distribution of clay minerals along a weathered pyroclastic profile hong kong abstract the distribution of clay minerals along a weathered profile developed over crystal vitric tuffs are examined by x ray diffractometry xrd and scanning electron microscopy sem techniques chlorite and illite are the most abundant clay minerals in fresh and moderately decomposed rocks respectively chlorite is limited to fresh samples whereas illite and trace amounts of interstratified illite smectite are ubiquitous along the profile halloysite and kaolinite are the dominant clay minerals in highly to completely decomposed rocks halloysite clusters in moderately decomposed samples provide clear evidence of crystallization from solution whereas vermiform kaolinite books reveal evidence of transformation from illite in most samples in general as the intensity of weathering increases a kaolin to illite and kaolinite to halloysite ratios increase and b the morphology of halloysite varies from spheriodal clusters to tubular aggregates it is concluded that the nature type and abundance of clay minerals along the profile result from complex combinations of several different processes controlled mainly by three factors the pre weathering alteration history of parent rock the degree of weathering and microenvironmental conditions the relative role of each factor can vary significantly within the same profile as evidenced by mineralogical and petrographical characteristics the nature and type of clay minerals in fresh and moderately decomposed rocks can be attributed to pre weathering hydrothermal and or deuteric alterations on the other hand the degree of weathering regulates the nature type and abundance of clay minerals particularly kaolin group minerals in highly to completely decomposed rocks sesquioxides are sensitive to microenvironmetal conditions and can modify the distribution of clay minerals regardless of the degree of weathering of the rock

a comparison and test of various site response estimation techniques including three that are not reference site dependent abstract we compare various site response estimation techniques using after shock data of the 1989 loma prieta earthquake collected in oakland california because of recent interest in comparing results from weak and strong motion to infer any nonlinearity and between direct s and coda waves we pay particular attention to the uncertainties first sediment to bedrock spectral ratio estimates between pairs of sites are compared with those obtained from various generalized inversion approaches where the source and site effects of multiply recorded events are solved for simultaneously we find that the site amplification factors are very similar among these approaches but that the uncertainties can be significantly different depending on how the data are weighted we also examine and test three site response estimation techniques that do not rely on a reference site to estimate source and path effects the first involves a parameterized source and path effects inversion even when the bedrock data are excluded from consideration this approach is found to reveal the frequency dependence of site response at each of the sediment sites the second technique involves taking horizontal to vertical component spectral ratios receiver function type estimates of shear wave aftershock data these are also found to reveal the frequency dependence of site response at the sediment sites and the results for the bedrock site are relatively flat and near unity the third estimate is formed by taking horizontal to vertical component ratios of ambient seismic noise and these are shown to reveal the fundamental resonant frequency of the sediment sites unfortunately discrepancies exist among all of the site response estimates and with one dimensional predictions with respect to a frequency independent scaling factor nevertheless the highly frequency dependent character of site response is well constrained and the fact that non reference site dependent methods are capable of revealing this is promising for site specific hazard assessments in regions that lack adequate reference sites

bottom response to a tsunami earthquake submersible observations in the epicenter area of the 1993 earthquake off southwestern hokkaido sea of japan we conducted a research campaign of nine dives using the manned submersible vehicle shinkai 6500 in 1995 beneath the central okushiri ridge along the eastern margin of the sea of japan the main objective was to investigate coseismic response and bottom disturbance to the tsunamigenic 1993 offshore southwestern hokkaido earthquake ms 7 8 42 47 n 139 12 e in the northern aftershock area including the mainshock epicenter the whole aftershock area occupies the western half of source area of the related tsunami between the okushiri ridge and the neighboring shiribeshi trough to the east we found a gentle scarplet of the earthquake fault that bounds the first terrace and a zone of open gashes on the flat terrace a number of sand blows open cracks and other slope failures occupied the slope of the okushiri ridge on the uplifted hanging wall side of the tsunami source area some fractures and holes whose activity had ceased soon after the earthquake began to be buried by the 2 year accumulation of recent sediments in contrast the shiribeshi trough on the footwall of the fault and in the subsided domain of the tsunami source area suffered no remarkable disturbance other than gentle folding our submersible observations elucidated the seafloor response to tsunamigenic uplift of the hanging wall of a seismogenic thrust fault which displays the present time section of back thrusting with an embryonic subduction along the eastern margin of the sea of japan

karst bauxite deposits in the zagros mountain belt iran more than 190 occurrences of bauxitic lateritic deposits were investigated in seven areas within the zagros simply folded mountain belt in southwestern of iran the bauxitic horizons are situated in eroded major nw se trending anticlines and occur in karst cavities near or at the boundary between the sarvak and ilam formations uplift in the cenomanian turanian period had exposed the sarvak limestone to karst weathering and during a period of unconformity layers of ferruginous argillaceous limestone debris developed and accumulated on its surface the ferruginous argillaceous debris was partly converted to bauxite folding and faulting in oligocene miocene time with ensuing erosion exposed the bauxitic horizons on the limbs and cores of anticlines the karst bauxite deposits are probably of authigenic origin as evidenced by their lithologic associations textural and mineralogy

flow path of the 1993 hokkaido nansei oki earthquake seismoturbidite southern margin of the japan sea north basin inferred from anisotropy of magnetic susceptibility summary a magnetic fabric analysis has been carried out on standard cube samples from one gravity and three multiple cores extracted from the shiribeshi trough and okushiri basin in the southern margin of the japan sea north basin it is aimed at tracing the flow path of turbidites that are assumed to have deposited in response to the 1993 hokkaido nansei oki earthquake magnetic remanence was used for reorientation to the geographic coordinates magnetomineralogical investigations including low temperature magnetometry magnetic hysteresis loops and isothermal remanent magnetization irm acquisition experiments indicate that pseudosingle domain to multidomain magnetite is the principal magnetic carrier and is therefore capable of providing reliable anisotropy of magnetic susceptibility ams palaeocurrent direction estimates a well developed near horizontal magnetic foliation and minimum susceptibility axes lying close to vertical are recorded at all sites reflecting an original depositional fabric clearly defined magnetic lineation was observed at all sites and is considered to reflect the palaeocurrent direction down core changes of susceptibility and key ams parameters show good correspondence to occurrences of turbidite layers marking the increase of input of influx materials in agreement with results from recent marine surveys and izanagi side scan sonar images an nne transportation trend has been estimated for sediments at sites from the shiribeshi trough with a possible depositing path initiating from the slope bounding the south and southeastern margin down to the trough floor similarly a sse palaeocurrent direction has been estimated for sediments from the okushiri basin with evidence for a relatively strong transporting current flowing through the canyons along the steep slope bounding the north and northeastern margins of the basin the present results agree with the view that slope failure is the most probable mechanism for the down slope transport of the sand from the shelves and upper slopes down to floors of basins and troughs in the southern margin of the japan sea north basin they further support the ongoing assumption that the 1993 hokkaido nansei oki and other strong historical earthquakes together with associated tsunamis are the principal triggering forces for the down slope mass gravitational transport and formation of turbidites in this seismically active area

