the motion of rigid ellipsoidal particles in slow flows abstract preferred orientations of fabric elements in tectonites are usually interpreted with reference to two continuum models namely those of march 1932 and jeffrey 1922 it is argued that the first of these is usually inappropriate if the fabric elements are rigid inhomogeneities embedded in a deformable matrix jeffrey s model is more applicable but until recently its use has been limited to problems involving axisymmetric particles and simple flow geometries in this paper jeffrey s equations have been solved numerically in order to investigate the behaviour of more general systems the motions of two particle shapes one a prolate spheroid the other a triaxial ellipsoid are considered in parallel for four specified flow geometries which involve pure or simple shear and combinations of both any departures from particle axisymmetry or from simple flow geometries have a significant effect on particle behaviour compared with that predicted by spheroid simple flow solutions

the metamorphic history of eucrites and eucrite related meteorites and the case for late metamorphism we report induced thermoluminescence tl data for separates from three howardite eucrite and diogenite hed meteorites and the vaca muerta mesosiderite the results of thermal modeling of the surface of their parent body are also described the tl sensitivities for matrix samples from the lew 85300 302 and 303 paired eucrites and the bholghati howardite are lower than the tl sensitivities for the clasts which is consistent with regolith working of the matrix in fairly mature regoliths within an isochemical series of hed meteorites tl sensitivity reflects metamorphic intensity but clast to clast variations in the tl sensitivities of the vaca muerta mesosiderite and clasts in the eet 87509 513 and 531 paired howardite primarily reflect differences in mineralogy and petrology thermoluminescence peak temperatures indicate that all the components from the lew 85300 302 and 303 paired eucrites experienced a reheating event involving temperatures 800 c which is thought to have been due to impact heating and therefore that the event was concurrent with or postdated brecciation the vaca muerta clasts are essentially unmetamorphosed but the induced tl data indicate that the remaining howardite eucrite dioenite and mesosiderite hedm meteorites experienced metamorphism to a variety of intensities but involving temperatures 800 c cause a change in tl peak temperature feldspars from a variety of terrestrial and extraterrestrial sources show this behavior and x ray diffraction and kinetic studies suggest that it is indirectly related to al si disordering cooling rates are not consistent with autometamorphism following the initial igneous event or with heating by subsequent eruptions of lava onto the surface of the hed parent body instead our thermal models suggest that the metamorphism occurred within a regolith ejecta blanket of up to a few kilometers thick with different levels of metamorphism corresponding to different thicknesses of blanket between essentially 0 and 2 km rather than different burial depths in a regolith of uniform thickness we argue that metamorphism occurred 3 9 ga ago and was associated with the resetting of the ar ar system for the hed meteorites

chemical characteristics and origin of h chondrite regolith breccias abstract we report petrologic data and contents of ag bi cd co cs ga in rb se te tl and zn trace elements spanning the volatility mobility range in light and dark portions of h chondrite regolith breccias and l chondrite fragmental breccias the chemical petrologic characteristics of h chondrite regolith breccias differ from those of non brecciated chondrites or fragmentai breccias petrologic characteristics and at least some trace element contents of h chondrite regolith breccias reflect primary processes contents of the most volatile mobile elements may reflect either primary or secondary processing possibly within layered h chondrite parent object s chemical petrologic differences existed in different regions of the parents regolith formation and gardening and meteoroid compaction were not so severe as to alter compositions markedly

seismicity variations associated with aseismic transients in guerrero mexico 1995 2006 primarily aseismic deformation transients in subduction zones sometimes associated with tremors and low frequency earthquakes are a newly recognized mode of deformation stressing in the up dip seismogenic zone is increased episodically due to down dip transientslips andeacheventmaymakeitmorepronetofailureinalargethrustearthquake itisimportantforseismichazardassessment to search and identify patterns of seismicity variation associated with transients the guerrero mexico region is chosen for this study because of long term continuous geodetic observations and abundant seismicity in the shallow subduction zone we search the gcmt and neic catalogs for earthquakeswithdepths lessthan100kmbetween1995and2006withintheareacoveringthe regionaffected by major transients since 1996 a completeness magnitude of mc 4 5 is determined for the neic catalog used in this study based on the maximum likelihood method three large transients in 1998 2001 2002 and 2006 are all temporally correlated with high seismic rates in the studied area in particular transients are either preceded by a cluster of extensional earthquakes relatively far inland from the trench or followed by shallow thrustearthquakes closetothe trench in somecases such asthe 2001 2002 transient both typesofactivityare foundbordering the transient the assembled evidence suggests that transients may serve as a mechanism of stress communication between distant seismicity clusters in shallow subduction zones 2007 elsevier b v all rights reserved

effects of experimental deformation on the remanent magnetization of sediments abstract changes in direction and in intensity of the remanent magnetization of sediments were studied during experimental deformation leading to an axial shortening of 20 30 the remanence was produced before shortening by anhysteretic magnetization in an alternating field of 90 mt superimposed on a parallel steady field of 1 mt at various inclinations with respect to the sample the samples were sandstones marls and volcanic sediments the results show that the direction of magnetization is stable during the deformation within the experimental precision the intensity of magnetization decreases during shortening by an amount which depends on the type of rock about 30 for sandstones and about 5 for marls and volcanic sediments the march model does not account for the data and a discontinuous deformation must be invoked the evolution of the young modulus of sandstones during cyclic loading and unloading shows first a decrease in relation to crack density growth then an increase showing a localization of the fracturation and finally a deformation by displacement of microblocks an interpretation is given after a discussion of the results obtained by other authors with plasticine and artificial clays the amplitude of the decrease and of the rotation of the remanent magnetization could be a function of the size of the magnetic grains compared with the scale of the fracturation during non homogeneous processes of deformation

