coseismic and postseismic slip distribution of the 2003 mw 6 5 chengkung earthquake in eastern taiwan elastic modeling from inversion of gps data abstract the chengkung earthquake with m l 6 6 occurred in eastern taiwan at 12 38 local time on december 10th 2003 based on the main shock relocation and aftershock distribution the chengkung earthquake occurred along the previously recognized n20 e trending chihshang fault this event did not cause human loss but significant cracks developed at the ground surface and damaged some buildings after 1951 taitung earthquake there was no larger m l 6 earthquake occurred in this region until the chengkung earthquake as a result the chengkung earthquake is a good opportunity to study the seismogenic structure of the chihshang fault the coseismic displacements recorded by gps show a fan shaped distribution with maximal displacement of about 30 cm near the epicenter the aftershocks of the chengkung earthquake revealing an apparent linear distribution helps us to construct the clear fault geometry of the chihshang fault in this study we employ a half space angular elastic dislocation model with gps observations to figure out the slip distribution and seismological behavior of the chengkung earthquake on the chihshang fault the elastic half space dislocation model reveals that the chengkung earthquake is a thrust event with minor left lateral strike slip component the maximum coseismic slip is located around the depth of 20 km and up to 1 1 m the slips are gradually decreased to less than 10 cm near the surface part of the chihshang fault the seismogenic fault plane which is constructed by the delineation of the aftershocks demonstrates that the chihshang fault is a high angle fault however the fault plane changes to a flat plane at depth of 20 km in addition a significant part of the measured deformation across the surface fault zone for this earthquake can be attributed to postseismic creep the postseismic elastic dislocation model shows that most afterslips are distributed to the upper level of the chihshang fault and most afterslips consist of both of dip and left lateral slip the model results show that the chihshang fault may be partially locked or damped near surface during coseismic slip after the mainshock the strain which cumulated near the surface was released by postseismic creep resulting in significant postseismic deformation

major element and ree compositions of pliocene sediments in southwest japan implications for paleoweathering and paleoclimate abstract the history of the east asian monsoon and the relationship between the development of the monsoon climate tectonics and global climate are complicated and controversial earlier studies have indicated that the east asian monsoon fluctuated in the asian interior during the pliocene thus the chemical weathering record in coastal regions of east asia can be the key to elucidating its evolution as well as the kuroshio current variability the present study clarifies the chemical weathering conditions in southwest japan based on the concentrations of major elements and rare earth elements rees in lacustrine muddy sediments the chemical weathering was moderate between 4 4 and 3 8 ma between 3 8 and 3 4 ma chemical weathering significantly intensified as indicated by the high values of the chemical index of alteration that reached a maximum of 98 as well as the high concentrations of rees and light rees against heavy rees and kaolinite rich clay mineral compositions despite the wide variation in source rock compositions and grain sizes the degree of chemical weathering remained moderate during the early pleistocene the intense chemical weathering on land in southwest japan from 3 8 to 3 4 ma may have been regulated by alternating periods of warm and humid climate brought by the invasion of the kuroshio current and the intensification of the east asian summer monsoon

varieties of a single cosmopolitan diatom species associated with surface water masses in the north pacific abstract a time series of 65 sediment trap samples representing 48 month changes in diatom flora and 62 sediment core tops from the western north pacific ocean were analyzed varieties of a single diatom species were found to be characteristic of two surface water masses bounded by the kuroshio current thalassionema nitzschioides var incurvata var inflata and var parva dominate in warm saline waters in the subtropical gyre while t nitzschioides sensu stricto is abundant in less saline waters northwest of this current time series data on percent abundances for the three t nitzschioides varieties in the t nitzschioides complex are compared with path variations of the current south of japan inter annual fluctuations in percent abundance are linked to changes in surface water masses over the sediment traps in association with migration of the kuroshio paths this finding makes the percent abundance a useful tool for deciphering path migrations of the kuroshio current in the geologic past down core analyses of two sediment cores collected beneath the modern kuroshio current were performed a sharp increase in percent abundances from 12 to 9 kyr bp with an abrupt change around 11 kyr bp records the previously reported transition of the kuroshio current from a predominantly offshore path to its modern path path migrations of the kuroshio current may be inferred from percent abundances of these diatoms which comprise a new proxy for delineating the paleoclimate of the northwestern pacific in relation to changes in northward heat transport from the western equatorial pacific ocean by the western boundary current

