metallogenesis at paleo spreading centers lead isotopes in sulfides rocks and sediments from the troodos ophiolite cyprus abstract new pb isotopic data for metalliferous deposits and pelagic sediments from the troodos ophiolite complex cyprus are presented we use these data to re evaluate the genetic models for these deposits in the light of recent results obtained for different types of hydrothermal sites presently active on spreading ridges in contrast to previous conclusions of earlier studies we find that the troodos hydrothermal deposits sulfides as well as umbers and mn crusts have isotopic compositions very similar to that of most of the rocks from this ophiolite complex they display a 207 pb 204 pb ratio higher than present day typical ridges this result has been interpreted as evidence for a subduction related origin of the troodos ophiolite this different geodynamic setting of the ophiolite is also the reason for the isotopic difference between troodos and semail oman sulfides the latter being typical of a normal oceanic crust when examined in more detail the troodos sulfide results are very homogeneous within one site but show significant differences from one site to another at least three different isotopic end members are required to interpret these variations one of these end members is found in the pelagic sediments data analyzed here which have a 207 pb 204 pb typical of continental crust signature higher than that of the rocks and sulfides on present ridges the involvement of such a component has been similarly described for the guaymas basin and for the gorda rise deposits however some of the isotopic variations observed between sulfides cannot be interpreted only by this end member one possibility is that a second sedimentary component as yet unidentified has been involved in the hydrothermal circulation as recently demonstrated for red sea brines finally the determination of the exact proportion of pb leached out of the ophiolite basaltic crust itself would require a more complete knowledge of the initial isotopic heterogeneities within the massif indeed several rock results are significantly less radiogenic than those of the sulfides which however show themselves initial compositions this could result either from a sediment contribution to the sulfide pb or from a biased sampling of the massif heterogeneities this question remains open in the present state of the data

nonlinear soil response of a borehole station based on one dimensional inversion during the 2005 fukuoka prefecture western offshore earthquake the objective of this article is to present the nonlinear response of a soft sedimentary site based on a one dimensional inversion by a genetic algorithm of the shear wave velocity structure and damping factors of a borehole soil column during the 2005 fukuoka prefecture western offshore earthquake first we confirm that according to the source rupture mechanism the major and minor axes in the horizontal plane at the borehole station are the transverse and radial directions respectively then in order to corroborate in the linear domain the s wave transfer function of the borehole s logging we perform time dependent spectral ratios analyses on small aftershocks finally we show qualitative evidence of nonlinearity during the main shock associated with a significant shift toward low frequencies of several resonant modes and we evaluate the degree of nonlinearity by inverting the shear wave veloc ity structure and damping factors because of a directional effect present only in the major axis around 8 hz which prevents the use of the conventional objective function that minimizes the integrated residuals between observed and theoretical ratios we introduce a simple objective function that depends only on peaks frequency and amplitude the efficiency of the objective function and the robustness of the inversion are shown by performing eight independent inversions converging to very similar minima

unraveling the evolution of chondrite parent asteroids by precise u pb dating and thermal modeling u th pb isotopic data are reported for mineral fractions individual chondrules and fractions of chondrule fragments from the equilibrated ordinary chondrite richardton h5 chondrules and milligram sized fractions of pyroxene rich chondrule fragments contain highly radiogenic pb and concordant or nearly concordant u th pb isotopic systems and are suitable for precise pb pb age determinations olivine and sulfide have low u concentrations and contain less radiogenic pb the ages of individual chondrules pyroxene rich and phosphate fractions are determined using u pb and pb pb isochron and model date calculations the pb pb isochron date of 4562 7 1 7 ma of the richardton chondrules and chondrule fragments is resolved from the pb pb isochron date of 4550 7 2 6 ma obtained from multiple phosphate fractions possible biases of the isochron dates due to single stage approximation of multi stage evolution contamination with modern common pb and disturbance to the system by reheating are examined and are found to be insignificant the chondrule and phosphate dates are interpreted as the timing of cessation of pb diffusion during cooling following metamorphism in chondrite parent bodies the difference in estimated closure temperatures 950 1150 k for pyroxenes and 700 800 k for phosphates temperature estimates are based on published diffusion rates for pb in pyroxenes and apatite allows evaluation of the average cooling rate at 26 13 k million years for the richardton parent body over the period of 4563 4551 my thermal modeling of the h chondrite parent body which is assumed to be asteroid 6 hebe heated by decay of 26al suggests a scenario in which accretion initiated at 1 7 m y after formation of calcium aluminum rich inclusions and continued for 3 5 m y

the age and emplacement of obducted oceanic crust in the urals from smnd and rbsr systematics the urals contain a 2000 km belt of mafic ultramafic bodies the sm nd and rb sr systematics of two of these bodies the kempersai massif in the south ural mountains and the voykar syninsky ophiolite complex in the polar ural mountains have been examined these data confirm the hypothesis that these bodies represent fragments of pre collision oceanic crust and establish constraints on the nature and timing of events in the uralian orogeny two kempersai gabbros define sm nd internal isochrons of 397 20 my and 396 33 my with e nd t 8 7 0 6 and 8 4 1 3 respectively whole rock samples of pillow basalt diabase gabbros troctolite and a metasediment give sm nd values which lie on this isochron indicating that these rocks are genetically related and have an igneous crystallization age of 397 my whole rock samples of voykar syninsky diabase gabbros and clinopyroxenite give sm nd values which lie on or within 1 e unit of this isochron indicating an age and e nd t virtually identical to those of kempersai e nd t for the kempersai and voykar syninsky mafic samples range from 7 3 to 9 0 with an average value of 8 4 this indicates that the urals ophiolites are derived from an ancient depleted mantle source and are most plausibly pieces of the oceanic crust and lithosphere the fact that a metasediment has the same e nd 397 my as the other samples indicates derivation from an oceanic source with negligible continental input e nd t for the massifs is 1 5 e units lower than the average for modern morbs this may be due to the differential evolution of the morb source over the past 397 my and in conjunction with data for other ophiolites and mesozoic morb suggests that over the past 750 my the source for morb has evolved at a rate less than or equal to its rate of evolution averaged over the age of the earth initial 87 sr 86 sr ratios are highly variable ranging from e sr t 25 2 for a gabbro to 70 3 for a highly serpentinized harzburgite this reflects the effects of seawater alteration which is particularly strong on ultrabasic rocks we conclude that the long belt of mafic ultramafic rocks in the urals which includes the kempersai and voykar syninsky massifs represents segments of siluro devonian oceanic crust our igneous age for kempersai in conjunction with other age constraints suggest that these segments of oceanic crust formed at least 80 my before the collision that produced the urals

