space geodetic tools provide early warnings for earthquakes and volcanic eruptions development of space geodetic techniques such as global navigation satellite system and synthetic aperture radar in last few decades allows us to monitor deformation of earth s surface in unprecedented spatial and temporal resolution these observations combined with fast data transmission and quick data processing enable us to quickly detect and locate earthquakes and volcanic eruptions and assess potential hazards such as strong earthquake shaking tsunamis and volcanic eruptions these techniques thus are key parts of early warning systems help identify some hazards before a cataclysmic event and improve the response to the consequent damage

quasi real time fault model estimation for near field tsunami forecasting based on rtk gps analysis application to the 2011 tohoku oki earthquake mw 9 0 1 real time crustal deformation monitoring is extremely important for achieving rapid understanding of actual earthquake scales because the measured permanent displacement directly gives the true earthquake size seismic moment mw information which in turn provides tsunami forecasting we have developed an algorithm to detect estimate static ground displacements due to earthquake faulting from real time kinematic gps rtk gps time series the new algorithm identifies permanent displacements by monitoring the difference of a short term average sta to a long term average lta of the gps time series we assessed the noise property and precision of the rtk gps time series with various baseline length conditions and orbits and discerned that the real time ephemerides based on the international gnss service igs are sufficient for crustal deformation monitoring with long baselines up to 1 000 km we applied the algorithm to data obtained in the 2011 off the pacific coast of tohoku earthquake mw 9 0 to test the possibility of coseismic displacement detections and further we inverted the obtained displacement fields for a fault model the inversion estimated a fault model with mw 8 7 which is close to the actual mw of 9 0 within five minutes from the origin time once the fault model is estimated tsunami waveforms can be immediately synthesized using pre computed tsunami green s functions the calculated waveforms showed good agreement with the actual tsunami observations both in arrival times and wave heights suggesting that the rtk gps data by our algorithm can provide reliable rapid tsunami forecasting that can complement existing tsunami forecasting systems based on seismic observations

fe mg interdiffusion in wadsleyite the role of pressure temperature and composition and the magnitude of jump in diffusion rates at the 410 km discontinuity abstract the limited stability range of wadsleyite seriously impedes our ability to constrain kinetic parameters e g activation energy activation volume using experiments carried out over a wide range of temperature and pressure we have carried out a new measurement to extend the experimental temperature range of the dataset of chakraborty et al chakraborty s knoche r schulze h rubie d c dobson d ross n l angel r j 1999 enhancement of cation diffusion rates across the 410 kilometer discontinuity in earth s mantle science 283 362 365 to the maximum possible limit for that experimental setup this result allows us to i obtain a better constrained value for activation energy for fe mg diffusion in wadsleyite at 15 gpa 230 kj mol and ii characterize the compositional dependence of fe mg diffusion in wadsleyite evaluation of all data available in the literature i e this study chakraborty et al 1999 farber d l williams q ryerson f j 2000 divalent cation diffusion in mg2sio4 spinel ringwoodite phase wadsleyite and olivine implications for the electrical conductivity of the mantle j geophys res 105 513 529 kubo t shimojuko a ohtani e 2004 fe mg interdiffusion rates in wadsleyite and the diffusivity jump at the 410 km discontinuity phys chem miner 31 456 464 reveals that there is a strong pressure dependence of the diffusion coefficient activation volume 14 cm3 mol the expression d m 2 s 1 24 10 6 exp 11 8 0 86 x mg exp 229 000 p 15 13 9 10 3 j mol r t is an excellent description of all experimentally measured diffusion coefficients in wadsleyite and points to consistency between the various studies from different laboratories that used different methods this expression should provide a robust basis for extrapolation of diffusion data for wadsleyite to conditions removed from the experimental ones e g for modeling processes in the interiors of cold subducting slabs moreover characterization of fo2 and water contents of wadsleyites in the current study and consideration of the pressure dependence of diffusion rates in olivines confirms that the jump in diffusion rates at the olivine wadsleyite boundary in the transition zone is at least six orders of magnitude increased water contents in wadsleyite can cause the actual enhancement kubo et al 2004 to be as much as seven orders of magnitude taken together with the observation that diffusive mixing is practically impossible in the lower mantle holzapfel c rubie d c frost d j langenhorst f 2005 fe mg interdiffusion in mg fe sio3 perovskite and lower mantle reequilibration science 309 1707 1710 has a maximum at the lithosphere asthenosphere boundary in the olivine bearing upper mantle holzapfel c chakraborty s rubie d c frost d j 2007 effect of pressure on fe mg ni and mn diffusion in fexmg1 x 2sio4 olivine phys earth planet int 162 186 198 and decreases with depth within the transition zone this work these results establish the base of the lithosphere and the top of the mantle transition zone as the key regions for mixing and erasure of chemical heterogeneities in the mantle

very high rate 10 hz gps seismology for moderate magnitude earthquakes the case of themw6 3 l aquila central italy event accepted for publication in journal of geophysical research copyright 2010 american geophysical union

kinematic rupture scenarios and synthetic displacement data an example application to the cascadia subduction zone scenario ruptures and ground motion simulation are important tools for studies of expected earthquake and tsunami hazards during future events this is particularly important for large mw8 and very large mw8 5 events for which observations are still limited in particular synthetic waveforms are important to test the response of earthquake and tsunami warning systems to large events these systems are not often exercised in this manner we will show an application of the karhunen loeve kl expansion to generate stochastic slip distributions of large events with an example application to the cascadia subduction zone we will discuss how to extend the static slip distributions obtained from the k l expansion to produce kinematic rupture models and generate synthetic long period displacement data at the sampling rates of traditional gnss stations we will validate the waveforms produced by this method by comparison to a displacement based ground motion prediction equation gmpe obtained from gnss measurements of large earthquakes worldwide

coherent and subsequent incoherent ringwoodite growth in olivine of shocked l6 chondrites abstract pervasive replacement of original olivine grains by ringwoodite adjacent to a shock melt vein of yamato 791384 l6 chondrite was observed with a feg sem in these olivines we observed three distinct olivine ringwoodite textures arranged in a spatially successive arrangement from the wall of the shock melt vein into the olivine grains 1 polycrystalline ringwoodite 2 oriented several sets of ringwoodite lamellae and 3 oriented single lamellae tem images show that the polycrystalline and oriented several sets of lamellae parts consist of polycrystalline ringwoodite indicating that phase transformation from olivine to ringwoodite is controlled by incoherent growth mechanism on the other hand the set of oriented single lamellae consists of thin ringwoodite platelets