photomosaics of the cathodoluminescence of 60 sections of meteorites and lunar samples 1 cathodoluminescence cl petrography provides a means of observing petrographic and compositional properties of geological samples not readily observable by other techniques we report the low magnification cl images of 60 sections of extraterrestrial materials the images we report include ordinary chondrites including type 3 ordinary chondrites and gas rich regolith breccias enstatite chondrites co chondrites and a cm chondrite eucrites and a howardite lunar highland regolith breccias and lunar soils the cl images show how primitive materials respond to parent body metamorphism how the metamorphic history of el chondrites differs from that of eh chondrites how dark matrix and light clasts of regolith breccias relate to each other how metamorphism affects eucrites the texture of lunar regolith breccias and the distribution of crystallized lunar spherules lunar chondrules and how regolith working affects the mineral properties of lunar soils more particularly we argue that such images are a rich source of new information on the nature and history of these materials and that our efforts to date are a small fraction of what can be done

composition and classification of clasts in the st mesmin ll chondrite breccia abstract seven samples of the unique st mesmin meteorite have been analyzed by instrumental and radiochemical neutron activation analysis for na ca sc cr mn fe co ni zn ga ge se in sm yb ir and au st mesmin is unique in being the only ordinary chondrite known to contain an unmelted xenolith of another ordinary chondrite data for two host matrix samples and three light clasts are consistent with their classification as ll chondrite material the composition of the large dark xenolith confirms earlier evidence that it is an h chondrite volatile abundances are consistent with it being highly shocked petrologic type 4 material in an olivine microporphyry siderophile abundances are mostly about 0 13 times ll abundances an apparent indication of metal loss during the shock melting which produced the clast as in other regolithic chondrites the dark host has higher contents of highly volatile elements than do the light clasts we suggest that this results from a combination of differences in intensity of preexisting metamorphism as well as a redistribution of volatiles during regolith gardening the h group xenolith in st mesmin is a relatively recent addition to the parent body

thermoluminescence constraints on the metamorphic shock and brecciation history of basaltic meteorites abstract induced thermoluminescence measurements have been performed on eighteen eucrites thirteen howardites plus seven splits from the bholghati howardite six diogenites and fifteen mesosiderites in order to help clarify their metamorphic shock and brecciation history the tl sensitivities of the basaltic meteorites reflect their bulk composition and the effects of 1 igneous processes diogenites and mesosiderites and 2 the mixing of materials of different compositions e g diogenitic and eucritic during brecciation howardites can be observed two previously unclassified mesosiderites lew87006 and eet87500 are assigned to class a and b respectively on the basis of their tl sensitivities the eucrites show a 15 fold range of tl sensitivities which correlate with petrographie indicators of metamorphic intensity we therefore describe a petrologic type scale based on tl and petrographie evidence where the least metamorphosed eucrites are type 1 and most equilibrated are type 8 we see no evidence for two discrete metamorphic environments corresponding to the equilibrated and unequilibrated eucrites the temperature of the dominant tl peak observed for basaltic meteorites and experiments in which four eucrites with diverse petrographie properties were annealed at various temperatures in the laboratory suggests the metamorphic equilibration temperatures for most basaltic meteorites were 800 c this estimate is generally consistent with palaeotemperatures determined from two pyroxene olivine pyroxene and oxygen isotope equilibria assuming this temperature was typical of conditions during metamorphism then burial depths for type 5 eucrites were 350 m and

the irradiation history of the ghubara l5 regolith breccia we measured cosmic ray products noble gases radionuclides thermoluminescence and nuclear tracks and trace element contents and mineralogy of samples of three orthogonal and mutually intersecting cores 41 46 cm long of a 101 6 kg ghubara individual 1958 805 at the natural history museum london the xenoliths like the host have high concentrations of trapped solar gases and are heavily shocked while contents of noble gases and degree of shock loading in this individual and three others differ somewhat the data indicate that ghubara is a two generation regolith breccia contents of cosmogenic 26al and 10be and low track densities indicate that the ghubara individuals were located more than 15 cm below the surface of an 85 cm meteoroid because of its large size ghubara s cosmic ray exposure age is poorly defined to be 15 20 ma from cosmogenic nuclides ghubara s terrestrial age based on 14c data is 2 3 ka not only is ghubara the first known case of a 2 generation regolith breccia on the macro scale it also has a complicated thermal and irradiation history

change in seismic activity in the tokai region related to weakening and strengthening of the interplate coupling abstract we investigate the relationship between changes in seismicity and crustal deformations in the tokai region we describe how seismicity in the subducted slab increased remarkably in the fall of 2000 and decreased in the fall of 2001 while in contrast the crust seismicity decreased in the fall of 2000 and increased in the fall of 2001 we note that the trend of horizontal displacement at gps stations changed coincidentally and we propose interpreting the increase and decrease in seismic activities and the changes in crustal deformations in a unified way based on changes in the state of the interplate coupling i e the back slip rate was reduced in the fall of 2000 and was partially restored in the fall of 2001 we explain why reduction of the back slip rate increases seismogenic stress in the slab and decreases stress in the crust we also describe the substantial positive dilatation observed in the region around mt fuji in the fall of 2000 and suggest that the remarkable increase of low frequency earthquakes beneath mt fuji in october 2000 may have been caused by deceleration of the converging motion of the izu micro plate with the eurasian plate the decrease of the subduction velocity of the izu micro plate on the suruga trough in late 2000 would also have contributed to weakening of the interplate coupling beneath the tokai region since reduction of the relative velocity between overriding and subducting plates produces the same effect on the plate interface as a diminishing back slip rate however subduction of the izu micro plate on the suruga trough was accelerated in early 2003 which may have caused increases in both slab and crust seismicities in that period