temporal changes of subsurface velocities during strong shaking as seen from seismic interferometry 1 we apply a deconvolution method to a strong motion data set recorded at the surface and in boreholes in northeast honshu japan we try to characterize the nonlinear effects of the subsurface soil during strong shaking and show the change of the subsurface velocity structure during the shaking the deconvolved waveforms reflect the subsurface velocity structure and their horizontal and vertical components correspond to s and p wave respectively traveling from the borehole to the ground surface the strong motion records with smaller values of peak acceleration do not include significant nonlinear effects so the deconvolved waveforms of the observed accelerations can be well simulated by the program shake91 for high acceleration motions during the shaking of two separate earthquakes large reductions of near surface velocities are seen in results for the 2008 iwate miyagi nairiku earthquake the large high frequency ground motions over 4g at one near source station caused a nonlinear response of the soil and the reduction of the average shear wave velocity reached 24 this corresponds to a stiffness change of over 75 the soil properties and the stiffness coefficient which changed during the shaking did not fully recover after the shaking leaving a static change

identification of the non linear behaviour of liquefied and non liquefied soils during the 1995 kobe earthquake summary a method based on the non linear system identification technique is suggested for estimating the contents of the non linear components which are the result of quadratic cubic and higherorder non linearities in the ground response during the strong motion the method is applied to data from the near fault zone of the 1995 kobe earthquake and the contents of linear and non linear components in the ground response changing with time during the strong motion are estimated for port island pi sgk and tks sites located at 2 6 and 15 km from the fault plane respectively at pi the non linear part of the response increased with developing liquefaction it was as high as 40 60 per cent of the intensity of the response at sgk and tks sites the non linear components of the response did not exceed 40 and 13 per cent of the intensity of the response respectively odd order non linear components predominated in the soil response whereas even order non linear components increased and became comparable with odd order ones in liquefied soils and in cases of high intensity of the strong motion when the loading parts of the stress strain relations of the upper layers gained noticeable even components as a whole the contents of odd order and even order components in the soil response are determined by the shapes of the stress strain relations in the upper most non linear soil layers at the three sites changes in spectra of earthquake signals in subsurface soil layers were substantial as a result of the high non linearity of the soil behaviour and spectra of signals on the surface tend to take the form of e f f k the limiting spectral shape was achieved during the kobe earthquake at pi and sgk sites the proposed methods for processing vertical array records allow understanding of seismic wave transformations in subsurface soils and are useful for predicting the soil behaviour during future earthquakes

nonlinear soil behavior examined on the basis of propagation time observed at the kik net ichinoseki nishi vertical array abstract the iwate miyagi nairiku earthquake 14 june 2008 m 7 2 depth 8 km caused severe damage in the southern part of iwate and the northern part of miyagi prefectures in japan the kik net ichinoseki nishi vertical array site iwth25 operated by the national research institute for earth science and disaster prevention nied is situated near the epicenter the observed peak ground accelerations at the surface in the up down east west and north south directions were respectively 3866 cm s 2 1432 cm s 2 and 1143 cm s 2 the extreme ground motions recorded at this site provide valuable information about the wave propagation and soil degradation at a large strain level we examined the nonlinear soil behavior at the site due to the earthquake on the basis of normalized input output minimization niom analysis first we analyzed 279 records observed before the iwate miyagi nairiku earthquake and estimated the vertical propagation time initial value between the bottom of the well and the ground surface by taking into account incidence angles then we analyzed the records of the iwate miyagi nairiku earthquake and 179 events that occurred after it from 14 june 2008 to 19 october 2009 the results revealed that 1 the s wave propagation time increased from 0 265 s to about 0 35 s because of the nonlinear behavior of the soil 2 this propagation time change corresponded to a 60 reduction in the shear moduli of the upper soil layers surface to 64 m depth and a strain level of 1 10 3 3 a gradual decrease in the propagation time with decreasing seismic intensity was observed soon after the principal motions however 4 the propagation times in the coda part and for the events after the iwate miyagi nairiku earthquake were still larger than the initial value indicating that the shear rigidities of soils remained less than their values before the earthquake for more than a year

quantification of cyclic mobility parameters in liquefiable soils from inversion of vertical array records abstract high frequency acceleration pulses recorded during recent damaging earthquakes show that the evolution of pore water pressure in liquefiable soils may have a significant effect on earthquake ground motions such observations suggest that advanced constitutive soil models capable of treating the phase transformation behavior of liquefiable soils should be used for reliable predictions of earthquake site response advanced constitutive models require knowledge of the dilatancy parameters that describe the potential of soils to generate excess pore water pressure we demonstrate that these dilatancy parameters can be determined directly from field observations by inverting strong motions recorded on vertical arrays i e installation of surface and borehole accelerometers we analyze the records of the 1987 m 6 6 superstition hills earthquake the 1993 m 7 8 kushiro oki japan earthquake and the 2011 m 9 0 tohoku japan earthquake to quantify the dilatancy parameters at the wildlife liquefaction array wla at kushiro port kp and the kik net site fksh14 respectively synthetic acceleration time series obtained from the minimum misfit models are describing the time and frequency evolution of the observations more precisely than previously published models dilatancy parameters obtained for wla and kp suggest that soils at these sites were more resistant to liquefaction than predicted from field and laboratory tests we also infer a high liquefaction resistance crr 7 5 0 5 for the site fksh14 which exhibited dilation pulses of up to during the tohoku earthquake these findings indicate that even soils with a strong liquefaction resistance may exhibit cyclic mobility effects during strong and prolonged ground motions

nonlinear ground motion amplification by sediments during the 1994 northridge earthquake it has been known since at least 1898 ref 1 that sediments can amplify earthquake ground motion relative to bedrock for the weak ground motion accompanying small earthquakes the amplification due to sediments is well understood in terms of linear elasticity hooke s law 2 but there has been a long standing debate regarding the amplification associated with the strong ground motion produced by large earthquakes the view of geotechnical engineers based largely on laboratory studies is that hooke s law breaks down at larger strains causing a reduced nonlinear amplification seismologists on the other hand have tended to remain sceptical of this nonlinear effect mainly because the relatively few strong motion observations seemed to be consistent with linear elasticity although some recent earthquake studies have demonstrated nonlinear behaviour under certain circumstances3 4 the significance of nonlinearity for the type of stiff soil sites found in the greater los angeles region remains unresolved5 here we report that ground motion amplification due to sediments for the main shock of the 1994 northridge earthquake was up to a factor of two less than the amplification observed for its aftershocks these observations imply significant nonlinearity in such amplification and bring into question the use of measurements of weak ground motion to predict the strong ground motion at sedimentary sites