some insight on why bam iran was destroyed by an earthquake of relatively moderate size 1 the bam iran earthquake of 2003 resulted in one of the worst human disaster in recent years yet the magnitude of the event mw 6 6 was relatively moderate we show that the remarkable recording of the ground motion produced in the city itself contains some clues which help explain this disaster we identify three factors whose unfortunate combination led to the strong ground shaking which destroyed the city 1 the rayleigh like speed of the rupture 2 the high slip velocity which exceeded 2m s over a large part of the fault 3 the strong directivity which focused the elastic energy released directly toward the city

near field probabilistic seismic hazard analysis of metropolitan tehran using region specific directivity models ground motions are affected by directivity effects at near fault regions which result in low frequency cycle pulses at the beginning of the velocity time history the directivity features of near fault ground motions can lead to significant increase in the risk of earthquake induced damage on engineering structures the ordinary probabilistic seismic hazard analysis psha does not take into account such effects recent studies have thus proposed new frameworks to incorporate directivity effects in psha the objective of this study is to develop the seismic hazard mapping of tehran city according to near fault psha procedure for different return periods to this end the directivity models required in the modified psha were developed based on a database of the simulated ground motions the simulated database was used in this study because there are no recorded near fault data in the region to derive purely empirically based pulse prediction models the results show that the directivity effects can significantly affect the estimate of regional seismic hazard

surface displacements and source parameters of the 2003 bam iran earthquake from envisat advanced synthetic aperture radar imagery 1 the mw 6 6 26 december 2003 bam iran earthquake was one of the first earthquakes for which envisat advanced synthetic aperture radar asar data were available using interferograms and azimuth offsets from ascending and descending tracks we construct a three dimensional displacement field of the deformation due to the earthquake elastic dislocation modeling shows that the observed deformation pattern cannot be explained by slip on a single planar fault which significantly underestimates eastward and upward motions se of bam we find that the deformation pattern observed can be best explained by slip on two subparallel faults eighty five percent of moment release occurred on a previously unknown strike slip fault running into the center of bam with peak slip of over 2 m occurring at a depth of 5 km the remainder occurred as a combination of strike slip and thrusting motion on a southward extension of the previously mapped bam fault 5 km to the east

validation of teleseismic inversion of the 2004 mw 6 3 les saintes lesser antilles earthquake by 3d finite difference forward modeling we study the 21 november 2004 mw 6 3 les saintes earthquake that occurred south of the island of guadeloupe at a shallow depth damaging some buildings on the island the objective of this work is to assess the potential of a teleseismic source study to reproduce local ground motion the velocity model of this area is not currently well known and the near field seismograms are affected by paths and site effects we first analyze this earthquake as a point source and then as an extended fault using teleseismic broadband waveform inversion approach from the p and sh waveforms at stations well distributed in azimuth we obtain two stable and reliable solutions of the spatiotemporal history of the earthquake rupture on each nodal plane the models show a rupture duration of 6 sec and a maximum slip of about 1 m but have different locations of the main asperity we then carry out the forward modeling of the seismic wave propagation at the regional scale coupled with the obtained kinematic source models taking into account the topography the bathymetry and the sea layer we investigate if one of the fault models could produce synthetics that match the local observed ground motions the simulation results provide a better understanding of the uncertainty of source path and site effects even if our knowledge of the underground geological structure is limited to the 1d stratified model it is inferred that the 1d model does not seem to be appropriate in the northern direction middle of guadeloupe island due to the unknown basin structure while it is relatively sufficient in the eastern and the northwestern directions from the source by careful comparison of the synthetic and observed displacement seismograms in terms of main phase forms and arrival times at low frequency especially at the closest station gbga the fault model with northeast faulting is estimated to be the more relevant to the measured local ground motions