imaging p and s attenuation in the sacramento san joaquin delta region northern california we obtain 3d q p and q s models for the delta region of the sacramento and san joaquin rivers a large fluvial agricultural portion of the great valley located between the sierra nevada batholith and the san francisco bay coast ranges region of active faulting path attenuation t values have been obtained for p and s data from 124 distributed earthquakes with a longer variable window for s based on the energy integral we use frequency dependence with an exponent of 0 5 consistent with other studies and weakly favored by the t s data a regional initial model was obtained by solving for q as a function of seismic velocity in the final model the great valley basin has low q with very low q 50 for the shallowest portion of the delta there is an underlying strong q contrast to the ophiolite basement which is thickest with highest q under the sacramento basin and a change in structure is apparent across the suisun bay as a transition to thinner ophiolite moderately low q is found in the upper crust west of the delta region along the faults in the eastern north bay area whereas moderately high q is found south of the delta implying potentially stronger ground motion for earthquake sources to the south very low q values in the shallow crust along parts of the major fault zones may relate to sediment and abundant microfractures in the lower crust below the san andreas and calaveras hayward rodgers creek fault zones the observed low q is consistent with grain size reduction in ductile shear zones and is lowest under the san andreas which has large cumulative strain similarly moderately low q in the ductile lower crust of the bay area block between the major fault zones implies a broad distributed shear zone online material distribution of earthquake magnitude figures of t values 3d initial regional velocity and q models station terms and q p inversion with 1d initial q p model

incipient subduction and deduction along the eastern margin of the japan sea the eastern margin of the japan sea has been under convergent tectonics since sometime after the pliocene the suture line is on the ocean continent boundary between the japan yamato basins and the tohoku northeast japan arc incipient subduction and obduction of the oceanic and sub oceanic crust are observed along the suture line with the occurrence of numerous n s trending fault bounded ridges and troughs focal mechanism solutions of several compressional type earthquakes with magnitudes of m 6 9 to 7 7 which have occurred along the zone are consistent with the observation of geological thrust faults the convergent stresses in the japan sea may be due to india eurasia collision and its associated intra plate or inter microplate movements in east asia the eastward movement of the amurian plate causes baikal extension along its western margin and the japan sea convergence along its eastern margin

basin waves on a seafloor recording of the 1990 upland california earthquake implications for ground motions from a larger earthquake abstract the velocity and displacement time series from a recording on the seafloor at 74 km from the 1990 upland earthquake m 5 6 are dominated by late arriving waves with periods of 6 to 7 sec these waves are probably surface waves traveling across the los angeles basin response spectra for the recording are in agreement with predictions from empirical regression equations and theoretical models for periods less than about 1 sec but are significantly larger than those predictions for longer periods the longer period spectral amplitudes are controlled by the late arriving waves which are not included in the theoretical models and are underrepresented in the data used in the empirical analyses when the motions are scaled to larger magnitude the results are in general agreement with simulations of wave propagation in the los angeles basin by graves 1998

genesis of the dogankuzu and mortas bauxite deposits taurides turkey separation of al fe and mn and implications for passive margin metallogeny the taurides region of turkey is host to a number of important bauxite al rich laterite and mn deposits the most important bauxite deposits dog ankuzu and mortas are karst related unconformity type deposits in upper cretaceous limestone the bottom contact of the bauxite ore is undulatory and bauxite fills depressions and sinkholes in the footwall limestone whereas its top surface is concordant with the hanging wall limestone the thickness of the bauxite varies from 1 to 40 m and consists of bohmite hematite pyrite marcasite anatase diaspore gypsum kaolinite and smectite the strata bound sulfide and sulfate bearing low grade lower part of the bauxite ore bed contains pyrite pseudomorphs after hematite and is deep red in outcrop owing to supergene oxidation the lower part of the bauxite body contains local intercalations of calcareous conglomerate that formed in fault controlled depressions and sinkholes bauxite ore is overlain by fine grained fe sulfidebearing and calcareous claystone and argillaceous limestone which are in turn overlain by massive compact limestone of santonian age that 50 m thick limestone is in turn overlain by well bedded bioclastic limestone of campanian or maastrichtian age rich with rudist fossils fracture fillings in the bauxite orebody are up to 1 m thick and consist of bluish gray green pyrite and marcasite 20 with bohmite diaspore and anatase these sulfide veins crosscut and offset the strata bound sulfide zones sulfur for the sulfides was derived from the bacterial reduction of seawater sulfate and fe was derived from alteration of oxides in the bauxite iron sulfides do not occur within either the immediately underlying or overlying limestone the platform limestone and shale that host the bauxite deposits formed at a passive margin of the tethys ocean extensive vegetation developed on land as the result of a humid climate thereby creating thick and acidic soils and enhancing the transport of large amounts of organic matter to the ocean alteration of the organic matter provided co2 that contributed to formation of a relatively 12 c rich marine footwall limestone relative sea level fall resulted from strike slip faulting associated with closure of the ocean and local uplift of the passive margin that uplift resulted in karstification and bauxite formation in topographic lows as repre

episodic seafloor mud brecciation due to great subduction zone earthquakes the nankai trough off southwest japan has an 1300 yr historical record of great earthquakes including the most recent the a d 1944 tonankai m 8 2 earthquake evaluation of the activity of an individual submarine fault is difficult when only onland observations are available submarine core records can pinpoint individual fault activity here we present integrated ocean drilling program iodp nankai trough seismogenic zone experiment data from the shallow portion iodp expedition 316 drilled and cored several holes in the shallow portion of the offshore tonankai earthquake area including sites in the hanging wall of a margin dominating splay fault that has previously been interpreted to have ruptured coseismically during megathrust earthquakes x ray computed tomography scanning revealed that the uppermost core at one site contains repeated occurrences of mud breccia radioisotope dating of the uppermost mud breccia indicates a deposition time consistent with the 1944 tonankai earthquake suggesting that the mud breccia layers result from episodic brecciation caused by seismic shaking mud brecciation provides a potential new tool to reconstruct ancient earthquake history in subduction zones

discovery of the ree minerals and its geological significance in the quyang bauxite deposit west guangxi china most of the karstic bauxite deposits in china are enriched in ree and the ree has commonly been considered to be adsorbed on the surface of clay or diaspore minerals as ion state however occurrence of ree minerals in the bauxite deposits has not been reported by far in the quyang bauxite deposit from guangxi province we find ree minerals the minerals are parisite and churchite parisite is widely distributed in the ooids and matrix inducing positive ce anomaly of the ores whereas churchite is rare and occurred in the core of ooid the compositions of the ree minerals show the eu anomaly can change gently during the weathering and the eu anomaly analyses suggest that the ree in the ores are mostly derived from the underlying carbonates the parisite is formed in an alkaline condition while churchite in an acidic situation the co existence of the two minerals in the ores suggests the permian environment for bauxite formation is complex with great change of ph value moreover parisite is inferred to be formed earlier than the churchite

dense array recordings in the san bernardino valley of landers big bear aftershocks basin surface waves moho reflections and three dimensional simulations abstract fourteen geos seismic recorders were deployed in the san bernardino valley to study the propagation of short period t 1 to 3 sec surface waves and moho reflections three dense arrays were used to determine the direction and speed of propagation of arrivals in the seismograms the seismograms for a shallow d 1 km m 4 9 aftershock of the big bear earthquake exhibit a very long duration 60 sec of sustained shaking at periods of about 2 sec array analysis indicates that these late arrivals are dominated by surface waves traveling in various directions across the valley some energy is arriving from a direction 180 from the epicenter and was apparently reflected from the edge of the valley opposite the source a close in aftershock 25 km depth 7 km displays substantial short period surface waves at deep soil sites a three dimensional 3d finite difference simulation produces synthetic seismograms with durations similar to those of the observed records for this event indicating the importance of s wave to surface wave conversion near the edge of the basin flat layered models severely underpredict the duration and spectral amplification of this deep soil site i show an example where the coda wave amplitude ratio at 1 to 2 hz between a deep soil and a rock site does not equal the s wave amplitude ratio because of the presence of surface waves in the coda of the deep soil site for one of the events studied 90 km there are sizable phases that are critically reflected from the moho pmp and sms at one of the rock sites the sms phase has a more peaked spectrum that the direct s wave

