local site effects in atakoy istanbul turkey due to a future large earthquake in the marmara sea summary since the 1999 izmit and duzce earthquakes in northwest turkey many seismic hazard studies have focused on the city of istanbul an important issue in this respect is local site effects strong amplifications are expected at a number of locations due to the local geological conditions in this study we estimate the local site effects in the atakoy area southwestern istanbul by applying several techniques using synthetic data hybrid 3 d modelling and 1 d modelling and comparing to empirical data we apply a hybrid 3 d finite difference method that combines a complex source and wave propagation for a regional 1 d velocity model with site effects calculated for a local 3 d velocity structure the local velocity model is built from geological geotechnical and geomorphological data the results indicate that strongest spectral amplifi cations sa in the atakoy area occur around 1 hz and that amplification levels are largest for alluvial sites where sa reaching a factor of 1 5 2 can be expected in the case of a large earth quake we also compare our results to h v horizontal to vertical component of the recorded signal spectral ratios calculated for microtremor data recorded at 30 sites as well as to ambient noise synthetics simulated using a 1 d approach because the applied methods complement each other they provide comprehensive and reliable information about the local site effects in atakoy added to that our results have significant implications for the southwestern parts of istanbul built on similar geological formations for which therefore similar sa levels are expected

re estimated effects of deep episodic slip on the occurrence and probability of great earthquakes in cascadia abstract mazzotti and adams 2004 estimated that rapid deep slip during typically two week long episodes beneath northern washington and southern british columbia increases the probability of a great cascadia earthquake by 30 100 times relative to the probability during the 58 weeks between slip events because the corresponding absolute probability remains very low at 0 03 per week their conclusion is that though it is more likely that a great earthquake will occur during a rapid slip event than during other times a great earthquake is unlikely to occur during any particular rapid slip event this previous estimate used a failure model in which great earthquakes initiate instantaneously at a stress threshold we refine the estimate assuming a delayed failure model that is based on laboratory observed earthquake initiation laboratory tests show that failure of intact rock in shear and the onset of rapid slip on pre existing faults do not occur at a threshold stress instead slip onset is gradual and shows a damped response to stress and loading rate changes the characteristic time of failure depends on loading rate and effective normal stress using this model the probability enhancement during the period of rapid slip in cascadia is negligible

determination of trapping pressure and temperature of petroleum inclusions using pvt simulation software a case study of lower ordovician carbonates from the lunnan low uplift tarim basin abstract we report a case study carried out on lower ordovician reservoir carbonates of the lunnan low uplift tarim basin to determine trapping pressures and temperatures of petroleum inclusions from the intersection of isochores of coeval petroleum and aqueous fluid inclusions using pvt sim software there are four types of petroleum inclusions from this sequence their trapping pressures and temperatures are type i 80 105 c 199 230 bar type ii 135 145 c 235 250 bar type iii 155 165 c 344 360 bar and type iv 220 252 c 345 390 bar respectively which are consistently higher than their homogenization temperature and saturation pressures by about 5 15 c and 25 70 bar to confirm the reliability of the pvt simulation approach fluid inclusions were synthesized in calcite under controlled temperature and pressure conditions and studied using the same methods the calculated trapping pressure and temperature of the synthetic petroleum inclusions closely match the actual pressure and temperature applied in the experiment by reference to the burial and geothermal history of the tarim host rocks it was inferred that types i ii and iii petroleum inclusions represent fluids associated with three distinct phases of petroleum emplacement in the lower ordovician strata of this area occurring during late silurian to early devonian cretaceous to early tertiary and late tertiary respectively type iv petroleum inclusions occur only in some fine calcite veins from few samples and are believed to be related to an anomalous thermal event in this area on the basis of the trapping pressures and trapping temperatures of the petroleum inclusions three main phases of the petroleum filling of the lower ordovician reservoirs can be delineated phase i and phase iii petroleum events were related to petroleum migration and accumulation from the lunnan low uplift or nearby area the petroleum of the phase ii petroleum event appears to have originated from middle and upper ordovician source rocks in the northern slope area of the manjiaer depression with a long distance migration

petroleum geology of the puguang sour gas field in the sichuan basin sw china abstract the puguang sour gas field in northeastern sichuan basin is the largest gas discovery in the paleozoic marine strata in china with at least 9 trillion cubic feet tcf of proven gas reserves it is one of the many anticlinal structures formed during the indo sinian orogeny with gas being trapped in a composite structure lithology pool the presence of the upper permian coal measures lower silurian and lower cambrian marine shales provided excellent hydrocarbon source rocks the lower triassic and upper permian oolitic dolomites serve as high quality reservoir rocks with 10 25 porosity and 1 1000 md permeability largely due to diagenetically produced secondary porosity the lower and middle triassic evaporate beds have acted as the direct top seal for the large lower triassic upper permian gas accumulation the thick upper triassic and jurassic mudstone beds regionally cap the underlying marine carbonate strata the deep seated basement faults acted as vertical hydrocarbon migration conduits during faulting and became effective flow barriers when the faulting ceased the deep burial of a paleo oil accumulation in reservoirs rich in sulfate resulted in extensive thermochemical sulfate reduction tsr this together with the new gas injection and structural reconfiguration transformed a paleo oil pool to a large sour gas pool