strong motion and teleseismic waveform inversions for the source process of the 2003 bam iran earthquake the bam earthquake m w 6 5 occurred on 26 december 2003 in southeastern iran causing a major disaster in the city of bam a remarkable vertical peak ground acceleration value of 988 cm s2 and two horizontal pulses were recorded inside the damaged city previous analyses showed that the earthquake was caused by a subsurface rupture on an unknown strike slip fault in this study we attempt to determine the precise fault location and source process of the 2003 bam earthquake by performing a multiple time window linear waveform inversion of teleseismic and strong motion data both individually and jointly we examined the general features of the fault location and the source process by analyzing the teleseismic displacement waveforms and determined the precise features and fault geometry by inverting the three components of strong motion velocity records the final estimate of the source process of the 2003 bam earthquake was determined by joint inversion of the datasets our results show that a single fault model characterized by the appropriate location of the hypocenter rake angle variations and the rayleigh like speed of the rupture front can satisfactorily explain the three components of the strong motion records at bam station

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

the 2003 december 26 bam earthquake iran mw 6 6 aftershock sequence summary from 2003 december 29 to 2004 january 30 a dense seismological network of 23 stations was installed in the epicentral area of the 2003 december 26 bam earthquake to study the aftershock seismicity we select the 331 earthquakes recorded at a minimum of 10 stations with rms less than 0 1 s and uncertainties less than 1 km to infer the precise geometry of the seismicity in the fault region we also process the data with the double difference technique to confirm the results the aftershock cluster is 25 km long trends north south and is located 5 km west of the bam baravat escarpment exactly beneath the observed surface breaks at depth aftershocks are concentrated between 6 and 20 km beneath the upper layer of relatively low velocity that experienced the maximum slip and they dip slightly westward the southernmost part of the aftershock cluster is narrow and defines the rupture zone that is likely the bam baravat fault at depth however it is unlikely that it is connected at surface to the bam baravat escarpment but more likely to the co seismic ruptures south of bam on the contrary the distribution of the northernmost aftershocks spread into a more complex pattern which is consistent with a northward propagation of the rupture along the fault plane the focal mechanisms are consistent with right lateral strike slip faulting on n s trending faults parallel to the bam baravat escarpment

the 2003 bam se iran earthquake precise source parameters from satellite radar interferometry summary differential radar interferometry provided high quality near field deformation data for the 2003 bam earthquake and therefore strong constraints on its source parameters the ruptured fault segments could be clearly detected by using a sobel edge filter on the phase unwrapped deformation field the estimated total rupture length is about 24 km more than 80 per cent of the seismic moment was released from its southern segment of about 13 km where the slip reached a maximum of up to 270 cm resulting in a stress drop of at least 6 mpa in addition optical remote sensing data show that the bam fault is not a single fault but consists of a 4 5 km wide fault system with the known main branch running between the city of bam and baravat the fault ruptured by the bam earthquake appears to continue the nw branch of this fault system from bam city southwards based on these results we suggest that the bam earthquake ruptured a hidden or new fault and that in this process an unusually strong asperity was involved

simulation of selected strong motion records of the 2003 mw 6 6 bam earthquake se iran the modal summation ray tracing methods in the wkbj approximation

source fault structure of the 2003 bam earthquake southeastern iran inferred from the aftershock distribution and its relation to the heavily damaged area existence of the arg e bam fault proposed 1 we investigate the hypocenter distribution of aftershocks of the december 26 2003 bam earthquake mw 6 5 by using a temporal seismic network the hypocenters distribute linearly over about 20 km in parallel with a line 3 5 km west of the geological bam fault and extend from the south of bam city to the heavily damaged area in the eastern part of the city including the historical mud brick citadel arg e bam based on the hypocenter distribution we propose a schematic 3 d structural model of a new fault that we have named the arg e bam fault we suggest that the bam earthquake occurred not in the bam fault but in the arg e bam fault bam city is located just above northern part of the arg e bam fault and also on the rupture propagation direction from the asperity this may be one of the main reasons why eastern part of bam city suffered the heaviest damage

