inflation a deep intrusion was detected by insar on the western flank of the volcano between march and may 1997 in the following months this intrusion rose up leading to a seismic swarm occurring in january 1998 in the western sector this now shallow intrusion is confirmed by gps data from 1998 to 2000 a general deflation affecting the upper part of the volcano was detected over the whole study period a continuous eastward to south eastward motion of the eastern sector of the volcano was also evidenced the analytical inversions of gps data inferred a plane dipping about 12 ese located beneath the eastern flank of the volcano at a depth of 1 4 km b s l the movement along this plane is able to reproduce the observed south eastward motion of a sector bounded northward by the pernicana fault westward by the north east rift and the south rift and southward by the mascalucia tremestieri trecastagni fault system insar data have validated this model

development of cenozoic basins in thailand abstract there are over 60 cenozoic basins distributed in various parts of thailand both onshore and offshore these basins are mainly n s trending half grabens or grabens and most were initiated in the late oligocene the structural framework of the basins is generally governed by n s trending extensional faults which are spatially related to the movement of the nw se and ne sw trending strike slip faults that have been active since the oligocene the nw se faults are the principal dextral strike slip faults whereas the ne sw faults are the conjugate sinistral strike slip faults the collision of the india craton with southern asia since 40 50 ma caused clockwise rotation of southeast asia and movements on the strike slip faults with the associated development of cenozoic basins in this region four major cenozoic basins mergui pattani malay and phitsanulok contain up to 8000 m of sediments generally the cenozoic fills are continental sediments except in the mergui basin in the andaman sea where the sedimentary fill is mainly marine sediments fluviatile with occasional lacustrine deposits were prominent in the gulf of thailand and onshore basins during the oligocene to early miocene from early to middle miocene widespread perennial lake conditions were well developed in the onshore basins and in the western graben area of the gulf of thailand a change in tectonic and or climatic conditions took place in the middle to late miocene times resulting in the cessation of perennial lake conditions and development of a regional unconformity

dynamic inversion of ground deformation data for modelling volcanic sources etna 1991 93 the 1991 93 etna eruption that represented the most important recent eruptive event both in terms of duration 472 days and total volume of erupted lava ca 250 106 m caused marked ground deformation measured by using different geodetic techniques such as edm gps levelling and tiltmetry an inversion termed dynamic because it took into account the sequence of events considering both the separate and cumulative effects of two sources a shallow tensile crack and a deeper ellipsoidal deflating source was performed it was based on 163 data collected by the different techniques plus 2 geometrical conditions for constraining the geometry of the crack on the surface the final solution furnished a good fit for all measurements defining a shallow tensile crack located inside the volcanic edifice which represents the effect of the intrusion and a depressuring body with centre at ca 3000 m b s l which could represent the centre of a generalized and more complex deflation of the volcanic edifice during the course of the eruption

episodic inflation and complex surface deformation of akutan volcano alaska revealed from gps time series abstract akutan is one of the most active volcanoes in the aleutian island arc studies involving seismic gps and insar data have observed activity and deformation on the island since 1996 in this study we inverted measurements of volcanic deformation observed using three components of motions at 12 continuous gps sites to define magma source parameters using mogi point source okada dislocation and yang spheroid and ellipsoid models in order to analyze the evolution of this magma source we split the gps data into five consecutive time periods and one period that incorporates all available data these time periods were designed around two inflation events in 2008 and 2014 when a sudden and significant increase in vertical velocity was observed inversion of these time periods independently allowed us to create a magma volume time series that is related to the physical migration of magma defined by the estimated source parameters the best fit model parameters resulting from these inversions describes magma storage in the form of an oblate spheroid centered on the northeastern rim of the caldera of akutan volcano extending from a depth of 7 km to 8 km with a length of 3 5 km a strike of n165 e and a dip of 63 from the horizontal to the southwest our model results were compared with seismic studies and found to support previous interpretations of episodic inflation beneath akutan volcano with complicated magma storage at intermediate depths the inflation event observed in 2008 was estimated to be the result of an injection of magma of 0 08 km 3 that was followed in 2014 by an additional increase in volume of 0 06 km 3 no periods of deflation were observed in the gps data after these events and we believe the total volume of magma accumulated in this region 0 2 km 3 remains in a shallow storage system beneath akutan volcano

formation of arcs and backarc basins inferred from the tectonic evolution of southeast asia since the late cretaceous abstract results of the geological and geophysical surveys in the daito ridges and basin in the northern west philippine basin suggest that the daito ridge was an arc facing toward the south from the late cretaceous to the early tertiary the late cretaceous and tertiary history of southeast asia is evaluated based on these data in the daito ridges and basins and reconstructed based on overall plate kinematics that have operated in this area during the late cretaceous the daito ridge and the east philippine islands were positioned along the boundary between the indian and pacific plates the western half of the philippines setting on the indian plate approached from the south and collided with the east philippine daito arc either during the latest paleocene or the earliest eocene it is inferred that the bulk of the philippine archipelago rotated clockwise and borneo spun counterclockwise during the tertiary from the reconstruction the formation of backarc basins and their spreading direction are assessed as a result some primary causes and significant characteristics are suggested for the opening of backarc basins in southeast asia first opening of some backarc basins commenced with or was triggered by collisions second backarc basins opened approximately parallel to oceanic plate motion third the formation of some backarc basins was triggered by the approach of a hot spreading center fourth the spreading mode or direction of backarc basins was greatly affected by the configuration of the surrounding continent and was also rearranged to spread approximately parallel to oceanic plate motion the formation of backarc basins and their spreading direction can be reasonably explained by plate kinematics however the generative force responsible for their formation is possibly within the subduction system particularly to form horizontal tensional force in backarc side

episodic rifting and subsidence in the south china sea the south china sea experienced at least three stages of rifting and two intervening stages of sea floor spreading since the early cretaceous its evolution can be described by an episodic model of tectonism one of thermal cooling and subsidence pulsed by temporally and spatially confined heating events analysis of regional geologic and geophysical data suggests episodes of rifting and associated thermal activities initiated during the late cretaceous the late eocene and the late early miocene the rift system corresponding to the first episode trends northeast southwest whereas those of the second and third trend east west these two trends coincide with the orientations of the major tectonic lineations within the basin age estimates from heat flow and bathymetric data suggest the oceanic crust in the southwest subbasin is considerably older 55 ma than that in the northwest 35 36 ma or east 32 ma subbasins the episodic tectonic model is supported by basin subsidence analysis subsidence especially subsidence rate curves derived from the regional well data demonstrates that unlike a classic atlantic passive margin thermal subsidence in the south china sea was punctuated by rapid subsidence events which are chronologically consistent with the rifting episodes in terms of hydrocarbon potential the episodes of rifting and drifting would be conducive to the development of overprinted structures and the deposition of several discrete transgressive packages of source rocks and reservoirs separated by widespread unconformities the thermal maturity of sedimentary organic matter affected by episodic rifting and subsidence may be greater than expected on a purely passive margin of equivalent age that had not experienced repeated heating