ground motion relations for eastern north america predictive relations are developed for ground motions from eastern north american earthquakes of 4 0 m 7 25 at distances of 10 r 500 km the predicted parameters are response spectra at frequencies of 0 5 to 20 hz and peak ground acceleration and velocity the predictions are derived from an empirically based stochastic ground motion model the relations differ from previous work in the improved empirical definition of input parameters and em pirical validation of results the relations are in demonstrable agreement with ground motions from earthquakes of m 4 to 5 there are insufficient data to adequately judge the relations at larger magnitudes although they are consistent with data from the saguenay m 5 8 and nahanni m 6 8 earthquakes the underlying model parameters are constrained by empirical data for events as large as m 6 8

sensitivity of ground motion simulations to earthquake source parameters a case study for istanbul turkey following the disastrous earthquakes in izmit and duzce along the north anatolian fault in 1999 the earthquake hazard in the istanbul area became a great concern in this study we simulate strong ground motions caused by a scenario earthquake m 7 5 in the marmara sea and investigate the effect of varying the input parameters on the broadband frequency ground motion simulations are based on a multiasperity source model that involves the combined rupture of the north anatolian fault segments beneath the marmara sea we use a hybrid model combin ing a deterministic simulation of the low frequencies 0 1 1 0 hz with a semisto chastic simulation of the high frequencies 1 0 10 0 hz computation at each fre quency range is performed separately and the total ground motion is combined in the time domain computations are linear and are performed at bedrock level thereby not taking any effect of local geological conditions into account we calculate a total of 17 earthquake scenarios corresponding to different source and attenuation param eters to study their effect on the ground motion the most significant parameters in terms of ground shaking level are the rise time rupture velocity rupture initiation point and stress drop the largest variability of strong ground motions is observed in regions adjacent to asperities and is associated with frequencies higher than 5 hz for lower frequencies our simulated velocity spectra within the istanbul area are fairly stable among scenarios the average standard deviations of all ground motion measures are less than 35 of the mean online material figures of peak ground acceleration and peak ground velocity and their differences to the reference scenario values

trapping pressure estimation of single gaseous inclusion using pvt simulation and its preliminary application in ne sichuan china abstract in this paper we proposed an alternative way to estimate volumetric vapour liquid ratio of gaseous or light petroleum inclusions without fluorescence using regularly shaped inclusions to estimate volumetric vapour liquid ratios through geometric methods the method was applied to the inclusions from the rock samples of the lower triassic feixianguan and jialingjiang formations ne sichuan china the trapping pressures of inclusion fluids were calculated by integrating pvt simulation software volumetric liquid vapour ratios determined by the proposed method and homogenization temperatures measured by microthermometry fluid densities and gas oil ratios gor were also estimated the estimated trapping pressures and temperatures are slightly lower for the jialingjiang formation 29 69 31 33 mpa 93 5 105 2 c than for the feixianguan formation 31 02 34 38 mpa 98 148 c and the trapping time of the inclusions in the jialingjiang formation and feixianguan formation were estimated at about 173 170 ma and 178 168 ma respectively the distribution of high pressures correlates with the presence of pyro bitumen in the reservoir rocks suggesting the migrated fluid is derived mainly from the secondary cracking of oil the modeled fluid density and gor correspond to a typical light oil or condensate suggesting an origin for the trapped hydrocarbons as an intermediate product in this process

scenario source models and strong ground motion for future mega earthquakes application to lima central peru the 2011 moment magnitude m w 9 0 tohoku oki japan earthquake occurred in a region where giant megathrust earthquakes were not expected this earthquake proved the difficulty in assessing seismic hazard by relying mainly on information from historical and instrumental seismicity to help improve the seismic hazard assessment for such rare events we propose a methodology to estimate the slip distribution of future megathrust earthquakes based on a model of interseismic coupling distribution in subduction margins as well as information of historical earthquakes and apply the method to the central peru region lima the slip model obtained from geodetic data represents the large scale features of asperities within the megathrust which is appropriate for simulation of long period waves and tsunami modeling for the simulation of a broadband strong ground motion we add small scale heterogeneities to the source slip to be able to simulate high frequencies to achieve this purpose we propose broadband source models constructed by adding short wavelength slip distributions obtained from a von karman power spectral density function to the slip model inferred from interseismic geodetic data using these slip models and assuming several hypocenter locations we calculate a set of strong ground motions for lima and incorporate site effects obtained from microtremors surveys and geotechnical data our simulated average pseudospectral accelerations period 0 3 s are above graphic 1 for wide areas in lima which may be critical in terms of damage of low to midrise masonry and reinforced concrete buildings which characterize the majority of buildings in lima 1 embed inline graphic 1 gif