oligocene through palaeogene neogene boundary foraminifera of the northern mesohellenic basin macedonia greece biostratigraphy and palaeoecologic implications abstract foraminifera of the oligocene and early miocene siliciclastic units from the northern part of the mesohellenic basin macedonia northern greece provide good biostratigraphic potential taxa identified from a number of sections cropping out in the study area indicate that these deposits fan in zones p20 upper part p21 p22 and most of zone n4 of blow s zonal scheme the occurrence within the lowest part of the pendalofos formation of abundant globigerinoides primordius together with other earliest miocene planktonics defines the base of the miocene although a remarkable planktonic foraminiferal turnover occurred close to the palaeogene neogene boundary the benthic populations do not show any clear change except in relation to palaeoecologic conditioning analysis of benthic foraminifera led to the definition of a palaeodepth curve indicating that the deposition during the late oligocene and early miocene occurred in a middle to upper mostly bathyal and outer neritic conditions the distribution of selected benthic foraminifera is compared with sedimentologically derived depositional environments the correlation between the major global unconformities predicted by the exxon coastal onlap chart and the mesohellenic succession is based on the joint use of biochronologic and biostratigraphic palaeoecologic tools

seismic geomorphology and growth architecture of a miocene barrier reef browse basin nw australia abstract the cenozoic succession of browse basin is characterized by a carbonate system that developed from a non tropical ramp in eocene lower miocene times to a tropical rimmed platform in the middle miocene the evolution of the platform was unraveled through the interpretation of the seismic geomorphology and borehole data of the middle miocene tropical reef system the first reef structures developed during the early middle miocene as narrow linear reef belts with an oblique orientation with respect to shelf strike direction subsequently they prograded toward the platform margin to form a barrier reef with a minimum length of 40 km the barrier reef itself comprises three distinct ridges separated by progradational steps the second and third step are separated by a karstified horizon which is interpreted to represent the global sea level fall shortly before the serravallian tortonian boundary the following third ridge formed in a slightly downstepped position during the sea level lowstand and initial transgressive phase further sea level rise during the early tortonian first drowned the barrier reef system and subsequently also the patch reefs and relic atolls that had established in a backstepped position in the platform interior the similar evolution of the browse basin reef system and other contemporaneous carbonate systems indicates a strong impact of eustatic sea level changes relatively large subsidence rates in the study area possibly augmented the eustatic sea level rise in the tortonian and hence contributed to the drowning of the reef system however the initiation and final demise of the reef system was also governed by global and regional climate variations the first seismically defined reefs developed simultaneous to a maximum in the transport capacity of the indonesian throughflow which brings warm low salinity waters to the north west shelf reef drowning followed the restriction of this seaway close to the middle to early miocene boundary this near closure of the indonesian seaway possibly led to a regional amplification of the global middle to late miocene cooling trend and hampered the potential of the reef system to keep up with the rising sea level

the middle miocene climatic transition in the southern ocean evidence of paleoclimatic and hydrographic changes at kerguelen plateau from planktonic foraminifers and stable isotopes abstract middle miocene 14 8 11 9 ma deep sea sediments from odp hole 747a kerguelen plateau southern indian ocean contain abundant well preserved and diverse planktonic foraminiferal assemblages a detailed study of the climatic and hydrographic changes that occurred in this region during the middle miocene climatic transition led to the identification of an intense cooling phase the middle miocene shift abundance fluctuations of planktonic foraminiferal species with different paleoclimatic affinities and oxygen and carbon stable isotopes have been integrated in a multi proxy approach reconstruction of changes in foraminiferal faunal composition and diversity through time were the basis for identification of three foraminiferal biofacies the most prominent faunal change took place at 13 8 ma when a fauna with warm water affinity marked by high abundance of globorotalia miozea group and globoturborotalita woodi plexus was replaced by an oligotypic opportunistic fauna with typical polar characters and dominated by neogloboquadrinids this faunal change is interpreted as the result of foraminiferal migration from adjacent bioprovinces caused by modifications in climate and hydrography a positive 2 0 shift in 18o interpreted as the mi3 event and a related positive 1 0 shift in 13c corresponding to the cm6 event accompanied this faunal turnover these are interpreted to reflect substantial reorganization of southern ocean waters the northward migration of the polar front and a strong increase in primary productivity the second faunal change took place at 12 9 ma and was characterized by the gradual decrease in abundance of the neogloboquadrinids and the recovery of globorotalia praescitula scitula group and globigerinita glutinata a positive 1 5 shift in 18o interpreted as the mi4 event and a concurrent gradual negative shift in 13c accompanied this faunal change witnessing further modifications of the climate ocean system variations in sea surface temperature considered as the main factor causing changes of surface hydrography at the kerguelen plateau seem to have been driven by obliquity and long term eccentricity thus suggesting a key role played by the astronomical forcing on the evolution of southern ocean dynamics during the middle miocene also an evident 1 2 myr modulation of the 13c record suggests a main control of the long term obliquity cycles on the carbon cycle dynamics particularly the mi3 cm6 events exactly fit with a node of the 1 2 myr modulation cycles this confirms the key role played by orbital parameters on high latitude temperatures and antarctic ice volume and indirectly on global carbon burial and or productivity this climatic transition was marked also by changes in surface hydrography from 14 8 to 13 8 ma an intermediate strength thermocline controlled by seasonality developed just below the photic zone weaker seasonality characterized the interval from 13 8 to 12 9 ma when the thermocline became shallower and sharper and favored intermediate water foraminifers from 12 9 ma seasonality increased again and an intermediate strength thermocline re developed

