upper crustal structure of central java indonesia from transdimensional seismic ambient noise tomography summary delineatingthecrustalstructureofcentraljavaiscrucialforunderstandingitscomplextectonic setting however seismic imaging of the strong heterogeneity typical of such a tectonically active region can be challenging particularly in the upper crust where velocity contrasts are strongestandsteepbodywaveraypathsprovidepoorresolution toovercomethesedifficulties we apply the technique of ambient noise tomography ant to data collected during the merapi amphibious experiment meramex which covered central java with a temporary deployment of over 120 seismometers during 2004 may october more than 5000 rayleigh wave green s functions were extracted by cross correlating the noise simultaneously recorded at available station pairs we applied a fully non linear 2 d bayesian probabilistic inversion technique to the retrieved traveltimes features in the derived tomographic images correlate well with previous studies and some shallow structures that were not evident in previous studies are clearly imaged with ant the kendeng basin and several active volcanoes appear with very low group velocities and anomalies with relatively high velocities can be interpreted in terms of crustal sutures and or surface geological features

a critical reappraisal of preconsolidation pressure interpretations using the oedometer test over the past 70 years a number of methods have been proposed for the interpretation of the characteristic vertical effective yield stress or preconsolidation pressure of compressible soils as defined using the standard oedometer test the concept of the preconsolidation pressure has been extraordinarily useful in geotechnical engineering for analysing and predicting settlement behaviour and for normalizing other engineering parameters for comparative purposes defining this characteristic stress however is often problematic and relies heavily on graphical techniques that are subject to some uncertainty particularly when using semi log plots for this purpose this paper illustrates fundamental difficulties with the interpretation of oedometer test and presents an alternative technique for defining unambiguous values of the vertical effective yield stress

crustal thickness beneath mt merapi and mt merbabu central java indonesia inferred from receiver function analysis abstract in this study we analysed 2708 receiver functions rfs using data recorded by 53 seismographic stations that surround mt merapi and mt merbabu two volcanos in central java to map the boundary between earth s crust and upper mantle we observe that a number of rfs from this new dataset have complex signals and do not exhibit typical rf characteristics in particular where the converted ps signal from the moho discontinuity is the clearest and strongest amplitude arrival following the p onset this effect may be related to complex shallow velocity structure due to the presence of magmatic rocks and sediments further analysis of the rf results using the h method suggests that moho depth varies between 27 and 32 km beneath the array with no apparent correlation between crustal thickness and surface topography as one might expect from airy isostacy for instance the moho is quite shallow beneath mt merapi up to 27 km depth despite its elevation of nearly 3 km this may be a consequence of dynamic support from an active upper mantle coupled with erosion and or weakening of the lower crust due to the active volcanic plumbing system to the north of mt merapi the moho is deeper 30 31 km depth below mt merbabu vp vs ratio estimates from the h method are relatively high 1 9 beneath the mt merapi and kendeng basin area which may indicate the presence of a zone of hydrous and active partial melting in the underlying crust lower vp vs ratios 1 7 are found beneath mt merbabu which may be due to its relative lack of volcanic activity compared to mt merapi

mercury intrusion and permeability of louiseville clay several theories have been proposed to correlate the permeability hydraulic conductivity with the pore size distribution of soils and it seemed interesting to determine if these theories could be applied to natural clays for this purpose permeability and mercury intrusion porosimetry tests were performed on a champlain sea clay for both intact and remoulded conditions after compression of the specimens to strains varying from 0 to 42 the results show that for either intact or remoulded soil conditions there is a relationship between the pore size parameters and the permeability of the clay however there is no unique relationship for both intact and remoulded clays and for the silt and clay considered in previous studies consequently mercury intrusion porosimetry alone cannot be usepto evaluate the permeability of soils in general plusieurs thkories ont ctc proposces pour corrcler la permiabilite conductivitk hydraulique avec la distribution des grosseurs de pore des sols et il a semblc intiressant de verifier si ces theories pourraient 2tre appliquees aux argiles naturelles a cette fin des essais de permcabilitc et de porosimctrie a intrusion de mercure okt ctc rcaliscs sur l argile de la mer champlain dans des conditions tant intactes que remanikes apris la compression des specimens a des dcformations variant de 0 a 42 les rcsultats demontrent que pour des conditions soit intactes ou remanices il existe une relation entre les paramitres de grosseur de pore et la permcabilitc de l argile cependant il n existe pas de relation unique pour les argiles tant intactes que remanices et pour le limon et l argile ctudics antkrieurement en conscquence la porosimctrie a intrusion de mercure ne peut pas a elle seule tre utilisce pour cvaluer la permcabilitc des sols en general mots clds permcabilitc argile porosimctrie a intrusion de mercure structure traduit par la rcdaction

geotechnical and geophysical characteristics of muskeg samples from alberta canada abstract a series of laboratory tests have been performed to explore the geotechnical and geophysical characteristics of fibrous muskeg i e grassy bog using undisturbed block samples obtained from alberta canada the basic index properties of muskeg show similar values to the reference data for other organic soils and they significantly differ from those of typical inorganic soils due to high organic content muskeg has high water content high compressibility and high initial permeability the effective stress and porosity play a major role in controlling the stress dependent geophysical properties of shear wave velocity real permittivity and electrical conductivity the values of peak drained friction angle obtained in the direct shear tests are in the range of 26 to 51

mineralogical and microstructural development of the sediments on the mid norwegian margin abstract as a contribution to the understanding of the mechanisms and causes for storegga slide the mineralogy and microstructure of samples from a series of boreholes from the slide neighbourhood have been analysed the results show a change from kaolinite rich oozes through smectite rich fossilferous clays clayey oozes to illite dominated hemipelagic and glacial sediments from the brygge eocene to earliest miocene to kai earliest miocene to late pliocene to naust formations late pliocene to present respectively the deposits are interpreted as the effect of denudation of weathered regolith and an increase in physical erosion in conjunction with the deterioration of the climate and the initiation of glacial cycles during the late cenozoic during the quaternary climate has controlled the mixing of current transported fine grained sediments that are probably derived from the region around the faeroe islands and coarser grained glacial sediments containing a broad spectrum of minerals eroded from the north sea and scandinavian mainland since currents have been most important during warm periods sediments from these periods are finer grained and contain more smectite than the glacial sediments however it is concluded that the mineralogical differences between finer grained sediments from warm periods and the coarser grained glacial sediments are not great enough to explain the ubiquitous utilisation of glacial marine hemipelagic sediments as slip planes for the slides in the area but that this is probably a consequence of the differences in the grain size distribution of the sediments voids that may be casts left behind by gas hydrates have been observed

engineering properties of fibrous peats this state of the art paper presents an interpretation of the permeability compressibility and shear strength of fibrous peats using data from laboratory tests on undisturbed block samples of two fibrous peats as well as extensive laboratory and field data from the literature on fibrous peat deposits engineering properties of fibrous peats are significantly different from those of most inorganic soils however the same fundamental mechanisms and factors determine behavior of both inorganic soils and fibrous peats fibrous peat deposits possess very high initial permeability typically 1 000 times the initial permeability of soft clay and silt deposits upon compression the permeability of fibrous peats decreases dramatically with a ratio of permeability change index to in situ void ratio equal to 0 25 as compared to 0 50 for soft clay and silt deposits fibrous peats display extreme compressibility to the increase in effective vertical stress with compression index values right after preconsolidation pressure 5 to 20 times the corresponding compressibility of typical soft clay and silt deposits among geotechnical materials fibrous peats display the highest ratios of secondary compression index to compression index in the range of 0 05 to 0 07 the values of coefficient of earth pressure at rest for normally consolidated young fibrous peat deposits are in the range of 0 30 to 0 35 as compared to 0 45 to 0 65 for inorganic soils the values of friction angle from triaxial compression tests for fibrous peats are in the range of 40 to 60 as compared to less than 35 for soft clay and silt compositions for fibrous peats the ratios of undrained shear strength in compression to preconsolidation pressure are usually in the range of 0 50 to 0 75 as compared to 0 32 for soft clay and silt deposits for surficial fibrous peat deposits the ratio of vane shear strength to preconsolidation pressure is near 1 0 as compared to 0 12 to 0 35 for inorganic soft clay and silt deposits for fibrous peats the ratio of undrained young s modulus to undrained shear strength is in the range of 20 to 80

generation of peraluminous granitic magma in a post collisional setting a case study from the eastern qilian orogen ne tibetan plateau abstract early paleozoic peraluminous granites are abundant in the eastern part of the qilian orogen northeastern margin of the tibetan plateau a combined study involving geochronology whole rock geochemical and sr nd hf isotopic compositions for three early paleozoic peraluminous granitic plutons jishishan ledu and shichuan plutons from the eastern qilian orogen was carried out to evaluate the causes of chemical variations and generation mechanisms of peraluminous granitic magmas these granitic plutons have magma crystallization ages of 455 427 ma and are moderately to strongly peraluminous a cnk 1 03 1 18 geochemical and sr nd hf isotopic data indicate that they consist substantially of crust derived melts the jishishan and ledu peraluminous granites were dominantly produced by partial melting of precambrian orthogneisses the shichuan monzogranites with low hree contents e g yb 0 80 1 83 ppm and slightly negative end t 5 3 to 2 3 and positive ehf t 1 6 to 3 4 could be derived from immature crustal materials relatively high average zircon saturation temperatures 750 c for each pluton obvious negative eu anomalies eu eu 0 28 0 80 and low pb ba ratios 0 03 0 16 for the jishishan ledu and shichuan granites are consistent with crustal melting involving biotite breakdown under fluid absent conditions our results suggest that compositional variations of moderately to strongly peraluminous granitic magmas are mainly controlled by source compositions and melting conditions while the processes such as mixing with mantle derived magma fractional crystallization restite unmixing and peritectic assemblage entrainment were insignificant or only play secondary roles in their genesis late ordovician to middle silurian crustal anatexis in the eastern central qilian was probably linked with slab break off which may be an important mechanism in addition to lithospheric delamination for the generation of moderately to strongly peraluminous granites in a post collisional setting