terrestrial alteration mineral assemblages in the nwa 10416 olivine phyric shergottite abstract we report on the alteration history of the olivine phyric highly depleted hd shergottite northwest africa nwa 10416 paying particular attention to the origin of the aqueous alteration seen affecting the meteorite s olivine megacrysts the rock s interior displays 1 mm zoned altered olivine megacrysts set in a groundmass of clinopyroxene unzoned olivine and interstitial plagioclase and maskelynite synchrotron micro x ray diffraction xrd and transmission electron microscopy tem show that plagioclase and maskelynite have been partially replaced by kaolinite the relict olivine megacryst cores display a unique concentric colouration for martian meteorites having central amber coloured zones surrounded by a brown mantle zone with the rims remaining clear and unaltered this colouration is a result of fluid alteration and partial replacement with hydration tem analysis revealed the 200 nm scale banded and largely amorphous nature of the alteration but with some 20 relict crystalline olivine patches although the coloured olivine zones show cation and anion site vacancies compared to stoichiometric olivine a relict igneous compositional trend is preserved in the megacrysts from mg rich altered cores mg 76 to unaltered stoichiometric rims fo53 synchrotron fe k x ray absorption near edge structure xanes analysis revealed that the coloured zones of the megacryst have different fe oxidation values high ferric contents are present in the brown mantle zones fe3 fe 0 92 and the amber zones fe3 fe 0 30 whereas the clear rims are ferrous this suggests alteration occurred in an oxidising environment and that the sharp contrast in colour of the megacryst brown to clear is a record of a relict fluid reaction front in order to test the terrestrial or extraterrestrial origin of the alteration olivine material from a shock melt vein was analysed by tem the analysis revealed 0 952 nm curved d spacing s from clay alteration undisturbed by any shock effects strongly suggesting a terrestrial origin the d spacing values most likely represent a collapsed saponite or vermiculite showing that in some places olivine has been replaced by crystalline clay oxygen isotope analysis of bulk 17o 0 309 0 009 2 and amber coloured megacryst material 0 271 0 002 2 are also consistent with terrestrial alteration we propose a model in which during the meteorite s time in northwest africa low temperature likely acidic groundwater exploited fractures the fluid altered the olivine megacrysts in a way that was controlled by the pre existing igneous compositional zonation with mg rich olivine being more susceptible to alteration in this fluid environment the plagioclase and maskelynite were also altered to a high degree after the alteration event it is likely that nwa 10416 had a significant residence time in northwest africa accounting for terrestrial calcite and the dehydration of some clay phases

mineralogical constraints on the thermal history of martian regolith breccia northwest africa 8114 abstract martian meteorite northwest africa nwa 8114 a paired stone to nwa 7034 provides an opportunity to examine the thermal history of a martian regolith and study near surface processes and ancient environmental conditions near an impact crater on mars our study reports petrographic and alteration textures and focuses on pyroxene and iron oxide grains some of the pyroxene clasts show exsolution lamellae indicating a high temperature magmatic origin and slow cooling however transmission electron microscopy reveals that other predominantly pyroxene clasts are porous and have partially re crystallised to form magnetite and a k bearing feldspathic glassy material together with relict pyroxene this breakdown event was associated with oxidation with up to 25 fe3 fe in the relict pyroxene measured using fe k xanes by comparison with previous studies this breakdown and oxidation of pyroxene is most likely to be a result of impact shock heating being held at a temperature above 700 c for at least 7 days in an oxidising regolith environment we report an approximate 40ar 39ar maximum age of 1 13 1 25 ga for an individual separated augite clast the disturbed nature of the spectra precludes precise age determination in section this clast is porous and contains iron oxide grains this shows that it has undergone the high temperature partial breakdown seen in other relict pyroxene clasts and has up to 25 fe3 fe we infer that the age corresponds to the impact shock heating event that led to the high temperature breakdown of many of the pyroxenes after consolidation of the impact ejecta blanket high temperatures above 700 c may have been maintained for long enough to remobilise and congruently partially melt some of the alkali feldspar clasts to produce the feldspar veins and aureoles that crosscut and in some cases surround the oxidised pyroxene however the veins could alternatively be the result of a hydrothermal event in the impact regolith a simple fourier cooling model suggests that a regolith of at least five metres depth would be sufficient to maintain temperatures associated with the pyroxene breakdown for over seven days low temperature hydrous alteration took place forming goethite identified via xrd xanes and ftir comparing with previous studies the goethite is likely to be terrestrial alteration pseudomorphing martian pyrite

mineralogical study of brown olivine in northwest africa 1950 shergottite and implications for the formation mechanism of iron nanoparticles martian meteorites in particular shergottites contain darkened olivine so called brown olivine whose color is induced by iron nanoparticles formed in olivine during a shock event the formation process and conditions of brown olivine have been discussed in the northwest africa 2737 nwa 2737 chassignite however formation conditions of brown olivine in nwa 2737 cannot be applied to shergottites because nwa 2737 has a different shock history from that of shergottites therefore this study observed brown olivine in the nwa 1950 shergottite and discusses the general formation process and conditions of brown olivine in shergottites our observation of nwa 1950 revealed that olivine is heterogeneously darkened between and within grains different from brown olivine in nwa 2737 xanes analysis showed that brown olivine contains small amounts of fe3 and tem stem observation revealed that there is no sio rich phase around iron metal nanoparticles these observations indicate that iron nanoparticles were formed by a disproportionation reaction of olivine 3fe2 olivine fe0metal 2fe3 olivine volivine where volivine means a vacancy in olivine some parts of brown olivine show lamellar textures in sem observation and raman peaks in addition to those expected for olivine implying that brown olivine experienced a phase transition to e g ringwoodite in order to induce heterogeneous darkening heterogeneous high temperature of about 1500 1700 k and shock duration of at least 90 ms are required this heterogeneous high temperature resulted in high postshock temperature 900 k inducing back transformation of most high pressure phases therefore in spite of lack of high pressure phases nwa 1950 martian meteorites with brown olivine experienced higher pressure and temperature compared to other highly shocked meteorite groups

fine structures of planar deformation features in shocked olivine a comparison between martian meteorites and experimentally shocked basalts as an indicator for shock pressure

39ar 40ar age and thermal history of martian dunite nwa 2737 abstract we report an 39 ar 40 ar age determination of a whole rock sample of the olivine rich martian meteorite northwest africa nwa 2737 those extractions releasing 0 48 of the 39 ar define an 39 ar 40 ar isochron age of 160 190 ma when evaluated in various ways higher temperature extractions show increasing ages that eventually exceed the reported sm nd age of 1 42 ga at least part of this excess 40 ar may have been shock implanted from the martian atmosphere we considered two possible interpretations of the ar ar isochron age utilizing the measured ar diffusion characteristics of nwa 2737 and a thermal model which relates ar diffusion to the size of a cooling object after shock heating one interpretation that 40 ar was only partially degassed by an impact event 11 ma ago the cre age appears possible only if nwa 2737 was shock heated to temperatures 600 c and was ejected from mars as an object a few 10 s of cm in diameter the second interpretation which we prefer is that nwa experienced an earlier more intense shock event which left it residing in a warm ejecta layer and a less intense event 11 ma ago which ejected it into space our evaluation would require nwa 2737 to have been heated by this first event to a temperature of 300 500 c and buried in ejecta to a depth of 1 20 m these conclusions are compared to model constraints on meteorite ejection from mars reported in the literature the second mars ejection impact 11 ma ago probably heated nwa 2737 to no more than 400 c nwa 2737 demonstrates that some martian meteorites probably experienced shock heating in events that did not eject them into space