precambrian ophiolite belts of southern siberia russia and their metallogeny abstract greenstone and ophiolite belts of different ages in southern siberia are compared the archaean olondo greenstone belt 3 0 2 9 ga within the aldan shield is different from younger ophiolite belts the early proterozoic baikal muya ophiolite belt 1 9 ga containing both komatiites and a complete ophiolitic sequence of the tholeiite series and the late proterozoic early cambrian 0 6 0 52 ga kurtushibin and ilchir ophiolite belts in western and eastern sayan are fairly comparable with young ophiolites and modern crust of oceanic type in the olondo greenstone belt there are komatiite and tholeiite series that are represented by both volcanic rocks and differentiated sills but no dyke complex is present in the baikal muya ophiolite belt there are metavolcanic rocks including komatiites and komatiitic basalts a dyke complex upper cumulate gabbros and lower metaperidotites ophiolites of the kurtushibin belt in the western sayan and ilchir belt in eastern sayan are examples of complete ophiolitic sequences with long and complicated evolution histories including development of a marianite boninite series of primitive island arc type asbestos chromite fe ti oxide polymetallic and gold deposits occurring precambrian ophiolites are briefly described when ophiolites appeared about 2 0 1 9 ga ago cr ni cu and asbestos were concentrated within them the composition of ophiolites and associated ores changed significantly with time a change in upper mantle convection may be the key to the magmatic and metallogenic evolution

geochronological constraints on the emplacement history of an anorthosite rapakivi granite suite u pb zircon and baddeleyite study of the korosten complex ukraine u pb zircon baddeleyite ages obtained for the korosten anorthosite rapakivi granite complex ukrainian shield suggest that different magmatic phases were emplaced during a period of ca 30 million years as a series of distinct igneous episodes the earliest 1789 1 2 0 ma anorthosites were followed by 1781 3 3 2 ma dykes of plagiogranite porphyries the emplacement of a major rapakivi granite phase took place at 1767 4 2 2 ma and was followed by emplacement of layered intrusions of anorthosites gabbronorites diabases and ultrabasic rocks between 1761 and 1758 ma the minimum duration of magmatism of about 30 million years the 6 15 million years interval between igneous pulses and alternation of discrete episodes of basic and felsie magmatism are common features of major anorthositemangerite charnockite rapakivi granite complexes temporal distribution of igneous activity in the korosten complex shows that the gabbro anorthosites and the granites are not comagmatic although they are possibly cogenetic and that at least four portions of granitic and basic magmas were generated during a relatively long period of at least 30 million years the time gap of about 20 25 million years between early basic and later and more voluminous granitic magmatism characteristic of the korosten pluton wiborg and salmi batholiths probably reflects the duration of extensional processes before the generation of large volumes of magma in the lower crust

time lapse changes of seismic velocity in the shallow ground caused by strong ground motion shock of the 2000 western tottori earthquake japan as revealed from coda deconvolution analysis abstract a large earthquake shock often drops the seismic velocity of the shallow ground however it is not clear whether the dropped velocity recovers shortly after the earthquake shock or not the purpose of this article is to report the time lapse changes of seismic velocity in the shallow ground after the 2000 western tottori earthquake japan we deconvolve the coda record of small earthquakes registered on the ground surface by that registered at the 100 m depth in a borehole at a station that experienced a strong shock from the mainshock because coda waves are mostly composed of randomly scattered s waves deconvolution of the two coda records enables us to obtain a robust image of the ground structure assuming that the shear modulus was reduced at the depth of 0 11 m we estimate the shear modulus change in each time period after the mainshock by fitting synthetic coda deconvolution to the observed one from 1 to 16 hz as a result the shear modulus dropped to 52 of the value obtained before the mainshock a few minutes after the strong earthquake shock this caused a decrease in the s wave velocity of 30 and an increase in s wave travel time of 17 msec the shear modulus continued to recover for over 1 yr following the logarithm of the lapse time it recovered to 69 83 87 and 97 of the value obtained before the mainshock in the periods of 0 to 1 week 1 week to 1 month 1 month to 1 yr and 1 to 4 yr after the mainshock respectively

lead isotopic study of the xigaze ophiolite tibet the problem of the relationship between magmatites gabbros dolerites lavas and tectonites harzburgites abstract the pb isotopic study of the xigaze ophiolite tibet shows that the tectonic harzburgites and magmatic gabbros dolerites lavas units bear different isotopic signatures the harzburgitic rocks show much higher207pb 204pb values than the samples from the magmatic unit analyses of primary magmatic clinopyroxenes separated from the harzburgites confirmed that this difference is real and not due to secondary alteration processes u pb analysis allowed determination of the crystallization age of the magmatites at 120 10 m y this age is compatible with paleontological age determinations and thus demonstrates that u pb behaved more or less as a closed system since formation of the ophiolite if an exchange with seawater has occurred it must necessarily have happened shortly after crystallization of the xigaze oceanic crust dolerite dykes crossing the harzburgites show similar pb isotopic composition as the magmatites indicating that they were emplaced when the ultramafic rocks were already brittle however the time difference of the emplacement was probably not larger than 280 m y this makes it evident that two sources with different isotopic signatures one similar to normal morb the other with much higher207pb 204pb ratios were active in the immediate neighborhood one possible environment which can account for this association is a propagating ridge

the petrochemistry of ophiolite gabbroic complexes a key for the classification of ophiolites into low ti and high ti types ophiolites have been divided into two groups high ti and low ti types these can be discriminated by studying the fractionation trends of both gabbroic complexes this work and lavas and dykes 16 particularly in the tio2 m i diagram the first type typically shows morb like magmas whereas in the second the magma types have a spectrum of composition from mid ocean ridge basalts to island arc tholeiites and boninite like magmas often occur high ti ophiolites are petrologically and geochemically similar to major oceanic and ensialic back arc basin crusts as well as oceanic crust generated during the intermediate and late stage opening of intraoceanic back arc basins parental magmas and fractionation processes of low ti ophiolites fit with an hypothesis of their formation in the early stage of opening of intraoceanic back arc basins