multistage anatexis during tectonic evolution from oceanic subduction to continental collision a review of the north qaidam uhp belt nw china abstract the north qaidam ultra high pressure uhp metamorphic belt in the northern tibetan plateau is considered as a typical alpine type uhp metamorphic belt due to the early paleozoic subduction of the qaidam block beneath the qilian block the well preserved paleozoic metatexite migmatite diatexite migmatite felsic sheet dyke and anatectic granite in the north qaidam uhp metamorphic belt provide us with an excellent opportunity to study the generation transport and final fate of crustal melt and geodynamic processes associated with orogenesis based on structural relationships petrology geochronology whole rock geochemistry and sr nd isotope data the early paleozoic anatexis during oceanic subduction to continental collision in the north qaidam uhp metamorphic belt can be further divided into three stages of development 470 ma 446 428 ma and 432 420 ma the first stage granitic leucosomes are rich in k poor in na with low sr y and enrichment of large ion lithophile elements liles which were probably derived from partial melting of ancient felsic gneiss in continental arc circumstances during oceanic subduction the second stage na rich leucosomes and tonalite plutons are characterized by high na sr sr y and la yb and low heavy rare earth elements hrees with positive end t values of 0 1 4 3 and zircon ehf t values of 8 3 10 2 similar to typical tonalite trondhjemite granodiorites ttgs these ttg like magmas were produced through partial melting of newly emplaced gabbroic rocks with arc affinity under high pressure hp granulite facies conditions in a thickened lower crust during continental collision the volumetrically significant migrated plutons evolved from ttg like melt will become segments of continental crust and contribute to crustal growth with partial residual products of hp granulite and or garnet pyroxenite to the mantle by delamination the third stage of anatexis was preserved in both migmatitic uhp gneiss and eclogite in the xitieshan and luliangshan terranes the kfs rich felsic leucosomes inside uhp gneisses in the third stage are characterized by high alkali contents and low mafic component with feot mgo tio2 2 0 2 high la yb and sr y and low y and hrees 3 high al2o3 and low mg values and 4 enriched in liles e g rb ba k sr pb and poor in high field strength elements hfses partial melting of uhp eclogite and felsic gneiss during the initial retrogression stage with pl rich and kfs rich leucosome formation was triggered by dehydration melting involving predominant zoisite and muscovite the anatectic melts from partial melting of deeply subducted uhp gneiss have accumulated and migrated outside the deeply subducted crustal slice in the form of syn collisional plutons the melt evolution from the leucosomes produced at the early exhumation stage to syn collisional granitoids produced at the late exhumation might contribute greatly to the exhumation of the north qaidam uhp metamorphic belt from mantle depths to the lower crustal levels

the tectonic transition from oceanic subduction to continental subduction zirconological constraints from two types of eclogites in the north qaidam orogen northern tibet abstract in the plate tectonics theory continental subduction is pulled by subduction of dense oceanic crust in practice however it is not easy to demonstrate that preceding oceanic crust exposes as oceanic type eclogite together with continental type eclogite in collisional orogens the north qaidam orogen in northern tibet is an ultrahigh pressure uhp metamorphic belt that contains the two types of eclogites providing us with an excellent opportunity to study the tectonic transition from oceanic subduction to continental subduction in order to constrain the protolith nature and metamorphic evolution of eclogites we performed a combined study of zircon u pb ages trace elements mineral inclusions and o hf isotopes for various eclogites from the orogen we discriminate the two types of eclogites by their differences in zircon u pb ages and o hf isotopes cl dark zircon domains exhibit high th u ratios steep hree patterns and significantly negative eu anomalies indicating that they are protolith zircons of magmatic origin with different extents of metamorphic recrystallization relict magmatic zircon domains in type i eclogites yield neoproterozoic protolith ages of 830 ma and hf model ages of 850 1100 ma whereas those in type ii eclogites yield cambrian protolith u pb ages of 489 ma and hf model ages of 500 650 ma most of the cl bright zircon domains show low th u ratios flat hree patterns and no negative eu anomalies and contain mineral inclusions of garnet omphacite and rutile indicating their growth under eclogite facies metamorphic conditions these metamorphic domains have consistent eclogite facies metamorphic ages of 433 440 ma throughout the north qaidam orogen regardless of the eclogite types and locations the metamorphic zircon domains in type i eclogites mostly exhibit 18o values higher than normal mantle values whereas type ii eclogites mostly have 18o values lower than the normal mantle values the difference in the 18o values indicates that their protoliths underwent different temperatures of hydrothermal alteration at different tectonic settings combining zircon u pb ages and o hf isotope compositions with local tectonics it is inferred that type i eclogites were metamorphosed from neoproterozoic continental mafic rocks whereas type ii eclogites were metamorphosed from oceanic mafic rocks that were subducted prior to the continental subduction the consistent eclogite facies metamorphic ages for the two types of eclogites indicate that the exhumed oceanic type eclogite was detached from the subducted oceanic crust and then entrained by the exhuming continental crust therefore the coexistence of oceanic and continental type eclogites in the north qaidam orogen demonstrates the tectonic transition from oceanic subduction to continental collision in the early paleozoic

compressibility of natural soils subjected to long term acidic contamination this paper presents the results of a systematic analysis aimed at establishing whether acidic pore fluids can affect the properties of natural soils in particular their compressibility marine deposits with different mineral compositions and undisturbed soil structure were collected for this research from three coastal areas in japan pleistocene clays from the osaka and ariake bays were obtained from boreholes at a depth of more than 10 m whereas the kawasaki mud a relatively young deposit of holocene was dredged from the bed of the tokyo bay soil specimens were placed in special containers which were designed to reproduce the process of long term soil water chemical interaction and leached with solutions of sulfuric acid for different periods of time ranging from 1 to 9 months at the end of each time interval standard compression tests were performed to study the behavior of soil in an acidic environment it was found that clay mineralogy and soil structure had a significant effect on the compressibility of clays at low ph in the case of the osaka and ariake clays the compressibility significantly increased with a decrease in ph values a finding that was primarily attributed to changes in the soil s structure in contrast the effect of acidic leaching on the properties of kawasaki mud was observed to be the opposite laboratory data showed that in acidic medium the compressibility of soil decreased presumably due to the collapse of the diffuse double layer

crustal thickness beneath central and east java indonesia inferred from p receiver functions abstract we compute receiver functions from teleseismic earthquake data recorded at the dense meramex network in central and east java indonesia in order to map the moho depths h and the bulk crustal vp vs ratio we apply the h stacking technique of zhu and kanamori 2000 though the interpretation of the results is hampered by the high complexity of the recorded waveforms in the context of a high noise level and of the heterogeneous assemblage of continental fragments and ophiolitic suture zones forming southeast asia we were able to derive an average crustal thickness of about 34 km support for the assumption of ophiolitic basement in the center of the island related to the meratus suture zone comes from shallowing of the moho to about 30 km beneath the kendeng zone north and west of the kendeng zone the moho is imaged at anomalous depths down to 39 km the observed anomalies line up along the hypothetical boundary between the continental sw borneo fragment and the meratus suture and are indicative of crustal thickening caused by overthrusting and compressional deformation in the context of a former collision zone resulting vp vs ratios cannot be inferred reliably due to the complexity of the waveforms our results do not corroborate the hypothesis of a major structural change along the southern coast at the division between central and east java likewise we do not find clear evidence for the existence of the postulated muria progo lineament

dynamic response of mercer slough peat the behavior of a peat from mercer slough in bellevue wash was investigated by a program of field and laboratory testing the peat was very soft very weak and highly compressible water contents averaged approximately 600 and in situ shear wave velocities were measured at 12 30 m s cyclic triaxial and resonant column testing indicated that the modulus reduction and damping behavior of mercer slough peat was significantly influenced by strain amplitude and effective confining pressure and was weakly influenced by loading frequency and overconsolidation ratio comparison of the behavior of mercer slough peat with other highly organic soils suggests a trend of increasing linearity and decreasing damping with increasing effective confining pressure site response analyses indicated strong response at low frequencies with spectral shapes that differ significantly from the standard shapes implied by current codes

depositional and post depositional geochemistry and its correlation with the geotechnical properties of marine clays in ariake bay japan the mineralogy geochemistry and geotechnical properties of clay samples in ariake bay japan are presented the mineralogy and geochemistry are discussed in terms of depositional and post depositional processes and the correlations of the clay mineralogy and geochemistry with the geotechnical properties were examined by multiple regression analysis the most predominant clay mineral in the deposits was found to be smectite the vertical distribution of trace elements in the deposits was indicative of the periodical changes in the parent materials involved in the depositional processes the chloride concentration in the pore water varied according to a change in the sea level from brackish to marine and then brackish towards the surface the higher iron oxide contents near the surface and in the deepest zones were the results of pyrite oxidation in the deposits due to weathering under subaerial conditions smectite content was the most predominant governing factor for the consistency limits and activi

potential freshening impacts on fines migration and pore throat clogging during gas hydrate production 2 d micromodel study with diatomaceous ubgh2 sediments abstract the methane gas hydrate stored in natural sediments is considered a potential gas resource countries such as china india japan and korea are interested in commercializing this resource and offshore field pilot tests for gas production have been conducted using depressurization methods to destabilize gas hydrate and facilitate the migration of methane to the production well however fine grained sediments fines which are present even in coarse grained gas hydrate bearing sediments can be resuspended in the production fluid subsequently clogging pore throats in the formation and reducing the overall production efficiency we conducted laboratory tests to evaluate the suspension and clogging potential of fines collected from the ulleung basin east sea korea during the 2010 ulleung basin gas hydrate expedition 2 ubgh2 experimental results reveal that diatoms are prevalent in the sediment and largely control the suspension and clogging behavior fluid flow experiments in 2d micromodels show clogging occurs even when injecting the minimum sediment concentration 0 1 wt in the fluid through micromodels with pore throat widths at the high end of the anticipated range for ubgh2 gas hydrate bearing sands 100 m mobile gas fluid interfaces forming during gas hydrate dissociation accentuate clogging by concentrating and mobilizing fines sedimentation tests show pore water freshening during dissociation is not anticipated to change the potential for diatoms to become entrained in the pore water flow even for the observed gas hydrate saturations of 80 muscovite and illite are also significant components of the tested sediment however and pore water freshening increases their potential for resuspension and clogging overall the resuspension and clogging potential of these fine sediments should increase as gas hydrate dissociation progresses in the thin gas hydrate bearing sands investigated in the ulleung basin

collection and three dimensional modeling of gps and tilt data at merapi volcano java we study here the deformations associated with the november 1996 to march 1997 eruption period at mount merapi central java one of the most active volcanoes in indonesia this activity period includes a vertical explosion on january 17 and an increase of the lava dome volume by about 3 106 m3 two global positioning system gps campaigns have been carried out on a six benchmark network at the beginning and at the end of the period relative displacements with respect to the reference point show an average subsidence of 6 5 cm a multicomponent tilt station installed on the southeast flank 3 km from the summit recorded a tilt of 11 1 0 7 rad in the tangential direction and 0 9 0 4 rad in the radial direction these data are interpreted using a three dimensional 3 d elastic model based on the mixed boundary element method and a near neighbor monte carlo inversion interpretation of tilt data requires an accurate mesh for discretizing the 3 d topography the final result supports a horizontal elliptic magma source located 8 5 0 4 km below the summit and 2 0 4 km to the east of it in particular the data cannot be consistent with the location of a magma chamber determined from seismic activity analysis i e 2 km below the summit the computed depth depends strongly on the source shape and cannot be constrained properly because of the small amount of data the computed deflation of 11 2 106 m3 is about 3 times larger than the observed increase in the lava dome volume this difference is attributed to rock avalanches and pyroclastic flows on the flanks of the volcano