feeding system and magma storage beneath mt etna as revealed by recent inflation deflation cycles 1 ground deformation at mt etna detected by three gps surveys carried out in 2004 2005 and 2006 is analyzed the data set encompasses the 2004 2005 eruptions and foreruns those of 2006 a wide deflation of the entire volcano was detected from 2004 to 2005 accompanying the 2004 2005 eruption conversely an evident inflation phase from 2005 to 2006 followed this eruption and preceded the 2006 one in both cases the deflation inflation cycle was accompanied by a continuous seaward motion of the eastern flank we inverted both data sets 2004 2005 deflation and 2005 2006 inflation using an optimization algorithm based on the genetic algorithm ga in order to detect the ground deformation sources the wide contraction measured during the eruption reveals the drainage of a sill shaped magma reservoir located by data inversions at a depth of about 4 5 km b s l the pressurizing source modeled for the 2005 2006 time interval indicates a refilling of the shallower near vertical plumbing system of the volcano this could indicate a change in the geometry of the feeding system active after the 2004 2005 eruption with a new and shallower magma storage that could have enabled the resumption of volcanic activity that was observed at summit craters in 2006 these results improve the imaging of the plumbing system of mt etna volcano

geodetic analysis of dike intrusion and motion of the magma reservoir beneath the summit of kilauea volcano hawaii 1970 1985 we use leveling and trilateration data collected on kilauea volcano to constrain the location of deformation sources caused by magma accumulation intrusion and eruption for the 13 inflationary epochs examined combinations of an expanding point source and one or two opening rectangular dislocations mimic inflation of the summit reservoir and formation of dike s respectively the combined model adequately accounts for the deformation data and is consistent with the seismicity observed during each epoch for 10 deflationary epochs however the data require only a contracting point source confidence in these results is gained by noting that locations of the sources of both inflation and deflation are coincident within the observed uncertainties of the data the function of network geometry and the inversion procedure it appears therefore that magma accumulation at kilauea volcano may be characterized by the growth of dikes during inflation of the summit reservoir drainage of the reservoir on the other hand is not accompanied by significant closure of dikes in contrast to previous studies e g fiske and kinoshita 1969 dvorak et al 1983 that do not include the dislocation or dike growth component of summit magma accumulation and concluded that the source of inflation migrates over a 5 km2 area we find that a single magmatic reservoir source accounts for data collected during all inflationary and deflationary epochs results which compare favorably with those obtained from the point ellipsoid model can be used to estimate the distribution of stresses within the volcano in the near field of the source

spreading direction in the central south china sea recent work1 2 indicates that the south china sea is an atlantictype marginal basin of late tertiary age magnetic anomalies in the eastern part of the sea are consistent with seafloor spreading directed approximately north south1 2 we present here a new morphostructural study based on coupled seabeam mapping and single channel seismic reflection profiling which reveals dominant normal fault scarps striking n50 e between 113 and 119 e longitude near the axis of this basin such a structural fabric implies a nw se spreading direction at least in the 150 200 km wide axial region of the south china sea and places new constraints on geodynamic models for the formation of this basin in the tectonic and palaeogeographic framework of south east asia and the south west pacific

petrographic characteristics of coal from the lati formation tarakan basin east kalimantan indonesia the present paper entails the petrographic characterization on limited coal samples drawn from the tarakan basin eastern kalimantan indonesia these coals contain a high concentration of huminite which in turn is dominated by telohuminite as a result of telohuminite content they have high gi and tpi values they contain low concentrations of liptinite and inertinite macerals the dominant microlithotype is vitrite based on the macerals and microlithotypes of these coals their paleodepositional environment has been reconstructed accordingly it is deciphered that these coals have originated under telmatic condition there was predominance of wood derived tissues and increased subsidence rate prevailed in the basin moreover during the time of their evolution there were alternate phases of oxic and anoxic moor conditions with intermittent moderate to high flooding in the basin

mount etna dense array local earthquake p and s tomography and implications for volcanic plumbing inversion for the three dimensional velocity structure of mount etna is performed with a data set of arrival times of p and s waves of local earthquakes from temporary dense arrays of three component seismographs a high v p body revealed by the original tomography without nearby stations is confirmed and its image is sharpened using new velocity constraints provided by refraction data synthetic tests of v p and v p v s and comparison with an independent artificial source tomography with a fundamentally different geometry consistently calibrate the significance threshold of the resolution indicators the trustworthy part of the image shows a high v p body centered under the southern part of valle del bove above the 6 km below sea level deep basement which extends towards sea level and may be rooted in or through the crust it has a large contrast of over 1 km s with the surrounding sediments and sharp lateral limits and can thus be regarded as made of intrusive material of magmatic origin the massive high v p body is heterogeneous in v p v s the regions inside it where v s is relatively low can then be suspected of containing a proportion of melt or be fractured and act as pressure links or transport zones such features may be structurally linked and appear to be activated in eruptive phenomena by taking into account the heterogeneities in structure and physical state retrieved by seismic tomography a succession of seismic events deformational episodes and geochemical variation in lavas can be discussed with respect to the well observed eruptions

tectonic features of the southern sumatra western java forearc of indonesia 1 multichannel reflection seismic profiles along the active sunda arc where the indo australian plate subducts under the overriding eurasian margin revealed two accretionary wedges the inner wedge i is of assumed paleogene age and the outer wedge ii is of neogene to recent age the inner wedge i is composed of tectonic flakes stretching from southeast sumatra across the sunda strait to northwest java implying a similar plate tectonic regime in these areas at the time of flake development during upper oligocene today wedge i forms the outer arc high and the backstop for the younger outer wedge ii the missing outer arc high of the southern sunda strait is explained by a combination of neogene transtension due to a clockwise rotation of sumatra with respect to java and by arc parallel strike slip movements the rotation created transtensional pull apart basins along the western sunda strait semangka graben as opposed to transpression and inversion on the eastern sunda strait within the new detected krakatau basin the arc parallel transpressional mentawai strike slip fault zone mfz was correlated from the sumatra forearc basin to the northwest java forearc basin off the sunda strait northward bending branches of the mfz are connected with the right lateral sumatra fault zone sfz along the volcanic arc segment on sumatra it is speculated that the sfz was attached to the cimandiri pelabuhan ratu strike slip fault of java prior to the presumed rotation of sumatra and that since the late lower miocene the main slip movement shifted from the volcanic arc position to the forearc basin area due to increasingly oblique plate convergence