nd sr pb systematics and age of the kings river ophiolite california implications for depleted mantle evolution sm nd whole rock and mineral data for the kings river ophiolite define two isochrons of 485 21 ma and 285 45 ma age with end 483 10 7 0 5 and end 285 9 9 1 1 respectively the 483 ma isochron is defined by samples of the main igneous construct samples from crosscutting diabase dikes and flaser gabbro sheets within the peridotite unit yield the 285 ma isochron the 483 ma data provide the first evidence of lower paleozoic oceanic crust in the sierran ophiolite belt new u pb analyses of zircons from a plagiogranite lying on the 483 ma sm nd isochron yield upper and lower intercepts with the concordia of 430 60 200 and 183 15 ma published zircon ages have underestimated the primary age of the ophiolite by 200 300 m y due to the effects of polymetamorphism the 483 ma samples have initial 87sr 86sr 0 7023 0 7030 206pb 204pb 17 14 17 82 207pb 204pb 15 37 15 52 208pb 204pb 36 80 37 38 the 285 ma samples have similar initial 87sr 86sr but more radiogenic pb the range in sr and pb compositions is probably due to introduction of radiogenic sr and pb during multiple post emplacement metamorphic events the high end low 87sr 86sr 206pb 204pb 207pb 204pb 208pb 204pb of the least disturbed samples are clearly diagnostic of a midocean ridge origin for the 483 ma portion of the ophiolite igneous activity at 285 ma is thought to have occurred in an arc or back arc setting or perhaps along a leaky transform the initial end 483 10 7 is indistinguishable from that of the similar age trinity peridotite jacobsen et al 1984 this value is the highest yet reported for the mesozoic or paleozoic depleted mantle and requires either a mantle source that was depleted 850 m y earlier than average or a source more highly depleted than average alternatively if such values were more typical of the early paleozoic mantle than is currently thought then there has been little evolution of the depleted mantle over the last 500 m y this requires that the modern mantle has been refluxed by material with low end such as continental crust

simulation of ground motion from strong earthquakes of kamchatka region 1992 1993 at rock and soil sites to estimate the parameters of ground motion in future strong earthquakes characteristics of radiation and propagation of seismic waves in the kamchatka region were studied regional parameters of radiation and propagation of seismic waves were estimated by comparing simulations of earthquake records with data recorded by stations of the kamchatka strong motion network acceleration time histories of strong earthquakes mw 6 8 7 5 depths 45 55 km that occurred near the eastern coast of kamchatka in 1992 1993 were simulated at rock and soil stations located at epicentral distances of 67 195 km in these calculations the source spectra and the estimates of frequency dependent attenuation and geometrical spreading obtained earlier for kamchatka were used the local seismic wave amplification was estimated based on shallow geophysical site investigations and deep crustal seismic explorations and parameters defining the shapes of the waveforms the duration etc were selected showing the best fit to the observations the estimated parameters of radiation and propagation of seismic waves describe all the studied earthquakes well based on the waveforms of the acceleration time histories models of slip distribution over the fault planes were constructed for the studied earthquakes station pet can be considered as a reference rock station having the minimum site effects the intensity of ground motion at the other studied stations was higher than at pet due to the soil response or other effects primarily topographic ones at soil stations ins aer and dch the parameters of soil profiles homogeneous pyroclastic deposits were estimated and nonlinear models of their behavior in the strong motion were constructed the obtained parameters of radiation and propagation of seismic waves and models of soil behavior can be used for forecasting ground motion in future strong earthquakes in kamchatka

estimation of nonlinear time dependent soil behavior in strong ground motion based on vertical array data to improve our understanding of nonlinear elastic properties of soils a method is proposed of estimation of stress strain relations of soils in situ in strong ground motion based on vertical array data strong motion records provided by seismic vertical arrays allow estimation of nonlinear stress strain relations in soil layers at different depths from the surface down to the location of the deepest device as an example records obtained during the main shock of the 1995 kobe earthquake at port island sgk and tks sites were used to estimate the stress strain relations in the soil profiles for different layers different types of nonlinear stress strain relations were selected according to the profiling data to account for temporal changes in the soil behavior consecutive parts of records were examined and for successive time intervals the relations were found showing the best fit approximation to the observed data at port island and sgk sites where the strongest accelerations were recorded the obtained stress strain relations showed systematic changes in the upper layers 0 14 m such as a progressive reduction of the slopes of the stress strain curves due to liquefaction at port island and reduction and recovery of the slopes at sgk and tks sites at the three sites the stress strain relations remained stable in layers below 11 14 m thus the proposed approach gives us a representation of the soil behavior in layers at different depths in strong ground motion it allows calculation of the propagation of arbitrary seismic signals in the studied profiles and estimation of nonlinear components in the ground response by the nonlinear system identification technique the method can also be applied to evaluate the ground response at sites where profiling data are available and an imposed motion can be estimated

bay of islands and little port complexes revisited age geochemical and isotopic evidence confirm suprasubduction zone origin the bay of islands complex of the humber arm allochthon west newfoundland contains the best exposed ophiolite in the appalachian orogen associated structural slices the little port and skinner cove complexes also contain rocks formed in an oceanic domain although their relationship to the bay of islands complex remains controversial to constrain the origin of the complexes and obtain a better understanding of the geology of the humber arm allochthon we have undertaken an integrated geochronological geochemical and isotopic study a u pb zircon age of ma for the little port complex and a zircon and baddeleyite age of 484 5 ma for the bay of islands complex have been obtained geochemical and isotopic data on trondhjemitic rocks from the two complexes indicate that petrogenetic models for these rocks must account for fundamental differences in source materials and mineralogy during differentiation the little port complex trondhjemites are characterized by initial end of 1 to 1 whereas those

effects of interaction between ultramafic tectonite and mafic magma on nd pb sr isotopic systems in the neoproterozoic chaya massif baikal muya ophiolite belt sm nd rb sr and u pb isotopic systems have been studied in minerals and whole rocks of harzburgites and mafic cumulates from the chaya massif baikal muya ophiolite belt eastern siberia in order to determine the relationship between mantle ultramafic and crustal mafic sections geological relations in the chaya massif indicate that the mafic magmas were emplaced into and interacted with older solid peridotite hand picked acid leached primary rock forming and accessory minerals olivine orthopyroxene clinopyroxene and plagioclase from the two harzburgite samples show coherent behavior and yield147sm 144nd 143nd 144nd and238u 204pb 206pb 204pb mineral isochrons corresponding to ages of 640 58 ma 95 confidence level and 620 71 ma respectively these values are indistinguishable from the crystallization age of the chaya mafic units of 627 25 ma a weighted average of internal isochron sm nd ages of four mafic cumulates the rb sr and sm nd isotopic systems in the harzburgite whole rock samples were disturbed by hydrothermal alteration these alteration related isotopic shifts mimic the trend of variations in primary isotopic compositions in the mafic sequence thus emphasizing that isotopic data for ultramafic rocks should be interpreted with great caution on the basis of initial sr and nd values ultramafic and mafic rocks of the chaya massif can be divided into two groups 1 harzburgites and the lower mafic unit gabbronorites withend 6 6 to 7 1 andesr 11 to 16 and 2 websterite of the lower unit and gabbronorites of the upper mafic unit end 4 6 to 6 1 andesr 8 to 9 initial pb isotopic ratios are identical in all rocks studied with mean values of206pb 204pb 16 994 0 023 and207pb 204pb 15 363 0 015 the similarity of ages and initial isotopic ratios within the first group indicates that the isotopic systems in the pre existing depleted peridotite were reset by extensive interaction with basaltic magma during formation of the mafic crustal sequence the isotopic data agree with a hypothesized formation of the chaya massif in a suprasubduction zone environment