joint inversion of active and passive seismic data in central java seismic and volcanic activities in central java indonesia the area of interest of this study are directly or indirectly related to the subduction of the indo australian plate in the framework of the merapi amphibious experiments meramex a network consisting of about 130 seismographic stations was installed onshore and offshore in central java and operated for more than 150 days in addition 3 d active seismic experiments were carried out offshore in this paper we present the results of processing combined active and passive seismic data which contain traveltimes from 292 local earthquakes and additional airgun shots along three offshore profiles the inversion was performed using the updated lotos 06 code that allows processing for active and passive source data the joint inversion of the active and passive data set considerably improves the resolution of the upper crust especially in the offshore area in comparison to only passive data the inversion results are verified using a series of synthetic tests the resulting images showan exceptionally strong low velocity anomaly 30 per cent in the backarc crust northward of the active volcanoes in the upper mantle beneath the volcanoes we observe a low velocity anomaly inclined towards the slab which probably reflects the paths of fluids and partially melted materials in the mantle wedge the crust in the forearc appears to be strongly heterogeneous the onshore part consists of two high velocity blocks separated by a narrow low velocity anomaly which can be interpreted as a weakened contact zone between two rigid crustal bodies the recent java mw 6 3 earthquake 2006 05 26 utc occurred at the lower edge of this zone its focal strike slip mechanism is consistent with the orientation of this contact

eclogite facies metamorphism in impure marble from north qaidam orogenic belt geodynamic implications for early paleozoic continental arc collision abstract in the north qaidam ultrahigh pressure uhp metamorphic belt impure marble and interbedded eclogite represent a particular sedimentary provenance and tectonic setting which have important implications for a controversial problem the dynamic evolution of early paleozoic subduction collision complexes in this contribution detailed field work mineral chemistry and whole rock geochemistry are presented for impure marble to provide the first direct evidence for the recycling of carbonate sediments under ultrahigh pressures during subduction and collision in the yuka terrane in the north qaidam uhp metamorphic belt according to conventional geothermobarometry pre peak subduction to 0 8 1 3 gpa 485 569 c was followed by peak uhp metamorphism at 2 5 3 3 gpa 567 754 c and cooling to amphibolite facies conditions at 0 6 0 7 gpa 571 589 c u pb dating of zircons from impure marble reveals a large group with ages ranging from 441 to 458 ma peak at 450 ma a smaller group ranging from 770 to 1000 ma peak at 780 ma and minor 1 8 ga zircon aged ca 430 ma uhp metamorphism the youngest detrital zircons suggest a maximum depositional age of ca 442 ma and a burial rate of ca 1 0 1 1 cm yr when combined with p t conditions and uhp metamorphic age the ree and trace element patterns of impure marble with positive sr and u anomalies negative high field strength elements nb ta zr hf and ti and ce anomalies imply that the marble had a marine limestone precursor impure marble intercalated with micaschist and eclogite was similar to limestone and siltstone protoliths deposited in continental fore arc or arc setting with basic volcanic activity therefore the yuka terrane most likely evolved in a continental island arc setting during the paleozoic these data suggest that metasediments were derived from a mixture of proterozoic continental crust and juvenile early paleozoic oceanic and or island arc crust in addition their protoliths were likely deposited in a terrigenous dominated forearc marine basin rather than an intracontinental basin environment further evidence that some continental arc volcanic rock may have been the source of eclogite in the north qaidam these sediments formed in a forearc basin close to the qaidam block to the north were transported in the subduction zone to 100 110 km depth with uhp metamorphism prior to exhumation meanwhile the new results suggest that subduction erosion occurred along the active continental margin during the qaidam block with north dipping subduction indicating that the north qaidam uhp metamorphic belt may have formed during continental arc collision

instabilities along ocean margins a geomorphological and geotechnical perspective due to the growing development of offshore activities along margins in the search for more natural resources there has been a greater need for understanding the mechanics of slope formation in these areas one aspect of this relates to the problems associated with slope stability issues this article presents an perspective view of some geomorphological and geotechnical aspects related to instabilities along ocean margins in order to properly address the issues of slope stability and other mass movements we need to improve our technology in the field of sampling high resolution seismic and in situ measurements ultimately the goal is to be able to carry out proper risk assessment analysis pertaining to submarine mass movement this could be achieved by integrating the geotechnical characterisation of mass movements into a risk assessment methodology which can then be applied on a regional basis with the initiation of a project on continental slope stability costa during the year 2000 major advances are expected on our understanding of the mechanics of submarine mass movements

island arc volcanic rocks in the north qaidam uhp belt northern tibet plateau evidence for ocean continent subduction preceding continent continent subduction abstract a suite of early paleozoic island arc volcanic rocks consisting mainly of basaltic lavas and some intermediate silicic rocks crops out in the north qaidam basin northeastern tibet plateau these rocks have been extensively metamorphosed under greenschist facies conditions and hence differ from the older proterozoic intermediate mafic volcanic rocks which have generally experienced amphibolite facies metamorphism the early paleozoic volcanic rocks are divided into three groups based on their geochemical characteristics 1 vtg i consists of island arc tholeiitic basalts basaltic andesites and andesites that crop out in jilusu and shuangkoushan 2 vtg ii which are high al alkaline and sub alkaline basalts in jilusu and 3 vtg iii an assemblage of highly depleted morb type basalts andesites and dacites that occurs mostly in shuangkoushan groups vtg i and ii are considered to be the products of mature island arcs produced in two stages in the first stage following initiation of ocean continent subduction the island arc tholeiites were generated by partial melting of the subsiding oceanic crust and mantle wedge beneath the island arc as subduction progressed and accelerated calc alkaline and high al basalts were formed and the crust beneath the island arc was thickened the highly depleted morb type lavas vtg iii have boninitic affinities and are believed to have been generated from depleted mantle material modified by subduction zone fluids possibly in the fore arc region the island arc tholeiites are dated at 514 2 8 5 ma whereas uhp eclogite in the north qaidam belt has been dated at 494 ma these ages suggest that ocean continent subduction took place in the north qaidam basin in the early paleozoic and was followed shortly by continent continent collision and subduction which produced the uhp rocks

multichannel analysis of surface waves masw for offshore geotechnical investigations abstract multichannel analysis of surface wave masw surveys are commonly used onshore to produce shear wave velocity vs profiles this paper describes its use in offshore geotechnical investigations underwater masw umasw where the focus was on the upper 15 m of the sediment profile to aid the design of structures such as marine pipelines cable routes and shallow anchor systems umasw was shown to provide reliable data in irish offshore conditions in water depths of up to 50 m the receiver spacing and array length rather than the characteristics of the air gun seismic energy source were the primary control on signal penetration and resolution of individual sediment layers good resolution of the properties of the upper 5 m of sediment was found by reducing the receiver spacing to as low as 0 3 m a test site with a broad intertidal zone allowed coincident land marine and direct measurements to be compared and vs profiles obtained from umasw onshore masw and by seismic cone testing scptu were in good agreement vs profiles estimated from published correlations with cptu data in sandy sediments agreed well with the measured values inversion of data using different software packages showed only a minor variation in results

the causes of the high friction angle of dutch organic soils abstract dutch organic soils have been found in past experiments to possess extremely high effective strength parameters since this finding is not expected and the phenomenon has yet to be explained the high yield strength value is not used in practice understanding the abnormal properties of dutch organic soils would thus be beneficial from the practical point of view a programme aimed at understanding the unusual properties of dutch organic soils non peat soils in particular was performed on the representative organic soils in dutch nature reserve park oostvaardersplasen ovp near almere highly variable fabric of these organic soils was characterized by computed tomography x ray scanner and environmental electronic microscope recognized fabric is in line with the geology of the ovp site the multi scale investigation as presented eventually identified the major role played by subhorizontal laminae and other non organic microstructural elements microfossil skeleton in the high values of ovp organic soils deformation mechanisms of the microstructural elements are proposed and these make the unusual geotechnical properties explainable organics as involved were believed to have a primary contribution in increasing atterberg limits and compressibility and to allow the generation of high pore water pressures and low effective confining pressures during shearing it has been also observed that high value is always correlated to the low effective confining pressure

deglacial pulses of deep ocean silicate into the subtropical north atlantic ocean records of biogenic opal export in the north atlantic ocean show pronounced maxima during each glacial termination over the past 550 000 years consistent with a strong deglacial reduction in the formation of silicate poor glacial north atlantic intermediate water and a consequent increase in upward silicate transport the southern ocean is thought to have an important role in driving glacial interglacial changes in atmospheric carbon dioxide concentrations but the mechanism responsible for carbon dioxide release upon deglaciation remains unclear based on a record of biogenic opal export that exhibits opal maxima during each glacial termination of the past 550 000 years nele meckler et al propose that deglacial reduction in glacial north atlantic intermediate water led to downward mixing of warm low density surface water ultimately triggering antarctic overturning and carbon dioxide release to the atmosphere growing evidence suggests that the low atmospheric co2 concentration of the ice ages resulted from enhanced storage of co2 in the ocean interior largely as a result of changes in the southern ocean1 early in the most recent deglaciation a reduction in north atlantic overturning circulation seems to have driven co2 release from the southern ocean2 3 4 5 but the mechanism connecting the north atlantic and the southern ocean remains unclear biogenic opal export in the low latitude ocean relies on silicate from the underlying thermocline the concentration of which is affected by the circulation of the ocean interior here we report a record of biogenic opal export from a coastal upwelling system off the coast of northwest africa that shows pronounced opal maxima during each glacial termination over the past 550 000 years these opal peaks are consistent with a strong deglacial reduction in the formation of silicate poor glacial north atlantic intermediate water2 gnaiw the loss of gnaiw allowed mixing with underlying silicate rich deep water to increase the silicate supply to the surface ocean an increase in westerly wind driven upwelling in the southern ocean in response to the north atlantic change has been proposed to drive the deglacial rise in atmospheric co2 refs 3 4 however such a circulation change would have accelerated the formation of antarctic intermediate water and sub antarctic mode water which today have as little silicate as north atlantic deep water and would have thus maintained low silicate concentrations in the atlantic thermocline the deglacial opal maxima reported here suggest an alternative mechanism for the deglacial co2 release5 6 just as the reduction in gnaiw led to upward silicate transport it should also have allowed the downward mixing of warm low density surface water to reach into the deep ocean the resulting decrease in the density of the deep atlantic relative to the southern ocean surface promoted antarctic overturning which released co2 to the atmosphere