tectonic strain and paleomagnetism experimental investigation a porous clay rich sandstone with a natural remanent magnetisation shows complex changes in the orientation of the remanence vector when the sandstone is subjected to experimental deformation at 100 mpa room temperature and constant natural strain rates of 1 10 5 s 1 the paleomagnetic vector does not simply rotate away from the axis of compression when the rock is shortened perpendicular to bedding the remanence vector rotates toward the bedding as expected but the remanence also rotates toward bedding when the rock is shortened parallel to bedding moreover in some cases the remanence vector changes azimuth within the specimen during experimental deformation thus bedding anisotropy and the accompanying mineral fabric anisotropy are more influential than strain in controlling deflections of the paleomagnetic vector in this study this anisotropy also influences the post deformational behaviour of remanence 4 months after deformation some cores shortened perpendicular to bedding relaxed their remanence vectors back towards the pre deformational attitude whereas some other cores continued to show progressive changes intragranular recoverable elastic strains in the magnetic grains may be partly responsible for the experimentally induced deflections of remanence

simple shear experiments on magnetized wax hematite samples c a e s s laboratoire de geophysique interne uniuersite de rennes 1 f 35042 rennes francereceived july 1 1991 revision accepted may 28 1992abstractwe present the results of a series of simple shear experiments on hematite bearing paraffin wax samples homogeneousand continuous deformation was obtained up to a shear strain value of y 1 4 by deforming the samples in atemperature controlled bath and at a constant strain rate of 9x10 5 s r during deformation hematite plateletsprogressively rotate which has been checked by measuring the anisotropy of magnetic susceptibility ams principalsusceptibility directions tend to parallel the corresponding principal strain directions and ams intensity increases withincreasing strain this supports the idea that the hematite population develops a preferred orientation by progressive rigidrotation within the paraffin matrix before each deformation step an isothermal remanent magnetization irm was given to the samples within ara finite strain plane the containing the shear direction and normal to the shear plane with various initial angles to theshear direction ranging from 0 to 180 after each deformation step the irm was measured it showed no deflectiontowards the a finite strain direction in contrast it did show a systematic rotation within the ara plane always in the samesense as the rotation of strain axes e g counterclockwise in sinistral shear furthermore irm deviation is of the sameorder of magnitude for each initial direction from 0 to 180 this contradicts the passive behaviour model that haspreviously been shown to hold for irm in coaxially deformed samples finally we show that in the shear strain range of ourexperiments y 0 to 1 4 the deviation of irm depends only on the shear value and not on its initial direction and thatthis deviation is equal to the rigid rotation angle of the shear strain tensor

the thermal and radiation exposure history of lunar meteorites we have measured the natural and induced thermoluminescence tl of seven lunar meteorites in order to examine their crystallization irradiation and recent thermal histories lunar meteorites have induced tl properties similar to apollo samples of the same provenance highland or mare indicating similar crystallization and metamorphic histories macalplne hills 88104 5 has experienced the greatest degree of impact regolith processing among the highland dominated meteorites the basaltic breccia que 94281 is dominated by mare component but may also contain a significant highland component for the mare dominated meteorites eet 87521 may have a significant highland impact melt component while asuka 881757 and y 793169 have been heavily shocked the thermal history of y 793169 included slow cooling either during impact processing or during its initial crystallization our natural tl data indicate that most lunar meteorites have apparently been irradiated in space a few thousand years with most less than 15 000 a elephant moraine 87521 has the lowest irradiation exposure time being less than 1 000 a either the natural tl of alha81005 asuka 881757 and y 82192 was only partially reset by lunar ejection or these meteorites were in small perihelia orbits less than or equal to 0 7 au

detection and monitoring of ongoing aseismic slip in the tokai region central japan analysis of global positioning system data shows that the rate of crustal deformations in the tokai region of japan a seismic gap area changed over the past 18 months kalman filtering analysis shows aseismic slip on the plate boundary in the western tokai region centered on lake hamana adjacent to the anticipated tokai earthquake source area the cumulative moment magnitude reaches 6 7 in june 2002 with a relative slip increase northeast of lake haman from january 2002 an existence of aseismic slip in the western tokai supports the hypothesis of a silent event as the cause of uplifting several days before the 1944 tonankai earthquake