the fate of rodinia in the light of the discovery of ca 1000 ma old ophiolites in the central asian orogenic belt of siberia

nonlinear soil behavior at the kashiwazaki kariwa nuclear power plant during the niigata chuetsu oki earthquake july 16 2007 records of the niigata chuetsu oki earthquake july 16 2007 mw 6 6 depth 17 km and its aftershocks from seismic vertical arrays deployed at the territory of the kashiwazaki kariwa nuclear power plant 15 km from the fault are used to study the soil behavior down to 250 m during strong ground motion nonlinear models of soil behavior during the main shock and six aftershocks are constructed and stresses and strains induced by the strong motion in the soil layers at various depths are estimated the data are processed using the method developed by pavlenko and irikura bull seismol soc am 96 6 2131 2145 2003 and previously applied for studying the soil behavior in near fault zones during the 1995 kobe and 2000 tottori earthquakes a rather good agreement between the recorded and simulated acceleration time histories testifies to the validity of the obtained vertical distributions of stresses and strains in soil layers in the upper softer layers 45 m at the territory of the plant the shear moduli were reduced by 30 35 during the main shock and by 1 5 3 during the aftershocks the constructed models of soil behavior can be used in scenario earthquake shaking maps of japan where based on source modeling parameters the level of strong motion can be evaluated for the territory of the power plant in future earthquakes with various magnitudes and fault planes using methods of stochastic finite fault modeling of ground motions from the chuetsu oki earthquake we estimated input motion to the soil layers during the main shock and found that it differs from the imposed motion recorded by the deepest sensor of the vertical array by slightly decreased by a factor of 1 2 low frequency f 10 hz spectral components

a wavelet based seismogram inversion algorithm for the in situ characterization of nonlinear soil behavior we present a full waveform inversion algorithm of downhole array seismogram recordings that can be used to estimate the inelastic soil behavior in situ during earthquake ground motion for this purpose we first develop a new hysteretic scheme that improves upon existing nonlinear site response models by allowing adjustment of the width and length of the hysteresis loop for a relatively small number of soil parameters the constitutive law is formulated to approximate the response of saturated cohesive materials and does not account for volumetric changes due to shear leading to pore pressure development and potential liquefaction we implement the soil model in the forward operator of the inversion and evaluate the constitutive parameters that maximize the cross correlation between site response predictions and observations on ground surface the objective function is defined in the wavelet domain which allows equal weight to be assigned across all frequency bands of the non stationary signal we evaluate the convergence rate and robustness of the proposed scheme for noise free and noise contaminated data and illustrate good performance of the inversion for signal to noise ratios as low as 3 we finally employ the proposed scheme to downhole array data and show that results compare very well with published data on generic soil conditions and previous geotechnical investigation studies at the array site by assuming a realistic hysteretic model and estimating the constitutive soil parameters the proposed inversion accounts for the instantaneous adjustment of soil response to the level and strain and load path during transient loading and allows results to be used in predictions of nonlinear site effects during future events

nonlinear soil amplification its corroboration in taiwan nonlinear ground response at two strong motion arrays in taiwan is studied using the spectral ratio technique at the smart1 array we calculate the frequency dependent soil amplification functions as a ratio of the spectra at alluvium to rock sites and study their dependence on the excitation level hor izontal components of shear waves are considered we compare 1 the average spectral ratios on weak and strong motions 2 the ratios for the mainshocks and aftershocks and 3 the ratios for the strong shear waves and their coda at the smart1 array weak motions have a peak horizontal acceleration pha less than 30 gal strong motions are in the range of 100 to 267 gal comparison of the average weak and strong motion spectral ratios shows a significant deamplification of strong motion between 2 and 9 hz exceeding the error margin estimated by the standard deviations the maximum deamplifi cation occurs at approximately 6 5 hz where the average weak motion ampli fication is 2 9 versus 0 40 in the strong motion a similar pattern is exhibited by the ratios calculated for the mainshocks and the aftershocks as well as for the shear waves and their coda the spectral ratio calculated from a single re alization of coda is identical to the average ratio obtained from many small earthquakes at the smart2 we analyze spectral ratios between the stations on pleistocene terrace deposits and recent alluvium which characterize the rel ative response at these two types of sediments weak motion is pha less than 13 gal while strong motion extends from 100 to 295 gal strong motion spec tral ratios between terrace and alluvial sites are consistently reduced in the fre quency range from 1 to 10 hz compared with the weak motion this effect is insensitive to the variation in distance between stations from 7 9 to 11 4 km as well as the azimuthal change of up to 80 in the station pair strike we attribute the observed discrepancies between weak and strong motion ampli fications to the differential nonlinear response occurring at terrace and alluvial sites our results document a significant nonlinear ground response at both ar rays

a nd and sr isotopic study of the trinity peridotite implications for mantle evolution field evidence indicates that the trinity peridotite was partially melted during its rise as a part of the upwelling convecting mantle at a spreading center a sm nd mineral isochron for a plagioclase lherzolite yields an age t 427 32 ma and initial e nd 10 4 0 4 which is distinctly higher than that expected for typical depleted mantle at this time this age is interpreted as the time of crystallization of trapped melt in the plagioclase lherzolite p t field this time of crystallization probably represents the time when the massif was incorporated as a part of the oceanic lithosphere the sm nd model age of the plagioclase lherzolite total rock is t chur nd 3 4 ae this suggests that the trinity peridotite was derived from a mantle that was depleted rather early in earth history the peridotite contains many generations of pyroxenite dikes and some microgabbro dikes we report data for two dikes that clearly crosscut the main metamorphic fabric of the peridotite a microgabbro dike yields a sm nd mineral isochron age of t 435 21 ma and e nd 6 7 0 3 a pyroxenite dike yields an initial e nd 7 3 0 4 the initial e nd values for the pyroxenite and gabbro dikes are fairly similar to those for the depleted mantle at this time and are distinct from the lherzolite demonstrating that they are not genetically related rb sr data do not give any coherent pattern however some bounds can be put on initial sr values of e sr 21 for the plagioclase lherzolite and e sr 8 7 for the microgabbro dike it is plausible that the dikes represent cumulates left behind from island arc magmas that rose through the the oceanic lithosphere within the vicinity of a subduction zone major and trace elements and sm nd isotopic data indicate a multiple stage history for the trinity peridotite a small melt fraction was extracted from an undepleted source 3 4 ae or more ago to produce the proto lherzolite a large fraction of melt 12 to 23 was extracted from the proto lherzolite to produce the present rock the lherzolite was then crosscut by dikes from average depleted mantle 0 44 ae ago the data are compatible with the depleted mantle source being formed very early in earth history although most available data indicate that the depleted upper mantle has been relatively well stirred through time the trinity data suggest that very ancient nd isotopic values are preserved and thus chemical and physical heteorgeneities are sometimes preserved in the depleted source of mid ocean ridge basalts as well as the oceanic lithosphere which they intrude