origin and evolution of the west philippine basin a new interpretation abstract combined analyses of the magnetic lineations and seafloor structures of the west philippine basin show that it was formed by spreading from the central basin spreading center in two distinctly different spreading phases before and after subduction was initiated along the palau kyushu trend at 45 ma b p these episodes are recognized by differences in the strike of the magnetic lineations spreading rates density and strike of fracture zones and basement relief from 60 45 ma b p spreading was ne sw relative to present orientations at a half rate of 44 mm a at about 45 ma b p the spreading direction changed to a more n s direction with a reconfiguration of the central basin spreading center into numerous short e w segments offset by closely spaced n s transform faults spreading slowed to a half rate of 18 mm a and ceased at 35 ma b p thus the west philippine basin originated at 45 ma b p by the trapping of normal ocean crust west of the initial subduction along the palau kyushu trend the 45 35 ma b p period represents the dying phase of spreading on the central basin spreading center following isolation of the west philippine basin from the plate driving forces of the pacific

multicyclic history of the northern india continental margin northwestern himalaya 1 the geologic evolution of northern india is best recorded in the stratigraphic succession of the zanskar range northwestern himalaya which represents the most complete transect through this ancient continental margin sedimentary history began in the late proterozoic and recorded a late pan african orogenic event around the cambrian ordovician boundary when the gondwana supercontinent was eventually assembled the following long period of epicontinental deposition in shallow seas linked to palaeo tethys lasted until the early permian when a neo tethyan rift began to open between paleo india and the cimmerian microcontinents neo tethyan history can be subdivided into two sedimentary megasequences both recording a major tectonic and magmatic event in the lower part the first one began with breakup in the late permian and lasted until the end of the jurassic the second one started in the early cretaceous with the final detachment of india from gondwana and the opening of the indian ocean and ended with the india eurasia collision in the early eocene the two megasequences can be in turn subdivided into six transgressive regressive supersequences bounded by tectonically enhanced unconformities basal sandstone units of early permian late permian norian callovian early cretaceous and paleocene age are invariably associated with oolitic ironstones or reworked glauco phosphorites and mark the transgre sive part of each supersequence next condensed nodular carbonates or shales with pelagic fauna are typically overlain by thick shallowing upward marly units capped by regressive platformal carbonates the six tectono eustatic supercycles reflect successive rifting episodes which punctuated the progressive separation of india from the rest of gondwana and document the combination of plate microplate reorganizations and eustatic climatic and oceanographic changes in the tethyan domain after the onset of collision between india and asia close to the paleocene eocene boundary obduction of the remnants of the neo tethys ocean floor onto the indian margin began and the latter underwent multiphase deformation with fold thrust shortening followed by heating and extension after the main metamorphic event ophiolitic nappes were re thrusted and finally emplaced with their sedimentary sole on top of the passive margin succession

major unconformities termination of extension events and associated surfaces in the south china seas review and implications for tectonic development abstract the distribution of unconformities and end of cenozoic rifting events in the south china seas scs reflects both the modes of rift development and the effects of driving mechanisms continental rifting began in the eastern basins during the paleocene and propagated westwards to the vietnam basin margin in the late eocene continental breakup around 32 28 ma caused a regional reduction or cessation in extensional activity particularly affecting basins furthest from the spreading centre basins in the slope and deepwater area north of the spreading centre exhibit reduced fault activity until 21 20 ma propagation of oceanic crust westwards between 25 and 23 ma and termination of seafloor spreading sometime between 20 5 and 16 ma affected fault activity in the qiongdongnan and nam con song basins in the phu khanh basin and south in the dangerous grounds area extension continued until about 16 ma ending at the red unconformity the end of seafloor spreading around 20 5 ma reflects loss of extensional driving force as thinned continental crust entered the nw borneo subduction zone controversially a key component of the driving force maybe attributed to slab pull a transitional period of about 5 7 my between the onset of subduction of continental crust and final jamming of the subduction zone deep regional unconformity dru is inferred the last pulse of extension was focussed in the western scs and terminated around 10 5 ma detailed understanding of proto south china seas development remains uncertain and controversial

a new algorithm for modelling simple and double mogi magma sources in active volcanoes accuracy sensitivity limitations and implications a new algorithm for modelling one or two mogi magma sources in actively deforming volcanoes is proposed using santorini thera greece volcano as a test site this algorithm is based on a quasi deterministic grid scan search followed by a topological inversion in rn space it avoids point solutions and local minima and is primarily designed for gps observations it can be extended to other types of magma sources defined by closed functions and to other types of data a validation of the method used an accuracy oriented approach a comparison between true or reference and inverse modelled magma sources which revealed bias free precise magma source solutions a validation of the algorithm for false alarms i e for identification of non existent sources produced by computation artefacts was also made computed solutions correspond to point sources affecting idealized media homogeneous elastic half spaces and hence ignore errors induced by magma source and lithology complexities which should be superimposed to obtain the total error budget still the solutions allow modelling of the propagation of measurement errors because of the mathematical model adopted this problem has previously been ignored a sensitivity analysis of results obtained using this method permit us to predict and quantify expected bias and uncertainties in modelled magma sources as a function of their depth and of the observation networks increased bias and noise in solutions for specific observations networks and types of data are inferred and this may explain reported discrepancies in various magma source models some implications for the santorini volcano which had an unrest episode in 2011 2012 are that the algorithm can lead to less noisy solutions of the mogi sources that the surface deformation may be recognized as resulting from inflation of two spherical sources and that differences in magma source models using different types of data may only indicate predictable uncertainties in the solutions

continuous soil co2 and discrete plume so2 measurements at mt etna italy during 1997 2000 a contribution to volcano monitoring continuous monitoring of soil co2 dynamic concentration which is proportional to the co2 flux through the soil was carried out at a peripheral site of mt etna during the period november 1997 september 2000 using an automated station the acquired data were compared with so2 flux from the summit craters measured two to three times a week during the same period the high frequency of data acquisition with both methods allowed us to analyze in detail the time variations of both parameters anomalous high values of soil co2 dynamic concentration always preceded periods of increased flux of plume so2 and these in turn were followed by periods of summit eruptions the variations were modeled in terms of gas efflux increase due to magma ascent to shallow depth and its consequent depressurization and degassing this model is supported by data from other geophysical and volcanological parameters the rates of increase both of soil co2 dynamic concentration and of plume so2 flux are interpreted to be positively correlated both to the velocity of magma ascent within the volcano and to lava effusion rate once magma is erupted at the surface low rates of the increase were recorded before the nine month long 1999 subterminal eruption higher rates of increase were observed before the violent summit eruption of september november 1999 and the highest rates were observed during shorter and very frequent spike like anomalies that preceded the sequence of short lived but very violent summit eruptions that started in late january 2000 and continued until late june of the same year furthermore the time interval between the peaks of co2 and so2 in a single sequence of gas anomalies is likely to be controlled by magma ascent velocity