genesis of ree minerals in the karstic bauxite in western guangxi china and its constraints on the deposit formation conditions abstract karstic bauxites in western guangxi china comprise two subtypes permian bauxite and quaternary bauxite the quaternary bauxite originated from the breaking up rolling and accumulating of permian bauxite in karstic depressions in quaternary various types of rare earth element ree minerals were discovered during the formation of the permian and quaternary bauxites from the xinxu longhe and tianyang bauxite deposits in this study five types of ree minerals including bastnasite parisite cerianite rhabdophane and churchite were identified bastnasite and parisite are the most abundant and they are widely developed in the permian ore and also present in the quaternary ore obvious variations in bastnasite and parisite ree compositions were observed which is ascribed to distinctions in the source materials in the primary weathering profile from different areas the mode of occurrence of bastnasite and parisite suggests they were mainly precipitated under alkaline and reducing conditions during the permian bauxite forming stage and underwent intensive corrosion in the quaternary churchite was formed during the permian weathering stage under acidic condition both cerianite and rhabdophane occur in fractures within the permian bauxite ore indicating that both formed during the quaternary weathering stage it is considered that the rhabdophane enriched in ce have formed locally in the process of that the ce3 released from bastnasite rapidly entered the rhabdophane lattice before being oxidized to ce4 cerianite was mainly found in association with mn al hydroxides suggesting that the released ce3 was oxidized into ce4 and precipitated cerianite in fractures within the permian bauxite ore mass balance equations reveal a depletion in nearly all rees during the transformation from the permian to the quaternary bauxite ore mainly caused by the dissolution of bastnasite and parisite the genesis of the ree minerals together with the occurrence of other minerals indicates that intensively acidic and oxidizing conditions developed before the formation of the permian bauxite ore towards the end of the permian the conditions became reducing and alkaline favorable for the large scale bauxitization the quaternary bauxite forming stage was characterized by variable ph and eh conditions with acidic ph 4 6 and oxidizing eh 2 conditions at the surface of the exposed permian bauxite ore

cerium anomalies in lateritic profiles the ree geochemistry and mineralogy have been studied in four lateritic profiles one derived from a syenite akongo sw cameroon the others being developed on a gneissic basement and located along a soil toposequence goyoum e cameroon there is a fractionation between lree and hree in the lateritic samples during weathering the weathered residual products being enriched in lree from la to eu and depleted in hree from gd to lu sampled waters are enriched in hree in relation to the syenite host rock a positive ce anomaly has been found systematically at the top of the saprolite beneath a zone of iron oxide accumulation in the laterite up to 2000 ppm ce may be present in the akongo profile cerianite ceo2 is present as very fine coatings in non ferruginous clayey domains primary ree bearing accessory minerals are weathered at the bottom of the profile specifically allanite and apatite are transformed into florencite and rhabdophane but these phases have no ce anomaly all the data are interpreted as the result of the following processes 1 1 ree leaching in a reducing environment 2 2 oxidation of ce3 to ce4 in an oxidizing environment 3 3 deposition of cerium as cerianite whereas the other ree remain in solution

quantitative mineralogical characterization of karst bauxite deposits in the southern apennines italy the southern italian karst bauxite deposits occur at a late cretaceous hiatus on a bahamian type carbonate platform succession cropping out in the southern apennines and are mainly located in the abruzzi mountains in apulia gargano peninsula and murge area and in campania the bauxites of southern italy are presently uneconomic but can be considered as a model analogue for economic karst bauxite ores the texture of the bauxite deposits is mainly oolitic to pisolitic but can also be arenitic conglomeratic suggesting reworking of evolved lateritic soils the minerals boehmite and hematite are more abundant in the ooids whereas kaolinite is found at high levels in the groundmass and titanium oxides are also present furthermore small amounts of rare earth elements have been detected in most of the bauxite occurrences scanning electron microscopy with energy dispersive spectrometry sem eds and geochemical analyses on several of the deposits confirmed the diagenetic texture of the bauxite and provided an estimate of the mineralogy of the different components and their chemical composition the mineralogical and petrographic characteristics of bauxite are crucial for the bayer process and can influence its economic evaluation both the particle size distribution in the ore and the presence of reactive silica phases associated with ti and fe oxides can reduce the efficiency of processing quantitative analyses combining different methods x ray diffraction xrd rietveld quantitative phase analysis qpa and qemscan have been carried out on a limited number of samples from two of the bauxite districts of the campania region the matese mountains and the caserta province qemscan analysis allowed a more rapid quantification of mineralogy including trace detrital phases and assessment of the individual textural characteristics of the bauxite lithotypes showing a detailed image of the distribution of economic and noneconomic minerals and their intergrowths this methodology can augment or replace other time consuming quantitative phase analyses for mineralogical studies of bauxites provided that the species identification protocol sip database has been carefully validated by preliminary use of xrd and sem eds both xrd qpa and qemscan analytical techniques can be complementary for bauxite ore evaluation and a very powerful tool for exploitation and mineral processing

trace element content of karst bauxites and their parent rocks in the mediterranean belt this work deals with a concise but comprehensive study of trace element distribution in the bauxite deposits of mediterranean belt although the alloctonous and mainly detritic characters of several karst bauxite deposits are well established their parent rock has remained largely enigmatic evidence is available that some chemical elements notably zr cr and ga are largely immobile during the weathering and diagenesis and study of such trace elements in karst bauxites permits to make an approach to the lithological nature of their parent rocks it is shown by reference to analyses of bauxites from mediterranean areas that all the deposits studied are aligned from a cr rich pole related to ultramafics to another pole rich in ga and zr contents and in genetical relation with acidic parent rocks the results obtained by this way have been controlled by application of trace element accumulation coefficient which permits to distinguish four principal zones of bauxite derived from the parent rock of different lithological characters fig 3

observations of loma prieta aftershocks from a dense array in sunnyvale california a small aperture 300 m four station array was deployed in sunnyvale california for 5 days to record aftershocks of the loma prieta earthquake of october 1989 the purpose of the array was to study the seismic response of the alluvium filled santa clara valley and the role of surface waves in the seismic shaking of sedimentary basins strong motion records of the loma prieta mainshock indicate that surface waves produced the peak velocities and displacements at some sites in the santa clara valley we use the recordings from the dense array to determine the apparent velocity and azimuth of propagation for various arrivals in the seismograms of four aftershocks with magnitudes between 3 6 and 4 4 apparent velocities are generally observed to decrease with increasing time after the s wave in the seismograms phases arriving less than about 8 sec after the s wave have apparent velocities comparable to the s wave and appear to be body waves multiply reflected under the receiver site or reflected by crustal interfaces for times 10 to 30 sec after the direct s wave we observe long period 1 to 6 sec arrivals with apparent velocities decreasing from 2 5 to 0 8 km sec we interpret these arrivals to be surface waves and conclude that these surface waves produce the long duration of shaking observed on the aftershock records much of the energy in the 40 sec after the s wave is coming approximately from the direction of the source although some arrivals have backazimuths as much as 60 different from the backazimuths to the epicenters two of the aftershocks show arrivals coming from 30 to 40 more easterly than the epicenters this energy may have been scattered from outcrops along the southeastern edge of the basin in contrast the deepest aftershock studied d 17 km displays later arrivals with backazimuths 30 to 40 more westerly than the epicenter a distinct arrival for one of the aftershocks propagates from the southwest possibly scattered from the western edge of the basin synthetic seismograms derived from a plane layered crustal model do not produce the long period love waves observed in the waveforms of the ml 4 4 aftershock these love waves may be generated by the conversion of incident s waves or rayleigh waves near the edge of the basin