shallow dynamic overshoot and energetic deep rupture in the 2011 mw 9 0 tohoku oki earthquake strong spatial variation of rupture characteristics in the moment magnitude mw 9 0 tohoku oki megathrust earthquake controlled both the strength of shaking and the size of the tsunami that followed finite source imaging reveals that the rupture consisted of a small initial phase deep rupture for up to 40 seconds extensive shallow rupture at 60 to 70 seconds and continuing deep rupture lasting more than 100 seconds a combination of a shallow dipping fault and a compliant hanging wall may have enabled large shallow slip near the trench normal faulting aftershocks in the area of high slip suggest dynamic overshoot on the fault despite prodigious total slip shallower parts of the rupture weakly radiated at high frequencies whereas deeper parts of the rupture radiated strongly at high frequencies

source inversion of w phase speeding up seismic tsunami warning w phase is a long period phase arriving before s wave it can be interpreted as superposition of the fundamental first second and third overtones of spheroidal modes or rayleigh waves and has a group velocity from 4 5 to 9 km s 1 over a period range of 100 1000 s the amplitude of long period waves better represents the tsunami potential of an earthquake because of the fast group velocity of w phase most of w phase energy is contained within a short time window after the arrival of the p wave at a distance of 50 w phase energy is contained within 23 min after the origin time which is the distinct advantage of using w phase for rapid tsunami warning purposes we use a time domain deconvolution method to extract w phases from the broad band records of global seismic networks the bandwidth of w phase is approximately from 0 001 to 0 01 hz and we bandpass filter the data from 0 001 to 0 005 hz in most cases having extracted w phase from the vertical component records we perform a linear inversion using a point source to determine mw and the source mechanism for several large earthquakes including the 2004 sumatra andaman earthquake the 2005 nias earthquake the 2006 kuril is earthquake and the 2007 sumatra earthquake w phase inversion yields reliable solutions and holds promise of the use of w phase for rapid assessment of tsunami potential

revising the shock classification of meteorites the current shock classification scheme of meteorites assigns shock levels of s1 unshocked to s6 very strongly shocked using shock effects in rock forming minerals such as olivine and plagioclase the s6 stage 55 90 gpa 850 1750 c relies solely on localized effects in or near melt zones the recrystallization of olivine or the presence of mafic high pressure phases such as ringwoodite however high whole rock temperatures and the presence of high pressure phases that are unstable at those temperatures and pressures of zero gpa e g ringwoodite are two criteria that exclude each other each type of high pressure phase provides a minimum shock pressure during elevated pressure conditions to allow the formation of this phase and a maximum temperature of the whole rock after decompression to allow the preservation of this phase rocks classified as s6 are characterized not by the presence but by the absence of those thermally unstable high pressure phases high pressure phases in or attached to shock melt zones form mainly during shock pressure decline this is because shocked rocks 60 gpa experience a shock wave with a broad isobaric pressure plateau only during low velocity 4 5 km s 1 impacts which rarely occur on small planetary bodies e g the moon and asteroids the mineralogy of shock melt zones provides information on the shape and temporal duration of the shock wave but no information on the general maximum shock pressure in the whole rock

formation of high pressure minerals in shocked l6 chondrite yamato 791384 constraints on shock conditions and parent body size we have studied the high pressure phases observed in yamato 791384 l6 chondrite host meteorite mainly consists of olivine pyroxenes and plagioclase glass mineral fragments observed in the veins and the vein margin region of the host meteorite were partially or totally transformed into high pressure phases ringwoodite majorite akimotoite naalsi3o8 hollandite and jadeite matrix of the shock vein contains majorite pyrope solid solution the spatial distribution indicates that high pressure phases are present in the shock veins and host rocks adjacent to the shock veins investigation of the high pressure phases revealed that in y791384 fragments and adjacent matrix were subjected to pressures around of 18 23 gpa and the vein experienced temperatures around 2300 c during the shock event ringwoodite lamellae were observed in the host olivine adjacent to the vein kinetic investigation for ringwoodite lamellar growth in olivine indicates that the shocked meteorite experienced the pressure for at least 4 s such long duration of the pressure pulse indicates that the size of the parent body was greater than 10 km

shock induced metallic iron nanoparticles in olivine rich martian meteorites magnetic anomalies observed by the mars global surveyor mission are attributed to crustal remanence snc shergotty nakhla chassigny meteorites are likely samples of the martian crust and are amenable to mineralogical and magnetic measurements essential to the understanding of the origin of magnetic anomalies the recently discovered chassignite nwa 2737 and lherzolitic shergottite nwa 1950 display unusual magnetic characteristics that argue for a different magnetic carrier than the oxides and sulfides previously invoked in snc meteorites nwa 2737 the second member of the chassignite group is a dunite with unusually dark brown olivines and large magnetic susceptibility while chassigny contains green olivines and is nearly a pure paramagnet dark olivines are also found in nwa 1950 a lherzolitic shergottite which has singular magnetic properties when compared with other shergottites the dark olivine color is due to the presence of fe and feni metal nanoparticles identified both by tem and by magnetic measurements their size distribution encompasses the superparamagnetic to single domain transition at 30 k 10 nm range and explains the magnetic properties of the bulk rocks the formation of these nanoparticles is attributed to heating during the shock events that affected nwa 2737 and nwa 1950 the production of metal particles by shock induced reduction of olivine has been invoked on surfaces deprived of atmosphere but never observed on earth or mars therefore metal formed by shock in the heavily cratered noachian crust is a possible carrier for crustal magnetic remanence widespread surface formation of metal nanoparticles could provide the precursor for the oxidized particles goethite hematite observed in the martian soils c 2007 elsevier b v all rights reserved

seismology speed and size of the sumatra earthquake we now have a clearer picture of the seismic features of last year s gigantic event our seismological results reveal that indonesia s devastating sumatra andaman earthquake on 26 december 2004 was 2 5 times larger than initial reports suggested second only to the 1960 chilean earthquake in recorded magnitude they indicate that it slowly released its energy by slip along a 1 200 km fault generating a long rupture that contributed to the subsequent tsunami now that the entire rupture zone has slipped the strain accumulated from the subduction of the indian plate beneath the burma microplate has been released and there is no immediate danger of a similar tsunami being generated on this part of the plate boundary although large earthquakes on segments to the south still present a threat