focal zone of a future tokai earthquake inferred from the seismicity pattern around the plate interface abstract a future large tokai earthquake has been considered to be the most urgent problem of impending disasters in the central part of the japanese islands since the first warning was announced in 1976 recent progress in observations has provided a great amount of data thus making a detailed investigation possible in this study based on the seismicity and the focal mechanism patterns of microearthquake data the mechanical situation that governs plate interactions around the tokai district was investigated it was found that the seismicity in the subducting philippine sea slab is composed of three characteristic groups of activities intense activity beneath lake hamana a linear cluster extending from lake hamana toward the northwest and a broad cluster expanding over the inland area in the west of suruga bay we propose that these activities occur inside the subducting oceanic crust and reflect the present stress state acting there the mechanism inducing these activities is assumed to come from two stress sources the lateral stretching of the slab and the partial locking between both plates this interpretation leads to the hypothesis that the broad cluster in the west of suruga bay represents a stress concentration due to locking the activity beneath lake hamana is proposed to represent shearing motion induced there and is interpreted to form the boundary between the rupture zones of the 1944 tonankai earthquake and a future large tokai earthquake these analyses resulted in identifying the wide inland area extending from the west coast of suruga bay to lake hamana to be a focal zone of a future tokai earthquake the zone proposed in this study indicates a significant deviation in its strike from the original model proposed by ishibashi in that the former parallels the nankai trough while the latter parallels the suruga trough

crustal deformation caused by magma migration in the northern izu islands japan intense crustal activity including earthquake swarms eruptions and a caldera formation in the northern izu islands started on june 26 2000 accompanied with large crustal deformation permanent gps data reveals the spatial pattern and time evolution of ground deformation the observations reveal shrinking and subsidence of miyakejima and extension between kouzushima and niijima we constructed a source model to explain the observed displacements during the period between june 26 and the end of august the model consists of a deflation source 0 12km beneath miyakejima tensile faults 1 04km located between miyakejima and kouzushima and several shear faults mass balance considerations suggest that a large amount of magma migrated 30km from miyakejima toward kouzushima

radar enabled recovery of the sutter s mill meteorite a carbonaceous chondrite regolith breccia doppler weather radar imaging enabled the rapid recovery of the sutter s mill meteorite after a rare 4 kiloton of tnt equivalent asteroid impact over the foothills of the sierra nevada in northern california the recovered meteorites survived a record high speed entry of 28 6 kilometers per second from an orbit close to that of jupiter family comets tisserand s parameter 2 8 0 3 sutter s mill is a regolith breccia composed of cm mighei type carbonaceous chondrite and highly reduced xenolithic materials it exhibits considerable diversity of mineralogy petrography and isotope and organic chemistry resulting from a complex formation history of the parent body surface that diversity is quickly masked by alteration once in the terrestrial environment but will need to be considered when samples returned by missions to c class asteroids are interpreted

the natural thermoluminescence of meteorites iii lunar and basaltic meteorites natural thermoluminescence tl data have been obtained for the lunar meteorite macalpine hills 88104 5 and for 65 eucrites howardites diogenites and mesosiderites in order to investigate their recent thermal and radiation histories all these meteorites have low levels of natural tl compared to chondrites which is primarily because they display anomalous fading i e fading by non classical mechanisms however some have especially low natural tl 5 krad at 250 c in the glow curve which cannot be attributed to anomalous fading or thermal fading over especially large terrestrial ages and which must reflect heating within the last 105 106 y in some cases this heating may have been associated with shock e g lew85303 or regolith processes kapoeta but in most cases bununu lowicz the diogenites alha77256 alha84001 eet79002 and maybe others solar heating at perihelia 0 8 au may be responsible for the low tl values the fraction of basaltic meteorites thought to have had small perihelia about 20 is comparable to the fraction of chondrites with low natural tl and to the fraction of observed falls and fireballs with small perihelia this may imply ejection from the asteroid belt via similar mechanisms assuming plausible values for cosmic ray dose rate and that the natural tl of mac88104 5 was totally drained by ejection from the moon the parameters for tl decay determined in the present study suggest that the moon earth transit times for mac88104 and mac88105 were 2 000 and 1 800 y respectively compared with 19 000 and 2 500 y for y791197 and alha81005 respectively although they are clearly not paired the possibility that mac88104 5 and alha81005 were ejected from the moon by the same event should be considered since diverse rock types are found in close proximity on the lunar surface the natural tl data confirm most previous published pairings among basaltic meteorites and suggest others

spatiotemporal patterns of clustered and non clustered seismic activity in the shin etsu and tokai regions central japan we investigated spatiotemporal patterns of seismicity in the shin etsu region and tokai region central japan by separating the seismicity into clustered and non clustered activity we found that clustered activity occurred at various sites during short periods in each investigated region and that an alternation of active and quiet periods was clear for the clustered activity in contrast non clustered earthquakes occur at an almost constant rate and active or quiet periods can not be distinguished in the non clustered activity some evidence suggests that an increase of clustered activity indicates a buildup of the regional stress field

lithification of gas rich chondrite regolith breccias by grain boundary and localized shock melting we studied the fine grained matrices 150 m of 14 gas rich ordinary chondrite regolith breccias in an attempt to decipher the nature of the lithification process that converted loose regolith material into consolidated breccias we find that there is a continuous gradation in matrix textures from nearly completely clastic class a to highly cemented class c breccias in which the remaining clasts are completely surrounded by interstitial shock melted material we conclude that this interstitial material formed by shock melting in the porous regolith in general the abundances of solar wind implanted 4he and 20ne are inversely correlated with the abundance of interstitial shock melted feldspathic material chondrites with the highest abundance of interstitial melted material class c experienced the highest shock pressures and temperatures and suffered the most extensive degassing it is this interstitial feldspathic melt that lithifies and cements the breccias together those breccias with very little interstitial melt class a are the most porous and least consolidated