probabilistic seismic hazard analysis for sumatra indonesia and across the southern malaysian peninsula abstract the ground motion hazard for sumatra and the malaysian peninsula is calculated in a probabilistic framework using procedures developed for the us national seismic hazard maps we constructed regional earthquake source models and used standard published and modified attenuation equations to calculate peak ground acceleration at 2 and 10 probability of exceedance in 50 years for rock site conditions we developed or modified earthquake catalogs and declustered these catalogs to include only independent earthquakes the resulting catalogs were used to define four source zones that characterize earthquakes in four tectonic environments subduction zone interface earthquakes subduction zone deep intraslab earthquakes strike slip transform earthquakes and intraplate earthquakes the recurrence rates and sizes of historical earthquakes on known faults and across zones were also determined from this modified catalog in addition to the source zones our seismic source model considers two major faults that are known historically to generate large earthquakes the sumatran subduction zone and the sumatran transform fault several published studies were used to describe earthquakes along these faults during historical and pre historical time as well as to identify segmentation models of faults peak horizontal ground accelerations were calculated using ground motion prediction relations that were developed from seismic data obtained from the crustal interplate environment crustal intraplate environment along the subduction zone interface and from deep intraslab earthquakes most of these relations however have not been developed for large distances that are needed for calculating the hazard across the malaysian peninsula and none were developed for earthquake ground motions generated in an interplate tectonic environment that are propagated into an intraplate tectonic environment for the interplate and intraplate crustal earthquakes we have applied ground motion prediction relations that are consistent with california interplate and india intraplate strong motion data that we collected for distances beyond 200 km for the subduction zone equations we recognized that the published relationships at large distances were not consistent with global earthquake data that we collected and modified the relations to be compatible with the global subduction zone ground motions in this analysis we have used alternative source and attenuation models and weighted them to account for our uncertainty in which model is most appropriate for sumatra or for the malaysian peninsula the resulting peak horizontal ground accelerations for 2 probability of exceedance in 50 years range from over 100 g to about 10 g across sumatra and generally less than 20 g across most of the malaysian peninsula the ground motions at 10 probability of exceedance in 50 years are typically about 60 of the ground motions derived for a hazard level at 2 probability of exceedance in 50 years the largest contributors to hazard are from the sumatran faults

strain partitioning during oblique plate convergence in northern sumatra geodetic and seismologic constraints and numerical modeling global positioning system gps measurements along the subduction zone of northern sumatra 2 s to 3 n reveal that the strain associated with the oblique convergence of the australian plate with eurasia is almost fully partitioned between trench normal contraction within the forearc and trench parallel shear strain within a few tens of kilometers of the sumatran fault kinematic analyses of interplate earthquake slip vectors provide slip rates on the sumatran fault within a few millimeters per year of gps and geologic rates giving us more confidence in the use of slip vectors for inferring slip partitioning elsewhere the inferred slip rate on the sumatran fault is 1 3 less than the full margin parallel component of plate motion an across forearc rotation in the slip vectors suggests that the missing arc parallel shear occurs seaward of the geodetic network between the forearc islands and the trench simple finite element models are used to explore the conditions under which the change in the principal strain rate directions between the forearc and the arc region can occur modeling suggests that neither a preexisting strike slip fault nor a zone of thermally induced lithospheric weakness in the overriding plate is needed for strain partitioning to occur in general forearc slivers form over the region of interplate coupling and are driven along strike by the basal shear a volcanic arc can help the partitioning process by localizing the margin parallel shear strain in the upper plate if its crust and mantle are weaker than its surroundings interplate slip vectors and geodetic results from sumatra together suggest that the highest coupling on the plate boundary occurs beneath and seaward of the forearc islands consistent with inferences about the rupture zones of great nineteenth century earthquakes there the sumatra example suggests that geodetic measurements of interseismic margin parallel shear strain at oblique convergent margins can be used to map the landward extent of the relatively high basal stress beneath the overriding plate if one can correct for strain localization caused by weak upper plate strike slip faults

estimation of strong ground motion from the great 1964 mw 9 2 prince william sound alaska earthquake we are generating physically plausible near field synthetic ground motions for the great 1964 prince william sound alaska earthquake compatible with available seismological data tectonic information and eyewitness accounts the first objective of this study is the simulation of the low frequency i e f 0 03 hz strong ground motions on selected locations and on a dense grid of observation points extending over the shallow dipping causative fault of the 1964 alaska earthquake in order to accomplish this task we are utilizing the slip model proposed by johnson et al 1996 based on a joint inversion of tsunami waveforms and geodetic data the calculations are carried out using the discrete wavenumber representation method bouchon and aki 1977 bouchon 1979 and the generalized transmission and reflection coefficient technique luco and apsel 1983 the second objective of this study is the reconstruction of the strong ground motion time histories and response spectra that the city of anchorage experienced during the 1964 alaska earthquake the low frequency i e f 0 03 hz ground motions are generated using the methodology described previously the intermediate frequency i e 0 03 f 0 50 hz ground motions are simulated by convolving green s functions generated by the discrete wavenumber representation method with far field radiation pulses of circular cracks sato and hirasawa 1973 dong and papageorgiou 2002a the high frequency i e 0 5 f 8 0 hz ground motions are simulated using the stochastic modeling approach the three independently derived ground motion components are then properly combined to generate synthetic broadband ground motion time histories and response spectra for the city of anchorage due to the 1964 prince william sound earthquake the third objective of this study is the validation of the synthetic strong ground motions for the 1964 alaska earthquake against observed tectonic deformation ground motion estimates inferred from descriptions of structural damage and eyewitness accounts in summary the analysis presented in this study contributes to a better understanding of the seismological aspects of the 1964 alaska earthquake and provides synthetic time histories and response spectra for engineering applications compatible with all available information i e seismological tectonic and eyewitness accounts it should be noted however that the generated strong ground motions are not necessarily unique nor do they reflect the entire uncertainty that characterizes the problem under investigation