capacity of dynamically embedded plate anchors as assessed through field tests a dynamically embedded plate anchor depla is a rocket shaped anchor that penetrates to a target depth in the seabed by the kinetic energy obtained through free fall and by the anchor s self weight after embedment the central shaft is retrieved leaving the anchor flukes vertically embedded in the seabed the flukes constitute the load bearing element as a plate anchor this paper presents and considers field data on the embedment depth loss due to the plate anchor keying process and the subsequent bearing capacity factor of the plate anchor element the loss in plate anchor embedment was significantly higher than that reported from corresponding centrifuge tests and is reflected in the larger padeye displacements required to mobilize peak capacity in the field tests measured plate capacities and plate rotations during keying indicate that the end of keying coincides with the peak anchor capacity experimental bearing capacity factors are in the range nc 14 3 14 6 which is appreciably higher than ex

a release to rest model for dynamically installed anchors abstractdynamically installed anchors are torpedo shaped anchors that are installed by dropping them through the ocean such that they self bury in the soft seabeds typically encountered in deep wat

petrology and geochronology of eclogites from the western segment of the altyn tagh northwestern china abstract the eclogites from the western segment of the altyn tagh occur as lens or boundins within quartzofeldspathic gneisses or pelitic gneisses characterized by amphibolite facies parageneses the petrographic features and reaction textures testify to three main metamorphic stages 1 the peak eclogite facies stage p 15 kbar t 665 880 c 2 the granulitic facies stage p 11 14 kbar t 670 800 c and 3 the amphibolite facies stage p 6 3 9 5 kbar t 619 738 c during decompression the trace element rare earth element and sm nd isotopic data suggest that most of the eclogites have protolith features resembling transitional type t type mid ocean ridge basalt morb the well preserved eclogite was selected for sm nd and u pb isotopic dating the sm nd isotopic data yield a whole rock garnet omphacite isochron of 500 10 ma age the u pb isotopic measurement of zircons from the same eclogite shows that the four grain populations are near concordant and are well plotted on concordia giving a weighted mean age of 503 9 5 3 ma the two different geochronological methods yield a similar age which is interpreted as the peak metamorphic age of eclogites and reflects the existence of a mountain root related to continental subduction during early paleozoic moreover based on the comparison with similar rocks in the northern margin of the qaidam basin a displacement of 350 400 km for the altyn tagh fault have been estimated

a microstructural investigation of osaka bay clay the impact of microfossils on its mechanical behaviour a recent microstructural investigation of osaka bay clay sediments has revealed the presence of abundant microfossils particularly in the marine layers which appear to influence directly the micr

compressibility and monotonic shearing behaviour of toronto peat abstract the shearing behaviour of organic soils such as peat under monotonic loading can be very different than those of inorganic soils due to the presence of fibers a series of one dimensional consolidation direct simple shear and bender element tests are conducted to investigate the compressibility and the monotonic shear strength of a peat deposit from the port lands area of toronto ontario canada laboratory specimens are trimmed from block samples collected from a depth of about 4 0 to 4 5 m the samples organic content ranges from about 42 to 60 with a fiber content of 20 to 30 because of their moderate organic and water 180 237 contents the peat samples are found to be less compressible with a slower consolidation rate than several other surficial peat deposits reported in the literature all samples exhibit a ductile shearing behaviour with undrained strength ratios ranging from 0 32 to 0 57 and a residual effective friction angle of about 30 the monotonic tests are further examined within the framework of critical state soil mechanics bender element measurements are used to develop empirical relationships between several engineering parameters of toronto peat with shear wave velocity

upper mantle seismic wave velocity effects of realistic partial melt geometries we investigate seismic wave velocity reduction resulting from the presence of partial melt in the upper mantle the amount of shear and bulk modulus reduction produced by the presence of a connected network of realistically shaped and naturally organized melt inclusions is found using finite element calculations the geometries of the inclusions are taken directly from laboratory experiments of mantle melting with finite element meshes constructed to conform to these shapes the shear and bulk moduli of the composite material are found for both the unrelaxed isolated inclusions and relaxed pressure equalized inclusions cases by assigning appropriate material properties to the fluid modulus reduction from deformation simulations of a solid containing realistically shaped and ellipse shaped melt inclusions quantify the effect of melt pocket cuspateness and melt pocket organization on seismic velocity reduction the three dimensional response is estimated from two dimensional distributions of the melt phase by determining the mode ii and mode iii components of elastic modulus reduction separately and summing their effects in general cuspate and naturally organized melt inclusions cause greater velocity reduction it is shown that v and vs reduction per percent partial melt are at least 3 6 and 7 9 respectively even higher values for velocity reduction are possible above 1 melt fraction if melt exists only in tubules below 1 melt fraction the lower more conservative values of velocity reduction are 070 greater for vp and 84 greater for vs than the analytically determined values for ellipsoidal inclusions somewhat greater effects are possible if nonrandom organization of melt occurs on scales greater than our model

study of the structure of a sensitive champlain clay and of its evolution during consolidation scanning electron microscopy and mercury intrusion porosimetry are used in parallel to identify the structure of a medium sensitivity champlain clay the clay structure is observed firstly on intact remolded and oven dried soils and secondly on soils consolidated at various levels in one dimensional compression both methods of investigation reveal for the intact soil the existence of an aggregated structure characterized by an interaggregate and an intra aggregate porosity remolding affects interaggregate links but does not destroy aggregates the observation of clay structure at various levels of one dimensional compression shows that the collapse of the structure is progressive the largest interaggregate pores being the first affected as the consolidation proceeds smaller and smaller pores are affected for a given pressure increment only the largest existing pores are affected a structure anisotropy has been seen to develop with increasing compression the scanning electron microscope and the me

tomographic evidence for localized lithospheric shear along the altyn tagh fault seismic tomography across the altyn tagh fault at the north edge of the tibetan plateau reveals a low p wave velocity anomaly below the fault down to 140 kilometers this anomaly probably reflects strike slip shear in the lithosphere slip partitioning may also induce a wedge of crust from the tarim basin to plunge into the mantle

new early and late carboniferous paleomagnetic results from the qaidam block nw china implications for the paleogeography of central asia abstract there is an ongoing debate regarding the paleogeographic evolution of the qaidam block 37 3 n 96 4 e in northwest china during the late paleozoic to provide a reliable constraint on the paleogeographic reconstruction and to determine the relationship with the adjacent area we performed a paleomagnetic investigation of early and late carboniferous sediments from the qaidam block stepwise thermal demagnetization successfully isolated high unblocking temperature characteristic directions from the samples the tilt corrected mean direction of the early carboniferous sediments is ds is 298 6 46 4 with 95 4 7 and n 15 sites corresponding to a paleopole at 3 2 n 147 5 e with a95 4 8 the late carboniferous paleomagnetic direction is ds is 320 1 46 1 with 95 5 3 and n 8 sites corresponding to a paleopole at 15 1 n 132 2 e with a95 5 4 a positive fold test for the early carboniferous paleomagnetic directions and consistency with the kiaman reversed superchron for the late carboniferous paleomagnetic directions indicates the primary origin of the characteristic remanence of the studied section the new paleomagnetic results suggest that the qaidam block was located at about 27 n and did not undergo significant n s movement during the carboniferous however the qaidam block experienced a counter clockwise rotation of about 21 during this period comparisons of the paleomagnetic results from the major blocks of central asia suggest that the qaidam block may have experienced a relatively rapid northward movement and collided with the tarim block after the late permian based on the paleomagnetic poles of the qaidam block and adjacent blocks we present a tentative paleogeographic reconstruction for central asia during the early and late carboniferous

an oedometer test study on the preconsolidation stress of glaciomarine clays stress history is usually determined by interpreting the results of oedometer tests to obtain the preconsolidation stress using traditional methods such as those proposed by casagrande and janbu both these methods are based on the assumption that the soil experiences a change in stiffness from a stiff response to a soft response close to the preconsolidation stress disturbed soils however especially overconsolidated clays of low plasticity exhibit a soft response at low stresses thereby making the interpretation of oedometer tests using traditional methods extremely difficult using data mainly from the haltenbanken area offshore norway a study was undertaken to investigate the various methods and testing procedures available to determining stress history oedometer verification tests were also performed on reconstituted specimens to compare interpreted values with the actual applied preconsolidation stress this paper describes the results of the study by illustrating the variation in the inter

stress dependent and strength properties of gas hydrate bearing marine sediments from the ulleung basin east sea korea abstract this paper presents a comprehensive laboratory experimental characterization of the host sediment from natural hydrate bearing sediments recovered during the ulleung basin gas hydrate expedition 2 ubgh2 in 2010 the basic geotechnical properties are characterized and compared with previously reported data the mineralogy and microstructure analyses confirm that the sediments mainly consist of illite kaolinite chlorite calcite and montmorillonite with a high concentration of microfossils diatoms the presence of microfossils may affect many of the geotechnical properties including plasticity activity specific surface and grain size the tested specimens have a relatively high initial void ratio with a high compression index e g cc ranging from 0 6 to 1 0 and swelling index e g cs ranging from 0 1 to 0 25 the shear wave velocities measured during loading indicate a high sensitivity to the stress state which demonstrates the critical role of effective stress in controlling the stiffness of the sediments the peak friction angles are determined to be 17 6 24 6 for clay and silt sediments and 27 1 for high sand fraction specimens the stress dependent and strength parameters obtained in this study may be very useful for performing stability analyses during hydrate dissociation and production

modelling the engineering behaviour of fibrous peat formed due to rapid anthropogenic terrestrialization in hangzhou china abstract peat is a very variable but normally weak material while engineering failures involving peat are common the full diversity of engineering behaviours exhibited by peat has not been well classified due to its large range of possible compositions this paper presents the behaviour of a fibrous peat which is a fill made ground originating from the most recent dredging of the west lake a site of cultural and historic importance in china given its relatively unique mechanism of deposition the distinctive characteristics of this peat are presented in comparison to other peats reported in the literature highlighting its unique engineering behaviour a laboratory study carried out on the peat at jiangyangfan eco park located in hangzhou china identifies that it has its special aspects when compared to other peats the shearing behaviour of peat can be described using the framework of critical state theory the most prominent characteristic of the west lake peat is that its undrained stress path bends towards the left at the very beginning of shearing which indicates that plastic deformation occurs at very small stress ratios a constitutive model based on critical state theory for predicting the undrained shear behaviour of this type of peat from low stress to critical state levels is presented this model also includes several elements of peat behaviour previously reported and it may therefore be applied to a wider range of peat soils