magnetic and electric field observations during the 2000 activity of miyake jima volcano central japan magnetic and electric field variations associated with the 2000 eruption of miyake jima volcano are summarized for about 1 week prior to the july 8 phreatic explosion significant changes in the total intensity were observed at a few stations which indicated uprising of a demagnetized area from a depth of 2 km towards the summit this nonmagnetic source can be regarded as a vacant space itself electric and magnetic field variations were observed simultaneously associated with the tilt step event which was the abrupt v50 s inflation at a few km depth within the volcano followed by gradual recovery vseveral hours the electric field is ascribed to the electrokinetic effect most probably due to forced injection of fluids from the source while the magnetic field to the piezomagnetic effect due to increased pressure large magnetic variations amounting to a few tens of nt were observed at several stations since july 8 and they turned almost flat after the august 18 largest eruption magnetic changes are explained mostly by the vanishing of magnetic mass in the summit and additionally by the thermal demagnetization at a rather shallow depth a large increase in the self potential by 130 mv was also observed near the summit caldera associated with the august 18 eruption which suggests that the hydrothermal circulation system sustained within the volcano for the past more than 10 years was destroyed by this eruption 9 2002 published by elsevier science b v

slow slip phenomena in cascadia from 2007 and beyond a review recent technological advances combined with more detailed analyses of seismologic and geodetic observations have fundamentally changed our understanding of the ways in which tectonic stresses arising from plate motions are accommodated by slip on faults the traditional view that relative plate motions are accommodated by a simple cycle of stress accumulation and release on locked plate boundary faults has been revolutionized by the serendipitous discovery and recognition of the significance of slow slip phenomena mostly in the deeper reaches of subduction zones the cascadia subduction zone located in the pacific northwest of the conterminous united states and adjacent canada is an archetype of exploration and learning about slow slip phenomena these phenomena are manifest as geodetically observed aseismic transient deformations accompanied by a previously unrecognized class of seismic signals although secondary failure processes may be involved in generating the seismic signals the primary origins of both aseismic and seismic phenomena appear to be episodic fault slip probably facilitated by fluids on a plate interface that is critically stressed or weakened in cascadia this transient slip evolves more slowly and over more prolonged durations relative to the slip in earthquakes and it occurs between the 30 and 40 km depth contours of the plate interface where information was previously elusive although there is some underlying organization that relaxes nearly all the accrued plate motion stresses along the entirety of cascadia we now infer that slow slip evolves in complex patterns indicative of propagating stress fronts our new understanding provides key constraints not only on the region where the slow slip originates but also on the probable characteristics of future megathrust earthquakes in cascadia herein we review the most significant scientific issues and progress related to understanding slow slip phenomena in cascadia and highlight some of their societal implications we provide a comprehensive review from the big picture as inferred from studies of regional scale monitoring data to the details revealed by innovative focused experiments and new instrumentation we focus on what has been learned largely since 2007 when several major investments in monitoring and temporary deployments dramatically increased the quality and quantity of available data

chemical and physical studies of type 3 chondrites 2 thermoluminescence of sixteen type 3 ordinary chondrites and relationships with oxygen isotopes thermoluminescence tl sensitivity values for sixteen type 3 ordinary chondrites fourteen of them from antarctica have been measured the values obtained normalized to the tl sensitivity of the dhajala meteorite range from 1 6 allan hills a77216 to 0 010 allan hills a77176 and include two reckling peak a80207 and allan hills a77176 that are particularly low they fill a hiatus in the tl distribution that previously existed between st mary s county and bishunpur the latter being a meteorite with one of the lowest tl sensitivities known the histogram of tl sensitivity values now shows a single distribution with higher values preferred it resembles the histogram for l chondrites occupying the petrologic types 3 4 5 and 6 there is a tendency for the tl sensitivity of meteorites to decrease as 18o increases equilibrated meteorites have tl sensitivities of 5 50 and 18o 4 5 to 5 0 while the most primitive meteorites with tl 0 01 have 18o 5 7 to 6 2 meteorites with intermediate tl have intermediate 18o theoretically it is possible that the range of 18o values observed may reflect progressive loss of o in the form of co at very low temperatures but very restrictive physical conditions and a complex history seem to be required

the thermoluminescence sensitivity metamorphism relationship in ordinary chondrites experimental data on the mechanism and implications for terrestrial systems hydrothermal annealing experiments have been performed on samples of the sharps meteorite in order to investigate the mechanism responsible for the metamorphism related 105 fold range in the thermoluminescence tl sensitivity in ordinary chondrites duplicate 50 mg samples of meteorite were annealed under the following conditions a 168 h at 785 c and 1 kbar b the same time temperature and pressure but with 2 wt water c 174 h at 855 c and 0 77 kbar with 2 wt water and 2 molal sodium disilicate nadisi d the same time temperature and pressure as the preceding samples but with 10 wt h2o and 2 molal nadisi samples annealed under the first three sets of conditions showed little or no change in their tl sensitivities however the samples annealed with 10 wt water and 2 molal nadisi showed a 3 to 10 fold increase in tl sensitivity and the temperature of the tl peak was suggestive of feldspar in the high temperature form we suggest that these data are consistent with the tl sensitivity metamorphism relationship in ordinary chondrites being due to the formation of the tl phosphor feldspar by the crystallization of chondrule glass