rupture propagation of the 2004 parkfield california earthquake from observations at the upsar using a short baseline seismic array u s geological survey parkfield dense seismograph array upsar about 12 km west of the rupture initiation of the 28 september 2004 m 6 0 parkfield california earthquake we have observed the movement of the rupture front of this earthquake on the san andreas fault the sources of high frequency arrivals at upsar which we use to identify the rupture front are mapped onto the san andreas fault using their apparent velocity and back azimuth measurements of apparent velocity and back azimuth are calibrated using aftershocks which have a compact source and known location aftershock back azimuths show considerable lateral refraction consistent with a high velocity ridge on the southwest side of the fault we infer that the initial mainshock rupture velocity was approximately the rayleigh speed with respect to slower side of the fault and the rupture then slowed to about 0 66 near the town of parkfield after 2 sec the last well correlated pulse 4 sec after s is the largest at upsar and its source is near the region of large accelerations recorded by strong motion accelerographs and close to northern extent of continuous surface fractures on the southwest fracture zone coincidence of sources with preshock and aftershock distributions suggests fault material properties control rupture behavior high frequency sources approximately correlate with the edges of asperities identified as regions of high slip derived from inversion of strong motion waveforms

seismic coupling of interface modes in sedimentary basins a recipe for disaster abstract coupling between an evanescent p wave and a rayleigh wave can occur when the two modes share the same phase velocity at an interface the result is a new distinctive monochromatic mode of large amplitude and finite duration that may reverberate in a bounded layer generating stationary patterns due to constructive and destructive interference such modes may be responsible for earthquake damage in the valley of mexico and perhaps in other sedimentary basins vulnerable to seismic disasters on soft ground

behavior of sm and nd in a lateritic soil profile a study of lateritic soils and samples of ground and river waters was carried out in the nsimi zoetele a tropical watershed in the southern cameroon the nd isotopic compositions and concentrations of nd and sm were determined it was found that the nd isotopic composition of the river waters was much more radiogenic than the parent rocks and that the nd in the waters is not homogeneous but is carried by different dissolved and complexed components that are not isotopically homogenized the soil profile shows a regular increase in e nd going from the parent rock e nd 36 to e nd 18 near the top of the profile the nd transported in the river is thus not representative of the parent rock but reflects the results of differential weathering of constituent minerals and the redeposition of ree in phosphates and a significant contribution of radiogenic nd from dust the concentration of nd in the river water is far above that found in temperate climate rivers and thus this type of tropical river may play a dominant role in the marine nd and ree budget it is suggested that the correlation of ree with doc is related to doc fixing some dissolved ree but that the ree in solution is governed by other mechanisms no major shifts were found in sm nd however a regular progression from the parent rock through the lateritic profile was found the upper laterite profile shows large almost uniform depletions in all ree below tb and enrichment above complementary behavior was found in the lower part of the section the concentration of nd relative to the immobile elements zr and ti in the laterite is depleted by a factor of 10 th nd and sm are enriched in the lowest zone sampled and must reflect redeposition of ree from the upper part of the weathering section and is associated with phosphate formation it is concluded that the soil evolution involves both differential dissolution of primary phases from the parent rock significant to major input of ree from atmospheric dust from other regions and the formation of diagenetic phases particularly phosphates

regional three dimensional seismic velocity model of the crust and uppermost mantle of northern california 1 we present a three dimensional 3d tomographic model of the p wave velocity vp structure of northern california we employed a regional scale double difference tomography algorithm that incorporates a finite difference travel time calculator and spatial smoothing constraints arrival times from earthquakes and travel times from controlled source explosions recorded at network and or temporary stations were inverted for vp on a 3d grid with horizontal node spacing of 10 to 20 km and vertical node spacing of 3 to 8 km our model provides an unprecedented comprehensive view of the regional scale structure of northern california putting many previously identified features into a broader regional context and improving the resolution of a number of them and revealing a number of new features especially in the middle and lower crust that have never before been reported examples of the former include the complex subducting gorda slab a steep deeply penetrating fault beneath the sacramento river delta crustal low velocity zones beneath geysers clear lake and long valley and the high velocity ophiolite body underlying the great valley examples of the latter include mid crustal low velocity zones beneath mount shasta and north of lake tahoe

growth of hematite and boehmite in concretions from ancient karst bauxite clue for past climate abstract in the peri adriatic apulia carbonate platform southern ltaly late cretaceous karst bauxites mark an emergence period during a wet tropical climate bauxite formed through clay accumulation in the karst in situ bauxitization and late formation of iron rich concretions in a water unsaturated pedogenic environment the concretions which are geochemical recorders of the environment of formation have a large core of al hematite surrounded by a cortex of alternating al hematite and boehmite boehmite forms instead of al hematite at lower water activity values using a model of molecular diffusion and assuming the fluid flow negligible the time necessary for growth of the concretions has been calculated the average sized core grew in 180 ka the al hematite accretionary band grew in 8 ka whereas the boehmite accretionary band grew in 4 5 ka the average bulk concretions possibly formed in 300 400 ka the growth of the concretions is assumed to be a two stage process in the first stage the core grew in a relatively long period of wet tropical climate in the second stage drier conditions favouring boehmite stability alternated to a wetter climate favouring al hematite stability the growth of the bulk concretions is consistent with the earth s long eccentricity cycle

the mechanism of the 1983 japan sea earthquake as inferred from long period surface waves and tsunamis abstract the source process of the japan sea earthquake of may 26 1983 is studied by using the long period surface waves and tsunamis the moment tensor inversion of rayleigh waves which consider the lateral heterogeneity of the earth is developed and applied to the ida records of this event the moment tensor solution and first motion data indicate that the mechanism is dip slip and the seismic moment is 7 6 1027 dyne cm the fault is estimated to be 120 km in length 40 km in width and dips eastward with a dip angle of 30 from the aftershock distribution tsunami simulation for an actual topography is made to restrain the slip on the fault the aftershock area and the tsunami records suggest that the fault is divided into two segments the northern part strikes nnw and slips 4 m while the southern part strikes nne and slips 5 m the fault geometry the aspect ratio and the stress drop of this event are similar to those of the 1964 niigata earthquake but differ from those of the earthquakes in the pacific coast of japan

mass change calculations in altered rock series a technique is presented whereby precursors of altered rocks in a fractionated rock series can be identified and changes in chemical components mass and volume accurately calculated the procedure utilizes elements with high degrees of immobility in hydrothermal and associated interactive water rock systems igneous rock series and sedimentary and metamorphic rocks with primary continuity of chemical composition are amenable to this treatment in the procedure for igneous rocks best fit fractionation lines are established for an immobile igneous compatible incompatible element pair the latter element functioning as the fractionation monitor alteration paths are linear and pass through the origin intersections of the fractionation and alteration lines yield the immobile element concentrations in the precursors to the altered rocks mobile components are determined from fractionation lines and monitor values total mass changes are proportional to the displacement of altered samples from the fractionation line masses of other elements in an altered sample reconstructed values are recalculated to the concentration of the monitor element in the precursor chemical changes are the differences between the calculated precursor compositions and the reconstructed altered rock compositions errors are mainly a function of the positioning of the fractionation lines