imaging fluid related subduction processes beneath central java indonesia using seismic attenuation tomography abstract we use local earthquake data observed by the amphibious temporary seismic meramex array to derive spatial variations of seismic attenuation qp in the crust and upper mantle beneath central java the path averaged attenuation values t of a high quality subset of 84 local earthquakes were calculated by a spectral inversion technique these 1929 t values inverted by a least squares tomographic inversion yield the 3d distribution of the specific attenuation qp analysis of the model resolution matrix and synthetic recovery tests were used to investigate the confidence of the qp model we notice a prominent zone of increased attenuation beneath and north of the modern volcanic arc at depths down to 15 km most of this anomaly seems to be related to the eocene miocene kendeng basin mainly in the eastern part of the study area enhanced attenuation is also found in the upper crust in the direct vicinity of recent volcanoes pointing towards zones of partial melts presence of fluids and increased temperatures in the middle to upper crust the middle and lower crust seems not to be associated with strong heating and the presence of melts throughout the arc enhanced attenuation above the subducting slab beneath the marine forearc seems to be due to the presence of fluids

proprietes caracteristiques des argiles de l est du canada the compilation of numerous geotechnical data has allowed the definition of the main physical mechanical and hydraulic properties of marine and lacustrine clays of eastern canada as well as the establishment of correlations between some of these properties the possible uses of these correlations are described this study shows that the clays of eastern canada exhibit a behaviour similar to that of other clays but that they are characterized by a higher degree of structuration keywords physical properties mechanical properties hydraulic properties clays canada correlations journal translation

crust and subduction zone structure of southwestern mexico southwestern mexico is a region of complex active tectonics with subduction of the young rivera and cocos plates to the south and widespread magmatism and rifting in the continental interior here we use receiver function analysis on data recorded by a 50 station temporary deployment of seismometers known as the mars mapping the rivera subduction zone array to investigate crustal structure as well as the nature of the subduction interface near the coast the array was deployed in the mexican states of jalisco colima and michoacan crustal thickness varies from 20 km near the coast to 42 km in the continental interior the rivera plate has steeper dip than the cocos plate and is also deeper along the coast than previous estimates have shown inland there is not a correlation between the thickness of the crust and topography indicating that the high topography in northern jalisco and michoacan is likely supported by buoyant mantle high crustal vp vs ratios greater than 1 82 are found beneath the trenchward edge of magmatism including below the central jalisco volcanic lineament and the michoacan guanajuato volcanic field implying a new arc is forming closer to the trench than the trans mexican volcanic belt elsewhere in the region crustal vp vs ratios are normal the subducting rivera and cocos plates are marked by a dipping shear wave low velocity layer we estimate the thickness of the low velocity layer to be 3 to 4 km with an unusually high vp vs ratio of 2 0 to 2 1 and a drop in s velocity of 25 we postulate that the low velocity zone is the upper oceanic crust with high pore pressures the low velocity zone ends from 45 to 50 km depth and likely marks the basalt to eclogite transition

undrained shear strength of pleistocene clay in osaka bay this study presents the undrained shear characteristics of holocene and pleistocene clay samples from depths of 20 200 m under the seabed in osaka bay automated triaxial k0 consolidation tests and anisotropically consolidated undrained triaxial compression and extension tests are conducted using the recompression method the average undrained strength ratio su v0 is 0 33 sd 0 03 when the extension strength is defined as the peak strength or the strength at an axial strain of 15 while su v0 is 0 29 sd 0 04 when the extension strength is defined as the shear stress at the axial strain corresponding to the peak compression strength circular arc stability analyses are carried out with the modified fellenius and bishop methods for the design cross section of the seawall structure of the kansai international airport to study the effects of different definitions of shear strength the seawall is founded on 19 m of soft holocene clay and 10 m of pleistocene sand overlying the pleistocene clay the s

statistical relationships between piezocone measurements and stress history of clays a database containing piezocone soundings from 205 clay sites around the world has been compiled for the calibration of an analytical cone penetration model and the development of statistical correlations yield stresses from laboratory oedometer tests were used as reference values for determining the stress history of natural clay deposits both simple and multiple regression analyses were performed on these data to evaluate correlative trends several simplified empirical relationships were identified for use in practice with the most reliable in relating preconsolidation stress to net cone tip resistance key words cone tip resistance overconsolidation ratio ocr preconsolidation pressure piezocone statistical relationships stress history

nonlinear dynamic properties of a fibrous organic soil the nonlinear dynamic properties of a fibrous peaty organic soil beneath a levee in the sacramentosan joaquin delta in california are described herein thin walled tube samples were obtained from f

the romeriksporten railway tunnel drainage effects on peatlands in the lake northern puttjern area this study presents the results of an investigation of drainage effects of the romeriksporten railway tunnel on peatlands in the lake northern puttjern area drainage impacts on peatlands occurred in marked depressions reflecting faults or weakness zones in bedrocks the impacts were most evident near the tunnel trace but dry peatlands and streams were observed as far as 600 m from the tunnel trace several types of drainage effects were observed on peatland surfaces after tunnelling surface subsidence and formation of local depressions peat slides peat cracking dry peat holes and death of vegetation the effects depended clearly on peatland properties the greatest and most damaging effects were associated with thick peat layers around open water surface here lowering of the water table caused peat slides such areas will generally be extremely vulnerable to lowering of the water level the magnitude of subsidence of peatlands depends on peat thickness peat decomposition and groundwater lowering even after seven years with artificial infiltration in bedrock wells in dry periods to counteract water table lowering peat subsidence and peat slides were evident demonstrating that temporary draw down of water can result in irreversible impacts on peatlands to better be able to avoid damaging effects of tunnel drainage on environment investigations of properties of peatlands above possible tunnel traces should be integrated in the planning procedure for tunnel constructions in mires above such traces the occurrence of floating peat mats degree of peat decomposition peat thickness deliveries of water from surrounding catchments in dry periods and possible pathways of leakage through subsoils and bedrocks should be examined as basis for assessment of vulnerability of peatlands to tunnel drainage and selection of tunnel traces that evade the most vulnerable peatlands when such areas can not be avoided requirements should be set to the tightening of the tunnel to prevent damaging water draw downs in dry periods observations of drainage effects on peatland surfaces can complement hydrological information from measurements of tunnel leakages and groundwater levels and thus contribute to provide a broader picture of hydrological impacts and bedrock hydrogeology

the poisson ratio of the australian crust geological and geophysical implications the poisson ratio which depends on the vp vs ratio provides much tighter constraints on the crustal composition than either the compressional or the shear velocity alone the crustal poisson ratio can be determined from the joint analysis of the travel times of waves converted at the moho and of crustal multiples reflected at the top of the moho we have analyzed the records of the permanent stations installed on the australian continent complemented by the data of the skippy experiment the results reveal substantial variations in the poisson ratio in the different tectonic units for the proterozoic crust an increase of the poisson ratio with increasing crustal thickness is systematically observed while for the phanerozoic crust the poisson ratio tends to decrease for increasing crustal thicknesses these observations are in remarkable agreement with the results of the deep seismic soundings that were performed in the former soviet union the variations observed in the proterozoic provinces can perhaps be explained by underplating of mafic materials at the base of the crust fl 2000 elsevier science b v all rights reserved

early paleozoic orocline in the central china orogen abstract the altun qilian kunlun orogen as a western segment of the central china orogen has experienced a tectonic evolution of the proto tethys ocean and the early paleozoic orogenic movement to produce multiple stage early paleozoic structures and rocks the corresponding ophiolites metamorphic rocks and granites in the orogen show some similarities in petrology and geochemistry especially isotopic geochronology this indicates that they should be under the same subduction accretion system during the early paleozoic while there is diachronism of evolutionary time along strike combined with the paleomagnetic data and plate reconstruction the north qinling central qilian central altun oulongbuluke qaidam east kunlun and west kunlun micro continents from gondwana made up a chain like superterrane within the northern proto tethys ocean based on the detailed structural analysis and spatial and temporal distribution of the main rocks the proto tethys ocean subducted southward and formed a nearly linear subduction zone the tarim qaidam micro continent was likely to have drifted as a unit and mostly rotated relatively counterclockwise in the early paleozoic under the southward oblique subduction collision some large scale dextral strike slip faults developed and the relative displacement and rotation of continents micro continents and tectonic belts also took place in the region making the subduction zone bent to form a s shaped pattern in plan view in this paper we suggest that they are coupled oroclines and put forward a kinematic evolution model the shangdan ocean likely closed no earlier than the formation of the oroclines generating a curved suture zone bypassing east qaidam further linked southward to the central kulun suture although the coupled oroclines was displaced and destroyed by subsequent superimposed structures especially in the west of the altun orogen and east of the qaidam areas the early paleozoic tectonic unconformity and depositional systems developed in the tarim basin and the s shaped pattern of the paleostructures and hydrocarbon reservoirs provide evidence for its existence

compressibility and creep of a diatomaceous soil abstract diatomaceous soils are composed by a mix of sand fines and fossilized diatoms which are unicellular microalgae composed by a strong silica frustule of 10 to 100 m in size with rough surface and enclosing a void that could give the soil a very low dry density due to high water storage capacity within frustules diatomaceous soils present high liquid limit and classifies as high plastic silt mh in classical soil mechanics low density and high plasticity are properties associated to very soft soils however previous studies have reported that diatomaceous soils could mobilize high shear strength and present relatively high yield stress due to large diversity of natural diatomaceous soils in nature their geotechnical singularities are still not fully understood and reported data on undisturbed samples remain scarce in this paper a laboratory experimental study is presented on a diatomaceous soil from mejillones bay in northern chile focused on compressibility and creep microscopic observations and mineralogical analyses indicate that the soil contains siliceous diatom frustules of 10 to 60 m in size which gives the soil a very low dry density and high natural water content compression tests on undisturbed samples results in yield stress much higher than the overburden pressure high contrast between compressibility before and after yielding and significant creep strains the diatomaceous soil does not follow empirical correlations typically used in soil mechanics and is significantly more compressible than fine soils with similar geotechnical classification qualitative microscopic observations after compression show that a large amount of frustules have crushed which probably explains the high compressibility of the soil

dynamic properties of sherman island peat the dynamic properties of peat have been identified as a major source of uncertainty in the evaluation of seismic hazards throughout the sacramento san joaquin delta in northern california this paper summarizes the results of a laboratory study of the dynamic properties of a layer of peaty organic soil underlying the south levee on sherman island near the western side of the delta conventional shelby tube sampling procedures were able to obtain high quality samples because of the compactness of this peat layer located between depths of 9 and 16 m the samples tested were very fibrous and had ash contents of 35 56 staged cyclic triaxial loading was used to measure the stress strain behavior of several specimens under cyclic shear strains ranging from about 0 0005 to 10 other tests included piezo ceramic bender element tests to measure the shear wave velocity of specimens within the triaxial device and undrained monotonic triaxial compression and extension tests the effects of loading frequency cyclic degradation consolidation stress history and structural anisotropy are evaluated the resulting modulus reduction and damping relationships for the sherman island peat are compared with published results for other peats solid waste materials and mineral soils