experimental and numerical modeling of irm rotation in deformed synthetic samples abstract the effect of strain upon isothermal remanent magnetization irm carried by hematite particles embedded in a plasticine matrix has been investigated magnetized artificial hand samples were deformed by simple coaxial shortening after deformation the hand samples were cut into 8 15 specimens and each specimen s irm measured hence a mean irm direction was obtained for each shortening step the main results are 1 when the initial direction of irm is parallel to the shortening axis 3 the hand sample mean irm stays parallel to 3 during deformation however individual magnetization directions are deflected towards the flattening plane and thus the specimen directions are scattered by strain this is accompanied by a significant decrease of magnetization intensity 2 in contrast when the initial direction of irm is perpendicular to 3 the shortening results in a clustering of specimen magnetization directions the mean direction being unchanged this is accompanied by a slight increase of magnetization intensity 3 in all other cases where initial irm direction makes an intermediate angle with shortening direction deformation induces a deviation of each specimen irm toward the flattening plane this results in an overall deflection of hand sample mean irm the amount of rotation increases with strain intensity changes of grouping and intensity depend on the initial angle between irm and 3 defining a continuum in behavior between irm directions being either parallel to 3 or perpendicular to 3 finally it is shown that all the experimental changes in irm due to deformation direction grouping intensity can be modeled by a passive marker rotation of hematite planar particles

chemical and physical studies of type 3 chondrites vii annealing studies of the dhajala h3 8 chondrite and the thermal history of chondrules and chondrites abstract samples of the dhajala h3 8 chondrite have been annealed for 10 hours at 600 700 800 900 and 1000 c and at 1000 c for 1 2 20 and 100 h and their thermoluminescence tl properties measured the tl sensitivity decreased by a factor of 2 after annealing at but at higher temperatures fell by an order of magnitude an abrupt increase in the temperature of the tl peak from 172 9 cto231 8 c and a steady increase in the width of the peak from 169 7 cto212 5 c were caused by the annealing treatment the tl phosphor in dhajala is thought to be feldspar predominantly in the high temperature disordered form but the present data indicate that a contribution from the low temperature form is also present and that this low temperature component is converted to the high form by the annealing treatment the low temperature feldspar is located in a few of the chondrules 20 of those separated from the meteorite which are also noteworthy for having high tl sensitivities these chondrules must have suffered greater crystallization of their mesostasis than the other chondrules and equilibrated to lower temperatures it is argued that for compositional reasons their mesostasis constituted less of a barrier to diffusion and therefore equilibration presumably the post metamorphic cooling rate of the meteorite through the stability field of the low form was slow enough to permit some crystallization and the width and temperature of the tl peaks for petrologic types 3 5 3 9 are somehow related to cooling rate based on tl there is no indication of a correlation between petrologic type and cooling rate for types 3 5 3 9 this is not consistent with a simple single internally heated meteorite parent body

correlating seismicity parameters and subsidence in the tokai region central japan 1 we demonstrate that transients in subsidence rate in the tokai area of central japan correlate with changes in the rate and size distribution of earthquakes three largely independent seismic catalogs cover this region national research institute for earth science and disaster prevention nied japanese meteorological agency jma and japan university network catalog junec comparing seismicity patterns between these three data sets offers a unique opportunity to verify seismicity anomalies based on independent sources a study of data quality magnitude reporting consistency and consistency across the three data sources reveals that the nied data for the period 1981 2002 are best suited for seismicity analysis we spatially and temporally map seismicity rates finding that a significant decrease in the earthquake rate of m 2 0 events coincides with an accelerated subsidence period however this anomaly disappears when including smaller magnitudes in the analysis this relative quiescence of larger events can readily be explained when interpreting the transient in seismicity in the framework of a change in the earthquake size distribution or b value the background b value of about 0 8 increased in the period 1987 5 1989 5 to a value of b 1 2 a highly significant change that can be confirmed in all three data sets the correlation between subsidence and b value change is significant stress tensor inversions of focal mechanism data for the anomalous period show an increase in thrusting type earthquakes while a unique interpretation of the relationship between subsidence and b value is not possible we propose that an increase in the locking stress a slow stick event is consistent with all observations

chemical and physical studies of type 3 chondrites iv annealing studies of a type 3 4 ordinary chondrite and the metamorphic history of meteorites abstract samples of a type 3 4 chondrite have been annealed at 400 1000 c for 1 200 hours their thermoluminescence properties determined and analyzed for k na mn sc and ca by instrumental neutron activation analysis after annealing at 900 c the samples showed a 50 decrease in tl sensitivity while after annealing at 1000 c it fell to 0 1 0 01 times its unannealed value and loss of na and k occurred the tl and compositional changes resemble those observed for the equilibrated kernouve chondrite after similar annealing treatments except that the sharp tl decrease and element loss occurred at 1100 c this difference is presumably due to petrographic differences in the feldspar of the two meteorites the temperature and the width of the tl peak showed a discontinuous increase after annealing at 800 c peak temperature jumped from 130 to 200 c and peak width increased from 90 to 150 c the activation energies for these tl changes are 7 10 kcal mole similar increases in the tl peak temperature have been reported in tl studies of amelia va albite where they were associated with the low to high temperature transformation however the activation energy for the transformation is 80 kcal mole these changes in tl emission characteristics resemble trends observed in type 3 ordinary chondrites and it is suggested that type 3 3 3 5 chondrites have a low feldspar as tl phosphor and 3 5 have high feldspar as the phosphor thermoluminescence therefore provides a means of palaeothermometry for type 3 ordinary chondrites