the diversity of large earthquakes and its implications for hazard mitigation with the advent of broadband seismology and gps significant diversity in the source radiation spectra of large earthquakes has been clearly demonstrated this diversity requires different approaches to mitigate hazards in certain tectonic environments seismologists can forecast the future occurrence of large earthquakes within a solid scientific framework using the results from seismology and gps such forecasts are critically important for long term hazard mitigation practices but because stochastic fracture processes are complex the forecasts are inevitably subject to large uncertainty and unexpected events will continue to surprise seismologists recent developments in real time seismology will help seismologists to cope with and prepare for tsunamis and earthquakes combining a better understanding of earthquake diversity with modern technology is the key to effective and comprehensive hazard mitigation practices

linear and nonlinear computations of the 1992 nicaragua earthquake tsunami numerical computations of tsunamis are made for the 1992 nicaragua earthquake using different governing equations bottom frictional values and bathymetry data the results are compared with each other as well as with the observations both tide gauge records and runup heights comparison of the observed and computed tsunami waveforms indicates that the use of detailed bathymetry data with a small grid size is more effective than to include nonlinear terms in tsunami computation linear computation overestimates the amplitude for the later phase than the first arrival particularly when the amplitude becomes large the computed amplitudes along the coast from nonlinear computation are much smaller than the observed tsunami runup heights the average ratio or the amplification factor is estimated to be 3 in the present case when the grid size of 1 minute is used the factor however may depend on the grid size for the computation

aseismic slow slip on an inland active fault triggered by a nearby shallow event the 2008 iwate miyagi nairiku earthquake mw6 8 1 using gps observations we have detected an aseismic slip event on the intraplate dedana fault that was triggered by the iwate miyagi nairiku earthquake mw6 8 13 jun 2008 utc on a nearby but separate fault the observations cannot be satisfactorily explained in terms of either viscoelastic relaxation or poroelastic rebound and we cannot explain the observed displacement time series without presuming that aseismic slip occurred on the dedana fault this slip was likely triggered by the mainshock stress change the detection of future such aseismic slip events on intraplate faults is likely to require denser geodetic networks than are currently in operation but is important for fully characterizing the seismic hazard associated with intraplate earthquakes

modeling the rupture process of the 2003 september 25 tokachi oki hokkaido earthquake using 1 hz gps data received 10 september 2004 accepted 3 october 2004 published 3 november 2004 1 high rategpshasthepotentialtorecoverbothdynamic and static displacements accurately we analyze 1 hz gps data recorded during the 2003 tokachi oki earthquake the 1 hz gps displacement waveforms show good agreement with integrated accelerometer records except for low frequency noise that are inherently present in integrated seismic records the gps waveforms were inverted to model the spatio temporal evolution of the fault slip during the rupture the slip is found to propagate downdip in the subduction zone with largest moment release 50 km northwest of the hypocenter the region of largest slip agrees in general with traditional seismic studies indicating that 1 hz gps can be used for finite fault studies the 1 hz gps slip model shows clearer contrast with afterslip distributions than those inferred from strong motion data possibly because 1 hz gps is more sensitive to cumulative slip distribution index terms 1294 geodesy and gravity instruments and techniques 7209 seismology earthquake dynamics and mechanics 7212 seismology earthquake ground motions and engineering citation miyazaki s k m larson k choi k hikima k koketsu p bodin j haase g emore and a yamagiwa 2004 modeling the rupture process of the 2003 september 25 tokachi oki hokkaido earthquake using 1 hz gps data geophys res lett 31 l21603 doi 10 1029 2004gl021457

ejection of martian meteorites we investigated the transfer of meteorites from mars to earth with a combined mineralogical and numerical approach we used quantitative shock pressure barometry and thermodynamic calculations of post shock temperatures to constrain the pressure temperature conditions for the ejection of martian meteorites the results show that shock pressures allowing the ejection of martian meteorites range from 5 to 55 gpa with corresponding post shock temperature elevations of 10 to about 1000 c with respect to shock pressures and post shock temperatures an ejection of potentially viable organisms in martian surface rocks seems possible a calculation of the cooling time in space for the most highly shocked martian meteorite allan hills alh 77005 was performed and yielded a best fit for a post shock temperature of 1000 c and a meteoroid size of 0 4 to 0 6 m the final burial depths of the sub volcanic to volcanic martian rocks as indicated by textures and mineral compositions of meteorites are in good agreement with the postulated size of the potential source region for martian meteorites during the impact of a small projectile 200 m as defined by numerical modeling artemieva and ivanov 2004 a comparison of shock pressures and ejection and terrestrial ages indicates that on average highly shocked fragments reach earth crossing orbits faster than weakly shocked fragments if climatic changes on mars have a significant influence on the atmospheric pressure they could account for the increase of recorded ejection events of martian meteorites in the last 5 ma

existence of interplane earthquakes and neutral stress boundary between the upper and lower planes of the double seismic zone beneath tohoku and hokkaido northeastern japan abstract using data from the recently constructed nationwide dense seismic network we determined the hypocenters and focal mechanisms of many intermediate depth intraslab earthquakes within the pacific slab beneath northeastern japan the results show that in addition to the upper and lower planes of the double seismic zone a considerable number of intraslab earthquakes also occur between the two planes this interplane earthquake activity is not homogeneously distributed in space being high beneath eastern hokkaido and the fore arc regions of southeast and central tohoku the focal mechanisms of the interplane earthquakes tend to be of the down dip compressional type dc in tohoku and the hokkaido corner but down dip tensional type de in eastern hokkaido upper plane earthquakes are characterized by dc type stress while lower plane earthquakes are de type in both tohoku and eastern hokkaido the existence of interplane earthquakes enables estimation of the position of the neutral plane between the upper plane dc stress and the lower plane de stress we did so by applying stress tensor inversions to focal mechanism data obtained in the present study and japan meteorological agency jma data the results show that the neutral plane is located about 22 km beneath the upper plate interface beneath tohoku but only about 10 km beneath the upper surface beneath eastern hokkaido this difference in the location of the neutral plane may be due to the difference in buoyancy force exerted by the less dense metastable olivine wedge that is a result of the oblique plate subduction beneath hokkaido comparison of large intraslab earthquakes beneath the two regions shows that their aftershock areas are limited by the neutral plane suggesting that large earthquake ruptures are confined to either the dc or de stress field and do not go beyond the neutral plane

earth s free oscillations excited by the 26 december 2004 sumatra andaman earthquake at periods greater than 1000 seconds earth s seismic free oscillations have anomalously large amplitude when referenced to the harvard centroid moment tensor fault mechanism which is estimated from 300 to 500 second surface waves by using more realistic rupture models on a steeper fault derived from seismic body and surface waves we approximated free oscillation amplitudes with a seismic moment 6 5 10 22 newton meters that corresponds to a moment magnitude of 9 15 with a rupture duration of 600 seconds the fault rupture models represent seismic observations adequately but underpredict geodetic displacements that argue for slow fault motion beneath the nicobar and andaman islands