assimilation of peridotite in zoned calc alkaline plutonic complexes evidence from the big jim complex washington cascades the big jim complex is a concentrically zoned ultramafic to felsic plutonic complex which intruded the pelitic chiwaukum schist most of the major plutonic rock types from websterite through hornblendite gabbronorite hornblende gabbro and diorite to granodiorite enclose harzburgite and metaperidotite xenoliths similar to foliated metaperidotite lenses included in the chiwaukum schist the larger xenoliths preserve tectonite fabrics all have mg s mole fraction mgo mgo feo from 0 90 to 0 89 the same as those of chiwaukum metaperidotites and distinctly different from undeformed big jim dunite mg s 0 84 to 0 82 and websterite 0 82 to 0 78 contact relations indicate widespread stepwise replacement of harzburgite by pyroxenite hornblendite gabbro and diorite thermodynamic modelling using an expanded regular solution model for silicate liquids ghiorso 1985 ghiorso and carmichael 1985 predicts that reaction between olivine fo90 and a liquid with the composition of big jim diorite 1 5 wt h2o at 1 100 c and 3 kb would produce websterite mg s 0 75 to 0 81 and dunite 0 79 to 0 82 this process is exothermic and results in a negative change in volume since it increases total solid mass under conditions of decreasing temperature modelled crystal fractionation with assimilation of olivine reproduces important features of the chemical variation observed in the big jim complex where crystal fractionation alone fails the big jim complex has affinities with other ultramafic to felsic plutonic complexes such as the bear mountain complex snoke et al 1981 1982 and the emigrant gap complex james 1971 the latter have wehrlite and clinopyroxenite rather than websterite but both have concentric zoning with olivine bearing rock types surrounded by successively more felsic pyroxenite gabbro and diorite in general concentrically zoned complexes of this type may form where magma reacts with mantle derived wall rock or ultramafic cumulates assimilation of peridotite in fractionating magma may be important in subduction related magmatic arcs

nd sr isotopic study of primitive lavas from the troodos ophiolite cyprus evidence for a subduction related setting primitive lavas from the troodos ophiolite have a large variation in initial 143 nd 144 nd ratios from nd 7 9 to 0 8 which precludes a mid ocean ridge origin initial 87 sr 86 sr ratios vary from 0 70415 to 0 70705 the range of nd values may be accounted for by a two component mixing model whereby variable amounts of a light rare earth element ree enriched component with nd between 5 and 7 has interacted with a depleted iherzolite source with nd 8 this is consistent with an arc related setting where fluids derived from a subducting slab induce further melting in an overlying iherzolite source

spectral element modelling of seismic wave propagation in visco elastoplastic media including excess pore pressure development numerical modelling of seismic wave propagation considering soil nonlinearity has become a major topic in seismic hazard studies when strong shaking is involved under particular soil conditions indeed when strong ground motion propagates in saturated soils pore pressure is another important parameter to take into account when successive phases of contractive and dilatant soil behaviour are expected here we model 1 d seismic wave propagation in linear and nonlinear media using the spectral element numerical method the study uses a three component 3c nonlinear rheology and includes pore pressure excess the 1 d 3c model is used to study the 1987 superstition hills earthquake ml 6 6 which was recorded at the wildlife refuge liquefaction array usa the data of this event present strong soil nonlinearity involving pore pressure effects the ground motion is numerically modelled for different assumptions on soil rheology and input motion 1c versus 3c using the recorded borehole signals as input motion the computed acceleration time histories show low frequency amplification and strong high frequency damping due to the development of pore pressure in one of the soil layers furthermore the soil is found to be more nonlinear and more dilatant under triaxial loading compared to the classical 1c analysis and significant differences in surface displacements are observed between the 1c and 3c approaches this study contributes to identify and understand the dominant phenomena occurring in superficial layers depending on local soil properties and input motions conditions relevant for site specific studies

changes in shear moduli of liquefied and nonliquefied soils during the 1995 kobe earthquake and its aftershocks at three vertical array sites acceleration records of the 1995 kobe earthquake and its first after shocks provided by vertical arrays at port island pi sgk and tks sites were used to estimate changes in the shear moduli of subsurface soils caused by strong ground motion shear moduli estimates are based on stress strain relations deter mined for consecutive time intervals during the mainshock and aftershocks we found that in the upper 0 13 m at pi reclaimed fill above the groundwater level the shear modulus decreased by 80 90 of its initial value owing to liquefaction signs of its recovery appeared 3 5 min after the decrease in the intensity of strong motion at depths of 13 18 m reclaimed fill below the water level and 27 32 5 m water saturated sand at pi 0 11 m at sgk and 0 14 m at tks water saturated alluvium the shear modulus decrease was estimated at about 80 50 60 60 70 and 50 respectively recovery began immediately after the decrease in the intensity of strong motion and was completed within a few minutes the results show that the behavior of the upper layers at sites pi and sgk where the highest accelerations were recorded was dynamically unstable so far as the method can be applied to any site where vertical array records and profiling data are available ac cumulation of representative data on nonlinear soil behavior during strong motion for various soil conditions is desirable summarizing and generalizing these data we may be able to predict soil behavior in future earthquakes