slow slip events and seismic tremor at circum pacific subduction zones 1 it has been known for a long time that slip accompanying earthquakes accounts for only a fraction of plate tectonic displacements however only recently has a fuller spectrum of strain release processes including normal slow and silent earthquakes or slow slip events and continuous and episodic slip been observed and generated by numerical simulations of the earthquake cycle despite a profusion of observations and modeling studies the physical mechanism of slow slip events remains elusive the concurrence of seismic tremor with slow slip episodes in cascadia and southwestern japan provides insight into the process of slow slip a perceived similarity between subduction zone and volcanic tremor has led to suggestions that slow slip involves fluid migration on or near the plate interface alternatively evidence is accumulating to support the notion that tremor results from shear failure during slow slip global observations of the location spatial extent magnitude duration slip rate and periodicity of these aseismic slip transients indicate significant variation that may be exploited to better understand their generation most slow slip events occur just downdip of the seismogenic zone consistent with rate and state dependent frictional modeling that requires unstable to stable transitional properties for slow slip generation at a few convergent margins the occurrence of slow slip events within the seismogenic zone makes it highly likely that transitions in frictional properties exist there and are the loci of slow slip nucleation slow slip events perturb the surrounding stress field and may either increase or relieve stress on a fault bringing it closer to or farther from earthquake failure respectively this paper presents a review of slow slip events and related seismic tremor observed at plate boundaries worldwide with a focus on circum pacific subduction zones trends in global observations of slow slip events suggest that 1 slow slip is a common phenomena observed at almost all subduction zones with instrumentation capable of recording it 2 different frictional properties likely control fast versus slow slip 3 the depth range of slow slip may be related to the thermal properties of the plate interface and 4 the equivalent seismic moment of slow slip events is proportional to their duration mo different from the mo 3 scaling observed for earthquakes

the effects of grain scale deformation on the bloomsburg formation pole previous paleomagnetic results from the silurian bloomsburg formation in the central appalachian valley and ridge province suggest that the bloomsburg s characteristic magnetization is a synfolding magnetization acquired during the acadian orogeny however there is little geological evidence to support extensive acadian folding in the central appalachians a more favorable explanation is that the characteristic magnetization originated as a prefolding silurian magnetization and has been altered by grain scale deformation to mimic a synfolding devonian remagnetization in order to investigate whether penetrative deformation has altered the bloomsburg formation s characteristic signal the relationship between strain and remanence was examined around three central appalachian valley and ridge folds structural analysis of mesoscopic and microscopic features along with center to center finite strain analysis at these three folds indicates a deformation sequence that includes prefolding layer parallel shortening overprinted by top to the foreland bedding parallel shear and flexural slip flow folding inclination of the characteristic magnetization varies systematically with the magnitude of finite strains this relationship between strain and remanence suggests that the characteristic magnetization has been progressively rotated toward shallower inclinations by penetrative deformation analogous to rigid particle rotation in a viscously deforming matrix using directions from sites with relatively low finite strain values a new bloomsburg formation pole is calculated at 18 7 n 107 4 e k 58 4 a95 8 2 this new pole falls on the silurian track of the north american apparent polar wander path between the silurian wabash reef pole and the silurian devonian andreas pole in addition these results suggest that previously reported 20 30 difference in declination of site mean directions north arid south of the pennsylvania salient may also be the result of grain scale reorientation of the remanence carrying grains and not oroclinal bending

experimental strain of isothermal remanent magnetization in ductile sandstone abstract a macroscopically ductile sandstone to which a homogeneous isothermal remanent magnetization irm was applied has been deformed at 150 mpa confining pressure and constant strain rate of 10 5 s 1 hydrostatic compaction does not produce a deflection of the irm vector although it is reduced in intensity pure shear producing shortening in the range 2 to 35 steadily reduces the intensity of magnetization but also homogeneously rotates the remanence vector toward the plane of flattening the amount of rotation is slightly less than that expected for a non material line undergoing homogeneous strain deformation selectively removes weakly coercive components of remanence as revealed by alternating field af demagnetization during deformation a weak deformational viscous remanent magnetization dvrm is acquired from the pressure vessel this is different from a conventional viscous remanent magnetization vrm in that it is not acquired when the specimen is subject to hydrostatic confining pressure alone even for periods three times longer than the longest deformation test

spatiotemporal gravity changes at miyakejima volcano japan caldera collapse explosive eruptions and magma movement 1 calderas are ubiquitous topographic features of volcanos yet caldera formation itself has not been recorded intensively by modern measurement techniques here we report the spatiotemporal gravity changes before and after caldera collapse at the miyakejima volcano japan in 2000 a gravity decrease of as much as 145 gal 1 gal 10 8 m s2 at the summit area since june 1998 was detected 2 days prior to the collapse interpreted as reflecting the formation of a large void beneath the volcano gravity changes detected after the initiation of collapse can mostly be corrected by the effect of collapsed topography from which a rapid rate of collapse of more than 1 6 107 m3 d can be inferred correcting for the effect of topography change we identified a temporal decrease in gravity from the middle of july to late august despite ground subsidence the gravity decrease is interpreted as a reduction of the density in a cylindrical conduit attributed to water inflow from an ambient aquifer that also promoted intensive magma water interaction and subsequent explosive eruptions from september to at least november 2000 gravity values at all sites increased significantly by a degree that cannot be explained by ground displacement alone we interpret this temporal evolution as primarily due to magma ascent and refilling of the conduit