intraseasonal variability of high resolution doppler imager winds in the equatorial mesosphere and lower thermosphere analyses of high resolution doppler imager hrdi daytime equatorial zonal winds indicate significant variability on time scales of 20 121 days these appear as transient oscillations in the equatorial zonal mean zonal wind between 70 and 100 km the oscillations are characterized by two maxima near 75 and 95 km that are out of phase separated by a minimum near 80 km these features move downward in time and exhibit equatorial symmetry with maximum values at the equator during 1994 maximum amplitudes of the intraseasonal oscillation are 20 m s 1 in january and 30 m s 1 in june the intraseasonal variability present in hrdi winds is qualitatively consistent with variations on similar timescales reported at christmas island it has been hypothesized that the wind patterns at christmas island result from modulated gravity wave driving eckermann et al 1997 the results of the present study strongly support this view

seismology speed and size of the sumatra earthquake we now have a clearer picture of the seismic features of last year s gigantic event our seismological results reveal that indonesia s devastating sumatra andaman earthquake on 26 december 2004 was 2 5 times larger than initial reports suggested second only to the 1960 chilean earthquake in recorded magnitude they indicate that it slowly released its energy by slip along a 1 200 km fault generating a long rupture that contributed to the subsequent tsunami now that the entire rupture zone has slipped the strain accumulated from the subduction of the indian plate beneath the burma microplate has been released and there is no immediate danger of a similar tsunami being generated on this part of the plate boundary although large earthquakes on segments to the south still present a threat

geodetic observations of interseismic strain segmentation at the sumatra subduction zone deformation above the sumatra subduction zone revealed by global positioning system gps geodetic surveys shows nearly complete coupling of the forearc to the subducting plate south of 0 5 s and half as much to the north the abrupt change in plate coupling coincides with the boundary between the rupture zones of the 1833 and 1861 mw 8 thrust earthquakes the rupture boundary appears as an abrupt change in strain accumulation well into the interseismic cycle suggesting that seismic segmentation is controlled by properties of the plate interface that persist through more than one earthquake cycle structural evidence indicates that differences in basal shear stress may be related to elevated pore pressure in the north

accretion mass wasting and partitioned strain over the 26 dec 2004 mw9 2 rupture offshore aceh northern sumatra abstract the aceh segment of the sunda arc absorbed the largest slip along the 26 december 2004 mw9 2 subduction earthquake rupture and caused the highest and most disastrous tsunami run ups sea floor disruption marks the frontal active part of the accretionary prism along that segment an rov bathymetric and seismic survey r v natsushima jamstec 2 3 2005 revealed pervasive and deeply rooted fracturing along the upper trench slope grabens and ejecta clasts from fluid escape along the crest of an anticline ridge coupled with mass wasting and erosional scouring on the slope below it specific features of the disruption and its patchy distribution suggest coseismic faulting and folding with gravitational collapse of the steepened anticline forelimb the same ridge 40 km along strike was pristine disruption was also generally undetected by rov on the ache basin side of the forearc ridge suggesting a minor role for shaking only some of the faults in the imbricate and segmented accretionary structure ruptured but together they may account for 2004 sea floor rupture along the aceh segment this hypothesis accounts for unusual thrust aftershocks and suspended sediment along the frontal active part of the prism it can also account for the huge tsunami heights in northern sumatra because faults in the prism are steeper than the megathrust down dip and because slip may be larger in the prism following prior blind ruptures rare but large coseismic deformation of the prism can generally account for the erosional morphology of trench slopes and for al least some tsunami earthquakes on the landward side of the forearc high the west andaman fault borders the aceh basin and branches southward into a fault crossing obliquely the forearc high seismic profiles at the bifurcation image a flower structure with strain partitioning and an active dextral pull apart this fault system however did not release significant strain in 2004