tsunami forecast by joint inversion of real time tsunami waveforms and seismic or gps data application to the tohoku 2011 tsunami correctly characterizing tsunami source generation is the most critical component of modern tsunami forecasting although difficult to quantify directly a tsunami source can be modeled via different methods using a variety of measurements from deep ocean tsunameters seismometers gps and other advanced instruments some of which in or near real time here we assess the performance of different source models for the destructive 11 march 2011 japan tsunami using model data comparison for the generation propagation and inundation in the near field of japan this comparative study of tsunami source models addresses the advantages and limitations of different real time measurements with potential use in early tsunami warning in the near and far field the study highlights the critical role of deep ocean tsunami measurements and rapid validation of the approximate tsunami source for high quality forecasting we show that these tsunami measurements are compatible with other real time geodetic data and may provide more insightful understanding of tsunami generation from earthquakes as well as from nonseismic processes such as submarine landslide failures

using 1 hz gps data to measure deformations caused by the denali fault earthquake the 3 november 2002 moment magnitude 7 9 denali fault earthquake generated large permanent surface displacements in alaska and large amplitude surface waves throughout western north america we find good agreement between strong ground motion records integrated to displacement and 1 hertz global positioning system gps position estimates collected 140 kilometers from the earthquake epicenter one hertz gps receivers also detected seismic surface waves 750 to 3800 kilometers from the epicenter whereas these waves saturated many of the seismicinstruments in the same region high frequency gps increases the dynamic range and frequency bandwidth of ground motion observations providing another tool for studying earthquake processes

near field tsunami forecasting from cabled ocean bottom pressure data 1 we propose a method for near field tsunami forecasting from data acquired by cabled offshore ocean bottom tsunami meters obtms in real time we first invert tsunami waveforms recorded at obtms to estimate the spatial distribution of initial sea surface displacements in the tsunami source region without making any assumptions about fault geometry and earthquake magnitude then we synthesize the coastal tsunami waveforms from the estimated sea surface displacement distribution to improve the reliability of the tsunami forecasting we use updated obtm data to repeat the forecast calculation at 1 min intervals we tested our method by simulating the 1896 sanriku tsunami earthquake which caused a devastating tsunami with maximum runup height of 38 m along the pacific coast of northeastern japan instead of real obtm records proxies were used the simulation demonstrated that our method provided accurate estimations of coastal arrival times and amplitudes of the first peak of the tsunami more than 20 min before the maximum amplitude wave reached the coastal site nearest to the source we also applied the method to real data of a small tsunami that was caused by a local earthquake and successfully forecasted the tsunami at coastal tide stations we found that accuracy of our estimated coastal tsunami amplitudes can be affected by the spatial relationship between the tsunami source and the offshore observation stations our numerical simulation showed that even more accurate tsunami amplitude forecasts would be achieved by deployment of additional offshore stations separated by a distance comparable to the trench parallel length of the tsunami source

fast determination of earthquake magnitude and fault extent from real time p wave recordings s u m m a r y this work is aimed at the automatic and fast characterization of the extended earthquake source through the progressive measurement of the p wave displacement amplitude along the recorded seismograms we propose a straightforward methodology to quickly characterize the earthquake magnitude and the expected length of the rupture and to provide an approximate estimate of the average stress drop to be used for earthquake earlywarning and rapid response purposes we test the methodology over a wide distance and magnitude range using a massive japan earthquake accelerogram data set our estimates of moment magnitude source duration length and stress drop are consistent with the ones obtained by using other techniques and analysing the whole seismic waveform in particular the retrieved source parameters follow a self similar constant stress drop scaling median value of stress drop 0 71 mpa for the m 9 0 2011 tohoku oki event both magnitude and length are underestimated due to limited available p wave time window ptws and to the low frequency cut off of analysed data we show that in a simulated real time mode about 1 2 seconds would be required for the source parameter determination of m 4 5 events 3 10 seconds for m 6 7 and 30 40 s for m 8 8 5 the proposed method can also provide a rapid evaluation of the average slip on the fault plane which can be used as an additional discriminant for tsunami potential associated to large magnitude earthquakes occurring offshore

shear induced ringwoodite formation in the martian shergottite dar al gani 670 abstract shock produced melt veins in the martian shergottite dar al gani 670 crosscut large olivine crystals the upper part of one of these crystals appears to be sheared off and displaced along the shock vein from the olivine vein interface small lamellae of ringwoodite grow into the host crystal the 1 3 m wide and up to 20 m long lamellae consist of small bands and blocks and are orientated along specific crystallographic orientations texture and composition i e more fe rich than the host olivine indicate that lamellae formed via incoherent diffusion controlled growth it is suggested that a combination of high particle velocities and shock induced defects lead to enhanced diffusion rates in addition shearing caused grain size reduction allowing rapid fe mg interchange and induced lattice defects serving as nucleation sites for ringwoodite crystallographic orientation of ringwoodite lamellae indicates that during shock deformation the 001 hk 0 slip system was activated in olivine natural high pressure phases in martian meteorite allow to constrain phase transitions taking place in the inaccessible earth s mantle high pressure shear instabilities of olivine at subduction zones in 400 700 km depth are considered being responsible for deep earthquakes at such p t conditions breakdown of olivine results in formation of ringwoodite filled micro anticracks which interact with each other finally leading to catastrophic shear failure our results strongly suggest that shearing itself contributes to a runaway process of enhanced ringwoodite formation and thus reinforces catastrophic material failure that may result in deep earthquakes

shock events in the solar system the message from minerals in terrestrial planets and asteroids impacts are central to the origin and evolution of planets of the solar system the shapes of craters which can reach up to 1 000 km in diameter on the moon provide critical information on the large scale dynamics of the impact and related shock minerals formed at high pressure and temperature found in shocked terrestrial rocks and meteorites give additional and complementary insights on the shock process at a smaller scale typically from a few micrometers to a few millimeters local flaws in rocks such as voids and mineral interfaces are the preferential sites for the formation of high pressure melts and minerals calculations based on the physics of shocks and the thermodynamics and kinetics of mineral transformations provide orders of magnitude for the duration transient pressure and prevailing temperature conditions of shock events case studies on shocked terrestrial and extraterrestrial materials illustrate the links between these parameters and impact duration many of the high pressure min

merging tsunamis of the 2011 tohoku oki earthquake detected over the open ocean 1 tsunamis often travel long distances without losing power and severely devastate some coastal areas while leaving others with little damage this unpredictable situation has been a major challenge for accurate and timely tsunami forecasting to facilitate early warning and possible evacuations of affected coastal communities without disturbing the lives of others here we show evidence from satellite altimetry observations of the 2011 tohoku oki earthquake induced tsunami that sheds light on this issue three satellites observed the same tsunami front and for the first time one of them recorded a tsunami height about twice as high as that of the other two model simulations based on the gps derived earthquake source and constrained by measurements of seafloor motions near the hypocenter confirm that the amplified tsunami is one of several jets formed through topographic refraction when tsunamis travel along ocean ridges and seamount chains in the pacific ocean this process caused the tsunami front to merge as it propagates resulting in the doubling of the wave height and destructive potential in certain directions we conclude that the potential of merging tsunamis should be emphasized in mapping tsunami hazards and assessing risk levels at key coastal facilities