continuous monitoring of soil co2 flux on mt etna the 2004 2005 eruption and the role of regional tectonics and volcano tectonics 1 the soil co2 flux on mt etna as recorded by the etnagas network an automatic system for measuring soil co2 flux and meteorological parameters started to increase strongly about 5 months prior to the onset of the 2004 2005 eruption and decreased a few months before the end of the eruption time delays in the occurrences of anomalies in soil co2 flux at different sites in the geochemical network constrain the relationship between soil co2 flux distributions and the tectonic framework of etna volcano the anomalies observed before the 2004 2005 eruption support the intrusion of new undegassed magma into the upper feeding system of the volcano 20 km below sea level magma subsequently rose slowly in the volcano conduits thereby triggering the onset of the 2004 2005 eruption the time delays in the occurrences of anomalies in combination with spectral analysis indicate the importance of tectonic and volcanotectonic structures in driving the ascent of deep gases within the crust moreover greatest amplitude pulsations of the low frequency components of the co2 flux signals were correlated with the paroxystic activities of the 2004 2005 eruption this study confirms that co2 flux variation is a useful indicator for volcanic activity in the surveillance of the mt etna and similar basaltic volcanoes

degassing of so2 and co2 at mount etna sicily as an indicator of pre eruptive ascent and shallow emplacement of magma abstract we studied soil co 2 emissions together with crater so 2 fluxes from mt etna during the period july 1997 to march 1999 this period was characterized by high levels of volcanic activity and ended with the onset of a 10 month long sub terminal eruption on february 4 1999 soil co 2 degassing was measured at two sites p39 on the lower sw flank of etna and p78 on the e flank known for being connected to deep faults that allow the escape of magmatic gas site p39 is inferred to drain gas from a deep 15 km magma reservoir whereas site p78 is connected to a shallower 5 10 km reservoir based on the temporal variations of measured soil co 2 and crater so 2 data five intervals of anomalous degassing were recognized each of them is interpreted as due to massive gas release from a magma batch that is moving toward the surface the time lag between the occurrence of degassing anomalies of co 2 and those of so 2 agrees well with the different depth of exsolution of the two gases our data also indicate a step like migration of magma to the surface which bears on the existence of at least three different temporary storage levels within etna s feeder system lastly the observed anomalies preceded by months to weeks increases in the summit activity of mt etna including the february 4 1999 eruption comparison between the amounts of degassing magma during each interval of anomalous degassing based on so 2 fluxes and erupted volumes of lava during the same periods seems to indicate that the 1999 eruption was largely fed by magma that started entering the upper feeder system of etna about 1 year earlier

simple kinetic models of petroleum formation part i oil and gas generation from kerogen modern basin analysis uses kinetic models to predict the extent of petroleum generation within potential source rocks the global kinetic model presented here assigns kinetic parameters based on gross depositional environment and stratigraphic age this is useful in areas of low geochemical knowledge including exploration frontiers five kerogen kinetic organofacies each characterized by a specific organic matter input and early diagenetic overprint can broadly be related to sedimentary facies age associations even using seismic sequence stratigraphy alone a aquatic marine siliceous or carbonate evaporite any age b aquatic marine siliciclastic any age c aquatic non marine lacustrine phanerozoic d e terrigenous non marine ever wet coastal mesozoic and younger and f terrigenous non marine coastal late palaeozoic and younger routine pyrolysis data allow partitioning of organic carbon in the immature source rock into four initial components oil oil generative gas generative and inert separate kinetic parameters for the oil and gas generative fractions allow computation of the evolving concentration and composition of the products it was assumed that the activation energy distributions for each fraction were normally distributed non linear regression of large combined laboratory and field data sets varying by up to 12 orders of magnitude in heating rate established optimum values for the required ten 5 2 kinetic parameter sets a emean e differences in kinetic parameters can be reconciled with known chemical properties although our knowledge base is still inadequate to construct kinetic models from first principles mean activation energies governing oil generation increase systematically in the order a f causing a corresponding increase in generation temperature at a reference heating rate 2 c ma 1 the oil generation window 10 90 oil generative kerogen degraded increases from ca 95 135 c to 145 175 c organofacies c has the tightest energy distribution and narrowest oil generation window the gas generation window ranges from ca 105 155 c to 175 220 c thermal stress results from a combination of temperature and time an order of magnitude increase decrease in heating rate elevates depresses reaction temperatures by ca 15 c heating rates in subsiding sedimentary basins can vary by two orders of magnitude dramatic differences in generation temperature can result if the heating rate and organofacies effects compound thus global oil and gas generation temperature thresholds constitute blunt instruments with which to screen the petroleum potential of sedimentary basins because unexpelled oil provides a potential feedstock for oil to gas cracking in the source rock quantitative models of petroleum generation become really useful only when coupled with models of oil gas cracking and expulsion for example the frequently observed association between gas provinces and coals cannot be explained solely by their generation behaviour

late cretaceous to early tertiary structural elements of west kalimantan abstract recent geological and geophysical mapping in west kalimantan has allowed the definition of three domains with distinct geological and geophysical characteristics which were imprinted on the region by early cretaceous to eocene convergent tectonic events subduction related granitoids intruded low grade regional metamorphic rocks during the early cretaceous forming the schwaner mountains domain extending east west across the southern and central part of west kalimantan this is flanked in the northwest by a complex sequence of sedimentary and volcanic rocks ranging in age from late carboniferous to cretaceous which comprise the northwest kalimantan domain deformed cretaceous flysch deposits east of the northwest kalimantan domain form an accretionary complex representing the southern continuation of the extensive dominantly tertiary accretionary wedge in sarawak the boundary between the cretaceous accretionary domain and rocks of the northwest kalimantan domain is a fault which we interpret as a transform that marked the western limit of late cretaceous southward subduction beneath west kalimantan growth of the accretionary complex resulted in uplift of a ridge of melange and flysch deposits on which a half graben extensional basin formed and accumulated thick lacustrine deposits a sedimentary basin developed between continental rocks to the south and the emergent ridge comprising accretionary complex rocks and outer shelf deposits to the north in the position of a forearc basin as accretion proceeded the locus of underthrusting migrated northward and a second melange ridge and sedimentary basin developed farther to the north the evidence for accretionary processes and the association of these with sedimentary basin formation supports the hypothesis that an ancient south dipping subduction zone existed in the eastern part of west kalimantan during late cretaceous to early tertiary times