geotechnical characterization of soft soil deposits in northern poland abstract this paper presents a geotechnical characterization of deltaic soft soil deposits in the vistula marshlands northern poland it shows the limited applicability of organic soil classifications based on cone penetration tests cptu and dilatometer tests dmt none of the in situ based classifications correctly identifies peat analysis of the behaviour of contractive dilative soil layers according to robertson s updated classification 2016 is shown to be in agreement with volumetric changes observed during triaxial compression tests the coefficient of primary compression cc is found to decrease exponentially with the initial bulk density d0 and to increase linearly with the in situ water content wc the presented geotechnical characterization and reference data can be used for foundation design and soil improvement in the soft organic soils of northern poland

singularities of geotechnical properties of complex soils in seismic regions volcanic activity results in a wide range of soil types with very unusual characteristics the most remarkable of which are volcanic ash clays containing the clay minerals allophane and imogolite in addition to these soils volcanic activity often produces the special environmental conditions that result in the formation of diatomaceous soils namely water rich in dissolved silica these soils consist of individual particles containing intraparticle voids filled with water resulting in a very unique porous particle morphology that is quite different than stereotypical sedimentary soils this paper presents a series of careful laboratory tests on samples of both materials found in chile these tests demonstrate that soils weathered from volcanic ash develop yield pressures that are similar to the preconsolidation pressure of sedimentary soils this type of soil also shows a dramatic change in properties due to drying in addition diatomaceous soils and those containing allophane have very low densities in spite of which they develop remarkably high shear strength the need for their properties to be properly understood and taken into account in geotechnical design especially seismic design is emphasized since the location of these soils generally coincides with earthquake activity which like volcanic activity arises from tectonic plate interaction

diatom ooze crucial for the generation of submarine mega slides numerous studies invoke weak layers to explain the occurrence of submarine mega slides 100 km3 in particular those on very gentle slopes 3 failure conditions are thought to be met only within this layer which is embedded between stable sediments although key to understanding failure mechanisms little is known about the nature and composition of such weak layers mainly because they are destroyed with the landslides this study is the first to place detailed constraints on the weak layer for one of the submarine mega slides that occurred on the nearly flat subtropical northwest african continental slopes integrating results from the ocean drilling program with high resolution seismic reflection data we show that the failure surfaces traced into the undisturbed sedimentary sequence coincide with thin 10 m diatom ooze layers capped by clay as diatom oozes are common on many continental margins we suggest a new margin independent failure mechanism to explain submarine mega slides at low gradient continental slopes globally diatom oozes are susceptible to building up excess pore fluid during burial due to their high compressibility and water content if a low permeable clay cap prevents upward drainage excess pore pressures accumulate at the ooze clay interface causing the shearing resistance to increase at a lower rate than the shear stress until failure can occur changes in global climate affect the abundance of diatoms and thus formation of diatom oozes thereby preconditioning the sediments for failure however the actual timing of failure is independent of environmental changes

metamorphic evolution of the eiksunddal eclogite complex western norway and some tectonic implications the metamorphic evolution of the western gneiss region of norway wgr can be evaluated from examination of eclogites formed as an integral part of the gneiss terrain ie in situ petrologic data from one of the larger country rock eclogites within the northwestern part of wgr have been used to construct a p t t path for this crustal volume textural relations as well as mineral composition and zonation suggest an early period of amphibolite facies conditions followed by movement along a very steep positive p t gradient towards very high pressure p 25 kb and moderate temperature t 600 c orthopyroxene coexisting with garnet at such conditions was poor in al 0 5 wt al2o3 and is preserved in the cores of orthopyroxene grains in garnet websterites the increasing al content of orthopyroxene towards garnet and increasing edenite substitution rimwards in zoned amphiboles suggest a period of decompression accompanied by heating towards the metamorphic maximum at t 750 c p 20kb garnet zoning reflects a general prograde history but the reactions that control the zoning are insensitive to pressure changes jadeitic pyroxenes may have formed in the gneisses at p max but would revert to plagioclase subsequent to the metamorphic maximum giving rise to the observed mineralogy further decompression and cooling continued towards high rank amphibolite facies conditions this p t t path reflects crustal thickening to 80 90 km during caledonian time the uplift path is qualitatively similar to theoretically derived paths in which uplift is assumed to be controlled by erosion however uplift following the metamorphic maximum may have been accelerated by a period of suture progradation

volcanism mineralization and metamorphism at the xitieshan pb zn deposit nw china insights from zircon geochronology and geochemistry abstract the footwall volcanic rocks of the ordovician tanjianshan group in the world class xitieshan pb zn deposit have experienced prolonged arc volcanism followed by strong metamorphism and deformation this has resulted in a complex thermal history and led to ambiguity in interpretation of zircon geochronological results an integrated study involving textural characterization cl imaging trace element analysis ti in zircon thermometry and la icpms u pb dating has provided tight constraints on the age and genesis of the zircon groups in the volcanic rocks the temperature of metamorphism and deformation indicated by metacryst minerals and micro structures in the volcanic rocks ranges from 550 to 650 c which partially overlaps with the lower temperature range of zircon crystallization 600 750 c calculated using the ti in zircon thermometer cathodoluminescence images and trace element compositions confirm a magmatic origin for the zircons which have also been variably altered by metamorphic fluids two ranges of u pb ages 475 470 ma and 460 450 ma have been obtained on typical magmatic zircons and are interpreted to represent pre mineralization arc volcanism in the xitieshan deposit a younger age group of 440 430 ma for the fluid modified zircons is considered to record post ore metamorphism during the north qadaim orogeny thus we propose that the original exhalative ores at the xitieshan pb zn deposit formed at 450 440 ma

settlement over peat on the a5 at pant dedwydd near cerrigydrudion north wales the a5 london to holyhead trunk road suffers from large and varied settlements at pant dedwydd where it crosses a geotrophic peat bog developed on the glacial drift that overlies bedrock of silurian denbigh grits group recent carriageway settlements have created an undulating profile over a 100 m stretch restricting forward visibility and posing recurring and persistent difficulties for highway maintenance the highly compressible peat underlies almost 400 m of highway ranges up to 7 m deep and a typical profile consists of an upper sphagnum peat layer and a basal reedy woody and sedge grass peat the highway was originally constructed by thomas telford in 1819 as a low floating embankment over the organic terrain increases in traffic over the intervening period together with successive asphalt overlays have resulted in a history of major repairs and although records are incomplete it is likely that the carriageway is now over 2 m thick over parts of the bog comprehensive geological investigations carried out to characterize the peat deposit included dynamic probe holes boreholes and a trial pit no unusual subsurface conditions were identified however scrub willow or grey sallow salix cinerea was observed growing in spiraea thickets alongside the deepest hollows in the highway the willows may contribute to the road subsidence by extraction of water from the peat beneath the carriageway accordingly removal of the scrub willow and conventional re grading of the carriageway have been recommended to correct the existing problem

estimation of soil strength in fine grained soils by instrumented free fall sphere tests the dynamic response of a sphere in soft clay is considered through field tests in which a 0 25 m dia steel sphere was allowed to free fall in water and dynamically penetrate the underlying soft soil the test data collected in a lake and a sea environment relate to sphere velocities of up to 8 m s reaching sphere invert embedments close to ten diameters an inertial measurement unit located within the sphere measured the motion response of the sphere during free fall and penetration in soil the resulting acceleration data were used within a simple framework that accounts for both geotechnical shearing resistance and fluid mechanics drag resistance but cast in terms of a single capacity factor that can be expressed in terms of the non newtonian reynolds number the merit of the framework is demonstrated by using it as a forward model in a series of inverse analyses that calculate the undrained shear strength profile from acceleration data measured in free fall sphere tests the good match between th

quality of samples retrieved from great depth and its influence on consolidation properties pleistocene sediments deposited in osaka bay have been extensively investigated to depths of up to 400 m consolidation properties especially preconsolidation pressure are somewhat scattered with depth the quality of samples retrieved from great depths has been evaluated based on the indices calculated from the volumetric strain or the void ratio changes in the recompression process the study reveals that these indices do not simply increase with an increase in sampling depth the potential for sample disturbance during sample setting in the constant rate of strain crs oedometer was also investigated these tests have revealed that the preconsolidation pressure as measured in the laboratory is not influenced significantly by swelling in addition preconsolidation pressures indicate that the sediments are slightly overconsolidated with a departure from normally consolidated behaviour that could be explained by cementation key words sampling preconsolidation pressure sample disturbance oedomet

characterisation of ballina clay this paper describes a comprehensive characterisation study carried out on clay from the national soft soil testing facility located at ballina in northern new south wales nsw australia ballina clay represents the estuarine soft clays of high to extremely high plasticity from the richmond river valley in nsw they are structured and lightly overconsolidated with an average organic content around 3 index properties as well as mechanical parameters were estimated from laboratory tests performed on tube specimens retrieved using a fixed piston sampler index characterisation tests were combined with constant rate of strain tests incremental loading tests and stress path triaxial testing to evaluate compressibility stiffness permeability and strength parameters these deposits display very high compressibility and a low undrained shear strength which is larger in triaxial compression ballina clay shows a non linear stress strain response either in one dimensional compression or undrained shearing t

dynamic characterization of the mejillones basin in northern chile using combined geophysical field measurements abstract the mejillones peninsula located in northern chile represents a site of interest for seismic hazards assessment due to 100 year seismic gap the potentially large site effects and the presence of the most important port in the region in addition the western edge of the pampa mejillones is limited by the mejillones fault which controls the development of the mejillones basin to the east in this research we created a dynamic characterization of the northern portion of the basin using an integrated modeling of geophysics observations these observations were gravimetric method magneto telluric method mt and multichannel analysis of surface waves the results of the geophysical campaign show soil thicknesses up to 750 m on the deeper zone with steeper slopes to the west and lower slopes to the east in agreement with the normal fault half graben basin geometry the sedimentary stratum is characterized by shear velocities between 300 and 700 m s extremely low electrical resistivities below 1 m and densities from 1 4 to 1 8 g cm3 the integrated interpretation allowed us to generate a spatial and petrophysical model of the mejillones basin from which we studied the seismic behavior of the zone preliminary results of the dynamic site amplification using the spectral element method show peak ground accelerations pga of almost 100 higher than the solicitation and stronger basin edge effects in this work we demonstrate that the presented methodology integrated geophysical characterization and numerical simulation can be applied to characterize any deep forearc basin to quantify their seismic response in order to assess their seismic hazard