near fault strong motion complexity of the 2000 tottori earthquake japan from a broadband source asperity model abstract the october 6 2000 tottori earthquake that occurred in central japan was an intermediate size strike slip event that produced a very large number of near field strong motion recordings the large amount of recorded data provides a unique opportunity for investigating a source asperity model of the tottori earthquake that combined with a hybrid strong motion simulation technique is able to reproduce the observed broadband frequency near fault ground motion we investigated the optimum source asperity parameters of the tottori earthquake by applying a genetic algorithm ga inversion scheme to optimise the fitting between simulated and observed response spectra and peak ground acceleration pga values we constrained the initial model of our inversion by using the heterogeneous slip distribution obtained from a kinematic inversion of the source of previous studies we used all the observed near fault ground motions 100 m from the borehole strong motion network of japan kik net which are little affected by surficial geology site effects the calculation of broadband frequency strong ground motion 0 1 10 hz is achieved by applying a hybrid technique that combines a deterministic simulation of the wave propagation for the low frequencies and a semi stochastic modelling approach for the high frequencies for the simulation of the high frequencies we introduce a frequency dependent radiation pattern model that efficiently removes the dependence of the pattern coefficient on the azimuth and take off angle as the frequency increases the good agreement between the observed and simulated broadband ground motions shows that our inversion procedure is successful in estimating the optimum asperity parameters of the tottori earthquake and provides a good test for the strong ground motion simulation technique the ratio of background stress drop to average asperity stress drop from our inversion is nearly 50 in agreement with the theoretical asperity model of das and kostrov das s kostrov b v 1986 fracture of a single asperity on a finite fault a model for weak earthquakes earthquake source mechanics agu pp 91 96 and an empirical ratio of asperities to rupture area seismol res lett 70 1999 59 80 the simulated radiation pattern is very complex for epicentral distances within half the fault length but it approaches the radiation of a double couple point source for larger distances the rupture velocity and rise time have a significant influence on the peak ground velocity pgv distribution around the fault an increase in rupture velocity produces a similar effect on the ground motion as a reduction in rise time

simulated strong ground motions for the great m 9 3 sumatra andaman earthquake of 26 december 2004 on 26 december 2004 a devastating earthquake of m 9 3 occurred offshore northern sumatra due to the size of this earthquake and the accompanying tsunami wave disastrous consequences have been observed in several countries around the indian ocean the tectonics in the region are characterized by the oblique north northeast oriented subduction of the indian australian plate under the sunda microplate with a rate of 6 6 5 cm yr this oblique convergence results in strain partitioning where the trench perpendicular thrust faulting along the subducting slab accommodates the east west component of the motion whereas the north south component of the motion is probably accommodated by the right lateral strike slip faulting along the great sumatran fault and the mentawi fault source parameters of the 26 december 2004 event have been used for modeling the resulting ground motions in the nearby affected regions results give an insight on the importance of ground shaking in the total destruction of places like banda aceh northern sumatra indonesia the modeling is performed for a multiasperity finite fault using a hybrid procedure combining deterministic modeling at low frequencies and semistochastic modeling at high frequencies results show that strong shaking was distributed over a large area including northwestern sumatra and its offshore islands in banda aceh which experienced significant damage bedrock velocities reached 60 cm sec with duration of the shaking of ca 150 sec the largest ground motions occurred near the strongest asperities of the fault plane where velocities of 200 cm sec are modeled for bedrock conditions

rupture process of the 2004 sumatra andaman earthquake the 26 december 2004 sumatra andaman earthquake initiated slowly with small slip and a slow rupture speed for the first 40 to 60 seconds then the rupture expanded at a speed of about 2 5 kilometers per second toward the north northwest extending 1200 to 1300 kilometers along the andaman trough peak displacements reached 15 meters along a 600 kilometer segment of the plate boundary offshore of northwestern sumatra and the southern nicobar islands slip was less in the northern 400 to 500 kilometers of the aftershock zone and at least some slip in that region may have occurred on a time scale beyond the seismic band

the great sumatra andaman earthquake of 26 december 2004 the two largest earthquakes of the past 40 years ruptured a 1600 kilometer long portion of the fault boundary between the indo australian and southeastern eurasian plates on 26 december 2004 seismic moment magnitude mw 9 1 to 9 3 and 28 march 2005 mw 8 6 the first event generated a tsunami that caused more than 283 000 deaths fault slip of up to 15 meters occurred near banda aceh sumatra but to the north along the nicobar and andaman islands rapid slip was much smaller tsunami and geodetic observations indicate that additional slow slip occurred in the north over a time scale of 50 minutes or longer

apparent stress scaling for tectonic and induced seismicity model and observations abstract a macroscopic model of seismic sources provides a scaling relationship for the apparent stress treated as a function of three independent parameters seismic moment rupture area size and average slip acceleration these parameters represent three different factors kinematic geometric and material this relationship allows us to distinguish and explain the following statistical characteristics of the log apparent stress versus log seismic moment plot the regional trends represented by a series of 1 2 slope lines are related to the averaged shape of slip velocity pulses so they reflect kinematic characteristics of the rupture process the global trend represented by the 1 6 slope line is expected to characterize sets of events of wide range of rupture area sizes and assumes dependence of rupture area size on total slip so it is related to the rupture initiation propagation and arrest conditions therefore it reflects earthquake rupture dynamics additional shiftings among the trend lines obtained for the smallest induced tremors larger tectonic earthquakes and slow tsunami earthquakes reflect differences between the intact rock failure and the frictional slip failure that is between fracture energies of these different earthquake classes