a general inversion scheme for source site and propagation characteristics using multiply recorded sets of moderate sized earthquakes abstract we derive an inversion scheme that fits the logarithms of seismic body wave spectra to 2 source shapes conditioned by anelastic attenuation with a frequency independent q the residuals from this fit are then projected onto the set of sources and sites with the source terms damped to estimate residual source spectra and site response spectra this two part inversion process is iterated until the square of the residuals summed over frequency for all recordings is minimized the absolute amplitudes of the source and site spectra are determined by fitting the site response spectra to estimates of the site amplification derived from geotechnical data we apply this inversion process to three sets of recordings of loma prieta aftershocks the first data set contains s waves recorded both in the marina district and at nearby hard rock stations we constrain the site response using the s wave velocity measured in a nearby borehole the absolute site amplifications for the marina stations are 15 to 20 at 1 hz and 10 at 2 5 hz the other two data sets comprise the p and s wave recordings from 28 aftershocks ranging in size from m d 2 1 to 4 6 obtained at accelerograph sites near the epicentral area the p and s wave attenuations determined from the inversions are q 414 and 380 while the average near site attenuations are t 0 012 and 0 026 sec respectively the average ratio of the s to p wave seismic moments is 1 1 0 1 the ratio of the p to s wave corner frequencies is 1 24 0 11 and the ratio of s to p wave radiated energy is 13 9 3 2 the brune stress drops for these aftershocks range from 8 to 800 bars the largest earthquakes exhibit the largest stress drops but there is no apparent dependence of stress drop on seismic moment for earthquakes with 10 19 m 0 21 dyne cm

seismic site characterization of an urban sedimentary basin livermore valley california site response basin edge induced surface waves and 3d simulations thirty two accelerometers were deployed in the livermore valley california for approximately one year to study sedimentary basin effects many local and near regional earthquakes were recorded including the 24 august 2014 m w 6 0 napa california earthquake the resulting ground motion data set is used to quantify the seismic response of the livermore basin a major structural depression in the california coast range province bounded by active faults site response is calculated by two methods the reference site spectral ratio method and a source site spectral inversion method longer period 1 s amplification factors follow the same general pattern as bouguer gravity anomaly contours site response spectra are inverted for shallow shear wave velocity profiles which are consistent with independent information frequency wavenumber analysis is used to analyze plane wave propagation across the livermore valley and to identify basin edge induced surface waves with back azimuths different from the source back azimuth finite element simulations in a 3d velocity model of the region illustrate the generation of basin edge induced surface waves and point out strips of elevated ground velocities along the margins of the basin online material figures comparing 5 damped acceleration response spectra for data and synthetics

geochemistry of the apulian karst bauxites southern italy chemical fractionation and parental affinities article i nfo this study focuses on a late cretaceous karst bauxite deposit in the murge area of the apulia district southern italy the first analysis of the vertical distributions of a wide range of elements including rees and selected trace elements throughout the deposit was shown in order to identify the processes determining element frac tionation during the evolution of the bauxite the studied karst bauxite deposit exhibits an ooidal texture is mineralogically homogeneous and contains higher abundances of boehmite than of hematite kaolinite and anatase the major element composition of the bauxite is dominated by elevated concentrations of sio2 t io2 a l2o3 a nd fe2o3 and analyses of element mo bility within the bauxite indicate that all elements except for nb and ni and to a lesser extent cr are depleted relative to the immobile element ti r mode factor analysis revealed a number of key findings i some low solubility elements e g zr th ti v ga were concentrated in detrital zircon and monazite zr th in anatase ti v and possibly in boehmite and hematite ga during the later stages of bauxitisation ii fe and cr were concentrated during wet conditions whereas al and co accumulated during dry conditions iii distributions of the light rees lrees and the heavy rees hrees are controlled by the same processes suggesting that little lree hree fractionation occurred during bauxite formation and iv the behaviour of cerium is different from that of the other rees and highly variable cerium anomalies are observed across the deposit with three characteristic ce ce maxima with values ofn2 parisite was the only authigenic cerium mineral detected during this study thus we propose a three step model to explain the distribution of ce cerianite is dissolved by cerium reduction is transported by downward moving meteoric water per descensum and finally parisite is precipi tated this cycle was repeated several times in the apulian karst bauxite in response to eh decreases under alka line conditions promoted by fluctuations in the groundwater level finally we used the value of the eu anomaly todiscuss theparental affinity or protolith of thebauxite the value of the eu anomaly min eu eu 0 76 max eu eu 0 89 indicates that the bauxite was not derived from carbonates but rather that the majority of the bauxite was influenced by intermediate to mafic magmatic sources eu eu vs sm nd diagram suggests that the parental material for the bauxite was derived from a combination of a distant magmatic source and clastic material derived from a continental margin northern africa to the south

initiation of ophiolite emplacement a modern example from okushiri ridge northeast japan arc abstract submersible dives by shinkai 2000 discovered thickly piled back arc basin basalts and an overlying sequence of siliceous hemipelagites and turbidites on the western fault escarpment of the okushiri ridge off western hokkaido the okushiri ridge is an allochthonous tectonic block marked by an east dipping main boundary thrust and a west dipping back thrust the block is interpreted to have formed as a result of the plate convergence between the northeast japan and eurasian plates and all available data including seismic profiles and geochemical analyses suggest that the okushiri ridge constitutes a piece of oceanic crust of the japan basin ultimately this piece of oceanic crust will be incorporated into the japan magmatic arc the okushiri ridge therefore demonstrates that tectonic inversion i e the change from extension to compression plays an important role in ophiolite emplacement

strong motion from surface waves in deep sedimentary basins it is widely recognized that long period surface waves generated by conversion of body waves at the boundaries of deep sedimentary basins make an important contribution to strong ground motion the factors controlling the amplitude of such motion however are not widely understood a study of pseudovelocity response spectra of strong motion records from the los angeles basin shows that late arriving surface waves with group velocities of about 1 km sec dominate the ground motion for periods of 3 sec and longer the rate of amplitude decay for these waves is less than for the body waves and depends significantly on period with smaller decay for longer periods the amplitude can be modeled by the equation batchmode documentclass fleqn 10pt legalpaper article usepackage amssymb usepackage amsfonts usepackage amsmath pagestyle empty begin document mathrm log y f mathbf m r mathrm e c br mathrm b end document where y is the pseudovelocity response f m r e is an attenuation relation based on a general strong motion data set m is moment magnitude r e is the distance from the source to the edge of the basin r b is the distance from the edge of the basin to the recording site and b and c are parameters fit to the data the equation gives values larger by as much as a factor of 3 than given by the attenuation relationships based on general strong motion data sets for the same source site distance it is clear that surface waves need to be taken into account in the design of long period structures in deep sedimentary basins the ground motion levels specified by the earthquake provisions of current building codes in california at least accommodate the long period ground motions from basin edge generated surface waves for periods of 5 sec and less and earthquakes with moment magnitudes of 7 5 or less located more than 20 km outside the basin there may be problems at longer periods and for earthquakes located closer to the basin edge the results of this study suggest that anelastic attenuation may need to be included in attempts to model long period motion in deep sedimentary basins to obtain better data on surface waves in the future operators of strong motion networks should take special care for the faithful recording of the long period components of ground motion it will also be necessary to insure that at least some selected recorders once triggered continue to operate for a time sufficient for the surface waves to traverse the basin with velocities of about 1 km sec that time will be as long as 100 sec for a basin the size of the los angeles basin