early paleozoic to devonian multiple accretionary model for the qilian shan nw china abstract the qilian shan located in the northern tibetan plateau of nw china has an excellent record of early to middle paleozoic subduction accretion that resulted from convergence between the alax and qaidam blocks but there is no consensus about its detailed tectonic history this paper summarizes its tectonic divisions and discusses its tectonic evolution from the cambrian to devonian the belt has the following tectonic divisions in the far north the southern passive margin of the alax block is juxtaposed against an early cambrian to ordovician marianan type intra oceanic arc north qilian the north qilian arc is separated from a japanese type arc central qilian to the south by a high pressure metamorphic belt composed mostly of ophiolitic slices and oceanic crusts the central qilian is bounded to the south by a wide melange zone south qilian consisting of ophiolitic slices and continental margin sequences farther to the south lies the oulongbuluk microcontinent that is separated from the qaidam block and farther south by an ultrahigh pressure metamorphic belt tectonostratigraphic analysis together with geochemical geochronological and geophysical data indicates a complex evolution by subduction accretion processes from the cambrian to the devonian before final amalgamation and docking to the northern alax block this model solves the long lasting discussion on the polarity of subduction in paleozoic time this multiple subduction accretion history sheds light on the continuity of paleozoic sutures along the qilian shan and the nature of the altyn tagh fault and thus contributes to an improved understanding of the tectonic architecture of central asia

an overview of the seismicity of merapi volcano java indonesia 1983 1994 abstract from 1982 to 1995 merapi volcano java indonesia experienced two main eruptive cycles from 1984 to 1986 and from 1992 to 1994 each cycle had a duration slightly larger than 2 years four major eruptive events occurred in 1984 1986 1992 and 1994 these eruptions were monitored by a telemetered seismic network we present an overview of the seismicity observed between 1983 and 1995 from seismological observations several types of characteristic events are recognised volcanotectonic earthquakes are standard microearthquakes either shallow an aseismic zone is situated between two seismic zones at a depth between 1 5 and 2 5 km below the summit we postulate that it is a small shallow magma reservoir where magma injected from below can be stored temporarily we try to relate seismic observations during both eruptive cycles to the initial injection of deep magma to the superficial magma system the first eruption in each case seems to involve magma enriched in gas that extrudes the content of the conduit and explodes the old dome a regular outflow of magma follows the initial explosion and gradually a dome is building up then it stops and a period of repose is observed later a second episode of dome growth occurs the height of the dome reaches a maximum corresponding to a state of lithostatic equilibrium the time delay of more than 2 years between the beginning and the end of a cycle may result from crystallisation in a volatile rich magma and from the building up of pressure in the superficial magma pocket some important events like the collapse of the dome on 22 november 1994 are not preceded by any seismic precursor when it reaches a large volume the dome is not stable and is likely to collapse by gravity for instance after the sudden influx of matter or gas or after a heavy rain on merapi tremors are observed but do not always precede a dangerous event

engineering geological characterization of clayey diatomaceous earth deposits encountered in highway projects in the tengchong region yunnan china abstract a type of clayey diatomaceous earth of pliocene mangbang formation n2m was encountered in highway projects in the tengchong region of yunnan province southwest china the tengchong clayey diatomaceous earth is characterized using multiple test methods such as granulometric analysis chemical analysis x ray diffraction xrd and scanning electron microscopy sem analysis shrinkage and swelling tests unconfined or uniaxial compression test triaxial test and direct shear tests the chemical and mineralogical compositions physical and hydraulic properties and engineering properties of the clayey diatomaceous earth are presented in this paper it is revealed that the tengchong clayey diatomaceous earth is an unusual soil or rock which has characteristics of both typical diatomaceous earth and swelling clayey soil or soft clay rock the diatoms in the earth enhance the connection between micro structures and improve the mechanical properties of diatomaceous earth however due to the existence of a significant amount of swelling clay minerals the tengchong clayey diatomaceous earth becomes swelling soft rock and is prone to engineering problems or geohazards based on the test results a number of issues regarding classification discrimination and geohazard control related with the clayey diatomaceous earth are discussed to provide both some basic understanding and new insight into the characteristics of the clayey diatomaceous earth deposits

merapi central java indonesia an outline of the structural and magmatological evolution with a special emphasis to the major pyroclastic events abstract merapi volcano in the central part of java is regarded as the most active and most dangerous volcano in indonesia on the basis of field studies and geochronological data its history is divided into four periods ancient middle recent and modern merapi according to our preliminary age data the ancient period may have begun around 40 000 y bp and lasted until 14 000 y bp when the middle period begun the recent period begun around 2200 y bp and was replaced by the modern period after the eruption of 1786 during the middle merapi stage a mount st helens type edifice collapse occurred our data suggest that his event is younger than 6700 y bp and older than 2200 y bp during the recent merapi stage violent magmatic to phreatomagmatic eruptions twice interrupted the growth of the volcano the older gumuk phreatoplinian deposits cover the entire cone charcoal found within these deposits gave 14c ages of 2200 and 1470 y bp the overlying sambisari ash deposits were emplaced by violent pyroclastic surges directed towards the south i e to the present location of the town of yogyakarta they buried the shivaitic temple of sambisari at the start of the 15th century modern merapi is characterised by the persistent growth of a summit dome periodically interrupted by partial or total collapse of the dome to generate frequent merapi type nuees ardentes blocks and ash flows and associated surges or more exceptionally fall back st vincent type nuees ardentes scoria flows in contrast previous stages were characterised by effusion of long lava flows alternating with violent explosive phases generating essentially st vincent type nuees ardentes merapi lavas are calc alkaline with a compositional range between 49 5 and 60 5 wt sio2 moreover high k basaltic andesites represent about 90 of merapi lavas disequilibrium features are common in the mineralogical assemblage plagioclase orthopyroxene clinopyroxene olivine amphibole titanomagnetite scarce alkali feldspar macroscopic and microscopic textural heterogeneities are related to magma mixing that may have buffered the compositions of lavas and caused the restricted range of compositions our studies of past activity at merapi provide some insights into future activity and to related volcanic hazards it is clear that merapi has the potential of eruptions much more powerful than observed during the historic period

mexico city soil behavior at different strains observations and physical interpretation the unique mechanical properties of mexico city soils plot as extreme values on most geotechnical engineering charts the purpose of this study is to analyze salient properties and to propose conceptual models to explain them in particular mechanical parameters synthesized from published laboratory data are systematically organized in terms of strain level three strain regions are identified the threshold strains at the boundaries between these strain regions are examined in terms of microscale processes that participate at different strains

early palaeozoic north qaidam uhp metamorphic belt on the north eastern tibetan plateau and a paired subduction model an early palaeozoic uhp metamorphic belt was recently discovered in the north qaidam mountains in the north eastern part of the tibet plateau the belt contains abundant eclogite with lesser amounts of garnet peridotite and gneiss the paragneiss contains abundant zircon with coesite inclusions whereas the eclogite has garnet with coesite pseudomorphs and omphacite with exsolved quartz the calculated peak metamorphic conditions for the eclogite are t 730 c and p 2 8 gpa the garnet peridotites are magnesium rich with mg s 100 mg mg fe up to 92 olivine in the peridotites is highly magnesian fo 91 5 and tio2 poor and is typical of low t garnet peridotites calculated peak metamorphic conditions for the peridotites are t 837 c and p 2 5 gpa u pb and sm nd isotope dating indicate that continental subduction started during the early ordovician 495 ma the north qaidam uhp together with the north qilian hp belt about 300 km to the north constitute a pair of genetically related early palaeozoic subduction zones along the northern margin of the tibet plateau

geotechnical properties of deep oceanic sediments recovered from the hydrate occurrence regions in the ulleung basin east sea offshore korea abstract this study presents comprehensive geotechnical data of the natural marine sediments cored from the hydrate occurrence regions during the ulleung basin gas hydrate expedition 1 ubgh1 east sea offshore korea in 2007 geotechnical soil index properties of the ulleung basin sediments including grain size distribution porosity water content atterberg limits specific gravity and specific surface area were experimentally determined these soil index properties were correlated to geotechnical engineering parameters e g shear strength and friction angle by using well known empirical relationships by performing standard consolidation tests on both undisturbed specimens as recovered from the original core liner after hydrate dissociation and remolded specimens stress dependent mechanical and hydraulic properties e g compressibility and hydraulic conductivity were measured the experimental results provide important engineering parameters and demonstrate the effect of hydrate presence and consequential dissociation to index properties engineering parameters and innate sediment structures

the formation of pangea abstract the making of pangea is the result of large scale amalgamation of continents and micro continents which started at the end of the neoproterozoic with the formation of gondwana as pieces were added to gondwana on its south american antarctica and australia side ribbon like micro continents were detached from its african and south chinese side cadomia in the late neoproterozoic avalonia and hunia in the ordovician galatia in the devonian and cimmeria in the permian cadomia was re accreted to gondwana but the other ribbon continents were accreted to baltica north china laurussia or laurasia finding the origin of these numerous terranes is a major geological challenge recently a global plate tectonic model was developed together with a large geological geodynamic database at the lausanne university covering the last 600 ma of the earth s history special attention was given to the placing of gondwana derived terranes in their original position using all possible constraints we propose here a solution for the variscan terranes another paper deals with the altaids the galatian super terrane was detached from gondwana in the devonian during the opening of paleotethys and was quickly separated into four sub terranes that started to by pass each other the leading terranes collided at the end of the devonian with the hanseatic terrane detached from laurussia in the carboniferous gondwana started to impinge onto the amalgamated terranes creating the variscan chain and the pangean super continent east of spain paleotethys remained opened until the triassic subducting northward under laurasia roll back of the paleotethyan slab triggered the collapse of most of the european variscan orogen which was replaced by series of permian rifts some of them becoming oceanized back arc basins during the triassic major force changes at the pangean plate limits at the end of the triassic provoked its break up through the opening of the proto caribbean central atlantic alpine tethys oceanic seaways

modeling the density at merapi volcano area indonesia via the inverse gravimetric problem 1 merapi is a high risk andesitic volcano in central java indonesia very little information is known about the detailed regional density structure around merapi and its neighbor volcano merbabu we compute a subsurface three dimensional 3 d model of anomalous density for the volcanoes merapi and merbabu in central java indonesia by inversion of the gravity field as input for the inversion methodology gravity observations from 443 points whose 3 d coordinates are determined by gps are used the inversion algorithm is based on an explorative approach to fit a least squares condition including a balancing factor between the minimization of the residuals and the anomalous mass a mean density about 2242 kg m3 for the region of merapi and merbabu has been computed by least squares adjustment results of the inversion show major low density contrasts up to 242 kg m3 and positive structures about 264 kg m3 referred to the determined mean density a density anomaly relative high with densities up to 264 kg m3 is connecting the volcanoes in a 152 course from nw to se and might be built of older basaltic lava low density contrasts about 242 kg m could be found in agreement with magnetotelluric and electromagnetic results generally the identified high and low density bodies are in agreement with the results of other geophysical methods such as electromagnetic and magnetotelluric prospecting or geological formations and structures a porosity about 21 is derived for the largest negative density bodies about 242 kg m3 furthermore the density model gives some new information about the controversial origin of a hill formation near merapi and is also used to discuss the possible existence of a shallow magma chamber which is also a controversial subject generally the density model serves as basic information for the interpretation of geodetic and geophysical observations and confirms existing results from magnetotellurics electromagnetics and seismic data interpretation