millimeter level ultra long period multiple earth circling surface waves retrieved from dense high rate gps network abstract high rate gps networks have proven to be capable of continuously recording strong ground motion which is valuable for studying earthquake rupture processes and seismic hazard mitigation previous studies of high rate gps usually resolved dynamic ground displacements of some major seismic phases stronger than a few millimeters in this study we explore the feasibility of retrieving much weaker ground motions sub millimeter in long duration records by stacking high rate gps network we processed data of the 2011 tohoku oki earthquake recorded by more than 600 high rate gps stations of the plate boundary observatory pbo and analyzed kinematic displacement results with seismic array methods from these high rate gps seismograms we identified abundant seismic phases not only including clear body waves such as multiple s waves s ss sss ssss traveling along minor major great circle arc and ssssss beyond 360 degrees but also the r1 r5 rayleigh waves and g1 g6 love waves some of which travel around the earth multiple times many of these seismic phases have not been reported by previous high rate gps studies the group velocity dispersion curves extracted from multiple earth circling love waves of high rate gps are consistent with those of broadband seismic records in the period from 150 to 600 s which can sample the mantle structure down to top of the lower mantle thus important for understanding interaction between upper mantle and lower mantle so the dense high rate gps networks should be useful for deep mantle research as an additional valuable dataset with the development of multi system gnss and the more precise modeling of error sources high rate gnss data should have great potential for accurately detecting more geodynamic processes with much wider bandwidth in geoscience studies

northwest africa 1950 mineralogy and comparison with antarctic lherzolitic shergottites nwa 1950 is a new lherzolitic shergottite recently recovered from morocco and is the first sample of this group found outside antarctica major constituent phases of nwa 1950 are olivine pyroxenes and plagioclase glass maskelynite and the rock shows a two distinct textures poikilitic and non poikilitic typical of lherzolitic shergottites in poikilitic areas several millimeter sized pyroxene oikocrysts enclose cumulus olivine and chromite in contrast pyroxenes are much smaller in non poikilitic areas and olivine and plagioclase glass are more abundant olivine in non poikilitic areas is more fe rich fa29 31 and shows a narrower distribution than that in poikilitic areas fa23 29 pyroxenes in non poikilitic areas are also more fe rich than those in poikilitic areas that show continuous chemical zoning suggesting fractional crystallization under a closed system these observations indicate that pyroxene in non poikilitic areas crystallized from evolved interstitial melts and olivine was re equilibrated with such melts nwa 1950 shows similar mineralogy and petrology to previously known lherzolitic shergottites alh 77005 lew 88516 y 793605 and grv 99027 that are considered to have originated from the same igneous body on mars olivine composition of nwa 1950 is intermediate between those of alh 77005 grv 99027 and those of lew 88516 y 793605 but is rather similar to alh 77005 and grv 99027 the subtle difference of mineral chemistry especially olivine composition can be explained by different degrees of re equilibration compared to other lherzolitic shergottites perhaps due to different location in the same igneous body thus nwa 1950 experienced a high degree of re equilibration similar to alh 77005 and grv 99027

microstructural investigations on strongly stained olivines of the chassignite nwa 2737 and implications for its shock history abstract olivines from the meteorite northwest africa 2737 nwa 2737 show unique characteristics such as strong brownish staining the occurrence of perpendicular sets of bright lamellae and the exsolution of metallic nanoparticles these features were investigated by transmission electron microscopy and spectroscopic techniques to understand their formation and consequent implications for the shock history of nwa 2737 areas showing optically an intense brown staining are characterised by the occurrence of finely dispersed metallic nanoparticles an extreme high density 10 16 m 2 of polygonised dislocations with burgers vector 001 and a high abundance of trivalent iron 16 as determined by electron energy loss spectroscopy in contrast the bright lamellae contain individual dislocation lines with burgers vector 001 of a slightly lower density 10 14 m 2 almost no metallic nanoparticles and significantly lower trivalent iron content model mass balance calculations suggest that the high content of trivalent iron can be incorporated as a laihunite component into the cores of polygonised dislocations this is charge balanced by the formation of metallic nanoparticles trivalent iron is likely responsible for the intense brown colour whereas nanoparticles darken these areas considerably and cause an intense red slope in the infrared range the proposed diffusion of trivalent iron into the cores of polygonised dislocations and the associated exsolution of metallic iron nanoparticles are likely fundamental processes for intense olivine staining during meteoritic impacts in general detailed analyses of variously stained regions suggest that the bright lamellae have experienced slightly higher shock induced strain causing a recrystallisation of olivine which occurred simultaneously with the polygonisation and exsolution processes resulting in the olivine staining of adjacent areas the existence of individual dislocations can be interpreted as the result of a two stage shock history for nwa 2737 after a first impact the material of nwa 2737 was likely embedded in a hot ejecta blanket this would ensure sufficient time at elevated temperatures for the polygonisation of dislocations and the recrystallisation of bright lamellae a second impact resulted in the emission of individual dislocations into recrystallised olivine and the ejection of that meteorite from mars

trench normal variation in observed seafloor displacements associated with the 2011 tohoku oki earthquake 1 seafloor geodetic measurements using the gps acoustic technique just above the rupture area of the 2011 tohoku oki earthquake revealed strong trench normal variation in the horizontal crustal displacement associated with the earthquake one set of observations at a site only 50 km away from the trench yielded the most trench ward data ever reported with an accuracy better than 1 m it showed a coseismic displacement of up to 31 m whereas another set of observations 100 km away from the trench showed a 15 m displacement these horizontal data as well as vertical data from pressure gauges and tsunami observations strongly indicate that the seismic slip reached the trench they are also likely to contribute quantitatively to further investigations that reveal the coseismic behavior of the frontal wedge of the overriding plate in the source region along the japan trench

rapid modeling of the 2011 mw 9 0 tohoku oki earthquake with seismogeodesy 1 rapid characterization of finite fault geometry and slip for large earthquakes is important for mitigation of seismic and tsunamigenic hazards saturation of near source weak motion and problematic integration of strong motion data into displacements make this difficult in real time combining gps and accelerometer data to estimate seismogeodetic displacement waveforms overcomes these limitations by providing mm level three dimensional accuracy and improved estimation of coseismic deformation compared to gps only methods we leverage collocated gps and accelerometer data from the 2011 mw 9 0 tohoku oki japan earthquake by replaying them in simulated real time mode using a novel approach to account for fault finiteness we generate an accurate centroid moment tensor solution independently of any constraint on the slab geometry followed by a finite fault slip model the replay of gps and seismic data demonstrates that robust models could have been made available within 3 min of earthquake initiation