evolution of the boundary between the philippine sea plate and australia palaeomagnetic evidence from eastern indonesia abstract the boundary between the philippine sea and australian plates is the left lateral sorong fault system of eastern indonesia until recently modelling this boundary for the period before about 5 ma was difficult the tertiary motion of the philippine sea plate was uncertain and palaeomagnetic data from areas adjacent to the fault were lacking recent geological and palaeomagnetic studies of the area north of the sorong fault have elucidated the tertiary motion history of the philippine sea plate providing a reference for examining movements within the fault system we report new palaeomagnetic data from within the sorong fault zone from the islands of taliabu and obi taliabu is part of the sula platform and is considered to be derived from australia pelagic limestones from the upper cretaceous tanamu formation of taliabu yielded a direction of d 329 1 i 34 9 implying counter clockwise rotation and a formation latitude of 19 5 s sula and misool are postulated to be part of a single microcontinent which had a different late cretaceous mid tertiary movement history from australia the sula platform was transported to its present position by movement along the sorong fault system in the late miocene obi includes rocks of philippine sea and australian origin all the new sites are in rocks of philippine sea plate origin since the early neogene the philippine sea plate which includes all islands north of the sorong fault has rotated 40 clockwise and moved 10 15 northwards philippine sea plate rocks within the sorong fault zone record similar latitude shifts but different rotations in north obi the upper oligocene anggai river formation and the middle miocene woi formation record 60 and 30 counter clockwise rotations respectively the sense of rotation is consistent with motion within a left lateral fault system with the philippine sea and australian plates providing the shear couple in contrast the woi formation in southeast obi records 15 20 clockwise rotation this area is separated from the zone of counter clockwise movement in north obi by a strand of the sorong fault arc volcaniclastic rocks from the upper cretaceous leleobasso formation of northwest obi have a primary magnetisation with a mean direction of d 357 1 i 21 9 these rocks formed at 11 n or 11 s depending on the interpreted rotation history and indicate a pacific rather than indian ocean origin a volcanic arc at the southern edge of the philippine sea plate collided with eastern new guinea at 25 ma the philippine sea australia plate boundary then changed from subduction to strike slip as the philippine sea plate began its neogene rotation initiating the sorong fault system we suggest that many of the arc fragments in the new guinea orogenic belt originated in the southern philippine sea plate arc which has subsequently been dismembered by strike slip faulting

the structure and stratigraphy of deepwater sarawak malaysia implications for tectonic evolution abstract the structural stratigraphic history of the north luconia province sarawak deepwater area is related to the tectonic history of the south china sea the sarawak basin initiated as a foreland basin as a result of the collision of the luconia continental block with sarawak sarawak orogeny the foreland basin was later overridden by and buried under the prograding oligocene recent shelf slope system the basin had evolved through a deep foreland basin flysch phase during late eocene oligocene times followed by post oligocene molasse phase of shallow marine shelf progradation to present day seismic interpretation reveals a regional early miocene unconformity emu separating pre oligocene to miocene rifted basement from overlying undeformed upper miocene pliocene bathyal sediments seismic well data and subsidence analysis indicate that the emu was caused by relative uplift and predominantly submarine erosion between 19 and 17 ma ago the subsidence history suggests a rift like subsidence pattern probably with a foreland basin overprint during the last 10 ma modelling results indicate that the emu represents a major hiatus in the sedimentation history with an estimated 500 2600 m of missing section equivalent to a time gap of 8 10 ma the emu is known to extend over the entire nw borneo margin and is probably related to the sabah orogeny which marks the cessation of sea floor spreading in the south china sea and collision of dangerous grounds block with sabah gravity modelling indicates a thinned continental crust underneath the sarawak shelf and slope and supports the seismic and well data interpretation there is a probable presence of an overthrust wedge beneath the sarawak shelf which could be interpreted as a sliver of the rajang group accretionary prism alternatively magmatic underplating beneath the sarawak shelf could equally explain the free air gravity anomaly the sarawak basin was part of a remnant ocean basin that was closed by oblique collision along the nw borneo margin the closure started in the late eocene in sarawak and moved progressively northeastwards into sabah until the middle miocene the present day nw sabah margin may be a useful analogue for the oligocene miocene sarawak foreland basin

large scale ground deformation of etna observed by gps between 1994 and 2001 we have processed thirty global positioning system gps campaigns carried out at etna from 1994 to early 2001 between the last two main flank eruptions of the mt etna sicily italy this rest period allowed us to investigate the deep magma plumbing system of the mt etna the temporal dynamics of twenty three points observed three times or more were analyzed all the time series show a first order linear trend during the five years period it suggests that the volcano was continuously deformed by the action of a deep source while a discrete activity of the volcano was observed at the summit we have interpreted the residual deformation field as the result of an major eastward motion of the eastern flank of the volcano

structural evolution and strike slip tectonics off north western sumatra abstract based on new multi channel seismic data swath bathymetry and sediment echosounder data we present a model for the interaction between strike slip faulting and forearc basin evolution off north western sumatra between 2 n and 7 n we examined seismic sequences and sea floor morphology of the simeulue and aceh forearc basins and the adjacent outer arc high we found that strike slip faulting has controlled the forearc basin evolution since the late miocene the mentawai fault zone extends up to the north of simeulue island and was most probably connected farther northwards to the sumatran fault zone until the end of the miocene since then this northern branch jumped westwards initiating the west andaman fault in the aceh area the connection to the mentawai fault zone is a left hand step over in this transpressional setting the tuba ridge developed we found a right lateral strike slip fault running from the conjunction of the west andaman fault and the tuba ridge in ssw direction crossing the outer arc high as a result extrusion formed a marginal basin north of simeulue island which is tilted eastwards by uplift along a thrust fault in the west the shift of strike slip movement in the aceh segment is accompanied by a relocation of the depocenter of the aceh basin to the northwest forming one major neogene unconformity the simeulue basin bears two major neogene unconformities documenting that differences in subsidence evolution along the northern sumatran margin are linked to both forearc evolution related to subduction processes and to deformation along major strike slip faults

seismic stratigraphy and cenozoic evolution of west sumatra forearc basin late tertiary neogene sediments deposited in the sunda forearc reveal the stratigraphic and structural evolution of this active plate margin a dense grid of multichannel seismic reflection data and information from 17 exploratory wells were used to establish a detailed seismic stratigraphic framework of the forearc region from 0 to 6 n several important tectonic cycles are recognized paleogene orogeny neogene subsidence and late tertiary tectonism superimposed on these regional tectonic events are three major transgressive regressive cycles of sedimentation related to changes in sea level and provenance paleogene and older metasedimentary and metamorphic rocks comprise basement beneath the landward inner margin of the forearc basin both basement rocks and lower tertiary sedimentary rocks were deformed and eroded approximately 25 to 30 ma the continental shelf was exposed to subaerial erosion and basin deposits were restricted offshore coincident with a worldwide lowstand of sea level in the oligocene the paleogene orogeny probably occurred prior to the erosional event that cut the prominent angular unconformity on the shelf the neogene history of forearc basin development is characterized by subsidence and nearly continuous sedimentation a basal transgression began in latest oligocene time and culminated in the middle miocene alternating sequences of limestone and shale comprise two second order cycles of sedimentation that are superimposed on an overall transgressive event a major regressive sequence followed in the pliocene owing to an influx of siliciclastic clay silt and sand derived from sumatra sedimentation rates were high and large volumes of terrigenous material were deposited in deltaic systems on the shelf the shelf slope break prograded basinward nearly 10 km 6 mi through lateral accretion and aggradation during a relative highstand or stillstand of sea level