re examination of the 1940 shakotan oki earthquake and the fault parameters of the earthquakes along the eastern margin of the japan sea abstract the fault model of the 1940 shakotan oki japan earthquake of aug 1 1940 is re examined on the basis of magnitude aftershock distribution and tsunami data from a careful examination of the s p time distribution of aftershocks and comparison of the tide gauge records with numerical simulation of tsunami the fault area is estimated to be 100 km 35 km the slip 1 5 m and the seismic moment 2 4 1027 dyn cm the fault parameters estimated in this study are significantly different from those of fukao and furumoto and do not support their conclusion that this event has a very long duration and is a tsunami earthquake the source process time is estimated to be 30 s which is normal for an earthquake of this size fault parameters of six earthquakes along the eastern margin of the japan sea including the shakotan oki event are compiled and compared with those of inter plate earthquakes in the pacific ocean different relations from well known scaling laws of the inter plate shocks are found for the earthquakes in the japan sea dip angles aspect ratios of the fault and the average stress drop are larger in the japan sea than those of the pacific events although the seismic moment release per unit fault length is the same the differences can be interpreted in terms of a recent plate boundary model in which the young immature boundary between the north american and the eurasian plates lies at the eastern margin of the japan sea they also partially reflect the different excitation of the tsunami in the japan sea and the pacific ocean

northern california seismic attenuation 3d qp and qs models the geological complexity of northern california and its accreted terranes produces pronounced regional variations in the attenuation 1 q of earthquake waves using local earthquakes 3d q p and q s models have been obtained for this region that includes the san andreas fault system the great valley the sierra nevada batholith and the gorda subduction volcanic system path attenuation t values were determined from p and s spectra of 959 spatially distributed earthquakes magnitude 2 5 6 0 using 1254 stations from northern california earthquake data center networks and mendocino and sierra nevada temporary arrays the t data were used in q inversions using existing 3d velocity models and basic 10 km node spacing uneven data coverage was accommodated with linking nodes into larger areas for useful q images across the 3d volume results at shallow depth show very low q in the sacramento delta the eureka area and parts of the san francisco bay area in the brittle crust low q tends to be associated with regions of fault zones and microearthquakes in the ductile lower crust low q is observed below fault zones with large cumulative displacement and inferred grain size reduction with apparent broad ductile shear zones across the fault system in the coast ranges underlying active arc volcanoes low q features are apparent below 20 km depth under the long valley caldera two distinct partial melt features at 3 and 15 km depth are inferred moderately high q is associated with sierra nevada and salinian igneous rocks whereas the franciscan subduction complex shows moderately low q prominent high q relates to the great valley ophiolite the pattern of path specific attenuation rate from 3d q is generally similar to the pattern of psuedospectral acceleration residuals for the south napa earthquake indicating that it may be beneficial to incorporate 3d q models into future ground motion prediction equations for northern california online material figures of q p and q s resolution and station delays for t and table of q p v p q s and v s

genetic relationship between the emeishan plume and the bauxite deposits in western guangxi china constraints from u pb and lu hf isotopes of the detrital zircons in bauxite ores abstract the formation processes and alumina sources of the large and super large bauxite deposits that have developed in west guangxi in the yangtze block have been debated for a long time shrimp zircon u pb dates combined with in situ hf isotopic data of the detrital zircons from permian bauxite ores in the western guangxi province china provide new constraints on the genesis of the bauxites in west guangxi u pb dating ages of the detrital zircons cluster around 256 ma and 261 ma this is consistent with the emplacement age of the emeishan plume thus it has been determined that the detrital zircons come from magmatic rocks related to the emeishan plume and that the emeishan plume has significant control on the formation of bauxites in addition this work presents new evidence for the evolution of the emeishan plume most of the e hf t values of the zircons around 256 ma and 261 ma are negative varying widely from 1 3 to 16 1 this data indicates the melting of yangtze block basement rocks and the mixing of magmas generated both from the mantle and from the crust occurred at the periphery of the plume in the main phase of emeishan lip magmatism this study verified that the plume induced uplift exposed carbonates as well as the mafic and felsic rocks generated by the emeishan plume to long periods of intense weathering under humid tropical conditions the weathering remnants of the high alumina magmatic rocks and carbonates were deposited on or transported to the paleokarst surface and converted to bauxites

ce anomalies in the textural components of upper cretaceous karst bauxites from the apulian carbonate platform southern italy the chemical and mineralogical composition of upper cretaceous apulian karst bauxites southern italy and their textural components i e ooids and matrix has been studied the bulk samples are composed of boehmite hematite anatase and kaolinite the samples collected along a vertical profile show a downward enrichment for the elements rb sr ba ni and cr a similar distribution is observed in deposits bauxitized in situ at the expense of matrix like material collected in the karst zone the ooids consist mainly of hematite with minor boehmite and anatase whereas in the matrix boehmite prevails on hematite kaolinite and anatase in the void fillings in the matrix there is a ca fluorocarbonate having a ce ce of 5 8 the ooids with the exception of ce are enriched in ree and show a higher la yb ch ratio relative to the matrix the matrix exhibits a large positive ce anomaly whereas the ooids have negative ce anomaly the ce fractionation between the textural components can be explained assuming 1 ce oxidation and cerianite precipitation in the uppermost part of the deposits 2 scavenging of ree from ce depleted percolating solutions by the iron oxide inducing both ree enrichment and ce negative anomalies in ooids 3 remobilization of cerium as fluoride complex as a consequence of more acidic conditions in the uppermost part of the deposit and precipitation of ce3 as fluorocarbonate mineral toward the carbonate bedrock barrier at alkaline ph alternatively the cerium remobilization possibly as a carbonate fluoride complex could be due to an eh decrease favoured by a rise of the groundwater level

noise to signal a microtremor study at liquefaction sites in the new madrid seismic zone understanding how sedimentary basins respond to seismic wave energy generated by large earthquake events is a significant concern for seismic hazard estimation this study explores the use of microtremors or ambient noise for evaluating strong motion site effects the study focuses on the mississippi embayment in the new madrid seismic zone where widespread liquefaction and ground failure occurred during the 1811 1812 earthquake sequence spectral analyses of microtremor data at sites representing different environments of deposition and sedimentary facies different embayment thicknesses and varying liquefaction susceptibility show correlations between 1 calculated vulnerability indices and evidence of liquefaction 2 sediment thickness and fundamental resonant frequency and 3 subsurface stratigraphic boundaries and observed peaks in horizontal to vertical spectral ratios results of the study suggest that the microtremor method could be helpful in identifying those areas most vulnerable to

site amplification at five locations in san francisco california a comparison of s waves codas and microtremors abstract we compare microtremor data to weak motion s wave and coda recordings at sites in san francisco in order to clarify the range of applicability of microtremor data to ground motion prediction we also compare s wave results to coda results for each type of data we compute spectral ratios of motions from two soil rock station pairs and from an uphole downhole pair in the marina district we compute horizontal vertical ratios nakamura9s method at a soil site a rock site and the surface and borehole instruments in the station pair analyses microtremor data show amplifications at the same fundamental frequency as s waves but the frequencies of other peaks do not agree the amplification at frequencies higher than 2 hz is greater in the microtremor data station pair ratios of coda data generally show spectral peaks occurring at the same frequencies but with levels varying from one to four times the amplification from s wave ratios nakamura9s method of analyzing microtremors agrees better with s wave station pair results than the microtremor station pair method over a limited frequency band that varies from station to station

recurrence interval of big earthquakes along the atotsugawa fault system central japan results of seismo geological survey 1 the atotsugawa fault system afs characterized by high seismicity of micro earthquakes is an active zone of right lateral strike slip faults in central japan we carried out seismo geological studies of three sites on the system one is in the middle of the master atotsugawa fault agf one is at the end and another is on a branching mozumi sukenobe fault msf trenching surveys demonstrated a maximum recurrence interval of 3 000 years which is similar to that of the central agf 2 500 years this might indicate a uniform behavior in the seismogenic zone despite the apparent segmentation in the shallower agf another geo slicing survey at msf depicted a scarce interval of 13 500 years about six times longer than that of the master fault two simultaneous events on both agf and msf occurred in 1858 a d and at about 17 300 years ago suggesting an intermittent cooperation between the master and branch faults of afs