ability of 1 hz gps data to infer the source process of a medium sized earthquake the case of the 2008 iwate miyagi nairiku japan earthquake 1 we demonstrate the ability of 1 hz global positioning system gps data to infer a medium sized m6 class earthquake source process through an inversion study of the 2008 iwate miyagi nairiku japan earthquake m 6 9 1 hz gps waveforms for this earthquake are compared and show good agreement with strong motion waveforms ground motions are well recorded at a sufficient number of gps stations in and around source region allowing us to perform waveform inversion using 1 hz gps data only the 1 hz gps inversion result shows fairly good agreement with a joint inversion of geodetic and strong motion data such as the seismic moment mw 6 9 cumulative slip distribution and rupture propagation such agreements demonstrate that 1 hz gps is able to infer the dynamic features of the rupture process as well as permanent or static slip even for a m6 class medium sized earthquake

martian dunite nwa 2737 integrated spectroscopic analyses of brown olivine received 5 october 2007 revised 13 december 2007 accepted 6 march 2008 published 18 june 2008 1 a second martian meteorite has been identified that is composed primarily of heavily shocked dunite northwest africa nwa 2737 this meteorite has several similarities to the chassigny dunite cumulate but the olivine is more mg rich and most notably is very dark and visually brown carefully coordinated analyses of nwa 2737 whole rock and olivine separates were undertaken using visible and near infrared reflectance

fe3 in shocked olivine crystals of the alha 77005 meteorite abstract alha 77005 a shocked achondrite of the shergottite group is unique in containing cumulus olivine crystals which display a brownish color in thin section mossbauer epr and optical spectroscopic studies show the presence of fe 3 in the olivine approximately 4 5 wt of the total iron in the olivine 24 wt as feo is in the trivalent state the fe 3 ions preferentially occupy m2 lattice positions charge transfer between fe 3 and fe 2 as well as between fe 3 and oxygen ligands causes a broad absorption band in the optical spectrum at high energies which is the reason for the olivine color it is concluded that the color of the alha 77005 olivine is preterrestrial and may be the result of shock induced oxidation of the olivine crystals on the meteorite parent body

petrology geochemistry and cosmic ray exposure age of lherzolitic shergottite northwest africa 1950 northwest africa nwa 1950 is a new member of the lherzolitic shergottite clan of the martian meteorites recently found in the atlas mountains the petrological mineralogical and geochemical data are very close to those of the other known lherzolitic shergottites the meteorite has a cumulate gabbroic texture and its mineralogy consists of olivine fo66 to fo75 low and high ca pyroxenes en 78 fs 19 wo 2 en 60 fs 26 w 14 en 53 fs 16 wo 31 en 45 fs 14 wo 41 and plagioclase an 57 ab 41 or 1 to an 40 ab 57 or 3 entirely converted into maskelynite during intense shock metamorphism accessory minerals include phosphates merrillite chromite and spinels sulfides and a glass rich in potassium the oxygen isotopic values lie on the fractional line defined by the other snc meteorites delta 17 o 0 312 parts per thousand the composition of nwa 1950 is very similar to the other lherzolitic shergottites and suggests an origin from the same magmatic system or at least crystallization from a close parental melt cosmogenic ages indicate an ejection age similar to those of the other lherzolitic shergottites the intensity of the shock is similar to that observed in other shergottites as shown by the occurrence of small melt pockets containing glass interwoven with stishovite

shock induced transformation of olivine to a new metastable mg fe 2sio4 polymorph in martian meteorites transient high pressures and temperatures generated during meteor or asteroid impacts induce mineral phase transformations that can mimic those occurring at depth within the silicate mantle of terrestrial planets olivine mg fe 2sio4 the primary constituent of the earth s upper mantle and of chondritic meteorites transforms to the high pressure polymorphs wadsleyite and ringwoodite mg fe 2sio4 that are observed in shocked chondrites the observed phase transitions place constraints on the shock p t conditions attained and they lead to models that describe the impact event we studied the olivines present within two newly catalogued martian meteorites nwa 2737 and nwa 1950 using micro raman spectroscopy and high resolution transmission electron microscopy hrtem techniques the shock conditions were not sufficient to cause melting or transformation of the olivines into wadsleyite or ringwoodite mg fe 2sio4 the shocked olivines are dark coloured in hand specimen and thin section due to the presence of fexniy metallic nanoparticles formed during the shock molecular dynamics simulations md are consistent with the observation that the shocked olivines give rise to a new orthosilicate polymorph mg fe 2sio4 that is formed metastably during the shock process and that is subsequently recovered to ambient conditions the presence of the new mg fe 2sio4 polymorph in shocked ultrabasic rocks including meteorites may have remained undetected due to its structural and spectroscopic similarities with olivine the existence of the metastable phase transition also allows rationalising previously unexplained results of shock compression experiments on olivines mg fe 2sio4 is also formed at ambient pressure as a metastable intermediate during back transformation from wadsleyite

heterogeneous mineral assemblages in martian meteorite tissint as a result of a recent small impact event on mars the microtexture and mineralogy of shock melts in the tissint martian meteorite were investigated using scanning electron microscopy raman spectroscopy transmission electron microscopy and synchrotron micro x ray diffraction to understand shock conditions and duration distinct mineral assemblages occur within and adjacent to the shock melts as a function of the thickness and hence cooling history the matrix of thin veins and pockets of shock melt consists of clinopyroxene ringwoo dite stishovite embedded in glass with minor fe sulfide the margins of host rock olivine in contact with the melt as well as entrained olivine fragments are now amorphosed silicate perovskite magnesiowustite or clinopyroxene magnesiowustite the pressure stabilities of these mineral assemblages are 15 gpa and 19 gpa respectively the 200 lm wide margin of a thicker mm size up to 1 4 mm shock melt vein contains clinopyroxene olivine with central regions comprising glass vesicles fe sulfide spheres fragments of host rock within the melt are polycrystalline olivine after olivine and tis sintite glass after plagioclase from these mineral assemblages the crystallization pressure at the vein edge was as high as 14 gpa the interior crystallized at ambient pressure the shock melts in tissint quench crystallized during and after release from the peak shock pressure crystallization pressures and those determined from olivine dissociation therefore represent the minimum shock loading shock deformation in host rock minerals and complete transformation of plagioclase to maskelynite suggest the peak shock pressure experienced by tissint p 29 30 gpa these pressure estimates support our assessment that the peak shock pressure in tissint was significantly higher than the minimum 19 gpa required to transform olivine to silicate perovskite plus magnesiowustite small volumes of shock melt 100 lm quench rapidly 0 01 s whereas thermal equilibration will occur within 1 2 s in larger volumes of melt 1 mm 2 the apparent variation in shock pressure recorded by variable mineral assemblages within and around shock melts in tissint is consistent with a shock pulse on the order of 10 20 ms combined with a longer duration of post shock cooling and complex thermal history this implies that the impact on mars that shocked and ejected tissint at 1 ma was not exceptionally large