tropospheric corrections of sar interferograms with strong topography application to etna the accuracy of spaceborne geodetic techniques including sar interferometry is limited by the time and spatial variation and altitude dependance of the propagation delay of electomagnetic waves in the lower troposphere particularly in mountainous areas in this paper we use a 1d model developed for tropospheric corrections of gps and doris measurements to correct sar data the differential tropospheric delay is computed at each pixel of the interferogram from ground temperature humidity and pressure using two empirical parameters calibrated from several radio soundings acquired in various latitude and climate conditions it is shown that with such a model given the 3300 meters topography of etna tropospheric variations can generate up to 4 phase rotations between the top and the bottom of the volcano in 16 out of the 20 interferograms processed with images acquired between august 1992 and october 1993 correction of the tropospheric effect reduces the number of fringes associated with the 1991 93 eruption from previous estimates the remaining deformation is consistant with a deforming source located at a depth of 14 1 km during the second half of the eruption the subsidence rate at the top of the volcano is roughly stable at 13 3 mm month these values are in good agreement with tiltmeter data collected on etna during the same period and with the estimated volume of erupted material no significant deformation can be observed during the last month of eruption inflation of the volcano seems to resume immediately after the end of the eruption at a rate of 3 mm month

reprint of nature and significance of the west baram and tinjar lines nw borneo abstract a key consideration in tectonic models for se asia and opening of the south china sea is the role that the west baram and tinjar lines of nw borneo may have played in accommodating the motion of crustal blocks displaced from asia following india s collision there are few studies that focus on these lines using onshore geological studies and offshore seismic data to address the origin and tectonic significance of these this paper concludes that rather than a major transform boundary between luconia and the dangerous grounds the west baram line marks the boundary between domains of continental crust that underwent differential extension in the eocene the baram basin is underlain by hyperextended continental crust on the ne side of the baram line the strong contrast in the geological features across the tinjar and west baram lines likely reflects ancient differences in crustal rheology with luconia being the more rigid block although lack of significant strike slip faulting along the west baram line poses problems for tectonic models in which a wide proto south china sea is subducted beneath nw borneo intra plate deformation such as partial inversion of the dangerous grounds rift offers a potential mechanism to mass balance blocks displaced from asia with the reduced strike slip motion along the west baram line

elastic moduli evolution and accompanying stress changes with increasing crack damage implications for stress changes around fault zones and volcanoes during deformation summary the elastic moduli of rock in areas susceptible to crack damage such as within fault zones or volcanic edifices can be subject to large modifications knowledge of how elastic moduli may vary in such situations is important for both the reliable modelling of volcano deformation and stability and for linear and non linear elastic crack models for earthquake rupture furthermore it has previously been shown that changes in elastic moduli can induce changes in the stress field surrounding faults here we report both uniaxial experimental measurements of changes in elastic moduli during increasing amplitude cyclic stressing experiments on a range of different rock types basalts sandstones and granite and the results of modelled stress modifications the trend in elastic moduli evolution with increasing damage was remarkably similar for each rock type with the exception of essentially crack free intrusive basalt that exhibited very minor changes in general young s modulus decreased by between 11 and 32 per cent and poisson s ratio increased by between 72 and 600 per cent over the total sequence of loading cycles these changes are attributed to an increasing level of anisotropic crack damage within the samples our results also show that acoustic emission ae output during any loading cycle only commenced when new crack damage was generated this corresponded to the level of stress where ae ceased during the unloading portion of the previous cycle using the multilayer elastic model of faulkner et al we demonstrate that the damage induced changes in elastic moduli also result in significant decreases in differential stress increases in mean stress and rotation of the applied greatest principal stress relative to the orientation of the mechanical layering the similar trend in the evolution of the elastic moduli of all the rocks tested suggests that stress modification in the damage zone of faults might take the same form regardless of the lithology through which the fault runs these observations are discussed in terms of their applicability to both fault zones and deformation at volcanoes

dynamics of mount etna volcano inferred from static and kinematic gps measurements 1 ground deformations measured on mount etna from late 1995 to mid 1998 using gps observations are analyzed four gps surveys were carried out during the considered period in 1995 the gps network consisted of 18 stations on the volcanic edifice and 6 stations around it during the 1996 survey 22 new monuments were added along a n s profile crossing the summit craters area this profile was surveyed by a semikinematic method allowing greater spatial detail to be achieved on the uppermost part of the volcano the comparisons between the gps surveys are reported here in terms of horizontal and vertical displacements for each station and also in terms of areal dilatation and strain distribution this last parameter continues its ascending trend at a rate of 5 strain yr 1 already shown in the previous period after the end of the 1991 1993 flank eruption inversion of the ground deformation patterns permits investigation of the evolution of both the position and dynamics of magma reservoirs beneath the volcano consistently associated with a general eastward sliding of its eastern sector this study allows us to define the nonuniqueness of ground deformation sources through the investigated period suggesting that the plumbing system of the volcano is made up of a complex system of single intrusions occurring at different times

the pearl river mouth basin a rift basin and its geodynamic relationship with the southeastern eurasian margin abstract based on multichannel seismic reflection profiles exploration well data and gravity studies the tectonic development of the pearl river mouth basin is discussed in terms of the geodynamic evolution of the southeastern eurasian margin the area around the pearl river mouth basin has been dominated by two episodes of rifting of the attenuated continental crust along the south china margin from the late cretaceous to the early oligocene the rifting brought about ruptures of various magnitudes in various segments of the basin regional normal faults have been produced and resulted in the formation of three major subbasins zhu 1 zhu 2 and zhu 3 which are separated by local uplifts and are characterized by horst and graben structures regional subsidence prevailed throughout the late oligocene recent period and resulted in a tilted continental shelf upon which rests a unified rift basin the pearl river mouth basin a three stage model involving doming rifting and drifting is proposed for the tectonic evolution of the pearl river mouth basin the uplifting and rifting of the continental crust along the south china margin are related to the late episodes of the yanshan orogeny during the late cretaceous early oligocene period when the intensity of rifting decreased the thermal subsidence of the continental margin of south china prevailed during the late oligocene recent period of the himalaya orogeny