estimation of the high frequency radiation of the 2000 tottori japan earthquake based on a dynamic model of fault rupture application to the strong ground motion simulation abstract in the present study we investigate the high frequency hf radiation mechanism of the 2000 tottori earthquake in japan based on a 3d spontaneous fault rupture dynamic model we generalize the model of hf radiation of a suddenly stopping circular crack madariaga 1977 boatwright 1982 to the radiation from a general 3d rupture in a planar fault where hf is radiated during gradual changes of rupture velocity at the rupture front local rupture velocity changes are expressed as the divergence of local rupture velocity vectors that are derived from gradients of rupture times from the dynamic model our numerical model of the tottori earthquake indicates that rupture velocity changes are largely induced by barriers locally stronger fault sections across the fault plane and that hf radiation mainly originates within asperities large stress drop regions in areas where the product of dynamic stress drop and rupture velocity changes is maximum we develop a strong ground motion simulation methodology that incorporates hf radiation inferred from a dynamic fault rupture model using this methodology we investigate the hf radiation of the tottori earthquake by inverting observed near source acceleration envelopes of the earthquake our inversion results corroborate that hf radiation originates within asperities and show that significant hf radiation represents no more than a 20 of the total asperity area our results show that the incorporation of a directivity factor on the basis of a well defined physical rupture model to the radiation pattern leads to a significant improvement in fitting of observed ground motions our simulated near source strong ground motions of the tottori earthquake are also able to reproduce the 2 radiation theoretically predicted in 2d dynamic fault rupture models

observation of an ultraslow large scale wave near the tropical tropopause an analysis is made of very high resolution radiosonde data taken at seven western pacific island stations during toga coare tropical ocean global atmosphere and coupled ocean atmosphere response experiment evidence is found for a wave near the tropopause with periods 30 40 days and with very slow 3 m s 1 eastward propagation this oscillation appears quite coherent across the region considered a 37 longitude spread the oscillation has a short vertical wavelength 3 km and is strongly attenuated above the tropopause and thus would be very hard to observe in either satellite data or conventional meteorological analyses

strong ground motion estimation in the sea of marmara region turkey based on a scenario earthquake we perform a broadband frequency bedrock strong ground motion simulation in the marmara sea region turkey based on several fault rupture scenarios and a source asperity model the technique combines a deterministic simulation of seismic wave propagation at low frequencies with a semi stochastic procedure for the high frequencies to model the high frequencies we applied a frequency dependent radiation pattern model which efficiently removes the effective dependence of the pattern coefficient on the azimuth and take off angle as the frequency increases the earthquake scenarios considered consist of the rupture of the closest segments of the north anatolian fault system to the city of istanbul our scenario earthquakes involve the rupture of the entire north anatolian fault beneath the sea of marmara namely the combined rupture of the central marmara fault and north boundary fault segments we defined three fault rupture scenarios based on the location of the hypocenter selecting a preferred hypocentral location near a fault bend for each case we analysed the effect of location of the asperity within the central marmara fault on the subsequent ground motion as well as the influence of anelasticity on the highfrequency attenuation characteristics the fault and asperity parameters for each scenario were determined from empirical scalings and from results of kinematic and dynamic models of fault rupture we calculated the resulting time series and spectra for ground motion at istanbul and evaluated the sensitivity of the predictions to choice of model parameters the location of the hypocenter is thus shown to be a critical parameter for determining the worst scenario earthquake at istanbul we also found that anelasticity has a significant effect on the regional attenuation of peak ground accelerations our simulated ground motions result in large values of acceleration response spectra at long periods which could be critical for building damage at istanbul during an actual earthquake d 2004 elsevier b v all rights reserved

origins of natural gases from marine strata in northeastern sichuan basin china from carbon molecular moieties and isotopic data abstract to determine the origin maturity formation mechanism and secondary process of marine natural gases in northeastern sichuan area molecular moieties and carbon isotopic data of the carboniferous and triassic gases have been analyzed typical samples of marine gas precursors including low maturity kerogen dispersed liquid hydrocarbons dlhs in source rocks residual kerogen and oil have been examined in a closed system and several published geochemical diagrams of gas origins have been calibrated by using laboratory data results show that both carboniferous and triassic gases in the study area have a thermogenic origin migration leads to stronger compositional and weak isotopic fractionation and is path dependent carboniferous gases and low h 2 s gases are mainly formed by secondary cracking of oil whereas high h 2 s gases are clearly related to the tsr thermal sulfate reduction process gases in ne sichuan show a mixture of heavy 13 c enriched methane in comparison to the lower maturated ethane of triassic gas samples suggesting a similar source and maturity for ethane and propane of carboniferous gases and a mixture of heavy ethane to the propane for triassic gases based on the data plotted in the diagram of chung et al 1988 the residual kerogen from silurian marine shale and palaeo oil reservoirs are the main source for carboniferous gases and that the residual kerogen from silurian and permian marine rocks and permian paleao oil reservoirs constitute the principal source of triassic gases