interplate coupling in the tokai district central japan deduced from continuous gps data i invert gps displacement rates in the tokai district to investigate strain accumulation associated with the anticipated tokai earthquake i apply a representation of interseismic strain accumulation at subduction zones by savage 1983 and estimate a distribution of virtual normal fault slip back slip on the plate boundary surface estimated back slip takes its maximum value of 30 40mm year under the sea of enshu this value is nearly equal to the relative plate motion there implying almost complete coupling back slip is smaller under suruga bay and its direction is different from the relative motion between the eurasian and the philippine sea plates localized deformation at the northern tip of the philippine sea plate may be responsible for this discrepancy partitioning tectonic strain due to the plate convergence into faults on both sides of the izu peninsula and also distributed strain inside the peninsula

metamorphism of eucrite meteorites studied quantitatively using induced thermoluminescence eucrite meteorites1 are especially important in studies of the early solar system because they are the simplest and most ancient products of a process that was widespread in the inner solar system2 3 basaltic volcanism they are also the meteorites for which there is least doubt of an asteroidal origin4 5 after volcanism the eucrites experienced a period of metamorphism6 either inside the asteroid as it cooled from igneous temperatures7 or on the surface of the asteroid as a result of impact heating8 induced thermoluminescence studies provide a new and quantitative means of determining relative metamorphic intensities for these meteorites using this technique we show that the eucrites constitute a continuous metamorphic series and not as commonly assumed two groups of metamorphosed and non metamorphosed meteorites9 these studies are the first application of the induced thermoluminescence technique to igneous rocks and we suggest that the method may well have application to other basalts

chemical studies of h chondrites iii regolith evolution of the fayetteville chondrite parent abstract data for ag au bi cd co cs ga in rb sb se te tl and zn in consortium samples of solar gas and track rich dark matrix and dark and light clasts in the fayetteville h chondrite regolith breccia were determined by radiochemical neutron activation analysis the matrix proved chemically homogeneous at a level never before observed in an ordinary chondrite most dark clasts had similar mean trace element concentrations as matrix but were compositionally much more heterogeneous two clasts were unusual one having apparently formed from impact melted soil the other representing a mixture of 90 matrix 10 c2m chondrite the single light clast proved compositionally similar to h4 6 chondrite falls except for its higher contents of labile bi cd in and tl relative to matrix all other samples seemed cs deficient other h chondrite regolith breccias studied in the past had shown peculiar cs and or rb contents so that these alkalis seem diagnostic of such breccias dark portions of such breccias apparently represent compacted regolith soil produced by isochemical comminution of normal dark and light clasts the dark clasts in turn likely represent primordial nebular condensate although it is possible that they represent planetary cold traps that garnered labile elements generated elsewhere in the parent body

thermoluminescence and the shock and reheating history of meteorites iv the induced tl properties of type 4 6 ordinary chondrites abstract the induced thermoluminescence tl properties of 121 equilibrated ordinary chondrites have been measured the samples were 74 h and 47 l chondrites of which 33 h and 32 l were from antarctica the distribution of tl sensitivities for non antarctic l chondrites differs from that of non antarctic h chondrites consistent with a greater proportion of the former class suffering post metamorphic shock data on the effect of laboratory annealing on tl sensitivity and step wise ar release measurements enable the meteorites to be sorted into three shock related temperature groups

preferred orientation developed by rigid markers in two dimensional simple shear strain a theoretical and experimental study abstract in a homogeneous two dimensional deformation linear markers embedded in a viscous matrix develop a preferred orientation along the principal axis of the strain ellipse theoretical analysis of marker rotation under two dimensional simple shear is used to derive an orientation distribution function this function shows that the relative density maximum increases with progressive strain its value being equal to the major minor strain ellipse axis ratio moreover the density is equal to the unity along the lines of no finite longitudinal strain experimentally observed preferred orientation is in good agreement with the expected theoretical distribution

thermoluminescence and the origin of the dark matrix of fayetteville and similar meteorites abstract the induced thermoluminescence properties and carbon contents of the dark matrix and light clasts of 6 regolith breccias have been measured the tl sensitivity of the matrix normalized to that of the clasts decreases from 0 8 to 0 3 with increasing inert gas content increasing abundances of highly volatile elements and carbon and decreasing amounts of interstitial grain boundary glass for meteorites with the highest inert gas contents fayetteville and leighton the matrix samples have broader tl peaks by 10 c and lower peak temperatures by 10 c than the light clasts whereas meteorites with low inert gas contents e g pantar do not show this difference in the tl properties of the two lithologies it is argued that the data are consistent with the formation of the dark matrix by comminution of the light clasts with the addition of a component perhaps cm like chondrites with tl properties distinct from those of ordinary chondrites the present data are inconsistent with the matrix being a new primitive material akin to type 3 ordinary chondrites or with the dark matrix being related to the clasts by purely thermal processes

the richfield ll3 chondrite richfield is a moderately shocked shock stage s4 ll3 7 genomict breccia find consisting mainly of light colored recrystallized clasts and dark clasts exhibiting significant silicate darkening a few impact melt rock clasts and ll5 chondrite clasts also occur the cosmic ray exposure age of 14 5 ma is indistinguishable from the main exposure peak for ll chondrites 15 ma although the exposure ages indicate little he loss the gas retention ages indicate high gas losses that must have occurred prior to or during ejection from the ll parent body