nonlinear behavior of soils revealed from the records of the 2000 tottori japan earthquake at stations of the digital strong motion network kik net acceleration records of the tottori earthquake 6 october 2000 pro vided by stations of the digital strong motion network kik net show clear evidence of the nonlinearity of soil response at sites located in near fault zones in this study records of the mainshock of the tottori earthquake are analyzed and stresses and strains induced by the strong motion in the upper 100 or 200 m of soil are recon structed at sites located within 80 km from the fault plane for reconstructing stresses and strains the method is applied which we developed and used previously for studying the response of soils during the 1995 kobe earthquake nonlinear time dependent stress strain relations in the soil layers are estimated based on vertical array records a good agreement between the observed and simulated accelerograms of the tottori earthquake testifies to the validity of the obtained vertical distributions of stresses and strains in the soil layers we also evaluated variations of the shear moduli of the soil layers caused by the strong motion at stations located at different distances from the fault plane changes in the rheological properties of the upper soil layers were found at the stations closest to the fault plane a similarity in stress strain relations describing the behavior of similar soils during the 1995 kobe earth quake and the 2000 tottori earthquake was obtained indicating the possibility of precasting soil behavior in future earthquakes at sites where profiling data are available

controls on the sr and nd isotopic compositions of hydrothermally altered rocks from the pindos ophiolite greece abstract the sr and nd isotopic behaviour of hydrothermally altered basaltic rocks from the pindos ophiolite nw greece has been investigated samples were obtained mainly from rocks affected by intense hydrothermal alteration in field areas believed to represent hydrothermal discharge zones formed at a mesozoic seafloor spreading centre 87 sr 86 sr ratios in the altered rocks show a narrow range of values intermediate between those of seawater and fresh rock regardless of the degree of alteration this has been interpreted as the result of high overall water rock ratios which were sufficient to produce a homogeneous overprint throughout most of the hydrothermal cell a sr shift index which uses the sr isotopic composition and sr concentration of both rock and fluid has been derived to express the degree of sr exchange between rock and seawater it has been used to investigate the variations in water rock interaction between known hydrothermal systems and to compare ophiolite hosted with modern oceanic systems the results indicate that even when compared on such a uniform basis all the known present day hydrothermal systems are generally more rock dominated than those of pindos and other ophiolites 143 nd 14 nd ratios in the altered rocks are much less markedly affected but may show a shift from original magmatic values the results presented here suggest that this effect cannot simply be attributed to exchange with seawater nd these shifts must result from seawater transporting basaltic nd of a different isotopic composition from elsewhere in the volcanic pile into the zones of intense alteration this study has shown that sr and nd isotopes vary independently as a result of their different original distribution as well as their contrasting geochemical mobility

estimation of nonlinear soil behavior during the 1999 chi chi taiwan earthquake the 1999 chi chi taiwan earthquake mw 7 6 was one of the strongest earthquakes in recent years recorded by a large number of strong motion devices though only surface records are available the obtained strong motion database indicates the variety of ground responses in the near fault zones in this study accelerograms of the chi chi earthquake were simulated at rock and soil sites and models of soil behavior were constructed at seven soil sites tcu065 tcu072 tcu138 chy026 chy104 chy074 and chy015 for which parameters of the soil profiles are known down to depths of at least 70 m and at 24 other soil sites for which parameters of the soil profiles are known down to 30 40 m all the sites were located within 50 km from the fault for reconstructing stresses and strains in the soil layers we used a method similar to that developed for the estimation of soil behavior based on vertical array records as input for the soil layers acceleration time histories simulated by stochastic finite fault modelling with a prescribed slip distribution over the fault plane were taken in spite of the largeness of the earthquake s magnitude and the proximity of the studied soil sites to the fault plane the soil behavior at these sites was relatively simple i e a fairly good agreement between the spectra of the observed and simulated accelerograms and between their waveforms was obtained even in cases where a single stress strain relation was used to describe the behavior of whole soil thickness down to 70 80 m during strong motion obviously this is due to homogeneity in the characteristics of soil layers in depth at all the studied sites resonant phenomena in soil layers down to 40 60 m and nonlinearity of soil response were the main factors defining soil behavior at tcu065 tcu110 tcu115 chy101 chy036 and chy039 liquefaction phenomena occurred in the upper soil layers estimated strains achieved 0 6 0 8 at other stations maximum strains in the soil layers were as high as 0 1 0 4 according to our estimates thus valuable data on the in situ soil behavior during the chi chi earthquake was obtained similarity in the behavior of similar soils during the 1995 kobe 2000 tottori japan and chi chi taiwan earthquakes was found indicating the possibility of forecasting soil behavior in future earthquakes in the near fault zones of the three earthquakes hard type soil behavior and resonant phenomena in the upper surface layers prevail both leading to high acceleration amplitudes on the surface

petrology and geochemistry of metamorphosed komatiites and basalts from the tungurcha greenstone belt aldan shield abstract supracrustal rocks of the tungurcha greenstone belt in the western aldan shield occur as enclaves of actinolite schist and amphibolite within 3 2 ga old tonalitic gneisses geological and chemical data indicate the supracrustal rocks were komatiites and tholeiites the high magnesium rocks have been subdivided into three groups based on al ti and gd yb ratios one group has approximately chondritic al ti and gd yb and corresponds to al undepleted komatiite of the type found in munro township nesbitt et al 1979 a second group has lower al ti and higher solgd yb and is similar to al depleted komatiite of the type found in the barberton greenstone belt in the third group al ti is even lower and gd yb higher than in the other two groups but ca al is similar to that of the second group this third type of komatiite shows strong enrichment of incompatible elements and its low al ti is attributed to ti enrichment not al depletion the sm nd age of komatiites is 3232 199 ma nd 0 7 0 2 and that of the basalts 2873 88 ma nd 2 1 0 3 significant scatter is apparent even amongst samples from a single flow and it is believed that the scatter results not from differences in initial isotopic compositions but from disturbance of the sm nd system during later metamorphism in view of the large errors and the difference between the two results little significance can be placed on either the age or the initial isotopic compositions

near surface versus fault zone damage following the 1999 chi chi earthquake observation and simulation of repeating earthquakes we observe crustal damage and its subsequent recovery caused by the 1999 m7 6 chi chi earthquake in central taiwan analysis of repeating earthquakes in hualien region 70 km east of the chi chi earthquake shows a remarkable change in wave propagation beginning in the year 2000 revealing damage within the fault zone and distributed across the near surface we use moving window cross correlation to identify a dramatic decrease in the waveform similarity and delays in the s wave coda the maximum delay is up to 59 ms corresponding to a 7 6 velocity decrease averaged over the wave propagation path the waveform changes on either side of the fault are distinct they occur in different parts of the waveforms affect different frequencies and the size of the velocity reductions is different using a finite difference method we simulate the effect of postseismic changes in the wavefield by introducing s wave velocity anomaly in the fault zone and near the surface the models that best fit the observations point to pervasive damage in the near surface and deep along fault damage at the time of the chi chi earthquake the footwall stations show the combined effect of near surface and the fault zone damage where the velocity reduction 2 7 is twofold to threefold greater than the fault zone damage observed in the hanging wall stations the physical models obtained here allow us to monitor the temporal evolution and recovering process of the chi chi fault zone damage