evidence for equatorial kelvin modes in nimbus 7 lims abstract eastward propagating disturbances over the equator are diagnosed in two independent nimbus 7 lims limb infrared monitor of the stratosphere data sets they are evident consistently at several pressure levels throughout the stratosphere and account for much of the temperature variance in the tropics the disturbances which can be seen in wavenumbers 1 3 are in phase and symmetric about the equator latitudinally evanescent and have short moderate vertical phase structure 10 40 km which progresses downward wavenumber 1 has spectral components which propagate eastward at periods of 6 7 8 6 days 54 69 m s 1 and 3 5 4 0 days 115 135 m s 1 wavenumber 2 exhibits eastward propagating variance at periods of 6 0 7 5 days 31 39 m s 1 and 3 8 4 3 days 55 62 m s 1 the faster waves appear principally in the upper stratosphere these features are in reasonable agreement with the structure and dispersion characteristics of simple quasi separable kelvin modes with the exception of the slower w

individual characterization of petroleum fluid inclusions composition and p t trapping conditions by microthermometry and confocal laser scanning microscopy inferences from applied thermodynamics of oils abstract this paper proposes a new method to characterize individual oil bearing fluid inclusions it uses both the homogenisation temperatures measured by microthermometry and the degree of gas bubble filling measured by confocal laser scanning microscopy in conjunction with thermodynamic modelling for describing liquid gas phase transitions and the volumetric behaviour of hydrocarbon mixtures it is associated with a two parameter compositional model that describes the wide range of compositions of petroleums we show that this method can give 1 useful estimations of the compositions and pressure temperature entrapment conditions of oils in fluid inclusions and 2 insights into the various processes that have affected these fluids either before entrapment liquid gas unmixing gas leaching mixing etc or after leakage etc

indonesian earthquake earthquake risk from co seismic stress last year s indonesian earthquake has increased seismic hazard in the region the scale of death and destruction caused by the recent sumatra andaman islands earthquake and its tsunami has raised concerns that another earthquake might be triggered on the contiguous sunda trench subduction zone a new calculation of stress distribution here and on the neighbouring sumatra fault reveals stress build up on both structures severe enough to increase the already high earthquake hazard this finding makes the need for an indian ocean tsunami warning system all the more pressing following the massive loss of life caused by the sumatra andaman earthquake in indonesia and its tsunami the possibility of a triggered earthquake on the contiguous sunda trench subduction zone is a real concern we have calculated the distributions of co seismic stress on this zone as well as on the neighbouring vertical strike slip sumatra fault and find an increase in stress on both structures that significantly boosts the already considerable earthquake hazard posed by them in particular the increased potential for a large subduction zone event in this region with the concomitant risk of another tsunami makes the need for a tsunami warning system in the indian ocean all the more urgent

distribution of magma beneath the toba caldera complex north sumatra indonesia constrained by three dimensional p wave velocities seismicity and gravity data 1 we estimate the one and three dimensional p wave velocity structure beneath the toba caldera complex a 30 100 km topographic depression in north sumatra using arrival time data of local earthquakes recorded by a 40 station seismic network that operated for 4 months inversions reveal the presence of p velocities up to 37 below normal that likely map the distribution of magma within this subduction related volcanic system considered the world s largest in the upper 10 km of crust the largest low velocity region underlies the southern two thirds of the depression and coincides with a gravity low centered over the resurgent dome a smaller volume of low velocities is observed in the upper crust under the north end of the depression separating the two regions is a zone of locally high velocities indicating that the shallow subcaldera magma system is composed of two separate reservoirs not a single one that extends the entire length of the caldera complex above each low velocity region is a postcollapse volcano that erupted mostly mafic lavas after the last major caldera collapse 74 kyr ago a low velocity column below one of these volcanoes can be traced into the uppermost mantle and corresponds with a planar distribution of low frequency earthquakes in the 20 to 40 km depth range the low frequency earthquakes apparently record the migration of melt in the mafic roots of this large volume crustal magma system

seismo tectonics of the andaman nicobar islands abstract the epicentres of 345 earthquakes that occurred between january 1967 and december 1982 in a region bounded by 4 n to 16 n latitudes and 90 e to 98 e longitudes were plotted in order to study the seismicity of this region most of the earthquakes in this region are shallow focus the greatest focal depth being about 250 km in the northern part of this region north of 10 5 n tne earthquake foci are aligned along two branches which strike northeastwards no intermediate depth earthquakes are associated with the eastern branch south of 10 5 n the foci are located along a zone striking north northwest focal mechanism solutions are reported for 24 earthquakes that occurred in this region during this period the first motions of p and pkp phases were used to determine the mechanism solutions five of these events occurred in northern sumatra and the rest occurred in the andaman nicobar islands the mechanism solutions of the shallow focus earthquakes in northern sumatra are characterized by a predominant component of thrust and strike slip faulting the inferred orientation of slip vectors deduced from mechanisms of shallow focus events is nearly northeast mechanism solutions of 13 shallow focus events that occurred in the andaman nicobar islands are characterized by thrust normal and strike slip faulting the orientation of slip vectors deduced from thrusting mechanisms is consistent with the underthrusting of the indian ocean under the andaman nicobar islands in a northeasterly direction normal faulting mechanism solutions of these islands suggest that they are tectonically similar to island arcs the results reported in this study show for the first time using mechanism solutions the existence of underthrusting along the andaman nicobar islands for which there is ample geological evidence