site response and basin waves in the sacramento san joaquin delta california the sacramento san joaquin delta is an inland delta at the western extent of the central valley levees were built around swampy islands starting after the civil war to reclaim these lands for farming various studies show that these levees could fail in concert from shaking from a major local or regional earthquake resulting in salty water from the san francisco bay contaminating the water in the delta we installed seismographs around the delta and on levees to assess the contribution of site response to the seismic hazard of the levees cone penetrometer testing shows that the upper 10 s of meters of soil in the delta have shear wave velocities of about 200 m s which would give a strong site response seismographs were sited following two strategies pairs of stations to compare the response of the levees to nearby sites and a more regional deployment in the delta site response was determined in two different ways a traditional spectral ratio tsr approach of s waves using station bdm of the berkeley digital seismic net as a reference site and using sh sv ratios of noise or nakamura s method both estimates usually agree in spectral character for stations whose response is dominated by a resonant peak but the most obvious peaks in the sh sv ratios usually are about two thirds as large as the main peaks in the tsrs levee sites typically have large narrow resonances in the site response function compared to sites in the farmland of the delta these resonances at a frequency of about 1 3 hz have amplitudes of about 15 with tsr and 10 12 with nakamura s method sites on farmland in the delta also have amplifications but these are typically broader and not as resonant in appearance late slow rayleigh waves were recorded at stations in the delta have a dominant period of about one second and are highly monochromatic results from a three station array at the holland marina suggest that they have a phase velocity of about 600 m s and arrive at about the same azimuth as the straight line back azimuth to the source a dispersion curve determined for the basin or valley waves yields a shallow velocity profile that increases from about 350 m s in the upper 0 2 km to about 1 1 km s at a depth of about 2 km

is northern honshu a microplate abstract seismic slip vectors along the japan trench the eastern margin of the japan sea and the sagami trough are compared with global relative plate motions rm2 minster and jordan 1978 to test a new hypothesis that northern honshu japan is part of the north american plate this hypothesis also claims that the eastern margin of the japan sea is a nascent convergent plate boundary kobayashi 1983 nakamura 1983 seismic slip vectors along the japan trench are more parallel to the direction of the pacific north american relative motion than that of the pacific eurasian relative motion however the difference in calculated relative motions is too small avoid to the possibility that a systematic bias in seismic slip vectors due to anomalous velocity structure beneath island arcs causes this apparent coincidence seismic slip vectors and rates of shortening along the eastern margin of the japan sea for the past 400 years are also consistent with the relative motion between the north american and eurasian plates calculated there seismic slip vectors and horizontal crustal strain patterns revealed by geodetic surveys in south kanto beneath which the philippine sea plate is subducting indicate two major directions one is the relative motion between the north american and philippine sea plates and the other that between the eurasian and philippine sea plates one possible interpretation of this is that the eastern margin of the japan sea may be in an embryonic stage of plate convergence and the jump of the north american eurasian plate boundary from sakhalin central hokkaido to the eastern margin of the japan sea has not yet been accomplished in this case northern honshu is a microplate which does not have a driving force itself and its motion is affected by the surrounding major plates behaving as part of either the eurasian or north american plate another possibility is that the seismic slip vectors and crustal deformations in south kanto do not correctly represent the relative motion between plates but represent the stresses due to non rigid behaviors of part of northern honshu

paleoseismology of deep sea faults based on marine surveys of northern okushiri ridge in the japan sea 1 the eastern margin of the japan sea is an incipient convergent margin characterized by distributed active faults and large scale earthquakes to evaluate the earthquake potential of the northern margin the source area of the 1940 shakotan hanto oki earthquake m7 5 was reexamined and the earthquake recurrence interval was estimated by combining bathymetric seismic and dive survey data with a tsunami simulation seismic profiling clarified that five anticlines have formed in and around this source area during the last 1 8 million years the balanced cross section of one anticline supports that thrust faults extend to the base of the upper brittle crust at about 11 km depth and total slip is about 850 m dive surveys identified fresh collapses along the forelimbs of two anticlines inversion of observed tsunami waveforms to estimate the slip distribution suggests that these two anticlines were the sources of the 1940 earthquake the other three anticlines may be seismic gaps the dive surveys collected debris layers possible records of paleoearthquakes in muddy sediments from the rate of muddy sediment deposition around the anticlines the minimum recurrence interval of earthquakes was estimated to be about 1100 years from structural modeling the average interval was about 6400 years assuming that fault slip started 1 8 million years ago and 3 m of slip occurred during each earthquake taking into account the above results and the instantaneous plate convergent rate between the okhotsk and amurian plates the recurrence interval was inferred to be 1100 to a few thousand years

analysis of wave propagation in the valley of mexico from a dense array of seismometers a dense array of seismometers was installed and operated in the botanical garden of unam within the valley of mexico during april and may 1994 the slow surface velocities at the array require an approach to array analysis with the capability of measuring arrival time differences between stations of less than the sampling interval of the data applying the method to principal component seismograms from earthquakes at local and regional ranges from a number of directions provides the first quantitative information on the composition of the wave field incident upon mexico city phases that propagate through the entire crust such as the initial p and lg waves cross the array with the expected backazimuth on the other hand surface waves in the 2 5 to 5 sec period band which are sensitive to uppercrustal structure show systematic rotations of backazimuth these suggest changes in upper crustal structure or point scatterers located north and south of mexico city for earthquakes outside of the valley of mexico no significant energy was observed propagating across the array from the east from the lake zone thus although it is clear that seismic waves resonate within the lake zone little if any of this energy is transmitted into the hill zone where the array was located however long duration ground motions are observed at the array with evidence of multipathing a back projection of these late off azimuth arrivals indicates that their sources correlate with the boundaries of the quaternary volcanics of the trans mexican volcanic belt

argillite debris converted to bauxite during karst weathering evidence from immobile element geochemistry at the olmedo deposit sardinia the olmedo bauxite deposit occurs in the nurra district of northwest sardinia it forms a stratiform horizon in cretaceous limestone and marl uplift in mid cretaceous had exposed recently deposited limestone to karst weathering and a layer of argillaceous debris accumulated on its surface and was partly converted to bauxite intermediate products were desiccated marl bauxitic argillite and argillaceous bauxite subsidence followed and the bauxite was preserved by the deposition of late cretaceous limestone and other sediments uplift in oligocene miocene time with ensuing erosion exposed the bauxite horizon to its present configuration concentrations of normative minerals illustrate chemical processes and the build up of al in the bauxite horizon plots of chemical data and correlation coefficients show that al ti zr nb th cr and v were immobile during the bauxitization process mass changes point to large net removal of si mg and k from the system although some of this material and slightly mobile al were reprecipitated in the underlying argillite and altered marl immobile element ratios trace the source of the bauxite to the underlying argillaceous limestone al in the bauxite was accumulated from the degradation of 25 to 50 m of the argillaceous limestone