a microstructure approach to the sensitivity and compressibility of some eastern canada sensitive clays investigation of micro macro relationships in soils most often concerns granular soils in which both the elemental unit the grain and the physical laws governing inter grain interactions appear to be better known the situation is different for clays because the elementary unit and the inter unit interactions at the micro scale are more difficult to characterise in fine grained soils it has been shown that an intermediate level corresponding to the way clay and fine grained particles are arranged together had to be considered so as to link microscopic features to macroscopic behaviour an investigation of the change in microstructure during compression carried out some time ago on a sensitive clay from canada demonstrated that studying the changes in pore size distribution provides a satisfactory description of microstructure changes during compression the analysis is applied here to six other sensitive clays first a careful examination of the intact and remoulded microstructure is conducted in o

detailed seismic imaging of merapi volcano indonesia from local earthquake travel time tomography abstract mt merapi located in central java indonesia is one of the most active volcanoes in the world it has been subjected to numerous studies using a variety of methods including tomographic imaging in an attempt to understand the structure and dynamics of its magmatic plumbing system results of previous seismic tomographic studies that include mt merapi poorly constrain the location of its underlying magma source due to limited data coverage in order to comprehensively understand the internal structure and magmatism of mt merapi a project called domerapi was conducted in which 53 broadband seismic stations were deployed around mt merapi and its neighbourhood for approximately 18 months from october 2013 to april 2015 in this study we compare vp vs and vp vs tomograms constructed using data obtained from local domerapi and regional seismic networks with those obtained without domerapi data we demonstrate that the data from the domerapi seismic network are crucial for resolving key features beneath the volcano such as high vp vs ratios beneath the merapi summit at 5 km and 15 km depths which we interpret as shallow and intermediate magma bodies respectively furthermore west east vertical sections across mt merapi and a dormant less active volcano mt merbabu exhibit high vp vs and low vp vs ratios respectively directly beneath their summits this observation likely reflects the presence for mt merapi and absence for mt merbabu of shallow magma bodies near the surface

geochronology geochemistry and sr nd hf isotopic compositions of mafic ultramafic intrusions in the niubiziliang ni cu sulfide deposit north qaidam orogenic belt nw china implications for magmatic source geodynamic setting and petrogenesis abstract whole rock geochemical and sr nd isotopic data and zircon u pb hf isotopic data are reported for mafic ultramafic intrusions in the niubiziliang ni cu sulfide deposit located in the westernmost segment of the north qaidam orogenic belt nqob nw china ni cu sulfide ores of economic interest are found within these intrusions with the niubiziliang iii and iv intrusions hosting most of the ni cu mineralization the niubiziiang mafic ultramafic intrusions intrude biotite plagioclase gneiss of the paleoproterozoic dakendaban group zircons separated from the gabbro plagioclase bearing clinopyroxenite and olivine websterite yield u pb ages of 389 2 373 2 and 380 2 ma respectively indicating a genetic linkage with middle late devonian regional magmatism 390 370 ma gabbro zircons have ehf t values of 4 2 10 9 with older tdm1 ages 0 86 0 59 ga the niubiziliang intrusions contain many xenoliths of paleoproterozoic biotite plagioclase gneiss and the intrusions have similar trace element patterns with strong enrichment in liles e g k rb and th and moderate depletion in hfses e g nb ta p and ti the major and trace element characteristics and sr nd hf isotopic compositions indicate the parental magmas originated from a metasomatized asthenospheric mantle source that had previously been modified by subduction related fluids the magmas experienced significant crustal contamination both in the magma chamber and during ascent triggering sulfur over saturation that resulted in the deposition and enrichment of sulfides considering the tectonic evolution of this region we infer that the niubiziliang mafic ultramafic intrusions formed in a post collisional extensional setting related to delamination of the subcontinental lithosphere

linking high pressure mafic granulite ttg like tonalitic trondhjemitic leucosome and pluton and crustal growth during continental collision

physical chemical and mineralogical properties of mexico city sediments a geotechnical perspective the authors appreciate the interest of the discussers in the paper and offer the following comments as indicated in the paper the results presented were obtained as part of a comprehensive research program on the microstructure of mexico city sediments being conducted at the national university of mexico a second site has been studied and the corresponding paper has been written in which correlation of the profiles of geotechnical properties of the sediments with their profiles of physical chemical and mineralogical properties has been investigated the discussers compare the mexico city sediments with illitic sensitive clays in canada the united states and norway we believe their discussion estimates in an alternate scenario which did not in our judgement optimally represent the circumstances of the just case the focus of our article principally mexico city sediments are predominant disintegration products of andesitic rocks and fine and ultrafine volcanic ash furthermore the discussers indicate that variations in carbonate content may have only a small influence on observed variations in the engineering behavior of deposits with high water content which is the case for mexico city sediments all of the ramon lopez velarde park core was checked with scanning electron microscopy and we did not find carbonate precipitation except at a depth of 4 m from the surface so the role of carbonate cementation is doubtful phase contacts are developed in highly compacted clays or cemented clays and are distinguished by the presence of direct contacts between the structural elements and by a new phase carbonates developed at the contacts cementing the particles coagulation contacts are widespread in young clays and poorly cemented clays the structural elements do not directly touch each other and structural cohesion is de termined by molecular and possibly magnetic and dipole interaction furthermore the coagulation contacts allowed the soil to reach a restructured form after it was altered which happened in the mexico city sediments the authors agree that the processes by which the amorphous material content is determined are chemically aggressive as suggested by the discussers overall however the authors feel that the role of the amorphous material is mainly responsible for the properties of mexico city sediments the authors will investigate further quantitative interpretations in mexico city sediments

p and s velocity structure of the crust and the upper mantle beneath central java from local tomography inversion here we present the results of local source tomographic inversion beneath central java the data set was collected by a temporary seismic network more than 100 stations were operated for almost half a year about 13 000 p and s arrival times from 292 events were used to obtain three dimensional 3 d vp vs and vp vs models of the crust and the mantle wedge beneath central java source location and determination of the 3 d velocity models were performed simultaneously based on a new iterative tomographic algorithm lotos 06 final event locations clearly image the shape of the subduction zone beneath central java the dipping angle of the slab increases gradually from almost horizontal to about 70 a double seismic zone is observed in the slab between 80 and 150 km depth the most striking feature of the resulting p and s models is a pronounced low velocity anomaly in the crust just north of the volcanic arc merapi lawu anomaly mla an algorithm for estimation of the amplitude value which is presented in the paper shows that the difference between the fore arc and mla velocities at a depth of 10 km reaches 30 and 36 in p and s models respectively the value of the vp vs ratio inside the mla is more than 1 9 this shows a probable high content of fluids and partial melts within the crust in the upper mantle we observe an inclined low velocity anomaly which links the cluster of seismicity at 100 km depth with mla this anomaly might reflect ascending paths of fluids released from the slab the reliability of all these patterns was tested thoroughly

geotechnical characterization of marine sediments in the ulleung basin east sea the geotechnical characteristics of ulleung basin sediments are explored using depressurized samples obtained at 2100 m water depth and 110 m below the sea floor geotechnical index tests x ray diffraction and sem images were obtained to identify the governing sediment parameters chemical composition and mineralogy we use an instrumented multi sensor oedometer cell to determine the small strain stiffness zero lateral strain compressibility and electromagnetic properties and a triaxial device to measure shear strength sem images show a sediment structure dominated by microfossils with some clay minerals that include kaolinite illite and chlorite the preponderant presence of microfossils determines the high porosity of these sediments defines their microstructure and governs all macroscale properties the shear wave velocity increases as the vertical effective stress increases on the other hand porosity permittivity electrical conductivity and hydraulic conductivity decrease with increasing confinement all these parameters exhibit a bi linear response with effective vertical stress due to the crushable nature of microfossils well established empirical correlations used to evaluate engineering parameters do not apply for these diatomaceous sediments which exhibit higher compressibility than anticipated based on correlations with index properties settlements will be particularly important if gas production is attempted using depressurization because this approach will cause both hydrate dissociation and increase in effective stress

compressibility behaviour and properties of peaty soils from dian chi lake area china abstract peat deposits are widely encountered in many parts of the world and present various challenges for the geotechnical engineering community because of their low bearing capacity and very high compressibility and creep potential this paper describes extensive index and oedometer testing to investigate the compressibility behaviour properties of deep strongly to completely humified peat and highly organic fine grained soil layers at the northeast shore of dian chi lake in kunming southwest china a region that recently is experiencing significant infrastructure construction compared to surficial peat deposits the peaty soil layers investigated with organic contents ranging 23 5 80 0 have been subjected to a 6 7 m depth of inorganic soil overburden such that they have substantially lower water content and void ratio and higher preconsolidation stress nevertheless with deduced c cc 0 04 0 07 cr cc 0 14 0 18 and ck e0 0 23 the dian chi peaty soils exhibit similarities with surficial fibrous peats from other countries regions unlike fibrous peats however the dian chi peaty soils have extremely low permeability with deduced kv values of the order of 1 10 9 to 1 10 10 m s consistent with their hunification level existing linear cc w0 correlations were found inadequate for the dian chi peaty soils such that a new cc w0 correlation is proposed from curve fitting of the gathered experimental data to better capture their non linear relationship

geo engineering properties of eemian peats from radzymin central poland in the light of static cone penetration and dilatometer tests abstract the paper presents the results of field studies testing the reaction of eemian peats on the mechanical effect of standard measurement tools cpt cptu marchetti dilatometer based on the collected undisturbed samples macroscopic observations were made and sem observations were conducted to identify the microstructural features a fibrous structure and advanced diagenetic changes have been noted in the studied peats despite their relatively young age these may have resulted from an exceedingly strong structural reinforcement which causes that the studied sediments cannot be treated as low bearing soils diagenetic processes caused farfetched changes of the mechanical properties which is reflected e g in classification normograms standardized diagrams may lead to false conclusions the presented studies of organic soils are an example of strong influence of structural features and diagenetic phenomena on the results obtained for native soils at the same time they imply particular caution in the interpretation of the substratum properties based only on the commonly used in situ tests the values and variability of the collected parameters have been presented as frequency distributions additionally the apparent character of the properties of preconsolidation parameters ocr has been shown

a triaxial investigation of kinematic yielding in sand the elastic plastic behaviour of a reconstituted sand is considered under triaxial conditions covering a wide range of strains monotonic probing tests are used to identify two types of kinematic yield surface for samples with loose and dense initial states under drained and undrained conditions and after different patterns of consolidation plastic strain development and global stiffness degradation are found to be closely interrelated and the interpretation involves decoupling the elastic and plastic strain components the sizes and the shapes of the loci are strongly affected by effective stress states and histories including any periods allowed for creep and ageing a tentative qualitative micromechanical explanation is offered for the phenomena observed