instantaneous geodetic positioning at medium distances with the global positioning system we evaluate a new method of global positioning system gps data analysis called instantaneous positioning at spatial scale lengths typical of interstation spacings in a modern crustal motion network this method is more precise and versatile than traditional gps static and kinematic processing of multi epoch batches of data the key to instantaneous positioning is the ability to resolve integer cycle phase ambiguities with only a single epoch of dual frequency phase and pseudorange data rendering receiver cycle slips irrelevant we estimate three dimensional relative coordinates and atmospheric zenith delay parameters independently every 30 s over a 12 week period for baseline distances of 50 m 14 km and 37 km horizontal precision of a single epoch coordinate solution is about 15 mm and vertical precision is about 7 8 times worse removing that component of each time series which repeats with a period of exactly 1 sidereal day and thus manifests signal multipath reduces the scatter by about 50 in all components solution averaging of the high frequency time series can be performed using any number of measurement epochs to further improve coordinate precision we demonstrate that the daily coordinates estimated with instantaneous positioning are more precise by 20 50 per coordinate component than those estimated with 24 hour batch processing spectral analysis of the single epoch solutions indicates that the flicker noise characteristic of gps time series observed in lower frequency bands also affects gps solutions in the frequency band 0 01 mhz to 10 mhz we argue that the flicker noise is induced by tropospheric effects since modern gps receivers are capable of observing at frequencies as high as 10 hz our technique significantly overlaps and complements the frequency band of broadband seismology and benefits other research areas such as earthquake geodesy volcanology and gps meteorology

rapid determination of earthquake magnitude using gps for tsunami warning systems 1 the 26 december 2004 sumatra earthquake mw 9 2 9 3 generated the most deadly tsunami in history yet within the first hour the true danger of a major oceanwide tsunami was not indicated by seismic magnitude estimates which were far too low mw 8 0 8 5 this problem relates to the inherent saturation of early seismic wave methods here we show that the earthquake s true size and tsunami potential can be determined using global positioning system gps data up to only 15 min after earthquake initiation by tracking the mean displacement of the earth s surface associated with the arrival of seismic waves within minutes displacements of 10 mm are detectable as far away as india consistent with results using weeks of data after the event these displacements imply mw 9 0 0 1 indicating a high tsunami potential this suggests existing gps infrastructure could be developed into an effective component of tsunami warning systems

detection of arbitrarily large dynamic ground motions with a dense high rate gps network 1 we describe the detection of teleseismic surface waves from the 3 november 2002 mw 7 9 denali fault earthquake in alaska with a dense network of 1 hz gps stations in southern california about 3900 km from the event relative horizontal displacements with amplitudes in excess of 15 mm and duration of 700 seconds agree with integrated velocities recorded by nearby broadband seismometers with an rms difference of 2 3 mm the displacements are derived from independent 1 hz instantaneous positions demonstrating that a gps network can provide direct measurements of arbitrarily large dynamic and static ground horizontal displacements at periods longer than 1 s and amplitudes above 2 mm with an inherent precision signal to noise that improves indefinitely with amplitude without clipping and in real time high rate real time gps networks can enhance earthquake detection and seismic risk mitigation and support other applications such as intelligent transportation and civil infrastructure monitoring

shock metamorphism of elephant moraine a79001 implications for olivine ringwoodite transformation and the complex thermal history of heavily shocked martian meteorites abstract lithology a of martian meteorite elephant moraine eet a79001 contains fragments entrained within a 100 m thick shear induced shock vein these fragments the shock vein matrix and walls of olivine along the vein as well as shock deformation and transformation in rock forming minerals in the bulk rock were investigated using scanning electron microscopy the electron microprobe and raman spectroscopy the presence of ringwoodite the spinel structured high pressure mg fe 2 sio 4 polymorph has been confirmed in eeta79001 for the first time ringwoodite occurs within and around the shock vein exhibiting granular and lamellar textures in both textures ringwoodite consists of 500 nm size distinct grains ringwoodite lamellae are 115 nm to 1 3 m wide planar fractures in olivine provided sites for heterogeneous nucleation of ringwoodite analyses performed on the largest grains 1 m show that ringwoodite is consistently higher in iron fa 27 4 32 4 relative to surrounding olivine fa 25 1 267 7 implying that there was fe mg exchange during their transformation and therefore their growth was diffusion controlled in the shock environment diffusion takes place dynamically i e with concurrent deformation and grain size reduction this results in enhanced diffusion rates 10 8 m 2 s over nm m distances shock deformation in host rock minerals including strong mosaicism pervasive fracturing polysynthetic twinning pyroxene only extensive shock melting local transformation of olivine to ringwoodite and complete transformation of plagioclase to maskelynite in the bulk rock indicate that eeta79001 was strongly shocked the short shock duration 0 01 s combined with a complex thermal history resulted in crystallization of the 100 m thick shock vein in eeta79001 during the pressure release and partial back transformation of ringwoodite to olivine based on the pressure stabilities of clinopyroxene ringwoodite crystallization at the shock vein margin began at 18 gpa olivine and clinopyroxene crystallized at

efficient waveform tomography for lithospheric imaging implications for realistic two dimensional acquisition geometries and low frequency data summary we provide a series of numerical experiments designed to test waveform tomography under i a reduction in the number of input data frequency components efficient waveform tomography ii sparse spatial subsampling of the input data and iii an increase in the minimum data frequency used these results extend the waveform tomography results of a companion paper using the same third party 2 d wide angle synthetic viscoelastic seismic data computed in a crustal geology model 250 km long and 40 km deep with heterogeneous p velocity s velocity density and q factor structure accurate velocity models were obtained using efficient waveform tomography and only four carefully selected frequency components of the input data 0 8 1 7 3 6 and 7 0 hz this strategy avoids the spectral redundancy present in full waveform tomography and yields results that are comparable with those in the companion paper for an 88 per cent decrease in total computational cost because we use acoustic waveform tomography the results further justify the use of the acoustic wave equation in calculating p wave velocity models from viscoelastic data the effect of using sparse survey geometries with efficient waveform tomography were investigated for both increased receiver spacing and increased source spacing sampling theory formally requires spatial sampling at maximum interval of one half wavelength 2 5 km at 0 8 hz for data with receivers every 0 9 km conforming to this criterion artefacts in the tomographic images were still minimal when the source spacing was as large as 7 6 km three times the theoretical maximum larger source spacings led to an unacceptable degradation of the results when increasing the starting frequency image quality was progressively degraded acceptable image quality within the central portion of the model was nevertheless achieved using starting frequencies up to 3 0 hz at 3 0 hz the maximum theoretical sample interval is reduced to 0 67 km due to the decreased wavelengths the available sources were spaced every 5 0 km more than seven times the theoretical maximum and receivers were spaced every 0 9 km 1 3 times the theoretical maximum higher starting frequencies than 3 0 hz again led to unacceptable degradation of the results