oligocene and miocene carbonate platform development in the browse basin australian northwest shelf abstract extensive 2d and 3d seismic reflection data calibrated by wells provide new insights into the lateral extent morphology internal architecture and age of carbonate platforms in the subsurface of the browse basin australian northwest shelf nws the oldest carbonate build ups are interpreted as a giant bryozoan build up complex of oligocene age 34 03 27 8 ma in the late burdigalian tropical reef growth began and numerous reef rimmed carbonate platforms progressively coalesced into an extensive barrier reef from the mid langhian to the early tortonian the browse basin contained an elongate along margin barrier reef system over 500 km long this barrier reef possibly extended in the southwest into the northern carnarvon basin after the early tortonian reefs on top or landward of this major barrier reef system were smaller and less connected this significant reduction in area covered by reef rimmed platforms likely resulted from cooling following the mid miocene climate optimum and relatively high subsidence rates the reef rimmed carbonate platforms that formed between the late burdigalian and the early tortonian are very similar throughout the browse basin platform development after the early tortonian was regionally diverse high subsidence rates in the northern browse basin are interpreted to have promoted the development of thick aggrading platforms lower subsidence in the south led to thinner more widespread platforms recurrently shifting location in response to eustatic change the final phase of reef decline around 6 ma coincides with an increase in current driven drift sedimentation current related winnowing of sediments from the lagoons and slopes of the remaining carbonate platforms likely contributed to their final drowning

near fault strong motion complexity of the 2003 bam earthquake iran and low frequency ground motion simulation summary the 2003 december 26 bam earthquake was an intermediate size strike slip event that occurred beneath the bam city causing more than 26000 fatalities the record of the only near fault station bam station shows a clear long period pulse in almost fault normal direction suggesting a near fault forward directivity effect contributing to the heavy damage observed in bam city in this study the long period 0 1 1 5hz strong ground motions were simulated to answer some ambiguities in source parameters for fully description of the observed motion in different components at bam station to this end the hisada s kinematic model accounting for both heterogeneous source characteristics and underground geology is applied to simulate the long period ground motion different source scenarios suggested by previous studies are examined and the optimum scenario that could provide the best fitting between the simulated and observed motions for different components was introduced the slip model and asperities as well as velocity structure parameters are optimized in order to have the best possible fit between the simulated and observed velocity time histories and spectra the good agreements between the simulated and observed low frequency motions indicate a successful identification of source and slip parameters of the bam earthquake and provide a good test for the simulation technique furthermore the uniqueness of the identified source parameters and the slip model is further checked against the observed near and far field recordings of the bam earthquake a good agreement between the simulated and the observed waveforms provides a base for model verification and results confirmation

mid late miocene vegetation and environments in southeast china insights from a marine palynological record in northwestern taiwan abstract taiwan island represents the exposed accretionary prism developed by eastward subduction of south china sea scs oceanic lithosphere beneath the philippine sea plate since the middle miocene there are many well documented data about the biostratigraphic correlation except for palynological studies here we present a new palynological record of mid late miocene deposits from the chuhuangkeng section miaoli northwestern taiwan which reveals a vegetation and paleoelevation reconstruction in southeast china during the middle to late miocene corresponding to the time interval of about 14 5 5 5 ma most samples yielded well preserved palynomorphs and the palynological results suggest that the dominant vegetation was the mixed coniferous broadleaved forests in the coastal mountains of southeast china cmsc during the mid late miocene moreover based on large amounts of tsuga and picea pollen we hypothesized that a subalpine conifer forest then flourished in the cmsc and the estimated maximum paleoelevation might be up to 3000 m above sea level a s l during the mid late miocene being 1000 1500 m higher than today these findings offer a new perspective to comprehend the paleotopographic evolution of china and the source area of taiwan s spruce forests additionally the high abundance of pinus tsuga picea pollen and fern spores also suggests an enhancement of the easm during the mid late miocene