modeling the effects of eruptive and seismic activities on flank instability at mount etna italy 1 the identification and evaluation of trigger mechanisms for volcano flank instabilities and or collapse represent a key issue for risk assessment in densely populated volcanic areas as well as in long distance settings particularly in case of island or coastal volcanoes here we address quantitatively the effects of external seismic and inner magmatic forcing on the stress strain state associated to flank instabilities at mount etna sicily southern italy by means of a 2 d finite difference method numerical modeling modeled seismic actions include strong near field strong far field and low magnitude near field earthquakes magmatic actions consider the inner pressure changes induced by energetic lava fountains in the summit crater area and subvertical and oblique dike ascent below the summit area model results are validated in light of available monitoring data and recent eruptive activity numerical results show that the main strain effects are produced by high magnitude near field earthquakes expected return time of 103 yrs and by vertical uprise of a magma dike below the volcano summit area maximum displacements in the order of tens of centimeters may involve the summit area up to some 106 m3 m over some kilometers laterally stress releases up to 107 pa may affect a limited portion of the magmatic conduit thus favoring major effusive flank eruptions major catastrophic events such as volcano flank collapse should not be expected by applying either individually or combined the aforementioned actions

spatial mapping of the b value at mount etna italy using earthquake data recorded from 1999 to 2005 1 the spatial pattern of the b value of the frequency magnitude relation has been analyzed using gridding techniques beneath mount etna italy a regional data set of 2900 events with md duration magnitude 1 5 up to 15 km depth occurring between august 1999 and december 2005 has been used two regions with an abnormally high b value have been found one centered beneath the southern part of the valle del bove above the 6 km below sea level bsl deep basement and the other beneath the summit region 2 km bsl east of the central craters we can infer that these high b value anomalies are regions of increased crack density and or high pore pressure related to the presence of nearby magma storage this interpretation is supported by all the available geophysical evidence such as tomographic studies and geodetic deformation measurements the data set has also been subdivided into five periods corresponding to different phases of volcanic activity 2001 preeruption 2001 eruptive 2002 2003 preeruption 2002 2003 eruptive and 2002 2003 posteruption the minimum magnitude of completeness mc and the b value were computed for each period a volume of anomalously high b values can be observed in each of these periods except for the 2002 2003 preeruption interval this approach has allowed the detection of the transient presence of magmatic intrusions during the various periods evaluated

geology of a miocene collision complex buton eastern indonesia the island of buton in eastern indonesia is part of a neogene collision zone that encompasses much of the eastern margin of sulawesi miocene collision of microcontinents with a west dipping subduction zone emplaced the tukang besi platform tbp against buton and the sula platform sp against the east arm of sulawesi and thrust large ophiolite sheets eastward over the imbricated margins of the platforms reconnaissance observations of the resulting collision complex in buton wolio complex indicate that imbricate west dipping thrust sheets and overturned folds are the predominant structural element although later steep faults offset the imbricate stack and largely control present map patterns the wolio complex consists of the sedimentary turumbia sequence peridotite and two distinct groups of metamorphic rocks the turumbia sequence makes up most of the eastern part of the wolio complex and consists mostly of deep water limestone ranging in age from late triassic through late eocene or oligocene it is interpreted as a deep water facies of the western tbp margin ophiolitic rocks are represented in present outcrop only by massive peridotite in the western part of the wolio complex but the compositions of clasts in conglomerates overlying the wolio complex indicate that a full ophiolite succession was exposed to erosion during the collision metabasite and metachert ranging in grade from greenschist to amphibolite facies are found locally in fault contact with peridotite and are interpreted as the remnants of a metamorphic sole developed at the base of the ophiolite pelitic phyllite and quartzite in northeastern buton probably represent a slice of the continental basement of the tbp for similar rocks have been dredged from the northeast margin of the tbp and also form the pre mesozoic basement of the sp the middle to upper miocene tondo formation in buton consists of clastic strata derived from uplift and erosion of the wolio complex placing an upper limit on the age of tbp collision we infer a middle miocene time of collision with oblique convergence continuing into late miocene time in contrast sparse biostratigraphic data place the age of the sp east arm collision in the late miocene separate microcontinents may have collided successively with different parts of the buton sulawesi convergent margin or a single large microcontinent may have been fragmented during oblique collision

origin of marginal basins of the nw pacific and their plate tectonic reconstructions abstract geometry of basins can indicate their tectonic origin whether they are small or large the basins of bohai gulf south china sea east china sea japan sea andaman sea okhotsk sea and bering sea have typical geometry of dextral pull apart the java makassar celebes and sulu seas basins together with grabens in borneo also comprise a local dextral transform margin type basin system similar to the central and southern parts of the shanxi basin in geometry the overall configuration of the philippine sea resembles a typical sinistral transpressional pop up structure these marginal basins except the philippine sea basin generally have similar or compatible rift history in the cenozoic but there do be some differences in the rifting history between major basins or their sub basins due to local differences in tectonic settings rifting kinematics of each of these marginal basins can be explained by dextral pull apart or transtension these marginal basins except the philippine sea basin constitute a gigantic linked dextral pull apart basin system formation of the gigantic linked dextral pull apart basin system in the nw pacific is due to nne to ene ward motion of east eurasia this mainly was a response to the indo asia collision which started about 50 ma ago the displacement of east eurasia can be estimated using three aspects 1 the magnitude of pull apart of the dextral pull apart basin system 2 paleomagnetic data from eastern eurasia and the region around the arctic and 3 the shortening deficits in the large tibetan plateau all the three aspects indicate that there was a large amount 1000 to 1200 km of northward motion of the south china block and compatible movements of other blocks in eastern eurasia during the rifting period of the basin system such a large amount of motion of the eastern eurasia region contradicts any traditional rigid plate tectonic reconstruction but agrees with the more recent concepts of non rigidity of both continental and oceanic lithosphere over geological times based on these three estimates the method developed for restoration of diffuse deformation of the eurasian plate and the region around the arctic and the related kinematics of the marginal basins we present plate tectonic reconstructions of these marginal basins in global plate tectonic settings at the four key times 50 35 15 and 5 ma the plate tectonic reconstructions show that the first order rift stage and post rift stage of the marginal basins are correlated with the first order slow uplift stage and the rapid uplift stage of the tibetan plateau respectively the proto philippine sea basin was trapped as a sinistral transpressional pop up structure at a position that was 20 south of its present position at about 50 ma ago or earlier while the japan arc migrated eastward during the rifting period of the japan sea basin the shikoku basin opened and the parece vela basin widened