extreme nd isotopic variation in the trinity ophiolite complex and the role of melt rock reactions in the oceanic lithosphere peridotites dykes and gabbros from the 470 420 ma trinity ophiolite complex of northern california exhibit large geochemical rare earth element ree and nd isotopic variations on the small scales which are indicative of a complex history the trinity ophiolite which covers an area of 1600 km2 consists of three distinct units 1 a 2 4 km thick sheet of plastically deformed peridotites including various ultrabasic lithologies plagioclase and spinel lherzolite harzburgite wherlite and dunite the peridotite unit is a fragment of mantle lithosphere of oceanic affinity 2 a series of small 1 km diameter undeformed gabbroic massifs 3 several generations of basic dykes the peridotites display the largest geochemical and isotopic variations with nd t values ranging from 10 down to 0 in the gabbroic massifs and intrusive dykes the variation in model nd t values is reduced to 7 nd units 0 to 7 as a general rule peridotites gabbros and dykes with nd t values around 0 or 3 give less depleted l light ree patterns than do those with nd t values in the range 7 to 10 in the peridotites the nd isotopic variations take place over very short distances with jumps as large as 7 nd units occurring on scales of less than 20 m comparison with available age data indicates that the peridotites with nd t 10 could be slightly older than the intrusive gabbro massifs and basic dykes 470 ma vs 420 ma strontium isotopic data used in connection with sm nd results demonstrate that the 10 nd units variation displayed by the trinity peridotite is a primary feature and not an artefact due to ree mobility during seawater interaction the variable nd isotopic signatures and variable lree patterns in the trinity peridotite cannot represent mantle source characteristics as there is evidence that this unit was partially melted when it rose as part of the upwelling convecting mantle field petrographic geochemical and isotopic data rather suggest that the observed heterogeneity is due to local reactions between a 470 ma proto peridotite with nd t 10 and younger 420 ma basaltic melts with lower nd t values i e the gabbroic massifs and the dykes the gabbros and basic dykes of the trinity complex have geochemical and isotopic compositions similar to the arc basalts from the adjacent copley formation so it is proposed that the younger melts are related to arc magmatism

isotopic and trace element composition of volcanic glasses from the akaki canyon cyprus implications for the origin of the troodos ophiolite abstract we report major elements k rb cs sr ba sc cr ni hf ta th and ree concentrations and isotopic compositions of sr nd pb and o of carefully handpicked volcanic glasses from the akaki river section of the troodos ophiolite complex on the basis of sr and o isotopic composition and fe 2 o 3 feo ratios nine of the ten glasses analyzed are considered to be fresh even with respect to those elements that are easily affected by alteration the glasses range in composition from basaltic andesite to dacite incompatible element concentrations in the mafic compositions are low 10 chondritic and the light ree are strongly depleted however the ratios of low field strength elements k rb cs sr th to high field strength elements ta hf ti and rare earth elements are higher than those in n morb nd isotopic compositions show a very small range with e nd t 80ma varying from 6 5 to 7 5 initial 87 sr 86 sr ratios range from 0 7033 to 0 7040 pb isotope ratios have a restricted range with 206 pb 204 pb 18 60 18 70 207 pb 204 pb 15 55 15 59 and 208 pb 204 pb 38 08 38 51 the oxygen isotopic composition for fresh glasses falls within the range reported for fresh mafic mantle derived volcanics with 18 o varying from 5 4 to 6 5 all geochemical characteristics of the troodos volcanic glasses are similar to those observed in supra subduction zone volcanics but we cannot distinguish between an early stage island arc or back arc origin for the troodos ophiolite on a geochemical basis only however considering our data and previously published geologic and geochemical data we suggest that the troodos ophiolite formed in the earliest stages of island arc development

problems regarding the macroseismicity of the calabro sicilian region a review abstract starting from previous macroseismic studies on some historical and recent calabro sicilian earthquakes the methodological problems of the characterization and modelling of macroseismic fields and intensity attenuation are discussed in particular the correlation between the macroseismic fields and the geostructural framework of the region concerned is investigated by an appropriate analysis of the structures as surveyed by wise et al 1979 it has been possible to indicate how in the areas characterized by an essentially unimodal diagram of lineament distribution showing a maximum with a high value of prevalence and kurtosis the macroseismic fields have a strong anisotropy with a clear preferential propagation direction which is consistent with the principal mode of the lineament distribution on the contrary in the areas characterized by a multimodal diagram having little dispersion and with a maximum having no distinct prevalence isoseismal lines do not clearly show elongation directions in the case of macroseismic fields which extend over areas of different structural characteristics the correlation is more complex with regard to the irpinia earthquake of november 23 1980 it may be observed how moving away from the mesoseismic area the preferential propagation of intensity shows an azimuthal variation which remains consistent with the different prevailing lineament domains finally the difficulty of elaborating a single attenuation model which is satisfactory for earthquakes in different areas and at different hypocentral depths is pointed out noting that the geostructural and dynamic framework of the seismogenetic and regional areas cannot be disregarded for a correct interpretation of the macroseismic fields

characteristics of soil response in near fault zones during the 1999 chi chi taiwan earthquake distribution of parameters characterizing soil response during the 1999 chi chi taiwan earthquake mw 7 6 around the fault plane is studied the results of stochastic finite fault simulations performed in pavlenko and wen 2008 and constructed models of soil behavior at 31 soil sites were used for the estimation of amplification of seismic waves in soil layers average stresses strains and shear moduli reduction in the upper 30 m of soil as well as nonlinear components of soil response during the chi chi earthquake amplification factors were found to increase with increasing distance from the fault or with decreasing the level of input motion to soil layers whereas average stresses and strains shear moduli reduction and nonlinear components of soil response decrease with distance as r 1 the area of strong nonlinearity where soil behavior is substantially nonlinear the content of nonlinear components in soil response is more than 40 50 of the intensity of the response and spectra of oscillations on the surface take the smoothed form close to e f f n is located within 20 25 km from the fault plane 1 4 of its length nonlinearity decreases with increasing distance from the fault and at 40 50 km from the fault 1 2 of the fault length soil response becomes virtually linear comparing soil behavior in near fault zones during the 1999 chi chi the 1995 kobe mw 6 8 and the 2000 tottori japan mw 6 7 earthquakes we found similarity in the behavior of similar soils and predominance of the hard type of soil behavior resonant phenomena in upper soil layers were observed at many studied sites however during the chi chi earthquake they involved deeper layers down to 40 60 m than during lesser magnitude kobe and tottori earthquakes