source area and rupture parameters of the 31 december 1881 mw 7 9 car nicobar earthquake estimated from tsunamis recorded in the bay of bengal 1 on the morning of 31 december 1881 a submarine earthquake beneath the andaman islands generated a tsunami with a maximum crest height of 0 8 m that was recorded by eight tide gauges surrounding the bay of bengal since the earthquake occurred 8 years before the construction of the world s first teleseismic recording seismometer little has been known about its rupture parameters or location waveform and amplitude modeling of the tsunami indicate that it was generated by a mw 7 9 0 1 rupture on the india andaman plate boundary resulting in 10 60 cm of uplift of the island of car nicobar the rupture consisted of two segments the northern 40 km long segment is separated from the southern 150 km long segment by a 100 km region corresponding to the westward projection of the west andaman spreading center the main rupture occurred between 8 5 n and 10 n with a total area of 150 km 60 km dipping 20 e with a mean slip of 2 7 m the recurrence time for 1881 type events is estimated to be 114 200 years on the basis of inferred gps convergence rates and inferred plate closure vectors although slip partitioning in the region may extend this estimate by as much as 30

radiosonde observations of equatorial atmosphere dynamics over indonesia 1 equatorial waves and diurnal tides this paper describes the characteristics of the mean winds equatorial waves with periods ranging from 4 to 20 days and diurnal tides determined by analyzing the profiles of wind velocity temperature and humidity obtained every 5 7 hours in the height range up to about 35 km with a height resolution of 150 m during an observation campaign conducted february 27 to march 22 1990 in east java indonesia the structures of the mean winds in the troposphere and lower stratosphere seemed to be affected by the australian monsoon and the quasi biennial oscillation respectively frequency spectra indicated that the equatorial waves as well as the diurnal tides were dominant below about 25 km while gravity waves with periods shorter than 4 days became more significant above 25 km a 7 day oscillation showing an antiphase relation between the eastward and northward components and exhibiting large amplitudes was observed in the lower troposphere the time height variations of the activity of this 7 day oscillation were clearly correlated with a region of high relative humidity perturbations in the zonal wind and temperature with wave periods varying from 15 to 17 days were also enhanced in the troposphere while kelvin waves with periods of about 7 and 20 days were detected in the lower stratosphere and activity near the tropopause was conspicuously enhanced we found that the 20 day kelvin wave greatly modified the structure of the tropopause such as the minimum temperature the tropopause height and the values of the brunt vaisala frequency squared n2 which further suggests the effects of kelvin waves on the transportation of tropospheric water vapor into the stratosphere and on the downward mixing of stratospheric minor constituents into the troposphere the observed profiles of the diurnal oscillation were compared with those of a numerical model assuming only migrating tides which reasonably agreed above about 25 km below 25 km however the observed amplitudes were 1 1 5 m s exceeding those of the model about 10 times moreover the phase profiles involved fluctuations with small vertical scales suggesting interference by many nonmigrating tides with short vertical wavelengths

a flying start then a slow slip the human tragedy caused by the sumatra andaman earthquake moment magnitude 9 3 on 26 december 2004 and its companion nias earthquake moment magnitude 8 7 on 28 march 2005 is difficult to comprehend these earthquakes the largest in 40 years have also left seismologists searching for the words and tools to describe the enormity of the geological processes involved four papers in this issue discuss aspects of a rupture process of surprising complexity the first such event to test the sensitivity and range of many new technologies a surprising feature of the earthquake is that after the initial rapid rupture subsequent slip of the plate interface occurred with decreasing speed toward the north

strong ground motion simulation of the 12 may 2008 mw 7 9 wenchuan earthquake using various slip models abstract on 12 may 2008 a devastating earthquake of m w 7 9 occurred in the sichuan province of china the earthquake had disastrous consequences and cost more than 69 000 lives the rupture occurred along a 300 km long fault dipping northwest along the longmen shan fold thrust belt which separates the longmen shan of the tibetan plateau in the northwest from the sichuan basin in the southeast and is associated with a significant change in the crustal thickness we simulate the ground shaking due to the wenchuan earthquake by applying a hybrid broadband frequency strong ground motion simulation technique that combines deterministic simulation of low frequencies 0 1 1 0 hz with semistochastic modeling of high frequencies 1 0 10 hz we use three available finite fault slip models obtained from waveform inversion as input models for the earthquake scenarios the resulting simulations reveal large variations in ground shaking due to the rupture complexity in terms of a variety of factors including the location of asperities and the width of the fault plane the applied methodology successfully reproduces the strong ground motion distribution and frequency content of the seismic waves the simulated ground motions when calibrated with the recorded data can also be used to verify the finite fault slip models based on different teleseismic data and inversion schemes comparison with the damage distribution from reconnaissance field observations confirms the fault rupture complexity the applied simulation methodology provides a promising platform for predictive studies