predicting co2 occurrence on a regional scale southeast asia example abstract prediction of co 2 occurrence in natural gases is difficult owing to the interplay among basinal sources e g volcanic emanations carbonate hydrolysis and metamorphism organic diagenesis and maturation reservoir processes e g mineralogical transformations and poorly understood physicochemical phenomena e g differential solubility of gas components carbonate buffering phase segregation published approaches to assessing co 2 risk are based either on circumstantial evidence of basinal influences or statistical analysis of reservoir attributes the present study presents the results of empirical statistical and neural network analysis of co 2 abundance in natural gas and discusses potentially influential basinal and reservoir attributes to quantify risk factors for anomalous co 2 occurrences in southeast asia the results of this study indicate that tectonic setting including basement crustal age basement fault density reservoir temperature and reservoir pressure are key elements controlling co 2 abundance assignment of co 2 risk at the basin level can be roughly approximated using the results of this study more accurate assessments of co 2 risk at the basin play field and reservoir levels require more comprehensive geological and geochemical data as well as consideration of potentially influential physico chemical processes

mt etna volcano modelling of ground deformation patterns of recent eruptions and considerations on the associated precursors abstract the study of the ground deformation associated with the recent eruptions of the etna volcano 1981 1989 1991 93 furnished the opportunity to observe different behaviour relating to the eruptive activity and suggested different feeding and penetration mechanisms inside the volcano edifice in particular the analytical modelling of geodetic data was applied to study the strain sources of these eruptions by the application of single and multiple source models i e composed of two single sources in particular a single tensile dislocation was used to model the se fracture associated with the 1989 eruption a double tensile dislocation was adopted to interpret and model the deformation pattern of the 1981 eruption a double source composed of a tensile dislocation for the final eruptive fracture and a depressuring body for the deflation during the eruption course was considered for the 1991 93 eruption the results of this modelling show that however the final uprising system i e the tensile mechanisms inside the volcano edifice involved the same structure oriented approximately nnw sse this structure was activated by different eruption mechanisms with associated different deformation patterns during these three recent eruptions a review of the methodologies applied and main results obtained in modelling of different sources and mechanisms is presented here the analysis of the deformation data and the performed modelling evidence that the associated precursors can strongly change for the different eruptions in addition the implications both in terms of how the volcano works and in terms of ground deformation precursors are discussed

nature and significance of the west baram and tinjar lines nw borneo abstract a key consideration in tectonic models for se asia and opening of the south china sea is the role that the west baram and tinjar lines of nw borneo may have played in accommodating the motion of crustal blocks displaced from asia following india s collision there are few studies that focus on these lines using onshore geological studies and offshore seismic data to address the origin and tectonic significance of these this paper concludes that rather than a major transform boundary between luconia and the dangerous grounds the west baram line marks the boundary between domains of continental crust that underwent differential extension in the eocene the baram basin is underlain by hyperextended continental crust on the ne side of the baram line the strong contrast in the geological features across the tinjar and west baram lines likely reflects ancient differences in crustal rheology with luconia being the more rigid block although lack of significant strike slip faulting along the west baram line poses problems for tectonic models in which a wide proto south china sea is subducted beneath nw borneo intra plate deformation such as partial inversion of the dangerous grounds rift offers a potential mechanism to mass balance blocks displaced from asia with the reduced strike slip motion along the west baram line

impulsive tilt variations on mount etna volcano 1990 1993 abstract this study was focussed on the analysis of the fast ground deformations impulsive anomalies recorded at the mt etna tilt array from 1990 to 1993 a period that preceded accompanied and followed the 1991 1993 eruption these fast deformations were recorded as transient anomalies ranging from a few hours to days 1 2 observed contemporaneously at several tilt stations and characterized by variations ranging from one to tens of microradians the signals evidenced volcanic dynamics characterized by tilt anomalies during the non eruptive periods 1990 1993 the pre eruptive period november december 1991 the beginning of the eruption 14 15 december 1991 and the eruption course 1992 in particular pre seismic co eruptive and co seismic anomalies were recorded during the pre eruptive period and the eruption onset in these cases interpretations of the phenomena and comparison to modelling studies are provided furthermore tilt variations affecting the global volcanic edifice were also observed one year before the eruption when they were followed by seismicity and during the eruption course without seismicity we interpreted this last class of tilt variations as due to the push of the magma uprising along the main nnw sse structure crossing mt etna

the feeding of the eruptive activity of etna volcano the regional stress field as a constraint to magma uprising and eruption an analysis of the structural lineaments as observed on the middle and upper slopes of etna volcano was made with the aim of checking stress distribution within the volcanic structure

volcano wide fringes in ers synthetic aperture radar interferograms of etna 1992 1998 deformation or tropospheric effect mount etna 3300 m is the volcano that has been first and most studied by differential synthetic aperture radar previous papers gave evidence for a large scale deformation of the entire edifice consistent with unrest episodes but with a poor fit with classical elastic models also atmospheric effects on mountainous areas are known to be very significant accordingly interferograms may reflect both deformation and tropospheric effects we investigate here the possibility of evaluating and correcting tropospheric effects directly from the interferograms from 38 ers synthetic aperture radar ascending scenes taken from 1992 to 1999 we have computed 238 interferograms the amount of data allows us to analyze how the coherence is maintained over long periods of time and thus how it reveals the location of permanent scatters from a simple analysis of phase elevation relation we give evidence for the clear difference in pattern between stratified tropospheric effects and large scale deformation produced by a source in a three dimensional elastic body with topography using combination of inversion processes we analyze both deformation source and tropospheric effects for the complete set of 238 interferograms finally time evolution of the parameters and modeling probability estimation are retrieved for each sar image estimated relative change in tropospheric delay varies in time from 2 7 to 3 0 1 2 fringes they are consistent with other tropospheric estimations at etna based on ground met and global positioning system observations on the same period of time magmatic volume variations remain below error bars and thus cannot be estimated properly finally some of the interferograms may be entirely explained by the difference in tropospheric conditions between the two acquisition periods without the need to invoking a deformation of the volcano

the lusi mud volcano triggering controversy was it caused by drilling abstract following the yogyakarta earthquake on may 27th 2006 the subsequent eruption of a mud volcano has been closely observed and analyzed by the geological community the mud volcano known as lusi began erupting near the banjarpanji 1 exploration well in sidoarjo east java indonesia lusi offers a unique opportunity to study the genesis and development of a mud volcano for the first time this paper presents all raw and interpreted drilling data so any interested party can perform their own assessment our study suggests that lusi mud volcano was a naturally occurring mud volcano in an area prone for its mud volcanism pressure analysis done on the banjarpanji well shows that the pressure exerted at the well is lower than the fracture pressure at the last casing shoe and suggests that the well was intact and did not suffer an underground blowout this is further supported by evidence and observation made during drilling such as circulation was done on an open bop and subsequent relief wells sonan and temperature log runs this study offers a different alternative to earlier hypothesis that events at the banjarpanji well were the trigger for the lusi mud volcano more work is needed by the scientific community to study the sequence of events in order to explain and clarify the real trigger of lusi