a review of tertiary climate changes in southern south america and the antarctic peninsula part 2 continental conditions abstract climate changes in southern south america and the antarctic peninsula during the tertiary show a strong correlation with ocean warming and cooling events which are in turn related to tectonic processes during periods of accelerated sea floor spreading and mid ocean ridge activity sea levels rose so that parts of the continents were flooded and forests were destroyed however this was balanced by the large scale release of co2 during volcanic outgassing and carbonate precipitation on the continental shelves which caused rising air temperatures and the poleward expansion of sub tropical and temperate forests cooling episodes generally caused an increase in the north south thermal gradient because of an equatorward shift in climate belts so that the westerly winds intensified and brought higher rainfall to the lower latitudes an increase in wind blown dust caused temperatures to drop further by reflecting sunlight back into space the rising andes range had a marked influence on climate patterns up to the middle miocene it was still low enough to allow summer rainfall to reach central and north central chile but after about 14 ma it rose rapidly and effectively blocked the spill over of moisture from the atlantic ocean and amazon basin at this time the cold humboldt current was also established which together with the andes helped to create the arid diagonal of southern south america stretching from the atacama desert to the dry steppes of patagonia this caused the withdrawal of subtropical forests to south central chile and the expansion of sclerophytic vegetation to central chile however at the same time it intercepted more rain from the northeast causing the effect of the south american monsoon to intensify in northwestern argentina and southern bolivia where forest communities presently occur in patagonia glaciation started as early as 10 5 ma but by 7 ma had become a prominent feature of the landscape and continued apparently uninterruptedly into the pleistocene the antarctic peninsula saw its first mountain glaciation between 45 and 41 ma with major ice sheet expansion commencing at about 34 ma isolated stands of nothofagus forests were still present in low lying areas suggesting that the glaciers were initially wet based but dry based glaciers were established at around 8 ma although temperatures rose briefly during the messinian pliocene transition causing sub antarctic flora to retreat to higher elevations of the transantarctic mountains the present cold polar conditions were finally established by about 3 ma

three dimensional simulation of the near fault ground motion for the 1995 hyogo ken nanbu kobe japan earthquake abstract the 17 january 1995 hyogo ken nanbu earthquake is a typical example showing that the ground motions along basin edge faults can be very destructive in this study we simulate the near fault ground motion from this earthquake based on a kinematic fault model and a simplified 3d velocity structure of the kobe area the kinematic earthquake rupture and the wave propagation are modeled using a 3d finite difference method fdm our simulation identifies the basin edge effect as an important factor that influenced the ground motion amplification pattern in the kobe area we found that the coupling of the source directivity and basin edge effects causes impulsive ground motions with extremely high amplitude at periods greater than 1 sec and in a narrow zone offset less than 1 km from the basin edge the combination of these effects acted to create a fairly continuous band of amplification that extends about 30 km in an elongated zone parallel to the basin edge boundary in some areas localized site effects might have been as important as the abovementioned effects but they cannot explain the continuity of the extended east west zone of damage