the july 12 1993 hokkaido nansei oki japan earthquake coseismic slip pattern from strong motion and teleseismic recordings we employ a finite fault inversion scheme to infer the distribution of coseismic slip for the july 12 1993 hokkaido nansei oki earthquake using strong ground motions recorded by the japan meteorological agency within 400 km of the epicenter and vertical p waveforms recorded by the global digital seismograph network at teleseismic distances the assumed fault geometry is based on the location of the aftershock zone and comprises two fault segments with different orientations a northern segment striking at n20 e with a 30 dip to the west and a southern segment with an n20 w strike for the southern segment we use both westerly and easterly dip directions to test thrust orientations previously proposed for this portion of the fault the variance reduction is greater using a shallow west dipping segment suggesting that the direction of dip did not change as the rupture propagated south from the hypocenter this indicates that the earthquake resulted from the shallow underthrusting of hokkaido beneath the sea of japan static vertical movements predicted by the corresponding distribution of fault slip are consistent with the general pattern of surface deformation observed following the earthquake fault rupture in the northern segment accounts for about 60 of the total p wave seismic moment of 3 4 1020 n m and includes a large circular slip zone 4 m peak near the earthquake hypocenter at depths between 10 and 25 km slip in the southern segment is also predominantly shallower than 25 km but the maximum coseismic displacements 2 0 2 5 m are observed at a depth of about 5 km this significant shallow slip in the southern portion of the rupture zone may have been responsible for the large tsunami that devastated the small offshore island of okushiri localized shallow faulting near the island however may require a steep westerly dip to reconcile the measured values of ground subsidence

contribution to the geochemistry of the rare earth elements in the karst bauxite deposits of yugoslavia and greece abstract distribution of the rare earth elements ree including la lu y along vertical profiles is presented for four well studied karst bauxite deposits from yugoslavia and greece for one deposit from jamaica la and y contents are given all deposits a downward enrichment of the ree culminating at the base where authigenic ree minerals have been formed this ree pattern is characteristic for karst bauxites formed in situ through the bauxitization of argillaceous material collected in karstic depressions in this way the highest enrichment of the ree in the sedimentary cycle has been achieved both light ree lree and heavy ree hree were mobile during the bauxitization process and were concentrated at the alkaline barrier of the carbonate footwall in four out of five studied deposits the ratios lre hree and la y in bauxites decrease downwards showing an enrichment of the hree relative to lree a further fractionation of the ree took place in the formation of authigenic ree minerals which exhibit a very high enrichment of lree relative to hree in spite of this these minerals and bauxites in four studied deposits have a general similarity of the ree distribution patterns which indicate a close genetic relationship

the july 1998 papua new guinea earthquake mechanism and quantification of unusual tsunami generation the unusual tsunami generated by the july 17 1998 papua new guinea earthquake was investigated on the basis of various geophysical observations including seismological data tsunami waveform records and on land and submarine surveys the tsunami source models were constructed for seismological high angle and low angle faults splay fault and submarine slumps far field and near field tsunamis computed from these models were compared with the recorded waveforms in and around japan and the measured heights along the coast around sissano lagoon respectively in order to reproduce the far field tsunami waveforms small sources such as splay fault or submarine slump alone were not enough and a seismological fault model was required relocated aftershock distribution and observed coastal subsidence were preferable for the low angle fault but the low angle fault alone could not reproduce the large near field tsunamis the low angle fault with additional source possibly a submarine slump is the most likely source of the 1998 tsunami although other possibilities cannot be excluded computations from different source models showed that the far field tsunami amplitudes are proportional to the displaced water volume at the source and the comparison with the observed tsunami amplitudes indicated that the displaced water volume at the 1998 tsunami source was 0 6 km3 the near filed tsunami heights on the other hand are determined by the potential energy of displaced water and the comparison with the observed heights showed that the potential energy was 2 x 1012 j

content and mode of occurrences of rare earth elements in the zagrad karstic bauxite deposit niksic area montenegro abstract three vertical sections through the zagrad deposit of jurassic karst bauxite in central montenegro have provided knowledge of the vertical distribution of major and some selected trace elements including rare earth elements ree variations in the mineralogy particularly those hosting ree have been studied this has revealed the presence of authigenic mineral phases such as xenotime mottramite and monazite best proved using raman microprobe analysis as well as residual phases such as zircon titanite and monazite the mobility of the elements during bauxitization processes has been studied to show that the ree minerals ensure progressive concentration of these elements during removal of major elements through weathering the similarity of normalized ree in the bauxite to the typical post archean australian shales paas and upper continental crust ucc profile and the preserved eu anomaly are evidence that the bauxite was not derived from carbonates and represents alteration of shale marly limestone and volcanogenic or proximal igneous sourced detritus that accumulated in the original karst landform mass change during bauxitization using ti as index element and compared to paas composition revealed almost 100 depletion of si and weak enrichment in al deeper parts of the deposit with authigenic minerals exhibit very strong enrichment in all ree the bauxite ores have high ree contents 693 5 6953 4 ppm especially lree contents 582 8 4882 9 ppm while hree contents 106 6 2070 5 ppm are much lower

are microtremors useful in site response evaluation we have reviewed the applicability of microtremor measurements to evaluate site response of soft soils to this end we evaluated three different techniques commonly used to estimate site effects from microtremor measurements interpretation of fourier amplitude spectra computation of spectral ratios relative to a firm reference station and finally computation of spectral ratios of horizontal components relative to the vertical component of ground motion nakamura s technique these techniques are applied to microtremor records obtained in three cities in mexico mexico city oaxaca and acapulco these cities differ in their local geological conditions and in their seismotectonic environment in order to evaluate the results obtained from microtremor measurements we compare them with standard spectral ratios of the intense s wave part of weak or strong motion records obtained at the same sites our results showed that microtremor measurements can be used to estimate the dominant period of a site with very acceptable reliability in the range 0 3 to 5 hz the best results were obtained with nakamura s technique which also gives a rough estimate of amplification of seismic waves when the local geology is relatively simple simple numerical simulations indicate that the underlying assumptions of nakamura s technique are consistent with the propagation of rayleigh waves these simple numerical simulations also explain why different researchers have been able to successfully characterize 1d site effects using microtremor records regardless of whether they consider microtremors to consist of surface or body waves our results strongly suggest that the technique by nakamura effectively compensates for source effects in microtremor measurements which eliminates a major limitation to their application in earthquake engineering

site effects in a volcanic environment a comparison between hvsr and array techniques at colima mexico colima city is the capital of the mexican federal state of the same name it is located close to the pacific coast and is subjected to a large seismic risk we present a microzonation study in this city based on microtremors using single station and array measurements we applied horizontal to vertical spectral ratios hvsr analysis to single station measurements at 310 sites within the city concentrating measurements in zones that were damaged by the january 2003 m 7 4 earthquake the results show that a seismic zonation based exclusively on single station microtremor measurements is not a reliable alternative when the local geology is complex and site effects are not the result of a single impedance contrast for this reason we applied two independent analysis techniques to array measurements of microtremors the spatial autocorrelation spac method and the refraction microtremor remi method we used linear arrays to record 25 sec microtremor windows at eight sites within the city which were analyzed with those two techniques the result of both techniques of analysis is a phase velocity dispersion curve which can be inverted to obtain a shallow s wave velocity profile two of the sites were the location of shallow 50 m boreholes where p and s wave velocity profiles were measured using a p s suspension log the phase velocity dispersion curves obtained from the remi and spac analyses of the microtremor records showed very good agreement the velocity profiles inverted from the phase velocity dispersion curves showed good agreement with the suspension logging measurements at one of the two sites where they were available and poor agreement at the other site the transfer functions computed from the inverted soil profiles are in good agreement with previous estimates of local amplification from spectral ratios analysis of earthquake records our results are compatible with previous indications of site effects and explain the failure of single station microtremor measurements when the concept of dominant frequency loses its meaning finally we propose an estimate of local site amplification at the city of colima which will be useful for future predictions of ground motion at this city