early pliocene closing of the indonesian seaway evidence from north east indian ocean and tropical pacific deep sea cores abstract deep sea cores from sites 214 and 758 a ninetyeast ridge north east indian ocean 761 b wombat plateau north east indian ocean and 586 b ontong java plateau tropical pacific are ideally located for comparison of late neogene planktic foraminiferal biogeography and paleoceanographic records of tropical indian and pacific oceans to infer the timing of closing of the indonesian seaway a consistent stratigraphy was developed between sites 214 and 586 b using graphic correlation and was integrated with the paleomagnetic time scale of berggren et al 1985 to provide an accurate chronology to compare interocean stratigraphic ranges of late neogene planktic foraminifera tropical planktic foraminifera occur throughout each sequence at all sites at each site the miocene pliocene boundary is defined by the first appearance of globorotalia tumida 5 2 ma the early late pliocene boundary by the first appearance of globigerinoides fistulosus 3 2 ma and the pliocene pleistocene boundary by the last appearance of g fistulosus 1 6 ma neogene planktic foraminiferal assemblages at sites 214 758a 761 b and 586b are generally similar until the beginning of the pliocene 5 2 ma when the faunal record indicates divergence a notable difference is complete absence of early pliocene taxon pulleniatina spectabilis from all the indian ocean sites this difference suggests that the indonesian seaway became an effective biogeographic barrier to planktic foraminifera at the beginning of the pliocene however there is still exchange of surface waters through this seaway earlier studies suggested a middle to late miocene occurrence for this biogeographic barrier p spectabilis evolved from p primalis in the equatorial pacific at about 5 2 ma it is a short ranging early pliocene species spanning about 1 3 my and occurred only in pacific unlike earlier suggestions of a broader distribution into the indian ocean

the 2003 bam iran earthquake rupture of a blind strike slip fault a magnitude 6 5 earthquake devastated the town of bam in southeast iran on 26 december 2003 surface displacements and decorrelation effects mapped using envisat radar data reveal that over 2 m of slip occurred at depth on a fault that had not previously been identified it is common for earthquakes to occur on blind faults which despite their name usually produce long term surface effects by which their existence may be recognised however in this case there is a complete absence of morphological features associated with the seismogenic fault that destroyed bam

source process and slip model of 2005 dahuiyeh zarand earthquake iran using inversion of near field strong motion data summary on 2005 february 22 the dahuiyeh zarand earthquake mw 6 5 struck one of the most seismically active regions in south central iran east of zarand city in kerman province causing more than 500 fatalities the causative fault of the 2005 dahuiyeh zarand earthquake a reverse fault striking nearly ew and dipping to the north was located within a mountainous region and therefore more difficult to identify compared to the range bounded faults its identification after the 2005 event is very important for both the estimation of seismic hazard as well as for the damage and fatality functions we have inverted six three component near field strong motion waveforms to obtain the complete earthquake rupture history and slip distribution accelerograms are bandpass filtered with 0 2 1 0 hz and a length of 15 17 s of the waveforms is inverted the lack of absolute timing has been successfully overcome by estimating from the velocity model of the region the propagation of p and s waves from the epicentre to the stations the final fault slip model and the estimated source parameters are able to explain the observed waveforms the rupture is found to be bilateral with a maximum slip of 2 4 m concentrated on two asperities in the west and east sides of the nucleation point at depths of 6 12 km the western asperity is located to the east of zarand city and beneath the dahuiyeh village which might explain why the dahuiyeh village was totally destroyed by this earthquake

major neogene events of the southeastern pacific the chilean and peruvian record abstract according to the biochronostratigraphic model proposed the neogene marine deposits in chile and peru represent two independent transgressive sequences alloformations separated by a major regional hiatus the earlier sequence nseps i would stretch from the top of the early miocene up to the base of the late miocene ca 19 10 m y b p the upper sequence nseps ii would correspond in turn to the late pliocene ca 3 5 1 6 m y b p the regional hiatus separating both sequences would encompass the late miocene and the early pliocene ca 10 3 5 m y b p the planktonic foraminiferal events described suggest an age of terminal early miocene middle miocene and late pliocene respectively the paleoclimatic events recorded are three a warming event lasting from the terminal early miocene to the end of the middle miocene mmwe 18 11 5 m y b p a cooling event of the middle late pliocene lpce 2 5 0 2 m y b p and warming event spanning most of the late pliocene lpwe 3 5 2 2 m y b p restricted to the surface and intermediate sea waters of the middle and low latitudes the last paleoclimatic event not recorded as such so far is both synchronous and mutually exclusive in latitudinal terms with the second one three tectonic regional events are analyzed the quechuan 1 phase 19 1 5 m y b p the quechuan 2 phase 10 1 m y b p and the geographic rhodanian phase 3 5 0 5 m y b p in the studied area there is no late miocene marine sedimentary record to confirm the terminal tortonian or quechuan 3 tectonic phase ca 7 m y b p admitted to occur in the volcanoclastic continental sequences of northern chile and southern peru